text: In 1970 Simpson, William Dietrich and John David Anglin discovered that some impulsive sun flares produce energetic particles among which Helium-3, a light non-radioactive isotope of helium with two protons and one neutron, is at least ten times more abundant than Helium-4, a non-radioactive and light isotope of helium. On Earth, Helium-4 is what makes up about 99.986% of the helium here. In 1973 his instruments on Pioneer 10 and 11 indicated a cosmic ray intensity increase of about 1 percent per AU. In 1975 he found that during the low point of activity three years prior, the abundance of cosmic ray helium was strangely enhanced at these very low energies, as opposed to it dropping off with declining energies like the protons do, toward zero energy.

text: In 1970 Simpson, William Dietrich and John David Anglin discovered that some

entity_name: Solar flare

text: impulsive sun flares

text: produce energetic particles among which

text: , a light non-radioactive

entity_name: Isotope

text: isotope

text: of

entity_name: Helium

text: helium

text: with two

entity_name: Proton

text: protons

text: and one neutron, is at least ten times more abundant than

text: , a non-radioactive and light isotope of helium. On

entity_name: Earth

text: Earth

text: is what makes up about 99.986% of the helium here. In 1973 his instruments on

entity_name: Pioneer 10

text: Pioneer 10

text: and

entity_name: Pioneer 11

text: indicated a cosmic ray intensity increase of about 1 percent per AU. In 1975 he found that during the low point of activity three years prior, the abundance of cosmic ray helium was strangely enhanced at these very low energies, as opposed to it dropping off with declining energies like the protons do, toward

entity_name: Zero-energy universe

text: zero energy

method: Bert-ConvKNRM

text: Three group 3 elements occur naturally, scandium, yttrium, and either lanthanum or lutetium. Lanthanum continues the trend started by two lighter members in general chemical behavior, while lutetium behaves more similarly to yttrium. While the choice of lutetium would be in accordance with the trend for period 6 transition metals to behave more similarly to their upper periodic table neighbors, the choice of lanthanum is in accordance with the trends in the s-block, which the group 3 elements are chemically more similar to They all are silvery-white metals under standard conditions. The fourth element, either actinium or lawrencium, has only radioactive isotopes. Actinium, which occurs only in trace amounts, continues the trend in chemical behavior for metals that form tripositive ions with a noble gas configuration; synthetic lawrencium is calculated and partially shown to be more similar to lutetium and yttrium. So far, no experiments have been conducted to synthesize any element that could be the next group 3 element. Unbiunium (Ubu), which could be considered a group 3 element if preceded by lanthanum and actinium, might be synthesized in the near future, it being only three spaces away from the current heaviest element known, oganesson.

text: Three group 3 elements occur naturally, scandium, yttrium, and either lanthanum or lutetium. Lanthanum continues the trend started by two lighter members in general chemical behavior, while lutetium behaves more similarly to yttrium. While the choice of lutetium would be in accordance with the trend for

entity_name: Period 6 element

text: period 6

text: transition metals to behave more similarly to their upper periodic table neighbors, the choice of lanthanum is in accordance with the trends in the s-block, which the group 3 elements are chemically more similar to They all are silvery-white metals under standard conditions. The fourth element, either actinium or lawrencium, has only radioactive

text: isotopes

text: . Actinium, which occurs only in

entity_name: Trace radioisotope

text: trace amounts

text: , continues the trend in chemical behavior for metals that form tripositive ions with a

entity_name: Noble gas

text: noble gas

text: configuration;

entity_name: Synthetic element

text: synthetic

text: lawrencium is calculated and partially shown to be more similar to lutetium and yttrium. So far, no experiments have been conducted to

text: synthesize

text: any element that could be the next group 3 element.

entity_name: Extended periodic table

entity_section: Superactinides

text: Unbiunium (Ubu)

text: , which could be considered a group 3 element if preceded by lanthanum and actinium, might be synthesized in the near future, it being only three spaces away from the current heaviest element known,

entity_name: Oganesson

text: oganesson

method: Bert-DRMMTKS

text: The explosion and fire threw hot particles of the nuclear fuel and also far more dangerous fission products, radioactive isotopes such as caesium-137, iodine-131, strontium-90 and other radionuclides, into the air: the residents of the surrounding area observed the radioactive cloud on the night of the explosion.

text: The explosion and fire threw hot particles of the

entity_name: Nuclear fuel

text: nuclear fuel

text: and also far more dangerous

entity_name: Nuclear fission product

text: fission product

text: s, radioactive isotopes such as

text: and other

entity_name: Radionuclide

text: radionuclides

text: , into the air: the residents of the surrounding area observed the radioactive cloud on the night of the explosion.

text: On Earth (and elsewhere), trace amounts of various elements continue to be produced from other elements as products of natural transmutation processes. These include some produced by cosmic rays or other nuclear reactions (see cosmogenic and nucleogenic nuclides), and others produced as decay products of long-lived primordial nuclides. For example, trace (but detectable) amounts of carbon-14 (C) are continually produced in the atmosphere by cosmic rays impacting nitrogen atoms, and argon-40 (Ar) is continually produced by the decay of primordially occurring but unstable potassium-40 (K). Also, three primordially occurring but radioactive actinides, thorium, uranium, and plutonium, decay through a series of recurrently produced but unstable radioactive elements such as radium and radon, which are transiently present in any sample of these metals or their ores or compounds. Three other radioactive elements, technetium, promethium, and neptunium, occur only incidentally in natural materials, produced as individual atoms by natural fission of the nuclei of various heavy elements or in other rare nuclear processes.

text: On Earth (and elsewhere), trace amounts of various elements continue to be produced from other elements as products of natural

entity_name: Nuclear transmutation

text: transmutation

text: processes. These include some produced by

entity_name: Cosmic ray

text: cosmic ray

text: s or other nuclear reactions (see

entity_name: Cosmogenic nuclide

text: cosmogenic

text: and

entity_name: Nucleogenic

text: nucleogenic

text: nuclides), and others produced as

entity_name: Decay product

text: decay product

text: s of long-lived

entity_name: Primordial nuclide

text: primordial nuclide

text: s. For example, trace (but detectable) amounts of

text: (C) are continually produced in the atmosphere by cosmic rays impacting

entity_name: Nitrogen

text: nitrogen

text: atoms, and argon-40 (Ar) is continually produced by the decay of primordially occurring but unstable potassium-40 (K). Also, three primordially occurring but radioactive

entity_name: Actinide

text: actinide

text: s,

entity_name: Thorium

text: thorium

entity_name: Uranium

text: uranium

text: , and

entity_name: Plutonium

text: plutonium

text: , decay through a series of recurrently produced but unstable radioactive elements such as radium and

entity_name: Radon

text: radon

text: , which are transiently present in any sample of these metals or their ores or compounds. Three other radioactive elements,

entity_name: Technetium

text: technetium

entity_name: Promethium

text: promethium

text: , and

entity_name: Neptunium

text: neptunium

text: , occur only incidentally in natural materials, produced as individual atoms by natural

entity_name: Nuclear fission

text: fission

text: of the

entity_name: Atomic nucleus

text: nuclei

text: of various heavy elements or in other rare nuclear processes.

method: UNH-ecn

method: dangnt-nlp

text: Theory predicts that many apparently "stable" isotopes/nuclides are radioactive, with extremely long half-lives (discounting the possibility of proton decay, which would make all nuclides ultimately unstable). Of the 254 nuclides never observed to decay, only 90 of these (all from the first 40 elements) are theoretically stable to all known forms of decay. Element 41 (niobium) is theoretically unstable via spontaneous fission, but this has never been detected. Many other stable nuclides are in theory energetically susceptible to other known forms of decay, such as alpha decay or double beta decay, but no decay products have yet been observed, and so these isotopes are said to be "observationally stable". The predicted half-lives for these nuclides often greatly exceed the estimated age of the universe, and in fact there are also 27 known radionuclides (see primordial nuclide) with half-lives longer than the age of the universe.

text: Theory predicts that many apparently "stable" isotopes/nuclides are radioactive, with extremely long half-lives (discounting the possibility of

entity_name: Proton decay

text: proton decay

text: , which would make all nuclides ultimately unstable). Of the 254 nuclides never observed to decay, only 90 of these (all from the first 40 elements) are theoretically stable to all known forms of decay. Element 41 (

entity_name: Niobium

text: niobium

text: ) is theoretically unstable via

entity_name: Spontaneous fission

text: spontaneous fission

text: , but this has never been detected. Many other stable nuclides are in theory energetically susceptible to other known forms of decay, such as alpha decay or double beta decay, but no decay products have yet been observed, and so these isotopes are said to be "observationally stable". The predicted half-lives for these nuclides often greatly exceed the estimated age of the universe, and in fact there are also 27 known radionuclides (see

text: primordial nuclide

text: ) with half-lives longer than the age of the universe.

text: For atoms with low atomic numbers, a nucleus that has more neutrons than protons tends to drop to a lower energy state through radioactive decay so that the neutron–proton ratio is closer to one. However, as the atomic number increases, a higher proportion of neutrons is required to offset the mutual repulsion of the protons. Thus, there are no stable nuclei with equal proton and neutron numbers above atomic number Z = 20 (calcium) and as Z increases, the neutron–proton ratio of stable isotopes increases. The stable isotope with the highest proton–neutron ratio is lead-208 (about 1.5).

text: For atoms with low atomic numbers, a nucleus that has more neutrons than protons tends to drop to a lower energy state through radioactive decay so that the

entity_name: Neutron–proton ratio

text: neutron–proton ratio

text: is closer to one. However, as the atomic number increases, a higher proportion of neutrons is required to offset the mutual repulsion of the protons. Thus, there are no stable nuclei with equal proton and neutron numbers above atomic number Z = 20 (calcium) and as Z increases, the neutron–proton ratio of stable isotopes increases. The stable isotope with the highest proton–neutron ratio is

entity_name: Isotopes of lead

text: (about 1.5).

text: Most of the period 6 elements are toxic(for instance lead) and produce heavy element poisoning. Promethium, polonium, astatine and radon are radioactive, and therefore present radioactive hazards.

text: Most of the period 6 elements are toxic(for instance lead) and produce

text: heavy element poisoning

text: . Promethium, polonium, astatine and radon are radioactive, and therefore present radioactive hazards.

method: UNH-tfidf-stem

method: UNH-tfidf-ptsim

method: UNH-tfidf-lem

text: An element is a chemical substance that is made up of a particular kind of atoms and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmutated into another element through a nuclear reaction. This is so, because all of the atoms in a sample of an element have the same number of protons, though they may be different isotopes, with differing numbers of neutrons.

text: An

entity_name: Chemical element

text: element

text: is a chemical substance that is made up of a particular kind of atoms and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmutated into another element through a

entity_name: Nuclear reaction

text: nuclear reaction

text: . This is so, because all of the atoms in a sample of an element have the same number of protons, though they may be different

text: isotope

text: s, with differing numbers of neutrons.

text: The next group is the primordial radioactive nuclides. These have been measured to be radioactive, or decay products have been identified (Te-130, Ba-130). There are (currently) 32 of these, of which 28 have half-lives considerably longer than the age of the universe (13.8 billion years). With most of these 28, decay is difficult to observe and for most purposes they can be regarded as effectively stable. Bismuth-209 is notable as the only natural occurring isotope of an element long considered stable. A further 4 nuclides, thorium-232, uranium-238, potassium-40 and uranium-235 have half lives between 14 billion and 700 million years, which means they have experienced measurable decay since the formation of the solar system about 4.6 billion years ago, but still exist on earth in significant quantities. They are the primary source of radiogenic heat and radioactive decay products. Together, there are a total of 286 primordial nuclides.

text: The next group is the primordial radioactive nuclides. These have been measured to be radioactive, or decay products have been identified (Te-130, Ba-130). There are (currently) 32 of these, of which 28 have half-lives considerably longer than the age of the universe (13.8 billion years). With most of these 28, decay is difficult to observe and for most purposes they can be regarded as effectively stable.

text: is notable as the only natural occurring isotope of an element long considered stable. A further 4 nuclides,

entity_name: Isotopes of thorium

text: and

text: have half lives between 14 billion and 700 million years, which means they have experienced measurable decay since the formation of the solar system about 4.6 billion years ago, but still exist on earth in significant quantities. They are the primary source of

entity_name: Radiogenic nuclide

entity_section: Radiogenic heating

text: radiogenic heat

text: and radioactive decay products. Together, there are a total of 286

text: primordial nuclides

text: The set of monoisotopic elements overlap but are not the same as the set of 22 mononuclidic elements, which are characterized as having essentially only one isotope (nuclide) found in nature.  The reason for this is the occurrence of certain long-lived radioactive primordial nuclides in nature, which may form admixtures with the monoisotopics, and thus prevent them from being naturally mononuclidic. This happens in the cases of 7 () of the monoisotopic elements. These isotopes are monoisotopic, but due to the presence of the long lived radioactive primordial nuclide, are not mononuclidic. These elements are vanadium, rubidium, indium, lanthanum, europium, rhenium and lutetium. See the list below; in two noted cases (indium and rhenium), the long-lived radionuclide is actually the most abundant isotope in nature, and the stable isotope is less abundant.

text: The set of monoisotopic elements overlap but are not the same as the set of 22

entity_name: Mononuclidic element

text: mononuclidic element

text: s, which are characterized as having essentially only one isotope (nuclide) found in nature.  The reason for this is the occurrence of certain long-lived radioactive

text: primordial nuclide

text: s in nature, which may form admixtures with the monoisotopics, and thus prevent them from being naturally mononuclidic. This happens in the cases of 7 () of the monoisotopic elements. These isotopes are monoisotopic, but due to the presence of the long lived radioactive primordial nuclide, are not mononuclidic. These elements are

entity_name: Vanadium

text: vanadium

entity_name: Rubidium

text: rubidium

entity_name: Indium

text: indium

entity_name: Lanthanum

text: lanthanum

entity_name: Europium

text: europium

entity_name: Rhenium

text: rhenium

text: and

entity_name: Lutetium

text: lutetium

text: . See the list below; in two noted cases (indium and rhenium), the long-lived radionuclide is actually the most abundant isotope in nature, and the stable isotope is less abundant.

text: Radon is chemically stable, but it is radioactive and does not have a stable isotope. Its most stable isotope, Rn, has a half-life of 3.8 days. Its uses are due to its radioactivity rather than its chemistry and it requires specialist handling outside of industrial gas industry norms. It can however be produced as a by-product of uraniferous ores processing. Radon is a trace naturally occurring radioactive material (NORM) encountered in the air processed in an ASU.

text: Radon is chemically stable, but it is

entity_name: Radioactive decay

text: radioactive

text: and does not have a

entity_name: Stable isotope ratio

text: stable isotope

text: . Its most stable

text: isotope

entity_name: Isotopes of radon

text: Rn

text: , has a

entity_name: Half-life

text: half-life

text: of 3.8 days. Its uses are due to its radioactivity rather than its chemistry and it requires specialist handling outside of industrial gas industry norms. It can however be produced as a by-product of

entity_name: Uranium ore

text: uraniferous ores

text: processing. Radon is a trace

entity_name: Naturally occurring radioactive material

text: naturally occurring radioactive material

text: (NORM) encountered in the air processed in an ASU.

text: On 16 September 2001 the French press reported slightly higher than acceptable radioactivity levels aboard Charles de Gaulle, thought to be caused by a faulty isolation element. It was later discovered that the radioactivity levels matched the design, but that the regulations concerning acceptable radioactivity levels had changed. While the United States was preparing its response to the September 11 attacks in the form of Operation Enduring Freedom, French media complained about the lack of deployable French military power. At the same time, the Defence Commission reported the maintenance of the Fleet to be substandard. In this context, Charles de Gaulle, then under repairs, was again an object of criticism, with former President Valéry Giscard d'Estaing describing it as a "half-aircraft-carrier" and requesting launching of the second carrier vessel (named PA2) in order to guarantee an availability rate of 100%.

text: On 16 September 2001 the French press reported slightly higher than acceptable radioactivity levels aboard Charles de Gaulle, thought to be caused by a faulty isolation element. It was later discovered that the radioactivity levels matched the design, but that the regulations concerning acceptable radioactivity levels had changed. While the United States was preparing its response to the

entity_name: September 11 attacks

text: September 11 attacks

text: in the form of

entity_name: Operation Enduring Freedom

text: Operation Enduring Freedom

text: , French media complained about the lack of deployable French military power. At the same time, the Defence Commission reported the maintenance of the Fleet to be substandard. In this context, Charles de Gaulle, then under repairs, was again an object of criticism, with former President

entity_name: Valéry Giscard d'Estaing

text: Valéry Giscard d'Estaing

text: describing it as a "half-aircraft-carrier" and requesting launching of the second carrier vessel (named PA2) in order to guarantee an availability rate of 100%.

text: Radioactive covers many different styles of hip hop fusions, being alternative hip hop as principal musical genre. Hardcore hip hop is represented on the tracks "Radioactive Introduction", "Throw It Up", "Get Away", and "Slumerican Shitizen". A horrorcore rap style is used in "Growin' Up in the Gutter", whereas "Hard White (Up in the Club)" is a crunk party track. "Let's Roll", "Write Your Name", and "Radio" follow a pop rap style, with catchy hooks and beats. "Animal" is a fast-paced hip hop party track with a dubstep influenced beat. "Good Girl" utilizes an R&B-tinged feel, while "The Hardest Love Song in the World" is a g-funk hip hop track. Yelawolf covers a variety of lyrical themes in these album, from gangsta rap lyrics in "Get Away" and "Throw It Up", to more conscious and slightly political tracks such as "Made in the USA", "Slumerican Shitizen", "Write Your Name", and "The Last Song". "Radio" is about the internet taking over how music and music videos are received by fans. It also refers to radio stations playing the same songs constantly and singers being discovered via the internet. The song contains several references to rock and rap artists and their songs from the past. The album's final track, titled "The Last Song" described as very personal about Yelawolf's life, and it's a very emotional final letter to his absent biological father and talks about other past struggles.

text: Radioactive covers many different styles of hip hop fusions, being

entity_name: Alternative hip hop

text: alternative hip hop

text: as principal musical genre.

entity_name: Hardcore hip hop

text: Hardcore hip hop

text: is represented on the tracks "Radioactive Introduction", "Throw It Up", "Get Away", and "Slumerican Shitizen". A

entity_name: Horrorcore

text: horrorcore

text: rap style is used in "Growin' Up in the Gutter", whereas "

entity_name: Hard White (Up in the Club)

text: Hard White (Up in the Club)

text: " is a

entity_name: Crunk

text: crunk

text: party track. "

entity_name: Let's roll

text: Let's Roll

text: ", "Write Your Name", and "

entity_name: Radioactive (Yelawolf album)

text: Radio

text: " follow a

entity_name: Pop-rap

text: pop rap

text: style, with catchy hooks and beats. "Animal" is a fast-paced hip hop party track with a

entity_name: Dubstep

text: dubstep

text: influenced beat. "Good Girl" utilizes an

entity_name: Rhythm and blues

text: R&B

text: -tinged feel, while "The Hardest Love Song in the World" is a

entity_name: G-funk

text: g-funk

text: hip hop track. Yelawolf covers a variety of lyrical themes in these album, from

entity_name: Gangsta rap

text: gangsta rap

text: lyrics in "Get Away" and "Throw It Up", to more conscious and slightly political tracks such as "Made in the USA", "Slumerican Shitizen", "Write Your Name", and "The Last Song". "Radio" is about the internet taking over how music and music videos are received by fans. It also refers to radio stations playing the same songs constantly and singers being discovered via the internet. The song contains several references to rock and rap artists and their songs from the past. The album's final track, titled "The Last Song" described as very personal about Yelawolf's life, and it's a very emotional final letter to his absent biological father and talks about other past struggles.

text: By their chemical nature, rock minerals contain certain elements and not others; but in rocks containing radioactive isotopes, the process of radioactive decay generates exotic elements over time. By measuring the concentration of the stable end product of the decay, coupled with knowledge of the half life and initial concentration of the decaying element, the age of the rock can be calculated. Typical radioactive end products are argon from decay of potassium-40, and lead from decay of uranium and thorium. If the rock becomes molten, as happens in Earth's mantle, such nonradioactive end products typically escape or are redistributed. Thus the age of the oldest terrestrial rock gives a minimum for the age of Earth, assuming that no rock has been intact for longer than the Earth itself.

text: By their chemical nature,

entity_name: Rock (geology)

text: rock

entity_name: Mineral

text: mineral

text: s contain certain

text: elements

text: and not others; but in rocks containing radioactive isotopes, the process of

text: radioactive decay

text: generates exotic elements over time. By measuring the

text: concentration

text: of the stable end product of the decay, coupled with knowledge of the

text: half life

text: and initial concentration of the decaying element, the age of the rock can be calculated. Typical radioactive end products are

text: argon

text: from decay of

text: potassium

text: -40, and

text: lead

text: from decay of

text: uranium

text: and

text: thorium

text: . If the rock becomes molten, as happens in Earth's

text: mantle

text: , such nonradioactive end products typically escape or are redistributed. Thus the age of the oldest terrestrial rock gives a minimum for the age of Earth, assuming that no rock has been intact for longer than the Earth itself.

text: Technetium, with atomic number (denoted Z) 43, is the lowest-numbered element in the periodic table of which all isotopes are radioactive. The second-lightest exclusively radioactive element, promethium, has an atomic number of 61. Atomic nuclei with an odd number of protons are less stable than those with even numbers, even when the total number of nucleons (protons + neutrons) is even, and odd numbered elements have fewer stable isotopes.

text: Technetium, with

text: atomic number

text: (denoted Z) 43, is the lowest-numbered element in the periodic table of which all isotopes are

text: radioactive

text: . The second-lightest exclusively radioactive element,

text: promethium

text: , has an atomic number of 61.

text: Atomic nuclei

text: with an odd number of

text: proton

text: s are less stable than those with even numbers, even when the total number of

text: nucleon

text: s (protons +

text: neutron

text: s) is even, and odd numbered elements have fewer stable

text: isotope

text: s.

text: Only about 4% of the total mass of the universe is made of atoms or ions, and thus represented by chemical elements. This fraction is about 15% of the total matter, with the remainder of the matter (85%) being dark matter. The nature of dark matter is unknown, but it is not composed of atoms of chemical elements because it contains no protons, neutrons, or electrons. (The remaining non-matter part of the mass of the universe is composed of the even more mysterious dark energy).

text: Only about 4% of the total mass of the universe is made of atoms or

text: ions

text: , and thus represented by chemical elements. This fraction is about 15% of the total matter, with the remainder of the matter (85%) being

text: dark matter

text: . The nature of dark matter is unknown, but it is not composed of atoms of chemical elements because it contains no protons, neutrons, or electrons. (The remaining non-matter part of the mass of the universe is composed of the even more mysterious

text: dark energy

text: In the late 19th century onward, the atomic theory underwent significant improvements, which shaped the further history of thorium. Thorium was first observed to be radioactive in 1898, independently, by the German chemist Gerhard Carl Schmidt and later that year, the Polish-French physicist Marie Curie. It was the second element that was found to be radioactive, after the 1896 discovery of radioactivity in uranium by Henri Becquerel. Between 1900 and 1903, Ernest Rutherford and Frederick Soddy showed how thorium decayed at a fixed rate over time into a series of other elements. This observation led to the identification of half-life as one of the outcomes of the alpha particle experiments that led to their disintegration theory of radioactivity. The biological effect of radiation was discovered in 1903; the danger presented by radioactivity to health and environment was the reason thorium was phased out of use in applications that did not explicitly use the radioactivity. Since the 1930s, it has been widely acknowledged that thorium possesses a minor threat to human organisms in large quantities.

text: In the late 19th century onward, the

text: atomic theory

text: underwent significant improvements, which shaped the further history of thorium. Thorium was first observed to be radioactive in 1898, independently, by the German chemist

text: Gerhard Carl Schmidt

text: and later that year, the Polish-French physicist

text: Marie Curie

text: . It was the second element that was found to be radioactive, after the 1896 discovery of radioactivity in uranium by

text: Henri Becquerel

text: . Between 1900 and 1903,

text: Ernest Rutherford

text: and

text: Frederick Soddy

text: showed how thorium decayed at a fixed rate over time into a series of other elements. This observation led to the identification of

text: half-life

text: as one of the outcomes of the

text: alpha particle

text: experiments that led to their disintegration theory of

text: radioactivity

text: . The biological effect of radiation was discovered in 1903; the danger presented by radioactivity to health and environment was the reason thorium was phased out of use in applications that did not explicitly use the radioactivity. Since the 1930s, it has been widely acknowledged that thorium possesses a minor threat to human organisms in large quantities.

text: All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus. Additionally, elements may exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide. Some nuclides are inherently unstable. That is, at some point in time, an atom of such a nuclide will undergo radioactive decay and spontaneously transform into a different nuclide. This transformation may be accomplished in a number of different ways, including alpha decay (emission of alpha particles) and beta decay (electron emission, positron emission, or electron capture). Another possibility is spontaneous fission into two or more nuclides.

text: All ordinary

text: matter

text: is made up of combinations of

text: chemical element

text: s, each with its own

text: atomic number

text: , indicating the number of

text: proton

text: s in the

text: atomic nucleus

text: . Additionally, elements may exist in different

text: isotope

text: s, with each isotope of an element differing in the number of

text: neutron

text: s in the nucleus. A particular isotope of a particular element is called a

text: nuclide

text: . Some nuclides are inherently unstable. That is, at some point in time, an atom of such a nuclide will undergo

text: radioactive decay

text: and spontaneously transform into a different nuclide. This transformation may be accomplished in a number of different ways, including

text: alpha decay

text: (emission of

text: alpha particle

text: s) and

text: beta decay

text: electron

text: emission,

text: positron

text: emission, or

text: electron capture

text: ). Another possibility is

text: spontaneous fission

text: into two or more nuclides.

text: The project became controversial in 2009 when a study performed by Avner Vengosh of Duke University revealed the Disi water to be highly radioactive.  Water was tested from 37 existing wells in the aquifer, and all but one had concentrations of radioactive radium-226 and radium-228 isotopes that exceeded international standards for drinking water.  Some of the water tested exceeded standards by 2,000%. Drinking water with these isotopes has been linked to bone cancer and leukemia. Though expensive, the water could be purified of the radioactive isotopes through ion-exchange purification.

text: The project became controversial in 2009 when a study performed by Avner Vengosh of

text: Duke University

text: revealed the Disi water to be highly

text: radioactive

text: .  Water was tested from 37 existing wells in the aquifer, and all but one had concentrations of radioactive

text: and

text: isotopes that exceeded

text: international standards for drinking water

text: .  Some of the water tested exceeded standards by 2,000%. Drinking water with these isotopes has been linked to

text: bone cancer

text: and

text: leukemia

text: . Though expensive, the water could be purified of the radioactive isotopes through

text: ion-exchange purification

text: Immediately after element 172 (unseptbium, the last period 8 element), the first noble gas after oganesson (the last period 7 element), it was originally expected that another long transition series like the superactinides should begin, filling the 6g, 7f, 8d, and perhaps 6h shells. These electrons would be very loosely bound, rendering extremely high oxidation states possibly easy to reach. Element 184 (unoctquadium) was significantly targeted in early predictions, as it was originally speculated that 184 would be a proton magic number.

text: Immediately after element 172 (unseptbium, the last period 8 element), the first noble gas after

text: oganesson

text: (the last period 7 element), it was originally expected that another long transition series like the

text: superactinide

text: s should begin, filling the 6g, 7f, 8d, and perhaps 6h shells. These electrons would be very loosely bound, rendering extremely high oxidation states possibly easy to reach. Element 184 (unoctquadium) was significantly targeted in early predictions, as it was originally speculated that 184 would be a proton magic number.

text: A radioactive tracer, or radioactive label, is a chemical compound in which one or more atoms have been replaced by a radioisotope so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products. Radiolabeling is thus the radioactive form of isotopic labeling.

text: A radioactive tracer, or radioactive label, is a

text: chemical compound

text: in which one or more atoms have been replaced by a

text: radioisotope

text: so by virtue of its

text: radioactive decay

text: it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products. Radiolabeling is thus the radioactive form of

text: isotopic labeling

text: Rutherford came to the conclusion that the number of protons in a radioactive element could change – through a process of decay where parts of the nucleus are ejected from the atom. Rutherford named these fragments of ejected nucleus alpha particles.

text: Rutherford came to the conclusion that the number of protons in a radioactive element could change – through a process of decay where parts of the nucleus are ejected from the atom. Rutherford named these fragments of ejected nucleus

text: alpha particles

text: In 1900 he became a demonstrator in chemistry at McGill University in Montreal, Quebec, where he worked with Ernest Rutherford on radioactivity.He and Rutherford realized that the anomalous behaviour of radioactive elements was because they decayed into other elements.This decay also produced alpha, beta, and gamma radiation. When radioactivity was first discovered, no one was sure what the cause was. It needed careful work by Soddy and Rutherford to prove that atomic transmutation was in fact occurring.

text: In 1900 he became a demonstrator in

text: chemistry

text: at

text: McGill University

text: in

text: Montreal

text: Quebec

text: , where he worked with

text: Ernest Rutherford

text: on

text: radioactivity

text: .He and Rutherford realized that the anomalous behaviour of radioactive elements was because they

text: decayed

text: into other elements.This decay also produced

text: alpha

text: beta

text: , and

text: gamma radiation

text: . When radioactivity was first discovered, no one was sure what the cause was. It needed careful work by Soddy and Rutherford to prove that atomic

text: transmutation

text: was in fact occurring.

text: Atoms of the same element have the same number of protons, called the atomic number. Within a single element, the number of neutrons may vary, determining the isotope of that element. The total number of protons and neutrons determine the nuclide. The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay.

text: Atoms of the same

text: element

text: have the same number of protons, called the

text: atomic number

text: . Within a single element, the number of neutrons may vary, determining the

text: isotope

text: of that element. The total number of protons and neutrons determine the

text: nuclide

text: . The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing

text: radioactive decay

text: The number of protons in the nucleus defines to what chemical element the atom belongs: for example, all copper atoms contain 29 protons. The number of neutrons defines the isotope of the element. The number of electrons influences the magnetic properties of an atom. Atoms can attach to one or more other atoms by chemical bonds to form chemical compounds such as molecules. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature, and is the subject of the discipline of chemistry.

text: The number of protons in the nucleus defines to what

text: chemical element

text: the atom belongs: for example, all

text: copper

text: atoms contain 29 protons. The number of neutrons defines the

text: isotope

text: of the element. The number of electrons influences the

text: magnetic

text: properties of an atom. Atoms can attach to one or more other atoms by

text: chemical bond

text: s to form

text: chemical compounds

text: such as

text: molecule

text: s. The ability of atoms to associate and dissociate is responsible for most of the physical changes observed in nature, and is the subject of the discipline of

text: chemistry

text: Polonium was discovered in 1898 by Marie and Pierre Curie, when it was chemically separated out of uranium ore and identified solely by its strong radioactivity: it was the first element to be so discovered. It was named after Marie Curie's homeland of Poland. Applications of polonium are sparse and dependent on its radioactivity: they include heaters in space probes, antistatic devices, and sources of neutrons and alpha particles. Its intense radioactivity makes it dangerously toxic to life.

text: Polonium was discovered in 1898 by

text: Marie

text: and

text: Pierre Curie

text: , when it was chemically separated out of uranium ore and identified solely by its strong radioactivity: it was the first element to be so discovered. It was named after Marie Curie's homeland of

text: Poland

text: . Applications of polonium are sparse and dependent on its radioactivity: they include heaters in space probes,

text: antistatic device

text: s, and sources of

text: neutron

text: s and

text: alpha particle

text: s. Its intense radioactivity makes it dangerously toxic to life.

text: In 1868, Janssen and Lockyer independently observed a yellow line in the solar spectrum that did not match that of any other element. In 1895, in each case at around the same time, Ramsay, Cleve, and Langlet independently observed helium trapped in cleveite. André-Marie Ampère predicted an element analogous to chlorine obtainable from hydrofluoric acid, and between 1812 and 1886 many researchers tried to obtain it. Fluorine was eventually isolated by Moissan, in 1886. In 1894, Lord Rayleigh and Ramsay discovered argon by comparing the molecular weights of nitrogen prepared by liquefaction from air and nitrogen prepared by chemical means. It was the first noble gas to be isolated. In 1898, within a period of three weeks, Ramsay and Travers successively separated krypton, neon and xenon from liquid argon by their differences in boiling points. In 1898, Dorn discovered a radioactive gas resulting from the radioactive decay of radium; Ramsay and Robert Whytlaw-Gray subsequently isolated radon in 1910.

text: In 1868,

text: Janssen

text: and

text: Lockyer

text: independently observed a yellow line in the solar spectrum that did not match that of any other element. In 1895, in each case at around the same time, Ramsay, Cleve, and Langlet independently observed

text: helium

text: trapped in

text: cleveite

text: André-Marie Ampère

text: predicted an element analogous to chlorine obtainable from

text: hydrofluoric acid

text: , and between 1812 and 1886 many researchers tried to obtain it. Fluorine was eventually isolated by

text: Moissan

text: , in 1886. In 1894,

text: Lord Rayleigh

text: and

text: Ramsay

text: discovered argon by comparing the molecular weights of nitrogen prepared by liquefaction from air and nitrogen prepared by chemical means. It was the first noble gas to be isolated. In 1898, within a period of three weeks, Ramsay and Travers successively separated krypton, neon and xenon from liquid argon by their differences in boiling points. In 1898,

text: Dorn

text: discovered a radioactive gas resulting from the radioactive decay of radium; Ramsay and

text: Robert Whytlaw-Gray

text: subsequently isolated radon in 1910.

text: This particular man-made diamond being made of radioactive C-14 will also posses radioactivity. Hence, due to its own radioactive field it will generate small currents. For practical and safe use this radioactive diamond will be enclosed inside a non-radioactive man-made diamond (made from C-12).

text: The Mattauch isobar rule, formulated by Josef Mattauch in 1934, states that if two adjacent elements on the periodic table have isotopes of the same mass number, one of these isotopes must be radioactive. Two nuclides that have the same mass number (isobars) can both be stable only if their atomic numbers differ by more than one. However, this rule cannot make predictions on the half-lives of these radioisotopes.

text: The Mattauch isobar rule, formulated by

text: Josef Mattauch

text: in 1934, states that if two adjacent

text: elements

text: on the

text: periodic table

text: have

text: isotope

text: s of the same

text: mass number

text: , one of these

text: isotopes

text: must be

text: radioactive

text: . Two

text: nuclide

text: s that have the same mass number (

text: isobars

text: ) can both be stable only if their

text: atomic number

text: s differ by more than one. However, this rule cannot make predictions on the

text: half-lives

text: of these

text: radioisotope

text: s.

text: Neptunium is a chemical element with symbol Np and atomic number 93. A radioactive actinide metal, neptunium is the first transuranic element. Its position in the periodic table just after uranium, named after the planet Uranus, led to it being named after Neptune, the next planet beyond Uranus. A neptunium atom has 93 protons and 93 electrons, of which seven are valence electrons. Neptunium metal is silvery and tarnishes when exposed to air. The element occurs in three allotropic forms and it normally exhibits five oxidation states, ranging from +3 to +7. It is radioactive, poisonous, pyrophoric, and can accumulate in bones, which makes the handling of neptunium dangerous.

text: Neptunium is a

text: chemical element

text: with symbol Np and

text: atomic number

text: 93. A

text: radioactive

text: actinide

text: metal, neptunium is the first

text: transuranic element

text: . Its position in the

text: periodic table

text: just after

text: uranium

text: , named after the planet

text: Uranus

text: , led to it being named after

text: Neptune

text: , the next planet beyond Uranus. A neptunium atom has 93

text: proton

text: s and 93 electrons, of which seven are

text: valence electron

text: s. Neptunium metal is silvery and

text: tarnish

text: es when exposed to air. The element occurs in three

text: allotropic

text: forms and it normally exhibits five

text: oxidation state

text: s, ranging from +3 to +7. It is

text: radioactive

text: poisonous

text: pyrophoric

text: , and can accumulate in

text: bone

text: s, which makes the handling of neptunium dangerous.

text: From the late 1940s to the early 1960s, the early days of the synthesis of heavier and heavier transuranium elements, it was predicted that since such heavy elements did not occur naturally, they would have shorter and shorter half-lives to spontaneous fission, until they stopped existing altogether at around element 108 (now known as hassium). Initial work in the synthesis of the actinides appeared to confirm this. The nuclear shell model, introduced in the late 1960s, stated that the protons and neutrons formed shells within a nucleus, somewhat analogous to electrons forming electron shells within an atom. The noble gases are unreactive due to their having full electron shells; thus it was theorized that elements with full nuclear shells – having so-called "magic" numbers of protons or neutrons – would be stabilized against radioactive decay. A doubly magic isotope, having magic numbers of both protons and neutrons, would be especially stabilized, and it was calculated that the next doubly magic isotope after lead-208 would be flerovium-298 with 114 protons and 184 neutrons, which would form the centre of a so-called "island of stability". This island of stability, supposedly ranging from copernicium (element 112) to oganesson (118), would come after a long "sea of instability" from elements 101 (mendelevium) to 111 (roentgenium), and the flerovium isotopes in it were speculated in 1966 to have half-lives in excess of a hundred million years. It took thirty years for the first isotopes of flerovium to be synthesized. More recent work suggests that the local islands of stability around hassium and flerovium are due to these nuclei being respectively deformed and oblate, which make them resistant to spontaneous fission, and that the true island of stability for spherical nuclei occurs at around unbibium-306 (with 122 protons and 184 neutrons).

text: From the late 1940s to the early 1960s, the early days of the synthesis of heavier and heavier

text: transuranium element

text: s, it was predicted that since such heavy elements did not occur naturally, they would have shorter and shorter half-lives to

text: spontaneous fission

text: , until they stopped existing altogether at around element 108 (now known as

text: hassium

text: ). Initial work in the synthesis of the

text: actinide

text: s appeared to confirm this. The

text: nuclear shell model

text: , introduced in the late 1960s, stated that the

text: proton

text: s and

text: neutron

text: s formed shells within a nucleus, somewhat analogous to

text: electron

text: s forming

text: electron shell

text: s within an atom. The

text: noble gas

text: es are

text: unreactive

text: due to their having full electron shells; thus it was theorized that elements with full nuclear shells – having so-called "

text: magic

text: " numbers of protons or neutrons – would be stabilized against

text: radioactive decay

text: . A doubly magic

text: isotope

text: , having magic numbers of both protons and neutrons, would be especially stabilized, and it was calculated that the next doubly magic isotope after

text: would be flerovium-298 with 114 protons and 184 neutrons, which would form the centre of a so-called "

text: island of stability

text: ". This island of stability, supposedly ranging from

text: copernicium

text: (element 112) to

text: oganesson

text: (118), would come after a long "sea of instability" from elements

text: (mendelevium) to

text: (roentgenium), and the flerovium isotopes in it were speculated in 1966 to have half-lives in excess of a hundred million years. It took thirty years for the first isotopes of flerovium to be synthesized. More recent work suggests that the local islands of stability around hassium and flerovium are due to these nuclei being respectively deformed and

text: oblate

text: , which make them resistant to spontaneous fission, and that the true island of stability for spherical nuclei occurs at around

text: unbibium

text: -306 (with 122 protons and 184 neutrons).

text: Each chemical element has a unique atomic number (Z) representing the number of protons in its nucleus. Most elements have differing numbers of neutrons among different atoms, with these variants being referred to as isotopes. For example, carbon has three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. Isotopes are never separated in the periodic table; they are always grouped together under a single element. Elements with no stable isotopes have the atomic masses of their most stable isotopes, where such masses are shown, listed in parentheses.

text: Each chemical element has a unique atomic number (Z) representing the number of protons in its nucleus. Most elements have differing numbers of

text: neutron

text: s among different atoms, with these variants being referred to as

text: isotope

text: s. For example, carbon has three naturally occurring isotopes: all of its atoms have six protons and most have six neutrons as well, but about one per cent have seven neutrons, and a very small fraction have eight neutrons. Isotopes are never separated in the periodic table; they are always grouped together under a single element. Elements with no stable isotopes have the atomic masses of their most stable isotopes, where such masses are shown, listed in parentheses.

text: At first, it seemed as though the new radiation was similar to the then recently discovered X-rays. Further research by Becquerel, Ernest Rutherford, Paul Villard, Pierre Curie, Marie Curie, and others showed that this form of radioactivity was significantly more complicated. Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula. Rutherford and his student Frederick Soddy were the first to realize that many decay processes resulted in the transmutation of one element to another. Subsequently, the radioactive displacement law of Fajans and Soddy was formulated to describe the products of alpha and beta decay.

text: At first, it seemed as though the new radiation was similar to the then recently discovered

text: X-rays

text: . Further research by Becquerel,

text: Ernest Rutherford

text: Paul Villard

text: Pierre Curie

text: Marie Curie

text: , and others showed that this form of radioactivity was significantly more complicated. Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula. Rutherford and his student

text: Frederick Soddy

text: were the first to realize that many decay processes resulted in the

text: transmutation

text: of one element to another. Subsequently, the

entity_name: Radioactive displacement law of Fajans and Soddy

text: radioactive displacement law of Fajans and Soddy

text: was formulated to describe the products of

text: alpha

text: and

text: beta decay

text: In the United Kingdom, the authorities discover a man unconscious who is radioactive. They also learn he has a double, and the good man agrees to help find his evil double before he destroys the world.

text: Radioactivity is a rare property; minerals may be composed of radioactive elements. They could be a defining constituent, such as uranium in uraninite, autunite, and carnotite, or as trace impurities. In the latter case, the decay of a radioactive element damages the mineral crystal; the result, termed a radioactive halo or pleochroic halo, is observable by various techniques, such as thin-section petrography.

text: Radioactivity

text: is a rare property; minerals may be composed of radioactive elements. They could be a defining constituent, such as uranium in

text: uraninite

text: autunite

text: , and

text: carnotite

text: , or as trace impurities. In the latter case, the decay of a radioactive element damages the mineral crystal; the result, termed a radioactive halo or

text: pleochroic halo

text: , is observable by various techniques, such as thin-section petrography.

text: In the Marvel Comics universe, the Titanic Three was the team of 3 supervillains: Titanium Man, Radioactive Man and Crimson Dynamo.  While the Radioactive Man was a Chinese super-villain, the other members of the team were from the Soviet Union.  Thus the team was one of the several reflections of the Cold War in the Marvel Universe.

text: In the

text: Marvel Comics

text: universe

text: , the Titanic Three was the team of 3

text: supervillain

text: s:

text: Titanium Man

text: Radioactive Man

text: and

text: Crimson Dynamo

text: .  While the Radioactive Man was a Chinese super-villain, the other members of the team were from the Soviet Union.  Thus the team was one of the several reflections of the

text: Cold War

text: in the Marvel Universe.

text: As of 2010, there are 118 known elements (in this context, "known" means observed well enough, even from just a few decay products, to have been differentiated from other elements). Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities: technetium, atomic number 43; promethium, number 61; astatine, number 85; francium, number 87; neptunium, number 93; and plutonium, number 94. These 94 elements have been detected in the universe at large, in the spectra of stars and also supernovae, where short-lived radioactive elements are newly being made. The first 94 elements have been detected directly on Earth as primordial nuclides present from the formation of the solar system, or as naturally occurring fission or transmutation products of uranium and thorium.

text: As of 2010, there are 118 known elements (in this context, "known" means observed well enough, even from just a few decay products, to have been differentiated from other elements). Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities:

text: technetium

text: , atomic number 43;

text: promethium

text: , number 61;

text: astatine

text: , number 85;

text: francium

text: , number 87;

text: neptunium

text: , number 93; and

text: plutonium

text: , number 94. These 94 elements have been detected in the universe at large, in the spectra of stars and also supernovae, where short-lived radioactive elements are newly being made. The first 94 elements have been detected directly on Earth as

text: primordial nuclide

text: s present from the formation of the solar system, or as naturally occurring fission or transmutation products of uranium and thorium.

text: Fossils in this region are often slightly radioactive, and remains of Animantarx were actually discovered following a radiological survey of the area performed by Ramal Jones, which located a higher level of radioactivity at a certain location. Subsequent excavation at this site turned up the fossil skeleton of Animantarx; no bones had been exposed on the surface.

text: Fossils in this region are often slightly

text: radioactive

text: , and remains of Animantarx were actually discovered following a radiological survey of the area performed by Ramal Jones, which located a higher level of radioactivity at a certain location. Subsequent excavation at this site turned up the fossil skeleton of Animantarx; no bones had been exposed on the surface.

text: Following run 13, an attempt was made to wash a fuel element in the wash cell. During the operation, an explosion occurred of sufficient magnitude to lift the shield plug out of the wash cell. It is believed the tetralin-related decomposition products caused a substantial amount of sodium to be trapped in the fuel rod elements by blocking drain holes. There were no reported injuries or fatalities associated with the wash-cell explosion. As a result of the explosion, no further washing of the elements was done. Measurements from within the reactor building indicated extremely high radioactivity levels throughout the building. Within several days radioactivity in the high bay had been reduced to normal levels, except for the area immediately around the wash cells.

text: The wind measurably increased the radiation levels up to 100 miles away from the disaster site. Radioactive iodine, which can lead to increased risk of thyroid cancer if absorbed into the body, was released into the air along with other fission products. To counteract the radioactive iodine the distribution of potassium iodide is used, as it prevents the absorption of the potentially dangerous radioisotopes of that element. Since Chernobyl, distributing potassium iodide to children has been a standard response when risk of radioactivity release is high.

text: During normal operation, plants have to monitor gas and liquid radioactive effluent releases.  The only type that requires continuous monitoring is radioactive noble gasses, although some require monitoring only for every discharge.  Other types of radiation must be monitored weekly or monthly according to the regulations.

text: Radioactivity was discovered in 1896 by Henri Becquerel in uranium, and subsequently observed by Marie and Pierre Curie in thorium and in the new elements polonium and radium. In 1899, Ernest Rutherford separated radioactive emissions into two types: alpha and beta (now beta minus), based on penetration of objects and ability to cause ionization. Alpha rays could be stopped by thin sheets of paper or aluminium, whereas beta rays could penetrate several millimetres of aluminium. In 1900, Paul Villard identified a still more penetrating type of radiation, which Rutherford identified as a fundamentally new type in 1903 and termed gamma rays.  Alpha, beta, and gamma are the first three letters of the Greek alphabet.

text: Radioactivity was discovered in 1896 by

text: Henri Becquerel

text: in

text: uranium

text: , and subsequently observed by

text: Marie

text: and

text: Pierre Curie

text: in

text: thorium

text: and in the new elements

text: polonium

text: and

text: radium

text: . In 1899,

text: Ernest Rutherford

text: separated radioactive emissions into two types: alpha and beta (now beta minus), based on penetration of objects and ability to cause ionization. Alpha rays could be stopped by thin sheets of paper or aluminium, whereas beta rays could penetrate several millimetres of aluminium. In 1900,

text: Paul Villard

text: identified a still more penetrating type of radiation, which Rutherford identified as a fundamentally new type in 1903 and termed

text: gamma ray

text: s.  Alpha, beta, and gamma are the first three letters of the

text: Greek alphabet

text: To detect hybridization of the probe to its target sequence, the probe is tagged (or "labeled") with a molecular marker of either radioactive or (more recently) fluorescent molecules; commonly used markers are P (a radioactive isotope of phosphorus incorporated into the phosphodiester bond in the probe DNA) or Digoxigenin, which is a non-radioactive, antibody-based marker. DNA sequences or RNA transcripts that have moderate to high sequence similarity to the probe are then detected by visualizing the hybridized probe via autoradiography or other imaging techniques. Normally, either X-ray pictures are taken of the filter, or the filter is placed under UV light. Detection of sequences with moderate or high similarity depends on how stringent the hybridization conditions were applied — high stringency, such as high hybridization temperature and low salt in hybridization buffers, permits only hybridization between nucleic acid sequences that are highly similar, whereas low stringency, such as lower temperature and high salt, allows hybridization when the sequences are less similar. Hybridization probes used in DNA microarrays refer to DNA covalently attached to an inert surface, such as coated glass slides or gene chips, to which a mobile cDNA target is hybridized.

text: To detect

text: hybridization

text: of the probe to its target sequence, the probe is tagged (or "labeled") with a

text: molecular marker

text: of either radioactive or (more recently) fluorescent molecules; commonly used markers are

text: P

text: (a

text: radioactive

text: isotope

text: of

text: phosphorus

text: incorporated into the

text: phosphodiester

text: bond in the probe DNA) or

text: Digoxigenin

text: , which is a non-radioactive,

text: antibody

text: -based marker. DNA sequences or RNA transcripts that have moderate to high sequence similarity to the probe are then detected by visualizing the hybridized probe via

text: autoradiography

text: or other imaging techniques. Normally, either X-ray pictures are taken of the filter, or the filter is placed under UV light. Detection of sequences with moderate or high similarity depends on how stringent the hybridization conditions were applied — high stringency, such as high hybridization temperature and low salt in hybridization buffers, permits only hybridization between

text: nucleic acid

text: sequences that are highly similar, whereas low stringency, such as lower temperature and high salt, allows hybridization when the sequences are less similar. Hybridization probes used in DNA

text: microarray

text: s refer to DNA covalently attached to an inert surface, such as coated glass slides or gene chips, to which a mobile cDNA target is hybridized.

text: Hora initiated advanced schemes of laser driven fusion energy and became Director of the  foundation of SAFE (Society to Advance Fusion Energy) with the President Luella LaMeer Slaner from the traditional billionaires North of Manhattan and George H. Miley as Executive Director, to push through a law for spending $20 Billions for nuclear fusion research finally signed by President Jimmy Carter in 1980. This led finally to the scheme of laser pulses of 30 kilojoule energy to produce Gigajoule energy from the clean reaction of uncompressed proton-boron fuel  resulting in less radioactivity than burning coal.

text: Hora initiated advanced schemes of laser driven fusion energy and became Director of the  foundation of SAFE (Society to Advance Fusion Energy) with the President Luella LaMeer Slaner from the traditional billionaires North of Manhattan and

text: George H. Miley

text: as Executive Director, to push through a law for spending $20 Billions for nuclear fusion research finally signed by President

text: Jimmy Carter

text: in 1980. This led finally to the scheme of laser pulses of 30 kilojoule energy to produce Gigajoule energy from the clean reaction of uncompressed proton-boron fuel  resulting in less radioactivity than burning coal.

text: By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form, also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single proton element hydrogen up to the 118-proton element oganesson. All known isotopes of elements with atomic numbers greater than 82 are radioactive, although the radioactivity of element 83 (bismuth) is so slight as to be practically negligible.

text: By definition, any two atoms with an identical number of protons in their nuclei belong to the same

text: chemical element

text: . Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (

text: , by far the most common form, also called protium), one neutron (

text: deuterium

text: ), two neutrons (

text: tritium

text: ) and

text: more than two neutrons

text: . The known elements form a set of atomic numbers, from the single proton element

text: hydrogen

text: up to the 118-proton element

text: oganesson

text: . All known isotopes of elements with atomic numbers greater than 82 are radioactive, although the radioactivity of element 83 (

text: bismuth

text: ) is so slight as to be practically negligible.

text: Anomalous "hot spots" have been discovered in areas far beyond the adjacent region. For example, experts cannot explain how radioactive caesium from the reactors at Fukushima ended up in Kanagawa more than  to the south.

text: After a period of time performing as "The Rock N' Roll Chicken Heads" and "The Chicken Heads", Joe and the Chicken Heads permanently changed their name to "The Radioactive Chicken Heads" in mid-2004. According to their website, the "official" tongue-in-cheek reason behind the name change was due to "new government regulations which require all radioactive farm products to be labeled clearly".

text: In 1902, they produced a "Theory of Atomic Disintegration" to account for all their experiments. Up till then atoms were assumed to be the indestructable basis of all matter and although Curie had suggested that radioactivity was an atomic phenomenon, the idea of the atoms of radioactive substances breaking up was a radically new idea. Rutherford and Soddy demonstrated that radioactivity involved the spontaneous disintegration of atoms into other types of atoms (one element spontaneously being changed to another).

text: In 1902, they produced a "Theory of Atomic Disintegration" to account for all their experiments. Up till then atoms were assumed to be the indestructable basis of all matter and although Curie had suggested that radioactivity was an atomic phenomenon, the idea of the atoms of radioactive substances breaking up was a radically new idea. Rutherford and Soddy demonstrated that radioactivity involved the spontaneous disintegration of

text: atom

text: s into other types of atoms (one element spontaneously being changed to another).

text: The ISS has a planned pressurized volume of approximately 1,000 cubic meters, a mass of approximately 400,000 kilograms, approximately 100 kilowatts of power output, a truss 108.4 meters long, modules 74 meters long, and a crew of six. Building the complete station will require more than 40 assembly flights. As of March 2011, 26 Space Shuttle flights have docked with ISS to add elements, and 9 other Shuttle flights have flown logistics-servicing missions to ISS without adding major external elements. These 35 Shuttle missions include 9 SpaceHab and 10 MPLM logistics-servicing missions in various combinations. The last two planned Shuttle flights are due to add one of the two final elements of ISS, followed by one last Proton launch with the planned delivery of the ERA. Other assembly flights have consisted of modules lifted by the Russian Proton rocket or in the case of Pirs and Poisk by a Soyuz-U rocket.

text: The ISS has a planned pressurized volume of approximately 1,000 cubic meters, a mass of approximately 400,000 kilograms, approximately 100 kilowatts of power output, a truss 108.4 meters long, modules 74 meters long, and a crew of six. Building the complete station will require more than 40 assembly flights. As of March 2011,

entity_name: Assembly of the International Space Station

text: 26 Space Shuttle flights

text: have docked with ISS to add elements, and

entity_name: List of human spaceflights to the International Space Station

text: 9 other

text: Shuttle flights have flown logistics-servicing missions to ISS without adding major external elements. These 35 Shuttle missions include 9

text: SpaceHab

text: and

text: 10 MPLM

text: logistics-servicing missions in various combinations. The last two planned Shuttle flights are due to add one of the two final elements of ISS, followed by one last Proton launch with the planned delivery of the

text: ERA

text: . Other assembly flights have consisted of modules lifted by the Russian Proton rocket or in the case of

text: Pirs

text: and

text: Poisk

text: by a

text: Soyuz-U

text: rocket.

text: Early researchers found that an electric or magnetic field could split radioactive emissions into three types of beams. The rays were given the names alpha, beta, and gamma, in order of their ability to penetrate matter. While alpha decay was observed only in heavier elements of atomic number 52 (tellurium) and greater, the other two types of decay were produced by all of the elements. Lead, atomic number 82, is the heaviest element to have any isotopes stable (to the limit of measurement) to radioactive decay. Radioactive decay is seen in all isotopes of all elements of atomic number 83 (bismuth) or greater. Bismuth, however, is only very slightly radioactive, with a half-life greater than the age of the universe; radioisotopes with extremely long half-lives are considered effectively stable for practical purposes.

text: Early researchers found that an

text: electric

text: or

text: magnetic field

text: could split radioactive emissions into three types of beams. The rays were given the names

text: alpha

text: beta

text: , and

text: gamma

text: , in order of their ability to penetrate matter. While alpha decay was observed only in heavier elements of atomic number 52 (

text: tellurium

text: ) and greater, the other two types of decay were produced by all of the elements. Lead,

text: atomic number

text: 82, is the heaviest element to have any isotopes stable (to the limit of measurement) to radioactive decay. Radioactive decay is seen in all isotopes of all elements of atomic number 83 (

text: bismuth

text: ) or greater. Bismuth, however, is only very slightly radioactive, with a half-life greater than the age of the universe; radioisotopes with extremely long half-lives are considered effectively stable for practical purposes.

text: The judges manage to defeat them but it turns out one of the werewolves is Judge Bram, who had taken the Long Walk. An infected Judge Korkoran also transformed before being subdued by a headbutt from Dredd. With these subjects to work on Tech Judge Cassidy discovers a radioactive compound that is causing the changes, which he names Cassidium.

text: In the early 20th century a series of products claiming medicinal properties, which contained radioactive elements were marketed to the general public. This does not include certain medications that contain radioactive isotopes (e.g. iodine-131 for its oncological uses) but pertains to elixirs and other medications that made preposterous claims (see below) that were neither scientific nor verifiable.

text: In the early 20th century a series of products claiming medicinal properties, which contained radioactive elements were marketed to the general public. This does not include certain medications that contain radioactive isotopes (e.g.

text: for its oncological uses) but pertains to elixirs and other medications that made preposterous claims (see below) that were neither scientific nor verifiable.

text: Neutron activation analysis (NAA) is a nuclear process used for determining the concentrations of elements in a vast amount of materials. NAA allows discrete sampling of elements as it disregards the chemical form of a sample, and focuses solely on its nucleus. The method is based on neutron activation and therefore requires a source of neutrons. The sample is bombarded with neutrons, causing the elements to form radioactive isotopes. The radioactive emissions and radioactive decay paths for each element are well known. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the elements within it. A particular advantage of this technique is that it does not destroy the sample, and thus has been used for analysis of works of art and historical artifacts. NAA can also be used to determine the activity of a radioactive sample.

text: Neutron activation analysis (NAA) is a

text: nuclear

text: process used for determining the concentrations of

text: elements

text: in a vast amount of materials. NAA allows discrete

text: sampling

text: of elements as it disregards the chemical form of a sample, and focuses solely on its nucleus. The method is based on

text: neutron activation

text: and therefore requires a source of

text: neutron

text: s. The sample is bombarded with neutrons, causing the elements to form radioactive isotopes. The

text: radioactive emissions

text: and radioactive decay paths for each element are well known. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the elements within it. A particular advantage of this technique is that it does not destroy the sample, and thus has been used for analysis of works of art and historical artifacts. NAA can also be used to determine the

text: activity

text: of a radioactive sample.

text: 3% of the mass consists of fission products of U and Pu (also indirect products in the decay chain); these are considered radioactive waste or may be separated further for various industrial and medical uses. The fission products include every element from zinc through to the lanthanides; much of the fission yield is concentrated in two peaks, one in the second transition row (Zr, Mo, Tc, Ru, Rh, Pd, Ag) and the other later in the periodic table (I, Xe, Cs, Ba, La, Ce, Nd). Many of the fission products are either non-radioactive or only short-lived radioisotopes. But a considerable number are medium to long-lived radioisotopes such as Sr, Cs, Tc and I. Research has been conducted by several different countries into segregating the rare isotopes in fission waste including the "fission platinoids" (Ru, Rh, Pd) and silver (Ag) as a way of offsetting the cost of reprocessing; however, this is not currently being done commercially.

text: 3% of the mass consists of fission products of U and Pu (also indirect products in the

text: decay chain

text: ); these are considered

text: radioactive waste

text: or may be separated further for various industrial and medical uses. The fission products include every element from

text: zinc

text: through to the

text: lanthanide

text: s; much of the fission yield is concentrated in two peaks, one in the second transition row (

text: Zr

text: , Mo, Tc,

text: Ru

text: Rh

text: Pd

text: Ag

text: ) and the other later in the periodic table (

text: I

text: Xe

text: Cs

text: Ba

text: La

text: Ce

text: , Nd). Many of the fission products are either non-radioactive or only short-lived

text: radioisotopes

text: . But a considerable number are medium to long-lived radioisotopes such as Sr, Cs, Tc and I. Research has been conducted by several different countries into segregating the rare isotopes in fission waste including the "fission platinoids" (Ru, Rh, Pd) and silver (Ag) as a way of offsetting the cost of reprocessing; however, this is not currently being done commercially.

text: The term "element" is used for atoms with a given number of protons (regardless of whether or not they are ionized or chemically bonded, e.g. hydrogen in water) as well as for a pure chemical substance consisting of a single element (e.g. hydrogen gas). For the second meaning, the terms "elementary substance" and "simple substance" have been suggested, but they have not gained much acceptance in English chemical literature, whereas in some other languages their equivalent is widely used (e.g. French corps simple, Russian простое вещество).A single element can form multiple substances differing in their structure; they are called allotropes of the element.

text: The term "element" is used for atoms with a given number of protons (regardless of whether or not they are

text: ionized

text: or chemically bonded, e.g. hydrogen in

text: water

text: ) as well as for a pure

text: chemical substance

text: consisting of a single element (e.g. hydrogen gas). For the second meaning, the terms "elementary substance" and "simple substance" have been suggested, but they have not gained much acceptance in

text: English

text: chemical literature, whereas in some other languages their equivalent is widely used (e.g.

text: French

text: corps simple,

text: Russian

text: простое вещество).A single element can form multiple substances differing in their structure; they are called

text: allotropes

text: of the element.

text: There will be three different type of storage facilities: for the spent nuclear fuel, nuclear fuel waste and radioactive waste.

text: Due to algae forming in the pool and a buildup of radioactive sludge, it is impossible to determine exactly how much radioactive waste is stored in the FGMSP. British authorities have not been able to provide the Euratom inspectors with precise data and the European Commission has thus sued Great Britain in the European Court of Justice. According to Greenpeace there is an expected 1300 kg of plutonium, 400 kg of which is in mud sediments.

text: Due to algae forming in the pool and a buildup of radioactive sludge, it is impossible to determine exactly how much radioactive waste is stored in the FGMSP. British authorities have not been able to provide the Euratom inspectors with precise data and the European Commission has thus sued Great Britain in the European Court of Justice. According to

text: Greenpeace

text: there is an expected 1300 kg of plutonium, 400 kg of which is in mud sediments.

text: Major products exported to Kazakhstan by India include pharmaceuticals, medical products, Tea, Telephone apparatus, Raw tobacco and construction machinery. Major Exports from Kazakhstan and imported by India include: petroleum oils, oils from bituminous minerals; radioactive chemincal elements; asbestos and titanium.

text: Major products exported to Kazakhstan by India include pharmaceuticals, medical products, Tea, Telephone apparatus, Raw tobacco and construction machinery. Major Exports from Kazakhstan and imported by India include: petroleum oils, oils from bituminous minerals; radioactive chemincal elements;

text: asbestos

text: and titanium.

text: A free neutron is unstable, decaying to a proton, electron and antineutrino with a mean lifetime of just under 15 minutes (). This radioactive decay, known as beta decay, is possible since the mass of the neutron is slightly greater than the proton. The free proton is stable. Neutrons or protons bound in a nucleus can be stable or unstable, however, depending on the nuclide. Beta decay, in which neutrons decay to protons, or vice versa, is governed by the weak force, and it requires the emission or absorption of electrons and neutrinos, or their antiparticles.

text: A free neutron is unstable, decaying to a proton, electron and

text: antineutrino

text: with a

text: mean lifetime

text: of just under 15 minutes (). This

text: radioactive decay

text: , known as

text: beta decay

text: , is possible since the mass of the neutron is slightly greater than the proton. The free proton is stable. Neutrons or protons bound in a nucleus can be stable or unstable, however, depending on the

text: nuclide

text: . Beta decay, in which neutrons decay to protons, or vice versa, is governed by the

text: weak force

text: , and it requires the emission or absorption of electrons and neutrinos, or their antiparticles.

text: Since 2011 Sarı has been working on creating ceramics works that take advantage of the glow properties of the radioactive uranium silicates. Sarı has been working with technology and art in parallel implementing works of art by using the techniques of uranium silicate's phosphorus effects on porcelain bodies since 2011. According to Sarı, there are two shades of red (copper red and uranium red) that are very difficult to achieve in glaze and ceramics and that a small surface of uranium red can be produced by burning uranium nitrate in high temperature. He was able to experiment with radioactive rare elements during his PhD studies in Sofia and that he was able to successfully significantly reduce alpha particle radiation from glaze and ceramics using radioactive uranium by using lead and lithium oxide layer coating which is further coated by glass layers. On 30 November 2012 Sarı held a seminar on "Uranium in Ceramic Art" at Vuzf University and also held a solo exhibition demonstrating this work with red uranium. On 27 June 2012 Sarı gave a guest lecture and held a workshop on uses of rare elements in ceramic glazes and glass bodies, cromatic glazes, Turkish blue glaze, preparation of safety floric acid bath for mat glazing at University of Applied Arts Vienna. On 15 September 2012 Sarı presented his paper with the topic "Uses of The Rare Elements into Ceramic Glazes and Glass Bodies" in the Sixth International Eskişehir Terra Cotta Symposium where he discussed the behavior within glazed ceramic/porcelain bodies of attained rare earth elements.

text: Since 2011 Sarı has been working on creating ceramics works that take advantage of the glow properties of the

text: radioactive

text: uranium

text: silicate

text: s. Sarı has been working with technology and art in parallel implementing works of art by using the techniques of uranium silicate's phosphorus effects on porcelain bodies since 2011. According to Sarı, there are two shades of red (copper red and uranium red) that are very difficult to achieve in glaze and ceramics and that a small surface of uranium red can be produced by burning uranium nitrate in high temperature. He was able to experiment with radioactive rare elements during his PhD studies in Sofia and that he was able to successfully significantly reduce

text: alpha particle

text: radiation from glaze and ceramics using radioactive uranium by using lead and lithium oxide layer coating which is further coated by glass layers. On 30 November 2012 Sarı held a seminar on "Uranium in Ceramic Art" at

text: Vuzf University

text: and also held a solo exhibition demonstrating this work with red uranium. On 27 June 2012 Sarı gave a guest lecture and held a workshop on uses of rare elements in ceramic glazes and glass bodies, cromatic glazes, Turkish blue glaze, preparation of safety floric acid bath for mat glazing at

text: University of Applied Arts Vienna

text: . On 15 September 2012 Sarı presented his paper with the topic "Uses of The Rare Elements into Ceramic Glazes and Glass Bodies" in the Sixth International Eskişehir Terra Cotta Symposium where he discussed the behavior within glazed ceramic/porcelain bodies of attained rare earth elements.

text: When Fajans worked at the laboratory of Ernest Rutherford (with Henry G. Moseley) he was researching properties of the radioactive rows. He identified the half-lives of the uranium-actinium row and thorium nuclides. He discovered the phenomenon of the electrochemical branching of the radioactive rows. Afterwards Fajans was working on the electrochemical properties of elements as a result of the radioactive changes, and he formulated the law of the radioactive shifts which was later named the radioactive displacement law of Fajans and Soddy (Frederick Soddy received the Nobel Prize in chemistry in 1921 for his isotopic research). In 1913, together with Oswald Helmuth Göhring, he discovered the radionuclide of a new element, which was later called protactinium. Fajans and Otto Hahn were the discoverers of the formula that defined the conditions of the precipitation and absorption of radioactive substances. It is very significant in the context of radiochemical methods of separating and cleaning radioactive substances found in the smallest number.

text: When Fajans worked at the laboratory of

text: Ernest Rutherford

text: (with

text: Henry G. Moseley

text: ) he was researching properties of the radioactive rows. He identified the

text: half-lives

text: of the

text: uranium

text: actinium

text: row and

text: thorium

text: nuclides. He discovered the phenomenon of the electrochemical branching of the radioactive rows. Afterwards Fajans was working on the electrochemical properties of elements as a result of the radioactive changes, and he formulated the law of the radioactive shifts which was later named the

text: Frederick Soddy

text: received the Nobel Prize in chemistry in 1921 for his isotopic research). In 1913, together with

text: Oswald Helmuth Göhring

text: , he discovered the radionuclide of a new element, which was later called

text: protactinium

text: . Fajans and

text: Otto Hahn

text: were the discoverers of the formula that defined the conditions of the precipitation and absorption of radioactive substances. It is very significant in the context of radiochemical methods of separating and cleaning radioactive substances found in the smallest number.

text: After the discovery of radioactivity by Henri Becquerel and Marie Curie in 1896, it was generally believed that atmospheric electricity, ionization of the air, was caused only by radiation from radioactive elements in the ground or the radioactive gases or isotopes of radon they produce. Measurements of ionization rates at increasing heights above the ground during the decade from 1900 to 1910 showed a decrease that could be explained as due to absorption of the ionizing radiation by the intervening air.

text: After the discovery of

text: radioactivity

text: by

text: Henri Becquerel

text: and

text: Marie Curie

text: in 1896, it was generally believed that atmospheric electricity,

text: ionization

text: of the

text: air

text: , was caused only by

text: radiation

text: from radioactive elements in the ground or the radioactive gases or isotopes of

text: radon

text: they produce. Measurements of ionization rates at increasing heights above the ground during the decade from 1900 to 1910 showed a decrease that could be explained as due to absorption of the ionizing radiation by the intervening air.

text: Some radioactive materials in "exclusive use" with low specific activity radioactive materials will not bear the label, however, the RADIOACTIVE placard is required.

text: Some

text: radioactive materials

text: in "exclusive use" with low

text: specific activity

text: radioactive materials will not bear the label, however, the RADIOACTIVE placard is required.

text: Berta Karlik was an Austrian physicist. She worked for the University of Vienna, eventually becoming the first female professor at the institution. While working with Ernst Foyn she published a paper on the radioactivity of seawater.  She discovered that the element 85 astatine is a product of the natural decay processes. The element was first synthesized in 1940 by Dale R. Corson, K. R. MacKenzie, and Emilio Segrè, after several scientists in vain searched for it in radioactive minerals.

text: Berta Karlik was an

text: Austrian

text: physicist

text: . She worked for the

text: University of Vienna

text: , eventually becoming the first female professor at the institution. While working with Ernst Foyn she published a paper on the radioactivity of seawater.  She discovered that the element 85

text: astatine

text: is a product of the natural decay processes. The element was first synthesized in 1940 by

text: Dale R. Corson

text: K. R. MacKenzie

text: , and

text: Emilio Segrè

text: , after several scientists in vain searched for it in radioactive minerals.

text: Berkelium is a transuranic radioactive chemical element with symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the University of California Radiation Laboratory where it was discovered in December 1949. This was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

text: Berkelium is a

text: transuranic

text: radioactive

text: chemical element

text: with symbol Bk and

text: atomic number

text: 97. It is a member of the

text: actinide

text: and

text: transuranium element

text: series. It is named after the city of

text: Berkeley, California

text: , the location of the

text: University of California Radiation Laboratory

text: where it was discovered in December 1949. This was the fifth transuranium element discovered after

text: neptunium

text: plutonium

text: curium

text: and

text: americium

text: The number of protons in the atomic nucleus also determines its electric charge, which in turn determines the number of electrons of the atom in its non-ionized state. The electrons are placed into atomic orbitals that determine the atom's various chemical properties. The number of neutrons in a nucleus usually has very little effect on an element's chemical properties (except in the case of hydrogen and deuterium). Thus, all carbon isotopes have nearly identical chemical properties because they all have six protons and six electrons, even though carbon atoms may, for example, have 6 or 8 neutrons. That is why the atomic number, rather than mass number or atomic weight, is considered the identifying characteristic of a chemical element.

text: The number of protons in the atomic nucleus also determines its

text: electric charge

text: , which in turn determines the number of

text: electron

text: s of the atom in its

text: non-ionized

text: state. The electrons are placed into

text: atomic orbital

text: s that determine the atom's various

text: chemical properties

text: . The number of neutrons in a nucleus usually has very little effect on an element's chemical properties (except in the case of

text: hydrogen

text: and

text: deuterium

text: ). Thus, all carbon isotopes have nearly identical chemical properties because they all have six protons and six electrons, even though carbon atoms may, for example, have 6 or 8 neutrons. That is why the atomic number, rather than

text: mass number

text: or

text: atomic weight

text: , is considered the identifying characteristic of a chemical element.

text: An isotopic tracer, (also "isotopic marker" or "isotopic label"), is used in chemistry and biochemistry to help understand chemical reactions and interactions. In this technique, one or more of the atoms of the molecule of interest is substituted for an atom of the same chemical element, but of a different isotope (like a radioactive isotope used in radioactive tracing). Because the labeled atom has the same number of protons, it will behave in almost exactly the same way as its unlabeled counterpart and, with few exceptions, will not interfere with the reaction under investigation. The difference in the number of neutrons, however, means that it can be detected separately from the other atoms of the same element.

text: An isotopic tracer, (also "isotopic marker" or "isotopic label"), is used in

text: chemistry

text: and

text: biochemistry

text: to help understand chemical

text: reactions

text: and interactions. In this technique, one or more of the

text: atom

text: s of the

text: molecule

text: of interest is substituted for an atom of the same

text: chemical element

text: , but of a different

text: isotope

text: (like a

text: radioactive

text: isotope used in

text: radioactive tracing

text: ). Because the labeled atom has the same number of protons, it will behave in almost exactly the same way as its unlabeled counterpart and, with few exceptions, will not interfere with the reaction under investigation. The difference in the number of

text: neutron

text: s, however, means that it can be detected separately from the other atoms of the same element.

text: In 1949 athabascaite was discovered by S. Kaiman while he was researching radioactive materials around Lake Athabasca near Uranium City.

text: In 1949

text: athabascaite

text: was discovered by S. Kaiman while he was researching

text: radioactive materials

text: around Lake Athabasca near Uranium City.

text: Francium is an alkali metal whose chemical properties mostly resemble those of caesium. A heavy element with a single valence electron, it has the highest equivalent weight of any element. Liquid francium—if created—should have a surface tension of 0.05092 N/m at its melting point. Francium's melting point was calculated to be around 27 °C (80 °F, 300 K). The melting point is uncertain because of the element's extreme rarity and radioactivity. Thus, the estimated boiling point value of 677 °C (1250 °F, 950 K) is also uncertain.

text: Francium is an alkali metal whose chemical properties mostly resemble those of caesium. A heavy element with a single

text: valence electron

text: , it has the highest

text: equivalent weight

text: of any element. Liquid francium—if created—should have a

text: surface tension

text: of 0.05092

text: N

text: /m at its melting point. Francium's melting point was calculated to be around 27 °C (80 °F, 300 K). The melting point is uncertain because of the element's extreme rarity and

text: radioactivity

text: . Thus, the estimated boiling point value of 677 °C (1250 °F, 950 K) is also uncertain.

text: Elements are composed of one or more naturally occurring isotopes. The unstable (radioactive) isotopes are either primordial or postprimordial. Primordial isotopes were a product of stellar nucleosynthesis or another type of nucleosynthesis such as cosmic ray spallation, and have persisted down to the present because their rate of decay is so slow (e.g. uranium-238 and potassium-40). Post-primordial isotopes were created by cosmic ray bombardment as cosmogenic nuclides (e.g., tritium, carbon-14), or by the decay of a radioactive primordial isotope to a radioactive radiogenic nuclide daughter (e.g. uranium to radium). A few isotopes are naturally synthesized as nucleogenic nuclides, by some other natural nuclear reaction, such as when neutrons from natural nuclear fission are absorbed by another atom.

text: Elements are composed of one or more naturally occurring isotopes. The unstable (radioactive) isotopes are either

text: primordial

text: or postprimordial. Primordial isotopes were a product of

text: stellar nucleosynthesis

text: or another type of nucleosynthesis such as

text: cosmic ray spallation

text: , and have persisted down to the present because their rate of decay is so slow (e.g.

text: and

text: ). Post-primordial isotopes were created by

text: cosmic ray

text: bombardment as

text: cosmogenic nuclide

text: s (e.g.,

text: tritium

text: ), or by the decay of a radioactive primordial isotope to a radioactive

text: radiogenic nuclide

text: daughter (e.g.

text: uranium

text: to

text: radium

text: ). A few isotopes are naturally synthesized as

text: nucleogenic

text: nuclides, by some other natural

text: nuclear reaction

text: , such as when neutrons from natural

text: nuclear fission

text: are absorbed by another atom.

text: Not long after Henri Becquerel discovered radioactivity in uranium salts, Madame Curie discovered both polonium and radium as two new radioactive elements also present with uranium.The relatively high specific activity and moderate half-life of 1,600 years of Ra-226, the main radioisotope of radium found in uranium ore, made for a material which when mixed with a phosphor allowed for a glow-in-the-dark substance.

text: Not long after

text: Henri Becquerel

text: discovered

text: radioactivity

text: in uranium salts,

text: Madame Curie

text: discovered both

text: polonium

text: and

text: radium

text: as two new radioactive elements also present with uranium.The relatively high

text: specific activity

text: and moderate

text: half-life

text: of 1,600 years of

text: , the main

text: radioisotope

text: of radium found in uranium ore, made for a material which when mixed with a

text: phosphor

text: allowed for a glow-in-the-dark substance.

text: Injection of radioactive tracers, along with the other substances in hydraulic-fracturing fluid, is often used to determine the injection profile and location of fractures created by hydraulic fracturing. Patents describe in detail how several tracers are typically used in the same well. Wells are hydraulically fractured in different stages. Tracers with different half-lives are used for each stage.  Their half-lives range from 40.2 hours (Lanthanum-140) to 28.90 years (Strontium-90). Amounts per injection of radionuclide are listed in the US Nuclear Regulatory Commission (NRC) guidelines. The NRC guidelines also list a wide range or radioactive materials in solid, liquid and gaseous forms that are used as field flood or enhanced oil and gas recovery study applications tracers used in single and multiple wells. According to the NRC, some of the most commonly used include Antimony-124, Bromine-82, Iodine-125, Iodine-131, Iridium-192, and Scandium-46. A 2003 publication by the International Atomic Energy Agency (IAEA) provides a detailed description of tracer use, confirms the frequent use of most of the tracers above, and says that Manganese-56, Sodium-24, Technetium-m, Silver-m, Argon-41, and Xenon-133 are also used extensively because they are easily identified and measured. Other potentially suitable tracers are named in various patents. In terms of quantities used, the NRC gives the following examples: Iodine-131, gas form, 100 millicuries total, not to exceed 20 millicuries per injection; Iodine-131, liquid form, 50 millicuries total, not to exceed 10 millicuries per injection; Iridium-192, "Labeled" frac sand, 200 millicuries total, not to exceed 15 millicuries per injection; Silver-110m, liquid form, 200 millicuries total, not to exceed 20 millicuries per injection

text: Injection of radioactive tracers, along with the other substances in hydraulic-fracturing fluid, is often used to determine the injection profile and location of fractures created by hydraulic fracturing. Patents describe in detail how several tracers are typically used in the same well. Wells are hydraulically fractured in different stages. Tracers with different half-lives are used for each stage.  Their half-lives range from 40.2 hours (

text: ) to 28.90 years (

text: ). Amounts per injection of radionuclide are listed in the US

text: Nuclear Regulatory Commission

text: (NRC) guidelines. The NRC guidelines also list a wide range or radioactive materials in solid, liquid and gaseous forms that are used as field flood or enhanced oil and gas recovery study applications tracers used in single and multiple wells. According to the NRC, some of the most commonly used include

text: , and

text: . A 2003 publication by the

text: International Atomic Energy Agency

text: (IAEA) provides a detailed description of tracer use, confirms the frequent use of most of the tracers above, and says that

text: , Technetium-m, Silver-m,

text: , and

text: are also used extensively because they are easily identified and measured. Other potentially suitable tracers are named in various patents. In terms of quantities used, the NRC gives the following examples: Iodine-131, gas form, 100 millicuries total, not to exceed 20 millicuries per injection; Iodine-131, liquid form, 50 millicuries total, not to exceed 10 millicuries per injection; Iridium-192, "Labeled" frac sand, 200 millicuries total, not to exceed 15 millicuries per injection; Silver-110m, liquid form, 200 millicuries total, not to exceed 20 millicuries per injection

text: The elements in group 13 are also capable of forming stable compounds with the halogens, usually with the formula MX (where M is a boron-group element and X is a halogen.) The only exception to this is thallium(III) iodide. Fluorine, the first halogen, is able to form stable compounds with every element that has been tested (except neon and helium), and the boron group is no exception. It is even hypothesized that nihonium could form a compound with fluorine, NhF, before spontaneously decaying due to nihonium's radioactivity. Chlorine also forms stable compounds with all of the elements in the boron group, including thallium, and is hypothesized to react with nihonium. All of the elements will react with bromine under the right conditions, as with the other halogens but less vigorously than either chlorine or fluorine. Iodine will react with all natural elements in the periodic table except for the noble gases, and is notable for its explosive reaction with aluminium to form 2AlI. Astatine, the heaviest halogen, has only formed a few compounds, due to its radioactivity and short half-life, and no reports of a compound with an At–B, –Al, –Ga, –In, –Tl, or –Nh bond have been seen, although scientists think that it should form salts with metals.

text: The elements in group 13 are also capable of forming stable compounds with the

text: halogens

text: , usually with the formula MX (where M is a boron-group element and X is a halogen.) The only exception to this is

text: thallium(III) iodide

text: Fluorine

text: , the first halogen, is able to form stable compounds with every element that has been tested (except

text: neon

text: and

text: helium

text: ), and the boron group is no exception. It is even hypothesized that nihonium could form a compound with fluorine, NhF, before spontaneously decaying due to nihonium's radioactivity.

text: Chlorine

text: also forms stable compounds with all of the elements in the boron group, including thallium, and is hypothesized to react with nihonium. All of the elements will react with

text: bromine

text: under the right conditions, as with the other halogens but less vigorously than either chlorine or fluorine.

text: Iodine

text: will react with all natural elements in the periodic table except for the noble gases, and is notable for its explosive reaction with aluminium to form 2AlI.

text: Astatine

text: , the heaviest halogen, has only formed a few compounds, due to its radioactivity and short half-life, and no reports of a compound with an At–B, –Al, –Ga, –In, –Tl, or –Nh bond have been seen, although scientists think that it should form salts with metals.

text: Since radioactive decay is exponential with a constant probability, each process could as easily be described with a different constant time period that (for example) gave its "(1/3)-life" (how long until only 1/3 is left) or "(1/10)-life" (a time period until only 10% is left), and so on. Thus, the choice of  and  for marker-times, are only for convenience, and from convention. They reflect a fundamental principle only in so much as they show that the same proportion of a given radioactive substance will decay, during any time-period that one chooses.

text: The use of radioactive tracer elements in ion uptake assays allows the calculation of km, Ki and Vmax and determines the initial change in the ion content of the cells. Mg decays by the emission of a high-energy beta or gamma particle, which can be measured using a scintillation counter. However, the radioactive half-life of Mg, the most stable of the radioactive magnesium isotopes, is only 21 hours. This severely restricts the experiments involving the nuclide. Also, since 1990, no facility has routinely produced Mg, and the price per mCi is now predicted to be approximately US$30,000. The chemical nature of Mg is such that it is closely approximated by few other cations.  However, Co, Mn and Ni have been used successfully to mimic the properties of Mg in some enzyme reactions, and radioactive forms of these elements have been employed successfully in cation transport studies. The difficulty of using metal ion replacement in the study of enzyme function is that the relationship between the enzyme activities with the replacement ion compared to the original is very difficult to ascertain.

text: On 5 January 2012 the Nambu (south) Clean Center, a waste incinerator in Kashiwa, Chiba, was taken out of production by the city council because the storage room was completely filled with 200 metric tons of radioactive ash that could not disposed of in landfills. Storage at the plant was full, with 1049 drums, and some 30 tons more were still to be taken out of the incinerator. In September 2011, the factory was closed for two months for the same reason. The Center's special advanced procedures were able to minimize the volume of the ash, but radioactive cesium was concentrated to levels above the national limit of 8.000 becquerels per kilogram for waste disposal in landfills. It was not possible to secure new storage space for the radioactive ash. Radiation levels in Kashiwa were higher than in surrounding areas, and ashes containing up to 70,800 becquerels of radioactive cesium per kilogram – higher than the national limit – were detected in the city. Other cities around Kashiwa were facing the same problem: radioactive ash was piling up. Chiba prefecture asked Abiko and Inzai to accept temporary storage at the Teganuma waste-disposal facility located at their border. But this met strong opposition from their citizens.

text: On 5 January 2012 the Nambu (south) Clean Center, a waste incinerator in

text: Kashiwa, Chiba

text: , was taken out of production by the city council because the storage room was completely filled with 200 metric tons of radioactive ash that could not disposed of in landfills. Storage at the plant was full, with 1049 drums, and some 30 tons more were still to be taken out of the incinerator. In September 2011, the factory was closed for two months for the same reason. The Center's special advanced procedures were able to minimize the volume of the ash, but radioactive cesium was concentrated to levels above the national limit of 8.000 becquerels per kilogram for waste disposal in landfills. It was not possible to secure new storage space for the radioactive ash. Radiation levels in Kashiwa were higher than in surrounding areas, and ashes containing up to 70,800 becquerels of radioactive cesium per kilogram – higher than the national limit – were detected in the city. Other cities around Kashiwa were facing the same problem: radioactive ash was piling up. Chiba prefecture asked

text: Abiko

text: and

text: Inzai

text: to accept temporary storage at the Teganuma waste-disposal facility located at their border. But this met strong opposition from their citizens.

text: For a summary table showing the number of stable and radioactive nuclides in each category, see radionuclide. There exist twenty-nine chemical elements on Earth that are radioactive. They are those that contain thirty-four radionuclides that date before the time of formation of the solar system, and are known as primordial nuclides. Well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes such as potassium-40. Another fifty or so shorter-lived radionuclides, such as radium and radon, found on Earth, are the products of decay chains that began with the primordial nuclides, or are the product of ongoing cosmogenic processes, such as the production of carbon-14 from nitrogen-14 by cosmic rays. Radionuclides may also be produced artificially in particle accelerators or nuclear reactors, resulting in 650 of these with half-lives of over an hour, and several thousand more with even shorter half-lives. See this list of nuclides for a list of these, sorted by half life.

text: For a summary table showing the number of stable and radioactive nuclides in each category, see

text: radionuclide

text: . There exist twenty-nine

text: chemical element

text: s on Earth that are radioactive. They are those that contain thirty-four radionuclides that date before the time of formation of the solar system, and are known as

text: primordial nuclide

text: s. Well-known examples are

text: uranium

text: and

text: thorium

text: , but also included are naturally occurring long-lived radioisotopes such as

text: . Another fifty or so shorter-lived radionuclides, such as

text: radium

text: and

text: radon

text: , found on Earth, are the products of

text: decay chain

text: s that began with the primordial nuclides, or are the product of ongoing

text: cosmogenic

text: processes, such as the production of

text: from

text: by

text: cosmic rays

text: . Radionuclides may also be

text: produced artificially

text: in

text: particle accelerators

text: or

text: nuclear reactors

text: , resulting in 650 of these with half-lives of over an hour, and several thousand more with even shorter half-lives. See this

text: list of nuclides

text: for a list of these, sorted by half life.

text: Isotopes are atoms of the same element (that is, with the same number of protons in their atomic nucleus), but having different numbers of neutrons. Thus, for example, there are three main isotopes of carbon. All carbon atoms have 6 protons in the nucleus, but they can have either 6, 7, or 8 neutrons. Since the mass numbers of these are 12, 13 and 14 respectively, the three isotopes of carbon are known as carbon-12, carbon-13, and carbon-14, often abbreviated to C, C, and C. Carbon in everyday life and in chemistry is a mixture of C (about 98.9%), C (about 1.1%) and about 1 atom per trillion of C.

text: Isotope

text: s are atoms of the same element (that is, with the same number of

text: proton

text: s in their

text: atomic nucleus

text: ), but having different numbers of

text: neutron

text: s. Thus, for example, there are three main isotopes of carbon. All carbon atoms have 6 protons in the nucleus, but they can have either 6, 7, or 8 neutrons. Since the mass numbers of these are 12, 13 and 14 respectively, the three isotopes of carbon are known as

text: , and

text: , often abbreviated to C, C, and C.

text: Carbon

text: in everyday life and in chemistry is a

text: mixture

text: of C (about 98.9%), C (about 1.1%) and about 1 atom per trillion of C.

text: Curie and Joliot showed that when lighter elements such as boron and aluminium were bombarded with α-particles, there was a continuous emission of radioactive radiations, even after the α−source had been removed. They showed that the radiation was due to the emission of a particle carrying one unit positive charge with mass equal to that of an electron.

text: Curie and Joliot showed that when lighter elements such as

text: boron

text: and

text: aluminium

text: were bombarded with α-particles, there was a continuous emission of radioactive radiations, even after the α−source had been removed. They showed that the radiation was due to the emission of a particle carrying one unit positive charge with mass equal to that of an electron.

text: Paleontology seeks to map out how living things have changed through time. A substantial hurdle to this aim is the difficulty of working out how old fossils are. Beds that preserve fossils typically lack the radioactive elements needed for radiometric dating. This technique is our only means of giving rocks greater than about 50 million years old an absolute age, and can be accurate to within 0.5% or better. Although radiometric dating requires very careful laboratory work, its basic principle is simple: the rates at which various radioactive elements decay are known, and so the ratio of the radioactive element to the element into which it decays shows how long ago the radioactive element was incorporated into the rock. Radioactive elements are common only in rocks with a volcanic origin, and so the only fossil-bearing rocks that can be dated radiometrically are a few volcanic ash layers.

text: Paleontology seeks to map out how living things have changed through time. A substantial hurdle to this aim is the difficulty of working out how old fossils are. Beds that preserve fossils typically lack the radioactive elements needed for

text: radiometric dating

text: . This technique is our only means of giving rocks greater than about 50 million years old an absolute age, and can be accurate to within 0.5% or better. Although radiometric dating requires very careful laboratory work, its basic principle is simple: the rates at which various radioactive elements

text: decay

text: are known, and so the ratio of the radioactive element to the element into which it decays shows how long ago the radioactive element was incorporated into the rock. Radioactive elements are common only in rocks with a volcanic origin, and so the only fossil-bearing rocks that can be dated radiometrically are a few volcanic ash layers.

text: Isotopes have been produced with enough protons to plant them upon an island of stability but with too few neutrons to even place them upon the island's outer "shores". It is possible that these elements possess unusual chemical properties and, if they have isotopes with adequate lifespans, would be available for various practical applications (such as particle accelerator targets and as neutron sources as well). In particular, the very small critical masses of transplutonic elements (possibly as small as grams) implies that if stable elements could be found, they would enable small and compact nuclear bombs either directly or by serving as primaries to help ignite fission/fusion secondaries; this possibility motivated much of the early research and multiple nuclear tests by the United States (including Operation Plowshare) and the Soviet Union aimed at producing such elements.

text: Isotopes have been produced with enough protons to plant them upon an island of stability but with too few neutrons to even place them upon the island's outer "shores". It is possible that these elements possess unusual chemical properties and, if they have isotopes with adequate lifespans, would be available for various practical applications (such as particle accelerator targets and as

text: neutron source

text: s as well). In particular, the very small critical masses of transplutonic elements (possibly as small as grams) implies that if stable elements could be found, they would enable small and compact nuclear bombs either directly or by serving as primaries to help ignite fission/fusion secondaries; this possibility motivated much of the early research and multiple nuclear tests by the United States (including

text: Operation Plowshare

text: ) and the Soviet Union aimed at producing such elements.

text: After a radioactive isotope (Strontium-90) was found in cows milk in 1959, the concern for the environmental effects of the nuclear arms race increased exponentially. This sparked songs about the invisibility of environmental effects like radioactive isotopes. In his song "Mack the Bomb," Pete Seeger wrote a comparison between a shark and Strontium-90, explaining that the threat of a shark is at least visible, unlike radioactive isotopes.  In 1962, Malvina Reynolds also wrote a song called "What Have They Done to the Rain?", which was inspired by above-ground nuclear testing, and how it was putting Strontium-90 into the air, then into soil through rain, which is how it got into cows and their milk.

text: After a radioactive isotope (

text: ) was found in cows milk in 1959, the concern for the environmental effects of the

text: nuclear arms race

text: increased exponentially. This sparked songs about the invisibility of environmental effects like radioactive isotopes. In his song "Mack the Bomb,"

text: Pete Seeger

text: wrote a comparison between a shark and Strontium-90, explaining that the threat of a shark is at least visible, unlike radioactive isotopes.  In 1962,

text: Malvina Reynolds

text: also wrote a song called "

text: What Have They Done to the Rain?

text: ", which was inspired by above-ground nuclear testing, and how it was putting Strontium-90 into the air, then into soil through rain, which is how it got into cows and their milk.

text: The conventional deuterium + tritium ("D-T") fusion process produces energetic neutrons which render reactor components radioactive with activation products. The appeal of helium-3 fusion stems from the aneutronic nature of its reaction products. Helium-3 itself is non-radioactive. The lone high-energy by-product, the proton, can be contained using electric and magnetic fields. The momentum energy of this proton (created in the fusion process) will interact with the containing electromagnetic field, resulting in direct net electricity generation.

text: The conventional

text: deuterium

text: tritium

text: ("D-T") fusion process produces energetic neutrons which render reactor components

text: radioactive

text: with

text: activation product

text: s. The appeal of helium-3 fusion stems from the

text: aneutronic

text: nature of its reaction products. Helium-3 itself is non-radioactive. The lone high-energy by-product, the

text: proton

text: , can be contained using electric and magnetic fields. The momentum energy of this proton (created in the fusion process) will interact with the containing electromagnetic field, resulting in direct net electricity generation.

text: A neutral atom has the same number of electrons as protons. Thus different isotopes of a given element all have the same number of electrons and share a similar electronic structure. Because the chemical behavior of an atom is largely determined by its electronic structure, different isotopes exhibit nearly identical chemical behavior.

text: The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force. Nuclear fusion occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at the core of the Sun protons require energies of 3–10 keV to overcome their mutual repulsion—the coulomb barrier—and fuse together into a single nucleus. Nuclear fission is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay. The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies the number of protons in a nucleus, the atom changes to a different chemical element.

text: The number of protons and neutrons in the atomic nucleus can be modified, although this can require very high energies because of the strong force.

text: Nuclear fusion

text: occurs when multiple atomic particles join to form a heavier nucleus, such as through the energetic collision of two nuclei. For example, at the core of the Sun protons require energies of 3–10 keV to overcome their mutual repulsion—the

text: coulomb barrier

text: —and fuse together into a single nucleus.

text: Nuclear fission

text: is the opposite process, causing a nucleus to split into two smaller nuclei—usually through radioactive decay. The nucleus can also be modified through bombardment by high energy subatomic particles or photons. If this modifies the number of protons in a nucleus, the atom changes to a different chemical element.

text: Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable).

text: Radiochemistry

text: is the chemistry of radioactive materials, where radioactive

text: isotope

text: s of elements are used to study the properties and

text: chemical reaction

text: s of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable).

text: The sources of radioactivity are not exclusive of human activity. The natural radioactivity does not come from human sources: it covers up to ¾ of the total radioactivity in the world and has its origins in the interaction of terrestrial elements with high energy cosmic rays (cosmogenic radionuclides) or in the existing materials on Earth since its formation (primordial radionuclides). In this regard, there are differences in the levels of radioactivity throughout the Earth's crust. India and mountains like the Alps are among the areas with the highest level of natural radioactivity due to their composition of rocks and sand.

text: The sources of radioactivity are not exclusive of human activity. The

text: natural radioactivity

text: does not come from human sources: it covers up to ¾ of the total radioactivity in the world and has its origins in the interaction of terrestrial elements with high energy

text: cosmic rays

text: cosmogenic radionuclides

text: ) or in the existing materials on

text: Earth

text: since its formation (

text: primordial radionuclides

text: ). In this regard, there are differences in the levels of radioactivity throughout the

text: Earth's crust

text: India

text: and mountains like the

text: Alps

text: are among the areas with the highest level of natural radioactivity due to their composition of

text: rocks

text: and

text: sand

text: Only appears in "Marvel Family" #22. Prisoner 887432 is given the chance to get off execution in exchange for being a test subject for a medical experiment. He is given radioactive salt to build up immunity to radiation poisoning, like arsenic immunity. Finally he is so radioactive his clothes burn away and he wears a lead suit, finally his chains melt away. He kills the two scientists with a charge of deadly rays. He takes the remaining radioactive capsules as he needs to take one every few hours to keep his powers. At a police athletic meet at the stadium he tries to make the cops leave as he hates cops, they recognize him as an escaped killer, but their bullets melt before they hit him, he then starts burning the cops. Billy Batson is there and turns into Captain Marvel, who is immune to the radioactive rays. Radioactive Man takes another capsule, then starts fires in the stands to slow down Captain Marvel (who stamps out the flames) enough to allow him to escape. He then starts hunting cops and burning them to death. Billy reports on this, then transforms into Captain Marvel and disguises himself as a cop and waits in the neighborhood Radioactive Man has been operating in. When he tries burning him, Marvel reveals himself and puts him in jail. He takes the capsules without which his powers will die out and takes them to a hospital. But Radioactive Man had one capsule concealed in his mouth, he regains his powers and melts the bars. Police arrive at airport that day with radium for Center hospital, Radioactive Man needs more radioactive salt, but Captain Marvel stops the rays from burning the guards and captures Radioactive Man with a lead cable. Billy then says his powers wore off without a new dose, he is once again prisoner 887432, and his death sentence has been changed to life imprisonment.

text: There followed a period of intense research into radioactivity, including the determination that the element thorium is also radioactive and the discovery of additional radioactive elements polonium and radium by Marie Skłodowska-Curie and her husband Pierre Curie.

text: There followed a period of intense research into radioactivity, including the determination that the element

text: thorium

text: is also radioactive and the discovery of additional radioactive elements

text: polonium

text: and

text: radium

text: by

text: Marie Skłodowska-Curie

text: and her husband

text: Pierre Curie

text: There are conflicting reports about what level of radioactivity can be in the water processed by Landysh; some sources state that it can only process low-level water whilst other sources state it can handle medium- and low-level water; all sources agree that it can process up 7,000 m per year. There have been questions raised about the effectiveness of the decontamination process, especially regarding the removal of caesium-137. Landysh uses a combination of filtration, ion exchange and reverse osmosis to remove radioactive material from water. After collecting and concentrating the radioactive materials, they are mixed with cement and placed in 200-litre barrels for further radioactive waste management.

text: There are conflicting reports about what level of radioactivity can be in the water processed by Landysh; some sources state that it can only process low-level water whilst other sources state it can handle medium- and low-level water; all sources agree that it can process up 7,000 m per year. There have been questions raised about the effectiveness of the decontamination process, especially regarding the removal of

text: . Landysh uses a combination of

text: filtration

text: ion exchange

text: and

text: reverse osmosis

text: to remove

text: radioactive material

text: from water. After collecting and concentrating the radioactive materials, they are mixed with

text: cement

text: and placed in 200-litre barrels for further radioactive waste management.

text: For larger nuclei, the shells occupied by nucleons begin to differ significantly from electron shells, but nevertheless, present nuclear theory does predict the magic numbers of filled nuclear shells for both protons and neutrons. The closure of the stable shells predicts unusually stable configurations, analogous to the noble group of nearly-inert gases in chemistry. An example is the stability of the closed shell of 50 protons, which allows tin to have 10 stable isotopes, more than any other element. Similarly, the distance from shell-closure explains the unusual instability of isotopes which have far from stable numbers of these particles, such as the radioactive elements 43 (technetium) and 61 (promethium), each of which is preceded and followed by 17 or more stable elements.

text: For larger nuclei, the shells occupied by nucleons begin to differ significantly from electron shells, but nevertheless, present nuclear theory does predict the magic numbers of filled nuclear shells for both protons and neutrons. The closure of the stable shells predicts unusually stable configurations, analogous to the noble group of nearly-inert gases in chemistry. An example is the stability of the closed shell of 50 protons, which allows

text: tin

text: to have 10 stable isotopes, more than any other element. Similarly, the distance from shell-closure explains the unusual instability of isotopes which have far from stable numbers of these particles, such as the radioactive elements 43 (

text: technetium

text: ) and 61 (

text: promethium

text: ), each of which is preceded and followed by 17 or more stable elements.

text: Francium ( ) is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K. It is one of the two least electronegative elements, the other being caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron. Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. It was the last element discovered in nature, rather than by synthesis. Outside the laboratory, francium is extremely rare, with trace amounts found in uranium and thorium ores, where the isotope francium-223 continually forms and decays. As little as 20–30 g (one ounce) exists at any given time throughout the Earth's crust; the other isotopes are entirely synthetic. The largest amount produced in the laboratory was a cluster of more than 300,000 atoms.

text: Francium ( ) is a

text: chemical element

text: with symbol Fr and

text: atomic number

text: 87. It was formerly known as

text: eka

text: caesium

text: and

text: actinium

text: K. It is one of the two least

text: electronegative

text: elements, the other being

text: caesium

text: . Francium is a highly

text: radioactive

text: metal that decays into astatine,

text: radium

text: , and

text: radon

text: . As an

text: alkali metal

text: , it has one

text: valence electron

text: . Francium was discovered by

text: Marguerite Perey

text: in

text: France

text: (from which the element takes its name) in 1939. It was the last element discovered in

text: nature

text: , rather than by synthesis. Outside the laboratory, francium is extremely rare, with trace amounts found in

text: uranium

text: and

text: thorium

text: ores, where the

text: isotope

text: francium-223 continually forms and decays. As little as 20–30 g (one ounce) exists at any given time throughout the

text: Earth's crust

text: ; the other isotopes are entirely synthetic. The largest amount produced in the laboratory was a cluster of more than 300,000 atoms.

text: The high short-term radioactivity of spent nuclear fuel is primarily from fission products with short half-life.The radioactivity in the fission product mixture is mostly short-lived isotopes such as I-131 and Ba, after about four months Ce, Zr/Nb and Sr take the largest share, while after about two or three years the largest share is taken by Ce/Pr, Ru/Rh and Pm.Note that in the case of a release of radioactivity from a power reactor or used fuel, only some elements are released. As a result the isotopic signature of the radioactivity is very different from an open air nuclear detonation where all the fission products are dispersed.

text: The high short-term

text: radioactivity

text: of

text: spent nuclear fuel

text: is primarily from fission products with short

text: half-life

text: .The radioactivity in the fission product mixture is mostly short-lived isotopes such as

text: and Ba, after about four months Ce, Zr/Nb and Sr take the largest share, while after about two or three years the largest share is taken by Ce/Pr, Ru/Rh and Pm.Note that in the case of a release of radioactivity from a power reactor or used fuel, only some elements are released. As a result the isotopic signature of the radioactivity is very different from an open air nuclear detonation where all the fission products are dispersed.

text: Lyrically, the 1975 version of the song plays upon the meaning of its title, with the line "Discovered by Madame Curie (In fact, Natural radioactivity was discovered by Henri Becquerel (and independently by Silvanus Thompson); induced radioactivity by Irène Joliot-Curie, Marie Curie's daughter. Curie coined the term "radioactivity").

text: Lyrically, the 1975 version of the song plays upon the meaning of its title, with the line "Discovered by

text: Madame Curie

text: (In fact,

text: Natural radioactivity

text: was discovered by

text: Henri Becquerel

text: (and independently by

text: Silvanus Thompson

text: induced radioactivity

text: by

text: Irène Joliot-Curie

text: , Marie Curie's daughter. Curie coined the term "radioactivity").

text: Hydrogen is the only element whose isotopes have different names that are in common use today. The H (or hydrogen-2) isotope is usually called deuterium, while the H (or hydrogen-3) isotope is usually called tritium. The symbols D and T (instead of H and H) are sometimes used for deuterium and tritium. The IUPAC states in the 2005 Red Book that while the use of D and T is common, it is not preferred because it can cause problems in the alphabetic sorting of chemical formulae. The ordinary isotope of hydrogen, with no neutrons, is sometimes called "protium". (During the early study of radioactivity, some other heavy radioactive isotopes were given names, but such names are rarely used today.)

text: Hydrogen is the only

text: element

text: whose isotopes have different names that are in common use today. The H (or hydrogen-2) isotope is usually called

text: deuterium

text: , while the H (or hydrogen-3) isotope is usually called

text: tritium

text: . The symbols D and T (instead of H and H) are sometimes used for deuterium and tritium. The

text: IUPAC

text: states in the 2005

text: Red Book

text: that while the use of D and T is common, it is not preferred because it can cause problems in the alphabetic sorting of

text: chemical formula

text: e. The ordinary isotope of hydrogen, with no neutrons, is sometimes called "

text: protium

text: ". (During the early study of radioactivity, some other heavy radioactive isotopes were given

text: names

text: , but such names are rarely used today.)

text: The heaviest three primordial nuclides, Th, U, and U, are the only isotopes beyond bismuth that have half-lives measured in billions of years. Thus, they are the only such heavy isotopes to have survived since their production around ten billion years ago. Hence, thorium and uranium are the only important primordial radioactive elements. Even then, the half-life of Th is only a billionth that of Bi, the last classically stable nuclide. Th is the only isotope of thorium occurring in significant quantities in nature today, and thus thorium is usually considered to be a mononuclidic element. The reason for the existence of this "island of relative stability" at thorium and uranium, where the longest-lived isotopes have half-lives of millions or billions of years, is because the most stable isotopes of these elements have closed nuclear shells; nevertheless, since thorium and uranium have more protons than bismuth, their nuclei are thus still susceptible to alpha decay because the strong nuclear force is not strong enough to overcome the electromagnetic repulsion between their protons.

text: The heaviest three primordial nuclides, Th,

text: U

text: , and

text: U

text: , are the only isotopes beyond bismuth that have half-lives measured in billions of years. Thus, they are the only such heavy isotopes to have survived since their production around ten billion years ago. Hence, thorium and uranium are the only important

text: primordial

text: radioactive elements. Even then, the half-life of Th is only a billionth that of Bi, the last classically stable nuclide. Th is the only isotope of thorium occurring in significant quantities in nature today, and thus thorium is usually considered to be a

text: mononuclidic element

text: . The reason for the existence of this "island of relative stability" at thorium and uranium, where the longest-lived isotopes have half-lives of millions or billions of years, is because the most stable isotopes of these elements have closed nuclear shells; nevertheless, since thorium and uranium have more protons than bismuth, their nuclei are thus still susceptible to

text: alpha decay

text: because the strong nuclear force is not strong enough to overcome the electromagnetic repulsion between their protons.

text: 23 isotopes of silicon have been discovered. Five of these are naturally occurring. The most common is stable silicon-28, followed by stable silicon-29 and stable silicon-30. Silicon-32 is a radioactive isotope that occurs naturally as a result of radioactive decay of actinides, and via spallation in the upper atmosphere. Silicon-34 also occurs naturally as the result of radioactive decay of actinides.

text: isotopes of silicon

text: have been discovered. Five of these are naturally occurring. The most common is stable silicon-28, followed by stable silicon-29 and stable silicon-30. Silicon-32 is a radioactive isotope that occurs naturally as a result of radioactive decay of

text: actinides

text: , and via

text: spallation

text: in the upper atmosphere. Silicon-34 also occurs naturally as the result of radioactive decay of actinides.

text: Under acidic conditions, the carbonyl group of the acyl compound 1 is protonated, which activates it towards nucleophilic attack. In the second step, the protonated carbonyl (2) is attacked by a nucleophile (H−Z) to give tetrahedral intermediate 3. Proton transfer from the nucleophile (Z) to the leaving group (X) gives 4, which then collapses to eject the protonated leaving group (H−X), giving protonated carbonyl compound 5. The loss of a proton gives the substitution product, 6. Because the last step involves the loss of a proton, nucleophilic acyl substitution reactions are considered catalytic in acid. Also note that under acidic conditions, a nucleophile will typically exist in its protonated form (i.e. H−Z instead of Z).

text: Under

text: acid

text: ic conditions, the carbonyl group of the acyl compound 1 is protonated, which activates it towards nucleophilic attack. In the second step, the protonated carbonyl (2) is attacked by a nucleophile (H−Z) to give tetrahedral intermediate 3. Proton transfer from the nucleophile (Z) to the leaving group (X) gives 4, which then collapses to eject the protonated leaving group (H−X), giving protonated carbonyl compound 5. The loss of a proton gives the substitution product, 6. Because the last step involves the loss of a proton, nucleophilic acyl substitution reactions are considered catalytic in acid. Also note that under acidic conditions, a nucleophile will typically exist in its protonated form (i.e. H−Z instead of Z).

text: Ernest Rutherford and Frederick Soddy jointly  had continued their work on radioactive materials and concluded that radioactivity was due to a spontaneous transmutation of atomic elements. In radioactive decay, an element breaks down into another, lighter element, releasing alpha, beta, or gamma radiation in the process. They also determined that a particular isotope of a radioactive element decays into another element at a distinctive rate. This rate is given in terms of a "half-life", or the amount of time it takes half of a mass of that radioactive material to break down into its "decay product".

text: Ernest Rutherford

text: and

text: Frederick Soddy

text: jointly  had continued their work on radioactive materials and concluded that radioactivity was due to a spontaneous transmutation of atomic elements. In radioactive decay, an element breaks down into another, lighter element, releasing alpha, beta, or

text: gamma

text: radiation

text: in the process. They also determined that a particular isotope of a radioactive element decays into another element at a distinctive rate. This rate is given in terms of a "

text: half-life

text: ", or the amount of time it takes half of a mass of that radioactive material to break down into its "decay product".

text: Gary Kurfirst, who managed Talking Heads and Deborah Harry, bought the Mackenzies contract and issued their second album through his own label Radioactive, a subsidiary of MCA. After another single failed to chart, the group were persuaded to leave Radioactive by their management. The Mackenzies continued to write material; Manson was also given the opportunity to record lead vocals on a number of tracks planned for the band's third album. Although MCA had no desire to further their commitments to Goodbye Mr. Mackenzie, the label expressed interest in recording an album with Manson, and after hearing several demos, Kurfirst signed Manson to Radioactive as a solo artist, with the remaining Mackenzies performing as her backing band to circumvent the band's existing deal with MCA. Manson's contract obligated her to deliver at least one album and, at the sole option of Radioactive, up to six additional albums.

text: Gary Kurfirst

text: , who managed

text: Talking Heads

text: and

text: Deborah Harry

text: , bought the Mackenzies contract and issued their second album through his own label

text: Radioactive

text: , a subsidiary of

text: MCA

text: . After another single failed to chart, the group were persuaded to leave Radioactive by their management. The Mackenzies continued to write material; Manson was also given the opportunity to record lead vocals on a number of tracks planned for the band's third album. Although MCA had no desire to further their commitments to Goodbye Mr. Mackenzie, the label expressed interest in recording an album with Manson, and after hearing several

text: demos

text: , Kurfirst signed Manson to Radioactive as a solo artist, with the remaining Mackenzies performing as her backing band to circumvent the band's existing deal with MCA. Manson's contract obligated her to deliver at least one album and, at the sole option of Radioactive, up to six additional albums.

text: He was the leading scientist with the discovery experiments of the chemical elements darmstadtium (Ds, atomic number 110),  roentgenium (Rg, 111) and copernicium (Cn, 112). He made substantial contributions to the discovery experiments of the elements bohrium (Bh, 107), hassium (Hs, 108)  and meitnerium (Mt, 109). He participated in the discovery of the element flerovium (Fl, 114) at the Flerov Laboratory of Nuclear Reactions (FLNR) in Dubna, Russia, and his research group confirmed data measured on the synthesis of the elements flerovium and livermorium (Lv, 116) at FLNR. He identified many new isotopes located at the proton drip-line, among those the isotope Lu, the first case of radioactive emission of protons from the ground-state of a nucleus. His speciality is nuclear spectroscopy and heavy ion reactions.

text: He was the leading scientist with the discovery experiments of the chemical elements

text: darmstadtium

text: Ds

text: atomic number

text: roentgenium

text: Rg

text: , 111) and

text: copernicium

text: Cn

text: , 112). He made substantial contributions to the discovery experiments of the elements

text: bohrium

text: Bh

text: , 107),

text: hassium

text: Hs

text: , 108)  and

text: meitnerium

text: Mt

text: , 109). He participated in the discovery of the element

text: flerovium

text: Fl

text: , 114) at the

text: Flerov Laboratory of Nuclear Reactions

text: (FLNR) in

text: Dubna

text: , Russia, and his research group confirmed data measured on the synthesis of the elements flerovium and

text: livermorium

text: Lv

text: , 116) at FLNR. He identified many new isotopes located at the

text: proton drip-line

text: , among those the isotope

text: Lu

text: , the first case of radioactive emission of protons from the ground-state of a nucleus. His speciality is nuclear spectroscopy and heavy ion reactions.

text: Additionally, more than 4,000 tons of radioactive waste are stored at San Onofre.

text: Additionally, more than 4,000 tons of

text: radioactive waste

text: are stored at San Onofre.

text: It is further claimed that if radioactive isotopes such as uranium are present, the cell enables the hydrogen nuclei to fuse with these isotopes, transforming them into stable elements and thus neutralizing the radioactivity; and this would be achieved without releasing any radiation to the environment and without expending any energy. A televised demonstration on June 11, 1997, on Good Morning America was not conclusive because there was no measurement of the radioactivity of the beads after the test, thus it cannot be discarded that the beads had simply absorbed the uranium ions and become radioactive themselves. In 2002, the neutralization of radioactive isotopes has only been achieved through intense neutron bombardment in a nuclear reactor or large scale high energy particle accelerator, and at a large expense of energy.

text: It is further claimed that if

text: radioactive

text: isotope

text: s such as

text: uranium

text: are present, the cell enables the hydrogen nuclei to fuse with these isotopes, transforming them into stable

text: elements

text: and thus neutralizing the radioactivity; and this would be achieved without releasing any radiation to the environment and without expending any energy. A televised demonstration on June 11, 1997, on

text: Good Morning America

text: was not conclusive because there was no measurement of the radioactivity of the beads after the test, thus it cannot be discarded that the beads had simply absorbed the uranium ions and become radioactive themselves. In 2002, the neutralization of radioactive isotopes has only been achieved through intense neutron bombardment in a

text: nuclear reactor

text: or large scale high energy

text: particle accelerator

text: , and at a large expense of energy.

text: The Jordan Radioactive Storage Facility is a proposed national storage facility in Amman for Jordan's radioactive waste and nuclear materials.

text: The Jordan Radioactive Storage Facility is a proposed national storage facility in

text: Amman

text: for Jordan's radioactive waste and

text: nuclear materials

text: The free proton (a proton not bound to nucleons or electrons) is a stable particle that has not been observed to break down spontaneously to other particles. Free protons are found naturally in a number of situations in which energies or temperatures are high enough to separate them from electrons, for which they have some affinity. Free protons exist in plasmas in which temperatures are too high to allow them to combine with electrons. Free protons of high energy and velocity make up 90% of cosmic rays, which propagate in vacuum for interstellar distances. Free protons are emitted directly from atomic nuclei in some rare types of radioactive decay. Protons also result (along with electrons and antineutrinos) from the radioactive decay of free neutrons, which are unstable.

text: The free proton (a proton not bound to nucleons or electrons) is a stable particle that has not been observed to break down spontaneously to other particles. Free protons are found naturally in a number of situations in which energies or temperatures are high enough to separate them from electrons, for which they have some affinity. Free protons exist in

text: plasmas

text: in which temperatures are too high to allow them to combine with

text: electron

text: s. Free protons of high energy and velocity make up 90% of

text: cosmic ray

text: s, which propagate in vacuum for interstellar distances. Free protons are

text: emitted directly

text: from

text: atomic nuclei

text: in some rare types of

text: radioactive decay

text: . Protons also result (along with electrons and

text: antineutrino

text: s) from the

text: radioactive decay

text: of free neutrons, which are unstable.

text: The K-431, completed around 1965 as unit K-31, was a Project 675 (Echo II) class submarine with two pressurized water reactors, each 70 MW capacity and using 20% enriched uranium as fuel. On 10 August 1985, the submarine was being refuelled at the Chazhma Bay naval facility near Vladivostok. The submarine had been refuelled and the reactor tank lid was being replaced. The lid was laid incorrectly and had to be lifted again with the control rods attached. A beam was supposed to prevent the lid from being lifted too far, but this beam was positioned incorrectly, and the lid with control rods was lifted up too far. At 10:55 AM the starboard reactor became prompt critical, resulting in a criticality excursion of about 5·10 fissions and a thermal/steam explosion. The explosion expelled the new load of fuel, destroyed the machine enclosures, ruptured the submarine's pressure hull and aft bulkhead, and partially destroyed the fuelling shack, with the shack's roof falling 70 metres away in the water. A fire followed, which was extinguished after 4 hours, after which assessment of the radioactive contamination began. Most of the radioactive debris fell within 50–100 metres of the submarine, but a cloud of radioactive gas and particulates blew to the northwest across a 6 km stretch of the Dunay Peninsula, missing the town of Shkotovo-22, 1.5 km from the dock. The contaminated forest area was later surveyed as 2 km in a swath 3.5 km long and 200 to 650 metres wide. Initial estimates of the radioactive release were about 74 PBq (2 MCi) of noble gases and 185 PBq (5 MCi) of other fission products, but most of this was short-lived isotopes; the estimated release inventory one hour after the accident was about 37 TBq (1000 Ci) of non-noble fission products. In part because the reactor did not contain spent fuel, the fraction of biologically active isotopes was far smaller than in the case of the Chernobyl disaster.

text: The K-431, completed around 1965 as unit K-31, was a Project 675 (

text: Echo II

text: ) class submarine with two

text: pressurized water reactor

text: s, each 70 MW capacity and using 20%

text: enriched uranium

text: as fuel. On 10 August 1985, the submarine was being refuelled at the Chazhma Bay naval facility near

text: Vladivostok

text: . The submarine had been refuelled and the reactor tank lid was being replaced. The lid was laid incorrectly and had to be lifted again with the control rods attached. A beam was supposed to prevent the lid from being lifted too far, but this beam was positioned incorrectly, and the lid with control rods was lifted up too far. At 10:55 AM the

text: starboard

text: reactor became

text: prompt critical

text: , resulting in a

text: criticality excursion

text: of about 5·10

text: fissions

text: and a thermal/steam explosion. The explosion expelled the new load of fuel, destroyed the machine enclosures, ruptured the submarine's pressure hull and aft bulkhead, and partially destroyed the fuelling shack, with the shack's roof falling 70 metres away in the water. A fire followed, which was extinguished after 4 hours, after which assessment of the

text: radioactive contamination

text: began. Most of the radioactive debris fell within 50–100 metres of the submarine, but a cloud of

text: radioactive

text: gas and

text: particulate

text: s blew to the northwest across a 6 km stretch of the

text: Dunay Peninsula

text: , missing the town of

text: , 1.5 km from the dock. The contaminated forest area was later surveyed as 2 km in a swath 3.5 km long and 200 to 650 metres wide. Initial estimates of the radioactive release were about 74

text: PBq

text: MCi

text: ) of

text: noble gas

text: es and 185 PBq (5 MCi) of other

text: fission product

text: s, but most of this was short-lived

text: isotope

text: s; the estimated release inventory one hour after the accident was about 37 TBq (1000 Ci) of non-noble fission products. In part because the reactor did not contain spent fuel, the fraction of biologically active isotopes was far smaller than in the case of the

text: Chernobyl disaster

text: In 1948, a radioactive mineral discovered in Congo, Sengierite, was named in his honor.

text: In 1948, a radioactive mineral discovered in Congo,

text: Sengierite

text: , was named in his honor.

text: Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay. When such nuclides are referred to in relation to specific elements, they are usually termed stable isotopes.

text: Stable nuclides are

text: nuclide

text: s that are not radioactive and so (unlike

text: radionuclide

text: s) do not spontaneously undergo

text: radioactive decay

text: . When such nuclides are referred to in relation to specific elements, they are usually termed

text: stable isotope

text: s.

text: All methods based on the radioactive decay belong to this category. The principle at the base of radiometric dating is that natural unstable isotopes, called 'parent isotopes', decay to some isotope which is instead stable, called the 'daughter isotope'. Under the assumptions that (1) the initial amount of parent and daughter isotopes can be estimated, and (2) after the geologic material formed, parent and daughter isotopes did not escape the system, the age of the material can be obtained from the measurement of isotope concentrations, through the laws of radioactive decay.Methods of this kind are usually identified with the names of the parent/daughter elements. The radiometric methods under this category are:

text: All methods based on the

text: radioactive decay

text: belong to this category. The principle at the base of

text: radiometric dating

text: is that natural unstable

text: isotope

text: s, called 'parent isotopes', decay to some

text: isotope

text: which is instead stable, called the 'daughter isotope'. Under the assumptions that (1) the initial amount of parent and daughter isotopes can be estimated, and (2) after the geologic material formed, parent and daughter isotopes did not escape the system, the age of the material can be obtained from the measurement of isotope concentrations, through the laws of

text: radioactive decay

text: .Methods of this kind are usually identified with the names of the parent/daughter elements. The radiometric methods under this category are:

text: Marie Skłodowska-Curie was a Polish-born French physicist and chemist who is famous for her pioneering research on radioactivity. She and her husband are considered to have laid the cornerstone of the nuclear age with their research on radioactivity. Marie was fascinated with the work of Henri Becquerel, a French physicist who discovered in 1896 that uranium casts off rays similar to the X-rays discovered by Wilhelm Röntgen. Marie Curie began studying uranium in late 1897 and theorized, according to a 1904 article she wrote for Century magazine, "that the emission of rays by the compounds of uranium is a property of the metal itself—that it is an atomic property of the element uranium independent of its chemical or physical state." Curie took Becquerel's work a few steps further, conducting her own experiments on uranium rays. She discovered that the rays remained constant, no matter the condition or form of the uranium. The rays, she theorized, came from the element's atomic structure. This revolutionary idea created the field of atomic physics and the Curies coined the word radioactivity to describe the phenomena.

text: Marie Skłodowska-Curie

text: was a Polish-born French physicist and chemist who is famous for her pioneering research on

text: radioactivity

text: . She and her husband are considered to have laid the cornerstone of the nuclear age with their research on radioactivity. Marie was fascinated with the work of

text: Henri Becquerel

text: , a French physicist who discovered in 1896 that uranium casts off rays similar to the

text: X-ray

text: s discovered by

text: Wilhelm Röntgen

text: . Marie Curie began studying uranium in late 1897 and theorized, according to a 1904 article she wrote for Century magazine, "that the emission of rays by the compounds of uranium is a property of the metal itself—that it is an atomic property of the element uranium independent of its chemical or physical state." Curie took Becquerel's work a few steps further, conducting her own experiments on uranium rays. She discovered that the rays remained constant, no matter the condition or form of the uranium. The rays, she theorized, came from the element's atomic structure. This revolutionary idea created the field of

text: atomic physics

text: and the Curies coined the word radioactivity to describe the phenomena.

text: In May 1968, anti-nuclear activists alleged that Swordfish had released radioactive coolant water into the harbor of Sasebo, Japan where she was moored at the time. Some sources state that Japanese scientists discovered levels up to twenty times normal background, others, that they could not detect any increase in radioactivity. The Japanese protested the incident to the United States, and Japanese Premier Eisaku Sato stated that U.S. nuclear ships would no longer be allowed to call at Japanese ports unless their safety could be guaranteed.

text: In May 1968, anti-nuclear activists alleged that Swordfish had released radioactive coolant water into the harbor of

text: Sasebo, Japan

text: where she was moored at the time. Some sources state that Japanese scientists discovered levels up to twenty times normal background, others, that they could not detect any increase in radioactivity. The Japanese protested the incident to the United States, and Japanese Premier

text: Eisaku Sato

text: stated that U.S. nuclear ships would no longer be allowed to call at Japanese ports unless their safety could be guaranteed.

text: There are nine known isotopes of helium, but only helium-3 and helium-4 are stable. In the Earth's atmosphere, one atom is  for every million that are . Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. The most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements; the alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged into complete shells. It was also formed in enormous quantities during Big Bang nucleosynthesis.

text: There are nine known

text: isotope

text: s of helium, but only

text: and

text: are

text: stable

text: . In the Earth's atmosphere, one atom is  for every million that are . Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. The most common isotope, helium-4, is produced on Earth by

text: alpha decay

text: of heavier radioactive elements; the alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its

text: nucleon

text: s are arranged into

text: complete shells

text: . It was also formed in enormous quantities during

text: Big Bang nucleosynthesis

text: In case of a radioactive release, most plants have a system designed to remove radioactivity from the air to reduce the effects of the radioactivity release on the employees and public. This system usually consists of containment ventilation that removes radioactivity and steam from primary containment. Control room ventilation ensures that plant operators are protected. This system often consists of activated charcoal filters that remove radioactive isotopes from the air.

text: In case of a radioactive release, most plants have a system designed to remove radioactivity from the air to reduce the effects of the radioactivity release on the employees and public. This system usually consists of containment ventilation that removes radioactivity and steam from primary containment. Control room ventilation ensures that plant operators are protected. This system often consists of

text: activated charcoal

text: filters that remove radioactive isotopes from the air.

text: Aluminium-26, Al, is a radioactive isotope of the chemical element aluminium, decaying by either of the modes beta-plus or electron capture, both resulting in the stable nuclide magnesium-26. The half-life of Al is 7.17 years. This is far too short for the isotope to survive to the present, but a small amount of the nuclide is produced by collisions of argon atoms with cosmic ray protons.

text: Aluminium-26, Al, is a

text: radioactive

text: isotope

text: of the

text: chemical element

text: aluminium

text: , decaying by either of the

text: modes

text: beta-plus

text: or

text: electron capture

text: , both resulting in the stable

text: nuclide

text: magnesium

text: -26. The

text: half-life

text: of Al is 7.17 years. This is far too short for the isotope to survive to the present, but a small amount of the nuclide is produced by collisions of

text: argon

text: atoms with

text: cosmic ray

text: proton

text: s.

text: At a news conference TEPCO Chairman Tsunehisa Katsumata announces that it is unclear how the problems at the plant will be resolved. An immediate difficulty is the removal of large quantities of radioactive water in the basement buildings, but also salt build up inside the reactors, from using seawater for cooling, will need to be removed. Building concrete walls to enclose the reactors in a shield is being considered, as had been done at Chernobyl. The Environmental Protection Agency (EPA) finds radioactive iodine in milk in the United States.

text: In nuclear physics, the valley of stability (also called the nuclear valley, energy valley, or beta stability valley) is a characterization of the stability of nuclides to radioactivity based on their binding energy.   Nuclides are composed of protons and neutrons.  The shape of the valley refers to the profile of binding energy as a function of the numbers of neutrons and protons, with the lowest part of the valley corresponding to the region of most stable nuclei.  The line of stable nuclides down the center of the valley of stability is known as the line of beta stability.  The sides of the valley correspond to increasing instability to beta decay (β or β). The decay of a nuclide becomes more energetically favorable the further it is from the line of beta stability.  The boundaries of the valley correspond to the nuclear drip lines, where nuclides become so unstable they emit single protons or single neutrons.  Regions of instability within the valley at high atomic number also include radioactive decay by alpha radiation or spontaneous fission.  The shape of the valley is roughly an elongated paraboloid corresponding to the nuclide binding energies as a function of neutron and atomic numbers.

text: In

text: nuclear physics

text: , the valley of stability (also called the nuclear valley, energy valley, or beta stability valley) is a characterization of the stability of

text: nuclide

text: s to

text: radioactivity

text: based on their binding energy.   Nuclides are composed of

text: proton

text: s and

text: neutron

text: s.  The shape of the valley refers to the profile of binding energy as a function of the numbers of neutrons and protons, with the lowest part of the valley corresponding to the region of most

text: stable nuclei

text: .  The line of stable nuclides down the center of the valley of stability is known as the

text: line of beta stability

text: .  The sides of the valley correspond to increasing instability to

text: beta decay

text: (β or β). The decay of a nuclide becomes more energetically favorable the further it is from the line of beta stability.  The boundaries of the valley correspond to the

text: nuclear drip line

text: s, where nuclides become so unstable they emit

text: single protons

text: or

text: single neutrons

text: .  Regions of instability within the valley at high atomic number also include radioactive decay by

text: alpha radiation

text: or

text: spontaneous fission

text: .  The shape of the valley is roughly an elongated

text: paraboloid

text: corresponding to the nuclide

text: binding energies

text: as a function of neutron and atomic numbers.

text: A chemical element or element is a species of atoms having the same number of protons in their atomic nuclei (i.e. the same atomic number, Z). There are 118 elements that have been identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. There are 80 elements that have at least one stable isotope and 38 that have exclusively radioactive isotopes, which decay over time into other elements. Iron is the most abundant element (by mass) making up Earth, while oxygen is the most common element in the Earth's crust.

text: A chemical element or element is a species of

text: atom

text: s having the same number of

text: proton

text: s in their

text: atomic nuclei

text: (i.e. the same

text: atomic number

text: , Z). There are 118 elements that have been identified, of which the first 94 occur naturally on

text: Earth

text: with the remaining 24 being

text: synthetic elements

text: . There are 80 elements that have at least one stable

text: isotope

text: and 38 that have exclusively

text: radioactive isotopes

text: , which decay over time into other elements.

text: Iron

text: is the

text: most abundant element

text: (by

text: mass

text: ) making up Earth, while

text: oxygen

text: is the most common element in the

text: Earth's crust

text: "Radioactive" is a song by American rock band Imagine Dragons for their major-label debut EP Continued Silence and later on their debut studio album, Night Visions (2012), as the opening track. "Radioactive" was first sent to modern rock radio on October 29, 2012, and released to contemporary radio on April 9, 2013. Musically, "Radioactive" is an electronic rock and alternative rock song with elements of dubstep and contains cryptic lyrics about apocalyptic and revolutionist themes.

text: "Radioactive" is a song by American

text: rock

text: band

text: Imagine Dragons

text: for their major-label debut

text: EP

text: Continued Silence

text: and later on their debut studio album,

text: Night Visions

text: (2012), as the opening track. "Radioactive" was first sent to modern rock radio on October 29, 2012, and released to contemporary radio on April 9, 2013. Musically, "Radioactive" is an

text: electronic rock

text: and

text: alternative rock

text: song with elements of

text: dubstep

text: and contains cryptic lyrics about apocalyptic and revolutionist themes.

text: As the atom came to be better understood, the nature of radioactivity became clearer. Some larger atomic nuclei are unstable, and so decay (release matter or energy) after a random interval. The three forms of radiation that Becquerel and the Curies discovered are also more fully understood. Alpha decay is when a nucleus releases an alpha particle, which is two protons and two neutrons, equivalent to a helium nucleus. Beta decay is the release of a beta particle, a high-energy electron. Gamma decay releases gamma rays, which unlike alpha and beta radiation are not matter but electromagnetic radiation of very high frequency, and therefore energy. This type of radiation is the most dangerous and most difficult to block. All three types of radiation occur naturally in certain elements.

text: As the atom came to be better understood, the nature of radioactivity became clearer. Some larger atomic nuclei are unstable, and so

text: decay

text: (release matter or energy) after a random interval. The three forms of

text: radiation

text: that Becquerel and the Curies discovered are also more fully understood.

text: Alpha decay

text: is when a nucleus releases an

text: alpha particle

text: , which is two

text: proton

text: s and two

text: neutron

text: s, equivalent to a

text: helium

text: nucleus.

text: Beta decay

text: is the release of a

text: beta particle

text: , a high-energy

text: electron

text: Gamma decay

text: releases

text: gamma rays

text: , which unlike alpha and beta radiation are not matter but

text: electromagnetic radiation

text: of very high

text: frequency

text: , and therefore

text: energy

text: . This type of radiation is the most dangerous and most difficult to block. All three types of radiation occur naturally in

entity_name: List of elements by stability of isotopes

text: certain elements

text: There are many different types of radioactive decay. A decay, or loss of energy from the nucleus, results when an atom with an initial type of nucleus, called the parent radionuclide (or parent radioisotope), transforms into a daughter nuclide. The transformation produces an atom in a different state (a nucleus containing a different number of protons and neutrons). In some decays, the parent and the daughter nuclides are different chemical elements, and thus the decay process results in the creation of an atom of a different element. This is known as a nuclear transmutation.

text: There are many different types of radioactive decay. A decay, or loss of energy from the nucleus, results when an atom with an initial type of nucleus, called the parent

text: radionuclide

text: (or parent radioisotope), transforms into a daughter nuclide. The transformation produces an atom in a different state (a nucleus containing a different number of

text: proton

text: s and

text: neutron

text: s). In some decays, the parent and the daughter nuclides are different

text: chemical element

text: s, and thus the decay process results in the creation of an atom of a different element. This is known as a

text: nuclear transmutation

text: Wednesday 19 February 2014 late in the evening a leakage was found near a storage tank with radioactive water. The water contained 230.000.000 bq/l. The water did flow over the barrier around the tank, into the grounds around it. TEPCO estimated that some 100 metric tons were lost.  After the waterflow into the tank was cut off, the leakage stopped, According to TEPCO nothing was flown into the ocean nearby. Further investigations were done after the cause of the leakage. A valve was opened by error, this caused an inflow of water to the tank. Around 2 p.m. on 19 Feb. an alarm went off, indicating that the tank was dangerously filled. This alarm was ignored, because no radioactive water was transferred to the tank. The tank, however, got overfilled, and the radioactive access water left the tank along the rain-gutter. Because all rainwater is directed outside the barriers around the tanks, the overflowing radioactive water seeped directly into the grounds. According to TEPCO all leakage was due to human error. The patrols were doubled to twice a day, and the number of workers involved was increased 6 times to 60 people. Because the leak was about 700 meters from the coastal line, TEPCO did believe that none of this water had reached the ocean.

text: On the other hand, in the analysis of trace elements, as is often the case in radiochemistry, coprecipitation is often the only way of separating an element. Since the trace element is too dilute (sometimes less than a part per trillion) to precipitate by conventional means, it is typically coprecipitated with a carrier, a substance that has a similar crystalline structure that can incorporate the desired element. An example is the separation of francium from other radioactive elements by coprecipitating it with caesium salts such as caesium perchlorate. Otto Hahn is credited for promoting the use of coprecipitation in radiochemistry.

text: On the other hand, in the analysis of trace elements, as is often the case in

text: radiochemistry

text: , coprecipitation is often the only way of separating an element. Since the trace element is too dilute (sometimes less than a part per trillion) to precipitate by conventional means, it is typically coprecipitated with a carrier, a substance that has a similar crystalline structure that can incorporate the desired element. An example is the separation of

text: francium

text: from other radioactive elements by coprecipitating it with

text: caesium

text: salts such as

text: caesium perchlorate

text: Otto Hahn

text: is credited for promoting the use of coprecipitation in radiochemistry.

text: Some isotopes that are classed as stable (i.e. no radioactivity has been observed for them) are predicted to have extremely long half-lives (sometimes as high as 10 years or more). If the predicted half-life falls into an experimentally accessible range, such isotopes have a chance to move from the list of stable nuclides to the radioactive category, once their activity is observed. E.g. Bi and W were formerly classed as stable, but have been recently (2003) found to be alpha-active. However, such nuclides do not change their status as primordial when they are found to be radioactive.

text: Some isotopes that are classed as stable (i.e. no radioactivity has been observed for them) are predicted to have extremely long half-lives (sometimes as high as 10 years or more). If the predicted half-life falls into an experimentally accessible range, such isotopes have a chance to move from the list of stable nuclides to the radioactive category, once their activity is observed. E.g. Bi and W were formerly classed as stable, but have been recently (2003) found to be

text: alpha

text: -active. However, such nuclides do not change their status as primordial when they are found to be radioactive.

text: Having arisen from the fields of knowledge representation, description logic and formal ontology, Semantic Web languages have a closer relationship to philosophical ontology than do conventional programming languages such as Java or Python. Accordingly, the nature of metaclasses is informed by philosophical notions such as abstract objects, the abstract and concrete, and type-token distinction.  Metaclasses permit concepts to be construed as tokens of other concepts while retaining their ontological status as types.  This enables types to be enumerated over, while preserving the ability to inherit from types.  For example, metaclasses could allow a machine reasoner to infer from a human-friendly ontology how many elements are in the periodic table, or, given that number of protons is a property of chemical element and isotopes are a subclass of elements, how many protons exist in the isotope hydrogen-2.

text: Having arisen from the fields of

text: knowledge representation

text: description logic

text: and

text: formal ontology

text: , Semantic Web languages have a closer relationship to

text: philosophical ontology

text: than do conventional programming languages such as

text: Java

text: or

text: Python

text: . Accordingly, the nature of metaclasses is informed by philosophical notions such as

text: abstract objects

text: , the

text: abstract and concrete

text: , and

text: type-token distinction

text: .  Metaclasses permit concepts to be construed as tokens of other concepts while retaining their ontological status as types.  This enables types to be enumerated over, while preserving the ability to inherit from types.  For example, metaclasses could allow a machine reasoner to infer from a human-friendly ontology how many

text: elements

text: are in the

text: periodic table

text: , or, given that

text: number of protons

text: is a property of chemical element and isotopes are a subclass of elements, how many protons exist in the isotope

text: Unlike the Schrödinger's cat thought experiment which used hydrocyanic acid and a radioactive decay trigger, this version involves a life-terminating device and a device that measures the spin value of protons. Every 10 seconds, the spin value of a fresh proton is measured. Conditioned upon that quantum bit, the weapon is either deployed, killing the experimenter, or it makes an audible "click" and the experimenter survives.

text: Unlike the

text: Schrödinger's cat

text: thought experiment which used hydrocyanic acid and a radioactive decay trigger, this version involves a life-terminating device and a device that measures the

text: spin value

text: of protons. Every 10 seconds, the spin value of a fresh proton is measured. Conditioned upon that quantum bit, the weapon is either deployed, killing the experimenter, or it makes an audible "click" and the experimenter survives.

text: In nuclear physics and radioactivity, isodiaphers refers to nuclides which have different atomic numbers and mass numbers but the same neutron excess, which is the difference between numbers of neutrons and protons in the nucleus. For example, for both  and  the difference between the neutron number (N) and proton number (Z) is N − Z = 54.

text: In

text: nuclear physics

text: and

text: radioactivity

text: , isodiaphers refers to

text: nuclide

text: s which have different

text: atomic number

text: s and

text: mass number

text: s but the same

text: neutron excess

text: , which is the

text: difference

text: between numbers of

text: neutron

text: s and

text: proton

text: s in the

text: nucleus

text: . For example, for both  and  the difference between the

text: neutron number

text: (N) and

text: proton number

text: (Z) is N − Z = 54.

text: The test does not directly assert the presence of radioactive material. A successful test asserts that the claim of no radioactive material present is unlikely given the reading (and therefore ...). The double negative (disproving the null hypothesis) of the method is confusing, but using a counter-example to disprove is standard mathematical practice. The attraction of the method is its practicality. We know (from experience) the expected range of counts with only ambient radioactivity present, so we can say that a measurement is unusually large. Statistics just formalizes the intuitive by using numbers instead of adjectives. We probably do not know the characteristics of the radioactive suitcases; We just assumethat they produce larger readings.

text: The entire silicon-burning sequence lasts about one day in the core of a contracting massive star and stops after nickel-56 has become the dominant abundance. The explosive burning caused when the supernova shock passes through the silicon-burning shell lasts only seconds but is the major contributor to nucleosynthesis in the mass range 28-60.  The star can no longer release energy via nuclear fusion because a nucleus with 56 nucleons has the lowest mass per nucleon of all the elements in the sequence. The next step up in the alpha-particle chain would be Zn, which has slightly more mass per nucleon and thus is less thermodynamically favorable. Ni (which has 28 protons) has a half-life of 6.02 days and decays via β decay to Co (27 protons), which in turn has a half-life of 77.3 days as it decays to Fe (26 protons). However, only minutes are available for the Ni to decay within the core of a massive star.  This establishes Ni  as the most abundant of the radioactive nuclei created in this way. Its radioactivity energizes the late supernova light curve and creates the pathbreaking opportunity for gamma-ray-line astronomy.  See SN 1987A light curve for the aftermath of that opportunity.

text: The entire silicon-burning sequence lasts about one day in the core of a contracting massive star and stops after nickel-56 has become the dominant abundance. The explosive burning caused when the supernova shock passes through the silicon-burning shell lasts only seconds but is the major contributor to nucleosynthesis in the mass range 28-60.  The star can no longer release energy via nuclear fusion because a nucleus with 56 nucleons has the lowest

text: mass

text: per

text: nucleon

text: of all the elements in the sequence. The next step up in the alpha-particle chain would be Zn, which has slightly more mass per nucleon and thus is less thermodynamically favorable. Ni (which has 28 protons) has a

text: half-life

text: of 6.02 days and decays via

text: β decay

text: to Co (27 protons), which in turn has a half-life of 77.3 days as it decays to Fe (26 protons). However, only minutes are available for the Ni to decay within the core of a massive star.  This establishes Ni  as the most abundant of the radioactive nuclei created in this way. Its radioactivity energizes the late

text: supernova

text: light curve

text: and creates the pathbreaking opportunity for gamma-ray-line astronomy.  See

text: SN 1987A light curve

text: for the aftermath of that opportunity.

text: Protons have a positive charge and a mass 1,836 times that of the electron, at . The number of protons in an atom is called its atomic number. Ernest Rutherford (1919) observed that nitrogen under alpha-particle bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it proton.

text: Protons have a positive charge and a mass 1,836 times that of the electron, at . The number of protons in an atom is called its

text: atomic number

text: Ernest Rutherford

text: (1919) observed that nitrogen under alpha-particle bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it

text: proton

text: is an intermediate in the first step of the proton-proton chain reaction. The first step of the proton-proton chain reaction is a two-stage process; first, two protons fuse to form a diproton:

text: is an intermediate in the first step of the

text: proton-proton chain reaction

text: . The first step of the proton-proton chain reaction is a two-stage process; first, two protons fuse to form a diproton:

text: Citations of D.N.  Poenaru et al.  papers on heavy particle radioactivities started in 1984 after the first experimental confirmation by Rose and Jones of the 14C radioactivity of 223Ra.

text: Otto Hahn is considered a pioneer of radioactivity and radiochemistry and discovered nuclear fission, the scientific and technological basis of atomic energy.

text: Otto Hahn

text: is considered a pioneer of

text: radioactivity

text: and

text: radiochemistry

text: and discovered

text: nuclear fission

text: , the scientific and technological basis of

text: atomic energy

text: The first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, an excited nucleus emits a gamma ray almost immediately upon formation (it is now understood that a nuclear isomeric transition, however, can produce inhibited gamma decay with a measurable and much longer half-life). Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium. Villard knew that his described radiation was more powerful than previously described types of rays from radium, which included beta rays, first noted as "radioactivity" by Henri Becquerel in 1896, and alpha rays, discovered as a less penetrating form of radiation by Rutherford, in 1899. However, Villard did not consider naming them as a different fundamental type. Villard's radiation was recognized as being of a type fundamentally different from previously named rays, by Ernest Rutherford, who in 1903 named Villard's rays "gamma rays" by analogy with the beta and alpha rays that Rutherford had differentiated in 1899. The "rays" emitted by radioactive elements were named in order of their power to penetrate various materials, using the first three letters of the Greek alphabet: alpha rays as the least penetrating, followed by beta rays, followed by gamma rays as the most penetrating. Rutherford also noted that gamma rays were not deflected (or at least, not easily deflected) by a magnetic field, another property making them unlike alpha and beta rays.

text: The first gamma ray source to be discovered historically was the

text: radioactive decay

text: process called gamma decay. In this type of decay, an

text: excited

text: nucleus emits a gamma ray almost immediately upon formation (it is now understood that a nuclear

text: isomeric transition

text: , however, can produce inhibited gamma decay with a measurable and much longer half-life).

text: Paul Villard

text: , a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from

text: radium

text: . Villard knew that his described radiation was more powerful than previously described types of rays from radium, which included

text: beta ray

text: s, first noted as "radioactivity" by

text: Henri Becquerel

text: in 1896, and

text: alpha ray

text: s, discovered as a less penetrating form of radiation by Rutherford, in 1899. However, Villard did not consider naming them as a different fundamental type. Villard's radiation was recognized as being of a type fundamentally different from previously named rays, by

text: Ernest Rutherford

text: , who in 1903 named Villard's rays "gamma rays" by analogy with the beta and alpha rays that Rutherford had differentiated in 1899. The "rays" emitted by radioactive elements were named in order of their power to penetrate various materials, using the first three letters of the Greek alphabet:

text: alpha ray

text: s as the least penetrating, followed by

text: beta ray

text: s, followed by gamma rays as the most penetrating. Rutherford also noted that gamma rays were not deflected (or at least, not easily deflected) by a magnetic field, another property making them unlike alpha and beta rays.

text: The overall theory is that radioactive rock has always been present in the earth, and it is generally harmless to human populations.  Further, Cigar Lake and Oklo have proven that actinides do not easily migrate via ground water or other means.  Spent fuel consists of radioactive ceramic, cooled until its short-half-life radioactives have decayed, so its heat-production is negligible.  When initially made, the ceramic fuel is also wrapped in sealed tubes of corrosion-resistant zirconium alloy.  Therefore, spent fuel is not water-soluble in any conventional sense, and is mechanically sturdy.  The other elements: crystalline bedrock, corrosion-resistant copper cylinders, etc. have been scientifically proven to reduce the exposure to ground water, and the rate at which it can penetrate to the fuel and dissolve it. Further, if correctly sited, any leakage will enter seawater, providing a safe dilution to decay.  Geological stability against earthquakes and other extreme events can be further reduced by careful site-selection. These safety factors multiply, extending the containment lifetime until most radioactive elements in the fuel have decayed, and only the longest-lived, least-radioactive isotopes remain.  At this point, the contents of the repository are at least as safe as natural deposits of uranium. The process has been extensively studied and depends on well-understood chemistry and geology.

text: The overall theory is that radioactive rock has always been present in the earth, and it is generally harmless to human populations.  Further, Cigar Lake and Oklo have proven that

text: actinides

text: do not easily migrate via ground water or other means.  Spent fuel consists of radioactive ceramic, cooled until its short-half-life radioactives have decayed, so its heat-production is negligible.  When initially made, the ceramic fuel is also wrapped in sealed tubes of corrosion-resistant

text: zirconium alloy

text: .  Therefore, spent fuel is not water-soluble in any conventional sense, and is mechanically sturdy.  The other elements: crystalline bedrock, corrosion-resistant copper cylinders, etc. have been scientifically proven to reduce the exposure to ground water, and the rate at which it can penetrate to the fuel and dissolve it. Further, if correctly sited, any leakage will enter seawater, providing a safe dilution to decay.  Geological stability against earthquakes and other extreme events can be further reduced by careful site-selection. These safety factors multiply, extending the containment lifetime until most radioactive elements in the fuel have decayed, and only the longest-lived, least-radioactive isotopes remain.  At this point, the contents of the repository are at least as safe as natural deposits of uranium. The process has been extensively studied and depends on well-understood chemistry and geology.

text: While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one type of atom at each position on the periodic table. The term isotope was coined by Margaret Todd as a suitable name for different atoms that belong to the same element. J.J. Thomson created a technique for separating atom types through his work on ionized gases, which subsequently led to the discovery of stable isotopes.

text: While experimenting with the products of

text: radioactive decay

text: , in 1913

text: radiochemist

text: Frederick Soddy

text: discovered that there appeared to be more than one type of atom at each position on the periodic table. The term

text: isotope

text: was coined by

text: Margaret Todd

text: as a suitable name for different atoms that belong to the same element. J.J. Thomson created a technique for separating atom types through his work on ionized gases, which subsequently led to the discovery of

text: stable isotope

text: s.

text: Most commercial nuclear power plants release gaseous and liquid radiological effluents into the environment as a byproduct of the Chemical Volume Control System, which are monitored in the US by the EPA and the NRC. Civilians living within  of a nuclear power plant typically receive about 0.1 μSv per year. For comparison, the average person living at or above sea level receives at least 260 μSv from cosmic radiation.All reactors in the United States are required by law to have a containment building.  The walls of containment buildings are several feet thick and made of concrete and therefore can stop the release of any radiation emitted by the reactor into the environment. If a person is to worry about an energy source that releases large amounts of radiation into the environment, they should worry about coal-fired plants.  Hundreds of tons of uranium and thorium are contained in the ash released into the environment by coal-fired plants.   Coal-fired plants are not required to retain their radioactive wastes like nuclear power plants are but rather “expel their radioactive by-products into the environment and expose people to anywhere from one hundred to four hundred times more radiation than nuclear plants do” (Cravens 2007).  Coal-fired plants are much more hazardous to people’s health than nuclear power plants as they release much more radioactive elements into the environment.

text: Most commercial nuclear power plants release gaseous and liquid radiological effluents into the environment as a byproduct of the Chemical Volume Control System, which are monitored in the US by the EPA and the NRC. Civilians living within  of a nuclear power plant typically receive about 0.1

text: μSv

text: per year. For comparison, the average person living at or above sea level receives at least 260 μSv from

text: cosmic radiation

text: .All reactors in the United States are required by law to have a containment building.  The walls of containment buildings are several feet thick and made of concrete and therefore can stop the release of any radiation emitted by the reactor into the environment. If a person is to worry about an energy source that releases large amounts of radiation into the environment, they should worry about coal-fired plants.  Hundreds of tons of uranium and thorium are contained in the ash released into the environment by coal-fired plants.   Coal-fired plants are not required to retain their radioactive wastes like nuclear power plants are but rather “expel their radioactive by-products into the environment and expose people to anywhere from one hundred to four hundred times more radiation than nuclear plants do” (Cravens 2007).  Coal-fired plants are much more hazardous to people’s health than nuclear power plants as they release much more radioactive elements into the environment.

text: In the fall of 1907, Sahlbom was admitted to the University of Basel. To proceed with her studies, she declined a research offer from Sjögren. Advised by Friedrich Fichter from the University of Basel, Sahlbom completed her thesis, an investigation on a capillary analysis of colloidal solutions. In 1910 Sahlbom presented the thesis at the University of Neuchâtel, and she earned a doctorate in chemical physics. In 1914, with input from Helge Backlund, Sahlbom set up a laboratory in Stockholm, where she specialized in aqueous mineralogy. A self-employed chemical analyst, Sahlbom was contracted by mineralogists and petrographers for her proficient work. In 1916 she published a second report on mineralogy and radioactivity, with 400 springs and wells analyzed. The paper confirmed that the radioactivity of mineral waters was related to geology. Overall, acid and primary rocks resulted in the most radioactive emanation; mafic and sedimentary rocks demonstrated less radioactivity.

text: In the fall of 1907, Sahlbom was admitted to the

text: University of Basel

text: . To proceed with her studies, she declined a research offer from Sjögren. Advised by

text: Friedrich Fichter

text: from the University of Basel, Sahlbom completed her thesis, an investigation on a capillary analysis of

text: colloidal

text: solutions. In 1910 Sahlbom presented the thesis at the

text: University of Neuchâtel

text: , and she earned a doctorate in

text: chemical physics

text: . In 1914, with input from Helge Backlund, Sahlbom set up a laboratory in Stockholm, where she specialized in aqueous mineralogy. A self-employed chemical analyst, Sahlbom was contracted by mineralogists and

text: petrographers

text: for her proficient work. In 1916 she published a second report on mineralogy and radioactivity, with 400 springs and wells analyzed. The paper confirmed that the radioactivity of mineral waters was related to geology. Overall, acid and primary rocks resulted in the most radioactive emanation; mafic and sedimentary rocks demonstrated less radioactivity.

text: 118 chemical elements are known to exist. All elements to element 94 are found in nature, and the remainder of the discovered elements are artificially produced, with isotopes all known to be highly radioactive with relatively short half-lives (see below). The elements in this list are ordered according to the lifetime of their most stable isotope. Of these, three elements (bismuth, thorium, and uranium) are primordial because they have half-lives long enough to still be found on the Earth, while all the others are produced either by radioactive decay or are synthesized in laboratories and nuclear reactors. Only 13 of the 38 known-but-unstable elements (assuming the total number of elements is 118) have isotopes with a half-life of at least 100 years. Every known isotope of the remaining 25 elements is highly radioactive; these are used in academic research and sometimes in industry and medicine. Some of the heavier elements in the periodic table may be revealed to have yet-undiscovered isotopes with longer lifetimes than those listed here.

text: chemical elements

text: are known to exist. All elements to element 94 are found in nature, and the remainder of the

entity_name: Timeline of chemical element discoveries

text: discovered elements

text: are artificially produced, with isotopes all known to be highly

text: radioactive

text: with relatively short half-lives (see below). The elements in this list are ordered according to the lifetime of their most stable isotope. Of these, three elements (

text: bismuth

text: thorium

text: , and

text: uranium

text: ) are primordial because they have half-lives long enough to still be found on the Earth, while all the others are produced either by

text: radioactive decay

text: or are

text: synthesized

text: in laboratories and

text: nuclear reactors

text: . Only 13 of the 38 known-but-unstable elements (assuming the total number of elements is 118) have isotopes with a half-life of at least 100 years. Every known isotope of the remaining 25 elements is highly radioactive; these are used in academic research and sometimes in industry and medicine. Some of the heavier elements in the periodic table may be revealed to have yet-undiscovered isotopes with longer lifetimes than those listed here.

text: TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN) measures the mass of short-lived isotopes with high precision.  Radioactive isotopes from ISAC are sent to TITAN to undergo cooling, charge-breeding and trapping.  The entire process occurs in about 10 milliseconds, allowing radioactive isotopes with short half lives to be studied.

text: List of the elements are available by name, atomic number, density, melting point, boiling point and by symbol, as well as ionization energies of the elements. The nuclides of stable and radioactive elements are also available as a list of nuclides, sorted by length of half-life for those that are unstable. One of the most convenient, and certainly the most traditional presentation of the elements, is in the form of the periodic table, which groups together elements with similar chemical properties (and usually also similar electronic structures).

text: List of the elements are available by name, atomic number, density, melting point, boiling point

text: and

text: by symbol

text: , as well as

entity_name: Molar ionization energies of the elements

text: ionization energies of the elements

text: . The nuclides of stable and radioactive elements are also available as a

text: list of nuclides

text: , sorted by length of half-life for those that are unstable. One of the most convenient, and certainly the most traditional presentation of the elements, is in the form of the

text: periodic table

text: , which groups together elements with similar chemical properties (and usually also similar electronic structures).

text: The mamiya/sekor 55mm 1:1.4 is known to have radioactive thorium glass elements.

text: In 1902 Bohuslav Brauner suggested there was an element with properties intermediate between those of the known elements neodymium (60) and samarium (62); this was confirmed in 1914 by Henry Moseley who, having measured the atomic numbers of all the elements then known, found there was no element with atomic number 61. In 1926, an Italian and an American group claimed to have isolated a sample of element 61; both "discoveries" were soon proven to be false. In 1938, during a nuclear experiment conducted at Ohio State University, a few radioactive nuclides were produced that certainly were not radioisotopes of neodymium or samarium, but there was a lack of chemical proof that element 61 was produced, and the discovery was not generally recognized. Promethium was first produced and characterized at Oak Ridge National Laboratory in 1945 by the separation and analysis of the fission products of uranium fuel irradiated in a graphite reactor. The discoverers proposed the name "prometheum" (the spelling was subsequently changed), derived from Prometheus, the Titan in Greek mythology who stole fire from Mount Olympus and brought it down to humans, to symbolize "both the daring and the possible misuse of mankind's intellect." However, a sample of the metal was made only in 1963.

text: In 1902

text: Bohuslav Brauner

text: suggested there was an element with properties intermediate between those of the known elements

text: neodymium

text: (60) and

text: samarium

text: (62); this was confirmed in 1914 by

text: Henry Moseley

text: who, having measured the atomic numbers of all the elements then known, found there was no element with atomic number 61. In 1926, an Italian and an American group claimed to have isolated a sample of element 61; both "discoveries" were soon proven to be false. In 1938, during a nuclear experiment conducted at

text: Ohio State University

text: , a few radioactive nuclides were produced that certainly were not radioisotopes of neodymium or samarium, but there was a lack of chemical proof that element 61 was produced, and the discovery was not generally recognized. Promethium was first produced and characterized at

text: Oak Ridge National Laboratory

text: in 1945 by the separation and analysis of the fission products of uranium fuel irradiated in a graphite reactor. The discoverers proposed the name "prometheum" (the spelling was subsequently changed), derived from

text: Prometheus

text: , the Titan in Greek mythology who stole fire from Mount Olympus and brought it down to humans, to symbolize "both the daring and the possible misuse of mankind's intellect." However, a sample of the metal was made only in 1963.

text: If a gamma ray is emitted from a radioactive element within the human body due to radioactive decay, and its energy is sufficient to escape then it can be detected. This would be by means of either a scintillation detector or a semiconductor detector placed in close proximity to the body. Radioactive decay may give rise to gamma radiation which cannot escape the body due to being absorbed or other interaction whereby it can lose energy; so account must be taken of this in any measurement analysis.

text: If a gamma ray is emitted from a radioactive element within the human body due to

text: radioactive decay

text: , and its energy is sufficient to escape then it can be detected. This would be by means of either a

text: scintillation detector

text: or a

text: semiconductor detector

text: placed in close proximity to the body. Radioactive decay may give rise to gamma radiation which cannot escape the body due to being absorbed or other interaction whereby it can lose energy; so account must be taken of this in any measurement analysis.

text: Francium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium and actinium K. It is the second-least electronegative element, behind only caesium, and is the second rarest naturally occurring element (after astatine). Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron.

text: Francium is a

text: chemical element

text: with symbol Fr and

text: atomic number

text: 87. It used to be known as

text: eka

text: caesium

text: and

text: actinium

text: K. It is the second-least

text: electronegative

text: element, behind only caesium, and is the

text: second rarest

text: naturally occurring element (after

text: astatine

text: ). Francium is a highly

text: radioactive

text: metal that decays into

text: astatine

text: radium

text: , and

text: radon

text: . As an

text: alkali metal

text: , it has one

text: valence electron

text: The last portion of the EM spectrum to be discovered was associated with radioactivity. Henri Becquerel found that uranium salts caused fogging of an unexposed photographic plate through a covering paper in a manner similar to X-rays, and Marie Curie discovered that only certain elements gave off these rays of energy, soon discovering the intense radiation of radium. The radiation from pitchblende was differentiated into alpha rays (alpha particles) and beta rays (beta particles) by Ernest Rutherford through simple experimentation in 1899, but these proved to be charged particulate types of radiation. However, in 1900 the French scientist Paul Villard discovered a third neutrally charged and especially penetrating type of radiation from radium, and after he described it, Rutherford realized it must be yet a third type of radiation, which in 1903 Rutherford named gamma rays. In 1910 British physicist William Henry Bragg demonstrated that gamma rays are electromagnetic radiation, not particles, and in 1914 Rutherford and Edward Andrade measured their wavelengths, finding that they were similar to X-rays but with shorter wavelengths and higher frequency, although a 'cross-over' between X and gamma rays makes it possible to have X-rays with a higher energy (and hence shorter wavelength) than gamma rays and vice versa. The origin of the ray differentiates them, gamma rays tend to be a natural phenomena originating from the unstable nucleus of an atom and X-rays are electrically generated (and hence man-made) unless they are as a result of bremsstrahlung X-radiation caused by the interaction of fast moving particles (such as beta particles) colliding with certain materials, usually of higher atomic numbers.

text: The last portion of the EM spectrum to be discovered was associated with

text: radioactivity

text: Henri Becquerel

text: found that

text: uranium

text: salts caused fogging of an unexposed photographic plate through a covering paper in a manner similar to X-rays, and

text: Marie Curie

text: discovered that only certain elements gave off these rays of energy, soon discovering the intense radiation of

text: radium

text: . The radiation from pitchblende was differentiated into alpha rays (

text: alpha particle

text: s) and beta rays (

text: beta particle

text: s) by

text: Ernest Rutherford

text: through simple experimentation in 1899, but these proved to be charged particulate types of radiation. However, in 1900 the French scientist

text: Paul Villard

text: discovered a third neutrally charged and especially penetrating type of radiation from radium, and after he described it, Rutherford realized it must be yet a third type of radiation, which in 1903 Rutherford named

text: gamma ray

text: s. In 1910 British physicist

text: William Henry Bragg

text: demonstrated that gamma rays are electromagnetic radiation, not particles, and in 1914 Rutherford and

text: Edward Andrade

text: measured their wavelengths, finding that they were similar to X-rays but with shorter wavelengths and higher frequency, although a 'cross-over' between X and gamma rays makes it possible to have X-rays with a higher energy (and hence shorter wavelength) than gamma rays and vice versa. The origin of the ray differentiates them, gamma rays tend to be a natural phenomena originating from the unstable nucleus of an atom and X-rays are electrically generated (and hence man-made) unless they are as a result of

text: bremsstrahlung

text: X-radiation caused by the interaction of fast moving particles (such as beta particles) colliding with certain materials, usually of higher atomic numbers.

text: Rutherford realised that if an atom is losing protons, its identity is changing at the same time, since an atom’s identity is governed by its proton number. Radioactive decay causes atoms of one element to transmute into atoms of a different element.  He then sought to artificially engineer a specific transmutation.

text: Green engineering encompasses numerous ways to improve processes and products to make them more efficient from an environmental and sustainable standpoint. Every one of these approaches depends on viewing possible impacts in space and time. Architects consider the sense of place. Engineers view the site map as a set of fluxes across the boundary. The design must consider short and long-term impacts. Those impacts beyond the near-term are the province of sustainable design. The effects may not manifest themselves for decades. In the mid-twentieth century, designers specified the use of what are now known to be hazardous building materials, such as asbestos flooring, pipe wrap and shingles, lead paint and pipes, and even structural and mechanical systems that may have increased the exposure to molds and radon. Those decisions have led to risks to people inhabiting these buildings.  It is easy in retrospect to criticize these decisions, but many were made for noble reasons, such as fire prevention and durability of materials. However, it does illustrate that seemingly small impacts when view through the prism of time can be amplified exponentially in their effects.Sustainable design requires a complete assessment of a design in place and time. Some impacts may not occur until centuries in the future. For example, the extent to which we decide to use nuclear power to generate electricity is a sustainable design decision. The radioactive wastes may have half-lives of hundreds of thousands of years. That is, it will take all these years for half of the radioactive isotopes to decay. Radioactive decay is the spontaneous transformation of one element into another. This occurs by irreversibly changing the number of protons in the nucleus. Thus, sustainable designs of such enterprises must consider highly uncertain futures. For example, even if we properly place warning signs about these hazardous wastes, we do not know if the English language will be understood.All four goals of green engineering mentioned above are supported by a long-term, life cycle point of view. A life cycle analysis is a holistic approach to consider the entirety of a product, process or activity, encompassing raw materials, manufacturing, transportation, distribution, use, maintenance, recycling, and final disposal. In other words, assessing its life cycle should yield a complete picture of the product.The first step in a life cycle assessment is to gather data on the flow of a material through an identifiable society. Once the quantities of various components of such a flow are known, the important functions and impacts of each step in the production, manufacture, use, and recovery/disposal are estimated. Thus, in sustainable design, engineers must optimize for variables that give the best performance in temporal frames.

text: Colloquially, radioactive materials can be described as "hot," and non-radioactive materials can be described as "cold."  There are instances in which cold iodide is administered to people in order to prevent the uptake of hot iodide by the thyroid gland.  For example, blockade of thyroid iodine uptake with potassium iodide is used in nuclear medicine scintigraphy and therapy with some radioiodinated compounds that are not targeted to the thyroid, such as iobenguane (MIBG), which used to image or treat neural tissue tumors, or iodinated fibrinogen, which is used in fibrinogen scans to investigate clotting.  These compounds contain iodine, but not in the iodide form.  However, since they may be ultimately metabolized or break down to radioactive iodide, it is common to administer non-radioactive potassium iodide to insure that metabolites of these  radiopharmaceuticals is not sequestered by thyroid gland and inadvertently administer a radiological dose to that tissue.

text: Colloquially, radioactive materials can be described as "hot," and non-radioactive materials can be described as "cold."  There are instances in which cold iodide is administered to people in order to prevent the uptake of hot iodide by the thyroid gland.  For example, blockade of thyroid iodine uptake with potassium iodide is used in

text: nuclear medicine

text: scintigraphy

text: and therapy with some radioiodinated compounds that are not targeted to the thyroid, such as

text: iobenguane

text: MIBG

text: ), which used to image or treat neural tissue tumors, or iodinated fibrinogen, which is used in

text: fibrinogen scans

text: to investigate clotting.  These compounds contain iodine, but not in the iodide form.  However, since they may be ultimately metabolized or break down to radioactive iodide, it is common to administer non-radioactive potassium iodide to insure that metabolites of these  radiopharmaceuticals is not sequestered by thyroid gland and inadvertently administer a radiological dose to that tissue.

text: In a parody of Chronicle, Bart, Lisa and Milhouse are walking through a forest. Bart scares Lisa with dead owls, and she hits Milhouse's nose with the camera, making him lose his balance and fall into a giant hole. Bart and Lisa decide to jump into the hole to rescue him, making all the three stuck inside of it with nuclear waste from the nuclear power plant. The radioactive goo explodes, sending all three of them back outside the hole. When they wake up, Milhouse and Lisa discover that they have gained telekinesis, so they decide to use the powers for selfish purposes. Lisa only makes a few changes, but Milhouse goes mad with powers only to be struck by lightning. Lisa says she did not do it, making the family curious to discover who did this. They then realize that Maggie also has telepathic powers, as she was using a radioactive rod as a pacifier. Maggie then uses her powers to benefit the world, such as turning Homerzilla into a larger Barney the Dinosaur before taking a nap. The episode ends with Kang and Kodos complaining that once again, they only have made a cameo appearance.

text: In a parody of

text: Chronicle

text: , Bart,

text: Lisa

text: and Milhouse are walking through a forest. Bart scares Lisa with dead owls, and she hits Milhouse's nose with the camera, making him lose his balance and fall into a giant hole. Bart and Lisa decide to jump into the hole to rescue him, making all the three stuck inside of it with nuclear waste from the nuclear power plant. The radioactive goo explodes, sending all three of them back outside the hole. When they wake up, Milhouse and Lisa discover that they have gained

text: telekinesis

text: , so they decide to use the powers for selfish purposes. Lisa only makes a few changes, but Milhouse goes mad with powers only to be struck by lightning. Lisa says she did not do it, making the family curious to discover who did this. They then realize that

text: Maggie

text: also has telepathic powers, as she was using a radioactive rod as a pacifier. Maggie then uses her powers to benefit the world, such as turning Homerzilla into a larger

text: Barney the Dinosaur

text: before taking a nap. The episode ends with

text: Kang and Kodos

text: complaining that once again, they only have made a cameo appearance.

text: Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope (except for technetium, element 43 and promethium, element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System. At over 1.9 years, over a billion times longer than the current estimated age of the universe, bismuth-209 (atomic number 83) has the longest known alpha decay half-life of any naturally occurring element, and is almost always considered on par with the 80 stable elements. The very heaviest elements (those beyond plutonium, element 94) undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized.

text: Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one

text: stable isotope

text: (except for

text: technetium

text: , element 43 and

text: promethium

text: , element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are

text: unstable

text: to the point that radioactive decay of all isotopes can be detected. Some of these elements, notably

text: bismuth

text: (atomic number 83),

text: thorium

text: (atomic number 90), and

text: uranium

text: (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of the explosive

text: stellar nucleosynthesis

text: that produced the

text: heavy metals

text: before the formation of our

text: Solar System

text: . At over 1.9 years, over a billion times longer than the current estimated age of the universe,

text: (atomic number 83) has the longest known

text: alpha decay

text: half-life of any naturally occurring element, and is almost always considered on par with the 80 stable elements. The very heaviest elements (those beyond plutonium, element 94) undergo radioactive decay with

text: half-lives

text: so short that they are not found in nature and must be

text: synthesized

text: The mass number of an element, A, is the number of nucleons (protons and neutrons) in the atomic nucleus. Different isotopes of a given element are distinguished by their mass numbers, which are conventionally written as a superscript on the left hand side of the atomic symbol (e.g. U). The mass number is always a whole number and has units of "nucleons". For example magnesium-24 (24 is the mass number) is an atom with 24 nucleons (12 protons and 12 neutrons).

text: The

text: mass number

text: of an element, A, is the number of

text: nucleon

text: s (protons and neutrons) in the atomic nucleus. Different isotopes of a given element are distinguished by their mass numbers, which are conventionally written as a superscript on the left hand side of the atomic symbol (e.g. U). The mass number is always a whole number and has units of "nucleons". For example

text: (24 is the mass number) is an atom with 24 nucleons (12 protons and 12 neutrons).

text: A dramatically different test shot was the "Sedan" test of Operation Storax on July 6, 1962, a 104 kiloton shot for the Operation Plowshare which sought to discover whether nuclear weapons could be used for peaceful means in creating lakes, bays or canals. The explosion displaced twelve million tons of earth, creating a crater  wide and  deep in Area 10. For an underground shot, a relatively large amount of energy was vented to the atmosphere, estimated to be 2.5 kilotons (7.4 bars of pressure). Two radioactive dust clouds rose up from the explosion and traveled across the United States, one at  and the other at . Both dropped radioactive particles across the USA before crossing into the sky above the Atlantic Ocean. Among many other radioisotopes, the clouds carried  of I.

text: A dramatically different test shot was the

text: "Sedan" test

text: of

text: Operation Storax

text: on July 6, 1962, a 104 kiloton shot for the

text: Operation Plowshare

text: which sought to discover whether nuclear weapons could be used for peaceful means in creating lakes, bays or canals. The explosion displaced twelve million tons of earth, creating a crater  wide and  deep in Area 10. For an underground shot, a relatively large amount of energy was vented to the atmosphere, estimated to be 2.5 kilotons (7.4 bars of pressure). Two radioactive dust clouds rose up from the explosion and traveled across the United States, one at  and the other at . Both dropped radioactive particles across the USA before crossing into the sky above the Atlantic Ocean. Among many other radioisotopes, the clouds carried  of I.

text: Most definitions of the term 'refractory metals' list the extraordinarily high melting point as a key requirement for inclusion. By one definition, a melting point above  is necessary to qualify. The five elements niobium, molybdenum, tantalum, tungsten and rhenium are included in all definitions, while the wider definition, including all elements with a melting point above , includes a varying number of nine additional elements: titanium, vanadium, chromium, zirconium, hafnium, ruthenium, rhodium, osmium and iridium. The artificial elements, being radioactive, are never considered to be part of the refractory metals, although technetium has a melting point of 2430 K or 2157 °C and rutherfordium is predicted to have melting point 2400 K or 2100 °C.

text: Most definitions of the term 'refractory metals' list the extraordinarily high melting point as a key requirement for inclusion. By one definition, a melting point above  is necessary to qualify. The five elements niobium, molybdenum, tantalum, tungsten and rhenium are included in all definitions, while the wider definition, including all elements with a melting point above , includes a varying number of nine additional elements:

text: titanium

text: vanadium

text: chromium

text: zirconium

text: hafnium

text: ruthenium

text: rhodium

text: osmium

text: and

text: iridium

text: . The

text: artificial element

text: s, being radioactive, are never considered to be part of the refractory metals, although

text: technetium

text: has a melting point of 2430 K or 2157 °C and

text: rutherfordium

text: is predicted to have melting point 2400 K or 2100 °C.

text: Two main approaches to reduce radiation damage are reducing the amount of energy deposited in the sensitive material (e.g. by shielding, distance from the source, or spatial orientation), or modification of the material to be less sensitive to radiation damage (e.g. by adding antioxidants, stabilizers, or choosing a more suitable material).In addition to the electronic device hardening mentioned above, some degree of protection may be obtained by shielding, usually with the interposition of high density materials (particularly lead, where space is critical, or concrete where space is available) between the radiation source and areas to be protected. For biological effects of substances such as radioactive iodine the ingestion of non-radioactive isotopes may substantially reduce the biological uptake of the radioactive form, and chelation therapy may be applied to accelerate the removal of radioactive materials formed from heavy metals from the body by natural processes.

text: Two main approaches to reduce radiation damage are reducing the amount of energy deposited in the sensitive material (e.g. by shielding, distance from the source, or spatial orientation), or modification of the material to be less sensitive to radiation damage (e.g. by adding antioxidants, stabilizers, or choosing a more suitable material).In addition to the electronic device hardening mentioned above, some degree of protection may be obtained by shielding, usually with the interposition of high density materials (particularly lead, where space is critical, or concrete where space is available) between the radiation source and areas to be protected. For biological effects of substances such as radioactive

text: iodine

text: the ingestion of non-radioactive isotopes may substantially reduce the biological uptake of the radioactive form, and

text: chelation therapy

text: may be applied to accelerate the removal of radioactive materials formed from heavy metals from the body by natural processes.

text: The tables of elements are sorted in order of decreasing number of nuclides associated with each element. (For a list sorted entirely in terms of half-lives of nuclides, with mixing of elements, see List of nuclides.) Stable and unstable (marked decays) nuclides are given, with symbols for unstable (radioactive) nuclides in italics. Note that the sorting does not quite give the elements purely in order of stable nuclides, since some elements have a larger number of long-lived unstable nuclides, which place them ahead of elements with a larger number of stable nuclides. By convention, nuclides are counted as "stable" if they have never been observed to decay by experiment or from observation of decay products (extremely long lived nuclides unstable only in theory, such as tantalum-180m, are counted as stable).

text: The tables of elements are sorted in order of decreasing number of nuclides associated with each element. (For a list sorted entirely in terms of half-lives of nuclides, with mixing of elements, see

text: List of nuclides

text: .) Stable and unstable (marked decays) nuclides are given, with symbols for unstable (radioactive) nuclides in italics. Note that the sorting does not quite give the elements purely in order of stable nuclides, since some elements have a larger number of long-lived unstable nuclides, which place them ahead of elements with a larger number of stable nuclides. By convention, nuclides are counted as "stable" if they have never been observed to decay by experiment or from observation of decay products (extremely long lived nuclides unstable only in theory, such as tantalum-180m, are counted as stable).

text: Under conditions of higher temperature and pressure, such as those found in novae and x-ray bursts, the rate of proton captures exceeds the rate of beta-decay, pushing the burning to the proton drip line.  The essential idea is that a radioactive species will capture a proton before it can beta decay, opening new nuclear burning pathways that are otherwise inaccessible.  Because of the higher temperatures involved, these catalytic cycles are typically referred to as the hot CNO cycles; because the timescales are limited by beta decays instead of proton captures, they are also called the beta-limited CNO cycles.

text: Under conditions of higher temperature and pressure, such as those found in

text: nova

text: e and

text: x-ray bursts

text: , the rate of proton captures exceeds the rate of beta-decay, pushing the burning to the

text: proton drip line

text: .  The essential idea is that a radioactive species will capture a proton before it can beta decay, opening new nuclear burning pathways that are otherwise inaccessible.  Because of the higher temperatures involved, these catalytic cycles are typically referred to as the hot CNO cycles; because the timescales are limited by beta decays instead of proton captures, they are also called the beta-limited CNO cycles.

text: Naturally Occurring Radioactive Materials (NORM) and Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) consist of materials, usually industrial wastes or by-products enriched with radioactive elements found in the environment, such as uranium, thorium and potassium and any of their decay products, such as radium and radon.

text: Naturally Occurring Radioactive Materials (NORM) and Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) consist of materials, usually

text: industrial waste

text: s or by-products enriched with

text: radioactive elements

text: found in the environment, such as

text: uranium

text: thorium

text: and

text: potassium

text: and any of their decay products, such as

text: radium

text: and

text: radon

text: The AEC had a history of involvement in experiments involving radioactive iodine. In a 1949 operation called the "Green Run," the AEC released iodine-131 and xenon-133 to the atmosphere which contaminated a  area containing three small towns near the Hanford site in Washington. In 1953, the AEC ran several studies on the health effects of radioactive iodine in newborns and pregnant women at the University of Iowa. Also in 1953, the AEC sponsored a study to discover if radioactive iodine affected premature babies differently from full-term babies. In the experiment, researchers from Harper Hospital in Detroit orally administered iodine-131 to 65 premature and full-term infants who weighed from . In another AEC study, researchers at the University of Nebraska College of Medicine fed iodine-131 to 28 healthy infants through a gastric tube to test the concentration of iodine in the infants' thyroid glands.

text: The AEC had a history of involvement in experiments involving

text: radioactive iodine

text: . In a 1949 operation called the "

text: Green Run

text: ," the AEC released

text: and

text: to the atmosphere which contaminated a  area containing three small towns near the

text: Hanford site

text: in Washington. In 1953, the AEC ran several studies on the health effects of radioactive iodine in newborns and pregnant women at the

text: University of Iowa

text: . Also in 1953, the AEC sponsored a study to discover if radioactive iodine affected

text: premature

text: babies differently from full-term babies. In the experiment, researchers from Harper Hospital in

text: Detroit

text: orally administered iodine-131 to 65 premature and full-term infants who weighed from . In another AEC study, researchers at the

text: University of Nebraska College of Medicine

text: fed iodine-131 to 28 healthy infants through a gastric tube to test the concentration of iodine in the infants' thyroid glands.

text: On 2 July samples of tapwater taken in Tokyo Shinjuku ward radioactive caesium-137 was detected for the first time since April. The concentration was 0.14 becquerel per kilogram and none was discovered yesterday, which compares with 0.21 becquerel on 22 April, according to the Tokyo Metropolitan Institute of Public Health. No caesium-134 or iodine-131 was detected. The level was below the safety limit set by the government. "This is unlikely to be the result of new radioactive materials being introduced, because no other elements were detected, especially the more sensitive iodine", into the water supply, were the comments of Hironobu Unesaki, a nuclear engineering professor at Kyoto University.

text: Radioactivity was discovered in 1896 by the French scientist Henri Becquerel, while working with phosphorescent materials. These materials glow in the dark after exposure to light, and he suspected that the glow produced in cathode ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it. All results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper. These radiations were given the name "Becquerel Rays".

text: Radioactivity was discovered in 1896 by the

text: French

text: scientist

text: Henri Becquerel

text: , while working with

text: phosphorescent

text: materials. These materials glow in the dark after exposure to light, and he suspected that the glow produced in

text: cathode ray tube

text: s by

text: X-ray

text: s might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent

text: salt

text: s on it. All results were negative until he used

text: uranium salts

text: . The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper. These radiations were given the name "Becquerel Rays".

text: After the Bikini Atoll nuclear tests in 1954, the Japanese government asked the Geochemical Laboratory to analyze and monitor radioactivity in the seawater and in rainfall. A Japanese fishing trawler had been downwind from the tests at the time they occurred, and its occupants became ill from the effects. Saruhashi found that it took a year and a half for the radioactivity to reach Japan in the seawater.By 1964, the radioactivity levels showed that the western and eastern North Pacific ocean water had mixed completely, and by 1969, the traces of radioactivity had spread throughout the Pacific. This was some of the first research showing how the effects of fallout can spread across the entire world, and not just affect the immediate area. Later, in the 1970s and 80s, she turned her attention to studying acid rain and its effects.

text: After the

text: Bikini Atoll nuclear tests

text: in 1954, the

text: Japanese government

text: asked the Geochemical Laboratory to analyze and monitor radioactivity in the seawater and in rainfall. A Japanese

text: fishing trawler

text: had been downwind from the tests at the time they occurred, and its occupants became ill from the effects. Saruhashi found that it took a year and a half for the radioactivity to reach

text: Japan

text: in the seawater.By 1964, the radioactivity levels showed that the western and eastern North

text: Pacific

text: ocean

text: water had mixed completely, and by 1969, the traces of radioactivity had spread throughout the Pacific. This was some of the first research showing how the effects of fallout can spread across the entire world, and not just affect the immediate area. Later, in the 1970s and 80s, she turned her attention to studying

text: acid rain

text: and its effects.

text: In the standard periodic table, the elements are listed in order of increasing atomic number (the number of protons in the nucleus of an atom). A new row (period) is started when a new electron shell has its first electron. Columns (groups) are determined by the electron configuration of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g. oxygen and selenium are in the same column because they both have four electrons in the outermost p-subshell). Elements with similar chemical properties generally fall into the same group in the periodic table, although in the f-block, and to some respect in the d-block, the elements in the same period tend to have similar properties, as well. Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it.

text: In the standard periodic table, the elements are listed in order of increasing atomic number (the number of

text: proton

text: s in the

text: nucleus

text: of an atom). A new row (

text: period

text: ) is started when a new electron shell has its first electron. Columns (

text: groups

text: ) are determined by the

text: electron configuration

text: of the atom; elements with the same number of electrons in a particular subshell fall into the same columns (e.g.

text: oxygen

text: and

text: selenium

text: are in the same column because they both have four electrons in the outermost p-subshell). Elements with similar chemical properties generally fall into the same group in the periodic table, although in the f-block, and to some respect in the d-block, the elements in the same period tend to have similar properties, as well. Thus, it is relatively easy to predict the chemical properties of an element if one knows the properties of the elements around it.

text: Zircophyllite is radioactive, but the radioactivity is barely detectable.

text: All of the remaining radioactive isotopes have half-lives that are less than an hour and the majority of these have half-lives that are less than 3 minutes. This element has numerous meta states with the most stable being Ag (t 418 years), Ag (t 249.79 days) and Ag (t 8.28 days).

text: All of the remaining

text: radioactive

text: isotopes have half-lives that are less than an hour and the majority of these have half-lives that are less than 3 minutes. This element has numerous

text: meta state

text: s with the most stable being Ag (t 418 years), Ag (t 249.79 days) and Ag (t 8.28 days).

text: Th is a radioactive isotope of thorium that can be used to date corals and determine ocean current flux. Ionium was a name given early in the study of radioactive elements to the Th isotope produced in the decay chain of U before it was realized that ionium and thorium are chemically identical. The symbol Io was used for this supposed element. (The name is still used in ionium-thorium dating.)

text: Th is a

text: radioactive

text: isotope

text: of

text: thorium

text: that can be used to date

text: coral

text: s and determine

text: ocean current

text: flux. Ionium was a name given early in the study of radioactive elements to the Th

text: isotope

text: produced in the

text: decay chain

text: of

text: U

text: before it was realized that ionium and

text: thorium

text: are chemically identical. The symbol Io was used for this supposed element. (The name is still used in

text: ionium-thorium dating

text: Since the fuel is contained in graphite pebbles, the volume of radioactive waste is much greater, but contains about the same radioactivity when measured in becquerels per kilowatt-hour. The waste tends to be less hazardous and simpler to handle. Current US legislation requires all waste to be safely contained, therefore pebble-bed reactors would increase existing storage problems. Defects in the production of pebbles may also cause problems. The radioactive waste must either be safely stored for many human generations, typically in a deep geological repository, reprocessed, transmuted in a different type of reactor, or disposed of by some other alternative method yet to be devised. The graphite pebbles are more difficult to reprocess due to their construction, which is not true of the fuel from other types of reactors. Proponents point out that this is a plus, as it is difficult to re-use pebble-bed reactor waste for nuclear weapons.

text: Since the fuel is contained in graphite pebbles, the volume of

text: radioactive waste

text: is much greater, but contains about the same

text: radioactivity

text: when measured in

text: becquerel

text: s per kilowatt-hour. The waste tends to be less hazardous and simpler to handle. Current US

text: legislation

text: requires all waste to be safely contained, therefore pebble-bed reactors would increase existing storage problems. Defects in the production of pebbles may also cause problems. The radioactive waste must either be safely stored for many human generations, typically in a

text: deep geological repository

text: , reprocessed,

text: transmuted

text: in a different type of reactor, or disposed of by some other alternative method yet to be devised. The graphite pebbles are more difficult to reprocess due to their construction, which is not true of the fuel from other types of reactors. Proponents point out that this is a plus, as it is difficult to re-use pebble-bed reactor waste for

text: nuclear weapons

text: Radium ( ) is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226, which has a half-life of 1601 years and decays into radon gas. Because of such instability, radium is luminescent, glowing a faint blue. Radium, in the form of radium chloride, was discovered by Marie Skłodowska-Curie and Pierre Curie in 1898. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1910. Since its discovery, it has given names likeradium A and radium C to several isotopes of other elements that are decay products of radium-226. In nature, radium is found in uranium ores in trace amounts as small as a seventh of a gram per ton of uraninite. Radium is not necessary for living organisms, and adverse health effects are likely when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity.

text: Radium ( ) is a

text: chemical element

text: with

text: atomic number

text: 88, represented by the symbol Ra. Radium is an almost pure-white

text: alkaline earth metal

text: , but it readily

text: oxidize

text: s on exposure to air, becoming black in color. All isotopes of radium are highly

text: radioactive

text: , with the most stable

text: isotope

text: being

text: , which has a

text: half-life

text: of 1601 years and

text: decays

text: into

text: radon

text: gas. Because of such instability, radium is

text: luminescent

text: , glowing a faint blue. Radium, in the form of

text: radium chloride

text: , was

text: discovered

text: by

text: Marie Skłodowska-Curie

text: and

text: Pierre Curie

text: in 1898. They extracted the radium compound from

text: uraninite

text: and published the discovery at the

text: French Academy of Sciences

text: five days later. Radium was isolated in its

text: metal

text: lic state by Marie Curie and

text: André-Louis Debierne

text: through the

text: electrolysis

text: of radium chloride in 1910. Since its discovery, it has given names like

text: radium A

text: and

text: radium C

text: to several isotopes of other elements that are

text: decay product

text: s of radium-226. In nature, radium is found in

text: uranium

text: ores in trace amounts as small as a seventh of a gram per ton of

text: uraninite

text: . Radium is not necessary for living organisms, and adverse health effects are likely when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity.

text: Californium is a radioactive metallic chemical element with symbol Cf and atomic number 98. The element was first made in 1950 at the University of California Radiation Laboratory in Berkeley, by bombarding curium with alpha particles (helium-4 ions). It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). The element was named after the university and the state of California.

text: Californium is a

text: radioactive

text: metallic

text: chemical element

text: with symbol Cf and

text: atomic number

text: 98. The element was first made in 1950 at the

text: University of California

text: Radiation Laboratory

text: in

text: Berkeley

text: , by bombarding

text: curium

text: with

text: alpha particle

text: s (

text: ion

text: s). It is an

text: actinide

text: element, the sixth

text: transuranium element

text: to be

text: synthesized

text: , and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the

text: unaided eye

text: (after

text: einsteinium

text: ). The element was named after the university and the state of

text: California

text: The CG2 SN series of surge arrestors formerly produced by C P Clare, are advertised as being non-radioactive, and the datasheet for that series states that some members of the CG/CG2 series (75-470V) are radioactive.

text: The number of protons within the atom's nucleus is called atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons. The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.

text: The number of protons within the

text: atom's nucleus

text: is called

text: atomic number

text: and is equal to the number of

text: electron

text: s in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of

text: neutron

text: s. The number of

text: nucleon

text: s (both protons and neutrons) in the nucleus is the atom's

text: mass number

text: , and each isotope of a given element has a different mass number.

text: Naturally occurring decay heat is a significant source of the heat in the interior of the Earth.  Radioactive isotopes of uranium, thorium and potassium are the primary contributors to this decay heat, and this radioactive decay is the primary source of heat from which geothermal energy derives.

text: Naturally occurring decay heat is a significant source of the heat in the interior of the

text: Earth

text: .  Radioactive isotopes of

text: uranium

text: thorium

text: and

text: potassium

text: are the primary contributors to this decay heat, and this

text: radioactive decay

text: is the primary source of heat from which

text: geothermal energy

text: derives.

text: Some mutilated murder victims are discovered in a radioactive bomb site.

text: Radon is formed as one intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead. Thorium and uranium are the two most common radioactive elements on earth; they have been around since the earth was formed. Their naturally occurring isotopes have very long half-lives, on the order of billions of years. Thorium and uranium, their decay product radium, and its decay product radon, will therefore continue to occur for tens of millions of years at almost the same concentrations as they do now. As radon itself decays, it produces other radioactive elements called radon progeny (also known as radon daughters) or decay products. Unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as dust particles in the air. If such contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.

text: Radon is formed as one intermediate step in the normal radioactive

text: decay chain

text: s through which

text: thorium

text: and

text: uranium

text: slowly decay into

text: lead

text: . Thorium and uranium are the two most common radioactive elements on earth; they have been around since the earth was formed. Their naturally occurring isotopes have very long half-lives, on the order of billions of years. Thorium and uranium, their decay product

text: radium

text: , and its decay product radon, will therefore continue to occur for tens of millions of years at almost the same concentrations as they do now. As radon itself decays, it produces other radioactive elements called radon progeny (also known as radon daughters) or decay products. Unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as dust particles in the air. If such contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.

text: In a parody of The Diving Bell and the Butterfly, Homer begins to decorate the house for Halloween and is reaching for a decoration in a box. Unfortunately, there is a real Black Widow spider in the box and when Homer grabs what he thinks is a plastic spider, he is bitten by it. The bite leaves Homer paralyzed and unable to speak. When Lisa reads for him, she discovers that he can communicate through farting. The Simpson family is amazed at the result and Lisa helps Homer tell Marge how he feels about her. When he is again bitten by another spider (a radioactive one this time), he gains the ability to shoot spider webs out of his rear end and have the same abilities as Spider-Man, though he is still unable to move or talk.

text: In a parody of

entity_name: The Diving Bell and the Butterfly (film)

text: The Diving Bell and the Butterfly

text: , Homer begins to decorate the house for Halloween and is reaching for a decoration in a box. Unfortunately, there is a real

text: Black Widow spider

text: in the box and when Homer grabs what he thinks is a plastic spider, he is bitten by it. The bite leaves Homer

text: paralyzed

text: and unable to speak. When Lisa reads for him, she discovers that he can communicate through

text: farting

text: . The Simpson family is amazed at the result and Lisa helps Homer tell Marge how he feels about her. When he is again bitten by another spider (a radioactive one this time), he gains the ability to shoot spider webs out of his rear end and have the same abilities as

text: Spider-Man

text: , though he is still unable to move or talk.

text: Another difficulty the engineers struggled with was how to deal with radioactive contamination. Once the canyons began processing irradiated slugs, the machinery would become so radioactive that it would be unsafe for humans ever to come in contact with it. The engineers therefore had to devise methods to allow for the replacement of any component via remote control. They came up with a modular cell concept, which allowed major components to be removed and replaced by an operator sitting in a heavily shielded overhead crane. This method required early practical application of two technologies that later gained widespread use: Teflon, used as a gasket material, and closed-circuit television, used to give the crane operator a better view of the process.

text: Another difficulty the engineers struggled with was how to deal with radioactive contamination. Once the canyons began processing irradiated slugs, the machinery would become so radioactive that it would be unsafe for humans ever to come in contact with it. The engineers therefore had to devise methods to allow for the replacement of any component via remote control. They came up with a modular cell concept, which allowed major components to be removed and replaced by an operator sitting in a heavily shielded overhead crane. This method required early practical application of two technologies that later gained widespread use:

text: Teflon

text: , used as a gasket material, and

text: closed-circuit television

text: , used to give the crane operator a better view of the process.

text: Radioactive tracers - Since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. Examples:

text: Radioactive tracer

text: s - Since radioactive isotopes behave, chemically, mostly like the inactive element, the behavior of a certain chemical substance can be followed by tracing the radioactivity. Examples:

text: where  is the atomic number, i.e. the number of protons in the atomic nucleus of this element;  is the upper energy level;  is the lower energy level; and  is the Rydberg constant (). Meaningful values are returned only when  is greater than . Note that this equation is valid for all hydrogen-like species, i.e. atoms having only a single electron, and the particular case of hydrogen spectral lines are given by Z=1.

text: where  is the atomic number, i.e. the number of protons in the atomic nucleus of this element;  is the upper energy level;  is the lower energy level; and  is the

text: Rydberg constant

text: (). Meaningful values are returned only when  is greater than . Note that this equation is valid for all hydrogen-like species, i.e. atoms having only a single electron, and the particular case of hydrogen spectral lines are given by Z=1.

text: Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electric force due to their positive charge. These two forces compete, leading to some combinations of neutrons and protons being more stable than others. Neutrons stabilize the nucleus, because they attract protons, which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus; if too many or too few neutrons are present with regard to the optimum ratio, the nucleus becomes unstable and subject to certain types of nuclear decay. Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. Many other rare types of decay, such as spontaneous fission or cluster decay are known. (See radioactive decay for details.)

text: Atomic

text: nuclei

text: consist of

text: proton

text: s and

text: neutron

text: s, which attract each other through the

text: nuclear force

text: , while protons repel each other via the

text: electric force

text: due to their positive

text: charge

text: . These two forces compete, leading to some combinations of neutrons and protons being more stable than others. Neutrons stabilize the nucleus, because they attract protons, which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing

text: ratio of neutrons to protons

text: is needed to form a stable nucleus; if too many or too few neutrons are present with regard to the optimum ratio, the nucleus becomes unstable and subject to certain types of

text: nuclear decay

text: . Unstable isotopes decay through various

text: radioactive decay pathways

text: , most commonly

text: alpha decay

text: beta decay

text: , or

text: electron capture

text: . Many other rare types of decay, such as

text: spontaneous fission

text: or

text: cluster decay

text: are known. (See

text: radioactive decay

text: for details.)

text: Przybylski's Star also contains many different short-lived actinide elements with actinium, protactinium, neptunium, plutonium, americium, curium, berkelium, californium, and einsteinium being detected. Other radioactive elements discovered in this star include technetium and promethium.

text: Przybylski's Star also contains many different short-lived

text: actinide

text: elements with

text: actinium

text: protactinium

text: neptunium

text: plutonium

text: americium

text: curium

text: berkelium

text: californium

text: , and

text: einsteinium

text: being detected. Other radioactive elements discovered in this star include

text: technetium

text: and

text: promethium

text: There are no stable isotopes of astatine. However, there are three naturally occurring radioactive isotopes of astatine produced via radioactive decay of uranium, neptunium, and plutonium. These isotopes are astatine-215, astatine-217, and astatine-219. A total of 31 isotopes of astatine have been discovered, with atomic masses ranging from 193 to 223.

text: There are no stable

text: isotopes of astatine

text: . However, there are three naturally occurring radioactive isotopes of astatine produced via radioactive decay of

text: uranium

text: neptunium

text: , and

text: plutonium

text: . These isotopes are astatine-215, astatine-217, and astatine-219. A total of 31 isotopes of astatine have been discovered, with atomic masses ranging from 193 to 223.

text: The USNRC provides licensing for the entombment process, as well as providing license they research and develop programs to help decommission nuclear power plants. USNRC will continue the development of rule making for entombment. NRC will ask the company that are running power plants to set some money aside while the power plant is being run for future shut down cost. The NRC has decided that in order for nuclear entombment to be a possible, a long-term structure must be created specifically for the encasing of the radioactive waste. If the structures are not correctly built water can seep into them and come out with radioactive waste that can infect the public. The NRC itself imposes acts such as the Nuclear Waste Policy Act of 1982 and the Low-level radioactive waste policy to help regulate state governments on the procedures and precautions needed to dispose of the nuclear waste. The Nuclear Waste Policy of 1982 states that both the federal government's are responsible to provide a permanent disposal facility for high-level radioactive waste and spent nuclear fuel. As well  with the Nuclear Waste Policy Act of 1982,  which gives states the responsibility to dispose of low-level waste and provides facilities to the states that will be regulated by the NRC or by states who have agreed to follow §274 of the Atomic Energy Act.

text: The

text: USNRC

text: provides licensing for the entombment process, as well as providing license they research and develop programs to help decommission nuclear power plants. USNRC will continue the development of rule making for entombment. NRC will ask the company that are running power plants to set some money aside while the power plant is being run for future shut down cost. The NRC has decided that in order for nuclear entombment to be a possible, a long-term structure must be created specifically for the encasing of the radioactive waste. If the structures are not correctly built water can seep into them and come out with radioactive waste that can infect the public. The NRC itself imposes acts such as the

text: Nuclear Waste Policy Act of 1982

text: and the

entity_name: Low-level radioactive waste policy of the United States

text: Low-level radioactive waste policy

text: to help regulate state governments on the procedures and precautions needed to dispose of the nuclear waste. The Nuclear Waste Policy of 1982 states that both the federal government's are responsible to provide a permanent disposal facility for high-level radioactive waste and spent nuclear fuel. As well  with the Nuclear Waste Policy Act of 1982,  which gives states the responsibility to dispose of low-level waste and provides facilities to the states that will be regulated by the NRC or by states who have agreed to follow §274 of the

text: Atomic Energy Act

text: Rhenium ( meaning: "Rhine") was the last-discovered of the elements that have a stable isotope (other new elements discovered in nature since then, such as francium, are radioactive). The existence of a yet-undiscovered element at this position in the periodic table had been first predicted by Dmitri Mendeleev. Other calculated information was obtained by Henry Moseley in 1914. It is generally considered to have been discovered by Walter Noddack, Ida Tacke, and Otto Berg in Germany. In 1925 they reported that they had detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite. In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite. It was estimated in 1968 that 75% of the rhenium metal in the United States was used for research and the development of refractory metal alloys. It took several years from that point before the superalloys became widely used.

text: Rhenium ( meaning: "

text: Rhine

text: ") was the last-discovered of the elements that have a stable isotope (other new elements discovered in nature since then, such as

text: francium

text: , are radioactive). The existence of a yet-undiscovered element at this position in the

text: periodic table

text: had been first predicted by

text: Dmitri Mendeleev

text: . Other calculated information was obtained by

text: Henry Moseley

text: in 1914. It is generally considered to have been discovered by

text: Walter Noddack

text: Ida Tacke

text: , and

text: Otto Berg

text: in

text: Germany

text: . In 1925 they reported that they had detected the element in platinum ore and in the mineral

text: columbite

text: . They also found rhenium in

text: gadolinite

text: and

text: molybdenite

text: . In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite. It was estimated in 1968 that 75% of the rhenium metal in the

text: United States

text: was used for research and the development of

text: refractory metal

text: alloys. It took several years from that point before the superalloys became widely used.

text: Fallout Boy also appears in a real-life comic book titled Radioactive Man, published by Bongo Comics (a comic created in part by Matt Groening, the creator of The Simpsons). In these comic books, Fallout Boy's real name is Rod Runtledge, he has a brother named Dodd. They live in Zenith City. Rod is a high school nerd living with his aunt, Aunt June. Fallout Boy was an average book worm, until one day, he was at a Radioactive demonstration, where he met up with Claude Kane. A tall piece of machinery fell towards them. Claude grabbed Rod and jumped over the rail, Claude holding onto the machine. The machine came to life, and as the ray passed through Claude, who became Radioactive Man, it hit Rod. Rod then got a pint-sized version of RM's powers and became Fallout Boy.

text: Fallout Boy also appears in a real-life comic book titled Radioactive Man, published by

text: Bongo Comics

text: (a comic created in part by

text: Matt Groening

text: , the creator of The Simpsons). In these comic books, Fallout Boy's real name is Rod Runtledge, he has a brother named Dodd. They live in Zenith City. Rod is a

text: high school

text: nerd

text: living with his aunt, Aunt June. Fallout Boy was an average book worm, until one day, he was at a Radioactive demonstration, where he met up with Claude Kane. A tall piece of machinery fell towards them. Claude grabbed Rod and jumped over the rail, Claude holding onto the machine. The machine came to life, and as the ray passed through Claude, who became Radioactive Man, it hit Rod. Rod then got a pint-sized version of RM's powers and became Fallout Boy.

text: In alpha decay (which typically occurs in the heaviest nuclei) the radioactive element decays by emitting a helium nucleus (2 protons and 2 neutrons), giving another element, plus helium-4. In many cases this process continues through several steps of this kind, including other types of decays (usually beta decay) until a stable element is formed.

text: In

text: alpha decay

text: (which typically occurs in the heaviest nuclei) the radioactive element decays by emitting a helium nucleus (2 protons and 2 neutrons), giving another element, plus helium-4. In many cases this process continues through several steps of this kind, including other types of decays (usually beta decay) until a stable element is formed.

text: The radioactive decay of elements in the Earth's mantle and crust results in production of daughter isotopes and release of particles and heat energy, or radiogenic heat. Four radioactive isotopes are responsible for the majority of radiogenic heat, uranium-238 (U), uranium-235 (U), thorium-232 (Th), and potassium-40 (K). Due to a lack of rock samples from below 200 km depth, it is not possible to do a simple radiogenic heat estimate of known radioactive isotope concentrations in rock throughout the whole mantle. For the Earth's core, geochemical studies indicate that it would not be a significant source of radiogenic heat due to an expected low concentration of radioactive elements. Radiogenic heat production in the mantle is linked to the structure of mantle convection, a topic of much debate, and it is thought that the mantle may either have a layered structure with a higher concentration of radioactive heat-producing elements in the lower mantle, or small reservoirs enriched in radioactive elements dispersed throughout the whole mantle.

text: The

text: radioactive decay

text: of elements in the Earth's mantle and crust results in production of daughter

text: isotope

text: s and release of particles and heat energy, or

text: radiogenic heat

text: . Four radioactive isotopes are responsible for the majority of radiogenic heat,

text: (U),

text: (U),

text: (Th), and

text: (K). Due to a lack of rock samples from below 200 km depth, it is not possible to do a simple radiogenic heat estimate of known radioactive isotope concentrations in rock throughout the whole mantle. For the Earth's core,

text: geochemical

text: studies indicate that it would not be a significant source of radiogenic heat due to an expected low concentration of radioactive elements. Radiogenic heat production in the mantle is linked to the structure of

text: mantle convection

text: , a topic of much debate, and it is thought that the mantle may either have a layered structure with a higher concentration of radioactive heat-producing elements in the lower mantle, or small reservoirs enriched in radioactive elements dispersed throughout the whole mantle.

text: Salted versions of both fission and fusion weapons can be made by surrounding the core of the explosive device with a material containing an element that can be converted to a highly radioactive isotope by neutron bombardment. When the bomb explodes, the element absorbs neutrons released by the nuclear reaction, converting it to its radioactive form. The explosion scatters the resulting radioactive material over a wide area, leaving it uninhabitable far longer than an area affected by typical nuclear weapons. In a salted hydrogen bomb, the radiation case around the fusion fuel, which normally is made of some fissionable element, is replaced with a metallic salting element. Salted fission bombs can be made by replacing the neutron reflector between the fissionable core and the explosive layer with a metallic element. The energy yield from a salted weapon is usually lower than from an ordinary weapon of similar size as a consequence of these changes.

text: Salted versions of both

text: fission

text: and

text: fusion weapons

text: can be made by surrounding the core of the explosive device with a material containing an element that can be converted to a highly

text: radioactive isotope

text: by

text: neutron

text: bombardment. When the bomb explodes, the element absorbs neutrons released by the nuclear reaction, converting it to its radioactive form. The explosion scatters the resulting radioactive material over a wide area, leaving it uninhabitable far longer than an area affected by typical nuclear weapons. In a salted

text: hydrogen bomb

text: , the radiation case around the

text: fusion fuel

text: , which normally is made of some

text: fissionable

text: element

text: , is replaced with a metallic salting element. Salted fission bombs can be made by replacing the

text: neutron reflector

text: between the fissionable core and the explosive layer with a metallic element. The energy

text: yield

text: from a salted weapon is usually lower than from an ordinary weapon of similar size as a consequence of these changes.

text: This is a summary table of decay class for the ~986 nuclides with half-lives longer than one hour, given in this list of nuclides. Numbers may change slightly in the future, as nuclides radioactive only in theory are observed to be radioactive, half-life measurements improve, or new isotopes are discovered.

text: The opening narration briefly introduces the viewer to the ant and its behavior.  It takes note how ants use pheromones to communicate, and how they cause an obligatory response that must be obeyed.  "But humans don't have to worry about that...."  As the opening credits roll, barrels of radioactive waste are being dumped off a boat into the ocean.  Eventually one of the barrels washes up on the shore and begins to leak a silvery goo attractive to local ants.

text: The Waste Isolation Pilot Plant, was designed as a pilot, test study site for deep geologic storage of radioactive waste. It is managed by the U.S. Department of Energy (DOE) and currently serves as the nation's only deep geological repository for transuranic (TRU) nuclear waste generated by the military and defense industry. It is located in Southern New Mexico near the border of Texas and Mexico. It has been disposing of waste 2,150 feet underground in the ancient Permian Sea salt formation since 1999, accepting waste from 22 national atomic legacy sites. Designed to last tens thousand years, the WIPP site had its first leak of airborne radioactive materials on February 1, 2014. 140 employees working underground at the time were sheltered indoors. 13 of these tested positive for internal radioactive contamination. Internal exposure to radioactive isotopes is more serious than external exposure, as these particles lodge in the body for decades, irradiating the surrounding tissues, thus increasing the risk of future cancers and other health effects. A second leak at the plant occurred shortly after the first, releasing plutonium and other radiotoxins, causing concern for communities living near the repository. Since opening in 1999, the WIPP "pilot site" has received over 11,000 shipments of TRU waste (transuranic waste). During the February 14, 2014 leak, 22 workers were exposed to radioactive materials. Don Hancock, Director of the Nuclear Waste Safety Program for the SouthWest Research and information Center describes the theory of how nitrate salts in the "kitty litter" absorbent interacted with plutonium causing the breach of one or more 55-gallon drums stored at WIPP through a chemical reaction that caused an inflagration. Fundamental questions remain regarding the Department of Energy's clean up standards for WIPP, as there is not a "clean-up" standard or regulation for the underground site, by either the DOE oversight or the company contracted to oversee the site, Nuclear Waste Partnership. Over the past 15 years, 91,000 cubic meters of radioactive waste, and more than 171,000 containers of radioactive waste have been placed at WIPP - more than any other site in the country.

text: The discovery of radioactivity introduced another factor in the calculation. After Henri Becquerel's initial discovery in 1896, Marie and Pierre Curie discovered the radioactive elements polonium and radium in 1898; and in 1903, Pierre Curie and Albert Laborde announced that radium produces enough heat to melt its own weight in ice in less than an hour. Geologists quickly realized that this upset the assumptions underlying most calculations of the age of Earth.These had assumed that the original heat of the Earth and Sun had dissipated steadily into space, but radioactive decay meant that this heat had been continually replenished.  George Darwin and John Joly were the first to point this out, in 1903.

text: The discovery of

text: radioactivity

text: introduced another factor in the calculation. After

text: Henri Becquerel

text: 's initial discovery in 1896,

text: Marie

text: and

text: Pierre Curie

text: discovered the radioactive elements

text: polonium

text: and

text: radium

text: in 1898; and in 1903, Pierre Curie and

text: Albert Laborde

text: announced that radium produces enough heat to melt its own weight in ice in less than an hour. Geologists quickly realized that this upset the assumptions underlying most calculations of the age of Earth.These had assumed that the original heat of the Earth and Sun had dissipated steadily into space, but radioactive decay meant that this heat had been continually replenished.  George Darwin and John Joly were the first to point this out, in 1903.

text: As often happens in science, radioactivity came close to being discovered nearly four decades earlier in 1857, when Abel Niepce de Saint-Victor, who was investigating photography under Michel Eugène Chevreul, observed that uranium salts emitted radiation that could darken photographic emulsions. By 1861, Niepce de Saint-Victor realized that uranium salts produce "a radiation that is invisible to our eyes". Niepce de Saint-Victor knew Edmond Becquerel, Henri Becquerel's father.  In 1868, Edmond Becquerel published a book, La lumière: ses causes et ses effets (Light:  Its causes and its effects).  On page 50 of volume 2, Edmond noted that Niepce de Saint-Victor had observed that some objects that had been exposed to sunlight could expose photographic plates even in the dark.<ref>In the nineteenth and twentieth centuries, uranium was used to color glass and porcelain glaze.  See:

text: As often happens in science, radioactivity came close to being discovered nearly four decades earlier in 1857, when

text: Abel Niepce de Saint-Victor

text: , who was investigating photography under

text: Michel Eugène Chevreul

text: , observed that uranium salts emitted radiation that could darken photographic emulsions. By 1861, Niepce de Saint-Victor realized that uranium salts produce "a radiation that is invisible to our eyes". Niepce de Saint-Victor knew Edmond Becquerel, Henri Becquerel's father.  In 1868, Edmond Becquerel published a book, La lumière: ses causes et ses effets (Light:  Its causes and its effects).  On page 50 of volume 2, Edmond noted that Niepce de Saint-Victor had observed that some objects that had been exposed to sunlight could expose photographic plates even in the dark.<ref>In the nineteenth and twentieth centuries, uranium was used to color glass and porcelain glaze.  See:

text: Containment systems are designed to prevent the release of radioactive material into the environment.

text: The early researchers also discovered that many other chemical elements, besides uranium, have radioactive isotopes. A systematic search for the total radioactivity in uranium ores also guided Pierre and Marie Curie to isolate two new elements: polonium and radium. Except for the radioactivity of radium, the chemical similarity of radium to barium made these two elements difficult to distinguish.

text: The early researchers also discovered that many other

text: chemical element

text: s, besides uranium, have

text: radioactive isotope

text: s. A systematic search for the total radioactivity in uranium ores also guided

text: Pierre

text: and

text: Marie Curie

text: to isolate two new elements:

text: polonium

text: and

text: radium

text: . Except for the radioactivity of radium, the chemical similarity of radium to

text: barium

text: made these two elements difficult to distinguish.

text: In July 1898, Curie and her husband published a joint paper announcing the existence of an element which they named "polonium", in honour of her native Poland, which would for another twenty years remain partitioned among three empires (Russian, Austrian, and Prussian).  On 26 December 1898, the Curies announced the existence of a second element, which they named "radium", from the Latin word for "ray". In the course of their research, they also coined the word "radioactivity".

text: In July 1898, Curie and her husband published a joint paper announcing the existence of an element which they named "

text: polonium

text: ", in honour of her native Poland, which would for another twenty years remain

text: partitioned among three empires

text: Russian

text: Austrian

text: , and

text: Prussian

text: ).  On 26 December 1898, the Curies announced the existence of a second element, which they named "

text: radium

text: ", from the

text: Latin

text: word for "ray". In the course of their research, they also coined the word "

text: radioactivity

text: After marrying, Segrè sought a stable job, and became professor of physics and director of the Physics Institute at the University of Palermo. He found the equipment there primitive and the library bereft of modern physics literature, but his colleagues at Palermo included the mathematicians Michele Cipolla and Michele De Franchis, the mineralogist Carlo Perrier and the botanist Luigi Montemartini. In 1936 he paid a visit to Ernest O. Lawrence's Berkeley Radiation Laboratory, where he met Edwin McMillan, Donald Cooksey, Franz Kurie, Philip Abelson and Robert Oppenheimer. Segrè was intrigued by the radioactive scrap metal that had once been part of the laboratory's cyclotron. In Palermo, this was found to contain a number of radioactive isotopes. In February 1937, Lawrence sent him a molybdenum strip which was emitting anomalous forms of radioactivity. Segrè enlisted Perrier's help to subject the strip to careful chemical and theoretical analysis, and they were able to prove that some of the radiation was being produced by a previously unknown element. In 1947 they dubbed it technetium, as it was the first artificially synthesized chemical element.

text: After marrying, Segrè sought a stable job, and became professor of physics and director of the Physics Institute at the

text: University of Palermo

text: . He found the equipment there primitive and the library bereft of modern physics literature, but his colleagues at Palermo included the mathematicians

text: Michele Cipolla

text: and

text: Michele De Franchis

text: , the mineralogist

text: Carlo Perrier

text: and the botanist

text: Luigi Montemartini

text: . In 1936 he paid a visit to

text: Ernest O. Lawrence

text: 's

text: Berkeley Radiation Laboratory

text: , where he met

text: Edwin McMillan

text: Donald Cooksey

text: Franz Kurie

text: Philip Abelson

text: and

text: Robert Oppenheimer

text: . Segrè was intrigued by the radioactive scrap metal that had once been part of the laboratory's

text: cyclotron

text: . In Palermo, this was found to contain a number of radioactive

text: isotope

text: s. In February 1937, Lawrence sent him a

text: molybdenum

text: strip which was emitting anomalous forms of

text: radioactivity

text: . Segrè enlisted Perrier's help to subject the strip to careful chemical and theoretical analysis, and they were able to prove that some of the radiation was being produced by a previously unknown element. In 1947 they dubbed it

text: technetium

text: , as it was the first artificially synthesized

text: chemical element

text: On 1 August 2008 the Navy reported to CNN that the Houston was found to have been leaking radioactive water for months while on patrol and visiting stations in Japan, Guam and Hawaii.  The problem was discovered the previous month during servicing at Pearl Harbor. One crewman was exposed to radioactive water but not injured. The Navy reported that the Houston's leak released only a "negligible" amount of radioactivity. The Navy later expanded the estimated time the leak existed to nearly two years, although they maintained the amount of radioactivity leaked was very small - "less than a smoke detector".

text: On 1 August 2008 the Navy reported to CNN that the Houston was found to have been leaking radioactive water for months while on patrol and visiting stations in

text: Japan

text: Guam

text: and

text: Hawaii

text: .  The problem was discovered the previous month during servicing at Pearl Harbor. One crewman was exposed to radioactive water but not injured. The Navy reported that the Houston's leak released only a "negligible" amount of radioactivity. The Navy later expanded the estimated time the leak existed to nearly two years, although they maintained the amount of radioactivity leaked was very small - "less than a smoke detector".

text: The new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine (as had the discoveries of electricity and magnetism, earlier), and a number of patent medicines and treatments involving radioactivity were put forward.

text: The new phenomenon of radioactivity was seized upon by the manufacturers of

text: quack medicine

text: (as had the discoveries of

text: electricity

text: and

text: magnetism

text: , earlier), and a number of

text: patent medicine

text: s and treatments involving radioactivity were put forward.

text: Asimov also explained how he began with the idea that Earth was radioactive from an atomic war.  As he learned more, he became unhappy with the notion, reckoning that a war would not make the crust radioactive without also wiping out all life, hence the revised notion in Robots and Empire.

text: Asimov also explained how he began with the idea that Earth was radioactive from an atomic war.  As he learned more, he became unhappy with the notion, reckoning that a war would not make the crust radioactive without also wiping out all life, hence the revised notion in

text: Robots and Empire

text: Also in the USA, Regulatory Guide 1.21, Measuring, Evaluating, and Reporting Radioactivity in Solid Wastes and Releases of Radioactive Materials in Liquid and Gaseous Effluents from Light-Water-Cooled Nuclear Power Plants is highly relevant to this CPAM application.

text: Following certain field work, Mikhail, Darkstar and Vanguard (the three best-trained students of Phobos's school) were reunited and organized by the government into the elite Soviet Super-Soldiers, a team of Soviet government agents. Ursus was given the code name Ursa Major (though he is also known as 'Major Ursus'). The first mission of the Soviet Super-Soldiers was to investigate the contained radioactive area of Khystym known as the Forbidden Zone and to stop the Presence. There they encountered the Hulk, and discovered that their former teacher Professor Phobos was engaged in a project to radioactively contaminate all of the Soviet Union in order to foster the birth of more mutants whose powers he could eventually siphon. The Soviet Super-Soldiers, aided by the Hulk, thwarted Phobos's plan and brought him before the government to stand trial.

text: Following certain field work, Mikhail, Darkstar and Vanguard (the three best-trained students of Phobos's school) were reunited and organized by the government into the elite

text: Soviet Super-Soldiers

text: , a team of Soviet government agents. Ursus was given the code name Ursa Major (though he is also known as 'Major Ursus'). The first mission of the Soviet Super-Soldiers was to investigate the contained radioactive area of Khystym known as the Forbidden Zone and to stop the

text: Presence

text: . There they encountered the

text: Hulk

text: , and discovered that their former teacher Professor Phobos was engaged in a project to radioactively contaminate all of the Soviet Union in order to foster the birth of more mutants whose powers he could eventually siphon. The Soviet Super-Soldiers, aided by the Hulk, thwarted Phobos's plan and brought him before the government to stand trial.

text: Of the 94 naturally occurring elements, 84 are considered primordial and either stable or weakly radioactive. The remaining 10 naturally occurring elements possess half lives too short for them to have been present at the beginning of the Solar System, and are therefore considered transient elements. (Plutonium is usually also considered a transient element because primordial plutonium has by now decayed to almost undetectable traces.) Of these 10 transient elements, 5 (polonium, radon, radium, actinium, and protactinium) are relatively common decay products of thorium, uranium, and plutonium. The remaining 6 transient elements (technetium, promethium, astatine, francium, neptunium, and plutonium) occur only rarely, as products of rare decay modes or nuclear reaction processes involving uranium or other heavy elements.

text: Of the 94 naturally occurring elements, 84 are considered

text: primordial

text: and either

text: stable

text: or weakly radioactive. The remaining 10 naturally occurring elements possess

text: half lives

text: too short for them to have been present at the beginning of the

text: Solar System

text: , and are therefore considered transient elements. (Plutonium is usually also considered a transient element because primordial plutonium has by now decayed to almost undetectable traces.) Of these 10 transient elements, 5 (

text: polonium

text: radon

text: radium

text: actinium

text: , and

text: protactinium

text: ) are relatively common

text: decay products

text: of

text: thorium

text: uranium

text: , and

text: plutonium

text: . The remaining 6 transient elements (

text: technetium

text: promethium

text: astatine

text: francium

text: neptunium

text: , and

text: plutonium

text: ) occur only rarely, as products of rare decay modes or nuclear reaction processes involving uranium or other heavy elements.

text: Prior to the widespread use of fluorescence in the past three decades radioactivity was the most common label.

text: Prior to the widespread use of

text: fluorescence

text: in the past three decades radioactivity was the most common label.

text: Xanthiosite is an arsenate mineral first discovered in Germany in 1858; it may also be found in Greece.  It is not radioactive.

text: Xanthiosite is an

text: arsenate

text: mineral first discovered in

text: Germany

text: in 1858; it may also be found in

text: Greece

text: .  It is not

text: radioactive

text: His second film, Radioactive Dreams, was awarded the Golden Raven at the 5th Brussels International Fantastic Film Festival in 1987. "Radioactive Dreams" recently screened at Exhumed Films' 2013 eX Fest.

text: His second film,

text: Radioactive Dreams

text: , was awarded the Golden Raven at the 5th

entity_name: Brussels International Fantastic Film Festival

text: Brussels International Fantastic Film Festival

text: in 1987. "Radioactive Dreams" recently screened at

text: Exhumed Films

text: ' 2013 eX Fest.

text: No adverse health effects from the radioactivity or the other trace elements have been demonstrated, and calculations show that the level of radioactivity is probably much too low to be detected in the population. These unusual soils are very rich in phosphate, but it is not accessible to plants, being in the very insoluble form of iron phosphate, or crandallite. It is thought that similar radioactive soils may exist on Lifou and Mare near New Caledonia, and Rennell in the Solomon Islands, but no other locations are known.

text: No adverse health effects from the radioactivity or the other trace elements have been demonstrated, and calculations show that the level of radioactivity is probably much too low to be detected in the population. These unusual soils are very rich in

text: phosphate

text: , but it is not accessible to plants, being in the very insoluble form of

text: iron phosphate

text: , or crandallite. It is thought that similar radioactive soils may exist on

text: Lifou

text: and

text: Mare

text: near

text: New Caledonia

text: , and

text: Rennell

text: in the

text: Solomon Islands

text: , but no other locations are known.

text: Despite thorium's radioactivity, the element has remained in use for a long time for applications not exploiting the effect as no suitable alternatives could be found. While a 1981 study estimated that a dose from using a thorium mantle every weekend would be safe for a person,  this was not the case for people manufacturing the mantles (and thus contacting many) as well as soils around some factory sites. A major shift occurred as late as in the 1990s, when most of these applications that do not depend on thorium's radioactivity declined quickly due to safety and environmental concerns as suitable safer replacements have been found. Due to concerns, some manufacturers have switched to other materials, such as yttrium, although these are usually either more expensive or less efficient. Other manufacturers continue to make thorium mantles, but moved their factories to developing countries. As recently as 2007, some companies continued to manufacture and sell thorium mantles without giving adequate information about their radioactivity, with some even fraudulently claiming them to be non-radioactive while in reality using large quantities of thorium, up to 259 milligrams per mantle.

text: Despite thorium's radioactivity, the element has remained in use for a long time for applications not exploiting the effect as no suitable alternatives could be found. While a 1981 study estimated that a dose from using a thorium mantle every weekend would be safe for a person,  this was not the case for people manufacturing the mantles (and thus contacting many) as well as soils around some factory sites. A major shift occurred as late as in the 1990s, when most of these applications that do not depend on thorium's radioactivity declined quickly due to safety and environmental concerns as suitable safer replacements have been found. Due to concerns, some manufacturers have switched to other materials, such as yttrium, although these are usually either more expensive or less efficient. Other manufacturers continue to make thorium mantles, but moved their factories to

text: developing countries

text: . As recently as 2007, some companies continued to manufacture and sell thorium mantles without giving adequate information about their radioactivity, with some even fraudulently claiming them to be non-radioactive while in reality using large quantities of thorium, up to 259 milligrams per mantle.

text: At the same time, Daneel and Giskard are engaged in a struggle of wits with Fastolfe's rivals: the roboticists Kelden Amadiro and Vasilia Aliena, Fastolfe's estranged daughter. Frustrated by his series of failures, Amadiro accepts an ambitious and unscrupulous apprentice, Levular Mandamus, who plans to destroy the population of the Earth by a newly developed weapon, the "nuclear intensifier", with which to accelerate the natural radioactive decay in the upper crust of the Earth, thereby making the surface of the Earth radioactive. R. Daneel and R. Giskard discover the roboticists' plan, and attempt to stop Amadiro; but are hampered by the First Law of Robotics,

text: At the same time, Daneel and Giskard are engaged in a struggle of wits with Fastolfe's rivals: the

text: roboticist

text: s Kelden Amadiro and

text: Vasilia Aliena

text: , Fastolfe's estranged daughter. Frustrated by his series of failures, Amadiro accepts an ambitious and unscrupulous apprentice, Levular Mandamus, who plans to destroy the population of the Earth by a newly developed weapon, the "nuclear intensifier", with which to accelerate the natural

text: radioactive decay

text: in the upper crust of the Earth, thereby making the surface of the Earth radioactive. R. Daneel and R. Giskard discover the roboticists' plan, and attempt to stop Amadiro; but are hampered by the

text: First Law of Robotics

text: Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable). Much of radiochemistry deals with the use of radioactivity to study ordinary chemical reactions. This is very different from radiation chemistry where the radiation levels are kept too low to influence the chemistry.

text: Radiochemistry is the

text: chemistry

text: of

text: radioactive

text: materials, where radioactive

text: isotope

text: chemical reaction

text: s of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable). Much of radiochemistry deals with the use of

text: radioactivity

text: to study ordinary

text: chemical reaction

text: s. This is very different from

text: radiation chemistry

text: where the radiation levels are kept too low to influence the chemistry.

text: Despite the different techniques used for non-radioactive assays, they require that ligands exhibit similar binding characteristics to its radioactive equivalent. Thus, results in both non-radioactive and radioactive assays will remain consistent.  One of the largest differences between radioactive and non-radioactive ligand assays are in regards of dangers to human health. Radioactive assays are harmful in that they produce radioactive waste; whereas, non-radioactive ligand assays utilize a different method to avoid producing toxic waste. These methods include, but are not limited to, fluorescence polarization (FP), fluorescence resonance energy transfer (FRET), and surface plasmon resonance (SPR). In order to measure process of ligand-receptor binding, most non-radioactive methods require that labeling avoids interfering with molecular interactions.

text: Despite the different techniques used for non-radioactive assays, they require that ligands exhibit similar binding characteristics to its radioactive equivalent. Thus, results in both non-radioactive and radioactive assays will remain consistent.  One of the largest differences between radioactive and non-radioactive ligand assays are in regards of dangers to human health. Radioactive assays are harmful in that they produce radioactive waste; whereas, non-radioactive ligand assays utilize a different method to avoid producing toxic waste. These methods include, but are not limited to, fluorescence polarization (FP),

text: fluorescence resonance energy transfer

text: (FRET), and

text: surface plasmon resonance

text: (SPR). In order to measure process of ligand-receptor binding, most non-radioactive methods require that labeling avoids interfering with molecular interactions.

text: These 53 stable nuclides have an even number of protons and an odd number of neutrons. They are a minority in comparison to the even-even isotopes, which are about 3 times as numerous. Among the 41 even-Z elements that have a stable nuclide, only two elements (argon and cerium) have no even-odd stable nuclides. One element (tin) has three. There are 24 elements that have one even-odd nuclide and 13 that have two odd-even nuclides. Of 35 primordial radionuclides there exist four even-odd nuclides (see table at right), including the fissile . Because of their odd neutron numbers, the even-odd nuclides tend to have large neutron capture cross sections, due to the energy that results from neutron-pairing effects. These stable even-proton odd-neutron nuclides tend to be uncommon by abundance in nature, generally because, to form and enter into primordial abundance, they must have escaped capturing neutrons to form yet other stable even-even isotopes, during both the s-process and r-process of neutron capture, during nucleosynthesis in stars. For this reason, only  and  are the most naturally abundant isotopes of their element.

text: These 53 stable nuclides have an even number of protons and an odd number of neutrons. They are a minority in comparison to the even-even isotopes, which are about 3 times as numerous. Among the 41 even-Z elements that have a stable nuclide, only two elements (argon and cerium) have no even-odd stable nuclides. One element (tin) has three. There are 24 elements that have one even-odd nuclide and 13 that have two odd-even nuclides. Of 35 primordial radionuclides there exist four even-odd nuclides (see table at right), including the

text: fissile

text: . Because of their odd neutron numbers, the even-odd nuclides tend to have large

text: neutron capture

text: cross sections, due to the energy that results from neutron-pairing effects. These stable even-proton odd-neutron nuclides tend to be uncommon by abundance in nature, generally because, to form and enter into primordial abundance, they must have escaped capturing neutrons to form yet other stable even-even isotopes, during both the

text: s-process

text: and

text: r-process

text: of neutron capture, during

text: nucleosynthesis in stars

text: . For this reason, only  and  are the most naturally abundant isotopes of their element.

text: While experimenting with the products of radioactive decay, in 1913 radiochemist Frederick Soddy discovered that there appeared to be more than one element at each position on the periodic table. The term isotope was coined by Margaret Todd as a suitable name for these elements.

text: radioactive decay

text: , in 1913

text: radiochemist

text: Frederick Soddy

text: discovered that there appeared to be more than one element at each position on the

text: periodic table

text: . The term

text: isotope

text: was coined by

text: Margaret Todd

text: as a suitable name for these elements.

text: Between 21 March and mid-July, around 2.7 × 10 Bq of caesium-137 (about 8.4 kg) entered the ocean, with about 82 percent having flowed into the sea before 8 April. However, the Fukushima coast has some of the world's strongest currents and these transported the contaminated waters far into the Pacific Ocean, thus causing great dispersion of the radioactive elements. The results of measurements of both the seawater and the coastal sediments led to the supposition that the consequences of the accident, in terms of radioactivity, would be minor for marine life as of autumn 2011 (weak concentration of radioactivity in the water and limited accumulation in sediments). On the other hand, significant pollution of sea water along the coast near the nuclear plant might persist, due to the continuing arrival of radioactive material transported towards the sea by surface water running over contaminated soil. Organisms that filter water and fish at the top of the food chain are, over time, the most sensitive to caesium pollution. It is thus justified to maintain surveillance of marine life that is fished in the coastal waters off Fukushima. Despite caesium isotopic concentration in the waters off of Japan being 10 to 1000 times above concentration prior to the accident, radiation risks are below what is generally considered harmful to marine animals and human consumers.

text: Radon was the fifth radioactive element to be discovered, in 1899 by Ernest Rutherford and Robert B. Owens, after uranium, thorium, radium and polonium.  In 1900 Friedrich Ernst Dorn reported some experiments in which he noticed that radium compounds emanate a radioactive gas he named Radium Emanation (Ra Em). Before that, in 1899, Pierre and Marie Curie observed that the gas emitted by radium remained radioactive for a month. Later that year, Robert B. Owens and Ernest Rutherford, at McGill University in Montreal, noticed variations when trying to measure radiation from thorium oxide. Rutherford noticed that the compounds of thorium continuously emit a radioactive gas that retains the radioactive powers for several minutes, and called this gas emanation (from Latin "emanare"—to elapse and "emanatio"—expiration), and later Thorium Emanation (Th Em). In 1901, he demonstrated that the emanations are radioactive, but credited the Curies for the discovery of the element. In 1903, similar emanations were observed from actinium by André-Louis Debierne and were called Actinium Emanation (Ac Em).

text: Radon was the fifth radioactive element to be discovered, in 1899 by

text: Ernest Rutherford

text: and

text: Robert B. Owens

text: , after uranium, thorium, radium and polonium.  In 1900

text: Friedrich Ernst Dorn

text: reported some experiments in which he noticed that radium compounds emanate a radioactive gas he named Radium Emanation (Ra Em). Before that, in 1899,

text: Pierre

text: and

text: Marie Curie

text: observed that the gas emitted by radium remained radioactive for a month. Later that year, Robert B. Owens and Ernest Rutherford, at

text: McGill University

text: in

text: Montreal

text: , noticed variations when trying to measure radiation from thorium oxide. Rutherford noticed that the compounds of thorium continuously emit a radioactive gas that retains the radioactive powers for several minutes, and called this gas emanation (from Latin "emanare"—to elapse and "emanatio"—expiration), and later Thorium Emanation (Th Em). In 1901, he demonstrated that the emanations are radioactive, but credited the Curies for the discovery of the element. In 1903, similar emanations were observed from actinium by

text: André-Louis Debierne

text: and were called Actinium Emanation (Ac Em).

text: Note that there are two breaks where the unstable elements technetium (atomic number: 43) and promethium (atomic number: 61) would be. These are both extremely rare, since on Earth they are only produced through the spontaneous fission of very heavy radioactive elements (for example, uranium, thorium, or the trace amounts of plutonium that exist in uranium ores), or by the interaction of certain other elements with cosmic rays. Both of the first two of these elements have been identified spectroscopically in the atmospheres of stars, where they are produced by ongoing nucleosynthetic processes. There are also breaks where the six noble gases would be, since they are not chemically bound in the Earth's crust, and they are only generated by decay chains from radioactive elements and are therefore extremely rare there. The eight naturally occurring very rare, highly radioactive elements (polonium, astatine, francium, radium, actinium, protactinium, neptunium, and plutonium) are not included, since any of these elements that were present at the formation of the Earth have decayed away eons ago, and their quantity today is negligible and is only produced from the radioactive decay of uranium and thorium.

text: Note that there are two breaks where the unstable elements

text: technetium

text: (atomic number: 43) and

text: promethium

text: (atomic number: 61) would be. These are both extremely rare, since on Earth they are only produced through the

text: spontaneous fission

text: of very heavy

text: radioactive

text: elements (for example,

text: uranium

text: thorium

text: , or the trace amounts of

text: plutonium

text: that exist in uranium ores), or by the interaction of certain other elements with

text: cosmic ray

text: s. Both of the first two of these elements have been identified spectroscopically in the atmospheres of stars, where they are produced by ongoing nucleosynthetic processes. There are also breaks where the six

text: noble gas

text: es would be, since they are not chemically bound in the Earth's crust, and they are only generated by decay chains from radioactive elements and are therefore extremely rare there. The eight naturally occurring very rare, highly radioactive elements (

text: polonium

text: astatine

text: francium

text: radium

text: actinium

text: protactinium

text: neptunium

text: , and

text: plutonium

text: ) are not included, since any of these elements that were present at the formation of the Earth have decayed away eons ago, and their quantity today is negligible and is only produced from the

text: radioactive decay

text: of uranium and thorium.

text: High-level radioactive waste management concerns how  radioactive materials created during production of nuclear power and nuclear weapons are dealt with. Radioactive waste contains a mixture of short-lived and long-lived nuclides, as well as non-radioactive nuclides. There was reported some 47,000 tonnes of high-level nuclear waste stored in the USA in 2002.

text: High-level radioactive waste management concerns how

text: radioactive

text: materials created during production of

text: nuclear power

text: and

text: nuclear weapon

text: s are dealt with. Radioactive waste contains a mixture of short-lived and long-lived nuclides, as well as non-radioactive nuclides. There was reported some 47,000 tonnes of high-level nuclear waste stored in the USA in 2002.

text: The discovery of nuclear fission occurred in 1938 in the buildings of Kaiser Wilhelm Society for Chemistry, today part of the Free University of Berlin, following nearly five decades of work on the science of radioactivity and the elaboration of new nuclear physics that described the components of atoms. In 1911, Ernest Rutherford proposed a model of the atom in which a very small, dense and positively charged nucleus of protons (the neutron had not yet been discovered) was surrounded by orbiting, negatively charged electrons (the Rutherford model). Niels Bohr improved upon this in 1913 by reconciling the quantum behavior of electrons (the Bohr model). Work by Henri Becquerel, Marie Curie, Pierre Curie, and Rutherford further elaborated that the nucleus, though tightly bound, could undergo different forms of radioactive decay, and thereby transmute into other elements. (For example, by alpha decay: the emission of an alpha particle—two protons and two neutrons bound together into a particle identical to a helium nucleus.)

text: The discovery of nuclear fission occurred in 1938 in the buildings of

text: Kaiser Wilhelm Society

text: for Chemistry, today part of the

text: Free University of Berlin

text: , following nearly five decades of work on the science of

text: radioactivity

text: and the elaboration of new

text: nuclear physics

text: that described the components of

text: atom

text: s. In 1911,

text: Ernest Rutherford

text: proposed a model of the atom in which a very small, dense and positively charged

text: nucleus

text: of

text: proton

text: s (the

text: neutron

text: had not yet been discovered) was surrounded by orbiting, negatively charged

text: electron

text: s (the

text: Rutherford model

text: Niels Bohr

text: improved upon this in 1913 by reconciling the quantum behavior of electrons (the

text: Bohr model

text: ). Work by

text: Henri Becquerel

text: Marie Curie

text: Pierre Curie

text: , and Rutherford further elaborated that the nucleus, though tightly bound, could undergo different forms of

text: radioactive decay

text: , and thereby

text: transmute

text: into other elements. (For example, by

text: alpha decay

text: : the emission of an

text: alpha particle

text: —two protons and two neutrons bound together into a particle identical to a

text: helium

text: nucleus.)

text: The nuclear drip line is the boundary delimiting the zone in which atomic nuclei lose stability due to the transmutation of neutrons, causing an isotope of one element to mutate into an element with one more proton. Atomic nuclei except for protium (the most common isotope of hydrogen which consists of a proton and no neutrons) contain both protons and neutrons—the number of protons defines the identity of that element (i.e., carbon always has 6 protons), but the number of neutrons within that element may vary (carbon-12 and its isotope carbon-13, for example). The number of isotopes each element may have is visually represented by plotting boxes, each of which represents a unique nuclear species, on a graph with the number of neutrons increasing on the X axis and number of protons increasing along the Y axis. The resulting chart is commonly referred to as the table of nuclides, and is to nuclear physics what the periodic table of the elements is to chemistry.

text: The nuclear drip line is the boundary delimiting the zone in which atomic nuclei lose stability due to the transmutation of neutrons, causing an isotope of one element to mutate into an element with one more proton. Atomic nuclei except for protium (the most common isotope of

text: hydrogen

text: which consists of a proton and no neutrons) contain both protons and neutrons—the number of protons defines the identity of that element (i.e., carbon always has 6 protons), but the number of neutrons within that element may vary (carbon-12 and its isotope carbon-13, for example). The number of isotopes each element may have is visually represented by plotting boxes, each of which represents a unique nuclear species, on a graph with the number of neutrons increasing on the X axis and number of protons increasing along the Y axis. The resulting chart is commonly referred to as the

text: table of nuclides

text: , and is to

text: nuclear physics

text: what the

text: periodic table of the elements

text: is to

text: chemistry

text: All isotopes of a chemical element contain the same number of protons with varying numbers of neutrons.  The element hydrogen has three naturally occurring isotopes, H, H and H, which are sometimes referred to as protium (H), deuterium (D) and tritium (T), respectively.  Both H and H are stable indefinitely, while H is unstable and undergoes beta decay to form He.  While there are some important applications of H in geochemistry (such as its use as an ocean circulation tracer) these will not be discussed further here.

text: All isotopes of a chemical element contain the same number of protons with varying numbers of neutrons.  The element hydrogen has three naturally occurring

text: isotopes

text: , H, H and H, which are sometimes referred to as protium (H), deuterium (D) and tritium (T), respectively.  Both H and H are stable indefinitely, while H is

text: unstable

text: and undergoes beta decay to form He.  While there are some important applications of H in geochemistry (such as its use as an

text: ocean circulation tracer

text: ) these will not be discussed further here.

text: In nuclear physics, the following fundamental relationship governs radioactive decay: the number of radioactive atoms  in a sample of a radioactive isotope decays at a rate proportional to .  This leads to the first order linear differential equation

text: In

text: nuclear physics

text: , the following fundamental relationship governs

text: radioactive decay

text: : the number of radioactive atoms  in a sample of a radioactive

text: isotope

text: decays at a rate proportional to .  This leads to the first order linear differential equation

text: After radioactive water was discovered in a tunnel under reactor 2 on 18 December, the government directed TEPCO to survey the plant's underground facilities and check for more accumulation of radioactive water.  TEPCO finds an additional 500 tons of water containing 16,200 Bq/cm of radioactive caesium in a pit near reactor 2, and 600 tons of 860 Bq/cm water near reactor 3.

text: The projected cost would be $14–16 billion and the period of realization 12–14 years.  The elements of MEK were initially designed to be launched into space by the Energia heavy booster, resembling the Saturn V moon booster by its payload capacity.  Later however, in order to lower the cost of the mission, the elements of MEK were redesigned to be launched by a Proton or Angara rocket. The overall weight of MEK is about 400 tons. The flight from earth orbit to Mars will be powered by ion thruster engines.

text: The projected cost would be $14–16 billion and the period of realization 12–14 years.  The elements of MEK were initially designed to be launched into space by the Energia heavy booster, resembling the

text: Saturn V

text: moon booster by its payload capacity.  Later however, in order to lower the cost of the mission, the elements of MEK were redesigned to be launched by a

text: Proton

text: or

text: Angara

text: rocket. The overall weight of MEK is about 400 tons. The flight from earth orbit to Mars will be powered by

text: ion thruster

text: engines.

text: Some radioactive materials have short half-lives; some have long half-lives. Uranium and thorium have long half-lives, and so persist in Earth's crust, but radioactive elements with short half-lives have generally disappeared. This suggested that it might be possible to measure the age of Earth by determining the relative proportions of radioactive materials in geological samples. In reality, radioactive elements do not always decay into nonradioactive ("stable") elements directly, instead, decaying into other radioactive elements that have their own half-lives and so on, until they reach a stable element. Such "decay series", such as the uranium-radium and thorium series, were known within a few years of the discovery of radioactivity, and provided a basis for constructing techniques of radiometric dating.

text: Some radioactive materials have short half-lives; some have long half-lives.

text: Uranium

text: and

text: thorium

text: have long half-lives, and so persist in Earth's crust, but radioactive elements with short half-lives have generally disappeared. This suggested that it might be possible to measure the age of Earth by determining the relative proportions of radioactive materials in geological samples. In reality, radioactive elements do not always decay into nonradioactive ("stable") elements directly, instead, decaying into other radioactive elements that have their own half-lives and so on, until they reach a

text: stable element

text: . Such "decay series", such as the uranium-radium and thorium series, were known within a few years of the discovery of radioactivity, and provided a basis for constructing techniques of radiometric dating.

text: There are many other kinds of radioactivity, e.g. cluster decay, proton decay, various beta-delayed decay modes (p, 2p, 3p, n, 2n, 3n, 4n, d, t, alpha, f), fission isomers, particle accompanied (ternary) fission, etc. The height of the potential barrier, mainly of Coulomb nature, for emission of the charged particles is much higher than the observed kinetic energy of the emitted particles. The spontaneous decay can only be explained by quantum tunneling in a similar way to the first application of the Quantum Mechanics to Nuclei given by G. Gamow for alpha decay.

text: There are many other kinds of radioactivity, e.g. cluster decay,

text: proton decay

text: , various beta-delayed decay modes (p, 2p, 3p, n, 2n, 3n, 4n, d, t, alpha, f),

text: fission isomer

text: s, particle accompanied (ternary) fission, etc. The height of the potential barrier, mainly of Coulomb nature, for emission of the charged particles is much higher than the observed kinetic energy of the emitted particles. The spontaneous decay can only be explained by

text: quantum tunneling

text: in a similar way to the first application of the Quantum Mechanics to Nuclei given by G. Gamow for alpha decay.

text: Early 20th century chemist Henry Moseley speculated that the answer to the number of protons lay in the nucleus. By firing a radioactive source at copper, he was able to knock electrons from their atoms, releasing a burst of energy in the form of an x-ray. When measured, the x-rays always had the same energy, unique to copper. He discovered each element released x-rays of different energies.  Moseley’s brilliance was to realise the x-ray energy is related to the number of protons inside the atom: the atomic number.

text: Early 20th century chemist

text: Henry Moseley

text: speculated that the answer to the number of protons lay in the nucleus. By firing a radioactive source at copper, he was able to knock electrons from their atoms, releasing a burst of energy in the form of an

text: x-ray

text: . When measured, the x-rays always had the same energy, unique to copper. He discovered each element released x-rays of different energies.  Moseley’s brilliance was to realise the x-ray energy is related to the number of protons inside the atom: the

text: atomic number

text: The hazards to people and the environment from radioactive contamination depend on the nature of the radioactive contaminant, the level of contamination, and the extent of the spread of contamination. Low levels of radioactive contamination pose little risk, but can still be detected by radiation instrumentation. If a survey or map is made of a contaminated area, random sampling locations may be labeled with their activity in becquerels or curies on contact. Low levels may be reported in counts per minute  using a scintillation counter.

text: The hazards to people and the environment from radioactive contamination depend on the nature of the radioactive contaminant, the level of contamination, and the extent of the spread of contamination. Low levels of radioactive contamination pose little risk, but can still be detected by radiation instrumentation. If a survey or map is made of a contaminated area, random sampling locations may be labeled with their activity in

text: becquerels

text: or

text: curies

text: on contact. Low levels may be reported in

text: counts per minute

text: using a

text: scintillation counter

text: At the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. In 1897, J. J. Thomson of Cambridge University discovered the electron and soon after the French scientist Becquerel as well as the couple Pierre and Marie Curie investigated the phenomenon of radioactivity. In a series of pioneering scattering experiments Ernest Rutherford at the University of Manchester  discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles.

text: At the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. In 1897,

text: J. J. Thomson

text: of

text: Cambridge University

text: discovered the

text: electron

text: and soon after the French scientist

text: Becquerel

text: as well as the couple

text: Pierre

text: and

text: Marie Curie

text: investigated the phenomenon of

text: radioactivity

text: . In a series of pioneering scattering experiments

text: Ernest Rutherford

text: at the

text: University of Manchester

text: discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully

text: transmuted

text: the first element by bombarding

text: nitrogen

text: with

text: alpha particle

text: s.

text: If reprocessing is undertaken only to reduce the radioactivity level of spent fuel it should be taken into account that spent nuclear fuel becomes less radioactive over time. After 40 years its radioactivity drops by 99.9%, though it still takes over a thousand years for the level of radioactivity to approach that of natural uranium. However the level of transuranic elements,including plutonium-239, remains high for over 100,000 years, so if not reused as nuclear fuel, then those elements need secure disposal because of nuclear proliferation reasons as well as radiation hazard.

text: If reprocessing is undertaken only to reduce the radioactivity level of spent fuel it should be taken into account that spent nuclear fuel becomes less radioactive over time. After 40 years its radioactivity drops by 99.9%, though it still takes over a thousand years for the level of radioactivity to approach that of natural uranium. However the level of

text: transuranic element

text: s,including

text: , remains high for over 100,000 years, so if not reused as nuclear fuel, then those elements need secure disposal because of

text: nuclear proliferation

text: reasons as well as radiation hazard.

text: Although every element up to bismuth (element 83) has an isotope that is practically stable for all purposes ("classically stable"), with the exceptions of technetium and promethium (elements 43 and 61), all elements from polonium (element 84) onward are noticeably radioactive. Of these, thorium (element 90) is the most stable, closely followed by uranium (element 92): the isotope Th has a half-life of 14.05 billion years, about three times the age of the earth, and even slightly longer than the generally accepted age of the universe (about 13.8 billion years). As such, Th still occurs naturally today: four-fifths of the thorium present at Earth's formation has survived to the present. Thorium and uranium are thus the most well-studied of all the radioactive elements.

text: Although every element up to

text: bismuth

text: (element 83) has an isotope that is practically stable for all purposes ("classically stable"), with the exceptions of

text: technetium

text: and

text: promethium

text: (elements 43 and 61), all elements from

text: polonium

text: (element 84) onward are noticeably radioactive. Of these, thorium (element 90) is the most stable, closely followed by uranium (element 92): the isotope Th has a half-life of 14.05 billion years, about three times the

text: age of the earth

text: , and even slightly longer than the generally accepted

text: age of the universe

text: (about 13.8 billion years). As such, Th still occurs naturally today: four-fifths of the thorium present at Earth's formation has survived to the present. Thorium and uranium are thus the most well-studied of all the radioactive elements.

text: A series of different experimental methods exist, these have been designed to enable the measurement of a range of different elements in different matrices. To reduce the effect of the matrix it is common to use the chemical extraction of the wanted element and/or to allow the radioactivity due to the matrix elements to decay before the measurement of the radioactivity. Since the matrix effect can be corrected for by observing the decay spectrum, little or no sample preparation is required for some samples, making neutron activation analysis less susceptible to contamination.

text: A series of different experimental methods exist, these have been designed to enable the measurement of a range of different elements in different matrices. To reduce the effect of the

text: matrix

text: it is common to use the chemical extraction of the wanted element and/or to allow the radioactivity due to the matrix elements to decay before the measurement of the radioactivity. Since the matrix effect can be corrected for by observing the decay spectrum, little or no sample preparation is required for some samples, making neutron activation analysis less susceptible to contamination.

text: In 1905 Albert Einstein formulated the idea of mass–energy equivalence. While the work on radioactivity by Becquerel and Marie Curie predates this, an explanation of the source of the energy of radioactivity would have to wait for the discovery that the nucleus itself was composed of smaller constituents, the nucleons.

text: In 1905

text: Albert Einstein

text: formulated the idea of

text: mass–energy equivalence

text: . While the work on radioactivity by

text: Becquerel

text: and

text: Marie Curie

text: predates this, an explanation of the source of the energy of radioactivity would have to wait for the discovery that the nucleus itself was composed of smaller constituents, the

text: nucleon

text: s.

text: As the universe expands, it cools. Free neutrons and protons are less stable than helium nuclei, and the protons and neutrons have a strong tendency to form helium-4. However, forming helium-4 requires the intermediate step of forming deuterium. Before nucleosynthesis began, the temperature was high enough for many photons to have energy greater than the binding energy of deuterium; therefore any deuterium that was formed was immediately destroyed (a situation known as the deuterium bottleneck). Hence, the formation of helium-4 is delayed until the universe became cool enough for deuterium to survive (at about T = 0.1 MeV); after which there was a sudden burst of element formation. However, very shortly thereafter, at twenty minutes after the Big Bang, the universe became too cool for any further nuclear fusion and nucleosynthesis to occur. At this point, the elemental abundances were nearly fixed, and only change was the result of the radioactive decay of the two major unstable products of BBN, tritium and beryllium-7.

text: As the universe expands, it cools.

text: Free neutron

text: s and protons are less stable than helium nuclei, and the protons and neutrons have a strong tendency to form helium-4. However, forming helium-4 requires the intermediate step of forming deuterium. Before nucleosynthesis began, the temperature was high enough for many photons to have energy greater than the binding energy of deuterium; therefore any deuterium that was formed was immediately destroyed (a situation known as the deuterium bottleneck). Hence, the formation of helium-4 is delayed until the universe became cool enough for deuterium to survive (at about T = 0.1 MeV); after which there was a sudden burst of element formation. However, very shortly thereafter, at twenty minutes after the Big Bang, the universe became too cool for any further nuclear fusion and nucleosynthesis to occur. At this point, the elemental abundances were nearly fixed, and only change was the result of the

text: radioactive

text: decay of the two major unstable products of BBN,

text: tritium

text: and

text: Because of its cost and radioactivity, experimental chemical research is seldom performed with radon, and as a result there are very few reported compounds of radon, all either fluorides or oxides. Radon can be oxidized by powerful oxidizing agents such as fluorine, thus forming radon difluoride. It decomposes back to elements at a temperature of above 250 °C. It has a low volatility and was thought to be . Because of the short half-life of radon and the radioactivity of its compounds, it has not been possible to study the compound in any detail. Theoretical studies on this molecule predict that it should have a Rn–F bond distance of 2.08 Å, and that the compound is thermodynamically more stable and less volatile than its lighter counterpart . The octahedral molecule  was predicted to have an even lower enthalpy of formation than the difluoride. The higher fluorides RnF and RnF have been claimed, and are calculated to be stable, but it is doubtful whether they have yet been synthesized. The [RnF] ion is believed to form by the following reaction:

text: Because of its cost and radioactivity, experimental chemical research is seldom performed with radon, and as a result there are very few reported compounds of radon, all either

text: fluoride

text: s or

text: oxide

text: s. Radon can be

text: oxidized

text: by powerful oxidizing agents such as

text: fluorine

text: , thus forming

text: radon difluoride

text: . It decomposes back to elements at a temperature of above 250 °C. It has a low

text: volatility

text: and was thought to be . Because of the short half-life of radon and the radioactivity of its compounds, it has not been possible to study the compound in any detail. Theoretical studies on this molecule predict that it should have a Rn–F

text: bond distance

text: of 2.08

text: Å

text: , and that the compound is thermodynamically more stable and less volatile than its lighter counterpart . The

text: octahedral molecule

text: was predicted to have an even lower

text: enthalpy of formation

text: than the difluoride. The higher fluorides RnF and RnF have been claimed, and are calculated to be stable, but it is doubtful whether they have yet been synthesized. The [RnF]

text: ion

text: is believed to form by the following reaction:

text: On 3 August, the prefecture Shimane, in western Japan, conducted radiation checks on all beef cattle to ease consumer concerns about food safety. Starting from the second week of August all cattle were tested. Late July at one farm in this prefecture rice-straw was discovered with radioactive caesium levels exceeding the government safety guide. Although all other tests of beef cattle found far lower levels of radioactivity than the government standard, prices of beef from Shimane plummeted and wholesalers avoided all cattle from the prefecture. All processed beef would undergo preliminary screening, and meat registering 250 becquerels per kilogram or more of radioactive caesium – half the government safety level – would be tested further.

text: On 3 August, the prefecture

text: Shimane

text: , in western Japan, conducted radiation checks on all beef cattle to ease consumer concerns about food safety. Starting from the second week of August all cattle were tested. Late July at one farm in this prefecture rice-straw was discovered with radioactive caesium levels exceeding the government safety guide. Although all other tests of beef cattle found far lower levels of radioactivity than the government standard, prices of beef from Shimane plummeted and wholesalers avoided all cattle from the prefecture. All processed beef would undergo preliminary screening, and meat registering 250 becquerels per kilogram or more of radioactive caesium – half the government safety level – would be tested further.

text: The atomic number of an element is equal to the number of protons in each atom, and defines the element. For example, all carbon atoms contain 6 protons in their atomic nucleus; so the atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of the same element having different numbers of neutrons are known as isotopes of the element.

text: The

text: atomic number

text: of an element is equal to the number of protons in each atom, and defines the element. For example, all carbon atoms contain 6 protons in their

text: atomic nucleus

text: ; so the atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of the same element having different numbers of neutrons are known as

text: isotope

text: s of the element.

text: As nuclei grow bigger still, this disruptive effect becomes steadily more significant. By the time polonium is reached (84 protons), nuclei can no longer accommodate their large positive charge, but emit their excess protons quite rapidly in the process of alpha radioactivity—the emission of helium nuclei, each containing two protons and two neutrons. (Helium nuclei are an especially stable combination.) Because of this process, nuclei with more than 94 protons are not found naturally on Earth (see periodic table). The isotopes beyond uranium (atomic number 92) with the longest half-lives are plutonium-244 (80 million years) and curium-247 (16 million years).

text: As nuclei grow bigger still, this disruptive effect becomes steadily more significant. By the time

text: polonium

text: is reached (84 protons), nuclei can no longer accommodate their large positive charge, but emit their excess protons quite rapidly in the process of alpha radioactivity—the emission of helium nuclei, each containing two protons and two neutrons. (Helium nuclei are an especially stable combination.) Because of this process, nuclei with more than 94 protons are not found naturally on Earth (see

text: periodic table

text: ). The isotopes beyond uranium (atomic number 92) with the longest half-lives are plutonium-244 (80 million years) and curium-247 (16 million years).

text: Protons and neutrons, being distinct types of particles, occupy different quantum states.  One can think of two different "pools" of states, one for protons and one for neutrons.  Now, for example, if there are significantly more neutrons than protons in a nucleus, some of the neutrons will be higher in energy than the available states in the proton pool.  If we could move some particles from the neutron pool to the proton pool, in other words change some neutrons into protons, we would significantly decrease the energy.  The imbalance between the number of protons and neutrons causes the energy to be higher than it needs to be, for a given number of nucleons.  This is the basis for the asymmetry term.

text: Marie Curie began her investigations by testing a uranium ore called pitchblende with an electrometer. She discovered it was four times more radioactive than pure uranium, and wondered if this was due to the presence of an even more radioactive element in the pitchblende.

text: Marie Curie

text: began her investigations by testing a uranium ore called

text: pitchblende

text: with an electrometer. She discovered it was four times more radioactive than pure uranium, and wondered if this was due to the presence of an even more radioactive element in the pitchblende.

text: Elements with atomic numbers 1 through 40 are all stable, while those with atomic numbers 41 through 82 (except technetium and promethium) are metastable. The half-lives of these metastable "theoretical radionuclides" are so long (at least 100 million times longer than the estimated age of the universe) that their radioactive decay has yet to be detected by experiment. Elements with atomic numbers 83 through 94 are unstable to the point that their radioactive decay can be detected. Three of these elements, bismuth (element 83), thorium (element 90), and uranium (element 92) have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy elements before the formation of our solar system. For example, at over 1.9 years, over a billion times longer than the current estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any naturally occurring element. The very heaviest 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half-lives and cannot be produced as daughters of longer-lived elements, and thus they do not occur in nature at all.

text: Elements with atomic numbers 1 through 40 are all stable, while those with atomic numbers 41 through 82 (except technetium and promethium) are metastable. The half-lives of these metastable "

entity_section: Nuclides with no experimentally observed decays

text: theoretical radionuclides

text: " are so long (at least 100 million times longer than the estimated

text: age of the universe

text: ) that their radioactive decay has yet to be detected by experiment. Elements with atomic numbers 83 through 94 are unstable to the point that their radioactive decay can be detected. Three of these elements, bismuth (element 83), thorium (element 90), and uranium (element 92) have one or more isotopes with half-lives long enough to survive as remnants of the explosive

text: stellar nucleosynthesis

text: that produced the heavy elements before the formation of our solar system. For example, at over 1.9 years, over a billion times longer than the current estimated age of the universe,

text: has the longest known

text: alpha decay

text: half-life of any naturally occurring element. The very heaviest 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half-lives and cannot be produced as daughters of longer-lived elements, and thus they do not occur in nature at all.

text: Induced radioactivity occurs when a previously stable material has been made radioactive by exposure to specific radiation. Most radioactivity does not induce other material to become radioactive. This Induced radioactivity was discovered by Irène Curie and F. Joliot in 1934 and received the Nobel Prize in 1935 for this discovery.  This is also known as man-made radioactivity. The phenomenon by which even light elements are made radioactive by artificial or induced methods is called artificial radioactivity.

text: Induced radioactivity occurs when a previously stable material has been made

text: radioactive

text: by exposure to specific

text: radiation

text: . Most radioactivity does not induce other material to become radioactive. This Induced radioactivity was discovered by

text: Irène Curie

text: and

text: F. Joliot

text: in 1934 and received the Nobel Prize in 1935 for this discovery.  This is also known as man-made radioactivity. The phenomenon by which even light elements are made radioactive by artificial or induced methods is called artificial radioactivity.

text: He also observed that the intensity of radioactivity of a radioactive element decreases over a unique and regular amount of time until a point of stability, and he named the halving time the "half-life." In 1901 and 1902 he worked with Frederick Soddy to prove that atoms of one radioactive element would spontaneously turn into another, by expelling a piece of the atom at high velocity. In 1906 at the University of Manchester, Rutherford oversaw an experiment conducted by his students Hans Geiger (known for the Geiger counter) and Ernest Marsden. In the Geiger–Marsden experiment, a beam of alpha particles, generated by the radioactive decay of radon, was directed normally onto a sheet of very thin gold foil in an evacuated chamber. Under the prevailing plum pudding model, the alpha particles should all have passed through the foil and hit the detector screen, or have been deflected by, at most, a few degrees.

text: He also observed that the intensity of radioactivity of a radioactive element decreases over a unique and regular amount of time until a point of stability, and he named the halving time the "

text: half-life

text: ." In 1901 and 1902 he worked with Frederick Soddy to prove that atoms of one radioactive element would spontaneously turn into another, by expelling a piece of the atom at high velocity. In 1906 at the University of Manchester, Rutherford oversaw an experiment conducted by his students

text: Hans Geiger

text: (known for the

text: Geiger counter

text: ) and

text: Ernest Marsden

text: . In the

text: Geiger–Marsden experiment

text: , a beam of alpha particles, generated by the radioactive decay of

text: radon

text: , was directed normally onto a sheet of very thin gold foil in an evacuated chamber. Under the prevailing

text: plum pudding model

text: , the alpha particles should all have passed through the foil and hit the detector screen, or have been deflected by, at most, a few degrees.

text: In 1972 the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter was held and in 1975 the USSR ratified the agreement to limit the dumping of high-level radioactive wastes in the oceans. In 1983 many Convention members signed a voluntary moratorium on all dumping of radioactive wastes at sea, but the USSR did not sign and continued to dispose of low-level radioactive reactor coolant water from its nuclear submarines. Leaks and intentional releases of radioactive materials from Russian facilities in the Far East prompted Japan to offer financial aid for Russia to build facilities to treat low-level radioactive water in 1994. By 1996 a design for a floating processing facility was accepted and contracts issued to the Tomen Corporation (Japan), Babcock & Wilcox (USA) and  the Amurskiy shipyard (Russia). Landysh was built at the Amurskiy  shipyard in Komsomolsk-on-Amur, completed in 1998 and commissioned in 2000. Landysh remained at Zvezda shipyard in Bolshoy Kamen until 2011. As of May 9, 2011 discussions between Rosatom, the Russian nuclear agency, and Japan concerning the dispatch of Landysh to Japan were still ongoing. Japanese reluctance to accept Russian assistance may be linked to the Kuril Islands dispute between Russia and Japan.

text: In 1972 the

entity_name: London Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter

text: Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter

text: was held and in 1975 the

text: USSR

text: ratified the agreement to limit the dumping of high-level radioactive wastes in the oceans. In 1983 many Convention members signed a voluntary moratorium on all dumping of radioactive wastes at sea, but the USSR did not sign and continued to dispose of low-level radioactive reactor coolant water from its nuclear submarines. Leaks and intentional releases of radioactive materials from Russian facilities in the Far East prompted Japan to offer financial aid for Russia to build facilities to treat low-level radioactive water in 1994. By 1996 a design for a floating processing facility was accepted and contracts issued to the Tomen Corporation (Japan),

text: Babcock & Wilcox

text: (USA) and  the Amurskiy shipyard (Russia). Landysh was built at the Amurskiy  shipyard in

text: Komsomolsk-on-Amur

text: , completed in 1998 and commissioned in 2000. Landysh remained at

text: Zvezda shipyard

text: in

text: Bolshoy Kamen

text: until 2011. As of May 9, 2011 discussions between

text: Rosatom

text: , the Russian nuclear agency, and Japan concerning the dispatch of Landysh to Japan were still ongoing. Japanese reluctance to accept Russian assistance may be linked to the

text: Kuril Islands dispute

text: between Russia and Japan.

text: There is a debate over what should constitute an acceptable scientific and engineering foundation for proceeding with radioactive waste disposal strategies. There are those who have argued, on the basis of complex geochemical simulation models, that relinquishing control over radioactive materials to geohydrologic processes at repository closure is an acceptable risk. They maintain that so-called "natural analogues" inhibit subterranean movement of radionuclides, making disposal of radioactive wastes in stable geologic formations unnecessary. However, existing models of these processes are empirically underdetermined: due to the subterranean nature of such processes in solid geologic formations, the accuracy of computer simulation models has not been verified by empirical observation, certainly not over periods of time equivalent to the lethal half-lives of high-level radioactive waste. On the other hand, some insist deep geologic repositories in stable geologic formations are necessary. National management plans of various countries display a variety of approaches to resolving this debate.

text: In Earth's continental crust, the decay of natural radioactive isotopes has had significant involvement in the origin of geothermal heat. The continental crust is abundant in lower density minerals but also contains significant concentrations of heavier lithophilic minerals such as uranium. Because of this, it holds the largest global reservoir of radioactive elements found in the Earth. Especially in layers closer to Earth's surface, naturally occurring isotopes are enriched in the granite and basaltic rocks. These high levels of radioactive elements are largely excluded from the Earth's mantle due to their inability to substitute in mantle minerals and consequent enrichment in partial melts. The mantle is mostly made up of high density minerals with high contents of atoms that have relatively small atomic radii such as magnesium (Mg), titanium (Ti), and calcium (Ca).

text: In Earth's continental crust, the decay of natural radioactive isotopes has had significant involvement in the origin of geothermal heat. The continental crust is abundant in lower density minerals but also contains significant concentrations of heavier

text: lithophilic

text: minerals such as uranium. Because of this, it holds the largest global reservoir of radioactive elements found in the Earth. Especially in layers closer to Earth's surface, naturally occurring isotopes are enriched in the granite and basaltic rocks. These high levels of radioactive elements are largely excluded from the Earth's mantle due to their inability to substitute in mantle minerals and consequent enrichment in partial melts. The mantle is mostly made up of high density minerals with high contents of atoms that have relatively small atomic radii such as magnesium (Mg), titanium (Ti), and calcium (Ca).

text: The additional radioactivity in the biosphere caused by human activity due to the releases of man-made radioactivity and of Naturally Occurring Radioactive Materials (NORM) can be divided into several classes.

text: Uranium is a silvery-gray metallic weakly radioactive chemical element. It has the chemical symbol U and atomic number 92. The most common isotopes in natural uranium are U (99.27%) and U (0.72%). All uranium isotopes present in natural uranium are radioactive and fissionable, and U is fissile (will support a neutron-mediated chain reaction). Uranium, thorium, and potassium are the main elements contributing to natural terrestrial radioactivity.

text: Uranium is a silvery-gray

text: metal

text: lic weakly

text: radioactive

text: chemical element

text: . It has the

text: chemical symbol

text: U and

text: atomic number

text: 92. The most common

text: isotope

text: s in natural uranium are

text: U

text: (99.27%) and

text: U

text: (0.72%). All uranium isotopes present in natural uranium are

text: radioactive

text: and

text: fissionable

text: , and U is

text: fissile

text: (will support a neutron-mediated chain reaction). Uranium,

text: thorium

text: , and

text: potassium

text: are the main elements contributing to natural terrestrial radioactivity.

text: Many historians consider the discovery of artificially produced radionuclides by Frédéric Joliot-Curie and Irène Joliot-Curie in 1934 as the most significant milestone in nuclear medicine. In February 1934, they reported the first artificial production of radioactive material in the journal Nature, after discovering radioactivity in aluminum foil that was irradiated with a polonium preparation. Their work built upon earlier discoveries by Wilhelm Konrad Roentgen for X-ray, Henri Becquerel for radioactive uranium salts, and Marie Curie (mother of Irène Curie) for radioactive thorium, polonium and coining the term "radioactivity." Taro Takemi studied the application of nuclear physics to medicine in the 1930s. The history of nuclear medicine will not be complete without mentioning these early pioneers.

text: Many historians consider the discovery of artificially produced radionuclides by

text: Frédéric Joliot-Curie

text: and

text: Irène Joliot-Curie

text: in 1934 as the most significant milestone in nuclear medicine. In February 1934, they reported the first artificial production of radioactive material in the journal

text: Nature

text: , after discovering radioactivity in aluminum foil that was irradiated with a polonium preparation. Their work built upon earlier discoveries by

text: Wilhelm Konrad Roentgen

text: for X-ray,

text: Henri Becquerel

text: for radioactive uranium salts, and

text: Marie Curie

text: (mother of Irène Curie) for radioactive thorium, polonium and coining the term "radioactivity."

text: Taro Takemi

text: studied the application of

text: nuclear physics

text: to medicine in the 1930s. The history of nuclear medicine will not be complete without mentioning these early pioneers.

text: There are three ways a radiographer will ensure they are not exposed to higher than required levels of radiation, time, distance, shielding. The less time that a person is exposed to radiation the lower their dose will be. The further a person is from a radioactive source the lower the level of radiation they receive, this is largely due to the inverse square law. Lastly the more a radioactive source is shielded by either better or greater amounts of shielding the lower the levels of radiation that will escape from the testing area. The most commonly used shielding materials in use are sand, lead (sheets or shot), steel, spent (non-radioactive uranium) tungsten and in suitable situations water.

text: Gold is currently considered the heaviest monoisotopic element (bismuth formerly held that distinction, but bismuth-209 has been found to be slightly radioactive).

text: Gold is currently considered the heaviest

text: monoisotopic element

text: bismuth

text: formerly held that distinction, but

text: has been found to be slightly radioactive).

text: Radionuclides used in radiopharmaceuticals are mostly radioactive isotopes of elements with atomic numbers less than that of bismuth, that is, they are radioactive isotopes of elements that also have one or more stable isotopes. These may be roughly divided into two classes:

text: Radionuclides used in radiopharmaceuticals are mostly radioactive

text: isotopes

text: of elements with atomic numbers less than that of

text: bismuth

text: , that is, they are radioactive isotopes of elements that also have one or more stable isotopes. These may be roughly divided into two classes:

text: A chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z. The mass number is the sum of the number of protons and neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number; atoms of an element which have different mass numbers are known as isotopes. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13.

text: A chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of

text: proton

text: s in the nuclei of its atoms, known as the

text: atomic number

text: and represented by the symbol Z. The

text: mass number

text: is the sum of the number of protons and neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number; atoms of an element which have different mass numbers are known as

text: isotope

text: s. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element

text: carbon

text: , but atoms of carbon may have mass numbers of 12 or 13.

text: Radiochemistry, radiation chemistry and nuclear chemical engineering play a very important role for uranium and thorium fuel precursors synthesis, starting from ores of these elements, fuel fabrication, coolant chemistry, fuel reprocessing, radioactive waste treatment and storage, monitoring of radioactive elements release during reactor operation and radioactive geological storage, etc.

text: It is a two-dimensional graphical representation in the Segrè-arrangement with the neutron number N on the abscissa and the proton number Z on the ordinate. Each nuclide is represented at the intersection of its respective neutron and proton number by a small square box with the chemical symbol and the nucleon number A. By columnar subdivision of such a field, in addition to ground states also nuclear isomers can be shown. The coloring of a field (segmented if necessary) shows in addition to the existing text entries the observed types of radioactive decay of the nuclide and a rough classification of their relative shares: stable, nonradioactive nuclides completely black, primordial radionuclides partially black, proton emission orange, alpha decay yellow, beta plus decay/electron capture red, isomeric transition (gamma decay, internal conversion) white, beta minus decay blue, spontaneous fission green, cluster emission violet, neutron emission light blue. For each radionuclide its field includes (if known) information about its half-life and essential energies of the emitted radiation, for stable nuclides and primordial radionuclides there are data on mole fraction abundances in the natural isotope mixture of the corresponding chemical element. Furthermore, for many nuclides cross sections for nuclear reactions with thermal neutrons are quoted, usually for the (n, γ)-reaction (neutron capture), partly fission cross sections for the induced nuclear fission and cross sections for the (n, α)-reaction or (n, p)-reaction. For the chemical elements cross sections and relative atomic masses (both averaged over natural isotopic composition) are specified (the relative atomic masses partially as an interval to reflect the variability of the composition of the element's natural isotope mixture). For the nuclear fission of U and Pu with thermal neutrons, percentage isobaric chain yields of fission products are listed.

text: It is a two-dimensional graphical representation in the

text: Segrè

text: -arrangement with the

text: neutron number

text: N on the

text: abscissa

text: and the

text: proton number

text: Z on the

text: ordinate

text: . Each

text: nuclide

text: is represented at the intersection of its respective neutron and proton number by a small square box with the

text: chemical symbol

text: and the

text: nucleon number

text: A. By columnar subdivision of such a field, in addition to

text: ground state

text: s also

text: nuclear isomer

text: s can be shown. The coloring of a field (segmented if necessary) shows in addition to the existing text entries the observed types of

text: radioactive decay

text: of the nuclide and a rough classification of their relative shares:

text: stable, nonradioactive nuclides

text: completely black,

text: primordial radionuclides

text: partially black,

text: proton emission

text: orange,

text: alpha decay

text: yellow,

text: beta plus decay

text: electron capture

text: red,

text: isomeric transition

text: gamma decay

text: internal conversion

text: ) white,

text: beta minus decay

text: blue,

text: spontaneous fission

text: green,

text: cluster emission

text: violet,

text: neutron emission

text: light blue. For each

text: radionuclide

text: its field includes (if known) information about its

text: half-life

text: and essential energies of the emitted radiation, for stable nuclides and primordial radionuclides there are data on

text: mole fraction

text: abundances in the

text: natural isotope mixture

text: of the corresponding

text: chemical element

text: . Furthermore, for many nuclides

text: cross sections

text: for

text: nuclear reaction

text: s with

text: thermal neutrons

text: are quoted, usually for the (n, γ)-reaction (

text: neutron capture

text: ), partly fission cross sections for the induced

text: nuclear fission

text: and cross sections for the (n, α)-reaction or (n, p)-reaction. For the chemical elements cross sections and

text: relative atomic mass

text: es (both averaged over natural isotopic composition) are specified (the relative atomic masses partially as an interval to reflect the variability of the composition of the element's natural isotope mixture). For the nuclear fission of

text: U

text: and

text: Pu

text: with thermal neutrons, percentage

text: isobaric chain yields

text: of

text: fission product

text: s are listed.

text: Although prompt (i.e. not beta-delayed) proton emission was observed from an isomer in cobalt-53 as early as 1969, no other proton-emitting states were found until 1981, when the proton radioactive ground states of lutetium-151 and thulium-147 were observed at experiments at the GSI in West Germany. Research in the field flourished after this breakthrough, and to date more than 25 isotopes have been found to exhibit proton emission. The study of proton emission has aided the understanding of nuclear deformation, masses and structure, and it is a wonderfully pure example of quantum tunneling.

text: Although prompt (i.e. not beta-delayed) proton emission was observed from an isomer in

text: as early as 1969, no other proton-emitting states were found until 1981, when the proton radioactive ground states of

text: and

text: were observed at experiments at the

entity_name: GSI Helmholtz Centre for Heavy Ion Research

text: GSI

text: in West Germany. Research in the field flourished after this breakthrough, and to date more than 25 isotopes have been found to exhibit proton emission. The study of proton emission has aided the understanding of nuclear deformation, masses and structure, and it is a wonderfully pure example of

text: quantum tunneling

text: The radioactive decay of K in the Earth's mantle ranks third, after Th and U, as the source of radiogenic heat.  The core also likely contains radiogenic sources, although how much is uncertain.  It has been proposed that significant core radioactivity (1-2 TW) may be caused by high levels of U, Th, and K.

text: The radioactive decay of K in the Earth's mantle ranks third, after

text: Th

text: and

text: U

text: , as the source of

text: radiogenic heat

text: .  The core also likely contains radiogenic sources, although how much is uncertain.  It has been proposed that significant core radioactivity (1-2 TW) may be caused by high levels of U, Th, and K.

text: Xiangjiangite is a phosphate mineral discovered near and named for the Xiang Jiang River in China. Xiangjiangite is radioactive.

text: Xiangjiangite is a

text: phosphate mineral

text: discovered near and named for the

text: Xiang Jiang River

text: in

text: China

text: . Xiangjiangite is

text: radioactive

text: Studies of the "radioactivity", that soon revealed the phenomenon of radioactive decay, provided another argument against considering chemical elements as fundamental nature's elements. Despite these discoveries, the term atom stuck to Dalton's (chemical) atoms and now denotes the smallest particle of a chemical element, not something really indivisible.

text: Studies of the "radioactivity", that soon revealed the phenomenon of

text: radioactive decay

text: , provided another argument against considering

text: chemical element

text: s as fundamental nature's elements. Despite these discoveries, the term atom stuck to Dalton's (chemical) atoms and now denotes the smallest particle of a chemical element, not something really indivisible.

text: Some organs concentrate certain elements and hence radionuclide variants of those elements. This action may lead to much lower removal rates. For instance, the thyroid gland takes up a large percentage of any iodine that enters the body. Large quantities of inhaled or ingested radioactive iodine may impair or destroy the thyroid, while other tissues are affected to a lesser extent. Radioactive iodine-131 is a common fission product; it was a major component of the radioactivity released from the Chernobyl disaster, leading to nine fatal cases of pediatric thyroid cancer and hypothyroidism. On the other hand, radioactive iodine is used in the diagnosis and treatment of many diseases of the thyroid precisely because of the thyroid's selective uptake of iodine.

text: Some organs concentrate certain elements and hence radionuclide variants of those elements. This action may lead to much lower removal rates. For instance, the

text: thyroid

text: gland takes up a large percentage of any

text: iodine

text: that enters the body. Large quantities of inhaled or ingested

text: radioactive iodine

text: may impair or destroy the thyroid, while other tissues are affected to a lesser extent. Radioactive iodine-131 is a common

text: fission product

text: ; it was a major component of the radioactivity released from the

text: Chernobyl disaster

text: , leading to nine fatal cases of pediatric

text: thyroid cancer

text: and

text: hypothyroidism

text: . On the other hand, radioactive iodine is used in the diagnosis and treatment of many diseases of the thyroid precisely because of the thyroid's selective uptake of iodine.

text: The conditions inside certain types of nuclear reactors with high neutron flux can cause induced radioactivity. The components in those reactors may become highly radioactive from the radiation to which they are exposed. Induced radioactivity increases the amount of nuclear waste that must eventually be disposed, but it is not referred to as radioactive contamination unless it is uncontrolled.

text: The conditions inside certain types of

text: nuclear reactor

text: s with high

text: neutron flux

text: can cause induced radioactivity. The components in those reactors may become highly radioactive from the radiation to which they are exposed. Induced radioactivity increases the amount of

text: nuclear waste

text: that must eventually be disposed, but it is not referred to as

text: radioactive contamination

text: unless it is uncontrolled.

text: A thorium atom has 90 protons and therefore 90 electrons, of which four are valence electrons. Thorium metal is silvery and tarnishes black when exposed to air, forming the dioxide. Thorium is weakly radioactive: all its known isotopes are unstable. Thorium-232 (Th), which has 142 neutrons, is the most stable isotope of thorium and accounts for nearly all natural thorium, with six other natural isotopes occurring only as trace radioisotopes. Thorium has the longest half-life of all the significantly radioactive elements, 14.05 billion years, or about the age of the universe; it decays very slowly through alpha decay to radium-228 (Ra), starting a decay chain named the thorium series that ends at stable lead-208 (Pb). Thorium is estimated to be about three to four times more abundant than uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare earth metals.

text: A thorium atom has 90

text: proton

text: s and therefore 90

text: electron

text: s, of which four are

text: valence electron

text: s. Thorium metal is silvery and

text: tarnish

text: es black when exposed to air, forming the dioxide. Thorium is weakly radioactive: all its known

text: isotope

text: s are unstable. Thorium-232 (Th), which has 142

text: neutron

text: s, is the most stable isotope of thorium and accounts for nearly all natural thorium, with six other natural isotopes occurring only as

text: trace radioisotope

text: s. Thorium has the longest half-life of all the significantly radioactive elements, 14.05 billion years, or about the

text: age of the universe

text: ; it decays very slowly through

text: alpha decay

text: to

text: (Ra), starting a

text: decay chain

text: named the

text: thorium series

text: that ends at stable

text: lead

text: -208 (Pb). Thorium is estimated to be about three to four times more

text: abundant

text: than uranium in the Earth's crust, and is chiefly refined from

text: monazite

text: sands as a by-product of extracting

text: rare earth metal

text: s.

text: Radioactivity was discovered using potassium uranyl sulfate, KUO(SO).

text: Radioactivity

text: was discovered using potassium uranyl sulfate, KUO(SO).

text: Because this is the number of protons, the atomic number must be a whole number – there cannot be any fractional values. Moseley realised it was the atomic number, not the atomic weight that determines the order of the elements. What’s more, because the atomic number increases in whole numbers from one element to the next there can be no extra elements between Hydrogen (atomic number 1) and Uranium (atomic number 92) – there can only be 92 elements, there is no room for any more.

text: Radioactive waste treatment is the treatment and containment of radioactive waste.

text: Radioactive waste treatment

text: is the treatment and containment of radioactive waste.

text: Forsmark Nuclear Power Plant is a nuclear power plant in Forsmark, Sweden, and also the site of the Swedish Final repository for radioactive operational waste. It is operated by a subsidiary of Vattenfall.

text: Forsmark Nuclear Power Plant is a

text: nuclear power plant

text: in

text: Forsmark

text: Sweden

text: , and also the site of the Swedish Final repository for radioactive operational waste. It is operated by a subsidiary of

text: Vattenfall

text: Both John Herschel and William Whewell systematized methodology: the latter coined the term scientist. When Charles Darwin published On the Origin of Species he established evolution as the prevailing explanation of biological complexity. His theory of natural selection provided a natural explanation of how species originated, but this only gained wide acceptance a century later. John Dalton developed the idea of atoms. The laws of thermodynamics and the electromagnetic theory were also established in the 19th century, which raised new questions which could not easily be answered using Newton's framework. The phenomena that would allow the deconstruction of the atom were discovered in the last decade of the 19th century: the discovery of X-rays inspired the discovery of radioactivity. In the next year came the discovery of the first subatomic particle, the electron.

text: Both

text: John Herschel

text: and

text: William Whewell

text: systematized methodology: the latter coined the term

text: scientist

text: . When

text: Charles Darwin

text: published

text: On the Origin of Species

text: he established

text: evolution

text: as the prevailing explanation of biological complexity. His theory of

text: natural selection

text: provided a natural explanation of how

text: species

text: originated, but this only gained wide acceptance a century later.

text: John Dalton

text: developed the idea of

text: atom

text: s. The laws of

text: thermodynamics

text: and the

text: electromagnetic theory

text: were also established in the 19th century, which raised new questions which could not easily be answered using Newton's framework. The phenomena that would allow the deconstruction of the

text: atom

text: were discovered in the last decade of the 19th century: the discovery of

text: X-ray

text: s inspired the discovery of

text: radioactivity

text: . In the next year came the discovery of the first subatomic particle, the

text: electron

text: Explosive nucleosynthesis occurs too rapidly for radioactive decay to decrease the number of neutrons, so that many abundant isotopes with equal and even numbers of protons and neutrons are synthesized by the silicon quasiequilibrium process. During this process, the burning of oxygen and silicon fuses nuclei that themselves have equal numbers of protons and neutrons to produce nuclides which consist of whole numbers of helium nuclei, up to 15 (representing Ni). Such multiple-alpha-particle nuclides are totally stable up to Ca (made of 10 helium nuclei), but heavier nuclei with equal and even numbers of protons and neutrons are tightly bound but unstable. The quasiequilibrium produces radioactive isobars  Ti, Cr, Fe, and Ni, which (except Ti) are created in abundance but decay after the explosion and leave the most stable isotope of the corresponding element at the same atomic weight. The most abundant and extant isotopes of elements produced in this way are Ti, Cr, and Fe. These decays are accompanied by the emission of gamma-rays (radiation from the nucleus), whose spectroscopic lines can be used to identify the isotope created by the decay. The detection of these emission lines were an important early product of gamma-ray astronomy.

text: Explosive nucleosynthesis occurs too rapidly for radioactive decay to decrease the number of neutrons, so that many abundant isotopes with equal and even numbers of protons and neutrons are synthesized by the silicon quasiequilibrium process. During this process, the burning of oxygen and silicon fuses nuclei that themselves have equal numbers of protons and neutrons to produce nuclides which consist of whole numbers of helium nuclei, up to 15 (representing Ni). Such multiple-alpha-particle nuclides are totally stable up to Ca (made of 10 helium nuclei), but heavier nuclei with equal and even numbers of protons and neutrons are tightly bound but unstable. The quasiequilibrium produces radioactive

text: isobars

text: Ti, Cr, Fe, and Ni, which (except Ti) are created in abundance but decay after the explosion and leave the most stable isotope of the corresponding element at the same atomic weight. The most abundant and extant isotopes of elements produced in this way are Ti, Cr, and Fe. These decays are accompanied by the emission of gamma-rays (radiation from the nucleus), whose

text: spectroscopic lines

text: can be used to identify the isotope created by the decay. The detection of these emission lines were an important early product of gamma-ray astronomy.

text: Supernova radioactivity dominates light curves and the chemistry of dust condensation is also dominated by radioactivity. Dust is usually either carbon or oxides depending on which is more abundant, but Compton electrons dissociate the CO molecule in about one month. The new chemical astronomy of supernova solids depends on the supernova radioactivity:

text: This tendency for fission product nuclei to beta-decay is the fundamental cause of the problem of radioactive high level waste from nuclear reactors. Fission products tend to be beta emitters, emitting fast-moving electrons to conserve electric charge, as excess neutrons convert to protons in the fission-product atoms. See Fission products (by element) for a description of fission products sorted by element.

text: This tendency for fission product nuclei to beta-decay is the fundamental cause of the problem of

text: radioactive

text: high level waste

text: from nuclear reactors. Fission products tend to be

text: beta emitters

text: emitting

text: fast-moving

text: electron

text: s to conserve

text: electric charge

text: , as excess neutrons convert to protons in the fission-product atoms. See

text: Fission products (by element)

text: for a description of fission products sorted by element.

text: Kristensen discovered Limnognathia maerski, the first (and so far only) known species in the group, in a radioactive spring on Disko Island in 2000.

text: Kristensen discovered

text: Limnognathia maerski

text: , the first (and so far only) known species in the group, in a radioactive spring on

text: Disko Island

text: in 2000.

text: Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the atomic nucleus of an isotope is unstable, compounds containing this isotope are radioactive. Tritium is an example of a radioactive isotope.

text: Isotope

text: s of a

text: chemical element

text: differ only in the mass number. For example, the isotopes of

text: hydrogen

text: can be written as

text: H

text: H

text: and

text: H

text: , with the mass number at top left. When the

text: atomic nucleus

text: of an isotope is unstable, compounds containing this isotope are

text: radioactive

text: Tritium

text: is an example of a radioactive isotope.

text: In 1901, Rutherford and Frederick Soddy showed that alpha and beta radioactivity involves the transmutation of atoms into atoms of other chemical elements. In 1913, after the products of more radioactive decays were known, Soddy and Kazimierz Fajans independently proposed their radioactive displacement law, which states that beta (i.e., ) emission from one element produces another element one place to the right in the periodic table, while alpha emission produces an element two places to the left.

text: In 1901, Rutherford and

text: Frederick Soddy

text: showed that alpha and beta radioactivity involves the

text: transmutation

text: of atoms into atoms of other chemical elements. In 1913, after the products of more radioactive decays were known, Soddy and

text: Kazimierz Fajans

text: independently proposed their

text: radioactive displacement law

text: , which states that beta (i.e., ) emission from one element produces another element one place to the right in the

text: periodic table

text: , while alpha emission produces an element two places to the left.

text: In the years that followed, radioactivity was extensively investigated, notably by the husband and wife team of Pierre Curie and Marie Curie and by Ernest Rutherford and his collaborators. By the turn of the century physicists had also discovered three types of radiation emanating from atoms, which they named alpha, beta, and gamma radiation. Experiments by Otto Hahn in 1911 and by James Chadwick in 1914 discovered that the beta decay spectrum was continuous rather than discrete. That is, electrons were ejected from the atom with a continuous range of energies, rather than the discrete amounts of energy that were observed in gamma and alpha decays. This was a problem for nuclear physics at the time, because it seemed to indicate that energy was not conserved in these decays.

text: In the years that followed,

text: radioactivity

text: was extensively investigated, notably by the husband and wife team of

text: Pierre Curie

text: and

text: Marie Curie

text: and by

text: Ernest Rutherford

text: and his collaborators. By the turn of the century physicists had also discovered three types of

text: radiation

text: emanating from atoms, which they named

text: alpha

text: beta

text: , and

text: gamma

text: radiation. Experiments by

text: Otto Hahn

text: in 1911 and by

text: James Chadwick

text: in 1914 discovered that the beta decay

text: spectrum

text: was continuous rather than discrete. That is, electrons were ejected from the atom with a continuous range of energies, rather than the discrete amounts of energy that were observed in gamma and alpha decays. This was a problem for nuclear physics at the time, because it seemed to indicate that

text: energy was not conserved

text: in these decays.

text: At the beginning of the 20th century it was widely believed that atoms never change: an atom of one element stayed that way forever.  Rutherford had already revealed the structure of an atom to consist mostly of empty space with a dense nucleus of protons at the centre, and Henry Mosley had shown that it is the number of protons that gives an atom its identity as a particular element. An atom of the element carbon has 6 protons, whilst an atom with 7 protons is one of nitrogen.

text: At the beginning of the 20th century it was widely believed that atoms never change: an atom of one element stayed that way forever.

text: Rutherford

text: had already revealed the structure of an atom to consist mostly of empty space with a dense nucleus of protons at the centre, and Henry Mosley had shown that it is the number of protons that gives an atom its identity as a particular element. An atom of the element carbon has 6 protons, whilst an atom with 7 protons is one of nitrogen.

text: Since radioactivity was discovered around the turn of the 20th century, the main application of radioluminescence has been in radioluminescent paint, used on watch and compass dials, gunsights, aircraft flight instrument faces, and other instruments, to allow them to be seen in the dark.  Radioluminescent paint consists of a mixture of a chemical containing a radioisotope with a radioluminescent chemical (phosphor).  The continuous radioactive decay of the isotope's atoms releases radiation particles which strike the molecules of the phosphor, causing them to give off light.  The constant bombardment by radioactive particles causes the chemical breakdown of many types of phosphor, so radioluminescent paints lose some of their luminosity over their working life.

text: Since radioactivity was discovered around the turn of the 20th century, the main application of radioluminescence has been in

text: radioluminescent paint

text: , used on

text: watch

text: and

text: compass

text: dials,

text: gunsight

text: s,

text: aircraft flight instrument

text: faces, and other instruments, to allow them to be seen in the dark.  Radioluminescent paint consists of a mixture of a chemical containing a

text: radioisotope

text: with a radioluminescent chemical (

text: phosphor

text: ).  The continuous

text: radioactive decay

text: of the isotope's atoms releases radiation particles which strike the molecules of the phosphor, causing them to give off light.  The constant bombardment by radioactive particles causes the chemical breakdown of many types of phosphor, so radioluminescent paints lose some of their luminosity over their working life.

text: Tritium, or hydrogen-3, with one proton and two neutrons, was produced by proton and neutron collisions in the early universe as well, but it has since radioactively decayed to helium-3. Modern tritium cannot be explained by big bang nucleosynthesis because of tritium's short half-life of 12.3 years. Today's tritium concentration is instead governed by nuclear reactions and cosmic rays. The radioactive beta decay of tritium to helium releases an electron and an antineutrino, with an average energy release of 18.6 MeV. It is important to note that this is classified as a relatively weak beta reaction, so the radioactivity cannot permeate skin. Tritium is thus only hazardous if directly ingested or inhaled.

text: Tritium

text: , or hydrogen-3, with one proton and two neutrons, was produced by proton and neutron collisions in the early universe as well, but it has since

text: radioactively decayed

text: to

text: . Modern tritium cannot be explained by

text: big bang nucleosynthesis

text: because of tritium's short

text: half-life

text: of 12.3 years. Today's tritium concentration is instead governed by

text: nuclear reactions

text: and

text: cosmic rays

text: . The radioactive beta decay of tritium to helium releases an electron and an antineutrino, with an average energy release of 18.6 MeV. It is important to note that this is classified as a relatively weak beta reaction, so the radioactivity cannot permeate skin. Tritium is thus only hazardous if directly ingested or inhaled.

text: The natives return in 1969 and stay for ten years, but doctors notice a radioactive element left over by the blast, Cesium 137, and the natives leave the island again.

text: Radioactive waste is waste that contains radioactive material. Radioactive waste is usually a by-product of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine. Radioactive waste is hazardous to most forms of life and the environment, and is regulated by government agencies in order to protect human health and the environment.

text: Radioactive waste is

text: waste

text: that contains

text: radioactive

text: material. Radioactive waste is usually a

text: by-product

text: of

text: nuclear power

text: generation and other applications of

text: nuclear fission

text: or

text: nuclear technology

text: , such as

text: research

text: and

text: medicine

text: . Radioactive waste is

text: hazardous

text: to most forms of life and the environment, and is

text: regulated

text: by government agencies in order to protect human health and the environment.

text: Radioactivity naturally decays over time, so radioactive waste has to be isolated and confined in appropriate disposal facilities for a sufficient period until it no longer poses a threat. The time radioactive waste must be stored for depends on the type of waste and radioactive isotopes. It can range from a few days for highly radioactive isotopes to millions of years for slightly radioactive ones. Current major approaches to managing radioactive waste have been segregation and storage for short-lived waste, near-surface disposal for low and some intermediate level waste, and deep burial or partitioning / transmutation for the high-level waste.

text: Radioactivity naturally decays over time, so radioactive waste has to be isolated and confined in appropriate disposal facilities for a sufficient period until it no longer poses a threat. The time radioactive waste must be stored for depends on the type of waste and radioactive isotopes. It can range from a few days for highly radioactive isotopes to millions of years for slightly radioactive ones. Current major approaches to managing radioactive waste have been segregation and storage for short-lived waste, near-surface disposal for low and some intermediate level waste, and

text: deep burial

text: or

text: partitioning / transmutation

text: for the high-level waste.

text: In 1896, Henri Becquerel found that rays emanating from certain minerals penetrated black paper and caused fogging of an unexposed photographic plate. His doctoral student Marie Curie discovered that only certain chemical elements gave off these rays of energy. She named this behavior radioactivity.

text: In 1896,

text: Henri Becquerel

text: found that rays emanating from certain minerals penetrated black paper and caused fogging of an unexposed photographic plate. His doctoral student

text: Marie Curie

text: discovered that only certain chemical elements gave off these rays of energy. She named this behavior

text: radioactivity

text: Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. They separated out an element similar to bismuth from pitchblende in July 1898, that turned out to be polonium. They then separated out a radioactive mixture consisting mostly of two components: compounds of barium, which gave a brilliant green flame color, and unknown radioactive compounds which gave carmine spectral lines that had never been documented before. The Curies found the radioactive compounds to be very similar to the barium compounds, except that they were more insoluble. This made it possible for the Curies to separate out the radioactive compounds and discover a new element in them. The Curies announced their discovery to the French Academy of Sciences on 26 December 1898. The naming of radium dates to about 1899, from the French word radium, formed in Modern Latin from radius (ray): this was in recognition of radium's power of emitting energy in the form of rays.

text: Radium was

text: discovered

text: by

text: Marie Sklodowska-Curie

text: and her husband

text: Pierre Curie

text: on 21 December 1898, in a

text: uraninite

text: sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. They separated out an element similar to

text: bismuth

text: from pitchblende in July 1898, that turned out to be

text: polonium

text: . They then separated out a radioactive mixture consisting mostly of two components: compounds of

text: barium

text: , which gave a brilliant green flame color, and unknown radioactive compounds which gave

text: carmine

text: spectral line

text: s that had never been documented before. The Curies found the radioactive compounds to be very similar to the barium compounds, except that they were more insoluble. This made it possible for the Curies to separate out the radioactive compounds and discover a new element in them. The Curies announced their discovery to the

text: French Academy of Sciences

text: on 26 December 1898. The naming of radium dates to about 1899, from the French word radium, formed in Modern Latin from radius (ray): this was in recognition of radium's power of emitting energy in the form of rays.

text: Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in nuclear medicine is spilled (accidentally or, as in the case of the Goiânia accident, through ignorance), the material could be spread by people as they walk around. Radioactive contamination may also be an inevitable result of certain processes, such as the release of radioactive xenon in nuclear fuel reprocessing. In cases that radioactive material cannot be contained, it may be diluted to safe concentrations. For a discussion of environmental contamination by alpha emitters please see actinides in the environment.

text: Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in

text: nuclear medicine

text: is spilled (accidentally or, as in the case of the

text: Goiânia accident

text: , through ignorance), the material could be spread by people as they walk around. Radioactive contamination may also be an inevitable result of certain processes, such as the release of radioactive

text: xenon

text: in

text: nuclear fuel reprocessing

text: . In cases that radioactive material cannot be contained, it may be diluted to safe concentrations. For a discussion of environmental contamination by

text: alpha

text: emitters please see

text: actinides in the environment

text: Henri Becquerel discovered radioactivity by using uranium in 1896. Becquerel made the discovery in Paris by leaving a sample of a uranium salt, KUO(SO) (potassium uranyl sulfate), on top of an unexposed photographic plate in a drawer and noting that the plate had become "fogged". He determined that a form of invisible light or rays emitted by uranium had exposed the plate.

text: Henri Becquerel

text: discovered

text: radioactivity

text: by using uranium in 1896. Becquerel made the discovery in Paris by leaving a sample of a uranium salt, KUO(SO) (potassium uranyl sulfate), on top of an unexposed

text: photographic plate

text: in a drawer and noting that the plate had become "fogged". He determined that a form of invisible light or rays emitted by uranium had exposed the plate.

text: Tin (Sn) is the element with the greatest number of stable isotopes (ten; three of them are potentially radioactive but have not been observed to decay), which is probably related to the fact that 50 is a "magic number" of protons. 29 additional unstable isotopes are known, including the "doubly magic" tin-100 (Sn) (discovered in 1994) and tin-132 (Sn). The longest-lived radioisotope is Sn, with a half-life of 230,000 years. The other 28 radioisotopes have half-lives less than a year.

text: Tin

text: (Sn) is the element with

text: the greatest number of stable isotopes

text: (ten; three of them are potentially radioactive but have not been observed to decay), which is probably related to the fact that 50 is a "

text: magic number

text: " of protons. 29 additional unstable isotopes are known, including the "

text: doubly magic

text: " tin-100 (Sn) (discovered in 1994) and tin-132 (Sn). The longest-lived radioisotope is Sn, with a half-life of 230,000 years. The other 28 radioisotopes have half-lives less than a year.

text: This element was the first one discovered by the Curies while they were investigating the cause of pitchblende radioactivity. Pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated radium.

text: This element was the first one discovered by the Curies while they were investigating the cause of

text: pitchblende

text: radioactivity

text: . Pitchblende, after removal of the radioactive elements

text: uranium

text: and

text: thorium

text: , was more radioactive than the uranium and thorium combined. This spurred the Curies to search for additional radioactive elements. They first separated out polonium from pitchblende in July 1898, and five months later, also isolated

text: radium

text: In 1896, Henri Becquerel discovered radioactivity.  It was only a little over a quarter of a century (1925) until the first radioactive tracer study in animals was performed by George de Hevesy, and the next year (1926) the first diagnostic tracer study in humans was performed by Herman Blumgart and Otto Yens.

text: In 1896,

text: Henri Becquerel

text: discovered

text: radioactivity

text: .  It was only a little over a quarter of a century (1925) until the first radioactive tracer study in animals was performed by

text: George de Hevesy

text: , and the next year (1926) the first diagnostic tracer study in

text: humans

text: was performed by Herman Blumgart and Otto Yens.

text: It was reported that radioactive iodine was detected in the tap water in Fukushima, Tochigi, Gunma, Tokyo, Chiba, Saitama, and Niigata, and radioactive cesium in the tap water in Fukushima, Tochigi and Gunma. Radioactive cesium, iodine, and strontium were also detected in the soil in some places in Fukushima. There may be a need to replace the contaminated soil. Many radioactive hotspots were found outside the evacuation zone, including Tokyo. Food products were also found contaminated by radioactive matter in several places in Japan. On 5 April 2011, the government of the Ibaraki Prefecture banned the fishing of sand lance after discovering that this species was contaminated by radioactive cesium above legal limits. As late as July 2013 slightly elevated levels of radioactivity were found in beef on sale at Tokyo markets. No death or morbidity has so far been reported as a result of the radioactive emissions.

text: It was reported that radioactive iodine was detected in the tap water in Fukushima, Tochigi, Gunma, Tokyo, Chiba, Saitama, and Niigata, and radioactive cesium in the tap water in Fukushima, Tochigi and Gunma. Radioactive cesium, iodine, and strontium were also detected in the soil in some places in Fukushima. There may be a need to replace the contaminated soil. Many radioactive hotspots were found outside the evacuation zone, including Tokyo. Food products were also found contaminated by radioactive matter in several places in Japan. On 5 April 2011, the government of the

text: Ibaraki Prefecture

text: banned the fishing of

text: sand lance

text: after discovering that this species was contaminated by radioactive

text: cesium

text: above legal limits. As late as July 2013 slightly elevated levels of radioactivity were found in beef on sale at Tokyo markets. No death or morbidity has so far been reported as a result of the radioactive emissions.

text: Proton emission is not seen in naturally occurring nuclides. Proton emitters can be produced via nuclear reactions, usually utilizing linear particle accelerators (linac).  Although prompt (i.e. not beta-delayed) proton emission was observed from an isomer in cobalt-53 as early as 1969, no other proton-emitting states were found until 1981, when the proton radioactive ground states of lutetium-151 and thulium-147 were observed at experiments at the GSI in West Germany. Research in the field flourished after this breakthrough, and to date more than 25 nuclides have been found to exhibit proton emission. The study of proton emission has aided the understanding of nuclear deformation, masses and structure, and it is an example of quantum tunneling.

text: Proton emission is not seen in naturally occurring nuclides. Proton emitters can be produced via

text: nuclear reaction

text: s, usually utilizing linear particle accelerators (

text: linac

text: ).  Although prompt (i.e. not beta-delayed) proton emission was observed from an isomer in

text: and

text: were observed at experiments at the

text: GSI

text: in West Germany. Research in the field flourished after this breakthrough, and to date more than 25 nuclides have been found to exhibit proton emission. The study of proton emission has aided the understanding of nuclear deformation, masses and structure, and it is an example of

text: quantum tunneling

text: High levels of contamination may pose major risks to people and the environment. People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an accident (or a deliberate initiation) involving large quantities of radioactive material. The biological effects of external exposure to radioactive contamination are generally the same as those from an external radiation source not involving radioactive materials, such as x-ray machines, and are dependent on the absorbed dose.

text: High levels of contamination may pose major risks to people and the environment. People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an

entity_name: Nuclear and radiation accidents and incidents

text: accident

text: (or a

text: deliberate initiation

text: ) involving large quantities of radioactive material. The

text: biological effects of external exposure

text: to radioactive contamination are generally the same as those from an external radiation source not involving radioactive materials, such as

text: x-ray

text: machines, and are dependent on the

text: absorbed dose

text: Radioactive beams of specific isotopes are widely used in the fields of experimental physics, biology and materials science. The production and formation of these radioactive atoms into an ionic beam for study is an entire field of research carried out at many laboratories throughout the world. The first isotope separator was developed at the Copenhagen Cyclotron by Bohr and co-workers using the principle of electromagnetic separation. Today, there are many laboratories around the world which supply beams of radioactive ions for use. Arguably the principal Isotope Separator On-Line (ISOL) is ISOLDE at CERN, which is a joint European facility spread across the Franco-Swiss border near the city of Geneva. This laboratory uses mainly proton spallation of uranium carbide targets to produce a wide range of radioactive fission fragments that are not found naturally on earth. During spallation (bombardment with high energy protons), a uranium carbide target is heated to several thousand degrees so that radioactive atoms produced in the nuclear reaction are released. Once out of the target, the vapour of radioactive atoms travels to an ionizer cavity. This ionizer cavity is a thin tube made of a refractory metal with a high work function allowing for collisions with the walls to liberate a single electron from a free atom (surface ionization effect). Once ionized, the radioactive species are accelerated by an electrostatic field and injected into an electromagnetic separator. As ions entering the separator are of approximately equal energy, those ions with a smaller mass will be deflected by the magnetic field by a greater amount than those with a heavier mass. This differing radius of curvature allows for isobaric purification to take place. Once purified isobarically, the ion beam is then sent to the individual experiments. In order to increase the purity of the isobaric beam, laser ionization can take place inside the ionizer cavity to selectively ionize a single element chain of interest. At CERN, this device is called the Resonance Ionization Laser Ion Source (RILIS). Currently over 60% of all experiments opt to use the RILIS to increase the purity of radioactive beams.

text: work function

text: allowing for collisions with the walls to liberate a single electron from a free atom (

text: surface ionization

text: effect). Once ionized, the radioactive species are accelerated by an electrostatic field and injected into an electromagnetic separator. As ions entering the separator are of approximately equal energy, those ions with a smaller mass will be deflected by the magnetic field by a greater amount than those with a heavier mass. This differing radius of curvature allows for isobaric purification to take place. Once purified isobarically, the ion beam is then sent to the individual experiments. In order to increase the purity of the isobaric beam, laser ionization can take place inside the ionizer cavity to selectively ionize a single element chain of interest. At CERN, this device is called the Resonance Ionization Laser Ion Source (RILIS). Currently over 60% of all experiments opt to use the RILIS to increase the purity of radioactive beams.

text: Proton-rich nuclides can be produced by sequentially adding one or more protons to an atomic nucleus. Such a nuclear reaction of type (p,γ) is called proton capture reaction. By adding a proton to a nucleus, the element is changed because the chemical element is defined by the proton number of a nucleus. At the same time the ratio of protons to neutrons is changed, resulting in a proton-richer isotope of the next element. This led to the original idea for the production of p-nuclei: free protons (the nuclei of hydrogen atoms are present in stellar plasmas) should be captured on heavy nuclei (seed nuclei) also already present in the stellar plasma (previously produced in the s- and/or r-process).

text: Proton-rich nuclides can be produced by sequentially adding one or more protons to an

text: atomic nucleus

text: . Such a

text: nuclear reaction

text: of type (p,γ) is called proton capture reaction. By adding a proton to a nucleus, the

text: element

text: is changed because the chemical element is defined by the

text: proton number

text: of a nucleus. At the same time the ratio of protons to

text: neutron

text: s is changed, resulting in a proton-richer isotope of the next element. This led to the original idea for the production of p-nuclei: free protons (the nuclei of

text: hydrogen

text: atom

text: s are present in stellar

text: plasmas

text: ) should be captured on heavy nuclei (seed nuclei) also already present in the stellar plasma (previously produced in the

text: s-

text: and/or

text: r-process

text: The becquerel (symbol Bq) (pronounced:  ) is the  SI derived unit of radioactivity. One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The becquerel is therefore equivalent to an inverse second, s. The becquerel is named after Henri Becquerel, who shared a Nobel Prize with Pierre Curie and Marie Curie in 1903 for their work in discovering radioactivity.

text: The becquerel (symbol Bq) (pronounced:  ) is the

text: SI derived unit

text: of

text: radioactivity

text: . One becquerel is defined as the

text: activity

text: of a quantity of radioactive material in which one

text: nucleus

text: decays per

text: second

text: . The becquerel is therefore equivalent to an inverse second,

text: s

text: . The becquerel is named after

text: Henri Becquerel

text: , who shared a

text: Nobel Prize

text: with

text: Pierre Curie

text: and

text: Marie Curie

text: in 1903 for their work in discovering radioactivity.

text: Not all neutrons are emitted as a direct product of fission;  some are instead due to the radioactive decay of some of the fission fragments.  The neutrons that occur directly from fission are called "prompt neutrons," and the ones that are a result of radioactive decay of fission fragments are called "delayed neutrons." The fraction of neutrons that are delayed is called β, and this fraction is typically less than 1% of all the neutrons in the chain reaction.

text: Not all neutrons are emitted as a direct product of fission;  some are instead due to the

text: radioactive decay

text: of some of the fission fragments.  The neutrons that occur directly from fission are called "

text: prompt neutron

text: s," and the ones that are a result of radioactive decay of fission fragments are called "delayed neutrons." The fraction of neutrons that are delayed is called β, and this fraction is typically less than 1% of all the neutrons in the chain reaction.

text: The lightest chemical elements are hydrogen and helium, both created by Big Bang nucleosynthesis during the first 20 minutes of the universe in a ratio of around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of the next two elements, lithium and beryllium. Almost all other elements found in nature were made by various natural methods of nucleosynthesis. On Earth, small amounts of new atoms are naturally produced in nucleogenic reactions, or in cosmogenic processes, such as cosmic ray spallation. New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay, beta decay, spontaneous fission, cluster decay, and other rarer modes of decay.

text: The lightest chemical elements are hydrogen and

text: helium

text: , both created by

text: Big Bang nucleosynthesis

text: during the

text: first 20 minutes of the universe

text: in a

text: ratio

text: of around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of the next two elements,

text: lithium

text: and

text: beryllium

text: . Almost all other elements found in nature were made by various natural methods of

text: nucleosynthesis

text: . On Earth, small amounts of new atoms are naturally produced in

text: nucleogenic

text: reactions, or in

text: cosmogenic

text: processes, such as

text: cosmic ray spallation

text: . New atoms are also naturally produced on Earth as

text: radiogenic

text: daughter isotope

text: s of ongoing

text: radioactive decay

text: processes such as

text: alpha decay

text: beta decay

text: spontaneous fission

text: cluster decay

text: , and other rarer modes of decay.

text: On the other hand, carbon-14 naturally decays by radioactive beta decay, whereby one neutron is transmuted into a proton with the emission of an electron and an anti-neutrino.  Thus the atomic number increases by 1 (Z: 6→7) and the mass number remains the same (A = 14), while the number of neutrons decreases by 1 (N: 8→7).  The resulting atom is nitrogen-14, with seven protons and seven neutrons:

text: On the other hand,

text: naturally decays by radioactive

text: beta decay

text: , whereby one neutron is transmuted into a proton with the emission of an

text: electron

text: and an

text: anti-neutrino

text: .  Thus the atomic number increases by 1 (Z: 6→7) and the mass number remains the same (A = 14), while the number of neutrons decreases by 1 (N: 8→7).  The resulting atom is

text: , with seven protons and seven neutrons:

text: While isotopes with atomic numbers higher than lead (82) are known to be radioactive, an "island of stability" has been proposed for some elements with atomic numbers above 103. These superheavy elements may have a nucleus that is relatively stable against radioactive decay. The most likely candidate for a stable superheavy atom, unbihexium, has 126 protons and 184 neutrons.

text: While isotopes with atomic numbers higher than

text: lead

text: (82) are known to be radioactive, an "

text: island of stability

text: " has been proposed for some elements with atomic numbers above 103. These

text: superheavy element

text: s may have a nucleus that is relatively stable against radioactive decay. The most likely candidate for a stable superheavy atom,

text: unbihexium

text: , has 126 protons and 184 neutrons.

text: Radioactive has received mixed to positive reviews. Before release, the album was noted by the influential hip-hop magazine The Source as being a near classic, with a 4.5/5 rating. At Metacritic the album received an average score of 62 out of 100, based on 16 reviews. Acclaimed Hip-hop magazine XXL gave the album a 4/5 (XL) rating, saying "more than not, the album is a standout effort that introduces the full-range of his talents as an MC with crafty songwriting abilities and deft ear for a sonic palette". Prefix Magazine stated that it was "hard to view Radioactive in any context that doesn’t label it as a total artistic failure" and that Yelawolf was "rolling over to commercial demands". PopMatters echoed this sentiment, calling the album a "misguided grasp at populism" and criticising Yelawolf's willingness to "play second fiddle" to A&R demands. Complex Magazine rated Radioactive as #18 in the 25 Best Albums of 2011. Noted hip hop magazine XXL, Radioactive was ranked at number 10 of the best albums of 2011.

text: Radioactive has received mixed to positive reviews. Before release, the album was noted by the influential hip-hop magazine

text: The Source

text: as being a near classic, with a 4.5/5 rating. At Metacritic the album received an average score of 62 out of 100, based on 16 reviews. Acclaimed Hip-hop magazine

text: XXL

text: gave the album a 4/5 (XL) rating, saying "more than not, the album is a standout effort that introduces the full-range of his talents as an MC with crafty songwriting abilities and deft ear for a sonic palette". Prefix Magazine stated that it was "hard to view Radioactive in any context that doesn’t label it as a total artistic failure" and that Yelawolf was "rolling over to commercial demands".

text: PopMatters

text: echoed this sentiment, calling the album a "misguided grasp at populism" and criticising Yelawolf's willingness to "play second fiddle" to A&R demands.

text: Complex Magazine

text: rated Radioactive as #18 in the 25 Best Albums of 2011. Noted

text: hip hop

text: magazine

text: XXL

text: , Radioactive was ranked at number 10 of the best albums of 2011.

text: Most fission products have too many neutrons to be stable so they are radioactive by beta decay, converting neutrons into protons by throwing off beta particles (electrons) and gamma rays. Their half lives range from milliseconds to about 200,000 years. Many decay into isotopes that are themselves radioactive, so from 1 to 6 (average 3) decays may be required to reach stability. In reactors, the radioactive products are the nuclear waste in spent fuel. In bombs, they become radioactive fallout, both local and global.

text: Most fission products have too many neutrons to be stable so they are radioactive by

text: beta decay

text: , converting neutrons into protons by throwing off beta particles (electrons) and gamma rays. Their half lives range from milliseconds to about 200,000 years. Many decay into isotopes that are themselves radioactive, so from 1 to 6 (average 3) decays may be required to reach stability. In reactors, the radioactive products are the nuclear waste in spent fuel. In bombs, they become radioactive fallout, both local and global.

text: The serum levels of LH (Leutenizing Hormone) and FSH (follicle Stimulating Hormone) were measured using a double antibody method and an RIA kit. The rat’s LH-I-9 and FSH-I-9 were labeled with 125-I using the chloramines-T- method with LH-RP-3 and FSH-I-9 being the controls. The chloroamines-T-method is used to label small concentrations of a certain substances by producing a very specific radioactive tracer molecule—which in this case is radioactively labeled Iodine, the element that is normally used to label peptides using this technique.

text: Due to the abundance of radioactive elements that can be incorporated into zircons, they are also susceptible to damage from radioactive decay through the process of metamictization. As radioactive elements within the crystal lattice decay, they bombard the interior of the crystal with radioactive particles. This weakens the crystal and leave it fractured or destroyed. This increases the chance of isotopes leaking out of the crystal and affecting titanium, or other elements, measurements.

text: Due to the abundance of radioactive elements that can be incorporated into zircons, they are also susceptible to damage from radioactive decay through the process of

text: metamictization

text: . As radioactive elements within the crystal lattice decay, they bombard the interior of the crystal with radioactive particles. This weakens the crystal and leave it fractured or destroyed. This increases the chance of isotopes leaking out of the crystal and affecting titanium, or other elements, measurements.

text: Supported financially by the Rockefeller Foundation, Hevesy had a very productive year. He developed the X-ray fluorescence analytical method, and discovered the Samarium alpha-ray. It was here he began the use of radioactive isotopes in studying the metabolic processes of plants and animals, by tracing chemicals in the body by replacing part of stable isotopes with small quantities of the radioactive isotopes. In 1923, Hevesy published the first study on the use of  the naturally radioactive Pb as radioactive tracer to follow the absorption and translocation in the roots, stems and leaves of Vicia faba, also known as the broad bean.

text: Supported financially by the

text: Rockefeller Foundation

text: , Hevesy had a very productive year. He developed the X-ray fluorescence analytical method, and discovered the

text: Samarium

text: alpha-ray. It was here he began the use of

text: radioactive isotope

text: s in studying the metabolic processes of plants and animals, by tracing chemicals in the body by replacing part of stable isotopes with small quantities of the radioactive isotopes. In 1923, Hevesy published the first study on the use of  the naturally radioactive Pb as radioactive tracer to follow the absorption and

text: translocation

text: in the roots, stems and leaves of

text: Vicia faba

text: , also known as the broad bean.

text: Pierre and Marie further explored radioactivity by working to separate the substances in uranium ores and then using the electrometer to make radiation measurements to ‘trace’ the minute amount of unknown radioactive element among the fractions that resulted. Working with the mineral pitchblende, the pair discovered a new radioactive element in 1898. They named the element polonium, after Marie's native country of Poland. On December 21, 1898, the Curies detected the presence of another radioactive material in the pitchblende. They presented this finding to the French Academy of Sciences on December 26, proposing that the new element be called radium. The Curies then went to work isolating polonium and radium from naturally occurring compounds to prove that they were new elements. In 1902, the Curies announced that they had produced a decigram of pure radium, demonstrating its existence as a unique chemical element. While it took three years for them to isolate radium, they were never able to isolate polonium. Along with the discovery of two new elements and finding techniques for isolating radioactive isotopes, Curie oversaw the world's first studies into the treatment of neoplasms, using radioactive isotopes. With Henri Becquerel and her husband, Pierre Curie, she was awarded the 1903 Nobel Prize for Physics. She was the sole winner of the 1911 Nobel Prize for Chemistry. She was the first woman to win a Nobel Prize, and she is the only woman to win the award in two different fields.

text: Pierre and Marie further explored radioactivity by working to separate the substances in uranium ores and then using the

text: electrometer

text: to make radiation measurements to ‘trace’ the minute amount of unknown radioactive element among the fractions that resulted. Working with the mineral

text: pitchblende

text: , the pair discovered a new radioactive element in 1898. They named the element

text: polonium

text: , after Marie's native country of Poland. On December 21, 1898, the Curies detected the presence of another radioactive material in the pitchblende. They presented this finding to the

text: French Academy of Sciences

text: on December 26, proposing that the new element be called

text: radium

text: . The Curies then went to work isolating polonium and radium from naturally occurring compounds to prove that they were new elements. In 1902, the Curies announced that they had produced a decigram of pure radium, demonstrating its existence as a unique chemical element. While it took three years for them to isolate radium, they were never able to isolate polonium. Along with the discovery of two new elements and finding techniques for isolating radioactive isotopes, Curie oversaw the world's first studies into the treatment of

text: neoplasm

text: s, using radioactive isotopes. With Henri Becquerel and her husband, Pierre Curie, she was awarded the 1903

text: Nobel Prize for Physics

text: . She was the sole winner of the 1911

text: Nobel Prize for Chemistry

text: . She was the first woman to win a Nobel Prize, and she is the only woman to win the award in two different fields.

text: As the production of radioactive atoms by the ISOL technique depends on the free atom chemistry of the element to be studied, there are certain beams which cannot be produced by simple proton bombardment of thick actinide targets. Refractory metals such as tungsten and rhenium do not emerge from the target even at high temperatures due to their low vapour pressure. In order to produce these types of beams, a thin target is required. The Ion Guide Isotope Separator On Line (IGISOL) technique was developed in 1981 at the University of Jyväskylä cyclotron laboratory in Finland. In this technique, a thin uranium target is bombarded with protons and nuclear reaction products recoil out of the target in a charged state. The recoils are stopped in a gas cell and then exit through a small hole in the side of the cell where they are accelerated electrostatically and injected into a mass separator. This method of production and extraction takes place on a shorter timescale compared to the standard ISOL technique and isotopes with short half-lives (sub millisecond) can be studied using an IGISOL. An IGISOL has also been combined with a laser ion source at the Leuven Isotope Separator On Line (LISOL) in Belgium. Thin target sources generally provide significantly lower quantities of radioactive ions than thick target sources and this is their main drawback.

text: As the production of radioactive atoms by the ISOL technique depends on the free atom chemistry of the element to be studied, there are certain beams which cannot be produced by simple proton bombardment of thick actinide targets.

text: Refractory

text: metals such as tungsten and rhenium do not emerge from the target even at high temperatures due to their low vapour pressure. In order to produce these types of beams, a thin target is required. The Ion Guide Isotope Separator On Line (IGISOL) technique was developed in 1981 at the University of Jyväskylä

text: cyclotron

text: laboratory in

text: Finland

text: . In this technique, a thin uranium target is bombarded with protons and nuclear reaction products recoil out of the target in a charged state. The recoils are stopped in a gas cell and then exit through a small hole in the side of the cell where they are accelerated electrostatically and injected into a mass separator. This method of production and extraction takes place on a shorter timescale compared to the standard ISOL technique and isotopes with short half-lives (sub millisecond) can be studied using an IGISOL. An IGISOL has also been combined with a laser ion source at the Leuven Isotope Separator On Line (LISOL) in Belgium. Thin target sources generally provide significantly lower quantities of radioactive ions than thick target sources and this is their main drawback.

text: All of the elements have some isotopes that are radioactive (radioisotopes), although not all of these radioisotopes occur naturally. The radioisotopes typically decay into other elements upon radiating an alpha or beta particle. If an element has isotopes that are not radioactive, these are termed "stable" isotopes. All of the known stable isotopes occur naturally (see primordial isotope). The many radioisotopes that are not found in nature have been characterized after being artificially made. Certain elements have no stable isotopes and are composed only of radioactive isotopes: specifically the elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic numbers greater than 82.

text: All of the elements have some isotopes that are radioactive (

text: radioisotopes

text: ), although not all of these radioisotopes occur naturally. The radioisotopes typically decay into other elements upon radiating an

text: alpha

text: or

text: beta particle

text: . If an element has isotopes that are not radioactive, these are termed "stable" isotopes. All of the known stable isotopes occur naturally (see

text: primordial isotope

text: ). The many radioisotopes that are not found in nature have been characterized after being artificially made. Certain elements have no stable isotopes and are composed only of radioactive isotopes: specifically the elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic numbers greater than 82.

text: There are 254 stable primordial nuclides and 32 radioactive primordial nuclides, but only 80 primordial stable elements (1 through 82, i.e. hydrogen through lead, exclusive of 43 and 61, technetium and promethium respectively) and three radioactive primordial elements (bismuth, thorium, and uranium). Bismuth's half-life is so long that it is often classed with the 80 primordial stable elements instead, since its radioactivity is not a cause for serious concern. The numbers of elements are smaller, because many primordial elements are represented by more than one primordial nuclide. See chemical element for more information.

text: There are 254 stable primordial nuclides and 32 radioactive primordial nuclides, but only 80 primordial stable elements (1 through 82, i.e. hydrogen through lead, exclusive of 43 and 61,

text: technetium

text: and

text: promethium

text: respectively) and three radioactive primordial elements (bismuth, thorium, and uranium). Bismuth's half-life is so long that it is often classed with the 80 primordial stable elements instead, since its radioactivity is not a cause for serious concern. The numbers of elements are smaller, because many primordial elements are represented by more than one primordial nuclide. See

text: chemical element

text: for more information.

text: In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron.  There is currently no experimental evidence that proton decay occurs.

text: In

text: particle physics

text: , proton decay is a

text: hypothetical

text: form of

text: radioactive decay

text: in which the

text: proton

text: decays into lighter

text: subatomic particle

text: s, such as a neutral

text: pion

text: and a

text: positron

text: .  There is currently no experimental evidence that proton decay occurs.

text: Helium-3 (He-3, also written as He, see also  helion) is a light, non-radioactive isotope of helium with two protons and one neutron (common helium having two neutrons). Its hypothetical existence was first proposed in 1934 by the Australian nuclear physicist Mark Oliphant while he was working at the University of Cambridge Cavendish Laboratory. Oliphant had performed experiments in which fast deuterons collided with deuteron targets (incidentally, the first demonstration of nuclear fusion).  Helium-3 was thought to be a radioactive isotope until it was also found in samples of natural helium,  which is mostly helium-4, taken both from the terrestrial atmosphere and from natural gas wells. Other than H, helium-3 is the only stable isotope of any element with more protons than neutrons.

text: Helium-3 (He-3, also written as He, see also

text: helion

text: ) is a light, non-

text: radioactive

text: isotope

text: of

text: helium

text: with two

text: proton

text: s and one

text: neutron

text: (common helium having two neutrons). Its hypothetical existence was first proposed in 1934 by the Australian

text: nuclear physicist

text: Mark Oliphant

text: while he was working at the

text: University of Cambridge

text: Cavendish Laboratory

text: . Oliphant had performed experiments in which fast

text: deuteron

text: s collided with deuteron targets (incidentally, the first demonstration of

text: nuclear fusion

text: ).  Helium-3 was thought to be a

text: radioactive isotope

text: until it was also found in samples of natural helium,  which is mostly

text: , taken both from the terrestrial atmosphere and from

text: natural gas

text: wells. Other than

text: H

text: , helium-3 is the only stable isotope of any element with more protons than neutrons.

text: Actinium is a radioactive chemical element with symbol Ac (not to be confused with the abbreviation for an acetyl group) and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902. Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table. It is also sometimes considered the first of the 7th-period transition metals, although lawrencium is less commonly given that position.

text: Actinium is a radioactive

text: chemical element

text: with symbol Ac (not to be confused with the abbreviation for an

text: acetyl group

text: ) and

text: atomic number

text: 89, which was discovered in 1899. It was the first

text: non-primordial radioactive element

text: to be isolated.

text: Polonium

text: radium

text: and

text: radon

text: were observed before actinium, but they were not isolated until 1902. Actinium gave the name to the

text: actinide

text: series, a group of 15 similar elements between actinium and

text: lawrencium

text: in the

text: periodic table

text: . It is also sometimes considered the first of the 7th-period

text: transition metal

text: s, although lawrencium is less commonly given that position.

text: In 1913, Soddy also showed that an atom moves lower in atomic number by two places on alpha emission, higher by one place on beta emission. This was discovered at about the same time by Kazimierz Fajans, and is known as the radioactive displacement law of Fajans and Soddy, a fundamental step toward understanding the relationships among families of radioactive elements. Soddy published ''The Interpretation of Radium'' (1909) and Atomic Transmutation (1953).

text: In 1913, Soddy also showed that an atom moves lower in

text: atomic number

text: by two places on alpha emission, higher by one place on beta emission. This was discovered at about the same time by

text: Kazimierz Fajans

text: , and is known as the

text: , a fundamental step toward understanding the relationships among families of radioactive elements. Soddy published ''The Interpretation of Radium'' (1909) and Atomic Transmutation (1953).

text: Since its decommissioning, Caldas’ mine pit, which is approximately 180 meters (590 feet) deep and contains a diameter of about 1,200 meters (3,937 feet), has turned into a giant lake of acid water. Additionally, radioactive residues remain in the unit – approximately 11,000 tons of torta 2, a combination of uranium concentrate and thorium, and thousands of tons of mesothorium – making Caldas the country’s biggest radioactive waste deposit.

text: A proton pump is any process that creates a proton gradient across a membrane.  Protons can be physically moved across a membrane; this is seen in mitochondrial Complexes I and IV.  The same effect can be produced by moving electrons in the opposite direction. The result is the disappearance of a proton from the cytoplasm and the appearance of a proton in the periplasm.   Mitochondrial Complex III uses this second type of proton pump, which is mediated by a quinone (the Q cycle).

text: A proton pump is any process that creates a proton gradient across a membrane.  Protons can be physically moved across a membrane; this is seen in mitochondrial Complexes I and IV.  The same effect can be produced by moving electrons in the opposite direction. The result is the disappearance of a proton from the cytoplasm and the appearance of a proton in the periplasm.   Mitochondrial Complex III uses this second type of proton pump, which is mediated by a quinone (the

text: Q cycle

text: Isobars are atoms (nuclides) of different chemical elements that have the same number of nucleons. Correspondingly, isobars differ in atomic number (or number of protons) but have the same mass number. An example of a series of isobars would be S, Cl, Ar, K, and Ca. The nuclei of these nuclides all contain 40 nucleons; however, they contain varying numbers of protons and neutrons.

text: Isobars are atoms (

text: nuclide

text: s) of different

text: chemical element

text: s that have the same number of

text: nucleon

text: s. Correspondingly, isobars differ in

text: atomic number

text: (or number of

text: proton

text: s) but have the same

text: mass number

text: . An example of a series of isobars would be

text: S

text: Cl

text: Ar

text: K

text: , and

text: Ca

text: . The nuclei of these nuclides all contain 40 nucleons; however, they contain varying numbers of protons and neutrons.

text: The rare earth elements are often found together. The longest-lived isotope of promethium has a half life of 17.7 years, so the element exists in nature in only negligible amounts (approximately 572 g in the entire Earth's crust). Promethium is one of the two elements that do not have stable (non-radioactive) isotopes and are followed by (i.e. with higher atomic number) stable elements (the other being technetium).

text: The rare earth elements are often found together. The longest-lived isotope of promethium has a half life of 17.7 years, so the element exists in nature in only negligible amounts (approximately 572 g in the entire Earth's crust). Promethium is one of the two elements that do not have stable (non-radioactive) isotopes and are followed by (i.e. with higher atomic number) stable elements (the other being

text: technetium

text: Rutherford went on to use alpha particles to accidentally produce what he later understood as a directed nuclear transmutation of one element to another, in 1917. Transmutation of elements from one to another had been understood since 1901 as a result of natural radioactive decay, but when Rutherford projected alpha particles from alpha decay into air, he discovered this produced a new type of radiation which proved to be hydrogen nuclei (Rutherford named these protons). Further experimentation showed the protons to be coming from the nitrogen component of air, and the reaction was deduced to be a transmutation of nitrogen into oxygen in the reaction

text: Rutherford went on to use alpha particles to accidentally produce what he later understood as a directed

text: nuclear transmutation

text: of one element to another, in 1917. Transmutation of elements from one to another had been understood since 1901 as a result of natural

text: radioactive decay

text: , but when Rutherford projected alpha particles from alpha decay into air, he discovered this produced a new type of radiation which proved to be hydrogen nuclei (Rutherford named these

text: proton

text: s). Further experimentation showed the protons to be coming from the nitrogen component of air, and the reaction was deduced to be a transmutation of nitrogen into oxygen in the reaction

text: A proton is a subatomic particle, symbol  or , with a positive electric charge of +1e elementary charge and mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collectively referred to as "nucleons". One or more protons are present in the nucleus of every atom. They are a necessary part of the nucleus. The number of protons in the nucleus is the defining property of an element, and is referred to as the atomic number (represented by the symbol Z). Since each element has a unique number of protons, each element has its own unique atomic number. The word proton is Greek for "first", and this name was given to the hydrogen nucleus by Ernest Rutherford in 1920. In previous years Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by collision. Protons were therefore a candidate to be a fundamental particle and a building block of nitrogen and all other heavier atomic nuclei.

text: A proton is a

text: subatomic particle

text: , symbol  or , with a positive

text: electric charge

text: of +1e

text: elementary charge

text: and mass slightly less than that of a

text: neutron

text: . Protons and

text: neutron

text: s, each with masses of approximately one

text: atomic mass unit

text: , are collectively referred to as "

text: nucleon

text: s". One or more protons are present in the

text: nucleus

text: of every

text: atom

text: . They are a necessary part of the nucleus. The number of protons in the nucleus is the defining property of an element, and is referred to as the

text: atomic number

text: (represented by the symbol Z). Since each

text: element

text: has a unique number of protons, each element has its own unique atomic number. The word proton is Greek for "first", and this name was given to the hydrogen nucleus by

text: Ernest Rutherford

text: in 1920. In previous years Rutherford had discovered that the hydrogen nucleus (known to be the lightest nucleus) could be extracted from the nuclei of nitrogen by collision. Protons were therefore a candidate to be a

text: fundamental particle

text: and a building block of nitrogen and all other heavier atomic nuclei.

text: The principle behind the use of radioactive tracers is that an atom in a chemical compound is replaced by another atom, of the same chemical element. The substituting atom, however, is a radioactive isotope. This process is often called radioactive labeling. The power of the technique is due to the fact that radioactive decay is much more energetic than chemical reactions. Therefore, the radioactive isotope can be present in low concentration and its presence detected by sensitive radiation detectors such as Geiger counters and scintillation counters. George de Hevesy won the 1943 Nobel Prize for Chemistry "for his work on the use of isotopes as tracers in the study of chemical processes".

text: The principle behind the use of radioactive tracers is that an

text: atom

text: in a

text: chemical compound

text: is replaced by another atom, of the same chemical element. The substituting atom, however, is a radioactive isotope. This process is often called radioactive labeling. The power of the technique is due to the fact that radioactive decay is much more energetic than chemical reactions. Therefore, the radioactive isotope can be present in low concentration and its presence detected by sensitive

text: radiation detector

text: s such as

text: Geiger counter

text: s and

text: scintillation counter

text: s.

text: George de Hevesy

text: won the 1943

text: Nobel Prize for Chemistry

text: "for his work on the use of isotopes as tracers in the study of chemical processes".

text: During 1992 radioactive radium was discovered at the RAF Carlisle site by accident when a member of the Royal Observer Corps walked across a patch of ground testing a recently recalibrated PDRM82 geiger counter. After further investigations it was realised that the RAF had incinerated thousands of luminous dials from the old wartime trainer aircraft in accordance with the disposal policy of the 1940s and 1950s known as "bash, bury or burn". The resulting radioactive ash had been scattered and used during later landscaping of the site.

text: During 1992

text: radioactive radium

text: was discovered at the RAF Carlisle site by accident when a member of the Royal Observer Corps walked across a patch of ground testing a recently recalibrated

text: geiger counter

text: . After further investigations it was realised that the RAF had incinerated thousands of luminous dials from the old wartime trainer aircraft in accordance with the disposal policy of the 1940s and 1950s known as "bash, bury or burn". The resulting radioactive ash had been scattered and used during later landscaping of the site.

text: Matt Murdock (voiced by Edward Albert), the son of prize-fighter Jack Murdock, was shocked to discover that his father had worked a deal with Wilson Fisk, the Kingpin of Crime. Running from his father in shame, the devastated youth was almost killed by a chemical truck hauling radioactive waste, which splashed into his eyes and blinded him. His father swore revenge against the Kingpin, for it was the Kingpin's truck that had almost killed Matt; however, the crime lord learned of Jack's intentions and had him killed before he could reveal the information to the authorities, for it was illegal to carry radioactive waste in New York.

text: Matt Murdock (voiced by

text: Edward Albert

text: ), the son of prize-fighter

text: Jack Murdock

text: , was shocked to discover that his father had worked a deal with Wilson Fisk, the Kingpin of Crime. Running from his father in shame, the devastated youth was almost killed by a chemical truck hauling radioactive waste, which splashed into his eyes and blinded him. His father swore revenge against the Kingpin, for it was the Kingpin's truck that had almost killed Matt; however, the crime lord learned of Jack's intentions and had him killed before he could reveal the information to the authorities, for it was illegal to carry radioactive waste in New York.

text: In the 19th century, experimenters began to detect unexpected forms of radiation: Wilhelm Röntgen caused a sensation with his discovery of X-rays in 1895; in 1896 Henri Becquerel discovered that certain kinds of matter emit radiation on their own accord. In 1897, J. J. Thomson discovered the electron, and new radioactive elements found by Marie and Pierre Curie raised questions about the supposedly indestructible atom and the nature of matter. Marie and Pierre coined the term "radioactivity" to describe this property of matter, and isolated the radioactive elements radium and polonium. Ernest Rutherford and Frederick Soddy identified two of Becquerel's forms of radiation with electrons and the element helium. Rutherford identified and named two types of radioactivity and in 1911 interpreted experimental evidence as showing that the atom consists of a dense, positively charged nucleus surrounded by negatively charged electrons. Classical theory, however, predicted that this structure should be unstable. Classical theory had also failed to explain successfully two other experimental results that appeared in the late 19th century. One of these was the demonstration by Albert A. Michelson and Edward W. Morley—known as the Michelson–Morley experiment—which showed there did not seem to be a preferred frame of reference, at rest with respect to the hypothetical luminiferous ether, for describing electromagnetic phenomena. Studies of radiation and radioactive decay continued to be a preeminent focus for physical and chemical research through the 1930s, when the discovery of nuclear fission opened the way to the practical exploitation of what came to be called "atomic" energy.

text: In the 19th century, experimenters began to detect unexpected forms of radiation:

text: Wilhelm Röntgen

text: caused a sensation with his discovery of

text: X-ray

text: s in 1895; in 1896

text: Henri Becquerel

text: discovered that certain kinds of matter emit radiation on their own accord. In 1897,

text: J. J. Thomson

text: discovered the

text: electron

text: , and new radioactive elements found by

text: Marie

text: and

text: Pierre Curie

text: raised questions about the supposedly indestructible atom and the nature of matter. Marie and Pierre coined the term "

text: radioactivity

text: " to describe this property of matter, and isolated the radioactive elements

text: radium

text: and

text: polonium

text: Ernest Rutherford

text: and

text: Frederick Soddy

text: identified two of Becquerel's forms of radiation with electrons and the element

text: helium

text: . Rutherford identified and named two types of radioactivity and in 1911 interpreted experimental evidence as showing that the atom consists of a dense, positively charged nucleus surrounded by negatively charged electrons. Classical theory, however, predicted that this structure should be unstable. Classical theory had also failed to explain successfully two other experimental results that appeared in the late 19th century. One of these was the demonstration by

text: Albert A. Michelson

text: and

text: Edward W. Morley

text: —known as the

text: Michelson–Morley experiment

text: —which showed there did not seem to be a preferred frame of reference, at rest with respect to the hypothetical

text: luminiferous ether

text: , for describing electromagnetic phenomena. Studies of radiation and radioactive decay continued to be a preeminent focus for physical and chemical research through the 1930s, when the discovery of

text: nuclear fission

text: opened the way to the practical exploitation of what came to be called

text: "atomic" energy

text: Most naturally occurring nuclides are stable (about 254; see list at the end of this article); and about 32 more (total of 286) are known radioactives with sufficiently long half-lives (also known) to occur primordially. If the half-life of a nuclide is comparable to, or greater than, the Earth's age (4.5 billion years), a significant amount will have survived since the formation of the Solar System, and then is said to be primordial. It will then contribute in that way to the natural isotopic composition of a chemical element. Primordially present radioisotopes are easily detected with half-lives as short as 700 million years (e.g., U). This is the present limit of detection, as shorter-lived nuclides have not yet been detected undisputedly in nature.

text: Most naturally occurring

text: nuclide

text: s are stable (about 254; see list at the end of this article); and about 32 more (total of 286) are known radioactives with sufficiently long half-lives (also known) to occur primordially. If the half-life of a

text: nuclide

text: is comparable to, or greater than, the Earth's age (4.5 billion years), a significant amount will have survived since the

entity_name: Formation and evolution of the Solar System

text: formation of the Solar System

text: , and then is said to be

text: primordial

text: . It will then contribute in that way to the natural isotopic composition of a chemical element. Primordially present radioisotopes are easily detected with half-lives as short as 700 million years (e.g.,

text: U

text: ). This is the present limit of detection, as shorter-lived nuclides have not yet been detected undisputedly in nature.

text: During 1903 and 1904, English scientists published research about radioactivity in the scientific journal Nature. In the first 1904 issue, R. J. Strutt identified that radium was detected in the gases of Bath springs. In the next issue, Baron Blythswood and H. S. Allen reported evidence of radioactive gases in Buxton mineral springs. Based on the findings, Sjögren recommended Sahlbom to analyze radioactivity in Swedish waters and referred her to Alexander Classen in Aachen. In 1904 Sahlbom was a pupil of Classen and reviewed radioactive techniques. In 1905 the initial iron springs she tested produced data that deviated, including among adjacent springs. In 1906, advocated by spas, she continued to analyze springs in central and southern Sweden. Her findings demonstrated a lack of correlation between the chemical composition of water resources and radioactivity as well as the depth of wells and radioactivity. A correlation between the geology of water resources and radioactivity was exhibited. Sandstone bedrock in Helsingborg and wells in granite displayed among the highest concentrations of radioactive gases. Sahlbom derived that water resources amassed radioactive gases from flowing through bedrock that contained radium. In 1907 Sahlbom and Sjögren published a paper on 59 springs and wells in Sweden. The paper supported evidence of radioactive emanation in mineral waters.

text: During 1903 and 1904, English scientists published research about

text: radioactivity

text: in the scientific journal

text: Nature

text: . In the first 1904 issue,

text: R. J. Strutt

text: identified that

text: radium

text: was detected in the gases of

text: Bath

text: springs. In the next issue,

text: Baron Blythswood

text: and H. S. Allen reported evidence of radioactive gases in

text: Buxton

text: mineral springs. Based on the findings, Sjögren recommended Sahlbom to analyze radioactivity in Swedish waters and referred her to

text: Alexander Classen

text: in

text: Aachen

text: . In 1904 Sahlbom was a pupil of Classen and reviewed radioactive techniques. In 1905 the initial iron springs she tested produced data that deviated, including among adjacent springs. In 1906, advocated by spas, she continued to analyze springs in central and southern Sweden. Her findings demonstrated a lack of correlation between the chemical composition of water resources and radioactivity as well as the depth of wells and radioactivity. A correlation between the geology of water resources and radioactivity was exhibited.

text: Sandstone

text: bedrock

text: in

text: Helsingborg

text: and wells in granite displayed among the highest concentrations of radioactive gases. Sahlbom derived that water resources amassed radioactive gases from flowing through bedrock that contained radium. In 1907 Sahlbom and Sjögren published a paper on 59 springs and wells in Sweden. The paper supported evidence of radioactive emanation in mineral waters.

text: In Rome Enrico Fermi bombarded heavier elements with neutrons and found the products to be radioactive.  By 1934 Fermi had used neutrons to induce radioactivity in 22 different elements, many of these elements of high atomic number.  Noticing that other experiments with neutrons at his laboratory seemed to work better on a wooden table than a marble table, Fermi suspected that the protons of the wood were slowing the neutrons and so increasing the chance for the neutron to interact with nuclei.  Fermi therefore passed neutrons through paraffin wax to slow them and found that the radioactivity of bombarded elements increased by a hundredfold.   The cross section for interaction with nuclei is much larger for slow neutrons than for fast neutrons.  In 1938 Fermi received the Nobel Prize in Physics "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons".

text: In Rome Enrico Fermi bombarded heavier elements with neutrons and found the products to be radioactive.  By 1934 Fermi had used neutrons to induce radioactivity in 22 different elements, many of these elements of high atomic number.  Noticing that other experiments with neutrons at his laboratory seemed to work better on a wooden table than a marble table, Fermi suspected that the protons of the wood were slowing the neutrons and so increasing the chance for the neutron to interact with nuclei.  Fermi therefore passed neutrons through paraffin wax to slow them and found that the radioactivity of bombarded elements increased by a hundredfold.   The

text: cross section

text: for interaction with nuclei is much larger for slow neutrons than for fast neutrons.  In 1938 Fermi received the Nobel Prize in Physics "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of

text: nuclear reaction

text: s brought about by slow neutrons".

text: The remaining 24 heavier elements, not found today either on Earth or in astronomical spectra, have been produced artificially: these are all radioactive, with very short half-lives; if any atoms of these elements were present at the formation of Earth, they are extremely likely, to the point of certainty, to have already decayed, and if present in novae, have been in quantities too small to have been noted. Technetium was the first purportedly non-naturally occurring element synthesized, in 1937, although trace amounts of technetium have since been found in nature (and also the element may have been discovered naturally in 1925). This pattern of artificial production and later natural discovery has been repeated with several other radioactive naturally occurring rare elements.

text: The remaining 24 heavier elements, not found today either on Earth or in astronomical spectra, have been produced artificially: these are all radioactive, with very short half-lives; if any atoms of these elements were present at the formation of Earth, they are extremely likely, to the point of certainty, to have already decayed, and if present in novae, have been in quantities too small to have been noted.

text: Technetium

text: was the first purportedly non-naturally occurring element synthesized, in 1937, although trace amounts of technetium have since been found in nature (and also the element may have been discovered naturally in 1925). This pattern of artificial production and later natural discovery has been repeated with several other radioactive naturally occurring rare elements.

text: On 19 January 2012, 500 tons of highly contaminated water were found in a pit near the No.2 reactor at a facility to store highly contaminated water. The pit had a valve which was used for pumping in seawater. This water had 16,200 becquerels of radioactive cesium per cubic centimeter. The highest level of radioactive substances found in this survey. Another 600 tons of water containing 860 becquerels of radioactive elements per cubic centimeter was found in a pit near the No.3 reactor, this is a very low level of radioactivity. According to TEPCO it was unlikely that water from these pits could flow into the ocean, because there no change of contamination was found. How the water could flow into the tunnels was still under investigation.

text: Film badges used to measure exposure to radioactivity indicated that no observers at N-10,000 had been exposed to more than 0.1 roentgens, but the shelter was evacuated before the radioactive cloud could reach it. The explosion was more efficient than expected and the thermal updraft drew most of the cloud high enough that little fallout fell on the test site. The crater was far more radioactive than expected due to the formation of trinitite, and the crews of the two lead-lined Sherman tanks were subjected to considerable exposure. Anderson's dosimeter and film badge recorded 7 to 10 roentgens, and one of the tank drivers, who made three trips, recorded 13 to 15 roentgens.

text: Film badges used to measure exposure to radioactivity indicated that no observers at N-10,000 had been exposed to more than 0.1

text: roentgens

text: , but the shelter was evacuated before the radioactive cloud could reach it. The explosion was more efficient than expected and the thermal updraft drew most of the cloud high enough that little fallout fell on the test site. The crater was far more radioactive than expected due to the formation of trinitite, and the crews of the two lead-lined Sherman tanks were subjected to considerable exposure. Anderson's dosimeter and film badge recorded 7 to 10 roentgens, and one of the tank drivers, who made three trips, recorded 13 to 15 roentgens.

text: Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as a decay product of radium. Its most stable isotope, Rn, has a half-life of 3.8 days. Radon is one of the densest substances that remains a gas under normal conditions. It is also the only elemental gas under normal conditions that has no stable isotopes, and is considered a health hazard due to its radioactivity. Intense radioactivity has also hindered chemical studies of radon and only a few compounds are known.

text: Radon is a

text: chemical element

text: with symbol Rn and

text: atomic number

text: 86. It is a

text: radioactive

text: , colorless, odorless, tasteless

text: noble gas

text: , occurring naturally as a

text: decay product

text: of

text: radium

text: . Its most stable

text: isotope

text: Rn

text: , has a

text: half-life

text: of 3.8 days. Radon is one of the densest substances that remains a

text: gas

text: under normal conditions. It is also the only elemental gas under normal conditions that has no stable isotopes, and is considered a health hazard due to its radioactivity. Intense radioactivity has also hindered chemical studies of radon and only a few compounds are known.

text: On August 12, 2012, researchers at the RIKEN Nishina Center for Accelerator-Based Science in Japan, claimed to have synthesised element 113 by colliding zinc nuclei (with 30 protons each) into a thin layer of bismuth (which contains 83 protons). In December 2015, IUPAC recognized the element and assigned the priority of the discovery to RIKEN. For the first time in history a team of Asian physicists will name a new element. In March 2016, Kosuke Morita, the leader of the RIKEN team, proposed the name "nihonium" to IUPAC, after its place of discovery and referencing Japanese chemist Masataka Ogawa's 1908 discovery of rhenium, which he named "nipponium". IUPAC accepted the proposal and set a term expiring 8 November to collect comments, after which the final name would be formally established at a conference.On 8 June 2016, IUPAC disclosed the name of element 113 as nihonium. Prior to the formal approval by the IUPAC Council, a five-month public review was set, expiring 8 November 2016; the name was officially approved on 28 November 2016.

text: On August 12, 2012, researchers at the RIKEN Nishina Center for Accelerator-Based Science in Japan, claimed to have synthesised element 113 by colliding zinc nuclei (with 30 protons each) into a thin layer of bismuth (which contains 83 protons). In December 2015, IUPAC recognized the element and assigned the priority of the discovery to RIKEN. For the first time in history a team of Asian physicists will name a new element. In March 2016, Kosuke Morita, the leader of the

text: RIKEN

text: team, proposed the name "nihonium" to IUPAC, after its place of discovery and referencing Japanese chemist

text: Masataka Ogawa

text: 's 1908 discovery of

text: rhenium

text: , which he named "nipponium". IUPAC accepted the proposal and set a term expiring 8 November to collect comments, after which the final name would be formally established at a conference.On 8 June 2016, IUPAC disclosed the name of element 113 as nihonium. Prior to the formal approval by the IUPAC Council, a five-month public review was set, expiring 8 November 2016; the name was officially approved on 28 November 2016.

text: The same year, his doctoral student James Chadwick discovered the neutron, which was immediately recognized as a potential tool for nuclear experimentation because of its lack of an electric charge. Experimentation with bombardment of materials with neutrons led Frédéric and Irène Joliot-Curie to discover induced radioactivity in 1934, which allowed the creation of radium-like elements at much less the price of natural radium. Further work by Enrico Fermi in the 1930s focused on using slow neutrons to increase the effectiveness of induced radioactivity. Experiments bombarding uranium with neutrons led Fermi to believe he had created a new, transuranic element, which was dubbed hesperium.

text: The same year, his doctoral student

text: James Chadwick

text: discovered the

text: neutron

text: , which was immediately recognized as a potential tool for nuclear experimentation because of its lack of an electric charge. Experimentation with bombardment of materials with neutrons led

text: Frédéric

text: and

text: Irène Joliot-Curie

text: to discover

text: induced radioactivity

text: in 1934, which allowed the creation of radium-like elements at much less the price of natural radium. Further work by

text: Enrico Fermi

text: in the 1930s focused on using

text: slow neutron

text: s to increase the effectiveness of induced radioactivity. Experiments bombarding uranium with neutrons led Fermi to believe he had created a new, transuranic element, which was dubbed

text: hesperium

text: The number of possible elements is not known. A very early suggestion made by Elliot Adams in 1911, and based on the arrangement of elements in each horizontal periodic table row, was that elements of atomic weight greater than 256± (which would equate to between elements 99 and 100 in modern-day terms) did not exist. A higher—more recent—estimate is that the periodic table may end soon after the island of stability, which is expected to centre around element 126, as the extension of the periodic and nuclides tables is restricted by proton and neutron drip lines. Other predictions of an end to the periodic table include at element 128 by John Emsley, at element 137 by Richard Feynman, and at element 155 by Albert Khazan.

text: The number of possible elements is not known. A very early suggestion made by Elliot Adams in 1911, and based on the arrangement of elements in each horizontal periodic table row, was that elements of atomic weight greater than 256± (which would equate to between elements 99 and 100 in modern-day terms) did not exist. A higher—more recent—estimate is that the periodic table may end soon after the

text: island of stability

text: , which is expected to centre around

text: element 126

text: , as the extension of the periodic and nuclides tables is restricted by proton and neutron

text: drip lines

text: . Other predictions of an end to the periodic table include at element 128 by

text: John Emsley

text: , at element 137 by

text: Richard Feynman

text: , and at element 155 by Albert Khazan.

text: The energy and the type of the ionizing radiation emitted by a radioactive substance are also important factors in determining its threat to humans. The chemical properties of the radioactive element will determine how mobile the substance is and how likely it is to spread into the environment and contaminate humans. This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive decay products within a decay chain before ultimately reaching a stable state.

text: The energy and the type of the

text: ionizing radiation

text: emitted by a radioactive substance are also important factors in determining its threat to humans. The chemical properties of the radioactive

text: element

text: will determine how mobile the substance is and how likely it is to spread into the environment and

text: contaminate

text: humans. This is further complicated by the fact that many radioisotopes do not decay immediately to a stable state but rather to radioactive

text: decay product

text: s within a

text: decay chain

text: before ultimately reaching a stable state.

text: This proved that the unknown radioactive source originated from the decay of uranium and, coupled with the previous observation that the source was different chemically from all known elements, proved beyond all doubt that a new element had been discovered. McMillan and Abelson published their results in a paper entitled Radioactive Element 93 in the Physical Review on May 27, 1940. They did not propose a name for the element in the paper, but they soon decided on the name neptunium since Neptune is the next planet beyond Uranus in our solar system.

text: This proved that the unknown radioactive source originated from the decay of uranium and, coupled with the previous observation that the source was different chemically from all known elements, proved beyond all doubt that a new element had been discovered. McMillan and Abelson published their results in a paper entitled Radioactive Element 93 in the

text: Physical Review

text: on May 27, 1940. They did not propose a name for the element in the paper, but they soon decided on the name neptunium since

text: Neptune

text: is the next planet beyond

text: Uranus

text: in our solar system.

text: Helium-4 ( or ) is a non-radioactive isotope of the element helium. It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consists of two protons and two neutrons.

text: Helium-4 ( or ) is a non-

text: radioactive

text: isotope

text: of the element

text: helium

text: . It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an

text: alpha particle

text: , and consists of two

text: proton

text: s and two

text: neutron

text: s.

text: In practice, for both practical and safety reasons, almost all recent applications of the "doubly labeled water" method use water labeled with heavy but non-radioactive forms of each element (deuterium and oxygen-18). In theory, radioactive heavy isotopes of the elements could be used for such labeling; this was the case in many early applications of the method.

text: In practice, for both practical and safety reasons, almost all recent applications of the "doubly labeled water" method use water labeled with heavy but non-radioactive forms of each element (

text: deuterium

text: and

text: ). In theory, radioactive heavy isotopes of the elements could be used for such labeling; this was the case in many early applications of the method.

text: In 1896, Henri Becquerel was investigating phosphorescence in uranium salts when he discovered a new phenomenon which came to be called radioactivity. He, Pierre Curie and Marie Curie began investigating the phenomenon. In the process, they isolated the element radium, which is highly radioactive. They discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the Greek letters. Some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. All of the early researchers received various radiation burns, much like sunburn, and thought little of it.

text: In 1896,

text: Henri Becquerel

text: was investigating

text: phosphorescence

text: in

text: uranium

text: salts when he discovered a new phenomenon which came to be called

text: radioactivity

text: . He,

text: Pierre Curie

text: and

text: Marie Curie

text: began investigating the phenomenon. In the process, they isolated the element

text: radium

text: , which is highly radioactive. They discovered that radioactive materials produce intense, penetrating rays of three distinct sorts, which they labeled alpha, beta, and gamma after the

text: Greek letters

text: . Some of these kinds of radiation could pass through ordinary matter, and all of them could be harmful in large amounts. All of the early researchers received various

text: radiation burn

text: s, much like

text: sunburn

text: , and thought little of it.

text: Cluster decay, also named heavy particle radioactivity or heavy ion radioactivity,  is a type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment. Ternary fission into three fragments also produces products in the cluster size. The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number A = A - A and atomic number Z = Z - Z where A = N + Z. For example:

text: Cluster decay, also named heavy particle radioactivity or heavy ion radioactivity,  is a type of nuclear decay in which an atomic nucleus emits a small "cluster" of

text: neutron

text: s and

text: proton

text: s, more than in an

text: alpha particle

text: , but less than a typical binary

text: fission fragment

text: Ternary fission

text: into three fragments also produces products in the cluster size. The loss of protons from the parent nucleus changes it to the nucleus of a different element, the daughter, with a mass number A = A - A and atomic number Z = Z - Z where A = N + Z. For example:

text: It is now known by direct observation that much of the light curve (the graph of luminosity as a function of time) after the explosion of a Type II Supernova such as SN 1987A is provided its energy by those predicted radioactive decays. Although the luminous emission consists of optical photons, it is the radioactive power absorbed by the ejected gases that keeps the remnant hot enough to radiate light. The radioactive decay of Ni through its daughters Co to Fe produces gamma-ray photons , primarily of 847keV and 1238keV, that are absorbed and dominate the heating and thus the luminosity of the ejecta at intermediate times (several weeks) to late times (several months). Energy for the peak of the light curve of SN1987A was provided by the decay of Ni to Co (half life 6 days) while energy for the later light curve in particular fit very closely with the 77.3 day half-life of Co decaying to Fe. Later measurements by space gamma-ray telescopes of the small fraction of the Co  and Co gamma rays that escaped the SN 1987A remnant without absorption confirmed earlier predictions that those two radioactive nuclei were the power sources.

text: It is now known by direct observation that much of the

text: light curve

text: (the graph of luminosity as a function of time) after the explosion of a

text: Type II Supernova

text: such as SN 1987A is provided its energy by those predicted

text: radioactive decay

text: s. Although the luminous emission consists of optical photons, it is the radioactive power absorbed by the ejected gases that keeps the remnant hot enough to radiate light. The

text: radioactive decay

text: of

text: Ni

text: through its daughters

text: Co

text: to

text: Fe

text: produces gamma-ray

text: photon

text: s , primarily of 847keV and 1238keV, that are absorbed and dominate the heating and thus the luminosity of the ejecta at intermediate times (several weeks) to late times (several months). Energy for the peak of the light curve of SN1987A was provided by the decay of

text: Ni

text: to Co (half life 6 days) while energy for the later light curve in particular fit very closely with the 77.3 day half-life of

text: Co

text: decaying to Fe. Later measurements by space gamma-ray telescopes of the small fraction of the Co  and Co gamma rays that escaped the

text: SN 1987A

text: remnant without absorption confirmed earlier predictions that those two radioactive nuclei were the power sources.

text: Under certain circumstances, each of the states is permitted to regulate ocean dumping in waters within their own jurisdiction. The Ocean Dumping Act requires that the EPA Administrator applies the standards and criteria binding upon the United States that are stated in the 1972 Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matters. During this convention, more than 85 countries agreed in the prohibition of dumping in the ocean the next elements: mercury, cadmium and other substances such as DDT and PCBs, solid wastes and persistent plastics, oil, high-level radioactive wastes, and chemical and biological warfare agents; and requires special permits for other heavy metals, cyanides and fluorides, and medium- and low-level radioactive wastes.

text: Other radioisotopes have an affinity for particular tissues, such as plutonium into bone, and may be retained there for years in spite of their foreign nature.In summary, not all radiation is harmful. The radiation can be absorbed through multiple pathways, varying due to the circumstances of the situation. If the radioactive material is necessary, it can be ingested orally via stable isotopes of specific elements. This is only suggested to those that have a lack of these elements however, because radioactive material can go from healthy to harmful with very small amounts. The most harmful way to absorb radiation is that of absorption because it is almost impossible to control how much will enter the body.

text: The pioneers of radioactivity were chemist Bertram B. Boltwood and the energetic Rutherford. Boltwood had conducted studies of radioactive materials as a consultant, and when Rutherford lectured at Yale in 1904, Boltwood was inspired to describe the relationships between elements in various decay series. Late in 1904, Rutherford took the first step toward radiometric dating by suggesting that the alpha particles released by radioactive decay could be trapped in a rocky material as helium atoms. At the time, Rutherford was only guessing at the relationship between alpha particles and helium atoms, but he would prove the connection four years later.

text: The pioneers of radioactivity were chemist

text: Bertram B. Boltwood

text: and the energetic Rutherford. Boltwood had conducted studies of radioactive materials as a consultant, and when Rutherford lectured at Yale in 1904, Boltwood was inspired to describe the relationships between elements in various decay series. Late in 1904, Rutherford took the first step toward radiometric dating by suggesting that the

text: alpha particle

text: s released by radioactive decay could be trapped in a rocky material as

text: helium

text: atoms. At the time, Rutherford was only guessing at the relationship between alpha particles and helium atoms, but he would prove the connection four years later.

text: The stability of nuclei decreases greatly with the increase in atomic number after plutonium, the heaviest primordial element, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day, with an exception of dubnium-268. No elements with atomic numbers above 82 (after lead) have stable isotopes. Nevertheless, because of reasons not very well understood yet, there is a slightly increased nuclear stability around atomic numbers 110–114, which leads to the appearance of what is known in nuclear physics as the "island of stability". This concept, proposed by University of California professor Glenn Seaborg, hypothesizes why superheavy elements last longer than predicted. Oganesson is radioactive and has a half-life that appears to be less than a millisecond. Nonetheless, this is still longer than some predicted values, thus giving further support to the idea of this "island of stability".

text: The stability of nuclei decreases greatly with the increase in atomic number after

text: plutonium

text: , the heaviest

text: primordial element

text: , so that all isotopes with an atomic number above

text: decay radioactively

text: with a

text: half-life

text: under a day, with an exception of

text: dubnium

text: -268. No elements with

text: atomic number

text: s above 82 (after

text: lead

text: ) have stable isotopes. Nevertheless, because of

text: reasons

text: not very well understood yet, there is a slightly increased nuclear stability around atomic numbers

text: , which leads to the appearance of what is known in nuclear physics as the "

text: island of stability

text: ". This concept, proposed by

text: University of California

text: professor

text: Glenn Seaborg

text: , hypothesizes why

text: superheavy element

text: s last longer than predicted. Oganesson is

text: radioactive

text: and has a

text: half-life

text: that appears to be less than a

text: millisecond

text: . Nonetheless, this is still longer than some predicted values, thus giving further support to the idea of this "island of stability".

text: All radioactivity of F-FDG, both the 20% which is rapidly excreted in the first several hours of urine which is made after the exam, and the 80% which remains in the patient, decays with a half-life of 110 minutes (just under 2 hours). Thus, within 24 hours (13 half-lives after the injection), the radioactivity in the patient and in any initially voided urine which may have contaminated bedding or objects after the PET exam, will have decayed to 2 = 1/8192 of the initial radioactivity of the dose. In practice, patients who have been injected with F-FDG are told to avoid the close vicinity of especially radiation-sensitive persons such as infants, children and pregnant women, for at least 12 hours (7 half-lives, or decay to 1/128th the initial radioactive dose).

text: The Curies regarded mediumistic séances as "scientific experiments" and took detailed notes. According to historian Anna Hurwic, they thought it possible to discover in spiritualism the source of an unknown energy that would reveal the secret of radioactivity. On July 24, 1905, Pierre Curie reported to his friend Gouy: "We have had a series of séances with Eusapia Palladino at the [Society for Psychical Research]."

text: Three Mile Island-2 was an accident of a completely different type from Chernobyl.  Chernobyl was a design flaw-caused power excursion causing a steam explosion resulting in a graphite fire, uncontained, which lofted radioactive smoke high into the atmosphere; TMI was a slow, undetected leak that lowered the water level around the nuclear fuel, resulting in over a third of it shattering when refilled rapidly with coolant.  Unlike Chernobyl, TMI-2's reactor vessel did not fail and contained almost all of the radioactive material.  Containment at TMI did not fail.  A small quantity of radioactive gases from the leak were vented into the atmosphere through specially designed filters under operator control.  A government report concluded that the accident caused no increase in cancer rates for local residents.

text: Three Mile Island-2 was an accident of a completely different type from Chernobyl.  Chernobyl was a design flaw-caused power excursion causing a steam explosion resulting in a graphite fire, uncontained, which lofted radioactive smoke high into the atmosphere; TMI was a slow, undetected leak that lowered the water level around the nuclear fuel, resulting in over a third of it shattering when refilled rapidly with coolant.  Unlike Chernobyl, TMI-2's reactor vessel did not fail and contained almost all of the radioactive material.

text: Containment

text: at TMI did not fail.  A small quantity of radioactive gases from the leak were vented into the atmosphere through specially designed filters under operator control.  A government report concluded that the accident caused no increase in cancer rates for local residents.

text: In early work, Rutherford discovered the concept of radioactive half-life, proved that radioactivity involved the nuclear transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation.  This work was done at McGill University in Canada. It is the basis for the Nobel Prize in Chemistry he was awarded in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances", for which he is the first Canadian and Oceanian Nobel laureate, and remains the only laureate born in the South Island.

text: In early work, Rutherford discovered the concept of radioactive

text: half-life

text: , proved that radioactivity involved the nuclear transmutation of one chemical element to another, and also differentiated and named

text: alpha

text: and

text: beta radiation

text: .  This work was done at

text: McGill University

text: in Canada. It is the basis for the

text: Nobel Prize in Chemistry

text: he was awarded in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances", for which he is the first Canadian and Oceanian Nobel laureate, and remains the only laureate born in the

text: South Island

text: In chemistry, the number of protons in the nucleus of an atom is known as the atomic number, which determines the chemical element to which the atom belongs. For example, the atomic number of chlorine is 17; this means that each chlorine atom has 17 protons and that all atoms with 17 protons are chlorine atoms. The chemical properties of each atom are determined by the number of (negatively charged) electrons, which for neutral atoms is equal to the number of (positive) protons so that the total charge is zero. For example, a neutral chlorine atom has 17 protons and 17 electrons, whereas a Cl anion has 17 protons and 18 electrons for a total charge of −1.

text: In

text: chemistry

text: , the number of protons in the

text: nucleus

text: of an atom is known as the

text: atomic number

text: , which determines the

text: chemical element

text: to which the atom belongs. For example, the atomic number of

text: chlorine

text: is 17; this means that each chlorine atom has 17 protons and that all atoms with 17 protons are chlorine atoms. The chemical properties of each atom are determined by the number of (negatively charged)

text: electron

text: s, which for neutral atoms is equal to the number of (positive) protons so that the total charge is zero. For example, a neutral chlorine atom has 17 protons and 17 electrons, whereas a Cl

text: anion

text: has 17 protons and 18 electrons for a total charge of −1.

text: Among the nine underground tests, which were carried between 1962 and 1969 and codenamed Anacostia (5.2 kilotons, 1962), Kennebec (<5 kilotons, 1963), Par (38, kilotons, 1964), Barbel (<20 kilotons, 1964), Tweed (<20 kilotons, 1965), Cyclamen (13 kilotons, 1966), Kankakee (20-200 kilotons, 1966), Vulcan (25 kilotons, 1966) and Hutch (20-200 kilotons, 1969), the last one was most powerful and had the highest yield of transuranium elements. In the dependence on the atomic mass number, the yield showed a saw-tooth behavior with the lower values for odd isotopes, due to their higher fission rates. The major practical problem of the entire proposal was however collecting the radioactive debris dispersed by the powerful blast. Aircraft filters adsorbed only about 4 of the total amount and collection of tons of corals at Enewetak Atoll increased this fraction by only two orders of magnitude. Extraction of about 500 kilograms of underground rocks 60 days after the Hutch explosion recovered only about 10 of the total charge. The amount of transuranium elements in this 500-kg batch was only 30 times higher than in a 0.4 kg rock picked up 7 days after the test. This observation demonstrated the highly nonlinear dependence of the transuranium elements yield on the amount of retrieved radioactive rock. In order to accelerate sample collection after explosion, shafts were drilled at the site not after but before the test, so that explosion would expel radioactive material from the epicenter, through the shafts, to collecting volumes near the surface. This method was tried in the Anacostia and Kennebec tests and instantly provided hundreds kilograms of material, but with actinide concentration 3 times lower than in samples obtained after drilling; whereas such method could have been efficient in scientific studies of short-lived isotopes, it could not improve the overall collection efficiency of the produced actinides.

text: Among the nine underground tests, which were carried between 1962 and 1969 and codenamed Anacostia (5.2

text: kilotons

text: As experimental nuclear physics progresses, it is becoming more and more important to study the most exotic of radioactive nuclei. In order to do so, more inventive techniques are required to create nuclei with extreme proton/neutron ratios. An alternative to the ISOL techniques described here is that of fragmentation beams, where the radioactive ions are produced by fragmentation reactions on a fast beam of stable ions impinging on a thin target (usually of beryllium atoms). This technique is used, for example, at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University and at the Radioactive Isotope Beam Factory (RIBF) at RIKEN, in Japan.

text: As experimental nuclear physics progresses, it is becoming more and more important to study the most exotic of radioactive nuclei. In order to do so, more inventive techniques are required to create nuclei with extreme proton/neutron ratios. An alternative to the ISOL techniques described here is that of fragmentation beams, where the radioactive ions are produced by fragmentation reactions on a fast beam of stable ions impinging on a thin target (usually of beryllium atoms). This technique is used, for example, at the

entity_name: National Superconducting Cyclotron Laboratory

text: National Superconducting Cyclotron Laboratory

text: (NSCL) at Michigan State University and at the

text: Radioactive Isotope Beam Factory

text: (RIBF) at

text: RIKEN

text: , in Japan.

text: Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter, between particles made of quarks, such as the collision of cosmic rays made of nuclei (ordinary protons and neutrons). Mesons are also frequently produced artificially in high-energy particle accelerators in the collisions of protons, anti-protons, or other particles.

text: Mesons are not produced by radioactive decay, but appear in nature only as short-lived products of very high-energy interactions in matter, between particles made of quarks, such as the collision of

text: cosmic ray

text: s made of nuclei (ordinary protons and neutrons). Mesons are also frequently produced artificially in high-energy particle accelerators in the collisions of protons, anti-protons, or other particles.

text: According to the Big Bang theory, stable isotopes of the lightest five elements (H, He, and traces of Li, Be, and B) were produced very shortly after the emergence of the universe, in a process called Big Bang nucleosynthesis. These lightest stable nuclides (including deuterium) survive to today, but any radioactive isotopes of the light elements produced in the Big Bang (such as tritium) have long since decayed. Isotopes of elements heavier than boron were not produced at all in the Big Bang, and these first five elements do not have any long-lived radioisotopes. Thus, all radioactive nuclei are, therefore, relatively young with respect to the birth of the universe, having formed later in various other types of nucleosynthesis in stars (in particular, supernovae), and also during ongoing interactions between stable isotopes and energetic particles. For example, carbon-14, a radioactive nuclide with a half-life of only 5,730 years, is constantly produced in Earth's upper atmosphere due to interactions between cosmic rays and nitrogen.

text: According to the

text: Big Bang theory

text: , stable isotopes of the lightest five elements (

text: H

text: He

text: , and traces of

text: Li

text: Be

text: , and

text: B

text: ) were produced very shortly after the emergence of the universe, in a process called

text: Big Bang nucleosynthesis

text: . These lightest stable nuclides (including

text: deuterium

text: ) survive to today, but any radioactive isotopes of the light elements produced in the Big Bang (such as

text: tritium

text: ) have long since decayed. Isotopes of elements heavier than boron were not produced at all in the Big Bang, and these first five elements do not have any long-lived radioisotopes. Thus, all radioactive nuclei are, therefore, relatively young with respect to the birth of the universe, having formed later in various other types of

text: nucleosynthesis

text: in

text: star

text: s (in particular,

text: supernova

text: e), and also during ongoing interactions between stable isotopes and energetic particles. For example,

text: , a radioactive nuclide with a half-life of only 5,730 years, is constantly produced in Earth's upper atmosphere due to interactions between cosmic rays and nitrogen.

text: Early protoplanets had more radioactive elements, the quantity of which has been reduced over time due to radioactive decay. Heating due to radioactivity, impact, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones their heavier elements sank to the center, whereas lighter elements rose to the surface. Such a process is known as planetary differentiation. The composition of some meteorites show that differentiation took place in some asteroids.

text: Early protoplanets had more

text: radioactive

text: elements, the quantity of which has been reduced over time due to

text: radioactive decay

text: . Heating due to radioactivity, impact, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones their heavier

text: element

text: s sank to the center, whereas lighter elements rose to the surface. Such a process is known as

text: planetary differentiation

text: . The composition of some

text: meteorite

text: s show that differentiation took place in some

text: asteroid

text: s.

text: The 1903 Nobel Prize in Physics was awarded jointly to Becquerel for his discovery and to Pierre Curie and Marie Curie for their subsequent research into radioactivity. Rutherford was awarded the Nobel Prize in Chemistry in 1908 for his "investigations into the disintegration of the elements and the chemistry of radioactive substances".

text: The 1903

text: Nobel Prize

text: in Physics was awarded jointly to Becquerel for his discovery and to

text: Pierre Curie

text: and Marie Curie for their subsequent research into radioactivity. Rutherford was awarded the Nobel Prize in Chemistry in 1908 for his "investigations into the disintegration of the elements and the chemistry of radioactive substances".

text: Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom. The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table.

text: Isotopes are variants of a particular

text: chemical element

text: which differ in

text: neutron number

text: . All isotopes of a given element have the same number of

text: protons

text: in each

text: atom

text: . The term isotope is formed from the Greek roots isos (

text: ἴσος

text: "equal") and topos (

text: τόπος

text: "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the

text: periodic table

text: As a result of large production of uranium and presence of other radioactive elements such thorium, radon or radioactive dust the radioactive background of the city is remarkable with the zones of radioactive anomaly which are spread around the city.

text: The Fission Product Pilot Plant, building 3515 at Oak Ridge National Laboratory, was built in 1948 to extract radioactive isotopes from liquid radioactive waste.  It was formerly known as the 'ruthenium-106 tank arrangement'. It is a relatively small facility; the task of extracting radioactive isotopes later took place at a number of specialised buildings nearby.

text: The Fission Product Pilot Plant, building 3515 at

text: Oak Ridge National Laboratory

text: , was built in 1948 to extract radioactive isotopes from liquid radioactive waste.  It was formerly known as the '

text: ruthenium

text: -106 tank arrangement'. It is a relatively small facility; the task of extracting radioactive isotopes later took place at a number of specialised buildings nearby.

text: The area was contaminated in 1968 with Plutonium and other radioactive elements following a B-52 bomber crash.

text: The area was contaminated in 1968 with

text: Plutonium

text: and other radioactive elements following a

text: B-52 bomber crash

text: There may have been observations of . In 2000, physicists first observed a new type of radioactive decay in which a nucleus emits two protons at once—perhaps a  nucleus. The team led by Alfredo Galindo-Uribarri of the Oak Ridge National Laboratory announced that the discovery will help scientists understand the strong nuclear force and provide fresh insights into the creation of elements inside stars. Galindo-Uribarri and co-workers chose an isotope of neon with an energy structure that prevents it from emitting protons one at a time. This means that the two protons are ejected simultaneously. The team fired a beam of fluorine ions at a proton-rich target to produce , which then decayed into oxygen and two protons. Any protons ejected from the target itself were identified by their characteristic energies. There are two ways in which the two-proton emission may proceed. The neon nucleus might eject a 'diproton'—a pair of protons bound together as a  nucleus—which then decays into separate protons. Alternatively, the protons may be emitted separately but at the same time—so-called 'democratic decay'. The experiment was not sensitive enough to establish which of these two processes was taking place.

text: There may have been observations of . In 2000, physicists first observed a new type of radioactive decay in which a nucleus

text: emits two protons

text: at once—perhaps a  nucleus. The team led by Alfredo Galindo-Uribarri of the Oak Ridge National Laboratory announced that the discovery will help scientists understand the strong nuclear force and provide fresh insights into the

text: creation of elements inside stars

text: . Galindo-Uribarri and co-workers chose an isotope of neon with an energy structure that prevents it from emitting protons one at a time. This means that the two protons are ejected simultaneously. The team fired a beam of fluorine ions at a proton-rich target to produce , which then decayed into oxygen and two protons. Any protons ejected from the target itself were identified by their characteristic energies. There are two ways in which the two-proton emission may proceed. The neon nucleus might eject a 'diproton'—a pair of protons bound together as a  nucleus—which then decays into separate protons. Alternatively, the protons may be emitted separately but at the same time—so-called 'democratic decay'. The experiment was not sensitive enough to establish which of these two processes was taking place.

text: Researchers use radioactive atoms to determine the age of materials that were once part of a living organism. The age of such materials can be estimated by measuring the amount of radioactive carbon they contain in a process called radiocarbon dating. Similarly, using other radioactive elements, the age of rocks and other geological features (even some man-made objects) can be determined; this is called Radiometric dating. Environmental scientists use radioactive atoms, known as tracer atoms, to identify the pathways taken by pollutants through the environment.

text: Researchers use radioactive atoms to determine the age of materials that were once part of a living organism. The age of such materials can be estimated by measuring the amount of radioactive carbon they contain in a process called

text: radiocarbon dating

text: . Similarly, using other radioactive elements, the age of rocks and other geological features (even some man-made objects) can be determined; this is called

text: Radiometric dating

text: . Environmental scientists use radioactive atoms, known as

text: tracer atoms

text: , to identify the pathways taken by pollutants through the environment.

text: 230 tons of highly radioactive water is discovered in a tunnel below a building that stores contaminated water, raising questions about TEPCO's inspection and management capabilities. TEPCO admits that this radioactive water may be mixing with the ground water, yet claims that the tunnel is not connected to the sea.

text: The test succeeded in liberating large quantities of natural gas; however the resulting radioactivity left the gas contaminated and unsuitable for applications such as cooking and heating homes. Although projected public radiation exposures from commercial use of stimulated gas had been reduced to less than 1% of background, it became clear in the early 1970s that public acceptance within the U.S. of any product containing radioactivity, no matter how minimal, was difficult if not impossible. The Department of Energy began a cleanup of the site in the 1970s which was completed in 1998.  A buffer zone put in place by the state of Colorado still exists around the site.  A January 2005 report by the DOE stated that radioactivity levels were normal at the surface and in groundwater, though a later report due in 2007 was expected to more fully explore if there was subsurface contamination and whether or not radioactivity was still spreading outward from the blast site itself.

text: The test succeeded in liberating large quantities of natural gas; however the resulting radioactivity left the gas contaminated and unsuitable for applications such as cooking and heating homes. Although projected public radiation exposures from commercial use of stimulated gas had been reduced to less than 1% of background, it became clear in the early 1970s that public acceptance within the U.S. of any product containing radioactivity, no matter how minimal, was difficult if not impossible. The

text: Department of Energy

text: began a cleanup of the site in the 1970s which was completed in 1998.  A

text: buffer zone

text: put in place by the state of Colorado still exists around the site.  A January 2005 report by the DOE stated that radioactivity levels were normal at the surface and in

text: groundwater

text: , though a later report due in 2007 was expected to more fully explore if there was subsurface contamination and whether or not radioactivity was still spreading outward from the blast site itself.

text: After his arrival in the USA he established, with his brother Alexander, the Canadian Radium and Uranium Corp of New York and became its president to sell the newly discovered rich ores in northern Canada, and later also in Colorado. George B. Pegram and his associates at Columbia University, who did some of the initial work on the Manhattan Project, sought Pregel's assistance because they did not have sufficient money to buy the uranium. Pregel gave them the first uranium used in the experiments. Pregel's company also built radioactive neutron sources and radioactive luminescent signs.

text: After his arrival in the USA he established, with his brother Alexander, the Canadian Radium and Uranium Corp of New York and became its president to sell the newly discovered rich ores in northern Canada, and later also in Colorado.

text: George B. Pegram

text: and his associates at Columbia University, who did some of the initial work on the Manhattan Project, sought Pregel's assistance because they did not have sufficient money to buy the uranium. Pregel gave them the first uranium used in the experiments. Pregel's company also built radioactive neutron sources and radioactive luminescent signs.

text: Paleontology seeks to map out how life evolved across geologic time. A substantial hurdle is the difficulty of working out fossil ages. Beds that preserve fossils typically lack the radioactive elements needed for radiometric dating. This technique is our only means of giving rocks greater than about 50 million years old an absolute age, and can be accurate to within 0.5% or better. Although radiometric dating requires careful laboratory work, its basic principle is simple: the rates at which various radioactive elements decay are known, and so the ratio of the radioactive element to its decay products shows how long ago the radioactive element was incorporated into the rock. Radioactive elements are common only in rocks with a volcanic origin, and so the only fossil-bearing rocks that can be dated radiometrically are volcanic ash layers, which may provide termini for the intervening sediments.

text: Paleontology seeks to map out how life evolved across geologic time. A substantial hurdle is the difficulty of working out fossil ages. Beds that preserve fossils typically lack the radioactive elements needed for

text: radiometric dating

text: . This technique is our only means of giving rocks greater than about 50 million years old an absolute age, and can be accurate to within 0.5% or better. Although radiometric dating requires careful laboratory work, its basic principle is simple: the rates at which various radioactive elements

text: decay

text: are known, and so the ratio of the radioactive element to its decay products shows how long ago the radioactive element was incorporated into the rock. Radioactive elements are common only in rocks with a volcanic origin, and so the only fossil-bearing rocks that can be dated radiometrically are volcanic ash layers, which may provide termini for the intervening sediments.

text: Natural radioactive elements are present in very low concentrations in earth's crust, and are brought to the surface through human activities such as oil and gas exploration or mining, and through natural processes like leakage of radon gas to the atmosphere or through dissolution in ground water. Another example of TENORM is coal ash produced from coal burning in power plants. If radioactivity is much higher than background level, handling TENORM may cause problems in many industries and transportation.

text: Natural

text: radioactive elements

text: are present in very low concentrations in earth's crust, and are brought to the surface through human activities such as

text: oil and gas exploration

text: or

text: mining

text: , and through natural processes like leakage of

text: radon

text: gas to the atmosphere or through dissolution in ground water. Another example of TENORM is

text: coal ash

text: produced from coal burning in

text: power plants

text: . If radioactivity is much higher than background level, handling TENORM may cause problems in many industries and transportation.

text: Whereas the mass number simply counts the total number of neutrons and protons and is thus a natural (or whole) number, the atomic mass of a single atom is a real number giving the mass of a particular isotope (or "nuclide") of the element, expressed in atomic mass units (u). In general, the mass number of a given nuclide differs in value slightly from its atomic mass, since the mass of each proton and neutron is not exactly 1 u; since the electrons contribute a lesser share to the atomic mass as neutron number exceeds proton number; and (finally) because of the nuclear binding energy. For example, the atomic mass of chlorine-35 to five significant digits is 34.969 u and that of chlorine-37 is 36.966 u. However, the atomic mass in u of each isotope is quite close to its simple mass number (always within 1%). The only isotope whose atomic mass is exactly a natural number is C, which by definition has a mass of exactly 12, because u is defined as 1/12 of the mass of a free neutral carbon-12 atom in the ground state.

text: Whereas the mass number simply counts the total number of neutrons and protons and is thus a natural (or whole) number, the

text: atomic mass

text: of a single atom is a

text: real number

text: giving the mass of a particular isotope (or "nuclide") of the element, expressed in

text: atomic mass unit

text: s (u). In general, the mass number of a given nuclide differs in value slightly from its atomic mass, since the mass of each proton and neutron is not exactly 1 u; since the electrons contribute a lesser share to the atomic mass as neutron number exceeds proton number; and (finally) because of the

text: nuclear binding energy

text: . For example, the atomic mass of chlorine-35 to five significant digits is 34.969 u and that of chlorine-37 is 36.966 u. However, the atomic mass in u of each isotope is quite close to its simple mass number (always within 1%). The only isotope whose atomic mass is exactly a

text: natural number

text: is C, which by definition has a mass of exactly 12, because u is defined as 1/12 of the mass of a free neutral carbon-12 atom in the ground state.

text: In 1901, Frederick Soddy and Ernest Rutherford discovered that radioactivity was part of the process by which atoms changed from one kind to another, involving the release of energy. Soddy wrote in popular magazines that radioactivity was a potentially “inexhaustible” source of energy, and offered a vision of an atomic future where it would be possible to “transform a desert continent, thaw the frozen poles, and make the whole earth one smiling Garden of Eden.” The promise of an “atomic age,” with nuclear energy as the global, utopian technology for the satisfaction of human needs, has been a recurring theme ever since. But "Soddy also saw that atomic energy could possibly be used to create terrible new weapons".

text: In 1901,

text: Frederick Soddy

text: and

text: Ernest Rutherford

text: discovered that

text: radioactivity

text: was part of the process by which atoms changed from one kind to another, involving the release of energy. Soddy wrote in popular magazines that radioactivity was a potentially “inexhaustible” source of energy, and offered a vision of an atomic future where it would be possible to “transform a desert continent, thaw the frozen poles, and make the whole earth one smiling Garden of Eden.” The promise of an “atomic age,” with nuclear energy as the global, utopian technology for the satisfaction of human needs, has been a recurring theme ever since. But "Soddy also saw that atomic energy could possibly be used to create terrible new weapons".

text: Decay products are important in understanding radioactive decay and the management of radioactive waste.

text: Decay products are important in understanding radioactive decay and the management of

text: radioactive waste

text: The most significant challenge at Hanford is stabilizing the  of high-level radioactive waste stored in 177 underground tanks. By 1998, about a third of these tanks had leaked waste into the soil and groundwater. , most of the liquid waste has been transferred to more secure double-shelled tanks; however, of liquid waste, together with  of salt cake and sludge, remains in the single-shelled tanks.  DOE lacks information about the extent to which the 27 double-shell tanks may be susceptible to corrosion. Without determining the extent to which the factors that contributed to the leak in AY-102 were similar to the other 27 double-shell tanks, DOE cannot be sure how long its double-shell tanks can safely store waste. That waste was originally scheduled to be removed by 2018. , the revised deadline was 2040. Nearby aquifers contain an estimated  of contaminated groundwater as a result of the leaks. ,  of radioactive waste is traveling through the groundwater toward the Columbia River. This waste is expected to reach the river in 12 to 50 years if cleanup does not proceed on schedule. The site includes  of solid radioactive waste.

text: In 1923, four predicted elements were still missing from the periodic table: 43 (technetium) and 61 (promethium) are radioactive elements and are only present in trace amounts in the environment, thus making elements 75 (rhenium) and 72 (hafnium) the last two unknown non-radioactive elements. Since rhenium was discovered in 1925, hafnium was the next-to-last element with stable isotopes to be discovered.

text: In 1923, four predicted elements were still missing from the periodic table: 43 (

text: technetium

text: ) and 61 (

text: promethium

text: ) are radioactive elements and are only present in trace amounts in the environment, thus making elements 75 (

text: rhenium

text: ) and 72 (hafnium) the last two unknown non-radioactive elements. Since rhenium was discovered in 1925, hafnium was the next-to-last element with stable isotopes to be discovered.

text: From 1946 to 1953, at the Walter E. Fernald State School in Massachusetts, in an experiment sponsored by the U.S. Atomic Energy Commission and the Quaker Oats corporation, 73 mentally disabled children were fed oatmeal containing radioactive calcium and other radioisotopes, in order to track "how nutrients were digested". The children were not told that they were being fed radioactive chemicals; they were told by hospital staff and researchers that they were joining a "science club".

text: From 1946 to 1953, at the

text: Walter E. Fernald State School

text: in Massachusetts, in an experiment sponsored by the U.S. Atomic Energy Commission and the

text: Quaker Oats

text: corporation, 73 mentally disabled children were fed

text: oatmeal

text: containing radioactive

text: calcium

text: and other

text: radioisotope

text: s, in order to track "how nutrients were digested". The children were not told that they were being fed radioactive chemicals; they were told by hospital staff and researchers that they were joining a "science club".

text: Radioactivity was discovered by Henri Becquerel in 1896. The theorical foundations and mathematical framework of Special Relativity were laid by Henri Poincaré, before Albert Einstein used them in 1905 and later.

text: Radioactivity

text: was discovered by

text: Henri Becquerel

text: in 1896. The theorical foundations and mathematical framework of Special Relativity were laid by

text: Henri Poincaré

text: , before

text: Albert Einstein

text: used them in 1905 and later.

text: Low-level radioactive waste has been discharged into the Irish Sea as part of operations at Sellafield since 1952. The rate of discharge began to accelerate in the mid- to late 1960s, reaching a peak in the 1970s and generally declining significantly since then. As an example of this profile, discharges of plutonium (specifically Pu) peaked in 1973 at  falling to  by 2004. Improvements in the treatment of waste in 1985 and 1994 resulted in further reductions in radioactive waste discharge although the subsequent processing of a backlog resulted in increased discharges of certain types of radioactive waste. Discharges of technetium in particular rose from  in 1993 to a peak of  in 1995 before dropping back to  in 2004. In total  of Pu was discharged over the period 1952 to 1998. Current rates of discharge for many radionuclides are at least 100 times lower than they were in the 1970s.

text: Low-level

text: radioactive

text: waste has been discharged into the Irish Sea as part of operations at Sellafield since 1952. The rate of discharge began to accelerate in the mid- to late 1960s, reaching a peak in the 1970s and generally declining significantly since then. As an example of this profile, discharges of

text: plutonium

text: (specifically

text: Pu

text: ) peaked in 1973 at  falling to  by 2004. Improvements in the treatment of waste in 1985 and 1994 resulted in further reductions in radioactive waste discharge although the subsequent processing of a backlog resulted in increased discharges of certain types of radioactive waste. Discharges of

text: technetium

text: in particular rose from  in 1993 to a peak of  in 1995 before dropping back to  in 2004. In total  of Pu was discharged over the period 1952 to 1998. Current rates of discharge for many

text: radionuclides

text: are at least 100 times lower than they were in the 1970s.

text: Radioactive waste is generated from the nuclear weapons program, commercial nuclear power, medical applications, and corporate and university-based research programs. Some of the materials LLW consists of are: "gloves and other protective clothing, glass and plastic laboratory supplies, machine parts and tools, and disposable medical items that have come in contact with radioactive materials". Waste is generally categorized as high level waste (HLW) and low-level waste (LLW). LLW contains materials such as irradiated tools, lab clothing, ion exchanger resins, animal carcasses, and trash from defense, commercial nuclear power, medical, and research activities. These materials usually have radioactivity that have short half lives—from ranges of multiple days to several hundred years. In 1990, 1.1 million cubic feet of LLW was produced. Currently, U.S. reactors generate about 40,000 cubic meters of low-level radioactive waste per year, including contaminated components and materials resulting from reactor decommissioning.

text: Radioactive waste

text: is generated from the

text: nuclear weapons

text: program, commercial

text: nuclear power

text: , medical applications, and corporate and university-based research programs. Some of the materials LLW consists of are: "gloves and other protective clothing, glass and plastic laboratory supplies, machine parts and tools, and disposable medical items that have come in contact with radioactive materials". Waste is generally categorized as

text: high level waste

text: (HLW) and

text: low-level waste

text: (LLW). LLW contains materials such as irradiated tools, lab clothing, ion exchanger resins, animal carcasses, and trash from defense, commercial nuclear power, medical, and research activities. These materials usually have

text: radioactivity

text: that have short

text: half lives

text: —from ranges of multiple days to several hundred years. In 1990, 1.1 million cubic feet of LLW was produced. Currently, U.S. reactors generate about 40,000 cubic meters of

text: low-level radioactive waste

text: per year, including contaminated components and materials resulting from reactor

text: decommissioning

text: There are two stable and naturally occurring isotopes of bromine, bromine-79 and bromine-81. A total of 32 isotopes of bromine have been discovered, with atomic masses ranging 67 to 98. There is one stable and naturally occurring isotope of iodine, iodine-127. However, there are trace amounts in nature of the radioactive isotope iodine-129, which occurs via spallation and from the radioactive decay of uranium in ores. Several other radioactive isotopes of iodine have also been created naturally via the decay of uranium. A total of 38 isotopes of iodine have been discovered, with atomic masses ranging from 108 to 145.

text: There are two stable and naturally occurring

text: isotopes of bromine

text: , bromine-79 and bromine-81. A total of 32 isotopes of bromine have been discovered, with atomic masses ranging 67 to 98. There is one stable and naturally occurring

text: isotope of iodine

text: . However, there are trace amounts in nature of the radioactive isotope

text: , which occurs via spallation and from the radioactive decay of uranium in ores. Several other radioactive isotopes of iodine have also been created naturally via the decay of uranium. A total of 38 isotopes of iodine have been discovered, with atomic masses ranging from 108 to 145.

text: New Zealand-born chemist and physicist  Ernest Rutherford is considered to be "the father of nuclear physics." Rutherford is best known for devising the names alpha, beta, and gamma to classify various forms of radioactive "rays" which were poorly understood at his time (alpha and beta rays are particle beams, while gamma rays are a form of high-energy electromagnetic radiation). Rutherford deflected alpha rays with both electric and magnetic fields in 1903. Working with Frederick Soddy, Rutherford explained that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions.

text: New Zealand-born chemist and physicist

text: Ernest Rutherford

text: is considered to be "the father of

text: nuclear physics

text: ." Rutherford is best known for devising the names

text: alpha

text: beta

text: , and

text: gamma

text: to classify various forms of radioactive "rays" which were poorly understood at his time (alpha and beta rays are particle beams, while gamma rays are a form of high-energy

text: electromagnetic radiation

text: ). Rutherford deflected alpha rays with both electric and magnetic fields in 1903. Working with

text: Frederick Soddy

text: , Rutherford explained that

text: radioactivity

text: is due to the

text: transmutation

text: of elements, now known to involve

text: nuclear reactions

text: Henri Becquerel discovered radioactivity in 1896 while working with phosphorescent materials. His work confirmed and explained earlier observations regarding uranium salts by Abel Niépce de Saint-Victor in 1857.

text: Henri Becquerel

text: discovered

text: radioactivity

text: in 1896 while working with

text: phosphorescent

text: materials. His work confirmed and explained earlier observations regarding

text: uranium

text: salts by

text: Abel Niépce de Saint-Victor

text: in 1857.

text: Underwater tests were conducted to assess the damages to Navy boats and materials. The location for these tests was chosen to be Enewetak. This location was chosen due to the uniformity of the bottom of the sea around Enewetak. This is critical for the tests so that proper moorings of the target ships can be secured on the sea floor. The underwater explosions create a bubble from the expended energy of the blast. This bubble is due to the vaporization of water that directly absorbs the heat of the blast. This bubble may break the surface depending on how much energy is dispersed and the depth of the nuclear device. The bubble displaces large amounts of water that then collapses in on the bubble after all the energy is expended. The water collapsing in on the cavity is call the "radioactive pool" and has the highest concentration of radioactive material.

text: Transmutation of transuranium elements (TRUs, i.e. actinides minus actinium to uranium) such as the isotopes of plutonium (about 1wt% in the Light Water Reactors' used nuclear fuel) or the minor actinides (MAs, i.e. neptunium, americium, and curium, about 0.1wt% each in LWRs' UNF) has the potential to help solve some problems posed by the management of radioactive waste by reducing the proportion of long-lived isotopes it contains. (This does not rule-out the need for a Deep Geological Repository (DGR) for High radioactive Level Waste (HLW).) When irradiated with fast neutrons in a nuclear reactor, these isotopes can  undergo nuclear fission, destroying the original actinide isotope and producing a spectrum of radioactive and nonradioactive fission products.

text: Transmutation of

text: transuranium element

text: s (TRUs, i.e.

text: actinides

text: minus

text: actinium

text: to

text: uranium

text: ) such as the

text: isotope

text: s of

text: plutonium

text: (about 1wt% in the

text: Light Water Reactor

text: s' used

text: nuclear fuel

text: ) or the minor actinides (MAs, i.e.

text: neptunium

text: americium

text: , and

text: curium

text: , about 0.1wt% each in LWRs' UNF) has the potential to help solve some problems posed by the management of

text: radioactive waste

text: by reducing the proportion of long-lived isotopes it contains. (This does not rule-out the need for a Deep Geological Repository (DGR) for High radioactive Level Waste (HLW).) When irradiated with

text: fast neutrons

text: in a

text: nuclear reactor

text: , these isotopes can  undergo

text: nuclear fission

text: , destroying the original

text: actinide

text: isotope and producing a spectrum of radioactive and nonradioactive

text: fission products

text: SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud (a nearby dwarf galaxy). It occurred approximately 51.4 kiloparsecs from Earth, approximately 168,000 light-years, close enough that it was visible to the naked eye. It could be seen from the Southern Hemisphere. It was the closest observed supernova since SN 1604, which occurred in the Milky Way itself. The light from the new supernova reached Earth on February 23, 1987. As it was the first supernova discovered in 1987, it was labeled “1987A”. Its brightness peaked in May with an apparent magnitude of about 3 and slowly declined in the following months. It was the first opportunity for modern astronomers to study the development of a supernova in detail, and observations have provided much insight into core-collapse supernovae. Of special importance, SN1987A provided the first chance to confirm by direct observation the radioactive source of the energy for visible light emissions by detection of predicted gamma-ray line radiation from two of its abundant radioactive nuclei, Co and Co. This proved the radioactive nature of the long-duration post-explosion glow of supernovae.

text: SN 1987A was a

text: supernova

text: in the outskirts of the

text: Tarantula Nebula

text: in the

text: Large Magellanic Cloud

text: (a nearby

text: dwarf galaxy

text: ). It occurred approximately 51.4

text: kiloparsecs

text: from

text: Earth

text: , approximately 168,000

text: light-year

text: s, close enough that it was visible to the

text: naked eye

text: . It could be seen from the Southern Hemisphere. It was the closest observed supernova since

text: SN 1604

text: , which occurred in the

text: Milky Way

text: itself. The light from the new supernova reached Earth on February 23, 1987. As it was the first supernova discovered in 1987, it was labeled “1987A”. Its brightness peaked in May with an

text: apparent magnitude

text: of about 3 and slowly declined in the following months. It was the first opportunity for modern

text: astronomers

text: to study the development of a supernova in detail, and observations have provided much insight into

text: core-collapse supernova

text: e. Of special importance, SN1987A provided the first chance to confirm by direct observation the radioactive source of the energy for visible light emissions by detection of predicted gamma-ray line radiation from two of its abundant radioactive nuclei,

text: Co

text: and

text: Co

text: . This proved the radioactive nature of the long-duration post-explosion glow of supernovae.

text: Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a proton is ejected from a nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state (or a low-lying isomer) of very proton-rich nuclei, in which case the process is very similar to alpha decay. For a proton to escape a nucleus, the proton separation energy must be negative - the proton is therefore unbound, and tunnels out of the nucleus in a finite time. Proton emission is not seen in naturally occurring isotopes; proton emitters can be produced via nuclear reactions, usually using linear particle accelerators.

text: Proton emission (also known as proton radioactivity) is a rare type of radioactive decay in which a

text: proton

text: is ejected from a

text: nucleus

text: . Proton emission can occur from high-lying excited states in a nucleus following a

text: beta decay

text: , in which case the process is known as beta-delayed proton emission, or can occur from the ground state (or a low-lying

text: isomer

text: ) of very proton-rich nuclei, in which case the process is very similar to

text: alpha decay

text: . For a proton to escape a nucleus, the proton separation energy must be negative - the proton is therefore unbound, and

text: tunnels

text: out of the nucleus in a finite time. Proton emission is not seen in naturally occurring isotopes; proton emitters can be produced via

text: nuclear reaction

text: s, usually using

text: linear particle accelerator

text: s.

text: A common example of a radioactive decay alteration is when a radioactive element bearing zircon or allanite crystal becomes metamict or amorphous due to structural damage.

text: A common example of a radioactive decay alteration is when a

text: radioactive element

text: bearing

text: zircon

text: or

text: allanite

text: crystal

text: becomes

text: metamict

text: or

text: amorphous

text: due to structural damage.

text: An elaborated APXS setup is equipped with a sensor head containing six curium sources having the total radioactive decay rate of several tens of millicuries (roughly a gigabecquerel). The sources are collimated on the sample, and the energy spectra of the alpha particles and protons scattered from the sample are analyzed (the proton analysis is implemented only in some spectrometers). These spectra contain quantitative information on all major elements in the samples except for hydrogen, helium and lithium.

text: An elaborated APXS setup is equipped with a sensor head containing six curium sources having the total radioactive decay rate of several tens of

text: millicuries

text: (roughly a

text: gigabecquerel

text: ). The sources are collimated on the sample, and the energy spectra of the alpha particles and protons scattered from the sample are analyzed (the proton analysis is implemented only in some spectrometers). These spectra contain quantitative information on all major elements in the samples except for hydrogen, helium and lithium.

text: The relativistic Dirac equation has problems for elements with more than 137 protons. For such elements, the wave function of the Dirac ground state is oscillatory rather than bound, and there is no gap between the positive and negative energy spectra, as in the Klein paradox. More accurate calculations taking into account the effects of the finite size of the nucleus indicate that the binding energy first exceeds the limit for elements with more than 173 protons. For heavier elements, if the innermost orbital (1s) is not filled, the electric field of the nucleus will pull an electron out of the vacuum, resulting in the spontaneous emission of a positron; however, this does not happen if the innermost orbital is filled, so that element 173 is not necessarily the end of the periodic table.

text: The

text: relativistic

text: Dirac equation has problems for elements with more than 137 protons. For such elements, the wave function of the Dirac ground state is oscillatory rather than bound, and there is no gap between the positive and negative energy spectra, as in the

text: Klein paradox

text: . More accurate calculations taking into account the effects of the finite size of the nucleus indicate that the binding energy first exceeds the limit for elements with more than 173 protons. For heavier elements, if the innermost orbital (1s) is not filled, the electric field of the nucleus will pull an electron out of the vacuum, resulting in the

text: spontaneous emission of a positron

text: ; however, this does not happen if the innermost orbital is filled, so that element 173 is not necessarily the end of the periodic table.

text: After an overhaul, Pioneer set out on 25 February 1962 to begin the 1962 field season, running a deep-sea sounding line to Hawaii. Departing Pearl Harbor on 16 March 1962, she resumed her survey of the North Pacific Ocean, running a sounding line to 35 degrees 30 minutes North latitude, and another sounding line to San Francisco, where she arrived on 25 March 1962. After 20 of her personnel attended Radiation and Decontamination School, she departed California on 20 April 1962 and conducted an investigation of Pacific waters which had seen recent underwater nuclear tests, including water temperature measurements, chemical analyses, measurements of radioactivity and of the different elements making up the radioactive water in the area of an underwater nuclear explosion, and study of the effects of radioactivity on plant and animal life in and near the test areas. She completed the project on 25 June 1962 and returned to California, arriving at Oakland. She had conducted gravimetric measurements continuously throughout the voyage.

text: After an overhaul, Pioneer set out on 25 February 1962 to begin the 1962 field season, running a deep-sea sounding line to Hawaii. Departing Pearl Harbor on 16 March 1962, she resumed her survey of the North Pacific Ocean, running a sounding line to

text: 35 degrees

text: 30 minutes North latitude, and another sounding line to San Francisco, where she arrived on 25 March 1962. After 20 of her personnel attended Radiation and Decontamination School, she departed California on 20 April 1962 and conducted an investigation of Pacific waters which had seen recent underwater nuclear tests, including water temperature measurements,

text: chemical analyses

text: , measurements of radioactivity and of the different elements making up the radioactive water in the area of an underwater nuclear explosion, and study of the effects of radioactivity on plant and animal life in and near the test areas. She completed the project on 25 June 1962 and returned to California, arriving at

text: Oakland

text: . She had conducted gravimetric measurements continuously throughout the voyage.

text: The negatively charged electron has a mass equal to  of that of a hydrogen atom. The remainder of the hydrogen atom's mass comes from the positively charged proton. The atomic number of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton. Different isotopes of the same element contain the same number of protons but differing numbers of neutrons. The mass number of an isotope is the total number of nucleons (neutrons and protons collectively).

text: The negatively charged electron has a mass equal to  of that of a

text: hydrogen

text: atom. The remainder of the hydrogen atom's mass comes from the positively charged

text: proton

text: . The

text: atomic number

text: of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton. Different

text: isotope

text: s of the same element contain the same number of protons but differing numbers of neutrons. The

text: mass number

text: of an isotope is the total number of

text: nucleon

text: s (neutrons and protons collectively).

text: It was later discovered that radioactive waste had been disposed of a half mile away at the Middlesex Municipal Landfill. The site was used from 1955 to 1967 for the sampling and storage of thorium residues, and was decontaminated, certified, and released for unrestricted use in 1967. During the decontamination process, radioactive materials were carried away by wind and rain to the yards of nearby residents.

text: It was later discovered that

text: radioactive waste

text: had been disposed of a half mile away at the Middlesex Municipal

text: Landfill

text: . The site was used from 1955 to 1967 for the sampling and storage of thorium residues, and was decontaminated, certified, and released for unrestricted use in 1967. During the decontamination process, radioactive materials were carried away by wind and rain to the yards of nearby residents.

text: During his investigations of radioactivity, Ernest Rutherford coined the terms alpha rays, beta rays and gamma rays for the three types of emissions that occur during radioactive decay.

text: During his investigations of radioactivity,

text: Ernest Rutherford

text: coined the terms

text: alpha rays

text: beta rays

text: and

text: gamma ray

text: s for the three types of emissions that occur during

text: radioactive decay

text: The most stable nuclei fall within certain ranges or balances of composition of neutrons and protons: too few or too many neutrons (in relation to the number of protons) will cause it to decay. For example, in beta decay a nitrogen-16 atom (7 protons, 9 neutrons) is converted to an oxygen-16 atom (8 protons, 8 neutrons) within a few seconds of being created. In this decay a neutron in the nitrogen nucleus is converted by the weak interaction into a proton, an electron and an antineutrino. The element is transmuted to another element, with a different number of protons.

text: The most stable nuclei fall within certain ranges or balances of composition of neutrons and protons: too few or too many neutrons (in relation to the number of protons) will cause it to decay. For example, in

text: beta decay

text: a

text: nitrogen

text: -16 atom (7 protons, 9 neutrons) is converted to an

text: oxygen

text: -16 atom (8 protons, 8 neutrons) within a few seconds of being created. In this decay a neutron in the nitrogen nucleus is converted by the

text: weak interaction

text: into a proton, an electron and an

text: antineutrino

text: . The element is transmuted to another element, with a different number of protons.

text: All fission reactions necessarily generate fission products, the radioactive remains of the atomic nuclei split by the fission reactions. Many fission products are either highly radioactive (but short-lived) or moderately radioactive (but long-lived), and as such are a serious form of radioactive contamination if not fully contained. Fission products are the principal radioactive component of nuclear fallout.

text: All fission reactions necessarily generate

text: fission products

text: , the radioactive remains of the atomic nuclei split by the fission reactions. Many fission products are either highly radioactive (but short-lived) or moderately radioactive (but long-lived), and as such are a serious form of

text: radioactive contamination

text: if not fully contained. Fission products are the principal radioactive component of

text: nuclear fallout

text: An alpha particle X-ray spectrometer (APXS) is a spectrometer that analyses the chemical element composition of a sample from the scattered alpha particles, and fluorescent X-rays after the sample is irradiated with alpha particles and X-rays from radioactive sources. This method of analysing the elemental composition of a sample is most often used on space missions, which require low weight, small size, and minimal power consumption. Other methods (e.g. mass spectrometry) are faster, and do not require the use of radioactive materials, but require larger equipment with less modest power requirements. A variation is the alpha proton X-ray spectrometer, such as on the Pathfinder mission, which also detects protons.

text: An alpha particle X-ray spectrometer (APXS) is a

text: spectrometer

text: that analyses the chemical element composition of a sample from the scattered

text: alpha particle

text: s, and fluorescent

text: X-ray

text: s after the sample is irradiated with alpha particles and X-rays from radioactive sources. This method of analysing the elemental composition of a sample is most often used on space missions, which require low weight, small size, and minimal power consumption. Other methods (e.g.

text: mass spectrometry

text: ) are faster, and do not require the use of radioactive materials, but require larger equipment with less modest power requirements. A variation is the alpha proton X-ray spectrometer, such as on the

text: Pathfinder mission

text: , which also detects

text: protons

text: In a p-process protons are added to stable or weakly radioactive atomic nuclei. If there is a high proton density in the stellar plasma, even short-lived radionuclides can capture one or more protons before they beta decay. This quickly moves the nucleosynthesis path from the region of stable nuclei to the very proton-rich side of the Chart of Nuclides. This is called rapid proton-capture.

text: In a p-process protons are added to stable or weakly

text: radioactive

text: atomic nuclei

text: . If there is a high proton density in the stellar plasma, even short-lived

text: radionuclides

text: can capture one or more protons before they

text: beta decay

text: . This quickly moves the

text: nucleosynthesis

text: path from the region of stable nuclei to the very proton-rich side of the

text: Chart of Nuclides

text: . This is called rapid proton-capture.

text: Clayton created new tools for calculating the interstellar abundances of radioactive nuclei in the Galaxy. In 1964 he discovered a new method for measuring the age of interstellar nuclei based on the larger than expected observed abundances of stable daughters of radioactive nuclei. The decays of rhenium-187 to osmium-187 and of uranium and thorium to three differing isotopes of lead (Pb) defined the cosmoradiogenic chronologies. Merging his method with an earlier method based only on the abundances of uranium and thorium themselves still did not yield a precise galactic age, however. Clayton wrote that the discord arose from inadequate treatments of both the history of star formation in the Galaxy and of the rate of infall of pristine metal-free gas onto the young Milky Way, compounded by a prevailing but erroneous technique for computation of the radioactive abundances within interstellar gas. Clayton reasoned that interstellar gas contains higher concentrations of shorter-lived radioactive nuclei than do the stars. With that insight he invented in 1985 new mathematical solutions for the simplified differential equation of galactic abundance evolution that for the first time rendered these relationships transparent, ending decades of confusion. Clayton calculated an age of 13-15 billion years for the oldest galactic nuclei, which would necessarily be approximately equal to the age of our galaxy. More recently radioactive  cosmochronology has diminished in importance because more accurate techniques for determining the age of the Milky Way have been discovered in the microwave background; but agreement confirmed correctness of his treatment of radioactivity in astronomy. His analytic mathematical models demonstrated that the concentration of short-lived radioactive nuclei in interstellar gas had routinely been underestimated by the factor 1/(k+1), where k is an integer near 2 or 3 that measures the steepness of the rate of decline of the infall of pristine gas onto our galaxy. In a parallel scientific development the identities and initial abundances of  shorter-lived radioactive nuclei that remained alive at variable levels within the interstellar gas cloud that formed the early solar system, but which are now extinct, has grown in importance with more experimental discoveries of such nuclei within the meteorites. These are called extinct radioactivities because none remain on earth today. Simultaneous solution for their abundances became the guiding principle for a new discipline of galactic abundance evolution that focuses on nucleosynthesis near the solar interstellar cloud during the billion years preceding solar birth. In 1983, at a time when astrophysicists were relying on only a uniform model of a well mixed interstellar gas,  Clayton introduced a new aspect of the ISM that has proven to be essential for understanding the abundances of the extinct radioactivities; namely the time required for isotopic mixing between freshly synthesized atoms ejected from supernovae with distinct physical phases of interstellar gas. He showed that owing to those time delays allowing more interstellar decay of radioactive nuclei, each phase of interstellar gas contains a distinctly different concentration of each of the extinct radioactive nuclides; but that the early solar system radioactivities measured specifically only abundances in the dense molecular-cloud phase in which the solar system had been born. In the 21st century many researchers have begun to present their own calculations of the effect of interstellar inter-phase mixing, often unaware of Clayton's (1983) paper owing to intervening decades. These aspects of interstellar phase mixing will remain important for decades to come while astronomers probe the circumstances of solar birth using accurate meteoritic data revealing the abundances of the extinct radioactive nuclei. Clayton gave emphasis to extinct radioactivity in the Glossary of his 2003 book on isotopes in the cosmos. Chapters 16 and 17 of "Catch a Falling Star".

text: Isotopes are different forms of elements; they have a different number of neutrons in the nucleus, meaning they have very similar chemical properties, but different mass.  The weight difference means that some isotopes are discriminated against in chemical processes – for example, plants find it easier to incorporate the lighter C than heavy C. Other isotopes are only produced as a result of the radioactive decay of other elements, such as Sr, the daughter isotope of Rb.  Rb, and therefore Sr, is common in the crust, so abundance of Sr in a sample of sediment (relative to Sr) is related to the amount of sediment which originated in the crust, as opposed to from the oceans.

text: Isotopes

text: are different forms of elements; they have a different number of neutrons in the nucleus, meaning they have very similar chemical properties, but different mass.  The weight difference means that some isotopes are discriminated against in chemical processes – for example, plants find it easier to incorporate the lighter

text: C

text: than heavy

text: C

text: . Other isotopes are only produced as a result of the radioactive decay of other elements, such as Sr, the daughter isotope of

text: Rb

text: .  Rb, and therefore Sr, is common in the crust, so abundance of Sr in a sample of sediment (relative to Sr) is related to the amount of sediment which originated in the crust, as opposed to from the oceans.

text: All of the alkali metals except lithium and caesium have at least one naturally occurring radioisotope: sodium-22 and sodium-24 are trace radioisotopes produced cosmogenically, potassium-40 and rubidium-87 have very long half-lives and thus occur naturally, and all isotopes of francium are radioactive. Caesium was also thought to be radioactive in the early 20th century, although it has no naturally occurring radioisotopes. (Francium had not been discovered yet at that time.) The natural long-lived radioisotope of potassium, potassium-40, makes up about 0.012% of natural potassium, and thus natural potassium is weakly radioactive. This natural radioactivity became a basis for a mistaken claim of the discovery for element 87 (the next alkali metal after caesium) in 1925. Natural rubidium is similarly slightly radioactive, with 27.83% being the long-lived radioisotope rubidium-87.

text: All of the alkali metals except lithium and caesium have at least one naturally occurring

text: radioisotope

text: and

text: are

text: trace radioisotope

text: s produced

text: cosmogenic

text: ally, potassium-40 and

text: have very long

text: half-lives

text: and thus occur naturally, and all

text: isotopes of francium

text: are

text: radioactive

text: . Caesium was also thought to be radioactive in the early 20th century, although it has no naturally occurring radioisotopes. (Francium had not been discovered yet at that time.) The natural long-lived radioisotope of potassium, potassium-40, makes up about 0.012% of natural potassium, and thus natural potassium is weakly radioactive. This natural radioactivity became a basis for a mistaken claim of the discovery for element 87 (the next alkali metal after caesium) in 1925. Natural rubidium is similarly slightly radioactive, with 27.83% being the long-lived radioisotope rubidium-87.

text: Positrons are produced naturally in β decays of naturally occurring radioactive isotopes (for example, potassium-40) and in interactions of gamma quanta (emitted by radioactive nuclei) with matter.  Antineutrinos are another kind of antiparticle created by natural radioactivity (β decay). Many different kinds of antiparticles are also produced by (and contained in) cosmic rays. In January 2011, research by the American Astronomical Society discovered antimatter (positrons) originating above thunderstorm clouds; positrons are produced in gamma-ray flashes created by electrons accelerated by strong electric fields in the clouds. Antiprotons have also been found to exist in the Van Allen Belts around the Earth by the PAMELA module.

text: Positrons are produced naturally in β decays of naturally occurring radioactive isotopes (for example,

text: ) and in interactions of gamma quanta (emitted by radioactive nuclei) with matter.

text: Antineutrino

text: s are another kind of antiparticle created by natural radioactivity (β decay). Many different kinds of antiparticles are also produced by (and contained in)

text: cosmic rays

text: . In January 2011, research by the

text: American Astronomical Society

text: discovered antimatter (positrons) originating above

text: thunderstorm

text: clouds; positrons are produced in gamma-ray flashes created by electrons accelerated by strong electric fields in the clouds. Antiprotons have also been found to exist in the

text: Van Allen Belt

text: s around the Earth by the

text: PAMELA module

text: Some studies have shown that thyroglobulin (Tg) testing combined with neck ultrasound is more productive in finding disease recurrence than full- or whole-body scans (WBS) using radioactive iodine. However, current protocol (in the USA) suggests a small number of clean annual WBS are required before relying on Tg testing plus neck ultrasound. When needed, whole body scans consist of withdrawal from thyroxine medication and/or injection of recombinant human Thyroid stimulating hormone (TSH). In both cases, a low iodine diet regimen must also be followed to optimize the takeup of the radioactive iodine dose. Low dose radioiodine of a few millicuries is administered. Full body nuclear medicine scan follows using a gamma camera. Scan doses of radioactive iodine may be I or I.

text: Some studies have shown that thyroglobulin (Tg) testing combined with neck

text: ultrasound

text: is more productive in finding disease recurrence than full- or

text: whole-body scans

text: (WBS) using radioactive iodine. However, current protocol (in the USA) suggests a small number of clean annual WBS are required before relying on Tg testing plus neck ultrasound. When needed, whole body scans consist of withdrawal from thyroxine medication and/or injection of recombinant human

text: Thyroid stimulating hormone

text: (TSH). In both cases, a low iodine diet regimen must also be followed to optimize the takeup of the radioactive iodine dose. Low dose radioiodine of a few millicuries is administered. Full body

text: nuclear medicine

text: scan follows using a

text: gamma camera

text: . Scan doses of radioactive iodine may be

text: I

text: or

text: I

text: The cluster in which HD 162826 and the Sun formed is believed to have been an open cluster, permitting the stars to scatter widely over time. The stars in this cluster were not too closely packed during their formation to disrupt planetary disk development, but were not so far apart as to prevent the seeding of Earth with radioactive elements produced by a nearby supernova.

text: The cluster in which HD 162826 and the Sun formed is believed to have been an

text: open cluster

text: , permitting the stars to scatter widely over time. The stars in this cluster were not too closely packed during their formation to disrupt

text: planetary disk

text: development, but were not so far apart as to prevent the seeding of Earth with

text: radioactive elements

text: produced by a nearby

text: supernova

text: The phantom consists of 10 polyethylene bottles, either cylinders or elliptical cylinders, that represent the head, neck chest, abdomen, thighs, calves, and arms.  Each section is filled with a radioactive solution, in water, that has the amount of radioactivity proportional to the volume of each section.  This simulates a homogeneous distribution of material throughout the body.  The solution will also be acidified and contain stable element carrier so that the radioactivity does not plate out on the container walls.

text: The phantom consists of 10

text: polyethylene

text: bottles, either cylinders or elliptical cylinders, that represent the head, neck chest, abdomen, thighs, calves, and arms.  Each section is filled with a radioactive solution, in water, that has the amount of radioactivity proportional to the volume of each section.  This simulates a homogeneous distribution of material throughout the body.  The solution will also be acidified and contain stable element carrier so that the

text: radioactivity

text: does not plate out on the container walls.

text: Although it is estimated that about 32 primordial nuclides are radioactive (list below), it becomes very difficult to determine the exact total number of radioactive primordials, because the total number of stable nuclides is uncertain. There exist many extremely long-lived nuclides whose half-lives are still unknown. For example, it is known theoretically that all isotopes of tungsten, including those indicated by even the most modern empirical methods to be stable, must be radioactive and can decay by alpha emission, but  this could only be measured experimentally for . Nevertheless, the number of nuclides with half-lives so long that they cannot be measured with present instruments—and are considered from this viewpoint to be stable nuclides—is limited. Even when a "stable" nuclide is found to be radioactive, the fact merely moves it from the stable to the unstable list of primordial nuclides, and the total number of primordial nuclides remains unchanged.

text: Although it is estimated that about 32 primordial nuclides are

text: radioactive

text: (list below), it becomes very difficult to determine the exact total number of radioactive primordials, because the total number of stable nuclides is uncertain. There exist many extremely long-lived nuclides whose half-lives are still unknown. For example, it is known theoretically that all

text: isotope

text: s of

text: tungsten

text: , including those indicated by even the most modern empirical methods to be stable, must be radioactive and can decay by

text: alpha emission

text: , but  this could only be measured experimentally for . Nevertheless, the number of nuclides with half-lives so long that they cannot be measured with present instruments—and are considered from this viewpoint to be

text: stable nuclides

text: —is limited. Even when a "stable" nuclide is found to be radioactive, the fact merely moves it from the stable to the unstable list of primordial nuclides, and the total number of primordial nuclides remains unchanged.

text: The initial ISS plan included a Docking and Storage Module (DSM). This planned Russian element was intended to provide facilities for stowage and an additional docking port, and would have been launched to the station on a Proton launch vehicle. The DSM would have been mounted to Zarya

text: The initial ISS plan included a Docking and Storage Module (DSM). This planned Russian element was intended to provide facilities for stowage and an additional docking port, and would have been launched to the station on a

text: Proton

text: launch vehicle. The DSM would have been mounted to Zarya

text: The technique uses the injection of ultrashort acting radioactive substances commonly bound to water or deoxyglucose. The deoxyglucose method directly measures brain metabolism whereas the radioactively labeled water is effective at measuring brain blood flow.

text: Mister Drake's Duck is a 1951 British science fiction comedy film directed by Val Guest and starring Douglas Fairbanks Jr., Yolande Donlan, Jon Pertwee, Wilfrid Hyde-White and Reginald Beckwith. The screenplay concerns Mr Drake, a farmer, who discovers that his hens have started laying radioactive eggs.

text: Mister Drake's Duck is a 1951 British

text: science fiction

text: comedy film

text: directed by

text: Val Guest

text: and starring

text: Douglas Fairbanks Jr.

text: Yolande Donlan

text: Jon Pertwee

text: Wilfrid Hyde-White

text: and

text: Reginald Beckwith

text: . The screenplay concerns Mr Drake, a farmer, who discovers that his hens have started laying

text: radioactive

text: eggs.

text: Bocking has one school called Bocking Church Street School. It used to have another school called Edith Borthwick School but they move to Springwood Drive in Braintree in September 2015 because their old school in Bocking is too small.

text: At the age of three, she made the connection between fish to eat and the living creatures themselves and decided to become a vegetarian.

text: These natural reactors are extensively studied by scientists interested in geologic radioactive waste disposal. They offer a case study of how radioactive isotopes migrate through the Earth's crust. This is a significant area of controversy as opponents of geologic waste disposal fear that isotopes from stored waste could end up in water supplies or be carried into the environment.

text: The first copy of BusinessWorld was sold on July 27, 1987. In the same year, BusinessWorld became the first among local dailies to use desktop publishing, and in 1991 it incorporated World Press, Inc., a fully owned printing subsidiary of the firm located in Antipolo, Rizal.

text: The first copy of BusinessWorld was sold on July 27, 1987. In the same year, BusinessWorld became the first among local dailies to use

text: desktop publishing

text: , and in 1991 it incorporated World Press, Inc., a fully owned printing subsidiary of the firm located in

text: Antipolo, Rizal

text: Many odd-odd radionuclides (like tantalum-180) with comparatively short half lives are known. Usually, they beta-decay to their nearby even-even isobars that have paired protons and paired neutrons. Of the nine primordial odd-odd nuclides (five stable and four radioactive with long half lives), only  is the most common isotope of a common element. This is the case because it is a part of the CNO cycle. The nuclides  and  are minority isotopes of elements that are themselves rare compared to other light elements, whereas the other six isotopes make up only a tiny percentage of the natural abundance of their elements.

text: Many odd-odd radionuclides (like tantalum-180) with comparatively short half lives are known. Usually, they beta-decay to their nearby even-even

text: isobars

text: that have paired protons and paired neutrons. Of the nine primordial odd-odd nuclides (five stable and four radioactive with long half lives), only  is the most common isotope of a common element. This is the case because it is a part of the

text: CNO cycle

text: . The nuclides  and  are minority isotopes of elements that are themselves rare compared to other light elements, whereas the other six isotopes make up only a tiny percentage of the natural abundance of their elements.

text: The Granite Reef Diversion Dam, constructed near the confluence of the Salt and Verde rivers, does not actually hold back a reservoir but is used to divert water from those rivers into the system of canals feeding into the Phoenix area. It was actually the first of the dams constructed, finished in 1906 to replace the Arizona Dam, which had been washed away by floods the previous year.

text: The

text: Granite Reef Diversion Dam

text: , constructed near the confluence of the Salt and Verde rivers, does not actually hold back a reservoir but is used to divert water from those rivers into the system of canals feeding into the Phoenix area. It was actually the first of the dams constructed, finished in 1906 to replace the Arizona Dam, which had been washed away by floods the previous year.

text: In 1904 J. J. Thomson considered a Le Sage-type model in which the primary ultramundane flux consisted of a hypothetical form of radiation much more penetrating even than x-rays. He argued that Maxwell's heat problem might be avoided by assuming that the absorbed energy is not converted into heat, but re-radiated in a still more penetrating form. He noted that this process possibly can explain where the energy of radioactive substances comes from - however, he stated that an internal cause of radioactivity is more probable. In 1911 Thomson went back to this subject in his article "Matter" in the Encyclopædia Britannica Eleventh Edition. There he stated, that this form of secondary radiation is somewhat analogous to how the passage of electrified particles through matter causes the radiation of the even more penetrating x-rays. He remarked:

text: In 1904

text: J. J. Thomson

text: considered a Le Sage-type model in which the primary ultramundane flux consisted of a hypothetical form of radiation much more penetrating even than x-rays. He argued that Maxwell's heat problem might be avoided by assuming that the absorbed energy is not converted into heat, but re-radiated in a still more penetrating form. He noted that this process possibly can explain where the energy of radioactive substances comes from - however, he stated that an internal cause of

text: radioactivity

text: is more probable. In 1911 Thomson went back to this subject in his article "Matter" in the

entity_name: Encyclopædia Britannica Eleventh Edition

text: Encyclopædia Britannica Eleventh Edition

text: . There he stated, that this form of secondary radiation is somewhat analogous to how the passage of electrified particles through matter causes the radiation of the even more penetrating x-rays. He remarked:

text: After the discovery of X-rays by Wilhelm Röntgen, many scientists began to work on ionizing radiation. One of these was Henri Becquerel, who investigated the relationship between phosphorescence and the blackening of photographic plates. When Becquerel (working in France) discovered that, with no external source of energy, the uranium generated rays which could blacken (or fog) the photographic plate, radioactivity was discovered. Marie Curie (working in Paris) and her husband Pierre Curie isolated two new radioactive elements from uranium ore. They used radiometric methods to identify which stream the radioactivity was in after each chemical separation; they separated the uranium ore into each of the different chemical elements that were known at the time, and measured the radioactivity of each fraction. They then attempted to separate these radioactive fractions further, to isolate a smaller fraction with a higher specific activity (radioactivity divided by mass). In this way, they isolated polonium and radium. It was noticed in about 1901 that high doses of radiation could cause an injury in humans. Henri Becquerel had carried a sample of radium in his pocket and as a result he suffered a high localised dose which resulted in a radiation burn. This injury resulted in the biological properties of radiation being investigated, which in time resulted in the development of medical treatments.

text: After the discovery of

text: X-ray

text: s by

text: Wilhelm Röntgen

text: , many scientists began to work on ionizing radiation. One of these was

text: Henri Becquerel

text: , who investigated the relationship between

text: phosphorescence

text: and the blackening of

text: photographic plate

text: s. When Becquerel (working in France) discovered that, with no external source of energy, the uranium generated rays which could blacken (or fog) the photographic plate, radioactivity was discovered.

text: Marie Curie

text: (working in Paris) and her husband

text: Pierre Curie

text: isolated two new radioactive elements from uranium ore. They used

text: radiometric

text: methods to identify which stream the radioactivity was in after each chemical separation; they separated the uranium ore into each of the different chemical elements that were known at the time, and measured the radioactivity of each fraction. They then attempted to separate these radioactive fractions further, to isolate a smaller fraction with a higher specific activity (radioactivity divided by mass). In this way, they isolated

text: polonium

text: and

text: radium

text: . It was noticed in about 1901 that high doses of radiation could cause an injury in humans.

text: Henri Becquerel

text: had carried a sample of radium in his pocket and as a result he suffered a high localised dose which resulted in a

text: radiation burn

text: . This injury resulted in the biological properties of radiation being investigated, which in time resulted in the development of medical treatments.

text: Hafling (;  ) is an Italian comune (municipality).

text: Hafling (;  ) is an Italian

text: comune

text: (municipality).

text: Tetravalent thorium compounds are usually colourless or yellow, like those of silver or lead, as the Th ion has no 5f or 6d electrons. Thorium and uranium are the most investigated of the radioactive elements because their radioactivity is slight enough to not pose major problems of handling and accessibility and they may be safely handled in a normal laboratory.

text: Tetravalent thorium compounds are usually colourless or yellow, like those of

text: silver

text: or lead, as the Th ion has no 5f or 6d electrons. Thorium and uranium are the most investigated of the radioactive elements because their radioactivity is slight enough to not pose major problems of handling and accessibility and they may be safely handled in a normal laboratory.

text: The basic approach is to label a candidate drug using the radioisotope carbon-14, and then administer the compound to human volunteers at levels typically about 100 times lower than the proposed therapeutic dosage (from around 1 to 100 micrograms but not above). How the body responds – for example, its conversion of the original drug into other molecules, and how long they stay in the body. The amount of radioactivity administered is typically around 200 nano Curies, which is low as to be considered 'non-radioactive' by authorities.

text: The basic approach is to

text: label

text: a candidate drug using the radio

text: isotope

text: , and then administer the compound to human volunteers at levels typically about 100 times lower than the proposed therapeutic dosage (from around 1 to 100

text: microgram

text: s but not above). How the body responds – for example, its conversion of the original drug into other molecules, and how long they stay in the body. The amount of radioactivity administered is typically around 200 nano

text: Curies

text: , which is low as to be considered 'non-radioactive' by authorities.

text: The radioactivity of all radioactive waste diminishes with time. All radionuclides contained in the waste have a half-life—the time it takes for half of the atoms to decay into another nuclide—and eventually all radioactive waste decays into non-radioactive elements (i.e., stable nuclides). Certain radioactive elements (such as plutonium-239) will remain hazardous to humans and other creatures for hundreds or thousands of years. Other radionuclides remain radioactive for millions of years (though most of these products have so little activity as a result of their long half-lives that their radiation is lost in the background level). Thus, these wastes must be shielded for centuries and isolated from the living environment for millennia. Since radioactive decay follows the half-life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like iodine-129 will be much less intense than that of a short-lived isotope like iodine-131. The two tables show some of the major radioisotopes, their half-lives, and their radiation yield as a proportion of the yield of fission of uranium-235.

text: The radioactivity of all radioactive waste diminishes with time. All radionuclides contained in the waste have a

text: half-life

text: —the time it takes for half of the atoms to decay into another

text: nuclide

text: —and eventually all radioactive waste decays into non-radioactive elements (i.e.,

text: stable nuclide

text: s). Certain radioactive elements (such as

text: ) will remain hazardous to humans and other creatures for hundreds or thousands of years. Other radionuclides remain radioactive for millions of years (though most of these products have so little activity as a result of their long half-lives that their radiation is lost in the

text: background level

text: ). Thus, these wastes must be shielded for centuries and isolated from the living

text: environment

text: for millennia. Since radioactive decay follows the half-life rule, the rate of decay is inversely proportional to the duration of decay. In other words, the radiation from a long-lived isotope like

text: will be much less intense than that of a short-lived isotope like

text: . The two tables show some of the major radioisotopes, their half-lives, and their

text: radiation yield

text: as a proportion of the yield of fission of uranium-235.

text: Literally translated, "Le Super Manège" means "The Super Ride". This reflects its significance in introducing inverting rides to the park. The ride originally opened as "Corkscrew".

text: SYERS previous version has also been used with the Lockheed U-2 reconnaissance aircraft.

text: SYERS previous version has also been used with the

text: Lockheed U-2

text: reconnaissance aircraft

text: The Radioactive Substances Act 1993 (RSA93) deals with the control of radioactive material and disposal of radioactive waste in the United Kingdom.