An
extinct radionuclideA radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created radiation particle within the nucleus, or else to an atomic electron . The radionuclide, in this process, undergoes radioactive decay,...
is one which was thought to have been formed by a primordial process such as stellar nucleogenesis in the
supernovaA supernova is a stellar explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun could emit over...
(s) which contributed radioisotopes to the early solar system, about 4.6 billion years ago. Generally, radioisotopes with a decay
half-lifeHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
shorter than about 100 million years are not found in nature, unless known to be generated continuously by a natural process, such as cosmic rays, or a
decay chainIn nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
of much longer lived isotopes, such as
uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
or
thoriumThorium is a chemical element with the symbol Th and atomic number 90. It is a naturally occurring, slightly radioactive metal. Thorium is estimated to be about three to four times more abundant than uranium in the earth's crust...
.
An
extinct radionuclideA radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created radiation particle within the nucleus, or else to an atomic electron . The radionuclide, in this process, undergoes radioactive decay,...
is one which was thought to have been formed by a primordial process such as stellar nucleogenesis in the
supernovaA supernova is a stellar explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. During this short interval, a supernova can radiate as much energy as the Sun could emit over...
(s) which contributed radioisotopes to the early solar system, about 4.6 billion years ago. Generally, radioisotopes with a decay
half-lifeHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
shorter than about 100 million years are not found in nature, unless known to be generated continuously by a natural process, such as cosmic rays, or a
decay chainIn nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations...
of much longer lived isotopes, such as
uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
or
thoriumThorium is a chemical element with the symbol Th and atomic number 90. It is a naturally occurring, slightly radioactive metal. Thorium is estimated to be about three to four times more abundant than uranium in the earth's crust...
. These short-lived isotopes are thus seen only as extinct radionuclides, presenting now as only a superabundance of their stable decay products.
Examples of extinct radionuclides include
iodine-129Iodine-129 is long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission decay products, where it serves as both tracer and potential radiological contaminant.-Formation and decay:129I is primarily...
(the first to be noted in 1960, and inferred from excess
xenon-129Naturally occurring xenon is made of nine stable isotopes. Xenon has the second highest number of stable isotopes. Only tin, with 10 stable isotopes, has more...
concentrations in meteorites, in the xenon-iodine dating system),
aluminium-26Aluminium has multiple isotopes. Only 27Al and 26Al occur naturally, however 27Al has a natural abundance of 99.9+ %. Standard atomic mass is 26.9815386 u. 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons...
(also inferred from extra
magnesium-26Magnesium-26 is an isotope of magnesium.atomic mass: 25.9825930 u
excess mass: -16214 keV
binding energy: 216681 keV
beta decay energy: -4000 keVatomic percent abundance: 11.01%
spin: 0+...
found in meteorites), and Iron-60.
List of extinct radionuclides
A partial list of radionuclides which are not found in nature, but for which decay products are found, is:
| Isotope |
Halflife (Myr The symbol myr was formerly used in English-language geology and astronomy as a unit of one million years.It is an abbreviation for 'million years' and lower case is usually used....
) |
| Samarium-146 Naturally occurring samarium is composed of four stable isotopes, 144Sm, 150Sm, 152Sm and 154Sm, and three extremely long-lived radioisotopes, 147Sm , 148Sm and 149Sm , with 152Sm being the most abundant...
|
103 |
| Curium-247 - Table :- Notes :* Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses....
|
16 |
| Lead-205 Lead has four stable isotopes - 204Pb, 206Pb, 207Pb, 208Pb. The longest-lived radioisotopes are 205Pb with a half-life of ~15.3 million years and 202Pb with a half-life of ~53,000 years. The standard atomic mass is 207.2 u...
|
15 |
| Hafnium-182 - Table :- Notes :* Evaluated isotopic composition is for most but not all commercial samples.* Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.* Uncertainties are given in...
|
9 |
| Palladium-107 Palladium-107 is the second longest lived and least radioactive of the 7 long-lived fission products...
|
7 |
| Caesium-135 Caesium-135 is one of the isotopes of caesium. It is mildly radioactive, undergoing low-energy beta decay to barium-135 with a half-life of 2.3 million years. It is one of only 7 long-lived fission products, and the only alkaline one; in nuclear reprocessing it stays with Cs-137 and other...
|
3 |
| Technetium-97 Technetium is one of the two elements in the first 83 that have no stable isotopes ; the other such element is promethium...
|
3 |
| Gadolinium-150 Naturally occurring gadolinium is composed of 6 stable isotopes, 154Gd, 155Gd, 156Gd, 157Gd, 158Gd and 160Gd, and 1 radioisotope, 152Gd, with 158Gd being the most abundant...
|
2 |
| Zirconium-93 93Zr is a radioisotope of zirconium with a half life of 1.53 million years, decaying with a low-energy beta particle to Niobium-93m, which decays with a halflife of 14 years and a low-energy gamma ray to ordinary 93Nb. It is one of only 7 long-lived fission products...
|
2 |
| Technetium-98 Technetium is one of the two elements in the first 83 that have no stable isotopes ; the other such element is promethium...
|
2 |
| Dysprosium-154 Naturally occurring dysprosium is composed of 7 stable isotopes, 156-Dy, 158-Dy, 160-Dy, 161-Dy, 162-Dy, 163-Dy and 164-Dy, with 164-Dy being the most abundant . 28 radioisotopes have been characterized, with the most stable being 154-Dy with a half-life of 3.0E+6 years, 159-Dy with a half-life of...
|
1 |
Some notable isotopes with shorter lives still being produced on Earth include:
- Manganese-53
Naturally occurring manganese is composed of 1 stable isotope; 55Mn. 18 radioisotopes have been characterized with the most stable being 53Mn with a half-life of 3.7 million years, 54Mn with a half-life of 312.3 days, and 52Mn with a half-life of 5.591...
and beryllium-10Beryllium-10 is a radioactive isotope of beryllium. It is formed mainly by cosmic ray spallation. Be-10 has a half-life of 1.51*10
6 years, and decays by beta decay to stable Boron-10 with a maximum energy of 556.2 keV....
are produced by cosmic ray spallationCosmic ray spallation is a form of naturally occurring nuclear fission and nucleosynthesis. It refers to the formation of elements from the impact of cosmic rays on an object. Cosmic rays are highly energetic charged particles from outside of Earth ranging from stray electrons to alpha particles....
on dust in the upper atmosphere.
- Uranium-236
Uranium-236 is an isotope of Uranium that is neither fissile with thermal neutrons, nor very good fertile material, but is generally considered a nuisance and long-lived radioactive waste. It is found in spent nuclear fuel and in the reprocessed uranium made from spent nuclear fuel.-Creation and...
is produced in uranium ores by neutrons from other radioactives.
- Iodine-129
Iodine-129 is long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission decay products, where it serves as both tracer and potential radiological contaminant.-Formation and decay:129I is primarily...
is produced from tellurium-130 by cosmic-ray muons and from cosmic ray spallation of stable xenon isotopes in the atmosphere.
Radioactives with half-lives shorter than one million years are also produced: for example,
carbon-14Carbon-14,
14C, or radiocarbon, is a radioactive isotope of carbon discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, though its existence had been suggested already in 1934 by Franz Kurie. Its nucleus contains...
by cosmic ray production in the atmosphere (half life 5730 years).
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