Radionuclide: Difference between revisions

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
VisualWikitext
imported>GreenC bot
Rescued 1 archive link. Wayback Medic 2.5 per WP:URLREQ#fda.gov
 
imported>Radiobioneer
m Typo edited in Table "Examples", i.e. lowercase start in Comment section.
 
Line 1: Line 1:
{{short description|Atom that has excess nuclear energy, making it unstable}}
{{short description|Atom that has excess nuclear energy, making it unstable}}
{{use dmy dates|date=August 2025}}
{{Lede too long|date=August 2025}}
{{distinguish|radionucleotide (disambiguation){{!}}radionucleotide}}
{{distinguish|radionucleotide (disambiguation){{!}}radionucleotide}}


A '''radionuclide''' ('''radioactive nuclide''', '''radioisotope''' or '''radioactive isotope''') is a [[nuclide]] that has excess numbers of either [[neutron]]s or [[proton]]s, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as [[gamma radiation]]; transferred to one of its [[electron]]s to release it as a [[Internal conversion|conversion electron]]; or used to create and emit a new [[particle]] ([[alpha particle]] or [[beta particle]]) from the nucleus. During those processes, the radionuclide is said to undergo [[radioactive decay]].<ref>{{cite book |first=R. H. |last=Petrucci |first2=W. S. |last2=Harwood |first3=F. G. |last3=Herring |title=General Chemistry |edition=8th |publisher=Prentice-Hall |year=2002 |pages=1025–26 |isbn=0-13-014329-4 }}</ref> These emissions are considered [[ionizing radiation]] because they are energetic enough to liberate an electron from another atom. The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay.<ref name="not-predict">{{cite web|url=http://www.iem-inc.com/prhlfr.html|title=Decay and Half Life|access-date= 2009-12-14}}</ref><ref name="IntroductionToHealthPhysics">{{cite book |title=Radiation Protection and Dosimetry: An Introduction to Health Physics |last1=Stabin |first1=Michael G. |editor1-first=Michael G |editor1-last=Stabin |isbn=978-0387499826 |year=2007 |publisher=[[Springer Publishing|Springer]] |chapter=3 |doi=10.1007/978-0-387-49983-3|url=https://cds.cern.ch/record/1105894  <!--correct parameter-->|type=Submitted manuscript }}</ref><ref name="RadiationOncologyPrimer">{{cite book |title=Radiation Oncology Primer and Review |isbn=978-1620700044 |last1=Best |first1=Lara |last2=Rodrigues |first2=George |last3=Velker |first3=Vikram |publisher=[[Demos Medical Publishing]] |year=2013 |chapter=1.3}}</ref><ref>{{cite book |title=Modern Nuclear Chemistry |isbn=978-0-471-11532-8 |last1=Loveland |first1=W. |last2=Morrissey |first2=D. |author3-link=Glenn T. Seaborg |last3=Seaborg |first3=G.T. |publisher=Wiley-Interscience |year=2006 |page=57|bibcode=2005mnc..book.....L }}</ref> However, for a collection of atoms of a single nuclide the decay rate, and thus the [[half-life]] (''t''<sub>1/2</sub>) for that collection, can be calculated from their measured [[decay constant]]s. The range of the half-lives of radioactive atoms has no known limits and spans a time range of over 55 orders of magnitude.
[[File:NuclideMap stitched 2.png|thumb|Chart of known [[nuclides]] {{As of|2013|lc=y}}. The vast majority are radionuclides.]]


Radionuclides occur naturally or are artificially produced in [[nuclear reactor]]s, [[cyclotron]]s, [[particle accelerator]]s or [[radionuclide generator]]s. There are about 730 radionuclides with half-lives longer than 60 minutes (see [[list of nuclides]]). Thirty-two of those are [[primordial radionuclide]]s that were created before the Earth was formed. At least another 60 radionuclides are detectable in nature, either as daughters of primordial radionuclides or as radionuclides produced through natural production on Earth by cosmic radiation. More than 2400 radionuclides have half-lives less than 60 minutes. Most of those are only produced artificially, and have very short half-lives. For comparison, there are 251 [[stable nuclide]]s.  
A '''radionuclide''' ('''radioactive nuclide''', '''radioisotope''' or '''radioactive isotope''') is a [[nuclide]] that is unstable and known to undergo [[radioactive decay]] into a different nuclide, which may be another radionuclide (see [[decay chain]]) or be stable. [[Radiation]] emitted by radionuclides is almost always [[ionizing radiation]] because it is energetic enough to liberate an electron from another atom.  


All [[chemical element]]s can exist as radionuclides. Even the lightest element, [[hydrogen]], has a well-known radionuclide, [[tritium]]. Elements heavier than [[lead]], and the elements [[technetium]] and [[promethium]], exist only as radionuclides.  
[[Radioactive decay]] is a random [[process]] at the level of single [[Atom|atoms]]: it is impossible to [[Prediction|predict]] when one particular atom will decay.<ref name="not-predict">{{cite web|url=http://www.iem-inc.com/prhlfr.html|title=Decay and Half Life|access-date= 2009-12-14}}</ref><ref>{{cite book |title=Modern Nuclear Chemistry |isbn=978-0-471-11532-8 |last1=Loveland |first1=W. |last2=Morrissey |first2=D. |author3-link=Glenn T. Seaborg |last3=Seaborg |first3=G.T. |publisher=Wiley-Interscience |year=2006 |page=57|bibcode=2005mnc..book.....L }}</ref> However, for a collection of atoms of a single nuclide, the decay rate (considered as a statistical average), and thus the [[half-life]] (''t''<sub>1/2</sub>) for that nuclide, can be calculated from the measurement of the decay. The range of the half-lives of radioactive atoms has no known limits and spans a time range of over 55 orders of magnitude.


Unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm. The degree of harm will depend on the nature and extent of the radiation produced, the amount and nature of exposure (close contact, inhalation or ingestion), and the biochemical properties of the element; with increased risk of cancer the most usual consequence. However, radionuclides with suitable properties are used in [[nuclear medicine]] for both diagnosis and treatment.  An imaging tracer made with radionuclides is called a [[radioactive tracer]]. A [[pharmaceutical drug]] made with radionuclides is called a [[radiopharmaceutical]].
Radionuclides occur naturally and are artificially produced in [[nuclear reactor]]s, [[cyclotron]]s, [[particle accelerator]]s or [[radionuclide generator]]s. There are 735 known radionuclides with half-lives longer than an hour (see [[list of nuclides]]); 35 of those are [[primordial radionuclide]]s whose presence on Earth has persisted from its formation, and another 62 are detectable in nature, continuously produced either as [[Decay product|daughter products]] of primordial radionuclides or by [[Cosmic ray|cosmic radiation]]. More than 2400 radionuclides have half-lives less than 60 [[minutes]]. Most of those are only produced artificially, and have very short half-lives. For comparison, there are 251 [[stable nuclide]]s.  


==Origin==
All the [[chemical element]]s have radionuclides - even the lightest element, [[hydrogen]], has one well-known radionuclide, [[tritium]] (though [[helium]], [[lithium]], and [[boron]] have none with half-life over a second). Elements heavier than [[lead]] ([[Atomic number|''Z'']] > 82), and the elements [[technetium]] and [[promethium]], have only radionuclides and do not exist in stable forms, though [[bismuth]] can be treated as stable with the half-life of [[Bismuth-209|its natural isotope]] being over a trillion times longer than the current [[age of the universe]].
 
Artificial production methods of radionuclides include [[Neutron source|neutron sources]] such as [[nuclear reactors]], as well as [[particle accelerators]] such as [[cyclotrons]].
 
Exposure to radionuclides generally has, due to their radiation, a harmful effect on [[Organism|organisms]] including [[humans]], although low levels of exposure occur naturally. The degree of harm will depend on the [[nature]] and extent of the radiation produced ([[Alpha decay|alpha]], [[Beta decay|beta]], [[Gamma ray|gamma]], or [[Neutron radiation|neutron]]), the amount and nature of exposure (close contact, [[inhalation]] or [[ingestion]]), and the biochemical properties of the element ([[toxicity]]). Increased risk of [[cancer]] is considered unavoidable, and worse cases experience [[radiation-induced cancer]], [[chronic radiation syndrome]] or [[acute radiation syndrome]]. Radionuclides are [[weaponized]] by the [[Nuclear fallout|fallout effects]] of [[nuclear weapons]] and by [[radiological weapons]].
 
Radionuclides with suitable properties are used in [[nuclear medicine]] for both diagnosis and treatment. An imaging tracer made with radionuclides is called a [[radioactive tracer]]. [[Radionuclide therapy]] is a form of [[radiotherapy]]. A [[pharmaceutical drug]] made with radionuclides is called a [[radiopharmaceutical]].
 
==Origins==


===Natural===
===Natural===
On Earth, naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and [[cosmogenic]] radionuclides.
On Earth, naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and [[cosmogenic]] radionuclides. <!-- This classification is problematic. The term 'secondary radionuclides' is not universal, and when used often includes cosmogenics. -->
* Radionuclides are produced in [[stellar nucleosynthesis]] and [[supernova explosions]] along with stable nuclides. Most decay quickly but can still be observed astronomically and can play a part in understanding astronomic processes. Primordial radionuclides, such as [[uranium]] and [[thorium]], exist in the present time because their [[half-life|half-lives]] are so long (>100 million years) that they have not yet completely decayed. Some radionuclides have half-lives so long (many times the age of the universe) that decay has only recently been detected, and for most practical purposes they can be considered stable, most notably [[bismuth-209]]: detection of this decay meant that [[bismuth]] was no longer considered stable. It is possible decay may be observed in other nuclides, adding to this list of primordial radionuclides.
* Radionuclides are produced in [[stellar nucleosynthesis]] and [[supernova explosions]] along with stable nuclides. Most decay quickly, but some can be observed astronomically and can play a part in understanding astrophysical processes. Primordial radionuclides, such as [[uranium]] and [[thorium]], still exist because their [[half-life|half-lives]] are so long (>100 million years) that the Earth's initial content has not yet completely decayed. Some radionuclides have half-lives so long (many times the age of the universe) that decay has only recently been detected, and for most practical purposes they can be considered stable, most notably [[bismuth-209]]: detection of this decay meant that [[bismuth]] was no longer considered stable. It is possible that decay may be observed in other nuclides now considered stable, adding to the list of primordial radionuclides.{{cn|date=July 2025}}
* Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. They arise in the [[decay chain]] of the primordial isotopes [[thorium-232]], [[uranium-238]], and [[uranium-235]]. Examples include the natural isotopes of [[polonium]] and [[radium]].
* Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. They arise in the [[decay chain]] of the primordial isotopes [[thorium-232]], [[uranium-238]], and [[uranium-235]] - such as the natural isotopes of [[polonium]] and [[radium]] - some are also produced by natural [[spontaneous fission|fission]] and other [[nucleogenic]] processes.{{cn|date=July 2025}}
* [[Cosmogenic isotopes]], such as [[carbon-14]], are present because they are continually being formed in the atmosphere due to [[cosmic ray]]s.<ref>{{cite book |url = https://books.google.com/books?id=RqEhyic9VJMC&pg=PA134| pages = 134 |title = Environmental Radioactivity: From Natural, Industrial, and Military Sources |isbn = 9780122351549 |last1 = Eisenbud |first1 = Merril |last2 = Gesell |first2 = Thomas F |date = 1997-02-25| publisher = Elsevier }}</ref>
* [[Cosmogenic isotopes]], such as [[carbon-14]], are present because they are continually being formed on Earth, typically in the atmosphere, due to the action of [[cosmic ray]]s.{{cn|date=July 2025}}


Many of these radionuclides exist only in trace amounts in nature, including all cosmogenic nuclides. Secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be very rare. For example, polonium can be found in [[uranium]] ores at about 0.1&nbsp;mg per [[metric ton]] (1 part in 10<sup>10</sup>).<ref>Bagnall, K. W. (1962). "The Chemistry of Polonium". Advances in Inorganic Chemistry and Radiochemistry 4. New York: Academic Press. pp. 197–226. doi:10.1016/S0065-2792(08)60268-X. {{ISBN|0-12-023604-4}}. Retrieved June 14, 2012., p. 746</ref><ref>Bagnall, K. W. (1962). "The Chemistry of Polonium". Advances in Inorganic Chemistry and Radiochemistry 4. New York: Academic Press., p. 198</ref> Further radionuclides may occur in nature in virtually undetectable amounts as a result of rare events such as spontaneous fission or uncommon cosmic ray interactions.
Many of these radionuclides exist only in trace amounts in nature, including all cosmogenic nuclides. Secondary radionuclides in a [[decay chain]] will occur in proportion to their half-lives, so short-lived ones will be very rare. For example, polonium can be found in [[uranium]] ores at a concentration about 1 part 10<sup>10</sup> of uranium (0.1&nbsp;mg per [[metric ton]]) by calculating the ratio of half-lives of [[polonium-210]] to [[uranium-238]], its ultimate parent.{{cn|date=July 2025}}


===Nuclear fission===
===Nuclear fission===
Radionuclides are produced as an unavoidable result of [[nuclear fission]] and [[thermonuclear device|thermonuclear explosions]]. The process of nuclear fission creates a wide range of [[fission products]], most of which are radionuclides. Further radionuclides can be created from irradiation of the nuclear fuel (creating a range of [[actinides]]) and of the surrounding structures, yielding [[activation products]]. This complex mixture of radionuclides with different chemistries and radioactivity makes handling [[nuclear waste]] and dealing with [[nuclear fallout]] particularly problematic.{{cn|date=November 2023}}
Radionuclides are produced as an unavoidable result of [[nuclear fission]] and [[nuclear weapon|nuclear explosions]]. The process of nuclear fission creates a wide range of [[fission products]], most of which are radionuclides. Further radionuclides are created from irradiation of the nuclear fuel (creating a range of [[actinides]]) and of the surrounding structures, yielding [[activation products]]. This complex mixture of radionuclides with different chemistries and radioactivity makes handling [[nuclear waste]] and dealing with [[nuclear fallout]] particularly problematic.{{cn|date=November 2023}}


===Synthetic===
===Synthetic===
[[File:Artificial nuclide americium-241 emitting alpha particles inserted into a cloud chamber for visualisation.jpg|thumb|[[Artificial]] [[nuclide]] [[americium-241]] emitting [[alpha particle]]s inserted into a [[cloud chamber]] for visualisation]]
[[File:Artificial nuclide americium-241 emitting alpha particles inserted into a cloud chamber for visualisation.jpg|thumb|[[Americium-241]] emitting [[alpha particle]]s inserted into a [[cloud chamber]]]]
[[Synthetic radionuclide]]s are deliberately synthesised using [[nuclear reactor]]s, particle accelerators or radionuclide generators:<ref>{{Cite web |date=2016-07-15 |title=Radioisotopes |url=https://www.iaea.org/topics/nuclear-science/isotopes/radioisotopes |access-date=2023-06-25 |website=www.iaea.org |language=en}}</ref>
[[Synthetic radionuclide]]s are created in [[nuclear reactor]]s or by particle accelerators (not necesssarily on purpose) or as decay products of such:<ref>{{Cite web |date=2016-07-15 |title=Radioisotopes |url=https://www.iaea.org/topics/nuclear-science/isotopes/radioisotopes |access-date=2023-06-25 |website=www.iaea.org |language=en}}</ref>
* As well as being extracted from nuclear waste, radioisotopes can be produced deliberately with nuclear reactors, exploiting the high flux of [[neutron]]s present. These neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is [[iridium-192]]. The elements that have a large propensity to take up the neutrons in the reactor are said to have a high [[neutron cross-section]].
* As well as being extracted from nuclear waste, radioisotopes can be produced deliberately with nuclear reactors, exploiting the high flux of [[neutron]]s present. These neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is [[iridium-192]], from activation of [[iridium]] targets. The elements that have a large propensity to take up neutrons in the reactor are said to have a high [[neutron cross-section]], but even at low cross-sections this process is generally economical.
* Particle accelerators such as [[cyclotron]]s accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate protons at a target to produce positron-emitting radionuclides, e.g. [[fluorine-18]].
* Particle accelerators such as [[cyclotron]]s accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate (most often) protons at a target to produce positron-emitting radionuclides, e.g. [[fluorine-18]].
* Radionuclide generators contain a parent radionuclide that decays to produce a radioactive daughter. The parent is usually produced in a nuclear reactor. A typical example is the [[technetium-99m generator]] used in [[nuclear medicine]]. The parent produced in the reactor is [[molybdenum-99]].
* [[Radionuclide generator]]s, standard for many medical isotopes, contain a parent radionuclide that decays to produce a shorter-lived radioactive daughter. A typical example is the [[technetium-99m generator]], which employs [[molybdenum-99]] produced in a reactor.


==Uses==
==Uses==
Radionuclides are used in two major ways: either for their radiation alone ([[irradiation]], [[nuclear battery|nuclear batteries]]) or for the combination of chemical properties and their radiation (tracers, biopharmaceuticals).
Radionuclides are used in two major ways: either for their radiation alone ([[irradiation]], [[nuclear battery|nuclear batteries]]) or for the combination of chemical properties and their radiation (tracers, biopharmaceuticals). For scientific study they may be used for their chemical properties alone when there is no stable form of that element.
* In [[biology]], radionuclides of [[carbon]] can serve as [[radioactive tracer]]s because they are chemically very similar to the nonradioactive nuclides, so most chemical, biological, and ecological processes treat them in a nearly identical way. One can then examine the result with a radiation detector, such as a [[Geiger counter]], to determine where the provided atoms were incorporated. For example, one might culture plants in an environment in which the [[carbon dioxide]] contained radioactive carbon; then the parts of the plant that incorporate atmospheric carbon would be radioactive. Radionuclides can be used to monitor processes such as [[DNA replication]] or [[amino acid]] transport.
* In [[biology]], radionuclides (most often of [[carbon]]) can serve as [[radioactive tracer]]s because they are chemically very similar to the nonradioactive nuclides, so most chemical, biological, and ecological processes treat them in a nearly identical way. One can then examine the result with a radiation detector, such as a [[Geiger counter]], to determine where the provided atoms were incorporated. For example, one might culture plants in an environment in which the [[carbon dioxide]] contained radioactive carbon; then the parts of the plant that incorporate atmospheric carbon would be radioactive. Radionuclides can be used to monitor processes such as [[DNA replication]] or [[amino acid]] transport.{{cn|date=July 2025}}
* in [[physics]] and [[biology]] radionuclide X-ray fluorescence spectrometry is used to determine [[chemical composition]] of the [[Chemical compound|compound]]. [[X-ray|Radiation]] from a radionuclide source hits the sample and excites characteristic X-rays in the sample. This radiation is registered and the chemical composition of the sample can be determined from the analysis of the measured spectrum. By measuring the energy of the characteristic radiation lines, it is possible to determine the [[Atomic number|proton number]] of the [[chemical element]] that emits the radiation, and by measuring the number of emitted [[photon]]s, it is possible to determine the [[concentration]] of individual chemical elements.
* in [[physics]] and [[biology]] radionuclide [[X-ray fluorescence]] (conventional X-ray sources may also be used) is used to determine [[chemical composition]] of the [[Chemical compound|compound]]. [[X-ray|Radiation]] from a radionuclide source hits the sample and excites characteristic X-rays in the sample. This radiation is registered and the chemical composition of the sample can be determined from the analysis of the measured spectrum. By measuring the energy of the characteristic radiation lines, it is possible to determine the [[Atomic number|proton number]] of the [[chemical element]] that emits the radiation, and by measuring the number of emitted [[photon]]s, it is possible to determine the [[concentration]] of individual chemical elements.{{cn|date=July 2025}}
* In [[nuclear medicine]], radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about internal anatomy and the functioning of specific organs, including the [[human brain]].<ref>{{cite journal|last1=Ingvar|first1=David H.|author-link1=:sv:David H. Ingvar|last2=Lassen|first2=Niels A.|author-link2=Niels A. Lassen|title=Quantitative determination of regional cerebral blood-flow in man|journal=[[The Lancet]]|year=1961|volume=278|issue=7206|pages=806–807|url=http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2861%2991092-3/fulltext|doi=10.1016/s0140-6736(61)91092-3|url-access=subscription}}</ref><ref>{{cite journal|last1=Ingvar|first1=David H.|author1-link=:sv:David H. Ingvar|last2=Franzén|first2=Göran|title=Distribution of cerebral activity in chronic schizophrenia|journal=[[The Lancet]]|year=1974|volume=304|issue=7895|pages=1484–1486|url=http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2874%2990221-9/abstract|doi=10.1016/s0140-6736(74)90221-9|pmid=4140398|url-access=subscription}}</ref><ref>{{cite journal|last1=Lassen|first1=Niels A.|author-link1=Niels A. Lassen|last2=Ingvar|first2=David H.|author-link2=:sv:David H. Ingvar|last3=Skinhøj|first3=Erik|author-link3=:da:Erik Skinhøj|title=Brain Function and Blood Flow| journal=[[Scientific American]]|volume=239|issue=4|pages=62–71|date=October 1978|doi=10.1038/scientificamerican1078-62|pmid=705327|bibcode=1978SciAm.239d..62L}}</ref> This is used in some forms of tomography: [[single-photon emission computed tomography]] and [[positron emission tomography]] (PET) scanning and [[Cherenkov luminescence imaging]]. Radioisotopes are also a method of treatment in [[hemopoietic]] forms of tumors; the success for treatment of solid tumors has been limited. More powerful gamma sources [[sterilization (microbiology)|sterilise]] syringes and other medical equipment.
* In [[nuclear medicine]], radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about internal anatomy and the functioning of specific organs, including the [[human brain]].<ref>{{cite journal|last1=Ingvar|first1=David H.|author-link1=:sv:David H. Ingvar|last2=Lassen|first2=Niels A.|author-link2=Niels A. Lassen|title=Quantitative determination of regional cerebral blood-flow in man|journal=[[The Lancet]]|year=1961|volume=278|issue=7206|pages=806–807|url=http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2861%2991092-3/fulltext|doi=10.1016/s0140-6736(61)91092-3|url-access=subscription}}</ref><ref>{{cite journal|last1=Ingvar|first1=David H.|author1-link=:sv:David H. Ingvar|last2=Franzén|first2=Göran|title=Distribution of cerebral activity in chronic schizophrenia|journal=[[The Lancet]]|year=1974|volume=304|issue=7895|pages=1484–1486|url=http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2874%2990221-9/abstract|doi=10.1016/s0140-6736(74)90221-9|pmid=4140398|url-access=subscription}}</ref><ref>{{cite journal|last1=Lassen|first1=Niels A.|author-link1=Niels A. Lassen|last2=Ingvar|first2=David H.|author-link2=:sv:David H. Ingvar|last3=Skinhøj|first3=Erik|author-link3=:da:Erik Skinhøj|title=Brain Function and Blood Flow| journal=[[Scientific American]]|volume=239|issue=4|pages=62–71|date=October 1978|doi=10.1038/scientificamerican1078-62|pmid=705327|bibcode=1978SciAm.239d..62L}}</ref> This is used in some forms of tomography: [[single-photon emission computed tomography]] and [[positron emission tomography]] (PET) scanning and [[Cherenkov luminescence imaging]]. Radioisotopes are also a method of treatment in [[hemopoietic]] forms of tumors; the success for treatment of solid tumors has been limited. More powerful gamma sources [[sterilization (microbiology)|sterilise]] syringes and other medical equipment.
* In [[food preservation]], radiation is used to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables. [[Food irradiation]] usually uses beta-decaying nuclides with strong gamma emissions like [[cobalt-60]] or [[caesium-137]].
* In [[food preservation]], radiation is used to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables. [[Food irradiation]] usually uses strong gamma emitters like [[cobalt-60]] or [[caesium-137]].{{cn|date=July 2025}}
* In [[Industrial sector|industry]], and in [[mining]], radionuclides are used to examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels.
* In [[Industrial sector|industry]], and in [[mining]], radiation from radionuclides may be used to examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels.
* In [[spacecraft]], radionuclides are used to provide power and heat, notably through [[radioisotope thermoelectric generator]]s (RTGs) and [[radioisotope heater unit]]s (RHUs).
* In [[spacecraft]], radionuclides are used to provide power and heat, notably through [[radioisotope thermoelectric generator]]s (RTGs) and [[radioisotope heater unit]]s (RHUs).{{cn|date=July 2025}}
* In [[astronomy]] and [[physical cosmology|cosmology]], radionuclides play a role in understanding stellar and planetary process.
* In [[particle physics]], radionuclides help discover new physics ([[physics beyond the Standard Model]]) by measuring the energy and momentum of their beta decay products (for example, [[neutrinoless double beta decay]] and the search for [[weakly interacting massive particles]]).<ref>{{cite journal|doi=10.1103/RevModPhys.78.991|title=Tests of the standard electroweak model in nuclear beta decay|journal=Reviews of Modern Physics|volume=78|issue=3|pages=991–1040|year=2006|last1=Severijns|first1=Nathal|last2=Beck|first2=Marcus|last3=Naviliat-Cuncic|first3=Oscar|bibcode=2006RvMP...78..991S|arxiv = nucl-ex/0605029 |s2cid=18494258}}</ref>
* In [[particle physics]], radionuclides help discover new physics ([[physics beyond the Standard Model]]) by measuring the energy and momentum of their beta decay products (for example, [[neutrinoless double beta decay]] and the search for [[weakly interacting massive particles]]).<ref>{{cite journal|doi=10.1103/RevModPhys.78.991|title=Tests of the standard electroweak model in nuclear beta decay|journal=Reviews of Modern Physics|volume=78|issue=3|pages=991–1040|year=2006|last1=Severijns|first1=Nathal|last2=Beck|first2=Marcus|last3=Naviliat-Cuncic|first3=Oscar|bibcode=2006RvMP...78..991S|arxiv = nucl-ex/0605029 |s2cid=18494258}}</ref>
* In [[ecology]], radionuclides are used to trace and analyze pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers.
* In [[ecology]], radionuclides are used to trace and analyze pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers.{{cn|date=July 2025}}
* In [[geology]], [[archaeology]], and [[paleontology]], natural radionuclides are used to measure ages of rocks, minerals, and fossil materials.<!-- When radioactive carbon, for example, is in the atmosphere, it rapidly becomes separated from its decay products. Once it is bound up in a solid, such as wood or paper, its decay products must remain in place. Therefore, by measuring how much of these decay products have accumulated, one can estimate the time when the carbon was captured into solid form. -->
* In [[geology]], [[archaeology]], and [[paleontology]], natural radionuclides are used to measure ages of rocks, minerals, and fossil materials. This is called [[radiometric dating]]. <!-- When radioactive carbon-14, for example, is in the atmosphere, it rapidly becomes separated from its decay products. Once it is bound up in a solid, such as wood or paper, its decay products must remain in place. Therefore, by measuring how much of these decay products have accumulated, one can estimate the time when the carbon was captured into solid form. -->


==Examples==
==Examples==
Line 47: Line 56:
{|  class="wikitable sortable"
{|  class="wikitable sortable"
! Isotope !! ''Z'' !! ''N'' !! half-life !! DM !! DE<br /> [[keV]] !! Mode of formation !! Comments
! Isotope !! ''Z'' !! ''N'' !! half-life !! DM !! DE<br /> [[keV]] !! Mode of formation !! Comments
|-
|-
! [[Tritium]] (<sup>3</sup>H)
! [[Tritium]] (<sup>3</sup>H)
Line 117: Line 125:
! [[Gadolinium-153]]
! [[Gadolinium-153]]
| 64 || 89 || 240 d || EC ||
| 64 || 89 || 240 d || EC ||
| Synthetic || Calibrating nuclear equipment, bone density screening
| Synthetic || calibrating nuclear equipment, bone density screening
|-
|-
! [[Bismuth-209]]
! [[Bismuth-209]]
Line 125: Line 133:
! [[Polonium-210]]
! [[Polonium-210]]
| 84 || 126 || 138 d || α || 5307
| 84 || 126 || 138 d || α || 5307
| Decay product || Highly toxic, used in [[poisoning of Alexander Litvinenko]]
| Decay product || highly toxic, used in [[poisoning of Alexander Litvinenko]]
|-
|-
! [[Radon-222]]
! [[Radon-222]]
Line 141: Line 149:
! [[Uranium-238]]
! [[Uranium-238]]
| 92 || 146 || 4.5{{E|9}} y || α || 4267
| 92 || 146 || 4.5{{E|9}} y || α || 4267
| Primordial || Main Uranium isotope
| Primordial || main uranium isotope
|-
|-
! [[Plutonium-238]]
! [[Plutonium-238]]
Line 158: Line 166:
| 98 || 154 || 2.64 y || α/SF || 6217
| 98 || 154 || 2.64 y || α/SF || 6217
| Synthetic || undergoes spontaneous fission (3% of decays), making it a powerful neutron source, used as a reactor initiator and for detection devices
| Synthetic || undergoes spontaneous fission (3% of decays), making it a powerful neutron source, used as a reactor initiator and for detection devices
|-
![[Isotopes of lutetium#Lutetium-177|Lutetium-177]]
|71 || 106 || 6.6443(9) d || |β<sup>−</sup> || 497 (78.6 %), 384 (9.1 %), 176 (12.2 %)
| Synthetic || used predominantly in targeted radionuclide therapy (TRT) against somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs)
|
|}
|}
Key: ''Z''&nbsp;=&nbsp;[[atomic number]]; ''N''&nbsp;=&nbsp;[[neutron number]]; DM&nbsp;=&nbsp;decay mode; DE&nbsp;=&nbsp;decay energy; EC&nbsp;=&nbsp;[[electron capture]]
Key: ''Z''&nbsp;=&nbsp;[[atomic number]]; ''N''&nbsp;=&nbsp;[[neutron number]]; DM&nbsp;=&nbsp;decay mode; DE&nbsp;=&nbsp;decay energy; EC&nbsp;=&nbsp;[[electron capture]]


===Household smoke detectors===
===Household [[Smoke detector|smoke detectors]]===
[[File:Americium-241.jpg|thumb|Americium-241 container in a smoke detector.]]
[[File:Americium-241.jpg|thumb|Americium-241 container in a smoke detector.]]


[[File:Americium-241 Sample from Smoke Detector.JPG|thumb|Americium-241 capsule as found in smoke detector. The circle of darker metal in the center is americium-241; the surrounding casing is aluminium.]]
[[File:Americium-241 Sample from Smoke Detector.JPG|thumb|[[Americium-241|Americium]]-241 capsule as found in smoke detector. The circle of darker metal in the center is americium-241; the surrounding casing is aluminium.]]


Radionuclides are present in many homes as they are used inside the most common household [[smoke detector]]s. The radionuclide used is [[americium-241]], which is created by bombarding plutonium with neutrons in a nuclear reactor. It decays by emitting [[alpha particle]]s and [[gamma radiation]] to become [[neptunium-237]]. Smoke detectors use a very small quantity of <sup>241</sup>Am (about 0.29 micrograms per smoke detector) in the form of [[americium dioxide]]. <sup>241</sup>Am is used as it emits alpha particles which ionize the air in the detector's [[ionization chamber]]. A small electric voltage is applied to the ionized air which gives rise to a small electric current. In the presence of smoke, some of the ions are neutralized, thereby decreasing the current, which activates the detector's alarm.<ref>{{cite web|url=http://www.world-nuclear.org/info/inf57.html|title=Smoke Detectors and Americium|work=world-nuclear.org|url-status=dead|archive-url=https://web.archive.org/web/20101112082137/http://www.world-nuclear.org/info/inf57.html|archive-date=2010-11-12}}</ref><ref>[http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-htm/fs23am241.htm Office of Radiation Protection – Am 241 Fact Sheet – Washington State Department of Health] {{webarchive|url=https://web.archive.org/web/20110318173013/http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-htm/fs23am241.htm |date=2011-03-18 }}</ref>
Radionuclides are present in many homes as they are used inside the most common household [[smoke detector]]s. The radionuclide used is [[americium-241]], which is created by bombarding plutonium with neutrons in a nuclear reactor. It decays by emitting [[alpha particle]]s and [[gamma radiation]] to become [[neptunium-237]]. Smoke detectors use a very small quantity of <sup>241</sup>Am (about 0.29 micrograms per smoke detector) in the form of [[americium dioxide]]. <sup>241</sup>Am is used as it emits alpha particles which ionize the air in the detector's [[ionization chamber]]. A small electric voltage is applied to the ionized air which gives rise to a small electric current. In the presence of smoke, some of the ions are neutralized, thereby decreasing the current, which activates the detector's alarm.<ref>{{cite web|url=http://www.world-nuclear.org/info/inf57.html|title=Smoke Detectors and Americium|work=world-nuclear.org|url-status=dead|archive-url=https://web.archive.org/web/20101112082137/http://www.world-nuclear.org/info/inf57.html|archive-date=2010-11-12}}</ref><ref>[http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-htm/fs23am241.htm Office of Radiation Protection – Am 241 Fact Sheet – Washington State Department of Health] {{webarchive|url=https://web.archive.org/web/20110318173013/http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-htm/fs23am241.htm |date=2011-03-18 }}</ref>
Line 172: Line 185:


==Summary table for classes of nuclides, stable and radioactive==
==Summary table for classes of nuclides, stable and radioactive==
Following is a summary table for the [[list of nuclides|list of 989 nuclides]] with half-lives greater than one hour. A total of 251 nuclides have never been observed to decay, and are classically considered stable. Of these, 90 are believed to be absolutely stable except to [[proton decay]] (which has never been observed), while the rest are "[[observationally stable]]" and theoretically can undergo radioactive decay with extremely long half-lives.
Following is a summary table for the [[list of nuclides|list of 986 nuclides]] with half-lives greater than one hour. A total of 251 nuclides have never been observed to decay, and are classically considered stable. Of these, 90 are believed to be absolutely stable except to [[proton decay]] (which has never been observed), while the rest are "[[observationally stable]]" and theoretically can undergo radioactive decay with extremely long half-lives.{{cn|date=July 2025}}


The remaining tabulated radionuclides have half-lives longer than 1 hour, and are well-characterized (see [[list of nuclides]] for a complete tabulation). They include 30 nuclides with measured half-lives longer than the estimated age of the universe (13.8&nbsp;billion years<ref>{{cite web |title = Cosmic Detectives |url=http://www.esa.int/Our_Activities/Space_Science/Cosmic_detectives
The remaining tabulated radionuclides have half-lives longer than 1 hour, and are well-characterized (see [[list of nuclides]] for a complete tabulation). They include 31 nuclides with measured half-lives longer than the estimated age of the universe (13.8&nbsp;billion years<ref>{{cite web |title = Cosmic Detectives |url=http://www.esa.int/Our_Activities/Space_Science/Cosmic_detectives
|publisher = The European Space Agency (ESA) |date = 2013-04-02 |access-date = 2013-04-15}}</ref>), and another four nuclides with half-lives long enough (>&nbsp;100&nbsp;million years) that they are radioactive [[primordial nuclide]]s, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the [[Solar System]], about 4.6 billion years ago. Another 60+ short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides are known solely from artificial [[nuclear transmutation]].
|publisher = The European Space Agency (ESA) |date = 2013-04-02 |access-date = 2013-04-15}}</ref>), and another four nuclides with half-lives long enough (>&nbsp;100&nbsp;million years) that they are radioactive [[primordial nuclide]]s, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the [[Solar System]], about 4.6 billion years ago. Another 60+ short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides are known solely from artificial [[nuclear transmutation]].{{cn|date=July 2025}}


Numbers are not exact, and may change slightly in the future, as "stable nuclides" are observed to be radioactive with very long half-lives.
Numbers may change slightly in the future as some nuclides now classified as stable are observed to be radioactive with very long half-lives.{{cn|date=July 2025}}


This is a summary table<ref>Table data is derived by counting members of the list; see [[WP:CALC]]. References for the list data itself are given below in the reference section in [[list of nuclides]]</ref> for the 989 nuclides with half-lives longer than one hour (including those that are stable), given in [[list of nuclides]].
This is a summary table<ref>Table data is derived by counting members of the list; see [[WP:CALC]]. References for the list data itself are given below in the reference section in [[list of nuclides]]</ref> for the 986 nuclides with half-lives longer than one hour (including those that are stable), given in [[list of nuclides]].
{| class="wikitable sortable" width="100%"
{| class="wikitable sortable" width="100%"
! width="300" |Stability class
! width="300" |Stability class
Line 201: Line 214:
| Total of classically [[stable nuclide]]s.
| Total of classically [[stable nuclide]]s.
|-
|-
| Radioactive [[primordial nuclide]]s.
| Radioactive [[primordial nuclide]]s
| align="center"| 35
| align="center"| 35
| align="center"| 286
| align="center"| 286
| Total primordial elements include [[uranium]], [[thorium]], [[bismuth]], [[rubidium-87]], [[potassium-40]], [[tellurium-128]] plus all stable nuclides.
| Total primordial elements include [[uranium]], [[thorium]], [[bismuth]], [[rubidium-87]], [[potassium-40]], [[tellurium-128]] plus all stable nuclides.
|-
|-
| Radioactive nonprimordial, but naturally occurring on Earth.
| Radioactive nonprimordial, but naturally occurring on Earth
| align="center"| 61
| align="center"| 62
| align="center"| 347
| align="center"| 348
| [[Carbon-14]] (and other isotopes generated by [[cosmic rays]]) and daughters of radioactive primordial elements, such as [[radium]], [[polonium]], etc. 41 of these have a half life of greater than one hour.
| [[Carbon-14]] (and other isotopes generated by [[cosmic rays]]) and daughters of radioactive primordial elements, such as [[radium]] and [[polonium]], of which 32 have a half-life of greater than one hour, also long-lived [[fission products]].
|-
|-
| Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful [[radiotracer]]s.
| Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful [[radiotracer]]s.
| align="center"| 662
| align="center"| 638
| align="center"| 989
| align="center"| 986
| These 989 nuclides are listed in the article [[List of nuclides]].
| These comprise the remainder of the [[list of nuclides]].
|-
|-
| Radioactive synthetic (half-life < 1.0 hour).
| Radioactive synthetic (half-life < 1.0 hour).
Line 221: Line 234:
| Includes all well-characterized synthetic nuclides.
| Includes all well-characterized synthetic nuclides.
|-
|-
|}
==List of commercially available radionuclides==
{{See also|List of nuclides|Table of nuclides}}
This list covers common isotopes, most of which are available in very small quantities to the general public in most countries. Others that are not publicly accessible are traded commercially in industrial, medical, and scientific fields and are subject to government regulation.
===Gamma emission only===
{| class="wikitable" Border="1"
|-
! Isotope
! [[Specific activity|Activity]]
! Half-life
! Energies ([[Electronvolt|keV]])
|-
| [[Barium-133]]
| 9694&nbsp;TBq/kg (262 Ci/g)
| 10.7 years
| 81.0, 356.0
|-
| [[Cadmium-109]]
| 96200&nbsp;TBq/kg (2600 Ci/g)
| 453 days
| 88.0
|-
| [[Cobalt-57]]
| 312280&nbsp;TBq/kg (8440 Ci/g)
| 270 days
| 122.1
|-
| [[Cobalt-60]]
| 40700&nbsp;TBq/kg (1100 Ci/g)
| 5.27 years
| 1173.2, 1332.5
|-
| [[Europium-152]]
| 6660&nbsp;TBq/kg (180 Ci/g)
| 13.5 years
| 121.8, 344.3, 1408.0
|-
| [[Manganese-54]]
| 287120&nbsp;TBq/kg (7760 Ci/g)
| 312 days
| 834.8
|-
| [[Sodium-22]]
| 237540&nbsp;Tbq/kg (6240 Ci/g)
| 2.6 years
| 511.0, 1274.5
|-
| [[Zinc-65]]
| 304510&nbsp;TBq/kg (8230 Ci/g)
| 244 days
| 511.0, 1115.5
|-
| [[Technetium-99m]]
| {{val|1.95|e=7}}&nbsp;TBq/kg (5.27 × 10<sup>5</sup> Ci/g)
| 6 hours
| 140
|}
===Beta emission only===
{| class="wikitable" Border="1"
|-
! Isotope
! Activity
! Half-life
! Energies (keV)
|-
| [[Strontium-90]]
| 5180&nbsp;TBq/kg (140 Ci/g)
| 28.5 years
| 546.0
|-
| [[Thallium-204]]
| 17057&nbsp;TBq/kg (461 Ci/g)
| 3.78 years
| 763.4
|-
| [[Carbon-14]]
| 166.5&nbsp;TBq/kg (4.5 Ci/g)
| 5730 years
| 156.5
|-
| [[Tritium]] (Hydrogen-3)
| 357050&nbsp;TBq/kg (9650 Ci/g)
| 12.32 years
| 18.6
|}
===Alpha emission only===
{| class="wikitable" Border="1"
|-
! Isotope
! Activity
! Half-life
! Energies (keV)
|-
| [[Polonium-210]]
| 166500&nbsp;TBq/kg (4500 Ci/g)
| 138.376 days
| 5304.5
|-
| [[Uranium-238]]
| 12580&nbsp;kBq/kg (0.00000034 Ci/g)
| 4.468 billion years
| 4267
|}
===Multiple radiation emitters===
{| class="wikitable" Border="1"
|-
! Isotope
! Activity
! Half-life
! Radiation types
! Energies (keV)
|-
| [[Caesium-137]]
| 3256&nbsp;TBq/kg (88 Ci/g)
| 30.1 years
| Gamma & beta
| G: 32, 661.6 B: 511.6, 1173.2
|-
| [[Americium-241]]
| 129.5&nbsp;TBq/kg (3.5 Ci/g)
| 432.2 years
| Gamma & alpha
| G: 59.5, 26.3, 13.9 A: 5485, 5443
|}
|}


Line 354: Line 239:
{{Portal|Physics}}
{{Portal|Physics}}
* [[List of nuclides]] shows all radionuclides with half-life > 1 hour
* [[List of nuclides]] shows all radionuclides with half-life > 1 hour
* [[Hyperaccumulators table – 3]]
* [[Hyperaccumulators table – 3]] (includes organisms noted for accumulating radionuclides)
* [[Radioactivity in biology]]
* [[Radioactivity in biology]]
* [[Radiometric dating]]
* [[Radiometric dating]]
Line 373: Line 258:
==External links==
==External links==
{{commons category|Radionuclides}}
{{commons category|Radionuclides}}
* [http://www.epa.gov/rpdweb00/radionuclides/index.html EPA – Radionuclides] – EPA's Radiation Protection Program: Information.
* [https://archive.today/20121212005306/http://www.epa.gov/rpdweb00/radionuclides/index.html EPA – Radionuclides] – EPA's Radiation Protection Program: Information.
* [https://web.archive.org/web/20100216011400/http://www.fda.gov/Food/FoodSafety/FoodContaminantsAdulteration/ChemicalContaminants/Radionuclides/UCM078341#level98 FDA – Radionuclides] – FDA's Radiation Protection Program: Information.
* [https://web.archive.org/web/20100216011400/http://www.fda.gov/Food/FoodSafety/FoodContaminantsAdulteration/ChemicalContaminants/Radionuclides/UCM078341#level98 FDA – Radionuclides] – FDA's Radiation Protection Program: Information.
* [http://www.nndc.bnl.gov/chart/ Interactive Chart of Nuclides] – A chart of all nuclides
* [http://www.nndc.bnl.gov/chart/ Interactive Chart of Nuclides] – A chart of all nuclides

Latest revision as of 22:01, 7 November 2025

Template:Short description Template:Use dmy dates Template:Lede too long Script error: No such module "Distinguish".

File:NuclideMap stitched 2.png
Chart of known nuclides Template:As of. The vast majority are radionuclides.

A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that is unstable and known to undergo radioactive decay into a different nuclide, which may be another radionuclide (see decay chain) or be stable. Radiation emitted by radionuclides is almost always ionizing radiation because it is energetic enough to liberate an electron from another atom.

Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay.[1][2] However, for a collection of atoms of a single nuclide, the decay rate (considered as a statistical average), and thus the half-life (t1/2) for that nuclide, can be calculated from the measurement of the decay. The range of the half-lives of radioactive atoms has no known limits and spans a time range of over 55 orders of magnitude.

Radionuclides occur naturally and are artificially produced in nuclear reactors, cyclotrons, particle accelerators or radionuclide generators. There are 735 known radionuclides with half-lives longer than an hour (see list of nuclides); 35 of those are primordial radionuclides whose presence on Earth has persisted from its formation, and another 62 are detectable in nature, continuously produced either as daughter products of primordial radionuclides or by cosmic radiation. More than 2400 radionuclides have half-lives less than 60 minutes. Most of those are only produced artificially, and have very short half-lives. For comparison, there are 251 stable nuclides.

All the chemical elements have radionuclides - even the lightest element, hydrogen, has one well-known radionuclide, tritium (though helium, lithium, and boron have none with half-life over a second). Elements heavier than lead (Z > 82), and the elements technetium and promethium, have only radionuclides and do not exist in stable forms, though bismuth can be treated as stable with the half-life of its natural isotope being over a trillion times longer than the current age of the universe.

Artificial production methods of radionuclides include neutron sources such as nuclear reactors, as well as particle accelerators such as cyclotrons.

Exposure to radionuclides generally has, due to their radiation, a harmful effect on organisms including humans, although low levels of exposure occur naturally. The degree of harm will depend on the nature and extent of the radiation produced (alpha, beta, gamma, or neutron), the amount and nature of exposure (close contact, inhalation or ingestion), and the biochemical properties of the element (toxicity). Increased risk of cancer is considered unavoidable, and worse cases experience radiation-induced cancer, chronic radiation syndrome or acute radiation syndrome. Radionuclides are weaponized by the fallout effects of nuclear weapons and by radiological weapons.

Radionuclides with suitable properties are used in nuclear medicine for both diagnosis and treatment. An imaging tracer made with radionuclides is called a radioactive tracer. Radionuclide therapy is a form of radiotherapy. A pharmaceutical drug made with radionuclides is called a radiopharmaceutical.

Origins

Natural

On Earth, naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and cosmogenic radionuclides.

  • Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides. Most decay quickly, but some can be observed astronomically and can play a part in understanding astrophysical processes. Primordial radionuclides, such as uranium and thorium, still exist because their half-lives are so long (>100 million years) that the Earth's initial content has not yet completely decayed. Some radionuclides have half-lives so long (many times the age of the universe) that decay has only recently been detected, and for most practical purposes they can be considered stable, most notably bismuth-209: detection of this decay meant that bismuth was no longer considered stable. It is possible that decay may be observed in other nuclides now considered stable, adding to the list of primordial radionuclides.Script error: No such module "Unsubst".
  • Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. They arise in the decay chain of the primordial isotopes thorium-232, uranium-238, and uranium-235 - such as the natural isotopes of polonium and radium - some are also produced by natural fission and other nucleogenic processes.Script error: No such module "Unsubst".
  • Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed on Earth, typically in the atmosphere, due to the action of cosmic rays.Script error: No such module "Unsubst".

Many of these radionuclides exist only in trace amounts in nature, including all cosmogenic nuclides. Secondary radionuclides in a decay chain will occur in proportion to their half-lives, so short-lived ones will be very rare. For example, polonium can be found in uranium ores at a concentration about 1 part 1010 of uranium (0.1 mg per metric ton) by calculating the ratio of half-lives of polonium-210 to uranium-238, its ultimate parent.Script error: No such module "Unsubst".

Nuclear fission

Radionuclides are produced as an unavoidable result of nuclear fission and nuclear explosions. The process of nuclear fission creates a wide range of fission products, most of which are radionuclides. Further radionuclides are created from irradiation of the nuclear fuel (creating a range of actinides) and of the surrounding structures, yielding activation products. This complex mixture of radionuclides with different chemistries and radioactivity makes handling nuclear waste and dealing with nuclear fallout particularly problematic.Script error: No such module "Unsubst".

Synthetic

File:Artificial nuclide americium-241 emitting alpha particles inserted into a cloud chamber for visualisation.jpg
Americium-241 emitting alpha particles inserted into a cloud chamber

Synthetic radionuclides are created in nuclear reactors or by particle accelerators (not necesssarily on purpose) or as decay products of such:[3]

  • As well as being extracted from nuclear waste, radioisotopes can be produced deliberately with nuclear reactors, exploiting the high flux of neutrons present. These neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is iridium-192, from activation of iridium targets. The elements that have a large propensity to take up neutrons in the reactor are said to have a high neutron cross-section, but even at low cross-sections this process is generally economical.
  • Particle accelerators such as cyclotrons accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate (most often) protons at a target to produce positron-emitting radionuclides, e.g. fluorine-18.
  • Radionuclide generators, standard for many medical isotopes, contain a parent radionuclide that decays to produce a shorter-lived radioactive daughter. A typical example is the technetium-99m generator, which employs molybdenum-99 produced in a reactor.

Uses

Radionuclides are used in two major ways: either for their radiation alone (irradiation, nuclear batteries) or for the combination of chemical properties and their radiation (tracers, biopharmaceuticals). For scientific study they may be used for their chemical properties alone when there is no stable form of that element.

  • In biology, radionuclides (most often of carbon) can serve as radioactive tracers because they are chemically very similar to the nonradioactive nuclides, so most chemical, biological, and ecological processes treat them in a nearly identical way. One can then examine the result with a radiation detector, such as a Geiger counter, to determine where the provided atoms were incorporated. For example, one might culture plants in an environment in which the carbon dioxide contained radioactive carbon; then the parts of the plant that incorporate atmospheric carbon would be radioactive. Radionuclides can be used to monitor processes such as DNA replication or amino acid transport.Script error: No such module "Unsubst".
  • in physics and biology radionuclide X-ray fluorescence (conventional X-ray sources may also be used) is used to determine chemical composition of the compound. Radiation from a radionuclide source hits the sample and excites characteristic X-rays in the sample. This radiation is registered and the chemical composition of the sample can be determined from the analysis of the measured spectrum. By measuring the energy of the characteristic radiation lines, it is possible to determine the proton number of the chemical element that emits the radiation, and by measuring the number of emitted photons, it is possible to determine the concentration of individual chemical elements.Script error: No such module "Unsubst".
  • In nuclear medicine, radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about internal anatomy and the functioning of specific organs, including the human brain.[4][5][6] This is used in some forms of tomography: single-photon emission computed tomography and positron emission tomography (PET) scanning and Cherenkov luminescence imaging. Radioisotopes are also a method of treatment in hemopoietic forms of tumors; the success for treatment of solid tumors has been limited. More powerful gamma sources sterilise syringes and other medical equipment.
  • In food preservation, radiation is used to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables. Food irradiation usually uses strong gamma emitters like cobalt-60 or caesium-137.Script error: No such module "Unsubst".
  • In industry, and in mining, radiation from radionuclides may be used to examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels.
  • In spacecraft, radionuclides are used to provide power and heat, notably through radioisotope thermoelectric generators (RTGs) and radioisotope heater units (RHUs).Script error: No such module "Unsubst".
  • In particle physics, radionuclides help discover new physics (physics beyond the Standard Model) by measuring the energy and momentum of their beta decay products (for example, neutrinoless double beta decay and the search for weakly interacting massive particles).[7]
  • In ecology, radionuclides are used to trace and analyze pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers.Script error: No such module "Unsubst".
  • In geology, archaeology, and paleontology, natural radionuclides are used to measure ages of rocks, minerals, and fossil materials. This is called radiometric dating.

Examples

The following table lists properties of selected radionuclides illustrating the range of properties and uses.

Isotope Z N half-life DM DE
keV		 Mode of formation Comments
Tritium (3H) 1 2 12.3 y β− 19 Cosmogenic lightest radionuclide, used in artificial nuclear fusion, also used for radioluminescence and as oceanic transient tracer. Synthesized from neutron bombardment of lithium-6 or deuterium
Beryllium-10 4 6 1,387,000 y β− 556 Cosmogenic used to examine soil erosion, soil formation from regolith, and the age of ice cores
Carbon-14 6 8 5,700 y β− 156 Cosmogenic used for radiocarbon dating
Fluorine-18 9 9 110 min β+, EC 633/1655 Cosmogenic positron source, synthesised for use as a medical radiotracer in PET scans.
Aluminium-26 13 13 717,000 y β+, EC 4004 Cosmogenic exposure dating of rocks, sediment
Chlorine-36 17 19 301,000 y β−, EC 709 Cosmogenic exposure dating of rocks, groundwater tracer
Potassium-40 19 21 1.24Template:E y β−, EC 1330 /1505 Primordial used for potassium-argon dating, source of atmospheric argon, source of radiogenic heat, largest source of natural radioactivity
Calcium-41 20 21 99,400 y EC Cosmogenic exposure dating of carbonate rocks
Cobalt-60 27 33 5.3 y β− 2824 Synthetic produces high energy gamma rays, used for radiotherapy, equipment sterilisation, food irradiation
Krypton-81 36 45 229,000 y β+ Cosmogenic groundwater dating
Strontium-90 38 52 28.8 y β− 546 Fission product medium-lived fission product; probably most dangerous component of nuclear fallout
Technetium-99 43 56 210,000 y β− 294 Fission product most common isotope of the lightest unstable element, most significant of long-lived fission products
Technetium-99m 43 56 6 hr γ,IC 141 Synthetic most commonly used medical radioisotope, used as a radioactive tracer
Iodine-129 53 76 15,700,000 y β− 194 Cosmogenic longest lived fission product; groundwater tracer
Iodine-131 53 78 8 d β− 971 Fission product most significant short-term health hazard from nuclear fission, used in nuclear medicine, industrial tracer
Xenon-135 54 81 9.1 h β− 1160 Fission product strongest known "nuclear poison" (neutron-absorber), with a major effect on nuclear reactor operation.
Caesium-137 55 82 30.2 y β− 1176 Fission product other major medium-lived fission product of concern
Gadolinium-153 64 89 240 d EC Synthetic calibrating nuclear equipment, bone density screening
Bismuth-209 83 126 2.01Template:Ey α 3137 Primordial long considered stable, decay only detected in 2003
Polonium-210 84 126 138 d α 5307 Decay product highly toxic, used in poisoning of Alexander Litvinenko
Radon-222 86 136 3.8 d α 5590 Decay product gas, responsible for the majority of public exposure to ionizing radiation, second most frequent cause of lung cancer
Thorium-232 90 142 1.4Template:E y α 4083 Primordial basis of thorium fuel cycle
Uranium-235 92 143 7Template:Ey α 4679 Primordial fissile, main nuclear fuel
Uranium-238 92 146 4.5Template:E y α 4267 Primordial main uranium isotope
Plutonium-238 94 144 87.7 y α 5593 Synthetic used in radioisotope thermoelectric generators (RTGs) and radioisotope heater units as an energy source for spacecraft
Plutonium-239 94 145 24,110 y α 5245 Synthetic used for most modern nuclear weapons
Americium-241 95 146 432 y α 5486 Synthetic used in household smoke detectors as an ionising agent
Californium-252 98 154 2.64 y α/SF 6217 Synthetic undergoes spontaneous fission (3% of decays), making it a powerful neutron source, used as a reactor initiator and for detection devices
Lutetium-177 71 106 6.6443(9) d β− 497 (78.6 %), 384 (9.1 %), 176 (12.2 %) Synthetic used predominantly in targeted radionuclide therapy (TRT) against somatostatin receptor-positive gastroenteropancreatic neuroendocrine tumors (GEP-NETs)

Key: Z = atomic number; N = neutron number; DM = decay mode; DE = decay energy; EC = electron capture

Household smoke detectors

File:Americium-241.jpg
Americium-241 container in a smoke detector.
File:Americium-241 Sample from Smoke Detector.JPG
Americium-241 capsule as found in smoke detector. The circle of darker metal in the center is americium-241; the surrounding casing is aluminium.

Radionuclides are present in many homes as they are used inside the most common household smoke detectors. The radionuclide used is americium-241, which is created by bombarding plutonium with neutrons in a nuclear reactor. It decays by emitting alpha particles and gamma radiation to become neptunium-237. Smoke detectors use a very small quantity of 241Am (about 0.29 micrograms per smoke detector) in the form of americium dioxide. 241Am is used as it emits alpha particles which ionize the air in the detector's ionization chamber. A small electric voltage is applied to the ionized air which gives rise to a small electric current. In the presence of smoke, some of the ions are neutralized, thereby decreasing the current, which activates the detector's alarm.[8][9]

Impacts on organisms

Radionuclides that find their way into the environment may cause harmful effects as radioactive contamination. They can also cause damage if they are excessively used during treatment or in other ways exposed to living beings, by radiation poisoning. Potential health damage from exposure to radionuclides depends on a number of factors, and "can damage the functions of healthy tissue/organs. Radiation exposure can produce effects ranging from skin redness and hair loss, to radiation burns and acute radiation syndrome. Prolonged exposure can lead to cells being damaged and in turn lead to cancer. Signs of cancerous cells might not show up until years, or even decades, after exposure."[10]

Summary table for classes of nuclides, stable and radioactive

Following is a summary table for the list of 986 nuclides with half-lives greater than one hour. A total of 251 nuclides have never been observed to decay, and are classically considered stable. Of these, 90 are believed to be absolutely stable except to proton decay (which has never been observed), while the rest are "observationally stable" and theoretically can undergo radioactive decay with extremely long half-lives.Script error: No such module "Unsubst".

The remaining tabulated radionuclides have half-lives longer than 1 hour, and are well-characterized (see list of nuclides for a complete tabulation). They include 31 nuclides with measured half-lives longer than the estimated age of the universe (13.8 billion years[11]), and another four nuclides with half-lives long enough (> 100 million years) that they are radioactive primordial nuclides, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the Solar System, about 4.6 billion years ago. Another 60+ short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides are known solely from artificial nuclear transmutation.Script error: No such module "Unsubst".

Numbers may change slightly in the future as some nuclides now classified as stable are observed to be radioactive with very long half-lives.Script error: No such module "Unsubst".

This is a summary table[12] for the 986 nuclides with half-lives longer than one hour (including those that are stable), given in list of nuclides.

Stability class Number of nuclides Running total Notes on running total
Theoretically stable to all but proton decay 90 90 Includes first 40 elements. Proton decay yet to be observed.
Theoretically stable to alpha decay, beta decay, isomeric transition, and double beta decay but not spontaneous fission, which is possible for "stable" nuclides ≥ niobium-93 56 146 All nuclides that are possibly completely stable (spontaneous fission has never been observed for nuclides with mass number < 232).
Energetically unstable to one or more known decay modes, but no decay yet seen. All considered "stable" until decay detected. 105 251 Total of classically stable nuclides.
Radioactive primordial nuclides 35 286 Total primordial elements include uranium, thorium, bismuth, rubidium-87, potassium-40, tellurium-128 plus all stable nuclides.
Radioactive nonprimordial, but naturally occurring on Earth 62 348 Carbon-14 (and other isotopes generated by cosmic rays) and daughters of radioactive primordial elements, such as radium and polonium, of which 32 have a half-life of greater than one hour, also long-lived fission products.
Radioactive synthetic half-life ≥ 1.0 hour). Includes most useful radiotracers. 638 986 These comprise the remainder of the list of nuclides.
Radioactive synthetic (half-life < 1.0 hour). >2400 >3300 Includes all well-characterized synthetic nuclides.

See also

Script error: No such module "Portal".

Notes

Template:Reflist

References

  • Script error: No such module "Citation/CS1".
  • Script error: No such module "citation/CS1".
  • Script error: No such module "citation/CS1".

Further reading

  • Script error: No such module "citation/CS1".

External links

Template:Sister project

Template:Radiation Template:Radiopharmaceuticals

Template:Authority control

  1. ↑ Script error: No such module "citation/CS1".
  2. ↑ Script error: No such module "citation/CS1".
  3. ↑ Script error: No such module "citation/CS1".
  4. ↑ Script error: No such module "Citation/CS1".
  5. ↑ Script error: No such module "Citation/CS1".
  6. ↑ Script error: No such module "Citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ Script error: No such module "citation/CS1".
  9. ↑ Office of Radiation Protection – Am 241 Fact Sheet – Washington State Department of Health Template:Webarchive
  10. ↑ Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Table data is derived by counting members of the list; see WP:CALC. References for the list data itself are given below in the reference section in list of nuclides
Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Radionuclide&oldid=3155834"