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A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a
nuclide A nuclide (or nucleide, from atomic nucleus, nucleus, also known as nuclear species) is a class of atoms characterized by their number of protons, ''Z'', their number of neutrons, ''N'', and their nuclear energy state. The word ''nuclide'' was coi ...

nuclide
that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as
gamma radiation A gamma ray, or gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuc ...
; transferred to one of its
electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...

electron
s to release it as a
conversion electron Internal conversion is a non-radioactive decay process wherein an excited atomic nucleus, nucleus interacts electromagnetism, electromagnetically with one of the Atomic orbital, orbital electrons of the atom. This causes the electron to be emitted ...
; or used to create and emit a new
particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical property, physical or chemical , chemical properties ...

particle
(
alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Proton ...
or
beta particle A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron The electron is a subatomic particle, symbol or , whose electric charge Electric charge is the physical property of matter that cau ...
) from the nucleus. During those processes, the radionuclide is said to undergo
radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

radioactive decay
. These emissions are considered
ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionization, ionize atoms or molecules by detaching electrons from them. The particles g ...
because they are powerful 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. However, for a collection of atoms of a single nuclide the decay rate, and thus the
half-life Half-life (symbol ''t''1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay Radioactive decay (al ...
(''t''1/2) for that collection, can be calculated from their measured
decay constant Image:Plot-exponential-decay.svg, upright=1.5, A quantity undergoing exponential decay. Larger decay constants make the quantity vanish much more rapidly. This plot shows decay for decay constant (λ) of 25, 5, 1, 1/5, and 1/25 for x from 0 to 5. A ...
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. Radionuclides occur naturally or are artificially produced in
nuclear reactor A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclea ...

nuclear reactor
s,
cyclotron . The magnet is painted yellow. A cyclotron is a type of particle accelerator , a synchrotron collider type particle accelerator at Fermi National Accelerator Laboratory (Fermilab), Batavia, Illinois, USA. Shut down in 2011, until 2007 it wa ...

cyclotron
s,
particle accelerator , a synchrotron collider type particle accelerator at Fermi National Accelerator Laboratory (Fermilab), Batavia, Illinois, USA. Shut down in 2011, until 2007 it was the most powerful particle accelerator in the world, accelerating protons to an en ...
s or
radionuclide generator A radionuclide generator is a device which provides a local supply of a short-lived radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an uns ...
s. There are about 730 radionuclides with half-lives longer than 60 minutes (see
list of nuclides This list of nuclides shows observed nuclides that either are stable or, if radioactive, have half-lives longer than one hour. This represents isotopes of the first 105 elements, except for elements 87 (francium Francium is a chemical elemen ...
). Thirty-two of those are
primordial radionuclide In geochemistry Geochemistry is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Testability, ...
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 about 252
stable nuclide 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. The ...
s. (In theory, only 146 of them are stable, and the other 106 are believed to decay via
alpha decay
alpha decay
,
beta decay (the accompanying antineutrino is omitted). The inset shows beta decay of a free neutron. Neither of these depictions shows the intermediate virtual boson. In nuclear physics, beta decay (''β''-decay) is a type of radioactive decay Rad ...

beta decay
,
double beta decay In nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Other forms of nuclear matter are also studied. Nuclear physics should not be confused with atomic physics, which studi ...
,
electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...

electron capture
, or
double electron capture Double electron capture is a decay mode Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus The atomic nucleus is the sma ...
.) All
chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same numbers of protons in their atomic nu ...
s can exist as radionuclides. Even the lightest element,
hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

hydrogen
, has a well-known radionuclide,
tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleu ...

tritium
. Elements heavier than
lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate h ...

lead
, and the elements
technetium Technetium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same nu ...

technetium
and
promethium Promethium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same n ...

promethium
, exist only as radionuclides. (In theory, elements heavier than
dysprosium Dysprosium is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same n ...

dysprosium
exist only as radionuclides, but some such elements, like
gold Gold is a chemical element with the Symbol (chemistry), symbol Au (from la, aurum) and atomic number 79, making it one of the higher atomic number elements that occur naturally. In a pure form, it is a brightness, bright, slightly reddish yel ...

gold
and
platinum Platinum is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

platinum
, are
observationally stable 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. The ...
and their half-lives have not been determined). 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 Nuclear medicine is a medical specialty A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include children (paediatrics Pediatrics (American and Briti ...
for both diagnosis and treatment. An imaging tracer made with radionuclides is called a
radioactive tracerA radioactive tracer, radiotracer, or radioactive label, is a chemical compound in which one or more atoms have been replaced by a radionuclide so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tra ...
. A
pharmaceutical drug A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug File:Aspirine macro shot.jpg, Uncoated aspirin Tablet (pharmacy), tablets, consisting of about 90% acetylsalicylic acid, along w ...
made with radionuclides is called a
radiopharmaceutical Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom An atom is the smallest unit of ordin ...

radiopharmaceutical
.


Origin


Natural

On Earth, naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, and
cosmogenic Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by their number of proton A proton is a subatomic particle, symbol or , with a ...
radionuclides. *Radionuclides are produced in
stellar nucleosynthesis Stellar nucleosynthesis is the creation (nucleosynthesis) of chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance cons ...
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 Uranium is a chemical element with the Symbol (chemistry), symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence elect ...

uranium
and
thorium Thorium is a weakly radioactive decay, radioactive metallic chemical element with the Symbol (chemistry), symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderatel ...

thorium
, exist in the present time because their
half-lives Half-life (symbol ''t''1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents a ...
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 Bismuth-209 (209Bi) is the isotope of bismuth with the longest known half-life of any radioisotope that undergoes α-decay (alpha decay). It has 83 protons and a magic number (physics), magic number of 126 neutrons, and an atomic mass of 208.9803987 ...

bismuth-209
: detection of this decay meant that
bismuth Bismuth is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same numbe ...

bismuth
was no longer considered stable. It is possible decay may be observed in other nuclides, adding to this list of primordial radionuclides. *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 In nuclear science Nuclear physics is the field of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, it ...
of the primordial isotopes
thorium-232 Thorium Thorium is a weakly radioactive decay, radioactive metallic chemical element with the Symbol (chemistry), symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is mo ...
,
uranium-238 Uranium-238 (238U or U-238) is the most common isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons ...
, and
uranium-235 Uranium-235 (235U) is an Isotopes of uranium, isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope th ...

uranium-235
. Examples include the natural isotopes of
polonium Polonium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same numb ...

polonium
and
radium Radium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same nu ...

radium
. *
Cosmogenic isotopes Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclide A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by their number of proton A proton is a subatomic particle, symbol or , with a ...
, such as
carbon-14 Carbon-14 (14C), or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleag ...

carbon-14
, are present because they are continually being formed in the atmosphere due to
cosmic ray Cosmic rays are high-energy proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approxi ...
s. 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 Uranium is a chemical element with the Symbol (chemistry), symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence elect ...

uranium
ores at about 0.1 mg per
metric ton The tonne ( or ; symbol: t) is a Metric_units#Mass, metric unit of mass equal to 1,000 kilograms. It is commonly referred to as a metric ton in the United States. It is equivalent to approximately international avoirdupois pound, pound ...
(1 part in 1010). 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.


Nuclear fission

Radionuclides are produced as an unavoidable result of
nuclear fission Nuclear fission is a reaction Reaction may refer to a response (disambiguation), response to an action, event, or exposure. Examples: *Adverse drug reaction *Allergy, Allergic reaction *Chemical reaction *Chain reaction (disambiguation) *Comment ...

nuclear fission
and thermonuclear explosions. The process of nuclear fission creates a wide range of
fission products Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission In nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions. Oth ...
, most of which are radionuclides. Further radionuclides can be created from irradiation of the nuclear fuel (creating a range of
actinides The actinoid ( IUPAC nomenclature, also called actinide ) series encompasses the 15 metallic chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, a ...
) and of the surrounding structures, yielding
activation productsActivation products are materials made radioactive by neutron activation. Fission products and actinides produced by neutron absorption of nuclear fuel itself are normally referred to by those specific names, and ''activation product'' reserved for ...
. This complex mixture of radionuclides with different chemistries and radioactivity makes handling
nuclear waste Radioactive waste is a type of hazardous waste Hazardous waste is waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance which is discarded after primary use, or is worthless, defective and of no use. A by-produ ...
and dealing with
nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioact ...
particularly problematic.


Synthetic

Synthetic radionuclides are deliberately synthesised using
nuclear reactor A nuclear reactor, formerly known as an atomic pile, is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclea ...

nuclear reactor
s, particle accelerators or radionuclide generators: *As well as being extracted from nuclear waste, radioisotopes can be produced deliberately with nuclear reactors, exploiting the high flux of
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behav ...

neutron
s present. These neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is
iridium-192 There are two natural isotopes Isotopes are variants of a particular chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure subs ...
. The elements that have a large propensity to take up the neutrons in the reactor are said to have a high
neutron cross-section In nuclear and particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'natur ...
. *Particle accelerators such as
cyclotron . The magnet is painted yellow. A cyclotron is a type of particle accelerator , a synchrotron collider type particle accelerator at Fermi National Accelerator Laboratory (Fermilab), Batavia, Illinois, USA. Shut down in 2011, until 2007 it wa ...

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 Fluorine-18 (18F) is a fluorine Fluorine is a chemical element with the Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard conditions for temperature and pressure, standard conditions as a highly tox ...

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 A technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope Technetium-99m, 99mTc of technetium from a decaying sample of molybdenum-99. 99Mo has a half-life of 66 hours and can be ea ...
used in
nuclear medicine Nuclear medicine is a medical specialty A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include children (paediatrics Pediatrics (American and Briti ...
. The parent produced in the reactor is
molybdenum-99 Molybdenum (42Mo) has 33 known isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different nu ...
.


Uses

Radionuclides are used in two major ways: either for their radiation alone (
irradiation Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a ...

irradiation
, nuclear batteries) or for the combination of chemical properties and their radiation (tracers, biopharmaceuticals). *In
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Developmenta ...

biology
, radionuclides of
carbon Carbon (from la, carbo "coal") is a chemical element with the Symbol (chemistry), symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—making four electrons available to form covalent bond, covalent chemical bonds. ...

carbon
can serve as
radioactive tracerA radioactive tracer, radiotracer, or radioactive label, is a chemical compound in which one or more atoms have been replaced by a radionuclide so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tra ...
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 A Geiger counter (also known as a Geiger–Müller counter) is an electronic instrument used for detecting and measuring ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles o ...

Geiger counter
, to determine where the provided atoms were incorporated. For example, one might culture plants in an environment in which the
carbon dioxide Carbon dioxide (chemical formula ) is a colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalent bond, covalently double bonded to two oxygen atoms. It occurs naturally in At ...

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 is un'zipped' and unwound, then each separated strand (turquoise) acts as a template for replicating a new partner strand (green). Nucleotides (bases) are matched to synthesize the new partner strands into two new double helices. In molecular biolo ...

DNA replication
or
amino acid Amino acids are organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen chemical bond, bonds. Due to carbon's ability to Catenation, c ...

amino acid
transport. *In
nuclear medicine Nuclear medicine is a medical specialty A medical specialty is a branch of medical practice that is focused on a defined group of patients, diseases, skills, or philosophy. Examples include children (paediatrics Pediatrics (American and Briti ...
, 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 The human brain is the central organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. ...

human brain
. This is used in some forms of tomography:
single-photon emission computed tomography Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma ray A gamma ray, or gamma radiation (symbol γ or \gamma), is a penetrating form of electromagneti ...
and
positron emission tomography Positron emission tomography (PET) is a functional imaging Functional imaging (or physiological imaging), is a medical imaging technique of detecting or measuring changes in metabolism, blood flow, regional chemical composition, and absorptio ...
(PET) scanning and Cherenkov luminescence imaging. Radioisotopes are also a method of treatment in
hemopoietic Haematopoiesis (, from Ancient Greek, Greek , 'blood' and 'to make'; also hematopoiesis in American English; sometimes also h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from hematopoieti ...
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 Food preservation includes food processing Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain A gr ...

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. *In
industry Industry may refer to: Economics * Industry (economics) In macroeconomics, an industry is a branch of an economy that produces a closely related set of raw materials, goods, or services. For example, one might refer to the wood industry ...
, and in
mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. These deposits form a mineralized commodity that is of economic interest to t ...

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
spacecraft File:Space Shuttle Columbia launching.jpg, 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the Hubble Space Telescope, and the ISS. (''Columbia'' STS-1, maiden launch, which had a white external tank, ...

spacecraft
, radionuclides are used to provide power and heat, notably through
radioisotope thermoelectric generator A radioisotope thermoelectric generator (RTG, RITEG) is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive Radioactive decay (also known as nuclear decay, radi ...
s (RTGs) and
radioisotope heater unit Image:Radioisotope heater unit.gif, Diagram of a radioisotope heater unit Radioisotope heater units (RHU) are small devices that provide heat through radioactive decay. They are similar to tiny radioisotope thermoelectric generators (RTG) and norm ...
s (RHUs). *In
astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies astronomical object, celestial objects and celestial event, phenomena. It uses mathematics, physi ...
and
cosmology Cosmology (from Ancient Greek, Greek κόσμος, ''kosmos'' "world" and -λογία, ''-logia'' "study of") is a branch of astronomy concerned with the study of the chronology of the universe. Physical cosmology is the study of the universe's ...
, radionuclides play a role in understanding stellar and planetary process. *In
particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...
, radionuclides help discover new physics (
physics beyond the Standard Model Physics beyond the Standard Model (BSM) refers to the theoretical developments needed to explain the deficiencies of the Standard Model, such as the inability to explain the fundamental parameters of the standard model, the strong CP problem, neu ...
) by measuring the energy and momentum of their beta decay products (for example,
neutrinoless double beta decay The neutrinoless double beta decay (0νββ) is a commonly proposed and experimentally pursued theoretical radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) ...
and the search for
weakly interacting massive particles Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter. There exists no clear definition of a WIMP, but broadly, a WIMP is a new elementary particle which interacts via gravi ...
). *In
ecology Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms In biology ...
, 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
geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes by which th ...

geology
,
archaeology Archaeology or archeology is the study of human activity through the recovery and analysis of material culture. Archaeology is often considered a branch of socio-cultural anthropology, but archaeologists also draw from biological, geological ...
, and
paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (geology), epoch (roughly 11,700 years before present). It includes th ...
, natural radionuclides are used to measure ages of rocks, minerals, and fossil materials.


Examples

The following table lists properties of selected radionuclides illustrating the range of properties and uses. Key: ''Z'' = 
atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of the electromagnetic radiation emitted (shown) when an electron jumps from one ...
; ''N'' = 
neutron number The neutron number, symbol ''N'', is the number of neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitu ...
; DM = decay mode; DE = decay energy; EC = 
electron capture Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Th ...

electron capture


Household smoke detectors

Radionuclides are present in many homes as they are used inside the most common household
smoke detector A smoke detector is a device that senses smoke, typically as an indicator of fire. Commercial smoke detectors issue a signal to a fire alarm control panel as part of a fire alarm system, while household smoke detectors, also known as smoke alarms, ...

smoke detector
s. The radionuclide used is
americium-241 Americium-241 (241Am, Am-241) is an isotope of americium. Like all isotopes of americium, it is radioactive, with a half-life of 432.2 years. 241Am is the most common isotope of americium as well as the most prevalent isotope of americium in nucle ...

americium-241
, which is created by bombarding plutonium with neutrons in a nuclear reactor. It decays by emitting
alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Proton ...
s and
gamma radiation A gamma ray, or gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuc ...
to become
neptunium-237 Neptunium (93Np) is usually considered an artificial element, although trace quantities are found in nature, so a standard atomic weight The standard atomic weight (''A''r, standard(E)) of a chemical element Image:Simple Periodic Table Cha ...

neptunium-237
. Smoke detectors use a very small quantity of 241Am (about 0.29 micrograms per smoke detector) in the form of
americium dioxide Americium dioxide (AmO2) is a black compound of americium. In the solid state AmO2 adopts the fluorite, CaF2 structure. It is used as a source of alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two proton ...
. 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.


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."


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 252 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 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. The ...
" and theoretically can undergo radioactive decay with extremely long half-lives. The remaining tabulated radionuclides have half-lives longer than 1 hour, and are well-characterized (see
list of nuclides This list of nuclides shows observed nuclides that either are stable or, if radioactive, have half-lives longer than one hour. This represents isotopes of the first 105 elements, except for elements 87 (francium Francium is a chemical elemen ...
for a complete tabulation). They include 30 nuclides with measured half-lives longer than the estimated age of the universe (13.8 billion years), 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. Numbers are not exact, and may change slightly in the future, as "stable nuclides" are observed to be radioactive with very long half-lives. This is a summary tableTable 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 This list of nuclides shows observed nuclides that either are stable or, if radioactive, have half-lives longer than one hour. This represents isotopes of the first 105 elements, except for elements 87 (francium Francium is a chemical elemen ...
for the 989 nuclides with half-lives longer than one hour (including those that are stable), given in
list of nuclides This list of nuclides shows observed nuclides that either are stable or, if radioactive, have half-lives longer than one hour. This represents isotopes of the first 105 elements, except for elements 87 (francium Francium is a chemical elemen ...
.


List of commercially available radionuclides

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


Beta emission only


Alpha emission only


Multiple radiation emitters


See also

*List of nuclides shows all radionuclides with half-life > 1 hour *Hyperaccumulators table – 3 *Radioactivity in biology *Radiometric dating *Radionuclide cisternogram *Uses of radioactivity in oil and gas wells


Notes


References

* * *


Further reading

*


External links


EPA – Radionuclides
– EPA's Radiation Protection Program: Information.
FDA – Radionuclides
– FDA's Radiation Protection Program: Information.
Interactive Chart of Nuclides
– A chart of all nuclides
National Isotope Development Center
– U.S. Government source of radionuclides – production, research, development, distribution, and information
The Live Chart of Nuclides – IAEA Radionuclides production simulator – IAEA
{{Authority control Radioactivity Isotopes Nuclear physics Nuclear chemistry