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A radionuclide is an atom with an unstable Goat, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created radiation particle within the nucleus, or else to an atomic electron (see internal conversion) . The radionuclide, in this process, undergoes radioactive decay, and emits a gamma ray(s) and/or subatomic particles. These particles constitute ionizing radiation. Radionuclides may occur naturally, but can also be artificially produced. Image File history File links Mergefrom. ... // $79 is the most common price but needle sources commonly go for $50 and the higher class emitters go for up to $140 ISOTOPE, ACTIVITY, HALF-LIFE, ENERGIES (KeV) Barium 133 1uCi 10. ... Properties For other meanings of Atom, see Atom (disambiguation). ... This article is about the domestic species. ... . Internal conversion is a radioactive decay process where an excited nucleus interacts with an electron in one of the lower electron shells, causing the electron to be emitted from the atom. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... This article is about electromagnetic radiation. ... Helium atom (not to scale) Showing two protons (red), two neutrons (green) and a probability cloud (gray) of two electrons (yellow). ... Radiation hazard symbol. ...

Radionuclides are often referred to by chemists and physicists as radioactive isotopes or radioisotopes, and play an important part in the technologies that provide us with food, water and good health. However, they can also constitute real or perceived dangers. For other uses, see Isotope (disambiguation). ...

Origin

Naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides and cosmogenic radionuclides. Primordial radionuclides originate mainly from the interiors of stars and, like uranium and thorium, are still present because their half-lives are so long that they have not yet completely decayed. Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Despite their relatively "short" half-lives, they are found in nature because their supply is always being replenished. This article is about the astronomical object. ... This article is about the chemical element. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Actinides Group, Period, Block n/a, 7, f Appearance silvery white Standard atomic weight 232. ... This article is about the computer game. ... Cosmogenic refers to rare radioactive isotopes created when cosmic radiation interacts with an atomic nucleus. ... Carbon-14 is the radioactive isotope of carbon discovered February 27, 1940, by Martin Kamen and Sam Ruben. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...

Artificially produced radionuclides can be produced by nuclear reactors, particle accelerators or by radionuclide generators: Core of a small nuclear reactor used for research. ...

• Radioisotopes produced with nuclear reactors exploit the high flux of neutrons present. The neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is thallium-201.
• Particle accelerators such as cyclotrons accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate protons at a target to produce positron emitting radioisotopes e.g. fluorine-18.
• Radionuclide generators contain a parent isotope that decays to produce a radioisotope. 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.

Trace radionuclides are those that occur in tiny amounts in nature either due to inherent rarity, or to half-lives that are significantly shorter than the age of the Earth. Synthetic isotopes are not naturally occurring on Earth, but they can be created by nuclear reactions. This article or section does not adequately cite its references or sources. ... A pair of Dee electrodes with loops of coolant pipes on their surface at the Lawrence Hall of Science. ... Fluorine-18 is a fluorine radioisotope which is an important source of positrons. ... Technetium-99m is a metastable nuclear isomer of technetium-99, symbolized as 99mTc. ... The first technetium cow (a device for separating Tc-99m from its parent isotope, Mo-99) at Brookhaven National Laboratory. ... Shown above is the bone scintigraphy of a young woman. ... There are 35 known isotopes of Molybdenum (Mo) ranging in atomic mass from 83 to 117, as well as four metastable nuclear isomers. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... In nuclear physics, a nuclear reaction is a process in which two nuclei or nuclear particles collide to produce products different from the initial particles. ...

Uses

Radionuclides are used in two major ways: for their chemical properties and as sources of radiation. Radionuclides of familiar elements such as carbon can serve as tracers because they are chemically very similar to the non-radioactive nuclides, so most chemical, biological, and ecological processes treat them in a near identical way. One can then examine the result with a radiation detector, such as a geiger counter, to determine where the provided atoms ended up. For example, one might culture plants in an environment in which the carbon dioxide contained radioactive carbon; then the parts of the plant that had laid down atmospheric carbon would be radioactive. For other uses, see Radiation (disambiguation). ... For other uses, see Carbon (disambiguation). ... A radioactive tracer is a substance containing a radioactive isotope (radioisotope). ... This article or section does not cite any references or sources. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ...

In medicine, radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about a person's internal anatomy and the functioning of specific organs. This is used in some forms of tomography: single photon emission computed tomography and positron emission tomography scanning. Single photon emission computed tomography (SPECT) is a nuclear medicine tomographic imaging technique using gamma rays. ... Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three-dimensional image or map of functional processes in the body. ...

Radioisotopes are also a promising method of treatment in hemopoietic forms of tumors, while the success for treatment of solid tumors has been limited so far. More powerful gamma sources sterilise syringes and other medical equipment. About one in two people in Western countries are likely to experience the benefits of nuclear medicine in their lifetime. Sterilization (or Sterilisation) is the elimination of all transmissible agents (such as bacteria, prions and viruses) from a surface or piece of equipment. ... Shown above is the bone scintigraphy of a young woman. ...

In biochemistry and genetics, radionuclides label molecules and allow tracing chemical and physiological processes occurring in living organisms, such as DNA replication or amino acid transport. Biochemistry (from Greek: , bios, life and Egyptian kēme, earth[1]) is the study of the chemical processes in living organisms. ... This article is about the general scientific term. ... DNA replication. ... This article is about the class of chemicals. ...

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. Various preserved foods Food preservation is the process of treating and handling food in such a way as to stop or greatly slow down spoilage to prevent foodborne illness while maintaining nutritional value, density, texture and flavor. ...

In agriculture and animal husbandry, radionuclides also play an important role. They produce high intake of crops, disease and weather resistant varieties of crops, to study how fertilisers and insecticides work, and to improve the production and health of domestic animals. Shepherd with his sheep in Făgăraş Mountains, Romania. ...

Industrially, and in mining, radionuclides 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. This article is about mineral extractions. ...

Most household smoke detectors contain the radionuclide americium formed in nuclear reactors, saving many lives. A smoke detector or smoke alarm is a device that detects smoke and issues an alarm to alert nearby people that there is a potential fire. ... General Name, Symbol, Number americium, Am, 95 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery white sometimes yellow Standard atomic weight (243) g·mol−1 Electron configuration [Rn] 5f7 7s2 Electrons per shell 2, 8, 18, 32, 25, 8, 2 Physical properties Phase solid Density (near... Core of a small nuclear reactor used for research. ...

Radionuclides 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. Natural radionuclides are used in geology, archaeology, and paleontology to measure ages of rocks, minerals, and fossil materials. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... For referencing in Wikipedia, see Wikipedia:Citing sources. ... Paleontology, palaeontology or palæontology (from Greek: paleo, ancient; ontos, being; and λόγος, logos, knowledge) is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. ...

Dangers

If radionuclides are released into the environment, through accident, poor disposal, or other means, they can potentially cause harmful effects of radioactive contamination. They can also cause damage if they are excessively used during treatment or in other ways applied to living beings. This is called radiation poisoning. Radionuclides can also cause malfunction of electrical devices. The radiation warning symbol (trefoil). ... Radiation poisoning, also called radiation sickness, is a form of damage to organ tissue due to excessive exposure to ionizing radiation. ...

References

• Carlsson J et al.:Tumour therapy with radionuclides: assessment of progress and problems. Radiotherapy and Oncology, Volume 66, Issue 2, February 2003, Pages 107-117. PMID 12648782. Available online as full text.

http://www.uic.com.au/nip27.htm

See also

• radiometric dating
• ionizing radiation
• Radionuclide cisternogram

Radiometric dating (often called radioactive dating) is a technique used to date materials, based on a comparison between the observed abundance of particular naturally occurring radioactive isotopes and their known decay rates. ... Radiation hazard symbol. ... A Radionuclide cisternogram is medical test which involves injecting a tracer through a needle into a patients cerebral spinal fluids (CSF) to check to see if it is flowing properly, or determine if there is a leak (also known as a CSF fistula) from the brain into the nasal...

External links

• PocketRad - A source for radioactive isotopes
• EPA - Radionuclides - EPA's Radiation Protection Program: Information.
• Interactive Chart of Nuclides - A chart of all nuclides