Radionuclide



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A radionuclide is an ionizing radiation. Radionuclides may occur naturally, but can also be artificially produced.

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.

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 cosmic rays. Despite their relatively "short" half-lives, they are found in nature because their supply is always being replenished.

Artificially produced radionuclides can be produced by nuclear reactors, particle accelerators or by radionuclide generators:

  • Radioisotopes produced with nuclear reactors exploit the high flux of Iridium-192. The elements that have a large propensity to take up the neutrons in the reactor have a high Barnes Number.
  • 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 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.

Uses

Radionuclides are used in two major ways: for their chemical properties and as sources of radiation. Radionuclides of familiar elements such as carbon dioxide contained radioactive carbon; then the parts of the plant that had laid down atmospheric carbon would be radioactive.

In positron emission tomography scanning.

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.

In amino acid transport.

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.

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.

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.

Most household smoke detectors contain the radionuclide americium formed in nuclear reactors, saving many lives.

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.

Dangers

If radionuclides are released into the environment, through accident, poor disposal, or other means, they can potentially cause harmful effects of radiation poisoning. Radionuclides can also cause malfunction of electrical devices.

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

 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Radionuclide". A list of authors is available in Wikipedia.