Practica

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Radioactive contamination

Radioactive contamination, also called radiological contamination, is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids or gases (including the human body), where their presence is unintended or undesirable (from IAEA definition).[1]
Such contamination presents a hazardbecause of the radioactive decay of the contaminants, which emit harmful ionising radiation such as alpha or beta particles, gamma rays orneutrons. The degree of hazard is determined by the concentration of the contaminants, the energy of the radiation being emitted, the type of radiation, and the proximity of the contamination to organs of the body. It is important to be clear that thecontamination gives rise to the radiation hazard, and the terms "radiation" and "contamination" are not interchangeable.
Contamination may affect a person, a place, an animal, or an object such as clothing. Following an atmospheric nuclear weapon discharge or a nuclear reactor containment breach, the air, soil, people, plants, and animals in the vicinity will become contaminated by nuclear fuel and fissionproducts. A spilled vial of radioactive material like Uranyl nitrate may contaminate the floor and any rags used to wipe up the spill. Cases of widespread radioactive contamination include the Bikini Atoll, the Rocky Flats Plant in Colorado, theFukushima Daiichi nuclear disaster, the Chernobyl disaster, and the area around the Mayak facility in Russia.
Cleaning up contamination resultsin radioactive waste unless the radioactive material can be returned to commercial use by reprocessing. In some cases of large areas of contamination, the contamination may be mitigated by burying and covering the contaminated substances with concrete, soil, or rock to prevent further spread of the contamination to the environment. If a person's body is contaminated by ingestion or by injury and standardcleaning cannot reduce the contamination further, then the person may be permanently contaminated.
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]Sources of contamination
Global airborne contaminationAtmospheric nuclear weapon tests almost doubled the concentration of 14C in the Northern Hemisphere. Plot of atmospheric14C, New Zealand[2] and Austria.[3] The New Zealand curve is representativefor the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. .[4]
Radioactive contamination is typically the result of a spill or accident during the production, or use of, radionuclides (radioisotopes); these have unstable nuclei which are subject to radioactive decay.
Less typically, nuclear fallout is the distribution of radioactive contamination by a nuclearexplosion. The amount of radioactive material released in an accident is called the source term.
Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in nuclear medicine is spilled (accidentally or, as in the case of the Goiânia incident, through ignorance), the material could be spread by people as they walk around. Radioactive contaminationmay also be an inevitable result of certain processes, such as the release of radioactive xenon in nuclear fuel reprocessing. In cases that radioactive material cannot be contained, it may be diluted to safe concentrations. For a discussion of environmental contamination by alpha emitters please see actinides in the environment.
Contamination does not include residual radioactivematerial remaining at a site after the completion of decommissioning. Therefore, radioactive material in sealed and designated containers is not properly referred to as contamination, although the units of measurement might be the same.
Being within the intended "Containment" differentiates radioactive material from radioactive contamination. When radioactive materials are concentrated to a detectable level...