Radioactive contamination
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2008-06-14T21:09:16Z
Gregz08
6705509
/* Low level contamination */ typo
{{unreferenced|date=December 2007}}
{{Pollution}}
[[Image:Radiation warning symbol.svg|thumb|right|The radiation warning symbol (''trefoil'').]]
[[Image:Periodic Table by Radioactivity.PNG|right|450px|thumb|Periodic table colored according to the radioactivity of the most stable isotope .<br>
(1) <span style="color:blue">stable elements.</span><br>
(2) <span style="color:green">radioactive elements with isotopes with very long decay half-times.</span> Their half-live of over a million years gives them very small, if not negligible radioactivities and thus may be handled without any precautions.</span><br>
(3) <span style="color:#FFD800">radioactive elements that may present low health hazards.</span> Their half-time of over 500 years allows them to have commercial applications due to the fact that their radiation levels are near the [[background radiation|background one]].<br>
(4) <span style="color:#FF7E00">radioactive elements that are known to pose high safety risks.</span> Their half-life of over a day and their radioactivity levels make them have little potential for any commercial use.<br>
(5) <span style="color:red">highly radioactive elements.</span> Because of their half-time as low as a couple of minutes, they pose severe health risks and is unlikely that they will receive any use outside basic research.</span><br>
(6) <span style="color:brown">extremely radioactive elements.</span> Very little is known about these elements, and will likely never receive any attention outside research laboratories.</span>]]
'''Radioactive contamination''' is the uncontrolled distribution of [[radioactive decay|radioactive]] material in a given environment. The amount of radioactive material released in an accident is called the '''source term'''.
== Sources of contamination ==
Radioactive contamination is typically the result of a spill or accident during the production or use of [[radionuclide]]s (radioisotopes), an unstable nucleus which has excessive energy. Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in [[nuclear medicine]] is accidentally spilled, the material could be spread by people as they walk around. Radioactive contamination may also be an inevitable result of certain processes, such as the release of radioactive [[xenon]] in [[nuclear reprocessing|nuclear fuel reprocessing]]. In cases that radioactive material cannot be contained, it may be diluted to safe concentrations. [[Nuclear fallout]] is the distribution of radioactive contamination by a [[nuclear explosion]]. For a discussion of environmental contamination by [[alpha particle|alpha]] emitters please see [[actinides in the environment]]. Containment is what differentiates radioactive material from radioactive contamination. Therefore, radioactive material in sealed and designated containers is not properly referred to as contamination, although the units of measurement might be the same.'''
==Measurement==
Radioactive contamination may exist on surfaces or in volumes of material or air. In a [[nuclear power plant]], detection and measurement of radioactivity and contamination is often the job of a [[Certified Health Physicist]].
=== Surface contamination ===
Surface contamination is usually expressed in units of radioactivity per unit of area. For [[SI]], this is [[becquerel]]s per [[square meter]] (or Bq/m²). Other units such as picoCuries per 100 cm² or [[counts per minute|disintegrations per minute]] per square [[centimeter]] (1 dpm/cm² = 166 2/3 Bq/m²) may be used. Surface contamination may either be fixed or removable. In the case of fixed contamination, the radioactive material cannot by definition be spread, but it is still measurable.
==Hazards==
In practice there is no such thing as zero radioactivity. Not only is the entire world constantly bombarded by [[cosmic ray]]s, but every living creature on earth contains significant quantities of [[carbon-14]] and most (including humans) contain significant quantities of [[potassium-40]]. These tiny levels of radiation are not any more harmful than sunlight, but just as excessive quantities of sunlight can be dangerous, so too can excessive levels of radiation.
=== Low level contamination ===
The hazards to people and the environment from radioactive contamination depend on the nature of the radioactive contaminant, the level of contamination, and the extent of the spread of contamination. Low levels of radioactive contamination pose little risk, but can still be detected by radiation instrumentation. In the case of low-level contamination by isotopes with a short half-life, the best course of action may be to simply allow the material to naturally [[radioactive decay|decay]]. Longer-lived isotopes should be cleaned up and properly disposed of, because even a very low level of radiation can be life-threatening when in long exposure to it. Therefore, whenever there's any radiation in an area, many people take extreme caution when approaching.
=== High level contamination ===
High levels of contamination may pose major risks to people and the environment. People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an [[nuclear accident|accident]] (or a [[nuclear weapon|deliberate initiation]]) involving large quantities of radioactive material. The [[radiation poisoning|biological effects of external exposure]] to radioactive contamination are generally the same as those from an external radiation source not involving radioactive materials, such as [[x-ray]] machines, and are dependent on the [[absorbed dose]].
=== Biological effects ===
See also: [[Radiation poisoning]]
The biological effects of internally deposited [[radionuclide]]s depend greatly on the activity and the biodistribution and removal rates of the radionuclide, which in turn depends on its chemical form. The biological effects may also depend on the chemical [[toxicity]] of the deposited material, independent of its radioactivity. Some radionuclides may be generally distributed throughout the body and rapidly removed, as is the case with [[tritium|tritiated water]]. Some radionuclides may target specific organs and have much lower removal rates. For instance, the [[thyroid]] gland takes up a large percentage of any [[iodine]] that enters the body. If large quantities of radioactive iodine are inhaled or ingested, the thyroid may be impaired or destroyed, while other tissues are affected to a lesser extent. Radioactive iodine is a common [[nuclear fission|fission product]]; it was a major component of the radiation released from the [[Chernobyl disaster]], leading to many cases of pediatric [[thyroid cancer]] and [[hypothyroidism]]. On the other hand, radioactive iodine is used in the diagnosis and treatment of many diseases of the thyroid precisely because of the thyroid's selective uptake of iodine.
== Means of contamination ==
Radioactive contamination can enter the body through [[ingestion]], [[inhalation]], [[absorption]], or [[injection (medicine)|injection]]. For this reason, it is important to use [[personal protective equipment]] when working with radioactive materials. Radioactive contamination may also be ingested as the result of eating contaminated plants and animals or drinking contaminated water or milk from exposed animals. Following a major contamination incident, all potential pathways of internal exposure should be considered.
==See also==
* [[Background radiation]]
* [[Chernobyl disaster]]
* [[Criticality accident]]
* [[Exotic pollution]]
* [[Ionizing Radiation]]
* [[Kory Johnson]]
* [[Nuclear and radiation accidents]]
* [[Radiation biology]]
* [[Radiation poisoning]]
* [[Radioactive waste]]
* [[Radiophobia]]
* [[Relative Biological Effectiveness]]
* [[Rongelap Atoll]]
<!--Categories-->
[[Category:Radioactive waste]]
[[Category:Nuclear accidents]]
[[Category:Nuclear safety]]
[[Category:Radiobiology]]
[[Category:Hazards]]
[[bg:Радиоактивно замърсяване]]
[[es:Contaminación radiactiva]]
[[fr:Pollution radioactive]]
[[ja:被曝]]
[[pl:Skażenie radioaktywne]]
[[ru:Радиационная экология]]
[[zh:放射性污染]]