Nuclear and radiation accidents
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Image:Atmospheric radiation to human.jpg Template:TOCright This article covers notable accidents involving nuclear devices and radioactive materials. In some cases, these incidents involve people being injured or killed due to the release of radioactive contamination. Most incidents involve accidental releases that have caused contamination, but had no other immediate effects. Due to government and business secrecy, it is difficult to determine with certainty the extent of some events listed below.
Because of the different nature of the events it is best to divide the list into nuclear and radiation accidents. An example of nuclear accident might be one in which a reactor core is damaged such as Three Mile Island, while an example of a radiation accident might be some event such as a radiography accident where a worker drops the source into a river or sticks it in his pocket. These radiation accidents such as those involving the radiography sources often as not as widely reported in the popular press but they often have as much, or even greater, ability to cause serious harm to both workers and the public than the well known nuclear accidents.
Radiation accidents are more common than nuclear accidents, and are often limited in scale. For instance at Soreq a worker suffered a dose which was similar to one of the highest doses suffered by a worker on site at Chernobyl on day one, but, because the gamma source was never able to leave the 2 metre thick concrete enclosure, it was not able to harm many others.
The web page at the IAEA which deals with recent accidents is [1]. The safety significance of nuclear accidents can be assessed and conveyed using the IAEA International Nuclear Event Scale.
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Accident types
Loss of coolant accident
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Criticality accidents
Criticality accidents and power excursions in nuclear reactors, for example the Chernobyl accident. In a smaller scale accident at Sarov a man working with highly enriched uranium was irradiated while attempting an experiment involving a sphere of fissile material. The Sarov accident is interesting because the system remained critical for many days before it could be stopped. This is an example of a limited scope accident where only a few people can be harmed, while no release of radioactivity into the environment occurred. A well known example of this type of accident occurred in Japan in 1999 [2].
Decay heat
Decay heat accidents where the heat generated by the radioactive decay causes harm. In a nuclear reactor that has been shut down, a loss of coolant accident can damage the core, for instance at Three Mile Island a recently shutdown (SCRAMed) PWR reactor was left for a length of time without cooling water. As a result the nuclear fuel was damaged, and the core was partly melted.
Transport
Transport accidents can cause a release of radioactivity resulting in contamination or shielding to be damaged resulting in direct irradiation. In Cochabamba a defective gamma radiography set was transported in a passenger bus as cargo. The gamma source was outside the shielding, and it irradiated some bus passengers.
In the United Kingdom, it was revealed in a recent court case that a radiotherapy source was transported from Leeds to Sellafield with defective shielding. The shielding had a gap on the underside. It is thought that no human has been seriously harmed by the escaping radiation.
Equipment failure
Equipment failure is one possible type of accident, recently at Białystok in Poland the electronics associated with a particle accelerator used for the treatment of cancer suffered a malfunction [3]. This then lead to the overexposure of at least one patient. While the initial failure was the simple failure of a semiconductor diode, it set in motion a series of events which led to a radiation injury.
Human error
Human error has been responsible for some accidents, for instance a person miscalculated the activity of a teletherapy source. This then lead to patients being given the wrong dose of gamma rays. In the case of radiotherapy accidents, an underexposure is as much an accident as an overexposure as the patients may not get the full benefit of the proscribed treatment. Also, humans have made errors while attempting to service plant and equipment which has resulting in overdoses of radiation, such as the Nevvizh and Soreq irradiator accidents.
Lost source
Lost source accidents[4][5] are ones in which a radioactive source is lost, stolen or abandoned. The source then might cause harm to humans or the environment. For example, see the event in Lilo where sources were left behind by the Soviet army. Another case occurred at Yanango where a radiography source was lost, also at Samut Prakarn a cobalt-60 teletherapy source was lost [6] and at Gilan in Iran a radiography source harmed a welder [7]. The best known example of this type of event is the Goiânia accident which occured in Brazil.
Others
Some accidents defy classification. These accidents happen when the unexpected occurs with a radioactive source. For instance if a bird grabs a radioactive source containing radium from a windowsill and then was to fly away with it, returning to its nest and then the bird dies shortly afterwards from direct irradiation then it is the case that a minor radiation accident has occured. As the act of placing the source on a window sill by a human was the event which permitted the bird access to the source, it is unclear how such an event should be classified (if is a lost source event or a something else). If you read Radium lost and found[8][9] you will encounter the tale of a pig walking about with a radium source inside, this was a radium source lost from a hospital.
Also some accidents are "normal" industrial accidents which happen to involve radioactive material, for instance a runaway reaction at Tomsk (see red oil) caused radioactive material to be spread around the site.
For a list of many of the most important accidents please see the IAEA site [10].
Civilian nuclear accidents
- Main article: List of civilian nuclear accidents
Civilian radiation accidents
- Main article: List of civilian radiation accidents
Military nuclear accidents
- Main article: List of military nuclear accidents
See also
- International Nuclear Events Scale
- List of disasters
- List of nuclear reactors - a comprehensive annotated list of the world's nuclear reactors
- Radiation
- United States military nuclear incident terminology
- Fuel element failure
References & External Links
- Schema-root.org: Nuclear Power Accidents 2 topics, both with a current news feed
- US Nuclear Regulatory Commission (NRC) website with search function and electronic public reading room
- International Atomic Energy Agency website with extensive online library
- Canada's Nuclear Safety Commission (CNSC)
- Concerned Citizens for Nuclear Safety Detailed articles on nuclear watchdog activities in the US
- World Nuclear Association: Radiation Doses Background on ionizing radiation and doses
- Canadian Centre for Occupational Health & Safety More information on radiation units and doses.
- Radiological Incidents Database Extensive, well-referenced list of radiological incidents.
- Nuclear Files.org List of nuclear accidents
- Annotated bibliography of military and civilian nuclear accidents from the Alsos Digital Library
- Critical Hour: Three Mile Island, The Nuclear Legacy, And National Security Online book by Albert J. Fritsch, Arthur H. Purcell, and Mary Byrd Davis (2005)cs:Jaderná havárie
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