List of nuclear and radiation accidents

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(Tagged December 2005)

Image:Atmospheric radiation to human.jpg

1 Accident types
2 Civilian nuclear accidents
3 Civilian radiation accidents
4 Military nuclear accidents
5 See also
6 References & External Links

This article covers notable accidents involving nuclear and radioactive material. 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.

The list includes both nuclear and radiation accidents.

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 a greater ability) to cause serious harm to both workers and the public than the well known nuclear accidents.

It is also important to note that radiation accidents are more common than nuclear accidents, and oftein the scale of a radiation accident is limited. 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 well sheilded (circia 2 m of concrete) enclosure it was not able to harm many others. In this case the follwing analogy can be applied 'a man entered a lions den and was attacked at Soreq, while at Chernobyl the lion escaped from his den and was able to attack bystanders'.

It is important to keep everything in perspective, for instance the Chernobyl accident was very bad, and it is an event which has captured the public's attention. But the Bhopal disaster was much bigger, but because it was not a nuclear or radiation accident it has not captured the public's attention. In a similar way the accident in Japan which killed two people and seriously injured one has had much more attention than the Ladbroke Grove rail crash which occurred within days of the criticality in Japan.

The web page at the IAEA which deals with recent accidents is [1].

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Accident types

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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].

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Decay heat

Decay heat accidents where the heat generated by the radioactive decay causes harm. In a nuclear reactor which 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.

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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.

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Equipment failure

Equipment failure is one possible type of accident, recently at Bialystock 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.

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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, for example see the Nevvizh and Soreq irradiator accidents.

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Lost source

Lost source accidents 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 Soviet army. Another case occurred at Yanango where a radiography source was lost, also at Samut Prakarn a cobalt-60 teletherapy source was lost [4] and at Gilan in Iran a radiography source harmed a welder [5].

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Others

Some accidents defy classification, these are accidents where the unexpected occurs involving a radioactive device. For instance it is thought that a bird once grabbed a radium containing medical source from a windowsill and flew away with it. The source has never been recovered, it is thought that the bird flew back to its nest and died shortly afterwards from direct irradiation. As the act of placing the source on a windowsill by a human was the event which permitted the bird access to the source, it is unclear how such an event should be classified.

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 [6].

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