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Thursday, November 6, 2008

People injured in nuclear accidents

Nuclear power plants are generally touted to be safe (with the exception of Chernobyl or Three Mile), but like any other facility, there have been accidents in which people have been injured. Link to read:

A criticality accident, sometimes referred to as an excursion or a power excursion, occurs when a nuclear chain reaction accidentally occurs in fissile material, such as enriched uranium or plutonium. This releases neutron radiation which is highly dangerous to surrounding personnel and causes induced radioactivity in the surroundings.
Nuclear fission normally is supposed to occur inside reactor cores and inside some test facilities. However, if fission occurs due to an accidental cause, such as a criticality accident, the radiation emitted poses a high risk of serious injury or even death to workers up to at least 20 metres (66 feet) away. Although dangerous, the low densities of fissile material and the long insertion time involved in these events limit the fission yield and peak power, preventing them from becoming a large scale nuclear explosion.

Criticality can be achieved by using metallic uranium or plutonium or by mixing compounds or liquid solutions of these elements. The isotopic mix, the shape of the material, the chemical composition of solutions, compounds, alloys, composite materials, and the surrounding materials all influence whether the material will go critical, i.e., sustain a chain reaction.
The calculations that predict the likelihood of a material going into a critical state can be complex, so both civil and military installations that handle fissile materials employ specially trained criticality officers to monitor operations and prevent criticality accidents

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