Wigner energy
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Wigner energy is created inside nuclear reactors that use graphite, a form of carbon, as neutron moderator. When the graphite is bombarded with neutrons from the reactor core, crystalline dislocations occur as a result of the Wigner effect, causing the graphite rods to swell and begin storing the energy. This energy is problematic for nuclear reactors because it can be spontaneously and rapidly released from the graphite in the form of heat, and unplanned excess heat is not a desirable situation within a nuclear reactor.
The Windscale fire was an incident where plant operators used a process known as annealing in an attempt to reduce stored Wigner energy. This required shutting off the core's cooling system and allowing internal temperatures to rise, resulting in a gradual bleeding-off of Wigner energy. The first fifteen attempts of this process was completed successfully, but due to inaccurate temperature monitoring in the core, the sixteenth resulted in extremely high temperatures and a chain reaction. This led to canisters of materials in the core rupturing and subsequently igniting, causing a release of radioactive gases and particulates into the atmosphere. A more serious incident was averted when the fire was extinguished using a high-risk strategy of flooding the core with water.
External links
- An article on the Windscale fire, by the Lake District Tourist Board (http://www.lakestay.co.uk/1957.htm)de:Wigner-Energie