Wigner effect

Wigner energy (detected by Eugene Paul Wigner ) is the energy which can be stored in the crystal lattice of graphite. It plays a role in the graphite- safety nuclear reactors.

Physical background

During operation of the reactor, the graphite is irradiated by fast neutrons. This carbon atoms from the crystalline lattice structure can be moved to interstitial sites. The graphite expands thereby easily and it develops crystal defects, save the energy. The graphite is partly metamict. This stored energy is referred to as a Wigner energy. It can be spontaneously and abruptly released as heat. Since such an uncontrolled temperature rise is a security risk, which is stored in presenter Wigner energy must not be too large.

The flaws begin at about 250 ° C to recombine and thereby set the Wigner energy is slowly released. Therefore, can the moderator " Bake ". To the reactor for some time must be maintained at an appropriately high temperature. In graphite-moderated reactors, the high temperature " bake " is automatic in operation, as the core temperature is sufficiently high.

When trying the stored Wigner energy of the air-cooled graphite moderator of the reactor Pile no. 1 at Windscale to reduce (today better known as Sellafield ), it came 1957 to the Windscale fire, one of the most serious accidents in the civilian nuclear technology before the Chernobyl disaster.