The Wigner effect (named for its discoverer, E. P. Wigner), also known as the discomposition effect, is the displacement of atoms in a solid caused by neutron radiation. Any solid can be affected by the Wigner effect, but the effect is of most concern in neutron moderators, such as graphite, that are used to slow down fast neutrons. The material surrounding the moderator receives a much smaller amount of neutron radiation, and from slower neutrons, and is not as worrisome.
An interstitial atom and its associated vacancy are known as a Frenkel defect.
Read more about Wigner Effect: Explanation, Dissipation of Wigner Energy, Intimate Frenkel Pairs
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