Wigner effect

E. Wigner, Effects of the electron interaction on the energy levels of electrons in metals, Trans. Faraday Soc. 34 678-685 (1938). 

Local defects in the molecular plane of graphite may involve fracture zones with 4- and 8-membered rings, as seen in Fig. 1, causing angle strain and lowering the aromaticity they may become annealed on heating (see above the Wigner effect). Other defects were enumerated by Dias (3. ... 

E.Creutz, H. Jupnik, and E.P.Wigner, Effect of Temperature on Total Resonance Absorption of Neutrons by Spheres of Uranium Oxide , J. Appl. Phys. 26, 276 (1955). 

E.P. Wigner, Effect of Small Perturbations on Pile Period , CP-3048, June 13, 1945. 

Wigner effect will be less pronounced. In the reactor actor, and M c is the migration area for neutrons in the... 

The Wigner effect was once a potential problem in the Hanford reactors. However, since the graphite operating temperatures have been increased, the stored energy is released during the normal operating cycle and special annealing runs are not required. 

Fast neutron irradiation of graphite causes displacement of lattice atoms and leads to graphite growth and distortion. The Wigner effect in graphite is also a problem in some high power research reactors. For these reactors, embrittlement of beryllium components must also be considered. 

The first line went into production with the preliminary aim of training personnel and, in doing so, producing featured blocks to accurate dimensions. By the end of June, two lines had been conunissioned and a satisfactory rate of machining had been achieved, just as scientists at Harwell discovered a phenomenon known as the Wigner effect, where blocks of graphite expanded in size as they were subjected to more and more neutron bombardment. This had been already observed in American reactors, and the practical implication was that the Windscale lattices as currently... 

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