Abstract
Fast neutron emitted from the fission or fusion nuclear reactions induces various kinds of crystalline defects into ceramics. These defects can cause degradation of material properties. Dislocation loops are frequently formed in crystalline materials after high fluence fast neutron irradiation. These structures have been analyzed based on high-resolution electron microscopy and image simulations based on defects models. Local atomic configurations of interstitial loops formed in SiC, AlN and Si3N4 are reviewed. These loops are commonly formed on the closest packing plane in each crystal, and more than one layer is arranged to form specific atomic configurations in spite of an extra thickness corresponding only one tetrahedral layer. Physical property changes of these materials are discussed based on the presence of these defects.
