Determination of effective charge states for point radiation defects in fusion ceramic materials

Point defects in fusion ceramic materials under irradiation can have an effective charge due to ionization and covalent chemical bonding. The kinetics of charged point defects in these materials is determined by their effective charge and this kinetics is completely different from non-charged point defects in metals. The experimental investigation of point defect charge states in ceramic materials is rather difficult. In this paper, a new method is proposed for the investigation of charge states of point defects in irradiated ceramic materials. This method is based on a new theoretical model and experimental observations of defect cluster formation near permanent sinks, such as grain boundaries. Previous experimental investigations show that a denuded zone is formed in irradiated ceramic materials near free surfaces and grain boundaries. The effect of an applied electric field on the formation of interstitial-type point defect clusters (dislocation loops) near grain boundaries in irradiated ceramic materials is investigated. For this purpose a new theoretical model is suggested, which takes into account the effect of an applied electric field on the denuded zone formation. It is shown that the denuded zone size depends on point defect charge and direction of applied electric field. The obtained theoretical results are compared with experimental data.