Influence of cascade micropores on diffusion fluxes of point defects in reactor vessels materials

The main mechanism determining radiation embrittlement of the materials of reactor vessels are considered to be a change in the cohesive strength of the grain boundaries resulting from the segregation of surface-active impurities (mainly phosphorous), hardening of the material by precipitations of a second phase, segregation of impurities onto interphase surfaces of the precipitate-matrix interface and an associated increase in the hardening effect of the radiation precipitations. The materials of reactor vessels are irradiated at a temperature of 250–300°C which is insufficiently high for the thermal activation of diffusion processes. When describing the process of an accelerated diffusion of copper and phosphorous atoms by irradiation, a model has so far normally been used which neglects the cascade mechanism for generating defects and also the formation and evolution of point defect complexes. Individual studies taking account of the reduction in the efficiency of generating point defects in cascades due to the formation of micropores contain certain deficiencies. The present work is devoted to developing and analyzing a satisfactory model of radiation damage which is to a considerable extent free of these deficiencies. Translated from Atomnaya énergiya, Vol. 86, No. 5, pp. 370–383, May, 1999.