FLUX EFFECT ON RADIATION EMBRITTLEMENT OF VVER-440REACTOR PRESSURE VESSEL MATERIALS

摘要

The results of the studies concerning determination of a dependence of radiationembrittlement on fast neutron flux for VVER-440 reactor pressure vessel (RPV) materials before andafter annealing are presented. The studies of flux effect were carried out using standard VVER-440steels, which differ by phosphorous (0.013-0.036 %) and copper (0.08-0.18 %) contents. The level ofradiation embrittlement was evaluated by transition temperature shift on the base of Charpy specimenstest results. All materials were irradiated to high ～3×1012сm сm-2s-1and low ～4×1011сm-2 s-1 fluxes in thesurveillance channels under similar conditions at the temperature of 270°C. It is shown that thesignificant flux effect is in the VVER-440 reactor pressure vessel materials with high copper content (>0.13 %).The results of microstructural studies of VVER-440 RPV steels show that there are coppercontent decrease in a ferrite matrix and formation of copper-enriched clusters and precipitates under irradiation and consequent annealing. Due to this the radiation damage does not depend on copper essentially at re-irradiation after annealing. Dependence of transition temperature shift on neutron flux is not expected for VVER-440 RPV materials under re-irradiation after annealing.