Radiation embrittlement of WWER-type reactor pressure vessel materials under reirradiation after annealing

Pressure vessel annealing is the unique method of irradiated reactor pressure vessel materials (RPVM) properties recovery. The present paper gives the results of investigation on recovery of the properties of the irradiated RPVM after annealing, repeated radiation (embrittlement) of RPVM during repeated irradiation (reirradiation) after annealing. The reembrittlement behaviour could be described by vertical, lateral and conservative shift of the initial transition temperature shift (TTS). The most restrictive conservative shift approach is used in the assessment of residual lifetime of annealed vessels. But experimental data and analysis shows that lateral shift approach could be representatively used to remove unnecessary conservatism. (author)