Behavior of mechanical properties of nickel-alloyed reactor pressure vessel steel under neutron irradiation and post-irradiation annealing

The effect of neutron irradiation and post-irradiation thermal annealing on tensile and impact properties of Cr-Ni-Mo steel used for WWER-1000 reactor pressure vessel (RPV) manufacturing was studied. A gap in yield stress and ultimate tensile stress fluence dependence at the fluence range of 0-3 x 1 0(23) neutrons m(-2) was observed while ductile-to-brittle transition tempe rature (DBTT) was continuously increasing with damage dose. The post-irradi ation annealing recovery of tensile properties was found to be higher than the one of impact properties. Over-recovery of tensile properties due to 46 0 and 490 degrees C post-irradiation annealings were observed. The annealin g effectiveness of WWER-440 and WWER-1000 grades was compared. Nickel was s upposed to affect both the radiation sensitivity and the post-irradiation r esidual DBTT shift of WWER-1000 type steel. (C) 1998 Elsevier Science S.A. All rights reserved.