Comparison of Transition Temperature Shifts Between Static Fracture Toughness and Charpy-v Impact Properties Due to Irradiation and Post-Irradiation Annealing for Japanese A533B-1 Steels

摘要

It is assumed in the integrity analysis of reactor pressure vessel (RPV) that the irradiation-induced shift of fracture toughness in the ductile-brittle transition region is the same as the Charpy transition temperature shift. To confirm this assumption, both shifts are compared using irradiated and post-irradiation annealed RPV steels made by Japanese manufacturers. Five ASTM A533B class 1 plates having high- and low-level impurities, which correspond to first generation and modern Japanese reactors are used in this study. Neutron irradiation of precracked Charpy-v (PCCv) specimens as well as standard Charpy-v specimens was carried out at the Japan Materials Testing Reactor (JMTR). The values of fast neutron fluence for this study are 2 to 13Xl0~(19) (n/cm~2, E>lMeV) considering typical fluence values at the EOL and extended operation of Japanese PWRs. The irradiation temperature was controlled within the range of 290+-10°C. Thermal annealing treatments at 350°C and 450°C for 100 hours were performed for irradiated PCCv and Charpy-v specimens. The master curve approach according to ASTM Test Method for Determination of Reference Temperature, T_0, for Ferritic Steels in the Transition Range (El921) was applied using PCCv specimens. The irradiation-induced shifts of the reference temperature, ΔT_0, obtained in this study were spread in the range of 10 to 200°C. The annealing recoveries of the reference temperature were compared with those of the Charpy transition temperature. Although large scatter was seen in the relation between ΔT_0 values and Charpy 41J shifts, both shifts were almost the same in the average.