抄録
In the surveillance program for reactor pressure vessel (RPV), Charpy impact properties are measured concerning neutron irradiation embrittlement. Fracture toughness values are estimated by assuming that radiation effect on fracture toughness is equivalent to that on Charpy properties. Therefore, it is necessary to establish the correlation between both properties especially on irradiation embrittlement. In this paper, we present the fracture toughness data obtained by applying the master curve approach that was adopted recently in the ASTM test method E1921. Materials used in this study are five ASTM A533B class 1 steels and one weld metal. The specimen size effect on the reference temperature in the ductile-brittle transition range was studied by comparing the data by Charpy-size, 25mm thick CT and larger size specimens. Neutron irradiation for Charpy-size specimens as well as standard Charpy-v specimens was carried out at the Japan Materials Testing Reactor (JMTR). The shifts of the reference temperature on fracture toughness due to neutron irradiation are compared with Charpy transition temperature shifts. Correlation between the reference temperature on fracture toughness and Charpy transition temperatures is established. Based on the correlation, the optimum test temperature for fracture toughness testing is suggested. The method to determine a lower bound fracture toughness curve is also discussed.
