Correlation between Cleavage Fracture Toughness and Charpy Impact Properties in the Transition Temperature Range of Reactor Pressure Vessel Steels

Abstract

In the surveillance program for the reactor pressure vessel, fracture toughness is estimated by assuming that the shift of transition temperature on fracture toughness is equivalent to the shift on measured Charpy impact properties. Therefore, it is necessary to establish the correlation between both shifts of transition temperature. In this study, we applied the master curve approach adopted in the ASTM E1921 method to fracture toughness testing. The materials used are five ASTM A533B class 1 steels and one weld metal. Neutron irradiation for Charpy-size fracture toughness test specimens and standard Charpy-v specimens was carried out at the Japan Materials Testing Reactor (JMTR). A correlation between the reference temperature on fracture toughness and Charpy transition temperatures before and after irradiation is established. Based on this correlation, the optimum test temperature for fracture toughness testing is suggested. The method to determine a lower bound fracture toughness curve is also discussed.