Development of fracture toughness curve for PTS evaluation of reactor pressure vessels incorporating Master curve concept

The reactor pressure vessel is made of ferritic low alloy steel, which has fracture behaviors that include ductile to brittle transition temperature and decrease of fracture toughness in the beltline region of the reactor pressure vessel steel due to irradiation embrittlement. Decrease of fracture toughness due to irradiation during plant operation needs to be taken into account in the assessment of the reactor pressure vessel against pressurized thermal shock events. A large number of fracture toughness data were accumulated in domestic PWR plant surveillance program tests and knowledge on the fracture toughness evaluations, such as scattering, were obtained through research works. In this study, fracture toughness curve for the assessment of domestic reactor pressure vessels were developed taking into consideration the latest knowledge on fracture toughness evaluations, including investigations on fracture toughness data scattering and fracture toughness curve reliability.