Embrittlement and fracture toughness of highly irradiated austenitic steels for vessel internals of WWER type reactors. Part 2. Relation between irradiation swelling and irradiation embrittlement. Physical and mechanical behavior

Abstract

The mechanical test results and fractographic observations reported in Part 1 are discussed from the standpoint of possible fracture mechanisms in austenitic steels subjected to intensive neutron irradiation. We put forward the mechanisms that relate the γ →α-transformation to the occurrence of a ductile–brittle transition in the irradiated austenitic steels and presents a criterion that defines the irradiation conditions whereby the γ →α-transformation leads to the ductile–brittle transition. Some possible reasons for the deterioration of the material ultimate strength at a very high (above 20%) level of swelling are discussed.