Abstract
The JSME fitness-for-service code provides a fracture assessment method based on the linear-elastic fracture mechanics for neutron irradiated reactor internals. This method is adopted since a neutron irradiation decreases fracture toughness of austenitic stainless steels used for reactor internals, and is not necessarily based on the actual fracture behavior for the irradiated stainless steels. In this study, fracture modes for compact specimens and a core shroud, which consisted of irradiated stainless steels, were investigated by using tensile and fracture toughness test data for stainless steels irradiated in the BWR condition. A fracture assessment diagram was used to investigate the fracture modes. As a result of an investigation, it was indicated that the fracture mode for a core shroud was considered to be elastic-plastic fracture, even when the core shroud had relatively large through-wall crack. Moreover, it was found that an application of elastic-plastic fracture assessment method significantly affected the structural integrity evaluation for core shroud with a crack.
