Irradiation effects on austenitic stainless steels for structural materials of IFMIF components

Full text of publication follows: Austenitic stainless steel, such as 316 stainless steel is one of the candidate structural materials for the target component and test modules of the International Fusion Materials Irradiation Facility IFMIF, as well as that for ITER shield blanket. Anticipated displacement damage levels for the ITER shield blanket are as large as 3 displacements per atom (dpa), while those for the IFMIF target components and test modules will attain a high damage level of 50 dpa or even higher, depending on the service period. The anticipated operating temperature of the components is lower than 400 deg. C; therefore irradiation will cause hardening and reduction of elongation, as well as degradation of fracture toughness. This paper reviews the degradation of mechanical properties of austenitic stainless steels introduced by irradiation to some tens of dpa level; degradation of fatigue properties, fracture toughness and ductility, as well as irradiation induced creep. Additional data, especially those at temperatures lower than 300 deg. C, are also introduced. The results have been obtained during the collaborative irradiation experiment between JAEA and US-DOE using HFIR. Irradiation causes degradation in mechanical properties of the austenitic stainless steels. However, residual ductility and fracture toughness still seem to be large enough for the application as structural materials. This, however, does not assure that the current design criterion is applicable for the component engineering. A dedicated effort to develop engineering design criteria also needs to be accomplished. (authors)