IRRADIATION PERFORMANCE OF STAINLESS-STEELS FOR ITER APPLICATION

The proposed normal operating temperature range far the ITER first wal l/shield structure (100-250 degrees C) is below the temperature regime s for void swelling (400-600 degrees C) and for grain boundary embritt lement (500-700 degrees C). However, the neutron doses for the basic p erformance phase (3-4 dpa) and the extended performance phase (20-30 d pa) are such that large changes in yield strength, deformation mode, a nd strain hardening capacity will be encountered which could significa ntly affect fracture properties, Yield strength increases rapidly with dose in the 60-300 degrees C regime with the increase tending to satu rate at 1-3 dpa. Under certain conditions, radiation hardening is acco mpanied by changes in the stress-strain relationship with the appearan ce of an initial yield drop and a significant reduction in strain hard ening capacity, This paper reviews the low temperature (< 400 degrees C) tensile and fracture toughness properties changes seen in 300-serie s stainless steels after neutron irradiation and discusses the implica tions for the design of the ITER first wall/shield.