Irradiation performance of stainless steels for ITER application

The proposed normal operating temperature range far the ITER first wall/shield structure (100-250 degrees C) is below the temperature regimes for void swelling (400-600 degrees C) and for grain boundary embrittlement (500-700 degrees C). However, the neutron doses for the basic performance phase (3-4 dpa) and the extended performance phase (20-30 dpa) are such that large changes in yield strength, deformation mode, and strain hardening capacity will be encountered which could significantly affect fracture properties, Yield strength increases rapidly with dose in the 60-300 degrees C regime with the increase tending to saturate at 1-3 dpa. Under certain conditions, radiation hardening is accompanied by changes in the stress-strain relationship with the appearance of an initial yield drop and a significant reduction in strain hardening capacity, This paper reviews the low temperature (< 400 degrees C) tensile and fracture toughness properties changes seen in 300-series stainless steels after neutron irradiation and discusses the implications for the design of the ITER first wall/shield.