Effect of temperature change on the irradiation hardening of the structural alloys for ITER blanket and ITER TBM irradiated to 1.5 dpa in JMTR

A reduced activation ferritic steel and an austenitic stainless steel were irradiated at temperatures of 230 °C and 350 °C in an irradiation capsule with temperature control capability independent from reactor power to accumulated damage levels of about 1.5 displacement per atom (dpa). For some of the specimens temperature was changed during irradiation. The temperature change reduced the irradiation hardening of the austenitic steel. Conversely, it slightly increased the hardening of the reduced activation ferritic steel. The mechanism of the observed temperature change effect and the impact of the additional hardening on the residual ductility is discussed.