Irradiation effects on reduced activation ferritic/martensitic steels-tensile, impact, fatigue properties and modelling

At temperatures below 400 degrees C, irradiation often causes hardening and reduction of elongation as well as toughness degradation to a considerable degree. Data, however, indicate that these changes remain in manageable ranges for ITER-TBM application. Moreover, the saturation tendency of these changes with neutron dose suggests that some of the reduced activation ferritic/martensitic steels are feasible even for future DEMO applications. It is also stressed that the development of a design methodology that is compatible with the large irradiation induced property changes is essential to enable these applications. Modelling activities for the macroscopic mechanical response are expected to play key roles in design methodology development. Macroscopic models of plasticity (a constitutive equation) and cyclic softening behaviour after irradiation are discussed. The significance of the models for estimating microstructural change during irradiation and beneficial effects of the heat treatment for irradiation performance are also introduced.