Technical challenges on material and design criteria development for fusion in-vessel components

Preparation of irradiation database is essential for the design activity of fusion reactor in-vessel components since it is difficult to suppress the irradiation-induced degradation of material properties within the negligible level. On the other hand, the preparation of irradiation database corresponding to the real fusion in-vessel environment in the level that the existing design codes require for new material is not realistic. This limitation is due to the limited capability of irradiation experiments, and the fusion neutron irradiation environment is not available for the next ten years. The probability-based design method could be a potential alternative approach to evaluating the possibility of components' failure, where the material property is defined with a probability density function. The statistical analyses of data are required to provide the function, and a case study on as prepared and post-irradiation tensile properties of Japanese reduced activation ferritic/martensitic steel F82H was conducted. It was indicated that the most data show a normal distribution, but post-irradiation elongation data shows a possibility to follow a Weibull distribution.