Effect of irradiation hardening on brittle fracture performance of box-shaped blanket fabricated by F-82H

Fusion reactor blankets designed for DEMO are based on a water cooled ceramic breeder. The unstable fracture of the box-shaped blanket would occur by the superimposition of three factors as follows: (1) it is the reduction of fracture toughness for structural materials, such as F-82H, caused by the significant irradiation hardening, (2) it is the formation of cracks which act as the initiation point of the fracture, and (3) it is the excessive tensile load caused by the inner pressure to In-Box loss of coolant accident (LOCA). In the present study, application of Weibull stress criterion to fracture assessment is to investigate the effect of irradiation hardening on the brittle fracture performance of box-shaped blanket fabricated by F-82H. Both structural analysis of the box-shaped blanket simulating In-Box LOCA and deformation behavior analysis of irradiated toughness specimens were conducted by elastic-plastic finite element analysis (FEA). Weibull stress values calculated from FEA of irradiated toughness specimens were higher than those from FEA of irradiated structural components. It, therefore, is considered that the irradiation hardening of structural materials would not promote the brittle fracture at the corner of rectangular coolant tubes of the blankets caused by the load of In-Box LOCA.