Crack propagation tests of first wall materials by cyclic irradiation with an electron beam

In this study, cyclic high heat flux beam irradiation tests were performed for clarifying the crack propagation mechanisms of type 316 austenitic stainless steel and molybdenum alloy TZM. In the experiments, a surface-cracked specimen was set in a vacuum chamber in a specimen jig which was connected to a load-cell. And a pulsed electron beam was used to simulate the high heat flux of a fusion reactor. The electron beam has a peak value of 12-20 MW/m2 and 0.5 s operation time in every 30 s. After specified cycles of irradiation, the specimen was fractured by mechanical fatigue load. In all 316SS and some TZM specimens, thermal fatigue crack propagation was observed. To evaluate such a fatigue crack growth behavior only in 316SS, non-linear fracture mechanics analyses were performed based on finite element analysis. And these results were correlated with the non-linear fracture mechanics parameter. (orig.)