Crack propagation in first wall of fusion reactor by cyclic thermal stress

To clarify the crack propagation behavior of first wall materials under high thermal load cycles, cyclic high heat flux loading tests were carried out on SUS316. A specimen with a thickness of 5 mm was used, and the tests were performed under three types of external load conditions in order to investigate the effect of stationary tensile stress, simulating gravitational load on the first wall. To get rid of the effect of creep, the duration time of the beam was limited to 0.5 s in every 30 s high heat flux loading cycle. Two-dimensional thermal and elasto-plastic stress analyses and non-linear fracture mechanics analysis were carried out, and the fatigue crack propagation lengths were evaluated using Ĵ-integral amplitude ΔĴeff. Through this study, it was concluded that crack propagation lengths were decreased by applying stationary moderate tensile load, and that the evaluated crack lengths roughly agreed with experimental ones.