EVALUATION OF FRACTURE STRENGTH AND RESIDUAL LIFETIME OF MATERIALS DAMAGED BY SIMULATED PLASMA DISRUPTION

In this study, the surface damage of type 304 stainless steel, which is one of the candidates for the first-wall structural material in the fusion reactor, at plasma-disruption loading is simulated by high heat flux NBI. Influences of the surface damage on the fracture strength and the residual lifetime are studied. The results obtained are summarized as follows: (1) the present surface damage gives qualitatively a good simulation for plasma-disruption loading; (2) the fracture strength of the damaged material is improved by the existence of a melted layer, which has a higher hardness. There is no effect of microcracks in the melted layer on the fracture strength, and the plastic collapse criterion still stands; (3) the fatigue strength of the damaged material is reduced considerably due to the existence of microcracks in the melted layer; (4) numerical simulations of fatigue-crack growth are successfully attempted. It is shown that the residual lifetime can be predicted quantitatively by the present method.