The plasma facing components in a tokamak type fusion reactor are subjected to intense heat load during a plasma disruption. The effects of the resulting high heat flux on the wall materials must be evaluated. The authors performed high heat flux tests with a high-frequency rastering beam as the heat source and thermal and stress analyses to investigate the thermo-mechanical behaviors of candidate wall materials. Based on the results of the studies, melting, evaporation and crack initiation, propagation behaviors of metallic and carbon materials are discussed. The heat transfer enhancement of melted metal motion of metallic materials, and the particle emission of carbon materials is important to the disagreement between experimental and analytical results on melting and evaporation. For stainless steel, a lot of micro-cracks with a depth of about 0.1 mm along dendrites initiated in the resolidified zone. They did not propagate in the non-melted zone. For tungsten, cracks with a depth of a few millimeters initiated from the periphery zone of the heated surface and propagated into the non-melted zone with repeated heating.
Development of advanced high heat flux and plasma-facing materials