Vertical target and FW erosion during off-normal events and impurity production and transport during ELMs typical for ITER-FEAT

During off-normal events besides evaporation macroscopic erosion might occur. In carbon-based materials (CBMs) macroscopic erosion means brittle destruction and dust formation and in metals melt layer motion and droplet splashing. Dust, melt flow, droplet splashing and redeposited evaporated material produce complex layers with considerable surface roughness and drastically reduced heat conductivity. Moreover flaking and easy levitation of particles might occur. Subsequent ELMs when depositing their energy into such layers might enhance impurity production because of increased heating of the hot spots. For vertical targets and for first walls (FWs) macroscopic erosion is analyzed. For a simplified hot spot scenario a first estimation on maximum tolerable ELM energy is given