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 occu r. In cal bon-based materials (CBMs) macroscopic erosion means brittle dest ruction and dust formation and in metals melt layer motion and droplet spla shing. Dust, melt flow, droplet splashing and redeposited evaporated materi al produce complex layers with considerable surface roughness and drastical ly reduced heat conductivity. Moreover flaking and easy levitation of parti cles might occur. Subsequent ELMs when depositing their energy into such la yers might enhance impurity production because of increased heating of the hot spots. For vertical targets and for first walls (FWs) macroscopic erosi on is analyzed. For a simplified hot spot scenario a first estimation on ma ximum tolerable ELM energy is given. (C) 2001 Elsevier Science B.V. All rig hts reserved.