Engineering and materials issues in designing a cold-gas divertor

Abstract

One of the key challenges facing the International Thermonuclear Experimental Reactor (ITER) Project is the development of plasma-facing components (PFCs) that can withstand the severe environmental conditions at the plasma edge. The most intensely loaded element of the PFCs is the divertor. The divertor must handle high fluxes of energetic plasma particles and electromagnetic radiation without excessive impurity buildup in the plasma core. The “cold-plasma-target” mode of divertor operation proposed for ITER expands the divertor design window to include several alternate heat sink and armor materials that were not available for the previous “high recycling divertor” approach. In particular, beryllium armor can now be considered with copper, niobium and vanadium heat sink materials; and helium or liquid metal coolants are feasible in addition to water. This paper presents material properties and compatability assessments for these materials and coolants along with parametric studies of thermal and mechanical performance. A viable design window is found for copper and niobium heat sinks with beryllium armor, but not for vanadium unless thin (∼ 1 mm) coolant structures can be accomodated mechanically.