Metallic materials as plasma facing components

The design and fabrication of suitable plasma facing components for fusion devices are difficult tasks with often conflicting requirements. Most operating devices utilize stainless steel as the first wall material and graphite for the main limiters. There are potential problems with the extrapolation of graphite to power producing reactors and, hence, the evaluation of metallic alternatives is important. Prime candidate metals are beryllium and tungsten for plasma interactive components. There are several potential advantages to metallic components over graphite or ceramics. In general, metals have superior fracture toughness, are inert chemically to the hydrogen atmosphere, have a better developed fabrication and joining technology, and better resistance to neutron damage. Metals are limited, however, in their ability to withstand disruption damage and, with the exception of beryllium, require a very low edge temperature to avoid sputtering problems. The current status of research in the areas of erosion, tritium permeation and inventory, thermal stress and fatigue, off-normal events, neutron irradiation and fabrication on these and other metals is reviewed and compared to the prime non-metal choice of graphite