FATIGUE LIFE OF THE PLASMA-FACING COMPONENTS IN PULSAR

The PULSAR project is a multi-institutional effort to determine the ad vantages that can be gained by building a tokamak with an entirely ind uctive current drive. This machine, which would operate in a pulsed mo de, would feature reduced capital and operating costs compared with st eady-state devices requiring complex current drive systems. However, a pulsed reactor would need an energy storage system and face greater s tructural demands from cyclic fatigue. This paper presents the results of the fatigue analyses for the plasma-facing components of PULSAR. P ULSAR features two major engineering designs: a liquid lithium-cooled vanadium alloy design and a helium-cooled silicon carbide composite de sign. Results are given for each. It is shown that the superior therma l and strength properties of the vanadium alloy allow a much wider spe ctrum of design options. The SiC composite properties cause significan tly more difficulty for the designer and, in particular, no credible d esign is found for a divertor fabricated solely from the SiC composite . This conclusion is based on current (limited) data for the thermophy sical properties and fatigue strength of SiC fiber composites. The dev elopments in these composites needed to create a viable SiC composite diverter are discussed.