Safety and environmental comparisons of stainless steel with alternative structural materials for fusion reactors

Using the FuseDose II computer code, we calculated and compared several indices of safety and environmental (S ampersand E) hazards for conceptual magnetic-fusion reactor designs based on a variety of structural materials-stainless steel, ferritic steel, vanadium-chromium-titanium alloy, and silicon-carbide-and, for comparison, the fuel of a liquid-metal fast breeder fission reactor. FuseDose II is a second-generation code derived from the Fuse-Dose code used in the U.S. Department of Energy's Committee on Environmental, Safety, and Economic Aspects of Magnetic Fusion Energy (ESECOM) study in the late 1980s. The comparisons update and extend those of the ESECOM study by adding the stainless-steel case, some new indices, graphical representation of the results, and other refinements. The results of our analysis support earlier conclusions concerning the S ampersand E liabilities of stainless steel: The use of stainless steel would significantly reduce the S ampersand E advantages of fusion over fission that are implied by the indices we consider, compared with the advantages portrayed in the ESECOM results for lower-activation fusion materials. The dose potentials represented by the radioactive materials that conceivably could be mobilized in severe accidents are substantially higher for the stainless steel case than for the lower activation fusion designs analyzed by ESECOM, and the waste disposal burden imposed by a stainless steel fusion reactor, though significantly smaller than that associated with a fission reactor of the same output, is high enough to rule out the chance of qualification for shallow burial under current regulations (in contrast to some of the lower activation fusion cases). This work underscores the conclusion that research to demonstrate the viability of the low-activation materials is essential if fusion is to achieve its potential for large and easily demonstrated S ampersand E advantages over fission. 37 refs., 17 figs., 8 tabs