A NEW FUEL MATERIAL FOR ONCE-THROUGH WEAPONS PLUTONIUM BURNING

For the burning of plutonium derived from nuclear warheads, once-throu gh type oxide fuels have been studied by considering their proliferati on resistance and environmental safety as well as their technological backgrounds of fuel fabrication and reactors. From phase relations of ceramic materials and their chemical properties, it seems that a two-p hase mixture of a fluorite-type phase and alumina has favorable charac teristics as a once-through-type fuel of plutonium burning. It also se ems that the fluorite-type phases such as thoria and fully stabilized zirconia are acceptable as host phases of plutonium because of high so lid solubility of the actinide elements and fission products, irradiat ion stability, and chemical stability. The spent fuels finally obtaine d will become mineral-like waste forms, which could be buried under de ep geological formations without further processing. From reactor burn up calculations with the use of the fuels, light water reactors (LWRs) with the larger volume ratio of moderator to fuel than 1.4, such as c onventional LWRs, are considered to be suitable for the once-through p lutonium burning. Furthermore, such LWRs can transmute nearly 99% of P u-239 and 85 % of initial loaded weapons-grade plutonium. The quality of plutonium becomes completely poor in the spent fuels.