The uranium recovered from LWR spent fuels, containing an amount of 235U comparable to that in the natural uranium, can be recycled as uranium fuels for LWRs by re-enrichment using a conventional centrifuge cascade. However, the remade fuel is inferior to the original fuel produced from the natural uranium on the burn-up performance, because the former includes 236U as a neutron absorber which is yielded in the spent fuel and then enhanced in the re-enrichment process. Therefore, a few times recycle of recovered uranium may be available but its successive recycle is not recommendable because of successive decline in burn-up resulting from 236U accumulating in remade fuels. In this study, an idea of uranium fuel recycling is proposed which is of the feed-back of recovered uranium to a uranium enriching cascade. Since this cascade processes a mixture of natural and recovered uranium, the product contains 236U enriched but diluted with the 236U-free bulk of natural uranium. In this process, the concentration of 236U in the fuels reaches a balance with increase in recycle times. The multi-recycling fuels perform the burn-up degrees in PWRs declining but comparing favorably with conventional uranium ones. The multi-recycling system not only makes effective use of nuclear fuel resources, but also dissolves the problem of accumulating inventory in the storage of recovered uranium taking the major volume of spent fuels.

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