Effects Of Reprocessed Uranium Multi-recycle On Proliferation Resistance Of Plutonium And Uranium

Abstract:

Effects of the reprocessed uranium (RepU) multi-recycle on proliferation resistance of plutonium (Pu) and uranium (U) has been studied. Non-fissile isotope ²³⁶U is generated from ²³⁵U during the burn up in the reactor. Typical isotope ratio of ²³⁶U to the remaining ²³⁵U isotope in the RepU from the used fuel in light water reactor varies from 0.4 to 1.0, depending on the initial enrichment and the burnup. During burnup, by further absorbing neutrons, some of ²³⁶U becomes ²³⁸Pu via ²³⁷Np. ²³⁸Pu has strong proliferation resistance because of the high decay heat and spontaneous fission neutron emission. During the centrifuge re-enrichment of ²³⁵U in the RepU, ²³⁶U is also re-enriched together with ²³⁵U. The ratio of ²³⁶U to ²³⁵U after re-enrichment of the RepU is roughly 0.3 to 0.4 up to 5% ²³⁵U enrichment. Hence, the centrifuge re-enriching of the RepU makes it difficult to produce weapon-grade high-enriched ²³⁵U because ²³⁶U is also enriched together. After the re-enriched RepU is burned again in the reactor, naturally ²³⁵U is reduced by fission to release energy during the burning and the content of ²³⁶U after the first recycle is further increased compared to that after the first cycle. The content of ²³⁸Pu after the first recycle is also further increased compared to that after the first cycle, which means the proliferation resistance of Pu is further increased after the first recycle. By repeating this process, the production of highly enriched weapon-grade U becomes more difficult from the multi-recycle RepU. ²³⁶U in RepU is an attractive isotope to make protect Pu and U from adversarial use. Recycle of minor actinides for protected Pu production (P3), proposed earlier by Saito elsewhere, and the recycle of the RepU proposed here are both useful and important for the peaceful uses of nuclear energy.