Nuclear proliferation resistance assessment of fuel cycles closed with complete co-processing of spent fuel

Purex (Plutonium Uranium Recovery by Extraction) is the standard reprocessing method used for the recovery of Uranium (U) and Plutonium (Pu) in spent fuel. Products of the standard reprocessing of spent fuel discharged from a typical LWR are separated and highly pure streams of U and Pu with fissile contents of roughly 0.85 wt.% (U-235 in U) and 70 wt.% (Pu-239+Pu-241 in Pu) respectively. Because of the economic and technological conditions and safeguard concerns, alternative methods or modifications for standard reprocessing including complete co-processing have been proposed. Complete co-processing is based on the Purex process and is an easier way of recovering U and Pu from spent fuel compared to standard reprocessing. In addition, since the U and Pu recovered together from spent fuel, it does not yield pure Pu and it is advantageous with regard to safeguards. The product obtained from complete co-processing of spent fuel is a U + Pu mixture with a total fissile content of around 1.5 wt% (U-235+Pu-239+Pu-241 in U + Pu), which is not suitable for direct use in LWRs and special approaches are required for recycling it. This study focuses on the assessment of nuclear proliferation resistance of fuel cycles closed with complete co-processing and different recycling scenarios for U + Pu product. To assess the proliferation resistance, intrinsic proliferation barriers including the amount of material to be diverted for significant quantity (SQ) of Pu, isotopic content of Pu, and radiation barrier of diverted material are compared for spent fuels generated in the cycles for one GWe-yr electricity production. To assess the impact of burnup on the proliferation resistance of cycles, all calculations are performed for the burnup values 33 GWd/tHM, 40 GWd/tHM, and 50 GWd/tHM. Results showed that the closed fuel cycle in which the U + Pu product from the complete co-processing is blended with 10 wt.% enriched uranium and recycled as mixed oxide fuel possesses the highest proliferation resistance. Besides, intrinsic nuclear proliferation barriers of all the fuel cycles investigated are positively affected by an increase in burnup.