A new back-end cycle strategy for enhancing separation, transmutation and utilization of materials (Adv.-ORIENT cycle)

Abstract

To minimize the ecological burden originating in nuclear fuel recycling, a new R&D strategy, the Adv.-ORIENT ( Advanced Optimization by Recycling Instructive Eleme nts) cycle was set forth. In this context, mutual separation of f-elements, such as minor actinide (MA)/lanthanide (Ln) and Am/Cm, are essential to enhance the MA (particularly 241Am) burning. Isotope separation before transmutation is also inevitably required in the case of some long-lived fission products (LLFPs) like 126Sn, 135Cs, etc. The separation and utilization of rare metal fission products (RMFPs: Ru, Rh, Pd, Tc, Se, Te, etc.) are offering a new direction in the partitioning and transmutation (P&T) field. 99Tc and 106Ru, well-known interfering nuclides in reprocessing, should be removed prior to the actinide stream. Separation of exothermic nuclides 90Sr, 137Cs as well as MA will significantly help to mitigate the repository tasks. A key separation tool is ion exchange chromatography (IXC) by a tertiary pyridine resin having soft donor nitrogen atoms. This method has provided individual recovery of pure Am and Cm products with a Pu/U/Np fraction from irradiated fuel in just a 3-step separation. A catalytic electrolytic extraction (CEE) method by Pd adatom has been employed to separate, purify and fabricate RMFP catalysts. Differently functioned ion exchangers, e.g., ammonium molybdophosphate (AMP), have been investigated for the separation of Cs +. Theoretical and laboratory studies on the isotope separation of LLFPs were begun for 79Se, 126Sn and 135Cs.