Study of safeguards system on dry reprocessing for fast breeder reactor

A 'Feasibility Study on the Commercialized Fast Breeder Reactor (FBR) Cycle System' is underway at Japan Nuclear Cycle Development Institute (JNC). Concepts to commercialize the FBR fuel cycle are being created together with their necessary research and development (R and D) tasks. 'Dry,' non-aqueous, processes are candidates for FBR fuel reprocessing. Dry reprocessing technology takes advantage of proliferation barriers, due to the lower decontamination factors achievable by the simple pyrochemical processes proposed. The concentration o f highly radioactive impurities and non-fissile materials in products from a dry reprocess is generally significantly larger than the normal aqueous (Purex) process. However, the safeguards of dry reprocesses have not been widely analyzed. In 2000, JNC and Los Alamos National Laboratoiy (LANL) initiated a joint research program to study the safeguards aspects of dry reprocessing. In this study, the safeguardability of the three options: metal electrorefining, oxide electrowinning, and fluoride volatility processes, are assessed. FBR spent fuels are decladded and powdered into mixed oxides (MOX) at the Head-End process either by oxidation-reduction reactions (metal electrorefining and fluoride volatility) or mechanically (oxide electrowinning). At the oxide electrowinning process, the spent MOX he1 powder is transferred to chloride in molten salt and nuclear materials are extracted onto cathode as oxides. For metal electrorefining process, on the other hand, the MOX fuel is converted to chloride in molten salt, and nuclear materials are extracted onto cathode as a metal fomi. At lhe fluoride volatility process, the MOX fuel powder is converted to U and /PuF6 (gaseous form) in a fluidized bed; plutonium and uranium fluorides are separated by volatilization properties and then are converted to oxides. Since the conceptual design of a dry reprocessing plant is incomplete, the operational mode, vessel capacities, residence times, and campaigns are not fully defined. Preliminary estimates of the longest acccptable campaign length while still meets loss detection goals were made using typical measurement errors and annual throughputs of plutonium within the facility. For all reprocessing facilities, both in-process inventory and the input/output materials measurements must be determined for closing the materials balance. Usually, operations are to be shut down periodically and plants are to be completely cleaned out to recover all materials in measurable forms during inventories. If there is no cleanout between campaigns, fluctuations of in-process inventory have to be monitored. We conclude that the three dry reprocessing methods will have adequate safeguardability, if limited to small-scale campaigns or to low annual throughputs. For a large scale, e.g,. 50 t(HM)/y FBR fuel reprocessing plant, there remain challenges to be addressed through process development in JNC and safeguards R and D study with LANL.