The effort for the nuclear material recovery from the reprocessing process and relevant MC&A in the TRP Decommissioning Project (II)

Tokai Reprocessing Plant (TRP) shifted to the decommissioning phase for about 70 years starting from 2018. As the first step of the decommissioning activity, TRP conducted “flush-out plan” with three major steps to recover the nuclear materials, which are remained in the process from the suspension of reprocessing operation in 2007, prior to the decontamination and dismantle of equipment.  TRP had the discussion with the International Atomic Energy Agency (IAEA) and the Japanese National Regulation Authority (NRA) for the applicability of nuclear material accountancy (NMA) and safeguards measures during the flush-out process. The result of flushout stage A which is the process recovering of sheared powder around the shearing machine was reported in 64th Annual Meeting of the Institute of Nuclear Materials Management. Then, the work for flush-out process to recover plutonium solution (stage B) and uranium solution (stage C) including the different flow of the designed reprocessing operation conducted from March 2023 to February 2024. TRP established the transfer method and NMA method to recover the nuclear materials as much as possible and determine the precise amount of nuclear material. Flush-out activities based on the above investigation contributed the improvement of cumulate Material Unaccounted For and the decrease of frequency of the inspection. In this paper, we report the result of the performed effort and achievement of flush-out activity about stage B and stage C.