Flush-out for Tokai Reprocessing Plant decommissioning, 3; Disposal of the low-concentration Pu solution

Yanagibashi, Futoshi; Nagaoka, Shinichi ; Isobe, Hiroyasu; Yasuda, Takeshi; Yada, Yuji; Suzuki, Shohei; Tokoro, Hayate; Kusaka, Shota; Shoji, Keita; Samoto, Hirotaka 

Tokai Reprocessing Plant (TRP) retained nuclear materials, such as low-concentration Pu solution due to TRP's shift to decommissioning in anticipation of resuming reprocessing. Pu solution required disposal as Flush-out before decontamination of equipment. Considering the operational range, the processing period, and the utilization after processing, Pu solution was transferred to high-active liquid waste tanks without evaporation or MOX conversion. During transferring, there was a critical risk due to Pu polymer formation caused by increasing in liquid temperature and decreasing in acid concentration. Based on past experience, U solution was mixed before transfer, and the acid concentration of the receiving tanks was adjusted. These measures prevented Pu polymer formation, ensured critical safety, and completed the disposal of low-concentration Pu solution.