Characterization of the dissolver sludge of MOX spent fuel at the Tokai Reprocessing Plant

Suzuki, Kazuyuki ; Hatanaka, Akira; Samoto, Hirotaka ; Suwa, Toshio ; Tanaka, Kosuke  ; Tanaka, Yukiyoshi

The properties of the sludge in dissolver vessels from the reprocessing of ATR-MOX and ATR-UO fuels were investigated on the pilot-plant scale at the Tokai Reprocessing Plant (TRP). This sludge is mainly composed of platinum-group elements, zircaloy fragments, and post-precipitates from the dissolver solution. The sludge deposited on the dissolver causes difficulties such as pipe clogging. The characteristics of the sludge collected from the dissolver vessels, which affect the reprocessing operation, were revealed through chemical composition analysis using ICP-AES, and XRD. It was confirmed that the major component of the sludge was zirconium molybdate, and no significant differences between ATR-MOX and ATR-UO fuels were observed in terms of the sludge compositions. In order to gain further understanding of the properties of the sludge, the distributions of Pu and other trace elements were EPMA.