Dissolution behavior of irradiated mixed oxide fuel with short stroke shearing for fast reactor reprocessing

Ikeuchi, Hirotomo  ; Sano, Yuichi   ; Shibata, Atsuhiro  ; Koizumi, Tsutomu; Washiya, Tadahiro 

An efficient dissolution process was established for future reprocessing in which MOX fuels with high plutonium contents and dissolver solution with high heavy-metal concentrations will be treated. This dissolution process involves short stroke shearing of fuels (10 mm in length). The dissolution kinetics of irradiated mixed-oxide fuels and the effects of the Pu content, heavy-metal concentration and fuel form on the dissolution rate were investigated. Irradiated fuel was decreased with increasing Pu content. Kinetic analysis based on the fragmentation model indicated that the dissolution rate of irradiated fuel was affected not only by the volume ratio of liquid to solid ( ratio), but also by the exposed surface area ( ratio). The penetration rate of nitric acid is expected to be decreased at high heavy-metal concentrations by a reduction in the ratio, but enhanced by shearing the fuel pieces with short strokes and thus enlarging the ratio.