Study of solvent degradation in reprocessing MOX spent fuel; Solvent degradation and its effect on Pu purification cycle

Kawaguchi, Yoshihito; Morimoto, Kazuyuki; Kitao, Takahiko ; Oyama, Koichi ; Omori, Eiichi

30% Tributyl phosphate (TBP)/n-dodecane is used on PUREX process in Tokai Reprocessing Plant (TRP). TBP is degraded to di-butyl phosphate (DBP), mono-butyl phosphate (MBP) etc. mainly caused by radiation, extracted element and hydrolysis. In this study, we studied TBP degradation kinetic equation, Pu concentration in high DBP concentration solution after stripping Pu from the solution by diluted HNO, DBP concentration in mixer-settler and effect for process while MOX spent fuel was reprocessed and operation was stopped with Pu loaded on solution for 20 days. As a result of this study, we obtained the equation of TBP degradation. Moreover, the maximum DBP concentration in mixer-settler while reprocessing MOX spent fuel was 91 ppm, DBP concentration while stopping operation was 2000 ppm and we found out there was nothing out of the ordinary on the process after the process was restarted.