Method of processing spent fuel

In a reprocessing process for spent fuels and wet recovery process for scrapped fuels, since an organic solvent used in the extraction step are generally degradated due to the effects of radioactive rays or acids, they are reused after removing degradation products by means of sodium hydroxide and sodium carbonate solution. However, the organic solvents degradated considerably can no more be regenerated and, since they contain much sodium, their de-voluming treatment is restricted to complicate the solidification treatment. In view of the above, the degradation products are removed from the degraded solvents by using a vacuum-freeze-drying method and a vacuum-distillation method for the spent solvents in a solvent cleaning step, and the recovered solutions are reused as well as the most of the radioactive materials are recovered as residues, to thereby reduce the volume of the liquid wastes and simplify the liquid wastes treatment. Further, solutions of plutonium and uranium are powderized by means of the vacuum-freeze-drying method, and resultant nitrates are applied with thermal decomposition, denitration and reduction under calcination into oxide powder. (N.H.)