Development of New Solvent Extraction System for Nuclear Fuel Reprocessing

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This research has been conducted to develop an efficient extraction system for transuranium elements. Since tetra- and hexavalent actinoids are readily extractable from nitric acid solutions by a number of extractants, the studies on reprocessing or waste processing have focused on the development of an efficient extraction system for trivalent actinoids and pentavalent neptunium. Critical survey of literatures conducted in this research showed that acidic or neutral (bidentate) organophosphorus compounds are so far better extractants for trivalent actinoids. Following this evaluation, diisodecyl phosphoric acid, which is one of the acidic organophosphorus compounds, were successfully applied to extract neptunium from high-level radioactive waste solutions. On the other hand, the possibility of using chelating agents in waste processing was examined with using several newly synthesized acylpyrazolone derivatives. Although these derivatives showed better extraction of Am(III) and Np(V) than other chelating extractants, they were not effective enough to extract actinoids from highly acidic waste solutions.