Reprocessing method for spent nuclear fuel

Spent nuclear fuels are dissolved in a first aqueous solution of nitric acid, and U and Pu obtained in the first aqueous solution of nitric acid are transferred to a first organic solution by a codecontamination treatment. They are transferred to a second aqueous solution of nitric acid by a back extraction treatment. The second aqueous solution of nitric acid to which a reducing agent is added for converting Pu into the trivalent state which is hardly transferred to an organic phase is brought into contact with a second organic solution. With such procedures, a U organic solution having U as a main ingredient and a second aqueous solution of nitric acid containing U and Pu having a ratio of U to Pu on the weight basis of within a range of 1 to 10 is obtained. Accordingly, loss of Pu is remarkably reduced, and control for obtaining a predetermined U/Pu ratio is facilitated. In addition, man-power can be saved for the purification step of U, and products of U and Pu can be manufactured in a facility at a reduced cost. (T.M.)