Reduction of U(VI) and some fission products in HNO₃ media by galvanostatic electrolysis

In order to investigate the applicability of the galvanostatic reduction of uranium(VI) to U(IV) in the electrolytic reduction and ion exchange (ERIX) Process, a novel aqueous reprocessing technique for spent mixed uranium and plutonium oxide (MOX) fuels for fast-breeder reactors (FBR), an improved electrolytic cell was developed and fundamental electrolytic properties were examined using U and some fission products (FPs) in HNO₃ media. As the result of the electrolysis for a 200 cm³ solution of 0.5 M (M = mol/dm³) U(VI), 6 M HNO₃, and 0.5 M N₂H₄, it was found that more than 99% of U(VI) was reduced to U(IV) before the shift to the side reaction when the initial constant current supplied was no higher than 10 A. It was also found that the reduction of U(VI) to U(IV) was achieved using the cell under coexistence with the FPs, e.g. noble metals, which are easily deposited by the electrolytic reduction.