ELECTROLYTIC REDUCTION AND ELECTROREFINING OF URANIUM TO DEVELOP PYROCHEMICAL REPROCESSING OF OXIDE FUELS

Two series of pyrochemical reprocessing tests for oxide fuels, consisting of pretreatment, electrolytic reduction, and electrorefining processes, were conducted using similar to 100 g of UO(2). In the pretreatment process, UO(2) pellets of the starting material were oxidized into U(3)O(8) powder, which simulated fuel decladding by voloxidation. Then, UO(2) sinter with a porosity of 30 to 38% was fabricated from the U(3)O(8) powder. Two cathode baskets charged with 100 g of the UO(2) sinter were prepared, and two electrolytic reduction tests were carried out in a LiCl-Li(2)O electrolyte at 650 degrees C. The results suggested that the reduction to uranium metal could be completed within 10 h with the current efficiency >62%. It was verified that the porous UO(2) sinter was of great advantage to the electrolytic reduction process. In the subsequent electrorefining process, the reduction products were charged in two anode baskets, and electrolysis was carried out in a LiCl-KCl-UCl(3) electrolyte at 500 degrees C. Within 8 h, most of the uranium metal was anodically dissolved into the electrolyte with the current efficiency >88%. Dendritic uranium metal was collected on a stainless steel cathode. Consequently, it was demonstrated that a refined uranium metal could be produced from UO(2) pellets with a high degree of efficiency.