Separation of Thorium and Uranium by Sulfide Method

For the recovery of nuclear materials from spent fuel, a novel reprocessing process based on sulfide chemistry has been proposed. In this paper, the sulfurization behavior of thorium and uranium oxides was studied using carbon disulfide. When U3O8 was reacted with CS2, it was reduced to UO2 at temperatures lower than 673 K, while sulfuruization of UO2 was observed at temperatures higher than 773 K forming UOS and US2. On the other hand, no reaction was observed for ThO2 up to 773 K. Similar results were obtained for the mixture of U3O8 and ThO2. The obtained results were also compared with thermodynamic consideration. Then, separation of uranium from thorium was suggested by selective sulfurization of uranium oxides. Finally, it was summarized that most of thorium oxide could be recovered as ThO2 after the separation of sulfurized uranium oxides.