Sulfurization of rare-earth oxides in simulated spent fuel

Shinohara, Genki*; Sato, Nobuaki*; Kirishima, Akira*; Tochiyama, Osamu*; Sato, Soichi 

For the recovery of uranium from spent nuclear fuel, the sulfide reprocessing process has been proposed. The process consists of voloxidation and sulfurization steps followed by either magnetic separation or selective leaching steps. In this process, selective sulfurization of the rare-earth elements is applied, while the uranium oxide remains unreacted. The sulfurization of rare-earth oxides RO (R=Nd, Eu) was examined using CS, and found that they formed oxysulfide and sulfides even at temperatures lower than 500C. From the results of the sulfurization of RO in the simulated spent fuel, it was found that RO for Nd and Eu were selectively sulfurized by CS at 500C forming NdS and EuS, respectively, while uranium remained as UO. Effects of sulfurizing temperature and time were also investigated and compared with the results of thermodynamic consideration.