Journal of Nuclear Fuel Cycle and Waste Technology

Electrolytic reduction technology is essential for the purpose of adopting pyroprocessing into spent oxide fuel as an alternative option in a back-end fuel cycle. Spent fuel consists of various metal oxides, and each metal oxide releases an oxygen element depending on its chemical characteristic during the electrolytic reduction process. In the present work, an electrolytic reduction behavior was estimated for voloxidized spent fuel based on the assumption that each metal-oxygen system is independent and behaves as an ideal solid solution. The electrolytic reduction was considered as a combination of a Li recovery and chemical reactions between the metal oxides such as uranium oxide and the produced Li metal. The calculated result revealed that most of the metal oxides were reduced by the process. It was evaluated that a reduced fraction of lanthanide oxides increased with a decreasing Li2O concentration. However, most of the lanthanides were expected to be stable in their oxide forms. In addition, a semi-empirical model for describing U3O8 electrolytic reduction behavior was proposed by considering Li diffusion and a chemical reaction between U3O8 and Li. Experimental data was used to determine model parameters and, then, the model was applied to calculate the reduction yield with time and to estimate the required time for a 99.9% reduction.

Keywords

Pyroprocessing,Spent Oxide Fuel,Electrolytic Reduction,Model,Simulation