Multiphysics Simulation Study of the Electrorefining Process of Spent Nuclear Fuel from LiCl-KCl Eutectic Molten Salt

Electrorefining is an important unit operation for the pyroprocessing of spent nuclear fuel; however, the uncontrolled growth of uranium dendrites traps molten salt into the deposited uranium, increases the short-circuit risk, decreases the current efficiency, and thus hinders the engineering application of the electrorefining technology. In this study, the finite element method is applied to the study of the electrorefining dynamics subjected to convection, diffusion, electromigration, and electrode reaction. The velocity field, concentration field, electric field, and flux density field are evaluated. The local current density on the cathode is evaluated under different overall current densities, overpotentials, cathodic shapes and positions for the evaluation of dendritic growth. Finally, it is concluded that the uranium will be deposited priorly onto the cathode tip and the frontside of the cathode facing the anode, the position of the electrode and the shape of the cathode tip will not have significant influence to the priority of deposition, and a glass insulated tip can effectively improve the uneven growth of uranium dendrites on the cathode surface as proposed by Srihari et al. (Sep. Sci. Technol. 51, 1397).