Three-dimensional multispecies current density simulation of molten-salt electrorefining

Abstract

This study presents three-dimensional simulation results of multispecies and multi-reaction electrorefining for spent nuclear waste treatment. Fluid-dynamic behavior of electrorefining is analyzed by commercial computational fluid-dynamics code. The results of local fluid dynamics are coupled with one-dimensional electrochemical reaction analysis code in order to predict local current density distribution. The new approach shows current distribution patterns over the cathode surface in LiCl–KCl molten-salt electrolyte. The current density distribution patterns are analyzed for various electrode rotational speeds and diverse applied currents and the results show a good agreement with general principle of mass transfer observations. Spatially periodic and vertically striped pattern of current density is predicted at the cathode side due to mass transfer depression at separation points. These slow mass transfer regions are vulnerable to be contaminated by transuranic elements. High rotational cathode speed and slow rotational anode speed are favorable to achieve uniform current density distribution with high applied current. The developed three-dimensional simulation will provide an improved understanding of complex electrochemical and transport phenomena that cannot be experimentally investigated and can be used to improve efficiency of electrorefiner design with high uranium throughput and small effluence of radioactive transuranic elements.