Modelling the growth profile of dendritic uranium deposits from molten salt electrorefining

A 2D axial electrokinetic mean-field model was developed using the level set method, which well predicts the structural characteristics of the dendritic uranium deposit in molten salt. This model reproduces the average dimensions of the deposit and is validated by comparison with experimental observations. The simulation results emphasize two important controlling parameters, the bulk concentration of uranium in molten salt and the initial current density. High bulk concentration conditions (> 4.78 wt%) tend to reduce the volume of the deposit and improves its compactness. In addition, large initial current density will promote the growth of dendrite due to the diffusion limit effect. An umbrella-like structure can be observed on the surface of the molten salt, which gets larger and thinner with the rising of current density. However, this model fails to capture the anomalous dendrites, which cannot be assumed as a dense region in simulation and appeared in the experiment at high bulk concentration (> 10 wt%) and a range of current density between -200 and -800 mA/cm2. Finally, an electrochemical map of dendritic deposits pattern as a function of initial current density and bulk concentration was constructed based on simulation and experimental results.