To conclude, the electrochemical reduction of uranium dioxide to uranium metal has been studied in a lithium chloride–potassium chloride eutectic molten salt at 450°C. Both electrochemical and synchrotron X-ray techniques have been utilised to deduce the electrochemical reduction potential, mechanism and reduction pathway. The electrochemical reduction potential of the UO2|U couple is dependent on the activity of oxide ions existing within the melt. The electrochemical reduction of uranium dioxide to uranium metal seems to occur in a single, 4-electron-step, process; indicated by a single reduction peak (C1) in the cyclic voltammograms and also by the exclusion of any other phases in the EDXD data. The electrochemical reduction may be impeded by an increase in oxo-acidity of the molten salt. That is, O2− ions that are liberated by the electroreduction may not react at the counter electrode and, thus, not be removed from the molten salt. This could be due to the electrode geometry and/or the inherent microstructure of the working electrode: a high tortuosity, for example, would impede the diffusion of O2− ions out of the working electrode. This could then cause an increase in the activity of oxide ions existing within the melt and hence inhibit the electrochemical reduction – exploration of the microstructure of working electrodes will be the focus of future work.
