Electrorefining of metallized spent nuclear fuel (SNF) in molten salt electrolytes is one of the prospective steps of pyrochemical processing of SNF. The purpose of refining electrolysis is to produce a cathodic deposit of fissile materials (i.e. uranium) while electropositive fission products (e.g., platinum group noble metals) are retained in the anode material. 3LiCl–2KCl eutectic based molten salts have a relatively low melting point and can be used as working media for SNF electrorefining. In the present study the anodic dissolution processes of model U–Pd alloys with different palladium concentrations were investigated in 3LiCl–2KCl–UCl₃ (ca. 7 wt. % of U) based melts at 550 °C using a variety of techniques.

Anodic polarization curves showed only a single oxidation wave that can be attributed to uranium metal dissolution. Increasing palladium content in the alloy from 1.5 to 10 wt. % did not noticeably affect the character of the polarization curves. These results were confirmed by the analysis of the non-stationary chronopotiograms. The performed calculations indicated a three-electron scheme of uranium dissolution from U–Pd alloys. The anodic current densities not exceeding ca. 1 A/cm² were recommended for further investigation. Increase anodic current density over 1 A/cm² is undesirable due to possible salt passivation phenomenon.

In a separate series of experiments prolonged anodic dissolution of uranium-palladium alloys were performed in a galvanostatic regime. In this case the cathodic space was separated from the bulk of the melt by an inert membrane. It was found that palladium species were not observed in the electrolytes when anodic current densities of ca. 0.35 and 0.6 A/cm² were applied (Figure).

The obtained results were confirmed during the experiments on U–Pd alloy electrorefining that were performed using a semi-industrial scale electrolysis set-up.