Electrorefining of irradiated experimental metallic fuel at high lanthanides concentration in the LiCl–KCl electrolyte

Highlights: • Efficient recovery of actinides from irradiated metallic fuel METAPHIX-2 was demonstrated by electrorefining process. • High separation factors of actinides (An) over lanthanides (Ln) were achieved in electrolyte with high concentration of Ln. • Grouped selectivity of the actinides recovery was proven for later and final stages of the electrorefining process. • Aluminium cathode was proven suitable for recovery of all actinides, while only uranium was deposited on the inert cathodes. • Zirconium co-dissolution from the fuel had no effect on the process efficiency and on the structure of the deposits. - Abstract: An electrorefining process for homogeneous group-selective recovery of actinides from metallic nuclear fuel in molten LiCl–KCl has been investigated. The present study follows up on the previously achieved results on recovery of actinides from both non-irradiated and irradiated test metallic fuels. In the current work, METAPHIX-2 fuel initially composed of U₇₁–Pu₁₉-Zr₁₀ alloy irradiated to ∼7 at.% was processed. The experiments were focused on evaluation of selectivity of actinides over lanthanides during the electrorefining process in an electrolyte containing different concentrations of dissolved lanthanides up to 6.5 wt%, simulating the later and final stages of the process. In addition, a comparison of use of the solid reactive aluminium and solid inert cathodes for homogeneous recovery of all actinides was studied, as well as the effect of zirconium co-dissolution from the fuel on the process efficiency and on the structure of the deposits. The reactive aluminium electrode was proven suitable for homogeneous recovery of all actinides, while at the given conditions only uranium could be deposited on the inert cathodes. Very high group-selectivity of the process for actinides was demonstrated, even at high concentration of lanthanides in the electrolyte.