A mesh-type assembly and stirrer assembly were developed to improve the performance of liquid cadmium cathodes for the electrodeposition of U and Ce from LiCl-KCl molten salt at 773 K. The thermodynamic basis for electrodepositing U and Ce was established through the calculation of equilibrium potentials and cyclic voltammograms, while also examining the co-deposition of Li. Thereafter, U and Ce electrodeposition was performed by galvanostatic electrolysis, and the current efficiency was determined. It was found that both assemblies effectively hampered the growth of U dendrites and Ce-Cd dendritic alloys. However, the utilization of the mesh-type assembly resulted in a greater current efficiency for U, with the maximum deposited amount attaining 7.7 wt% U/Cd without causing U dendrites formation. In contrast, the current efficiency for Ce was enhanced after using the stirrer assembly due to an improved diffusion flux of Ce ions. Finally, cathode deposits were characterized by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction, which revealed that disrupted fine U dendrites were randomly scattered in the Cd bulk, and that the CeCd11 dendritic alloys were also damaged, leading to an increased atomic ratio of Ce to Cd at the Cd bottom.
Molten LiCl-KCl salt and liquid cadmium are proposed as the electrolyte and the reactive cathode for the electrorefining of spent nuclear fuels, but they can be corrosive to the structural alloys. The down-selection of existing materials through corrosion testing is necessary to ensure the longevity of the electrorefiner vessel and electrode assemblies. Haynes C276, Inconel 600, AISI 316L stainless steel, and 42CrMo low-alloy steel were exposed to a LiCl-KCl melt at 500 °C for 500 h in an argon atmosphere. All alloys suffered from dissolution attacks with the presence of oxide islands or a porous oxide layer on the surface. AISI 316L, T91 steel, and tungsten specimens were submitted to corrosion tests in liquid cadmium at 500 °C for 120 h. The corrosion of AISI 316L and T91 stainless steel was predominated by chemical oxidation, with the additional occurrence of severe Ni dealloying and Cd penetration on AISI 316L. Destabilization of the Cr oxide layer by cadmium was discovered, resulting in the formation of CdCrO4. Tungsten only suffered from a dissolution attack at a rate of 0.50 mm/a.Keywords:corrosion;molten salts;liquid cadmium;SEM
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