Cyclic Voltammetry on Zr, Sn, Fe, Cr and Co in LiCl-KCl Salts at 500°C for Electrorefining of Irradiated Zircaloy-4 Cladding

To achieve a better understanding of Zircaloy-4 electrorefining in LiCl-KCl at 500°C, redox behaviors of Zr, Sn, Cr, Fe and Co, were examined by cyclic voltammetry using tungsten working and counter electrode. Zr metal can be produced from Zr 4+ through two step reduction and ZrCl is generated as an intermediate product. As ZrCl 4 concentration decreases, ZrCl would be easily reduced into Zr metal. In addition, Zr 2+ formation would be unlikely at low ZrCl 4 concentration. The redox reactions of the other elements are much simpler than Zr. The reduction of Zr 4+ into ZrCl was close to irreversible but the reduction reactions of the other elements are close to reversible. The diffusion coefficients and apparent reduction potentials were calculated using equations for a reversible or irreversible reaction. The diffusion coefficients are in the order of 10 −9 m 2 /s and Zr is less reductive than other elements.