In this work, the electrochemical behavior of zirconium was studied on an inert molybdenum electrode at 550 °C in a LiCl-KCl-K₂ZrF₆ molten salt system, which is considered as an ideal electrolyte for the zirconium electrorefining process. Several transient electrochemical techniques were used such as cyclic voltammetry, chronopotentiometry, square wave voltammetry, and open circuit chronopotentiometry. The reduction of Zr (IV) was determined to follow a two-step mechanism of Zr (IV)/Zr (II) and Zr (II)/Zr. The diffusion coefficient of Zr (IV) was investigated with cyclic voltammetry and chronopotentiometry, and the results turned out to be in fair agreement from the both methods, as to be 4.26×10^-5 and 4.98×10^-5 cm²/s, respectively. The present study aims to provide a theoretical reference for the Zr electrorefining process.

Chemical-grade zirconium contains about 1–3 wt% hafnium, which is harmful for nuclear applications due to its high neutron-capture cross section. In the present paper, Zr-Hf separation in Sn-Cu-Zr-Hf and Cu-Zr-Hf alloy systems using molten salt containing CuCl₂ or CuF₂ was thermodynamically evaluated and lab-scale experiments on zirconium and hafnium separation in different molten salt systems were conducted. The best single-step Hf removal efficiency and Zr-Hf separation factor of about 95% and 9.0, respectively, were obtained with a NaCl-CaCl₂-CuCl₂ (3 wt%) molten salt system at 850°C and the CuCl₂/Hf stoichiometric ratio of 1.5.