Electrochemical and Thermodynamic Properties of Uranium on the Liquid Bismuth Electrode in LiCl-KCl Eutectic

Abstract

This work presents the electrochemical behaviors of U on a liquid Bi electrode and the formation of Bi-U intermetallic compounds in LiCl-KCl eutectic. It was found that the deposition of U on the liquid Bi electrode was a two-step process. The activity coefficient of U in the liquid Bi was determined by coulometric titration and in-situ open circuit chronpotentiometry versus two different reference electrodes at the temperature range of 723 to 813K. The solubility of U in liquid Bi was evaluated by pulse electrolysis. Furthermore, thermodynamic properties of Bi-U intermetallic compounds were measured by open circuit chronopotentiometry. The linear dependence of the Gibbs free energy of formation as a function of temperature was obtained, from which the enthalpy and entropy of formation were also determined. The activities and partial molar Gibbs free energies of U in two phase coexisting states were calculated through the measurement of electromotive force. Galvanostatic electrolysis was then conducted to prepare Bi-U intermetallic compound in the LiCl-KCl-UCl3 melt on a liquid Bi electrode. The phase composition and microstructure of the alloy was characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS).