Measurements of CeCl₃ properties on liquid cadmium cathode (LCC) in LiCl-KCl eutectic salt as basic safeguarding application in pyro-processing technology - 5125

Full text of publication follows. Pyro-processing technology has been developed as a promising method for the recovery and recycle of uranium and actinide elements from used nuclear fuel. One of the key processes in pyro-processing is an electrorefining system where uranium is selectively recovered by using a solid cathode in lithium-potassium chloride (LiCl-KCl) eutectic molten salt at a high temperature. Then, uranium and transuranic elements are simultaneously recovered by replacing the solid cathode with a liquid cadmium cathode (LCC) because their reduction potentials become close on LCC. Uranium is the major element in the electrorefining process, thus the assessment of accurate thermochemical data of the element in the molten salt is extremely important in terms of material detections and accountability toward safeguard. Recently, many studies have been done on the thermochemical properties of uranium with solid cathode, but the properties of uranium on LCC have not been fully understood. Therefore, it is necessary to accumulate the kinetic properties of uranium and actinides on the LCC in the LiCl-KCl. In addition, these kinetic properties can be used to enhance the recent kinetics modeling regarding to the safeguarding purposes in this reprocessing technology. Cerium chloride (CeCl₃) has been selected as a surrogate material for uranium chloride (UCl₃) because cerium has similar ionic size and electrochemical potential that is nearer to uranium than most lanthanides. For the performance of the electrochemical studies, electrochemical cell and electrode assembly consisting of cathode, anode, and reference electrodes have been designed and installed in a bench-scale furnace. Different electrochemical techniques will be used to investigate the properties of CeCl₃ on the LCC. Open circuit potential (OCP) method will be performed to obtain equilibrium potentials, and cyclic voltammetry (CV) will be done to determine the apparent standard potentials and diffusion coefficients of CeCl₃ at different temperatures. In addition, exchange current density of CeCl₃ is a crucial value in the development of the physics-based models. The development of an experimental method to determine exchange current density on the surface of LCC in LiCl-KCl eutectic salt will be discussed. (authors)