Investigate of electrochemical properties of Nd(II) and Nd(III) in eutectic LiCl–KCl molten salt

Abstract

Pyroprocessing is one of the promising methods to reprocess the spent nuclear fuel. Neodymium (Nd) constitutes about one third of rare earth in fission products, however, the electrochemical properties of Nd have not been thoroughly understood, especially the exchange current. In the present study, the transit electrochemical methods of cyclic voltammetry and square wave voltammetry were applied to study the properties of Nd in LiCl–KCl system. The reduction of Nd³⁺ was determined as a two-step reaction with Nd³⁺/Nd²⁺ to be a reversible but Nd²⁺/Nd to be a quasi or irreversible reactions. Additionally, parameters such as the diffusion coefficient, exchange current, and apparent potential were derived from the cyclic voltammetry curves. Their relationship with temperature and concentration was investigated under 723 K, 773 K, 823 K with concentrations of 3 wt%, 6 wt% and 9 wt%. The present study contributes significantly to rich the database of Nd in LiCl–KCl molten salt and to understand the electrochemical behaviors of Nd during electrochemical separation of spent nuclear fuel.