Electrochemistry of Uranium in Molten LiCl-KCl Eutectic

TLDR

The Institute for Transuranium Elements is compiling an accurate database of actinide behavior in chloride melts to support nuclear fuel reprocessing development. Cyclic voltammetry and chronopotentiometry on a tungsten electrode were used to probe uranium electrochemistry in LiCl‑KCl eutectic, from which thermochemical properties were derived. Uranium in the melt undergoes a two‑step reduction, with similar diffusion coefficients for the two redox species, measured standard potentials, determined Gibbs free energies of the dilute solutions, and activity coefficients spanning a specified range.

Abstract

The Institute for Transuranium Elements (ITU) is building up an accurate database of actinide behavior in chloride melts in support of its nuclear fuel reprocessing development program. The electrochemical properties of uranium, dissolved in LiCl-KCl eutectic melt, were investigated by transient electrochemical techniques, such as cyclic voltammetry (CV) and chronopotentiometry on an inert tungsten electrode. It was shown that is reduced to by a two-step mechanism corresponding to and transitions. In the range, the diffusion coefficients of and were similar and equal to: and . The apparent standard potentials of and redox systems were vs. and vs. , respectively. Some thermochemical properties of uranium solutions were also derived from the electrochemical measurements. The Gibbs free energies of dilute solution of and in the LiCl-KCl were determined to be: and in kJ , respectively. In the range, the activity coefficients γ of and range between and , respectively.