Electrorefining Experiments to Recover Uranium with a Cadmium-Lithium Anode and Their Theoretical Evaluation

Abstract

Molten salt electrorefining experiments were performed using a liquid metal anode made of cadmium-lithium alloy to recover uranium to a solid cathode from the spent molten salt. The concentration of U³⁺ in the molten salt effectively decreased from 1.38 wt% to less than 0.01 wt%. However, it was revealed that about 10 to 40% of uranium was not recovered by the solid cathode. This U deficit was thought to be caused by the U reduction around the Cd-Li anode. The following two mechanisms were proposed: 1) electrochemical deposition of uranium and 2) dissolution of the atomic lithium (Li⁰) into the LiCl-KCl eutectic salt and concomitant reduction of U³⁺ by the Li⁰.

A computer code PALEO was developed to interpret these results more quantitatively. It was found that the PALEO code was able to simulate the evolution of U³⁺ concentration in the salt as well as the electrodes potential reasonably well and the mechanisms of 1) and 2) could explain the dependency of U deficit if the diffusion coefficient of Li⁰ in the salt is larger than that of Li⁺.

KEYWORDS:

• uranium
• recovery molten salt
• electrorefining
• metallic fuel
• cadmiumlithium anode
• simulation code
• diffusion layer
• thickness
• diffusion coefficient
• lithium
• activity coefficient