Exhaustive electrolysis for recovery of actinides from molten LiCl–KCl using solid aluminium cathodes

Abstract

An electrorefining process in molten chloride salts using solid aluminium cathodes is being developed in Institute for Transuranium Elements in order to separate actinides (An) from spent nuclear fuel. In this process, the fuel including fission products (FP) is dissolved into an electrolyte. Without purification of the salt, the process would have to be stopped when the FP concentration would become too high to allow a selective deposition of An on the cathode. Exhaustive electrolysis is proposed as the first purification step, consisting of a group-selective recovery of An on solid aluminium cathodes. On the anodic side, chlorine gas is produced by electrochemical decomposition of the salt. In order to prove the feasibility of the method, two galvanostatic electrolyses were carried out and the potentials of both electrodes were constantly monitored. Uranium was recovered from LiCl–KCl melts containing UCl3 and a mixture of UCl3–NdCl3, in which its concentration decreased from 1.7 to 0.1 wt% with no co-deposition of neodymium. Although the maximum applicable current densities were relatively low, the results are promising, demonstrating high current efficiency and selectivity of the proposed method. A design and application of a special chlorine gas producing inert anode is also discussed.