Processing of fast neutron reactor fuel by electrorefining: Thematic overview

Abstract

This work provides basic knowledge on the spent fuel management on the basis of the published literature data on electrorefining. This review examines three main areas of work devoted to electrorefining. These are electrodeposition and electrodissolution using solid and liquid electrodes, as well as mass transfer in phases present during electrorefining. As part of this research, the composition of the irradiated metallic fuel was estimated. Due to the great potential difference between solid cathodes, it is possible to separate actinides from lanthanides. The co-deposition of metallic Pu and U in the eutectic LiCl-KCl melt containing UCl3 and PuCl3 indicates stable co-precipitation of U and Pu at U3+ concentration less than ~0.2 wt. Periodically performed electrical transport of ions to liquid (Cd) and solid cathodes in the galvanic mode made it possible to deposit preferentially U on the solid cathode, and Pu and Am on the liquid cathode. Oxidation of these metals caused fluctuations in the anode potential. The electrode processing after electrorefining is investigated. This process consists of oxidizing the actinides remaining in the liquid electrode by adding CdCl2 and removing the associated chloride by high-temperature distillation. During the electrorefining of irradiated metallic fuel, the fission products accumulate in the molten salt. Reduction of uranium on a solid cathode from a spent molten salt using a liquid Cd-Li anode is considered. A model that describes electrorefining with a liquid metal anode, solid cathode, and molten LiCl-KCl salts, is presented. The formation of plutonium at the surface of a solid cathode is analyzed. In a one-dimensional model of an electrorefiner, it is shown that the concentration of Pu at the cathode cannot be predicted from the Cm concentration in the melt. © 2020 John Wiley & Sons Ltd