Application of Graphite as a Cathode Material for Electrorefining of Uranium

Abstract

The conventional electrorefiners to treat a metallic spent fuel equipped with a steel cathode have a sticking characteristic that hinders their overall processing efficiency. The critical question in order to enhance their throughput is how to decrease the sticking coefficient of the cathode. In order to realize this purpose, the conventional steel cathode was replaced with a graphite one. The graphite cathode exhibited self-scraping behavior in which the electrodeposited uranium dendrite falls from the cathode surface on its own without any kind of mechanical operation such as a scraping and rotation of the electrode. This self-scraping phenomenon of the graphite cathode was interpreted to be due to the formation of a uranium graphite intercalation compound. In this self-scraping mechanism, uranium atoms elongate at the graphite’s outermost layer by an intercalation reaction, so the deposited uranium dendrite falls off spontaneously as the gravitational force exceeds the bonding strength of the layers. Based on our preliminary work, a self-scraping should increase the efficiency of an electrorefiner due to the elimination of a mechanical scraping as well as the electrolytic stripping steps of the cathode.