The study of metallic uranium production by pyrochemical mix-conversion of U3O8

Abstract

A pyrochemical conversion of U3O8 into metallic uranium by chemical and electrochemical reactions have been studied. Triuranium octaoxide was chlorinated by carbon tetrachloride gas in a stream of argon at different temperatures. The optimal conditions of the solid phase transformation were found, the conversion rate of U3O8 is up to 99.30%. The mechanism of U4+ ions reduction into metal uranium by the transient electrochemical technique in the fused 3LiCl-2KCl eutectic was studied. The results revealed that the U4+ ions reduction to metallic uranium on inert electrode is a two-step reaction, which includes single electron exchange and three electrons exchange. The first step of reaction is reversible and it is controlled by the rate of the mass transfer in the scanning region 0.002–0.2 V/s, while the second step of reaction is irreversible. The diffusion coefficients of U4+ and U3+ ions were determined by the cyclic voltammetry. The galvanostatic electrolysis of the LiCl-KCl-UCl4 melt led to the formation of metallic uranium on an inert solid plate and the formation of intermetallic compounds of different composition on the active liquid gallium cathode. It is concluded that U4+ ions is easily reduced to metallic uranium in a short period of time during the galvanostatic electrolysis in molten salts.