Electronic absorption spectral study of the oxidation of uranium dioxide in chloride melts

Abstract

The reaction of uranium dioxide with melts of alkali metal chlorides (LiCl, LiCl–KCl and NaCl–CsCl) under oxidising conditions was followed spectroscopically between 550 and 700°C. The reaction proceeds ia initial intermediate uranyl chloro species and finally results in the formation of sparingly soluble alkali metal uranates(VI). The addition of aluminium chloride to the melt changes the mechanism of the oxidation so that a soluble uranyl chloride complex is the final product. The electronic absorption spectra of solutions of alkali metal uranates in chloride melts have been recorded for the first time. Solutions of monouranates are stable with time, but diuranates tend to react with alkali chloride melts to form monouranate species.