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

The reaction of uranium dioxide with melts of alkali metal chlorides (LiCl, LiCl-KCl and NaCl-CsCl) under oxidising conditions was followed spectrosco pically between 550 and 700 degrees C. The reaction proceeds via initial in termediate uranyl chloro species and finally results in the formation of sp aringly soluble alkali metal uranates(vi). The addition of aluminium chlori de to the melt changes the mechanism of the oxidation so that a soluble ura nyl chloride complex is the final product. The electronic absorption spectr a of solutions of alkali metal uranates in chloride melts have been recorde d for the first time. Solutions of monouranates are stable with time, but d iuranates tend to react with alkali chloride melts to form monouranate spec ies.