Study of the photochemical reduction of U(VI) by organic compounds

U(IV) has been considered in the past to be a plutonium reductant in fuel reprocessing. The present work was undertaken to study the stability of photochemically produced U(IV) for this purpose. Photolysis of uranyl ion in HNO3 medium was carried out in different spectral regions and also in the presence of various reducing agents (viz. EtOH, TBP etc.) to see the stability of the U(IV) formed. In phosphoric acid medium, photolysis of U(VI)-EtOH system was found to give a greenish coloured gelatinous precipitate of U(IV) phosphate. Absorption spectrum of the intermediate U(V), known to be involved in the overall reduction process, was studied using the flash photolysis technique. Experiments were also carried out to evaluate the rate constants for quenching of excited uranyl ion by various other organic extractants for uranium. (author)