Some aspects of radiation chemistry of aqueous solutions of neptunium and americium ions

This paper is a review of experimental results obtained by the authors while studying radiation chemistry of alkaline and acid aqueous solutions of neptunium and americium ions. The oxidation of hexavalent neptunium and americium in alkaline solutions up to heptavalent state by ion-radicals O- has been studied. The yields of the formation of neptunium(VII) from γ-radiolysis in the presence of N2O, K2S2O8, NaBrO have been determined and the mechanism of the process has been proposed. By the pulse radiolysis method with fast spectrophotometrical registration of short-lived species the rate constant of the oxidation of Np(VI) by ion-radical O- has been estimated. The review contains the data on radiolysis of perchloric acid solutions of NpO2+ and Am3+ in the presence of N2O or XeO3. The pulse radiolysis method has been used for the study of oxidation of Am3+ up to Am(IV), the disproportionation of Am(IV) and the interaction of Am(IV) with H2O2 and HO2. This method has also been used to obtain ion Am2+. (author)