A critical evaluation of the redox properties of uranium, neptunium and plutonium ions in acidic aqueous solutions - (Technical report)

Standard redox potentials, E-s(o) and redox processes of U, Np and Pu ions in acidic aqueous solutions are reviewed and evaluated critically. The E(o) s of reversible redox processes, MO22+/MO2+ and M4+/M3+ (M: U, Np or Pu) ad opted are those proposed mainly by Riglet es al. on the basis of the precis e correction of formal potentials, E(o/)s, according to the improved theore tical approach to estimate the activity coefficient. Electrode processes of the U, Np and Pu ions are discussed in terms of current-potential curves, measured so far by polarography, voltammetry or flow coulometry. Special at tention is paid to the irreversible MO2+/ M4+ reactions. Disproportionation reactions of MO2+ are also discussed. New substances are introduced as int ermediates during reductions of MO2+ to M-4(+) or disproportionations of MO 2+.