Reactivity of neptunium and plutonium in relation to inorganic free radicals in aqueous solutions

Rate constants of NO3, SO4-, Cl2-, Br2-, I2-, OH radicals with neptunium and plutonium ions are measured by pulsed radiolysis method. It is shown that the rate of Np3+ reaction with OH is limited by diffusion and makes up (4.0±0.4)x109 l/(molxs) while for other reactions it is lower than the diffusion limit. Linear dependence of logarithm of rate constant of Np3+ and Pu3+ reactions with holide radicals on reacting particle redox potential difference is detected. Mathematical modelling of Pu3+ oxidation in sulphuric acid solution under effect of γ-irradiation is performed and undetermined H atom reaction rate constants are evaluated