Kinetics of the radiation chemical reactions of tervalent and quadrivalent actinides and lanthanides in carbonate solutions

Abstract

The reactions of the ions of tervalent and quadrivalent actinides and lanthanides with hydrated electrons eaq− and CO3− radicals in concentrated carbonate solutions have been studied by microsecond pulse radiolysis, using spectrophotometric recording of short-lived particles. It is shown that the rate of the reactions of eaq− with carbonato complexes of Ce(IV), Pu(IV), and Np(IV) is controlled by diffusion. The carbonato complex of Eu(III) reacts with eaq−appreciably more slowly. A linear relationship is obtained between the logarithm of the rate constant for the reactions of CO3− with the carbonato complexes of Am(III), Ce(III), and Pu(III) and the redox potential of the complexes. The rate of the reaction of CO3− with Np(III) in carbonate solutions is controlled by diffusion.