Studies on Speciation of Americium, Technetium and Neptunium in Simulated Vitrified-Waste Leachates

Abstract

ABSTRACTPhysico-chemical forms of several radionuclides are being investigated in order to characterize the migrating species in a deep geologic repository. Under ground water bicarbonate and carbonate concentration levels, Am(CO3)2 has been observed to be the most important complex while the formation of Am(OH)(CO3)22− has been indicated, stability constants of Am-complexes have been calculated, and a distribution diagram of Am(III) species as a function of pH is presented. Speciation of Tc has been studied using radiochemical and electromigration methods in oxic and anoxic environments; in effective diffusion coefficient of 1.37 × 10−5 cm2 S−1 for ToO4− has been obtained. Preliminary studies on Np(V) indicate that NpO2+ does not form strong complexes with carbonate and bicarbonate ions at ground water concentrations.