Studies of the speciation of plutonium and other actinides in natural groundwater using anion exchange resin

The chemical speciation of radionuclides can have a dramatic effect on mobility in groundwater, because sorption by soil depends on speciation. An anion exchange technique has been developed and used to study the chemical speciation of radionuclides in a contaminant plume originating from an infiltration pit used for managing low-level wastes. The principle radionuclides present include 3H, 90Sr, 60Co and 106Ru, but plutonium and other actinides are also present at very low levels. The major dissolved species of 60Co, 106Ru and actinides in this plume are anionic and are strongly adsorbed by anion exchange resins. The anion exchange technique has been used to concentrate the anionic species from up to 6 L of groundwater and then chromatographically separate them by elution with salt and acid solutions. The development work focussed on 60Co and 106Ru, which are easier to measure than the actinides. The same technique was subsequently used to concentrate and separate the anionic species of Np, Pu, Am and Cm isotopes in the plume. The technique can be used analytically to measure changes in radionuclide speciation. It can also be combined with other techniques, such as size exclusion chromatography, to further characterize species in fractions collected during separation.