The use of batch tests as a screening tool for radionuclide sorption characterization studies, Hanford, Washington, U.S.A

The U.S. Department of Energy was studying the feasibility of locating a high-level radioactive waste repository in basalt at the Hanford site in south-central Washington. This is a saturated site where ground water transport of radionuclides away from a repository is the mechanism for release to the accessible environment. Sorption as defined herein is the predominant means by which the movement of radionuclides are retarded in a ground water flow system. This work presents preliminary laboratory batch testing results in the context of the entire site system sorption characterization strategy. An anoxic experimental approach was used with basalt flow top core samples recovered from depths of 915 m (3000 ft) below the earth surface. The kinetics of sorption were relatively slow and increased in the order U < Se < Sr, Ra. Proportionate removal increased in the order Se < U < Sr < Ra. Freundlich isotherms were linear for Sr, U, and Se over the concentrations tested. The batch results were helpful from a screening standpoint to indicate the direction of further testing, but were unsatisfactory by themselves to explain sorption behavior adequately. (author)