Abstract
ABSTRACT
The siting of low-level radioactive waste disposal facilities requires locations having suitable soil materials beneath the proposed facility. These soils should be selected or designed to control water infiltration and ponding and enhance adsorption of radionuclides. This paper has investigated the effect of four soil additives on the hydraulic conductivity and adsorption characteristics of two natural soils, a glacial till and a marine clay. The additives studied in this paper were andisol, bentonite, clinoptilolite and hematite. The results of the hydraulic conductivity testing indicated that remolding and recompacting the soils produced a more homogenous soil having lower hydraulic conductivities. Comparison of the hydraulic conductivity and adsorptive behavior of the background soils, the additives, and mixtures of background soils and additives indicated that andisol and clinoptilolite provided the most improvement with respect to increasing adsorption capacity for iodide and strontium, respectively, with little effect on the hydraulic conductivity. The extent of adsorption and the effects of the additives on adsorption were highly pH dependent. The impact of the additives was most significant at acidic pH for both strontium and iodide adsorption because at high pH iodide adsorption was minimal for any of the materials tested and all of the background soils adsorbed a significant amount of strontium at high pH. These results suggest that engineered soils, comprised of a mixture of soil and additives, when used below a low-level radioactive waste disposal facility can enhance the ability of a site to retard off-site migration of radionuclides.
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