Characterization of Radionuclide Behavior in Low-Level Waste Sites

Our laboratory is investigating the subsurface migration of radionuclides in groundwater at the Maxey Flats, Kentucky, shallow land burial site and at a low-level aqueous waste disposal facility. At Maxey Flats, radionuclide and tracer data indicate groundwater communication between a waste trench and an adjacent experimental study area. Areal distributions of radionuclides in surface soil confirm that contamination at Maxey Flats has been largely contained on site. Of the radionuclides detected in the surface soil, only 3H and 60Co concentrations appear to be derived from waste. Plutonium exists in the anoxic subsurface waters at Maxey Flats as a reduced, anionic complex; some of the plutonium appears to be complexed with EDTA, whereas organic acids seem to be associated with 137Cs and 90Sr. At the aqueous waste disposal site, 3H and mainly anionic species of certain radionuclides, including 60Co, 106Ru, 99Tc, 131I, and traces of 238,239,240Pu, appear to migrate from a trench through soil adjacent to the trench. Radionuclides in the particulate and cationic forms appear to be efficiently retained by the soil. In general, observations indicate that the physicochemical form of the radionuclides mediates their subsurface migration in groundwater at both waste disposal sites.