Laboratory and Field Studies Related to Radionuclide Migration at the Nevada Test Site in Support of the Underground Test Area Program and Hydrologic Resources Management Project. October 1, 1999-September 30, 2000.
This report describes work done by Chemistry Division personnel at Los Alamos National Laboratory (LANL) during FY 2000 for the US Department of Energy/Nevada Operations Office (DOE/NV). Ours is part of a multiagency program supported by the Defense Programs and Environmental Restoration Divisions of DOE/NV. The missions of both of these divisions are strongly affected by the extent of radioactive contamination of the underground environment of the Nevada Test Site (NTS) because this influences the use of land and water resources there. We are attempting to develop a descriptive model that accounts for the present distribution of radionuclides and predicts future movement within or outside NTS boundaries. The LANL Chemistry Division contribution to this effort during the past year consisted of measurements of radionuclide concentrations in water samples collected from cavities or chimneys of nuclear test locations on the NTS. Because we have been sampling some of these locations for many years, we are able to identify trends in the data that give us insights into how radionuclides may become part of the hydrologic source term; that is, how they become mobile with groundwater. As a complement to this work, we did our first field test of a downhole probe that allows us to measure in situ water temperature, pH, specific conductance, dissolved oxygen, and oxidation-reduction potential. These parameters influence the speciation of radionuclides dissolved in groundwater and affect how they may interact with their geologic environment. Also, we continued to use our capability to measure colloid concentrations in our samples because there is a correlation between colloids and certain radionuclides at some locations.
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