Characterization of Contaminant Transport Using Naturally Occurring U-Series Disequilibria

The main goal of the research is to understand the migratory behavior of radioactive contaminants in subsurface fractured systems by using naturally occurring U-series radionuclides as tracers under in-situ physico-chemical and hydrogeologic conditions. Naturally-occurring uranium- and thorium-series radioactive disequilibria can provide information on the rates of adsorption-desorption and transport of radioactive contaminants as well as on fluid transport and rock dissolution in a natural setting. This study will also provide an improved understanding of the hydrogeologic features of the site and their impact on the migration of radioactive contaminants. We intend to produce a realistic model of radionuclide migration in the Snake River Plain Aquifer beneath the INEEL by evaluating the retardation processes involved in the rock/water interaction. The major tasks are to (1) determine the natural distribution of U, Th, Pa and Ra isotopes in the groundwater as well as in rock minerals and sorbed phases, and (2) study rock/water interaction processes using U/Th series disequilibrium and a statistical analysis based model code for the calculation of in-situ retardation factors of radionuclides and rock/water interaction time scales