Diffusion of Tritiated Water and Chloride in Basalt-Bentonite Mixtures

Effective diffusion coefficients of tritiated water and chloride (³⁶Cl) were measured in mixtures of crushed basalt and bentonite as functions of temperature (20 to 90°C) and mixture bulk density (1.5 to 1.9 Mg/m³). A quick-freeze technique was used to halt the diffusion process so the tracer distributions could be determined by slicing the core and analyzing slices by liquid scintillation methods. Linear and multiplelinear regression analyses were performed on both data sets. The regression equations were then used to predict diffusion coefficient values outside the range of densities used in these experiments. The predicted values agree very well with published data. Correlation of diffusion coefficients with temperature was highly significant for both elements. Dependence of chloride diffusion on clay density was much larger than for tritium.