The purpose of this study was to determine the unsaturated hydraulic properties of High Level Waste simulant by applying inverse modeling and parameter estimation methods and data obtained by experiments.
Saltcake simulant was placed in column equipped with tensiometers and flow meters. Variable pressure boundary conditions ranging from 100 to 500 cm were applied along the column, outflow and the pressure head were measured with respect to time. The experimental data was analyzed using an inverse modeling software and the van Genuchten's hydraulic parameters for unsaturated porous media were determined. In addition, the unsaturated hydraulic conductivities were obtained as a function of the moisture content. Hydraulic conductivities ranged from 5.36E-5 to 4.29E-2 cm/hr. The data was analyzed to determine the percentage reduction in storage capacity as a function of applied pressure. The experimental results were compared with output from direct simulations of interstitial fluid drainage from a column and showed good agreement.
While there are several studies on determining the saturated hydraulic conductivities, this work demonstrates that the van Genuchten unsaturated model is a valid model and can be applied for three dimensional modeling and for determining the level of separation of radioactive waste (Cs 137) using interstitial fluid drainage.