Tracer transport modeling with the Alliances platform in the presence of evapotranspiration

Abstract

Abstract The knowledge and understanding of water flow and solute transport in the unsaturated zone is becoming increasingly important especially in mitigation of groundwater pollution. Fate of radionuclide in the geological environment is a topic to address in performance and safety assessment studies for nuclear waste disposal and may be modeled considering flow and transport in porous media. However, often, due to the heterogeneity and anisotropy of the real systems, the computer simulations may be difficult to render the real behavior. This paper addresses the simulation of a tracer transport in the unsaturated zone of the Saligny site, the potential location for the Romanian low and intermediate level waste (LILW) disposal. Computation was based on experimental data and was performed with the Alliances platform, a numerical tool developed by French organizations CEA, ANDRA and EDF. In order to obtain information regarding the solute migration in depth and the solute lateral dispersion, the dispersivity coefficients of iodine were investigated in order to match the experimental concentration determined on samples from different locations of the site. A close fit of the simulation over experimental data for the water saturation profile at a depth of 0.5 m in transient state was targeted by taking into account evapotranspiration in order to obtain a realistic estimation of the water infiltration in the porous media. Dispersivity coefficients obtained from the simulation of the tracer transport are in good order of magnitude for the unsaturated area and allow to have a good preview of the tracer plume. However, further investigations are recommended on new samples in order to validate the migration of the tracer plume as expected.