Sensitivity analysis of groundwater lifetime expectancy to hydro-dispersive parameters: The case of ANDRA Meuse/Haute-Marne site

Within the framework of deep geological nuclear waste disposal investigations, ANDRA (French National Radioactive Waste Management Agency) has built a numerical model of groundwater flow and hydro-dispersive mass transport with the aim to analyze the characteristics of solutes transfer throughout the multilayered aquifer system including the clay host formation. As an exploratory tool, a sensitivity analysis was conducted on the average time for a water molecule flowing through the potential repository emplacement to reach the limits of the model. The correlated hydraulic conductivities and porosities of 14 hydrogeological layers are the uncertain hydro-dispersive parameters under study. A derivative-based method (Elementary Effects) is compared to regression-based global sensitivity analysis techniques (Standardized regression coefficients and Response Surface Method). As a result, the main behavior of the groundwater flow and mass transport through the multilayered system was captured. The relative effects of advective and dispersive processes are analyzed, however some uncertainties remain on the non-linear features of some input factors and their contribution to interaction processes.