Diffusive parameters of tritiated water (HTO) and U in chalk

Complete text of publication follows: The Cretaceous Chalk of the Basin of Paris is known for its aquifer which constitutes one of the main important groundwater resource in France. Previous study indicates that this chalk exhibits a double porosity (matrix and fracture) providing pathways for both slow and rapid migration of water. The presented study is part of an ongoing project aiming at understanding and predicting the chemical contaminant transfer properties through chalk formation. This project is based on a multidisciplinary approach (field investigations, U-series disequilibria and geochemical modelling). Mobility through the matrix porosity of U and tritiated water (HTO) taken as an inert tracer, was studied according to diffusion experiments on four different samples. Diffusive parameters, e. g. accessible porosity and effective diffusion coefficient, of HTO and U in samples were determined. Additional measurements of porosity were achieved according to mercury porosimetry and to water content. Results are discussed regarding to the distribution of porosity (micro, meso and macro porosity) and to both mineralogical and textural characteristics