Micro-structure of bentonite clay and diffusion coefficient given by multiscale homogenization analysis

Bentonite consists of nanometer scale of smectitic clay minerals (mainly montmorillonite) and micrometer scale of macro-grains (mainly quatz). Properties of saturated bentonite are characterized by hydrated clay minerals. For a diffusion problem in bentonite we developed a new multiscale homogenization analysis (HA) procedure which relates microscale characteristics with a macroscopic behavior. We discuss diffusion properties of tritium water (HTO) compared with experimental data. Microscopic properties of the montmorillonite hydrate such as diffusivity of chemical species which are used in HA are determined by a molecular dynamics (MD) simulation method. We show the calculated results are consistent with macroscale experimental data.