Role of clay microstructure in caesium diffusion through compacted bentonite

A deep Geological repository is at present the most acceptable way of storing radioactive waste away from biosphere. It entails a combination of waste form, waste packages, engineered seals and geology to ensure long-term isolation of long half-life radionuclides. Smectite rich natural clay, generally referred as bentonite, is an important engineered barrier material, controlling rheological - mechanical properties of the barrier and transport of contaminants through it. Owing to changing geochemical conditions in surroundings of the barrier system, clay characteristics change over time. This work aims to investigate the effect of major cations of the surrounding groundwater on the diffusion properties of Cs⁺ in smectite rich natural clay of Indian origin. To investigate diffusion characteristics of Cs⁺ in compacted montmorillonite-rich natural clay (Barmer region, Western India) in conditions wherein the natural clay is saturated predominantly with either Na⁺ or K⁺ exchange ions, a transient-state diffusion of caesium in Na⁺- and K⁺-saturated clays was carried out