Activation energy for diffusion of chloride ions in compacted sodium montmorillonite

摘要

Diffusion of chloride ions in compacted montmorillonite was studied for a performance assessment as buffer material in geological disposal of high-level radioactive waste. The apparent diffusion coefficients were from 6.8×10~-12 to 2.2×10~-10 m~2 s~-1 for sodium montmorillonite at dry densities from 1.0 to 1.8 Mg m~-3 at diffusion temperatures from 278 to 323 K. The activation energy increased from 14 kJ mol~-1(lower than that in free water, 17.4 kJ mol~-1)to 25 kJ mol~-1(higher than that in free water), as the dry density increased from 1.0 to 1.8 Mg m~-3.