Study of sorption and diffusion of 137Cs in compacted bentonite saturated with saline water at 60degC

The effect of compaction of bentonite on the sorption behavior of 137Cs was studied for the safety assessment of the high level radioactive waste. The diffusion coefficients (effective De and apparent Da) and the distribution coefficient for sorption Kd for 137Cs in compacted and dispersed bentonite saturated with saline water were investigated at 60degC by four different sorption and diffusion experiments: the in-diffusion, through-diffusion, reservoir-depletion and batch sorption experiments. The system of the through-diffusion experiment was carefully designed to maintain the boundary conditions of constant concentration at each end of the specimen. De and Da were found to be reproducible and showed good consistency among three of the diffusion experiments (through-diffusion, in-diffusion and reservoir depletion). Kd of 137Cs in compacted bentonite determined from the three types of diffusion experiments was in good accordance with that determined by the batch sorption experiment for dispersed bentonite. (author)