Diffusion of radioactive anion and cation in silver-calcium-bentonite

In the geological disposal of nuclear waste, the simultaneous reduction of diffusion rate of cationic and anionic radioactive species is essential. Natural calcium-bentonite only reduces the diffusion rate of cations, not anions. In this study, the half of calcium ions is bentonite was exchanged to silver ions to reduce diffusion rates of both of radioactive cation (¹³⁷Cs⁺) and anions (³⁶Cl⁻, ¹³¹I⁻) at the same time. This is due to the precipitation of silver halides in the interlayer space. The diffusion rate of both anionic and cationic radioactive species are small in compacted the silver-calcium bentonite.