Nuclear Waste Industry

Bentonite in Nuclear Waste Management

Commercially available in the form of bentonite powder, sodium smectite clay acts as a very powerful water flow barrier and cation exchanger. The hydraulic conductivity is on the order of 10−14 to 10−13 m/s at bulk densities between 1·9 and 2·2 g/cm3 after water uptake to reach maximum saturation.
The swelling ability generates near contact with confining structures, which makes bentonite suitable for borehole and shaft sealing as an overpack of rock-deposited radioactive canisters. The hydraulic conductivity of smectite gels is still sufficiently low at bulk densities between 1·1 and 1·3 g/cm3 to make them useful as effective grout for the sealing of rock fractures.
The longevity in a granite environment is very important and some of the excellent sealing properties of smectites are maintained by the ultimate residue of transformation, hydrous mica ('illite').