Fig. 1.14. Illustration of nuclear waste disposal facility (repository) for high-level radioactive wastes

The bentonite serves the following functions (Kanno and Wakamatsu, 1992) in the repositories:

(a)  buffer material delays the movement of groundwater that intrudes into the repository and reaches the container and delays the migration of radionuclides from the corroded containers to the host rock

(b) holds the containers in place and prevent transfer of excessive stresses to the containers against creep of the host rock; and

(c)  transfers heat generated in the waste to the host rock

The bentonite carries several advantages for this purpose because of its low hydraulic conductivity; low water diffusivity; and high amounts of adsorption capacity, cation exchange capacity, and swelling potentials. The determination of swelling pressures and swelling potentials in these facilities requires the application of unsaturated soil mechanics.