Deep geological disposal is, at present, one of the
preferred alternatives for the safe disposal of a highlevel
radioactive waste (HLW). Crystalline rocks, clayrich
rocks, and rock salt have been considered as suisuitable
host media where a repository for a HLW can be
built. HLW would be placed in horizontal drifts or vertical
boreholes excavated to considerable depths in an
appropriate rock (Chapman and McKinley, 1987). After
the emplacement of a container, the space between the
containers and the surrounding host rock is filled with a
buffer material which constitutes an engineered barrier.
Bentonite has been considered as a candidate buffer
material for the disposal of HLW because of its low
permeability, high sorption capacity, self sealing cha-