Spent nuclear fuels will be eventually disposed of. They will be located in the canister, then the canister will be placed in the repository for disposal, surrounded by the buffer. Bentonite, a natural absorbent aluminum phyllosilicate consisting mostly of montmorillonite, is considered as buffer materials in South Korea. The spent nuclear fuels generate decay heat for a very long time. Thus the bentonite will be exposed to the elevated temperature condition, whereas groundwater will wet and saturate the bentonite with time. The bentonite will be exposed to dry, then to wet condition. For the safety of the disposal repository, the bentonite must maintain its required properties to delay groundwater reaching the surface of a canister [1]. Major concern to this include illitization, the transformation of smectite to illite [2,3].
In connection with our research program on Korean bentonite and its performance [4], we discuss geochemical characteristics (e.g., mineralogical changes, dehydration, volume changes, etc.) for Korean bentonite under the elevated temperature (i.e., higher than 100 ℃). The Korean bentonite loses interlayered waters at lower temperature, however holds them better at higher temperature as compared with the well-known MX-80 bentonite.
