Abstract: In order to study the impact on bentonite under irradiation and heat simultaneous effect, the modified Na-bentonite taken from Gaomiaozi in Inner Mongolia was studied. The samples were heated to 90 ℃ and irradiated with different dose rates and cumulative doses. The results show that: when the cumulative dose was 0.37 MGy or 0.74 MGy, the water absorption, pH value, cation exchange capacity, layer charge and cell size of montmorillonite of aging samples were smaller than those of reference samples, and reduced by maximum of 18.4%, 7.8%, 3.4%, 2.9% and 15.6%, respectively. These effects decreased with the decrease of dose rate, but the aging effect had small on thermal stability and mineral compositions. It is proposed that these influencing factors on bentonite properties should be considered in the design of engineering barriers of geological disposal repository.

Key words: modified Na-bentonite, coupling effects of irradiation and heat, dose rate effect, physicochemical properties, microstructure