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• Thermo-mechanical characteristics of two bentonites from India are presented. • Variation of swell pressures of bentonite with variation in thermal loading and densities is presented. • The development of time swelling curves for various thermal histories is presented. • The swell pressures of both the bentonite decreased with an increase in the thermal loading. The deep geological disposal system is an internationally adopted option for the disposal of high-level nuclear waste (HLW). It consists of a highly expansive bentonite, which is used as a buffer material and as a part of an engineered barrier system. Bentonite provides sufficient swelling pressure and low hydraulic conductivity to the barrier system giving long-term stability. The high-temperature waste canister in DGR and the variation in temperature due to thermal gradient impose a thermal loading on the compacted bentonite buffer and may alter the swelling pressures of the compacted bentonite. Hence it is necessary to investigate the influence of thermal loading on the swelling pressure of compacted bentonite. The paper discusses an assessments of swell pressures of two compacted bentonites (Barmer 1 (B 1) and Barmer 2 (B 2)) from Barmer district of Rajasthan, India with initial dry densities of 1.5 Mg/m3, 1.75 Mg/m3, and 2 Mg/m3 and subjected to 110 °C and 200 °C, hydrated with distilled water. The swelling load is recorded and compared with non-heated samples of same densities. Experimental and theoretical evidences indicated that the swelling pressure of heated compacted bentonite decreased with an increase in the temperature. Statistical analysis is also presented with the help of analysis of variance (ANOVA). [ABSTRACT FROM AUTHOR]

The bentonite is compacted around the steel canister containing high-level waste to ensure the sealing of the canister by blocking the entry of harmful radiations emitted due to the reactions of active radionuclides. However, the canister continuously exhibits a high temperature (150 °C–200 °C) due to radioactive waste decay over a long time, which creates a thermal history on the surrounded compacted bentonite. Corrosion can generate changes in the bentonite buffer, which comes in direct contact with the canister and may lead to a change in its swelling ability. This study investigates the influence of corrosion products on the swell pressure of compacted bentonite specimens subjected to thermal history. Two Bentonite samples (B 1 and B 2) from the Barmer district of Rajasthan, India, were mixed with corrosion products and compacted at dry densities 1.5 Mg/m3, 1.75 Mg/m3 and 2.0 Mg/m3. These specimens were subjected to thermal histories at 110 °C and 200 °C and saturated with distilled water. The decrease in the swell pressure values was observed with the corrosion product and the increase in temperature of induced thermal history—comparatively, more time required for saturation in the presence of corrosion products than in its absence. The alteration in montmorillonite minerals might have occurred under the induced thermal history and corrosion reaction. [ABSTRACT FROM AUTHOR]