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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]

• The influence of thermal and chemical gradient saturated on bentonite is presented. • A lab-scale set up was fabricated which would create a thermal and chemical gradient. • The degree of saturation decreased towards heating end from the hydration end. • Reduction in cation exchange capacity was noted at various levels of samples. • The micro-structural investigations revealed the mineralogical changes. Compacted bentonite is being used as a buffer material for the safe dumping of high-level radioactive wastes (HLW) in the deep geological repository (DGR) due to its favorable physicochemical properties. However, the temperature variation, probably because of continuous heat emitting canister (initially −150 °C to 250 °C) and geothermal gradient, affect its performance. There would be bentonite iron interface reactions due to the corrosion of steel canister, which might cause reactive transport through the compacted bentonite buffer. Therefore, it is essential to know the influence of a combination of thermal as well as a chemical gradient on the reactive transport through the compacted bentonite buffer in terms of its physicochemical, thermomechanical, mineralogical stability. The purpose of this particular study is to establish the field conditions in the lab by fabricating a small scale set up which would create a thermal gradient on the compacted Barmer bentonite (B 1 and B 2) samples (compacted at 1.5 Mg/m3, 1.75 Mg/m3 and 2 Mg/m3 densities) by heating its one side at 60 °C, 110 °C, 150 °C and 200 °C temperatures for 28 days each and the system was hydrated by distilled water from the other side and was kept in touch with the metallic iron powder. It was observed that the degree of saturation of both bentonites decreased with an increase in temperature as well as density. However, the cation exchange capacity at lower density reduced more than that of higher density. The microstructural observation revealed the presence of impurities between the lamella of bentonite after 28 days that might be hematite. [ABSTRACT FROM AUTHOR]