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High-level heat-emitting long-lived vitrified radioactive waste produced during recycling of the spent nuclear fuel is under consideration for permanent disposal in deep geological formations with appropriate thermomechanical, hydrogeological and geochemical properties. The capability of these rock formations ensuring long-term confinement and isolation of such waste from the environment is significantly controlled by their efficiency in smoothly dissipating the heat emanating from the waste. A number of rock types such as basalt, granite, clay stones, volcanic tuff, argillites, etc. are being evaluated worldwide as well as in India. In this study, a granite from Jalore and bentonite from Barmer, both from Rajasthan, India, have been evaluated for their heat dissipation capacity. The study revealed that the temperature within granite at the centre of the canister reached 55.21°C, resulting in a thermal stress of 25.50 MPa. Bentonite experienced a temperature of 67.42°C in the central part with maximum thermal stress and displacement of 1.78 MPa and 0.446 mm respectively. A displacement of 0.997 mm was recorded at the granite-bentonite interface. Thus, no significant microcrack formation or undesirable displacement was observed within the granite as well as in bentonite, suggesting their capability to isolate and confine the heat-emitting source for extended periods. [ABSTRACT FROM AUTHOR]

• 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]