Abstract
AbstractCorrosion of steel canisters, disposed of in a repository for high-level waste (HLW), leads to generation of hydrogen gas for a long period after the repository's closure. The accumulation of hydrogen gas may lead to significant desaturation and unacceptable build-up of pressure in the backfilled disposal tunnels if the gas cannot escape through the low-permeability host rock. Consequently, the investigation of gas migration is of high relevance in the assessment of the repository's performance.In this paper, the results of numerical investigations on gas migration performed using the computer code TOUGH2 (USA) are presented. The objective was to investigate migration of gas generated in a single disposal tunnel of a conceptual geological repository in a clay formation, which was suggested for benchmark studies in the European Commission project FORGE (Fate Of Repository GasEs). The analysis was focused on evaluation of the impact of an initial temperature in the repository and of different tortuosity models on gas migration. It was revealed that gas migration results were dependent on tortuosity model, while temperature variation in the repository had minor impact.
Highlights
GAS influence on the long-term safety of geological repositories has been investigated for more than fifteen years
Two isothermal analyses assuming a lower (10°C) and a higher (30°C) initial temperature in the disposal tunnel compared to a reference case (20°C) in the Fate of Repository Gases (FORGE) benchmark were performed
In the 30°C temperature case, the molecular diffusion coefficient of dissolved H2 increased and the total mass flux of gaseous hydrogen toward the access drift decreased by 7.5% and the total mass flux of dissolved hydrogen towards the undisturbed clay formation increased by 43.2% compared to the reference case
Summary
GAS influence on the long-term safety of geological repositories has been investigated for more than fifteen years. Two isothermal analyses assuming a lower (10°C) and a higher (30°C) initial temperature in the disposal tunnel compared to a reference case (20°C) in the FORGE benchmark were performed.
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