Thermal Behaviour of Backfill Material for a Nuclear Fuel Waste Disposal Vault

The concept of disposing of used nuclear fuel in engineered rock formations is being studied in the Canadian Nuclear Fuel Waste Management Program. After the used fuel is emplaced in the vault, the vault would be backfilled. The backfill has to satisfy a number of engineering requirements. A reference backfill with satisfactory hydraulic, thermal and mechanical properties has already been selected. As the used fuel in the waste containers decays, heat will be generated and this heat will raise the temperature of the backfill material. The performance of the reference backfill material was evaluated over the temperature range 20–100°C. This paper addresses the results of experiments on thermal response and pressure development in the backfill for the period shortly after vault closure.