Numerical Analysis of Gas Generation and Migration in a Radioactive Waste Disposal Cell of a Deep Geological Repository

In a deep geological repository (DGR) for the long-term disposal of radioactive waste, gases(e.g., hydrogen (H2), carbon dioxide (CO2) and methane (CH4)) can be generated through anumber of processes, such as corrosion of various metals and alloys and degradation oforganic materials. If gas induced pressure exceeds the containment capacity of theengineered barrier systems (EBS) or the host rock, the gases could migrate through thesebarriers and potentially expose people and the environment to radiation. Therefore, a goodunderstanding on the long-term performance of these barriers against gas migration is animportant component in DGR design and safety assessment. In the present work, a numericalmodel has been developed to simulate the diffusion of CO2(one of the gas species) in the nearfield of a DGR with the generation from related chemical reactions. The generation of CO2was investigated to determine if it is a critical factor to impact the DGR safety underCanadian geological formations. A commercial computational fluid dynamics (CFD) code,ANSYSFluent was used for the calculations. The model consideredpH and temperature effectson CO2migration under Canadian DGR geochemistry conditions