Hydrothermal modeling for the efficient design of thermal loading in a nuclear waste repository

•Three-dimensional hydrothermal modeling for HLW repository is performed.•The model reduces the peak temperature in the repository by about 10 °C.•Decreasing the tunnel distance is more efficient to improve the disposal density.•The EDZ surrounding the deposition hole increases the peak temperature.•The peak temperature for the double-layer repository remains below the limit.

The thermal analysis of a geological repository for nuclear waste using the three-dimensional hydrothermal model is performed. The hydrothermal model reduces the maximum peak temperature in the repository by about 10 °C compared to the heat conduction model with constant thermal conductivities. Decreasing the tunnel distance is more efficient than decreasing the deposition hole spacing to improve the disposal density for a given thermal load. The annular excavation damaged zone surrounding the deposition hole has a considerable effect on the peak temperature. The possibility of double-layer repository is analyzed from the viewpoint of the thermal constraints of the repository. The maximum peak temperature for the double-layer repository is slightly higher than that for the single-layer repository, but remains below the temperature limit.