Abstract: It is of great significance to investigate the long-term performance of core disposal element of high-level radioactive waste under coupled thermo-hydro-mechanical condition, especially for the site experiments and repository conceptual design. In this work, a coupled thermo-hydro-mechanical model was proposed based on the core disposal element. The finite element numerical simulation software COMSOL Multiphysics was employed to conduct the 3D numerical simulation on the core disposal element under different disposal concepts. The simulation results indicate that the minimum disposal distance between deposition holes obtained by thermal transfer simulation is larger than that by coupled thermo-hydro-mechanical simulation, when disposing 1 canister, 2 canisters, and 3 canisters vertically in the deposition hole. That’s because the increase in water saturation of the buffer material is not considered in the thermal transfer simulation, resulting in a smaller thermal conductivity coefficient of the buffer material. However, the disposal spacing derived from thermal transfer simulation provides a more secure approach for disposal elements. It can be seen that as the number of canisters in the deposition hole increases, the average disposal area of the canisters slightly increases. The results of thermal transfer analysis indicate that it is optimal to allocate one canister per deposition hole in terms of disposal area conservation alone. For horizontally disposal, the overall heat transfer to the outside of the deposition hole deteriorates is slower than vertically disposal. The results of thermal transfer analysis indicate that it is optimal to disposal vertically.

Key words: geological disposal of high-level radioactive waste, repository conceptual design, thermo-hydro-mechanical coupling, numerical simulation, heat transfer