Numerical analysis of the influence of the number of waste canister in borehole on the temperature, stress, and displacement in the near field of the high-level waste repository

Abstract

Safe disposal of high-level waste is a challenging problem facing the scientific, technological, and engineering communities. The actual high-level waste disposal is closely related to the number of waste canisters in a single borehole. The influence of the number of waste canisters in a single borehole on the near-field temperature, stress, and displacement of the repository is directly related to the safety and cost of waste disposal. In this paper, based on the conceptual model of the high-level waste repository, the influence of the number of waste canisters in a single vertical borehole on the near-field temperature, stress, and displacement of the high-level waste repository was calculated and analyzed by using the 3DEC program. The results show that as the number of waste canisters in a single borehole increases, its heat release capacity is enhanced, and the temperature in the same area near the repository increases gradually; the temperature gradient increases gradually. The more waste canisters in a single borehole, the higher the temperature of the observation point near the same location of the repository (about 30°C), the temperature difference is getting larger and larger, and the average increase of temperature difference at observation point is about 8.1°C. The change of normal stress at the observation point is obvious when the waste canister releases heat for about 0–1 year; after that, the compressive stress decreased slightly, and then the stress and time curve was basically horizontal; the stress difference is getting larger and larger; the average increase of stress difference is about 0.0545MPa.The general trend of observation point displacement is that when the waste canister releases heat for about 0–1 year, displacement increases greatly, and then displacement increases less and presents a linear distribution trend; the displacement difference is getting larger and larger; the average increase of displacement difference is about 0.00034m. The thermal superposition effect of waste canisters added in a single borehole in engineering design cannot be ignored, and it showed that attention should be paid to the number of waste canisters in the disposal pit.