Canister spacing in a high level radioactive nuclear waste repository based on heat conduction

One of the core problems in the design of canister spacing in the repository for disposing high-level radioactive waste is the evolution of the temperature field. On the basis of the layered thermal analysis model for a single waste canister, the expression for temperature increment at any position of surrounding rock in the repository is obtained through the superposition principle. The Laplace domain solution is numerically inverted by the Crump method, and the near-field temperature evolution of the repository under multi-waste canister exothermic system is obtained. Under the adjacent tunnel spacing of 40 m, the initially estimated value of the waste canister spacing is determined by the line graph of the peak temperature of the waste canister surface, the thermal conductivity of the rock and the waste canister spacing. Finally, the influences of the relevant parameters on the surface temperature of the waste canister are analyzed. The results show that the peak temperature of the waste canister surface appeares in the 6th year under the exothermic condition of a single waste canister, and the peak temperature appeares in the 80th year under the multi-waste canister exothermic system. Taking the thermal conductivity of 2.4 W/(m×K) and 2.8 W/(m×K) for the rock as examples, the appropriate spacing of waste canisters is 12.2 and 13.5 m, respectively. The greater the waste canister spacing, the greater the thermal conductivity of bentonite and rock, the smaller the peak temperature of the waste canister surface will be. The thicker the bentonite layer, the less the heat flux inside the waste canister will spread out. The research results can provide a reference for the dimensioning design and safety assessment of the repository.