Validation of the fully-analytical solution with temperature superposition for the nuclear waste repository

Abstract

Temperature distributions and evolutions in high-level radioactive waste (HLW) disposal repository are usually obtained by numerical simulation or analytical solution. For the use of analytical solution to calculate the temperature distributions of one disposal panel in the repository, the temperatures from every nuclear waste canister were superposed for calculating the whole effects of all the canisters, and the disposal tunnels, which are filled with backfill materials, were ignored to simplify the deducing process. Yet the accuracy of the temperature superposition has not been validated and the influence of tunnels on temperature has not been evaluated. In this paper, a disposal panel with 1189 waste canisters was modelled by the finite element method for analyzing the temperature distributions and evolutions. The size of numerical domain was determined by studying the temperature distributions. When the distance between the outer edges and outermost canisters surface was set as 700 m or above, the influence of boundaries on calculated results can be ignored. A disposal panel with tunnels was modelled to study the influence of tunnels on temperature evolution, and the results show that the tunnels have practically no effect on the temperature evolution. Finally, the comparison of temperatures calculated by numerical simulation and analytical solution was done to validate the analytical solution with the superposition method.