A new thermal analysis model with three heat conduction layers in the nuclear waste repository

A mathematical model for three layer media with different thermal conductivities is presented for analyzing the three-dimensional heat conduction of the repository. The solutions to the temperature distribution in the bentonite block layer, bentonite pellet layer and surrounding rock were derived through applying the Fourier and Laplace transforms upon the heat conduction equations. These analytical solutions can be used to obtain the evolution of temperature fields at the repository site. Finally, a parametric study is carried out to assess the effects of geometry dimension and thermal conductivity on the thermal performance. The results show that the three layer model was demonstrated more accurately to simulate the temperature field in the repository through comparative analysis with the existing double layer model and line heat source model. The thickness of the bentonite pellet layer will lead to a significant increase in the peak buffer layer temperature because of its low thermal conductivity.