Effect of Boundary Conditions on Thermohydraulic Behaviour of Clay Buffer used in Nuclear Waste Repository

This paper reports the results of a numerical study on heat and moisture transport through a buffer layer made of clay as used in nuclear waste repository. Galerkin's weighted residual finite element method along with Newton-Raphson method has been used for the solution of the non-linear coupled governing equations used to represent the heat and moisture transport through unsaturated clay material. After validating the code numerical simulation results were obtained for heat and moisture variations within the buffer material for Dirichlet temperature boundary conditions in the range, 50oC < T < 155oC and heat flux boundary conditions in the range, 130 W/m2 < q < 560 W/m2, with an aim to simulate the boundary conditions which the clay barrier will be subjected to in real situations. The temperature and moisture variations within the clay buffer are discussed from the point of view of thermo-hydraulic behavior of clay under the above boundary conditions.