Abstract
The migration of hazardous substances in a bentonite barrier layer is a key issue for the safety of nuclear waste storage. This study develops a thermo-hydro-mechanical coupling model to simulate the contaminant migration in a bentonite barrier layer of the nuclear waste storage chamber. In particular, the Richard’s equation is used to describe the groundwater flow in the bentonite barrier layer with variable saturation. Thermal diffusion and concentration diffusion are coupled with the layer deformation and fluid flow. The migration rate and diffusion range of hazardous substances in the bentonite barrier layer are numerically simulated. These numerical simulations show that the heat release from nuclear waste can induce a temperature gradient and deformation, and thus significantly affects both transfer rate and concentration distribution of dilute substances. These multi-physical couplings under different initial saturation may significantly modify the sealing efficiency of an unsaturated bentonite barrier layer and thus this model is of great significance in the safety evaluation of a nuclear waste disposal repository.
Highlights
The contaminant migration in a landfilling barrier is a key issue for the safety of nuclear waste storage [1,2,3]
This paper proposes a thermo-hydro-mechanical coupling model for the contaminant migration in an unsaturated bentonite barrier layer
The safety performance of bentonite backfilling for nuclear waste storage is evaluated through parametric study
Summary
The contaminant migration in a landfilling barrier is a key issue for the safety of nuclear waste storage [1,2,3]. The landfilling barrier is usually a bentonite backfilling layer for the leakage prevention of radioactive contaminants. This leakage prevention or sealing capacity of a barrier layer evolves under the combination actions of seepage, temperature and loading. The path and speed of contaminant transport may be significantly modified in the nuclear waste storage process [5,6]. The mechanism of contaminant migration in the barrier layer is complicated, including convection, diffusion and adsorption and their interactions [7], and should be investigated with multi-physical couplings
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