Numerical simulation of a temporary repository of radioactive material

Abstract

The use of computer simulations techniques is an advantageous tool in order to evaluate and select the most appropriated site for radionuclides confinement. Modelling different scenarios allow to take decisions about which is the most safety place for the final repository. In this work, a bidimensional numerical simulation model for the analysis of dispersion of contaminants trough a saturated porous media using finite element method (FEM), was applied to study the transport of radioisotopes in a temporary nuclear repository localized in the Vadose Zone at Pena Blanca, Mexico. The 2D model used consider the Darcy's law for calculating the velocity field, which is the input data for in a second computation to solve the mass transport equation. Taking into account radionuclides decay the transport of long lived U-series daughters such as ${}^{238}\!\text{U}$, ${}^{234}\!\text{U}$, and ${}^{230}\!\text{Th}$ is evaluated. The model was validated using experimental data reported in the literature obtaining good agreement between the numerical results and the available experimental data. The simulations show preferential routes that the contaminant plume follows over time. The radionuclide flow is highly irregular and it is influenced by failures in the area and its interactions in the fluid-solid matrix. The resulting radionuclide concentration distribution is as expected. The most important result of this work is the development of a validated model to describe the migration of radionuclides in saturated porous media with some fractures.