Coupled thermo-hydro-mechanical analysis of a deep geological repository for final disposal of spent nuclear fuel in Brazil

The Brazilian nuclear program includes nuclear power plants fueled by enriched uranium that require a final disposal solution. A viable option for the underground disposal of spent nuclear fuel (SNF) is a deep geological repository (DGR). This study simulates the thermo-hydro-mechanical (T-H-M) performance of rock media subjected to the radiogenic heat loads from spent nuclear fuel in a deep geological repository using a multibarrier concept. At maximum temperatures as high as 131.79 °C and vertical stresses greater than 55 MPa between fuel containers the isolation buffer effectively reduced the temperature and stress between the containers and rock media. The behavior of gas and liquid phases showed to be more complex than observed in strictly thermal analysis, and the prescribed separation between canisters, originally aimed to mitigate radionuclides migration, showed to be as effective for long-term stability of the DGR.