Modeling of coupled processes in full-scale engineered barrier system performance experiment at Horonobe Underground Research Laboratory, Japan

Abstract

In the geological disposal of high-level radioactive waste, the overpack lifetime and initial conditions of radionuclide migration are essential considerations along with the assessments of the environmental conditions, including study of the evolution of near-field thermal, hydrological, mechanical, and chemical processes following the emplacement of an engineered barrier system. In this study, experimental data from an in situ full-scale engineered barrier experiment at Horonobe Underground Research Laboratory were used to assess the applicability of a simulation model to evaluate near-field coupled processes. Simulation results indicate that the thermal and hydraulic properties generally explain the temperature and saturation distributions and that it is crucial to capture changes in pore water characteristics as an indicator of changes in saturation. The application of the simplified unsaturated elastoplastic constitutive model improves the reproducibility of the swelling deformation behavior of buffer materials.