Research on Evaluation of Coupled Thermo-Hydro-Mechanical Phenomena against Full-scale In-situ Engineered Barrier Experiment

Chijimatsu, Masakazu*; Amemiya, Kiyoshi*

In order to achieve the geological disposal of radioactive waste in safe, it is necessary to ensure the stability of the engineered barrier system (EBS). One of the most important factors for the stability of the EBS is the emplacement technology of the EBS. It is considered that the stability of the EBS is secured by the properly emplacement based on the design requirement. In this research, the methods filling the gap between buffer and rock or buffer and over-pack were examined. Bentonite pellets were tested as the filling materials. To research the time-dependent phenomena of bentonite pellets after swelling, permeability tests were conducted with different period. Furthermore, to clarify the effect of test fluid, permeability test was conducted with synthetic seawater to compare the result with that of the test with distilled water. After emplacement of the engineered barrier system, it is expected that the near-field environment will be impacted by phenomena such as heat dissipation by conduction and other heat transfer mechanisms, infiltration of groundwater from the surrounding rock in to the engineered barrier system, stress imposed by the overburden pressure and generation of swelling pressure in the buffer due to water infiltration. In order to recognize and evaluate these coupled phenomena, it is necessary to make a confidence of the mathematical models and computer codes based on the information about the in-situ experiments regarding the engineered barrier system. In this research, technical investigations about the in-situ full-scale experiment (called Prototype Repository Project) in Aspo HRL facility by SKB of Sweden were performed. In order to evaluate the coupled phenomena in the engineered barrier, we use the new swelling model based on the theoretical approach. In this paper, we introduce the modeling approach and applicability about the new model.