Coupled hydro-transport analysis study on geochemical environmental change caused by tunnel excavation using geological data obtained from the Horonobe URL project

Suzuki, Hideaki; Fujita, Tomoo ; Fujisaki, Kiyoshi*

The development of excavation disturbed zone (EDZ) around the disposal tunnel affects such as the corrosive environment of the over-pack and environmental condition of the nuclear species migration on the geological disposal for the high-level radioactive waste (HLW). It is necessary to consider affect of EDZ in the realistic numerical simulation of the long-term behavior of near-filed HLW repository after emplacement of engineered barrier system. This study presents the results on the analysis assessment on geochemical reaction with the evolution of the unsaturated zone around the tunnel with consideration of Horonobe area geological environment, using the developed coupled Thermo-Hydro-Mechanical and Chemical (THMC) processes analysis model. As a result, this model is applied a change of the solution composition by degasification of the carbon dioxide gas to the pore water and the change of the oxidation-reduction potential due to unsaturated zone around the tunnel.