Groundwater recovery experiment using an underground gallery in fractured crystalline rock

Onoe, Hironori ; Iwatsuki, Teruki  ; Saegusa, Hiromitsu; Onuki, Kenji; Takeuchi, Ryuji  ; Sanada, Hiroyuki; Ishibashi, Masayuki; Sato, Toshinori  

The selection of a geological disposal site for high-level radioactive waste (HLW) will be done taking into consideration performance of the geological environment. Geological environments would likely be influenced for several decades by changes due to the construction and operation of a large underground facility such as a HLW repository. Therefore, the post-closure recovery of the geological environment after backfilling of a facility is an important aspect for the safety assessment of geological disposal of HLW. With a focus on the hydraulic pressure and hydrochemical recovery processes around underground galleries in fractured crystalline rock, the groundwater recovery experiment will be conducted at the Mizunami Underground Research Laboratory to evaluate the natural groundwater and hydrochemical recovery of the rock mass. This paper provides an outline of the groundwater recovery experiment plan and progress of the supporting field investigations.