Evaluating the mass transport characteristics for fault zone in mudstone at the Horonobe Underground Research Laboratory

Takeda, Masaki ; Ishii, Eiichi   ; Ono, Hirokazu ; Tachi, Yukio  ; Ito, Tsuyoshi*; Nemoto, Kazuaki*

Fault zones have the potential to act as flow paths, and the characterization of solute transport in such zones in mudstone is important for developing the solute transport model required in the safety assessment for the geological disposal of radioactive waste. In this paper we characterize the solute transport properties of fault-zones fractures in a mudstone at the Horonobe Underground Research Laboratory (Horonobe URL) with results of in situ tracer migration tests by different tracer-injection methods using stable tracers. The flow paths are evaluated from the distributions of fractures and sorbing-tracer concentrations on the fractures surfaces.