Development of geological models in the Mizunami Underground Research Laboratory project. Updating results of 'Shaft460 geological model' and 'Shaft500 geological model' in Phase II

Japan Atomic Energy Agency (JAEA) at Tono Geoscience Center (TGC) has been promoting a geoscientific research project named the Mizunami Underground Research Laboratory (MIU) project in crystalline rock environment in order to establish scientific and technological basis for geological disposal of high-level radioactive waste (HLW). The geoscientific research at MIU is planned to be carried out in three overlapping phases; Surface-based Investigation Phase (Phase I), Construction Phase (Phase II) and Operation Phase (Phase III). Currently, the project is under the Construction Phase (Phase II) and the Operation Phase (Phase III). In the phase II, the geological models have been updated six times (Shaft180 geological model, Pilot500 geological model, Substage200 geological model, Stage300 geological model, Shaft460 geological model and Shaft500 geological model) based on the increasing data of geological mapping and borehole investigation at the shafts and research galleries. These geological models represent distribution of lithofacies and geological structures based on the geological investigation. In order to evaluate relationship between understanding of geology and progress of investigations, compilation of the history of geological models updating is useful. The history of updating from Shaft180 geological model to Stage300 geological model was already published. Thus this document mainly describes the Shaft460 and Shaft500 geological models by updating the existed model at the Phase II. (author)