Development of geological models in the Mizunami Underground Research Laboratory project. Updating from 'Shaft500 geological model' to 'Stage500 geological model' in Phase II

Tono Geoscience Center (TGC) of Japan Atomic Energy Agency (JAEA) is pursuing a geoscientific research and development project namely the Mizunami Underground Research Laboratory (MIU) Project in crystalline rock environment in order to construct scientific and technical basis for geological disposal of High-level Radioactive Waste (HLW). The MIU Project has three overlapping phases: Surface-based Investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III). In the Phase II, the geophysical and geological surveys, and the borehole investigation of the research galleries were carried out and the results obtained were used to validate and update the geological model. Through these surveys and analysis work, we confirmed the geological properties and the distribution of model components and evaluated the accuracy of these research methods. This report presents the geological model updated based on the information of the distributions of lithofacies and geological structures at depth 500m research galleries, and besides, the validity of the geological model of the site scale developed in the Phase I is confirmed by comparing with the updated model. (author)