GEOLOGICAL INVESTIGATION CRITERIA FOR NUCLEAR POWER PLANT SITE: A REVIEW

This study reviews the regulatory guides of geological investigations applied to NPP (nuclear power plant) siting in U.S.A., Japan, China and IAEA (International Atomic Energy Agency), and recommends possible regulatory guides to the investigation ranges and depths for NPP siting. Based on the review and analysis of the regulatory guides, the geological investigation can be categorized into four levels - ‘regional', ‘near regional', ‘site vicinity' and ‘the site', based on distance from the site and the investigation degree of the detail. ‘Regional' level of investigation (within a radius of about 150km from the reactor) is expected to define tectonic provinces and environments around the site region. This level of investigation should define all the regional tectonic structures and prospective seismogenic sources that might have an effect on the safety of the projected NPP. Regarding the distance of the investigation from the site, it is noteworthy to consider ‘how far' is reasonably far enough to detect all the possible seismogenic sources that could generate a considerable vibratory ground motion to the projected NPP sites. ‘Near regional' level of investigation (within a radius of about 40km from the reactor) is to verify all the details of regional geological aspects of the region. Size of the area for the investigation should be large enough to define all geological and structural units that may include or be related to the site in space or time. ‘Site vicinity' level of investigation (within a radius of about 5km from the reactor) is to ‘scan' any possible sources of permanent surface deformation at the site and define their distributions and characteristics in 3-D. This level of investigation should be involved more detailed survey than information or results obtained by regional and near regional investigations and be included equally-spaced drilling operations, trench works and geophysical explorations. ‘The site' level of investigation (within a radius of about 1km from the reactor) is to assure that the foundation of the site is sound and acceptable for NPP facilities. This level of investigation should provide engineering information of the foundation, and sufficient data to verify clearly that reactor and safety-related structures should not be constructed on the capable fault.