DEVELOPMENT OF POLICY AND PROCEDURES OF REGULATORY INSPECTION APPLIED TO UNDERGROUND OPENINGS FOR SAFETY-RELATED NUCLEAR FACILITIES

Safety-related nuclear facilities shall be installed on a stable foundation with minimal potentiality of geological hazards such as collapse, faulting, or any other types of ground deformation that could affect the nuclear safety. For a nuclear site with potential for such hazardous phenomena, a proper safety measure or reinforcement must be applied to remove any possible adverse effects from them or minimize these affects to satisfy the design bases and regulatory requirements. During the stage of site characterization study for the application of the construction permit (CP), geological, seismological and geotechnical surveys are carried out to find out site suitability and geological condition of the site for the planned nuclear facilities. After the issuance of CP, all the data and models produced at the site characterization stage must be confirmed at the final foundation surface of the facilities during the construction stage. Major activities involved in underground constructions are blasting, excavation, mapping, reinforcement and measurement in general. For the purpose of the geological and seismological safety, besides of the stability of the underground openings and the safety of the working environment, it is required more detailed and conservative standards and requirements for the construction of tunnels or any other types of underground openings for the installation of the safety-related nuclear facilities then any other types of constructions. Some examples of the regulatory practices applied to fulfill the safety purpose in Korean nuclear sites are such as controlled blasting to give minimal effect to adjacent safety-related facilities and foundations, detailed geological mapping (including record of fault characterization and establishment of structural frameworks) covering all the geological surfaces that contact with safety-related facilities, and quality control of all the records and documents produced during the construction.

This paper presents a part of the results from a research project to develop regulatory inspection guides, applicable internationally, based on regulatory inspection practices that have been applied to the constructions of underground openings, including NPP cooling water intake tunnels, at Korean nuclear construction sites in recent years.