ADDRESSING GEOLOGIC SITE CHARACTERIZATION ISSUES IN PUBLIC HEARINGS REQUIRED BY LAW FOR LICENSING NUCLEAR POWER PLANTS AT THE U.S. NRC - A PRACTICAL EXAMPLE

The proposed William States Lee III nuclear power plant site in Cherokee County, South Carolina, is located at the original site of the Cherokee Nuclear Station (CNS), which was licensed for construction in early 1970 but abandoned in early 1980 prior to completion. Original CNS Unit 1 corresponds to proposed Lee Unit 1 and lies under original foundation concrete, creating a novel issue for implementing the NRC’s Geologic Mapping License Condition (GMLC). The GMLC requires a licensee to map lithologies and tectonic and non-tectonic features in excavations for safety-related engineered structures to ensure no significant potential exists for hazard due to surface deformation at a new plant site. Because concrete cover precluded examination of foundation rocks in the Lee Unit 1 excavation by NRC geologists, at an October 2016 public hearing convened for the Lee site, as required by the Atomic Energy Act of 1954, as amended (Public Law 114-92), the NRC Chairman asked staff how foundation materials were evaluated to confirm the applicant’s conclusion that no significant potential exists for tectonic deformation at Lee Unit 1. (Non-tectonic deformation was not an issue because foundation materials are crystalline basement.) Staff provided testimony explaining that the evaluation was accomplished by systematically conducting the following activities: (1) Examining the original CNS foundation geologic maps; (2) Comparing lithologies, faults, fractures, and shear zones captured on the original CNS maps with rock types and tectonic features observed at adjacent Lee Unit 2 and in the surrounding area; (3) Examining outcrops at the southeastern edge of CNS concrete that expose a prominent northwest-striking shear zone mapped at CNS Unit 1; (4) Comparing foundation rocks in archived CNS Unit 1 core with archived and new core samples from Lee Units 1 and 2; and (5) Reviewing radiometric age dates acquired for CNS and examining relative age relationships between exposed tectonic features at Lee Unit 2 and in the surrounding area, with both data sources documenting that shearing occurred more than 145 Ma ago. The NRC will adhere to its mission of protecting public health and safety by requiring the licensee to implement the GMLC for Lee Unit 2 to ensure no tectonic features exist that might produce surface deformation at Unit 2.