The Nuclear Regulatory Commission’s (NRC) independent Advisory Committee on Reactor Safeguards (ACRS) recently completed its review of a License Renewal Application (LRA) considering operations at a nuclear power plant in the United States. The NRC relies on the ACRS for its independent, unbiased review of these applications. In a letter to the NRC Chairman, ACRS referenced the proposed analytical methodology and monitoring program developed by Simpson Gumpertz & Heger (SGH). The letter indicated that the program “establishes a robust analytical methodology, supported by a comprehensive large scale test program, for the treatment and monitoring of alkali-silica reaction-affected Seismic Category I structures” at the plant.
SGH collaborated with our client to develop this program after SGH confirmed the presence of alkali-silica reaction (ASR) in concrete structures at the plant, which prompted this comprehensive response. The program includes an analytical methodology for structural evaluation and a system of proactive monitoring for any future ASR expansions at impacted Seismic Category I structures, including:
- Developing load factors to incorporate ASR loading into the design basis load combinations while preserving the inherent conservatism of the codes of record
- Developing the structural analysis and evaluation procedures for all Seismic Category I structures
- Developing the field data collection procedures for structural evaluation
- Performing structural evaluations of all Seismic Category I structures
- Developing and monitoring program for future ASR expansion, and associated threshold limits
- Implementing the program throughout the plant
- Preparing structural modifications for specific members to meet design requirements
SGH supported our client by presenting to the NRC during audits and responded to requests for additional information. NRC accepted the SGH-developed methodology document and its application to structural analysis, and has recently prepared its draft safety evaluation report. SGH also presented to the ACRS for related license amendment and License renewal requests.