NL-24-0276, Post-Audit Supplement to License Amendment Request to Revise Renewed Facility Operating Licenses to Adopt an Alternative Seismic Method for Categorization of Structures, Systems, and Components
| ML24208A169 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 07/26/2024 |
| From: | Coleman J Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-24-0276 | |
| Download: ML24208A169 (1) | |
Text
3535 Colonnade Parkway Birmingham, AL 35243 Tel. 205.992.5000 Regulatory Affairs July 26, 2024 Docket Nos.: 50-321 NL-24-0276 50-366 10 CFR 50.90 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Southern Nuclear Operating Company Edwin I. Hatch Nuclear Plant - Units 1 and 2 Post-Audit Supplement to License Amendment Request to Revise Renewed Facility Operating Licenses to Adopt an Alternative Seismic Method for Categorization of Structures, Systems, and Components By letter dated February 20, 2024 [ADAMS Accession Number ML24051A239], pursuant to the provisions of Section 50.90 of Title 10 of the Code of Federal Regulations (10 CFR 50.90),
Southern Nuclear Operating Company (SNC) requested amendments to Edwin I. Hatch Nuclear Plant (HNP) Units 1 and 2 renewed facility operating licenses DPR-57 and NPF-5, respectively.
The proposed amendment would modify the licensing basis to implement a change to the approved voluntary implementation of the provisions of 10 CFR 50.69, Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors, by incorporating the use of an alternative seismic method, in addition to the peer reviewed, plant-specific HNP seismic probabilistic risk assessment (SPRA) into the previously approved 10 CFR 50.69 categorization process, as allowed by NRC-endorsed industry guidance. On July 10, 2024, the NRC staff held an audit to gain understanding, to verify information, and to identify information that will require docketing to support the basis of the licensing or regulatory decision regarding the requested license amendment.
The enclosure to this letter provides information the NRC staff identified during the audit as requiring docketing.
The conclusions of the No Significant Hazards Consideration Determination Analysis and Environmental Consideration contained in the license amendment request have been reviewed and are unaffected by this supplement.
This letter contains no regulatory commitments. This letter has been reviewed and determined not to contain security-related information.
Enclosure to NL-24-0276 Response to NRC Audit Question related to Proposed Alternative Seismic Method for SSC Categorization (This Enclosure consists of 4 pages, including this cover page.)
Enclosure to NL-24-0276 Response to NRC Audit Question related to Proposed Alternative Seismic Method for SSC Categorization E1-2
Background
By letter dated February 20, 2024 [ADAMS Accession Number ML24051A239], pursuant to the provisions of Section 50.90 of Title 10 of the Code of Federal Regulations (10 CFR 50.90),
Southern Nuclear Operating Company (SNC) requested amendments to Edwin I. Hatch Nuclear Plant (HNP) Units 1 and 2 renewed facility operating licenses DPR-57 and NPF-5, respectively.
The proposed amendment would modify the licensing basis to implement a change to the approved voluntary implementation of the provisions of 10 CFR 50.69, Risk-informed categorization and treatment of structures, systems and components for nuclear power reactors, by incorporating the use of an alternative seismic method, in addition to the peer reviewed, plant-specific HNP seismic probabilistic risk assessment (SPRA) into the previously approved 10 CFR 50.69 categorization process, as allowed by NRC-endorsed industry guidance.
On July 10, 2024, the NRC staff held an audit to gain understanding, to verify information, and to identify information that will require docketing to support the basis of the licensing or regulatory decision regarding the requested license amendment. This enclosure provides information the NRC staff identified during the audit as requiring docketing.
NRC Question Section 3.1.1, Categorization Process Using Alternative Seismic Method for Tier 2 Sites, of the LAR enclosure asserts that the licensee will follow the same alternative seismic approach in the 10 CFR 50.69 categorization process for Hatch as that approved by the NRC staff for LaSalle County Station (LaSalle) with the following two clarifications.
- 1. The Hatch LAR cites EPRI Report 3002017583, Alternative Approaches for Addressing Seismic Risk in 10 CFR 50.69 Risk-Informed Categorization, dated February 2020 (ML21082A170) with the markups provided in attachment 2 of the LaSalle 10 CFR 50.69 request for additional information (RAI) responses dated October 16, 2020 (ML20290A791) and January 22, 2021 (ML21022A130), whereas the 10 CFR 50.69 categorization process approved by the NRC staff for LaSalle cited non-docketed EPRI 3002012988, Alternative Approaches for Addressing Seismic Risk in 10 CFR 50.69 Risk-Informed Categorization, dated July 2018.
- 2. The Hatch LAR incorporates the LaSalle 10 CFR 50.69 RAI response dated October 1, 2020 (ML20275A292) that addresses process issues associated with the proposed alternative seismic approach, but it specifically excludes the response to LaSalle RAI APLC 50.69-RAI No. 12 because it addresses external events that are outside the scope of this request.
A recent Brunswick LAR dated August 17, 2023 (ML23229A456) also asserts how the applicant will follow the same alternative seismic approach in the 10 CFR 50.69 categorization process as that approved by the NRC staff for LaSalle with the following two exceptions.
- 1. The site-specific LaSalle information (e.g., seismic capacity discussions, etc.) from the LaSalle 10 CFR 50.69 LAR and other LaSalle licensing responses do not apply.
Enclosure to NL-24-0276 Response to NRC Audit Question related to Proposed Alternative Seismic Method for SSC Categorization E1-3
- 2. The configuration control checklist described in the LaSalle submittal implies that a specific checklist was developed for 10 CFR 50.69 reviews. The applicant did not incorporate this checklist, but rather described its own configuration control and periodic review processes.
Please describe if the proposed amendment incorporates site-specific LaSalle information in the approved LaSalle 10 CFR 50.69 LAR and RAI responses.
- a. If the proposed amendment incorporates site-specific LaSalle information in the approved LaSalle 10 CFR 50.69 LAR and RAI responses, describe the impact of incorporating site-specific LaSalle information in the proposed Hatch 10 CFR 50.69 categorization process.
SNC Response:
The proposed Hatch Nuclear Plant (HNP) License Amendment Request (LAR) does not incorporate site-specific LaSalle information from the approved LaSalle 10 CFR 50.69 LAR or Request for Additional Information (RAI) responses. HNP site-specific seismic capacity information is described in Section 3.1.1 of the enclosure to the HNP LAR.
- b. If the proposed amendment does not incorporate site-specific LaSalle information in the approved LaSalle 10 CFR 50.69 LAR and RAI responses, clarify where an exception to the site-specific LaSalle information is addressed in the LAR.
SNC Response:
An exception to the site-specific LaSalle information is the configuration control checklist that was developed for the LaSalle 10 CFR 50.69 reviews. The LaSalle configuration control checklist was not provided in their LAR or RAI responses; however, some aspects of this checklist are provided in Section 3.5, Feedback and Adjustment Process, of the LaSalle LAR.
Southern Nuclear Operating Companys (SNCs) Probabilistic Risk Assessment (PRA) configuration control process does not use a checklist for this purpose. As noted in the HNP LAR:
The SNC configuration control process requires that changes to the plant, including a physical change to the plant and changes to documents, are evaluated to determine the impact to drawings, design bases, licensing documents, programs, procedures, and training.
Rather than employing a configuration control checklist, SNCs PRA configuration maintenance process monitors PRA inputs against various changes (e.g., plant modification and procedures; change in state of knowledge; American Society of Mechanical Engineers (ASME) / American Nuclear Society (ANS) standard revision; U.S. Nuclear Regulatory Commission (NRC) information, etc.). The proceduralized use of this approach helps maintain configuration control of the various PRA models to reflect the as-built, as-operated
Enclosure to NL-24-0276 Response to NRC Audit Question related to Proposed Alternative Seismic Method for SSC Categorization E1-4 plant. Another aspect of configuration control is to provide traceability of calculations or notebooks documenting the PRA models and their applications.
To maintain the PRA models representative of the as-built, as-operated plant, the PRA model configuration process requires changes that have a potential to impact PRA to be logged in a model maintenance log (MML) database. A risk impact assessment (qualitative, bounding, or quantitative) is then performed to evaluate the impact of a change on the PRA model(s). SNCs PRA configuration maintenance procedure provides detailed information for maintaining PRA model(s) consistent with the as built, as operated plant.
After the PRA models go through the periodic update process, systems previously categorized per 10 CFR 50.69 are reviewed and the low safety significance (LSS) / high safety significance (HSS) categorization of components within the system(s) may be revised based on the updated model.
Site-specific LaSalle information regarding site-specific characteristics (i.e., inputs to the EPRI seismic categorization process rather than the process itself) is not incorporated into the proposed amendment for Plant Hatch. Examples of site-specific LaSalle information that is not incorporated into the HNP LAR are the use of site-specific Ground Motion Response Spectra (GMRS) and Safe Shutdown Earthquake (SSE) response spectra to support the determination of each plant as a Tier 2 plant and the background information referenced in the historical seismic references discussions, which cite the various post-Fukushima seismic reviews for each plant. The cited references are specific to each plant and contain site-specific information.