ML22063A000

Requests for Additional Information from Risk Branch Regarding 120V Inverter LAR

ML22063A000
Person / Time
Site:	Seabrook
Issue date:	01/25/2022
From:	Justin Poole Plant Licensing Branch 1
To:	Levander M, Moul D NextEra Energy Seabrook
Poole J, NRR/DORL/LPLI, 415-2048
References
EPID L-2021-LLA-0131
Download: ML22063A000 (3)

Text

From: Poole, Justin To: Levander, Matthew Cc: Mack, Jarrett; Danna, James

Subject:

Request for Additional Information RE: 120V Inverter LAR from the Risk Branch Date: Tuesday, January 25, 2022 10:52:00 AM Attachments: L-2021-LLA-0131 Risk RAIs final.pdf

Matt, By letter dated July 21, 2021, as supplemented by letter dated September 22, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML21202A238 and ML21278A309, respectively), NextEra Energy Seabrook, LLC (NextEra, the licensee) requested changes to the Technical Specifications (TSs) for Renewed Facility Operating License NPF-86 for Seabrook Station, Unit No. 1 (Seabrook). The proposed changes would revise TS 3/4.8.3, Onsite Power Distribution - Operating, by increasing the Allowed Outage Time (AOT) for the 120-volt (V) alternating current (AC) vital instrument panel inverters, establishing a new required action for two inoperable 120 VAC vital instrument panel inverters of the same electrical train and related administrative changes.

The Supplement dated September 22, 2021 superseded the July 21, 2021, application. In reviewing the submitted information, the U.S. Nuclear Regulatory Commission (NRC) staff has determined that additional information is necessary to complete its review.

On January 7, 2022, the NRC staff sent NextEra the DRAFT RAIs to ensure that the questions are understandable, the regulatory basis is clear, there is no proprietary information contained in the RAIs, and to determine if the information was previously docketed. On January 24, 2022, the NRC and NextEra held a clarifying call. During the call, NextEra requested a response date of 30 days from the date of this email. The NRC staff informed NextEra that this timeframe is acceptable. The attached is the final version of the RAIs. These RAIs will be put in ADAMS as a publicly available document.

Justin C. Poole Project Manager NRR/DORL/LPL I U.S. Nuclear Regulatory Commission (301)415-2048

REQUESTS FOR ADDITIONAL INFORMATION (RAIs) REGARDING THE LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATION 3/4.8.3, ONSITE POWER DISTRIBUTION - OPERATING SEABROOK STATION, UNIT NO. 1 DOCKET NO. 50-443 By application dated July 21, 2021, and as supplemented by letter dated September 22, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML21202A238 and ML21278A309, respectively), NextEra Energy Seabrook, LLC (NextEra, the licensee) requested changes to the Technical Specifications (TSs) for Renewed Facility Operating License NPF-86 for Seabrook Station, Unit No. 1 (Seabrook). The proposed changes would revise TS 3/4.8.3, Onsite Power Distribution - Operating, by increasing the Allowed Outage Time (AOT) for the 120-volt (V) alternating current (AC) vital instrument panel inverters, establishing a new required action for two inoperable 120 VAC vital instrument panel inverters of the same electrical train and related administrative changes. The Supplement dated September 22, 2021 superseded the July 21, 2021, application.

The NRS staff has determined that the following additional information is needed to complete the review of the Seabrook license amendment request (LAR) supplement dated September 21, 2021.

Regulatory Requirements and Guidance The NRC staff used the following regulatory guidance to review the LAR:

Regulatory Guide (RG) 1.177, Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications, Revision 2, supplements RG 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, Revision 3, and refers to it for many technical details.

In RG 1.174, the staff describes its evaluation approach and acceptance guidelines which follow from the key principles of risk-informed regulation. In implementing these principles, the staff expects, in part that:

Uncertainty receives appropriate consideration in the analyses and interpretation of findings, including use of a program of monitoring, feedback, and corrective action to address key sources of uncertainty. NUREG-1855 provides acceptable guidance for the treatment of uncertainties in risk-informed decisionmaking.

In RG 1.174, Section 6.3, Licensee Submittal Documentation, the NRC staff describes the information that it requires to reach the conclusion that the proposed licensing basis change is

consistent with the key principles of risk-informed regulation and NRC staff expectations. This information includes identifying:

Key assumptions in the PRA that impact the application (e.g., voluntary licensee actions), elements of the monitoring program, and commitments made to support the application. As defined in the ASME/ANS PRA standard endorsed in RG 1.200, an assumption is labeled key when it may influence (i.e., have the potential to change) the decision being made.

NRC Staff RAIs ABLB RAI - 1 In LAR Attachment 3, Section 3, Sources of Model Uncertainty, although the licensee stated that potential sources of generic and plant-specific uncertainty that represent possible impact on risk-informed applications identified were reviewed thoroughly. No sources of uncertainty were identified as having a significant impact on the results of this evaluation, no additional information was provided for the staff to make the determination.

Therefore, the NRC staff requests that the licensee provide a description of the sources of model uncertainties, the key assumptions made, and discuss any conservativism or non-conservativism introduced by the analysis approach to the internal events and internal flooding events PRA models.

ABLB RAI - 2 A stand-alone bounding calculation was used to determine the potential impact of the fire events for the proposed extension. Clarify whether the resulting total site fire frequency used in this assessment will also be used as the baseline risk metric in future full power fire PRA applications. Alternatively, describe how this permanent change will be incorporated into the fire PRA.