ML24116A253

Final Request for Additional Information for LAR to Revise SR 3.8.1.2 Note 3 (EPID: L- 2023-LLA-0135)

ML24116A253
Person / Time
Site:	Prairie Island
Issue date:	04/25/2024
From:	Ballard B Plant Licensing Branch III
To:	Kivi J, Mark Miller Northern States Power Co
Ballard, Brent
References
EPID: L- 2023-LLA-0135
Download: ML24116A253 (1)

Text

From: Brent Ballard To: Miller, Michael A; Kivi, Jeffrey L Cc: Jeff Whited

Subject:

Prairie Island Units 1 & 2 - Final Request for Additional Information for LAR to Revise SR 3.8.1.2 Note 3 (EPID: L-2023-LLA-0135)

Date: Thursday, April 25, 2024 2:43:00 PM Attachments: Final RAI for LAR to Revise SR 3.8.1.2.docx

Good afternoon, Mike and Jeff,

By application dated September 28, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23271A205), as supplemented by letter dated December 5, 2023 (ML23339A060), Northern States Power Company (NSPM, the licensee), a Minnesota Corporation, doing business as Xcel Energy, submitted a license amendment request for the Prairie Island Nuclear Generating Plant, Units 1 and 2 (Prairie Island). The proposed amendment would revise Prairie Island Technical Specification 3.8.1, AC Sources - Operating, surveillance requirement 3.8.1.2, Note 3, to remove details describing a modified emergency diesel generator start and reference to manufacturers recommendations.

The NRC staff has determined that additional information is needed to complete its review. Attached is NRC staffs request for additional information (RAI).

A clarification call was held on April 25, 2024, with NSPM. The amplifying information preceding the RAI questions was revised for clarity, as discussed on the call. The NRC staff is requesting a response to the RAI within 30 days of the date of this email, which is May 25, 2024. Please let me know if you have any questions.

Thank you, Brent

Brent Ballard Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 301-415-0680

REQUEST FOR ADDITIONAL INFORMATION

LICENSE AMENDMENT REQUEST TO

REVISE TECHNICAL SPECIFICATION 3.8.1

PRAIRIE ISLAND NUCLEAR GENERATING PLANT

NORTHERN STATES POWER COMPANY

DOCKET NO. 50-282 AND 50-306

EPID L-2023-LLA-0135

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Background===

By application dated September 28, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23271A205), as supplemented by letter dated December 5, 2023 (ML23339A060), Northern States Power Company (NSPM, the licensee), a Minnesota Corporation, doing business as Xcel Energy submitted a license amendment request for the Prairie Island Nuclear Generating Plant, Units 1 and 2 (Prairie Island). The proposed amendment would revise Prairie Island Technical Specifications (TS) 3.8.1, AC Sources -

Operating, surveillance requirement (SR) 3.8.1.2, Note 3, to remove details describing a modified emergency diesel generator (DG) start and reference to manufacturers recommendations.

Regulatory Requirements

The regulatory requirements related to the content of the TSs are set forth in Title 10 of the Code of Federal Regulations (10 CFR) Section 50.36, Technical specifications. This regulation requires that the TSs include items in five specific categories. These categories include:

(1) safety limits, limiting safety system settings and limiting control settings; (2) limiting conditions for operation (LCOs); (3) SRs; (4) design features; and (5) administrative controls.

Section 50.36(c)(3) states: Surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation (LCO) will be met.

Request for Additional Information

The NRC staff has reviewed the application and supplement and determined that additional information is necessary to complete its review.

Current SR 3.8.1.2 states: Verify each DG starts from standby conditions and achieves steady state voltage > 4084 V and < 4400 V, and frequency > 59.5 Hz and < 60.5 Hz.

Current SR 3.8.1.2 Note 3 states: A modified DG start involving idling and gradual acceleration to synchronous speed may be used for this SR in consideration of manufacturers recommendations. When modified start procedures are not used, the time, voltage, and frequency tolerances of SR 3.8.1.6 must be met.

Revised SR 3.8.1.2, Note 3 would state: A modified DG start may be used for this SR. When modified start procedures are not used, the time, voltage, and frequency tolerances of SR 3.8.1.6 must be met.

In the supplement dated December 5, 2023, the licensee proposed to relocate the details of a modified DG start test to the proposed revised TS Bases and includes the underlying reason and intent of Note 3 and its effect on SR 3.8.1.2 in the revised TS Bases.

Revised TS Bases for SR 3.8.1.2 would state: Note 3 of SR 3.8.1.2 allows for a modified (slow)

DG start procedure, which could include idling and/or a longer time for acceleration, that may be used to reduce long-term stress and wear on diesel engines.

LAR section 2.3, Reason for Proposed Changes, states: SR 3.8.1.2, Note 3, contains details that are not necessary to ensure operability; therefore, these details are not required to be in the TS to provide adequate protection of the public health and safety.

LAR section 3.0, Technical Evaluation, states:

The proposed change to SR 3.8.1.2, Note 3, will remove detail from TS that is not necessary to ensure operability. Detail to provide consistent implementation of the TS is located in other licensee-controlled documents. NSPM considers manufacturers recommendations as part of operating and testing procedures and proposed design modifications.

NSPM operating and testing procedures are informed by design specifications, vendor technical manuals, and the operating experience program that has diverse inputs including NRC generic correspondence, notifications from the Institute of Nuclear Power Operations (INPO), and technical bulletins from manufacturers. Therefore, it is not necessary to specify consideration of manufacturers recommendations for DG starting in SR 3.8.1.2, Note 3. The details of what constitutes a modified start, such as idling and acceleration, are more appropriately located in other licensee-controlled documents.

The supplement dated December 5, 2023, states:

The modified start of SR 3.8.1.2 is intended to reduce the stress and wear on the diesel engines by allowing more time for starting than the fast start of SR 3.8.1.6, which requires that the DG starts from standby condition and achieves voltage of at least 3740 V and frequency of at least 58.8 Hz within 10 seconds. The procedures for a modified start (referred to as the slow start surveillance procedures) for the Unit 1 and Unit 2 DGs are different because the DGs were provided by different manufacturers. The most notable difference is that the Unit 1 DG modified start is manually controlled and the Unit 2 DG modified start is built into the DG controls. Specifically, the Unit 1 DG slow start procedures include approximately one minute idling time before manually raising engine speed and the Unit 2 DG slow start procedures include a built-in slow test mode with a slower acceleration as part of the governor control system. There are no planned changes to the Unit 1 or Unit 2 slow start surveillance procedures associated with the proposed license amendment.

In light of recent modifications developed to improve the Unit 2 DGs control systems, it became apparent to NSPM that the level of procedural detail in the TS SR note is not necessary to achieve the intent of the TS SR. The intent of SR 3.8.1.2 is to demonstrate that the DG can be started and achieve the required steady-state voltage and frequency; no time limitations apply. SR 3.8.1.6 is the test that ensures availability of the standby electrical power supply within ten seconds. In addition, the current Note 3 could hinder the incorporation of industry and site operating experience related to DG reliability and could become unintentionally restrictive to future improvements.

The staff notes the following:

- The modified DG start in Note 3 is part of the SR 3.8.1.2 that must be met to ensure the operability of the DG. The modified DG start that the TS allows for SR 3.8.1.2 to ensure the operability of the DG is the one that considers the recommendations of the manufacturer. Thus, the words in consideration of the manufacturers recommendations, are details that help ensure an adequate modified DG start for SR 3.8.1.2.

- Including the words in consideration of the manufacturers recommendations, in SR 3.8.1.2 Note 3 does not preclude the licensee from considering the diverse inputs that informed NSPM testing procedures, but it is consistent with the use of those words or similar ones in the application and supplement. In addition, including those words in SR 3.8.1.2 Note 3 does not add time limitations to the SR 3.8.1.2 and it still allows meeting the intent of SR 3.8.1.2, which is to demonstrate that the DG can be started and achieve the required steady-state voltage and frequency.

- The words in consideration of manufacturers recommendations, are included in Prairie Island current SR 3.8.1.3 Note 1.

- In the supplement, the first paragraph quoted above states that the DG modified start includes idling and/or a longer time for acceleration but the terms could in the proposed revised TS Bases seems to indicate the modified DG start does not have to include idling and/or a longer time for acceleration. Also, the supplement states that the modified start of SR 3.8.1.2 is intended to reduce the stress and wear on the diesel engines, but the term may in the proposed revised TS Bases seems to indicate that the intent of the modified start can be something other than to reduce long-term stress and wear on diesel engines.

The staff has the following questions:

RAI-1

As stated above, Section 3.0 of the LAR states NSPM considers manufacturers recommendations as part of operating and testing procedures. Explain why the words in consideration of manufacturers recommendations for the modified DG start in the current SR 3.8.1.2 Note 3 are removed from the TS and not relocated to the TS Bases.

RAI-2

Clarify the use of words could and may in the revised TS Bases for SR 3.8.1.2. Indicate if the modified DG start for each DG has other main steps and outcome that are not captured in the revised TS Bases.