05000259/LER-2024-003, Valid Specified System Actuation Caused the Automatic Start of Emergency Diesel Generators

Valid Specified System Actuation Caused the Automatic Start of Emergency Diesel Generators

ML24303A034
Person / Time
Site:	Browns Ferry
Issue date:	10/29/2024
From:	Komm D Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
LER 2024-003-00
Download: ML24303A034 (1)

LER-2024-003, Valid Specified System Actuation Caused the Automatic Start of Emergency Diesel Generators

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
2592024003R00 - NRC Website

text

Post Office Box 2000, Decatur, Alabama 35609-2000 October 29, 2024 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-33 and DPR-52 NRC Docket Nos. 50-259 and 50-260 Subject:

Licensee Event Report 50-259/2024-003-00 The enclosed Licensee Event Report provides details of a breaker trip which automatically started Emergency Diesel Generators on Browns Ferry Nuclear Plant, Units 1 and 2. The Tennessee Valley Authority is submitting this report in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.73(a)(2)(iv)(A), as an event or condition that resulted in the unplanned, valid, manual or automatic actuation of emergency AC electrical power systems.

There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact David J. Renn, Nuclear Site Licensing Manager, at (256) 729-2636.

Respectfully, Daniel A. Komm Site Vice President Enclosure: Licensee Event Report 50-259/2024-003 Valid Specified System Actuation Caused the Automatic Start of Emergency Diesel Generators cc (w/ Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant 1\\14 TENNESSEE VALLEY AUTHORITY

U.S. Nuclear Regulatory Commission Page 2 October 29, 2024 DJR:RWC Enclosure bcc (w/ Enclosure):

A. Aboulfaida K. S. Adams M. B. Bruce D. M. Delk R. C. Dreke S. T. Earley C. Edmondson D. E. Ferrell J. E. Gordon K. D. Hulvey J. T. Johnson D. Komm E. Q. Leonard R. Medina M. W. Oliver J. L. Paul M. Rasmussen T. S. Rausch D. J. Renn C. L. Rice D. K. Riggs M. Sivaraman J. A. Yarbrough ECM

Abstract

On August 30, 2024, at 1051 Central Daylight Time Breaker 1622 failed to close during the transfer of Shutdown Bus 1 from 4kV Unit Board 1A to 4kV Unit Board 2B. This failure resulted in deenergizing 4kV Shutdown (SD) Boards A and B, and the A and B Emergency Diesel Generators started and tied to their respective 4kV SD Boards in response.

The cause of the event was a loose LS-9 appliance lug which resulted in a loss of power on 4kV SD Boards A and B. As corrective action, the lug was repaired. Additional actions to prevent recurrence will include, briefing of operators and maintenance personnel on this event, as well as procedure enhancements to operating instructions.

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ID Page 6 of 6 A. Immediate Corrective Actions Troubleshooting on Breaker 1622 and identified a loose wire on the charging spring limit switch. This wire was tightened and reattached.

B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future To prevent a recurrence of this event, BFN will perform the following corrective actions:

Verify the completion of Work Order (WO) 124788330, which replaces the LS-9 appliance lug for BFN-0-BKR-211-000D/001.

Verify that WOs exist to inspect safety-related 4kV Siemens breakers identified in the extent of condition and replaces their appliance lugs as required.

Conduct briefings to operations and maintenance personnel regarding this event.

Revise 0-OI-57A, Switchyard and 4160V AC Electrical System, to include the guidance on precautions and limitations associated with the charging spring failure light.

VII. Previous Similar Events at the Same Site A review of the BFN Licensee Event Reports (LERs) over the last five years revealed two similar events at BFN:

LER 50-296/2024-002-00 describes a breaker trip which automatically started an EDG on BFN, Unit 3. This event was believed to have been caused by an intermittent loose connection, which was resolved during troubleshooting activities.

LER 50-296/2020-001-00 describes an offsite lightning strike which caused the loss of the 4 kV SD BDs on BFN, Unit 3, and automatic actuated its EDGs.

VIII. Additional Information There is no additional information.

IX. Commitments There are no new commitments.