05000296/LER-2025-001-01, Automatic Reactor Scram Following Main Generator Trip
| ML25149A021 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/29/2025 |
| From: | Komm D Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LER 2025-001-01 | |
| Download: ML25149A021 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2962025001R01 - NRC Website | |
text
Post Office Box 2000, Decatur, Alabama 35609-2000 May 29, 2025 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 3 Renewed Facility Operating License No. DPR-68 NRC Docket No. 50-296
Subject:
Licensee Event Report 50-296/2025-001-01
Reference:
Letter from TVA to NRC, "Licensee Event Report 50-296/2025-001-00,"
dated April 9, 2025 (ML25099A030)
The enclosed Licensee Event Report provides details of an Automatic Reactor Scram Following Main Generator Trip. 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 automatic actuation of the Reactor Protection System, the Primary Containment Isolation System, and the Emergency Diesel Generators. Revision 1 to this report includes information from the cause evaluation that was not previously reported.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact David J. Renn, Site Compliance Manager, at (256) 729-2636.
Respectfully, Daniel A. Komm Site Vice President Enclosure: Licensee Event Report 50-296/2025-001 Automatic Reactor Scram Following Main Generator Trip cc (w/ Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant NRC Project Manager - Browns Ferry Nuclear Plant
ENCLOSURE Browns Ferry Nuclear Plant Unit 3 Licensee Event Report 50-296/2025-001-01 Automatic Reactor Scram Following Main Generator Trip See Enclosed
Abstract
On February 8, 2025, at 2248 Central Standard Time, while at approximately 70 percent rated thermal power, Unit 3 experienced a main generator trip causing an automatic reactor scram. Plant equipment responded as expected and Unit 3 was transitioned to Mode 4. The Unit 3 isophase bus electrical fault was most likely initiated by a combination of particulate buildup on standoff insulators and elevated humidity. The root cause of the event was that the station failed to maintain an adequate maintenance strategy for the bus duct system due to perceived system reliability.
Repairs were made to the main generator bus which allowed the reactor to restart and sync to the electrical grid on March 6, 2025. Actions planned include revising the applicable Preventive Maintenance items and procedure to inspect and clean all insulators and ensure proper grounding connections.
Page 6 of 6 Access hatches for all the Unit 3 and Unit 1 insulators will be provided in upcoming refuel outages (1990732-010 and -013).
VII. Previous Similar Events at the Same Site
A search of LERs from BFN, Units 1, 2, and 3 over the last five years identified no similar events.
VIII. Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].