05000259/LER-2024-002, Reactor Scram Due to Generator Step-Up Transformer Failure
| ML24176A102 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 06/24/2024 |
| From: | Sivaraman M Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LER 2024-002-00 | |
| Download: ML24176A102 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2592024002R00 - NRC Website | |
text
Post Office Box 2000, Decatur, Alabama 35609-2000 June 24, 2024 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Unit 1 Renewed Facility Operating License No. DPR-33 NRC Docket No. 50-259
Subject:
Licensee Event Report 50-259/2024-002 Reactor Scram due to Generator Step-Up Transformer Failure The enclosed Licensee Event Report provides details of the Reactor Scram due to Generator Step-Up Transformer Failure on Browns Ferry Nuclear Plant Unit 1. 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, Primary Containment Isolation System, the High-Pressure Coolant Injection System, and the Reactor Core Isolation Cooling System.
There are no new regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact David J. Renn, Site Licensing Manager, at (256) 729-2636.
Respectfully, Manu Sivaraman BFN Site Vice President Enclosure: Licensee Event Report 50-259/2024-002 Reactor Scram due to Generator Step-Up Transformer Failure 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 1 Licensee Event Report 50-259/2024-002-00 Reactor Scram due to Generator Step-Up Transformer Failure See Enclosed
Abstract
On April 24, 2024, at 2215 Central Daylight Savings Time, while Unit 1 was at 100 percent rated thermal power, Browns Ferry Nuclear Plant Unit 1 experienced an automatic reactor scram due to a fault within the 1B Main Transformer. All plant equipment responded as expected, and Unit 1 was transitioned to Mode 4.
The cause of the transformer failure is currently under investigation. The root cause of the transformer failure will not be known until a forensic tear down is complete.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A), as an automatic actuation of the Reactor Protection System, Primary Containment Isolation System, the High-Pressure Coolant Injection System, and the Reactor Core Isolation Cooling System.
A. Immediate Corrective Actions
Engineering developed support/refute matrix to identify the cause of the transformer failure. The cause was unable to be determined but was narrowed down to an internal winding fault or core fault.
Hitachi Energy performed an initial internal inspection on the 1B transformer.
1A, 1B, and 1C transformer oil samples were sent off for evaluation.
Unit 1 Generator was inspected to ensure no damage occurred during the fault.
Unit 1/2 spare GSU transformer testing was performed to ensure health before placing into service.
Additional monitoring was placed on the Unit 1/2 spare GSU transformer for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of energization.
B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future The failed transformer has been isolated and will be forensically disassembled preventing it from any future service. Any significant findings from the forensic disassembly that result in substantial changes to the corrective action plan will be reported in a revised LER.
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.