05000328/LER-2025-002-01, Manual Reactor Trip Due to a Failed Closed Main Feedwater Regulating Valve
| ML25275A002 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  (DPR-079) |
| Issue date: | 10/01/2025 |
| From: | Michael K Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LER 2025-002-01 | |
| Download: ML25275A002 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(b)(3)(iv)(A) |
| 3282025002R01 - NRC Website | |
text
Sequoyah Nuclear Plant, Post Office Box 2000, Soddy Daisy, Tennessee 37384 October 1, 2025 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Unit 2 Renewed Facility Operating License No. DPR-79 NRC Docket No. 50-328
Subject:
Licensee Event Report 50-328/2025-002-01, Manual Reactor Trip due to a Failed Closed Main Feedwater Regulating Valve Reference: TVA Letter submitted to NRC dated August 20, 2025, Licensee Event Report 50-328/2025-002-00, Manual Reactor Trip due to a Failed Closed Main Feedwater Regulating Valve.
The enclosed licensee event report has been revised with supplemental information concerning a manual reactor trip due to a failed closed main feedwater regulating valve that resulted in lowering steam generator water levels. This revised report reflects the results of the causal analysis and associated corrective actions. This event was previously reported in accordance with 10 CFR 50.73(b)(3)(iv)(A) as an event that resulted in actuation of the Reactor Protection System and Auxiliary Feedwater System. Changes to the reference report are indicated by revision bars on the right-side margin of the page.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Mr. Rick Medina, Site Compliance Manager, at (423) 843-8129 or rmedina4@tva.gov.
Respectfully, Kevin Michael Site Vice President Sequoyah Nuclear Plant Enclosure: Licensee Event Report 50-328/2025-002-01 cc:
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant
Abstract
On June 24, 2025, at 0351 eastern daylight time, SQN Unit 2 operators performed a manual reactor trip.
Unit 2 was manually tripped due to lowering water level in the Loop 1 Steam Generator caused by a Loop 1 Main Feedwater Regulating Valve (MFRV) malfunction. All plant safety systems responded as designed. This event did not adversely affect the health and safety of plant personnel or the general public.
The root cause for this event was determined to be the MFRV diaphragm provided by the vendor did not meet the vendors specifications for the valve. Corrective actions for the event include identifying vendor-specified characteristics and acceptance criteria for diaphragms for the MFRVs. Characteristics to consider include dimensions, material hardness, Fourier Transform Infrared Spectroscopy (FTIR) traces, and hole template conformity. Additionally, the diaphragms will be required to receive a receipt inspection for testing to confirm the identified characteristics.
Page 5 of 5 C. For failure that rendered a train of a safety system inoperable, estimate of the elapsed time from discovery of the failure until the train was returned to service There was no failure that rendered a train of a safety system inoperable.
VI.
Corrective Actions
This event was entered into the Tennessee Valley Authority Corrective Action Program under condition report number 2021907.
A. Immediate Corrective Actions
Once troubleshooting discovered that MFRV 2-FCV-03-35 failed, an extent of condition review was completed for the Unit 2 and Unit 1 MFRVs.
B. Corrective Actions to Prevent Recurrence or to reduce the probability of similar events occurring in the future Corrective actions for the event include identifying vendor-specified characteristics and acceptance criteria for diaphragms of Nitrile and/or EPDM for MFRVs. Characteristics to consider include dimensions, material hardness, Fourier Transform Infrared Spectroscopy (FTIR) traces, and hole template conformity. Additionally, the diaphragms will be required to receive a receipt inspection for testing to confirm the identified characteristics.
VII. Previous Similar Events at the Same Site
There were no previous similar events at SQN occurring within the last three years.
VIII. Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments.