05000370/LER-2025-002, Reactor Trip, Auxiliary Feedwater Actuation, and Refueling Water Storage Tank Inoperability Due to Relief Valve Leak
| ML25343A343 | |
| Person / Time | |
|---|---|
| Site: | Mcguire (NPF-017) |
| Issue date: | 12/09/2025 |
| From: | Rollins T Duke Energy Carolinas |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RA-25-0286 LER 2025-002-00 | |
| Download: ML25343A343 (0) | |
| Event date: | |
|---|---|
| Report date: | |
| 3702025002R00 - NRC Website | |
text
~ -, DUKE
~ ENERGY Serial No: RA-25-0286 December 9, 2025 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTENTION: Document Control Desk
Subject:
Duke Energy Carolinas, LLC McGuire Nuclear Station, Unit 2 Docket No. 05000370 Renewed License No. NPF-17 Licensee Event Report 2025-002-00 Nuclear Condition Report Number 02571809 Travis Rollins Manager Nuclear Support Services Duke Energy MG01VP I 12700 Hagers Ferry Road Huntersville, NC 28078 o: 980.875.4646 Travis. Rollins@duke-energy.com 10 CFR 50.73 Pursuant to 10 CFR 50.73 Section (a)(2)(i)(B), attached is Unit 2 Licensee Event Report (LER) 2025-002-00, regarding a reactor trip, Auxiliary Feedwater actuation, and Refueling Water Storage Tank inoperability due to a relief valve leak.
This event is considered to have no significance with respect to the health and safety of the public. There are no regulatory commitments contained in this LER.
If questions arise regarding this LER, please contact Jeff Sanders at 980-875-4680.
Sincerely, Travis B. Rollins Duke Energy McGuire Nuclear Station Manager, Nuclear Support Services Attachment
U.S. Nuclear Regulatory Commission RA-25-0286 Page 2 cc:
Julio F. Lara Administrator Region II (Acting)
U.S. Nuclear Regulatory Commission Marquis One Plaza 245 Peachtree Center Avenue NE Suite 1200, 30303-1257 J. Klos Project Manager (McGuire)
U.S. Nuclear Regulatory Commission Mail Stop O-9-E3 11555 Rockville Pike Rockville, MD 20852 Chris Safouri NRC Senior Resident Inspector McGuire Nuclear Station
Abstract
On October 9, 2025, with Unit 2 in Mode 1 and operating at approximately 20 percent power to support previously scheduled maintenance activities, Control Room personnel observed a decreasing trend in the Volume Control Tank (VCT) level estimated at approximately 4 gpm. The lowering level in VCT was due to leakage from the Unit 2 Boric Acid Blender Outlet Relief Valve (2NV-483), which discharges into the Reactor Coolant System letdown line upstream of the VCT. Subsequently, suction for the Chemical and Volume Control pumps were realigned to the Refueling Water Storage Tank (RWST) and normal letdown was secured to isolate the leak. Operations performed a rapid downpower and tripped the Unit 2 reactor per procedural guidance from approximately 5% power at 0100 on October 10, 2025. Upon reactor trip, the motor driven auxiliary feed pumps were manually started to maintain Steam Generator levels. Further, transition of the Chemical and Volume Control pumps suction to the RWST resulted in reducing inventory below the minimum volume requirement per Technical Specifications, rendering the single train system inoperable for approximately 38 minutes.
The primary cause of the event was less than adequate risk recognition of unresolved erratic behavior of an adjacent control valve which resulted in high cycle vibrational fatigue of the relief valve bellows. The relief valve has been replaced, and corrective actions will be implemented to appropriately address the cause. This event had a very low impact on plant risk and there was no impact to the health and safety of the public.
LICENSEE EVENT REPORT (LER)
(See Page 2 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
SAFETY ANALYSIS
The McGuire Unit 2 manual reactor trip described above is considered to be an uncomplicated reactor trip event with no impact on public health and safety. A post-trip review found no critical procedure or human performance issues with the operator response to the event. No equipment important to plant safety was out of service at the time of the reactor trip, and no equipment failures or malfunctions occurred to challenge operator responses. Therefore, it is concluded that the conditional core damage probability for the Unit 2 reactor trip was very low and did not cause a significant increase in risk to the public. The very brief reduction in RWST inventory was minor and within the margin between the usable RWST volume at Technical Specification minimum level and the volume assumed in Safety Analysis modeling. Therefore, this event had no impact on the health and safety of the public, and a very low impact on overall plant risk.
ADDITIONAL INFORMATION
A review of previous Licensee Event Reports was conducted to determine if this was a recurring event (i.e.,
similar event with the same cause or same failure mode). No previous occurrences that involved the same underlying cause and/or failure mode as this event was identified within the past three years.