05000528/LER-2025-004, Train a Emergency Diesel Generator Emergency Stop with System Actuation
| ML25156A355 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/05/2025 |
| From: | Spina J Arizona Public Service Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 102-08952-JLS/JJM LER 2025-004-00 | |
| Download: ML25156A355 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| 5282025004R00 - NRC Website | |
text
10 CFR 50.73 A member of the STARS Alliance, LLC Callaway
- Diablo Canyon
- Palo Verde
- Wolf Creek Jennifer L. Spina Vice President Nuclear Regulatory & Oversight Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7602 Tel: 623.393.4621 102-08952-JLS/JJM June 5, 2025 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Palo Verde Nuclear Generating Station (PVNGS) Unit 1 Docket No. STN 50-528 / Renewed License No. NPF-41 Licensee Event Report 2025-004-00 Enclosed, please find the Licensee Event Report (LER) 50-528/2025-004-00 that has been prepared and submitted pursuant to 10 CFR 50.73. This LER reports an event in which Unit 1 had a valid specified system actuation of the Unit 1 Train A Emergency Diesel Generator after a Loss of Power signal was received via the Train A Balance of Plant Engineered Safety Features Actuation System (BOP-ESFAS). In addition, Unit 1 declared an Unusual Event (UE) Emergency Classification, Emergency Action Level (EAL) CU2.1, loss of all but one Alternating Current (AC) power source to emergency buses for 15 minutes or longer, as a result of this event.
In accordance with 10 CFR 50.4, copies of this LER are being forwarded to the Nuclear Regulatory Commission (NRC) Regional Office, NRC Region IV, and the Senior Resident Inspector.
No new commitments are being made to the NRC by this letter.
Should you need further information regarding this submittal, please contact Matthew S. Cox, Department Leader, Nuclear Regulatory Affairs, at (623) 393-5753.
Sincerely, JLS/JJM/cr Enclosure: Unit 1 Licensee Event Report 2025-004-00 cc:
J. Monninger NRC Region IV Regional Administrator W. T. Orders NRC NRR Project Manager for PVNGS A. Tran NRC Acting Senior Resident Inspector for PVNGS Spina, Jennifer (Z08962)
Digitally signed by Spina, Jennifer (Z08962)
Date: 2025.06.05 11:53:16 -07'00'
ENCLOSURE Unit 1 Licensee Event Report 2025-004-00
Abstract
On April 10, 2025, the Unit 1 Train A Emergency Diesel Generator (EDG) was supplying power to the Train A 4.16 kilovolts (kV) Class 1E bus. At approximately 06:58 Mountain Standard Time (MST), the control room received alarms indicating voltage fluctuations on the Train A EDG. This resulted in a loss of power (LOP) on the Train A Class 1E bus. Following the LOP, the Balance of Plant Engineered Safety Features Actuation System (BOP-ESFAS) sent start signals to the Train A EDG while the Train A EDG was running. At 07:01 MST, control room operators initiated an emergency stop on the Train A EDG. Additionally, the Train B EDG and `Train B 4.16 kV Class 1E bus were unavailable for planned maintenance. Power was restored at 07:03 MST when the control room connected normal off-site power through an alternate 4.16 kV non-class engineered safety feature (ESF) transformer. Once power was reestablished, the control room systematically restarted Train A essential systems.
The root cause investigation is in progress and the results will be reported in a supplement to this Licensee Event Report (LER).
No similar events have occurred at PVNGS in the prior three years. Page of
- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
052 050
8. PREVIOUS SIMILAR EVENTS
No similar events have occurred at PVNGS in the prior three years.
4 4
Palo Verde Nuclear Generating Station (PVNGS) Unit 1 00528 2025 004 00