05000251/LER-2025-004, Unit 4, Unplanned Reactor Scram
| ML25226A035 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 08/14/2025 |
| From: | Mack K Florida Power & Light Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-2025-140 LER 2025-004-00 | |
| Download: ML25226A035 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2512025004R00 - NRC Website | |
text
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U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re:
Turkey Point Unit 4 Docket No. 50-251 Renewed Facility Operating License No. DPR-41 Reportable Event: 2025-04-00 Date of Event: June 21, 2025 Unplanned Reactor Scram August 14, 2025 L-2025-140 10 CFR 50.73 The attached Licensee Event Report (LER), Turkey Point Unit 4 LER 2025-04-00, Unplanned Reactor Scram, is being submitted pursuant to the requirements of 10 CFR
- 50. 73( a)(2)(iv)(A), System Actuation.
This event did not have an adverse effect on the health and safety of the public.
Should you have any questions regarding this submission, please contact Maribel Valdez, Fleet Licensing Manager, at 561-904-5164.
This letter contains no new or modified regulatory commitments.
Sincerely,
- ~.Z::::L i<.llfrth A. ~
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Director, Lie sing and Regulatory Compliance Florida Power & Light Company Attachment: Turkey Point Unit 4 LER 2025-04-00, Emergency Diesel Generator Actuation cc:
USNRC Regional Administrator, Region II USNRC Project Manager, Turkey Point Nuclear Plant USNRC Senior Resident Inspector, Turkey Point Nuclear Plant Mr. Clark Eldredge, Florida Department of Health Florida Power & Light Company 9760 SW 344th Street, Homestead, FL 33035
Attachment Turkey Point Unit 4 LER 2025-04-00 Turkey Point Unit 4 LER 2025-04-00, Unplanned Reactor Scram Florida Power & Light Company 9760 SW 344th Street, Homestead, FL 33035
Abstract
At 1438 EDT on June 21, 2025, while at 100 percent power and in Mode 1, Turkey Point Unit 4 experienced an unplanned reactor trip and spurious Safety Injection (SI) signal when the 4A 4kV [EIIS: EA] bus locked out. The cause of the bus lockout was due to the 4A 4kV bus protective relay scheme responding to an overcurrent condition sensed from the 4A Emergency Diesel Generator (EOG) [EIIS: NB] due to the 4A EOG voltage balance relay being left in the actuated position after planned testing. In addition to the unplanned reactor trip, an actuation of the Auxiliary Feedwater (AFW) [EIIS: SA] occurred. Due to the unplanned reactor trip and AFW initiation, this event is being reported pursuant to 10 CFR 50. 73(a)(2)(iv)(A), System Actuation.
Description of Event
- 2. DOCKET NUMBER
- 3. LER NUMBER I
00251 D
NUMBER NO.
I YEAR SEQUENTIAL REV
~-,
04 1-0 At 1438 EDT on June 21, 2025, while at 100 percent power and in Mode 1, Turkey Point Unit 4 experienced an unplanned reactor trip and spurious Safety Injection (SI) signal when the 4A 4kV [EIIS: EA] bus locked out. The cause of the bus lockout was due to the 4A 4kV bus protective relay scheme responding to an overcurrent condition sensed from the 4A Emergency Diesel Generator (EOG) [EIIS: NB] due to the 4A EOG voltage balance relay being left in the actuated position after planned testing. In addition to the unplanned reactor trip, an actuation of the Auxiliary Feedwater (AFW) [EIIS: SA]
occurred.
There were no structures, systems, or components inoperable at the start of the event that contributed to the event.
Cause of Event
The root cause of this event was attributed to a latent procedure trap in O-PME-005.22, Testing and Independent Verification of Operational Trip Test. Specifically, there was unclear procedural steps for placing and removing HOLDs on voltage balance relays. With the 4A EOG voltage balance relay left in the actuated position, combined with a blown fuse, XRCG-C Phase fuse, in the 4A 4KV Bus voltage reference circuit, a 4kV bus lockout occurred when the 4A EOG was synched to the 4A 4kV bus.
Analysis of Event
This event resulted in an unplanned trip. This event was complicated by the generation of a SI signal. In addition, the event did not have any impacts on the following:
- Personnel safety (actual or potential)
- Environmental safety
- Radiological safety
- Actual nuclear safety significance Due to the unplanned reactor trip and AFW initiation, this event is being reported pursuant to 10 CFR 50.73(a)(2)(iv)(A),
System Actuation.
This event did not result in a Safety System Functional Failure.
Corrective Actions
The issue was corrected by placing the 4A EOG balancing relay in the unactuated position and the replacement of the XRCG-C Phase fuse. Planned actions include fabricating a non-conductive, high-visibility tool (wedge) for EOG Voltage Balance Relay testing and revising O-PME-005.22.
Similar Events
A review of events over the past 5 years did not identify any similar events with the same cause as this event. Page 2
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