05000338/LER-2025-002, Automatic Reactor Trip Due to PRNI High Negative Rate
| ML25351A290 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 12/17/2025 |
| From: | Joel Jenkins Virginia Electric & Power Co (VEPCO) |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 25-281 LER 2025-002-00 | |
| Download: ML25351A290 (0) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3382025002R00 - NRC Website | |
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Dominion Energy Virginia North Anna Power Station 1022 Haley Drive, Mineral, VA 23117 DominionEnergy.com
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Dominion
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Energy 10CFR50.73 Virginia Electric and Power Company North Anna Power Station 1022 Haley Drive Mineral, Virginia 23117 December 17, 2025 Attention: Document Control Desk Serial No.:
25-281 U. S. Nuclear Regulatory Commission Washington, DC 20555-0001
Dear Sir or Madam:
NAPS:
RAP Docket Nos.: 50-338 License Nos.: NPF-4 Pursuant to 1 0CFR50.73, Virginia Electric and Power Company hereby submits the following Licensee Event Report applicable to North Anna Power Station Unit 1.
Report No. 50-338/2025-002-00 This report has been reviewed by the Facility Safety Review Committee and will be forwarded to the Management Safety Review Committee for its review.
James Jenkins Site Vice President North Anna Power Station Enclosure Commitments contained in this letter: None cc:
J. Lara - NRC Region II Administrator Region II NRC Senior Resident Inspector - North Anna Power Station
Abstract
On October 21, 2025, at 2108 hours0.0244 days <br />0.586 hours <br />0.00349 weeks <br />8.02094e-4 months <br /> with Unit 1 in Mode 1, 7 4% power, an automatic reactor trip occurred due to power range nuclear instrument high negative rate. The cause of the negative rate was due to control rod C7 dropping into the core. Control rod C7 dropped due to a relaxing of pin prongs that caused the Stationary Coil circuit to open. A 4-hour report was made per 1 O CFR 50.72(b)(2)(iv)(B) for a Reactor Protection System (RPS) Actuation and an 8-hour report was made per 10 CFR 50.72(b)(3)
(iv)(A) for a valid Engineered Safety Feature actuation for the Auxiliary Feedwater (AFW) Pumps actuating as designed during the event.
Unit 2 was not impacted by this event. This event is reportable per 10 CFR 50.73(a)(2)(iv)(A) for RPS actuation and valid AFW actuation. The health and safety of the public were not affected by this event.
1.0 Description of Event
- 2. DOCKET NUMBER
- 3. LER NUMBER I
00338 Cl NUMBER NO.
I YEAR SEQUENTIAL REV
~-I 002 1-G On October 21, 2025, at 2108 hours0.0244 days <br />0.586 hours <br />0.00349 weeks <br />8.02094e-4 months <br /> with Unit 1 in Mode 1, 7 4% power, an automatic reactor trip occurred due to power range nuclear instrument (EIIS Component DET, System IG) high negative rate. The cause of the negative rate was due to control rod (EIIS Component ROD, System AA) C? dropping into the core. The Auxiliary Feedwater (AFW) Pumps (EIIS Components P, System BA) actuated as designed during this event. The reactor trip and AFW pumps starting are reportable per 10 CFR 50.73(a)(2)(iv)(A) as System Actuations.
rrhe direct cause of this event was the loss of continuity to the stationary gripper coil for control rod C7. The cause of C?
clropping into the core was a relaxing of the pin prongs resulting in reduced pin spread on the " E" Pin. This resulted in a poor connection on the plug side of the Patch Panel connection inside of containment. The poor connection caused the Stationary Coil circuit to open. This resulted in the Stationary Coil losing its holding current. The Stationary Gripper then opened, dropping C?. C? dropped from 233 to 183 steps, and this created a change in flux that was picked up by nuclear instruments N41 and N43. This satisfied the 2/4 NI High Negative Flux Rate Trip, which opened the Reactor Trip Breakers (EIIS Component BKR, System AA).
2.0 Significant Safety Consequences and Implications
No significant safety consequences resulted from this event due to plant equipment performing as designed. The health and safety of the public were not affected by this event.
3.0 Cause of the Event
rrhe direct cause of this event was the loss of continuity to the stationary gripper coil for control rod C?. A Root Cause Evaluation (RCE) is being performed for this event and is not yet completed. An LER supplement will be submitted upon completion and approval of the RCE.
4.0 Immediate Corrective Action
rrhe plug for control rod C7 was replaced.
5.0 Additional Corrective Actions
An RCE is being performed for this event and is not yet completed. An LER supplement will be submitted upon completion and approval of the RCE. The LER supplement will include the identified corrective actions.
6.0 Actions to Prevent Recurrence
- 2. DOCKET NUMBER
- 3. LER NUMBER I
00338 SEQUENTIAL REV NUMBER NO.
002 1-0
~n RCE is being performed for this event and is not yet completed. An LER supplement will be submitted upon completion and approval of the RCE. The LER supplement will include the identified corrective actions.
7.0 Similar Events
A similar event occurred in May of 2024 at North Anna, LER N1-2024-001.
8.0 Additional Information
Unit 2 was not impacted by this event. The health and safety of the public were not affected by this event. Page 3
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