05000338/LER-2024-001, Automatic Reactor Trip Due to Prni High Negative Rate

Automatic Reactor Trip Due to Prni High Negative Rate

ML24211A003
Person / Time
Site:	North Anna
Issue date:	07/25/2024
From:	Hilbert L Virginia Electric & Power Co (VEPCO)
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
24-249 LER 2024-001-00
Download: ML24211A003 (1)

LER-2024-001, Automatic Reactor Trip Due to Prni High Negative Rate

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3382024001R00 - NRC Website

text

10CFR50.73

Virginia Electric and Power Company North Anna Power Station 1022 Haley Drive Mineral, Virginia 23117

July 25, 2024

Attention: Document Control Desk Serial No.: 24-249 U. S. Nuclear Regulatory Commission NAPS: RAP Washington, DC 20555-0001 Docket Nos.: 50-338 License Nos.: NPF-4

Dear Sir or Madam:

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. 50-338/2024-001-00 This report has been reviewed by the Facility Safety Review Committee and will be forwarded to the Management Safety Review Committee for its review.

Sincerely,

Lisa Hilbert Site Vice President North Anna Power Station

Enclosure Commitments contained in this letter: None cc: United States Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave,, NE, Suite 1200 Atlanta, Georgia 30303-1257

NRC Senior Resident Inspector North Anna Power Station

Abstract

On May 29, 2024, at 0624 hours0.00722 days <br />0.173 hours <br />0.00103 weeks <br />2.37432e-4 months <br /> with Unit 1 in Mode 1, 100% 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 K4 dropping into the core. A 4-hour report was made per 10 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.

The direct cause of this event was the loss of continuity to the stationary gripper coil for control rod K4. The cause of the loss of continuity is yet to be determined and a supplement will be submitted upon completion of the cause evaluation.

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

On May 29, 2024, at 0624 hours0.00722 days <br />0.173 hours <br />0.00103 weeks <br />2.37432e-4 months <br /> with Unit 1 in Mode 1, 100% 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) K4 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.

rThe direct cause of this event was the loss of continuity to the stationary gripper coil for control rod K4. The cause of the loss of continuity is yet to be determined and a supplement will be submitted upon completion of the cause evaluation.

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

The direct cause of this event was the loss of continuity to the stationary gripper coil for control rod K4. The cause of the loss of continuity is yet to be determined and a supplement will be submitted upon completion of the cause evaluation.

4.0 Immediate Corrective Action

The plug for control rod K4 was replaced.

5.0 Additional Corrective Actions

This information will be provided in the supplement.

6.0 Actions to Prevent Recurrence This information will be provided in the supplement.

7.0 Similar Events

No similar events have been noted at North Anna.

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.