ML24268A312

Automatic Reactor Trip Due to Prni High Negative Rate

ML24268A312
Person / Time
Site:
Issue date:	09/24/2024
From:	Hilbert L Virginia Electric & Power Co (VEPCO)
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
24-249A LER 2024-001-01
Download: ML24268A312 (1)

Text

VIRGINIA ELECTRIC AND POWER COMPANY

RICHMOND, VIRGINIA 23261 10CFR50.73

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

September 24, 2024

Attention: Document Control Desk Serial No.: 24-249A 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. 50-338/2024-001-01 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 NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 04/30/2027 (04-02-2024) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons

/¥0-"'"""'*4,\\ LICENSEE EVENT REPORT {LER) learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U. S. Nuclear Regulatory

~... *; (See Page 2 for required number of digits/characters for each block) Commission, Washington, DC 20555-0001, or by email to lnfocollects.Resource@nrc.gov, and the 0MB reviewer

..:..,,,'> -tio~ at: 0MB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nuclear Regulatory

...... (See NUREG-1022, R.3 for instruction and guidance for completing this form Commission, 725 17th Street NW, Washington, DC 20503. The NRC may not conduct or sponsor, and a person is httg://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) not required to respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid 0MB control number.

1. Facility Name ~ 050 2. Docket Number 3. Page North Anna Power Station 00338 1 OF 3 052

4. Title Unit 1 Automatic Reactor Trip due to PRNI High Negative Rate

5. Event Date 6. LER Number 7. Report Date 8. Other Facilities Involved

Month Day Year Year Sequential Revision Month Day Year Facility Name Docket Number Number No. 050

Docket Number 05 29 2024 2024 - 001 - 01 09 24 2024 Facility Name 052

9. Operating Mode r** Power Level 1 100

11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 10 CFR Part 20 20.2203{a)(2)(vi) 10 CFR Part 50 50. 73{a){2){ii)(A) 50. 73( a){2){viii){A) 73.1200{a) 20.2201{b) 20.2203{a)(3){i) 50.36{c){1){i){A) 50.73{a){2){ii){B) 50. 73( a){2){viii){B) 73.1200{b) 20.2201{d) 20.2203{a){3){ii) 50.36{c){1){ii){A) 50.73{a){2){iii) 50. 73( a){2){ix){A) 73.1200{c) 20.2203{a){1) 20.2203{a){4) 50.36{c)(2) 0 50.73{a){2){iv){A) 50.73{a){2){x) 73.1200{d) 20.2203{a)(2){i) 10 CFR Part 2:1 50.46{a){3){ii) 50. 73{a){2){v){A) 10 CFR Part 73 73.1200{e) 20.2203{a){2)(ii) 21.2{c) 50.69{g) 50. 73{a){2){v){B) 73. 77{a){1) 73.1200{f) 20.2203( a){2)(i ii) 50.73{a){2){i){A) 50. 73{a){2){v){C) 73. 77( a){2){i) 73.1200(9) 20.2203{a){2){iv) 50. 73{a){2){i){B) 50. 73{a){2){v){D) 73. 77{a){2){ii) 73.1200{h) 20.2203{a){2){v) 50. 73( a){2){i){C) 50. 73{a){2){vii)

OTHER (Specify here, in abstract, or NRG 366A).

12. Licensee Contact for this LER

Licensee Contact Phone Number (Include area code)

Lisa Hilbert, Site Vice President (540) 894-2101

13. Complete One Line for each Component Failure Described in this Report

Cause System Component Manufacturer Reportable to IRIS Cause System Component Manufacturer Reportable to IRIS X M CON W893 y

14. Supplemental Report Expected Month Day Year

15. Expected Submission Date No Yes {If yes, complete 15. Expected Submission Date)

16. Abstract (Limit to 1326 spaces, i.e., approximately 13 single-spaced typewritten lines)

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. Control rod K4 dropped due to a relaxing of pin prongs that caused the Stationary Coil circuit to open. 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.

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.

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0 M B: NO. 3150-0104 EXPIRES: 04/30/2027 (04-02-2024) Estimated burden per response to comply with this mand a tory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments LICENSEE EVENT R EPOR T (L ER ) regarding burden estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U. S.

Nudear Regulatory Commission, Washington, DC 20555-0001, or by email to CONTINUATION SHEET lnfocollects.Resource@nrc.gov, and the 0MB reviewer at: 0MB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nuclear Regulatory Commission, 725 17th Street NW,

(See NUREG-1022, R.3 for instruction and guidance for completing this form Washington, DC 20503. The NRC may not conduct or sponsor, and a person is not required to http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid 0MB control number.

1. FACILITY NAME 2. DOCKET NUMBER 3. LER NUMBER YEAR SEQUENTIAL REV

'North Anna Power Station 050 I 00338 D NUMBER NO.

052 I ~ -I 001 1-0

NARRATIVE 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.

The direct cause of this event was the loss of continuity to the stationary gripper coil for control rod K4. The cause of K4 dropping 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 K4. K4 dropping 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

rThe direct cause of this event was the loss of continuity to the stationary gripper coil for control rod K4. The cause of K4 dropping 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 JB-672 Patch Panel connection inside of containment. The poor connection caused the Stationary Coil circuit to open.

4.0 Immediate Corrective Action

The plug for control rod K4 was replaced.

NRC FORM 366A (04-02-2024) Page 2 of 3 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 04/30/2027 (04-02-2024) Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments LICENSEE EVENT REPORT (LER) regarding burden estimate to the FOIA, Library, and Information Collections Branch (T-6 A10M), U.S.

Nudear Regulatory Commission, Washington, DC 20555-0001, or by email to CONTINUATION SHEET lnfocollects.Resource@nrc.gov, and the 0MB reviewer at: 0MB Office of Information and Regulatory Affairs, (3150-0104), Attn: Desk Officer for the Nuclear Regulatory Commission, 725 17th Street NW, (See NUREG-1022, R.3 for instruction and guidance for completing this form Washington, DC 20503. The NRC may not conduct or sponsor, and a person is not required to http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/) respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid 0MB control number.

1. FACILITY NAME 2. DOCKET NUMBER 3. LER NUMBER YEAR SEQUENTIAL REV

'North Anna Power Station 050 I 00338 D NUMBER NO.

052 ~- I 001 1-0 I

NARRATIVE 5.0 Additional Corrective Actions

Update 1/2-ECM-1901-01," Disconnecting and Connecting CROM, RPI, and Head Vent Valves and CROM and RPI Resistance Testing," Section 6.5, CROM Coil Resistance Testing, to require manipulating the CROM Connectors during resistance checks to ensure no poor connections exist. This will consist of all the JB-671 and JB-672 Patch Panel CROM Connectors and any Reactor Head CROM Connectors that were disconnected. Manipulating the connectors during resistance checks will result in erratic or high resistance readings for any plugs that are not able to make a good connection. A step will also be added to clean the plug and receptacle as necessary.

6.0 Actions to Prevent Recurrence

Engineering to work with Westinghouse to design, procure, and implement a pin spread testing tool for the CROM Patch Panel Connectors for Unit 1 and Unit 2. Update 1/2-ECM-1901-01 to provide guidance for use of these tools prior to reconnecting the CROM Cables.

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.

NRC FORM 366A (04-02-2024) Page 3 of 3