05000339/LER-2024-001-01, Loss of Generator Field for 2J Eog During 2-PT-82.28

Loss of Generator Field for 2J Eog During 2-PT-82.28

ML24233A245
Person / Time
Site:	North Anna
Issue date:	08/20/2024
From:	Hilbert L Virginia Electric & Power Co (VEPCO)
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
24-210A LER 2024-001-01
Download: ML24233A245 (1)

LER-2024-001, Loss of Generator Field for 2J Eog During 2-PT-82.28

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3392024001R01 - NRC Website

text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 10CFR50.73 Vir:ginia Electric and Power Company North Anna Power Station 1022 Haley Drive Mineral, Virginia 23117 August 20, 2024 Attention: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Dear Sir or Madam:

Serial No.:

24-210A NAPS:

RAP Docket Nos.: 50-339 License Nos.: NPF-7 Pursuant to 10CFR50.73, Virginia Electric and Power Company hereby submits the following Licensee Event Report applicable to North Anna Power Station Unit 2.

Report No. 50-339/2024-001-01 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,

/4~ adtr--

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 April 18, 2024, at 1355 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.155775e-4 months <br /> with Unit 2 in Mode 1, 100% power, during the performance of 2-PT-82.28,

,, 2J Diesel Generator Test (Simulated Loss of Off-Site Power)" the electrical generator failed to flash the field which resulted in a no voltage condition. The engine operated at rated speed of 900 RPM/ 60 Hz with a local room annunciator " Loss of Field Flash" locked in alarm. The 2J EOG was subsequently shut down and placed in quarantine in support of failure investigation.

Investigation into the issue identified the voltage regulator control system K1 M relay was found in the closed position. This condition would result in a loss of field flash or prevention of field flash of the electrical generator and subsequently no generator voltage output. This event is reportable per 10 CFR 50.73(a)(2)(i)(B) as a Condition Prohibited by Technical Specifications.

l The direct cause of this event is foreign material within the K1 M preventing proper operation. 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

00339 NUMBER NO.

I YEAR SEQUENTIAL REV J~~~ ~ 1 001 1 ~ ~

On April 18, 2024, at 1355 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.155775e-4 months <br /> with Unit 2 in Mode 1, 100% power, during the performance of 2-PT-82.28, " 2J Diesel Generator Test (Simulated Loss of Off-Site Power)" the electrical generator (El IS System EK, Component GEl\\l) failed to

!flash the field which resulted in a no voltage condition. The engine operated at rated speed of 900 RPM/ 60 Hz with a local room annunciator" Loss of Field Flash" locked in alarm. The 2J Emergency Diesel Generator (EOG) (EIIS System EK, Component DG) was subsequently shut down and placed in quarantine in support of failure investigation. Investigation into the issue identified the voltage regulator control system Ki M relay was found in the closed position. This condition would result in a loss of field flash or prevention of field flash of the electrical generator and subsequently no generator voltage output. This event is reportable per 10 CFR 50. 73(a)(2)(i)(B) as a Condition Prohibited by Technical Specifications. During the fault exposure period for the 2J EOG, the 2H EOG was inoperable on two occasions for a total of 4.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. However, the 2H EOG was still available to perform its design function during those periods of time.

NOTE: The K1 relay (EIIS Component 53) is comprised of two separate components, Ki R is the generator field flash relay which is mechanically connected (clipped on) to the K1 M portion which is the electrical coil and field shutdown portion. The K1 R provides the latching mechanism which holds the K1 M in the " picked up" position when coil power is removed from K1 M. Both components together are referred to as K1.

2.0 Significant Safety Consequences and Implications No significant safety consequences resulted from this event. 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 is foreign material within the K1 M preventing proper operation. There are two postulated causes for FM entry into the relay. The first scenario would be the potential for a small piece of plastic wrapping material to have been introduced during the wrapping and boxing / packaging process by the relay vendor. In the second scenario, it is postulated that during the unpackaging of the K1 Rand K1 M relay components, a small piece of clear plastic FM either tore off during unpackaging or a small piece entered the relay. The K1 relay was installed 2 years ago. As described above, the K1 relay is comprised of two separate components and K1 R is designed to slide on top of the K1 M relay clipping into place.

, It appears that the foreign material, which resembles a piece of clear plastic, was inside the relay since its installation. While he source of the foreign material cannot be definitively proven, as it is possible for the FM to have entered the relay during che manufacture process, packaging, unwrapping, or site assembly. The material would have been in a location internal of he relay not visible to site electrical maintenance performing site assembly and installation. Over the past two years, the K1 R relay has functioned as intended with total of 24 successful tests. However, during testing on April 18th, 2024, the presence of the plastic foreign material caused it to bind, preventing the contacts from changing state as designed. This

' malfunction resulted in the EOG failing to produce any output voltage because of the absence of flashing the field.

4.0 Immediate Corrective Action I

2. DOCKET NUMBER

3. LER NUMBER 00339 I YEAR SEQUENTIAL REV I\\IUI\\/IBER NO.

• 12024 I m I 001 I

~ ~

Upon removal of the foreign material, the relay was mechanically cycled noting no abnormal conditions or binding. The K'I relay was then functionally tested (electrically energized and deenergized) by engineering noting proper operation with no abnormal conditions confirming the foreign material was the cause for relay failure.

I 5.0 Additional Corrective Actions Work orders were created to inspect the K1 relays for ail EDGs for foreign material and to functionally test each K1 r*elay.

These work orders have been completed and no foreign material was found in the other K1 relays.

16.0 Actions to Prevent Recurrence t

Revise 0-EPM-0702-04 " Inspection of EOG ' K' Relays and Contacts" to inspect the interior of the relay to identify any

• oreign materials or unusual particles that do not belong. Use a light source to illuminate the interior for enhanced visibility.

Utilize a can of compressed air and position the nozzle at a safe distance to avoid damage to relay components. Apply 1short bursts of air to dislodge and remove any potential debris. In addition to the above steps include an Independent Verification (IV) step to verify the absence of foreign materials inside the relay.

7.0 Similar Events No similar events have been noted at North Anna.

8.0 Additional Information The health and safety of the public were not affected by this event. Page 3

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