05000338/LER-2021-002, Unanalyzed Condition Due to App R Concerns with Cable Separation

Unanalyzed Condition Due to App R Concerns with Cable Separation

ML22035A167
Person / Time
Site:	North Anna
Issue date:	09/17/2021
From:	Madden F Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Miller G
References
21-321 LER 2021-002-00
Download: ML22035A167 (6)

LER-2021-002, Unanalyzed Condition Due to App R Concerns with Cable Separation

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
3382021002R00 - NRC Website

text

10CFR50.73 Virginia Electric North Anna -'"fll'IEll.11" --.--::,,,......

1022 Haley Drive Mineral, Virginia 17 September 17, 2021 Attention: Document Control Desk Serial No.:

21-321 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Dear Sir or Madam:

NAPS:

CNC Docket Nos.: 50-338, 50-339 License Nos.: NPF-4, NPF-7 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 and Unit 2.

Report No. 50-338/2021-002-00 This report has been reviewed by the Facility Safety Review Committee and will be forwarded to the Management Safety Review Committee for its review.

Sincerely, Fred Mladen 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

Serial No.21-321 LER N1-2021-002-00 Unanalyzed Condition Due to App R Concern Identified With Cable Separation be page 1 of 2 (hard copy distribution):

Mr. D. G. Stoddard Mr. G. T. Bischof Mr. M. D. Sartain Mr. G. Crenshaw Mr. M. Harris Ms. K. H. Barret Station Records Licensing File be (electronic distribution):

Mr. F. Mladen Mr. D. Lawrence Mr. J. R. Daugherty Mr. G. Lippard Ms. L. A. Hilbert Mr. J. H. Jenkins Mr. S. W. Morris Mr. B. L. Standley Mr. W. M. Adams Mr. C. A. McClain Mr. J. E. Collins Mr. G. B. Scott Mr. B. K. Ravan Mr. J. B. Russell Mr. G. R. Simmons Mr. R. S. Galbraith Mr. J. W. Lloyd Mr. J. A. Perry Mr. C. S. Patterson Mr. N. S. Turner Mr. M. A. Hofmann Mr. F. V. Errico Mr. J. Henderson Mr. C. D. Sly Mr. J. A. Langan Mr. M. Moore Ms. E. N. Combs Mr. D. V. Atkinson Mr. S. A. Luchau Mr. M. LaPrade Mr. G. H. Young Mr. M. S. Hanson Ms. B. M. Perkins Mr. J. R. Roth MSRC I N2SW, Senior Vice President, Chief Nuclear Officer IN2NW, Senior Vice President, Nuclear Operations IN2NW, Vice President, Nuclear Engineering and Fleet Support Clearinghouse, Director Corporate Risk Management ODEC IN2NW, Licensing NAPS (VOA package)

NAPS, Licensing NAPS, Site Vice President SPS, Site Vice President MPS, Site Vice President VCS, Site Vice President NAPS, Plant Manager NAPS, Director Station Safety and Licensing NAPS, Director Engineering I N2NW, Director Nuclear Regulatory Affairs I N3SW, Director Nuclear Engineering & Fuel IN2NW, Director Nuclear Performance Improvement & Training IN3NE, Manager Nuclear Fleet Emergency Preparedness NAPS, Manager Operations NAPS, Manager Maintenance NAPS, Manager Nuclear Training NAPS, Manager RP & Chemistry NAPS, Manager Design Engineering NAPS, Manager Nuclear Site Engineering Clearinghouse, Manager, Corporate Risk Engineering Clearinghouse, Manager, Corporate Risk Management NAPS, Manager, Organizational Effectiveness NAPS, Manager, EP/Licensing NAPS, Supervisor Nuclear Corrective Action

_ SPS, Director Station Safety and Licensing IN2NW, Licensing Manager MPS, Licensing Manager VCS, Supervisor Nuclear Licensing IN2NW, Licensing I N2NW, Nuclear Performance Assessment IN3SW, Supervisor Nuclear Safety Analysis I N3SW, Supervisor Fuel Performance Analysis NAPS, Organization Effectiveness/OE SPS, Organization Effectiveness /OE MPS, Organization Effectiveness /OE I N2NW, MSRC Coordinator eRoom Document Repository

Serial No.21-321 LER N1-2021-002-00 Unanalyzed Condition Due to App R Concern Identified With Cable Separation be page 2 of 2 Verification of Accuracy

1. CR 1177199 App R concern identified with cable separation associated with U 1 &U2 EOG and Emergency bus operation

2. CA8539011 Rea~onable Assurance of Safety.

3. CA8539529 Request for Engineering Assistance

4. CA8543316 Review EOG Start circuits for possibility of negative ground on the EOG batteries

5.

• CA8539530*Re-evaluat6 items 2 and 3 for Ms*o scenarios

6. Operations Narr~tive Logs 07/20/21

7. Event Notificatiorr#55375 on 07/22/21 at 2028

8. FSRC Meeting No.21-046 on September 17, 2021

Commitments

None Action Plan Implement Corrective Actions identified in Reasonable Assurance of Safety (CA8539011)

Changes to the UFSAR or QA Topical Report None

Abstract

On July 20, 2021 at 1707 hours0.0198 days <br />0.474 hours <br />0.00282 weeks <br />6.495135e-4 months <br />, an apparent non-compliance with 1 0CFR50, Appendix R, Section 111.G.2 (separation of redundant fire safe shutdown equipment) was identified. On July 22, 2021 at 1751 hours0.0203 days <br />0.486 hours <br />0.0029 weeks <br />6.662555e-4 months <br />, a further review of the affected control circuits for the Unit 1 and Unit 2 Emergency Diesel Generator (EOG) output breakers and Emergency Bus feeder breakers identified a concern that breaker position interlocks routed to or through non-safety related components or spaces may affect the ability to provide emergency power on the affected unit due to impacts on the control power circuits during an Appendix R fire associated with a loss of offsite power. An 8-hour non-emergency report was made per 10 CFR 50.72(b)(3)(ii)(B) for an unanalyzed condition. Hourly fire watches were established in the affected areas.

The cause of this condition is the station's original post-fire safe shutdown analysis did not accurately assess the impact on the equipment from associated cable damage due to fire for the select cables. Risk mitigating actions have been developed, implemented, and will continue to be performed until appropriate permanent corrective actions are in place to mitigate this condition.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(B) for "Any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety."

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http/ /www. n rc.q<21£Lr_~9_ctLQQ~:J!Dl9_9._g::_gol lections/n u reqs/staff /sr1022/r:3/l

3. LER NUMBER North Anna Power Station, Units 1 and 2

NARRATIVE

Plant Operating Conditions Prior to the Event Unit 1 - Mode 1, 100 percent Rated Thermal Power Unit 2 - Mode 1, 100 percent Rated Thermal Power

1.0 Description of Event

05000-338 YEAR 2021 SEQUENTIAL NUMBER 002 REV NO.

00 On July 20, 2021 at 1707 hours0.0198 days <br />0.474 hours <br />0.00282 weeks <br />6.495135e-4 months <br />, an apparent non-compliance with 1 0CFR50, Appendix R, Section 11I.G.2 (separation of redundant fire safe shutdown equipment) was identified during the development of the North Anna Fire Probabilistic Risk Assessment. On July 22, 2021 at 1751 hours0.0203 days <br />0.486 hours <br />0.0029 weeks <br />6.662555e-4 months <br />, a further review of the affected control circuits for the Unit 1 and Unit 2 Emergency Diesel Generator (EOG) output breakers (EIIS Component BKR, System EK) and Emergency Bus feeder breakers (EIIS Component BKR, System EK) identified a concern that breaker position interlocks routed to or through non-safety related components or spaces may affect the ability to provide emergency power on the affected unit due to impacts on the control power circuits during an Appendix R fire associated with a loss of offsite power. An 8-hour non-emergency report was made per 10 CFR 50. 72(b)(3)(ii)(B) for an unanalyzed condition. This event is reportable in accordance with 10 CFR 50. 73(a)(2)(ii)(B) for "Any event or condition that resulted in the nuclear power plant being in an unanalyzed condition that significantly degraded plant safety."

Several control cables were identified within common fire areas that, if fire damaged, could prevent the availability of both trains of Emergency Diesel Generators (EDGs) (EIIS Component DG, System EK) to start and power their respective emergency buses (EIIS Component BU, System EB) required by the station's current Appendix R analysis. The following issues were found:

1.

Fire damage to control power cables for EOG output breakers may result in loss of control power and inability to power the emergency bus without manual operator actions outside of the main control room.

2.

Hot shorts on the normal/alternate supply breakers (EIIS Component BKR, System EK) could result in spurious breaker operations that may prevent EDGs and/or emergency buses from performing its Appendix R function.

2.0 Significant Safety Consequences and Implications

No significant safety consequences resulted from this event. During this timeframe, North Anna Units 1 and 2 operated at 100% power. The health and safety of the public were not affected by this event.

3.0 Cause of the Event

The cause of this condition is the station's original post-fire safe shutdown analysis did not accurately assess the impact on the equipment from associated cable damage due to fire for the select cables. In addition, the Multiple Spurious Operations review effort failed to recognize applicability of EOG/Emergency Power scenarios for some areas for the plant.

4.0 Immediate Corrective Action

Hourly fire watches were established in the Unit 1 and Unit 2 Turbine Buildings, Unit 1 and Unit 2 Cable Spreading Rooms, and Unit 1 and Unit 2 Normal Switchgear Rooms to mitigate the risk of fire and aid in early detection of fire. Risk mitigating actions have been developed, implemented, and will continue to be performed until appropriate permanent corrective actions are in place to mitigate this condition.

5.0 Additional Corrective Actions

YEAR 2021 a

SEQUENTIAL NUMBER 002 REV NO.

00 A Reasonable Assurance of Safety (RAS) was developed with risk mitigating actions implemented until final resolution is completed. Procedures ECA-0.0 (Loss of All AC Power) and Flex Support Guidelines (FSGs) were reviewed to mitigate the results of a loss of all AC power conditions. Periodic reviews of applicable procedures and Fire Fighting Strategies for fires in areas of concern have been established. Prior to any unavailability of the Turbine Driven Auxiliary Feedwater (TDAFW) pump (EIIS Component P, System BA), guidance has been provided to pre-stage the Beyond Design Basis (BOB) Auxiliary Feedwater Pump.

The station is currently developing design changes to redesign the circuits to eliminate the vulnerability.

6.0 Actions to Prevent Recurrence The applicable control cables associated with the EOG output breakers, and Emergency Bus normal and alternate feeder breakers will be modified to regain compliance as required by Appendix R Safe Shutdown Analysis.

7.0 Similar Events A review of internal operating experience was performed, and no similar events were identified that were previously reported to the Nuclear Regulatory Commission.

8.0 Additional Information

Units 1 and 2 continued to operate at 100% power, Mode 1 during this discovery. Page~ of~