ML19350A004

License Amendment Request Addition of 24-Hour Completion Time for an Inoperable Reactor Trip Breaker Response to NRC Request for Additional Information

ML19350A004
Person / Time
Site:	Surry
Issue date:	12/12/2019
From:	Mark D. Sartain Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
19-131A
Download: ML19350A004 (7)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 December 12, 2019 10 CFR 50.90 U. S. Nuclear Regulatory Commission Serial No.: 19-131A Attention: Document Control Desk NRA/GDM: R1 Washington, DC 20555-0001 Docket Nos.: 50-280 50-281 License Nos.: DPR-32 DPR-37 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 LICENSE AMENDMENT REQUEST ADDITION OF 24-HOUR COMPLETION TIME FOR AN INOPERABLE REACTOR TRIP BREAKER RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION By letter dated May 15, 2019 (Serial No.19-131) [ADAMS Accession No. ML19143A201], Virginia Electric and Power Company (Dominin Energy Virginia) submitted a license amendment request (LAR) for Surry Power Station (Surry) Units 1 and 2. The LAR proposes a revision to the Surry TS to provide a completion time (CT) of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore an inoperable Reactor Trip Breaker (RTB) to operable status.

Under the proposed revised TS, if an inoperable RTB is not returned to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the unit would be required to be in hot shutdown within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The 24-hour CT provides additional time to perform maintenance activities at power while minimizing the risk associated with the loss of the component function.

In an email dated November 13, 2019, from Mr. Vaughn Thomas (NRC Project Manager) to Mr. Gary Miller (Dominion Energy Virginia), the NRC technical staff requested additional information to facilitate their review of the LAR. The NRC's request and Dominion's response are provided in the attachment to this letter.

The information provided in this letter does not affect the conclusions of the significant hazards consideration or the environmental assessment included in our May 15, 2019 LAR.

Serial No. 19-131A Docket Nos. 50-280/281 Page 2 of 3 Should you have any questions or require additional information, please contact Mr. Gary D. Miller at (804) 273-2771.

Respectfully, Mark D. Sartain Vice President - Nuclear Engineering and Fleet Support Commitments contained in this letter: None

Attachment:

Response to NRC Request for Additional Information COMMONWEALTH OF VIRGINIA )

)

COUNTY OF HENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mr. Mark D. Sartain, who is Vice President -

Nuclear Engineering and Fleet Support, of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this /2 day of :-Ucbc.c: , 2019.

My Commission Expires: '2..y L<A ;u, 2. ol.3 .

Serial No. 19-131A Docket Nos. 50-280/281 Page 3 of 3 cc: U.S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Avenue, NE Suite 1200 Atlanta, GA 30303-1257 State Health Commissioner Virginia Department of Health James Madison Building - 7th floor 109 Governor Street Suite 730 Richmond, VA 23219 Mr. Vaughn Thomas NRC Project Manager - Surry U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 04 F-12 11555 Rockville Pike Rockville, MD 20852-2738 Mr. G. Edward Miller NRC Senior Project Manager - North Anna U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 09 E-3 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Surry Power Station

Serial No. 19-131A Docket Nos. 50-280/281 RAI Response LAR- RTB CT Addition Attachment RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION Virginia Electric and Power Company (Dominion Energy Virginia)

Surry Power Station Units 1 and 2

Serial No. 19-131A Docket Nos. 50-280/281 RAI Response LAR - RTB CT Addition Attachment RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION SURRY POWER STATION UNITS 1 AND 2 By letter dated May 15, 2019 (Serial No.19-131) [ADAMS Accession No. ML19143A201], Virginia Electric and Power Company (Dominion Energy Virginia) submitted a license amendment request (LAR) for Surry Power Station (Surry) Units 1 and 2. The LAR proposes a revision to the Surry TS to provide a completion time (CT) of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore an inoperable Reactor Trip Breaker (RTB) to operable status.

In an email dated November 13, 2019, from Vaughn Thomas (NRC Project Manager) to Gary Miller (Dominion Energy Virginia), the NRC technical staff requested additional information to facilitate their review of the LAR. The NRC's request and Dominion Energy Virginia's response are provided below.

NRC Request APLA RA/ 01 - Avoidance of Risk Significant Plant Configurations RG 1.177, An Approach for Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications," (ADAMS Accession No. ML100910008) states, "[t]he licensee should provide reasonable assurance that risk-significant plant equipment outage configurations will not occur when specific plant equipment is out of service consistent with the proposed TS [technical specification] change."

The LAR states that the proposed change to the RTB completion time (CT) has been developed using the risk-informed processes described in WCAP-15376-P-A, "Risk Informed Assessment of the RTS and ESFAS Surveillance Test Intervals and Reactor Trip Breaker Test and Completion Times," Revision 1. LAR Section 3.3 states that a "detailed review of PRA importance metrics (Risk Achievement Worth, Fussell-Vesely) from the Tier 1 PRA model did not reveal any risk significant maintenance configurations when one RTB [reactor trip breaker] is unavailable." Furthermore, LAR Section 6.0 identifies only one system (i.e., Anticipated Transient without Scram (ATWS) Mitigating System Actuation Circuitry (AMSAC)) where no maintenance will be planned while one RTB is inoperable. However, Section 8. 5 of WCAP-15376 identifies restrictions that should be placed on certain equipment when an RTB is out of service (i.e., reactor coolant system (RCS) pressure relief system, auxiliary feedwater flow, AMSAC, turbine trip, activities that degrade other components of the Reactor Protection System (RPS) (including master relays or slave relays and activities that cause analog channels to be unavailable), and AC and DC power distributions that support the restricted components). Considering these observations; Explain how the importance factors were used to assess the risk-significant plant equipment configurations while an RTB is out of service during the extended CT.

Include the criteria used (e.g., Risk Achievement Worth (RAW) and Risk Reduction Page 1 of 3

Serial No. 19-131A Docket Nos. 50-280/281 RAI Response LAR - RTB CT Addition Attachment Worth (RRW) threshold values, etc.) to determine risk significance. In the response, also confirm (i.e., include justification) that the unavailability of the systems/components identified in Section 8.5 of WCAP-15376 (i.e., RCS pressure relief system, auxiliary feedwater flow, ASMAC, turbine trip, other RPS components including master and slave relays, and AC and DC power distribution) along with an out-of-service RTB would not create a risk significant configuration.

Dominion Energy Virginia Response The detailed review of PRA importance metrics (Risk Achievement Worth [RAW],

Fussell-Vesely [FV]) involved analysis of the Tier 1 cutsets to determine if any risk significant structure, system, or component (SSC) unavailability basic events occurred in the same cutsets as RTB unavailability basic events. Basic events were considered risk significant if they had a Risk Achievement Worth (RAW) value greater or equal to 2.0 or a Fussell Vesely (FV) value greater or equal to 4.5E-3. Of the three basic events identified, two represented maintenance on an emergency diesel generator, which is already prohibited by procedure while one RTB is inoperable. The other risk significant basic event identified represented maintenance on the diesel-driven fire pump; however, the FV and RAW importance data for this basic event from the cutsets with one inoperable RTB are less than the FV and RAW values for this basic event in the base PRA cutsets. Therefore, this basic event does not represent a vulnerable configuration that would require more control than the application of the Maintenance Rule (a)(4) program.

As noted, Section 6.0 of the LAR requires that AMSAC maintenance is not planned while one RTB is inoperable. The other equipment identified in Section 8.5 of WCAP-15376 was reviewed to confirm that no additional prohibitions on maintenance are required when an RTB is inoperable. The details of this review are provided below:

- RCS Pressure Relief System o The cutsets associated with this system stems from multiple relief valves failing closed and a loss of primary and auxiliary secondary cooling.

Importance metrics (FV and RAW) values for test and maintenance on components associated with this system are under the thresholds for risk significance.

- Auxiliary Feedwater (AFW) Flow o The AFW system's risk significance largely results from cutsets involving loss of offsite power (LOOP) events, which are not affected by having an inoperable RTB. Surry has a high degree of AFW redundancy due to the availability of an AFW cross-tie between Units 1 and 2. AFW unavailability basic events that are risk significant in the base Surry PRA results are still risk significant in the Tier 1 analysis results; however, AFW FV and RAW values are not significantly impacted by RTB unavailability.

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Serial No. 19-131A Docket Nos. 50-280/281 RAI Response LAR - RTB CT Addition Attachment

- Turbine Trip o There are several redundant actuations to ensure the turbine trips, one of which is AMSAC initiation. These numerous and redundant turbine trip initiators/actuations ensure the turbine trip function will not be impacted due to an inoperable RTB.

- Other Reactor Protection System (RPS) Components Including Master and Slave Relays o The other RPS components would be the redundant train after removing one RTB train from service. This is procedurally prohibited when one RTB is inoperable.

- AC and DC Power Distribution o Removing these systems from service is already procedurally prohibited when an RTB is inoperable.

Based on the foregoing, there is reasonable assurance that the Maintenance Rule (a)(4) process will ensure vulnerable plant configurations are avoided when an RTB is inoperable.

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