ML15215A368

Millstone Power Station Unit 3 - Response to Third Request for Additional Information Regarding License Amendment Request for Implementation of WCAP-14333 and WCAP-15376 Reactor Trip System Instrumentation and Engineered Safety Feature Actu

ML15215A368
Person / Time
Site:	Millstone
Issue date:	07/27/2015
From:	Sartain M D Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
15-344, TAC MF4131, WCAP-14333, WCAP-15376
Download: ML15215A368 (7)

Text

5000 Dominion Boulevard, Glen Allen, VA 23060 Dominion"' Web Address: www.dom.com' July 27, 2015U.S. Nuclear Regulatory Commission Serial No. 15-344Attention: Document Control Desk NLOS/WDC R0Washington, DC 20555 Docket No. 50-423License No. NPF-49DOMINION NUCLEAR CONNECTICUT. INC.MILLSTONE POWER STATION UNIT 3RESPONSE TO THIRD REQUEST FOR ADDITIONAL INFORMATION REGARDINGLICENSE AMENDMENT REQUEST FOR IMPLEMENTATION OF WCAP-14333 ANDWCAP-15376. REACTOR TRIP SYSTEM INSTRUMENTATION AND ENGINEEREDSAFETY FEATURE ACTUATION SYSTEM INSTRUMENTATION TEST TIMES ANDCOMPLETION TIMES (TAC NO. MF41 31)By letter dated May 8, 2014 and supplemented by a letter dated August 14, 2014, DominionNuclear Connecticut, Inc. (DNC) submitted a license amendment request (LAR) for MillstonePower Station Unit 3 (MPS3). The proposed amendment would revise TS 3/4.3.1, "ReactorTrip System Instrumentation," and TS 3/4.3.2, "Engineered Safety Feature Actuation SystemInstrumentation." These proposed changes are based on Westinghouse Electric CompanyLLC topical reports WCAP-14333-P-A, Revision 1, "Probabilistic Risk Analysis of the RPS andESFAS Test Times and Completion Times," and WCAP-1 5376-P-A, Revision 1, "Risk-Informed Assessment of the RTS and ESFAS Surveillance Test Intervals and Reactor TripBreaker Test and Completion Times." In an email dated September 22, 2014, the NuclearRegulatory Commission (NRC) transmitted a request for additional information (RAI) to DNCrelated to the LAR. DNC responded to the RAI on October 15, 2014. In an email dated March17, 2015, the NRC transmitted a second RAI. DNC responded to the RAI on May 18, 2015.In an email dated June 25, 2015, the NRC transmitted a third RAI as a follow up to theresponses in the May 18, 2015 response letter.The attachment to this letter provides DNC's response to the NRC's third RAI.If you have any questions regarding this submittal, please contact Wanda Craft at (804) 273-4687.Sincerely,wO A \~I' ONhY 1tIJtLIC! ~Commonwealth of Virgirtia MakD ati I Meg. #1 40542 -'Mark .Satainl My ommisionExpires May 31, 201!8Vice President -Nuclear Engineering -COMMONWE.ALTH OF VIRGINIA)COUNTY OF HENRICO)The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mark 0. Sartain, who is VicePresident -Nuclear Engineering of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is duly authorized to execute and file theforegoing document in behalf of that Company, an that the s ~tements in the document are true to the best of his knowledge and belief.Acknowledged before me this 22._"ray of /"kl. 2015.My Commission Expires: S'- Nota.ry ________' _________ (~

Serial No. 15-344Docket No. 50-423Page 2 of 2Commitments made in this letter: None

Attachment:

Response to Third Request for Additional Information Regarding License AmendmentRequest for Implementation of WCAP-14333 and WCAP-15376, Reactor Trip SystemInstrumentation and Engineered Safety Feature Actuation System Instrumentation TestTimes and Completion Timescc: U.S. Nuclear Regulatory CommissionRegion I2100 Renaissance Blvd, Suite 100King of Prussia, PA 19406-2713R. V. GuzmanSenior Project ManagerU.S. Nuclear Regulatory CommissionOne White Flint North, Mail Stop 08-C 211555 Rockville PikeRockville, MD 20852-2738NRC Senior Resident InspectorMillstone Power StationDirector, Radiation DivisionDepartment of Energy and Environmental Protection79 Elm StreetHartford, CT 06106-5127 Serial No. 15-344Docket No. 50-423ATTACHMENTRESPONSE TO THIRD REQUEST FOR ADDITIONAL INFORMATIONREGARDING LICENSE AMENDMENT REQUEST FOR IMPLEMENTATION OFWCAP-1 4333 AND WCAP-15376. REACTOR TRIP SYSTEMINSTRUMENTATION AND ENGINEERED SAFETY FEATURE ACTUATIONSYSTEM INSTRUMENTATION TEST TIMES AND COMPLETION TIMESDOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 3 Serial No. 15-344Docket No. 50-423Attachment, Page 1 of 4By letter dated May 8, 2014 and supplemented by a letter dated August 8, 2014,Dominion Nuclear Connecticut, Inc. (DNC) submitted a license amendment request([AR) for Millstone Power Station Unit 3 (MPS3). The proposed amendment wouldrevise TS 3/4.3.1, "Reactor Trip System Instrumentation," and TS 3/4.3.2, "EngineeredSafety Feature Actuation System Instrumentation." These proposed changes are basedon Westinghouse Electric Company LLC topical reports WCAP-14333-P-A, Revision 1,"Probabilistic Risk Analysis of the RPS and ESFAS Test Times and Completion Times,"and WCAP-15376-P-A, Revision 1, "Risk-Informed Assessment of the RTS and ESFASSurveillance Test Intervals and Reactor Trip Breaker Test and Completion Times." Inan email dated September 22, 2014, the Nuclear Regulatory Commission (NRC)transmitted a request for additional information (RAI) to DNC related to the LAR. DNCresponded to the RAI on October 16, 2014. In an email dated March 17, 2015, the NRCtransmitted a second RAI. DNC responded to the RAI on May 18, 2015. In an emaildated June 25, 2015, the NRC transmitted a third RAI as a follow up to the responses inthe May 18, 2015 response letter. This attachment provides DNC's response to theNRC's RAI.RAI 1.1 (follow up to PRA RAI 1)The response to PRA RAI 1 states that: "These statements do not apply to the Tier 2restrictions listed in Attachment 4 of the LAR," in reference to Tier 2 restrictions onpages 15 and 17 of the LAR. Please explain this statement.DNC ResponseThe statement was meant to convey that the Tier 2 restrictions listed in Attachment 4 ofthe [AR apply when a logic train or reactor trip breaker is tested in bypass.The wording of the Tier 2 restrictions listed in Attachment 4 of the [AR was revised andcontinues to apply when a logic train or reactor trip breaker are tested in bypass. Seethe response to RAI 4 in the May 18, 2015 response letter for the revised wording.RAI 5.1 (follow up to PRA RAI 5)PRA RAI 5 is based on information in the LAR Section 4.2.1, "WCAP-14333 Tier 2Restrictions," rather than WCAP-153 76. The LAR states that there are no Tier 2limitations when a slave relay, master relay, or analog channel is inoperable. Thisconclusion appears to be based on information provided in Tables Ql 1. and Q18.1Ifrom a letter dated December 20, 1996, transmitting a response to a request foradditional information regarding WCAP-14333. Please explain how this Tier 2conclusion was reached and whether the information in these tables, which includes anassessment of master or slave relay maintenance in Q18. 1, was considered.

Serial No. 15-344Docket No. 50-423Attachment, Page 2 of 4DNC ResponseLAR Section 4.2.1 is a discussion of the Westinghouse evaluation of Tier 2 restrictions.DNC considered the information from the Westinghouse evaluation as documented inTables QII.l and Q18.1 when determining Tier 2 restrictions. The Westinghouseevaluation determined the system importances individually for plant configurations withno ongoing test and maintenance activities and for plant configurations with ongoingtest or maintenance activities on the analog channels, master relays, slave relays, andlogic trains. The importances were compared between the cases with individualcomponents unavailable and all components available. With respect to the analogchannels, master relays and slave relays, the Westinghouse evaluation determined theimportance rankings among the affected systems did not change. That is the basis forthe statement there are no Tier 2 restrictions when a slave relay, master relay or analogchannel is inoperable.RAI 6.1 (follow up to PRA RAI 6)The/licensee's response to PRA RAI 6 describes the process to determine if Tier 2 orTier 3 compensatory measures are needed for the LAR proposed changes with respectto fire-related risk. The process, according to the response, incorporates qualitativeinsights based on fire mitigation strategy as follows:* Identify components that, when removed from service, render the unit with nocore damage mitigation success paths* Remove those components that are Technical Specification limited (i.e., have anallowed outage time (AOQT) < 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) AND require transitioning to mode 5The response appears to "or" these conditions together in that for components thatmeet either criterion, Technical Requirements Manual actions are established when afire risk significant component is removed from service for greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Thesecond condition related to removing components that are Technical Specification (TS)limited does not consider potential risk significance. Based on the RAI response, itappears some components may not be qualitatively (or quantitatively) considered forTier 2 or Tier 3 during the proposed TS bypass times or completion times which are<- 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Therefore, describe an acceptable Tier 2 and Tier 3 process with respect tofire-related risk and the results of the Tier 2 assessment.DNC ResponseThe Tier 2 and Tier 3 process with respect to fire-related risk and the results of the Tier2 assessment is provided below. DNC used the guidance provided in NUMARC 93-01,Revision 4A Section 11.3.4.3 when assessing fire risk within the 10 CFR 50.65(a)(4)

Serial No. 15-344Docket No. 50-423Attachment, Page 3 of 4process. As a result of the clarification call associated with this RAI, a subset of thecriteria used to identify fire risk significant components within (a)(4) was applied to theequipment considered in the LAR. The criteria are:1. Incorporate quantitative PRA insights* Identify the components corresponding to random failure andtest/maintenance basic events with internal events core damage frequencyrisk achievement worth (CDF RAW) > 2.0.*Remove those components not listed on the Safe Shutdown Equipment List(SSEL).2. Incorporate qualitative insights based on fire mitigation strategy* Identify components that, when removed from service, render the unit with nocore damage mitigating success paths.The reactor protection system (RPS) components affected by the proposed amendmentare not fire risk significant and thus, any fire risk incurred would be due to the additionalequipment removed from service.Based on the fire risk significant criteria listed above, components only meeting criterion1 are less risk significant than components meeting criterion 2 since redundantequipment would be available to mitigate fire scenarios when criterion 1-onlycomponents are out of service. Furthermore, the risk of these configurations isadequately managed by Technical Requirements Manual (TRM) risk managementactions. As a result, criterion 1-only components do not warrant additional Tier 2 or Tier3 compensatory measures.Alternatively, criterion 2 components provide the only available core damage mitigationsuccess path for certain fire scenarios and therefore, have high fire risk significance dueto the lack of redundancy. Consequently, components meeting criterion 2 are deemedreasonable candidates for developing a Tier 2 or Tier 3 compensatory measure.The turbine driven AFW pump is the only component that meets criterion 2 and hasalready been included in the proposed Tier 2 restrictions (i.e., AFW system componentswill not be removed from service when a reactor trip breaker is inoperable formaintenance). As a result, no additional Tier 2 or Tier 3 compensatory measures arerecommended.RAI 12.1 (follow up to PRA RAI 12)The LAR Table 1 provides a comparison between WCAP-14333 analysis assumptionsand plant-specific parameters. PRA RAI 12 requested an explanation whether theWCAP-14333 Tier I analysis remained bounding for these plant-specific values. Theresponse to PRA RAI 12 states that the plant-specific values for MPS3 shown in Table Serial No. 15-344Docket No. 50-423Attachment, Page 4 of 4I of Attachment 3 of the LAR are consistent with those of Vogtle Electric GeneratingPlant (Vogtle) as shown on Table 1 on page 297 (Enclosure 5, page E5-2) of WCAP-14333-P-A, Revision 1, Supplement 1, dated September 2003. However, a review ofTSTF-418 shows that this reference is dated after the NRC staff's approval letter ofTSTF-418 (ADAMS Accession No. ML 030920633). Therefore, the referenceddocument does not appear to have been part of the NRC staff's review of TSTF-4 18,nor does it appear to be provided as a reference supporting the proposed TS changesin the LAR. Please provide an explanation as requested in PRA RAI 12, consistent withthe TSTF-418 traveler which the LAR is requesting to adopt.DNC ResponseGiven that less testing/maintenance is being performed on some slave relays and thereactor trip breakers, the unavailability of these components will be less than thatassumed in the WCAP. Since the MPS3 unavailability values are less than those usedin the WCAP, MPS3 is bounded by the WCAP risk analysis.