ML14365A040
| ML14365A040 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 12/04/2014 |
| From: | Rencurrel D W South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-14003198, STI: 33992006, TAC MF3319, TAC MF3320 | |
| Download: ML14365A040 (10) | |
Text
Nuclear Operating CompanySouth Texas Pro/ect Electric Generating Station PO B&u 2839 /483 _ ___ _ _ _December 4, 2014NOC-AE-1400319810 CFR 50.90U.S. Nuclear Regulatory CommissionAttention: Document Control DeskWashington, DC 20555-0001South Texas ProjectUnits 1 and 2Docket Nos. STN 50-498, STN 50-499STPNOC Response to Request for Additional InformationRegarding the License Amendment Request for Technical Specification 3.3.1,Reactor Trip System Instrumentation, Functional Unit 20 (TAC Nos. MF 3319 and MF 3320)References: 1. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk,"Supplement to License Amendment Request Proposed Revision toTechnical Specification 3.3.1, Functional Unit 20, 'Reactor Trip Breakers',"June 9, 2014 (ML14184B363)2. E-mail from B.K. Singal, NRC, to L.P Sterling, STPNOC, "Request forAdditional Information Amendment to Revise Technical Specifications 3.3.1Functional Unit 20, 'Reactor Trip Breakers', South Texas Project, Units 1 and2, Docket Nos. 50-498 and 50-499", November 5, 2014 (ML14309A786)3. E-mail from B.K. Singal, NRC, to L.P. Sterling, STPNOC, "Request forAdditional Information, South Texas Project Units 1 and 2, LicenseAmendment of TS 3.3.1, 'Reactor Trip System Instrumentation', FunctionalUnit 20, Docket Nos. 50-498 and 50-499", November 5, 2014(ML14309A788)On June 9, 2014, STP Nuclear Operating Company (STPNOC) submitted a license amendmentrequest to revise Technical Specification (TS) 3.3.1, "Reactor Trip System Instrumentation," withrespect to the required actions and allowed outage times for inoperable reactor trip breakers,Functional Unit 20 [Reference 1]. In two e-mails dated November 5, 2014 [Reference2][Reference 3], the NRC requested additional information related to the STPNOC amendmentrequest. Attachment 1 provides the STPNOC response to the Requests for AdditionalInformation (RAI).AoojSTI: 33992006 NOC-AE-14003198Page 2 of 3There are no commitments in this letter.If there are any questions regarding this letter, please contact Wendy Brost at (361) 972-8516 orme at (361) 972-7867.I declare under penalty of perjury that the foregoing is true and correct.Executed onD.W. RencurrelSenior Vice President of OperationswebAttachment:1. Response to Requests for Additional Information, License Amendment Request,Revision to TS 3.3.1, Functional Unit 20, "Reactor Trip Breakers" NOC-AE-1 4003198Page 3 of 3cc:(paper copy)(electronic copy)Regional Administrator, Region IVU. S. Nuclear Regulatory Commission1600 East Lamar BoulevardArlington, TX 76011-4511Balwant K. SingalSenior Project ManagerU.S. Nuclear Regulatory CommissionOne White Flint North (MS 8 B1)11555 Rockville PikeRockville, MD 20852NRC Resident InspectorU. S. Nuclear Regulatory CommissionP.O. Box 289, Mail Code: MN116Wadsworth, TX 77483Steve FrantzMorgan, Lewis & Bockius LLPBalwant K. SingalU. S. Nuclear Regulatory CommissionJohn RaganChris O'HaraJim von SuskilNRG South Texas LPKevin PolioCris EugsterL. D. BlaylockCPS EnergyPeter NemethCrain Caton & James, P.C.C. MeleJohn WesterCity of AustinRichard A. RatliffRobert FreeTexas Department of State Health Services
Attachment
1NOC-AE-14003198Page 1 of 7RESPONSE TO REQUESTS FOR ADDITIONAL INFORMATIONLICENSE AMENDMENT REQUESTREVISION TO TS 3.3.1, FUNCTIONAL UNIT 20, "REACTOR TRIP BREAKERS"By letter dated January 6, 2014 [Reference 1], as supplemented by letter dated June 9, 2014[Reference 2], STP Nuclear Operating Company (STPNOC) submitted a license amendmentrequest (LAR) to revise South Texas Project (STP), Unit 1 and 2, Technical Specification (TS)3.3.1, "Reactor Trip System Instrumentation," Table 3.3-1. The proposed amendment wouldrevise TS 3.3.1 allowed outage times and required actions for inoperable reactor trip breakers,Functional Unit 20, to be consistent with those generically approved in NUREG-1 431, StandardTechnical Specifications, Westinghouse Plants, Revision 4.On November 5, 2014 the Nuclear Regulatory Commission (NRC) submitted two sets ofRequests for Additional Information (RAIs) via separate e-mails [Reference 3][Reference 4]. TheNRC RAls and STPNOC's responses to the RAIs are included below.NRC Request -RAI 1Westinghouse Topical Report WCAP-1 5376-P-A, Revision 1, "Risk-Informed Assessment of theRTS (Reactor Trip System) and ESFAS (Engineered Safety Features Actuation System)Surveillance Test Intervals and Reactor Trip Breaker Test and Completion Times," (AgencywideAccess and Management System (ADAMS) Accession No. ML030870542) analysis did notreport uncertainty bounds for the proprietary data estimates, which may have an influence onplant-specific results. Please explain how the licensee considered the uncertainty in the dataconsistent with the guidance in Regulatory Guide (RG) 1.174, Revision 2, "An Approach forUsing Probabilistic Risk-Assessment in Risk-Informed Decisions on Plant Specific Changes tothe Licensing Basis," (ADAMS Accession No. ML100910006) and RG 1.177, Revision 1, "AnApproach for Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications," (ADAMSAccession No. ML1 00910008) to ensure that the conclusions of WCAP-1 5376 remain valid forthe plant-specific case.STPNOC Response:A formal assessment of the change in Core Damage Frequency (CDF) and Large EarlyRelease Frequency (LERF) was not performed for this LAR, rather, the applicability ofWestinghouse topical report WCAP 15376-P-A was demonstrated.The purpose of an uncertainty analysis is to ensure the contribution and impacts ofuncertainties to the Probabilistic Risk Assessment (PRA) results are within theacceptance guidelines set forth in RG 1.174 and RG 1.177. Table 1 in Attachment A ofReference 2 demonstrates that the total CDF and total LERF are much less than thelimits discussed in RG 1.174 for making risk-informed changes. The estimated value ofthe Anticipated Transient Without Scram (A TWS) contribution to CDF is small comparedto the acceptance goal -approximately 4.3E-08 per year compared to an acceptanceguideline of 1. OE-06 per year as described in RG 1.174 criteria.Sufficient margin is provided such that a detailed uncertainty analysis would not affectthe conclusion that the PRA results of WCAP 15376-P-A are applicable to STP andwithin the acceptance guidelines set forth in RG 1.174 and 1. 177.
Attachment
1NOC-AE-14003198Page 2 of 7NRC Request -RAI 2The licensee stated that "the quality of the South Texas project (STP) Probabilistic RiskAssessment (PRA) was reviewed by the Nuclear Regulatory Commission (NRC) as part of theprocess for approving Risk Managed Technical Specifications (RMTS) at the South TexasProject." The licensee stated that NRC staff reviewed Revision 5 of their PRA model as part ofthe RMTS application (Final Safety Evaluation for RMTS program ADAMS Accession Number:ML071780186). However, this application is supported by Revision 7.2 of the STP PRA model.NRC Request -RAI 2aa) Please explain whether any updates, upgrades, and peer reviews, as defined byASME (American Society of Mechanical Engineers)/ANS (American Nuclear Society)RA-Sa-2009, "Standard for Level 1/Large Early Release Frequency Probabilistic RiskAssessment for Nuclear Power Plant Applications," have been performed since thelicensee's RMTS submittal.STPNOC Response:Revision 5 of the PRA model was in effect for the STP RMTS submittal. Two updateshave been performed since Revision 5: Revision 6 and Revision 7.2. Theserevisions include industry and plant specific data updates, but do not affect themethodology of evaluating the risk associated with reactor trip breakers (RTBs) orTS 3.3.1.Revision 7.2 was also an upgrade that changed the fundamental method ofevaluating STP's Loss of Offsite Power (LOOP) recovery analysis, which also did notimpact the RTBs or TS 3.3. 1. The LOOP recovery analysis was the subject of theonly peer review performed since the STP RMTS submittal and is not applicable tothis LAR.NRC Request -RAI 2bb) Please provide the Facts and Observations (F&Os) and their dispositions from recentor previous peer reviews that are applicable to the proposed Technical Specificationrevision in this License Amendment Request (LAR).STPNOC Response:As discussed in the response to RAI 2a, the only peer review conducted since theSTP RMTS submittal was for the LOOP recovery analysis. This peer review does notaffect the risk associated with A TWS nor the RTBs. During a LOOP control rodsdrop to the bottom of core unless binding in the control rod channels is present,therefore, this analysis does not impact the RTBs.
Attachment
1NOC-AE-14003198Page 3 of 7NRC Request- RAI 2cc) Please explain how the risk from external events is considered for this LAR.STPNOC Response.External events are modeled in the Average Maintenance at Power PRA. Externalevents make up 40.58% of the CDF as shown in the table below.STP RV72 INITIATOR JE CDF %CDFI Frequency~,Externfal Events ~ _____ ___Tornado Induced Failure of Switchyard and 1.22E-06 1.1 E-06 18.31Essential Cooling PondFire Zone 047 Scenario X 1.46E-05 3.65E-07 6.02Switchyard and Essential Cooling PondFailure Due to Breach of Main Cooling 3.20E-07 2.91E-07 4.80ReservoirFire Zone 071 Scenario X 2.34E-07 2. 13E-07 3.51Fire Zone 047 Scenario B 2.72E-03 2.09E-07 3.45Control Room Fire Scenario 18 2.12E-06 9.12E-08 1.50Fire Zone 047 Scenario BC 3.18E-06 5.91E-08 0.98Seismic Event, 0. 4g Acceleration 7. 74E-07 4.04E-08 0.67Control Room Fire Scenario 23 1.61E-06 2.62E-08 0.43Seismic Event, 0.6g Acceleration 6. 14E-08 2.08E-08 0.34Fire Zone 147 Scenario 0 1.08E-03 1. 19E-08 0.20External Flooding Scenarios 2 Through 6 1.05E-08 9.49E-09 0.16Seismic Event, 0.2g Acceleration 2.89E-06 9.35E-09 0.15Seismic Event, 0. Ig Acceleration 3.02E-05 1. 73E-09 0.03Control Room Fire Scenario 10 3.43E-06 1.04E-09 0.02Flood Induced LOOP -Scenario 1 3.20E-06 5.41E-10 0.01Group Subtotal 3.87E-03 2.46E-06 40.58Both channels of Solid State Protection System (SSPS) are considered failed for thecontrol room fire scenario 18 (FR18) initiator and all seismic initiators. Operatoraction to manually trip the reactor is credited in all external events.There is no increase to risk of an unavailable SSPS channel for FR18 and theseismic initiators because both SSPS channels are considered failed. Note that forthe Tornado, Breach of the Main Cooling Reservoir, and the other External FloodingScenarios, a LOOP is included in the scenario, so that the signals to the RTBs arenot relevant. For other external events the increase of risk due to only having oneSSPS channel available is small because the Allowed Outage Time only adds a fewhours of unavailability and the model credits operator action to manually trip thereactor.
Attachment
1NOC-AE-14003198Page 4 of 7NRC Request -RAI 3RGs 1.174 and 1.177 establish the need for an implementation and monitoring program toensure that extensions to Technical Specification Completion Times or bypass test times do notdegrade operational safety over time and that no adverse effects occur from unanticipateddegradation or common-cause mechanisms. Please explain how the licensee monitors thereliability and availability of the RTS instrumentation.STPNOC Response:The following surveillance procedures are performed for the RTS instrumentation:* Trip Actuating Device Operational Test (TADOT) surveillances for each train ofRTS instrumentation including testing of the reactor trip bypass breaker, turbinetrip relay testing, and automatic shunt trip testing for each train are performed atleast once every nine months for both RTS trains* Response time testing and reactor trip breaker gripper release surveillances forboth RTS trains including automatic undervoltage trip testing and gripper releasetesting is performed at least once per 18 monthsThe following Preventative Maintenance (PM) activities are performed for the RTSinstrumentation:" Contingency maintenance support for the reactor trip breaker TADOTsurveillance is performed as needed* Thermography inspections to verify the integrity of cabinets, wiring, fasteners,and electrical connections on components associated with the RTS system isperformed every 26 weeks* Inspection and testing of each RTB and reactor trip bypass breaker is performedevery refueling outage* Lubrication and overhaul of each RTB and reactor trip bypass breaker isperformed every 9 yearsThese surveillances and PMs are performed at their respective frequencies andperiodically reviewed for any needed changes.
Attachment
1NOC-AE-14003198Page 5 of 7NRC Request -New Action 12ABasis for the RequestThe licensee is proposing to add New Action 12A to Function 20, Reactor Trip Breakers, in TS3.3.1, "Reactor Trip System Instrumentation," Table 3.3-1. The licensee stated in its applicationthat this change is consistent with NUREG-1431, Revision 4.0, "Standard TechnicalSpecifications, Westinghouse Plants."New Action 12A states:"With one of the diverse trip features (undervoltage or shunt trip attachment) inoperable,within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> restore it to OPERABLE status or initiate action to fully insert all rods;and within the next hour place the rod control system in a condition incapable of rodwithdrawal."The licensee stated that New Action 12A would address the condition where one diverse tripfeature for a reactor trip breaker is inoperable when the reactor trip breakers are in the closedposition and the control rod drive system is capable of rod withdrawal in Modes 3, 4, and 5. Thelicensee also stated that the proposed changes to TS 3.3.1, Table 3.3-1, New Action 12Aaddress a condition that is not in South Texas Project (STP) TSs.Request for Additional InformationSince New Action 12A is not in the licensee's current licensing basis (CLB), please explain whyNew Action 12A is needed and provide a technical evaluation for this change. In addition,please explain, given the CLB TS, how would the inoperability of a diverse trip feature impactthe operability of a reactor trip breaker during the modes of applicability. Please includediscussion of any TS actions entered, since this New Action 12A is currently not in STP's TSs.STPNOC Response:New Action 12A is being proposed to clarify the actions to take to address an inoperablediverse trip feature (reactor trip breaker undervoltage mechanism or shunt tripmechanism) while operating in Modes 3, 4, and 5. New Action 12A would provide thesame option for Modes 3, 4, and 5 that Action 12 provides for Modes I and 2.The RTBs are in the electrical power supply line from the control rod drive motorgenerator set power supply to the Control Rod Drive Mechanisms (CRDMs). Opening ofthe RTBs interrupts power to the CRDMs, which allows the shutdown rods and controlrods to fall into the core by gravity. During normal operation the output from the SSPS isa voltage signal that energizes the undervoltage coils in the RTBs and bypass breakers,if in use. When the required logic matrix combination is completed, the SSPS outputvoltage signal is removed, the undervoltage coils are de-energized, the breaker trip leveris actuated by the de-energized undervoltage coil and the RTBs and bypass breakersare tripped open. This allows the shutdown rods and control rods to fall into the core. Inaddition to the de-energization of the undervoltage coils, each breaker is also equippedwith a shunt trip device that is de-energized to trip the breaker open upon receipt of areactor trip signal from the SSPS. Either the undervoltage coil or the shunt tripmechanism is sufficient by itself, thus providing a diverse trip mechanism.
Attachment
1NOC-AE-14003198Page 6 of 7With one of the diverse trip features inoperable, the reactor trip breakers would still openin the event that the other diverse trip feature is de-energized.For Modes I and 2 in the current S TP TSs, the inoperability of a diverse trip featurewould require entering Action 12 to restore the feature to operable status within 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />sor declare the breaker inoperable and enter Action 9 to be in Hot Standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.For Modes 3, 4, and 5 in the current STP TSs when the Reactor Trip System breakersare in the closed position, the inoperability of a diverse trip feature would requireentering Action 10 to restore the inoperable channel to operable status within 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />sor open the RTBs within the next hour.New Action 12A has the same result as the current Action 10. In new Action 12A, if thediverse trip feature is not returned to operable status within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the rod controlsystem is placed in a condition incapable of rod withdrawal within the next hour.
Attachment
1NOC-AE-14003198Page 7 of 7References1. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "LicenseAmendment Request Proposed Revision to Technical Specification 3.3.1, FunctionalUnit 20, 'Reactor Trip Breakers'," January 6, 2014 (ML14035A075)2. Letter from G.T. Powell, STPNOC, to NRC Document Control Desk, "Supplement toLicense Amendment Request Proposed Revision to Technical Specification 3.3.1,Functional Unit 20, 'Reactor Trip Breakers'," June 9, 2014 (ML14184B363)3. E-mail from B.K. Singal, NRC, to L.P Sterling, STPNOC, "Request for AdditionalInformation Amendment to Revise Technical Specifications 3.3.1 Functional Unit 20,'Reactor Trip Breakers', South Texas Project, Units 1 and 2, Docket Nos. 50-498 and 50-499", November 5, 2014 (ML14309A786)4. E-mail from B.K. Singal, NRC, to L.P. Sterling, STPNOC, "Request for AdditionalInformation, South Texas Project Units 1 and 2, License Amendment of TS 3.3.1,'Reactor Trip System Instrumentation', Functional Unit 20, Docket Nos. 50-498 and 50-499", November 5, 2014 (ML14309A788)