ML17068A296

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TSTF Slides for TSTF-564, Safety Limit MCPR, Pre-Submittal Meeting on 11/1/2016
ML17068A296
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Site: Technical Specifications Task Force
Issue date: 11/01/2016
From: Joyce R
Technical Specifications Task Force
To:
Office of Nuclear Reactor Regulation
Honcharik M, NRR DSS, 301-415-1774
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ML16308A402 List:
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TAC MF8485
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Technical Specifications Task Force A Joint Owners Group Activity TSTF TSTFPreSubmittalMeetingfor TSTF564,"SafetyLimitMCPR[Minimum CriticalPowerRatio]"

November1,2016 RyanJoyce ViceChair,BWROGLicensingCommittee 1

Technical Specifications Task Force A Joint Owners Group Activity TSTF Introduction

  • Today'smeetingistodiscussTSTFtravelerTSTF564, "SafetyLimitMCPR,"whichtheTSTFplanstosubmittothe NRCforapproval.
  • TSTF564revisestheSafetyLimit(SL)valueandmethodof calculationfortheMinimumCriticalPowerRatio(MCPR),

SL2.1.1.2,forBoilingWaterReactor(BWR)plantsusing GlobalNuclearFuelorWestinghousefuel.

  • AdraftofthetravelerwasprovidedtotheNRCpriortothe meeting.
  • TheTSTF'sgoalforthismeetingistoensurethatthe submittalprovidesthenecessaryandsufficientinformation fortheNRCtoefficientlyreviewthetraveler.

2

Technical Specifications Task Force A Joint Owners Group Activity TSTF Introduction

  • Thiseffortissupportedby:

- TheBoilingWaterReactorsOwners'Group (BWROG)LicensingCommittee

- TheTechnicalSpecificationsTaskForce

- TheBWROGReloadAnalysisandCore ManagementCommittee(RACMC)

- GlobalNuclearFuel(GNF)

- WestinghouseElectric 3

Technical Specifications Task Force A Joint Owners Group Activity TSTF CurrentRequirements

  • Title10oftheCodeofFederalRegulations(10CFR),

Part50,paragraph50.36(c)(1)(i)(A),inpart,states:

Safetylimitsfornuclearreactorsarelimitsupon importantprocessvariablesthatarefoundtobe necessarytoreasonablyprotecttheintegrityof certainphysicalbarriersthatguardagainstthe uncontrolledreleaseofradioactivity.

4

Technical Specifications Task Force A Joint Owners Group Activity TSTF CurrentRequirements

  • NUREG1433andNUREG1434,theBWR/4and BWR/6StandardTechnicalSpecifications(STS),

respectively,defineMinimumCriticalPowerRatio (MCPR)inSection1.1,"Definitions,"as:

TheMCPRshallbethesmallestcriticalpower ratio(CPR)thatexistsinthecore[foreachclass offuel].TheCPRisthatpowerintheassembly thatiscalculatedbyapplicationofthe appropriatecorrelation(s)tocausesomepointin theassemblytoexperienceboilingtransition, dividedbytheactualassemblyoperatingpower.

5

Technical Specifications Task Force A Joint Owners Group Activity TSTF CurrentRequirements

  • STSSafetyLimit2.1.1.2states:

Withthereactorsteamdomepressure785psig andcoreflow10%ratedcoreflow:

MCPRshallbe[1.07]fortworecirculationloop operationor[1.08]forsinglerecirculationloop operation.

  • Thereactorsteamdomepressureandcoreflowlimit mayvarybyplant.
  • Thetwoloopoperation(TLO)andsingleloop operation(SLO)SafetyLimitMCPR(SLMCPR)values areplantspecific.

6

Technical Specifications Task Force A Joint Owners Group Activity TSTF CurrentRequirements

  • TheSLMCPRvalueiscalculatedasthepointatwhich 99.9%ofthefuelrodswouldnotbesusceptibleto boilingtransition.
  • Itisrecognizedthattheonsetoftransitionboiling wouldnotnecessarilyresultindamagetoBWRfuel rods,butthecriticalpoweratwhichboiling transitioniscalculatedtooccurhasbeenadoptedas aconvenientlimit.

7

Technical Specifications Task Force A Joint Owners Group Activity TSTF CurrentRequirements

AllMCPRs shallbegreaterthanorequaltothe MCPRoperatinglimitsspecifiedintheCOLR[Core OperatingLimitsReport].

  • TS3.2.2isapplicablewhenThermalPoweris25%

RTP(ratedthermalpower),oraplantspecific thermalpowerlimit.

8

Technical Specifications Task Force A Joint Owners Group Activity TSTF CurrentRequirements

  • TheSLMCPRlimitiscalculatedforeachBWRonacycle bycyclebasisusingNRCapprovedmethodologies.

- TheSLMCPRlimitensuresthatnofueldamageresults duringnormaloperation.

  • TheOperatingLimitMCPR(OLMCPR)valuesspecifiedin thelicenseecontrolledCOLRaredeterminedusingNRC approvedmethodologieslistedinSection5.6,"Core OperatingLimitsReport(COLR),"oftheTS.

- TheOLMCPRlimitsensurethatnofueldamageresults duringanticipatedoperationaloccurrences(AOOs)by confirmingtheSLMCPRisnotviolatedduringanAOO.

9

Technical Specifications Task Force A Joint Owners Group Activity TSTF NeedforChange

  • ThecurrentmethodusedtodeterminetheSLMCPR valueresultsinfrequent,acceleratedlicense amendmentsthatunnecessarilychallengethe licenseeandtheNRC.
  • Thecyclespecificcoredesignisdependentonthe previouscycleburnup,sothedesignforthesubsequent cycleistypicallyfinalizedlateinthepreviousfuelcycle.
  • ThecurrentSLMCPRvalueisaffectedbythecycle specificdesign,suchascorepowerdistribution,fuel type,andoperatingpowerflowdomain.

10

Technical Specifications Task Force A Joint Owners Group Activity TSTF NeedforChange

  • IftheSLMCPRvalueforthesubsequentcycleisless conservativethanthecurrentTS,aTSchangeisneeded.
  • SubmittalstomodifytheSLMCPRtypicallyrequestan acceleratedNRCreview(i.e.,lessthanoneyear)to supportthescheduledstartofthesubsequentfuelcycle.

- TheTSTFidentified10requeststorevisetheSLMCPR valueapprovedin2015and2016.

- TheaveragelicenseerequestedNRCreviewtimewas 7months.

  • 7of10requestedareviewin6monthsorless.

11

Technical Specifications Task Force A Joint Owners Group Activity TSTF NeedforChange

  • TherearemethodsofdeterminingtheSLMCPRthat arenotcycledependentandsatisfytheregulations.
  • TheequivalentPWR(Babcock&Wilcox,Westinghouse, CombustionEngineering,andAP1000)safetylimitis basedonaDeparturefromNucleateBoilingRatio(DNBR) limit,whichissimilartotheBWRSLMCPR.
  • ThePWRsafetylimitisonlydependentontheDNBR correlationsforthefueltype(s)inthereactor.
  • ThePWRDNBRsafetylimitisnotcycledependentandis typicallyonlyrevisedwhenthefueltypechanges.

12

Technical Specifications Task Force A Joint Owners Group Activity TSTF ProposedChange

  • TheproposedchangerevisestheSLMCPR methodologyforallBWRplantsusingGNFor Westinghousefuel.

- TSTF564isnotapplicabletoBWRplantsusing AREVAfuel.

  • Theproposedchangewillsubstantiallyreducethe needforcyclespecificchangestotheSLMCPRand theneedforacceleratedNRCreviewofthose changes.

13

Technical Specifications Task Force A Joint Owners Group Activity TSTF ProposedChange

  • Forplantsadoptingtheproposedchange,Safety Limit 2.1.1.2isrevisedtostate:

Withthereactorsteamdomepressure 785psig andcoreflow10%ratedcoreflow:

MCPRshallbe[1.07].

NochangesareproposedtotheMCPRdefinitioninTS Section1.1orTS3.2.2,"MCPR."

14

Technical Specifications Task Force A Joint Owners Group Activity TSTF ProposedChange

  • ThefuelproductspecificSafetyLimitMCPRvalueis determinedbasedontheproduct'sexperimentally determinedcriticalpowerratioandastatisticalanalysisthat providesa95%probabilityata95%confidencelevel(95/95) fortheonesideduppertolerancelimitthatdependsonthe numberofsamplesinthecriticalpowerdatabase.

15 Vendor FuelType ProposedSLMCPR GNF GE14 1.06 GNF GNF2 1.07 Westinghouse Optima2 1.06 Westinghouse Optima3 1.06

Technical Specifications Task Force A Joint Owners Group Activity TSTF ProposedChange

  • ProposethatGNFandWestinghousesendproprietary lettersdescribinghowtheSLMCPRvaluesare determinedbasedontheproprietaryCPRstatistics,tobe referencedinthetraveler.
  • ForcoresloadedwithamixofGNForWestinghousefuel products,theSLMCPRisbasedonthelargest(i.e.,most limiting)oftheSLMCPRvaluesforthefuelproductsthat arefreshoronceburntatthestartofthecycle.
  • IntheSTS,theexistingphrase"fortworecirculationloop operationor[1.08]forsinglerecirculationloop operation"willberetainedasaplantspecificoption(i.e.,

bracketed)forBWRplantsthatdonotadoptthetraveler.

16

Technical Specifications Task Force A Joint Owners Group Activity TSTF ProposedChange

  • TheSafetyLimit2.1.1.2BasesandTS3.2.2Basesare revisedtoreflecttheproposedchange.
  • IntheSTS,brackets(indicatingplantspecific information)andReviewer'sNotesareusedtoadd thenewinformationwhileretainingtheexisting descriptionforplantsthatdonotadoptthe proposedchange.

17

Technical Specifications Task Force A Joint Owners Group Activity TSTF BasisforChange

  • ThemethodofcalculationfortheSLMCPRisrevised fromensuringthat99.9%oftherodswouldnotbe susceptibletotransitionboilingtoensuringthat thereisa95%probabilityata95%confidencelevel thatnorodswillbesusceptibletotransitionboiling basedonthecorrelationstatisticsalone.
  • ThisisconsistentwiththePWRDNBRsafetylimit, whichcorrespondstoa95%probabilityata95%

confidencelevelthatDNBwillnotoccurbasedon thecorrelationstatisticsalone.

  • Bothstatisticalapproachesareacceptable.

18

Technical Specifications Task Force A Joint Owners Group Activity TSTF BasisforChange

  • TheproposedSLMCPRisbasedonlyontheCPR correlationuncertaintydeterminedfortheGNFor Westinghousefueltype(s)inthereactor.

- ThisisconsistentwiththePWRDNBRSafetyLimit.

  • Plantandcyclespecificuncertainties,includingSLO and TLO reactorflowuncertainties,arenolongerincludedin theSLMCPR,soonlyasinglelimitisneeded.
  • Theplantandcyclespecificuncertainties,including reactorflow,willcontinuetobeincludedintheOLMCPR (TS3.2.2)limit.Therefore,themargintoboiling transitionremainsunchanged.

19

Technical Specifications Task Force A Joint Owners Group Activity TSTF BasisforChange

  • Nochangestothemethodofdeterminingthe OLMCPR(i.e.,theLCO 3.2.2limit)areproposed.

- ThecurrentSLMCPRstatisticalcalculation (i.e.,MCPR99.9%)willcontinuetobeperformed usingtheNRCapprovedmethodology.

- TheOLMCPRCOLRlimitswillcontinuetobe determinedbycombiningthecyclespecific MCPR99.9%valueandthetransientCPR component.

20

Technical Specifications Task Force A Joint Owners Group Activity TSTF ProposedModelApplication

  • Thetravelercontainsamodelapplicationforplant specificadoptionoftheproposedchange.
  • Licenseesadoptingthetravelerusingthemodel applicationmustprovide:

- VerificationthatthetravelerandNRCsafety evaluationareapplicable.

- Thetypeoffueltobeinthereactorandthe proposedSafetyLimitbasedonthetableinthe travelerandtheReviewer'sNoteintheTSBases.

- Adiscussionofanyvariationsfromthetraveler, suchasTSnumberingortitles.

21

Technical Specifications Task Force A Joint Owners Group Activity TSTF Conclusion

  • TherevisedSLMCPRmethodofcalculationforGNF andWestinghousefuelwillcontinuetomeetthe regulatorydefinitionofasafetylimitandprotectthe integrityofthefuelrodcladdingagainstthe uncontrolledreleaseofradioactivity.

22

Technical Specifications Task Force A Joint Owners Group Activity TSTF Discussion 23

Technical Specifications Task Force A Joint Owners Group Activity TSTF BackupSlides 24

Technical Specifications Task Force A Joint Owners Group Activity TSTF DeterminationofProposedSLMCPRvalue

  • TheproposedSLMCPRvalueisdesignatedasMCPR95/95
  • ForeachGNFandWestinghouseBWRfuelproduct (designatedi),theMCPR95/95(i) iscalculatedusingthat productsexperimentallydeterminedcriticalpowerstatistics asfollows:

MCPR95/95(i) =µi +i*i (Eq.1)

Where,

µi isthemeanExperimentalCriticalPowerRatio(ECPR),

i isthestandarddeviationoftheECPRs,and i isastatisticalparameterchosentoprovide95%probabilityat95%

confidence(95/95)fortheonesideduppertolerancelimitthat dependsonthenumberofsamples(Ni)inthecriticalpower database.

iisafuelproductline,suchasGE14,GNF2,OPTIMA2,OPTIMA3,etc.

25

Technical Specifications Task Force A Joint Owners Group Activity TSTF StatisticalTreatmentofMCPR95/95 Thestatisticalparameter,i,iscalculatedusingformulasattributedto MaryGibbonsNatrella (1963)asrecommendedbytheNationalInstitute ofStandardsandTechnology(NIST)intheirEngineeringStatistics Handbook(Reference1).Fora95/95probability/confidencelevel,thei valuesareshowninthetablebelowasafunctionofdatabasesize(Ni).

StatisticalParameter,i,at(95/95) fortheOneSidedUpperToleranceLimit 26 DatabaseSize, Ni i

500 1.7625 750 1.7401 1000 1.7270 1250 1.7181 1500 1.7115 2000 1.7024

Technical Specifications Task Force A Joint Owners Group Activity TSTF StatisticalTreatmentofMCPR95/95 Assumingatypicalcriticalpowerdatabaseof1000datapointswithno bias(i.e.,µi =1.0),thefollowingtableillustratesrepresentative MCPR95/95(i) valuesasafunctionofthedatabasestandarddeviation.

RepresentativeMCPR95/95 ValuesforNi=1000 TheSLMCPRisdeterminedtotwodigitspastthedecimalusingstandard roundingpractices.

27 StandardDeviation,i

(%)

SLMCPR95/95 2.0 1.03 2.5 1.04 3.0 1.05 3.5 1.06 4.0 1.07 4.5 1.08 5.0 1.09

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