ML15134A327

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5/21/2015, Meeting Slide for Browns Ferry Nuclear Plant Regarding Extended Power Uprate License Amendment Request Probabilistic Risk Assessment
ML15134A327
Person / Time
Site: Browns Ferry  
Issue date: 05/21/2015
From: Doyle G
Tennessee Valley Authority
To:
Office of Nuclear Reactor Regulation
Saba F DORL/LPL2-2 301-415-1447
References
TAC MF4851, TAC MF4852, TAC MF4853
Download: ML15134A327 (23)
v • d • e


Text

Browns Ferry Nuclear Plant Extended Power Uprate License Amendment Request Probabilistic Risk Assessment Gerry Doyle Director EPU May 21, 2015

BFN EPU - Agenda Browns Ferry EPU License Amendment Request PRA

Introductions

OverviewandSchedule BrownsFerryNuclearPlantProbabilisticRiskAssessment (PRA)

Questions/Comments G.Doyle G.Doyle D.Kearnaghan G.Doyle l 2

BFN EPU - Overview and Schedule Browns Ferry EPU License Amendment Request PRA

  • New consolidated Browns Ferry Nuclear Plant (BFN)

Extended Power Uprate (EPU) License Amendment Request (LAR) submittal SupersedespreviousBFNEPUsubmittals AddressescurrentBFNconditionsandlicensingbasis(e.g.,AREVA ATRIUM10XMfueltype)

UsestheformatofRS001,ReviewStandardforExtendedPower Uprates AddressespreviousapplicableNRCRequestsforAdditional Information(RAIs)

Appliesimprovedsubmittalverificationprocesstoensure completenessandaccuracy l 3

BFN EPU - Overview and Schedule Browns Ferry EPU License Amendment Request PRA l 4

BFN EPU - Overview and Schedule Browns Ferry EPU License Amendment Request PRA Weareheretopresentanddiscussourapproachtodeveloping thePRAportionoftheBFNEPULAR

  • ThecurrentBFNPRAmodelsweredevelopedassumingEPU conditions TodeterminethedeltaCoreDamageFrequency(CDF)anddelta LargeEarlyReleaseFrequency(LERF)valuesfortheBFNEPULAR, changestotheexistingPRAmodelswerenecessary Thepurposeofthismeetingistodiscusstheapproachusedfor changingtheexistingPRAmodelstoallowcalculationoftheCurrent LicensedThermalPower(CLTP)CDFandLERFvalues l 5

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA

Background

  • BFNispursuingapoweruprate CLTP3458MWth EPU3952MWth
  • ConstantPressurePowerUprate 1050psia SteamDomePressure
  • MaximumExtendedLoadLineLimitAnalyses power/flowmapisretained

Background(continued)

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA l 7

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA ScopeofRiskEvaluation

  • AtPowerRisk

AnticipatedTransientswithoutScram(ATWS)

  • InternalFlooding
  • InternalFires
  • SeismicEvents
  • OtherExternalEvents
  • ShutdownRisk l 8

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA Methodologies

  • QuantitativeMethodologies InternalEvents InternalFires CDFandLERFcalculatedforEPUandCLTPconditions Deltariskcalculated
  • QualitativeMethodologies SeismicEvents OtherExternalEvents ShutdownRisk CDFandLERFestimatedusingconservativemethods l 9

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA QuantitativeRiskEvaluationProcess InternalEventsandFiresOnly

  • DefinePRAscopeforEPUandCLTP
  • ReviewEPUchangesforPRAImpact Physicalmodifications Procedurechanges Setpoint adjustments Plantoperatingconditions
  • IdentifyPRAmodelelementsimpacted
  • EvaluateEPUandCLTPthermalhydraulics
  • Revisemodelsasnecessary
  • Quantifyresults l 10

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA InternalEventsModel

  • EPUModel ConsideredEPUmodificationsscheduledforimplementationpostEPU Licenseissuance ThermalHydraulic(T/H)Analysisperformedat120%OriginalLicensed ThermalPower(OLTP)(MAAP4.0.7)

Operatoractiontimesareshorterduetohigherdecayheat Increasedprobabilityofstuckopenreliefvalvesassumed Higherhumanerrorprobabilities IncreaseddependenciesforHumanErrorProbabilities(HEPs)

NoneoftheEPUmodificationsresultedinaPRAlogicmodelchange

  • CLTPModel IncludedEPUmodificationsimplementedpriortoEPULicenseissuance UsedcurrentBFNPRAModelofRecordasbasis T/HAnalysisperformedat105%OLTP(MAAP4.0.7)

Increasedallowableoperatoractiontimes l 11

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA FirePRAModel

  • DevelopedtosupportNationalFireProtection Association(NFPA)805Transition
  • EPUModel CreditsEmergencyHighPressureMakeupPumpandotherFireRisk Modifications T/HAnalysisperformedat120%OLTP(MAAP4.0.7)

Operatoractiontimesareshorterduetohigherdecayheat Increasedprobabilityofstuckopenreliefvalvesassumed Higherhumanerrorprobabilities NoneoftheEPUmodificationsresultedinaPRAlogicmodelchange

  • CLTPmodel CreditsEmergencyHighPressureMakeupPumpandotherFireRisk Modifications IncludedEPUmodificationsimplementedpriortoEPULicenseissuance T/HAnalysisperformedat105%OLTP(MAAP4.0.7)

Increasedoperatoractiontimeswithlessdecayheat l 12

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA QualitativeRiskEvaluationProcess

  • SeismicandOtherExternalEvents ReviewexistingIndividualPlantExaminationsforExternal Events(IPEEEs)

DetermineEPUimpactoninitiators Determineifnewvulnerabilitiesexist AssessriskforCLTPandEPUconditions

  • ShutdownRisk Initiatingevents Successcriteria TimetoBoil TimetoCoreUncovery Humanreliability AssessriskforCLTPandEPUconditions l 13

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA AggregationofRisk

  • SummedindividualcontributionsofCDFand summedindividualcontributionsofLERF QuantifiedInternalEventsandFireValues DevelopedestimatesforSeismicandExternalEvents l 14

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA PRAQuality

  • PRAModelshavebeenpeerreviewed ASME/ANSRASa2009PRAStandardasendorsedbyRevision2of RegulatoryGuide(RG)1.200,AnApproachforDeterminingtheTechnical AdequacyofPRAResultsforRiskInformedActivities Part2forInternalEvents-Peerreviewconductedin2009 Additionalfocusedscopepeerreviewofinternaleventsplannedfor2015 Part4forFirePRA-Peerreviewconductedin2012 AdditionalfocusedscopepeerreviewoffireeventsconductedMay2015
  • Applicationofmodelsconsistentwith:

RS001,ReviewStandardforExtendedPowerUprates NUREG0800,StandardReviewPlan,Chapter19.2,AppendixD,Useof RiskInformationinReviewofNonriskinformedLicenseAmendments

  • Evaluationofchangeinriskconsistentwith:

RG1.174,AnApproachforUsingPRAinRiskInformedDecisionsonPlant SpecificChangestotheLicensingBasis l 15

Facts and Observations Browns Ferry EPU License Amendment Request PRA FactsandObservations(F&Os)

  • F&Osweregeneratedduringpriorpeerreviews AllF&Osdispositioned NoF&OsimpacttheEPUconclusions CapabilityCategoryIIismetwithdispositionoftheF&Os
  • FocusedscopepeerreviewstocloseF&Os ExpecttosubstantiallyreducethenumberofF&Os l 16

Total Risk Results CDF LERF Frequencies are units of per reactor-year

==

Conclusion:==

The change in CDF and LERF for BFN Units 1, 2, and 3 due to transitioning to EPU power results in a small and acceptable increase in risk (i.e., RG 1.174, Region II of Figures 4 and 5)

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA l 17

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA KeyRiskInsights

  • SmallchangeinriskduetoEPUtransition Changeinriskdrivenprimarilybyfiresequences
  • Factorsinriskincrease Increaseddecayheat Shortenedtimeforimportantoperatoractions
  • Dominantsequences(InternalEventsandFires)

Involvelossofinventorymakeupinwhichthereactor pressureremainshigh ImportantOperatorActions Manualcontrolofreactorlevelwithhighpressuresystems Manualdepressurizationofreactorvessel l 18

Key Risk Insights (continued)

  • Seismic risk Minimal EPU impact on seismic risk External eventno impact on seismic initiating event frequency Proposed EPU modifications qualitatively reviewed to verify no seismic risk impact
  • Shutdown risk Minimal EPU impact on shutdown risk Decay heat is highershorter times to boil and uncover core However, system time windows to perform operator actions are long (hours)
  • Other external events (high winds, tornados, transportation, etc.)

Minimal EPU impact on external event risk BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA l 19

SensitivityAnalyses

  • InternalEventsPRA IncreasedFailureProbabilities ScreeningHEPs RPVoverpressureprobability IncreasedInitiatingEventFrequencies GeneralTransients LOCAs
  • FirePRA IncreasedHEPs IncreasedFrequencyofLubeOilFireScenarios Conservativefireseverityfactorswereusedfor:

Condensatepumps Condensateboosterpumps Feedwater pumps

  • Conservativesensitivitycasesdidnotresultinchangestorisk conclusions RG1.174CDF/LERFAcceptanceCriteriamet(RegionII)

BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA l 20

Conclusions

  • BFNPRAmodelsaretechnicallyadequateforthisnon riskinformedEPUapplication
  • EPUimpactonBFNCDFandLERFissmallandwithin RegionIIofRG1.174AcceptanceGuidelines
  • Basedonsmallriskimpact,EPUdoesnotcreatespecial circumstancesthatchallengethepresumptionof adequateprotectiontothehealthandsafetyofthe public BFN EPU - PRA Browns Ferry EPU License Amendment Request PRA l 21

BFN EPU - Acronyms Browns Ferry EPU License Amendment Request PRA l 22 LOCAs - Loss of Coolant Accidents Mlbm/hr - Million pounds mass per hour MWth - Megawatts thermal NFPA - National Fire Protection Association OLTP - Original Licensed Thermal Power psia - pounds per square inch absolute PRA - Probabilistic Risk Assessment RAIs - Requests for Additional Information RG - Regulatory Guide T/H - Thermal Hydraulic ANS - American Nuclear Society ASME - American Society of Mechanical Engineers ATWS - Anticipated Transients Without Scram BFN - Browns Ferry Nuclear Plant CDF - Core Damage Frequency CLTP - Current Licensed Thermal Power EPU - Extended Power Uprate F - Farenheit F&Os - Facts and Observations HEPs - Human Error Probabilities IPEEEs - Individual Plant Examinations for External Events LAR - License Amendment Request LERF - Large Early Release Frequency

BFN EPU - Questions/Comments Browns Ferry EPU License Amendment Request PRA l 23

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