ML14234A282

2014/08/18 NRR E-mail Capture - STP risk-informed GSI-191 Meeting on 8/20/14

ML14234A282
Person / Time
Site:	South Texas
Issue date:	08/18/2014
From:	Harrison A W South Texas
To:	Singal B K Division of Operating Reactor Licensing
References
MF2400, MF2401
Download: ML14234A282 (82)

Text

1NRR-PMDAPEm Resource From:Harrison Albon [awharrison@STPEGS.COM]

Sent:Monday, August 18, 2014 7:05 PM To:Singal, Balwant Cc:Oesterle, Eric; Mitchell, Eliza

Subject:

RE: Out-of-Office (August 18 to August 29, 2014)

Attachments:

8-20-14 NRC Meeting backup slides.pptxHere are the backup slides in case we need them.

From: Harrison Albon Sent: Monday, August 18, 2014 5:55 PM To: 'Singal, Balwant' Cc: Oesterle, Eric; Mitchell, Eliza

Subject:

RE: Out-of-Office (August 18 to August 29, 2014)

Here is the main set of slides for the STP risk-informed GSI-191 meeting on 8/20/14.

Call me if you have questions.

Wayne Harrison STP Licensing (979) 292-6413

From: Singal, Balwant [mailto:Balwant.Singal@nrc.gov

] Sent: Thursday, August 14, 2014 2:45 PM To: Harrison Albon Cc: Oesterle, Eric; Mitchell, Eliza

Subject:

RE: Out-of-Office (August 18 to August 29, 2014)

Wayne, Wayne, Please copy the following NRC staff members on your e-mail forwarding the presentation slides:

Oesterle, Eric Eric.Oesterle@nrc.gov Mitchell, Eliza Eliza.Mitchell@nrc.gov Thanks.

Balwant K. Singal Senior Project Manager (Comanche Peak, STP, Diablo Canyon, and Palo Verde) Nuclear Regulatory Commission Division of Operating Reactor Licensing

Balwant.Singal@nrc.gov Tel: (301) 415-3016 Fax: (301) 415-1222

2From: Harrison Albon [mailto:awharrison@STPEGS.COM

] Sent: Thursday, August 14, 2014 12:58 PM To: Singal, Balwant Cc: Lyon, Fred; Blossom, Steven; Kee, Ernie

Subject:

RE: Out-of-Office (August 18 to August 29, 2014)

Balwant,

You asked yesterday when we would have slides to you for the 8/20 meeting. We'll have them to you (or Fred) by COB on Monday, probably before.

Regards, Wayne Harrison STP Licensing

(979 292-6413 From: Singal, Balwant [mailto:Balwant.Singal@nrc.gov

] Sent: Thursday, August 14, 2014 10:30 AM To: 'Hope, Timothy' (Timothy.Hope@luminant.com); Sterling, Lance; Harrison Albon; Carl.Stephenson@aps.com

pns3@pge.com Cc

Lyon, Fred; Watford, Margaret; Oesterle, Eric; Markley, Michael

Subject:

Out-of-Office (August 18 to August 29, 2014)

I will be out-of-office from August 18 to August 29, 2014. Please contact the following NRC staff members for Project Manager assistance:

Fred Lyon at 301-415-2296 for Comanche Peak, South Texas Project, and Diablo Canyon.

Eric Oesterle at 301-415-1014 for Palo Verde.

Thanks. Balwant K. Singal Senior Project Manager (Comanche Peak, STP, and Palo Verde)

Nuclear Regulatory Commission Division of Operating Reactor Licensing Balwant.Singal@nrc.gov Tel: (301) 415-3016 Fax: (301) 415-1222

Hearing Identifier: NRR_PMDA Email Number: 1521 Mail Envelope Properties (8C918BCF8596FB49BD20A610FA5920CF0208358E)

Subject:

RE: Out-of-Office (August 18 to August 29, 2014) Sent Date: 8/18/2014 7:05:10 PM Received Date: 8/18/2014 7:07:08 PM From: Harrison Albon Created By: awharrison@STPEGS.COM Recipients: "Oesterle, Eric" <Eric.Oesterle@nrc.gov>

Tracking Status: None "Mitchell, Eliza" <Eliza.Mitchell@nrc.gov> Tracking Status: None "Singal, Balwant" <Balwant.Singal@nrc.gov> Tracking Status: None

Post Office: CEXMBX03.CORP.STPEGS.NET Files Size Date & Time MESSAGE 2666 8/18/2014 7:07:08 PM 8-20-14 NRC Meeting backup slides.pptx 1122509

Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date: Recipients Received:

BackupSlidesBackup Slides CASADevelopmentPlanCASA Development Plan*Aggressive SQA plan in place to achieve Appendix B certification

-Alion SQA plan meets intent of IEEE standards and requirements from man y plantsqyp-Specifically checked for STP approved software list

• Source code under configuration managementTortoiseSVN(windowsshelltoSubversion

©)-TortoiseSVN(windows shell to Subversion

©)-CM plan approved

• Version 1.7 to release following V&V (Nov 1 st???)-Changes made to answer RAIs

-Address issue tracking reports

-GeneralizesumpconfigurationdefinitionGeneralize sump configuration definition

-Auto documentation feature 2

CASAV&VElementsCASA V&V Elements*Software Requirements Specification

-Functional description of capabilities

• Theory Manual

-Reference independent from SRS for convenient updateseeecedepedetoSSocoeetupdates

• Software Design Description

-Subroutine-level architecture

• UsersGuide

• Users Guide-Installation process and verification

-Example problem, definition of user inputVifitiTtPldRt

• Verification Test Plan and Report-Comprehensive check of suitability/adequacy

• Issue Tracking Report (ITR) system

-Bugzillareport and disposition (integrated with SVN)

-Issue notification chain (Alion to users, users to NRC) 3 CASAV&VActivityStatusCASA V&V Activity Status*Software ReqsSpecification -final review

• Theory Manual -in preparation

• Software Design Description -final review

• Users Guide -v1.7 almost complete

• Verification Test Plan (with archive documentation)

-Now building checklists from SRS

-Vol3 equation verification by independent team ->50% complete

• Confirm printed equation

• Confirm implementation

• Confirm I/O and results using test routines (partial)

-Automated Tests (dry runs com plete)(yp)*Data Arrays, Function calls, input data checks

-Vignette case studies -beginning

• Issue Tracking Reports

-Populating Bugzillaarchive

-in progress

-Issue disposition -in progress 4

PurposeofVISTACorrelation Purpose of VISTA Correlation

• IndependentlyconfirmsconservativeIndependently confirms conservative application of NUREG/CR-6224

-NochangetoLARisproposed

-No change to LAR is proposed*Addresses NRC concerns with 6224Fiifi(f)-Factorization of porosity (exponents o f )-Uniform bed compression (now differential)

-Limited range of test conditions (Re scaling)

-Stratified bed configurations (case studies) 5 ReScalinginViscous/InertialTransition Re Scaling in Viscous/Inertial TransitionLappleand Shepard (1940)Viscous RegimeInertial Regime(Momentum Transfer)Cliihlhdlidbdibdb Classic experiments suggest t hat total hydraulic drag can be described by a low-order function of Reynolds number in the viscous/inertial transition.

6 VISTAAttributesVISTA Attributes

• Good agreement with HTVL test dataGoodageeetttestdata

• Robust Reynolds number correlation confirms applicabilit y of existin g test data to STPppyg*Exponential drag law -(Reynolds 1883)

-Preserves both theoretical limits (Raleigh 1892)

• Stokes (viscous), Newton (inertial)

• "Adapts" to transition because coefficients are lfitftifR also fit as functions of Re*Maximizes use of independent debris propertiesSilliibdi/

• Still sensitive to bed compress ion/strata7 VISTAFindingsVISTA Findings*Bed configuration is the most sensitive remaining edcoguatosteostsesteeag assumption

-Uncertainty in spatial profile of porosity and surface area lead to largest discrepancy between prediction and measurement

-JustifiesSTPassumptionofmaximumcompressionJustifies STP assumption of maximum compression

• Independent confirmation of head loss for STP Reynolds flow conditions illustrates 6224 yconservatism as applied

-Maximum bed compression

-Factor of 5 uncertainty measure 8

L* Approach llan supporting CHL ca lculation*STPCHLCorrelationObjectiveSTP CHL Correlation Objective

-Address concerns that the conservatism in chemically

-inducedheadloss(CHL)quantificationchemically induced head loss (CHL) quantification is based on engineering judgment

-ProvidetechnicalvalidationbasedonbestProvide technicalvalidation based on best available data that the chemical "bump up" is conservative 9

L*EndProduct L End Product*Technicalevaluationof "bumpup"basedonTechnical evaluation of bump up based on engineering judgment

• Providesasupplementalmethodologyfor

• Provides a supplemental methodology for chemical effects quantification that improves resolutionbyusingstrainertestdataandresolution by using strainer test data and WCAP-16530-NP calculator results 10 L*Development L Development

• Evaluation of both strainer and vertical head loss test

-Concept of L* developed

• grams of precipitate available to filter across a strainer surface areaarea*Allows comparison of strainer results to vertical head loss results

• Allows use of deterministic tools in risk informed space

• CHLinvestigatedasafunctionofprecipitatetype

• CHL investigated as a function of precipitate type-AlOOHCHL per gram was largest response

• Enhanced conservatism durin g data minin ggg-Removal of declining or non-increasing head loss when chemicals are added11 L*Correlation L Correlation 1078 934 56CHL (ft)0123STP strainer test data Correlation 0050010001500200025003000L* (g/m2)

• Correlation provides conservative CHL results when compared to actual test data 12 L* Evaluation Compared to Strainer Tests121416Thin BedFull Bed 1Full Bed 2 6

81012CHL (ft)STP CHL correlation 0

2 40200400600800100012001400L*(/2)L* (g/m2)1.21.41.61.8STP CHL correlationSt. Lucie 2 DBA strainer results 040.6 0.81.0CHL (ft)0.00.20.4020040060080010001200L* (g/m2)13 L* Compared to Multiplicative hlflChemical HL Inflation12Bump Up Train 1Chemical bump-up occurs 10Bump Up Train 2Bump up Train 3Correlation Train 1Correlation Train 2CorrelationTrain3 68NCHL+ CHL) (ft)

Correlation Train 3NCHL Train 1NCHL Train 2 NCHLTrain 3 24THL (N0205001000150020002500Ti(i)Time (min)NCHL -non-chemical head loss or conventionalCHL-chemically induced head loss THL -total head loss 14 Conclusions of L* and "bump up" icomparison*Evaluationofthe "bumpup"approachbytheEvaluation of the bump up approach by the supplemental CHL approach, which is derived from technical data

-Provides supports that the "bump up" approach conservatively assesses riskIdtifiittitifthb

-Identifies improvemen t opportunities for the bump-up approach*Improvements only increase resolution of total head loss quantities and does NOTchange risk 15 SSIB,HeadLoss:RAI15SSIB, Head Loss: RAI 15*The NRC staff has generally not accepted correlations for the qualification of PWR strainers for several reasons. Please, explain why the following general concerns with the use of correlations are not an issue for the STP application:a)Correlations have not been validated for the full range ofdebrisloadsandmorphologies of debris loads and morphologies b)Correlations do not address nonhomogeneous debris beds)Clihbliddfhfll c)Correlations have not been validated for the full range of potential flow conditions and strainer geometries d)There is si gnificant uncertaint y in the model

)gyparameters used to describe physical attributes of the constituents 16 SSIB,HeadLoss:RAI16SSIB, Head Loss: RAI 16*The staff is concerned that the validation testing is not representative of the plant. Please, provide additional information:a)If the vertical loop tests are important to the conclusions, please, provide details why the STP HTVL tests are valid, considering that similar tests in different facilities had different resultsb)How was it determined that debris transported to a horizontal strainer is similar to transport to a plant strainer (with similar head loss)c)Demonstrate that the correlation used by STP is valid for plant specific geometry and plant conditions d)Discuss how NUREG

/CR-6224 could be used to predict HL

)/pexpected under conditions of STP flume tests 17 SSIB,HeadLoss:RAI17SSIB, Head Loss: RAI 17*- there is little or no testing that has been conducted under conditions similar to those at STP.a)Debris constituents in validation testing are not plant specificb)Debris sizes in validation testing are not plant-specificc)Little validation testing conducted at STP velocities and nonevalidatedthecorrelation none validated the correlationd)Validation testing did not include prototypical strainer geometries e)HTVLtestingdidnotsimulatepotentiallyimportant e)HTVL testing did not simulate potentially important aspects of debris bed formationf)Records from early testing not available, so conclusions fromearlytestingmustbelimitedfrom early testing must be limited.18 SSIB,HeadLoss:RAI18SSIB, Head Loss: RAI 18*Implementation of the correlation in the STP model makes specific assumptions. Justify that the assumptions and use of correlation is realistic or conservativea)Beds are homogeneous and representative of the plantb)Bed is assumed to accumulate with the manufactured density. Please, explain why this is valid or requantify using new densityc)Please, explain how NUREG/CR-6224 correlation compression function is applied d)Please,explainwhylinearmassweightingforsurface

-to-d)Please, explain why linear mass weighting for surfacetovolume ratio is acceptablee)Provide technical basis for coating material packing fractionsfractions 19 SSIB,Invessel:RAI37SSIB, Invessel: RAI 37*Pleaseprovidethetechnicalbasisforassumingthat Please provide the technical basis for assuming that 7.5 grams is an acceptable limit for a cold-leg break at STP when considering the potential for boric acid precipitation.

20 SSIB,InvesselRAI37ResponseSSIB, InvesselRAI 37 Response*7.5 g/FA is a "threshold of concern".5g/satesod ococe-sharp, single-value to maintain clarity on performance metric

• Full debris deposition on the fuel for conservatism difblbfflbfibdi-no credit for barrel-to-baffle bypass fiber deposits or lower plenum mixing

• Failureat75g/FAentersthecoreFailure at 7.5 g/FA enters the core*Lower than 15g/FA chosen after WCAP chemical load added to fueloadaddedtoue 21 APLABRAIs APLAB RAIs*CASAGrande

-PlantConfiguration:RAI1bCASA Grande Plant Configuration:

RAI 1b, 2b, 3*HRA:RAI35

• HRA: RAI 3, 5*Uncertainties: RAI 1, 2, 4, 5, 6

• Stable end state: PRA Success RAI 3c

• Use of different distributions 22 APLA,CASA

-PlantConfig:RAI1bAPLA, CASAPlant Config: RAI 1b*ProvidetechnicaljustificationforusingonlyProvide technical justification for using only nominal values of time-temperature curves 23 APLA, CASA-Plant Config: RAI 1bResponse*Not possible to choose "conservative" profiles across entire duration of the event

• Performed additional TH analyses to support use of nominaltemperatureprofiles nominal temperature profilesBkSiWorking Working WkiWorking CaseBreak Size (Diameter) gHHSI PumpsgLHSI PumpsWorking CS PumpsgCont. Fan CoolersCase Description15"-915 inches3136Dual LHSI Pump (Loops 3 & 4) Failure15"-22a15 inches2226Single Train (Loop 4) Failure15"-22b15 inches2226Single Train (Loop 3) Failure 15"-22a-4/6Fans15inches2224SingleTrain(Loop4)Failure(4ContFansOperating)15-22a-4/6Fans 15 inches2224Single Train (Loop 4) Failure (4 Cont. Fans Operating)15"-26a15 inches1226Single Train (Loop 4) + HHSI Pump (Loop 3) Failure15"-26b15 inches1226Single Train (Loop 3) + HHSI Pump (Loop 4) Failure15"-4315 inches1116Dual Train (Loops 3 & 4) Failure8"-438 inches1116Dual Train (Loops 3 & 4) Failure 24 APLA,CASA

-PlantConfig:RAI2bAPLA, CASAPlant Config: RAI 2b*ProvidetechnicaljustificationforassumingProvide technical justification for assuming only nominal operating conditions of flow ratesandthermalhydraulicconditionsrates and thermal hydraulic conditions 25 APLA, CASA-Plant Config: RAI 2bResponse*Useofnominalflowratesprovidesamore Use of nominal flow rates provides a more realistic evaluation of risk when competing factorsmakeitdifficulttodefineconservativefactors make it difficult to define conservative conditions.

• UseofnominalvaluesprovidesresultsthatAPLA, CASA-Plant Config: RAI 2b

• Use of nominal values provides results that are reasonable and probable for use in a holisticriskinformedevaluationholistic, risk-informed evaluation

.26 APLA,CASA

-PlantConfig:RAI3APLA, CASAPlant Config: RAI 3*A qualitative argument is provided why a quatateaguetspodedyacombination of pumps failing in the same train is "worse" than the same set of pumps failing in dffdifferent trains. a)Justify this assumption and clarify whether an iilifdengineering analysis was per formedb)State if this assumption always increases conditionalprobabilityofstrainerfailureconditional probability of strainer failurec)State if this assumption always increases conditionalprobabilityofin

-vesselfailureconditional probability of invessel failure27 APLA, CASA-Plant Config: RAI 3Response*Acursoryengineeringanalysisbasedon A cursory engineering analysis based on proportion of total flow to each strainer provided the basis for Assumption 2b

• Effects of debris penetration were found to contradict traditional engineering judgment

• Extra parameter evaluations were performed

-Small increase in CDF (1.5%) caused b y in-vessel ()yfailures for pump failures on separate trains

-Supplement provided with detailed statistics 28 APLAB, STP PRA Model-Human lbllReliability Analysis: RAI 3a

• PleasestateifCASAGrandemodelsplant Please state if CASA Grande models plant conditions that would occur if three containmentspraytrainswererunningegcontainment spray trains were running, e.g. --Sump flow ratesWashdownrates-Washdownrates-RWST drain-down times 29 APLAB, STP PRA Model-Human lbllReliability Analysis: RAI 3a Response

• Containment s pray flows onl y affect sum p flow pyyprate and sump flow rate dependent physical phenomenaSpraysecurementmodelledasnormaldistribution

-Spray securement modelled as normal distribution with 20 +/-5 minute mean and STD

• RWST switchover modelled as point values with 2 containment sprays operational (most probable)

• Failed debris washdowntaken from deterministic analysiswith2spraysoperationalanalysis with 2 sprays operational

• Statistical sampling allows for failure of manual action to secure s pray pump, but this failure is pypp,not enforced 30 APLAB, STP PRA Model-Human lbllbReliability Analysis: RAI 3 b*PleasestateifCASAGrandemodelsplant Please state if CASA Grande models plant conditions that would occur if operators fail to secureallcontainmentspray(CS)longtermsecure all containment spray (CS) long term e.g. --Sumpflowrates

-Sump flow rates-WashdownratesRWSTdraindowntimes

-RWST drain-down times31 APLAB, STP PRA Model-Human lbllReliability Analysis: RAI 3a Response

• CASAGranddidnotmodelplantconditionsCASA Grand did not model plant conditions that would occur if operators failed to secure CSlongterm CS long term.*CASA Grande samples user-defined Post-LOCA timeatwhichallCSaresecure time at which all CS are secure*User-defined distribution was truncated a high CSif75hCS securement t ime of 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.*Plant conditions not modelled for failure of long term CS securement 32 APLAB, STP PRA Model-Human lbllReliability Analysis: RAI 3c

• IfeitherquestiontoCSsecurementRAI

'sisnoIf either question to CS securement RAIs is no provide technical basis, and explain how PRA meetsASMEHLR

-HR-Grequirementtomeets ASME HLRHRG requirement to perform an assessment of post initiator humanfailureeventsusingawelldefiedand human failure events using a well defied and self-consistent process that addresses scenario-specificinfluenceonhuman scenariospecific influence on human performance 33 APLAB, STP PRA Model-Human lbllReliability Analysis: RAI 3a Response

• ThePRAdoesincludetorepresentfailureto The PRA does include to represent failure to trip one CS pump as well as failure to trip all CSpumpslaterinsequence CS pumps later in sequence*For the STP CASA Grande evaluation these CS securementoperatoractionfailureswerenotsecurement operator action failures were not modeledFilttiCSldldiid

-Failure to trip one CS pump wou ld evenly divide debris to all strainers resulting in lower head-lossThismaybeslightlyunconservativeforinvessel-This may be slightly unconservativefor in-vessel effects 34 ESGBRAIsESGB RAIs*Coatings:RAI126Coatings:

RAI 1, 2, 6*Chemical Effects: RAI 1 35 ESGB,Coatings:RAI1ESGB, Coatings:

RAI 1*ProvidebasisfortheunqualifiedcoatingsProvide basis for the unqualified coatings epoxy distribution size.

36 ESGB,Coatings:RAI1ResponseESGB, Coatings:

RAI 1 Response*AutoclavetestingperformedbyK&Lon 1Autoclave testing performed by K&L on Comanche Peak supplied coatings chips

• Alionperformedcharacterizationofchiptype 2*Alion performed characterization of chip type and sizeMfhiihdiidiidli

-Masses of chips weighed in individual size categoriesTheindividualweightfromeachsizecategorywas

-The individual weight from each size category was divided by the total of all categories to yield mass fractionsfractions 37 ESGB, Coatings: RAI 1 Supporting Information

• Coatings samples were tested in two baskets, one Coatgssapeseetestedtobasets,oesubmerged and one unsubmerged

-Unsubmerged basket had higher mass percentage of fines and fine chips after testing

-Chip debris that escaped both baskets was taken from autoclavefloorandaddedtounsubmergedbasketforautoclave floor and added to unsubmerged basket for conservatism

• This resulted in a higher mass fraction of fines and fine chips

-Mass fractions from unsubmerged basket were used to define failed size fractions for unqualified epoxy in STP CASA Grande evaluation 38 ESGB,Coatings:RAI2ESGB, Coatings:

RAI 2*ProvideZOIusedforbothepoxyandIOZProvide ZOI used for both epoxy and IOZ qualified coatings.

39 ESGB,Coatings:RAI2ResponseESGB, Coatings:

RAI 2Response*A 4D ZOI was used for both qualified zinc and IOZ OasusedobotquaedcadOcoatings.Supporting Information

• WCAP-16568 testin g shows an avera ge loss of 1ggabout 0.1 mil at 3.68 L/D where jet directly impacts coupon (generally within 2-inch radius)

• Extrapolation of data shows zero erosion and 4.28 L/D40 ESGB,Coatings:RAI6aESGB, Coatings:

RAI 6a*Describewhathasbeendonetoensurethat Describe what has been done to ensure that STP unqualified coatings are the same as coatingusedinEPRItesting 1coating used in EPRI testing41 ESGB,Coatings:RAI6aResponseESGB, Coatings:

RAI 6a Response*ManufacturecoatingtypeisoftenunavailableManufacture coating type is often unavailable for unqualified coatings.

• GenericcoatingstypesatSTP(i.e.epoxy, Generic coatings types at STP (i.e. epoxy, alkyd, etc.) matched with generic coatings types from the EPRI study 1*Generic unqualified coatings sample types labeled in EPRI study were taken from 1multiple plants with different visual and physical characteristics 42 ESGB,Coatings:RAI6bESGB, Coatings:

RAI 6b*EPRItestersstatedthattheymadenoattempt 1EPRI testers stated that they made no attempt to quantify debris on the filter. Provide additionjustificationforusingthistestdatato addition justification for using this test data to assign failure time to unqualified coatings.

43 ESGB,Coatings:RAI6bResponseESGB, Coatings:

RAI 6b Response*Estimated failure timing of unqualified coatings statedauetgouquaedcoatgswas based off visual inspection of filter discoloration.

• Alkyds had the highest average detachment from testing (33.9%).

-Alkyds tested were visually pigmented with a variety of colors (gray, silver, red, yellow, blue, blue-green)

-Alkydfailuremayconservativelybiasfailuretimingto 1Alkyd failure may conservatively bias failure timing to the maximum unqualified coatings failure rate of alkyds 44 ESGB,Coatings:RAI6cESGB, Coatings:

RAI 6c*STPseekstoreducethefailureofunqualifiedSTP seeks to reduce the failure of unqualified coatings from the deterministic methodology percentageof100%to6%Provideadditionalpercentage of 100% to 6%. Provide additional justification for the current failure timing analysisanalysis. 45 ESGB,Coatings:RAI6cResponseESGB, Coatings:

RAI 6c Response*AlkydshavegreatestinfluenceoninterpretationAlkyds have greatest influence on interpretation of filter photographs because of distinctive coloration and hi ghest avera ge detachment gg*EPRI analysis states "With regard to timing of the coatingfailures,thefiltersdonotdemonstratea 1coating failures, the filters do not demonstrate a definitive time of failure however in subjective terms it a ppears that much of the failure ppoccurred in the 24-to 48-hour timeframe" 46 ESGB,Coatings:RAI6cResponseESGB, Coatings:

RAI 6c Response*If "much of the failures" is 21% and the total average detachment is 27% for all coatin gs types 6% failure is found at gyp24 hours.Failure Percentage Vs. Time

• Increasing the subjective 70%80%90%100%lureamount of "much of the failures" to a higher percentage would yield a lowerpercentageoffailed 30%40%50%60%ercent Coatings Failower percentage of failed coatings at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> than the STP assumed 6%.Ifbjtithd(24 hr., 6%)

0%10%20%020406080100120140160180 Pe*If subjective amount changed to 55% of available failure, the failed percentage at 24-hours doubles to 12%. Parametric Time (hr)evaluations have shown that risk is insensitive to this range of added particulate.

47 ESGB,Coatings:RAI6cResponseESGB, Coatings:

RAI 6c Response*Artificially setting 100% failure over the 7 days and assuming "much of the failures" is 89% and 55%

(red and blue curves (respectively) with 5% residual failure (48 to 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br />).

• Interpreting "much of the failures as 89% (red curve) yields the STP assumed 6% filt24h80%90%100%reFailure Percentage Vs. Time failure at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> *If subjective amount changed to 55% (blue curve) of (24 hr., 40%)

30%40%50%60%

70%cent Coatings Failuavailable failure, the failed percentage at 24-hours is 40

%. This would contradict the observedaveragedetachment(24 hr., 6%)

0%10%20%30%020406080100120140160180 PercTi(h)observed average detachment of 27%Time (hr)48 ESGB,ChemicalEffects:RAI1aESGB, Chemical Effects: RAI 1a*Please justify not correlatin g the chemical bum p up factor to jygppthe conventional head loss since the same debris bed affects both values 49 ESGB, Chemical Effects: RAI 1a Response*Chemical"bump-up" factor

-Appliesmaximumheadlossfromchemicalinteractionwiththe Applies maximum head loss from chemical interaction with the highest filtration debris bed

• Based on test data (thin bed not included)

-Conventional head loss is correlated to break size with maximum hiliififlhdl chemical interaction for increase o f total head loss-Distributions provide opportunity for smaller breaks to have high HL

-Simplifies the chemical and bed interaction complexity with ticonservatism*Supporting calculations

-Technical approach to support and evaluate applied "engineering jd"judgment"-Allows estimation or detailed quantification of the strength and weakness of bump up approachAkfth"b"dtdtitik

-Assesses wea kness of the "bump up" do not underestimate risk because of conservatisms used in generation of "bump up" 50 ESGB,ChemicalEffects:RAI1bESGB, Chemical Effects: RAI 1b*In order to help the staff judge the magnitude of the chemical head loss bump-up factor, please provide, by performing realizations for the existing CASA Grande model, a relative frequency plot of chemical effects for STP in terms of absolute units (e.g., feet of H 2O) for the [llbk][dibk]dSBLOCA [small break LOCA], MBLOCA

[medium break LOCA], and LBLOCA [large break LOCA].

51 ESGB, Chemical Effects: RAI 1bResponse1.0E-021.0E-011.0E+00LBLOCA1.0E-061.0E-051.0E-04 1.0E-03Frequency (%)

1.0E-09 1.0E-08 1.0E-07Head Loss (Feet of Water) 1.0E-041.0E-031.0E-021.0E-011.0E+00(%)MBLOCA1.0E-10 1.0E-091.0E-081.0E-07 1.0E-061.0E-05Frequency (1.0E-121.0E-11Head Loss (Feet of Water) 52 ESGB,ChemicalEffects:RAI 1cESGB, Chemical Effects: RAI 1c*Please provide additional details on how the results from the Chemical Head Loss Experiment (CHLE) testing, WCAP-16530-NP, "Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSI-191," calculations, and reasonable engineering judgment were used in hdlfhlddllh the development of the exponentia l PDF. In a ddition, please supp ly the basis for choosing the exponential form of the PDF over others, e.g.,

Weibull"53 ESGB, Chemical Effects: RAI 1c Response*The exponential PDF was chosen:

-Shape-Convenience of fitting statistics of the mean and truncated tail probability

• Only mean is needed to fully specify distribution

• CHLtestingandWCAP 16530NPcalculationswereusedto

• CHL testing and WCAP-16530-NP calculations were used to determine the bump-up multiplier that exist at the highest probability of the PDF

• EngineeringjudgmentbasedonreviewofSTPstrainertest

• Engineering judgment based on review of STP strainer test was used to determine a mean bump up multiplier

• The maximum values were values capable of producing a quantifiablenumberofchemicallyinducedfailuresquantifiable number of chemically induced failures-6.8X (SBLOCA), 8.1X (MBLOCA), and 10.7X (LBLOCA) higher than the DBA multiplicative response.

54 ESGB,ChemicalEffects:RAI 1dESGB, Chemical Effects: RAI 1d*Please provide a detailed technical basis for the mean bump up factors shown for the SBLOCA, MBLOCA, and LBLOCA. The NRC staff has observed head loss testing where the greatest chemical bump-up factors are associated with thinner beds. Please discuss why the mean bump up fldbhhfllfbbl factor wou ld be higher for a LBLOCA. P lease explain if it is more pro bable that a debris bed for smaller and medium breaks (assuming the bed coverage criterion is met) would consist primarily of fiber fines that are themostreadilytransportabletothestrainerIngeneralfinerfiberbeds the most readily transportable to the strainer. In general, finer fiber beds tend to lead to greater head loss 55 ESGB, Chemical Effects: RAI 1dResponse*Mean bump-up

-Based on STP strainer testing of DBA bed and 30-day worst-case chemical precipitate mode

-Conservatism applied

• SBLOCAappliesmultiplierbasedonstrainertestsSBLOCA applies multiplier based on strainer tests*MBLOCA and LBLOCA increases the multiplier

• Bump up mean multipliers applied to thinner beds were confirmed higher than a DBA determined multiplier. However, sensitivity dldhhbdbhlhh modeling require d the thin bed mean to be much larger than that observed in other strainer testing

• It is not expected that small and medium break debris consists primarilyoffinesbecause primarily of fines because-Every break generates the same volumetric proportions of fiber glass

-One set of debris-size dependent transport fractions is applied for every breaky56 APLAB HRA RAI 3

• Top Event OSI represents securing one train of Containment S pray early given three initiate

Top pyyg;pEvent OFFS represents securing all Containment Spray later as directed by technical support center(a)Does CASA Grande reflect conditions if all three ContainmentSpraycontinuetorun?Containment Spray continue to run?Statistical sampling of trip time does not preclude long term operation of three trains; however, this condition was not explicitly considered 57 APLABHRARAI3,continued APLAB HRA RAI 3, continued (b) Does CASA Grande reflect conditions if

()Containment Spray is not secured in the long term?No. While the time of tripping the pumps is sampled, truncation considerations preclude this timetogobeyond75hoursPlantconditionsare time to go beyond 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Plant conditions are not modeled for the condition where operator fail to secure long-term containment spray.

58 APLABHRARAI3,continued APLAB HRA RAI 3, continued(c) Provide justification if the answer to (a) or (b) is "no."ThePRAcontainsthenecessarylogicstructureto The PRA contains the necessary logic structure to represent the conditions of interest. However, no specific CASA Grande results for these conditions were available atthetimeofmodelquantificationWhilefailuretotrip at the time of model quantification

. While failure to trip one pump might lead to conservative results with respect to potential NSPH conditions due to sump screen loading (debriswouldbetransportedtotwosumpscreensrather (debris would be transported to two sump screens rather than three), the approach may be unconservativewith respect to the filtration of debris by the sump strainers.

59 APLABHRARAI 5APLAB HRA RAI 5*How were Casa Grande results developed to oeeCasaGadeesutsdeeopedtoreflect combinations of success and failure of the operator actions: (1) securing one train of lhContainment Spray ear ly given t hree trains initiate; (2) securing all trains of Containment Spraylaterintheeventresponse;(3)switchoverSpray later in the event response; (3) switchover to sump recirculation; and (4) switchover to hot

leg injection. How was consitenc ybetween the gjyPRA scenario and information developed in CASA Grande assured?

60 APLABHRARAI5,continued APLAB HRA RAI 5, continued

• The first two actions are included in the PRA model as switches; they were included to support sensitivity analyses, if later desired

• The success or failure of the first two tasks does not impact the success or failure of the remaining two actions.

• Action 3 is required to avoid fuel damage; action 4 is only queried if action 3 was successful

• Failure of action 4 is assumed to result in fuel damage for cold leg breaks; conversely success of action 4 precludes

the possibilit y of boron precipitation (after the time of pypp(switchover to hot leg injection), minimizing need for status of actions to be communicated between the PRA and CASA Grande61 APLAB RAI 2: Arithmetic vs.

Geometric Means

• RAI Statement:*Volume 3, Assumption 3.a (page 76 of 248) states that the geometric-mean aggregation of LOCA frequencies in NUREG-1829 is the most appropriate set of resultstouseforthisevaluationThebasisprovidedisthatgeometric meanresults to use for this evaluation

. The basis provided is that geometric

-mean aggregation produces frequency estimates that are approximately the same as the median estimates of the panelists. There is no justification about why the median estimate is preferred and emphasis on the median conflicts with the RG 1.174 guidance that the mean values be used for decision making. Furthermore, iftiiNUREG1829Sti764hthtthfthithti information in NUREG-1829, Section 7.6.4 shows that the use of the arithmetic mean instead of the geometric mean would increase the LOCA frequency by an order of magnitude or more for some LOCA categories and may therefore substantially increase the risk estimates. Consequently, selection of the geometric mean is a ke y assumption and selection of the arithmetic mean re presents an yppalternative reasonable assumption as defined by RG 1.200. This is supported by RG 1.174, Section 2.5, which states that "the licensee should [identify] key assumptions in the PRA that impact the application." Sensitivity studies provide important information about how some of the key assumptions affect the final resultsasdiscussedinRG1174Section253PleaseprovideCDFLERF results as discussed in RG 1.174 Section 2.5.3. Please provide CDF, LERF, CDF, and LERF using the arithmetic mean aggregation of LOCA frequencies in NUREG-1829.

62 APLAB RAI 2: Arithmetic vs.

Geometric Means

• RAIResponse:

• RAI Response:*Despite the above caveat Weight Required on Expert A in thWihtdGMtAhiNUREG-1829 contains in its Executive Summary, the body of NUREG-1829, along with the literatureoncombiningexpert 5th50th95ththe Weighted GM to Achieve the AM:literature on combining expert opinion, makes a strong case for using GM rather than AM at

least when:

(i)theelicitedprobabilitiesconcern 5th50th95th73.6%72.4%70.1%

• (i) the elicited probabilities concern rare-events, *(ii) the opinions of the individual experts are disparate,

• and(iii)weseekacombinationrule

• and (iii) we seek a combination rule that represents a reasonable notion of the center of the group's opinion.

63 APLAB RAI 3A, 3B, 3C: Plant Configuration

• RAI Statement:*Volume 3, Assumption 2b provides a qualitative argument for why a combinationofpumpsfailinginthesametrainis "worse"thanthecombination of pumps failing in the same train is worse than the same set of pumps failing in different trains.A) Please justify this assumption and clarify if an engineering analysis was performed in su pport of this assum ption.yppppB) Please state if this assumption always increases the conditional probability of strainer failure (i.e., is this a conservative

assumption?).C) Please state if this assumption always increases the conditional probability of in-vessel effects.

64 APLAB RAI 3A, 3B, 3C: Plant Configuration

• RAI Response:p*Analysis of Case 22 suggests the condition in which all pumps fail on the sametrainleadstothe largestsumpfailurefrequency.

same train leads to the largest sumpfailurefrequency.*For vesselfailurefrequency, three cases (Cases 22-2, 22-3, and 22-5) in which the HHSI and LHSI pumps fail on different trains result in larger frequencies than when these pumps fail on the same train.*The change in CDF reported in Volume 2 is 2.88E-08 per year.*The CDF obtained by replacing Case 22-1 with Case 22-3 is: 2.88E-08 + [3.24E-02 x 1.17E-08] = 2.92E-08 per year, a 1.5% increase.

65 NUREG-1829 RelatedRAI

'sRelated RAIs APLAB RAI 2: Modeling LOCA Frequency

& Break Size Under DEGB-Only Breaks

• RAIStatement:

RAI Statement:*NUREG-1829 states that, in general, a complete rupture of a pipe is morelikelythanapartialruptureItappearshoweverthatSTP's more likely than a partial rupture. It appears, however, that STP's methodology leads to the opposite result (i.e., a rupture of a given size is more likely to be caused by a partial rupture of a large pipe than a com plete rupture of a smaller pipe).pppp)A) Please illustrate the results of your method by comparing the frequency of partial versus complete breaks for a set of representative pipe sizes.B) Please describe whether the methodology described in the STP pilot is consistent with the assumption of NUREG-1829 or provide justification for an alternate approach.

67 APLAB RAI 2: Modeling LOCA Frequency

& Break Size Under DEGB-Only Breaks

• RAIResponse:

RAI Response:*Under the implemented "continuum" model with a hybrid approach, theprobabilityapipeexperiencesaDEGBgiventhatithasabreakisthe probability a pipe experiences a DEGB given that it has a break is 0.165.*Under the top-down only approach for the "continuum" model, the probabilityapipeexperiencesaDEGBgiventhatithasabreakis probability a pipe experiences a DEGB given that it has a break is 0.0746.*Using the NUREG-1829 frequencies without considering RI-ISI frequency information (no hybrid approach) increases the probability of a DEGB by more than a factor of 2.21.

68 APLAB RAI 3: Justification of the Use of 25-Year Frequency Estimates

• RAIStatement:

RAI Statement:*Section 2.5.5 states that it is incumbent on the licensee to demonstratethatthechoiceofreasonablealternative hypotheses demonstrate that the choice of reasonable alternative hypotheses

, adjustment factors, or modeling approximations or methods to those adopted in the PRA model would not significantly change the

assessment. Also

, it is assumed that the STP plants will continue to

,poperate for more than 25 years; RG 1.174 Section 3 states that the licensee should define an implementation and monitoring program to ensure that no unexpected adverse safety degradation occurs do to thechange the change.A) Please justify the use of the 25-year frequency estimates rather than the 40-year estimates provided by NUREG-1829. Provide CDF, LERF, CDF, and LERF usin g the 40-year estimates.

,,gy69 APLAB RAI 3: Justification of the Use of 25-Year Frequency Estimates

• RAIResponse:

RAI Response:*Using 40-year frequency frequency estimates, CDF increases to 6.91E-08, a factor of about 242.4. 70 APLAB RAI 4A: Discrepancy Between LOCA FrequencyMeans forJohnsonDistributions&

• RAIStatement:

Frequency Means for Johnson Distributions

& NUREG-1829 RAI Statement:*Typically, statistical sampling simulations will develop random variablesthatpreservethemeanofthedistributionfromwhichthe variables that preserve the mean of the distribution from which the variables are sampled. STP has chosen to fit a Johnson bounded distribution that matches the expert-provided 5th, 50th, and 95th percentiles in NUREG-1829

, but does not match the mean values.

p,The properties of the distribution are such that, as fit, the mean of the fitted distribution is always less than the experts' means from the distributions in NUREG-1829.

A)PllihthSTPltidtfth A) Please explain why the STP evaluation departs from the regulatory position in RG 1.174 regarding the use of mean values.

71 APLAB RAI 4A: Discrepancy Between LOCA FrequencyMeans forJohnsonDistributions&

Frequency Means for Johnson Distributions

& NUREG-1829

• RAIResponse:

RAI Response:*Analyze means of Johnson distributionsasafunctionof distributions

, as a function of .*x-axis: Ratio of to elicited 95thpercentile 95percentile*Means grow with , but level off for large values of *Evenataratioof100,the Even at a ratio of 100, the Johnson means fall short of the NUREG-1829 means, most prominently in categories 5and65 and 672 APLAB RAI 4B: Explanation of the Johnson DitibtiGiLOCAF*RAI Statement:

Distribution Governing LOCA Frequency*Typically, statistical sampling simulations will develop random variables that preserve the mean of the distribution from which the variables are ldSTPhhtfitJhbddditibtitht sampled. STP has chosen to fit a Johnson bounded distribution that matches the expert-provided 5th, 50th, and 95th percentiles in NUREG-1829, but does not match the mean values. The properties of the distribution are such that, as fit, the mean of the fitted distribution is alwayslessthantheexperts

'meansfromthedistributionsinNUREGalways less than the experts means from the distributions in NUREG-1829.B) The Johnson fit to 5th, 50th, and 95th percentiles is not unique. Alternative accurate fits can be constructed with arbitrary values of the scaleparameterThescaleparameterdefinesaboundonthe scale parameter

.The scale parameter defines a bound on the maximal frequencies sampled in the Monte Carlo model. By increasing the value of ,the relative proportion of large to medium to small breaks can be altered, especially in the extrapolation range beyond the 95thpercentilePleaseprovideatechnicaljustificationfortheselection 95th percentile

. Please provide a technical justification for the selection of the scale parameter (other selections appear possible that could change the outputs by CASA Grande).

73 APLAB RAI 4B: Explanation of the Johnson DitibtiGiLOCAFDistribution Governing LOCA Frequency*RAI Response:p*Using the means of the Johnson distributions as metric for relative contributionofLOCAeventsby contribution of LOCA events by category:*Somewhat underestimate the contribution categories 5 and 6 as compared to using the implied meansfromNUREG

-1829means from NUREG1829,*Overestimate the contribution of these categories versus the implied NUREG-1829 means if we use the 99th or 99.9th percentiles and a large value for .*Fixing to twice the 95 thpercentile: Underestimate the contribution to categories 5 and 6, even using 99 thor 99.0thpercentilesrelativetoNUREG percentiles

, relative to NUREG-1829 means.

74 APLAB RAI 4C: Impact of Johnson Distribution SltiCDFLERFCDFLERF*RAI Statement:

Selection on CDF, LERF, CDF, LERF*Typically, statistical sampling simulations will develop random variables that preserve the mean of the distribution from which the variables are ldSTPhhtfitJhbddditibtitht sampled. STP has chosen to fit a Johnson bounded distribution that matches the expert-provided 5th, 50th, and 95th percentiles in NUREG-1829, but does not match the mean values. The properties of the distribution are such that, as fit, the mean of the fitted distribution is alwayslessthantheexperts

'meansfromthedistributionsinNUREGalways less than the experts means from the distributions in NUREG-1829.C) Please provide the maximum expected difference between the CDF, LERF, CDF, and LERF developed from bounded Johnson distributionsthatconsideralternativevaluesofthescaleparameterdistributions that consider alternative values of the scale parameter

, and other distributions that would preserve mean values reported in NUREG-1829. Note, in particular, that alternative bounded Johnson distributions with large values of the scale parameter can be built to accuratelyfittheNUREG-18295th50thand95thpercentilesand accurately fit the NUREG-1829 5th, 50th, and 95th percentiles

, and produce mean estimates closer to the NUREG-1829 values than current fits used by STP.

75 APLAB RAI 4C: Impact of Johnson Distribution SltiCDFLERFCDFLERF*RAI Response:Selection on CDF, LERF, CDF, LERFp*Our estimates of changes in CDF, CDF, LERF, and LERF are modest as we range the Johnson scale parameterfrom a factor of 1.25 up to a ftf100tith95thtilfthfiliitdffactor of 100 times the 95th percentile of the frequencies elicited from experts in NUREG-1829. More specifically, point estimates of CDF and LERF increase by no more than 2% for the specific values of we consider here.

76 APLAB RAI 4C: Impact of Johnson Distribution SltiCDFLERFCDFLERF*RAIResponse:

Selection on CDF, LERF, CDF, LERFRAI Response:

77 EPNB RAI 6: Consistency of Weld Frequencies ithRIISIP*RAI Statement:

with RI-ISI Program*By letter dated September 10, 2012, the NRC approved the risk-informed in-service ins pection (RI-ISI) program for the third 10-year p()pgyin-service inspection interval at STP, Units 1 and 2 (ADAMS Accession No. ML12243A343). Please discuss the following:A) Please state if the LOCA frequency estimates used for welds in theGSI-191submittalareconsistentwiththeLOCAfrequency the GSI191 submittal are consistent with the LOCA frequency estimates used in the RI-ISI program. If the comparison is appropriate, please provide numerical examples of the comparison.

If the comparison is not appropriate, please provide explanation.

B)IftheLOCAfrequenciesforweldsarenotconsistentbetween B) If the LOCA frequencies for welds are not consistent between the two analyses, (1) please identify the differences and explain why there are differences, and (2) please discuss why the LOCA

frequencies proposed in the GSI-191 submittal are acceptable if theyarenotconsistentwiththatoftheRIISIprogram they are not consistent with that of the RI-ISI program.78 EPNB RAI 6: Consistency of Weld Frequencies ithRIISIPwith RI-ISI Program*RAI Response:p*The mean frequencies reported in NUREG-1829 are preserved in the mean frequencies used to compute CDF. Using RI-ISI instead, these thfilddbftf4431518d227f three frequencies would decrease by factors of 4.43, 15.18, and 2.27 for small, medium, and large breaks.*If we use only RI-ISI frequencies to construct the distribution over break size and weld case, the probability mass increases by factors of 5.03, 2038d1568ithtiti45d6 20.38, and 15.68 in the respective categories 4, 5, and 6.79