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#REDIRECT [[NG-11-0135, Clarification of Information Contained in License Amendment Request (TSCR-120): Application for Technical Specification Change Re Risk-Informed Justification for Relocation of Specific Surveillance Frequency Requirements to Licensee.]]
| number = ML111110507
| issue date = 04/20/2011
| title = Duane Arnold - Clarification of Information Contained in License Amendment Request (TSCR-120): Application for Technical Specification Change Re Risk-Informed Justification for Relocation of Specific Surveillance Frequency Requirements to L
| author name = Costanzo C R
| author affiliation = NextEra Energy Duane Arnold, LLC
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000331
| license number = DPR-049
| contact person =
| case reference number = NG-11-0135, TSCR-120, TSTF-425, Rev 3
| document type = Letter
| page count = 8
| project =
| stage = Request
}}
 
=Text=
{{#Wiki_filter:Attachment to NG-11-0135 Page 1 of 6 Request for Clarifying Information - NextEra Energy Duane Arnold Probabilistic Risk Assessment Model for Use in Implementing TSTF-425, Rev.1
 
During a teleconference held on March 29, 2011 between the NRC Staff and NextEra Energy Duane Arnold personnel, the Staff requested that information contained in Attachment 2 of the referenced application (Documentation of PRA Technical Adequacy) be clarified to assist the Staff in eval uating the Duane Arnold Energy Center (DAEC) Probabilistic Risk Assessment (PRA) model. Specifically, the following information was requested:
: 1)  The application states that Revi sion 6 of the DAEC PR A, currently under development, will be the model used to implement this Technical Specification (TS) change upon approval. When is it expected to be finalized and issued for use?
 
Response:
As stated in the application, Revision 6 is intended to also support the conversion of the DAEC Fire Plan to the NFPA-805 standard. As the license amendment request for the Fire Plan conversion is currently scheduled for submission by June 29, 2011, Revision 6 of the DAEC PRA will be implemented no later than that date. 
: 2)  The application discusse s the results of the Peer Review conducted on the DAEC PRA model, Revision 5C. That review resulted in the identifica tion of 83 potential gaps to meeting Capability Category II in the Supporting Requirements of the ASME Standard. However, the Tables provided in Attachment 2 of the submittal only discuss 30 of those items. Please provide a discussion of the di sposition of all 83 identified items and the expected status of any open items when Revision 6 of the model is issued.
 
Response:
The intent of the Attachment 2 Tables was to discuss only those items that remained in an "open" status at the time of the application and to bin them into separate Tables by significance. Therefore, any item which had already been dispositioned and closed in the Revision 6 model was not reported in the Tables because they no longer represented gaps to Capability Category II. Because Peer Reviews often result in findings that may represent potential gaps in more than one Supporting Requirement in the ASME Standard, there was overlap between the li ne items found in the 3 Tables in the application which makes a simple tallying of them back to the original 83 items difficult. 
 
Subsequent to the original application, NextEra Energy performed a follow-up Focused Peer Review to validate the closure of those previously identified 83 items from the 2007 Peer Review. In addition, that review utilized the current version of the ASME Standard (RA-Sb-2009). 
 
Attachment to NG-11-0135 Page 2 of 6 The Focused Peer Review team found that NextEra Energy had appropriately incorporated most of the 83 previously identified items into Revision 6. However, not all of the closures were found to fully meet Capability Category II requirements, which resulted in new open items, in addition to those items that remained open at the time of the Focused Peer Review. The final result was a total of 12 items that were assessed as not meeting Capability Category II per the current ASME Standard. Of these 12 items, five will be addressed and incorporated into Revision 6 of the DAEC model upon issuance prior to June 29, 2011. The remaining seven items are judged to have either no, or only minor, impact on the model's ability to support this applic ation. The following Table describes those seven open items. 
 
In order to not repeat the confusion created by binning them into "gaps," "findings," and "suggestions," as was done in the original Attachment 2 Tables, we have simplified the presentation of the current open items on the pending Revision 6 of the DAEC PRA model into a single Table.
 
Attachment to NG-11-0135 Page 3 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6ASMESRsCategoryIISRDetailsDescriptionofGAPImpactonQuantificationImportancetoApplicationIE B301AGROUPinitiatingeventsonlywhenthefollowingcanbeassured:
(a) eventscanbeconsideredsimilarintermsofplantresponse,successcriteria,timing,andtheeffectontheoperabilityandperformanceofoperatorsandrelevantmitigatingsystems;or(b) eventscanbesubsumedintoagroupandboundedbytheworstcaseimpactswithinthe"new"group.AVOIDsubsumingeventsintoagroupunless:(i) theimpactsarecomparabletoorlessthanthoseoftheremainingeventsinthatgroup,AND(ii) itisdemonstratedthatsuchgroupingdoesnotimpactsignificantaccidentsequences.SeveralfindingsandsuggestionsunderHLR AandHLR Bhavebeendispositioned/resolved,butthesubsuming(IEB3)andscreening(IE C4(C6))ofinitiatingeventsdoesnotmeetthestandard.Thefollowingprovidesexamplesummarizes(IENotebook,includingAppendixH): RBCCW(failsCRD,whichiscreditedforearlyinjection)issubsumedbyTT,butRBCCWisnotfailedgivenTT. GSW(failsRBCCW,CRD,Feedwater,etc.)issubsumedbyTC,butthesesystemsarenotfailedgivenTC. TheimpactsofReferenceandVariableLegBreaksarenotadequatelydescribedandaresubsumedbyLossofFW.MostlikelywouldbeamanualshutdownwithcomplicationsversesaLossofFW.Giventhatimmediateshutdownwouldoccurgivenabreak,theseshouldbemodeled.Section2.4.8describedthelowriskfromthese,butthisdoesnotmeetstandardforscreening. 1A1/1A2busfailuresandpartiallossoffeedwater(onepump)arebinnedtoTT,butthisimpactisnotmodeledgivenTT. 1A3/1A4busfailuresaresubsumedwithTT.Impactonlossofchargers[TS3.8.4.]etc.andpossibilitythatfailureisaproblemcouldleadtoanimmediateshutdown.Notes11and12suggestthatonlynormalpowersourceislost,butemergencypowerisalsounavailableifbusfails.RECOMMENDATION:FollowIE B3andC6withregardtosubsumingandscreeningormoreimportantlymodeltheaboveinitiatingevents.ModelingtheseadditionalinitiatorswillbetterdefinecertainaccidentsequencesandamoreaccuratelydetermineassociatedSSCimportance.Overallcalculatedriskslightlyincrease;significantlyforspecificfunctionsassociatedwiththeinitiatingevent.Someapplicationsmayseeaslightdecreaseinriskmargin.Althoughtheimportanceofaffectedcomponentsisnotfullyconsidered;theirimpactcanbeaddressedforspecific5bapplicationsusingsensitivityanalysis,qualitativeanalysis,boundinganalysisorexplicitmodelinginaccordancewiththeNEI04 10guidance.SY A5 01AINCLUDEtheeffectsofbothnormalandalternatesystemalignments,totheextentneededforCDFandLERFdetermination.TheSBOeventtreedoesnottakecreditforcontainmentventingusinganalternatealignmentwhenthepneumaticsupplyislost.DAECprocedureSAMP706providesdetaileddirectionforventingPCgivenanunavailablepneumaticsupply.TheContainmentVentnotebookdoesnotcredit/discussthisprocedure.
RECOMMENDATION:Addcontainmentventingtotheeventtreealongwithoperatoractionsandcomponentalignmentsneededtoventcontainmentwithoutthepneumaticsupplysystem.CreditingtheB5bprocedurethatimplementscontainmentventingwithoutapneumaticsupplywillreduceoverallcalculatedrisk.WillhaveamoresignificantimpactonSBOsequences.Willimproveresultsfor5bapplicationsespeciallythosefunctionsassociatedwithSBO.Withoutthischangethemodelisconservative.
Attachment to NG-11-0135 Page 4 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6ASMESRsCategoryIISRDetailsDescriptionofGAPImpactonQuantificationImportancetoApplicationSY C2 01ADOCUMENTthesystemfunctionsandboundary,theassociatedsuccesscriteria,themodeledcomponentsandfailuremodesincludinghumanactions,andadescriptionofmodeleddependenciesincludingsupportsystemandcommoncausefailures,includingtheinputs,methods,andresults.ThereisnoFireWaterSystem(AlternateInjection)notebookorequivalentinformationinanothernotebook.Theoperatoractiontoalignfirewaterforinjectionismodeledbutthecomponentsarebasedontheargumentthattheprobabilityoftheactionsubsumesthecomponentfailurerates.RECOMMENDATION:Developnewsystemnotebookforuseoffirewaterasanalternateinjectionsource.Documentingtheuseofthefirewatersystemasanalternateinjectionsourcewillfacilitateamorethoroughevaluationofthisfunction.Creditingfirewaterinjection(lateintheevent)willdecreaseoverallrisk,especiallyforSBOsequences.Willimproveresultsfor5bapplicationsespeciallythosefunctionsassociatedwithSBO.
Withoutthischangethemodelisconservative.HR A1 01AForequipmentmodeledinthePRA,IDENTIFY,throughareviewofproceduresandpractices,thosetestandmaintenanceactivitiesthatrequirerealignmentofequipmentoutsideitsnormaloperationalorstandbystatus.HRANotebook(AppendixJ,TableJ 1)includesasystematicapproachtoidentifyingtestandmaintenanceactivitiesthroughasystembysystemreviewofpotentialmisalignments.Thismeetsthehighlevelrequirementtousea"systematicapproach"andisjudgedtobeadequatebythePeerReviewteam.However,theSRwordingrequires"areviewofproceduresandpractices"whichwasnotfollowed.Asaresult,thePRteammustassessthisSRas"notmet."RECOMMENDATION:ReassessthisSRwhentheAddendumBofthePRAStandardisreleased.Thecurrentproposedrevisiondeletestherequirementfor"areviewofproceduresandpractices".Noimpact.Asnotedbythereviewteamasystematicapproachwasusedtoidentifypotentiallysignificantmisalignments.Basedonthisreview,onlytheproceduresthatwereassociatedwiththesealignmentswerereviewedfurther.DAECnotedthattheydidreviewalltheproceduresbutdidnotdocumentthisreview.ThedraftrevisionofaddendumBtoHR A1thatiscurrentlyinreviewdeletestherequirementfor"areviewofproceduresandpractices".NoimpactsinceDAECstaffdidreviewallprocedures;howevertheydidnotdocumentthisreview.HR A2 01AIDENTIFY,throughareviewofproceduresandpractices,thosecalibrationactivitiesthatifperformedincorrectlycanhaveanadverseimpactontheautomaticinitiationofstandbysafetyequipment.HRANotebook(AppendixJ,TableJ 1)includesasystematicapproachtoidentifyingcalibrationactivitiesthroughasystembysystemreviewofpotentialmiscalibrations.Thismeetsthehighlevelrequirementtousea"systematicapproach"andisjudgedtobeadequatebythePeerReviewteam.However,theSRwordingrequires"throughareviewofproceduresandpractices"whichwasnotfollowed.Asaresult,thePRteammustassessthisSRas"notmet."RECOMMENDATION:ReassessthisSRwhentheAddendumBofthePRAStandardisreleased.Thecurrentproposedrevisiondeletestherequirementfor"areviewofproceduresandpractices".Noimpact.Asnotedbythereviewteamasystematicapproachwasusedtoidentifypotentiallysignificantmiscalibrations.Basedonthisreview,onlytheproceduresassociatedwiththeseacionswerereviewedfurther.DAECnotedthattheydidreviewalltheproceduresbutdidnotdocumentthisreview.ThedraftrevisionofaddendumBtoHR A1thatiscurrentlyinreviewdeletestherequirementfor"areviewofproceduresandpractices".NoimpactsinceDAECstaffdidreviewallprocedures;howevertheydidnotdocumentthisreview.
Attachment to NG-11-0135 Page 5 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6ASMESRsCategoryIISRDetailsDescriptionofGAPImpactonQuantificationImportancetoApplicationHR C1 01AForeachunscreenedactivity,DEFINEahumanfailureevent(HFE)thatrepresentstheimpactofthehumanfailureattheappropriatelevel,i.e.,function,system,train,orcomponentaffected.Anumberofpre IEHFEsareidentifiedformodelinginthePRA.GenerallytheseHFEsareatthetrainorsystemlevel,asappropriate.However,asmallsetwereidentifiedatthesystemlevelwithoutrelatedtrain levelHFEs.ItispossiblethatthetrainlevelHFEmaybeimportanttosystemunavailability.Forexample,miscalibrationofDGfueloilleveltransmittersisdoneatthesystemlevel,butnotatthetrainlevel.Atthetrainlevel,theHFEwouldbe8e 3,comparedwithindependentfailureoftheleveltransmitterof5e 4.Inothercases,theHFEisatthetrainlevel,butnocorrespondingsystemleveldependentHFEisincluded.Forexample,failuretorestoreRHRSWpostTMisdevelopedatthetrainlevel,butnocommonmisalignmentofbothtrainsisconsidered.RECOMMENDATION:Reviewthedifferencesbetweenthemodelingofsystemimpactvstrain.Roughly10preinitiatorsareaffected.Theprobabilityforthesepreinitiatorsislow.Thereforeaddressingthisfindingisexpectedtohaveaminorimpactonoverallrisk.Mayhaveaminorimpactonsome5bapplications.QU D5a01AIDENTIFYsignificantcontributorstoCDF,suchasinitiatingevents,accidentsequences,equipmentfailures,commoncausefailures,andoperatorerrors[CatI].INCLUDESSCsandoperatoractionsthatcontributetoinitiatingeventfrequenciesandeventmitigation[CatII].RECOMMENDATION:FaulttreesarerequiredforsupportsysteminitiatingeventsinordertosatisfythisSR[CatII].CategoryIwasmet.Addinginitiatingeventfaulttreeswillnotalteroverallresultsifthefaulttreeresultsareinagreementwiththeoriginalpointestimates.HowevertherewillbeanincreaseinriskimportanceassociatedwithoperatoractionsandSSCsthatareincludedintheinitiatingeventfaulttrees.AlthoughtheimportanceofaffectedSSCsonaninitiatingeventmaynotbefullyconsidered;theirimpactcanbeaddressedforspecific5bapplicationsusingsensitivityanalysis,qualitativeanalysis,boundinganalysisorexplicitmodelinginaccordancewiththeNEI04 10guidance.
Attachment to NG-11-0135 Page 6 of 6 These open items are contained in a controlled database that, by NextEra Energy procedure, must be reviewed prior to beginning any PRA application. Therefore, each open item will be reviewed as part of the Surveillance Test Interval change assessment.
If an open item has a potential impact on the results, then additional assessments (sensitivities) will be performed in accordance with the guidance contained in NEI 04-10.
 
In summary, with the exception of the se ven items listed in the above Table, all previously identified items that represent gaps to Capability Category II will be fully incorporated into Revision 6 of the DAEC PRA model upon formal issuance.}}

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