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
| ML111110507 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 04/20/2011 |
| From: | Costanzo C NextEra Energy Duane Arnold |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NG-11-0135, TSCR-120, TSTF-425, Rev 3 | |
| Download: ML111110507 (8) | |
Text
April 20, 2011 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Duane Arnold Energy Center Docket No. 50-331 Renewed Op. License No. DPR-49 NEXTera M
ENERGY~
DUANE
~
ARNOLD NG-11-0135 10 CFR 50.90 Clarification of Information Contained in License Amendment Request (TSCR-120):
Application for Technical Specification Change Regarding Risk-Informed Justification for the Relocation of Specific Surveillance Frequency Requirements to a Licensee Controlled Program (TSTF-425, Rev. 3)
Reference:
License Amendment Request (TSCR-120): Application for Technical Specification Change Regarding Risk-Informed Justification for the Relocation of Specific Surveillance Frequency Requirements to a Licensee Controlled Program (TSTF-425, Rev. 3), NG-11-0037, dated February 23, 2011 In the referenced letter, NextEra Energy Duane Arnold, LLC (hereafter NextEra Energy Duane Arnold) requested a revision to the Technical Specifications (TS) for the Duane Arnold Energy Center (DAEC) pursuant to 10 CFR 50.90. Attachment 2 of that application contained a description of the Probabilistic Risk Assessment (PRA) model of the DAEC. The purpose of that description was to demonstrate the adequacy of the PRA model that will support the implementation of this TS change upon approval by the Nuclear Regulatory Commission (NRC).
In a conference calion March 29, 2011, the NRC Staff requested that we clarify certain information in that attachment regarding the PRA model currently under development. The attachment to this letter contains the requested clarifications.
NextEra Energy Duane Arnold, LLC, 3277 DAEC Road, Palo, IA 52324
Document Control Desk NG-11-0135 Page 2 of2
..,--~- -----
1 This clarification does not impact the 10 CFR 50.92 evaluation of "No Significant Hazards Consideration" previously provided in the referenced application.
This letter makes no new commitments or changes to any existing commitments.
If you have any questions or require additional information, please contact Steve Catron at 319-851-7234.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on April 20, 2011 Christopher R. Costanzo Vice President, Duane Arnold Energy Center NextEra Energy Duane Arnold, LLC
Attachment:
Clarification of DAEC PRA Model Description cc:
M. Rasmusson (State of Iowa)
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 of the referenced application (Documentation of PRA Technical Adequacy) be clarified to assist the Staff in evaluating the Duane Arnold Energy Center (DAEC)
Probabilistic Risk Assessment (PRA) model. Specifically, the following information was requested:
- 1) The application states that Revision 6 of the DAEC PRA, 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 discusses the results of the Peer Review conducted on the DAEC PRA model, Revision 5C. That review resulted in the identification 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 disposition 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 line 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 models ability to support this application. 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.6 ASMESRs CategoryIISRDetails DescriptionofGAP ImpactonQuantification ImportancetoApplication IEB301A
GROUPinitiatingeventsonlywhenthe followingcanbeassured:
(a) eventscanbeconsideredsimilarin termsofplantresponse,success criteria,timing,andtheeffectonthe operabilityandperformanceof operatorsandrelevantmitigating systems;or (b) eventscanbesubsumedintoagroup andboundedbytheworstcaseimpacts withinthe"new"group.
AVOIDsubsumingeventsintoagroup unless:
(i) theimpactsarecomparabletoorless thanthoseoftheremainingeventsin thatgroup, AND (ii) itisdemonstratedthatsuchgrouping doesnotimpactsignificantaccident sequences.
SeveralfindingsandsuggestionsunderHLRAandHLRBhavebeen dispositioned/resolved,butthesubsuming(IEB3)andscreening (IEC4(C6))ofinitiatingeventsdoesnotmeetthestandard.The followingprovidesexamplesummarizes(IENotebook,including AppendixH):
RBCCW(failsCRD,whichiscreditedforearlyinjection)is subsumedbyTT,butRBCCWisnotfailedgivenTT.
GSW(failsRBCCW,CRD,Feedwater,etc.)issubsumedbyTC,but thesesystemsarenotfailedgivenTC.
TheimpactsofReferenceandVariableLegBreaksarenot adequatelydescribedandaresubsumedbyLossofFW.Most likelywouldbeamanualshutdownwithcomplicationsversesa LossofFW.Giventhatimmediateshutdownwouldoccurgivena break,theseshouldbemodeled.Section2.4.8describedthelow riskfromthese,butthisdoesnotmeetstandardforscreening.
1A1/1A2busfailuresandpartiallossoffeedwater(onepump)are binnedtoTT,butthisimpactisnotmodeledgivenTT.
1A3/1A4busfailuresaresubsumedwithTT.Impactonlossof chargers[TS3.8.4.]etc.andpossibilitythatfailureisaproblem couldleadtoanimmediateshutdown.Notes11and12suggest thatonlynormalpowersourceislost,butemergencypoweris alsounavailableifbusfails.
RECOMMENDATION:FollowIEB3andC6withregardtosubsuming andscreeningormoreimportantlymodeltheaboveinitiatingevents.
Modelingtheseadditionalinitiatorswill betterdefinecertainaccidentsequences andamoreaccuratelydetermine associatedSSCimportance.
Overallcalculatedriskslightlyincrease; significantlyforspecificfunctions associatedwiththeinitiatingevent.Some applicationsmayseeaslightdecreasein riskmargin.
Althoughtheimportanceofaffected componentsisnotfullyconsidered; theirimpactcanbeaddressedfor specific5bapplicationsusing sensitivityanalysis,qualitative analysis,boundinganalysisor explicitmodelinginaccordancewith theNEI0410guidance.
SYA501A INCLUDEtheeffectsofbothnormaland alternatesystemalignments,totheextent neededforCDFandLERFdetermination.
TheSBOeventtreedoesnottakecreditforcontainmentventing usinganalternatealignmentwhenthepneumaticsupplyislost.DAEC procedureSAMP706providesdetaileddirectionforventingPCgiven anunavailablepneumaticsupply.TheContainmentVentnotebook doesnotcredit/discussthisprocedure.
RECOMMENDATION:Addcontainmentventingtotheeventtree alongwithoperatoractionsandcomponentalignmentsneededto ventcontainmentwithoutthepneumaticsupplysystem.
CreditingtheB5bprocedurethat implementscontainmentventingwithouta pneumaticsupplywillreduceoverall calculatedrisk.Willhaveamoresignificant impactonSBOsequences.
Willimproveresultsfor5b applicationsespeciallythose functionsassociatedwithSBO.
Withoutthischangethemodelis conservative.
Attachment to NG-11-0135 Page 4 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6 ASMESRs CategoryIISRDetails DescriptionofGAP ImpactonQuantification ImportancetoApplication SYC201A DOCUMENTthesystemfunctionsand boundary,theassociatedsuccesscriteria, themodeledcomponentsandfailure modesincludinghumanactions,anda descriptionofmodeleddependencies includingsupportsystemandcommon causefailures,includingtheinputs, methods,andresults.
ThereisnoFireWaterSystem(AlternateInjection)notebookor equivalentinformationinanothernotebook.Theoperatoractionto alignfirewaterforinjectionismodeledbutthecomponentsare basedontheargumentthattheprobabilityoftheactionsubsumes thecomponentfailurerates.
RECOMMENDATION:Developnewsystemnotebookforuseoffire waterasanalternateinjectionsource.
Documentingtheuseofthefirewater systemasanalternateinjectionsourcewill facilitateamorethoroughevaluationof thisfunction.Creditingfirewaterinjection (lateintheevent)willdecreaseoverallrisk, especiallyforSBOsequences.
Willimproveresultsfor5b applicationsespeciallythose functionsassociatedwithSBO.
Withoutthischangethemodelis conservative.
HRA101A ForequipmentmodeledinthePRA, IDENTIFY,throughareviewofprocedures andpractices,thosetestandmaintenance activitiesthatrequirerealignmentof equipmentoutsideitsnormaloperational orstandbystatus.
HRANotebook(AppendixJ,TableJ1)includesasystematicapproach toidentifyingtestandmaintenanceactivitiesthroughasystemby systemreviewofpotentialmisalignments.Thismeetsthehighlevel requirementtouseasystematicapproachandisjudgedtobe adequatebythePeerReviewteam.However,theSRwording requiresareviewofproceduresandpracticeswhichwasnot followed.Asaresult,thePRteammustassessthisSRasnotmet.
RECOMMENDATION:ReassessthisSRwhentheAddendumBofthe PRAStandardisreleased.Thecurrentproposedrevisiondeletesthe requirementforareviewofproceduresandpractices.
Noimpact.Asnotedbythereviewteama systematicapproachwasusedtoidentify potentiallysignificantmisalignments.
Basedonthisreview,onlytheprocedures thatwereassociatedwiththesealignments werereviewedfurther.DAECnotedthat theydidreviewalltheproceduresbutdid notdocumentthisreview.
ThedraftrevisionofaddendumBtoHRA1 thatiscurrentlyinreviewdeletesthe requirementforareviewofprocedures andpractices.
NoimpactsinceDAECstaffdid reviewallprocedures;howeverthey didnotdocumentthisreview.
HRA201A IDENTIFY,throughareviewofprocedures andpractices,thosecalibrationactivities thatifperformedincorrectlycanhavean adverseimpactontheautomaticinitiation ofstandbysafetyequipment.
HRANotebook(AppendixJ,TableJ1)includesasystematicapproach toidentifyingcalibrationactivitiesthroughasystembysystemreview ofpotentialmiscalibrations.Thismeetsthehighlevelrequirementto useasystematicapproachandisjudgedtobeadequatebythePeer Reviewteam.However,theSRwordingrequiresthroughareviewof proceduresandpracticeswhichwasnotfollowed.Asaresult,thePR teammustassessthisSRasnotmet.
RECOMMENDATION:ReassessthisSRwhentheAddendumBofthe PRAStandardisreleased.Thecurrentproposedrevisiondeletesthe requirementforareviewofproceduresandpractices.
Noimpact.Asnotedbythereviewteama systematicapproachwasusedtoidentify potentiallysignificantmiscalibrations.
Basedonthisreview,onlytheprocedures associatedwiththeseacionswerereviewed further.DAECnotedthattheydidreview alltheproceduresbutdidnotdocument thisreview.
ThedraftrevisionofaddendumBtoHRA1 thatiscurrentlyinreviewdeletesthe requirementforareviewofprocedures andpractices.
NoimpactsinceDAECstaffdid reviewallprocedures;howeverthey didnotdocumentthisreview.
Attachment to NG-11-0135 Page 5 of 6 ASMECategoryIISRsNotMetinDAECModel,Rev.6 ASMESRs CategoryIISRDetails DescriptionofGAP ImpactonQuantification ImportancetoApplication HRC101A Foreachunscreenedactivity,DEFINEa humanfailureevent(HFE)thatrepresents theimpactofthehumanfailureatthe appropriatelevel,i.e.,function,system, train,orcomponentaffected.
AnumberofpreIEHFEsareidentifiedformodelinginthePRA.
GenerallytheseHFEsareatthetrainorsystemlevel,asappropriate.
However,asmallsetwereidentifiedatthesystemlevelwithout relatedtrainlevelHFEs.ItispossiblethatthetrainlevelHFEmaybe importanttosystemunavailability.Forexample,miscalibrationofDG fueloilleveltransmittersisdoneatthesystemlevel,butnotatthe trainlevel.Atthetrainlevel,theHFEwouldbe8e3,comparedwith independentfailureoftheleveltransmitterof5e4.Inothercases, theHFEisatthetrainlevel,butnocorrespondingsystemlevel dependentHFEisincluded.Forexample,failuretorestoreRHRSW postTMisdevelopedatthetrainlevel,butnocommonmisalignment ofbothtrainsisconsidered.
RECOMMENDATION:Reviewthedifferencesbetweenthemodeling ofsystemimpactvstrain.
Roughly10preinitiatorsareaffected.The probabilityforthesepreinitiatorsislow.
Thereforeaddressingthisfindingis expectedtohaveaminorimpactonoverall risk.
Mayhaveaminorimpactonsome 5bapplications.
QUD5a01A IDENTIFYsignificantcontributorstoCDF, suchasinitiatingevents,accident sequences,equipmentfailures,common causefailures,andoperatorerrors[CatI].
INCLUDESSCsandoperatoractionsthat contributetoinitiatingeventfrequencies andeventmitigation[CatII].
RECOMMENDATION:Faulttreesarerequiredforsupportsystem initiatingeventsinordertosatisfythisSR[CatII].
CategoryIwasmet.Addinginitiatingevent faulttreeswillnotalteroverallresultsifthe faulttreeresultsareinagreementwiththe originalpointestimates.Howeverthere willbeanincreaseinriskimportance associatedwithoperatoractionsandSSCs thatareincludedintheinitiatingevent faulttrees.
Althoughtheimportanceofaffected SSCsonaninitiatingeventmaynot befullyconsidered;theirimpactcan beaddressedforspecific5b applicationsusingsensitivity analysis,qualitativeanalysis, boundinganalysisorexplicit modelinginaccordancewiththeNEI 0410guidance.
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 seven 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.