ML17265A823

LER 98-037-01:on 990422,determined That Ice Condenser Bypass Leakage Exceeds Design Basis Limit.Caused by Pressure Seal Required by Revised W Design Not Incorporated Into Aep Design.Numerous Matl Condition Walkdowns & Assessments Made

ML17265A823
Person / Time
Site:	Cook
Issue date:	05/24/1999
From:	BERRY L R INDIANA MICHIGAN POWER CO.
To:
Shared Package
ML17265A821	List: ML17265A820 ML17265A823
References
LER-98-037, LER-98-37, NUDOCS 9906030254
Download: ML17265A823 (6)

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NRCFORM366AU.S.NUCLEARREGULATORYCOMMISSION16.19981L(CENSEEEVENTREPORT(LER)TEXTCONTINUATIONFACILITYNAMEI1)DOCKETI2)LERNUMBERIelPAGEI3)CookNuclearPlantUnit1O5000-315SEQUENTIALREVISION3OF5NUMBERNUMBER199803701TEXT(Ifmorespecejsreqvfred,vseaddidonelcopiesofNRCForm866A)I17)Withthecurrenticecondenserdesign,thebottomoftheicebasketsis10ftabovethebottomofthelowerplenumfioor.Whenaneventoccurs,theairandsteamentertheIcecondenserlowerplenumandcanpressurizetheareaupto12psi,exposingtheDBSsealattheendwallstothatsamepressure.Duetothedesignoftheseal,itisconservativelyassumedthatthesealwillfailandallowthesteamtobypasstheicebasketsandenterintouppercontainmentdirectly.CauseOfTheEventTheindividualbypassconditionsreportedintheoriginalLERwereattributedtounauthorizedmodifications.Atackofdocumentedconfigurationandinadequateimplementationofthedesignchangecontrolprocessresultedinthecreationof.bypasspathsviamaterialsubstitutions,originalconstructiondiscrepancies,Inadequateservicelife,andunseatingofsparepenetrationsduringtheperformanceofworkactivities.Therootcauseofthecumulativebypasswasattributedtolackofunderstandingofthedesignbasisofcontainmentasasystem,andofthedividerbarrierinparticular.Thiswascoupledwithalackofacomprehensiveinspectionprogramfordetectionofdefectsanddamagetothedividerbarrier.TheapparentcauseofthenewlydiscoveredicecondenserbypassisthatthepressuresealrequiredbyarevisedWestinghousedesignwasnotincorporatedintotheAEPdesign.Thereasonforthisdiscrepancyisunknown.AccordingtotheoriginalWestinghouseicecondenserdesign,theicebasketsonthecontainmentwall'sidestartedattheleveloftheicecondenserbottomslabandextendedupward58feet.Thisdesignwastoensurethatailsteamenteringtheicecondenserwouldtravelthroughtheicebasketsbeforeenteringuppercontainment.Withthisdesign,onlyaventilationbarrierwasneededtosealtheendwalls.Later,Westinghouseimplementedanewdesignwhichlocatedthebottomsofallicebaskets10ftabovetheicecondenserbottomslab.ThisisthebasketdesignthatwasinstalledatCookNuclearPlant.However,whenthelaterdesignwasintroduced,theventilationbarrierwasnotupgradedtoaincludeapressuresealcapableofwithstanding24psi.AnalslsOfTheEventTheoriginallyidentifiedconditionwasdeterminedtobereportableonAugust12,1998,inaccordancewith10CFR50.72(b)(2)(i),asadegradedconditiondiscoveredwhitetheunitisshutdownthat,iffoundwhilethereactorwasoperating,wouldhaveresultedintheplantbeinginanunanalyzedcondition,andanENSnotificationwasmadeat1530hoursEDT.TheoriginalLERwassubmittedinaccordancewith10CFR50.73(a)(2)(ii)asaneventorconditionoutsidethedesignbasisoftheplant.AnadditionalicecondenserbypassconditioninvolvingtheDBSidentifiedonApril22,1999wasalsodeterminedtobereportablepursuanttotherequirementsof10CFR50.73(a)(2)(ii).TheDBSicecondenserbypassconditionisapplicabletobothunits.ForUnit2,refertoLERsupplement316l98-004-01.TheknownbypassflowpathssummarizedbelowrepresenttheconditionasreportedonAugust12,1998:RefuelingCavityDrainsBackdraftdamperofairreturnfansIceCondenserAirHandlingUnitline1-CPS-209,1-CPS-2101-VMO-101DividerBarrierHatchesGlycolLinesthroughIceCondenserEndWallOpenAreainFt22.200.360.0050.0171.0691.40.66TOTALNRCFORM366AI6.199815.71 NRCFORM36BAU.S.NUCLEARREGULATORYCOMMISSIONIB-1998)LlCENSEEEVENTREPORT(LER)TEXTCONTINUATIONDOCKETIz)LERNUMBER(BlPAGEI31CookNuclearPlantUnit105000-315YEAR1998SEQUENTIALNUMBER037REvisioN4OF5NUMBER01Theknownbypassflowpathssummarizedbelowrepresentthecurrentcondition:RefuelingCavityDrainsBackdraftdamperofairreturnfansIceCondenserAirHandlingUnitline1-CPS-209,1-CPS-2101-VMO-101DividerBarrierHatchesGlycolLinesthroughIceCondenserEndWallCEQStaiiwellandVentWellDrainLinesCEQFanRoomDividerBarrierSealOpenAreainFt22.200.360.0050.0(repaired)0.0(repaired)1,40.660.10.00730.78TOTAL35.51Thecumulativebypasshasbeenevaluated,andithasbeenconcludedthatthesafetysignificanceofthisconditionisnegligible.Therefore,therewerenoimplicationstothehealthandsafetyofthepublic.UpdatedFinalSafetyAnalysisReport(UFSAR)Chapter5,Section5.2.2.4statesthatthedesignbasisbypass'areais5ft2.UFSARChapter14.0describestheaccidentanalysesfordifferentsizepipebreaksandtheallowableicecondenserbypassflowforeachcase.Analysisresultsindicateavalueof35ft2astheallowabledeckleakageareaforthe,entirespectrumofbreaksizes.Thelimitingcaseisan8inchbreakwithonespraypumpoperating(2000gpmat80,degreesF).AsecondUFSARanalysis,usingamorerealisticmethod,statesthatwithonespraypumpthedeckleakagecouldbe56ft2foran8inchbreak.Thisanalysistakescreditforpassiveheatsinksandadditionalcontainmentspray.Thustheidentifiedvalueofhistoricalvalueofbypass(approximately30.78+5.71=36.49ft2)forUnit1isboundedbyUFSARanalysis,butisoutsideoftheicecondenserdesignbasisvalueof5It2.Therefore,sincetheplantwasnotinan'nanalyzedcondition,theENSreportmadeAugust12,1998,inaccordancewith10CFR50.72(b)(2)(i),wasdeterminedtohavebeenunnecessary.CORRECTIVEACTIONSNumerousmaterialconditionwaikdownsandassessmentshavebeenperformed,whichhaveincreasedthepotentialtoidentifybypasspathsinthedividerbarrier.Significantdegradedconditionsresultingindividerbarrierbypassarebeingcorrectedviacorrectivemaintenanceordesignchangesastheyareidentified.TheRefuelingCavityDrainsarepermanentbypasses,whichofcoursewillremainopen.Thebackdraftdamperoftheairreturnfans,icecondenserAHUfineandtheCEQstairwellandventweildrainlinebypassesarecurrentlynotscheduledforrepairandrepresentaninsignificantcontributiontothecumulativeicecondenserbypass.TheDBSicecondenserbypasswillbecorrectedviaadesignchangepriortoMode4.Topreventunauthorizedorinadvertentdesignchanges,12PMI5040.DCP.001"DesignChangeDetermination",hasbeendevelopedandimplemented.Toenhancerecognitionofadesignchange,12PMI2291.PLAN.001'WorkControlPlanningProcess,"isbeingimplemented,Additionally,theUFSARvalidationprojectwillenhancethequalityofthedesignbasisandconfigurationdocumentation.Containmentisoneoftheselectedsystems.Procedure12EHP6040PER.154,"ContainmentDividerBarrierWalkdown,"hasbeendevelopedtoguideinspectionofthedividerbarrieronarefuelingoutagefrequencyforpossiblebypasspaths.Thisprocedureincludesprovisionstoensurethatthedesignbasisallowablecumulativebypassisnotexceeded,throughcorrectionandlortrackingofanyidentifiedbypasspaths.NRCFORM366A16.1998)

NRCFORM366AU.S.NUCLEARREGULATORYCOMMISSION(6-1998ILICENSEEEVENTnEPORT(LER)TEXTCONTINUATIONDOCKET(2ILERNUMBER(6IPAGE(3)CookNuclearPlantUnit105000-315YEAR1998SEQUENTIALNUMBER037REVISION5QP5NUMBER01SIMILAREVENTS316/98-00440NRCFORM366A16.1998)