Information Notice 2000-20, Potential Loss of Redundant Safety Related Equipment Due to Lack of a High-Energy Line Break Barriers

Potential Loss of Redundant Safety Related Equipment Due to Lack of a High-Energy Line Break Barriers

ML003760571
Person / Time
Issue date:	12/11/2000
From:	Marsh L B Operational Experience and Non-Power Reactors Branch
To:
References
IN-00-020
Download: ML003760571 (5)

UNITEDSTATESNUCLEARREGULATORYCOMMISSIONOFFICEOFNUCLEARREACTORREGULATIONWASHINGTON,D.C.20555December11,2000NRCINFORMATIONNOTICE2000-20:POTENTIALLOSSOFREDUNDANTSAFETY-RELATEDEQUIPMENTBECAUSEOFTHELACK OFHIGH-ENERGYLINEBREAKBARRIERS

Addressees

Allholdersofoperatinglicensesorconstructionpermitsfornuclearpowerreactors.

Purpose

TheU.S.NuclearRegulatoryCommission(NRC)isissuingthisinformationnoticetoalertaddresseestothediscoveryofseveralhigh-energylinebreak(HELB)concernsabout redundantsafety-relatedequipmentatD.C.CookNuclearPlant,Units1and2.Afailureof redundantsafety-relatedequipmentmayresultinrisk-significantconfigurations.Itisexpected thattherecipientswillreviewtheinformationforapplicabilitytotheirfacilitiesandconsider correctiveactions,asappropriate.However,suggestionscontainedinthisinformationnotice arenotNRCrequirements;therefore,nospecificactionorwrittenresponseisrequired.BackgroundAsaresultofthenumeroussafetyissuesidentifiedatCook1and2sinceAugust1997,theNRCanalyzedtherisksignificanceofCookissuesusingtheAccidentSequencePrecursor (ASP)programmethodology.Ofthe141issuesanalyzed,fourwerefoundtobeaccident sequenceprecursorssincetheirconditionalcoredamagefrequenciesweregreaterthan 1.0x10-6/year.TwoofthesefourissuesinvolvedpostulatedHELBscenariosthatmayleadtofailureofredundantsafety-relatedsystems(seeLicenseeEventReports(LERs)316/98-005 and315/99-026fordetails).Withinthesetwoissuestherearethreescenariosthataredescribedbelow:

ÿAbreakinaUnit2mainsteamlineormainfeedwaterlinecoulddegradetheabilityofthecomponentcoolingwater(CCW)pumpsofbothunitstoperformtheirfunction.All fiveCCWpumpsforCook1&2areinthesameroom.Thepumpsarenotqualifiedfor theharshenvironmentofaHELB.Therefore,allofthepumpsmayfailonexposureto thehighhumidityandhightemperaturescausedbyamainsteamlineoramain feedwaterlinebreakinthepipechaseadjoiningtheroom.ML003760571 IN2000-20Page2of3ÿAbreakinthehigh-pressurefeedwaterheatersorassociatedpipingnearthedoortotheswitchgearroomcoulddegradetheabilityofbothtrainsof600Vsafety-relatedbuses.

Thedoorbetweentheswitchgearroomandtheturbinebuildingisnormallyopenand maynotcloseintheeventofaHELB.Bothtrainsof600Vsafety-relatedbusesarein theswitchgearroomandthebusesarenotqualifiedforaharshenvironment.

Therefore,bothtrainsofsafety-related600Vbusesmayfailonexposuretothehigh humidityandhightemperaturesofaHELB.ÿAHELBintheturbinebuildingcoulddegradetheabilityofallthreeauxiliaryfeedwater(AFW)pumps.Thedoortotheturbine-drivenAFWpumpisnormallyopenandmaynot closeintheeventofaHELB.Thetwomotor-drivenAFWpumpsareinroomswhose ventilationintakeisfromtheturbinebuilding.AFWpumpsarenotqualifiedforaharsh environment.Therefore,allAFWpumpsmayfailonexposuretothehighhumidityand hightemperaturesofaHELBintheturbinebuilding.DiscussionConditionsconducivetoarisk-significantconfiguration:Fourconditionsmustcoexisttoproducearisk-significantconfigurationlikethatatCook.Thesefourconditionsare(1)lackofaHELBbarrierbetweentheredundanttrainsofasystemthatis neededtomitigateaccidents,(2)thelackofenvironmentalqualificationfortheredundant componentsoftrainslocatedinthesamearea,(3)thepresenceofhigh-energypipingin adjacentareas,and(4)thelackofaHELBbarrierbetweenadjacentpipingandtheredundant safetysystemtrains.Relationshipoftherisk-significantconfigurationtoregulatoryguidance:Section3.6.1oftheStandardReviewPlan(SRP)andNRRPlantSystemsBranchTechnicalPositionSPLB3-1(formerlyAPCSB3-1)provideregulatoryguidanceontheplantdesignfor protectionagainstpostulatedpipingfailuresoutsidecontainment.WhenSPLB3-1isusedasa guidetomeettherequirementsoftheGeneralDesignCriterion4of10CFRPart50, AppendixA,themethodusedtoconformwiththatregulatoryguidancedependsuponwhenthe constructionpermitapplicationsweretenderedandtheoperatinglicensesissued.SectionB.4 ofSPLB3-1providesdetailsonthedependenceofitsapplicabilitytothedatesonwhich constructionpermitsweretenderedoroperatinglicenseswereissued.GenericLetter87-11,issuedonJune11,1987,transmittedRevision2oftheMechanicalEngineeringBranch(MEB)TechnicalPositionMEB3-1.Thisrevisionprovidedadditional guidanceonlocationswherepipebreaksshouldbepostulated.Revision2ofMEB3-1allows theeliminationofpipe-whiprestraints,jet-impingementshields(placedtomitigatetheeffectsof arbitraryintermediateruptures),andotherrelatedchanges.However,therevisiondoesnot relievelicenseesfromtheneedtoconformtotheguidancerelatingtoHELBeffectsonessential systemsandcomponents.Essentialsystemsandcomponentsaresystemsandcomponents requiredtoshutdownthereactorandmitigatetheconsequencesofapostulatedpipingfailure, withoutoffsitepower.EventhoughapplicationofRevision2oftheMEB3-1pipebreakcriteria maynotrequirepostulatingbreaksnearareasthathousetheredundantequipmentand installingpiperestraints,licenseesareexpectedtocomplywiththeirlicensingbasisand regulatorycommitmentsforpostulatingacrackatthelocationmostdamagingtothe IN2000-20Page3of3essentialstructuresandsystems.Forexample,theGiambussoletterof1972(NUREG-0800,StandardReviewPlan3.16.1,AppendixB,Rev.2,October1999)specifiesthatwherepipes carryinghigh-energyfluidsareroutednearstructuresandsystemsnecessaryforsafe shutdownoftheplant,supplementalprotectionofthosestructuresandsystemsshallbe providedtocopewiththeenvironmentaleffects(includingtheeffectsofjet-impingement)ofa singlepostulatedopencrackatthelocationmostdamagingtothoseessentialstructuresand systems.NUREG-1728,"AssessmentofRiskSignificanceAssociatedWithIssuesIdentifiedatD.C.CookNuclearPowerPlant,"Volumes1&2werepublishedinOctober2000.Thisreport documentstheresultsofananalysisoftherisksignificanceatD.C.CookNuclearPowerPlant, Units1&2sinceAugust1997.ThisNUREGmaybeaccessedelectronicallyattheNRC's PublicElectronicReadingRoomatwww.nrc.gov/NRC/ADAMS/index.html.Thisinformationnoticerequiresnospecificactionorwrittenresponse.Ifyouhaveanyquestionsabouttheinformationinthisnotice,pleasecontactoneofthetechnicalcontactslisted below,theappropriateregionaloffice,ortheappropriateOfficeofNuclearReactorRegulation (NRR)projectmanager./RA/LedyardB.Marsh,ChiefEventsAssessment,GenericCommunicationsandNon-PowerReactorsBranchDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationTechnicalcontacts:S.D.Weerakkody,RESY.C.Li,NRR301-415-6374301-415-2772 E-mail:sdw1@nrc.govE-mail:ycl@nrc.govC.D.Petrone,NRR301-415-1027 E-mail:cdp@nrc.gov

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ListofRecentlyIssuedNRCInformationNotices IN2000-20Page3of3essentialstructuresandsystems.Forexample,theGiambussoletterof1972(NUREG-0800,StandardReviewPlan3.16.1,AppendixB,Rev.2,October1999)specifiesthatwherepipes carryinghigh-energyfluidsareroutednearstructuresandsystemsnecessaryforsafe shutdownoftheplant,supplementalprotectionofthosestructuresandsystemsshallbe providedtocopewiththeenvironmentaleffects(includingtheeffectsofjet-impingement)ofa singlepostulatedopencrackatthelocationmostdamagingtothoseessentialstructuresand systems.NUREG-1728,"AssessmentofRiskSignificanceAssociatedWithIssuesIdentifiedatD.C.CookNuclearPowerPlant,"Volumes1&2werepublishedinOctober2000.Thisreport documentstheresultsofananalysisoftherisksignificanceatD.C.CookNuclearPowerPlant, Units1&2sinceAugust1997.ThisNUREGmaybeaccessedelectronicallyattheNRC's PublicElectronicReadingRoomatwww.nrc.gov/NRC/ADAMS/index.html.Thisinformationnoticerequiresnospecificactionorwrittenresponse.Ifyouhaveanyquestionsabouttheinformationinthisnotice,pleasecontactoneofthetechnicalcontactslisted below,theappropriateregionaloffice,ortheappropriateOfficeofNuclearReactorRegulation (NRR)projectmanager./RA/LedyardB.Marsh,ChiefEventsAssessment,GenericCommunicationsandNon-PowerReactorsBranchDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationTechnicalcontacts:S.D.Weerakkody,RESY.C.Li,NRR301-415-6374301-415-2772 E-mail:sdw1@nrc.govE-mail:ycl@nrc.govC.D.Petrone,NRR301-415-1027 E-mail:cdp@nrc.gov

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ListofRecentlyIssuedNRCInformationNoticesDISTRIBUTION:INFilePUBLICAccessionNo.:ML003760571Toreceiveacopyofthisdocument,indicateintheboxC=Copyw/oattachment/enclosureE=Copywithattachment/enclosureN=NocopyOFFICEREXBTechEdDLPMEMEBSPSBRESC:REXBNAMECPetronePKleeneJStangEImbroRBarrettPBaranowsky*LMarsh DATE//0010/10/00*11/18/00*11/30/00*12/4/00*12/5/0012/11/00OFFICIALRECORDCOPY

______________________________________________________________________________________OL=OperatingLicense CP=ConstructionPermitAttachmentIN2000-20 Page1of1LISTOFRECENTLYISSUEDNRCINFORMATIONNOTICES_____________________________________________________________________________________InformationDateof NoticeNo.SubjectIssuanceIssuedto______________________________________________________________________________________2000-19ImplementationofHumanUseResearchProtocolsInvolving U.S.NuclearRegulatory CommissionRegulated Materials12/05/2000Allmedicaluselicensees2000-18SubstandardMaterialSuppliedbyChicagoBulletProof Systems11/29/2000All10CFRPart50licenseesandapplicants.Allcategory1fuel facilities.All10CFRPart72 licenseesandapplicants2000-17S1CrackInWeldAreaofReactorCoolantSystemHotLegPiping AtV.C.Summer11/16/2000AllholdersofOLfornuclearpowerreactorsexceptthosewho haveceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel2000-17CrackInWeldAreaofReactorCoolantSystemHotLegPiping AtV.C.Summer10/18/2000AllholdersofOLfornuclearpowerreactorsexceptthosewho haveceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel2000-16PotentialHazardsDuetoVolatilizationofRadionuclides10/5/2000AllNRClicenseesthatprocessunsealedbyproductmaterial2000-15RecentEventsResultinginWholeBodyExposures ExceedingRegulatoryLimits9/29/2000Allradiographylicensees2000-14Non-VitalBusFaultLeadstoFireandLossofOffsitePower9/27/2000AllholdersofOLfornuclearpowerreactors2000-13ReviewofRefuelingOutageRisk9/27/2000AllholdersofOLfornuclearpowerreactors2000-12PotentialDegradationofFirefighterPrimaryProtective Garments9/21/2000Allholdersoflicensesfornuclearpower,research,andtest reactorsandfuelcyclefacilities