RIS 2000-12, Resolution of Generic Safety Issue B-55, Improved Reliability of Target Rock Safety Relief Valves
| ML003726865 | |
| Person / Time | |
|---|---|
| Issue date: | 08/07/2000 |
| From: | Matthews D Division of Regulatory Improvement Programs |
| To: | |
| Hammer C, NRR/DE, 415-2791 | |
| References | |
| TAC MA8606 RIS-00-012 | |
| Download: ML003726865 (4) | |
UNITEDSTATESNUCLEARREGULATORYCOMMISSIONOFFICEOFNUCLEARREACTORREGULATIONWASHINGTON,DC20555-0001August7,2000NRCREGULATORYISSUESUMMARY2000-12RESOLUTIONOFGENERICSAFETYISSUEB-55,"IMPROVEDRELIABILITYOFTARGETROCKSAFETYRELIEFVALVES"
ADDRESSEES
Allholdersofoperatinglicensesfornuclearpowerreactors,exceptthoselicenseeswhohavepermanentlyceasedoperationsandhavecertifiedthatfuelhasbeenpermanentlyremoved fromthereactorvessel.
INTENT
TheU.S.NuclearRegulatoryCommission(NRC)isissuingthisregulatoryissuesummary(RIS)tonotifyaddresseesaboutthestaff'sresolutionofGenericSafetyIssue(GSI)B-55,"Improved ReliabilityofTargetRockSafetyReliefValves."ThisRISdoesnottransmitanynew requirementsorstaffpositions.Nospecificactionorwrittenresponseisrequired.
BACKGROUND
INFORMATIONTargetRocksafetyreliefvalves(SRVs)arecurrentlyinstalledinthemainsteamsystemsof22boiling-waterreactors(BWRs).Therehavebeenseveraloccurrencesofimproper operationoftheseSRVsbothinspuriouslyopeningandblowingdownthereactorcoolantand inopeningatpressuressignificantlyabovetechnicalspecificationrequirements.Therearetwo differentdesignsofTargetRockSRVs.Theearlierdesignisthethree-stageSRV,whichhas hadahistoryofspuriouslyopeningandfailingtoreseat.Thisbehaviorwasexhibitedduring severaleventswhichmostlyoccurredinthe1970s.Thelaterdesignisthetwo-stageSRV,
whichisamodificationofthethree-stageSRVandwasdesignedtoeliminatethespurious openingandblowingdownproblem.Currently,thereare11BWRsthatusethree-stageSRVs, and11BWRsthatusetwo-stageSRVs.GSIB-55wasprioritizedbytheNRCstaffasa"medium"priorityissueonthebasisofconcernsaboutthethree-stageSRVs.Beginningin1978,two-stageSRVswereinstalledinseveral BWRsandduringoperationandsurveillancetesting,thesetwo-stageSRVshadproblemswith openingatpressuresexceedingthetechnicalspecificationlimits.Asaresult,thestaffalso includedthisupwardsetpointdriftprobleminGSIB-55forresolution.ML003726865 RIS2000-12Page2of3SUMMARYOFISSUETheBWROwnersGroup(BWROG),GeneralElectricCompany(GE),andtheindividuallicenseesundertookseveralactionstoimprovetheperformanceofthree-stageandtwo-stage SRVs.Forthethree-stageSRVs,licenseesbeganimplementingGEServiceInformationLetter (SIL)196,Supplement3,whichrecommendedincreasingtheSRVsetpointstoraisethe simmermarginbetweenthenormalreactorpressureandtheSRVsetpoints.Licenseesalso beganimplementingmorefrequentmaintenanceandtestingofthethree-stagevalves.These activitieswereaimedatreducingthethree-stagepilotvalveseatleakageandhavebeenshown tobeeffectivethroughsuccessfuloperatingexperienceovermanyyears.Forthetwo-stage SRVs,theprimarycauseoftheupwardsetpointdriftproblemwasdeterminedtobecorrosion bondingofthepilotvalvedisktoitsseat.Toreduceorcounteractthecorrosionbonding, severaldesignimprovementsweredevelopedandimplemented,andthreedifferent modificationswereultimatelyfoundtosignificantlyimproveperformance.Thesethree modificationsare(1)theinstallationofionbeamimplantedplatinumpilotvalvedisks,(2)the installationofStellite21pilotvalvedisks,and(3)theinstallationofadditionalpressureactuation switches.TheionbeamimplantedplatinumandStellite21pilotvalvediskshaveimprovedthe performanceofthetwo-stageSRVsbyreducingthecorrosionbondingofthepilotvalvedisks totheirseats.Additionalpressureactuationswitchescounteracttheeffectsofcorrosion bondingbyactuatingtheSRVsatthepropersetpointswithexternalairpower.AsaresultoftheactionsthathavebeentakenbyBWROGandtheindividualBWRlicenseestoimprovetheperformanceofTargetRockSRVs,thestaffhasclosedGSIB-55.Theissue closeoutisdocumentedinamemorandumfromS.J.Collins,Director,NRCOfficeofNuclear ReactorRegulationtoW.D.Travers,NRCExecutiveDirectorforOperations,dated December17,1999,whichmaybefoundintheNRCAgencywideDocumentsAccessand ManagementSystem(ADAMS)underAccessionNumberML993620214.Insummary,thestaff determinedthattheBWROGandthelicenseeshavesignificantlyimprovedtheperformanceof thethree-stageandtwo-stageTargetRockSRVsandthattheyarecontinuingtoevaluateand improvetheperformanceoftheSRVs,asnecessary,withsufficientresources.Therefore,the stafffoundthatnonewrequirementswerenecessaryasaresultofthisgenericissue.If,inthe future,thestafffindsthatactionsneedtobetakentoimprovetheperformanceoftheseSRVs, theexistingqualityassurance,maintenancerule,andcodesandstandardsregulations(i.e.,
10CFRPart50,AppendixB;10CFR50.65;and10CFR50.55a)providethestaffwith regulatorymechanismsforpursuingadditionalimprovements,ifneeded,onaplant-specific
basis.BackfitDiscussionThisRISrequestsnoactionorwrittenresponse.Consequently,thestaffdidnotperformabackfitanalysis.FederalRegisterNotificationAnoticeofopportunityforpubliccommentwasnotpublishedintheFederalRegister becausethisRISisinformational,andthepublicwasaffordednumerousopportunitiestocommentin meetingswiththeBWROwnersGroupasthematterwasbeingstudied,andattheNRCstaff's presentationtotheAdvisoryCommitteeonReactorSafeguardsonOctober1,1999,onthe proposedresolutionofGSIB-55.
RIS2000-12Page3of3Ifthereareanyquestionsaboutthismatter,pleasecontactthepersonlistedbelowortheappropriateOfficeofNuclearReactorRegulationprojectmanagerforaspecificnuclearpower plant./RA/CharlesE.AderFORDavidB.Matthews,DirectorDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationAttachment:ListofRecentlyIssuedNRCRegulatoryIssueSummaries Technicalcontact:GaryHammer,NRR301-415-2791 E-mail:cgh@nrc.gov RIS2000-12Page3of3Ifthereareanyquestionsaboutthismatter,pleasecontactthepersonlistedbelowortheappropriateOfficeofNuclearReactorRegulationprojectmanagerforaspecificnuclearpower plant./RA/CharlesE.AderFORDavidB.Matthews,DirectorDivisionofRegulatoryImprovementPrograms OfficeofNuclearReactorRegulationAttachment:ListofRecentlyIssuedNRCRegulatoryIssueSummaries Technicalcontact:GaryHammer,NRR301-415-2791 E-mail:cgh@nrc.govDistribution:EMEBRFJShapakerFChernyHVandermolenPUBLICREXBr/f DOCUMENTNAME:C:\AccessionNo.ML003726865.wpd*SeepreviousconcurrenceINDICATEINBOX:"C"=COPYW/OATTACHMENT/ENCLOSURE,"E"=COPYW/ATT/ENCL,"N"=NOCOPYOFFICEEMEB:DECTECH:EDNEMEB:DECEMEB:DECRES:DSAREDD:DED:DENAMEGHammer*BCalure*DTerao*EImbro*FEltawila*RWessman*JStrosnider*DATE5/25/005/18/005/26/006/9/006/14/006/20/006/21/00
OFFICEADPTOGCREXB:DRIPD:DRIPNAMEBSheron*BPoole*LMarsh*DMatthewsDATE6/22/008/1/008/2/008/7/00OFFICIALRECORDCOPY
_______________________________________________________________________________________OL=OperatingLicense CP=ConstructionPermitAttachmentRIS2000-12 Page1of1LISTOFRECENTLYISSUEDNRCREGULATORYISSUESUMMARIES
_____________________________________________________________________________________RegulatoryIssueDateofSummaryNo.SubjectIssuanceIssuedto
_____________________________________________________________________________________2000-11NRCEmergencyTelecommunicationsSystem6/30/2000Allholdersofoperatinglicensesfornuclearpowerreactors2000-10TechnicalInformationofFacilitatePublicAccesstotheU.S.NRC
AgencywideDocumentsAccess andManagementSystem (ADAMS)6/30/2000AllNRClicensees2000-09StandardReviewPlanforLicenseeRequeststoExtendthe TimePeriodsEstablishedfor InitiationofDecommissioning Activities06/26/2000Allmateriallicenseesregulatedinaccordancewith10CFRParts30,
40,and702000-08VoluntarySubmissionofPerformanceIndicatorData03/29/2000AllholdersofOLsfornuclearreactors,exceptforthose licenseeswhohavepermanently ceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel2000-07UseofRisk-InformedDecisionmakinginLicense AmendmentReviews03/28/2000AllholdersofOLsfornuclearreactors,exceptforthose licenseeswhohavepermanently ceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel2000-06ConsolidatedLineItemImprovementProcessforAdopting StandardTechnicalSpecifications ChangesforPowerReactors03/20/2000AllholdersofOLsfornuclearreactors,exceptforthose licenseeswhohavepermanently ceasedoperationsandhave certifiedthatfuelhasbeen permanentlyremovedfromthe reactorvessel