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{{#Wiki_filter:CATEGORY1REGULATORINFORMATIONDISTRIBUTION.STEM(RIDS)ACCESSIONNBR:9605150395DOC.DATE:96/05/14NOTARIZED:NOFACIL:50-335St.LuciePlant,Unit1,FloridaPower6Light,Co.AUTH.NAMEAUTHORAFFILIATIONBOHLKE,W.H.FloridaPoweraLightCo.RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk) | |||
==SUBJECT:== | |||
ForwardssupplementalinforeSGtubeinspforUnitl.DISTRIBUTIONCODE:A001DCOPIESRECEIVED:LTRENCLSIZE:TITLE:ORSubmittal:GeneralDistributionDOCKETI05000335NOTESRECIPIENTIDCODE/NAMEPD2-3LAWIENSiL.,COPIESRECIPIENTLTTRENCLIDCODE/NAME11PD2-3PD11COPIESLTTRENCL11INTERNAL:ACRSNRR/DE/EMCBNRR/DSSA/SPLBNUDOCS-ABSTRACTEXTERNAL:NOAC6611111111F&CENTER1RCBNRR/DSSA/SRXBOGC/HDS3NRCPDRDCUMNNOTETO,ALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMOWFNSD-5(EXT.415-2083)TOELIMINATEYOURNAMEFROMDISTRIBUTIONLISTSFORDOCUMENTSYOUDON'TNEED!TOTALNUMBEROFCOPIESREQUIRED:LTTR,.18.ENCL:17 Y4Ag~4AJ~~ | |||
~~)ll~VIFloridaPower5LightCompany,P.O.Box128,FortPierce,FL34954-0128May14,1996L-96-12910CFR50.4U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C.20555RE:St.LucieUnit1DocketNo.50-335SupplementalInformationSteamGeneratorTubeInsectionDuringatelephoneconversationonMay7,1996,theNRCstaffidentifiedseveralconcernswithrespecttothestructuralandleakintegrityofsteamgeneratortubeindicationsidentifiedbyFloridaPowerandLightCompany(FPL),inthesludgepile,ateggcratesupports,andatdrilledtubesupportplates.SeveraloftheseconcernswereidentifiedasaresultofameetingwithNRConApril22,1996,whenFPLdiscussed,inpart,thesteamgeneratortubeintegrityprogramforSt.LucieUnit1.Theinformationrequestedduring,thephonecallisattached.Pleasecontactusifthereareanyquestionsaboutthissubmittal.Verytrulyyours,W.H.BohlkeVicePresidentSt.LuciePlantWHB/GRMAttachmentcc:StewartD.Ebneter,RegionalAdministrator,RegionII,USNRCSeniorResidentInspector,USNRC,St.LuciePlant96051503959605i47PDRADQCK050003356LPDRIIanFPLGroupcompany | |||
~~~hi,p1 St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage1Forindicationsattheeggcratesupportplatesandinthesludgepile:NRCREQUEST1.Fortheplannedin-situpressuretestingofthemostsignificantflaws,provideinformationontheadjustmentstothetestpressuretoaccountfor(1)temperaturedifferencesbetweenoperatingconditionsandthetest,(2)materialproperties,and(3)lockedtubesupportplateconditions.Providethecriteriatobeusedforselectingthetubestobein-situpressuretested,thenumberoftubesthatwillbetested,andtheprocedureforthetest(e.g.,withorwithoutareinforcingbladder).DuetoNRCstaffconcernsregardingtheabilitytodepthsizethesetypesofindications,providethebasisforconcluding.thatyouwillselectthetubeswiththemostsignificantflaws.FPLRESPONSEFPLwillusein-situpressuretestingtoverifythestructuraladequacyofthemostsignificanteddycurrenttest(ECT)indicationsatdrilledsupportplate,freespan,eggcratesandsludgepilelocations.FPLwillinitiallyconductin-situpressuretestingwithoutaburstbladdertoassessleakageintegrity.Leakage,ifobserved,willbemeasuredatnormaloperatingdifferentialpressureandathigherpressures.Ifleakageexceedsmakeupcapacity,theburstbladderwillthenbeinstalledtoachievethedesiredtestpressures.Tubeselectionforin-situpressuretestingwillbeconductedbyleadECTdataanalysisandengineeringpersonnel.SelectioncriteriawillbebasedonreviewofECTdataforavarietyofflawcharacteristicsincludinglength,maximumdepth,averagedepth,voltage(amplitude),location,potentialfortubesupportlock-up,numberofflawsinatube,andflawgrowthrate.Duetothevarietyofflawcharacteristicsinvolved,analyticaljudgmentandevaluationexperienceisrequiredforassessingtheseverityofflawsindications. | |||
'h,I St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage2Selectionofflawindicationsforin-situpressuretestingwillbebasedonbobbincoilinspectiontechniquesthatarequalifiedfordetectionanddepthsizingofintergranularattack/stresscorrosioncracking(IGA/SCC)ateggcratesupports,freespanandsludgepilelocations.CandidateindicationswillalsobeinspectedwithMRPCtechniquestoassesstheflawcharacteristicsdiscussedabove.Candidateindicationsforin-situpressuretestingatdrilledsupportplatelocationswillalsobeinspectedbybobbincoilandMRPCtechniques.Selectionofcandidateindicationsatdrilledsupportplatelocationswillrelyonacombinationofdepthandvoltageinformationaswellastheotherflawcharacteristicsdiscussedabove.Adjustmentstoin-situtestpressurewillincludea13%increasefortemperaturebasedonbursttestingof3/4inchby0.048inchAlloy600tubesamplesatoperatingandroomtemperatures.Testpressureforcircumferentialflawsatthetubeexpansiontransitionwillalsobeincreasedby8.5%forlockedsupportplateconditionsbasedona40inchspanbetweenthetubesheetandthefirsteggcratesupport.Theadjustedpressuresare:FlawADJUSTEDOrientationNOPD/PAxial1622psiCircumferential1744psiADJUSTED1.4xSLBD/P3955psi4253psiADJUSTED3xNOPD/P4865psi5231psiNOPD/PTubedifferentialpressureatnormaloperatingsystempressures.NOPD/P=1435psi.SLBD/P'ubedifferentialpressureduringSteamlinebreak.SLBD/P=2500psi.In-situpressuretestingofflawedsteamgeneratortubingisbecomingarelativelycommonindustrypractice.Industryexperiencewithin-situpressuretestinghasbeenpositiveintermsofassuringthatadequatestructuralmarginsexist.FPLwillusefieldprovenequipmentandexperiencedpersonnelforin-situpressuretesting.Between10and20ofthemostsignificantindicationsfromalllocations(eggcrate,sludgepile,drilledsupportplate,orfreespan)willbein-situ St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage3pressuretested.In-situpressuretestresultsareexpectedtodemonstratethatconservativemarginsforstructuralintegrityareprovidedutilizingtheECTdepthsizingtechniques.REQUEST2.Giventhestaffconcernsregardingthedepthsizingtechnique,provideadiscussionofthefeasibilityof,andanyplansyouhave,forperformingheliumleaktestingtoconfirmthatnothrough-wallcracksarepresent.Thisactionwouldprovidesupportinginformationthatindicationssizedlessthan100%through-wallareinfactlessthan100%through-wallprovidednoleakagewasdetectedforthesetubes.Thistestalsohasthepotentialtopermittheidentificationofthesourceofanyprimary-to-secondaryleakageobservedduringthelastcycle(e.g.,ifleakageisattributedtoaplug,thistestmayprovideadditionalconfidencethatalltheleakageisfromtheplug).FPLRESPONSEFPLhasreviewedheliumleakdetectioneffortswithaleakdetectionvendorandseveralutilities.Themajorityofleakdetectioneffortswithheliumhavebeenforleakageinexcessof50gallonsperday(gpd).LeakageatSt.LucieUnit1isestimatedat2-4gpd.Theuseofheliumleaktestingforleakagewhichislessthan5gpdisextremelylimitedandisnotexpectedtobeeffective.Also,heliumtestingisnotexpectedtoidentifyleakagethroughaperforatedtubewhichcontainsaleakingtubeplugduetothecolumnofwaterwhichistypicallypresentabovetheplug.Further,thedifficultyinmaintainingapositivepressurewithheliumonthesecondarysystemmakesthistestdifficulttoimplement.TheFPLapproachincludesextensiveinspections,in-situpressuretestingandimprovedon-lineleakagemonitoringatSt.LucieUnit1.FPLbelievesthatheliumleaktestingwillprovidelittleornobenefitbeyondtheinformationandinsightprovidedbytheothertechniquesbeingemployed.NRCREQUEST3.Provideyourplansandscheduleforperforminganestimateoftheconditionalprobabilityofburstgivenamainsteamline | |||
''!) | |||
IIj1(~~St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage4breakgiventhenumberofindications,themaximumgrowthrateobserved,andtheeddycurrentuncertainties.FPLRESPONSEFPLwillperformacalculationfortheprobabilityoftubeburstbasedontheAPTECHEngineeringmodelofthePaloVerdeSteamgenerator.Thiscalculationwill'valuatetheas-leftconditionoftheSt.LucieUnit1steamgeneratorsandprojecttheendofthenextcycleconditionsbasedonthenumberofindications,growthratesandeddycurrentuncertaintiesforalllocationsinthesteamgenerator.Thecalculationoftubeburstprobabilitywillbesubmittedapproximately6monthsafterstartupfromthecurrentrefuelingoutage(SL1-14).NRCREQUEST4.Provideyourcriteriafordeterminingwhetherornotamid-cycleinspectionisnecessaryasaresultofeddycurrenttesting,in-situpressuretesting,heliumleaktesting,andconditionalprobabilityofburst(e.g.,1E-2),asappropriate.FPLRESPONSETheECTinspectiondataforalllocationsinthesteamgeneratorwillbethebasisfortheassessmentoftheneedforamid-cycleinspection.Thefactorsconsideredwillincludein-situpressuretestresultsandtheprobabilityofburstcalculationconservativelyestimatedbasedonECTexaminationresults.Acalculatedprobabilityoftubeburstsubstantiallygreaterthan1X10willbeconsideredasinputtotheneedforamid-cycleinspection.NRCREQUEST5.ProvideyourplanswithrespecttonotifyingthestaffifanyindicationwouldnotbeabletowithstandtheloadingspecifiedinDraftRegulatoryGuide1.121.Thisshouldaddressreportingindicationswhoselengthexceedsthecriticallengthassuminga100%through-wallflaw.andindicationswhosedepthexceedsthecriticaldepthassuminganinfinitelylongflaw. | |||
St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage5FPLRESPONSEFPLwillinformtheNRCprojectmanagerforSt.LucieUnits1and2,viatelephone,oftheprogressoftheinspectionsaftertheyareapproximately50%,75%and100$complete.FPLwilldiscussthegeneralstateoftheinspection,thenumberandsizeoftheindicationsandcandidateindicationsforin-situpressuretesting.TheNRCprojectmanagerwasupdatedbyphoneon5/13/96atapproximately25%completion.Resultsfromthein-situpressuretestswillbeprovided,viatelephone,within24hoursofcompletionofthein-situtestprogram.NRCREQUEST6.Discussyourplanswithrespecttosubmittingasummaryoftheinspectionresultsandtheabovementionedheliumandin-situpressuretestresults.FPLRESPONSEResultsfromtheeddycurrentinspectionswillbesubmittedaspartofthespecialreportrequiredbyTechnicalSpecification4.4.5.5.b.Theresultsfromthein-situpressuretestingwillbesubmittedwithin10daysofcompletionofthein-situtestprogram.ZZ.Forindicationsatthedrilledholetubesupportplateswhichyouplantosizeandleaveinservice:NRCREQUESTa.Discussthequalificationdatatosupporttheabilitytosizethetypesofindicationsthatwillremaininservice(e.g.,volumetricindications).Includethetubepulldataorothertestdatathatconfirmsthatthemorphologyofthequalificationdataisconsistentwiththemorphologyoftheindicationsinthefield. | |||
)~%'I St.LucieUnit1DocketNo.50-335~,L-96-129AttachmentPage6FPLRESPONSEQualificationdatafordetectionandsizingofIGA/SCCindicationsatdrilledsupportplatesusingbobbincoilinspectiontechniqueshasbeenprovidedtotheNRCviatheElectricPowerResearchInstitute(EPRI)aspartofEPRINP-6201,Revision4,PWRSteamGeneratorTubeExaminationGuidelines.ThedatademonstratesthatthebobbincoiltechniqueexceedsthedetectionrequirementsofEPRINP-6201,AppendixHwithaprobabilityofdetection(POD)of80%ata90%confidencelevelforflawspenetrating40%throughwall.However,bobbincoiltechniquesfailedtomeetthesizingrequirementssincetheyresultedinarootmeansquareerror(RMSE)of29%(AppendixHrequireslessthanorequalto25%RMSE).FPLhasconsideredtworepairoptionsforeddycurrentindicationsatthe9thand10thdrilledsupportplates.Option1reliesonbobbincoiltechniquesfordetection,andrequiresMRPCexaminationofallflawindicationsreported.Allindicationswhicharecrack-likebyMRPCexaminationwillberemovedfromservice.Non-crackMRPCindicationswillbesizedusingtheEPRIbobbincoiltechnique(RMSE=29%).Indications40%orgreaterthroughwall,orindicationswith>10%growth,sincethepriorinspectionwillberemovedfromservice.Option2alsoreliesonbobbincoiltechniquesfordetection,andrequiresMRPCexaminationofallflawindicationsreported.However,thisoptionrequiresthatallindicationswhichareconfirmedbyMRPCexaminationberemovedfromservice.FPLconsidersoption2excessivelyconservative.Therefore,ourcurrentplanistouseOption1aboveandtoin-situpressuretestthemostsignificantdrilledsupportplateindicationstodemonstratethatadequatestructuralmarginsexistforflawswhichwillremaininserviceintheseregions.TheStaffalsorequestedthatFPLdiscussourplansforsizingIGA/SCCindicationswhicharelocatedinfreespanregions.OurcurrentplanistoapplyOption1,asdiscussedabovefor y~e~~~~St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage7drilledsupportplateindications,forindicationslocatedinthefreespanregions.Tubesremovedin1985provideafullrangeofintergranularmodesofattackfrompatchesoflGAtodiscretecracks.Depthsizingusingpostmortemeddycurrentcalibrationcurveshaveresultedin10yearsofoperationwithoutsignificantinserviceleakage.Basedonextensivepriorinspections,FPLhasathroughunderstandingoftheextentofdegradationintheSt.Luciesteamgenerators.FPLexpectsthatchangesincorrosionmorphologyorincreasesingrowthratewouldhaveresultedinsubstantialinserviceleakageifeddycurrentsizingcriteriawerenonconservative.Generaleddycurrentresponsehasremainedconstantsince1984,withtheonlychangesbeinganincreaseinthenumberofaffectedlocations.Consistencyineddycurrentresponseandlackofsignificantoperationalleakageprovideassurancethatcorrosionmorphologyisbeingadequatelymonitored.NRCREQUESTb.Addressthecomments/questionslistedaboveforeggcratesupportandsludgepileindications(items1through6),asappropriate.FPLRESPONSETheresponsetoquestions1-6for'ggcrateandsludgepileindicationsincludetheresponsesfordrilledsupportplateindications. | |||
}} | }} |
Revision as of 15:20, 25 April 2018
ML17228B489 | |
Person / Time | |
---|---|
Site: | Saint Lucie ![]() |
Issue date: | 05/14/1996 |
From: | BOHLKE W H FLORIDA POWER & LIGHT CO. |
To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
References | |
L-96-129, NUDOCS 9605150395 | |
Download: ML17228B489 (15) | |
Text
CATEGORY1REGULATORINFORMATIONDISTRIBUTION.STEM(RIDS)ACCESSIONNBR:9605150395DOC.DATE:96/05/14NOTARIZED:NOFACIL:50-335St.LuciePlant,Unit1,FloridaPower6Light,Co.AUTH.NAMEAUTHORAFFILIATIONBOHLKE,W.H.FloridaPoweraLightCo.RECIP.NAMERECIPIENTAFFILIATIONDocumentControlBranch(DocumentControlDesk)
SUBJECT:
ForwardssupplementalinforeSGtubeinspforUnitl.DISTRIBUTIONCODE:A001DCOPIESRECEIVED:LTRENCLSIZE:TITLE:ORSubmittal:GeneralDistributionDOCKETI05000335NOTESRECIPIENTIDCODE/NAMEPD2-3LAWIENSiL.,COPIESRECIPIENTLTTRENCLIDCODE/NAME11PD2-3PD11COPIESLTTRENCL11INTERNAL:ACRSNRR/DE/EMCBNRR/DSSA/SPLBNUDOCS-ABSTRACTEXTERNAL:NOAC6611111111F&CENTER1RCBNRR/DSSA/SRXBOGC/HDS3NRCPDRDCUMNNOTETO,ALL"RIDS"RECIPIENTS:PLEASEHELPUSTOREDUCEWASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMOWFNSD-5(EXT.415-2083)TOELIMINATEYOURNAMEFROMDISTRIBUTIONLISTSFORDOCUMENTSYOUDON'TNEED!TOTALNUMBEROFCOPIESREQUIRED:LTTR,.18.ENCL:17 Y4Ag~4AJ~~
~~)ll~VIFloridaPower5LightCompany,P.O.Box128,FortPierce,FL34954-0128May14,1996L-96-12910CFR50.4U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,D.C.20555RE:St.LucieUnit1DocketNo.50-335SupplementalInformationSteamGeneratorTubeInsectionDuringatelephoneconversationonMay7,1996,theNRCstaffidentifiedseveralconcernswithrespecttothestructuralandleakintegrityofsteamgeneratortubeindicationsidentifiedbyFloridaPowerandLightCompany(FPL),inthesludgepile,ateggcratesupports,andatdrilledtubesupportplates.SeveraloftheseconcernswereidentifiedasaresultofameetingwithNRConApril22,1996,whenFPLdiscussed,inpart,thesteamgeneratortubeintegrityprogramforSt.LucieUnit1.Theinformationrequestedduring,thephonecallisattached.Pleasecontactusifthereareanyquestionsaboutthissubmittal.Verytrulyyours,W.H.BohlkeVicePresidentSt.LuciePlantWHB/GRMAttachmentcc:StewartD.Ebneter,RegionalAdministrator,RegionII,USNRCSeniorResidentInspector,USNRC,St.LuciePlant96051503959605i47PDRADQCK050003356LPDRIIanFPLGroupcompany
~~~hi,p1 St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage1Forindicationsattheeggcratesupportplatesandinthesludgepile:NRCREQUEST1.Fortheplannedin-situpressuretestingofthemostsignificantflaws,provideinformationontheadjustmentstothetestpressuretoaccountfor(1)temperaturedifferencesbetweenoperatingconditionsandthetest,(2)materialproperties,and(3)lockedtubesupportplateconditions.Providethecriteriatobeusedforselectingthetubestobein-situpressuretested,thenumberoftubesthatwillbetested,andtheprocedureforthetest(e.g.,withorwithoutareinforcingbladder).DuetoNRCstaffconcernsregardingtheabilitytodepthsizethesetypesofindications,providethebasisforconcluding.thatyouwillselectthetubeswiththemostsignificantflaws.FPLRESPONSEFPLwillusein-situpressuretestingtoverifythestructuraladequacyofthemostsignificanteddycurrenttest(ECT)indicationsatdrilledsupportplate,freespan,eggcratesandsludgepilelocations.FPLwillinitiallyconductin-situpressuretestingwithoutaburstbladdertoassessleakageintegrity.Leakage,ifobserved,willbemeasuredatnormaloperatingdifferentialpressureandathigherpressures.Ifleakageexceedsmakeupcapacity,theburstbladderwillthenbeinstalledtoachievethedesiredtestpressures.Tubeselectionforin-situpressuretestingwillbeconductedbyleadECTdataanalysisandengineeringpersonnel.SelectioncriteriawillbebasedonreviewofECTdataforavarietyofflawcharacteristicsincludinglength,maximumdepth,averagedepth,voltage(amplitude),location,potentialfortubesupportlock-up,numberofflawsinatube,andflawgrowthrate.Duetothevarietyofflawcharacteristicsinvolved,analyticaljudgmentandevaluationexperienceisrequiredforassessingtheseverityofflawsindications.
'h,I St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage2Selectionofflawindicationsforin-situpressuretestingwillbebasedonbobbincoilinspectiontechniquesthatarequalifiedfordetectionanddepthsizingofintergranularattack/stresscorrosioncracking(IGA/SCC)ateggcratesupports,freespanandsludgepilelocations.CandidateindicationswillalsobeinspectedwithMRPCtechniquestoassesstheflawcharacteristicsdiscussedabove.Candidateindicationsforin-situpressuretestingatdrilledsupportplatelocationswillalsobeinspectedbybobbincoilandMRPCtechniques.Selectionofcandidateindicationsatdrilledsupportplatelocationswillrelyonacombinationofdepthandvoltageinformationaswellastheotherflawcharacteristicsdiscussedabove.Adjustmentstoin-situtestpressurewillincludea13%increasefortemperaturebasedonbursttestingof3/4inchby0.048inchAlloy600tubesamplesatoperatingandroomtemperatures.Testpressureforcircumferentialflawsatthetubeexpansiontransitionwillalsobeincreasedby8.5%forlockedsupportplateconditionsbasedona40inchspanbetweenthetubesheetandthefirsteggcratesupport.Theadjustedpressuresare:FlawADJUSTEDOrientationNOPD/PAxial1622psiCircumferential1744psiADJUSTED1.4xSLBD/P3955psi4253psiADJUSTED3xNOPD/P4865psi5231psiNOPD/PTubedifferentialpressureatnormaloperatingsystempressures.NOPD/P=1435psi.SLBD/P'ubedifferentialpressureduringSteamlinebreak.SLBD/P=2500psi.In-situpressuretestingofflawedsteamgeneratortubingisbecomingarelativelycommonindustrypractice.Industryexperiencewithin-situpressuretestinghasbeenpositiveintermsofassuringthatadequatestructuralmarginsexist.FPLwillusefieldprovenequipmentandexperiencedpersonnelforin-situpressuretesting.Between10and20ofthemostsignificantindicationsfromalllocations(eggcrate,sludgepile,drilledsupportplate,orfreespan)willbein-situ St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage3pressuretested.In-situpressuretestresultsareexpectedtodemonstratethatconservativemarginsforstructuralintegrityareprovidedutilizingtheECTdepthsizingtechniques.REQUEST2.Giventhestaffconcernsregardingthedepthsizingtechnique,provideadiscussionofthefeasibilityof,andanyplansyouhave,forperformingheliumleaktestingtoconfirmthatnothrough-wallcracksarepresent.Thisactionwouldprovidesupportinginformationthatindicationssizedlessthan100%through-wallareinfactlessthan100%through-wallprovidednoleakagewasdetectedforthesetubes.Thistestalsohasthepotentialtopermittheidentificationofthesourceofanyprimary-to-secondaryleakageobservedduringthelastcycle(e.g.,ifleakageisattributedtoaplug,thistestmayprovideadditionalconfidencethatalltheleakageisfromtheplug).FPLRESPONSEFPLhasreviewedheliumleakdetectioneffortswithaleakdetectionvendorandseveralutilities.Themajorityofleakdetectioneffortswithheliumhavebeenforleakageinexcessof50gallonsperday(gpd).LeakageatSt.LucieUnit1isestimatedat2-4gpd.Theuseofheliumleaktestingforleakagewhichislessthan5gpdisextremelylimitedandisnotexpectedtobeeffective.Also,heliumtestingisnotexpectedtoidentifyleakagethroughaperforatedtubewhichcontainsaleakingtubeplugduetothecolumnofwaterwhichistypicallypresentabovetheplug.Further,thedifficultyinmaintainingapositivepressurewithheliumonthesecondarysystemmakesthistestdifficulttoimplement.TheFPLapproachincludesextensiveinspections,in-situpressuretestingandimprovedon-lineleakagemonitoringatSt.LucieUnit1.FPLbelievesthatheliumleaktestingwillprovidelittleornobenefitbeyondtheinformationandinsightprovidedbytheothertechniquesbeingemployed.NRCREQUEST3.Provideyourplansandscheduleforperforminganestimateoftheconditionalprobabilityofburstgivenamainsteamline
!)
IIj1(~~St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage4breakgiventhenumberofindications,themaximumgrowthrateobserved,andtheeddycurrentuncertainties.FPLRESPONSEFPLwillperformacalculationfortheprobabilityoftubeburstbasedontheAPTECHEngineeringmodelofthePaloVerdeSteamgenerator.Thiscalculationwill'valuatetheas-leftconditionoftheSt.LucieUnit1steamgeneratorsandprojecttheendofthenextcycleconditionsbasedonthenumberofindications,growthratesandeddycurrentuncertaintiesforalllocationsinthesteamgenerator.Thecalculationoftubeburstprobabilitywillbesubmittedapproximately6monthsafterstartupfromthecurrentrefuelingoutage(SL1-14).NRCREQUEST4.Provideyourcriteriafordeterminingwhetherornotamid-cycleinspectionisnecessaryasaresultofeddycurrenttesting,in-situpressuretesting,heliumleaktesting,andconditionalprobabilityofburst(e.g.,1E-2),asappropriate.FPLRESPONSETheECTinspectiondataforalllocationsinthesteamgeneratorwillbethebasisfortheassessmentoftheneedforamid-cycleinspection.Thefactorsconsideredwillincludein-situpressuretestresultsandtheprobabilityofburstcalculationconservativelyestimatedbasedonECTexaminationresults.Acalculatedprobabilityoftubeburstsubstantiallygreaterthan1X10willbeconsideredasinputtotheneedforamid-cycleinspection.NRCREQUEST5.ProvideyourplanswithrespecttonotifyingthestaffifanyindicationwouldnotbeabletowithstandtheloadingspecifiedinDraftRegulatoryGuide1.121.Thisshouldaddressreportingindicationswhoselengthexceedsthecriticallengthassuminga100%through-wallflaw.andindicationswhosedepthexceedsthecriticaldepthassuminganinfinitelylongflaw.
St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage5FPLRESPONSEFPLwillinformtheNRCprojectmanagerforSt.LucieUnits1and2,viatelephone,oftheprogressoftheinspectionsaftertheyareapproximately50%,75%and100$complete.FPLwilldiscussthegeneralstateoftheinspection,thenumberandsizeoftheindicationsandcandidateindicationsforin-situpressuretesting.TheNRCprojectmanagerwasupdatedbyphoneon5/13/96atapproximately25%completion.Resultsfromthein-situpressuretestswillbeprovided,viatelephone,within24hoursofcompletionofthein-situtestprogram.NRCREQUEST6.Discussyourplanswithrespecttosubmittingasummaryoftheinspectionresultsandtheabovementionedheliumandin-situpressuretestresults.FPLRESPONSEResultsfromtheeddycurrentinspectionswillbesubmittedaspartofthespecialreportrequiredbyTechnicalSpecification4.4.5.5.b.Theresultsfromthein-situpressuretestingwillbesubmittedwithin10daysofcompletionofthein-situtestprogram.ZZ.Forindicationsatthedrilledholetubesupportplateswhichyouplantosizeandleaveinservice:NRCREQUESTa.Discussthequalificationdatatosupporttheabilitytosizethetypesofindicationsthatwillremaininservice(e.g.,volumetricindications).Includethetubepulldataorothertestdatathatconfirmsthatthemorphologyofthequalificationdataisconsistentwiththemorphologyoftheindicationsinthefield.
)~%'I St.LucieUnit1DocketNo.50-335~,L-96-129AttachmentPage6FPLRESPONSEQualificationdatafordetectionandsizingofIGA/SCCindicationsatdrilledsupportplatesusingbobbincoilinspectiontechniqueshasbeenprovidedtotheNRCviatheElectricPowerResearchInstitute(EPRI)aspartofEPRINP-6201,Revision4,PWRSteamGeneratorTubeExaminationGuidelines.ThedatademonstratesthatthebobbincoiltechniqueexceedsthedetectionrequirementsofEPRINP-6201,AppendixHwithaprobabilityofdetection(POD)of80%ata90%confidencelevelforflawspenetrating40%throughwall.However,bobbincoiltechniquesfailedtomeetthesizingrequirementssincetheyresultedinarootmeansquareerror(RMSE)of29%(AppendixHrequireslessthanorequalto25%RMSE).FPLhasconsideredtworepairoptionsforeddycurrentindicationsatthe9thand10thdrilledsupportplates.Option1reliesonbobbincoiltechniquesfordetection,andrequiresMRPCexaminationofallflawindicationsreported.Allindicationswhicharecrack-likebyMRPCexaminationwillberemovedfromservice.Non-crackMRPCindicationswillbesizedusingtheEPRIbobbincoiltechnique(RMSE=29%).Indications40%orgreaterthroughwall,orindicationswith>10%growth,sincethepriorinspectionwillberemovedfromservice.Option2alsoreliesonbobbincoiltechniquesfordetection,andrequiresMRPCexaminationofallflawindicationsreported.However,thisoptionrequiresthatallindicationswhichareconfirmedbyMRPCexaminationberemovedfromservice.FPLconsidersoption2excessivelyconservative.Therefore,ourcurrentplanistouseOption1aboveandtoin-situpressuretestthemostsignificantdrilledsupportplateindicationstodemonstratethatadequatestructuralmarginsexistforflawswhichwillremaininserviceintheseregions.TheStaffalsorequestedthatFPLdiscussourplansforsizingIGA/SCCindicationswhicharelocatedinfreespanregions.OurcurrentplanistoapplyOption1,asdiscussedabovefor y~e~~~~St.LucieUnit1DocketNo.50-335L-96-129AttachmentPage7drilledsupportplateindications,forindicationslocatedinthefreespanregions.Tubesremovedin1985provideafullrangeofintergranularmodesofattackfrompatchesoflGAtodiscretecracks.Depthsizingusingpostmortemeddycurrentcalibrationcurveshaveresultedin10yearsofoperationwithoutsignificantinserviceleakage.Basedonextensivepriorinspections,FPLhasathroughunderstandingoftheextentofdegradationintheSt.Luciesteamgenerators.FPLexpectsthatchangesincorrosionmorphologyorincreasesingrowthratewouldhaveresultedinsubstantialinserviceleakageifeddycurrentsizingcriteriawerenonconservative.Generaleddycurrentresponsehasremainedconstantsince1984,withtheonlychangesbeinganincreaseinthenumberofaffectedlocations.Consistencyineddycurrentresponseandlackofsignificantoperationalleakageprovideassurancethatcorrosionmorphologyisbeingadequatelymonitored.NRCREQUESTb.Addressthecomments/questionslistedaboveforeggcratesupportandsludgepileindications(items1through6),asappropriate.FPLRESPONSETheresponsetoquestions1-6for'ggcrateandsludgepileindicationsincludetheresponsesfordrilledsupportplateindications.