ML17249A867
| ML17249A867 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 04/29/1980 |
| From: | WHITE L D ROCHESTER GAS & ELECTRIC CORP. |
| To: | ZIEMANN D L Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8005050232 | |
| Download: ML17249A867 (19) | |
Text
REGULATORYINFORMATIONDISTRIBUTIONSYSTEM(RIDS)ACCESSIONNBR>>8005050232DOC~DATE~80/09/29NOTARIZED:NODOCKETFACIL:50200RobertEmmetGinnaNuclearPlantiUnitliRochesterG05000244AUTH'AMEAUTHORAFFIL'IATIONWHITEsL~D,RochesterGas8ElectricCorp.RECIP,NAMERECIPIENTAFFILIATIONOfficeof'uclearReactorRegulationZIKMANNgD,L~Procedures5TestReviewBranch
SUBJECT:
ForwardsApr1980steamgeneratorinsprept8evaluat'ionofresultsiinresponsetoNRCrequest,DISTRIBUTIONCODE:A001SCOPIESRECEIYKD:ITRIENCL~SIZE:TITLE:GeneralDistributionfotafterIssuanceofOperatingLic~W.+c.C.le&8'.enSsvX8K.NOTESI<bRECIPIENTCOPIESRECIPIENTCOPIESIDCODE/NAMELTTRENCLIDCOOK/NAMELTTRENCLACTION:05BC0ggW~7INTERNALi0+R12K17ENGRBR19PLANTSYSBR21EFLTTRTSYSOELDE)<TERNAL:03LPDR23ACRS1211111160?NRCPDR15'OREPERFBR18REACSFTYBR20EEBEPB~DORSTSGROUPLEADR1'<)NSIC16hillyg)gg9VTOTALNUMBEROFCOPIESREQUIRED:LTTR~ENCL IHI'JNII1wr1~t1(AlltI!1 80000gyp,-rPP@Z/PIIKSISllltlllI'JIIINII-r"'"'"-~ROCHESTERGASANDELECTRICCORPORATIONo89EASTAVENUE,ROCHESTER,N.Y.14649LEOND.WHITE.JR.VICKPRKSIDKNTTKLKPHDNK*RK*CDDKTIS,546-2700April29,1980DirectorofNuclearReactorRegulationAttention:Nr.DennisL.Ziemann,ChiefOperatingReactorsBranchNo.2U.S.NuclearRegulatoryCommissionWashington,DC20555
Subject:
SteamGeneratorInspectionResultsandAnalysisR.E.GinnaNuclearPowerPlant,UnitNo.1DocketNo.50-244
DearNr.Ziemann:
1In,responseto'areguestofDr.,B.D.Liau'fyourstaffwearesubmittingforyourinformationareportonthe1980SteamGeneratorInspectionandan,evaluationoftheresults.Pleasefindattachedonecopyofeach.1AttachmentA-April1980SteamGeneratorInspectionAttachmentB-EvaluationofResultsVerytrulyyours,L.D.Whit,Jr.gp(
~~~4lICg1lil AttachmentAAril1980SteamGeneratorInsectionAprogramofplannededdycuirentexaminationswasconductedonbothloop"A"and"B"steamgeneratorsatR.E.GinnaNuclearPowerPlantfromApril3-8,1980duringthescheduledrefuelingandmaintenanceoutage.Thepurposeoftheseexaminationswastoassesstheintegrityofthesteamgeneratortubingandtakecor-rectiveactionstoassurereliableandsafeoperationduringthenextoperatingfuelcycle.Theseexaminationsconsistedofamultifreguencyeddycurrentexaminationtodetectandmeasurepotentialtubedefects.Thisisthethirdyearofmultifrequencyeddycurrent.examinationsattheGinnaplant.Thefourfrequencieschosenwereasfollows:a.400KHzDifferential,b.200KHzDifferential,c.100KHzDifferential,d.100KHzAbsolute.Alongwiththefourfreguencies,asupportplateandtubesheetmixwasutilizedbycombiningtheinputsfromthe400KHzand200KHzdifferentialfrequencies.Thismixallowedformoreaccuratein-terpretationofsignalsfromareasofthesteamgeneratorwherethesignalfromsupportstructuresinterferewithsignalsgeneratedfromtubingflaws.Theexaminationsconsistedofa100percentinspectionofbothsteamgeneratorsinletsandtheoutletsreceivingapproximatelya25percentinspection.Minimumtubelengthexaminedwasfromthefirst.supportplatedownthroughthetubesheetcrevice.TubeswerealsoexaminedovertheU-bendregionandtothesixthsupport,plate.WithNtheexceptionofindicationswhichwillbediscussedinthetext, 1
therewerenotanysubtlechangesnotedoverpreviousyearsdata.Thesteamgeneratoroutletsdidnotshowanyreportableindications.Inthe"A"steamgeneratorinlet,onlyonetube(R16C88)requiringpluggingwasfound.Itdisplayeda50%smallvolumeindication2inchesabovethetopofthetubesheet.The"B"steamgenerator,whichhadtwo(2)creviceindicationsinAprilof1979andeleven(ll)creviceindicationsintheDe-cember1979showedthirtyone(31)creviceindicationsatthistime.Theseindicationsfallintotwocategories,thefirstbeing13indi-cationswhichwereidentifiedatallexaminationfrequenciesandareasfollows:R17C35R18C35R18C36R14C38R17C40R17C41R15C41-38~15"abovetubeend-<20%,15"abovetubeend-48'18"abovetubeend-58~15"abovetubeend-60~18"abovetubeend-60~18"abovetubeend-67~18"abovetubeendR15C42R14C43R19C44R24C45R24C46R21C54"75~os85~0I-9560~0/15"abovetubeend12"abovetubeend10"abovetubeend15"abovetubeend15"abovetubeend15"abovetubeendThesecondcategoryincluded18indicationsthatweredetectedwiththe100KHzabsolutefrequencyonly.Theseindicationswereanabnormalverticalchannelsignalonthebrushstripchartrecorderthat,resembledthesignalsat100KHzabsoluteofthe13tubesfoundattheotherfrequencies.Therefore,thefollowingtubesareconsideredtobeundercreviceattack:R14C32R15C34R16C34R17C34R18C34R15C35R16C35R17C36R16C37R19C37R18C38R19C38R13C39R18C41R15C44R14C46R18C46R18C48These31tubeswithcreviceindications,withtheexception,ofthreeR24C45,R24C46andR21C54,allfit.intoapatternwiththeprevious13tubesfoundinthetwoexaminationin1979,asshown r
3inFiguresIandII.Inadditiontothese,threetubesinthe"B"inletwerefoundwithdefectsabovethetubesheetasfollows:R32C16-41%,smallvolumeindication,2"abovetubesheetR45C48-46%,24"abovetubesheetR45C47-36%,24"abovetubesheet.Aftereddycurrentdataanalysiswascompletecreviceindicationswereidentifiedonlyinthe"B"steamgeneratorinletandnotinthe"A"steamgenerator.Twotubesfromthe"B"steamgeneratorinletandonetubefromtheoutletwerechosen.fortubepulling.Thesetubes,R17C41-60%indication18"abovethetubeend,R15C44-smallest100KHzabsolutesignal,andR17C40-out-let(coldleg)tubewithnoindication,buttheoppositeendofaninl'ettubewithanindicator,weredeterminedastubesthatwouldpotentiallygivevaluableinformationconcerningthedamagemechanismandalsoallowforthreedifferentcrevicestohavedepositsremovedforchemicalanalysis.Thetubepullingoperationswentasfollows:R17C41-60%indication18"abovetubeenda~b.cd.markedIDat14",24"and26"fromtubeendtubestartedpullingataforceof4500psithendroppedto2500psiforshortperiodoftime,averageremainderpulledat1500psi.totallengthcut69.5",totalpulledlength72"givingapproximately2.5"elongationor3.5%.honedsamplefromcrevice.2.R15C44-small100KHzabsolutesignalincreviceregiona~b.c~d.markedIDat14",24"and26"fromtubeendtubestartedpullingat,aforceof2400psidroppedto1800thenincreasedforanaveragepullof2100psitotallengthcut,was69.5",totalpulledlength72.06"honedsamplefromcrevice.3.R17C40-Noindicationfromoutleta.markedIDattopoftubesheet.b.tubestartedpullingataforceof3200droppedtoapproximately1100fortheremainderofthepull c.totallengthcutwas69.5",totalpulledlength69.875".d.honedsamplefromcrevice.Theproposedhypothesisforthecrevicecrackingmechanismisageneralintergranularcorrosionattack(IGA)thattakesplacedowninthetubesheetcrevicearea.Aftertheintergranularcorrosionattackhaspenetrateddeepenoughintothetubewalltheremainingwallcracksduetostresscausedeitherbypressureand/orthermalloadsonthetube.TheactivespeciesinvolvedinthisattackispostulatedtobeacausticsolutionofNaOH,however,Na2S04,orNaSi03mayalsobeinvolved.Crevicedepositanalysisandthepulledtubesurfacedepositanalysisshouldhelpidentifytheactualspeciesinvolvedinthisattack.Thisconcentrationofcausticisbelievedtobefrompreviousphosphatechemistryoperation(priortoNovember1974)andnottobefxomtheallvolatiletreatment(AVT)operatingchemistrythatGinnahasusedthelastfiveandonehalfyears.ItispostulatedthatthemolarratiobetweenNaandPOinthecrevicehasbeenin-4creasinginthecreviceasP04hasbeenslowlyremovedduringwettingsandsubsequentdryouts.ThisactionleavesbehindfreeNaandOH,whichwouldraisethepHandproducecausticcreviceconditions.Anumberofactionshavebeentakentogainadditionalinforma-tionconcerningthecauseofcreviceintergranular'corrosionattackandtoreducethepropensityforcxeviceattack.Theseactionsin-cludeamoresophisticatededdycurrentinspection,tubepulling,tubesheetwaterlancing,cxeviceflushingboilout,continuedclosecontrolofsecondarychemistry,andamid-cycleFallsteamgeneratorinspection.
~~
Ouruseofmultifrequencyeddycurrent,inspectionincludinga100KHzabsoluteexaminationhasallowedtheidentificationandpluggingofotherwiseundetectedattackwithinthecreviceregion.Tubeswhichmight.otherwisebesusceptibletocrackgrowthandresultinprimarytosecondaryleakageareplugged.ThethreetubeswhichhavebeenpulledandarebeingexaminedbyWestinghouseElectricCorporationshouldyieldvaluableinforma-tionconcerningdamagemechanismandchemicalspecies.Asinallprevioussteamgeneratorinspections,anextensiveprogramofwaterlancingonthesecondarysidehasbeencarriedout.Thus,thequantityofsludgeinthesecondarysideisminimized.Acreviceflushingboiloutprocedurewillbeemployedtofurtherreducethepotentiallydetrimentalmaterialinthetubesheet,crevice.TheprogramtobeemployedatGinnaisbased,inpart,onprogramspreviouslyemployedatKansaiElectricPowerCompanyatMehamaUnit2andbyWisconsinElectricPowerCompanyatPointBeachUnit1.TheprogramatGinnawillinvolveapproxi-matelytwenty-twocycles.Boricacidwillbeaddedduringanumberofthesecycleswiththeobjectiveofneutralizingthecausticsolutioninthecrevices.Duringstartupandplantoperation,thefull.flowcondensatedemineralizerswillcontinuetobeusedandcarefulcontrolofsecondarychemistrywillbemaintained.Operatingexperiencehasdemonstratedourabilitytomaintainexcellentchemistryconditionsonthesecondaryside.
l
~~Finally,weplantoshutdownGinnaStationintheFallof1980toreexaminethesteamgenerators.Thisinspectionshouldaidxnestablishingtheeffectivenessof'correctiveactionsbeingappliednowandtoplanninganyfuturecorrectiveactions.
FigureIRG6E.steamgenera,tor-BIrlletCreviceXnaxcatxonsqlSSSlSSE6$797175757II94745a34i&95755S35I494745454I393735333I292725232ll9I7l5l3II9753COLUMNSlo747270626052S4442.3!o03232822ISI4l2IO864~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4440454341~~~~~~~~~~~~~~~~~~~~~~~~~~~3e36373532333I302S29~~~~~~262523~~2l-=20~~~~-0----OC.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ROWSs16l2IO9723I-:.=:-MAN@AxNMarch79-2k-December79-llNOZZLE=4/25/80ABC1 1J
-FigureIIRGaBst;earnGeoqraQgr-BInletCreviceIndicationsRl898785%6I791175757I194745l341695755535I494745454I393735333I292725232IIQI7l5l3II975390888L8288lo7472708III4I2105Q545254444243'f323282.lo22I8I6I4l2I086COLUMNS0"00.~~~~~~~~~~~~~~~~~~~'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'~~~~~~~~~~~Q~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~t~~~~~~~l~~~~ROWS45424l40383634323I302928262522232IISI6I4I2IIIO86523I=:l-MANV/AYNOZZLE~-April80-314/25/80AEC AttachmentBEvaluationofResultsTheresultsofthesteamgeneratorinspectionhavebeenreviewedtodeterminewhetherthereareanyunreviewedsafetyquestionsorwhetherachangeintheTechnicalSpecificationsisrequired.TheconclusionhasbeenreachedthattherearenounreviewedsafetyquestionsandthatnochangeinTechnicalSpecificationsisrequired.Thecurrentsafetyanalysisassumesthat10%ofthesteamgeneratortubesareplugged.Currentpluggedlevelsarewellbelow10%,3.74%intheAand3.44%intheB.Therefore,thecurrentanalysisremainsvalid.ThecurrentTechnicalSpecificationlimitisO.lgpmineithersteamgeneratorwhenaveragedover24hours.Thislimitwaspro-posedonApril25,1975andwasreviewedandapprovedbytheNRCinlicenseamendmentno.7datedMay14,1975.Thislimitwasestablishedtoensuretubeintegrityfollowingdesignbasiseventsundertheconditionoftubecrackingsuperimposeduponthinningofthetubeto60%ofthewallremaining.Testsandanalysesperformedandapprovedin1975demonstratedthatifleakagewaslimitedto0.1gpm,thenthemaximumpossiblecracksizewaslimited.Evenassumingthatthemaximumlengthcrackoccurredonapreviouslythinnedareawhen50%tubewallremained,tubesdidnotfailduringdesignbasistransients.A40%plugginglimitwas,therefore,establishedtoprovidealevelofconservatism.
WhereastheTechnicalSpecificationwereestablishedbasedondefectsoccurringabovethetubesheet,crevicecracksseenthisoutageandintheprevioustwooutagesarebelowthesurfaceofthelttubesheet.Thetubeinthevicinityofthecrevicecrackispro-videdsupportbythetubesheetandtheprevioussafetyanalysisoftubeintegritymaybeconservativelyapplied.Tubeclearanceswithinthetubesheetmayvaryfrommanufacturingtolerancesfrom.016inchesto.022inchesonthediameter.Theseclearancesarefurtherreducedinoperationbythedepositsandcorrosion'roductsinthecrevices.Therefore,thetubesinthecreviceareaaretightlyconfinedwithin,thetubesheet,whichprovidesreinforce-menttothetubewallmaterialintheareaofthecreviceswheretheintergranularcorrosionattackhasbeenfound.Thiswouldreducetubedistressunderabnormalloadingsprohibitingsignificantcrackingorrupture.Further,thinninginthecreviceregionhasnotbeenobserved,thusprovidingsignificantadditionalmargin.Basedontheseconsiderations,thereisnounreviewedsafetyquestionandnochangeintheTechnicalSpecificationsisrequired.Plantoperationmay,therefore,resume.