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{{#Wiki_filter: | {{#Wiki_filter:CATEGORYREGULATORY INFORMATION DISTRIBUTION SYSTEM"(RIDS)" | ||
4ACCESSION NBR:9804200484 DOC.DATE: | |||
98/04/14NOTARIZED: | |||
YESFACIL:50-315 DonaldC.CookNuclearPowerPlant,Unit1,IndianaM50-316Donald.C.CookNuclearPowerPlant,Unit2,IndianaMAUTH;NAME AUTHORAFFILIATION FITZPATRICK,E. | |||
IndianaMichiganPowerCo.RECIP.NAME RECIPIENT AFFILIATION DocumentControlBranch(Document ControlDesk)DOCKET¹0500031505000316 | |||
==SUBJECT:== | ==SUBJECT:== | ||
ForwardsresponsetoGL97-06," | ForwardsresponsetoGL97-06,"Degradation ofSGIntervals. | ||
DISTRIBUTION CODE:ZOOIDCOPIESRECEIVED:,LTR iENCLiSIZE:TITLE:ORSubmittal: | |||
GeneralDistribution NOTES:RECIPIENT IDCODE/NAME PD3-3LASTANG,JCOPIESLTTRENCL,1111RECIPIENT IDCODE/NAME PD3-3PDCOPIESLTTRENCL11EINTERNAL.-ENT---1NRR/DE/EMCB NRR/DSSA/SPLB NUDOCS-ABSTRACT EXTERNAL: | |||
et~~ | NOAC11111111NRR/DE/ECGB/A NRR/DRCH/HICB NRR/DSSA/SRXB OGC/HDS2NRCPDR1111111011DNOTETOALL"RIDS"RECIPIENTS: | ||
PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATION REMOVEDFROMDISTRIBUTION LISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION, CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION 415-2083TOTALNUMBEROFCOPIESREQUIRED: | |||
LTTR13ENCL12 IndianaMichigan~PowerCompany500CircleDriveBuchanan, Ml491071395 IlfNENANAMICHIGANPQWMApril14,1998AEP:NRC:1166AM DocketNos.:50-31550-316U.S.NuclearRegulatory Commission ATTN:DocumentControlDeskMailStop0-Pl-17Washington, D.C.20555-0001 Gentlemen: | |||
~~ | DonaldC.CookNuclearPlantUnits1and2RESPONSETONRCGENERICLETTER(GL)97-06DEGRADATION OFSTEAMGENERATOR INTERNALS Thisletteranditsattachment provideinformation requested inGL97-06,concerning steamgenerator internals degradation. | ||
Sincerely, pugE.E.Fitzpatrick VicePresident J'SWORNTOANDSUBSCRIBED BEFOREMEgATHIS~DAYOF~/Z.,1998NotaryPublic/.Sd//vlbAttachment Z.A.AbramsonA.B.BeachMDEQ-DW&RPDNRCResidentInspector 8.R.SampsonUNDALBOEI.CKENotaryPublic,BerrienCounty,MlMCommission ExpiresJanuary21,200I2001yQoI9804200484 9804l4PDRADOCK050003iSpPDR ATTACHMENT TOAEP:NRC:1166AMRESPONSETONRCGENERICLETTER97-06DEGRADATION OFSTEAMGENERATOR INTERNALS 5.~'Attachment toAEP:NRC:1166AM Page1INTRODUCTION Genericletter(GL)97-06wasissuedto'alertaddressees toforeignanddomesticfindingsofdamagetosteamgenerator (SG)internals, emphasize theimportance ofperforming comprehensive examinations ofSGinternals, andrequestinformation thatwillenabletheNRCstafftoverifytheinternals ofCookNuclearPlant'sSGsconform-tothecurrentlicensing basis.BACKGROUND ANDDESCRIPTION OFCIRCUMSTANCES Frenchauthorities havereportedvariousSGtubesupportplate(TSP)damagemechanisms. | |||
Damagehas.-includedwastageintheuppermost TSPduetomisapplication of.achemicalcleaningprocess,brokenTSPligaments resulting frominadequate clearance for,differential thermalexpansion, andTSPwastageatvariouselevations apparently involving acorrosion orerosion-corrosion mechanism ofundetermined origin.Otherins'tances ofinternals degradation includewrapperdrop/cracking ataforeignutilitythatissuspected tohavebeencausedbyseverecoolingtransients, andinstances oferosion-corrosion ofeggcratesupportsinuntubedareasinitiated "byunknowncausesthatoccurredatadomesticfacility. | |||
Theseinstances. | |||
highlight thepotential fordegradation mechanisms thatmayleadtoTSPandtubewrapperdamage..Asaresultofthisconcern,GL97-06requests: | |||
1.Discussion ofanyprogramsinplacetodetectdegradation ofSGinternals andadescription ofinspection plans(scope,frequency, methods,andequipment) | |||
.Thisdiscussion should.address.thefollowing information foreachfacility. | |||
a~b.C.Whetherinspection recordshavebeenreviewedforindications ofTSPsignalanomalies fromeddycurrenttestingofSGtubes'hat maybeindicative ofsupportplateorligamentdamage.Whethervisualorvideocamerainspections havebeenperformed onthesecondary sidetogaininformation onthecondition ofSGinternals (e.g.,supportplates,tubebundlewrappers, etc.).Whetherdegradation, ofSGinternals hasbeendetected, andhowitwasassessedanddispositioned. | |||
2.Intheeventnoprogramisinplacetodetectinternals degradation, provideadiscussion orjustification fordevelopment ofaprogramorwhysuchaprogramisnot:needed.. | |||
PriortoissuanceofthisGL,Westinghouse OwnersGroup(WOG),ElectricPowerResearchInstitute (EPRI),andNuclearEnergyInstitute (NEI)developed anactionplantoassessthesusceptibility ofSGsecondary "sidedegradation. | |||
Weintendtofollowtheindustryactionplanasmodifiedbyoursite-specific experience. | |||
Includedintheactionplanisarequirement tounderstand thecausalfactorsinvolvedinthedegradation experienced intheFrenchunits.Thisinformation iscapturedinEPRIreportGC-109558, "SteamGenerator Internals Degradation: | |||
Attachment toAEP:NRC:1166AM Page2ModesofDegradation DetectedinEdFUnits".Thisreportwassubmitted'o theNRCviaanNEZletter,datedDecember19,1997.-WOGhasreviewedEPRZGC-109558 relativetothe,designofseries51SGsanddetermined limitedpotential susceptibility. | |||
Forplantswithseries51SGs,thisconclusion isdocumented inWCAP-15002, revision1,."Evaluation ofEdFSteamGenerator Internals Degradation | |||
-ImpactofCausalFactorsonWestinghouse | |||
.51SeriesSteamGenerators", | |||
December1997.Theseries51SGsarethemostsimilarmodelSGtothatoftheElectricith deFrance(EdF).unitsandareinstalled inunit1.WCAP-.15002, revision1,documents visualinspections performed attheseries51SGplants.Ztwasconcluded | |||
.thatthenumber.ofplantsthathavebeeninspected andtheinspection resultsdemonstrate thatthecausalfactorsidentified byEdFdonotjeopardize thecontinued operability ofWestinghouse series51SGs.Thisconclusion issupported bythe-capability ofeddycurrentinspections to,detect. | |||
detrimental effectsontubingduetowearcausedbyTSPligamentdegradation, loose'parts, andsecondary side'lowdistribution changes.Foreignobjectsearchandretrieval | |||
~effortsaretypically conducted asstandardpracticetodiscoveror~retrievelooseparts,thuslimitingthepotential fordamage.AresponsetoGL97-06hasbeencompleted forunit1addressing thesusceptibility oftheunit1SGstointernals degradation, specificunit1inspection practices andrecentinspection results,along,withadiscussion ofsubsequent plantoperation withpotential SGinternals degradation ofthetypeexperienced;in theFrenchunits(andothertypesofdegradation experienced domestically) | |||
~Thisdiscussion beginsinthe"UNIT1SGPROGRAM(INTERNALS 1NSPECTION) | |||
"sectionofthisattachment. | |||
BecauseadetailedWestinghouse evaluation hasnotbeenperformed | |||
,forourunit2SGs,inspection recommendations have.beenidentified onaninterimbasis.Industryrepresentatives haveindicated that'valuations shouldbecompleted byMay1998,andtheresultswillbefactoredintotheunit2SGprogram.Assuch.theresponseto'tem1forunit,2,whichisdetailedinthe"UNIT2SGPROGRAM(INTERNALS INSPECTION)" | |||
sectionofthisattachment, maybemodifiedinthefutureasdictatedbytheresultsofthependingevaluation. | |||
UNIT1SGPROGRAMINTERNALS INSPECTION SGDescritionUnit1containsfourWestinghouse series51SGsthatwereplacedinservicein1975.Keydesignfeaturesincludealloy600millannealedtubing,apartialdepthhardrollexpansion atthetube-to-tubesheet joint,anddrilledcarbonsteelsupportplates.Thenominaltubeoutsidediameter(OD)is0.875incheswithanominalwallthickness of0.050inches.Thefourunit1SGsarepresently scheduled forreplacement intheyear2000. | |||
Attachment to=AEP:NRC:1166AMPage3RelatedIndustFindinsAsdiscussed inWCAP-15002, revision1,eighteenplantswithseries51SGssuppliedinformation totheWOGconcerning resultsofSGsecondary sideinspections andrelevanttubeinspections forTSPconditions. | |||
Theseresultsdidnotreportdetection ofseveralmodesofdegradation experienced intheEdFunits.Thereis-noevidenceofpost-chemical cleaninginspections indicating any.significant materialloss,noristhereevidenceofwrapperhavingdropped.WhileTSPligamentcrackinghasoccurredinunitswithcarbonsteelsupport,plateswithdrilled'ound holesand.flow'oles,thereisnoevidenceindicating TSPligamentcrackingorthinningthatisprogressive andcontinuing. | |||
Thefollowingtablesummarizes theapplicable WOGconclusions concerning thesusceptibility ofSGslikeouiunit1series51SGstosecondary sideinternals degradation. | |||
TABLE1DEGRADATION TYPEErosionCorrosion: | |||
MoistureSeparator TSPFlowHole/Ligaments FeedRing/8-Tubes Cracking: | |||
TSPLigaments NearWedges**TSPLigaments NearPatchPlatesCarbonSteelTSPLigaments (randomareas)LEVELOFSUSCEPTIBILITY NNX*"Other:WrapperNearSupports**NWrapperDrop**NX~oservexnsomeSGsN=notsusceptible toEdFcasualfactorsL~lowsusceptibility toEdFcasualfactors*~variousindication ofdegradation maybeartifacts ofmanufacturing relatedtopatchplateplugweldsand/ordrillingalignment | |||
**variousWestinghouse designfeatures'rebeneficial relativetosomeoftheSGdesignfeaturesofforeignmanufacturers Site-SecificFindinsTheunit1SGswerelastinspected inthespringof1997.In~additiontothestandardeddycurrenttubeinspection, additional measureswereperformed toassuretheintegrity oftheSGinternals. | |||
Theseinspections, coupledwithrelatedfindingsfrompreviousinspections, demonstrate thatthe'reasnotedintable1havebeenperiodically examinedwithnoabnormalconditions | |||
.noted. | |||
et~~Attachment toAEP:NRC:1166AM Page4Thefollowing discussion presentstheinternals inspection scopeandfindingsfortheunit11997refueling outage(U1R97).A100%computerdatascreening (CDS)sortwasperformed onthelowfrequency bobbincoildatafromeachSGtoaddressthepotential forTSPdamageorligamentcracking. | |||
Indications ofpossibleligamentdamagewereexaminedusingamotorized rotatingpancakecoil(MRPC)probe.Theindications weresubsequently dispositioned ashavingnodegradation found(NDF)ordetermined tobealignedwiththepatchplate,thusyieldinga"false"indication. | |||
Onetube,R39/C22inSG11wasnotedtohavea0.78'oltMRPCindication attheseventhhotlegsupportplate,nearthewedgelocation. | |||
Researchofthepreviousoutagedataconfirmed thiscondition hasbeenpresentforatleastthreeyears.Thisindication willcontinuetobemonitored duringfutureeddycurrentinspections. | |||
Regarding theperformance ofsecondary sidevisualinspections, thefollowing activities wereperformed ineachSG(unlessotherwise noted)duringtheU1R97foreignobjectsearchandretrieval operations: | |||
~Pre-Sludge LanceInspection | |||
-Avisualinspection wasperformed toidentifythetubing/sludge conditions atthetubesheet prior,tolancing.Thisinspection includedtheannulusanddividerlane.~Post-Lance Inspection | |||
-Avisualinspection wasperformed toverifytheeffectiveness ofthesludgeremovalprocessandgeneraltubesheet/tubing conditions atthetopofthetubesheet. | |||
Theinspection consisted oftheannulus,dividerlaneandaninnerbundlepassinboththehotandcoldlegsides..WrapperBarrelInspection | |||
-Thisvisualinspection wasperformed to.verifytheintegrity ofthewrapperbarrelsupportstructure. | |||
FirstTubeSupportLigament(2,SGs)-Thisinspection involvedavisualreviewofthefirstTSPbetweenthewrapperbarrelandthetubebundledirectlyabovethehandhold: | |||
Thepre/post-lance inspections confirmed" theeffectiveness ofthesludgeremovaloperations andthegeneralcondition ofthetubingatthetubesheet. | |||
Noanomalies orloosepartswerenotedbytheinspection. | |||
Thewrapperbarrelinspection producednoevidenceofslippageormovement. | |||
Additional verification oftheintegrity ofthesupportstructure wasprovidedbythesuccessful installation ofthesludgelanceequipment. | |||
Thelackofanyinterferences'uring thisinstallation providedassurance thatnodeformation had~occurred. | |||
Inspections ofthefirstsupportplateidentified nosignsofanomalies ineitherofthetwoSGsinspected. | |||
Whilenoinspections wereperformed duringU1R97ontheupperinternals, previousinspections haveidentified onlyminimalwear.'uring the1995inspection, fifteenJ-nozzles andthefeedringteesectionofoneSG.wereinspected. | |||
TheJ-nozzles weretermedtobeinverygoodcondition, withnothinningobservedonthethermallinerandtee.Priortothe1995inspection, extensive inspections wereconducted in1989inwhichvisualinspections wereconducted | |||
.ontheJ-nozzles ofthreeSGs.Thevisualexamination ofoneof l~ | |||
Attachment toAEP:NRC:1166AM Page5theseSGswassupplemented byanaddedultrasonic test(UT)examination. | |||
NeitherthevisualorUTexaminations notedanyapparentdegradation. | |||
Theseinspections haveindicated thatdegradation intheupperinternals isaslowprogressing phenomena. | |||
Basedonminimaldegradation todateandthenearendoflifefortheseSGs,noexaminations wereperformed duringU1R97.SafetAssessment Thefollowing safetyconcernshavebeenpostulated byWOGrelativetotheFrenchSGinternals degradation experience. | |||
~Lossofsupportinthetube.bundleleadingtowear,andpossibleprimary-to-secondary leakageorinadequate burstmargins.Increased TSPdeformation duringapostulated loss-of-coolant accident(LOCA)plussafeshutdownearthquake (SSE)'event,resulting inunacceptable SGtubecollapseorsecondary-to-primaryinleakage. | |||
i~Generation ofalooseobjectinthesecondary sideofaSGthatmayresultintubewearorimpacting, andpossiblyprimary-to-secondary leakage.Asdiscussed below,industryexperience andvariousstandardpractices aretypically employedtoprovideassurance ofSGintegrity andnegatethepotential forthese'oncerns. | |||
Asevidenced fromthepreviously discussed U1R97inspection results,ourunit1experiences andpractices mirrorthatoftheindustry. | |||
Basedon'reviewofthetable1information, theonlydegradation typesthatmayoccurdomestically thatcouldresult,inthelossofTSPintegrity areTSPflowhole/ligament erosion-corrosion, TSPligamentcrackingnearthepatchplates,andTSPligamentcrackinginrandomareas.Thereisnoindustryevidenceofpost-chemical cleaninginspections indicating. | |||
significant materialloss,noris'thereevidenceofanywrapperhavingdropped.WhileTSP'ligament crackinghasoccurredinunitswithcarbonsteel.supportplateswithdrilledroundholesandflowholes,thereisnoevidenceindicating TSPligamentcrackingorthinningthatisprogressive andcontinuing. | |||
Utilities withseries51SGswithcarbon'steelsupportplatesinspectasignificant percentage ofSGtubeseveryoutagewithabobbincoilprobe(unit1inspects100%).Ifsectionsofthetubesupportweremissing,itwouldbereadilydetectable becauseofalackofeddycurrent.responseattheTSPelevation. | |||
Thereisnoincreased susceptibility toligamentcrackingnearthewedgesupportsintheseries51SGdesign.Eithertherearenoflowholesextending totheperiphery | |||
'atthewedgelocations, or=.thewedgesarenotweldedtotheTSPs,asisthecasewiththeEdF51MSG.Existingcalculations evaluating theeffectsofLOCAplusSSEloadingsonthetubebundlecontinuetoapplyindetermining whethercertaintubesshouldbeexcludedfromapplication ofthevoltagebasedpluggingcriteria, orwhethercertaintubesshouldberemovedfromserviceinplantsthatdonotcurrently havethecriteria, butmayhaveSGtubesexperiencing | |||
~crackingatTSPintersections. | |||
Attachment toAEP:NRC:1166AM Page6Anotheroccurrence resulting fromSGinternaldegradation thatmay.affectaSGinperforming itsintendedsafetyfunctionisthepotential fortubewearandprimary-to secondary leakageduetothegeneration ofalooseobjectonthesecondary sideoftheSG.Thismayoccurduetoerosion-corrosion ofthemoistureseparators, feedring/J-nozzle, orTSPflowholes,ortheoccurrence ofTSPligamentcracking. | |||
Ifprimary-to-secondary leakageshouldoccurbecauseoftubewearfromalooseobject,theexpectedconsequences wouldbeboundedbyasingletuberuptureeventand,therefore, wouldremainwithinthecurrentlicensing basisoftheplant.Itisourpositionthatlooseobjectsshouldberemovedwheneverpossible. | |||
Tubesobservedtohavevisibledamageareeddycurrentinspected andpluggedasnecessary. | |||
ElementsoftheSGprogram,includi'ng eddycurrentinspection, foreignobjectsearchandretrieval duringeachrefueling outage,andloosepartsmonitoring areinplacetohelpensurethemaintenance oftubeintegrity duringplantoperation. | |||
Becausenointernals degradation ofconsequence hasbe'enobservedontheunit1SGs,itisexpectedthat,neartermdegradation wouldbelimitedinextent,suchthat'thetubeswillremaincapableofsustaining theconditions ofnormaloperations, including operational transient, designbasisaccidents, externalevents,andnaturalphenomena, permitting theaffectedSGtoperformitssafetyfunction. | |||
Inservice InsectionPlanBecauseof.thependingSGreplacement, itisprojected thattheunit1SGswillundergoonlyonemoreinspection priortothereplacement outage.Basedonthepreviousdiscussions, theupcominginspection planwillcloselymirroractivities performed in1997.Theplannedworkscope issummarized asfollows.A100%CDSscanwillbeperformed onthebobbincoildatafor.evidenceofsupportplate/ligament damage.Indication disposition willbebyMRPCprobe.Notethatthebobbincoilexamination willbeperformed on100%ofthein-service tubing.Foreignobjectsearchandretrieval operations willbeperformed ineachSGtoaccessthetubingandsupportstructure conditions aswellasverifythesludgeconditions withintheSGs.Accessible tubesheet surfacesandtubesatthetopofthetubesheet willbetargetedduringtheinspection. | |||
Duringsludgelanceoperations tobeperformed ineachSG,itwillbeverifiedthatthelancingequipment canbeinsertedwithoutinterference. | |||
Successful installation willprovideverification ofwrapperintegri.ty. | |||
Ifinterference isdetected, thelowerwrappersupportblockswillbevisuallyinspected. | |||
Thewrapperblock'inspection willalsobeconducted ifanyevidenceoftubedamageintheperiphery ofthefirstTSPisdetected. | |||
Inspections willbeperformed onthefirstanduppermost TSPofoneSGtoassessfoulingconditions andidentifyanyevidenceofcorrosion ordamage. | |||
~~Attachment toAEP:NRC:1166AM Page7Basedonsiteinspection experience, noupper-bundleinspections areplannedduringtheupcominginspection. | |||
Shouldtheunit.1SGsbereplacedduringthenextoutage,ourinspection planwillberevisedappropriately. | |||
-UNIT2SGPROGRAMINTERNALS INSPECTION SGDescritionIn1989,thefouroriginalunit2Westinghouse series53.SGswerereplacedwithWestinghouse series54FSGs.Keydesignfeaturesofthereplacement SGs.includethermally treatedalloy690tubing,afulldepthhydraulic expansion atthetube-to-tubesheet | |||
'joint,quatrefoil stainless steelsupportplates,.increased row1U-bendradius,andheattreatedlowrowU-bends.ThenominaltubeODis0.875inches,withanominalwallthickness of0.050inches.RelatedIndustrFindinsAsdiscussed inWCAP-15002, revision1,twelveplantswithseriesD,E,44F,andFSGssuppliedinformation totheWOGconcerning resultsofSGsecondary sideinspections andrelevanttubeinspections forTSPconditions. | |||
Forthemost,part,thefindingsdidnotreportdetection ofseveralmodesofdegradation experienced intheEdFunits.Thereisnoevidenceofpost-chemicalcleaninginspections indicating significant materialloss,.noristhereevidenceofanywrapper,havingdropped.WhileTSPligamentcrackinghasoccurredinunitswithcarbonsteelsupportplateswithdrilledroundholesandflowholes,thereisnoevidenceindicating TSPligamentcrackingorthinningthatisprogressive andcontinuing. | |||
Thefollowingtablesummarizes theapplicable WOGconclusions concerning thesusceptibility ofSGsliketheunit2series54FSGs.tosecondary sideinternals degradation. | |||
TABLE2DEGRADATION TYPELEVELOFSUSCEPTIBILITY ErosionCorrosion: | |||
MoistureSeparator TSPFlowHole/Ligaments FeedRing/8-Nozzles Cracking: | |||
TSPLigaments | |||
***WrapperNearSupports*+Other:NAWrapperDrop** | |||
Attachment toAEP:NRC:1166AM Page8XLNA~*aobservedinsomeSGslowsusceptibility notapplicable variousindication ofdegradation maybeartifacts ofmanufacturing relatedtopatchplateplugweldsand/ordrillingalignment variousWestinghouse | |||
.designfeatures'arebeneficial relativetosomeoftheSGdesignfeaturesofforeignmanufacturers Site-SecificFindinsTheunit2SGswerelastinspected inthefallof1997.Inadditiontothestandardeddy"currenttubei.nspection, othermeasureswereperformed toassuretheintegrity oftheSGinternals. | |||
Theseinspections, coupledwithrelatedfindingsfrom'revious inspections anddesignattributes oftheunit2series54FSGs,demonstrate | |||
.,thattheareasofinterestas,noted"intable2havebeenaddressed withnoabnormalconditions noted.Thefollowing discussion presentstheinternals inspection scopeandfindingsfortheunit21997refueling outage(U2R97).Thefollowing activities wereperformed ineachSG(unlessotherwise noted)duringtheU2R97foreignobjectsearchandretrieval operations. | |||
~Pre-sludge LanceInspection | |||
-Avisualinspection wasperformed toidentifythetubing/sludge, conditions atthetubesheet priortolancing.Thisinspection includedtheannulusanddividerlane.Post-Lance Inspection | |||
-Avisualinspection wasperformed toverifytheeffectiveness ofthesludgeremovalprocessandthegeneraltubesheet/tubing conditions onthetopofthetubesheet. | |||
Areasreviewedconsisted oftheannulus,dividerlaneandaninnerbundlepass.onboththehot.andcoldlegsides.~Sixthand'Seventh TSP.(OneSG)-Avisualinspection reviewedthesixthandseventhTSPstoaccesssludgeconditions andfoulingconditions intheupperregionoftheoneSG.Thepre/post-lance inspection confirmed theeffectiveness ofthesludgeremovaloperations andthegeneralcondition ofthetubingat'hetubesheet. | |||
No,,degradation orsignsofabnormalities werenotedduringtheinspection. | |||
Theuppersupportplateinspection notednosignsofdamagedcomponents ordegradation. | |||
Regarding TSPdamage.orligamentcracking, eddycurrentassessments werenotperformed becausethequatrefoil broachedholesupportplatedesignmakesthistechnique notapplicable fordetecting damage.Noabnormalities weredetectedinthisareaduringtheforeignobjectsearchandretrieval operations thatwouldsuggestdamageofthisnature.Ingeneral,erosion-corrosion induceddegradation isviewedasalowsusceptibility eventbecausetheplatesareconstructed ofstainless steel.Specificinspection ofthewrapperbarrelareawasnotperformed. | |||
However,wrapperconditions didnotaffecttheinstallation ofthe Attachment toAEP:NRC:1166AM Page9sludgelancingequipment thatwasperformed ineachSG.Therefore, itwasconcluded thatthewrapperhadnotslippedormoved.Whilenoinspections wereperformed duiingU2R97,on, theupperinternals, previousinspections havebeenperformed. | |||
Duringthe1994inspection, tenJ-nozzles andthefeedringteesectionofoneSGwereinspected. | |||
Noerosionwasnotedduringtheinspection. | |||
Theoriginal, feedrings/J-nozzles werereplacedwhentheunit2SGswerereplacedin1989.Thereplacement feedrings areconstructed ofextrastrongcarbonsteelandtheJ-nozzles aremade.from,alloy600,whichislesssusceptible toerosiondamagethan.thetypicalcarbonsteelJ-nozzles. | |||
Theseinspections indicatethatdegradation intheupperinternals isaslowprogressing phenomena., | |||
Basedonminimaldegradation to-date,noexaminations werescheduled'for U2R97.SafetAssessment Asnotedintheunit1safetyassessment, thefollowing safetyconcernshavebeenpostulated bytheWOGrelativetotheFrenchSGinternals degradation experience. | |||
~>>Lossofsupportleadingtowearandpossibleprimary-to-secondary leakageorinadequate burstmargins..Moresignificant TSPdeformation duringapostulated LOCAplusSSEevent,resulting inunacceptable SGtubecollapseorsecondary-to-primary inleakage. | |||
Generation ofalooseobjectinthesecondary sideofaSGwhichmayresultintubewearorimpacting andpossiblyprimary-to-secondary leakage.Asdiscussed below,design.features, industryexperience, andvariousstandardpractices aretypically employedto-provideassurance ofSGintegrity andnegatethepotential fortheseconcerns. | |||
Previously discussed U2R97inspection resultsindicateourunit2experiences andpractices aresimilartothatoftheindustry. | |||
Basedonareviewofthetable2information, theonlydegradation typesthatmayoccurdomestically thatwouldlikelyresultinthelossofTSPintegrity areTSPflowhole/ligament erosion-corrosion, TSPligamentcrackingnearthepatchplates,andTSPligamentcrackinginrandomareas.Thereisnoindustryevidenceofpost-chemicalcleaninginspections resulting inthediscovery ofanysignificant materialloss,noristhere.evidence ofanywrapperhavingdropped.NoTSPligamentindications havebeenfoundinsteamgenerators withstainless steelTSPs.Thispopulation includestheunit2SGs.Noincreased susceptibility toligamentcrackingnearthewedgesupportshasbeenidentified intheseriesD,E,44F,andF(unit.2)SGsdesigns.Existingcalculations evaluating theeffectsofLOCAplusSSEloadingsonthetubebundlecontinuetoapplyindetermining whethercertaintubesshouldbeexcludedfromapplication ofthevoltagebasedpluggingcriteria, orwhethercertain.tubesshouldberemovedfromserviceinplantsthatdonotcurrently haveacriteriabutmayhaveSGtubesexperiencing crackingatTSPintersections. | |||
Attachment toAEP:NRC:1166AM Page10Anotheroccurrence resulting fromSGinternaldegradation thatmayaffectaSGinperforming itsintendedsafetyfunctionisthe"potential fortubewearandprimary-to-secondary leakageduetothegeneration ofalooseobjectonthesecondary sideoftheSG.Thismayoccurbecauseoferosion-corrosion ofthemoistureseparators ortheoccurrence ofTSPligamentcracking. | |||
I11a | Ifprimary-to-secondary leakageshouldoccurduetotubewearfromalooseobject,theexpectedconsequences wouldbeboundedbyasingletuberuptureeventandwouldremainwithinthecurrentlicensing basisoftheplant.Itisourpositionthatlooseobjectsshouldberemovedwheneverpossible., | ||
Tubesobservedtohavevisibledamageareeddycurrentinspected andpluggedasnecessary. | |||
ElementsoftheSGprogram,including eddycurrentinspection, foreignobjectsearchandretrieval duringeachrefueling outage,andloosepartsmonitoring areinplacetohelpensurethemaintenance oftubeintegrity duringplantoperation. | |||
Becausenointernals degradation ofconsequence hasbeenobservedontheunit2SGs,itisexpectedthatfuturedegradation wouldbelimitedinextentsuchthatthetubeswillremaincapableofsustaining theconditions ofnormaloperations, including operational transient, designbasisaccidents, externalevents,andnaturalphenomena, permitting theaffectedSGtoperformitssafetyfunction. | |||
Basedontheabove,implementation ofthefollowing inspection planisplannedontheunit2SGstoaddressthevarioustypesofSGsecondary sideinternals degradation thatmayoccurinWestinghouse-designed SGs.Thisplanmaybeamended,pendingtheresultsofadetailedindustryevaluation thatisexpectedtobecompleted bymid-1998. | |||
Inservice InsectionPlanGiventheprimarysideeddycurrent,inspection resulting inaC-1classification andtheabsenceofsecondary sidefindingsduringthelastinspection, noinspection activities areplannedattheendofthecurrentcycle(cycle12).Inspection scopeforthesubsequent outagehasnotbeenfinalized. | |||
However,ataminimum,plannedsecondary sideinspections willbesimilartothoseperformed in1997.Theplannedworkscope issummarized asfollows.Foreignobjectsearchandretrieval operations willbeperformed ineachSGtoaccessthetubingandsupportstructure conditions aswellasverifythesludgeconditions withintheSGs.Accessible tubesheet surfacesandtubesatthetopofthetubesheet willbetargetedduringtheinspection. | |||
Duringsludgelanceoperations tobeperformed ineachSG,itwillbeverifiedthatthelancingequipment canbeinsertedwithoutinterference. | |||
Successful installation willprovideverification ofwrapperintegrity. | |||
Ifinterference isdetected, thelowerwrappersupportblockswillbevisuallyinspected. | |||
Thewrapperblockinspection willalsobeconducted ifevidenceoftubedamageintheperiphery ofthefirstTSPisdetected. | |||
Inspections willbeperformed onthefirstanduppermost TSPofoneSGtoassessfoulingconditions andidentifyevidenceofcorrosion ordamage. | |||
I11a Attachment to.AEP:NRC:1166AM Page11Toverifyconditions intheupperbundlearearemainconsistent withpastinspections, an.inspection willbeperformed onthemoistureseparator unitsandapopulation ofJ-nozzles andthefeedringteeareaofoneSG.CONCLUSIONS Theaforementioned inspection programsare,basedonindustryexperience andoursite-specific inspection findings. | |||
Webelievetheseprogramsareofanaturetoadequately addressconcernsofinternals degradation asnotedinGL97-06.}} |
Revision as of 07:14, 29 June 2018
ML17334B729 | |
Person / Time | |
---|---|
Site: | Cook |
Issue date: | 04/14/1998 |
From: | FITZPATRICK E INDIANA MICHIGAN POWER CO. |
To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
References | |
AEP:NRC:1166AM, GL-97-06, GL-97-6, NUDOCS 9804200484 | |
Download: ML17334B729 (17) | |
Text
CATEGORYREGULATORY INFORMATION DISTRIBUTION SYSTEM"(RIDS)"
4ACCESSION NBR:9804200484 DOC.DATE:
98/04/14NOTARIZED:
YESFACIL:50-315 DonaldC.CookNuclearPowerPlant,Unit1,IndianaM50-316Donald.C.CookNuclearPowerPlant,Unit2,IndianaMAUTH;NAME AUTHORAFFILIATION FITZPATRICK,E.
IndianaMichiganPowerCo.RECIP.NAME RECIPIENT AFFILIATION DocumentControlBranch(Document ControlDesk)DOCKET¹0500031505000316
SUBJECT:
ForwardsresponsetoGL97-06,"Degradation ofSGIntervals.
DISTRIBUTION CODE:ZOOIDCOPIESRECEIVED:,LTR iENCLiSIZE:TITLE:ORSubmittal:
GeneralDistribution NOTES:RECIPIENT IDCODE/NAME PD3-3LASTANG,JCOPIESLTTRENCL,1111RECIPIENT IDCODE/NAME PD3-3PDCOPIESLTTRENCL11EINTERNAL.-ENT---1NRR/DE/EMCB NRR/DSSA/SPLB NUDOCS-ABSTRACT EXTERNAL:
NOAC11111111NRR/DE/ECGB/A NRR/DRCH/HICB NRR/DSSA/SRXB OGC/HDS2NRCPDR1111111011DNOTETOALL"RIDS"RECIPIENTS:
PLEASEHELPUSTOREDUCEWASTE.TOHAVEYOURNAMEORORGANIZATION REMOVEDFROMDISTRIBUTION LISTSORREDUCETHENUMBEROFCOPIESRECEIVEDBYYOUORYOURORGANIZATION, CONTACTTHEDOCUMENTCONTROLDESK(DCD)ONEXTENSION 415-2083TOTALNUMBEROFCOPIESREQUIRED:
LTTR13ENCL12 IndianaMichigan~PowerCompany500CircleDriveBuchanan, Ml491071395 IlfNENANAMICHIGANPQWMApril14,1998AEP:NRC:1166AM DocketNos.:50-31550-316U.S.NuclearRegulatory Commission ATTN:DocumentControlDeskMailStop0-Pl-17Washington, D.C.20555-0001 Gentlemen:
DonaldC.CookNuclearPlantUnits1and2RESPONSETONRCGENERICLETTER(GL)97-06DEGRADATION OFSTEAMGENERATOR INTERNALS Thisletteranditsattachment provideinformation requested inGL97-06,concerning steamgenerator internals degradation.
Sincerely, pugE.E.Fitzpatrick VicePresident J'SWORNTOANDSUBSCRIBED BEFOREMEgATHIS~DAYOF~/Z.,1998NotaryPublic/.Sd//vlbAttachment Z.A.AbramsonA.B.BeachMDEQ-DW&RPDNRCResidentInspector 8.R.SampsonUNDALBOEI.CKENotaryPublic,BerrienCounty,MlMCommission ExpiresJanuary21,200I2001yQoI9804200484 9804l4PDRADOCK050003iSpPDR ATTACHMENT TOAEP:NRC:1166AMRESPONSETONRCGENERICLETTER97-06DEGRADATION OFSTEAMGENERATOR INTERNALS 5.~'Attachment toAEP:NRC:1166AM Page1INTRODUCTION Genericletter(GL)97-06wasissuedto'alertaddressees toforeignanddomesticfindingsofdamagetosteamgenerator (SG)internals, emphasize theimportance ofperforming comprehensive examinations ofSGinternals, andrequestinformation thatwillenabletheNRCstafftoverifytheinternals ofCookNuclearPlant'sSGsconform-tothecurrentlicensing basis.BACKGROUND ANDDESCRIPTION OFCIRCUMSTANCES Frenchauthorities havereportedvariousSGtubesupportplate(TSP)damagemechanisms.
Damagehas.-includedwastageintheuppermost TSPduetomisapplication of.achemicalcleaningprocess,brokenTSPligaments resulting frominadequate clearance for,differential thermalexpansion, andTSPwastageatvariouselevations apparently involving acorrosion orerosion-corrosion mechanism ofundetermined origin.Otherins'tances ofinternals degradation includewrapperdrop/cracking ataforeignutilitythatissuspected tohavebeencausedbyseverecoolingtransients, andinstances oferosion-corrosion ofeggcratesupportsinuntubedareasinitiated "byunknowncausesthatoccurredatadomesticfacility.
Theseinstances.
highlight thepotential fordegradation mechanisms thatmayleadtoTSPandtubewrapperdamage..Asaresultofthisconcern,GL97-06requests:
1.Discussion ofanyprogramsinplacetodetectdegradation ofSGinternals andadescription ofinspection plans(scope,frequency, methods,andequipment)
.Thisdiscussion should.address.thefollowing information foreachfacility.
a~b.C.Whetherinspection recordshavebeenreviewedforindications ofTSPsignalanomalies fromeddycurrenttestingofSGtubes'hat maybeindicative ofsupportplateorligamentdamage.Whethervisualorvideocamerainspections havebeenperformed onthesecondary sidetogaininformation onthecondition ofSGinternals (e.g.,supportplates,tubebundlewrappers, etc.).Whetherdegradation, ofSGinternals hasbeendetected, andhowitwasassessedanddispositioned.
2.Intheeventnoprogramisinplacetodetectinternals degradation, provideadiscussion orjustification fordevelopment ofaprogramorwhysuchaprogramisnot:needed..
PriortoissuanceofthisGL,Westinghouse OwnersGroup(WOG),ElectricPowerResearchInstitute (EPRI),andNuclearEnergyInstitute (NEI)developed anactionplantoassessthesusceptibility ofSGsecondary "sidedegradation.
Weintendtofollowtheindustryactionplanasmodifiedbyoursite-specific experience.
Includedintheactionplanisarequirement tounderstand thecausalfactorsinvolvedinthedegradation experienced intheFrenchunits.Thisinformation iscapturedinEPRIreportGC-109558, "SteamGenerator Internals Degradation:
Attachment toAEP:NRC:1166AM Page2ModesofDegradation DetectedinEdFUnits".Thisreportwassubmitted'o theNRCviaanNEZletter,datedDecember19,1997.-WOGhasreviewedEPRZGC-109558 relativetothe,designofseries51SGsanddetermined limitedpotential susceptibility.
Forplantswithseries51SGs,thisconclusion isdocumented inWCAP-15002, revision1,."Evaluation ofEdFSteamGenerator Internals Degradation
-ImpactofCausalFactorsonWestinghouse
.51SeriesSteamGenerators",
December1997.Theseries51SGsarethemostsimilarmodelSGtothatoftheElectricith deFrance(EdF).unitsandareinstalled inunit1.WCAP-.15002, revision1,documents visualinspections performed attheseries51SGplants.Ztwasconcluded
.thatthenumber.ofplantsthathavebeeninspected andtheinspection resultsdemonstrate thatthecausalfactorsidentified byEdFdonotjeopardize thecontinued operability ofWestinghouse series51SGs.Thisconclusion issupported bythe-capability ofeddycurrentinspections to,detect.
detrimental effectsontubingduetowearcausedbyTSPligamentdegradation, loose'parts, andsecondary side'lowdistribution changes.Foreignobjectsearchandretrieval
~effortsaretypically conducted asstandardpracticetodiscoveror~retrievelooseparts,thuslimitingthepotential fordamage.AresponsetoGL97-06hasbeencompleted forunit1addressing thesusceptibility oftheunit1SGstointernals degradation, specificunit1inspection practices andrecentinspection results,along,withadiscussion ofsubsequent plantoperation withpotential SGinternals degradation ofthetypeexperienced;in theFrenchunits(andothertypesofdegradation experienced domestically)
~Thisdiscussion beginsinthe"UNIT1SGPROGRAM(INTERNALS 1NSPECTION)
"sectionofthisattachment.
BecauseadetailedWestinghouse evaluation hasnotbeenperformed
,forourunit2SGs,inspection recommendations have.beenidentified onaninterimbasis.Industryrepresentatives haveindicated that'valuations shouldbecompleted byMay1998,andtheresultswillbefactoredintotheunit2SGprogram.Assuch.theresponseto'tem1forunit,2,whichisdetailedinthe"UNIT2SGPROGRAM(INTERNALS INSPECTION)"
sectionofthisattachment, maybemodifiedinthefutureasdictatedbytheresultsofthependingevaluation.
UNIT1SGPROGRAMINTERNALS INSPECTION SGDescritionUnit1containsfourWestinghouse series51SGsthatwereplacedinservicein1975.Keydesignfeaturesincludealloy600millannealedtubing,apartialdepthhardrollexpansion atthetube-to-tubesheet joint,anddrilledcarbonsteelsupportplates.Thenominaltubeoutsidediameter(OD)is0.875incheswithanominalwallthickness of0.050inches.Thefourunit1SGsarepresently scheduled forreplacement intheyear2000.
Attachment to=AEP:NRC:1166AMPage3RelatedIndustFindinsAsdiscussed inWCAP-15002, revision1,eighteenplantswithseries51SGssuppliedinformation totheWOGconcerning resultsofSGsecondary sideinspections andrelevanttubeinspections forTSPconditions.
Theseresultsdidnotreportdetection ofseveralmodesofdegradation experienced intheEdFunits.Thereis-noevidenceofpost-chemical cleaninginspections indicating any.significant materialloss,noristhereevidenceofwrapperhavingdropped.WhileTSPligamentcrackinghasoccurredinunitswithcarbonsteelsupport,plateswithdrilled'ound holesand.flow'oles,thereisnoevidenceindicating TSPligamentcrackingorthinningthatisprogressive andcontinuing.
Thefollowingtablesummarizes theapplicable WOGconclusions concerning thesusceptibility ofSGslikeouiunit1series51SGstosecondary sideinternals degradation.
TABLE1DEGRADATION TYPEErosionCorrosion:
MoistureSeparator TSPFlowHole/Ligaments FeedRing/8-Tubes Cracking:
TSPLigaments NearWedges**TSPLigaments NearPatchPlatesCarbonSteelTSPLigaments (randomareas)LEVELOFSUSCEPTIBILITY NNX*"Other:WrapperNearSupports**NWrapperDrop**NX~oservexnsomeSGsN=notsusceptible toEdFcasualfactorsL~lowsusceptibility toEdFcasualfactors*~variousindication ofdegradation maybeartifacts ofmanufacturing relatedtopatchplateplugweldsand/ordrillingalignment
- variousWestinghouse designfeatures'rebeneficial relativetosomeoftheSGdesignfeaturesofforeignmanufacturers Site-SecificFindinsTheunit1SGswerelastinspected inthespringof1997.In~additiontothestandardeddycurrenttubeinspection, additional measureswereperformed toassuretheintegrity oftheSGinternals.
Theseinspections, coupledwithrelatedfindingsfrompreviousinspections, demonstrate thatthe'reasnotedintable1havebeenperiodically examinedwithnoabnormalconditions
.noted.
et~~Attachment toAEP:NRC:1166AM Page4Thefollowing discussion presentstheinternals inspection scopeandfindingsfortheunit11997refueling outage(U1R97).A100%computerdatascreening (CDS)sortwasperformed onthelowfrequency bobbincoildatafromeachSGtoaddressthepotential forTSPdamageorligamentcracking.
Indications ofpossibleligamentdamagewereexaminedusingamotorized rotatingpancakecoil(MRPC)probe.Theindications weresubsequently dispositioned ashavingnodegradation found(NDF)ordetermined tobealignedwiththepatchplate,thusyieldinga"false"indication.
Onetube,R39/C22inSG11wasnotedtohavea0.78'oltMRPCindication attheseventhhotlegsupportplate,nearthewedgelocation.
Researchofthepreviousoutagedataconfirmed thiscondition hasbeenpresentforatleastthreeyears.Thisindication willcontinuetobemonitored duringfutureeddycurrentinspections.
Regarding theperformance ofsecondary sidevisualinspections, thefollowing activities wereperformed ineachSG(unlessotherwise noted)duringtheU1R97foreignobjectsearchandretrieval operations:
~Pre-Sludge LanceInspection
-Avisualinspection wasperformed toidentifythetubing/sludge conditions atthetubesheet prior,tolancing.Thisinspection includedtheannulusanddividerlane.~Post-Lance Inspection
-Avisualinspection wasperformed toverifytheeffectiveness ofthesludgeremovalprocessandgeneraltubesheet/tubing conditions atthetopofthetubesheet.
Theinspection consisted oftheannulus,dividerlaneandaninnerbundlepassinboththehotandcoldlegsides..WrapperBarrelInspection
-Thisvisualinspection wasperformed to.verifytheintegrity ofthewrapperbarrelsupportstructure.
FirstTubeSupportLigament(2,SGs)-Thisinspection involvedavisualreviewofthefirstTSPbetweenthewrapperbarrelandthetubebundledirectlyabovethehandhold:
Thepre/post-lance inspections confirmed" theeffectiveness ofthesludgeremovaloperations andthegeneralcondition ofthetubingatthetubesheet.
Noanomalies orloosepartswerenotedbytheinspection.
Thewrapperbarrelinspection producednoevidenceofslippageormovement.
Additional verification oftheintegrity ofthesupportstructure wasprovidedbythesuccessful installation ofthesludgelanceequipment.
Thelackofanyinterferences'uring thisinstallation providedassurance thatnodeformation had~occurred.
Inspections ofthefirstsupportplateidentified nosignsofanomalies ineitherofthetwoSGsinspected.
Whilenoinspections wereperformed duringU1R97ontheupperinternals, previousinspections haveidentified onlyminimalwear.'uring the1995inspection, fifteenJ-nozzles andthefeedringteesectionofoneSG.wereinspected.
TheJ-nozzles weretermedtobeinverygoodcondition, withnothinningobservedonthethermallinerandtee.Priortothe1995inspection, extensive inspections wereconducted in1989inwhichvisualinspections wereconducted
.ontheJ-nozzles ofthreeSGs.Thevisualexamination ofoneof l~
Attachment toAEP:NRC:1166AM Page5theseSGswassupplemented byanaddedultrasonic test(UT)examination.
NeitherthevisualorUTexaminations notedanyapparentdegradation.
Theseinspections haveindicated thatdegradation intheupperinternals isaslowprogressing phenomena.
Basedonminimaldegradation todateandthenearendoflifefortheseSGs,noexaminations wereperformed duringU1R97.SafetAssessment Thefollowing safetyconcernshavebeenpostulated byWOGrelativetotheFrenchSGinternals degradation experience.
~Lossofsupportinthetube.bundleleadingtowear,andpossibleprimary-to-secondary leakageorinadequate burstmargins.Increased TSPdeformation duringapostulated loss-of-coolant accident(LOCA)plussafeshutdownearthquake (SSE)'event,resulting inunacceptable SGtubecollapseorsecondary-to-primaryinleakage.
i~Generation ofalooseobjectinthesecondary sideofaSGthatmayresultintubewearorimpacting, andpossiblyprimary-to-secondary leakage.Asdiscussed below,industryexperience andvariousstandardpractices aretypically employedtoprovideassurance ofSGintegrity andnegatethepotential forthese'oncerns.
Asevidenced fromthepreviously discussed U1R97inspection results,ourunit1experiences andpractices mirrorthatoftheindustry.
Basedon'reviewofthetable1information, theonlydegradation typesthatmayoccurdomestically thatcouldresult,inthelossofTSPintegrity areTSPflowhole/ligament erosion-corrosion, TSPligamentcrackingnearthepatchplates,andTSPligamentcrackinginrandomareas.Thereisnoindustryevidenceofpost-chemical cleaninginspections indicating.
significant materialloss,noris'thereevidenceofanywrapperhavingdropped.WhileTSP'ligament crackinghasoccurredinunitswithcarbonsteel.supportplateswithdrilledroundholesandflowholes,thereisnoevidenceindicating TSPligamentcrackingorthinningthatisprogressive andcontinuing.
Utilities withseries51SGswithcarbon'steelsupportplatesinspectasignificant percentage ofSGtubeseveryoutagewithabobbincoilprobe(unit1inspects100%).Ifsectionsofthetubesupportweremissing,itwouldbereadilydetectable becauseofalackofeddycurrent.responseattheTSPelevation.
Thereisnoincreased susceptibility toligamentcrackingnearthewedgesupportsintheseries51SGdesign.Eithertherearenoflowholesextending totheperiphery
'atthewedgelocations, or=.thewedgesarenotweldedtotheTSPs,asisthecasewiththeEdF51MSG.Existingcalculations evaluating theeffectsofLOCAplusSSEloadingsonthetubebundlecontinuetoapplyindetermining whethercertaintubesshouldbeexcludedfromapplication ofthevoltagebasedpluggingcriteria, orwhethercertaintubesshouldberemovedfromserviceinplantsthatdonotcurrently havethecriteria, butmayhaveSGtubesexperiencing
~crackingatTSPintersections.
Attachment toAEP:NRC:1166AM Page6Anotheroccurrence resulting fromSGinternaldegradation thatmay.affectaSGinperforming itsintendedsafetyfunctionisthepotential fortubewearandprimary-to secondary leakageduetothegeneration ofalooseobjectonthesecondary sideoftheSG.Thismayoccurduetoerosion-corrosion ofthemoistureseparators, feedring/J-nozzle, orTSPflowholes,ortheoccurrence ofTSPligamentcracking.
Ifprimary-to-secondary leakageshouldoccurbecauseoftubewearfromalooseobject,theexpectedconsequences wouldbeboundedbyasingletuberuptureeventand,therefore, wouldremainwithinthecurrentlicensing basisoftheplant.Itisourpositionthatlooseobjectsshouldberemovedwheneverpossible.
Tubesobservedtohavevisibledamageareeddycurrentinspected andpluggedasnecessary.
ElementsoftheSGprogram,includi'ng eddycurrentinspection, foreignobjectsearchandretrieval duringeachrefueling outage,andloosepartsmonitoring areinplacetohelpensurethemaintenance oftubeintegrity duringplantoperation.
Becausenointernals degradation ofconsequence hasbe'enobservedontheunit1SGs,itisexpectedthat,neartermdegradation wouldbelimitedinextent,suchthat'thetubeswillremaincapableofsustaining theconditions ofnormaloperations, including operational transient, designbasisaccidents, externalevents,andnaturalphenomena, permitting theaffectedSGtoperformitssafetyfunction.
Inservice InsectionPlanBecauseof.thependingSGreplacement, itisprojected thattheunit1SGswillundergoonlyonemoreinspection priortothereplacement outage.Basedonthepreviousdiscussions, theupcominginspection planwillcloselymirroractivities performed in1997.Theplannedworkscope issummarized asfollows.A100%CDSscanwillbeperformed onthebobbincoildatafor.evidenceofsupportplate/ligament damage.Indication disposition willbebyMRPCprobe.Notethatthebobbincoilexamination willbeperformed on100%ofthein-service tubing.Foreignobjectsearchandretrieval operations willbeperformed ineachSGtoaccessthetubingandsupportstructure conditions aswellasverifythesludgeconditions withintheSGs.Accessible tubesheet surfacesandtubesatthetopofthetubesheet willbetargetedduringtheinspection.
Duringsludgelanceoperations tobeperformed ineachSG,itwillbeverifiedthatthelancingequipment canbeinsertedwithoutinterference.
Successful installation willprovideverification ofwrapperintegri.ty.
Ifinterference isdetected, thelowerwrappersupportblockswillbevisuallyinspected.
Thewrapperblock'inspection willalsobeconducted ifanyevidenceoftubedamageintheperiphery ofthefirstTSPisdetected.
Inspections willbeperformed onthefirstanduppermost TSPofoneSGtoassessfoulingconditions andidentifyanyevidenceofcorrosion ordamage.
~~Attachment toAEP:NRC:1166AM Page7Basedonsiteinspection experience, noupper-bundleinspections areplannedduringtheupcominginspection.
Shouldtheunit.1SGsbereplacedduringthenextoutage,ourinspection planwillberevisedappropriately.
-UNIT2SGPROGRAMINTERNALS INSPECTION SGDescritionIn1989,thefouroriginalunit2Westinghouse series53.SGswerereplacedwithWestinghouse series54FSGs.Keydesignfeaturesofthereplacement SGs.includethermally treatedalloy690tubing,afulldepthhydraulic expansion atthetube-to-tubesheet
'joint,quatrefoil stainless steelsupportplates,.increased row1U-bendradius,andheattreatedlowrowU-bends.ThenominaltubeODis0.875inches,withanominalwallthickness of0.050inches.RelatedIndustrFindinsAsdiscussed inWCAP-15002, revision1,twelveplantswithseriesD,E,44F,andFSGssuppliedinformation totheWOGconcerning resultsofSGsecondary sideinspections andrelevanttubeinspections forTSPconditions.
Forthemost,part,thefindingsdidnotreportdetection ofseveralmodesofdegradation experienced intheEdFunits.Thereisnoevidenceofpost-chemicalcleaninginspections indicating significant materialloss,.noristhereevidenceofanywrapper,havingdropped.WhileTSPligamentcrackinghasoccurredinunitswithcarbonsteelsupportplateswithdrilledroundholesandflowholes,thereisnoevidenceindicating TSPligamentcrackingorthinningthatisprogressive andcontinuing.
Thefollowingtablesummarizes theapplicable WOGconclusions concerning thesusceptibility ofSGsliketheunit2series54FSGs.tosecondary sideinternals degradation.
TABLE2DEGRADATION TYPELEVELOFSUSCEPTIBILITY ErosionCorrosion:
MoistureSeparator TSPFlowHole/Ligaments FeedRing/8-Nozzles Cracking:
TSPLigaments
- WrapperNearSupports*+Other:NAWrapperDrop**
Attachment toAEP:NRC:1166AM Page8XLNA~*aobservedinsomeSGslowsusceptibility notapplicable variousindication ofdegradation maybeartifacts ofmanufacturing relatedtopatchplateplugweldsand/ordrillingalignment variousWestinghouse
.designfeatures'arebeneficial relativetosomeoftheSGdesignfeaturesofforeignmanufacturers Site-SecificFindinsTheunit2SGswerelastinspected inthefallof1997.Inadditiontothestandardeddy"currenttubei.nspection, othermeasureswereperformed toassuretheintegrity oftheSGinternals.
Theseinspections, coupledwithrelatedfindingsfrom'revious inspections anddesignattributes oftheunit2series54FSGs,demonstrate
.,thattheareasofinterestas,noted"intable2havebeenaddressed withnoabnormalconditions noted.Thefollowing discussion presentstheinternals inspection scopeandfindingsfortheunit21997refueling outage(U2R97).Thefollowing activities wereperformed ineachSG(unlessotherwise noted)duringtheU2R97foreignobjectsearchandretrieval operations.
~Pre-sludge LanceInspection
-Avisualinspection wasperformed toidentifythetubing/sludge, conditions atthetubesheet priortolancing.Thisinspection includedtheannulusanddividerlane.Post-Lance Inspection
-Avisualinspection wasperformed toverifytheeffectiveness ofthesludgeremovalprocessandthegeneraltubesheet/tubing conditions onthetopofthetubesheet.
Areasreviewedconsisted oftheannulus,dividerlaneandaninnerbundlepass.onboththehot.andcoldlegsides.~Sixthand'Seventh TSP.(OneSG)-Avisualinspection reviewedthesixthandseventhTSPstoaccesssludgeconditions andfoulingconditions intheupperregionoftheoneSG.Thepre/post-lance inspection confirmed theeffectiveness ofthesludgeremovaloperations andthegeneralcondition ofthetubingat'hetubesheet.
No,,degradation orsignsofabnormalities werenotedduringtheinspection.
Theuppersupportplateinspection notednosignsofdamagedcomponents ordegradation.
Regarding TSPdamage.orligamentcracking, eddycurrentassessments werenotperformed becausethequatrefoil broachedholesupportplatedesignmakesthistechnique notapplicable fordetecting damage.Noabnormalities weredetectedinthisareaduringtheforeignobjectsearchandretrieval operations thatwouldsuggestdamageofthisnature.Ingeneral,erosion-corrosion induceddegradation isviewedasalowsusceptibility eventbecausetheplatesareconstructed ofstainless steel.Specificinspection ofthewrapperbarrelareawasnotperformed.
However,wrapperconditions didnotaffecttheinstallation ofthe Attachment toAEP:NRC:1166AM Page9sludgelancingequipment thatwasperformed ineachSG.Therefore, itwasconcluded thatthewrapperhadnotslippedormoved.Whilenoinspections wereperformed duiingU2R97,on, theupperinternals, previousinspections havebeenperformed.
Duringthe1994inspection, tenJ-nozzles andthefeedringteesectionofoneSGwereinspected.
Noerosionwasnotedduringtheinspection.
Theoriginal, feedrings/J-nozzles werereplacedwhentheunit2SGswerereplacedin1989.Thereplacement feedrings areconstructed ofextrastrongcarbonsteelandtheJ-nozzles aremade.from,alloy600,whichislesssusceptible toerosiondamagethan.thetypicalcarbonsteelJ-nozzles.
Theseinspections indicatethatdegradation intheupperinternals isaslowprogressing phenomena.,
Basedonminimaldegradation to-date,noexaminations werescheduled'for U2R97.SafetAssessment Asnotedintheunit1safetyassessment, thefollowing safetyconcernshavebeenpostulated bytheWOGrelativetotheFrenchSGinternals degradation experience.
~>>Lossofsupportleadingtowearandpossibleprimary-to-secondary leakageorinadequate burstmargins..Moresignificant TSPdeformation duringapostulated LOCAplusSSEevent,resulting inunacceptable SGtubecollapseorsecondary-to-primary inleakage.
Generation ofalooseobjectinthesecondary sideofaSGwhichmayresultintubewearorimpacting andpossiblyprimary-to-secondary leakage.Asdiscussed below,design.features, industryexperience, andvariousstandardpractices aretypically employedto-provideassurance ofSGintegrity andnegatethepotential fortheseconcerns.
Previously discussed U2R97inspection resultsindicateourunit2experiences andpractices aresimilartothatoftheindustry.
Basedonareviewofthetable2information, theonlydegradation typesthatmayoccurdomestically thatwouldlikelyresultinthelossofTSPintegrity areTSPflowhole/ligament erosion-corrosion, TSPligamentcrackingnearthepatchplates,andTSPligamentcrackinginrandomareas.Thereisnoindustryevidenceofpost-chemicalcleaninginspections resulting inthediscovery ofanysignificant materialloss,noristhere.evidence ofanywrapperhavingdropped.NoTSPligamentindications havebeenfoundinsteamgenerators withstainless steelTSPs.Thispopulation includestheunit2SGs.Noincreased susceptibility toligamentcrackingnearthewedgesupportshasbeenidentified intheseriesD,E,44F,andF(unit.2)SGsdesigns.Existingcalculations evaluating theeffectsofLOCAplusSSEloadingsonthetubebundlecontinuetoapplyindetermining whethercertaintubesshouldbeexcludedfromapplication ofthevoltagebasedpluggingcriteria, orwhethercertain.tubesshouldberemovedfromserviceinplantsthatdonotcurrently haveacriteriabutmayhaveSGtubesexperiencing crackingatTSPintersections.
Attachment toAEP:NRC:1166AM Page10Anotheroccurrence resulting fromSGinternaldegradation thatmayaffectaSGinperforming itsintendedsafetyfunctionisthe"potential fortubewearandprimary-to-secondary leakageduetothegeneration ofalooseobjectonthesecondary sideoftheSG.Thismayoccurbecauseoferosion-corrosion ofthemoistureseparators ortheoccurrence ofTSPligamentcracking.
Ifprimary-to-secondary leakageshouldoccurduetotubewearfromalooseobject,theexpectedconsequences wouldbeboundedbyasingletuberuptureeventandwouldremainwithinthecurrentlicensing basisoftheplant.Itisourpositionthatlooseobjectsshouldberemovedwheneverpossible.,
Tubesobservedtohavevisibledamageareeddycurrentinspected andpluggedasnecessary.
ElementsoftheSGprogram,including eddycurrentinspection, foreignobjectsearchandretrieval duringeachrefueling outage,andloosepartsmonitoring areinplacetohelpensurethemaintenance oftubeintegrity duringplantoperation.
Becausenointernals degradation ofconsequence hasbeenobservedontheunit2SGs,itisexpectedthatfuturedegradation wouldbelimitedinextentsuchthatthetubeswillremaincapableofsustaining theconditions ofnormaloperations, including operational transient, designbasisaccidents, externalevents,andnaturalphenomena, permitting theaffectedSGtoperformitssafetyfunction.
Basedontheabove,implementation ofthefollowing inspection planisplannedontheunit2SGstoaddressthevarioustypesofSGsecondary sideinternals degradation thatmayoccurinWestinghouse-designed SGs.Thisplanmaybeamended,pendingtheresultsofadetailedindustryevaluation thatisexpectedtobecompleted bymid-1998.
Inservice InsectionPlanGiventheprimarysideeddycurrent,inspection resulting inaC-1classification andtheabsenceofsecondary sidefindingsduringthelastinspection, noinspection activities areplannedattheendofthecurrentcycle(cycle12).Inspection scopeforthesubsequent outagehasnotbeenfinalized.
However,ataminimum,plannedsecondary sideinspections willbesimilartothoseperformed in1997.Theplannedworkscope issummarized asfollows.Foreignobjectsearchandretrieval operations willbeperformed ineachSGtoaccessthetubingandsupportstructure conditions aswellasverifythesludgeconditions withintheSGs.Accessible tubesheet surfacesandtubesatthetopofthetubesheet willbetargetedduringtheinspection.
Duringsludgelanceoperations tobeperformed ineachSG,itwillbeverifiedthatthelancingequipment canbeinsertedwithoutinterference.
Successful installation willprovideverification ofwrapperintegrity.
Ifinterference isdetected, thelowerwrappersupportblockswillbevisuallyinspected.
Thewrapperblockinspection willalsobeconducted ifevidenceoftubedamageintheperiphery ofthefirstTSPisdetected.
Inspections willbeperformed onthefirstanduppermost TSPofoneSGtoassessfoulingconditions andidentifyevidenceofcorrosion ordamage.
I11a Attachment to.AEP:NRC:1166AM Page11Toverifyconditions intheupperbundlearearemainconsistent withpastinspections, an.inspection willbeperformed onthemoistureseparator unitsandapopulation ofJ-nozzles andthefeedringteeareaofoneSG.CONCLUSIONS Theaforementioned inspection programsare,basedonindustryexperience andoursite-specific inspection findings.
Webelievetheseprogramsareofanaturetoadequately addressconcernsofinternals degradation asnotedinGL97-06.