ML17329A091
| ML17329A091 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 01/31/1991 |
| From: | RAO G V, RISHEL R D WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML17329A090 | List: |
| References | |
| MT-MNA-035(91), MT-MNA-35(91), NUDOCS 9107230292 | |
| Download: ML17329A091 (46) | |
Text
MT-MNA-035 (91)9i07230292 9i07i5PDRADOCK050003ihPPDRMETALLURGICAL INVESTIGATION OFWALLTHINNINGANDLEAKAGEOFTHEBMITHIMBLETUBINGATD.C.COOKUNIT2GuttiV.RaoJanuary1991n-Approved:
R.D.Rishel,ManagerMetallurgical 5Nondestructive AnalysisWorkperformed undershoporderAIAP-138WESTINGHOUSE ELECTRICCORPORATION NuclearandAdvancedTechnology DivisionP.0.Box2728Pittsburgh, Pennsylvania 15230-2728 1990Westinghouse ElectricCorp.5069s:10/012991 TABLEOFCONTENTS1INTRODUCTION 2EXAMINATIONS ANDTESTS2.1SurfaceExaminations 2.2Metal1ographicExaminations 2.3NearMorphology Examinations bySurfaceReplication 2.4HardnessMeasurements 2.5FuelNozzleGeometryExaminations 3RESULTSANDDISCUSSION 44CONCLUSIONS 5069s/013091:
10 LISTOFTABLESTableNo.TitleSummaryofHardnessMeasurements S069s/013091:10 00 FigureNoLISTOFILLUSTRATIONS TitleSchematic Representation oftheReactorVesselBottomMountedInstrumentation ThimbleTubeSystem2.1Macrophotograph Illustrating theAs-Received Condition oftheLeaked(Perforated)
ThimbleTube"C-7"2.2Macrophotograph Illustrating theAs-Received Appearance ofSeverelyHornThimbleTube"A-9"2.3Metallographic Examination ResultsofaTransverse SectionThroughtheLeakRegionoftheThimbleTube"C-7"Metallography ResultsofanAxialSectionThroughtheSeverlyHornRegionoftheThimbleTube"A-9"2.5ScanningElectronMacrograph Illustrating theOverviewofthePlasticReplicaoftheHornRegioninThimbleTubeC-7Identifying Locations andMicrograph NumbersWhereHigherMagnification SEMwasConducted.
2,6ScanningElectronMacrograph ofthePlasticReplicaTakenfromtheHornRegionofThimbleTube"A-9"Identifying Locations andMicrograph NumbersWhereHigherMagnification SEMwasConducted.
2.7ScanningElectronMacrograph ofthePlasticReplicaTakenfromtheWornRegionoftheThimbleTubeC-7,Identifying Locations WhereNigherMagnification SEMwasConducted.
2.8SEMPhotomicrographs Illustrating theSurfaceMorphology oftheUnscarred andScarredRegionsinSampleC-7.5069s/013091 10 SEMPhotomicrographs Illustrating theSurfaceMorphology oftheUnscarred and.ScarredRegionsinSampleC-7.SEMPhotomicrographs Illustrating theWearMorphology SeenatLocations 39and41Identi.fied (inFigure2.5)ontheReplicaFrom"C-7"2.11Higher'Magnification SEMPhotomicrographs Illustrating theWearMorphology SeenatLocation39oftheReplicafromC-7(Figure2.10).2.12SEMPhotomicrographs Illustrating theWearMorphology Seen'tLocations 31,33and34ofReplica(Figure2.5)fromC-7Sample.2.13SEMPhotomicrographs Illustrating theHearMorphology SeenatLocations 19,22and24(Figure2.5)oftheReplicaTakenfromSampleC-7.SEMPhotomicrographs Illustrating theWearMorphology SeenatLocations 29and30(Figure2-5),ClosetotheThroughHallLeakageRegionoftheSampleC-7.2.15SEMPhotomicrographs Illustrating theWearMorphology SeenatLocations 8,9,and10(Figure2.6)oftheReplicaFromA-9Sample.2.16SEMPhotomicrographs Illustrating theWearMorphology SeenatLocations 21,22and23(Figure2.6)oi'heReplicafromSampleA-9.2.17SEMPhotomicrographs Illustrating theHearMorphology SeenatLocations 24and25(Figure2.6)oftheReplicafromSampleA-9.Schematic Representation ofFuelBundl.eBottomNozzle.5069s/013091:101V
~J-00 SECTION
1.0INTRODUCTION
Thisreportsummarizes thefindingsofthemetallurgical investigation ofthewearandleakageofthereactorvesselbottommountedinstrumentation (BMI)thimbletubesatD.C.CookUnit2.Thereactorvesselinstrumentation thimbleisasmalltubingwithanoutsidediameterrangingfrom0.300in.to0.385in.andawallthickness rangingfrom0.05in.to0.06in.respectively, depending ontheplant.Thethimbletubingismadeof'coldworked316stainless steelmaterialalthoughmostrecentlycoldworked316Lgradehasbeenappliedtolimitthecobaltcontent.Aschematic representation ofthereactorvesselBHIthimblesystemisillustrated inFigure1.1.Thecurrentreportsummarizes theevaluations andresultsofoneseverelywornandoneleakythimbletubefromD.C.CookUnit2.Theevaluations, conducted attheHestinghouse hotcellfacilities centeredontwo,approximately threefeetlongthimbletubesegmentscontaining thewearaffectedregionsandincludedthefollowing majortasks:oSurfaceexaminations oHetallographic examinations oDetailedwearmorphology evaluations, andoHardnessmeasurements Theoverallpurposeoftheinvestigation wastoestablish themechanism andcauseofthethimbletubeleakageandfurthertodevelopinformation thatwouldbehelpfulfortakingcorrective actions.5069s:10/020591 oo0 SECTION2.0TESTSANDEXAMINATIONS 2'urfaceExaminainTheas-received condition ofthethimbletubesampleswereexaminedvisuallyandbylowmagnification lightopticalmicroscopy forevidenceofcracks,wear,surfaceattackorotherdamageanddeposits.
Theresultsofthesurfaceexamination weredocumented bythemacrophotographs illustrated inFigures2.1and2.2.2.2Mt11rhiExamininsMetallographic examinations wereconducted onthethimbletubesamplessectioned axiallyandtransversely throughthewornand/orleakregionstoexaminethelocationandextentofweardamage,thewearscargeometryandthematerialmicrostructure.
Theresultsofthemetallurgical examinations areillustrated inFigures2.3and2.4.2.3WarMrh1ExmintinrfRlitinPriortosectioning formetallography, thewornandleakregionofthethimbletubesampleswerepreparedforsurfacereplication andplasticreplicaswerepulledfromtheaffectedregion.Thereplicaswerepreparedbygoldsputtering undervacuumandwereexaminedbyscanningelectronmicroscopy to'stablish themorphology andmechanism oftheweardamage.Theresultsofthes'eexaminations areillustrated inFigures2.5through2.17.2.4HrnMrmnHardnesstraversemeasurements wereconducted onpolishedsectionsofthewornregionofthethimbletubestoexaminethe'natureofdeformation andworkhardening associated withtheweardamage.Theresultsofthehardnesstraversemeasurements aresummarized inTable1,5069s:10/020591 00 2.5FuelNozz1mtrExamintinTheinsidediametersurfacegeometryofthefuelbundlebottomnozzleattheentryoftheinstrument tubewasexaminedandcomparedwiththimblewearscargeometrytoestablish theirrelationship ifany.Thenozzlegeometryisschematically illustrated inFigure2.18.5069s:10/020591
SECTION3.0RESULTSANDDISCUSSION Theresultsofthesurfaceexamination oftheas-received thimbletubesamplesareillustrated inFigures2.1and2.2.Figure2.1illustrates thesurfaceappearance ofthewearscarinflicted ontheleakedthimbleC-7.Thescarwhichextendedapproximately over0.5in.inlengthismadeupoftwosteps.Thedeepeststepwhichcorresponds tothemostseverelywornregioncontained athrough-wall perforation contributingtotheleakage.Thesideviewshowninthetopphotomacrograph clearlyshowsthepresenceof1circumferentially orientedwearmarksassociated.
withthewearscar.Inadditiontothetwosteppedwearscar,thepresenceofanaxiallyorientedwavyscarcanalsobeseenhere.Thescarappearance suggeststhatitmayhavebeeninflicted bysurfacescrapingortoolingactionagainstasharpcornermostlikelyduringinsertion orretraction ofthethimble.Figure2.2illustrates thesurfaceappearance (sideandtopviews)ofthewearscarinthimbleA-9.Thescarappearance isverysimilartotheoneseeninthimbleC-7.Thetwosteppedwallthinningandthepresenceofcircumferential wearmarkscanbeclearlyseen.Thethinningatthedeepestscarlocationappearstohavejustfallenshortofathrough-wall perforation.
Thetotallengthofthetwosteppedwearregionagaincorresponded toapproximately 0.5in.inlength.Theresultsofthemetallographic examination ofthethimbletubesamplesareillustrated inFigures2.3and2.4.Figure2.3illustrates themetallography resultsofatransverse sectionthroughthethrough-wall perforation onthimbletubeC-7.Thelocations wherehardnessmeasurements weretakenfromarealsoindicated here.Severalsignificant observations areapparentfromtheillustration.
Thethimble.tubewear(thinning) appearstohaveextendedcircumferenti allyoveranangularregionof240'.Thegeneralmicrostructure didnotrevealanyevidenceofsubstructure characteristics ofdeformation exceptatthethinnestregionoftheterminations neartheperforation.
Thethinnestsectionneartheterminations measuredapproximately 0.06in.thick.Noevidenceofanycoldworkwasapparentatthewearsurface.Thehardnessmeasurements (summarized inTable1)confirmed someworkhardening ofthethin5069s:10/020591 terminations presumably duetobendingattheperforation.
Figure2.4illustrates themetallography resultsofanaxialsectionthroughthewornregionofthethimbleA-9.,Hereagain,althoughthereisasignificant reduction inwallthickness duetowear,'ogrossdeformation
'orcoldworkisseeninthematerial.
Thisisfurtherevidenced bythehardnessvalueslistedinTable1.Thehardnessvaluesatthethinnestregionherearecomparable tothehardnessvaluestakenfromtheregionaffectedbywear.Theseobservations suggestthatthecontactand/orimpactloadsinvolvedinthewearprocessmayhavebeenrelatively low.Noticeable isthelackofdeformation orbendingatthethinligamentsectionofthewearscarinFigure2.4.Thehighermagnificationscanningelectronmicroscopy resultsofthewearmorphology bysurfacereplication areillustrated inFigures2.5through2.17.Figures2.5through2.7illustrate thelowmagnification photomacrographs ofthesurfacereplicastakenfromthewornregionsoftheC-7andA-9thimblesidentifying locations wherehighermagnification SEHwasconducted.
Figures2.8through2.17illustrate thehighermagnification scanningelectronmicrographs detailingthewearmorphology seenatdesignated locations (indicated inFigures2.5through2.7).Figure2.8illustrates thesurfacemorphology oftheunaffected (asfinished) andwearaffectedregionsinthimbleC-7.Theunaffectedregion (micrograph
¹16)suggeststhepresenceofmechanical toolingmarksperhapscharacteristic ofthetubefabrication processwhilethemorphology seenattheaffectedregionappearsdistinctly different, characterizing thewearprocess.Figure2.9illustrates theregionofintersection ofwornandunaffected regionsinthimbleC-7.Theaxiallyoriented(horizontal) toolingmarksrepresenting theunaffected surfaceregionterminates intoawornregionofcircumferentially oriented(vertical) wearscars.Similarobservations seenattheunaffected andwearregionsofthimbleA-9areillustrated inFigures2.13and2.16.Figures2.10and2.17illustrate thetypicalwearmorphology seenatthelessseverelywornregions(upperstepregion'fwearscar)ofthethimblesC-7andA-9.Themorphology resembles circumferentially
- oriented, regularly spaced"boatshaped"shallowmarks.Highermagnification viewsofthesemarks,illustrated inFigures2.10(b)and2.11suggestsasurfaceformedbyrubbingorfrettingaction.Themorphology seenherealsosuggestssomerateofjettingorerrosiveactionofthefluid.Asecondtypeofwearmorphology seenatthemoreseverely(deep)5069s:10'/020591 0
'k~~wornlowerstepregionsofthewearscarareillustrated inFigures2.12and2.13,Themorphology seenheresuggestsmateriallossintheformofirregularly shapedflakes,presumably duetohigherdeformation orloads.Thistypeofplanarflake-like morphology isseenatthedeeperstepsurfaceandclosertotheperforation regions.Thesurfacemorphology seenattheterminationsimmediately adjacenttotheperforation isillustrated inFigure2.14.Thesurfacemorphology seenhereresembles deformation bandscharacteristic ofslipbandsineachgrain.Thethickness ofthethimbletubehereisconsidered verysmallapproaching thatofagrainsizesothatthedeformation slipbandsineachcrystal(grain)areclearlyapparenthere.Aschematic representation ofthegeometryofthefuelbundlebottomnozzleisillustrated inFigure2.18.Closeexaminations ofthenozzleinsidediametersurfacegeometryatthethimblepenetration clearlyrevealsacloseandconsistent relationship withthetwosteppedgeometryofthethimbletubewearscar.Thenozzlepenetration width(0.5in)isalsoincloseagreement withtheaxiallengthofthewearscar.Thisclearlyestablishes thatthethimbletubewearoccurredbythemovementofthethimbleatthenozzlepenetration.
Theprimarywaterflowvelocities andflowconditions inthisregionareknowntoinducethimbletubevibrations.
Itisbelievedthatthesevibrations mayhavecausedadequatemotionandcontactloadsresulting intheobservedthimbletubewear.5069s:10/020591 0
TABLE1SUMMARYOFHARDNESSMEASUREMENT RESULTS(LOCATIONS ASMARKEDINFIGURES2.2AND2.3)LocationI.D.HarnVHN4msTransverse 1n2852742902972703093922504102803742605069s:10/020591 0
SECTION
4.0CONCLUSION
S oBasedontheoverallresultsoftheevaluations itisconcluded thatleakageintheD.C.CookthimbletubeoccurredbytheODsurfacewearatthebottomfuelnozzlepenetration, mostlikelycausedbyflowinducedvibrations ofthethimbletube.oThewearmorphology ofthethimbletubeshowedatleasttwodisti.nctly different typesofwearconditionsdepending onthelocationanddepthofthewearsuggesting varyingdegreesofdisplacement, contactloadsand~fluidjettingconditions alongthelengthofthethimbletubesatthenozzlepenetration.
oCircumferential configuration ofthewearscarsuggested thatthethimbletubetonozzleborecontactoccurredonlyononesideofthethimbletubeduringthewearprocess.oLackofcoldworkatthewearscarsuggested thatrelatively lowimpactloadswereinvolvedinthewearprocess.5069s:10/020591 I~I4f!,'/If/J.w//+</whr~lg)IRSSp!,!,Ill"(fjj-g~IIg.;g,(II--ggI~g~Is-!~s~.s 0
Itlif/IU.S.A.Jd.iljiiIilflff*'*"ITrttrliS.A.I4~Ave"(~~Circumferential 1'itWearScarCWaveyScarklFigure2.1Hacrophotograph Illustrating theAs-Received Condition oftheLeaked(Perforated)
ThimbleTube"C-7" Figure2.2Hacrophotograph Illustrating theAs-Received Appearance ofSeverelyHornThimbleTube"A-9" 240o.6200X,~~ter200Xr4g4tA.IL~W>>50X200XFigure2.3Metal1ographicExamination ResultsofaTransverse SectionThroughtheLeakRegionoftheThimbleTube"C-7"(Hardness Measurement Locations areMarked) 200X200X.200XCt((>>w~(XX23.50Xr.Ih>>5,~.Figure2.4200X200X200XMetallography ResultsofAnAxialSectionThroughtheSeverlyHornRegionoftheThimbleTube"A-9"(Hardness Measurement Locations areIndicated) 00 LeakagePerforation FLUl'HAI(BLR:
..kEYLIAf~K'I lx142191V~9091>l421OkVirnrA",~L'(JR
'rHiH8x14.299'.LE"~REPLiCA191:V09093Figure2.5ScanningElectronHacrograph Illustrating theOverviewofthePlasticReplicaoftheHornRegioninThimbleTubeC-7Identifying Locations andHicrograph NumbersHhereHigherHagnification SEHwasConducted.
4zi:t-3-iFLVYiTREPLICAx14.5..@8001H:.,-,C3FLUB'THIl1BLE-,x1Q,510LV~lINIMBLE=>FLUXT.1x<ssAlNBLE'O'EPLli'n 110kVo6002Figure2.6ScanningElectronMacrograph ofthePlasticReplicaTakenfromtheWornRegionofThimbleTube"A-9"Identifying Locations andMicrograph NumbersWhereHigherMagnification SEMwasConducted.
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FlUR-iH-i*tiSLE REPLICA"8'"i,x998t00prs~18kV¹88iZ~;~.T,,-gQ'.glq)L)f
$<FLIILlTHI)'l)LEI10pm18kV¹88i8E'VFLHTHIIBLE::kEFLICBILOS~2888i8kV.~.yBr.E='t$jg¹88i6Figure2.8SEHPhotomicrographs Illustrating theSurfaceMorphology oftheUnscarred andScarredRegionsinSampleC-7.
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!;<'!j'~~g~~~.~I'0P.QFDNTAIti5LE"REPL"I~R'V"'.:Cbbprn,xi9919kVCc,%':iDi'i%iA'~it'.F".:
"=(Fri'ita~~V4]
4bprnxi99818kVe8986',PL4TAA~fN"h.:hEPLKKR"B"<4'~Sbptnxi88818kV~8889Figure2.9SEMPhotomicrographs
.Illustrating theSurfaceMorphology oftheUnscarred andScarredRegionsinSampleC-7.
¹8839x258i8kVCwg'CO'0'fH'Ihe'L.'E----,'AE'.WK I-CA'fi"'~~.'.
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f,'%*-4'Ia)"~~+.w-jL,F,LUXtHINBL.C',REBELf5'8'h>>.:xi888I8f;V¹884(b)Figure2.10SEHPhotomicrographs Illustrating theWearMorphology SeenatLocations 39and41Identified (inFigure2.5)ontheReplicafrom"C-7" 0
I~h~I50~-'pBI~'--PL'UXTi-i(ik2666~..>>S~~,~E'.-'-'-,KEiCiih'QPts'e6kV~88ii'.,:';m','i4,."'...'\-*"',fz,'.,gg~fp'~Il--';."'--l.Ž--.;""::-'.
~!~g~ggTA6'ih~+QgQ~tA~xa58e6669~66i6~~'SC"~xi888i8k~>Figure2.11HigherHagnification SEHPhotomicrographs Illustrating theHearHorphology SeenatLocation39oftheReplicafromC-7(Figure2.10).
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'~URTAINSLE;.:.:~BCPLkbaal"8'"'""kCOurn18kV¹883i.jp).'4p.gf,',~~gt.4'lqqj,
~aov~'.x188818kV¹8834~Tg>>I.(c...z,-A.,ag8PXOptAixi88818kV¹8833Figure2.12SEHPhotomicrographs Illustrating theWearHorphology SeenatLocations 31,33and34ofReplica(Figure2.5)fromC-7Sample.
~~If~jIF~"w*~"\a~%\hEIJQHABlE.:~RVPIiC!Pmx288818kV08824tIr".."'~f1OVfAx266616kVe66Q-Figure2.13SENPhotomicrographs Illustrating theHearMorphology SeenatLocations 19,22and24(Figure2.5)oftheReplicaTakenfromSampleC-7.
Figure2.14SEMPhotomicrographs Illustrating theHearMorphology SeenatLocations 29and30(Figure2-5),ClosetotheThroughWallLeakageRegionoftheSampleC-7.
P-Figure215SEHPhotomicrographs Illustrating theHearHorphology SeenatLocations 8,9,and10(Figure2.6)oftheReplicaFromA-9Sample.Ii8.8~28
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t24)P<>>p+$E+)peWIFigure2.16.SEHPhotomicrographs Illustrating theWearHorphology SeenatLocations 2l,22and23(Figure2.6)oftheReplicafromSampleA-9.XOptn18lY-
011 ANFBOTTOMNOZZLETHIMBLETUBEAPPARENTWEARSCARFROMC7ANDA9THIMBLESTHROUGHWALLLEAKAGE5QTTIIHEXNUTI-lCOREPLATECRUCIFORM GUIDETUBEFigure2.18Schematic Representation oftheGeometryattheThimbleTubetoFuelBundleBottomNozzleIntersection Illustrating theWearLocation.