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
REGULATORY INFORMATION DISTRIBUTION SYSTEM(RIDS)ACCESSION NBR>>8005050232 DOC~DATE~80/09/29NOTARIZED:
NODOCKETFACIL:50200RobertEmmetGinnaNuclearPlantiUnitliRochester G05000244AUTH'AMEAUTHORAFFIL'IATION WHITEsL~D,Rochester Gas8ElectricCorp.RECIP,NAMERECIPIENT AFFILIATION Officeof'uclear ReactorRegulation ZIKMANNgD,L~Procedures 5TestReviewBranch
SUBJECT:
ForwardsApr1980steamgenerator insprept8evaluat'ion ofresultsiin responsetoNRCrequest,DISTRIBUTION CODE:A001SCOPIESRECEIYKD:I TRIENCL~SIZE:TITLE:GeneralDistributionfotafterIssuanceofOperating Lic~W.+c.C.le&8'.enSsvX8K.NOTESI<bRECIPIENT COPIESRECIPIENT COPIESIDCODE/NAME LTTRENCLIDCOOK/NAME LTTRENCLACTION:05BC0ggW~7INTERNALi0+R12K17ENGRBR19PLANTSYSBR21EFLTTRTSYSOELDE)<TERNAL:
03LPDR23ACRS1211111160?NRCPDR15'OREPERFBR18REACSFTYBR20EEBEPB~DORSTSGROUPLEADR1'<)NSIC16hillyg)gg9VTOTALNUMBEROFCOPIESREQUIRED:
LTTR~ENCL IHI'JNII1wr1~t1(AlltI!1 80000gyp,-rPP@Z/PIIKS ISllltlllI'JIIINII
-r"'"'"-~ROCHESTER GASANDELECTRICCORPORATION o89EASTAVENUE,ROCHESTER, N.Y.14649LEOND.WHITE.JR.VICKPRKSIDKNT TKLKPHDNK
- RK*CDDKTIS,546-2700 April29,1980DirectorofNuclearReactorRegulation Attention:
Nr.DennisL.Ziemann,ChiefOperating ReactorsBranchNo.2U.S.NuclearRegulatory Commission Washington, DC20555
Subject:
SteamGenerator Inspection ResultsandAnalysisR.E.GinnaNuclearPowerPlant,UnitNo.1DocketNo.50-244
DearNr.Ziemann:
1In,responseto'areguestofDr.,B.D.Liau'fyourstaffwearesubmitting foryourinformation areportonthe1980SteamGenerator Inspection andan,evaluation oftheresults.Pleasefindattachedonecopyofeach.1Attachment A-April1980SteamGenerator Inspection Attachment B-Evaluation ofResultsVerytrulyyours,L.D.Whit,Jr.gp(
~~~4lICg1lil Attachment AAril1980SteamGenerator InsectionAprogramofplannededdycuirentexaminations wasconducted onbothloop"A"and"B"steamgenerators atR.E.GinnaNuclearPowerPlantfromApril3-8,1980duringthescheduled refueling andmaintenance outage.Thepurposeoftheseexaminations wastoassesstheintegrity ofthesteamgenerator tubingandtakecor-rectiveactionstoassurereliableandsafeoperation duringthenextoperating fuelcycle.Theseexaminations consisted ofamultifreguency eddycurrentexamination todetectandmeasurepotential tubedefects.Thisisthethirdyearofmultifrequency eddycurrent.examinations attheGinnaplant.Thefourfrequencies chosenwereasfollows:a.400KHzDifferential, b.200KHzDifferential, c.100KHzDifferential, d.100KHzAbsolute.
Alongwiththefourfreguencies, asupportplateandtubesheetmixwasutilizedbycombining theinputsfromthe400KHzand200KHzdifferential frequencies.
Thismixallowedformoreaccuratein-terpretation ofsignalsfromareasofthesteamgenerator wherethesignalfromsupportstructures interfere withsignalsgenerated fromtubingflaws.Theexaminations consisted ofa100percentinspection ofbothsteamgenerators inletsandtheoutletsreceiving approximately a25percentinspection.
Minimumtubelengthexaminedwasfromthefirst.supportplatedownthroughthetubesheetcrevice.TubeswerealsoexaminedovertheU-bendregionandtothesixthsupport,plate.WithNtheexception ofindications whichwillbediscussed inthetext, 1
therewerenotanysubtlechangesnotedoverpreviousyearsdata.Thesteamgenerator outletsdidnotshowanyreportable indications.
Inthe"A"steamgenerator inlet,onlyonetube(R16C88)requiring pluggingwasfound.Itdisplayed a50%smallvolumeindication 2inchesabovethetopofthetubesheet.The"B"steamgenerator, whichhadtwo(2)creviceindications inAprilof1979andeleven(ll)creviceindications intheDe-cember1979showedthirtyone(31)creviceindications atthistime.Theseindications fallintotwocategories, thefirstbeing13indi-cationswhichwereidentified atallexamination frequencies andareasfollows: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"abovetubeendThesecondcategoryincluded18indications thatweredetectedwiththe100KHzabsolutefrequency only.Theseindications wereanabnormalverticalchannelsignalonthebrushstripchartrecorderthat,resembled thesignalsat100KHzabsoluteofthe13tubesfoundattheotherfrequencies.
Therefore, thefollowing tubesareconsidered tobeundercreviceattack:R14C32R15C34R16C34R17C34R18C34R15C35R16C35R17C36R16C37R19C37R18C38R19C38R13C39R18C41R15C44R14C46R18C46R18C48These31tubeswithcreviceindications, withtheexception, ofthreeR24C45,R24C46andR21C54,allfit.intoapatternwiththeprevious13tubesfoundinthetwoexamination in1979,asshown r
3inFiguresIandII.Inadditiontothese,threetubesinthe"B"inletwerefoundwithdefectsabovethetubesheetasfollows:R32C16-41%,smallvolumeindication, 2"abovetubesheetR45C48-46%,24"abovetubesheetR45C47-36%,24"abovetubesheet.Aftereddycurrentdataanalysiswascompletecreviceindications wereidentified onlyinthe"B"steamgenerator inletandnotinthe"A"steamgenerator.
Twotubesfromthe"B"steamgenerator inletandonetubefromtheoutletwerechosen.fortubepulling.Thesetubes,R17C41-60%indication 18"abovethetubeend,R15C44-smallest100KHzabsolutesignal,andR17C40-out-let(coldleg)tubewithnoindication, buttheoppositeendofaninl'ettubewithanindicator, weredetermined astubesthatwouldpotentially givevaluableinformation concerning thedamagemechanism andalsoallowforthreedifferent crevicestohavedepositsremovedforchemicalanalysis.
Thetubepullingoperations wentasfollows:R17C41-60%indication 18"abovetubeenda~b.cd.markedIDat14",24"and26"fromtubeendtubestartedpullingataforceof4500psithendroppedto2500psiforshortperiodoftime,averageremainder pulledat1500psi.totallengthcut69.5",totalpulledlength72"givingapproximately 2.5"elongation or3.5%.honedsamplefromcrevice.2.R15C44-small100KHzabsolutesignalincreviceregiona~b.c~d.markedIDat14",24"and26"fromtubeendtubestartedpullingat,aforceof2400psidroppedto1800thenincreased foranaveragepullof2100psitotallengthcut,was69.5",totalpulledlength72.06"honedsamplefromcrevice.3.R17C40-Noindication fromoutleta.markedIDattopoftubesheet.b.tubestartedpullingataforceof3200droppedtoapproximately 1100fortheremainder ofthepull c.totallengthcutwas69.5",totalpulledlength69.875".d.honedsamplefromcrevice.Theproposedhypothesis forthecrevicecrackingmechanism isageneralintergranular corrosion attack(IGA)thattakesplacedowninthetubesheetcrevicearea.Aftertheintergranular corrosion attackhaspenetrated deepenoughintothetubewalltheremaining wallcracksduetostresscausedeitherbypressureand/orthermalloadsonthetube.Theactivespeciesinvolvedinthisattackispostulated tobeacausticsolutionofNaOH,however,Na2S04,orNaSi03mayalsobeinvolved.
Crevicedepositanalysisandthepulledtubesurfacedepositanalysisshouldhelpidentifytheactualspeciesinvolvedinthisattack.Thisconcentration ofcausticisbelievedtobefrompreviousphosphate chemistry operation (priortoNovember1974)andnottobefxomtheallvolatiletreatment (AVT)operating chemistry thatGinnahasusedthelastfiveandonehalfyears.Itispostulated thatthemolarratiobetweenNaandPOinthecrevicehasbeenin-4creasinginthecreviceasP04hasbeenslowlyremovedduringwettingsandsubsequent dryouts.ThisactionleavesbehindfreeNaandOH,whichwouldraisethepHandproducecausticcreviceconditions.
Anumberofactionshavebeentakentogainadditional informa-tionconcerning thecauseofcreviceintergranular
'corrosion attackandtoreducethepropensity forcxeviceattack.Theseactionsin-cludeamoresophisticated eddycurrentinspection, tubepulling,tubesheetwaterlancing,cxeviceflushingboilout,continued closecontrolofsecondary chemistry, andamid-cycle Fallsteamgenerator inspection.
~~
Ouruseofmultifrequency eddycurrent,inspection including a100KHzabsoluteexamination hasallowedtheidentification andpluggingofotherwise undetected attackwithinthecreviceregion.Tubeswhichmight.otherwise besusceptible tocrackgrowthandresultinprimarytosecondary leakageareplugged.ThethreetubeswhichhavebeenpulledandarebeingexaminedbyWestinghouse ElectricCorporation shouldyieldvaluableinforma-tionconcerning damagemechanism andchemicalspecies.Asinallprevioussteamgenerator inspections, anextensive programofwaterlancingonthesecondary sidehasbeencarriedout.Thus,thequantityofsludgeinthesecondary sideisminimized.
Acreviceflushingboiloutprocedure willbeemployedtofurtherreducethepotentially detrimental materialinthetubesheet,crevice.TheprogramtobeemployedatGinnaisbased,inpart,onprogramspreviously employedatKansaiElectricPowerCompanyatMehamaUnit2andbyWisconsin ElectricPowerCompanyatPointBeachUnit1.TheprogramatGinnawillinvolveapproxi-matelytwenty-two cycles.Boricacidwillbeaddedduringanumberofthesecycleswiththeobjective ofneutralizing thecausticsolutioninthecrevices.
Duringstartupandplantoperation, thefull.flowcondensate demineralizers willcontinuetobeusedandcarefulcontrolofsecondary chemistry willbemaintained.
Operating experience hasdemonstrated ourabilitytomaintainexcellent chemistry conditions onthesecondary side.
l
~~Finally,weplantoshutdownGinnaStationintheFallof1980toreexamine thesteamgenerators.
Thisinspection shouldaidxnestablishing theeffectiveness of'corrective actionsbeingappliednowandtoplanninganyfuturecorrective actions.
FigureIRG6E.steamgenera,tor
-BIrlletCreviceXnaxcatxons qlSSSlSSE6$
797175757I I94745a34i&95755 S35I494745454I 393735333I 292725232l l9I7l5l3II9753COLUMNSlo747270626052S4442.3!o03232822ISI4l2IO864~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4440454341~~~~~~~~~~~~~~~~~~~~~~~~~~~3e36373532333I302S29~~~~~~262523~~2l-=20~~~~-0----OC.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ROWSs16l2IO9723I-:.=:-MAN@AxNMarch79-2k-December 79-llNOZZLE=4/25/80ABC1 1J
-FigureIIRGaBst;earnGeoqraQgr
-BInletCreviceIndications Rl898785%6I 791175757I 194745l341695755535I49474545 4I393735333I292725232I IQI7l5l3II975390888L8288lo7472708III4I2105Q545254444243'f323282.lo22I8I6I4l2I086COLUMNS0"00.~~~~~~~~~~~~~~~~~~~'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'~~~~~~~~~~~Q~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~t~~~~~~~l~~~~ROWS45424l40383634323I302928262522232IISI6I4I2IIIO86523I=:l-MANV/AYNOZZLE~-April80-314/25/80AEC Attachment BEvaluation ofResultsTheresultsofthesteamgenerator inspection havebeenreviewedtodetermine whetherthereareanyunreviewed safetyquestions orwhetherachangeintheTechnical Specifications isrequired.
Theconclusion hasbeenreachedthattherearenounreviewed safetyquestions andthatnochangeinTechnical Specifications isrequired.
Thecurrentsafetyanalysisassumesthat10%ofthesteamgenerator tubesareplugged.Currentpluggedlevelsarewellbelow10%,3.74%intheAand3.44%intheB.Therefore, thecurrentanalysisremainsvalid.ThecurrentTechnical Specification limitisO.lgpmineithersteamgenerator whenaveragedover24hours.Thislimitwaspro-posedonApril25,1975andwasreviewedandapprovedbytheNRCinlicenseamendment no.7datedMay14,1975.Thislimitwasestablished toensuretubeintegrity following designbasiseventsunderthecondition oftubecrackingsuperimposed uponthinningofthetubeto60%ofthewallremaining.
Testsandanalysesperformed andapprovedin1975demonstrated thatifleakagewaslimitedto0.1gpm,thenthemaximumpossiblecracksizewaslimited.Evenassumingthatthemaximumlengthcrackoccurredonapreviously thinnedareawhen50%tubewallremained, tubesdidnotfailduringdesignbasistransients.
A40%plugginglimitwas,therefore, established toprovidealevelofconservatism.
WhereastheTechnical Specification wereestablished basedondefectsoccurring abovethetubesheet,crevicecracksseenthisoutageandintheprevioustwooutagesarebelowthesurfaceofthelttubesheet.Thetubeinthevicinityofthecrevicecrackispro-videdsupportbythetubesheetandtheprevioussafetyanalysisoftubeintegrity maybeconservatively applied.Tubeclearances withinthetubesheetmayvaryfrommanufacturing tolerances from.016inchesto.022inchesonthediameter.
Theseclearances arefurtherreducedinoperation bythedepositsandcorrosion'roducts inthecrevices.
Therefore, thetubesinthecreviceareaaretightlyconfinedwithin,thetubesheet,whichprovidesreinforce-menttothetubewallmaterialintheareaofthecreviceswheretheintergranular corrosion attackhasbeenfound.Thiswouldreducetubedistressunderabnormalloadingsprohibiting significant crackingorrupture.Further,thinninginthecreviceregionhasnotbeenobserved, thusproviding significant additional margin.Basedontheseconsiderations, thereisnounreviewed safetyquestionandnochangeintheTechnical Specifications isrequired.
Plantoperation may,therefore, resume.