ML17325B566
| ML17325B566 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 01/27/1999 |
| From: | OKEEFE M J, OLEARY T J INDIANA MICHIGAN POWER CO. |
| To: | |
| Shared Package | |
| ML17325B564 | List: |
| References | |
| NUDOCS 9904300150 | |
| Download: ML17325B566 (33) | |
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ssTechnical Position:
Unit1SteamGenerator LayupChemistry outofSpecification DuringSeptember 24,1997toDecember31,1997.~Soosis:\Thistechnical positiondocuments theevaluation oftheoutofspecification parameters andthepotential effectonsteamgenerator corrosion duringthetimeperiodfromSeptember 24,1997toDecember31,1997.Duringthisperiod,theunitremainedinmode5.Revisions 6and7ofprocedure 12THP6020CHM.201,SteamGenerator, governedthesteamgenerator chemistry specifications forallmodesofoperation, including layup(Ref1and2),duringthisperiod.Thechemistry controldetailedintheSteamGenerator procedure wasdeveloped usingtheguidelines inEPMTR-102134-R4, PWRSecondary WaterChemistry Guidelines-Revision 4,November1996(Ref3).Following theunit1shutdownwhichcommenced onSeptember 8,thesteamgenerators werenotplacedimmediately intowetlayupasthelengthoftheoutagewasnotdetermined.
Layupofthesteamgenerators wassubsequently startedon.September 24.Initially, onlycarbohydrazide wasusedasanoxygenscavenger.
Thesteamgenerators weredrainedandrefilledbetweenDecember6and9,1997,toadjustthepHandoxygenscavengers.
Withtherefill,bothhydrazine andcarbohydrazide wereusedasoxygenscavengers.
Steamgenerator 12wasdrainedandrefilledDecember18,1997,duetoelevatedsulfateconcentration.
According tothemonthlyreports,theappropriate amountsofchemicals wereaddedwhenthesteamgenerators wereplacedinwetlayupinSeptember.
Althoughnotcompletely documented inthemonthlyreports,fromthelayupdataitappearstheappropriate amountsofchemicals wereaddedwhenthesteamgenerators weredrainedandrefilledinDecember.
DuringJanuary1998,thesteamgenerators werepreparedforstartup.Thestartupdidnotoccurandthesteamgenerators werereturnedtolayupinFebruary1998wheretheyhaveessentially remained.
Independent reviewsofthelayupdataindicated thatsomeparameters wereattimesoutofspecification duringtheperiodfromSeptember 24,1997,toDecember31,1997.Theparameters thatwereoutofspecification includedboron,ethanolamine, pH,hydrazine andcarbohydrazide.
Duringtheperiod,theunitunderwent aheatuptoabout180'Fto195'Ffourtimes.Whileavailable datacouldnotconfirm,itispossiblethatsomeoralloftheseheatupswereinpreparation toentermode4andunitrestart.Ifthiswereindeedthecase,pH,hydrazine andcarbohydrazide wouldbecontrolled lowerthantypicallayuplevelstoprepareforoperating chemistry control.Contaminants andpotential corrosive species,sodium,chlorideandsulfate,weremaintained withinspecification andweregenerally verylowduringtheperiod.Inordertodetermine theimpactoftheoutofspecification condition onthesteamgenerator integrity, athoroughreviewofchemistry datafortheperiodwasconducted.
Thedatathatwasevaluated wastakenfromdatasheets12THP6020ADM.010Attachment 1,withtheexception ofcondensate storagetankdissolved oxygendatathatwastakenfromCDMS.Therawdataandgrapheddataareincludedinthistechnical positionasattachments 1and2respectively.
9904300i50 990422PDRADQCK05000$i51pPDRPage1of23 Discussion:
Boron:gBoricacidisanadditiveusedtomitigateoutsidediameterstresscorrosion
- cracking, ODSCC,ofthesteamgenerator tubesduringoperation.
Thecontrolparameter forboricacidisboron.Duringoperation, boronconcentration inthesteamgenerator ismaintained atabout5to10ppm.Duringstartup,1000to2000ppmboronisusedforcreviceflushingandabout50ppmboronisusedfortheboricacidsoak.Astheenvironment conducive toODSCCisnotpresentduringshutdown, boricacidisnotneededduringlayup.Ifboricacidispresentinthelayupsolution, itcandepressthepH.Theconsequence ofelevatedboricacidlevelsduringlayupistheneedtousemoreamountsofethanolamine, ETA,whichisusedtoraisethepHofthelayupsolution.
ETAisusedduringoperation andlayuptoadjustpH.Itdoesnotofitselfpresentacorrosion concernforthesteamgenerators.
TheEPRIguidelines (Ref3)donotidentifyacorrosion concernwithelevatedlevelsofboricacidduringlayup.Theguidelines identifytheconsequence ofelevatedboricacidlevelsduringlayupastheneedtousemoreamountsofETA.Theupperlimitforboronduringlayupis1ppm.DuringtheperiodfromSeptember 24,1997toDecember31,1997,theboronwasabovethe1ppmlimitasshownontheattachedgraph.WhenpHwasraisedabove9.8andtheconcentrations ofhydrazine andcarbohydrazide wereincreased significantly priortoDecember15,1997,theindicated boronconcentrations alsoincreased significantly.
Itisunlikelythatthesevalueswereaccurate.
Noboricacidhadbeenadded,.the steamgenerators hadbeendrainedtwicesincetheshutdownandthereportedlevelswereabouttentimesnormaloperating levels.Itismorelikelythatthereportedvalueswerearesultofinterference withtheanalytical methodcoincident withthehighpHandhydrazine levels.SomesampleswerecheckedusingICPMSandnoboronwasdetectedwhenthereportedboronlevelswererangingfromabout20to70ppm.Subsequent conversion totheICPMSmethodforboronanalysisinlayupsolutions inJanuary1998,resultedinthereportedboronlevelsbeinglessthan1ppm.Thepossibleinterference mayhave'also contributed tothereportedboronlevelsbeingabove1ppmduringthepreviouspartofthelayup.Regardless ofwhetherthevalueswereaccurate, havingborongreaterthan1ppmduringthisperioddidnotresultinanincreaseinsteamgenerator corrosion.
H~hliAETAisusedtoraisethepHofthesecondary sideduringoperation andlayuptominimizecorrosion oflowalloyorcarbonsteel.Theupperlimitof50ppmforETAduringlayupisbasedonenvironmental considerations whendrainingthesteamgenerators.
Thereisnocorrosion concernswithlayuprelative'to theupperlimitofETA.Theprocedure wasrevisedeffective February6,1998,toraisetheupperETAlimitto100ppm.ETAdoesnotpresentacorrosion concern.TheEPRIguidelines (Ref3)donotsetlimitsforthepHadditiveduringlayup,ratherPage2of23 0
thelevelofpHadditiveisdetermined bythedesiredpHlevel.Acorrosion concernwithhighlevelsofthepHadditiveisnotidentified.
~IDuringtheperiodunderreview;ETAwasabovethe50ppmlimitinsteamgenerators 11and12foressentially theentireperiod.Forsteamgenerators 13and14,ETAwasabovethe50ppm*limitforashortperiodinmidNovemberandfromDecember8to31,1997.Thehighconcentrations duringDecemberwereusedeffectively toraisethepHinthesteamgenerators toprovidecorrosion protection.
Anincreaseinsteamgenerator corrosion wouldnotresultfromtheperiodwhenETAlevelswereabove50ppmasETAisnotcorrosive tosteamgenerator materials atthelevelsexperienced.
N~iOUseofnitrogenoverpressure duringlayupisrecommended butnotrequiredbyprocedure 12THP6020CHM.205Rev1,SteamGenerator WetLay-up(Ref4),andtheEPRIguidelines (Ref3).Thepurposeistominimizeairingressabovethewaterlevelduringlayup.Theuseofnitrogenoverpressure isdependent onthemodetheunitisin,thelengthoftheoutageandthemaintenance scheduled tobeperformed onthesteamgenerators,-feedwater andsteampiping,turbineandcondensers.
Thepersonnel safetyhazardisaprimaryconcernwhendetermining ifnitrogenwillbeused.Nitrogenoverpressure istypically u'sed'for extendedoutagesinmodes5and6when,.asdescribed above,plantconditions permit.Itisnotatypicalthatanitrogenoverpressure wasnotmaintained duringtheentirelayupperiod.Priortoplacingthesteamgenerators ininitiallayupinSeptember, theyweredrainedwithanitrogenoverpressure.
Thisprevented airingress.Afteraddinglayupchemicals andfillingthesteamgenerators, theywerespargedwithnitrogen.
Thespargingalongwithdrainingundernitrogenensureanoxygenfreeenvironment inthesteamgenerators duringlayup.Spargingwasdonerepeatedly duringtheperiodunderreview.Steamgenerators 11and14werespargedattheendofOctober.Steamgenerators 12,13and14werespargedbetweenNovember10and13.Allsteamgenerators werespargedbeforeandafterthedrainsandrefillsinDecemberandattheendofDecember.
Nitrogenuseduringtheperiodwasacceptable.
Itprovidedanoxygenfreeenvironment andcorrosion protection.
HandOxenScavenerCarbohdrazideand/orHdrazine'~Theseparameters arebeingaddressed togetherastheirfunctionofcorrosion protection duringlayupisinterrelated.
Carbohydrazide andhydrazine canbeusedtogetherorindividually.
Page3of23 Unlikeunderoperating conditions, pHisacontrolparameter forlayup.ElevatedpHinconjunction withanoxygenscavenger isusedtoprovidecorrosion protection ofthelowalloyorcarbotisteel'components ofthesteamgenerators.
Thesecomponents includethetubesheet, tubesupportplates,wrapper,shell,andthefeedring.Topreventlocalized attack,suchaspitting,ofthealloy600steamgenerator tubesduringlayup,reducingconditions shouldbemaintained orthepHshouldbegreaterthan8.5.Also,chlorideandsulfateconcentrations shouldbekeptbelow1ppm(Ref3and7).Inanoxygenated environment, elevatedpHinconjunction withanoxygenscavenger aidsintheformation ofastableironoxidefilmoncarbonsteelcomponents.
Thisfilmhelpstominimizecorrosion byactingasabarriertodiffusion.
Intheabsenceofoxygen,thereisnosignificant corrosion ofsteelinneutralornearneutralwateratambientconditions (Ref5,6).Intheabsenceofoxygenandminimumlevelsofothercorroding speciessuchaschlorideandsulfate,itisexpectedthattheresultwouldbethesameatthelayuptemperatures of140'Fto195'F.Mostofthetestdatacontained inreference 6wereobtainedusingcleanedcarbonsteelspecimens withnoexistingprotective layer.Thecarbonsteelsurfacesinthesteamgenerators enteranoutagewithaprotective oxidelayerasaresultofthereducing, highpHenvironment presentduringoperation.
Therefore, thetestconditions usedinreference 6aremuchmoreseverethantheconditions inthesteamgenerators duringlayup.Perprocedure 12THP6020CHM.201,thelowerlimitforlayuppHis9.2whenusingcarbohydrazide astheoxygenscavenger and9.8whenusinghydrazine.
Carbohydrazide isveryreactiveandtendstoreactquickly,significantly fasterthanhydrazine, toscavengeoxygenandpassivate themetalsurfacesin'thesteamgenerator.
Aresultofthisreactionisthegeneration ofcarbondioxide.ThisactstodepressthepH,whichisthereasonforthelowerpHlimitwhenusingcarbohy'drazide.
Thelowerlimitgivenintheprocedure forcarbohydrazide andhydrazine is10ppmand75ppmrespectively.
TheEPRIguidelines recommend aminimumpHof9.8andminimumhydrazine concentration of75ppmtoprovidecorrosion protection duringlayup.Theguidelines donotspecifically addresscarbohydrazide butallowalternatives tohydrazine.
ThehighminimumlevelsforpHandhydrazine areintendedtoprovideprotection underaeratedconditions andtoprovideprotection intheeventofairingress.Asdiscussed inreferences 5,6and7,pHandhydrazine levelsneednotbeashighiftheenvironment isdeaerated andwithoutsignificant levelsofothercontaminants.
Itisconservative andgoodpracticetomaintaintheelevatedlevelsintheeventofairingress.However,inadeaerated environment, corrosion protection existswithoutthesehighlevels.FromthestartoflayuptothedrainandrefillonDecember6to9,1997,carbohydrazide wasusedastheoxygenscavenger.
Carbohydrazide wasbelowthelowerlimitforthisperiod.Asufficient amountofcarbohydrazide wasaddedwhenthe,steamgenerators wereinitially placedinwetlayuptoachievealevelneartheupperlimitof40ppm.However,thecarbohydrazide reactedquicklytopassivate theinternalmetalsurfacesofthesteamgenerators andasignificant levelwasnotmaintained inthesteamgenerators.
Duringthistime,thepHintwoofthesteamgenerators, 12and14,wasmaintained above9.2.ThepHinsteamgenerator 11wasabove9.2Page4of23 Iexceptfortwoweekspreceding thedrainandrefillwhenthepHwasatabout9.0.ThepHinsteamgenerator 13wasabove9.2exceptforoneweekpreceding thedrainandrefillwhenthepHwas9.1.'ollowing thedrainandrefill,hydrazine andcarbohydrazide wereused.Hydrazine andcarbohydrazide wereabovethelowerlimitsforsteamgenerator 11.Hydrazine wasabovethelowerlimitforsteamgenerator 12.Carbohydrazide wasbelowthelowerlimitpartofthetime,rangingfrom5.3to20.8ppm.Forsteamgenerator 13,hydrazine wasbelowthelowerlimitpartofthetime,rangingfrom47to194ppm.Carbohydrazide wasbelowthelowerlimit,rangingfrom5.4to8.1ppm.Forsteamgenerator 14,hydrazine wasbelowthelowerlimitpartofthetime,rangingfrom55.2to162.8ppm.Carbohydrazide wasbelowthelowerlimitpartofthetime,rangingfrom8.5to13.6ppm.Thehydrazine valuesreportedonDecember15are~apparently inerrorbasedonhydrazine levelsbeforeandafterDecember15,andthefactthatanotherchemicaladditionwasnotmade.Following thedrainandrefill,thepHwasmaintained
~atorabove9.8.Duringtheperiodunderreview,dissolved oxygeninthesteamgenerators was0ppb.Thedissolved oxygeninthefillsource,unit1condensate storagetank,duringtheinitialandsubsequent fillswaslow.Chlorideandsulfatewerewithinlimitsduringtheperiodandgenerally maintained low.Sulfatedidspikeup'uringthesecondhalfofDecemberbutwasmaintained withinlimits.Theenvironment inthesteamgenerators wasdeoxygenated.
Thecarbonsteelsurfacesinthesteamgenerators haveanexistingprotective oxidelayerenteringtheoutage.Anoxygenscavenger wasaddedwiththeinitialfillthatactedtopassivate thecarbonsteelsurfaces.
Oxygenscavengers, bothcarbohydrazide andhydrazine, wereaddedduringsubsequent fillsandasignificant residualmaintained.
ThepHwaselevatedandabove9.2forallormostofthetimeuptotheDecember6to9period.Following thisitwasgenerally greaterthanorequalto9.8.Contaminant levels,suchaschlorideandsulfate,werelow.Asaresultoftheseconditions, adequatecorrosion protection wasprovidedduringtheperiod.Position:
Considering theenvironment wasdeoxygenated, pHwaselevatedandcontaminant levelswerelow,adequatecorrosion protection wasprovidedduringtheperiodofSeptember 24toDecember31,1997.Theconditions inthesteamgenerators duringtheperiodofSeptember 24toDecember31,1997whenlayupchemistry wasoutofspecification didnotpresentanincreased riskofcorrosion overthatwhichwouldhavebeenpresenthadthechemistry beenmaintained withinspecification theentiretime.Performthefollowing actions:1.Revise12THP6020CHM.205,SteamGenerator%et Layup,toincludethelowerlimitforcarbohydrazide andhydrazine duringlayupthathadbeendeletedfrom12THP6020CHM.201inrev8.Page5of23 2.Toprovideoptimalcorrosion protection intheeventofoxygeningressduringlayup,increasetheminimumpHlimitto9.8whenusingcarbohydrazide.
3.Perform'an internalvisualinspection ofsecondary sideofatleastonesteamgenerator intheareaofthewaterlevelduringlayup.Althoughthechemistry dataindicates thatcorrosion protection wasprovided, theinspection isprudentconsidering thelengthoftheoutage.Page6of23
References:
1.12'THP6020CHM.201,Revision6,SteamGenerator, Effective DateSeptember 11,1997.2.12THP6020CHM.201,Revision7,SteamGenerator, Effective DateOctober6,1997.3.PWRSecondaWaterChemistGuidelines-Revision 4,Project2493,S520FinalReport.PaloAlto,CA.:ElectricPowerResearchInstitute, November1996.TR-102134-R4.
4.12THP6020CHM.205,Revision1,SteamGenerator WetLay-up,Effective DateFebruary28,1997.5.H.H.UhligandR.W.Revie.Corrosion AndCorrosion ControlThirdEdition.NewYork:J.WileyEcSons,1985pp.91-99.6.J.A.Armantano andV.P.Murphy."StandbyProtection ofHighPressureBoilers"Proceedings ofthe25AnnualWaterConfer'ence oftheEngineers'ociety ofWesternPennsylvania, Pittsburgh, PA.,September 28-30,1964,pp.111-124.7.LaboratoProramtoExamineEffectsofLaConditions onPittinofAllo600,ResearchProjectS124-1FinalReport.PaloAlto,CA.:ElectricPowerResearchInstitute, April1983.NP-3012.Preparedby:/Date:Approvedby:P~~~Ci~Date:Page7of23 Attachment 19.3Lp0Lp0neiinanenornmopPage8of23
Attachment 1ayupemisryaaeesatearoppm24ppfn2ppb0IumppboneppbuaeoronppbppmppmmmoniapplTIegaommentsgacaoeaupopargeorreeasenoraineaupoeauporainrei,a.ga,.ga,gacaroassumeeatupo-rougyrazineieyinaccuraeoesncorrespon wioeraarainppminrainsampe, reipargeorreeaserainonormopvapppyppPage9of23 Attachment 1ayupemisryaaeesateparoppm24ppm2ppboiumppboneppbuateoronppbppmppmmmoniappmommens2499.2.63.80e4gagacaroeaupopargeorreeasenoraineaupoeauporainrei,a.ga,.ga,gacaroassumeeaupo-rougyrazineieyinaccurae oesncorrespon wioeraapargeorreeaserainonormop:vauerepo easessancecae.<pporcarorazie,<pporissoveoxygenPage10of23 Attachment 1ayupemisryaaeesatearoppm24ppfn2ppboiumppboneppbuateppboronppmppfnmmoniappmommens9/24egagacaropargeorreeasenorainpargeorreeaseno raineaupoeauporei,a.ga,.gaeaupo-roug,gacaroassumeyrazineieyinaccurae oesncorrespon wioeraaprg:vauerepo easessancecae.<pporcaroraze,<pporissoveoxygenPage11of23
Attachment 2SGpHSG'sdrained8refilled~SG11~SG12~SG13~SG14MinpHlimitCO0-000CO~hDhDQltQCOCOVCOCOCOCODateCOtO0)COMC)COCOMMMCPCOCOPage13of23 Attachment 2Carbo,N2H4ppm160.000SG11Carbo,Hydrazine, DO2DO2ppm120.00080.000N2H4Limit75-350ppm CarboLimit10-40ppm24ISGdrained8refilled~Carbo~Hydrazine
~DO240.0000.000CD00000Co~h3lQCn(D(O(O(OVVCOCOCOVVDateCOCDM4)0(OVCDhDhDhDG0CDCOV0Page14of23
Attachment 2Carbo,N,H4ppm280.000SG52Carbo,Hydrazine, DO,DO2ppm24ppppN2HLimit75-350PPm 200.000160.000120.000CarboLimit10-40ppmN2H412/15valueinaccurate SGdrained8~Carbo~Hydrazine
~00280.00040.0000.000COh3COCOCO~hJCJllVCOCOVVOh3COCOhDCOVCODateMtQCOCD~C)COCOCO,VCOVhJCPCOCOVV0Page15of23
Attachment 2Carbo,N,H4ppm200.000160.000120.00080.000-SG13Carbo,Hydrazine, DO2N,H,Limit75-350ppm CarboLimit10-40ppmalue-inaeeuret SGdrained8refilledDO2ppm~Carbo~Hydrazine
~00240.0000.000CDOO0hDCacnCOCDCD444CD4OOhDCOCOCDCOVCDCODateh3M4lCD~OCOCDVCD4tV4COCD0Page16of23 Attachment 2Carbo,N2H~ppm200.000160.000120.000.80.000SG14Carbo,Hydrazine, DO2N2H<Limit75-350ppm CarboLimit10-40ppmN+~tM4271&rdumnaccurat SGdrained8refilledDO>ppm~Carbo~Hydrazine
~DO240.0000.000CO(OVV(0CDCDCDVVh3CDCOCOVVDateMCDCDMh3(gO(DCD4MMMh3CP(D(OCOPage17of23
Attachment 28oronppm80.0070.0060.00Boronupperlimit1ppmSGBoronSG'sdrained8fille50.0040.0030.0020.00~SG11~SG12~SG13~SG1410.000.00CDtQCDCDMh3CDtOCDCDCJlCDCDDateCDtOCDCDCDVlOtOCDPage18of23 Attachment 2ETAppm180.00SGETA160.00140.00120.00100.0080.0060.00SG'sdrained8fille~SG11SG12~SG13~SG1440.0020.00ETAupperlimit50ppm0.00CO0000co~toeCO'COCOVVVCOCOVCODateCOCDCDCOCDtoCOCDVVVPage19of23 Attachment 2Nappb7.06.0Naupperlimit1000ppbSGNa5.04.03.02.0rairefilledSG11~SG12~SG13~SG141.00.0C)COCOQlCOOOh3MCJlCOCOCOVDate(nCO4)OCOCOVCOMCOCOPage20of23
Attachment 2Clppb45.0SGCI40.035.0CIupperlimit1000ppbSG'sdrained830.0.25.020.015.0~SG11~SG12~SG13~SG1410.05.00.0DCOCOCODh3Dh3QlCOCOVVCODateCOCOCOh34)COCOCOVPage21of23 Attachment 2SO4ppb1000.0900.0800.0700.0600.0500.0400.0300.0200.0100.00.0SOupperlimit1000ppbSGSOSG'sdrained8efille~SG11~SG12~SG13~SG14COOh3COCO00coCOCOQOhDhJCOCOCOVCOVCOCOVDateCDCO4)OCOCOMCOhDCPCOCOVPage22of23 Attachment 2WbUnit1CSTDO2180160140CSTcrosstiedwithU2120100~CSTDO806040200(O{O0000'4x~Ca~tQMcnQ(o(DCO{DCOVVV{OCO{D{ODate{O{Oh3h34)CDCO{OtQ0(O{Dh3Cil{O{OPage23of23
ATTACHMENT 2TOAEP:NRC:1295B SUMMARYOFUNIT1STEAMGENERATOR LAYUPCHEMISTRY FROMJANUARY1g1999TOFEBRUARY18'999 ATTACHMENT 2TOAEP:NRC:1295B SUMMARYOFUNIT1STEAMGENERATOR LAYUPCHEMISTRY FROMJANUARY1,1999TOFEBRUARY18,1999