ML17037B906
| ML17037B906 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 03/08/1978 |
| From: | Varga S A Office of Nuclear Reactor Regulation |
| To: | Rhode G K Niagara Mohawk Power Corp |
| References | |
| NUREG-0313 | |
| Download: ML17037B906 (24) | |
Text
MAR08f978DocketNo2,50-43.0 NiagaraMohawkPowerCorporation ATXM:Ikr.Gerlad.K.DiodeVicePresident
-Mrgineering 300ErieBoulevard NestSyracuse, New,York13202Gentlemen:
SUBJECT:
NBCSTAFFPOSXTICMOHTHEUSEOFAUSTEMXTIC STAINLESS STEELINBOILIHGPPZERREACTORFACXLITXESWIHE BILEHHbJTNU~+SZATIC8,UNIT2Duringthepastseveralyears,theMCanditspredecessor agency,theABC,haveconducted anextensive investigation toevaluatethecrackingofaustenitic stainless steelpiping.Thiseffortwasinitiated following thedetection inlate1974andearly1975ofaseriesofcracksinthepipingofboilingwaterreactorfacilities.
Asaresultofthisinvestigation, wehaveconcluded thatthetypesofaustenitic stainless steelcurrently usedinboilingwaterreactorpipingaresusceptible tostresscorrosion cracking.
Thestaffbelievestheprobability isextremely lowthatsuchstresscorrosion cracksvillpropagate farenoughtocreateasignificant safetyhazardtothepublic.However,wehavealsoconcluded thatstepsshouldbetakentoelimi-natethiscondition.
Tothisend,wehavedeveloped apositiontosetforthacceptable reethodstoreducethesusceptibility ofboilingwaterreactorpipingtostresscorrosion cracking.
Thispositioniscontained inHUREG-0313, datedJuly1977,acopyofwhichisenclosed.
Pehavealsoincorporated thepositioncontained inNUREG-0313 asBranchTechnical PositionNTEB5-7andissueditas.arevisiontotheStandardReviewPlan.,Youshouldnotethattheimplen~tation schedulesetforthinthepositionprovidesforvaryingdegreesofconformance, depending uponthestatusoftheapplication.
1'equirethatyouprovideascheduleforyourresponsetothispositionwithin14daysofreceiptofthisletter.Yourresponseshouldaddresseachofthesubsections inSectionIIandXIXoftheposition.
Forty(40)c'opiesofyourresponseareneededforusebythestMf.OKKICK~SVRNAMKWOATS~NRCFORM318(9-76)NRCM02404UIS,OOVKRNMKNT PRINTINO,OI'PICK>
1979429924 k~<<<<Ijk<<!<<!'-k<<V,'k.<<e NiagaraMohawkPowerCorporation
.-2-MAR081978lfyourequireanyclarification ofthisrequest,pleasecontactthestaff'sassignedLicensing Project2~1anager.
(Thisrequestforgenericinformation wasapprovedbyGEOunderablanketclearance Ho.R0071.Thisclearance expiresSeptember 30,"1978.
Sincerely,
Enclosure:
NUREG-0313, datedJuly1977Or<'lso'P~~"407/StevenA.Varga,ChiefLightRaterReactorsBranchNo.4DivisionofProjectt4anagement ccvr/enclosure:
Seepage3DFFICS~SURNAME~DATd~WcmSAIItja/oz,/780)/f/78NRCFORM318(9-76)NRCM02404U,S,OOVSRNMSNT FRINTINOOFFICSsISTSd2dd24 44ef>i9;y9RAMK)p)>Fdhole~(p(~~
.gF'~s' NiagaraMohawkPowerCorporation
--JAR08l9/9ccs.EugeneB.Thomas,Jr.LeBoeuf,Lamb,Leiby&MacRae1757NStreet,N.W.Washington, D.C.20036AnthonyZ.Roisman,Esq.Roisman,Kessler&Cashdan102515thStreet,NWWashington, D.C.20036Mr.RichardGoldsmith SyracuseUniversity CollegeofLawE.I.WhiteHallCampusSyracuse,"Sew"York
'13210T.K.DeBoer,DirectorTechnological Development ProgramsNewYorkStateEnergyOfficeSwanStreetBuildingCore1-2ndFloorEtrpireStatePlazaAlbany,NewYork12223 0~y1hJB NUREG-0313TECHNICAL REPORTONMATERIALSELECTION ANDPROCESSING GUIDELINES FORBWRCOOLANTPRESSUREBOUNDARYPIPINGManuscript Completed:
July1977DatePublished:
July1977DivisionofOperating ReactorsDivisionofSystemsSafetyOfficeofNuclearReactorRegulation U.S.NuclearRegulatory Commission Washington, D.C.20555
TABLEOFCONTENTSI."INTRODUCTION II.SUMMARYOFACCEPTABLE METHODSTOMINIMIZECRACKSUSCEPTIBILITY III.INSERVICE INSPECTION ANDLEAKDETECTION REQUIREMENTS FORBWRsWITHVARYINGCONFORMANCE TOMATERIALSELECTION ANDPROCESSING GUIDELINES IV.IMPLEMENTATION OFMATERIALSELECTION ANDPROCESSING GUIDELINES V.GENERALRECOMMENDATIONS
~~1~\34~9.10
I.INTRODUCTION Small,hairlinecracksinaustenitic stainless steelpipinginboilingwaterreactor(BWR)facilities wereobservedasearlyas1965.Ineachcase,itwasbelievedthatthesituation hadbeencorrected orsubstan-tiallyreducedbybettercontrolofwelding,contaminants and/ordesignmodifications.
InSeptember, 1974,whenthefirstofaseriesofcracksinthepipingofthemoremodernBWRswasfoundatDresdenUnitNo.2.,thethenAtomicEnergyCommission (AEC)initiated anintensive investiga-tiontoevaluatethecause,extent,andsafety.implications oftheobservedcracking.
InJanuary1975,aspecialPipeCrackingStudyGroupwasformedtocoordinate andaccelerate thestaff'scontinuing invest'iga-tionsoftheoccurrences ofpipecracking.
Thisgroupincludedrepresen-tativesoftheNuclearRegulatory Commission (NRC)andtheirconsultants.
InOctober,1975,theStudyGroupissuedareport,NUREG-75/067 "Tech-nicalReport,Investigation andEvaluation ofCrackinginAustenitic Stainless SteelPipingofBoilingWaterReactorPlants."Duringthesamegeneraltimespan,theGeneralElectricCompany(GE)conducted anindepen-dentevaluation ofthecrackingoccurrences andsubmitted theirfindingsandrecommendations totheNRC.ThispapersetsforththeNRCtechnical positionbasedontheinformation available atthistime.Plantoperating historyindicates thatType304and316austenitic stainless steelpipinginthereactorcoolantpressureboundaryofboilingwaterreactorsaresusceptible tostresscorrosion
.cracking.
Studieshaveshownthatsuchcrackingiscausedbyacombination of.thepresenceofsignificant amountsofoxygeninthecoolant,highstresses, andsomesensitization ofmetaladjacenttowelds.Suchcrackshaveoccurredintheheataffectedzonesadjacenttoweldsbutarenotexpectedtooccuroutsidetheseareas,providedthatthepipematerialisproperlyannealed.
Piperunscontaining stagnantorlowvelocityfluidshavebeenobservedtobemoresusceptible tostresscorrosion crackingthanpipescontaining acontinuously flowingfluidduringplantoperation.
Historically, thesecrackshavebeenidentified eitherbyvolumetric examination, byleakdetection systems,orbyvisualinspection.
Becauseoftheinherenthighmaterialtoughness ofaustenitic stainless steelpiping,stresscorrosion crackingisunlikelytocausearapidlypropagating failureresulting inaloss-of-coolant accident.
Althoughtheprobability isextremely lowthatthesestresscorrosion crackswillpropagate farenoughtocreateasignificant safetyhazardttothepublic,thepresenceofsuchcracksisundesirable.
Stepsshouldtherefore betakentominimizestresscorrosion crackinginBWRpipingsystemstoeliminate thiscondition andtoimproveoverallplantreliability.
Itisthepurposeofthispositiontosetforthacceptable methodstoreducethestresscorrosion crackingsusceptibility ofBWRpipingandtherebyalsoprovideanincreased levelofreactorcoolantpressureboundaryintegrity.
Recognizing thatthemoststraightforward and desirable approachormethodsmaynotbepracticable, orevenpossible, forallplants,thebasesforvaryingdegreesofconformance toourguidelines areprovided.
Augmented inservice inspection andleakdetec-tionrequirements areestablished forplantsthathavenotfullyimplemented theprovisions
.contained inPartIIofthisdocument.
II.SUMMARYOFACCEPTABLE METHODSTOMINIMIZECRACKSUSCEPTIBILITY Thematerialselection andprocessing guidelines listedbelowidentifyalternative acceptable methodstominimizesusceptibility tostresscorrosion inBWRpressureboundarypiping.Itisexpectedthatadoptionofthesepractices willresultinahighdegreeofprotection againststresscorrosion cracking.
1.Corrosion Resistant Materials Allpipeandfittingmaterialincluding weldmetalshouldbeofatypeandgradethathasbeenshowntobehighlyresistant tooxygen-assisted stresscorrosion intheas-installed condition.
Unstabilized wroughtaustenitic stainless steelwith>0.035/carbondoesnotmeetthisrequirement unlessallsuchpipingincluding weldsisinthesolutionannealedcondition.
Theacceptability ofalternative materials, processes, orothermethodsftoprovideanadequatedegreeofcorrosion resistance willbemadeonacase-by-case basis.2.Corrosion Resistant "SafeEnds"Allunstabilized wroughtaustenitic stainless steelpipingwithcarboncontents>0.0355shouldbeinthesolutionannealedcondition.
Ifweldsjoiningthesematerials arenotsolutionannealed, theyshouldbemadebetweencase(orweldoverlaid) austenitic stainless steelsurfaces(5/minimumferrite)orothermaterials havinghighresistance tooxygen-assisted stresscorrosion.
Thejointdesignmustbesuchthatanyunstabilized wroughtaustenitic stainless steelcontaining
>0.0351.carbon,whichmaybecomesensitized asaresultoftheweldingprocess,isnotexposedtothereactorcoolant.3.Otherproposedmethodstoprovideprotection againststresscorrosion crackingwillbereviewedonacasebycasebasis.Regulatory Guide1.44"ControloftheUseofSensitized Stainless Steel",datedMay,1973willberevisedtoprovideadditional guidanceonacceptable practices.
III.INSERVICE INSPECTION ANDLEAKDETECTION REUIREMENTS FORBWRsWITHVARYINGCONFORMANCE TOMATERIALSELECTION ANDPROCESSING GUIDELINES 1..ForplantswhereallASMECodeClassIreactorcoolantpressureboundarypipingsubjecttoinservice inspections underSectionXImeetstheguidelines statedinPartII,noaugmented inservice inspection orleakdetection requirements arenecessary.
2.Pipinginallotherplantsissubjecttoadditional inservice inspection andleakdetection requirements, asdescribed below.Thedegreeofinspection ofsuchpipingdependsonwhetherthespecificpipingrunsareconforming ornon-conforming, andonwhetherthespecificpipingrunsareclassified as"Service Sensitive".
"ServiceSensitive" linesaredefinedasthosethathaveexperienced crackinginservice,orthatareconsidered tobeparticularly susceptible tocrackingbecauseofhighstress,orbecausetheycontainrelatively
- stagnant, intermittent, orlowflowcoolant.Examplesofpipingrunsconsidered tobeservicesensitive include,(butarenotlimitedto):corespraylines,recirculating by-passlines(or"stubtubes"onplantsthathaveremovedtheby-passlines)CRDhydraulic returnlines,isolation condenser lines,andshutdownheatexchanger lines.A.Fornon-conforming linesthatarenotservicesensitive:
(1)Inservice inspection ofthenon-conforming linesshouldbeconducted inaccordance withtheschedulespecified inASMECode,SectionXI-Subsection IWB,asrequiredbytheapplicable examination Categories B-FandB-J,withtheexception thattherequiredexamination shouldbecompleted innomorethan80months(twothirdsofthetimeperscribed inthescheduleintheASNEBoilerandPressureVesselCodeSectionXI).Ifexaminations conducted duringthefirst80monthperiodrevealnoincidence ofstresscorrosion
- cracking, theexamination schedulethereafter canreverttothescheduleperscribed inSectionXIoftheASMEBoilerandPressureVesselCode.
Thepipingareassubjecttoexamination, themethodofexamina-tion,theallowable indication standards andexamination pro-ceduresshouldcomplywiththerequirements oftheEditionandAddendaoftheASMECode,SectionXIidentified asapplicable by10CFRPart50,Section50.55a,Paragraph (g),"CodesandStandards."
(2)Thereactorcoolantleakagedetection systemshouldbeoperatedunderthefollowing Technical Specification requirements inordertoenhancethediscovery ofunidentified leakagethatmayincludethrough-wall cracksdeveloped inaustenitic stainless steelpiping:a.Thesourceofreactorcoolantleakageshouldbeidentifiable totheextentpractical, usingleakagedetection andcollec-tionsystemsthatmeetthepositiondescribed inSectionC,Regulatory PositionofRegulatory Guide1.45,"ReactorCoolantPressureBoundaryLeakageDetection Systems,"
oranacceptable equivalent system.b.Plantshutdownshouldbeinitiated forinspection andcorrective actionwhentheleakagesystemindicates, withinaperiodoffourhoursorless,anincreaseintherateofunidentified leakageinexcessoftwogallonsperminute,orwhenthetotalunidentified leakageattainsarateoffivegallonsperminute,whichever occursfirst.
c.Unidentified leakageshouldincludeallleakageotherthan:1.Leakageintoclosedsystems,suchaspumpsealorvalvepackingleakagethatiscaptured, metered,andconducted toasumporcollecting tank,2.Leakageintothecontainment atmosphere fromsourcesthatarespecifically locatedandknowneithernottointerfere withtheoperation oftheunidentified leakagedetection system,nornottobefromathrough-wall crackinthepipingwithinthereactorcoolantpressureboundary.
B.Fornon-conforming linesthatareservicesensitive:
(1)Theleakagedetection requirements described inIII.Aabove,shouldbeimplemented.
(2)Theweldsandadjoining areasofbypasspipingofthedischarge valvesinthemainrecirculation loops,andoftheaustenitic stainless steelreactorcorespraypipinguptoandincluding thesecondisolation valveshouldbeexaminedateachreactorrefueling outageoratotherscheduled orunscheduled plantshutdowns.
Successive examinations neednotbe=closer'han sixmonths,ifshutdowns occurmorefrequently thansixmonths.Thisrequirement appliestoallbypasslineswhetherthe4-inchvalveiskeptopenorclosedduringoperation.
Intheeventtheseexaminations findthepipingfree.ofunacceptable indications forthreesuccessive inspections, theexamination maybeextendedtoeach36monthperiod(plusorminusbyasmuchas12months)coinciding witharefueling outage.Inthesecases,thesuccessive examination maybelimitedtoonebypasspiperun,andonereactorcorespraypipingrun~(3)Theweldsandadjoining areasofotherservice.sensitive pipingshouldbeexaminedonasamplingbasis.Forexample,ifasystemconsistsofseveralbranchrunswithessentially symmetric pipingconfigurations thatperformsimilarsystemfunctions, anacceptable inspection programshouldincludeatleastone,butnotlessthan25K,ofthesimilarbranchruns.Thefrequency ofsuchexaminations shouldbeasdescribed in2above.Ifunacceptable flawindications aredetectedinanybranchrun,theremaining branchrunsamongthegroupshouldbeexamined.
intheeventtheexaminations revealnounacceptable indica-tionswithinthreesuccessive inspections, theexamination schedulemayreverttotheASMEBoilerandPressureVesselCode,SectionXI,"Inservice Inspection ofNuclearPowerPlant,Components" withtheexception that.therequiredexamination shouldbecompleted duringeach80monthperiod(two-thirds thetimeperscribed inthescheduleintheASNECodeSectionXI).
(4)Themethodofexamination, theallowable indication standards andexamination procedures shouldcomplywiththerequirements oftheEditionandAddendaoftheASMECode,SectionXIidentified asapplicable by10,CFRPart50,Section50.55a,Paragraph (g),"CodesandStandards."
IV.IMPLEMENTATION OFMATERIALSELECTION ANDPROCESSING GUIDELINES 1.Forplantsthatapplyforaconstruction permitaftertheissuedateofthisdocument, allASMECodeClassIreactorcoolantpressureboundarylinesshouldconformtotheguidelines statedinPartII.*2.Forplantsunde'rreview,butforwhichaconstruction permithasnotyetbeenissued,allservicesensitive linesshouldconformtotheguidelines statedinPartII.OtherASMECodeClassIreactor,coolantpressureboundarylinesshouldconformtoPartIII4to,theextentpracticable.
3.Forplantsthathavebeenissuedaconstruction permit,ASMECodeClassIreactorcoolantpressureboundarylinesshouldconformtotheguidelines statedinPartIItotheextentpracticable.
- Afterrevision, Regulatory Guide1~44maybeusedasguidanceforacceptable materials, process,orothermethods. 4.Forplantsthathavebeenissuedanoperating license,servicesensitive linesshouldbemodifiedtoconformtotheguidelines statedinPartII,totheextentpracticable.
Linesinwhichcrackingisexperienced shouldbereplacedwithpipingthatconformstotheguidelines statedinPartII.V.,"GENERALRECOMMENDATIONS ThemeasuresoutlinesinPartIIofthisdocumentprovideforpositiveactionsthatareconsistent withthecurrenttechnology.
Theimplemen-tationoftheseactionsshouldmarkedlyreducethesusceptibility tostresscorrosion crackinginBWRs.Itisrecognized thatadditional techniques areavailable tolimitthecorrosion potential ofBWRcoolantpressureboundarymaterials andimprovetheoverallsystemintegrity.
Theseincludeplantdesignandoperational considerations toreducesystemexposuretopotentially aggressive environment, improvematerialfabrication andweldingtechniques andprovisions forvolumetric inspec-tioncapability inthedesignofweldjoints.Specifically, considera-tionshouldbegivento:1.Minimizing thetotalextentofthecoolantpressureboundarywithspecialemphasisonstagnantorlowflowlines.2.Reducingtheoxygencontentoftheprimarycoolant.
'0
DISTRIBUTION W/ENCLOSURE:
DocketFilePDRLocalPDRLWR84FileM.ServiceProjectManagerWF'aneS.A.VargaDISTRIBUTION W/0ENCLOSURE:
R'.BoydR.DeYoungD.VassalloF.Williams.H.'Sm'ithR.MattsonJ.KnightS.PawlickiH.ConradI8E(3)ELDL.CrockerK.Gollerbcc:TICACRS(15)NSIC P+~~