ML18141A456

On the Unacceptability of the 25 F Embrittlement Exclusion in the Beltline Region Tlr. (TLR-RES/DE/CID/2013-01)

ML18141A456
Person / Time
Issue date:	05/21/2018
From:	Allen Hiser Division of Materials and License Renewal
To:
Rezai A, NRR-DMLR 415-1328
References
TLR-RES/DE/CIB/2013-01
Download: ML18141A456 (20)

Text

On the Unacceptability of the 25 F Embrittlement Exclusion in the Beltline Region TLR (TLR-RES/DE/CIB-2013-01)

Allen Hiser Office of Nuclear Reactor Regulation Division of Materials and License Renewal Materials Information Exchange Meeting May 22, 2018 Rockville, MD

Topics

• TechnicalLetterReports

• TLRRES/DE/CIB201301

• PerspectiveRelatedtoExcludingT<25F 2

Issue

• Industryhastakenaconclusionstatement(relatedto exclusionofirradiationembrittlementeffectsforT<25F) fromanREStechnicalletterreport(TLR)andimplemented itinplantspecificlicenseamendmentrequestsanda genericreportasifitisanacceptableNRCstaffposition

• AstheNRChasbeguntoissuerequestsforadditional informationontheuseofthisproposal,therehasbeen confusionbytheindustryonwhyitsuseisnotacceptable

• TheNRCapprovedonelicenseamendmentrequest(LAR) withthisproposal,whichinthiscasedidnotaffectthe acceptabilityoftheLAR

- Thesafetyevaluationdidnotexplicitlyaddressthe unacceptableuseoftheT<25Fexclusion 3

ClarificationofTLRs-Purpose,ProcessesandSignificance

• PurposeofRESTechnicalLetterReports(TLRs):

- ProvideastatusupdatetoNRRforresearchprojectsonce acriticalmilestonehasbeenachievedtodocument researchfindings,surveys,stateoftheartassessments, dataanalysis,etc.

- Documentonepartofalargeresearchprojectthatwillbe integratedwithothers

• Morecompleteorimportantinformation,including conclusionsandincorporatingNRRreviewcomments, generallyarepublishedindocumentssuchasformal NUREGandNUREG/CRreports 4

ComparisonswithNUREGReports ProcessforNUREGsisestablished,structuredandgenerally includesextensiveinternalreview-publicationisasignificant agencyaction

- NocomparableformalreviewandissuanceprocessforTLRs

- UseofTLRsfacilitatesexpeditedcommunicationoffindings NUREGsincludedisclaimerstatementand(forRESreports)a Forewordtoprovidecontexttothereport

- TLRsincludenocomparableprovisions Historically,NUREGshavebeenoneoftheprimarymeansofNRCs communication

- MorerecentpostingofTLRsaspublicinADAMSenableseasyaccess

- Thishascreatedconfusionontheacceptability,relevanceandutilityof resultsmadepublicinTLRs 5

NRCStaffRegulatoryPositions

• NRCstaffregulatorypositionsareprovidedin regulations,regulatoryguidesandotherformal documentslabeledassuch

• Ingeneral, statementsinNUREGreports,NUREG CRs,TLRsarenot NRCstaffregulatorypositions

• ExceptionsincludetheGALLandGALLSLR reports,whichprovideguidanceonacceptable agingmanagementprogramsforlicenserenewal andSLR,respectively 6

TLRonRPVBeltline

• TLRRES/DE/CIB201301,"EvaluationoftheBeltlineRegion forNuclearReactorPressureVessels,(ML14318A177)

- IssuedNovember14,2014

- Oneofaseriesofplannedtechnicalletterreportsplannedby REStosupportapossible10CFRPart50,AppendixG rulemaking

• AsstatedinSection4,theRESstaffrecommends:

- Embrittlementeffectsmaybeneglectedforanyregionofthe RPVifeitherofthefollowingconditionsaremet:

1) neutronfluenceislessthan1x1017 n/cm2 (E>1.0MeV)atEOL,or 2) themeanvalueofT30 estimatedusinganETC[embrittlement trendcurve]acceptabletothestaffislessthan25°FatEOL.The estimateofT30 atEOLshallbemadeusingbestestimatechemistry values.

Item1)isconsistentwithRegulations-notanissue.

Item2)isnotconsistentwithRegulations-abasisforthis provisionisnotprovidedintheTLR.

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RegulatoryIssueSummary201411 InformationonLicensingApplicationsforFractureToughness RequirementsforFerriticReactorCoolantPressureBoundary Components IssuedOctober14,2014 toprovideguidance...onthescopeanddetailofinformationthat shouldbeprovidedinreactorvesselfracturetoughnessand associatedpressuretemperature(PT)limitslicensingapplications allferriticcomponentswithintheentirereactorvesselmustbe consideredinthedevelopmentofPTlimits,andtheeffectsof neutronradiationmustbeconsideredforanylocationsthatare predictedtoexperienceaneutronfluence exposuregreaterthan 1x1017 n/cm2 (E>1MeV) attheendofthelicensedoperating period.

Nodiscussionregardingexclusionofembrittlementeffectsif T30is lessthan25°F.

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25FTLRRecommendation

• Basisisnotclearlypostulated,discussednor supportedintheTLR-firststatedinthe summaryofresultswithoneaccompanying graph

• Conflictswithrelevantregulationsandnot consistentwithRIS201411 9

RelevantRegulations 10CFR50AppendixG,II.F-BeltlineorBeltlineregionofreactor vesselmeanstheregionofthereactorvessel...thatarepredicted toexperiencesufficientneutronradiationdamagetobeconsidered intheselectionofthemostlimitingmaterialwithregardto radiationdamage 10CFR50AppendixH,III.A-Nomaterialsurveillanceprogramis requiredforreactorvesselsforwhich...thepeakneutronfluence attheendofthedesignlifeofthevesselwillnotexceed1017 n/cm2 (E>1MeV).

10CFR50AppendixG,IV.A-Forthereactorvesselbeltline materials,includingwelds,platesandforgings,thevaluesofRTNDT andCharpy uppershelfenergymustaccountfortheeffectsof neutronradiation 10

MoreRelevantRegulations 10CFR50.61-PTSRule

- (a)(3)ReactorVesselBeltlinemeanstheregionofthereactorvessel...

thatarepredictedtoexperiencesufficientneutronradiationdamageto beconsideredintheselectionofthemostlimitingmaterialwithregardto radiationdamage-samedefinitionas10CFR50,AppendixG

- (a)(4)RTNDT meansthereferencetemperatureforareactorvessel material,underanyconditions.Forthereactorvesselbeltlinematerials, RTNDT mustaccountfortheeffectsofneutronradiation

- (a)(7)RTPTS meansthereferencetemperature,RTNDT,evaluatedfortheEOL Fluenceforeachofthevesselbeltlinematerials,usingtheproceduresof paragraph(c)ofthissection

- (c)(1)(iv) RTNDT isthemeanvalueofthetransitiontemperatureshift,or changeinRTNDT,duetoirradiation,andmustbecalculatedusingEquation 3.

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MoreRelevantRegulations

• 10CFR50.61a-AlternatePTSRule

- (a)Termsinthissectionhavethesamemeaningasthose presentedin10CFR50.61(a),withtheexceptionoftheterm ASMECode.

- (c)(1)EachlicenseeshallhaveprojectedvaluesofRTMAX-X for eachreactorvesselbeltlinematerialfortheEOLfluenceof thematerial. TheassessmentofRTMAX-X valuesmustusethe calculationproceduresgiveninparagraphs(f)and(g)ofthis section.

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MoreRelevantRegulations

• 10CFR50,AppendixH

- (I)thetestproceduresandreportingrequirements mustmeettherequirementsofASTME18582to theextentpracticable...

• ASTME18582

- 10.2.1Determinetheradiationinducedtransition temperatureshiftsbymeasuringthedifferencein the41J(30ftlbf)...indextemperaturesbefore andafterirradiation.Theindextemperaturesshall beobtainedfromtheaveragecurves.

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RegulatoryGuide1.99,Rev.2 RadiationEmbrittlementofReactorVesselMaterials

• Theadjustedreferencetemperature(ART)for eachmaterialinthebeltlineisgivenbythe followingexpression:

- ART=InitialRTNDT +RTNDT +Margin(1)

• RTNDT isthemeanvalueoftheadjustmentIn referencetemperaturecausedbyirradiationand shouldbecalculatedasfollows:

- RTNDT =(CF)f(0.280.10logf) 14

Perspective-Part1

• RESTLRandRISwereunderdevelopmentduring thesametimeframe.

• The25°Frecommendationwasincludedinthe RESTLRasaconsiderationbytheRESstaff-the regulatorypositionespousedintheRIS specificallydidnotincludethisprovision.

• ApubliccommentonGALLSLRRPVmaterial surveillanceprogramguidancerecommended implementationofthe25°Fexclusion-this recommendationwasrejectedbythestaff.

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TechnicalAssessment

• HighestART(andpotentialnozzlestresses)definePTlimit curves

- ART=InitialRTNDT +RTNDT +Margin

• Changingshiftsofupto25°Fto0°Fresultsindecreasing ARTbyupto50°F,byalsoreducingthemarginterm.This canbeasignificantchange.

• Incertaincases,the25°Fproposalmayimpact identificationoflimitingmaterialsforART,resultingin developmentofincorrect(nonconservative)PTlimits.

• Relatedbutnotdeterminativeitem-Researchprograms examiningneutronfluence(revisionofRG1.190)indicate thatfluenceprojectionsforextendedbeltlinematerialsand nozzlesmaybeunderpredicted;RTNDT wouldincreasefor thesematerials.

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SummaryofRegulatoryProvisionsand TechnicalAssessment

• Relevantregulationsstatethatcalculationsmustaccount forradiationeffectsforthosematerialswithfluencegreater than1017 n/cm2 (E>1MeV),asdescribedinRIS201411.

• Noprovisioninanyoftheregulationspermitsexclusionof RTNDT orT30 lessthan25°F.

• AcceptanceoftheTLRproposalcouldresultinplant operationwithnonconservativePTlimits(AppendixG violation).

• Currentview:

Disalloweliminationofembrittlementeffects ifRTNDT orT30 lessthan25°F 17

Perspective-Part2 Regulationsrelatedtoreactorpressurevesselintegritydonot permitexclusionofRTNDT orT30 lessthan25°F.

TLRdoesnotprovideanadequatetechnicalbasisforanexemption fromtheregulatoryrequirements.

UseofallRTNDT orT30(even<25°F)isaconservativepositionto estimateRPVtoughness,whichhasbeenalongstandinggoal.

Plantsubmittalsandtopicalreportsshouldnotusethisprovision withoutanadequatetechnicalbasistosupportanexemption requestorstaffapproval,asrequired.

Forpriorsubmittalsandindustrytopicalreports:

- IftheresultingPTlimitsremainunchanged,supplementwiththe correctARTvalueforeachRPVbeltlinematerial.

- IftheresultingPTlimitschange,needtoensurethatthecorrectART valueforeachRPVbeltlinematerialareusedtorevisePTlimitsinthe LAR,andtheplantspecificapplicationreport.

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Conclusions

• TLRisnotanacceptablebasisforneglecting embrittlementeffectsifRTNDT orT30 less than25°F.

• CurrentNRCpositionisdescribedinRIS 201411:RPVtoughnesscalculationsmust accountforradiationeffectsforthose materialswithfluencegreaterthan1017 n/cm2 (E>1MeV),withoutexclusionevenif RTNDT orT30 lessthan25°F.

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Conclusions

• Asalways,NRCstaffispreparedtoreview anyindustryproposalwhichprovidesan adequatetechnicalbasisfortheproposal.

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