e531

StandardPracticefor

SurveillanceTestingofHigh-TemperatureNuclearComponentMaterials1ThisstandardisissuedunderthefixeddesignationE531;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.

1.Scope

1.1Thispracticecoversproceduresforspecimentestingtoestablishchangesoccurringinthemechanicalpropertiesduetoirradiationandthermaleffectsofnuclearcomponentmetallicmaterialswherethesematerialsareusedforhightemperatureapplicationsabove370°C(700°F).

2.ReferencedDocuments2.1ASTMStandards:

A370TestMethodsandDefinitionsforMechanicalTestingofSteelProducts2E3MethodsofPreparationofMetallographicSpecimens3E8TestMethodsforTensionTestingofMetallicMaterials3E21TestMethodsforElevatedTemperatureTensionTestsofMetallicMaterials3E23TestMethodsforNotchedBarImpactTestingofMetallicMaterials3E29PracticeforUsingSignificantDigitsinTestDatatoDetermineConformancewithSpecifications4E45TestMethodsforDeterminingtheInclusionContentofSteel3E112TestMethodsforDeterminingtheAverageGrainSize3E139PracticeforConductingCreep,Creep-Rupture,andStress-RuptureTestsofMetallicMaterials3E184PracticeforEffectsofHigh-EnergyNeutronRadia-tionontheMechanicalPropertiesofMetallicMaterials,E706(IB)5E185PracticeforConductingSurveillanceTestsforLightWater-CooledNuclearPowerReactorVessels,E706(IF)5E206DefinitionsofTermsRelatingtoFatigueTestingandtheStatisticalAnalysisofFatigueData6E261PracticeforDeterminingNeutronFluenceRate,Flu-ThisrecommendedpracticeisunderthejurisdictionofASTMCommitteeE10onNuclearTechnologyandApplicationsandisthedirectresponsibilityofSubcom-mitteeE10.02onBehaviorandUseofMetallicMaterialsinNuclearSystems.CurrenteditionapprovedMarch26,1976.PublishedJuly1976.OriginallypublishedasE531–75.LastpreviouseditionE531–75.2AnnualBookofASTMStandards,Vol01.03.3AnnualBookofASTMStandards,Vol03.01.4AnnualBookofASTMStandards,Vol14.02.5AnnualBookofASTMStandards,Vol12.02.6Discontinued—see1986AnnualBookofASTMStandards,Vol03.01.

1ence,andSpectrabyRadioactivationTechniques5E399TestMethodforPlane-StrainFractureToughnessofMetallicMaterials3E453PracticeforExaminationofFuelElementCladdingIncludingtheDeterminationoftheMechanicalProperties5E482GuideforApplicationofNeutronTransportMethodsforReactorVesselSurveillance,E706(IID)5E844GuideforSensorSetDesignandIrradiationforReactorSurveillance,E706(IIC)53.SignificanceandUse

3.1Therequirementscontainedhereincanbeusedasabasisforestablishingconditionsforsafeoperationofcriticalcomponents.Therequirementsprovideforgeneralplantas-sessmentandverificationthatmaterialsmeetdesigncriteria.Thetestspecimensandprocedurespresentedinthispracticeareforguidancewhenestablishingasurveillanceprogram.3.2Thispracticeforhigh-temperaturematerialssurveil-lanceprogramsisusedwhennuclearreactorcomponentmaterialsaremonitoredbyspecimentesting.Periodictestingisperformedthroughtheservicelifeofthecomponentstoassesschangesinselectedmaterialpropertiesthatarecausedbyneutronirradiationandthermaleffects.Thepropertiesarethoseusedasdesigncriteriafortherespectivenuclearcomponents.Theextentofmaterialpropertychangecausedbyneutronirradiationdependsonthecompositionandstructureoftheinitialmaterial,itsconditioningincomponentfabrication,aswellasthenatureoftheirradiationexposure.Theneedforsurveillancearisesfromaconcernofspecificmaterialbehaviorunderallirradiationconditionsincludingspectrumandrateeffectsonmaterialproperties.

4.DescriptionofTerm

4.1testspecimen—acouponorapieceofmetalcutfromalargermetalpiecewhichisthenformedtofinalsizefortestingtodeterminephysicalormechanicalproperties.

5.TestSpecimens

5.1Pre-ExposureMaterialCharacterization—Itisimpor-tantthattestspecimenmaterialsbecharacterizedpriortoexposureandthatthefollowingshouldbeconsideredasaminimum:

5.1.1Processhistory,materialdesignation,manufacturer,

Copyright©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959,UnitedStates.

1

heatnumber,weldandfabricationproceduresused,andheattreatment,

5.1.2Originallocationandorientationintheparentmate-rial,

5.1.3Specimenweightanddimensions,

5.1.4Metallographiccharacteristics(grainsize,microstruc-ture,andinclusioncontentestablishedinaccordancewithTestMethodsE45andE112),

5.1.5Chemicalanalysisresults,

5.1.6AllspecimensshallbetakenfromthespecifiedlocationandorientationspecifiedinTestMethodsandDefini-tionsA370andTestMethodsE8,and

5.1.7Mechanicalpropertiesincludingyieldstrength,tensilestrength,stressrupturelife,creepstrength,fatiguestrength,andimpactstrengthasafunctionoftesttemperature.

5.1.8Theinformationdescribedin5.1.1-5.1.7shouldbereportedinasingledocument.

5.2PostExposureMaterialCharacterization—Afterexpo-sure,thefollowingshouldbereported:

5.2.1Observationsfromvisualexamination,

5.2.2Changesinspecimenweightanddimensions,

5.2.3Metallographiccharacteristics(grainsize,microstruc-ture,andinclusioncontent),

5.2.4Resultsofchemicalanalysis,

5.2.5Appropriatemechanicalpropertiesbeingsurveyedincludingconsiderationsofchangesintensilestrength,stress-to-rupturestrength,creepstrength,fatiguestrength,impactstrength(controltestsarerecommendedtobeperformedsimultaneouslywiththetestsofexposedspecimenstoensurethatdeviationsintestresultscanbeattributedtotheexposedspecimen’senvironmentandnottovariationsintestingmeth-ods),and

5.2.6Optionalquantitativeexaminationofsurfacechemis-tryandsubsequentchanges.

5.2.7Exposedtestspecimensshouldbecleanedinaccor-dancewithacceptedcleaningprocedures.(RefertoSubcom-mitteeG01.08forpracticesforpreparing,cleaning,andevalu-atingtestspecimens.)

5.3SpecimenPreparation—Testspecimensshallbestan-dardrecommendedspecimenswherepossibleasdescribedinTestMethodsE8,E21andE23andPracticeE139.TheuseofthewordspecimenorwordstestspecimenasusedinthispracticeisdescribedinSection4.

5.3.1Thetestareaofaspecimen(forexample,Charpynotch,reducedsectionofafatiguespecimen)maybeleftunfinishediffurtherenvironmentalexposurepriortotestingisanticipated.

5.3.2Size—Ingeneral,duetothelimitedspaceavailableinsurveillancecapsulesthesmallersizesoftestspecimensarerecommended.Whereitisnotpossibletousespecimensoftherecommendedsize,theleastdeviationpossiblefromrecom-mendedsizesshouldbeadheredto.Non-standardspecimensshallbeevaluatedpriortouseassurveillancespecimenstoensurethattestresultsfromtheuseofnon-standardspecimenscanbecorrelatedwithtestresultsfromspecimensofrecom-mendedsize.Intheeventthatnon-standardspecimensareusedforsurveillancespecimens,thearchive,baseline,andthermalcontrolspecimensshallbeidenticalwiththesurveillancespecimens.

5.3.3SurfaceCondition—Testspecimenswheresurfaceconditioniscriticaltothetestresultsshouldnotbefinishmachinedinsuchcriticalareas(Charpynotch,fatiguespeci-mentestarea,surfaceofdensitychangesample)untiljustpriortotest.Specimensshouldbeoversizedtoallowforremovalofatleast0.1mmofsurfacepriortotest.Wherepossible,testspecimenswiththeexceptionofweightchangespecimensshallbeencapsulatedinaninertenvironmentsoastodeter-mineonlytheeffectofneutronirradiationandtemperatureonmechanicalorphysicalproperties.Itisrecognizedtheintegrityoftheencapsulationmaybebreachedinsomecasesduringlongexposureandanallowanceforfinalmachiningevenoftheencapsulatedspecimensshouldbeconsidered.Thiswillensureameaningfulcomparisonbetweenbaselineandexposedspeci-mens.

5.3.4NumberofSpecimens—Thenumberofspecimensemployedformechanicalpropertytestingshouldbeselectedsoastoincludeeachcriticalcomponentthatvariessignificantlyincomposition,processing,orinexposureconditionsfromsimi-larcomponents.Specificrecommendationsastonumberofspecimenswillbefoundintherespectivespecimensections.Atleastfoursetsofspecimensshallbeincludedineachsurveillanceprogram.

5.3.5Material—Testspecimensshallbetakenfromthematerialusedincomponentfabrication.Thematerialshallbeprocessedatthesametimeasthecomponentorprocessedinafashionidenticaltothecomponentsurveyed.Weldandheat-affectedzonetestspecimensshallbetakenfromequivalentmaterialweldedatthesametimeastheparticularcomponentorequivalentmaterialweldedwiththesameweldingparam-eters.Itisnotnecessarytoincludeeachheatorminorvariation,butonlytoselectthosereceivingthehighestexpo-sureorthosepreviouslyfoundtobemostsensitivetoneutronirradiationandtemperatureorthosethatcanrestricttheoperationofthereactor.Testspecimensmaybetakenfromcomponentsperiodicallyremovedfromthereactorforotherreasons.Thesespecimenscanbeusedtoprovidesupplementalsurveillanceinformation.Forthisinformationtobemeaningfulafullcharacterizationofthepre-exposureconditionmustbeavailablealongwithmeasuredexposureconditions.

5.4TensionTestSpecimens—ThetypeandsizeofspecimentobeusedshallconformtothesmallersizesasrecommendedinTestMethodsE8andE21.Eitherthreadedorbutton-headendswillbeacceptable.Forplateorsheetspecimens,pinendsasdescribedinTestMethodsE8arerecommended.ThelocationandorientationoftestspecimensshallbeasdefinedinTestMethodsE8orTestMethodsandDefinitionsA370,orinPracticeE185.Bothbasemetalandweldmetalspecimenswillbetaken.Asetoftensionspecimensshallconsistofthreeeachbasemetalandweldmetal.

5.5CreepandStress-RuptureinSpecimens—Thetypeandsizeofspecimentobeusedshallbethesameasthoseusedfortensionspecimensexceptthatbutton-headorpinned-endspecimensarerecommendedforhigh-temperaturetesting.PracticeE453describestheattentionthatmustbepaidtospecimenalignmentanddimensionaltolerances.Onesetof

testsshallbeconductedattheoperatingtemperatureofthecomponentofinterest.Asetshallcompriseaminimumofsixstressrupturetestsatsixdifferentstresslevels.Thestresslevelsshouldbeselectedsothatthetime-to-rupturerangesfromnotlessthan100htoatleast3000h.Creepstrainmeasurementsmaybemadeifdesired.

5.6Low-CycleFatigueSpecimens—Forbasemetalthetypeandsizeofspecimentobeusedmaybethe“hourglass”typewiththreadedorbutton-headendsasshowninFig.1.Forweldmetalspecimenstheuniformgagetypemaybeused.Machin-ingandpolishingofthetestspecimensshallbeperformedwithcaresoastominimizetheeffectsofspecimenpreparationonfatiguelife.Inthefinalstagesofmachining,materialshallberemovedintheradialthicknessamountsof0.2mmuntil0.1mmremains.Afterexposurethefinal0.075mmshallberemovedbycylindricalgrindingatnomorethan0.005mmperpass.Thefinal0.025mmshallbebuffedandfinishedwithan0.2µmRa(8µin.AA)surfaceroughness.Afterpolishing,allremaininggrindingandpolishingmarksshallbelongitudinalandanycircumferentialgrindingmarksmustberemoved.Thefinishedspecimensshallbedegreasedinsuitablesolvent.Specimenstobeexposedtoliquidsodiumshallnotbedegreasedinhalogenatedsolvents.Ifsurfaceobservationsaretobemade,thetestspecimenmaybeelectropolishedin

accordancewithMethodsE3.Testspecimensthataresuscep-tibletocorrosioninroom-temperatureairshallbestoredassoonaspracticableafterpreparationinaninertdrygasorvacuum.Asetofspecimensshallconsistofteneachofbasemetalandweldmetal.

5.7SwellingSpecimens—Theswellingspecimensshallberightcircularcylinders5.0mmdiameterand10.0mmlong.Thesharp-corneredspecimensshallbefinishedbyturningorgrindingandhaveasurfacefinishof0.2µmRa(8µin.AA).Thespecimensshallbedegreasedinsuitablesolventandstoredinaninertgasorvacuum.

5.8CharpyImpactSpecimens—ThespecimenstobeusedshallconformtotheCharpyV-notchspecimensrecommendedinTestMethodsE23.Thenotchshallnotbeformedpriortoexposureasasurveillancespecimen.Thelocationandorien-tationoftestspecimensshallbeasdefinedinPracticeE185andTestMethodsandDefinitionsA370.Asetofspecimensshallbemadeupoftwelveeachbasemetal,heat-affectedzone,andweldmetal.

6.IrradiationConditions

6.1Introduction—Theintentofthesectiononirradiationconditionsistoprovideguidanceonhowtoplacesurveillancesamplestoobtainthedesiredirradiationconditionsintermsof

NOTE1—A=0.2µmRa(8minAA).

MetricConversion

mm0.36.358.412.6812.7019.138.182.6

in.0.010.2500.330.4990.5000.751.53.25

FIG.1StandardHour-GlassLowCycleFatigueSpecimen(ThreadedEnds(a)andButtonHead(b))

temperature,neutronflux,andneutronspectrumtoensurearealisticevaluationofthecomponentthatthesurveillancespecimenisrepresenting.

6.2IrradiationTemperature—Itisveryimportantthatad-equateconsiderationbegiventotestspecimenstoensurethattheyexperiencethecorrecttemperatureduringirradiation.Temperaturemustbecontrolledforthesurveillancespecimenstomatchasnearlyaspossiblethetemperatureofthecompo-nentbeingsurveyed.Whentemperaturevariationsarisebe-causeofseparationofthesurveillancespecimensfromthecomponent,additionalspecimensshouldbeincludedinotherpositionswhichwillcoveratemperaturerangeincludingthecomponentoperatingtemperature.Theirradiationtemperatureshallbegivenandthemethodfordeterminationshallbedocumented.

6.3FluxandSpectrum:

6.3.1Thesizeofcertainreactorcomponentsmayintroduceirradiationconditionsthatcoverawiderangeofneutronfluxesandspectra.Accordingly,surveillanceirradiationscarriedoutatlocationsotherthanexactlyincontactwiththecomponentofinterestwillrequireconsiderationofthechangeinneutronfluxandspectrumbetweencomponentandsurveillancelocation.Frequently,surveillancespecimensareplacedsuchthattheneutronfluxishigherthanatthecomponentofinterest;dueconsiderationmustthenbegiventochangesinneutronenergyspectrumwhenmakingsuchcompromises.

6.3.2Alsoofconsiderableimportanceduringelevatedtem-peratureexposurearetheeffectsoftime-at-temperature.Itshouldberecognizedthattheplacementofsurveillancespeci-mensinaregionofhigherfluxmaychangethetotaloutcomeforagivenneutronfluencejustbecauseofthedifferenttime-temperatureeffect;thatis,thehigherfluxlevelproducesashorterirradiationtime,andprecludespotentialaging-typeeffects.Inthecasewheresurveillancespecimensareplacedincertainhighneutron-fluxregionssoastoattainaspecificfluencelevelmorequicklythanthecomponentitself,anappropriatedamage-equivalencefactororanalysisschemeshouldbeusedinevaluatingthetestresultsfromthesamplesforrelatingtotheexpectedresultsfromthecomponent.6.4CoolantEnvironment:

6.4.1Thechoiceofenvironmentforasurveillancespeci-mendependsontheotherreactorenvironmentssurroundingthespecimenitself.Iftemperatureshigherthanprovidedbythesurveillanceenvironmentareneeded,thesecanbeattainedbyusinganinertgasblanketbetweenthespecimenandthecapsuleenclosure.

6.4.2Itisintendedthatspecimensbeevaluatedsolelyforirradiation,timeandtemperatureeffects;therefore,otheren-vironmentalinfluencesshallbeminimizedorprecludedifatallpossible.However,ifalternativereactorcoolantsorotherenvironmentalfactorsmustbeused,theireffectsuponthesurveillancespecimensshouldbecarefullyevaluatedwithrespecttothetestresultsandtheconclusionsdrawntherefrom.6.5SpecimenWithdrawalSchedule—Thespecimenwith-drawalscheduleshallbeasspecifiedinPracticeE185,CaseB,basedonthepercentageofcomponentlifeasspecifiedinTable1.

7.MeasurementofNeutronExposure

7.1Theneutronfluxandneutronenergyspectrumatthesurveillancelocationshallbegivenaswellasthemethodusedfordetermination.Allassumptionsshouldbeclearlystated,andallphysicalconstants,suchascrosssections,halflives,fissionyields,etc.,shouldbelisted.Theneutronfluxlevelshouldbedeterminedusingmorethanonesinglefluxdetectormaterial.Itisrecommendedthataseriesofdetectorsbeusedforthefluencedeterminationitself,andalsoforsubsequentuseineitherverifyingtheresultsofreactorphysicsspectrumcodecalculationsorinunfoldinganeutronspectrumfromtheactivationdataitself.

7.2Guidanceforuseofmultiple-fluxdetectorsinspectrumevaluationproceduresisgivenintheRelatedMaterialsection7underthetitle,“DiscussionofComputerCodesforDetermin-ingNeutronFluxSpectrabyMultipleFoilMeasurements.”Aspecificpracticeforneutrondosimetryinhigh-temperaturereactorirradiationshasnotbeenwritten,butguidanceisavailablefromGuideE482,whichwaswrittenbySubcom-mitteeE10.05forlightwaterpowerreactorirradiations.TheselectionofspecificfluxdetectormaterialscanbeaidedbyreferencetoGuideE844.MeasurementtechniquesandgeneralguidancearegiveninPracticeE261.

8.Swelling

8.1Introduction—Thepurposeoftheswellingsurveillancewouldapplyonlywhenthedesignconsiderationrequiresthatswellingbewithinareasonablelimitanddesignestimatesrequireswellingsurveillanceforthecomponent.Theswellingcouldbeevaluatedfromdestructiveexaminationofperiodi-callyremovedcomponentsorinthecaseofmorepermanentcomponents,theevaluationofa5-gportionofatensionspecimenorCharpyspecimenrelatedtothecomponent.Thesensitivityofirradiationinducedswellingtoirradiationtem-perature,flux,andspectrumwouldrequireverycloseattentiontotheirradiationconditionsoftheswellingspecimensothattheyapproximateascloselyaspossiblethatofthecomponent.Ifpossible,theswellingspecimenshouldbeattachedtothecomponent;however,wherethecomponentisinanonacces-sibleposition,otherpositionscouldbeconsidered.

8.2SwellingEvaluationBasedonDimensionalChanges—Dimensionalchangesincludingconsiderationsforcalibration,surfacepreparation,temperature,andlengthsshallbeinaccordancewithSection7ofPracticeE453.SpecifiedlimitingvaluesshallbeinaccordancewithPracticeE29.

8.3DensityMeasurementstoEvaluateSwelling—DensitymeasurementsshallbeconductedinaccordancewithSection12ofPracticeE453.

9.CreepandStress-RuptureTests

9.1Introduction—Theintentofcreepandstress-rupturetestsistoprovidesupplementaldatawhensignificantmaterialspropertieschangesarefirstindicatedfromshorttermmechani-calpropertiestestsonspecimensremovedfromthereactor.Thecreepstrainmeasurementsaremadetoverifythatthematerialmeetsthedesigncriteria(ifdimensionaltolerancesarecritical).

7See1974AnnualBookofASTMStandards,Part45.

10.FatigueTests

10.1Introduction—Theintentoffatiguetestsistoprovidedatafromwhichtheservicelifeandsafeoperationofthosecriticalcomponentsasdefinedbythedesignerscanbemoni-tored.Thefatiguetestsshouldbeappliedtospecimensrepresentativeofthecomponents.Thespecimensmaybesamplesinsertedinthereactoratstartuportakenfromcomponentswhichhavebeeninserviceandhavebeenremovedtoascertaintheintegrityofotherremainingcompo-nentsforfurtherservice.(AstandardisinpreparationbyASTMCommitteeE–9.)10.2TypeofTest:

10.2.1AxialorBendingTests—Axialstraincontrolledcy-clictestingattemperaturescorrespondingtocomponentoper-atingtemperaturesisrecommendedforthelowandaxialpush-pullorcompletelyreversedbendingarerecommendedintheintermediateandhighliferange(105to107cycles).

10.2.2FractureMechanicsTypeTests—Theuseoffracturemechanicstechniquesindesignandsafetyanalysesprovidesaquantitativemeansforassessingtheservicelifeofcomponentscontainingflaws(eitherrealorhypothetical).Therefore,inclu-sionoffracture-mechanics-typefatiguespecimensinsurveil-lanceprogramsisrecommended.

10.2.2.1Severalacceptablespecimendesignsexist,includ-ingcenter-notched,single-edge-notched,bend,andcompactspecimens(seeTestMethodE399forthelattertwotypes).Thespecimendesignchosenshouldhaveawelldocumentedsolutionforthestressintensityfactor(K).Themaximumfatigueloadingsshouldbesuchthatplasticityshouldbeconfinedtoasmall(relativetotheplanardimensionsofthespecimen)regioninthevicinityofthecracktip.

10.3ConductoftheTest—Themajortestparameters,tem-perature,cyclicfrequency,stressratioAorR(seeDefinitionsE206),loadingwaveform,andenvironment,shouldbese-lectedtocorrespondascloselyaspracticaltotheexpectedcomponentoperatingconditionsforalltypesoftests.

10.3.1Forstraincontrolledpush-pullteststhestressshouldbemonitoredtodeterminetheextentofcyclichardeningorsoftening.

10.3.2Forsub-criticalcrackgrowthteststhecracklengthandthenumberoffatiguecyclescorrespondingtothatcracklengthwillbedeterminedperiodicallythroughouteachtest.Cracklengthsmaybedeterminedperiodicallythroughouteachtest.Cracklengthsmaybedeterminedwithanydevice(for

example,cathetometer,eddycurrent,ultrasonic,electricalresistance,etc.)possessingsuitableaccuracyandresolutionforthespecimenemployed.

11.Report

11.1Theresultsofthesetestswillcoverlongperiodsoftimeanditisessentialthateachreportbecomplete.Pre-exposureconditionofthespecimen,detailsofexposureandenvironment,testingequipment,andtechniqueshallbein-cludedinthereportofresults.Ifcertaindetailshavebeenadequatelyreportedelsewhere,areferencetothatreportissufficient.

11.1.1TensionTesting—Thefollowingrequirementsforreportingareminimumrequirements.

11.1.1.1Specimendimensionsandtype,11.1.1.2Temperature,11.1.1.3Testatmosphere,11.1.1.4Strainrate,

11.1.1.5Extensometerandtestingmachinemodelnumber,accuracy,andrangeused,

11.1.1.6Temperature-measuringsystemandaccuracy,and11.1.1.7Yieldpoint(ifapplicable),tensilestrength,uniformandtotalelongation,andreductionofarea.Anautographicload-elongationrecordisdesirable.

11.1.2CreepandStressRuptureTesting—ThereportingprocedureinPracticeE139shallbefollowed.11.1.3FatigueTesting:

11.1.3.1FractureMechanicsTypeTests—ThereportingprocedureinTestMethodE399shallbefollowed.Themethodofcalculatingcrackgrowthrates(forexample,graphicaldifferentiation,differentiationofamathematically-fittedfunc-tion,orpoint-by-slopes)shouldbestated.Customarily,thelogarithmoffatigue-crackgrowthrateisplottedasafunctionofthelogarithmofthestressintensityfactoryrange.However,severalrelationshipsareavailablethatcorrelatetemperature,frequency,andstressratio,andthesemaybeusedifappropri-ate.

11.1.3.2AxialorBendingTests—(Standardinpreparation.)11.1.4CharpyImpactTesting—ThereportingprocedureinTestMethodsE23shallbefollowed.

12.Keywords

12.1irradiation;nuclearreactorvessels(hightemperature);radiationexposure;surveillance(ofnuclearreactorvessels)

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