Seismic Qualification of NPP Structures

SeismicQualificationofNPPStructures,SystemsandEquipmentComponents

MarekTengler

NuclearResearchInstitutein e,November2125,2011

SeismicEngineeringKnowledgeTransferSeminar

ww

w.s

teve

nson

.cz

remsed00711.ujv.rev0

2/41 SeismicQualificationofNPPStructures,SystemsandEquipmentComponents

STEVENSON AND ASSOCIATES Office in Czech Republic a. s., Vejprnicka 56, CZ 318 00 Pilsen, Czech Republic

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OverviewofExistingStandards PrinciplesofEquipmentSeismicQualification(SQ) AnalysisMethods ExperimentalMethods MethodologyofSQincludingGIPandPracticalExamples

TOPICS



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1.OVERVIEWOFEXISTINGSTANDARDS

National Nuclear Law,

Convention on Nuclear Safety

Documents of the National Nuclear Authority,

relevant IAEA documents

Other relevant national and international codes, norms and standards, industrial standards

as IEC, IEEE, ASME, PNAE, KTA etc.

HierarchyofLegislation,Codes,NormsandStandardsRelatedtoSeismicQualification



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2.OVERVIEWOFEXISTINGSTANDARDS (Contd)

~4500OtherStandardsCitedinRegulatoryDocuments

Reference:NUREG/CR5973,PNL8462Rev.3,CodesandStandardsandOtherGuidanceCitedinRegulatoryDocuments,PublishedAugust1996.



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2.SEISMICQUALIFICATION MOTHERHOOD STD.

IEC 980:1989 IEEE Std 344-2004

ASME QME-1-2007 Consequentialapplicablestandardsofseismicqualification:

Partialstandardsoftribalstandards:IECseries600682,600683(standardsformechanicalandvibrationresistance)

Specificstandards:IEC255213,C37.981987,IEEEStd3822006,IEEEStd3171983etc.



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2.SEISMICQUALIFICATION INTRODUCTION

WithintheseismicsectionoftheEQprogram,allsafetyrelatedequipmentmustproveitsseismicadequacytowithstandtheeffectsoftheearthquakecorrespondingtothemaximumdesignearthquake(SSE,S2,SL2).Onepartoftheseismicadequacyverificationisthedemonstrationtheequipmentiscapabletowithstandthecumulativedegradationeffectoffiveprojectdesignearthquakes(OBE,S1,SL1),whichmustnotaffecttheresistanceoftheequipmenttotheimpactofthemaximumdesignearthquake(SSE,S2,SL2).

Theseismicqualificationmustassuretheequipmentwillholditscapabilitytoperformtherequiredsafetyfunctionsduringand/orafteraseismiceventkeepingsuchastatethatcorrespondstotheendofitsqualifiedlife.



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2.SEISMICQUALIFICATION SEISMICCLASIFICATION

TheequipmentofanNPPsafetysystemsisgroupedintoseismicclasses (subclasses)accordingtothefollowingdefinitions(Generaldefinition):

1(A)fullfunctionalityisrequireduptoandincludingthemaximumdesignearthquakelevel(SSE,S2,SL2).

1(B)onlymechanicalintegrityisrequired(i.e.strengthandleaktightness)inaccordancewithrelevantstrengthstandardsandregulations;partialfailuresofthefunctionalityareadmitteduptoandincludingthemaximumdesignearthquakelevel(SSE,S2,SL2).

1(C)onlystabilityisrequired,i.e.toavoidseismicinteractionswithotherSSC(tokeepthestablepositionmostly);partialfailuresofthefunctionalityaswellasthemechanicalintegrityareadmitteduptoandincludingthemaximumdesignearthquakelevel(SSE,S2,SL2).



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2.SEISMICQUALIFICATION SEISMICINPUT

Seismicconditions ofthebuildings arerepresentedbyrequiredresponsespectra(RRS)ofthelocations,onwhichtheequipmentsubjecttoqualificationisinstalled.

FiguresonnextpageshowanexampleoftheRRS(smoothed)formaximumdesignearthquake(SSE,S2,SL2).

ThesmoothingofcalculatedRRScanbedoneusingthemethoddescribedinUSNRCRG1.122.

Thespectrashallcorrespondtothesignificantplaces(floororstructures)situatedinsidetheseismicclassifiedcivilstructures(buildings)whereclassifiedequipmenttobeinstalled.



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2.SEISMICQUALIFICATION SEISMICINPUT(Contd)

RRSenvelope,horizontaldirection.EarthquakelevelSSE,S2,SL2.

RRSenvelope,verticaldirection.EarthquakelevelSSE,S2,SL2



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Theaccelerationsneededtodeterminetheseismicexcitationwiththeintensityoftheprojectdesignearthquake(OBE,S1,SL1)arederivedfromtheshownRRSofmaximumdesignearthquakeastheonehalfoftheaccelerationRRSSSE(S2,SL2)forthespecifiedfrequency.

Fortheequipmentwhichisconnectedwithapipelinesysteminaverygoodmanner,liketemperaturesensors,valveactuatorsetc.,andwhichrequirethedemonstrationoftheirfunctionality,aspecifictechniqueoftheseismicqualificationneedstobeapplied.Suchequipmentactsasthepipelinecomponentsandtheyaresubjectedtoveryhardseismicloads.Theseloadsaregeneratedintheplaceoftheequipmentastheseismicresponseofthepipelinesystem.Amplifiedexcitationforcesareofthediscretenaturewithasingledominantfrequency.ToqualifytheequipmentconnectedwithpipelinesystemstheseismicexcitationderivedfromtheRIMcurvemustbeadditionallyappliedtogenericseismicqualificationRRStests.



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RequiredInputMotion(RIM)curve(seeIEEEStd382).LevelSSE,S2,SL2.



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2.SEISMICQUALIFICATION METHODS

Todemonstratetheseismicadequacyofseismiccategory1structures,systemsandequipmentcomponentsthefollowingmethodsareused:

(a)seismicanalyses(mainpipelines,mainmechanicalcomponents,anchorageofequipment),

(b) seismictests(activemechanicalcomponents,electricalandI&Ccomponents),

(c)earthquakeexperienceandindirectprocedures(smallborepipes,HVACducts,additionalapproachtoverifyseismicadequacyofequipmentcomponentsasmountedusingtheGIPVVERprocedure).



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4.QUALIFICATIONBYSEISMICANALYSIS

Purpose:Tedeterminedcriticalresponseparametersofequipmenttobeevaluatedforoperationalandseismicloadsbycalculation.

Generalmethodsofresponsecalculation:

Handcalculus(simplyequation);

FiniteElementMethod;

Combinationofbothabovementioned.



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4.QUALIFICATIONBYSEISMICANALYSIS(Contd)

Methodsofthecalculationofseismicresponse

- Staticanalysisforstiffcomponentswithnaturalfrequencyabove33Hz;

Equivalentstaticanalysisforsimplycomponents

Responsespectramethodcomplexcomponentslineardynamicbehaviorassumed

Timehistorymethodcomplexcomponentslinearandnonlineardynamicbehaviorassumed



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Assessmentofbaseparametersofcomponentcapacity

- Integrityofpressureboundary(housing,nozzles);

Capacityofinternals;

Supports(supportingstructure)capacity;

Anchor/fixtureresistance.



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Assessmentofperformancecapabilityofcomponent

Inaddition,fordocumentationofperformancecapability(functionality)ofactivemechanicalcomponentsareevaluatedparametersthataffectingtheirperformanceofdemandedsafetyfunction:

- Totalrelativedisplacementsofmovingandstaticpartstoassesstheircollisionsduringinducedseismicmotionsdepletionofdesignspacingsbetweenparts.

Totalreactionforcesandoveralldisplacementsinpointofpartsplacingjamingofbearings.

Totaldeformationinplacesofacontactofsealingareasviolationofpressuretightness.

- Otherspecificparametersrelatingtoevaluatedcomponent.



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4.QUALIFICATIONBYSEISMICANALYSIS EXAMPLE

MathFEmodeloftheflapvalveDN1000



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4.QUALIFICATIONBYSEISMICANALYSIS EXAMPLE(Contd)

SeismicexcitationRIMaccordinglyIEEEStd3822006



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MaximumresultingdistributionoftotaldisplacementsatexcitationinZdirection,max.11.4mm



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Evaluation Maximum Displacements

Place of maximum displacement Loading

Max. displ. X [mm]

Max. displ. Y [mm]

Max. displ. Z [mm]

Max. displ [mm]

Max. total displacement

[mm]

Allowable displacement

[mm]

NOC 0,0 0,0 0,3 0,3

SSE X 1,5 2,0 1,5 2,6

SSE Y 4,7 5,6 2,9 5,7 Disc of flap

SSE Z 1,1 1,6 11,3 11,4

11,5 20,0

Evaluation of sliding bearings in flap shaft

Loading Fy [kN] Fz

[kN] Stress [MPa]

Max. stress [MPa]

Allowable stress [MPa]

NOC 1,43 3,83 1,29

SSE X 5,00 1,07 1,62

SSE Y 12,25 1,24 3,90

SSE Z 3,30 11,42 3,77

5,19 30,0




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5.QUALIFICATIONBYSEISMICTEST GENERALLY

TheseismictestsofequipmentinNPPsaregenerallypreferredmethodsforthequalificationprogramof

Activetechnologicalequipment(e.g.valvesandtheiractuators)

Electricalequipment(e.g.switchgears)

I&Cequipment(cabinetsandpanels)

Sensitiveequipmentcomponentslikerelays,contactors,circuitbreakers,transmitters,sensorsetc.

Theseismiccapacityofsuchequipmentinregardoftheirfunctionalityduringandafteranearthquakeisimpossible,difficultorunreliabletoevaluatebyothermethods.



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5.QUALIFICATIONBYSEISMICTEST DIVISION

SEISMICINPUTMOTION

Singlefrequencymotion(withassumptiontheequipmentwillbesubjectedtosteadyvibrationswithonedominantfrequency,seeRIM,or,iftheexaminationofthenaturalfrequenciesandthedampingvaluesoftheequipmentisperformed);

Multifrequencymotion(generallypreferredfortheverificationoftheseismiccapabilityoftheequipment,themotionsimulationisveryclosetothetypicalearthquakemotion).Inmultifrequencyseismictestingtwoapproachesareapplied:

o Testwithrandomexcitation(inputseismicmotionappliedonthetestpieceisgivenbysynthetictimehistory;TRScorrespondstorealquakemotion);

o Testwithcomplexsineexcitation(inputseismicmotionappliedonthetestpieceisgivenbythesuperpositionofcomplexsinewaves)



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5.EXPERIMENTALMETHODS EXCITATIONDIRECTIONS

TESTSAMPLEORIENTATION

Singleaxistests(seismicinputmotionisappliedonlyinonedirection);

Biaxialtests(seismicinputmotionisappliedintwodirections)

o Biaxialinstallationtestingfortwoindependentdirections(seismicinputmotionforeachdirectionisstatisticallyindependent);

o Singleaxisinstallationtestsfortwodependentdirections(seismicplatformmovesoninclinedplane);

Triaxialtests(seismicinputmotionappliedinthreedirections/axesofatestpiecesimultaneously).

o Triaxialinstallationtestperformedwithsimultaneousbutindependentinputwaveformintothethreepreferredaxesofthespecimen;

o Biaxialinstallation(vertical/horizontal)testswithindependentsimultaneousexcitationsignalsinhorizontalandverticalplane.



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5.EXPERIMENTALMETHODS RRS

RequiredResponseSpectrum(RRS)istheresponsespectrumissuedbytheuserofthequalifiedequipmentorbytheusersagentaspartofthespecificationforqualification.RRSrepresentsarequirementtobemet.Theyarepreparedforallthreeorthogonalspacedirectionsoratleastforhorizontalandverticaldirections.

RequiredResponseSpectrapreparation

Createdtocoverapplicationforwholebuilding/wholeplant;

EnvelopeofbroadenedandsmoothedFRSforequipmentinstallationlocation(equipmentanchoredtotherelevantfloor/structure);

MultipleofbroadenedandsmoothedFRSduetoexcitationappliedonlyinonedirection(factor1.5);

MultipleofbroadenedandsmoothedFRSduetoequipmentinstallationonotherstructuresorequipment(usingamplificationfactor);

Combinationofpreviousboth.



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5.EXPERIMENTALMETHODS RRSVS.TRS

TestResponseSpectra(TRS)arecalculatedfromtherecordingsoftheactualmotionoftheshakingtable.TRSshallenveloptheRRSortheapplicableportionoftheRRStakingintoaccountthedynamiccharacteristicsoftheequipmenttested(naturalfrequency).TRSshallbecomputedwith1/3octave(ornarrower)bandwidthresolution.

TRSandRRScomparisonismadefororallthreeorthogonalspacedirectionsoratleastforhorizontalandverticaldirectionsandforfiveOBE(S1,SL1)earthquakesfollowedbyoneSSE(S2,SL2)earthquakes.Howeverinsteadof5OBE(S1,SL1)earthquakesthespecimenmaybesubjectedto2testscorrespondingtolevelSSE(S2,SL2).

TRSandRRSarecomparedwhichhavethesamedampingvalue.Recommendeddampingvalueis5%damping.ItisacceptabletocompareRRSwithTRSofhigherdampingvaluethenisthedampingvalueofRRS,nevertheless,TRSmustenvelopRRS.

Iftheresonancephenomenadoesnotexistbelow5Hz,theRRSshouldbeenvelopedforfrequencyvaluesabove3.5Hz.Bandwidth13.5Hz,howevershouldbecovereduptolevelprovidedbytestingdevice.Ifresonancephenomenaexistbelow5Hz,TRSshallenvelopRRSfrom1Hz.



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5.EXPERIMENTALMETHODS RRSVS.TRS(Contd)



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6.QUALIFICATIONBYEXPERIENCE/INDIRECTMETHOD

In1982havebeenestablishedSeismicQualificationUtilityGroup,witapurposedofcoordinatingandfoundingworksondevelopmentofstudyaboutbehaviorofmechanicalandelectricalcomponentsincaseofdestructiveearthquakes.Firstphaseofthoseworksfinishedalreadyin1978,whenhavebeenpublishedreportdefined20equipmentclassesindentifiedasinevitableforsafeshutdownofnuclearunits.Thereportevaluatedfeaturesofdifferentequipmentclassesduringsevereearthquakeandfoundedcriteriaofseismiccapacity,i.e.caveats,thathavebeendevelopedforeachequipmentclass.Ithasbeenalsodeterminedthecapacityspectrumofequipment,socalled,BoundingSpectrum,BS.



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6.QUALIFICATIONBYEXPERIENCE/INDIRECTMETHOD



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6.QUALIFICATIONBYEXPERIENCEGIPThescopeofequipmentcoveredbythe currentversionoftheGIP procedureincludes, thefollowingtwentyclassesofmechanicalandelectricalequipment:

(1)MotorControlCenters;

(2)LowVoltageSwitchgears;

(3)MediumVoltageSwitchgears;

(4)Transformers;

(5)HorizontalPumps;

(6)VerticalPumps;

(7)FluidOperatedValves;

(8)MotorOperatedandSolenoid OperatedValves;

(9)Fans(ventilators);

(10)AirHandlers;

(11)Chillers;

(12)AirCompressors;

(13)MotorGenerators;

(14)EngineGenerators;

(15)DistributionPanels;

(16)BatteriesonRacks;

(17)BatteryChargersand Inverters;

(18)InstrumentsonRacks;

(19)TemperatureSensors;

(20)I&CPanelsandCabinets.



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6.QUALIFICATIONBYEXPERIENCE GIP (Contd)

EuropeanandparticularlyVVERtyperelays,switches,transmittersandelectricpenetrationsaresignificantlydifferentfromthoseincludedintotheoriginalGIPdatabases.ThesetwoclassesofequipmentarenotincludedinspecificmodifiedprocedureforEuropeanNPPs,socalledGIPVVERprocedure(orGIPInternational),andtheirseismicverificationshallbebasedontesting.

Inadditiontotwentyclasseslistedabove,theGIPVVERprocedurealsoincludesguidelinesforsimplifiedanalyticalseismicevaluationofthefollowingclassesofequipment:

(23)CableSupportingStructures(basedmainlyontheEPRImethodology);

(24)Tanks,HeatExchanger,Filters(TANKVcomputercode,basedonthepublicavailabledocuments);

(25)PipelinesandHVACDucts(basedonthepublicavailabledocuments).

GIPVVERalsoincludestwospecialguidelinestoverifyadequacyofanchorageandseismicadequacyofnonbearingmasonrywalls.



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6.GIPVVERPROCEDURE WALKDOWNPROCEDURE

TheGIPaswellastheGIPVVERortheDOEGIPisprimarilyascreeningandwalkdownprocedure.However,ifanequipmentitemisclassifiedasanoutlier,rigorousapproachesastestingonshakingtable,deepstudyofinputdata,sophisticatedanalysisetc.maybeusedtoverifyitsseismicadequacy.Generally,fourmajorstepsofthisprocedurewhenappliedevaluationofseismicadequacyofclassesofequipmentidentifiedaboveareasfollows:

selectionofSeismicReviewTeam(SRT);

identificationofequipmenttheseismicadequacyshallbeevaluatedandsetuptheSeismicEquipmentList(SEL);

screeningverificationandwalkdowns;

outlieridentificationandresolution.



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6.GIPVVERPROCEDURE WALKDOWNPROCEDURE(Contd)

AnengineeringjudgmentisthemajortoolusedbySRTduringthescreeningverificationandwalkdownstoevaluateseismicadequacyoftheequipment.TheSRTshouldincludethesystemengineers,plantoperationpersonnel,experiencedandprofessionallytrainedseismiccapacityengineers,andalsopersonneltoidentifyandevaluateessentialrelays(ifnecessary).

Seismicevaluationengineersshouldhaveatleast3yearsexperienceinseismicdesignorqualificationofnuclearsafetyrelatedstructures,systemsandcomponents.Theyshouldhaveatleastabachelorsdegreeincivilormechanicalengineeringandformalinstructioninstructuraldynamicanalysis.Theyshouldalsohavecompletedatleasta3daycourseincludingfieldanalysisintheuseofGIPVVERmethodologyinseismicevaluationofnuclearfacilitysafetyrelatedSSCs.ItisforbiddentousetheGIPVVERprocedurewithoutdeepstudyofcorrespondingdocumentation,trainingandpracticalexperience.



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6.GIPVVERPROCEDURE CRITERIA

Thebasiccriteriatoverifyseismicadequacyofanequipmentitemduringthescreeningwalkdownare(seealsoschema&flow):

seismiccapacitygreaterthanseismicdemand(bycomparisonofthecorrespondingISRSRLE(SL2,SSE)orGRSRLE(SL2,SSE)totheBoundingSpectrum;

similaritytotheequipmentintheseismicexperiencedatabases(checkingofcaveats,basedonwalkdownandinformationavailablefromdocumentation);

adequateanchorageofequipment (calculationsorengineeringjudgment,basedonwalkdownsandinformationavailablefromdocumentation);

potentialseismicinteractionsevaluated(basedonwalkdowns).

TheGIPVVERprocedureusestwoboundingspectra(BS):

(a) BSattachedtoPGA=0.33g(thesameasintroducedbySSRAPandusedbyGIP);

(b) BSattachedtoPGA=0.50g(1.5timesSSRAPBS)forselectedVVERequipmentclasses,whichareevidentlyrobustandrugged.



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6.GIPVVERPROCEDURE SCHEMA&FLOW

START

DOES CAPACITY EXCEED DEMAND?

ARE INTERACTIONS ACCEPTABLE?

ARE FOUR ABOVE CRITERIA MET?

IS ANCHORAGE ADEQUATE?

ARE CAVEATS MET?

VERIFIED

CHOOSE ALTERNATE METHODSFOR CAPACITY/DEMAND

CAPACITY/DEMAND OUTLIER

CAVEAT OUTLIER

DETAIL INVESTIGATION

ANCHORAGE OUTLIER

INTERACTION OUTLIER

IDENTIFICATION AND RESOLUTION OF OUTLIERS

CHOOSE ALTERNATE METHODSFOR CAPACITY

(DETAIL INVESTIGATION)

DETAIL INVESTIGATION

YES

YES

YES

YES

YES

NO

NO

NO

NO

NO



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6.GIPVVERPROCEDURE CAPACITYSPECTRA



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6.GIPVVERPROCEDURE CAPACITYVS.DEMAND

A.ComparisonwithRLE(SL2,SSE)GroundResponseSpectra(GRS)2)

Thiscanbeusedwhentheequipmentitemismountedbelowabout12mabovetheeffectivegradeandwhenthenaturalfrequencyofequipmentisgreaterthan12Hz3)

BSGRSRLE(SL2,SSE)(5%damping)4)

B.ComparisonwithRLE(SL2,SSE)InStructureResponseSpectra(ISRS)1.5xBSrealistic(median,mean,bestestimated)ISRSRLE(SL2,SSE)(5%damping)4)

Notes:(1)Applyatleastoneofthesetworules,whichapplicable.(2)ThecriterionAcanbeusedonlywiththewellrigidbuildingstructuresasthelowerconcretereactorbuilding.Donotusethiscriterionwithevidentlyflexiblebuildingstructures.(3)Donotapplythe12Hzlimitforequipmentmountedonpipingsystems(valves,valveoperatorsetc.).(4)Thesecriteriashallbemetforallthreeorthogonalspatialdirections.



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6.GIPVVERPROCEDURE SIMILARITY

SimilarityofVVERtypeequipmenttoequipmentincludedinthedatabases ofseismicresistantequipmentisthemostimportantkeystoneofpracticalapplicationoftheGIPVVERprocedure.Generally,theprincipalofsimilarityisbaseduponcomparisonofequipmentdynamicandphysicalcharacteristics.Theproceduretoestablishsimilaritywithinaneachequipmentclassincludesthefollowingcomparisons:

mostprobablemodesofmalfunction(basedonrecognizedbehaviorofallcriticaldevices);

predominantresonantandcriticalfrequenciesandmodeshapes;

criticaldamping;

mostimportantphysicalequipmentcharacteristics,likeequipmentsize,massandposition(vertical,horizontal,inclinedetc.);generalmaking,qualityofmaking,ageofequipment;locationofthecenterofgravity,presenceandlocationofcantileveredparts;implementationofheavyand/ormovinginternalparts;implementationofsupportsandanchorage;implementationofattachedlines,substructures,devicesetc.;presenceofdevices(mechanicalorelectrical)sensitivetovibrationsandshocks.



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6.GIPVVERPROCEDURE ANCHORAGE

Thescreeningapproachtoverifyofequipmentanchorageisbaseduponacombinationofinspections,calculations,andengineeringjudgment.

Inspectionsconsistofmeasurementsandvisualevaluationsoftheequipmentanditsanchorage,supplementedbyuseofplantdocumentationanddrawings.Calculationsshouldbeperformedtocomparetheanchoragecapacitytothecorrespondingloading(demand)imposedupontheanchorage.Engineeringjudgmentisalsoanimportantpartintheevaluationofequipmentanchorage.

Generally,evaluationtheadequacyofequipmentanchorageincludes:

anchorageinstallationinspection,

anchoragecapacitydetermination,

anchoragedemanddetermination,

comparisonofcapacitytodemand.



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6.GIPVVERPROCEDURE SEISMICINTERACTIONS

Thefourseismicinteractioneffectsthatareconsideredare:

proximity(impactsofadjacentequipmentorstructuresonsafetyrelatedequipmentduetotheirrelativemotionduringanearthquake),

structuralfailureandfallingofoverheadoradjacentstructures,systems,orequipmentcomponents),

flexibilityofattachedlinesandcables,

floodingduetoearthquakeinducedfailuresoftanksorvessels.

Seismic Qualification of NPP Structures

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