ML22256A301

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Enclosure 1: Changes to Hermes PSAR Chapters 3, 4, and 6
ML22256A301
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Issue date: 09/13/2022
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KP-NRC-2209-009
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KP-NRC-2209-009 Changes to Hermes PSAR Chapters 3, 4, and 6 (Non-Proprietary)

PreliminarySafetyAnalysisReport

DesignofStructures,Systems,andComponents

KairosPowerHermesReactor 339 Revision0 Table3.62:DesignandConstructionCodesandStandardsforFluidSystems Components SafetyRelated (Note1)

NonSafetyRelated,ContainingRadioactiveMaterials (Note2)

NonSafetyRelated,Not ContainingRadioactive Materials(Note3)

PressureVessels

(>15psig)

ASMECode,SectionIII, Division5,ClassAorB (Reference4)(Note6)

ASMECode,SectionVIII,Division1or ASMECode,SectionVIII,Division2 (Reference5)

LocalBuildingCode PipingandValves

ASMECode,SectionIII, Division5,ClassAorB (Reference4)(Note 6)N/A ANSI/ASMEB31.1/B31.3(References6and7)

(Note4andNote5)

Pumps N/A Manufacturersstandards or API610,API674,API675(References8,9,and10)

AtmosphericStorage Tanks N/A API650 (Reference11)

StorageTanks (015psig)

ASMECode,SectionIII, Division5,ClassAorB (Reference4)(Note 6)N/A API620 (Reference12)

CoreSupportStructures ASMECode,SectionIII, Division5,Subsection HG/HH(Reference4)

(Note6)

N/A N/A Notes:

1. TheonlysafetyrelatedfluidcontainingcomponentsintheKPFHRisarethereactorvessel,includingtheupperandlowerheads,nozzles andprimarysaltpumpwell,andDecayHeatRemovalSystemcomponents,includingthestoragetanks,thermosyphonthimbles,andthimble feedwaterlines.
2. OnlyapplicabletoSSCswhosefailurehasthepotentialtoexceed100mremTEDEatthesiteboundary.
3. Thiscolumnincludesnonsafetyrelatedsystemsthatcontainnoradioactivematerialornonsafetyrelatedsystemsthatdonotcontain enoughradioactivematerialtohaveapotentialtoexceed100mremTEDEatthesiteboundary.
4. PipingSystemsaretobedesignedascategory"M"systemsifthesystemprocessesradioactivematerialinexcessoftheA2quantitiesgiven inAppendixAto10CFRPart71.

PreliminarySafetyAnalysisReport

DesignofStructures,Systems,andComponents

KairosPowerHermesReactor 340 Revision0

5. ASMEBPVCSectionIIappliedonlytopressureretainingcomponents.

5.6. ComponentswillbedesignedandfabricatedusingthetechnicalguidanceinASMECode,SectionIII,Division5,withdepartures.Specifically, HermeswillimplementanANSI/ANS15.8QualityAssuranceProgram,asdescribedinSection12.9ratherthantheNQA1standardspecified intheASMEcode.Therefore,thecomponentswillnotmeetASMECode,SectionIII,Division5requirementsthataredependentonortied specificallytoanNQA1program.AppropriatedepartureswillbetakentothequalityassurancerelatedguidanceoftheASMECode requirementsforHermescomponents,includingstampingandcertificationrequirementsintheCodethataredependenton implementationofanNQA1program.DeparturesfromotherASMECoderequirementsarealsoanticipatedandwillbeidentifiedwiththe OperatingLicenseApplication.Suchdepartureswillstillmeettheintentofthecodetechnicalguidanceandprovidereasonableassuranceof componentperformance.

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 412 Thereisextensiveexperience(References5,6,and7)withB4Cunderirradiation.Inaddition,theB4C meltingtemperatureismorethan1000CabovetheHermesoperatingtemperatures.

ThecontrolandshutdownelementsanddrivemechanismsarealsoanalyzedtomeetASMESectionIII, DivisionV5(Reference8)loadsduetooperationalstepping,reactortrip,stuckelement,fatigue,and shippingandhandling.Allstressesinthecomponentsofthereactivityelementsarewithinlimits.

MaterialsutilizedintheRCSSelementsarequalifiedfortheiroperatingenvironment.Materialsare chosentoensurereactorcoolantinduceddiffusionbondingdoesnotoccuratinterfaceswhere movementorseparationisnecessary.

Thecontrolandshutdownelementsaretestedtoensurethatwearduringcontrolandshutdown elementmovementisacceptable.

TheseevaluationsdemonstrateconformancewithPDC4.

PDC23 ThesafetyrelatedreactortripfunctionoftheRCSSisinitiatedbythereactorprotectionsystemthrough thereactortripsystem(RTS)andisbasedonredundanttripdeterminationsignalstoautomaticallyopen thereactortripbreakers.RemovalofpowerfromtheelectromagneticclutchintheRCSSallowsthe controlandshutdownelementstofallintothecorebygravity.Normallyopenrelaysareutilizedforthis systemsuchthatduringoperationtheyareenergizedallowingthesystemtooperate.WhentheRTS actuates,theenergyholdingtherelaysclosedisremovedandthislossofsupplypowerinitiatesa reactortrip.TheRCSSaccomplishessafeshutdown(i.e.,reactortrip)viagravityinsertionofthecontrol andshutdownelementsonareactortripsignal;oronalossofnormalelectricalpowerafterashort timedelaytomitigatespurioustrips.TheelectricalsystemdesignisdescribedinChapter8.Thereactor controlandreactorprotectionsystemarchitecturearedescribedinChapter7.Thesefeatures,in conjunctionwithChapter7,demonstrateconformancetoPDC23.

PDC26 ThecontrolandshutdownelementsmeettherequirementsofPDC26.Thecompliancewiththe requirementsinPDC26isdiscussedinSection4.5.

PDC28 Thecontrolelementstraversetheirfullrangeofmovementin100seconds.Thismaximumdesignspeed isanalyzedinChapter13toensurethattherateofreactivityadditiondoesnotimpactthesafety significantportionsofthereactorcoolantboundaryandalsodoesnotdisturbthecoreandinternalsand impaircoolingofthecore.

PDC29 TheRCSSsupportsahighprobabilityofaccomplishingitsdesignfunction,becausethetripfunctionis safetyrelatedandtheelementsareinsertedviagravity.Therearetwomeansofinsertingnegative reactivityandthesetwomeanscontainsufficientnegativereactivitysuchthatthehighestworth reactivityelementcanfailtoinsert,andthesafetyrelatedfunctioncanstillbeachieved.Thefirstmeans ofinsertingreactivitywouldbetousethemotortolowertheelementintothecoreregion.Thesecond meansisuponareactortripwhichreleasestheelements,allowingthemtodropintothecoreby gravity.

Thecontrolandshutdownelementinsertionversustimewillbeprovidedintheapplicationforan OperatingLicense.AconservativecontrolelementdroptimevalueisusedinChapter13.Thesefeatures demonstrateconformancetoPDC29fortheRCSS.

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 413 4.2.2.4 TestingandInspection Thecontrolandshutdownelementsareperiodicallyinspectedtoensurethatthereisnounacceptable wearorotherdamagetothecladdingthatencapsulatestheB4Cabsorbermaterial.Inaddition,the reactorcoolantisperiodicallyexaminedforanincreaseinboronfromB4Cabsorbermaterial,which providesanindicationofcontrolandshutdownelementcladdingfailure.

RCSSelementinsertiontimesandshutdownmarginareperiodicallyconfirmedtobewithinsafety analysislimitsbysurveillancerequirementsprovidedinthetechnicalspecifications(seeChapter14).

4.2.3 NeutronStartupSource Aneutronstartupsourceisusedtoprovideanadequateneutronfluxtothesourcerangedetectors duringinitialandsubsequentplantstartups.Thestartupneutronsourceallowsmonitoringofthe changeinneutronmultiplicationduringtheadditionoffuelandtheapproachtocriticality.The neutronstartupsourcedoesnotperformanysafetyrelatedfunctions.

Theneutronsource(s)willbelocatedinthereflectorregionofthereactorneartheoutsideedgeof thecore,inproximitytoanexcoresourcerangedetector.Thesourcewillhavesufficientstrength toprovideadetectablecountrate.

Thesourcematerialisencasedinametalsheath.Theneutronstartupsourceiscompatiblewiththe chemical,thermal,andirradiationconditionsexpectedinthereflector.Theneutronstartupsource canberemovedandreplacedduringthelifeoftheplant,ifneeded.

4.2.4 References

1. ElectricPowerResearchInstitute,UraniumOxycarbide(UCO)TristructuralIsotropic(TRISO)Coated ParticleFuelPerformance,TopicalReportEPRIAR(NP)A,3002019978,November2020.
2. KairosPower,LLC,FuelQualificationMethodologyfortheKairosPowerFluorideSaltCooledHigh TemperatureReactor(KPFHR),KPTR011P,June2020.
3. KairosPower,LLC,KPFHRFuelPerformanceMethodology,KPTR010P,June2021.
4. NuclearRegulatoryCommission,ElectricPowerResearchInstitute-SafetyEvaluationforTopical Report,UraniumOxycarbide(UCO)TristructuralIsotropic(TRISO)CoatedParticleFuelPerformance:

TopicalReportEPRIAR1(NP),August11,2020.

5. Fryger,B.,Gosset,D.,&Escleine,J.M.,IrradiationPerformancesoftheSuperphenixTypeAbsorber Element,AbsorberMaterials,ControlRodsandDesignofBackupReactivityShutdownSystemsfor BreakevenandBurnerCoresforReducingPlutoniumStockpiles,1995.
6. Pitner,A.L.,&Russcher,G.E.,IrradiationofBoronCarbidePelletsandPowdersinHanfordThermal Reactors,1970.
7. Demars,R.V.,Dideon,C.G.,Thornton,T.A.,Tulenko,J.S.,Pavinich,W.A.,&Pardue,E.B.S.,

IrradiatonBehaviorofPressurizedWaterReactorControlMaterials,NuclearTechnology,62(1),

7580,1983.

7.8. AmericanSocietyofMechanicalEngineers,ASMEBoiler&PressureVesselCode,SectionIII,Division 5,HighTemperatureReactors.2017.

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 428 4.3 REACTORVESSELSYSTEM 4.3.1 Description Thissectionprovidesanoverviewofthereactorvesselsystem(seeFigure4.31)whichincludesthe reactorvesselandthereactorvesselinternals.Thereactorvesselformsamajorelementofthereactor coolantboundaryandtheinertgasboundary.Thereactorvesselandvesselinternalsdefinetheflow pathforreactorcoolantandfuelintothecore.Thereactorvesselsystemcontainsthereactorcoreand providesforcirculationofreactorcoolantandpebblesaswellasinsertionofthereactivitycontroland shutdownelementsthroughthereactorcore.

Thereactorvesselsystemprovidesaflowpathforreactorcoolanttotransferheatfromthereactorcore totheprimaryheattransportsystem(PHTS)duringnormaloperations.Thereactorcoolantentersthe reactorvesselthroughtwosideinletnozzlesandflowsdownwardthroughadowncomerannulus formedbetweenthemetalliccorebarrelandthereactorvesselshell.Coolantflowmovesthroughthe reflectorsupportstructureandisdistributedintothecorebythedesignofthereflectorblocks.Upon exitingthecore,thecoolantleavesthereactorvesselviatheprimarysaltpump(PSP)(seeSection5.1.1) whichdrawssuctiondirectlyfromapoolofreactorcoolantabovethecoreandinsidethevessel.An antisiphonfeatureisprovidedtolimitlossofvesselinventoryintheeventofabreakinthePHTS.

Thereactorvesselsystemalsoprovidesaflowpathforpebblestoallowonlinerefuelinganddefueling ofthereactorcorebythepebblehandlingandstoragesystem(PHSS)(Section9.3)duringnormal operation.ThePHSSinsertspebblesintothereactorvesselanddeliversthemtothefuelingchutebelow thereactorcorebythepebbleinsertionline(Section9.3.1).Thebuoyantpebblesfloatupward,and pebblesinsertedviatheinsertionlinewilljointhepackedpebblebedinthereactorcore.Upon circulatingthroughthecore,thepebblesaccumulateinthedefuelingchuteatthetopofthereactor core.Thepebbleextractionmachine(PEM)(Section9.3.1)atthetopofthereactorcoreremoves pebblesfromthereactorvessel(seeFigure4.32.)

DuringpostulatedeventswhenthePHTSandtheprimaryheatrejectionsystem(PHRS)arenot available,thereactorvesselprovidesanalternativeflowpathasdiscussedinSection4.6.1toallow naturalcirculationofthereactorcoolanttoremoveheatfromthereactorcore.Thereactorcoolant leavingthecoreflowsbackintothedowncomerannulusviafluidicdiodes.Theheatfromthecoreis transferredtothereactorvesselshellwhichtransferstheheattothedecayheatremovalsystem(DHRS)

(Section6.3).

Thereactorvesselsysteminterfaceswithfuel(Section4.2.1),primaryheattransportsystem(PHTS)

(Section5.1),reactivitycontrolandshutdownsystem(RCSS)(Section4.2.2),reactorvesselsupport system(RVSS)(Section4.7),decayheatremovalsystem(DHRS)(Section6.3),pebblehandlingand storagesystem(PHSS)(Section9.3),reactorthermalmanagementsystem(RTMS)(Section9.1.5),inert gassystem(IGS)(Section9.1.2),inventorymanagementsystem(IMS)(Section9.1.4),and instrumentationandcontrols(Chapter7).

4.3.1.1 ReactorVessel Thereactorvesselisaverticalcylinderdesignwithflattopandbottomheads.Thevesselhousesthe reactorvesselinternals.Thereactorvesselshellandbottomheadprovideamajorelementofthe reactorcoolantboundary.Thevesselisconstructedof316Hstainlesssteel(SS)withER1682weld metalandisdesignedandfabricatedperusingthetechnicalguidanceinASMEBPVCSectionIII,Division 5(Reference1)withdeparturesasshowninTable3.62.Itcontainstheinventoryofreactorcoolant suchthatthereactorcoreiscoveredbythecoolantduringnormaloperationandpostulatedevent.

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 429 Therearenopenetrationsorattachmentstothevesselbelowthecoolantlevel.Thedesignofthe reactorvesselallowsforonlinemonitoring,inserviceinspection,andmaintenance.

4.3.1.1.1 VesselTopHead Thereactorvesseltophead(seeFigure4.32)isaflat316HSSdiscboltedandflangedtothevessel shell.Thisinterfaceisdesignedforleaktightnessbutisnotcreditedasbeingleaktightinsafety analyses.Thevesseltopheadcontrolstheradialandcircumferentialpositionsofthereflectorblocksto ensureastablecoreconfigurationforallconditions(e.g.,reactortripandcoremotion).Thetophead containspenetrations,asshowninFigure4.32andTable4.31,intoandoutofthevesselandprovides fortheattachmentofsupportingequipmentandcomponents(e.g.,reactivitycontrolelements,pebble handlingandstoragesystemcomponents,materialsamplingport,neutrondetectors,thermocouples, etc.).Thetopheadsupportsthevesselmaterialsurveillancesystem(MSS)whichprovidesaremote meanstoinsertandremovematerialandfueltestspecimensintoandfromthereactortosupport testing.

4.3.1.1.2 VesselShell Thereactorvesselisa316HSScylindricalshellthat,alongwiththevesselbottomhead,servestoform thesafetyrelatedreactorcoolantboundarywithinthereactorvessel.Itcontainsandmaintainsthe inventoryofreactorcoolantinsidethevessel.Theshellprovidesthegeometryforcoolantinletand vesselsurfacefortheDHRSwhichtransfersheatfromthereactorvesselduringpostulatedevents.The insideoftheshelluses316HSStabstomaintainthecorebarrelinacylindricalgeometryandhasa weldedconnectionatthetopofthecorebarrel.

4.3.1.1.3 VesselBottomHead Thereactorvesselbottomheadisaflat316HSSdiscthatisweldedtothevesselshell.Itcontainsand maintainstheinventoryofthereactorcoolantinsidethevessel,supportsthevesselinternals,maintains thereactorcoolantboundaryandprovidesflowgeometryforlowpressurereactorcoolantinlettothe core.Hydrostatic,seismicandgravityloadsonthevesselandvesselinternalsaretransferredtothe bottomheadandaretransferredtotheRVSS.

4.3.1.2 ReactorVesselInternals Thereactorvesselinternalstructuresincludethegraphitereflectorblocks,corebarrelandreflector supportstructure.Thevesselinternalstructuresdefinetheflowpathsofthefuelandreactorcoolant, provideaheatsink,apathwayforinstrumentationinsertion,controlandshutdownelementinsertion, aswellasprovideneutronshieldingandmoderationsurroundingthecore.Thereactorvesselinternal structuresaredesignedandfabricatedusingthetechnicalguidanceinASMEBPVCSectionIII,Division5 (Reference1)withdeparturesasshowninTable3.62.Thedesignofthestructuressupportinspection andmaintenanceactivitiesaswellasmonitoringofthereactorvesselsystem.

4.3.1.2.1 ReflectorBlocks ThereflectorblocksareconstructedofgradeETU10graphite.Thereflectorblocksprovideaheatsink forthecoreandarerestrainedensuringalignmentofthepenetrationstoinsertandwithdrawcontrol elements.Thereflectorblocksarebuoyantinthereactorcoolant.Thebottomreflectorblocksare machinedwithcoolantinletchannelsfordistributionofcoolantinletflowintothecore.Thetop reflectorblocksaremachinedwithcoolantoutletchannelstodirectthecoolantexitingfromthecore intotheupperplenum,fromwhichthePSPdrawssuction.Thetopreflectorblocksalsoformapebble defuelingchute,asshowninFigure4.31,todirectthepebblesfromthecoretothepebbleextraction machine(PEM),allowingonlinedefuelingofthereactor(seeSection9.3).Thereflectorblocksalso

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 431 ConsistentwithPDC32,thereactorvesselpermitsinspection,monitoring,orfunctionaltestingof importantareasandfeaturestoassessstructuralintegrityandleaktightnessofthesafetyrelated portionsofthereactorcoolantboundary.

ConsistentwithPDC35,thereactorvesselinternalswillassuresufficientcorecoolingduringpostulated eventsandremoveresidualheat.Thesafetyfunctionofthefluidicdiodeistoprovideaflowpathvia naturalcirculationtotransferheatfromthereactorcoreduringandfollowingpostulatedeventssuch thatfuelandreactorinternalstructuredamagethatcouldinterferewithcontinuedeffectivecore coolingisprevented.

ConsistentwithPDC74,thedesignofthereactorvesselandreflectorblocksshallbesuchthattheir integrityandgeometryaremaintainedduringpostulatedeventstopermitsufficientinsertionofthe controlandshutdownelementsprovidingforreactorshutdown.

4.3.3 SystemEvaluation The316HSSstructuresofthereactorvesselsystemarefabricatedandtestedinaccordancewithto meettheintentofReference1standardswithdeparturesasshowninTable3.62.The316HSSvessel internalsalsosatisfythechemistryrestrictionsoftheASMESectionIIIcodeinDivision5,ArticleHGB 2000.PertheASMEstandard,ER1682weldmetalwillbeusedinfabricationofthe316Hstructures.

Commensuratewiththesafetyrelatedfunctionofthereflectorblockinensuringacceptabledesign limitsandmaintainingthereactorcoolantflowpath,qualityrelatedcontrolswillbeplacedontheETU 10graphite.ThegraphitereflectorwillbedesignedtomeettheintentofReference1standardswith departuresasshowninTable3.62.KPFHRspecificationsandprocurementdocumentsincorporateand referencetheapplicableguidanceandASMEstandards.Thequalityassuranceprogramisdescribedin Section12.9.ThesecontrolsdemonstrateconformancewithPDC1.

Thereactorvesselsystemmakesupaportionofthereactorcoolantboundary.Thereactorvesseland graphitereflectorblocksarethereforedesignedtomaintaingeometryduringasafeshutdown earthquaketoensurethevesselintegrity,insertionofnegativereactivityviatheRCSS,andtomaintain theflowpath.Thereactorvesselandvesselinternalswillhavedynamicbehaviorsduringadesignbasis earthquake.Theseincludefluidstructureinteractionwithinthevessel,oscillatoryresponseof componentsmountedtothereactortophead,i.e.,headmountedoscillators,andrelativemovementof graphitereflectorblockswithrespecttooneanotherwithinthecoolant.Thesedynamicbehaviorsare accountedforinthedesignofthereactoranditsinternals,toensurecontinuedfunctionalityduringand afteradesignbasisearthquake.Modelsareusedtounderstandfluidmigrationtendenciesconsidering thepebblebed,reflectorblocks,corebarrel,andotherreactorvesselinternalfeatures.Theinsights gainedfromtheanalysisofthesemodelsareusedtodesignthereactortopreventdamagetothevessel duringadesignbasisearthquake.Thereactorvessel,vesselinternals,andvesselattachmentssuchas theRCSSareclassifiedasSDC3perASCE4319SeismicDesignCriteriaforStructures,Systems,and ComponentsinNuclearFacilities(Reference2).Thereactorvesselwillalsobeprotectedfromthe failureofnearbynonsafetyrelatedSSCsduringadesignbasisearthquakebyseismicallymounting, physicallyseparating,orusingabarriertoprecludeadverseinteraction,andfromfailureofattached nonsafetyrelatedSSCs,suchasattachedpiping(e.g.,bydesignforpreferentialfailureofthenonsafety componentisawaythatdoesnotimpactthevessel).ThesefeaturesdemonstratecompliancewithPDC 2.

Thereactorvesselcanaccommodateinternalandexternalstaticanddynamicloads.Thethermal expansionofthereactorvesselshellandbottomheadissupportedbythereactorvesselsupportsystem (RVSS)(seeSection4.7)duringreactorstartup,normaloperation,andpostulatedevents.Mechanical loadingsfromstaticweight,seismicload,andforcesfromthepebblebed,coolant,andcore

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 458 4.7 REACTORVESSELSUPPORTSYSTEM 4.7.1 Description Thereactorvesselsupportsystem(RVSS)providesstructuralsupporttothereactorvesselsupportthe fullweightofthereactorvesselwithfuelandcoolant,vesselinternals,andallheadmounted components.Thesystemtransmitspressure,seismic,andthermalloadstothecavitystructuresduring normaloperationanddesignbasisearthquakes.TheRVSSprovidesadequatethermalmanagementto supportthevesselsthermalexpansionwhiletransitioningfromroomtemperatureatassemblyto nominaloperatingtemperatureforprimarycoolantfill.TheRVSSalsosupportsthevesselsthermal expansionduringpostulatedevents.

TheRVSSinterfaceswiththereactorvessel(seeSection4.3),thereactorthermalmanagementsystem (RTMS)(SeeSection9.1.5),andthesafetyrelatedportionoftheReactorBuilding(seeSection3.5).The safetyrelatedportionoftheReactorBuildingisseismicallyisolatedtoreduceseismicloads(seeSection 3.5.3).

Thebottomsupportconsistsofasupporttray,ledge,supportcolumns,supportpads,baseplate,vessel connector,andanchoringconnectorasshowninFigure4.71.Allthecomponentsaremadeof316H stainlesssteel.Thereactorvesselbottomheadsitsdirectlyontopofthetrayandisconnectedtothe traybythevesselconnectortopreventupliftandshear.Theledgearoundtheedgeofthetraycontains spilledFlibeincaseofleakage.Thetrayisreinforcedby316HSSsupportcolumnswhicharesizedand spacedappropriatelytoprovidestructuralsupportforthetotalweightofthevessel,vesselinternals, headcomponents,coolant,andfuel.Thesupportcolumnsareweldedontothesupportpadwhich allowsrelativeslidingwiththeunderlyingbaseplatetoaccommodatethermalexpansion.Thesupport padshaveslottedholestoallowrelativeslidingwiththeanchoringconnectors.Theanchoring connectorspreventthereactorvesselandRVSSfromupliftandshear.TheRVSSisdesignedand fabricatedperusingthetechnicalguidanceinASMEBPVCSectionIII,Division5(20179)(Reference1)as showninTable3.62.

TheRTMSprovidesthermalmanagementforthebottomsupportwithaloadbearingmetallicinsulation materialwhichactsasathermalbreakthatreducesheatlossandcoolingloadfortheRVSSsupport columns.ThebottominsulationoftheRTMS,asshowninFigure4.71,protectsthereactorbuilding cavityconcretefromthermaleffects.TheRVSSisalsoverticallyanchoredtothefoundationthroughthe bottominsulation.Thebottomsupportinsulationinterfaceaccommodatesrelativethermalexpansion betweenthesupportcolumnsandtheinsulationmaterial.

Therearenolateralseismicrestraintsforthereactorvesselandtheheadmountedcomponents.The RVSSisdesignedtokeepthereactorvesselfromupliftandshearduringseismicevents.Thedesignalso leveragesseismicisolationoftheReactorBuildingtoreduceseismiceffectsonthereactorvessel,RVSS, andtheheadmountedcomponents(seeSection4.3).

4.7.2 DesignBasis ConsistentwithPDC2,theRVSScanwithstandtheeffectsofnaturalphenomenaandtoperformits safetyfunctionintheeventofadesignbasisearthquake.

ConsistentwithPDC4,theRVSSaccommodatestheenvironmentalconditionsassociatedwithnormal operation,maintenance,testing,andpostulatedevents.

ConsistentwithPDC74,thedesignofthereactorstructuralsupportsystemensurestheintegrityofthe reactorvesselduringpostulatedeventstosupportthegeometryforpassiveremovalofresidualheat Highlightedtextwaspreviously changed.Submittedon63022 (ML22181B158).

PreliminarySafetyAnalysisReport

EngineeredSafetyFeatures

KairosPowerHermesReactor 613 Revision0 Table6.34:ApplicableDesignCodesandStandardsfortheDHRS Code Title Applicability ASMESec.IIIDiv.5ClassB (Reference1)

ASMEBoilerand PressureVesselCode

-HighTemperature Reactors MTheDHRSmetallicpressureboundaryand supportswillbedesignedandfabricatedusing thetechnicalguidanceinASME,SectionIII, Division5,withdeparturesasshowninTable 3.62.Ingeneral,lowtemperatureservice correspondstotherequirementsofASMESec.

IIIDiv.1subsectionNC.Thisappliestomost DHRScomponents.Therisersareanexception andmustfollowrulesforhightemperature service.Theseprovideadditionalmodifications toDiv.1rules.

ASMESec.XIDiv.1and2 (Reference2)

RulesforInservice InspectionofNuclear PowerPlant Components Providesrulesandguidelinesfortestingand inspectionofDHRSpressureboundaryand structuralcomponents.

ASCE4319(Reference3)

SeismicDesign Criteriafor Structures,Systems, andComponentsin NuclearFacilities Providesdesigncriteriaforseismicanalysisof reactorcomponents(includingDHRS).

ASCE416(Reference4)

SeismicAnalysisof SafetyRelated NuclearStructures Providesadditionaldesigncriteriaforsafety relatedsystems(includingDHRS)thatexpand uponASCE4319.

ACI34913(Reference5)

CodeRequirements forNuclearSafety RelatedConcrete Structuresand Commentary ApplicabletocavitysupportstructuresforDHRS panelsandpotentiallythecondenserpool construction.

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