ML22259A141

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Kairos Power, LLC, Changes to Preliminary Safety Analysis Report (PSAR) Chapters 3 and 4
ML22259A141
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Issue date: 09/16/2022
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KPNRC2209012

ChangestoPSARChapters3and4 (NonProprietary)

PreliminarySafetyAnalysisReport

DesignofStructures,Systems,andComponents

KairosPowerHermesReactor 318 Revision0 SeismicresponseanalysisisperformedfollowingChapter4ofASCE416usingdeterministic,linear analysis.Therelativeimportanceofsoilstructureinteractioneffects,usingthecharacterizationofthe subsurfacematerialssupportingtheSDC3structures,definedcompatiblewiththosedescribedin Section2.5,areconsideredbasedontheguidanceinChapter5ofASCE416.

3.4.1.7 SeismicQualification LimitstatesforSDC3SSCsareassignedbasedonthetargetseismicperformancegoalsofASCE4319 (seeSection3.4).Specificcriteriaforthequalificationofstructuresandsystemsandcomponentsare outlinedinSection3.6.

3.4.2 NonSafetyRelatedSSCSeismicDesign(SDC2SSCs)

NonSafetyRelatedSeismicDesign(SDC2)SSCsaredesignedaccordingtothelocalbuildingcode,the 2012IBC.FortheSDC2seismicinput,thedesignbasisgroundmotionisdefinedinaccordancewiththe deterministicprocessesoflocalbuildingcode,the2012IBC,whichreferstoASCE/SEI710 (Reference6).

SitespecificgroundmotionparametersaredeterminedperChapter21ofASCE/SEI710.Thesite responseanalysisusedtoinformtheSDC3(Section2.5)inputwillbeusedtodeterminetherisk targetedmaximumconsideredearthquake(MCER)forthesite.

SeismicanalysisandqualificationofSDC2SSCsisalsoperformedinaccordancewiththe2012IBC.

SeismicdesignrequirementsforSDC2structuresfollowChapter12ofASCE/SEI710.Seismicdesignfor SDC2systemsandcomponentsfollowChapter13ofASCE/SEI710.ExceptionstoASCE/SEI710for SDC2structures,asrequiredbytheTennesseebuildingcode,areappliedasneeded.

3.4.3 SeismicInstrumentation Seismicinstrumentationthatenablesthepromptprocessingofthedataatthesiteisinstalledfor monitoring.

Thepurposeoftheinstrumentationisto(1)permitacomparisonofmeasuredresponsesofthesitewith estimatedresponsescorrespondingtothedesignbasisgroundmotion,(2)andpermitfacilityoperators tounderstandthepossibleextentofdegradedperformancewithinthefacilityimmediatelyfollowingan earthquake.Instrumentationisalsoused,and(3)beabletodeterminewhenadesignbasisearthquake eventhasoccurredthatwarrantsinspectionandmaintenanceactivities.

3.4.3.1 LocationandDescriptionofSeismicInstrumentation Theseismicinstrumentationconsistsoftriaxialtimehistoryaccelerometerslocatedinthefreefield andinthesafetyrelatedportionoftheReactorBuilding.Thefreefieldinstrumentismountedonrock orcompetentgroundgenerallyrepresentativeofthedynamicsitecharacteristics.Theinstrumentation recordstimehistorydataattimeincrementssuitabletocapturetherangeofvibrationfrequenciesin thedesignbasisearthquakespectra.Seismicinstrumentationisdesignedsuchthatifthereisalossof power,recordingstilloccurs.Instrumentationishousedinappropriateweatherandcreatureproofed enclosures.

3.4.3.2 SeismicInstrumentationOperabilityandCharacteristics Theseismicinstrumentationoperatesduringallmodesoffacilityoperation.Plantproceduresprovide forkeepingaminimumrequirednumberofseismicinstrumentsinserviceduringfacilityoperation.The seismicinstrumentationdesignincludesprovisionsforinservicetesting.Theseismicinstrumentsare capableofperiodicchannelchecksduringnormalfacilityoperationandinplacefunctionaltesting.

PreliminarySafetyAnalysisReport

DesignofStructures,Systems,andComponents

KairosPowerHermesReactor 322 Revision0 ThesafetyfunctionsofthesafetyrelatedportionoftheReactorBuildingare:

ProtectionofsafetyrelatedSSCsfromdesignbasisnaturalphenomenaandexternalhazards StructuralsupportforsafetyrelatedSSCslocatedonthesafetyrelatedportionoftheReactor Building ProtectionfromadverseeffectsofnonsafetyrelatedSSCsfailuresontheabilityofsafetyrelated SSCstoperformtheirsafetyfunctions Preventinteractionsbetweenreactorcoolant(Flibe)andwatercontainedinconcreteinthesafety relatedportionofthereactorbuilding.

3.5.2 DesignBases ConsistentwithPDC1,thesafetyrelatedportionoftheReactorBuildingisdesignedinaccordance withindustrycodesandstandards,andthequalityassuranceprogramdescribedinSection12.9.

ConsistentwithPDC2,thesafetyrelatedportionoftheReactorBuildingisdesignedtoprovide protectionforsafetyrelatedSSCshousedwithintoperformtheirsafetyfunctionsindesignbasis meteorological,water,andseismiceventsasdescribedinSections3.2,3.3,and3.4.

ConsistentwithPDC3,thesafetyrelatedportionoftheReactorBuildingisdesignedwithdesign featurestominimize,consistentwithothersafetyrequirements,theprobabilityandeffectoffires andexplosions.

ConsistentwithPDC75,theReactorBuildingisdesignedtoprotectthegeometryofthedecayheat removalsystemfrompostulatednaturalphenomenaevents.

ConsistentwithPDC76,theReactorBuildingisdesignedtopermitappropriateperiodicinspection andsurveillanceofsafetyrelatedstructuralareas.

3.5.3 SystemEvaluation AlthoughthenonsafetyrelatedportionoftheReactorBuildingsurroundsthesafetyrelatedportionof theReactorbuilding,thenonsafetyrelatedportionisnotcreditedinthesafetyanalysis.Neitherthe safetyrelatednornonsafetyrelatedportionoftheReactorBuildingiscreditedinthesafetyanalysisto performasafetyrelatedcontainmentfunctionforretentionoffissionproductssincethedesignrelies onafunctionalcontainmentconcept(seeChapter13).Similarly,thenonsafetyrelatedportionofthe ReactorBuildingisnotcreditedtoprovidephysicalprotectiontosafetyrelatedSSCsfromtheeffectsof normalorhighwinds(seeSection3.5.3.1),orfromtheeffectsofdesignbasisearthquakes(seeSection 3.5.3.3).Finally,thenonsafetyrelatedportionofthereactorbuildingisnotcreditedtoprovide protectiontosafetyrelatedSSCsfromtheeffectsofwaterdamage(seeSection3.5.3.2).However,the shapeoftheexteriorroofprecludesadverseeffectsrelatedtoaccumulationofwaterandice.Alistof loadcombinationsforthesafetyrelatedportionoftheReactorBuildingisprovidedinTable3.51.

ConsistentwithPDC1,thesafetyrelatedportionofthereactorbuildingisunderthequalityassurance programdescribedinChapter12.ThesafetyrelatedportionoftheReactorBuildingisdesignedtothe localbuildingcode,ASCE/SEI710(Reference1),andaugmentedforspecificdesignbasisnatural phenomenaasdescribedbelow.ThenonsafetyrelatedportionoftheReactorBuildingisdesignedto localbuildingcodeswhichinvokeASCE/SEI710.

ConsistentwithPDC3,thesafetyrelatedportionoftheReactorBuildingisdesignedtoperformits safetyfunctionintheeventofafirehazard.ThesafetyrelatedportionoftheReactorBuildingincludes designfeatureswhichminimizetheprobabilityandeffectoffiresandexplosionsbytheuseoflow combustiblematerialsandphysicalseparation.Thesedesignfeatures,inconjunctionwiththefire protectionprogramdescribedinSection9.4,provideassurancethatthesafetyrelatedportionofthe ReactorBuildingconformstoPDC3.

PreliminarySafetyAnalysisReport

DesignofStructures,Systems,andComponents

KairosPowerHermesReactor 328 Revision0 Table3.51:LoadCombinationsfortheSafetyRelatedPortionoftheReactorBuilding ServiceLevel LoadCombination A

D+L+To+Ro B

D+L+To+Ro+Eo D+L+Ti+Ri+Eo C

D+L+To+Ro+Ess D+L+Ts+Rs+Ess D

D+L+Ta+Ra+Wt D+L+Ta+Ra+Ess LoadNomenclature:

D Deadloads L

Liveloads To Thermalloadsduringstartup,normaloperating,orshutdownconditions Ti ThermalloadsduringServiceLevelBloadings Ta ThermalloadsduringServiceLevelDloadings Ts ThermalloadsduringServiceLevelCloadings Ro Pipereactionsduringstartup,normaloperating,orshutdownconditions Ri PipereactionsduringServiceLevelBloadings Ra PipereactionsduringServiceLevelDloadings Rs PipereactionsduringServiceLevelCloadings Eo Loadsgeneratedby1/3ofdesignbasisearthquake(thedesignbasisearthquakeisalso thesafeshutdownearthquake[SSE])

Ess LoadsgeneratedbySSE Wt Accidentalloadsduetomissileimpacteffects

PreliminarySafetyAnalysisReport

DesignofStructures,Systems,andComponents

KairosPowerHermesReactor 332 Revision0 3.6.2 ClassificationofStructures,Systems,andComponents SSCsareassignedsafety,seismic,andqualityclassificationsconsistentwiththeirsafetyfunctions.These classificationsaredescribedbelow.Table3.61providesasummaryoftheseclassificationsforallSSCs.

3.6.2.1 SafetyClassification SSCshavetwopossiblesafetyclassifications:safetyrelatedornonsafetyrelated.AnSSCisclassifiedas safetyrelatedifitmeetsthedefinitionofsafetyrelatedfrom10CFR50.2(withexceptionsasdescribed inSection1.2.3).FortheKPFHRtechnology,thedefinitionofsafetyrelatedismodifiedfrom10CFR 50.2,tobe:

Safetyrelatedstructures,systems,andcomponentsmeansthosestructures,systems,and componentsthatarereliedupontoremainfunctionalduringandfollowingdesignbasisevents toassure:

(1)Theintegrityoftheportionsofthereactorcoolantboundaryreliedupontomaintaincoolant levelabovetheactivecore; (2)Thecapabilitytoshutdownthereactorandmaintainitinasafeshutdowncondition;or (3)Thecapabilitytopreventormitigatetheconsequencesofaccidentswhichcouldresultin potentialoffsiteexposurescomparabletotheapplicableguidelineexposuressetforthin10CFR 50.34(a)(1)or10CFR100.11 NotethatfortheKPFHRtechnology,thedefinitionabovereflectsanexemptionfromthedefinitionsin 10CFR50.2thatincludetheterminologyintegrityofthereactorcoolantpressureboundary.As describedinSection1.2.3andtheRegulatoryAnalysisfortheKairosPowerSaltCooled,High TemperatureReactorTopicalReport(Reference1),thisexemptionisnecessarybecausethetechnology associatedwiththeKPFHRisbasedonanearatmosphericpressuredesignandthereactorcoolant boundarydoesnotprovideasimilarpressurerelatedorfissionproductretentionfunctionaslightwater reactorsforwhichthesedefinitionswerebased.

SSCsthatdonotmeetthedefinition,asmodifiedabove,areclassifiedasnonsafetyrelated.

3.6.2.2 SeismicClassification SSCsareclassifiedinoneoftwoSeismicDesignCategories(SDC)consistentwithASCE4319 (Reference2).SafetyrelatedSSCsareclassifiedasSDC3.Section3.4discussestheSDC3classification andSection3.5discussesrequirementsforSSCsthatarerequiredtomaintaintheirfunctionintheevent ofadesignbasisearthquake.Thedesignbasisearthquakeisalsothesafeshutdownearthquake(SSE).

AllsafetyrelatedSSCsarelocatedinthesafetyrelatedportionoftheReactorBuilding,whichis discussedinSection3.5.1.

ThecreditedsafetysystemsdesignedtofunctioninapostulatedeventaredescribedinChapter13.For adesignbasisearthquake,theSDC3SSCsthatarereliedupontoperformaspecificcreditedsafety functionarelistedinTable3.61.

Safetyrelatedsystemsandcomponentsarequalifiedtomaintaintheirsafetyfunctionduringadesign basisearthquake,afteradesignbasisearthquake,orboth,dependingonthefunctionperformed.For example,thereactorvesselisrequiredtoperformitssafetyfunction(i.e.,maintainstructuralintegrity) bothduringandafteradesignbasisearthquake,whereasthedecayheatremovalsystemisrequiredto performitssafetyfunctiononlyaftertheevent,andnotduring.Thespecificsafetyfunction,therefore, isusedtodefinetheASCE4319LimitStatethatisusedtoqualifytheSDC3SSCs.

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 42 Table4.11:ReactorParameters Parameter Value ThermalPower(MWth) 35 ReactorCoolantOutletTemperature(°C) 620 ReactorCoolantInletTemperature(°C) 550 ReactorVesselOperatingPressure(bar)

<2 ReactorCoolantType Flibe FuelType TRISOparticle;UCOkernel FuelMatrix Pebble EquilibriumFuelEnrichment(wt%)

<19.75 ReflectorType ETU10Graphite ControlMaterial B4C NeutronSpectrum Thermal

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 429 coolantlevel.Thedesignofthereactorvesselallowsforonlinemonitoring,inserviceinspection,and maintenance.

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.Thedesignofthestructures supportinspectionandmaintenanceactivitiesaswellasmonitoringofthereactorvesselsystem.

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 providemachinedchannelsforinsertionandwithdrawalofthereactivitycontrolandshutdown elementsdescribedinSection4.2.2.

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 431 ConsistentwithPDC35,thereactorvesselinternalswillassuresufficientcorecoolingduringpostulated eventsandremoveresidualheat.Thesafetyfunctionofthefluidicdiodeistoprovideaflowpathvia naturalcirculationtotransferheatfromthereactorcoreduringandfollowingpostulatedeventssuch thatfuelandreactorinternalstructuredamagethatcouldinterferewithcontinuedeffectivecore coolingisprevented.

ConsistentwithPDC74,thedesignofthereactorvesselandreflectorblocksshallbesuchthattheir integrityandgeometryaremaintainedduringpostulatedeventstopermitsufficientinsertionofthe controlandshutdownelementsprovidingforreactorshutdown.

4.3.3 SystemEvaluation The316HSSstructuresofthereactorvesselsystemarefabricatedandtestedinaccordancewith Reference1standards.The316HSSvesselinternalsalsosatisfythechemistryrestrictionsoftheASME SectionIIIcodeinDivision5,ArticleHGB2000.PertheASMEstandard,ER1682weldmetalwillbe usedinfabricationofthe316Hstructures.Commensuratewiththesafetyrelatedfunctionofthe reflectorblockinensuringacceptabledesignlimitsandmaintainingthereactorcoolantflowpath, qualityrelatedcontrolswillbeplacedontheETU10graphite.KPFHRspecificationsandprocurement documentsincorporateandreferencetheapplicableguidanceandASMEstandards.Thequality assuranceprogramisdescribedinSection12.9.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).Thesefeaturesdemonstratecompliancewith PDC2.

Thereactorvesselcanaccommodateinternalandexternalstaticanddynamicloads.Thethermal expansionofthereactorvesselshellandbottomheadissupportedbythereactorvesselsupportsystem (RVSS)(seeSection4.7)duringreactorstartup,normaloperation,andpostulatedevents.Mechanical loadingsfromstaticweight,seismicload,andforcesfromthepebblebed,coolant,andcore componentsaretransferredtothevesselshell,tothebottomhead,andthentotheRVSS.Thelateral loadpathofthevesselsupportisdesignedtoprecludedamagetothedecayheatremovalsystemand ensurethevesselmaintainsitsintegrityandremainsinanuprightposition.Thedesignofthevessel shellresistshoopstressesfromthepressureinthedowncomerandsupportsthetransferofstaticand dynamicloadsbetweenthevesseltopheadandthevesselbottomheadtotheRVSS.Therearealsono pressurizedpipingsystemsinoraroundthereactorvessel,thusprecludinghighenergylinehazards.

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 432 HeavyloadconsiderationsareaddressedinSection9.8.4,CranesandRigging.Thesefeatures demonstratecompliancewithPDC4.

Corecoolingismaintainedthroughthedesignofthereactorvesselandthereactorvesselinternals.As describedinSection4.3.1.2,thevesselandvesselinternalsdefinethecoolantflowpath.Topreclude degradationtothevesselduetocorrosionofthestainlesssteel,thereflectorblocksandthevesselare baked(i.e.,heateduniformly)toremoveresidualmoisturepriortocomingintocontactwithcoolant.

Thereflectors,whichactasaheatsinkinthecore,arespacedtopreventtheformationoftensileand bendingstressesandaccommodatethermalexpansionandhydraulicforcesduringnormaloperation andpostulatedevents.Thegapsbetweenthegraphiteblockssupportcoolantflowtothereflectorthus maintainingacoolablecoregeometryandprecludingreflectordegradationbyoverheating.Maintaining acoolablecoregeometryandadequatecoolantflowthroughthecoreensuresthevesselwall temperatureisbelowdesignlimitswhichpreventvesselfailure.Dynamicbehaviorofthereactor,its support,anditsinternalsareanalyzedanddesignedtoensurevesselintegrityandcoregeometryare maintainedinadesignbasisearthquaketoadegreesufficienttoensurepassiveheatremoval.The vessel,aspartofthereactorcoolantboundary,ensuresthecontainmentofradionuclidesbyensuring thecoolantisconfinedandtheTRISOparticlesinthefuelpebblesareprotectedfromdamage.These featuresdemonstrateconformancetoPDC10.

TodemonstratecompliancewithPDC14,thereactorvesselisfabricated,erected,andtestedsoasto haveanextremelylowprobabilityofleakage,rapidlypropagatingfailure,andgrossrupture.Thereactor vesselmaterialsandweldmetalwillbequalifiedforuseasdescribedinKairosPowertopicalreport MetallicMaterialsQualificationfortheKairosPowerFluorideSaltCooledHighTemperatureReactor, KPTR013P(Reference3).The316HSSofthereactorvesselasfabricatedandtestedinaccordance withReference1standardshasahighfracturetoughnessatreactoroperatingconditions,thusreducing thelikelihoodofcrackpropagation.Thedesignofthereactorvesselandvesselinternalssupporta10 yearoperatinglifetime.Thisisaccomplishedbyoperatingthereactorvesselwithintheasdesigned operationalandtransientconditionstressesandbymonitoringforchanges(e.g.,irradiationand thermallyinduceddegradation,corrosion,creep)tothereactorvesselduringinserviceinspectionand testing.TheRVSSreactorvesselbottomheadinterfaceisdesignedtoallowaccessforweldinspections.

Thereactorvesseltopheadsupportsinserviceinspectionofattachmentsandpenetrations.

Thereactorvesselshellandbottomheadmaintainacoolantpathwayforcoolingthereactorcoreand ensuresubmergenceoffuelpebblesinthecore.Thereactorvesselisfabricated,erected,andtestedin accordancewithReference1asaClassAcomponenttoaccountforthermalandphysicalstressesduring normaloperationandpostulatedevents.Thevesselisfabricatedfrom316HSSbasemetalandER1682 weldmetalusingagastungstenarcweldingprocess.Reference1providesforweldmentstressrupture factorsuptoatemperatureof650°CforER1682weldmetalwith316Hbasemetal.Testingprovides stressrupturefactorsupto816°Cforweldmaterialwith316Hbasemetal(Reference3).Theplant controlsystemwilldetectleakagefromthereactorvesselandcatchbasinsareusedtodetectleaksin nearbycoolantcarryingsystems.ThesefeaturesdemonstratecompliancewithPDC30.

Reactorvesselstressrupturefactorsaredeterminedupto816°Ctoencompasstransientconditions.

Thestressrupturefactorsaredeterminedbyacreeprupturetestonthevesselbasematerialwithweld metalunderthegastungstenarcweldingprocess.Thevesselprecludesmaterialcreep,fatigue,thermal, mechanical,andhydraulicstresses.Theleaktightdesignofthereactorvesselheadminimizesairingress intothecovergasandprecludescorrosionoftheinternals.Thehightemperature,highcarbongrade 316HSSofthecorebarrelandreflectorsupportstructurehavehighcreepstrengthandareresistantto radiationdamage,corrosionmechanisms,thermalaging,yielding,andexcessiveneutronabsorption.

LoadcombinationsforthereactorvesselsystemandtheRVSSareprovidedinTable4.32andTable4.7

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 433 1.Vesselfluencecalculations,asdescribedinSection4.5,confirmadequatemarginrelativetothe effectsofirradiation.Thefastneutronfluencereceivedbythereactorvesselfromthereactorcoreand pebbleinsertionandextractionlinesisattenuatedbythecorebarrel,thereflector,andthereactor coolant.Coolantpuritydesignlimitsarealsoestablishedinconsiderationoftheeffectsofchemical attackandfoulingofthereactorvessel.ThesefeaturesdemonstrateconformancewithPDC31.

TheMSSutilizescouponsandcomponentmonitoringtoconfirmthatirradiationaffectedcorrosionis nonexistentormanageable.The316HSSreactorvesselandER1682weldmaterial,asapartofthe reactorcoolantboundary,willbeinspectedforstructuralintegrityandleaktightness.Asdetailedin Reference3,fracturetoughnessissufficientlyhighin316HSSunderreactoroperatingconditionsthat additionaltensileorfracturetoughnessmonitoringandtestingprogramsareunnecessary.These featuresdemonstrateconformancetoPDC32.

Fluidicdiodesareusedtoestablishaflowpathforcontinuousnaturalcirculationofcoolantinthecore duringpostulatedeventstoremoveresidualheatfromthereactorcoretothevesselwall.Duringand followingapostulatedevent,thehotcoolantfromthecoreflowsfromtheupperplenumthroughthe lowflowresistancedirectionofthefluidicdiodetothecoolerdowncomervianaturalcirculation, therebycoolingthecorepassively.Continuouscoolantflowthroughthereactorcorepreventspotential damagetothevesselinternalsduetooverheatingtherebyensuringthecoolablegeometryofthecoreis maintained.Theantisiphonfeaturealsolimitsthelossofreactorcoolantinventoryfrominsidethe reactorvesselintheeventofaPHTSbreach.ThesefeaturesdemonstratecompliancewithPDC35.

Thedowncomer,graphitereflectorblocks,andfluidicdiodesarepassivecomponentsdesignedto maintainstructuralintegrityduringpostulatedeventstomaintainanaturalcirculationpathanda coolablecoregeometryforremovalofdecayheat.Thereactorvesselinternalsarequalifiedin accordancewithReference3andReference4andaredesignedtoperformtheirfunctionduringseismic eventsasnotedabove.Basedonthedesignandqualification,therearenocrediblefailuremechanisms withinthedesignbasisofthecorebarrelandthegraphitestructuresthatresultinalossofstructural integrity.Therefore,degradationofthenaturalcirculationflowpathrequiredtosupportdecayheat removalisnotexpectedduringnormalorpostulatedeventsandsuchfailureswouldbebeyondthe designbasis.However,graphitedustisexpectedtobepresentinsmallquantitiesinthesystemand couldbepostulatedtoaccumulateinportionsofthereactorcoolantpathway.Thefunctionalcapability ofthenormalflowpathcanbeperiodicallyconfirmedduringoperationbymonitoringtemperature changestotheexitfromthereactorvessel.Similarly,theportionsofthereactorcoolantflowpaththat areuniquetonaturalcirculation(diodepathwayandfluidicdiode)arecapableofbeingconfirmed duringnormaloperationsviatemperaturechangesacrossthediodeandacrossthepathway.

Additionally,thefluidicdiodesaredesignedtopermitperiodicremoteinspectionsviapenetrationson thevesseltopheadtoensurethepathwayremainsunobstructed.Instrumentationfortemperature measurementacrossthefluidicdiodeispermittedviathesamepenetrationsusedforvisualinspection.

ThesefeaturesandcapabilitiesdemonstrateconformancetoPDC36andPDC37.Additionalfunctions performedbytheDHRStosupportpassivedecayheatremovalaredescribedinSection6.3.

Thereactorvesselreflectorblockspermitinsertionofthereactivitycontrolandshutdownelements.The ETU10gradegraphiteofthereflectorblocksiscompatiblewiththereactorcoolantchemistryandwill notdegradeduetomechanicalwear,thermalstressesandirradiationimpactsduringthereflectorblock lifetime.ThegraphitereflectormaterialisqualifiedasdescribedintheKairosPowertopicalreport GraphiteMaterialQualificationfortheKairosPowerFluorideSaltCooledHighTemperatureReactor, KPTR014(Reference4).Toprecludedamagetothereflectorduetoentrainedmoistureinthegraphite, thereflectorblocksarebaked(i.e.,heateduniformly)priortocomingintocontactwithcoolantand thereactorvesselisdesigntoprecludeairingress.Thereflectors,whichactasaheatsinkinthecore, Highlighted text previously added.

Submitted on 8-31-22.

(ML22243A250)

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 436 Table4.32:LoadCombinationsfortheReactorVesselSystem ServiceLevel LoadCombination A

D+L+To+Po+Ro B

D+L+To+Po+Ro+Eo D+L+Ti+Pi+Ri+Eo C

D+L+To+Po+Ro+Ess D+L+Ts+Ps+Rs+Ess D

D+L+Ta+Pa+Ra+Wt D+L+Ta+Pa+Ra+Ess LoadNomenclature:

D Deadloads L

Liveloads To Thermalloadsduringstartup,normaloperating,orshutdownconditions Ti ThermalloadsduringServiceLevelBloadings Ta ThermalloadsduringServiceLevelDloadings Ts ThermalloadsduringServiceLevelCloadings Po Pressureloadsduringstartup,normaloperating,orshutdownconditions Pi PressureloadsduringServiceLevelBloadings Ps PressureloadsduringServiceLevelCloadings Pa PressureloadsduringServiceLevelDloadings Ro Pipereactionsduringstartup,normaloperating,orshutdownconditions Ri PipereactionsduringServiceLevelBloadings Ra PipereactionsduringServiceLevelDloadings Rs PipereactionsduringServiceLevelCloadings Eo Loadsgeneratedby1/3designbasisearthquake(thedesignbasisearthquakeisalsothe safeshutdownearthquake[SSE])

Ess LoadsgeneratedbySSE Wt Accidentalloadsduetomissileimpacteffects

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 460 4.7.3 SystemEvaluation TheRVSSsupportsthereactorvesselintheeventofanearthquakeorothernaturalphenomenonthus ensuringtheintegrityofthereactorvesselanditsabilitytoretainreactorcoolant.Thebottomsupport meetsASCE4319(2019)(Reference2)andprecludeslinearbucklinginthevesselsupportcolumns understaticanddesignbasisearthquakeloads.Thebottomsupportisalsoverticallyanchoredtothe cavitytopreventthevesselfromupliftduringadesignbasisearthquake.Thevesselconnectorsmeet Reference2andprovidesufficientlateralandupliftsupporttothevesselandthevesseltophead components.Thereactorcavityisalsoseismicallyisolatedtoreduceseismicloads.Loadcombinations fortheRVSSandsafetyrelatedportionsoftheReactorBuildingareprovidedinTable4.71andTable 3.51.ThesedesignfeaturesdemonstratecompliancewithPDC2fortheRVSS.

TheRVSSisprotectedfromdischargingfluidsbycatchbasins.Sensorsandprobesinstalledoncatch basinsincludingthebottomsupporttraycanbeusedasameansofleakdetectiontoprecludedamage totheRVSS.TherearenopressurizedpipingsystemsinproximitytotheRVSSthusprecludingbydesign anyimpactsfromhighenergylineconsiderations.TheRVSSaccommodatesthereactorvessel temperatureloadingcyclesincombinationwithrelevantmechanicalloadingcyclestoensurecreep fatiguedamagesareprecluded.TheRVSScanalsoaccommodatethegrowthofthereactorvesseldueto thermalexpansionbetweenstartupandequilibriumconditions.ThesedesignfeaturessatisfyPDC4for theRVSS.

PDC74statesrequiresthedesignofthereactorvesselandreactorsystemshallbesuchthattheir integrityismaintainedduringpostulatedevents(1)toensurethegeometryforpassiveremovalof residualheatfromthereactorcoretotheultimateheatsinkand(2)topermitsufficientinsertionofthe neutronabsorberstoprovideforreactorshutdown.TheRVSSmaintainstheintegrityofthereactor vesselbyremovingheatviatheRTMS,activelyduringnormaloperationandpassivelyduringpostulated events.Fissionproductdecayheatandotherresidualheatfromthereactorcoreistransferredtothe reactorvessel;thentotheanchoredsurfacebytheRVSS.ThesupportcolumnsoftheRVSSaresizedand spacedtomaximizeheattransferbetweenthebottomsupportandtheenvironment.Thethermalbreak betweentheRVSSandthereactorbuildingprovidedbythebottomsupportinsulationensuresthe concreteintegritymeetsACI34913tosupportmaintenanceandinspectionofthevesselbottom head/vesselshellweldandtoensureconditionsinthesurroundingcavitydonotexceedmaximum allowableparameters.ThisdemonstratescompliancewithPDC74fortheRVSS.

4.7.4 TestingandInspection TheRVSStemperaturewillbemonitoredduringoperationforconformancewithdesignlimits.TheRVSS willbeincludedinaninserviceinspectionprogramwhichwillbesubmittedatthetimeoftheOperating LicenseApplication.

4.7.5 References

1. ASMEBoiler&PressureVesselCode,SectionIII,Division5(2019)
2. ASCE4319,SeismicDesignCriteriaforStructures,Systems,andComponentsinNuclear Facilities.
3. ACI34913,CodeRequirementsforNuclearSafetyRelatedConcreteStructuresand Commentary

PreliminarySafetyAnalysisReport

ReactorDescription

KairosPowerHermesReactor

Revision0 461 Table4.71:LoadCombinationsfortheReactorVesselSupportSystem ServiceLevel LoadCombination A

D+L+To+Ro B

D+L+To+Ro+Eo D+L+Ti+Ri+Eo C

D+L+To+Ro+Ess D+L+Ts+Rs+Ess D

D+L+Ta+Ra+Wt D+L+Ta+Ra+Ess LoadNomenclature:

D Deadloads L

Liveloads To Thermalloadsduringstartup,normaloperating,orshutdownconditions Ti ThermalloadsduringServiceLevelBloadings Ta ThermalloadsduringServiceLevelDloadings Ts ThermalloadsduringServiceLevelCloadings Ro Pipereactionsduringstartup,normaloperating,orshutdownconditions Ri PipereactionsduringServiceLevelBloadings Ra PipereactionsduringServiceLevelDloadings Rs PipereactionsduringServiceLevelCloadings Eo Loadsgeneratedby1/3SSE Ess LoadsgeneratedbySSE Wt Accidentalloadsduetomissileimpacteffects

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