ML22210A319
| ML22210A319 | |
| Person / Time | |
|---|---|
| Site: | Hermes File:Kairos Power icon.png |
| Issue date: | 07/29/2022 |
| From: | Kairos Power |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML22210A317 | List: |
| References | |
| KP‐NRC‐2207‐009 | |
| Download: ML22210A319 (5) | |
Text
KPNRC2207009
ChangestoPSARChapter4andChapter6 (NonProprietary)
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
EngineeredSafetyFeatures
KairosPowerHermesReactor 68 Revision0 TheDHRSisdesignedandlocatedtominimizetheprobabilityandeffectoffiresandexplosionsbythe useoflowcombustiblematerialsandphysicalseparation.Thesedesignfeatures,inconjunctionwiththe fireprotectionplandescribedinSection9.4,provideassurancethattheDHRSdemonstrate conformancewiththerequirementsinPDC3.
TheDHRSisdesignedwithmaterialsthatwillwithstandtheradiationenvironmentofthereactorcavity andenvironmentaltemperaturesupto800°CtoensuretheDHRSiscapableofperformingitssafety functionunderconditionsassociatedwithnormaloperation,maintenance,testing,andpostulated events.TheDHRSisdesignedagainstequipmentfailuresthatcouldresultfromFlibespills.Pipewhip andothersimilardynamicfailuresareavoidedbythelowpressuredesignoftheDHRSandtheuseof restraints.EachcomponentoftheDHRSisdesignedsuchthatfailureofonecomponentdoesnot cascadeandcausefailuresofnearbysafetysystems,includingotherDHRScomponents.Thesedesign considerationsdemonstrateconformancewiththerequirementsinPDC4.
Naturalcirculationinthereactorcoretransfersdecayheatfromthefueltothereactorvesselshellwhen normalcoolingisnotavailable,asdescribedinSection4.6.3.Thermalhydrauliccalculations demonstratethattheDHRSiscapableofpassivelyremovingasufficientamountofdecayheatfromthe reactorvesselforatleast72hoursfollowingpostulatedeventssuchthatthereactorvesseltemperature remainsbelowitsdesignlimitof816°Candisdecreasingbytheendofthe72hourperiod.Inaddition, fueltemperaturesremainbelowtheirdesignlimits.TheDHRSisdesignedwithsufficientredundancy, leakdetectioncapability,andisolationtoensurethesafetyfunctioncanbeperformedassumingasingle failure.Thesystemincludesfourindependentloopsandmaintainstheabilitytoperformitsfunction withthelossofasingleloop.Isolationofthefourwaterstoragetanksfromoneanotherensuresthat damageatonetanklocationdoesnotresultinatotallossofDHRSinventory.Thethimbles,separators, andthimblefeedwaterandsteamreturnpipingareallcontainedwithintheleakbarrier.Theleak barrierprovidesleakdetectioncapabilityandensuresthatafailureoftheprimaryDHRSpressure boundarydoesnotpreventthesystemfromperformingitsheatremovalfunction.TheseDHRSdesign features,alongwiththenaturalcirculationcharacteristicsofthereactorcore,demonstrate conformancewiththerequirementsinPDC34andPDC35.
TheDHRSdesignincludesthecapabilityforonlinemonitoringofleakstomonitorforsystemintegrity andtoensurethatDHRSinventoryremainssufficienttoperformthesafetyrelatedheatremoval function.Thewaterlevelinthestoragetanksisalsocapableofbeingmonitoredtoensurethatsufficient inventoryispresentattheonsetofapostulatedeventtoprovidesufficientcoolingcapacity.TheDHRS isalsosufficientlyaccessibletoperforminspectionsforsystemintegrity.ThesefeaturessatisfyPDC36.
Whenthereactorisabovethresholdpower,theDHRSisanalwaysonoperatingconditionwhich providesanongoingdemonstrationofsystemavailability.Thetransitionfromnormaltopostulated eventoperationcanalsobefunctionallytested.Thesefeaturesdemonstrateconformancewiththe requirementsinPDC37.
6.3.4 TestingandInspection ThedetailsoftheinspectionandtestingprogramforDHRStosatisfytheapplicableportionsofASME SectionXI,Division1and2,RulesforInserviceInspectionofNuclearPowerPlantComponents (Reference2)willbedescribedintheapplicationforanOperatingLicense.
WaterstoragetankinventoryismonitoredtoensuretheDHRSoperability.TheDHRScontinuous operationisalsomonitoredtoensureDHRSavailabilitywhendemanded.DHRSoperabilityiscontrolled byatechnicalspecification,asdescribedinChapter14.
PreliminarySafetyAnalysisReport
EngineeredSafetyFeatures
KairosPowerHermesReactor 69 Revision0 6.3.5 References
- 1. AmericanSocietyofMechanicalEngineers,ASMEBoilerandPressureVesselCode,Sec.IIIDiv.5, BPVCSectionIIIRulesforConstructionofNuclearFacilityComponentsDivision5High TemperatureReactors,2019.
- 2. AmericanSocietyofMechanicalEngineers,ASMEBoilerandPressureVesselCode,Sec.XIDiv.1and 2,BPVSSectionXIRulesforInserviceInspectionofNuclearPowerPlantComponents,2019.
3.2. AmericanSocietyofCivilEngineers,ASCE/SEI4319,SeismicDesignCriteriaforStructures,Systems, andComponentsinNuclearFacilities,2020.
4.3. AmericanSocietyofCivilEngineers,ASCE/SEI416,SeismicAnalysisofSafetyRelatedNuclear Structures,2017.
5.4. AmericanConcreteInstitute,ACI34913,CodeRequirementsforNuclearSafetyRelatedConcrete StructuresandCommentary,2014.
PreliminarySafetyAnalysisReport
EngineeredSafetyFeatures
KairosPowerHermesReactor 613 Revision0 Table6.34:ApplicableDesignCodesandStandardsfortheDHRS Code Title Applicability ASMESec.IIIDiv.5ClassB (Reference1)
ASMEBoilerand PressureVesselCode
-HighTemperature Reactors Metallicpressureboundaryandsupports.In general,lowtemperatureservicecorrespondsto therequirementsofASMESec.IIIDiv.1 subsectionNC.ThisappliestomostDHRS components.Therisersareanexceptionand mustfollowrulesforhightemperatureservice.
TheseprovideadditionalmodificationstoDiv.1 rules.
ASMESec.XIDiv.1and2 (Reference2)
RulesforInservice InspectionofNuclear PowerPlant Components Providesrulesandguidelinesfortestingand inspectionofDHRSpressureboundaryand structuralcomponents.
ASCE4319(Reference23)
SeismicDesign Criteriafor Structures,Systems, andComponentsin NuclearFacilities Providesdesigncriteriaforseismicanalysisof reactorcomponents(includingDHRS).
ASCE416(Reference34)
SeismicAnalysisof SafetyRelated NuclearStructures Providesadditionaldesigncriteriaforsafety relatedsystems(includingDHRS)thatexpand uponASCE4319.
ACI34913(Reference45)
CodeRequirements forNuclearSafety RelatedConcrete Structuresand Commentary ApplicabletocavitysupportstructuresforDHRS panelsandpotentiallythecondenserpool construction.