ML22284A156
| ML22284A156 | |
| Person / Time | |
|---|---|
| Site: | Hermes File:Kairos Power icon.png |
| Issue date: | 10/11/2022 |
| From: | Kairos Power |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML22284A154 | List: |
| References | |
| KP-NRC-2210-007 | |
| Download: ML22284A156 (7) | |
Text
KP-NRC-2210-007 Changes to Hermes PSAR Chapters 3, 4, 6, and 14 (Non-Proprietary)
PreliminarySafetyAnalysisReport
DesignofStructures,Systems,andComponents
KairosPowerHermesReactor 342 Revision1
- 6. ComponentswillbedesignedandfabricatedusingthetechnicalguidanceinASMECode,SectionIII,Division5,withdepartures.Specifically, HermeswillimplementanANSI/ANS15.8QualityAssuranceProgram,asdescribedinSection12.9ratherthantheNQA1standardspecified intheASMEcode.Therefore,thecomponentswillnotmeetASMECode,SectionIII,Division5requirementsthataredependentonortied specificallytoanNQA1program.AppropriatedepartureswillbetakentothequalityassurancerelatedguidanceoftheASMECode requirementsforHermescomponents,includingstampingandcertificationrequirementsintheCodethataredependenton implementationofanNQA1program.DeparturesfromotherASMECoderequirements,ifany,arealsoanticipatedandwillbeidentified andjustifiedwiththeOperatingLicenseApplication.Suchdepartureswillstillmeettheintentofthecodetechnicalguidanceandprovide reasonableassuranceofcomponentperformance.
PreliminarySafetyAnalysisReport
ReactorDescription
KairosPowerHermesReactor
Revision1 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 vesselbottomplenumformedbythereflectorsupportstructureandisdistributedintothecorebythe designofthereflectorblocks.Uponexitingthecore,thecoolantleavesthereactorvesselviathe primarysaltpump(PSP)(seeSection5.1.1)whichdrawssuctiondirectlyfromapoolofreactorcoolant abovethecoreandinsidethevessel.Designfeaturesareprovidedinfluidsystemsconnectedtothe reactorvesseltolimitlossofcoolantinventoryintheeventofabreakinthosesystemsasdescribedin Sections5.1,9.1.4,and9.3.
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.)
DuringpostulatedeventswhenthePHTSisnotavailable,thereactorvesselprovidesanalternativeflow pathasdiscussedinSection4.6.1toallownaturalcirculationofthereactorcoolanttoremoveheatfrom thereactorcore.Thereactorcoolantleavingthecoreflowsintothehotwell,fluidicdiodepathway, fluidicdiode,throughacorebarrelpenetration,andbackintothedowncomerannulusasshownin Figure4.31.Theheatfromthecoreistransferredtothereactorvesselshellwhichtransferstheheatto thedecayheatremovalsystem(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 metalandisdesignedandfabricatedusingthetechnicalguidanceinASMEBPVCSectionIII,Division5 (Reference1)withdeparturesasshowninTable3.62.Itcontainstheinventoryofreactorcoolantsuch
PreliminarySafetyAnalysisReport
ReactorDescription
KairosPowerHermesReactor
Revision1 429 thatthereactorcoreiscoveredbythecoolantduringnormaloperationandpostulatedevent.Thereare nopenetrationsorattachmentstothevesselbelowthecoolantlevel.Thedesignofthereactorvessel allowsforonlinemonitoring,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, reactivityshutdownelements,pebblehandlingandstoragesystemcomponents,materialsamplingport, thermocouples,etc.).Thetopheadsupportsthevesselmaterialsurveillancesystem(MSS)which providesaremotemeanstoinsertandremovematerialtestspecimensintoandfromthereactorto supporttesting.Aholddownstructuresubassemblyisweldedunderneaththevesseltophead.This structurecontactswiththetopsurfaceofthegraphitereflectorandprovidesstructuralsupportagainst upwardloadsduringnormaloperationandmostpostulatedevents.Asecondaryholddownstructureis installedthroughtheuppergraphitelayers,extendingfromthereflectortopintosubmergedgraphite layerstotransferupwardloadsfromsubmergedgraphitetothevesseltopheadduringpostulatedair ingressevents.Thesecondaryholddownstructureextendstobelowtheminimumreactorvessel coolantlevelthatcouldresultfrompostulatedsaltspillevents.
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.
PreliminarySafetyAnalysisReport
ReactorDescription
KairosPowerHermesReactor
Revision1 432 4.3.3 SystemEvaluation The316HSSstructuresofthereactorvesselsystemarefabricatedandtestedtomeettheintentof Reference1standardswithdeparturesasshowninTable3.62.The316HSSvesselinternalsalsosatisfy thechemistryrestrictionsoftheASMESectionIIIcodeinDivision5,ArticleHGB2000.PertheASME standard,ER1682weldmetalwillbeusedinfabricationofthe316Hstructures.Commensuratewith thesafetyrelatedfunctionofthereflectorblockinensuringacceptabledesignlimitsandmaintaining thereactorcoolantflowpath,qualityrelatedcontrolswillbeplacedontheET10graphite.Thegraphite reflectorwillbedesignedtomeettheintentofReference1standardswithdeparturesshowninTable 3.62.KPFHRspecificationsandprocurementdocumentsincorporateandreferencetheapplicable guidanceandASMEstandards.ThequalityassuranceprogramisdescribedinSection12.9.These controlsdemonstrateconformancewithPDC1.
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,thusprecludingpipewhiphazards.Heavy loadconsiderationsareaddressedinSection9.8.4,CranesandRigging.Thesefeaturesdemonstrate compliancewithPDC4.
Corecoolingismaintainedthroughthedesignofthereactorvesselandthereactorvesselinternals.As describedinSection4.3.1.2,thevesselandvesselinternalsdefinethecoolantflowpath.Topreclude degradationtothevesselduetocorrosionofthestainlesssteel,thereflectorblocksandthevesselare baked(i.e.,heateduniformly)toremoveresidualmoisturepriortocomingintocontactwithcoolant.
PreliminarySafetyAnalysisReport
EngineeredSafetyFeatures
KairosPowerHermesReactor 613 Revision1 Table6.34:ApplicableDesignCodesandStandardsfortheDHRS Code Title Applicability ASMESec.IIIDiv.5ClassB (Reference1)
ASMEBoilerand PressureVesselCode
-HighTemperature Reactors TheDHRSmetallicpressureboundaryand supportswillbedesignedandfabricatedusing thetechnicalguidanceinASME,SectionIII, Division5,withdeparturesasshowninTable 3.62.
ASCE4319(Reference2)
SeismicDesign Criteriafor Structures,Systems, andComponentsin NuclearFacilities Providesdesigncriteriaforseismicanalysisof reactorcomponents(includingDHRS).
ASCE416(Reference3)
SeismicAnalysisof SafetyRelated NuclearStructures Providesadditionaldesigncriteriaforsafety relatedsystems(includingDHRS)thatexpand uponASCE4319.
ACI34913(Reference4)
CodeRequirements forNuclearSafety RelatedConcrete Structuresand Commentary ApplicabletocavitysupportstructuresforDHRS panelsandpotentiallythecondenserpool construction.
PreliminarySafetyAnalysisReport
TechnicalSpecifications
KairosPowerHermesReactor 144 Revision1 Section SectionName LCOorCondition Basis 2.2 LSSS Thehighpowerfluxtrip functionshallnotexceedan upperboundlimitasspecified inthesafetyanalysis.
Limitingtheupperboundlimitwill ensurethatthereactorwilltripprior tochallengingasafetylimitassumed inthesafetyanalysis.
3.0 LimitingConditionsforOperation(LCOs)
LCOsarederivedfromthesafetyanalysisandareimplementedadministrativelyorby controlandmonitoringsystemstoensuresafeoperationofthefacility.
TheLCOsarethelowestfunctionalcapabilityorperformancelevelrequiredforsafe operationofthefacility.
TheproposedsubjectsofLCOsareprovidedbelow.
3.1 ReactorCore Parameters Pebbleweariswithin acceptablelimitstosupport pebblereinsertion.
Theobjectiveistoensurethatpebble weariscontrolledwithinlimits assumedbyorassociatedwithsafety analyses,topreventreinsertionif wearexceedsthoselimits.
Reactorpowershallnotexceed thelicensedreactorpower level.
Theobjectiveistolimitthemaximum operatingpowertoensurethatthe safetylimitswillnotbeexceeded.
3.2 Reactor Controland Safety Systems Reactivitycoefficientsare withinlimitsovertheallowable rangeofoperation.
Theobjectiveistoinferorcalculate reactivitycoefficientsduringnormal plantoperationtolimittheseverityof areactivitytransient.
Reactorprotectionsystem operability Theobjectiveistospecifythe requirementtohaveanoperable reactorprotectionsystemtoensure thatthesafetylimitswillnotbe exceeded.
3.3 Coolant Systems Reactorcoolantchemical compositionismaintained withinallowablelimits.
Theobjectiveistoensurethatthe thermophysicalpropertiesand chemicalcompositionofthereactor coolantaremaintainedwithinlimits assumedbyorassociatedwithsafety analyses.