ML22237A326
| ML22237A326 | |
| Person / Time | |
|---|---|
| Site: | Hermes File:Kairos Power icon.png |
| Issue date: | 08/25/2022 |
| From: | Kairos Power |
| To: | Office of Nuclear Reactor Regulation |
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| ML22237A324 | List: |
| References | |
| KP‐NRC‐2208‐010 | |
| Download: ML22237A326 (11) | |
Text
KPNRC2208010
Enclosure1 ChangestoPSARChapters3,4,5,9and14 (NonProprietary)
Preliminary Safety AnalysisReport Design ofStructures,Systems,andComponents
PrincipalDesignCriteria SARSection PDC 26, Reactivitycontrolsystems 4.2.2 4.5 PDC 28, Reactivitylimits 4.2.2, 7.3
PDC 29, Protectionagainst anticipatedoperation occurrences 4.2.2, 7.3, 7.5
PDC 30, Qualityofreactorcoolantboundary 4.3
PDC 31, Fracturepreventionofreactorcoolantboundary 4.3
PDC 32, Inspectionofreactorcoolantboundary 4.3
PDC 33, Reactorcoolantinventorymaintenance 4.3, 9.1.4, 9.3
PDC 34, Residual heatremoval 4.6, 6.3
PDC 35, Passiveresidual heatremoval 4.3, 4.6, 6.3
PDC 36, Inspectionofpassiveresidual heatremovalsystem 6.3
PDC 37, Testing ofpassiveresidual heatremovalsystem 6.3
PDC 44, Structuralandequipmentcooling 9.1.5, 9.7
PDC 45, Inspectionofstructuralandequipmentcoolingsystems 9.1.5, 9.7
PDC 46, Testing ofstructuralandequipmentcoolingsystems 9.1.5, 9.7
PDC 60, Control ofreleasesofradioactivematerialstothe 5.1, 9.1.3, 9.2,11.2 environment PDC 61, Fuelstorageandhandlingandradioactivitycontrol 9.3
PDC 62, Preventionofcriticalityinfuelstorageandhandling 9.3
PDC 63, Monitoringfuelandwastestorage 9.3, 11.2
PDC 64, Monitoringradioactivityreleases 9.1.2, 9.1.3, 9.2
PDC 70, Reactorcoolantpuritycontrol 9.1.1
PDC 71, Reactorcoolantheatingsystems 9.1.5
PDC 73, Reactorcoolantsysteminterfaces 5.2
Kairos PowerHermesReactor 37 Revision0 Preliminary Safety AnalysisReport ReactorDescription
Thereflectorblocksformanupperplenumandafluidic diode,whichisastainlesssteel passivedevice thatconnectstheupperplenumtothetopofthedowncomeras showninFigure4.31. Thediode introducesahigherflowresistanceinonedirection,whilehavingalowerflowresistanceintheother direction.Thedioderestrictsflowfromthehigherpressure downcomer intotheupperplenumduring conditionswithforcedcirculation.Theflowpassesin thelowresistance direction ofthediodefromthe upperplenumtothetopofthedowncomer drivenbynatural circulation.
Thegraphitereflectorblocksreflectneutronsbackinto thecore, increasingthefuelutilizationwhile protectingthereactorvesselfromfluencebasedforms ofdegradation.Furtherdiscussionofthe reflectorsneutroniccharacteristicsaredetailedinSection4.5.
4.3.1.2.2 CoreBarrel The 316HSScorebarrel createsanannularspacebetweenitselfand thereactorvesseland definesthe downcomerflowpathforthecoolant.Thecorebarrel includescutoutfeatureswhichlimitthesiphoning ofreactorcoolant intheeventofabreakin thevessel coldleg, andThecorebarrel hasaflangedtop whichiswelded totheinnerwallofthevesselshell.The barrel iskeptconcentrictotheshellbyradial tabswhich allow fordifferentialthermal expansion.
4.3.1.2.3 ReflectorSupportStructure The316HSSreflectorsupportstructure,as showninFigure4.31, definestheflowpathfromthe downcomerannulusintothecoreas wellas providessupporttothegraphitereflectorblocks.The reflectorsupportstructureensuresastable coreconfigurationforall conditions (e.g.,reactortripand coremotion)bycontrollingtheradialandcircumferential positionsofthereflector blocks.
4.3.2 Design Basis ConsistentwithPDC 1, thesafetyrelate d portionsofthereactorvesselandreactorvesselinternalsare fabricatedandtestedin accordancewithgenerallyrecognizedcodesandstandards.
ConsistentwithPDC 2, thereactor vesselandreactorvesselinternalsperformtheir safetyfunctionsin theeventofasafeshutdown earthquakeandothernatural phenomenahazards.
ConsistentwithPDC 4, thereactor vesselandreactorvesselinternalsaccommodatetheenvironmental conditionsassociated withnormaloperation,maintenance,testing,andpostulatedevents.
ConsistentwithPDC 10, thereactorvesselandinternals maintainageometryandcoolantflowpathto ensurethatthespecifiedacceptablesystemradionuclidereleasedesign limits(SARRDLs)willnotbe exceededduring normaloperation includingpostulatedevents.
ConsistentwithPDC 14, thereactorvesselisfabricated andtested tohaveanextremely lowprobability ofabnormalleakageorsuddenfailure ofthereactorcoolantboundarybygrossrupture.
ConsistentwithPDC 30, reactorvesselisfabricated,andtestedtoqualitystandards, andpreandin serviceinspections, as wellas testing wherepracticable,willbe used todetectandidentifythelocation ofcoolantleakage.
ConsistentwithPDC 31, thereactorvesselhassufficient margintowithstandstresses underoperating, maintenance,testing,andpostulatedeventssuchthat thereactorcoolantboundarydoesnot degrade due totheeffectsofneutron embrittlement,corrosion,materialwear, fatigue,stress rupture,thermal loads, orfailure duetostressruptureandfracture.Thedesign shallaccountfor residual,steadystate, andtransientstressesandconsiderflawsize.
Kairos PowerHermesReactor Revision0430 Preliminary Safety AnalysisReport ReactorDescription
ConsistentwithPDC 32, thereactorvesselpermitsinspection,monitoring,orfunctional testingof importantareasandfeaturestoassess structuralintegrity andleaktightness ofthesafetyrelated portionsofthereactorcoolantboundary.
ConsistentwithPDC 33, thecorebarreldesignincludesantisiphon featurestolimitreactor coolant inventory lossin theeventofbreaksinthePHTScold leg.
ConsistentwithPDC 35, thereactorvesselinternalswillassuresufficientcorecooling duringpostulated eventsandremoveresidualheat.Thesafetyfunctionofthefluidic diode istoprovideaflowpathvia natural circulationtotransferheatfromthereactorcoreduringandfollowingpostulated eventssuch thatfuelandreactor internalstructuredamage thatcouldinterferewithcontinued effectivecore coolingisprevented.
ConsistentwithPDC 74, thedesign ofthereactorvesselandreflectorblocksshallbe suchthattheir integrityandgeometryaremaintainedduringpostulatedeventstopermitsufficientinsertion ofthe controlandshutdownelementsproviding forreactorshutdown.
4.3.3 SystemEvaluation The316HSSstructuresofthereactorvesselsystemarefabricatedandtestedinaccordancewith Reference1standards.The316HSSvessel internalsalsosatisfy thechemistryrestrictionsoftheASME SectionIIIcodeinDivision5, ArticleHGB2000. PertheASMEstandard,ER1682 weldmetalwillbe used infabrication ofthe316Hstructures.Commensurate withthesafetyrelated functionofthe reflectorblockinensuringacceptabledesignlimitsandmaintainingthereactorcoolantflowpath, qualityrelated controlswillbe placed ontheETU10 graphite.KPFHRspecificationsandprocurement documentsincorporate andreferencetheapplicableguidanceandASMEstandards.Thequality assuranceprogramisdescribed inSection12.9.These controlsdemonstrate conformancewithPDC 1.
Thereactorvesselsystemmakesupaportionofthereactor coolantboundary.Thereactorvesseland graphitereflector blocksarethereforedesignedtomaintaingeometryduringasafeshutdown earthquaketoensurethevesselintegrity,insertionofnegativereactivityviatheRCSS,andtomaintain theflowpath.Thereactorvesselandvesselinternalswillhavedynamicbehaviorsduringadesignbasis earthquake.Theseincludefluidstructure interactionwithinthevessel,oscillatoryresponseof componentsmounted tothereactortophead,i.e.,headmounted oscillators,andrelativemovementof graphitereflector blockswithrespecttooneanotherwithinthecoolant.Thesedynamicbehaviorsare accountedforin thedesign ofthereactoranditsinternals, toensurecontinuedfunctionalityduring and after adesignbasisearthquake. Modelsareusedtounderstandfluid migrationtendenciesconsidering thepebblebed,reflector blocks,corebarrel,andotherreactor vesselinternalfeatures.Theinsights gained fromtheanalysisofthesemodelsareusedtodesignthereactortopreventdamagetothevessel duringadesignbasisearthquake. Thereactorvessel,vesselinternals, andvesselattachmentssuchas theRCSSareclassifiedas SDC3 perASCE4319 SeismicDesign Criteria forStructures,Systems,and Componentsin NuclearFacilities(Reference2).Thereactor vesselwillalsobeprotectedfromthe failureofnearbynonsafety relatedSSCsduringadesignbasisearthquakebyseismicallymounting, physicallyseparating, orusingabarriertoprecludeadverseinteraction,andfromfailureofattached nonsafety relatedSSCs, suchas attachedpiping(e.g.,bydesignforpreferentialfailureofthenonsafety component isawaythatdoesnotimpactthevessel).Thesefeaturesdemonstratecompliance withPDC 2.
Thereactorvesselcanaccommodateinternalandexternalstaticanddynamic loads.Thethermal expansion ofthereactorvesselshellandbottomheadissupportedbythereactorvesselsupportsystem (RVSS)(see Section4.7)duringreactorstartup,normaloperation,andpostulatedevents.Mechanical loadingsfromstaticweight,seismicload,andforcesfromthepebblebed,coolant,andcore
Kairos PowerHermesReactor Revision0431 Preliminary Safety AnalysisReport ReactorDescription
metal underthegastungstenarc welding process.The vesselprecludesmaterialcreep, fatigue,thermal, mechanical,andhydraulicstresses.Theleaktightdesignof thereactorvesselheadminimizesair ingress intothecovergasandprecludescorrosion of the internals. The hightemperature,highcarbongrade 316HSSof the corebarrelandreflector supportstructure havehighcreepstrength andare resistantto radiationdamage, corrosion mechanisms,thermalaging, yielding,and excessiveneutron absorption.
Vesselfluencecalculations,asdescribedinSection4.5, confirm adequatemarginrelative totheeffects of irradiation.Thefastneutronfluencereceivedbythe reactorvesselfromthereactorcoreandpebble insertionandextractionlinesisattenuatedbythe corebarrel, the reflector,andthe reactorcoolant.
Coolantpurity designlimitsarealsoestablishedinconsiderationoftheeffects of chemicalattackand foulingof thereactorvessel.Thesefeaturesdemonstrate conformancewithPDC31.
TheMSS utilizescouponsandcomponent monitoring toconfirmthatirradiationaffected corrosion is nonexistent ormanageable.The316HSSreactorvesseland ER1682weldmaterial, asapartof the reactorcoolant boundary,willbeinspectedforstructuralintegrityandleak tightness. Asdetailedin Reference3,fracturetoughnessissufficientlyhighin316HSSunderreactoroperatingconditionsthat additionaltensileorfracturetoughnessmonitoringandtesting programsareunnecessary. These features demonstrateconformancetoPDC32.
AntisiphoncutoutsareabovethePHTScoldlegwithcoolantonbothsidesofthecorebarrel during normaloperation.Intheeventofacoldlegbreak, reactorcoolantlevel isexpectedtodecreaseand the covergas moves intothedowncomertobreakthesiphonthusprecludingcoolantfrombeing siphoned belowthefluidicdiodeflowpathwayelevation.ThesedesignfeaturesdemonstrateconformancetoPDC 33.
Fluidicdiodesareusedtoestablishaflowpathforcontinuousnatural circulationofcoolantinthecore duringpostulated eventstoremoveresidualheatfromthereactorcoretothevessel wall.Duringand followingapostulatedevent,thehotcoolantfromthecoreflowsfromtheupperplenumthroughthe lowflowresistancedirectionofthefluidicdiodetothecoolerdowncomervianatural circulation, therebycoolingthecorepassively.Continuouscoolantflowthroughthereactorcorepreventspotential damagetothevessel internalsduetooverheating therebyensuringthecoolablegeometryofthecoreis maintained.Theanti siphonfeaturealsolimitsthelossofreactorcoolantinventoryfrominsidethe reactorvessel intheeventofaPHTSbreach.ThesefeaturesdemonstratecompliancewithPDC35.
Thereactorvessel reflectorblockspermitinsertionofthereactivitycontrolandshutdownelements.The ETU10gradegraphiteofthereflectorblocksiscompatiblewiththereactorcoolantchemistryandwill notdegrade duetomechanical wear,thermal stressesandirradiationimpactsduringthereflectorblock lifetime.Thegraphitereflectormaterialis qualifiedasdescribedin theKairosPowertopicalreport GraphiteMaterial QualificationfortheKairosPowerFluorideSaltCooledHighTemperatureReactor, KPTR014(Reference4).Toprecludedamagetothereflectorduetoentrainedmoistureinthegraphite, thereflectorblocksarebaked(i.e.,heateduniformly)priortocomingintocontactwithcoolantand thereactorvesselisdesigntoprecludeairingress.Thereflectors,whichactasaheatsinkinthecore, arespacedtoaccommodatethermalexpansionandhydraulicforcesduringnormal operationand postulatedevents.Thegapsbetweenthegraphiteblocksalsoallowforcoolanttoprovidecoolingtothe reflectorblocks.Thereactorvesselpermitstheinsertionofthereactivitycontrol andshutdown elementsaswell. Thevesselis classifiedasSDC3perASCE4319andwill maintainitsgeometryto ensuretheRCSSelementscanbeinsertedduringpostulatedeventsincluding adesignbasisearthquake.
ThesefeaturesdemonstratecompliancewithPDC74.
Kairos PowerHermesReactor Revision0433 Preliminary Safety AnalysisReport ReactorDescription
4.6 THERMALHYDRAULIC DESIGN 4.6.1 Description Thethermalhydraulicdesignofthereactorisacombinationofdesignfeaturesthatenableeffective heattransportfromthefuelpebbletothereactorcoolantandeventuallytotheheatrejection system ofthe reactor,consideringtheeffects ofbypassflowandflownonuniformity.Thedesignfeaturesthat playakeyroleinthethermalhydraulicdesignofthereactorsysteminclude thefuelpebble (seeSection 4.2.1),reactor coolant (seeSection 5.1),reactorvesseland reactorvesselinternalstructures(see Section4.3), the primary heattransportsystem(PHTS)(seeSection5.1), and theprimary heatrejection system(PHRS)(seeSection5.2).Thermal hydrauliccomputercodesandevaluationmodels are discussedin Section4and5ofReference1,andSection4ofReference2.
4.6.1.1 CoreGeometry Thecoregeometryismaintainedin partbythereactorvesselinternalsincludingthereflectorblocks whichkeepthepebblesinageneral cylindrical coreshape.Coolantinlet channelsin thegraphite reflectorblocksareemployedtolimit thecorepressuredrop.Theuseofpebblesin apackedbed configurationalsocreateslocalvelocityfieldsthatenhancepebbletocoolant heattransfer.Thereactor thermalhydraulic designusesthefollowingheattransfermechanismstoextractthefissionheat.
Pebbleto coolantconvectiveheattransfer Pebble radiativeheattransfer Pebbleto pebble heattransferbypebblecontactconduction Pebbleto pebble heattransferbyconductionthroughthereactorcoolant Heattransfertothegraphitereflector bymodesofconduction,convection,andradiation.
4.6.1.2 CoolantFlow Path Duringnormaloperation,reactor coolantatapproximately550°Centers thereactorvesselfromtwo PHTScold legnozzlesandflowsthroughadowncomerformed betweenthemetalliccorebarrel andthe reactor vesselshell as shown inFigure4.61. Thecoolantisdistributed alongthevesselbottomhead throughthereflectorsupportstructure,upthrough coolantinletchannelsinthereflector blocksandthe fuelingchuteandintothecorewithaportionofthecoolantbypassingthecoreviagapsbetweenthe reflectorblocks.Thecoolanttransfersheatfromfuelpebbleswhicharebuoyantinthecoolantand providescooling tothereflector blocks andthecontrolelementsviaengineeredbypass flow.Coolant travelsoutoftheactivecorethroughtheupperplenumviathecoolantoutletchannelsandexitsthe reactor vesselviathePHTS outlet.Themaximum vesselexittemperatureis620°Canddependentonthe amount ofcorrespondingbypass flowthroughthereflector blocks.
Duringpostulatedeventswherethenormal heatremovalpaththroughthePHTSisnolongeravailable, includingwhen thePHTSisdrained,afluidicdiode(seeSection4.3),isused tocreateanalternateflow path.Duringsuchevents, forcedflowfromtheprimary saltpump(PSP)isalsonotavailable.Thefluidic diode thendirectsflowfromthehotwelltothedowncomerasshownin Figure4.61. Thisopensthe pathfor continuousflowvianatural circulation.Duringnormaloperation,whilethePSPisinoperation, thefluidic diodeminimizesreverseflow.
Kairos PowerHermesReactor Revision0453 Preliminary Safety AnalysisReport ReactorDescription
4.6.4 TestingandInspection Reactorcoolanttemperatures,flow,andcorepower willbeperiodicallymonitored duringoperationsto be withinspecifiedlimits.Instrumentationwillalsobeperiodicallycalibrated.
4.6.5 References
- 1. Kairos PowerLLC,KPFHR CoreDesign andAnalysisMethodology,KPTR 017 P,Revision0.
- 2. Kairos PowerLLC,Postulated EventMethodology,KPTR 018 P, Revision0.
Kairos PowerHermesReactor Revision0455 Preliminary Safety AnalysisReport HeatTransportSystems
5.1.3 SystemEvaluation Thedesignof thenonsafetyrelated PHTSissuchthatafailureof componentsof the PHTSdoesnot affect theperformanceof safetyrelatedSSCsduetoadesignbasisearthquake.Inadditiontoprotective barriers,the PHTSpipeconnectionstothe reactorvesselnozzleshavesufficientlysmallwallthickness, suchthatifloadedbeyondelasticlimits,inelasticresponseoccursinthe PHTSpipingwhichisnonsafety related.Thesefeatures,alongwiththeseismicdesigndescribedinSection3.5,demonstrate conformancewiththe requirementsinPDC 2forthePHTS.
WhilethePHTSisaclosedsystem,thereareconceivablescenariosthatmayresultinthereleaseof radioactiveeffluents.Thefueldesignlocatesthe fuelparticlesneartheperipheryof thefuelpebble, enhancingthe abilityof thefueltotransferheattothecoolant. Thethermalhydraulic analysisof the core(seeSection4.6)ensuresthatadequatecoolant flow ismaintainedtoensurethat SARRDLs,as discussedin Section6.2,arenotexceeded.Thesefeaturesdemonstrateconformancewiththe requirementsinPDC 10.
Thedesignof thereactorcoolant,inpart, ensuresthat power oscillationscannotresultinconditions exceeding SARRDLs.Thereactoriskept nearambientpressureandthereactorcoolantinthePHTSdoes notexperiencetwophaseflow. Thecoolanthasahighthermalinertia makingthe reactorresilientto thermal hydraulicinstabilityevents.Thesefeatures, inpart, demonstrate conformancewiththe requirementsinPDC 12.
Thefunctionalcontainment isdescribed inSection6.2.Thedesign reliesprimarilyonthemultiple barriers withinthe TRISOfuelparticlesto ensurethattheradiologicaldose attheexclusionarea boundaryas aconsequence of postulatedeventsmeetsregulatorylimits.However,thereactorcoolant alsoserves asadistinctphysicalbarrier forfuelsubmergedinFlibebyproviding retentionof fission productsthatescapethe fuel.Thedesign of thereactorcoolant compositionprovides,inpart, ameans tocontrolthe accidentalreleaseof radioactive materialsduringnormalreactoroperationand postulatedevents(PDC 60),and supports,in part, demonstrationof the functional containment aspects.
Thedesignaspectsof the reactorcoolantarediscussedinReference5.1.51.TheFlibealsoaccumulates radionuclidesfromfissionproducts,andtransmutationproducts fromtheFlibeand Flibeimpurities.The retentionpropertiesof theFlibearecreditedinthe safetyanalysisasabarrier to releaseof radionuclidesaccumulatedinthecoolant,and radionuclideconcentration islimitedbytechnical specifications.The transportof radionuclidesthroughFlibeisbased onthermodynamicdatathatwillbe justifiedinthe applicationforanOperating License.Thesefeaturesdemonstrateconformancewiththe requirementsinPDC 16.
ThePSP casingdesign setsthe inletelevation of theantisiphonsurfaceforthehotlegshouldaleak occurintheexternalportionof thePHTS.Inthe event of abreakinthe externalportionof thePHTShot legThisantisiphonfeaturelimitsthe lossof reactorcoolantinventoryfrominside thereactor vesselthe eventofaPHTSbreachorinbreachesofinventorymanagementsystempipingconnectedtothePHTS (seeSection9.1.4.), reactorcoolantlevelis expectedtodecreaseandthe covergasmoves intothe pump well tobreakthesiphon.Thisprecludescoolantfrombeingsiphonedbelowtheelevationofthe PSPcasing. Theseanti siphonfeaturesdemonstratecompliancewithPDC33.
Thedesignof thePHTScontrolsthereleaseof radioactivematerials ingaseous and liquideffluentsin the eventthePHTSworkingfluidisinadvertentlyreleasedtotheatmospherevialeaks inthe piping system.ThePHTSSSCsthatarepartof the reactorcoolantboundaryaredesigned totheASMEB31.3 Code(for thepiping)andSectionVIII(forthePHX)suchthatleaks areunlikely. Meansareprovidedfor detecting and,totheextentpractical,identifyingthe locationof the sourceof reactorcoolant leakagein the PHTSSSCs. A postulatedeventinthePHTSwouldbe aPHXtubefailure.ThiseventwouldcauseFlibe
Kairos PowerHermesReactor 54 Revision0 Preliminary Safety AnalysisReport Auxiliary Systems
interactions. The IMSisdesignedtopreferentiallyfailinawaythatdoesnotimpacttheRVsystem.This satisfiesPDC 2fortheIMS.
The IMSisdesigned suchthatsafetyrelatedsystems inproximityto theIMSareprotectedagainstthe dynamiceffectspotentiallycreatedbythefailureof IMSequipment.TheIMSisalow pressuresystem, as the reactorcoolantpressures areboundedbythereactor coolantstatichead pressures,thus precludingpipe whip.ThissatisfiesPDC 4fortheIMS.
The IMSisdesigned toprecludetheinadvertentdraining oftheRVduring normaloperation andduring RVfill/drainoperations. During normaloperation,when thereactorvesselisfueled,theRVfill/drain transfer lineisequippedwithpassiveRVisolationfeaturessuchascaps,flanges,and/or atransferline disconnect,designedtopreclude inadvertentreactorcoolantdrainingfromtheRVbysiphoning.In the eventofaleakintheRVfill/draintransferline,whileconnected tothereactorvesselduring fueled operation,thereactorcoolantleakisdetectedbytheplantcontrolsystem, thePSPistripped, and the RVcovergaspressureislimitedtoanupperboundthusprecludingtheejectionofreactor coolant throughthetransfer linediptube.DuringRVfill/drain operations,thereactorvesselisdefueled, andthe fill/drainlineisconnected,anisolationvalveisused tointerruptthereactorcoolantflowandacover gasinletisused tobreakthesiphoninthetransferlines.Thesedesignfeaturessatisfythe requirements ofPDC 33.
The RVcoolantlevelmanagementline shortdiptubeand overflowweir designspreclude inadvertent reactorcoolantdrainingfromtheRVintotheRVlevel managementtank.Asleveldropsin responsetoa breakin thereactorcoolantlevel managementline, covergaswouldfill theshortdiptubeandwould breakthesiphon.Additionally, theoverflowweiris designedinawaythatprecludestheuncoveringof fuelduetothermal expansionofthereactorcoolant.Intheeventofaleakin theRVlevel management tankortransferline, thereactorcoolantleakis detectedbytheplantcontrolsystem, andthepumpfor thereactorlevelmanagement istrippedtominimizetheoverflowofreactorcoolantfromtheRV throughtheoverflowweir.Aslevel dropsinresponsetoabreakin thereactorcoolantlevel managementline,covergaswouldfill theoverflowweirandwouldbreakthesiphon.Thisdesign configurationsatisfiestherequirementsofPDC33.
The IMSencompassesaPHTSdrainline,equippedwithaPHTSdrainvalve,whichinterfaceswiththe PHTSfill/drain tank.ThePHTSdesigncontainsanRVantisiphonfeature(see Section5.1), thus precludinginadvertentreactorcoolantdrainfromtheRV,precludingtheIMSfromdrainingtheRV.
Thesedesignfeaturessatisfy therequirementsofPDC 33.
The makeupinventoryfunctionofIMSisnotreliedontomitigatethe consequencesofapostulated event.AsdescribedinSection4.3, thesafetyrelatedportionsofthereactorcoolantboundaryare limitedtothereactor vesselandafailure ofthereactorvesselisprecludedbydesign.Therefore, the makeupfunctionalrequirementsofPDC 33 havebeen addressedbydesign.
The systemisexpectedtohandlereactorcoolantwithfission as wellas activationproducts;therefore, the systemwillbedesigned tominimizecontaminationandsupporteventualdecommissioning, consistentwiththerequirementsof10 CFR20.1406.
9.1.4.4 TestingandInspection ThecomponentsoftheIMS,includingvalves, tanks,pumpsandothercomponents, arelocatedsuch thattheyareaccessiblefor periodicinspectionandtesting.
9.1.4.5 References
- 1. AmericanSocietyofMechanical Engineers, Process Piping,ASMEB31.3.2016.
Kairos PowerHermesReactor 917 Revision0 Preliminary Safety AnalysisReport Auxiliary Systems
graphiteorareexpectedtocool quicklysuchthatoxidation,ifany,would be minimalandnot affectthe acceptabilityofthe pebbleforreuse.Thesedesignfeaturessatisfy therequirementsofPDC 3forthe PHSS.Fire protectionsystems arefurther discussed inSection9.4.
The pebblehandlingportion ofthePHSSisprotectedfromtheeffectsofdischargingfluids.Thereareno pressurizedpipingsystemsinoraroundthe PHSSthusprecluding thedesignfromhighenergyline considerations.A hypotheticalwaterlinebreakintheareaofthestoragesystemdoesnotposea criticalityriskas theanalysessupportingthestoragesystemassumecompletesubmergenceand internal floodingof thestoragecanistersinwater.ThePHSSisdesignedinconsideration ofthe highradiation environmentwhereequipmentwillbefunctioning.ThePHSSdesignalsoconsidersand accountsforthe temperaturewithinthesystemtoprecludeoxidationofgraphitepebbles.ThestainlesssteelPHSS storagecanistersaredesignedtoaccommodatepressureduetotheaccumulationofradionuclidesand thermalloadsassociated withtheamount ofspentfuelloadedineachcanisterduring normaland postulatedeventconditions.The canistersarealsodesignedtoaccommodatethetensilestress exerted duringtransferand arecompatiblewithhandlingequipment.Theinteriorofthestainlesssteel canisters isalsodesignedtoaccountforradiolysisproductsfromspentnuclearfuelandensurestheintegrityof the canister,seal, and weldthusprecludingthepotentialreleaseofradionuclidesfromthe canister.
Thesedesignfeaturesdemonstratethatthe PHSSsatisfiesthe environmentalanddynamiceffectsin PDC 4.
The PHSSinterfaceswiththereactorvesselatthePEM and thepebbleinsertion line.The elevation of the PEMrelativetothecoolant freesurfaceissuchthatcoolantinventorylossfromthereactorvesselis limitedintheeventthePEM breaks.Thepebbleinsertion lineisdesignedtolimit inventorylosstoan elevation nolower thantheprimarysaltpumpelevation,intheeventofabreakintheinsertionline.
Thepebbleinsertionlineusesoverflowprotectioncutoutstodirectanycoolantin theinsertionline backdownintothereactorvessel. C over gas fills the line to break the siphon.Thesedesignfeatures of thePHSS satisfytherequirementsin PDC33.
PDC 61 requiresthatthesafetyrelatedportionsofthePHSSthatcontain radioactivitybedesignedto ensure(1)capabilitytopermitappropriateperiodicinspectionandtestingofcomponents,(2)suitable shieldingforradiation protection,(3)appropriate containment,confinement,andfiltering,(4)residual heatremovalcapability,and(5)significantreductioninfuelstoragecoolingunderpostulatedevent conditionsisprecluded.ThedesignfeatureswhichaddressPDC 61 forthePHSSarediscussed below:
TheTRISOfuelparticleprovidesafunctionalcontainmentas describedinSection6.2.Radioactive materialandfissionproductsarecontainedwithintheparticle unlesstheTRISOlayers are compromisedordefective(see Section 4.2.1).Thefuelpebble,as described in Section 4.2.1,is designedtoprecludephysicaldamage orchangesingeometrytotheTRISOparticle during anticipatedloadsfromnormaloperation,storage,shippingandhandling.Therefore, theTRISO particleiscreditedfor theconfinementofradioactive materialsrather thanthePHSS.Thepebble canexperiencethermalandmechanicalloadswhilebeinghandled,inspected,operated,andstored; however, suchloadsdonotintroduce incremental failuresofTRISOparticles.Furthermore,thePHSS designprecludespebbledamagefromoverheatingandoxidation.Heatremovalmechanismswithin thesystem,suchas thermalradiation andconvectionvianatural circulation,aresufficientto removethedecayheatproducedbyindividualpebblesduringtheirtransitthroughthePHSS.Also, oxidationassociated withair ormoisture ingressintothePHSSisnegligible for pebblesat temperaturesexperiencedin thesystem.Thesystemalsominimizespebblewear.ThelimitingPHSS malfunctionevent,whichisdiscussedinSection13.1.5, doesnotcausetemperatureexcursions, oxidation,ormechanicalstresses ontheTRISOparticles. Therefore,containment andconfinement ofradioactivityismaintainedbytheTRISOparticles.
Kairos PowerHermesReactor 929 Revision0 PreliminarySafetyAnalysisReport TechnicalSpecifications
Section SectionName LCOorCondition Basis
Inletgassystempressureis Theobjectiveistolimitthe maintainedwithinanupper quantityandpressureof boundlimit. spilledFlibeorcovergasto ensureapostulatedevent doesnotexceedlimits.
Argonpurityinthecovergasis Theobjectiveistolimit maintainedwithinanupper radionuclidesintheFlibe boundlimit. belowsolubilitylimitswhere solutesoluteinteractionscan beneglected.
Thequantityofmaterialsatrisk Theobjectiveistolimitthe inthegasspaceoftheprimary quantityofmaterialsatrisk heattransportsystemandthe inthecovergastoensurea primaryheatrejectionsystemis postulatedeventdoesnot maintainedwithinanupper exceedlimits.
boundlimit.
Thequantityofairinthereactor Theobjectiveistolimitthe Highlightedtextwasadded coolantsystemduringsteady airingresstothereactor previously.Submitted2/18/22 stateismaintainedwithinan coolantsystemtoprevent (ML22049B556) upperboundlimit. voidaccumulationand corrosion.
3.4 EngineeredSafetyDecayheatremovalsystem Theobjectiveistospecifythe Features operability requirementtohavean operabledecayheatremoval systemtoensurethatthe safetylimitswillnotbe exceeded.
Reactorvesselintegrity Theobjectiveistospecifya designoperating temperaturelimittoensure thesafetylimitisnot exceededforpostulated events.
3.5 VentilationSystems N/A N/A
3.6 EmergencyPower N/A N/A
KairosPowerHermesReactor 145 Revision0