ML22285A229
| ML22285A229 | |
| Person / Time | |
|---|---|
| Site: | Hermes File:Kairos Power icon.png |
| Issue date: | 10/12/2022 |
| From: | Kairos Power |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML22285A227 | List: |
| References | |
| KP‐NRC‐2210‐006 | |
| Download: ML22285A229 (4) | |
Text
KPNRC2210006 ChangestoPSARChapter4 (NonProprietary)
PreliminarySafetyAnalysisReport ReactorDescription KairosPowerHermesReactor
Revision1 410 Thecontrolelementsarepositionedviaacounterweightedwinchsystem(Figure4.28).Theshutdown elementsarealsopositionedbyacounterweightedwinch,buttheyaretypicallyonlyfullyinsertedor fullywithdrawn.Inthecounterweightedwinchsystem,awireropeisconnectedtotheelement,and travelsuparoundthesheaveanddowntoacounterweight.Thecounterweightallowsthewireropeto wraparoundthesheavewithouthavingtoanchorthewirerope,similartoacapstan.Thesheave, commonlyknownasawinchdrum,isrotatedbyanelectricmotor.Thereisanelectricclutchbetween themotorandthesheave.Themotorallowssmallandcontrolledmovementsoftheelement.The maximumwithdrawalandinsertiontimefortheshutdownandcontrolelementsis100secondsoverthe fullrangeofmotionformotordrivenoperations.
Onareactortrip,theelectricclutchopens,whichallowsthesheavetorotatefreely.Withthesheave rotatingfreely,theshutdownandcontrolelementsarereleasedfromtheirdrivesanddropintothecore andreflector,respectively,asaresultofgravity.Thecontrolandshutdownelementsreach90 percentfullinsertionbygravityinnomorethan10seconds.Althoughboththecontrolelementsandthe shutdownelementsreceiveareactortripsignal,thereleaseoftheclutchfortheshutdownelements providestheprimarysafetyrelatedreactortripreleasemechanism.
Controlandshutdownelementpositionismonitoredusingtwoindependentanddiversemethods.The motorpositionismeasuredusinganabsoluteencoderallowingthedeterminationoftheanglethe sheavehassweptfromaknownreferencepoint,whichdirectlycorrelatestotheelementposition.The secondpositionmeasurementdeviceisahighdensityreedswitcharray.Similartoexistingreedswitch positionmeasurementdesigns,thisinstrumentmeasuresthepositionofthecounterweightoveritsfull rangeofmotion.Thereedswitcharrayprovidesananalogsignal,andtheencoderprovidesadigital signalandthetwousedtogetherprovidestheabilitytodeterminetheelementposition,whileallowing realtimefunctionalchecks.
ThematerialsusedintheRCSSareshowninTable4.24.TheprimarymaterialsaretheB4Cabsorber materialandthestainlesssteel316Hcladding.Theoperatingconditionsaresuchthatthecontroland shutdownelementsareimmersedinreactorcoolantandexperiencetemperaturesupto700°Cduring operation.Theupperportionsofthecontrolandshutdownelementsareexposedtoreactorcovergas abovethereactorcoolantfreesurface.Thecontrolandshutdowndrivemechanismsabovethevessel aremaintainedattemperaturesbelowtheirmechanicallimits.TheB4Cneutronabsorbermaterialis containedinpellets,whicharestackedinSS316Hcylindricaltubes(pressurizedwithinertgas).The controlandshutdowndrivemechanismsarealsomadeofstainlesssteel.
4.2.2.2 DesignBasis ConsistentwithPDC2,thesafetyrelatedportionoftheRCSSperformstheshutdownfunctionunder designbasisnaturalphenomenaevents.
ConsistentwithPDC4,thesafetyrelatedportionoftheRCSSaccommodatestheeffectsofthe environmentalconditionsduringnormalplantoperationaswellasduringpostulatedeventsasaresult ofequipmentfailures.
ConsistentwithPDC23,thesafetyrelatedportionoftheRCSSfailsintoasafestateintheeventof adverseconditionsorenvironments.
ConsistentwithPDC26,theRCSSprovidesanindependentanddiversemeansofcontrollingreactivityto assurethatshutdownmarginismaintainedandthatSARRDLsarenotexceededunderconditionsof normaloperation.Inaddition,theRCSSprovidesameansofinsertingnegativereactivityatasufficient ratetoassurewithappropriatemarginformalfunctionsandalsoprovideameanstomaintainthe reactorshutdownforfuelloading,inspectionandrepair.
PreliminarySafetyAnalysisReport ReactorDescription KairosPowerHermesReactor
Revision1 411 ConsistentwithPDC28,theRCSShasappropriatelimitsonthepotentialamountandrateofreactivity increasetoensuretheeffectsofpostulatedreactivityeventscanneitherdamagethesafetyrelated elementsofthereactorcoolantboundaryordisturbthecoreandinternalssuchtheabilitytocoolthe coreisimpaired.Thesystemallowsonlyoneelementtomoveatagiventime.
ConsistentwithPDC29,theRCSS,inconjunctionwithreactorprotectionsystems,assuresanextremely highprobabilityofaccomplishingitssafetyrelatedfunctions.
4.2.2.3 SystemEvaluation TheRCSSmeetsthedesignbasesasdescribedbelow:
PDC2 AsnotedinSection4.2.2.1,theshutdownelementsareinsertedintoguidestructuresintheupper reflectorandthendirectlyintothepebblebed.Theguidestructuresandreflectorblocksensurethe abilityoftheshutdownelementstoinsertunderconditionsofreflectorblockmisalignmentthatcould potentiallyoccurinadesignbasisearthquake.ThedesignbasisearthquakeisdescribedinSection3.4.
Thisseismicanalysisdeterminesthemaximumdeflectionoftheinsertionpath.Insertioncapabilitywill beassessedinaonetime,outofpile,atscaletestpriortoinitialoperation,withandwithoutmaximum deflectionofthatdeflectstheshutdownelementguidestructuresconsistentwiththemaximum misalignmentcausedbysuchaneventandaccountsfortheexpectedchangesinpebblebedpacking fractionandconcurrentinsertionofallthreeshutdownelementsintothepebblebed.Thethree shutdownelementinsertiontimesandinsertiondepthsisaremeasuredandcomparedtotheinsertion timetestingperformedwithnodeflectionoftheupperreflectorguidestructures.Thetestingis performedtoconfirmthattheelementinsertiontimeiswithintheinsertiontimeassumedinthe postulatedeventanalysisinChapter13undertheconditionofmaximumexpectedmisalignmentofthe upperreflectorguidestructuresfromadesignbasisearthquake.Thetestswillalsoconfirmthatthe shutdownelementsfullyinserttothedepthassumedintheshutdownmargincalculationsinTable4.5
- 5. Additionally,thereflectorblocksmaintaintheelementinsertionpathwayasdescribedinSection4.3.
TheseshutdownelementdesignfeaturesprovideconformancetoPDC2.
PDC4 ThesafetyrelatedportionsoftheRCSSarecompatiblewiththeenvironmentalconditionsthattheywill besubjectedtoduringnormaloperation,maintenance,testing,andpostulatedevents.
TheRCSSshutdownelementsaremadewithstainlesssteelcladding.Wearratesduetoflowinduced vibrationareexpectedtobelowincomparisontothoseoftypicaloperatingreactorswithstainlesssteel claddinggiventhelowercoreflowrates(<0.13meter/second)inthedesign.Theneutronabsorbing materialisenclosedintwostainlesssteelbarrierstomitigatethelossofneutronabsorbingmaterialin theshutdownelements.Theshutdownelementsare qualificationtestedoutofpilepriortooperationandaconservativewearlimitisestablishedtoensure thatwearduringshutdownelementmovementisacceptable.Theshutdownelementscanberemoved forinspectionorreplacedifnecessary.Inaddition,theshutdownelementsarenotadverselyaffectedby neutronandgammaheating.
Analysisisperformedontheshutdownelementstodeterminetheinternalgasreleaseandswellingof theB4Cduringnormaloperationovertheirdesignlifetime.Theresultingincreaseingaspressureis analyzedtoensurethatstressesontheshutdownelementtubesarewithinallowablestresslimitsforSS 316H.Inaddition,theeffectsofirradiationonSS316Handcladwearareaccountedforinthestress analysis.
PreliminarySafetyAnalysisReport ReactorDescription KairosPowerHermesReactor
Revision1 413 Theshutdownelementpositionandreactivityinsertionversustimewillbeprovidedintheapplication foranOperatingLicense.Aconservativeshutdownelementdroptimeandreactivityinsertionvalueis usedinChapter13.ThesefeaturesdemonstrateconformancetoPDC29fortheRCSS.
4.2.2.4 TestingandInspection Theshutdownelementsareperiodicallyinspectedtoensurethatthereisnounacceptablewearorother damagetothecladdingthatencapsulatestheB4Cabsorbermaterial.Inaddition,thereactorcoolantis periodicallyexaminedforanincreaseinboronfromB4Cabsorbermaterial,whichprovidesanindication ofshutdownelementcladdingfailure.
RCSSshutdownelementinsertiontimesandshutdownmarginareperiodicallyconfirmedtobewithin safetyanalysislimitsbysurveillancerequirementsprovidedinthetechnicalspecifications(seeChapter 14).
4.2.3 NeutronStartupSource Aneutronstartupsourceisusedtoprovideanadequateneutronfluxtothesourcerangeexcore detectorsduringinitialandsubsequentplantstartups.Thestartupneutronsourceallows monitoringofthechangeinneutronmultiplicationduringtheadditionoffuelandtheapproachto criticality.Theneutronstartupsourcedoesnotperformanysafetyrelatedfunctions.
Theneutronsource(s)willbelocatedinthereflectorregionofthereactorneartheoutsideedgeof thecoreandoptimallylocatedrelativetoanexcoresourcerangedetectorforbestdetectabilityof criticality.Thesourcewillhavesufficientstrengthtoprovideadetectablecountrate.
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,Revision2.July2022.
3.
KairosPower,LLC,KPFHRFuelPerformanceMethodology,KPTR010PA,May2022.
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.,
IrradiationBehaviorofPressurizedWaterReactorControlMaterials,NuclearTechnology,62(1),
7580,1983.
8.
AmericanSocietyofMechanicalEngineers,ASMEBoiler&PressureVesselCode,SectionIII,Division 5,HighTemperatureReactors.2017.