ML22353A625

Kairos Power LLC, Transmittal of Changes to Preliminary Safety Analysis Report Chapter 6 and Response to NRC Question on Dhrs Testing

ML22353A625
Person / Time
Site:	Hermes File:Kairos Power icon.png
Issue date:	12/19/2022
From:	Hastings P Kairos Power
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
KP-NRC-2212-003
Download: ML22353A625 (1)

Text

KP-NRC-2212-003 Kairos Power LLC www.kairospower.com 707 W Tower Ave, Suite A 5201 Hawking Dr SE, Unit A 2115 Rexford Rd, Suite 325 Alameda, CA 94501 Albuquerque, NM 87106 Charlotte, NC 28211 December 19, 2022 Docket No. 50-7513 US Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Kairos Power LLC Transmittal of Changes to Preliminary Safety Analysis Report Chapter 6 and Response to NRC Question on DHRS Testing

References:

1. Letter, Kairos Power LLC to Document Control Desk, Submittal of the Preliminary Safety Analysis Report for the Kairos Power Fluoride Salt-Cooled, High Temperature Non-Power Reactor (Hermes), Revision 1, September 29, 2022 (ML22272A594)

2. Audit Plan, Nuclear Regulatory Commission, Kairos Power, LLC - Plan for a General Audit of The Hermes Constructure Permit Application, February 10, 2022 (ML22039A336)

3. Letter, Kairos Power LLC to Document Control Desk, Transmittal of Response to NRC Question on DHRS Testing from PSAR Section 6.3 Audit on Hermes Preliminary Safety Analysis Report, September 1, 2022 (ML22244A236)

In September 2022, Kairos Power submitted Revision 1 of the Preliminary Safety Analysis Report (PSAR)

(Reference 1) as part of the Construction Permit Application (CPA) for the Hermes non-power reactor.

This letter transmits changes to the pages of the PSAR to address NRC feedback received on Chapter 6 in the General Audit (Reference 2). Changes to the pages of the PSAR are provided in Enclosure 1. Kairos Power requests NRC review of these changes as part of the continued review of the Hermes CPA.

Additionally, on September 1, 2022, Kairos Power submitted a response to an NRC question on DHRS testing (Reference 3). The NRC asked a follow-up question on additional DHRS performance phenomena as part of the General Audit. In addition to the phenomena listed in the Kairos Power response, the design verification process will also evaluate phenomena associated with material and mechanical performance of the DHRS during startup of the system including:

thermal shock effects on material properties, flow-induced vibration effects on DHRS components, and metal fatigue effects due to stress and thermal cycling.

If you have any questions or need any additional information, please contact Drew Peebles at peebles@kairospower.com or (704) 275-5388, or Darrell Gardner at gardner@kairospower.com or (704) 769-1226.

KP-NRC-2212-003 Page 2 I declare under penalty of perjury that the foregoing is true and correct.

Executed on December 19, 2022 Sincerely, Peter Hastings, PE Vice President, Regulatory Affairs and Quality

Enclosures:

Changes to PSAR Chapter 6 xc (w/enclosure):

William Jessup, Chief, NRR Advanced Reactor Licensing Branch Benjamin Beasley, Project Manager, NRR Advanced Reactor Licensing Branch Edward Helvenston, Project Manager, NRR Advanced Reactor Licensing Branch Samuel Cuadrado de Jesus, Project Manager, NRR Advanced Reactor Licensing Branch Matthew Hiser, Project Manager, NRR Advanced Reactor Licensing Branch

KP-NRC-2212-003 Changes to PSAR Chapter 6 (Non-Proprietary)

PreliminarySafetyAnalysisReport

EngineeredSafetyFeatures

KairosPowerHermesReactor 68 Revision1 precludeasafetyrelatedSSCfromperformingitssafetyfunction.Designfeaturesaddressingdifferential displacementarediscussedinSection3.5.Thereactorbuildingalsoprovidescivilstructuralsupportfor theDHRSandprotectionofsafetyrelatedcomponentsfromexternalhazardssuchaswind,tornadoes, floods,andwindinducedmissileevents.TheDHRSdesignrequirementsforseismicandothernatural hazardsdemonstrateconformancewiththerequirementsinPDC2.

TheDHRSisdesignedandlocatedtominimizetheprobabilityandeffectoffiresandexplosionsbythe useoflowcombustiblematerialsandphysicalseparation.Thesedesignfeatures,inconjunctionwiththe fireprotectionplandescribedinSection9.4,provideassurancethattheDHRSdemonstrate conformancewiththerequirementsinPDC3.

TheDHRSisdesignedwithmaterialsthatwillwithstandtheradiationenvironmentofthereactorcavity andenvironmentaltemperaturesupto800750°CtoensuretheDHRSiscapableofperformingitssafety functionunderconditionsassociatedwithnormaloperation,maintenance,testing,andpostulated events.TheDHRSisdesignedagainstequipmentfailuresthatcouldresultfromFlibespills.Pipewhip andothersimilardynamicfailuresareavoidedbythelowpressuredesignoftheDHRSandtheuseof restraints.EachcomponentoftheDHRSisdesignedsuchthatfailureofonecomponentdoesnot cascadeandcausefailuresofnearbysafetysystems,includingotherDHRScomponents.Thesedesign considerationsdemonstrateconformancewiththerequirementsinPDC4.

Naturalcirculationinthereactorcoretransfersdecayheatfromthefueltothereactorvesselshellwhen normalcoolingisnotavailable,asdescribedinSection4.6.3.Thermalhydrauliccalculations demonstratethattheDHRSiscapableofpassivelyremovingasufficientamountofdecayheatfromthe reactorvesselwithoutrelianceonelectricpowerforupto7daysasneededtomitigatepostulated events,suchthatthereactorvesseltemperatureremainsbelowitsdesignlimitandisdecreasing.In addition,fueltemperaturesremainbelowtheirdesignlimits.TheDHRSisdesignedwithsufficient redundancy,leakdetectioncapability,andisolationtoensurethesafetyfunctioncanbeperformed assumingasinglefailure.Thesystemincludesfourindependentloopsandmaintainstheabilityto performitsfunctionwiththelossofasingleloop.Isolationofthefourwaterstoragetanksfromone anotherensuresthatdamageatonetanklocationdoesnotresultinatotallossofDHRSinventory.The thimbles,separators,andthimblefeedwaterandsteamreturnpipingareallcontainedwithintheleak barrier.Theleakbarrierprovidesleakdetectioncapabilityandensuresthatafailureoftheprimary DHRSpressureboundarydoesnotpreventthesystemfromperformingitsheatremovalfunction.These DHRSdesignfeatures,alongwiththenaturalcirculationcharacteristicsofthereactorcore,demonstrate conformancewiththerequirementsinPDC34andPDC35.

TheDHRSdesignincludesthecapabilityforonlinemonitoringofleakstomonitorforsystemintegrity andtoensurethatDHRSinventoryremainssufficienttoperformthesafetyrelatedheatremoval function.Thewaterlevelinthestoragetanksisalsocapableofbeingmonitoredtoensurethatsufficient inventoryispresentattheonsetofapostulatedeventtoprovidesufficientcoolingcapacity.TheDHRS isalsosufficientlyaccessibletoperforminspectionsforsystemintegrity.ThesefeaturessatisfyPDC36.

Whenthereactorisabovethresholdpower,theDHRSisanalwaysonoperatingconditionwhich providesanongoingdemonstrationofsystemavailability.Thetransitionfromnormaltopostulated eventoperationcanalsobefunctionallytested.Thesefeaturesdemonstrateconformancewiththe requirementsinPDC37.

PreliminarySafetyAnalysisReport

EngineeredSafetyFeatures

KairosPowerHermesReactor 612 Revision1 Table6.33:ThimbleParameters Parameter Value Material StainlessSteel Designpressure(psig) 30 Designtemperature(°CF) 7501500 Numberpersteamseparator 6

Length(in) 144 Thimblewallouterdiameter(in) 2.875