ML23304A480

LLC Response to NRCs Request for Docketing of Resolved Audit Responses, Chapter 12, Response to Sdaa Question 12.2-1, Re Information Related to Radiation Sources

ML23304A480
Person / Time
Site:	05200050
Issue date:	10/31/2023
From:	NuScale
To:	Office of Nuclear Reactor Regulation
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Text

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ResponsetoSDAAAuditQuestion

QuestionNumber:A-12.2-1

ReceiptDate:04/10/2023

Question:

NuScaleSDASection12.2.1.2,ReactorCoolantSystemdiscussesnitrogen-16(N-16) concentrationsinreactorcoolant. ItindicatesthatN-16concentrationshavebeencalculatedat thecoreexit,thetopoftheupperriser/steamgeneratorentrance,andatvariouspointsalong thechemicalandvolumecontrolsystem(CVCS)letdownline.SDATable12.2-4,"Nitrogen-16 PrimaryCoolantConcentrationsatFullPower"providestheN-16concentrationsat"coreexit,"

"Topofupperriser/entrancetoSG,""CVCSletdownline,"and"CVCSheatexchanger."

InTR-12342-NP,"EffluentRelease(GALEReplacement)MethodologyandResults,"itindicates thatthereactorcoolantlooptransittimeisapproximately46seconds,whichismorethansixN-16half-lives(intheNuScaleDCAdesign,thelooptransittimewasapproximately69seconds, orapproximatelytenhalf-livesandN-16concentrationsweregenerallyinsignificantincoolant outsideofthereactorcontainment). SDATable12.2-4indicatesthatthereactorcoolantN-16 concentrationis200uCi/gramatthecoreexitand2.4uCi/gramattheCVCSletdownlineinthe reactordowncomer(whichislessthanacompletereactorcoolantloop).ThisdecreaseinN-16 sourcestrengthisequivalenttooversixN-16half-livesfromthetimethecoolantexitsthecore toitreachestheCVCSletdownline,assumingtheconcentrationprovidedisattheentranceto theCVCSline(intheDCAtheN-16concentrationexitingthecorewassmalleranddecayeda littlemorethansixhalf-livesbythetimeitenteredtheCVCSletdownlinebutasindicated above,thecoolantlooptransittimewasmuchgreaterintheDCA).

Inaddition,Table12.2-7,"ChemicalandVolumeControlSystemComponentSourceTerms-SourceStrengths,"providessourcetermenergystrengthsforcomponentsintheCVCSsystem, whichareusedinplantshieldingcalculations.Itincludesasourcespectrum(?)for"CVCSpipe chasephotonspectraN-16,"andaseparatesourcespectrum(?)for"CVCSLetdown-71.3 secondsdecay."Since71.3secondsistenN-16half-lives,staffassumesthissourcetermwas providedbecauseatthistimeN-16isdecayedtoapointwhereN-16isinsignificant.However, thelocationthatthisoccursintheCVCSpipingisnotspecifiedanditisunclearifN-16is

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consideredinCVCSequipment(oriftheN-16sourcetermissignificantenoughthatitneedsbe consideredforthisequipment).Finally,itisuncleariftheChapter12shieldingandzoning calculationsortheequipmentqualificationdosesprovidedinSDATable3C-6,"Normal OperatingEnvironmentalConditions,"considerN-16inthecoolant,asappropriate.

Informationneeded: AdditionalclarificationisneededregardingtheN-16reactorcoolant concentrations,includingthetransittimeofcoolantfromthecoreexittotheentranceofthe CVCSletdownlineandatwhichpointintheCVCSletdownlineTable12.2-4isreferring.Also, additionalinformationisneededregardingtheN-16concentrationsinCVCScomponentsandat differentlocationsintheCVCSline.Inordertofacilitatethisreviewpleaseprovidecalculation packagesrelevanttotheN-16sourceterminthereactorcoolantsystemandCVCS.

Response

Thereactorcoolantsystem(RCS)N-16concentrationatthecoreexitis200µCi/g(SDA Table12.2-4).PrimarycoolantenterstheRCSdischargelineinthedowncomerregion, travelsupwardsoutsideofcontainment,exitsthemodulebaythroughthepoolwall penetrationandintotheverticalCVCSpipechaseintheRXBgalleryonEL100-0.This locationisdescribedastheCVCSletdownlineinTable12.2-4,((2(a)(c),ECI,resultinginanRCSN-16concentrationof2.4µCi/g. ((

}}2(a)(c),ECITheCVCSletdownlinepipingwithin theverticalpipechaseisevaluatedusingthe2.4µCi/gN-16concentrationfortheentire length.

PrimarycoolantcontinuesdownwardthroughtheverticalCVCSpipechasetotheCVCS heatexchanger(HX)cubicleonEL55-0.Themodeledtransittimebetweenthe((

}}2(a)(c),ECI,resultingin anRCSN-16concentrationof0.77µCi/g.TheCVCSHXisevaluatedusingthe0.77µCi/g N-16concentrationattheCVCSHXinlet(SDATable12.2-4).TheCVCSletdownlinepiping withintheCVCSrecirculationpumproomsonEL40-0isevaluatedusingthesame0.77
µCi/gN-16concentration

TheLRWSdegasifiervesselsonEL25-0receiveprimaryletdowndischargedfromthe CVCSafterpassingthroughtheCVCSHXs.Thedegasifiervesselsareevaluatedusingthe

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CVCSLetdown-71.3secondsdecay(SDATable12.2-7),whichisbasedonadecayof thesharedsystemsCVCSHXinletsourceterm,withadecay(transit)timeof71.3seconds (tenN-16half-lives)torepresentreductionofN-16downtoinsignificantlevels.

TheN-16concentrationsdescribedaboveareconsistentwiththeshieldinganalysisandthe radiationzonemapsinSection12.3.Thesedoseratessupportthenormaloperationsdose criterialistedinTable3C-6,therefore,N-16wasaccountedforinequipmentqualification.

NuScalehasprovidedthefollowingcalculationsforstaffreviewintheeRRlocation"SDAA Chapter12AuditResponseA-12.2-1."

((

}}2(a)(c),ECI

NuScaleletternumberLO-140025providesthespreadsheetsandassociatedfilesforstaff review.

NochangestotheSDAAarenecessary.

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