ML23137A116

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Draft Slides for Advisory Committee on Reactor Safeguards Subcommittee Meeting Regarding Use of Accident Tolerant Fuel Lead Test Assemblies
ML23137A116
Person / Time
Site: Vogtle  Southern Nuclear icon.png
Issue date: 06/02/2023
From: Markley M
Plant Licensing Branch II
To:
Southern Nuclear Operating Co
Shared Package
ML23137A114 List:
References
EPID L-2022-LLA-0097
Download: ML23137A116 (1)
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Text

NRC Staff Presentation Accident Tolerant Fuel (ATF)

Lead Test Assemblies (LTAs)

Vogtle, Units 1 and 2 June 21, 2023

OPENING REMARKS Joseph Donoghue, Director Division of Safety Systems Office of Nuclear Reactor Regulation

OPENING REMARKS - Continued

  • NRCappreciatestheopportunitytoshare theseproposedchangeswiththeACRS.
  • Memberfeedbackisvaluable.
  • NRCdoesnotrequireanACRSletterreportto proceedbutwouldgreatlybenefitfromone.
  • AnACRSletterreportwouldinformexpected futurebatchloadingrequestsforhigher enrichmentand/orhigherburnup.

3

PRESENTERS

  • LicensingActions
  • Chapter15Accident Analysis,LOCA,&Non LOCA
  • CodeAnalysis,Core Physics,andCladding
  • FuelHandling Storage
  • Conclusion
  • JohnLamb-DORL/NRR
  • CharleyPeabody-SNSB/DSS/NRR
  • BrandonWise-SFNB/DSS/NRR
  • KentWood-SFNB
  • JosephDonoghue, DirectorDSS/NRR 4

LICENSING ACTIONS

  • SNCrequested:

- AmendmentstoLicenseCondition2.DandTSs:(1)

TS3.7.18,FuelAssemblyStorageintheFuel StoragePool,(2)TS4.2.1,FuelAssemblies,and (3)TS4.3,FuelStorage.

- ThreeExemptions

  • 10CFR50.46and10CFRpart50,AppendixKtoallow theuseofcoatedAXIOMcladding,withADOPTfuel pelletsenrichedupto6weightpercentU235.

LICENSING ACTIONS - Continued

  • LoadfourWestinghouseLTAswithadvancedATF features:

- AdvancedDopedPelletTechnology(ADOPT)uranium dioxide(UO2)fuel,

- AXIOMcladding,chromiumcoating,

- fourrodsperLTAwithupto6 weightpercent enrichmentU235.

  • SNCisnotrequestinghigherburnupgreater thanitscurrentlicensingbasisof60,000 MWd/MTU.

6

LTA DESIGN

  • TheLTAsareWestinghouse17x17PRIMEOptimizedFuel Assemblydesignandeachcontain:

- Upto132rodswithWestinghouseADOPTUO2 pelletsat maximumof5weightpercentenrichmentandcoated AXIOMcladding,

- 3rodswithWestinghouseADOPTUO2pelletsatmaximum of6weightpercentenrichmentandcoatedAXIOM

cladding,

- 1rodwithWestinghouseADOPTUO2pelletsatmaximum of6weightpercentenrichmentanduncoatedAXIOM

cladding,

- AllotherrodswillhaveUO2pelletsatmaximumof5 weightpercentenrichment,ZrB2 IFBAcoatedpelletsand coatedAXIOMcladding.

7

UFSAR CHAPTER 15 ACCIDENT ANALYSIS

  • General Accident Analysis, Core Source Term, and Radiological Dose Consequences

- Most accidents, as well as source term, dose consequences, and design transients see negligible changes from placing 16 higher enriched LTA fuel rods into a core of 50,952 active rods.

- Avg enrichment of the core is only increased 0.0003% by 4 LTAs.

- Avg core enrichment remains ~ 4.4 - 4.6%.

8

UFSAR CHAPTER 15 ACCIDENT ANALYSIS - Continued

-This increase in enrichment is not a significant driver of increased source term, dose consequences, or cooling requirements, and is within the bounding assumptions and safety margins of the existing analyses which conservatively assume 5.00% enrichment for establishing source term and dose consequences.

9

LOCA ACCIDENT ANALYSES

  • LOCA&SteamLineBreakMassandEnergyReleases

- Thecontainmentresponsefortheseaccidentsis primarilyimpactedbyRCSinitialpressureand temperatureconditions,aswellasthebreak locationandareaparameters.

- Sincetheseparametersareunchangedbythe LAR,theanalysesofrecordremainboundingfor bothshortandlongtermresponses.

- Downstreamcontainmentandcompartment responsesarealsonotimpacted.

10

LOCA ACCIDENT ANALYSES -

Continued

  • LargeandSmallBreakLOCAAnalyses

-LargeandSmallBreakLOCAEvaluation Model(EM)computercodeswerere evaluatedwithLTAdata.

-BothEMsdemonstratedthat10CFR50.46 acceptancecriteriaforLOCAscontinueto bemetwithoutanycodemodifications.

11

NON-LOCA ACCIDENT ANALYSES Vendor(Westinghouse)evaluatedSteamLineBreaks,Locked Rotor,LossofRCSFlow,andControlRodEjection

  • Noimpacttocomputercodes,methodology,or acceptancecriteria.
  • LTAgeometry,materialproperties,andreactivity feedbackcharacteristicshavenosubstantiveimpacts ontheanalysesandremainwithinexistingmargins.

12

NON-LOCA ACCIDENT ANALYSES - Continued AdditionalconsiderationforControlRod Ejectioneventanalysis

  • Applicationandsupplementsdesignate thatwhileLTAsmaybeplacedincertain limitingcorelocations,theLTAsmayonly beutilizedinsuchlocationswhichare nonlimitingwithrespecttothecontrol rodejectionanalysis.

13

Neutronics

  • SNC uses the PARAGON lattice physics code and NEXUS for neutronics calculations.

- There is no significant deviation in the neutron flux spectrum.

Therefore, there is reasonable assurance that these codes will adequately model the LTAs.

  • PARAGON and NEXUS have been compared to the PARAGON2 code, which has been shown to be acceptable at enrichments greater than 5 wt% U-235.

- PARAGON2 has been shown to be acceptable to analyze the neutronic performance of new, unapproved fuel designs,

  • No proposed changes to the nuclear design process.

14

CORE PHYSICS

  • Fluxspectrumwillcontinuetobedominatedbycoresident fuel.
  • Peakingfactorsremainlessthanwhatisassumedinthe UFSAR.
  • DifferencesbetweenLTAsandcoresidentfuelaremodeled explicitly.
  • NeutronicimpactoftheLTAsareconfinedtotheLTAs 15

THERMAL HYDRAULICS

  • ThecodesandmethodsusedbySNCforthermalhydraulic analysesaremostlyunaffectedbytheLTAs.
  • Nochangestoanythermalhydraulicrelatedacceptance criteriaareproposedandthereisnoexpectedlossofmargin.
  • Coatedcladdingismodeledasanincreaseintheouter diameteroftheAXIOMcladding.Thisresultsinanegligible reductioninflowareaduetothethincoatingthickness.

16

AXIOM CLADDING

  • WCAP18456P/NPapprovedDecember16, 2022
  • AXIOMcladdingrequiresanexemptionfrom theapplicabilityrequirementsof10CFR50.46 andAppendixK.

17

AXIOM CLADDING - Continued

  • AXIOMcladdingisazirconiumalloywhichhasdemonstrated betterinreactorperformancecomparedtotheOptimized ZIRLOalloy.

- TheNRCstaffexpectsAXIOMcladdingtoperformatleast aswellasOptimizedZIRLOcladding,whichisusedinthe coresidentfuel.

  • TheNRCstaffdeterminedthattheuseofAXIOMcladdingin theseLTAsisacceptablebecausethereisnoexpectedlossof safetymarginorreductioninacceptancecriteria.

18

CHROMIUM COATING

  • Mostfuelrodswillhaveathinchromium coatingforincreasedcorrosion resistance.

-SNCdoesnotcreditthechromium coatinginitsanalyses.

19

CHROMIUM COATING - Continued

  • Thereisnoexpectedlossofsafetymarginassociated withthechromiumcoating.

- ATFISG202001statesthereducedcladding emissivityisapotentialadverseeffectofa chromiumcoatedrodthatcouldincreasePCT.

- SNCsanalysesindicatethatduringLOCA conditionsthedifferenceinemissivitybetween coatedanduncoatedcladdinghaslittleeffecton PCT.

20

HIGHER ENRICHMENT

  • FourrodsineachLTAwillbeenrichedtoa maximumof6weightpercentU235.
  • Mostcodesandmethodswherefuel enrichmentisasignificantparameterhave eitherbeenapprovedforuseorcontaindata andmodelsforenrichmentsgreaterthan5 weightpercentU235.
  • TheneutronicimpactoftheLTAsisexpected tobesmallandconfinedtotheLTA.

21

ADOPT FUEL PELLETS

  • WCAP18482P/NPapprovedJune13, 2022

-LicenseesmustdemonstratethatCRE models,methods,andacceptance criteriaareapplicabletofueldesigns containingADOPTfuelpellets 22

ADOPT FUEL PELLETS - Continued

  • ADOPTfuelpelletscontainsmallamountsofchromia andaluminaandhavehigherdensitythanstandard UO2 pellets.

- ADOPTfuelpelletshaveagreaterquantityof fissilematerialandmaybemoresensitiveto reactivityinitiatedaccidents,suchasarod ejectionaccident(REA).

- SNChasstatedthattheLTAswillnotbeplacedin positionsthatlimitingwithrespecttoREAs.

23

FUEL HANDLING & STORAGE

  • SNCneedsanexemptionto10CFR50.68 Paragraph(b)(7)forthefuelrods enrichedaboveamaximumof5.0 weightpercentU235
  • EachLTAislimitedtofourrodsata maximumof6.0weightpercentU235.

24

FUEL HANDLING & STORAGE-Continued

  • Thosefourrodsadd0.015%moreU235to thefuelassembliesrelativetotheVogtleNew FuelStorageRack(NFSR)analysisofrecord (AOR)andVogtleSpentFuelPool(SFP)AOR maximumenrichmentof5.0weightpercent U235.
  • ThatislessthanathirdoftheU235 enrichmentmanufacturinguncertaintyof 0.05%

25

FUEL HANDLING & STORAGE -

Continued

  • HigherTheoreticalDensity(TD)intheADOPTpellets addsmoreU235tothefuelassembliesthanthe fourfuelrodsenrichedtoamaximumof6wt/%.

- VogtleNFSRAORused96%TD.

- VogtleSFPAORused97.5%TD.

- ADOPTTDof98.3%islimitedto136rodsperLTA.

(half)

- IncreasedTDadds1.185%moreU235toLTAs relativetoNFSRAORand0.412%moreU235 toLTAsrelativetoSFPAOR.

26

FUEL HANDLING & STORAGE -

Continued

  • ThetotalincreaseinU235fortheVogtle NFSRandSFPrelativetotheAORsis 1.2%and0.427%respectively.

-TherelativeincreaseinU235content isdeterminedtoaidinevaluatingthe potentialimpactonreactivityinthe NFSRandSFP.

27

FUEL HANDLING & STORAGE -

Continued

  • NewFuelStorageRacks

- ExemptioncreditstheIFBAintheLTAswhereas theVogtleNFSRAORdoesnot.

- SNCestimatedtheLTAs128IFBArodsat1.5x Boron10loadingprovidesubstantialreactivity holddownrelativetoitscurrentAORfortheNFSR

  • 0.12keffforfullyflooded
  • 0.10keffforoptimummoderation 28

FUEL HANDLING & STORAGE -

Continued

  • NewFuelStorageRacks Continued

-NRCstaffreviewedtheestimatesand believesthesubstantialreactivity marginprovidedbytheIFBAprovides reasonableassurance10CFR50.68 Paragraphs(b)(2)[NFSRfullyflooded]

and(b)(3)[NFSRoptimummoderation]

willbemet.

29

FUEL HANDLING & STORAGE -

Continued

  • SpentFuelPoolStorageRacks

-ExemptionlimitsSFPstoragetotwoUnit2 storageconfigurations

-Thetwooutoffour(2oo4)configuration,

  • arepeating2x2arrayofalternatingfresh unburnedandunpoisonedfuel assemblieswithemptystoragecells,and 30

FUEL HANDLING & STORAGE -

Continued

  • SpentFuelPoolStorageRacks Continued

- allcell(4oo4)configuration,

  • arepeating2x2arraywitheachstoragecell filledwithafuelassemblymeetingthe specifiedburnup/enrichmentrequirements

- NostorageinanyotherUnit2storage configurationisallowed.

- NostorageinUnit1SFPisallowed.

31

FUEL HANDLING & STORAGE -

Continued

  • Twooutoffour(2oo4)configuration

-ExemptioncreditstheIFBAinthe LTAswhereastheVogtleSFPAOR doesnot.

  • SimilartoNFSR 32

FUEL HANDLING & STORAGE -

Continued

  • Twooutoffour(2oo4)configuration Continued

- SNCestimatedtheLTAs128IFBArodsat1.5xB10 loadingprovidesubstantialreactivityholddown relativetoitscurrentAORfortheSFP

  • 0.15keff

- Thatmarginwilldecreasebutremainsubstantial relativetoafreshunpoisoned fuelassembly.

  • NUREG/CR6760,StudyoftheEffectofIntegral BurnableAbsorbersforPWRBurnupCredit 33

FUEL HANDLING & STORAGE -

Continued

  • Fouroutoffour(4oo4)configuration

-ExemptioncreditsburnupintheLTAs.

  • TheAORburnuprequirementisabout40 GWd/MTUanda64GWd/MTULTAburnup limitprovidesa24GWd/MTUorgreaterthan 8%inkeff marginfortheLTAs.

- Slightlymorethana5weightpercentfuel assemblywouldrequire.

34

FUEL HANDLING & STORAGE -

Continued

  • Fouroutoffour(4oo4)configuration Continued

- SNCsetarequirementfortheLTAstohave64 GWd/MTUofburnup.

- NRCstaffusedVogtlesSFPAORtoestimateafuel assemblywithallfuelrodsat6weightpercent wouldrequire53GWd/MTU.

- SNCsburnuprequirementprovidessubstantial margin.

35

FUEL HANDLING & STORAGE -

Continued

  • SFPAccident

- SNCdeterminedamultiplemissloadingeventthat collocatedtheunburnedLTAswasthelimitingaccident.

  • Multiplemisloadings aretypicallythelimitingaccident.

- SNCestimatedthecollocatedLTAswouldbe<0.95keff withtheTSSolubleBoronrequirementof2000ppm.

  • Thisestimatedidnothavesubstantialmarginto precludeadetailedanalysis.

36

FUEL HANDLING & STORAGE -

Continued

  • SFPAccident Continued

-TheSNCestimatedidnotinclude creditfortheIFBA.

-The twooutoffour(2oo4)evaluation showedtheIFBAprovidessignificant margin.

37

FUEL HANDLING & STORAGE -

Continued

  • SFPConclusion

- SNCexemptionrequestcontainssubstantial marginforthetwooutoffourandfouroutof fourstorageconfigurations.

- WhentheIFBAisconsideredinthemultiple misloadingaccidentthereisconsiderablemargin.

- Therefore,theNRCstaffbelievesthereis reasonableassurancethat10CFR50.68Paragraph (b)(4)willbemet.

38

CONCLUSION

  • TheNRCstaffdeterminedthatthereis reasonableassurancethatthehealthand safetyofthepublicwillnotbeendangeredby allowingSNCtheuseoffourATFLTAsforup totwocyclesoperationinVogtle,Unit2.
  • TheNRCstaffwelcomesanACRSletterreport.

39

ITEMS FOR DISCUSSION AT ACRS FULL COMMITTEE

  • July14-ACRSFullCommitteeMeeting
  • LicensingAction-Amendmentand Exemptionsto10CFR50.68(b)(7),10CFR50.

46,and10CFRPart50,AppendixK

  • Technicalareasofemphasisrequestedby ACRSSubcommitteemembers 40

ACRONYMS

  • ATF-AccidentTolerantFuel
  • LTAs-LeadTestAssemblies
  • NRC-U.S.NuclearRegulatoryCommission
  • ACRS-AdvisoryCommitteeonReactorSafeguards
  • SNC-SouthernNuclearOperatingCompany
  • NRR-OfficeofNuclearReactorRegulation
  • DSS-DivisionofSafetySystems
  • DORL-DivisionofOperatingReactorLicensing
  • SNSB-NuclearSystemsPerformanceBranch
  • SFNB-NuclearMethods&FuelAnalysisBranch 41

ACRONYMS - Continued TS-TechnicalSpecification CFR-CodeofFederalRegulations U235-Uranium235 UO2-UraniumDioxide MWd - MegawattDay MTU-MetricTonUranium ZrB2 - ZirconiumDiboride IFBA-IntegralFuelBurnableAbsorber LOCA-LossofCoolantAccident EM-EvaluationModel RCS-ReactorCoolantSystem DNBR-DeparturefromNucleateBoilingRatio 42

ACRONYMS - Continued

  • PCT-PeakCladdingTemperature
  • REA-RodEjectionAccident
  • TD-TheoreticalDensity
  • NFSR-NewFuelStorageRack
  • SFP-SpentFuelPool
  • AOR-AnalysisofRecord
  • B10- Boron10
  • ppm-PartsPerMillion 43
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