ML19093B817

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RIC 2019 - TH35 Presentation - Overview of Upgrades to Maccs Dispersion Modeling Capabilities
ML19093B817
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Issue date: 02/12/2019
From: Jonathan Barr, Bixler N, Clayton D, Keith Compton
Office of Nuclear Regulatory Research, Sandia
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2/12/2019 1

OverviewofUpgradestoMACCS DispersionModelingCapabilities 2019NRCRegulatoryInformationConference AtmosphericTransportandDispersionModelingforSevere AccidentConsequenceAnalysis K.Compton*,J.Barr*,N.Bixler**,andD.Clayton**

  • U.S.NuclearRegulatoryCommission
    • SandiaNationalLaboratories

2/12/2019 2

Outline

- SevereaccidentconsequenceanalysiswiththeMELCOR AccidentConsequenceCodeSystem(MACCS)

- OverviewofcurrentMACCSatmospherictransportand dispersion(ATD)modelcapabilities

- Ongoingdispersionmodelenhancements

- Potentialnearfielddispersionmodelenhancements 2

2/12/2019 3

OverviewofSevereAccidentConsequenceAnalysis 3

Typicallyincludesmodelingtheradioactivereleasetotheatmosphere Analysestypicallyestimatethedosesandhealtheffectsfrominhalation, cloudshine,groundshine,skindeposition,andingestion(e.g.,water,milk, meat,crops),aswellascostsandotherimpactsassociatedwithprotective actionstoreduceexposure

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ConsiderationsforSevereAccidentAssessments

  • Severeaccidentprobabilisticconsequenceassessments

- Realisticassessment

- Prospectiveanalysis

- Multiplefiguresofmerit

- Widetemporalandspatialscales

  • Computationalefficiencyneededformodelingmultiple possibleprospectiveweatherconditions
  • TraditionalATDapproachforprobabilisticconsequence analysisistouseaGaussianplumesegmentmodel 4

2/12/2019 5

MACCSModules ATMOS

- Sourcetermdefinition

- Weathersamplingalgorithms

- Atmospherictransport,dispersion,anddeposition EARLY(1to40days)

- Dosesasmodifiedbyemergencyphasecountermeasuressuchas sheltering,evacuation,relocation,andpotassiumiodideingestion

- Allowsmodelingofmultiplepopulationcohorts

- Acuteandlatenthealtheffectsfromearlyacuteexposure CHRONC(1weekto>50years)

- Dosesasmodifiedbyintermediateandrecoveryphaseprotectiveactions suchasrelocation,temporaryandpermanentinterdiction,and decontamination

- Latenthealtheffectsfromchronicexposuretodepositedmaterial

- Economicimpactfromearlyandlatephaseprotectiveactions 5

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ATMOS:MeteorologicalData

  • MACCSATMOSGaussianplumesegmentmodeltypically readsdatafromafilecontaining1yearsworthofobserved hourlymeteorologicaldata(8,760observations)

- Windspeed(at10meters)

- Winddirection(sectorintowhichwindisblowing)

- Stabilityclass(typicallybasedonlapserate)

- Accumulatedprecipitation

  • Eachplumesegmentusesupto1,000hoursofmeteorological datafrommeteorologicalfile
  • Upto500plumesegmentscanbedefined
  • Typicalpracticeistosampleapproximately1,000different accidentinitiationtimesfromthe8,760potentialhourlystart times 6

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ATMOS ATDModelPlumeDispersion StraightlineGaussianplumesegmentmodel Userspecifiedplumedispersionparameterization

- Distancebasedpowerlawformulation

- Distancebasedlookuptables:allowformulationsthatdonotfitasimple powerlaw(e.g.,BriggsorEimutisandKonicekformulations)

Horizontalandverticalscalingfactors(YSCALEandZSCALE)

- ZSCALEtypicallyusedtoaccountforsurfaceroughnesseffectsonvertical dispersion Longrangedispersion:timebasedplumegrowthmodel 7

y a

x b

=

z c

x d

=

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ATMOS GaussianPlumeModelModifications 8

Virtualsourcemodel

- Accountsforbuildingwakeeffectsand timevaryingmeteorologicalconditions

- Usercanspecifyinitialplumedimensionsto simulateinitialdispersionfromwakeeffects PlumeMeander

- Userselectablemodelappliescorrectionsto transversedispersioncoefficients

- Originalmodel(accountsforsamplingtime)

- AlternativemodelbasedonNUREG/CR2260 (accountsforwindspeedandstability)

MACCSalsoincludesmodificationstoaccountforplumerise,wetdeposition, anddrydeposition

2/12/2019 9

ATMOS(GaussianPlumeSegment):AirConcentration Illustrationshowinghow plumesegmentsmovewith windshiftingfromnorthwest tonortheast Eachsegmenthasitsown widthdependingonthe amountofdispersionthathas occurredasitexperiences varyingweatherconditions Eachsegmenthasaunique lengthdependingonwind speed Wetanddrydeposition(not shown)resultsinplume depletionandbuildupof groundconcentration 9

2/12/2019 10 AccuracyofMACCS Probabilisticconsequenceanalysisapplicationsgenerallyrequire thegenerationofthestatisticaldistributionofconsequencevalues overannualweatherdata(i.e.,weatheraveragedcalculations)

ATDmodelfidelityforprobabilisticconsequenceanalysisis traditionallyconsideredlesssignificantthanforemergency responsetoolsbecauseofthestatisticalnatureofprobabilistic consequenceanalyses However,questionsabouttheadequacyoftheGaussianplume modelforprobabilisticconsequenceanalyseshavebeenraised sinceatleastthe1980s Apreviousstudy(NUREG/CR6853)showedthatMACCSis generallywithinafactoroftwooftheNationalAtmospheric ReleaseAdvisoryCentersLagrangianOperationalDispersion Integrator(LODI)codeforweatheraveragedcalculations 10

2/12/2019 11 EvaluationAttributesforPotentialAlternativeATDCodes

  • Essentialfeatures

- TreatsLagrangianparticles

- Codeexecutablefilescanbedistributedtousers(eitherbySandia NationalLaboratoriesordirectlyfromthedeveloper)

- Sourcecodeavailableincasemodificationsarerequiredfor integration

- Codehasadequatequalityassurance(QA)

- Treatsthreedimensional(3D)windfield(griddeddata)

  • Desirablefeatures

- Canmodelbothpuffsandparticles

- Supportsavarietyofgriddedweatherdataformats

- Facilitatesgraphicalpostprocessing 11

2/12/2019 12 FeaturesofPotentialAlternativeATDCodes 12 HYSPLIT FLEXPART LODI CALPUFF RASCAL SCIPUFF Dispersion Lagrangian/

Gaussian Lagrangian Lagrangian/

Gaussian Gaussian Gaussian Gaussian Developer/

Primary Customers NOAA&Aus.

BureauofMet./

NASA, Universities, NorwegianInst.

forAirResearch/

Europe LLNL/

DOE TRC/

EPA PNNL/

NRC Titan/

DTRA, U.S.Army Weather Data Anygriddeddata WRF, MM5 WRF,ADAPT
CALMET, MM5,etc.

Surfacedata Surfaceor griddeddata Surface Roughness Userinputatany resolution,or 1degree Userinputatany resolution Userinputat any resolution Userinputat any resolution Userinputat any resolution Unknown Availability/

SourceCode NOAA/Yes NorwegianInst.

forAirResearch/

Europe/Yes Onlyvia Web/No TRC/No NRC/Yes Titan/No QA/Verifica tionand Validation Yes,open literature Openliterature Yes,open literature Yes Yes Yes Platforms Unix/Linux, PC,Mac Unix/Linux,PC Unix/Linux PC PC PC Graphics Yes Userplotsoutput Yes Yes Yes Yes Computer Time Canbehigh/

needsmultiple processors Canbehigh/

needsmultiple processors Canbehigh/

needs multiple processors Canbe high Moderate Canbehigh

2/12/2019 13 SelectedAlternativeATDCode:HYSPLIT SelectedforintegrationintoMACCSasamodernalternativetothe Gaussianplumesegmentmodel DevelopedandmaintainedbytheNationalOceanicandAtmospheric Administration(NOAA)AirResourcesLaboratory Cancomputetrajectoriesaswellascomplextransport,dispersion, chemicaltransformation,anddeposition Acceptsawidevarietyofpubliclyavailablegriddedmeteorologicaldata, includingbothNorthAmericanandglobaldatasets Modelsdispersionusingeitherpuffsorparticles:

[P]uffsexpanduntiltheyexceedthesizeofthemeteorologicalgridcell(either horizontallyorvertically)andthensplitintoseveralnewpuffs,eachwithitsshareofthe pollutantmass.*

[A]fixednumberofparticlesareadvectedaboutthemodeldomainbythemeanwind fieldandspreadbyaturbulentcomponent.*

13

2/12/2019 14 PotentialMACCSEnhancementsforNonLightWater Reactors(NonLWRs)

  • Evaluatingpotentialcodedevelopmentneedsfor designspecificissues

- Radionuclidescreening

- Radionuclidechemicalform

- Aerosolsize

- Aerosolshapefactor

- Radionuclideswithcomplextransportcharacteristics(e.g.,tritium)

  • Evaluatingpotentialcodedevelopmentneedsforsiterelated issues

- Nearfieldatmospherictransport

- Decontaminationmodeling 14

2/12/2019 15 NearFieldAtmosphericTransport MACCScurrentlyhasasimplevirtualsourcemodelforbuildingwake effects;itsuserguide(NUREG/CR6613)cautionsagainstusecloserthan 500meters LicenseesfornonLWRs(andsmallmodularreactors)desireasmaller emergencyplanningzoneandsiteboundarythanforlargeLWRs; therefore,bettermodelingofnearfieldphenomenamaybebeneficial 15 Schulman,L.L.,D.G.Strimaitis,andJ.S.Scire(2000).DevelopmentandEvaluationofthePRIMEPlumeRiseand BuildingDownwashModel,JournaloftheAir&WasteManagementAssociation,50:3,378-390 Windtunnelsimulationofstreamlinesnearacubicbuilding

2/12/2019 16 NearFieldAtmosphericTransport Variousoptionsforaddressing nearfieldATD

- ModificationstoGaussianplumesegment ATDmodel

- LagrangianparticletrackingATDusing simplified3Dwindfieldmodels

- LagrangianparticletrackingATDusingCFD modelingof3Dwindfield Considerationsforevaluatingoptions

- Extentofpracticalacceptanceintheuser community

- Simplicityofuse

- Computationalefficiency

- Costandtimeefficiency

- Accuracy

- Feasibilityforprobabilisticapplication 16 ExampleQUICURBsimulationofwind vectors ExampleQUICPLUMEsimulationofurban transportanddispersion QUICFactsheet,LosAlamosNationalLaboratory

2/12/2019 17 Summary

  • ThecurrentversionofMACCSisanefficientandhighly flexibleprobabilisticconsequenceanalysistoolwithmany userconfigurableoptions
  • Codeenhancementsarenearingcompletiontointroduce resultscomputedbyHYSPLITintoMACCS
  • Examiningtheapplicabilityofcurrentandpotential approachesformodelingnearfielddispersionphenomena wherebuildingwakesmaybeimportant 17

2/12/2019 18 ACRONYMSANDREFERENCES Acronyms ATD:AtmosphericTransportandDispersion FLEXPART:FLEXiblePARTicleDispersionModel HYSPLIT:HybridSingleParticleLagrangianIntegratedTrajectoryModel LODI:LagrangianOperationalDispersionIntegrator MACCS:MELCORAccidentConsequenceCodeSystem NOAA:NationalOceanicandAtmosphericAdministration QUIC:QuickUrban&IndustrialComplexDispersionModelingSystem References Chanin,D.,andM.L.Young(1998).CodeManualforMACCS2:Volume1,UsersGuide (NUREG/CR6613),SandiaNationalLaboratories,Albuquerque,NM,May1998 Molenkamp,C.R.,N.E.Bixler,C.W.Morrow,J.V.Ramsdell,Jr.,andJ.A.Mitchell(2004).Comparisonof AverageTransportandDispersionAmongaGaussian,aTwoDimensional,andaThreeDimensional Model(NUREG/CR6853),LawrenceLivermoreNationalLaboratory,Livermore,CA,October2004 Schulman,L.L.,D.G.Strimaitis,andJ.S.Scire(2000).DevelopmentandEvaluationofthePRIMEPlume RiseandBuildingDownwashModel,JournaloftheAir&WasteManagementAssociation,50:3,378-390 Snell,W.G.,andR.W.Jubach(1981).TechnicalBasisforRegulatoryGuide1.145,AtmosphericDispersion ModelsforPotentialAccidentConsequenceAssessmentsatNuclearPowerPlants(NUREG/CR2260),

NUSCorporation,Rockville,MD,October1981 18

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