General information
Description of the reference case 
Development of the SA code and ut coupling and status 
Description of the input uncertainty parameters and the uncertainty methodology
Development of uncertainty analysis - first results 
Issues to be reported
Conclusion

Michela Angelucci

Sandro Paci

English

Archivio della Ricerca - Università di Pisa

06/04/2021MUSA has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 847441.MUSA – WP4 SecondIntermediate Reporting09/04/2021Michela Angelucci, Sandro Paci University of PisaCONTENTGENERAL INFORMATIONDESCRIPTION OF THE REFERENCE CASEDEVELOPMENT OF THE SA CODE AND UT COUPLING ANDSTATUSDESCRIPTION OF THE INPUT UNCERTAINTY PARAMETERSAND OF THE UNCERTAINTY METHODOLOGYDEVELOPMENT OF UNCERTAINTY ANALYSIS - FIRST RESULTSISSUES TO BE REPORTEDCONCLUSIONS21206/04/2021GENERAL INFORMATIONoOrganization: University of Pisa oContact person(s)/author(s): Sandro Paci, Michela AngeluccioSevere accident code and version: MELCOR 2.2 v. 18019oUncertainty Tool and version: Dakota through SNAP env.o Computing environment (hardware):oOperative systems: Windows 10 Pro / Windows Server 2019 DatacenteroRAM: 16 GB / 64 GBoCPU characteristics: i9-10885H CPU / Xeon Gold 52183DESCRIPTION OF THE REFERENCE CASEDescription of the reference caseo SNL Nodalization with few changes:o Core power – MUSA spec.o Tmelt (UO2-INT and ZRO2-INT)o COR_CR activatedo Deposition Surfaces in containmento RN1 Default v2.*o MACCS featuresReference: mainly “MELCOR Best Practices as Applied in the State-of-the-Art Reactor Consequence Analyses (SOARCA) Project”43406/04/2021DESCRIPTION OF THE REFERENCE CASE5e.g. PARAMETER1 Release of iodine from top of the bundle [% of i.i.]2 Release of Caesium from top of the bundle [% of i.i.]3 Caesium retention in the circuit [% of Cs released from the core]4 Aerosol amount in the containment’s atmosphere [g]5 Total gaseous iodine amount in the containment’s atmosphere [g]6 Total iodine aerosols amount in the containment’s atmosphere [g]7 Total deposited/adsorbed iodine amount in the containment [g]Table : List of FOMs selected by the Partner for the WP4 FPT1 exerciseFigures: Plot of the FOMs01020304050607080901000 10000 20000 30000% i.i.Time (s)Iodine ReleaseEXPMELCOR01020304050607080901000 10000 20000 30000% i.i.Time (s)Cesium ReleaseEXPMELCOR00.10.20.30.40.50.60.70 10000 20000 30000Cs Fractional RetentionTime (s)Cesium RetentionMELCOREXP0102030405060700 10000 20000 30000 40000Aerosol amount (g)Time (s)Aerosol in containmentEXPMELCORDEVELOPMENT OF THE SA CODE AND UT COUPLING (AND STATUS)As underlined in ENEA presentation, currently the “replacement samples” option is not available whenusing the SNAP/GUI. Therefore, if one calculation fails, it prevents Uncertainty Analysis finalization:o New Python Directed job-stream feature has been added in SNAP MELCOR and DAKOTA coupling through SNAP:PYTHON DIRECTED STREAM6Figure: Sketch of the severe accident code and uncertainty tool calculation schemeMELGENMELCORDakota – VariatesFOMsDakota –Analysis & ReportAPTPLOTPlot –FOM vs time5606/04/2021DEVELOPMENT OF THE SA CODE AND UT COUPLING (AND STATUS)7Figure: Sketch of the severe accident code and uncertainty tool calculation schemeDESCRIPTION OF INPUT UNCERTAINTY PARAMETERS AND UNCERTAINTY METHODOLOGY8Reference values Range of Variation PDF Type Note*1CHI –Aerosol dynamic shape factor1.0 Min=1.0  Max=5.0 Beta *As from WP22GAMMA –Aerosol agglomeration shape factor1.0 Min=1.0  Max=5.0 Beta *As from WP23FSLIP –Particle slip coefficient1.257 Min=1.2  Max=1.3 Beta *As from WP24STICK –Particle sticking coefficient1.0 Min=0.5  Max=1.0 Beta *As from WP25TURBDS –Turbulence dissipation rate0.001 Min=0.00075  Max=0.00125 Uniform *As from WP26TKGOP –Ratio of the thermal conductivity of the gas overthat for the particle0.05 Min=0.006  Max=0.06 Log-uniform *As from WP27FTHERM –Thermal accommodation coefficient2.25 Min=2.0  Max=2.5 Uniform *As from WP28DELDIF –Diffusion boundary layer thickness1.0e-5 Min=0.000005  Max=0.0002 Uniform *As from WP2Table: Partner input uncertainty parameters and PDF7806/04/20219Partner ChoiceUncertainty Methodology used probabilistic method to propagate input uncertaintyMethod used to define the required numberof samplesWilks formulaSampling method Monte Carlo SamplingProbability and confidence level selected 95%, 95%Statistical analysis of the FOMsmin value, max value, mean, median standard deviation,cumulative distribution function (CDF), probability densityfunction (PDF)Sensitivity coefficients to characterize thecorrelation between the input uncertaintyparameters and the FOMPearson, SpearmanTable : Partner uncertainty methodology (brief description in a tabular form)DESCRIPTION OF INPUT UNCERTAINTY PARAMETERS AND UNCERTAINTY METHODOLOGYDEVELOPMENT OF UNCERTAINTY ANALYSIS - FIRST RESULTS10Figure: Aerosol amount in the containment (g)First results91006/04/2021ISSUES TO BE REPORTEDoSNAP (Dakota Uncertainty Plugin - GUI):Problems in handling failed MELCOR calculations ExtractionData & Uncertainty steps failoSNAP (Python Directed Stream):o script phase seems not user friendlyo “replacement samples” option: additional samplings created, but failed calculations not re-runo stream manager failures when adding jobs to the streamo “generate_report” failsoNo problems when running MELCOR/SNAP/DAKOTA in our 32-corevirtual machine11CONCLUSIONSStatus of the activity:o Input Deck check & improvement: DONEo Reference case: DONEo SA/UT coupling: IN PROGRESSo First UA: IN PROGRESSDelay if any:o Currently no delay related to COVIDChallenges:o Coupling phase not straight-forwardo Choice of Parameters: few data available – human errorAdditional remarks:o Need of clarifications on the implementation of “replacement samples” in the SNAPenvironment121112

MUSA WP4 Second Intermediate Reporting

https://arpi.unipi.it/bitstream/11568/1097986/1/MUSA_PPT_WP4_INTERMEDIATE%20REPORTING_UNIPI_April2021.pdf

MUSA WP4 Second Intermediate Reporting

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