During normal plasma operation the erosion of the ”plasma facing components” occurs and the dusts formed tends to deposit onto the divertor surface. In case of an In-vessel LOCA, these dusts may resuspend and transported to the VV Pressure Suppression System.

Define the maximum amount of mobilized dust is an issue of main concern. MELCOR v1.8.6 hasn’t a resuspension model and an attempt to introduce a resuspension model in MELCOR was performed

Gonfiotti, Bruno

Paci, Sandro

English

During normal plasma operation the erosion of the ”plasma facing components” occurs and the dusts formed tends to deposit onto the divertor surface. In case of an In-vessel LOCA, these dusts may resuspend and transported to the VV Pressure Suppression System.
Define the maximum amount of mobilized dust is an issue of main concern. MELCOR v1.8.6 hasn’t a resuspension model and an attempt to introduce a resuspension model in MELCOR was performed

GONFIOTTI, BRUNO

PACI, SANDRO

Archivio della Ricerca - Università di Pisa

27/03/20171Authors: Bruno Gonfiotti, Sandro PaciUniversity of Pisa – Department of Civil and Industrial EngineeringEmail: bruno.gonfiotti@for.unipi.it9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 An attempt to introduce a resuspension model in MELCOR 1.8.6 for fusion applications9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Content of the presentationIntroduction – The problem;Selection of a resuspension model;The “ECART model”;Implementation in MELCOR - Limitations;Validation;Conclusions & Future perspectives.27/03/201729th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Introduction – The problem During normal plasma operation the erosion of the ”plasma facing components” occurs; The dusts formed tend to deposit onto the divertor surface; In case of an In-vessel LOCA, these dusts may resuspend; Resuspended dusts may be transported to the VV Pressure Suppression System (VVPSS); Define the maximum amount of mobilized dustis an issue of main concern; MELCOR v1.8.6 for fusion applications hasn’t a resuspension model; In MELCOR v2.2 for LWRs a resuspension is implemented (Force Balance Model); An attempt to introduce a resuspension model in MELCOR was performed.VacuumVessel (VV)BlanketDivertorPLASMA9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Introduction – The problem During normal plasma operation the erosion of the ”plasma facing components” occurs; The dusts formed tend to deposit onto the divertor surface; In case of an In-vessel LOCA, these dusts may resuspend; Resuspended dusts may be transported to the VV Pressure Suppression System (VVPSS); Define the maximum amount of mobilized dustis an issue of main concern; MELCOR v1.8.6 for fusion applications hasn’t a resuspension model; In MELCOR v2.2 for LWRs a resuspension is implemented (Force Balance Model); An attempt to introduce a resuspension model in MELCOR was performed.VacuumVessel (VV)BlanketDivertorIn-vessel LOCAVVPSS27/03/201739th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Selection of a resuspension modelDifferent models are available in literature, but they can be all subdivided intoTWO CATEGORIESFORCE BALANCEmodelsENERGY TRANSFER modelsThe particles resuspend if the aerodynamic forces exceed the adhesion forcesThe particles resuspend if enough rotational energy is transferred by the fluid motionECART modelMELCOR V2.2 modelASTEC modelRock & Roll model and derivatesReeks, Reed & Hall model9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 The “ECART model” Why the ECART model? It is simple; It was already validated for fusion applications. How it works?27/03/201749th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 The “ECART model”P1P2Fg FaFcAdhesive forces (Fad)Fg GravitationalFc Cohesive (intermolecular attraction)Fa Friction adhesive (sliding and rolling resistance)9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 The “ECART model”ṁP1Adhesive forces (Fad)Fg GravitationalFc Cohesive (intermolecular attraction)Fa Friction adhesive (sliding and rolling resistance)Turbulent burstFdFbAerodynamic forces (Fae)Fd Drag (shear stress on wall)Fc Burst (breaking of laminar sub-layer)Laminarsub-layer27/03/201759th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 The “ECART model”Adhesive forces (Fad) Aerodynamic forces (Fae)Resuspension occurs when:<1.E-061.E-051.E-041.E-031.E-021.E-011.E+001.E-08 1.E-06 1.E-04 1.E-02 1.E+00Resuspension Rate [1/s]Resulting force [µ N]STORMARTPARESS T10y=0.4037F(r)0.6003y=90.28F(r)1.269λ=0.4037∙F(r)0.6003λ=90.28∙F(r)1.269ΔF(r)> 3.065e-4  µNΔF(r)< 3.065e-4  µNIf ΔF(r) = Fae – Fad, the resuspension rate (λ) can be expressed as shown9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Implementation in MELCOR - Limitations The model was implemented through Control Functions (CFs); About 200 CFs are needed for each CV; The model is not identical to the ECART one because correlations needing iterative calculations were substituted with explicit correlations;  The aerosol population is subdivided into only 5 groups; The CFs calculate only the resuspension rate for each group, and the resuspended mass is computed at the end of the calculation through a dedicated Microsoft Excel ® file; The model runs independently from the RN package; Only the total amount of resuspended mass is computed. The fate of the resuspended particles is not tracked.27/03/201769th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 ValidationSeveral tests were selected to be part of the validation matrix. The selection was based on: Tests employed to validate the model implemented in ECART; Tests employed to validate the model implemented in MELCOR v2.2; Tests referring to the peculiar “plant conditions”.STORMARTReeks &HallBraatenSTARDUSTAWTS-IIBISEECARTMELCOR PLANT9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 EC. MEL. PL. N° of tests Tests characteristics Ref.✔ ✔ 5 - Atmospheric pressure- Multi-layer deposit[1] [2] [3] ✔ ✔ 7 - Atmospheric pressure- Multi-layer deposit[1] [4]✔ 7 - Atmospheric pressure- Monolayer deposit[1] [5]✔ 141* - Atmospheric pressure- Monolayer deposit[1] [5]✔ ✔ 41*- Pressure increasing from 1 kPa to 100 kPa- Multi-layer deposit[6] [7]✔ 5- Pressure below atmospheric one (constant)- Multi-layer deposit[8]✔ 30 - Atmospheric pressure- Mono-layer deposit (?)[9]TOTAL 236ValidationSTORMARTReeks &HallBraatenSTARDUSTAWTS-IIBISE* Several tests were executed with the same boundary conditions.27/03/201779th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Validation – STARDUST testsT3T4PiT2 T1FExternal conditioning modulesTePeVacuumPumpTankTrayValve AValve BCompressedair line W, C, or SS particles; Particles deposited on the tray; Air inlet through valve A or B; Two pressurization rates: 0.3 kPa/s and 3 kPa/s; Initial conditions: 1 kPa and 110 °C; Tests end when the atmospheric pressure is reached.9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Validation – STARDUST testsInletPressurization rate [kPa/s]Range of velocities impacting the tray [m/s]Velocitiesinvestigated [m/s]A 0.3 1 – 5 1 – 2.5 – 5A 3 5 – 10 5 – 7.5 – 10B 0.3 50 – 100 50 – 75 – 100B 3 200 – 300 200 – 250 – 300 Simple nodalization; Tank is adiabatic; Range of velocities impacting the tray calculated through CFD calculations; Flow velocity tuned through the hydraulic diameter of the tank.TankInlet CVTrayAAir InletB27/03/201789th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Validation – STARDUST tests Simple nodalization; Tank is adiabatic; Range of velocities impacting the tray calculated through CFD calculations; Flow velocity tuned through the hydraulic diameter.TankInlet CVTrayAAir InletBGroup GMD [m] W mass distribution1 2.15e-7 0.0092 3.22e-7 0.1043 4.30e-7 0.2574 5.37e-7 0.3295 6.45e-7 0.3009th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Validation – STARDUST testsEXPERIMENTAL – MELCOR v1.8.6 – ECART0.010.00780.0020.00460 0 00.00250.E+002.E-034.E-036.E-038.E-031.E-021.E-02EXP. 1 EXP. 2 EXP. 3 EXP.4 5 7.5 10 EC.Resuspended fraction [-]Inlet A – 3 kPa/s27/03/201799th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Validation – STARDUST testsEXPERIMENTAL – MELCOR v1.8.6 – ECART0.010.00780.0020.00460 0 00.00250.E+002.E-034.E-036.E-038.E-031.E-021.E-02EXP. 1 EXP. 2 EXP. 3 EXP.4 5 7.5 10 EC.Resuspended fraction [-]0.1040.0480.0420.030.0260.0520.0780.1070. 20. 40. 60. 80.10.150 5 100 .Resuspended fraction [-]Inlet B – 0.3 kPa/s9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Validation – STARDUST tests1 10.022 0.030 0.0370.914 0.970 0.989 100.10.20.30.40.50.60.70.80.91EXP. 1EXP. 2 200 250 300 200 250 300 EC.Resuspended fraction [-]Inlet B – 3 kPa/s At the end of the tests, large tungsten agglomerates were found; Probably, tungsten agglomerates while rolling onto the tray; Increasing the tungsten size of 10 times improves the MELCOR predictions.EXPERIMENTAL – MELCOR v1.8.6 – MELCOR v.1.8.6 (10 GMD) – ECART27/03/2017109th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Conclusions & Future perspectives An attempt to introduce a resuspension model in MELCOR 1.8.6 for fusion applications was shown; The model was derived from the model implemented in the ECART code; The model was implemented by mean of CFs; Small variations were introduced to avoid iterative calculations; The model was validated against several tests; For the STARDUST tests, the model showed a good agreement with the experimental data if only more than the 5% of initial mass is resuspended; For almost all the other validation tests, the model showed conservative estimations.9th European MELCOR User’s Group (EMUG) – Madrid, 6 - 7 April 2017 Conclusions & Future perspectives Improve the model: Reduce the CFs needed. Some CFs are now employed for diagnostic purposes; Introduce an agglomeration model in function of the “Drag-Burst forces” ratio; Increase the aerosol groups number to 10 (instead of 5); Create CFs for the calculation of the resuspended mass (avoid Microsoft Excel ® file); Coupling with the RN package: Inject the resuspended mass during the time step Δtn as an aerosol source during the time step Δtn+1; If needed, further expand the validation matrix.

An attempt to introduce a resuspension model in MELCOR 1.8.6 for fusion applications

https://arpi.unipi.it/bitstream/11568/849930/1/Gonfiotti%20-%20Resuspension%20model%20%5bPrintable%5d.pdf

An attempt to introduce a resuspension model in MELCOR 1.8.6 for fusion applications

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