CFD calculations of the coolant mixing in Pressurised Water Reactors
Numerical investigations on coolant mixing in Pressurised Water Reactors (PWR) have been performed at the HZDR for almost a decade. The work was aimed at describing the mixing phenomena relevant for both safety analysis, particularly in steam line break and boron dilution scenarios, and mixing phenomena of interest for economical operation and the structural integrity.
With the set-up of the ROCOM test facility, a unique data base has been created to be used for the validation of Computational Fluid Dynamics (CFD) codes for the application to turbulent mixing in nuclear reactors. Benchmark problems based on selected experiments were used to study the effect of different turbulent mixing models under various flow conditions, to investigate the influence of the geometry, the boundary conditions, the grid and the time step in the CFD analyses. In doing the calculations the Best Practice Guidelines for nuclear reactor safety calculations have been followed.
A selection of the performed work:
- stationary and transient flow and mixing studies of the coolant in the PWR Konvoi and the ROCOM test facility with CFX-4 and CFX-5 during
- boron dilution transients (start-up of the first coolant pump)
- main steam line break scenarios
- density driven flows after an inherent dilution with ECC injection (generic experiments at the ROCOM test facility)
- participation in the ISP-43 CFX-4, (Figure 1)
- participation in the OECD benchmark on VVER-1000 reactors, (Figure 2)
- flow and mixing studies in the VVER-440 and VVER-1000 type reactors (Figure 3)
- post test calculation of pump start-up experiments at the Gidropress VVER-1000 reactor mock-up
- TRIO_U validation on a ROCOM experiment using a LES approach
Results of the ROCOM CFD- Analysis
The CFD calculations were carried out with the CFD-codes CFX-4 and CFX-5 on the Rossendorf 100-processor RedHat LINUX cluster (dual CPU compute nodes XEON, 3.2 GHz, ~1.3 Gflops, each containing 2 GBytes RAM).
Using the block-structured code CFX-4 internals were modelled using the porous media approach and additional body forces. Sensitivity studies showed, that the k-ε turbulence model together with the higher order HYBRID discretization scheme give the best results.
Within CFX-5 it was possible, to model all internals of the RPV of ROCOM in detail. A production mesh with 7 Million elements was generated (Figure 4). Detailed and extensive grid studies were made. It was shown, that a detailed model of the perforated drum in CFX-5 give the best agreement with the experiments. Sensitivity studies showed, that the SST turbulence model and the automatic wall functions together with higher order discretization schemes should be used if possible.
In the case of stationary mixing, the maximum value of the averaged mixing scalar at the core inlet was found in the sector below the inlet nozzle, where the tracer was injected (Figures 7-10). There is a good agreement between the measurement and the CFD calculations, especially in the averaged global mixing scalar at the core inlet (Figure 7). At the local position of the maximum mixing scalar the time course of the measurement and the calculations is also in good agreement (Figure 8).
At the start-up case of one pump due to a strong impulse driven flow at the inlet nozzle the horizontal part of the flow dominates in the downcomer (Figures 5 and 6). The injection is distributed into two main jets, the maximum of the tracer concentration at the core inlet appears at the opposite part of the loop where the tracer was injected.
|Figure 1 Babcock 2x4loop||Figure 2 WWER-1000|
|Figure 3 WWER-440||Fig. 4 Detailed hybrid grid model CFX-5 (ROCOM)|
|Fig. 5 CFD-results of the start-up of the first pump after 9s||Fig. 6 Start-up of the first pump streamlines representing the flow field|
|Fig. 7 Time dependent averaged mixing scalar at the core inlet||Fig. 8 Time dependent local mixing scalar at the core inlet, near wall position|
|Fig. 9 Mixing scalar at azimuthal positions of the core inlet near the wall, (t=10.0 s)||Fig. 10 Plateau averaged mixing scalar at the core inlet|
Stieglitz, R.; Mull, T.; Höhne, T.; Rieger, U.; Buettner, K.
Section Reports: 2012 Annual Meeting on Nuclear Technology - Part 5
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Numerical simulation of the insulation material transport in a PWR core under loss of coolant conditions
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Höhne, T.; Kliem, S.; Rohde, U.
Buoyancy driven mixing studies of natural circulation flows using ROCOM experiments and CFD
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Höhne, T.; Schaffrath, A.
Fachsitzung: „CFD-Methoden für sicherheitsrelevante Fragestellungen“
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Loginov, M. S.; Komen, E.; Höhne, T.
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Moretti, F.; Melideo, D.; Del Nevo, A.; D’Auria, F.; Höhne, T.; Lisenkov, E.; Bucalossi, A.; Gallori, D.
Experimental investigation of in-vessel mixing phenomena in a VVER-1000 scaled test facility during unsteady asymmetric transients
Nuclear Engineering and Design 241(2011)8, 3068-3075
Anwendung von CFD-Methoden für den Kern sowie den Primärkreislauf von LWR
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Da Silva, M. J.; Thiele, S.; Höhne, T.; Vaibar, R.; Hampel, U.
Experimental studies and CFD calculations for buoyancy driven mixing phenomena
Nuclear Engineering and Design 240(2010)9, 2185-2193
CFD-simulation of the VVER thermal hydraulic benchmark V1000CT2 using ANSYS CFX
Science and Technology of Nuclear Installations 2009(2009), Article ID 835162
Moretti, F.; Melideo, D.; Del Nevo, A.; DAuria, F.; Höhne, T.; Lisenkov, E.
CFD validation against slug mixing experiment
Science and Technology of Nuclear Installations (2009), Article ID 436218
Kliem, S.; Höhne, T.; Rohde, U.; Weiß, F.-P.
Experiments on slug mixing under natural circulation conditions at the ROCOM test facility using high resolution measurement technique and numerical modeling
Nuclear Engineering and Design 240(2010)9, 2271-2280
Rohde, U.; Höhne, T.; Krepper, E.; Kliem, S.
Application of CFD codes in nuclear reactor safety analysis
Science and Technology of Nuclear Installations 2010(2010), Article ID 198758
Höhne, T.; Kliem, S.; Vaibar, R.
Experimental and numerical modeling of transition matrix from momentum to buoyancy-driven flow in a pressurized water reactor
Journal of Engineering for Gas Turbines and Power - Transactions of the ASME 131(2009)1, 012906
Kliem, S.; Hemström, B.; Bezrukov, Y.; Höhne, T.; Rohde, U.
Comparative evaluation of coolant mixing experiments at the ROCOM, Vattenfall, and Gidropress test facilities
Science and Technology of Nuclear Installations 2007(2007), 25950
Numerical simulation of coolant mixing in a pressurized water reactor with different CFD methods based on complex meshes
International Journal of Nuclear Energy Science and Technology 3(2007)4, 399-412
Höhne, T.; Kliem, S.
Modeling of a Buoyancy-Driven Flow experiment in Pressurized Water Reactors using CFD-Methods
Nuclear Engineering and Technology 39(2007)4, 327-336
Moretti, F.; Melideo, D.; DAuria, F.; Höhne, T.; Kliem, S.
CFX simulations of ROCOM slug mixing experiments
Journal of Power and Energy Systems 2(2008)2, 720-733
Höhne, T.; Kliem, S.; Rohde, U.; Weiss, F.-P.
Boron Dilution Transients during natural circulation flow in PWR experiments and CFD simulations
Nuclear Engineering and Design 238(2008), 1987-1995
Rohde, U.; Höhne, T.; Kliem, S.; Hemström, B.; Scheuerer, M.; Toppila, T.; Aszodi, A.; Boros, I.; Farkas, I.; Muehlbauer, P.; Vyskocil, V.; Klepac, J.; Remis, J.; Dury, T.
Fluid mixing and flow distribution ín a primary circuit of a nuclear pressurized water reactor Validation of CFD codes
Nuclear Engineering and Design 237(2007)15-17, 1639-1655
Cartland Glover, G. M.; Höhne, T.; Kliem, S.; Rohde, U.; Weiss, F.-P.; Prasser, H.-M.
Hydrodynamic phenomena in the downcomer during flow rate transients in the primary circuit of a PWR
Nuclear Engineering and Design 237(2007)7, 732-748
Höhne, T.; Kliem, S.; Weiß, F.-P.
Modeling of a buoyancy-driven flow experiment at the ROCOM test facility using the CFD-Code ANSYS CFX
atw - International Journal for Nuclear Power 3(2007), 168-174
Kliem, S.; Sühnel, T.; Rohde, U.; Höhne, T.; Prasser, H.-M.; Weiß, F.-P.
Experiments at the mixing test facility ROCOM for benchmarking of CFD-codes
Nuclear Engineering and Design 238(2008), 566-576
Rohde, U.; Höhne, T.; Kliem, S.
Using CFD to simulate turbulent mixing in nuclear reactor pressure vessels
ANSYS Solutions 7(2006)2, 27-28
Vallee, C.; Höhne, T.; Prasser, H.-M.; Sühnel, T.
Experimental investigation and CFD simulation of horizontal air/water slug flow
Kerntechnik 71(2006)3, 95-103
Kliem, S.; Kozmenkov, Y.; Höhne, T.; Rohde, U.
Analyses of the V1000CT-1 benchmark with the DYN3D/ATHLET and DYN3D/RELAP coupled code systems including a coolant mixing model validated against CFD calculations
Progress in Nuclear Energy 48(2006), 830-848
Höhne, T.; Kliem, S.; Bieder, U.
Modeling of a buoyancy-driven flow experiment at the ROCOM test facility using the CFD-codes CFX-5 and TRIO_U
Nuclear Engineering and Design 236(2006)12, 1309-1325
Rohde, U.; Kliem, S.; Höhne, T.; Karlsson, R.; Hemström, B.; Lillington, J.; Toppila, T.; Elter, J.; Bezrukov, Y.
Fluid mixing and flow distribution in the reactor circuit - Part 1: Measurement data base
Nuclear Engineering and Design, 235(2005), 421-443
Hertlein, R.; Umminger, K.; Kliem, S.; Prasser, H.-M.; Höhne, T.; Weiß, F.-P.
Experimental and Numerical Investigation of Boron Dilution Transients in Pressurized Water Reactors
Nuclear Technology, vol. 141,January 2003, pp. 88-107
Prasser, H.-M.; Grunwald, G.; Höhne, T.; Kliem, S.; Rohde, U.; Weiss, F.-P.
Coolant mixing in a PWR - deboration transients, steam line breaks and emergency core cooling injection - experiments and analyses
Nuclear Technology 143 (2003) 37-56
Untersuchung der Kühlmittelvermischung in Druckwasserreaktoren
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Cooperations and References
- strategic partnership with ANSYS CFX, Otterfing
- UCL Belgium
- Kompetenzverbund Kerntechnik Germany
- CFD network Germany
- TU Dresden
- ETH Zürich, Switzerland
- AREVA Erlangen, Germany
- CEA Grenoble, France
- University Pisa, Italy
- Gesellschaft für Reaktorsicherheit GRS, Garching and Cologne, Germany
- TÜV Nord/ TÜV Süd, Germany
- VGB Powertech
- EON Kernkraft, Hannover, Germany
- TOPFLOW pressure tank
- CFD-simulations for stratified flows
- CFD simulation of fibre material transport in a PWR core under loss of coolant conditions
- CFD development group