Contact

Dr. Thomas Höhne
Computational Fluid Dynamics
t.hoehneAthzdr.de
Phone: +49 351 260 - 2425
Fax: +49 351 260 - 12425

CFD calculations of the coolant mixing in Pressurised Water Reactors

Background

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.

Validation Matrix

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 1 Babcock 2x4loop Figure 2 WWER-1000
Figure 3 WWER-440 Detailed hybrid grid model CFX-5 (ROCOM)
Figure 3 WWER-440 Fig. 4 Detailed hybrid grid model CFX-5 (ROCOM)
CFD-results of the start-up of the first pump after 9s Start-up of the first pump streamlines representing the flow field
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
Time dependent averaged mixing scalar at the core inlet Time dependent local mixing scalar at the core inlet, near wall position
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
Mixing scalar at azimuthal positions of the core inlet near the wall, (t=10.0 s)
Experiment CFX 5
Experiment CFX 5
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

Publications

Stieglitz, R.; Mull, T.; Höhne, T.; Rieger, U.; Buettner, K.
Section Reports: 2012 Annual Meeting on Nuclear Technology - Part 5
atw - International Journal for Nuclear Power 58(2013)1, 43-44

Höhne, T.; Grahn, A.; Kliem, S.; Rohde, U.; Weiss, F.-P.
Numerical simulation of the insulation material transport in a PWR core under loss of coolant conditions
Nuclear Engineering and Design 258(2013), 241-248

Höhne, T.; Kliem, S.; Rohde, U.
Buoyancy driven mixing studies of natural circulation flows using ROCOM experiments and CFD
Chemie Ingenieur Technik 83(2011)8, 1282-1289

Höhne, T.; Schaffrath, A.
Fachsitzung: „CFD-Methoden für sicherheitsrelevante Fragestellungen“
atw - International Journal for Nuclear Power 56(2011)7, 419-423

Loginov, M. S.; Komen, E.; Höhne, T.
Application of Large-Eddy Simulation to Pressurized Thermal Shock: assessment of the accuracy
Nuclear Engineering and Design 240(2011), 2034-2045

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

Höhne, T.
Anwendung von CFD-Methoden für den Kern sowie den Primärkreislauf von LWR
atw - International Journal for Nuclear Power 8/9(2009), 546-548

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

Höhne, T.
CFD-simulation of the VVER thermal hydraulic benchmark V1000CT–2 using ANSYS CFX
Science and Technology of Nuclear Installations 2009(2009), Article ID 835162

Moretti, F.; Melideo, D.; Del Nevo, A.; D’Auria, 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

Höhne, T.
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.; D’Auria, 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

Höhne, T.
Untersuchung der Kühlmittelvermischung in Druckwasserreaktoren
atw 12, S. 774-775

Höhne, T.; Grunwald, G.; Prasser, H.-M.
Experimental Investigations on the Four-Loop Test Facility ROCOM
Kerntechnik 65/5-6, S. 212-215

Cooperations and References

Links

Contact

Dr. Thomas Höhne


Contact

Dr. Thomas Höhne
Computational Fluid Dynamics
t.hoehneAthzdr.de
Phone: +49 351 260 - 2425
Fax: +49 351 260 - 12425