CFD simulations of Gidropress mixing facility experiments in the framework of TACIS project R2.02/02


CFD simulations of Gidropress mixing facility experiments in the framework of TACIS project R2.02/02

Höhne, T.; Rohde, U.; Melideo, D.; Moretti, F.; D’Auria, F.; Shishov, A.; Lisenkov, E.

The main objective for the quantification of the fluid mixing in the downcomer and the lower plenum is the demonstration of the safety of the nuclear plant during non-symmetrical transients. This concerns two main topics: The risk of fragile brittle of the Reactor Pressure Vessel (RPV) during Pressurized Thermal Shock (PTS) transients and the risk of core reactivity excursion during non-symmetrical transient such as Main Steam Line Breaks (MSLB) or Boron Dilution Transients (BDT). The corresponding fluid mixing scenarios are studied in the 1:5 scaled VVER-1000 reactor model at OKB “Gidropress” in the framework of a TACIS project: “Development of safety analysis capabilities for VVER-1000 transients involving spatial variations of coolant properties (temperature or boron concentration) at core inlet”.

An extensive experimental program was running, studying different flow conditions in the reactor mock up, like the start of the 1st coolant pump or natural circulation conditions with density differences of the primary coolant. Pre and post test CFD simulations were carried out for code validation and for a deeper understanding of the flow and mixing behavior in the VVER-1000 reactor also in the future of the project. The 3-D computational fluid dynamics (CFD) codes provide an effective tool for mixing calculations. The CFD-Code used was ANSYS CFX. The geometric details of the construction internals inside the RPV have a strong influence on the flow field and on the mixing. Therefore, an exact representation of the inlet region, the spacer in the downcomer, the elliptical perforated plate and the complicated structures in the lower plenum was necessary. All parts of the lower plenum structures were modeled in detail. The final computational grid contained 6.5 Million nodes. Results of selected experiments and corresponding CFD calculations will be described and discussed in the paper and conclusions will be drawn.

Keywords: CFD; VVER-1000; Coolant Mixing

  • Contribution to proceedings
    TOPSAFE 2008, 01.-03.10.2008, Dubrovnik, Kroatia
    CD-ROM, paper 063
  • Lecture (Conference)
    TOPSAFE 2008, 01.-03.10.2008, Dubrovnik, Kroatia

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Publ.-Id: 11144