On the Importance of Validation When Using Commercial Cfd Codes in Nuclear Reactor Safety

In this validation work two turbulence models (k-ε and SST model) and two grids (a finer hybrid grid and a tetrahedral coarser grid) are considered in order to model helium release and dispersion. Simulation results are compared against an experiment of jet release phenomena in the Battelle Model Containment facility (BMC), a multi-compartment facility with a total volume of about 560 m. In the selected test, HYJET Jx7, helium was released into the containment at a speed of 42 m/s over a time of 200 s. Although the k-ε model is the most commonly used turbulence model in most CFD applications, it does not provide the most accurate predictions for this application. Alternatively the SST turbulence model has been employed giving more accurate results. This investigation provides a confirmation that the validation of commercial CFD codes is always required in order to select the more suitable physical models and computational grids for each specific application.