Numerical simulation of flow and mixing in ROCOM facility using uniform and non-uniform inlet flow velocity profiles

Water loss and depressurization of the primary circuit of a PWR lead to the actuation of the safety injection system (ECC). The cold water injected in the cold legs of the primary circuit is mixed partially with high temperature water. The cold water may cause a thermal shock to the reactor pressure vessel (RPV). The latter is more severe if the safety injection water enters the reactor vessel without mixing beforehand. The simulation and assessment of the mixing can be made using CFD codes. In the present framework, three-dimensional simulations are carried out using the CFD code ANSYS CFX, to investigate the mixing phenomenon in the Rossendorf Coolant Mixing Model (ROCOM) test facility. The predicted flow vertical velocity and tracer concentration distributions are presented and compared to the experimental data. Furthermore, the impact of the inlet velocity profile on the numerical results is assessed. The present results seem to confirm the capability of the CFD modeling to simulate the mixing phenomenon, which remains a key parameter for predicting the whole RPV behavior under abnormal cooling conditions.