Simulating the steam dumping process of a pressurized relief tank is a challenging engineering problem, due to the massive computing resource requirements and its complex physical models. This study gave a comprehensive 3D numerical study for the transient dumping process from the PRT (Pressurizer Relief Tank) to the room containing the tank. The physical model, geometry design and meshing strategy, along with the numerical techniques, have been described in detail. Through parallel simulations based on the open source CFD toolbox OpenFOAM, numerical results for the temperature, pressure, and the velocity distribution are presented. The results show that the maximum velocity throughout the whole domain is 967 m/s over Mach 2 and the maximum pressure on the roof of the room is 2.8 atm. It could provide the guidance information for the safety design of the reactor coolant system. Additionally, comparison cases between OpenFOAM and CFX are tested, and it turns out that OpenFOAM could produce comparable accuracy with commercial CFD software and scale to much more computing cores in parallel simulations.
