Evaluation of Coolant Mixing Characteristics in the Lower Plenum of a Scaled PWR With OpenFOAM

Abstract In the realm of nuclear reactor design, ensuring uniform flow rates at the core inlet of Pressurized Water Reactors (PWR) is vital for safety, impacting cooling functions and “fuel hot spot” criteria. This intricate balance is influenced by fluid dynamics in the reactor pressure vessel’s lower plenum, essential for both hydraulic and structural plant design. The geometric configuration of the lower plenum significantly influences the hydraulic characteristics of the Pressurized Water Reactor (PWR). The flow behavior at lower plenum and downcomer (closer to reactor core) has influences on the distribution of the flow entering the reactor core. To reach a comprehensive understanding of the thermal hydraulic phenomena in the downcomer and plenum of a scaled PWR reactor pressure vessel, numerical investigations was pursued, employing 3D computational fluid dynamics (CFD) simulations, with a thorough comparative analysis against experimental data obtained through Particle Image Velocimetry (PIV), this PIV analysis allow the visualization and understanding of flow mixing characteristics providing valuable insights into the suspended particles’ behavior. The geometric model with a 3-loop configuration was meticulously developed, and subsequent meshing and simulations were executed employing OpenFOAM. The selected test case emulated a scaled Pressurized Water Reactor (PWR) reactor pressure vessel, solving a 3D Navier Stokes equations. The simulation incorporated a transient flow algorithm coupled with a standard k-epsilon turbulence model. Explicit meshing was applied throughout. Due to the computational complexity, the utilization of high-performance computing resources was imperative to ensure expedited and accurate results. The results offer a clear representation of flow patterns within the lower plenum of a PWR, significantly augmenting considerations related to nuclear safety. The computational capability of CFD facilitates the evaluation of various flow distribution device concepts, providing engineers with advanced tools for nuanced insights into their advantages and disadvantages in reactor design.