Development of CFD methodology for investigating thermal-hydraulic characteristics in a PWR dome

• This study develops a detailed CFD model for the dome of Maanshan NPP.
• Flow and heat transfer features in the upper plenum and dome are captured.
• Leakage flow to the dome cannot be neglected in the nuclear safety analysis.
• Higher EDY and RIY are obtained using the calculated temperature on the RPV head.
• It is conservative to take the cold-leg temperature to estimate the EDY and RIY.

This study aims to develop a detailed computational fluid dynamics (CFD) model to investigate the flow and heat transfer characteristics in the dome of a pressurized water reactor (PWR). The upper plenum is also considered in order to simulate the possible coolant leak to the dome via the gaps of upper support plate. The essential solid components within the solution domain, including the upper core plate, the guide tube assemblies, the support columns, and the rod cluster control, are realistically modeled, instead of the porous-medium approximation. Through the detailed-geometry CFD simulation, the thermal-hydraulic features in the upper plenum, individual guide tube assembly, and the dome can be obtained. And, the temperature distribution on the reactor pressure vessel (RPV) head can be used to estimate the values of total effective degradation years (EDY) and reinspection years (RIY) for monitoring the crack initiation and growth on the head. Present calculated results also reveal that the original values of EDY and RIY using the cold-leg temperature as the head temperature by the Maanshan staff is conservative.