Comparative study on the effect of reactor internal structure geometry modeling methods on the prediction accuracy for PWR internal flow distribution

• The effect of geometry modeling method of reactor internal structures was examined.
• Real Geometry Model showed better agreement with the measurement.
• Considering the real geometry of the reactor internal structures is important.
• Licensing applicants should validate the applicability of Porous Medium Model.

Internal structures, especially those located in the upstream of a reactor core, may have a significant influence on the core-inlet flow-rate distribution; depending on both their shapes and the relative distance between the internal structures and the core inlet. In this study, in order to examine the effect of the method used to model the geometry of the internal structure of reactors, on the accuracy of prediction for the scaled-down APR+(Advanced Power Reactor Plus) flow distribution, simulations with real geometry modeling were conducted with the commercial computational fluid dynamics software, ANSYS CFX R.14. The results predicted were compared with those produced with a porous medium assumption. It was concluded that the core-inlet flow distribution could be predicted more accurately by considering the real geometry of the internal structures located in the upstream of the core inlet. Therefore, if sufficient computing power is available, an exact representation of these internal structures (e.g., the lower-support-structure bottom-plate and ICI (In-Core Instrumentation) nozzle-support plate), is needed for accurate simulation of reactor internal flow.