Development and Validation of CFD Analysis Method for Core Flow Distribution in a 1/5 Scale Model of APR1000 Reactor

The APR1000 (Advanced Power Reactor 1000) is a next-generation pressurized water reactor (PWR) developed from the APR1400 design, featuring enhanced safety and compliance with European Utility Requirements (EUR) for European market entry. Accurate flow distribution at the reactor core inlet is essential for maintaining safety indicators such as cooling performance, DNBR, and thermal margin. This study establishes and validates a computational fluid dynamics (CFD) methodology to predict the core inlet flow distribution of the APR1000 reactor. A 1/5 scaled experimental model was constructed, and CFD simulations were conducted using ANSYS FLUENT and ANSYS CFX software. Various grid densities and turbulence models—including Standard k-ε, SST, RNG k-ε, and Reynolds Stress Model (RSM)—were evaluated f or their impact on flow accuracy. Grid sensitivity analysis showed that even coarse grids provided reliable results, enhancing computational efficiency without significant loss of accuracy. Among the turbulence models, SST and RNG k-ε showed the best agreement with experimental data. Notably, the SST model in ANSYS CFX achieved the highest correlation with experimental results, demonstrating the lowest RMSE and MAE values compared to ANSYS FLUENT. These findings confirm the robustness of the developed CFD methodology for APR1000 design and safety assessments, supporting optimized reactor design and reducing the risk of intellectual property disputes during international expansion. Future research will explore a wider range of operating conditions and emergency scenarios to further enhance CFD-based safety analyses for advanced nuclear reactors.