CANFLEX fuel bundle CFD analysis: Evaluation of different levels of modeling detailing

Nuclear energy plays a key role in sustainable development, with Computational Fluid Dynamics (CFD) simulations enhancing reactor safety and performance. In CANDU reactors, accurate fuel bundle modeling is crucial for reliable thermal-hydraulic analysis. While previous studies have investigated 37-rod and CANFLEX bundles, research on the 43-rod CANFLEX bundle in an Advanced CANDU Reactor-700 (ACR-700) remains limited, particularly using intermediate-scale modeling. This study addresses this gap by evaluating two CFD models in the ACR-700. The Porous Model treats the fuel bundle as a porous medium and a porous jump condition is applied in the transition between regions. The Rod Model represents the coolant flow around a simplified fuel bundle with no connecting pads, with end-plates also treated as porous jumps to reduce computational cost. Steady-state simulations were conducted in ANSYS R19.3 using $k-\omega$ SST turbulence model. The results indicate that the Porous Model captures global pressure drop and coolant temperature evolution while maintaining low computational cost. The Rod Model provides three-dimensional flow and thermal contours, capturing local effects while preserving agreement with design data. Both models showed mesh convergence, with Grid Convergence Index (GCI) analysis confirming the reliability of the Rod Model’s pressure predictions, that showed good agreement with experimental data, serving as an initial validation of the model’s accuracy. The findings contribute to the development of modeling strategies for CANDU reactors.