Numerical simulation of turbulent flow through a 37-element CANDU fuel bundle

In this paper, a comprehensive Computational Fluid Dynamics (CFD) model containing the entire bundle subchannels and the inlet endplate subchannels for a 37-element simulated CANDU fuel bundle is developed for the first time. Results from this study, obtained for different mass flow rates, revealed the presence of strong turbulent swirling flow in many bundle subchannels around the entrance region. Several spikes from the power spectrum densities of (a) the computed pressures at different points inside the subchannels and (b) the unsteady forces and rolling moments on various fuel element walls are appeared to be associated with the turbulent wakes formed as the coolant enters the fuel bundle through the inlet endplate subchannels.

► Three-dimensional flow through a 37-element CANDU fuel bundle is investigated using LES.
► CFD results reveal the presence of strong turbulent swirling flow in the entrance region.
► Study reveals the flow through bundle subchannels as mixed cross and parallel flows.
► Changes of dominant frequencies of forces with flow rate indicate the vortex shedding phenomenon.
► This study identifies the mechanism of flow-induced bundle vibration during normal operations.