CFD analysis on a three by three nuclear fuel bundle with five spacer grid assemblies

Abstract

This study has been conducted to investigate the flow characteristics for SMART 3×3 rod bundle with various turbulence models, namely, κ-ɛ model, κ-ω shear stress transport (SST) model and Baseline (BSL) Reynolds stress model. Commercial code CFX 12.0 was used for the simulation, and pressure drop, second flow intensity, flow velocity and temperature fields were predicted. For the development of an adequate computational model to simulate such a complex geometry, a grid sensitivity study was first examined. In addition, a pressure drop test for SMART rod bundle was shortly introduced, which test was done at Korea Atomic Energy Research Institute and compared with simulation results. From the comparison, with the SST model and BSL model similar pressure drop values were obtained. Maximum surface temperatures in the cross-section increase with the increase in the steps of the span (spacer grid assembly) and the temperature immediately decreases just after the mixing vane and then the temperature slowly rises. Compared with experimental results, the SST model had a similar maximum temperature pattern along rod axis. Also, it was interesting to find that the turbulence model did not affect the secondary flow intensity while affecting the flow velocity values. As a result, the most appropriate turbulence model and the grids were able to be determined.