CFD Validation of Void Distribution in a Rod Bundle With Spacer

As CFD (Computational Fluid Dynamics) continues to grow in the nuclear industry the need for validation is essential to this growth. The focus of this paper is to highlight the validation of AREVA’s 2-Phase CFD models in a rod bundle with spacer. The experimental work is based on void distribution measurements using a 64×64 wire mesh sensor at the Paul Scherrer Institute adiabatic test loop fuel rod bundle (SUBFLOW). The 2-Phase models are based on the Eulerian multiphase framework where the interaction models are further developed using user routines in a commercial CFD tool to achieve stability and accuracy in a rod bundle configuration with a spacer. The 2-Phase CFD models coincide with the SUBFLOW experiments in showing the effect of void collecting in the center of the sub-channels slightly downstream of the spacer and further downstream the smaller bubbles migrate toward the rod surfaces whereas the larger bubbles stay in the sub-channels. Good agreement is achieved between CFD and void distribution experiments. The multi-phase CFD method was used by AREVA to improve the performance of the new products GAIA and ATRIUM™ 11.