Experimental investigation on split-mixing-vane forced mixing in pressurized water reactor fuel assembly

In nuclear fuel assembly mixing vanes are fabricated on the spacer grids to promote diversion cross flow and turbulent mixing. In order to investigate the decay of diversion cross flow and turbulent mixing induced by the split mixing vanes, particle image velocimetry (PIV) measurement is carried out to acquire high-fidelity flow field data in a 5 x 5 rod bundle with mixing vane spacer grid. Intensities of turbulence, secondary and cross flow, inter-subchannel mixing are obtained based on the experimental data and fitted as exponential functions of normalized distance from the spacer grid. Two decay phases are identified from the experiments. A blending function is introduced to unify the near-wake and far-wake decay functions of turbulent mixing intensity. Based on the measured differential pressure between neighboring subchannels, a correlation of cross-flow pressure loss coefficient K(g )is proposed, i.e. K-g proportional to I-cf(-1.09). (C) 2020 The Author(s). Published by Elsevier Ltd.