Numerical simulation of the effect of rod bowing on critical heat flux

Abstract

Abstract The paper demonstrates the CFD capability to predict the effect of rod bowing on CHF. The applicability and performance of the models are validated based on the Weatherhead experimental data for vertical pipe and NUPEC PWR subchannel and bundle test (PSBT) International Benchmark for rod bundle. The capability of the existing CFD method in predicting CHF is studied both qualitatively and quantitatively. Based on the validated method, the effect of the bowed rod on CHF is evaluated. The bow is assumed to occur at the midspan between two spacer grids in the region where DNB is predicted to occur. The results indicate that rod bowing has a deleterious effect on CHF, but this adverse bowing effect is dependent on the closure (i.e., the ratio of the change of the fuel rod gap to the nominal gap). There is no effect on CHF for closure between 0 and 50%, but adverse effect on CHF for closure larger than 50%, even more considerable effect as the closure increases to larger than 85%. The findings can be used to assist in designing the test fuel rod before the rod bowing CHF experiment.