Analysis of mixing data relevant to wire wrapped fuel assembly thermal-hydraulic design

Abstract

In this report analysis of recent experimental data is presented using the ENERGY code. A comparison of the accuracy of three types of experiments is also presented along with a discussion of uncertainties in utilizing this data for various code calibration purposes. The existence of internal swirl is discussed. The two empirical coefficients in ENERGY are determined from the data within a certain range of accuracy. This range is dictated to a large extent by the accuracy of the experiments and to a smaller extent by the ability of the code to utilize all sets of data in each experiment. The effect of geometry and bundle size on mixing and swirl flow is discussed. A realistic estimate of the degree of accuracy within which we can predict temperature distribution within the bundle and along the duct of a 217-pin wire wrapped fuel assembly of an LMFBR is presented. Gaps in data which need to be filled in to enhance our confidence in predicting coolant te! mperature distributions in a 217-pin LMFBR fuel bundle, are given. A brief description of two experiments that would fill these data gaps is presented. A novel experiment which would be very useful for both fuel and poison assembly mixing studies is described. Conclusions drawn from this study are believed to be quite general in nature.