Study on pressure drop prediction of Tight Lattice Fuel Assembly using CFD

This paper presents a prediction method about pressure drop of the tight lattice fuel assembly. To evaluate the core performance, the pressure drop of fuel assembly is important parameter for the reliability and safety. The shape of fuel assembly is complicated and the shape has a strong effect on pressure drop. Therefore, to obtain the pressure drop of fuel assembly, the experiments are needed. However the experiments need a lot of time and money. The purpose of this study is to predict the pressure drop of the tight lattice fuel assembly using CFD (computational fluid dynamics) and law of two phase flow similarity without experiments. Prediction method for pressure drop is, first the shape of fuel assembly was reproduced by 3D-CAD, then to evaluate the parameters depending on the shape using CFD analysis under the single phase flow condition. And then, to calculate pressure drop of two phase flow using law of two phase flow similarity. The predicted results by this method were compared with the experimental results of 3 types of the tight lattice fuel assemblies, 7-rod, 14-rod, and 37-rod fuel assembly. Fluid conditions (pressure, mass flux and quality) of test results covered the typical operating range of the LWR fuel assembly. It was found from comparison result that this method can predict the pressure drop of the LWR fuel assembly with sufficient accuracy. The prediction accuracy (predicted value/test value) is about 10%. (author)