Abstract
Safety analysis is one of essential tools for the design, operation and safety of nuclear power plants (NPPs). Traditional safety analysis for NPPs depends on system codes with more conservative assumptions or margins to ensure the plant safety, which would scarify the operation flexibility and efficiency. With advantages of dramatic progress in computer power, Computational Fluid Dynamics (CFD) is gradually adopted in the nuclear safety analysis. In addition, Taipower has licensed some safety analysis cases using or partially using the CFD. The most important things for the CFD simulations are the establishment of mesh and models as well as the error estimation. The thermal-hydraulic phenomena related to the reactor safety are so complicated that the models adopted in the commercial CFD may not reasonably capture these characteristics. Independent simulations and cross-check are necessary for the regulator staff to review the CFD issues. Therefore, it is crucial for the regulatory staff to investigate the CFD modeling and assessment. Focusing on modeling the characteristics of fuel bundle flow, this project is to investigate the CFD methodology, influence of different mesh models and its uncertainty. These simulation results can assist the regulator staff in providing the basis of review guidelines for this issue.