Development of nuclear fuel assembly 3D reduced model and modal analysis

Due to the geometric complexity of fuel assembly (FA), virtually all reactor dynamic analysis models incorporated drastically simplied FA by lumped mass and beam. Considering the rapid advances of computer technology and analysis software, improving reactor dynamic analysis by 3D model is now possible. As a first step toward this goal, this research investigates and attempts to develop a reduced 3D FA dynamic analysis model to assess more accurate and detailed dynamic response of FA. A modal analysis of a 3D FA model was developed and showed the responses of the FA. The model was tuned to the test results up to 4th modes which were the upper value of test results. The model showed 3D response of FA and revealed additional modes of dynamic behaviors such as torsional motion and composite of bending and torsional motion.