Development of seismic analysis method considered FSI effect on a neutron reflector for APWR reactor internals

A Neutron Reflector (NR) is a new structure designed for improving the structure reliability of Advanced Pressurized Water Reactors (APWR,). The NR is placed in a narrow gap between the NR and a Core Barrel (CB). In the case of a structure surrounded by liquid in a narrow gap, the added fluid mass and the damping increases compared with in the air. This effect is famous for Fluid-Structure Interaction effect (FSI effect) in the narrow gap and it depends on the vibration displacement of the structure. A new method to estimate the added fluid damping for this case has been introduced by some of the authors in 2001, which is based on a narrow passage flow theory (Morita et al., 2001). Following this theory, a vibration test was performed to assess the appropriateness of the analysis method employed to measure the response of the NR during an earthquake (Nakamura et al., 2002). In this paper, results of a model test are shown comparing the data with the calculated ones based on the new analysis method that is combined the above method with the ANSYS computer code. As a result, a new seismic analysis method using the above theory was developed. The analytical results are in good agreement with the test results. (authors)