Seismic analysis and verification test on a neutron reflector for APWR reactor internals

A Neutron Reflector (NR) is a new structure designed for use in the reactor internals of a Japanese Advanced Pressurized Water Reactor (APWR). It can be used in place of the conventional Baffle-Former Assembly. A vibration test is performed to assess the appropriateness of the method of analysis employed to measure the response of the NR to seismic activity. The NR test model is a one-fourth scale model of the actual size and was designed based on a similarity law, but the test model is not simple due to the modification of two kinds of nonlinear effects. One is the friction effect, which occurs in some positions such as on the Lower Core Plate and between the NR blocks. The other is the fluid-structure interaction effect, which occurs in the narrow gap between the NR and Core Barrel, and which depends on the displacement of the structures. The NR test model was set on a 6x6 meter, three-dimensional shaking table to simulate the response of the NR to seismic excitation. The authors analyzed the test results of the vibration behavior of a stacked block structure similar to the NR structure. In addition, the authors performed a vibration analysis on the test model and, by comparing these analysis results with the test results, the authors verified the appropriateness of the analysis method used for the seismic evaluation of the NR. (author)