A study of the dynamic response of BWR core structures to earthquakes is reviewed in this paper. A structure which vibrates in a liquid is significantly affected by fluid inertia. A BWR core consists of several hundred of fuel elements and these fuel elements, being submerged in hot water, are hydrodynamically coupled with each other, when they are vibrated by an earthquake. A practical method is devised to analyze the vibration of the fuel-elements/water system. Dynamic characteristics of a core are identified by the method and checked by a series of experiments. Finally a simple single-degree-of-freedom model is shown to be effective in the seismic design analysis of a BWR core.
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