Study of simplification of model on vibration analysis of vertical two-dimensional VHTR core

Because the Experimental VHTR (very high-temperature gas-cooled Reactor) Core consists of about 2000 graphite blocks in total and each block can move individually during seismic excitation, it is important to know behavior of the core under earthquake. As a step of seismic study, full-block-model is simplified to lump some blocks and the model analysis was conducted. The present report describes feature of simplified models and vibration characteristics of two-dimensional vertical slice core. Results are as follow: (1) While the 8-block-model analysis is useful for parameter survey, the 10-block-model analysis is accuracy satisfactorily for detailed analysis. (2) The increase of simplification of analysis model decreases soft spring characteristics of the column and shifts gradually the resonance frequency to high frequency region. (3) The practical range of simplified model analysis is limited to input wave acceleration level. (4) It made clear that input wave frequency, acceleration and orifice gap width had effects upon vibration characteristics of the two-dimensional vertical core. (author)