Abstract
This study adopts the multiple boiling channel model developed previously by the authors and the external force method regarding the seismic induced vertical acceleration to investigate the effects of seismic vibration on the system's nonlinear behaviors. With the normal operating state of an ABWR as a reference case, the influences of seismic parameters, i.e. peak acceleration and vibration frequency, and system parameters, such as inlet subcooling, axial power distribution, channel length, inlet and outlet loss coefficients, on the system behaviors are carried out in this study. The impact of external vertical acceleration on the system transients may depend on their imposed amplitudes and frequencies. For this multi-channel boiling system, the dominating effect of vertical accelerations may interact with channel-to- channel interactions to present more complex nonlinear oscillations. The strengths of resonance oscillations are consistent with the stability degree of the initial state when the seismic vibration frequency is equal to the system's natural frequency. The preliminary analysis indicates that the natural circulation system is more susceptive to the impact of seismic acceleration with respect to the forced circulation system.