Limit cycle analysis of nuclear coupled density-wave oscillations

Recent tests at commercial boiling water reactors (BWRs) have demonstrated the existence of limit cycles for nuclear coupled density-wave oscillations (NCDWOs) at off-normal conditions. This paper presents the application of a simplified nonlinear BWR core model to determine the potential magnitude and limiting mechanisms of severe NCDWOs, and an approximate determination of the limit cycle using singular perturbation analysis. In this model, the point kinetics equation with infinite-delayed approximation and linear reactivity feedback to both fuel temperature and coolant density is used. This model correctly predicts the magnitude of the Vermont Yankee power oscillations