Monitoring the stability of BWR oscillation by nonlinear time series modeling

Monitoring the dynamics evolution of BWR oscillation has great importance in evaluating safety of the nuclear systems. Time series analysis methodology has been widely accepted as a powerful tool for this subject. BWR stability has been so far evaluated by decaying ratio (DR) calculated from the impulse response function of autoregressive (AR) model. To explore much more reliable method for detecting BWR instability, this paper introduces a nonlinear time series analysis approach namely exponential autoregressive (ExpAR) modeling. The ExpAR model is available for revealing types of nonlinear dynamics such as fixed point, limit cycle, and even chaos. Furthermore, the model is real-time estimated so that it is suitable for the purpose of on-line BWR instability detection. Empirical analysis of typical benchmark neutronic signal shows the effectiveness of this proposal.