STABILITY MONITORING OF BOILING WATER-REACTORS BY TIME-SERIES ANALYSIS OF NEUTRON NOISE

A method of monitoring stability of boiling water reactors (BWRs) has been developed, and is reported in this paper. The stability parameters were derived from empirical discrete-time modeling of process noise signals and neutron noise signals. Data were taken from an operating BWR-4, and used to perform univariate analysis of average power range monitor (APRM), and local power range monitor signals, and multivariate analysis of APRM and the process signals, reactor pressure, and core flow rate. The parameters such as decay ratio, damping ratio, and characteristic frequency of oscillation, which represent the system stability, were estimated from the impulse response of the system. The impulse response was determined by using the time series models and contains information about the closed loop dynamics of a BWR.