Time dependence of linear stability parameters of a BWR

In this work we present several tools to study the time dependence of the linear stability parameters of a BWR using neutron noise analysis. Particularly, we have studied the variation in time of the fundamental frequency of a signal using the short-time Fourier transform and we have compared this method with the calculation of a time dependent Power Spectral Density (PSD) function. The temporal variation of the decay ratio is analysed using a method based on an autoregressive model to fit the different blocks of the signal. The performance of the tools presented is compared analysing analytic signals and a real signal of Forsmark 1&2 Stability Benchmark. (C) 2003 Elsevier Science Ltd. All rights reserved.