Development of Reactor Noise Monitor

Abstract

A reactor noise monitor has been developed to provide a tool that serves the real time routine function of detecting anomalous states of operation in power reactors. In this monitor, RMS (root mean square) values and average frequencies of noise signals are calculated on a real time basis. The average frequency is defined as the frequency averaged by weighting with PSD (power spectral density) of the noise signal and proved to be equivalent to the ratio of an RMS value of the differentiated noise signal to an RMS value of the noise signal itself. Thus, the average frequency can be obtained on a real time basis by using a differentiator, an RMS calculator and a divider. The frequency components of 12 kinds of signals ranging of 0.01–36 Hz are divided into two or three frequency regions by band-pass filters and the RMS value and the average frequency of each frequency region are obtained by the digital calculation method. The performance of this monitor was tested by using a simulated anomalous signal with a peak on its PSD. From the test, it is proved that this monitor can detect more than changes of the RMS value and average frequency. The functions of this monitor were also confirmed at the actual BWR power plant. In addition, a method to detect peak location of PSD is developed and the accuracy of the peak frequency measurement of the proposed method is investigated to be satisfactory.