The Polarity Correlation of Reactor Noise in the Frequency Domain

Abstract

A newly developed special two-detector cross-correlation experiment of zero-power reactor-noise analysis is applied to determining characteristic kinetic-reactor parameters. This method–called polarity correlation in the frequency domain–is based on the detailed analysis of the stochastic Coherence Function, in contrast to the analysis of auto and/or cross power spectral density functions. The coherence function is easily obtained by polarity correlation of two filtered random-neutron-noise signals simultaneously sampled in a reactor system using neutronsensitive detectors in the current mode of operation.The advantage and the progress in using this technique is both its simplicity and the automatic elimination of the equipment frequency response, which is of special importance when analyzing fast-reactor-noise spectra.A series of prompt-neutron-decay constant measurements was performed on several configurations of the STARK and SNEAK facilities. Moreover, special attention and effort is dedicated to reactivity shutdown measurements by the polarity correlation method. An on-line reactivity meter is described which is particularly suited to making reactivity measurements in large plutonium fueled reactors. Shutdown reactivity measurements were performed down to -8 dollars.