Power Noise Spectra of a Water Reactor in Low Frequency Region

Abstract

The power noise measurements were carried out on the Kyoto University Reactor at various reactor power levels under natural convection for two kinds of core configuration with different temperature coefficients of reactivity. Analysis of the results revealed strong noise in the low frequency region at higher power levels, even with a core configuration of essentially zero temperature coefficient of total reactivity.
A conventional theoretical model assuming a white noise input in reactivity and a reactor trans-fer function with temperature-reactivity feedbacks was adopted for comparison with the observed data, but it resulted in considerable disagreement at higher power levels.
As a result, it is concluded that there must exist other power effects not yet clarified in the reactivity feedbacks or in the noise inputs to the reactor, which are responsible for the experimental noise spectrum distortion in the low frequency region.