Detection of Control Rod Vibration by Neutron Noise Analysis

Reactor noise measurements at Pakistan Research Reactor were analyzed for the magnitude and frequency spectrum of the fluctuation of neutron density. The measurements were aimed at determining the effect of (a) the magnitude of reactor power, (b) coolant flow rate, and (c) position of control rods on the fluctuation of reactor power. Two peaks in the power spectral density of neutron noise are explained to be due to control rod vibration. A one-dimensional thermal-hydraulic model of the reactor core was also developed to explain the remaining noise spectra on the basis of coolant temperature fluctuation.