A Method for Measuring Absolute Reactor Power through Neutron Fluctuation

Abstract

A new principle is presented for obtaining absolute reactor power by processing the random fluctuation of neutron flux based on the stochastic nature of nuclear reactions. The required combination of instruments to carry out experiments is described, and experimental results o!Jtained in a swimming pool reactor are reported. The power spectral density of the output current of an ion chamber located near the reactor core is determined by reactor kinetic parameters such as delayed neutron yield, life time, iJ (mean number of neutrons generated per fission) and counter efficiency as well as by the total number of neutrons in the core, which is a measure of absolute power. Using either logarithmic amplifier or reactivity meter, absolute reactor power can be measured without any inlormation about detector efficiency. This method has such merits as easiness and simplicity in operation, ability to measure absolute power in the range 0.01~100 W where other methods are inapplicable, and negligible effect of changes in core configuration or in detector position. The results of actual reactor experiments with this method proved to agree fairly well with those of absolute measurement hy gold foil activation.