Source range neutron flux count rate system incorporating method and apparatus for eliminating noise from pulse signal

This patent describes an apparatus for generating nuclear reactor source level neutron pulse count rates selectively filtered to reduce frequency burst noise. It comprises: detector means generating a pulse signal representative of neutron emissions and containing frequency burst noise; pulse count rate signal generating means repetitively generating a pulse count rate signal from the pulse signal representative of pulses counted in a time interval of selected duration, with the pulse count rate signal for the most recent interval being the current pulse count rate signal; pulse count rate signal limit generating means generating from previous values of the pulse count rate signal a statistical limit inside of which the current pulse count rate signal should statistically remain within a preselected probability; comparison means comparing the current pulse count rate signal with the statistical limit; and output generating means including means generating a selectively filtered pulse count rate signal having a value of the current pulse count rate signal when the current pulse count rate signal is inside of the statistical limit and clamping means clamping the selectively filtered pulse count rate signal to the statistical limit when the current pulse count rate signal is outside the statistical limit