Abstract: According to an embodiment, a neutron measurement apparatus has: a neutron detector; a preamplifier that amplifies an output signal of the neutron detector and outputs a neutron detection signal; a pulse counting unit that measures the neutron intensity by using pulse counting method by which the neutron detection signal is used to count the number of individual pulses; a Campbell measurement unit that measures the neutron intensity by using Campbell method by which a time average of squares of AC component of the neutron detection signal is calculated; a correction constant calculation unit that calculates a correction constant for correcting an output of the Campbell measurement unit by using an output of the pulse counting unit and an output of the Campbell measurement unit; and a correction value calculation unit that outputs, based on the output of the Campbell measurement unit, a corrected value by using the correction constant.

Abstract: According to an embodiment, a neutron measurement apparatus has: a neutron detector; a gamma ray detector; a neutron detector signal processing unit which performs Fourier transform on the signals received for a prescribed period, generates neutron detector signal frequency data in a frequency domain, calculates the neutron-detection signal power spectrum and stores it; a gamma-ray detector signal processing unit which performs Fourier transform on the signals received for a prescribed period, generates gamma ray detector signal frequency data in a frequency domain, calculates gamma ray detector signal power spectrum and stores it; and a neutron calculation unit which generates a neutron signal by removing a part contributed by the gamma ray detector signal power spectrum from the neutron detector signal power spectrum.

Abstract: According to an embodiment, a neutron measurement apparatus has: a neutron detector; a gamma ray detector; a neutron detector signal processing unit which performs Fourier transform on the signals received for a prescribed period, generates neutron detector signal frequency data in a frequency domain, calculates the neutron-detection signal power spectrum and stores it; a gamma-ray detector signal processing unit which performs Fourier transform on the signals received for a prescribed period, generates gamma ray detector signal frequency data in a frequency domain, calculates gamma ray detector signal power spectrum and stores it; and a neutron calculation unit which generates a neutron signal by removing a part contributed by the gamma ray detector signal power spectrum from the neutron detector signal power spectrum.

Abstract: According to an embodiment, a neutron measurement apparatus has a neutron detector; a pre-amplifier; a first AC amplifier which extracts and amplifies an AC component; a bandwidth limiter which obtains a signal of a range of a predetermined frequency domain based on the output of the first AC amplifier; a neutron signal interval calculation unit which derives a neutron signal interval, that is a period of time during which a significant signal is being generated, from the AC component of the neutron detection signal; and a mean square value calculation unit which calculates a mean square value of outputs of the bandwidth limiter for a range corresponding to the neutron signal interval.

Abstract: According to an embodiment, a neutron measurement apparatus has: a neutron detector; a preamplifier that amplifies an output signal of the neutron detector and outputs a neutron detection signal; a pulse counting unit that measures the neutron intensity by using pulse counting method by which the neutron detection signal is used to count the number of individual pulses; a Campbell measurement unit that measures the neutron intensity by using Campbell method by which a time average of squares of AC component of the neutron detection signal is calculated; a correction constant calculation unit that calculates a correction constant for correcting an output of the Campbell measurement unit by using an output of the pulse counting unit and an output of the Campbell measurement unit; and a correction value calculation unit that outputs, based on the output of the Campbell measurement unit, a corrected value by using the correction constant.

Abstract: According to one embodiment, a stability computation monitoring device monitors in real time reactor power oscillation based on signals from neutron detectors. The device has: a detection sampling section sampling signals from the plurality of neutron detectors to output a detection sampling signal for each neutron detector; a local power monitoring section converting the detection sampling signal into a neutron flux signal; a low-pass filter applying low-pass filtering to neutron flux signal; a down-sampling section performing down-sampling for the neutron flux signals that have passed through the low-pass filter at a period longer than the detection sampling period; a wavelet transformation section applying Discrete Wavelet transformation to the neutron flux signals that have been subjected to the down-sampling to compute a DWT wavelet coefficient of each level; and a monitoring section monitoring the wavelet coefficient computed by the wavelet transformation section.

Abstract: According to one embodiment, a neutron flux level computing component has: an analog signal processing system that amplifies an AC component of a detector output signal from a neutron detector and performs filtering for removal of a high-frequency component; a digitization system that converts, at a certain sampling period, an output signal from the analog signal processing system into a digital time-series signal; a wavelet analysis system that performs discrete wavelet transformation using the digital time-series signal to compute a wavelet coefficient; and a digital signal processing system that computes a mean square value of the wavelet coefficients and converts the computed mean square value into a neutron flux level value.

Abstract: An embodiment of a reactor power stability monitoring system has: a time averaging unit that calculates a time average value of the local neutron flux signals; a harmonic wave difference calculation unit that extracts, as an AC component signal, a difference between the local neutron flux signal and the time average value calculated by the time averaging unit; a low-pass filter that performs low-pass filtering of the AC component signal; a down-sampling unit that down-samples a low-frequency alternate current component signal that has passed through the low-pass filter, at intervals that are longer than the detection sampling intervals and shorter than the averaging time and that are shorter than or equal to intervals (necessary to detect oscillation inside the core; and a Fourier transform unit that performs Fourier transformation of the down-sampled low-frequency AC component signal to output a frequency spectral density distribution.

Abstract: A neutron measurement apparatus includes: an analog signal processor; a digitizing processor; an FFT calculation processor; and a signal processor. The analog signal processor amplifies alternating current components of detector output signals output from a neutron detector, and filters to remove high frequency components from the output signals, which the digitizing processor digitizes at a constant sampling period in a time series; the FFT calculation processor converts certain of the signals in a time domain from the digitizing processor into signals in a frequency domain, and filters the signals in the frequency domain; and the signal processor selects and extracts signals having required frequency components through the calculation processing on the FFT calculation processor, to calculate power spectral densities of the extracted signals, and to convert the calculated power spectral densities into a neutron measurement value.

Abstract: Disclosed is a method of monitoring the neutron sensitivity of a neutron detector. Voltage having a predetermined potential difference is applied between an anode and a cathode without irradiating the neutron detector with neutrons to permit an &agr;-ray to be emitted from the nuclear fission substance. The &agr;-ray ionizes the ionizing gas to form an &agr;-ray current (I&agr;) flowing between the anode and the cathode. The current (I&agr;) thus formed is monitored. Also, with the monitoring region in which the applied voltage and the &agr;-ray current (I&agr;) bear a substantially proportional relationship, obtained is an extrapolated zero-volt &agr;-ray current (I&agr;0) at 0V of the applied voltage between the anode and the cathode from the proportional relationship by an extrapolating method, and the extrapolated zero-volt &agr;-ray current (I&agr;0) is correlated with the neutron sensitivity.

Abstract: Disclosed is a method of monitoring the neutron sensitivity of a neutron detector. Voltage having a predetermined potential difference is applied between an anode and a cathode without irradiating the neutron detector with neutrons to permit an &agr;-ray to be emitted from the nuclear fission substance. The &agr;-ray ionizes the ionizing gas to form an &agr;-ray current (I&agr;) flowing between the anode and the cathode. The current (I&agr;) thus formed is monitored. Also, with the monitoring region in which the applied voltage and the &agr;-ray current (I&agr;) bear a substantially proportional relationship, obtained is an extrapolated zero-volt &agr;-ray current (I&agr;0) at 0V of the applied voltage between the anode and the cathode from the proportional relationship by an extrapolating method, and the extrapolated zero-volt &agr;-ray current (I&agr;0) is correlated with the neutron sensitivity.

Abstract: A power range monitor apparatus includes a plurality of average power range monitors for calculating/monitoring local power values, average reactor power values, and core flow rate values, a plurality of rod block monitors for monitoring the average values of local power values, and a plurality of flow rate signal converters for converting the signal form of recirculation rate detection signals. The flow rate signal converters concurrently transmit recirculation rate detection signals as digital signals to the average power range monitors. The average power range monitors obtain core flow rate signals from the respective recirculation rate detection signals, use them to monitor the average reactor power, and transmit them to the rod block monitors. The rod block monitors select optimal values from average reactor power values and core flow rate signals to perform a monitoring operation.