Mitsubishi Electric Corporation

Toshihide Aiba

Kenichi Moteki

Hajime Nakajima

Atsushi Saito

Hiroshi Nishizawa

Kenji Inomata

Masateru Hayashi

Tetsushi Azuma

Toshimitsu Nakai

Masakazu Nakanishi

In an encore nuclear instrumentation system which is equipped with a movable type neutron detector, an object of the invention is to control measurement errors due to the degradation of the system. The incore nuclear instrumentation system includes a neutron detector which is to be installed in a nuclear reactor stored in a containment vessel, and an instrumentation unit which has a current detector circuit and is to be installed on the outside of the containment vessel. An output signal of the neutron detector is inputted into the current detector circuit, and the instrumentation unit remembers a matrix which shows a relation among a reactor power of the nuclear reactor, a gain of the current detector circuit, and an output voltage Vn of the current detector circuit, and the calibration of the current detector circuit is performed with reference to the matrix.

Incore nuclear instrumentation system

A detector signal-processing circuit comprises the following: a current/voltage conversion part that converts the current value of a neutron detector to a voltage value; a variable gain amplification part that performs amplification by a first-step variable gain using a D/A converter; a current level response-use resistance circuit that selects the measurement range in accordance with the voltage value; temperature measurement units for measuring the temperature of the resistance circuit for current level response; a temperature compensation part for commanding gain compensation by the D/A converter on the basis of the measured temperature; and a selective adjustment control part for selective control of the measurement range and adjustment of the variable gain of the variable gain amplification part. Due to this configuration, neutron flux can be measured with high precision while maintaining a constant output precision, before and after switching of the measurement range.

Out-of-core nuclear instrumentation device

A dose rate monitoring device includes: a first energy compensation coefficient operation part obtaining a first energy compensation coefficient to incident radiation using the first compensation coefficient table, a first dose rate operation part obtaining a first compensation dose rate of incident radiation using the first energy compensation coefficient and G (E) function, a second energy compensation coefficient operation part obtaining a second energy compensation coefficient to incident radiation using a second compensation coefficient table, a second dose rate operation part obtaining a second compensation dose rate of incident radiation using a second energy compensation coefficient, a dose rate switching section which select an output according to the magnitude of a ratio of the first compensation dose rate to the second compensation dose rate, and a display operating section which displays the first compensation dose rate or the second compensation dose rate which the dose rate switching section outputs.

Dose rate monitoring device

Three semiconductor detectors are installed at positions where incidence of radiation on a scintillation detector is not blocked, at equal intervals centered on a central axis of the scintillation detector and at equal angles with respect to a plane which is at a right angle to the central axis. An energy compensation factor is determined on the basis of an average pulse height value obtained from a second pulse height spectrum obtained by analog voltage pulses which are output from these semiconductor detectors, and energy characteristics of a high-range dose rate obtained by a direct-current voltage which is output from the scintillation detector are compensated for.

Dose rate measuring device

A radioactivity analyzing apparatus for analyzing a radionuclide contained in a sample material. The apparatus includes a radiation detector that detects a radiation to be detected emitted from the sample material and a radiation analyzer configured to analyze the radiation based on an output from the radiation detector. The radiation analyzer includes a pulse-height analyzer configured to extract a pulse-height distribution from a pulse signal being output from the radiation detector and depending on the radiation, an inverse-problem operator configured to perform an inverse-problem solution of the pulse-height distribution to extract an energy spectrum of the radiation, and a deterioration detector configured to determine a deterioration state of the radiation detector based on the extracted energy spectrum.

Radioactivity analyzing apparatus

A radioactive gas monitoring device includes a sample chamber into which a sampled gas is introduced; a plastic scintillation detector outputting first detection signal pulses; an inorganic crystal scintillation detector outputting second detection signal pulses; a first measurement unit calculating a first count rate from the first detection signal pulses to output the first count rate, and issuing a first alert when the first count rate becomes higher than a first preset level and issuing a second alert when the first count rate becomes higher than a second preset level higher than the first preset level; and a second measurement unit calculating a second count rate from the second detection signal pulses to output the second count rate, and issuing a third alert when the second count rate becomes higher than a third preset level.

Radioactive gas monitoring device

In order to provide a high accuracy radiation dose rate measurement system by good energy characteristics without deteriorating the original energy characteristics of a low dose rate range due to widening range, the dose rate measurement system is composed of: a radiation detector which sends a discrete current pulse having electric charge proportional to incident radiation energy and a DC voltage in which a DC current proportional to the radiation energy is converted; a high voltage power source which supplies a high voltage that operates the radiation detector; and a measurement unit in which the current pulse and the DC voltage are applied from the radiation detector to be converted to a low range dose rate and a high range dose rate respectively, and the low range dose rate and the high range dose rate are switched to be sent depending on the dose rates.

Dose rate measurement system

A radiation detector outputs an analog pulse for incident radiation, and a signal processing portion is furnished with a wave height measuring function of converting the analog pulse inputted therein to a digital form and then measuring a peak wave height of the analog pulse and a wave height spectrum measuring function of measuring a wave height spectrum on the basis of measured wave height data, computes a dose rate and mean energy on the basis of measured wave height spectral data, and outputs computation results. The signal processing portion computes the dose rate and the mean energy on the basis of the wave height spectral data in a same wave height range on a same time axis. It thus becomes possible to provide accurate information based on which to determine whether a rise in dose rate is contributed by natural radon and thoron or contributed by a reactor facility.

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Tokyo, Japan

Toshihide Aiba