JPH0498190A - Neutron measuring device - Google Patents

Abstract

PURPOSE:To improve the neutron flux detection precision by providing a noise reducing circuit for reducing a noise component included in a neutron detection signal. CONSTITUTION:A preamplifier 9 amplifies only a specified frequency band of neutron flux detection signals, and a noise component (n) is included in an output signal from this. An output signal from the preamplifier 9 is given to a noise reducing circuit 10, and an exceeding part over a noise cut level c, positive and negative, is eliminated so as to reduce the noise component (n). The output signal from the noise reducing circuit 10 with the noise component (n) reduced is further given to a mean square circuit 12 of a central operation panel 11 where its mean square value is determined by a mean square process. A mean square value signal is given to an indicator 13 and a recording gauge 14 of the central operation panel 11 to be displayed and recorded, while it is given to a trip circuit 15, so a trip signal is given to a nuclear reactor protective system 16, alarming device 17, computer 18, etc., when this root mean value exceeds a set value.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a neutron measuring device for measuring the in-reactor neutron flux in the intermediate power range of a nuclear reactor, and particularly relates to a neutron measuring device for measuring in-reactor neutron flux. The present invention relates to a neutron measurement device that improves neutron flux detection accuracy by reducing noise that is mixed into neutron flux detection signals due to in-furnace vibrations.

(Prior Art) Generally, a nuclear couplant is provided with a neutron measuring device to monitor the output of the reactor.

This neutron measurement device needs to monitor a wide range of approximately 9 digits (approximately 107% to 100%) up to the rated 100% of the reactor output, so the neutron source region measurement device, intermediate region measurement device, and output region measurement device By overlapping each other with each other, a monitoring range of about 9 digits is covered.

Among these, the intermediate region measuring device monitors the intermediate region from about 104% to 10%, and is equipped with a neutron detector that can be inserted into and withdrawn from the reactor.

In addition, the intermediate region measurement device uses fissile material coated on the cathode surface within the neutron detector. ．． 5U) Nuclear fission during neutron irradiation ionizes the inert gas in the neutron detector, and only a certain frequency band of the alternating current component of this ionization signal is extracted and amplified by a preamplifier.

For example, J'! The preamplifier band-amplifies the ionization signal from 8 kHz to 16 kHz with its low frequency preamplifier and from 300 kHz to 600 kHz with its high frequency preamplifier.

Thereafter, this neutron flux detection signal is squared averaged and then indicated to an indicator.

In addition, the neutron measurement device has a five-digit monitoring range (approximately 10-4%
~10%) is divided into 10 ranges and is designed to be able to be monitored.As a protection against fuel damage due to abnormal reactivity addition due to withdrawal of control rods at reactor startup, reactor scram caused by reactor startup. It has a nuclear reactor protection function. Also, the mid-range monitor typically has eight channels in the case of a BWR plant, and the neutron detectors are evenly distributed within the core.

(Problems to be Solved by the Invention) However, in such a conventional intermediate region measuring device, there is a risk that vibration noise caused by fluid vibration in the reactor during reactor scram or the like may be mixed into the neutron flux detection signal.

That is, the MI cable connected to the neutron detector is connected to a coaxial cable outside the reactor and then connected to the preamplifier.

Here, when mechanical deformation or the like is applied to the neutron detector, the capacitance changes, so a charging (discharging) current flows, which appears as a noise output.

The greater the change in capacitance, the greater the charging (discharging) current, and therefore the greater the AC amplifier output. This phenomenon also applies to M'I cables.

With respect to such noise in a neutron detector, it is possible to reduce the generation of vibration noise by tightening the machining accuracy between the cathode and anode in the neutron detector.

However, as for the M1 cable, the core wire inside the M1 cable is covered with SiO2 powder and is not fixed to a rigid, so the current technology is unable to reduce the capacitance change due to the vibration, that is, the vibration noise. I can't. For this reason, the vibration caused by the emergency insertion of the control rod into the reactor caused noise to be added to the detector signal of the intermediate region measuring device, and this noise could cause the plant to erroneously scram.

Therefore, the present invention has been made in consideration of such circumstances, and its purpose is to provide a neutron measurement device that can improve the accuracy of neutron flux detection.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention is configured as follows.

In other words, the present invention includes a neutron detector that detects neutron flux in the intermediate power region of a nuclear reactor, a preamplifier that band-amplifies the neutron flux detection signal from this neutron detector, and a neutron detector that is connected to the preamplifier. MI to electrically connect
A neutron measurement device having a cable is characterized in that a noise reduction circuit is provided to reduce noise components contained in the neutron detection signal.

(Operation) Neutron flux in the intermediate power range of the nuclear reactor is detected by a neutron detector.

However, this neutron flux detection signal may include a vibration noise component caused by, for example, fluid vibration during a nuclear reactor scram or mechanical deformation of an MI cable.

Therefore, when the AC component in a certain frequency band in this neutron flux detection signal is extracted by the preamplifier and band-amplified, the noise component is also amplified, and the error in the detected value increases significantly. There is a possibility that it will happen.

However, in the present invention, the noise of the neutron flux detection signal from the neutron detector is reduced by the noise reduction circuit, so that the neutron flux detection accuracy can be improved and the reliability can be improved.

(Example) An example of the present invention will be described below based on FIGS. 1 and 2.

FIG. 1 is an overall configuration diagram of an embodiment of the present invention. In the figure, a neutron measuring device 1 includes a neutron detector 3 installed in a reactor pressure vessel 2, and a neutron flux in the intermediate power range of the reactor. It is designed to detect.

The neutron detector 3 ionizes an inert gas by fission of a fissile material (235U) coated on the internal cathode surface when irradiated with neutrons, and outputs this ionization signal as a neutron flux detection signal.

An M1 cable 4 electrically connected to the neutron detector 3 extends outside the reactor pressure vessel 2 and is connected to a metal cable 6 via a connector 5.

The metal cable 6 extends outside through a penetration 7a that is a penetration portion of a reactor containment vessel 7 that houses the reactor pressure vessel 2, and is connected to a preamplifier panel 8 and a nozzle amplifier 9.

The preamplifier 9 amplifies only a specific frequency band of the neutron flux detection signal, and the output signal therefrom contains a noise component n as shown in FIG.

As described above, this noise component n is generated, for example, when a control rod is urgently inserted into the reactor during a reactor scram and the reactor fluid vibrates, or when the MI cable 4 is subjected to mechanical deformation. The amplitude is extremely large.

Therefore, the output signal from the preamplifier 9 is applied to a noise reduction circuit 10 to delete the signal exceeding the noise cut level 1c shown in FIG. 2, thereby reducing the noise component n.

The output signal from the noise reduction circuit 10 in which the noise component n has been reduced is further transmitted to the root mean square circuit 12 of the central operation panel 11.
is given, and the square mean is calculated here to obtain the root mean square value.

This root mean square value signal is given to the indicator 13 and recorder 14 of the central operation panel 11 for display and recording, and is also given to the trip circuit 15, and is sent to the trip circuit 15 when the mean square value exceeds the set value. Sometimes, a trip signal is given to a reactor protection system 16, an alarm device 17, a computer 18, etc. (not shown).

Next, the operation of this embodiment will be explained.

The neutron detector 3 detects neutron flux in the intermediate power range of the nuclear reactor, and provides the neutron flux detection signal to the preamplifier 9 of the preamplifier board 8 via the MI cable 4 and the metal cable 6.

In this preamplifier 9, the neutron flux detection signal is band-amplified in that specific frequency band, and then the noise reduction circuit 10
, and the portion exceeding the noise cut level pc is deleted, and the noise component n is reduced.

The output signal from the noise reduction circuit 10 in which this noise component n has been reduced is further given to the root mean square circuit 12 of the central operation panel 11, where the square mean is taken, and the root mean square value signal is output to the indicator. 13 and a recorder 14 for display and recording, and also to a trip circuit 15.

In the trip circuit 15, when the root mean square value signal exceeds the set value, a trip signal is sent to the reactor protection system 16 or alarm device 17.
, computer 18, etc., and their respective operations are performed.

Therefore, according to this embodiment, the noise component n included in the neutron flux detection signal detected by the neutron detector 3 can be reduced by the noise reduction circuit 10.
The neutron flux detection accuracy can be improved and the reliability of the neutron measuring device 1 can be improved.

〔Effect of the invention〕

As explained above, the present invention can easily reduce only the noise included in the neutron flux detection signal detected by the neutron detector using the noise reduction circuit, thereby increasing the neutron flux detection accuracy and improving the neutron measurement device. Reliability can be increased.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of a neutron measuring device according to the present invention, and FIG. 2 is a diagram showing the waveform of an output signal of the preamplifier shown in FIG. 1. 1... Neutron measurement device, 2... Reactor pressure vessel, 3...
...Neutron detector, 4...MI cable, 8...Preamplifier panel, ...Preamplifier, 10...Noise reduction outlet, 11...Central operation panel, 12...root mean square circuit.

Claims (1)

[Claims] A neutron detector that detects neutron flux in an intermediate power range of a nuclear reactor, a preamplifier that band-amplifies a neutron flux detection signal from this neutron detector, and the neutron detector is electrically connected to this preamplifier. What is claimed is: 1. A neutron measuring device comprising: an MI cable, comprising: a noise reduction circuit for reducing noise components contained in the neutron detection signal;