JPH01244396A - Neutron flux measuring system - Google Patents

Abstract

PURPOSE:To prevent the production of useless scram by noise while heightening availability factor without harming the safety of a nuclear power plant by setting a dummy sensor and subtracting the signals of the dummy sensor from that of a true sensor. CONSTITUTION:A dummy sensor 100, which has the same structure, shape and construction materials as a true sensor 2, without applying fissionable material on an anode is set. The signals of the dummy sensor 100 are regulated by an adjuster 101. In a preamplifier 8, the output of the dummy sensor 100 is subtracted from that of the true sensor 2. The difference of the output, namely, the output of synthesized neutron flux measuring system does not include peak signals which are included in the output of the true sensor 2 and useless scram by earthquake, impact and the like can be avoided without generating scram signals from the result of processing of an electronic circuit in the latter part.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a neutron flux detection device used in nuclear power plants, etc., and particularly relates to signal processing that can withstand vibrations caused by earthquakes, impacts, etc. Regarding equipment.

(Conventional technology) Conventional equipment is described in Nuclear Reactor Course, ■, Nuclear Reactor Instrumentation Control, p.4
1-p44. As described in the May 1974 issue of Thermal Power Generation Technology Association, boiling water reactors (hereinafter referred to as BWRs)
) had the following structure.

[Problem to be solved by the invention]

Conventionally, the following measures have been taken for the entire nuclear power plant in response to vibrations caused by earthquakes and impacts, with safety first.

(1) Assuming an earthquake so large that it can be called hypothetical, we will determine the magnitude and frequency of vibration of each structure and equipment during an earthquake through experiments and analysis, and create a design that can withstand the earthquake.

(2) At power plants, large numbers of seismometers and accelerometers are installed in structures and equipment, so that when vibrations larger than a room occur, they can be detected locally and globally, and Stop(
Appropriate measures, including Scrum (hereinafter abbreviated as Scrum), will be taken with sufficient margin.

The neutron flux measurement system that is the subject of this invention has previously been commercialized through sufficient experimentation and analysis based on the basic concept of fail-safe, and furthermore, the electronic circuit section has extremely high vibration resistance characteristics. Sufficient consideration has been given to fixing it on an excellent rack (holding shelf). Due to thorough fail-safe measures, if something happens (specifically, if the magnitude of the detected neutron flux signal exceeds a certain value even momentarily), control rods will be inserted into the reactor in an emergency, resulting in a reduction in power output or Completely stop nuclear fission inside the reactor.

In particular, let us consider a case in which a signal from a neutron flux instrumentation system is detected as an apparently increased signal and the reactor is shut down, even though the neutron flux to be measured has not actually increased. (In the opposite case, the signal from the neutron flux instrumentation system must not appear to increase even though the neutron flux is increasing. From a fail-safe perspective, in this case (Measures have been taken to prevent the increase of the apparent signal due to vibration.) The possibility that the apparent signal increases due to vibration can be categorized into: (1) vibration of the sensor body, (2) vibration of cables, connectors, etc., and (2) vibration of the electronic circuit. It can be divided into things. In (1), the neutron flux is locally uneven and has a mountain-like distribution, and the signal of the neutron flux instrumentation system fluctuates as the sensor moves between valleys and peaks due to vibration. The gap between these peaks and valleys is a few percent at most (around 4%)
, and there is sufficient leeway at the Scrum level.

What occurs in common with (1) and (2) is the possibility that the capacitance C determined by the structure changes.

Both the sensor and the cable (usually called a coaxial MI cable) have an anode in the center and a cathode on the outside, and have a capacitance C between them. Vibrations change the distance between the poles, causing flow.

Also, as a common cause in (1) and (2), there is a possibility that piezoelectric force based on the piezo effect is generated due to deformation due to percussion.

In addition, (3) requires complicated calculations, and various calculations can be made, but this does not pose a problem in practice because miniaturization and centralized management using vibration-proof racks are possible.

As can be seen from the above explanation, even though the physical quantity to be detected by the sensor (neutron flux in this case) does not actually increase, the output signal of the neutron measuring device increases, causing the reactor to fail (on the fail-safe side). There may be a situation where there is a scrum.

This differs from scrams using seismometers installed in various parts of nuclear power plants, and there is no need to scram (if the seismometers are more sensitive). Although this poses no problem in terms of safety, it is not desirable from the standpoint of stable power supply and economic efficiency.

The purpose of the present invention is to extremely reduce the possibility of neutron flux becoming larger than a predetermined value and causing a scram based on vibrations generated within the neutron flux instrumentation system due to earthquakes, impacts, etc., without compromising safety. It is about providing the means.

[Means to solve the problem]

The above purpose is to replace a sensor (hereinafter referred to as a dummy sensor) that has zero sensitivity to the physical quantity that is the sensor's detection target with a conventional sensor (a sensor that has a predetermined sensitivity to the physical quantity that is the target of measurement, which is referred to below as a dummy sensor). The signal transmission cables, connectors, and signal processing electronic circuits used for the true sensor and the dummy sensor are the same, and the intermediate sensor leading to the final stage instrumentation system output is installed in parallel with the dummy sensor. This is achieved by subtracting the signal coming from the dummy sensor from the signal coming from the true sensor at the corresponding point either directly or after performing appropriate processing.

In the case of BWR, the physical quantity is neutron flux (especially thermal neutron flux), the real sensor is a fission counter, and the dummy sensor has the same structure, shape, and two dimensions as the real sensor, and is different from the real sensor. Fissile material U2”δ coated on the anode
is not coated.

[Effect]

During normal use, the dummy sensor has an output value of zero.

Therefore, even if the true sensor output from the measuring device is subtracted from the dummy sensor output, the measured value will still be indicated.
The function is exactly the same as before.

In the event of an earthquake or impact, the area affected is wide.

Various effects can be considered due to the vibrations caused.

Now, suppose that due to some factor, a signal N other than the neutron flux appears in the output of the measuring device coming from the true sensor under almost the same environmental conditions inside the nuclear reactor.

There is an extremely high possibility that substantially the same signal N' will appear in the output of the measuring device coming from a dummy sensor having exactly the same structure and shape.

In principle, the signal N on the true sensor can be calculated by subtracting the signal N' on the way to the output stage.
It can be kept to a sufficiently modest value.

Therefore, in terms of earthquakes and strikes, there will be no careless scrum.

〔Example〕

Embodiments of the present invention will be described below using a BWR neutron flux measuring device as an example.

Figure 1 shows an intermediate region monitor (hereinafter IRM) sensor 2 used at startup among neutron body sensors placed inside the core 1 of a boiling water reactor (hereinafter referred to as BWR), and a local power region used in the high power range. Monitors (hereinafter referred to as LPRMs) 3 are shown, and when the detected value becomes larger than a predetermined value, control rods 4 are urgently inserted (scram) to stop nuclear fission in the reactor.

An IRM sensor 2 will be taken up as an example of the embodiment of the present invention. First, I will provide an overview of current IRM devices.

In the IRM detector, as shown in FIG. 2, an anode 5 and a cathode 6 are arranged on a concentric axis, a constant voltage is applied between them, and argon gas or the like is insulated and sealed with ceramic. A fissile material such as U2311 is coated on the anode 5, and the neutrons that fly here cause nuclear fission, and the ionizing current of the argon gas at that time is transmitted through a 10m to 20m coaxial cable 7 called an MI cable. It is taken out and sent to the subsequent electronic processing circuit. FIG. 3 shows this electronic circuit in more detail. Since the IRM is responsible for the relatively low neutron flux level at startup, it is greatly affected by gamma rays. For this reason, this electronic circuit smoothes the signal using a type of root-mean-square circuit called the Campbell method, and the preamplifier 8. Bandwidth amplifier9. Square circuit 10. Average circuit 11. This is achieved by the amplifier circuit 12.

IRM uses a relatively wide range of changes in neutron flux at startup (I
Xl 0'nV to 1.5X1013nV), a wide range of calculation accuracy is ensured by the range changeover switch 13. Further, the trip circuit 14 is an IRM
It has the function of issuing an alarm based on checking the upper and lower limits of the measured value, commanding to prevent control rod withdrawal, and commanding a scram when the IRM measured value shows an abnormally high value.

On the other hand, FIG. 4 shows the operation panel 15 and display panel 1 of the IRM.
6 is shown. Corresponding to the mode switch 17, various functional tests are performed, and IRM measurement values and status are centrally displayed.

Examples of application of the present invention to the above-described conventional IRM configuration will be described below.

First, it has the same structure, shape, and material as the IRM sensor (true sensor) 2 shown in Fig. 2, and has U23 on the anode.
Dummy IRM sensor 1 without applying fissile material of grade 6
Prepare 00. This is placed at an appropriate position within the reactor core as shown in FIG. By the same signal transmission means as true sensor 2,
This dummy sensor is connected to the electronic circuit shown in FIG. FIG. 3 shows an example in which the difference between the true sensor and the dummy sensor is taken in the preamplifier 8. In this way, as shown in Fig. 5, the neutron flux instrumentation system output φT becomes
If noise other than neutron flux is picked up and scram occurs, they have the same structure, shape, and material.

It is highly likely that a similar signal will appear on the dummy instrumentation system output φD. Conversely, as long as the output φD of the dummy instrumentation system is close to zero, the detection value of the true sensor will be ``excluding the effect of gamma rays.''
It can be safely assumed that this is a detection signal of neutron flux.

The synthesized neutron flux instrumentation system output (φT - φD), which takes the difference between these two at the point of preamplifier 8, does not include the peak signal included in φd, and as a result of processing in the electronic circuit at the subsequent stage, the scram signal is generated. This prevents unnecessary scrams from occurring due to earthquakes, impacts, etc.

In particular, in the case of an IRM sensor, background noise due to gamma rays occupies a relatively large component.

If the dummy sensor and the real sensor are located at the same location, the argon gas will be ionized by gamma rays by the same amount, so by taking the difference between the two, the effect of the background noise of gamma rays will be completely canceled out. As a result, calculation accuracy can be significantly improved.

This effect can be expected to some extent even when the dummy sensor and true sensor are installed at different locations.

In FIG. 5, it is assumed that signals with approximately the same waveform and magnitude appear simultaneously on the true sensor 20 and the dummy sensor 100 due to earthquakes, blows, etc., but in some cases, signals with different waveforms or one signal may be larger than the other. It is conceivable that the signal may be generated with a delay. In the worst case, if the maximum value of the true sensor 20 and the negative maximum value of the dummy sensor 100 match exactly in time, the output of the synthetic neutron flux instrumentation system φT-
The maximum value of φ0 becomes larger than the neutron flux instrumentation system output φd. The adjuster 101 in FIG. 3 performs processing to adjust the dummy sensor signal φD in order to cope with such a problem.

Specifically, the most effective method is to remove the negative value of the dummy sensor signal φD, ie.

Output. Alternatively, the absolute value 1φD1 is output.

This is based on the idea that it is not harmful if the synthetic neutron flux instrumentation system output (φT−φD) suddenly decreases due to noise, but it is necessary to prevent it from increasing rapidly.

Alternatively, if you can predict in advance that the length of the cable will be significantly different between the true sensor and the dummy sensor, or that there will be a difference in the amount of noise generated due to differences in installation conditions, use a phase shift circuit or It is also conceivable to add a gain adjustment circuit as an adjustment function.

On the other hand, in the example shown in FIG. 3, the difference between the signal φT from the true sensor and the signal φD from the dummy sensor is taken at the connection point A of the preamplifier 8. At the connection point B and the output connection point C of the final stage amplifier 12,
It is also conceivable to connect the signals from the dummy sensors and calculate the difference signal (φD−φD) in each amplifier. At this time, as a matter of course, at point B, the signal φD from the dummy sensor is a signal obtained through the dummy sensor, MI cable, connector, transmission cable, and the preamplifier 108 having the same specifications as the preamplifier 8 ( If necessary, use one with an adjuster 101). Furthermore, at point 0, in addition to the preamplifier 108, a bandpass amplifier 9. Square circuit 10. A band amplifier 109 with the same specifications as the averaging circuit 11 and the amplifier circuit 12; and the square circuit 110. Average circuit 111. A signal obtained via an amplifier 112 and a range switch 113 (with an adjuster 101 if necessary) is used as φD.

The advantages and disadvantages of where these difference signals (φD−φD) are taken are as follows.

As represented by point A, when the difference is taken at the point closest to the detection end (sensor), only the parts that are most difficult to evaluate against earthquakes and impacts, such as the sensor itself and cables, are targeted, and the reliability of the dummy signal itself is evaluated. However, it is powerless when noise occurs in the subsequent electronic circuit.

Taking the difference at the point closest to the final output stage, as represented by the 0 point, can protect against noise generated in the entire range from the sensor to the final output stage due to earthquakes and impacts, but it also reduces the reliability of the dummy signal itself. becomes a problem (because it passes various calculation elements).

The above describes how to install dummy sensors for one IRM instrumentation system.In a 1100M We class BWR, the IRM has about 8 channels, but independent dummy sensors are installed for all of them. It is not a good idea to do this, but it is practical to provide two dummy sensors and distribute them to the IRM of the channel.

Further, in order to prevent sensitivity deterioration, IRMs are usually inserted into the furnace only when necessary. FIG. 6 shows a pinion rack 19, a position switch 21. A situation in which the motor 20 and the drive controller are operated and a situation in which the signal from the IRM sensor 2 is sent to the monitor circuit 23 via the MI cable 7 and the flexible cable 24 are shown. The monitor circuit 23, as shown in FIG.
Components 8, 9, 10, 11, 12゜13.14, 25
, 26.27.

Like the IRM real sensor, the dummy sensor is realized by a drive mechanism that allows it to be inserted into the reactor core when necessary.
It is ideal in the sense that they have the same mechanism and specifications, but since the dummy sensor is not coated with U2δ5, there is no risk of deterioration and it can be fixed in the furnace. In FIG. 5, a dummy sensor 100 is fixed in the furnace and an MI cable with the same specifications as the MI cable 7 is installed.
Cable 1o7. A situation is shown in which a flexible cable 124 having the same specifications as the flexible cable 24 is installed.

Recently, there are some long-life IRMs that are permanently fixed in the reactor core, but in this case, it is naturally desirable that the dummy sensors also have the same specifications and are fixed.

On the other hand, in the IRM instrumentation in which this dummy sensor is installed, it is desirable to add the following functions to the operation panel 15 and the display panel 16. That is, in FIG. 4, one of the selections of the mode switch 17 is zero adjustment 1 and 2, and a simulated signal is applied to each range instead of the signal of the real sensor 2 to calibrate the electronic circuit. It has become. Therefore, dummy sensor 1
A simulated signal is also applied in place of the 00 signal so that the electronic circuit connected to the dummy sensor can be calibrated.
Correspondingly, a "dummy normally open" selection point 28 is provided on the mode switch of the operation panel 15, and if there is a problem with the dummy sensor signal processing electronic circuit, an indicator lamp 29 will notify you that "dummy is defective". do. In addition, in case of a failure on the dummy sensor signal processing side or when the noise suppression function by the dummy sensor of the present invention is not used, a disconnection switch is provided inside the adjuster 110 shown in FIG. 3 to disconnect the φD signal. The dummy bypass display section 30 of the display panel 16 shown in FIG.

The next example is the LPRM3 shown in FIG. 1, which is one of the same <BWR neutron flux sensors.

The conventional configuration is shown below.

The LPRMs are arranged almost evenly in the horizontal and vertical directions within the reactor core, with 43 strings (first
As shown in the figure, there are four installed in the -string, so there are a total of 172).

The basic principle and structure of the LPRM sensor is the IR shown in Figure 2.
Similar to the M sensor, it measures the ionization current of argon gas when fissile material such as U'' coated on the anode undergoes fission due to incoming neutrons.Each sensor is fixedly installed at a fixed position within the reactor core. Via MI cable, transmission cable.

It is connected to the electronic arithmetic circuit shown in FIG. This electronic arithmetic circuit basically consists of two types of output monitor cards. One of them is the power supply 3 that supplies constant voltage to each LPRM3.
This is a local output monitor card 34 consisting of a section 32 that amplifies the signal Φd obtained with 1, and a trip circuit 33 that issues a command to scram the reactor when the result is greater than a predetermined value Limit (LPRM). The other is an average output circuit 35 (there are 6 channels) that calculates the average value (hereinafter abbreviated as APRM) of signals corresponding to 24 LPRMs out of 172 output signals of the DC amplifier 32.
, the APRM instruction value for each channel is a predetermined value Li
This is an average output monitor card 37 comprised of a trip circuit 36 that issues a command to scram the reactor when the value exceeds m1t (APRM).

This predetermined value for issuing a scram command is Limit (
APRM) is set smaller (severer) than Limit (LPRM).

Furthermore, in FIG. 6, the term equivalent to the fuel surface heat flux is monitored using LPRM, APRM, recirculation flow rate signals, etc.
Also shown is a Rondo block monitor card 38 that defines the operation of each control rod.

A case where the present invention is applied to the above conventional configuration will be described.

As with the IRM sensor, in the case of the LPRM sensor, the only difference between the dummy sensor and the real sensor is that no fissile material is coated on the anode. The exact same MI cables, transmission cables, and connectors are used.

Signal ΦT from the true sensor and signal ΦD from the dummy sensor
At which stage is it best to take the difference between
As with RM, various types can be considered depending on the purpose and characteristics. In the case of LPRM as the first candidate, as shown in FIG.
(indicated by connection point A in the figure).

Furthermore, in order to deal with noise that may occur in the electronic circuit, the signal ΦD from the dummy sensor is connected to a DC amplifier 1032 made with exactly the same specifications as the DC amplifier 32.
After passing through, subtract it (shown at connection point B in Figure 7)
You can also do that. However, in this case, the DC amplifier 32
Inside the sensor is a variable gain GT to compensate for deterioration in detection sensitivity due to depletion of fissile material on the anode of the true sensor.
(Manual setting) is provided, so do not forget to set the variable gain Go in the DC amplifier 1032 for the dummy sensor to the same value when adjusting the variable gain GT. It is desirable to be able to change the GO by

On the other hand, although not all LPRM signals are sent to the APRM, the APRM itself is equipped with the function of issuing a scram command, and its setting value is considerably lower in the APRM. Noise caused by a phenomenon that affects the entire reactor is more likely to be scrammed by a command from the APRM. Therefore, it is also meaningful to subtract Φ0 from the average value Φd on the output side of the average circuit 35 of the APRM (indicated by connection point C in FIG. 7).

Above, we have explained how to find the difference between ΦT and ΦD, but I
As in the case of RM, the noise component signal in Φ and Φ
If the deviation or difference in the waveform of the 0 signal causes a worse result (the noise component of ΦT and the vibration waveform of ΦD are 18
When there is a risk of deviation of about 0 degrees), the signal ΦD
, adjuster 100 immediately before subtracting from ΦT
It is best to use one that has passed 4. adjuster 100
4 is equivalent to adjuster 101 in Figure 3.

(1) Negative value cutting, (2) absolute value calculation, (3) amplitude gain adjustment, (4) phase delay calculation, etc. are used singly or in combination.

On the other hand, the installation location of the dummy sensor 1003 in the furnace is
As shown in the figure, it is possible to add one more in the cavity in the conventional LPRM guide tube 39. That is,
Inside the guide tube 39 is a mobile in-core instrumentation system (hereinafter referred to as TIP) 4.
0 (Used for LPRM correction with a traveling type detector, and based on this result, the DC amplifier 32 or 10
M connected to the LPRM 42 and other LPRMs in cross section with the guide tube 41 (adjusting the variable gain of 32)
A dummy sensor cable 44 according to the present invention can be built into the I cable 43. The positions of the dummy sensors in the height direction are the four LPPMs A in FIG.

You can freely choose a point that does not overlap B, C, or D.

On the other hand, if a dummy sensor for IRM is also to be fixed in the furnace, it is advantageous in terms of cost to install it inside the LPRM guide tube as shown in FIG.

In particular, there are many LPRMs, but in principle, one dummy sensor can be installed and the dummy sensor signal can be distributed to the LPRM of each true sensor to obtain the difference signal, but this is not reliable. From the point of view, the dummy sensor signal may become a common failure mode.

Therefore, in order to improve the reliability of the dummy sensor signal itself, in particular,
This is necessary for an LPRM that is constantly operating in the output range. (IRM is only used at startup, but of course it is also meaningful to make the dummy sensor more reliable).

Therefore, as shown in FIGS. 9 and 10, a plurality of dummy sensors 1003 are arranged three-dimensionally within the reactor core.

Then, the purpose of use or the signal difference (Φ
T-ΦD) (for example, 6 channels of A
Dummy sensors located close to the LPRM connected to the PRM are grouped into several small groups, taking into consideration the following: Let this number be n. Assuming that dummy sensors belong to each of n groups, for these dummy sensors, (1) take the average value, (2) remove the maximum value or minimum value, (3) The average ΦD1 obtained by combining processing such as root mean square root calculation is determined by the averaging circuit 2000, and the difference signal is transmitted to M true sensors LPRM3 divided into specific n groups. Take. In other words, the highly reliable signal Φos(
i=1.2. ....

n) is used.

In the simplest case, approximately five dummy sensors are provided, the largest and smallest dummy sensors are discarded, the average of the remaining three is taken as the dummy sensor output ΦD, and the negative value component is cut. , a configuration such as subtracting from all first-stage amplifiers of LPRM, which is a true sensor, can be considered.

Furthermore, from the perspective of using a neutron flux instrumentation system that has taken these measures, even if the present invention can actually avoid unnecessary scrams during earthquakes and impacts,
There is a great need to know (a) whether a noise signal is also generated in the dummy sensor, and (b) where the noise signal is generated. Therefore, as shown in Figure 9,
The signal of dummy sensor D is converted to 'rt, T which is the true sensor.
Regardless of which point in 2 is subtracted from, the signal from the dummy sensor is also processed until the final stage, and the signal status is displayed as the processing progresses from Ao to Bo to Co in the figure. I'll do what I do. In the future, electronic circuit components will become increasingly smaller and packaged, and as manufacturing becomes more uniform, Ao, AI, A2 e Bo, B1, BZ t Co, CI, and Cz will become more and more popular in all aspects. It will be the same product. Conversely, some kind of noise
For example, if it occurs in Ao, there is a high possibility that it will occur in Ax. Therefore, if the state of each dummy sensor is displayed at the break of the calculation block, the number of sensors will be small, the cost will be low, and the location where noise is generated can be identified to some extent.

For example, even though display 3001 is at zero level, if there is a significant change in displays 3002 and 3003, an abnormal signal will be generated in calculation block Bo due to an earthquake or impact, and at this time display 3000 will also have a significant change. When a change is observed, it can be determined that an abnormal signal has also occurred in the equivalent calculation block B1.

In addition, although abnormal signals that were not at zero level were observed in any of the displays 3001, 3002, and 3003,
When there was no abnormality in the display 3000, an abnormality occurred in the sensor and cable side and the calculation block Ao, but with the present invention, there is a high possibility that unnecessary scrams could be avoided (block A o' .To identify whether it is block Ao or not, it is necessary to directly display the input signal of Ao, but this is often difficult because the signal is weak).

In the case of true sensor T2, it is very clear that 1 display 3003
The effect of the present invention can be confirmed when the display 3004 fluctuates rapidly even though there is an abnormality in the display 3001. , 3002. Displays 3001 and 3002 may be technically difficult and expensive, but it is best to at least add display 3003 to both true sensors TL and T2.

This is preferable in terms of confirming the effect.

Although the two sides of the IRM and LPRM of a BWR have been described as an example, the present invention can be applied in exactly the same way to an ex-core neutron instrumentation system or an in-core neutron instrumentation system of a pressurized watercolor reactor. It can also be applied to neutron instrumentation systems where the energy levels of the neutrons to be measured differ, such as heavy water reactors and fast breeder reactors. Specifically, in addition to the type of sensor that measures the ionization current of gas due to nuclear fission, which was taken up in this example, there are also sensors called self-powered sensors, but in short, various types of sensors can be used to A dummy sensor that is designed not to react to neutron flux, which is a physical quantity, may be used as a dummy sensor. Techniques for this purpose are usually very easy to implement. The present invention applies to all devices in which the signal from the dummy sensor is subtracted from the signal from the real sensor and the display method is performed based on this embodiment, depending on the characteristics of each instrumentation electronic circuit.

In particular, by monitoring the status of the dummy instrumentation system added for this purpose, it is possible to identify the noise generation site and further improve the IR
Regarding the M system, there is a possibility that the influence of gamma rays can be reduced.

〔Effect of the invention〕

According to the present invention, by providing an instrumentation system that does not cause unnecessary scrams due to noise, it is possible to improve the operating rate without impairing the safety of a nuclear power plant.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram of a neutron detector in a BWR core according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of the neutron detector, and Fig. 3 is an IR
M and electronic circuit diagram, Figure 4 is a front view of IRM operation and display panel, and Figure 5 is a neutron signal processing diagram. Figure 6 is a diagram of IRM insertion and transfer and fixed type, Figure 7 is LP
RM and an electronic circuit diagram, FIG. 8 is a sectional view of an LPRM string, FIG. 9 is an explanatory diagram of a dummy sensor group and a true sensor group, and FIG. 10 is an explanatory diagram of abnormality detection by dummy sensor monitoring. 2... IRM sensor, 3... LPRM sensor, 10
0...Dummy IRM sensor, 1003...Dummy L
PRM sensor. '$10 8 sweat days-u't f r-'pa

Claims (1)

[Claims] 1. A neutron instrumentation system characterized by providing a dummy sensor and subtracting the signal from the dummy sensor from the signal from the real sensor. 2. The neutron meter according to claim 1, wherein in the IRM, the locations for the subtraction are a preamplifier input point, or, a differential amplifier input point, or, an output amplifier input point, or, and a final output stage. Equipment system. 3. The neutron instrumentation system according to claim 1, wherein in LPRM, the location for the subtraction is at the input point of the amplifier and after the final output stage. 4. The neutron instrumentation system according to claim 1, wherein the subtraction location is the final output stage of the APRM. 5. The neutron instrumentation system according to claim 1, wherein a plurality of the dummy sensors are provided and averaging processing is performed among the dummy sensors. 6. In claim 1, the true sensors are divided into several groups, the dummy sensors are also divided into the same number of groups, averaging processing is performed within the groups, and the dummy sensors are paired with the group of true sensors. A neutron instrumentation system that is characterized by taking the difference at one point. 7. In claim 1, the signal from the dummy sensor is subjected to processing consisting of any one or a combination of negative value cutting, absolute value calculation, phase delay, amplitude gain adjustment, and damper. A neutron instrumentation system characterized in that the neutron instrumentation system is subtracted from the signal from the true sensor after aging. 8. The neutron instrumentation system according to claim 2, wherein the dummy sensor for the IRM region is fixed within the reactor. 9. The neutron instrumentation system according to claim 3, wherein the dummy sensor for the IRM is installed in the LPRM support tube. 10. In claim 2, adjusting the gain for the signal from the dummy sensor for the IRM,
A neutron instrumentation system characterized by having a calibration switch including a zero adjustment, etc., and a display of the results on an operation panel and a display panel. 11. The neutron instrumentation system according to claim 3, wherein the dummy sensor for the LPRM is provided in the LPRM support tube. 12. The neutron instrumentation system according to claim 3, wherein the signal from the dummy sensor for the LPRM is subtracted at the output stage of the APRM. 13. According to claim 12, the neutron is characterized in that the state is notified at the final stage and in the middle of the processing circuit from the dummy sensor, making it possible to identify the effect of the device and the abnormal noise generating part. Instrumentation system. 14. The neutron instrumentation system according to claim 2, wherein the dummy sensor is installed in the IRM so as to reduce background noise due to gamma rays. 15. In claim 3, when the gain of the amplifier circuit on the true sensor side in the LPRM is adjusted, the gain of the amplifier circuit on the dummy sensor side also changes in conjunction, and this can be confirmed. A neutron instrumentation system characterized by: