JPS6073364A - Wide range monitoring apparatus - Google Patents

Abstract

PURPOSE:To enable the monitoring of single output proportional to the logarithm of neutron flux changing over a wide range of 10 figures or more, by changing over two sets of measuring circuits having different measuring ranges. CONSTITUTION:Neutron flux detection output from a wide band amplifier 17 is supplied to the logarithmic ratio measuring circuit 23 in a low band side and the cambel measuring circuit in a high band side. A change-over judge circuit 25 compares respective outputs of circuits 23, 24 with a reference value considered in the hysteresis characteristics of comparators 251, 252 and a change-over circuit 26 is controlled through a logical circuit 253. By this mechanism, the circuit 23 or the circuit 24 is selected corresponding to detection output in the low band side or the high band side and single output proportional to the logarithm of neutron flux changing over a wide range of 10 figures or more can be monitored.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a device for monitoring the output of a nuclear reactor used in a nuclear power plant, etc. This invention relates to a device that monitors the output of a nuclear reactor by detecting neutron flux density.

[Technical background of the invention]

In this type of monitoring device, the output of the reactor changes over a wide range of more than 10 orders of magnitude when converted to the neutron medium density level when the reactor is started or stopped. It is necessary to monitor the neutron flux density, which varies over such a wide range. Because the area is too wide, it is impossible to measure the entire area with one measurement and monitoring technology, so we combined several four measurement and monitoring technologies with different monitoring ranges.
We are monitoring the entire area. For example, the entire monitoring range is divided into two parts, one of which uses pulse counting technology for the low neutron flux range, and the other high neutron flux range uses Campbell measurement technology, so that the range can be changed from the low power range of the reactor to the high power range. We are monitoring the entire area.

By the way, la is composed of one type of detector over a wide range.
Achieving monitoring using a type I monitoring device is beneficial not only in terms of the cost of reactor instrumentation but also in terms of facilitating operation and simplifying maintenance.

For this reason, Japanese Patent Publication No. 48-18436 discloses a device for generating a single output signal proportional to the logarithm of the neutron flux varying over a sufficiently wide range of neutron fluxes to require at least two different types of monitoring techniques. [Name: Gintom Pulse Monitoring Device (USP No. 3579127) There is a wide range monitoring device as shown in the publication.

This random pulse monitoring device has a configuration as shown in FIG.

A high voltage from a DC power source 14 is applied between a pair of electrodes 12@13 of the nuclear fission ion chamber 11 via an impedance element 15. The electrode 13 of the fission ion chamber 11 to which the impedance element 15 is connected provides an ionized signal to the input side of the broadband amplifier 17 via a capacitor 16 . The signal amplified by the broadband amplifier 17 is applied to a logarithmic counting channel 19 and a Campbell type channel 20 via a cable 18. This logarithmic counting channel 19 handles the low frequency side of the total measurement range divided into two, and consists of a high frequency bandpass filter amplifier 191 and a logarithmic count rate circuit 192.
A logarithmic count rate circuit 192 outputs a signal proportional to the logarithm of the incident neutron flux level as a channel output. Furthermore, the Campbell type channel 20 is a channel that handles the high frequency side of the total measurement range divided into two, and includes a high frequency bandpass filter amplifier 201, an average rectifier circuit 203, and an amplifier 2 that outputs a signal proportional to the logarithm.
03, the input signal amplified by the high frequency band simple wave amplifier 201 from the differential amplifier 2 fl 4 has an average of -1! After being detected by the flow circuit 202, it is converted into a signal proportional to the incident neutron flux level by the logarithmic amplifier 203, and the bias voltage 20
5 and the difference is taken by a differential amplifier 204, and the differential amplifier 2
From the output side of 04, it is zero when the input is less than the counting rate corresponding to the bias voltage, and when the input is more than the counting rate, the differential amplifier 20
The output of 4 becomes the output of the channel. The output signal of each channel is input to the coupling circuit 21. This coupling circuit 2
1 adjusts the proportional relationship of the output of each channel to the incident neutron flux level to be the same, and as a result of the adjustment, a predetermined count is calculated at a predetermined count rate value in a region where the output of the logarithmic counting channel and the output of the Campbell type overlap in the linear region. The output of the logarithmic counting channel above the counting rate value is clamped at a constant level of 1%, and the bias of the differential amplifier is adjusted so that the output is cut off below the predetermined counting rate value. By adding the output of the Campbell type channel, an output is obtained from this connection point 211 in which the output of the logarithmic counting channel and the output of the Campbell type are connected in a connected manner.

Next, the operation of the wide range monitor device configured as described above will be explained.

The DC component of the output from the nuclear fission ion chamber 11 is cut off by a capacitor 16, and the output is applied to the input sides of a logarithmic count rate channel 19 and a Campbell type channel 20. The logarithmic count rate channel 19 outputs a signal proportional to the neutron flux density up to a certain value (FIG. 22). When the neutron flux density value is exceeded, a loss in output voltage occurs due to pulse resolution counting loss, and as the neutron flux density value increases, the output voltage decreases.

It exhibits characteristics as shown in FIG. 2A.

The output from the Campbell-shaped channel 20 is shown in FIG.
2 (same as the value 22 in Figure 2), an output signal proportional to the neutron flux density value can be obtained; however, below this neutron flux density value, circuit noise or backlash may occur. Due to ground radiation noise, etc., a portion that is not proportional to the neutron flux occurs. It exhibits characteristics as shown in FIG. 3B.

Therefore, in the area where the measurement areas of the logarithmic counting channel and the Campbell type channel overlap in a straight line, it is possible to maintain a predetermined neutron flux without causing the phenomenon of pulse resolution loss and without the influence of circuit noise and background radiation interference. (22 neutron flux values in Figures 2 and 3) are determined,
The coupling circuit 2 uses this predetermined neutron flux value as a boundary, and the lower one is the sum of the output of the logarithmic counting channel (Fig. 2 A) and the zero signal of the differential amplifier (Fig. 3 B), which is the cutoff (Fig. 3 B). Fourth
Figure A) is output, and the higher one is the output of the logarithmic counting channel clamped to a predetermined level (Figure 2, 23), plus the output of the Campbell channel whose cut-off has been released (Figure 3 B). 4B), it became possible to continuously measure a wide range of measurement areas, from the measurement area of the logarithmic channel to the measurement area of the Campbell channel. Note that the neutron flux value of 22 in Figure 4 is 22 in Figures 2 and 3.
shows the same value as .

However, this type of wide-range neutron monitor suffers from (a) abnormalities in the indicated output due to a decrease in the output of the logarithmic counting circuit in the high neutron flux range, and (b) noise due to high levels of background gamma rays after reactor shutdown. Abnormality in the indicated output (C) There are problems such as failure to monitor the rate of increase in reactor output.

In other words, regarding problem (a), if the neutron flux level increases further, there is a region where the output voltage of the logarithmic counting channel decreases from the rising direction to the falling direction due to resolution 6 counting loss, as shown in Figure 2A. . When the level falls below the predetermined clamp level (Figure 2, 23), the clamp function no longer works, and as the neutron flux increases, the output of the logarithmic count rate channel changes as shown in Figure 4, A1. show. As a result, the output characteristic of the coupling circuit 21 becomes a response as shown in FIG. 4A-B-B, and there are parts that are not proportional to the neutron flux value. If the ratio is lost, the reactor's output may not be able to be monitored.

Regarding problem (b), if a nuclear reactor is operating at rated power and then shuts down, immediately after that the neutron flux level decreases rapidly, but the background gamma ray level is very high, and this high back Due to the noise caused by ground gamma rays, the output of the Campbell channel cannot drop below a certain noise level as shown in Figure 3 B2, and it is no longer cut off below the expected neutron flux level, so the effect of this is on the coupling circuit. appears on the output side of Naturally, the output/signal of the coupling circuit 21 immediately after the nuclear reactor is shut down will exhibit a response different from the actual neutron flux level as shown in FIG. 4, 83-H. In particular, the output-neutron flux characteristic curve no longer shows a proportional relationship near the planned neutron flux value.

Regarding problem (C), generally when starting up a nuclear reactor, 11
, changing the neutron flux at a subsidized rate of increase.

If there is a sudden change in the reactor power during this rise, it will interfere with the operation of the reactor, so the rate of change (period) of the neutron flux is monitored, and if there is a sudden change more than planned, the nuclear Furnace protection measures are taken, including furnace scram. Wide range neutron monitors are also required for period monitoring. Therefore, a given neutron level and power level that is intended to be switched from the first intermediate signal to the second intermediate signal or vice versa is required to be the same one neutron flux level.

However, in the conventional device, the setting level 22 for limiting the output voltage of the first logarithmic counting channel as shown in FIG. 2A and the setting level 22 for blocking the second intermediate signal as shown in FIG. //, 22///, and exhibits a characteristic in which the output voltage is not proportional to the logarithm of the neutron flux at a certain predetermined neutron flux level. In other words, if the values of the planned neutron flux levels of the two intermediate signal limits are different as shown in Figure 5, the rate of increase in the actual reactor power is constant between these levels as the neutron flux level increases. Even if there is, the period monitoring output will respond as if the neutron flux level has not changed.

If there is such a deviation, there is a drawback that when the reactor output fluctuates at a slow rate near the planned level as shown in FIG. 6, the waveform of the fluctuation cannot be faithfully reproduced.

〔the purpose〕

The present invention eliminates the above drawbacks and provides a wide iNiλ of more than 10 orders of magnitude.
The object of the present invention is to provide a wide range monitoring device that obtains a single output proportional to the logarithm of the neutron flux varying over the range.

Another object of the present invention is to provide a wide range monitor device that switches from a count rate circuit to a Campbell circuit without having a non-direct storage part and obtains a single output over a wide range of one () digit or more. .

Another object of the present invention is to provide a wide range monitor device capable of monitoring periods with a single output from the count rate circuit to the Campbell circuit without discontinuous characteristics.

[Summary of the invention]

In a wide range monitor device that obtains a single output over a wide range of 10 digits by switching between a logarithmic counting circuit and a Campbell measurement circuit, the output of the logarithmic counting circuit is compared with a voltage corresponding to the first neutron flux value. , a first comparison circuit that outputs the comparison signal and the output of the Campbell measurement circuit are compared at a voltage corresponding to a second neutron flux value that is slightly near the first neutron flux and smaller than the first neutron value. , a second comparator circuit that outputs a comparatively determined signal and a comparison determination signal of the first and second comparison circuits are input, and the output of the logarithmic counting circuit is equal to or higher than the voltage corresponding to the first neutron flux value. a logic determination circuit that outputs a switching signal to the Campbell measurement circuit side such that the output of the Campbell measurement circuit is less than or equal to the pressure corresponding to the second neutron flux value, the switching signal is switched to the logarithmic counting circuit side. and a switching circuit which inputs the output of the Campbell measurement circuit and the output of the logarithm a1'' number circuit, and selects and connects each input side to the output side using the switching command signal, and when the reactor output increases, The output of the logarithmic counting circuit is switched to the output of the Campbell measurement circuit at the first neutron flux value, and when the reactor output decreases, the output of the Campbell measurement circuit is switched to the output of the Campbell measurement circuit at the second neutron flux value, which is lower than the first neutron flux value. Each objective was achieved by switching between the Campbell measurement circuit and the logarithmic counting circuit while maintaining hysteresis.

An embodiment of the present invention will be described in detail below with reference to the drawings. Components having the same functions as those in the circuit configuration shown in FIG. 1 will be described with the same numbers assigned.

In FIG. 7, a high voltage is applied between an anode 13 and a cathode 12 by a DC power supply 14 via an impedance element in a neutron flux detector 11 for detecting neutron flux in a nuclear reactor. The signal of the neutron detector 11 generated in the impedance element is supplied to the input side of the broadband amplifier 170 via the capacitor 16 that cuts the DC component. This broadband decrease/increase 1
The output side of the corner unit 17 is connected via a cable 18 to a logarithmic counting circuit 2 which receives the low frequency side of the two divided measurement ranges.
The neutron detector 1
Amplify and supply the output of 7.

The logarithmic counting circuit 23 includes a pulse amplifier 231 that amplifies the output of the broadband amplifier 17, and a logarithmic counting ratio device 232 that inputs the output of the pulse amplifier 231, calculates the logarithm of the output signal, and outputs a signal proportional to the neutron flux. , and a variable gain amplifier 233 that amplifies the output of the logarithmic counting converter 232 and outputs the output of the logarithmic counting circuit 23.

The output of this logarithmic counting circuit 23 with respect to the input neutron flux has characteristics as shown in FIG. 2A, and the neutron flux level value 2
It has a low frequency measurement range of 2 or less. Note that logarithmic counting circuit 2
3 is a variable gain amplifier 233 whose output is adjusted to match the input/output characteristics of the Campbell measuring circuit 24 with respect to the neutron flux.

The Campbell measuring circuit 24 is a high frequency band amplifier 24 that amplifies only high frequency components of the output of the wide band amplifier 17.
1. A root mean square circuit 242 that inputs the output of this 24-frequency band bandwidth filter 241, calculates the root mean square of the input signal, and outputs the result.
, a logarithmic conversion circuit 243 that inputs the output of the mean square circuit and takes the logarithm of the input, a circuit 244 that shifts the output level of the logarithmic conversion circuit, and a variable gain DC amplifier 245 that amplifies the level-shifted logarithmic signal. The output side of the variable gain DC amplifier 245 obtains a signal with the characteristics shown in FIG. 3 for the input neutron flux. Shift, variable gain 1 is flow'9
It is possible to vary the slope of the output of the Campbell measurement circuit with respect to the neutron flux by the gain of the Kabata device 245, and to match the input/output characteristics of the logarithmic counting circuit 23.

The switching determination circuit 25 has hysteresis and can vary the hysteresis width, and has a predetermined neutron flux level value 22 (
A first comparator that increases the ratio of the voltage signal and the output of the logarithmic counting circuit 23 by +1, which corresponds to the value obtained by adding hysteresis (Fig. 2, Fig. 3 22) and hysteresis 1 G (Fig. 8 31). 251, which has hysteresis and whose hysteresis width can be varied, and which corresponds to a value obtained by subtracting the hysteresis width value from a predetermined neutron flux level value 22 (FIG. 8, 32), is compared with the output of the Campbell measurement circuit 24. The outputs of the second comparator 252 and each comparator are input, and when the output of the logarithmic counting circuit is rising, the output of the logarithmic counting circuit 23 is the value obtained by adding hysteresis to the voltage signal for a predetermined neutron flux level. When the output of the Campbell measuring circuit 24 is falling, the first switching signal for switching from the logarithmic counting circuit side to the Campbell measuring circuit side is set by subtracting the hysteresis width from the voltage value corresponding to the predetermined neutron flux level. It consists of a logic circuit 253 that outputs a second switching signal for switching the subtracted value from the Campbell measuring circuit 24 to the logarithmic counting circuit 23 measurement when the output of the Campbell measuring circuit 24 is in the upper range;
When the output of the logarithmic counting circuit 23 rises, the switching point is 2 in Figure 2.
The neutron flux at the switching point is switched from the logarithmic counting circuit to the Campbell measurement circuit at a value larger than the neutron flux value 2 by the hysteresis width, and when the output of the Campbell measurement circuit decreases, the neutron flux 1i at the switching point is increased by the hysteresis width. Switching is made from the Campbell measuring circuit to the logarithmic counting circuit at a neutron flux value as small as possible.

[(II) The switching circuit 26 which receives the first and second switching signals of the switching determination circuit 23 and performs the switching operation receives the output signal of the logarithmic counting circuit 23 at its first input terminal and the Campbell measurement signal at its second input terminal. The output signals of the circuit 24 are respectively inputted, and these input terminals are selectively connected to the switching command trace output j':14 of the switching determination circuit 25.

The DC amplifier 27 which inputs the output of the off-I external circuit 26 sends the output to the wide range monitor output terminal 28 and the period circuit 2.
90 input side, and supplies the output of the period circuit 29 to the period end Qm 3 U.

The operation of such a circuit configuration will be explained below with reference to FIG.

The logarithmic counting circuit 23 outputs a second signal corresponding to the neutron flux level.
As shown in Figure A, a signal with an output characteristic curve is output which is logarithmically proportional up to the neutron flux level of @1o8, becomes saturated at the neutron flux level of 108 or more, and then decreases.

The Campbell measurement circuit 24 outputs a signal with an output characteristic curve that corresponds to the neutron flux level and becomes nonlinear below the neutron flux level of 108 as shown in Figure 3B, and is logarithmically proportional when the neutron flux level exceeds 108. be done.

A predetermined neutron flux level in the overlapping region of the output characteristic curves of the logarithmic counting circuit 23 and the Campbell measuring circuit 24 in the 1M11M region, for example, 108 neutron flux level value 2
2, the gain of the logarithmic counting circuit 23, the shift amount of the Campbell measuring circuit 24, and the gain are respectively adjusted so as to match the characteristic curve A-B in FIG.

When the neutron flux level value tends to increase, the switching determination circuit 25 determines the voltage value corresponding to the neutron flux level obtained by adding a hysteresis width to the point 22 of the predetermined neutron flux level (see FIG.
1) and the output of the logarithmic counting circuit are compared in the first comparator 251, and when the output of the logarithmic counting circuit exceeds the voltage corresponding to the predetermined neutron east level plus the hysteresis width value, the output of the switching circuit 26 is compared. The output terminal connected to the first input terminal can be switched to the second input terminal. In the case of a downward trend, the voltage corresponding to the neutron flux obtained by subtracting the hysteresis width from the predetermined neutron flux level is compared with the output of the Campbell measurement circuit in the second comparator 252, and when the output of the Campbell measurement circuit falls below that voltage, the switching circuit is activated. The output end connected to the second input end of the output terminal is switched and connected to the first input end.

Therefore, the switching level of the switching circuit 26 is different when the reactor output increases and when the reactor output decreases.

That is, the switching determination circuit 25 provides hysteresis at the switching point. Avoid switching with hysteresis in this way; if the difference between the switching level of the Campbell measurement circuit and the switching level of the logarithmic counting circuit is within the hysteresis width, it will be absorbed by this hysteresis effect, and the difference in switching level will be absorbed. No influence appears on the output side of the switching circuit. Similarly, the influence of background radiation can also be removed if it is within the hysteresis width. Furthermore, at high neutron flux levels where the output of the logarithmic counting circuit decreases, whether or not to switch is determined by the output level of the logarithmic counting circuit when the reactor output increases, and by the output level of the Campbell measurement circuit when the reactor output decreases. Since each determination is made, even if a resolution loss phenomenon occurs in the neutron detector, its influence can be completely eliminated.

As a result, at the output end of the switching circuit, a logarithmic counting circuit and a Campbell measuring circuit are combined, and a logarithmically proportional 101
A linear and continuous neutron flux-output voltage characteristic over 0 digits was obtained. In particular, since there are no discontinuities at switching points, it has become possible to accurately measure the waveform of fluctuations in the reactor's output.

As described above, the present invention makes the linear regions of the outputs of the logarithmic counting circuit and the Campbell measurement circuit, which take the logarithm of the output of the neutron detector, match a predetermined linear equation, and the switching determination circuit is configured to , the output of the logarithmic counting circuit is used when the reactor output increases, and the output of the Campbell measurement circuit is used when the output decreases to switch the neutron flux level values, and the switching circuit is configured to switch with hysteresis. Abnormality in the indicated output due to a decrease in the output of the logarithmic count rate circuit in the high neutron flux range,
2. Abnormality in instruction output due to noise caused by background gamma rays in high l novels after reactor shutdown, 3. Problems in monitoring the rate of increase in reactor power; 4. It has the effect of eliminating abnormalities in the indicated output caused by the difference in the neutron flux-output/voltage characteristics between the logarithmic counting circuit and the Campbell measurement circuit, and has a remarkable effect in monitoring the neutron flux level that liquefies over 1010 orders of magnitude. play.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional random pulse monitoring device;
3, 4, 5, and 6 are diagrams for explaining the operation of the random pulse monitoring device shown in FIG. 1, and FIG.
This figure shows the circuit configuration of the wide range monitor device of the present invention, and FIG. 8 is a diagram for explaining the operation of the wide range monitor device of FIG. 7. Engineering 1 - Neutron detector 17 - Broadband amplifier 23... Logarithmic counting circuit 231 Pulse amplifier 232 - Logarithmic counting rate circuit 233 Variable gain amplifier 24 - Campbell measurement circuit 241 Frequency band amplifier 242... Root mean square circuit 243... - Logarithmic conversion circuit 244... Shift circuit 245 Variable gain DC amplifier 25 - Switching determination circuit 251 - First comparator 252... Second comparator 253... Logic circuit 261... Switching circuit 271 - DC amplifier 29.・Period circuit patent attorney Kensuke Norichika and one other person 102 104 101+ 10" 10101 (+1
21014 Neutron East - Neutron East - Figure 4 Neutron flux - Figure 5 +o2 +o4 +o6 108 101010121
(114 Neutron East No. 6 Figure 10210110610810I01012101・1
Neutron East Procedural Amendment (Spontaneous) 86W5?3, -y Director General of the Japan Patent Office 1 Display of the case Patent Application No. 180485/1985 2 Name of the invention Wide range monitor device 3 Relationship with the tampering case Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. 4, Agent Address: 1-i-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo 100 Tokyo Shibaura Electric Co., Ltd. Tokyo Office Specification and drawings 6 Description of contents 1, Invention Name: Wide Range Monitoring Device 2, Claims The output of the neutron detector is input to a logarithmic count rate measurement circuit and a Campbell measurement circuit that have different neutron measurement ranges and output signals proportional to the logarithm of the neutron flux. , selects the output of the logarithmic count rate measurement circuit when the neutron flux is less than a predetermined neutron flux in the overlap section of the linear region proportional to the logarithm of the neutron flux, and selects the output of the Campbell measurement circuit when the neutron flux is greater than the predetermined neutron flux, and converts it into the logarithm of the neutron flux. In a device that selectively outputs a linearly proportional and continuous single signal, a second judgment level 'T'l'- having a hysteresis characteristic and corresponding to the output of the logarithmic count rate measuring circuit and a predetermined neutron flux a first comparator that outputs a first discrimination signal that is compared with a value obtained by increasing or decreasing a signal corresponding to a signal corresponding to a signal corresponding to a sexual threat, and an output of the Campbell measurement circuit and the neutron detector; a second comparator that outputs a second determination signal that is compared with a second determination level for determining the resolution counting area; a first determination signal;
Logic that manually inputs the second discrimination signal and outputs the first selection signal when the content of the discrimination signal is smaller than the 7 judgment level, and outputs the second selection signal when at least one of the discrimination signals has the content larger than the judgment level. input the output of the logarithmic count rate measuring circuit and the output of the Campbell measuring circuit, and output the output of the logarithmic count rate measuring circuit when the first selection signal is received, and output the output of the Campbell measuring circuit when the second selection signal is received. A wide range monitor device characterized by comprising a switching circuit connected to the side. 3. Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a device for monitoring the output of a nuclear reactor used in a nuclear power generation shed, and particularly relates to a device for monitoring the output of a nuclear reactor used in a nuclear power generation shed, and in particular to a device for monitoring the output of a nuclear reactor used in a nuclear power plant. This invention relates to a device that monitors the output of a nuclear reactor by detecting neutron flux density. [Technical Background of the Invention] This type of monitoring device needs to monitor the neutron flux density, which changes over a wide range by more than 10 orders of magnitude when the reactor power is converted to the neutron flux density level during reactor startup and shutdown. be. Since it is impossible to measure the entire area with a single measurement and monitoring technique, several measurement and monitoring techniques with different monitoring ranges are combined to monitor the entire area. For example, in a BWR start-up region monitoring system, the entire monitoring range is divided into two, one of which uses pulse counting technology for the low neutron flux range, and Campbell measurement technology for the other high neutron flux range, and the reactor The entire area from the low output area to the high output area is monitored. Achieving monitoring over a wide area with one type of monitoring device consisting of one type of detector is beneficial in terms of reducing the cost of reactor splitting, making operation easier, and simplifying maintenance. be. This requires at least two different monitoring techniques7'! , as a device for generating a single output signal proportional to the logarithm of the neutron flux varying over a sufficiently wide range of neutron fluxes, is disclosed in Japanese Patent Publication No. 18436/1989 (named Rantom Pulse Monitoring Device (USP No. 3,579,127)).
There is a wide range monitor device as shown in the publication. This random pulse monitoring device has a configuration as shown in FIG. A high voltage from a DC power supply 14 is applied between a pair of electrodes 12 and 13 of the nuclear fission ion chamber 11 via an impedance element 15. The electrode 13 of the fission ion chamber 11 to which the impedance element 15 is connected provides an ionized signal to the input side of the broadband amplifier 17 via a capacitor 16 . The signal amplified by broadband amplifier 17 is transmitted via cable 18 to logarithmic rate channel 19 and Campbell type channel 20. This logarithmic argument rate channel 19 is for the low frequency side of the total measurement range divided into two, and is amplified by the high frequency band filter amplifier 191 and the logarithmic count rate circuit 192. The input pulse signal is logarithmized by a logarithmic count rate circuit 192, and a signal proportional to the logarithm of the pulse argument rate of incident neutrons is output as a channel output. Additionally, the Campbell-shaped channel 20 covers the entire measurement range by 2
A high frequency band filter amplifier 201, an average rectifier circuit 202, an amplifier 203 which outputs a signal proportional to the logarithm, and a differential amplifier 204, which handles the high frequency side of the divided components, are amplified by the high frequency band filter amplifier 201. The input signal is detected by an average rectifier circuit 202 and then sent to a logarithmic amplifier 203.
It is converted into a signal proportional to the logarithm of the incident neutron flux, and the difference with the bias voltage 205 is taken by the differential intensifier 11 @ device 204.
This is the output of Chang Yi Lu. The output signals of each channel are input to the coupling circuit 21. This coupling circuit 21 adjusts the proportional relationship of the output of each channel to the logarithm of the neutron flux so that it coincides with a straight line proportional to the logarithm. For example, at a predetermined count rate value in the area where the and the neutron flux (nv) overlap in the linear region, the output of the logarithmic rate channel that is above the predetermined count rate value is clamped at a predetermined level and cut below the predetermined count rate value. adjusting the bias 205 of the differential amplifier 204 of the Campbell type channel to the off state, and summing the output of the logarithmic rate channel and the output of the Campbell type channel at a coupling point 211;
From this coupling point 211, an output signal is obtained in which the output of the logarithmic rate channel and the output power of the Campbell type channel are sequentially combined. Next, the operation of the wide range monitor device configured as described above will be explained. The DC component of the output from the nuclear fission ion chamber 11 is cut off by a capacitor 16, and the output is applied to the input sides of a logarithmic count rate channel 19 and a Campbell type channel 20. The logarithmic ratio channel 19 outputs a signal proportional to the logarithm of the neutron flux up to a certain neutron flux density value (see FIG. 22). When the neutron flux value is exceeded, a loss of output voltage occurs due to the effect of pulse resolution counting loss of the fission ion chamber, and as the neutron flux value increases, the output voltage decreases. It exhibits characteristics as shown in FIG. 2A. The output from the Campbell-shaped channel 20 is shown in FIG.
2 (same as the value 22 in Figure 2), an output signal proportional to the logarithm of the neutron flux value can be obtained, but below this neutron flux value, circuit noise, background radiation noise, etc. Therefore, there is a part that is not proportional to the neutron flux. It exhibits characteristics as shown in FIG. 3B. Therefore, in the region where the measurement regions of the logarithmic count rate channel and the Campbell type channel overlap in the straight section, a predetermined number of neutrons can be measured without causing the phenomenon of pulse resolution count loss and without being affected by circuit noise or background radiation noise. The flux value (22 neutron flux values in the third picture of Fig. 2) is determined, and the coupling circuit 21 uses this predetermined neutron flux value as a boundary, and the lower one is the output of the logarithmic count rate channel (Fig. 2 A).
The sum (Fig. 4 A) of the zero signal of the differential amplifier (Fig. 3 B) which becomes the cutoff is output, and the higher one is a predetermined level (the second
By outputting the sum (Fig. 4 B) of the output of the Campbell type channel whose cutoff has been canceled (Fig. 3 B) to the output of the logarithmic count rate channel clamped in Fig. 23), the logarithmic count rate channel is The measurement area was wide ranging from the measurement area of the ratio channel to the measurement area of the Campbell-shaped channel. Note that the neutron flux value of 22 in Figure 4 is 22 in Figures 2 and 3.
shows the same value as . However, this type of wide-range monitor device has the following problems: (a) Abnormality in the indicated output due to a decrease in the output of the logarithmic ratio circuit in the high neutron flux range (b) High-level backland γ after /i; Abnormality in the command output due to noise caused by the line (C) There are problems such as a failure to monitor the rate of increase in reactor output. In other words, regarding problem (a), if the neutron flux level increases further, the output voltage of the logarithmic count rate channel will decrease from the increase due to the resolution side number loss of the fission ion chamber, as shown in Figure 2A. The area decreasing in the direction is left and right. When the clamp level falls below a predetermined clamp level (Figure 2, 23), the clamp function does not work, and as the neutron flux increases, the response as shown in Figure 4 A1 occurs in the logarithmic count rate channel. The output shows. As a result, the output characteristic of the coupling circuit 21 does not respond as shown in FIG. 4A-B-B1, and there are portions where the neutron flux is high and is not proportional to the neutron flux value. If the ratio was lost, there was a risk that the reactor's output could no longer be monitored. Regarding problem (b), if a nuclear reactor is operating at rated power and then shuts down, immediately after that the neutron flux level decreases rapidly, but the background gamma ray level is very high, and this high back As shown in Fig. 3 B2, the output of the Campbell channel, which eliminates the noise caused by ground gamma rays, is below the predetermined neutron flux (Fig. 3 22).
The noise level will not drop below a certain level, and the neutron flux will not be cut off below the planned neutron flux level.
The effect appears on the output side of the coupling circuit. Nature,
The output signal of the coupling circuit 21 immediately after the reactor is stopped is shown in Figure 4B.
The response will be different from the actual neutron flux level as shown in 3-B. In particular, the output-neutron flux characteristic curve no longer shows a proportional relationship near the planned neutron flux value. Regarding problem (c), generally when starting up a nuclear reactor, the neutron flux is changed at a predetermined rate of increase. If there is a sudden change in the reactor power during this rise, it will interfere with the operation of the reactor, so the rate of change in neutron flux (period) is monitored, and if there is a sudden change more than planned, the reactor Reactor insurance measures including scram will be taken. Wide range monitoring devices are also required to perform beriod monitoring. A certain neutron level and power level intended to switch from the first intermediate signal to the second intermediate signal or vice versa is required to be the same one neutron flux level. However, in the conventional device, the setting level 22 for limiting the output voltage of the first logarithmic rate channel as shown in FIG. 2A and the setting level 22 for cutting off the second intermediate signal as shown in FIG. ', 22'' (Figure 5)
The output voltage is not proportional to the logarithm of the neutron flux at a certain planned neutron flux level. In other words, if the values of the planned neutron flux levels of the two intermediate signal limits are different as shown in Figure 5, the rate of increase in the actual reactor power will be constant as the neutron flux level increases between these levels. However, the period monitoring output is
It responds as if the neutron flux level had not changed. If there is such a discrepancy, there is a drawback that when the reactor output fluctuates at a slow speed near the planned level as shown in Figure 6, it is not possible to faithfully reproduce the fluctuations. . [Objective] The present invention eliminates the above drawbacks and provides a wide range monitor that switches between two measurement circuits with different measurement ranges and obtains a single output proportional to the logarithm of the neutron flux, which varies over a wide range of more than 10 orders of magnitude. The goal is to provide equipment. Another object of the present invention is to switch the count rate measuring circuit and the Campbell measuring circuit with hysteresis at the time of switching.
The object of the present invention is to provide a wide range monitor device that can obtain a single output over a wide range of orders of magnitude or more. [Summary of the present invention] The present invention determines a neutron flux level of, for example, 108 nV at which the output linearity region of the logarithmic count rate measurement circuit and the output linearity region of the Campbell measurement circuit overlap, and corresponds to this neutron flux. Predetermined for the first judgment level! The first judgment signal obtained by comparing the obtained 116 and the output of the divisor ratio measurement circuit with hysteresis corresponds to a neutron flux larger than the neutron flux at the first judgment level. Second to do
The value obtained by adding or subtracting a predetermined voltage to the judgment level is combined with the second judgment excitation signal obtained by comparing the output of the Campbell measurement circuit with hysteresis, and the result is determined when a predetermined logical formula is satisfied. Since the configuration is configured so that the output of the logarithmic count rate measuring circuit or the output of the Campbell measuring circuit is selected according to the logical expression, the Campbell measuring circuit is disconnected when measuring the logarithmic count rate measuring circuit, thereby reducing noise caused by background RFG. I was able to make it unaffected. Furthermore, the output of the logarithmic count rate measuring circuit no longer becomes the output of the wide range monitor in a neutron flux range of 1010 or more, for example, where the output of the logarithmic count rate measuring circuit decreases depending on the resolution counting results. Furthermore, the present invention has a hysteresis characteristic that switches between the output of the logarithmic count rate measurement circuit and the output of the Campbell measurement circuit at a neutron flux of, for example, 108, so that the neutron flux is 10? Even vertical fluctuations in the vicinity are absorbed as long as they are within the hysteresis range, making it possible to faithfully reproduce the fluctuations in the reactor's neutron flux on the output side. An embodiment of the present invention will be described below with reference to the drawings of FIGS. 7 and 8. Components having the same functions as those in the circuit configuration shown in FIG. 1 are given the same numbers, and the description thereof will be omitted. In FIG. 7, a high voltage is applied between an anode 13 and a cathode 12 by a DC power supply 14 via an impedance element 15 in a neutron flux detector 11 that detects neutron flux in a nuclear reactor. Neutron detector 1 generated in impedance element 15
The signal No. 1 is supplied to the input terminal of a broadband amplifier 17 via a capacitor 16 that cuts the DC component. The output side of this wide bandwidth 1 separator 17 is connected via a cable 18 to a logarithmic count rate measuring circuit 23 which has the low frequency range of the entire measurement range divided into t2 and a high frequency range of the divided into 2 parts. It is connected to each input side of the Campbell measuring circuit 24 in charge, and amplifies and supplies the output of the middle 17 tron detector) d-. The front 6 self-logarithmic count rate measuring circuit 23 includes a pulse amplifier 2311 that amplifies the output of the wideband amplifier 17; a logarithmic count rate unit 232 that inputs the output of this pulse amplifier 231 and outputs a signal proportional to the logarithm of the input signal; , amplifies the output of this logarithmic counting rate meter 232, and outputs the logarithmic counting rate measuring circuit 23.
It consists of a variable gain amplifier 233 which outputs an output from the variable gain amplifier 233. This logarithmic count rate measuring circuit 23 has characteristics such that the output with respect to the input neutron flux has the characteristics as shown in FIG. 2A (indicated by a solid line), and the neutron flux level 22 in FIG. The same value is taken.) With the following low frequency measurement range, the logarithmic count rate measurement circuit 23 calculates the output with respect to the neutron flux to the gain of the variable gain amplifier 233 40 t ;A. The input/output characteristics are made to match on a straight line proportional to the logarithm expressed by the part A in the equation shown in FIGS. The Campbell measurement circuit 24 receives the neutron flux 22 or more in FIG. A root mean square circuit 242 that takes the root mean square of and outputs it, a logarithmic conversion circuit 243 that inputs the output of this root mean square circuit and takes the logarithm of the input, and an output of the logarithmic conversion circuit 243') E level kfc
The circuit 244 for shifting and the variable gain DC amplifier 245 for amplifying the level-shifted logarithmic signal are connected to the neutron flux input to the output side of the variable gain DC amplifier 245 in FIG. 3B (shown by a solid line). ), the output of the Campbell measurement circuit 24 is shifted in the vertical direction by the shift circuit 244 (FIG. 4B), and the gain of the variable gain DC amplifier 245 is used to obtain a signal with the characteristics shown in FIG. The outflow characteristic τ is completely variable with respect to the neutron flux of the circuit, and the outflow characteristic τ
Match. The reversal determination circuit 25 has a hysteresis characteristic and applies a predetermined voltage (hysteresis width value) to the voltage value of the first determination level corresponding to the neutron flux level 1 shift 22 (22 in the Jz diagram and FIG. 3). Karo, subtraction 9' negative pressure and logarithmic count rate measurement circuit 23
When comparing the output of
The determination signal that indicates that the output of the logarithmic count rate measuring circuit is large when the value is large (Fig. 8, 31) is determined when the neutron flux falls below a value of 108 or more and is smaller than the predetermined neutron flux (Fig. 8, 22). A first comparator 251 outputs a comparatively determined signal in which the output of the logarithmic count rate measuring circuit is small when the value (32 in FIG. 8) is reached, and a first comparator 251 has a hysteresis characteristic and has a predetermined neutron flux (22 in FIG. 8). The voltage and Campbell measurement circuit 24 are obtained by adding or subtracting a predetermined voltage to the voltage at the second judgment level corresponding to the neutron flux level (shown in the figure) that is one or two orders of magnitude larger than
A second comparator 252 compares the output with hysteresis and outputs a signal that determines whether or not it is in the pulse resolution count value region. The first comparator 251 assumes that the output of 23 is small.
When the comparative discrimination signal from the second comparator 252 and the output of the Campbell measuring circuit 24 are all input, the first switching signal is set, and when the output of the logarithmic count rate measuring circuit 23 is large. The switching circuit 26 receives the first and second switching signals of the switching determination circuit 25 from the first comparator 251 to perform switching operation, and the switching circuit 26 receives the output signal of the logarithmic count rate measuring circuit 23 at its first input terminal, Input the output signal of the Campbell measuring circuit 24 to the input terminal seven times, m1
When the switching signal is given, the first input terminal is set to the output terminal, and when the second switching signal is given, the second input terminal is set to the output terminal.
In accordance with the switching command from the switching determination circuit 25, the output terminal V and the input terminal are selectively connected to each other so that the flow is switched. The DC sweeper 27 which receives all the outputs of the switching circuit 26 has its output connected to the wide range monitor output terminal 28 and the input side of the period circuit 29, and supplies the output of the rL1 period circuit 29 to the period output terminal 30. The circuit configuration will be described below with reference to FIG. 8. The logarithmic count rate measuring circuit 23 outputs a second signal corresponding to the neutron flux.
A signal proportional to the logarithm of the neutron flux is output from 101 to 109 as shown in Figure A (actual), and that 10
When the value exceeds 9, the influence of the pulse resolution counting loss of the neutron detector appears, and a signal is output which is not proportional to the logarithm and has an output characteristic that decreases after being saturated at a certain neutron flux. From the Campbell measurement circuit 24, corresponding to the neutron flux, as shown in Figure 3B (actual #), the neutron flux is less than about 106, which is less than the number of neutrons, and the neutron flux is more than 106. When this happens, an input/output characteristic curve is shown in which a signal proportional to the logarithm of the neutron flux is output. Because of the necessary force to make these direct storage parts coincide with the straight line of the functional formula of the ratio second u to the logarithm of the neutron flux, in the ta dimension-counting rate measurement circuit 23, - A gain of 233 is applied to the Campbell tailgate path 24, and the shift level of the shift circuit and the gain of the DC amplifier 24 are
The adjusted gain of 5 coincides with the straight line represented by A-B in FIGS. 4 and 8. The region from 1ψ to 109 at the bottom of the input/output characteristic curve of the Campbell measuring circuit and the region from 106 to 1゛09 at the top of the input/output characteristic curve of the logarithmic count rate measuring circuit are 1.
overlap over the range 06 to 109. Campbell dil1 that partially overlaps like this
The output of the foot circuit and the output of the logarithmic count rate measuring circuit are provided to a switching determination circuit 25 and a switching circuit 26. This switching judgment circuit 25 uses a first comparator 252 to determine d>1 corresponding to the overshipping neutron flux 109 to 109, for example, 108 neutron flux. The output of the circuit 23 is compared with hysteresis, and when neutrons rise, tOS
The determination signal that determines that the output of the logarithmic count rate measuring circuit 23 is large when the neutron flux exceeds the neutron flux (Fig. 8, 31) is determined to be large when the neutrons reach the point where the neutron flux falls below the neutron flux of 108 (Fig. 8, 32). ) when the number 1 becomes ``1 number rate measuring circuit 2
A discrimination signal indicating that the output of 3 is small a is output, and again! @
2 comparator 252, from about 1 to 108 neutron fluxes.
The output of the Campbell measuring circuit 24 is compared with the output of the Campbell measurement circuit 24 by adding or subtracting a predetermined voltage to the second judgment level corresponding to the neutron flux of 109 to 1011 three digits above, and the first comparison signal, the second The comparison signal is one-dimensional calculation circuit 253
given to. In the logic operation circuit 253, the logarithmic count rate measurement circuit 23
When the logical product of the first comparison signal whose output is small and the second comparison signal whose output from the Campbell measuring circuit 24 is small, that is, when the neutron flux increases, the signal shown in FIG.
1 or less, and when falling, the output of the logarithmic count rate measuring circuit 23 is selected at a value of 32 or less in FIG. When the logical sum of the signal and the second specific signal having a large output from the Campbell measurement circuit 24 is established, that is, when the neutrons are rising, the Campbell measurement is performed at 31 or more in Fig. 8, and when the neutrons are falling, the signal is 32 or more in Fig. 8. A second switching signal for selecting the output of the circuit is applied to the switching circuit 26. Switching circuit 2
6 operates according to instructions, the neutron flux increases from a low level,
Even when the point reaches 108, the logarithmic count rate measurement circuit 23 is still selected, and when the point reaches 108 or more (Fig. 8, 31), the Campbell measurement circuit 24 is selected, and the neutron flux decreases from the high range.
Even at 10B, the Campbell measuring circuit 247 is still selected, and when it reaches 32 in FIG. 8, the logarithmic count rate measuring circuit 23 is selected. Note that at a neutron flux of 101P or more where the phenomenon of pulse-resolved sighting loss occurs, the second comparator 252 generates a second comparison signal in which the output of the Campbell measurement circuit 24 is greater than the determination level. In the region where the output of the logarithm n1° number rate measuring circuit 23 is below the first judgment level due to pulse decomposition sighting loss, the logic operation circuit 253 selects the output of the logarithmic count rate measuring circuit 23 based on the output of the second comparator 252. No other signal is applied to the switching circuit 26. The l-th comparator 251 of the switching judgment circuit 25 has a hysteresis characteristic as shown in FIG. 32), the discrimination signal changes. When the hysteresis r is provided in this way, when the reactor output fluctuates near the neutron flux level of 108, when the fluctuation width of the fluctuation is narrower than the hysteresis width,
The appearance of fluctuations absorbed by the hysteresis effect can be faithfully reproduced on the output side of the switching circuit. In addition, due to the hysteresis effect, even if a deviation occurs due to poor adjustment or drift between the output of the Campbell measurement circuit at 108 neutron flux and the output of the logarithmic count rate measurement circuit at 108 neutron flux, the deviation will be within the hysteresis width. If so, the frequency of switching can be reduced, and the number of circuits in which the signal on the output side of the switching circuit changes can be reduced. On the output side of the switching circuit that is switched by the switching judgment circuit, neutrons rise and rise at 108 neutron flux.
The neutron flux exceeds t and reaches the value shown in Figure 8, 31, and the neutron flux decreases below 108, reaching the value shown in Figure 8, 32. , the neutron region above the value in Figure 8, 31, and descending to the 8th
The neutron flux in the neutron range above the value shown in Figure 332 is handled by the total Campbell measuring circuit, and the neutron flux is linear and without discontinuities over more than 10 orders of magnitude in proportion to the logarithm of the neutron flux.
We were able to extract the neutron detection signal with output voltage characteristics. [Effect] As described above, in the present invention, the output of the logarithmic count rate measuring circuit and the output of the Campbell measuring circuit overlap, and the first determination level corresponding to the neutron flux of 108 which is proportional to the logarithm corresponds to the predetermined neutron flux. A discrimination signal obtained by comparing the signal value with hysteresis and the output of the logarithmic count rate measuring circuit, and a second t4 corresponding to a neutron flux of 108 or more.
1 by adding or subtracting the signal corresponding to a predetermined neutron flux to a certain level.
The outputs of the direct and Campbell measurement circuits are compared with hysteresis to find out how they compare with the nine signals. When the output of the logarithmic count rate measurement circuit and the output of the Campbell measurement circuit both satisfy the condition t'' that is small, that is, the neutrons rise. Sometimes the output of the logarithmic count rate measuring circuit is used when the output of the logarithmic count rate measuring circuit is larger than the output of the logarithmic count rate measuring circuit or the output of the Campbell measuring circuit, that is, when the output of the logarithmic count rate measuring circuit is larger than that of the neutron. Force; when rising, more than 31 in Fig. 8,
Since the output of the Campbell measurement circuit is selected when the neutron flux is 32 or more in FIG. 8 during descent, it is possible to prevent the output of the logarithmic count rate measurement circuit from being erroneously selected in the neutron flux region of 108 or more. In addition, since a hysteresis function is added to the comparator that compares the output of the logarithmic counting rate i11!1 constant circuit and the first judgment level, the Campbell measurement circuit can be easily used to prevent circuit drift and drift at 108 neutrons. The noise level due to the difference between the output and the output of the logarithmic count rate measurement circuit or the background gamma gland at the sieve level after the reactor shuts down is within the hysteresis width, and the noise is absorbed and does not occur as a change on the output side, so adjust it. , handling becomes easier. Furthermore, in this application, when switching from the output of the logarithmic count rate measuring circuit to the output of the Campbell measuring circuit, or vice versa, there was a difference between the output level of the Campbell measuring circuit and the output level of the logarithmic count rate measuring circuit. However, if the fluctuation is within the hysteresis range, it has the effect of faithfully reproducing the fluctuation of the reactor's output on the output side of the switching circuit. 4. Brief explanation of the drawings Figure 1 is a configuration diagram of a conventional random pulse monitoring device;
Figure 3, Figure 4, Figure 5 and Figure IA6 are the construction B of the random pulse monitoring device of Figure 1! Fig. 7 is a diagram showing the circuit configuration of the wide range monitor device of the present invention, and Fig. 8 is a diagram showing the circuit configuration of the wide range monitor device of the present invention. FIG. ii・・・・・・・・・・・・ Neutron detector 17
...... Wide area amplifier 23...-
・・・・・・・・・ Logarithmic counting rate 6111 constant circuit 23
1 ・・・・・・・・・・・・ Pulse increase q= 52
32 ・・・・・・・・・・・・Logarithmic count rate circuit 2
33・・・・・・・・・・・・・・・ Variable gain amplifier 2
4・・・・・・・・・・・・・・・ Campbell measurement circuit 241 ・・・・・・・・・・・・・・・ High frequency band amplifier 242・・・・・・・・・・・・... Root mean square circuit 243 ...... Logarithmic conversion circuit 244 ...... Shift circuit 245 ...... ...... Variable gain DC amplifier 25 ......... Switching foot circuit 251 ...... First comparison Container 252...... Second comparator 2
53 ・・・・・・・・・・・・ Logic circuit 26
・・・・・・・・・・・・・・・ Switching circuit 27 ・
・・・・・・・・・・・・ DC amplifier 29 ・・・・・・・・・
・・・・・・・・・ Period circuit agent Patent attorney
Noriyuki Chika and 1 other person 1 Figure 1 +! If-East 0 Neutron flux - 10210'10'10' 1010101210
“Neutron flux −

Claims (1)

[Claims] The logarithmic counting circuit and Campbell circuit, which input the output of the neutron detector, match the linear regions of the outputs proportional to the logarithm to the desired linear equation, and switch in the overlapping sections in the linear regions of these outputs to form the logarithmic counting circuit. A signal that is continuously proportional to the level of neutron flux that varies over a wide range due to the output of the switching circuit and the output of the Campbell circuit is extracted from the output side of the switching circuit. When the output of the logarithmic counting circuit exceeds the voltage, the output terminal of the switching circuit is switched from the output of the logarithmic counting circuit to the output of the Campbell measuring circuit, and the voltage value obtained by subtracting a predetermined value from the predetermined voltage is compared with the voltage of the Campbell measuring circuit. The method is characterized by comprising a switching determination circuit that switches the output end of the switching circuit from the output of the Campbell measurement circuit to the output of the logarithmic counting circuit when the output of the switching circuit becomes small, and the switching circuit is switched with hysteresis. Wide range monitor device.