Measurement circuit, measurement device, and measurement method

Abstract

The measurement circuit (1) includes a variable gain amplifier (14) that amplifies an input signal based on the output of a fission counter (2) with a gain that is changed exponentially with respect to a gain control signal; a generation circuit (15) that generates the mean square of the output of the variable gain amplifier (14); and a feedback generation unit (20) that feeds back the output of the generation circuit (15) to generate the gain control signal that controls the gain of the variable gain amplifier (14), and also generates an output signal indicating the measured value of radiation based on the gain control signal. The measurement circuit (1) can achieve a wide dynamic range and high-precision measurement.

Description

Technical Field

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[0001] The present disclosure relates to a measurement circuit, a measurement device, and a measurement method.

Background Art

[0002] As a method for measuring a neutron beam, a measurement circuit using the Campbell measurement method is known (see, for example, Patent Document 1). Further, in such a measurement circuit using the Campbell measurement method, for example, a square operation is realized by utilizing the exponential characteristics of a transistor. Further, in a conventional measurement circuit for compressing the dynamic range of the resulting signal, logarithmic conversion is performed after the square operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the measurement accuracy and the dynamic range in the above-described conventional measurement circuit depend on the characteristics of a transistor such as exponential characteristics, temperature characteristics, and leak characteristics, for example, it is necessary to select a transistor with good characteristics in the conventional measurement circuit, and it has been difficult to realize a wide dynamic range and high-precision measurement.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a measurement circuit, a measurement device, and a measurement method capable of realizing a wide dynamic range and high-precision measurement.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present disclosure is A measurement circuit for measuring radiation using the Campbell method, an input signal based on the output of a nuclear fission counter tube, a gain control signal This characteristic is that the change in the amplification factor appears exponentially. A variable gain amplifier that amplifies with a gain that changes exponentially, a generation circuit that generates the mean square of the output of the variable gain amplifier, and a gain control signal that controls the gain of the variable gain amplifier by feeding back the output of the generation circuit, and the gain control signal The result is output as the measured value in the Campbell measurement method by an addition / subtraction circuit. This measurement circuit includes a feedback generation unit.

[0007] Furthermore, one aspect of this disclosure is a measuring device equipped with the measuring circuit described above.

[0008] Furthermore, one aspect of this disclosure is: A measurement method for measuring radiation using the Campbell method, A variable gain amplifier controls the input signal, which is based on the output of a fission counter, with a gain control signal. This characteristic is that the change in the amplification factor appears exponentially. The process involves a step of amplifying with a gain that changes exponentially, a step of a generation circuit generating the mean square of the output of the variable gain amplifier, and a feedback generation unit feeding back the output of the generation circuit to generate the gain control signal that controls the gain of the variable gain amplifier, and the gain control signal The result is output as the measured value in the Campbell measurement method by an addition / subtraction circuit. This is a measurement method that includes the step of doing the following. [Effects of the Invention]

[0009] According to this disclosure, a wide dynamic range and high-precision measurement can be achieved. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing an example of a measurement circuit according to the first embodiment. [Figure 2] This figure shows the equivalent circuit of the measurement circuit according to the first embodiment. [Figure 3] This is a flowchart showing an example of the operation of the measurement circuit according to the first embodiment. [Figure 4] This is a block diagram showing an example of a measurement circuit according to the second embodiment. [Figure 5] This is a block diagram showing an example of a nuclear instrumentation system according to a third embodiment. [Modes for carrying out the invention]

[0011] Hereinafter, a measurement circuit, a measurement device, and a measurement method according to one embodiment of the present disclosure will be described with reference to the drawings.

[0012] [First Embodiment] Figure 1 is a block diagram showing an example of a measurement circuit 1 according to the first embodiment. The measurement circuit 1 according to the first embodiment is used in nuclear power reactors (e.g., pressurized water reactors (PWRs), boiling water reactors (BWRs)). The measurement circuit 1 is a Campbell measurement circuit that measures neutron flux using the Campbell measurement method. The Campbell method is a technique that applies the principle that the mean square of the input signal (the detection signal from fission counter 2) is proportional to the neutron flux.

[0013] As shown in Figure 1, the measurement circuit 1 comprises a capacitor 11, an amplification circuit 12, a bandpass filter 13, a variable gain amplifier 14, a root mean square circuit 15, and a feedback generation unit 20. A fission counter 2 is connected to the measurement circuit 1, and the measurement circuit 1 receives the pulse signal output from the fission counter 2 as an input signal and outputs an output signal that shows a measured value proportional to the logarithm of the neutron flux.

[0014] The fission counter tube 2 is a detector for detecting neutrons, and outputs a pulse signal (detection signal) with a certain probability each time a neutron passes through the tube. The pulse signal output by the fission counter tube 2 is input to the measurement circuit 1 as an input signal.

[0015] Capacitor 11 extracts the AC component of the pulse signal output from fission counter 2 and outputs it to amplification circuit 12.

[0016] The amplifier circuit 12 is, for example, an amplifier IC (Integrated Circuit) composed of an analog circuit. The amplifier circuit 12 amplifies the AC component of the pulse signal extracted by the capacitor 11 to match the input level of the subsequent band-pass filter 13. The amplifier circuit 12 outputs the amplified AC component of the pulse signal to the band-pass filter 13.

[0017] The band-pass filter 13 is, for example, a circuit composed of an analog signal processing circuit and may be realized by a band-pass filter IC. The band-pass filter 13 passes a partial frequency band of the pulse signal output by the nuclear fission counter tube 2, attenuates noise components outside the frequency band of the pulse signal and signals in a band not suitable for the subsequent signal processing circuit, and outputs to the variable gain amplifier 14.

[0018] The variable gain amplifier 14 is, for example, an IC of a variable gain amplifier composed of an analog signal processing circuit. The variable gain amplifier 14 is an amplifier whose gain (amplification factor, gain) can be changed in an exponential relationship with respect to a linear gain control signal for the signal output by the band-pass filter 13 (input signal based on the output of the nuclear fission counter tube 2). The variable gain amplifier 14 changes its gain (amplification factor, gain) in an exponential relationship based on the linear gain control signal generated by the feedback generation unit 20 described later, and outputs a logarithmic value signal amplified with the changed gain.

[0019] The root mean square circuit 15 is, for example, an IC of a root mean square circuit composed of an analog signal processing circuit. The root mean square circuit 15 generates the root mean square value of the output of the variable gain amplifier 14, and further generates the square root of the root mean square value and outputs the square root of the root mean square value. Note that the root mean square circuit 15 is an example of a generation unit that generates the root mean square value of the output of the variable gain amplifier 14.

[0020] The feedback generation unit 20 feeds back the output of the root mean square circuit 15 to generate a gain control signal that controls the gain of the variable gain amplifier 14. The feedback generation unit 20 also generates an output signal based on the gain control signal that indicates the measured value of neutron radiation (an example of radiation) (a measured value proportional to the logarithm of the neutron flux).

[0021] Furthermore, the feedback generation unit 20 includes a reference voltage generation unit 21, an adder 22, an amplification circuit 23, an addition / subtraction circuit 24, and an addition / subtraction circuit 25.

[0022] The reference voltage generation unit 21 generates a reference voltage Vin. The reference voltage Vin generated by the reference voltage generation unit 21 is supplied to the adder 22.

[0023] The adder 22 is an analog adder that adds analog signals. The adder 22 outputs a signal Vi which is the sum of the reference voltage Vin and the inverted signal of the output of the root mean square circuit 15. In other words, the adder 22 outputs a signal Vi which is the difference between the output voltage of the root mean square circuit 15 and the reference voltage, obtained by subtracting the output of the root mean square circuit 15 from the reference voltage Vin.

[0024] The amplification circuit 23 is, for example, an amplifier IC composed of analog circuits. The amplification circuit 23 amplifies the output of the adder 22 by an amplification factor A (A times) and outputs it as the signal Vout. The amplification circuit 23 outputs the output signal (signal Vout) to the addition / subtraction circuits 24 and 25.

[0025] The addition / subtraction circuit 24 is, for example, an analog addition / subtraction circuit composed of an analog signal processing circuit, and is an addition / subtraction circuit for a gain control signal. The addition / subtraction circuit 24 adjusts the signal Vout, which is the output of the amplification circuit 23, to the input signal level of the gain control signal of the variable gain amplifier 14, and outputs it as a gain control signal. The addition / subtraction circuit 24 outputs the level-adjusted signal Vout as a gain control signal to the variable gain amplifier 14. The output signal of the addition / subtraction circuit 24 corresponds to a gain control signal based on the signal Vout. As a result, the feedback generation unit 20 generates a gain control signal based on the difference between the output voltage of the root mean square circuit 15 and the reference voltage Vin.

[0026] The addition / subtraction circuit 25 is, for example, an analog addition / subtraction circuit composed of an analog signal processing circuit, and is an addition / subtraction circuit for the output signal. The addition / subtraction circuit 25 adjusts the signal Vout, which is the output of the amplification circuit 23, to the input signal level of the device (higher-level device) that receives the output signal of the measurement circuit 1, and outputs it as an output signal. The output signal output by the addition / subtraction circuit 25 corresponds to a measured value proportional to the logarithm of the neutron flux.

[0027] Next, the operation of the measurement circuit 1 according to this embodiment will be described with reference to the drawings. First, referring to Figure 2, we will explain that the measurement circuit 1 according to this embodiment corresponds to the logarithm of the mean square of the input signal, which is the output signal using the Campbell measurement method.

[0028] Figure 2 shows the equivalent circuit of the measurement circuit 1 according to this embodiment. The circuit shown in Figure 2 is an equivalent circuit obtained by replacing the measurement circuit 1 shown in Figure 1 with a general negative feedback circuit configuration.

[0029] In Figure 2, the feedback circuit 26 is a feedback circuit having the characteristics of function β, and corresponds to the capacitor 11, amplifier circuit 12, bandpass filter 13, variable gain amplifier 14, and root mean square circuit 15 shown in Figure 1.

[0030] Furthermore, the adder 22 and amplifier circuit 23 are the same as those shown in Figure 1.

[0031] In Figure 2, the reference voltage Vin represents the reference voltage generated by the reference voltage generation unit 21 described above, the signal Vi represents the input signal of the amplification circuit 23, and the signal Vout represents the output signal of the amplification circuit 23.

[0032] Furthermore, the amplification factor A represents the amplification factor (gain) of the amplification circuit 23. The function β is a function that represents the characteristics of the feedback circuit 26, and converts the input signal V into β(V).

[0033] In the equivalent circuit shown in Figure 2, the following relationship (1) holds between the signal Vout and the signal Vi.

[0034]

number

[0035] Furthermore, if we eliminate signal Vi using the relationship in equation (1) above, we obtain the following equation (2).

[0036]

number

[0037] Here, A, which represents the amplification factor, is dimensionless and ideally has an infinite value, so the value multiplied by A is "0" (zero). As a result, equation (3) below holds true.

[0038]

number

[0039] Furthermore, by applying the feedback circuit 26 to the right-hand side of equation (3), the following equation (4) is obtained, given the variable gain amplifier 14 and root mean square circuit 15 shown in Figure 1.

[0040]

number

[0041] Here, the variable Vsig represents the input signal to the variable gain amplifier 14, and variables a and b are values ​​determined by the characteristics of the variable gain amplifier 14. The input signal, which is variable Vsig, is amplified by the variable gain amplifier 14, then squared and averaged by the root mean square circuit 15, and then the square root is calculated. Note that the averaging operation does not affect terms other than variable Vsig, so it can be separated into the product of variable Vsig and the other terms.

[0042] From the above, by substituting equation (3) relating to the reference voltage Vin with equation (4) relating to the function β, squaring both sides, and then taking the logarithm and rearranging, we obtain the following equation (5).

[0043]

number

[0044] Furthermore, by substituting variables a' and b' into equation (5), we finally obtain equation (6) below.

[0045]

number

[0046] From the above, as shown in equation (6), the output signal (signal Vout) of the amplification circuit 23 can be expressed as a linear equation with respect to the logarithm of the mean square of the input signal (variable Vsig) of the variable gain amplifier 14, and characteristics proportional to the logarithm of the Campbell measurement method are obtained.

[0047] In this manner, the measurement circuit 1 feeds back a signal Vout, which is the difference between the input signal (variable Vsig) based on the output of the fission counter 2, which has passed through a variable gain amplifier 14 with a gain control function that responds exponentially and a root mean square circuit 15, and the reference voltage Vin, as a control signal for the variable gain amplifier 14. The measurement circuit 1 outputs an output signal based on this signal Vout as an output signal that shows a measured value proportional to the logarithm of the neutron flux.

[0048] Next, with reference to Figure 3, the operation of the measurement circuit 1 according to this embodiment will be described. Figure 3 is a flowchart showing an example of the operation of the measurement circuit according to this embodiment.

[0049] As shown in Figure 3, the measurement circuit 1 first amplifies the detection signal obtained by extracting the AC component from the output of the fission counter 2 (step S101). The capacitor 11 of the measurement circuit 1 extracts the AC component from the output (pulse signal) of the fission counter 2, and the amplification circuit 12 of the measurement circuit 1 amplifies the detection signal with the extracted AC component to match the input level of the bandpass filter 13. The amplification circuit 12 outputs the amplified detection signal to the bandpass filter 13.

[0050] Next, the measurement circuit 1 removes noise components and signals in frequency bands unsuitable for the subsequent signal processing circuit from the detection signal amplified by the bandpass filter 13 (step S102). The bandpass filter 13 allows a portion of the frequency band of the pulse signal output by the fission counter 2 to pass through, attenuating noise components and signals in frequency bands unsuitable for the subsequent signal processing circuit outside the frequency band of the pulse signal, and outputs it to the variable gain amplifier 14.

[0051] Next, the measurement circuit 1 amplifies the output of the bandpass filter 13 with a gain that is changed exponentially with respect to the gain control signal using the variable gain amplifier 14 (step S103). Based on the gain control signal generated by the feedback generation unit 20, the variable gain amplifier 14 changes its gain (amplification ratio, gain) and outputs a logarithmic signal that is amplified by the changed gain from the output signal of the bandpass filter 13.

[0052] Next, the measurement circuit 1 generates the mean square (root mean square) of the output of the variable gain amplifier 14 (step S104). The root mean square circuit 15 of the measurement circuit 1 outputs a signal indicating the root mean square of the output of the variable gain amplifier 14 to the adder 22 of the feedback generation unit 20.

[0053] Next, the measurement circuit 1 feeds back the result of generating the mean square (root mean square) value to generate a gain control signal that controls the gain of the variable gain amplifier 14 (step S105). The feedback generation unit 20 of the measurement circuit 1 generates a gain control signal based on the difference between the output voltage of the root mean square circuit 15 and the reference voltage Vin. The adder 22 outputs a signal Vi, obtained by subtracting the output voltage of the root mean square circuit 15 from the reference voltage Vin, to the amplifier circuit 23, and the amplifier circuit 23 outputs a signal Vout corresponding to the gain control signal.

[0054] Next, the measurement circuit 1 generates an output signal indicating the measured value of the neutron beam (neutron flux) based on the gain control signal (step S106). The feedback generation unit 20 of the measurement circuit 1 outputs an output signal based on the output (signal Vout) of the amplification circuit 23 as a measured value proportional to the logarithm of the neutron beam (neutron flux).

[0055] The processes from step S101 to step S106 are repeatedly executed for the duration that the measurement circuit 1 is measuring the neutron beam (neutron flux).

[0056] As described above, the measurement circuit 1 according to this embodiment comprises a variable gain amplifier 14, a root mean square circuit 15 (generation circuit), and a feedback generation unit 20. The variable gain amplifier 14 amplifies the input signal based on the output of the fission counter 2 with a gain that is changed exponentially with respect to the gain control signal. The root mean square circuit 15 (generation circuit) generates the mean square of the output of the variable gain amplifier 14. The feedback generation unit 20 feeds back the output of the root mean square circuit 15 (generation circuit) to generate a gain control signal that controls the gain of the variable gain amplifier 14, and also generates an output signal indicating the measured value of radiation (for example, an output signal proportional to the logarithm of the measured value of radiation) based on the gain control signal.

[0057] As a result, the measurement circuit 1 according to this embodiment, by using a variable gain amplifier 14 before the root mean square circuit, can not only extend the dynamic range of the input signal to the dynamic range of the variable gain amplifier 14, but also, because the gain of the variable gain amplifier 14 responds with an exponential characteristic, logarithmic scaling is also performed before the root mean square circuit. As a result, the measurement circuit 1 according to this embodiment can achieve a wide dynamic range. Furthermore, by using feedback from the feedback generation unit 20, the signal level input to the root mean square circuit 15 (generation circuit) becomes constant, and processing can be performed in a signal region with good accuracy and response speed without being affected by the nonlinearity of the characteristics of the root mean square circuit 15 (generation circuit). Therefore, the measurement circuit 1 according to this embodiment can achieve a wide dynamic range (high dynamic range) and high-precision measurement.

[0058] For example, in conventional measurement circuits that use the characteristics of transistors, the dynamic range depends on the range in which the exponential characteristics of the transistor hold true, making it difficult to achieve a wide dynamic range. Therefore, it was necessary to use a multi-stage measurement circuit configuration that supports multiple ranges and switch between them to accommodate a wide dynamic range. In contrast, the measurement circuit 1 according to this embodiment can achieve a wide dynamic range (high dynamic range) on its own because it depends on the dynamic range of the variable gain amplifier 14, eliminating the need for a multi-stage configuration like conventional measurement circuits.

[0059] Furthermore, in this embodiment, the generation circuit is a root mean square circuit 15 that outputs the square root of the mean square.

[0060] As a result, the measurement circuit 1 according to this embodiment can use a circuit that calculates the Root Mean Square (RSM), which is commonly used, by using the root mean square circuit 15, thus enabling more accurate measurement using a simpler method.

[0061] Furthermore, in this embodiment, the feedback generation unit 20 generates a gain control signal based on the difference between the output voltage of the root mean square circuit 15 and the reference voltage Vin.

[0062] As a result, the measurement circuit 1 according to this embodiment can keep the signal level input to the root mean square circuit 15 (generation circuit) within a certain range by performing feedback control using the difference with the reference voltage Vin. This allows processing to be performed in a signal region with good accuracy and response speed, without being affected by the nonlinearity of the characteristics of the root mean square circuit 15 (generation circuit).

[0063] Furthermore, in this embodiment, the variable gain amplifier 14 and the root mean square circuit 15 are composed of analog signal processing circuits.

[0064] As a result, by configuring the measurement circuit 1 according to this embodiment with an analog signal processing circuit, concerns about common software failures, such as those that occur when implemented with digital signal processing, are eliminated, and more reliable measurements can be achieved.

[0065] Furthermore, in applications related to nuclear reactors, if measurement circuits are implemented using digital processing, there is a concern about common software failures, where, for example, if a failure occurs in one digital processing unit, a similar failure may occur simultaneously in other digital processing units. In contrast, when analog signal processing is used, there is no such concern about common software failures. Therefore, the measurement circuit 1 according to this embodiment can achieve more reliable measurements in applications related to nuclear reactors.

[0066] Furthermore, the measurement method according to this embodiment includes a first step (amplification step), a second step (mean squares generation step), and a third step (feedback generation step). In the first step (amplification step), the variable gain amplifier 14 amplifies the input signal based on the output of the fission counter 2 with a gain that is changed exponentially with respect to the gain control signal. In the second step (mean squares generation step), the root mean square circuit 15 (generation circuit) generates the mean squares of the output of the variable gain amplifier 14. In the third step (feedback generation step), the feedback generation unit 20 feeds back the output of the root mean square circuit 15 (generation circuit) to generate a gain control signal that controls the gain of the variable gain amplifier 14, and also generates an output signal indicating the measured value of radiation (for example, an output signal proportional to the logarithm of the measured value of radiation) based on the gain control signal.

[0067] As a result, the measurement method according to this embodiment achieves the same effects as the measurement circuit 1 described above, enabling a wide dynamic range (high dynamic range) and high-precision measurement.

[0068] [Second Embodiment] Next, with reference to the drawings, a measurement circuit 1a according to the second embodiment will be described. In the second embodiment, a modified example will be described in which a mean square circuit 15a is used instead of the mean square circuit 15, which is the generation circuit in the first embodiment.

[0069] Figure 4 is a block diagram showing an example of a measurement circuit 1a according to the second embodiment. As shown in Figure 4, the measurement circuit 1a comprises a capacitor 11, an amplification circuit 12, a bandpass filter 13, a variable gain amplifier 14, a mean square circuit 15a, and a feedback generation unit 20. A fission counter 2 is connected to the measurement circuit 1a, and the measurement circuit 1a receives the pulse signal output from the fission counter 2 as an input signal and outputs an output signal that shows a measured value proportional to the logarithm of the neutron flux.

[0070] In the explanation of Figure 4, the same reference numerals are used for components identical to those in Figure 1, and their explanations are omitted.

[0071] The mean squares circuit 15a is, for example, an IC of a mean squares circuit composed of an analog signal processing circuit. The mean squares circuit 15a generates the mean squares of the output of the variable gain amplifier 14 and outputs the mean squares. The mean squares circuit 15a is an example of a generation unit that generates the mean squares of the output of the variable gain amplifier 14. In other words, the generation circuit in this embodiment is the mean squares circuit 15a that outputs the mean squares.

[0072] In this embodiment, the configuration is identical to the first embodiment, except that the generation circuit is replaced with a mean-square circuit 15a. Furthermore, the operation of the measurement circuit 1a in this embodiment is the same as described above, except that the (1 / 2) of the variable a' in equation (6) is eliminated by using the mean-square circuit 15a.

[0073] In the measurement circuit 1a according to this embodiment, the (1 / 2) of the variable a' in equation (6) is eliminated, so it is necessary to take this into consideration when using the output signal (signal Vout). In other respects of the measurement circuit 1a, it is the same as in the first embodiment. Furthermore, the operation of the measurement circuit 1a is the same as that of the first embodiment shown in Figure 3 above, so its explanation is omitted here.

[0074] As described above, the measurement circuit 1a according to this embodiment comprises the variable gain amplifier 14, the mean squares circuit 15a (generation circuit), and the feedback generation unit 20. The mean squares circuit 15a (generation circuit) generates the mean squares of the output of the variable gain amplifier 14.

[0075] As a result, the measurement circuit 1a according to this embodiment achieves the same effects as the first embodiment, enabling a wide dynamic range (high dynamic range) and high-precision measurement.

[0076] Furthermore, in this embodiment, the generation circuit is a mean square circuit 15a that outputs the mean squares value.

[0077] As a result, the measurement circuit 1a in this embodiment can omit the process of generating the square root of the mean square by using the mean square circuit 15a, and the generation circuit can be made simpler.

[0078] [Third Embodiment] Next, with reference to Figure 5, a nuclear instrumentation device 10 according to a third embodiment will be described.

[0079] Figure 5 is a block diagram showing an example of a nuclear instrumentation device 10 according to the third embodiment. The nuclear instrumentation device 10 according to the third embodiment is a measuring device for measuring neutron flux in a nuclear reactor such as a pressurized water reactor (PWR) or a boiling water reactor (BWR).

[0080] As shown in Figure 5, the nuclear instrumentation device 10 includes a measurement circuit 1(1a). The nuclear instrumentation device 10 receives pulse signals output by fission counters 2 installed in the reactor containment vessel 30 as input signals and supplies them to the measurement circuit 1(1a).

[0081] Furthermore, the nuclear instrumentation device 10 outputs a measured value proportional to the logarithm of the neutron flux, which is the output signal of the measurement circuit 1(1a), to the monitoring and control device 40, based on the pulse signal output by the fission counter tube 2.

[0082] The monitoring and control device 40 monitors and controls the reactor based on a measurement value proportional to the logarithm of the neutron flux received from the nuclear instrumentation device 10.

[0083] As described above, the nuclear instrumentation device 10 (measuring device) according to this embodiment is equipped with the measuring circuit 1 of the first embodiment or the measuring circuit 1a of the second embodiment. As a result, the nuclear instrumentation device 10 (measurement device) according to this embodiment achieves the same effects as the measurement circuit 1 of the first embodiment and the measurement circuit 1a of the second embodiment, enabling a wide dynamic range (high dynamic range) and high-precision measurement in neutron flux measurement.

[0084] This disclosure is not limited to the embodiments described above and may be modified without departing from the spirit of this disclosure. For example, in each of the embodiments described above, the measurement circuit 1(1a) and the nuclear instrumentation device 10 were described in terms of their application to reactors such as pressurized water reactors (PWRs) and boiling water reactors (BWRs), but the invention is not limited to these, and may also be used in other nuclear facilities such as fusion reactors.

[0085] Furthermore, although the above embodiments describe the measurement circuit 1(1a) and nuclear instrumentation device 10 as being used for measuring neutron beams, they are not limited to this and may be applied to the measurement of other types of radiation.

[0086] Furthermore, although the above embodiments describe an example in which the measurement circuit 1(1a) is composed of analog processing circuits, it is not limited to this, and some or all of the components may be realized by digital signal processing.

[0087] Furthermore, the aforementioned nuclear instrumentation device 10 has a computer system inside. The process for measuring the neutron flux is stored in program form on a computer-readable recording medium, and the above process is performed by reading and executing this program on the computer. Here, a computer-readable recording medium refers to a magnetic disk, magneto-optical disk, CD-ROM, DVD-ROM, semiconductor memory, etc. Alternatively, this computer program may be distributed to a computer via a communication line, and the computer that receives this distribution may execute the program.

[0088] Furthermore, some or all of the functions of the measurement circuit 1(1a) described above may be implemented as an integrated circuit such as an LSI (Large Scale Integration). Each of the above functions may be individually processed. Alternatively, some or all of these components may be integrated to form a processor. Furthermore, the method of integrated circuit implementation is not limited to LSIs; it may also be implemented using dedicated circuits or general-purpose processors. In addition, if advances in semiconductor technology lead to the emergence of integrated circuit implementation technologies that can replace LSIs, integrated circuits using such technologies may be used. [Explanation of symbols]

[0089] 1,1a...Measurement circuit, 2...Fission counter tube, 10...Nuclear instrumentation device, 11...Capacitor, 12,23...Amplification circuit, 13...Bandpass filter, 14...Variable gain amplifier, 15...Root mean square circuit, 15a...Mean mean square circuit, 20...Feedback generation unit, 21...Reference voltage generation unit, 22...Adder, 24,25...Addition / subtraction circuit, 26...Feedback circuit, 30...Reactor containment vessel, 40...Monitoring / control device

Claims

1. A measurement circuit for measuring radiation by the Campbell method, A variable gain amplifier that amplifies an input signal based on the output of a nuclear fission counter with a gain that changes exponentially with respect to the amplification factor, where the change in the gain control signal is exponential. A generation circuit that generates the mean square of the output of the variable gain amplifier, A feedback generation unit that feeds back the output of the generation circuit to generate the gain control signal that controls the gain of the variable gain amplifier, and outputs the gain control signal as a measured value in the Campbell measurement method using an addition / subtraction circuit. A measurement circuit equipped with the following features.

2. The generation circuit is a root mean square circuit that outputs the square root of the mean square. The measurement circuit according to claim 1.

3. The generation circuit is a mean square circuit that outputs the mean squares. The measurement circuit according to claim 1.

4. The feedback generation unit generates the gain control signal based on the difference between the output voltage of the generation circuit and the reference voltage. The measurement circuit according to claim 1.

5. The variable gain amplifier and the generation circuit are configured with analog signal processing circuits. The measurement circuit according to claim 1.

6. A measuring device comprising a measuring circuit according to any one of claims 1 to 5.

7. A measurement method for measuring radiation by the Campbell measurement method, The variable gain amplifier amplifies an input signal based on the output of a fission counter with a gain that changes exponentially, where the change in the gain control signal is exponential with respect to the amplification factor. The generation circuit includes the step of generating the mean square of the output of the variable gain amplifier, The feedback generation unit feeds back the output of the generation circuit to generate the gain control signal that controls the gain of the variable gain amplifier, and outputs the gain control signal as a measured value in the Campbell measurement method using an addition / subtraction circuit. Measurement methods including

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