JPH07140252A - Criticality alarm system - Google Patents

Abstract

PURPOSE:To enable a radiation detection signal from which the influence of noise has been eliminated to be detected by providing a radiation detector with a shielded radiation detector which detects only noise signals. CONSTITUTION:A radiation detecting portion 1 comprises a radiation detector 2 and a shielded radiation detector 2a having the same specifications as the detector 2, surrounded by a shield 3, and making a pair with the detector 2. Only a signal which is the combination of a radiation signal detected on the side of the detector 2 and a noise signal entering the ambient area of the detector 2 and a signal cable 4 from the outside, and a noise signal entering a signal cable 4a without ambient radiation being detected on the side of the detector 2a because of the presence of the shield 3, are inputted to an arithmetic portion 6 through the same conduit tube 5. The arithmetic portion 6 performs arithmetic on these two input signals, and outputs a signal of the arithmetic result to a discriminating portion 7. When this input signal exceeds a set threshold, the discriminating portion 7 judges that criticality has reached and then outputs a signal to an alarm 8. The alarm 8 then issues alarming sounds and outputs a signal for stopping facility operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is to detect the occurrence of a criticality in a nuclear fuel material handling facility such as a reprocessing facility, notify the worker, and stop the operation of the facility to detect the criticality. To a criticality warning device for preventing

[0002]

2. Description of the Related Art Conventionally, as a criticality warning device, the following two types of criticality patterns are assumed, and two types are used for each criticality pattern so that each criticality can be detected. One of them is a criticality warning device that detects the criticality with the initial spike. The criticality with the initial spike is characterized by enormous fission in a short time, and the dose rate is significantly higher than the normal level. Regarding such a criticality, it is judged to be critical by using a dose rate type criticality alarm device and confirming that the dose rate exceeds a predetermined threshold value.

The other is a criticality warning device called a delayed type which detects a criticality. With this late-onset criticality, the dose rate increases only slightly. Therefore, with respect to such a delayed type criticality, it is judged to be critical by using an integrated dose type criticality warning device and confirming that the integrated dose exceeds a predetermined threshold value.

[0004]

In the above-mentioned two types of criticality alarm devices, the threshold values set by each of the criticality alarm devices are normally detected from the viewpoint of performing criticality detection at an early stage and reducing exposure of workers. It is preferable to set as low as possible so that a false alarm due to fluctuation of the ground level is not generated.

However, when this threshold value is set low, there is a problem in that it is likely to be affected by noise from the outside, so that a false alarm is likely to occur. Especially, the false alarm of criticality directly brings about a decrease in the operating rate of the processing facility because the facility is stopped, and has a great influence on the entire facility. Therefore, there has been a demand for the development of a highly reliable critical alarm device with few false alarms.

An object of the present invention is to provide a shielded radiation detector for detecting only a noise signal in the radiation detector so as to obtain a radiation detection signal in which the influence of noise is eliminated, thereby providing a highly reliable criticality. To provide an alarm device.

[0007]

In order to achieve the above object, a criticality alarm device according to the invention of claim 1 is a radiation detector and a shielded radiation detector in which a radiation detector having the same specifications is surrounded by a shield. And a radiation detection unit provided adjacent to each other as a pair, the radiation detector and the shielded radiation detector in the radiation detection unit are independently connected to each other, and a signal cable provided side by side, and a signal input from both signal cables It is characterized in that it comprises an arithmetic unit for performing arithmetic processing, a discriminating unit for discriminating the criticality by comparing the arithmetic result with a threshold value, and an alarm device for issuing an alarm or the like in response to a criticality discriminating signal in the discriminating unit.

According to a second aspect of the criticality warning apparatus, a radiation detector is provided adjacent to a pair of a radiation detector in which a radiation detector having the same specifications as the radiation detector is surrounded by a shield. The radiation detector and the shielded radiation detector in the radiation detection unit are independently connected to each other, and the signal cable provided side by side and the arithmetic unit for arithmetically processing the signals input from both the signal cables are set as one set, and a plurality of sets are provided. .

Further, by inputting the calculation results in the respective calculation units, comparing the respective calculation results with the threshold values, and calculating the calculation results and the threshold values collectively obtained from a plurality of sets of calculation units combined as necessary. And a warning device that issues a warning or the like according to the criticality judgment made by the judgment unit.

A criticality alarm device according to a third aspect of the present invention includes a radiation detector and a radiation detection section in which a radiation detector and a shielded radiation detector in which a radiation detector having the same specifications is surrounded by a shield are provided as a pair so as to be adjacent to each other. The radiation detector and the shielded radiation detector in the radiation detection unit are independently connected to each other, and the signal cable provided side by side and the arithmetic unit for arithmetically processing the signals input from both the signal cables are set as one set, and a plurality of sets are provided. .

Further, an auxiliary calculation unit for inputting the calculation result in each of the calculation units and calculating each calculation result and an average, an arithmetic mean, and the calculation result from this auxiliary calculation unit and a threshold value are compared. And a warning device that issues a warning or the like according to the criticality judgment made by the judgment unit.

[0012]

According to the first aspect of the present invention, the radiation signal detected at one radiation detector side of the radiation detection section is added to the noise signal that has entered from the outside to the surroundings and the signal cable and is input to the calculation section. However, on the other side of the shielded radiation detector, the radiation is blocked by the surrounding shield in the radiation detector and is not detected, and only the noise signal that has entered the signal cable is input to the calculation unit.

Therefore, when the calculation unit subtracts the input signal on the shielded radiation detector side from the input signal on the radiation detector side, the noise signal is removed and only the radiation signal on the radiation detection unit is obtained. The radiation signal is compared with a predetermined threshold value by the discrimination unit, and if it exceeds this threshold value, it is judged to be critical and a signal is output to the alarm device. The alarm device outputs an operation stop signal of the equipment together with an alarm to prevent the alarm from becoming critical.

According to the second aspect of the present invention, the plurality of radiation signals output from the computing units respectively connected to the plurality of radiation detecting units are input to the discriminating unit, and the radiation results of the respective radiation signals and the threshold value are calculated. The criticality is determined by comparison, and by comparing a threshold value with a calculation result obtained from a plurality of sets of calculation units combined as necessary. The alarm device outputs an operation stop signal of the equipment together with the alarm by the signal of the criticality determination to prevent the criticality.

According to a third aspect of the present invention, the plurality of radiation signals output from the computing units respectively connected to the plurality of radiation detecting units are input to the auxiliary computing unit, and the radiation results of the radiation signals and the average of the radiation signals are inputted. , Or arithmetic operation such as arithmetic mean is performed, and the determination unit determines the criticality by comparing the calculation result with a threshold value. When this result is determined to be critical, the alarm device outputs an alarm and an operation stop signal of the equipment to prevent the criticality.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. The first embodiment is an example of a set of radiation detection units.
As shown in the block diagram of FIG. 1, the radiation detection unit 1 is a shielded radiation detector in which the radiation detector 2 and a radiation detector having the same specifications as the radiation detector 2 are surrounded by a shield 3 to shield the surrounding radiation. 2a are installed as a pair, and the radiation detected by each of them is the signal S at the detected dose.
(T) and the signal Sa (T) are converted and output to the calculation unit 6 through the same conduit 5 by the signal cables 4 and 4a.

At this time, the signal input to the arithmetic unit 6 is
In both cases, signal A (T) and signal A with spatial noise added
a (T). In the calculation unit 6, [signal A (T) -signal A
a (T)] is subtracted, and the signal S (T) of the calculation result is output to the determination unit 7. When the input signal S (T) exceeds a preset threshold value,
When it is determined that the criticality has been reached, a signal is issued to the alarm device 8, and the alarm device 8 notifies the worker of an alarm by sound, light, or a combination thereof, and stops the operation of the facility (not shown). It is configured.

Further, regarding each part in the above configuration,
Since the radiation detector 2 and the shielded radiation detector 2a need to detect a signal related to the dose of radiation, those that output a signal proportional to the detected dose of radiation are adopted, and gamma rays are used as the detected radiation. And neutrons are realistically considered.

As the radiation detector 2 and the shielded radiation detector 2a, a scintillation counter, a proportional counter or the like for gamma rays, and a He-3 counter, BF-3 counter, B-10 counter for neutron rays. , Fission chamber, etc. The shield 3 shields radiation to be detected. Therefore, when shielding gamma rays, lead is used, and when shielding neutron rays, water, polyethylene, etc. are used. Use a structural material that is effective in blocking radiation.

Next, the operation of the above configuration will be described. The radiation dose incident on the radiation detector 2 of the radiation detection unit 1 is converted into a signal S (T), and the signal cable 4
Is output to the calculation unit 6 through.

At this time, the signal A input by the arithmetic unit 6
(T) is the signal S (T) relating to the radiation dose detected by the radiation detector 2 as shown in the following equation (1), and is calculated from the surface of the signal cable 4 between the radiation detector 2 and the arithmetic unit 6. Spatial noise signal N (T) due to incident electromagnetic waves
Will be added. A (T) = S (T) + N (T) (1)

On the other hand, the shielded radiation detector 2a is a radiation detector of the same specifications which is arranged adjacent to the radiation detector 2 and has a sufficient thickness to block the radiation detected by the radiation detector 2 around the radiation detector 2. It is shielded by the shield 3 of the sand. The signal Aa (T) input from the shielded radiation detector 2a to the arithmetic unit 6 via the signal cable 4a is expressed by the following equation (2).
The spatial noise signal Na (T) due to the electromagnetic waves incident from the surface of the signal cable 4a connected between the radiation detector 2a and the arithmetic unit 6 as shown in FIG. Aa (T) = Na (T) (2)

Further, the signal cable 4 and the signal cable 4a
Of the same structure and size, and when they are housed in the same conduit 5, the spatial noise signal N (T) due to the electromagnetic waves incident from the surface of the signal cable 4 and the signal cable 4a
Noise signal Na due to electromagnetic waves incident from the surface of the
(T) can be regarded as equal as shown in the following equation (3). N (T) = Na (T) (3)

Therefore, in the arithmetic unit 6, [A
By subtracting (T) −Aa (T)], the effect of the spatial noise signal Na (T) due to the electromagnetic wave can be removed, and the radiation of the radiation in the radiation detector 2 can be expressed by the following equation (4). Only the signal S (T) for the dose can be obtained. S (T) = A (T) -Aa (T) (4)

Further, the arithmetic unit 6 corresponds to the above-mentioned two types of criticality warning devices, performs the following arithmetic processing, and then outputs the result to the discriminating unit 7. (1) In the case of a dose rate type critical warning device, the time resolution of the radiation detector 2 is as shown in the radiation dose characteristic diagram of FIG. 2 (a) and the radiation dose rate characteristic diagram of FIG. 2 (b). The signal S (T) relating to the dose obtained for each ΔT is divided by the time resolution ΔT to obtain the signal S (T) / ΔT relating to the dose rate.
Is calculated every time ΔT elapses.

By performing such calculation in the calculation device 6, the signal S (I) / ΔT, S relating to the dose rate is obtained.
(I + 1) / ΔT, S (I + 2) / ΔT ..., Are continuously calculated.

(2) In the case of the integrated dose type critical warning device, as shown in the concept of the radiation dose characteristic diagram of FIG. 3A and the integrated dose characteristic diagram of FIG. Signal S (I) related to the dose obtained for each time resolution ΔT,
A signal regarding the integrated dose obtained for each predetermined time width Δτ (Δτ = n × ΔT, where n is a natural number) by adding S (I + 1), ..., S (n-1 + I) one after another.

[0028]

[Equation 1] Is calculated every time ΔT elapses.

By performing such calculation, a signal relating to the integrated dose for each predetermined time width Δτ

[Equation 2] Is calculated continuously.

In the discriminating section 6, the dose rate or the integrated dose, which is continuously sent from the arithmetic unit 6 for each time resolution ΔT of the radiation detector 2 and the shielded radiation detector 2a, and the threshold L for the dose rate. ₁ or the threshold value L ₂ relating to the integrated dose is compared, and as shown in the radiation dose characteristic diagram of FIG. 4 and the cumulative dose characteristic diagram of FIG. 5, the signal S (I) / ΔT relating to the dose rate, or Signal regarding the integrated dose

[0031]

[Equation 3] Exceeds the threshold L ₁ for each dose rate or the threshold L ₂ for integrated dose,

[0032]

[Equation 4] Then, the alarm device 8 is activated.

As a result, the signal transmitted from the radiation detector 2 to the arithmetic unit 6 is a combination of the influence of the dose of radiation to be detected and the influence of spatial noise due to the electromagnetic waves incident from the surface of the signal cable 4. On the other hand, the signal transmitted from the shielded radiation detector 2a to the arithmetic unit 6 is not affected by the radiation dose to be detected,
Only the contribution from the spatial noise due to the electromagnetic wave incident from the surface of the signal cable 4a is provided.

Further, the alarm device 8 issues an alarm by sound or light, or a combination thereof to notify the worker, and outputs a signal for stopping the operation of the equipment to prevent it from becoming critical. .

The second embodiment is provided with a plurality of sets of radiation detecting units. As shown in the block diagram of FIG. 6, the plurality of sets of radiation detecting units 1 ₍₁₎ to 1 _(M) are each Multiple sets of radiation detectors 2 ₍₁₎ and shielded radiation detectors 2a ₍₁₎ (M
Set 2 _(M) and 2a _(M) ).

Each set of radiation detectors 2 ₍₁₎ to 2 _(M) ,
And, the signals obtained from the shielded radiation detectors 2a _{(1) to} 2a _{( M)} are passed through the respective conduits 5 to the respective calculation units 6 _{(1) to} 6 _(M) by the independent signal cables 4 and 4a. The signal S ₍₁₎ (T) / ΔT, ... S _(M) (T) / ΔT relating to each dose rate, which is the calculation result of the calculation units 6 _{(1) to} 6 _(M)
Is input to the determination unit 9 to make a comprehensive determination, and the alarm device 8 outputs an alarm and a signal for stopping the operation of the equipment based on the result.

The operation of the second embodiment is that the radiation detectors 2 in each of the radiation detectors 1 ₍₁₎ to 1 _(M) .
_{(1) to} 2 _(M) and shielded radiation detectors 2a _{(1) to} 2a
_The signal S ₍₁₎ (T) / ΔT, ... S related to the dose rate detected by _(M) and obtained through the operation units 6 _{(1) to} 6 _(M)
(M) (T) / ΔT, or signal related to integrated dose

[0038]

[Equation 5] And the threshold value L ₁ relating to the dose rate or the threshold value L ₂ relating to the integrated dose are compared in the discriminating unit 9, and the threshold value at which a signal obtained from a predetermined m number (m <M) is set. When the value is exceeded, the alarm device 8 is activated. A so-called "m" out of "M" redundancy function is provided.

As a result, as compared with the case of using a plurality of sets of the single critical alarm device of the first embodiment described above, there is an effect that the reliability is further improved by comparing the functions of each set or selecting the sets.

The third embodiment is shown in the block diagram of FIG. Each of the plurality of sets of radiation detectors 1 ₍₁₎ to 1 _(M) includes a plurality of sets (M set 2 _(M) and a set of the radiation detector 2 ₍₁₎ and the shielded radiation detector 2a _(1). 2a _(M) ), and the signals from the radiation detectors 2 _{(1 )} to 2 _(M) and the shielded radiation detectors 2a _{(1) to} 2a _{(M) of} each set are calculated by the respective calculation units 6. _{(1) to} 6 _{(M) are} individually calculated and auxiliary calculation device 10
Entered in.

In this auxiliary arithmetic unit 10, each set of arithmetic units 6
Signal S related to dose rate obtained from _{(1) to} 6 _(M)
(1) (T) / ΔT, ..., S _(M) (T) / ΔT, and signal related to integrated dose

[0042]

[Equation 6] (S ₍₁₎ (T) + …… +
S _(M) (T) / (ΔT × M) and

[0043]

[Equation 7] To the signal AVE (S
₍₁₎ (T) / ΔT, ..., S _(M) (T) / ΔT) and

[0044]

[Equation 8] And Further, the auxiliary computing device 10 is configured by connecting a discriminating section 7 and an alarm device 8.

According to the above-mentioned configuration, the accuracy of the criticality judgment is improved by the various calculations carried out by the auxiliary calculation device 10 in consideration of the installation locations of the radiation detectors 1 ₍₁₎ to 1 _(M). Therefore, the reliability of the criticality warning device can be improved. When the radiation detectors 1 ₍₁₎ to 1 _(M) are installed in a wide area, the influence of radiation from the radiation source varies depending on the set of the radiation detectors 1 ₍₁₎ to 1 _(M). Therefore, it is possible to improve the accuracy of the criticality warning by the optimum number of groups and the combination thereof in relation to the installation location of the radiation source and the radiation detection units 1 ₍₁₎ to 1 _(M) .

The arithmetic units 6 _{(1) to} 6 _(M) may be independent for each group, or may be of a multi-channel type if multi-channel signals can be calculated in parallel. You may use the required number of types.
Furthermore, when only one computing unit 6 is required, the computing unit 6
The auxiliary arithmetic unit 10 can be eliminated by adding the arithmetic processing function of the auxiliary arithmetic unit 10 shown in FIG.

[0047]

As described above, according to the present invention, the spatial noise due to electromagnetic waves from the surroundings such as the radiation detector and the signal cable is effectively eliminated, so that the influence of noise in the radiation detection signal is removed and the signal / noise is eliminated. A signal with a high ratio can be obtained. Therefore, there is an effect that the safety of the reprocessing facility and the like is further improved by adopting the highly reliable criticality warning device by the highly accurate criticality detection.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a criticality warning device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of dose and dose rate.

FIG. 3 is a characteristic diagram of added dose and integrated dose.

FIG. 4 is a relationship diagram between a dose rate and a threshold value.

FIG. 5 is a diagram showing the relationship between integrated dose and threshold value.

FIG. 6 is a block configuration diagram of a criticality warning device according to a second embodiment of the present invention.

FIG. 7 is a block configuration diagram of a criticality warning device according to a third embodiment of the present invention.

[Explanation of symbols]

1,1 ₍₁₎ , 1 ₍₂₎ , 1 _(M) ... Radiation detector, 2, 2
₍₁₎ , 2 ₍₂₎ , 2 _(M) ... Radiation detector, 2a, 2
a ₍₁₎ , 2a ₍₂₎ , 2a _(M) ... Shielding radiation detector, 3 ...
Shield, 4, 4a ... Signal cable, 5 ... Conduit, 6, 6
₍₁₎ , 6 ₍₂₎ , 6 _(M) ... Computation unit, 7, 9, 11 ... Discrimination unit,
8 ... Alarm device, 10 ... Auxiliary calculation device.

Claims (3)

[Claims] 1. A radiation detector provided adjacent to each other as a pair of a shielded radiation detector in which a radiation detector having the same specifications as the radiation detector is surrounded by a shield, and a radiation detector and shielded radiation in the radiation detector. A signal cable that is independently connected to each of the detectors and is provided side by side, a calculation unit that performs a calculation process on the signals input from both signal cables, and a determination unit that determines the criticality by comparing the calculation result with a threshold value. A critical warning device comprising a warning device which issues a warning or the like in response to a criticality judgment signal in the judging section. 2. A radiation detector provided adjacent to each other as a pair of a shielded radiation detector having a radiation detector having the same specifications as the radiation detector surrounded by a shield, and a radiation detector and shielded radiation detection in the radiation detector. And a plurality of sets of the signal cables that are installed side by side and a calculation unit that processes the signals input from the both signal cables as one set, and the calculation results of the calculation units are input. And a threshold value determining unit that determines the criticality by comparing the respective operation results and the threshold value, and comparing the operation results and the threshold value obtained from a plurality of operation units that are combined as necessary. And a warning device that issues a warning or the like according to the criticality judgment in 1. 3. A radiation detector provided adjacent to each other as a pair of a shielded radiation detector in which a radiation detector having the same specifications as the radiation detector is surrounded by a shield, and a radiation detector and shielded radiation detection in the radiation detector. And a plurality of sets of the signal cables that are installed side by side and a calculation unit that processes the signals input from the both signal cables as one set, and the calculation results of the calculation units are input. Each of the calculation results, and an auxiliary calculation unit that performs calculation such as averaging or addition averaging, a determination unit that determines the criticality by comparing the calculation result from this auxiliary calculation unit with a threshold value, and the criticality in this determination unit. A critical warning device comprising a warning device that issues a warning or the like when judged.