JPH06230174A - Criticality detector - Google Patents

Abstract

PURPOSE:To detect both fast and slow critical phenomena using a single radiation detector. CONSTITUTION:The criticality detector for converting radiation into an analog radiation dose rate and detecting a fast criticality using an analog comparison circuit 24 further comprises an A-D converting means 26 for converting the analog signal converted through the radiation detecting means 21 into a digital signal, means 29 for accumulating thus converted digital signal for every predetermined time interval and storing the accumulated signal, a digital comparison circuit 30 for comparing the accumulated value stored in the accumulating means 29 with a preset digital accumulated value trip level, and a slow criticality detecting means 23 for outputting a trip signal when the accumulated value exceeds the trip level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a criticality detection device used when handling nuclear fuel materials, etc., and in particular, it detects a criticality state that causes a criticality accident appropriately in accordance with a plurality of different radiation dose rate changes. The present invention relates to a criticality detection device.

[0002]

2. Description of the Related Art In a conventional criticality detection apparatus, a radiation detector 1 is installed on the site side as shown in FIG. 4, and a radiation determination circuit 1 on the central monitoring side is provided to the radiation detector 1 via a transmission line 10. 11 is connected.

The radiation detector 1 includes a scintillation detector 2 which outputs an analog signal obtained by converting a radiation dose rate into a voltage value, an amplifier 3 which amplifies the analog signal to a predetermined signal level, and an amplifier 3 from the amplifier 3. An analog comparison circuit 7 is provided which compares the output potential 4 output with the reference potential 5 and outputs a trip signal 6 when the output potential 4 exceeds the reference potential 5. The trip signal from the analog comparison circuit 7 is provided. 6 drives the cable driver 8. Then, a predetermined logic level signal is output from the cable driver 8 and sent to the logic determination circuit 11 via the transmission line 10.

Here, the logic determination circuit 1 on the central monitoring side
When the radiation detector 1 transmits a predetermined logic level signal, the radiation detector 1 determines that the radiation dose rate by the radiation detector 1 has reached the trip level, and the required alarm signal based on the determination result. Is output or the required equipment is automatically tripped to prevent accidents.

[0005]

However, the above-described criticality detection device detects the first criticality of the analog signal level having the response characteristic of a quick rise among the radiation dose rates detected by the scintillation detector 2. It is possible, but it is not possible to detect slow criticality with slow response characteristics.

The present invention has been made in view of the above situation, and not only the first criticality can be obtained by using one detector,
It is an object of the present invention to provide a criticality detection device capable of simultaneously detecting slow criticality.

[0007]

In order to solve the above-mentioned problems, the invention corresponding to claim 1 detects a radiation dose rate by a radiation detector, and based on the analog level of the detected radiation dose rate. In the criticality detection device that outputs a trip signal by means of the radiation detector,

Of the radiation detection means for converting the radiation dose rate into a required analog signal, and among the analog signals obtained by this radiation detection means, the analog signal level having a quick rising response characteristic is a predetermined analog level. A first criticality detection means for outputting, for example, a trip signal when exceeding, and an AD conversion means for converting the analog signal obtained by the radiation detection means into a digital signal,
An integration storage means for integrating and storing the digital signals converted by the A / D conversion means for each predetermined period, and an integration value stored in the integration storage means is compared with a preset predetermined digital integration value level. With digital comparison means,
It is a criticality detection device provided with slow criticality detection means for outputting, for example, a trip signal when the stored integrated value exceeds the digital integrated value level.

[0009]

Therefore, in the invention according to claim 1, by taking the above-mentioned means, a relatively steep rising characteristic of the analog signal corresponding to the radiation dose rate detected by the radiation detecting means can be obtained. At the first criticality shown, the first criticality detection means compares the analog signal level output from the radiation detection means with a predetermined analog level, and when the analog signal level exceeds the predetermined analog level, the first criticality detection signal, For example, it outputs a trip signal.

On the other hand, on the output side of the radiation detecting means, A-
A D conversion means, an integration storage means, and a digital comparison means are provided, and an analog signal corresponding to the radiation dose rate output from the radiation detection means is converted into a digital signal by the A-D conversion means, and the digital signal is converted every predetermined period. If the signals are integrated by the integration storage means, it is possible to capture and store the slow criticality exhibiting a slow response characteristic. Then, the stored integrated value is compared with a preset digital integrated value level by a digital comparison means, and when the stored integrated value exceeds the predetermined digital integrated value level, a slow critical value, for example, a trip signal is output. To do. Therefore, it is possible to simultaneously detect the fast criticality and the slow criticality using one radiation detector.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a criticality detecting device according to the present invention. This criticality detection device is an improved version of the configuration of the radiation detector itself, and the other parts have substantially the same configuration as the conventional device. Therefore, in this apparatus, the same parts as those of the conventional apparatus are designated by the same reference numerals, and detailed description thereof will be omitted.

That is, the radiation detector 20 used in the apparatus of the present invention detects the radiation and converts the dose rate of the radiation into an analog signal converted into a voltage.
1 is provided. A scintillation detector, for example, is used as the radiation detecting means 21, but it goes without saying that various other radiation detectors may be used.

At the output side of the radiation detecting means 21, a fast critical detecting means 22 for detecting a fast critical from an analog signal level having a quick rising response characteristic and a slow critical detecting a slow response characteristic are detected. Slow criticality detection means 23 is provided.

The first criticality detection means 22 compares an analog signal level obtained by converting the radiation dose rate obtained by the radiation detection means 21 into a voltage with a preset reference level, that is, an analog trip level E, and outputs a trip signal. A cable driver 2 provided with an analog comparison circuit 24 for outputting and outputting a logic signal of a predetermined level according to the output of the analog comparison circuit 24 as required.
5 are provided.

On the other hand, the slow criticality detecting means 23 converts the analog signal output from the radiation detecting means 21 into an analog signal corresponding to the radiation dose rate into a digital signal 26.
Besides, a clock signal source 2 for generating a reference clock
7. PLD (program logic device: Progra
m-able Logic Device) 28 is provided. This P
The LD 28 has a function of outputting various timing signals such as AD conversion based on a reference clock, memory storage described later, and digital comparison.

Further, the slow criticality detecting means 23 has a P
A memory 29 for accumulating and storing a digital signal obtained by converting the analog signal corresponding to the radiation dose rate by the AD converting means 26 based on the timing signal from the LD 28 for a predetermined period, and the timing signal from the PLD 28. A digital comparison circuit 30 that compares the integrated value received and stored in the memory 29 with a preset digital integrated value trip level F is provided, and if necessary, a predetermined value is output according to the output of the digital comparison circuit 30. A cable driver 24 that outputs a level logic signal is provided. Next, the operation of the above device will be described.

Usually, the fast critical has a waveform showing a fast response characteristic as shown in FIG. Therefore, the radiation dose rate analog signal output from the radiation detection means 21 is introduced into the analog comparison circuit 24, and the analog trip level (E) is previously set as the reference potential at the other input end of the analog comparison circuit 24. Ok
When the radiation dose rate analog signal level exceeds the analog trip level (E), the analog comparison circuit 24 can output a trip signal. That is, with regard to the first criticality, the criticality can be detected depending on whether or not the analog signal level of the radiation dose rate exceeds the analog trip level (E).

However, as shown in FIG. 2, there is only a slight change from the background level BG, and the critical state is judged by the duration thereof. In the case of criticality, it is not possible to perform slow criticality detection, and thus trip detection, only by comparing the radiation dose rate analog signal level values as described above.

Therefore, while receiving the timing signal from the PLD 28, the radiation dose rate analog signal is converted into a digital signal by the A / D conversion means 26 at regular intervals.
When the analog signal level becomes equal to or higher than a predetermined BG + α, the digital signals are sequentially integrated and stored in the memory 29.
I will remember it. Here, the initial integration threshold value of the digital signal is BG + α, for example, if the initial integration threshold value is BG or more, a certain time has elapsed as long as the radiation dose rate analog signal level exceeds BG. This is because a slow critical warning or trip signal is always issued.

Therefore, in order to avoid such a problem,
While the integration is performed when BG + α or more in advance, the reset is performed again when the integration value does not exceed the digital integration value trip level F (see FIG. 3) set in advance by the system even if the integration is performed for a certain period. A new integration operation is performed for a certain period. Further, when the radiation dose rate analog signal level continues to be BG + α or less for a certain period or longer, the reset is similarly performed regardless of the presence or absence of the integrated value, and the new integration is performed again. This is because the integrated result has a negative value and the digital integrated value trip level F is substantially increased.

As described above, under the instruction of the PLD 28, the outputs of the AD converting means 26 are integrated for a certain period of time and stored in the memory 29, and then the digital comparison timing signal from the PLD 28 is similarly digitally compared. It is sent to the circuit 30. Here, the digital comparison circuit 30 includes a memory 29.
The integrated value stored in is compared with a predetermined digital integrated value trip level F, and when the stored integrated value exceeds level F, a trip signal is output and the cable driver 2
Supply to 5. Therefore, a predetermined logic level signal is output from the cable driver 25 and transmitted to the central monitoring side.

The integrated time is (b) and (c) in FIG.
Since the integrated values (b) 'and (c)' shown in FIG. 3 are obtained according to the analog level shown in FIG. 3, the response time until the trip level is generated and the digital integrated time are t as shown in FIG.
1 and t2. Also, although it is not the first critical level, it is lower than the analog trip level E as shown in FIG.
Also, the signal level is higher than BG + α (d)
The instantaneous noise shown in may occur, but if these noises (d) are summed up each time,
Since the digital integrated value trip level F is substantially lowered, for example, the intermediate level G is set in advance, and when the analog value exceeds the intermediate level G, the integration is not performed.

Therefore, according to the configuration of the above-described embodiment, the analog value of the radiation dose rate output from the radiation detecting means 21 is converted into a digital value inside one radiation detector 20 for criticality detection. And the digital value is integrated and stored for each predetermined period, and the stored integrated value and the digital integrated value trip level are compared, and when the stored integrated value exceeds the integrated value trip level, Since the trip signal is output, not only the fast critical having a steep change characteristic can be monitored, but also the slow critical over a long time with a low radiation level can be accurately determined and measured, and the trip signal can be output. Particularly, in the case of slow criticality, a slight change from BG can be digitally converted, integrated and compared, and a trip signal can be output.

In the above embodiment, the radiation detecting means 2
The output level of 1 is reset when the state of BG + α or less occurs for longer than a predetermined period. Instead of this reset, an arithmetic processing algorithm that integrates a negative value as zero is used. Good. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0026]

As described above, according to the present invention, 1
Both fast and slow critical phenomena can be detected using one radiation detector. Especially in the case of slow criticality, subtle changes from BG can be accurately measured by digital conversion and integration comparison, and trip conditions can be accurately measured. Can be determined.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a criticality detection device according to the present invention.

FIG. 2 is a diagram showing a change characteristic of a radiation dose rate analog value output from a radiation detecting means.

FIG. 3 is a diagram illustrating a slow critical digital integrated value of the change characteristics of the radiation dose rate analog value shown in FIG. 2.

FIG. 4 is a block diagram of a conventional criticality detection device.

[Explanation of symbols]

10 ... Transmission path, 11 ... Logic determination circuit, 20 ... Radiation detector, 21 ... Radiation detection means, 22 ... Fast criticality detection means, 23 ... Slow criticality detection means, 24 ... Analog detection circuit, 25 ... Cable driver, 26 ... A-D conversion means, 27 ... Clock signal source, 28 ... PLD, 29 ... Memory, 30 ... Digital comparison circuit.

Claims (1)

[Claims] 1. A criticality detector for detecting a radiation dose rate by a radiation detector and detecting a critical phenomenon from an analog signal of the detected radiation dose rate, wherein the radiation detector is configured to detect the radiation dose rate as a radiation dose rate. Of the radiation dose rate converted by the radiation detection means, and of the radiation dose rate analog signals obtained by the radiation detection means, when the analog signal level having a quick rising response characteristic exceeds a predetermined analog level First criticality detection means for judging, A-D conversion means for converting the analog signal of the radiation dose rate obtained by the radiation detection means into a digital signal, and the digital signal converted by this A-D conversion means A cumulative storage means for cumulatively storing for each period, a cumulative value stored in the cumulative storage means, and a predetermined preset value. A digital comparison means for comparing with a digital integrated value level, and a slow criticality detection means for determining a slow criticality when the stored integrated value exceeds the predetermined digital integrated value level. Criticality detection device.