JPH08220290A - Criticality warning system - Google Patents

Abstract

PURPOSE: To detect a process even up to slow criticality, together with fast criticality, as early as possible and properly. CONSTITUTION: In this criticality warning system, a trip signal is transmitted from a radiation detector 10 laid in a criticality monitor zone to a warning judgement circuit 7 laid in a central control section, when a radiation detected with the detector 10 exceeds a trip level. In this case, the detector 10 is provided with a sampling means 12 for sampling radiation levels at the preset intervals, and a slow criticality detection means 11 for finding the rising rate of the radiation level from a value sampled with the means 12 and then detecting slow criticality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a criticality warning system for detecting a criticality accident in a facility that handles nuclear fuel material, and particularly to a warning by detecting each of a fast (prompt) criticality and a slow (slow) criticality. It relates to an output criticality warning system.

[0002]

2. Description of the Related Art Nuclear fuel facilities consist of uranium enrichment, fuel processing,
It consists of a wide variety of facilities for fuel transportation / storage, reprocessing, and waste treatment / storage. In such facilities, radioactive materials are scattered throughout the facility and move within the facility depending on the work process.Therefore, protective measures must be taken to prevent reaching a critical level in any technically assumed case. I have to. Conventionally, nuclear fuel facilities have been equipped with a criticality warning system as a countermeasure against a criticality accident.

FIG. 6 shows an example of the configuration of a criticality warning system installed in a nuclear fuel facility. The scintillation detector 2 of the radiation detector 1 installed in the criticality monitoring area outputs an analog signal corresponding to the detected radiation dose, and the analog signal is current-voltage converted by the amplifier 3 to convert the radiation level into a voltage. It is given to the comparator 4. The comparator 4 compares the reference potential set from the reference voltage setting device 5 with the input potential given from the amplifier 3, and the comparison result is transmitted from the site to the central logic determination circuit 7 via the transmission line 8 by the cable driver 6. Is transmitted.

The logic decision circuit 7 installed in the center decides the comparison result transmitted from the radiation detector 1 in the field as a logic level, and when the input potential of the comparator 4 exceeds the reference potential, a critical value is reached. Output an alarm.

By the way, there are two types of criticality: slow criticality and fast criticality. As shown in FIG. 3, the fast criticality causes the analog count rate of the scintillation detector 2 to increase instantaneously, but the slow criticality gradually increases and trips. Reach the level.

[0006]

However, since the conventional criticality warning device detects the criticality by comparing the analog level of the radiation dose rate output from the scintillation detector 2 with the trip level, a response is not obtained. There is no problem in detecting the first criticality in which the radiation dose rate exceeds the trip level almost simultaneously with the criticality, but it is difficult to detect the slow criticality in which the radiation dose rate rises slowly after reaching the criticality in an early and stable manner. It was

The present invention has been made in view of the above circumstances, and provides a criticality warning system capable of detecting both fast criticality and slow criticality as early and surely as possible with one detector. With the goal.

[0008]

The present invention has taken the following means in order to achieve the above object. The present invention corresponding to claim 1 is a criticality warning for sending a trip signal from the radiation detector to an alarm judgment circuit installed in a central control unit when the radiation level exceeds a trip level in a radiation detector installed in a criticality monitoring area. In the system, sampling means provided in the radiation detector for sampling the radiation level at a predetermined interval, and variation of the radiation level from at least two consecutive sampling values provided in the radiation detector and output from the sampling means. Slow criticality detection means for obtaining a curve and detecting the slow criticality from the slope thereof.

According to the second aspect of the present invention, when the radiation level of a radiation detector installed in a criticality monitoring area exceeds a trip level, a trip signal is sent from the radiation detector to an alarm determination circuit installed in the central control unit. In the criticality warning system, sampling means provided in the radiation detector for sampling the radiation level at predetermined intervals, and an increase rate of the radiation level obtained from the sampling value of the sampling means provided in the radiation detector, Slow criticality detection means for detecting the slow criticality based on the rate of increase.

According to a third aspect of the present invention, when a radiation detector installed in a criticality monitoring area has a radiation level exceeding a trip level, a trip signal is sent from the radiation detector to an alarm determination circuit installed in a central control unit. In the criticality warning system, sampling means provided in the radiation detector for sampling the radiation level at a predetermined interval and a transmission path provided for the sampling value of the sampling means separately from the transmission path of the trip signal are used. And transmitting means for transmitting the radiation level to the central management unit and a sampling curve of the radiation level provided in the central management unit to obtain a variation curve of the radiation level, and the slow criticality is detected from the slope. Slow criticality detection means.

[0011]

The present invention has the following effects by taking the above measures. According to the present invention corresponding to claim 1, the radiation level detected by the radiation detector is sampled at predetermined intervals by the sampling means and input to the slow criticality detection means. In the slow criticality detection means, a variation curve of the radiation level is obtained from the sampling value of the radiation level. If the slope of the radiation level fluctuation curve is larger than a predetermined slope, it is determined to be slow critical. The result of this judgment is sent to the alarm judgment unit of the central management unit and subjected to a predetermined logical operation, and finally a criticality warning is output.

According to the present invention corresponding to claim 2, the radiation level detected by the radiation detector is sampled at a predetermined interval by the sampling means and input to the slow criticality detection means. In the slow criticality detection means, the rising rate of the radiation level is obtained from the sampling value of the radiation level. If the increase rate of the radiation level exceeds the specified value, it is judged as slow critical. This judgment result is sent to the alarm judgment unit of the central management unit.

According to the present invention corresponding to claim 3, the radiation level detected by the radiation detector is sampled at predetermined intervals by the sampling means. This sampling value is transmitted to the central management unit via the transmission line by the transmission means. In the central management unit, the slow criticality detecting means calculates a variation curve of the radiation level from the sampling value of the radiation level, and detects the slow criticality from the gradient.

[0014]

Embodiments of the present invention will be described below. FIG. 1 shows the overall configuration of a criticality warning system according to an embodiment. The parts having the same functions as those of the system of FIG. 6 described above are designated by the same reference numerals.

In the criticality warning system of this embodiment, the radiation detector 10 installed at the site and the logic judgment circuit 7 installed in the center are connected via a transmission line 8, and the radiation detector 10 is connected to the logic judgment circuit. A signal transmitted to the transmission line 7 via the transmission line 8 determines whether or not the alarm output is necessary.

The radiation detector 10 comprises a scintillator detector 2 consisting of a plastic scintillator and a photomultiplier. An amplifier 3 for converting a current signal into a voltage is connected to the output side of the scintillator detector 2, and the output terminal of the amplifier 3 is connected to one input terminal of a comparator 4. To the other input terminal of the comparator 4, a reference voltage setting device 5 corresponding to a trip level for detecting the fast critical is connected. The output stage of the comparator 4 is connected to a cable driver 6 driven by a trip output when the input potential from the amplifier 3 exceeds the reference voltage, and the cable driver 6 transmits the transmission line 8
Is connected to the field end of.

Inside the radiation detector 10, there is provided an MPU 11 as a slow criticality detecting means for monitoring the output signal of the scintillator detector 2 and detecting the slow criticality. The output of the amplifier 3 of the MPU 11 is the A / D converter 1
The trip output when the slow criticality is detected is input to the cable driver 6 through the digital output circuit 13 while being input via the digital signal output circuit 20. MP
The detection of the slow criticality in U11 is executed based on the flowchart shown in FIG. RAM14 is MPU1
The data can be written / read from 1 and various data for slow criticality detection are stored, for example.

Next, the operation of this embodiment configured as described above will be described. The detection of the first criticality is performed by the comparator 4 comparing the input voltage corresponding to the radiation level output from the amplifier 3 with the reference voltage, as in the alarm system of FIG. When the first criticality occurs, the input voltage corresponding to the radiation level exceeds the reference voltage corresponding to the trip level (E) due to the first criticality (A), as shown in FIG. Trip output is provided to 6. As a result, a trip signal is transmitted to the transmission path 8 and transmitted to the central logic determination circuit 7. On the other hand, if a slow criticality accident occurs,
As shown in (4), since the input voltage does not exceed the reference voltage in the comparator 4 until a considerable time has elapsed from the occurrence of the accident, the trip output is not performed.

Here, the slow criticality detection principle is as follows. When a slow criticality accident occurs, the radiation level has an ascending curve as shown by throw 1 (D) in FIG. Throw 2 (C) is an example of the rate of increase below the criticality judgment.
As shown in FIG. 4, if the radiation level output from the amplifier 3 is sampled at intervals of, for example, 2 seconds, the slope of the rising curve, which is the slow characteristic, can be detected from the difference between two consecutive sampling values. Therefore, if the slope of the rising curve of the radiation level at the time of the slow criticality accident is set as the rising regulation value A, and if the slow characteristic obtained from the difference between consecutive sampling values exceeds the rising regulation value A, the radiation level Can be judged to be critical without exceeding the trip level (E).

In this embodiment, the MPU 11 performs early detection of a slow criticality accident based on the flowchart of FIG. That is, the radiation level is fetched from the A / D converter 12 at an interval of 2 seconds (step S1), and the subtraction value M obtained by subtracting the previously fetched radiation level from the radiation level fetched this time is compared with the predetermined rising regulation value A. Yes (step S2). If the condition of “specified rise value A <subtraction value M” is satisfied, it is judged whether or not the condition is continuously satisfied a plurality of times (three times in the present embodiment) (step S3), and three times continuously. If the condition of “specified rise value A <subtraction value M” is satisfied, it is determined that a slow criticality accident has occurred, and a trip command is given to the digital output circuit 13 to cause the digital output circuit 13 to output it. To drive. As a result, a trip signal is transmitted to the transmission path 8 and transmitted to the central logic determination circuit 7.

In step S3, the judgment condition that the condition of "specified rise value A <subtraction value M" is satisfied three times in succession is included in the judgment condition as shown in FIG. This is to prevent a malfunction when is superimposed.

As described above, according to this embodiment, the radiation detector 10 in the field has a function of detecting the slow criticality from the gradient of the radiation level, and the OR of the fast critical and the slow criticality is provided.
Since the trip signal is sent to the transmission line 8 with
A single detector 10 can detect both fast and slow critical phenomena, and in particular can detect slow criticality early.

According to the present embodiment, when the condition of the prescribed rise value A <the subtraction value M is satisfied continuously for a plurality of times, it is judged as the slow criticality and the trip signal is generated, so that the malfunction due to the noise can be prevented. , Can generate a highly reliable critical alarm.

FIG. 5 shows the configuration of a modification of the above embodiment. This modification is an example in which the central logic determination circuit has a slow criticality detection function. In the radiation detector 20 installed on site, the A / D converter 12 for sampling the radiation level output from the amplifier 3 is connected to the parallel / serial conversion circuit 21 and the electric / optical conversion circuit 22 in series, and the optical fiber cable 23 is connected. It is connected to the site end. The components necessary for detecting the first criticality are provided in the radiation detector in the same manner as in the above embodiment.

In the central logic determination circuit 30, the optical / electrical converter 31 is provided at the end of the optical fiber cable 23 on the central side.
Also, the MPU 33 as the slow criticality detection means is connected via the serial / parallel converter 32 in series.
The MPU 33 has a function of detecting the slow criticality by using the data stored in the RAM 34 according to the same detection principle as that of the above-described embodiment. The trip command output when the MPU 33 detects the slow criticality is the digital output circuit 3
5 to the OR circuit 36 from the digital output circuit 35.
A trip signal is input to the logic determination unit via the. The OR circuit 36 is supplied with a fast critical trip signal transmitted from the radiation detector 20 on site via the transmission line 8.

According to such a modification, there is an advantage that the number of parts on the site side where the environment is severe can be reduced and the reliability can be improved. The present invention is not limited to the above embodiment.
For example, the sampling cycle of the radiation level input to the MPUs 11 and 34 may be shortened to remove the ripple component having a high possibility of noise, and the rising rate may be determined by a moving average of about 10 seconds.

[0027]

As described above in detail, according to the present invention,
It is possible to provide a criticality alert system that can detect both the first criticality and the slow criticality as early and surely as possible with a single detector.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a criticality warning system according to an embodiment of the present invention.

FIG. 2 is a flow chart for slow criticality detection in the criticality alert system of one embodiment.

FIG. 3 is a diagram showing rise curves of radiation levels such as fast critical and slow critical.

FIG. 4 is a diagram for explaining a detection principle of a slow characteristic.

FIG. 5 is a diagram showing a modified example of the criticality warning system.

FIG. 6 is a configuration diagram of a conventional criticality warning system.

[Explanation of symbols]

1, 10, 20 ... Radiation detector, 2 ... Scintillator detector, 3 ... Amplifier, 4 ... Comparator, 5 ... Reference voltage setting device, 6 ... Cable driver, 7 ... Logic determination circuit,
8 ... Transmission path, 11, 33 ... MPU, 12 ... A / D converter, 13, 35 ... Digital output circuit, 14, 34 ... RA
M.

Claims (3)

[Claims] 1. A criticality warning system for sending a trip signal from a radiation detector installed in a critical monitoring area to an alarm judgment circuit installed in a central management unit when the radiation level exceeds a trip level, Sampling means provided in the detector for sampling the radiation level at predetermined intervals, and a radiation level variation curve is obtained from at least two consecutive sampling values output from the sampling means, provided in the radiation detector. A criticality warning system comprising: a slowness criticality detecting means for detecting a slowness criticality from the inclination. 2. A criticality warning system for sending a trip signal from the radiation detector to an alarm judgment circuit installed in a central control unit when the radiation level of the radiation detector installed in the criticality monitoring area exceeds a trip level, Sampling means provided in the detector for sampling the radiation level at a predetermined interval, and the radiation rate increase rate obtained from the continuous sampling values provided in the radiation detector and output from the sampling means, and the increase rate Slow criticality detection means for detecting slow criticality based on the above. 3. A criticality warning system for sending a trip signal from a radiation detector installed in a criticality monitoring area to an alarm judgment circuit installed in a central control unit when the radiation level exceeds a trip level, Sampling means provided in a detector for sampling the radiation level at a predetermined interval, and a sampling value of the sampling means is transmitted to the central management unit by using a transmission path provided separately from the transmission path of the trip signal. A transmission means; and a slow criticality detection means provided in the central management unit, for obtaining a variation curve of the radiation level from a sampling value of the radiation level sent by the transmission means, and detecting a slow criticality from the slope thereof. The criticality warning system characterized by the above.