JP2878930B2 - Radiation monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation monitoring apparatus for detecting a radiation abnormality.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram showing a conventional radiation monitoring apparatus, in which 1 is a radiation detector, 2 is a preamplifier, and 3 is a detector via a preamplifier 2. A main amplifier for amplifying the signal, 4 is a wave height discriminator for shaping and discriminating the detector signal passed through the amplifiers 2 and 3, and 5 is a counter or rate meter for converting a signal sequence into a count value or a count rate. , 6 is a display for displaying the count value or count rate, 7 is a recorder for continuously recording the result, 8 is an alarm transmitter, 9 is a signal changeover switch, 10 is a test signal generator, and 11 is a high voltage power supply. , 1
2 is a shutter drive circuit, 13 is a shutter arranged near the radiation detector 1, 14 is a radiation source for irradiating the radiation detector 1 with a predetermined radiation dose, and 15 is a measurement container (or piping) for containing a fluid to be measured. ) And 16 are radioactivity contained in the fluid in the measurement container 15. The detector 1 is arranged outside the measurement container 15.

Next, the operation will be described. Measurement container 15
Radiation emitted from the radioactive substance 16 flowing in the inside is detected by the detector 1 arranged close to the measurement container 15. The detection pulse signal enters the main amplifier 3 via the preamplifier 2 and is amplified. The amplified pulse signal is subjected to wave height discrimination and shaping by the wave height discriminator 4 and is then counted or counted by the counter or rate meter 5. It is converted into a count signal. The counting result is displayed on the display 6 and simultaneously recorded continuously by the recorder 7. Also,
The counting signal branched from the counter or the rate meter 5 is
The alarm value is compared with the set value by the alarm transmitter 8, and when the set value is exceeded, an alarm is issued to notify the operator of the abnormality of the monitoring target. Further, the shutter 13 is opened by operating the shutter drive circuit 12, and the detector 1 is irradiated with radiation from the radiation source 14. The detector 1 detects radiation from the radiation source 14 and outputs a predetermined pulse signal, and displays a predetermined count value or count rate by the above-described operation processing. This allows the operator to confirm that the device is operating properly.

[0004]

Since the conventional radiation monitoring apparatus is configured as described above, the alarm set value is fixed, and the operator knows the abnormality from the result of a simple comparison with the measured value. Will be. For this reason, there is a defect that it is not possible to know the fluctuation abnormality during the period up to the alarm set value, that is, the minute fluctuation of the radiation. For the purpose of compensating for the above-mentioned drawbacks, it has also been practiced to input a measured value (counting signal) of the apparatus to another computer and calculate the rate of change of the measured value, for example, to know the abnormality of the change. However, in any case, there is a disadvantage that it is not possible to distinguish whether the change in the measured value is due to a change in the radiation concentration, which is the original measurement target, or a change in the characteristics of the apparatus itself. For this reason, in order to identify the radiation abnormality, the abnormality is confirmed by separately analyzing the radioactivity of the fluid to be measured.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and detects a minute change in a measured value and determines whether the change is due to an increase in radiation or a characteristic abnormality in the apparatus. It is an object of the present invention to obtain a radiation monitoring device that can identify whether the radiation monitoring is performed.

[0006]

A radiation monitoring apparatus according to the present invention comprises: a radiation detecting means; a counting means (counter or rate meter 5) for measuring a count value or a counting rate of an output pulse signal from the detecting means. Distribution signal measuring means (multiplexed wave height analyzer 17) for analyzing the peak value of the output pulse signal to measure the peak height distribution signal; and waveform measuring means (waveform observation device 1) for measuring the signal waveform of the output pulse signal.
8) Compared with the normal state, if the count value or the count rate fluctuates and the distribution signal and the signal waveform do not fluctuate, it is an abnormality due to an increase in radiation. Abnormal type discriminating means (computer 19) for discriminating that there is an abnormality.

[0007]

In the radiation monitoring apparatus according to the present invention, the abnormal type discriminating means detects a change in a count value or a counting rate, a distribution signal, and a waveform, and determines whether the radiation increase abnormality or the apparatus side abnormality is based on the detection result.

[0008]

【Example】

Embodiment 1 FIG. Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a radiation monitoring apparatus according to the present invention. Components similar to those of the conventional example shown in FIG. In FIG. 1, 17 is the main amplifier 3
A pulse height analyzer for measuring a pulse height distribution of an output signal pulse having passed through the apparatus, a waveform observing device for measuring a signal pulse waveform, a count value of a counter, a pulse height distribution data from a multiple pulse height discriminator, and a waveform observing device. , A computer for inputting waveform data from the computer, performing arithmetic processing, 20 is a CRT, 21 is a printer, and 22 is a storage device for storing the calculation results.
It should be noted that the detector 1 is constantly irradiated with a predetermined amount of radiation from the radiation source 14.

Next, the operation will be described. Here, an embodiment using a plastic scintillation detector (hereinafter abbreviated as a PL detector) as the detector 1 will be described. The PL detector usually detects radiation from the surrounding environment and outputs a pulse signal. This pulse signal is amplified by the preamplifier 2 and the main amplifier 3, subjected to wave height discrimination by the wave height discriminator 4, and converted into a count value (measured value 1) by the counter 5.
On the other hand, the pulse signal branched from the main amplifier 3 is input to the multiplex pulse height analyzer 17, where the pulse height distribution signal (spectrum) is measured (measured value 2). At the same time, the pulse signal is input to an oscilloscope as the waveform observation device 18, and the signal waveform is observed (measured value 3). These measured values 1 to 3 are input to the computer 19 and are calculated according to the flow shown in FIG.

[0010] Now, when something abnormal occurs in the plant,
When a minute radioactive leakage occurs and a small amount of the radioactive substance 16 flows into the fluid to be measured entering the measurement container 15, the radiation signal from the radioactive substance 16 is counted through the same process as described above, and the measured value 1 is obtained. Increases. Measurement 1
It is known that, for example, by a known statistical process (whiteness test or the like) (step S1), when the indication rises, the measured value fluctuation pattern differs from the normal radiation fluctuation. Is determined to be abnormal. That is, the fluctuation of the statistic is checked (step S2),
If there is a change in the statistics, there is a possibility of radiation abnormality, and if there is no change, there is no radiation abnormality. Then measured value 2
Calculates the reference peak position by the light pulser built in the PL detector (step S3), and confirms the deviation from the normal peak position of the spectrum stored in advance (step S4). If the peak position is at the predetermined normal position,
There is no drift (device abnormality caused by environmental change, etc.), and it is determined that it is normal. If there is a deviation from the predetermined position (this occurs when the environmental condition changes, such as when the gain setting of the device is changed), a warning message of “drift abnormality” is transmitted. If there is no change in the peak position, the difference between the normal energy spectrum (initial spectrum) and the normal energy spectrum in the predetermined energy region of the spectrum is obtained from the measured value 2 (step S5), and the difference is confirmed (step S5). S6). In the case of the PL detector, if the characteristic deterioration progresses, a change occurs in the spectrum. If there is a change in the spectrum, a warning message of "detector abnormality" is transmitted. In parallel with step S3, the count value of the reference peak is obtained (step S3).
7) By comparing with the initial value (step S8), if there is a difference from the count value, an alarm message of "measurement system abnormality" is transmitted. When there is no difference between the counted value and the initial value, that is, when the waveform is normal, the waveform data of the measured value 3 is compared with the initial waveform data (step S9). Send an alert message. If there is no change in the signal waveform from the preamplifier 2 to the counter 5, the PL detector and the signal processing system are normal, and it is determined that "radiation increase (abnormal)" from the measured object. That is, the determination as “radiation abnormality” is made when the statistic of the measured value 1 fluctuates, the measured value 2 is normal, and the measured value 3 does not change. Done. In summary, when there is a change in the distribution signal compared to the normal state, it is determined that the apparatus is abnormal, and when the count value or the count rate has a change compared to the normal state, the change in the distribution signal and signal waveform. When there is no such information, the computer 19 including the AND circuit 30 that determines that the abnormality is due to an increase in radiation constitutes an abnormal type determining unit.

Embodiment 2 FIG. Note that the same effect as in the first embodiment can be obtained by using a rate meter instead of the counter 5 and using the count rate as the output as the measured value 1.

Embodiment 3 FIG. In the first embodiment, the case where the PL detector is used as the detector 1 has been described. However, when another type of detector, for example, a NaI detector (a sodium iodide detector) is used, FIG. As shown, the presence or absence of detector degradation is confirmed by calculating the resolution of the reference peak from the spectrum measurement result, and the soundness of the detector is determined. That is, as shown in FIG.
Thereafter, the resolution of the reference peak is calculated (step S1).
0), it is determined whether or not the resolution is abnormal (step S).
11) If there is an abnormality, a "detector abnormality" is transmitted, and if there is no abnormality, it is determined that there is a possibility of radiation increase, and AND
The process of the circuit 30 is to wait. Therefore, the processing 100 of steps S10 and S11 surrounded by a dotted line is different from the first embodiment.

Embodiment 4 FIG. Further, when a GM tube (Gaigummula tube) is used as the detector 1, FIG.
As shown in (1), a peak search is performed from the spectrum measurement result (step S12), and the presence or absence of after-pulse peaks other than the initial peak is confirmed (step S1).
3), determine the soundness of the detector. In the case of this embodiment,
After the determination of “detector abnormality”, the determination of “drift abnormality” is performed. In addition, the count rate of pulses equal to or higher than the pulse height discrimination level (a level set for cutting noise) is compared with the spectrum measurement value and the count signal (Step S).
14) If there is a difference in the count, there is a possibility of a radiation abnormality, and if there is no difference in the count, it is determined that the measurement system is abnormal (step S15). That is, the processing 200 surrounded by a broken line is different from the processing of the embodiment 1.2.

To briefly explain the gist of the first to fourth embodiments, when the detector is a PL scintillation detector, the wave height distribution in the low wave height distribution region, the NaI scintillation In an apparatus using a detector, the resolution of the detector is used, and in a GM tube, the number of peaks is used.

Embodiment 5 FIG. In addition, if a pressure sensor is provided on the fluid pipe to be measured and a temperature sensor is provided near the radiation detector, a fluctuation component of the counting signal of the radiation detector due to a pressure change of the measurement fluid and a temperature change of the detector may be removed. Thus, the presence or absence of a radiation abnormality and a device side abnormality can be confirmed more accurately. That is, as shown in FIG. 5, a pressure sensor 31 is added to the measurement container 15 and a temperature sensor 32 is added near the radiation detector 1. Then, these signals are input to the processing device 33. (Here, the signal processing device 33 is provided with a device subsequent to the preamplifier 2 in FIG. 1 and performs the flow processing in FIGS. 2 to 4.) When a signal fluctuation of the detector 1 occurs, The presence or absence of an abnormality is determined according to the above-mentioned flow, but the fluctuation of the count signal when there is an output a from the pressure sensor 31 and the temperature sensor 32 is not used as a material for determining the abnormality.

Embodiment 6 FIG. Each of the above embodiments is configured to determine the presence or absence of an abnormality based on a signal detected by one detector 1, but as shown in FIG.
Responsible for the same radioactive leakage monitoring target (measurement vessel 15) as (equivalent to detector 1), but outputs a signal from another detector B36 for detecting radiation at a different location in the vessel 15 and an output signal from the reactor 34. When the signal is input to the processing device 37 and the signal of the detector A35 fluctuates, by checking the presence or absence of the abnormality of the device according to the above-described flow, and comparing the result with the result of the abnormality determination of the output signal of the detector B36, It is possible to more appropriately determine whether the fluctuation event is due to radiation or a change in device characteristics. In other words, this is effective when the container 15 is long, etc., and enables quick abnormality determination. In addition, since there are two detectors, more reliable abnormality determination can be performed.

Embodiment 7 FIG. Further, as shown in FIG. 7, the reactor 34, the detector A35, and another process system B3 related to the process system A38 to be monitored by the detector.
9 and a plurality of plant information, which are the outputs of these reactors and detectors, are transmitted to a signal processing device 40.
, And can be compared with each other to monitor a plurality of process systems.

Embodiment 8 FIG. In addition, the background radiation level of the environment around the detector due to the change in the reactor power is estimated,
By removing the influence of this on the instruction, it is possible to more accurately confirm the presence or absence of abnormality in the fluctuation of the measured value.

As described above, according to each of the above-described embodiments, the detection system and the statistic of the detector signal (measured value) are obtained, and at the same time, the spectrum measurement and the abnormality determination flow according to the type of the detector are used. Since the configuration is such that the operation soundness of the measurement system can be confirmed, the presence or absence of a radiation abnormality can be confirmed earlier than the abnormality detection by the alarm function of the conventional radiation monitoring apparatus, which can be used to prevent the spread of plant accidents. Also,
The waveform observation device 18 measures the waveform of the detector signal,
By confirming whether or not a signal other than the detector has entered, such as whether noise is superimposed, or whether there is an abnormality in the signal processing system, it is possible to confirm a disturbance abnormality from outside the measurement system.
Further, by combining other detectors with the furnace output signal and the like as in the sixth embodiment, more appropriate and accurate abnormality determination can be made.

[0020]

As described above, according to the radiation monitoring apparatus of the present invention, the radiation detecting means, the output pulse signal counting means, the distribution signal measuring means, and the waveform measuring means are compared with those in the normal state. An abnormal type discriminating means for judging an abnormality due to an increase in radiation when the count value or the count rate fluctuates and there is no fluctuation in the distribution signal and the signal waveform; , It is possible to detect a minute change in the measured value, and to determine whether the change is due to an increase in radiation or a characteristic abnormality on the device side, and detect an abnormality at an early stage. Further, according to the radiation monitoring apparatus of the present invention, the constitution is such that the fluctuation of the count value due to the fluctuation of the pressure of the measurement fluid and the fluctuation of the ambient temperature of the detector is removed, or the count value and the reactor output at a plurality of parts are removed. With this configuration, the abnormality can be more accurately and reliably determined.

[Brief description of the drawings]

FIG. 1 is a block diagram of a radiation monitoring apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a signal processing flow according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a signal processing flow according to a third embodiment of the present invention;

FIG. 4 is a diagram showing a signal processing flow according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing Embodiment 5 of the present invention.

FIG. 6 is a block diagram showing a sixth embodiment of the present invention.

FIG. 7 is a block diagram showing Embodiment 7 of the present invention.

FIG. 8 is a block diagram illustrating an example of a conventional radiation monitoring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radiation detector 5 Counter or rate meter (counting means) 17 Multiple wave height analyzer (distributed signal measuring means) 18 Waveform observing apparatus (waveform measuring means) 19 Calculator (abnormal kind discriminating means)

Claims (7)

(57) [Claims] 1. A radiation detecting means, a counting means for measuring a count value of an output pulse signal from the detecting means, and a distribution signal measuring means for analyzing a peak value of the output pulse signal to measure a peak height distribution signal. And a waveform measuring means for measuring the signal waveform of the output pulse signal, and when the count value fluctuates and the distribution signal and the signal waveform do not fluctuate as compared with the normal state, it is an abnormality due to an increase in radiation. A radiation monitoring apparatus comprising: an abnormal type determination unit configured to determine an abnormality on the device side when a signal fluctuates. 2. A radiation detecting means, a counting means for measuring a counting rate of an output pulse signal from the detecting means, a distribution signal measuring means for analyzing a peak value of the output pulse signal and measuring a peak height distribution signal. And a waveform measuring means for measuring the signal waveform of the output pulse signal. If the count rate fluctuates and the distribution signal and the signal waveform do not fluctuate as compared with the normal state, it is an abnormality due to an increase in radiation. A radiation monitoring apparatus comprising: an abnormal type determination unit configured to determine an abnormality on the device side when a signal fluctuates. 3. A radiation detecting means comprising a plastic scintillation detector, a counting means for measuring a count value of an output pulse signal from the detecting means, and a peak value of the output pulse signal being analyzed to determine a low level as a peak height distribution signal. Distribution signal measuring means for measuring the peak value distribution in the wave polymer region; waveform measuring means for measuring the signal waveform of the output pulse signal; and a distribution signal and a signal having a variation in the count value as compared with a normal state. A radiation monitoring apparatus comprising: an abnormal type determination unit configured to determine an abnormality due to an increase in radiation when there is no change in the waveform and to determine an abnormality on the device side when there is a change in the distribution signal. 4. A radiation detecting means, which is a sodium iodide detector, a counting means for measuring a count value of an output pulse signal from the detecting means, and a crest value of the output pulse signal which is analyzed as a crest distribution signal. Distribution signal measuring means for measuring the resolution of the detector, waveform measuring means for measuring the signal waveform of the output pulse signal, and fluctuations in the distribution signal and the signal waveform due to a change in the count value as compared with a normal state. A radiation monitoring apparatus comprising: an abnormal type determination unit configured to determine an abnormality due to an increase in radiation when there is no abnormality, and to determine an abnormality on the device side when there is a variation in a distribution signal. 5. The radiation detecting means is a Geiger-Mura tube, a counting means for measuring a count value of an output pulse signal from the detecting means, and a crest value of the output pulse signal is analyzed to determine a peak number as a crest distribution signal. A distribution signal measuring means for measuring, a waveform measuring means for measuring a signal waveform of the output pulse signal, and a radiation signal when the count value fluctuates and the distribution signal and the signal waveform do not fluctuate as compared with a normal state. A radiation monitoring apparatus comprising: an abnormality type determining unit configured to determine that the abnormality is caused by the increase and that the distribution signal fluctuates and is determined to be an abnormality on the device side. 6. A pressure detecting means for detecting a pressure of a measurement fluid to be measured by said radiation detecting means, a temperature detecting means for detecting an ambient temperature of said radiation detector, and a temperature detecting means and a pressure detecting means. A means for removing a fluctuation component of the count value of said radiation detecting means in accordance with the output of said radiation detecting means from the count value measured by said radiation detecting means. Item 6. The radiation monitoring device according to item 4 or 5. 7. A plurality of radiation detection means, wherein the radiation detection means is provided in a plurality, and the radiation detection means is provided with a reactor power detection means for detecting an output of a reactor supplying a measurement fluid to be measured. A means for judging whether there is a radiation increase abnormality or a device side abnormality based on the count value measured in step 1 and the reactor power measured by the reactor power detection means, has been added to the abnormal kind determination means. Item 6. The radiation monitoring device according to item 1, item 3, item 4, item 5, or item 5.