JPH0697265B2 - Digital radiation monitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a digital radiation monitoring apparatus installed in a nuclear power plant that handles radioactive materials.

(Prior Art) In general, a radiation monitoring device is installed in a nuclear power plant such as a nuclear power plant that handles radioactive substances. This radiation monitoring device detects radiation by a radiation detector installed in each area and process of the atomic weight plant, and continuously monitors the radioactivity level by a measuring device, and the radioactivity level is predetermined. When the level exceeds a certain level, an alarm to that effect is issued to the operator. As this type of radiation monitor device, an analog type radiation monitor device has been widely used conventionally. This analog radiation monitor detects radiation with an analog radiation detector (GM tube detector, etc.) installed in each area and process of a nuclear power plant, and the measurement device (logarithmic dose rate meter, etc.) emits the radiation. The operation level is calculated in an analog manner and the meter is displayed by hardware.

By the way, in such an analog type radiation monitor, when the background level is usually out of the measurement range of the monitor, the meter display is as shown by the broken line A in FIG. Further, since the lower limit alarm set value L for generating the lower limit alarm when the monitor device is abnormal can be set only within the measurement range of the monitor device, the lower limit alarm is generated and released in such a state. Therefore, in this case, it is usually impossible to determine whether the background level is low or whether there is an abnormality in the monitor device and the instruction is low. Therefore, in the analog radiation monitor,
In order to confirm the soundness of the monitoring device, the individual analogs installed in the plant so that the meter display is forced to the state shown by the solid line B in FIG. 5 (state above the lower limit alarm set value L). A bug source (radiation source) is attached to the radiation detector, and the lower limit alarm is generated only when the monitor device is abnormal.

However, such a device has various problems as follows.

(A) Since a bag source (radiation source) is attached to each analog radiation detector, for example, 50 units are attached per plant, the management thereof is very difficult.

(B) The set value of the bug source needs to be set as low as possible in consideration of the influence on the measuring device, and the half-life of the bug source, the accuracy of the measuring device, and the sensitivity of each detector are corrected. It is necessary, and it is very difficult to set and adjust the setting value of the bug source.

For example, a method for adjusting a bug source of a detector whose measuring range of the measuring device is 10 ^-1 to 10 ³ mR / H is shown below. That is, lower limit alarm set value = 0.1% (10mv), lower limit reset span = 2 ± 1% (FS), bug source half-life Sr about 28.8 years,
If the amount of attenuation in one year is 2.4%, considering the reset span difference from the lower limit, 3.1% or more ≒ 1.3 × 10 ^-1 mR / H or more, and considering the attenuation of the bug source, 2.5% or more ≈ 1.26 × 10 ^-1 mR / H or more, so the deflection of the pointer due to the bug source must be (1.3 + 1.26) × 10 ^-1 = 2.56 × 10 ^-1 mR / H or more. Here, considering the installation error of the bug source itself of about 5%, (2.56 × 10 ^-1 mR / H) ± 2.5% = 2 to 3.2 × 10 ^-1 mR / H is set as the initial setting value by the bug source. There is a need to. Therefore, in order to obtain such a value, a bug source of about 0.5 μCi is attached to each analog radiation detector.

(Problems to be Solved by the Invention) As described above, in the conventional analog radiation monitor, it is necessary to attach a bug source to each analog radiation detector in order to confirm the soundness of the monitor. There was a problem.

The object of the present invention is to eliminate the need to attach a bug source,
An object of the present invention is to provide a digital radiation monitor device capable of confirming the soundness of the monitor device.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention is directed to a digital radiation detector installed in a nuclear power plant that handles radioactive substances and detecting radiation, and this digital radiation detector. The radioactivity level measured by the radiation detector is bar-displayed on a display means having a measurement range within a predetermined range and continuously monitored, and when the radioactivity level exceeds a predetermined level, the fact is indicated. In a digital radiation monitor device composed of a measuring device that generates an alarm, a function that digitally displays the measured value below the lower limit of the measurement range on the display means, and a lower limit alarm is issued when the monitor device body is abnormal The lower limit alarm set value for setting the lower limit of the measurement range is set to be equal to or lower than the lower limit of the measurement range.

(Operation) Therefore, in the digital radiation monitoring apparatus of the present invention, since the lower limit alarm set value can be set to be equal to or lower than the lower limit of the measuring range, even if the normal background level is equal to or lower than the lower limit of the measuring range of the measuring apparatus, If the lower limit alarm set value is set to be less than or equal to the value, the lower limit alarm is generated only when the monitor device is abnormal, so that it is possible to eliminate the need for a bug source. In addition, since the measured value below the lower limit of the measuring range of the measuring device can be digitally displayed, even if the measured value is between the lower limit of the measuring range and the lower limit alarm set value, the soundness of the monitor device is displayed by the digital display. It becomes possible to confirm.

(Example) Hereinafter, one example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of a digital radiation monitor apparatus according to the present invention. This digital radiation monitor device is, as shown in the figure, a digital radiation detector 1
And a field unit 2 and a measuring device 3. In addition, the digital radiation detector 1 and the field unit 2
Is connected with a coaxial cable 4, and the field unit 2 and the measuring device 3 are connected with an optical fiber cable 5.

Here, the digital radiation detector 1 is installed in each area and process of a nuclear power plant that handles radioactive substances, and for example, a pulse type detector is used. The digital radiation detector 1 is provided with a minute signal processing circuit and a high voltage power source for the detector, detects radiation, converts an analog signal corresponding to the radiation into a digital signal, and outputs the digital signal. In addition, the field unit 2 is equipped with a transmission circuit and an electric / optical conversion circuit, and in order to transmit signals for N channels of detectors (for example, 16 channels) to the measuring device 3 by optical multiplex transmission, optical multiplexing is performed. Is to do. Further, the measuring device 3 is capable of processing detector signals for M channels (for example, 32 channels at maximum) by one unit, and includes an optical / electrical conversion circuit 31, a control unit 32, a display control unit 33, and a graphic. Display unit 34 and analog output unit
35, a digital output section 36, and a communication circuit 37. Reference numeral 38 is a bus line for connecting the optical / electrical conversion circuit 31, the control unit 32, the analog output unit 35, the digital output unit 36, and the communication circuit 37 to each other.

Here, the optical / electrical conversion circuit 31 converts an optical signal transmitted from the field unit 2 into an electric signal corresponding to the optical signal and outputs the electric signal. Further, the control unit 32 receives the output signal from the optical / electrical conversion circuit 31 as an input, and uses the following (a) to (i).
It has each function of.

(A) A function of calculating the monitor level based on the output signal from the optical / electrical conversion circuit 31. (B) A function of analogly outputting the calculation result in (a) to an external recorder or the like via the analog output unit 35. (C) A function of outputting the calculation result in (a) via the communication circuit 37 in response to a data transmission request from a host computer or the like. (D) Display the calculation result in (a) Control unit 33
A function of displaying a bar and digital display on the graphic display unit 34 in response to a data display request from the. (E)
A function of generating an alarm output to that effect through the digital output unit 36 when the radioactivity level becomes equal to or higher than a predetermined level as a result of the calculation in (a). (F) Measuring device 3
A function that digitally displays the measured value below the lower limit of the measurement range of the graphic display unit 34 via the display control unit 33.
(G) A function of setting a lower limit alarm set value for generating a lower limit alarm when the monitor device body is abnormal to be equal to or lower than the lower limit of the measurement range of the measuring device 3. (H) A function of generating a lower limit alarm output to the outside through the digital output unit 36 when the monitor device body is abnormal. (I) It is determined whether the lower limit alarm output due to (h) is caused by the abnormality of the digital radiation detector 1 or the measuring device 3, and the determination result is graphically displayed via the display control unit 33. Function to display digitally on part 34. The graphic display unit 34 is, for example, an EL display.

In the digital radiation monitor configured as described above, the radiation detection signal detected by the digital radiation detector is converted into a digital signal and input to the field unit 2 through the coaxial cable 4. Optical multiplexing is performed in the field unit 2, an input signal is converted into an optical signal, and the signal is optically multiplexed and transmitted to the measuring device 3 through the optical fiber cable 5.

On the other hand, in the optical / electrical conversion circuit 31 of the measuring device 3, the optical signal transmitted from the field unit 2 is converted into an electrical signal and output. Then, in the control section 32, the monitor level is calculated based on this electric signal, and the calculation result is analog-outputted to an external recorder or the like via the analog output section 35. The result of this calculation is output via the communication circuit 37 in response to a data transmission request from a host computer or the like. Furthermore, the measured value of the radioactivity level that is the result of this calculation, in response to a data display request from the display control unit 33,
The sound is displayed on the graphic display unit 34 as a bar and digitally, and the soundness of the monitor device can be confirmed. In this case, when the radioactivity level which is the above calculation result becomes equal to or higher than a predetermined level, an alarm output to that effect is generated to the outside through the digital output unit 36 and notified to the operator. It

On the other hand, the measured value of the radioactivity level which is the above calculation result,
When the measured value is below the lower limit of the measurement range of the measuring device 3, only the measured value is digitally displayed on the graphic display unit 34 via the display control unit 33, and the soundness of the monitor device can be confirmed. Further, the lower limit alarm set value for issuing the lower limit alarm when the monitor device is abnormal is, for example, when the normal background level is equal to or lower than the lower limit of the measurement range of the measuring device 3, for example, the normal background level. Is set to the value of. Therefore, even if the background level is usually lower than the lower limit of the measuring range of the measuring device 3, the lower limit alarm output is not generated. On the contrary,
When an abnormality (generally downscale) occurs in the monitor device, the above-mentioned calculation result becomes less than or equal to the lower limit alarm set value, and a lower limit alarm output to that effect is generated to the outside through the digital output unit 36, This makes it possible to confirm that fact. When the lower limit alarm output is generated, the measuring device 3 is set in the calibration mode as shown in FIG.
It is determined whether the generation of the lower limit alarm output is due to an abnormality of the digital radiation detector 1 or the measuring device 3 by inputting a simulated pulse to the display and whether or not the display is normally performed. The determination result is digitally displayed on the graphic display unit 34 via the display control unit 33. That is, if the display by the simulated pulse is normally performed, it means that "the digital radiation detector 1 is abnormal". Conversely, if the display by the simulated pulse is not normally performed, then "the measuring device 3 is abnormal". The message will be displayed.

FIG. 2 shows a display example of a bar display and a digital display of the measured value when the measured value of the radioactivity level as the calculation result is within the measurement range of the measuring device 3. Further, FIG. 3 shows a display example of digital display of the measured value when the measured value of the radioactivity level as the calculation result is less than or equal to the lower limit of the measurement range of the measuring device 3. As shown in FIG. 3, when the normal background level is below the lower limit of the measurement range of the measuring device 3,
By setting that value as the lower limit alarm set value, even if the measured value is between the lower limit of the measurement range and the lower limit alarm set value L, the measured value is displayed on the digital display and the monitoring device is sound. You can check the sex.

As described above, in the digital radiation monitoring apparatus of the present embodiment, the lower limit alarm set value L can be set to be equal to or lower than the lower limit of the measuring range of the measuring apparatus 3, so that the background level is usually the lower limit of the measuring range of the measuring apparatus 3. Even if it is below, if you set the lower limit alarm setting value corresponding to that value, the lower limit alarm will be generated only when the monitoring device is above,
It is possible to eliminate the need for bug sources that were previously required. Therefore, it is necessary to attach a bug source to each analog radiation detector, which is very difficult to manage, and it is very difficult to set and adjust the setting value of the bug source. All the points can be eliminated. In addition, since the measured value below the lower limit of the measuring range of the measuring device 3 can be digitally displayed, even when the measured value is between the lower limit of the side fixed range of the measuring device 3 and the lower limit alarm setting value L, the digital value concerned can be displayed. The display makes it possible to confirm the soundness of the monitor device. Further, even if the background level is usually lower than the lower limit of the measuring range of the measuring device 3, the lower limit alarm output can be generated only when the monitor device is abnormal, and in this case, the lower limit alarm output is generated by a digital method. It is also possible to determine which of the radiation detector 1 and the measuring device 3 is caused by the abnormality.

Although the field unit 2 is provided between the digital radiation detector 1 and the measuring device 3 in the above embodiment, this is not essential to the present invention. Further, in the above embodiment, when the normal background level is lower than or equal to the lower limit of the measurement range of the measuring device 3, the lower limit alarm set value is set to a value corresponding to the normal background level. It's good.

[Effects of the Invention] As described above, according to the present invention, in a digital radiation monitor device composed of a digital radiation detector and a measurement device, the measured value below the lower limit of the measurement range is digitally displayed on the display means. Function and the function to set the lower limit alarm set value for generating the lower limit alarm when the monitor unit is abnormal to be less than or equal to the lower limit of the measurement range. It is possible to provide a digital radiation monitor device capable of confirming the soundness of the monitor device while making it unnecessary.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital radiation monitor apparatus according to the present invention, FIGS. 2 and 3 are views showing display examples of measured values in the same embodiment, and FIG. 4 is the same embodiment. Flow chart for explaining the calibration operation in
FIG. 5 is a diagram showing a display example of measured values in the related art. 1 ... Digital radiation detector, 3 ... Measuring device, 31 ... Light /
Electrical conversion circuit, 32 ... Control unit, 33 ... Display control unit, 34 ... Graphic display unit, 35 ... Analog output unit, 36 ... Digital output unit, 37 ... Communication circuit, 38 ... Bus line.

Claims (1)

[Claims] 1. A digital radiation detector which is installed in a nuclear power plant that handles radioactive substances and detects radiation, and a display means having a measurement range of a radioactivity level measured by the digital radiation detector in a predetermined range. In a digital radiation monitor device, which comprises a bar display and continuous monitoring, and a measuring device which issues an alarm to that effect when the radioactivity level exceeds a predetermined level, the measurement A function to digitally display the measured value below the lower limit of the range on the display means, and a function to set the lower limit alarm set value for generating the lower limit alarm when the monitor device is abnormal to the lower limit of the measurement range or less. A digital radiation monitor device, comprising: