JPH0562711B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a radiation measuring device.

[Technical background of the invention]

BACKGROUND ART Conventionally, there is a device called an area radiation monitor (hereinafter referred to as ARM) that monitors radiation in nuclear power plant facilities. ARM monitors gamma ray levels in certain areas of a nuclear power plant facility.

FIG. 3 is a block diagram showing the configuration of such an ARM.

Geiger-Muller tube (hereinafter referred to as GM tube) 1
When gamma rays are incident on a radiation detector consisting of a radiation detector, etc., a pulse is generated from the GM tube 1 due to the ionization effect. The pulse passes through a capacitor 3, is amplified by a pulse amplifier 5, and is input to a pulse height discrimination circuit 7. Only pulses larger than the discrimination set value are extracted by the pulse height discrimination circuit 7, waveform-shaped by the waveform shaping circuit 9, logarithmically converted by the diode pump circuit 11, and converted into a DC voltage.
3 and the indicating device 1 in the central control room.
5 is output. Note that power is supplied to the radiation detector 1 from a high-voltage power supply 17 via a signal cable 19. FIG. 4 is a circuit diagram showing a specific configuration of the diode pump circuit 11. As shown in the figure, the diode pump circuit is composed of a capacitor, a resistor, and a diode pump.
In addition, the part surrounded by the dotted line in FIG. 3 is housed in one box as the detection converter 21, and is installed on the field side. On the other hand, the display device 15 and high voltage power supply 17 are provided on the control room side.

(Problems with the background technology) When using a GM tube as a radiation detector, it is generally difficult to predict the lifespan of the GM tube, and for this reason, there has been no method to detect deterioration of the GM tube. The pipes could deteriorate rapidly, and in such cases it was necessary to urgently obtain GM pipes and replace them.

[Purpose of the invention]

The present invention has been made in view of the above, and an object of the present invention is to provide a radiation measuring device that can accurately detect deterioration of a radiation detector at an early stage with a simple device configuration.

[Summary of the invention]

In order to achieve the above object, the present invention provides a radiation measuring device using a radiation detector made of a semiconductor, including leakage current detection means for constantly detecting leakage current of the radiation detector, and a level of the detected leakage current. and a deterioration determining means for determining deterioration of the radiation detector based on.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a block diagram showing the configuration of a radiation measuring device according to a first embodiment of the present invention, and elements having the same functions as those constituting the conventional example shown in FIG. 3 are given the same numbers. However, the explanation of that element will be omitted.

In this embodiment, a semiconductor detector 23 (hereinafter referred to as SSD) is used as a radiation detector. SSD23
As the SSD 23 deteriorates, the leakage current increases, so in this embodiment, this leakage current is constantly monitored and used as an index of the deterioration of the SSD 23.

In Figure 1, SSD23 as a radiation detector
A resistor 25 is provided at the cathode side terminal of the resistor 25, and the other end of the resistor 25 is connected to a DC voltage high level (V ₀ ) line. Further, a capacitor 27 is connected to the intersection of the cathode side terminal of the SSD 23 and the resistor 25, and a capacitor 29 is connected to the other end of the capacitor 27.
is connected to the input side of a charge amplifier 31 which is connected in parallel. The output of the charge amplifier 31 passes through the wave height discrimination circuit 7, the waveform shaping circuit 9, the diode pump circuit 11, and the output amplifier 13 to the alarm indicating device 33.
connected to.

On the other hand, a capacitor 35 whose one end is grounded is connected to the anode side terminal of the SSD 23. A resistor 37 is located at the intersection of the anode side terminal of the SSD 23 and the capacitor 35.
The input side of the leakage current amplifier 39 connected in parallel is connected, and the output of the leakage current amplifier 39 is connected to the alarm indicating device 33.

A comparator (not shown) is connected to the leakage current amplifier 39 in the alarm indicating device 33, and when the output of the leakage current amplifier 39 becomes larger than a set reference value,
Generates a deterioration alarm for SSD23.

Next, the operation of this embodiment will be explained.

When the SSD 23 is not irradiated with radiation, the SSD 23 is reverse-biased by the resistor 25, so only leakage current io flows. However, since the charge amplifier 31 is coupled through the capacitor 27, this leakage current io The current flows into the current amplifier 39.

On the other hand, when the SSD 23 is irradiated with radiation, a pulsed signal current ix is generated. This signal current ix flows to the charge amplifier 31 through the capacitor 27, but does not flow to the leakage current amplifier 39 because the capacitor 35 is bypassed in terms of alternating current. Therefore, the leakage current amplifier 39
, only the leakage current io flows.

This leakage current io is amplified by a leakage current amplifier 39 and input to the comparator (not shown) in the alarm indicating device 33. When the SSD 23 deteriorates and the leakage current increases, the output of the leakage current amplifier 39 becomes larger than the reference value, and the alarm/instruction device 33 generates an alarm. This alarm prompts the operator to replace the SSD 23.
Note that the signal current ix is supplied to the pulse height discrimination circuit 7 via the charge amplifier 31, and is subjected to radiation dose measurement processing as in the conventional example described above.

FIG. 2 is a block diagram of a radiation measuring device according to a second embodiment of the present invention, in which elements having the same functions as those of the first embodiment are given the same numbers. Its feature is that in the first embodiment, the radiation measurement value and leakage current were transmitted to the alarm/instruction device 33 as analog signals, whereas in the present embodiment, digital transmission is performed.

That is, in this embodiment, the pulsed signal current ix amplified by the charge amplifier 31
is inputted to the counter circuit 41 through the pulse height discrimination circuit 7, counted, and outputted to the data transmission circuit 43. On the other hand, the leakage current io amplified by the leakage current amplifier 39 is input to an analog-to-digital converter 45 (hereinafter referred to as AD converter), digitally converted, and input to the data transmission circuit 43. The data transmission circuit 43 digitally transmits the digitized radiation measurement values and leakage current values to a remote central controller 47.

Thereafter, the central controller 47 monitors the transmitted radiation detection value and leakage current value, and issues a deterioration alarm for the SSD 23 especially when the leakage current exceeds a reference value.

Note that by connecting the central controller 47 to the process computer 49, it becomes possible to manage multiple detection converters 21b and 21c. The part indicated by the dotted line in the figure represents the detection converter 21b on the field side, and the inside of the detection converter 21c indicated by the dotted line has the same configuration as the inside of the detection converter 21b. Note that the leakage current io may also be generated due to temperature changes, so in the first and second embodiments described above, a temperature sensor (not shown) is provided near the SSD 23 to prevent the leakage current from changing depending on the temperature. It is also possible to determine whether the problem has occurred because of the problem, or whether the problem has occurred due to deterioration of the SSD 23.

Further, when the radiation dose is high, by performing a relative comparison between the radiation detection signal and the leakage current, it is also possible to distinguish between the leakage current and the radiation detection signal at a high dose.

〔Effect of the invention〕

As explained above, according to the present invention, a radiation measuring device using a radiation detector made of a semiconductor is provided, and the level of leakage current of the radiation detector is constantly detected to prevent deterioration of the radiation detector. Since the determination is made, deterioration of the radiation detector can be detected accurately and early with a simple device configuration.

[Brief explanation of drawings]

1 and 2 are the first and second embodiments of the present invention, respectively.
FIG. 3 is a block diagram of the embodiment, FIG. 3 is a block diagram of a conventional example, and FIG. 4 is a circuit diagram of a diode pump circuit. 23...SSD, 25...Resistance, 27,35,3
7...Capacitor, 33...Alarm/indication device, 3
9... Leak current amplifier, 41... Counter circuit, 43... Data transmission circuit, 45... A/D converter, 47... Central controller, 49... Process calculator.

Claims (1)

[Claims] 1. A radiation measuring device using a radiation detector made of a semiconductor, comprising: leakage current detection means for constantly detecting leakage current of the radiation detector; A radiation measuring device comprising: a deterioration determining means for determining deterioration of a radiation detector;