JPH04208893A - Area radiation monitor - Google Patents

Abstract

PURPOSE:To easily know radiation energy and half life by providing a radiation detection means to output a number of pulses corresponding to the radiation intensity and a radiation level surveillance means to count the outputs and survey a gross radiation-level. CONSTITUTION:In a radiation monitor part 20, pulse number per second is counted in a counting rate meter 21 for the pulse signals sent from a radiation detection part 10 and it is measured to output as a gross radiation level. On the other hand, at each pulse height discriminater 22a,...,22n of the radiation monitor part 20, a predetermined discrimination level for each energy and the radiation level from the radiation detector part 10 are compared. Only when the radiation level is higher than the discrimination level, the radiation level is selectively taken in and output, and then the species is easily identified from the output state.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is applicable to monitoring work environments, radiation levels, process radiation levels, etc. in nuclear power plants and other facilities that handle radioactive materials. The present invention relates to area radiation monitors, and in particular to area radiation monitors that are equipped with technologies such as radiation level monitoring, radiation energy monitoring (nuclide monitoring), and energy calibration.

(Prior Art) In general, this type of area radiation monitor includes a radiation detection section 1 installed at a desired location in a facility that handles radioactive materials, and an output of this radiation detection section 1 as shown in Fig. 4. and a radiation monitor section 4 that measures and monitors at a location away from the detection location, and the former radiation detection section 1 includes a GM tube detector or semiconductor detector that outputs a number of pulses corresponding to the intensity of radiation. In addition to 2, an amplifier 3 and the like are provided, and the latter radiation monitoring section 4 is provided with a count rate meter 5 that counts the pulses output from the amplifier 2, for example, as the number of pulses per second. Only gross radiation levels are monitored. Although the above-mentioned area radiation monitors vary depending on the scale of the plant, usually several dozen channels are installed per plant to measure and monitor radiation levels in various locations.

By the way, when measuring radiation, three pieces of information are required: ■ Radiation intensity; ■ Radiation energy; ■ Radiation half-life; however, the purpose of installing an area radiation monitor is to measure the amount of exposure and the amount of radiation released to the outside. Since this is the monitoring of radiation, the intensity of the radiation described in (2) above, that is, the level of radiation, is mainly measured and monitored.

However, in practice, when the radiation level changes during measurement, it becomes extremely important not only to measure the radiation level, but also to identify the nuclide of the radiation and trace the source of the radiation from that nuclide.

Therefore, conventionally, a nuclide analyzer is installed separately from the area radiation monitor, and the nuclide analyzer is operated when necessary to identify the nuclide.

(Problem to be solved by the invention) However, the above-mentioned nuclide analyzers are extremely expensive, and the number of such devices installed is at most one per plant. Inability to adequately respond to changes when they occur. Also,
If it cannot be handled easily in terms of plant content, scale, installation, etc., it may not be able to fully demonstrate its original function, and there is a problem of lack of flexibility in practice.

On the other hand, if a semiconductor detector is used as the radiation detector 2,
Since it has a higher energy resolution ability than conventional GM tube detectors, it is possible to measure radiation energy and also determine half-life from the radiation energy at the same time.

Therefore, it is conceivable to measure radiation energy using a semiconductor detector as described above, but in this case, energy calibration is required, and since a calibration source is used, the calibration work is extremely complicated. Therefore, it is not practical.

The present invention has been developed in view of the above circumstances, and it is possible to determine radiation levels, radiation energy, half-life, etc. using the same configuration as a normal radiation monitor, and it is flexible in terms of cost, convenience, and ease of handling. The purpose is to provide a rich area radiation monitor.

Furthermore, another object of the present invention is to provide an area radiation monitor that allows simple and 8-crystal radiation energy calibration and that allows accurate monitoring of nuclides.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention outputs a number of pulses corresponding to the intensity of radiation, and has an energy resolution ability, and Radiation level monitoring means, such as a radiation detector that responds to visible light, counts the output of the radiation detector as 1 to monitor the gross radiation level; radiation energy monitoring means for monitoring the radiation level of the output of the detector for each radiation energy; and energy calibration means for calibrating the radiation energy by inputting a calibration optical pulse signal proportional to the radiation energy into the radiation detector. This configuration is equipped with the following features.

(Function) Therefore, by taking the above-mentioned measures, the present invention can monitor the radiation level by counting the pulses from the radiation detector as the number of pulses per second with the radiation level monitoring means, and can also monitor the radiation energy. The nuclide can be monitored by measuring the pulse output from the radiation detector by height, that is, by radiation energy, in the monitoring means.

Furthermore, if the radiation detector has a photoreaction, the light intensity or pulse width of the light is changed according to the radiation energy by utilizing the fact that the amount of light corresponds to the radiation energy. By feeding the pulse signal to a radiation detector, radiation energy can be accurately calibrated.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the apparatus of the present invention.

In the figure, reference numeral 10 denotes a radiation detection unit for detecting the working environment, radiation level, process radiation level, radiation energy, etc. in a nuclear power plant or other facility that handles radioactive materials. For example, the semiconductor detector 11 converts the pulse signal into a number of electrical pulses corresponding to the intensity of the pulse signal, has an energy resolution ability, and has a function of responding to visible light. In addition to the amplifier 12 that outputs the signal, a light emitting element 13 such as an LED is installed near the semiconductor detector 11, and an optical signal control circuit 14 is installed to output a calibration optical pulse signal from the light emitting element 13. It is provided.

20 is a radiation monitor unit that measures and monitors the gross radiation level and radiation energy from the output of the radiation detection unit 10. Generally, among the outputs of radiation level 10,
The number of pulses per second corresponds to the intensity of the radiation, and the height of the pulse (wave height) corresponds to the energy of the radiation.

Therefore, this radiation monitor section 20 includes the radiation detection section 1.
a counting rate meter 21 that measures and outputs the gross radiation level A by counting the pulses output from 0 as the number of pulses per second; and a plurality of radiation energies al'+ a2+
..., aゎ, that is, the wave height discrimination circuit 22a as a radiation energy monitoring means having the function of measuring and monitoring a plurality of nuclides.

2'2n are provided. In monitoring these nuclides, the radiation energy is divided into n groups, and a pulse height discrimination circuit 22a is provided for each radiation energy.

..., 22n are made to correspond, and each radiation energy group is selected and output. Therefore, which wave height discrimination circuit 22
The nuclide can be identified depending on whether many discrimination result signals are obtained from a, . . . 122n. At this time, as shown in FIG. 2, the wave height discrimination circuit 22a is divided into n groups within the measurement range (time) of the count rate meter.

..., 22n may be divided into 1/n ranges to discriminate the radiation level.

Next, the operation of the apparatus configured as above will be explained.

First, during radiation monitoring, the radiation detecting unit 10 detects the intensity of radiation in the installation area using the semiconductor radiation detector 11, and detects the number of cells corresponding to the intensity of the radiation and the height corresponding to the radiation energy. After converting to pulse, amplifier 1
2 to the radiation monitor section 20.

Here, in the radiation monitor section 20, the number of pulses per second is counted by the counting rate meter 21 for the pulse signal sent from the radiation detection section 10, and the result is measured and output as 1 bell of gross radiation.

On the other hand, each wave height discriminator 22a of the radiation monitor section 20,...
・, 22n compares the predetermined discrimination level for each energy with the radiation level from the radiation detection unit 10, and selectively captures the radiation level if the radiation level is higher than each discrimination level. If the output is outputted using the nuclides, the nuclide can be easily identified from the output status.

Next, we will discuss energy calibration. This energy calibration is performed because it is necessary to keep the discrimination level of each pulse height discriminator 22a to 22n constant, and normally a calibration radiation source is used, but in this device, an optical signal is used. The reason for this is that since the intensity of light corresponds to the energy of radiation, it is possible to calibrate the energy by changing the intensity of light. Although it is possible to change the intensity of the light, in practice it is difficult to change only the intensity of the light due to the effects of operating conditions and installation environment, etc.
Energy calibration is performed by pulse width modulating the optical signal. Specifically, a driving pulse signal is output from the optical signal control circuit 14 having a pulse transmission function to control the light emitting element 13.
A pulsed optical signal is emitted from the semiconductor detector 11 and enters the semiconductor detector 11 . Note that the number of times the light emitting element 13 emits light per second (
frequency) corresponds to the radiation level, and the intensity of the light (
The amount of light emitted) corresponds to radiation energy.

In this case, although the number of times the light is emitted can be accurately controlled, the amount of light cannot be accurately controlled as described above.

Therefore, in this apparatus, the optical signal control circuit 14 adjusts the amount of light by changing the pulse width of the driving pulse signal to obtain a calibration optical pulse signal, and the basis for its accuracy will be explained. Generally, the semiconductor detector 11 and the like including the amplifier 12 have a certain time constant, so the amplifier 1
2, an output waveform as shown in FIG. 3(b) is obtained.

Here, the output {circle around (2)} of the amplifier 12 can be obtained from the following equation, assuming that the time constant is τ.

v-v. (1-e-”') -(1) However,
In the above formula, V. is a pulse height corresponding to the amount of light from the light emitting element 12.

In equation (1), if the pulse width T is made smaller than the time constant τ, equation (1) becomes equivalent to equation (2).

v+=v, )・(T/τ) ...(2)
Therefore, the output V of the amplifier 12 is proportional to the pulse width T. Here, since the time constant τ and the pulse width T can be accurately controlled, highly accurate calibration is possible by pulse width modulation.

Note that the present invention is not limited to the above embodiments.

That is, for example, the semiconductor detector 11 is used as a radiation detector.
However, other detectors may be used as long as they have the same function. Furthermore, in the above embodiment, the output for each energy group is extracted on the radiation monitoring section 20 side, or after this is performed on the radiation detection section 10 side, it is transmitted to the radiation monitoring section 20 side individually or by multiplexing. good.

In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, a normal area radiation monitor is simply provided with a wave height discrimination means, so the configuration is simple and convenient to handle, and moreover, radiation energy, half-life, etc. can be easily determined. It is possible to know. In addition, it is possible to provide an area radiation monitor that can easily calibrate radiation energy and monitor nuclides accurately and stably.

[Brief explanation of the drawing]

Figures 1 to 3 are shown to explain an embodiment of the area radiation monitor according to the present invention. Figure 1 is a configuration diagram showing an embodiment of the device of the present invention, and Figure 2 is a radiation level A diagram explaining the relationship between the measurement classification of radiation energy and radiation energy,
FIG. 3 is a diagram illustrating the relationship between time constants when performing calibration using a calibration optical pulse signal, and FIG. 4 is a schematic configuration diagram of a conventional device. 10...Radiation detection section, 11...Semiconductor detector, 1
2... Amplifier, 13... Light emitting element, 14... Optical signal control circuit, 20... Radiation monitor section, 21... Count rate meter, 22a-22n... Wave height discrimination circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (2)

[Claims] (1) A radiation detector that outputs a number of pulses according to the intensity of radiation, has energy resolution ability, and responds to visible light, and calculates the gross radiation level by counting the output of this radiation detector. radiation level monitoring means for monitoring the radiation level; radiation energy monitoring means for monitoring the radiation level of the output of the radiation detector for each radiation energy grouped by radiation energy; An area radiation monitor comprising: energy calibration means for calibrating radiation energy by entering the radiation detector. (2) The energy calibration means includes a light emitting element provided in the vicinity of the radiation detector, and performs pulse width modulation on the optical signal generated from the light emitting element to calibrate the radiation energy proportional to the radiation energy from the light emitting element. 2. The area radiation monitor according to claim 1, further comprising an optical signal control circuit that generates an optical pulse signal.