JPH01250883A - Radioactive gas measuring instrument - Google Patents

Abstract

PURPOSE:To make the measuring instrument compact by providing a ventilation type ionizing box-shaped betagamma ray detector, a semiconductor type or enclosed type ionization type gamma-ray detector incorporated in a draft type ionizing box, and a data processor which performs the separate arithmetic operation of a betaray and a gamma ray. CONSTITUTION:Piping 11 is connected to a facility air discharge duct, etc., and the draft type ionizing box-shaped betagamma ray detector 12 and a sampling pump 13 are connected thereto in series. The semiconductor or enclosed type gamma ray detector 15 is incorporated in the detector 12. A pump 13 is put in operation for a prescribed period to sample radioactive gas emitted from an air discharge cylinder, etc., in the detector 12. In this state, the detectors 12 and 15 detect ionizing current signals proportional to a betagamma ray and a gamma ray and supply their detection signals to the data processor 16. The processor 16 converts the ionizing current signals proportional to the concentration of the radioactive gas sent from the detectors 12 and 15 analog to digital and performs the separate arithmetic operation of the beta ray and gamma ray. Consequently, the device is made compact greatly and the beta ray and gamma ray are easily separated and measured.

Description

[Detailed Description of the Invention] [Object of the Invention] (Field of Industrial Application) The present invention relates to a radioactive gas measuring device that measures the concentration of radioactive gas containing radioactivity released into the atmosphere from a facility exhaust duct, etc. In particular, the present invention relates to a radioactive gas measuring device that can reliably separate β rays and γ rays.

(Conventional technology) Generally, radioactive gas containing radioactivity is released into the air from exhaust ducts and stacks of various facilities that handle nuclear power and radioactive materials. It is very important to measure and manage this.

By the way, conventionally, when determining the tllll isotropic gas concentration, as shown in FIG. A sampling pump 4 is connected in series and is installed on the output side of the gas chamber 3b at the subsequent stage. The sampling pump 4 sucks the radioactive gas containing radioactivity emitted from the trachea, etc., and samples it into each of the gas chambers 3a and 3b. The gas chambers 3a and 3b each have a β
! A detector 5a for gamma rays and a detector 5b for gamma rays are installed, and these detectors 5a and 5b detect a signal proportional to the concentration of radioactive gas sampled in the gas chambers 3a and 3b. .

6b. These measuring devices 6a and 6b statistically process the input signals to obtain a β-ray (γ-ray) measurement signal and a γ-ray measurement signal, and then guide them to a recorder 7 to indicate or record each measurement signal. 8 is piping.

(Problems to be Solved by the Invention) However, the conventional device as described above requires two gas chambers 3a and 3b, resulting in a large-scale configuration, and accordingly requires two different types of detectors. 5a, 5b
must be installed, and β! Since a GM tube is used as the detector 5a for <γ rays), the detection sensitivity and energy characteristics for low energy R1 are low. the result,
The lower measurement limit concentration is high, making it difficult to control the concentration in one shift according to legal regulations.

Moreover, even if statistical processing is performed from the measurement signal of the β-ray (γ-ray) detector 5a, the relationship β(γ)−γNβ will be obtained, and β
It was extremely difficult to separate β rays from <γ) rays.

The present invention was made in order to improve the above-mentioned problems, and it is possible to make the gas sampler part more compact and to reduce the β
An object of the present invention is to provide a radioactive gas measuring device that can easily separate and measure rays and gamma rays.

[Structure of the Invention] (Means for Solving Problem 1) In order to achieve the above object, the radioactive gas determination device according to the present invention includes a vented ionization chamber connected to piping for sampling radioactive gas containing radioactivity. A βγ-ray detector, a semiconductor or sealed ionization chamber-type γ-ray detector built into the ventilated ionization chamber that constitutes the βγ-ray detector, and the output of both of these detectors. The system is equipped with a data processing device that separates and calculates β rays and γ rays.

The data processing device mainly separates and measures β rays and γ rays, and furthermore, the data processing device separately measures β rays and γ rays. ,
a radioactive gas concentration calculation means for calculating the gamma ray and total concentration; storing coordinate data in advance in a coordinate memory, and
A display processing means is provided for storing the concentration data obtained by the radioactive gas concentration calculating means at a predetermined pixel position of the coordinate memory, and for reading out the contents of the image memory and displaying various concentrations graphically. This makes concentration management easier.

(Function) Therefore, by taking the above measures, the present invention has a ventilated ionization chamber that can detect β and γ rays on the outside, and a sealed Ti＠ chamber that can detect only γ rays on the inside. By using a double structure with a box or semiconductor detector, it is possible to measure β-γ rays and γ-rays without installing a special large detector, and it is possible to separate β-rays and γ-rays from the difference in the measured value signals. Can be measured.

(Example) Hereinafter, an example of the apparatus of the present invention will be described with reference to FIG. In the figure, 11 is a pipe connected to a facility exhaust duct, exhaust stack, etc., to which a ventilated ionization chamber-type βγ-ray detector 12 and a sampling pump 13 are connected in series to form a sampling line. There is. Note that a lead shielding material 14 is provided around the outer periphery of the βγ-ray detector 12 in order to suppress the disturbance of surrounding natural radiation.

A semiconductor type or sealed type III box type gamma ray detector 15 is built inside the β gamma ray detector 12, and this detector 1
5 and the output of the βγ ray detector 12 are each connected to a data processing device 16 with a CRT display. This data! ! The 21 processing device 16 includes an input processing means that receives signals from the βγ ray detector 12 and the γ ray detector 15 and converts analog signals into digital signals, a separation calculation means that separates β rays and γ rays, and a radioactive gas It is comprised of a radioactive gas concentration calculation means for determining the concentration, a display processing means for converting the calculation result into data that can be displayed graphically, an output processing means, and the like.

17 is a recorder. 18 is piping.

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

The sampling pump 13 is operated at predetermined cycles and at appropriate times to sample the III gas emitted from the exhaust stack and the like into the βγ ray detector 12 forming a gas ionization box shape. In this state, each detector 12.15 detects βγ rays and γ rays contained in the sampling gas
! III current signal is detected and the detection signal is supplied to the data processing device 16.

In this data processing device 16, each detector 12.1
After converting the +m current signal proportional to the radioactive gas concentration sent from 5, that is, an analog signal, into a digital signal, the β-ray and γ-ray separation calculation means are executed.

This separation calculation means uses the output of each detector 12.15 to separate the β rays based on the following formula.

β=A(βγ)-BT...(1) However, in the above equation, β is the β-ray count rate (cps), A is the correction coefficient,
βγ is the counting rate (CI) from the βγ ray detector 12),
B is the correction coefficient, γ is the counting rate from the γ-ray detector 15 (c
ps).

Once the β rays and the γ rays have been separated as described above, the gas concentration of each radiation is subsequently determined by calculation. First of all,
β is the concentration related to β rays. (μci/cn+3), then β1)=kN ・β ...(calculated using the following formula.kN is the conversion constant (μci/cn+3) determined for each nuclide.
-cra4/cps, β is the β-ray count rate (cps). On the other hand, the concentration related to γ rays is γ. (μci/cm3
), it can be expressed as γ[)”kN (γ−N e a > −(3). In the above equation (3), γ is the γ-ray count rate (cp
S), Naa is natural background (cpS). Furthermore, the total concentration β. +γ0 (μCi/Cm3) can be expressed as β0 +γo=kN (βγ−Neo). β
γ is the counting rate (c, p s ) from the βγ ray detector 12
It is.

Once the concentrations of β and γ and the total 1 degree of βγ have been obtained in the above manner, the display processing means of the data processing device 16 performs processing to enable graphic display, and displays them on the CRT display section. This display processing means stores horizontal and vertical axes, necessary character data, and dotted line data of regulatory values in predetermined pixel positions of the image memory as shown in FIG. Calculation of the determined concentrations β, γ, and βγ (store direct data).

Thereafter, if the contents of this image memory are sequentially read out in a predetermined order and displayed on the CRT display section, a display result as shown in FIG. 2 can be obtained. In particular, by displaying each concentration as a bar, the correlation between the regulated concentration and each nuclide concentration can be easily determined, which is very effective in managing the radioactive gas concentration.

Further, this display processing means can process and display data as shown in FIG.

In other words, if you display the historical trend of radioactive gas concentration from the start of R1 use as shown in Figure 3, you can
It is easy to manage the average concentration, cumulative concentration, etc.

Furthermore, this data processing device 16 executes output processing means. This output processing means has a counting rate (cps) of the calculation result.
), 11 degrees (μci/cm3) and instruct and record it on the recorder 17, or set the alarm level for each nuclide type in advance and set it on the nuclear detector 12.15.
An alarm is generated when the output exceeds the alarm level.

Therefore, according to the configuration of the embodiment as described above, the β-γ-ray detector and the γ-ray detector installed in the sampling section are each shaped like an ionization chamber and have a double structure, which greatly reduces the energy consumption compared to the conventional method. It has a compact structure and is very convenient to install. In addition, ventilation type IL1 box type β
By configuring the γ-ray detector 12 and the semiconductor-type or sealed ionization chamber-type γ-ray detector 15, both detectors 12.1
It becomes possible to separate β from the output difference of 5, and β rays and γ rays can be reliably separated even with low energy R1, and sufficient detection sensitivity can be ensured for controlling the regulated concentration.

In addition, since the data processing device 16 graphically displays the gas concentration obtained by the calculation means, it is easy to correlate the regulated concentration and each nuclide concentration, and maintenance and management can be performed reliably and monitoring performance can be greatly improved. .

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

[Effects of the Invention] As detailed above, the present invention provides the following various effects.

In claim 1, a semiconductor type or sealed '1111 box type gamma ray detector 15 is built and integrated inside a ventilated ionization chamber type β gamma ray detector, so that the gas sampler part is improved compared to the conventional one. It can be made significantly more compact, and it can be
The line can be separated into commercial lines and measured.

Further, in the second aspect, it is easy to separate and measure β rays and γ rays, the gas concentration can be determined with high precision, and monitoring performance can be improved by displaying graphics.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a partially cross-sectional configuration diagram showing an embodiment of a radioactive gas measuring device according to the present invention, FIGS. 2 and 3 are diagrams showing graphic display examples, and FIG. The figure is a configuration diagram of a conventional device. 12... Ventilated ionization chamber type beta gamma ray detector, 13... Sampling pump, 14... [Scattered materials, 15... Semiconductor type or sealed ionization chamber type gamma ray detector, 16... Data processing device, 17...recorder. Applicant's representative Patent attorney Takehiko Suzue 1, '51U! J Figure 2 A: Figure 53 B Figure 34

Claims (2)

[Claims] (1) A ventilated ionization chamber-type βγ-ray detector connected to piping that samples radioactive gas containing radioactivity, and this β
A semiconductor-type or sealed ionization chamber-type gamma-ray detector is integrated into the ventilated ionization chamber that constitutes the gamma-ray detector, and the output of both these detectors is used to detect β-rays and gamma-rays. A radioactive gas measuring device equipped with a data processing device that performs separate calculations. (2) The data processing device includes a separation calculation means for separating β-rays by subtracting the count rate detected by the gamma-ray detector from the count rate detected by the β-γ-ray detector; a radioactive gas concentration calculation means for calculating the concentration of each β ray, γ ray, and total from the β ray count rate separated by the β ray count rate and the γ ray count rate from the gamma ray detector; and a radioactive gas concentration calculation means that stores coordinate data in advance in a coordinate memory. a display processing means for storing the concentration data obtained by the radioactive gas concentration calculation means in a predetermined pixel position of the coordinate memory, and for reading out the contents of the image memory and displaying various concentrations graphically; The radioactive gas measuring device according to claim 1, further comprising: