JPH06258444A - Radiation measuring equipment - Google Patents

Abstract

PURPOSE:To provide a radiation measuring equipment having a function for measuring radon present in a gas with high sensitivity and a function for measuring radon in real-time. CONSTITUTION:A first ionization chamber 10 comprises an electrode container 18, a current collecting electrode 20, and a first power supply circuit 22 for applying voltage between them. A second ionization chamber 12 comprises a container 26, a substance adsorbing radon, an outer electrode 29, a current collecting electrode 30, and a second power supply circuit 32. The first power supply section 22 applies a negative voltage to the electrode container whereas the second power supply section 32 applies a positive voltage to the outer electrode. Consequently, a negative pulse is generated from the current collecting electrode 20 in the first ionization chamber 10 and a positive pulse is generated from the current collecting electrode 30 in the second ionization chamber 12. A signal processing circuit performs signal processing for every characteristics of these pulses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measuring device, and more particularly to a gas flow type ionization chamber.

[0002]

2. Description of the Related Art Radon and thoron are daughter nuclei of uranium and radium, which can exist as gases and are released from the earth to the atmosphere, and also from structures to indoor air.

Radon and thoron existing as gases (hereinafter referred to as radon) emit α rays of about 5 MeV.

Radon concentration in the air is usually 1 Bq / m.
It is about ³ . However, the concentration of radon varies greatly depending on the weather and location, and in some cases, it may exceed the limit concentration. For example, in a room close to a closed state, radon released from the wall accumulates in the indoor space. Radon (also thoron) has a relatively short half-life, and after a certain period of time (for example, 3 days), a saturated state is formed in the indoor space.

As described above, radon is present in the air we breathe and causes internal exposure to the body. Therefore, continuous monitoring of its concentration is significant. Although the range of α-rays is smaller than that of other β-rays, it is necessary to be careful when ingesting radon from excessive exhalation due to its high ionization density.

FIG. 4 shows the configuration of a conventional radon measuring device. In the gas (air) containing radon, after dust and the like are removed by the dust filter 110, ionized substances (ions) are removed by the ion precipitator 112,
It is introduced into the ionization chamber 114. The pump 116 is sucking gas, and the air that has passed through the ionization chamber 114 is discharged into the atmosphere.

Here, the ionization chamber 114 is composed of a metal electrode container 118 forming one electrode and a collector electrode 120 arranged at the center of the electrode container. Electrode container 118
A high voltage is applied between the collector electrode 120 and the collector electrode 120 by the direct current power source 122, and a part of the gas is ionized by the radiation of the radon, and the ions and electrons are carried to the electrodes by the electric field, respectively, and become a signal. Taken out. Specifically, after amplification by the vibration capacitance electrometer head 124,
For example, the vibration capacitance electrometer 126 measures the signal, and the radon concentration and the like are recorded in the recorder 128.

[0008]

However, the above-mentioned conventional apparatus cannot efficiently measure the radiation.

Therefore, the applicant of the present invention has proposed an ionization chamber in which an adsorbing substance for adsorbing a radioactive substance is arranged in the container.
That is, a radioactive substance (radon) is incorporated into the adsorbed substance, the amount of α rays is increased by accumulation, and radon is measured with high sensitivity. However, according to such a device, the real-time property is deteriorated because the accumulation effect is used.
In other words, it is impossible to grasp the fluctuation of the amount of radon in real time.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is a function capable of sensitively measuring a radioactive substance (especially radon) existing in a gas and a function capable of measuring the radioactive substance in real time. And to provide a radiation measuring apparatus having both.

[0011]

In order to achieve the above-mentioned object, the present invention is a radiation measuring apparatus including a first ionization chamber and a second ionization chamber in which a gas containing a radionuclide is circulated. The first ionization chamber is configured to apply a voltage with a predetermined polarity between a first collecting electrode, a first outer electrode surrounding the first collecting electrode, and the first collecting electrode and the first outer electrode.
A second power source, and the second ionization chamber includes a second collector electrode, a second outer electrode surrounding the second collector electrode, and the predetermined electrode between the second collector electrode and the second outer electrode. It is characterized by including a second power source for applying a voltage having a polarity opposite to that of the polarity, and an adsorbing substance for incorporating the radionuclide.

[0012]

According to the above construction, in the first ionization chamber, when the gas flows through the first outer electrode, the α rays emitted from the radioactive substance (such as radon) in the gas ionizes the gas atoms, As a result, either the ions or the electrons are captured by the first collecting electrode. As a result, a pulse of either positive pulse or negative pulse is generated at the collector electrode.

In the second ionization chamber, the radioactive substance in the gas is taken up by the adsorbent and accumulated. In the second ionization chamber, since the voltage is applied with the opposite polarity to the first ionization chamber, the other of the ions or electrons is captured by the collector electrode,
Either the positive pulse or the negative pulse, or the other polarity pulse occurs. In this case, the radon can be measured sensitively by the accumulation effect. Therefore, in the signal taken out from the collecting electrode (the same for both the first and second collecting electrodes), the pulse from one ionization chamber and the signal from the other ionization chamber can be measured. Since the pulse and the pulse have opposite polarities, pulse separation can be performed according to the polarity, and measurement can be performed for each polarity.

Therefore, one pulse measurement value indicates the radon amount in real time, and the other pulse measurement value indicates the radon amount due to the accumulation effect. From these two measurement results, the user can grasp the accurate radon amount (concentration) at a specific place and its variation, for example. If the adsorbing substance is electrically conductive, it can also be used as the second outer electrode.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of the radiation measuring apparatus according to the present invention. The device shown in FIG. 1 is for measuring the concentration of radon (including thoron) contained in air.

The radiation measuring apparatus of this embodiment includes a first ionization chamber 10 and a second ionization chamber 12 shown in FIG. 1, and a signal processing circuit 14 shown in FIG. The first ionization chamber 10 is
The second ionization chamber 12 is an ionization chamber that has excellent real-time properties and has good sensitivity. Hereinafter, each will be described in detail.

In FIG. 1, the air containing radon is
After dust and the like are removed by the dust filter 16, the dust is introduced into the first ionization chamber 10. An ion precipitator may be provided as in the conventional example.

The first ionization chamber 10 includes an electrode container 18 functioning as an outer electrode, a needle-shaped collector electrode 20, and a power source section 22.
It consists of and.

The electrode container 18 is made of metal or the like, and in this embodiment, a negative voltage is applied. That is, the power supply unit 22 applies a high DC voltage between the collecting electrode 20 and the electrode container 18, and in that case, the voltage is applied so that the electrode container 18 has a negative polarity with respect to the collecting electrode 20. It is carried out.

Therefore, when the α-rays emitted from the radon ionize the gas atoms in the electrode container 18, the electric field generated causes the ions to be guided to the electrode container 18 and the electrons to the collecting electrode 20.

Between the first ionization chamber 10 and the second ionization chamber 12, a partition wall 24 having a large number of small holes for gas flow is arranged, and the partition wall 24 is grounded. Here, the partition wall 24 is arranged as described below.
This is to prevent the radon accumulated in the second ionization chamber 12 from affecting the first ionization chamber. The partition wall 24 is made of, for example, an aluminum plate and has a thickness of, for example, 1 cm.
In the present embodiment, the second ionization chamber 12 includes a container 26,
It is composed of an adsorbent substance 28, an outer electrode 29, a collecting electrode 30, and a power supply section 32.

Adsorbent material 28 disposed on the inner surface of container 26
Is composed of, for example, activated carbon and has a thickness of several cm. By disposing the adsorbing substance 28 on the inner surface of the ionization chamber, the radon in the air can be removed from the adsorbing substance 28.
In other words, the radon concentration can be locally improved, and the α-ray (that is, radon) detection efficiency or sensitivity can be improved.

In the present embodiment, the collecting electrode 30 is structurally integrated with the collecting electrode 20, and in fact, one common collecting electrode is inserted through two ionization chambers connected in series.

The power supply 32 includes a collecting electrode 30 and an outer electrode 29.
Is for applying a DC high voltage between them and the voltage is applied with a polarity opposite to that of the power source section 22. That is, the voltage is applied with the electrode container 26 having the positive polarity, and the ions generated by the ionization of the gas are collected by the collector electrode 30.
The electrons are guided to the side and captured by the outer electrode 29.

In the present embodiment, the outer electrode 29 has a mesh shape and is arranged on the inner surface of the adsorbent substance 28. In the usual structure of the ionization chamber, the container 26 is used as the outer electrode like the ionization chamber 10, but in this embodiment, the adsorbing substance 28, which is an insulating substance, is arranged on the inner surface of the container 26, and an electric field is generated, but it is generated. Since it is difficult for the electrons to reach the container which is the outer electrode, the net-shaped outer electrode 29 is arranged further inside the adsorbed substance.

Therefore, if the adsorbing substance 28 is a conductive substance, the adsorbing substance can also be used as the outer electrode.
In addition, 34 is an insulating material.

Since the ionization chamber 10 and the ionization chamber 12 have opposite polarities of voltage application as described above, the generated pulses also have opposite polarities. That is, in the ionization chamber 10, FIG.
As shown in (A), a negative pulse is generated by the electrons being captured by the collecting electrode 20, and a positive pulse is generated by the ions being captured by the collecting electrode 30 in the ionization chamber 12.
As a result, the signal to be extracted becomes a mixture of positive pulses or negative pulses as shown in (C). In this way, by using a common collecting electrode, the structure can be simplified and the number of signal lines can be reduced.

The voltage application to each ionization chamber may basically have the opposite polarity, but as in this embodiment, the polarity is determined so that the electrons are trapped by the collecting electrode 20 in the ionization chamber 10. Is desirable. According to such a configuration, the ionization chamber 1
The real-time property of 0 can be sufficiently exerted. In addition,
It is desirable to set the applied voltage to the ionization chamber 12 that forms a pulse by ions to be relatively high. In addition, pump 3
6 is for air suction.

Regarding the arrangement of the two ionization chambers, it is desirable to provide the ionization chamber 10 having a real-time property in the front stage and the ionization chamber 12 having a storage effect and having good sensitivity in the rear stage. Ionization chamber 1
This is because, when No. 2 is provided in the former stage, the air whose radon concentration is lowered is introduced into the ionization chamber 10 in the latter stage.

In FIG. 2, the signals from the two ionization chambers shown in FIG. 1 are input to the pulse separation circuit 40 via the capacitor 38. The pulse separation circuit 40 includes a preamplifier 42 that amplifies only a negative pulse and a preamplifier 44 that amplifies only a positive pulse. Pulse separation is performed by these two preamplifiers.

The respective signals amplified by the preamplifiers 42 and 44 are further amplified by the charge type amplifiers 46 and 48, and the amplification result is recorded in the recorder 50. In this case, the detection results of the ionization chambers 10 and 12 can be recorded respectively, but it is also possible to prepare a table for converting the radon concentration based on the two detection results and use the table to calculate the radon concentration. In any case, according to the radiation measuring apparatus of the present embodiment, it is possible to obtain a measurement result with real-time property and an integrated measurement result measured under good sensitivity, so that the radiation measurement according to various applications A device can be provided.

[0033]

As described above, according to the present invention, it is possible to provide a radiation measuring apparatus having both a function capable of measuring radioactive substances existing in a gas with high sensitivity and a function capable of measuring in real time. is there. Therefore, a radiation device applicable to various purposes can be configured.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing two ionization chambers in a radiation measuring apparatus according to the present invention.

FIG. 2 is a block diagram showing a configuration of a signal processing circuit.

FIG. 3 is a waveform diagram showing a pulse generated in each ionization chamber and a pulse output from two ionization chambers.

FIG. 4 is an explanatory diagram showing a configuration of a conventional radiation measuring apparatus.

[Explanation of symbols]

 10 1st ionization chamber 12 2nd ionization chamber 18 Electrode container 20 Collection electrode 22 1st power supply part 26 Container 28 Adsorbed substance 29 Outer electrode 30 Collection electrode 32 2nd power supply part

Claims (1)

[Claims] 1. A radiation measuring apparatus including a first ionization chamber and a second ionization chamber for circulating a gas containing a radioactive substance, wherein the first ionization chamber includes a first collector electrode and the first collector electrode. A first power supply for applying a voltage with a predetermined polarity between the first outer electrode and the first outer electrode, and the second ionization chamber includes a second outer electrode. A second outer electrode surrounding the second collecting electrode; a second power supply for applying a voltage between the second collecting electrode and the second outer electrode with a polarity opposite to the predetermined polarity; A radiation measuring apparatus comprising: an adsorbing substance that takes in a substance.