JP2014106189A - Radioactive concentration measurement device, spatial dose rate measurement device and radioactive concentration measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily measure a radioactive concentration of a measured object, while suppressing an influence of a background.SOLUTION: A radioactive concentration measurement device 1 comprises: a storage container 21; a γ-ray detection part 27; a radioactive concentration identification part 31; and an output device 4. The storage container 21 stores a measured object (for example, sediment). The γ-ray detection part 27 is disposed in the storage container 21 so as to be surrounded by the measured object stored in the storage container 21, detects the γ-ray to be discharged from the measured object and outputs an electric signal. The radioactive concentration identification part 31 identifies a spatial dose rate DL (in-container spatial dose rate) within the storage container 21 on the basis of the electric signal from the γ-ray detection part 27, and identifies a radioactive concentration RC of the measured object on the basis of the identified in-container spatial dose rate DL. The output device 4 performs a screen display and the like of the in-container spatial dose rate DL and the radioactive concentration RC of the measured object.

Description

  The present invention relates to a device for measuring the radioactivity concentration of a solid or liquid object to be measured, an air dose rate measuring device used for measuring the radioactivity concentration of the object to be measured, and the radioactivity concentration of the object to be measured. It relates to a measuring method.

Patent document 1 is disclosing the measuring device of the radioactive concentration of gas. In Patent Document 1, a sampling pipe is connected to a process pipe through which a gas to be measured flows, and a measurement container is disposed in the middle of the sampling pipe. In Patent Document 1, the radiation dose in the measurement container is detected by a radiation detector, and the radioactivity concentration of the gas to be measured is specified based on the detection result.
Non-Patent Document 1 discloses a method for measuring the radioactivity concentration of soil or the like (hereinafter referred to as contaminated soil or the like) contaminated with a radioactive substance. In Non-Patent Document 1, contaminated soil or the like is stored in a round V-type container (V5 container: plastic container of 128 mmφ × 56 mmH) or a sandbag, the air dose rate on the surface is measured, and the measured value of this air dose rate Based on the above, the radioactive concentration of contaminated soil or the like is specified (see page 45 of Non-Patent Document 1).

JP 2005-009890 A

Ministry of Health, Labor and Welfare, Ionizing Radiation Worker Health Care Office, Decontamination, etc. Special Education Text Revised Edition, [online], Ministry of Health, Labor and Welfare Internet <URL: http://www.mhlw.go.jp/new-info/kobetu/roudou/gyousei/anzen/dl/120118-04-zentai.pdf>

By the way, in a region where decontamination such as contaminated soil is performed (decontamination target region), the background level (background air dose rate) may be 0.23 μSv / h or more.
On the other hand, if the radioactive concentration of the contaminated soil or the like is 3000 Bq / kg or less, the contaminated soil or the like is provided on the condition that a thickness of 30 cm from the surface of the contaminated soil or the like is secured by a material having a shielding effect such as earth and sand. Can be reused in road and breakwater construction.

However, when contaminated soil having a radioactivity concentration of about 3000 Bq / kg is stored in the above-mentioned V5 container and the air dose rate on the surface thereof is measured, it becomes about 0.2 μSv / h. Therefore, when determining whether or not the radioactive concentration of the contaminated soil is 3000 Bq / kg or less in the decontamination target area, in order to suppress the influence of the background that may be 0.23 μSv / h or more It was necessary to cover the surface other than the measurement surface of the air dose rate measuring device with thick lead, or to measure the air dose rate on the surface of the V5 container in the shielding room.
In view of such a situation, an object of the present invention is to easily measure the radioactivity concentration of an object to be measured such as contaminated soil while suppressing the influence of the background.

Therefore, the radioactivity concentration measuring apparatus according to the present invention measures the radioactivity concentration of a solid or liquid object to be measured, and the volume part that accommodates the object to be measured, and the volume part accommodated in the volume part. A gamma ray detector that is installed in the volume part so as to be surrounded by the object to be measured, detects a gamma ray emitted from the object to be measured, and outputs an electric signal; and a measurement object based on the electric signal A radioactivity concentration specifying unit for specifying the radioactivity concentration.
Further, in the method for measuring radioactivity concentration according to the present invention, the measurement object is accommodated in the volume portion using the radioactivity concentration measurement apparatus, γ-ray is detected by the γ-ray detection unit, and the electrical signal is emitted. The radioactivity concentration specifying unit transmits the radioactivity concentration of the object to be measured based on the electrical signal.

The air dose rate measuring apparatus according to the present invention is used for specifying the radioactivity concentration of a solid or liquid object to be measured, and includes a volume part for storing the object to be measured, and a volume part accommodated in the volume part. A gamma ray detection unit that is installed in the volume part so that the surrounding area is surrounded by the measured object, detects the γ rays emitted from the measurement object, and outputs an electrical signal; and an air dose based on the electrical signal An air dose rate specifying unit for specifying the rate.
Further, in the method for measuring a radioactivity concentration according to the present invention, the measurement object is accommodated in the volume using the above air dose rate measuring apparatus, γ-ray is detected by the γ-ray detector, and the electrical signal is spatially transmitted. The air dose rate is transmitted to the dose rate specifying unit, and the air dose rate specifying unit specifies the air dose rate based on the electrical signal, and the radioactivity concentration of the object to be measured is specified based on the specified air dose rate.

  According to the present invention, the gamma ray detector is surrounded by a solid or liquid object to be measured. As a result, the object to be measured suppresses the transmission of γ-rays from the outside and suppresses the influence of the background on the γ-ray detection unit, so the volume part itself needs to have a shielding property against γ-rays from the outside. In addition, there is no need to measure the radioactivity concentration of the measurement object in a shielded environment, and the radioactivity concentration of the measurement object can be easily measured.

The figure which shows schematic structure of the radioactive concentration measuring apparatus in 1st Embodiment of this invention. The figure which shows schematic structure of the radiation detection unit in embodiment same as the above The figure which shows the relationship between the radioactive concentration of the earth and sand in the container, the air dose rate in the container and the volume of the container Diagram showing γ-ray transmission characteristics of earth and sand Diagram showing the relationship between the air dose rate measurement location, the air dose rate measurement, and the radioactive concentration of the earth and sand in the containment vessel The figure which shows schematic structure of the air dose rate measuring apparatus in 2nd Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a schematic configuration of a radioactivity concentration measuring apparatus according to the first embodiment of the present invention. 2 (a) and 2 (b) each show a schematic configuration of a radiation detection unit constituting the radioactivity concentration measuring apparatus. Here, FIG. 2A shows a state in which a sediment discharge port of the storage container described later is closed, while FIG. 2B shows a state in which a sediment discharge port of the storage container described later is opened.

As shown in FIG. 1, the radioactivity concentration measurement apparatus 1 includes a radiation detection unit 2, a calculation device 3, and an output device 4.
The radiation detection unit 2 includes a storage container 21, a tubular member 25, and a γ-ray detection unit 27.
The container 21 includes a cylindrical container body 21a having an upper surface opening and a lower surface opening, and a lower lid member 21b that closes the lower surface opening of the container body 21a.
The storage container 21 forms the “volume part” of the present invention, and stores a solid or liquid measurement object. In the present embodiment, as an object to be measured, soil that is contaminated with radioactive substances (soil and sand containing radioactive substances) will be described as an example, but the object to be measured is not limited to this.

Of the storage container 21, the upper end portion (upper surface opening portion) of the container main body 21a functions as the earth and sand input port (measurement object input port) 23 of the storage container 21, and the lower end portion (lower surface opening) of the container main body 21b. Part) functions as a sediment discharge port (measurement object discharge port) 24 of the container 21. That is, the earth and sand to be measured can be put into the container 21 through the earth and sand slot 23. Moreover, the earth and sand in the storage container 21 can be discharged to the outside through the earth and sand outlet 24.
A part of the outer edge part of the lower lid member 21b is fixed to a part of the outer edge part of the lower end part (sediment discharge port 24) of the container main body 21a via a hinge (not shown). Therefore, the earth and sand discharge port 24 of the container 21 can be opened and closed by opening and closing the lower lid member 21b fixed to the container body 21a via the hinge. Here, the function of the “opening / closing means” of the present invention is realized by the lower lid member 21b and the hinge. The lower lid member 21b is closed and the sediment discharge port 24 is opened when the sediment is put into the storage container 21 and when the radioactive concentration of the sediment in the storage container 21 is measured (when the air dose rate in the container described later is measured). Close it. On the other hand, when discharging sediment from the inside of the storage container 21, the lower lid member 21b is opened and the sediment discharge port 24 is opened.

Inside the container 21, a metal tubular member 25 extending in the vertical direction is installed substantially at the center in plan view. The tubular member 25 is a bottomed circular tubular iron pipe, for example. The tubular member 25 is fixed to the container main body 21 a via the bracket 26.
The tubular member 25 is installed such that its upper part is located above the upper surface opening of the container 21 and its bottom part is located in the vertical center of the container 21. That is, the tubular member 25 extends from the outside of the storage container 21 to the approximate center of the storage container 21. A γ-ray detection unit 27 that detects γ-rays is installed at the bottom of the tubular member 25.
The γ-ray detection unit 27 includes, for example, a scintillator (not shown) that absorbs radiation energy (γ-ray energy) and generates fluorescence, and a photomultiplier tube (not shown) that converts light into an electric signal and amplifies it. ) And. The γ-ray detection unit 27 outputs an electrical signal (for example, a pulse signal) corresponding to the number of times of light emission by the scintillator and the light intensity to the arithmetic device 3 via a signal line 33 described later. Here, as the scintillator, for example, a NaI (Tl) scintillator or a CsI (Tl) scintillator is used. As the γ-ray detector 27, for example, a scintillation survey meter probe (not shown) is used. The probe here is
In addition to the configuration in which the scintillator crystal and the photomultiplier tube are incorporated, a configuration having only the scintillator crystal may be employed. In this case, the optical signal from the crystal is guided to the photomultiplier tube via an optical fiber or the like. The scintillation survey meter will be described in a second embodiment (see FIG. 6) described later.

A shield 28 can be inserted into the tubular member 25 above the γ-ray detection unit 27 in the inside thereof. The shield 28 is earth and sand, for example. In addition, when the presence or absence of the shield 28 has little influence on the radioactive concentration measurement (air dose rate measurement) of the earth and sand in the storage container 21, the shield 28 can be omitted.
The bottom of the tubular member 25 in which the γ-ray detection unit 27 is installed is surrounded by earth and sand accommodated in the accommodation container 21. In other words, the γ-ray detection unit 27 is installed in the storage container 21 so as to be surrounded by the earth and sand stored in the storage container 21. Note that the γ-ray detection unit 27 does not have to be completely surrounded by the earth and sand accommodated in the storage container 21, and the earth and sand can provide a desired attenuation effect on the background level BGL. The circumference | surroundings should just be enclosed to such an extent that the earth and sand required for measuring a radioactive density | concentration can be accommodated. The attenuation of the background level BGL will be described later with reference to FIG.

The calculation device 3 performs various calculations of the radioactivity concentration measurement apparatus 1 and includes a radioactivity concentration specifying unit 31. The radioactivity concentration specifying unit 31 includes an air dose rate specifying unit 32.
The air dose rate specifying unit 32 receives an electrical signal output from the γ-ray detection unit 27 of the radiation detection unit 2 via the signal line 33, and based on this electrical signal, the air dose in the central portion of the container 21. Rate (hereinafter referred to as “in-container air dose rate”).
The air dose rate specifying unit 32 specifies the in-container air dose rate based on the electrical signal from the γ-ray detection unit 27, for example, by executing the following processes (1) to (4).
(1) The above-described electrical signal (for example, pulse signal) from the γ-ray detection unit 27 is input to the air dose rate specifying unit 32 via the signal line 33.
(2) A count rate (cms) is obtained by counting the input electric signal for a certain period of time.
(3) In parallel with the processing of (2), light intensity (radiation energy) is obtained from the wave height of the electrical signal.
(4) The count rate obtained in (2) is converted into an in-container air dose rate (μSv / h). At the time of this conversion, the in-container air dose rate is corrected using the light intensity obtained in (3).
In this manner, the air dose rate specifying unit 32 specifies the air dose rate in the container.
In the present embodiment, the electrical signal from the γ-ray detection unit 27 is transmitted to the air dose rate specifying unit 32 via the signal line 33. However, the electrical signal transmission method is not limited to this, for example, γ The electrical signal from the line detection unit 27 may be transmitted to the air dose rate specifying unit 32 by wireless communication using a wireless device.

A signal corresponding to the in-container air dose rate specified by the air dose rate specifying unit 32 (in other words, the measured value of the air dose rate in the container 21) is output via the signal line 34 to the output device 4. Is transmitted to. In this embodiment, a signal corresponding to the air dose rate in the container is transmitted to the output device 4 via the signal line 34. However, the signal transmission method is not limited to this, for example, the signal is You may transmit to the output device 4 by the radio | wireless communication by a radio | wireless apparatus.
In the output device 4, the in-container air dose rate is output to the outside. Examples of the output form include character display and image display on a display (display unit), audio output by a notification unit, and printout by a printer (printing device). Note that the output device 4 may be formed integrally with the arithmetic device 3.

The radioactivity concentration specifying unit 31 specifies the radioactivity concentration of the earth and sand in the container 21 based on the in-container air dose rate specified by the air dose rate specifying unit 32.
Specifically, the radioactivity concentration specifying unit 31 specifies the radioactivity concentration of the earth and sand by converting the air dose rate in the container into the radioactivity concentration of the earth and sand based on the following formula (1). .
RC = K · DL (1)
Here, DL is the in-container air dose rate (measured value of the air dose rate in the container 21). K is a conversion factor. RC is the converted value of the radioactive concentration of earth and sand.

The conversion coefficient K is calculated | required by the following formula | equation (2).
K = K1, K2, K3, K4 (2)
Here, the coefficient K1 is a coefficient set according to the volume V of the storage container 21. The coefficient K1 is set so as to decrease as the volume V of the storage container 21 increases. The reason for this will be described with reference to FIG.

FIG. 3 shows the relationship between the radioactive concentration RC of the earth and sand in the container 21, the air dose rate DL in the container, and the volume V of the container 21. In FIG. 3, the background level is a negligible value. Further, in changing the volume V of the storage container 21, a plurality of storage containers 21 having similar shapes and different volumes V are used.
When the volume V of the container 21 is constant, the in-container air dose rate DL increases as the radioactive concentration RC of the earth and sand in the container 21 increases. This is because, as the radioactive concentration RC of the earth and sand in the storage container 21 increases, the dose of γ rays emitted from the earth and sand increases, and therefore the dose of γ rays detected by the γ ray detector 27 increases. .
Further, if the radioactive concentration RC of the earth and sand in the storage container 21 is constant, the in-container air dose rate DL increases as the volume V of the storage container 21 increases (in FIG. 3, V1 <V2 <V3). This is because, as the volume V of the storage container 21 increases, the amount of earth and sand accommodated in the storage container 21 increases, so that the dose of γ rays released from the earth and detected by the γ-ray detection unit 27 increases. .
In FIG. 3, assuming that the in-container air dose rate DL is constant, the radioactive concentration RC of the earth and sand in the storage container 21 decreases as the volume V of the storage container 21 increases.
In consideration of this characteristic, when the in-container air dose rate DL is converted into the radioactive concentration RC of the earth and sand using the equation (1), the coefficient K1 of the equation (2) is increased as the volume V of the container 21 increases. By making it smaller, the conversion coefficient K of the equation (1) is made smaller. Therefore, the coefficient K1 is set so as to decrease as the volume V of the storage container 21 increases.

The coefficient K2 in the equation (2) is a coefficient that is set according to the properties of the earth and sand (for example, elemental composition, specific gravity, and particle size distribution characteristics of the earth and sand).
The coefficient K3 in the equation (2) is a coefficient set in consideration of the type of radioactive material in the earth and sand.
The coefficient K4 in Expression (2) is a correction coefficient.

  Regarding the setting of the coefficients K1 to K4, each coefficient is input by an input device (not shown), and this input data is transmitted to the radioactivity concentration specifying unit 31 to convert the air dose rate DL in the container to the radioactivity concentration RC of the earth and sand. At the time of conversion, the input data may be substituted into Expression (1) and Expression (2). In addition, for each of the coefficients K1 to K4, a plurality of options are stored in advance in the radioactivity concentration specifying unit 31, and the selected option is selected by the equation (1) by selecting the option with an input device (not shown). Further, it may be substituted into the equation (2). In addition, about an input device, you may form integrally with the arithmetic unit 3, and you may form separately.

Returning to FIG. 1, a signal corresponding to the radioactivity concentration specified by the radioactivity concentration specifying unit 31 (in other words, the measured value of the radioactivity concentration of the earth and sand in the container 21) is transmitted via the signal line 35. Is transmitted to the output device 4. In the present embodiment, a signal corresponding to the measured value of the radioactive concentration of earth and sand is transmitted to the output device 4 via the signal line 35. However, the signal transmission method is not limited to this, for example, The signal may be transmitted to the output device 4 by wireless communication using a wireless device.
In the output device 4, the measured value of the radioactive concentration of earth and sand is output to the outside. Since the output form is the same as described above, the description thereof is omitted.

Next, the gamma ray transmission characteristics of the earth and sand accommodated in the container 21 will be described with reference to FIG.
FIG. 4A shows the relationship between the thickness ts of earth and sand in the container 21 and the air dose rate DL in the container. FIG. 4B shows the relationship between the thickness t of the object to be measured in the container 21 and the effective dose transmittance Pe. Here, in FIG.4 (b), when the earth and sand with specific gravity 1.6 are used as a to-be-measured object, the case where water with specific gravity 1.0 is used, and the case where concrete with specific gravity 2.1 is used , Shows. Moreover, the transmittance curve D1 shown in FIG. 4 (b) shows the relationship between the thickness ts of earth and sand having a specific gravity of 1.6 and the effective dose transmittance Pes, and the transmittance curve D2 shows water having a specific gravity of 1.0. The relationship between the thickness tw and the effective dose transmittance Pew is shown, and the transmittance curve D3 shows the relationship between the concrete thickness tc of specific gravity 2.1 and the effective dose transmittance Pec. The earth and sand shown in FIGS. 4A and 4B and the water and concrete shown in FIG. 4B are not contaminated by radioactive materials, respectively.

Here, the thickness t of the object to be measured means the minimum thickness of the object to be measured accommodated in the container 21, and the inner surface of the container 21 (for example, the container body 21 a) and the γ-ray detection. This corresponds to the minimum distance from the portion 27.
The effective dose transmittance Pe is the ratio of the in-container air dose rate DL to the background level BGL. 4A and 4B, the background level BGL is 0.4 μSv / h. FIG. 4B particularly shows the effective dose transmittance Pe for γ rays from cesium 137 (Cs-137). In preparing FIG. 4B, the “Radiation Facility Shielding Calculation Practice Manual 2007” (Nuclear Safety Technology Center) was referred to.

  As shown in FIGS. 4A and 4B, the in-container air dose rate DL and the effective dose transmittance Pes decrease as the thickness ts of the earth and sand increases. This is because as the thickness ts of the earth and sand increases, the dose of γ rays that pass through the earth and sand in the storage container 21 from the background and are detected by the γ ray detector 27 decreases. As in the case where the object to be measured is earth or sand, even if the object to be measured is water or concrete, the in-container air dose rate DL and the effective dose transmittance Pe decrease as the thickness t of the object to be measured increases. (See FIG. 4 (b)). However, when the volume V of the container 21 becomes extremely large, the dose of γ rays detected by the γ ray detector 27 tends to converge due to the shielding effect of the object to be measured itself.

As shown by the transmittance curve D1 in FIG. 4B, when the earth and sand thickness ts is about 30 cm, the effective dose transmittance Pes is about 0.1. That is, when the earth and sand thickness ts is about 30 cm, the background level BGL is attenuated to about 1/10 by the earth and sand in the container 21.
As shown by the transmittance curve D1 in FIG. 4B, the effective dose transmittance Pes is less than 0.01 when the earth and sand thickness ts is about 60 cm. That is, when the thickness ts of the earth and sand is about 60 cm, the background level BGL can be attenuated to 1/100 or less by the earth and sand in the storage container 21.
Therefore, when measuring the air dose rate DL in the container, depending on the degree of attenuation of the required background level BGL, and based on the transmission characteristics of γ-rays of earth and sand (for example, the above-described transmittance curve D1), The earth and sand thickness ts is set, and each dimension of the container 21 (particularly, the minimum distance between the inner surface of the container 21 and the γ-ray detection unit 27) is set based on the set earth and sand thickness ts. Can be done. This point is the same for the object to be measured other than earth and sand.

  As shown in FIG. 4 (b), the permeability curve D1 of earth and sand with a specific gravity of 1.6 is located below the permeability curve D2 of water with a specific gravity of 1.0 and the permeation of concrete with a specific gravity of 2.1. It is located above the rate curve D3. Therefore, when the thickness ts of the earth and sand, the thickness tw of the water, and the thickness tc of the concrete are the same, since Pew> Pes> Pec, the larger the specific gravity of the object to be measured, the larger the real dose transmittance. It can be seen that Pe is small. That is, it can be seen that the greater the specific gravity of the object to be measured, the greater the attenuation effect of the background level BGL by the object to be measured. In order to efficiently obtain the attenuation effect of the background level BGL by the device under test, the specific gravity of the device under test is preferably 1.0 or more.

In FIG. 4B, the effective dose transmittance Pe for γ-rays from cesium 137 is illustrated, and the earth and sand transmittance curve D1 is the water transmittance curve D2 and the concrete transmittance curve D3. As described above, the radioactive material other than cesium 137 also has the earth and sand permeability curve D1 located between the water permeability curve D2 and the concrete permeability curve D3.
Moreover, in FIG.4 (b), although demonstrated using the permeability curve D1 of the earth and sand whose specific gravity is 1.6, also about the permeability curve D1 of the earth and sand which can have a specific gravity of 1.3-1.8, Needless to say, it is located between the water permeability curve D2 having a specific gravity of 1.0 and the concrete permeability curve D3 having a specific gravity of 2.1.

Next, a method for measuring the radioactive concentration of earth and sand using the radioactive concentration measuring apparatus 1 will be described with reference to FIGS. 1 and 2.
First, the conversion coefficient K (coefficients K1 to K4) is set through an input device (not shown).
Next, in a state where the lower lid member 21 b is closed and the sediment discharge port 24 is closed, a predetermined amount of sediment is introduced into the storage container 21 from the sediment input port 23. In addition, about the earth and sand accommodated in the storage container 21, the said earth and sand may be classified with a sieve for the purpose of equalizing the density, distribution of a radioactive substance, etc. Moreover, a predetermined amount of water is added to the earth and sand. May be added to form a slurry.

Next, γ rays are detected by the γ ray detection unit 27, and the electrical signal is transmitted to the air dose rate specifying unit 32 of the radioactivity concentration specifying unit 31.
Next, the air dose rate specifying unit 32 specifies the in-container air dose rate DL based on the electrical signal.
Next, the radioactive concentration specifying unit 31 substitutes the in-container air dose rate DL and the set conversion coefficient K (coefficients K1 to K4) into the equations (1) and (2), and Specify the radioactivity concentration RC.

In-container air dose rate DL (measured value of air dose rate) specified by the air dose rate specifying unit 32 and radioactivity concentration RC (measurement of radioactivity concentration of earth and sand) specified by the radioactivity concentration specifying unit 31 Value) are output to the outside by the output device 4.
Next, the lower lid member 21b is opened, the earth and sand discharge port 24 is opened, and the earth and sand in the container 21 are discharged to the outside.
As described above, the radioactivity concentration of the earth and sand can be measured using the radioactivity concentration measurement apparatus 1.

Next, the effect by installing the gamma ray detection part 27 in the storage container 21 is demonstrated using FIG.
FIG. 5 shows the relationship between the air dose rate measurement place PL, the air dose rate measurement value (air dose rate D), and the radioactive concentration RC of the earth and sand in the container 21. In FIG. 5, the background level is a negligible value.
In FIG. 5, two measurement places PL1 and PL2 are illustrated as measurement places PL of the air dose rate.
The measurement place PL1 is an installation place of the above-described γ-ray detection unit 27 (that is, a substantially central part in the container 21) (see FIG. 1). The air dose rate D measured at the measurement place PL1 is the above-mentioned in-container air dose rate DL.
The installation place PL2 is set on the outer surface of the side wall of the container body 21a of the storage container 21 (see FIG. 1). The γ-ray detection unit installed at the measurement place PL2 has the same configuration as the γ-ray detection unit 27 described above. The air dose rate D measured at the measurement location PL2 is referred to as a container surface air dose rate DS and will be described below.

As shown in FIG. 5, the air dose rate D (in-container air dose rate DL, container surface air dose rate DS) increases as the radioactive concentration RC of the earth and sand in the storage container 21 increases in both the measurement locations PL1 and PL2. Becomes higher.
Moreover, in FIG. 5, when the radioactive concentration RC of the earth and sand in the storage container 21 is made constant, it turns out that the container space dose rate DL shows a value higher than the container surface space dose rate DS. That is, regarding the γ-rays emitted from the earth and sand in the storage container 21, the electrical signal of γ-rays obtained at the measurement place PL1 in the storage container 21 is the electrical of γ-rays obtained at the measurement place PL2 on the outer surface of the storage container 21. There are more than signals.
Therefore, by installing the γ-ray detection unit 27 in the storage container 21, more γ-ray electrical signals are obtained than the γ-ray electrical signal obtained when the γ-ray detection unit is installed on the outer surface of the storage container 21. Therefore, the radioactivity concentration measurement apparatus 1 can realize measurement with high accuracy or in a short time.

  According to the present embodiment, the radioactivity concentration measurement apparatus 1 is surrounded by a storage container 21 (volume part) that stores a measurement object (for example, earth and sand) and the measurement object stored in the storage container 21. And a gamma ray detector 27 that detects γ rays emitted from the object to be measured and outputs an electrical signal, and the radioactivity concentration of the object to be measured based on the electrical signal. And a radioactivity concentration specifying unit 31 for specifying. As a result, the object to be measured in the storage container 21 suppresses the transmission of γ rays from the outside and suppresses the influence of the background on the γ ray detection unit 27, so that the storage container 21 itself is γ from the outside. It is not necessary to have a shielding property against the line, and it is not necessary to measure the radioactivity concentration of the measurement object in the shielding environment, and the radioactivity concentration of the measurement object can be easily measured.

Further, according to the present embodiment, the minimum distance (the thickness t of the object to be measured) between the inner surface of the storage container 21 (volume part) and the γ-ray detection unit 27 is the transmission characteristic of γ rays in the object to be measured. Set based on. Thereby, the measurement object can be stored in the storage container 21 so that a desired attenuation effect is obtained with respect to the background level BGL at the time of measuring the radioactivity concentration of the measurement object.
In addition, according to the present embodiment, the radioactivity concentration measuring apparatus 1 further includes the tubular member 25 extending from the outside of the storage container 21 (volume part) to the approximate center of the storage container 21, and the γ-ray detection unit in the tubular member 25. 27 is arranged. Thereby, since the tubular member 25 functions as a protective cover for the γ-ray detection unit 27, it is possible to suppress the occurrence of breakage of the γ-ray detection unit 27. Moreover, about the gamma ray detection part 27 arrange | positioned in the tubular member 25, the replacement | exchange and maintenance can be performed easily. In this embodiment, the extending direction of the tubular member 25 is the vertical direction, but the extending direction of the tubular member 25 is not limited to this, and may be, for example, the horizontal direction.

  Further, according to the present embodiment, the radioactivity concentration measurement apparatus 1 further includes the shield 28 inserted into the tubular member 25. Thereby, since the gamma ray which goes to the gamma ray detection part 27 from a background can be attenuated by the shield 28, the influence of the background in the gamma ray detection part 27 can be suppressed.

  Further, according to the present embodiment, the radioactivity concentration specifying unit 31 specifies the in-container air dose rate DL based on the electrical signal from the γ-ray detection unit 27, and based on the specified in-container air dose rate DL. The radioactivity concentration RC of the object to be measured is specified. As a result, a larger number of γ-ray electrical signals than the γ-ray electrical signal obtained when the γ-ray detection unit is installed on the outer surface of the container 21 are obtained, and the in-container air dose rate DL is obtained based on the electrical signals. Since the radioactivity concentration RC of the object to be measured can be specified, the radioactivity concentration measurement apparatus 1 can realize measurement with high accuracy or in a short time.

  Further, according to the present embodiment, the volume portion is formed by the storage container 21, and the measured object inlet (sediment inlet 23) provided in the upper part and the measured object outlet (sediment outlet) provided in the lower part. The outlet 24) and opening / closing means (the lower lid member 21b and the hinge) for opening and closing the measured object discharge port. Thereby, the measurement object in the container 21 can be replaced with a relatively simple configuration.

  Moreover, according to this embodiment, the to-be-measured object accommodated in the storage container 21 is earth and sand containing a radioactive substance. Thereby, the earth and sand as the object to be measured in the storage container 21 suppresses the transmission of γ rays from the outside, so that the influence of the background on the γ ray detection unit 27 can be satisfactorily suppressed.

  Moreover, according to this embodiment, as a method for measuring the radioactivity concentration of an object to be measured (for example, earth and sand) using the radioactivity concentration measuring apparatus 1, the object to be measured is accommodated in the accommodating container 21 (volume part), The γ-ray detection unit 27 detects γ-rays, transmits the electrical signal to the radioactivity concentration specifying unit 31, and the radioactivity concentration specifying unit 31 calculates the radioactivity concentration RC of the object to be measured based on the electrical signal. Identify. Thereby, more γ-ray electrical signals than the γ-ray electrical signals obtained when the γ-ray detector is installed on the outer surface of the container 21 are obtained, and the radioactivity of the object to be measured is obtained based on the electrical signals. Since the concentration RC can be specified, the radioactivity concentration measurement apparatus 1 can realize measurement with high accuracy or in a short time.

  In addition, according to the present embodiment, the object to be measured is earth and sand containing a radioactive substance, and the earth and sand are classified by sieving before the earth and sand are accommodated in the container 21 (volume part), or Water is added to the earth and sand to form a slurry. Thereby, the density of earth and sand, distribution of the radioactive substance in earth and sand, etc. can be equalized.

FIG. 6 shows a schematic configuration of an air dose rate measuring apparatus according to the second embodiment of the present invention.
A different point from the radioactive concentration measuring apparatus in 1st Embodiment shown in FIG. 1 is demonstrated.
The air dose rate measuring device 50 has a configuration in which the portion other than the air dose rate specifying unit 32 in the radioactivity concentration specifying unit 31 is omitted and the signal line 35 is also omitted with respect to the above-described radioactivity concentration measuring device 1. have.
In the present embodiment, the air dose rate measuring device 50 may be configured to include the above-described scintillation survey meter. The scintillation survey meter can be configured to include a signal line 33, a calculation device 3, a signal line 34, and an output device 4 in addition to the above-described probe (γ-ray detection unit 27). Further, the arithmetic device 3 and the output device 4 can be integrally formed to form a scintillation survey meter main body. The scintillation survey meter body specifies the value of the air dose rate at the sensitive position of the probe (that is, the air dose rate DL in the container described above) by the air dose rate specifying unit 32, and externally via the output device 4. Can be output.
In this embodiment, based on the in-container air dose rate DL output by the output device 4, an operator or the like specifies the radioactive concentration RC of the earth and sand. Since this specific method is the same as the method for specifying the radioactive concentration of earth and sand in the above-described radioactive concentration specifying unit 31, the description thereof will be omitted. Similarly to the above-described radioactivity concentration specifying unit 31, a device for specifying the radioactivity concentration RC of earth and sand is separately provided based on the air dose rate DL specified by the air dose rate specifying unit 32, and this device is provided with this device. The radioactive concentration RC of the earth and sand specified in this way may be output to the outside by screen display or the like.

  In particular, according to the present embodiment, the air dose rate measuring device 50 is surrounded by the storage container 21 (volume part) that stores the measurement object (for example, earth and sand) and the measurement object stored in the storage container 21. A gamma ray detection unit 27 that is installed in the storage container 21 so as to be surrounded, detects γ rays emitted from the object to be measured, and outputs an electrical signal, and specifies an air dose rate based on the electrical signal. An air dose rate specifying unit 32. Thereby, since the object to be measured in the container 21 can suppress the transmission of γ rays from the outside, the influence of the background on the γ ray detection unit 27 can be suppressed.

  In addition, according to the present embodiment, as a method for measuring the radioactivity concentration of an object to be measured (for example, earth and sand) using the air dose rate measuring apparatus 50, the object to be measured (for example, earth and sand) in the storage container 21 (volume part). The γ-ray detection unit 27 detects γ-rays, transmits the electric signal to the air dose rate specifying unit 32, and the air dose rate specifying unit 32 determines the air dose rate in the container based on the electric signal. DL is specified, and the radioactivity concentration of the measurement object is specified based on the specified in-container air dose rate DL. As a result, a larger number of γ-ray electrical signals than the γ-ray electrical signal obtained when the γ-ray detection unit is installed on the outer surface of the container 21 are obtained, and the in-container air dose rate DL is obtained based on the electrical signals. Therefore, the in-container air dose rate DL can be specified with high accuracy or in a short time. Further, based on the in-container air dose rate DL, the object to be measured in the container 21 is measured. Can be determined with high accuracy or in a short time.

  In the first and second embodiments described above, after measuring the radioactive concentration of the earth and sand containing the radioactive substance, it is possible to sort the earth and sand for each radioactive concentration. This distribution technique can be used, for example, in a volume reduction plant that decontaminates and reduces contaminated soil and the like.

  In the first and second embodiments described above, the cross-sectional shape of the container main body 21a of the storage container 21 is circular. However, the cross-sectional shape of the container main body 21a is not limited to this, and may be rectangular, for example. . That is, the thickness t of the object to be measured (the minimum distance between the inner surface of the container 21 and the γ-ray detection unit 27 so that a desired background attenuation effect can be obtained by the object to be measured in the container 21. ) Is secured, the cross-sectional shape of the container body 21 can be any shape.

  In the first and second embodiments described above, the “solid or liquid object to be measured” has been described using earth and sand containing a radioactive substance. However, the object to be measured is not limited to this, for example, incineration Incineration fly ash generated in a furnace and containing radioactive material, grain containing radioactive material, and aqueous solution containing radioactive material may be used. Here, the “solid or liquid object to be measured” of the present invention can be accommodated in the volume part and can be deformed according to the shape of the volume part. Examples of the “solid or liquid object to be measured” of the present invention include a powder object to be measured, a granular object to be measured, a slurry object to be measured, and the like.

  Further, in the first and second embodiments described above, the step of putting the object to be measured into the container 21 from the outside, the step of measuring the radioactivity concentration of the object to be measured, and the object to be measured outside the container In this state, the amount of the object to be measured into the container 21 from the outside is equal to the amount of the object to be discharged from the container 21 to the outside. Two steps may be performed in parallel.

  Further, in the first and second embodiments described above, the volume part that accommodates the object to be measured is formed by the accommodating container 21, but the volume part that accommodates the object to be measured is not limited to this. When the object is in a liquid state, the volume part may be formed by a tubular member through which the object to be measured flows. In this case, the thickness of the object to be measured (minimum distance between the inner surface of the tubular member and the γ-ray detector) so that a desired background attenuation effect is obtained by the object to be measured in the tubular member. Should be secured.

  The illustrated embodiments are merely examples of the present invention, and the present invention is not limited to those directly described by the described embodiments, and various improvements and modifications made by those skilled in the art within the scope of the claims. Needless to say, it encompasses changes.

DESCRIPTION OF SYMBOLS 1 Radioactivity concentration measuring device 2 Radiation detection unit 3 Arithmetic device 4 Output device 21 Container (volume part)
21a Container body 21b Lower lid member 23 Sediment input port (measurement object input port)
24 earth and sand outlet (measurement object outlet)
25 Tubular member 26 Bracket 27 Gamma ray detection unit 28 Shield 31 Radioactivity concentration specifying unit 32 Air dose rate specifying unit 33, 34, 35 Signal line 50 Air dose rate measuring device

Claims (13)

An apparatus for measuring the radioactivity concentration of a solid or liquid measurement object,
A volume for accommodating the object to be measured;
A γ-ray detection unit installed in the volume part so as to be surrounded by the object to be measured housed in the volume part, and detecting an γ-ray emitted from the object to be measured and outputting an electric signal; ,
A radioactivity concentration specifying unit for specifying the radioactivity concentration of the object to be measured based on the electrical signal;
A radioactivity concentration measuring apparatus comprising:   The radioactivity concentration measurement according to claim 1, wherein a minimum distance between the inner surface of the volume part and the γ-ray detection unit is set based on transmission characteristics of γ-rays in the analyte. apparatus.   The radiation according to claim 1 or 2, further comprising a tubular member extending from the outside of the volume portion to substantially the center of the volume portion, wherein the γ-ray detection unit is disposed in the tubular member. Effective concentration measuring device.   The radioactive concentration measuring apparatus according to claim 3, further comprising a shield inserted into the tubular member.   The radioactivity concentration specifying unit specifies an air dose rate based on the electrical signal from the γ-ray detection unit, and specifies the radioactivity concentration of the object to be measured based on the specified air dose rate. The radioactivity concentration measuring apparatus according to claim 1, wherein:   The volume portion is formed by a storage container, and the storage container is provided with a measured object input port provided at an upper portion thereof, a measured object discharge port provided at a lower portion thereof, and an opening / closing for opening and closing the measured object discharge port. The radioactivity concentration measuring apparatus according to any one of claims 1 to 5, wherein the radioactivity concentration measuring apparatus comprises:   The radioactivity concentration measurement apparatus according to claim 1, wherein the object to be measured is earth and sand containing a radioactive substance. Using the radioactive concentration measuring device according to any one of claims 1 to 7,
The object to be measured is accommodated in the volume part,
Γ-ray is detected by the γ-ray detection unit, and the electrical signal is transmitted to the radioactivity concentration specifying unit,
A radioactivity concentration measurement method in which the radioactivity concentration specifying unit specifies the radioactivity concentration of the object to be measured based on the electrical signal. An air dose rate measuring device used for specifying the radioactivity concentration of a solid or liquid measurement object,
A volume for accommodating the object to be measured;
A γ-ray detection unit installed in the volume part so as to be surrounded by the object to be measured housed in the volume part, and detecting an γ-ray emitted from the object to be measured and outputting an electric signal; ,
An air dose rate specifying unit for specifying an air dose rate based on the electrical signal;
An air dose rate measuring device comprising:   10. The air dose rate measurement according to claim 9, wherein a minimum distance between an inner surface of the volume part and the γ-ray detection unit is set based on a transmission characteristic of γ-rays in the analyte. apparatus.   The air dose rate measuring apparatus according to claim 9 or 10, wherein the object to be measured is earth and sand. Using the air dose rate measuring device according to any one of claims 9 to 11,
The object to be measured is accommodated in the volume part,
Γ-ray is detected by the γ-ray detection unit, and the electrical signal is transmitted to the air dose rate specifying unit,
Identify the air dose rate based on the electrical signal in the air dose rate specifying unit,
Based on the specified air dose rate, the radioactivity concentration of the object to be measured is specified.
Method for measuring radioactivity concentration. The object to be measured is earth and sand containing a radioactive substance,
The method for measuring a radioactivity concentration according to claim 8 or 12, wherein water is added to the earth and sand to form a slurry prior to containing the earth and sand in the volume part.