JP2016033491A - Apparatus and method for separating contaminants - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contaminant separation apparatus and method, which allow for accurately measuring radiation concentration of contaminants and efficiently separating a large amount of contaminants.SOLUTION: A contaminant separation apparatus 10 of the present invention includes a container 11 for accommodating contaminants contaminated with radioactive nuclides, a radiation measurement section 12 provided in a part of the container 11, a radiation detector 13 located roughly in the center of the radiation measurement section 12, and separation means for separating contaminants accommodated in the container 11 on the basis of radiation concentration detected by the radiation detector 13. Dimensions of the radiation measurement section 12 are set to satisfy a condition expressed as D>L, where D represents a minimum distance between an inner wall surface of the radiation measurement section 12 and the radiation detector 13, and L represents a shielding distance required for shielding radiation from radioactive nuclides in contaminants by means of the self-shielding effect.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pollutant sorting device and a pollutant sorting method for sorting pollutants contaminated with radionuclides based on radioactivity concentration.

  Contaminated soil contaminated with radionuclides such as cesium is separated into highly contaminated soil exceeding the standard value for radioactive contamination and low-contaminated soil below the standard value, and the former is stored in the intermediate storage facility. And the latter can be reused under certain conditions.

  As a method for measuring the radioactive concentration of contaminated soil, there is a method of collecting the radioactive concentration of the entire contaminated soil by collecting a part of the contaminated soil as a sample and measuring the radioactive concentration of the collected sample. However, this method cannot measure the radioactive concentration of contaminated soil in-line (in-situ measurement) in a line for separating contaminated soil, so it takes a long time to separate a large amount of contaminated soil. There is a problem of end.

  In Patent Document 1, crushed pieces generated by crushing radioactively debris are continuously supplied onto a belt conveyor, and after adjusting the layer thickness of the crushed pieces moving on the belt conveyor, the crushed pieces A method is described in which fragments are separated by continuously measuring the radioactivity concentration. In this method, the radioactive concentration of the fragments can be measured in-line, so that a large amount of contaminants can be separated in a short time.

Japanese Patent Application Laid-Open No. 2014-9998

  The radioactivity concentration that is the standard for classification of contaminated soil is the radiation dose per unit mass (Bq / Kg). Therefore, in measuring the radioactivity concentration of contaminated soil, the density (volume and mass) of the soil to be measured is accurate. It is necessary to measure well.

  In the separation method described in Patent Document 1, since the crushed pieces (contaminants) continuously move on the belt conveyor, it is difficult to accurately measure the density of the measurement target substance. Therefore, since the measurement error of the radioactivity concentration becomes large, the set value for separating the radioactivity concentration must be set to a numerical value lower than the original reference value. As a result, the separation amount of high-concentration pollutants increases and the separation amount of low-concentration pollutants decreases, which increases the burden of storing high-concentration pollutants in intermediate storage facilities and reduces the reusable low-concentration pollutants. There is a problem that it ends up.

  The present invention has been made to solve the above-mentioned problems, and its main purpose is to pollutants that can accurately measure the radioactive concentration of pollutants and can efficiently separate a large amount of pollutants. It is to provide a separation apparatus and a contaminant separation method.

  In the present invention, a radioactivity measurement unit is provided in a part of a container for containing a pollutant, a radiation detector is disposed at the center of the radioactivity measurement unit, and the size of the radioactivity measurement unit is set so that the self-shielding of the contaminant It is larger than a sphere whose radius is the shielding distance due to the effect.

  That is, the pollutant separation device according to the present invention is arranged in a container that contains a pollutant contaminated with a radionuclide, a radioactivity measurement unit provided in a part of the container, and substantially at the center in the radioactivity measurement unit. A radiation detector and a separation means for separating contaminants contained in the container based on the radioactive concentration detected by the radiation detector. The size of the radioactivity measurement unit is set so that D> L, where D is the minimum distance and L is the shielding distance due to the self-shielding effect of the radiation dose from the radionuclide in the pollutant. Features.

  The pollutant separation method according to the present invention includes a step (a) of containing a pollutant contaminated with a radionuclide in a container, and a step (b) of detecting a radioactivity concentration of the pollutant contained in the container. And (c) separating the contaminants contained in the container based on the detected radioactivity concentration, and the radioactivity concentration is approximately at the center of the radioactivity measurement unit provided in a part of the container. When the minimum distance between the inner wall surface of the radioactivity measurement unit and the radiation detector is detected by the arranged radiation detector, and the shielding distance by the self-shielding effect of the radiation dose from the radionuclide in the pollutant is L , D> L, the size of the radioactivity measurement unit is set.

  According to the present invention, it is possible to provide a pollutant sorting apparatus and a pollutant sorting method that can accurately measure the radioactive concentration of pollutants and can efficiently sort a large amount of pollutants.

It is sectional drawing which showed typically the structure of the contaminant classification | fractionation apparatus in one Embodiment of this invention. It is the figure which showed typically the structure of the radioactivity measurement part in one Embodiment of this invention. It is the graph which showed the relationship between the radiation dose of the contaminant in the position of a radiation detector, and the distance from a radiation detector to the inner wall face of a radioactivity measurement part. It is the figure which showed the specific structure of the radioactivity measurement part in one Embodiment of this invention. It is the graph which showed the relationship between the detection count of the specific radiation of the contaminant in the position of a radiation detector, and the distance from a radiation detector to the inner wall surface of a radioactivity measurement part for every density of contaminant. It is the block diagram which showed the structure of the radioactive concentration calculation means in one Embodiment of this invention. It is the graph which showed the relationship between the air dose from a background, and the distance from the inner wall face of a radioactivity measurement part. It is the figure which showed typically the structure of the separation line of the contaminant in one Embodiment of this invention. It is the flowchart which showed the contaminant classification method in one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention.

  FIG. 1 is a cross-sectional view schematically showing the configuration of a pollutant sorting device according to an embodiment of the present invention. Here, the “contaminant” means a substance contaminated with a radionuclide, and includes a substance mixed with a substance not contaminated with a radionuclide. Moreover, the kind of pollutant is not limited, For example, contaminated soil, rubble, vegetation, etc. are included.

  As shown in FIG. 1, a pollutant sorting device 10 according to this embodiment includes a container 11 that contains a pollutant 20 contaminated with a radionuclide, and a radioactivity measurement unit 12 provided in a part of the container 11. , And a radiation detector 13 disposed substantially at the center in the radioactivity measurement unit 12. A part of the outer wall of the radioactivity measurement unit 12 is an openable / closable open / close unit 18. When the measurement of the radioactive concentration of the pollutant 20 is completed, the open / close unit 18 is opened and the pollutant 20 is discharged. The The discharged pollutant 20 is sorted based on the radioactive concentration detected by the radiation detector 13.

  Here, the radiation detector 13 is installed in a cylindrical storage container 14, and is protected from the contaminant 20 introduced into the container 11 by the storage container 14. The radiation detector 13 includes a detector capable of detecting radiation such as α rays and β rays in addition to γ rays. For example, a NaI scintillator or the like is used as a γ-ray detector. Moreover, the detection of the radiation dose by the radiation detector 13 can be calculated from the peak count rate of specific radiation (for example, cesium 134, cesium 137, etc.) measured by the radiation detector 13, for example.

  A mass detector 16 and a volume detector 17 are attached to the container 11, and the density of the contaminant 20 contained in the container 11 is measured using these. Here, for example, a load cell or the like is used as the mass detector 16. The volume detector 17 is, for example, a non-contact type level meter or a three-dimensional measuring device. When measuring the density, it is preferable to level the surface of the contaminant 20 supplied into the container 11 in advance.

By the way, the pollutant 20 such as polluted soil itself has a so-called self-shielding effect that shields the radiation dose from the radionuclide in the pollutant 20. Therefore, as shown in FIG. 2, when the radiation dose of the contaminant 20 around the radiation detector 13 is measured by the radiation detector 13 arranged at the approximate center in the radioactivity measuring unit 12, the radiation detector 13. As shown in FIG. 3, the radiation amount detected at 1 converges substantially when the distance from the radiation detector 13 exceeds a certain value. When the distance at which the radiation dose converges is the shielding distance L of the radiation dose from the radionuclide in the pollutant 20, the radiation detector 13 emits the radiation of the pollutant 20 inside the sphere whose radius is the shielding distance L. The amount is being measured. Strictly speaking, even after the radiation dose converges to a substantially constant value, the radiation dose increases little by little. Therefore, the shielding distance L in the present embodiment is not strictly determined but is defined as a value having a certain width. For example, when the distance at which the radiation dose starts to converge to a substantially constant value is L ₀ , the shielding distance L may be defined to include a range within ± 10% with respect to the value of L _0. Good. In addition, the shielding distance L in the present embodiment varies depending on the type of contaminant that is the measurement object of the radioactivity concentration, and also varies depending on the density of the contaminant as described later.

  Therefore, as shown in FIG. 2, the size of the radioactivity measurement unit 12 is set so that D> L, where D is the minimum distance between the inner wall surface of the radioactivity measurement unit 12 and the radiation detector 13. By doing so, the substance to be measured by the radiation detector 13 can be specified as the pollutant 20 in the sphere having the shielding distance L as a radius. Moreover, since the shielding distance L can be uniquely determined as a unique parameter of the pollutant 20, the volume V of the measurement target substance (the volume of a sphere having L as the radius) can be easily obtained. Therefore, if the density ρ of the pollutant is measured in advance, the mass M (M = V · ρ) of the measurement target substance can be easily obtained. Thereby, from the radiation dose Q detected by the radiation detector 13 and the mass M of the substance to be measured, the radioactive concentration N of the pollutant can be easily obtained using the following equation (1).

N = Q / M = Q / (V · ρ) (1)
Here, V is a volume of a sphere having a radius of L (V = 4 / 3πL ³ ).

  Incidentally, the radiation detector 13 shown in FIG. 2 is covered with the contaminant 20 without any gaps, but actually, as shown in FIG. 4, the radiation detector 13 is not contaminated with the contaminant. In order to protect it from 20, it is placed in a container 14. Since there is no contaminant 20 having a self-shielding effect in the storage container 14, the attenuation of radiation in the storage container 14 is very small. Accordingly, the range occupied by the measurement target substance of the radiation detector 13 is slightly different geometrically from a sphere having a radius of the shielding distance L as shown in FIG. 4, and the distance L from the outer periphery of the container 14 is constant. It becomes a range.

  Thus, the volume V ′ occupied by the substance to be measured of the actual radiation detector 13 is given by the following formula (2) in consideration of the shape of the container 14 with respect to the volume V of the sphere having the shielding distance L as the radius. ), It is necessary to perform geometric correction.

V ′ = K ₁ · V (K ₁ is a correction coefficient) (2)
In addition, in the range occupied by the measurement target substance of the radiation detector 13, the radiation dose from the contaminant 20 located away from the radiation detector 13 reaches the self-shielding effect of the contaminant 20 before reaching the radiation detector 13. It attenuates by. Therefore, when the radioactive concentration N of the pollutant 20 is obtained by the above equation (1), the substantial volume V ′ occupied by the measurement target substance of the radiation detector 13 is expressed by the following equation (3): It is necessary to perform correction in consideration of the attenuation of the radiation dose due to the self-shielding effect of the contaminant 20 on the volume V of the sphere having the shielding distance L as a radius.

V ″ = K ₂ · V (K ₂ is a correction coefficient) (3)
Further, since the radiation detector 13 is installed inside the storage container 14, the radiation dose from the contaminant 20 outside the storage container 14 is attenuated when passing through the storage container 14. Therefore, when the radioactive concentration N of the pollutant 20 is obtained by the above equation (1), the radiation dose Q detected by the radiation detector 13 is the shielding effect of the container 14 as shown in the following equation (4). It is necessary to perform correction in consideration of

Q ′ = K ₃ · Q (K ₃ is a correction coefficient) (4)
Thus, in calculating the actual radioactivity concentration N, the following equation (5) is used for the volume V of the sphere whose radius is the shielding distance L and the radiation dose Q detected by the radiation detector 13. It is necessary to calculate using a correction coefficient K as shown.

N = Q '/ M
= Q '/ (V' · ρ)
= K ₃ Q / (K ₁ · K ₂ · V · ρ)
= Q / (K · V · ρ) (5)
Here, K = K ₃ / (K ₁ · K ₂ ); V is a volume of a sphere having a radius of L (V = 4 / 3πL ³ ).

The above explains the principle of calculating the radioactivity concentration N, but K ₁ , K ₂ , K _3, and V are specific values depending on the radioactivity measurement unit 12 and the container 14 of the radiation detector 13. Therefore, in the implementation stage, it is not necessary to obtain each parameter independently in calculating the radioactivity concentration N. For example, the same radioactivity measurement unit 12 as that used in the implementation stage and the container 14 of the radiation detector 13 are prepared, and Q and ρ are experimentally measured using a sample contaminant and provided separately. An accurate radioactivity concentration N of the sample pollutant is measured with a radioactivity concentration meter (eg, germanium semiconductor detector). As a result, (K · V) can be obtained experimentally in advance from the equation (5).

By the way, the self-shielding effect of the contaminant 20 also varies depending on the density of the contaminant 20. FIG. 5 shows the specific radiation from the surrounding pollutant 20 sensed by the γ-ray detector 13 by changing the density ρ while keeping the radioactive concentration (Bq / kg) and measurement time of the pollutant 20 constant. It is the graph which showed the result of having respectively calculated the detection count (peak count rate x measurement time) of cesium 137). Here, the pollutant 20 uses contaminated soil, and the density ρ is changed to a range of 1.2 to 1.5 g / cm ³ (ρ ₁ > ρ ₂ > ρ ₃ > ρ ₄ ), and simulation calculation is performed. It was. As shown in FIG. 3, the relationship between the specific radiation detection count and the distance from the γ-ray detector 13 is substantially converged when the distance from the γ-ray detector 13 exceeds a certain value. . Here, the detection count obtained by the simulation calculation corresponds to the radiation dose shown in FIG.

  As shown in FIG. 5, when the density ρ of the pollutant 20 increases, the mass of the pollutant sensed by the γ-ray detector 13 increases, so that the specific radiation detection count increases, but the self-shielding effect also increases. On the contrary, the detection count of specific radiation decreases. However, although there is an influence of both increase and decrease, as a whole, when the density ρ of the contaminant 20 increases, the detection count of the specific radiation detected by the γ-ray detector 13 increases. Therefore, the volume V of the sphere whose radius is the shielding distance L needs to be determined using the density ρ of the contaminant 20 as a parameter. Therefore, when calculating the radioactive concentration N of the pollutant 20 using the above equation (5), the relationship between (K · V) and ρ is measured in advance for a plurality of pollutants having different densities. Therefore, it is necessary to obtain (K · V) based on the data.

  FIG. 6 is a block diagram showing the configuration of the radioactivity concentration calculating means in the present embodiment.

  As shown in FIG. 6, the radioactive concentration calculation means 50 includes a calculation unit 51 and a storage means 52. The calculation unit 51 includes the radiation amount Q of the contaminant 20 detected by the radiation detector 13 and the contaminant 20 measured by the density measuring means 54 (the mass detector 16 and the volume detector 17 attached to the container 11). Are input respectively.

  The storage means 52 stores data obtained by measuring in advance the relationship between (K · V) and ρ. In the calculation unit 51, for example, the radiation dose Q is calculated from the peak count rate (or detection count) of the specific radiation, and the density ρ of the pollutant and (K · V) based on the above equation (5). ) To calculate the radioactive concentration N of the pollutant 20.

  Data of the radioactivity concentration N calculated by the radioactivity concentration calculation means 50 is input to the classification means 53. The sorting means 53 compares the radioactivity concentration N with a reference value for classifying the radioactivity concentration. If the radioactivity concentration N is higher than the reference value, it is classified as a high-concentration pollutant, and if it is lower than the reference value. Sort as low-concentration pollutants.

  As described above, according to the pollutant sorting device in the present embodiment, the size of the radioactivity measurement unit 12 is made larger than a sphere whose radius is the shielding distance L due to the self-shielding effect of the pollutant 20. Thus, the range of the measurement target substance of the radiation detector 13 can be specified as a sphere having the shielding distance L as a radius, and thus the density (volume and mass) of the measurement target substance can be measured with high accuracy. Further, since the sphere having the radius of the shielding distance L is the maximum range in which the radiation detector 13 can measure the radiation dose of the contaminant, the maximum radiation dose can be measured. Therefore, the detection sensitivity of the radiation detector 13 can be increased.

  Further, as shown in FIG. 1, the radioactivity measurement unit 12 may be provided in a part of the container 11 that contains the contaminant 20, so that the range of the measurement target substance of the radiation detector 13 is extremely small. Can do. Thereby, a large amount of contaminants can be separated efficiently in a short time.

For example, when the shielding distance L is 30 cm, it is sufficient for the radioactivity measurement unit 12 to have a sufficient size of a sphere having a radius of 50 cm. On the other hand, the size of the container 11 can be determined arbitrarily. For example, when the size of the container 11 is a cylinder having a radius of 1 m and a height of 1 m, the volume of the radioactivity measuring unit 12 (about 0.5 m ³ ) can be about 1/6 of the volume of the container 11 (about 3 m ³ ).

  In the present embodiment, in order to efficiently separate a large amount of contaminants in a short time, the volume of the radioactivity measurement unit 12 is preferably at least 1/5 or less of the volume of the container 11. 1/10 or less is more preferable.

  By the way, when the separation of pollutants is performed in an area where radioactive contamination has occurred, the background radiation dose (air dose) is also very high. Therefore, if the radiation detector 13 also detects the air dose from the background, the measurement accuracy of the radioactive concentration of the pollutant is lowered. However, since the radiation detector 13 in this embodiment is disposed inside the radioactivity measurement unit 12, the air dose from the background is radiated due to the shielding effect of the pollutant 20 as shown in FIG. 7. It attenuates as the distance from the inner wall surface of the performance measuring unit 12 increases. Therefore, if the radiation detector 13 is arranged at a distance from the inner wall surface of the radioactivity measurement unit 12 to attenuate until the air dose from the background is sufficiently smaller than the radiation dose of the pollutant, The effect can be eliminated.

  In the present embodiment, the shape and size of the radioactivity measurement unit 12 are not particularly limited as long as the size of the radioactivity measurement unit 12 is set so that D> L. The minimum distance D between the inner wall surface of the radioactivity measurement unit 12 and the radiation detector 13 is obtained by subtracting the spatial distance in the storage container 14 of the radiation detector 13.

  In the present embodiment, the radiation detector 13 is disposed substantially at the center of the radioactivity measurement unit 12, but is not limited to the geometric center of the radioactivity measurement unit 12, and is centered on the radiation detector 13. The case where the sphere having the radius L is inside the radioactivity measuring unit 12 is also included.

  In the present embodiment, the radioactivity measurement unit 12 constitutes a part of the container 11 that contains the contaminant 20, but it does not necessarily have to be configured integrally with the container 11. If some of the contaminants contained in the container 11 are also contained in the radioactivity measurement unit 12, even if the radioactivity measurement unit 12 is physically separated from the container 11, Part of it.

  FIG. 8 is a diagram schematically showing the configuration of a separation line for assembling the pollutant sorting device in the present embodiment on site and performing a pollutant sorting operation.

  One batch of contaminants is supplied to the hopper 40, transferred by the belt conveyor 41, and supplied to the hopper 42 disposed above the stirring means 43. The pollutant supplied to the hopper 42 is put into the stirring means 43, where the concentration of the radionuclide in the pollutant is homogenized by stirring the pollutant. Thereby, since the radioactivity concentration of the measurement target substance in the radioactivity measurement unit 12 becomes uniform, the measurement error of the radioactivity concentration in the radiation detector 13 can be reduced.

  Next, the pollutant homogenized by the stirring means 43 is put into the container 11, and the radioactivity concentration of the pollutant is measured by the radiation detector 13 arranged at the approximate center in the radioactivity measuring unit 12. When the measurement is completed, all the contaminants in the container 11 are dropped onto the belt conveyor 44 from the radioactivity measurement unit 12. Contaminants dropped on the belt conveyor 44 are sorted based on the radioactivity concentration detected by the radiation detector 13. That is, low-concentration pollutants whose radioactivity concentration is lower than the reference value are transferred on the belt conveyor 44 and collected in the collection container 45, and high-concentration contaminants whose radioactivity concentration is higher than the reference value are opposite on the belt conveyor 44. It is transferred in the direction and collected in the collection container 46.

  When the separation of pollutants for one batch is completed, the next batch of pollutants is supplied to the hopper 40, and the above steps are repeated to separate the pollutants.

  In the separation line of the present embodiment, the stirring means 43 can be omitted if the radioactive concentration in the contaminant is uniform. In addition, before supplying the pollutant to the hopper 40, the concentration of the radionuclide in the pollutant may be homogenized using the stirring means 43 in advance.

  The separation line in the present embodiment is separated for each batch, but the measurement of the radioactive concentration of the pollutant is performed in-line (in-situ measurement) in the radioactivity measuring unit 12, so that a large amount of the pollutant is separated. Can be performed efficiently in a short time.

  FIG. 9 is a flowchart showing the pollutant sorting method in this embodiment.

  As shown in FIG. 9, first, it is determined whether or not the concentration of the radionuclide in the pollutant is homogenized (step S1). If it is homogenized, the contaminant is accommodated in the container 11 (step S3). If not homogenized, the contaminant is agitated to homogenize the concentration of the radionuclide (step S2), and then the contaminant is accommodated in the container 11 (step S3).

  Next, the radioactive concentration of the contaminant 20 accommodated in the container 11 is measured (step S4). The radioactivity concentration is detected by a radiation detector 13 disposed substantially at the center in the radioactivity measurement unit 12 provided in a part of the container 11. At this time, the size of the radioactivity measurement unit 12 is determined by D being the minimum distance between the inner wall surface of the radioactivity measurement unit 12 and the radiation detector 13, and shielding by the self-shielding effect of the radiation dose from the radionuclide in the contaminant 20. When the distance is L, D> L is set.

  Next, the contaminant 20 accommodated in the container 11 is sorted based on the detected radioactivity concentration (step S5). If the radioactivity concentration is higher than the reference value, it is classified as a high concentration pollutant (step S6), and if the radioactivity concentration is lower than the reference value, it is classified as a low concentration pollutant (step S7).

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

10 Pollutant separation device
11 containers
12 Radioactivity measurement unit
13 Radiation detector (γ-ray detector)
14 container
16 Mass detector
17 Volume detector
18 Opening and closing part
20 Pollutants
40, 42 hopper
41, 44 Belt conveyor
43 Stirring means
45, 46 Collection container
50 Radioactivity concentration calculation means
51 Calculation unit
52 Memory means
53 Sorting means
54 Density measuring means

That is, the pollutant separation device according to the present invention includes a container that contains a pollutant contaminated with a radionuclide, a radioactivity measurement unit that constitutes a part of the container and contains the pollutant, and a radioactivity measurement unit. A radiation detector, and a separation means for separating contaminants contained in the container based on the radioactive concentration detected by the radiation detector, and an inner wall surface of the radioactivity measurement unit, Radioactivity so that D> L, where D is the minimum distance from the radiation detector and L is the shielding distance specific to the type of pollutant due to the self-shielding effect of the radiation dose from the radionuclide in the pollutant. When the size of the measurement unit is set and the radiation dose of the contaminants around the radiation detector is measured, the distance from the radiation detector is separated, the radiation dose converges to a certain value, and further away Even if the radiation dose does not increase ₀ the time, screening length L is characterized in that in L = _{L 0} ± 10% of the range.

The pollutant separation method according to the present invention includes a step (a) of containing a pollutant contaminated with a radionuclide in a container, and a step (b) of detecting a radioactivity concentration of the pollutant contained in the container. And (c) separating the pollutant contained in the container based on the detected radioactivity concentration, and the radioactivity concentration forms a part of the container to contain the pollutant. Contaminant detected by a radiation detector arranged at the approximate center in the unit, D is the minimum distance between the inner wall surface of the radioactivity measurement unit and the radiation detector, and the contamination is due to the self-shielding effect of the radiation dose from the radionuclide in the contaminant The size of the radioactivity measurement unit is set so that D> L, where L is the shielding distance specific to the type, and when the radiation dose of contaminants around the radiation detector is measured, Radiation away from the radiation detector There converges to a constant value, when a distance more radiation amount away does not increase and the L _0, screening length L is characterized in that in L = L ₀ ± 10% of the range.

By the way, the pollutant 20 such as polluted soil itself has a so-called self-shielding effect that shields the radiation dose from the radionuclide in the pollutant 20. Therefore, as shown in FIG. 2, when the radiation dose of the contaminant 20 around the radiation detector 13 is measured by the radiation detector 13 arranged at the approximate center in the radioactivity measuring unit 12, the radiation detector 13. amount of radiation detected in, as shown in FIG. 3, the distance from the radiation detector 13 is converged becomes more than a constant. When the distance at which the radiation dose converges is the shielding distance L of the radiation dose from the radionuclide in the pollutant 20, the radiation detector 13 emits the radiation of the pollutant 20 inside the sphere whose radius is the shielding distance L. The amount is being measured. Note that the shielding distance L in the present embodiment is not strictly determined, but is defined as a value having a certain width. That is, when the radiation dose of the pollutant 20 around the radiation detector 13 is measured, the distance from the radiation detector 13 is separated and the radiation dose converges to a certain value, and the radiation dose does not increase even if it is further away. When the distance is L ₀ , the shielding distance L is defined as a distance including a range within ± 10% with respect to the value of L ₀ . In addition, the shielding distance L in the present embodiment varies depending on the type of contaminant that is the measurement object of the radioactivity concentration, and also varies depending on the density of the contaminant as described later.

That is, the pollutant separation device according to the present invention includes a container that contains a pollutant contaminated with a radionuclide, a radioactivity measurement unit that constitutes a part of the container and contains the pollutant, and a radioactivity measurement unit. A radiation detector, and a separation means for separating contaminants contained in the container based on the radioactive concentration detected by the radiation detector, and an inner wall surface of the radioactivity measurement unit, Radioactivity so that D> L, where D is the minimum distance from the radiation detector and L is the shielding distance specific to the type of pollutant due to the self-shielding effect of the radiation dose from the radionuclide in the pollutant. The size of the measurement unit is set, and when the radiation dose of the contaminants around the radiation detector is measured , the thickness of the contaminants around the radiation detector increases and the radiation dose converges to a certain value, radiation dose even if the number is more than the thickness When increased without thickness was L _0, screening length L is characterized in that in L = L ₀ ± 10% of the range.

The pollutant separation method according to the present invention includes a step (a) of containing a pollutant contaminated with a radionuclide in a container, and a step (b) of detecting a radioactivity concentration of the pollutant contained in the container. , based on radioactive concentration detected, and the step (c) fractionating contaminants contained in the container, the radioactivity concentration, radioactivity measurement to accommodate the contaminants constitute a part of the container Contaminant detected by a radiation detector arranged at the approximate center in the unit, D is the minimum distance between the inner wall surface of the radioactivity measurement unit and the radiation detector, and the contamination is due to the self-shielding effect of the radiation dose from the radionuclide in the contaminant The size of the radioactivity measurement unit is set so that D> L, where L is the shielding distance specific to the type, and when the radiation dose of contaminants around the radiation detector is measured, the thickness of the contaminants around the radiation detector Ete radiation dose converges to a constant value, when the radiation amount is increasing more thickness has a thickness that does not increase with L _0, screening length L is, that is in the L = L ₀ ± 10% in the range Features.

By the way, the pollutant 20 such as polluted soil itself has a so-called self-shielding effect that shields the radiation dose from the radionuclide in the pollutant 20. Therefore, as shown in FIG. 2, when the radiation dose of the contaminant 20 around the radiation detector 13 is measured by the radiation detector 13 arranged at the approximate center in the radioactivity measuring unit 12, the radiation detector 13. As shown in FIG. 3, the radiation amount detected in (1) converges when the distance from the radiation detector 13 becomes a certain distance or more. When the distance at which the radiation dose converges is the shielding distance L of the radiation dose from the radionuclide in the pollutant 20, the radiation detector 13 emits the radiation of the pollutant 20 inside the sphere whose radius is the shielding distance L. The amount is being measured. Note that the shielding distance L in the present embodiment is not strictly determined, but is defined as a value having a certain width. That is, when the radiation dose of the contaminant 20 around the radiation detector 13 is measured , the thickness of the contaminant around the radiation detector 13 increases, the radiation dose converges to a certain value, and the thickness further increases. When the thickness at which the radiation dose does not increase is L ₀ , the shielding distance L is defined as a distance including a range within ± 10% with respect to the value of L ₀ . In addition, the shielding distance L in the present embodiment varies depending on the type of contaminant that is the measurement object of the radioactivity concentration, and also varies depending on the density of the contaminant as described later.

Claims (12)

A container for containing contaminants contaminated with radionuclides;
A radioactivity measurement unit provided in a part of the container;
A radiation detector disposed substantially at the center in the radioactivity measurement unit;
A pollutant sorting device comprising a sorting means for sorting pollutants contained in the container based on the radioactive concentration detected by the radiation detector,
When the minimum distance between the inner wall surface of the radioactivity measuring unit and the radiation detector is D, and the shielding distance due to the self-shielding effect of the radiation dose from the radionuclide in the contaminant is L, D> L. In addition, a pollutant separation device in which the size of the radioactivity measurement unit is set. Density measuring means for measuring the density of the contaminant contained in the container;
A radioactivity concentration calculating means for calculating the radioactivity concentration of the pollutant,
When the radiation dose detected by the radiation detector is Q, and the density of the contaminant measured by the density measuring means is ρ,
The pollutant sorting device according to claim 1, wherein the radioactive concentration calculating means calculates a radioactive concentration N of the pollutant based on the following equation.
N = Q / (K ・ V ・ ρ)
Here, K is a correction coefficient, and V is the volume of a sphere having a radius L. The radioactivity concentration calculating means further comprises storage means for storing data obtained by measuring in advance the relationship between the (K · V) and ρ,
The pollutant separation device according to claim 2, wherein in the radioactive concentration calculation means, the (K · V) is determined based on data stored in the storage means. A stirring means for stirring the contaminant;
The contaminant separating apparatus according to claim 1, wherein the contaminant contained in the container is homogenized in concentration of the radionuclide by the stirring means.   The pollutant separation device according to claim 1, wherein a volume of the radioactivity measurement unit is at least 1/5 or less of a volume of the container.   The pollutant separation device according to claim 1, wherein the pollutant is contaminated soil contaminated with a radionuclide. A step (a) of containing a pollutant contaminated with a radionuclide in a container;
Detecting the radioactive concentration of the contaminant contained in the container (b);
A step (c) of separating contaminants contained in the container based on the detected radioactivity concentration,
The radioactivity concentration is detected by a radiation detector disposed substantially at the center in a radioactivity measurement unit provided in a part of the container,
When the minimum distance between the inner wall surface of the radioactivity measuring unit and the radiation detector is D, and the shielding distance due to the self-shielding effect of the radiation dose from the radionuclide in the contaminant is L, D> L. And a method for separating contaminants, wherein the size of the radioactivity measuring unit is set. The step (b)
Measuring the density ρ of the contaminant contained in the container;
Detecting a radiation dose Q of the contaminant,
The pollutant classification method according to claim 7, wherein the radioactive concentration N of the pollutant is calculated based on the following equation.
N = Q / (K ・ V ・ ρ)
Here, K is a correction coefficient, and V is the volume of a sphere having a radius L.
  The pollutant classification method according to claim 8, wherein (K · V) is determined based on data indicating a relationship between (K · V) and ρ measured in advance.   The method for separating pollutants according to claim 7, further comprising the step of homogenizing the concentration of the radionuclide contained in the container by stirring the pollutant before the step (a).   The volume of the said radioactivity measurement part is a pollutant classification method of Claim 7 which is at least 1/5 or less with respect to the volume of the said container.   The pollutant separation method according to claim 7, wherein the pollutant is contaminated soil contaminated with a radionuclide.

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