Radiation energy measuring device

Abstract

To provide a radioactivity measurement device that is excellent in waterproofness and strength, and can measure radioactive substance concentration continuously in real time even in deep environment water.SOLUTION: In order to solve the above problem, the radioactivity measurement device comprises: a water proof container 10 that is composed of a hollow plastic scintillator; a communication cable 20 that connects to an outer surface of the waterproof container 10; and an internal component 30 that includes a communication unit 31 provided inside of the waterproof container 10 to transmit and receive data via the communication cable 20, and a battery 32 of the communication unit 31. The waterproof container 10, which has an outer diameter X of 50 mm or less, and has no hole penetrating between an inside of the waterproof container 10 and an outside thereof, and the communication unit 31 and communication cable 20 are configured to transmit and receive the data in a non-contact state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a radiation measurement device that is excellent in waterproofness and strength and can measure the concentration of radioactive substances in real time and continuously even in deep environmental water.

Background Art

[0002] Radioactive nuclides such as uranium and thorium contained in the earth's crust, and their progeny nuclides, have been widely measured as useful indicators for geological surveys due to the specificity of their distribution. Among these, radon, which is a progeny nuclide of uranium, is a noble gas that dissolves in water while having a short half-life of 3.8 days. Therefore, radon has been used as an indicator showing the contribution of groundwater that has passed through strata containing uranium-series nuclides, and until now, the measurement of radon in environmental water has been carried out for the purpose of detecting groundwater gushing in rivers and coastal areas and changes in the flow of groundwater associated with crustal activities (see, for example, Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3). Therefore, in the measurement method disclosed in Non-Patent Document 1, pumping from water is necessary, and since labor for solvent extraction and a device for equilibration with air are required, real-time and continuous data acquisition has been difficult unless under limited conditions where there are sufficient land, power supply facilities, and human resources.

[0003] Conventionally, radon in environmental water has been measured by pumping water from rivers or observation wells, performing solvent extraction, condensing radon in a liquid scintillator, and analyzing it with a liquid scintillation counter, or by equilibrating the pumped water with air in a tube and measuring the radon transferred to the air by an ionization chamber or an electrostatic trapping method (see, for example, Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3). Therefore, in the measurement method disclosed in Non-Patent Document 1, pumping from water is necessary, and since labor for solvent extraction and a device for equilibration with air are required, real-time and continuous data acquisition has been difficult unless under limited conditions where there are sufficient land, power supply facilities, and human resources. On the other hand, these days, there is a high need to evaluate the impact on water resources due to disasters such as earthquakes, and there is a demand for constructing a system that can continuously observe the concentration of radioactive substances in environmental water such as groundwater. In such a situation, if there is a device that can continuously measure radon in the future, it may be used for detecting abnormalities in water resource management.

[0004] As a technique for continuously observing the concentration of radioactive substances in the environmental water mentioned above, for example, Patent Document 1 discloses a radioactivity measuring device comprising a radiation detector and a waterproof container made of a material that is waterproof and transparent to radiation, and provided to cover the radiation detector. Furthermore, Patent Document 2 discloses a radioactivity measuring device that uses a hollow container-shaped scintillator with a reflector and a photomultiplier tube installed inside it. These radioactivity measuring devices make it possible to monitor the concentration of radioactive materials in environmental water in real time. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-066393 [Patent Document 2] Publication No. 62-0551853 [Non-patent literature]

[0006] [Non-Patent Document 1] Hamada et al., "Groundwater Survey and Analysis Method Using Radon Concentration as an Indicator," Bulletin of the Institute of Agricultural Engineering, 1997, 36, pp. 17-50. [Non-Patent Document 2] Burnett et al, “A continuous monitor for assessment of 22Rn in the coastal ocean,” Journal of Radioanalytical and Nuclear Chemistry, 249, P1657-1724 [Non-Patent Document 3] Ishikawa et al., "Comparison of Radon Concentration Measurement Devices in Groundwater: Results Obtained with Liquid Scintillation Counter, IM Efficacy Meter, Ionization Chamber, and Radon Monitor," Radioisotopes, 53(3), pp. 133-140. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In areas where groundwater is used as a water resource, such as underground dams, multiple small boreholes (observation wells) are established for groundwater monitoring. It is desirable to use these observation wells to measure the concentration of radioactive materials at greater depths. However, the radioactivity measuring devices described in Patent Documents 1 and 2 could not be installed in such observation openings due to their size. Furthermore, measuring the concentration of radioactive materials in deeper groundwater requires high water resistance to prevent water from entering the internal equipment, as well as strength to withstand water pressure and impact upon contact. However, the radioactivity measuring devices described in Patent Documents 1 and 2 are intended for measuring the concentration of radioactive materials in relatively shallow waters, and further improvements in terms of high water resistance and strength were desired.

[0008] Therefore, the object of the present invention is to provide a radioactivity measuring device that is excellent in waterproofness and strength, and can measure the concentration of radioactive materials in real time and continuously, even in environmental water at great depths. [Means for solving the problem]

[0009] The present inventors conducted intensive research to solve the above-mentioned problems regarding a radioactivity measuring device for observing the concentration of radioactive materials in water. As a result, they found that by using a plastic scintillator as a waterproof container and having a communication unit installed inside the waterproof container transmit and receive data with a communication cable in a non-contact manner, it is not necessary to form a through hole for the communication cable in the waterproof container. Therefore, the strength and waterproofness of the waterproof container can be greatly improved compared to conventional technology. Furthermore, by reducing the outer diameter of the waterproof container to 50 mm or less, it is possible to miniaturize the radioactivity measuring device, so that it can be installed in the observation hole for groundwater observation mentioned above. Based on these findings, the present invention was completed.

[0010] This invention is based on the above findings, and its gist is as follows. (1) A radioactive substance concentration measuring device for observing the concentration of radioactive substances in water, comprising: A waterproof container composed of an inner-empty plastic scintillator, A communication cable connected to the outer surface of the waterproof container, Internal components provided inside the waterproof container, including a communication unit for transmitting and receiving data via the communication cable and a battery for the communication unit, and the waterproof container has an outer diameter of 50 mm or less and has no holes penetrating between the inside and outside of the waterproof container, wherein the communication unit and the communication cable perform data transmission and reception in a non-contact state.

[0011] (2) The radioactive substance concentration measuring device according to (1) above, wherein the internal components further include a photomultiplier tube.

[0012] (3) The radioactive substance concentration measuring device according to (1) or (2) above, wherein the internal components further include a data logger and / or a multi-channel analyzer.

[0013] (4) The radioactive substance concentration measuring device according to (1) or (2) above, wherein the battery charging is performed in a non-contact state with the outside.

[0014] (5) The radioactive substance concentration measuring device according to (1) or (2) above, wherein the radioactive substance concentration measuring device measures the radon concentration in water.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a radioactive substance concentration measuring device that is excellent in waterproofness and strength and can measure the concentration of radioactive substances in real time and continuously even in deep environmental water.

Brief Description of the Drawings

[0016] [Figure 1] It is a diagram schematically showing an embodiment of the radioactive substance concentration measuring device of the present invention.

Embodiments for Carrying Out the Invention

[0017] <Radiation Measuring Device> An embodiment of the radiation measuring device of the present invention will be described with reference to the drawings as necessary. As shown in FIG. 1, the radiation measuring device of the present invention includes a waterproof container 10 composed of an inner-empty plastic scintillator, a communication cable 20 connected to the outer surface of the waterproof container 10, and an internal component 30 provided inside the waterproof container 10, including a communication unit 31 that transmits and receives data via the communication cable 20 and a battery 32 of the communication unit 31.

[0018] Then, as shown in FIG. 1, the radiation measuring device of the present invention is characterized in that the waterproof container 10 has an outer diameter X of 50 mm or less, has no holes penetrating between the inside and outside of the waterproof container 10, and the communication unit 31 and the communication cable 20 transmit and receive data in a non-contact state. By forming the waterproof container 10 from a plastic scintillator, in addition to being able to form the device into an arbitrary shape, it is not necessary to separately provide a scintillator inside, so the device can be miniaturized. Furthermore, since the waterproof container 10 has a sealed structure without holes, better waterproof performance can be achieved, and cracks caused by holes can be prevented, so the strength can also be further increased. In addition, in the radiation measuring device of the present invention, since the communication unit 31 and the communication cable 20 transmit and receive data in a non-contact state, even when the waterproof container 10 has a sealed structure, data can be transmitted and received, and real-time and continuous measurement of the concentration of radioactive substances can be performed.

[0019] Furthermore, the environmental water targeted when the radioactivity measuring device of the present invention observes the concentration of radioactive materials is not particularly limited. Examples include environmental water in geological bodies of water such as rivers, lakes, ponds, bays, and inlets, as well as in artificial bodies of water such as reservoirs (reservoirs, dams, etc.), waterways, and ports. In addition, "water" when the radioactivity measuring device of the present invention observes the concentration of radioactive materials means any part of the aforementioned body of water, and the depth within the body of water is not particularly limited. Among these, in the present invention, it is preferable that the body of water to be measured is a reservoir, dam, underground dam, or other water storage facility, and more preferably a dam or underground dam. The radioactivity measuring device of the present invention can maintain its waterproofness and strength even when subjected to high water pressure when measuring radiation in deep environmental water, making it suitable for measuring the radioactivity of environmental water in water storage facilities. Furthermore, because the radioactivity measuring device of the present invention is miniaturized, it is possible to perform measurements while it is installed in an observation well of a dam or underground dam.

[0020] Furthermore, the "radioactive material" that is the target of concentration observation by the radioactivity measuring device of the present invention is any material that possesses radioactivity. The type of radioactive material is not particularly limited; examples include nuclear fuel materials, radioactive elements, radioactive isotopes, and activated materials that have been irradiated with neutrons. Among these, since the present invention uses a plastic scintillator as the scintillator, it has high sensitivity to alpha and beta rays, making it suitable for radionuclides that emit alpha and beta rays during their decay process, such as radon. 222 Rn), Tron ( 220 This invention is suitable for measuring radioactive substances such as Rn. Since such radioactive substances are often found in water, the present invention offers significant advantages in determining the concentration of these radioactive substances. In this invention, "radiation" refers to ionizing radiation that has a strong effect on the human body, such as alpha rays, beta rays, gamma rays, and neutron rays, while "radioactivity" refers to the ability to emit radiation. In this invention, the radiation mainly consists of "alpha rays," "beta rays," and "gamma rays," and in the following explanation, when "radiation" is mentioned, it may substantially refer to "alpha rays," "beta rays," and "gamma rays."

[0021] (waterproof container) As shown in Figure 1, the radioactivity measuring device of the present invention comprises a waterproof container 10 made of a hollow plastic scintillator. The waterproof container 10 is made of a scintillator and serves as a container for waterproofing and reinforcement, while also functioning as a device for detecting the presence and amount of radiation.

[0022] Examples of the plastic scintillator include a molded body made by mixing a fluorescent substance that emits fluorescence upon excitation by radiation into a plastic, or a plastic that emits light upon excitation by radiation (radiofluorescent plastic). By using a plastic scintillator as the waterproof container 10, it becomes possible to measure radiation while maintaining waterproofness.

[0023] Examples of the aforementioned plastics include polystyrene, polyvinyltoluene, polyethylene terephthalate, and other polyester compounds having aromatic rings. Among these, polyvinyltoluene or polyethylene terephthalate is preferred as a material due to its light transmittance, ease of processing, and manufacturing cost. Furthermore, the fluorescent substance is not particularly limited, and examples include 2,5-diphenyloxazole (also known as PPO) and 1,4-bis-2-(5-phenyloxazolyl)benzene (also known as POPOP).

[0024] Furthermore, regarding the plastic scintillator, a commercially available plastic scintillator can be used, and by adjusting its shape and outer diameter, a waterproof container 10 suitable for the radioactivity measuring device of the present invention can be obtained.

[0025] The shape of the waterproof container 10 is not particularly limited, other than being hollow, and can be appropriately changed depending on the conditions of the water body in which it is used. For example, the shape of the waterproof container 10 can be cylindrical, polygonal prism, spherical, ellipsoidal, flat, disc-shaped, rod-shaped, etc. Among these, from the standpoint of corresponding to the shape of the radiation detector 10, it is preferable to make the shape of the waterproof container 20 cylindrical or polygonal prism, and from the standpoint of minimizing water resistance in the water body and maximizing detection efficiency, it is more preferable to make it cylindrical.

[0026] Furthermore, as shown in Figure 1, the outer diameter X of the waterproof container 10 is 50 mm or less. As mentioned above, the radioactivity measuring device of the present invention is likely to be installed in narrow places such as observation holes in dams, so by making the outer diameter X small at 50 mm, it becomes possible to measure radiation even in narrow places. From a similar viewpoint, the outer diameter X of the waterproof container 10 is preferably 45 mm or less, and more preferably 40 mm or less. Furthermore, there is no particular limit to the lower limit of the outer diameter X of the waterproof container 10, and it can be set according to the size of the internal components 30 provided inside. The outer diameter X of the waterproof container 10 refers to the minor axis of the waterproof container 10. As shown in Figure 1, if the waterproof container 10 is cylindrical, this corresponds to the diameter of the circle. If the waterproof container 10 is tall, in the case of a polygonal prism or rod shape, it is the diameter of the cross-sectional shape perpendicular to the length direction, and in the case of a disc or plate shape, the shortest diameter of the flat surface corresponds to the outer diameter.

[0027] Furthermore, while the thickness T of the waterproof container 10 is not particularly limited, it is preferable that it has a thickness of 5 mm or more, and more preferably 10 mm or more, from the viewpoint of maintaining strength against water pressure and contact. The thickness T of the waterproof container 10 refers to the thickness of the thinnest part of the waterproof container, as shown in Figure 1.

[0028] Furthermore, the waterproof container 10 does not have any holes that penetrate between the inside and outside of the waterproof container 10. Normally, when a radioactivity measuring device is used underwater, holes are provided in the waterproof container for passing communication cables for sending and receiving data with a computer (not shown) such as an analysis means located on land, as well as other cables such as power cables. However, holes provided in the waterproof container may reduce its waterproof performance when used in bodies of water with high water pressure, and contact with rocks, concrete, etc., may cause damage to the waterproof container. In this invention, the absence of holes in the waterproof container 10 makes it possible to suppress a decrease in waterproof performance and strength, and to measure the concentration of radioactive materials in the environmental water at depths.

[0029] Although the waterproof container 10 is made of a plastic scintillator as described above, it may also include other components. For example, as shown in Figure 1, the waterproof container 10 may include a lid 11 to enhance the airtightness of the waterproof container 10. The lid 11 can be fixed with screws or similar fasteners, or it can be welded or glued to the surface.

[0030] Furthermore, the waterproof container 10 may also have a radiation shield (not shown) in part if necessary. This is because, by eliminating as much unwanted radiation (radiation originating from sources other than the water body being measured) as possible from the radiation detected by the radioactivity measuring device, the accuracy of detecting the concentration of radioactive materials at a specific location in the water can be improved. The material of the radiation shield 11 is not particularly limited as long as it has a radiation shielding effect, and known materials can be used. Examples include lead, iron, aluminum, and acrylic. By combining these materials, it is also possible to select and measure the type of radiation to be measured (alpha rays, beta rays, gamma rays).

[0031] In addition to the above, if the waterproof container is made of a plastic having an aromatic ring, such as polystyrene or polyvinyltoluene, the radon in the water will be distributed and absorbed, thus improving the counting efficiency, especially for measuring radon that emits alpha rays during its decay process. On the other hand, since the adsorption of radon onto the plastic delays the tracking of short-term changes in the radon concentration in the water, it is also possible to prevent the absorption of radon into the plastic by shielding it with a waterproof material in order to grasp short-term concentration changes.

[0032] (Communication cable) As shown in Figure 1, the radioactivity measuring device of the present invention further includes a communication cable 20 connected to the outer surface of the waterproof container 10. The communication cable 20 is not particularly limited, and the type and configuration of the cable can be appropriately selected depending on the type of communication by the communication unit 31 described later. Examples of cable types include flat-pair cables, coaxial cables, and optical fiber cables.

[0033] (Internal parts) As shown in Figure 1, the radioactivity measuring device of the present invention further comprises internal components 30 provided inside the waterproof container 10. As shown in Figure 1, the internal components 30 include a communication unit 31 and a battery 32 for the communication unit.

[0034] The communication unit 31 is a device for sending and receiving data with external devices (control devices, computers, etc.) via the communication cable 20. Furthermore, in the radioactivity measuring device of the present invention, as shown in Figure 1, the communication unit 31 and the communication cable 20 transmit and receive data in a non-contact manner. Because data is transmitted and received in a non-contact manner in this way, there is no need to provide a hole in the waterproof container 10 for passing the cable 20 through, which leads to an improvement in the waterproofness and strength of the waterproof container 10.

[0035] The communication method used by the communication unit 31 can be any method that enables contactless communication, and can be appropriately selected depending on cost and the conditions of the water body. For example, optical communication, wireless communication, infrared communication, Bluetooth, etc., can be used. Furthermore, if a more efficient contactless communication technology becomes available in the future, it may be adopted.

[0036] The battery 32 is primarily used to supply power for the communication unit. The battery 32 can be used only once, making the radiation measuring device disposable, or the radiation measuring device can be used repeatedly by charging the battery 32. When charging the battery 32, it is preferable to do so in a non-contact manner. This eliminates the need to provide a hole for passing the cable 20 through the waterproof container 10, thereby improving the waterproofness and strength of the waterproof container 10.

[0037] Furthermore, it is preferable that the internal component 30 further includes a photomultiplier element 34, as shown in Figure 1. This is because the signal acquired from the plastic scintillator can also be amplified by the photomultiplier element 34, making it easier to use as data in the control device or computer (not shown). In measuring environmental radioactivity, radiation from other nuclides such as potassium is present in addition to radon, so it is possible to obtain information on the number and energy of photons (spectrum) from the signal amplified by the photomultiplier tube 34 and discriminate between nuclides.

[0038] Furthermore, the internal components 30 preferably include equipment such as a data logger 33, a multi-channel analyzer (not shown), and a control panel (not shown), depending on the required performance.

[0039] Furthermore, the internal component 30 may further include a water level measuring means (not shown) for measuring the water level of the body of water to be measured. By using the water level measuring means, it is possible to confirm whether or not a radioactivity measuring device is located at a desired depth, and the background radiation dose can be calculated according to the water level measured by the water level measuring means, thereby enabling a more accurate determination of the radioactive material concentration.

[0040] (Other equipment) The radioactivity measuring device of the present invention may further include an analysis means (not shown) connected to the communication cable. The analysis means is connected to the waterproof container 10 via a connecting device such as a communication cable 20, and calculates the concentration of radioactive material based on a signal obtained from the plastic scintillator of the waterproof container 10. Furthermore, there are no particular limitations on the location where the analysis means is provided. For example, it may be installed on the ground and located outside the waterproof container 10, but it is also possible to configure all or part of the analysis means to be located inside the waterproof container 10.

[0041] Here, the calculation of the radioactive material concentration by the analysis means is performed by the control device or computer. The specific method for calculating the radioactive material concentration based on the signal obtained from the plastic scintillator is not particularly limited, and known techniques can be appropriately selected depending on the type of computer used and the circumstances.

[0042] As an example, the signal obtained from the plastic scintillator is converted into spectral data showing the relationship between radiation energy and count number. Then, processing such as smoothing is performed on this spectral data, and the count numbers corresponding to the total absorption peak of alpha rays, the continuous spectrum of beta rays, or the Compton edge of gamma rays are integrated and converted into the peak count rate of the radioactive material. Meanwhile, by determining the relationship between the peak count rate and the concentration of radioactive material in water obtained separately by sampling, the concentration of radioactive material can be obtained. [Industrial applicability]

[0043] According to the present invention, it is possible to provide a radioactivity measuring device that is excellent in waterproofness and strength, and can measure the concentration of radioactive materials in real time and continuously, even in deep environmental water. [Explanation of symbols]

[0044] 10 Waterproof container 11 Lid 20 Communication Cables 30 Internal parts 31 Communications Department 32 batteries 33 Maximum Logger 34 Photoelectron multiplier X Outer diameter of waterproof container T Waterproof container thickness

Claims

1. A radioactivity measuring device for observing the concentration of radioactive materials in water, A waterproof container consisting of an internal plastic scintillator, A communication cable connected to the outer surface of the aforementioned waterproof container, Internal components, including a communication unit that transmits and receives data via the communication cable and a battery for the communication unit, are provided inside the waterproof container. Equipped with, The aforementioned waterproof container has an outer diameter of 50 mm or less, and there are no holes penetrating from the inside to the outside of the waterproof container. A radioactivity measuring device characterized in that the communication unit and the communication cable transmit and receive data in a non-contact manner.

2. The radioactivity measuring device according to claim 1, characterized in that the internal component further includes a photoelectron multiplier element.

3. The radioactivity measuring device according to claim 1 or 2, characterized in that the internal components further include a data logger and / or a multichannel analyzer.

4. The radioactivity measuring device according to claim 1 or 2, characterized in that the battery is charged in a non-contact manner with the outside.

5. The radioactivity measuring device according to claim 1 or 2, characterized in that it measures the radon concentration in water.

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