JP2019066393A - Radioactivity measuring system - Google Patents

Radioactivity measuring system Download PDF

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JP2019066393A
JP2019066393A JP2017193857A JP2017193857A JP2019066393A JP 2019066393 A JP2019066393 A JP 2019066393A JP 2017193857 A JP2017193857 A JP 2017193857A JP 2017193857 A JP2017193857 A JP 2017193857A JP 2019066393 A JP2019066393 A JP 2019066393A
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water
radiation
concentration
radiation detector
radioactivity measuring
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JP7197878B2 (en
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聡 石田
Satoshi Ishida
聡 石田
周平 吉本
Shuhei Yoshimoto
周平 吉本
克志 白旗
Katsushi Shirahata
克志 白旗
健雄 土原
Takeo Tsuchihara
健雄 土原
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National Agriculture and Food Research Organization
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Abstract

To provide a radioactivity measuring system capable of precisely comprehending the concentration of radioactive matters in water at real time without using complicated equipment.SOLUTION: A radioactivity measuring system 1 for observing the concentration of radioactive matter in water, comprises: a radiation detector 10; a waterproof container 20 formed of a material which has waterproofness and transmits radiation and covering the radiation detector 10; and analysis means 30 configured to calculate the concentration of radioactive matter on the basis of signals acquired from the radiation detector 10.SELECTED DRAWING: Figure 1

Description

本発明は、複雑な設備を用いることなく、リアルタイムで且つ正確に、水中の放射性物質濃度を把握できる放射能測定装置に関する。   The present invention relates to a radioactivity measuring apparatus capable of grasping the concentration of radioactive substance in water in real time and accurately without using complicated equipment.

平成23年3月11日に発生した東北地方太平洋沖地震及びそれに伴う津波によって引き起こされた東京電力福島第一原子力発電所の事故によって、土壌等だけでなく、河川や、ため池、その他の水域についても放射性物質によって汚染された。特に、福島県内には3400箇所以上のため池が存在し、農業用水源として利用されていたが、その多くは水中から放射性セシウムが検出された。   Not only soil, etc., but also rivers, reservoirs, and other water areas, due to the accident at the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station, which was caused by the Tohoku Region Pacific Coast Earthquake that occurred on March 11, 2011, and the resulting tsunami. Was also contaminated by radioactive material. In particular, there were more than 3,400 reservoirs in Fukushima prefecture, which were used as agricultural water sources, but radioactive cesium was detected from the water in many cases.

その後、環境省や福島県、その他の各機関の除染作業によって、土壌中の放射性物質は除去され、営農が再開されている地域も増えている。ただし、河川やため池等から引かれた農業用水を通じて、放射性物質が水田に流入することが懸念されることから、現在、水中の放射性物質濃度を把握することが望まれていた。
そのため、従来は測定対象となる水域の水を、一旦サンプリングした後、分析施設で放射線検出器を用いて水中の放射性物質濃度を把握していた。
After that, radioactive materials in the soil have been removed by decontamination work by the Ministry of the Environment, Fukushima Prefecture, and other organizations, and the number of areas where farming has been resumed has increased. However, because there is concern that radioactive substances will flow into the paddy field through agricultural water drawn from rivers and reservoirs, it has been desired to grasp the concentration of radioactive substances in water at present.
Therefore, conventionally, once the water in the water area to be measured has been sampled once, the concentration of radioactive substances in the water has been grasped by using a radiation detector at an analysis facility.

しかしながら、水中の放射性物質については、水域の種類や、かんがい期や出水期等の時期によって大きく変化することから、一回のサンプリングによって測定するだけでなく、リアルタイム且つ連続的に観測できる技術の開発が強く望まれている。   However, since radioactive substances in water largely change depending on the type of water area and the period such as irrigation period or water discharge period, development of technology that can be observed in real time and continuously as well as measurement by one sampling Is strongly desired.

本発明の目的は、複雑な設備を用いることなく、リアルタイムで且つ正確に、水中の放射性物質濃度を把握できる放射能測定装置を提供することにある。   An object of the present invention is to provide a radioactivity measuring apparatus capable of grasping the concentration of radioactive substance in water in real time and accurately without using complicated equipment.

本発明者らは、上記課題を解決すべく鋭意研究を行った結果、水中の放射性物質濃度を測定するための放射線検出器を、防水性を有し且つ放射線を透過させる材料からなる防水容器で覆うとともに、解析手段を設けて、放射線検出器から取得した信号に基づき放射性物質濃度をリアルタイムに算出することによって、リアルタイムで且つ正確に水中の放射性物質濃度を把握できることを見出し、本発明を完成するに至った。   As a result of intensive studies to solve the above problems, the inventors of the present invention have found that a radiation detector for measuring the concentration of radioactive substances in water is a waterproof container made of a material that is waterproof and transmits radiation. It is found that it is possible to accurately grasp the radioactive substance concentration in water in real time and accurately by calculating the radioactive substance concentration in real time based on the signal acquired from the radiation detector while providing the covering means and analyzing the signal. It came to

本発明は、このような知見に基づきなされたもので、その要旨は以下の通りである。
(1)水中の放射性物質濃度を観測するための放射能測定装置であって、放射線検出器と、防水性を有し且つ放射線を透過させる材料からなり、前記放射線検出器を覆うように設けられた防水容器と、前記放射線検出器から取得した信号に基づいて放射性物質濃度を算出する解析手段と、を備えることを特徴とする、放射能測定装置。
The present invention has been made based on such findings, and the summary thereof is as follows.
(1) A radioactivity measuring device for observing the concentration of radioactive substances in water, comprising a radiation detector and a waterproof and radiation transmitting material, provided so as to cover the radiation detector A radiation measuring apparatus comprising: a waterproof container; and analysis means for calculating a radioactive substance concentration based on a signal acquired from the radiation detector.

(2)前記解析手段は、前記算出した放射性物質濃度から、測定対象となる水域以外に由来する放射線の線量(バックグラウンド放射線量)を差し引く、バックグラウンド除去処理を実施することを特徴とする、(1)に記載の放射能測定装置。 (2) The analysis means is characterized in that a background removal process is performed by subtracting the radiation dose (background radiation dose) originating from areas other than the water to be measured from the calculated radioactive substance concentration. The radioactivity measuring apparatus as described in (1).

(3)前記放射能測定装置は、前記測定対象となる水域の水位を測定する水位測定手段をさらに備え、前記解析手段は、前記水位測定手段の測定した水位に応じて、前記バックグラウンド放射線量を算出することを特徴とする、(1)又は(2)に記載の放射能測定装置。 (3) The radioactivity measuring apparatus further comprises a water level measuring means for measuring the water level of the water area to be measured, and the analysis means determines the background radiation dose according to the water level measured by the water level measuring means. The radioactivity measuring device according to (1) or (2), characterized in that

(4)前記放射線検出器は、シンチレータとしてNaI(Tl)、CsI(Tl)、CsI(Na)、LnBr3、ZnS(Ag)又はCsIを有することを特徴とする、(1)〜(3)のいずれかに記載の放射能測定装置。 (4) The radiation detector is characterized in that it has NaI (Tl), CsI (Tl), CsI (Na), LnBr 3, ZnS (Ag) or CsI as a scintillator. (1) to (3) The radioactivity measuring device according to any of the above.

(5)前記放射能測定装置は、前記測定対象となる水域の水底に設置されることを特徴とする、(1)〜(4)のいずれかに記載の放射能測定装置。 (5) The radioactivity measuring apparatus according to any one of (1) to (4), wherein the radioactivity measuring apparatus is installed at the bottom of the water area to be measured.

本発明によれば、複雑な設備を用いることなく、リアルタイムで且つ正確に、水中の放射性物質濃度を把握できる放射能測定装置を提供することが可能となる。   ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the radioactivity measuring apparatus which can grasp | ascertain the radioactive substance density | concentration in water accurately in real time, without using a complicated installation.

本発明の放射能測定装置の一実施形態について、模式的に示した図である。It is the figure shown typically about one embodiment of the radioactivity measuring device of the present invention. 本発明の放射能測定装置の放射線検出器から得られた信号に基づいて作製した光電効果のカウント数を示すスペクトルデータを示すグラフである。It is a graph which shows the spectral data which show the count number of the photoelectric effect produced based on the signal obtained from the radiation detector of the radioactivity measuring device of this invention. 河川の降水量と放射性Csの濃度のそれぞれの推移を示したグラフである。It is the graph which showed each transition of the precipitation of a river, and the density | concentration of radioactive Cs. 本発明の放射能測定装置の一実施形態を、実際に河川で使用した際の状態を示した写真である。It is the photograph which showed the state at the time of actually using one Embodiment of the radioactivity measuring apparatus of this invention in a river. 本発明の実施例で得られた、河川中のCsピーク計数、河川の水位及びCsの実測値のそれぞれの推移を示したグラフである。It is the graph which showed each transition of the Cs peak count in a river, the water level of a river, and the measured value of Cs obtained by the Example of this invention.

<放射能測定装置>
本発明の放射能測定装置の一実施形態について、必要に応じて図面を用いて説明する。
本発明の放射能測定装置は、水中の放射性物質濃度を観測するための放射能測定装置であって、図1に示すように、放射線検出器10と、防水性を有し且つ放射線を透過させる材料からなり、前記放射線検出器を覆うように設けられた防水容器20と、前記放射線検出器から取得した信号に基づいて放射性物質濃度を算出する解析手段30と、を備えることを特徴とする。
<Radioactivity measurement device>
One embodiment of the radioactivity measuring device of the present invention will be described as needed using the drawings.
The radioactivity measuring apparatus of the present invention is a radioactivity measuring apparatus for observing the concentration of radioactive substances in water, and as shown in FIG. 1, has a radiation detector 10, waterproofness and radiation transmission. It is characterized by comprising: a waterproof container 20 made of a material and provided to cover the radiation detector; and analysis means 30 for calculating a radioactive substance concentration based on a signal acquired from the radiation detector.

放射性物質濃度を測定するための放射線検出器10を、防水性を有し且つ放射線を透過させる材料からなる防水容器20で覆うことによって、防水を図りつつ放射線量を測定でき、さらに、解析手段30を設けて、放射線検出器10から取得した信号から放射性物質濃度をリアルタイムに算出するできる結果、リアルタイムで且つ正確に水中の放射性物質濃度を把握することが可能となる。そのため、かんがい期や出水期での、放射性物質濃度の増減についても、リアルタイムに把握することができるようになる。   By covering the radiation detector 10 for measuring the concentration of radioactive substances with a waterproof container 20 made of a material that is waterproof and made to transmit radiation, the radiation dose can be measured while achieving waterproofness, and analysis means 30 As a result, the radioactive substance concentration can be calculated in real time from the signal acquired from the radiation detector 10. As a result, the radioactive substance concentration in water can be accurately grasped in real time. Therefore, it is possible to grasp in real time also the increase and decrease of the radioactive substance concentration in the irrigation period and the flood period.

なお、本発明の放射能測定装置が放射性物質濃度を観測する際の、対象となる水域については、特に限定はされない。例えば、河川、湖、池、湾、入り江等の地学的水域や、貯水施設(ため池、ダムなど)、水路、港等の人工的水域が挙げられる。また、本発明の放射能測定装置が放射性物質濃度を観測する際の「水中」とは、前記水域中の任意の部分を意味し、水域中での深さ等は特に限定されない。   In addition, there is no limitation in particular about the water area used as the object at the time of the radioactivity measurement apparatus of this invention observing a radioactive substance density | concentration. For example, geological water areas such as rivers, lakes, ponds, bays, and coves, artificial water areas such as water storage facilities (such as ponds and dams), water channels, and ports. Further, "in water" when the radioactivity measuring device of the present invention observes the radioactive substance concentration means any part in the water area, and the depth in the water area is not particularly limited.

また、本発明の放射能測定装置による濃度観測の対象である「放射性物質」は、放射能を持った物質である。その種類については、特に限定はされず、例えば、核燃料物質や、放射性元素、又は、放射性同位体、中性子から生成された放射化物質などが挙げられる。その中でも、本発明では、特に、137Cs(セシウム)、134Cs(セシウム)、40K(カリウム)、214Bi(ビスマス)、228Ac(アクチニウム)、208Tl(タリウム)、212Pb(鉛)、235U(ウラン)等の放射性物質が対象となる。これらの放射性物質は水中に含まれることが多く、本発明によって放射性物質濃度を把握する利益が大きい。
なお、本発明での「放射線」とは、α線、β線、γ線、中性子線等の人体に与える影響の強い電離放射線のことであり、「放射能」とは、放射線を発する能力のことである。その中でも本発明では、放射線として、主に「γ線」を対象としており、以後の説明で「放射線」と記載する場合には、実質的に「γ線」を示すことがある。
Moreover, the "radioactive substance" which is an object of concentration observation by the radioactivity measuring device of the present invention is a substance having radioactivity. The type is not particularly limited, and examples thereof include nuclear fuel materials, radioactive elements, radioactive isotopes, and radioactive materials generated from neutrons. Among them, in the present invention, in particular, 137 Cs (cesium), 134 Cs (cesium), 40 K (potassium), 214 Bi (bismuth), 228 Ac (actinium), 208 Tl (thallium), 212 Pb (lead) Radioactive materials such as 235 U (uranium) are covered. These radioactive substances are often contained in water, and the benefits of grasping the radioactive substance concentration by the present invention are great.
In the present invention, "radiation" refers to ionizing radiation that has a strong influence on the human body, such as alpha rays, beta rays, gamma rays, and neutron rays, and "radioactivity" refers to the ability to emit radiation. It is. Among them, in the present invention, "gamma ray" is mainly targeted as radiation, and when "radiation" is described in the following description, "gamma ray" may be substantially indicated.

(放射線検出器)
本発明の放射能測定装置は、図1に示すように、放射線検出器10を備える。該放射線検出器10は、内部にシンチレータ等の放射線検出素子10aを有し、放射線の有無及び放射線量を検出するための機器である。
(Radiation detector)
The radioactivity measuring device of the present invention comprises a radiation detector 10 as shown in FIG. The radiation detector 10 has a radiation detection element 10a such as a scintillator inside, and is an apparatus for detecting the presence of radiation and the radiation dose.

前記放射線検出素子10aについては、放射線の有無及び放射線量を検出できるものであれば特に限定はされない。公知の放射線検出素子として、例えば、シンチレータ、電離箱、比例計数管、GM計数管、半導体検出器、熱ルミネッセンス素子、光ルミネッセンス素子、蛍光ガラス素子等が挙げられる。
その中でも、比較的容易且つ正確に放射線の種類及び放射線量を取得できる点から、前記放射線検出素子10aとして、シンチレータを用いることが好ましい。ここで、前記シンチレータとは、放射線を吸収し、励起されることにより発光する特性を示す物質の総称である。
The radiation detection element 10a is not particularly limited as long as the presence or absence of radiation and the radiation dose can be detected. Examples of known radiation detection elements include scintillators, ionization chambers, proportional counters, GM counters, semiconductor detectors, thermoluminescent elements, photoluminescent elements, fluorescent glass elements, and the like.
Among them, it is preferable to use a scintillator as the radiation detection element 10 a in that the type and radiation dose of radiation can be obtained relatively easily and accurately. Here, the scintillator is a generic term for a substance exhibiting a characteristic of absorbing radiation and emitting light upon being excited.

さらに、前記シンチレータは、放射線の中でもγ線に高い感度を有する、NaI(Tl)、CsI(Tl)、CsI(Na)、LnBr3、ZnS(Ag)又はCsIを用いることが好ましい。前記放射線吸収量の検出精度が高く、より正確に水中の放射性物質濃度を把握できるためである。さらに、NaI(Tl)、CsI(Tl)、CsI(Na)、LnBr3、ZnS(Ag)又はCsIを放射線受光素子として用いた場合、放射性物質の種類ごとに放射線量の検出を行うことが可能である。 Furthermore, among the radiations, it is preferable to use NaI (Tl), CsI (Tl), CsI (Na), LnBr 3, ZnS (Ag) or CsI which has high sensitivity to γ-ray among radiations. This is because the detection accuracy of the radiation absorption amount is high, and the radioactive substance concentration in water can be grasped more accurately. Furthermore, when NaI (Tl), CsI (Tl), CsI (Na), LnBr3 , ZnS (Ag) or CsI is used as a radiation receiving element, it is possible to detect the radiation dose for each type of radioactive substance. It is.

なお、前記放射線検出器10は、上述した放射線検出素子10a以外にも、放射線検出器に用いられる公知の部材を組み込むことが可能である。例えば、放射線検出素子10aとしてシンチレータを用いた場合には、後述する解析手段30へ送る信号を増幅するために、光電子増倍管(図示せず)を放射線検出器10内に組み込むことが可能である。   In addition to the radiation detection element 10a described above, the radiation detector 10 can incorporate known members used for the radiation detector. For example, when a scintillator is used as the radiation detection element 10a, it is possible to incorporate a photomultiplier (not shown) into the radiation detector 10 in order to amplify a signal sent to the analysis means 30 described later. is there.

(防水容器)
本発明の放射能測定装置は、図1に示すように、前記放射線検出器10を覆うように設けられた防水容器20を、さらに備える。
前記防水容器20は、防水性を有し且つ放射線を透過させる材料からなる。これによって、放射線検出器10を水に曝すことなく、水中の放射性物質濃度を直接的に把握できる。
(Waterproof container)
The radioactivity measuring device of the present invention further comprises a waterproof container 20 provided so as to cover the radiation detector 10 as shown in FIG.
The waterproof container 20 is made of a material that is waterproof and transmits radiation. Thereby, the radioactive substance concentration in water can be directly grasped without exposing the radiation detector 10 to water.

前記防水容器を構成する材料については、防水性を有し且つ放射線を透過させるものであれば、特に限定はされない。ただし、放射線を透過させる点からは、金属のような密度が大きい材料を避けることが好ましい。
具体的には、例えば、フェノール樹脂、エポキシ樹脂、メラミン樹脂、尿素樹脂、不飽和ポリエステル樹脂、アルキド樹脂、ポリウレタン、熱硬化性ポリイミド等の熱硬化性樹脂や、ポリエチレン、ポリプロピレン、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリスチレン、ポリ酢酸ビニル、ポリウレタン、ポリテトラフルオロエチレン、アクリル系樹脂、ポリカーボネート等の熱可塑性樹脂、天然樹脂などが挙げられる。それらの中でも、放射線の透過性、加工の容易性、製造コスト等の点から、ポリエチレン、ポリ塩化ビニル又はポリカーボネートを材料として含むことが好ましい。
The material constituting the waterproof container is not particularly limited as long as it is waterproof and transmits radiation. However, in order to transmit radiation, it is preferable to avoid materials with high density such as metals.
Specifically, for example, thermosetting resins such as phenol resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane, thermosetting polyimide, polyethylene, polypropylene, polyvinyl chloride, poly Thermoplastic resins such as vinylidene chloride, polystyrene, polyvinyl acetate, polyurethane, polytetrafluoroethylene, acrylic resins, polycarbonates, natural resins and the like can be mentioned. Among them, polyethylene, polyvinyl chloride or polycarbonate is preferably contained as a material from the viewpoint of radiation permeability, easiness of processing, production cost and the like.

前記防水容器20の形状についても、特に限定はされず、前記放射線検出器10の形状や、水域の状態によって適宜変更することができる。例えば、前記防水容器20の形を、円柱状、多角状、球状、楕円体状、平板状、円盤状、棒状等にすることが可能である。その中でも、前記放射線検出器10の形状に対応させる点からは、前記防水容器20の形状を、円柱状又は多角柱状とすることが好ましく、水域における水の抵抗が少ないという点からは、円柱状とすることがより好ましい。   The shape of the waterproof container 20 is also not particularly limited, and can be appropriately changed according to the shape of the radiation detector 10 and the state of the water area. For example, the shape of the waterproof container 20 can be cylindrical, polygonal, spherical, ellipsoidal, flat, disk-like, rod-like or the like. Among them, it is preferable to make the shape of the waterproof container 20 cylindrical or polygonal columnar from the point of corresponding to the shape of the radiation detector 10, and cylindrical from the viewpoint that the resistance of water in the water area is small. It is more preferable to

さらに、前記防水容器20は、前記放射線検出器10に水が触れないように、放射線検出器10を覆う必要があるところ、防水容器の水と接する部分が密閉されていれば、必ずしも全面を密閉する必要はない。図1に示すように、防水容器20の上部が水と接触していない場合には、上面については密閉しなくてもよい。   Furthermore, the waterproof container 20 is required to cover the radiation detector 10 so that water does not touch the radiation detector 10. If the portion of the waterproof container in contact with water is sealed, the entire surface is necessarily sealed. do not have to. As shown in FIG. 1, when the upper part of the waterproof container 20 is not in contact with water, the upper surface may not be sealed.

また、図1に示すように、前記防水容器20は、必要に応じてその内部に、放射線シールド11を有することが好ましい。前記放射線検出器10が検出する放射線のうち、不要なもの(測定対象となる水域以外に由来する放射線)をできるだけ排除することで、水中の放射性物質濃度の検出精度を高めることができるからである。
なお、前記放射線シールド11を設ける場所については、特に限定はされず、例えば図1に示すように、前記放射線検出器10の下面を覆うように設けることができる。この場合、土壌等に含まれる放射性物質に由来した下からの放射線を抑制することが可能である。また、同様に上からの放射線を抑制するために、前記放射線検出器10の上部に放射線シールド11を設けることもできる。
また、前記放射線シールド11の材料については、放射線を遮蔽する作用があるものであれば、特に限定はされず、公知のものを用いることができる。前記放射線シールド11の材料としては、密度の大きい材料、例えば、鉛、金、銀、鉄、コンクリート等が挙げられる。
In addition, as shown in FIG. 1, the waterproof container 20 preferably has a radiation shield 11 in its inside as needed. It is because the detection accuracy of the radioactive substance concentration in water can be raised by excluding unnecessary things (radiation derived from other than the water area which is a measurement object) among the radiation which the said radiation detector 10 detects as much as possible. .
The place where the radiation shield 11 is provided is not particularly limited. For example, as shown in FIG. 1, the radiation shield 11 can be provided so as to cover the lower surface of the radiation detector 10. In this case, it is possible to suppress the radiation from the bottom derived from the radioactive substance contained in the soil or the like. A radiation shield 11 can also be provided on the top of the radiation detector 10 in order to suppress radiation from above as well.
The material of the radiation shield 11 is not particularly limited as long as it has an effect of shielding radiation, and known materials can be used. Examples of the material of the radiation shield 11 include high density materials such as lead, gold, silver, iron, concrete and the like.

(解析手段)
本発明の放射能測定装置は、図1に示すように、解析手段30をさらに備える。該解析手段30は、図1に示すように、ケーブル等の接続機器を介して前記放射線検出器10と接続されており(図1では、アンプ33と接続されている。)、該放射線検出器10から取得した信号に基づいて放射性物質濃度を算出する。
なお、解析手段30の設けられる場所については特に限定はされない。例えば図1では、解析手段30が、地上に設置され、前記防水容器20の外に設けられているが、解析手段30の全部又は一部が、前記防水容器20の中に入るような構成とすることも可能である。
(Analytical means)
The radioactivity measuring device of the present invention further comprises an analysis means 30, as shown in FIG. As shown in FIG. 1, the analysis means 30 is connected to the radiation detector 10 via a connection device such as a cable (in FIG. 1, it is connected to the amplifier 33), and the radiation detector The radioactive substance concentration is calculated based on the signal acquired from 10.
The place where the analysis means 30 is provided is not particularly limited. For example, in FIG. 1, the analysis means 30 is installed on the ground and provided outside the waterproof container 20, but all or a part of the analysis means 30 enters the waterproof container 20. It is also possible.

ここで、前記解析手段30による放射性物質濃度の算出は、分析装置34によって行われる。放射線検出器10から取得した信号に基づき、放射性物質濃度を算出する具体的な方法については、特に限定はされず、使用する計算機の種類や、状況に応じて、公知の技術を適宜選択することができる。
一例として、前記放射線検出器10から取得した信号を、図2に示すように、波高分析器を用いて、光電効果のカウント数を示すスペクトルデータとした後、該スペクトルデータを元に、積算及びスムージング等の処理を行った後、放射線物質元素(Cs)のピーク係数(放射線物質の時間当たりの濃度(カウント数))へ変換する。一方で、ピーク係数とサンプリングによって別途得られた水中の放射性物質濃度との関係式を求めておくことで、放射性物質濃度を得ることができる。
Here, the calculation of the radioactive substance concentration by the analysis means 30 is performed by the analyzer 34. The specific method of calculating the radioactive substance concentration based on the signal acquired from the radiation detector 10 is not particularly limited, and a known technique may be appropriately selected according to the type of computer to be used and the situation. Can.
As an example, as shown in FIG. 2, the signal acquired from the radiation detector 10 is converted into spectrum data indicating the count number of photoelectric effect using a pulse height analyzer, and then integration and calculation is performed based on the spectrum data. After processing such as smoothing, it is converted to the peak coefficient (concentration per hour (count number) of the radioactive substance) of the radioactive substance element (Cs). On the other hand, the radioactive substance concentration can be obtained by obtaining a relational expression between the peak coefficient and the radioactive substance concentration in water separately obtained by sampling.

また、前記放射線検出器10から取得した信号については、図1に示すように、アンプ(増幅器)33によって、増幅させた後に、放射性物質濃度を算出するための分析装置34へと送ることもできる。前記分析装置34で利用しやすいデータとすることができるためである。   Further, as shown in FIG. 1, the signal obtained from the radiation detector 10 can be amplified by an amplifier 33 and then sent to an analyzer 34 for calculating the concentration of radioactive substances. . This is because the data can be easily used by the analyzer 34.

なお、前記アンプ33や、前記分析装置34の動作や、データの授受等についての制御は、例えば図1に示すように、制御盤32によって行うことができる。この制御盤32の動作については、手動によって行うことも可能であるが、ソフトウェア等によって自動化することもできる。   The control of the operation of the amplifier 33 and the analyzer 34, the exchange of data, and the like can be performed by a control panel 32, as shown in FIG. 1, for example. The operation of the control panel 32 can be performed manually, but can also be automated by software or the like.

なお、前記解析手段30に用いられる機材としては特に限定はされず、市販の電子計算機(コンピュータ)に、特定のソフトウェアを組み込むことで、解析手段30として用いることが可能である。また、図1では、解析手段30の中に電源31が組み込まれているが、電源を解析手段30とは独立した形で備えることも可能である。   The equipment used for the analysis unit 30 is not particularly limited, and can be used as the analysis unit 30 by incorporating specific software into a commercially available electronic computer (computer). Further, although in FIG. 1 the power supply 31 is incorporated in the analysis means 30, it is also possible to provide the power supply in a form independent of the analysis means 30.

そして、本発明の放射能測定装置では、図1に示すように、前記前記解析手段30が、算出した放射性物質濃度から、測定対象となる水域100以外に由来する放射線の線量(以下、「バックグラウンド放射線量」ということがある。)を差し引く、バックグラウンド除去処理35を実施することが好ましい。
通常、水域中の放射線濃度を観測する場合には、前記放射線検出器が、測定対象の水域100以外、例えば、大気中に含まれる放射線物質や、水底若しくは水域近くにある土壌中の放射線物質などに由来した放射線を同時に測定することとなる。そのため、バックグラウンド除去処理35を実施し、測定対象の水域100以外に由来したバックグラウンド放射線の影響を差し引くことによって、測定対象の水域100の放射性物質濃度を正確に観測することが可能になる。
Then, in the radioactivity measuring apparatus of the present invention, as shown in FIG. 1, the radiation concentration derived from other than the water area 100 to be measured is calculated from the radioactive substance concentration calculated by the analysis means 30 (hereinafter referred to as “back It is preferable to carry out a background removal process 35 by subtracting the background radiation dose.
Usually, when the radiation concentration in the water area is observed, the radiation detector is not the water area 100 to be measured, for example, a radiation substance contained in the atmosphere, a radiation substance in soil at the bottom of the water or near the water area, etc. The radiation derived from is to be measured simultaneously. Therefore, it is possible to accurately observe the radioactive substance concentration in the water area 100 to be measured by performing the background removal processing 35 and subtracting the influence of the background radiation derived from other than the water area 100 to be measured.

なお、一般的なバックグラウンド放射線の除去技術としては、十分な厚さの鉛等の金属からなる遮蔽物によって放射線検出器を覆うものが挙げられる。しかしながら、その場合、遮蔽物の大きさや重量が大きくなり、装置の作製や、測定場所での設置が困難となることが考えられる。また、前記遮蔽物によってバックグラウンド放射線の全てを除去することは困難であり、放射線検出器の全てを覆うと水中の放射線物質の濃度も観測できなくなることから、本発明のように、バックグランド除去処理を実施することが、装置作製の煩雑性や、観測精度の観点からも好ましい。
また、前記バックグラウンド放射線量については、常に一定ではないため、後述する水域の水位や、水域の濁度等に応じて、バックグラウンド放射線量を算出することがより好ましい。
In addition, as a general removal technique of background radiation, the thing which covers a radiation detector by the shield which consists of metals, such as lead with sufficient thickness, is mentioned. However, in this case, the size and weight of the shield become large, which may make it difficult to manufacture the device and install it at the measurement site. Moreover, it is difficult to remove all of the background radiation by the shield, and when all of the radiation detectors are covered, the concentration of the radioactive substance in the water can not be observed either. It is preferable to carry out the process also from the viewpoint of the complexity of the device production and the observation accuracy.
In addition, since the background radiation dose is not always constant, it is more preferable to calculate the background radiation dose according to the water level of the water area, the turbidity of the water area, and the like described later.

(水位測定手段)
また、本発明の放射能測定装置では、図1に示すように、前記測定対象となる水域100の水位を測定する水位測定手段40をさらに備え、前記解析手段30は、前記水位測定手段40の測定した水位に応じて、前記バックグラウンド放射線量を算出することがより好ましい。放射性物質濃度をより高精度に把握できるためである。
(Water level measurement means)
The radioactivity measuring apparatus of the present invention further comprises a water level measuring means 40 for measuring the water level of the water area 100 to be measured, as shown in FIG. It is more preferable to calculate the background radiation dose according to the measured water level. This is because the radioactive substance concentration can be grasped with higher accuracy.

上述したように、前記バックグラウンド放射線量については、常に一定ではなく、水位に応じて大きく変化するものである。例えば、水位が低い場合には、水による放射線遮蔽効果が小さいため、測定対象の水域以外に由来するバックグラウンド放射線量が大きくなり、一方、水位が高い場合には、水による放射線遮蔽効果が大きいため、測定対象の水域以外に由来するバックグラウンド放射線量が小さくなることが考えられる。そのため、水域100の水位を測定し、バックグラウンド放射線量の算出の条件として用いることによって、バックグラウンド処理35を正確且つリアルタイムに実施できる結果、放射性物質濃度をより高精度に算出できる。   As described above, the background radiation dose is not always constant, but largely changes according to the water level. For example, when the water level is low, the radiation shielding effect by water is small, so the background radiation dose originating from areas other than the water area to be measured becomes large, while when the water level is high, the radiation shielding effect by water is large Therefore, it is conceivable that the background radiation dose originating from areas other than the water to be measured is reduced. Therefore, by measuring the water level of the water area 100 and using it as the condition of the calculation of the background radiation dose, the background processing 35 can be performed accurately and in real time, and as a result, the radioactive substance concentration can be calculated more accurately.

なお、前記バックグラウンド放射線量の算出については、水位とバックグラウンド放射線量との関係を予め導出し、用意しておくことで、水位計40によって水位を測定するだけで、前記解析手段30において、リアルタイムにバックグラウンド除去35の処理を行うことが可能となる。   In addition, regarding the calculation of the background radiation dose, the relationship between the water level and the background radiation dose is derived in advance and prepared, and the analysis means 30 can be obtained simply by measuring the water level with the water level gauge 40, It is possible to perform processing of background removal 35 in real time.

ここで、前記水位計40については、特に限定はされず、使用目的に応じて公知のものを適宜使用することができる。
なお、図1では、前記水位計40による測定値を、前記解析手段30のバックグラウンド除去35のために用いているが、測定した水位を放射性物質濃度の算出に利用することもでき、その場合には、水位計40を分析装置34にも接続することができる。
Here, the water gauge 40 is not particularly limited, and a known one may be appropriately used according to the purpose of use.
In addition, in FIG. 1, although the measured value by the said water gauge 40 is used for background removal 35 of the said analysis means 30, the measured water level can also be utilized for calculation of a radioactive substance concentration, and in that case The water level gauge 40 can also be connected to the analyzer 34.

なお、水位が高い場合には、水による放射線遮蔽効果が大きいため、測定対象の水域以外に由来するバックグラウンド放射線量が小さくなることを説明したが、水域の水量の増す出水時には、放射性物質を吸着した粘土等が多く含まれるため、水中の放射性物質濃度自体は高くなることが知られている。
ここで、図3は、福島県のある河川について、7/1〜10/31までの期間における、降水量及び測定した放射性Cs濃度の推移を示したグラフである。図3では、降水量が多い、つまり河川の水位が高くなる場合には、水中のCs濃度が上がっていることがわかる。一方で、数日間降雨が無い時の河川水中の放射性Cs濃度はほぼゼロであり、この時測定される放射線量は全てバックグラウンドとなる。バックグラウンド放射線量は、水位が高いほど小さくなるので、水中のCs濃度がゼロである時にバックグラウンド放射線量と水位を測定しておけば、両者の関係を求めることができる。
In addition, when the water level is high, the radiation shielding effect by water is large, so it was explained that the background radiation dose originating from other than the water area to be measured is reduced. However, when the water volume increases in the water area, the radioactive substance It is known that the concentration of radioactive substances in water itself becomes high because the adsorbed clay and the like are contained in a large amount.
Here, FIG. 3 is a graph showing the transition of the amount of precipitation and the measured radioactive Cs concentration in a period from 7/1 to 10/31 for a river in Fukushima Prefecture. In FIG. 3, it can be seen that the Cs concentration in the water is rising when the amount of precipitation is high, that is, when the water level of the river is high. On the other hand, when there is no rainfall for several days, the radioactive Cs concentration in the river water is almost zero, and the radiation dose measured at this time becomes all the background. The background radiation dose decreases as the water level increases, so if the background radiation dose and the water level are measured when the Cs concentration in the water is zero, the relationship between the two can be determined.

さらに、前記バックグラウンド放射線量を算出する材料として、水位以外にも、水中の濁度を用いることも可能である。その場合、本発明の放射能測定装置は、任意の濁度計(図示せず)をさらに備えることも可能である。   Furthermore, it is also possible to use the turbidity in water besides the water level as a material for calculating the background radiation dose. In that case, the radioactivity measuring device of the present invention may further comprise an optional turbidity meter (not shown).

なお、本発明の放射能測定装置は、測定対象となる水域100において、どのように設置しても良いが、図1に示すように、前記測定対象となる水域100の水底100aに設置されることが好ましい。水底100aに設置することで、水域100の水が遮蔽材となるため、大気中に含まれる放射線物質や、水域近くにある土壌中の放射線物質等に由来したバックグラウンド放射線量を低減できるからである。なお、水底100aの下にある土壌101に由来したバックグラウンド放射線量については、上述したように、前記放射線検出器10の下に放射線シールド11を設けることで、低減することが可能である。   In addition, although the radioactivity measuring apparatus of this invention may be installed how in the water area 100 to be measured, as shown in FIG. 1, it is installed in the water bottom 100a of the water area 100 to be measured. Is preferred. Since the water in the water area 100 becomes a shielding material by being installed on the water bottom 100 a, the background radiation dose derived from the radiation substance contained in the air or the radiation substance in the soil near the water area can be reduced. is there. In addition, about the background radiation dose originating in the soil 101 under the water bottom 100a, it is possible to reduce by providing the radiation shield 11 under the said radiation detector 10 as mentioned above.

<放射能測定方法>
次に、本発明による放射能測定方法について説明する。
本発明の放射能測定方法は、図1に示すように、防水容器20内に設置した放射線検出器10によって、水中の放射線量を測定し、放射線検出器から取得した信号に基づいて放射性物質濃度を算出し、算出した放射性物質濃度から、測定対象となる水域100以外に由来する放射線の線量(バックグラウンド放射線量)を差し引く、バックグラウンド除去処理を実施することを特徴とする。
<Method of measuring radioactivity>
Next, the radioactivity measuring method according to the present invention will be described.
The radiation measurement method of the present invention, as shown in FIG. 1, measures the radiation dose in water by means of the radiation detector 10 installed in the waterproof container 20, and the concentration of radioactive substance based on the signal obtained from the radiation detector. The background removal process is performed by subtracting the radiation dose (background radiation dose) originating from areas other than the water area 100 to be measured from the calculated radioactive substance concentration.

上記構成を具備することで、防水を図りつつ、リアルタイムで且つ正確に水中の放射性物質濃度を把握できるとともに、バックグラウンド放射線の影響を取り除くことによって、測定対象の水域の放射性物質濃度をより高精度に把握することが可能となる。   With the above configuration, it is possible to accurately measure the concentration of radioactive substances in water in real time and accurately while waterproofing, and to remove the influence of background radiation to make the concentration of radioactive substances in the water area to be measured more accurate. It is possible to

本発明の放射能測定方法のその他の条件については、上述した本発明の放射能測定装置の中で記載された内容と同様である。   The other conditions of the radioactivity measuring method of the present invention are the same as the contents described in the aforementioned radioactivity measuring apparatus of the present invention.

以下に、実施例を挙げて本発明をさらに詳しく説明するが、本発明は下記の実施例に何ら限定されるものではない。   EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

(実施例)
図1に示すように、放射線検出器10と、防水容器20と、解析手段30と、水位測定手段40とを備える放射能測定装置1を作製した。
なお、放射線検出器10については、5インチNaIシンチレーション検出器を用いた。また、防水容器については、長さ:2m、外形200mmのVU(塩化ビニル)管を用い、前記5インチNaIシンチレータを、ほぼ隙間がない状態で収納し、前記5インチNaIシンチレータの上部及び底部に厚さ50mmの鉛からなる放射線シールドを設けた。さらに、水位測定手段40として、市販の水位計を用いた。
なお、解析手段30については、制御盤32、アンプ33を防水容器20内に組み込み、電源31は放射線検出器10からケーブルを防水容器20外に引き出し、地上に設置したバッテリーと結ぶことで供給した。分析装置34は、市販のノートパソコンにプログラムを組み込むことで、分析装置として用いた。
(Example)
As shown in FIG. 1, the radioactivity measuring device 1 provided with the radiation detector 10, the waterproof container 20, the analysis means 30, and the water level measurement means 40 was produced.
As the radiation detector 10, a 5-inch NaI scintillation detector was used. For waterproof containers, use a VU (vinyl chloride) tube with a length of 2 m and an outer diameter of 200 mm, and store the 5-inch NaI scintillator with almost no gaps, at the top and bottom of the 5-inch NaI scintillator. A 50 mm thick lead shield was provided. Furthermore, a commercially available water gauge was used as the water level measurement means 40.
In addition, about the analysis means 30, the control panel 32 and the amplifier 33 were incorporated in the waterproof container 20, and the power supply 31 pulled out the cable from the radiation detector 10 out of the waterproof container 20, and supplied by connecting with the battery installed on the ground. . The analyzer 34 was used as an analyzer by incorporating a program into a commercially available notebook computer.

(評価)
図4に示すように、作製した放射能測定装置1を用いて、河川中のセシウム137濃度(137Csピーク係数)を測定した。なお、測定対象の河川は、福島県双葉郡浪江町にある河川である。図4に示す測定期間は、2016年10月11日〜10月19日の9日間である。
測定結果として、図5に、河川の水位(cm)及び算出した137Csピーク係数(cps:カウント数/秒)の、9日間の推移を示す。また、評価指標として、適宜河川から採水し、137Cs濃度を実測して、9日間の推移を導出した。
(Evaluation)
As shown in FIG. 4, the cesium 137 concentration ( 137 Cs peak coefficient) in the river was measured using the produced radioactivity measuring apparatus 1. The river to be measured is a river located in Namie Town, Futaba-gun, Fukushima Prefecture. The measurement period shown in FIG. 4 is nine days from October 11, 2016 to October 19, 2016.
As measurement results, FIG. 5 shows the transition of the water level (cm) of the river and the calculated 137 Cs peak coefficient (cps: counts / second) over 9 days. In addition, as an evaluation index, we collected water from rivers as appropriate, measured the 137 Cs concentration, and derived the transition for 9 days.

図5から、出水時(水位が大きくなった時)には、算出した137Csピーク係数は、実測した137Cs濃度と同じ挙動で上昇していることがわかり、本発明の放射能測定装置1は、137Cs濃度を高い精度で観測できていることがわかった。
また、10月14日〜10月15日において実測によって得られた137Cs濃度がほぼゼロである期間の水位及びCsピーク係数の推移を確認すると、バックグラウンド放射線量を示すピーク係数が、水位の下降に伴って増加していることを確認できた。
From FIG. 5, it can be understood that the calculated 137 Cs peak coefficient is rising in the same behavior as the measured 137 Cs concentration at the time of water discharge (when the water level is increased), and the radioactivity measuring device 1 of the present invention It was found that the 137 Cs concentration could be observed with high accuracy.
In addition, when the transition of the water level and the Cs peak coefficient during the period when the 137 Cs concentration obtained by the measurement was approximately zero between October 14 and October 15 is confirmed, the peak coefficient indicating the background radiation dose is It could be confirmed that it increased with the descent.

本発明によれば、複雑な設備を用いることなく、リアルタイムで且つ正確に、水中の放射性物質濃度を把握できる放射能測定装置を提供することが可能となる。   ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the radioactivity measuring apparatus which can grasp | ascertain the radioactive substance density | concentration in water accurately in real time, without using a complicated installation.

10 放射線検出器
11 放射線シールド
20 防水容器
30 解析手段
31 電源
32 制御盤
33 アンプ
34 分析装置
35 バックグラウンド除去
40 水位測定手段
100 水域
101 土壌
DESCRIPTION OF SYMBOLS 10 radiation detector 11 radiation shield 20 waterproof container 30 analysis means 31 power supply 32 control board 33 amplifier 34 analyzer 35 background removal 40 water level measurement means 100 water area 101 soil

Claims (5)

水中の放射性物質濃度を観測するための放射能測定装置であって、
放射線検出器と、防水性を有し且つ放射線を透過させる材料からなり、前記放射線検出器を覆うように設けられた防水容器と、前記放射線検出器から取得した信号に基づいて放射性物質濃度を算出する解析手段と、を備えることを特徴とする、放射能測定装置。
A radioactivity measuring device for monitoring the concentration of radioactive substances in water, comprising
A radioactive substance concentration is calculated based on a signal obtained from a radiation detector, a waterproof container made of a waterproof and radiation transmitting material and provided to cover the radiation detector, and a signal obtained from the radiation detector. And an analysis means for measuring the radioactivity.
前記解析手段は、前記算出した放射性物質濃度から、測定対象となる水域以外に由来する放射線の線量(バックグラウンド放射線量)を差し引く、バックグラウンド除去処理を実施することを特徴とする、請求項1に記載の放射能測定装置。   The analysis means is characterized in that a background removal process is performed by subtracting the radiation dose (background radiation dose) originating from areas other than the water to be measured from the calculated radioactive substance concentration. The radioactivity measuring device as described in. 前記放射能測定装置は、前記測定対象となる水域の水位を測定する水位測定手段をさらに備え、
前記解析手段は、前記水位測定手段の測定した水位に応じて、前記バックグラウンド放射線量を算出することを特徴とする、請求項2に記載の放射能測定装置。
The radioactivity measuring device further comprises water level measuring means for measuring the water level of the water area to be measured;
The radioactivity measuring apparatus according to claim 2, wherein the analysis means calculates the background radiation dose according to the water level measured by the water level measurement means.
前記放射線検出器は、シンチレータとしてNaI(Tl)、CsI(Tl)、CsI(Na)、LnBr3、ZnS(Ag)又はCsIを有することを特徴とする、請求項1〜3のいずれか1項に記載の放射能測定装置。 The said radiation detector is characterized by having NaI (Tl), CsI (Tl), CsI (Na), LnBr3 , ZnS (Ag), or CsI as a scintillator. The radioactivity measuring device as described in. 前記放射能測定装置は、前記測定対象となる水域の水底に設置されることを特徴とする、請求項1に記載の放射能測定装置。
The said radioactivity measuring apparatus is installed in the water bottom of the water area which becomes the said measuring object, The radioactivity measuring apparatus of Claim 1 characterized by the above-mentioned.
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