JP2013083589A - Radioactive substance sorter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector for efficiently and simultaneously (in real time) detecting radiation made incident from all directions.SOLUTION: The radiation detector has radiation detecting means for detecting radiation, operation processing means for operating radiation information according to a signal detected by the radiation detecting means, and display means for displaying the radiation information operated by the operation processing means. The radiation detecting means has: an incidence surface where radiation formed on an outer wall surface of a near-spherical body is made incident; a scintillator for emitting fluorescence corresponding to the radiation made incident from the incidence surface enclosed inside the near-spherical body; a diffuse reflection surface where the fluorescence emitted by the scintillator provided on the outer wall surface of the near-spherical body is not transmitted from outside the near-spherical body but is diffused and reflected; and a light detection part for detecting the fluorescence emitted by the scintillator provided for a part of an outer peripheral part of the near-spherical body.

Description

  The present invention relates to a radiation sorting apparatus capable of detecting a specimen contaminated with a radioactive substance at high speed and with high accuracy and sorting the specimen from an uncontaminated specimen.

  A scintillation detector is used as a detection device that detects a radiation dose emitted from a subject contaminated with a radioactive substance such as α rays, β rays, and γ rays (Patent Document 1). For detection, a scintillation detector is placed opposite to the subject. Then, fluorescence (visible light) from the scintillator that is emitted from the subject and emits light in proportion to the amount of radiation incident from the incident window of the scintillation detector is detected by an optical sensor. At this time, the amount of radiation emitted from the subject is detected from the signal obtained by the optical sensor.

JP 2000-19255 A

  If the subject is large or small, the scintillation detector may be directed to the subject and the radiation amount emitted from the subject may be detected. However, when there are a small number of specimens and many specimens, it takes too much time to detect the specimens with a scintillation detector, and it is difficult to detect with high accuracy. When the number of objects is small and many, it is desired to detect the objects quickly and with high accuracy. For example, in the case of small agricultural products such as rice, wheat and soybeans, it is important to detect whether these are contaminated with radioactive substances at high speed and with high accuracy.

  The present invention quickly and highly accurately detects whether or not a subject is contaminated by a certain amount or more than a radioactive substance, and quickly selects a contaminated subject and a non-contaminated subject. An object of the present invention is to provide an apparatus for sorting out radioactive materials.

  The radiation screening apparatus according to the present invention includes a radiation detection unit that detects radiation emitted from the subject storage unit and radiated from the subject moving in one direction, and the radiation detection with respect to the moving direction of the subject. An air valve that is provided downstream of the unit, blows air onto the subject, and stores the subject in a first storage unit provided in a direction different from the one direction, and radiation obtained by the radiation detection unit A determination circuit that determines whether or not the amount is larger than a preset value and an air valve control circuit that controls driving of the air valve based on a signal from the determination circuit are provided.

  According to the present invention, whether or not a subject is contaminated with a certain amount or more than a radioactive substance can be detected quickly and with high accuracy, and a contaminated subject and an uncontaminated subject can be detected at high speed. A radiation sorting apparatus capable of sorting is obtained.

Schematic diagram of essential parts of Embodiment 1 of the present invention Explanatory drawing of the detection unit of a part of FIG. Explanatory drawing of other embodiment of a collimator Explanatory drawing of the radiation detection part of a part of FIG. Explanatory drawing of the detection unit of a part of Example 2 of the present invention. Explanatory drawing of Example 3 of this invention Explanatory drawing of the collimator used in Example 3

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  The radiation screening apparatus according to the present embodiment determines whether or not the radiation (α ray, β ray, γ ray, etc.) emitted from the subject is greater than a predetermined value, This is a simple and highly accurate selection of unexamined subjects. Here, when the subject is an agricultural product such as rice, wheat or soybean, or a livestock product such as edible meat, the human body (biological body) ingests these substances. This is a reference value that determines whether or not there is radiation energy (becquerel (Bq)) that affects the amount of radiation.

  FIG. 1 is a schematic view of a main part of a first embodiment of the radiation sorting apparatus of the present invention. The subject storage unit 1 stores a plurality of subjects 2 for detecting whether or not a certain amount of radiation (x-rays, α-rays, β-rays, γ-rays, cesium rays) is emitted.

  The subject 2 is dropped or released on one side at a constant speed or substantially constant speed. The subject 2 is a fine food product such as rice, wheat, or soybean. The subject 2 is falling at about 5 m / sec, for example. The radiation detector 3 (radiation monitor 3) detects the radiation dose (becquerel (Bq)) of radiation (for example, γ rays) emitted from the subject 2. The radiation detector 3 contains an electronic circuit. The determination circuit 4 determines whether or not the detection value obtained by the radiation detector 3 is larger than a predetermined value set in advance.

  The air valve control circuit 5 drives and controls the air valve 6 that radiates high-pressure air in a certain direction based on the determination signal from the determination circuit 4. The first storage box 7 stores the subject 2 blown away by the air from the air valve 6. The second storage box 8 stores the dropped subject 2 without being blown away by the air from the air valve 6.

  In this embodiment, when the determination circuit 4 determines that the radiation (radioactivity) emitted from the subject 2 detected by the radiation detector 2 is a predetermined constant value (0.01 becquerel (Bq)). The air valve control circuit 5 drives the air valve 6 to radiate air from the air valve 6. As a result, the subject 2 is blown off with air and stored in the first storage box 7.

  Since the subject 2 falls from the subject storage unit 1 at a substantially constant speed, the air valve 6 is driven after a certain time from the time detected by the radiation detector 3. As a result, only the subject 2 to be processed is stored in the first storage box 7. A subject 2 for which a radiation dose greater than a certain level is not detected by the radiation detector 2 is stored in the second storage box 8.

  As described above, whether or not the subject 2 is contaminated by a certain amount of radiation is detected quickly and with high accuracy, and the contaminated subject and the uncontaminated subject are separated and contaminated by a certain amount or more. The subject is removed so that it is not ingested by the human body.

  FIG. 2 is a schematic diagram of a main part of the detection unit 100 including the radiation detector 3 and the determination circuit 4 of FIG.

  Radiation emitted from the subject 2 (for example, gamma rays from 50 KEV to 1.5 MeV) is collected by the collimator 102 and guided to the scintillator 103. As shown in FIG. 3, the collimator 102 has a configuration in which a hollow shape 103a obtained by partially cutting a cone shape of a lead material and a cylindrical shape 103b are joined, and guides the radiation R emitted from the subject 101 in one direction. .

  In addition, the radiation detector 3 is accommodated in a cylindrical shape continuous with the conical shape of the collimator 102. The conical shape 103a of the collimator 102 and the cylindrical shape 103b in which the radiation detector 3 is housed are made of lead or tungsten (w) alloy.

  The opening diameter D1 on the subject 101 side of the conical shape 103a of the collimator 103 shown in FIG. 3 is 5 mm, and the length L1 is 20 mm. The cylindrical shape 103b has an opening diameter D2 of 20 mm and a length L2 of 30 mm. At this time, the time required for the subject 2 to pass through the aperture diameter D1 is about 1 mm second. The scintillator 103 uses a disk crystal such as CsI (TI) in which cesium iodide is doped with a small amount of thallium and NaI (TI) in which sodium iodide is doped with a small amount of thallium. The detection light photoelectrically converted into visible light is detected by a photoelectric conversion element (photosensor) 104 in proportion to the intensity of radiation incident on the scintillator 103. The photosensor 104 uses, for example, a photomultiplier tube or a photodiode (Si-PD).

  In this embodiment, a silicon fort diode (Si-PD) is used.

  In this embodiment, the entire collimator 102 that houses the scintillator 103 and the optical sensor 104 may be housed in a waterproof case, which is preferable for waterproofing and dustproofing.

  Reference numeral 105 denotes a charge amplifier, which integrates the charge of the input pulse, converts it to a pulse having a pulse height corresponding to the amount of the charge, and outputs it. The signal from the fort diode 104 is amplified and waveform shaping is performed. The signal output from the charge amplifier 105 is an analog signal. The determination circuit 4 includes a comparator 106 provided with a disk, and performs waveform shaping to match the input level of a standard logic element such as TTL from the signal output from the charge amplifier 105.

  Then, the radiation amount (energy) emitted from the subject 101 is discriminated. The signal discriminated by the comparator 106 is input to the air valve control circuit 5. The air valve control circuit 5 drives the air valve 6 to place the subject 2 in the first storage box when the radiation radiated from the subject 101 exceeds a predetermined value (a value that affects the human body) from the signal from the determination circuit 4 in advance. 7 to blow away and store. As a result, the subject 2 contaminated with a certain amount or more of radiation is selected.

  FIG. 4 is an explanatory diagram of a detection unit including the radiation detector 3 having the scintillator 103 and the optical sensor 104 of FIG. 2 and an electronic circuit. In FIG. 4, reference numeral 201 denotes an incident window through which radiation (γ rays) R is incident. Reference numeral 103 denotes a scintillator. An optical sensor 104 detects visible light emitted from the scintillator crystal 103.

  Reference numeral 202 denotes a reflector that reflects light emitted from the scintillator 103. A sealing case 203 seals the scintillator crystal 103 and the optical sensor 104. An electronic circuit 204 processes a signal output from the optical sensor 104. A case 206 holds and protects various members.

Reference numeral 205 denotes an input / output terminal from which a detection signal from the optical sensor 104 is output. As the scintillator 103, a crystal of CsI (TI) or NaI (TI) having a large blocking power for gamma rays such as Cs and a large light output is used. In addition, inorganic crystals such as organic crystals (anthracene), CaF ₂ (Eu), BaF ₂ are used for β rays. NaI (TI) is used for γ rays.

  FIG. 5 is a schematic view of a main part of a detection unit 100 used in the radioactive material sorting apparatus according to the second embodiment of the present invention. The signal processing system in FIG. 5 differs from the first embodiment in FIG. 2 in that the analog signal output from the radiation detector 3 is processed into a digital signal and output. The process until the radiation R emitted from the subject 101 is collected by the collimator 102, detected via the scintillator 103 and the optical sensor 104, and output as an analog signal from the charge amplifier 105 is the same as in FIG.

  In this embodiment, the determination circuit 4 has an analog-digital converter (ADC) 301 and a microprocessor 302.

  In this embodiment, the analog signal output from the charge amplifier 105 is converted into a digital signal by an analog-digital converter (ADC) 301. A digital signal from the ADC 301 is input to the microprocessor 302. The microprocessor 302 performs signal processing to detect the amount of radioactive energy emitted from the subject 101. At this time, the waveform from the signal from the ADC 301 is analyzed to obtain the pulse height count rate. Further, dose calculation is performed to calculate a sievert (Sv) relating to the degree of influence of radiation on the human body.

  The microprocessor 302 calculates the radioactivity (becquerel (Bq)) and dose rate (Cv) emitted per unit time (1 second). In the microprocessor 302, since the influence of the human body varies depending on the type of radiation, a sievert is obtained together with becquerel, and it is determined whether or not the subject 2 can be ingested, and the result is input to the air valve control circuit 5. ing.

  In the present embodiment, an output signal from the microprocessor 302 may be displayed on the display device 303 to inform the observer of how much radiation dose has been detected.

  In addition, the output signal may be transferred via the USB 304. Other configurations are the same as those of the first embodiment shown in FIG.

  In the radiation sorting apparatus of the present invention, when the subject is large and the number is small, such as livestock products, the radiation detector used in each embodiment detects the amount of radiation emitted from the subject and displays it on the display means You may use as a type | mold radiation detection apparatus. A plurality of radiation detectors 3 may be provided in the direction in which the subject 2 passes to detect radiation emitted from the subject 2 in various directions.

  FIG. 6 is a schematic diagram of a main part of the third embodiment when the detection unit 100 of FIG. 5 is applied to a portable radiation detection apparatus.

  In FIG. 6, the collimator 102 to the microprocessor 302 in FIG. 5 have the same configuration. In FIG. 6, the radiation data from the microprocessor 302 is displayed on the display means 401 such as a liquid crystal screen. In addition, the output signal may be transferred via the USB 402 or the like. Here, the radiation data includes, for example, elapsed time, sievert (Sv), becquerel (Bq), and the like.

  Also in this embodiment, the collimator shown in FIG. 3 may be used on the subject 101 side of the parabola detector 103.

  FIG. 7 is an explanatory diagram of the scintillator 103 when the subject 2 is large in this embodiment. The opening of the collimator 102 when the subject 2 is large is opposite to that shown in FIG. 2 and the opening on the subject side is large. According to this, it becomes easy to detect radiation emitted from various parts of the subject 101. This detection method is effective when the subject is large and few, since it does not take much detection time. The collimator 102 shown in FIG. 7 has an opening diameter of 50 mm, a length L11 of 30 mm, a length L12 of 30 mm, and an opening diameter D11 of 20 mm.

  As described above, according to each embodiment, it is possible to detect the radiation dose emitted from the subject using the scintillation detector, and to detect whether the radiation dose is a certain value or more at high speed and with high accuracy. . As a result, the human body can be prevented from ingesting agricultural and livestock products contaminated with radiation such as α rays, β rays, and γ rays, and adverse effects on the human body can be eliminated.

DESCRIPTION OF SYMBOLS 1,101 Subject storage part 2 Subject 3 Radiation detector 4,106 Judgment circuit 5 Air valve control circuit 6 Air valve 7 First storage part 8 Second storage part 102 Collimator 103 Scintillator 104 Photosensor 105 Charge amplifier 301 ADC converter 302 Micro Processor 303, 401 Display means

Claims (3)

A radiation detector that detects radiation emitted from the subject container and emitted from the subject moving in one direction;
An air valve provided downstream of the radiation detection unit with respect to the moving direction of the subject, blows air onto the subject, and stores the subject in a first storage unit provided in a direction different from the one direction. When,
A determination circuit for determining whether or not the radiation dose obtained by the radiation detection unit is larger than a preset value;
A radiation sorter having an air valve control circuit for controlling driving of an air valve based on a signal from the determination circuit.   2. The radioactive substance sorting apparatus according to claim 1, wherein the air valve control circuit drives the air valve after a lapse of a predetermined time from the time when the radiation detecting unit detects the radiation emitted from the subject.   It has a collimator made of lead or tungsten alloy by cutting out the apex portion of the cone shape and forming an opening through which the radiation emitted from the subject is incident, and the radiation detection unit is housed inside the collimator The radiation sorting apparatus according to claim 1 or 2, wherein