WO2021090584A1 - Radiation monitor and method for diagnosing same - Google Patents

Radiation monitor and method for diagnosing same Download PDF

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Publication number
WO2021090584A1
WO2021090584A1 PCT/JP2020/035135 JP2020035135W WO2021090584A1 WO 2021090584 A1 WO2021090584 A1 WO 2021090584A1 JP 2020035135 W JP2020035135 W JP 2020035135W WO 2021090584 A1 WO2021090584 A1 WO 2021090584A1
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Prior art keywords
radiation
alpha
emitting element
photons
rate
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PCT/JP2020/035135
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French (fr)
Japanese (ja)
Inventor
田所　孝広
上野　雄一郎
克宜 上野
修一 畠山
敬介 佐々木
晃 大曽根
渋谷　徹
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株式会社日立製作所
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Publication of WO2021090584A1 publication Critical patent/WO2021090584A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/17—Circuit arrangements not adapted to a particular type of detector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/20—Measuring radiation intensity with scintillation detectors
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/02—Devices or arrangements for monitoring coolant or moderator
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Definitions

  • This disclosure relates to a radiation monitor and its diagnostic method.
  • the radiation monitor may be installed in a place that is difficult for people to approach, it is desired to have a means for diagnosing whether or not the radiation monitor is operating normally from a remote place.
  • a radiation monitor is provided with a radiation detection unit for detecting radiation and a gamma ray source installed in the vicinity thereof, and the gamma ray source constantly injects radiation of a constant intensity into the radiation detection unit to instruct the radiation detection unit. By checking whether the value is above a certain value, it is confirmed whether the radiation monitor is operating normally.
  • a desired dose rate such as an air dose rate due to the dose rate from the gamma ray source. Therefore, when measuring the desired dose rate, gamma rays from the gamma ray source are detected as radiation. It is necessary to suppress the incident on the part.
  • a moving mechanism for moving the gamma ray source into the shield or a moving mechanism for moving the shield between the gamma ray source and the radiation detection unit is known.
  • a moving mechanism for moving the shield between the gamma ray source and the radiation detection unit is known.
  • these moving mechanisms there is a problem that a very large-scale system is required.
  • the above-mentioned gamma ray source requires a very strong radiation source, there is also a problem that management becomes complicated.
  • an optical pulse generator that generates an optical pulse is provided near or inside the radiation detector, and the optical pulse generator is used to inject an optical pulse into the radiation detector. At that time, the soundness of the radiation detector is confirmed based on the detection signal output from the radiation detector.
  • an optical pulse generator is provided near or inside the radiation detector. Therefore, if the soundness cannot be confirmed, the radiation detector may have a problem or light. It is difficult to determine if the pulse generator is defective. In addition, the optical pulse generator may not operate normally in a high temperature or high dose rate environment.
  • Patent Document 6 it is not necessary to provide an optical pulse generator near or inside the radiation detector. However, it is complicated because a light emitting unit for generating light having a wavelength different from the wavelength emitted by the radiation emitting element and a light selection filter for selectively extracting the light emitted by the radiation emitting element are required. There is a problem that an expensive system is required.
  • An object of the present invention has been made in view of the above problems, and to provide a radiation monitor and a radiation measurement method capable of easily and inexpensively confirming whether or not a device is operating normally from a remote location. Is.
  • a radiation monitor includes a radiation detection unit having a radiation emitting element that emits photons in response to incident radiation, an alpha ray emitting nuclei species that emits alpha rays and causes them to enter the radiation detection unit.
  • An optical transmission unit that transmits photons emitted by the radiation emitting element, an optical detection unit that detects photons transmitted by the optical transmission unit, and a count rate of photons detected by the optical detection unit. It has a measuring unit for measurement and an analysis unit for obtaining a radiation dose rate based on the counting rate measured by the measuring unit and diagnosing whether or not the radiation monitor is operating normally.
  • FIG. 1 is a diagram showing an example of the configuration of the radiation monitor according to this embodiment.
  • the radiation monitor 100 shown in FIG. 1 includes a radiation detection unit 10, an optical fiber 20, a light detection unit 30, a measurement device 40, and an analysis device 50.
  • the radiation detection unit 10 is a detection unit that detects radiation.
  • the radiation detection unit 10 includes a radiation emitting element 1 and an alpha ray emitting substance 2.
  • the radiation emitting element 1 emits photons according to the incident radiation.
  • Examples of the radiation emitting element 1 include an element obtained by adding a rare earth element such as yttrium, neodymium, cerium or praseodymium to a ceramic base material such as yttrium aluminum garnet.
  • the radiation emitting element 1 is not limited to this example, and for example, a single crystal body may be used as a base material.
  • Alpha ray emitting substance 2 is a substance containing an alpha ray emitting nuclide that emits alpha ray which is a kind of radiation.
  • the alpha ray emitting substance 2 may be composed only of the alpha ray emitting nuclide, or may be mixed with another substance.
  • Alpha ray emitting nuclides are, for example, nuclides having a half-life of one year or more.
  • nuclei examples include polonium 210, thorium 229, thorium 230, uranium 233, uranium 234, uranium 235, uranium 238, neptunium 237, plutonium 238, plutonium 239, americium 241, curium 243, curium 244, and curium 245. , Curium 246, Curium 247, Curium 248 and the like.
  • the alpha ray emitting substance 2 may contain a nuclide having a half-life of one year or more and a nuclide having a radiation equilibrium. In addition, it is desirable that the types and amounts of alpha-emitting nuclides are not subject to legal regulations regarding radioactive substances.
  • the optical fiber 20 is an optical transmission unit that optically connects the radiation light emitting element 1 of the radiation detection unit 10 and the light detection unit 30, and detects photons emitted by the radiation light emitting element 1 of the radiation detection unit 10. It transmits to unit 30.
  • the light detection unit 30 detects one photon emitted by the radiation emitting element 1 and transmitted through the optical fiber 20, and converts each photon into an electric signal (specifically, an electric pulse signal). Output.
  • the measuring device 40 is a measuring unit that measures a counting rate, which is the number of photons detected by the photodetector 30 per unit time, based on an electric signal from the photodetector 30.
  • the analysis device 50 calculates the radiation dose rate based on the counting rate measured by the measuring device 40, and diagnoses whether or not the radiation monitor 100 is operating normally.
  • the radiation dose rate is the air dose rate, which is the dose rate of gamma rays in the space where the radiation detection unit 10 is arranged.
  • the analysis device 50 stores and holds in a database information necessary for calculating the radiation dose rate and diagnosing the radiation monitor 100.
  • the database may be held by an external device (not shown) different from the analysis device 50.
  • 2 to 5 are diagrams showing an installation example of the alpha ray emitting substance 2.
  • the alpha ray emitting substance 2 is applied to the surface of the radiation emitting element 1 on the side opposite to the side to which the optical fiber 20 is connected (installed).
  • the alpha ray emitting substance 2 may be applied, for example, by vapor deposition or by physical sputtering.
  • the preformed alpha ray emitting substance 2 is arranged near the surface of the radiation emitting element 1 on the side opposite to the side to which the optical fiber 20 is connected.
  • the alpha ray emitting substance 2 is made sufficiently thin, and the energy loss of alpha rays due to the substance (usually a gas such as air) existing between the radiation emitting element 1 and the alpha ray emitting substance 2 becomes small.
  • the radiation emitting element 1 and the alpha ray emitting substance 2 are sufficiently close to each other. In this example, the alpha ray emitting substance 2 can be easily removed and changed.
  • the alpha ray emitting substance 2 is mixed in the radiation emitting element 1.
  • the alpha ray emitting substance 2 can be mixed with the radiation emitting element 1.
  • a light reflecting film 3 that reflects light is formed on a surface different from the surface of the radiation emitting element 1 to which the optical fiber 20 is connected.
  • the light reflecting film 3 is made of, for example, aluminum, silver, gold, chromium, or the like.
  • a preformed alpha ray emitting substance 2 is installed in the vicinity of the light reflecting film 3.
  • the material of the light reflecting film 3 is such that the radiation emitting element 1 (light reflecting film 3) and the alpha ray emitting substance 2 are sufficiently brought close to each other and the energy loss of alpha rays by the light reflecting film 3 is reduced. And the thickness should be adjusted.
  • the energy loss of alpha rays due to the light reflecting film 3 is 1/10 or less of the energy of alpha rays from the alpha ray emitting substance 2.
  • FIG. 6 is a diagram showing an example of a time change in the count rate of photons measured by the measuring device 40.
  • the horizontal axis represents time and the vertical axis represents photon counting rate.
  • the photon count rate is the air dose at the place where the radiation detection unit 10 is installed.
  • the value corresponds to the rate (dose rate of gamma rays).
  • the counting rate according to the dose rate of gamma rays (hereinafter, may be referred to as the counting rate of light by gamma rays) is substantially constant.
  • the alpha rays emitted from the alpha ray emitting substance 2 are incident on the radiation emitting element 1, a large amount of energy is applied to the radiation emitting element 1, so that the number of photons generated in the radiation emitting element 1 rapidly increases. As a result, the photon counting rate increases sharply. The rapidly increasing counting rate then decreases according to the emission attenuation time constant of the radiation emitting element 1 and returns to the counting rate of light by gamma rays.
  • the alpha ray emitting nuclide contained in the alpha ray emitting substance 2 when one alpha ray is incident on the radiation emitting element 1, the energy of about 5.5 MeV is generated in a short time. Since it is given to 1, the photon count rate increases sharply.
  • the count rate that rapidly increases due to the incident of alpha rays is It returns to the light count rate by gamma rays in a few milliseconds.
  • the analysis device 50 analyzes the time change of the counting rate of photons measured by the measuring device 40, and identifies the alpha ray influence time, which is the time when the counting rate is increased by alpha rays.
  • the analyzer 50 calculates a numerical value corresponding to the alpha rays incident on the radiation emitting element 1 based on the count rate of photons measured during the alpha ray influence time.
  • the alpha ray count rate (more specifically, the average count rate in a sufficiently long measurement time (for example, 1 s)) is calculated as the numerical value.
  • the analyzer 50 diagnoses whether or not the radiation monitor 100 is operating normally based on the alpha ray count rate.
  • the counting rate in the dose rate calculation time which is the time range other than the alpha ray influence time, is the counting rate according to the air dose rate. Therefore, the analysis device 50 measures the air dose rate in the space where the radiation detection unit 10 is arranged, based on the count rate in the dose rate calculation time.
  • the alpha ray emitting substance 2 corresponds to the emission attenuation time constant of the radiation emitting element 1. It is necessary to use alpha ray emitting nuclei of moderate intensity. For example, it is desirable that the alpha ray influence time is 1/10 or less of the dose rate calculation time.
  • the alpha ray influence time corresponding to one alpha ray is several milliseconds. Therefore, if the average number of alpha rays emitted from alpha ray emitting nuclides is 20 per second, and assuming that 10 of them are incident on the radiation emitting element 1, the alpha ray influence time per second is several tens of milliseconds. It becomes. In this case, the alpha ray effect time has almost no effect on the measurement accuracy of the air dose rate.
  • FIG. 7 is a flowchart for explaining the operation of the radiation monitor 100.
  • the photodetector 30 detects the photons emitted by the radiation incident on the radiation emitting element 1 of the radiation detection unit 10 and transmitted through the optical fiber 20 one by one, and converts the detected photons into an electric signal. And output (step S101).
  • the measuring device 40 measures the count rate of photons emitted by the radiation incident on the radiation emitting element 1 based on the electric signal from the photodetector 30, and notifies the analyzer 50 of the count rate (step S102). ).
  • the analysis device 50 analyzes the time change of the counting rate notified from the measuring device 40, and determines whether or not a sudden increase or decrease in the counting rate has occurred (step S103). For example, the analysis device 50 determines that a sudden increase or decrease in the counting rate has occurred when the counting rate becomes equal to or higher than the threshold value and then falls below the threshold value within a predetermined time.
  • the predetermined time is, for example, a time within about 10 times the emission attenuation time constant of the radiation emitting element 1.
  • the predetermined time is set in advance within 2.3 milliseconds because the emission attenuation time constant is 230 microseconds.
  • the threshold value may be determined according to the statistical accuracy (for example, standard error) of the air dose rate measured in advance.
  • the analyzer 50 calculates the measured counting rate as the counting rate of photons by gamma rays and sets it in advance based on the counting rate.
  • the average counting rate of photons by gamma rays within the measured measurement time is calculated (step S104).
  • the analysis device 50 refers to the database it holds, and calculates the air dose rate at the place where the radiation detection unit 10 is installed based on the database and the average counting rate of photons by gamma rays (step S105).
  • the database contains information showing the relationship between the average photon count rate and the air dose rate. Specifically, since there is a proportional relationship between the average photon count rate and the air dose rate, the database includes a proportional coefficient between the average photon count rate and the air dose rate. In this case, the analyzer 50 calculates the air dose rate by multiplying the average count rate of photons by gamma rays by the proportional coefficient in the first database.
  • step S103 YES
  • the analysis device 50 detects that a sudden increase / decrease in the counting rate has occurred as an alpha ray incident on the radiation emitting element 1. (Step S106).
  • the analyzer 50 sets the average value of the alpha ray count rate (the number of alpha rays incident on the radiation emitting element 1 per unit time) within the measurement time as the average value of the alpha rays based on the detection result in step S106. It is calculated as a counting rate (step S107).
  • the average value of the emission interval at which alpha rays are emitted from the alpha ray emitting nuclide of the alpha ray emitting substance 2 is not constant, the average value of the emission interval at a time when sufficient statistical accuracy is obtained is the radioactivity of the alpha ray emitting nuclide ( The value is proportional to the half-life). Therefore, when the half-life of alpha-emitting nuclides is sufficiently long, the average counting rate of alpha rays becomes almost constant if the measurement time is set to a time that provides sufficient statistical accuracy.
  • the analysis device 50 refers to the retained database and determines whether or not the average counting rate of alpha rays is included in the predetermined first range (step S108).
  • the database contains information indicating the first range.
  • the first range is determined, for example, according to the statistical accuracy of the average counting rate of alpha rays measured in advance.
  • step S108 When the average counting rate of alpha rays is included in the first range (step S108: YES), the analyzer 50 determines that the radiation monitor 100 is operating normally, and for example, the radiation monitor 100 operates normally. A message indicating that the message is being output is output (step S109). On the other hand, when the average counting rate of alpha rays is not included in the first range (step S108: NO), the analyzer 50 determines that the radiation monitor 100 is not operating normally, and for example, an abnormality has occurred. An alarm to that effect is output (step S110).
  • FIG. 8 is a diagram showing an example of a time change of the average counting rate of alpha rays calculated by the radiation monitor 100.
  • the horizontal axis represents time and the vertical axis represents the average counting rate.
  • an abnormality specifically, a disconnection of the optical fiber 20 has occurred in the radiation monitor 100.
  • the average counting rate of alpha rays is included in the range of statistical accuracy (first range). If the optical fiber 20 is disconnected at time t1, the average counting rate of alpha rays becomes zero, which is out of the range of statistical accuracy. As a result, the analysis device 50 detects the abnormality and determines that the radiation monitor 100 is not operating normally.
  • the radiation detection unit 10 has a radiation emitting element 1 that emits photons in response to the incident radiation.
  • the alpha ray emitting substance 2 emits alpha rays and causes them to enter the radiation detection unit 10.
  • the optical fiber 20 transmits the photons emitted by the radiation emitting element 1.
  • the photodetector 30 detects photons transmitted by the optical fiber 20.
  • the measuring device 40 measures the count rate of photons detected by the photodetector 30.
  • the analysis device 50 obtains the radiation dose rate based on the counting rate measured by the measuring device 40, and diagnoses whether or not the radiation monitor 100 is operating normally.
  • the radiation monitor 100 operating normally without removing the radiation monitor 100 or moving to the vicinity of the radiation detection unit 10 without using equipment such as an optical pulse generator and a light selection filter? It becomes possible to confirm whether or not. Therefore, it is possible to easily and inexpensively check whether or not it is operating normally from a remote location.
  • the analyzer 50 it is diagnosed whether or not the radiation monitor 100 is operating normally based on the numerical value corresponding to the alpha rays incident on the radiation emitting element 1, specifically, the count rate of the alpha rays incident on the radiation emitting element 1. Therefore, the analyzer 50 also requires special equipment.
  • FIGS. 9 to 11 An example of the radiation monitor according to the second embodiment of the present disclosure will be described with reference to FIGS. 9 to 11.
  • a numerical value corresponding to the alpha ray incident on the radiation emitting element 1 instead of the average counting rate of the alpha ray, a photon by an alpha ray (a photon generated by the alpha ray incident on the radiation emitting element 1). It is different from the first embodiment in that it diagnoses whether or not the radiation monitor 100 is operating normally based on the counting rate of.
  • FIG. 9 is a diagram showing an example of a time change of the photon count rate measured by the measuring device 40.
  • the horizontal axis represents time and the vertical axis represents photon counting rate.
  • the alpha rays emitted from the alpha ray emitting substance 2 are incident on the radiation emitting element 1, a large amount of energy is applied to the radiation emitting element 1, so that it is generated in the radiation emitting element 1.
  • the counting rate of photons increases sharply, then decreases according to the emission attenuation time constant of the radiation emitting element 1, and returns to the counting rate of photons according to gamma rays.
  • the value obtained by subtracting the sum of the count rates of photons by gamma rays at the alpha ray influence time from the sum of the count rates measured in the alpha ray influence time, which is the time when the count rate is increasing by alpha rays, is alpha. It is the count of photons by alpha rays in the line influence time. Further, the value obtained by dividing the photon count by alpha rays by the alpha ray influence time is the photon count rate by alpha rays.
  • FIG. 10 is a flowchart for explaining the operation of the radiation monitor 100 according to this embodiment.
  • step S106 the analyzer 50 subtracts the sum of the count rates of photons by gamma rays at the alpha ray influence time from the sum of the count rates measured at the alpha ray influence time when the count rate suddenly increases or decreases. , Calculate the count of photons by alpha rays at the alpha ray influence time. Then, the analysis device 50 divides the photon count by the alpha ray by the alpha ray influence time to calculate the photon count rate by the alpha ray (step S201).
  • the sum of the photon count rates by gamma rays in the alpha ray influence time is, for example, a value obtained by multiplying the average count rate calculated in step S105 by the alpha ray influence time.
  • the analysis device 50 refers to the database it holds and determines whether or not the average counting rate of photons due to alpha rays is included in the predetermined second range (step S202).
  • the database contains information indicating the second range.
  • the second range is determined, for example, according to the statistical accuracy of the average counting rate of photons by alpha rays measured in advance.
  • step S202 When the average counting rate of photons by alpha rays is included in the second range (step S202: YES), the analyzer 50 determines that the radiation monitor 100 is operating normally, and for example, the radiation monitor 100 is normal. A message indicating that the operation is being performed is output (step S203). On the other hand, when the average counting rate of photons due to alpha rays is not included in the second range (step S202: NO), the analyzer 50 determines that the radiation monitor 100 is not operating normally, and for example, an abnormality occurs. An alarm indicating that it has occurred is output (step S204).
  • FIG. 11 is a diagram showing an example of a time change of the average counting rate of photons due to alpha rays calculated by the radiation monitor 100.
  • the horizontal axis represents time and the vertical axis represents the average counting rate.
  • an abnormality specifically, radiation damage to the optical fiber 20 has occurred in the radiation monitor 100.
  • the average counting rate of photons by alpha rays is included in the range of statistical accuracy (second range).
  • the average counting rate of photons due to alpha rays gradually decreases, and the average counting rate falls out of the statistical accuracy range of the average counting rate.
  • the analysis device 50 detects the abnormality and determines that the radiation monitor 100 is not operating normally.
  • the present embodiment is different from the second embodiment in that a plurality of types of alpha ray emitting substances (alpha ray emitting nuclides) having different emitted alpha ray energies are provided.
  • FIG. 12 is a diagram showing an installation example of an alpha ray emitting substance in this embodiment.
  • the alpha ray emitting substance 2 there are three types of alpha ray emitting substances 21 to 23 having different energy of the alpha ray emitted.
  • the alpha ray emitting substance 2 is not limited to three types, and may be two types or four or more types.
  • the alpha ray emitting substances 21 to 23 are applied to the surface of the radiation emitting element 1 on the side opposite to the side to which the optical fiber 20 is connected, as in the example of FIG.
  • the alpha ray emitting substances 21 to 23 may be installed on the side opposite to the side to which the optical fiber 20 is connected in the radiation emitting element 1 as in the example of FIG. 3, or as in the example of FIG. It may be mixed in the radiation emitting element 1, or is installed in the vicinity of the light reflecting film 3 provided on a surface other than the surface to which the optical fiber 20 is connected in the radiation emitting element 1 as in the example of FIG. May be good.
  • FIG. 13 is a diagram showing an example of a time change of the photon count rate measured by the measuring device 40 in this embodiment.
  • the horizontal axis represents time and the vertical axis represents photon counting rate.
  • the alpha rays emitted from the alpha ray emitting substance 2 are incident on the radiation emitting element 1, a large amount of energy is applied to the radiation emitting element 1, so that it is generated in the radiation emitting element 1.
  • the counting rate of photons increases sharply, then decreases according to the emission attenuation time constant of the radiation emitting element 1, and returns to the counting rate of photons according to gamma rays.
  • the counting rate of photons by alpha rays is proportional to the energy of the alpha rays. Therefore, when three types of alpha ray emitting substances 21 to 23 having different alpha ray energies are used as the alpha ray emitting substance 2 as in the example of FIG. 12, three different magnitude counting rates are obtained. Be measured.
  • FIG. 14 is a flowchart for explaining the operation of the radiation monitor 100 according to the present embodiment. First, the same processing as in steps S101 to S106 and S201 described with reference to FIG. 10 is executed.
  • step S201 the analysis device 50 refers to the held database and determines whether the average counting rate of photons due to alpha rays is included in the second range (step S301).
  • the database includes a second range for each alpha ray emitting substance.
  • the analyzer 50 determines whether or not the average counting rate of photons by alpha rays is included in any of the three second ranges.
  • step S301 When the average counting rate of photons by alpha rays is included in the second range (step S301: YES), the analyzer 50 determines that the radiation monitor 100 is operating normally, and for example, the radiation monitor 100 is normal. A message indicating that the operation is being performed is output (step S302).
  • the analyzer 50 determines that there is a possibility that an abnormality has occurred in the radiation monitor 100.
  • the average counting rate of photons due to alpha rays from the alpha ray emitting substance 2 is calculated for each alpha ray emitting substance 2 (step S303).
  • the analyzer 50 calculates the average counting rate of photons by alpha rays for each alpha ray influence time for a certain period of time, classifies the average counting rate into three groups having different values (average counting rate), and each of them. Let the average counting rate of the group be the average counting rate of photons due to alpha rays from the alpha ray emitting substance 2 which is associated with the group in advance.
  • the analyzer 50 determines whether or not the average counting rate of photons due to alpha rays from each alpha ray emitting substance 2 changes at the same rate from the initial value (step S304).
  • the initial value is, for example, the average counting rate of photons by alpha rays measured in advance before the operation of the radiation monitor 100 is started. Further, when the rate of change from the initial value is included in a predetermined range, the analyzer 50 changes the average counting rate of photons due to alpha rays from each alpha ray emitting substance 2 at the same rate from the initial value. You may judge that it is.
  • the predetermined range is determined, for example, according to the statistical accuracy of the average counting rate of photons by alpha rays measured in advance. Further, the information indicating the predetermined range is included in, for example, the database held by the analysis device 50.
  • step S304 When each average counting rate does not change at the same rate (step S304: NO), the analyzer 50 determines that the radiation monitor 100 is not operating normally, and issues an alarm indicating that an abnormality has occurred, for example. Output (step S305).
  • step S304 When each average counting rate changes at the same rate (step S304: YES), the analyzer 50 calibrates the radiation monitor 100 (step S306).
  • the analyzer 50 may determine that the radiation monitor 100 is not operating normally.
  • FIG. 15 is a diagram for explaining an example of calibration of the radiation monitor 100.
  • the energy of alpha rays is shown, and the vertical axis shows the photon count rate.
  • the average count rate of photons by alpha rays for each alpha ray emitting substance 2 before the start of operation of the radiation monitor 100 (before operation) (marked with ⁇ ) and when the radiation monitor 100 is deteriorated (when deteriorated) ) Is shown as the average counting rate (x) of photons by alpha rays for each alpha ray emitting substance 2.
  • the radiation monitor 100 when the average counting rate of photons due to alpha rays for each alpha ray emitting substance 2 decreases at the same rate as the average counting rate (initial value) before the start of operation, the radiation monitor It can be considered that 100 has deteriorated.
  • the analyzer 50 adjusts each second range of the average counting rate of photons by alpha rays in the database according to the ratio. By doing so, the radiation monitor 100 is calibrated.
  • the analyzer 50 may calibrate the radiation monitor 100 by adjusting the relationship (proportional coefficient) between the average count rate and the air dose rate based on the ratio. This makes it possible to easily perform calibration during operation.
  • Radiation emitting element 2 Radiation emitting element 2
  • 21-23 Alpha ray emitting substance 3
  • Light reflecting film 10 Radiation detector 20:
  • Optical fiber 30 Photodetector 40: Measuring device 50: Analytical device 100: Radiation monitor

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Abstract

Provided is a radiation monitor for which it is possible to simply and inexpensively check whether the radiation monitor is operating normally from a location removed from the radiation monitor. A radiation detection unit 10 comprises a radiation emission element 1 that emits photons in response to incident radiation. An alpha-ray emitting substance 2 emits alpha rays such that the same strike the radiation detection unit 10. An optical fiber 20 transmits photons emitted from the radiation emission element 1. A photodetection unit 30 detects the photons transmitted by the optical fiber 20. A measurement device 40 measures the count rate of the photons detected by the photodetection unit 30. An analysis device 50 determines a radiation dose rate on the basis of the count rate measured by the measurement device 40 and determines whether the radiation monitor 100 is operating normally.

Description

放射線モニタ及びその診断方法Radiation monitor and its diagnostic method
　本開示は、放射線モニタ及びその診断方法に関する。 This disclosure relates to a radiation monitor and its diagnostic method.
　原子力発電所内の使用済み燃料貯蔵プール、原子炉圧力容器内外、原子炉格納容器内外、サプレッションプール内外、原子炉建屋内外、再処理施設、病院及び研究所等では、放射線の線量率を測定する放射線モニタが利用されている。 Radiation that measures the dose rate of radiation in spent fuel storage pools inside nuclear power plants, inside and outside the reactor pressure vessel, inside and outside the reactor containment vessel, inside and outside the suppression pool, inside and outside the reactor building, reprocessing facilities, hospitals and laboratories, etc. A monitor is being used.
　放射線モニタは、人が近寄りがたい場所に設置されることもあるため、放射線モニタが正常に動作しているか否かを離れた場所から診断する手段を備えることが望まれている。 Since the radiation monitor may be installed in a place that is difficult for people to approach, it is desired to have a means for diagnosing whether or not the radiation monitor is operating normally from a remote place.
　例えば、放射線モニタには、放射線を検出する放射線検出部と、その近傍に設置されたガンマ線源とを備え、ガンマ線源により放射線検出部に一定の強度の放射線を常時入射し、放射線検出部の指示値が一定値以上か否かを確認することで、放射線モニタが正常に動作しているか否かを確認するものがある。この種の放射線モニタでは、ガンマ線源による線量率により、空間線量率などの所望の線量率を測定することができないため、所望の線量率を測定する際には、ガンマ線源からのガンマ線が放射線検出部に入射することを抑制する必要がある。ガンマ線の入射を抑制する抑制機構としては、ガンマ線源を遮蔽体内へ移動させる移動機構、または、ガンマ線源と放射線検出部との間に遮蔽体を移動させる移動機構が知られている。しかしながら、これらの移動機構を用いるためには、非常に大がかりなシステムが必要となるという問題がある。また、上述したガンマ線源としては非常に強い放射線源が必要となるため、管理が煩雑になるという問題もある。 For example, a radiation monitor is provided with a radiation detection unit for detecting radiation and a gamma ray source installed in the vicinity thereof, and the gamma ray source constantly injects radiation of a constant intensity into the radiation detection unit to instruct the radiation detection unit. By checking whether the value is above a certain value, it is confirmed whether the radiation monitor is operating normally. In this type of radiation monitor, it is not possible to measure a desired dose rate such as an air dose rate due to the dose rate from the gamma ray source. Therefore, when measuring the desired dose rate, gamma rays from the gamma ray source are detected as radiation. It is necessary to suppress the incident on the part. As a suppression mechanism for suppressing the incident of gamma rays, a moving mechanism for moving the gamma ray source into the shield or a moving mechanism for moving the shield between the gamma ray source and the radiation detection unit is known. However, in order to use these moving mechanisms, there is a problem that a very large-scale system is required. Further, since the above-mentioned gamma ray source requires a very strong radiation source, there is also a problem that management becomes complicated.
　ガンマ線源を使用せずに放射線モニタが正常に動作しているか否かを診断する方法としては、光パルスを利用する方法が知られている。この方法を用いる場合、線量率の測定に対して、光パルスが影響を与えないような対策を施す必要がある。 As a method of diagnosing whether or not the radiation monitor is operating normally without using a gamma ray source, a method using an optical pulse is known. When this method is used, it is necessary to take measures so that the optical pulse does not affect the measurement of the dose rate.
　特許文献１～５に記載の技術では、放射線検出器の近傍又は内部に光パルスを発生させる光パルス発生器を設け、その光パルス発生器を用いて、放射線検出器に光パルスを入射し、その時に放射線検出器から出力される検出信号に基づいて、放射線検出器の健全性を確認している。 In the techniques described in Patent Documents 1 to 5, an optical pulse generator that generates an optical pulse is provided near or inside the radiation detector, and the optical pulse generator is used to inject an optical pulse into the radiation detector. At that time, the soundness of the radiation detector is confirmed based on the detection signal output from the radiation detector.
　また、特許文献６の技術では、放射線検出器の内部に設置された放射線発光素子に対して、放射線発光素子で発生する波長と異なる波長を有する光を、光ファイバ等の光伝送部を介して照射し、その照射光によって放射線検出素子で発生した光子を計数することで、放射線モニタが正常に動作しているか否かを確認している。 Further, in the technique of Patent Document 6, light having a wavelength different from the wavelength generated by the radiation emitting element is transmitted to the radiation emitting element installed inside the radiation detector via an optical transmission unit such as an optical fiber. By irradiating and counting the photons generated by the radiation detection element by the irradiation light, it is confirmed whether or not the radiation monitor is operating normally.
特許１８５３６０５号Patent No. 1853605 特許１９４２０３５号Patent No. 1942035 特許４１５７３８９号Patent No. 4157389 特許４６７９８６２号Patent No. 4679862 特許５３３６８３６号Patent No. 5336836 特開２０１８－０３６２０４号公報Japanese Unexamined Patent Publication No. 2018-032644
　特許文献１～５に記載の技術では、放射線検出器の近傍又は内部に光パルス発生器が設けられるため、健全性が確認できなかった場合に、放射線検出器に不具合が生じているのか、光パルス発生器に不具合が生じているのかを判断することが難しい。また、高温または高線量率の環境下では、光パルス発生器が正常に動作できない可能性もある。 In the techniques described in Patent Documents 1 to 5, an optical pulse generator is provided near or inside the radiation detector. Therefore, if the soundness cannot be confirmed, the radiation detector may have a problem or light. It is difficult to determine if the pulse generator is defective. In addition, the optical pulse generator may not operate normally in a high temperature or high dose rate environment.
　特許文献６に記載の技術では、放射線検出器の近傍又は内部に光パルス発生器を設ける必要がない。しかしながら、放射線発光素子で発光する波長と異なる波長の光を発生させるための発光部、及び、放射線発光素子で発光した光を選択的に取り出すための光選択フィルタ等が必要となるため、複雑で高価なシステムが必要となるという問題がある。 In the technique described in Patent Document 6, it is not necessary to provide an optical pulse generator near or inside the radiation detector. However, it is complicated because a light emitting unit for generating light having a wavelength different from the wavelength emitted by the radiation emitting element and a light selection filter for selectively extracting the light emitted by the radiation emitting element are required. There is a problem that an expensive system is required.
　本発明の目的は、上記課題を鑑みてなされたものであり、正常に動作しているか否かを離れた場所から簡易で安価に確認することが可能な放射線モニタ及び放射線測定方法を提供することである。 An object of the present invention has been made in view of the above problems, and to provide a radiation monitor and a radiation measurement method capable of easily and inexpensively confirming whether or not a device is operating normally from a remote location. Is.
　本開示の一態様に従う放射線モニタは、入射された放射線に応じて光子を放出する放射線発光素子を有する放射線検出部と、アルファ線を放出して前記放射線検出部に入射させるアルファ線放出核種と、前記放射線発光素子にて放出された光子を伝送する光伝送部と、前記光伝送部にて伝送された光子を検出する光検出部と、前記光検出部にて検出された光子の計数率を測定する測定部と、前記測定部にて測定された計数率に基づいて、放射線の線量率を求めるとともに、当該放射線モニタが正常に動作しているか否かを診断する解析部と、を有する。 A radiation monitor according to one aspect of the present disclosure includes a radiation detection unit having a radiation emitting element that emits photons in response to incident radiation, an alpha ray emitting nuclei species that emits alpha rays and causes them to enter the radiation detection unit. An optical transmission unit that transmits photons emitted by the radiation emitting element, an optical detection unit that detects photons transmitted by the optical transmission unit, and a count rate of photons detected by the optical detection unit. It has a measuring unit for measurement and an analysis unit for obtaining a radiation dose rate based on the counting rate measured by the measuring unit and diagnosing whether or not the radiation monitor is operating normally.
　本発明によれば、正常に動作しているか否かを離れた場所から簡易で安価に確認することが可能になる。 According to the present invention, it is possible to easily and inexpensively confirm whether or not it is operating normally from a remote location.
本開示の実施例１に係る放射線モニタの構成の一例を示す図である。It is a figure which shows an example of the structure of the radiation monitor which concerns on Example 1 of this disclosure. アルファ線放出物質の設置例を示す図である。It is a figure which shows the installation example of the alpha ray emitting substance. アルファ線放出物質の他の設置例を示す図である。It is a figure which shows the other installation example of the alpha ray emitting substance. アルファ線放出物質の他の設置例を示す図である。It is a figure which shows the other installation example of the alpha ray emitting substance. アルファ線放出物質の他の設置例を示す図である。It is a figure which shows the other installation example of the alpha ray emitting substance. 測定装置で測定される光子の計数率の時間変化の一例を示す図である。It is a figure which shows an example of the time change of the count rate of a photon measured by a measuring device. 本開示の実施例１に係る放射線モニタの動作を説明するためのフローチャートである。It is a flowchart for demonstrating the operation of the radiation monitor which concerns on Example 1 of this disclosure. アルファ線の平均計数率の時刻変化の一例を示す図である。It is a figure which shows an example of the time change of the average count rate of an alpha ray. 測定装置で測定される光子の計数率の時間変化の他の例を示す図である。It is a figure which shows another example of time change of the count rate of a photon measured by a measuring device. 本開示の実施例２に係る放射線モニタの動作を説明するためのフローチャートである。It is a flowchart for demonstrating the operation of the radiation monitor which concerns on Example 2 of this disclosure. アルファ線による光子の計数率の時刻変化の一例を示す図である。It is a figure which shows an example of the time change of the count rate of a photon by an alpha ray. アルファ線放出物質の他の設置例を示す図である。It is a figure which shows the other installation example of the alpha ray emitting substance. 測定装置で測定される光子の計数率の時間変化の他の例を示す図である。It is a figure which shows another example of time change of the count rate of a photon measured by a measuring device. 本開示の実施例３に係る放射線モニタの動作を説明するためのフローチャートである。It is a flowchart for demonstrating the operation of the radiation monitor which concerns on Example 3 of this disclosure. アルファ線による光子の計数率の時刻変化の一例を示す図である。It is a figure which shows an example of the time change of the count rate of a photon by an alpha ray.
　以下、本開示の実施例について図面を参照して説明する。 Hereinafter, examples of the present disclosure will be described with reference to the drawings.
　本開示の実施例１に係る放射線モニタの一例を図１～図８を用いて説明する。 An example of the radiation monitor according to the first embodiment of the present disclosure will be described with reference to FIGS. 1 to 8.
　図１は、本実施例に係る放射線モニタの構成の一例を示す図である。図１に示す放射線モニタ１００は、放射線検出部１０と、光ファイバ２０と、光検出部３０と、測定装置４０と、解析装置５０とを有する。 FIG. 1 is a diagram showing an example of the configuration of the radiation monitor according to this embodiment. The radiation monitor 100 shown in FIG. 1 includes a radiation detection unit 10, an optical fiber 20, a light detection unit 30, a measurement device 40, and an analysis device 50.
　放射線検出部１０は、放射線を検出する検出部である。放射線検出部１０は、放射線発光素子１と、アルファ線放出物質２とを有する。 The radiation detection unit 10 is a detection unit that detects radiation. The radiation detection unit 10 includes a radiation emitting element 1 and an alpha ray emitting substance 2.
　放射線発光素子１は、入射された放射線に応じて光子を放出する。放射線発光素子１としては、例えば、イットリウム・アルミ・ガーネットのようなセラミックの母材に、イットリビウム、ネオジム、セリウム又はプラセオジウム等の希土類元素を添加した素子が挙げられる。放射線発光素子１は、この例に限らず、例えば、母材に単結晶体が用いられたものでもよい。 The radiation emitting element 1 emits photons according to the incident radiation. Examples of the radiation emitting element 1 include an element obtained by adding a rare earth element such as yttrium, neodymium, cerium or praseodymium to a ceramic base material such as yttrium aluminum garnet. The radiation emitting element 1 is not limited to this example, and for example, a single crystal body may be used as a base material.
　アルファ線放出物質２は、放射線の一種であるアルファ線を放出するアルファ線放出核種を含む物質である。アルファ線放出物質２は、アルファ線放出核種のみで構成されてもよいし、別の物質と混合されていてもよい。アルファ線放出核種は、例えば、半減期が１年以上の核種である。このような核種としては、例えば、ポロニウム２１０、トリウム２２９、トリウム２３０、ウラン２３３、ウラン２３４、ウラン２３５、ウラン２３８、ネプツニウム２３７、プルトニウム２３８、プルトニウム２３９、アメリシウム２４１、アメリシウム２４３、キュリウム２４４、キュリウム２４５、キュリウム２４６、キュリウム２４７及びキュリウム２４８等が挙げられる。また、アルファ線放出物質２は、半減期が１年以上の核種と放射平衡が成立している核種を含んでもよい。また、アルファ線放出核種の種類及び量は、放射性物質に関する法的な規制の対象外となることが望ましい。 Alpha ray emitting substance 2 is a substance containing an alpha ray emitting nuclide that emits alpha ray which is a kind of radiation. The alpha ray emitting substance 2 may be composed only of the alpha ray emitting nuclide, or may be mixed with another substance. Alpha ray emitting nuclides are, for example, nuclides having a half-life of one year or more. Examples of such nuclei include polonium 210, thorium 229, thorium 230, uranium 233, uranium 234, uranium 235, uranium 238, neptunium 237, plutonium 238, plutonium 239, americium 241, curium 243, curium 244, and curium 245. , Curium 246, Curium 247, Curium 248 and the like. Further, the alpha ray emitting substance 2 may contain a nuclide having a half-life of one year or more and a nuclide having a radiation equilibrium. In addition, it is desirable that the types and amounts of alpha-emitting nuclides are not subject to legal regulations regarding radioactive substances.
　光ファイバ２０は、放射線検出部１０の放射線発光素子１と光検出部３０とを光学的に接続する光伝送部であり、放射線検出部１０の放射線発光素子１にて放出された光子を光検出部３０まで伝送する。 The optical fiber 20 is an optical transmission unit that optically connects the radiation light emitting element 1 of the radiation detection unit 10 and the light detection unit 30, and detects photons emitted by the radiation light emitting element 1 of the radiation detection unit 10. It transmits to unit 30.
　光検出部３０は、放射線発光素子１にて放出されて光ファイバ２０を伝送されてきた光子を１個ずつ検出し、各光子を電気信号（具体的には、電気パルス信号）に変換して出力する。 The light detection unit 30 detects one photon emitted by the radiation emitting element 1 and transmitted through the optical fiber 20, and converts each photon into an electric signal (specifically, an electric pulse signal). Output.
　測定装置４０は、光検出部３０からの電気信号に基づいて、光検出部３０にて検出された光子の単位時間当たりの数である計数率を測定する測定部である。 The measuring device 40 is a measuring unit that measures a counting rate, which is the number of photons detected by the photodetector 30 per unit time, based on an electric signal from the photodetector 30.
　解析装置５０は、測定装置４０にて測定された計数率に基づいて、放射線の線量率を算出するとともに、放射線モニタ１００が正常に動作しているか否かを診断する。放射線の線量率は、本実施例では、放射線検出部１０が配置された空間におけるガンマ線の線量率である空間線量率である。また、本実施例では、解析装置５０は、放射線の線量率の算出と放射線モニタ１００の診断とに必要な情報をデータベースに格納して保持している。しかしながら、データベースは解析装置５０とは別の外部装置（図示せず）にて保持されていてもよい。 The analysis device 50 calculates the radiation dose rate based on the counting rate measured by the measuring device 40, and diagnoses whether or not the radiation monitor 100 is operating normally. In this embodiment, the radiation dose rate is the air dose rate, which is the dose rate of gamma rays in the space where the radiation detection unit 10 is arranged. Further, in this embodiment, the analysis device 50 stores and holds in a database information necessary for calculating the radiation dose rate and diagnosing the radiation monitor 100. However, the database may be held by an external device (not shown) different from the analysis device 50.
　図２～図５は、アルファ線放出物質２の設置例を示す図である。 2 to 5 are diagrams showing an installation example of the alpha ray emitting substance 2.
　図２の例では、アルファ線放出物質２は、放射線発光素子１における光ファイバ２０が接続（設置）される側とは反対側の表面に塗布されている。アルファ線放出物質２は、例えば、蒸着により塗布されてもよいし、物理スパッタリングにより塗布されてもよい。この例の場合、アルファ線放出物質２自身によるアルファ線のエネルギ損失が小さくなるように、アルファ線放出物質２を十分薄くすることが望ましい。この例では、アルファ線放出物質２を容易に設置しつつ、アルファ線放出物質２の脱落を軽減することができる。 In the example of FIG. 2, the alpha ray emitting substance 2 is applied to the surface of the radiation emitting element 1 on the side opposite to the side to which the optical fiber 20 is connected (installed). The alpha ray emitting substance 2 may be applied, for example, by vapor deposition or by physical sputtering. In the case of this example, it is desirable to make the alpha ray emitting substance 2 sufficiently thin so that the energy loss of the alpha ray by the alpha ray emitting substance 2 itself is small. In this example, it is possible to reduce the dropout of the alpha ray emitting substance 2 while easily installing the alpha ray emitting substance 2.
　図３の例では、予め形成されたアルファ線放出物質２が、放射線発光素子１における光ファイバ２０が接続される側とは反対側の表面の近傍に配置されている。この例の場合、アルファ線放出物質２を十分薄くするとともに、放射線発光素子１とアルファ線放出物質２との間に存在する物質（通常、空気等の気体）によるアルファ線のエネルギ損失が小さくなるように、放射線発光素子１とアルファ線放出物質２とを十分に近づけることが望ましい。この例では、アルファ線放出物質２の取り外し及び変更などが容易となる In the example of FIG. 3, the preformed alpha ray emitting substance 2 is arranged near the surface of the radiation emitting element 1 on the side opposite to the side to which the optical fiber 20 is connected. In the case of this example, the alpha ray emitting substance 2 is made sufficiently thin, and the energy loss of alpha rays due to the substance (usually a gas such as air) existing between the radiation emitting element 1 and the alpha ray emitting substance 2 becomes small. As described above, it is desirable that the radiation emitting element 1 and the alpha ray emitting substance 2 are sufficiently close to each other. In this example, the alpha ray emitting substance 2 can be easily removed and changed.
　図４の例では、アルファ線放出物質２が放射線発光素子１に混入されている。例えば、放射線発光素子１の原料にアルファ線放出物質２を少量混ぜた原料を用いて放射線発光素子１を製作することで、アルファ線放出物質２を放射線発光素子１に混入させることができる。この例の場合、放射線発光素子１は放射線発光素子１で発光する光子に対して十分な透過性を有することが望ましい。この例では、図２及び図３の例と比べて、アルファ線のエネルギ損失の影響を抑制することが可能になる。 In the example of FIG. 4, the alpha ray emitting substance 2 is mixed in the radiation emitting element 1. For example, by manufacturing the radiation emitting element 1 by using a raw material obtained by mixing a small amount of the alpha ray emitting substance 2 with the raw material of the radiation emitting element 1, the alpha ray emitting substance 2 can be mixed with the radiation emitting element 1. In the case of this example, it is desirable that the radiation emitting element 1 has sufficient transparency to the photons emitted by the radiation emitting element 1. In this example, it is possible to suppress the influence of energy loss of alpha rays as compared with the examples of FIGS. 2 and 3.
　図５の例では、放射線発光素子１における光ファイバ２０が接続される面とは異なる面に、光を反射する光反射膜３が形成される。光反射膜３は、例えば、アルミニウム、銀、金又はクロムなどで形成される。また、光反射膜３の近傍に、予め形成されたアルファ線放出物質２が設置される。この例の場合、放射線発光素子１（光反射膜３）とアルファ線放出物質２とを十分に近づけるとともに、光反射膜３によるアルファ線のエネルギ損失が小さくなるように、光反射膜３の材料及び厚さが調整されることが望ましい。例えば、光反射膜３によるアルファ線のエネルギ損失は、アルファ線放出物質２からのアルファ線のエネルギの１／１０以下であることが望ましい。この例では、光の放射線発光素子１への入射率を高くすることが可能となる。 In the example of FIG. 5, a light reflecting film 3 that reflects light is formed on a surface different from the surface of the radiation emitting element 1 to which the optical fiber 20 is connected. The light reflecting film 3 is made of, for example, aluminum, silver, gold, chromium, or the like. Further, a preformed alpha ray emitting substance 2 is installed in the vicinity of the light reflecting film 3. In the case of this example, the material of the light reflecting film 3 is such that the radiation emitting element 1 (light reflecting film 3) and the alpha ray emitting substance 2 are sufficiently brought close to each other and the energy loss of alpha rays by the light reflecting film 3 is reduced. And the thickness should be adjusted. For example, it is desirable that the energy loss of alpha rays due to the light reflecting film 3 is 1/10 or less of the energy of alpha rays from the alpha ray emitting substance 2. In this example, it is possible to increase the incident rate of light on the radiation emitting element 1.
　図６は、測定装置４０で測定される光子の計数率の時間変化の一例を示す図である。図６では、横軸は時間を示し、縦軸は光子の計数率を示す。 FIG. 6 is a diagram showing an example of a time change in the count rate of photons measured by the measuring device 40. In FIG. 6, the horizontal axis represents time and the vertical axis represents photon counting rate.
　図６で示されたように、アルファ線放出物質２から放出されるアルファ線が放射線発光素子１に入射していない場合、光子の計数率は、放射線検出部１０が設置された場所の空間線量率（ガンマ線の線量率）に応じた値となる。図６の例では、ガンマ線の線量率に応じた計数率（以下、ガンマ線による光の計数率と呼ぶこともある）は略一定としている。 As shown in FIG. 6, when the alpha rays emitted from the alpha ray emitting substance 2 are not incident on the radiation emitting element 1, the photon count rate is the air dose at the place where the radiation detection unit 10 is installed. The value corresponds to the rate (dose rate of gamma rays). In the example of FIG. 6, the counting rate according to the dose rate of gamma rays (hereinafter, may be referred to as the counting rate of light by gamma rays) is substantially constant.
　また、アルファ線放出物質２から放出されるアルファ線が放射線発光素子１に入射した場合、放射線発光素子１に大きなエネルギが付与されるため、放射線発光素子１にて発生する光子が急激に増加し、それに伴い、光子の計数率が急激に増加する。急激に増加した計数率は、その後、放射線発光素子１の発光減衰時定数に従って減少し、ガンマ線による光の計数率に戻る。 Further, when the alpha rays emitted from the alpha ray emitting substance 2 are incident on the radiation emitting element 1, a large amount of energy is applied to the radiation emitting element 1, so that the number of photons generated in the radiation emitting element 1 rapidly increases. As a result, the photon counting rate increases sharply. The rapidly increasing counting rate then decreases according to the emission attenuation time constant of the radiation emitting element 1 and returns to the counting rate of light by gamma rays.
　例えば、アルファ線放出物質２に含まれるアルファ線放出核種として、アメリシウム２４１を用いた場合、１個のアルファ線が放射線発光素子１に入射すると、約５．５ＭｅＶのエネルギが短時間に放射線発光素子１に対して付与されるため、光子の計数率が急激に増加する。このとき、放射線発光素子１として、ネオジムが添加されたイットリウム・アルミニウム・ガーネットを用いた場合、光減衰時定数が２３０マイクロ秒であることから、アルファ線の入射により急激に増加した計数率は、数ミリ秒程度でガンマ線による光の計数率に戻る。 For example, when Americium-241 is used as the alpha ray emitting nuclide contained in the alpha ray emitting substance 2, when one alpha ray is incident on the radiation emitting element 1, the energy of about 5.5 MeV is generated in a short time. Since it is given to 1, the photon count rate increases sharply. At this time, when yttrium aluminum garnet to which neodymium is added is used as the radiation emitting element 1, since the light attenuation time constant is 230 microseconds, the count rate that rapidly increases due to the incident of alpha rays is It returns to the light count rate by gamma rays in a few milliseconds.
　解析装置５０は、測定装置４０で測定される光子の計数率の時間変化を解析して、アルファ線によって計数率が増加している時間であるアルファ線影響時間を特定する。解析装置５０は、アルファ線影響時間に測定された光子の計数率に基づいて、放射線発光素子１に入射したアルファ線に応じた数値を算出する。本実施例では、その数値としては、アルファ線の計数率（より具体的には、十分長い計測時間（例えば、１ｓ）における平均計数率）を算出する。解析装置５０は、アルファ線の計数率に基づいて、放射線モニタ１００が正常に動作しているか否かを診断する。 The analysis device 50 analyzes the time change of the counting rate of photons measured by the measuring device 40, and identifies the alpha ray influence time, which is the time when the counting rate is increased by alpha rays. The analyzer 50 calculates a numerical value corresponding to the alpha rays incident on the radiation emitting element 1 based on the count rate of photons measured during the alpha ray influence time. In this embodiment, the alpha ray count rate (more specifically, the average count rate in a sufficiently long measurement time (for example, 1 s)) is calculated as the numerical value. The analyzer 50 diagnoses whether or not the radiation monitor 100 is operating normally based on the alpha ray count rate.
　また、アルファ線影響時間以外の時間範囲である線量率算出時間における計数率は、空間線量率に応じた計数率となる。このため、解析装置５０は、線量率算出時間における計数率に基づいて、放射線検出部１０が配置された空間の空間線量率を測定する。 In addition, the counting rate in the dose rate calculation time, which is the time range other than the alpha ray influence time, is the counting rate according to the air dose rate. Therefore, the analysis device 50 measures the air dose rate in the space where the radiation detection unit 10 is arranged, based on the count rate in the dose rate calculation time.
　このとき、アルファ線影響時間が長いほど、空間線量率を測定するための線量率算出時間が短くなってしまうため、アルファ線放出物質２には、放射線発光素子１の発光減衰時定数に応じた適度な強度のアルファ線放出核種を使用する必要がある。例えば、アルファ線影響時間が線量率算出時間の１／１０以下となるようにすることが望ましい。 At this time, the longer the alpha ray influence time, the shorter the dose rate calculation time for measuring the air dose rate. Therefore, the alpha ray emitting substance 2 corresponds to the emission attenuation time constant of the radiation emitting element 1. It is necessary to use alpha ray emitting nuclei of moderate intensity. For example, it is desirable that the alpha ray influence time is 1/10 or less of the dose rate calculation time.
　なお、放射線発光素子１として、ネオジム添加のイットリウム・アルミニウム・ガーネットを用いた場合、１個のアルファ線に対応するアルファ線影響時間は、数ミリ秒である。このため、アルファ線放出核種から放出されるアルファ線が平均毎秒２０個である場合、その半分の１０個が放射線発光素子１に入射すると仮定すると、毎秒当たりのアルファ線影響時間は数１０ミリ秒となる。この場合、アルファ線影響時間は、空間線量率の測定精度に対してほぼ影響を与えない。 When yttrium aluminum garnet with neodymium added is used as the radiation emitting element 1, the alpha ray influence time corresponding to one alpha ray is several milliseconds. Therefore, if the average number of alpha rays emitted from alpha ray emitting nuclides is 20 per second, and assuming that 10 of them are incident on the radiation emitting element 1, the alpha ray influence time per second is several tens of milliseconds. It becomes. In this case, the alpha ray effect time has almost no effect on the measurement accuracy of the air dose rate.
　また、複数のアルファ線が短い時間間隔で放出されると、各アルファ線によるアルファ線影響時間が重なり合ってしまう恐れがある。このため、アルファ線放出核種の種類及び量は、各アルファ線によるアルファ線影響時間ができるだけ重なり合わないように調整されることが望ましい。 Also, if multiple alpha rays are emitted at short time intervals, there is a risk that the alpha ray influence times of each alpha ray will overlap. Therefore, it is desirable that the types and amounts of alpha-emitting nuclides be adjusted so that the alpha-ray influence times of each alpha-ray do not overlap as much as possible.
　図７は、放射線モニタ１００の動作を説明するためのフローチャートである。
　先ず、光検出部３０は、放射線検出部１０の放射線発光素子１に入射した放射線によって放出され、光ファイバ２０を伝送されてきた光子を１個ずつ検出し、その検出した光子を電気信号に変換して出力する（ステップＳ１０１）。 FIG. 7 is a flowchart for explaining the operation of the radiation monitor 100.
First, the photodetector 30 detects the photons emitted by the radiation incident on the radiation emitting element 1 of the radiation detection unit 10 and transmitted through the optical fiber 20 one by one, and converts the detected photons into an electric signal. And output (step S101).
　測定装置４０は、光検出部３０からの電気信号に基づいて、放射線発光素子１に入射した放射線によって放出された光子の計数率を測定し、その計数率を解析装置５０に通知する（ステップＳ１０２）。 The measuring device 40 measures the count rate of photons emitted by the radiation incident on the radiation emitting element 1 based on the electric signal from the photodetector 30, and notifies the analyzer 50 of the count rate (step S102). ).
　解析装置５０は、測定装置４０から通知された計数率の時間変化を解析して、計数率の急激な増減が発生したか否かを判断する（ステップＳ１０３）。例えば、解析装置５０は、計数率が閾値以上となり、その後、所定時間以内に閾値以下となった場合、計数率の急激な増減が発生したと判断する。所定時間は、例えば、放射線発光素子１の発光減衰時定数の１０倍程度以内の時間である。放射線発光素子１としてネオジム添加のイットリウム・アルミニウム・ガーネットが用いられた場合、発光減衰時定数が２３０マイクロ秒であるため、所定時間は、２．３ミリ秒以内に予め設定される。また、閾値は、予め測定した空間線量率の統計精度（例えば、標準誤差）に応じて定められてもよい。 The analysis device 50 analyzes the time change of the counting rate notified from the measuring device 40, and determines whether or not a sudden increase or decrease in the counting rate has occurred (step S103). For example, the analysis device 50 determines that a sudden increase or decrease in the counting rate has occurred when the counting rate becomes equal to or higher than the threshold value and then falls below the threshold value within a predetermined time. The predetermined time is, for example, a time within about 10 times the emission attenuation time constant of the radiation emitting element 1. When yttrium aluminum garnet with neodymium added is used as the radiation emitting element 1, the predetermined time is set in advance within 2.3 milliseconds because the emission attenuation time constant is 230 microseconds. Further, the threshold value may be determined according to the statistical accuracy (for example, standard error) of the air dose rate measured in advance.
　計数率の急激な増減が発生していない場合（ステップＳ１０３：ＮＯ）、解析装置５０は、測定された計数率を、ガンマ線による光子の計数率として算出し、その計数率に基づいて、予め設定された計測時間内におけるガンマ線による光子の平均計数率を算出する（ステップＳ１０４）。 When there is no sudden increase or decrease in the counting rate (step S103: NO), the analyzer 50 calculates the measured counting rate as the counting rate of photons by gamma rays and sets it in advance based on the counting rate. The average counting rate of photons by gamma rays within the measured measurement time is calculated (step S104).
　解析装置５０は、保持しているデータベースを参照し、そのデータベースとガンマ線による光子の平均計数率とに基づいて、放射線検出部１０が設置された場所の空間線量率を算出する（ステップＳ１０５）。データベースは、光子の平均計数率と空間線量率との関係を示す情報を含む。具体的には、光子の平均計数率と空間線量率とには比例関係があるため、データベースは、光子の平均計数率と空間線量率との比例係数を含む。この場合、解析装置５０は、ガンマ線による光子の平均計数率に第１のデータベース内の比例係数を乗算することで、空間線量率を算出する。 The analysis device 50 refers to the database it holds, and calculates the air dose rate at the place where the radiation detection unit 10 is installed based on the database and the average counting rate of photons by gamma rays (step S105). The database contains information showing the relationship between the average photon count rate and the air dose rate. Specifically, since there is a proportional relationship between the average photon count rate and the air dose rate, the database includes a proportional coefficient between the average photon count rate and the air dose rate. In this case, the analyzer 50 calculates the air dose rate by multiplying the average count rate of photons by gamma rays by the proportional coefficient in the first database.
　また、計数率の急激な増減が発生した場合（ステップＳ１０３：ＹＥＳ）、解析装置５０は、計数率の急激な増減が発生したことを、アルファ線が放射線発光素子１に入射したこととして検出する（ステップＳ１０６）。 Further, when a sudden increase / decrease in the counting rate occurs (step S103: YES), the analysis device 50 detects that a sudden increase / decrease in the counting rate has occurred as an alpha ray incident on the radiation emitting element 1. (Step S106).
　また、解析装置５０は、ステップＳ１０６の検出結果に基づいて、計測時間内におけるアルファ線の計数率（放射線発光素子１に入射したアルファ線の単位時間当たりの数）の平均値をアルファ線の平均計数率として算出する（ステップＳ１０７）。 Further, the analyzer 50 sets the average value of the alpha ray count rate (the number of alpha rays incident on the radiation emitting element 1 per unit time) within the measurement time as the average value of the alpha rays based on the detection result in step S106. It is calculated as a counting rate (step S107).
　なお、アルファ線放出物質２のアルファ線放出核種からアルファ線が放出される放出間隔は一定ではないが、十分な統計精度となる時間における放出間隔の平均値は、アルファ線放出核種の放射能（半減期）に比例した値となる。したがって、アルファ線放出核種の半減期が十分長い場合は、計測時間を十分な統計精度となる時間に設定しておけば、アルファ線の平均計数率はほぼ一定となる。 Although the emission interval at which alpha rays are emitted from the alpha ray emitting nuclide of the alpha ray emitting substance 2 is not constant, the average value of the emission interval at a time when sufficient statistical accuracy is obtained is the radioactivity of the alpha ray emitting nuclide ( The value is proportional to the half-life). Therefore, when the half-life of alpha-emitting nuclides is sufficiently long, the average counting rate of alpha rays becomes almost constant if the measurement time is set to a time that provides sufficient statistical accuracy.
　解析装置５０は、保持しているデータベースを参照して、アルファ線の平均計数率が所定の第１範囲に含まれるか否かを判断する（ステップＳ１０８）。なお、データベースは、第１範囲を示す情報を含む。第１範囲は、例えば、予め測定したアルファ線の平均計数率の統計精度に応じて定められる。 The analysis device 50 refers to the retained database and determines whether or not the average counting rate of alpha rays is included in the predetermined first range (step S108). The database contains information indicating the first range. The first range is determined, for example, according to the statistical accuracy of the average counting rate of alpha rays measured in advance.
　アルファ線の平均計数率が第１範囲に含まれる場合（ステップＳ１０８：ＹＥＳ）、解析装置５０は、放射線モニタ１００が正常に動作していると判断して、例えば、放射線モニタ１００が正常に動作している旨のメッセージを出力する（ステップＳ１０９）。一方、アルファ線の平均計数率が第１範囲に含まれない場合（ステップＳ１０８：ＮＯ）、解析装置５０は、放射線モニタ１００が正常に動作していないと判断して、例えば、異常が発生した旨のアラームを出力する（ステップＳ１１０）。 When the average counting rate of alpha rays is included in the first range (step S108: YES), the analyzer 50 determines that the radiation monitor 100 is operating normally, and for example, the radiation monitor 100 operates normally. A message indicating that the message is being output is output (step S109). On the other hand, when the average counting rate of alpha rays is not included in the first range (step S108: NO), the analyzer 50 determines that the radiation monitor 100 is not operating normally, and for example, an abnormality has occurred. An alarm to that effect is output (step S110).
　図８は、放射線モニタ１００にて算出されたアルファ線の平均計数率の時刻変化の一例を示す図である。図８では、横軸は時間を示し、縦軸は平均計数率を示す。また、時刻ｔ１で放射線モニタ１００に異常（具体的には、光ファイバ２０の断線）が生じている。 FIG. 8 is a diagram showing an example of a time change of the average counting rate of alpha rays calculated by the radiation monitor 100. In FIG. 8, the horizontal axis represents time and the vertical axis represents the average counting rate. Further, at time t1, an abnormality (specifically, a disconnection of the optical fiber 20) has occurred in the radiation monitor 100.
　図８に示されたように光ファイバ２０の断線が生じる時刻ｔ１よりも前では、アルファ線の平均計数率は統計精度の範囲（第１範囲）に含まれる。時刻ｔ１で光ファイバ２０の断線が生じると、アルファ線の平均計数率がゼロとなり、統計精度の範囲から外れる。これにより、解析装置５０は、異常を検知して、放射線モニタ１００が正常に動作していないと判断する。 As shown in FIG. 8, before the time t1 when the optical fiber 20 is disconnected, the average counting rate of alpha rays is included in the range of statistical accuracy (first range). If the optical fiber 20 is disconnected at time t1, the average counting rate of alpha rays becomes zero, which is out of the range of statistical accuracy. As a result, the analysis device 50 detects the abnormality and determines that the radiation monitor 100 is not operating normally.
　以上説明したように本実施例によれば、放射線検出部１０は、入射された放射線に応じて光子を放出する放射線発光素子１を有する。アルファ線放出物質２は、アルファ線を放出して放射線検出部１０に入射させる。光ファイバ２０は、放射線発光素子１にて放出された光子を伝送する。光検出部３０は、光ファイバ２０にて伝送された光子を検出する。測定装置４０は、光検出部３０にて検出された光子の計数率を測定する。解析装置５０は、測定装置４０にて測定された計数率に基づいて、放射線の線量率を求めるとともに、放射線モニタ１００が正常に動作しているか否かを診断する。 As described above, according to the present embodiment, the radiation detection unit 10 has a radiation emitting element 1 that emits photons in response to the incident radiation. The alpha ray emitting substance 2 emits alpha rays and causes them to enter the radiation detection unit 10. The optical fiber 20 transmits the photons emitted by the radiation emitting element 1. The photodetector 30 detects photons transmitted by the optical fiber 20. The measuring device 40 measures the count rate of photons detected by the photodetector 30. The analysis device 50 obtains the radiation dose rate based on the counting rate measured by the measuring device 40, and diagnoses whether or not the radiation monitor 100 is operating normally.
　このため、光パルス発生器及び光選択フィルタ等の設備を用いなくても、放射線モニタ１００を取り外したり、放射線検出部１０の近傍にいったりせずに、放射線モニタ１００が正常に動作しているか否かを確認することが可能になる。したがって、正常に動作しているか否かを離れた場所から簡易で安価に確認することが可能になる。 Therefore, is the radiation monitor 100 operating normally without removing the radiation monitor 100 or moving to the vicinity of the radiation detection unit 10 without using equipment such as an optical pulse generator and a light selection filter? It becomes possible to confirm whether or not. Therefore, it is possible to easily and inexpensively check whether or not it is operating normally from a remote location.
　特に放射線発光素子１に入射したアルファ線に応じた数値、具体的には放射線発光素子１に入射したアルファ線の計数率に基づいて放射線モニタ１００が正常に動作しているか否かが診断されるため、解析装置５０にも特別な機器が必要なり。 In particular, it is diagnosed whether or not the radiation monitor 100 is operating normally based on the numerical value corresponding to the alpha rays incident on the radiation emitting element 1, specifically, the count rate of the alpha rays incident on the radiation emitting element 1. Therefore, the analyzer 50 also requires special equipment.
　本開示の実施例２に係る放射線モニタの一例を図９～図１１を用いて説明する。本実施例では、放射線発光素子１に入射したアルファ線に応じた数値として、アルファ線の平均計数率の代わりに、アルファ線による光子（アルファ線が放射線発光素子１に入射したことで生じる光子）の計数率に基づいて、放射線モニタ１００が正常に動作しているか否かを診断する点で実施例１とは異なる。 An example of the radiation monitor according to the second embodiment of the present disclosure will be described with reference to FIGS. 9 to 11. In this embodiment, as a numerical value corresponding to the alpha ray incident on the radiation emitting element 1, instead of the average counting rate of the alpha ray, a photon by an alpha ray (a photon generated by the alpha ray incident on the radiation emitting element 1). It is different from the first embodiment in that it diagnoses whether or not the radiation monitor 100 is operating normally based on the counting rate of.
　図９は、測定装置４０で測定される光子の計数率の時間変化の一例を示す図である。図９では、横軸は時間を示し、縦軸は光子の計数率を示す。 FIG. 9 is a diagram showing an example of a time change of the photon count rate measured by the measuring device 40. In FIG. 9, the horizontal axis represents time and the vertical axis represents photon counting rate.
　実施例１で説明したように、アルファ線放出物質２から放出されるアルファ線が放射線発光素子１に入射した場合、放射線発光素子１に大きなエネルギが付与されるため、放射線発光素子１にて発生する光子の計数率は、急激に増加し、その後、放射線発光素子１の発光減衰時定数に従って減少し、ガンマ線に応じた光子の計数率に戻る。 As described in the first embodiment, when the alpha rays emitted from the alpha ray emitting substance 2 are incident on the radiation emitting element 1, a large amount of energy is applied to the radiation emitting element 1, so that it is generated in the radiation emitting element 1. The counting rate of photons increases sharply, then decreases according to the emission attenuation time constant of the radiation emitting element 1, and returns to the counting rate of photons according to gamma rays.
　このとき、アルファ線によって計数率が増加している時間であるアルファ線影響時間に測定された計数率の和から、アルファ線影響時間におけるガンマ線による光子の計数率の和を差し引いた値が、アルファ線影響時間におけるアルファ線による光子の計数となる。また、アルファ線による光子の計数を、アルファ線影響時間で除算した値がアルファ線による光子の計数率となる。 At this time, the value obtained by subtracting the sum of the count rates of photons by gamma rays at the alpha ray influence time from the sum of the count rates measured in the alpha ray influence time, which is the time when the count rate is increasing by alpha rays, is alpha. It is the count of photons by alpha rays in the line influence time. Further, the value obtained by dividing the photon count by alpha rays by the alpha ray influence time is the photon count rate by alpha rays.
　図１０は、本実施例による放射線モニタ１００の動作を説明するためのフローチャートである。 FIG. 10 is a flowchart for explaining the operation of the radiation monitor 100 according to this embodiment.
　先ず、図７を用いて説明したステップＳ１０１～Ｓ１０６と同様なの処理が実行される。 First, the same processing as in steps S101 to S106 described with reference to FIG. 7 is executed.
　ステップＳ１０６が終了すると、解析装置５０は、計数率の急激な増減が発生したアルファ線影響時間に測定された計数率の和から、アルファ線影響時間におけるガンマ線による光子の計数率の和を差し引いて、アルファ線影響時間におけるアルファ線による光子の計数を算出する。そして、解析装置５０は、アルファ線による光子の計数をアルファ線影響時間で除算して、アルファ線による光子の計数率を算出する（ステップＳ２０１）。なお、アルファ線影響時間におけるガンマ線による光子の計数率の和は、例えば、ステップＳ１０５で算出した平均計数率にアルファ線影響時間を乗算した値である。 When step S106 is completed, the analyzer 50 subtracts the sum of the count rates of photons by gamma rays at the alpha ray influence time from the sum of the count rates measured at the alpha ray influence time when the count rate suddenly increases or decreases. , Calculate the count of photons by alpha rays at the alpha ray influence time. Then, the analysis device 50 divides the photon count by the alpha ray by the alpha ray influence time to calculate the photon count rate by the alpha ray (step S201). The sum of the photon count rates by gamma rays in the alpha ray influence time is, for example, a value obtained by multiplying the average count rate calculated in step S105 by the alpha ray influence time.
　解析装置５０は、保持しているデータベースを参照して、アルファ線による光子の平均計数率が所定の第２範囲に含まれるか否かを判断する（ステップＳ２０２）。なお、データベースは、第２範囲を示す情報を含む。第２範囲は、例えば、予め測定したアルファ線による光子の平均計数率の統計精度に応じて定められる。 The analysis device 50 refers to the database it holds and determines whether or not the average counting rate of photons due to alpha rays is included in the predetermined second range (step S202). The database contains information indicating the second range. The second range is determined, for example, according to the statistical accuracy of the average counting rate of photons by alpha rays measured in advance.
　アルファ線による光子の平均計数率が第２範囲に含まれる場合（ステップＳ２０２：ＹＥＳ）、解析装置５０は、放射線モニタ１００が正常に動作していると判断して、例えば、放射線モニタ１００が正常に動作している旨のメッセージを出力する（ステップＳ２０３）。一方、アルファ線による光子の平均計数率が第２範囲に含まれない場合（ステップＳ２０２：ＮＯ）、解析装置５０は、放射線モニタ１００が正常に動作していないと判断して、例えば、異常が発生した旨のアラームを出力する（ステップＳ２０４）。 When the average counting rate of photons by alpha rays is included in the second range (step S202: YES), the analyzer 50 determines that the radiation monitor 100 is operating normally, and for example, the radiation monitor 100 is normal. A message indicating that the operation is being performed is output (step S203). On the other hand, when the average counting rate of photons due to alpha rays is not included in the second range (step S202: NO), the analyzer 50 determines that the radiation monitor 100 is not operating normally, and for example, an abnormality occurs. An alarm indicating that it has occurred is output (step S204).
　図１１は、放射線モニタ１００にて算出されたアルファ線による光子の平均計数率の時刻変化の一例を示す図である。図１１では、横軸は時間を示し、縦軸は平均計数率を示す。また、時刻ｔ２で放射線モニタ１００に異常（具体的には、光ファイバ２０の放射線損傷）が生じている。 FIG. 11 is a diagram showing an example of a time change of the average counting rate of photons due to alpha rays calculated by the radiation monitor 100. In FIG. 11, the horizontal axis represents time and the vertical axis represents the average counting rate. Further, at time t2, an abnormality (specifically, radiation damage to the optical fiber 20) has occurred in the radiation monitor 100.
　図１１に示されたように光ファイバ２０の放射線損傷が生じる時刻ｔ２よりも前では、アルファ線による光子の平均計数率は統計精度の範囲（第２範囲）に含まれる。時刻ｔ２で光ファイバ２０の放射線損傷が生じると、アルファ線による光子の平均計数率が徐々に減少し、平均計数率の統計精度の範囲から外れる。これにより、解析装置５０は、異常を検知して、放射線モニタ１００が正常に動作していないと判断する。 As shown in FIG. 11, before the time t2 when the radiation damage of the optical fiber 20 occurs, the average counting rate of photons by alpha rays is included in the range of statistical accuracy (second range). When radiation damage occurs in the optical fiber 20 at time t2, the average counting rate of photons due to alpha rays gradually decreases, and the average counting rate falls out of the statistical accuracy range of the average counting rate. As a result, the analysis device 50 detects the abnormality and determines that the radiation monitor 100 is not operating normally.
　本実施例では、アルファ線による光子の平均計数率に基づいて放射線モニタ１００が正常に動作しているか否かが診断されるため、正常に動作しているか否かを離れた場所から簡易で安価に確認することが可能になる。 In this embodiment, since it is diagnosed whether or not the radiation monitor 100 is operating normally based on the average counting rate of photons by alpha rays, it is easy and inexpensive to determine whether or not it is operating normally from a remote location. It will be possible to confirm to.
　本開示の実施例３に係る放射線モニタの一例を図１２～図１５を用いて説明する。本実施例では、放出するアルファ線のエネルギがそれぞれ異なる複数の種類のアルファ線放出物質（アルファ線放出核種）が設けられている点で実施例２とは異なる。 An example of the radiation monitor according to the third embodiment of the present disclosure will be described with reference to FIGS. 12 to 15. The present embodiment is different from the second embodiment in that a plurality of types of alpha ray emitting substances (alpha ray emitting nuclides) having different emitted alpha ray energies are provided.
　図１２は、本実施例におけるアルファ線放出物質の設置例を示す図である。図１２の例では、アルファ線放出物質２として、放出するアルファ線のエネルギがそれぞれ異なる３種類のアルファ線放出物質２１～２３を有する。なお、アルファ線放出物質２は、３種類に限らず、２種類でもよいし、４種類以上でもよい。 FIG. 12 is a diagram showing an installation example of an alpha ray emitting substance in this embodiment. In the example of FIG. 12, as the alpha ray emitting substance 2, there are three types of alpha ray emitting substances 21 to 23 having different energy of the alpha ray emitted. The alpha ray emitting substance 2 is not limited to three types, and may be two types or four or more types.
　図１２の例では、図２の例と同様に、アルファ線放出物質２１～２３は、放射線発光素子１における光ファイバ２０が接続される側とは反対側の表面に塗布されている。しかしながら、アルファ線放出物質２１～２３は、図３の例と同様に放射線発光素子１における光ファイバ２０が接続される側とは反対側に設置されてもよいし、図４の例と同様に放射線発光素子１に混入されていてもよいし、図５の例と同様に放射線発光素子１における光ファイバ２０が接続される面以外の面に設けられた光反射膜３の近傍に設置されてもよい。 In the example of FIG. 12, the alpha ray emitting substances 21 to 23 are applied to the surface of the radiation emitting element 1 on the side opposite to the side to which the optical fiber 20 is connected, as in the example of FIG. However, the alpha ray emitting substances 21 to 23 may be installed on the side opposite to the side to which the optical fiber 20 is connected in the radiation emitting element 1 as in the example of FIG. 3, or as in the example of FIG. It may be mixed in the radiation emitting element 1, or is installed in the vicinity of the light reflecting film 3 provided on a surface other than the surface to which the optical fiber 20 is connected in the radiation emitting element 1 as in the example of FIG. May be good.
　図１３は、本実施例における測定装置４０で測定される光子の計数率の時間変化の一例を示す図である。図１３では、横軸は時間を示し、縦軸は光子の計数率を示す。 FIG. 13 is a diagram showing an example of a time change of the photon count rate measured by the measuring device 40 in this embodiment. In FIG. 13, the horizontal axis represents time and the vertical axis represents photon counting rate.
　実施例１で説明したように、アルファ線放出物質２から放出されるアルファ線が放射線発光素子１に入射した場合、放射線発光素子１に大きなエネルギが付与されるため、放射線発光素子１にて発生する光子の計数率は、急激に増加し、その後、放射線発光素子１の発光減衰時定数に従って減少し、ガンマ線に応じた光子の計数率に戻る。 As described in the first embodiment, when the alpha rays emitted from the alpha ray emitting substance 2 are incident on the radiation emitting element 1, a large amount of energy is applied to the radiation emitting element 1, so that it is generated in the radiation emitting element 1. The counting rate of photons increases sharply, then decreases according to the emission attenuation time constant of the radiation emitting element 1, and returns to the counting rate of photons according to gamma rays.
　このとき、アルファ線による光子の計数率は、そのアルファ線のエネルギに比例する。このため、図１２の例のようにアルファ線放出物質２として放出するアルファ線のエネルギがそれぞれ異なる３種類のアルファ線放出物質２１～２３が用いられた場合、３つの異なる大きさの計数率が測定される。 At this time, the counting rate of photons by alpha rays is proportional to the energy of the alpha rays. Therefore, when three types of alpha ray emitting substances 21 to 23 having different alpha ray energies are used as the alpha ray emitting substance 2 as in the example of FIG. 12, three different magnitude counting rates are obtained. Be measured.
　図１４は、本実施例による放射線モニタ１００の動作を説明するためのフローチャートである。先ず、図１０を用いて説明したステップＳ１０１～Ｓ１０６及びＳ２０１と同様な処理が実行される。 FIG. 14 is a flowchart for explaining the operation of the radiation monitor 100 according to the present embodiment. First, the same processing as in steps S101 to S106 and S201 described with reference to FIG. 10 is executed.
　ステップＳ２０１が終了すると、解析装置５０は、保持しているデータベースを参照して、アルファ線による光子の平均計数率が第２範囲に含まれるかを判断する（ステップＳ３０１）。ここでは、アルファ線放出物質２として放出するアルファ線のエネルギがそれぞれ異なる３種類のアルファ線放出物質２１～２３が用いられているため、データベースは、第２範囲をアルファ線放出物質ごとに含む。解析装置５０は、アルファ線による光子の平均計数率が３つの第２範囲のいずれかに含まれているか否かを判断する。 When step S201 is completed, the analysis device 50 refers to the held database and determines whether the average counting rate of photons due to alpha rays is included in the second range (step S301). Here, since three types of alpha ray emitting substances 21 to 23 having different alpha ray energies are used as the alpha ray emitting substance 2, the database includes a second range for each alpha ray emitting substance. The analyzer 50 determines whether or not the average counting rate of photons by alpha rays is included in any of the three second ranges.
　アルファ線による光子の平均計数率が第２範囲に含まれる場合（ステップＳ３０１：ＹＥＳ）、解析装置５０は、放射線モニタ１００が正常に動作していると判断して、例えば、放射線モニタ１００が正常に動作している旨のメッセージを出力する（ステップＳ３０２）。 When the average counting rate of photons by alpha rays is included in the second range (step S301: YES), the analyzer 50 determines that the radiation monitor 100 is operating normally, and for example, the radiation monitor 100 is normal. A message indicating that the operation is being performed is output (step S302).
　一方、アルファ線による光子の平均計数率が第２範囲に含まれていない場合（ステップＳ３０１：ＮＯ）、解析装置５０は、放射線モニタ１００に異常が発生している可能性があると判断して、アルファ線放出物質２ごとに、そのアルファ線放出物質２からのアルファ線による光子の平均計数率をそれぞれ算出する（ステップＳ３０３）。例えば、解析装置５０は、一定期間、アルファ線影響時間ごとにアルファ線による光子の平均計数率を算出し、それらの平均計数率を値（平均計数率）の異なる３つのグループに分類し、各グループの平均計数率を予めグループと対応付けたアルファ線放出物質２からのアルファ線による光子の平均計数率とする。 On the other hand, when the average counting rate of photons by alpha rays is not included in the second range (step S301: NO), the analyzer 50 determines that there is a possibility that an abnormality has occurred in the radiation monitor 100. , The average counting rate of photons due to alpha rays from the alpha ray emitting substance 2 is calculated for each alpha ray emitting substance 2 (step S303). For example, the analyzer 50 calculates the average counting rate of photons by alpha rays for each alpha ray influence time for a certain period of time, classifies the average counting rate into three groups having different values (average counting rate), and each of them. Let the average counting rate of the group be the average counting rate of photons due to alpha rays from the alpha ray emitting substance 2 which is associated with the group in advance.
　解析装置５０は、各アルファ線放出物質２からのアルファ線による光子の平均計数率が初期値から同じ割合で変化しているか否かを判断する（ステップＳ３０４）。初期値は、例えば、放射線モニタ１００の運用が開始される前などに予め測定したアルファ線による光子の平均計数率である。また、初期値からの変化の割合が所定の範囲に含まれている場合、解析装置５０は、各アルファ線放出物質２からのアルファ線による光子の平均計数率が初期値から同じ割合で変化していると判断してもよい。所定の範囲は、例えば、予め測定したアルファ線による光子の平均計数率の統計精度に応じて定められる。また、所定の範囲を示す情報は、例えば、解析装置５０が保持しているデータベースに含まれる。 The analyzer 50 determines whether or not the average counting rate of photons due to alpha rays from each alpha ray emitting substance 2 changes at the same rate from the initial value (step S304). The initial value is, for example, the average counting rate of photons by alpha rays measured in advance before the operation of the radiation monitor 100 is started. Further, when the rate of change from the initial value is included in a predetermined range, the analyzer 50 changes the average counting rate of photons due to alpha rays from each alpha ray emitting substance 2 at the same rate from the initial value. You may judge that it is. The predetermined range is determined, for example, according to the statistical accuracy of the average counting rate of photons by alpha rays measured in advance. Further, the information indicating the predetermined range is included in, for example, the database held by the analysis device 50.
　各平均計数率が同じ割合で変化していない場合（ステップＳ３０４：ＮＯ）、解析装置５０は、放射線モニタ１００が正常に動作していないと判断して、例えば、異常が発生した旨のアラームを出力する（ステップＳ３０５）。 When each average counting rate does not change at the same rate (step S304: NO), the analyzer 50 determines that the radiation monitor 100 is not operating normally, and issues an alarm indicating that an abnormality has occurred, for example. Output (step S305).
　各平均計数率同じ割合で変化している場合（ステップＳ３０４：ＹＥＳ）、解析装置５０は、放射線モニタ１００の校正を行う（ステップＳ３０６）。 When each average counting rate changes at the same rate (step S304: YES), the analyzer 50 calibrates the radiation monitor 100 (step S306).
　なお、ステップＳ３０３においてアルファ線放出物質２ごとの平均計数率を算出することができなかった場合、解析装置５０は、放射線モニタ１００が正常に動作していないと判断してもよい。 If the average count rate for each alpha ray emitting substance 2 cannot be calculated in step S303, the analyzer 50 may determine that the radiation monitor 100 is not operating normally.
　図１５は、放射線モニタ１００の校正の一例を説明するための図である。図１５では、アルファ線のエネルギを示し、縦軸は光子の計数率を示す。 FIG. 15 is a diagram for explaining an example of calibration of the radiation monitor 100. In FIG. 15, the energy of alpha rays is shown, and the vertical axis shows the photon count rate.
　図１５では、放射線モニタ１００の運用が開始される前（運用前）のアルファ線放出物質２ごとのアルファ線による光子の平均計数率（〇印）と、放射線モニタ１００が劣化した時（劣化時）のアルファ線放出物質２ごとのアルファ線による光子の平均計数率（×印）とが示されている。 In FIG. 15, the average count rate of photons by alpha rays for each alpha ray emitting substance 2 before the start of operation of the radiation monitor 100 (before operation) (marked with ◯) and when the radiation monitor 100 is deteriorated (when deteriorated) ) Is shown as the average counting rate (x) of photons by alpha rays for each alpha ray emitting substance 2.
　図１５に示されたように、アルファ線放出物質２ごとのアルファ線による光子の平均計数率が運用開始前の平均計数率（初期値）に対して同じ割合で減少している場合、放射線モニタ１００が劣化しているとみなすことができる。この場合、その割合分だけ平均計数率が初期状態よりも低く算出されるため、解析装置５０は、その割合に応じて、データベース内のアルファ線による光子の平均計数率の各第２範囲を調整することで、放射線モニタ１００の校正を行う。同様に解析装置５０は、その割合に基づいて、平均計数率と空間線量率との関係（比例係数）を調整することで、放射線モニタ１００の校正を行ってもよい。これにより、運用中に校正を簡易に行うことが可能となる。 As shown in FIG. 15, when the average counting rate of photons due to alpha rays for each alpha ray emitting substance 2 decreases at the same rate as the average counting rate (initial value) before the start of operation, the radiation monitor It can be considered that 100 has deteriorated. In this case, since the average counting rate is calculated to be lower than the initial state by that ratio, the analyzer 50 adjusts each second range of the average counting rate of photons by alpha rays in the database according to the ratio. By doing so, the radiation monitor 100 is calibrated. Similarly, the analyzer 50 may calibrate the radiation monitor 100 by adjusting the relationship (proportional coefficient) between the average count rate and the air dose rate based on the ratio. This makes it possible to easily perform calibration during operation.
　以上説明したように本実施例によれば、放射線モニタを取り外すことなく、放射線検出部１０の近傍に行くことなく、簡易で安価に、運転中の動作確認及び校正が可能な高信頼性の放射線モニタを提供することが可能となる。 As described above, according to the present embodiment, highly reliable radiation capable of confirming operation and calibrating during operation easily and inexpensively without removing the radiation monitor and without going to the vicinity of the radiation detection unit 10. It becomes possible to provide a monitor.
　上述した本開示の実施形態は、本開示の説明のための例示であり、本開示の範囲をそれらの実施形態にのみ限定する趣旨ではない。当業者は、本発明の範囲を逸脱することなしに、他の様々な態様で本発明を実施することができる。 The above-described embodiments of the present disclosure are examples for the purpose of explaining the present disclosure, and the scope of the present disclosure is not intended to be limited only to those embodiments. One of ordinary skill in the art can practice the present invention in various other aspects without departing from the scope of the present invention.
　１：放射線発光素子　２、２１～２３：アルファ線放出物質　３：光反射膜　１０：放射線検出部　２０：光ファイバ　３０：光検出部　４０：測定装置　５０：解析装置　１００：放射線モニタ

  1: Radiation emitting element 2, 21-23: Alpha ray emitting substance 3: Light reflecting film 10: Radiation detector 20: Optical fiber 30: Photodetector 40: Measuring device 50: Analytical device 100: Radiation monitor

Claims (11)

  1. 　放射線の線量率を求める放射線モニタであって、
    　入射された放射線に応じて光子を放出する放射線発光素子を有する放射線検出部と、
    　アルファ線を放出して前記放射線発光素子に入射させるアルファ線放出核種と、
    　前記放射線発光素子にて放出された光子を伝送する光伝送部と、
    　前記光伝送部にて伝送された光子を検出する光検出部と、
    　前記光検出部にて検出された光子の計数率を測定する測定部と、
    　前記測定部にて測定された計数率に基づいて、放射線の線量率を求めるとともに、当該放射線モニタが正常に動作しているか否かを診断する解析部と、を有する放射線モニタ。     A radiation monitor that calculates the dose rate of radiation
    A radiation detector having a radiation emitting element that emits photons according to the incident radiation,
    Alpha-ray emitting nuclides that emit alpha rays and are incident on the radiation emitting device,
    An optical transmission unit that transmits photons emitted by the radiation emitting element, and
    An optical detection unit that detects photons transmitted by the optical transmission unit, and
    A measuring unit that measures the count rate of photons detected by the photodetector,
    A radiation monitor having an analysis unit that obtains a radiation dose rate based on the count rate measured by the measurement unit and diagnoses whether or not the radiation monitor is operating normally.
  2. 　前記解析部は、前記測定部にて測定された計数率に基づいて、前記放射線発光素子に入射したアルファ線に応じた数値を算出し、前記数値に基づいて、当該放射線モニタが正常に動作しているか否かを診断する、請求項１に記載の放射線モニタ。 The analysis unit calculates a numerical value corresponding to the alpha rays incident on the radiation emitting element based on the counting rate measured by the measurement unit, and the radiation monitor operates normally based on the numerical value. The radiation monitor according to claim 1, which diagnoses whether or not the radiation is present.
  3. 　前記数値は、前記アルファ線の計数率である、請求項２に記載の放射線モニタ。 The radiation monitor according to claim 2, wherein the numerical value is a counting rate of the alpha rays.
  4. 　前記数値は、前記放射線発光素子にて前記アルファ線に応じて放出された光子の計数率である、請求項２に記載の放射線モニタ。 The radiation monitor according to claim 2, wherein the numerical value is a counting rate of photons emitted by the radiation emitting element in response to the alpha rays.
  5. 　前記アルファ線放出核種は、前記放射線発光素子における前記光伝送部が設置された側の反対側の表面に塗布されている、請求項１に記載の放射線モニタ。 The radiation monitor according to claim 1, wherein the alpha ray emitting nuclide is applied to the surface of the radiation emitting element on the opposite side to the side where the optical transmission unit is installed.
  6. 　前記アルファ線放出核種は、前記放射線発光素子における前記光伝送部が設置された側の反対側の表面の近傍に配置されている、請求項１に記載の放射線モニタ。 The radiation monitor according to claim 1, wherein the alpha ray emitting nuclide is arranged in the vicinity of a surface on the opposite side of the radiation emitting element on which the optical transmission unit is installed.
  7. 　前記アルファ線放出核種は、前記放射線発光素子に混入されている、請求項１に記載の放射線モニタ。 The radiation monitor according to claim 1, wherein the alpha ray emitting nuclide is mixed in the radiation emitting element.
  8. 　前記放射線発光素子における前記光伝送部が設置された側の面とは異なる面に形成された光反射膜をさらに有し、
    　前記アルファ線放出核種は、前記光反射膜の表面と近傍との少なくとも一方に設けられている、請求項１に記載の放射線モニタ。     Further having a light reflecting film formed on a surface different from the surface on the side where the optical transmission unit is installed in the radiation emitting element.
    The radiation monitor according to claim 1, wherein the alpha ray emitting nuclide is provided on at least one of the surface and the vicinity of the light reflecting film.
  9. 　前記アルファ線放出核種は、エネルギがそれぞれ異なるアルファ線を放出する複数の核種を有し、
    　前記解析部は、前記核種ごとに前記アルファ線に応じて放出された光子の計数率を算出し、前記核種ごとの計数率に基づいて、当該放射線モニタを校正する、請求項４に記載の放射線モニタ。     The alpha ray emitting nuclide has a plurality of nuclides that emit alpha rays having different energies.
    The radiation according to claim 4, wherein the analysis unit calculates the count rate of photons emitted in response to the alpha rays for each nuclide, and calibrates the radiation monitor based on the count rate for each nuclide. monitor.
  10. 　前記アルファ線放出核種は、半減期が１年以上の核種を含む、請求項１に記載の放射線モニタ。 The radiation monitor according to claim 1, wherein the alpha ray emitting nuclide includes a nuclide having a half-life of one year or more.
  11. 　入射された放射線に応じて光子を放出する放射線発光素子を有する放射線検出部と、アルファ線を放出して前記放射線発光素子に入射させるアルファ線放出核種と、前記放射線発光素子にて放出された光子を伝送する光伝送部とを有する放射線モニタの診断方法であって、
    　前記光伝送部にて伝送された光子を検出し、
    　前記検出された光子の計数率を測定し、
    　前記測定された計数率に基づいて、放射線の線量率を求めるとともに、当該放射線モニタが正常に動作しているか否かを診断する、放射線モニタの診断方法。     A radiation detector having a radiation emitting element that emits photons in response to incident radiation, an alpha ray emitting nuclei that emits alpha rays and causes them to enter the radiation emitting element, and photons emitted by the radiation emitting element. A method of diagnosing a radiation monitor having an optical transmission unit for transmitting radiation.
    Detecting photons transmitted by the optical transmission unit,
    The counting rate of the detected photons was measured, and
    A method for diagnosing a radiation monitor, which obtains a radiation dose rate based on the measured counting rate and diagnoses whether or not the radiation monitor is operating normally.
PCT/JP2020/035135 2019-11-07 2020-09-16 Radiation monitor and method for diagnosing same WO2021090584A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4814269B1 (en) * 1968-06-12 1973-05-04
JPH08233944A (en) * 1995-02-24 1996-09-13 Mitsubishi Electric Corp Light source for calibration of radiation detector
JP2007205769A (en) * 2006-01-31 2007-08-16 Toshiba Corp Radiation detector
JP2009063510A (en) * 2007-09-07 2009-03-26 Hitachi Ltd Environmental radioactivity measurement and control system and analysis method for radioactivity intensity
JP2010271153A (en) * 2009-05-21 2010-12-02 Hitachi Ltd Radiation monitor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4814269B1 (en) * 1968-06-12 1973-05-04
JPH08233944A (en) * 1995-02-24 1996-09-13 Mitsubishi Electric Corp Light source for calibration of radiation detector
JP2007205769A (en) * 2006-01-31 2007-08-16 Toshiba Corp Radiation detector
JP2009063510A (en) * 2007-09-07 2009-03-26 Hitachi Ltd Environmental radioactivity measurement and control system and analysis method for radioactivity intensity
JP2010271153A (en) * 2009-05-21 2010-12-02 Hitachi Ltd Radiation monitor

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