JP2018179800A - Radiation detector and method of measuring radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector and a radiation measuring method capable of measuring even in a high dose rate environment, in relation to a radiation monitor for measuring charged particles or neutrons. A radiation detector (100) is connected to one pixel element (1a) of at least one pixel element (1a) and one pixel element (1a) of the pixel element (1a). 1, an optical fiber 10 for transmitting the photons generated in step 1, a photodetector 20 for converting the photons transmitted by the optical fiber 10 into an electric signal, and a measuring device for obtaining the count rate of the electric signal converted by the photodetector 20. 30 and an analysis/display device 40 that obtains a radiation dose rate based on the counting rate obtained by the measuring device 30, and changes in counting rate of each photon generated by the pixel-type detection element 1 with time. To measure. [Selection diagram]

Description

  The present invention relates to a radiation detector capable of measuring charged particles or neutrons and a method of measuring radiation.

  As a neutron image detector which is small and extremely inexpensive and at the same time processing speed of neutron imaging is extremely high, Patent Document 1 discloses that fluorescence generated by neutron incidence is one-dimensionally or at a constant interval. A neutron image detection method of collecting dimensionally and detecting the collected fluorescence to determine the incident position of neutrons, wherein when detecting the fluorescence, each photon detected and output using a photon measurement method The generated pulse signal is extracted based on a clock signal generated at the same interval width as the time width of the pulse signal generated by one photon, and the output pulse signal is counted, and when one neutron is incident. There is described a technique for obtaining a count distribution with the obtained incident position as a variable, calculating the center of gravity based on the obtained count distribution, and determining the neutron incident position.

JP, 2011-179863, A

  As a radiation detector which detects charged particles (alpha ray, beta ray, etc.) which exist conventionally, there are a gas detector, a scintillation detector, and a semiconductor detector.

  The gas detector has a structure in which a metal wire is placed in a gas-sealed container, and when charged particles ionize the gas in the detector, electrons are generated, and the electrons form a high electric field area near the metal wire. It is a detector which measures as an electric signal by amplifying with.

  However, in a high dose rate environment, the gas detector measures a large number of incident gamma rays and electrons due to Compton scattering from the enclosed gas and detector container material, so discrimination from charged particles is possible. Is difficult, and there is a problem.

  In a charged particle detector using a scintillation element, the scintillation element emits light when the charged particle is incident on the scintillation element. Then, the light emission is converted into an electric signal using a photomultiplier tube or the like, and charged particles are measured based on the electric signal. A large number of photons are generated when one charged particle is incident, but the number of generated photons is proportional to the energy of the incident charged particles, so a pulse-like electrical signal proportional to the number of generated photons is generated. By measuring the peak value, it is possible to measure the energy of the incident charged particle.

  However, with a scintillation detector, in a high dose rate environment, a large number of gamma rays are simultaneously incident on a scintillation element, and pulse-like electrical signals overlap, making it difficult to measure charged particles correctly. There is a problem with In order to prevent this, it is conceivable to cover the periphery of the scintillation element with a radiation shield such as lead, but the charged particles can not enter into the detector and the light emission necessary for detection is lost. Therefore, there is a problem that it is difficult to use in a high dose rate environment.

  A charged particle detector using a semiconductor element is generated by ionization by charged particles in a region (depletion layer) in which electrons and holes formed at the junction surface where p-type and n-type semiconductors are joined are hardly present. It is a detector that detects charged particles based on the electric signal generated by the movement of the electron-hole pairs to p-type and n-type respectively. When one charged particle is incident, a large number of electron-hole pairs are generated. Since the number of electron-hole pairs generated is proportional to the energy of the charged particle, the pulse height of the pulse-like electrical signal proportional to the number of electron-hole pairs generated is measured. It is possible to measure the energy of charged particles.

  However, even in a semiconductor detector, in a high dose rate environment, a large number of gamma rays are simultaneously incident on the semiconductor element, and pulse-like electric signals overlap, which makes it difficult to correctly measure charged particles. There is a problem with If the periphery of the semiconductor element is covered with a radiation shield such as lead in order to prevent it, charged particles can not enter into the detector as in the case of a scintillation detector, making it difficult to use. There's a problem.

  With respect to neutron detectors, like charged particle detectors, there are gas detectors, scintillation detectors and semiconductor detectors, but again, like charged particle detectors, it was difficult to measure under high dose rate environment .

  The object of the present invention relates to a radiation monitor for measuring charged particles and neutrons, and to provide a radiation detector and a method of measuring radiation which can be measured even in a high dose rate environment.

  The present invention includes a plurality of means for solving the above problems, and an example thereof is a pixel type detection element comprising at least one or more pixel elements, and one pixel element of the pixel type detection element. Optical fiber that transmits photons generated by the pixel type detection element, a light detection unit that converts photons transmitted by the optical fiber into an electrical signal, and the light detection unit A measuring device for determining the counting rate of the electric signal, and an analyzing device for determining the dose rate of radiation based on the counting rate determined by the measuring device, and one photon generated by the pixel type detection element Measuring the time change of the counting rate of

  According to the present invention, the high-dose-rate environment of the spent fuel storage pool in the nuclear power plant, inside and outside of the reactor pressure vessel, inside and outside of the reactor containment vessel, inside and outside the suppression pool, inside and outside the reactor building, and reprocessing facilities etc. Can also provide a radiation detector capable of measuring charged particles and neutrons, and a method of measuring radiation. Problems, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is a figure which shows an example of a structure of the radiation detector of Example 1 which is one Example suitable for this invention. FIG. 7 is a diagram showing another example of the configuration of the radiation detector of the first embodiment. FIG. 7 is a view showing the relationship between the photon emission characteristic and the absorbed dose rate of the detection element applied to Example 1. FIG. 6 is a view showing an example of the measurement result of radiation by the radiation detector in the first embodiment. FIG. 6 is a view showing charged particles and gamma rays incident on the detection element of Example 1; It is a figure which shows an example of a structure of the radiation detector of Example 2 which is one Example suitable for this invention. FIG. 18 is a diagram showing another example of the configuration of the radiation detector of the second embodiment. FIG. 7 is a view showing a state of charged particles generated by a nuclear reaction with neutrons, gamma rays and neutrons incident on the detection element of Example 2. It is a figure which shows an example of a structure of the radiation detector of Example 3 which is one Example suitable for this invention. FIG. 18 is a diagram showing another example of the configuration of the radiation detector of the third embodiment.

  Hereinafter, embodiments of the radiation detector and the radiation measuring method of the present invention will be described with reference to the drawings.

  First, an outline of a radiation detector and a method of measuring radiation will be described.

  The radiation detector of the present invention comprises a pixel type detection element, an optical fiber, a light detection unit, a measuring device, and an analysis / display device, and an optical fiber is connected to each of the pixel type detection elements. In the analysis / display device, the time change of the counting rate of each photon generated by the detection element is measured.

  For example, a pixel type detection element corresponding to an individual pixel and having one or more pixel elements in which a rare earth element is added to a ceramic base material is disposed in the measurement area.

  When charged particles are incident on such a pixel type detection element, electrons or rare earth atoms in the detection element become excited with high energy. From the high excited state, photons are generated when transitioning to the low excited or ground state.

  The generated photons are detected through an optical fiber by a light detection unit such as a photomultiplier or a photodiode. The light detection unit detects photons one by one and converts them into electrical signals. The counting rate of the electrical signal converted by the light detection unit is counted by the measuring device.

  The inventors of the present invention have found by experiments that there is a one-to-one relationship between the counting rate of each photon and the absorbed dose rate in the detection element. Moreover, when using a pixel type | mold detection element, it also discovered that it was possible to make the absorbed dose rate by a gamma ray several orders of magnitudes or more than the absorbed dose rate by charged particle | grains. Furthermore, in a high dose rate environment, when the dose rate is constant, there is almost no change in counting rate with time, and the count rate is almost constant, but when charged particles are incident, the absorbed dose rate rapidly increases. From the above, it has been found that the count rate increases rapidly and returns to the count rate before incidence in several times the light decay time constant of the detection element. Then, it was conceived that it becomes possible to measure each charged particle by measuring the time change of this increase and decrease, and came to the present invention.

  In the case of measuring neutrons, a material that generates charged particles by a nuclear reaction with neutrons is placed on the side of the detection element where neutrons are incident, and the opposite side is connected to an optical fiber to obtain neutrons. It has been found that charged particles produced by the nuclear reaction with can be detected in the same manner as in the case of detecting the above-mentioned charged particles, which makes it possible to measure neutrons even under a high dose rate environment. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Example 1
An example of a radiation detector and a radiation measurement method according to a first embodiment which is a preferred embodiment of the present invention will be described based on FIGS. 1 to 5. First, the configuration of the radiation detector will be described using FIG. 1 and FIG. FIG. 1 shows an example of the configuration of the radiation detector of the present embodiment, and FIG. 2 shows another example of the configuration of the radiation detector of the present embodiment.

  In FIG. 1, the radiation detector 100 includes a pixel type detection element 1, an optical fiber 10, a light detection unit 20, a measurement device 30, and an analysis / display device (analysis device) 40.

  The pixel type detection element 1 is an element composed of at least one or more pixel elements 1a, and is made of a material that generates photons of intensity corresponding to the dose rate of the radiation incident on each pixel element 1a. Therefore, when charged particles enter the pixel element 1 a of the pixel type detection element 1, electrons or rare earth atoms in the pixel element 1 a of the pixel type detection element 1 are in a high energy excited state. From the high excited state, photons are generated when transitioning to the low excited or ground state.

  One optical fiber 10 is connected to each pixel element 1a of the pixel type detection element 1, and the same number as the number of pixel elements 1a is provided. The optical fiber 10 transmits photons generated by the pixel element 1 a of the pixel type detection element 1 to the light detection unit 20 described later.

  The light detection unit 20 detects photons generated by the pixel element 1 a and transmitted through the optical fiber 10 one by one and converting them into an electric signal. Further, the converted electric signal is output to a measuring device 30 described later. The light detection unit 20 can adopt a photomultiplier or a photodiode such as an avalanche photodiode. By using these photomultipliers and the like, a single photon can be detected as one current-amplified electrical signal.

  The measuring device 30 is a device that is connected to the light detection unit 20 and obtains the counting rate of the electrical signal converted by the light detection unit 20. The measuring device 30 outputs the obtained counting rate to an analysis / display device 40 described later. As the measuring device 30, for example, a digital signal processor or the like can be adopted.

  The analysis and display device 40 is a device that converts the count rate of the electric signal obtained by the measurement device 30 into a dose rate of radiation and displays the value. The analysis and display device 40 uses the database of the storage unit 40a having a database that associates the counting rate of single-photon electrical signals with the dose rate of radiation, and the database of the storing unit 40a to calculate the radiation rate from the counting rate of the electrical signals. And a display unit 40c for displaying the converted dose rate of radiation. In addition, in the calculation unit 40b of the analysis and display apparatus 40 of this embodiment, the dose rate of radiation, particularly, charged particles is calculated based on the time change of the count rate of photons generated by the pixel type detection element 1 Do. Specifically, the analysis / display device 40 determines that the charged particles are incident on the pixel element 1 a when the count rate of photons generated in the pixel type detection element 1 increases and decreases in a pulse shape. The reason will be described later.

  As the analysis / display device 40, for example, a personal computer having the above-described function can be employed. In the present specification, the “counting rate of electrical signals” means the number of electrical signals measured per unit time.

  As in the case of the radiation detector 100A shown in FIG. 2, the pixel type detection element may be composed of one pixel element 1a.

  Here, the size of each of the pixel elements 1a of the pixel type detection element 1 is the count rate when photons generated by the pixel type detection element 1 are counted according to the dose rate of radiation at the place where the pixel type detection element 1 is installed. However, it is desirable to set the count rate equal to or less than when counting the photons generated by the pixel type detection element 1 when charged particles are incident on the pixel type detection element 1. The reason will be described below with reference to FIGS. 3 and 4. FIG. 3 shows the relationship between the photon emission characteristic and the absorbed dose rate of the detection element, and FIG. 4 shows an example of the measurement result.

  As shown in FIG. 3, the inventors have found that there is a one-to-one relationship between the emission rate of each photon (and hence the count rate) and the absorbed dose rate in the detection element. From this finding, it is understood that the absorbed dose rate in the pixel type detection element 1 can be measured by measuring the counting rate of each photon.

  In addition, when the pixel type detection element 1 is in a constant dose rate environment, the light count rate which is the measurement result of the dose rate also exhibits a constant value. Furthermore, as described above, when gamma rays are incident, almost no energy is given to the inside of the pixel type detection element 1, so as shown in FIG. 4, in a high gamma ray environment (that is, under a high dose rate environment) Also, photon counting rates by gamma rays will show relatively low values.

  On the other hand, when charged particles are incident on the pixel type detection element 1 in a high dose rate environment, as described above, the charged particles impart most of their energy to the inside of the pixel element 1a. The absorbed dose rate of 1 is a very high value. Therefore, as shown in FIG. 4, the count rate rapidly increases due to the incidence of charged particles, and returns to the count rate before the incidence in about several times the light decay time constant of the detection element. That is, when the time change of the count rate of photons is observed, the incidence of charged particles appears as a pulse-like waveform. By measuring the time change of such pulse-like increase and decrease, it becomes possible to measure each charged particle one by one.

  Therefore, the size of each of the pixel elements 1a of the pixel type detection element 1 is the count rate when photons generated by the pixel type detection element 1 are counted according to the dose rate of radiation at the place where the pixel type detection element 1 is installed. However, it is desirable that the count rate when counting the photons generated by the pixel type detection element 1 when charged particles enter the pixel type detection element 1 be equal to or less.

  The size of each pixel element 1 a of the pixel type detection element 1 is preferably equal to or less than the range of the charged particles incident on the pixel type detection element 1 in the pixel element 1 a. The reason will be described below with reference to FIG. FIG. 5 shows an example of charged particles and gamma rays incident on the pixel type detection element 1 of the radiation detector of this embodiment.

  A case where the size of the pixel element 1a of the pixel type detection element 1 is equal to or less than the range of the charged particles incident on the pixel type detection element 1 in the pixel element 1a will be considered. Since charged particles basically have high mass and low charge because they are charged, when charged particles enter the pixel type detection element 1, as shown in FIG. 5, the material constituting the pixel element 1a And the incident charged particles, most of the energy of the charged particles is given to the inside of the pixel element 1a. For this reason, the absorbed dose rate of the pixel type detection element 1 becomes a very high value.

  On the other hand, gamma rays have high permeability and high permeability to the material of the pixel element 1a. Therefore, even if gamma rays are incident on the pixel type detection element 1, as shown in FIG. 5, the gamma rays are transmitted with almost no loss of their energy, and most of the energy is not given to the inside of the pixel element 1a. From this, the absorbed dose rate of the pixel type detection element 1 becomes a very low value.

  From these facts, in order to increase the absorbed dose rate of charged particles, it is desirable to set the size of the pixel element 1a equal to or less than the range within the pixel element 1a of the charged particles incident on the pixel type detection element 1.

  As described above, it is desirable to set the size of the pixel element 1 a of the pixel type detection element 1 according to the dose rate of radiation at the installation position of the pixel type detection element 1. Therefore, the provisional dose rate of radiation dose rate in the measurement environment is measured beforehand by a detector different from the radiation detectors 100 and 100A of the present embodiment, and the provisional dose rate is measured by another detector. It is desirable to set the size of the pixel element 1a based on the value of.

  In addition, when the dose rate environment changes within the time of the time change of the pulse-like increase and decrease described above, it is considered that the measurement of charged particles may not be easy. However, in the case of using yttrium aluminum garnet doped with neodymium as an example of the pixel type detection element 1, the light attenuation time constant is about 230 microseconds, so the following can be obtained within about 1 millisecond: When the charged particles do not enter or the dose rate environment does not change rapidly, it is possible to measure each charged particle one by one with high accuracy.

  In addition, under a high dose rate environment, radiation degradation of the optical fiber 10 may occur, and this degradation is considered to degrade the transmission performance of photons. However, when the photon generated by the pixel type detection element 1 is a photon with a wavelength of 800 nm or more, the deterioration of the optical fiber due to the gamma ray occurs only at a level that causes little problem. From this, as a material of the pixel type detection element 1, a material which emits a photon of a wavelength of 800 nm or more by incidence of gamma rays or charged particles is desirable. As such a material, at least one or more rare earth elements selected from ytterbium, neodymium, cerium and praseodymium may be added to a ceramic base material containing yttrium, aluminum and garnet. As an example, when neodymium-doped yttrium aluminum garnet is used, it emits photons of 1064 nm upon incidence of gamma rays or charged particles, which is desirable as the material of the pixel type detection element 1.

  Next, an example of the radiation measurement method according to the present embodiment will be described.

  Prior to the measurement of radiation according to the present embodiment, the provisional value of the dose rate of radiation in the measurement environment is measured in advance by a detector different from the radiation detectors 100 and 100A of the present embodiment, It is desirable to set the size of the pixel element 1a on the basis of the dose rate measured by the detector.

  First, the pixel type detection element 1 consisting of at least one or more pixel elements 1a of the radiation detectors 100 and 100A is installed in the measurement environment. Then, photons generated by radiation incident on the pixel type detection element 1 are transmitted to the light detection unit 20 through the optical fiber 10. Then, the photon detection unit 20 detects photons one by one and converts them into electric signals.

  Thereafter, the counting rate of the converted electrical signal is determined by the measuring device 30 or the like, and the dose rate of radiation is determined based on the time change of the counting rate of each photon thus determined.

  Next, the effects of this embodiment will be described.

  The above-described radiation detectors 100 and 100A according to the first embodiment of the present invention have a pixel type detection element 1 including at least one or more pixel elements 1a, and one for each pixel element 1a of the pixel type detection element 1. An optical fiber 10 connected and transmitting photons generated by the pixel type detection element 1, a light detection unit 20 converting photons transmitted by the optical fiber 10 into an electric signal, and an electric signal converted by the light detection unit 20 And an analysis / display device 40 for obtaining a dose rate of radiation based on the count rate obtained by the measurement device 30, and one by one generated by the pixel type detection element 1 It measures the time change of the photon counting rate. In the radiation measurement method according to the first embodiment of the present invention, each photon generated by the radiation incident on the pixel type detection element 1 consisting of at least one or more pixel elements 1a is converted into an electric signal, The converted electric signal is counted to obtain the photon counting rate, and the dose rate of radiation is obtained based on the time change of the counting rate of each photon thus obtained.

  This makes it possible to detect charged particles even in high-dose-rate environments that are difficult to detect with conventional detectors, and can be used for spent fuel storage pools in nuclear power plants, inside and outside reactor pressure vessels, inside and outside reactor containment vessels. It is possible to provide a radiation detector suitably used inside and outside the suppression pool, inside and outside the reactor building, reprocessing facilities, hospitals, research institutes and the like.

  Further, the count rate when counting the photons generated by the pixel type detection element 1 according to the dose rate of the radiation at the installation position of the pixel type detection element 1 is the size of each of the pixel elements 1 a of the pixel type detection element 1 By making the count rate equal to or less than the count rate when photons generated by the pixel type detection element 1 are counted when the charged particles enter the pixel type detection element 1, the absorbed dose rate by the charged particle becomes the absorbed dose rate by gamma ray. In comparison, it can be surely enhanced and the detection efficiency of charged particles can be further improved.

  Furthermore, by setting the size of each of the pixel elements 1a of the pixel type detection element 1 to be equal to or less than the range of charged particles incident on the pixel type detection element 1 in the pixel element 1a, charging relative to the absorbed dose rate by gamma rays The dose rate absorbed by particles can be maximized, and the detection performance of charged particles can be further improved.

  Further, by setting the size of the pixel element 1a of the pixel type detection element 1 according to the dose rate of radiation at the installation position of the pixel type detection element 1, the absorbed dose rate by charged particles is made the absorbed dose rate by gamma ray. In comparison, it can be surely enhanced, and the detection efficiency of charged particles can be further improved.

  Furthermore, when the counting rate of photons generated in the pixel type detection element 1 increases and decreases in a pulse shape, the analysis and display device 40 determines that the charged particle is incident on the pixel element 1 a, thereby the charged particle 1. The incidence on each individual pixel type detection element 1 can be detected with higher accuracy, and the detection performance of charged particles can be further improved.

  In addition, the pixel-type detection element 1 is a radiation-emitting element in which at least one or more rare earth elements selected from yttria, neodymium, cerium, and praseodymium are added to a ceramic base material containing yttrium aluminum garnet. Thus, the light attenuation time constant can be made sufficiently short to maintain high detection accuracy, and highly accurate detection of charged particles can be achieved.

Example 2
Next, an example of a radiation detector and a radiation measurement method according to a second embodiment which is a preferred embodiment of the present invention will be described with reference to FIGS. The same reference numerals are given to the same components as in the first embodiment, and the description will be omitted. The same applies to the following embodiments.

  The radiation detector 100B shown in FIG. 6 and the radiation detector 100C shown in FIG. 7 basically have the same configurations as the radiation detector 100 in the first embodiment shown in FIG. 1 and the radiation detector 100A shown in FIG. It is.

  The radiation detectors 100B and 100C of this embodiment further have a nuclear reaction with neutrons on the opposite side to the side connected to the optical fiber 10 of the pixel type detection element 1 composed of one or more pixel elements 1a. The material 2 which produces | generates a charged particle by this is installed. In such radiation detectors 100B and 100C, the opposite side to the material 2 side is connected to the optical fiber 10. The installation position of the material 2 is not limited to this, and the material 2 can be installed all around the other part of the pixel type detection element 1 without installing the material 2 only at the connection part of the optical fiber 10.

  The size of each pixel element 1a of the pixel type detection element 1 of the radiation detectors 100B and 100C of the present embodiment is equal to or less than the range within the pixel element 1a of the charged particle generated in the material 2 by the nuclear reaction with neutrons. It is desirable to The reason will be described below with reference to FIG. FIG. 8 shows an example of the appearance of charged particles generated in the nuclear reaction with neutrons, gamma rays and neutrons incident on the detection element.

  As described above, when neutrons 90 enter the material 2, as shown in FIG. 8, the reaction between the neutrons and the material 2 generates charged particles 70. When the generated charged particles 70 are incident into the pixel type detection element 1, most of the energy is applied to the inside of the pixel element 1 a as in the case of the first embodiment, so the absorbed dose rate of the pixel type detection element 1 Is a very high value. On the other hand, as for the gamma ray 80, as in the first embodiment, the energy is hardly given to the inside of the pixel type detection element 1, and the photon count rate shows a relatively low value.

  Therefore, the count rate is rapidly increased by the incidence of charged particles, and returns to the count rate before the incidence in a time several times the light attenuation time constant of the detection element. It becomes possible to measure each charged particle one by one by measuring the time change of this increase and decrease, it becomes possible to measure one neutron one by one indirectly.

  Examples of the nuclide that forms charged particles by nuclear reaction with neutrons that constitute the material 2 include lithium 6 which is a lithium isotope and boron 10 which is a boron isotope. Lithium 6 absorbs neutrons and produces charged particles such as tritium and alpha rays. Boron 10 absorbs neutrons in the same manner as lithium 6 and produces charged particles such as lithium 7 and alpha rays. Therefore, it is desirable to use these nuclide or a compound containing these nuclide as the material 2 for producing charged particles by nuclear reaction with neutrons.

  The thickness of the above-mentioned material 2 is set to be equal to or less than the thickness at which the incident neutrons produce charged particles by nuclear reaction, absorption, or other reaction completely before and after the passage of the material 2 producing charged particles. Is desirable.

  Here, the charged particles generated in the above-described material 2 impart energy even in the above-described material 2. For this reason, in order to apply as much energy as possible to the pixel type detection element 1, the thickness of the above-mentioned material 2 is equal to or less than the thickness at which the total amount of incident neutrons disappears due to the reaction with the material 2. Thinner is desirable.

  The other configuration and operation are substantially the same as those of the radiation detectors 100 and 100B of the first embodiment described above, and the details will be omitted.

  According to the radiation detectors 100B and 100C of the second embodiment of the present invention, the material 2 that generates charged particles by a nuclear reaction with neutrons on the side opposite to the side connected to the optical fiber 10 of the pixel type detection element 1 As a result, neutrons can be detected even in a high dose rate environment, and almost the same as the radiation detectors 100 and 100A of the first embodiment and the method of measuring radiation described above, spent fuel in a nuclear power plant It is possible to provide a radiation detector suitably used in storage pool, reactor pressure vessel inside and outside, reactor containment vessel inside and outside, suppression pool inside and outside, reactor building indoor and outdoor, reprocessing facility, hospital and laboratory.

  In addition, by setting the thickness of the material 2 to be equal to or less than the thickness at which the total amount of the incident neutrons disappears by the reaction with the material 2 before and after the passage of the material 2, the generation efficiency of charged particles by the neutrons incident on the material 2 Since it can be made high and the detection of the charged particles can be performed with higher accuracy, the detection accuracy of neutrons in a high dose rate environment can be further improved.

  Furthermore, by using a compound containing lithium isotope or boron isotope or lithium isotope or boron isotope as the material 2, the material 2 is made of an element having high reaction efficiency with neutrons. The neutron detection accuracy can be further improved.

Example 3
Next, an example of a radiation detector according to a third embodiment which is a preferred embodiment of the present invention and a method of measuring the same will be described with reference to FIGS.

  The radiation detector 100D shown in FIG. 9 and the radiation detector 100D shown in FIG. 10 have the same configurations as the radiation detector 100 in the first embodiment shown in FIG. 1 and the radiation detector 100A shown in FIG.

  In the radiation detectors 100D and 100E of the present embodiment, further, in the portion of the optical fiber 10 between the pixel type detection element 1 and the light detection unit 20, a filter including a wavelength selection filter 50a or a wavelength attenuation filter 50b is installed. It is a thing.

  When the pixel type detection element 1 is installed in a high dose rate environment, at least a part of the optical fiber 10 connected to each pixel element 1a of the pixel type detection element 1 is also installed in the high dose rate environment. Ru. In such a case, since electrons due to Compton scattering of gamma rays are incident on the optical fiber 10 in a large amount, Cherenkov light by the electrons may be generated in the optical fiber 10, which may be a background of measurement.

  Here, the Cherenkov light generated has a characteristic of having a peak at 300 to 400 nm and decreasing as the wavelength becomes longer. On the other hand, in the pixel type detection element 1, photons of a certain wavelength are usually generated by the incidence of gamma rays and charged particles, so that only the wavelength of photons emitted from the pixel type detection element 1 is transmitted to detect light By providing the wavelength selection filter 50a that enables transmission to the point 20, just before the light detection unit 20 in the optical fiber 10, the background due to the Cherenkov light can be reduced, and the pixel type with higher accuracy can be obtained. The detection of photons generated by the detection element 1 and the associated improvement in the accuracy of the counting rate can be achieved.

  When neodymium-doped yttrium aluminum garnet is used as an example of the pixel type detection element 1, photons of 1064 nm are emitted by the incidence of gamma rays or charged particles. From this, it is possible to more effectively reduce the background due to the Cherenkov light by using the wavelength selection filter 50a that transmits 1064 nm photons.

  In addition, when the incidence rates of gamma rays and charged particles to the pixel type detection element 1 are large, it is expected that the photon counting rate exceeds the counting capability of the light detection unit 20. In that case, by installing the wavelength attenuation filter 50b in the portion of the optical fiber 10 between the pixel type detection element 1 and the light detection unit 20, the ratio of the photon count rate by gamma rays to the photon count rate by charged particles is changed. The photon incident on the light detection unit 20 can be made equal to or less than the counting ability of the light detection unit 20 without any problem, and even when the incidence of gamma rays and charged particles on the detection element is large, highly accurate measurement of radiation Can be obtained.

  The other configuration and operation are substantially the same as those of the radiation detectors 100 and 100A of the first embodiment described above, and the details will be omitted.

  Also in the radiation detectors 100D and 100E of the third embodiment of the present invention and the radiation measuring method, substantially the same effects as the radiation detectors 100 and 100A of the first embodiment and the radiation measuring method described above can be obtained.

  Further, by further providing the wavelength selection filter 50a in the portion of the optical fiber 10 between the pixel type detection element 1 and the light detection unit 20, it is possible to detect photons one by one with higher accuracy. Further, by further providing the wavelength attenuation filter 50b, it is possible to detect neutrons using detection of charged particles or charged particles even in an environment with a very high dose rate.

  In the case of a region where the dose rate is extremely high, the wavelength selection filter 50a and the wavelength attenuation filter 50b can be used in combination.

<Others>
The present invention is not limited to the above embodiments, and includes various modifications. The above embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. In addition, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... pixel type detection element 1a ... pixel element 2 ... material 10 containing the nuclide which discharge | releases a charged particle by nuclear reaction with neutrons 10 ... optical fiber 20 ... light detection part 30 ... measurement apparatus 40 ... analysis and display apparatus (analysis apparatus)
50a ... wavelength selection filter 50b ... wavelength attenuation filter 70 ... charged particle 80 ... gamma ray 90 ... neutron 100, 100A, 100B, 100C, 100D, 100E ... radiation detector

Claims (15)

A pixel type detection element comprising at least one or more pixel elements;
An optical fiber connected to one of the pixel elements of the pixel type detection element and transmitting photons generated by the pixel type detection element;
A light detection unit that converts photons transmitted by the optical fiber into an electrical signal;
A measuring device for obtaining a count rate of the electrical signal converted by the light detection unit;
An analyzer for determining a dose rate of radiation based on the count rate determined by the measurement device;
What is claimed is: 1. A radiation detector comprising: measuring a time change of a counting rate of photons generated by the pixel type detection element. In the radiation detector according to claim 1,
When counting the number of photons generated by the pixel type detection element according to the dose rate of radiation at the installation position of the pixel type detection element, the count rate of each pixel of the pixel type detection element is the pixel What is claimed is: 1. A radiation detector comprising: a count rate equal to or less than a count rate of photons generated by the pixel type detection element when charged particles are incident on the type detection element. In the radiation detector according to claim 1,
A radiation detector, wherein a size of each of the pixel elements of the pixel type detection element is equal to or less than a range in a detection element of charged particles incident on the pixel type detection element. In the radiation detector according to claim 1,
A size of the pixel element of the pixel type detection element is set according to a dose rate of radiation at an installation position of the pixel type detection element. In the radiation detector according to claim 1,
The radiation detector, wherein the analyzer determines that charged particles are incident on the pixel element when the count rate of photons generated by the pixel type detection element increases and decreases in a pulse shape. In the radiation detector according to claim 1,
A radiation detector characterized in that a material that generates charged particles by a nuclear reaction with neutrons is provided on the side opposite to the side of the pixel type detection element connected to the optical fiber. In the radiation detector according to claim 6,
The radiation detector, wherein the thickness of the material is equal to or less than the thickness at which the total amount of the neutrons which are incident upon the reaction with the material disappears before and after the passage of the material. In the radiation detector according to claim 6,
A radiation detector characterized in that a lithium isotope or a boron isotope, or a compound containing a lithium isotope or a boron isotope is used as the material. In the radiation detector according to claim 1,
A radiation detector, further comprising: a wavelength selection filter or a wavelength attenuation filter in a portion of the optical fiber between the pixel type detection element and the light detection unit. In the radiation detector according to claim 1,
The pixel type detection device is characterized in that a radiation light emitting device in which at least one or more rare earth elements selected from ytterbium, neodymium, cerium and praseodymium are added to a ceramic base material containing yttrium, aluminum and garnet is used. Radiation detector. A method of measuring radiation,
Converting each single photon generated by the radiation incident on the pixel type detection element consisting of at least one or more pixel elements into an electrical signal,
Counting the converted electrical signal to obtain a photon counting rate;
A radiation measurement method, comprising: determining a dose rate of radiation based on the time change of the counting rate of each photon. In the radiation measurement method according to claim 11,
When counting the number of photons generated by the pixel type detection element according to the dose rate of radiation at the installation position of the pixel type detection element, the count rate of each pixel of the pixel type detection element is the pixel A method of measuring radiation characterized by being equal to or less than a count rate when photons generated by the pixel type detection element are counted when charged particles enter the type detection element. In the radiation measurement method according to claim 11,
A method of measuring radiation, wherein the size of each of the pixel elements of the pixel type detection element is equal to or less than the range of the charged particles entering the pixel type detection element in the detection element. In the radiation measurement method according to claim 11,
The size of the pixel element of the pixel type detection element is set according to the dose rate of radiation at the installation position of the pixel type detection element. In the radiation measurement method according to claim 11,
A method of measuring radiation characterized in that when the count rate of photons generated by the pixel type detection element increases and decreases in a pulse-like manner, charged particles are determined to have entered the pixel element.

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