Radiation measurement device and method for measuring radiation

Abstract

To provide a radiation measurement device and a method for measuring a radiation which can measure neutrons derived from a measurement target object by reducing influence of gamma-rays from a surrounding radiation source.SOLUTION: A radiation measurement device 100 for measuring neutrons includes: an inactive gas 110 which emits light with longer wavelengths than a visible light band by applying a radiation; a solid neutron sensing unit 109 sensitive to neutrons, the solid neutron sensing unit reflecting the light emitted from the inactive gas 110; and a detection container 101 for holding the inactive gas 110 and the neutron sensing unit 109 in structurally different regions, the detection container having an optical window 111 for propagating light emission of the inactive gas 110 to the outside.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for measuring neutrons, and more particularly to a radiation measurement device and a radiation measurement method capable of discriminating and measuring neutrons in a gamma ray environment. [Background technology]

[0002] Patent Document 1 describes a neutron measurement device that includes at least one container that contains a neutron capture gas that captures neutrons and generates radiation, and a scintillator gas that generates light through interaction with the radiation, and has an opening formed therein, and whose inner surface is made of a material that generates light through interaction with the radiation, a light-collecting member that is attached to the opening and forms an enclosed space together with the container and guides the light generated by the scintillator gas, and a light detection unit that is provided outside the light-collecting member and detects light from the light-collecting member.

[0003] Patent Document 2 describes a neutron detector equipped with a neutron scintillator containing a phosphor that fluoresces in response to neutrons, an optical fiber that transmits light emitted by the phosphor, a photomultiplier tube that converts the light into an electric pulse, and a low-pass filter that passes pulses caused by the fluorescence emitted by the phosphor from the electric pulse and reduces high-frequency pulses caused by gamma rays. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6377502 [Patent Document 2] Patent No. 6953902 Summary of the Invention [Problem to be solved by the invention]

[0005] Neutron measurements are used as one of the methods for measuring nuclear fuel in facilities that handle uranium, plutonium, and spent nuclear fuel, as well as in research reactors and commercial nuclear power plants. When analyzing nuclear fuel with various histories, a portion of the nuclear fuel is sampled and its characteristics are investigated offline using dedicated analytical equipment. In addition, when it is not possible to sample and analyze a portion of the nuclear fuel, its characteristics are investigated offline using dedicated equipment that can reduce background noise.

[0006] However, sampling of nuclear fuel samples or investigations using dedicated equipment require equipment and facilities to perform analysis under each set of conditions, so the scope of application is extremely limited.

[0007] Due to the above-mentioned factors, there is a demand for a radiation measurement device and method capable of analyzing a measurement object by measuring neutrons even in a field where nuclear fuel is stored and managed.

[0008] When measuring neutrons from a measurement object in the field, it is necessary to consider the effects of other radiation sources placed in the vicinity. Neutron measurement devices used in conventional analysis are not designed to take into account the effects of surrounding radiation sources, making it difficult to apply them in the field, inline, or online.

[0009] In the field, neutron measurement in a gamma ray environment is required, especially when the measurement targets are spent nuclear fuel, radioactive waste, etc. For this reason, a radiation measurement device and method that can reduce the influence of surrounding radiation sources and measure neutrons originating from the measurement target is required.

[0010] For example, in order to perform field nuclear fuel analysis using neutrons in facilities that handle uranium, plutonium, or spent nuclear fuel, research reactors, and commercial nuclear plants, a radiation measurement device and method that can reduce the effects of other radiation sources located in the vicinity is required.

[0011] As an example of a technique for solving such a problem, there are techniques described in Patent Documents 1 and 2.

[0012] In Patent Document 1, a scintillator gas having a density several orders of magnitude lower than that of a solid scintillator is used to convert radiation into light, and the influence of gamma rays caused by other radiation sources placed in the vicinity can be reduced. However, a substance that generates light by interacting with radiation is placed on the inner surface, and this substance is a solid substance that emits light by interacting with radiation such as gamma rays, such as synthetic quartz, borosilicate glass, thallium-activated sodium iodide, and bismuth germanate, and has a higher sensitivity to gamma rays than the scintillator gas. Therefore, in an environment with a high gamma ray flux, the fluorescence of this substance becomes dominant, making it difficult to obtain fluorescence due to capture gamma rays caused by neutrons.

[0013] Furthermore, since the vessel contains neutron capture gas and scintillator gas, enlarging the vessel to improve neutron sensitivity also increases gamma-ray sensitivity, making it difficult to improve the signal-to-noise ratio from an equipment configuration perspective.

[0014] Furthermore, Patent Document 1 does not mention any method for reducing the effects of gamma rays caused by other radiation sources placed in the vicinity.

[0015] In Patent Document 2, neutron measurement in a gamma ray environment is achieved by using a low-pass filter to remove electrical pulses caused by fluorescence and Cherenkov light that are generated by interaction between the components that make up the neutron detector and gamma rays.

[0016] The filter function in Patent Document 2 utilizes the fact that the light emitted in wavelength shifting fibers and optical fibers is in a different frequency range from the light emitted by the neutron scintillator, but does not remove the light emitted by the interaction between the neutron scintillator itself and gamma rays. Furthermore, this neutron scintillator is a long rectangular parallelepiped resin composition in which phosphor particles are dispersed, and is constructed in a solid state, with high sensitivity to gamma rays. For this reason, it is difficult to completely remove the effects of gamma rays caused by other radiation sources placed in the vicinity.

[0017] An object of the present invention is to provide a radiation measurement device and a radiation measurement method capable of measuring neutrons originating from a measurement object by reducing the influence of gamma rays from ambient radiation sources compared to conventional methods. [Means for solving the problem]

[0018] The present invention includes multiple means for solving the above-mentioned problems. One example is a radiation measurement device for measuring neutrons, comprising: an inert gas that emits light with a wavelength longer than the visible light band when irradiated with radiation; a solid neutron sensitive part that is sensitive to neutrons and reflects the light emitted by the inert gas; and a detection vessel in which the inert gas and the neutron sensitive part are each held in structurally separate regions and which has an optical window that transmits the light emitted by the inert gas to the outside. Effect of the Invention

[0019] According to the present invention, it is possible to measure neutrons originating from a measurement object by reducing the influence of gamma rays from surrounding radiation sources compared to the conventional art. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing the configuration of a radiation measurement device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of a detection container according to the first embodiment. [Diagram 3] FIG. 2 is a diagram showing the emission spectrum of an inert gas induced by radiation in Example 1. [Figure 4] FIG. 4 is a diagram showing an output waveform of the photodetector according to the first embodiment. [Diagram 5] FIG. 4 is a diagram showing a peak value spectrum of the first embodiment. [Figure 6] FIG. 11 is a diagram showing a radiation measurement device equipped with a gamma ray correction detection container according to a second embodiment. [Figure 7] FIG. 11 is a diagram showing the configuration of a gamma ray correction detection container according to a second embodiment. [Figure 8]FIG. 1 shows the peak value spectrum of Example 2. [Figure 9] FIG. 11 is an enlarged view of the inner surface of the detection container according to the third embodiment. [Figure 10] FIG. 13 is a configuration diagram of a detection container according to a fourth embodiment. [Figure 11] FIG. 13 is a configuration diagram of a detection vessel equipped with a mesh-type neutron capture unit according to a fourth embodiment. [Figure 12] FIG. 13 is a configuration diagram of a detection vessel equipped with a mesh-type neutron capture unit according to a fourth embodiment. [Figure 13] FIG. 13 is a configuration diagram of a radiation measuring device mounted on a remote operation device of a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention relates to a technique for measuring neutrons, and has been made based on new findings obtained through various investigations in order to measure neutrons while discriminating between neutrons and gamma rays in a gamma ray environment.

[0022] Hereinafter, embodiments of the radiation measurement device and radiation measurement method of the present invention will be described with reference to the drawings. In the drawings used in this specification, the same or similar reference numerals are used to designate the same or corresponding components, and repeated description of these components may be omitted.

[0023] <Example 1> A radiation measurement apparatus and a radiation measurement method according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG.

[0024] First, the overall configuration of the radiation measurement device will be described with reference to Fig. 1. Fig. 1 shows a configuration diagram of the radiation measurement device.

[0025] A radiation measurement device 100 according to the first embodiment shown in FIG. 1 is a device for measuring neutrons, and includes a detection vessel 101, an optical fiber 102, an optical bandpass filter 103, a photodetector 104, and a light emission measurement device 105.

[0026] The detection vessel 101 is placed in a measurement area 106 in which a measurement object 107 that emits neutrons and surrounding objects 108 that are background gamma ray sources are placed. The measurement object 107 contains radioactive materials that emit neutrons. For example, neutrons caused by induced nuclear fission by neutron sources or nuclear materials such as Cf-252, Cm-244, and Am / Be, and neutrons caused by space neutrons or cosmic radiation are measured. The surrounding objects emit gamma rays that interfere with the measurement of neutrons originating from the measurement object 107.

[0027] In the detection vessel 101, an optical fiber 102 is optically connected to an optical window 111 described later, so that the light generated in the detection vessel 101 can be transmitted to the photodetector 104 even if the photodetector 104 is located remotely.

[0028] In this embodiment, a configuration is shown in which the light generated in the detection vessel 101 is transmitted using the optical fiber 102, with the aim of reducing the effects of gamma rays originating from the surrounding objects 108 and reducing worker exposure. Although not described in this embodiment, if the worker exposure is at an acceptable level and there is no need to consider the effects of gamma rays on the photodetector 104, it is possible to omit the optical fiber 102 from the device configuration.

[0029] The optical bandpass filter 103 is provided on the optical path between the optical fiber 102 and the photodetector 104, and is a filter that allows light of a predetermined emission wavelength to pass and blocks light of other wavelengths.

[0030] The photodetector 104 is optically connected to the optical fiber 102 via the optical bandpass filter 103, and converts the light transmitted through the optical bandpass filter 103 into an electric pulse. The converted electric pulse is output to a light emission amount measuring device 105.

[0031] The light emission measuring device 105 is an arithmetic processing unit that calculates the light emission intensity from the output of the photodetector 104, counts the light optically transmitted from the detection vessel 101, and calculates the count value caused by neutrons by taking the difference between the light emission intensity caused by gamma rays and the light emission intensity caused by neutrons. For example, it outputs a peak value spectrum from the voltage value and peak value of the electric pulse output from the photodetector 104 and the detection frequency of the electric pulse.

[0032] The configuration of the detection vessel is shown in Fig. 2. As shown in Fig. 2, the detection vessel 101 holds the inert gas 110 and the neutron sensitive part 109 in structurally separate regions, and has an optical window 111 that transmits the light emitted by the inert gas 110 to the outside.

[0033] As an example, this embodiment shows a configuration in which a solid neutron sensitive part 109 that is sensitive to neutrons and reflects light emitted by an inert gas 110 is applied to the inner surface of the detection vessel 101. This neutron sensitive part 109 may be contained somewhere inside the detection vessel 101, and other arrangement examples will be shown in Examples 4 and 5 below.

[0034] Furthermore, the shape of the detection container 101 may take various forms such as a cylinder, a rectangular parallelepiped, a sphere, etc. In this embodiment, a cylinder is shown as viewed from the side as an example.

[0035] A nuclear reaction occurs with neutrons 113 in the neutron sensitive section 109, causing charged particles 114 to be emitted.

[0036] It is desirable for the neutron sensitive portion 109 to be made of a material containing boron 10, lithium 6, or nitrogen 14, which has a high cross section for reaction with neutrons, and which has the function of reflecting light with a wavelength longer than the visible light band.

[0037] The neutron sensitive section 109 is desirably composed of one or more of boron nitride, lithium fluoride, lithium nitride, lithium hydroxide, lithium oxide, lithium chloride, lithium bromide, lithium iodide, lithium carbonate, lithium silicate, lithium tetraborate, lithium titanate, and lithium acetate.

[0038] For example, boron nitride can reflect light with a wavelength longer than the visible light band with high efficiency, and can effectively reflect light by minimizing the absorption of light originating from the inert gas described below.

[0039] Natural isotope abundance ratios of boron or lithium can be used for the neutron sensitive section 109. In addition, in order to increase the probability of reaction with neutrons 113 and to increase the sensitivity as a neutron detector, it is also possible to use a neutron sensitive section 109 using enriched boron enriched with boron-10 or enriched lithium enriched with lithium-6.

[0040] The nuclear reactions with neutrons 113 in the neutron sensitive section 109, which is equipped with boron 10, lithium 6, and nitrogen 14, are B-10(n,α)Li-7, Li-6(n,t)He-4, and N-14(n,p)C-14. The cross sections of these nuclear reactions with thermal neutrons are 3837×10 -24 cm 2 , 940.4×10 -24 cm 2 , 1.930×10 -24 cm 2 It is.

[0041] The inert gas 110 is a substance that emits light with a wavelength longer than the visible light band when irradiated with radiation, and is, for example, a mixed gas consisting of one or more of helium, neon, argon, krypton, xenon, and nitrogen, and is sealed inside the detection vessel 101. The charged particles 114 generated by these nuclear reactions are captured by the inert gas 110, and their kinetic energy is utilized to cause them to emit light. The inert gases 110 listed here have many emission lines in the range from vacuum ultraviolet (VUV) to the visible light band and infrared band. Although not directly related to the present invention, some of these inert gases 110 are widely used as light sources.

[0042] The light emission mechanism of the inert gas 110 as a light source differs from that of the present invention in that the origin of the light emission energy is the energy of radiation, whereas the present invention utilizes the light emission of the inert gas 110 induced by radiation.

[0043] Radiation-induced luminescence is also used in devices that utilize the luminescence from solid scintillators such as sodium iodide, as well as in laboratory physical experiments that cool and liquefy rare gases such as xenon and use the luminescence generated from the liquid.

[0044] The densities of the inert gases 110 are several orders of magnitude lower than solid matter. The densities of helium, neon, argon, krypton, xenon, and nitrogen are 0.179 kg / m, respectively. 3 , 0.90kg / m 3 , 1.79kg / m 3 , 3.74kg / m 3 , 131kg / m 3 , 1.25kg / m 3 , is.

[0045] The range of the charged particles 114 is shorter than that of gamma rays or X-rays. Although it is correlated with the length of the detection vessel 101 and the gas pressure of the inert gas 110, in order to obtain sufficient energy caused by neutrons, the kinetic energy is basically imparted to the inert gas 110 in the inert gas 110 region.

[0046] The interaction between gamma rays and a substance is proportional to the atomic number Z and density of the substance. The inert gas 110 is a gas and has a low density, so in principle it is difficult for the inert gas 110 to interact with gamma rays 112. Therefore, there is almost no light emission due to gamma rays 112. Depending on the material of the detection vessel 101, secondary electrons are generated by the interaction between the material of the detection vessel 101 and the gamma rays 112, and are emitted into the inert gas 110. When there are a large number of gamma rays 112 generated from the surrounding objects 108, the influence of the gamma rays 112 may not be negligible. In preparation for this case, it is desirable to use a material with a small atomic number or a small density for the material of the detection vessel 101. Examples of such a material include light metals such as aluminum and organic compounds such as plastic. For organic compounds, a material with high radiation resistance such as polyimide may be selected.

[0047] Light 115 generated by these nuclear reactions and gamma rays enters the optical window 111 directly, or is reflected by the neutron sensitive section 109 and enters the optical window 111 as reflected light 116. A material with high optical transparency is used for the optical window 111. For example, it is desirable to use synthetic quartz, BK7, anhydrous synthetic quartz, or the like.

[0048] The radiation-induced emission spectrum of the inert gas is shown in Figure 3. As shown in Figure 3, the inert gas 110 emits light in various wavelength bands due to radiation induction. The optical bandpass filter 103 narrows down the light that has passed through the optical fiber 102 to a bandpass range 117. Background sources from the viewpoint of light detection include, for example, Cherenkov light generated by the interaction of gamma rays 112 with the optical fiber 102 or with materials on the optical path. A bandpass range 117 is set by the optical bandpass filter 103 to remove light emission due to Cherenkov light, and light in a desired band is measured by the photodetector 104.

[0049] Furthermore, continued use of the optical fiber 102 and the optical window 111 in an environment with strong gamma rays 112 generates defects in the materials, making it difficult for light of a particular band to transmit through. In order to reduce this effect, a bandpass range 117 is set that excludes the particular band that is difficult to transmit through, thereby reducing the effect of gamma rays 112.

[0050] For example, when quartz or the like is used, the transmittance in the visible light band is degraded, but the transmittance in the near-infrared region is maintained, so that the optical bandpass filter 103 is set to transmit light in the near-infrared region or longer wavelength band than the emission wavelength of 780 nm or more by setting its lower wavelength limit to 780 nm or more, thereby reducing the influence of gamma rays 112. In this case, the photodetector 104 measures light in the infrared band.

[0051] The output waveform of the photodetector is shown in Figure 4. The amount of light generated in the detection vessel 101 is converted into an electric pulse 118. The voltage value of the electric pulse 118 correlates with the amount of light emission, and this amount of light emission correlates with the amount of energy imparted to the inert gas 110 due to radiation induction. In addition, the timing at which the electric pulse 118 is generated correlates with the timing of the radiation-induced light emission, and therefore occurs randomly.

[0052] The pulse height spectrum is shown in Figure 5. In the light emission measurement device 105, the electric pulses 118 shown in Figure 4 are counted for a certain period of time, the pulse height values ​​of the accumulated electric pulses 118 are analyzed, and the results are shown as a pulse height spectrum 119. Here, the case of observing the neutron response of boron-10 is shown as an example.

[0053] 5, when energy is imparted by the charged particles 114, in the decay process, alpha rays of 1.47 MeV or 1.78 MeV and Li-7 of 0.84 MeV or 1.01 MeV are emitted as the charged particles 114. In addition, a neutron-induced pulse-peak spectrum 120 is obtained as information including the effects of energy losses in the detection vessel 101 and the neutron sensitive part 109 themselves.

[0054] In addition, the above nuclear reaction with boron-10 produces 478 keV gamma rays, but these gamma rays are not measured.

[0055] The light emission caused by gamma rays is also shown in a peak value spectrum 119. The peak values ​​of the gamma ray-induced peak value spectrum 121 vary depending on the gamma ray energy, but if gamma ray energy of around 1 MeV is dominant, for example, a continuous distribution is shown with lower peak values ​​than the neutron-induced peak value spectrum.

[0056] Here, the peak value spectrum 119 itself shown by the light emission measuring device 105 cannot distinguish between neutrons and gamma rays. Therefore, the energy and range of the charged particles 114 originating from the neutron sensitive part 109 contained in the detection vessel 101, the energy of the gamma rays 112 originating from the surrounding object 108, and the energy imparted in the detection vessel 101, etc. are grasped in advance, and a neutron counting range 122 is determined in advance, the counts in the neutron counting range 122 are analyzed, and the presence or absence of neutrons detected and the magnitude of the count value are evaluated. That is, in this embodiment 1, the peak value spectrum 120 and the peak value spectrum 121 are not separated, and the number of neutrons is counted from the neutron counting range 122 determined in advance.

[0057] Next, a radiation measurement method for measuring neutrons according to this embodiment will be briefly described.

[0058] First, as described above, inert gas 110 that emits light with a wavelength longer than the visible light band when exposed to radiation, and detection vessel 101 that is sensitive to neutrons and has solid neutron sensitive part 109 that reflects the light emitted by inert gas 110, each held in a structurally separate region, are placed in an environment where neutrons are present, the light emitted by inert gas 110 is transmitted to the outside, the light optically transmitted from detection vessel 101 is counted, and the difference between the light emission intensity caused by gamma rays and the light emission intensity caused by neutrons is taken to calculate the count value caused by neutrons.

[0059] Next, the effects of this embodiment will be described.

[0060] The radiation measurement device 100 for measuring neutrons in the above-described embodiment 1 of the present invention includes an inert gas 110 that emits light of a wavelength longer than the visible light band when irradiated with radiation, a solid neutron sensitive part 109 that is sensitive to neutrons and reflects the light emitted by the inert gas 110, and a detection vessel 101 that holds the inert gas 110 and the neutron sensitive part 109 in structurally separate regions and has an optical window 111 that transmits the light emitted by the inert gas 110 to the outside.

[0061] In this way, the region sensitive to gamma rays and the region sensitive to neutrons are structurally separated by the solid neutron sensitive part 109 and the gaseous inert gas 110, and the light emitted from the inert gas 110 is reflected to the neutron sensitive part 109 in the detection vessel 101. This makes it possible to adjust the neutron sensitivity by the arrangement and area of ​​the solid neutron sensitive part 109, in addition to adjusting the volume of the inert gas, and reduces the effects of gamma rays from surrounding radiation sources, making it possible to measure neutrons originating from the object to be measured.

[0062] In addition, since the device further includes an optical fiber 102 optically connected to the detection container 101, a photodetector 104 optically connected to the optical fiber 102, and a luminescence intensity measuring device 105 that calculates the luminescence intensity from the output of the photodetector 104, the measurement results can be obtained on the device side, making it easier to process the measurement results.

[0063] Furthermore, the light emission measuring device 105 counts the light transmitted from the detection vessel 101, and calculates the neutron-induced count value by taking the difference between the light emission intensity caused by gamma rays and the light emission intensity caused by neutrons, thereby achieving a more accurate neutron coefficient.

[0064] Furthermore, since the neutron sensitive part 109 is provided on the inner surface of the detection vessel 101, a stable and reliable structure can be achieved.

[0065] Furthermore, by further providing an optical bandpass filter 103 on the optical path between the optical fiber 102 and the photodetector 104, unnecessary counts are eliminated, thereby improving the processing speed and accuracy.

[0066] Furthermore, by setting the lower wavelength limit of the optical bandpass filter 103 to 780 nm or more and the photodetector 104 measuring light in the infrared band, a material with high optical transparency such as quartz can be used for the optical window 111, and in that case, an area where transparency does not deteriorate can be utilized, thereby improving durability.

[0067] Furthermore, since the inert gas 110 is composed of one or more components selected from the group consisting of helium, neon, argon, krypton, xenon, and nitrogen, it can be composed of a lower substance than solid substances, thereby reducing interaction with the gamma rays 112 and enabling more accurate counting.

[0068] Furthermore, the neutron sensitive section 109 contains boron-10, lithium-6, and nitrogen-14. More specifically, the neutron sensitive section 109 is made of one or more of boron nitride, lithium fluoride, lithium nitride, lithium hydroxide, lithium oxide, lithium chloride, lithium bromide, lithium iodide, lithium carbonate, lithium silicate, lithium tetraborate, lithium titanate, and lithium acetate. This allows the neutron sensitive section 109 to be made of a material with a high reaction cross section with neutrons, making it possible to make the section less susceptible to the influence of background light due to an increase in the neutron-derived coefficient itself.

[0069] <Example 2> Second Embodiment A radiation measuring device and a radiation measuring method according to a second embodiment of the present invention will be described with reference to FIGS.

[0070] The second embodiment relates to a radiation measurement device and method for reducing the influence of gamma rays and improving the signal-to-noise ratio of neutron measurement.

[0071] A configuration diagram of a radiation measurement device equipped with a detection container for gamma ray correction is shown in Fig. 6. The radiation measurement device 200 of this embodiment shown in Fig. 6 includes a detection container for gamma ray correction 123, an optical fiber 102, an optical bandpass filter 103, a photodetector 104, a gamma ray luminescence amount measuring device 124, and a gamma ray luminescence amount measuring device 125 in addition to the angular configuration of the radiation measurement device 100 shown in Fig. 1.

[0072] The detection vessel 123 for gamma ray correction is disposed in the measurement area 106 in the same manner as the detection vessel 101 , and more preferably disposed in the vicinity of the detection vessel 101 .

[0073] A configuration diagram of the gamma ray correction detection vessel 123 is shown in Fig. 7. As shown in Fig. 7, the gamma ray correction detection vessel 123 has a wall surface and an optical window 111 with the same structure and specifications as the detection vessel 101, and is provided therein with a reflector 126 that does not react to neutrons (i.e., has a small cross-sectional area for reaction with neutrons) instead of the neutron sensitive part 109 in the detection vessel 101. Furthermore, the gamma ray correction detection vessel 123 contains an inert gas 110 with the same composition as the inert gas 110 contained in the detection vessel 101.

[0074] Since the gamma ray correction detection vessel 123 does not contain any material that is sensitive to neutrons 113, only the light emitted by the gamma rays 112 is transmitted to the gamma ray light emission amount measuring device 124 via the optical window 111, the downstream optical fiber 102, the optical bandpass filter 103, and the photodetector 104.

[0075] The gamma ray luminescence amount measuring device 124 has substantially the same configuration as the luminescence amount measuring device 105, and is an arithmetic processing unit that counts the light optically transmitted from the gamma ray correction detection container 123 and calculates the count value caused by the gamma rays 112.

[0076] The pulse height spectrum is shown in Fig. 8. In the pulse height spectrum 127 shown in Fig. 8, a pulse height spectrum 128 by the detection container 101 obtained by the luminescence amount measuring device 105 and a pulse height spectrum 129 by the gamma-ray correction detection container 123 obtained by the gamma-ray luminescence amount measuring device 124 are shown.

[0077] The gamma-ray correction light emission amount measuring device 125 calculates a count value due to neutrons by taking the difference in output between the pulse height spectrum of the light emission amount measuring device 105 and the pulse height spectrum of the gamma-ray light emission amount measuring device 124. Furthermore, a neutron counting range 130 is provided in a range of pulse height values ​​higher than the upper pulse height value upper limit of the pulse height value spectrum 129, and a count value due to neutrons is calculated.

[0078] The other configurations and operations are substantially the same as those of the radiation measurement device and radiation measurement method of the first embodiment described above, and the details are omitted.

[0079] The radiation measurement apparatus and radiation measurement method according to the second embodiment of the present invention also provide substantially the same effects as those of the radiation measurement apparatus and radiation measurement method according to the first embodiment described above.

[0080] Furthermore, by further providing a gamma ray correction detection vessel 123 having an inert gas 110 and an optical window 111, a gamma ray light emission measuring device 124 which counts the light optically transmitted from the gamma ray correction detection vessel 123 and calculates a count value caused by gamma rays, and a gamma ray light emission measuring device 125 for gamma ray correction which calculates a count value caused by neutrons by taking the difference between the output of the light emission measuring device 105 and the output of the gamma ray light emission measuring device 124, the influence of gamma rays can be further reduced, thereby making it possible to further improve the signal-to-noise ratio of neutron measurement.

[0081] <Example 3> Third Embodiment A radiation measurement apparatus and a radiation measurement method according to a third embodiment of the present invention will be described with reference to FIG.

[0082] The present embodiment 3 relates to a radiation measurement device that has two layers of neutron sensitive parts and measures neutrons. Fig. 9 shows an enlarged view of the inner surface of the detection vessel.

[0083] 9, a feature of the radiation measurement device 300 of this embodiment is the detection vessel 131. The neutron sensitive part inside the detection vessel 131 has a two-layer structure.

[0084] Of these, the first neutron sensitive portion 132, which constitutes the layer in contact with the inert gas 110, has a higher content of one or more of boron-10, lithium-6, or nitrogen-14 than the other layers (the second neutron sensitive portion 133, which will be the layer with the highest content if the neutron sensitive portion has three or more layers).

[0085] In contrast, the second neutron sensitive section 133 , which is a layer on the side not in contact with the inert gas 110 , is configured to have a lower content of boron-10, lithium-6, or nitrogen-14 than the first neutron sensitive section 132 .

[0086] In the radiation measurement device 300, neutrons 113 undergo a nuclear reaction with the first neutron sensitive part 132 or the second neutron sensitive part 133 in the detection vessel 131, emitting charged particles 114. Light 115 is emitted from the inert gas 110 due to the energy transfer of the charged particles 114. A part of this light 115 enters the first neutron sensitive part 132 and the second neutron sensitive part 133, and is reflected at one of the positions of these neutron sensitive parts, and reflected light 116 returns to the inert gas 110.

[0087] Here, it is desirable that the total thickness of the first neutron sensitive portion 132 and the second neutron sensitive portion 133 be equal to or greater than a specified thickness for reflecting light emitted from the inert gas 110 in order to efficiently reflect the light emitted from the inert gas 110.

[0088] In order for the charged particles 114 generated by the nuclear reaction with the neutrons 113 to reach the inert gas 110, they must pass through the first neutron sensitive part 132 itself. For this reason, the first neutron sensitive part 132 is configured to be as thin as possible.

[0089] On the other hand, a neutron sensitive part having a certain thickness is required to efficiently reflect the light emitted from the inert gas 110. When the thickness of the first neutron sensitive part 132 is thinner than the desired thickness required for reflecting light, the second neutron sensitive part 133 is used, and the total thickness of the first neutron sensitive part 132 and the second neutron sensitive part 133 is made equal to or greater than the desired thickness required for reflecting light.

[0090] The other configurations and operations are substantially the same as those of the radiation measurement device and radiation measurement method of the first embodiment described above, and the details are omitted.

[0091] The radiation measurement device and radiation measurement method of the third embodiment of the present invention can obtain substantially the same effects as those of the radiation measurement device and radiation measurement method of the first embodiment described above, and can further improve the neutron sensitivity while effectively reflecting the light 115 by the inert gas 110.

[0092] <Example 4> A radiation measuring device and a radiation measuring method according to a fourth embodiment of the present invention will be described with reference to FIGS.

[0093] The fourth embodiment relates to a radiation measurement device in which a neutron sensitive part is disposed inside a detection vessel.

[0094] A configuration diagram of the detection vessel is shown in Fig. 10. In a radiation measurement device 400A of this embodiment shown in Fig. 10, a neutron capture unit 138A composed of a neutron sensitive part 136 and a neutron sensitive part fixture 135 is provided in the internal space of the detection vessel 134.

[0095] 10, a plate-shaped neutron sensitive part fixing tool 135 is provided. The plate-shaped neutron sensitive part fixing tool 135 is disposed inside the detection vessel 134, and neutron sensitive parts 136 are provided on both sides of the neutron sensitive part fixing tool 135.

[0096] As another embodiment of the radiation measurement device and radiation measurement method of this embodiment, FIG. 11 is a diagram showing the configuration of a detection vessel equipped with a mesh-type neutron capture unit, and FIG. 12 is a detailed diagram showing the configuration of a detection vessel equipped with a mesh-type neutron capture unit 138B, in which the detection vessel 137 shown in FIG. 11 is rotated and viewed from a different angle.

[0097] 11 and 12, a radiation measurement device 400B according to a modification of this embodiment is the same as the radiation measurement device 400A shown in Fig. 10 in that a neutron capture unit composed of a neutron sensitive part 140 and a neutron sensitive part fixture 139 is provided in the internal space of the detection vessel 137, but the detection vessel 137 is provided with a mesh-type neutron capture unit 138B. Here, as an example, a plate-shaped mesh-type neutron capture unit 138B is provided.

[0098] As shown in Fig. 12, the mesh-type neutron capture unit 138B is composed of a mesh-type neutron sensitive unit fixture 139 and a mesh-type neutron sensitive unit 140. Neutrons 113 cause a nuclear reaction in the mesh-type neutron sensitive unit 140, and charged particles 114 are emitted. Light 115 generated in the inert gas 110 passes through the holes in the mesh-type neutron capture unit 138B. By providing the mesh-type neutron capture unit 138B, more paths can be provided for the light 115.

[0099] The other configurations and operations are substantially the same as those of the radiation measurement device and radiation measurement method of the first embodiment described above, and the details are omitted.

[0100] The radiation measurement apparatus and radiation measurement method according to the fourth embodiment of the present invention also provide substantially the same effects as those of the radiation measurement apparatus and radiation measurement method according to the first embodiment described above.

[0101] Furthermore, since the neutron capture units 138A, 138B, which are composed of the neutron sensitive units 136, 140 and the neutron sensitive unit fixing devices 135, 139, are provided in the internal space of the detection vessels 134, 137, it is possible to position the neutron sensitive units 136, 140 in accordance with the structure of the detection vessels 134, 137, the neutron sensitivity to be obtained, and even the path of the light generated from the inert gas.

[0102] In this embodiment, the neutron sensitive part 109 can also be provided on the inner surface of the detection vessels 134, 137. If the neutron sensitive part 109 is not provided, a reflective material can also be provided on the inner surface of the detection vessels 134, 137.

[0103] <Example 5> Fifth embodiment A radiation measuring device and a radiation measuring method according to the present invention will be described with reference to FIG.

[0104] The fifth embodiment relates to a radiation measurement device equipped with a remote operation device.

[0105] 13, a detection vessel 141 is mounted on a remote operation device 142 for remote operation. This allows measurements caused by neutrons to be obtained in a remote operation area, and the neutron flux in the remote operation area to be monitored.

[0106] Specifically, as shown in FIG. 13, the radiation measuring device 500 includes a detection container 141, an optical fiber 102, an optical bandpass filter 103, a photodetector 104, a light emission measuring device 105, a neutron monitoring and display device 144, a remote operation device 142, and a remote operation control device 143, and the radiation measuring device 500 is operated by an operator 145.

[0107] The configuration of the detection container 141 of the fifth embodiment can be any one or more of the detection containers 101, 131, 134, and 137 of any one of the first to fourth embodiments.

[0108] When performing any task in the measurement area 106, a worker 145 uses a neutron monitoring and display device 144 to obtain information about neutrons in the measurement area 106, while operating a remote operation device 142 in the measurement area 106 via a remote operation control device 143. Based on the obtained neutron information, the worker 145 performs the operation and manages the task.

[0109] The other configurations and operations are substantially the same as those of the radiation measurement device and radiation measurement method of the first embodiment described above, and the details are omitted.

[0110] The radiation measurement apparatus and radiation measurement method according to the fifth embodiment of the present invention also provide substantially the same effects as those of the radiation measurement apparatus and radiation measurement method according to the first embodiment described above.

[0111] In addition, a detection vessel 141 is mounted, and a remote operation device 142 for remote operation is further provided, which enables appropriate remote operation and operation management based on neutron monitoring information.

[0112] <Other> The present invention is not limited to the above-mentioned embodiment, but includes various modified examples. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to the embodiment having all of the described configurations.

[0113] It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace part of the configuration of each embodiment with the configuration of another embodiment. [Explanation of symbols]

[0114] 100, 200, 300, 400A, 400B, 500...Radiation measurement device 101, 131, 134, 137, 141…Detection container 102...Optical fiber 103...Optical bandpass filter 104...Photodetector 105...Luminescence measurement device 106…Measuring area 107...Measurement object 108... Peripheral objects 109,136...Neutron sensitive part 110...Inert gas 111...Optical window 112…Gamma rays 113…Neutron 114...Charged particle 115...light 116...Reflected light 117…Bandpass range 118...Electric pulse 119,127...Wave height spectrum 120...Neutron-induced pulse height spectrum 121...Gamma-ray-induced pulse height spectrum 122,130…Neutron counting range 123…Detection vessel for gamma ray correction 124... Gamma ray emission measurement device 125...Gamma-ray correction light emission measuring device 126...Reflective material 128...Pulse height spectrum by detection vessel 129...Pulse height spectrum using gamma ray correction detection vessel 132...First neutron sensitive part 133…Second neutron sensing part 135...Neutron sensitive part fixture 138A…Neutron capture section 138B…Mesh-type neutron capture section 139…Mesh-type neutron sensing part fixing device 140…Mesh-type neutron sensing section 142...Remote control device 143...Remote control device 144...Neutron monitoring and display device 145…Worker

Claims

1. A radiation measurement device that measures neutrons, An inert gas that emits light with a wavelength longer than the visible light band when exposed to radiation; a solid neutron sensitive portion that is sensitive to neutrons and reflects light emitted by the inert gas; a detection vessel in which the inert gas and the neutron sensitive portion are held in structurally separate regions, and which has an optical window for transmitting the light emitted by the inert gas to the outside. Radiation measurement device.

2. 2. The radiation measurement device according to claim 1, an optical fiber optically connected to the detection vessel; a photodetector optically connected to the optical fiber; and a light emission amount measuring device that calculates a light emission intensity from the output of the light detector. Radiation measurement device.

3. 3. The radiation measurement device according to claim 2, The luminescence measuring device counts the light transmitted from the detection vessel, and calculates a count value due to neutrons by taking the difference between the luminescence intensity due to gamma rays and the luminescence intensity due to neutrons. Radiation measurement device.

4. 3. The radiation measurement device according to claim 2, a gamma ray correction detection vessel having the inert gas and the optical window; a gamma ray emission amount measuring device that counts the light transmitted from the gamma ray correction detection vessel and calculates a count value attributable to gamma rays; and a gamma-ray correction light emission measuring device that calculates a count value caused by neutrons by calculating a difference between the output of the light emission measuring device and the output of the gamma-ray light emission measuring device. Radiation measurement device.

5. 2. The radiation measurement device according to claim 1, The neutron sensitive portion is provided on the inner surface of the detection vessel. Radiation measurement device.

6. 2. The radiation measurement device according to claim 1, The neutron sensitive part has a structure of two or more layers, a first neutron sensitive portion in which the layer in contact with the inert gas has a higher content of one or more of boron-10, lithium-6, or nitrogen-14 than other layers; A layer that does not come into contact with the inert gas is constituted by a second neutron sensitive portion having a lower content of the boron 10, the lithium 6, or the nitrogen 14 than the first neutron sensitive portion. Radiation measurement device.

7. 7. The radiation measurement device according to claim 6, The total thickness of the first neutron sensitive portion and the second neutron sensitive portion is equal to or greater than a predetermined thickness that reflects light emitted from the inert gas. Radiation measurement device.

8. 2. The radiation measurement device according to claim 1, A neutron capture unit consisting of the neutron sensitive part and a neutron sensitive part fixing device is provided in the internal space of the detection vessel. Radiation measurement device.

9. 2. The radiation measurement device according to claim 1, The detection container is mounted on the remote operation device for remotely operating the detection container. Radiation measurement device.

10. 3. The radiation measurement device according to claim 2, and an optical bandpass filter on the optical path between the optical fiber and the photodetector. Radiation measurement device.

11. The radiation measurement device according to claim 10, The lower wavelength limit of the optical bandpass filter is set to 780 nm or more, The photodetector measures light in the infrared range. Radiation measurement device.

12. 2. The radiation measurement device according to claim 1, The inert gas is composed of one or more components selected from the group consisting of helium, neon, argon, krypton, xenon, and nitrogen. Radiation measurement device.

13. 2. The radiation measurement device according to claim 1, The neutron sensitive portion contains boron-10, lithium-6, and nitrogen-14. Radiation measurement device.

14. 2. The radiation measurement device according to claim 1, The neutron sensitive portion is composed of one or more of boron nitride, lithium fluoride, lithium nitride, lithium hydroxide, lithium oxide, lithium chloride, lithium bromide, lithium iodide, lithium carbonate, lithium silicate, lithium tetraborate, lithium titanate, and lithium acetate. Radiation measurement device.

15. A radiation measurement method for measuring neutrons, comprising: a detection vessel in which an inert gas that emits light of a wavelength longer than the visible light band when irradiated with radiation and a solid neutron sensitive portion that is sensitive to neutrons and reflects the light emitted by the inert gas are held in separate structural regions, is placed in an environment in which neutrons are present; The light emitted from the inert gas is transmitted to the outside. Radiation measurement methods.

16. The radiation measurement method according to claim 15, The light transmitted from the detection vessel is counted, and the difference between the emission intensity caused by gamma rays and the emission intensity caused by neutrons is calculated to calculate the count value caused by neutrons. Radiation measurement methods.

17. The radiation measurement method according to claim 15, placing the gamma ray correction detection vessel holding the inert gas and the detection vessel in an environment in which the neutrons are present; Counting the light transmitted from the detection vessel; Counting the light transmitted from the gamma ray correction detection vessel to calculate a count value attributable to gamma rays; A count value caused by neutrons is calculated by taking a difference between the count value from the detection vessel and the count value caused by gamma rays. Radiation measurement methods.

18. The radiation measurement method according to claim 15, The detection container is mounted on a remote control device; Obtain neutron induced measurements in remote work areas and monitor neutron flux in remote work areas Radiation measurement methods.

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