Non-destructive Inspection Equipment

Abstract

To provide a nondestructive inspection device capable of performing an inspection by securing safety in a surrounding area concerning a nondestructive inspection to be performed by using neutrons with respect to an inspected object.SOLUTION: A nondestructive inspection device 1 comprises: a neutron irradiation section 10 for radiating a neutron beam in a predetermined irradiation direction D1; a gamma beam detection section 20 for detecting a gamma beam to be made incident from a predetermined detection direction D2 crossing with the irradiation direction D1; a device housing 30 which covers the neutron irradiation section 10 and the gamma beam detection section 20 and where an opening part 30a is formed on the irradiation direction D1 and on the detection direction D2; an outer shutter 31 for opening / closing the opening part 30a of the device housing 30; an external dose monitor 41 for detecting a radiation dose inside the device housing 30; an internal dose monitor 42 for detecting a radiation dose outside the device housing 30; and a control section 40 for prohibiting the opening of the outer shutter 31 when the radiation dose detected by at least one of the dose monitors 41, 42 exceeds a predetermined threshold.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a non-destructive inspection device for an object to be inspected using a neutron beam. [Background technology]

[0002] In recent years, there has been a demand for appropriate maintenance, repair, and renewal of aging infrastructure such as roads, bridges, tunnels, and buildings (hereinafter referred to as infrastructure structures).

[0003] In the inspection of such infrastructure structures, non-destructive inspection is carried out using radiation such as X-rays that can penetrate objects, making it possible to analyze the internal structure of the object being inspected without destroying it.

[0004] In particular, in recent years, non-destructive testing devices using neutron rays, which have higher penetrating power than X-rays, have been considered. For example, Patent Document 1 and Non-Patent Document 1 disclose a non-destructive testing method that can obtain the salt concentration distribution inside concrete by using neutron rays and gamma (γ) rays generated by the reaction between the neutron rays. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-85481 A [Non-patent literature]

[0006] [Non-Patent Document 1] RIKEN / Yasuo Wakabayashi, Yuichi Yoshimura, Maki Mizuta, Yujiro Ikeda, Yoshie Ohtake, "Non-destructive measurement method for chloride content in concrete (NPGA)" Japan Industrial Publishing Inspection Technology, February 2019 issue Summary of the Invention [Problem to be solved by the invention]

[0007] In technologies using neutron beams such as those described in Patent Document 1 and Non-Patent Document 1, safety measures are required to reduce radiation exposure of workers performing inspections on-site and other surrounding persons, to manage the amount of radiation exposure, and to prevent misuse or abuse of equipment containing radiation sources by others.

[0008] The present invention has been made to solve such problems, and its object is to provide a non-destructive testing device that can perform non-destructive testing of an object to be tested using neutron beams while ensuring safety for the surrounding area. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the non-destructive inspection device of the present invention comprises a neutron irradiation unit capable of irradiating a neutron beam in a predetermined irradiation direction, a radiation detection unit capable of detecting radiation incident from a predetermined detection direction intersecting the irradiation direction, a first housing covering the neutron irradiation unit and the radiation detection unit and having a first opening formed in the irradiation direction and the detection direction, a first shutter for opening and closing the opening of the first housing, a first dose detection unit for detecting the amount of radiation outside the first housing, a second dose detection unit for detecting the amount of radiation inside the first housing, and a control unit for prohibiting the first shutter from opening when the amount of radiation detected by at least one of the first dose detection unit and the second dose detection unit exceeds a predetermined threshold.

[0010] In addition, in the above-mentioned non-destructive inspection apparatus, the control unit may control the first shutter to open during inspection on condition that neither of the radiation amounts detected by the first dose detection unit and the second dose detection unit exceeds a predetermined threshold value.

[0011] In the non-destructive inspection device, the neutron irradiation unit includes a neutron source that emits a neutron beam, a second housing that covers the neutron source and has a second opening formed in the irradiation direction, The second housing may have a second shutter that opens and closes the second opening, and a third dose detection unit that detects an amount of radiation in the second housing, and the control unit may prohibit the first shutter and the second shutter from opening when an amount of radiation detected by at least one of the first dose detection unit, the second dose detection unit, and the third dose detection unit exceeds a predetermined threshold.

[0012] In addition, in the above-mentioned non-destructive inspection apparatus, the control unit may control the first shutter and the second shutter to be opened during inspection, on condition that none of the radiation doses detected by the first dose detection unit, the second dose detection unit, and the third dose detection unit exceed the predetermined threshold value.

[0013] In addition, in the above-mentioned non-destructive inspection device, the control unit may control the first shutter to be opened before the second shutter during inspection, and to open the second shutter after the radiation detection unit detects the radiation state before neutron beam irradiation.

[0014] In addition, in the above-mentioned non-destructive inspection device, the neutron irradiation unit may have a linear accelerator capable of emitting an accelerated charged particle beam, and a target unit capable of generating a neutron beam by being irradiated with the charged particle beam, and the control unit may prohibit the emission of charged particles from the linear accelerator and prohibit the opening of the first shutter when the amount of radiation detected by at least one of the first dose detection unit and the second dose detection unit exceeds a predetermined threshold.

[0015] In addition, in the above-mentioned non-destructive inspection apparatus, the control unit may control the linear accelerator to emit charged particles and the first shutter to open during inspection, on condition that neither of the amounts of radiation detected by the first dose detection unit and the second dose detection unit exceeds the predetermined threshold value.

[0016] In addition, in the above-mentioned non-destructive inspection device, the control unit may control the first shutter to be opened before the emission of charged particles from the linear accelerator during inspection, and to detect the radiation state before neutron beam irradiation using the radiation detection unit, and then to emit the charged particles from the linear accelerator. Effect of the Invention

[0017] According to the present invention using the above-mentioned means, in non-destructive testing using neutron rays on an object to be inspected, the test can be performed while ensuring safety for the surrounding area. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic configuration diagram showing a nondestructive inspection system according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic configuration diagram showing a nondestructive inspection system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] (First embodiment) First, a first embodiment of the present invention will be described.

[0021] 1 is a schematic diagram of a non-destructive inspection device 1 according to a first embodiment of the present invention. The configuration of the non-destructive inspection device 1 of this embodiment will be described below with reference to these drawings.

[0022] 1, in the nondestructive inspection device 1 of this embodiment, a neutron irradiation unit 10 and a gamma ray detection unit (radiation detection unit) 20 are provided in an apparatus housing (first housing) 30. The nondestructive inspection device 1 also has a control unit 40, to which are connected an external dose monitor 41 (first dose detection unit), an internal dose monitor 42 (second dose detection unit), a radiation source dose monitor 43 (third dose detection unit), which detect radiation doses at their respective installation locations, and an alarm 44 that issues an alarm. In this embodiment, the nondestructive inspection device 1 is placed on a bridge B made of concrete, which is an object to be inspected.

[0023] In the neutron irradiation unit 10, a neutron source 11 is provided in a source housing (second housing) 12. The neutron source 11 in this embodiment is a radioisotope that spontaneously generates a radial neutron beam, for example. 252 Cf radiation source.

[0024] The radiation source housing 12 has a hollow, generally cubic shape, and in this embodiment, a neutron beam irradiation hole (second opening) 12a is formed on the bottom surface. The radiation source housing 12 is also provided with a radiation source shutter (second shutter) 13 that opens and closes the irradiation hole 12a. The radiation source housing 12 and the radiation source shutter 13 are formed of a material capable of blocking neutron beams, such as lead or iron. The irradiation hole 12a is, for example, a circular hole, and the radiation source shutter 13 is an opening / closing plate member that slides on the bottom surface of the radiation source housing 12 to open and close the irradiation hole 12a by an actuator (not shown).

[0025] The neutron irradiation unit 10 configured in this manner can irradiate to the outside only the neutron beams directed downward where the irradiation holes 12a are provided, among the neutron beams radially irradiated from the neutron source 11. That is, in this embodiment, the downward direction is the irradiation direction D1 of the neutron beam. Moreover, the irradiation and stopping (non-irradiation) of the neutron beam can be controlled by opening and closing the radiation source shutter 13.

[0026] The gamma ray detection unit 20 includes a detector 21 capable of detecting gamma (γ) rays, a collimator 22, and a movable shaft 23.

[0027] The detector 21 is, for example, a germanium semiconductor detector (Ge detector). A collimator 22 is connected to the tip of the detector 21, and the detector 21 can detect the amount of gamma rays incident through the collimator 22.

[0028] The collimator 22 is a cylinder made of a material that blocks gamma rays, such as lead or iron, and has the function of narrowing down gamma rays incident from the outside to gamma rays in one direction toward the detector 21. That is, in this embodiment, the axial direction of the collimator 22 is the gamma ray detection direction D2. As shown in Fig. 1, the detection direction D2 intersects with the irradiation direction D1 at one point, and this intersection is the inspection position P inside the bridge B of the inspection object. If the salinity at this inspection position P is high, the amount of gamma rays detected by the detector 21 will be higher than usual.

[0029] A movable shaft 23 extending in the horizontal direction is provided at the rear end portion of the detector 21. The detector 21 can be swung vertically around the movable shaft 23 together with the collimator 22. By swung around the movable shaft 23 in this manner, the inspection position P can be moved in the irradiation direction D1.

[0030] The device housing 30 covers the neutron irradiator 10 and the gamma ray detector 20, and has openings 30a (first openings) formed in the irradiation direction D1 and the detection direction D2.

[0031] In detail, the device housing 30 has a hollow, generally rectangular parallelepiped shape and is made of a material capable of blocking neutron rays, such as lead, iron, etc. Inside the device housing 30, the neutron irradiation unit 10 is disposed on one horizontal side, and the gamma ray detection unit 20 is disposed on the other horizontal side.

[0032] An opening 30a is formed on the bottom surface of the device housing 30, the opening including the irradiation direction D1 and the detection direction D2. The shape of the opening 30a is not particularly limited as long as the irradiation direction D1 and the detection direction D2 are included within the opening, but in this embodiment, for example, the opening 30a is a rectangular hole. The opening range of the opening 30a is designed to include the range in which the detection direction D2 changes due to the swinging of the gamma ray detection unit 20 around the movable shaft 23.

[0033] Further, an outer shutter 31 (first shutter) for opening and closing the opening 30a is provided on the bottom surface of the device housing 30. The outer shutter 31 is made of a material capable of blocking neutron rays, such as lead or iron. The outer shutter 31 is a plate material that slides on the bottom surface of the device housing 30 to open and close the opening 30a by an actuator (not shown).

[0034] Wheels 32 are provided on the outside of the bottom surface of the device housing 30, allowing the device housing 30 to move freely along the bridge B. In this embodiment, the wheels 32 are provided directly on the device housing 30, but the device housing 30 may be movable by placing it on a dolly or a moving body, for example, even if the device housing 30 does not have wheels.

[0035] In this embodiment, an external dose monitor 41 is provided on the outer side of the top surface of the equipment housing 30, and the external dose monitor 41 detects the amount of radiation around the outside of the nondestructive inspection equipment 1. Also, an internal dose monitor 42 is provided on the inner side of the top surface of the equipment housing 30, and the internal dose monitor 42 detects the amount of radiation inside the nondestructive inspection equipment 1. Furthermore, a radiation source dose monitor 43 is provided on the inner side of the top surface of the radiation source housing 12, and the radiation source dose monitor 43 detects the amount of radiation inside the radiation source housing 12.

[0036] Examples of radiation that can be detected by each of the dose monitors 41, 42, and 43 include alpha (α) rays, beta (β) rays, and gamma (γ) rays. Each of the dose monitors 41, 42, and 43 can detect an air dose rate (microsieverts per hour (μSv / h)) as a radiation dose. Note that the types and amounts of radiation that can be detected are not limited to these, and any type that can detect the amount of radiation exposure to the human body can be used.

[0037] The alarm device 44 is provided on the outside of the top surface of the device housing 30, and has the function of issuing an alarm to those around the nondestructive testing device 1. The alarm from the alarm device 44 may, for example, emit an alarm sound, emit a voice to notify of danger, turn on or blink a warning light, or display a message. The alarm device 44 may not only simply issue an alarm, but may also instruct an action to be taken after the alarm or display the reason for the alarm. Actions to be taken after the alarm include, for example, evacuation, or issuing an evacuation advisory to the surrounding area.

[0038] The control unit 40 is a dedicated computer or a general-purpose computer with software installed, and although not shown, it has, for example, a calculation unit that performs calculation processing, a memory unit that can store information such as the gamma ray amount detected by the gamma ray detection unit 20 and the radiation amount detected by each dose monitor 41, 42, 43, a display unit that can display the calculation results, an input unit that accepts operations from outside, a communication unit that can communicate information with the outside, and the like.

[0039] The control unit 40 is electrically connected to the dose monitors 41, 42, 43, the source shutter 13, the outer shutter 31, and the alarm 44. The control unit 40 can execute at least safety-related control (hereinafter referred to as safety control) and inspection-related control (hereinafter referred to as inspection control) in the nondestructive inspection apparatus 1.

[0040] In the safety control, the control unit 40 controls the radiation source shutter 13, the outer shutter 31, and the alarm 44 in accordance with the radiation doses detected by the dose monitors 41, 42, and 43.

[0041] Specifically, the control unit 40 acquires the radiation dose detected by each of the dose monitors 41, 42, 43, and when any of the radiation doses exceeds a predetermined threshold, prohibits the radiation source shutter 13 and the outer shutter 31 from being opened, and issues an alarm using the alarm 44. As described above, at this time, in addition to issuing an alarm, it may also instruct an action to be taken after the alarm or display the reason for the alarm.

[0042] This predetermined threshold is set, for example, corresponding to each of the dose monitors 41, 42, 43, and in this embodiment, the threshold corresponding to the external dose monitor 41 is the first threshold T1, the threshold corresponding to the internal dose monitor 42 is the second threshold T2, and the threshold corresponding to the radiation source dose monitor 43 is the third threshold T3. In particular, the first threshold T1 is set to a value related to the amount of radiation exposure to the human body. And since the dose monitor closer to the neutron radiation source 11 usually has a higher radiation dose, the thresholds corresponding to the dose monitors closer to the neutron radiation source 11 are set to higher values. In other words, the first threshold T1 is larger than the second threshold T2 and the third threshold T3 in this order (T1 <T2<T3)。

[0043] Since the amount of radiation increases if an abnormality occurs in the non-destructive testing device 1 or if the device itself becomes radioactive after long-term use, the control unit 40 monitors the amount of radiation detected by each dose monitor 41, 42, 43, and when the corresponding threshold values ​​T1, T2, T3 are exceeded, the control unit 40 prohibits (locks) the source shutter 13 and outer shutter 31 from being opened and issues an alarm, thereby ensuring safety.

[0044] In controlling the inspection, the control unit 40 mainly controls the radiation source shutter 13, the outer shutter 31, and the gamma ray detection unit 20. Specifically, the control unit 40 opens the outer shutter 31 and the radiation source shutter 13 during the inspection, on the condition that the radiation dose detected by each dose monitor does not exceed a predetermined threshold value.

[0045] Particularly during inspection, the control unit 40 opens the outer shutter 31 before the radiation source shutter 13. More specifically, the control unit 40 opens the outer shutter 31, detects the amount of gamma rays before neutron beam irradiation with the gamma ray detection unit 20, and then opens the radiation source shutter 13 to irradiate neutron beams for inspection.

[0046] The control unit 40 performs the inspection by the inspection control after ensuring safety by the safety control. In the inspection of this embodiment, the gamma ray detection unit 20 detects gamma rays generated in response to the neutron rays irradiated from the neutron irradiation unit 10 to the object to be inspected, and the amount of chlorine (salt concentration) at the inspection position P is analyzed from the detected amount of gamma rays. Note that, as a specific method for analyzing the salt concentration in the object to be inspected, a conventionally known method may be used, for example, the collimation method or the gamma ray intensity comparison method described in the above-mentioned Non-Patent Document 1.

[0047] As described above, in the non-destructive inspection device 1 of this embodiment, the neutron irradiation unit 10 and the gamma ray detection unit 20 are covered by the device housing 30, and the dose monitors 41, 42, 43 are provided inside and outside the device housing 30 and inside the radiation source housing 12 to monitor the radiation dose. In other words, it is possible to monitor the amount of radiation exposure outside the device, and to monitor the activation of the device itself over a long period of use.

[0048] When the radiation dose detected by at least one of the dose monitors 41, 42, 43 exceeds a predetermined threshold, the control unit 40 prohibits the radiation source shutter 13 and the outer shutter 31 from being opened, thereby preventing the emission of neutron rays from the neutron irradiator 10 to the outside of the device housing 30 and suppressing an increase in the amount of radiation exposure in the surrounding area. At the same time, an alarm is sounded by the alarm 44, thereby alerting people in the vicinity, such as workers.

[0049] During the examination, the control unit 40 controls the radiation source shutter 13 and the outer shutter 31 to open, provided that none of the radiation doses detected by the dose monitors 41, 42, and 43 exceed a predetermined threshold, thereby enabling the examination to be performed while ensuring safety.

[0050] In particular, the control unit 40 controls the outer shutter 31 to be opened during the inspection, the gamma ray detection unit 20 to detect the amount of gamma rays before the neutron irradiation, and then the radiation source shutter 13 to be opened. Since the gamma ray detection unit 20 is provided in the device housing 30 together with the neutron irradiation unit 10, if the radiation source shutter 13 of the neutron irradiation unit 10 is opened simultaneously with or before the outer shutter 31 during the inspection, there is a risk that the gamma ray detection unit 20 will perform the inspection based on the amount of gamma rays inside the device housing 30. Therefore, by opening the outer shutter 31 before the radiation source shutter 13 during the inspection and detecting the amount of gamma rays outside the device housing 30 by the gamma ray detection unit 20, the radiation source shutter 13 can be opened, thereby making it possible to detect a more accurate amount of gamma rays and improve the accuracy of the inspection. Furthermore, if the outer shutter 31 is opened and the gamma ray detection unit 20 is unable to normally detect the amount of gamma rays before neutron irradiation, the inspection can be stopped at this point to prevent exposure to unnecessary neutron irradiation and ensure greater safety.

[0051] Second embodiment Next, a second embodiment of the present invention will be described.

[0052] 2 is a schematic diagram of a nondestructive inspection device 2 according to a second embodiment of the present invention. The configuration of the nondestructive inspection device 2 according to the second embodiment will be described below with reference to these drawings. Note that the same components as those in the first embodiment are given the same reference numerals, and detailed description will be omitted.

[0053] The neutron irradiation unit 10 of the first embodiment uses a neutron source 11, but the neutron irradiation unit 50 of the second embodiment is different in that it uses a linear accelerator 52. In addition, the nondestructive inspection device 2 of the second embodiment does not have a radiation source dose monitor.

[0054] The neutron irradiation unit 50 includes a power supply unit 51, a linear accelerator 52 that emits a proton beam, which is a charged particle beam, a deflection unit 53, a target unit 54, and an irradiation collimator 55.

[0055] More specifically, the power supply unit 51 is a generator that supplies power to each unit. The generator of the power supply unit 51 is preferably one that has a power generating performance capable of generating at least protons, which are charged particles, has little voltage fluctuation, and can withstand harmonic currents. The power supply unit 51 may also have a battery that can store the power generated by the generator.

[0056] The linear accelerator 52 has an ion source 52a that emits protons, and is connected from the ion source 52a to a deflection unit 53 via a cylindrical acceleration unit 52b. The acceleration unit 52b accelerates the protons generated in the ion source 52a and irradiates the deflection unit 53 with the protons as a proton beam.

[0057] The deflection unit 53 uses magnetic force to deflect the proton beam irradiated from the linear accelerator 52 in a direction approximately perpendicular to the direction of incidence of the proton beam, and emits the deflection toward the target unit 54. The deflection unit 53 has, for example, two opposing magnets, and has a magnetic field between the opposing magnets. The magnets are electromagnets, and a magnetic field with a predetermined magnetic flux density can be formed between the magnets by controlling the current flowing through the electromagnets. Note that the magnets may be permanent magnets as long as the magnetic flux density can be ensured.

[0058] The target section 54 generates a neutron beam by colliding with protons, and is formed, for example, containing beryllium. An irradiation collimator 55 is connected to the target section 54, which selects neutron beams in a predetermined direction from the neutron beams generated from the target section 54. The irradiation collimator 55 can increase the directivity of the irradiated neutron beam. The irradiation direction D1 of the neutron beam is downward, as in the first embodiment. Note that the path from the linear accelerator 52 to the target section 54 is structured to maintain a high vacuum state so as not to impede the flight of the charged particles.

[0059] The neutron irradiation unit 50 configured in this manner is electrically connected to the control unit 60. The control unit 60 controls the timing at which the ion source 52a emits protons, thereby making it possible to cause the neutron irradiation unit 50 to irradiate a neutron beam at any desired timing.

[0060] The control unit 60 of the second embodiment is electrically connected to the external dose monitor 41, the internal dose monitor 42, the outer shutter 31, and the alarm 44 in addition to the neutron irradiator 50. The control unit 60 can execute control related to safety in the nondestructive inspection apparatus 2 (hereinafter referred to as safety control) and control related to inspection (hereinafter referred to as inspection control).

[0061] In the safety control, the control unit 60 controls the ion source 52a, the outer shutter 31, and the alarm 44 in accordance with the radiation doses detected by the dose monitors 41 and 42.

[0062] Specifically, the control unit 60 obtains the radiation dose detected by each of the dose monitors 41, 42, and when any of the radiation doses exceeds a predetermined threshold, prohibits the ion source 52a from emitting protons, prohibits the outer shutter 31 from opening, and issues an alarm with the alarm 44. This predetermined threshold is the same as in the first embodiment, and a description thereof will be omitted.

[0063] In controlling the inspection, the control unit 60 mainly controls the ion source 52a, the outer shutter 31, and the gamma ray detection unit 20. Specifically, the control unit 60 opens the outer shutter 31 during the inspection to emit protons from the ion source 52a, on the condition that the amount of radiation detected by each of the dose monitors 41 and 42 does not exceed a predetermined threshold value.

[0064] Particularly during inspection, the control unit 60 opens the outer shutter 31 before the emission of protons by the ion source 52a. More specifically, the control unit 60 opens the outer shutter 31, detects the amount of gamma rays before neutron irradiation by the gamma ray detection unit 20, and then emits protons by the ion source 52a. Other inspection methods and the like are similar to those in the first embodiment, and therefore will not be described.

[0065] As described above, in the nondestructive inspection device 2 of the second embodiment, the neutron irradiation unit 50 and the gamma ray detection unit 20 are covered by the device housing 30, and the radiation dose is monitored by providing dose monitors 41, 42 inside and outside the device housing 30. In other words, it is possible to monitor the amount of radiation exposed to the outside of the device, and to monitor the activation of the device itself over a long period of use.

[0066] When the amount of radiation detected by at least one of the dose monitors 41, 42 exceeds a predetermined threshold, the control unit 60 prohibits the generation of protons by the ion source 52a and the opening of the outer shutter 31, thereby preventing the emission of neutron rays from the neutron irradiator 10 to the outside of the device housing 30 and suppressing an increase in the amount of radiation exposure in the surrounding area. At the same time, an alarm is sounded by the alarm 44, thereby alerting people in the vicinity, such as workers.

[0067] During the examination, the control unit 60 can perform the examination while ensuring safety by opening the outer shutter 31 and causing the ion source 52a to emit protons, provided that none of the radiation doses detected by the dose monitors 41, 42 exceed a predetermined threshold value.

[0068] In particular, the control unit 60 controls the outer shutter 31 to be opened during the inspection, the amount of gamma rays before the neutron irradiation by the gamma ray detection unit 20 to be detected, and then the ion source 52a to emit protons. Since the gamma ray detection unit 20 is provided in the device housing 30 together with the neutron irradiation unit 10, if the ion source 52a of the neutron irradiation unit 10 generates protons simultaneously with or before the outer shutter 31 during the inspection, the gamma ray detection unit 20 may perform the inspection based on the amount of gamma rays inside the device housing 30. Therefore, by opening the outer shutter 31 before the emission of protons by the ion source 52a during the inspection, and detecting the amount of gamma rays outside the device housing 30 by the gamma ray detection unit 20, the ion source 52a emits protons, thereby making it possible to detect a more accurate amount of gamma rays and improve the accuracy of the inspection. Furthermore, if the outer shutter 31 is opened and the gamma ray detection unit 20 is unable to normally detect the amount of gamma rays before neutron irradiation, the inspection can be stopped at this point to prevent exposure to unnecessary neutron irradiation and ensure greater safety.

[0069] Although the description of the embodiments of the present invention has been completed above, the aspects of the present invention are not limited to these embodiments.

[0070] In the above embodiment, the bridge B is described as the object to be inspected, but the object to be inspected is not limited to this. For example, the present invention can be applied to roads, walls of buildings and tunnels, pillars, and other concrete structures.

[0071] In the above embodiment, the neutron beam is irradiated downward from the device, but the neutron beam irradiation direction is not limited to this. For example, when the object to be inspected is a wall or a pillar, it is preferable to irradiate the neutron beam horizontally, and in such a case, an opening may be provided on the side of the device housing.

[0072] In addition, the direction of irradiation of the neutron beam is not limited to one direction, but may be multiple directions. For example, openings may be formed in the bottom and side of the device housing, and the direction of irradiation of the neutron beam may be switched between downward and horizontal depending on the object to be inspected.

[0073] Although the nondestructive inspection device of the above embodiment is configured to include only one gamma ray detection unit, the number of gamma ray detection units is not limited to one. Two or more gamma ray detection units may be provided as long as they can be accommodated within the device housing.

[0074] In the above embodiment, the gamma ray detector detects gamma rays to analyze the salt concentration distribution, but the radiation to be detected is not limited to gamma rays. For example, the non-destructive inspection device may detect thermal neutrons generated from an object to be inspected irradiated with neutron rays to detect voids and moisture in the object to be inspected.

[0075] In the above embodiment, when the radiation amount exceeds a predetermined threshold, the radiation source shutter 13 and the outer shutter 31 are prohibited from opening and the alarm 44 is activated. However, other thresholds may be set. For example, in the configuration of the first embodiment, since the radiation amount detected by the radiation source dose monitor 43 is also correlated with the energy of the neutron beam emitted by the neutron source 11, the control unit 40 may set a fourth threshold T4, and when the radiation amount detected by the radiation source dose monitor 43 falls below the fourth threshold, the radiation source shutter 13 and the outer shutter 31 may be prohibited from opening and the alarm 44 may be activated. This makes it possible to prevent a decrease in the accuracy of the inspection and unnecessary inspections due to insufficient energy of the neutron source 11. This also makes it possible to inform an operator or the like of the time to replace the neutron source. [Explanation of symbols]

[0076] 1, 2 Non-destructive testing equipment 10, 50 Neutron irradiation section 10a Irradiation hole (second opening) 11 Neutron Source 12 Source housing (second housing) 13 Source shutter (second shutter) 20 Gamma ray detection unit (radiation detection unit) 21 Detector 22 Collimator 23 Movable axis 30 Device housing (first housing) 30a Opening (first opening) 31 Outer shutter (first shutter) 32 wheels 40, 60 Control unit 41 External dose monitor (first dose detection unit) 42 Internal dose monitor (second dose detection unit) 43 Radiation source dose monitor (third dose detection unit) 44 Alarm 51 Power supply section 52 Linear accelerator 52a Ion source 52b Acceleration section 53 Deflection section 54 Target Section 55 Irradiation collimator

Claims

1. a neutron irradiation unit capable of irradiating a neutron beam in a predetermined irradiation direction; a radiation detection unit capable of detecting radiation incident from a predetermined detection direction intersecting the irradiation direction; a first housing that covers the neutron irradiation unit and the radiation detection unit and has a first opening formed in the irradiation direction and the detection direction; a first shutter that opens and closes an opening of the first housing; a first radiation amount detection unit that detects a radiation amount outside the first housing; a second radiation dose detection unit that detects a radiation dose in the first housing; a control unit that prohibits the first shutter from being opened when an amount of radiation detected by at least one of the first radiation amount detection unit and the second radiation amount detection unit exceeds a predetermined threshold; A non-destructive testing device comprising:

2. The control unit controls the first shutter to be opened during an examination on condition that neither of the radiation amounts detected by the first dose detection unit and the second dose detection unit exceeds a predetermined threshold. The non-destructive inspection device according to claim 1.

3. The neutron irradiation unit includes: A neutron source that emits neutron rays; a second housing covering the neutron source and having a second opening formed in the irradiation direction; a second shutter that opens and closes the second opening; a third dose detection unit that detects a radiation dose in the second housing, The control unit prohibits the first shutter and the second shutter from being opened when an amount of radiation detected by at least one of the first dose detection unit, the second dose detection unit, and the third dose detection unit exceeds a predetermined threshold. The non-destructive inspection device according to claim 1 or 2.

4. The control unit controls the first shutter and the second shutter to be opened during an examination on condition that none of the radiation amounts detected by the first dose detection unit, the second dose detection unit, and the third dose detection unit exceeds the predetermined threshold. The non-destructive inspection device according to claim 3.

5. 5. The non-destructive inspection device according to claim 4, wherein the control unit controls the first shutter to be opened before the second shutter during inspection, and the second shutter to be opened after the radiation detection unit detects a radiation state before neutron beam irradiation.

6. The neutron irradiation unit includes: a linear accelerator capable of emitting an accelerated charged particle beam; A target portion capable of generating a neutron beam by being irradiated with the charged particle beam, The control unit prohibits emission of charged particles from the linear accelerator and prohibits opening of the first shutter when the amount of radiation detected by at least one of the first dose detection unit and the second dose detection unit exceeds a predetermined threshold. The non-destructive inspection device according to claim 1 or 2.

7. The control unit controls the first shutter to be opened during an inspection and to emit charged particles from the linear accelerator, on the condition that neither of the radiation doses detected by the first dose detection unit and the second dose detection unit exceeds the predetermined threshold value. The non-destructive inspection device according to claim 6.

8. 8. The non-destructive inspection device according to claim 7, wherein the control unit controls the first shutter to be opened before the emission of charged particles from the linear accelerator during inspection, and to cause the radiation detection unit to detect a radiation state before neutron beam irradiation, and then to cause the emission of charged particles from the linear accelerator.

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