Non-destructive inspection system

Abstract

To provide a non-destructive inspection device that corrects a gamma dose from a measurement point with consideration to a change in an amount attenuation of a neutron dose reaching a measurement point of a measured object in a non-destructive inspection to be performed with respect to an inspected object using neutron, to more accurately estimate salinity concentration of the measured object.SOLUTION: A non-destructive inspection system 1 comprises: a neutron irradiation unit 10 that can radiate neutron of a first neutron dose; a neutron detection unit 20 that can detect a second neutron dose scattered inside an inspected object A with neutron irradiation from the neutron irradiation unit 10; a gamma ray detection unit 30 that detects a gamma dose to be discharged from the inspected object A with the neutron irradiation from the neutron irradiation unit 10; and an analysis unit 50 that calculate a content of a given substance on the basis of the gamma dose, and corrects the content of the given substance on the basis of the first neutron dose and the second neutron dose.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a non-destructive inspection system for an object to be inspected using radiation.

Background Art

[0002] In recent years, appropriate maintenance management, repair, and renewal have been desired for the aging of 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 performed in which the internal structure can be analyzed without destroying the object to be inspected by using radiation such as X-rays that are permeable to the object.

[0004] Particularly in recent years, non-destructive inspection devices using neutron rays with higher permeability than X-rays have also been studied. For example, Patent Document 1 and Non-Patent Document 1 disclose a non-destructive inspection method capable of obtaining the salt concentration distribution inside concrete by using neutron rays and gamma (γ) rays generated by the reaction of the neutron rays.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Here, in Non-Patent Document 1, a mortar specimen with adjusted salt concentration is irradiated with neutrons, and the salt concentration is calculated from the detected gamma-ray count rate (the number of gamma rays detected per unit time) using a previously obtained calibration curve (gamma-ray count rate versus concentration) that depends on concentration. The salt concentration is proportional to the count rate of gamma rays of a certain energy, and the higher the count rate, the higher the salt concentration. This relationship holds on the premise that the inside of the mortar specimen is in a uniform state without containing moisture or voids, and the amount of neutrons transmitted in the depth direction of the mortar specimen attenuates based on a predetermined attenuation curve. However, in the case of concrete, which is the actual object to be inspected, if there is moisture or voids at the measurement point or in the neutron irradiation route to the measurement point, the amount of neutron attenuation in the irradiation route will not match the predetermined attenuation curve due to scattering and radiation. In this case, since the number of neutrons (neutron dose) reaching the depth of the measurement point is different, the count rate (gamma-ray dose) of prompt gamma rays also changes, and an accurate salt concentration cannot be obtained from the calibration curve.

[0008] The present invention has been made to solve such problems, and its object is to correct the gamma-ray dose from the measurement point in a non-destructive inspection using neutrons on an object to be inspected, taking into account the change in the attenuation amount of the neutron dose reaching the measurement point of the object to be measured, so as to provide a non-destructive inspection apparatus capable of more accurately estimating the salt concentration of the object to be measured.

Means for Solving the Problems

[0009] To achieve the above object, the non-destructive inspection system according to the present invention includes a neutron irradiation unit capable of irradiating neutrons with a first neutron dose, a neutron detection unit capable of detecting a second neutron dose scattered inside the object to be inspected by the neutron irradiation from the neutron irradiation unit, a gamma-ray detection unit capable of detecting the gamma-ray dose emitted from the object to be inspected by the neutron irradiation, and an analysis unit that calculates the content of a predetermined substance based on the gamma-ray dose and corrects the content of the predetermined substance based on the first neutron dose and the second neutron dose.

[0010] Further, as the non-destructive inspection system, the content of the predetermined substance may be a salt concentration.

[0011] Further, as the non-destructive inspection system, the analysis unit may generate a distribution of moisture and / or voids contained in the object to be inspected from the second neutron dose.

[0012] Further, as the non-destructive inspection system, the neutron irradiation unit may have an accelerator, and may further include an irradiation control unit that controls the accelerator to irradiate neutrons with the first neutron dose.

[0013] Further, as the non-destructive inspection system, the neutron irradiation unit may have a radioisotope, and may further include a dose monitor capable of detecting neutrons with the first neutron dose.

[0014] Further, as the non-destructive inspection system, the neutron irradiation unit may be mounted on a moving body.

Advantages of the Invention

[0015] According to the present invention using the above means, in a non-destructive inspection performed on an object to be inspected using neutrons, by correcting the gamma dose from the measurement point using the neutron dose reaching the measurement point of the object to be inspected, the salt concentration of the object to be inspected can be estimated more accurately.

Brief Description of the Drawings

[0016]

Figure 1

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Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0018] (First Embodiment) First, the first embodiment of the present invention will be described.

[0019] FIG. 1 is a schematic configuration diagram of a non-destructive inspection system according to the first embodiment of the present invention. Hereinafter, the configuration of the non-destructive inspection device (non-destructive inspection system) 1 of the present embodiment will be described based on these drawings.

[0020] As shown in FIG. 1, in the non-destructive inspection device 1 of the present embodiment, a neutron irradiation unit 10, a thermal neutron detection unit 20, a gamma ray detection unit 30, and GNSS 61 are provided on a moving body 40. Further, the non-destructive inspection device 1 has a control analysis unit 50, and the neutron irradiation unit 10, the thermal neutron detection unit 20, the gamma ray detection unit 30, and GNSS 61 are connected. In the present embodiment, the non-destructive inspection device 1 is arranged on a bridge A made of concrete that is an object to be inspected, and while the moving body 40 moves on the bridge A, non-destructive inspection for salinity concentration measurement and moisture cavity distribution measurement is performed on an inspection point B below the moving body 40 as an object to be inspected.

[0021] In this embodiment, the neutron irradiation unit 10 includes a power supply (not shown), an ion source 11, a linear accelerator 12, a deflector 13, a target 14, and an irradiation collimator 15.

[0022] The ion source 11 generates hydrogen ions (protons). The linear accelerator 12 accelerates the protons generated by the ion source 11 to generate a proton beam P and irradiates the deflector 13. The deflector 13 has a plurality of magnets, for example, made of electromagnets, and deflects the proton beam P irradiated from the linear accelerator 12 in a direction substantially perpendicular to the incident direction of the proton beam P by magnetic force and emits it.

[0023] The target 14 is provided facing the emission side of the proton beam P of the deflector 13. The target 14 collides with the protons of the proton beam P incident from the deflector 13 to generate neutrons N, and is formed, for example, containing beryllium. An irradiation opening (not shown) for irradiating the neutrons N in a predetermined direction among the neutrons N generated from the target 14 to the outside is formed on the side of the target 14 facing the deflector 13. The irradiation opening has an irradiation collimator 15 for restricting the emission direction of the neutrons N. The neutrons N generated by the target 14 enter the bridge A substantially perpendicularly as a neutron beam traveling parallel to the axis of the irradiation direction D1 shown in FIG. 1 by passing through the inside of the irradiation collimator 15. Note that the path from the linear accelerator 12 to the target 14 has a structure capable of maintaining a high vacuum state so as not to hinder the flight of charged particles.

[0024] The thermal neutron detection unit 20 includes a thermal neutron detector 21 capable of detecting thermal neutrons Nb and a thermal neutron collimator 22 for enhancing the directivity of the thermal neutrons Nb incident on the thermal neutron detector 21. The thermal neutron detector 21 of this embodiment detects the thermal neutrons Nb backscattered from the vicinity of the inspection point B inside the bridge A, which is the object to be inspected, by the neutrons N irradiated from the target 14. In FIG. 1, the neutrons N irradiated from the target 14 are indicated by solid arrows, and the thermal neutrons Nb are indicated by dashed arrows.

[0025] The gamma-ray detector 30 has a gamma-ray detector 31 capable of detecting gamma (γ) rays, a gamma-ray collimator 32, and a movable shaft 33.

[0026] The gamma-ray detector 31 is, for example, a germanium semiconductor detector (Ge detector). A gamma-ray collimator 32 is connected to the tip of the gamma-ray detector 31, and the gamma-ray detector 31 can detect gamma rays incident through the gamma-ray collimator 32. The gamma-ray detector 31 of the present embodiment detects gamma rays G, so-called prompt gamma rays, emitted from inside the concrete, which is the object to be inspected, when neutrons N irradiated from the target 14 toward the inspection point B cause neutron capture reactions with various atomic nuclei in the tissue near the inspection point.

[0027] The gamma-ray collimator 32 is a cylindrical body made of a material that shields gamma rays, such as lead or iron, and has a function of narrowing down gamma rays G in one direction toward the gamma-ray detector 31 among the gamma rays incident from the outside. That is, in the present embodiment, the axial direction of the gamma-ray collimator 32 is the detection direction D2 of the gamma rays G. As shown in FIG. 1, the detection direction D2 intersects at a point on the irradiation direction D1, and this intersection point is the inspection point B inside the bridge A of the object to be inspected. When the salt concentration at this inspection point B is high, the gamma-ray dose of the gamma rays G detected by the gamma-ray detector 31 becomes higher than normal. In FIG. 1, the gamma rays G emitted from the vicinity of the inspection point B of the bridge A are indicated by a dashed arrow.

[0028] A movable shaft 33 extending in the horizontal direction is provided at the rear end portion of the gamma-ray detector 31. The gamma-ray detector 31 is integrally with the gamma-ray collimator 32 and can swing in the vertical direction about the movable shaft 33. By swinging the gamma-ray detector 31 around the movable shaft 33 in this way, it is possible to move the inspection point B on the irradiation direction D1.

[0029] The mobile body 40 is, for example, a vehicle or a cart of a size capable of mounting the neutron irradiation unit 10, the thermal neutron detection unit 20, the gamma-ray detection unit 30, and the GNSS 61, and can move freely in a substantially horizontal direction by having wheels 41. Further, an opening 42 is provided on the bottom surface of the mobile body 40 facing the bridge A. Thereby, a part of the thermal neutron detection unit 20 and the gamma-ray detection unit 30 can be disposed in the opening 42, and the inspection point B located below the opening 42 can be inspected.

[0030] The GNSS 61 is, for example, a GPS (Global Positioning System), and in the present embodiment, it is provided on the axis of the irradiation direction D1 of the neutron N, that is, directly above the inspection point B. The GNSS 61 can receive information from satellites and generate its own position coordinates and relative position information of the inspection point B.

[0031] The control and analysis unit 50 is a dedicated computer, a general-purpose computer installed with software, etc., and has, for example, an arithmetic unit that performs arithmetic processing, a storage unit, a display unit capable of displaying arithmetic results, etc., an input unit that receives operations from the outside, etc., a communication unit capable of communicating information with the outside, etc.

[0032] FIG. 2 is a block diagram of a configuration for performing control and analysis of the non-destructive inspection apparatus 1 according to the first embodiment of the present invention. The control and analysis unit 50 is connected to the neutron irradiation unit 10, the thermal neutron detector 21, the gamma-ray detector 31, the GNSS 61, the input unit 71, the output unit 72, and the storage unit 73 so as to be communicable by wire or wirelessly. Note that the input unit 71, the output unit 72, and the storage unit 73 may be mounted inside the control and analysis unit 50. Further, the control and analysis unit 50 includes an irradiation control unit 51 for controlling the neutron irradiation unit 10, an irradiation dose information generation unit 52, a moisture cavity distribution generation unit 53, a salt concentration calculation unit 54, a neutron attenuation amount calculation unit 55, and a correction unit 56 as an analysis unit for performing analysis, and a position information acquisition unit 57 for acquiring the position of the inspection point B.

[0033] The control and analysis unit 50 acquires the thermal neutron dose (the second neutron dose), which is the count rate of thermal neutrons Nb detected by the thermal neutron detector 21, the gamma-ray dose, which is the count rate of gamma rays G detected by the gamma-ray detector 31, and the position information of the inspection point B generated by the GNSS 61, and associates the acquired information of each dose with the position information of the inspection point B and stores them in the storage unit 73 as thermal neutron dose information and gamma-ray dose information, respectively. Further, the control and analysis unit 50 calculates the salt concentration, which is the chlorine content at the inspection point B, based on the acquired gamma-ray dose. Further, the control and analysis unit 50 generates a moisture cavity distribution based on the acquired thermal neutron dose. These can be output to the output unit 72 and the storage unit 73, for example, as analysis results.

[0034] The irradiation control unit 51 controls the linear accelerator 12. For example, the linear accelerator 12 can be controlled to irradiate the neutron irradiation unit 10 with pulsed neutrons of the first neutron dose that are discrete in time.

[0035] The irradiation dose information generation unit 52 generates irradiation dose information indicating the irradiation dose (the first neutron dose) of neutrons N emitted from the target 14 toward the inspection point B through the irradiation collimator 15 based on the control information acquired from the irradiation control unit 51, and stores it in the storage unit 73.

[0036] The moisture cavity distribution generation unit 53 generates moisture cavity distribution information in the depth direction of the inspection point B based on the thermal neutron dose information and the position information of the inspection point B, and stores it in the storage unit 73.

[0037] The salt concentration calculation unit 54 calculates the chlorine content at the inspection point B, that is, the salt concentration, based on the gamma-ray dose information to generate salt concentration information, and stores it in the storage unit 73. For the salt concentration analysis method in a specific object to be inspected, a conventionally well-known method may be used. For example, the collimate method or the gamma-ray intensity comparison method described in the above-mentioned Non-Patent Document 1 is used.

[0038] The neutron attenuation amount calculation unit 55 calculates the neutron attenuation amount in the depth direction of the inspection point B based on the water part cavity distribution information and the irradiation dose information at the inspection point B, generates neutron attenuation amount information, and stores it in the storage unit 73.

[0039] The correction unit 56 corrects the salt concentration information based on the neutron attenuation amount information and the irradiation dose information at the inspection point B, generates corrected salt concentration information, and stores it in the storage unit 73. Specifically, the neutron dose of the neutron N reaching the inspection point B is calculated from the irradiation dose information and the neutron attenuation amount information, and the difference from a predetermined attenuation curve is obtained to correct the salt concentration. For example, if water exists until the neutron N reaches the inspection point B, the thermal neutron dose due to scattering increases, the neutron attenuation amount increases, and the gamma ray dose also increases. Therefore, the salt concentration based on the gamma ray dose information is corrected to decrease. The same applies when there are cavities.

[0040] The position information acquisition unit 57 acquires the position information of the inspection point B from the GNSS 61 when the neutron N is irradiated from the neutron irradiation unit 10 to the inspection point B, and stores it in the storage unit 73.

[0041] Next, the operation of the non-destructive inspection device 1 according to the first embodiment will be described with reference to the flowchart shown in FIG. 3.

[0042] In step S1, the control analysis unit 50 acquires the position information of the inspection point B from the GNSS 61 in the position information acquisition unit 57.

[0043] In step S2, the control analysis unit 50 controls the neutron irradiation unit 10 in the irradiation control unit 51 to pulse-irradiate the neutron N with the first neutron dose. At this time, the control analysis unit 50 acquires the first neutron dose as irradiation dose information from the irradiation control unit 51 in the irradiation dose information generation unit 52, and stores it in the storage unit 73.

[0044] In step S3, the control analysis unit 50 acquires the thermal neutron dose (second neutron dose) from the thermal neutron detector 21 and stores it in the storage unit 73 as thermal neutron dose information. Further, the control analysis unit 50 acquires the gamma ray dose from the gamma ray detector 31 and stores it in the storage unit 73 as gamma ray dose information.

[0045] In step S4, based on the thermal neutron dose information, the control analysis unit 50 generates a moisture void distribution in the moisture void distribution generation unit 53 and stores it in the storage unit 73 as moisture void distribution information. Further, based on the gamma ray dose information, the control analysis unit 50 calculates the salt concentration in the salt concentration calculation unit 54 and stores it in the storage unit 73 as salt concentration information.

[0046] In step S5, based on the irradiation dose information and the moisture void distribution information, the control analysis unit 50 calculates the neutron attenuation amount in the neutron attenuation amount calculation unit 55 and stores it in the storage unit 73 as neutron attenuation amount information. Further, based on the calculated neutron attenuation amount information, the correction unit 56 performs correction processing on the salt concentration information and stores it in the storage unit 73 as corrected salt concentration information.

[0047] In step S6, the output unit 72 displays the corrected salt concentration information obtained by the correction process in step S5 in a form visible to the user. Further, according to the user's request, the position information, irradiation dose information, thermal neutron dose information, gamma ray dose information, moisture void distribution information, salt concentration information, and neutron attenuation amount information stored in the storage unit 73 can also be displayed.

[0048] In step S7, the control analysis unit 50 determines whether to end the measurement according to the user's request. For example, when the measurement within a predetermined measurement time and / or measurement range is completed, it is determined as discrimination (Y) and the process ends. When the measurement is not completed, it is determined as discrimination (N) and the process returns to step S1.

[0049] As described above, in the non-destructive inspection apparatus 1 of the present embodiment, neutrons N with a first neutron dose (irradiation dose) are irradiated from the neutron irradiation unit 10 to the inspection point B of the bridge A, which is the object to be inspected, and the salt concentration at the inspection point B is calculated based on the gamma-ray dose detected by the gamma-ray detector 31. Further, the non-destructive inspection apparatus 1 irradiates neutrons N with a first neutron dose from the neutron irradiation unit 10 to the inspection point B of the bridge A, which is the object to be inspected, and generates a moisture cavity distribution in the depth direction of the inspection point B based on the thermal neutron dose (second neutron dose) of the thermal neutrons Nb detected by the thermal neutron detector 21. That is, it is possible to measure the salt concentration at the inspection point B and generate a moisture cavity distribution in the depth direction with one device and one neutron beam irradiation. Further, the non-destructive inspection apparatus 1 calculates the neutron attenuation amount in the depth direction of the inspection point B from the moisture cavity distribution obtained from the thermal neutron dose (second neutron dose) and the irradiation dose (first neutron dose), and performs correction processing of the salt concentration based on the neutron attenuation amount. That is, by correcting the salt concentration calculated based on the gamma-ray dose from the inspection point B in consideration of the change in the attenuation amount of the neutron dose reaching the inspection point B of the bridge A, which is the object to be measured, the salt concentration at the inspection point B of the bridge A, which is the object to be measured, can be estimated more accurately. That is, it is possible to calculate a more accurate salt concentration in consideration of the variation in the attenuation amount due to moisture and cavities around the inspection point B.

[0050] Further, since each component of the non-destructive inspection apparatus 1 of the present embodiment is mounted on the moving body 40, it can be measured while moving.

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

[0052] FIG. 4 is a block diagram showing a non-destructive inspection system according to a second embodiment of the present invention. FIG. 5 is a schematic configuration diagram showing a salinity measuring device according to the second embodiment of the present invention. FIG. 6 is a schematic configuration diagram showing an example of a water cavity measuring device according to the second embodiment of the present invention. Hereinafter, the configuration of the non-destructive inspection system 2 according to the second embodiment will be described based on these figures. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0053] In the first embodiment, both the thermal neutron detection unit 20 for generating the water cavity distribution at the inspection point B and the gamma ray detection unit 30 for measuring the salinity were mounted on a single moving body 40. However, in the second embodiment, these are mounted on separate moving bodies as the thermal neutron detection unit 20a and the gamma ray detection unit 30b, respectively, to separate the functions, and are respectively used as the salinity measuring device 3a and the water cavity measuring device 3b. Another difference is that a neutron attenuation amount calculation unit 55c and a correction unit 56c for performing the correction process of the salinity are further provided separately.

[0054] As shown in FIG. 4, the non-destructive inspection system 2 is configured such that the salinity measuring device 3a, the water cavity measuring device 3b, and the correction processing unit 50c are connected to be communicable by wire or wirelessly. An input unit 71a, 71b, 71c, an output unit 72a, 72b, 72c, and a storage unit 73a, 73b, 73c are communicably connected to the salinity measuring device 3a, the water cavity measuring device 3b, and the correction processing unit 50c, respectively.

[0055] The salinity concentration measurement device 3a includes a neutron irradiation unit 10a, a gamma-ray detector 31a, a GNSS 61a, a source dose monitor 62a, and a control and analysis unit 50a. The control and analysis unit 50a is communicably connected to the neutron irradiation unit 10a, the gamma-ray detector 31a, the GNSS 61a, and the source dose monitor 62a. Also, the control and analysis unit 50a is a dedicated computer, a general-purpose computer installed with software, etc., and includes an irradiation control unit 51a for controlling the neutron irradiation unit 10a, an irradiation dose information generation unit 52a as an analysis unit for performing analysis, a moisture cavity distribution generation unit 53a, a salinity concentration calculation unit 54a, a neutron attenuation amount calculation unit 55a, and a correction unit 56a, and a position information acquisition unit 57a for acquiring the position of the inspection point B.

[0056] Next, the specific configuration of the salinity concentration measurement device 3a will be described with reference to FIG. 5. The salinity concentration measurement device 3a uses a radioactive isotope 16a as a neutron source in the neutron irradiation unit 10a.

[0057] In the salinity concentration measurement device 3a, the neutron irradiation unit 10a and the gamma-ray detection unit 30a are provided inside the device housing 81a. Also, the salinity concentration measurement device 3a has a control and analysis unit 50a, and the gamma-ray detection unit 30a and the source dose monitor 62a are connected to the control and analysis unit 50a.

[0058] In the neutron irradiation unit 10a, a radioactive isotope 16a as a neutron source is provided inside the source housing 82a. The radioactive isotope 16a is, for example 252 a Cf source.

[0059] The source housing 82a has a substantially cubic shape with a hollow interior, and in this embodiment, an irradiation hole 83a for neutron rays is formed on the bottom surface. Also, the source housing 82a is provided with a source shutter 84a for opening and closing the irradiation hole 83a. The source housing 82a and the source shutter 84a are formed of a material capable of shielding neutron rays, such as lead or iron. The irradiation hole 83a is, for example, a circular hole, and the source shutter 84a is an opening and closing plate member that slides on the bottom surface of the source housing 82a to open and close the irradiation hole 83a by an actuator (not shown).

[0060] A radiation source dose monitor 62a is provided inside the top surface of the radiation source housing 82a, and the radiation source dose monitor 62a detects the radiation dose inside the radiation source housing 82a.

[0061] The radiation that can be detected by the radiation source dose monitor 62a includes, for example, alpha (α) rays, beta (β) rays, and gamma (γ) rays. Also, the radiation source dose monitor 62a can detect the spatial dose rate (microSieverts per hour (μSv / h)) as the radiation dose.

[0062] The neutron irradiation unit 10a configured as described above can irradiate only the neutron rays traveling in the irradiation direction D1 where the irradiation hole 83a is provided, out of the neutron rays radially emitted from the radioisotope 16a, to the outside. And the irradiation and stop (non-irradiation) of the neutron rays can be controlled by opening and closing the radiation source shutter 84a.

[0063] Since the gamma ray detection unit 30a has the same configuration as the gamma ray detection unit 30 of the first embodiment, the description thereof is omitted.

[0064] The device housing 81a covers the neutron irradiation unit 10a and the gamma ray detection unit 30a, and an opening 42a is formed on the irradiation direction D1 and the detection direction D2. Specifically, the device housing 81a has a substantially rectangular parallelepiped shape with a hollow interior, and is formed of a material capable of shielding neutron rays, such as lead or iron. The neutron irradiation unit 10a is arranged on one side in the horizontal direction inside the device housing 81a, and the gamma ray detection unit 30a is arranged on the other side in the horizontal direction.

[0065] And on the bottom surface of the device housing 81a, an opening 42a is formed that includes the irradiation direction D1 and the detection direction D2 within the opening. Note that the opening range of the opening 42a is designed to include the range in which the detection direction D2 changes due to the swinging of the gamma ray detection unit 30a around the movable axis 33a.

[0066] Further, an outer shutter 86a for opening and closing the opening 42a is provided on the bottom surface of the apparatus housing 81a. The outer shutter 86a is formed of a material capable of shielding neutron rays such as lead and iron, for example. The outer shutter 86a is a plate material that slides on the bottom surface of the apparatus housing 81a to open and close the opening 42a by an actuator (not shown).

[0067] Further, a GNSS 61a is provided on the outer side of the top surface of the apparatus housing 81a. In the present embodiment, the GNSS 61a is provided on the axis of the irradiation direction D1 of the neutrons N, that is, directly above the inspection point B. The GNSS 61 can receive information from satellites and detect its own position coordinates and the position information of the inspection point B.

[0068] Further, wheels 41a are provided on the outer side of the bottom surface of the apparatus housing 81a, and the apparatus housing 81a can freely move around the inspection point B.

[0069] The control and analysis unit 50a is electrically connected to the radiation source dose monitor 62a, the radiation source shutter 84a, and the outer shutter 86a. The control and analysis unit 50a can execute at least control related to the inspection in the salinity concentration measurement device 3 (hereinafter referred to as inspection control).

[0070] In the inspection control, the control and analysis unit 50a mainly controls the radiation source shutter 84a, the outer shutter 86a, and the gamma-ray detection unit 30a. Specifically, the control and analysis unit 50a opens the outer shutter 86a and the radiation source shutter 84a during the inspection.

[0071] The control and analysis unit 50a detects the gamma rays G generated by the neutrons N irradiated from the neutron irradiation unit 10a to the inspection point B by the gamma-ray detection unit 30a, and calculates the salinity concentration at the inspection point B from the detected gamma-ray dose. The control and analysis unit 50a also acquires the irradiation dose of the neutrons N irradiated from the radiation source dose monitor 62a to the inspection point B. Further, the control and analysis unit 50a acquires the position information of the inspection point B from the GNSS 61a. Then, the control and analysis unit 50a associates the salinity concentration calculated for the inspection point B with the position information and the irradiation dose to generate salinity concentration information and stores it in the storage unit 73a.

[0072] The specific configuration of the moisture cavity measurement device 3b is as shown in FIG. 6. As is clear when compared with FIG. 1, the moisture cavity measurement device 3b has a configuration obtained by removing the gamma ray detection unit 30 and the associated analysis unit (specifically, the salt concentration calculation unit) from the non-destructive inspection device 1 of the first embodiment. Since the other functions are the same, detailed description is omitted. The moisture cavity measurement device 3b configured in this way stores in the storage unit 73c the moisture cavity distribution in the depth direction of the inspection point B in association with the position information.

[0073] The correction processing unit 50c (analysis unit) is, for example, a dedicated computer provided separately from the salt concentration measurement device 3a and the moisture cavity measurement device 3b, a general-purpose computer installed with software, etc., and is communicably connected to the salt concentration measurement device 3a and the moisture cavity measurement device 3b. The correction processing unit 50c acquires salt concentration information from the salt concentration measurement device 3a and moisture cavity distribution information from the moisture cavity measurement device 3b, respectively. Further, the correction processing unit 50c calculates the neutron attenuation amount in the depth direction at the inspection point B in the neutron attenuation amount calculation unit 55c based on the moisture cavity distribution information associated with the position information of the inspection point B, and performs correction processing on the salt concentration information associated with the position information of the same inspection point B based on the neutron attenuation amount. Note that the correction processing unit 50c may be mounted on the salt concentration measurement device 3a or the moisture cavity measurement device 3b.

[0074] As described above, in the non-destructive inspection system 2 of the second embodiment, the salt concentration measurement device 3a, the moisture cavity measurement device 3b, and the correction processing device are separated. Thereby, by using the existing large-sized moisture cavity measurement device 3b together, moisture cavity distribution information can be acquired and correction processing of the salt concentration can be performed, improving the measurement accuracy of the salt concentration. Also, in the measurement of the salt concentration, the radioactive isotope 16a is used as the neutron source, and in the measurement of the moisture cavity distribution, an accelerator is used as the neutron source. Thereby, the salt concentration measurement device 3a can be miniaturized.

[0075] (Third Embodiment) Next, a third embodiment of the present invention will be described.

[0076] FIG. 7 is a block diagram showing an outline of the non-destructive inspection system according to the third embodiment of the present invention. FIG. 8 is a schematic configuration diagram showing a salinity measuring device according to the third embodiment of the present invention. Hereinafter, the configuration of the non-destructive inspection system 2' according to the third embodiment will be described with reference to these figures. Note that the same components as those in the second embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0077] In the second embodiment, the neutron source of the salinity concentration measuring device 3a of the non-destructive inspection system 2 was the radioisotope 16a. However, the salinity measuring device 3d of the non-destructive inspection system 2' according to the third embodiment is different in that an accelerator is used as the neutron source as in the first embodiment.

[0078] The salinity measuring device 3d includes a neutron irradiation unit 10d, a gamma-ray detector 31d, a GNSS 61d, and a control and analysis unit 50d. The control and analysis unit 50d is communicably connected to the neutron irradiation unit 10d, the gamma-ray detector 31d, and the GNSS 61d. The control and analysis unit 50d is a dedicated computer, a general-purpose computer installed with software, etc., and includes an irradiation control unit 51d for controlling the neutron irradiation unit 10d, an irradiation dose information generation unit 52d and a salinity concentration calculation unit 54d as analysis units for performing analysis, and a position information acquisition unit 57d for acquiring the position of the inspection point B.

[0079] The specific configuration of the salinity measuring device 3d is shown in FIG. 8. The salinity measuring device 3d uses an accelerator as the neutron irradiation unit 10a as in the first embodiment. As is clear from comparison with FIG. 1 (first embodiment), the salinity measuring device 3d has a configuration obtained by removing the thermal neutron detection unit 20 and the associated analysis unit (not shown, specifically the moisture cavity distribution generation unit 53) from the non-destructive inspection device 1 of the first embodiment. Since the other configurations and functions are the same, detailed description thereof will be omitted. The salinity measuring device 3d configured as described above stores the salinity concentration at the inspection point B in association with the position information in the storage unit 73d.

[0080] Since the water void measurement device 3b and the correction processing unit 50c are the same as those in the second embodiment, their descriptions are omitted.

[0081] As described above, in the non-destructive inspection system 2' of the third embodiment, the salinity concentration measurement device and the water void distribution measurement device are mounted on separate moving bodies. Also, an accelerator is used as the neutron source for both. As a result, inspections can be performed easily and efficiently based on the irradiation dose and irradiation time suitable for each of the salinity concentration measurement and the water void distribution measurement.

[0082] Thus, the description of each embodiment of the present invention is completed, but the aspects of the present invention are not limited to these embodiments.

[0083] In the above embodiment, the bridge A is described as the object to be inspected, but the object to be inspected is not limited to this. For example, it is applicable to roads, buildings, tunnel walls, pillars, and other concrete structures.

[0084] Also, in the above embodiment, the gamma-ray detector detects gamma rays to calculate the chlorine content in the object to be inspected and generate the salinity concentration distribution, but the substance to be analyzed is not limited to chlorine. For example, iron, potassium, etc. with relatively large thermal neutron capture cross-sections may be used.

[0085] Also, in the above second embodiment, the neutron source of the water void measurement device 3b is an accelerator, but similar to the salinity concentration measurement device 3a, a neutron source using a radioactive isotope (RI) may be used to form a configuration as shown in FIG. 9 (fourth embodiment). By using a radioactive isotope as the neutron source, both the salinity concentration measurement device 3a and the water void measurement device 3e can be miniaturized, and inspections can be performed even in places where large moving bodies such as vehicles cannot enter.

Description of Reference Numerals

[0086] 1: Non-destructive inspection device 2, 2', 2'': Non-destructive inspection systems 3, 3a, 3d: Salinity concentration measurement devices 3b, 3e: Moisture cavity measurement device 10, 10a, 10d: Neutron irradiation unit 11: Ion source 12: Linear accelerator 13: Deflector 14: Target 15: Irradiation collimator 16a: Radioisotope 20: Thermal neutron detection unit 21, 21a: Thermal neutron detector 22: Collimator 30, 30a: Gamma ray detection unit 31, 31a, 31b, 31d: Gamma ray detector 32: Gamma ray collimator 33: Movable axis 40: Moving body 41a: Wheel 42, 42a: Opening 50, 50a, 50d: Control and analysis unit 50c: Correction processing unit 51, 51a, 51d: Irradiation control unit 52, 52a, 52d: Irradiation dose information generation unit 53, 53a: Moisture cavity distribution generation unit 54, 54a, 54d: Salt concentration calculation unit 55, 55a, 55c: Neutron attenuation amount calculation unit 56, 56a, 56c: Correction unit 57, 57a, 57d: Position information acquisition unit 62a: Source dose monitor 71, 71a, 71b, 71c: Input unit 72, 72a, 72b, 72c: Output unit 73, 73a, 73b, 73c, 73d: Memory unit 81a: Device housing 82a: Source housing 83a: Irradiation hole 84a: Source shutter 86a: Outer shutter A: Bridge B: Inspection target N: Neutron Nb: Thermal neutron

Claims

1. a neutron irradiation unit capable of irradiating neutrons of a first neutron dose; a neutron detection unit capable of detecting a second neutron dose scattered inside the object to be inspected by the neutron irradiation from the neutron irradiation unit; a gamma ray detection unit capable of detecting a gamma ray dose emitted from the object to be inspected by the neutron irradiation from the neutron irradiation unit; an analysis unit that calculates the content of the salt concentration based on the gamma ray dose and corrects the content of the salt concentration based on the first neutron dose and the second neutron dose; and the analysis unit generates a distribution of moisture and / or voids contained in the object to be inspected from the second neutron dose, and corrects the content of the salt concentration based on the first neutron dose and the distribution of moisture and / or voids. A non-destructive inspection system.

2. The analysis unit generates a distribution of moisture and / or voids contained in the inspection object from the second neutron dose, calculates a neutron attenuation amount based on the first neutron dose and the distribution of moisture and / or voids, and calculates from the neutron attenuation amount and the first neutron dose. The content of the salt concentration is corrected by obtaining the difference between the neutron dose and a predetermined attenuation curve. The non-destructive inspection system according to Claim 1.

3. The neutron irradiation unit uses an accelerator, and further includes an irradiation control unit that controls the accelerator to irradiate the first neutron dose. The non-destructive inspection system according to Claim 1 or 2.

4. The neutron irradiation unit uses a radioisotope, and further includes a dose monitor capable of detecting the first neutron dose. The non-destructive inspection system according to any one of Claims 1 to 3.

5. The neutron irradiation unit is mounted on a moving body. The non-destructive inspection system according to any one of Claims 1 to 4.

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