JP2019152497A - Method and device for nondestructive inspection of structure using muography - Google Patents

Abstract

To enable exploration of defects in small and medium infrastructure facilities such as bridges and incinerators, which have been difficult until now.SOLUTION: A method for nondestructive inspection of a structure using muography is characterized in including the steps of: installing a first shielding material 51 on the lower side of inspection objects (10, 20); detecting cosmic rays passing through the first shielding material 51 using a third detector 43; and performing nondestructive inspection on the inner structure of the inspection objects (10, 20) using low energy cosmic rays passing through the inspection objects (10, 20), which are extracted from the cosmic rays detected by a second detector 42 between the inspection objects (10, 20) and the first shielding material 51 and are equal to or lower than a first predetermined energy.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a non-destructive inspection method and apparatus for a structure using muography, and in particular, muography suitable for use in defect detection of small and medium infrastructure facilities such as bridges and incinerators, which has been difficult until now. The present invention relates to a nondestructive inspection method and apparatus for a structure to be used.

  A method (so-called muography) that uses cosmic ray particles (for example, muons, which are elementary particles generated by atmospheric collisions of cosmic rays) to inspect various structures, investigate the interior of volcanoes, underground cavities, etc. is known. It has been. This method uses the interaction between the object to be examined or investigated and cosmic rays, and the most common means is to estimate the internal situation from the image of the transmission difference of cosmic rays as in the X-ray transmission test. Is.

  Cosmic rays have various energies, and those with large energies reach several hundred GeV, and the greater the energy, the greater the permeability to matter.

  The estimation of the internal situation by cosmic rays is determined by the degree of attenuation or transmission when the cosmic rays pass through the inspection object. For example, as shown in FIG. In this case, the amount of attenuation is large (the amount of transmission is small). Conversely, as shown in FIG. 1B, the amount of attenuation is small (the amount of transmission is large) when a defect 10A such as a cavity exists. Thus, the presence or absence of a defect or the like can be estimated by grasping and evaluating the attenuation amount or transmission amount of cosmic rays.

  Therefore, for example, by using cosmic rays of energy that can be transmitted if there is a defect and cannot be transmitted if there is no defect, it is possible to clearly determine the presence or absence of the defect.

JP 2007-271400 A

  For example, in the bridge composite floor slab 20 illustrated in FIG. 2A, as shown in FIG. 2B, the thickness reduction 22A of the outer shell steel plate 22 due to water intrusion or the neutralization of the concrete 26, the alkali aggregate We want to explore internal damages that are not visible from the outside, such as reaction, corrosion expansion of reinforcing bars 24, cracks 26A of concrete 26 due to separation from reinforcing bars 24, and gravel 26B of concrete 26. However, the composite floor slab 20 is smaller in size than the inside of the volcano, the underground cavity, etc., and the defects to be detected are also small. This makes it difficult to detect the defect 10A.

  Patent Document 1 describes a method for detecting defects and the like by limiting the energy range of cosmic rays.

  However, Patent Document 1 uses a horizontal muon having a very large penetrating power with a zenith angle of 50 ° or more, and is not suitable for inspection of small defects in, for example, a composite floor slab of a bridge.

  The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to carry out a defect search for small / medium infrastructure facilities such as bridges and incinerators, which has been difficult until now.

  A cosmic ray has a range (distance from the incident surface until the cosmic ray incident on the material stops), that is, the transmission power to the material, depending on the amount of energy it has. The larger the range, the greater the range.

  The curve in FIG. 3 is a schematic diagram showing the relationship between cosmic ray energy and range. The one with large energy has a large range enough to penetrate the volcano.

  The inspection and investigation by cosmic ray transmission is to estimate the internal state from the difference in the amount of cosmic ray transmission at the inspection object. Therefore, it is desirable to use a cosmic ray component having a range around the thickness of the inspection object. This is because those having a range larger than the thickness of the inspection object pass through the inspection object regardless of whether or not there is a defect, so these components reduce the difference between the signal of the defect and the background signal. Because. On the other hand, if the range is small, there is a possibility that the detection position is erroneously detected, and the estimation accuracy of the flying direction of the cosmic rays is lowered.

  Therefore, it is desirable to use cosmic rays having an appropriate energy range, that is, an appropriate range. Particularly, since the high energy component deteriorates the detection performance of defects and the like, it is more effective to remove the high energy component.

  As shown in FIG. 4, cosmic ray energy discrimination is performed after first and second position-sensitive cosmic ray detectors (hereinafter simply referred to as detectors) 41 and 42 for detecting defects or the like of the inspection object 10. FIG. 5 shows a first cosmic ray shielding material (hereinafter simply referred to as a shielding material) 51 such as a metal body (for example, lead or iron) having a property of blocking cosmic rays in the energy region used in the inspection. As described above, when the signal is detected by the third detector 43 after passing through the first shielding member 51, the signal resulting from the cosmic ray having a large transmission power is deleted from the inspection signal.

  That is, cosmic rays are detected by any or all of the detectors 41, 42, and 43 depending on the magnitude of energy. Among the detected cosmic rays, the signal component of the high-energy cosmic rays detected by the third detector 43 is excluded, and the inspection object 10 is evaluated.

  The defect position is estimated by the position sensitive detector because the straight line connecting the passing points of the cosmic rays in a plurality of detectors (for example, 41 and 42) exists in the range passing through the inspection object 10. When the accuracy of specifying the passing point is deteriorated, the positional accuracy of the defect 10A is also deteriorated. Therefore, it is important to specify the passing point accurately.

  In cosmic rays in the region with a large zenith angle, the distance that passes through the atmosphere increases, so the low energy component decreases due to the effects of absorption and decay. On the other hand, in a region where the zenith angle is small, the distance passing through the atmosphere is small, and therefore a relatively large amount of low energy components are included. In particular, since there are more low energy components in the region of the zenith angle of 0 ° to 20 °, it is preferable to use cosmic rays in this range.

  Furthermore, as shown in FIG. 6 (A), when a cosmic ray having a large zenith angle (50 ° in FIG. 6 (A)) is used, the position and detection of the cosmic ray passing through the inspection object range 11 of the inspection object 10 are detected. Since the instrument 40 is separated, it is difficult to specify the actual position of the defect 10A from the measurement result. However, as shown in FIG. 6 (B), when a cosmic ray with a small zenith angle (20 ° in FIG. 6 (B)) is used, the inspection object range 11 is almost directly above the detector 40 and is detected. Since the number of cosmic rays to be detected is large and the actual position of the defect 10A can be easily identified, the position estimation accuracy is not lowered. For this reason as well, it is preferable to use cosmic rays in a region where the zenith angle is small.

  The configuration of the detector is not limited to FIG. Since the 1st detector 41 should just be able to detect the cosmic ray which pours down from space, the 1st detector 41 is located in the position away from the upper side of inspection object 10 (namely, the 2nd detector 42, the 1st shielding material). 51, a position away from the upper side of the detector main body 40 composed of the third detector 43).

  In the past, for example, a high energy component larger than several hundred MeV was removed. However, for example, a low energy component equal to or lower than 100 MeV may possibly deteriorate the inspection performance.

  Among the low energy components, a false detection component caused by, for example, a negative muon capture reaction in the second detector 42 at the subsequent stage of the inspection object 10 may reduce the contrast of the defect portion, and may also cause cosmic rays. It is also difficult to estimate the flight trajectory. From the above, it is desirable to remove low-energy component signals that degrade detection performance.

  Therefore, as in the modification examples shown in FIGS. 7 to 11, a second shielding member 52 made of, for example, lead or iron can be provided to exclude not only the high energy side but also the low energy side cosmic rays. .

  7 and 8, the second shielding material 52 for the low energy side, which is different from the first shielding material 51 for the high energy side, is used to prevent the low energy component from entering the inspection object 10. It is installed on the upper side.

  7 shows an example in which the second shielding member 52 is disposed on the upper side of the first detector 41, and FIG. 8 shows a second configuration between the first detector 41 and the inspection object 10. This is an example in which the shielding material 52 is provided.

  9 to 11 are different from the first shielding member 51 on the lower side or upper side of the inspection object 10 so as not to detect the scattered radiation due to the low energy component generated in the inspection object 10 as a signal. The second shielding material 52 on the low energy side is installed.

  FIG. 9 shows an example in which a second shielding member 52 is disposed between the inspection object 10 and the second detector 42, and FIG. 10 illustrates the first detector 41 disposed at a position away from the inspection object 10. In addition, an example in which the second shielding material 52 is disposed on the upper side of the inspection object 10, and FIG. 11 shows an example in which the second shielding material 52 is disposed between the inspection object 10 and the second detector 42. It is. As shown in FIGS. 10 and 11, when the first detector 41 is separated, a fourth detector 44 and a fifth detector 45 are provided, and the second detector 42 and the fourth detector 44 are provided. The incident direction of the cosmic rays can be specified by the combination of the first detector 41 and the fifth detector 45. This is the same even when the second shielding member 52 is not provided.

  Here, the first predetermined energy that shields the high energy side and the second predetermined energy that shields the low energy side are largely determined by the size of the inspection object and the defect to be detected, and thus cannot be determined unconditionally. However, as an example, when a 100 mm × 100 mm × 100 mm cavity in a 200 mm thick concrete is to be detected, the first predetermined energy for shielding the high energy side is several hundred MeV and the low energy side is shielded. The second predetermined energy to be set can be several tens MeV.

  The present invention has been made based on the above knowledge, by nondestructively inspecting the internal structure of the inspection object using a low-energy cosmic ray having a first predetermined energy or less that has passed through the inspection object. The problem is solved.

  Here, the low energy cosmic rays are included in cosmic rays having a zenith angle in the range of 0 ° to 20 °.

  Also, a cosmic ray is provided between the inspection object and the first shielding material by providing a first shielding material below the inspection object, detecting a cosmic ray that has passed through the first shielding material. The low-energy cosmic rays can be extracted by excluding them.

  Furthermore, low-energy cosmic rays having a second predetermined energy or less that is smaller than the first predetermined energy can be excluded.

  Moreover, the 2nd shielding material which excludes the low energy cosmic rays below the said 2nd predetermined energy smaller than the said 1st predetermined energy can be provided.

  The present invention also provides a first cosmic ray detector that detects a cosmic ray incident from the universe, a second cosmic ray detector that detects a cosmic ray that has passed through an inspection object, and the second cosmic ray. A first shielding member disposed below the detector; a third cosmic ray detector that detects cosmic rays that have passed through the first shielding member; and an output of the second cosmic ray detector. Computation means for detecting low energy cosmic rays below the first predetermined energy that have passed through the inspection object by removing the output signal of the third cosmic ray detector from the signal, By providing a non-destructive inspection apparatus for a structure that uses muography, the above-mentioned problem is similarly solved.

  Here, the first cosmic ray detector can be disposed above the inspection target range.

  Further, the first cosmic ray detector can be disposed at a position away from above the inspection target range.

  In addition, fourth and fifth cosmic ray detectors for detecting the incident direction of the cosmic rays can be further provided.

  Furthermore, a second shielding material that excludes low-energy cosmic rays having a second predetermined energy or less that is smaller than the first predetermined energy may be provided.

  Further, the second shielding material can be disposed on the upper side of the first cosmic ray detector.

  Further, the second shielding material can be disposed between the first cosmic ray detector and the first shielding material.

  Further, the second shielding material can be disposed between the inspection object and the second cosmic ray detector.

  Further, the second shielding material can be disposed above the inspection target range.

  According to the present invention, it is possible to search for defects in small / medium infrastructure facilities such as bridges and incinerators, which have been difficult until now.

Cross-sectional view schematically showing the principle of defect inspection by transmission of cosmic rays (A) Composite floor slab of bridge and (B) Cross section showing the defect state A diagram showing an example of the relationship between cosmic ray energy and cosmic ray range for explaining the principle of the present invention Sectional drawing which shows the example of arrangement | positioning of the detector for the high energy cosmic ray removal by this invention Cross-sectional view showing the same effect The figure which compares and shows the example of the relation between the inspection object range by the difference in the incident angle of cosmic rays, and the position shift of the detector Sectional drawing which shows the detector arrangement | positioning of the modification of FIG. Sectional drawing which shows another modification similarly Sectional drawing which shows another modification similarly Sectional drawing which shows another modification similarly Sectional drawing which shows another modification similarly (A) longitudinal cross-sectional view and (B) cross-sectional view showing the configuration of the first embodiment of the present invention The perspective view which shows the example of the detector used by the said embodiment. (A) longitudinal cross-sectional view and (B) cross-sectional view showing the configuration of the second embodiment of the present invention (A) Longitudinal sectional view and (B) Transverse sectional view similarly showing the configuration of the third embodiment

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

  In addition, this invention is not limited by the content described in the following embodiment and an Example. The constituent elements in the embodiments and examples described below include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those that are so-called equivalent ranges. Furthermore, the constituent elements disclosed in the embodiments and examples described below may be appropriately combined or may be appropriately selected and used.

  In the first embodiment of the present invention, as shown in FIG. 12, when the present invention is applied to the inspection of the composite floor slab 20 of the bridge 30, the second detector 42 is provided below the composite floor slab 20 of the bridge 30. The detector main body 40 including the first shielding member 51 and the third detector 43 is laminated and the first detector 41 is arranged above the detector main body 40 on the pavement 28 of the composite floor slab 20. It is set. In the figure, 34 is a bridge pier, 36 is a support, 38 is a telescopic device, 61, 62, and 63 are measuring instruments that measure the outputs of the first, second, and third detectors 41, 42, and 43, respectively, and 70 is a measuring instrument. This is an arithmetic unit that performs an operation according to the present invention on the outputs of the units 61, 62, and 63.

  By removing the output of the third detector 43 from the output of the second detector 42 by the computing unit 70, a signal of low energy cosmic rays can be extracted.

  As the detectors 41, 42, and 43, as illustrated in FIG. 13, a plurality of scintillation fibers 80 are disposed so as to be orthogonal to each other, and a multi-pixel photon counter (MPPC) 82 is disposed at one end of the scintillation fibers 80. Things can be used. In order to specify the flying direction of the cosmic rays, two layers are required as shown in FIG. 13. For example, the first detector 41 and the second detector 42 can form two layers. In addition to this, a nuclear plate, a drift chamber, or the like can be used as the detector.

  In the second embodiment of the present invention, as shown in FIG. 14, the first detector 41 is arranged on the composite floor slab 20 that is several meters away from the upper part of the detector body 40 and can be connected by a cable. . Furthermore, in order to specify the incident direction of the cosmic rays, the upper side (example of FIG. 14) or the lower side of the second detector 42 and the upper side (example of FIG. 14) or the lower side of the first detector 41. , Fourth and fifth detectors 44 and 45 are provided, respectively.

  In the figure, 64 and 65 are measuring instruments that measure the outputs of the fourth and fifth detectors 44 and 45.

  The other points are the same as those in the first embodiment, and a description thereof will be omitted.

  In the third embodiment of the present invention, as shown in FIG. 15, the first detector 41 and the fifth detector 45 are arranged in the vicinity of the bridge 30. If there is no shield in the zenith angle range of the cosmic rays to be used, the arrangement as in the third embodiment is also possible.

  Other points are the same as those in the second embodiment, and thus the description thereof is omitted.

  In the above embodiment, the second shielding member 52 that shields the low energy side is not provided in any of the above embodiments, but the detector main body 40 can be made as shown in FIG. 7 by adding the second shielding member 52. It is also possible to have a configuration as shown in FIG.

  As the shielding material, for example, metals such as lead and iron and alloys thereof, or a high-density material such as a mixture containing metal (for example, a resin mixed with metal powder) can be used.

  As shown in the embodiment, since it is not necessary to install an X-ray generator and a radiation management area necessary for using X-rays on the floor slab, inspection can be performed without obstructing traffic.

  The application object of the present invention is not limited to this, but other small and medium infrastructure facilities such as steel slabs other than synthetic slabs, PC slabs, incinerators, pipelines, underground tunnel cavities, dam walls, etc. It is clear that the present invention can be similarly applied to the defect inspection.

DESCRIPTION OF SYMBOLS 10 ... Inspection object 10A ... Defect 20 ... Composite floor slab 28 ... Pavement 30 ... Bridge 32 ... Girder 34 ... Bridge pier 36 ... Bearing 38 ... Telescopic device 40 ... Detector main body 41, 42, 43, 44, 45 ... (cosmic ray) ) Detector 51, 52 ... (cosmic ray) shielding material 61, 62, 63, 64, 65 ... Measuring instrument 70 ... Calculator 80 ... Scintillation fiber 82 ... Multi-pixel photon counter (MPPC)

Claims (14)

  A nondestructive inspection method for a structure using muography, wherein the internal structure of the inspection object is nondestructively inspected using a low-energy cosmic ray having a first predetermined energy or less that has passed through the inspection object.   The non-destructive inspection method for a structure using muography according to claim 1, wherein the low energy cosmic rays are included in cosmic rays having a zenith angle in a range of 0 ° to 20 °.   A first shielding material is provided below the object to be inspected, and cosmic rays transmitted through the first shielding material are detected and excluded from the cosmic rays detected between the object to be inspected and the first shielding material. The non-destructive inspection method for a structure using muography according to claim 1, wherein the low-energy cosmic rays are extracted.   The nondestructive inspection of a structure using muography according to any one of claims 1 to 3, wherein low-energy cosmic rays having a second predetermined energy or less smaller than the first predetermined energy are excluded. Method.   5. The non-structural structure using muography according to claim 4, further comprising a second shielding member that excludes low-energy cosmic rays that are smaller than the first predetermined energy and lower than the second predetermined energy. Destructive inspection method. A first cosmic ray detector for detecting cosmic rays incident from space;
A second cosmic ray detector that detects cosmic rays that have passed through the object to be inspected;
A first shielding material disposed below the second cosmic ray detector;
A third cosmic ray detector for detecting cosmic rays transmitted through the first shielding material;
An operation for detecting low-energy cosmic rays having a first predetermined energy or less, which has passed through the inspection object, by removing the output signal of the third cosmic ray detector from the output signal of the second cosmic ray detector. Means,
A non-destructive inspection device for structures using muography, characterized by comprising:   The non-destructive inspection apparatus for a structure using muography according to claim 6, wherein the first cosmic ray detector is disposed above an inspection target range.   7. The nondestructive inspection apparatus for a structure using muography according to claim 6, wherein the first cosmic ray detector is disposed at a position away from above the inspection target range.   9. The nondestructive inspection apparatus for a structure using muography according to claim 8, further comprising fourth and fifth cosmic ray detectors for detecting the incident direction of the cosmic rays.   The muography according to any one of claims 6 to 9, further comprising a second shielding material that excludes low-energy cosmic rays that are less than a second predetermined energy that is smaller than the first predetermined energy. Non-destructive inspection equipment for structures.   The nondestructive inspection apparatus for a structure using muography according to claim 10, wherein the second shielding material is disposed on an upper side of the first cosmic ray detector.   The non-destructive structure using muography according to claim 10, wherein the second shielding material is disposed between the first cosmic ray detector and the first shielding material. Inspection device.   11. The nondestructive inspection apparatus for a structure using muography according to claim 10, wherein the second shielding material is disposed between an inspection object and the second cosmic ray detector.   The non-destructive inspection apparatus for a structure using muography according to claim 10, wherein the second shielding material is disposed above an inspection target range.