JP2015215263A - Nondestructive inspection method and system thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nondestructive inspection system capable of simply detecting the state of an object to be inspected without being affected by fluctuations of a γ ray source and without causing the problem of restricting an arrangement position of a detector when a Compton-scattering γ ray is used.SOLUTION: The nondestructive inspection system comprises: a γ ray source 1 for irradiating an object 3 to be inspected with an X ray or a γ ray (hereafter, both together are referred to as a γ ray ) having at least two different peak energies; and a detector 2 for specifying a pattern having at least three peaks formed due to the thickness of the object 3 to be inspected on the basis of scattering γ ray energy distribution characteristics to detect the state of the object 3 to be inspected while detecting a scattering γ ray having the at least three different peak energies on the basis of Compton scattering caused by the result of the irradiation to acquire the scattering γ ray energy distribution characteristics representing signal intensity to the scattering γ ray energy of a scattering γ ray signal showing the detected scattering γ ray.

Description

  The present invention relates to a nondestructive inspection method and an apparatus therefor, and is particularly useful when applied to a nondestructive inspection utilizing Compton scattering.

  Non-destructive inspection using X-rays or γ-rays (hereinafter collectively referred to as γ-rays in the present specification) is widely used for inspection of piping of nuclear facilities. In this method, γ-rays are irradiated to a pipe or the like that is an inspection object, and a transmission image of the inspection object is analyzed to detect the degree of thinning (for example, see Patent Document 1).

  However, when inspecting the degree of thinning by obtaining a transmission image of the inspection object, the detector for detecting γ rays is placed on the opposite side of the inspection object with respect to the radiation source that irradiates γ rays. Need to be placed in.

  For this reason, the opposite side of the object to be inspected with respect to the radiation source is often a narrow part, or a sufficient space for disposing the detector cannot be secured due to the presence of obstacles such as other pipes.

On the other hand, if scattered gamma rays based on Compton backscattering are used, the radiation source and the detector can be arranged on the same side with respect to the inspection object. Compton backscattering means that, as shown in FIG. 8 (a), when the target T is irradiated with a predetermined γ-ray, the energy changes with the recoil electrons E _e that jump out in the direction of the angle Φ with respect to the γ-ray. A phenomenon in which the original γ rays are scattered as scattered γ rays. Here, the scattering angle θ of the scattered γ-ray is uniquely determined by the energy E _{0 of the} γ-ray irradiated to the target T and the scattered γ-ray energy E ₁ of the scattered γ-ray scattered. The case of scattering in a region where the scattering angle θ> 90 ° is particularly referred to as backscattering.

Therefore, as shown in FIG. 8B, if the γ-ray source 01 and the detector 02 are arranged so as to match the scattering angle θ> 90 °, the γ-ray source 01 and the detector 02 are inspected. It can arrange | position on the same side with respect to the piping 03 which is a thing, and the arrangement | positioning conditions of the detector 02 can be eased. Here, in the detector 02, as shown in FIG. 8C, the scattering uniquely identified by the scattering angle θ (the angle formed by the arrangement position of the γ-ray source 01 and the arrangement position of the detector 02). A scattered γ-ray energy distribution having a peak signal intensity is obtained at the scattered γ-ray energy E ₁ of γ-rays. In FIG. 8C, the horizontal axis represents the energy of the scattered γ-ray, and the vertical axis represents the signal intensity of the scattered γ-ray signal detected by the detector 02. The scattered γ-ray signal is a signal representing the intensity of the scattered γ-ray. Although not shown, a normal collimator is usually provided in front of the γ-ray source 01 and the detector 02.

On the other hand, as shown in FIG. 9A, the scattered γ-ray energy E of the back-scattered γ-ray when the pipe 03 which is the inspection object maintains a normal state without causing thinning on the inner periphery. _As shown in FIG. 9B, ₁ is larger than the case where the thinned portion 03A is formed on the inner periphery of the pipe 03 that is the inspection object. The thick portion of the pipe 03, which is the inspection object, is a high-density material such as iron, whereas the thinned portion 03A is low-density air, so that the γ-ray scattering intensity greatly decreases in the air portion. Because. For example, assuming that the energy E _{0 of} γ-rays emitted from the radioisotope iridium source, which is the γ-ray source 01, is 320 keV, the scattered γ-ray energy E ₁ of the scattered γ-rays when the scattering angle θ = 90 ° is 197 keV. It is uniquely determined. Accordingly, the signal intensity of the scattered γ ray energy E ₁ of the scattered γ ray becomes small when the reduced thickness portion 03A on the pipe 03 which is an inspection object is occurring.

Therefore, the occurrence of thinning can be detected by detecting the scattered γ-ray energy E ₁ of the scattered γ-rays in the scattered γ-ray energy distribution shown in FIG. 8C (see, for example, Non-Patent Document 1).

JP 2006-177841 A

(Japan) Atomic Energy Society of Japan "1995 Autumn Conference" (October 17-20, 1995, JAERI) Inspection technology from the surface of thermal insulation materials using Compton scattering, Toshiba Corporation, Akira Udaka, Takayuki Takashima, Goto Tetsuo

However, when the thinning is detected based on the signal intensity of the scattered γ-ray energy E ₁ of the scattered γ-ray in the scattered γ-ray energy distribution characteristics shown in FIG. 8C as described above, the fluctuation of the γ-ray source 01 is It becomes a problem. For example, when a radioisotope source is used as the γ-ray source, the intensity of the γ-ray irradiated from the γ-ray source 01 may fluctuate with time, and the reference signal intensity changes accordingly. This is because it becomes an impediment to highly accurate measurement.

As described above, the problem that the reference signal intensity changes is not only in the case of using Compton backscattering as in the case shown in FIG. 8, but in the case of the conventional transmission method using Compton scattering. The same occurs. That is, a problem that fluctuation of the signal intensity of such criteria as long as it utilizes only the magnitude of the signal intensity of the scattered γ ray energy E _1, not limited to backscattering generally occurs.

  In view of the above-described prior art, the present invention, in the case of using Compton scattered γ-rays, the state of the inspection object is not affected by fluctuations in the γ-ray source, and is further referred to as a restriction on the arrangement position of the detector. It is an object of the present invention to provide a nondestructive inspection method and apparatus capable of easily and accurately detecting without causing a problem.

The present invention that achieves the above object is based on the following knowledge. As shown in FIG. 1 (a), Compton scattering, as described above, by the γ ray energy E ₀ is irradiated to the target T1, recoil electrons E pops out direction of an angle Φ with respect to γ rays _e In addition, a phenomenon in which the original γ-rays are scattered as scattered γ-rays whose energy has changed, and such scattering may occur multiple times with a predetermined probability. FIG. 1A shows a mode of two-time scattering. In this case, by γ ray energy E ₀ is irradiated to the target T1 to become a single scattered γ ray energy E _21, once more scattered γ rays causes a second scattered at the same target T1, the energy E ₂₂ The twice scattered γ rays. At this time, the relationship between the energy E ₀ , E ₂₁ , E ₂₂ of each γ-ray, the one-time scattering angle θ ₁ , and the two-time scattering angle θ ₂ is expressed by the following equations (1) and (2).

Incidentally, the relationship between the scattering angle θ (= θ ₁ + θ ₂ ) and the scattered γ-ray energy E ₁ when the γ-ray with energy E ₀ is scattered only once in the target T1 is expressed by the following equation (3). .

  In general, as the number of scattering increases, the signal intensity decreases. Therefore, as the number of scattering increases, the scattered γ-ray signal becomes harder to detect on the scattered γ-ray energy distribution characteristic shown in FIG. Moreover, the scattered γ-ray signal based on multiple scattering usually appears on the lower energy side of the scattered γ-ray energy in the case of one-time scattering on the scattered γ-ray energy distribution characteristics shown in FIG.

However, as shown in FIG. 1B, by appropriately selecting the energy E ₀ and the scattering angle θ of the γ-rays irradiated from the γ-ray source 1 to the inspection object 3 that is a pipe, and increasing the measurement accuracy, the high energy side of the single scattering detector 2 in the energy E _1, can be observed a peak of two scattering energy E _22. That is, for example, when E ₀ = 320 keV and the scattering angle θ = 90 °, E ₁ = 197 keV from the equation (3), and E ₂₂ = 234 keV from the equations (1) and (2). Here, as a scattering angle for scattering back 90 ° (= θ = θ ₁ + θ ₂ ) by _two scatterings, the first scattering angle θ ₁ = 45 ° and the second scattering angle θ ₂ = 45. °.

FIG. 1C is a characteristic diagram showing a scattered γ-ray energy distribution characteristic in which a double scattering peak appears together with a single scattering. In the characteristic diagram shown in the figure, but less than the signal strength P1 of energy E _1, the signal strength P2 giving than once scattering peak energy E ₁ at a high energy side twice scattering peaks of energy E ₂₂ is observed Has been.

In the analysis of the energy distribution characteristic having a two-time scattering peak this time, as shown in FIG. 2 (a), there is no thinning in the inspection object 3, and as shown in FIG. 2 (c). In addition, it was found that there is a significant difference in the scattered γ-ray energy distribution characteristics between the case where the thinned portion 3A is provided. That is, when the thinning does not occur, as the scattered γ ray energy distribution characteristic shown in FIG. 2 (b), as expected, the signal strength P1 of one scattering peak energy E ₁ is the energy E ₂₂ is larger than 2 times the scattering peak in signal strength P2, as the reduced thickness portion 3A is increased, the difference between the signal intensity P2 of two scattering peaks of one scattering peak of signal intensity P1 and energy E ₂₂ energy E ₁ is's lead, so that the scattered γ ray energy distribution characteristics in the final illustrated in FIG. 2 (d), 2 times the scattering peak in signal strength P2 of the energy E ₂₂ than the signal strength P1 of one scattering peak energy E ₁ It turns out that the reversal phenomenon of becoming larger occurs.

The cause of the occurrence of the reverse phenomenon is considered as follows. In the case of single scattering shown in FIG. 3 (a), a pencil beam is emitted from a γ-ray source as a point source, and an ideal lead collimator is also installed as the observation point for the scattered γ-ray. Then, as for the signal intensity of the single scattering peak at the observation point, the scattering information of only one point (the intersection of the γ ray traveling axis and the lead collimator rotational symmetry axis) is obtained. For this reason, the one-time scattering peak is backscattered from the air in a region where the iron material is not present due to thinning or the like, and thus the scattered γ-rays rapidly decrease. On the other hand, in the case of double scattering shown in FIG. 3B, there are an infinite number of paths in the sample even if an ideal collimator is installed. In the figure, the vertical line of the sample portion represents a part of the path, which corresponds to the case of θ ₁ = θ ₂ = 45 °. Including double scattering in the case of θ ₁ ≠ θ ₂ and θ = θ ₁ + θ ₂ (= 90 °), the number of paths is further increased. However, in this case, since the energy position of the twice-scattered peak is slightly shifted, the twice-scattered peak is broad. Here, when the thickness of the iron sample is reduced due to thinning or the like, the portion corresponding to the thinned region (gray portion in the drawing) is scattered twice as shown in FIG. The region that does not occur but remains thin is still a region where scattering can occur twice. Therefore, it is considered that the decrease in the signal intensity of the two-time scattering accompanying the decrease in the sample thickness is more gradual than the decrease in the signal intensity of the one-time scattering. In some cases, it is considered that a phenomenon occurs in which the once-scattered peak and the twice-scattered peak intensity are reversed as in the present example.

  Since the double scattering peak is the signal intensity of the γ-ray signal that is not noise, using this well may lead to a new thinning detection technique. In other words, rather than looking at the magnitude of the signal intensity of one-time scattering, comparing the scattered γ-ray energy distribution characteristics with those in a healthy case, the occurrence of thinning of pipes, etc. It is considered that the state of an object can be detected. For example, as shown in FIG. 4, the signal intensity ratio (P2 / P1) between the once-scattered peak and the twice-scattered peak is taken, and if this ratio is equal to or greater than a predetermined threshold, it is determined that thinning has occurred. It is a technique. Moreover, since it is thought that this ratio changes according to the amount of thickness reduction of piping, the amount of thickness reduction can also be specified by the amount of change.

  The advantage of this method is that both the once-scattered peak and the twice-scattered peak are measured with the same radiation source and measurement configuration, so the dose of γ-rays to be irradiated changes with time by taking the signal intensity ratio. Even so, the influence can be reduced and highly accurate measurement can be performed. For example, even if the irradiation γ dose at the time of actual measurement changes with respect to the irradiation γ dose when the reference energy distribution characteristic is acquired using a healthy sample, the influence of the change can be canceled. So it is very effective.

  Further, for example, when an iridium radiation source is considered as an irradiation γ-ray source, the scattered γ-ray energy distribution characteristics were examined, and the following was found.

  FIG. 5A shows a case in which the thickness of the inspection object 3 is 5 mm, and (b), (c), (d), (e), and (f) are 5.5 mm, 5.8 mm, and 6 mm, respectively. FIG. 7 is a characteristic diagram showing scattered γ-ray energy characteristics when the thickness is 7 mm or 10 mm.

Since the energy of the main emitted γ-rays of the iridium radiation source is 317 keV and 468 keV, these are designated as E ₀ and E ₀ ′. In FIG. 5, the emission rate is 83% (317 keV for each nuclear decay of 317 keV and 468 keV). ) And 48% (468 keV).

  As is apparent from FIGS. 5A to 5F, it has been found that there is a significant difference in the scattered γ-ray energy distribution characteristics depending on the thickness of the inspection object 3. This occurs because the increase / decrease amount of the signal intensities S1 (317 keV), S2 (317 keV), S1 (468 keV), and S2 (468 keV) differs depending on the thickness of the inspection object 3. Here, the sign of S1 indicates that it is a once-scattered γ-ray, S2 indicates that it is a twice-scattered γ-ray, and (317 keV) and (468 keV) in () denote the respective incident γ-ray energies. Show.

  The characteristic of FIG. 5 is basically that the signal intensity changes of S2 (317 keV) and S2 (468 keV) which are two-time scattering peaks are not large, and S1 (317 keV) and S1 (468 keV) which are one-time scattering peaks. It shows that a pattern change occurs in the process of reversing the scattering peak intensity twice. Here, two different energies as γ rays (in this example, energy 317 keV and 468 keV) are irradiated, and the pattern type increases.

  In the example shown in FIG. 5, as the inspection object 3 becomes thinner, the shape in which the peaks of the signal strengths S1 (317 keV), S2 (317 keV), S1 (468 keV), and S2 (468 keV) are formed is V-shaped (FIG. 5 ( f), (e), (d)) → slope downward (FIGS. 5 (c), (b)) → mountain shape (FIG. 5 (A)), a pattern on the scattered γ-ray energy distribution characteristics Thus, the approximate thickness of the inspection object 3 can be grasped. In particular, in this example, since the pattern is remarkably changed in the vicinity of 5 mm (FIG. 5 (a)) to 6 mm (FIG. 5 (d)), it is considered that this example is effective for detecting the thinning in this range. . Of course, for quantitative evaluation, not only the pattern type but also the ratio of signal intensity S1 (317 keV) and S1 (468 keV), signal intensity S2 (317 keV) and S1 (468 keV) as shown in FIG. It goes without saying that the ratio is referred to, but it has been suggested that by using the pattern of energy distribution, a risk judgment material due to thinning can be easily given.

  The first aspect of the present invention based on such knowledge irradiates the inspection object with X-rays or γ-rays (hereinafter, collectively referred to as γ-rays) having at least two different peak energies. The scattered γ-rays having at least three different peak energies are detected based on the Compton scattering generated as a result of the above, and the scattered γ-rays representing the signal intensity of the scattered γ-ray signal representing the detected scattered γ-rays with respect to the scattered γ-ray energy A state of the inspection object by generating an energy distribution characteristic and using the scattered γ-ray energy distribution characteristic to identify a pattern formed by the at least three peaks due to the thickness of the inspection object It is in the nondestructive inspection method characterized by detecting.

  According to this aspect, since the pattern formed at the peak position of the signal intensity of at least three different scattered γ-ray energies is correlated with the thickness of the detection object, the inspection object is changed by the transition of the pattern. Thickness, for example, thinning can be accurately detected.

  According to a second aspect of the present invention, in the nondestructive inspection method according to the first aspect, the Compton scattering is Compton backscattering.

  According to this aspect, the scattered γ-ray detector can be disposed on the same side as the γ-ray source with respect to the inspection object, so that the degree of freedom in equipment arrangement is increased.

  According to a third aspect of the present invention, in the nondestructive inspection method according to the first or second aspect, the scattered γ-rays having at least three different peak energies include at least one twice-scattered γ-ray. It is in the nondestructive inspection method characterized by this.

  According to this aspect, since the twice-scattered γ-ray is used as one of the pattern recognitions, the types of γ-rays emitted from the γ-ray source can be reduced.

  According to a fourth aspect of the present invention, in the nondestructive inspection method according to any one of the first to third aspects, the ratio of the signal strengths of the two different scattered γ-ray signals is further considered. A non-destructive inspection method is characterized by detecting a state of an inspection object.

  According to this aspect, the state of the inspection object can be detected more easily and accurately.

  According to a fifth aspect of the present invention, there is provided a γ-ray source that irradiates an inspection object with X-rays or γ-rays having at least two different peak energies (hereinafter collectively referred to as γ-rays), and the occurrence of the irradiation Scattered γ-ray energy distribution representing a signal intensity of the scattered γ-ray signal representing the detected scattered γ-ray with respect to the scattered γ-ray energy based on Compton scattering that is detected and detecting scattered γ-rays having at least three different peak energies While detecting the characteristics, detection based on the scattered γ-ray energy distribution characteristics to identify the pattern formed by the at least three peaks due to the thickness of the inspection object and detect the state of the inspection object And a non-destructive inspection apparatus characterized by comprising:

  According to this aspect, since the pattern formed at the peak position of the signal intensity of at least three different scattered γ-ray energies is correlated with the thickness of the detection object, the inspection object is changed by the transition of the pattern. Thickness, for example, thinning can be accurately detected.

  According to a sixth aspect of the present invention, in the nondestructive inspection apparatus according to the fifth aspect, the Compton scattering is Compton backscattering, and the detector is disposed on the same side with respect to the inspection object. It is in the nondestructive inspection device characterized by being.

  According to this aspect, the scattered γ-ray detector can be disposed on the same side as the γ-ray source with respect to the inspection object, so that the degree of freedom in equipment arrangement is increased.

  According to a seventh aspect of the present invention, in the nondestructive inspection apparatus according to the fifth or sixth aspect, the scattered γ-rays having at least three different peak energies include at least one twice-scattered γ-ray. It is in the nondestructive inspection apparatus characterized by this.

  According to this aspect, since the twice-scattered γ-ray is used as one of the pattern recognitions, the types of γ-rays emitted from the γ-ray source can be reduced.

  An eighth aspect of the present invention is the nondestructive inspection apparatus according to any one of the fifth to seventh aspects, wherein the γ-ray source has at least two different isotopes having different peak energies. It is a nondestructive inspection device characterized by being formed of nuclides.

  According to this aspect, it is possible to emit a plurality of monochromatic γ rays satisfactorily.

  According to a ninth aspect of the present invention, in the nondestructive inspection apparatus according to any one of the fifth to seventh aspects, the γ-ray source includes at least two generated by collisions between electrons and laser light. A non-destructive inspection apparatus characterized by being a laser Compton scattered radiation source that irradiates gamma rays having different peak energies.

  According to this aspect, it is possible to arbitrarily generate monochromatic γ-rays having desired energy simply by changing the energy of electrons that collide with laser light.

  A tenth aspect of the present invention is the nondestructive inspection apparatus according to any one of the fifth to ninth aspects, wherein the detector further includes a ratio of signal intensities of the two different scattered γ-ray signals. The non-destructive inspection apparatus is characterized in that the state of the inspection object is detected in consideration of the above.

  According to this aspect, the state of the inspection object can be detected more easily and accurately.

  According to the present invention, based on the knowledge that the peak pattern formed by at least three different peaks has a specific change in the scattered γ-ray energy distribution as the thickness of the object to be inspected decreases. Can be used to detect the thickness of the inspection object. Here, the present invention does not compare the signal intensity based on the scattered γ-rays with other objects, but makes a predetermined determination based only on the change in the pattern shape of the peak. It will not be affected by the fluctuations.

It is a figure which shows typically the principle of this invention using the Compton backscattering 2 times scattering, (a) is explanatory drawing which shows 2 times scattering conceptually, (b) is explanatory drawing which shows apparatus arrangement | positioning in this case (C) is a characteristic view showing the scattered γ-ray energy distribution characteristic in which a double scattering peak is observed. In the figure which shows the principle of this invention typically, (a) and (b) are the cases where there is no thinning in the piping of the detection object, and (c) and (d) are the cases where there is thinning. In Compton backscattering, it is explanatory drawing which shows the path | route of the gamma ray irradiated to the iron sample in the case of the case of 1 time scattering and the case of 2 times scattering. It is a characteristic view which shows the characteristic with respect to the thickness of the iron sample of the signal intensity ratio (P2 / P1) of a 1 time scattering peak and a 2 times scattering peak. Assuming an iridium radiation source as an irradiation γ-ray source, scattered γ-rays obtained by superimposing scattered γ-rays from 317 keV and 468 keV, which are main emitted γ-ray energies, in accordance with a predetermined ratio for each nuclear decay. It is an energy distribution characteristic view. It is a characteristic figure which shows ratio of signal strength S1 (317 keV) and S1 (468 keV), and ratio of signal strength S2 (317 keV) and S1 (468 keV). It is a block diagram which shows the nondestructive inspection apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the principle of conventionally well-known Compton backscattering (single-time scattering) typically. It is explanatory drawing which shows typically the principle of the prior art which carries out nondestructive inspection of the thinning of piping using Compton backscattering.

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

FIG. 7 is a block diagram showing a nondestructive inspection apparatus according to an embodiment of the present invention. As shown in the figure, the nondestructive inspection apparatus according to this embodiment includes a γ-ray source 1 that irradiates γ-rays toward an inspection object 3 that is, for example, a pipe, and scattering based on Compton scattering obtained as a result of the irradiation. and a detector 2 for detecting γ-rays. The γ-ray source 1 is composed of an isotope radiation source that irradiates γ-rays having at least two different peak energies (E ₀ = 317 keV and E ₀ ′ = 468 keV in this embodiment). In the case of the present embodiment, an iridium isotope source is assumed as the γ-ray source 1, but there is no particular limitation on the nuclide. Moreover, when it is desired to use the γ-ray source 1 that irradiates γ-rays having three different peak energies, for example, a combination in which a cesium isotope source is added to an iridium isotope source can be considered.

  The detector 2 detects scattered γ-rays having signal intensity peaks at at least three different scattered γ-ray energies, based on Compton scattering that occurs as a result of γ-ray irradiation, and the scattered γ representing the detected scattered γ-rays. A scattered γ-ray energy distribution characteristic representing the signal intensity with respect to the scattered γ-ray energy of the line signal is obtained. An example of the scattered γ-ray energy distribution is shown in FIG. FIG. 5 shows an example in which an iridium isotope source is assumed, and γ-rays with energy of 317 keV and 468 keV are irradiated as main emitted γ-rays.

  In the case shown in FIG. 5, there are two main γ-ray energies irradiated from the γ-ray source 1 317 keV and 468 keV, but not only once scattered γ rays but also twice scattered γ rays in the processing on the detector 2 side. Can be used, even if there are two γ-ray energies irradiated from the γ-ray source 1 side, scattered γ-rays having at least three different peak energies can be obtained on the detector 2 side. Can do. Thus, based on the scattered γ-ray energy distribution characteristics, the pattern formed by at least three peaks due to the thickness of the inspection object 3 is specified to detect the state of the inspection object 3, for example, the thickness of the pipe. .

  As described above, this embodiment uses a pattern formed by at least three peaks of signal intensity in the scattered γ-ray energy distribution characteristic representing the signal intensity of the scattered γ-ray with respect to the scattered γ-ray energy. In this case, at least three peaks are required, but as described above, there are cases where two of the three peaks can use twice-scattered γ-rays based on γ-rays on the irradiation side. Therefore, when the twice-scattered γ-rays can be used, the γ-ray source 1 does not necessarily need to be a γ-ray source that irradiates γ-rays having three peak energies. It may be a γ-ray source that irradiates γ-rays having peak energy.

  Thus, the detector 2 detects a state such as thinning of the inspection object 3 by specifying a pattern formed by at least three peaks due to the thickness of the inspection object based on the scattered γ-ray energy distribution characteristics. To do.

  More specifically, the detector 2 includes an incident unit 2A that receives Compton backscattered γ rays, a signal processing unit 2B that generates a Compton backscattered γray signal representing Compton backscattered γrays, and a Compton backscattered γray signal. The storage unit 2D stored together with the thickness information of the corresponding inspection object, the information processing unit 2C that performs predetermined information processing based on the data stored in the storage unit 2D, and the detection result detected by the information processing unit 2C Is displayed. In the information processing unit 2C, the scattered γ-ray energy distribution characteristics for each thickness of the inspection object 3, that is, the characteristics shown in FIG. 5 are generated, and a pattern formed by three specific peaks in each characteristic diagram is generated. The thickness of the inspection object 3 is specified by comparison. For example, as shown in FIG. 5, the pattern shape formed by the peak is V-shaped (FIGS. 5 (f), (e), (d)), lower right shoulder (FIG. 5 (c), (b)) or The thickness of the inspection object 3 is specified depending on whether the shape is a mountain shape (FIG. 5A), and the degree of thinning is detected. Here, the characteristics shown in FIG. 6 may be taken into consideration when specifying the thinning or the like. The characteristic is created by the information processing unit 2C based on the storage contents of the storage unit 2D. Further, in order to specify the state of thinning or the like of the inspection object 3 in the information processing unit 2C, data regarding the scattered γ-ray energy distribution characteristics of the initial inspection object 3 for comparison is required. The data is stored in advance in the storage unit 2D.

  The detection result in the information processing unit 2C is visualized on the display unit 2E. When the inspection object 3 is a pipe and provides an indication of replacement based on the degree of thinning, for example, the pattern in which the peak is formed is V-shaped (FIGS. 5 (f), (e), (d)). In the case of good, lower right shoulder (FIGS. 5 (c) and (b)), thinning has occurred, but there is no need for replacement, and mountain-shaped (FIG. 5 (a)) thinning proceeds. Therefore, it is possible to display an instruction for replacement.

  As described above, in the detector 2 according to the present embodiment, as the thickness of the inspection object 3 becomes thinner, the peak pattern of the signal changes and becomes a pattern unique to thinning or the like. Therefore, it is possible to detect a change in state such as thinning of the inspection object 3 by observing the change in the pattern.

  Here, in this embodiment, the signal intensity is not compared with other objects, but a predetermined determination is made based only on the change in the pattern shape of the peak. It is not affected.

  Although the above embodiment is a case where the γ-ray source 1 is formed of an isotope source, it is not limited to an isotope source as long as it is a γ-ray source having at least two different peak energies. It may be a laser Compton scattering (LCS) radiation source that irradiates gamma rays having at least two different peak energies generated by collision between electrons and laser light. In this case, gamma rays of desired energy can be obtained by appropriately selecting the energy of the electrons and the wavelength of the laser light, and further the gamma ray energy obtained by adjusting the collision angle of the electrons with the laser light. Can be selected. Further, the case of using Compton backscattered γ rays has been described, but the present invention is not limited to backscattering. However, when using backscattering, since the γ-ray source 1 and the detector 2 can be arranged on the same side with respect to the pipe that is the inspection object 3, the degree of freedom in equipment arrangement is improved. Further, the inspection object 3 does not need to be a pipe, and does not necessarily need to detect thinning. It is useful as a nondestructive inspection apparatus that widely detects the dimensions of each part of an inspection object.

  INDUSTRIAL APPLICABILITY The present invention can be effectively used in an industrial field where non-destructive inspection is performed for maintenance, inspection, etc. of a power plant where inspection objects such as piping are arranged in a complicated manner.

DESCRIPTION OF SYMBOLS 1 γ-ray source 2 Detector 2A Incident part 2B Signal processing part 2C Information processing part 2D Storage part 2E Display part 3 Inspection object

Claims (10)

X-rays or γ-rays having at least two different peak energies (hereinafter collectively referred to as γ-rays) are irradiated onto the inspection object, and at least three different peak energies are based on Compton scattering generated as a result of the irradiation. And generating a scattered γ-ray energy distribution characteristic representing a signal intensity of the scattered γ-ray signal representing the detected scattered γ-ray with respect to the scattered γ-ray energy.
Using the scattered γ-ray energy distribution characteristic, the pattern formed by the at least three peaks due to the thickness of the inspection object is specified, and the state of the inspection object is detected. Non-destructive inspection method. In the nondestructive inspection method according to claim 1,
The non-destructive inspection method, wherein the Compton scattering is Compton backscattering. In the nondestructive inspection method according to claim 1 or 2,
The non-destructive inspection method, wherein the scattered γ-rays having at least three different peak energies include at least one twice-scattered γ-ray. In the nondestructive inspection method according to any one of claims 1 to 3,
Furthermore, a non-destructive inspection method characterized by detecting a state of the inspection object in consideration of a ratio of signal intensities of two different scattered γ-ray signals. A γ-ray source that irradiates the object to be inspected with X-rays or γ-rays having at least two different peak energies (hereinafter collectively referred to as γ-rays)
Based on Compton scattering generated as a result of the irradiation, scattered γ-rays having at least three different peak energies are detected, and a signal intensity of the scattered γ-ray signal representing the detected scattered γ-rays with respect to the scattered γ-ray energy is represented. While obtaining scattered γ-ray energy distribution characteristics, a pattern formed by the at least three peaks due to the thickness of the inspection object is identified based on the scattered γ-ray energy distribution characteristics, and the inspection object A non-destructive inspection apparatus comprising a detector for detecting a state. In the nondestructive inspection device according to claim 5,
The Compton scattering is Compton backscattering, and the detector is disposed on the same side with respect to the inspection object. In the nondestructive inspection device according to claim 5 or 6,
The non-destructive inspection apparatus characterized in that the scattered γ-rays having at least three different peak energies include at least one twice-scattered γ-ray. In the nondestructive inspection device according to any one of claims 5 to 7,
The non-destructive inspection apparatus, wherein the γ-ray source is formed of two or more isotope nuclides having at least two different peak energies each having different radiation energy. In the nondestructive inspection device according to any one of claims 5 to 7,
The non-destructive inspection apparatus, wherein the γ-ray source is a laser Compton scattered radiation source that irradiates γ-rays having at least two different peak energies generated by collisions between electrons and laser light. In the nondestructive inspection apparatus according to any one of claims 5 to 9,
The detector further detects a state of the inspection object in consideration of a ratio of signal intensities of two different scattered γ-ray signals.