JP2017101967A - Nondestructive inspection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nondestructive inspection method and its device capable of detecting an inspection object extensively and further capable of performing inspection without causing a problem of restriction in an installation position of a detector when Compton scattering γ ray is used.SOLUTION: A nondestructive inspection method includes a first process in which an X ray or a γ ray (hereinafter, referred to as a γ ray as a whole) is radiated on an inspection object 31 and scattered γ ray energy distribution characteristics is detected representing a signal strength for energy of a twice scattering γ ray that appears at a higher energy side than a once scattering γ ray based on Compton scattering in the inspection object, and a second process in which whether thinning exists or not in the inspection object is detected based on the scattered γ ray energy distribution characteristics.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a nondestructive inspection method and apparatus, 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. In Compton backscattering, as shown in FIG. 10 (a), when the target T is irradiated with predetermined γ-rays, the energy has changed along with recoil electrons E _e that jump in the direction of the angle Φ with respect to the γ-rays. 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 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.

Accordingly, as shown in FIG. 10B, 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. 10C, 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 in which the signal intensity reaches a peak at the γ-ray energy E ₁ is obtained. In FIG. 10C, 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. 11 (a), the energy E ₁ of the signal of the backscattered γ rays if that maintain normal state without occurring a reduction in thickness on the inner circumference pipe 03 which is an inspection object As shown in FIG. 11B, the strength is greater than when 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 irradiated from the radioisotope iridium source as the γ-ray source 01 is 320 keV, the energy E ₁ of the scattered γ-rays when the scattering angle θ = 90 ° is 197 keV, which is unique. It is decided. Accordingly, the signal intensity of the 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, occurrence of thinning can be detected by detecting the signal intensity of the scattered γ-ray energy E _{1 in} the scattered γ-ray energy distribution shown in FIG. 10C (see, for example, Non-Patent Document 1).

JP 2006-177841 A

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

However, as described above, when thinning is detected based on the signal intensity of the scattered γ-ray energy E _{1 in} the scattered γ-ray energy distribution characteristics shown in FIG. Therefore, there is a problem that a thinning detection error is likely to occur, and in order to detect the thinning range, scanning is necessary, and information in the depth direction is difficult to detect.

  In view of the above-described conventional technology, the present invention can detect the state of an inspection object widely when using Compton scattered γ-rays, and can detect without causing the problem of restriction of the arrangement position of the detector. An object is to provide a nondestructive inspection method and an apparatus therefor.

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 scattering energy E ₁ when the γ-ray of 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 characteristics shown in FIG. In addition, 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 pipe 3 that is the inspection object, 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 above equation (3), and E ₂₂ = 234 keV from the above 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 present invention, in the Compton backscattering, by observing the energy E ₂₂ due to the two scattering, it is intended to detect the thickness decrease of the object.
FIG. 2 shows a further schematic diagram of FIG.
In FIG. 2, (a) shows one-time scattering, whereas FIG. 2 (b) shows two-time scattering used in the present invention. That is, in one scattering in FIG. 2 (a), the incident gamma rays gamma ₀ having an energy E ₀ is scattered by the object 3A, once scattered gamma rays gamma ₁ energy E ₁ is detected. In FIG. 2 (b), the incident gamma rays gamma ₀ of energy _{E 0,} a single scattering occurs in the object 3A, once scattered gamma rays gamma ₂₁ next energy _{E 21,} then the second time by the object 3B scattering occurs twice scattered gamma rays gamma ₂₂ energy E ₂₂ that is detected.

In FIG. 3A, in the case of two-time scattering, only the two-time scattered γ-ray γ _{22 having the} energy E ₂₂ is detected. On the other hand, in FIG. 3B, in addition to the twice-scattered γ-ray γ _{22 having} the energy E ₂₂ , the one-time scattered γ-ray γ having the energy E ₁ that has passed through the object 3A and was scattered only once by the object 3C. _{1 is} also detected.

In the present invention, in the case of FIG. 3 (a), are also contemplated case of FIG. 3 (b), in the case of FIG. 3 _(b), and 2 times the scattered gamma rays gamma ₂₂ of _{E 22,} the energy E _Since the one-time scattered γ-ray γ ₁ is different in energy magnitude and detected time, it is easy to distinguish the two. Then, the once-scattered γ-ray γ _{1 with} the energy E ₁ can be used for detecting whether or not the object 3C is thinned, or can be excluded as unnecessary.

The principle of detecting the thinning due to such double scattering is considered as follows.
In the case of the two-time scattering shown in FIG. 4A, the γ-ray source 1 emits a pencil beam with a point source, and the detector 2 serving as the observation point of the scattered γ-ray is also an ideal lead collimator. Assuming that only one point is installed, the signal intensity of the double scattered peak in the detector 2 is the intersection point I ₂ between the γ-ray irradiation axis and the inspection object, and the intersection point I ₃ between the scattered γ-ray detection axis and the inspection object. In addition, the scattering information in the region R ₁ where the surface P ₁ including the intersection point I ₁ between the γ-ray irradiation axis and the scattered γ-ray detection axis and the inspection object 31 intersect is obtained. Therefore, two scattering peaks, once scattered gamma rays gamma ₂₁ passes through the region R ₁ in the ferrous material sample, is detected as 2 scattered gamma rays gamma _22. On the other hand, in the case of the two-time scattering shown in FIG. 4B, a part of the once-scattered γ-ray γ ₂₁ is detected as the two-scattered γ-ray γ ₂₂ by thinning and partly in the air Is done. Here, since the attenuation ratio of the once scattered γ-ray ₂₁ is larger in the iron than in the air, unlike the conventional case of detecting the thinning using the single scattering, when there is a thinning, as compared with a case healthy, signal strength of the two scattered gamma rays gamma ₂₂ is increased, the rate of increase depends on the size of the thinning.

As described above, in the present invention, the path from the occurrence of the first Compton scattering to the second Compton scattering after the γ-rays are incident on the object to be inspected is the target location for detecting the presence or absence of thinning. are those, either once scattered gamma rays gamma ₂₁ passes the constituents themselves of the test object, depending on whether the difference between passing through the space formed by the thinning, and detects the presence or absence of wall thinning.

  The first aspect of the present invention based on this knowledge is a one-time operation based on Compton scattering in the inspection object by irradiating the inspection object with X-rays or γ-rays (hereinafter collectively referred to as γ-rays). A first step of detecting a scattered γ-ray energy distribution characteristic representing a signal intensity with respect to the energy of the twice scattered γ-rays appearing on a higher energy side than the scattered γ-ray energy; And a second step of detecting the presence or absence of thinning in the inspection object.

  According to this aspect, the presence or absence of thinning in the detection target is detected based on the two-time scattering peak of Compton scattering depending on the state of the inspection target, such as pipe thinning. Destructive inspection can be simplified.

  According to a second aspect of the present invention, in the nondestructive inspection method described in the first aspect, the side that irradiates the inspection object with the γ-ray and the side that detects the twice-scattered γ-ray include The non-destructive inspection method is characterized by being on the same side.

  According to this aspect, the scattered γ-rays scattered due to Compton backscattering are detected to detect the state of thinning of the inspection object, so that the detection of the scattered γ-rays for the inspection object is detected. Can be performed on the same side as the γ-ray irradiation side. As a result, efficient non-destructive inspection can be realized with a large degree of freedom in arrangement of devices such as detectors.

  According to a third aspect of the present invention, in the non-destructive inspection method described in the second aspect, the second Compton scattering occurs after the first Compton scattering occurs when the γ-ray enters the inspection object. The non-destructive inspection method is characterized in that the path to the target location is a target location for detecting the presence or absence of the thinning.

  According to this aspect, since the signal intensity of the two-time Compton scattering greatly changes depending on whether or not there is thinning in the path, it is possible to effectively detect the presence or absence of thinning.

  According to a fourth aspect of the present invention, in the nondestructive inspection method according to the second or third aspect, a virtual first straight line extending in a direction of irradiating the γ-ray and a direction in which the twice-scattered γ-ray is detected. The virtual second straight line extending in the direction intersects with the irradiation side of the γ-ray and the detection side of the twice-scattered γ-ray of the inspection object, and in this state, from the inspection object In the nondestructive inspection method, the presence or absence of thinning of the inspection object is detected based on a peak of twice scattered γ rays based on the scattered γ rays.

  According to this aspect, a space can be secured in front of the inspection object, and the γ-ray irradiation source and the detector can be arranged relatively easily.

  According to a fifth aspect of the present invention, in the nondestructive inspection method according to the second or third aspect, a virtual first straight line extending in a direction of irradiating the γ-ray and a direction in which the twice-scattered γ-ray is detected. The virtual second straight line extending in the direction intersects with the irradiation side of the γ-ray and the detection side of the twice-scattered γ-ray of the inspection object, and in this state, from the inspection object In the nondestructive inspection method, the presence or absence of thinning of the inspection object is detected based on a peak of twice scattered γ rays based on scattered γ rays.

  According to this aspect, the γ-ray irradiation source and the detector can be arranged relatively compactly on the front side of the inspection object.

  According to a sixth aspect of the present invention, in the nondestructive inspection method according to any one of the first to fifth aspects, Compton scattering at a site different from a site where the presence or absence of the thinning of the inspection object is detected. The non-destructive inspection method is characterized by detecting a scattered γ-ray energy distribution characteristic representing a signal intensity with respect to energy of a once-scattered γ-ray based on the above, and detecting the presence or absence of thinning of the different parts.

  According to this aspect, by detecting the energy of the once-scattered γ-rays, it is possible to detect the thinning of the region different from the location based on the detection of the energy of the twice-scattered γ-rays by one detection.

  According to a seventh aspect of the present invention, in the nondestructive inspection method according to the sixth aspect, the first wall in which the inspection object intersects a straight line extending in the γ-ray irradiation direction on the γ-ray irradiation side. A member and a second wall member that intersects the straight line on a side opposite to the γ-ray irradiation side of the first wall member, the first wall member and the second wall member The presence or absence of thinning is detected by a scattered γ-ray energy distribution characteristic representing the signal intensity with respect to the energy of the twice-scattered γ-rays, and the presence or absence of thinning is detected by one-time scattered γ-rays based on the Compton scattering. The non-destructive inspection method is characterized in that the detection is performed with a scattered γ-ray energy distribution characteristic representing the signal intensity with respect to the energy of the light.

  In this aspect, it is possible to detect the thinned state of the first wall member and the thinned state of the second wall member.

  According to an eighth aspect of the present invention, in the nondestructive inspection method according to the seventh aspect, when detecting the scattered γ-ray signal, the time of the scattered γ-ray signal is based on the time when the γ-ray is irradiated. In consideration of a component along the axis, when detecting the presence or absence of thinning of the second wall member, a portion based on scattered γ rays from the first wall member is removed, and the second wall When detecting the presence or absence of thinning of the first wall member by removing a part of the component along the time axis of the scattered γ-ray signal so that the portion based on the scattered γ-ray from the member is selected A portion based on the scattered γ-rays from the second wall member is removed, and a portion based on the scattered γ-rays from the first wall member is selected along the time axis of the scattered γ-ray signal. A nondestructive inspection method is characterized in that a part of the components is removed and the presence or absence of thinning is detected.

  In such an aspect, the energy of the once-scattered γ-ray and the energy of the twice-scattered γ-ray can be easily distinguished, and the thinned state of the first wall member and the thinned state of the second wall member Can be detected relatively easily.

  According to a ninth aspect of the present invention, there is provided a γ-ray source that irradiates γ-rays toward an inspection object, a detector that detects scattered γ-rays scattered due to Compton scattering in the inspection object by the irradiation, In the non-destructive inspection apparatus, the signal intensity of the scattered γ-ray signal with respect to the scattered γ-ray energy is expressed, and the energy of the twice-scattered γ-ray that appears on the higher energy side than the energy beam of the once-scattered γ-ray Based on the scattered γ-ray energy distribution characteristics, the detector is configured to detect the presence or absence of thinning in the inspection object based on the peak of the twice-scattered γ-ray that is the peak of the signal intensity of the twice-scattered γ-ray. It is in the nondestructive inspection device characterized by the above.

  According to this aspect, the presence or absence of thinning in the detection target is detected based on the two-time scattering peak of Compton scattering depending on the state of the inspection target, such as pipe thinning. Destructive inspection can be simplified.

  According to a tenth aspect of the present invention, in the nondestructive inspection apparatus described in the ninth aspect, the γ-ray source and the detector are disposed on the same side with respect to the inspection object. The characteristic non-destructive inspection device.

  According to this aspect, the scattered γ-rays scattered due to Compton backscattering are detected to detect the state of thinning of the inspection object, so that the detection of the scattered γ-rays for the inspection object is detected. Can be performed on the same side as the γ-ray irradiation side. As a result, efficient non-destructive inspection can be realized with a large degree of freedom in arrangement of devices such as detectors.

  According to an eleventh aspect of the present invention, in the nondestructive inspection apparatus according to the tenth aspect, the second Compton scattering occurs after the first γ-ray is incident on the inspection object and the first Compton scattering occurs. The non-destructive inspection apparatus is characterized in that the path up to is a target location for detecting the presence or absence of the thinning.

  According to this aspect, since the signal intensity of the two-time Compton scattering greatly changes depending on whether or not there is thinning in the path, it is possible to effectively detect the presence or absence of thinning.

  According to a twelfth aspect of the present invention, in the nondestructive inspection apparatus according to the tenth or eleventh aspect, a virtual first straight line extending in a direction of irradiating the γ-ray from the γ-ray source, and the detector The virtual second straight line extending in the direction of detecting twice-scattered γ-rays intersects the side of the inspection object opposite to the irradiation side of the γ-rays and the detection side of the twice-scattered γ-rays. In the state, the non-destructive inspection apparatus detects presence or absence of thinning of the inspection object based on a peak of twice-scattered γ-ray based on the scattered γ-ray from the inspection object.

  According to this aspect, a space can be secured in front of the inspection object, and the γ-ray irradiation source and the detector can be arranged relatively easily.

  According to a thirteenth aspect of the present invention, in the nondestructive inspection apparatus according to the tenth or eleventh aspect, the virtual first straight line extending in the direction of irradiating the γ-ray from the γ-ray source, and the detector The virtual second straight line extending in the direction of detecting twice-scattered γ-rays intersects with the irradiation side of the γ-ray of the inspection object and the same side as the detection side of the twice-scattered γ-rays. In the state, the non-destructive inspection apparatus detects presence or absence of thinning of the inspection object based on a peak of twice-scattered γ-ray based on the scattered γ-ray from the inspection object.

  According to this aspect, the γ-ray irradiation source and the detector can be arranged relatively compactly on the front side of the inspection object.

  In a fourteenth aspect of the present invention, in the nondestructive inspection apparatus according to any one of the ninth to thirteenth aspects, Compton scattering at a site different from a site where the presence or absence of the thinning of the inspection object is detected. Non-destructive, characterized in that the detector is configured to detect a scattered γ-ray energy distribution characteristic representing the signal intensity with respect to the energy of the once-scattered γ-ray based on and to detect the presence or absence of thinning of the different parts In the inspection device.

  According to this aspect, by detecting the energy of the once-scattered γ-rays, it is possible to detect the thinning of the region different from the location based on the detection of the energy of the twice-scattered γ-rays by one detection.

  A fifteenth aspect of the present invention is the nondestructive inspection apparatus according to the fourteenth aspect, wherein the inspection object intersects a straight line extending in the γ-ray irradiation direction on the γ-ray irradiation side. In the case of having a second wall member that intersects the straight line on the side opposite to the γ-ray irradiation side of the member and the first wall member, whichever of the first wall member and the second wall member The presence or absence of one thinning is detected by the scattered γ-ray energy distribution characteristic indicating the signal intensity with respect to the energy of the two-time scattered γ-rays, and the presence or absence of the other thinning is detected by the energy of one-time scattered γ-rays based on the Compton scattering. The non-destructive inspection apparatus is characterized in that the detector is configured to detect with a scattered γ-ray energy distribution characteristic representing a signal intensity with respect to.

  In this aspect, it is possible to detect the thinned state of the first wall member and the thinned state of the second wall member.

  According to a sixteenth aspect of the present invention, in the nondestructive inspection apparatus according to the fifteenth aspect, when the scattered γ-ray signal is detected, the time of the scattered γ-ray signal is based on the time point when the γ-ray is irradiated. In consideration of a component along the axis, when detecting the presence or absence of thinning of the second wall member, a portion based on scattered γ rays from the first wall member is removed, and the second wall When detecting the presence or absence of thinning of the first wall member by removing a part of the component along the time axis of the scattered γ-ray signal so that the portion based on the scattered γ-ray from the member is selected A portion based on the scattered γ-rays from the second wall member is removed, and a portion based on the scattered γ-rays from the first wall member is selected along the time axis of the scattered γ-ray signal. The detector is configured to remove some of the components and detect the presence or absence of thinning. In the non-destructive inspection apparatus that.

  In such an aspect, the energy of the once-scattered γ-ray and the energy of the twice-scattered γ-ray can be easily distinguished, and the thinned state of the first wall member and the thinned state of the second wall member Can be detected relatively easily.

  According to the present invention, since the presence or absence of thinning in the detection target is detected based on the two-time scattering peak of Compton scattering depending on the state of the inspection target, such as pipe thinning, Destructive inspection can be simplified. In addition, the scattered γ-ray energy distribution characteristics of the scattered γ-rays, which can observe the double scattering peak due to the backscattered γ-rays that collide with the inspection object and scatter, detect the state of the inspection object such as thinning of the inspection object. As a result, the γ-ray source and the detector can be arranged on the same side with respect to the inspection object, and the arrangement conditions of the γ-ray source and the detector can be eased. The desired nondestructive inspection can be easily performed.

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. It is a figure which shows the principle of this invention typically, and (a) is a case of 1 time scattering, (b) is a case of 2 time scattering. In the figure which shows the principle of this invention typically, (a) is a case where there is no target object in an intersection, and (b) is a case. In the case of twice scattering in Compton backscattering, it is explanatory drawing which shows the path | route of the gamma ray irradiated to the iron sample, (a) when a sample is healthy, (b) when there is thinning in a sample It is. 1 is a block diagram showing a nondestructive inspection apparatus according to a first embodiment of the present invention. It is a figure explaining the variation of the nondestructive inspection apparatus of this invention. It is a block diagram which shows 2nd Embodiment nondestructive inspection apparatus. It is a figure explaining the nondestructive inspection apparatus which concerns on the 2nd Embodiment of this invention. It is a graph which shows the result of an Example. 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. In each figure, the same number is attached to the same part, and duplicate explanation is omitted.

<First Embodiment>
FIG. 5 is a block diagram showing the nondestructive inspection apparatus according to the first embodiment of the present invention. As shown in the figure, the nondestructive inspection apparatus according to the present embodiment includes a γ-ray source 1 that irradiates an inspection target 31 that is an inspection target in the present embodiment with γ rays, and a γ that is irradiated to the inspection target 31. And a detector 2 that performs a predetermined process by entering twice Compton backscattered γ-rays generated based on the line. The γ-ray source 1 and the detector 2 that receives the Compton backscattered γ-ray twice are disposed on the same side (left side in the figure) with respect to the inspection object 31.

  Here, although not shown, the γ-ray source 1 irradiates the inspection object 31 in a state where the directivity is improved by setting a lead collimator or the like and the traveling axis of the irradiation γ-ray is determined. Is done. By the irradiation of γ-rays, scattered γ-rays due to Compton backscattering are generated at the inspection object 31. The detector 2 is disposed on the same side as the γ-ray source 1 with respect to the inspection object 31 so as to detect scattered γ-rays.

By installing a lead collimator or the like in the detector 2 as well, the axis of scattered γ-rays to be detected is determined. In this embodiment, as shown in FIG. 5, the traveling axis of the irradiation γ rays and the detection axis of the scattered γ rays are at an intersection I ₁ on the opposite side of the γ-ray source 1 and the detector 2 with respect to the inspection object 31. Crossed.

  In this embodiment, the incident angle α1 at which the straight line from the γ-ray source 1 toward the inspection object 31 is incident on the surface of the inspection object 31 and the scattering angle α2 of the Compton backscattered γ-ray are the same. The relative position of the detector 2 with respect to the γ-ray source 1 is selected. Here, a lead block 11 is disposed on a line that serves as a reference between the incident angle α1 and the scattering angle α2. The lead block 11 is for separating the γ-ray source 1 side and the detector 2 side. By separating in this way, the γ-ray reflected from the surface of the inspection object 31 on the γ-ray source 1 side is shielded and prevented from entering the detector 2. In addition, it is not essential to arrange the lead block 11 in this way. Further, it is not essential that the γ-ray source 1 and the detector 2 have the above positional relationship (α1 = α2). Further, ideally, the γ-ray source 1 emits extremely thin γ-rays called a pencil beam, and the detector 2 has an incident surface as close to a point as possible.

  As the γ-ray source 1 in this embodiment, for example, a radioisotope iridium radiation source can be suitably applied. 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 that represents Compton backscattered γrays, and a Compton backscattered γray signal that is processed by inspection. The calculation processing unit 2C that detects the thinning state of the object 31, the storage unit 2D that stores the reference data of the inspection object 31 for detecting the thinning state, and the detection result detected by the calculation processing unit 2C. It has a display section 2E for displaying. More specifically, the signal processing unit 2B processes the Compton backscattered γ-ray to generate a scattered γ-ray energy distribution characteristic representing the signal intensity of the Compton backscattered γ-ray signal with respect to the scattered γ-ray energy. The storage unit 2D stores in advance a scattered γ-ray energy distribution characteristic (hereinafter referred to as a reference scattered γ-ray energy distribution characteristic) of a healthy inspection object 31 (which does not cause thinning).

In the arithmetic processing unit 2C, the scattered γ-ray energy distribution characteristic obtained by the signal processing unit 2B based on the actual measurement data of the γ rays incident in real time via the incident unit 2A and the reference scattering γ stored in the storage unit 2D By comparing with the line energy distribution characteristics, the presence or absence of thinning in the inspection object 31 and the degree (thickening amount) depending on the case are detected. Here, if occurred the reduced thickness portion on the inspection object 31 (see FIG. 4 (b)), as compared with the case healthy, signal strength of the two scattered gamma rays gamma ₂₂ is increased, the increase The proportion depends on the size of the thinning. Therefore, by comparing the reference scattered γ-ray energy distribution characteristics and the scattered γ-ray energy distribution characteristics obtained from the actual measurement data, the presence or absence of thinning in the inspection object 31 and the extent (thickness reduction) in some cases are detected. can do.

  Information such as the presence or absence of thinning as a result of predetermined data processing in the arithmetic processing unit 2C and the degree thereof are displayed on the display unit 2E.

  In the above-described embodiment, as shown in FIG. 6A, the γ-ray source 1 and the detector are arranged such that the intersection of the γ-ray irradiation direction and the γ-ray detection direction is located behind the detection target. However, as shown in FIG. 6B, the γ-ray source 1 and the detector are arranged so that the intersection of the γ-ray irradiation direction and the γ-ray detection direction is located in front of the detection target. 2 can be arranged. According to this, there exists an advantage that the whole apparatus can be arrange | positioned compactly.

<Second Embodiment>
A pipe 32 (see FIG. 7), which is an example of the inspection object 31, has two thick portions (wall portions) on one straight line that crosses the pipe 32 (see FIG. 7). That is, a thick portion on the same straight line on the γ-ray source 1 side (hereinafter referred to as “front side”) and a thick portion on the opposite side (hereinafter referred to as “back side”). is there. In the first embodiment, the presence or absence of thinning in the thick part on the near side of the pipe 32 that is the inspection object is detected. On the other hand, the thinning may occur also in the thick part on the back side of the pipe 32. In this embodiment, the thinning of the wall on the near side is measured by the γ-ray energy distribution characteristic of the twice-scattered γ-ray, and the thinning of the wall on the back side is measured by the γ-ray energy distribution characteristic of the once-scattered γ-ray. An example of measurement will be described.
Note that the intersection point I ₁ between the γ-ray irradiation direction and the γ-ray detection direction is located on the front surface of the thick portion on the back side of the region II.

  FIG. 7 is a block diagram showing a nondestructive inspection apparatus according to the second embodiment of the present invention. As shown in the figure, in the detector 12 of the nondestructive inspection apparatus according to this embodiment, an area selection unit 2F is interposed between the signal processing unit 2B and the arithmetic processing unit 2C. The region selection unit 2F selects only information on the region I or region II from the Compton backscattered γ-ray signal, which is theoretical data representing the Compton backscattered γ-ray incident through the signal processing unit 2B and the incident unit 2A. To do. That is, as shown in FIG. 8 (a), the Compton backscattered γ-ray signal Sγ whose position on the time axis is specified due to the difference in the optical path length from the γ-ray source 1 to the detector 2 is represented by the region I. Are detected separately from those based on twice-scattered γ-rays corresponding to and those based on once-scattered γ-rays corresponding to region II.

  According to the present embodiment, as shown in FIG. 8B, the signal component based on the Compton backscattered γ-rays that are scattered twice from the γ-ray source 1 in the region I of the pipe 32 and incident on the detector 2 is The signal components separated by the region selection unit 2F and once scattered in the region II and incident on the detector 2 are separated, and each is separated and supplied to the arithmetic processing unit 2C.

  Thus, according to the present embodiment, the time until the γ-rays irradiated from the γ-ray source 1 pass through only the thick portion on the near side of the pipe 32 and enter the detector 2, and the pipe 32. When the time until it enters the detector 2 is compared with the thick part on the back side, the two are separated by using the fact that the former time is shorter. That is, as shown in FIG. 8A, this is a region corresponding to the thick portion on the near side in the time characteristics of the signal intensity of the backscattered γ-ray signal obtained by the signal processing unit 2B based on theoretical data. It is possible to separate the energy distribution of the scattered γ rays caused by the region I and the region II that is a region corresponding to the thick portion on the back side. As a result, the back thinning portion can be detected by the change in the scattered γ-ray energy distribution characteristics of the backscattered γ-ray signal based on the one-time scattering in the region II. The thinned portion on the near side can be detected. That is, the presence or absence of thinning of the region II can be detected by reducing the backscattered γ-ray signal based on single scattering from the region II due to the occurrence of thinning. Further, the observation of the thinning of the region I is the same as that in the first embodiment.

<Other embodiments>
In the second embodiment described above, the observation of the thinning of the region II is obtained by changing the energy distribution of the Compton scattered γ ray once. However, the thinning of the region II is also observed using the double scattering peak. It can also be done. That is, the intersection of the irradiation direction of γ-rays and the detection direction of γ-rays is located on the back side of the thick part on the back side of region II or further through the thick part, In the thick part, if the path from the first Compton scattering to the second Compton scattering is made to pass through the thick part on the inner side, the second Compton scattering will occur after the first Compton scattering. by whether path thinning during up causing Compton scattering is present, or once scattered gamma rays gamma ₂₁ passes the constituents themselves of the test object, passes through a space formed by thinning This difference occurs, and the presence or absence of thinning can be detected as in the region I. Even in this case, the peak of region I and the peak of region II can be separated in consideration of time characteristics.

  FIG. 9 shows a simulation result obtained by measuring the energy distribution of the Compton scattered γ-ray twice for the sample in which the thinning is formed in a simulated manner in the configuration of the first embodiment. Here, an iron sample having a thickness of 10 mm is used as an inspection object, and the intersection of the γ-ray irradiation direction and the γ-ray detection direction is located 10 mm ahead of the sample, and the γ-ray irradiation direction and γ The angle formed with the line detection direction was 120 ° (incident angle 60 °).

  FIG. 9A shows a sample in which no thinning occurs, and FIG. 9B shows a case in which a thinning of 20 mm in length occurs at a depth of 5 mm on the back side, FIG. The case where a thickness reduction of 35 mm in length occurs at a depth of 5 mm on the back side is shown.

  As described above, it was found that the energy distribution of the Compton scattered γ-ray twice changed according to the size of the thinning, and the size of the thinning can be detected by quantifying this.

  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.

I, II area 1 γ-ray source 2 Detector 3, 31, 32 Piping (inspection object)

Claims (16)

X-rays or γ-rays (hereinafter collectively referred to as γ-rays) are irradiated twice on the inspection object and appear twice on the higher energy side than the energy of the once-scattered γ-rays based on Compton scattering in the inspection object. A first step of detecting a scattered gamma ray energy distribution characteristic representing a signal intensity with respect to the energy of the scattered gamma ray;
And a second step of detecting the presence or absence of thinning in the inspection object based on the scattered γ-ray energy distribution characteristics. In the nondestructive inspection method according to claim 1,
The non-destructive inspection method according to claim 1, wherein the side to be irradiated with the γ-ray and the side to detect the twice-scattered γ-ray are the same side. In the nondestructive inspection method according to claim 2,
The path from the occurrence of the first Compton scattering after the γ-ray is incident on the inspection object until the second Compton scattering is a target location for detecting the presence or absence of the thinning. Destructive inspection method. In the nondestructive inspection method according to claim 2 or 3,
The virtual first straight line extending in the direction of irradiating the γ-ray and the virtual second straight line extending in the direction of detecting the twice-scattered γ-ray are the irradiation side of the γ-ray of the inspection object and the 2 Crossing on the side opposite to the detection side of the double-scattered γ-ray, and in this state, based on the peak of the double-scattered γ-ray based on the scattered γ-ray from the inspection object, the thinning of the inspection object A nondestructive inspection method characterized by detecting presence or absence. In the nondestructive inspection method according to claim 2 or 3,
The virtual first straight line extending in the direction of irradiating the γ-ray and the virtual second straight line extending in the direction of detecting the twice-scattered γ-ray are the irradiation side of the γ-ray of the inspection object and the 2 Crossing on the same side as the detection side of the double scattered γ-ray, and in this state, whether or not the inspection object is thinned based on the peak of the double scattered γ-ray based on the scattered γ-ray from the inspection object Non-destructive inspection method characterized by detecting In the nondestructive inspection method according to any one of claims 1 to 5,
Detecting a scattered γ-ray energy distribution characteristic representing a signal intensity with respect to energy of a once-scattered γ-ray based on Compton scattering in a portion different from a portion where the presence or absence of the thinning of the inspection object is detected, and the different portion A non-destructive inspection method characterized by detecting the presence or absence of thinning of the metal. In the nondestructive inspection method according to claim 6,
The first wall member that intersects the γ-ray irradiation side with the straight line extending in the γ-ray irradiation direction of the inspection object, and the straight line on the opposite side of the first wall member from the γ-ray irradiation side. Having a second wall member intersecting with
The presence or absence of thinning of one of the first wall member and the second wall member is detected by a scattered γ-ray energy distribution characteristic representing the signal intensity with respect to the energy of the twice-scattered γ-ray, and the other thinning is performed. The non-destructive inspection method is characterized by detecting the presence or absence of a scattering γ-ray energy distribution characteristic representing the signal intensity with respect to the energy of the once-scattered γ-ray based on the Compton scattering. In the nondestructive inspection method according to claim 7,
When detecting the scattered γ-ray signal, a component along the time axis of the scattered γ-ray signal is taken into consideration with reference to the time point when the γ-ray is irradiated, and the presence or absence of thinning of the second wall member is detected. In this case, the time of the scattered γ-ray signal is such that the portion based on the scattered γ-rays from the first wall member is removed and the portion based on the scattered γ-rays from the second wall member is selected. When a part of the component along the axis is removed and the presence or absence of thinning of the first wall member is detected, a portion based on scattered γ rays from the second wall member is removed, and the first Non-destructive, characterized in that a part of the scattered γ-ray signal along the time axis is removed so that a portion based on scattered γ-rays from one wall member is selected and the presence or absence of thinning is detected Inspection method. In a nondestructive inspection apparatus having a γ-ray source that irradiates γ-rays toward an inspection object, and a detector that detects scattered γ-rays scattered due to Compton scattering in the inspection object by the irradiation,
Based on the scattered γ-ray energy distribution characteristic of the scattered γ-ray energy that represents the signal intensity of the scattered γ-ray signal relative to the scattered γ-ray energy and that appears on the higher energy side of the once scattered γ-ray energy line The non-destructive detector is characterized in that the detector is configured to detect the presence or absence of thinning in the inspection object based on a peak of the twice-scattered γ-ray that is a peak of the signal intensity of the twice-scattered γ-ray. Inspection device. In the nondestructive inspection device according to claim 9,
The non-destructive inspection apparatus, wherein the γ-ray source and the detector are arranged on the same side with respect to the inspection object. In the nondestructive inspection device according to claim 10,
The path from the occurrence of the first Compton scattering to the occurrence of the second Compton scattering after the γ-ray is incident on the inspection object is set as a target location for detecting the presence or absence of the thinning. Destructive inspection equipment. In the nondestructive inspection device according to claim 10 or 11,
A virtual first straight line extending in a direction of irradiating the γ-ray from the γ-ray source;
The virtual second straight line extending in the direction of detecting the twice-scattered γ-rays to the detector is the opposite side of the inspection object from the irradiation side of the γ-rays and the detection side of the twice-scattered γ-rays. Non-destructive inspection characterized in that, in this state, the presence or absence of thinning of the inspection object is detected based on the peak of the twice scattered γ-ray based on the scattered γ-ray from the inspection object. apparatus. In the nondestructive inspection device according to claim 10 or 11,
A virtual first straight line extending in a direction of irradiating the γ-ray from the γ-ray source;
An imaginary second straight line extending in the direction of detecting the twice-scattered γ-rays to the detector intersects on the same side as the irradiation side of the γ-rays and the detection side of the twice-scattered γ-rays of the inspection object. In this state, the non-destructive inspection apparatus detects the presence or absence of thinning of the inspection object based on the peak of the twice-scattered γ-ray based on the scattered γ-ray from the inspection object. . In the nondestructive inspection device according to any one of claims 9 to 13,
Detecting a scattered γ-ray energy distribution characteristic representing a signal intensity with respect to energy of a once-scattered γ-ray based on Compton scattering in a portion different from a portion where the presence or absence of the thinning of the inspection object is detected, and the different portion A non-destructive inspection apparatus characterized in that the detector is configured to detect the presence or absence of thinning. The nondestructive inspection apparatus according to claim 14,
The first wall member that intersects the γ-ray irradiation side with the straight line extending in the γ-ray irradiation direction of the inspection object, and the straight line on the opposite side of the first wall member from the γ-ray irradiation side. In having a second wall member intersecting
The presence or absence of thinning of one of the first wall member and the second wall member is detected by a scattered γ-ray energy distribution characteristic representing the signal intensity with respect to the energy of the twice-scattered γ-ray, and the other thinning is performed. The non-destructive inspection apparatus is characterized in that the detector is configured to detect the presence or absence of light by a scattered γ-ray energy distribution characteristic representing a signal intensity with respect to the energy of the once scattered γ-ray based on the Compton scattering. In the nondestructive inspection device according to claim 15,
When detecting the scattered γ-ray signal, a component along the time axis of the scattered γ-ray signal is taken into consideration with reference to the time point when the γ-ray is irradiated, and the presence or absence of thinning of the second wall member is detected. In this case, the time of the scattered γ-ray signal is such that the portion based on the scattered γ-rays from the first wall member is removed and the portion based on the scattered γ-rays from the second wall member is selected. When a part of the component along the axis is removed and the presence or absence of thinning of the first wall member is detected, a portion based on scattered γ rays from the second wall member is removed, and the first The detector is configured to detect the presence or absence of thinning by removing a part of the component along the time axis of the scattered γ-ray signal so that a portion based on the scattered γ-ray from one wall member is selected. Non-destructive inspection equipment characterized by