JP3477363B2 - Thickness measuring device by Compton scattering - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate thickness measuring device by Compton scattering, which is devised so as to improve the measurement accuracy. Note that Compton scattering occurs when radiation (X-rays or γ-rays) collides with atoms and bounces back without being absorbed by electrons when passing through an object.

[0002]

2. Description of the Related Art In a flue made of a steel plate or the like, if the wall thickness is reduced due to corrosion due to exhaust gas, a strength problem occurs. Therefore, it is necessary to inspect the plate thickness from the outside through an obstacle such as a heat insulating material without entering the flue to identify and repair the problem area. Such a situation, that is, the fact that it is necessary to inspect the plate thickness from the outside to identify and repair the problematic part is the same for the structures such as the combustion furnace, which are difficult to enter, in addition to the flue.

As a conventional metal plate thickness measuring method, there is a measuring method utilizing ultrasonic waves and eddy currents. In such a measuring method, it is necessary to bring a sensor close to the surface of the metal plate for measurement. . In order to measure the plate thickness by such a conventional measuring method, it is necessary to stop the plant and take a person inside the flue to measure from the inside, or peel off the heat insulating material outside the flue to measure.

Further, in the measuring method utilizing the transmission of radiation, it is necessary to bring a radiation source or a measuring instrument into the flue. Therefore, there are problems that the measurement takes time and that the heat insulating material needs to be reconstructed.

Further, in the past, there was a technique as shown in FIG. That is, when the surface of the plate 01 is irradiated with the primary X-ray 03 from the X-ray source 02, the plate 01 is irradiated by Compton scattering.
The secondary X-rays (scattered X-rays) 04 are generated from this. This secondary X
The intensity of the ray (scattered X-ray) 04 (the total amount of radiation scattered in all directions) is detected by the X-ray sensor 05. Board 0
Since it is known that the plate thickness of No. 1 and the total intensity of the secondary X-rays (scattered X-rays) 04 have the relationship shown in FIG. 11, the X-ray sensor 05 detects the secondary X-rays (scattered X-rays). The plate thickness can be detected by detecting the total intensity of 04.

However, in the conventional technique shown in FIG. 10, as shown in FIG. 11, the secondary X-ray intensity tends to saturate as the plate thickness increases, and the measurement accuracy decreases as the plate thickness increases. was there.

[0007]

As described above, in each of the conventional techniques, it is necessary to stop the plant, enter a person or a measuring instrument in the flue, or measure the thickness with a large thickness. However, there was a problem that

In view of the above-mentioned prior art, the present invention is capable of improving the detection accuracy by preventing the sensitivity from decreasing due to the increase of the plate thickness when measuring the plate thickness by utilizing the scattered radiation. An object is to provide a plate thickness measuring device by scattering.

[0009]

[0010]

[Means for Solving the Problems] The present invention for solving the above problems
The configuration of the invention is also a radiation source for irradiating a plate as a measurement object with primary radiation, and a secondary radiation generated by Compton scattering when the primary radiation passes through the plate. And a radiation detector having a position resolving function capable of detecting the incident position of the secondary radiation incident on the detection surface, and the thickness of the plate disposed on the detection surface of the radiation detector. And a detection head portion integrally formed with a slit member formed with a slit so as to pass only the secondary radiation that is generated from the direction and proceeds straight toward the detection surface. And the radiation detector is in the first position, and the radiation detector is rotatable about the rotation source and the detection head is movable in the front-back direction toward the plate. To the intensity of radiation detected by the radiation detector, 180 ° the radiation detector from the first position
The detection head unit is rotated and moved so that the radiation intensity detected by the radiation detector when rotating and further moving in the front-rear direction becomes equal to the front-back movement amount and rotation diameter of the detection head unit. A deviation angle detection function for calculating a deviation angle with respect to an incident angle when the primary radiation enters the plate,
A signal processing device having a plate thickness detection function for calculating the plate thickness of the plate based on the incident width and the distribution width of the secondary radiation detected by the radiation detector. .

According to the structure of the present invention, each slit of the slit member has a large number of holes along the traveling direction of the secondary radiation.
It is characterized in that a perforated lens formed by arranging is inserted.

[0012]

Further, the structure of the present invention is characterized in that the radiation source generates X-rays or γ-rays.

Further, the structure of the present invention is characterized in that the radiation detector is formed of a microchannel plate or an imaging intensifier .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a plate thickness measuring device according to a first embodiment of the present invention. As shown in the figure, an X-ray source (radiation source) 1 irradiates a primary X-ray 3 obliquely at an incident angle θ toward a plate thickness measurement point of a plate 2 to be measured. The irradiated primary X-rays 3 are incident on the plate 2 at the position e on the upper surface 2a of the plate 2, are transmitted through the plate 2, and are at the position f on the lower surface 2b of the plate 2.
Is emitted from the plate 2 to the outside. In the process in which the primary X-rays 3 pass through the plate 2 from the position e to the position f, secondary X-rays 4 are generated by Compton scattering.

The X-ray detector (two-dimensional radiation detector) 5 is
The detection surface 5a is arranged so as to obliquely face the upper surface 2a of the plate 2. As this X-ray detector 5,
A microchannel plate, an imaging intensifier, or the like having high sensitivity to X-rays and γ-rays is used.
Moreover, the X-ray detector 5 used in this embodiment has a position resolution function, that is, a function capable of detecting at which position on the detection surface 5a the X-ray is incident.

On the detection surface 5a of the X-ray detector 5, multistage slits (slit members) 6 are arranged. The lattice-shaped slits 6 are formed, for example, by stacking lead plates and plastic films in multiple stages. The lattice-shaped slits 6 are generated so that the slits are oriented in a direction in which only the secondary X-rays 4 generated from the thickness direction of the plate pass, that is, between the incident position e and the emission position f. Of the secondary X-rays 4, the secondary X-rays 4 are arranged so as to face only the secondary X-rays 4 traveling straight toward the detection surface 5a. In FIG. 1, φ indicates the emission angle of the X-ray component of the secondary X-ray 4 that advances straight toward the detection surface 5a.

Therefore, for example, at the point p of the depth t, the secondary X-ray 4 is generated by the Compton scattering of the primary X-ray 3 which is transmitted and attenuated by the transmission distance a, and the generated secondary X-ray 4 is generated. A component of the line 4 that travels toward the X-ray detector 5 is attenuated by passing through the transmission distance b, passes through the lattice-shaped slits 6, and enters the X-ray detector 5. It should be noted that, of the generated secondary X-rays, the component that does not go straight toward the X-ray detector 5 is eliminated by the slit 6. In addition, in order to remove the error corresponding to the slit pitch, the position is adjusted so that the X-ray intensity passing through an arbitrary slit becomes maximum.

The X-ray detector 5 has a detection surface 5a.
Among them, the position corresponding to each slit of the lattice slit 6 can be recognized as a slit number. Then, the X-ray detector 5 detects the number of slits through which the secondary X-rays 4 have passed (detects the slit number), and the distribution width of the secondary X-rays 4 (from position e to position corresponding to the distance to f) can be detected.

Since the intensity of the secondary X-rays 4 passing through each of the lattice slits 6 is determined by the plate thickness, it changes exponentially as shown in FIG. 2, and the intensity of the secondary X-rays on the lower surface 2b is changed. It becomes zero. Therefore, as described above, the X-ray detector 5 detects the number of slits through which the secondary X-rays 4 have passed (detects the slit number), and the distribution width of the secondary X-rays 4 (this Corresponds to the distance from position e to position f)
Can be detected. That is, in the present embodiment, the total intensity of the secondary X-rays 4 passing through each slit is not used for detecting the thickness, but the secondary X-rays 4 of the slits are incident on the slits. The distribution width of the secondary X-ray 4 is detected by discriminating the number of slits into which the secondary X-ray 4 is incident and discriminating between those that are incident and those that are not incident. The technical idea is greatly different from the conventional art in this respect.

The signal processing device 7 corresponds to the distribution width of the secondary X-rays 4 detected by the X-ray detector 5 (this corresponds to the distance from the position e to the position f, that is, the length of the plate in the thickness direction). Exist)
And the plate thickness T of the plate 2 is calculated based on the incident angle θ. Thus, the plate thickness T of the plate 2 can be accurately detected.

As shown in FIG. 3, the grid-like slits 6 are formed.
A perforated lens 8 formed by perforating an X-ray bent body such as aluminum with a perforated hole may be inserted into the X-ray transmitting portion (each slit). By inserting the perforated lens 8 in this way, the X-ray converging property is improved and the resolution is improved, while the secondary X-rays are prevented from entering from the upper surface 2a of the plate 2 and the X in the plate thickness direction is suppressed. The accuracy of line measurement resolution can be improved. In FIG. 3, 6a is a lead plate and 6b is a perforated hole.

Next, a plate thickness measuring device according to a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the incident angle of the primary X-ray 3 is detected, the inclination error is corrected so that the incident angle becomes the set incident angle, and the thickness is measured. The reason for making such a device is that the outer side of the plate 2 forming the flue is covered with a heat insulating material and a thin steel plate for protecting it, so that the plate 2
This is because the upper surface (front surface) 2a cannot be seen, and an accurate incident angle cannot be detected only from the outside.

As shown in FIG. 4, in the plate thickness measuring apparatus according to the second embodiment, the X-ray source 1 and the X-ray detector 15 in which the lattice slits 6 are arranged on the detection surface 15a are provided. An integrated detection head unit 10 is formed. The detection head unit 10 is supported by a support unit 11, and X
The detection head unit 10 is supported so as to be rotatable about the radiation source 1 as the center of rotation, and the entire detection head unit 10 is movable in the front-rear direction.

The X-ray detector 15 has the same position resolving function as the X-ray detector 5 and the function of detecting the intensity of the incident secondary X-ray 4.

Like the signal processing device 7, the signal processing device 17 has a function of calculating the plate thickness T of the plate 2 based on the distribution width of the secondary X-rays 4 detected by the X-ray detector 15 and the incident angle θ. have. Further, the signal processing device 17 stores and compares the X-ray intensities detected by the X-ray detector 15, detects the amount of forward and backward movement of the detection head unit 10, and performs a calculation described later to obtain a deviation angle α. It has a function.

When the deviation angle α with respect to the incident angle θ of the primary X-ray 3 is detected, the X-ray detector 15 is used to detect the intensity of the incident secondary X-ray 4. To detect the deviation angle α, first set the X-ray detector 15 to the sensor position I.
Then, the X-ray intensity incident on the X-ray detector 15 is measured.

Next, the detection head unit 10 is rotated by 180 ° about the X-ray source 1 as the center of rotation to position the X-ray detector 15 at the sensor position II. In this state (after rotating 180 °), the entire detection head 10 is moved in the front-back direction, and X
When the line intensity becomes equal to the X-ray intensity at the sensor position I, the forward / backward movement is stopped. This stopped position is referred to as sensor position III.

When the amount of forward and backward movement from the sensor position II to the sensor position III is Y, the signal processing device 17
Calculates the deviation angle α by performing the following calculation. In addition, D is a rotation diameter, which is predetermined. α = tan ^-1 Y / D

When the deviation angle α is detected as described above, the angle of the detection head unit 10 can be corrected by this deviation angle α, and the incident angle θ of the primary X-ray 3 can be accurately adjusted to the initial setting angle. When the incident angle θ reaches the initial setting angle, the same operation as in the first embodiment is performed to measure the plate thickness of the plate 2.

As described above, in the second embodiment, since the deviation angle α can be obtained and the incident angle with respect to the plate 2 can be corrected, the accuracy can be improved.

Next, a plate thickness measuring device according to a third embodiment of the present invention will be described with reference to FIG. As shown in the figure, the X-ray source 1 obliquely irradiates the plate 2 with the primary X-rays 3, and the secondary X-rays 4 are generated by Compton scattering due to the irradiation of the primary X-rays 3.

The X-ray detector 25 has a function of detecting the intensity (total intensity) of the incident secondary X-rays 4. That is,
The intensity signal of the secondary X-ray 4 incident on the detection surface 25a is integrated over the entire surface to detect the X-ray intensity. The X-ray detector 25 is supported by the support portion 20 and can move in a direction parallel to the optical axis of the primary X-ray 3.

On the detection surface 25a of the X-ray detector 25,
A multilayer cone-shaped slit 26 is arranged, and the focus of the cone-shaped slit 26 is arranged so as to coincide with the optical axis of the primary X-ray 3. In this way, since the focal point of the cone-shaped slit 26 is aligned with the optical axis of the primary X-ray 3, the secondary X-ray is prevented from entering from the upper surface 2a of the plate 2 and the X-ray measurement in the plate thickness direction is performed. The accuracy of resolution can be improved.

The signal processing device 27 detects the moving distance of the X-ray detector 25 while the X-ray detector 25 is detecting the secondary X-rays 4, and from this moving distance and the incident angle, The plate thickness T of the plate 2 is calculated.

In the third embodiment, the X-ray detector 25 and the cone-shaped slit 26 are arranged along the support portion 20 along the primary X-axis.
Move it parallel to the optical axis of line 3. At this time, when the focal point of the cone-shaped slit 26 is between the position e and the position f, the X-ray detector 25 detects the secondary X-ray 4 and outputs a detection signal. Therefore, when the X-ray detector 25 is moved, the X
The signal processor 27 detects the moving distance of the line detector 25. The detected moving distance corresponds to the distance between the position e and the position f.

The signal processing device 27 calculates the thickness T of the plate 2 based on the moving distance of the X-ray detector 25 (corresponding to the distance between the position e and the position f) and the incident angle θ.

FIG. 6 shows a main part of a plate thickness measuring device according to the fourth embodiment of the present invention. In this embodiment, the γ-ray source 31 is used as a radiation source, and the γ-ray source 31 outputs primary γ-rays (energy E ₁ ) 33. As the radiation detector, a semiconductor or gas detection type one-dimensional or two-dimensional gamma ray detector 35 having energy resolution is used. A slit 36 is arranged on the detection surface 35 a of the γ-ray detector 35. The gamma ray detector 35
A signal processing device for detecting the plate thickness of the plate 2 based on the distribution width of the secondary γ-rays (energy E ₂ ) 34 detected by is omitted in the drawing.

In the fourth embodiment, the γ-ray detector 3
5, only the γ-rays with energy intensity E ₂ (that is, the secondary γ-rays 34 generated by one-time scattering) are selected and detected. Therefore, multiple scattering components (scattered after the second scattering) It is possible to cancel the generated component) and improve the measurement accuracy. The reason will be described below.

As shown in FIG. 7, the scattered γ-rays are scattered with the scattering angle ε with respect to the incident γ-rays. At this time, as shown in FIG. 8, the energy after scattering changes depending on the scattering angle ε. Therefore, for example, when scattering occurs along the path shown in FIG. 6, as shown in FIG. 8, (1) first, the γ rays of energy E ₁ cause the γ rays of energy E ₂ , E ₃ , E ₅ to be γ.
(2) γ rays of energy E ₄ are generated by γ rays of energy E ₃ and γ rays of energy E ₅ are generated.
The rays generate gamma rays with energy E ₆ .

Therefore, as shown in FIG. 6, the γ-ray detector
35 is energy E₁, E_Four, E₆Γ rays of
It On the other hand, the γ-ray energy is distributed as shown in Fig. 9.
Therefore, the energy intensity is determined by the γ-ray detector 35.
E₂Γ-rays (that is, the secondary γ-rays 3 generated by scattering once)
By selecting and detecting only 4), multiple scattering components
(Components scattered after the second time, energy in the above example
Ruge strength is E_Four, E ₆Γ rays)
Therefore, the measurement accuracy can be improved.

Instead of the combination of the slit 36 and the one-dimensional γ-ray detector 35, the aperture and the zero-dimensional γ-ray are used.
A combination with a line detector may be used.

[0044]

As described above in detail with the embodiments, in the present invention, the radiation source for irradiating the plate as the object to be measured with the primary radiation, and the primary radiation transmits through the plate. The secondary radiation generated by Compton scattering at that time is detected , and the secondary radiation incident on the detection surface is detected.
A radiation detector for have a spatial resolution function capable of detecting the incident position, are arranged on the detection surface of the radiation detector, straight toward the detection surface is generated in the thickness direction of the plate A slit member formed with a slit so that only secondary radiation that advances is passed through,
A distribution width of the secondary radiation detected by the radiation detector, and a signal processing device that calculates the thickness of the plate based on the incident angle when the primary radiation enters the plate .

Since the plate thickness is detected by utilizing the distribution width of the secondary radiation in such a structure, even if the radiation intensity is saturated due to the increase in the plate thickness, the plate thickness is not affected by the saturation. Can be accurately detected.

Further, in the present invention, a radiation source for irradiating a plate as a measurement object with primary radiation and a secondary radiation generated by Compton scattering when the primary radiation passes through the plate are detected , Moreover, the secondary incident on the detection surface
Position resolution function that can detect the incident position of radiation
A radiation detector for have a, is disposed on the detection surface of the radiation detector and passes only the secondary radiation generated in the thickness direction of the plate comes to proceed straight toward the detection surface A detection head unit integrally formed with a slit member in which a slit is formed, and the detection head unit can be rotated about the radiation source as a rotation center, and the detection head unit is directed toward the plate in the front-back direction. A support that can be moved, a radiation intensity detected by the radiation detector when the radiation detector is in the first position, and the radiation detector that is rotated by 180 ° from the first position and further back and forth. Direction, the detection head unit is rotated and moved so that the radiation intensity detected by the radiation detector becomes equal to the radiation intensity detected by the radiation detector. A deviation angle detection function for calculating a deviation angle with respect to an incident angle when a ray enters the plate, a distribution width of secondary radiation detected by the radiation detector, and an incident angle based on the plate thickness of the plate. And a signal processing device having a plate thickness detecting function for calculation.

Since the deviation angle can be calculated in such a configuration, the plate thickness can be accurately detected by correcting the incident angle by the deviation angle. Moreover, even if the plate is covered with a heat insulating material or the like, the deviation angle can be reliably calculated,
Work such as peeling off the heat insulating material becomes unnecessary.

In the present invention, each slit of the slit member is provided with a large number of holes along the traveling direction of the secondary radiation.
The configuration is such that a fully formed porous lens is inserted. With such a configuration, it is possible to improve the resolution by increasing the radiation focusing property.

Further, in the present invention, the radiation source for irradiating the plate as the object to be measured with the primary radiation , and the detection surface of the secondary radiation generated by Compton scattering when the primary radiation passes through the plate. Radiation detector for detecting the total intensity of the secondary radiation incident on and a cone-shaped slit arranged on the detection surface of the radiation detector and having a focal point aligned with the optical axis of the primary radiation. A support portion for supporting the radiation detector so that the radiation detector can be moved in a direction parallel to the optical axis of the primary radiation; and a secondary radiation by the radiation detector when the radiation detector is moved. And a signal processing device that calculates the plate thickness of the plate based on the moving distance and the angle of incidence when the primary radiation enters the plate. And

With this structure, the plate thickness can be accurately detected from the moving distance of the radiation detector and the incident angle.

In the present invention, the radiation source is X
Line or γ-ray is generated, and the radiation detector has a high sensitivity so that it is formed of a microchannel plate or an imaging intensifier. By doing so, the plate thickness can be measured more accurately.

As described above, according to the present invention, even if the thickness of the inner wall (plate) of a structure such as a combustion furnace or a flue that is inaccessible to humans or robots is reduced due to corrosion or the like, the radiation is emitted to the combustion furnace or smoke. By irradiating from the outside of the road, the plate thickness can be accurately measured. Therefore, unlike the conventional measurement method, it is not necessary for a person to enter the flue, and the plate thickness can be accurately measured without peeling the heat insulating material outside the flue. At the same time, it is possible to measure the plate thickness without stopping the plant.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a plate thickness measuring device by Compton scattering according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a slit number and secondary X-ray intensity.

FIG. 3 is a configuration diagram showing a lattice-like slit provided with a perforated lens.

FIG. 4 is a configuration diagram showing a plate thickness measuring device by Compton scattering according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a plate thickness measuring device by Compton scattering according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram showing a main part of a plate thickness measuring device by Compton scattering according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram showing the relationship between incident γ-rays, scattered γ-rays, and scattering angles.

FIG. 8 is a characteristic diagram showing that energy changes due to scattering.

FIG. 9 is a characteristic diagram showing an example of a spectrum of scattered γ-rays incident on a γ-ray detector.

FIG. 10 is a configuration diagram showing a conventional plate thickness measuring device.

FIG. 11 is a characteristic diagram showing the relationship between plate thickness and scattered X-ray intensity.

[Explanation of symbols]

1 X-ray source 2 plates 2a upper surface 2b lower surface 3 Primary X-ray 4 Secondary X-ray 5,15,25 X-ray detector 5a, 15a, 25a Detection surface 6 lattice slits 26 cone slit 7, 17, 27 Signal processing device 8 Perforated lens 10 Detection head section 11 Support 20 Support 31 γ-ray source 33 Primary γ rays 34 Secondary gamma rays 35 γ-ray detector 35a Detection surface 36 slits

─────────────────────────────────────────────────── ─── Continuation of front page (72) Eiichi Yanagisawa, Eiichi Yanagizawa 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Kazuo Ideue 4 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 6-22 No. Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (56) Reference JP-A-55-82006 (JP, A) JP-A-3-59449 (JP, A) JP-A-5-322804 (JP, A) JP-A-8-61943 (JP, A) JP-A-11-190614 (JP, A) JP-A-10-9844 (JP, A) JP-A-7-230000 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01B 15/00-15/08 G01N 23/00-23/227 G21K 1/00-7/00

Claims (4)

(57) [Claims] 1. A radiation generation source for irradiating a plate, which is an object to be measured, with primary radiation, and a secondary radiation generated by Compton scattering when the primary radiation passes through the plate, and a detection surface. A radiation detector having a position resolving function capable of detecting the incident position of the secondary radiation incident on the radiation detector, and the radiation detector disposed on the detection surface of the radiation detector and generated in the thickness direction of the plate. A detection head unit integrally formed with a slit member in which a slit is formed so as to pass only the secondary radiation that advances straight toward the surface, and the detection head unit rotates the radiation generation source. A support part that can rotate about the center and that can move the detection head part in the front-back direction toward the plate; and the radiation detector when the radiation detector is in the first position. The detection head unit is rotated so that the radiation intensity detected by the radiation detector is equal to the radiation intensity detected by the radiation detector when the radiation detector rotates 180 ° from the first position and further moves in the front-rear direction. -Movement, based on the back-and-forth movement amount and rotation diameter of the detection head unit, a deviation angle detection function that calculates a deviation angle with respect to the incident angle when the primary radiation enters the plate, and the radiation detector detects the deviation angle. A plate thickness measuring device by Compton scattering, comprising: a signal processing device having a plate thickness detecting function for calculating the plate thickness of the plate based on a distribution width of secondary radiation and an incident angle. . Each slit wherein the slit member, <br/> of claim 1, characterized in that by inserting a porous hole lens formed by arranging a plurality of holes along the traveling direction of the secondary radiation Plate thickness measuring device by Compton scattering. Wherein the radiation generating source, a plate thickness measuring apparatus according co <br/> Nputon scattering of claim 1 or claim 2, characterized in that to generate the X-rays or γ-rays. 4. The radiation detector is formed of a microchannel plate or an imaging intensifier.
Alternatively, the plate thickness measuring device by Compton scattering according to claim 3 .