JP2008175796A - Drum inspection method, and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish an inspection method capable of detecting, from an outer surface side, a cross-sectional defect such as corrosion, rust and abrasion caused by a physical factor, generated in an inner face side of a drum for storing a low-level radioactive waste, and capable of specifying of a generation position thereof, and to measure a residual thickness in a cross-sectional defect part to obtain a data of a residual life. <P>SOLUTION: This drum inspection method for detecting, from the outer surface side, the cross-sectional defect generated in the inner face side of the drum 1 for storing the low-level radioactive waste, carries out primary inspection of detecting a thickness reduction portion generated in an inner face of the drum and of estimating a range thereof by a transverse ultrasonic wave, and secondary inspection of detecting a degree of thickness reduction by detecting vertically a flaw in the range obtained in the primary inspection, by a longitudinal ultrasonic wave. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drum can inspection method and apparatus for inspecting defects of a drum can containing low-level radioactive waste.

In recent years, liquid dripping has been confirmed from a part of a drum can containing low-level radioactive waste, and these liquid dripping is caused by a reduction in cross section due to rust. For example, as a method of inspecting a defective portion of a drum can, a support rod provided with an illumination lamp and a plurality of CCD cameras is mounted on a support member disposed close to the drum can conveyance line so as to be movable up and down. A CCD camera is inserted into the drum can, and each camera shoots the shooting area in the drum can at a predetermined position in the vertical direction. The shot image is temporarily held in memory, and then replayed from this memory to the monitor. In some cases, a still image is visually observed to determine a defect in each of the shooting shared areas (Patent Document 1).
Japanese Patent Laid-Open No. 9-288067

  By the way, an imaging sharing area in a drum can is imaged to detect a defect, and it cannot be used for detecting a defect of a drum can that contains a low-level radioactive waste and is sealed.

  The present invention takes this situation into consideration, and eliminates cross-sectional defects such as corrosion, rust, or wear caused by physical factors that occur on the inner surface of a drum can that stores low-level radioactive waste. It is an object of the present invention to provide a drum can inspection method and apparatus capable of obtaining a residual life data by measuring a residual thickness of a cross-sectional defect portion and establishing an inspection method capable of detecting the occurrence position of the cross-sectional defect.

  In order to solve the above problems and achieve the object, the present invention is configured as follows.

The invention according to claim 1 is a drum can inspection method for detecting a cross-sectional defect generated on the inner surface side of a drum can containing low-level radioactive waste from the outer surface side,
A primary inspection is performed to detect the thinned portion generated on the inner surface of the drum can by the ultrasonic wave of the transverse wave and to estimate the range,
A drum can inspection method characterized in that a secondary inspection is performed to detect the degree of thinning by performing vertical flaw detection in the range obtained in the primary inspection with longitudinal ultrasonic waves.

  According to a second aspect of the present invention, in the drum can inspection method according to the first aspect, the drum can is obtained by galvanizing both surfaces of an iron plate and applying a resin film to the surface of the galvanized surface. is there.

  The invention according to claim 3 is characterized in that in the primary inspection, the ultrasonic wave of the transverse wave is propagated from the upper end portion to the lower end portion of the side plate of the drum can and from the lower end portion to the upper end portion. The drum can inspection method according to claim 1 or claim 2.

  According to a fourth aspect of the present invention, in the primary inspection, the ultrasonic waves of the transverse waves are propagated from the circumferential outer edge portions of the top and bottom plates of the drum can to the central portion. 2. The drum inspection method according to 2.

The invention according to claim 5 is a drum can inspection device that detects a cross-sectional defect generated on the inner surface side of a drum can containing low-level radioactive waste from the outer surface side,
A primary inspection ultrasonic device for performing a primary investigation to detect and detect a thinned portion generated on the inner surface of the drum can by means of transverse ultrasonic waves;
A drum inspection apparatus comprising: a secondary inspection ultrasonic device for performing a secondary inspection for detecting a degree of thinning by performing a vertical flaw detection in a range obtained by the primary inspection by longitudinal ultrasonic waves. is there.

  The invention according to claim 6 is the drum can inspection apparatus according to claim 5, wherein the drum can is obtained by galvanizing both surfaces of an iron plate and applying a resin film on the surface of the galvanizing. is there.

  With the above configuration, the present invention has the following effects.

  In the first and fifth aspects of the invention, a primary inspection is performed to detect a thinned portion generated on the inner surface of the drum can by the ultrasonic wave of the transverse wave and to estimate the range, and the primary inspection is performed by the ultrasonic wave of the longitudinal wave. By performing a secondary inspection to detect the degree of thinning by performing vertical flaw detection in the obtained range, cross-sectional defects occurring on the inner surface side of the drum can containing low-level radioactive waste are detected from the outer surface side, and the occurrence The position can be specified, and the remaining thickness of the cross-sectional defect portion can be measured to obtain the remaining life data.

  In the invention according to claim 2 and claim 6, the drum can is galvanized on both sides of the iron plate, and a resin film is applied to the surface of the galvanized plate, and the inner surface of the drum can for storing low-level radioactive waste Cross-sectional defects due to rust generated on the side can be detected from the outer surface side.

  In the third aspect of the invention, the primary inspection is performed by propagating the ultrasonic wave of the transverse wave from the upper end portion to the lower end portion of the side plate of the drum can and from the lower end portion to the upper end portion to increase the entire range of the side plate of the drum can. It can be inspected with accuracy.

  In the invention according to claim 4, in the primary inspection, the ultrasonic wave of the transverse wave is propagated from the circumferential outer edge portion of the top plate and the bottom plate of the drum can to the center portion, and the entire range of the top plate and the bottom plate of the drum can is accurately detected. Can be inspected.

  Hereinafter, embodiments of the drum can inspection method and apparatus according to the present invention will be described. However, the embodiments of the present invention show the most preferable embodiments of the present invention, and the present invention is not limited thereto.

[Inspection object]
First, the inspection object will be described with reference to FIGS. FIG. 1 is a side view of a drum can, and FIG. 2 is a sectional view of a part of the drum can.

  The drum can 1 of this embodiment contains low-level radioactive waste. This drum can 1 has a side plate 10, a top plate 11, and a bottom plate 12, and as shown in FIG. 2, galvanized 1b is applied to both surfaces of an iron plate 1a, and a resin film 1c is provided on the surface of the galvanized 1b. . For example, the thickness of the iron plate 1a is 1.6 mm, the thickness of the zinc plating 1b is 0.02 mm, and the thickness of the resin film 1c is 0.03 mm. The resin film 1c uses, for example, an epoxy resin, but is not limited to this. In addition, the drum can 1 may be, for example, a coating on the iron plate 1a, and the structure of the drum can 1 is not particularly limited.

  Thus, the drum 1 containing the low-level radioactive waste may have a cross-sectional defect on the inner surface side due to corrosion, rust, or wear due to physical factors. Detect cross-sectional defects from the outer surface side. This drum can inspection method and apparatus will be described below.

[Primary inspection]
Next, the primary inspection will be described with reference to FIGS. 3 is a diagram showing the wave form of the SV wave, FIG. 4 is a diagram showing the wave form of the SH wave, FIG. 5 is a diagram showing a state in which the drum can be inspected from the top to the bottom, and FIG. FIG. 7 is a diagram showing drill holes in the top plate and the bottom plate, and FIG. 8 is a diagram showing a state in which the top plate and the bottom plate are inspected.
In the primary inspection, the primary inspection ultrasonic device 2 is used, and the detection and the range of the thinned portion occurring on the inner surface of the drum can 1 are estimated by the ultrasonic wave of the transverse wave. In the primary inspection, transverse ultrasonic waves are propagated from the upper end to the lower end of the side plate 10 of the drum can 1 and from the lower end to the upper end, and the entire range of the side plate 10 of the drum can 1 is inspected with high accuracy. Can do. In the primary inspection, transverse ultrasonic waves are propagated from the outer peripheral edge of the top plate 11 and the bottom plate 12 of the drum can 1 to the center, and the entire range of the top plate 11 and the bottom plate 12 of the drum can 1 is inspected with high accuracy. can do.
"Primary inspection ultrasonic device"
The primary inspection ultrasonic device 2 includes an ultrasonic probe 2a and an ultrasonic flaw detector 2b. The ultrasonic probe 2a uses a transverse wave vibrator 2a1, and this transverse wave vibrator 2a1 is a vibrator that generates a shear wave from the beginning by sliding vibration in accordance with an excitation voltage. A transverse wave is directional because it is a wave that vibrates in a direction perpendicular to the propagation direction. As shown in FIG. 3, the transverse wave radiated from a normal oblique angle probe is called an SV wave because it vibrates in a direction perpendicular to the flaw detection surface. A transverse wave oscillating in a direction parallel to the flaw detection surface or the plane under consideration is called an SH wave. Unlike the SV wave, the SH wave has a refraction angle of 90, as shown in FIG. It is possible to emit a transverse wave strongly in a direction close to.

  In the present invention, the SH wave is applied in consideration of the fact that the target drum can 1 is thin and that ultrasonic waves propagate through a certain distance.

  The ultrasonic flaw detector 2b includes a transmitter 2b1 and a receiver 2b2. The transmitter 2b1 drives the ultrasonic probe 2a, and displays data obtained by driving the ultrasonic probe 2a on the receiver 2b2.

"Contact medium"
The transverse wave (SV wave) generates a wave of each mode by transmitting a longitudinal wave from the transverse wave vibrator 2a1 and changing the incident angle to the drum 1. For this reason, the longitudinal wave transmitted from the transverse wave vibrator 2a1 can be easily incident on the steel material of the drum can 1 through a liquid such as water, oil, glycerin and the like.

On the other hand, in the SH wave, since the transverse wave of the transverse vibration generated by the transverse wave vibrator 2a1 is directly incident on the steel as a transverse wave, for the transverse wave that does not propagate in the liquid, the contact medium similar to the longitudinal wave is used in the steel material. Incident on the screen becomes impossible. Therefore, a contact medium dedicated to transverse waves having a certain degree of viscosity is used.
"Example"
(Inspection equipment)
As the ultrasonic flaw detector 2b, a UI-23Lf low-frequency ultrasonic flaw detector manufactured by Soiryo Electronics Co., Ltd. is used, and as the ultrasonic probe 2a, ultrasonic waves of 0.5C20HA90 manufactured by Inspection Technology Laboratory Co., Ltd. are used. A probe was used.

(Side plate inspection method)
As shown in FIG. 5, the ultrasonic probe 2a moved the upper end portion of the side plate 10 of the drum can 1 at intervals of, for example, 40 mm, and inspected the drill hole flaw generated on the side plate 10 of the drum can 1 from the upper side to the lower side. Moreover, as shown in FIG. 6, the ultrasonic probe 2a moved the lower end part of the side plate 10 of the drum can 1 at intervals of 40 mm, for example, and inspected the drill hole flaw generated on the side plate 10 of the drum can 1 from below to above. .

The processed drill holes are processed in nine locations so that the depth from the inner surface is in the range of 0.48 mm to 0.70 mm and the diameter is in the range of 3.34 mm to 4.07 mm and is distributed in the height direction of the side plate 10. And it was set as S1-S9 from the lower end part (bottom plate side).
The side lines were 9 measurement lines on the height direction extension lines of the drill holes of S1 to S9, and the measurement direction was measured in two directions from the upper side (top plate side) to the lower side (bottom plate side) and from the lower side to the upper side. The ultrasonic probe 2a was fixed using a holder in which a magnet was incorporated at the upper end and the lower end.

(Side plate inspection results)
In the measurement, the height of the reflected echo when the SH wave is incident / propagated from above and below the side plate toward the drill holes S1 to S9 is adjusted to 80% above the display unit of the ultrasonic flaw detector 2b. As shown in FIGS. 5 and 6, reflected echoes from the drill holes S1 to S9 for detection as shown in the flaw detection figure could be clearly confirmed on all measurement lines. A reflection echo from a drill hole on another survey line was detected on one survey line. For example, in the measurement from above the side line 7), it can be confirmed from the flaw detection figure that the drill holes S1 to S8 have been detected. Thus, by utilizing this beam expansion, the flaw detection area (range) in the primary measurement can be set, which becomes a factor for determining the flaw detection method of the side plate portion.

(Inspection method for bottom plate and top plate)
The top plate 11 and the bottom plate 12 were confirmed to detect the degree of detection of the drill holes processed into the top plate 11 and the bottom plate 12 using the SH wave ultrasonic probe 2a in the same manner as the side plate 10. As shown in FIG. 7, the processed drill holes have a depth from the inner surface in the range of 0.30 mm to 0.64 mm and a diameter of 2.65 mm to 3.83 mm, and the radii of the top plate 11 and the bottom plate 12. It processed into nine places so that it might distribute in a spiral shape, and it was set as B1-B9 from the center part. The side lines were 8 measurement lines on a line equally divided into 8 in the circumferential direction, and the measurement direction was measured from the circumferential outer edge of the top plate and the bottom plate to the center. The ultrasonic probe 2a was fixed using a holder in which a magnet was incorporated in the outer circumferential edge of the top plate and the bottom plate.

(Inspection results for bottom plate and top plate)
In the measurement, the height of the reflected echo when the SH wave is incident / propagated from the outer circumferential edge of the top plate and the bottom plate toward the center is adjusted to 80% on the display unit height of the ultrasonic flaw detector 2b. In particular, as shown in the flaw detection figure of FIG. 8, the reflected echo from the drill hole for the purpose of detection could be clearly confirmed in all measurement lines.

[Secondary inspection]
Next, the secondary inspection will be described with reference to FIGS. 9 is a diagram showing the wave form of longitudinal waves, FIG. 10 is a diagram showing the measurement principle, FIGS. 11 to 13 are diagrams showing the results of the simulated corrosion test plate thickness measurement, and FIG. 14 is the simulated corrosion test plate thickness artificial flaw remaining It is a figure which shows the table | surface of a thickness measurement result.

  The secondary inspection uses the secondary inspection ultrasonic device 20 to detect the degree of thinning by performing vertical flaw detection in the range obtained by the primary inspection using longitudinal ultrasonic waves.

"Secondary inspection ultrasonic device"
The secondary inspection ultrasonic device 20 includes an ultrasonic probe 20a and an ultrasonic flaw detector 20b. The ultrasonic probe 20a uses longitudinal wave transducers 20a1 and 20a2. The longitudinal wave transducer 20a1 is a transducer that generates a longitudinal wave from the beginning by sliding vibration in accordance with an excitation voltage. The wave vibrator 20a2 is a vibrator that receives a longitudinal wave. The most widely used for generating ultrasonic waves is the longitudinal wave vibrator 20a1. As shown in FIG. 9, the longitudinal wave vibrator 20 a 1 becomes thicker or thinner depending on the excitation voltage. A longitudinal wave is a wave that expands and contracts in the propagation direction and does not expand and contract in a direction perpendicular to the propagation direction.

  As shown in FIG. 10, the ultrasonic wave has a property of being reflected when there is a defect or the like during propagation. Ultrasonic plate thickness measurement is used as a method for measuring the thickness of a plate material by utilizing this property, and longitudinal waves are used for this ultrasonic plate thickness measurement. The speed of sound of an ultrasonic wave is independent of the frequency, and is determined by the type of ultrasonic wave and the propagating object, and the speed of sound of a longitudinal wave is about twice that of a transverse wave.

  In the ultrasonic plate thickness measurement, an ultrasonic wave is transmitted from the longitudinal wave transducer 20a1 and received by the same longitudinal wave transducer 20a2, and the plate thickness of the drum 1 that is the object is as thin as 1.6 mm. In order to obtain reflection from extremely low pitting corrosion, a two-element vertical probe in which transmission and reception are divided is used. The principle of the plate thickness measurement is that when an ultrasonic wave is incident on the steel material parallel to the front and back surfaces from the surface, the ultrasonic wave propagated in the steel is reflected in the same manner as if the light is reflected when reaching the back surface. Therefore, when an ultrasonic wave is incident perpendicularly to the back surface, it is reflected in the direction opposite to the incident direction, and the time required for reciprocation is known by receiving this. Since the speed of sound in the object is known, the distance (plate thickness) from the probe to the back surface can be known.

"Contact medium"
The longitudinal wave transmitted from the longitudinal wave vibrator 20a1 can be easily incident on the steel material of the drum can 1 through a liquid such as water, oil, or glycerin. In the secondary inspection, it was confirmed that an aqueous glycerin solution having a concentration of 75% or more or an acoustic coupling equivalent to or higher than this was obtained.
"Example"
(Inspection equipment)
As the ultrasonic flaw detector 20b, a UI-23L ultrasonic flaw detector with a pulse reflection method A scope display function manufactured by Ryoden Shonan Electronics Co., Ltd. is used, and as the ultrasonic probe 2a, 10C5 / 2ND manufactured by Japan Probe Co., Ltd. The two-element vertical probe was used.

(Inspection method)
After detecting pitting corrosion in the primary survey and specifying the site of occurrence, ultrasonic plate thickness measurement is applied as a method to measure the remaining thickness of the pitting corrosion site as a secondary survey. Whether the remaining thicknesses of the processed flaws of φ5 mm, φ10 mm, and φ20 mm processed 0.4 mm, 0.8 mm, and 1.2 mm can be measured, and the error between the measured value and the actual remaining thickness was compared.

  FIG. 11 to FIG. 13 show flaw detection patterns in an artificial flaw portion using a two-vibrator vertical probe, and FIG. 14 shows the remaining thickness measurement values. As a result of ultrasonic measurement, the remaining thicknesses of 0.8 mm and 1.2 mm were 0.1 mm thicker than the actual remaining thickness. However, when the measurement accuracy of the ultrasonic flaw detector is considered to be ± 0.1 mm, the measurement result is within the error range, and it seems that there is no problem in the measurement result. In such pitting corrosion thickness measurement, the reflection part is the top of the pitting corrosion sphere, so that irregular reflection increases and reflection from the thinnest part is difficult to obtain, so that it is displayed thicker.

  The present invention is applicable to a drum can inspection method and apparatus for inspecting a defect of a drum can containing low-level radioactive waste, and detects cross-sectional defects generated on the inner surface side of the drum can containing low-level radioactive waste from the outer surface side. In addition, it is possible to establish an inspection method capable of specifying the generation position and to measure the remaining thickness of the cross-sectional defect portion to obtain data on the remaining life.

It is a side view of a drum can. It is sectional drawing of a part of drum. It is a figure which shows the wave form of SV wave. It is a figure which shows the wave form of SH wave. It is a figure which shows the state which test | inspects from the upper direction of a drum can to the downward direction. It is a figure which shows the state which test | inspects from the downward direction of a drum can upwards. It is a figure which shows the drill hole of a top plate and a baseplate. It is a figure which shows the state which test | inspects a top plate and a baseplate. It is a figure which shows the wave form of a longitudinal wave. It is a figure which shows the measurement principle. It is a figure which shows the simulation corrosion test plate | board thickness measurement result. It is a figure which shows the simulation corrosion test plate | board thickness measurement result. It is a figure which shows the simulation corrosion test plate | board thickness measurement result. It is a figure which shows the table | surface of a simulated corrosion test board thickness artificial flaw part residual thickness measurement result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drum can 1a Iron plate 1b Zinc plating 1c Resin film 2 Primary inspection ultrasonic device 2a Ultrasonic probe 2a1 Transverse wave transducer 2b Ultrasonic flaw detector 2b1 Transmitter 2b2 Receiver 10 Drum 1 side plate 11 Top plate 12 Bottom plate 20 2 Next inspection ultrasonic device 20a Ultrasonic probe 20b Ultrasonic flaw detector 20a1, 20a2 Longitudinal wave vibrator S1-S9 Drill hole B1-B9 Drill hole

Claims (6)

The cross-sectional surface defects that occur on the inner side of the drum housing the low-level radioactive waste is drum testing method for detecting from the outer surface side,
A primary inspection is performed to detect the thinned portion generated on the inner surface of the drum can by the ultrasonic wave of the transverse wave and to estimate the range,
A drum inspection method comprising: performing a secondary inspection for detecting a degree of thinning by performing vertical flaw detection in a range obtained by the primary inspection with longitudinal ultrasonic waves.   2. The drum can inspection method according to claim 1, wherein the drum can is obtained by galvanizing both surfaces of an iron plate and applying a resin film to the surface of the galvanized surface.   The said primary test | inspection propagates the ultrasonic wave of the said transverse wave from the upper end part of the side plate of the said drum can to a lower end part, and is propagated from a lower end part to an upper end part. Drum can inspection method.   The drum inspection method according to claim 1, wherein the primary inspection causes the ultrasonic waves of the transverse waves to propagate from the circumferential outer edges of the top and bottom plates of the drum can to the center. A drum testing apparatus for detecting from the outer surface side sectional surface defects that occur on the inner side of the drum housing the low-level radioactive waste,
A primary inspection ultrasonic device for performing a primary investigation to detect and detect a thinned portion generated on the inner surface of the drum can by means of transverse ultrasonic waves;
A drum inspection apparatus, comprising: a secondary inspection ultrasonic device for performing a secondary inspection for detecting a degree of thinning by performing a vertical flaw detection in a range obtained by the primary inspection using longitudinal ultrasonic waves. The drum can inspection apparatus according to claim 5, wherein the drum can is obtained by galvanizing both surfaces of an iron plate and applying a resin film on the surface of the galvanized surface.