JP3194133B2 - Marking device for measuring residual stress of metal tube for nuclear reactor and method for measuring residual stress of metal tube using this device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a marking for measuring a residual stress in a metal pipe such as a nozzle penetrating portion where a metal pipe penetrates a lid body, for example, in an upper lid of a reactor vessel (hereinafter referred to as RV). The present invention relates to an apparatus and a method for measuring residual stress using the apparatus.

[0002]

2. Description of the Related Art Some cases of stress corrosion cracking (hereinafter referred to as SCC) have been reported overseas in the nozzle penetrating portion of the RV top cover, and there have been no reports of SCC occurrences in Japan, but preventive maintenance. From the viewpoint, there is a plant where the replacement of the RV top is performed, and there are plans to do so in the future. However, there is very little aging data on the member, and in particular, little is known about the residual stress that is the main cause of SCC generation, that is, what residual stress acts on the member to promote SCC generation. There is no present. This means that when trying to measure the residual stress of the member, for example, a non-destructive method using X-rays is too large to install the device in the vicinity of the member,
This is because it is difficult to secure a working time for accurately attaching the strain gauge to the contaminated member by the strain gauge method generally used in the destructive method.

[0003] Specifically, in the method using a strain gauge,
In order to attach the strain gauge, it is necessary to clean the surface of the object or to attach the strain gauge. Therefore, it is difficult to perform measurement at the penetration part of the RV head cap that has a limited working time due to radioactivity. Since the stress relief operation is performed after the strain gauge is attached, there is a risk that the strain gauge or the lead wire may be damaged before the stress measurement is performed, and the measurement may not be performed.

On the other hand, in the above-mentioned X-ray method, an X-ray source and an X-ray detector must be arranged in the immediate vicinity of an object, so that a larger work space is required than in a method using a strain gauge. In addition, since the measuring equipment becomes large, there is a problem that these apparatuses cannot be installed.

[0005]

According to the present invention, there is provided a method in which the nozzle section is contaminated, and the operation for replacing the RV top cover is a very short time because the operation time is very tight. Precautions such as degreasing and washing of the surface of the member cannot be sufficiently performed, so that the method is insensitive to surface contamination, and the residual stress of the nozzle portion of the RV upper lid is measured easily and quickly. The purpose is to tighten.

[0006]

That is, the marking apparatus for measuring residual stress according to the present invention, which meets the above-mentioned objects, inserts a marker head into the inside of a metal tube used in a nuclear reactor, and engraves a predetermined portion. A marking device for measuring residual stress to be applied, wherein a plurality of polygonal pyramid-shaped indenters are fixed at predetermined intervals with a top portion of the pyramid as a tip, and the marker head portion is supported, and A head drive mechanism for performing marking by the indenter by moving the marker head and pressing against the pipe wall, and supporting the head drive mechanism from outside the metal tube via a rod, and the head drive mechanism And an operation unit for operating.

Further, in the marking device of the present invention, the head driving mechanism causes the marker head to protrude outward in a radial direction of the metal tube, and the marker head pressed against the tube wall by the protrusion. It is also preferable to provide a reaction force receiving member that receives the reaction force of the portion and contacts another portion of the tube wall.

Further, in the marking device of the present invention, the rod is slidably and fixedly inserted into the rod between the operating portion and the head driving mechanism, and is connected to an insertion end of the metal tube. In addition, it is also preferable to provide a guide cap for positioning the marker head.

On the other hand, in the method for measuring residual stress of the present invention, the marker head is inserted into the metal tube using the marking device of the present invention as described above, and the marker head is connected to the tube by the head driving mechanism. Pressed against a wall to make a mark with the plurality of indenters, then cut off the tube wall on which the mark was made from the surroundings to release stress, and measured the distance between the above-mentioned marks measured in a state where the stress was released and the tip of the indenter. And measuring the residual stress of the pipe wall by comparing the distance with the distance.

[0010]

Since the marking device of the present invention employs a polygonal pyramid-shaped indenter, even if the apex is worn, for example, the position of the apex can be accurately determined by following the ridge line (generating line) of the pyramid. It is possible.

That is, in the above-described marking apparatus and measuring method of the present invention, it is possible to always accurately mark the distance between two points on the inner surface of the metal tube to be subjected to the residual stress. Precisely using a measuring microscope or the like, and by comparing this measured value with the distance between the tip of the marker indenter, without the need for pretreatment such as cleaning or polishing, and contaminated and Even in a thin metal tube, it is possible to easily and quickly measure the residual stress by remote control within a limited time.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

FIG. 1 is an overall view showing a marking apparatus for measuring residual stress according to an embodiment of the present invention, FIG. 2 is a partially omitted cross-sectional view showing an operation section and a head drive mechanism of the apparatus, and FIG. FIG. 4 is a partial cross-sectional view showing a state in which the head unit driving mechanism is viewed from below. As shown in FIG.
The marker head 2 is attached to the metal tube P of the nozzle penetrating portion K of the upper lid U.
And a plurality of stamps are made at predetermined locations.

That is, this marking device is shown in FIGS.
As shown in FIG. 5, the marker head 2 to which a plurality of polygonal pyramid-shaped indenters 1 are fixed at predetermined intervals, the marker head 2 is supported, and the marker head 2 is connected to a metal tube P. of moving so as to protrude radially outwardly, and the head portion driving mechanism 3 for performing engraving on the wall P ₁ by pressing the indenter 1, as shown in FIGS. 1 to 3, the head section drive mechanism 3 And an operation unit 5 for operating the head drive mechanism 3 from outside to the metal tube P via a hollow rod 4.

The marker head section 2 is, for example, shown in FIG.
2. A top c just above the center b of the bottom a as shown in FIG.
A plurality of indenters 1 having a regular triangular pyramid or a quadrangular pyramid are provided. These indenters 1 are made of a material having high hardness such as diamond, sapphire, or a hard metal.
Are fixed to the marker head 2 with the apex c of the pyramid as the tip and at a predetermined interval.

The fixing of the indenter 1 to the head portion 2 is performed by setting the line connecting the tips c of the indenter 1 to a straight line as shown in FIG. 7, a right-angled isosceles triangle as shown in FIG. A perfect equilateral triangle, a square as shown in FIG. 10, or FIG.
A rectangular shape as shown in FIG. Each of the indenters 1 is fixed to the marker head 2 by a strong adhesive.

Meanwhile, the head portion drive mechanism 3, the reaction force of Fig upon by protruding a marker head portion 2 as shown in 5, the marker head portion 2 which is pressed against the tube wall P ₁ by the projection receiving, abuts against the other part of the pipe wall P ₁ 2
It has a reaction force receiving member 6. This reaction force receiving member 6
Is screwed to the head drive mechanism 3, and by rotating this, the protrusion height can be adjusted according to the inner diameter of the metal tube P as shown in FIG. It is possible to make the indenter 1 of the head portion 2 accurately engrave.

As shown in FIGS. 2 and 3, the head drive mechanism 3 receives power transmitted by a motor 7 of the operation unit 5 through a drive shaft 8 inside the rod 4, as shown in FIGS. As shown in FIG. 4, the marker head 2 is projected and retracted by a rack 9 and a pinion 10. The projection and retreat of the marker head 2 are performed by operating a control switch provided on the operation unit 5. The strength of the marking by the indenter 1 is controlled by a torque limiter 12 provided between the motor 7 and the drive shaft 8 (the motor 7 can also be provided in the head drive mechanism). In addition, as shown in FIGS. 3 and 4, an indenter guard 11 that protects the retracted indenter 1 is provided above and below the marker head 2.

On the other hand, as shown in FIG. 2, a guide cap portion 13 is provided between the operation portion 5 and the head portion driving mechanism 3.
Are slidably inserted into the rod 4. The guide cap 13 is fixed to the rod 4 by tightening the knob 14, and engages with the insertion-side end of the metal tube P to position the marker head 2. . In addition, this guide cap portion 13
In addition, for example, a clamp 15 as shown in FIG. 1 may be additionally provided to more securely fix the metal pipe P.

In the method for measuring residual stress in a metal tube according to the embodiment of the present invention, the marker head 2 is inserted into the metal tube P as shown in FIG. 2 alms engraved by the plurality of the indenter 1 is pressed against the tube wall P ₁ by the head driving mechanism 3 as shown in FIG. 5, the stress opened to disconnect the tube wall P ₁ having been subjected to the stamping later from ambient to measure the residual stress of the tube wall P ₁ by comparing the distance between the tip distance and the indenter 1 between the marking measured while the stress releasing.

(Experimental Example 1) Using three or four marker head portions 2 as shown in FIGS.
The following verification was performed on a stainless steel pipe having a diameter of 70 mm, an outer diameter of 70 mm, and a length of 2 m. The following equation 1 was used to calculate the stress from the strain amount. The Young's modulus was calculated as 18000 kg / mm ² .

[0022]

## EQU1 ## x-direction stress σ _X = E · (1−γ ² ) · (ε _x
+ Ε _y · γ) y-direction stress σ _y = E · (1−γ ² ) · (ε _y + ε _x ·
γ) σ _x : x-direction stress E: Young's modulus ε _x : x-direction strain σ _y : y-direction stress γ: Poisson's ratio ε _y : y-direction strain

That is, a strain gauge (gauge length 1 mm, 120Ω, biaxial) is provided at one end of the pipe P in FIG.
After fixing to the position shown in (B), the end 50 mm was compressed with a compression tester, and when a certain load was reached, the engraved part was cut out from the opposite side of the pipe P, and between the two points in the pipe axial direction and the circumferential direction. Each distance was measured and compared with a strain gauge. Table 1 shows the results. In Table 1,-indicates a compressive force. However, four types of markers, a three-point marker and a four-point marker, were used, but the indenter was only a square pyramid diamond. As is clear from the above, it is understood that the measurement by the marking device and the measuring method of the present invention has obtained an accuracy equal to or higher than that of the method using the strain gauge. Below margin

[0024]

[Table 1]

[0025]

As described above, in the marking apparatus for measuring residual stress of a metal tube for a nuclear reactor according to the present invention, a plurality of polygonal pyramid-shaped indenters are fixed at predetermined intervals with the top of the pyramid as a tip. A head drive mechanism for supporting the marker head, moving the marker head and pressing against the tube wall to perform marking with the indenter, and a head drive mechanism for the pipe. And an operating section for operating the head section driving mechanism, which is externally supported via a rod, and always stamps the distance between two points on the inner surface of the metal tube accurately by the pyramidal indenter. It is possible to precisely measure the distance between the inscriptions after the stress is released and to compare the measured value with the distance between the indenter tips of the markers, especially before cleaning or polishing. It is possible to measure the residual stress easily and quickly by remote control within a limited time, even in a metal tube contaminated with radioactivity, which is difficult to measure, and which has been difficult to measure conventionally. Has a remarkable effect. The method for measuring the residual stress of the metal tube of the present invention is to perform the measurement using the marking device of the present invention, and even in the contaminated metal tube,
It is possible to measure the residual stress simply and quickly by remote operation and within a limited time.

[Brief description of the drawings]

FIG. 1 is an overall view showing a marking device for measuring residual stress according to an embodiment of the present invention.

FIG. 2 is a partially omitted sectional view showing the vicinity of an operation unit and a head unit driving mechanism of the apparatus.

FIG. 3 is a side view showing a head drive mechanism of the apparatus.

FIG. 4 is a partial cross-sectional view showing a state in which the head drive mechanism is viewed from below.

FIG. 5 is a bottom view showing the head drive mechanism with the indenter projected.

FIG. 6 is a bottom view showing a head drive mechanism in a state where an indenter is projected from metal tubes having different inner diameters.

FIG. 7A is a front view showing a two-point marker head used in the measurement method of the present invention. (B) The same is a side view.

FIG. 8A is a front view showing another example of the three-point marker head. (B) The same is a side view.

FIG. 9A is a front view showing another example of the three-point marker head. (B) The same is a side view.

FIG. 10A is a front view showing the four-point marker head. (B) The same is a side view.

FIG. 11A is a front view showing another example of the four-point marker head. (B) The same is a side view.

FIG. 12A is a front view showing a triangular pyramid-shaped indenter. (B) It is a side view.

FIG. 13A is a front view showing a quadrangular pyramid-shaped indenter. (B) It is a side view.

FIG. 14A is a schematic view showing a state of a stress measurement test using a pipe. (B) It is a schematic diagram which shows the state of the stress measurement test performed by changing 90 degree angle from FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Indenter 2 Marker head part 3 Head part drive mechanism 4 Rod 5 Operation part 6 Reaction force receiving member 7 Motor 8 Drive shaft 9 Rack 10 Pinion 11 Indenter guard 12 Torque limiter 13 Guide cap part 14 Knob 15 Clamp

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Nakajima 123, Osamu, Minami-Ina, Yasuma-machi, Seika-cho, Soraku-gun, Kyoto Prefecture Nuclear Safety Systems Research Institute, Inc. (72) Hiromichi Mitsuda Hirokazu Mitsuda 123, Otani Minami-Ina, Yasuma, Small Sub-unit, Otani Nuclear Safety Systems Laboratory Co., Ltd. (56) References JP-A-8-247914 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G21C 17/00-17/14

Claims (6)

(57) [Claims] 1. A marking device for measuring residual stress, wherein a marker head portion is inserted into a metal tube used in a nuclear reactor and a predetermined portion is marked, wherein a plurality of polygonal pyramid-shaped indenters are formed by the pyramid. A marker head section fixed at a predetermined interval with the top of the tip as a tip, and a head section drive for supporting the marker head section, moving the marker head section and pressing the pipe against the tube wall to perform marking with the indenter. A residual stress measurement of a metal tube for a nuclear reactor, comprising: a mechanism; and an operating unit for supporting the head unit driving mechanism via a rod from outside the metal tube and operating the head unit driving mechanism. Marking device. 2. The method according to claim 1, wherein the head drive mechanism causes the marker head to protrude radially outward of the metal tube, and receives a reaction force of the marker head pressed against the tube wall by the protrusion. 2. The marking device for measuring residual stress in a metal tube for a nuclear reactor according to claim 1, further comprising a reaction force receiving member abutting on another portion of the marking. 3. The marker head section is slidably and slidably inserted into the rod between the operation section and the head section driving mechanism, and is engaged with an insertion end of a metal tube. The marking device for measuring residual stress of a metal tube for a nuclear reactor according to claim 1 or 2, further comprising a guide cap portion for positioning. 4. The method according to claim 1, wherein the indenter is diamond, sapphire,
4. The metal pipe for a nuclear reactor according to claim 1, wherein the polygonal pyramid is formed of any one of a cemented carbide metal, and a shape of the polygonal pyramid formed by the indenter is a polygonal pyramid having a top portion at the center of a bottom surface. Marking device for measuring residual stress. 5. The residual stress of a metal tube for a nuclear reactor according to claim 1, wherein the plurality of indenters are arranged such that a line connecting the tips of the indenters forms a straight line or a polygon. Marking device for measurement. 6. The marking device according to claim 1, wherein the marker head is inserted into a metal tube used for a nuclear reactor, and the marker head is inserted into the head. The drive mechanism presses against the pipe wall to perform engraving with the plurality of indenters.Then, the engraved pipe wall is separated from the surroundings to release stress. A method for measuring the residual stress of a metal tube for a nuclear reactor, comprising measuring the residual stress of the tube wall by comparing the distance between the tips of the indenters with the distance.