JP3052559B2 - Inspection equipment for welded joints under the reactor pressure vessel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting a welded joint of a lower mirror of a reactor pressure vessel.

[0002]

2. Description of the Related Art In general, as one of inspections for confirming the soundness of a reactor pressure vessel, a flaw inspection is performed on a welded portion of the reactor pressure vessel. For example, the inspection is performed while the inspection device is moved along the welded portion by mounting the ultrasonic inspection device on a traveling vehicle and traveling along the inspection location.

[0003] In this case, if the inspection target is a girth weld joint provided in the lower part of the reactor pressure vessel, the skirt portion of the reactor pressure vessel exists outside the girth weld joint,
The inspection work environment of the girth welded joint becomes a narrow part, and in a periodic inspection or the like after the start of the operation of the reactor, the work environment becomes a radioactive atmosphere, so that the entry and exit of workers are easily restricted.

Conventionally, as a method for efficiently performing a periodic inspection under such an environment, for example, a guide rail for moving an ultrasonic flaw detector along a circumferential direction is provided on an inner peripheral surface of a skirt portion of a reactor pressure vessel. Ultrasonic waves while traveling on a carriage mounted on the guide rail and a probe attached to the carriage and moving on a linear guide or the like arranged in a direction perpendicular to the guide rail. A flaw detection apparatus for performing flaw detection has been considered.

[0005]

In such a flaw detection apparatus, a linear guide or the like provided for moving the probe in a direction perpendicular to the guide rails has at least a moving distance of the probe. It must have the same length as.

However, since structures such as control rod casings and the like are provided in the lower mirror section of the reactor pressure vessel, these structures may interfere with long linear guides and become flaw detectors. In addition, there has been a problem that it is difficult to move a cart equipped with the flaw detection device.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to enable a probe to be moved at a site to be inspected having a narrow portion and to improve the efficiency of an inspection operation. It is assumed that.

[0008]

In order to effectively solve the above problems, the present invention proposes the following four means.
The first means includes: a guide rail disposed along a circumferential direction inside a skirt portion formed in a lower mirror portion of the reactor pressure vessel; and a movable trolley attached to the guide rail and moved horizontally. A traveling vehicle mounted on the movable vehicle, transported to the inspection position, and separated from the movable vehicle to travel on an outer surface of the lower mirror portion in a direction orthogonal to a circumferential direction. The traveling vehicle has a magnet wheel magnetically attached to the outer surface of the lower mirror portion, and a magnet wheel which is magnetically magnetized to the outer surface of the lower mirror portion, is disposed in close contact with the outer surface of the lower mirror portion, and is in the vicinity of the welding joint. An inspection probe for performing a flaw detection inspection is provided, and the movable trolley is provided with an attachment / detachment mechanism for attaching / detaching the probe traveling vehicle. ing. The second means includes a lift mechanism having an attachment / detachment mechanism attached to the moving carriage, a traveling vehicle holding table attached to the lifting mechanism and moved toward and away from the outer surface of the lower mirror unit, and An inspection device for a welded joint under a reactor pressure vessel, comprising a clamp mechanism for positioning and fixing a traveling vehicle, has been proposed. The third means is an atom provided with a jack-up mechanism provided on the probe traveling vehicle, the jack-up mechanism being attached to the probe traveling vehicle and pressing the outer surface of the lower mirror portion to separate magnetic attachment between the magnet wheel and the lower mirror portion. We have proposed an inspection device for the welded joint of the lower part of the furnace pressure vessel. Fourth means is a reactor pressure vessel lower mirror section welding joint provided with a probe traveling mechanism, the probe traveling mechanism being attached to the probe traveling vehicle and moving the inspection probe in a circumferential direction. Has proposed an inspection device.

[0009]

According to the first means, the movable trolley is moved in the circumferential direction along the guide rail inside the skirt portion of the reactor pressure vessel. Then, the probe traveling vehicle mounted on the movable carriage is conveyed to the inspection position of the lower mirror section and positioned in the circumferential direction. At this position, when the attaching / detaching means is opened and the probe traveling vehicle is separated, the magnet wheel of the probe traveling vehicle magnetically attaches to the outer surface of the lower mirror portion. At this time, the inspection probe provided on the probe traveling vehicle is arranged in close contact with the outer surface of the lower mirror unit, and the inspection probe is moved while the probe traveling vehicle is moved in a direction perpendicular to the circumferential direction. By operating the contactor, a flaw detection inspection near the weld joint is performed. Then, after the inspection position has been inspected, the probe traveling vehicle is mounted on the movable carriage by the attaching / detaching means, and the movable carriage is moved to transport the probe traveling vehicle to the next inspection position. By repeating this work,
A flaw inspection near the weld joint of the lower pressure vessel of the reactor pressure vessel is performed over the entire circumference. According to the second means,
The traveling vehicle holding base to which the probe traveling vehicle is attached by the clamp mechanism is actuated by the lift mechanism to approach the outer surface of the lower mirror unit, and the magnet wheel is magnetically attached to the outer surface of the lower mirror unit. Thereafter, the clamp mechanism is released, and the lift mechanism is operated in the reverse direction to move the traveling vehicle holding table in a direction away from the outer surface of the lower mirror unit, thereby separating the traveling vehicle and the probe traveling vehicle. After the inspection is completed, the lift mechanism is operated to bring the traveling vehicle holder and the probe traveling vehicle into contact with each other. By operating the mechanism in the opposite direction, the probe vehicle is pulled away from the outer surface of the lower mirror. According to the third means, the magnet wheel is pulled away from the outer surface of the lower mirror portion by operating the jack-up mechanism attached to the probe traveling vehicle to press the outer surface of the lower net portion. According to the fourth means, by operating the probe moving mechanism, the probe for inspection is moved in the circumferential direction while the position of the probe traveling vehicle is fixed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the inspection apparatus for a welded joint under a reactor pressure vessel head according to the present invention will be described below with reference to FIGS. In each of these figures, reference symbol X is a reactor pressure vessel, Y is a lower mirror portion, Z is a skirt portion, A is a welded joint,
B is a control rod housing, C is a heat insulating material, 10 is an inspection device,
11 is a guide rail, 11a is an edge, 12 is a support bracket, 13 is a rack, 14 is a pinion, 15 is a movable carriage, 16 is a wheel, 16a is an engagement groove, 17 is a movable carriage drive mechanism, 17a is a motor, and 17b is a motor. Encoder, 17
c is a gear box, 18 is an attachment / detachment mechanism, 19 is a lift mechanism, 19a is a linear guide, 20 is a traveling vehicle holder, 21
Is a lift cylinder, 22 is a clamp mechanism, 22a is a positioning ridge, 22b is a positioning groove, 22c is a contact portion,
2d is a connecting leg, 22e is a clamp cylinder, 22f is a roller, 22g is a slope, 23 is a cable support device, 2
4 is a probe vehicle, 25 is a magnet wheel, 25a is a connection shaft, 25b is a bearing, 26 is a probe vehicle drive mechanism,
26a is a motor, 26b is an encoder, 26c is a gear box, 26d is a chain, 26e is a sprocket, 2
6f is a belt, 26g is a pulley, 27 is an inspection probe,
27a is a detector, 27b is a probe bracket, 27c is a probe pressing spring, 28 is a probe moving mechanism, 28a is a linear guide, 28b is a probe cylinder, 29 is a jack-up mechanism, and 29a is a jack. Up cylinder, 29
b is a link, 29c is a fulcrum, and 29d is an auxiliary roller.

As shown in FIG. 5, a lower mirror portion Y and a skirt portion Z are formed at a lower portion of the reactor pressure vessel X. It is assumed that the lower mirror portion Y and the skirt portion Z are formed of a ferromagnetic material such as low alloy steel. The lower mirror part Y has a spherically curved surface, and a plurality of control rod housings B for accommodating control rods inserted into the reactor pressure vessel X are provided in a portion corresponding to the bottom surface of the reactor pressure vessel X. Have been. The skirt portion Z is formed in a vertical cylindrical shape and supports the reactor pressure vessel X. The lower mirror portion Y at an intermediate position between the control rod housing B and the skirt portion Z is provided with a connection portion by a welding joint A over the entire circumference of the lower mirror portion Y.

The guide rail 11 is an annular track arranged in a horizontal state, and is disposed substantially immediately below the welded joint A with an interval from the outer surface of the lower mirror portion Y. The guide rail 11, for example, is formed in a cylindrical shape as shown in FIG. 5, and has a rolling surface on its upper and lower end surfaces for rolling a wheel 16 of a movable carriage 15 described later. The rolling surface has an edge 11a projecting up and down.
, And holds the movable carriage 15 so as not to fall off the guide rail 11.
The guide rail 11 is fixed to a heat insulating material C disposed below the reactor pressure vessel X by a support bracket 12 as shown in FIG. On the outer surface of the guide rail 11, a rack 13 having a tooth profile formed on the lower surface is attached. The rack 13 is provided in the circumferential direction along the guide rail 11 in parallel with the guide rail 11, and is engaged with a pinion 14 rotated by a movable carriage drive mechanism 17 described later to move the movable carriage 15 to the guide rail 1.
1 can be moved to a desired position.

The movable carriage 15 is attached to the guide rail 11 and the guide rail 1
A wheel 16 that guides along the vehicle 1, a moving vehicle drive mechanism 17 that moves the moving vehicle 15, and a detachable mechanism 18 that attaches and detaches a probe traveling vehicle 24 described below are attached.

The wheel 16 is mounted on the guide rail 1
Four wheels rolling in contact with one rolling surface, all of which are rotatably supported in the same plane, and contact two by two in the vertical direction of the guide rail 11. Are arranged as follows. On the outer surface of the wheel 16 that comes into contact with the rolling surface of the guide rail 11, an engagement groove 16a that is engaged with the edge 11a of the guide rail 11 is formed.

The moving carriage drive mechanism 17 includes a motor 17a for rotating the pinion 14, and an encoder 17b for detecting the rotational position of the pinion 14.
The pinion 14, the motor 17a, and the encoder 17b are connected to each other via a gear box 17c.

The attachment / detachment mechanism 18 includes a lift mechanism 19 attached to the movable carriage 15, a traveling vehicle holding table 20 which is moved toward and away from the outer surface of the lower mirror Y by the lifting mechanism 19, And a clamp mechanism 22 for positioning and fixing the probe traveling vehicle 24.

In the lift mechanism 19, a traveling vehicle holding base 20 is mounted on a linear guide 19a disposed vertically, and a lifting cylinder 21 is disposed between the traveling vehicle holding base 20 and the moving vehicle 15. By operating the lift cylinder 21, the traveling vehicle holding base 20 is moved in a direction to approach or separate from the outer surface of the lower mirror portion Y.

The clamp mechanism 22 includes the traveling vehicle holding base 2.
And a receiving part 20a which is provided at the upper part of the lower part 0 and is inclined at an angle substantially equal to the inclination of the tangent of the outer surface of the lower mirror part Y which is located above, and which is provided on the probe vehicle 24 and is in close contact with the receiving part 20a when connected And a positioning ridge 22 for positioning the connecting leg 22d with respect to the receiving portion 20a.
a, a positioning groove 22b and an abutting portion 22c, and a clamp cylinder 22e that holds the positioned connecting leg 22d and receiving portion 20a in a pressure-contact state.

The positioning ridge 22a is connected to the receiving portion 2
The positioning groove 22b is provided on the upper surface of the guide rail 11 in a direction orthogonal to the guide rail 11, and the positioning groove 22b is formed on the lower surface of the connecting leg 22d so as to be in close contact with the positioning ridge 22a. By disposing the carriages 22b in close contact with each other, the movable carriage 15 and the probe traveling vehicle 24 are restrained in a direction along the guide rails 11. The abutting portion 22c is provided on the inclined receiving portion 2.
0a is formed to protrude upward from the lower edge, and abuts the connecting leg 22d connected to the receiving portion 20a to move the probe traveling vehicle 24 in the direction orthogonal to the guide rail 11 with respect to the movable carriage 15. It is designed to be positioned.

The clamp cylinders 22e are arranged at both ends of the traveling vehicle holding base 20 along the guide rail 11 so as to face each other, and when the probe traveling vehicle 24 is connected to the traveling vehicle holding base 20. The cylinder rod is protruded, and a roller 22 f provided at the tip of the cylinder rod is connected to the connecting leg 22.
By pressing the connecting leg portion 22d and the receiving portion 20a against the slope 22g provided at the position d, the connecting leg portion 22d and the receiving portion 20a are held in a pressed state.

The probe traveling vehicle 24 drives, for example, two sets of four magnet wheels 25 attached to both ends of two connecting shafts 25a arranged in parallel with each other, and the magnet wheels 25. Probe driving mechanism 26
And a probe 27 for inspection arranged at a position surrounded by the four magnet wheels 25, and a probe for moving the probe 27 for inspection in a direction perpendicular to the traveling direction of the probe traveling vehicle 24. It has a moving mechanism 28 and a jack-up mechanism 29 for separating a set of magnet wheels 25 from the outer surface of the lower mirror part Y when connecting the probe traveling vehicle 24 and the moving carriage 15. Further, the probe traveling vehicle 24 is mounted on the guide rail 1.
The moving carriage 15 is mounted on a cradle so as to move in a direction orthogonal to the direction 1.

The magnet wheel 25 is arranged at a position where it can be simultaneously magnetized on the outer surface of the lower mirror part Y, and is rotatably supported by a bearing 25b supporting a connecting shaft 25a.

The probe driving mechanism 26 includes a motor 2 mounted on one connecting shaft 25a via a gear box 26c, a chain 26d and a sprocket 26e.
6a and an encoder 26b connected to the other connecting shaft 25a via a pulley 26g and a belt 26f.

When the magnet wheel 25 is magnetically attached to the outer surface of the lower mirror portion Y, the inspection probe 27 has a detecting portion 27a that comes into contact with the outer surface of the lower mirror portion Y, and a detecting portion 27a. A probe bracket 27b that holds the magnet wheel 25 so as to be slidable in the axial height direction, and is disposed between the probe bracket 27b and the detection unit 27a and attached to the outer surface of the lower mirror unit Y. A probe pressing spring 27c for urging the detection unit 27a in the outer surface direction of the lower mirror unit Y is provided.

The probe moving mechanism 28 includes a linear guide 28a that is disposed along the connecting shaft 25a of the magnet wheel 25 and supports the probe bracket 27b so as to move linearly. The inspection probe 27 is disposed between the touching vehicle 24 and the linear guide 28a.
And a probe cylinder 28b that moves linearly along the axis.

In the example shown in FIG. 4, the jack-up mechanism 29 is an L-shaped link that is rotatably mounted on a side surface of a traveling vehicle 24 located at both ends of a pair of magnet wheels 25 around a fulcrum 29c. 29b and the link 29
an auxiliary roller 29d rotatably attached to one end of the link shaft 25b about an axis parallel to the connection shaft 25a;
And a jack-up cylinder 29a that swings the link 29b around the fulcrum 29c. The jack-up mechanism 29 adjusts the respective distances from the fulcrum 29c to the axis of the auxiliary roller 29d and from the fulcrum 29c to the connecting portion of the jack-up cylinder 29a. At 29d, the outer surface of the lower mirror Y is pressed to
The magnet wheel 25 in a magnetically attached state is separated from the outer surface of the lower mirror portion Y on the outer surface of the lower mirror portion Y.

In each of the drawings, the cable support device 2
Reference numeral 3 denotes motors 17a and 26a for driving the moving carriage 15 and the probe vehicle 24, cables (reference numerals D) for the encoders 17b and 26b, and cylinders 21 and 22e.
-It supports a tube for supplying air to 28b and 29a.

In order to perform a flaw detection inspection of the welded joint A of the reactor pressure vessel lower mirror section Y using the inspection apparatus 10 configured as described above, first, the probe traveling vehicle 24 is moved to the traveling vehicle 15 The movable carriage drive mechanism 17 is operated while being mounted on the holding platform 20 to move the probe traveling vehicle 2 to a position in the circumferential direction of the inspection target location.
4 is conveyed. Next, the lift mechanism 19 is operated to bring the probe traveling vehicle 24 close to the outer surface of the lower mirror portion Y, and the probe traveling vehicle 2
The four magnet wheels 25 provided in 4 are magnetically attached to the outer surface of the lower mirror portion Y. At this time, the detection portion 27a of the inspection probe 27 attached to the probe traveling vehicle 24 is held in close contact with the outer surface of the lower mirror portion Y by the probe pressing spring 27c. In this state, the clamp mechanism 22 is released to disconnect the probe traveling vehicle 24 from the movable trolley 15, and the lift mechanism 19 is operated in the reverse direction to disconnect the two trolleys. As a result, the probe traveling vehicle 24 is independently attached to a position in the middle of the flaw detection inspection area on the outer surface of the lower mirror portion Y by the magnetic force of the magnet wheel 25, and can be moved in a direction orthogonal to the guide rail 11.

Then, while operating the probe traveling vehicle drive mechanism 26 to move the probe traveling vehicle 24 in a direction perpendicular to the guide rail 11, that is, in a direction perpendicular to the weld joint A, the inspection probe 27 is moved. By operating, a flaw detection inspection near the welded joint A is performed.

Next, when the probe traveling vehicle 24 reaches the end of the region where the flaw detection inspection is performed, the probe moving mechanism 28 is operated to move the inspection probe 27 to the stroke of the probe cylinder 28b. It is moved in the direction perpendicular to the traveling direction of the probe traveling vehicle 24 by the distance. Then, the probe traveling vehicle drive mechanism 26 is operated in the opposite direction to move the probe traveling vehicle 24 in the direction in which it has moved, and the inspection probe 27 is activated in the meantime. The flaw detection inspection of a different path by the stroke of the cylinder 28b is performed. Similarly, when reaching the other end of the area where the flaw detection inspection is performed, the probe cylinder 28b is operated in the reverse direction to return the flaw detection path of the inspection probe 27, and the probe driving vehicle is driven again. By performing the flaw inspection while reversing the mechanism 26,
The flaw detection inspection of the two different routes is completed, and the probe traveling vehicle 24 is returned to a position separated from the movable carriage 15.

In this state, the lift mechanism 1 of the movable carriage 15
9 is operated to raise the traveling vehicle holding base 20. Then, the receiving portion 20a of the traveling vehicle holding base 20 is
4 and the positioning leg 22a, the positioning groove 22b, and the abutting portion 22c, when the two are positioned in close contact with each other, the clamp mechanism 22 is operated to operate the probe traveling vehicle 24 and the movable truck. 15 is connected.

Here, the jack-up cylinder 29a
, The outer surface of the lower mirror portion Y is pressed by the auxiliary roller 29d, and one of the two magnetized magnet wheels 25 is separated from the outer surface of the lower mirror portion Y. The magnetic force for attaching to the lower mirror portion Y is weakened. Then, by moving the lift mechanism 19 and lowering the traveling vehicle holding table 20 in a state where the magnetic force is weakened in this way, the probe traveling vehicle 24 is completely separated from the lower mirror portion Y, and the moving vehicle driving mechanism By actuating 17, the movable cart 15 can be moved along the guide rail 11 to the circumferential position of the next inspection target location.

<Other Embodiments> In the inspection apparatus 10 for the welded joint A under the reactor pressure vessel head according to the present invention, the following technique can be adopted. (1) The number of magnet wheels 25 and wheels 16 should be 3 or 5 or more. (2) Lift cylinder 21 and probe cylinder 28
b, Another actuator is used in place of the clamp cylinder 22e and the jack-up cylinder 29a. (3) Instead of the positioning ridge 22a, the positioning groove 22b, and the abutting portion 22c, another positioning means is used. (4) Instead of the cylindrical guide rail 11, a flat guide rail is used, and the wheel 16 is arranged to rotate in a horizontal plane. (5) The edge 11a of the guide rail 11 and the engagement groove 16a of the wheel 16 are reversed.

[0034]

According to the first invention, that is, the apparatus for inspecting a welded joint of a lower part of a reactor pressure vessel according to the first aspect of the present invention, a movable carriage is moved in a circumferential direction along a guide rail inside a skirt. The traveling vehicle mounted on the traveling vehicle is positioned in the circumferential direction, the connection between the traveling vehicle and the traveling vehicle is released by releasing the attachment / detachment mechanism, and the magnet wheel is magnetically attached to the outer surface of the lower mirror unit. The inspection probe is operated while moving the probe traveling vehicle alone in the direction perpendicular to the circumferential direction in the worn state, so that the flaw inspection near the weld joint is performed. There is an effect that the mechanism can be configured compact. The second invention,
That is, the inspection device for the welded joint under the reactor pressure vessel mirror according to the invention of claim 2 has the effect of the inspection device according to the invention of claim 1, and the attachment / detachment mechanism includes a traveling vehicle mounted with a probe traveling vehicle. Since it has a vehicle holding base, a lift mechanism for moving the traveling vehicle holding base toward and away from the outer surface of the lower mirror portion, and a clamp mechanism for positioning and fixing the probe traveling vehicle on the traveling vehicle holding base, In the narrow part, the attachment and detachment of the traveling vehicle holding base and the probe traveling vehicle are reliably performed, and the effect that the reliability of maintenance work by remote control can be improved. A third invention, that is, an inspection device for a welded joint under a reactor pressure vessel head according to the invention of claim 3 has the effect of the inspection device according to the invention of claim 1 or 2, and has a probe traveling. The car is provided with a jack-up mechanism that presses the outer surface of the lower mirror section to separate the magnetic adhesion between the magnet wheel and the lower mirror section. It is possible to improve the repetition reliability of the removal operation of the probe traveling vehicle that is repeatedly performed in the flaw detection inspection.
The fourth invention, that is, the inspection apparatus for the welded joint under the reactor pressure vessel head according to the invention of the fourth invention has the above-mentioned effect and also moves the inspection probe to the probe vehicle in the circumferential direction. Since the probe moving mechanism is provided, it is possible to change the probe path of the inspection probe without moving the traveling path of the probe traveling vehicle, thereby improving the efficiency of the probe inspection. Can be.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing an embodiment of an inspection apparatus for a welded joint under a reactor pressure vessel head section according to the present invention.

FIG. 2 is a front view showing the inspection device of FIG. 1;

FIG. 3 is a front view showing a probe traveling vehicle of the inspection device of FIG. 1;

FIG. 4 is a front view showing a jack-up mechanism of the inspection device of FIG. 1;

FIG. 5 is a schematic view showing an implementation state of an inspection of a welded joint by the inspection device of FIG. 1;

[Explanation of symbols]

 X Reactor pressure vessel Y Lower mirror part Z Skirt part A Weld joint B Control rod housing C Insulation material D Cable 10 Inspection device 11 Guide rail 11a Edge 12 Support bracket 13 Rack 14 Pinion 15 Moving trolley 16 Wheel 16a Engaging groove 17 Moving Cart drive mechanism 17a Motor 17b Encoder 17c Gear box 18 Attaching / detaching mechanism 19 Lift mechanism 19a Linear guide 20 Traveling vehicle holding stand 20a Receiving part 21 Lifting cylinder 22 Clamp mechanism 22a Positioning ridge 22b Positioning groove 22c Abutting part 22d Connecting leg 22e Clamp cylinder 22f Roller 22g Slope 23 Cable support device 24 Probe traveling vehicle 25 Magnet wheel 25a Connecting shaft 25b Bearing 26 Probe traveling vehicle driving mechanism 26a Motor 26b Encoder 2 c Gear box 26d Chain 26e Sprocket 26f Belt 26g Pulley 27 Inspection probe 27a Detector 27b Probe bracket 27c Probe pressing spring 28 Probe moving mechanism 28a Linear guide 28b Probe cylinder 29 Jack-up mechanism 29a jack-up cylinder 29b link 29c fulcrum 29d auxiliary roller

Continuation of the front page (72) Inventor Akinori Kondo 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawa Shima-Harima Heavy Industries Co., Ltd. Toni Technical Center (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 29/00-29/28

Claims (4)

(57) [Claims] 1. A guide rail disposed along a circumferential direction inside a skirt portion formed in a lower mirror portion of a reactor pressure vessel, a movable trolley attached to the guide rail and horizontally turned. A probe traveling vehicle mounted on the movable vehicle and transported to the inspection position and separated from the movable vehicle and allowed to travel on the outer surface of the lower mirror portion in a direction orthogonal to the circumferential direction. A magnet wheel magnetically attached to the outer surface of the lower mirror portion, and a flaw detection inspection near the welded joint which is disposed in close contact with the outer surface of the lower mirror portion when the magnet wheel is magnetically attached to the outer surface of the lower mirror portion. An inspection probe for performing the inspection, and an attaching / detaching mechanism for attaching / detaching the traveling vehicle is provided on the movable trolley. 2. A detachable mechanism, comprising: a traveling vehicle holder on which a probe traveling vehicle is mounted; and a mounting member mounted between the traveling vehicle holder and the movable vehicle. 2. The inspection of a welded joint under a reactor pressure vessel bottom mirror according to claim 1, further comprising a lift mechanism for separating and a clamp mechanism for positioning and fixing the probe traveling vehicle on the traveling vehicle holding table. apparatus. 3. The probe traveling vehicle is provided with a jack-up mechanism for pressing an outer surface of the lower mirror portion to separate magnetic attachment between the magnet wheel and the lower mirror portion. Item 3. An inspection device for a welded joint under a reactor pressure vessel head section according to Item 2. 4. The probe traveling mechanism according to claim 1, wherein the probe traveling vehicle is provided with a probe moving mechanism for moving the inspection probe in a circumferential direction. Inspection equipment for welded joints under the reactor pressure vessel.