JPH0321895A - Inspecting device for thimble tube for in-furnace instrumentation - Google Patents

Abstract

PURPOSE:To confirm soundness remotely by providing a support structure which is positioned at a specific position on a lower reactor core plate, an underwater monitoring device which is supported rotatably on the support structure, and an information processing and displaying device. CONSTITUTION:A polar crane positions the eye bolts 22 of the inspecting device 20 so that through holes are aligned with the thimble tube 27. The tube 27 is pressed to project the tip from the reactor core plate 6. The tip part is photographed by an image pickup camera is projected on a monitor television 33. When such trouble as thickness reduction is confirmed on the television 33, an operation part 23 is operated to rotate a barrel 21b and rotate the underwater monitoring device 24, thereby grasping the circumference-directional thickness reduction state of the tube 27. When the thickness reduction is measured, the barrel 21b is stopped from rotating at the angular position where there is the thickness reduction and the image is enlarged by an image processor 32. Then a longitudinal and a lateral movement cursor are projected in the image on the television 33 through the operation of a microscaler 31 and moved along the external diameter of the tube 27 to measure numerals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thimble tube for in-core instrumentation, and more particularly to an inspection device for remotely inspecting and displaying the appearance of the thimble tube.

[Prior Art] In a nuclear reactor, as shown in FIG.
A large number of fuel assemblies 2 are loaded inside the reactor core 3. In order to improve power density, improve burnup, or stabilize xenon oscillations by controlling the power distribution within the core 3, a neutron detector (not shown) is installed in a predetermined part of the fuel assembly 2 described above. ) is provided to measure the local neutron flux within the reactor.

Although not shown, a hollow tube called an instrumentation tube runs through the center of each fuel assembly 2, and a thimble tube containing the above-mentioned neutron detector is connected from the bottom 1a of the reactor vessel 1 to the bottom 1a of the reactor vessel 1. It enters the hollow tube through the lower core support plate 5, lower core plate 6, etc., and extends to the top of the fuel assembly 2, that is, near the upper nozzle.

Outside the reactor vessel 1, this thimble tube passes through a conduit tube 8 from the seal table 7 to the bottom 1a of the reactor vessel, is guided into the reactor vessel 1 via a reactor vessel penetration pipe 9, and is guided into the reactor vessel 1 through a reactor vessel penetration pipe 9. A path from the bottom 1a to the lower core plate 6 passes through an in-core instrumentation guide pipe 10.

[Problem to be solved by the invention M] In this way, the thimble tube is
Since the thimble tube is surrounded by tubular members such as the thimble tube and the in-furnace instrumentation guide tube 10, it is not thought that the thimble tube will suffer wear or the like, and its integrity has not been confirmed in the past.

However, when reviewing information on recent nuclear reactor operating conditions overseas, it has become clear that thimble tubes also need to be inspected for wall thinning and leakage due to fretting wear.

Therefore, an object of the present invention is to provide a conventionally non-existent inspection device that can remotely confirm the health of a thimble tube for in-core instrumentation.

[Means for Solving the Problems] In order to achieve this object, an inspection device for a thimble tube for in-core nuclear instrumentation according to the present invention extends from below a lower core plate into a fuel assembly on the lower core plate. a support structure positioned at a predetermined position on the lower core plate for monitoring and inspecting the inserted core instrumentation thimble tube; and the support structure for monitoring the entire circumference of the thimble tube. It has an underwater monitoring device rotatably supported by the underwater monitoring device, and an information processing/display device connected to the underwater monitoring device and processing and displaying the outer diameter information of the thimble tube.

[Operation] First, a positioning bottle is inserted into the flow passage hole of the lower core plate to position the support structure at a predetermined position. When the support structure is in this position, pushing out the thimble tube from below allows the tip of the thimble tube to advance upwardly within the support structure, allowing the underwater monitoring device to move the thimble tube to the desired position. Can be monitored over a long period of time.

Additionally, the underwater monitoring device supported by the support structure is rotatable, so that the entire circumference of the thimble tube is monitored.

The outer diameter information of the thimble tube obtained by the underwater monitoring device is sent to an information processing and display device consisting of a camera control device, a microscaler, an image processing device, a monitor TV, etc., where the health of the thimble tube can be checked remotely. It is confirmed.

[Embodiments] Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts.

As explained in connection with the prior art with reference to FIG. 4, the tip of the thimble tube to be inspected according to the invention typically extends close to the top of the fuel assembly 2 (FIG. 1). Therefore, the thimble tube cannot be inspected in this state, so during periodic inspections, etc., the thimble tube should be pulled back until its tip is located near or inside the lower core plate 6. , 1st
Remove the upper lid 1b of the reactor vessel 1 shown in the figure,
Inner reactor upper structure 11 and fuel assembly 2 in reactor vessel 1
etc., to expose the lower core plate 6.

FIG. 1 shows an inspection device 20 according to the present invention installed in a reactor vessel in which the lower core plate 6 is exposed as described above. When the upper lid of the reactor vessel is removed, the reactor cavity where the reactor is installed is filled with water up to the level 13 shown in the figure, so the inspection device 20 can detect water from the vicinity of the lower core plate 6. It first includes an elongated support structure 21 extending above the water level 13 .

This support structure 2l, which rotatably supports the underwater monitoring device 24 at its lower end, consists of a hollow inner cylinder 21a and a hollow outer cylinder 21b surrounding the inner cylinder 21a. An eye bolt 22 is attached to the top of the inner cylinder 21a.
2 is engaged with a hook 15a of a machine hoist 15 that can run on the operation floor 14 of the reactor cavity, and the inspection device 20 can be hung. The L-shaped member extending from the machine hoist 15 is a fixture 15b for the support structure 21. An operating section 23 is provided at the top of the outer cylinder 2lb.
By this rotational operation of the operation part 23, the outer cylinder 2lb is moved to the inner cylinder 2.
It is rotatable about 1a.

As can be understood from FIG. 1, the outer cylinder 2lb consists of a plurality of cylindrical parts having flanges at both ends, and the flanges of adjacent cylindrical parts are connected to each other by bolts to form the outer cylinder 2lb. I am disciplined. Moreover, the inner cylinder 21a has a similar structure.

Next, as is clear from FIG. 2, which shows the lower end portion of the above-mentioned inspection device 20 in detail in an enlarged manner, the lower end of the outer cylinder Zlb includes:
A pedestal 26 is provided on which a positioning or guide pin 25 for the inspection device 20 extends downward.

This pedestal 26 consists of a lower stationary part 26a from which the above-mentioned positioning pin 25 extends, and an upper rotating part 26c rotatably connected to the lower stationary part 26a via a bearing 26b. The moving part 26c is appropriately fixed to the lower edge of the outer cylinder 2lb. Furthermore, a through hole 26d through which the thimble tube 27 is inserted is formed in the pedestal 26 as shown. Therefore, as shown in FIG.
The outer cylinder 2lb can be rotated by inserting it into a coolant passage hole (not shown) formed in the lower core plate 6 and then rotating the operating section 23 described above.

As described above, and as shown in FIG. 1, the tip 27a of the thimble tube 27 is located near the lower core plate 6 when the inspection device 20 of the present invention is installed. In order to perform inspection gradually from the tip 27a to the lower part, a notch or window 28 is provided at the lower end of the outer cylinder 2l1).
The thimble tube 27, which enters the lower end of the inner tube 21a that hangs slightly below the upper edge of the window 28 and is pushed upward, is passed through the window 28 to the underwater monitoring device 2.
4 allows for monitoring.

The underwater monitoring device 24 has an imaging camera 24a and an illuminator 24b, the illumination of the illuminator 24b is adjusted by a dimmer 29 via a line 29a, and e.g. a video signal from the imaging camera 24a is transmitted via a line 30a. and is sent from the camera control device 30. A monitor television 33 is connected to the camera control device 30 via a microscaler 31 and an image processing device 32, and the image of the thimble tube 27 is displayed on the cathode ray tube of the monitor television 33. . The above-mentioned devices 29 to 33, which constitute an information processing/display device 34 that is connected to the underwater monitoring device 24 and processes and displays information on the outer diameter of the thimble tube 27, are provided at appropriate positions outside the reactor vessel. .

Next, the operation of the inspection device 20 according to the present invention will be explained with reference to FIGS. 1 and 2. First, the eye bolt 22 of the inspection device 20 is suspended by a polar crane (not shown), and the positioning bin 25 is moved through the flow path of the lower core plate 6 so that the through hole 26d formed in the pedestal 26 is aligned with the thimble tube 27 to be inspected. Insert the inspection device W20 into the hole (not shown).
positioning. Next, the inspection device 20 is suspended from the polar crane to the machine hoist 15 shown in FIG. 1, and the inspection device 20 is held by the fixing jig 15b.

Thereafter, the thimble tube 27 is pushed in a known manner,
Its tip 27a is made to protrude upward from the lower core plate 6. The tip portion 27a is photographed by the imaging camera 24a and displayed on the monitor television 33. If there is no problem such as thinning, the thimble tube 27 is pushed further upward.

At this time, the thimble tube 27 enters the inner cylinder 21a and is guided by the inner cylinder 21a.

The thimble tube 27 is typically a hollow stainless steel tube with an outer diameter of about 81 mm, and since the thimble tube itself has poor self-sustainability, providing the inner tube 21a as described above prevents the thimble tube 27 from bending or bending. can be prevented.

If a problem such as thinning is confirmed on the monitor TV 33, operate the operation unit 23 to rotate the outer tube 21}, the underwater monitoring device 24 will also rotate, and the thimble tube 27
It is possible to grasp the thinning situation in the circumferential direction. To measure the thinning, the rotation of the outer cylinder 2lb is stopped at the angular position where the thinning is estimated to be the maximum value, and the image is enlarged (2, 4, 8 times) by the image processing device 32.

After that, by operating the microscaler 31, the monitor TV 3
The vertical and horizontal moving forces (see FIG. 3) are projected on the image No. 3 and measured along the outer diameter of the thimble tube 27. The microscaler 31 has a function of digitally displaying the read value on the monitor television 33 (the third
(see figure). In addition to the image enlarging function, the image processing device 32 also outputs electrical signals based on the brightness and darkness of the image to the monitor television 3.
3 and has a function that can be measured with a microscaler cursor, and the outer diameter or boundary of the thimble tube 27 can be clearly defined by the height of the signal, for example, 10μ.
To be able to obtain accurate outer diameter dimensions on the order of m (
(See Figure 3).

[Effect of the invention] By using the inspection device having the above structure, it is possible to remotely check the integrity of the entire circumference of the thimble tube for in-core nuclear instrumentation over a desired length, and to grasp the situation such as thinning of the core. I can do it.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the entire inspection apparatus according to the present invention;
FIG. 2 is an enlarged perspective view of the area indicated by the symbol ■ in FIG.
FIG. 3 is an explanatory diagram of a television monitor screen of the inspection apparatus according to the present invention, and FIG. 4 is a sectional view for explaining the in-core instrumentation system of a nuclear reactor. 2...Fuel assembly 6...Lower core plate 20...
- Inspection device 21... Support structure 24... Underwater monitoring device 27... Thimble tube 34...
Information processing/display device Fig. 2 6-111 Lower furnace temporary B-111 Inspection device 2 "1-1 Support structure ball 24-111 Tree middle monitoring station 27--Syn 7 le tube

Claims (1)

[Claims] An inspection device for an in-core nuclear instrumentation thimble tube extending from below a lower core plate and inserted into a fuel assembly on the lower core plate, comprising: a support structure positioned at a predetermined position on the lower core plate; , an underwater monitoring device rotatably supported by the support structure to monitor the thimble tube; and an information processing/display device connected to the underwater monitoring device and processing and displaying outer diameter information of the thimble tube. An inspection device for thimble tubes for in-core instrumentation.