JP2686640B2 - Fuel assembly internal inspection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel assembly inspection apparatus, and more particularly, to a condition of an outer surface of a fuel rod by inserting a fiber assembly zone into a fuel rod gap of the fuel assembly. The present invention relates to an inspection device that visually observes.

(Prior Art) Since the gap between the fuel rod and the spacer is very narrow in a fuel assembly, clad and foreign matter suspended in the coolant of the nuclear reactor may be caught, and it is necessary to remove it. ,
It is required to check those situations carefully.

Therefore, in order to visually inspect the condition of these foreign substances, conventionally, an inspection was performed to illuminate the lateral direction of the fuel assembly to find the foreign substances on the spacer. On the other hand, there was a problem that it was impossible to find anything that could be hidden by the spacer.

For this reason, the use of optical fibers has recently been attempted, and the development of inspection devices that apply image fibers has progressed. For example, a side-view type that consists of multiple fibers that enables observation of the fuel rod surface located laterally. A fiber collecting belt in which a plurality of fiberscopes are arranged in parallel and integrated into a sheet has been proposed by Jitsukai Sho 59-98401.

By the way, since the inspection equipment using these fiber assembly zones is for inspecting the fuel body used in the reactor, the fuel body is sunk in the pool of the reactor, and therefore the main part of the equipment Must be water resistant and remote controllable.

Further, since the amount of light is insufficient in water and in the central portion of the fuel assembly, the image fiber must be equipped with a light guide.

A light guide is usually a glass fiber, similar to an image fiber, that can guide light from a powerful light source. And such a light guide and an image fiber are combined and used in a strip | belt shape as a preferable aspect. This is because in order to obtain a high-quality image, the number of fiber strands must be increased, and the sheath must be placed in consideration of water resistance and radiation resistance.
This is because the entire diameter of the image fiber should be as large as possible within the range of the fuel rod gap.

From this point, it is advantageous to combine the light guides vertically to form a strip shape in order to obtain an image with the best image quality. For example, if the outer diameter is 2.5 mm, 5 with a water resistant sheath.
000 fiber strands are collected and good image quality can be obtained.

Further, if this is further expanded, it is possible to combine a plurality of image fibers into a strip shape, and as disclosed in the above-mentioned Japanese Utility Model Application Laid-Open No. 59-98401, the viewing angles of these image fibers are set in different directions. It is possible to secure a wide field of view toward the eye, which is extremely convenient for inspection of foreign matters and the like.

(Problems to be Solved by the Invention) However, since the image fiber as described above usually has a diameter of 2.5 to 3 mm including the sheath, it is very fragile.

Therefore, the handling of these image fibers in water is extremely important, and it is necessary to match the position of the fiber assembly zone with the gap of the fuel rod.

Further, when inserting the fiber assembly zone into the fuel rod gap, if foreign matter or the like is present, the advancement of the foreign matter is blocked, and further pushing may cause breakage of the fiber assembly zone.

The present invention pays attention to the above points and attempts to improve the handling device of the fiber assembly zone in water, which is coupled with the above points, to ensure the alignment between the fuel rod gap and the fiber assembly zone, and to improve the fiber assembly. The purpose of the present invention is to smooth the insertion of the band and to eliminate the risk of breakage of the fiber aggregate band due to foreign matter collision or the like at the time of advancing.

(Means for Solving the Problems) A feature of the inspection device of the present invention that achieves the above-mentioned object is that, as a first structure, a mechanism for inserting a fiber assembly zone into a gap between fuel rods forming a fuel assembly is The fiber center zone insertion mechanism is moved while receiving and transmitting sound waves, positioned at the position where the ultrasonic wave reception amount is minimum, and a gap center detection mechanism for advancing the fiber zone and inserting it into the fuel rod gap is attached.

In addition, the second structure according to claim 2 is added to the above apparatus and further protects the fiber collecting belt when the fiber collecting belt is retracted and when the fiber collecting belt is moved forward, the pressing force against the fiber collecting belt becomes a predetermined value or more. In this case, an overpressure prevention mechanism is provided to stop the forward movement.

Incidentally, when the fiber collecting belt is retracted, as a protector for protecting it, for example, a protective cover or the like, and as a mechanism for preventing overpressurization, a load cell for measuring the load of a spring is used.
When the load exceeds a certain value, a load cell method that stops moving forward is used.

(Operation) When the inside of the fuel polymer is inspected by using the above inspection device, the gap center detecting mechanism moves the fiber insertion mechanism while transmitting and receiving ultrasonic waves, for example.
The position is determined at the place where the amount of reflected ultrasonic waves received is the smallest.

At this time, the fiber assembly zone is retracted and hidden in a protective device, for example, a protective cover until it is determined to a predetermined position, the position is determined, and the arrangement is completed and the position of the fuel rod gap and the fiber assembly zone is determined. When is properly matched, the fiber assembly zone is advanced and inserted into the fuel rod gap.

When the fiber assembly belt collides with a foreign substance or the like during insertion and the forward movement is blocked, the overpressurization prevention mechanism operates when further pushing, and the forward movement is automatically performed immediately when the pressure exceeds a certain level. Stop.

Thus, it is easy to confirm the fuel rod status safely and accurately.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a fiber assembly zone insertion mechanism portion which is a main part of an inspection apparatus according to the present invention. In FIG. 1, (1) is an inspection table, which is a lateral direction with respect to a fuel assembly, that is, a direction perpendicular to a paper surface. A movable support base (3) which is movable on the rear side of the movable support (3) for supporting the fiber superposition zone (F) with a protective device (2) such as a protective cover in the middle thereof is provided on the other hand, while an ultrasonic transmitter / receiver (4) is provided. ) And an ultrasonic data processing unit (5), the gap center detecting mechanism (A) is mounted on the front part, and the fiber assembly zone (F) guided from the outside is the movable support base (3).
Is held by

The movable support base (3) of the fiber assembly zone (F) usually corresponds to the length of one side of the fuel assembly.
It is connected to a hydraulic cylinder (6) having a stroke length of 0 to 200 mm so as to be able to move forward and backward, and an overpressure prevention mechanism (B) consisting of a spring (7) and a displacement detection device (8) is provided. It is incorporated, and when the displacement of the spring (7) is detected and the value exceeds a certain set value, the forward movement is immediately stopped.

2 and 3 show an example of the structure of the fiber assembly zone (F) used in the above-mentioned device.
1) and the light guide (12) are combined and inserted into the sheath (13), and the image fiber (1
It is formed by arranging light guides (12) above and below with 1) in the middle and combining them in a strip shape. Both have a lens (14) and an image fiber (11) is a television camera (not shown). , And the light guide (12) is connected to a light source (not shown), respectively.

In this case, one image fiber (11) is shown in the figure, but a plurality of image fibers may be used, and a wide range of field of view may be secured by directing the viewing angles of the plurality of image fibers in different directions. It is also possible.

The diameter of the image fiber (11) is smaller than the fuel rod gap of the fuel assembly to be used and is not particularly limited as long as good image quality can be obtained. Not only the hydraulic cylinder but also a rack and pinion mechanism and other various types of mechanisms can be used.

Further, in the above-mentioned inspection device, the overpressurization preventing mechanism (B) uses a load cell for measuring the load of the spring (2), and when the load exceeds a certain value, a load cell method of stopping the forward movement is used. Of course, it is possible to substitute other methods.

Next, one example of the configuration of the collecting band inserting mechanism in the above device will be described more specifically.

First, a fiber aggregate structure with a total length of 20 m is manufactured by combining one image fiber (6) with an outer diameter of 2.5 mm and four light guides (12) and storing it in the sheath (13). Image fiber up to 200mm (11)
A light guide (12) was placed on the top and bottom, and assembled into a strip.

Then, the part following the tip 150 to 200 mm is held by the movable support table (3) on the inspection table, and the stroke length is 150 to 200 mm.
It was possible to move forward and backward using the hydraulic cylinder of.

On the other hand, a system using a spring was used as the overpressurization preventing mechanism, and the strength of the spring was set to 5 kg so that no more force would be applied to the fiber assembly zone (F). .

Thus, when the internal appearance of the fuel assembly was inspected by the inspection device having the above-mentioned mechanism, the inside of the fuel assembly could be confirmed extremely smoothly and safely.

(Effects of the Invention) In the internal inspection apparatus for a fuel assembly using the image fiber as described above, the mechanism for inserting the fiber assembly zone into the fuel rod gap of the fuel assembly has the center axis of the fiber assembly zone as fuel. It is provided with a gap center detection mechanism that is adjusted so as to match the center of the rod gap and that is composed of the ultrasonic receiver and the ultrasonic data processing unit described above. It is possible to position the fiber reliably in the center, and the fiber assembly can be inserted smoothly and stably, and a remarkable effect of improving the practicability and safety of the inspection device is achieved.

In addition, the device according to claim 2 is further provided with a protector and a mechanism for preventing overpressurization when the fiber collecting belt is retracted, so that the protection when the fiber collecting belt is retracted can be ensured and, of course, the fiber collecting belt can be inserted. Even if the vehicle collides with foreign matter and the forward movement is blocked, the stop mechanism will automatically operate, and the situation inside the fuel assembly can be safely assured without causing damage to the fiber assembly zone. Have.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of the inspection device of the present invention, and FIGS. 2 and 3 are schematic diagrams of fiber gathering bands used in the inspection device. (1) …… Inspection table, (2) …… Protective equipment, (3) …… Movable support stand, (4) …… Ultrasonic transmitter / receiver, (5) …… Ultrasonic data processing unit, (6) …… Hydraulic cylinder, (7) …… Spring, (8) …… Displacement detection device, (11) …… Image fiber, (12) …… Light guide, (A) …… Gap center detection mechanism, (B) …… Overpressurization prevention mechanism, (F) …… Fiber gathering zone,

Claims (2)

(57) [Claims] 1. An inspection apparatus for inserting a fiber assembly zone into a fuel rod gap of a fuel assembly and visually observing the condition of the outer surface of the fuel rod, and the like. A fuel polymer characterized by moving the fiber assembly zone insertion mechanism while performing it, positioning it at the position of the minimum ultrasonic reception amount, advancing the fiber assembly zone, and attaching a gap center detection mechanism to insert it into the fuel rod gap Internal inspection device. 2. The inspection apparatus according to claim 1, wherein the fiber collecting belt insertion mechanism further has a protector for protecting the collecting belt at the retracted position of the fiber collecting belt and the pressing force against the fiber collecting belt when advancing is a predetermined value or more. An internal inspection apparatus for a fuel assembly, which is provided with an overpressurization preventing mechanism for stopping the forward movement of the fuel assembly.