JPH0769463B2 - Removal and collection method of cladding in pressure pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses a clad removal collector having a fin for clad removal on the outside and a filter on the inside, and is moved in the pressure tube of a pressure tube reactor. A clad removal and collection method that separates the clad from the tube wall with a clad removal fin and allows the suspension containing the separated clad to pass through the filter to efficiently collect the clad without diffusing the clad into the surrounding area. It is about.

[Prior Art] In a pressure tube reactor, a clad (corrosion product) is generated on the inner wall of the pressure tube due to long-term use. If this clad is not removed, ultrasonic flaw detection, dimensional measurement, inner surface visual inspection, etc. cannot be performed during pressure tube monitoring.

Therefore, it is necessary to regularly remove the clad adhering to the inner wall of the pressure pipe. In the prior art, it was possible to mechanically remove the clad with a wiper or the like.

[Problems to be Solved by the Invention] However, as for the technique for effectively collecting the clad which has been peeled off, a sufficiently satisfactory technique has not been developed yet.

For example, if you try to collect with a filter etc. somewhere in the system while operating the coolant purification system, a considerable amount of clad will adhere to the pipes of the coolant circulation system or coolant purification system or the heat transfer pipes of the fuel exchanger. As a result, the radiation exposure at the time of periodic inspection has a great influence.

It is also conceivable to suspend the operation of the system and deposit the clad inside the refueling machine, but with such a technique, the dose of the refueling machine may increase dramatically and it may cause mechanical failure of the refueling machine. Absent.

Furthermore, even if the clad is removed and monitored at the same time as the pressure tube monitoring, the clad may enter a gap or the like of the mochitering device and the device may not operate normally, which is difficult to carry out.

Moreover, as shown in FIG. 4, there is no foothold in the vicinity of the fuel exchanger 12 under the pressure pipe 10 and work at high places is required, so that there are considerable restrictions in terms of equipment, and appropriate technology has not yet been developed. Didn't.

The object of the present invention is to solve the technical problems as described above, to efficiently collect the cladding in the pressure tube without unnecessarily diffusing the cladding, and thus to prevent an increase in radiation exposure in various operations after removal, and It is an object of the present invention to provide a method for removing and collecting clad in a pressure pipe, which is simple in terms of equipment and can be handled inexpensively by using a conventional device.

[Means for Solving the Problems] According to the present invention that can achieve the above object, a clad removal collector having a clad removal fin on the outside and a filter on the inside is attached to a glove of a fuel exchanger. Then, the clad adhering to the inner wall of the pressure tube is peeled off with a fin for removing the clad, and the suspension containing the clad forms a flow through the inside of the filter to trap the clad with the filter. It is a method of removing and collecting the clad in the pressure tube which is adapted to collect.

Here, the clad removing fins are circumferentially provided outside the upper end of the clad removing and collecting device, and have a shape such that the upper end expands.

As a method of directing the suspension containing the separated clad to the filter, a motor or impeller is installed inside the clad removal and collection device, and the impeller is rotationally driven to form a suspension flow in a certain direction. Alternatively, there is a method of making a downward flow by utilizing the pressure difference generated when pushing up the clad removal / collection device in the pressure pipe.

[Operation] Attach the clad removal collector to the grab of the fuel exchanger,
By moving the inside of the pressure pipe, the clad removing fin slides on the inner wall of the pressure pipe, and the clad adhering to the inner wall is separated. The separated clad becomes suspended in water and passes through the filter by the pressure difference generated by the movement of the device in the pipe or by the flow formed by the impeller rotated by the motor to be collected.

In this way, the removal of the clad and its collection can be performed almost simultaneously at the same location by moving the device, so the efficiency is high,
There is no risk that the clad will unnecessarily diffuse inside the system.

The clad collected in the filter is moved to an appropriate place together with the filter and treated as waste.

In terms of equipment, since it can be configured so that it can be attached to the glove of the fuel exchanger currently used, a large capital investment is not required and it can be handled at low cost.

[Embodiment] FIG. 1 is an explanatory view showing an embodiment of an apparatus suitable for use in the clad removing and collecting method according to the present invention.

This clad removing and collecting device 18 includes an upper frame 20 and a lower frame.
22 has a casing structure combined with
Removable to the glove (unit that has the function of removing fuel etc. from the core when the fuel etc. in the core is taken into the refueling machine or vice versa) in the tip 16 (see FIG. 4) of 12 It is designed to be movable inside the pressure pipe 10.

On the outside of the upper end of the upper frame body 20, a clad removing fin 24 having a circular shape and the upper end of which is widened is provided. The clad removing fins 24 are made of a soft material such as EPDM rubber, but are not limited thereto and may be made of metal or the like depending on the case. Below the clad removing fins 24, rotatable balls 26 or rollers are embedded and held substantially symmetrically at three or more places. The balls 26 and the like serve to center the device within the pressure tube. A plurality of baffle plates 28 are provided in the upper frame body 20 by changing the positions of their water passage ports 30, and a clad collecting filter 32 is provided below the baffle plates 28.

Inside the lower frame 22, a motor 34, an impeller 36 attached to its rotation shaft, and a battery for driving the motor 34 are installed.
38 incorporated.

FIG. 2 shows a clad removal and collection step in the pressure tube according to the present invention using such an apparatus.

First, as shown in A of the same figure, this device 18 is lifted by a crane or the like (not shown) and mounted on the glove 42 in the tip portion 16 of the fuel exchanger 12 (see B).

As shown in FIG. 4, the fuel exchanger 12 is located below the pressure tubes 10 which are correctly arranged in a large number, and is configured to be freely movable in a horizontal plane. This refueling machine 12
In addition to exchanging fuel, a pressure pipe monitoring device can be inserted into a predetermined pressure pipe at the time of pressure pipe monitoring, and various inspections can be performed by the monitoring device alone.
In the present invention, such a fuel exchanger 12 is also used as a moving mechanism of the clad removing / collecting device.

As shown in FIG. 2C, the fuel exchanger equipped with the clad removing and collecting device 18 is moved to the lower end of the predetermined pressure pipe 10 where the clad should be removed by the moving mechanism in the horizontal plane. Then, the glove 42 is driven to insert the device 18. This device 18
Rises while being centered by the balls 26, and the clad removing fins 24 are in contact with the inner surface of the pressure pipe 10, so that the clad 40 adhering to the inner wall of the pressure pipe is peeled off as it rises. The suspension containing the peeled clad is
The downward flow formed by the rotation of the impeller 36 (shown by an outline arrow in FIG. 1) flows through the water passage 30 of the baffle 28 to the filter 32. Then, the filter 32 collects the clad, and only clean water flows downward. In this way, by raising the present device 18 over the entire length of the pressure pipe 10, the clad 40 adhering to the inner wall of the pressure pipe 10 is peeled and removed, and the peeled clad is filtered.
Will be collected at 32. After that, the device 18 is returned to the initial position (see FIG. 2D), and such an operation is performed on the pressure pipe that requires the removal of the clad. After the removal and collection work of the clad is completed, it is removed from the fuel exchanger 12 again by a crane or the like as shown in FIG. 2E. Baffle
28 has a function of making it difficult for the clad trapped in the filter 32 to scatter around when performing such a removing operation.

The device 18 moves to a predetermined position and the upper frame 20 is moved to the lower frame.
It is separated from 22, and transferred together with the upper frame 20 to a waste storage place for storage.

FIG. 3 shows another example of the filter unit suitable for use in the present invention. Here, the baffle plate portion 50 and the filter portion 52 are integrated into a filter unit 54. In this way, since the filter unit 54 can be completely removed from the frame and can be treated as such, the amount of waste is reduced and the upper frame can be reused, which is economically advantageous and advantageous.

Although the preferred embodiments of the present invention have been described above in detail, it goes without saying that the present invention is not limited to such a configuration. In the above embodiment, a ball 26 is provided to center the device on the pressure tube. From the standpoint of the centering function, it is better to have such a ball or roller, but this is not essential, and the clad removing function can be fulfilled without it. Further, although the baffle plate is provided on the upper part of the filter, a plate-shaped body made of mesh or the like may be incorporated instead of the baffle plate.

A built-in battery 38 is incorporated as a power source for rotating the impeller 36, but it is also possible to supply power by a power cable via a grab. Further, in some cases, it is possible to use the pressure difference generated when the device is pushed up by the grab without using such a device to make a downward flow and thereby collect the clad by the filter.

[Effects of the Invention] The present invention attaches the clad removing and collecting device having the clad removing fins and the filter as described above to the graph of the fuel exchanger, moves it in the pressure pipe to separate the clad, and suspends the clad containing the separated clad. Since it is a method of collecting and removing the clad in the pressure tube, which was achieved by forcing the suspension to flow to the filter,
Since the clad can be separated and collected at the same time, the clad can be efficiently and intensively collected in the vicinity of the generation site, the clad diffusion to the periphery can be suppressed to a minimum, and the radiation exposure can be prevented from expanding.

Also, the device used is relatively simple in structure and inexpensive,
Since the refueling machine is used for the operation, the existing equipment can be used as it is, and most of the equipment can be reused, which is advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of a clad removing and collecting apparatus used in the method of the present invention, FIG. 2 is a process explanatory view showing the method of the present invention, and FIG. 3 is a filter suitable for use in the method of the present invention. -A cross-sectional view showing an example of a unit, and Fig. 4 is an explanatory view showing a positional relationship between a pressure pipe and a fuel exchanger. 10 …… Pressure pipe, 12 …… Refueling machine, 18 …… Clad removing and collecting device, 20 …… Upper frame, 22 …… Lower frame, 24 …… Clad removing fin, 32 …… Filter.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G21F 9/28 581 Z 9117-2G

Claims (1)

[Claims] 1. A clad-removing trap having a structure in which a clad-removing fin having a circumferential shape with an open upper end is provided outside the upper end of a cylindrical frame, and a filter is provided inside the frame. The device is attached to the glove of the fuel exchange machine and moved inside the pressure tube, and the clad adhering to the inner wall of the pressure tube is peeled off by the clad removing fins, and the suspension containing the clad flows through the inside of the filter. A method for removing and collecting clad in a pressure tube, characterized in that the clad is formed and the clad is collected by a filter.