JPH0769470B2 - Method for removing and collecting clad in pressure pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention uses a clad removal collector having a clad removal wiper, a clad adsorbent, and a magnet to move in a pressure tube of a pressure tube reactor. A method for removing and collecting the clad in the pressure pipe, in which the clad is removed from the pipe wall by the clad removing wiper, and the separated clad is magnetically adsorbed and collected by the magnet and the adsorbent without being diffused to the surroundings. Is.

[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. This clad adhesion hinders the implementation of ultrasonic flaw detection and dimension measurement in pressure tube monitoring, and visual inspection of the inner surface.

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 it with a filter etc. somewhere in the system while operating the coolant purification system, a large amount of clad will adhere to the heat transfer pipes or the like in the coolant circulation system or coolant purification system pipes or fuel exchangers. 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 which can achieve the above object, a clad removing and collecting device having a clad removing wiper portion, a clad adsorbent, and a magnet is mounted on a fuel exchanger. Inside the pressure tube, the clad adhering to the inner wall of the pressure tube is separated and removed by the wiper for removing the clad, and the clad is magnetically adsorbed and collected by the magnet and the adsorbent. This is a method of removing and collecting the clad.

As the clad removing and collecting device used here, for example, a large-diameter clad removing wiper part that is in sliding contact with the inner wall of the pressure tube is arranged at a plurality of intervals, and a slightly smaller diameter permanent magnet and adsorbent are provided between them. A configuration in which and are alternately arranged is desirable. As the adsorbent, for example, one obtained by collectively forming a thin stainless wire into a disc shape is suitable. Further, the outer diameter of the adsorbent may be increased so that the outer diameter of the adsorbent may be slidably contacted with the inner wall of the pressure tube so that the outer peripheral portion of the adsorbent also serves as the wiper portion, and the permanent magnet may be arranged therebetween.

[Operation] Attach the clad removal collector to the grab of the fuel exchanger,
By moving the inside of the pressure tube, the clad removing wiper portion slides on the inner wall of the pressure tube, and mechanically separates the clad adhering to the inner wall. The clad that has peeled off is in a floating state in water. Since the clad is mainly an oxide of iron, it is relatively easily attracted by the magnet and collected by the surrounding adsorbent. In the case where the adsorbent is an aggregate molded body of stainless fine wires, the once adsorbed clad does not dissipate during use, which is extremely convenient.

By moving the clad removing and collecting apparatus as described above, the clad can be removed and collected at almost the same place at the same time, so that the efficiency is high and there is no risk that the clad unnecessarily diffuses into the system.

The clad collected in the adsorbent or the like is moved to an appropriate place together with the clad removing and collecting device and treated as a waste.

Also in terms of equipment, the present invention can be configured so that it can be attached to the glove of the fuel exchanger currently used,
No large capital investment is required, and it can be handled at low cost.

[Embodiment] FIG. 1 is a process explanatory view showing an embodiment of the clad removing and collecting method according to the present invention, and FIG. 2 is an explanatory view showing an example of the clad removing and collecting apparatus used therein.

As shown in FIG. 2, the clad removal / collection device 18 includes a clad removal wiper portion 20 for mechanically removing the clad adhering to the inner wall of the pressure tube 10 and an adsorbed clad without adhering the separated clad. The adsorbent 22 is provided with a permanent magnet 24 for increasing the adsorbing force.

Here, the clad removing wiper section 20 has a large-diameter disk-like or annular structure that is slidably in contact with the inner wall of the pressure tube 10, and is arranged in two upper and lower stages. Further, permanent magnets 24 are disposed between them and above and below them. The adsorbent 22 and the permanent magnet 24 are set to have a diameter slightly smaller than that of the adsorbent 22 and the permanent magnet 24 so as to smoothly move in the pressure tube. Then, a collet portion 26 is provided at the lowermost portion thereof so that the grab inside the tip portion 16 (see FIG. 4) of the fuel exchanger 12 (when fuel etc. in the core is taken into the fuel exchanger or vice versa) In addition, the unit has a function of removing fuel from the core).

The clad removing wiper portion 20 is made of a soft material such as EPDM rubber, but is not limited thereto and may be a metal or the like depending on the case. As the adsorbent 22, for example, a SUS thin wire (fiber of about 10 to 100 μm) molded in a disc shape, a wire mesh or a multi-layered perforated plate can be used. In particular, it is advantageous to reduce the equivalent wire diameter of the adsorbent because a high gradient magnetic separation effect and a filter filtration effect can be expected, and the porosity for holding the clad can be increased.

Now, in the present invention, as shown in FIG. 1A, the clad removing and collecting device 18 is lifted by a crane or the like (not shown),
It is attached to the glove 42 in the tip portion 16 of the refueling machine 12 (first
(See Figure B).

The refueling machine 12 is located below the pressure tubes 10 which are regularly arranged as shown in FIG. 4, and is configured to be freely movable in a horizontal plane. In addition to the refueling of the refueling machine 12, at the time of pressure pipe monitoring, a pressure pipe monitoring device can be inserted into a predetermined pressure pipe 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. 1C, the fuel exchanger equipped with the clad removing and collecting device 18 is moved to the lower end of a predetermined pressure pipe 10 where the clad should be removed by a moving mechanism in a horizontal plane. Then, the grab 42 is driven to insert the clad removal and collection device 18. Since the clad removing wiper portion 22 is in contact with the inner surface of the pressure pipe 10, the clad 40 adhering to the inner wall of the pressure pipe is peeled off as it moves up and down. The clad that has been peeled off is an oxide of iron, and is therefore relatively easily adsorbed to the adsorbent 22 by the magnetic force of the permanent magnet 24. By vertically moving the clad removing and collecting device 18 over the entire length of the pressure tube 10, the clad 40 adhering to the inner wall of the clad 40 is mechanically separated and removed, and the separated clad is attracted to the permanent magnet 24 to attract the adsorbent. It will be adsorbed by 22 and collected.

After that, the device 18 is returned to the initial position (see FIG. 1D), and such an operation is performed on the pressure pipe in which the cladding needs to be removed. When the clad removal and collection work is completed, it is removed from the fuel exchanger 12 again by a crane or the like as shown in FIG. 1E, and transferred to a waste storage place for storage.

FIG. 3 shows another example of the clad removing and collecting apparatus suitable for use in the present invention. Here, the adsorbent 28 is configured to also serve as a wiper portion, and is set large so that the outer peripheral portion thereof is in sliding contact with the inner wall of the pressure pipe. Such adsorbents 28 are provided at two-stage intervals, and the permanent magnets 24 are provided between them and in the upper and lower portions, respectively. A collet portion 26 is provided at the lower end so that it can be attached to the glove of the refueling machine. The clad removing and collecting operation using such an apparatus may be exactly the same as that shown in FIG.

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. Wiper part for removing clad and adsorbent,
The shape and size of the magnets, the arrangement state, the number of arrangements, and the like can be appropriately changed according to the usage conditions and the like.

[Advantages of the Invention] The present invention attaches the clad removing and collecting device including the clad removing wiper portion, the adsorbent and the magnet to the fuel exchanger as described above, and moves the pressure cuvette to peel off the clad. Since this is a method for collecting and removing the clad in the pressure tube configured to magnetically attract and hold it with a magnet and an adsorbent, the clad can be mechanically separated and collected at the same time, so that the clad can be efficiently concentrated in the vicinity of the location. It has an excellent effect that it can be collected, the clad diffusion to the periphery can be suppressed to the minimum, and the spread of radiation can be prevented.

Also, the device used is relatively simple in structure and inexpensive,
Since the existing equipment can be used as it is because the operation is performed using the fuel exchanger, it is also advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an embodiment of a clad removing and collecting apparatus according to the method of the present invention, FIG. 2 is an explanatory view showing an embodiment of a clad removing and collecting apparatus suitable for use in it, and FIG. Is a cross-sectional view showing another example of the clad removing and collecting apparatus, and FIG. 4 is an explanatory view showing the positional relationship between the pressure pipe and the fuel exchanger. 10 …… Pressure pipe, 12 …… Refueling machine, 18 …… Clad removal collector, 20 …… Clad removal wiper, 22,28…
… Adsorbent, 24 …… Permanent magnet, 26 …… Collet part.

Claims (1)

[Claims] 1. A large-diameter clad removing wiper which is arranged at a plurality of steps and slidably contacts an inner wall of a pressure pipe, and small-diameter magnets and clad adsorbents which are alternately arranged between the wiper parts. The configured clad removal / collection device is installed in a fuel exchanger and moved inside the pressure tube.The clad adhering to the inner wall of the pressure tube is peeled and removed by the wiper part for clad removal. A method for removing and collecting clad in a pressure tube, characterized in that the clad is adsorbed and collected.