JPH071318B2 - Electromagnetic collection method of clad in pressure tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to the use of gravity to settle the clad separated from the tube wall of a pressure tube in a pressure tube nuclear reactor, and use an electromagnet to remove the clad inside the tip of the fuel exchanger. The present invention relates to a method of adsorbing to a collecting member and then removing the collecting member with the clad adhered to collect and remove the clad.

[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 hinders ultrasonic flaw detection, dimension measurement, and visual inspection of the inner surface 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, a method for effectively collecting the separated clad has not been technically solved yet.

For example, if you try to collect with a filter etc. somewhere in the system while operating the coolant purification system, there will be a considerable amount of clad in the pipes of the coolant recirculation system and coolant purification system or the heat transfer tubes of the heat exchanger. It will be attached, and it will have a great effect on radiation exposure during regular inspections.

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

Furthermore, even if an attempt is made to remove the clad at the same time as monitoring the pressure tube, the clad may enter a gap or the like in the monitoring device and the device may not operate normally, which makes it difficult to carry out.

Moreover, as shown in FIG. 4, there was no foothold in the vicinity of the fuel exchanger 12 below the pressure pipe 10 and work at high places was required, so there was a considerable restriction in terms of equipment, and an appropriate method could not be found. .

The object of the present invention is to solve the problems associated with the above-mentioned conventional techniques, and to efficiently collect and remove the clad in the pressure tube without unnecessarily diffusing the cladding, thus increasing the exposure in various operations after the removal. It is an object of the present invention to provide an electromagnetic trapping method for a clad in a pressure tube, which can prevent the above-mentioned problems and is simple in terms of equipment and can be handled inexpensively by using a conventional device.

[Means for Solving the Problems] In the present invention that can achieve the above object, an electromagnet is attached to the outside of the tip of a fuel exchanger, and a collecting member having a space vertically extending in the center is provided. The clad that is attached to the inside of the tip of the refueling machine and moves to the lower end of the pressure tube and settles due to gravity is adsorbed to the collection member by the electromagnet, and after the adsorption work is completed, the energization of the electromagnet is stopped and the fuel It is a method of electromagnetically collecting the clad in the pressure pipe in which the collecting member with the clad adsorbed is removed from the inside of the tip of the exchanger.

The clad can be peeled off from the inner wall of the pressure pipe mechanically, for example, by sliding a wiper or the like in the pipe.

[Operation] The clad adhered to the inner wall of the pressure pipe is peeled off from the inner wall of the pipe by a sliding operation such as a wiper. If the operation of the system is temporarily stopped, the separated clad will settle due to gravity. A trapping member is attached to the inside of the tip of the refueling machine at the lower end of the pressure pipe, and an electromagnet is installed outside the tip to energize it.Since the clad is mainly iron oxide, it is attracted by electromagnetic force. Adsorbs to the collection member relatively easily. Therefore, there is little risk that the clad unnecessarily diffuses into the system.

The clad thus collected is removed as a waste together with the collecting member after the energization of the electromagnet is stopped.

Further, in terms of equipment, it is possible to easily cope with the situation by slightly modifying the electromagnet on the outside of the tip of the currently used fuel exchanger and the collecting member on the inside of the tip.

[Embodiment] FIG. 1 is a process explanatory view showing an embodiment of the clad collecting method according to the present invention.

First, as shown in FIG. A, the electromagnet 14 is lifted by a crane or the like (not shown), and the "snout portion" of the fuel exchanger 12 is lifted.
It is attached to the outside of the tip portion 16 called. At the same time, connect the power cable, etc. Similarly, the collecting member 18 is lifted by a crane or the like and attached inside the tip portion 16 of the refueling machine 12 (see FIG. B). If the step 16a is provided on the inner surface of the tip portion 16, the collecting member 18 can be easily attached.

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. 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 for collecting the clad.

Now, the collecting member 18 used in the present invention has a space that extends vertically through the central portion thereof, and has a structure such that the shaft of the wiper for removing the clad can be freely inserted through the space.

As shown in FIG. 1C, the refueling machine 12 equipped with the electromagnet 14 and the collecting member 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 clad removing wiper 20 is slid up and down on its shaft 22 to mechanically separate the clad 24 adhering to the inner wall of the pressure tube 10.

At this time, if the operation of the system is temporarily stopped, the separated clad 24 sinks due to gravity. When the electromagnet 14 is energized, since the clad 24 is an oxide of iron, it is attracted by the electromagnetic force of the electromagnet 14 and is relatively easily adsorbed to the collecting member 18 (see FIG. 1D).

Such an operation is performed on the pressure tube that requires clad removal. When the adsorption work is completed, the energization of the electromagnet 14 is stopped, and the collecting member 18 is again removed from the inside of the tip portion 16 of the fuel exchanger 12 by a crane or the like as shown in FIG. 1E.
Then, the clad 24 is also taken out in the state where the clad 24 is still attached to the collecting member 18. The collecting member 18 is transferred to the waste storage and stored therein.

The shape of the collection member 18 used in the present invention may be any structure as long as it has a space vertically penetrated in the central portion as described above and the shaft portion or the like of the wiper for removing clad can be freely inserted, particularly the structure. There is no specific limitation.

For example, as shown in FIG. 2, if the inner surface of the cylindrical body 26 is provided with annular ridges 28 in multiple stages, the clad 24 once adsorbed during use is less likely to be scattered and accumulated in the ridges 28. Good results are obtained.

As a more preferable example of the collecting member, as shown in FIG. 3, there is a structure in which an adsorbent 32 having a cylindrical structure is attached inside a cylindrical case 30 having a large opening at the center of the bottom. The adsorbent 32 can be composed of a stainless steel thin wire (fiber of about 10 to 100 μm), a wire mesh or a multi-layered perforated plate. Further, if the equivalent wire diameter of the adsorbent is reduced, a high gradient magnetic separation effect and a filter filtration effect can be expected, and the porosity for holding the clad can be increased.

As the electromagnet, in addition to a general annular structure, rod-shaped electromagnets may be annularly arranged or a spiral electromagnet may be used.

[Advantages of the Invention] According to the present invention, as described above, the electromagnet is attached to the outside of the tip of the refueling machine, and the collecting member is attached to the inside of the tip of the fuel exchanger so that the clad falling by gravity is forcibly attracted to the collecting member by the electromagnet. Since it is a method of taking out the clad together with the collection member after that, the exfoliated clad can be efficiently and intensively collected in the vicinity of the generation site without being diffused into the system, which is an excellent effect. Is to have.

Further, in the present invention, since the clad that sinks due to gravity is electromagnetically adsorbed and collected, it is not necessary to significantly change the existing equipment, and the electromagnet and the collecting member can be attached outside or inside the tip of the fuel exchanger. This is extremely advantageous in terms of cost because it can be easily dealt with by making a slight modification.

Further, according to the present invention, it is possible to collect the clad at a high density and to take it out together with the collecting member, so that the operation is simple, and since the structure of the collecting member is simple, the processing cost is low.

[Brief description of drawings]

FIG. 1 is a process explanatory view showing an embodiment of a clad collecting method according to the present invention, FIG. 2 is a sectional view showing an example of a collecting member suitable for use in the present invention, and FIG. 3 is a collecting member. 4 is a cross-sectional view showing another example, and FIG. 4 is an explanatory view showing the positional relationship between the pressure pipe and the fuel exchanger. 10 …… Pressure tube, 12 …… Refueling machine, 14 …… Electromagnet, 16…
… Tip part, 18 …… Collection member, 20 …… Removal wiper, 24
...... Clad.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Hayashi Inventor Kenichi Hayashi 1-9-13 Akasaka, Minato-ku, Tokyo Power Reactor / Nuclear Fuel Development Corp. Headquarters (56) Reference JP-A-63-250596 (JP, A) JP 55-54500 (JP, A)

Claims (1)

[Claims] 1. An electromagnet is attached to the outside of the tip of the fuel exchanger, and a collecting member having a space vertically extending in the center is attached to the inside of the tip of the fuel exchanger to move to the lower end of the pressure pipe and settle by gravity. The adsorbing clad is adsorbed to the collecting member by the electromagnet, and after the adsorbing work is completed, the energization of the electromagnet is stopped, and the collecting member with the clad adsorbed is removed from the inside of the tip of the fuel exchanger. Method for electromagnetically collecting clad in pressure pipe.