JPS63314497A - Electromagnetic collection of clad in pressure pipe - Google Patents

Abstract

PURPOSE:To enable clad to be collected without unnecessarily dispersing it in a system by mounting an electromagnet and a collecting member on the outside and the inside of the distal ends of a fuel exchange machine, respectively, and attracting and taking out the clad falling under the gravity by an electromagnet. CONSTITUTION:An electromagnet 14 is lifted by a crane or the like and mounted on the outside of the distal end portion 16 of a fuel exchange machine 12. In the same manner, a collecting member 18 is lifted and mounted on the inside of the distal end portion 16 of the fuel handling machine 12. Then, the fuel exchange machine 12 mounted with the electromagnet 14 and the collecting member 18 is moved to the lower end of a given pressure pipe 10 from which clad is to be removed by a moving mechanism on a horizontal plane. Then, a wiper 20 for removing the clad is vertically slided by a shaft 22 and mechanically peels off the clad 24 attached to the inner wall of the pressure pipe 10. When the operation of a system is temporarily stopped at this time, the peeled clad 24 falls under the gravity. When the electromagnet 14 is electrified, the clad 24 is attracted by the electromagnet 14 and to the collecting member 18. Then, the electrification of the electromagnet 14 is stopped. The collecting member 18 is dismounted from the inside of the distal end portion 16 of the fuel exchange machine 12 and transported to a storage area to be stored.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses gravity to settle the cladding separated from the wall of the pressure tube in a pressure tube nuclear reactor, and uses an electromagnet to deposit the cladding inside the tip of the fuel exchanger. The present invention relates to a method of collecting and removing craft by adsorbing the craft to a collecting member and then removing the collecting member with the crud still attached.

[Prior Art] In a pressure tube nuclear reactor, crud (corrosion products) is generated on the inner wall of the pressure tube due to long-term use. This cladding obstructs the implementation of ultrasonic flaw detection, dimensional measurement, internal surface visual inspection, etc. during pressure pipe monitoring.

Therefore, it is necessary to periodically remove the crud adhering to the inner wall of the pressure pipe. In the prior art, it was possible to mechanically peel off the clad using a wiper or the like.

[Problems to be Solved by the Invention] However, a method for effectively collecting exfoliated cladding has not yet been technically solved.

For example, if you try to collect crud with a filter somewhere in the system while operating the coolant purification system, a considerable amount of crud may be collected in the pipes of the coolant recirculation system or coolant purification system, or the heat exchanger tubes of the heat exchanger. This will result in adhesion, which will have a large impact on radiation exposure during periodic inspections.

It is also possible to temporarily suspend system operation and allow crud to accumulate inside the refueling machine, but such a method would dramatically increase the radiation dose to the refueling machine and could cause mechanical failure of the refueling machine. do not have.

Furthermore, even if it is attempted to perform pressure pipe monitoring at the same time as crud removal, there is a risk that the crud will enter gaps in the monitoring device, causing the device to malfunction, making it difficult to implement.

Moreover, as shown in Fig. 4, there was no scaffolding near the fuel exchange 4i112 at the bottom of the pressure pipe 10, and work at height was required, so there were considerable restrictions in terms of equipment, and no suitable method could be found. .

The purpose of the present invention is to solve the problems faced by the conventional technology as described above, and to efficiently collect and remove crud in pressure pipes without unnecessary diffusion, thereby reducing the risk of increased radiation exposure during various operations after removal. It is an object of the present invention to provide a method for electromagnetically collecting crud in a pressure pipe, which can prevent such problems, is simple in terms of equipment, and can be handled at low cost using conventional equipment.

[Means for Solving the Problems] The present invention, which can achieve the above objects, has an electromagnet attached to the outside of the tip of the fuel exchanger, and a collection member having a vertical space in the center. It is installed inside the tip of the fuel exchanger and moved to the lower end of the pressure pipe, and the electromagnet adsorbs the crud that settles due to gravity to the collection member. After the adsorption work is completed, the electricity to the electromagnet is stopped and the fuel is removed. This is an electromagnetic collection method for crud in a pressure pipe, in which a collection member with crud adsorbed is removed from inside the tip of an exchanger.

The cladding may be peeled off from the inner wall of the pressure pipe mechanically, for example, by sliding a wiper or the like within the pipe.

[Operation] The craft adhering to the inner wall of the pressure pipe is peeled off from the inner wall of the pipe by the sliding operation of a wiper or the like.

If system operation is temporarily stopped, the separated crud will settle due to gravity. A collection member is installed inside the tip of the fuel exchanger at the lower end of the pressure pipe, and an electromagnet is installed outside the tip and is energized.Since the crud is mainly iron oxide, it is attracted by electromagnetic force. It is relatively easily adsorbed to the collection member. Therefore, there is little risk that the crud will unnecessarily diffuse into the system.

After the collected craft is de-energized, the collection member is removed and disposed of as waste.

In terms of equipment, this can be easily achieved by slightly modifying the currently used fuel exchanger so that an electromagnet can be attached to the outside of the tip and a collection member can be attached to the inside of the tip.

[Example] FIG. 1 is a process explanatory diagram showing an example of the crud collection method according to the present invention.

First, as shown in FIG. 1A, the electromagnet 14 is lifted up by a crane or the like (not shown) and attached to the outside of the tip 1-6, which is called the "snout section" of the fuel exchanger 12. At the same time, connect the power cable, etc. Similarly, lift the collection member 18 using a crane or the like and attach it to the inside of the tip 16 of the fuel exchanger 12 (see B in the same figure).A step 16a is provided on the inner surface of the tip 16. If this is done, the collection member 18 can be easily attached.

The fuel exchanger 12 is located below a large number of regularly arranged pressure pipes 10, as shown in FIG. 4, and is configured to be able to move freely in a horizontal plane. This fuel exchanger 1
In addition to performing fuel exchange, when monitoring pressure pipes, the pressure pipe monitoring device 2 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 It is also used to collect clans.

The collecting member 18 used in the present invention has a vertical space in the center thereof, and has a structure such that the shaft of a crud removing wiper or the like can freely pass through the space.

As shown in FIG. 1C, the fuel exchanger 12 equipped with the electromagnet 14 and the collecting member 18 is moved to the lower end of a predetermined pressure pipe 10 from which crud is to be removed by a moving mechanism in a horizontal plane. Then, the cladding removing wiper 20 is slid up and down by its shaft 22, and the cladding 24 adhering to the inner wall of the pressure pipe 10 is mechanically peeled off.

At this time, if the operation of the system is temporarily stopped, the separated cladding 24 will settle due to gravity.

When the electromagnet I4 is energized, since the cladding 24 is made of iron oxide, it is attracted to the electromagnetic skein of the electromagnet 14 and relatively easily adsorbed to the collection member 18 (see first diagram).

Such an operation is performed on the pressure pipe whose crud needs to be removed. Once the suction work is completed, the power to the electromagnet 14 is stopped, and the tip of the fuel exchanger 12 is removed again using a crane or the like as shown in Figure 1. 16. Remove the collection member 18 from inside.

Then, the cladding 24 is also taken out while remaining attached to the collection member 18. This collection member 18 is transferred to a waste storage facility and stored.

The shape of the collection member 18 used in the present invention may be any structure as long as it has a longitudinal space in the center as described above and allows the shaft of the crud removal wiper to freely pass therethrough. It has no structural limitations.

For example, as shown in FIG. 2, if the structure is such that the inner surface of the cylindrical body 26 is provided with annular protrusions 28 in multiple stages, the craft 24 that has been adsorbed during use will be collected in the protrusions 28 and will be difficult to dissipate. Good results can be obtained.

A more preferable example of the collection member is, as shown in FIG. 3, a structure in which a cylindrical adsorbent 32 is attached inside a cylindrical case 30 having a large opening at the center of the bottom.

This adsorbent 32 is made of stainless steel thin wire (10 to 100
It can be composed of multiple layers of wire mesh, perforated plates, etc.). Further, by reducing the diameter of the isometric line of the adsorbent, a high gradient magnetic separation effect and a filter filtration effect can be expected, and the porosity for holding the club can also be increased.

As the electromagnet, in addition to a general annular structure, a ring-shaped arrangement of rod-shaped electromagnets or a spiral electromagnet can also be used.

[Effects of the Invention] As described above, the present invention installs an electromagnet on the outside of the tip of the fuel exchanger and a collection member inside the tip, and forcibly attracts the crud that falls due to gravity to the collection member using the electromagnet. ,
Since the crud is then taken out along with the collection member, the peeled crud can be efficiently and intensively collected near the place of occurrence without spreading unnecessarily into the system, which has an excellent effect of preventing the spread of radiation exposure. It is something that you have.

In addition, since the present invention electromagnetically adsorbs and collects the crud that settles due to gravity, there is no need to significantly change the current equipment, and the electromagnet and collection member can be installed outside the tip of the fuel exchanger. It is also extremely advantageous in terms of cost since it can be easily accommodated by making slight modifications to the inside and outside.

Furthermore, the present invention has the advantage that the crud can be collected at high density, and that the collection member can be taken out together, making the operation simple, and that the structure of the collection member is simple, resulting in low processing costs.

[Brief explanation of the drawing]

FIG. 1 is a process explanatory diagram showing one embodiment of the crud collection method according to the present invention, FIG. 2 is a sectional view showing an example of a collection member suitable for use in the present invention, and FIG. 3 is a collection member FIG. 4 is an explanatory diagram showing the positional relationship between the pressure pipe and the fuel exchanger. 10...Pressure pipe, 12...Fuel exchange machine, 14...
Electromagnet, 16... Tip part, 1 day... Collection member, 20
...Removal wiper, 24...Clad. Patent applicant Power Reactor and Nuclear Fuel Development Corporation Shigeru Shigeru A B Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. Attach an electromagnet to the outside of the tip of the fuel exchanger, and attach a collection member with a vertical space in the center inside the tip of the fuel exchanger to move to the lower end of the pressure pipe and collect the crud that settles due to gravity. is adsorbed to the collection member by the electromagnet, and after the adsorption work is completed, electricity to the electromagnet is stopped and the collection member with the crud adsorbed is removed from inside the tip of the fuel exchanger. Electromagnetic collection method for cladding.