JPH0769464B2 - Collection method of cladding by permanent magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a pressure tube reactor, in which the clad separated from the tube wall of the pressure tube is settled by using gravity and magnetically attracted by a permanent magnet to be collected. It is about how to do it.

[Prior Art] In a pressure tube reactor, a clad (corrosion product) is generated on the inner wall of the pressure tube after 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, 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 cause a dramatic increase in 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 the clad in the pressure tube without unnecessarily diffusing the clad, thereby increasing the exposure in various operations after removal. It is an object of the present invention to provide a method of collecting clad in a pressure pipe that can be prevented and is simple in terms of equipment and can be inexpensively handled by using a conventional device.

[Means for Solving the Problems] In the present invention which can achieve the above objects, a collecting member having a structure having a permanent magnet and having a space vertically extending in the center is provided at the tip of a fuel exchanger. After mounting, move to the lower end of the desired pressure tube, force the magnetic force to adsorb the clad that sinks due to gravity, and after the adsorption work is completed, remove the collecting member from the tip of the fuel exchanger. It is a collection method.

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 collection member having a permanent magnet is installed at the lower end of the pressure tube. Since the clad is an oxide of iron, it is relatively easily magnetically attracted to and collected by the permanent magnet. Therefore, there is little risk that the clad unnecessarily diffuses into the system.

The clad magnetically adsorbed on the collecting member is removed together with the collecting member, and the clad is separated as it is or by removing the permanent magnet, and the clad is transferred to the waste storage place for storage.

In terms of equipment, this can be easily handled by modifying the tip of the currently used fuel exchanger to some extent so that a collecting member can be attached.

[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. 6A, the collecting member 14 is lifted by a crane or the like (not shown) and attached to the tip portion 16 of the refueling machine 12 called the "snout portion" (see FIG. B).
If the step 16a is provided on the inner surface of the tip portion 16, the collection member 14 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 collection member 14 used in the present invention includes a permanent magnet,
The structure has a vertically extending space at the center, and the shaft of the wiper for removing the clad can be freely inserted. This may be a permanent magnet alone or a magnet assembly in which a permanent magnet and a filler are combined.

As shown in FIG. 1C, the fuel exchanger 12 equipped with the collecting member 14 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 slide the cladding removing wiper 18 up and down on the shaft 20,
The clad 22 attached to the inner wall of the pressure pipe 10 is mechanically peeled off.

At this time, since the operation of the system is temporarily stopped, the separated clad 22 sinks due to gravity. The collecting member 14 is provided with a permanent magnet, and since the clad is an oxide of iron, it is relatively easily magnetically adsorbed (see FIG. 1D).

Such an operation is performed on the pressure tube that requires clad removal. When the suction work is completed, the collecting member 14 is removed from the tip portion 16 of the fuel exchanger 12 again by using a crane or the like as shown in FIG. 1E. Then, the clad 22 is also the collecting member.
It is taken out as it is attached to 14.

The collecting member 14 may be transferred to the waste storage as it is for storage, but a structure in which the clad does not directly contact the permanent magnet, for example, a structure in which the outer side of the permanent magnet is covered with a cover, the clad is removed by removing the cover. It is also possible to separate the clad from the permanent magnet and transfer only the clad to the waste storage for storage. This is preferable because the amount of waste treated is small.

The structure of the collecting member used in the present invention may be a structure that includes a permanent magnet, has a space longitudinally extending through the center thereof and allows the shaft of the wiper for removing the clad to be freely inserted, and is particularly structurally It has no restrictions. However, it is desirable to have a structure in which the clad that has been magnetically attracted is less likely to dissipate during use. For example, as shown in FIG. 2, permanent magnets 24 are stacked in a case 25 in multiple stages to provide a concave and convex inner surface to facilitate attachment and holding of a clad, and a magnet assembly 26 as shown in FIG. A structure in which the materials 30 are alternately housed in the case 32 is preferable. As the filler 30, for example, stainless fine wires (fibers of about 10 to 100 μm), wire nets, and perforated plates stacked in multiple layers can be used. Further, if the equivalent wire diameter of the filler 30 is made thin, a high gradient magnetic separation effect and a filter effect can be expected, and the porosity for holding the clad can be increased, and a preferable result can be obtained. In addition, rod-shaped permanent magnets may be arranged annularly or spiral permanent magnets may be used.

EFFECTS OF THE INVENTION The present invention is a method in which a collecting member is attached to the tip of a fuel exchanger as described above, and the clad falling by gravity is forcibly adsorbed and separated by the magnetic force of the permanent magnet. Has an effect that it can be efficiently and intensively collected in the vicinity of the generation site without being diffused into the system, and the spread of radiation can be prevented.

Further, since the present invention collects the clad that sinks using gravity, it is not necessary to significantly change the existing equipment, and a slight modification is made to the tip of the refueling machine so that a collecting member can be attached. It is easy to deal with the extent to which it is applied, which is extremely advantageous in terms of cost.

Further, in the present invention, the clad can be collected at a high density, and if the permanent magnet is provided with a cover, the clad can be separated together by removing the cover, so that the amount of waste generated can be minimized. The magnets can be reused, and the waste disposal cost can be reduced.

Moreover, unlike the case of using an electromagnet, there is an advantage that it is not necessary to connect a power cable or the like, and electrical insulation is not necessary, which makes the work easier.

[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 pipe, 12 …… Refueling machine, 14 …… Collection member, 16
...... Tip, 18 …… Clad removal wiper, 22 …… Clad.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location G21F 9/28 551 Z 9117-2G (72) Inventor Kenichi Tomomatsu 1-9 Akasaka, Minato-ku, Tokyo No. 13 Power Reactor / Nuclear Fuel Development Headquarters (56) Reference JP-A-60-8792 (JP, A) JP-A-60-247192 (JP, A) JP-A-63-250596 (JP, A) Actual Kaisho 59-154344 (JP, U)

Claims (1)

[Claims] 1. A clad member having a permanent magnet and having a space having a longitudinally extending space at its center is attached to the tip of a refueling machine to move to the lower end of a pressure pipe, and a clad which sinks due to gravity. A method for trapping a clad by a permanent magnet, wherein the trapping member is detached from the tip of the fuel exchanger after the adsorbing work is completed by forcibly adsorbing by a magnetic force.