JPH0711595B2 - Electromagnetic trapping method for cladding in pressure tube - 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 using gravity to electromagnetically collect the clad. , A method for separating only the clad.

[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 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. 3, there was no foothold near the fuel exchanger 12 below the pressure pipe 10 and work at high places was required, so there were considerable restrictions 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 an electromagnetic trapping method for a clad in a pressure tube 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] According to the present invention which can achieve the above object, an electromagnet having a space vertically extending through a central portion is attached to a tip portion of a refueling machine and a lower end of a desired pressure tube is attached. To the clad, and forcefully adsorb the clad that settles down due to gravity by electromagnetic force.After the adsorption work is completed, remove the electromagnet from the tip of the fuel exchanger, stop energizing it and remove the clad. This is an electromagnetic clad trapping 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. An electromagnet is installed at the lower end of the pressure tube and is energized. Since the clad is an oxide of iron, it is relatively easily adsorbed to the electromagnet. Therefore, there is little risk that the clad unnecessarily diffuses into the system.

The clad adsorbed on the electromagnet is removed together with the electromagnet and moved to an appropriate place to stop energization. Therefore, the amount of waste generated is minimized.

In terms of equipment, the tip of the currently used refueling machine can be easily modified by slightly modifying it so that an electromagnet can be attached, and the electromagnet can be reused.

[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 tip portion 16 which is called (see B in the figure). If the step 16a is provided on the inner surface of the tip portion 16, the electromagnet 14 can be easily attached. At the same time, connect the power cable and so on.

The refueling machine 12 is located below the pressure tubes 10 arranged in a large number as shown in FIG. 3, 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 electromagnet 14 used in the present invention has a space that extends vertically through the central portion thereof, and has a structure in which the shaft of the wiper for removing clad and the like can be freely inserted.

As shown in FIG. 1C, a fuel exchanger equipped with an electromagnet 14
12 is moved to the lower end of the predetermined pressure tube 10 where the cladding should be removed by a moving mechanism in the horizontal plane. Then, the clad removing wiper 18 is vertically slid on the shaft 20 to mechanically separate the clad 22 adhering to the inner wall of the pressure tube 10.

At this time, since the operation of the system is temporarily stopped, the separated clad 22 sinks due to gravity. When the electromagnet 14 is energized, it is relatively easily adsorbed to the electromagnet 14 because the clad is an oxide of iron (see FIG. 1D).

When the adsorption work is completed for the pressure pipe which requires the removal of the clad by such an operation, as shown in FIG. 1E, the crane is used again to move the electromagnet from the tip portion 16 of the fuel exchanger 12.
Remove 14. Then, the clad is also taken out while being attached to the electromagnet 14. The clad can be detached from the electromagnet 14 by moving the electromagnet 14 to a predetermined position and stopping the electrical connection to the electromagnet 14. The clad that has left is transferred to a waste repository for storage. The electromagnet 14 can be reused.

The electromagnet used in the present invention may have any shape as long as it has a space extending vertically through the central portion thereof, and the shaft portion of the wiper for removing the clad can be freely inserted, and there is no particular structural limitation. . However, for example, as shown in FIG. 2, if an electromagnet 26 having a structure in which annular protrusions 24 are provided on the inner surface in multiple stages is used, the clad 22 once adsorbed is stored in the protrusions 24 during use. Hard to dissipate and good results are obtained. Alternatively, rod-shaped electromagnets may be arranged in a ring or a spiral electromagnet may be used.

EFFECTS OF THE INVENTION Since the present invention is a method in which an electromagnet is attached to the tip of a fuel exchange machine as described above, the clad falling by gravity is forcibly adsorbed by an electromagnetic force, and then only the clad is separated.
It has an excellent effect that the separated clad can be efficiently and intensively collected in the vicinity of the generation site without being diffused into the system unnecessarily and the spread of radiation can be prevented.

In addition, since the present invention collects the clad that sinks by using gravity, it is not necessary to significantly change the existing equipment, and the tip of the refueling machine is slightly modified so that the electromagnet can be attached. It is very advantageous in terms of cost because it can be easily dealt with and the electromagnet can be repeatedly used.

Further, according to the present invention, the clad can be collected at a high density, and the removal from the electromagnet can be easily performed by simply turning off the power,
Since only the clad can be separated, the amount of waste generated can be minimized, and the waste processing cost can be reduced.

[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 an electromagnet suitable for use in the present invention, and FIG. 3 is a pressure pipe and a fuel exchanger. It is explanatory drawing which shows the positional relationship. 10 …… Pressure tube, 12 …… Refueling machine, 14 …… Electromagnet, 16…
… Tip, 18… Wiper for removing clad, 22… Clad.

Claims (1)

[Claims] 1. An adsorption work by moving an electromagnet having a space extending vertically through a central portion to a lower end of a pressure pipe attached to a tip portion of a refueling machine, and forcibly adsorbing a clad settling down by gravity by an electromagnetic force. After completion of the above procedure, the electromagnet is removed from the tip of the refueling machine, the energization of the electromagnet is stopped, and the adsorbed clad is separated.