JPS63309897A - Device for removing liquid metal sticking to fuel assembly - Google Patents

Abstract

PURPOSE:To greatly reduce initial cost and treatment cost by acting centrifugal force on a fuel assembly housed in a pot and physically removing the liquid metal sticking thereto. CONSTITUTION:The cylindrical pot 32 housing internally the fuel assembly is pivotally fitted in the upper part and is, therefore, inclined by the centrifugal force in such a manner that the bottom end parts from the center according to the rotating speed when a revolving shaft 30 is revolved at a high speed by a driving motor 54. The centrifugal force acts also on the internal fuel assembly and the liquid metal sticking thereto and the liquid metal is dropped down by the centrifugal force and is discharged from the aperture at the bottom end of the pot 32. Since the liquid metal is physically removed in such a manner without using steam and water, the gathered liquid metal is reusable. In addition, the need for a waste liquid storage tank and waste liquid treatment equipment is eliminated and, therefore, the initial cost and treatment cost are greatly reduced.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a device that uses centrifugal force to remove liquid metal adhering to a fuel assembly. The present invention relates to a device that can remove sodium coolant adhering to the coolant when it is taken out from the inside without using steam or water.

[Prior Art] When a fuel assembly of a fast breeder reactor is taken out from inside a reactor vessel, coolant sodium is attached to its surface. When reprocessing fuel, it is first necessary to remove adhering sodium.

Therefore, as a conventional technique, a cleaning device having a configuration as shown in FIG. 8 has been used. This device includes a cleaning pot 12 that can be opened and closed by a door valve IO located at the upper end, a steam generator 14 and a water injection device 16 connected to the upper part via piping 13, and a lower end of the cleaning pot 12. Pump 18, waste liquid storage tank 20, waste liquid treatment equipment 22
It is composed of etc.

Then, the fuel assembly 24 is placed in the cleaning bot 12, and water vapor is blown into the cleaning bot 12 from above to cause the sodium adhering to the fuel assembly 24 to gently react with the water vapor.
Water is poured into the washing pot 12 to wash away the sodium. The sodium-containing waste liquid generated by cleaning is stored in a waste liquid storage tank 20 and then treated in a waste liquid treatment facility 22.

[Problems to be Solved by the Invention] However, with such conventional technology, in addition to requiring a steam generator 14 and a water injection device 16, a large amount of waste liquid containing radioactive waste is generated during cleaning, and it is necessary to dispose of the waste liquid. There was a drawback that a large waste liquid storage tank 20 and waste liquid treatment equipment 22 were required.

The purpose of the present invention is to overcome the drawbacks of the prior art as mentioned above, to be able to simply physically remove liquid metal without using steam or water, so that the collected liquid metal can be reused, and to provide a solution for waste liquid storage. An object of the present invention is to provide a device for removing liquid metal adhering to a fuel assembly, which eliminates the need for a tank or waste treatment equipment, and can significantly reduce equipment costs and treatment costs.

[Means for Solving the Problems] The present invention, which can achieve the above-mentioned objects, includes a rotating shaft that is held in the vertical direction at the center, a rotational drive mechanism for the rotating shaft, and a fuel inside. The pot is equipped with a cylindrical pot having an opening at the lower end into which the assembly can be inserted and held, and the pot is pivotally connected at its upper part to an upper arm provided horizontally from the rotating shaft to respond to the rotation of the rotating shaft. This is a device for removing deposited liquid metal from fuel assemblies that are supported so as to tilt due to centrifugal force.

Fuel assemblies generate decay heat after use. If this is left unattended, the fuel may melt, so for example, a configuration has been adopted in which cooling gas is circulated throughout the device for cooling, or a configuration in which cooling gas is introduced using centrifugal force.

[Operation] When the rotary shaft is rotated at high speed by the rotary drive mechanism, the cylindrical pot containing the fuel assembly inside is pivoted at the top, so centrifugal force causes the bottom end to shift to the center depending on the rotation speed. Lean away from. At this time, centrifugal force acts on the internal fuel assembly and the adhering liquid metal, so the liquid metal gradually flows downward due to the centrifugal force and flows out from the bottom opening of the pot.

In this way, the liquid metal adhering to the fuel assembly can be almost completely removed by physical means without the use of steam, water, or the like. Unlike the prior art described above, the removed liquid metal is a single liquid metal that has not reacted with water vapor or the like, so it can be collected and reused, and a small storage facility is sufficient.

[Embodiment] FIGS. 1 and 2 are a front sectional view and a plan view showing an embodiment of the apparatus according to the present invention. This device includes a rotating shaft 30 that is vertically held upright at the center, a rotational drive mechanism for the rotating shaft 30, and a cylindrical pot 32 into which a fuel assembly is inserted and held.

In this embodiment, two pots 32 are arranged 180 degrees symmetrically with respect to the rotation axis 30, and an upper arm 3 is provided horizontally from the rotation axis 30 in a cross shape above them.
4 is pivotally attached to the tip of each with a pin. In addition, one end of a lower arm 36 is pivotally connected to the lower part of the pot 32, and the other end center side is a slide member 3 that slides along the rotation axis 30.
It is pivoted to 8. These support the pot 32 so that it is tilted by centrifugal force in accordance with the rotation of the rotating shaft 30. A stopper 40 is provided below the rotary shaft 30 so that the sliding range of the slide member 38 does not exceed a certain limit. The pot 32 is shown in FIG.
It has a cylindrical structure with an opening 42 so that the fuel assembly 24 can be inserted and held through the upper opening and sodium can be discharged from the lower part.

At the bottom of the rotating shaft 30, there is a plate 44, which is an elongated receiver that rotates integrally with the rotating shaft 30. In order to prevent sodium from scattering, this receiving plate 44 is bent around its periphery, and has a drain hole 46 in the center, and liquid sodium is collected in a circular groove 48 located below the drain hole 46. is flowing. Note that this circular groove 48 is connected to a pipe 50 through which it reaches a sodium storage tank (not shown).

The rotating shaft 30 is rotatably supported by upper and lower bearings, and its upper end extends through a wall surface and is connected to a drive motor 54 via a transmission device 52 made of gears or the like.

These transmission device 52, drive motor 54, etc. constitute a rotational drive mechanism.

The processing chamber 56 in which the rotating shaft 30, the bot 32, etc. are accommodated is isolated from the outside air and maintained in an inert gas atmosphere. The fuel assembly 24 is taken in and out by opening and closing a door valve 58 provided on the upper wall surface. Further, the processing chamber 56 is connected to a gas cooling device 62 and a pump 64 through a gas pipe 60, and is configured to cool the inside thereof.

The method of using such a device is as follows.

First, a cask car (not shown) carrying the fuel assembly onto the door pulp 58 stops, and the door valve 58 is opened to set the fuel assembly 24 into the bot 32 while being isolated from the outside air. Thereafter, the rotating shaft 30 is rotated 180 degrees, the fuel assembly 24 is similarly set in the other bot 32, and the door valve 58 is closed. When the rotary shaft 30 is rotated at high speed by the drive motor 54, centrifugal force acts on the bot 32, causing the liquid sodium adhering to the fuel assembly 24 to fall from the lower opening 42 into the tray 44. After the sodium accumulated in the tray 44 stops rotating, it is sent to the sodium storage tank through the central drain hole 46, through the groove 48 and the piping 50. The fuel assembly from which the adhering sodium has been removed in this way is lifted into the cask car again through the door valve 58.

The fuel assembly 24 generates decay heat after use.

If this is left as is, the fuel will dissolve, so it is necessary to cool it even when removing the attached sodium. For this reason, in this embodiment, the gas in the processing chamber is circulated by a pump 64 and cooled by a gas cooling device 62.

FIGS. 4 and 5 are a front sectional view and a plan view showing another embodiment of the present invention. Since the basic configuration is the same as that of the previous embodiment, corresponding parts are given the same reference numerals to simplify the explanation, and the explanation thereof will be omitted.

The difference between this embodiment and the first embodiment is that the cooling gas is guided from the top of the bot 32 to the inside of the fuel assembly 2 by utilizing the force of the gas flowing outward due to centrifugal force.
This is because cooling is performed in step 4. Cooling gas supply bag W
A pipe 66 (not shown) is connected to the upper part of the rotating shaft 30 via a coupling 68. The rotating shaft 30 has a hollow structure up to the upper arm 34, from which the cooling gas flows to the tip of the upper arm 34 (a branch pipe 70 is connected thereto, and the pin 72 at the end of the upper arm 34 is also hollow and connects to the branch pipe 7).
This is a structure in which gas from 0 is guided into the bot 32.

When the bot 32 rotates, the branch pipe 70 is connected to the bot 3 from the root.
The gas contained up to the lower end of the tube receives an outward force due to centrifugal force, causing a flow of cooling gas. This cools the fuel assembly 24. The gas flowing out from the lower end opening of the bot 32 flows into the processing chamber 56 and is eventually discharged from an outlet (not shown).

FIGS. 6 and 7 are a front sectional view and a plan view showing still another embodiment of the present invention. This embodiment is also basically the same as the above-mentioned embodiments, so corresponding parts are given the same reference numerals and a description thereof will be omitted. This embodiment differs from other embodiments in that the power of the supplied cooling gas rotates the rotary shaft 30 and the equipment attached thereto, and cools them at the same time. The point is that it has been devised to provide both rotational power and cooling.

A fluid operated motor 74 is provided above the processing chamber 56 . The fluid operated motor 74 is a combination of inner vanes 76 and outer vanes 78. The inner blade 76 is fixed to the upper ceiling of the processing chamber 56 and is connected to a supply pipe 82 from a cooling gas supply device 80 . Outer blade 7
8 is fixed to the rotating shaft 30 and the upper arm 34, and further outside the outer blade 78, a branch pipe 84 extends to a position supporting the bot 32 at the tip of the upper arm, and a hollow tube 84 supporting the bot 32 is fixed to the rotary shaft 30 and the upper arm 34. It is connected to shaft 86 and configured to direct cooling gas through it into port 32 . The upper bearing of the rotating shaft 30 can also be a static pressure bearing that uses supplied gas. Although a drive motor 54 and a transmission device 52 are provided in this embodiment as well, they are preliminary.

The operation of this device is as follows. Cooling gas supply device 8
Cooling gas supplied from 0 is sent to fluid operated motor 74 through supply pipe 82 .

The gas passing through the inner vane 76 causes the outer vane 78 to rotate;
This causes the rotating shaft 30 to rotate at high speed. The cooling gas then passes through branch pipe 84 and hollow shaft 86 to pot 32.
supplied to Inside the pot 32, cooling gas passes through the fuel assembly due to gas discharge pressure and centrifugal force, producing a cooling effect and an effect of removing adhering sodium by gas blowing, and the discharged gas is recovered from an exhaust port (not shown). Ru.

Although three preferred embodiments of the present invention have been described in detail above, it goes without saying that the present invention is not limited to only such configurations. For example, in each of the above-mentioned embodiments, 2
The pots are arranged 180 degrees symmetrically,
The number of pots containing fuel assemblies can be increased or decreased as required.

[Effects of the Invention] As described above, the present invention is configured to apply centrifugal force to the fuel assembly housed in the pot to tilt it and physically remove the adhering liquid metal. Since there is no need to use steam or water, the amount of equipment can be significantly reduced, and there is no need to remove moisture inside the equipment after liquid metal removal work, which can shorten the process and eliminate the possibility of incorrect operation. It also has excellent safety, as there is no risk of sodium or main fires.

In addition, since the recovered liquid metal is a single substance in the present invention, it can be reused as is, and unlike the conventional technology, no waste liquid is generated, eliminating the need for waste liquid storage tanks and waste liquid processing equipment, which significantly reduces equipment costs and processing costs. This has the effect of making it possible to achieve significant reductions.

[Brief explanation of drawings]

Fig. 1 is a front sectional view showing one embodiment of the device according to the present invention, Fig. 2 is a plan view thereof, Fig. 3 is a sectional view showing the structure of the pot, and Fig. 4 is another embodiment of the invention. A front sectional view showing
FIG. 5 is a plan view thereof, FIG. 6 is a front sectional view showing still another embodiment of the present invention, FIG. 7 is a plan view thereof, and FIG. 8 is an explanatory diagram showing an embodiment of the prior art. . 30... Rotating shaft, 32... Pot, 34... Upper arm, 44... Receiver is plate, 52... Transmission device, 54
...Drive motor, '56...Processing chamber. Patent applicant Power Reactor and Nuclear Fuel Development Corporation Shigeru Hitoshi Estimates Figure 6 Figure 7, Figure 8 1゜Y84.X\

Claims (1)

[Claims] 1. A rotating shaft held in the vertical direction at the center, a rotational drive mechanism for the rotating shaft, and a cylindrical pot with an opening at the lower end into which a fuel assembly can be inserted and held; A device for removing deposited liquid metal from a fuel assembly, characterized in that the upper arm is pivotally connected to an upper arm provided horizontally from the rotating shaft, and is supported so as to be tilted by centrifugal force according to rotation of the rotating shaft. .