JP2815376B2 - Reactor control rod drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor control rod drive, and more particularly to a reactor control rod drive suitable for a liquid metal sodium cooled reactor.

[Conventional technology]

A control rod drive for a liquid metal sodium cooled reactor has a drive shaft connected at its lower end to a control rod in a reactor vessel via a gripper, and a drive shaft for vertically moving the control rod. A latch shaft for opening and closing the latch finger of the gripper extends coaxially. The control rod is pulled out and inserted by moving the drive shaft up and down, and the connection and disconnection of the drive shaft and the control rod are performed by moving the latch shaft up and down.

By the way, since the control rod drive device extends through the rotary plug into and out of the reactor vessel, a boundary member for preventing the cover gas in the reactor from leaking out of the reactor vessel is provided. ing. The detailed structure of this part is shown in FIG.

The boundary member of the cover gas 9 in the reactor of the reactor control rod drive unit is provided at the upper end of the upper guide tube 3 that houses the drive shaft 15.
O-ring for sealing between 11 and mount 12 for control rod drive
13A, a stroke bellows 13, a latch bellows 14, and the like.

The sealing of the cover gas 9 in the reactor during the vertical movement of the drive shaft 15 for the vertical movement (pulling and insertion) of the control rod is performed by the stroke bellows 13.

The latch bellows 14 seals the reactor cover gas 9 when the latch shaft 16 moves up and down to open and close the latch finger of the gripper located at the lowermost end of the drive shaft 15 of the upper guide tube 3.

In addition, in the event that the boundary member of the in-reactor cover gas 9 is broken, a seal structure is provided as a backup to prevent the in-reactor cover gas 9 from leaking out of the reactor vessel.

The seal structure as this backup is a packing 17 which is a seal member between the upper end 11 of the upper guide tube 3 and the drive shaft 15.
And a packing 18 which is a seal member for the drive shaft 15 and the latch shaft 16.

The packing 17 is installed at the uppermost part of the upper guide tube 3, and seals while contacting the drive shaft 15 that moves up and down when the control rod 7 moves up and down. This packing 17 is
(Replace with a new one.)

On the other hand, the packing 18 is structurally composed of the drive shaft 15 and the latch shaft 16.
And a latch shaft for latching (gripping) and de-latching (releasing) the control rod 7.
When the up and down movement of the drive shaft 16 is performed, the up and down movement is performed together with the latch shaft 16 while being in contact with the inner surface of the drive shaft 15 to seal.

[Problems to be solved by the invention]

 The above conventional example has the following problems.

When the seal performance of the packing 18 of the seal portion between the drive shaft 15 and the latch shaft 16 is deteriorated during operation of the nuclear reactor or the like, and it is necessary to replace the seal with a new one, the guide tube 8 for the drive device is installed. After removing the drive unit, the entire upper guide tube 3 had to be taken out of the reactor vessel, washed to remove sodium and the like, and decomposed.

However, this replacement operation is a very difficult operation in practice, and cannot be performed in practice.

SUMMARY OF THE INVENTION An object of the present invention is to provide a reactor control rod drive device that makes maintenance-free a seal portion that seals a backup when a boundary member that seals an atmosphere in a reactor is damaged, thereby greatly improving maintainability. is there.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a boundary member that seals the atmosphere in a reactor with respect to a movable member,
A reactor control rod drive device having a seal portion for performing a backup seal when a boundary member is broken, wherein the backup seal portion is constituted by an axially expandable and contractable sealing means, and the axially expandable and contractible seal is provided. The means is made of a material different from the material of the seal member as the boundary member.

Further, in order to achieve the above object, the present invention provides a latch shaft which is coaxially arranged in a drive shaft for vertically moving a control rod, connects and disconnects the drive shaft and the control rod, and A reactor control rod drive device comprising: a boundary member for sealing a reactor atmosphere during operation; and a seal portion between a drive shaft and a latch shaft for performing backup sealing when the boundary member is damaged. And a backup seal between the latch shaft and the latch shaft is constituted by seal means capable of extending and contracting in the axial direction, and the seal means capable of extending and contracting in the axial direction is constituted by a material different from the material of the seal member as the boundary member. I do.

Further, in order to achieve the above object, the present invention provides a latch shaft which is coaxially arranged in a drive shaft for vertically moving a control rod, connects and disconnects the drive shaft and the control rod, and a vertical shaft of the latch shaft. A reactor control rod drive device comprising: a boundary member for sealing a reactor atmosphere during operation; and a seal portion between a drive shaft and a latch shaft for performing backup sealing when the boundary member is damaged. The back-up seal between the and the latch shaft is constituted by a sealing means capable of extending and contracting in the axial direction, and the boundary member and the back-up seal are disposed below the surface of the high-temperature liquid coolant.

[Action]

By forming the backup seal portion with sealing means that can expand and contract in the axial direction, for example, a welding bellows, when the movable member (latch shaft) moves up and down, this sealing means expands and contracts in the up and down direction to perform backup sealing. . At this time, the sealing means, which can expand and contract in the axial direction, is different from the conventional packing in that there is no sliding portion in the sealing structure, so that the sealing performance and durability are dramatically improved, especially when the material is metal, It is virtually maintenance free.

Further, by configuring the sealing means with a material different from that of the sealing member as the boundary member, failure of the backup sealing means can be avoided even under conditions in which the boundary member fails, thereby improving safety.

Further, by disposing the boundary member and the backup seal portion below the liquid surface of the high-temperature liquid coolant,
A relatively large space is secured inside the drive shaft, and this space can be effectively used for installation of equipment.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. The present embodiment is an example of a control rod driving device for a liquid metal sodium cooled reactor.

First, the overall configuration of the reactor control rod drive device will be described with reference to FIG.

The reactor control rod drive 1 is a drive unit having a drive 2
1B and an upper guide tube portion 1A having an upper guide tube 3.

In the upper guide tube portion 1A, the upper guide tube 3 has its upper end 11
Are supported at the upper surface position of the rotary plug 4, and are generally disposed in the reactor vessel in the atmosphere of the reactor cover gas 9 (argon, sodium vapor, etc.) and the liquid sodium 5. A lower end of the upper guide tube 3 is connected to a control rod 7 via a gripper 6, and a drive shaft 15 for vertically moving the control rod 7 extends coaxially. Latch shaft that opens and closes the 6 latch fingers
16 extend coaxially. The control rod 7 is a control rod guide tube 10
Is housed inside.

In the driving section 1B, the driving device 2 is housed in a driving device guide tube 8 (upper core mechanism) located on the rotary plug 4, and a lower end thereof is connected to an uppermost portion of the upper guide tube 3 to form a drive shaft. 15 and the latch shaft 16 are respectively moved up and down.

The drive unit 2 and the upper guide tube 3 can be separated and separately maintained at the time of regular inspection of the reactor.

FIG. 1 shows a detailed structure of the boundary member for the cover gas 9 in the reactor in a state where the driving device 2 is detached from the driving device guide tube 8.

The boundary member of the reactor cover gas 9 is composed of an O-ring 13A for sealing the upper end 11 of the upper guide tube 3 and the control rod drive mounting base 12, a stroke bellows 13, a latch bellows 14, and the like.

Drive shaft 15 for vertical movement (pull-out and insertion) of control rod 7
The seal of the cover gas 9 in the reactor during the vertical movement of
This is performed with the stroke bellows 13.

A latch shaft 16 for opening and closing the latch finger of the gripper 6 located at the lowermost end of the drive shaft 15 of the upper guide tube 3
The seal of the cover gas 9 in the reactor during the vertical movement of
This is performed by the latch bellows 14.

In addition, in the event that the boundary member of the in-reactor cover gas 9 is broken, a seal structure is provided as a backup to prevent the in-reactor cover gas 9 from leaking out of the reactor vessel.

The seal structure as this backup is a packing 17 which is a seal member between the upper end 11 of the upper guide tube 3 and the drive shaft 15.
And a welding bellows 20 which is a seal member between the drive shaft 15 and the latch shaft 16.

The packing 17 is installed at the uppermost part of the upper guide tube 3, and seals while contacting the drive shaft 15 that moves up and down when the control rod 7 moves up and down. This packing 17 is
(Replace with a new one.)

On the other hand, the upper end of the welding bellows 20
The lower end is connected to the drive shaft 15 by welding via a pipe 15A. When the latch shaft 16 moves up and down for connection and disconnection of the control rod 7, the welding bellows 20 expands and contracts in the vertical direction, and the drive shaft 15 and the latch shaft Seal between 16. This welding bellows 20
Unlike conventional packings, there is no sliding portion in the seal structure, so when the material is metal, the sealing performance and durability are dramatically improved, and the maintenance becomes substantially maintenance-free.

The detailed structure of the welding bellows 20 is shown in FIG. The welding bellows 20 is formed by alternately connecting the inner end and the outer end of an annular steel plate by welding, and has a structure capable of obtaining a relatively large expansion and contraction length.

The welding bellows 20 is made of a material different from the material of the latch bellows 14. As an example, when the material of the latch bellows 14 is a nickel alloy such as Inconel 718, the material of the welding bellows 20 is stainless steel such as SUS304 or 316. This reduces the possibility that both will fail at the same time under the same conditions, and improves safety.

As described above, according to this embodiment, in the seal structure for backing up the boundary member of the cover gas 9 in the reactor, the seal portion of the drive shaft 15 and the latch shaft 16 becomes maintenance-free, and the reactor control rod drive The maintainability of the device is greatly improved.

Further, since the welding bellows 20 is made of a material different from the material of the latch bellows 14, failure of the welding bellows 20 can be avoided even under conditions in which the latch bellows 14 fails, thereby improving safety.

Another embodiment of the present invention will be described with reference to FIGS.

The above-mentioned embodiment is an example in which the backup seal structure of the latch bellows 14 which is the boundary member of the cover gas 9 in the reactor is constituted by the welding bellows 20, but any sealing means that can expand and contract in the axial direction may be used. May be used. FIGS. 4 and 5 show an example in which one of the same bellows, which is one of the same bellows, is used as a sealing means capable of extending and contracting in the axial direction, and is formed by shaping a single cylindrical material into a wavy shape. The molded bellows 21 has the advantage that quality control of welding is not required.

FIG. 6 shows an example in which the diaphragm 22 is employed as a sealing means which can be expanded and contracted in the axial direction. Diaphragm 22
Although there is a demerit that the size in the radial direction becomes large, there is an advantage that there are few causes of failure because there are few curved portions.

Still another embodiment of the present invention will be described with reference to FIG. This embodiment is different from the above embodiment in the installation positions of the latch bellows 14 and the welding bellows 20. That is, in this embodiment, the back-up seal structure of the drive shaft 15 and the latch shaft 16 is the same as that of the embodiment of FIG. 1, but the latch bellows 14 is installed at the level located in the sodium 5. Corresponding to the above, the welding bellows 20 is also installed below the sodium 5 liquid level.

According to the present embodiment, since the latch bellows 14 and the welding bellows 20 are installed below the liquid level of sodium 5, a relatively large space is secured inside the drive shaft 15, especially inside the liquid level of sodium 5. This has the effect that this space can be effectively used for installation of equipment.

In the above embodiment, the drive shaft of the backup seal structure for the boundary member of the cover gas 9 in the reactor is used.
Although a sealing means which can be extended and contracted in the axial direction is employed for the seal portion of the latch shaft 15 and the latch shaft 16, a similar seal structure may be employed for the upper end of the upper guide tube 3 and the seal portion of the drive shaft 15 instead of the packing 17. As a result, this part is also maintenance-free, and the maintainability of the entire reactor control rod drive device is improved.

〔The invention's effect〕

According to the present invention, the seal portion for backing up the boundary member with respect to the atmosphere in the reactor, particularly the seal portion for the drive shaft 15 and the latch shaft 16 among the seal portions for backup between the drive shaft and the latch shaft, is maintenance-free. This greatly improves the maintainability of the reactor control rod drive.

Further, since the backup seal portion is made of a material different from the material of the seal portion as the boundary member, safety is improved.

Further, since the latch bellows and the welding bellows are installed in the sodium, the internal space of the drive shaft, particularly the internal space above the sodium level can be effectively used for installing the equipment.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of a reactor control rod driving device according to one embodiment of the present invention, and FIG. 2 is a schematic sectional view showing the entire structure of the reactor control rod driving device. FIG. 4 is an enlarged view of a welded bellows used as a backup seal member in the reactor control rod drive unit, and FIG. 4 is a reactor according to another embodiment of the present invention using a molded bellows as a backup seal member. FIG. 5 is an enlarged cross-sectional view of a main part of a control rod drive unit, FIG. 5 is an enlarged view of a molded bellows, and FIG. 6 is a main part of a reactor control rod drive unit using a diaphragm as another example of a seal member. FIG. 7 is an enlarged cross-sectional view, FIG. 7 is an enlarged cross-sectional view of a main part of a reactor control rod drive according to still another embodiment of the present invention, and FIG. 8 is an enlarged main part of a conventional reactor control rod drive. It is sectional drawing. DESCRIPTION OF SYMBOLS 1 ... Reactor control rod driving device 5 ... Sodium (liquid coolant) 7 ... Control rod 9 ... Reactor cover gas (atmosphere in reactor) 13 ... Stroke bellows (boundary member) 14 ... … Latch bellows (Boundary member) 15… Drive shaft 16… Latch shaft 17… Packing (backup seal) 20… Weld bellows (backup seal: seal means)

Claims (3)

(57) [Claims] 1. A reactor control rod drive device comprising: a movable member; a boundary member that seals an atmosphere in a reactor; and a seal portion that seals a backup when the boundary member is damaged. The part is constituted by sealing means which can be expanded and contracted in the axial direction, and the sealing means which can be expanded and contracted in the axial direction is formed of a material different from the material of the sealing member as the boundary member. . 2. A latch shaft disposed coaxially in a drive shaft for vertically moving a control rod, for connecting and disconnecting the drive shaft to and from the control rod, and sealing the atmosphere in the reactor when the latch shaft is vertically moved. A control rod drive device comprising a boundary member for performing the operation, and a seal portion between the drive shaft and the latch shaft for performing a backup seal when the boundary member is broken, wherein a backup seal between the drive shaft and the latch shaft is provided. The part is constituted by sealing means which can be expanded and contracted in the axial direction, and the sealing means which can be expanded and contracted in the axial direction is formed of a material different from the material of the sealing member as the boundary member. . 3. A latch shaft which is coaxially arranged in a drive shaft for vertically moving a control rod, connects and disconnects the drive shaft and the control rod, and seals the atmosphere in the reactor when the latch shaft is vertically moved. A control rod drive device comprising a boundary member for performing the operation, and a seal portion between the drive shaft and the latch shaft for performing a backup seal when the boundary member is broken, wherein a backup seal between the drive shaft and the latch shaft is provided. A nuclear reactor control rod driving device, wherein the portion is constituted by sealing means capable of extending and contracting in the axial direction, and the boundary member and the backup seal portion are disposed below the liquid surface of a high-temperature liquid coolant.