JPS6148876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shaft sealing device for a closed vessel such as an ex-core fuel storage tank or a nuclear reactor vessel in the field of nuclear reactors, for example.

First, an outline of the above-mentioned extra-core fuel storage tank will be explained as an example of the embodiment of the present invention. In Fig. 1, 1 is a storage container as an airtight container in which a drum-type fuel storage rack 2 is stored, 3 is a flexible plug serving as a lid for the container, and the shaft 4 on which the rack 2 is hung is a flexible plug. It passes through the opening and is pulled out to the outside, is supported by a thrust bearing, and is connected to the drive motor 5. In addition, liquid metal sodium 6 as a coolant and a cover gas 7 are sealed in the container 1.
A shaft sealing device 8 is provided between the shielding plug 3 and the shaft 4 to prevent leakage of the cover gas from the shaft penetrating portion, thereby forming an airtight boundary for the cover gas 7. Although not shown, a fuel passage is formed above the rack 2 and passes through the shield plug 3, and spent fuel is taken in and taken out of the rack 2 through this fuel passage.

Incidentally, a V-packet, an inflatable seal, or the like is usually used as the seal of the shaft sealing device. However, these seals inevitably deteriorate and lose their sealing function during long-term use.
Furthermore, since the fuel storage tank that handles spent fuel is always required to have high sealing performance from the standpoint of radiation control, it is necessary to remove the seal from the shaft seal device, inspect it, and replace it after it has been used for a predetermined period of time. Moreover, this seal replacement is required to be performed while maintaining the airtightness of the shaft sealing device in order to prevent leakage of the cover gas inside the tank. As a countermeasure for this, in addition to the main seal, we also have an inflatable seal for main seal replacement that is normally on standby when the main seal is inspected.
Conventionally, a system has been proposed in which the inflatable seal is used to seal the shaft during replacement, and the main seal can be removed together with the seal mounting base.
This conventional system had drawbacks such as a complicated mechanism and seal operation, the overall structure of the shaft seal being large, and maintenance required for the inflatable seal used to replace the main seal. In addition, there are some systems that use a simple contact-type metal seal as a seal for replacing the main seal, but simply contacting the metal seal with the mating member does not provide sufficient sealing performance and lacks reliability.

The present invention has been made in consideration of the above points, and its purpose is to provide a shaft sealing device for a sealed container that has a simple structure and operation, ensures a reliable shaft sealing function, and allows easy replacement of the main seal. It is in.

The present invention will be described in detail below based on illustrated embodiments intended for extra-core fuel storage.

In FIGS. 2 and 3, a sealing plug 3, which is a container lid, has a shaft seal casing 9 and a shaft seal casing 9, which protrudes outward from the sealing plug so as to surround the shaft 4, and is attached to the tip of the casing. A seal mount 11 made of a seal housing 10 is removably provided, and a main seal 12 facing the shaft 4 is mounted in a circumferential groove 13 on the inner peripheral surface of the seal housing 10. Reference numerals 14 and 15 designate O-rings as fixed seals installed on the sealing surfaces between the casing 9 and the seal housing 10 and between the damping plug 3 and the casing 9, respectively. Further, a seal ring 16 that is in contact with the main seal 12 is removably fitted on the outer periphery of the shaft 4, facing the main seal 12. 17 is an O-ring that seals between the seal ring 16 and the shaft 4. Although the main seal 12 may be in direct contact with the shaft 4, in order to maintain the integrity of the seal surface that rotates and slides against the main seal 12, a seal ring 16 is used as shown in the figure, and regular In general, it is convenient to replace the seal ring 16 with a new one because high sealing performance can be maintained.

In contrast to the main seal 12 described above, according to the present invention, a metal seal ring 18 with a square cross section is attached to the outer periphery of the shaft 4 at a location closer to the inner space of the container than the main seal 4 within the inner region of the seal mounting base 8. has been done. This metal seal ring 18 is the presser ring 1
It is fixed to the shaft 4 via a shaft 9, and its downward axial end surface protrudes from the shaft 4 so as to face the upper end surface of the opening of the stiffener plug 3. Further, as clearly shown in FIG. 3, the metal seal ring 18 has circumferential grooves 20 and 21 formed on its inner circumferential surface and axially lower end surface, respectively, and furthermore, between both circumferential grooves 20 and 21. Communication holes 22 are bored at a plurality of locations in the circumferential direction inside the ring. on the other hand,
The sealing plug 3 has a pressurized gas supply hole 23 opened in the upper end face facing the circumferential groove 21, and the other end of the hole 23 extends outward beyond the seal mounting base 11. The opening is connected to an external pressurized gas supply line 26 equipped with an inert gas source 24 and an on-off valve 25 .

Next, the operation of the above configuration will be described. During normal operation, the shaft 4 is supported by a thrust bearing at the position indicated by the chain line in the figure. Therefore, the metal seal ring 18 is separated from the upper surface of the shield plug 3 and retracted upward, and the main seal 12 forms an airtight boundary for the cover gas in the container.
Note that during this operation, the valve 25 of the pressurized gas supply line 26 is kept closed. To inspect or replace the main seal 12 from this state, first suspend the entire shaft from the operating position indicated by the chain line to the position indicated by the solid line, and place the metal seal 18 against the upper end surface of the seal plug 3. Forms a sealing surface that serves as an airtight boundary for the cover gas. Next, the valve 25 of the pressurized gas supply line 26 is opened, and an inert gas of the same type as the cover gas 7 in the container is applied from the pressurized gas source 24 to the circumferential grooves 20 and 21 of the metal seal ring 18 through the pressurized gas supply hole 23. Supply pressure. Note that the supply gas pressure is set higher than the pressure of the cover gas inside the container. Therefore, pressurized gas is blown out from the entire area of the circumferential grooves 20 and 21 toward the sealing surfaces between the metal seal ring 18 and the shaft 4 and between the metal seal ring 18 and the hardening plug 3, and the cover gas 7 is It is sealed in front of the metal seal ring 18.
In this state, the metal seal ring 1 is no longer
There is no possibility that the cover gas 7 in the container will leak through the sealing surface of the seal housing 1.
0 can be removed to freely replace the main seal 12. Similarly, the casing 9 and seal ring 16 can also be removed and the O-rings 14, 15 and 17 replaced. During this time, some gas supplied from the pressurized supply line 26 blows outward from the circumferential grooves 20 and 21 of the metal seal ring 18, but unlike the cover gas in the container, this gas is fresh and does not contain radiation or sodium vapor. It is safe because it is a safe gas. Note that after replacing the main seal 12, it can be reassembled by following the reverse procedure.

According to the above configuration of the present invention, by moving the metal seal ring together with the shaft to the operating position and supplying pressurized gas, leakage of the cover gas inside the container is reliably prevented, and the main seal is removed for inspection. ，
Replacement can be done easily and safely. Moreover, unlike inflatable seals made of flexible materials such as rubber, metal seal rings can withstand long-term use, and they can be used simply by touching the other side without sliding, so they are less likely to wear out. There is no need for maintenance on the metal seal ring itself, and the reliability of the shaft sealing device can be improved accordingly. In addition, the overall structure is simple and compact.

Note that the shaft sealing device of the present invention is not limited to the illustrated embodiment, and may be used as a shaft sealing device between the pressure vessel of the reactor main body and its upper rotating plug, or a hole for sealing a through hole drilled in the rotating plug. It can also be applied as a shaft sealing device for a plug. In this case, the shaft in the embodiment becomes a rotating plug or a hole plug. Furthermore, it goes without saying that it can be used as a shaft sealing device not only in the nuclear power field but also in a wide range of fields such as closed containers handling toxic gases.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the structure of an ex-core fuel storage tank as an example of the embodiment of the present invention, FIG.
It is a cross-sectional perspective view of the metal seal ring in a figure. DESCRIPTION OF SYMBOLS 1... airtight container, 3... tight plug as container lid, 4... shaft, 8... shaft sealing device, 11...
Seal mounting base, 12...Main seal, 18...Metal seal ring, 20, 21...Peripheral groove, 22...
Communication hole, 23... pressurized gas supply hole, 26... pressurized gas supply line.

Claims (1)

[Claims] 1. A shaft sealing device that seals between the opening of a sealed container and a shaft fitted into the opening, which is a seal mount that projects outward from the sealed container and is removably attached to surround the shaft. , the main seal is mounted on the inner peripheral surface of the seal mount facing the shaft, the main seal is mounted on the outer periphery of the shaft facing the end surface of the opening of the sealed container in the inner area of the seal mount, and the main seal is inspected. , a metal seal ring for replacing the main seal that contacts and seals against the end face of the other container during replacement, a circumferential groove formed on the inner peripheral surface of the metal seal ring and the axial end face opposite to the end face of the container, and a circumferential groove on both circumferential grooves. A communication hole is drilled in the metal seal ring to communicate with each other, and one end is opened facing the circumferential groove of the metal seal ring, and the other end is drilled in the airtight container so that an external pressurized gas supply line is connected. A shaft sealing device for an airtight container consisting of a pressurized gas supply hole.