JPH0382996A - Freeze seal structure - Google Patents

Abstract

PURPOSE:To remarkably reduce the number of workers and working times, to sharply make possible the reduction of radiation exposure of the workers by providing a partition plate with a sampling member and sampling solid impurities produced in a seal metal. CONSTITUTION:Solid impurities mainly existing on seal metal liquid surface and near it are picked up from a seal metal 13 in accordance with the movement of a partition plate 15 or a seal dam 14 with the use of a sampling plate 21 provided on the partition plate 15 to reach a feed and drain tube 22 having an opening part 24 upward of a member 21. The feed and drain tube 22 is directly connected to a seal metal feed and drain device 23 provided in the outside of a rotation plug 12, for instance, a vacuum pump of the device 23 is operated to vacuum-transfer the impurities reaching the opening part 24 to an impurities storage tank of the device 23. At the time the sound seal metal 13 of the liquid surface is not sampled by the member 21 due to the fact that the member 21 is in the form of a mesh, and the impurities pass it to remain in the dam 14. Accordingly, a backup seal member 16 is not removed and the impurities can be removed out of the plug 12.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a sealing device that uses frozen seal metal as a sealing material in a rotating plug sliding part of a reactor vessel of a fast breeder reactor. The present invention relates to a freeze seal structure suitable for automatically removing generated solid impurities and replenishing new metal.

[Conventional technology]

FIG. 7 shows the general arrangement of main equipment such as a reactor core including a fuel assembly, a sodium pump, and an intermediate heat exchanger in a tank-type fast breeder reactor.

Inside the reactor vessel l, there is a reactor core 2 at its center, and surrounding this reactor core 2 are a sodium pump 3 and an intermediate heat exchanger 4.
Equipment such as these are installed. In addition, at the top of the reactor core 2,
A two-part mechanism 5 is arranged. Most of these instruments are immersed in sodium 6 in vessel 1.

Two parts of the reactor vessel 1 include a roof slab 7 that also serves as a shield for radiation from the reactor core 2, and rotating plugs (a large-rotation plug 8 and a small-rotation plug 9) supported by the roof slab 7.
) to keep the furnace vessel 1 in a sealed state. By combining the rotational movements of the two large and small rotating plugs 8 and 9, all fuel assemblies in the reactor core 2 can be handled.

In addition, between the roof slab 7 and the two rotating plugs 8 and 9 and the liquid level of the sodium 6, a slightly pressurized argon gas or the like is placed between the roof slab 7 and the two rotating plugs 8 and 9 and the liquid level of the sodium 6. It is filled with inert gas.

A gap 10 between the roof slab 7 and a device that penetrates the roof slab 7, such as the sodium pump 3 or the intermediate heat exchanger 4, is sealed in order to maintain the airtightness of the furnace vessel 1.

That is, the gap between the equipment and the roof slab 7 is fixed by bolting using a sealing material such as a backing made of rubber or metal, or by welding via a cushioning member such as a bellows] . O is sealed.

Large rotation plug 8, roof slab 7 and large rotation plug 8
The gap 1 between the small rotation plug 9 and the small rotation plug 9. For OA, JP-A-58-
As shown in No. 1.86087, an alloy that melts when heated to about 100 to 200°C, which is a combination of metals such as B1°Sn and In, which is generally called freeze seal metal, is used as a sealing material. .

Figure 8 shows the gap O between the roof slab 7 and the rotating plug top 2.
A cross section of a freeze seal structure using freeze seal metal (seal metal) 13 is shown for the seal of A. The basic structure and sealing principle of the freeze seal structure 1i1A 10 A between the large rotation plug 8 and the small rotation plug 9 shown in FIG. 7 are completely the same.

In FIG. 8, the seal metal 13 is connected to the roof slab 7.
Freeze shield dam (shield dam) 14 installed on the side
is injected into. A partition plate 15 protruding from the rotating plug 12 so as to be immersed in the seal metal ring 3 forms a seal of the gap 10A, that is, a boundary of the furnace vessel 1.

The temperature of the seal metal medium 3 is maintained below its melting point during reactor operation, and is in a solid state.

Therefore, the sealing structure is strong enough to withstand sudden increases in the inert gas pressure within the reactor vessel 1 due to sudden accidents.

On the other hand, when handling fuel during a nuclear reactor shutdown, the seal metal 13 is heated and becomes a liquid. In the liquid state, the partition plate 15 can slide in the seal metal 13, that is, the rotary plug 12 can rotate.

Furthermore, in this state, the specific gravity of the seal metal 13 is high, so that it maintains sealing performance sufficient to withstand the inert gas pressure within the furnace vessel 1.

Note that the atmosphere on the atmospheric side of the seal metal 13 divided by the partition cutout 5 is maintained by attaching a backup seal member 16, especially for backing up boundary formation during reactor operation. It is also practiced to replace the space between the two with an inert gas atmosphere such as argon gas.

FIG. 9 shows an example in which the partition cutout 5 protrudes from the roof slab 7 side instead of from the rotary plug 12 side as shown in FIG. 8. In this case, the shield dam 14 is conversely connected to the rotating plug 1.
It is provided on the second side. Although there are structural differences in the mounting positions of the partition plate 15 and the like, the principle of the freeze seal structure and the roles of each member are the same as in the example shown in FIG. 8.

[Problem to be solved by the invention]

As is clear from the above-mentioned prior art, the freeze seal metal is originally covered on two sides with an inert gas such as argon gas.

By the way, the Journal of the Atomic Energy Society of Japan, Vol. 30. N
As reported in α12゜p, 1084-1091 (1988), the temperature of the thorium inside the reactor vessel during reactor operation is as high as about 500-600°C.
A considerable amount of sodium mist is generated from the sodium liquid surface, which reaches the freeze seal area and forms an alloy with the freeze seal metal that has a different composition from the original, increasing the melting temperature.

When rotating the rotary plug while the reactor is shut down, in order to maintain the integrity of the seal member 16 of the backup seal portion shown in FIGS. , and then the rotating plug must be rotated using a rotating mechanism, also not shown.

At this time, the sealing performance of the backup seal part is broken, and the atmosphere mixes into the inert gas such as argon gas that was filled on the atmosphere side of the seal metal.

As a result, the seal metal 13 oxidizes or absorbs moisture from the atmosphere, changing its alloy structure, and solid impurities generated thereby precipitate in the seal metal and cover the liquid level. Therefore, the rotational resistance force on the rotary plug increases, and in the worst case, the rotary plug may not be able to rotate.

In the above conventional techniques, it is difficult to replace the seal metal or remove impurities generated in the seal metal.

That is, conventionally, first, the backup seal member 16 shown in FIG. 8 or 9 is removed while the nuclear reactor is shut down. Using an impurity collection tool 18, an impurity removal tube 19, an impurity collection bag W20 for removing impurities by vacuum suction, etc. as shown in FIG. 10 or FIG. We are also supplying new seal metal.

With such a method, it is not only difficult to remove the 1.7A of impurities generated in the seal metal 13 on the reactor vessel 1 side, but also radioactive fission products may be present in the seal metal in reactors where fuel damage has occurred. In some cases, it may be contaminated with radiation, creating the problem of radiation exposure for workers.

The purpose of the present invention is to eliminate the need to remove the backup seal member, automatically remove impurities generated in the seal metal not only on the atmosphere side but also on the furnace vessel side, and replenish new seal metal as needed. It is an object of the present invention to provide a freeze seal structure capable of greatly reducing radiation exposure problems during work.

[Means to solve the problem]

In order to achieve the above object, the present invention fills a seal dam placed around a rotating plug on a container with a seal metal, and forms a seal between a partition plate immersed in the seal metal and the seal metal. However, we propose a freeze seal structure in which a rotating plug can freely rotate when the seal metal is melted, and a partition plate is equipped with a sampling member for collecting solid impurities generated in the seal metal.

The collected solid impurities are removed by means of suction to the outside of the container.

Further, the sampling member and the opening of the supply/discharge pipe corresponding to the sampling member may be provided both on the inside and outside of the partition plate.

Equipped with a means for detecting the amount of decrease in seal metal and a means for replenishing the insufficient seal metal through a supply/discharge pipe,
This means that seal metal can be automatically replenished.

The collection member can also be a cartridge-like member that has a capture capacity greater than the expected amount of solid impurities to be produced within a predetermined period of time and is replaced at predetermined intervals.

More specifically, the sampling member is a mesh-like member or a member having a plurality of holes that captures solid impurities while allowing healthy seal metal to pass through freely.

=10- [Function] In the present invention, the solid impurities that mainly exist at the seal tamel liquid level and near the liquid level are removed in the seal dam around the entire circumference of the rotating plug according to the rotation angle allowed for each rotating plug. As the partition plate or the seal dam moves, it is scooped up from within the seal metal by a collecting member provided at one or more locations on the partition plate so that the sample can be moved. The solid impurities scooped up reach a supply/discharge pipe having an opening above the collection member.

This supply/discharge pipe is directly connected to a seal metal supply/discharge device installed outside the one-turn plug, and by activating, for example, a vacuum pump of this supply device, the supply/discharge pipe opening can be reached on the sampling member. Vacuum transfer the impurities present to the impurity storage tank of the supply/discharge device.

At that time, the seal metal with a healthy liquid level whose composition has not changed will not be collected by the collection member and will pass through it into the seal dam because the collection member is mesh-like or has many holes. remain.

In addition, regardless of whether the partition plate is installed on the rotating plug side or the roof slab side, the sampling member installed on the partition plate
Rotation of the rotating plug results in relative movement within the shield dam. In other words, if there is a partition plate on the rotating plug side,
The collection member attached to this moves directly inside the shield dam,
If there is a partition plate on the roof slab side, the seal dam moves together with the rotating plug, so it appears that the sampling member provided on the partition plate moves to collect impurities in the seal metal.

On the other hand, in order to keep the amount of seal metal in the shield dam constant, the amount of liquid in the seal metal in the shield dam is measured using a liquid level meter or the like. The seal metal supply/discharge device receives a signal from a liquid level gauge, etc., and uses the opening force of a metal transfer pump, etc. to remove new seal metal as necessary, contrary to when removing impurities.
Seal metal is fed under pressure to the seal dam from the supply/discharge pipe provided on the partition plate.

In addition, if a replaceable cassette container with an intended capture capacity of solid impurities that is expected to accumulate during one period of periodic inspection of a fast breeder reactor = 11- is attached to the collection member, it is possible to use a vacuum pump, etc. Most of the above objects of the present invention can be achieved without providing a supply/discharge device including active equipment.

〔Example〕

Next, an example of the freeze seal structure according to the present invention will be described. However, the same reference numerals are given to the parts that perform the same functions as in the above conventional example, and the explanation thereof will be omitted.

The first drawing is a sectional view of an embodiment of the freeze seal structure according to the present invention. Freeze seal metal 13 is stored in a shield dam 14 provided on the roof slab 7 side. The temperature of the frozen seal metal 13 is lowered to below its melting point during operation of the nuclear reactor, and it is in a solid state. If it is necessary to rotate the rotary plug 12 while the operation is stopped, the temperature is raised above the melting point and the plug becomes liquid. The gap 1. is immersed in this seal metal 13. A partition plate 15 that forms the seal of the OA, that is, the boundary of the furnace vessel, protrudes from the rotary plug 12 side. A sampling member 21 extending from below the liquid level of the seal metal amount 3 to above the liquid level is attached to the side surface of the partition 12 and plate 15.

In this embodiment, an example in which the collection member 21 is attached to the installation side of the backup seal member 16 will be described first. Note that the space where the seal metal 13 is covered with the backup seal member work 6 is filled with an inert gas such as argon gas.

Further, the partition plate 15 has a built-in supply/discharge pipe 22 .

One of them is directly connected to a seal metal feeding device 23 provided outside the rotary plug 12, and the other is connected to the sampling member 2.
It is connected to a supply/discharge port 24 provided at the upper part of 1.

Details of the structure of the sampling member 21 etc. of the present invention are shown in FIGS. 2 and 3. Figure 2 is a cross-sectional view of the freeze seal structure of the present invention viewed from above, Figure 3 (a) is a bird's eye view when viewed from an angle, and Figure 3 (b) is a side view. It shows a bird's eye diagram of the case.

Most of the sampling member 21 connected to the supply/discharge pipe 22 in the partition plate 15 is made of a mesh-like member or a member with a plurality of holes. In this embodiment, a description will be given assuming that most of the parts that come into contact with the seal metal 13 are made of a mesh-like member.

Further, the collection member 21 is attached to the partition plate 15 so as to be inserted at a slight angle to the liquid level 25 of the seal metal 13 in the seal dam 14.

Note that it is not necessary to attach a large number of sampling members 21 and supply/discharge pipes 22 to the entire circumference of the sliding portion of the rotary plug 2, that is, the entire circumference of the partition plate 15. When the rotating plug 12 can rotate 360 degrees on the horizontal plane on the furnace vessel 1, the sampling member 21 etc.
At least one location is sufficient. If this is not possible, for example, if the rotation is only 180 degrees, the collection member 21 can be attached to the shield dam 14 by attaching it to two locations at 180-degree intervals or to multiple locations at closer intervals.
This is because it is the same as going around the inside (moving 360 degrees).

In this embodiment having such a configuration, when the rotary plug 12 is lifted by a rotary plug jack-up device (not shown) in order to rotate the rotary plug 12 during the operation stoppage 5, the back-up seal member of the seal metal 3 is removed. The sealing performance of 16 may be lost, the atmosphere may enter the inert gas atmosphere covered by this member, and the seal metal 13 may oxidize or absorb moisture from the atmosphere, resulting in a change in the alloy composition. . Also, small leaks may occur during reactor operation.

As a result, when solid impurities 17 are generated, in this embodiment, when the rotary plug 12 is rotated, the partition extractor 5 moves, and the sampling member 21 attached to it moves within the shield dam 14. Then, the solid impurity F generated in the seal metal 13 is scooped up and collected.

At this time, the supply/discharge device 23 provided outside the rotary plug 12
When the vacuum pump (not shown) is activated, the sampling member 21
The impurities 17 that have reached the upper supply/discharge port 24 or have been scooped up near this are sucked up into the supply/discharge device 23 through the supply/discharge pipe 22 .

The sucked up impurities 17 are stored in an impurity storage tank (not shown) of the wandering device 23. At this time, the healthy seal metal 13 that is liquid and has not changed its composition is not collected into the collection member 21 because the collection member 2 is mesh-like, but passes through it and remains in the seal dam 14. become.

Therefore, impurities 17 generated in the seal metal 13
, without removing the backup seal member 16.
The rotating plug can be removed from the top 2.

When removing solid impurities 17 under vacuum, if part of the healthy seal metal 13 is removed at the same time, or if a large amount of impurities 17 is generated, the seal metal 3 will gradually decrease.

Therefore, in the present invention, the amount of liquid in the seal metal 13 in the seal dam 14 is measured using a liquid level gauge (not shown), or the removed impurities 17 are measured, or the above measurement and measurement are combined, and the amount of liquid in the seal metal 13 is measured. Ascertain the amount of liquid in the seal dam 14. If the amount of "seal metal" 3 is insufficient than the specified amount, the necessary amount of new seal metal 13 is naturally dropped from the feeding device 23 onto the seal dam 14 using its weight ratio.
Alternatively, as a more reliable method, a transport pump (not shown) provided in the supply/discharge device 23 is operated to perform pressure feeding. The supply/discharge pipe 22 used for removing the impurities 17 can also be used as the transport pipe at this time.

By constantly measuring the decrease in seal metal 13 in the seal dam using the above method and analyzing the measurement results using, for example, a computer, it is possible to automatically supply the required amount of seal metal 3 when necessary.

FIG. 4 shows a modification of FIG. 1. In this example, the partition plate 15 is provided on the roof slab 7 side, and the shield dam 1
4 is installed on the rotary plug 12 side. in this case,
Although the arrangement of the members around the partition plate 15 is opposite to that shown in FIG. 1, the principle, method, etc. regarding the removal of impurities 17 from the seal metal 13 and the supply of new seal metal 13 are the same as those shown in FIG. 1. is the same as

In both the embodiments shown in FIG. 1 and FIG. 4, there is no need to remove the backup seal member 16. That is, in either case, there is no need to manually remove the solid impurity 17, so the backup seal member may be made a part of the roof slab 7, and there is no need to separate it structurally. This is the first
This eliminates the need to attach the back-up seal member 16 to the roof slab 7 as seen in Figures 1 and 4, and means that there is no slight leakage of the atmosphere through this seal part that would degrade the integrity of the seal metal 13. .

The above was an example in which the collection member 21 of the present invention was attached to the installation side of the backup seal member 16.
1 is the interval 1.1 on the upper side of the furnace vessel, that is, in the case of FIGS. 1 and 4. It is also possible to attach it to the OA side. FIG. 5 is a sectional view of the freeze seal structure in which the collection member 21 is installed on the side of the gap 10A, and FIG. FIG.

The difference between the example in Figure 5 and Figure 4 is that the impurity F-A is mixed with soot and lithium mist in the furnace vessel, and the composition differs from the original one, including the addition of sodium to form an alloy structure. That is what we are doing. In the unlikely event that the fuel is damaged, there is a high possibility that fission products are present.

Therefore, it is necessary to improve the airtightness of the supply/discharge pipe 22 and the supply/discharge device fi23, and to strictly shield the impurity storage tank and the like from radiation.

The embodiment shown in FIG. 6 is an example in which the embodiments shown in FIGS. 1 to 4 and the embodiment shown in FIG. 5 are combined.

As shown in FIG. 6, the collection members 21 and 21A on the backup seal member 16 side and the gap 10A side can be installed at the same location or at different locations. It is desirable to provide them separately. When provided separately in this way, it is possible to prevent unnecessary scattering and spread of fission products, and it is possible to adopt a final treatment and disposal method tailored to the properties of each removed impurity.

In addition, if you decide to replace the collection member completely with a new one at the time of regular inspection, connect a container with the collection member that has a capture capacity greater than the amount of impurities expected to accumulate during one period of periodic inspection, and connect it to the collection member.
This can also be replaced along with the collection member.

This method can also significantly reduce radiation exposure for workers compared to the conventional method of manually pumping up solid impurities.

Further, the present invention has shown an example in which the supply and exhaust pipes 22 are built into the partition plate 15, but when considering applying the present invention to the freeze seal structure of a nuclear reactor currently in operation, it is possible to replace the existing supply and discharge pipes with It goes without saying that if a structure is adopted in which the structure is attached to the side surface of the partition plate, the structure will be similar to that of the above embodiment, and the same effects will be obtained.

Further, although an embodiment in which the present invention is applied to a tank-type fast breeder reactor has been described, the present invention can also be applied to a loop-type fast breeder reactor without any problem.

〔Effect of the invention〕

According to the present invention, removal of solid impurities generated in the freeze seal metal and replenishment and replacement of new seal metal can be performed automatically and in a short time from the outside without removing a part of the freeze seal structure. Therefore, the number of people and 20 hours spent on these tasks can be significantly reduced, and the amount of radiation exposure per worker can also be significantly reduced.

In addition, the principles and structure of the present invention can be applied to existing fast breeder reactors without changing the conventional freeze seal structure, since the principle and structure of the present invention can be applied in the form of externally installing the sampling member and the supply/discharge pipe to the conventional partition plate. It is also available.

[Brief explanation of drawings]

The first construction drawing is a sectional view of one embodiment of the freeze seal structure according to the present invention, FIG. 2 is a sectional view of the embodiment shown in FIG. 1 viewed from above, and FIGS. A bird's-eye view of the structure viewed diagonally and from the side. Figure 4 is a diagram showing a modification of the embodiment in Figure 1. Figure 5 shows the installation of the collection member in the opposite position to that in Figure 1, with the partition plate in between. 6 is a cross-sectional view of the freeze seal structure in which the collection members of FIGS. 1 and 5 are combined, and FIG. 7 is a cross-sectional view of a conventional tank-type fast breeder reactor. Figure 8 is a cross-sectional view of a conventional freeze seal structure, Figure 9 is a diagram showing a modification of the conventional example in Figure 8, Figure 10 and the first diagram show a method for removing impurities from the conventional seal 2 metal. It is a diagram. 1. Reactor vessel, 2. Reactor core, 3. Sodium pump. 4. Intermediate heat exchanger, 5. Upper core mechanism, 6. Sodium, 7. Roof slab, 8. Large rotating plug,
9...Small rotation plug, l○, gap, 11...Seal part, Work 2...Rotary plug, 13.Seal metal, 14...
・Seal dam, 15 Partition plate, 16... Backup seal member, 17... Solid impurity, 18... Impurity sampling tool, 1
9...Each for impurity removal, 20...Impurity collection device,
21... Collection member, 22... Supply/discharge pipe, 23... Supply/discharge device, 24... Supply/discharge port, 25... Seal metal liquid level.

Claims (1)

[Claims] 1. A seal dam placed around a rotating plug on a container is filled with a seal metal, a seal portion is formed between a partition plate immersed in the seal metal and the seal metal, and the seal A freeze seal structure in which the rotary plug can freely rotate when metal is melted, characterized in that the partition plate is provided with a collection member for collecting solid impurities generated in the seal metal. 2. The freeze seal structure according to claim 1, further comprising means for sucking the collected solid impurities to the outside of the container. 3. The freeze seal structure according to claim 1 or 2, wherein the sampling member and an opening of a supply/discharge pipe corresponding to the sampling member are provided on both the inside and outside of the partition plate. 4. The apparatus according to any one of claims 1 to 3, further comprising means for detecting the amount of decrease in the seal metal and means for replenishing the insufficient seal metal through the supply/discharge pipe. Freeze seal structure as described. 5. The freeze seal structure according to claim 1, wherein the collection member is a member that has a capture capacity greater than the expected amount of solid impurities to be produced within a predetermined period and is replaced every predetermined period. . 6. Any one of claims 1 to 5, wherein the collection member is made of a mesh-like member or a member having a plurality of holes that captures the solid impurities while allowing the healthy seal metal to freely pass through. Freeze seal structure as described in item 1. 7. A fast breeder reactor comprising the freeze seal structure according to any one of 1 to 6 above.