JPH058559Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> This invention relates to the structure of a device that allows nuclear power components to be isolated from the outside air and replaced.

<Problems with conventional technology> Replacing nuclear power components, particularly rupture plates as safety components for fast breeder reactors, requires a replacement device that does not come into contact with outside air and is free of radioactive dust.

First, a layout diagram of a steam generator used in a fast breeder reactor will be explained with reference to FIG. 1 and an overall structural diagram shown in FIG. 2.

FIG. 3 shows a detailed structural diagram of the rupture plate 2 attached to the steam generator 1 as a pressure release function.

The steam generator 1 shown in FIG. 1 uses liquid sodium as a coolant, and its feature is that it has excellent heat conduction properties. Do not slow down neutrons. It has a high boiling point, is liquid in operating conditions, and can exchange heat at high temperatures without requiring pressurization. etc.

However, the disadvantage of liquid sodium is that it undergoes an explosive reaction when it comes into contact with water.

FIG. 2 shows a schematic diagram of a sodium-water reaction.

Specifically, when the heat transfer tube 7 is damaged, steam enters the sodium, causing a sodium-water reaction, and the pressure inside the steam generator 1 rises rapidly.

When the pressure suddenly increases and reaches a certain pressure, the rupture plate 2 connected to the release system piping 3, which is a pressure release line, ruptures and releases the pressure to the outside of the system.

Most of the sodium then passes through the discharge system piping and is collected in a reaction product storage container (not shown).

However, sodium adheres to the vicinity of the discharge system piping 3 through which most of the sodium passed and the ruptured rupture plate 2. Furthermore, it is known from past experiments that sodium vapor within the steam generator 1 adheres to the rupture plate 2 itself and its vicinity even during normal operation, not during an accident. When this sodium vapor reacts with moisture in the atmosphere, it becomes sodium hydroxide, which is extremely dangerous.

When cleaning such sodium equipment in the event of an accident or during routine inspections, workers must wear full masks to prevent internal radiation exposure during routine inspections of light water reactor nuclear power plants. It is necessary to wear a full mask, glasses to protect your eyes, rubber gloves, rubber boots, etc., and be careful not to come into contact with sodium vapor.

If it comes into contact with the eyes or directly, it may cause serious damage to the human body.

FIG. 10 shows the specific replacement capacity of the rupture plate 2 as an example of replacement of conventional sodium equipment.

First, in order to replace the ruptured rupture plate 2 (the ruptured disk 2b shown in FIG. 3), a temporary pedestal is assembled to a height that allows the replacement work. (3 people
The release system piping 3 and the destruction plate 2 are usually installed at the top of the sodium equipment as a pressure release function. next,
Using the upper support 8, a chain block 9 for raising and lowering the breaking plate 2 is attached. (If there is no support 8 for hanging the chain block 9, a temporary support will be provided.) Next, the holder 2a and the disk 2b are fixed on the chain block 9, and the bolts 6 are removed. (When removing bolt 6, gradually remove holder 2a and flange 5.
A gap is created between them, and the atmosphere comes into contact with the sodium vapor 14 adhering to the discharge system piping 3, holder 2a, and disk 2b. ) holder 2a,
When removing the disk 2b from the discharge system piping 3, quickly attach the vinyl sheets 10a and 10b to the holder 2.
a. Cover the disk 2b and flange 5,
Tie each with 15 grade wire.

Further, the holder 2a and the disk 2b suspended by the chain block 9 are placed in a storage box 12 and moved by a handcart 13 to a predetermined washing location. Cleaned holder 2a, replaced disk 2
The mounting method b is also performed with the reverse capacity shown above.

In the conventional replacement method described above, when the vinyl sheet is used to cover the sodium vapor, the atmosphere comes into contact with the sodium vapor. Also, the reacted sodium hydroxide is SCC
It is also a harmful substance for (stress corrosion cracking).
From this point of view as well, there has been a desire to develop an exchange device that can completely remove sodium vapor from the atmosphere without scattering it.

Even when such a destruction plate 2 is being operated regularly, replacement is carried out once every 1 to 3 years.
Destruction plate 2 in a DEMO class steam generator
There is one each in the superheater and evaporator, and there are three loops, so in a plant with a lifespan of 30 years, the destruction plate 2 will be broken 66 to 180 times during the lifespan.
will be replaced.

The above-mentioned conventional technology does not take into consideration the possibility that the sodium vapor 14 comes into contact with the atmosphere and generates harmful gas when replacing the destruction plate 2 (holder 2a, disk 2b), and is primitive. 14 in the atmosphere and sodium vapor.
It was a difficult task that was always fraught with danger.

<Purpose of the invention> The purpose of this invention is to avoid direct contact between the atmosphere and the sodium vapor 14 during replacement work,
In addition, while the sodium vapor is isolated, the destruction plate 2, which is a nuclear component, can be replaced safely and
The object of the present invention is to provide a device that can be easily used.

<Summary of Means> The above purpose is to provide a cover 29 that integrally surrounds the destruction plate 2 and the flange 5 for attachment, and a purge nozzle 2 that replaces the atmosphere inside the cover 29 with an inert gas.
5, and a jack 1 for raising and lowering the cover 29
8. Bellows 23 that allow the cover 29 to expand and contract
a, 23b and a fastener 22 for dividing the bellows 23a, 23b, and a fastener 22 for dividing the bellows 23a, 23b;
This is achieved by magnets 21a and 21b for partitioning 3b.

<Example> FIG. 4 shows the overall structure of the nuclear power member replacement device according to this invention.

By the jack 18 attached to the trolley 16,
It has a function of setting the pedestal in a predetermined position, and a structure that allows replacement work by cutting off the atmosphere and sodium vapor using the bellows 23 and sealing fittings 24. As shown in FIG. 7, the magnets 21a and 21b , and a sealing enclosure member 3 composed of a bellows structure having a vertical separation function in combination with a fastener 22.
0, consisting of a bellows enclosure 31.

FIG. 5 shows a state in which the cart according to the device of this invention is installed at a predetermined position (directly below the destruction plate 2).

FIG. 4 shows a state in which the seal fitting 24 is attached to the discharge system piping 3 by raising it to a predetermined height using the jack 18. Before installing the seal fitting 24, remove all but about four bolts 6 near the top. As mentioned in the prior art, if all bolts are removed, a gap will be created between the holder 2a and the flange 5, so leave about four bolts and attach the seal fitting 24 to the discharge system piping 3. . After all the bolts are removed, by turning the holder adjusting screw 27 in the direction in which the pedestal 20 widens, the "gagging" between the flange 5 and the holder 2a can be removed. The removal of the remaining four bolts described above is shown in FIG. This is carried out while the atmosphere and sodium vapor are blocked by maintenance gloves 28. Further, the seal fittings 24 are prepared for each pipe size, and are not removed until the replacement work is completed. (It must be installed because the sodium vapor 14 is attached to the release system piping.) Figure 6 shows the state before removing the holder 2a and disk 2b and removing the upper bellows 23a and lower bellows 23b. .

Note that inert gas is supplied from the purge nozzle 25 into the bellows 23a, 23b before the work to remove the four bolts described in the previous section.

FIG. 7 shows a state in which the upper bellows 23a and the lower bellows 23b are separated. FIG. 9 shows a detailed view of the bellows 23a, 23b. Jiyabara 23
By providing a separation function for a and 23b, the holder 2a and disk 2b can be (1) removed, (2) moved to the sodium cleaning room using a trolley, and (3) installed (restored). become.

Figure 9 shows the structure for separating the bellows. The upper bellows 23a are partitioned by the grindstone 21a.

Further, the lower bellows 23b are partitioned by the grindstone 21b, and the upper and lower bellows are separated by the fastener 22.

In addition, when returning, reversely, after attaching the fastener 22, the magnet 21a and the magnet 21b are removed.

FIG. 8 shows a detailed structural diagram of the pedestal.

It has a structure that can be adjusted to suit various holder sizes using holder adjustment screws 27, and the fixing and sliding of the pedestal are dovetailed.

<Function> The cover 29 is a fastener 22 and a rose 23.
a, 23b, sealing metal fitting 24, purge nozzle 2
5, a maintenance glove 28, and others.

The cover 29 is designed to isolate the sodium vapor that adheres to the inner surface of the discharge system piping 3 and floats in the atmosphere as vapor when the rupture plate 2 is replaced from the operator who is working on the replacement. Yes, if the operator is outside this cover 29,
It is no longer necessary to wear a full mask and special work clothes in consideration of sodium vapor.

The seal fitting 24 has the shape of a handbag stopper, and is connected to the flange 5 and the discharge system piping 3.
After enclosing the sodium vapor 14, the space between the sodium vapor 14 and the discharge system piping 3 is eliminated to prevent the sodium vapor 14 from leaking into the atmosphere outside the cover 29.

<Effects> According to this invention, when replacing the destruction plate 2,
A bellows 23 having a vertical separation function by a combination of magnets 21a, 21b and a fastener 22
By providing the elements a and 23b, the atmosphere and the sodium vapor 14 can be completely shut off, so that the generation of toxic gas due to the reaction between the atmosphere and the sodium vapor, which has been a problem in the prior art, can be completely prevented.

[Brief explanation of the drawing]

Fig. 1 is an overall layout of the steam generator and its surroundings to which the rupture plate 2, which is a nuclear power component, is attached. 3 is a detailed view of the rupture plate as a nuclear power member, FIG. 4 is a side view showing the overall structure of the bogie of this invention, FIG. 5A is a side view showing the relationship between the discharge pipe and the bellows enclosure, Figure 5B is a side view showing the relationship between the sealing enclosure member and the discharge pipe flange;
Figure A is a side view of the device of this invention, B is a front view,
7A is a side view of the connection points of this invention, B is a front view, FIG. 8A is a front view showing the detailed structure of the pedestal, B is a cross-sectional view of A, C is a cross-sectional view,
Figure 9 is a perspective view showing the detailed structure of the bellows;
FIG. 0 is a side view showing a replacement procedure according to the prior art. 16...Dolly, 20...cradle, 21a, 21
b, 21c...Magnet, 22...Fasner, 23
a... Upper bellows, 23b... Lower bellows,
24... Seal fitting, 25... Purge nozzle,
26... Handle for jacking, 28... Gloves for maintenance.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A hermetically sealed enclosing member that has a sealable opening and an inert gas supply nozzle and can hermetically surround a nuclear power component that requires replacement, and a bellows enclosure that accommodates a pedestal for the nuclear power component. , a device for raising and lowering the bellows enclosure, a connecting means for connecting the sealed enclosure member and the bellows enclosure at their open ends, each having an open end through which the pedestal can pass, and upper and lower sides of the connecting means. A nuclear power member exchange device characterized in that a sealing means is provided for making the sealing enclosure member and the bellows enclosure an independent sealing body when the connection is disconnected. 2. A nuclear power component exchange device as set forth in claim 1 of the utility model registration claim, in which work gloves are connected to the sealed enclosing member. 3. A nuclear power component exchange device according to claim 1 of the utility model registration claim, in which the connection means for connecting the sealed enclosure member and the bellows enclosure is a fastener. 4. Utility Model Registration Scope of claims 1 or 3, in the nuclear power component exchange device according to claim 1 or 3, in which the sealing means located above and below the fastener connection portion are connected by magnets.