JPH0452915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fast breeder reactor, and particularly to a freeze seal device for sealing a sliding surface of a shielding plug.

[Technical background of the invention and its problems]

Generally, a freeze seal device seals the sliding surfaces of two objects in relative contact with each other, and has the following configuration. That is, it is composed of a main freeze seal bucket that stores a low melting point metal (hereinafter referred to as freeze seal alloy), and a partition plate that is immersed in the freeze seal alloy without contacting the main freeze seal bucket and partitions two spaces. ing.

The above-mentioned main freeze seal device is mainly used for sealing the sliding surface of a shielding plug of a fast breeder reactor. At this time, a backup device is installed on the low pressure side to prevent the freeze seal alloy from flowing out from the main freeze seal tub due to the pressure difference between the inside and outside. Furthermore, when the two sliding surfaces do not move, the freeze seal alloy is solidified to prevent the freeze seal alloy from flowing out from the freeze seal tub due to the pressure difference.

In such a configuration, if the backup device fails or the main freeze seal bucket is damaged, the sealing function will be impaired and the
Freeze seal alloy flows into the furnace. The leaked freeze seal alloy then sticks to the gap in the rotary plug, making the rotary plug unable to rotate. In addition, the entire shielding plug had to be disassembled in order to repair the damaged part and recover the leaked freeze seal alloy.

Therefore, a freeze seal device that can prevent the freeze seal alloy from flowing into the furnace has been considered. This will be explained below with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal sectional view of a fast breeder reactor equipped with a freeze seal device, and FIG. 2 is a longitudinal sectional view of the freeze seal device. Reference numeral 1 in FIG. 1 indicates a reactor vessel, and inside this reactor vessel 1 there is a coolant 2.
A reactor core 3 consisting of a plurality of fuel assemblies, control rods, etc. is housed therein. A shielding plug 4 is installed to close the upper opening 1A of the reactor vessel 1. This shielding plug 4 is composed of a fixed plug 5 fixed to the reactor vessel 1 and a rotary plug 6 rotatably attached to the inner peripheral side of the fixed plug 5. A freeze seal device 7 is provided on the sliding portion of the rotary plug 6.

The freeze seal device 7 is constructed as shown in FIG. That is, a freeze seal tub 8 is attached to the fixed plug 5, and this freeze seal tub 8 includes a first freeze seal tub 8A integrally attached to the fixed plug 5, and a first freeze seal tub 8A inside the first freeze seal tub 8A. A second freeze seal tub 8B is integrally attached to the circumferential side. And the first freeze seal bucket 8
Freeze seal alloy 9 is housed in A. Also, the first and second freeze seal buckets 8
In A and 8B, annular members 10 and 11 are provided to protrude from the rotary plug 6. The freeze seal alloy 9 is partitioned by this annular member 11. Further, reference numeral 12 in the figure indicates a backup device.

According to the above structure, the freeze seal alloy 9 is normally housed in the first freeze seal tub 8A, as shown in FIG. In the unlikely event that the freeze seal alloy 9 overflows from the first freeze seal bucket 8A, the second freeze seal bucket 8B can receive the freeze seal alloy 9 and seal it into the furnace without impairing the sealing function. This structure prevents the alloy 9 from flowing in.

However, if all the freeze seal alloy 9 flows from the first freeze seal bucket 8A to the second freeze seal bucket 8B, there is a risk that it will further flow into the furnace, so it is necessary to reliably prevent the freeze seal alloy 9 from flowing into the furnace. There is a possibility that you may not be able to do so. Furthermore, if the first and second freeze seal buckets are provided twice, a larger space will be required, resulting in an increase in the size of the nuclear reactor.

[Purpose of the invention]

The present invention has been made based on the above points, and an object thereof is to provide a freeze seal device for a shielding plug that can reliably prevent freeze seal alloy from flowing into a furnace.

[Summary of the invention]

That is, the present invention provides an annular freeze seal bucket provided on the inner circumferential side of a fixed plug of a shielding plug that closes an upper opening of a reactor vessel, a freeze seal alloy housed in the freeze seal bucket, and the shielding plug. In the shielding plug and freeze seal device, the shielding plug and freeze seal device has a partition plate that is provided on the rotating plug and divides the inside of the freeze seal tub into an outer annular space and an inner annular space whose bottoms are in communication with each other, between the freeze seal tub and the rotating plug. A guard ring is provided to prevent the freeze seal alloy from overflowing to the rotating plug side, and the lower end of this guard ring is connected to the inner circumferential wall of the fixed plug, and the lower end of the guard ring is connected to the inner peripheral wall of the fixed plug so that An inflow alloy reservoir is formed to receive the overflowing freeze seal alloy.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 3 to 5. FIG. 3 is a sectional view of the freeze seal device according to this embodiment. It should be noted that the same parts as in the prior art will be described with the same reference numerals. A rotary plug 6 is rotatably attached to the fixed plug 5, and the fixed plug 5 and the rotary plug 6 constitute the shielding plug 4 . This rotating plug 6
A freeze seal device 51 is provided on the sliding portion of the slider. This freeze seal device 51 has the following configuration. That is, a freeze seal tub 52 is installed on the inner peripheral side of the fixed plug 5 via its flange 53, and is fixed to the fixed plug 5 with bolts 54. On the other hand, the rotating plug 6
A partition plate 55 projects downward from the side and divides the interior of the freeze seal tub 52 into an outer annular space 65 and an inner annular space 66 whose bottoms communicate with each other. It is immersed in freeze seal alloy 56 within 52 .
The inner body 57 of the freeze seal tub 52 is supported such that its upper edge 57A is engaged with a locking portion 58A of a guard ring 58 provided upright from the fixed plug 5 side. Further, from the partition plate 55 located above the support portion of the inner body 57 of the guard ring 58, a wall plate 59 is provided protruding from the partition plate 55 in the direction of the guard ring 58 so as to close the freeze seal tub 52.
As shown in FIG. 4, a plurality of inlet holes 60 are vertically formed at equal intervals in the circumferential direction at the upper end edge 57A of the inner body 57 and the engagement portion with the locking portion 58A of the guard ring 58. That is, in the event that the freeze seal alloy 56 in the freeze seal tub 52 overflows the inner body 57 of the freeze seal tub 52, it will flow into the freeze seal tub 5 through the inflow hole 60.
2. The freeze seal alloy 56 is configured to flow into the inflow alloy reservoir 61 formed by the guard ring 58 and the fixing plug 5, thereby preventing the freeze seal alloy 56 from flowing into the inside of the furnace. The inflow alloy reservoir 61 has a drain mechanism 6.
2 is connected, and the freeze seal alloy 56 that has flowed into the inflow alloy reservoir 61 is collected by this drain mechanism 62. Further, a nozzle 63 is embedded in the flange 53 of the freeze seal tub 52, and the backup device 1 is
The structure is such that the freeze seal back pressure from 2 is supplied into the freeze seal tub 52.

The operation will be explained based on the above configuration. First, during normal operation, that is, when the rotary plug 6 does not rotate, the freeze seal alloy 56 exhibits its sealing function in a solidified state. Next, when rotating the rotary plug 6, the freeze seal alloy 56 is melted by a heater or the like (not shown). At that time, the pressure in the space 65 is adjusted by supplying freeze seal back pressure from the backup device 12 into the space 65,
This prevents the freeze seal alloy 56 from being significantly biased or flowing out from the freeze seal tub 52 due to the pressure difference between the inside and outside. At this time, if the backup device 12 fails due to high pressure, the freeze seal alloy 56 is pushed down by the gas pressure in the space 65, and as a result, the freeze seal alloy 56 in the other space 66 is pushed up. This may cause the freeze seal alloy 56 to flow out of the freeze seal tub 52. However, in this embodiment, the freeze seal alloy 56 pushed up by the gas pressure of the backup device 12 either collides with the baffle plate 59 and bounces back toward the freeze seal tub 52, or the alloy flows through the inflow hole 60. Since it flows into the reservoir 61, the freeze seal alloy 56 does not flow into the inside of the furnace. Conventionally, the freeze seal tub 52 was installed in a cantilevered state, but in this embodiment, the inner body 57 of the freeze seal tub 52 is supported by the guard ring 58, so the mechanical strength is improved. As a result, demand capacity can be improved. Furthermore, when repairing a damaged part or recovering the leaked freeze seal alloy 56, conventionally the freeze seal alloy 56 flows down to the bottom of the gap between the fixed plug 5 and the rotating plug 6, so it is not necessary to dismantle the entire shielding plug 4 . This was necessary, and the work involved high radioactivity levels as the cover gas boundary inside the reactor was destroyed. On the other hand, in the case of this embodiment, since the inflow alloy reservoir 61 functions as a safety container for the freeze seal tub 52, the freeze seal alloy 56 is prevented from flowing into the gap between the fixed plug 5 and the rotating plug 6. do not have.
Furthermore, as shown in FIG. 5, a maintenance seal 67 is provided between the rotary plug 6 and the upper end of the card ring 58.
The cover gas boundary in the furnace can be maintained by applying
When repairing a damaged portion, the repair work can be carried out by simply dismantling the partition plate 55 and the upper part of the freeze seal tub 52, thereby improving workability and safety.

〔Effect of the invention〕

As described in detail above, the present invention provides a guard ring between the freeze seal tub and the rotating plug to prevent the freeze seal alloy from overflowing to the rotating plug side, and connects the lower end of the guard ring to the inner circumferential wall of the fixed plug. An inflow alloy reservoir was formed below the Freeze Seal tub to receive the Freeze Seal alloy overflowing from the Freeze Seal tub, so that the Freeze Seal alloy overflowing from the Freeze Seal tub was formed below the Freeze Seal tub. The inflow alloy can be received in the reservoir. Therefore, even if the freeze seal alloy should overflow from the freeze seal tub due to a failure of the backup device, it will not flow into the furnace, and safety can be improved.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing conventional examples.
FIG. 2 is a longitudinal sectional view of a fast breeder reactor, FIG. 2 is a longitudinal sectional view of a freeze seal device, FIGS. 3 to 5 are views showing an embodiment of the present invention, and FIG. 3 is a longitudinal sectional view of a freeze seal device. 4 is a perspective view showing a part of FIG. 3 in detail, and FIG. 5 is a sectional view illustrating repair work. 4 ... Shielding plug, 5... Fixed plug, 6...
Rotating plug, 51 ... Freeze seal device, 52
...Freeze seal bucket, 56...Freeze seal alloy, 57...Inner body, 58...Card ring,
59... Diyama board, 60... Inflow hole, 61... Inflow alloy reservoir.

Claims (1)

[Claims] 1. An annular freeze seal bucket provided on the inner peripheral side of the fixed plug of the shielding plug that closes the upper opening of the reactor vessel, a freeze seal alloy housed in the freeze seal bucket, and a rotating plug of the shielding plug. In the freeze seal device for a shielding plug, the freeze seal device is provided with a partition plate that divides the inside of the freeze seal tub into an outer annular space and an inner annular space whose bottoms communicate with each other, and the freeze seal is provided between the freeze seal tub and the rotating plug. A guard ring is provided to prevent the alloy from overflowing to the rotating plug side, and the lower end of this guard ring is connected to the inner peripheral wall of the fixed plug, so that the freeze overflow from the freeze seal tub is placed below the freeze seal tub. A freeze sealing device for a shielding plug, characterized in that an inflow alloy reservoir is formed to receive a sealing alloy.