JPH0652313B2 - Cover gas seal device for lifting core upper mechanism - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cover gas seal device for an elevating core upper part mechanism in a fast breeder reactor.

[Prior Art] An elevating core upper mechanism is disclosed in, for example, Japanese Patent Application Laid-Open No. 60-89794. The ascent of the upper core mechanism is carried out.

In order to prevent the cover gas sealed in the upper part of the reactor vessel from leaking into the space above the rotating plug from the gap between the rotating plug and the rotating core upper part mechanism, the cover gas sealing device is required. And

Conventionally, the cover gas sealing device for the lifting type upper core mechanism is
It is constructed as shown in FIGS. 6 (a) and (b) and FIGS. 7 (a) and (b).

The cover gas seal device shown in FIGS. 6 (a) and 6 (b) covers the upper part of the elevating core upper part mechanism 2 which is vertically inserted into the rotary plug 1, and is attached to the rotary plug 1 in an airtight and removable manner. It consists of an airtight container 3.

The cover gas sealing device shown in FIGS. 7 (a) and 7 (b) includes a cylindrical radiation shield 4 which is detachably attached to the rotating plug 1 so as to surround the upper half of the lifting core upper mechanism 2. The bellows 5 is arranged inside the radiation shield 4 and has an upper end portion which is airtightly and detachably attached to the upper surface of the rotating plug 1 at the outer upper end portion of the lifting core upper mechanism 2.

In FIGS. 6 (a) and (b) and FIGS. 7 (a) and (b), 6 is the core top portion, 7 is the sodium liquid level, and 8 is an inert gas serving as a cover gas.

[Problems to be Solved by the Invention] However, according to the above-mentioned conventional cover gas sealing device, when the airtight container 3 or the bellows 5 is removed, the activated inert gas containing sodium vapor filled in these parts is removed. In order to prevent the gas 8 from being diffused to the surroundings and contaminating the space above the rotary plug 1, it is necessary to sufficiently replace the inert gas with clean air before removing it.

In addition to the inner surfaces of the airtight container 3 and the bellows 5, the upper half of the elevating core upper mechanism 2 [during operation (Fig. 6 (a), Fig. 7 (a)]
Above the rotating plug in the above condition) is also contaminated by the adhesion of sodium vapor. Therefore, when the control rod drive device mounted on the lifting core upper mechanism 2 is maintained, the exposure dose of the worker is May increase.

Therefore, the present invention makes it possible to simplify the operation of replacing the activated inert gas containing sodium vapor with air to prevent the release of the activated inert gas containing sodium vapor into the space above the rotating plug, and It is an object of the present invention to provide a cover gas sealing device for a lifting / lowering core upper part mechanism, which is capable of reducing an exposure dose of an operator during maintenance of a control rod driving device or the like of the lifting / lowering core upper part mechanism.

[Means for Solving the Problems] In order to solve the above problems, the present invention is formed in a cylindrical shape surrounding the upper half of an elevating-type core upper mechanism inserted into a rotating plug so that the lower end can be lifted. The radiation shield is attached to the rotary plug in an airtight and removable manner, and the bellows is placed inside the radiation shield, and the upper end is attached airtightly to the inner upper end of the radiation shield, and the lower end of the bellows is airtight. And a seal ring that is airtightly and detachably attached to the outer intermediate portion of the lifting core upper mechanism and the inner lower end portion of the radiation shield.

[Operation] According to the above means, when the device is removed, the seal ring is airtightly attached to the inner lower end portion of the radiation shield so that the activated inert gas containing sodium vapor is separated from the bellows and the radiation shield. Sealed in the space between
The upper half of the lifting core upper mechanism of sodium vapor contained in the activated inert gas is airtightly attached to the outer middle part of the lifting core upper mechanism when the lifting core upper mechanism moves up and down. To be prevented.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is a vertical cross-sectional view of a cover gas sealing device in which an intermediate portion is omitted.

In the figure, 10 is an elevating type core upper part mechanism in which a control rod driving device 11 and the like are mounted, and it is attached to a rotating plug 12 so as to be able to move up and down. As shown in FIG. 2, the elevating core upper mechanism 10 is airtightly fixed by a ring-shaped mechanism fixing metal fitting 13 during the operation of the reactor. It is lifted and lowered by a crane (not shown) via a hanging metal fitting 14 provided on the.

A lower end of a cylindrical radiation shield 15 that surrounds the upper half of the lifting core upper mechanism 10 is airtightly and detachably mounted on the rotating plug 12. Inside the radiation shield 15,
A bellows 17 that constitutes a cover gas sealing device 16 is arranged together with this shield 15, and the upper end of the bellows 17 is
The radiation shield 15 is airtightly attached to the inner upper end portion 15a of the radiation shield 15. At the lower end of the bellows 17, the lifting core upper mechanism 10
A seal ring 18 that is airtightly and detachably attached is attached to the outer intermediate portion 10a and the lower end inner portion 15b of the radiation shield 15 in an airtight manner. On the outer periphery of the seal ring 18, a key groove 19b that engages with a vertical key 19a provided inside the radiation shield 15 is provided in order to prevent the bellows 17 from twisting.

The reel ring 18 is attached to the lower end of the radiation shield 15.
Is pressed obliquely from above and the inner lower end portion 15 of the radiation shield 15 is
A ring mounting rod 20 that is airtightly attached to b is provided so as to be airtight and movable. The outer end of the ring attachment rod 20 is connected by a link mechanism 22 to a rod operating device 21 attached to the outside of the radiation shield 15 in order to move the ring attachment rod 20 forward and backward.

On the other hand, as shown in FIGS. 3 and 4, the notch 23 provided inside the seal ring 18 is engaged with the tip end of the seal ring 18 at the outer intermediate portion 10a of the lifting core upper mechanism 10. The base end of the ring mounting metal fitting 24 for air-tightly attaching to the outer intermediate portion 10a of the lifting core upper mechanism 10 is
It is fixed to the lower end of a mounting bracket operating rod 25 that is rotatably erected on the outside of the upper half. The rotation range of the ring fitting 24 is limited by a stopper 26 standing on the outer upper half 10a of the lifting core upper mechanism 10.

In FIGS. 1 and 3, 27 is an elevating core upper mechanism.
A pin insertion hole provided on the outer side in the vicinity of the middle portion of the pin 10, and in this pin insertion hole 27, a shear pin 28 provided at the upper end of the elevated core-up mechanism 10 is supported by the radiation shield 15 in order to support it. Is inserted by operating the pin operating device 29.

Next, the operation of the cover gas sealing device 16 of the lifting type upper core mechanism 10 having the above-described configuration will be described with reference to FIGS. 5 (a), (b) and (c).

In order to raise the elevating core upper part mechanism 10 in order to replace the fuel assembly, first, the mechanism fixing bracket 13 is removed from the rotary plug 12, and the cover gas seal device 16 is attached as shown in FIG. 5 (a). After being mounted on the upper half of the lifting core upper mechanism 10 by a crane, as shown in FIG. 5 (b), the radiation shield 1
Attach the lower end of 5 to the upper surface of the rotary plug 12 in an airtight manner.

Then, by operating the rod operating device 21, the seal ring 18 airtightly attached to the inner lower end portion 15b of the radiation shield 15 by the ring attaching rod 20 is attached to the tip of the ring attaching member 24 by rotating the attaching member operating rod 25. Portion and the notch 23 of the seal ring 18 so as to be airtightly attached to the outer intermediate portion 10a of the elevating core upper mechanism 10, and then the ring mounting rod 20 is retracted by the operation of the rod operating device 21 to cause the seal ring 18 to move. The state of attachment of the radiation shield 15 to the inner lower end 15b of the radiation shield 15 is released.

Then, after the lifting type core upper part mechanism 10 is lifted by the crane through the hanging metal fitting 14, as shown in FIG. 5 (c), the shear pin 28 is inserted into the pin insertion hole 27 by the operation of the pin operating device 29.
, The lifting upper core mechanism 10 is supported by the radiation shield 15, the crane is removed from the hanging metal fitting 14, and the rotation of the rotary plug 12 and the operation of the fuel exchanger (not shown) allow the fuel assembly to be replaced. To do.

After the replacement of the fuel assembly is completed, the lifting core upper mechanism 10 is suspended by a crane, the shear pin 28 is pulled out from the pin insertion hole 27, and the lifting core upper mechanism 10 is lowered. After removing the cover gas seal device 16,
Also, the mechanism fixing bracket 13 is attached to the rotary plug 12. The activated inert gas containing sodium vapor is sealed between the bellows 17 and the radiation shield 15 of the removed cover gas sealing device 16.

In FIGS. 5 (a), (b), and (c), 30 is the core top, 31 is the sodium liquid level, and 32 is an inert gas that serves as a cover gas.

Further, in the above-mentioned embodiment, the elevating core upper part mechanism 10 is lifted and lowered by the crane, but the present invention is not limited to this, and other means such as a ball nut screw may be used.

As described above, according to the present invention, when the device is detached, the seal ring is airtightly attached to the inner lower end of the radiation shield so that the activated inert gas containing sodium vapor is bellows. Between the radiation shield and the radiation shield,
In addition, when the lifting core upper mechanism is lifted, a seal ring is airtightly attached to the outer middle part of the lifting core upper mechanism so that the sodium vapor contained in the activated inert gas is lifted up the lifting core upper mechanism. Since the adhesion to the half part is prevented, the operation to replace the space to prevent the activated inert gas containing sodium vapor from escaping to the space above the rotating plug when the device is removed is simplified. In addition, it is possible to reduce the exposure dose of the worker during maintenance of the control rod drive device of the lifting type upper core mechanism.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a cover gas sealing device for an elevating core upper mechanism showing an embodiment of the present invention.
Each of the figures is a cross-sectional view of its main part, FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3, and FIGS. 5 (a), (b), and (c) are cover gas sealing devices for the lifting core upper mechanism. Explanatory diagram of action of Fig.6
7 (a), (b) and FIGS. 7 (a), (b) are vertical cross-sectional views of a conventional cover gas seal device for an elevating core upper mechanism. 10 ... Elevating core upper mechanism, 10a ... Outer middle part 11 ... Control rod drive device, 12 ... Rotating plug 15 ... Radiation shield, 15a ... Inner upper end 15b ... Inner lower end 16 ... Cover gas seal device 17 ... Bellows, 18 ... Seal ring 20 ... Ring mounting rod 24 ... Ring mounting bracket

Claims (1)

[Claims] 1. A radiation shield which is formed in a cylindrical shape and surrounds an upper half of an elevating core upper part mechanism which is vertically inserted into a rotary plug and whose lower end is hermetically and detachably attached to the rotary plug. A bellows disposed inside the radiation shield and having an upper end airtightly attached to an inner upper end of the radiation shield, and an airtightly attached lower end of the bellows, and an outer intermediate portion of the lifting core upper mechanism and the radiation shield. A cover gas sealing device for an elevating core upper part mechanism, which comprises a seal ring which is airtightly and removably attached to a lower end portion inside a body.