JPS61230090A - Through-hole plug - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a through-hole plug installed in a shielding plug provided in the upper part of a nuclear reactor of a fast breeder reactor.

[Technical background of the invention]

FIG. 6 shows a schematic configuration of a fast breeder reactor, in which a reactor core consisting of a large number of core components 2 is formed inside a reactor vessel 1. Liquid sodium 3 is contained within the reactor vessel 1 as a coolant. The upper opening of the reactor vessel is closed by a shielding plug 4, and the shielding plug 4 is a fixed plug 5 fixed to the reactor vessel 1. It is composed of a plug 6. A fuel exchange device 7 is eccentrically attached to the rotating plug 6.
The reactor core components 2 can be handled and replaced inside the reactor vessel 1. At the time of fuel exchange, an elevating drive device 11 for vertically moving a fuel exchange device main body 10 (hereinafter abbreviated as FHM main body) is installed on the hold-down drive device 8 and door pulp 9 installed on the upper part of the rotary plug 6, and the elevating drive device The loaf 13 suspended from the hoist 12 installed on the upper part of the
The M main body 10 is moved up and down. In addition, the FHM main body 10 suspended from the lifting drive device 11 is a hold-down drive device! ! ! The FHM main body 10 is guided by the rotational movement of the hold-down shaft 15 suspended from the rotation bearing 14 on the upper part of the FHM main body 10, and moves to the position of the target core component 2. A gripper 17 attached to the tip of the core component 2 is used to grip the core component 2.

Next, when the core configuration type 1i2 has been replaced, the lifting drive device 11 and the FHM main body 10 are removed, and the state shown in FIG. 7 is achieved. In this case, the through hole to which the FHM main body 10 was attached has a release of 0i11! A through-hole plug 18 having shielding, heat shielding, and sealing functions is attached, and by r'AMing the door valve 9, the cover gas boundary of the reactor is in a state of being ffl closed. Further, as shown in FIG. 8, the through-hole plug 18 has a handling head shape 19 at its upper portion so that it can be handled by a handling machine. Further, a plug receiving stepped portion 22 for supporting the through-hole plug 18 on the hold-down shaft 15 and a latch mechanism 20 for preventing the through-hole plug 18 from being lifted in the event of a core accident are provided.

Further, a sealing device 21 is provided on the upper outer circumferential surface of the through-hole plug 18, and a gap 2 is provided between the through-hole plug 18 and the hold-down shaft 15 and communicates with the cover gas region in the furnace.
3 is formed.

[Problems with background technology]

Since there is a 1ial gap 23 between the through-hole plug 18 and the hold-down shaft 15 that communicates with the cover gas in the reactor, sodium vapor generated inside the reactor during reactor operation can enter this gap 23. There is a risk that the through-hole plug 18 will be hardened and the gap 23 will be closed, and in this case, it is difficult to pull out and reinsert the through-hole plug 18 using a handling machine. Also,
Since the sodium adhering to the surface of the through-hole plug 18 is radioactive, the handling machine (not shown) that pulls out and stores the through-hole plug 18 requires a large radiation shield made of lead with a thickness of 200 am+ or more. This was a major hindrance in terms of design, production, and cost. Furthermore, fission product gas (hereinafter referred to as FP gas) with extremely high radiation intensity generated in the reactor enters into this gap 23, so that a large thickness of radiation Il! is generated in the upper part of the reactor. A large amount of shielding materials had to be piled up, which caused problems in terms of layout and structure.

[Purpose of the invention]

An object of the present invention is to provide a through-hole plug that can prevent sodium vapor and FP gas from entering the gap formed between the through-hole plug and the hold-down shaft.

(Summary of the Invention) In order to achieve the above-mentioned object, the present invention provides a through-hole plug that is removably attached to a through-hole provided in a shielding plug in the upper part of a nuclear reactor. A stepped portion is provided on the wall surface of the through-hole located at the tip of the through-hole plug when the plug is installed, and a stepped portion is provided near the tip of the through-hole plug body on the side in the direction of attachment to the through-hole that is not bound to the through-hole plug body. The through-hole plug is characterized in that a plug tip member is provided that is connected in a state such that the plug tip member is brought into sealing contact with the stepped portion when the through-hole plug is installed in the through hole. .

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view partially showing a shielding plug 4 that closes the upper part of a reactor vessel of a fast breeder reactor, and a through-hole plug 18 is eccentrically attached to a rotating plug 6 of this shielding plug 4. Figure 1 shows the hold-down shaft 1 of the through-hole plug 18.
5 is shown in the attached state. The inner surface of the hold-down shaft 15 is provided with a stepped portion 22 for a plug receiver to support the weight of the through-hole plug 18 and a latch groove 25 for latching the through-hole plug 18 to prevent it from being lifted in the event of a core accident.

The hold-down shaft 15 is provided with a stepped part 24 for closing, and an outer cylinder body 28 attached to the lower part of the through-hole plug 18 comes into sealing contact with this stepped part 24, and the through-hole plug 18
The gap 23 between the hold-down shaft 15 and the hold-down shaft 15 is closed at its lower end. The through-hole plug 1 is attached to the upper part of the through-hole plug 18.
A handling head 19 that grips the through-hole plug 18 with a gripper (not shown) of a handling machine when pulling out or inserting the through-hole plug 8;
The ball latch mechanism 20 supported by the latch groove 25 provided in
A neck portion 26 is provided for resting on.

Further, a sealing device 21 is provided below the ball latch mechanism 20.
is provided, and this seal W121 prevents the in-furnace cover gas from flowing out to the upper part of the furnace.

An outer cylindrical body 28 attached to the lower part of the through-hole plug 18 covers the plug body 27. The outer cylindrical body 28 has support holes 2
9 is provided, and the outer cylinder body 28 is attached to the plug body 27 by an outer cylinder body mounting pin 30 having a diameter smaller than this support hole 29.
It is loosely attached to the Therefore, the outer cylinder body 28 is pressed by its own weight against the closing stepped portion 24 of the hold-down shaft 15 described above, and the lower end of the gap portion 23 is closed. A difference in thermal expansion occurs between the hold-down shaft 15 and the through-hole plug 18 due to the difference in temperature distribution.
In order to absorb this difference in thermal expansion, the diameter of the support hole 29 is made larger than the diameter of the outer cylinder mounting pin 30.

When the through-hole plug 18 is pulled out by a handling machine, the outer cylinder body 28 is suspended and supported by the outer cylinder body attachment bin 30. Further, inside the plug body 27, a hole 31 for a sodium melting heater i%lB is provided as a backup in case sodium sticks to the gap 23 due to a failure or the like.

Next, the effect of the above-described through-hole plug 18 will be explained.

The through-hole plug 18 is inserted into the hold-down shaft 15 by gripping the handling head 19 with a handler (not shown). First, the outer cylindrical body 28 at the lower end of the through-hole plug 18 hits the closing stepped part 24, and then,
Due to the play between the support hole 29 and the outer cylinder attachment pin 30, only the plug body 27 is lowered, and the plug receiver stops at a position where the neck 26 is placed on the stepped portion 22.

Next, the ball latch mechanism 20 supports the plug body 27 in the latch groove 25. During reactor operation, the hold-down shaft 15 and through-hole plug 18 may be damaged due to differences in temperature distribution.
Although a difference in thermal expansion occurs in the axial direction, this difference in thermal expansion is absorbed by the play between the support hole 29 and the outer cylinder mounting pin 30, and no restraining force is generated. During reactor operation, a large amount of sodium vapor is generated inside the reactor, but as mentioned above, the outer cylinder 28
Since the lower end of the gap 23 is closed by the stepped closing portion 24, this sodium vapor does not enter the gap 23. Therefore, sodium does not accumulate in the gap 23.

Similarly, since the lower end of the gap 23 is closed, the intrusion of the FP gas having high radiation intensity generated in the furnace into the gap 23 is greatly suppressed.

In the unlikely event that sodium adheres to the first part 23 due to a failure such as malfunction of the outer cylinder 28 or an operational error, an electric heater ( (not shown) is installed to melt and flow down the fixed sodium.

FIGS. 2 to 5 are sectional views of main parts of through-hole plugs showing other embodiments of the present invention.

In FIG. 2, an outer cylindrical body 3 that covers the lower part of the plug body 27
A flange 33 is provided at the upper end of the plug body 2, and the outer cylinder body 32 is supported by the plug body 27 by this flange 33. In this embodiment, the difference in axial thermal expansion between the hold-down shaft 15 and the through-hole plug 18 is absorbed by the loose flange support structure.

In FIG. 3, an outer cylindrical body 3 that covers the lower part of the plug body 27
A wire 35 is attached between the upper peripheral edge of the plug body 27 and the plug body 27, and the outer cylinder body 34 is suspended by the wire 35. In this embodiment, the hold-down shaft 15 and the through-hole plug 18 are
The difference in thermal expansion in the axial direction that occurs between the two is absorbed by the bending of the wire 35.

In FIG. 4, an outer cylindrical body 3 that covers the lower part of the plug body 27
A spring 37 is installed between the upper end circumference of the plug body 27 and the upper end of the plug body 27, as shown in FIG. The spring 37 absorbs the difference in thermal expansion in the axial direction between the through-hole plug 18 and the through-hole plug 18 .

In FIG. 5, a plug tip portion 38 having a structure in which the lower end portion is formed in a truncated conical shape and is connected to the upper portion of the disc via a columnar portion is suspended from a spring 39 on the plug body 27, and is also provided on the plug body 27. The plug tip 38 is inserted into the hole 40.
The upper part of the disk is loosely fitted. In this example, the first
・Stepped closure 124 and plug tip 8I138 in the figure
At the same time, the heat generated in the hold-down shaft 15 and the through-hole plug 18 in the axial direction is absorbed by the backlash in the differential hole portion 40 and the spring 39.

(Effects of the Invention) As described above, according to the present invention, since the sealing mechanism is installed between the through-hole plug provided in the shielding plug at the upper part of the reactor, sodium vapor can be held down between the through-hole plug and the shielding plug at the top of the reactor. It is possible to prevent deterioration in the operability of inserting and withdrawing the through-hole plug, which is caused by the plug penetrating into the gap between the plug and the shaft.

In addition, since it is possible to prevent sodium from entering the gap, it is possible to prevent radioactive sodium from adhering to the through-hole plug, increasing the gA ray intensity and deteriorating its handling when the through-hole plug is taken out of the furnace. It can be prevented.

Furthermore, since the intrusion of FP gas into the gap can be significantly reduced, the radiation shielding conditions in the upper part of the reactor can be significantly reduced, and the number of radiation shields can be reduced, making the structure and arrangement easier.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a state in which the through-hole plug of the present invention is installed, and FIGS. 2, 3, 4, and 5 each show other embodiments of the through-hole plug of the present invention. Main part longitudinal sectional view,
Figure 6 is a vertical cross-sectional view showing the schematic structure of a fast breeder reactor, Figure 7 is a vertical cross-sectional view showing the state of core components in the fast breeder reactor shown in Figure 6 when they are replaced, and Figure 8 is a conventional through-hole. FIG. 3 is a longitudinal cross-sectional view showing a state in which the plug is attached. 15... Hold down shaft, 18... Through hole plug, 19... Handling head, 20... Pole latch mechanism, 21... Seal mechanism, 22... Stepped plug receiving, 23...・8Wa, 24...-Stepped for closure, 2
5... Latch groove, 26... Neck, 27... Plug body, 28... Outer cylinder body, 29... Support hole, 30...
- Outer cylinder body mounting pin, 31... Sodium melting heater installation hole, 32.34.36... Outer cylinder body, 33... Flange, 35-... Wire, 37.39... Spring. Representative Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In a through-hole plug that is removably installed in a through-hole provided in a shielding plug in the upper part of a nuclear reactor, a through-hole wall surface that is located at the tip of the through-hole plug when the through-hole plug is installed in the through-hole. a stepped portion is provided in the through-hole plug body, a plug tip member connected to the through-hole plug body in a non-restricted state is provided near the tip portion of the through-hole plug body in the direction in which the through-hole plug body is attached to the through-hole; A through-hole plug, wherein the plug tip member is brought into sealing contact with the stepped portion when inserted into the hole.