JPS6044890A - Contamination preventive skirt structure of nuclear fuel transport container - 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 The present invention relates to a contamination prevention skirt structure for a nuclear fuel transport container.

The operation of storing or removing spent nuclear fuel in nuclear fuel transport containers (hereinafter simply referred to as transport containers) is carried out underwater in the fuel pool in order to reduce the exposure of handling workers to radiation emitted by spent nuclear fuel. It will be done. Therefore, the surface of the transport container is contaminated by radioactivity in the fuel pool water.

To prevent this, a contamination prevention cover is used to cover the outer surface of the container. Conventionally, a rubber bag-like cover, that is, a rubber bag, has been proposed as this pollution prevention cover. However, since it is made of rubber and is highly flexible, it is difficult to attach and detach it, and it is difficult to ensure its airtightness and durability due to the water pressure applied to the rubber bag in the fuel pool water.

The present invention was made in order to eliminate the above-mentioned point, and it is a thin metal plate that can be removed from a place on the outer surface of a transport container that is difficult to decontaminate, that is, a place where heat dissipation fins are attached. By covering the container with a plastic skirt and immersing it in the fuel pool water, radioactive contamination of the covered area by the fuel pool water is prevented, and furthermore, pressurized air is flowed into the space between the transportation container and the skirt for transportation. It is an object of the present invention to provide a lightweight pollution prevention skirt for a transport container that removes heat from the container and alleviates external pressure loads applied to the skirt due to water pressure.

A contamination prevention skirt structure for a nuclear fuel transport container according to the present invention will be explained based on the drawings.

FIG. 1 shows a transport container 1 with a contamination prevention skirt attached. Reference numeral 2 denotes a cylindrical skirt body made of sheet metal F4, which surrounds the transport container 1, except for the upper part, mainly at the location where the radiation fins are attached. Reinforcing annular ribs 2a are provided at appropriate intervals on the outer periphery of the skirt body 2 to create a lightweight structure that is strong against internal and external pressure, and a pressurized air port 3 and a pressurized air outlet 4 are provided at both ends, respectively. be. Therefore, since the skirt body 2 has a simple structure, it can be easily decontaminated.

Next, the structure for fixing the top of the skirt body 2 to the transport container 1 will be explained based on FIG. 2. 5 is an annular cover for sealing made of rubber, and an annular passage 5 m' is provided in the inner peripheral part 5a.
The outer peripheral part 5b is hermetically fixed to the outward flange 2b of the skirt body 2 with bolts 6, and the inner peripheral part 5a is fixed to the shoulder part of the transport container 1 by introducing pressurized air into the annular passage 5a'. Airtightness is maintained by locking between the inner surfaces of a plurality of downward L-shaped fixtures 7 fixed to the shoulder portion 1a and the side surface of the shoulder portion 1a. Reference numeral 8 denotes a skirt fastening fitting for fixing the skirt body 2 to the transport container 1. The lower surface 8 a' of the tip of one arm 8 a of the angled skirt fastening metal fitting 8 can be press-fitted to the upper surface of the fixture 7 .

The tip of the other arm 8b is provided with a cylindrical portion 8c that is orthogonal to the lower surface 8a' of the tip. Reference numeral 9 is a shaft integrally formed with the skirt body 2, which is identified by welding or the like to the vertically facing flange 2b of the skirt body through a member 10, and is inserted into the cylindrical portion 8c. 8 is rotatable and vertically movable with respect to the shaft 9. 11 is an upper nut, 12 is a lower nut, and the skirt tightening fitting is fixed to the shaft 9 by both nuts 11 and 12. A plurality of such skirt fastening fittings 8 are arranged on the upper outer periphery of the skirt body 2. Note that the other end of the shaft 9 is welded to the rib 2a.

The bottom surface 8a' of the tip of the skirt fastening fitting is locked to the top surface of the fixture 7, and the lower end of the skirt body 2 is locked to the bottom peripheral edge 1b of the transport container 1 as described later.
By adjusting the positions of 11' and 12 and fixing the position of the cylindrical portion 8c to the shaft 9, the skirt body 2 is fixed to the transport container 1.

Fig. 3 shows the current structure for supplying pressurized air to the passage 5m' of the annular cover, in which a notch 7a is provided in the fixture 7 and an air pipe 5c is inserted through the annular passage 5a' to the outside. It is connected to the protruding nozzle 5c'.

Next, the bottom structure of the skirt body 2 shown in FIG. 4 will be explained. An inward flange 2c is provided at the bottom of the skirt body 2, and an annular groove 2c' having a U-shaped cross section is provided at the inner end of the flange 2c, and an annular tube 13 made of rubber is encircled therein. be.

Then, the nozzle 13a attached to the annular tube 13 is made to protrude from the through hole provided in the annular groove 2c' and connected to the air pipe 14. Reference numeral 15 denotes a plurality of substantially L-shaped locking pieces hanging from the lower surface of the inward flange 2c, the upper end surface 15a of which is fixed to the lower surface of the inward flange 2c, and part of its vertical and horizontal inner surfaces. Along the outer surface of the annular groove 2c', the tip of the lateral inner surface serves as a locking portion 15b to the lower surface periphery 1b of the transport container 1.

FIG. 5 shows a structure for fixing the annular tube 13 to the annular groove 2c'. That is, a hole (13b't) fixed to the side wall of the annular tube 13 and an annular groove (2c') are fixed with a hole (13c) which projects outward through a nine-hole.

Next, a procedure for attaching the pollution prevention skirt according to the present invention to a transport container will be explained. Holding the pollution prevention skirt in an upright state, loosen the upper nut 11 and rotate the skirt fastening fitting 8 around the shaft 9 to take a position that avoids the upper opening position of the skirt body 2, and The annular cover 5 is rolled outward to expand its diameter, and the lifted transport container 1 is lowered through the upper opening of the skirt body 2, and the lower peripheral edge 1b of the transport container is connected to a plurality of locks provided on the skirt body. Place it on the locking part 15b of the piece. At this time, the annular tube 13 is connected to the air pipe 14 to a vacuum pump (not shown) and is positioned inside the annular groove 2a' so as not to interfere with the insertion of the transport container 1. The annular tube 13 is prevented from getting wedged between the transport container 1 and the skirt body 2. Next, the annular cover 5 is returned to its natural state,
Insert the inner peripheral part 5a below the fixture 7 and press it (pol) 7b
Fix it with. Then, rotate the skirt fastening fitting 8 inward, lock the lower surface 8a' of the tip of one arm to the upper part of the fixture 7, and adjust the positions of the upper nut 11 and the lower nut 12. The skirt body 2 is fixed to the transport container 1. Next, an air pipe 5c is connected to the annular passage 5&' of the annular cover.
In addition, pressurized air is supplied to the annular tube 13 through the air pipe 14 to expand the inner circumferential portion 5a of the annular cover and the annular tube 13, thereby ensuring airtightness between the skirt body 2 and the outer circumferential surface of the transport container 1. do. After the contamination prevention skirt is attached to the transport container 1, pressurized air is sent to the gap between the transport container 1 and the skirt body 2 through the pressurized air outlet 4, and a leakage test is performed by closing the pressure air outlet 4 to check for air leakage. After confirming that there is no spent nuclear fuel, the spent nuclear fuel is immersed in the fuel pool water and the spent nuclear fuel is stored in or removed from the transport container 1. At this time, the pressurized air outlet 4 is opened to allow pressurized air to flow through the gap between the transport container 1 and the skirt main body 2, to oppose the water pressure applied to the skirt main body 2 and to remove heat from the transport container 2.

The contamination prevention skirt structure for a nuclear fuel transport container according to the present invention includes a skirt body that is a cylindrical shape made of thin sheet metal that encloses the nuclear fuel transport container, and a skirt body that is fixed to the top of the skirt body and has an annular shape on the inner periphery. A rubber annular cover with a passage, a fixture provided on the shoulder of the nuclear fuel transport container to hold down the inner periphery of the annular cover, and an outward flange at the top of the skirt body that can rotate and move up and down. a skirt fastening fitting that is attached to the body and has one arm that can be locked to the fixture; an annular tube accommodated in an annular groove provided at the inner end of the inward flange at the lower end of the skirt body; and an inward flange. A locking piece that is vertically disposed on the lower surface and can be locked to the lower surface periphery of the nuclear fuel transport container, and a means for supplying pressurized air to the annular passage and the annular tube. The skirt body is fixed to the nuclear fuel transport container by locking the skirt fastening fitting to the fixing device and adjusting the position, and pressurized air is introduced into the annular passage and the annular tube of the annular cover to tighten the skirt. This structure maintains airtightness between the main body and the outer periphery of the nuclear fuel transport container.

Therefore, since the skirt body is made of rigid thin sheet metal, it is lightweight and easy to handle, and the nuclear fuel transport container can be easily inserted into and removed from the skirt, providing excellent airtightness and durability in the fuel pool water. We were able to provide a contamination prevention skirt structure for nuclear fuel transport containers. Furthermore, by circulating pressurized air through the gap between the skirt and the nuclear fuel transport container underwater in the fuel pool, heat is removed from the transport container and distortion caused by water pressure on the skirt body, which is made of thin sheet metal, is removed. We were able to prevent this and increase its airtightness and durability.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a nuclear fuel transport container equipped with a pollution prevention skirt according to the present invention, FIG. 2 is an enlarged cross-sectional view showing the structure for fixing the top of the skirt body to the transport container according to the present invention, and FIG. FIG. 4 is an enlarged sectional view showing the air supply structure to the annular passage of the annular cover, FIG. 4 is an enlarged sectional view showing the bottom structure of the skirt body, and FIG. 5 is an enlarged sectional view showing the fixing structure of the annular tube. l: Transport container, 1h: Shoulder, 1b: Bottom periphery, 2 varnish body, 2a: Annular rib, 2b = outward flange, 2
c: Inward flange, 2 c': yjJ-shaped groove, 3:
Pressure air inlet, 4: Pressure air outlet, 5: Annular cover, 5
1L=inner periphery, 5a': annular passage, 5b: outer periphery, 7:
Fixing tool, 8 Niskirt tightening fitting, 8a One arm, 8a
': lower surface of tip, 8b: other arm, 8c: cylindrical part, 9: shaft, 13: annular tube, 15: locking piece, 15b: locking part. Representative Patent Attorney 1) Toshiyuki Figure 2 Figure 3 C

Claims (1)

[Scope of Claims] 1. A cylindrical skirt body made of thin sheet metal that encloses a nuclear fuel transport container, and an annular rubber-made skirt whose outer periphery is fixed to the top of the skirt body and has an annular passage in its inner periphery. A cover, a fixing device provided on the shoulder of the nuclear fuel transport container to hold down the inner periphery of the annular cover, and an outwardly facing flange on the top of the skirt body, which is rotatably and vertically movable; a skirt fastening fitting that can be locked to the fixture; an annular tube accommodated in an annular groove provided at the inner end of the inward flange at the lower end of the skirt body; A locking piece that can be locked to the periphery of the lower surface of the container, and a means for supplying pressurized air to the annular passage and the annular tube; The skirt body is fixed to the nuclear fuel transport container by locking the skirt fastening fittings to the fixtures and adjusting the position, and pressurized air is introduced into the annular passage and the annular tube of the annular cover to tighten the skirt body and the nuclear fuel transport container. A contamination prevention skirt structure for a nuclear fuel transport container, which is characterized by maintaining airtightness between the container and the outer periphery. 2. The contamination prevention skirt structure for a nuclear fuel transport container according to claim 1, wherein the skirt body is provided with a pressurized air inlet and a pressurized air outlet.