JPH044237Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cover for a nuclear fuel transport container (hereinafter referred to as a cask).

When used nuclear fuel is transported, it is stored in a cask to shield it from radiation. Storage in the cask is carried out underwater in a fuel pool or other location while shielding it from radiation. At that time, the outside surface of the cask will be contaminated with radioactive materials in the water, so the outside surface must be decontaminated before the cask can be transported. However, the outer surface of the cask has fins, etc. and has a complicated surface condition, so decontamination takes a lot of time and effort. Therefore, before putting the cask into the pool, we put a cask cover on the outer surface of the cask outside the pool. The current situation is to avoid bringing the cask into direct contact with contaminated water.

As shown in Fig. 1, the conventional cask cover 2 is made of rubberized nylon fabric and covers the side and bottom surfaces of the cask 1 (the top surface cannot be covered because the fuel is taken in and out), and has a watertight fastener 3. Close it, seal the top with a steel band 8,
Moreover, the space between the cask 1 and the cover 2 is filled with fresh water and used by being immersed in pool water.

The installation of the fastener 3 of this conventional cover 2 is as follows:
One vertically long trunnion is provided, and the positions of the two trunnions 4, 4 on the upper side of the cask 1 are determined by making a hole in the cover 2 and protruding the trunnion 4 from the cover 2.
The cover 2 and trunnion 4 are sealed watertightly 5 and used.

The dimensions of cask 1 are approximately 5m in height, approximately 2m in diameter,
It weighs approximately 80 tons, and for safety reasons, measures must be taken to prevent it from tipping over at all times. In order to prevent this fall, the cask 1 is equipped with the above-mentioned trunnion 4 and fall prevention lugs 6 having holes at four locations on the outer periphery slightly below the trunnion. However, this anti-falling lug 6 was not used and was conventionally covered with a cover 2.

Now, the procedure for installing the conventional cask cover 2 is performed in the following order.

(a) Hang a hoist (not shown) on the trunnion 4 of the cask 1 and lift it up with an overhead crane.

(b) Put the cover 2 on from the bottom of the cask 1, close the fastener 3 close to the trunnion 4, and then lower the cask 1 to the floor.

(c) Using a temporary anti-falling lug 10 made of a steel ring or the like, pull several wires (not shown) diagonally downward on the outer circumference of the upper part of the cask 1, where it is not covered by the cover, and fix it to the floor.

(d) Remove the hanger from trunnion 4.

(e) Cover the cask 1 to the top, close the fastener 3, seal the top end of the cover 2 with a steel band 8, and insert a seal 5 into the hole in the trunnion 4.
do.

(f) Hang the hanging device on trunnion 4.

(g) Remove the temporary fall prevention lugs 10, wires, etc. mentioned above.

(h) After that, lift Cask 1 and place it in the pool.

Next, to remove the cask cover installed in this way, follow the steps in reverse.

As described above, since the conventional cover requires complicated procedures such as the use of an anti-fall device and a trunnion for attachment and removal, it takes a lot of effort and time. As a result, the risk of radiation exposure for workers was also increasing.

The present invention aims to solve the problems of the conventional cask cover installation and removal work, and an embodiment thereof will be described below with reference to FIG. 2 and subsequent figures.

As before, the bottom and sides of the cask 1 are covered with a cask cover. The trunnion 4 is designed so that the trunnion protrudes outward like a conventional cover. A vertically long fastener 3 is attached vertically from the upper end to the lower end of the cover. The cover is separated vertically from the top end to slightly below each anti-tip lug 6 of the cask 1, and is separated vertically from the top edge to a point slightly below each anti-tip lug 6.
It can be opened and closed.

With the above configuration, the cask cover installation work is performed in the following steps.

(a) Hang a hoist (not shown) on the trunnion 4 of the cask 1 and lift it up using an overhead crane.

(b) Open the vertically long fastener 3 of the cover 2 and spread it out on the floor.

(c) Lower the cask 1 to the center of the cover 2.

(d) Attach the wire 9 etc. to the fall prevention lug 6 and pull it diagonally downward to fix it on the floor.

(e) Remove the hanger from trunnion 4.

(f) Pull the cover 2 up to below the fall prevention lug 6 of the cask 1 to cover it, and close the vertically long fastener 3 to that point.

(g) Open the four fall prevention lug fasteners 7.

(h) Raise the cover 2 to the top of the cask 1 and close all the vertical fasteners 3.

(i) Close the fall prevention lug fastener 7 a little (approximately 20 to 30 cm) from the top end.

(j) Seal the upper end of the cover 2 with a steel band 8.

(k) Seal the trunnion 4 part of the cover 2.

(l) Hang the hanging device on trunnion 4.

(m) Remove the wire 9, etc. of the fall prevention lug 6.

(n) Close the fall prevention lug fastener 7 completely downward.

(o) After that, lift Cask 1 and place it in the pool.

Note that the cover 2 can be removed by performing the exact reverse of the installation procedure.

The present invention is constructed as described above. According to this, the tipping prevention lug 6 already attached to the cask body is made to protrude by opening the cask cover 2, and a wire or the like can be hung on it to prevent tipping. Therefore, the troublesome work of attaching and removing the temporary overturn prevention lug 10 made of a steel ring or the like on the upper part of the cask can be reduced as in the past, and this has a remarkable effect on improving the workability in handling the cask. It is something that plays.

[Brief explanation of the drawing]

Figure 1 is a front view of a conventional cask cover. Second
The figure is a perspective view of the cask cover according to the present invention, showing the fall prevention lug fastener in an open state. FIG. 3 shows a cask cover according to the present invention in which the top of the fastener for an anti-falling lug is slightly closed. In the figure: 1... cask, 2... cask cover, 3... fastener, 4... trunnion,
5... Seal, 6... Fall prevention rug, 7...
(For fall prevention rug) Fastener, 8... (For seal) Steel band, 9... (For fall prevention rug) Wire, 10... Temporary fall prevention rug.

Claims (1)

[Scope of utility model registration request] In the cover that covers the bottom and sides of the cask,
A vertical fastener 3 that can be opened and closed from the upper end to the lower part of the cover is provided, and a fastener 7 for fall prevention lugs is vertically installed from a position slightly below the position corresponding to each fall prevention lug attached to the cask to the upper end. A nuclear fuel transport container cover featuring: