JPS6054638B2 - How to transfer spent fuel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for transferring spent fuel between a spent fuel storage pool such as a nuclear power plant, a spent fuel reprocessing plant, or an intermediate storage facility and a cask.

At the above facilities, used fuel is transferred between storage pools and casks for transportation or storage, but since used fuel has strong radioactivity, sufficient care must be taken when handling it. It's necessary.

Conventionally, as shown in FIG.
The cask 2 is submerged in water, and the fuel F is put into the fuel basket 3 inside the cask 2, or conversely taken out from the fuel basket 3. However, this method has the disadvantage that water in the pool 1 contaminated with radioactivity adheres to the inner and outer surfaces of the cask 2, thereby contaminating the cask 2. Contamination of the outer surface of the cask 2 can be prevented by covering the cask 2 with a cover, but this is not preferable because not only is there a risk of contamination due to a defective cover, but the cover itself is also contaminated. Furthermore, since the heavy cask 2 is handled underwater, there is a safety problem. This invention was made in view of the above circumstances, and it dramatically reduces contamination on the inner and outer surfaces of the cask, and allows the cask to be handled safely.
Usage The purpose is to provide a method for transferring fuel.

Hereinafter, this invention will be explained in detail based on the embodiments shown in FIGS. 2 to 4.

The drawing shows a part of the spent fuel storage pool 10, in which a cask support stand 11 is provided above the water surface in one corner.

The cask support 11 is formed horizontally and continuously on the upper surface of the shield 13 that forms the two adjacent pool sides 12, and has a rectangular shape when viewed from above, with a hole 14 bored in the center thereof. . A stepped portion 15 for supporting the cask is formed at the peripheral edge of this hole 14. Plate-shaped shields 16 and 17 extending vertically downward are provided on two side edges of the cask support base 11 that are not in contact with the shield 13, respectively.
A basket passage 18 is formed inside these.
One of the shields 16 reaches the bottom surface 19 of the pool, and the other shield 17 reaches a required depth below the water surface, and the lower side thereof is connected to the fuel passage 20. And basket aisle 1
8, the space between the water surface of the pool 10 and the cask support stand 11 is covered by these shields 16, 17 and the pool 1.
0 shielding body 13. Pool bottom 1
Shielding body 17 and cask support stand 11 that have not reached 9
A wire lobe passage 21 is formed extending from the lower end of the shield 17 to the upper end of the cask support 11 and connecting the basket passage 18 inside the shield 17 and the outside of the shield 17. In order to prevent the ability of the shield 17 from decreasing,
This passage 21 is bent at two points at approximately right angles when viewed from above. A basket moving table 22 is attached to the basket passage 18 so as to be vertically movable, and is connected to a drive motor 24 by a chain 23.

A basket holder 25 that protrudes upward is provided at the center of the movable table 22, and a support ring holder 26 is provided around the holder 25, which is lower than this and is rotatable in a horizontal plane. ing. Also, pool 1
0 is equipped with a crane (not shown) that can freely move above it.

The cask 27 used in this embodiment has a cylindrical shape with a top wall and an open bottom, inside which a fuel basket 27 is placed.
9 is loaded, and a basket support ring 30, a disk-shaped shield 31, and a shield support ring 32 are attached. Furthermore, a sealing lid (not shown) is attached to the cask 27 to seal the basket loading/unloading port 33. Cask 2
7 is formed with two support ring grooves 34 and 35, and the groove wall 36 of the basket support ring groove 34 on the side of the basket loading/unloading port 33 has notches 37 at four places dividing the inner circumference into four equal parts. It is formed. Basket support ring 3
0 has an inner diameter smaller than the outer diameter of the fuel basket 29 and a slightly smaller outer diameter than the inner diameter of the basket support ring groove wall 36, and has groove walls 3 at four locations dividing the outer circumference into four equal parts.
A protrusion 38 corresponding to the notch 37 of No. 6 is formed.
The one shield support ring 32 and the support ring groove 35 also have a similar structure. Also, fuel basket 29
has a number of compartments for vertically holding each fuel. In the method of this invention, the operation for transferring the fuel F from the pool 10 to the tank 27 is as follows.

Prior to moving the fuel F, the empty fuel basket 29 and basket support ring 30 are placed on their respective holders 25 and 2.
6, and the moving platform 22 is positioned at the bottom of the water.

Then, the cask 27 and the like on the cask support stand 11 are removed to leave the upper part of the basket passage 18 open. When the above preparations are completed, the fuel in the pool 10 is transferred one by one to the fuel basket 29 by a crane.

The fuel F is held vertically at the lower end of the wire lobe of the crane, and the fuel F and the wire lobe are each connected to a fuel passage 20.
and the basket passage 1 through the wire lobe passage 21.
The fuel basket 29 in the fuel tank 8 is moved upward. Therefore, fuel F can be easily stored in each compartment of the fuel basket 29.
can be loaded. When the transfer of fuel to the fuel basket 29 is completed, the cask 27 is moved to the cask support stand 1.
It is fixed to the stepped portion 15 of No. 1.

At this time, the basket loading/unloading port 33 of the cask 27 faces downward. Then, the basket moving table 22 is moved upward to load the fuel basket 29 into the cask 27.
The cask 27 is positioned such that the notch 37 of the basket support ring groove wall 36 matches the protrusion 38 of the basket support ring 30 on the pedestal 26, and the cask 27
2 stops after the basket support ring 30 passes through the notch 37. When the moving table 22 stops, the cradle 26
That is, after rotating the basket support ring 30 approximately 452 times to fit the protrusion 38 of the support ring 30 into the groove 34,
The moving table 22 is moved down to near the water surface. The fuel basket 29 moves slightly downward together with the moving table 22, and the support ring 3
0 and is supported. Next, the shield 31 and the shield support ring 32 are stacked vertically and moved from the side of the cask support stand 11 directly below the cask 27 by appropriate means, and the moving table 22 is moved upward again to remove the shield. 31 and shield support ring 32 on two pedestals 25 and 2, respectively.
6 and inserted into the cask 27, and the support ring 32 is fitted into the groove 35 and fixed in the same manner as described above. Although not shown, the shield 31 and the shield support ring 32 are
It is placed in a recess formed in one of the pool side surfaces 12 above the water surface, and is moved directly below the cask 27 by a hydraulic cylinder, motor, etc., for example, as follows. That is, a horizontal rail extending below the cask support stand 11 is provided in the recess, and the cart is placed on this rail.
In order not to obstruct the vertical movement of the moving platform 22, the rails are arranged below both sides of the hole 14 of the cask support 11, and at least the basket holder 25 and the support ring holder 26 of the moving platform 22 can pass through the platform. Leave an opening. Further, an opening leading to the recess is provided on the upper surface of the shield 13 directly above the recess, and the shield 31 and the support ring 3 stacked one above the other are provided.
2 is placed on the trolley in the recess through this opening, and then the opening is closed with a lid made of a shielding body. and,
As described above, attach the basket support ring 30 to the cask 27.
After fitting the movable table 22 down to near the water surface,
The trolley carrying the shield 31 and the support ring 32 is moved from inside the recess along the rail to just below the cask 27. Next, the moving platform 2 is passed between the rails and through the opening of the trolley.
2 is moved upward, and the shield 31 and support ring 32 that were on the trolley are placed on the two pedestals 25 and 26, respectively, and loaded into the cask 27, and the shield is supported in the same way as the basket support ring 30. After the ring 32 is fitted onto the cask 27, the moving platform 22 is moved down to the bottom of the water. Note that the trolley is returned to the recess at an appropriate time after the shielding body 31 and the support ring 32 are placed on the moving platform 22 and before the moving platform 22 is moved down to the bottom of the water. However, the movement of the shield 31 and the support ring 32 is not limited to the above-mentioned method, and other known appropriate means may be used. In the above operation, the fuel basket 29, that is, the fuel F is
The worker is moved through the space between the water surface at 0 and the cask 27, but this space is surrounded by the shields 13, 16, 17, so there is no risk of the worker being exposed to radiation.

When the shield 31 and the support ring 32 are installed,
Lift up the cask 27 and attach the airtight lid.

When transferring fuel F from the cask 27 to the pool 10,
Just do the opposite of the above.

That is, the cask 27 containing the fuel F is fixed to the cask support stand 11 by removing only the sealing lid, the shield 31 and the support ring 32 are removed and moved to the side of the cask support stand 11, and the fuel basket 29 and Support ring 3
0 removed and moved to the bottom of the water, empty cask 27
is removed to open the upper part of the basket passage 18, and the fuel F in the fuel basket 29 is transferred to the pool 10 one by one using a crane.

In this embodiment, two support rings 30 and 32 are used, and two mounting operations are required. However, if the shield 31 is attached to the lower part of the fuel basket 29 in advance, the fuel basket 29 It is only necessary to attach one support ring at the same time as the cask is loaded, and furthermore, there is no need to move the shield 31 to the side of the cask support stand 11, so the structure of the apparatus is simplified.

Cask support stand 11. The structures of the shields 16, 17, the movable table 22, the drive mechanism of the movable table 22, etc. do not need to be limited to those of this embodiment, and can be modified as appropriate.

In the spent fuel transfer method according to the present invention, the cask 27 is supported above the water surface of the spent fuel storage pool 10 with the basket loading/unloading port 33 facing downward, and the space between the water surface of the pool 10 and the cask 27 is provided. The shield 13,1
Since the fuel basket 29 containing the spent fuel F is moved between the cask 27 and the pool 10, there is no need to immerse the cask 27 in the pool 10.

Therefore, contamination on the inner and outer surfaces of the cask 27 is reduced,
Moreover, the cask 27 can be handled safely.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing a conventional example, FIGS. 2 to 4 show an embodiment of the present invention, and FIG. 2 is a perspective view showing the main parts of the device used to carry out the invention. , FIG. 3 is a sectional view taken along line 1--2 in FIG. 2, and FIG. 4 is an enlarged sectional view taken along line 2--2 in FIG. 10... Spent fuel storage pool, 13, 16, 1
7... Shielding body, 27... Cask, 29
...Fuel basket, 33...Basket loading/unloading port, F...Spent fuel.

Claims (1)

[Claims] 1. Support the cask 27 above the water surface of the spent fuel storage pool 10 with the basket loading/unloading port 33 facing downward, and surround the space between the water surface of the pool 10 and the cask 27 with shields 13, 16, 17. , between the cask 27 and the pool 10, a fuel basket 2 containing usage fuel F is placed between the cask 27 and the pool 10.
How to use and transfer fuel to move 9.