JPH07218686A - Method and device for loading spent fuel assembly to canister - Google Patents

Abstract

PURPOSE:To perform loading of a spent fuel assembly to a canister without providing any special chamber, building and transportation equipment. CONSTITUTION:A canister body 4a is placed in a fuel. storage pool 1, a spent fuel assembly 2 is filled in the canister body 4a, a lid placer 17 is put on, the water in the lid placer 17 is replaced with the air, the water in the canister 4 is drained, a canister lid 4b is fixed by welding, the canister inside is dried and filled with inert gas, the air in the lid placer 17 is replaced with water, and the lid placer 11 is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for loading a canister for storage with a spent fuel body for filling a canister for storage with a spent fuel body at a nuclear power plant.

[0002]

2. Description of the Related Art A spent fuel unit used in a nuclear reactor of a nuclear power plant is stored in a fuel storage pool that is once filled with water, and then placed in a transportation container having a radiation shielding capacity for reprocessing and re-used. It is sent to the processing plant. Recently, with the increase of spent fuel bodies, one or more spent fuel bodies are sealed in a container called a metal canister having an airtight structure,
Plans for dry storage for medium to long term are in progress. Dry storage systems such as vault storage and silo storage are under study as low-cost, high-density and highly safe storage system for spent fuel. When these storage methods are adopted, it is necessary to carry out the spent fuel body from the fuel storage pool, store it in a canister in a cell (room) having a shielding and confining function, and seal it.

[0003]

Since such a cell fulfills the shielding function, a wall thickness of about 1 m is required.
The scale of floor area, ceiling height, etc. will be too large to fit in the reactor building that houses the reactor system. Further, a facility for transporting the spent fuel body from the fuel storage pool to the cells while shielding the radiation is required.

The present invention has been made in view of the above-mentioned problems, and by sealing a spent fuel body in a canister in a fuel storage pool, a cell or a cell for sealing the spent fuel body in the canister is provided. An object of the present invention is to provide a method and a device for loading a spent fuel unit onto a canister that does not require the transportation device described above.

[0005]

To achieve the above object, a canister, which is a container for storing a spent fuel body, is installed in a water-filled fuel storage pool with a lid removed.
After the spent fuel body is filled in the canister, the canister has a lid mounting space and is covered with a lid mounting device that detachably engages with the floor of the fuel storage pool to form a watertight space, and water in the lid mounting device is covered. After substituting the gas with water, the canister is drained of water, the canister is fitted with a lid previously incorporated in the lid attaching device and welded, and the canister is dried and filled with an inert gas. The gas in the lid attaching device is replaced with water, and the lid attaching device is removed.

Further, water draining, drying and filling with an inert gas in the canister are carried out from an inlet at the bottom of the canister, and after the inlet is closed by welding.

[0007] Further, a support stand provided on the bottom surface of the fuel storage pool for supporting the canister, a water treatment line detachably connected to a bottom joint of the canister, and a bottom stand of the canister installed on the support stand. A welder that closes the joint with welding, and a lid attachment device that has a lid attachment space for the canister installed with the lid removed from the support frame and detachably attaches to the floor of the fuel storage pool to form a watertight space. And a replacement device that replaces water in the lid mounting device with gas,
A lid welding device, which is provided in the lid attaching device and attaches a lid incorporated in advance in the lid attaching device to the canister, and welds the joint portion, is provided.

The water treatment line is connected to a drainage device for draining water in the canister, a drying device for drying the canister, and an inert gas filling device for filling the canister with an inert gas.

[0009]

The canister is installed on the support frame with the lid removed, and the spent fuel stored in the fuel storage pool is filled in the canister. Cover the canister on the support frame with the lid of the canister installed in the lid mounting device in advance, and after the lower end is watertight with the fuel storage pool floor, the gas is pumped to the lid mounting device by the displacement device, Replace with water. After water treatment in the canister is performed by a water treatment line connected to the inlet at the bottom of the canister, a lid welding device is used to attach a lid to the canister and perform welding. Next, after drying the canister and filling with an inert gas by the water treatment line, the water treatment line is removed from the joint port, and the joint port is welded closed by a welding machine attached to the support frame. Water is poured into the lid mounting device by the displacement device to replace the gas therein, and then the lid mounting device is pulled up from the fuel storage pool. The canister in the fuel storage pool, the filling of the spent fuel body, and the installation and removal of the lid attachment device are performed by the crane provided in the fuel storage pool.

Since one of the water treatment lines is connected to the bottom joint of the canister, the canister lid is connected before welding and the other is connected to the drainage device to drain the drain inside the canister, and after the lid welding, dry the canister. The device is switched to dry the inside of the canister, and the device is switched to an inert gas filling device to fill the canister with the inert gas.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of this embodiment. A fuel storage pool 1 for temporarily storing a spent fuel body 2 is arranged near a nuclear reactor of a nuclear power plant, and water is constantly sprinkled. On the ceiling of the fuel storage pool 1 is a crane for replacing the spent fuel body 2 in the reactor with a new fuel body, operating the lid of the reactor pressure vessel that houses the reactor, and moving the shielding material. The crane hook 3 is used in this embodiment.

The canister 4 is composed of a canister body 4a and a canister lid 4b. The canister body 4a has a cylindrical bottom portion, and the bottom portion is provided with pipes for draining water inside, drying, and filling helium (He) gas. An access port 6 is provided. The canister body 4a and the canister lid 4b are made of corrosion-resistant metal such as stainless steel that can withstand long-term storage. When filling the spent fuel body 2, the canister body 4a is installed on the support stand 7 and filled by the crane hook 3. Inside the support base 7, there are provided an inlet welding machine 8 for seal-welding the inlet 6, an inlet 6 and an inlet pipe 9 to be attached / detached by a remote control device (not shown).

The connecting pipe 9 is connected to a water treatment line 10,
The water treatment line 10 includes a drainage device 14 that drains the drain of the canister 4 through a valve 11, a drying device 15 that vacuums and dries the inside of the canister through a valve 12, and a valve 13
It is connected to the He filling device 16 for filling the helium gas via the.

The lid attaching device 17 is a device for attaching the canister lid 4b to the canister body 4a filled with the spent fuel body 2 by welding, and attaches the canister lid 4b to the canister body 4a placed on the support frame 7. It comprises a cylindrical surrounding wall 24 and a top plate 25 having a space necessary for the above, and the lower end of the surrounding wall 24 is kept watertight with the floor of the fuel storage pool 1. A pressure line 18 is provided on the top plate 25 of the lid attaching device 17.
Are connected to the air compressor 20 via a valve 19, and a valve 21 is provided at the lower end of the surrounding wall 24 to discharge or fill water in the lid mounting device 17.

The lower end of the surrounding wall 24 is located at the fuel storage pool 1
It is not always necessary to maintain watertightness with the floor and the valve 21 is not always necessary. That is, pressure line 1
The valve 19 of the pressurizing line 18 is closed when the water level in the lid attaching device 17 is lowered to a predetermined level by 8. When the water level fluctuates (rises), the valve 19 may be opened and the water level may be adjusted by the valve 19. As another method, compressed air is constantly sent from the pressurization line 18 and excess air leaks from the lower end of the surrounding wall 24 of the lid mounting device 17. As a result, the water in the lid mounting device 17 is discharged. When water is filled, the valve 19 is opened and the air compressor 20 is opened so that water flows from the lower end of the surrounding wall 24.

A lid holding device 22 for holding the canister lid 4b is provided on the top plate 25 of the lid attaching device 17, and a lid welding machine 23 that moves along the enclosure wall 24 is provided at the upper end position of the canister body 4a of the enclosure wall 24. Has been. The lid gripping device 22, the lid welding machine 23, the joint welding machine 8 and the valve 21 are all operated by remote control.

Next, the operation of the above apparatus will be described. FIG. 2 shows that a support base 6 is installed in a loading work area for a canister 4 provided at one corner of the fuel storage pool 1, a canister body 4a is installed on the support base 6, and then a spent fuel body 2 is loaded from a storage place by a crane hook 3 Lifting with canister body 4
The state of being loaded in a is shown. Depending on its specifications, the canister body 4a can accommodate one or more spent fuel bodies 2. After the canister body 4a is filled with the prescribed spent fuel body 2, the lid mounting device 17 is installed as shown in FIG. Upon installation, the valve 19 is opened, the air compressor 20 side is opened, the air inside the lid attachment device 17 is released while being released, and after reaching the floor of the fuel storage pool, the valve 21 is opened and the air compression is performed. Pressurized air is sent from the machine 20 to replace the water in the air. After almost all the water has been discharged, the valve 21 is closed.

Next, the valve 11 is opened and the drainage device 14 is operated to discharge the drain inside the canister body 4a.

When the lid mounting device 17 is installed at a predetermined position while the canister lid 4b is gripped by the lid gripping device 22 provided on the top plate 25, the canister lid 4b is guided by the guide provided on the upper end of the canister body 4a. And the upper end of the canister body 4a are aligned with each other, welding is performed by the lid welding machine 23, and the canister lid 4b is welded to the canister body 4a.

When the welding is completed, the valve 12 is opened and the drying device 15 is operated to vacuum dry the inside of the canister 4.
Next, the valve 13 is opened and the He filling device 16 is operated to fill the canister 4 with He gas.

After filling with He gas, the fitting port 6 and the fitting pipe 9 provided at the bottom of the canister body 4a are removed by remote control as shown in FIG. The coupling port 6 is of a quick coupler type that is closed when the coupling pipe 9 is removed, so that the filled He gas does not come out of the canister 4 or the outside gas does not enter the canister 4. Next, the inlet 6 is welded and closed using the inlet welder 8.

Next, the lid mounting device 17 is removed. Valve 19
When the valve 21 is opened and the air compressor 20 side is opened to release air, water enters through the valve 21 and the lid mounting device 17 is filled with water. In this state, it may be lifted by the crane hook 3. FIG. 4 shows a state in which the lid attaching device 17 is removed.

In the above embodiment, the water in the lid mounting device 17 was replaced with air, but it may be replaced with nitrogen gas.
Although the lid welder 23 moves along the surrounding wall 24 to perform welding, the lid welder 23 may be fixed and the canister body 4a may be rotated.

[0024]

As is apparent from the above description, the present invention has the following effects. All of the work of loading the spent fuel body into the canister can be performed under the surface of the water, and it is not necessary to provide a shielding facility due to the water shielding effect. Since this work can be performed in one corner of the fuel storage pool, there is no need to newly install a room or building. Since all of this work is done in the fuel storage pool, there is no need for a facility to transport spent fuel in the air.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a present embodiment.

FIG. 2 is a view showing a state in which a canister body is installed on a support base and a spent fuel body is taken in.

FIG. 3 is a view showing a state in which an engagement port at the bottom of a canister is closed by welding.

FIG. 4 is a view showing a state in which a canister is filled with a spent fuel body in water.

[Explanation of symbols]

 1 Fuel Storage Pool 2 Spent Fuel Body 3 Crane Hook 4 Canister 4a Canister Body 4b Canister Lid 6 Attachment Port 7 Supporting Stand 8 Attachment Port Welder 9 Attachment Pipe 10 Water Treatment Line 11, 12, 13, 19, 21 Valve 14 Drainage device 15 Drying device 16 He filling device (inert gas filling device) 17 Lid mounting device 18 Pressurization line 20 Air compressor (replacement device) 22 Lid gripping device 23 Lid welder 24 Enclosure 25 Top plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G21F 5/005 9/36 ZAB 7381-2G 511 A 7381-2G

Claims (4)

[Claims] 1. A canister, which is a container for storing a spent fuel body, is installed in a water-filled fuel storage pool with a lid removed, and after the spent fuel body is filled in the canister, the canister lid is attached. A canister is attached to the floor of the fuel storage pool in a detachable manner to form a watertight space, and the water in the canister is replaced with gas, and then the canister is drained to remove the canister. After attaching and welding the lid that was built in the lid attaching device in advance, after drying the canister and filling with the inert gas, replace the gas in the lid attaching device with water and remove the lid attaching device. A method of loading a spent fuel body into a canister, the method comprising: 2. The use according to claim 1, wherein draining of water, drying and filling with an inert gas in the canister are performed from an inlet at the bottom of the canister, and after the inlet is closed by welding. How to load the spent fuel into the canister. 3. A support stand installed on the bottom surface of the fuel storage pool for supporting the canister, a water treatment line detachably connected to a bottom joint of the canister, and a bottom stand of the canister installed on the support stand. A welder that closes the joint with welding, and a lid attachment device that has a lid attachment space for the canister installed with the lid removed from the support frame and detachably attaches to the floor of the fuel storage pool to form a watertight space. When,
A replacement device for replacing water in the lid mounting device with a gas, and a lid welding device provided in the lid mounting device for mounting a lid previously incorporated in the lid mounting device on a canister and welding the joint portion, A device for loading a spent fuel body onto a canister, characterized by comprising: 4. The water treatment line is connected to a drainage device for draining water in the canister, a drying device for drying the canister, and an inert gas filling device for filling the canister with an inert gas. Claim 3 characterized in that
A device for loading the described spent fuel body onto a canister.