JP2004069473A - Storage container made of concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a storage container made of concrete capable of maintaining soundness by preventing the leakage of radiation even in the case of the occurrence of earthquakes, drops, overturning, etc. <P>SOLUTION: The storage container made of concrete is provided with both an approximately tubular concrete container 12 made of concrete and a lid body 20 for blocking an upper end opening of the concrete container. The lower end of the the concrete container 12 is blocked by a bottom wall and comprises a housing part 22 inside. Radioactive materials are sealed in an approximately tubular canister 14, and the canister 14 is housed in the housing part. The concrete container 12 comprises a plurality of latch parts 34 provided for a lower end part inside the housing part. The canister comprises a plurality of flanges 32 provided in its lower end part for controlling displacements of the canister inside the housing part by engaging with the latch parts. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a concrete storage container having a so-called canister, which is a metal hermetically sealed container enclosing a radioactive substance.
[0002]
[Prior art]
Highly radioactive materials typified by spent fuel of nuclear reactors are reprocessed to recover useful substances such as plutonium that can be used again as fuel. These spent fuels are stored in a sealed state until reprocessing. As a method for storing such a highly radioactive substance, a wet method using a storage pool or the like, or a dry method using a cask or the like is known.
[0003]
The dry method is a storage method in which air is naturally cooled instead of water, and has attracted attention because its operating cost is lower than that of the wet method. There are various types of casks used for the dry method, and concrete casks that shield spent fuel with a concrete structure have received special attention because of their low cost. Concrete is excellent as a neutron shielding material and also has advantages such as obtaining necessary strength as a structure.
[0004]
Such a concrete cask is provided with a tubular concrete container whose top and bottom are closed, and a tubular metal sealed container filled with spent fuel, a so-called canister, is housed and arranged in the concrete container. Shields radioactive materials from spent fuel. In the concrete container, a space for flowing cooling air is provided around the canister.
[0005]
[Problems to be solved by the invention]
Transportation and storage of concrete casks as described above should be performed with great care and caution, but in the unlikely event of an accident, such as an earthquake during transportation, the concrete casks may fall onto the floor. You must also assume that you will fall or fall. Similarly, even when the concrete cask is stored in the storage, the concrete cask may fall over due to an earthquake or the like.
[0006]
When the concrete cask falls or falls as described above, the canister housed therein moves and collides with the inner wall of the concrete container. As a result, the canister is subjected to a large impact, and the wall portion or the welded portion between the primary lid and the secondary lid may be damaged. In this case, the radioactive substance leaks from the spent fuel stored in the canister, and the soundness cannot be ensured. Therefore, even in the event of an accident, there is a need for a concrete cask that can prevent radiation leakage and can store highly radioactive materials safely and reliably.
[0007]
The present invention has been made in view of the above points, and an object of the present invention is to provide a concrete storage container that can prevent radiation leakage even when an earthquake, a fall, a fall, or the like occurs, and can ensure soundness. .
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a concrete storage container according to an aspect of the present invention has a storage portion inside with a lower end closed by a bottom wall, and a substantially cylindrical concrete container formed of concrete. A lid closing the upper end opening of the concrete container, and a substantially cylindrical metal hermetic container which is housed in the housing portion of the concrete container and in which a radioactive substance is sealed,
The concrete container has an engaging portion provided at a lower end portion in the housing portion, and the metal hermetic container engages with an engaging portion of the concrete container provided at the lower end portion, and the inside of the housing portion It is characterized in that it has a projection for regulating the displacement of the metal sealed container.
[0009]
According to the concrete storage container configured as described above, even in the event of an earthquake or a fall or fall of the concrete storage container, movement of the metal closed container in the concrete container is prevented, and the concrete storage container is prevented from moving to the inner wall of the concrete container. Collision can be prevented. Therefore, the metal sealed container and the spent fuel assembly are not broken or damaged, and the leakage of the radioactive substance from the spent fuel can be prevented, and the soundness can be maintained. This makes it possible to obtain a concrete storage container capable of safely and reliably storing radioactive substances for a long period of time.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a concrete cask according to an embodiment of the present invention will be described in detail with reference to the drawings.
[0011]
As shown in FIGS. 1 to 3, a concrete cask 10 as a storage container made of concrete includes a concrete container 12 formed of concrete and functioning as a shielding structure. In the concrete container, a canister as a metal closed container is provided. 14 are stored.
[0012]
The canister 14 includes a cylindrical container body 40 whose lower end is closed, and a primary lid 13 and a secondary lid 15 which are welded to the upper end opening of the container main body and close the upper end opening. The container body 40 is made of, for example, a corrosion-resistant metal such as stainless steel, and has a wall thickness of about 15 to 20 mm.
[0013]
A plurality of spent fuel assemblies 18 are sealed in the container body 40 while being supported by the basket 16. These spent fuel assemblies 18 contain radioactive materials that generate heat due to decay heat and generate radiation. The canister 14 has a hermetically sealed structure so that the enclosed radioactive substance does not leak outside.
[0014]
As shown in FIGS. 1 to 3, the concrete container 12 has a cylindrical shape with a closed bottom, and is formed to have a height of about 6 m and a diameter of about 4 m, for example. It is formed to be about 0.8 to 1.0 m. The upper end opening of the concrete container 12 is closed by a concrete lid 20 whose outer surface is covered with a carbon steel plate or the like. The lid 20 is bolted to the upper end of the concrete container 12 by a plurality of bolts 21.
[0015]
An annular cushioning member 17 is mounted between the canister 14, the concrete container, and the lid 20 in a state of being in contact with the upper end of the canister 14 stored in the concrete container 12. The buffer member 17 is formed of, for example, steel or steel and wood, and prevents displacement of the canister 14 and absorbs an impact acting on the upper portion of the canister.
[0016]
In the concrete container 12, a cylindrical storage portion 22 is defined by the inner peripheral surface of the concrete container and the lid 20. The canister 14 is housed in the housing 22. The canister 14 is placed on a plurality of ribs 31 formed on the bottom surface of the housing 22.
[0017]
On the other hand, on the inner peripheral surface of the concrete container 12, a cylindrical liner 30 made of a metal such as carbon steel is provided. The liner 30 made of metal has a higher heat conductivity than concrete, promotes the transfer of heat generated from the spent fuel assembly 18, and emits radiation, mainly γ-rays, from the spent fuel assembly 18. It has the function of shielding.
[0018]
The canister 14 is coaxial with the concrete container 12 and has a predetermined gap between the outer peripheral surface and the inner peripheral surface of the concrete container 12, for example, a gap of about 10 cm. It is stored. In the concrete container 12, a cooling air passage 24 through which cooling air flows is formed by the gap between the outer peripheral surface of the canister 14 and the inner peripheral surface of the concrete container 12. The cooling air passage 24 is formed over the entire outer peripheral surface of the canister 14 and over the entire axial length of the outer peripheral surface.
[0019]
A plurality of, for example, four intake ports 26 are formed at the bottom of the concrete container 12, and, for example, four exhaust ports 28 are formed at the upper end of the concrete container 12, each of which communicates with the cooling air flow path 24. are doing. The four intake ports 26 are provided at substantially equal intervals along the circumferential direction of the concrete container 12 and open to the bottom outer peripheral surface of the concrete container 12. Further, the exhaust ports 28 are provided at substantially equal intervals along the circumferential direction of the concrete container 12 and open to the outer peripheral surface of the upper end portion of the concrete container 12.
[0020]
The intake port 26, the exhaust port 28, and the cooling air flow path 24 constitute a heat removal unit that removes heat from the concrete cask 10 by natural circulation cooling of air. That is, the outside air as cooling air introduced into the concrete container 12 from the air inlet 26 flows around the canister 14 through the cooling air flow path 24, and during that time, removes heat and cools the canister 14 and the concrete container 12. The cooling air heated and heated by the heat from the canister 14 is discharged from the exhaust port 28 to the outside of the concrete container 12.
[0021]
As shown in FIGS. 1 to 4, a plurality of, for example, three flanges 32 functioning as projections are integrally formed on the outer peripheral surface of the lower end portion of the canister 14. These flanges 32 protrude radially outward from the outer peripheral surface of the lower end portion of the canister 14 and are spaced apart in the circumferential direction of the canister.
[0022]
In the concrete container 12, a latch portion 34 functioning as an engagement portion is integrally formed on the inner peripheral surface of the lower end portion of the storage portion 22. The three latch portions 34 are provided corresponding to the flanges 32 of the canister 14. The latch portions 34 protrude from the inner peripheral surface of the liner 30 and extend in the circumferential direction, and are provided apart from each other in the circumferential direction.
[0023]
In a state where the canister 14 is stored in the storage portion 22 of the concrete container 12, the flanges 32 are engaged with the corresponding latch portions 34, respectively. That is, each flange 32 is located below the latch portion 34 and is engaged with the lower surface of the latch portion 34. When the canister 14 is housed, the canister 14 is inserted up to the bottom surface of the housing portion 22 at a position where the flange 32 is disengaged from the latch portion 34 and placed on the rib 31, and then the canister is turned around its central axis. . Thereby, each flange 32 engages with the corresponding latch portion 34.
Note that the number of the flanges 32 and the latch portions 34 is not limited to three, and can be increased or decreased as needed.
[0024]
According to the concrete cask 10 configured as described above, the latch portion 34 is provided at the lower end portion in the storage portion 22 of the concrete container 12, and the flange 32 provided on the outer peripheral surface of the lower end portion of the canister 14 is connected to the latch portion 34. By engaging, it is possible to restrict horizontal and vertical movements of the canister in the storage section 22. Therefore, even when an earthquake or a concrete cask falls or falls, the internal canister 14 can be prevented from moving and colliding with the inner wall of the concrete container 12 or the lid 20. This prevents the destruction and damage of the container body 40 and the spent fuel assembly 18 of the canister 14 and the damage of the welded portions of the primary and secondary lids, and prevents leakage of radioactive materials from spent fuel. And maintain soundness. Therefore, even in the event of an accident such as an earthquake, a fall, or a fall, it is possible to prevent leakage of radiation and obtain a concrete cask capable of safely and reliably storing highly radioactive substances.
[0025]
Further, according to the concrete cask having the above-described structure, the cushioning member 17 is provided between the upper end of the canister 14 and the lid 20, so that even if an earthquake, a fall of the concrete cask, a fall, or the like occurs, the storage portion 22 is provided. The movement of the canister 14 inside the canister can be more reliably prevented, and the soundness of the canister can be maintained more reliably.
[0026]
The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, the protrusion provided on the canister is not limited to the flange shape, but may be another shape such as a pin shape or a block shape. Similarly, the engaging portion provided on the concrete container side only needs to be formed so as to be able to engage with the protruding portion of the canister, and its shape can be variously selected as needed. Further, the wall thickness of the concrete wall constituting the concrete storage container, the plate thickness of the liner, and the material and shape of each component can be variously modified as necessary.
[0027]
【The invention's effect】
As described above in detail, according to the present invention, a concrete storage container capable of preventing radiation leakage even when an earthquake, a fall, or the like occurs, and capable of safely and stably storing radioactive materials for a long period of time. Can be provided.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a concrete cask according to an embodiment of the present invention, partially cut away.
FIG. 2 is a longitudinal sectional view of the concrete cask.
FIG. 3 is a sectional view taken along line AA of FIG. 2;
FIG. 4 is an exploded perspective view showing a lower end of a concrete container and a lower end of a canister of the concrete cask.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Concrete cask 12 ... Concrete container 14 ... Canister 18 ... Spent fuel assembly 17 ... Buffer member 20 ... Lid 22 ... Accommodation part 24 ... Cooling air flow path 26 ... Suction port 28 ... Exhaust port 32 ... Flange 34 ... Latch part 40 ... container body

Claims (3)

A substantially cylindrical concrete container having a lower end closed by a bottom wall and having a storage portion therein, and formed of concrete,
A lid closing the upper end opening of the concrete container,
A substantially cylindrical metal hermetic container that is stored in the storage portion of the concrete container and that contains a radioactive substance,
The concrete container has an engaging portion provided at a lower end portion in the housing portion, and the metal hermetic container engages with an engaging portion of the concrete container provided at the lower end portion, and the inside of the housing portion A storage container made of concrete, comprising a projection for restricting displacement of the metal hermetic container. The protrusion of the metal sealed container has a plurality of flanges each projecting radially outward from the lower end of the metal sealed container, and the plurality of flanges are provided to be spaced apart in the circumferential direction of the metal sealed container. ,
The concrete storage container according to claim 1, wherein the engagement portion of the concrete container has a plurality of latch portions each of which engages with the flange. The concrete storage container according to claim 1 or 2, further comprising a cushioning member provided between the concrete container and the lid in contact with an upper end of the metal closed container.

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