JP2002071896A - Canister, and concrete storage vessel equipped therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a canister and a concrete storage vessel capable of preventing radioactive leakage and maintaining the integrity even when the canister is dropped or toppled over. SOLUTION: The canister stored in a storage unit 22 of a concrete cask 10 comprises a substantially cylindrical metal sealing vessel 15 with a radioactive substance sealed therein, and a buffer leg 42 which is provided on a bottom of the sealing vessel to absorb the shock of the sealing vessel when it is dropped. A vessel side buffer unit 31 for absorbing the shock on the canister is provided on the bottom surface of the storage unit 22 of the concrete vessel 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal sealed container enclosing a radioactive substance, a so-called canister, and a concrete storage container provided with the same.

[0002]

2. Description of the Related Art Highly radioactive materials typified by spent fuel of a nuclear reactor are dismantled and reprocessed in order to collect useful materials such as plutonium which 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 of its lower operating cost as compared with the wet method, and is being developed. There are various types of casks used in the dry process, and concrete casks that shield spent fuel with concrete structures have attracted 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 has a cylindrical concrete container whose top and bottom are closed, and a cylindrical metal hermetic container in which spent fuel is sealed, a so-called canister, is housed and arranged in the concrete container. This shields radioactive materials from spent fuel.

In general, when storing spent fuel in a concrete cask, first, spent fuel is stored in a canister having an open upper end, and the upper end of the canister is sealed with a primary and secondary lid. Subsequently, the canister is conveyed to above the concrete cask, and then inserted into the cask storage section through the upper end opening of the concrete cask. Finally, the upper end opening of the cask is closed and closed with a lid, thereby completing the storing operation.

[0006]

The work for sealing, transporting, and storing the spent fuel as described above is performed with great care and caution. However, an accident such as an earthquake during transport of the canister may cause an accident. Must occur, and the canister must fall on the floor or fall down.

[0007] For example, assuming that the canister falls from a height of about 5 m onto the floor or into a storage section of a concrete cask, a large impact acts on the canister, and the peripheral wall of the canister buckles and breaks. Or the welds of the primary and secondary lids 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 if an accident occurs, a canister and a concrete cask that can prevent radiation leakage and store highly radioactive substances safely and reliably are required.

The present invention has been made in view of the above points, and an object of the present invention is to provide a canister and a concrete storage container that can prevent radiation leakage even when a fall or a fall occurs and can maintain soundness. Is to do.

[0009]

In order to achieve the above-mentioned object, a canister according to the present invention is provided with a substantially cylindrical metal sealed container in which a radioactive substance is sealed, provided at the bottom of the sealed container, and A shock absorber for absorbing the impact of the closed container at the time.

[0010] According to the above canister, the buffer portion is
It is characterized by having a cylindrical cushioning leg that can buckle and absorb shock when dropped. According to another canister, the shock absorber is characterized in that the shock absorber is provided with a shock-absorbing leg having a sharpened end that can sink into the floor when dropped.

According to the canister according to the present invention having the above-described structure, even if an earthquake or the like occurs during transportation and storage and the object falls on the floor or in a concrete storage container, the buffer portion is crushed. Alternatively, the shock can be reduced by the buffer portion being fitted, and the destruction or damage of the container body and the spent fuel assembly can be prevented. Therefore, even if the canister falls due to an accident or the like, it is possible to prevent the radioactive substance from leaking from the spent fuel and to maintain soundness.

Another canister according to the present invention is a substantially cylindrical metal hermetically sealed container in which a radioactive substance is sealed, and is attached to an upper outer periphery of the hermetically sealed container to absorb an impact when the hermetically sealed container falls. And a fall buffer.

According to the canister having the above structure, when the vehicle falls down,
The shock transmitted to the canister is absorbed by the fall buffer,
The destruction and damage of the container body and the spent fuel assembly can be prevented.

On the other hand, a concrete storage container according to the present invention has a lower end closed by a bottom wall and a storage portion for storing the canister therein, and is a substantially cylindrical concrete container formed of concrete. When,
The concrete container includes a lid that closes an upper end opening, and a container-side buffer unit that is provided on a bottom surface of the storage unit and absorbs an impact on the canister.

According to the concrete storage container having such a configuration, even if the canister falls into the storage portion of the concrete container due to an accident or the like, the fall of the container-side buffer portion is provided in addition to the buffer portion of the canister described above. Can absorb shock. As a result, it is possible to prevent radioactive substances from leaking from the spent fuel and to maintain soundness.

Another concrete storage container according to the present invention has a storage portion for storing the canister therein,
A substantially cylindrical concrete container formed of concrete, a lid closing the upper end opening of the concrete container, and a spirally wound coil provided between the bottom surface of the concrete container and the concrete container installation surface. And a damping portion for damping vibration and impact acting on the concrete container.

Further, another concrete storage container according to the present invention has a storage portion for storing the canister therein, and has a substantially cylindrical concrete container formed of concrete and an upper end opening of the concrete container. It has a closed lid, a laminated leaf spring provided between the bottom surface of the concrete container and the concrete container installation surface, and a damping portion for damping vibration and impact acting on the concrete container. And

According to the concrete storage container configured as described above, the damper provided at the bottom of the concrete container absorbs the vibration and the shock acting on the concrete container, so that damage to the concrete container can be prevented.
The generation of cracks can be prevented, and the radioactive substance can be stored safely and stably for a long period of time.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete cask according to a first embodiment of the present invention will be described below in detail with reference to the drawings.

As shown in FIGS. 1 to 3, a concrete cask 10 as a concrete storage container includes a concrete container 12 formed of concrete and functioning as a shielding structure. In the concrete container, a canister 14 is provided. It is stored. Canister 14
Has a cylindrical closed container 15 formed of metal and closed at both ends. A plurality of spent fuel assemblies 18 are sealed in the closed container while being supported by a basket 16. ing. These spent fuel assemblies 18 are, for example, spent fuel of a nuclear reactor, and contain radioactive materials that generate heat due to decay heat and generate radiation. The hermetically sealed container 15 has a hermetically sealed structure so that the enclosed radioactive substance does not leak outside.

As shown in FIGS. 1 and 2, the concrete container 12 of the concrete cask 10 has a cylindrical shape with a closed bottom, and has, for example, a height of about 6 m and a diameter of about 4 mm.
m, and the concrete wall thickness is about 0.9 m. Concrete container 12
Is closed by a concrete lid 20 whose outer surface is covered with a carbon steel plate. This lid 20
Are bolted to the upper end of the concrete container 12 by a plurality of bolts 21. The concrete container 1
Reinforcement (not shown) is provided in the concrete wall 2.

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 of the storage section 22. As shown in FIG. 4, the plurality of ribs 31 extend radially and each has a width of, for example, 10 to 20 m.
m and a height of about 50 mm. These ribs 31 function as a container-side buffer. That is,
When the canister 14 is stored in the storage portion 22 and the canister falls due to an accident and collides with the bottom wall of the concrete container, the rib 31 is deformed to absorb the collision energy, thereby damaging the canister 14. To reduce. In addition, each rib 31 may be formed hollow so as to further enhance the buffer effect.

As shown in FIGS. 1 to 3, the canister 14 is coaxial with the concrete container 12, and the outer peripheral surface thereof has a predetermined gap between the inner peripheral surface of the concrete container 12, for example. It is stored in the storage part 22 with a gap of about 10 cm.

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 container body 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.

A plurality of, for example, four intake ports 26 are formed at the bottom of the concrete container 12, and four exhaust ports 28 are formed at the upper end of the concrete container 12,
Each is communicated with the cooling air passage 24. The four air inlets 26 are provided at 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 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.

The intake port 26, the exhaust port 28, and the cooling air flow path 24 constitute a heat removing section for removing heat from the concrete cask 10 by natural circulation cooling of air.
That is, the outside air as the cooling air introduced into the concrete container 12 from the intake port 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.
Then, the cooling air heated and heated by the heat from the canister 14 is supplied from the exhaust port 28 to the concrete container 12.
Is discharged to the outside.

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.

Next, the configuration of the canister 14 will be described in detail. As shown in FIGS. 2 and 4, the closed container 15 of the canister 14 has a cylindrical container main body 40 with a closed lower end, and a primary lid (not shown) welded to the upper end opening of the container main body and closing the upper end opening. ) And a secondary lid 41;
It has. The container body 40 is, for example, SUS30
4. It is made of a corrosion-resistant metal such as SUS316, and its wall thickness is set to about 16 mm.

A cylindrical buffer leg 42 functioning as a buffer is attached to the bottom surface of the container body 40. The cushioning legs 62 are formed of, for example, stainless steel, have substantially the same outer diameter as the container main body 40, and are provided coaxially with the container main body. The wall thickness of the buffer leg 62 is thinner than the container body 40, for example, 5 mm, and 100 mm in height.
The canister 14 is accommodated in the accommodating portion 22 in a state where the buffer leg 62 is placed on the rib 31 on the concrete container 12 side.

According to the canister 14 configured as described above, since the buffer leg 42 provided at the bottom of the container body 40 is provided, even if the container body 40 receives a large impact due to a fall or the like, the container body 40 and the primary Further, damage to the secondary lid 41 can be prevented, and the spent fuel assembly 18 can be safely sealed and held.

That is, for example, when an earthquake or the like occurs while the canister 14 is being conveyed or stored and the canister 14 falls on the floor or in the concrete container 12, the buffer leg 42 of the canister is moved to the inner surface of the floor or the bottom wall of the concrete container. Collide with At this time, the shock absorbing leg 42 absorbs the shock by being buckled and crushed by the shock. Therefore, the container body 40 of the canister 14, the primary and secondary lids 4
1 and a spent fuel assembly 1 stored in a container body
8 can be reduced, and the destruction and damage of the container body and the spent fuel assembly, and the damage of the welded portions of the primary and secondary lids can be prevented. Therefore, even if the canister 14 falls due to an accident or the like, it is possible to prevent the radioactive substance from leaking from the spent fuel and maintain its soundness.

The concrete cask 1 having the above structure
According to No. 0, the rib 3 as a buffer is provided on the bottom of the storage portion 22.
1 is provided, the conveyance of the canister 14,
If the canister falls into the storage section 22 during the storage operation, the rib 31 deforms and absorbs the collision energy. Therefore, the canister 14 can be more reliably prevented from being damaged or destroyed in combination with the above-described buffering action of the buffer leg 42 of the canister 14.

Thus, according to the first embodiment,
Even if an accident such as a fall occurs, the leakage of radiation can be prevented, and a canister and a concrete cask that can safely and reliably store highly radioactive substances can be obtained.

Next, a canister and a concrete cask according to another embodiment of the present invention will be described. In the other embodiments described below, the same parts as those in the first embodiment are denoted by the same reference numerals, detailed description thereof will be omitted, and different parts will be described in detail. .

As shown in FIG. 6, according to the canister 14 according to the second embodiment of the present invention, the cylindrical buffer leg 42 attached to the bottom surface of the container main body 40 has the wall thickness of the container main body. The lower end 42a is formed to have a substantially equal wall thickness, and the lower end 42a is sharply formed like a knife edge.

According to the canister 14 having such a structure, since the lower end 42a of the buffer leg 42 is sharp, when the canister falls on the floor or into the concrete container 12, the lower end 42a of the buffer leg 42 is Dip into the bottom of the storage section of the concrete container. The shock absorbing leg 42 absorbs the impact of the fall when the lower end 42a is recessed. Therefore, similarly to the first embodiment, even when the canister 14 falls due to an accident or the like, the canister 14 can prevent the radioactive substance from leaking from the spent fuel and maintain its soundness.

Assuming that the canister 14 falls on the floor as described above, it is considered that the canister falls down sideways after dropping. Further, at the time of this fall, further impact may act on the canister.

Therefore, according to the third embodiment shown in FIG. 7, the canister 14 is not only a buffer leg 42 provided on the bottom surface of the container body 40, but also an annular overturn provided on the upper outer periphery of the container body. A buffer 44 is provided. The outer peripheral edge 44a of the tipping buffer 44 is sharply formed like a knife edge.

When the canister 14 having such a structure falls, the fall buffer 44 collides with the floor surface, and the outer peripheral edge of the canister 14 sinks into the floor. Then, the fall buffer 44 absorbs the impact of the fall when the outer peripheral edge 44a is recessed.
Therefore, even if the canister 14 falls or falls due to an accident or the like, the container body 40, the spent fuel assembly 18 is not broken or damaged, and the primary and secondary lid welds are not damaged. In addition, it is possible to prevent radioactive substances from leaking from spent fuel and maintain soundness.

As shown in FIGS. 8 to 10, a concrete cask 10 according to a fourth embodiment of the present invention is shown.
Is provided with a plurality of, for example, six attenuators 50 for attenuating impact and vibration acting on the concrete container 12. Each attenuator 50 includes a pair of upper and lower fixed bars 52 provided to face each other in parallel with each other, and a wire rope 54 attached to the fixed bar in a spirally wound state. These attenuators 50 are provided between the bottom surface of the concrete container 12 and the concrete container installation surface 55, and one of the fixed bars 52 is
And the other fixed bar is in contact with the installation surface 55.

The six attenuators 50 are arranged such that the winding central axis of the wire rope 54 extends substantially radially with respect to the central axis of the concrete container 12, and the circumference of the concrete container is They are equally spaced from each other along the direction.

By providing such an attenuator 50, it is possible to attenuate and absorb vibrations and shocks acting on the concrete container 12 due to an earthquake or the like. In particular, according to the attenuator 50 using the wire rope 54,
Vibration and shock can be attenuated and absorbed in three-dimensional directions. Therefore, the concrete container 12 and the canister 14 housed therein can be prevented from being damaged or cracked due to vibration, external impact, and the like, and the radiation shielding performance of the concrete cask 10 can be stably maintained.

It should be noted that the attenuator 50 is not limited to the one using the above-described wire rope, but may be a laminated leaf spring 5 formed by laminating a plurality of leaf springs as in the fifth embodiment shown in FIG.
6 may be used. And these attenuators 50 are provided in the concrete container 1 similarly to the above embodiment.
2 is provided between the bottom surface of the concrete container 2 and the installation surface 55, is arranged substantially radially with respect to the central axis of the concrete container 12, and is arranged at regular intervals along the circumferential direction of the concrete container. I have.

In the fifth embodiment configured as described above, vibrations and shocks acting on the concrete container 12 and the canister 14 housed therein are also reduced by the attenuator 5.
0 can attenuate and absorb, prevent damage to concrete containers and canisters, cracks, etc., and obtain a concrete cask 10 that can safely and stably store radioactive materials for a long period of time. .

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 buffer leg of the canister is not limited to a cylindrical shape,
Other shapes are also possible. The number of the attenuators 50 is six.
The number is not limited to one and can be increased or decreased as needed. Further, the wall thickness of the concrete wall constituting the container body 12 of the concrete storage container, the plate thickness of the liner, and the material and shape of each component can be variously modified as necessary.

[0046]

As described above in detail, according to the present invention, the provision of the buffer portion in the container body of the canister prevents the radiation from leaking even if the container falls or falls, thereby ensuring soundness. A possible canister can be provided. Further, by providing an attenuator at the bottom of the concrete container to absorb vibration and shock, it is possible to provide a concrete storage container capable of storing radioactive substances safely and stably for a long period of time.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a concrete cask according to a first embodiment of the present invention.

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 a sectional view taken along the line BB in FIG. 2;

FIG. 5 is a perspective view showing a partially broken canister stored in the concrete cask.

FIG. 6 is a side view showing a lower end of a canister according to a second embodiment of the present invention, partially cut away;

FIG. 7 is a perspective view showing a canister according to a third embodiment of the present invention, and a side view showing an upper end portion of the canister with a part cut away.

FIG. 8 is a longitudinal sectional view of a concrete cask according to a fourth embodiment of the present invention.

FIG. 9 is a perspective view showing a concrete cask attenuator according to the fifth embodiment.

FIG. 10 is a plan view of a concrete cask according to the fifth embodiment.

FIG. 11 is a longitudinal sectional view of a concrete cask according to a sixth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Concrete cax 12 ... Concrete container 14 ... Canister 15 ... Airtight container 18 ... Spent fuel assembly 20 ... Lid 22 ... Storage part 24 ... Cooling air flow path 26 ... Intake port 28 ... Exhaust port 40 ... Container main body 42 ... Buffer leg 50 ... Attenuator 54 ... Wire rope

Claims (13)

[Claims] 1. A substantially cylindrical metal sealed container in which a radioactive substance is sealed, and a buffer provided at the bottom of the sealed container for absorbing an impact of the sealed container when dropped. A canister characterized by the following: 2. The canister according to claim 1, wherein said shock-absorbing portion has a cylindrical shock-absorbing leg capable of absorbing a shock by buckling when dropped. 3. The canister according to claim 1, wherein the shock-absorbing portion includes a shock-absorbing leg having a sharp end which can be sunk into the floor when dropped. 4. The method according to claim 1, wherein the container is attached to an outer periphery of an upper portion of the closed container,
The canister according to any one of claims 1 to 3, further comprising a fall buffer for absorbing a shock when the closed container falls down. 5. The canister according to claim 4, wherein the tipping buffer part is formed in an annular shape and has a sharp edge part which can be sunk into the floor when falling. . 6. A substantially cylindrical metal closed container in which a radioactive substance is sealed, and a fall buffer attached to an outer periphery of an upper portion of the closed container to absorb a shock when the closed container falls down. A canister. 7. The canister according to claim 6, wherein the tipping buffer is formed in an annular shape and has a sharpened peripheral portion that can be sunk into the floor when the tipping over occurs. . 8. A concrete storage container accommodating the canister according to any one of claims 1 to 7, wherein a lower end is closed by a bottom wall, and a storage portion accommodating the canister is provided inside. A substantially cylindrical concrete container formed of concrete; a lid closing an upper end opening of the concrete container; a container-side buffer unit provided on a bottom surface of the storage unit for absorbing an impact on the canister; A storage container made of concrete, comprising: 9. The concrete storage container according to claim 8, wherein said container-side buffer has a plurality of radially extending ribs provided on said bottom surface. 10. A concrete storage container storing the canister according to any one of claims 1 to 7, wherein the storage container stores the canister therein and has a substantially cylindrical shape formed of concrete. A concrete container, a lid closing an upper end opening of the concrete container, and a wire rope spirally wound and provided between the bottom surface and the installation surface of the concrete container. A storage container made of concrete, comprising: a damping portion for damping the acting vibration and shock. 11. The attenuator comprises a plurality of attenuators each having the wire rope, wherein each attenuator has a winding center axis of the wire rope substantially in a radial direction with respect to a center axis of the concrete container. The concrete storage container according to claim 10, wherein the storage container is arranged so as to extend in a vertical direction. 12. A concrete storage container accommodating the canister according to any one of claims 1 to 7, wherein the container has an accommodation portion accommodating the canister therein, and has a substantially cylindrical shape made of concrete. A concrete container, a lid closing an upper opening of the concrete container, and a leaf spring provided between a bottom surface and an installation surface of the concrete container, and a damping device for damping vibration and impact acting on the concrete container. A storage container made of concrete, comprising: 13. The attenuating section includes a plurality of attenuators each having the above-mentioned leaf spring, and these attenuators are arranged substantially radially with respect to a central axis of the concrete container. The concrete storage container according to claim 12, wherein