JP2002022881A - Concrete storage vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete storage vessel capable of storing radioactive material safely, stably and for a long time. SOLUTION: In the containing part 22 of a vessel body 12 formed with concrete, a canister 14 sealed with radioactive material is contained and the upper end opening of the vessel body is sealed with a concrete lid 20. A heat removal part has an air intake piece 26 provided at the bottom of the vessel body, a first air exhaust path 28 provided at the upper end periphery of the vessel body, a second exhaust path 44 formed in the middle of the lid, an upper air path 38 provided in between the inner surface of the vessel body and the outer surface of the canister and connected with the air intake piece, the first air exhaust path and the upper air path, and an almost annular cooling air path 24. The air introduced from the air intake piece into the vessel body flows through the cooling air path and the upper air path, removes the heat generated from the canister and is exhausted out of the first and the second exhaust paths.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete storage container for storing and managing a radioactive substance that generates heat, a so-called concrete cask.

[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 its operating cost is lower than that of the wet method, and is being developed. There are various types of casks used for the dry process, and concrete casks that shield spent fuel with a concrete structure have attracted special attention because of their low cost. Concrete also has advantages such as obtaining necessary strength as a structure.

Such a concrete cask is provided with a cylindrical concrete container whose top and bottom are closed, and in this concrete container, a cylindrical metal sealed container filled with spent fuel, a so-called canister, is stored. Have been.

[0005] Generally, the canister is heated by the decay heat generated from the spent fuel to a high temperature of about 200 ° C. Therefore, the concrete cask has a heat removal structure for removing the decay heat generated from the spent fuel. Is provided. That is, an annular gap functioning as a cooling air flow path is formed between the inner peripheral surface of the concrete container and the outer peripheral surface of the canister, and an intake port is provided at a lower peripheral portion of the concrete container, and an upper end of the container is provided. Exhaust ports are provided in the peripheral portion, respectively. Then, the outside air as cooling air introduced into the concrete container from the intake port flows through the cooling air flow path and is naturally convected, and is discharged from the exhaust port, thereby removing heat from the canister and the concrete container to cool.

In the concrete cask constructed as described above, the spent fuel can be cooled and cooled by the heat removal structure described above.
The concrete layer ensures radiation shielding, and the canister ensures sealing of spent fuel. And concrete cask is safe for high radioactive material for a long time,
Moreover, it is necessary to stably store, and high radiation shielding performance is required for a long period of time.

[0007]

However, concrete, which is a shield for radioactive materials, is susceptible to heat and its strength is significantly reduced at high temperatures. In a configuration in which the canister and the concrete container are cooled by natural circulation of air, the maximum temperature of the concrete container is about 90.
℃, so during long-term use, while being affected by thermal stress due to the temperature difference between the inside and outside of concrete,
When the moisture in the concrete decreases, cracks may occur in the concrete container.

In particular, when the outer peripheral surface of the canister and the inner peripheral surface of the concrete container are cooled by the outside air flowing through the annular cooling air flow path as described above, the central portion of the canister is hardly cooled and maintains a high temperature state. Therefore, in the concrete cask, the central portion of the upper lid located opposite to the upper end of the canister is heated by radiant heat from the central portion of the upper end of the canister, and is more easily affected by the heat.

When a crack or the like occurs in the concrete container as described above, radiation shielding and sealing of radioactive materials cannot be ensured, and the safety and soundness of the concrete cask can be maintained. It will be difficult.

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 capable of safely and stably storing radioactive materials for a long period of time.

[0011]

In order to achieve the above object, a concrete storage container according to the present invention has a storage portion for storing a closed container in which a radioactive substance is sealed, and is formed of concrete. A substantially cylindrical container main body, a concrete lid closing an upper end opening of the container main body, an intake port provided at a bottom of the container main body, and a first exhaust provided at a peripheral edge of an upper end of the container main body. A second exhaust path formed in a central portion of the lid, an upper air flow path provided between an inner surface of the lid and an upper end surface of the closed container, and communicating with the second exhaust path; The intake port defined between the inner peripheral surface of the storage portion and the outer peripheral surface of the closed container,
A first exhaust passage, and a substantially annular cooling air passage communicating with the upper air passage, wherein the air introduced into the container body from the intake port flows through the cooling air passage and the upper air passage, A heat removal unit that removes heat generated from the radioactive substance and discharges the heat from the first and second exhaust paths.

In the concrete storage container according to the present invention, the second exhaust passage is provided on a central exhaust passage coaxially extending with the container main body, and on the upper surface of the lid body branched from the central exhaust passage. And a plurality of central exhaust ports that are open.

Further, a concrete storage container according to the present invention has a storage portion for storing a closed container in which a radioactive substance is sealed, and has a substantially cylindrical container body formed of concrete; A lid made of a concrete having a closed upper end opening, an intake port provided at the bottom of the container body, a first exhaust path provided at an upper peripheral edge of the container body, an inner peripheral surface of the storage portion, and A substantially annular cooling air flow path defined between the outer peripheral surface of the closed vessel and communicating with the intake port and the first exhaust path, extending substantially coaxially into the closed vessel, and opened at the upper and lower ends of the closed vessel; A central flow path, and a second exhaust path formed at the center of the lid and communicating with the central flow path. The air introduced into the container body from the intake port is supplied to the cooling air flow path and the central flow path. Radiated above the road Removing the heat generated by the quality, is characterized by comprising a heat removal portion for discharging from said first and second exhaust passage.

According to the concrete storage container configured as described above, the container body, the lid, and the canister are efficiently cooled by the cooling air introduced into the container body from the intake port, and cracks are generated by heat. And the radioactive substance can be stored safely and stably over a long period of time.

[0015]

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 FIG. 1, a concrete cask 10 as a storage container made of concrete includes a container body 12 formed of concrete and functioning as a shielding structure.
The canister 14 is housed in the container body. The canister 14 has a cylindrical metal sealed container 15 having both ends closed, and inside the metal sealed container,
A plurality of spent fuel assemblies 18 are sealed while being supported by the basket 16. These spent fuel assemblies 18 are, for example, spent fuel of a nuclear reactor, and contain radioactive substances that generate heat due to decay heat and generate radiation. The metal sealed container 15 has a welded sealed structure so that the enclosed radioactive substance does not leak outside.

The container body 12 of the concrete cask 10
As shown in FIGS. 1 to 3, has a closed bottom cylindrical shape and is formed to have a height of about 6 m and a diameter of about 4 m, for example, and a concrete wall thickness of about 0.9 m It is formed to the extent. The upper end opening of the container body 12 is a concrete lid 20 whose outer surface is covered with a carbon steel plate.
Is closed by The lid 20 is bolted to the upper end of the container body 12 by a plurality of bolts 21.

A leg 42 is provided below the container body 12, and an engagement recess 43 is formed in the leg so that a claw of an air lift (not shown) for transporting the concrete cask 10 can be inserted. ing.

The outer surface of the container body 12 is covered with an outer shell 40 made of metal, for example, carbon steel sheet. The outer shell 40 includes a substantially cylindrical inner liner 30 covering the inner peripheral surface of the container body 12 and a substantially cylindrical outer liner 3 covering the outer peripheral surface.
2. It is composed of an upper end liner 34 covering the upper end surface and a lower end liner 35 covering the bottom surface. The inner liner 30 is formed to have a thickness of, for example, about 40 mm, and the outer liner 32 is formed to have a thickness of about 10 mm.

In order to enhance the coupling between the container body 12 and the outer liner 32, a plurality of outer studs 36 are provided on the inner surface of the outer liner 32 over substantially the entire area of the outer liner in the axial direction. It protrudes into. A plurality of inner studs 37 are provided on the outer surface of the lower end of the inner liner 30, and protrude into the container body 12. Thus, only the lower end of the inner liner 30 is fixed to the container main body 12 by the inner stud 37, and the other portions are displaceable with respect to the inner peripheral surface of the container main body.

A cylindrical storage portion 22 is defined in the container body 12 by the inner liner 30 and the lid 20. The canister 14 is housed in the housing 22. The canister 14 is placed on a plurality of radially extending ribs 29 formed on the bottom surface of the storage section 22 and arranged coaxially with the container body 12. The outer peripheral surface of the canister 14 is the inner liner 3.
It is stored in the storage section 22 with a predetermined gap, for example, about 10 cm from 0.

The clearance between the outer peripheral surface of the canister 14 and the inner liner 30 forms a substantially annular cooling air passage 24 through which cooling air flows. 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 suction ports 26 are formed at the bottom of the container body 12 and communicate with the cooling air flow path 24, respectively. The four intake ports 26 are provided at equal intervals along the circumferential direction of the container body 12 and open to the bottom surface and the bottom outer peripheral surface of the container body 12. Also,
Four first exhaust passages 28 are formed at the upper end of the container main body 12 and communicate with the cooling air flow passages 24, respectively. The first exhaust ports 28 are provided at equal intervals along the circumferential direction of the container main body 12 and open to the outer peripheral surface of the upper end portion of the container main body 12. In addition, these first exhaust passages 28
It is defined by the upper end surface of the container body 12 and the lid 20.

Further, the upper end surface of the metal sealed container 14 and the lid 2
An upper air flow path 38 is formed between the cooling air flow path 24 and the lower surface of the cooling air flow path 24. Further, a second exhaust path 44 is formed at the center of the lid 20 and communicates with the upper air flow path 38. The second exhaust path 44 includes a central exhaust path 44 a extending coaxially with the container body 12, and a plurality of central exhaust ports 4 branched from the central exhaust path and opened on the upper surface of the central portion of the lid 20.
4b.

The intake port 26, the first exhaust path 28, the second exhaust path 44, the upper air flow path 38, and the cooling air flow path 24 constitute a heat removal section of the concrete cask 10. That is, the outside air as the cooling air introduced into the container body 12 from the air inlet 26 flows around the canister 14 through the cooling air flow path 24 and the upper air flow path 38, during which the canister 14 and the container body 12 , And the lid 20 are removed and cooled. The cooling air heated and heated by the heat from the canister 14 is supplied from the first and second exhaust passages 28 and 44 to the concrete cask 10.
Is discharged to the outside.

According to the concrete cask 10 according to the first embodiment configured as described above, the intake port 2
6. The outside air as cooling air introduced into the container body 12 from the cooling air passage 6 flows through the cooling air passage 24 and the upper air passage 38 to cause natural convection, and is discharged from the first and second exhaust passages 28 and 44. Thereby, the canister 14 and the concrete container can be efficiently cooled. In particular, by providing the upper air flow path 38 between the upper end of the canister 14, which is likely to be high in temperature, and the lid 20, and providing the second exhaust path 44 at the center of the lid, the heat removal efficiency is improved. The upper part and the central part of the lid can be sufficiently cooled to prevent excessive heating.

Therefore, the influence of heat on the container body 12, the lid 20, and the canister 14 can be reduced, and the occurrence of cracks can be suppressed. As a result, radiation shielding and radioactive substance sealing can be ensured, and the safety and soundness of the concrete cask can be maintained over a long period of time.

Next, a concrete cask according to a second embodiment of the present invention will be described. The same parts as those in the above-described 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 FIGS. 4 and 5, according to the second embodiment of the present invention, a concrete cask 10
The heat removal section includes a central flow path 50 extending through the canister 14, a second intake port 5 provided at the center of the bottom wall of the container body.
1 and a second exhaust passage 5 provided at the center of the lid 20
2 is provided.

More specifically, a substantially annular cooling air passage 24 through which cooling air flows is formed in the container body 12 by a gap between the outer peripheral surface of the canister 14 and the inner liner 30. This cooling air passage 24 is provided in the canister 1.
4 is formed over the entire outer peripheral surface and over the entire axial length of the outer peripheral surface. For example, four first intake ports 26 are formed in the outer peripheral portion of the bottom wall of the container body 12, and each of the first intake ports 26 communicates with the cooling air flow path 24. Four inlets 26
Are provided at equal intervals along the circumferential direction of the container body 12 and open to the bottom surface and the bottom outer peripheral surface of the container body 12. In the center of the bottom wall of the container body 12, a second air inlet 51 extending coaxially with the container body is formed.

At the upper end of the container body 12, four first exhaust passages 28 are formed, each of which communicates with the cooling air passage 24. The first exhaust ports 28 are provided at regular intervals from each other along the circumferential direction of the container main body 12.
The upper end has an opening at the outer peripheral surface. Further, a second exhaust path 44 is formed at the center of the lid 20.

The canister 14 has a central channel 50 extending coaxially therethrough. The lower end of the central flow path 50 opens to the bottom wall of the metal sealed container 15 and communicates with the second intake port 51, and the upper end of the central flow path 50 opens to the top wall of the metal sealed container and the second exhaust path 52. Is in communication with

According to the concrete cask 10 provided with the heat removing section configured as described above, the outside air introduced into the container main body 12 from the first air inlet 26 passes through the cooling air flow path 24 and flows into the canister 14. It flows around, during which the canister 14 and the container body 12 are removed and cooled. And
The cooling air heated and heated by the heat from the canister 14 flows from the first exhaust passage 28 to the concrete cask 1
It is discharged out of 0.

The outside air as cooling air is also introduced into the container body 12 from the second air inlet 51, and this outside air is
It flows through the canister 14 through the central flow path 50, during which the central part of the canister is removed and cooled. Then, the outside air heated and heated by the heat from the canister 14 passes through the second exhaust passage 52 and passes through the concrete cask 1.
It is discharged out of 0.

In the concrete cask 10 according to the second embodiment configured as described above, the outside air as the cooling air introduced into the container body 12 from the first and second air inlets 26 and 51 is also provided. The canister 14 and the concrete container can be efficiently cooled by flowing through the cooling air flow path 24 and the central flow path 50 to cause natural convection, and discharging from the first and second exhaust flow paths 28 and 52. In particular, the central portion, the upper end, and the central portion of the lid 20, which are likely to be heated to a high temperature, are sufficiently cooled, so that excessive heating can be prevented.

Accordingly, the influence of heat on the container body 12, the lid 20, and the canister 14 can be reduced, and the occurrence of cracks can be suppressed. This allows for radiation shielding,
The sealing of the radioactive material is ensured, and the safety and soundness of the concrete cask can be maintained for a long period of time.

As in the third embodiment shown in FIG. 6, a canister 14 is provided as a heat removing section in addition to the heat removing section of the concrete cask according to the first embodiment described above.
May be a concrete cask provided with a central channel 50 extending therethrough. Even in such a configuration, the first
The same operation and effect as in the second embodiment can be obtained.

In addition, 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 wall thickness of the concrete wall constituting the container body 12 and the material and shape of each component can be variously modified as necessary. Further, the number and shape of the intake port and the first and second exhaust ports can be changed as needed.

[0039]

As described in detail above, according to the present invention, the influence of heat on the container main body, the lid and the canister is reduced to suppress the generation of cracks, so that radioactive substances can be reduced for a long period of time. A concrete storage container that can be stored safely and stably can be provided.

[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 longitudinal sectional view of a concrete cask according to a second embodiment of the present invention.

FIG. 5 is a sectional view taken along line BB in FIG. 4;

FIG. 6 is a longitudinal sectional view of a concrete cask according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Concrete cask 12 ... Container main body 14 ... Canister 18 ... Spent fuel assembly 20 ... Lid 22 ... Storage part 24 ... Cooling air flow path 26 ... Intake port 28 ... 1st exhaust port 30 ... Inner liner 32 ... Outside Liners 44, 52: second exhaust port 44a: central exhaust path 44b: central exhaust port 50: central flow path 51: second intake port

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayuki Irie 2-1-1, Shinhama, Araimachi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Ryoji Taura 5007 Itozakicho, Mihara City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. (72) Inventor Kenichi Matsunaga 1-1-1, Wadazakicho, Hyogo-ku, Kobe City, Hyogo Prefecture Inside Kobe Shipyard, Mitsubishi Heavy Industries, Ltd.

Claims (5)

[Claims] 1. A substantially cylindrical container main body made of concrete and having a storage portion for storing a sealed container in which a radioactive substance is enclosed, and a concrete lid closing an upper end opening of the container main body. A body, an intake port provided at the bottom of the container body, a first exhaust path provided at a peripheral edge of an upper end of the container body, a second exhaust path formed at the center of the lid, An upper air passage provided between an inner surface and an upper end surface of the closed container and communicating with the second exhaust passage; and the intake air defined between an inner circumferential surface of the storage portion and an outer circumferential surface of the closed container. A substantially annular cooling air flow passage communicating with the opening, the first exhaust passage, and the upper air passage, and flowing air introduced into the container body from the suction opening into the cooling air flow passage and the upper air passage. To remove the heat generated from the radioactive material, And the second
A storage container made of concrete, comprising: a heat removal unit that discharges from an exhaust path. 2. The second exhaust path includes: a central exhaust path extending coaxially with the container body; and a plurality of central exhaust ports branched from the central exhaust path and opened on an upper surface of the lid. The storage container made of concrete according to claim 1 which has. 3. The heat removal section includes a central flow path extending substantially coaxially in the closed container and opening at upper and lower ends of the closed container and communicating with the intake port and the second exhaust path. The concrete storage container according to claim 1 or 2, wherein: 4. A substantially cylindrical container body made of concrete and having a housing portion for housing a sealed container in which a radioactive substance is sealed, and a concrete lid closing an upper end opening of the container body. A body, an intake port provided at a bottom of the container body, a first exhaust path provided at an upper peripheral edge of the container body, and a space defined between an inner peripheral surface of the storage portion and an outer peripheral surface of the closed container. A substantially annular cooling air flow passage communicating with the intake port and the first exhaust passage, a central flow passage extending substantially coaxially in the closed container and opening at upper and lower ends of the closed container, and a center of the lid body. A second exhaust passage formed in the portion and communicating with the central flow passage, wherein air introduced into the container body from the intake port flows through the cooling air flow passage and the central flow passage to be generated from the radioactive material Removing the heat, the first and second Concrete storage container characterized by comprising a heat removing portion for discharging from the exhaust passage, a. 5. The container according to claim 1, further comprising a plurality of first air inlets which are open at the outer periphery of a lower end of the container body and communicate with the cooling air passage, and which are open at the center of a bottom wall of the container body. The concrete storage container according to claim 4, further comprising a second intake port communicating with the central flow path.