JP2000065994A - Concrete cask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete cask capable of properly fulfilling the conditions of shielding capability, heat resistance and climate resistance which are different by the part of the cask. SOLUTION: A concrete cask 1 is provided with a sealed vessel 3 containing a radioactive object R, a concrete cask body 2 having a containing part 1a containing this closed vessel 3 and a lid 4 closing the upper opening 1b of this cask body 2. The cask body 2 is separated into a plurality of block pieces 201 to 215 which are used in a plurality as one with high heat resistance, high shield capability and one with high intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete cask used for intermediate storage of radioactive objects such as spent fuel generated from a nuclear power plant.

[0002]

2. Description of the Related Art A storage container (hereinafter referred to as a cask) for storing spent fuel generated from a nuclear power plant or the like has conventionally been formed of metal or reinforced concrete. However, a cask formed of metal or reinforced concrete is manufactured. Due to disadvantages such as high cost and time required for production, the use of concrete integrally formed in recent years has been increasing.

However, since concrete has a lower thermal conductivity than metal, a concrete cask has an air outlet at the upper part of the cask to release heat generated from the stored spent fuel to the outside air. Air intake ports are provided at the lower part of the cask, and the heat is released from the inside of the cask to the outside by the convection of air, thereby improving the durability of the concrete.

[0004]

Incidentally, the cask mainly has a shielding function. However, as described above, heat resistance is required around the air discharge port for removing heat, that is, the upper part of the cask. On the other hand, the shielding ability is not so required. In addition, the central portion of the cask is required to have high shielding ability, but is not required to have high heat resistance. However, in the inner part of the cask center,
Both shielding ability and heat resistance are highly required.

Further, heat resistance is not important around the air inlet of the cask, that is, the lower part of the cask, and the shielding property is not so required as in the central part. Strength is needed to support it. Further, the outer surface of the cask is required to have weather resistance separately from the above parts.

[0006] However, the conventional concrete cask is integrally manufactured from a homogeneous material.
There is a problem that it is difficult to manufacture so as to simultaneously satisfy the conditions in each of the above-described portions, and even if such manufacturing is possible, the cost increases.

[0007] The wall thickness of the cask is determined by the shielding factor required for the spent fuel in the initial stage of storage. However, the radiation source intensity of the spent fuel decreases as the storage period elapses. The thickness of the wall may be reduced. Therefore, for spent fuel stored for a long time,
Conventional integrated concrete casks are unnecessarily large and cause a problem of lowering the storage density of the warehouse.

Furthermore, the conventional concrete cask has a weight of 100 ton or more, and even if only the cask is transported, it is heavy and bulky, so that the transportation cost becomes extremely high. After the completion of the above, all of these must be disposed of as radioactive waste, so that there is a problem that the cost per one cask increases.

The present invention has been made to solve the above-mentioned problems, and is capable of appropriately satisfying conditions of shielding ability, heat resistance, and weather resistance which differ depending on the cask portion, and can reduce the cost. The purpose is to provide a cask.

[0010]

In order to achieve the above-mentioned object, the present invention comprises a concrete cask main body having a closed container and a storage section formed of a plurality of divided block pieces. By doing so, it is possible to appropriately meet the requirements of the shielding ability, heat resistance, and weather resistance that are different depending on the cask portion, and the cask before storing the spent fuel is transported by being divided into blocks. be able to.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A concrete cask according to the present invention comprises a closed container for storing a radioactive object, a concrete cask body having a storage portion for storing the closed container, and a lid for closing an upper opening of the cask body. In the cask provided with, the cask main body is divided into a plurality of block pieces, and these block pieces use one or more of those having high heat resistance, high shielding ability, and high strength It is. With this configuration, a concrete cask excellent in shielding ability, heat resistance, and weather resistance can be produced by using concrete pieces under appropriate conditions according to the portion of the cask body.

Further, the concrete cask of the present invention comprises:
In the above configuration, the cask main body has a three-part configuration of an upper portion, a central portion, and a bottom portion in the height direction. According to this configuration, when transporting the spent fuel before storage of the spent fuel, the concrete cask can be transported in a state of being divided into an upper portion, a central portion, and a bottom portion, whereby the transport efficiency is improved. .

[0013] Further, since it is divided into an upper part, a center part, and a bottom part, for example, a block piece to be combined with the upper part has a high heat resistance, a block piece to be combined with the center part has a high shielding ability, and a block part to be combined with the bottom part As the block pieces, those having high strength can be used, and thus, different conditions can be appropriately satisfied depending on the portion of the cask main body.

The cask main body divided into an upper part, a central part and a bottom part is divided into a plurality of parts at the upper part, the central part and the bottom part in the inner and outer peripheral directions. It is possible to reduce the size and weight by disassembling the block pieces combined on the outer surface side of the central portion and the bottom portion.

When the upper, central and bottom block pieces are further divided into a plurality of pieces in the inner and outer peripheral directions, the block pieces to be combined on the inner face side of the center part have high shielding ability and heat resistance. If a block piece to be combined with the outer surface side has high weather resistance, different conditions can be appropriately and reliably satisfied depending on the portion of the cask main body.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a concrete cask according to the present invention will be described below with reference to FIG. FIG. 1 is a central longitudinal sectional view of a concrete cask of the present invention. Concrete cask 1 of the present invention (hereinafter referred to as cask 1)
Is, for example, a closed container 3 for storing a radioactive object R such as a spent fuel, a concrete cask body 2 having a storage section 1a for storing the closed container 3, and a lid for closing an upper opening 1b of the cask body 2. 4 is provided.

The cask main body 2 is divided into a plurality of pieces, for example, a block piece 201 divided into an upper part, a central part, and a bottom part in the height direction, and further divided into three parts in the upper, central part, and the bottom part in the inner and outer peripheral directions. To 215 in combination. For example, the upper block pieces 201 and 20
The block pieces 201 and 202 are located inside the block piece 201 and outside the block piece 201.

The central portion is formed of block pieces 203 to 213.
These block pieces 203 to 213 are arranged such that the block pieces 203 and 204 are positioned inside from the top and the block pieces 205, 206 and 207 are positioned outside the block pieces 203 and 204 from the top. And
Outside the block pieces 205, 206, and 207, block pieces 208, 210, and 212 are located in order from the top, and outside these block pieces 208, 210, and 212, the block pieces 209, 211, and 213 are located in order from the top. ing.

The bottom portion is composed of block pieces 214 and 215. With respect to these block pieces 214 and 215, the block piece 215 forms the bottom surface of the cask body 2, and the block piece 214 is provided outside the block piece 215.
Is located. Then, the block pieces 201 to 214
Is formed in a cylindrical shape, and the block piece 215 is formed with a depression in the center of a disk shape.
01 to 215, the block pieces 201,
The storage portion 1a and the opening 1b are formed by the inner peripheral surfaces of the cylinders 03 and 204 and the depression of the block piece 215.

The inner peripheral surfaces of the cylinders of the block pieces 201, 203, and 204 and the recessed surface of the block piece 215 have the same thermal expansion coefficient as that of metal, for example, concrete in order to prevent evaporation of water from the concrete surface. A liner P of carbon steel or ferritic stainless steel is provided.

The block piece 201 and the block piece 202
Holes 201a and 202a penetrating the inner and outer peripheral surfaces and communicating with each other are formed in a part thereof. Hole 20
2a is formed perpendicular to the longitudinal direction of the cask 1, and the hole 201a is formed in a portion bent in the longitudinal direction of the cask 1 at an intermediate position to the inner and outer circumferences of the cylinder in order to prevent radiation from leaking. Are formed.

Then, the block piece 201 and the block piece 2
02 is aligned and combined so that the hole 201a and the hole 202a communicate with each other.
The air exhaust port 1c for heat removal is formed by the a. A liner P is provided on the inner peripheral surfaces of the holes 201a and 202a to prevent evaporation of water from the concrete surface.

The block piece 201 and the block piece 20
2 is located in the upper part of the cask 1, so that there is a possibility that cracks will be generated in the concrete due to a difference in thermal expansion due to heat or drying shrinkage. Is formed by

The block pieces 203 and 204 are
Since it is located at the center in the vertical direction in the cask 1 and is located on the inner surface, it is not necessary to have heat resistance as high as that of the block pieces 201 and 202. However, the heat resistance is higher than ordinary concrete, and It is formed of concrete having excellent performance, for example, alumina cement concrete using heavy aggregate.

The block piece 202 and the block pieces 209 and 2
11, 213 and 214 are provided on the outer surface of the cask 1,
Since the block pieces 208, 210, and 212 are located relatively outside in the cask 1, the concrete having high weather resistance, for example, high-density concrete or polymer impregnation (PI)
C) It is formed by concrete.

The block pieces 205, 206, 207
Since it is located relatively inside in the cask 1, it is formed of concrete having high shielding properties, for example, low-alkali cement concrete using heavy aggregate.

The block piece 215 is connected to the cask 1
Since it is located at the bottom of the concrete, it is made of concrete having high mechanical strength for supporting its own weight, for example, high-density concrete.

Further, the block piece 215 is formed with a hole 215a that penetrates the outer peripheral surface from the bottom of the central recess and communicates with a hole 214a of the block piece 214 described later. In the hole 215a, a portion bent in the longitudinal direction of the cask 1 is formed at an intermediate position to prevent radiation from leaking. In addition, for example, the block piece 215
Is divided into two, alumina cement concrete using heavy aggregate is used in the upper part, and high-density concrete is used in the lower part.

The block piece 214 includes a cask 1
A hole 214a penetrating the inner and outer peripheral surfaces perpendicular to the longitudinal direction of the block piece 215 and communicating with the hole 215a of the block piece 215 is formed. Then, the block piece 214 and the block piece 215
Are combined such that the holes 214a and 215a communicate with each other, the holes 214a and 215a form a cooling air intake 1d. In addition,
A liner P is provided on the inner peripheral surfaces of the holes 214a and 215a in order to prevent evaporation of water from the concrete surface.

In the cask 1 having the above structure, a closed container 3 for storing the radioactive object R is inserted into the storage portion 1a, and the opening 1b is made of concrete having excellent weather resistance and heat resistance, for example, high-density alumina cement concrete. The lid 4 is placed and thus stores the radioactive object R. When the cask 1 is composed of the block pieces 201 to 215, for each of the block pieces 201 to 215,
The overall strength is increased by combining the adjacent block pieces with bolts or the like.

The cask 1 is composed of divided block pieces 20
When the radiation source intensity decreases after a certain storage period, for example, the block pieces 202, 209, 211, 213, and 214 on the outer surface are disassembled to reduce the size and the weight. Can be
Therefore, the storage density in the warehouse can be improved, and movement at that time is also facilitated.

Furthermore, when the cask 1 of the present invention is reused, it is possible to replace only the deteriorated block pieces, so that it is not necessary to discard the entirety due to partial deterioration. Therefore, cost can be reduced.

In the cask 1 of the present invention, the cask main body 2 is divided into block pieces 201 to 215,
Improve durability and safety by using concrete with optimally set shielding capacity, heat resistance, weather resistance, and mechanical strength according to the top, center, inner circumference, bottom, and outer surface. be able to.

The present invention is not limited to the above embodiment, but can be variously modified. For example, although the block piece is divided into 15 in the above embodiment, it is divided into many parts at the upper part, the central part, the inner surface part of the central part, the bottom part, and the outer surface part. It may be divided into three parts, a bottom part and a bottom part.

The shape of the block pieces is not limited to the shapes of the block pieces 201 to 215 in the above embodiment.
Any shape may be used as long as it is easy to combine while shielding the inside and outside, and the strength of the combination can be maintained. Further, in the above embodiment, the block pieces 201 to 215 are made of concrete having an appropriate property according to the portion of the cask 1. However, for all the block pieces 201 to 215, the shielding ability, heat resistance, weather resistance, mechanical Concrete having excellent strength may be employed.

[0036]

As described above, the concrete cask of the present invention is constituted by dividing a concrete cask main body having a storage portion for storing a closed container into a plurality of block pieces, and these block pieces are heat-resistant. Since one or more of those with high heat resistance, high shielding ability, and high strength were used, the shielding ability, heat resistance, and weather resistance were improved using concrete pieces of appropriate conditions according to the part of the cask body. An excellent concrete cask can be created.

Further, the concrete cask of the present invention comprises:
In the above configuration, the cask main body is divided into three parts in the height direction, that is, an upper part, a central part, and a bottom part. Therefore, only the deteriorated block pieces can be replaced. When the concrete cask before transportation of the spent fuel is transported, the necessary block pieces can be transported in a divided state, so that the transportation becomes easy.

Further, in this configuration, when the block pieces to be combined at the top, the center, and the bottom are further divided into a plurality of pieces in the inner and outer peripheral directions, a greater effect can be obtained as well as the above effect, and the spent fuel can be stored. As a result, the volume of the concrete cask after the radiation source intensity decreases can be reduced, and the storage density can be increased.

For each of the divided block pieces of the cask body, the block piece combined with the upper part has high heat resistance, the block piece combined with the central part has high shielding ability, and the block piece combined with the inner surface of the central part. A piece with both high shielding ability and heat resistance is used, a block piece combined with the bottom is high in strength, and a block piece combined with the outer surface is one with high weather resistance. Design and manufacturing for improving durability are facilitated.

[Brief description of the drawings]

FIG. 1 is a central longitudinal sectional view showing a configuration of a concrete cask of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 (Concrete) cask 1a Storage part 1b Opening 2 Cask main body 3 Airtight container 4 Lid 201-215 Block piece P Liner R Radioactive object

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Nobuyuki Yamada 1-7-89, Minami Kohoku, Suminoe-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Inventor Yasufumi Fukaya 2-4-2 Daisaku, Sakura-shi, Chiba No. Inside the Autech Research Center Co., Ltd.

Claims (5)

[Claims] 1. A cask comprising: a closed container for storing a radioactive object; a concrete cask main body having a storage portion for storing the closed container; and a lid for closing an upper opening of the cask main body. Is divided into a plurality of block pieces, and these block pieces include
A concrete cask characterized by using one or more of those having high heat resistance, high shielding ability, and high strength. 2. The cask main body has a three-part structure of an upper part, a central part, and a bottom part in a height direction.
The concrete cask described. 3. A block piece combined with the upper part of the cask main body has a high heat resistance, a block piece combined with the central part has a high shielding ability, and a block piece combined with the bottom part has a high strength. The concrete cask according to claim 1 or 2, wherein the concrete cask is provided. 4. The concrete cask according to claim 1, wherein a plurality of block pieces to be combined with an upper portion, a central portion, and a bottom portion of the cask main body are further divided in the inner and outer peripheral directions. 5. A block piece combined with the inner surface side of the central portion of the cask main body has a high shielding ability and heat resistance, and a block piece combined with the outer surface side has a high weather resistance. 5. The method according to claim 1, wherein
A concrete cask according to any one of the above.