JP2009115455A - Transportation-cum-storage container of radioactive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transportation-cum-storage container of a radioactive material wherein an inertia force at a dropping time have little influence on a structure of an external container. <P>SOLUTION: This transportation-cum-storage container 1 is equipped with an internal container 2 storing the radioactive material, and the cylindrical bottomed external container 3 arranged outside the internal container 2, and showing γ-ray shielding function. The external container 3 includes an external cylindrical body 3A, and an external bottom plate 3C arranged on the end 3B of the external cylindrical body 3A. The external bottom plate 3C is arranged inside a columnar space 3D formed by the external cylindrical body 3A, and fixed to the inner circumference of the external cylindrical body 3A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a container for transporting and storing radioactive materials such as spent nuclear fuel.

  As this kind of technology, Patent Document 1 discloses a radioactive substance storage container (having a trunk body that shields γ-rays, a neutron shield disposed around the trunk body, and an outer cylinder that accommodates the neutron shield ( Cask) is disclosed. The trunk main body of the cask is composed of a bottomed cylindrical inner container mainly having a sealing function and a bottomed cylindrical outer container mainly having a gamma ray shielding function. The outer container is composed of a cylinder and a bottom plate. The bottom plate completely covers the cylindrical body in the axial direction, and is fixed to the end surface of the cylindrical body, for example, by welding or bolt fastening.

JP 2004-156930 A (paragraph numbers 0033 and 0034, FIG. 4A)

  However, in the configuration of Patent Document 1, the following problem occurs during a so-called 9-m drop test (vertical). That is, since the inertial force of the cylindrical body at the time of dropping directly acts on the fixing portion between the cylindrical body and the bottom plate, the state of fixing the bottom plate to the cylindrical body is hindered, and a large deformation of the outer container is allowed. As a result, the outer container cannot sufficiently protect the inner container. On the other hand, it is also one solution to perform a large-scale welding process so as not to hinder the fixed state. However, this requires a troublesome annealing process to remove the welding residual stress.

  The present invention has been made in view of these points, and a main object of the present invention is to provide a container for transporting and storing a radioactive substance that has a small influence on the structure of the outer container by the inertial force at the time of dropping. .

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to the first aspect of the present invention, there is provided a container for transporting and storing radioactive materials, which is configured as follows. That is, the container for transporting and storing a radioactive substance includes an inner container in which the radioactive substance is accommodated, and a bottomed cylindrical outer container that is disposed outside the inner container and exhibits a γ-ray shielding function. The outer container includes a cylindrical body and a bottom plate disposed at the end of the cylindrical body. The bottom plate is disposed inside a cylindrical space formed by the cylindrical body, and is fixed to the inner periphery of the cylindrical body. According to the above configuration, at the time of dropping, the cylindrical body collides against a collision target such as a work floor without passing through the bottom plate, so that the inertial force of the cylindrical body at the time of dropping is the same as that of the cylindrical body. It does not act directly on the fixed portion with the bottom plate, and in this sense, the influence of the inertial force at the time of dropping on the structure of the outer container is small.

  The container for transporting and storing the radioactive substance is further configured as follows. The bottom plate is disposed away from an end surface of the end portion of the cylindrical body. According to the above configuration, when falling, the cylinder collides with a collision target such as a work floor before the bottom plate and starts to deform, so that the deformation of the bottom plate is suppressed accordingly. .

  The container for transporting and storing the radioactive substance is further configured as follows. The container for transporting and storing radioactive material includes a bottom plate support member fixed to the cylindrical body. The bottom plate is fixed to the inner periphery of the cylindrical body by being sandwiched between the cylindrical body and the bottom plate supporting member. According to the above configuration, the bottom plate is fixed to the cylindrical body by a simple means of clamping.

  The container for transporting and storing the radioactive substance is further configured as follows. The bottom plate support member is fixed to the cylinder by shrink fitting. According to the above structure, it contributes to productivity.

  The container for transporting and storing the radioactive substance is further configured as follows. The cylinder of the outer container is shrink-fitted with respect to the inner container. According to the above structure, it contributes to productivity.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of a radioactive material transport / storage container according to a first embodiment of the present invention.

  In the present embodiment, the container 1 for transportation and storage is a bottomed cylindrical inner container 2 that accommodates a radioactive substance, and a bottomed cylindrical inner container 2 that is disposed outside the inner container 2 and exhibits a γ-ray shielding function. An outer container 3. The inner container 2 includes an inner cylinder 2A, an inner flange 2B welded to the upper end of the inner cylinder 2A, and an inner bottom plate 2C welded to the lower end of the inner cylinder 2A. The outer container 3 includes an outer cylindrical body 3A (cylindrical body) and an outer bottom plate 3C disposed on the end 3B of the outer cylindrical body 3A. The inner bottom plate 2C and the outer bottom plate 3C have substantially the same shape and are in surface contact with each other. The outer container 3 is thicker than the inner container 2. The outer cylinder 3A of the outer container 3 is shrink-fitted with respect to the inner cylinder 2A of the inner container 2.

  The transport and storage container 1 further includes a neutron shield 4 disposed on the outer peripheral side of the outer cylinder 3 </ b> A of the outer container 3, and an outer cylinder 5 disposed on the further outer peripheral side of the neutron shield 4. . The neutron shield 4 is interposed between the outer cylinder 3 </ b> A of the outer container 3 and the outer cylinder 5.

  The transport / storage container 1 further includes a plurality of trunnions 6 used for handling the transport / storage container 1, an upper lid 7, and a lower lid 8. The upper lid 7 closes the opening of the inner container 2, and is firmly fixed to the inner flange 2 </ b> B of the inner container 2 by a schematically illustrated bolt. The opening of the inner container 2 is closed by the upper lid 7 so that a radioactive substance storage space 9 is formed. The lower lid 8 covers the outer bottom plate 3C of the outer container 3 from the outside, and is fixed to the end portion 3B by a bolt or the like not shown.

  The inner container 2 is made of stainless steel or nickel steel, which is excellent in low temperature toughness, to ensure sealing performance. On the other hand, the outer container 3 can be of any type as long as it has a γ-ray shielding function. For example, a general carbon steel having no low temperature toughness is sufficient. Under such circumstances, the inner container 2 generally has higher material costs than the outer container 3.

  Please refer to FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. As shown in this figure, the neutron shield 4 is configured by arranging a plurality of block-shaped neutron shield blocks 4a in the circumferential direction, and each neutron shield block 4a is made of, for example, ethylene propylene rubber as an organic material containing hydrogen. Become. A large number of good thermal conductors 15 that thermally connect the outer cylinder 3A and the outer cylinder 5 of the outer container 3 are interposed between the adjacent neutron shielding blocks 4a. The good thermal conductor 15 is made of a material having good thermal conductivity, such as aluminum, aluminum alloy, copper, or copper alloy.

  Please refer to FIG. 1 again. The inner flange 2B is formed so as to cover the upper end of the outer cylinder 3A of the outer container 3. For this reason, the inertial force of the inner container 2 at the time of the vertical drop is also received by the upper end of the outer cylinder 3A of the outer container 3 through the inner flange 2B.

  Reference is now made to FIG. FIG. 2 is a partially enlarged view of FIG. As shown in this figure, the outer bottom plate 3C of the outer container 3 is a cylindrical space 3D formed by the outer cylindrical body 3A (shown roughly by a two-dot chain line. This two-dot chain line is a viewpoint for easy viewing of the drawing. To the inner circumference of the outer cylindrical body 3A, and is fixed by welding. The outer bottom plate 3C of the outer container 3 is disposed slightly apart from the end surface 3F of the end portion 3B inward. In this figure, the welding location indicated by reference numeral 3W is provided continuously or intermittently along an arc that is the boundary between the outer cylinder 3A and the outer bottom plate 3C of the outer container 3. With such a configuration, the end surface 3F of the end 3B of the outer container 3 is positioned as the bottom surface of the transport / storage container 1 as it is.

  The lower lid 8 covering the outer bottom plate 3C is composed of a neutron shielding material 10 made of the same material as the neutron shielding body 4 and a lid 11 made of the same material as the outer cylinder 5. Then, the inner bottom plate 2C, the outer bottom plate 3C, the neutron shielding material 10, and the lid 11 are stacked in this order. The lid 11 is fixed to the end 3B of the outer container 3 by, for example, welding or bolt fastening. In the present embodiment, the lid 11 is flush with the end surface 3F.

(Claim 1)
As described above, in the present embodiment, the transport / storage container 1 is configured as follows. In other words, the transport and storage container 1 includes an inner container 2 that stores a radioactive substance, and a bottomed cylindrical outer container 3 that is disposed outside the inner container 2 and exhibits a γ-ray shielding function. . The outer container 3 includes an outer cylindrical body 3A and an outer bottom plate 3C disposed on the end 3B of the outer cylindrical body 3A. The outer bottom plate 3C is disposed inside a cylindrical space 3D formed by the outer cylinder 3A, and is fixed to the inner periphery of the outer cylinder 3A. According to the above configuration, at the time of dropping, the outer cylindrical body 3A collides with a collision target such as a work floor without passing through the outer bottom plate 3C, so that the inertial force of the outer cylindrical body 3A at the time of dropping. Does not directly act on the fixing portion 3G between the outer cylindrical body 3A and the outer bottom plate 3C, and in this sense, the influence of the inertial force at the time of dropping on the structure of the outer container 3 is small.

  Furthermore, “the inertial force at the time of dropping has little influence on the structure of the outer container 3” means that the structure of the outer container 3 is superior in strength. The wall thickness of the inner container 2 required for securing can be reduced more or less.

(Claim 2)
The transport / storage container 1 is further configured as follows. That is, the outer bottom plate 3C is disposed away from the end surface 3F of the end 3B of the outer cylinder 3A. According to the above configuration, when falling, the outer cylindrical body 3A collides with a collision target such as a work floor before the outer bottom plate 3C and starts to deform, and accordingly, the outer bottom plate 3C. Is prevented from being deformed.

  If the deformation of the outer bottom plate 3C is suppressed in this way, the deformation of the inner bottom plate 2C of the inner container 2 is also suppressed at the same time. Therefore, as described above, it is possible to further reduce the wall thickness of the inner container 2 necessary for ensuring the sealing function of the inner container 2.

(Claim 5)
The transport / storage container 1 is further configured as follows. That is, the outer cylinder 3 </ b> A of the outer container 3 is shrink-fitted with respect to the inner container 2. According to the above structure, it contributes to productivity. That is, when the outer cylindrical body 3A of the outer container 3 is fixed to the inner container 2 by welding, an annealing process for removing the welding residual stress is required. On the other hand, if the outer cylindrical body 3A of the outer container 3 is fixed to the inner container 2 by shrink fitting, a troublesome step such as an annealing process becomes unnecessary. In this sense, it can be said that the configuration in which the outer cylindrical body 3A of the outer container 3 is shrink-fitted with respect to the inner container 2 contributes to productivity.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a view similar to FIG. 2 and according to the second embodiment of the present invention.

  In the present embodiment, the end surface 3F of the end portion 3B is flush with the outer bottom plate 3C, and the flange portion 3H protruding radially outward from the outer bottom plate 3C is slightly in the axial direction with respect to the outer cylindrical body 3A. Duplicate. And if the baseplate support member 12 which is formed in an annular shape and has an outer fitting portion 12a having a larger diameter than the outer cylindrical body 3A of the outer container 3, the outer fitting portion 12a is baked on the end portion 3B of the outer cylindrical body 3A. It is fixed to the end portion 3B by being externally fitted. At this time, the clamping surface 12b as the surface of the bottom plate support member 12 facing the end surface 3F of the outer container 3 in the axial direction is in pressure contact with not only the end surface 3F but also the flange portion 3H. Similarly, the clamping surface 3b as the surface of the end 3B facing the flange 3H in the axial direction is in pressure contact with the flange 3H. In this way, the outer bottom plate 3C is axially clamped by the clamping surface 12b of the bottom plate support member 12 and the clamping surface 3b of the end 3B, so that the outer bottom plate 3C is against the inner circumference of the outer cylindrical body 3A of the outer container 3. Strongly fixed.

  The lower lid 8 is disposed on the inner peripheral side of the bottom plate support member 12.

(Claim 3)
As described above, in the present embodiment, the transport / storage container 1 is configured as follows. That is, the transport / storage container 1 includes a bottom plate support member 12 that is fixed to the outer cylindrical body 3A. The outer bottom plate 3C is fixed to the inner periphery of the outer cylinder 3A by being sandwiched between the outer cylinder 3A and the bottom plate support member 12. According to the above configuration, fixing of the outer bottom plate 3C to the outer cylindrical body 3A is realized by simple means of clamping. That is, as described above, a troublesome step such as annealing is not necessary when compared with welding means. In the present embodiment, the inertia force of the outer bottom plate 3 </ b> C at the time of vertical drop is received by the bottom plate support member 12.

(Claim 4)
Further, the transport / storage container 1 is configured as follows. The bottom plate support member 12 is fixed to the outer cylinder 3A by shrink fitting. According to the above structure, it contributes to productivity. This means that the annealing process is not necessarily required just because the number of parts is increased by adding the bottom plate support member 12.

1 is a longitudinal sectional view of a radioactive material transport and storage container according to a first embodiment of the present invention. Partial enlarged view of FIG. FIG. 3 is a diagram similar to FIG. 2 and according to the second embodiment of the present invention. Sectional view taken along line 4-4 in FIG.

Explanation of symbols

1 Container for transportation and storage 2 Inner container 3 Outer container 3A Outer cylinder (cylinder)
3B End 3C Outer bottom plate (bottom plate)
3D cylindrical space

Claims (5)

An inner container for containing radioactive material;
A bottomed cylindrical outer container that is disposed outside the inner container and exhibits a γ-ray shielding function;
With
The outer container is composed of a cylinder and a bottom plate arranged at the end of the cylinder,
The bottom plate is disposed inside a cylindrical space formed by the cylinder, and is fixed to the inner periphery of the cylinder.
A container for transporting and storing radioactive materials In the container for transport and storage of radioactive material according to claim 1,
The bottom plate is disposed away from the end surface of the end of the cylindrical body,
A container for transporting and storing radioactive materials In the container for transport and storage of radioactive material according to claim 1 or 2,
A bottom plate support member fixed to the cylinder,
The bottom plate is fixed to the inner periphery of the cylinder by being sandwiched between the cylinder and the bottom plate support member.
A container for transporting and storing radioactive materials In the radioactive material transport and storage container according to claim 3,
The bottom plate support member is fixed to the cylinder by shrink fitting.
A container for transporting and storing radioactive materials In the container for transport and storage of radioactive material according to any one of claims 1 to 4,
The cylinder of the outer container is shrink-fitted against the inner container;
A container for transporting and storing radioactive materials

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