JP2008076270A - Transport-cum-storage cask for radioactive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transport-cum-storage cask for radioactive materials which is light in weight and can mitigate the bombardment due to its self-weight. <P>SOLUTION: A gamma-ray shielding layer 20 and a neutron shielding layer 21 are set up between an internal rim part 10 and an external rim part 19 in the transport-cum-storage cask 1 for radioactive materials. The cask 1 is equipped with a base plate 11 which is fixed onto one end face of the internal rim part 10 concentrically with it, which keeps the inner diameter larger than that of the internal rim part 10 and the outer diameter smaller than that of the external rim part 19, and a cylindrical support part 12 which is extended from the base plate 11 concentrically with the internal rim part 10 in the direction opposite to it and keeps the outer diameter smaller than that of the external rim part 19 on the outside end face in the axial direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transport and storage container for a radioactive substance having a radiation shielding function.

  Transport and storage containers (hereinafter referred to as containers) for radioactive materials such as spent nuclear fuel (hereinafter referred to as radioactive materials) generated at nuclear power plants, etc., have a sealing function to confine radioactive materials, A criticality prevention function to prevent criticality due to nuclear fission of the remaining uranium 235, a heat removal function to release the decay heat of the radioactive material and appropriately lower the temperature of the components of the container and spent nuclear fuel, and gamma rays and neutrons Four safety functions are required: a shielding function for shielding and lowering the dose rate outside the container to prevent radiation exposure.

  Containers are required to have structural strength to maintain these safety functions in the event of a fall accident or fire accident, and meet the standards under the conditions stipulated in the regulations such as drop collision conditions, fire resistance conditions, and immersion conditions. The container needs to be satisfactory.

  Conventionally, a container has been disclosed for enhancing the storage efficiency of a radioactive substance, excellent heat transfer performance, and effectively shielding gamma rays and neutrons (see, for example, Patent Document 1). In the container described in Patent Document 1, a gamma ray shielding layer and a neutron shielding layer are provided between an inner trunk portion and an outer trunk portion, and the gamma ray shielding layer and the neutron shielding layer are penetrated, and the inner trunk and the outer shell are penetrated. It is a container attached to the trunk and provided with a good heat conductor.

Japanese Patent No. 3342994

  By the way, as for the cylindrical conventional container currently disclosed by patent document 1, the trunk | drum, a bottom part, and a cover part are comprised from metal members, such as carbon steel. In addition, by providing a gamma ray shielding layer made of lead or the like having excellent gamma ray shielding performance, the thickness of the inner body portion can be reduced and the weight of the container can be reduced. Moreover, since the heat good conductor which penetrates a gamma ray shielding layer and a neutron shielding layer is provided, it is excellent in heat transfer performance. Furthermore, by using a lead block for the gamma ray shielding layer, the manufacture is easy because it is not necessary to carry out a so-called homogen treatment necessary for the lead casting operation.

  The homogen treatment is a treatment for bringing the lead layer into close contact with the outer surface of the inner cylinder for the purpose of improving heat transfer performance, and after applying a flux containing zinc chloride or the like on the outer surface of the inner cylinder, A lead-based solubilizer is dissolved and applied. Thereafter, lead is cast between the inner cylinder and the outer cylinder.

  However, since the outer diameter of this conventional container is substantially uniform from the head to the bottom, the shielding corner of the metallic body is excessive at the bottom corner, and the weight of the container is excessive. Needless to say, in such a container that generally increases in weight, in order to facilitate handling of the container, it is desirable that the container be lightweight, and there should be fewer metal members that lead to an increase in weight.

  In addition, this container has a flat bottom surface with almost no irregularities. In addition, the bottom outer diameter in contact with the floor surface is substantially the same as the outer diameter of the outer body portion of the container and has a large area in contact with the floor. Therefore, when the container and the floor surface collide with each other in the axial direction, the impact given to the container and the radioactive substance is increased.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transport and storage container for a radioactive substance that is light in weight and can mitigate the impact caused by its own weight.

Means and effects for solving the problems

  The radioactive substance transport / storage container according to the present invention relates to a radioactive substance transport / storage container in which a gamma ray shielding layer and a neutron shielding layer are provided between an inner trunk part and an outer trunk part. The radioactive substance transport / storage container according to the present invention has the following features in order to achieve the above object. That is, the radioactive substance transport / storage container of the present invention has the following features alone or in combination as appropriate.

  In order to achieve the above object, the first feature of the radioactive material transport and storage container according to the present invention is that it is fixed to one end face of the inner body portion concentrically with the inner body portion, and from the inner diameter of the inner body portion. A bottom plate having an outer diameter smaller than an outer diameter of the outer body portion, and extending from the bottom plate in a direction opposite to the inner body portion concentrically with the inner body portion, and outside the outer body portion. And a cylindrical support portion having an outer diameter smaller than the diameter at the outer end face in the axial direction.

  According to this configuration, compared to a conventional container whose bottom outer diameter is substantially the same as the outer diameter of the outer body, it is possible to reduce the number of metal members that lead to an increase in weight, and to reduce the weight of the container. Can do. Moreover, the bottom area which contacts a floor becomes small compared with the conventional container. For this reason, the impact when the container and the floor collide in the axial direction can be mitigated, and a radioactive substance transport / storage container with little damage to the radioactive substance contained in the container or the container can be obtained.

  In addition, when the container and the floor surface collide in the axial direction, the inner body portion in which the radioactive substance is stored can be effectively supported by the bottom plate, so that the structure is excellent.

  Furthermore, it becomes easy to attach an annular buffer to the bottom of the container using the support provided at the bottom. This also contributes to securing an area for receiving the container load.

  The second feature of the radioactive substance transport / storage container according to the present invention is that a plate-like bottom neutron shielding layer having a diameter substantially the same as the inner diameter of the support portion and a bottom neutron shielding is provided inside the support portion. A layer cover is housed in this order from the bottom plate side, and the hydrogen content per unit volume of the bottom neutron shielding layer is larger than the hydrogen content of the bottom plate, and the bottom neutron shielding layer cover in the axial direction The end face position on the outside of the support section is in a position recessed with respect to the end face position of the support portion.

  According to this configuration, since the bottom neutron shielding layer shields neutrons, the dose equivalent rate on the container surface can be reduced. In addition, since only the end surface of the support portion at the bottom is the installation surface, the grounded bottom area is further reduced compared to the case where the outer end surface of the bottom neutron shielding layer cover and the end surface of the support portion are on the same plane, It is possible to mitigate the impact when the floor collides with the floor surface in the axial direction.

  The third feature of the radioactive substance transport and storage container according to the present invention is that the inner diameter of the support portion is smaller than the outer diameter of the inner body portion, and the outer diameter of the support portion is the gamma ray shielding layer. It is larger than the inner diameter.

  According to this configuration, when the container and the floor surface collide with each other in the axial direction, the support portion at the bottom can be set to a minimum diameter that can receive a load due to the impact, and the weight of the container can be reduced. . Further, since the gamma ray shielding layer is made of a material having a high density, the gamma ray shielding layer can be effectively supported, and the structure is excellent.

  Further, a fourth feature of the radioactive substance transport / storage container according to the present invention is that at least one of the gamma ray shielding layer and the neutron shielding layer is formed of a block body divided into a plurality in the circumferential direction. In addition, a good thermal conductor is sandwiched between the block bodies adjacent to each other in the circumferential direction.

  According to this configuration, the shielding layer formed in a block shape can be manufactured in parallel with a separate process from the manufacturing of the container body, and the manufacturing time can be shortened. Note that conventional containers are often manufactured by casting a neutron shielding layer into the container body, and such parallel operations cannot be performed. In addition, when the use period of the container is over, the blocking layer formed in a block shape can be easily removed, and disassembly and recycling are easy.

  In addition, the decay heat of the radioactive substance is efficiently transferred from the inner body part to the outer body part by the good thermal conductor sandwiched between the block bodies, so that heat removal can be promoted.

  A fifth feature of the radioactive substance transport / storage container according to the present invention is that the block body is divided into a plurality of pieces in the axial direction, and the contact surfaces of the blocks adjacent to each other in the axial direction are inclined. It is formed in the uneven surface which a surface or an unevenness | corrugation meshes | engages.

  According to this structure, since it becomes the block-shaped shielding layer further divided | segmented, manufacture of a shielding layer becomes easy and it becomes easy to attach to a container. Moreover, the streaming of a radiation can be reduced because block bodies contact | abut on an inclined surface or an uneven surface.

  Further, a sixth feature of the radioactive substance transport / storage container according to the present invention is that the gamma ray shielding layer is made of any one material of lead, lead alloy, iron, carbon steel, and stainless steel. is there.

  According to this configuration, a relatively high density material is effective for the gamma ray shielding layer, and the use of any of the above materials can improve the gamma ray shielding performance.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  First, such a container is usually transported with shock absorbers fixed at both axial ends (head and bottom), and the container is protected from impact in the axial direction. Moreover, the outer diameter of the buffer is designed to be larger than the maximum outer diameter of the container, so that the container is protected from an impact in the radial direction. On the other hand, in a storage facility, a nuclear power plant, or the like, a container may be lifted and moved by a crane or the like without a shock absorber. As an accident event in such a case, there is abnormal landing on the concrete floor. This is based on the assumption that when handling the container with a crane or the like, the floor where the floor is naturally grounded so as not to be impacted slowly is accidentally grounded. The event is called abnormal implantation.

In such abnormal landing, the acceleration α [m / s ² ] generated in the container due to the collision between the container and the floor is determined under the conditions assumed as the following mathematical formulas (1) to (6). This can be expressed as Equation (7). Here, the container and the floor surface collide so that the axial direction of the container and the floor surface are orthogonal to each other.
(1) Ek = 1/2 · W · V ²
(2) Es = 1/2 · K · δ ²
(3) Es = Ek
(4) δ = ε · L
(5) K = E · A / L
(6) α = F / W = ε · E · A / W
(7) α = V · ((E · A) / (W · L)) ^1/2
Here, each variable is as follows.
Ek: Kinetic energy of container during abnormal landing [J]
Es: Strain energy of floor member [J]
F: Force generated in the container during abnormal landing [N]
W: Mass of container [kg]
A: Bottom area of container [m ² ]
ε: Crushing strain of floor member [−]
E: Young's modulus of floor member [N / m ² ]
L: Floor member thickness [m]
δ: Deformation amount of floor member [m]
V: Speed at which the container abnormally lands on the floor [m / s]
K: Spring constant of floor member [N / m]

  From equation (7), it can be seen that the acceleration generated in the container during abnormal landing is proportional to the bottom area of the container and inversely proportional to the mass of the container. From this, when a container with a certain weight and a floor surface with a certain condition collide in the axial direction, the acceleration generated in the container becomes smaller when the container bottom area is reduced, and the container is loaded inside the container. Damage to radioactive materials such as spent nuclear fuel can be reduced.

  FIG. 1 is a schematic view showing an axial cross section of a radioactive material transport and storage container according to an embodiment of the present invention.

  As shown in FIG. 1, the radioactive substance transport / storage container 1 (hereinafter referred to as the container 1) according to this embodiment includes a gamma ray shielding layer 20 and a neutron shielding between an inner trunk part 10 and an outer trunk part 19. A container 1 provided with a layer 21; a bottom plate 11 concentrically fixed to one end surface of the inner torso part 10; and a flange 17 welded to the head of the inner torso part 10; The primary lid 15a is detachably fitted and fixed to the flange 17 so as to form an accommodating space 22 in which a radioactive substance is accommodated.

  Further, on the outer side in the axial direction of the primary lid 15a, a secondary lid 15b having a head neutron shielding layer 16 therein is detachably fitted to and fixed to the flange 17, and further on the outer side in the axial direction of the secondary lid 15b. The tertiary lid 15 c is detachably fitted and fixed to the flange 17.

  Here, the outer diameter of the bottom plate 11 is larger than the inner diameter of the inner body portion 10 and smaller than the outer diameter of the outer body portion 19. Since the outer diameter of the bottom plate 11 is larger than the inner diameter of the inner body portion 10, the inner body portion 10 can be effectively supported by the bottom plate 11 when the container 1 and the floor surface collide in the axial direction. Further, a cylindrical support portion 12 extends concentrically with the inner body portion 10 from the bottom plate 11 in the opposite direction to the inner body portion 10, and the axially outer (bottom side) end surface of the container 1 of the support portion 12. The outer diameter of the support part 12 at 12 a is smaller than the outer diameter of the outer body part 19. Thereby, it has the shape from which the excess metal member was removed for the radiation shielding purpose in the outer peripheral part of the baseplate 11 and the support part 12. FIG.

  The inner diameter of the support portion 12 is smaller than the outer diameter of the inner body portion 10 and the same as the inner diameter of the inner body portion 10, and the outer diameter of the support portion 12 is larger than the inner diameter of the gamma ray shielding layer 20. It is the same as the outer diameter. Here, the support part 12 needs to endure the impact load of the container 1 main body in the case of abnormal landing. If the inner diameter of the support part 12 is the same as or larger than the outer diameter of the inner body part 10, the inertial force generated in the inner body part 10 containing the radioactive substance cannot be supported. Further, if the outer diameter of the support portion 12 is smaller than the inner diameter of the gamma ray shielding layer 20, the inertia force generated in the gamma ray shielding layer 20 cannot be supported. This is because the gamma ray shielding layer 20 is a material having a relatively high density and thus generates a large inertia force. Therefore, by adopting a structure like the support portion 12, the inner barrel portion 10 and the relatively high density gamma ray shielding layer 20 can be effectively supported.

  A plate-like bottom neutron shielding layer 13 and a bottom neutron shielding layer cover 14 having the same outer diameter as the inner diameter of the support portion 12 are housed in this order from the bottom plate 11 side. ing.

  Moreover, since the end surface position of the outer side (bottom surface side) of the bottom neutron shielding layer cover 14 in the axial direction of the container 1 is in a recessed position with respect to the end surface position of the support portion 12, the end surface of the support portion 12 faces downward. When the container 1 is installed so that its axial direction is perpendicular to the floor surface, only the support portion end surface 12a comes into contact with the floor surface. Thereby, compared with the case where the outer (bottom side) end surface of the bottom neutron shielding layer cover 14 and the end surface of the support portion 12 are on the same plane, the ground contact bottom area between the bottom surface and the floor surface of the container 1 is reduced. The impact when 1 and the floor collide in the axial direction can be reduced.

  Here, the secondary lid 15b excluding the bottom plate 11 and the head neutron shielding layer 16 is a carbon steel member, and the primary lid 15a is a stainless steel member, and mainly functions as a gamma ray shielding material. Moreover, the support part 12, the outer trunk | drum 19, and the bottom part neutron shielding layer cover 14 are carbon steel members, and the tertiary lid | cover 15c is a stainless steel member. The gamma ray shielding material used for the gamma ray shielding layer 20 is made of lead.

  As the gamma ray shielding material used for the gamma ray shielding layer 20, a relatively high density material is effective, and therefore, lead, lead alloy, iron, carbon steel, stainless steel, and the like are effective. The material of the primary lid 15a and the tertiary lid 15c may be, for example, carbon steel, and the material of the support portion 12 may be a metal material that has no problem in structural strength, such as carbon steel or stainless steel.

  Moreover, the neutron shielding material used for the neutron shielding layer 21, the head neutron shielding layer 16, and the bottom neutron shielding layer 13 has a hydrogen content per unit volume such as the inner trunk portion 10, the primary lid 15a, the bottom plate 11, and the like. It is larger than the member, more specifically, ethylene propylene rubber.

  With the above configuration, the metal member that leads to an increase in the weight of the container 1 can be reduced, so that the weight can be reduced, and the container 1 and the floor surface can be pivoted by reducing the bottom area. The impact when colliding in the direction can be reduced. For this reason, damage to the radioactive substance inside the container 1 can be reduced.

  Moreover, when the bottom part of the container 1 is a plane, it may not be easy to stabilize the installation to the floor surface with an unevenness | corrugation. On the other hand, when the container 1 according to the present embodiment is used, a floor surface with unevenness is provided as compared with the case where the outer end surface of the bottom neutron shielding layer cover 14 and the end surface of the support portion 12 are on the same plane. Installation to the stable.

  Next, FIG. 2 is an AA cross-sectional view of the radioactive substance transport / storage container 1 (container 1) shown in FIG. FIG. 3 is an enlarged view of a portion X in the AA sectional view shown in FIG.

  As shown in FIG. 2, the gamma ray shielding layer 20 is formed by a block body 74 divided into a plurality in the circumferential direction of the container 1, and the neutron shielding layer 21 is similarly divided into a plurality in the circumferential direction of the container 1. A block body 73 is formed. Further, a good thermal conductor 72 is sandwiched between the block bodies 73 and 74 adjacent to each other in the circumferential direction.

  The heat good conductor 72 is a comparatively long shape having a longitudinal direction in the axial direction of the container 1 obtained by bending a thin metal plate having excellent heat conductivity such as copper or aluminum into an L-shaped cross section. Are arranged adjacent to the outer peripheral surface of the inner body portion 10 at a predetermined interval in the circumferential direction, and the tip of the other side portion 72 is arranged so that the back surface thereof is pressed against the outer peripheral surface of the inner body portion 10. It is welded to the inner peripheral surface of the body part 19. By attaching the good thermal conductor 72 in this way, the heat of the inner trunk portion 10 is efficiently transferred to the outer trunk portion 19 through the good thermal conductor 72 and radiated from the outer trunk portion 19 to the outside. In addition, you may attach so that the back surface of the edge part 71 may contact | adhere by means, such as a volt | bolt and brazing, besides providing so that it may press-contact with the outer peripheral surface of the inner trunk | drum 10.

  The gamma ray shielding layer 20 is formed in a plurality of lead-made block bodies 74 having a thickness necessary for shielding gamma rays, and the cross-sectional shape thereof is a shape along the outer peripheral surface of the inner cylinder 10, and It is inserted between the outer body part 19 and the outer peripheral surface of the inner body part 10.

  Further, the neutron shielding layer 21 is formed in a plurality of block members 73 made of ethylene propylene rubber having a length necessary for shielding neutrons, and the cross-sectional shape thereof is a shape along the inner peripheral surface of the outer trunk portion 19. At the same time, it is inserted between the gamma ray shielding layer 20 and the outer body portion 19.

  Thus, the gamma-ray shielding layer 20 and the neutron shielding layer 21 are made into a plurality of block bodies, so that a conventional casting operation for forming the shielding layer is not required, and the structure is simplified.

  Therefore, the gamma-ray shielding layer 20 and the neutron shielding layer 21 formed in a plurality of blocks can be manufactured in parallel with a process different from the manufacturing of the main body of the container 1, and the manufacturing time can be shortened. Note that conventional containers are often manufactured by casting a neutron shielding layer into the container body, and such parallel operations cannot be performed. Further, when the use period of the container 1 is over, the blocking layer formed in a block shape can be easily removed, and disassembly and recycling are easy.

  FIG. 4 is a view showing the block bodies 91, 92, and 92 a divided into a plurality of parts in both the circumferential direction and the axial direction of the container 1. Here, FIG. 4A is a view when the contact surfaces of the block bodies are inclined surfaces, and FIGS. 4B and 4C are the uneven surfaces of the contact surfaces of the block bodies. FIG.

  As shown in FIG. 4, the gamma ray shielding layer 20 and the neutron shielding layer 21 may be formed as block bodies 91, 92, 92 a divided into a plurality of parts in both the circumferential direction and the axial direction of the container 1. good. In this case, since the length is shorter than that of the block bodies 73 and 74, the manufacture of the block body becomes easier and the attachment to the container 1 becomes easier.

  Note that the axial contact surface of the container 1 has an inclined surface 81 as shown in FIG. 4 (a), or as shown in FIGS. 4 (b) and 4 (c) in order to prevent radiation streaming. It is necessary to form like the stepped uneven surfaces 82 and 82a. This is because radiation such as gamma rays and neutrons is emitted radially in the radial direction of the container 1 so that the contact surfaces of the block bodies do not overlap with radiation radiating in the radial direction as much as possible.

  Here, as described above, each of the gamma ray shielding layer 20 and the neutron shielding layer 21 of the container 1 according to the present embodiment is formed in a plurality of block bodies, but is not limited to this structure. For example, the gamma ray shielding layer 20 may be formed by lead casting or the like.

  Next, FIG. 5 is a schematic cross-sectional view in the axial direction showing a state in which the buffer bodies 50 and 51 are attached to the radioactive substance transport / storage container 1 (container 1) shown in FIG. In addition, the same code | symbol is attached | subjected to the same member and the description is abbreviate | omitted.

  As shown in FIG. 5, the container 1 has an annular bottom buffer 50 covering the end surface 12 a of the support portion 12 and the outer peripheral surface 12 b in the vicinity of the end surface of the support portion 12 with respect to the bottom neutron shielding layer cover 14. It is detachably fixed in the axial direction. Similarly, an annular head cushion 51 that covers the end surface of the tertiary lid 15 c and the outer peripheral surface of the flange 17 is detachably fixed to the flange 17 in the axial direction.

  Further, a fixture 63 is provided on the inner side in the radial direction of the bottom buffer 50 and in contact with the end face 12a of the bottom support portion 12 and the bottom neutron shielding layer cover 14, and the fixture and bottom neutrons are provided. The shielding layer cover 14 is fixed by bolts 62 via spacers 61. The head cushion 51 is fixed to the flange 17 by a bolt (not shown).

  By mounting the bottom buffer body 50 and the head buffer body 51 on the container 1 in this way, the container 1 can be protected from impact during land and sea transportation.

  Here, the bottom buffer 50 is mounted in contact with the outer peripheral surface 12 b of the support 12. This is because when the bottom buffer 50 is mounted in contact with the outer body portion 19 in which the neutron shielding material is stored, the portion is an outer cylinder having a relatively thin plate thickness, so that the load of the falling event is reduced. This is because it is difficult to receive. If the pressure receiving area of the shock absorber is small, the crushing margin of the shock absorber increases, and in some cases, the shock absorber may be deformed until it hits the trunnion 23 for handling. Therefore, it is desirable to have a structure having a sufficient mounting allowance for proper mounting of the shock absorber. On the other hand, if the bottom neutron shielding layer cover 14 is enlarged as a whole, the weight becomes very large. Therefore, the structure of the present invention in which only the support portion 12 is extended is effective.

  The support portion 12 may be manufactured by welding a member of the support portion 12 formed in a ring shape to the bottom plate 11 with a bolt or a bolt, or by machining from a forged body integrated with the bottom plate 11. . In addition, it is desirable to gradually reduce the diameter of the region where the outer diameter decreases from the bottom plate 11 to the support portion 12 by inclining the taper to prevent stress concentration. However, if there is no structural problem, the shape may be deformed at a substantially right angle.

  Next, FIG. 6 is a schematic view of an axial cross section of a radioactive substance transport / storage container 2 (container 2), which is a modification of the radioactive substance transport / storage container 1 (container 1) shown in FIG. .

  In addition, in the container 2 of the present modification, the same constituent members (30, 31, 32, 33, 34, 35a, 35b, 35c, 36, 36) as the constituent members of the container 1 according to the embodiment of the present invention described above. 37, 39, 40, 41, 43) are used as constituent members of the container 1 (10, 11, 12, 13, 14, 15a, 15b, 15c, 16, 17, 19, 20, 21, 23). Each of them is shown in order, and description of similar components is omitted.

  FIG. 6 shows an example in which the inner diameter of the support portion 32 provided at the bottom of the container 3 is smaller than the inner diameter of the inner body portion 30 and the outer diameter of the support portion 32 is larger than the outer diameter of the gamma ray shielding layer 40. is there. Note that the end surface position on the outer side (bottom surface side) of the bottom neutron shielding layer cover 34 is in a position recessed with respect to the position of the end surface 32 a of the support portion 32 as in the case of the container 1.

  By forming the shape of the support portion 32 in this way, the thickness of the support portion 32 is increased. Thereby, compared with the support part 12 of the container 1, the intensity | strength of a support part can be raised.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

  For example, in the above embodiment, ethylene propylene-based rubber is used as the neutron shielding material, but is not limited thereto, and any material containing a large amount of hydrogen may be used. For example, water, ethylene glycol water, paraffin Silicon rubber, epoxy resin, vinyl ester resin and the like may be used. Further, by including boron, cadmium, or the like in the neutron shielding layer, it is possible to absorb neutrons decelerated due to collision with hydrogen.

  Also, from the viewpoint of easily manufacturing the container, it is desirable that the inner body part, the outer body part, and the support part are cylindrical, and the bottom plate is circular, but these shapes are polygonal. It may be. For example, the inner body part and the outer body part are formed by machining a cylindrical member such as cutting and having a flat surface formed on the outer peripheral surface or inner peripheral surface thereof, that is, substantially cylindrical. It may be. Further, the support portion may have a polygonal shape such as a quadrangular shape.

It is the schematic which shows the axial direction cross section of the transport and storage container of the radioactive substance which concerns on one Embodiment of this invention. It is AA sectional drawing of the transport and storage container of the radioactive substance shown in FIG. It is the X section enlarged view of AA sectional drawing shown in FIG. It is a figure which shows the block body divided | segmented into multiple in both the circumferential direction and the axial direction. It is the schematic of the axial cross section which shows the state which attached the buffer to the transport and storage container of the radioactive substance shown in FIG. It is the schematic of the axial cross section of the radioactive substance transport and storage container which is a modification of the radioactive substance transport and storage container shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transporting and storage container 10 of a radioactive substance Inner trunk | drum 11 Bottom plate 12 Support part 13 Bottom neutron shielding layer 14 Bottom neutron shielding layer cover 19 Outer trunk 20 Gamma ray shielding layer 21 Neutron shielding layer 70 Heat good conductor 73, 74 Block body 91, 92, 92a block body

Claims (6)

A radioactive material transport and storage container provided with a gamma ray shielding layer and a neutron shielding layer between an inner trunk part and an outer trunk part,
A bottom plate fixed to one end surface of the inner body portion concentrically with the inner body portion, having an outer diameter larger than the inner diameter of the inner body portion and smaller than the outer diameter of the outer body portion;
A cylindrical support portion extending concentrically with the inner body portion from the bottom plate in a direction opposite to the inner body portion and having an outer diameter smaller than an outer diameter of the outer body portion at an outer end surface in the axial direction; A transport and storage container for radioactive material, comprising: Inside the support part, a plate-like bottom neutron shielding layer and a bottom neutron shielding layer cover having substantially the same diameter as the inner diameter of the support part are housed in this order from the bottom plate side,
The hydrogen content per unit volume of the bottom neutron shielding layer is greater than the hydrogen content of the bottom plate,
2. The radioactive substance transport / storage container according to claim 1, wherein an end face position on an outer side of the bottom neutron shielding layer cover in the axial direction is in a position recessed with respect to an end face position of the support portion. An inner diameter of the support portion is smaller than an outer diameter of the inner body portion;
3. The radioactive substance transport / storage container according to claim 1, wherein an outer diameter of the support portion is larger than an inner diameter of the gamma ray shielding layer.   At least one of the gamma ray shielding layer and the neutron shielding layer is formed of a block body divided into a plurality in the circumferential direction, and a good thermal conductor is sandwiched between the block bodies adjacent to each other in the circumferential direction. The radioactive substance transport and storage container according to any one of claims 1 to 3, wherein the container is a radioactive substance transport and storage container.   The block body is divided into a plurality of pieces in the axial direction, and the contact surfaces of the blocks adjacent to each other in the axial direction are formed on an inclined surface or an uneven surface in which the unevenness engages. 4. A transport and storage container for radioactive substances according to 4.   The radioactivity according to any one of claims 1 to 5, wherein the gamma ray shielding layer is made of any one material of lead, lead alloy, iron, carbon steel, and stainless steel. Material transport and storage container.

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