Buffers and radioactive material storage containers

Abstract

To improve the durability against thermal degradation and cushioning performance of the cushioning material. [Solution] The buffer body 41 is a buffer body 41 that protects a radioactive material storage container, and comprises a support member 42 provided on the outside of the radioactive material storage container, and a buffer material 43 that is arranged on the support member 42 and absorbs impact by deforming. The buffer material 43 comprises buffer-carrying metal buffer materials 43a, 43b and a main buffer material 43c, and the metal buffer materials 43a, 43b are arranged adjacent to the main buffer material 43c and extending with respect to the heat transfer direction D1 in the support member 42.

Description

Technical Field

[0001] The present disclosure relates to a shock absorber for a radioactive material storage container that stores and holds radioactive materials, and to a radioactive material storage container.

Background Art

[0002] In nuclear facilities, radioactive waste such as spent fuel generated in nuclear reactors and the like is stored in radioactive material storage containers, transported to storage facilities, reprocessing facilities and the like, and then stored or reprocessed. The radioactive material storage container is composed of a bottomed cylindrical body part with an open top, and a lid part fixed to the top of the body part to close the opening. A shock absorber is provided at the axial end of the radioactive material storage container. The shock absorber absorbs impact by deforming when the radioactive material storage container falls, tips over, or collides.

[0003] The shock absorber is configured by arranging a cushioning material inside a support member. Since the cushioning material may degrade over long-term use depending on the used material and usage environment, it is preferable to monitor the degradation state of the cushioning material. As a technique for monitoring the degradation state of a cushioning material, for example, there is one described in Patent Document 1 below.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Metal cushioning materials are resistant to thermal degradation and have excellent thermal conductivity, but their cushioning performance is lower than that of resin or wood. On the other hand, resin and wood cushioning materials are susceptible to thermal degradation and have low thermal conductivity, but their cushioning performance is higher than that of metal cushioning materials. Cushioning performance refers to the ability of a cushioning material to reduce impact force by converting impact energy into deformation energy (equal to the integral value in the load-displacement graph) when an impact force acts on it, by deforming (crushing) while generating a predetermined deformation load. In this case, if the deformation load of the cushioning material is too large, the impact force cannot be reduced, and if it is too small, sufficient deformation energy cannot be secured. Conventional cushioning materials require improvements in the durability against thermal degradation and cushioning performance of the cushioning material placed inside the support member.

[0006] This disclosure aims to solve the aforementioned problems and to provide a buffer and a radioactive material storage container that can improve the thermal degradation resistance and buffering performance of the buffer material. [Means for solving the problem]

[0007] The buffer according to this disclosure is a buffer for protecting a radioactive material storage container, comprising a support member provided on the outside of the radioactive material storage container, and a buffer material disposed on the support member and absorbing impact by deformation, wherein the buffer material comprises a metal buffer material and a main buffer material having buffering properties, and the metal buffer material is disposed adjacent to the main buffer material and extends in the direction of heat transfer in the support member.

[0008] A radioactive material storage container according to this disclosure comprises a body, a lid that seals the body, and a buffer that protects the body and the lid, wherein the buffer comprises a support member provided on the outside of the radioactive material storage container and a buffer material disposed on the support member that absorbs impact by deforming, the buffer material comprises a buffering metal buffer and a main buffer, the metal buffer is adjacent to the main buffer and is arranged extending in the direction of heat transfer in the support member. [Effects of the Invention]

[0009] The buffer and radioactive material storage container of this disclosure can improve the thermal degradation resistance and buffering performance of the buffer material. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view showing a section of a radioactive material containment container that has been fractured. [Figure 2] Figure 2 is a plan view showing a radioactive material storage container fitted with a buffer according to the embodiment. [Figure 3] Figure 3 is a front view showing a radioactive material storage container with a buffer installed in a vertical position. [Figure 4] Figure 4 is a front view showing a radioactive material storage container with a buffer installed in a horizontal position. [Figure 5] Figure 5 is a schematic cross-sectional view showing the internal structure of the cushioning material according to the first embodiment. [Figure 6] Figure 6 is an enlarged schematic diagram illustrating the buffer in the part shown in Figure 2. [Figure 7] Figure 7 is a schematic partial cross-sectional view of the AA section shown in Figure 6. [Figure 8] Figure 8 is a schematic cross-sectional view showing the internal structure of the cushioning material according to the second embodiment. [Figure 9] Figure 9 is a schematic cross-sectional view showing the internal structure of the cushioning material according to the third embodiment. [Figure 10] Figure 10 is a schematic cross-sectional view showing the internal structure of a cushioning material according to a modified example of the first embodiment. [Figure 11] Figure 11 is a schematic cross-sectional view showing the internal structure of a cushioning material according to another modification of the first embodiment. [Figure 12] Figure 12 is an enlarged schematic diagram illustrating the other components of the buffer in the part shown in Figure 2. [Modes for carrying out the invention]

[0011] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited by these embodiments, and when there are a plurality of embodiments, configurations formed by combining the respective embodiments are also included. In addition, the constituent elements in the embodiments include those that can be easily assumed by those skilled in the art, those that are substantially identical, and those within the so-called equivalent scope.

[0012] [Background of the Invention] A cask serving as a radioactive material storage container is required to have a buffering function, and wood or foamed resin with excellent compressive strength is used as the cushioning material of the buffer. The cask needs to maintain long-term integrity. The present embodiment provides a buffer and a radioactive material storage container that can improve the durability performance against thermal deterioration and the buffering performance of the cushioning material.

[0013] [First Embodiment] <Radioactive Material Storage Container> Figure 1 is a partially cutaway perspective view of the radioactive material storage container.

[0014] As shown in Figure 1, a cask 11 serving as a radioactive material storage container includes a cask main body 12 that is a body portion, and a lid portion 13. The cask main body 12 has a main body cylinder 21. The main body cylinder 21 has a cylindrical shape (a circular cylindrical shape in the present embodiment), an opening 22 is formed at the upper end, and the lower end is closed. The main body cylinder 21 has a cavity 23 inside, and a basket 24 is provided in the cavity 23. The basket 24 is provided with a plurality of cells 25 capable of independently storing radioactive materials (for example, spent fuel assemblies). The main body cylinder 21 is a forged product made of carbon steel having a gamma ray shielding function, but stainless steel can also be used instead of carbon steel. In addition, the main body cylinder 21 may also use a cast product such as spheroidal graphite cast iron or carbon steel cast steel.

[0015] In the cask main body 12, an outer cylinder 26 is arranged on the outer peripheral surface of the main body barrel 21 with a predetermined gap therebetween. In the main body barrel 27, a plurality of copper heat transfer fins 27 for conducting heat transfer are provided in the circumferential direction between the outer peripheral surface and the inner peripheral surface of the outer cylinder 26. In the space surrounded by the outer cylinder 26 and the heat transfer fins 27 of the main body barrel 21, a resin (neutron shield) 28 which is a polymer material containing a large amount of hydrogen and containing boron or a boron compound having a neutron shielding function is provided.

[0016] The cask main body 12 is provided with a bottom portion 29 protruding downward from the closed lower end of the main body barrel 21. The bottom portion 29 has a space surrounded by the closed lower end of the main body barrel 21, and a resin (neutron shield) is provided in the space.

[0017] The cask main body 12 is provided with trunnions 30 for lifting the cask 11 on the main body barrel 21. The trunnions 30 are provided to penetrate from the main body barrel 21 through the outer cylinder 26, and protrude to the outermost periphery of the cask 11.

[0018] The lid part 13 is provided at the opening 22 of the main body barrel 21, closes the opening 22, and hermetically seals the main body barrel 21 (the cask main body 12). The lid part 13 is configured to include a primary lid 31 and a secondary lid 32. The primary lid 31 is formed in a disk shape using carbon steel or stainless steel that shields γ-rays as a material. The secondary lid 32 covers the primary lid 31 and is exposed to the outside of the cask 11, and similarly to the primary lid 31, is formed in a disk shape using carbon steel or stainless steel that shields γ-rays as a material. A resin (neutron shield) 28 may be provided between the primary lid 31 and the secondary lid 32. In addition, a tertiary lid or an adapter may be provided on the lid part in some cases.

[0019] The primary cover 31 is attached to the main body 21 by being fixed to the first stage portion 22a formed in the opening 22 of the main body 21 with bolts (not shown) made of carbon steel or stainless steel. The secondary cover 32 is attached to the main body 21 by being fixed to the second stage portion 22b formed in the opening 22 of the main body 21 with bolts (not shown) made of carbon steel or stainless steel. Although not shown, metal gaskets are provided between the primary cover 31 and the first stage portion 22a and between the secondary cover 32 and the second stage portion 22b. The metal gaskets ensure airtightness between the primary cover 31 and the first stage portion 22a and between the secondary cover 32 and the second stage portion 22b.

[0020] The cask body 12 surrounds the secondary lid 32 at the opening 22 of the main body 21, forming a cylindrical upper edge 22c that is visible on the outside of the cask 11. The upper edge 22c has its upper surface higher than the surface of the secondary lid 32 and surrounds the secondary lid 32. Multiple bolt holes 33 for attaching the buffer A, which will be described later, are provided on the upper surface of the upper edge 22c at intervals in the circumferential direction.

[0021] <Buffer> Figure 2 is a plan view showing a radioactive material storage container fitted with a buffer according to the embodiment. Figure 3 is a front view showing the radioactive material storage container fitted with a buffer in a vertical position. Figure 4 is a front view showing the radioactive material storage container fitted with a buffer in a horizontal position.

[0022] As shown in Figures 2 to 4, the cask 11, which serves as a container for radioactive material, is equipped with a buffer 41. The buffer 41 is attached to the cask 11 when it is transported to a storage facility, which is a storage location.

[0023] In a nuclear power plant, for example, spent fuel assemblies are stored in the cells 25 of the basket 24 of the main body shell 21 of the cask 11, and sealed by the lid 13. The cask 11 is transported, for example, from the nuclear power plant to a storage facility. A transport buffer (not shown) is attached to the cask 11 during transport. The cask 11 may also be transported with a storage buffer attached. Once transported to the storage facility, the transport buffer is removed from the cask 11, and it is stored upright on the floor F with the lid 13 facing upwards, and a buffer 41 is attached to the lid 13 side. Alternatively, during storage, the cask 11 is fitted into a frame 37 installed on the floor F by its bottom 29, or fixed to a frame by securing the trunnion, and stored in a vertical position with its central axis O aligned vertically. The cask 11 may also be stored horizontally with buffers attached to both ends.

[0024] The buffer body 41 includes a support member 42 and a cushioning material 43.

[0025] The support member 42 has a disc portion 51 and a cylindrical portion 52. The cylindrical portion 52 is integrally provided on the radially outer side of the disc portion 51. The support member 42 is made of a metal plate such as a steel plate and has a hollow shape, and is deformable by a predetermined load. The predetermined load is the load of a falling object or the load that is applied to the cask 11 when it hits the floor F if the cask 11, which is standing upright on the floor F, falls over. The support member 42 may also fall, for example, when it falls during transport, when it is dropped during handling when stored horizontally, or when it falls due to an earthquake. The disc portion 51 is positioned above the lid portion 13 of the cask 11 and along the surface of the secondary lid 32 that is exposed on the outside of the lid portion 13. The disc portion 51 is positioned to cover the surface of the secondary lid 32 and the surface of the upper edge 22c of the main body 21. The disc portion 51 is fixed to the main body 21 by bolts (not shown) attached to bolt holes 33 provided in the upper edge 22c. If a tertiary cover is provided as a lid, the disc portion 51 is positioned along the surface of the tertiary cover that is visible on the outside of the lid portion 13, and is positioned to cover the surface of the tertiary cover and the surface of the upper edge 22c of the main body 21.

[0026] The cylindrical portion 52 is positioned to surround the outside of the upper edge 22c of the cask body 12. That is, the cylindrical portion 52 is positioned radially outward from the lid portion 13 and protrudes radially outward from the cask body 12.

[0027] The cushioning material 43 is placed inside and supported by the support member 42. The cushioning material 43 deforms under a predetermined load. Because metal cushioning materials have high strength, the deformation load becomes large and they cannot reduce the impact force. Resin or wood cushioning materials can deform under a deformation load suitable for the cask. In this embodiment, the cushioning material 43 is constructed by combining wood, a porous material, a foamed material or polymer compound with a metal member.

[0028] As shown in Figure 4, the cask 11 may also be stored in a horizontal position with its central axis O aligned horizontally. The cask 11 is stored horizontally with its central axis O aligned horizontally, with the cask body 12 fitted onto a stand 38 installed on the floor F. In this case, a buffer 41 is attached to one side of the cask 11 along the central axis O (the lid 13 side), and a buffer 46 is attached to the other side along the central axis O (the bottom 29 side). In this embodiment, the buffer 46 is described as having a configuration almost the same as the buffer 41, but for example, if the structure of one side and the other side of the cask 11 are different, the buffer 46 will have a structure corresponding to that structure.

[0029] <Internal structure of the buffer> Figure 5 is a schematic cross-sectional view showing the internal structure of the cushioning material according to the first embodiment. In this embodiment, one direction in the horizontal plane in the plan view is defined as the X-axis direction, and the direction perpendicular to the X-axis direction is defined as the Y-axis direction.

[0030] As shown in Figure 5, the buffer body 41 has a support member 42 and a buffer material 43, with the buffer material 43 being arranged inside the hollow support member 42. The buffer material 43 comprises a metal buffer material 43a and a metal buffer material 43b and a main buffer material 43c, which are combined to form the buffer body 41.

[0031] The metal cushioning material 43a and the metal cushioning material 43b are components that improve the heat transfer performance of the buffer body 41. The metal cushioning material 43a and the metal cushioning material 43b are formed from metal members that have cushioning properties. Metal members that have cushioning properties include, for example, low-density metals such as aluminum, and metals that have been processed to have fragile structures such as holes and grooves. The metal cushioning material 43a is a cushioning material 43 that comes into contact with the end portion 11a of the cask 11. The metal cushioning material 43b is formed in the shape of a ring with a diameter smaller than the diameter of the disc portion 51 of the support member 42. The main cushioning material 43c is formed by combining blocks of resin or wood to fill the space between the metal cushioning material 43a and the metal cushioning material 43b.

[0032] The metal cushioning materials 43a and 43b are arranged adjacent to the main cushioning material 43c and extend in the direction of heat transfer D1 in the support member 42. For example, in the buffer body 41, if the temperature around the lid portion 13 of the cask 11 is high and the temperature near the outer circumference of the support member 42 is low, the heat transfer direction D1 is the direction in which heat from the cask 11 is transferred inside the support member 42. The heat transfer direction D1 includes the direction from the central axis O of the cask 11 toward the disc portion 51 and cylindrical portion 52 of the support member 42, the direction toward the disc portion 51 along the central axis O, and so on. In this embodiment, the metal cushioning materials 43a and 43b are arranged inside the support member 42 alongside the main cushioning material 43c.

[0033] The metal cushioning material 43a is formed in a ring shape with a diameter smaller than the diameter of the disc portion 51 of the support member 42. The metal cushioning material 43a is positioned at the axial end of the cask 11. The metal cushioning material 43a is provided along the cylindrical portion 52 of the support member 42, at a position away from the cylindrical portion 52. Part of the metal cushioning material 43a is exposed on the side where the cask 11 is attached, and the other part is exposed to the outside of the support member 42. The metal cushioning material 43a is positioned inside the buffer body 41 such that one end 43a1 is in contact with the end 11a of the cask 11.

[0034] The metal cushioning material 43b is formed in a ring shape with a diameter smaller than the diameter of the disc portion 51 of the support member 42. The metal cushioning material 43b is positioned at the axial end of the cask 11. The metal cushioning material 43b is provided along the disc portion 51 at a position where its outer circumference contacts the cylindrical portion 52 of the support member 42. Part of the metal cushioning material 43b is exposed on the side where the cask 11 is attached, and the other part is exposed on the outside of the support member 42. The metal cushioning material 43b is positioned inside the cushioning body 41 along the bottom of the support member 42 such that its inner end 43b1 contacts the circumferential surface portion 11b of the cask 11 when attached.

[0035] In this embodiment, one end 43a1 of the metal cushioning material 43a and the inner end 43b1 of the metal cushioning material 43b are exposed from the support member 42, but the embodiment is not limited to this. For example, one end 43a1 of the metal cushioning material 43a and the inner end 43b1 of the main cushioning material 43c may be configured to not be exposed from the support member 42, but to indirectly contact the cask 11 through the support member 42. Also, although the metal cushioning materials 43a and 43b are formed in a ring shape, they may be formed in a plate shape or cylindrical shape, for example, and placed inside the support member 42.

[0036] The main cushioning material 43c is composed of blocks incorporated into the ring-shaped space between the metal cushioning material 43a and the metal cushioning material 43b inside the support member 42. The main cushioning material 43c is composed of blocks incorporated into the space inside the metal cushioning material 43a inside the support member 42. The materials constituting the main cushioning material 43c may be a combination of materials with different compressive strengths, or a configuration using only materials with high compressive strength. Furthermore, the main cushioning material 43c is not limited to blocks of wood. For example, the main cushioning material 43c may be made of materials other than wood, such as foamed material, porous material, or polymer compound.

[0037] In this embodiment, the buffer body 41 is designed based on a temperature map obtained by measuring or simulating the internal temperature of the support member 42, and the arrangement and ratio of the metal buffer material 43a and metal buffer material 43b and the main buffer material 43c within the support member 42 are designed accordingly. For example, in areas where the internal temperature of the support member 42 tends to be high, the buffer body 41 is designed so that the proportion of metal buffer material 43a and metal buffer material 43b within the support member 42 is large. For example, the buffer body 41 is designed so that the metal buffer material 43a and metal buffer material 43b within the support member 42 are located in areas where the internal temperature of the support member 42 tends to be low. For example, in areas where the internal temperature of the support member 42 tends to be low, the buffer body 41 is designed so that the proportion of metal buffer material 43a and metal buffer material 43b within the support member 42 is small.

[0038] The buffer body 46 has a support member 42 and a buffer material 43, with the buffer material 43 being arranged inside the hollow support member 42. The buffer material 43 comprises a metal buffer material 46a and a metal buffer material 46b, and a main buffer material 46c, which are combined to form the buffer body 46. The metal buffer material 46a and the metal buffer material 46b are the same components as the metal buffer material 43a and the metal buffer material 43b of the buffer material 43 described above, and are components that improve the heat transfer performance of the buffer body 46. The main buffer material 46c is the same component as the main buffer material 43c of the buffer material 43 described above, and is composed of a block incorporated into the ring-shaped space between the metal buffer material 46a and the metal buffer material 46b inside the support member 42. The main buffer material 46c is composed of a block incorporated into the space inside the metal buffer material 46a inside the support member 42.

[0039] Figure 6 is an enlarged schematic diagram illustrating the buffer body of section P in Figure 2. Figure 7 is a schematic partial cross-sectional view of section AA shown in Figure 6. As shown in Figures 6 and 7, the metal buffer material 43a has a plurality of through holes 44 that pass through fixing members 45 that fix the support member 42 to the cask 11. The fixing members 45 include, for example, bolts. The metal buffer material 43a has through holes 44 formed at positions corresponding to the bolt holes 33 of the cask 11, and the buffer body 41 is fixed to the main body 21 by fixing members 45 attached to the through holes 44. The plurality of through holes 44 are formed in the buffer body 41 at predetermined intervals along the metal buffer material 43a. By forming a plurality of through holes 44 in the metal buffer material 43a, the buffer body 41 has improved the strength of its fixation to the cask 11 compared to having them in the main buffer material 43c. The region of the cask 11 with the through-hole 44 is a region that can easily support the reaction force of the buffer 41, and a metal buffer that is prone to large compressive loads can be provided in this region.

[0040] In the first embodiment, the buffers 41 and 46 are attached to the cask 11 such that the end portion 11a of the cask 11 is incorporated inside the cylindrical portion 52 of the support member 42. More specifically, the buffers 41 and 46 are fixed to the cask 11 by a fixing member 45 through a through hole 44 in the metal buffer material 43a.

[0041] <The function of buffers> With the buffers 41 and 46 attached to the cask 11, heat is transferred from the lid 13 of the cask 11 to the metal buffers 43a, 46a and 43b, 46b. The heat transferred from the cask 11 to the metal buffers 43a, 46a is then transferred to the disc portion 51 of the support member 42, and the heat transferred from the cask 11 to the metal buffers 43b, 46b is then transferred to the cylindrical portion 52 of the support member 42. As a result, the buffer 41 can dissipate heat from the cask 11 through the metal buffers 43a, 46a and 43b, 46b, thereby suppressing the transfer of heat from the cask 11 to the main buffers 43c, 46c, and efficiently cooling the cask 11. The buffers 41 and 46 suppress the thermal degradation of the cushioning material 43, thereby deforming the main cushioning material 43c and 46c inside the support member 42 when the cask 11 is dropped, tipped over, or hits something. As a result, the buffers 41 and 46 can suppress the thermal degradation of the main cushioning material 43c and 46c, thereby improving the thermal degradation resistance and cushioning performance of the cushioning material 43.

[0042] [Second Embodiment] Next, a second embodiment will be described. In the second embodiment, the configuration of the buffer 41 differs from that of the first embodiment. The buffer 41 in the second embodiment has the same configuration as the buffer 41 in the first embodiment, but the arrangement of the metal is changed when the maximum temperature of the main buffer material 43c exceeds the allowable value, etc. Note that in the second embodiment, parts that are common to the configuration of the first embodiment will not be described.

[0043] <Internal structure of the buffer> Figure 8 is a schematic cross-sectional view showing the internal structure of the cushioning material according to the second embodiment.

[0044] As shown in Figure 8, the buffer body 41 has a support member 42 and a buffer material 43, with the buffer material 43 being arranged inside the hollow support member 42. The support member 42 has a disc portion 51 and a cylindrical portion 52. The buffer material 43 is arranged and supported inside the support member 42. The buffer material 43 deforms under a predetermined load. The buffer material 43 is composed of a combination of a metal buffer material 43d and a main buffer material 43e. The metal buffer material 43d is arranged between the support member 42 and the main buffer material 43e. The buffer body 41 is arranged so that the metal buffer material 43d and the main buffer material 43e move away from the cask 11 in the direction of the central axis O of the cask 11.

[0045] The metal buffer material 43d is a component that improves the heat transfer performance of the buffer body 41. The metal buffer material 43d is made of a metal component with cushioning properties and is deformable by the predetermined load described above. The metal buffer material 43d has a cylindrical portion 43d2 integrally formed on the radially outer side of the disc portion 43d1. The metal buffer material 43d has a hollow shape and is provided inside the support member 42. Note that the metal buffer material 43d and the cylindrical portion 43d2 may be formed as separate components.

[0046] The disc portion 43d1 is positioned above the lid portion 13 of the cask 11, along the surfaces of the secondary lid 32 and tertiary lid that are visible on the outside of the lid portion 13. The disc portion 43d1 is positioned to cover the surface of the secondary lid 32 and the surface of the upper edge 22c of the main body 21. The disc portion 43d1 is fixed to the main body 21 by bolts (not shown) that are attached to bolt holes 33 provided in the upper edge 22c.

[0047] The cylindrical portion 43d2 is positioned to surround the outside of the circumferential portion 11b of the cask 11. For example, the cylindrical portion 43d2 may be positioned radially outward from the lid portion 13 and may protrude radially outward from the cask body 12.

[0048] The main cushioning material 43e is positioned on the outside of the support member 42 where the temperature is lower, thereby lowering the temperature of the component with a strict temperature limit. The main cushioning material 43e is composed of blocks incorporated into the ring-shaped space between the metal cushioning material 43d and the support member 42 within the support member 42. The materials constituting the main cushioning material 43e may be a combination of materials with different compressive strengths, similar to the main cushioning material 43c described above, or it may be a configuration using only materials with high compressive strength. Furthermore, the main cushioning material 43e is not limited to blocks of wood. For example, the main cushioning material 43e may be made of materials other than wood, such as foamed material, porous material, or polymer compound.

[0049] The main cushioning material 43e has a cylindrical portion 43e2 integrally formed on the radially outer side of the disc portion 43e1. The main cushioning material 43e is configured to have a metal cushioning material 43d placed adjacent to it inside the cylindrical portion 43e2. Note that the main cushioning material 43e and the cylindrical portion 43e2 may be formed as separate components.

[0050] The buffer body 46 has a support member 42 and a buffer material 43, with the buffer material 43 being placed inside the hollow support member 42. The buffer material 43 comprises a metal buffer material 46d and a main buffer material 46e, which are combined to form the buffer body 46. The metal buffer material 46d is a component similar to the metal buffer material 43d of the buffer material 43 described above, and is a component that improves the heat transfer performance of the buffer body 46. The main buffer material 46e is a component similar to the main buffer material 43e of the buffer material 43 described above, and is composed of a block incorporated inside the support member 42.

[0051] In the second embodiment, the buffers 41 and 46 are configured such that metal buffers 43d and 46d are incorporated into the cylindrical portions 43e2 and 46e2 of the main buffers 43e and 46e. The buffers 41 and 46 are then attached to the cask 11 such that the ends 11a of the cask 11 are incorporated into the cylindrical portions 43d2 and 46d2 of the metal buffers 43d and 46d. In detail, the buffers 41 and 46 are fixed to the cask 11 by fixing members 45 through through holes (not shown) in the metal buffers 43d and 46d, similar to the first embodiment.

[0052] <The function of buffers> With the buffers 41 and 46 attached to the cask 11, heat is transferred from the lid 13 of the cask 11 to the metal buffers 43d and 46d. Buffer 41 lowers the maximum temperature of the main buffers 43e and 46e by positioning the metal buffers 43d and 46d in an area close to the cask 11. Buffers 41 and 46 can reduce the maximum temperature region through heat conduction within the metal buffers 43d and 46d, thereby lowering the maximum temperature. By positioning the metal buffers 43d and 46d, buffers 41 and 46 can reduce the thickness of the main buffers 43e and 46e required for a given buffering performance, thus making heat dissipation easier and lowering the temperature of buffers 41 and 46. As a result, buffers 41 and 46 can dissipate or absorb heat from the cask 11 using the metal buffers 43d and 46d, thus suppressing the transfer of heat from the cask 11 to the main buffers 43e and 46e. The buffer body 41 suppresses the thermal degradation of the cushioning material 43, thereby deforming the main cushioning materials 43e and 46e inside the support member 42 when the cask 11 is dropped, tipped over, or hits something. As a result, the buffer bodies 41 and 46 can suppress the thermal degradation of the main cushioning materials 43e and 46e, thereby improving the thermal degradation resistance and cushioning performance of the cushioning material 43.

[0053] [Third Embodiment] Next, a third embodiment will be described. In the third embodiment, the configuration of the buffer body 41 is a combination of the configurations of the first and second embodiments. The buffer body 41 according to the third embodiment has the same configuration as the buffer body 41 according to the second embodiment, but the arrangement of the metal is changed when the maximum temperature of the main buffer material 43e exceeds the permissible value, etc. In the third embodiment, parts that are common to the configuration of the first and second embodiments will not be described.

[0054] <Internal structure of the buffer> Figure 9 is a schematic cross-sectional view showing the internal structure of the cushioning material according to the third embodiment.

[0055] As shown in Figure 9, the buffer body 41 has a support member 42 and a buffer material 43, with the buffer material 43 being placed inside the hollow support member 42. The support member 42 has a disc portion 51 and a cylindrical portion 52. The buffer material 43 is placed inside the support member 42 and supported. The buffer material 43 deforms under a predetermined load. The buffer material 43 is composed of a combination of metal buffer material 43a, metal buffer material 43b, metal buffer material 43d, and main buffer material 43c.

[0056] The metal cushioning materials 43a, 43b, and 43d are components that improve the heat transfer performance of the buffer body 41. The metal cushioning materials 43a, 43b, and 43d are formed from metal components that have cushioning properties. The metal cushioning materials 43a, 43b, and 43d may be formed integrally or individually. The metal cushioning material 43a is arranged to be in contact with the metal cushioning material 43d. The metal cushioning material 43b is formed in a ring shape with an inner diameter smaller than the diameter of the disc portion 51 of the support member 42 and larger than the outer diameter of the metal cushioning material 43d. The metal cushioning material 43d has a disc portion 43d1 with a diameter larger than the outer diameter of the metal cushioning material 43a, and a cylindrical portion 43d2 is integrally formed on the radially outer side of the disc portion 43d1. The metal cushioning material 43d has a hollow shape and is provided inside the support member 42.

[0057] The main cushioning material 43c is composed of a block incorporated into a ring-shaped space surrounded by metal cushioning material 43a, metal cushioning material 43b, and metal cushioning material 43d within the support member 42. The main cushioning material 43c is composed of a block incorporated into a space surrounded by metal cushioning material 43a and metal cushioning material 43d within the support member 42. The materials constituting the main cushioning material 43c may be a combination of materials with different compressive strengths, or a configuration using only materials with high compressive strengths may be used.

[0058] The buffer body 46 has a support member 42 and a buffer material 43, with the buffer material 43 being arranged inside the hollow support member 42. The buffer material 43 is composed of a combination of metal buffer material 46a, metal buffer material 46b, metal buffer material 46d and main buffer material 46c. Metal buffer material 46a, metal buffer material 46b, and metal buffer material 46d are the same components as metal buffer material 43a, metal buffer material 43b, and metal buffer material 43d of the buffer material 43 described above, and are components that improve the heat transfer performance of the buffer body 46. The main buffer material 46c is the same component as the main buffer material 43c of the buffer material 43 described above, and is composed of a block incorporated into the ring-shaped space between metal buffer material 46a, metal buffer material 46b, and metal buffer material 46d inside the support member 42. The main buffer material 46c is composed of a block incorporated into the space inside metal buffer material 46a inside the support member 42.

[0059] In the third embodiment, the buffers 41 and 46 are attached to the cask 11 such that the end portion 11a of the cask 11 is incorporated into the cylindrical portion 52 of the support member 42. More specifically, the buffers 41 and 46 are fixed to the cask 11 by a fixing member 45 through through holes 44 in the metal buffer materials 43a and 46a.

[0060] <The function of buffers> With the buffers 41 and 46 attached to the cask 11, heat is transferred from the lid 13 of the cask 11 to the metal buffers 43d and 46d, and then from the metal buffers 43d and 46d to the metal buffers 43a, 46a and 43b and 46b. The heat transferred from the cask 11 to the metal buffer 43d is then transferred to the disc portion 51 and cylindrical portion 52 of the support member 42. As a result, the buffers 41 and 46 can dissipate heat from the cask 11 through the metal buffers 43a, 46a, 43b, 46b, and 43d, 46d, thereby suppressing the transfer of heat from the cask 11 to the main buffers 43c and 46c. The buffers 41 and 46 suppress the thermal degradation of the cushioning material 43, thereby allowing the cushioning material 43 inside the support member 42 to deform when the cask 11 is dropped, tipped over, or hits something. As a result, the buffers 41 and 46 can suppress the thermal degradation of the main cushioning materials 43c and 46c, thereby improving the thermal degradation resistance and cushioning performance of the cushioning material 43.

[0061] [Modified examples of embodiments] Next, modifications of the embodiment will be described. Figure 10 is a schematic cross-sectional view showing the internal structure of the cushioning material according to a modification of the first embodiment. Figure 11 is a schematic cross-sectional view showing the internal structure of the cushioning material according to another modification of the first embodiment. In Figures 10 and 11, for the sake of simplicity, only the cushioning material 43 is shown in the cushioning body 41, and the support member 42 is omitted.

[0062] As shown in Figure 10, the buffers 41 and 46 each have a support member 42 and a buffer material 43, with the buffer material 43 being placed inside the hollow support member 42. The buffer material 43 is composed of a combination of metal buffer materials 43a', 46a' and metal buffer materials 43b', 46b' and main buffer materials 43c, 46c.

[0063] The metal cushioning materials 43a', 46a' and 43b', 46b' are components that improve the heat transfer performance of the buffer body 41. The metal cushioning materials 43a', 46a' and 43b', 46b' are formed from metal members with cushioning properties, similar to the metal cushioning materials 43a, 46a and 43b, 46b described above. The metal cushioning materials 43a', 46a' and 43b', 46b' are shorter in length than the metal cushioning materials 43a, 46a and 43b, 46b in the X-axis and Y-axis directions. The metal cushioning materials 43a', 46a' and 43b', 46b' are formed to a length such that one end contacts the cask 11, and the other end does not reach the disc portion 51 and cylindrical portion 52 of the support member 42.

[0064] As a result, the buffers 41 and 46 reduce the area in which the metal buffers 43a', 46a' and 43b', 46b' are arranged inside the support member 42, and the proportion of the main buffers 43c, 46c increases, so that the buffers 43 inside the support member 42 can be reliably deformed. Consequently, the buffer 41 can lower its temperature because heat is uniformly transferred through thermal conduction inside the metal buffers 43a', 46a' and 43b', 46b', thus suppressing thermal degradation of the main buffers 43c, 46c, and improving the thermal degradation resistance and buffering performance of the buffer 43.

[0065] As shown in Figure 11, the buffer body 41 has a support member 42 and a buffer material 43. The buffer body 41 has the buffer material 43 arranged inside the hollow support member 42. The buffer material 43 is composed of a combination of metal buffer materials 43a'', 46a'', and metal buffer materials 43b, 46b, and main buffer materials 43c, 46c.

[0066] The metal buffers 43a'', 46a'', similar to the metal buffers 43b and 46b, are components that improve the heat transfer performance of the buffer body 41. The metal buffers 43a'', 46a'', are formed from a metal component with buffering properties. The metal buffers 43a'', 46a'', have a longer width in the Y-axis direction than the metal buffers 43a and 46a described above. The metal buffers 43a'', 46a'', are formed to a length such that one end contacts the cask 11 and the other end contacts the disc portion 51 of the support member 42.

[0067] As a result, the buffers 41 and 46 increase the area in which the metal buffers 43a'', 46a'', are arranged inside the support member 42, allowing heat from the cask 11 to be quickly transferred to the disc portion 51 of the support member 42. Consequently, the buffers 41 and 46 can suppress the thermal degradation of the main buffers 43c, 46c, thereby improving the thermal degradation resistance and buffering performance of the buffer 43.

[0068] Figure 12 is an enlarged schematic diagram illustrating the other configurations of the buffer in part P of Figure 2. As shown in Figure 12, the metal buffer material 43a has a plurality of notches 43a2, and a through hole 44 is formed in each of the plurality of notches 43a2 that penetrates the fixing member 45. As a result, the metal buffer material 43a does not overlap with the area of ​​the fixing member 45, eliminating the need to form through holes 44 and thus reducing weight.

[0069] In the embodiment described above, the buffer body 41, 46 was described as having a buffer material 43 inside the support member 42, but it is not limited to this. For example, the buffer body 41 may have a buffer material 43 provided outside the support member 42, or the buffer material 43 may be provided both inside and outside the support member 42.

[0070] <Effects> A buffer 41 according to a first aspect of this disclosure is a buffer 41 for protecting a radioactive material storage container, comprising a support member 42 provided on the outside of the radioactive material storage container, and a buffer material 43 arranged on the support member 42 and absorbing impact by deforming. The buffer material 43 comprises buffering metal buffer materials 43a, 43b and a main buffer material 43c, the metal buffer materials 43a, 43b are adjacent to the main buffer material 43c and are arranged extending with respect to the heat transfer direction D1 in the support member 42. As a result, the buffer 41 can dissipate heat from the radioactive material storage container with the metal buffer materials 43a, 43b, thereby suppressing the transfer of heat from the radioactive material storage container to the main buffer material 43c. By suppressing the thermal degradation of the buffer material 43, the buffer 41 can deform the main buffer material 43c inside the support member 42 when the radioactive material storage container is dropped, toppled over, or hit. As a result, the buffer 41 can suppress the thermal degradation of the main buffer material 43c, thereby improving the thermal degradation resistance and buffering performance of the buffer material 43. Furthermore, the buffer 41 can contribute to maintaining the long-term integrity of the radioactive material storage container.

[0071] In the buffer body 41 according to the second aspect of this disclosure, a portion of the metal buffer materials 43a and 43b is exposed on the side where it is attached to the radioactive material storage container, and the other portion is exposed on the outside of the support member 42. As a result, the buffer body 41 can efficiently dissipate heat from the radioactive material storage container to the outside via the metal buffer materials 43a and 43b. Consequently, the buffer body 41 can further suppress the thermal degradation of the main buffer material 43c, thereby improving the thermal degradation resistance and buffering performance of the buffer material 43.

[0072] In the buffer 41 according to the third aspect of this disclosure, the metal buffer materials 43a and 43b are formed in a ring shape and are positioned at the axial end of the radioactive material storage container. This increases the surface area of ​​the buffer 41 that is in close proximity to the radioactive material storage container, allowing heat from the material storage container to be dissipated to the outside more efficiently through the metal buffer materials 43a and 43b.

[0073] In the buffer body 41 according to the fourth aspect of this disclosure, the metal buffer materials 43a and 43b have a plurality of through holes 44 that penetrate the fixing member 45 that fixes the support member 42 to the radioactive material storage container. As a result, by forming a plurality of through holes 44 in the metal buffer material 43a, the buffer body 41 can improve the strength of its fixation to the cask 11 compared to having them in the main buffer material 43c.

[0074] In the buffer 41 according to the fifth aspect of this disclosure, the buffer material 43 has a plurality of metal buffer materials 43a, 43b, and 43d that are arranged extending in the heat transfer direction D1. As a result, the buffer 41 can more efficiently dissipate heat from the material storage container to the outside through the plurality of metal buffer materials 43a, 43b, and 43d.

[0075] In the buffer body 41 according to the sixth aspect of this disclosure, the metal buffer material 43d is placed between the support member 42 and the main buffer material 43e. As a result, the buffer body 41 disperses heat from the radioactive material storage container with the metal buffer material 43d, thereby suppressing the transfer of heat to the main buffer material 43e.

[0076] A radioactive material storage container according to a seventh aspect of this disclosure comprises a cask body 12 which is the body of the container, a lid 13 which seals the cask body 12, and a buffer 41 which protects the cask body 12 and the lid 13. The buffer 41 comprises a support member 42 provided on the outside of the radioactive material storage container and a buffer material 43 which is disposed inside the support member 42 and absorbs shock by deforming. The buffer material 43 comprises buffering metal buffer materials 43a, 43b and a main buffer material 43c, the metal buffer materials 43a, 43b are adjacent to the main buffer material 43c and are arranged to extend with respect to the heat transfer direction D1 in the support member 42. As a result, the radioactive material storage container can suppress the transfer of heat from the radioactive material storage container to the main buffer material 43c of the buffer 41 because the buffer 41 can dissipate heat from the radioactive material storage container through the metal buffer materials 43a, 43b. The radioactive material storage container can deform the main buffer material 43c inside the support member 42 when the radioactive material storage container is dropped, toppled over, or hit by an impact by suppressing the thermal degradation of the buffer material 43c of the buffer body 41. As a result, the radioactive material storage container can suppress the thermal degradation of the main buffer material 43c of the buffer body 41, thereby improving the thermal degradation resistance and buffering performance of the buffer material 43. Furthermore, by improving the thermal degradation resistance and buffering performance of the buffer material 43, the radioactive material storage container can maintain its long-term integrity.

[0077] Although embodiments of the present disclosure have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above. [Explanation of Symbols]

[0078] 11. Cask (container for radioactive materials) 12 Cask body 13 Lid 21 Main body 22 Opening 31 Primary lid 32 Secondary lid 33 bolt holes 41,46 Buffer 42 Support member 43 Cushioning material 43a,43a',43a'',43b,43b',43d Metal cushioning material 43a1 One end 43a2 Notch 43c,43e Main buffer material 43d1, 43e1, 51 Disc section 43d2, 43e2, 52 Cylindrical section 44 Through holes 45 Fixing member 46a,46a',46a'',46b,46b',46d Metal buffer material 46c,46e Main buffer material 46d2, 46e2 Cylindrical section D1 Heat transfer direction O center axis

Claims

1. A buffer that protects a container for radioactive materials, A support member provided on the outside of the aforementioned radioactive material storage container, A cushioning material is placed on the support member and deforms to absorb impact, Equipped with, The cushioning material comprises a metal cushioning material and a main cushioning material that have cushioning properties. The aforementioned metal buffer is a buffer body positioned adjacent to the main buffer and extending in the direction of heat transfer in the support member.

2. The metal buffer material is partially exposed on the side where it is attached to the radioactive material storage container, and the other part is exposed on the outside of the support member. The buffer according to claim 1.

3. The metal buffer material is formed in a ring shape and is positioned at the axial end of the radioactive material storage container. The buffer according to claim 2.

4. The metal buffer material has a plurality of through holes formed therein that penetrate the fixing member that fixes the support member to the radioactive material storage container. The buffer according to claim 3.

5. The cushioning material comprises a plurality of metal cushioning materials arranged to extend in the heat transfer direction. The buffer according to claim 1.

6. The metal cushioning material is positioned between the support member and the main cushioning material. The buffer according to claim 1.

7. A radioactive material storage container comprising a body, a lid that seals the body, and a buffer that protects the body and the lid, The aforementioned buffer body A support member provided on the outside of the aforementioned radioactive material storage container, A cushioning material is placed on the support member and deforms to absorb impact, Equipped with, The cushioning material comprises a metal cushioning material and a main cushioning material that have cushioning properties. The aforementioned metal buffer material is positioned adjacent to the main buffer material and extends in the direction of heat transfer in the support member, thereby forming a radioactive material storage container.

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