Buffers and radioactive material storage containers

Abstract

In buffers and radioactive material storage containers, the deterioration of the buffering function is suppressed by inhibiting degradation. [Solution] A buffer body to be attached to a radioactive material storage container, which is provided with a heat dissipation section that releases internal heat to the outside.

Description

Technical Field

[0001] The present disclosure relates to a shock absorber mounted on a radioactive material storage container, 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 stored or reprocessed. The radioactive material storage container is composed of a cask main body having a bottomed cylindrical shape with an open upper part, and a lid part fixed to the upper part of the cask main body to close the opening. The radioactive material storage container is provided with shock absorbers during transportation and storage. The shock absorber is attached to an axial end of the radioactive material storage container. The shock absorber absorbs impact by deforming when the radioactive material storage container is dropped, tipped over, or collided with an object.

[0003] Examples of the shock absorber mounted on the radioactive material storage container include those described in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0005] A shock absorber is generally configured such that a shock absorbing material such as wood is covered with a metal plate. The shock absorber may deteriorate over long-term use depending on the used materials and usage environment. That is, since the radioactive material storage container stores radioactive waste, it becomes high in temperature, and heat is transferred from the radioactive material storage container to the shock absorber, causing the temperature of the shock absorber to rise. Therefore, there is a risk that deterioration of the shock absorber may be accelerated by the temperature rise.

[0006] This disclosure aims to solve the aforementioned problems and to provide a buffer that suppresses the decline in buffering function by suppressing deterioration. [Means for solving the problem]

[0007] The buffer provided in this disclosure for achieving the above objective is a buffer to be attached to a radioactive material storage container, and is provided with a heat dissipation section for releasing internal heat to the outside.

[0008] Furthermore, the radioactive material storage container of this disclosure is a radioactive material storage container fitted with the buffer, wherein the outer diameter of the buffer, including the heat dissipation section, is positioned within the dimensional limit range for transportation. [Effects of the Invention]

[0009] According to the buffer and radioactive material storage container of this disclosure, the deterioration can be suppressed, thereby preventing a decrease in the buffering function. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a partially cutaway schematic diagram showing the internal structure of a radioactive material storage container. [Figure 2] Figure 2 is a front view showing a radioactive material storage container with a buffer installed in a horizontal position. [Figure 3] Figure 3 is a plan view of the buffer installed in the radioactive material containment container. [Figure 4] Figure 4 is a cross-sectional view taken along line IV-IV of Figure 4, showing the internal structure of the buffer. [Figure 5] Figure 5 is a cross-sectional view (VV cross-sectional view in Figure 6) showing the buffer body of the first embodiment installed in a radioactive material storage container. [Figure 6] Figure 6 is a cross-sectional view taken along line VI-VI in Figure 5, showing the internal structure of the buffer. [Figure 7] Figure 7 is a cross-sectional view showing a buffer body of the second embodiment installed in a radioactive material storage container. [Figure 8]Figure 8 is a cross-sectional view showing a buffer body of the third embodiment installed in a radioactive material storage container. [Figure 9] Figure 9 is a schematic diagram showing the buffer body of the fourth embodiment installed in a radioactive material storage container. [Figure 10] Figure 10 is a cross-sectional view of XX in Figure 9, showing the internal structure of the buffer. [Figure 11] Figure 11 is a schematic diagram showing the buffer body of the fifth embodiment installed in a radioactive material storage container. [Figure 12] Figure 12 is a plan view showing the buffer body of the sixth embodiment. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0012] [First Embodiment] <Radioactive material storage container> Figure 1 is a partially cutaway schematic diagram showing the internal structure of a radioactive material storage container.

[0013] As shown in Figure 1, a cask 11 serving as a radioactive material storage container includes a cask body 12 and a lid portion 13. The cask 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) with an opening 22 formed at the upper end and the lower end closed. The main body cylinder 21 has a cavity 23 inside, and a basket 24 is disposed in the cavity 23. The basket 24 is provided with a plurality of cells (storage portions) 25 capable of individually 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. However, the main body cylinder 21 may use stainless steel instead of carbon steel. Further, the main body cylinder 21 may use a cast product such as spheroidal graphite cast iron or carbon steel cast steel.

[0014] In the cask body 12, an outer cylinder 26 is arranged with a gap on the outer peripheral surface of the main body cylinder 21. Between the outer peripheral surface of the main body cylinder 21 and the inner peripheral surface of the outer cylinder 26, a plurality of copper heat transfer fins 27 for performing heat conduction are provided at intervals in the circumferential direction. In the cask body 12, a resin 28 serving as a neutron shield is disposed in the space surrounded by the main body cylinder 21, the outer cylinder 26, and the heat transfer fins 27. The resin 28 is a polymer material containing a large amount of hydrogen, and contains boron or a boron compound having a neutron shielding function.

[0015] The cask body 12 is provided with a bottom portion 29 protruding downward from the closed lower end of the main body cylinder 21. The bottom portion 29 of the main body cylinder 21 has a space portion surrounded by the closed lower end of the main body cylinder 21, and a resin (neutron shield) is disposed in the space portion.

[0016] In the cask body 12, trunnions 30 for lifting the cask 11 are provided on the main body cylinder 21 at the upper portion and the lower portion of the cask 11 at a 90-degree pitch or a 180-degree pitch. The trunnions 30 are provided to penetrate from the main body cylinder 21 through the outer cylinder 26. The trunnions 30 protrude to the outermost peripheral side of the cask 11.

[0017] The lid portion 13 is positioned in the opening 22 of the main body 21. The lid portion 13 closes the opening 22 and seals the main body 21 (cask body 12). The lid portion 13 has a primary lid 31, a secondary lid 32, and a tertiary lid 33. The primary lid 31 is formed in a disc shape from carbon steel or stainless steel that shields against gamma rays. The secondary lid 32 covers the primary lid 31 and is visible on the outside of the cask 11, and like the primary lid 31, is formed in a disc shape from carbon steel or stainless steel that shields against gamma rays. A resin (neutron shield) 28 may be provided between the primary lid 31 and the secondary lid 32. The tertiary lid 33 is provided on the outside of the secondary lid 32, but the tertiary lid 33 may be omitted. The tertiary lid 33 is formed in a disc shape from carbon steel or stainless steel that shields against gamma rays, similar to the primary lid 31 and the secondary lid 32.

[0018] The primary cover 31 is fixed to the first stage portion 22a formed in the opening 22 of the main body 21 by bolts (not shown) made of carbon steel or stainless steel. The secondary cover 32 is fixed to the second stage portion 22b formed in the opening 22 of the main body 21 by 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. The tertiary cover 33 is fixed to the first stage portion 22c formed in the opening 22 of the main body 21 by bolts (not shown) made of carbon steel or stainless steel. A rubber O-ring is provided between the tertiary cover 33 and the main body 21 to ensure airtightness.

[0019] In a nuclear power plant, for example, multiple spent fuel assemblies are stored in the cells 25 of the basket 24 of the main body 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. During transport, the cask 11 is fitted with transport buffers (not shown). The transport buffers are fitted to the top and bottom of the cask body 12. The cask 11 is loaded on its side on the bed of a transport vehicle and transported to the storage facility.

[0020] <Placement of radioactive material storage containers> Figure 2 is a front view showing a radioactive material storage container with a buffer installed in a horizontal position.

[0021] As shown in Figure 2, the cask 11 can be fitted with buffers 41 and 42 at its axial ends. Buffer 41 is fitted to the bottom 29 of the cask body 12, which is one axial end of the cask 11, and buffer 42 is fitted to the lid 13, which is the other axial end of the cask 11.

[0022] In a nuclear power plant, for example, spent fuel assemblies are stored in the cells 25 (see Figure 1) 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. When the cask 11 is transported to the storage facility, the transport buffer is removed, a buffer 41 is attached to the bottom 29 of the cask body 12, and a buffer 42 is attached to the lid 13. Alternatively, the cask may be transported with buffer 41 attached instead of the transport buffer. The buffers 41 and 42 are transport buffers, but they may also be storage buffers.

[0023] The cask 11 is stored in a horizontal position with its central axis O aligned horizontally, with the cushioning bodies 41 and 42 attached. The cask 11 is supported on a stand 43 in a horizontal position. The stand 43 is provided with a plurality of support parts 44, and the cask 11 is supported, for example, by each trunnion 30 on a support part 44. However, the main body 21 of the cask 11 may also be supported. The cask 11 is stored in a horizontal position with its central axis O aligned horizontally by the stand 43. In this case, the cask 11 has the cushioning body 41 attached to one side (bottom 29 side) along the central axis O, and the cushioning body 42 attached to the other side (lid 13 side) along the central axis O. The cushioning bodies 41 and 42 have substantially the same configuration.

[0024] The cask 11 may also be stored in a vertical position with its central axis O aligned vertically. In this case, the cask 11 is placed vertically with its lid 13 facing upwards, and a buffer 42 is attached to the lid 13 side. When stored, the cask 11 is fitted into a frame (not shown) at 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.

[0025] <Buffer> Figure 3 is a plan view of the buffer attached to the radioactive material storage container, and Figure 4 is a cross-sectional view taken along line IV-IV in Figure 3, showing the internal structure of the buffer. Note that the buffers 41 and 42 described above have almost the same structure, and below we will describe in detail the buffer 42 attached to the lid 13 of the cask body 12 in the cask 11.

[0026] The buffer 42 comprises a structure 51, an outer shell member 52, and a shock absorber 53. The shock absorber 53 is positioned on the outside of the structure 51, and the outer shell member 52 covers the shock absorber 53 from the outside and is fixed to the structure 51. The buffer 42 is fixed to the lid 13 of the cask body 12 in the cask 11 by a plurality of bolts 45.

[0027] The structure 51 is composed of a disc member 61 and a cylindrical member 62, among other things. The cylindrical member 62 is connected to one of the flat sides of the disc member 61.

[0028] The outer shell member 52 has a disc portion 71 and a cylindrical portion 72. One end of the cylindrical portion 72 is integrally connected to the outer circumference of the disc portion 71 in the axial direction. The outer shell member 52 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 the falling object that is assumed to fall, or the load that acts on the cask 11 when the cask 11 falls. The outer diameter of the outer shell member 52 is larger than the outer diameter of the cask 11.

[0029] The shock absorber 53 is positioned on the outer axial and radial sides of the structure 51. The shock absorber 53 absorbs the impact generated when the cask 11 falls or collides by deforming. The shock absorber 53 is composed of multiple cushioning materials. The cushioning materials deform under a predetermined load and are preferably composed of materials such as wood, foam, polymer compounds, or porous materials. The multiple cushioning materials are, for example, blocks of wood, and the shock absorber 53 is formed by combining multiple blocks. The multiple blocks are divided in the circumferential and axial directions. Furthermore, it is preferable to place blocks with different strengths depending on their location.

[0030] The buffer body 42 is fixed to the lid portion 13 of the cask body 12 by multiple bolts 81. The shock absorber 53 consists of multiple tubular members 82 arranged at intervals in the circumferential direction, oriented axially. One end of each tubular member 82 in the axial direction is connected to the disc member 61 of the structure 51, and the other end in the axial direction is connected to the disc portion 71 of the outer shell member 52. Through holes 71a are formed in the disc portion 71 at the connection points of the tubular members 82. The buffer body 42 is fixed by multiple bolts 81 when the structure 51 is fitted to the bottom of the cask body. The bolts 81 are inserted from the outside of the buffer body 42 in the order of through holes 71a in the disc portion 71 and then the tubular members 82, with their tips passing through the mounting holes in the disc member 61 and screwed into the threaded holes of the lid portion 13.

[0031] <Heat removal structure of buffer body> Figure 5 is a cross-sectional view (VV cross-section in Figure 6) showing the buffer body of the first embodiment installed in a radioactive material storage container, and Figure 6 is a cross-sectional view (VI-VI in Figure 5) showing the internal structure of the buffer body.

[0032] The buffers 41 and 42 are attached to the cask 11. The cask 11 becomes hot because it contains radioactive waste. Therefore, the temperature of the buffers 41 and 42 rises as heat from the cask 11 is transferred to them. The buffers 41 and 42 are constructed by covering an impact absorber 53, which is placed on the outside of the structure 51, with an outer shell member 52.

[0033] The shock absorber 53 is composed of wood, foam, polymer compounds, etc. The buffer 42 deteriorates with long-term use depending on the materials used and the environment in which it is used. For example, the buffer material that makes up the shock absorber 53 may deteriorate in response to temperature changes, and the deterioration may be accelerated if the temperature of the buffer material rises.

[0034] Therefore, as shown in Figures 5 and 6, the buffers 41 and 42 of the first embodiment have a heat removal function. The buffers 41 and 42 have substantially the same configuration, and the buffer 42 will be described in detail.

[0035] The buffer body 42 is provided with fins 101 and 102 as heat dissipation parts that release internal heat to the outside. The fins 101 and 102 are formed from a metal material or graphene sheet with excellent thermal conductivity. Suitable metal materials include copper, iron, and aluminum. The fins 101 and 102 are plate-shaped, but their shape is not limited. The fins 101 and 102 are preferably low in strength, such as bellows-shaped or perforated shapes, so as not to affect the performance of the buffer material. Multiple fins 101 and 102 are arranged circumferentially at intervals (preferably equal intervals). The number of fins 101 and 102 is appropriately set according to the size of the buffer body 42.

[0036] Fins 101 and 102 are partially exposed to the outside of the buffer 42. One end of each fin 101 and 102 is positioned inside the shock absorber 53, while the other end penetrates the outer shell member 52 and is exposed to the outside.

[0037] The buffer body 42 is cylindrical in shape and has a recessed mounting portion 54 at the position where it is attached to the cask 11. The fin 101 is positioned between the mounting portion 54 and the disc portion 71 of the outer shell member 52. That is, one axial end of the fin 101 is exposed to the mounting portion 54, and the other axial end penetrates the disc portion 71 of the outer shell member 52 and is exposed to the outside. In this case, since one end of the fin 101 is exposed to the mounting portion 54, it can contact the lid portion 13 of the cask 11. Also, the other end of the fin 101 does not protrude outward from the outer surface of the disc portion 71 of the outer shell member 52 but forms the same plane.

[0038] The fin 102 has one radial end exposed to the mounting portion 54, and the other axial end penetrates the cylindrical portion 72 of the outer shell member 52 and is exposed to the outside. In this case, since one end of the fin 102 is exposed to the mounting portion 54, it can contact the outer circumference of the lid portion 13 of the cask 11. Also, the other end of the fin 102 does not protrude outward from the outer surface of the cylindrical portion 72 of the outer shell member 52 but forms the same plane.

[0039] <The heat-removing effect of buffers> The buffers 41 and 42 are attached to the cask 11, and heat is transferred from the cask 11, causing their temperature to rise. At this time, since the buffers 41 and 42 are provided with multiple fins 101 and 102, the heat from the shock absorber 53 is transferred to the multiple fins 101 and 102 and released to the outside through the multiple fins 101 and 102. As a result, the cushioning material of the shock absorber 53 in the buffers 41 and 42 is cooled and its temperature decreases, suppressing deterioration of the cushioning material due to temperature rise.

[0040] [Second Embodiment] Figure 7 is a cross-sectional view showing a buffer body of the second embodiment installed in a radioactive material storage container. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0041] As shown in Figure 7, the buffer body 42A of the second embodiment has a heat dissipation function. The buffer body 42A is provided with fins 111, 112, 113, and 114 as heat dissipation parts that release internal heat to the outside. The fins 111, 112, 113, and 114 are formed from a metal material with excellent thermal conductivity. Suitable metal materials include, for example, copper, iron, and aluminum. The fins 111, 112, 113, and 114 are plate-shaped, but their shape is not limited. Multiple fins 111, 112, 113, and 114 are arranged at intervals (preferably equal intervals) in the circumferential direction. The number of fins 111, 112, 113, and 114 is appropriately set according to the size of the buffer body 42A.

[0042] Fin 111 extends partially outside the buffer 42A. One end of fin 111 is positioned inside the shock absorber 53, and the other end penetrates the outer shell member 52 and extends to the outside. Fins 112, 113, and 114 are provided outside the buffer 42. One end of fins 112, 113, and 114 is fixed to the outside of the outer shell member 52, and the other end extends outward from the outer shell member 52.

[0043] The fin 111 is positioned between the mounting portion 54 and the disc portion 71 of the outer shell member 52. That is, one axial end of the fin 111 is exposed to the mounting portion 54, and the other axial end penetrates the disc portion 71 of the outer shell member 52 and extends outward. In this case, since one end of the fin 111 is exposed to the mounting portion 54, it can contact the lid portion 13 of the cask 11. The other end of the fin 111 also protrudes outward from the outer surface of the disc portion 71 of the outer shell member 52.

[0044] Fin 112 is positioned on the outer shell member 52. Specifically, one axial end of fin 112 is fixed to the outer surface of the disc portion 71 of the outer shell member 52, and the other axial end extends outward from the disc portion 71 of the outer shell member 52. Fin 113 is positioned on the outer shell member 52. Specifically, one radial end of fin 113 is fixed to the outer surface of the cylindrical portion 72 of the outer shell member 52, and the other radial end extends outward from the cylindrical portion 72 of the outer shell member 52. Fin 114 is positioned on the outer shell member 52. Specifically, one axial end of fin 114 is fixed to the outer surface of the outer shell member 52, and the other axial end extends outward from the outer shell member 52 towards the cask 11. Note that fins 113 and 114 may be pre-fixed to the buffer 42A, or they may be fixed to the buffer 42A after the buffer 42A is attached to the cask 11.

[0045] The buffer body 42A is attached to the cask 11, and heat is transferred from the cask 11, causing its temperature to rise. At this time, since the buffer body 42A is provided with multiple fins 111, the heat from the shock absorber 53 is transferred to the multiple fins 111 and released to the outside through the multiple fins 111. In addition, since the buffer body 42A is provided with multiple fins 112, 113, and 114, the heat from the shock absorber 53 is transferred to the outer shell member 52, and the heat from the outer shell member 52 is transferred to the multiple fins 112, 113, and 114 and released to the outside through the multiple fins 112, 113, and 114. As a result, the cushioning material of the shock absorber 53 in the buffer body 42A is cooled and its temperature decreases, suppressing deterioration of the cushioning material due to temperature rise.

[0046] [Third Embodiment] Figure 8 is a schematic diagram showing the buffer body of the third embodiment installed in a radioactive material storage container. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

[0047] As shown in Figure 8, the buffer body 42B of the third embodiment has a heat dissipation function. The buffer body 42B is provided with fins 121 and 122 as heat dissipation parts that release internal heat to the outside. The fins 121 and 122 are made of a metal material with excellent thermal conductivity. Suitable metal materials include, for example, copper, iron, and aluminum. The fins 121 and 122 are detachably attached to the buffer body 42B. The fins 121 and 122 can be attached to the buffer body 42B by, for example, hooks or bolts.

[0048] The fins 121 are arranged on the outer shell member 52. That is, one axial end of the fin 121 is fixed to the outer surface of the outer shell member 52, and the other axial end extends from the outer shell member 52 toward the cask 11. Multiple fins 121 are arranged at intervals (preferably equal intervals) in the circumferential direction. The number and shape of the fins 121 and 122 are appropriately set according to the size of the buffer body 42B.

[0049] The buffer body 42B has working holes 55 along the axial direction into which bolts 81 (see Figure 4) that are fixed to the cask 11 are inserted. Multiple working holes 55 are provided at circumferential intervals. The working holes 55 are composed of through holes 71a provided in the disc portion 71 of the outer shell member 52, and through holes 62a provided in the tubular member 82 and cylindrical member 62 (all see Figure 4). Multiple fins 122 are provided and are attached to multiple working holes 55. The base end of the fin 122 is fixed to the working hole 55, and the tip protrudes outward from the outer shell member 52.

[0050] The buffer 42B is attached to the cask 11, and heat is transferred from the cask 11, causing its temperature to rise. At this time, since the buffer 42B is provided with multiple fins 121 and 122, the heat from the shock absorber 53 is transferred to the multiple fins 121 and 122 and released to the outside through the multiple fins 121 and 122. As a result, the cushioning material of the shock absorber 53 in the buffer 42B is cooled and its temperature decreases, suppressing deterioration of the cushioning material due to temperature rise.

[0051] [Fourth Embodiment] Figure 9 is a schematic diagram showing the buffer body of the fourth embodiment installed in a radioactive material storage container, and Figure 10 is a cross-sectional view of XX in Figure 9 showing the internal structure of the buffer body. Note that components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

[0052] As shown in Figures 9 and 10, the buffer body 42C of the fourth embodiment has a heat dissipation function. The buffer body 42C is provided with fins 131 as heat dissipation parts that release internal heat to the outside. The fins 131 are formed of a metal material with excellent thermal conductivity. Suitable metal materials include, for example, copper, iron, and aluminum. The fins 131 are detachably attached to the buffer body 42C.

[0053] The fin 131 has a connecting member 132 and a fin body 133. The connecting member 132 is a ring-shaped band member that is detachably attached to the outer circumference of the buffer body 42C. The connecting member 132 can be attached to the buffer body 42C by, for example, a hook or bolt. Multiple fin bodies 133 are fixed to the outer circumference of the connecting member 132 at circumferential intervals. The fin body 133 is rod-shaped, with its base end fixed to the connecting member 132 and its tip extending outward. The number and shape of the fin bodies 132 are appropriately set according to the size of the buffer body 42C.

[0054] The buffer 42C is attached to the cask 11, and heat is transferred from the cask 11, causing its temperature to rise. At this time, since the buffer 42C is provided with multiple fins 131, the heat from the shock absorber 53 is transferred to the multiple fins 131 and released to the outside through the multiple fins 131. As a result, the cushioning material of the shock absorber 53 in the buffer 42C is cooled and its temperature decreases, suppressing deterioration of the cushioning material due to temperature rise.

[0055] [Fifth Embodiment] Figure 11 is a schematic diagram showing the buffer body of the fifth embodiment installed in a radioactive material storage container. Components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed explanations are omitted.

[0056] As shown in Figure 11, the buffer 42D of the fifth embodiment has a heat dissipation function. The buffer 42D has an insulating layer 141 inside. The insulating layer 141 is positioned opposite the mounting portion 54 that is attached to the cask 11. The insulating layer 141 is placed on the shock absorber 53. The insulating layer 141 is disc-shaped and its periphery is demarcated by the material that constitutes the shock absorber 53. It is preferable that the outer diameter of the insulating layer 141 is larger than the outer diameter of the lid portion 13 of the cask 11. The insulating layer 141 may be in close contact with the mounting portion 54.

[0057] The thermal insulation layer 141 is a hollow section 142. The hollow section 142 is partitioned by a metal member. That is, the hollow section 142 is a hollow disc member formed from a metal plate 143. The thermal insulation layer 141 is filled with air in the hollow section 142. However, the thermal insulation layer 141 may have a vacuum in the hollow section 142. Alternatively, the thermal insulation layer 141 may have an inert gas (for example, nitrogen gas or argon gas) filled in the hollow section 142. Alternatively, it may be filled with an insulating material such as foamed urethane.

[0058] Furthermore, the buffer body 42D is provided with fins 144 that serve as heat dissipation parts to release internal heat to the outside. The fins 144 are formed from a metal material with excellent thermal conductivity. Suitable metal materials include, for example, copper, iron, and aluminum. The fins 144 are plate-shaped, but their shape is not limited. Multiple fins 144 are arranged at intervals (preferably equal intervals) in the circumferential direction.

[0059] The fin 144 has one end positioned inside the shock absorber 53 and the other end extending outward through the outer shell member 52. The fin 144 is positioned between the mounting portion 54 and the cylindrical portion 72 of the outer shell member 52. That is, one radial end of the fin 144 is exposed to the mounting portion 54, and the other radial end extends outward through the cylindrical portion 72 of the outer shell member 52. In this case, since one end of the fin 144 is exposed to the mounting portion 54, it can contact the lid portion 13 of the cask 11. Also, the other end of the fin 144 protrudes outward from the outer surface of the cylindrical portion 72 of the outer shell member 52.

[0060] The buffer 42D is attached to the cask 11, and heat is transferred from the cask 11, causing its temperature to rise. At this time, since the buffer 42D has an insulating layer 141 inside, the heat transferred from the cask 1 to the shock absorber 53 is blocked, and the temperature rise of the shock absorber 53 is suppressed. In addition, since the buffer 42D has multiple fins 144, the heat transferred from the cask 11 to the shock absorber 53 and blocked by the insulating layer 141 is released to the outer periphery of the buffer 42D through the multiple fins 144. As a result, the cushioning material of the shock absorber 53 in the buffer 42D is cooled and its temperature decreases, suppressing deterioration of the cushioning material due to temperature rise.

[0061] [Sixth Embodiment] Figure 12 is a plan view showing the buffer body of the sixth embodiment. Note that components having the same function as those in the first embodiment described above are denoted by the same reference numerals, and detailed descriptions are omitted.

[0062] As shown in Figure 12, the buffer body 42E of the sixth embodiment has a heat dissipation function. The buffer body 42E is provided with fins 151 as heat dissipation parts that release internal heat to the outside. The fins 151 are made of a metal material with excellent thermal conductivity. Suitable metal materials include, for example, copper, iron, and aluminum. Multiple fins 151 are provided on the outer circumference of the buffer body 42E at intervals in the circumferential direction.

[0063] The buffer body 42E has a cylindrical shape, and a rectangular dimensional restriction range A for transport is set on the outer circumference of the buffer body 42E. The fin 151 is positioned on the outer circumference of the buffer body 42E within the dimensional restriction range A, that is, in region A1 between the outer circumference of the buffer body 42E and the dimensional restriction range A. The fin 151 extends outward from the outer circumference of the buffer body 42E. The fin 121 has a base end 152, a tip end 153, and a weak portion 154. The weak portion 154 is a part that is prone to buckling relative to the base end 152 and tip end 153, and is, for example, a bent portion. Note that the weak portion 154 is not limited to a bent portion, but may be, for example, a curved portion, a thin-walled portion, a perforated portion, a notched portion, etc. Alternatively, the weak portion may be formed by making the fin honeycomb or bellows-shaped.

[0064] The buffer 42E is attached to the cask 11, and heat is transferred from the cask 11, causing its temperature to rise. At this time, since the buffer 42E is provided with multiple fins 151, the heat from the shock absorber 53 is transferred to the multiple fins 151 and released to the outside through the multiple fins 151. As a result, the cushioning material of the shock absorber 53 in the buffer 42E is cooled and its temperature decreases, suppressing deterioration of the cushioning material due to temperature rise.

[0065] Furthermore, the fin 121 has a weak point 154. When the cask 11 tips over during storage and an impact acts on the buffer 42E, the fin 151 deforms with the weak point 154 as the pivot point. Therefore, regardless of the strength of the fin 151, the shock absorber 53 can deform appropriately and absorb the impact force.

[0066] [Effects of this embodiment] The buffer body according to the first embodiment is a buffer body 41, 41A, 41B, 41C, 41D, 41E, 42, 42A that is attached to a cask (radioactive material storage container) 11, and is provided with fins (heat dissipation parts) 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151 that release internal heat to the outside.

[0067] According to the first embodiment of the buffer, the heat transferred from the cask 11 to the buffers 41, 41A, 41B, 41C, 42, 42A, and 42B is released and removed to the outside via the fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, and 151. As a result, the temperature rise of the buffers 41, 41A, 41B, 41C, 41D, 41E, 42, and 42A is suppressed, and deterioration is suppressed, thereby preventing a decrease in the buffering function.

[0068] The buffer according to the second embodiment is the buffer according to the first embodiment, further comprising fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, and 151 made of a metallic material. This makes it easier for heat from the buffers 41, 41A, 41B, 41C, 42, and 42A to be transferred to the fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, and 151, and allows for efficient release of heat from the buffers 41, 41A, 41B, 41C, 42, and 42A.

[0069] The buffer according to the third embodiment is a buffer according to the first or second embodiment, further having a portion of the fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151 exposed to the outside. This allows the fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151 to efficiently dissipate heat from the buffers 41, 41A, 41B, 41C, 42, 42A, and also allows for miniaturization by shortening the length of the fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151.

[0070] The buffer according to the fourth embodiment is a buffer according to any one of the first to third embodiments, and furthermore, the fins 111, 122, and 144 extend from the inside to the outside. This increases the contact area between the fins 111, 122, and 144 and the outside air, thereby improving the heat dissipation efficiency.

[0071] The fifth embodiment of the buffer is a buffer according to any one of the first to fourth embodiments, further comprising a bottomed cylindrical outer shell member 52 and a cylindrical shock absorber 53 disposed inside the outer shell member 52, with one end of each fin 101, 102, 111, 144 positioned inside the shock absorber 53 and the other end penetrating the outer shell member 52 and exposed to the outside. This allows the fins 101, 102, 111, 144 to efficiently release heat from the shock absorber 53 to the outside.

[0072] The buffer according to the sixth embodiment is a buffer according to any one of the first to fifth embodiments, and furthermore, multiple fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151 are arranged at intervals in the circumferential direction. This allows the heat from the buffers 41, 41A, 41B, 41C, 41D, 41E, 42, 42A to be appropriately released by the fins 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151.

[0073] The seventh embodiment of the buffer is a buffer according to any one of the first to sixth embodiments, further having at least a portion of the fins 101, 102, 111, and 122 exposed at the mounting portion 54 attached to the cask 11. As a result, the fins 101, 102, 111, and 122 come into contact with the bottom of the cask 11, allowing the heat from the cask 11 to be properly released to the outside by the fins 101, 102, 111, and 122.

[0074] The eighth embodiment is a buffer according to any one of the first to seventh embodiments, and furthermore, the fins 121, 122, and 131 are detachably provided on the outer circumference. This allows the fins 121, 122, and 131 to be attached to the buffers 41B and 41C after they have been attached to the cask 11.

[0075] The ninth embodiment of the buffer is the same as the eighth embodiment, and further, the fin 151 extends outward from the outer circumference and has a weak portion 154. As a result, for example, when the cask 11 overturns and an impact acts on the buffer 41E, the fin 151 deforms with the weak portion 154 as a fulcrum, so that the shock absorber 53 of the buffer 41E deforms appropriately and absorbs the impact force.

[0076] The buffer according to the tenth embodiment is a buffer according to any one of the first to ninth embodiments, and further, a heat insulating layer 141 is arranged at a position opposite to the mounting portion 54 that is attached to the cask 11. As a result, the heat transferred from the cask 11 to the buffer 41D is blocked by the heat insulating layer 141, suppressing the temperature rise of the shock absorber 53, and thus suppressing deterioration of the buffer material due to temperature rise.

[0077] The radioactive material storage container according to the 11th embodiment is a cask (radioactive material storage container) 10 fitted with buffers 41, 41A, 41B, 41C, 41D, 41E, 42, 42A according to any one of the first to tenth embodiments, wherein the outer dimensions of the buffers 41, 41A, 41B, 41C, 41D, 41E, 42, 42A, including fins (heat dissipation parts) 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151 are arranged within the dimensional limit range for transport. This allows the cask 10 to be transported safely. [Explanation of symbols]

[0078] 11. Cask (container for radioactive material) 12 Cask body 13 Lid 29 Bottom 31 Primary lid 32 Secondary lid 41,41A,41B,41C,41D,41E,42,42A Buffer 43. Stand 44 Support part 51 Structure 52 Outer shell member 53 Shock absorber 54 Mounting part 55 Working holes 101, 102, 111, 112, 113, 114, 121, 122, 131, 144, 151 Fins (heat dissipation part) 132 Connecting member 133 Fin body 141 Insulation layer 142 Hollow part 143 Metal plate 154 Vulnerable parts

Claims

1. A buffer to be attached to a container for radioactive materials, A heat dissipation section is provided to release internal heat to the outside. buffer body.

2. The heat dissipation section is formed of a metal material. The buffer according to claim 1.

3. The heat dissipation section is partially exposed to the outside. The buffer according to claim 1.

4. The heat dissipation section extends from the inside to the outside, The buffer according to claim 1.

5. The heat dissipation portion has a bottomed cylindrical outer shell member and a cylindrical shock absorber disposed inside the outer shell member, with one end of the heat dissipation portion disposed inside the shock absorber and the other end penetrating the outer shell member and exposed to the outside. The buffer according to claim 1.

6. The heat dissipation section is arranged in multiple units with spacing in the circumferential direction. The buffer according to claim 1.

7. At least a portion of the heat dissipation part is exposed in the mounting portion that is attached to the radioactive material storage container. The buffer according to claim 1.

8. The heat dissipation section is detachably provided on the outer periphery. The buffer according to claim 1.

9. The heat dissipation portion extends outward from the outer periphery and has a weak portion. The buffer according to claim 8.

10. A heat insulating layer is positioned opposite to the mounting portion that is attached to the aforementioned radioactive material storage container. The buffer according to claim 1.

11. A radioactive material storage container fitted with the buffer described in claim 1, The outer diameter of the buffer body, including the heat dissipation section, is positioned within the dimensional limit range for transportation. A container for storing radioactive materials.

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