Buffer

Abstract

In buffers, the deterioration of the buffer is suppressed to prevent a decrease in buffering function. [Solution] A buffer body to be attached to a radioactive material storage container, wherein a porous tube is arranged inside.

Description

Technical Field

[0001] The present disclosure relates to a shock absorber mounted on 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 cask body having a bottomed cylindrical shape with an open top, and a lid part fixed to the upper part of the cask body to close the opening. The radioactive material storage container is provided with shock absorbers during transportation or 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] As a shock absorber to be mounted on a radioactive material storage container, for example, there is one described in Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0005] A shock absorber is generally configured by covering a shock absorbing material such as wood with a metal plate. The shock absorber may degrade after long-term use depending on the materials used and the usage environment. That is, since the radioactive material storage container stores radioactive waste, its temperature becomes high, and heat is transferred from the radioactive material storage container to the shock absorber, causing the temperature of the shock absorber to rise. The shock absorbing material used in the shock absorber is selected to have a moisture content not higher than a predetermined value, but the moisture content may fluctuate with the rise in temperature, which may accelerate the degradation of the shock absorber.

[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 of this disclosure for achieving the above objective is a buffer to be attached to a radioactive material storage container, wherein a porous tube is arranged inside. [Effects of the Invention]

[0008] According to the buffer material of this disclosure, deterioration can be suppressed, thereby preventing a decrease in the buffering function. [Brief explanation of the drawing]

[0009] [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 cross-sectional view of the radioactive material storage container along its radial direction. [Figure 3] Figure 3 is a front view showing a radioactive material storage container with a buffer attached in a horizontal position. [Figure 4] Figure 4 is a plan view of the buffer installed in the radioactive material storage container. [Figure 5] Figure 5 is a VV cross-sectional view of Figure 4, showing the internal structure of the buffer. [Figure 6] Figure 6 is a cross-sectional view showing the buffer body of the first embodiment installed in a radioactive material storage container. [Figure 7] Figure 7 is a cross-sectional view taken along line VII-VII of Figure 6, showing the internal structure of the buffer. [Figure 8] Figure 8 is a schematic diagram representing the discharge pipe. [Figure 9] Figure 9 is a cross-sectional view showing a buffer body of the second 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 third embodiment installed in a radioactive material storage container. [Figure 12] Figure 12 is a schematic diagram showing the buffer body of the fourth embodiment installed in a radioactive material storage container. [Figure 13] Figure 13 is a cross-sectional view taken along line XIII-XIII in Figure 12, showing the internal structure of the buffer. [Modes for carrying out the invention]

[0010] 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.

[0011] [First Embodiment] <Radioactive material storage container> Figure 1 is a partially cutaway schematic diagram showing the internal structure of a radioactive material storage container, and Figure 2 is a cross-sectional view along the radial direction of the radioactive material storage container.

[0012] As shown in Figures 1 and 2, the cask 11, as a radioactive material storage container, comprises a cask body 12 and a lid 13. The cask body 12 has a body shell 21. The body shell 21 is cylindrical (in this embodiment, cylindrical in shape), with an opening 22 at its upper end and a closed lower end. The body shell 21 has a cavity 23 inside, and a basket 24 is placed in the cavity 23. The basket 24 is provided with a plurality of cells (storage compartments) 25 capable of individually storing radioactive materials (e.g., spent fuel assemblies). The body shell 21 is a forged product of carbon steel having a gamma-ray shielding function. However, stainless steel may be used instead of carbon steel for the body shell 21. Alternatively, the body shell 21 may be a casting of spheroidal graphite cast iron or carbon steel cast steel.

[0013] 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 gap therebetween. The main body barrel 21 is provided with a plurality of copper heat transfer fins 27 for heat conduction at intervals in the circumferential direction between the outer peripheral surface and the inner peripheral surface of the outer cylinder 26. In the cask main body 12, a resin 28 as a neutron shield is arranged in the space surrounded by the main body barrel 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.

[0014] 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 of the main body barrel 21 has a space surrounded by the closed lower end of the main body barrel 21, and a resin (neutron shield) is arranged in the space.

[0015] In the cask main body 12, trunnions 30 for lifting the cask 11 are provided on the main body barrel 21 at the upper portion and the lower portion of the cask 11 at a pitch of 90 degrees or 180 degrees. The trunnions 30 are provided to penetrate from the main body barrel 21 through the outer cylinder 26. The trunnions 30 protrude to the outermost peripheral side of the cask 11.

[0016] The lid portion 13 is arranged at the opening 22 of the main body barrel 21. The lid portion 13 closes the opening 22 to hermetically seal the main body barrel 21 (the cask main 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 disk shape using carbon steel or stainless steel that shields gamma rays as a material. The secondary lid 32 covers the primary lid 31 and is exposed to the outside of the cask 11, and like the primary lid 31, is formed in a disk shape using carbon steel or stainless steel that shields gamma rays as a material. 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 outer side of the secondary lid 32, but the tertiary lid 33 may be omitted. Like the primary lid 31 and the secondary lid 32, the tertiary lid 33 is formed in a disk shape using carbon steel or stainless steel that shields gamma rays as a material.

[0017] 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.

[0018] 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.

[0019] <Placement of radioactive material storage containers> Figure 3 is a front view showing a radioactive material storage container with a buffer attached in a horizontal position.

[0020] As shown in Figure 3, 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.

[0021] 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.

[0022] The cask 11 is stored in a horizontal position with its central axis 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.

[0023] 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.

[0024] <Buffer> Figure 4 is a plan view of the buffer attached to the radioactive material storage container, and Figure 5 is a cross-sectional view of Figure 4, VV, 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.

[0025] 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 of the cask 11 by a plurality of bolts (not shown).

[0026] The structure 51 is composed of disc members 61, cylindrical members 62, and the like.

[0027] A cylindrical member 62 is connected to one of the flat surfaces 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] <Dehumidifying structure of the buffer> Figure 6 is a cross-sectional view showing the buffer body of the first embodiment installed in a radioactive material storage container, Figure 7 is a cross-sectional view of Figure 6 from VII-VII showing the internal structure of the buffer body, and Figure 8 is a schematic diagram showing the discharge pipe.

[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, porous materials, 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 due to temperature and humidity changes. In particular, humidity may fluctuate depending on the surrounding environment and temperature changes of the buffer material, and an increase in the humidity of the buffer material may accelerate deterioration.

[0034] Therefore, as shown in Figures 6 and 7, the buffers 41 and 42 of the first embodiment have a dehumidifying function. The buffers 41 and 42 have almost the same configuration, and the buffer 42 will be described in detail.

[0035] The buffer body 42 has perforated tubes 101, 102, 103, and 104 arranged inside. The perforated tubes 101, 102, 103, and 104 are formed from a metal material or graphene sheet with excellent thermal conductivity. Suitable metal materials include copper, iron, and aluminum. The perforated tubes 101, 102, 103, and 104 are preferably made of mesh-like cylindrical members as shown in Figure 8(a). However, the perforated tubes 101, 102, 103, and 104 may be cylindrical tubes with many holes formed in them, as shown in Figure 8(b). Also, the perforated tubes 101, 102, 103, and 104 are not limited to cylindrical tubes, but may be polygonal tubes.

[0036] As shown in Figures 6 and 7, the buffer body 42 is constructed by covering the outer shell member 52 with an impact absorber 53. Note that the structure 51 (see Figure 4) is omitted in Figures 6 and 7. The porous tube 101 is ring-shaped and is placed inside the impact absorber 53. The porous tube 101 forms a ring shape with the central axis O at its center inside the impact absorber 53. The porous tube 101 is placed on the disc portion 71 side of the outer shell member 52 inside the impact absorber 53. Note that although one porous tube 101 is placed inside the impact absorber 53, multiple porous tubes may be placed at intervals in the axial direction, or tubes with different outer diameters may be placed at intervals in the radial direction.

[0037] The perforated tubes 102 and 103 are arranged inside the shock absorber 53 along the vertical direction (radial direction of the buffer 42). The buffer 42 is installed when the cask 11 is placed horizontally during storage or transport. Since the cask 11 and the buffer 42 are cylindrical in shape, when the buffer 42 is installed on the cask 11, the centers of the cask 11 and the buffer 42 coincide approximately along the central axis O. When the cask 11 is placed horizontally, the central axis O of the cask 11 and the buffer 42 is aligned horizontally.

[0038] When the buffer body 42 is attached to the cask 11 which is positioned horizontally, the porous tubes 102 and 103 of the buffer body 42 are arranged along the vertical direction. That is, the buffer body 42 has a cylindrical shape and is provided with a recessed mounting portion 54 at the position where it is attached to the cask 11. The multiple porous tubes 102 along the radial direction of the buffer body 42 are positioned vertically above the mounting portion 54, and the multiple porous tubes 103 along the radial direction of the buffer body 42 are positioned vertically below the mounting portion 54. The ends (upper ends) of the multiple porous tubes 102 in the longitudinal direction (vertical direction) open above the buffer body 42, and the ends (lower ends) of the multiple porous tubes 103 in the longitudinal direction (vertical direction) open below the buffer body 42. The number of porous tubes 102 and 103 is set appropriately according to the size of the buffer body 42.

[0039] The perforated tubes 104 are arranged inside the shock absorber 53 along the axial direction (parallel to the central axis O) of the buffer 42. The ends of the multiple perforated tubes 104 are connected to the perforated tube 101 in the longitudinal direction (axial direction). That is, the inside of the perforated tube 01 and the inside of the multiple perforated tubes 104 are in communication. The number of perforated tubes 104 is set appropriately according to the size of the buffer 42.

[0040] The buffer body 42 has multiple flow channels 105 in the mounting portion 54 into which the lid portion 13 of the cask 11 is fitted. The flow channels 105 communicate with the porous tubes 102, 103, and 104. The flow channels 105 are, for example, grooves provided in the mounting portion 54 of the buffer body 42 (structure 51). The grooves are radial grooves or circumferential grooves. One end of the porous tube 102 opens above the buffer body 42, and the other end communicates with the flow channel 105. One end of the porous tube 103 communicates with the flow channel 105, and the other end opens below the buffer body 42. One end of the porous tube 104 is connected to the porous tube 101, and the other end communicates with the flow channel 105.

[0041] The porous tube 102 has an upper end that opens above the buffer body 42, and the porous tube 103 has a lower end that opens below the buffer body 42. However, lid members 106 and 107 may be provided as adjustment members to regulate the flow rate of gas flowing inside the porous tubes 102 and 103. When the humidity of the outside air is high due to weather conditions, etc., the outlet of the porous tube 102 is closed with lid member 106, and the inlet of the porous tube 103 is closed with lid member 107 to suppress contact between the outside air and the buffer material. In addition, a temperature measuring device and a humidity measuring device may be placed on the opening side of the porous tubes 102 and 103 to measure the temperature and humidity.

[0042] <Dehumidifying effect of buffer material> The buffers 41 and 42 are attached to the cask 11, and heat is transferred from the cask 11, causing their temperature to rise. As the temperature rises, the moisture contained in the buffer material that makes up the shock absorber 53 evaporates or moves to another adjacent buffer material. At this time, the moisture evaporated from the buffers 41 and 42 becomes steam and enters the interior of each porous tube 101, 102, 103, and 104 through the holes. The steam that enters the interior of each porous tube 101, 102, 103, and 104 flows through each porous tube 101, 102, 103, and 104 and the flow path 105, and is discharged to the outside from the upper end of the porous tube 102 due to the chimney effect. At this time, fresh outside air enters the interior from the lower end of the porous tube 103 due to the chimney effect.

[0043] Through the porous tubes 101, 102, 103, 104 and the flow path 105, water vapor-containing air is discharged to the outside from the upper end of porous tube 102 by the chimney effect, and dry air from the outside enters the interior of porous tube 103 from the lower end of porous tube 103 by the chimney effect. As a result, the temperature and humidity of the cushioning material of the shock absorber 53 in the buffer bodies 41 and 42 decrease, and deterioration of the cushioning material due to increased humidity is suppressed.

[0044] The dehumidification structure of the buffers 41 and 42 is not limited to the configuration described above. The buffers 41 and 42 only need to have porous tubes arranged inside, and their shape, position, and direction are not limited. However, it is preferable that the buffers 41 and 42 have porous tubes running vertically. It is preferable that one end of the porous tube in the longitudinal direction opens vertically upward, and the other end in the longitudinal direction opens vertically downward. For example, instead of the porous tubes 101, 102, 103, and 104, one or more porous tubes that penetrate the buffer 42 vertically may be arranged.

[0045] [Second Embodiment] Figure 9 is a cross-sectional view showing the buffer body of the second 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 descriptions are omitted.

[0046] As shown in Figures 9 and 10, the buffers 41A and 42A of the second embodiment have a dehumidifying function. The buffers 41A and 42A have almost the same configuration, and the buffer 42A will be described in detail.

[0047] The buffer body 42A has a porous tube 111 inside it. The porous tube 111 is positioned vertically (radially in the direction of the buffer body 42A) inside the shock absorber 53. The buffer body 42A is installed when the cask 11 is placed horizontally during storage or transport. Since the cask 11 and the buffer body 42A are cylindrical in shape, when the buffer body 42A is installed on the cask 11, the centers of the cask 11 and the buffer body 42A almost coincide at the central axis O. When the cask 11 is placed horizontally, the central axis O of the cask 11 and the buffer body 42A are aligned horizontally.

[0048] When the buffer body 42A is attached to the cask 11 which is positioned horizontally, the perforated tubes 111 of the buffer body 42A are arranged along the vertical direction. That is, the perforated tubes 111 along the radial direction of the buffer body 42A are positioned inside the shock absorber 53 on the side of the disc portion 71 of the outer shell member 52. Multiple perforated tubes 111 are provided. Multiple perforated tubes 111 are arranged with horizontal spacing between them. Multiple perforated tubes 111 are also arranged with axial spacing between them. In this case, some of the perforated tubes 111 may be exposed to the mounting portion 54 into which the lid portion 13 of the cask 11 is fitted. The ends (upper ends) of the multiple perforated tubes 111 in the longitudinal direction (vertical direction) open above the buffer body 42A, and the ends (lower ends) in the longitudinal direction (vertical direction) open below the buffer body 42A. The number of perforated tubes 111 is set appropriately according to the size of the buffer body 42A.

[0049] The buffer body 42A has a porous tube 112 inside. The porous tube 112 is U-shaped and is placed inside the shock absorber 53. Inside the shock absorber 53, the porous tube 112 forms a U-shape with the central axis O as its center. Inside the shock absorber 53, the porous tube 112 is placed on the cylindrical portion 72 side of the outer shell member 52. That is, the porous tube 112 is placed radially outward in the mounting portion 54. Multiple porous tubes 112 are provided. Multiple porous tubes 112 are placed at horizontal intervals. Multiple porous tubes 112 are also placed at axial intervals. Each end (upper end) of the multiple porous tubes 112 in the longitudinal direction (vertical direction) opens above the buffer body 42A. The number of porous tubes 112 is set appropriately according to the size of the buffer body 42A.

[0050] <Dehumidifying effect of buffer material> The buffers 41A and 42A are attached to the cask 11, and heat is transferred from the cask 11, causing their temperature to rise. As the temperature rises, the moisture contained in the buffer material that makes up the shock absorber 53 evaporates or moves to another adjacent buffer material. At this time, the moisture evaporated from the buffer material becomes steam and enters the interior of each porous tube 111 and 112 through the holes. The steam that enters the interior of each porous tube 111 and 112 flows through the interior of each porous tube 111 and 112 and is discharged to the outside from the upper end of the porous tube 111 and 112 due to the chimney effect. At this time, fresh outside air enters the interior from the lower end of the porous tube 111 due to the chimney effect.

[0051] Each of the porous tubes 111 and 112 allows water vapor-containing air to be expelled to the outside from the upper end of the porous tubes 111 and 112 by the chimney effect, while dry air from the outside enters the interior from the lower end of the porous tube 111 by the chimney effect. As a result, the temperature and humidity of the cushioning material of the shock absorber 53 in the buffer bodies 41A and 42A decrease, suppressing deterioration of the cushioning material due to increased humidity.

[0052] The dehumidification structure of the buffer 42A is not limited to the configuration described above. The buffer 42A may have only the porous tube 111. Alternatively, the buffer 42A may have the configuration of the buffer 42 of the first embodiment.

[0053] Furthermore, in the first and second embodiments, the dehumidification structure of the buffers 41, 41A, 42, and 42A attached to the horizontally positioned cask 11 was described. The dehumidification structure of the buffer attached to the horizontally positioned cask 11 and the dehumidification structure of the buffer attached to the vertically positioned cask 11 differ in the arrangement of the tubular members. In the vertically positioned cask 11, the buffer 42 is attached to the lid portion 13. In this case, the tubular members arranged in the buffer are arranged along the vertical direction. That is, the tubular members are arranged along the axial direction of the buffer 42. The tubular members arranged along the axial direction have their upper end in the longitudinal direction (vertical direction) open above the buffer 42, and their lower end in the longitudinal direction (vertical direction) open below the buffer 42.

[0054] [Third Embodiment] Figure 11 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.

[0055] As shown in Figure 11, the buffers 41B and 42B of the third embodiment have a dehumidifying function. The buffers 41B and 42B have almost the same configuration, and the buffer 42B will be described in detail.

[0056] The buffer body 42B has a porous tube 121 arranged inside. The porous tube 121 is arranged inside the shock absorber 53 along the vertical direction (radial direction of the buffer body 42B). When the buffer body 42B is attached to the cask 11 which is placed horizontally, the porous tube 121 of the buffer body 42B is arranged along the vertical direction. That is, the porous tube 121 along the radial direction of the buffer body 42B is arranged inside the shock absorber 53 on the side of the disc portion 71 of the outer shell member 52. Multiple porous tubes 121 may be arranged at intervals in the horizontal or axial direction. The end (upper end) of the porous tube 121 in the longitudinal direction (vertical direction) opens above the buffer body 42B, and the end (lower end) in the longitudinal direction (vertical direction) opens below the buffer body 42B.

[0057] The buffer body 42B is equipped with a gas supply device 122 that supplies dry gas to the porous tube 121. The porous tube 121 has an inlet 121a at its lower end and an outlet 121b at its upper end. The gas supply path 123 has its base end connected to a gas supply source 124 for the dry gas and its tip connected to the inlet 121a. Here, the dry gas is, for example, air or nitrogen. The gas supply path 123 is equipped with a pump 125 and a flow control valve 126. The pump 125 is connected to a power supply unit 127. The pump 125 is driven by power supplied from the power supply unit 127 and supplies the dry gas from the gas supply source 124 to the inlet 121a of the porous tube 121 via the gas supply path 123. The flow control valve 126 functions as an adjustment member that adjusts the flow rate of gas flowing inside the porous tube 121, and by adjusting its opening, it adjusts the flow rate of dry gas supplied from the gas supply path 123 to the porous tube 121.

[0058] Furthermore, a dehumidifier 128 is provided in the gas supply path 123. The dehumidifier 128 is, for example, a desiccant. The dehumidifier 128 is located downstream of the pump 125 in the gas supply path 123, but it may also be located upstream of the pump 125. The dehumidifier 128 removes moisture from the dry gas supplied from the gas supply path 123 to the porous tube 121, and supplies dry gas with a lower moisture content than the outside air to the porous tube 121, for example.

[0059] The power supply unit 127 may also be a power supply unit 127A having a thermoelectric element that can be attached to the cask 11. The thermoelectric element is flat and fixed to the outer surface of the cask 11. The thermoelectric element is, for example, a Peltier element. A Peltier element has P-type and N-type semiconductors joined to a metal electrode, and generates electricity when one flat surface is heated and the other flat surface is cooled, creating a temperature difference between the two flat surfaces. The thermoelectric element constituting the power supply unit 127A may be placed between the cask 11 and the buffer 42B. The gas supply device 122 operates with the power generated by the power supply unit 127A having the thermoelectric element, powering the pump 125.

[0060] <Dehumidifying effect of buffer material> The gas supply device 122 drives the pump 125 to supply dry gas from the gas supply source 124 to the inlet 121a of the porous tube 121 via the gas supply path 123. The dry gas supplied to the inlet 121a of the porous tube 121 rises inside the porous tube 121 and is discharged to the outside from the outlet 121b.

[0061] The buffers 41B and 42B are mounted on the cask 11, and heat is transferred from the cask 11, causing their temperature to rise. As the temperature rises, the moisture contained in the buffer material that makes up the shock absorber 53 evaporates or moves to another adjacent buffer material. At this time, the moisture evaporated from the buffer material becomes steam and enters the interior of the porous tube 121 through the holes. The steam that enters the interior of the porous tube 121 rises inside the porous tube 121 due to the dry gas supplied to the inlet 121a and is discharged to the outside from the outlet 121b.

[0062] The porous tube 121 causes water vapor-containing air to be pushed out from the upper end of the porous tube 121 by the dry gas supplied to the porous tube 121. As a result, the temperature and humidity of the cushioning material of the shock absorber 53 in the buffer bodies 41B and 42B decrease, and deterioration of the cushioning material due to increased humidity is suppressed.

[0063] In this configuration, the base end of the gas supply path 123 is connected to the dry gas supply source 124, and the tip end is connected to the inlet 121a. However, the configuration is not limited to this. For example, the base end of the gas supply path 123 may be connected to the outlet 121b of the porous pipe 121, and the tip end may be connected to the inlet 121a. In this case, the dry gas is circulated by driving the pump 125.

[0064] Furthermore, in the third embodiment, one type of porous tube 121 is arranged inside the buffers 41B and 42B, but the buffers 41 and 42 of the first embodiment or the buffers 41A and 42A of the second embodiment may also be used.

[0065] [Fourth Embodiment] Figure 12 is a schematic diagram showing the buffer body of the fourth embodiment installed in a radioactive material storage container, and Figure 13 is a cross-sectional view taken along line XIII-XIII in Figure 12, 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.

[0066] As shown in Figures 12 and 13, the buffers 41C and 42C of the fourth embodiment have a dehumidifying function and a humidity measuring function. The buffers 41C and 42C have almost the same configuration, and the buffer 42C will be described in detail.

[0067] The buffer body 42C has a porous tube 131 arranged inside. The porous tube 131 is arranged vertically (radially in the direction of the buffer body 42C) inside the shock absorber 53. When the buffer body 42C is attached to the cask 11 which is placed horizontally, the porous tube 131 of the buffer body 42C is arranged vertically. Multiple porous tubes 131 may be arranged at intervals in the horizontal or axial direction. The end (upper end) of the porous tube 131 in the longitudinal direction (vertical direction) opens above the buffer body 42C, and the end (lower end) in the longitudinal direction (vertical direction) opens below the buffer body 42C.

[0068] The buffer body 42C has a moisture detector 132 for detecting the moisture content of the shock absorber 53. Multiple moisture detectors 132 are arranged inside the shock absorber 53 in the buffer body 42C. Alternatively, the moisture detectors 132 may be arranged outside the shock absorber 53 in the buffer body 42C. The multiple moisture detectors 132 are arranged at intervals in the radial, circumferential, and axial directions of the shock absorber 53. The multiple moisture detectors 132 are connected to the control unit 133 and output the detection results to the control unit 133. A display unit 134 is connected to the control unit 133. The control unit 133 can perform a deterioration determination based on the moisture content of the buffer material detected by the moisture detectors 132. The control unit 133 can display the moisture content of the buffer material and the deterioration determination result on the display unit 134.

[0069] The moisture detector 132 is a voltage sensor that measures the voltage of the cushioning material in the shock absorber 53. The control unit 133 calculates the electrical resistivity based on the voltage of the cushioning material measured by the voltage sensor acting as the moisture detector 132, and calculates the moisture content based on the electrical resistivity. In this case, it is preferable to determine and map the relationship between the voltage, electrical resistivity, and moisture content of the cushioning material in advance through experiments or simulations.

[0070] Furthermore, the moisture detector 132 may be a piezoelectric element or a piezoelectric wire sensor, and measures the volume change of the cushioning material in the shock absorber 53. The control unit 133 calculates the moisture content based on the volume change of the cushioning material measured by the piezoelectric element or piezoelectric wire sensor acting as the moisture detector 132. In this case, it is preferable to determine and map the relationship between the volume change of the cushioning material and the moisture content in advance through experiments or simulations.

[0071] Furthermore, the moisture detector 132 may be a gas sensor or the like, and detects moisture in the gas (water vapor) generated from the cushioning material in the shock absorber 53. The control unit 133 calculates the moisture content by analyzing the moisture in the cushioning material detected by the gas sensor acting as the moisture detector 132. In this case, it is preferable to determine and map the relationship between the gas components of the cushioning material, the amount of moisture, and the moisture content in advance through experiments or simulations.

[0072] The moisture detector 132, the control unit 133, and the display unit 134 are connected to the power supply unit. Preferably, the power supply unit is a power supply unit having a thermoelectric element that can be attached to the cask 11 or the buffer 42C.

[0073] [Effects of this embodiment] The buffer body according to the first embodiment is a buffer body 41, 41A, 41B, 41C, 42, 42A, 42B, 42C that is attached to a cask (radioactive material storage container) 11, and has perforated tubes 101, 102, 103, 104, 111, 112, 121, 131 arranged inside.

[0074] According to the buffer according to the first embodiment, water vapor generated from the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C enters the interior through the holes of the porous tubes 101, 102, 103, 104, 111, 112, 121, and 131, and is then discharged to the outside through the porous tubes 101, 102, 103, 104, 111, 112, 121, and 131. Therefore, by suppressing the rise in temperature of the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C, humidity does not become unstable, and by suppressing deterioration, the decline in buffering function can be suppressed.

[0075] The buffer body according to the second embodiment is the buffer body according to the first embodiment, and furthermore, the porous tubes 101, 102, 103, 104, 111, 112, 121, and 131 are formed of a metallic material. As a result, the porous tubes 101, 102, 103, 104, 111, 112, 121, and 131 are efficiently heated by the heat transferred from the cask 11 to the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C, and the moisture contained in the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C can be efficiently heated by the porous tubes 101, 102, 103, 104, 111, 112, 121, and 131 and turned into water vapor.

[0076] The buffer body according to the third embodiment is a buffer body according to the first or second embodiment, and further, when the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, 42C are attached to the cask 11, the porous tubes 102, 103, 111, 121, 131 are arranged along the vertical direction. This allows water vapor generated from the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, 42C that have entered the porous tubes 102, 103, 111, 121, 131 to be properly discharged to the outside by the chimney effect.

[0077] The buffer body according to the fourth embodiment is a buffer body according to any one of the first to third embodiments, and furthermore, the porous tubes 102, 103, 111, 121, and 131 have one end in the longitudinal direction that opens vertically upward and the other end in the longitudinal direction that opens vertically downward. As a result, water vapor from the porous tubes 102, 103, 111, 121, and 131 can be discharged to the outside from the top due to the chimney effect, and outside air can be taken in from the bottom, and water vapor generated from the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C can be properly discharged to the outside.

[0078] The fifth embodiment of the buffer body is a buffer body 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, wherein the perforated tubes 102, 103, 111, 121, and 131 are arranged along the radial direction of the shock absorber 53, and one end and the other end in the longitudinal direction penetrate the outer shell member 52 and are open to the outside. This allows the perforated tubes 102, 103, 111, 121, and 131 to be properly arranged.

[0079] The buffer according to the sixth embodiment is a buffer according to any one of the first to fifth embodiments, and further, a flow path 105 is provided in which porous tubes 102, 103, and 104 are connected to a mounting portion 54 attached to the cask 11. As a result, the water vapor flowing through the flow path 105 is heated by the heat of the cask 11, and the water vapor can be efficiently discharged to the outside by the chimney effect.

[0080] The buffer according to the seventh embodiment is a buffer according to any one of the first to sixth embodiments, and is further provided with lid members 106, 107 or a flow control valve 126 as adjusting members for adjusting the flow rate of gas flowing inside the porous tubes 102, 103, 111, 112, 121, and 131. As a result, when the humidity of the outside air is high, the outlet and inlet of the porous tube 102 can be closed by the lid members 106, 107 or the flow control valve 126, thereby suppressing contact between the humid outside air and the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C.

[0081] The buffer body according to the eighth embodiment is a buffer body according to any one of the first to seventh embodiments, further comprising a dehumidifier 128 positioned at at least one of the longitudinal ends of the porous tubes 102, 103, 111, 112, 121, and 131. This allows the air supplied to the porous tubes 102, 103, 111, 112, 121, and 131 to be dehumidified by the dehumidifier 128, thereby enabling proper dehumidification of the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C.

[0082] The buffer body according to the ninth embodiment is a buffer body according to any one of the first to eighth embodiments, and is further provided with a gas supply device 122 that supplies dry gas to the porous tubes 101, 102, 103, 104, 111, 112, 121, and 131. By supplying dry gas to the porous tubes 101, 102, 103, 104, 111, 112, 121, and 131 via the gas supply device 122, dehumidification of the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C can be promoted.

[0083] The buffer according to the tenth embodiment is a buffer according to the ninth embodiment, further having a thermoelectric element that can be attached to the cask 11, and the gas supply device 122 is operated by the electricity generated by the thermoelectric element. This makes it possible to secure power for the gas supply device 122 using the heat of the cask 11, and simplifies the device by eliminating the need for a separate power supply unit.

[0084] The buffer according to the 11th embodiment is a buffer according to any one of the first to tenth embodiments, and further comprises a hollow outer shell member 52, an impact absorber 53 disposed inside the outer shell member 52, and a moisture detector 132 for detecting the moisture content of the impact absorber 53. As a result, the deterioration of the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C can be determined by detecting the moisture content of the impact absorber 53 with the moisture detector 132. [Explanation of Symbols]

[0085] 11. Cask (container for radioactive material) 12 Cask body 13 Lid 29 Bottom 31 Primary lid 32 Secondary lid 41,41A,41B,41C,42,42A,42B,42C Buffer 43. Stand 44 Support part 51 Structure 52 Outer shell member 53 Shock absorber 54 Mounting part 101,102,103,104,111,112,121,131 Porous pipe 105 Flow channel 106,107 Lid members 122 Gas supply device 123 Gas supply routes 124 Gas supply sources 125 pump 126 Flow control valve 127,127A power supply section 128 Dehumidifier 132 Moisture detector 133 Control Unit 134 Display section

Claims

1. A buffer to be attached to a container for radioactive materials, A porous tube is placed inside. buffer body.

2. The porous tube is formed of a metal material. The buffer according to claim 1.

3. When the buffer is installed in the radioactive material storage container, the porous tube is arranged along the vertical direction. The buffer according to claim 1.

4. The porous tube has one end in the longitudinal direction that opens vertically upward, and the other end in the longitudinal direction that opens vertically downward. The buffer according to claim 3.

5. The device comprises a bottomed cylindrical outer shell member and a cylindrical shock absorber disposed inside the outer shell member, wherein the porous tube is arranged along the radial direction of the shock absorber, and one end and the other end in the longitudinal direction penetrate the outer shell member and are open to the outside. The buffer according to claim 1.

6. A flow path is provided through which the porous tube communicates with the attachment portion that is attached to the radioactive material storage container. The buffer according to claim 1.

7. An adjustment member is provided to adjust the flow rate of gas flowing inside the porous tube. The buffer according to claim 1.

8. A dehumidifying device is arranged at at least one of the longitudinal ends of the porous tube. The buffer according to claim 1.

9. A gas supply device is provided to supply drying gas to the porous tube. The buffer according to claim 1.

10. The gas supply device has a thermoelectric element that can be attached to the radioactive material storage container, and the gas supply device operates using electricity generated by the thermoelectric element. The buffer according to claim 9.

11. It comprises a hollow outer shell member, an impact absorber disposed inside the outer shell member, and a moisture detector for detecting the moisture content of the impact absorber. The buffer according to claim 1.

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