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, having a tubular member arranged inside, with one end and the other end in the longitudinal direction open to the outside.

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 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 portion fixed to the upper part of the cask body to close the opening. The radioactive material storage container is provided with a shock absorber 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.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] A shock absorber is generally configured such that a cushioning material such as wood is covered with a metal plate. The shock absorber may deteriorate after long-term use depending on the material used and the usage environment. That is, since the radioactive material storage container stores radioactive waste, it becomes high in temperature, and heat is transmitted from the radioactive material storage container to the shock absorber, causing its temperature 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 body of this disclosure for achieving the above objective is a buffer body to be attached to a radioactive material storage container, wherein a tubular member is arranged inside, and one end in the longitudinal direction and the other end are open to the outside. [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 cross-sectional view showing a buffer body of the second embodiment installed in a radioactive material storage container. [Figure 9] Figure 9 is a cross-sectional view showing a modified example of the buffer body of the second embodiment installed in a radioactive material storage container. [Figure 10]Figure 10 is a schematic diagram showing the buffer body of the third embodiment installed in a radioactive material storage container. [Figure 11] Figure 11 is a schematic diagram showing the buffer body of the fourth embodiment installed in a radioactive material storage container. [Figure 12] Figure 12 is a cross-sectional view taken along line XII-XII in Figure 11, 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 with a gap on the outer peripheral surface of the main body barrel 21. On the main body barrel 21, a plurality of copper heat transfer fins 27 for heat conduction are provided at intervals in the circumferential direction between the outer peripheral surface of the main body barrel 21 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 part and the lower part 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 barrel 21 through the outer cylinder 26. The trunnions 30 protrude to the outermost peripheral side of the cask 11.

[0016] The lid part 13 is arranged at the opening 22 of the main body barrel 21. The lid part 13 closes the opening 22 to hermetically seal the main body barrel 21 (the cask main body 12). The lid part 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 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 cask 11 may also be supported by the cask body 12. 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 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] <Heat removal structure of buffer body> Figure 6 is a cross-sectional view showing the buffer body of the first embodiment installed in a radioactive material storage container, and Figure 7 is a cross-sectional view taken along line VII-VII of Figure 6, 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, and porous materials. 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 6 and 7, the buffers 41 and 42 of the first embodiment have a heat removal 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 a tubular member 101 positioned inside. One end and the other end of the tubular member 101 in the longitudinal direction are open to the outside of the buffer body 42. The tubular member 101 is formed from a metal material or graphene sheet with excellent thermal conductivity. Suitable metal materials include, for example, copper, iron, and aluminum. The tubular member 101 has a cylindrical shape, but it may also have a polygonal shape. Alternatively, instead of the tubular member 101, an air passage may be formed inside the buffer body 42.

[0036] The buffer body 42 is constructed by covering an 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 tubular member 101 has a linear shape and is placed inside the impact absorber 53, with one end and the other end in the longitudinal direction penetrating the outer shell member 52 and open to the outside. Multiple tubular members 101 are arranged in the impact absorber 53. The multiple tubular members 101 are arranged at intervals in the axial direction of the cask body 12 and at intervals in the radial direction of the cask body 12. Note that the number of tubular members 101 is set appropriately according to the size of the buffer body 42.

[0037] The buffer 42 is attached 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 attached to 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 tubular members 101 of the buffer body 42 are arranged along the vertical direction. The multiple tubular members 101 along the radial direction of the buffer body 42 have their longitudinal (vertical) ends (upper ends) open above the buffer body 42 and their longitudinal (vertical) ends (lower ends) open below the buffer body 42.

[0039] 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 multiple tubular members 101 are arranged on the disc portion 71 side of the mounting portion 54. However, some of the multiple tubular members 101 have, for example, a portion in the longitudinal direction (in this embodiment, the middle portion) exposed to the mounting portion 54 and able to contact the lid portion 13 of the cask 11.

[0040] Furthermore, the buffer body 42 is provided with working holes 55 along the axial direction for inserting bolts 81 (see Figure 5) that are fixed to the cask 11. 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 pipe member 82 and cylindrical member 62 (all see Figure 5). Multiple pipe members 101 are arranged between the multiple working holes 55 and do not interfere with the working holes 55.

[0041] The pipe member 101 has an upper end that opens above the buffer body 42 and 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 pipe member 101. When the temperature of the outside air is high due to weather conditions, etc., the outlet of the pipe member 101 is closed with lid member 106 and the inlet of the pipe member 101 is closed with lid member 107 to suppress heat exchange with the high-temperature outside air. In addition, a temperature measuring instrument and a humidity measuring instrument may be placed on the opening side of the pipe member 101 to measure the temperature and humidity.

[0042] <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, the heat from the buffers 41 and 42 is transferred to the pipe member 101, and the air inside the pipe member 101 is heated. The air heated inside the pipe member 101 rises through the chimney effect and is discharged to the outside from the upper end. At this time, fresh air from the outside flows into the pipe member 101 from the lower end due to the chimney effect.

[0043] In other words, when heat from the buffers 41 and 42 is transferred to the pipe member 101 and the air inside is heated, the heated air rises inside the pipe member 101 and is discharged to the outside from the upper end, while outside air enters the inside from the lower end of the pipe member 101. As a result, the air flowing inside the pipe member 101 cools the cushioning material of the shock absorber 53 in the buffers 41 and 42, causing its temperature to drop and suppressing deterioration of the cushioning material due to temperature rise.

[0044] [Second Embodiment] Figure 8 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.

[0045] As shown in Figure 8, the buffers 41A and 42A of the second embodiment have a heat removal function. The buffers 41A and 42A have almost the same configuration, and the buffer 42A will be described in detail.

[0046] The buffer body 42A has pipe members 101 and 102 arranged inside. Pipe member 101 is arranged inside the shock absorber 53 along the vertical direction (radial direction of the buffer body 42A). Pipe member 101 has a straight shape and is arranged along the vertical direction (radial direction of the buffer body 42A), with its longitudinal (vertical) end (upper end) opening above the buffer body 42A and its longitudinal (vertical) end (lower end) opening below the buffer body 42A. The number of pipe members 101 is set appropriately according to the size of the buffer body 42A.

[0047] The pipe member 102 is positioned inside the shock absorber 53, almost vertically (radially in the direction of the buffer 42A). The pipe member 102 has an upper straight section 102a, a curved section 102b, and a lower straight section 102c. The pipe member 102 has a curved section 102b that bypasses the mounting section 54 radially outward. The end (upper end) of the pipe member 102 in the longitudinal direction (vertical direction) opens above the buffer 42A, and the end (lower end) in the longitudinal direction (vertical direction) opens below the buffer 42A. The number of pipe members 102 is set appropriately according to the size of the buffer 42A.

[0048] Figure 9 is a cross-sectional view showing a modified example of the buffer body of the second embodiment installed in a radioactive material storage container.

[0049] The buffer body 42A has a tubular member 103 arranged inside. The tubular member 103 is arranged inside the shock absorber 53, almost vertically (radially in the direction of the buffer body 42A). The tubular member 103 has an upper straight section 103a, an upper curved section 103b, an intermediate straight section 103c, a lower curved section 103d, and a lower straight section 103e. The tubular member 102 has an upper curved section 103b that bypasses the mounting section 54 towards the axial disc section 71, an intermediate straight section 103c, and a lower curved section 103d. The end (upper end) of the tubular member 103 in the longitudinal direction (vertical direction) opens above the buffer body 42A, and the end (lower end) in the longitudinal direction (vertical direction) opens below the buffer body 42A. The number of tubular members 103 is set appropriately according to the size of the buffer body 42A.

[0050] <The heat-removing effect of buffers> The buffers 41A and 42A are attached to the cask 11, and heat is transferred from the cask 11, causing their temperature to rise. At this time, the heat from the buffers 41A and 42A is transferred to the pipe members 101, 102, and 103, and the air inside the pipe members 101, 102, and 103 is heated. The air heated inside the pipe members 101, 102, and 103 rises through the chimney effect and is discharged to the outside from the upper end. At this time, fresh air from the outside enters the inside of the pipe members 101, 102, and 103 from the lower end due to the chimney effect.

[0051] In other words, when heat from the buffers 41A and 42A is transferred to the pipe member 101 and the air inside is heated, the heated air rises inside the pipe members 101, 102, and 103 and is discharged to the outside from the upper end, while outside air enters the inside from the lower end of the pipe members 101, 102, and 103. As a result, the air flowing inside the pipe members 101, 102, and 103 cools the cushioning material of the shock absorber 53 in the buffers 41A and 42A, causing its temperature to drop and suppressing deterioration of the cushioning material due to temperature rise.

[0052] Furthermore, the heat removal structure of the buffers 41A and 42A is not limited to the configuration described above. The buffers 41A and 42A may consist only of the pipe member 102 or the pipe member 103.

[0053] Furthermore, in the first and second embodiments, the heat removal structure of the buffers 41, 41A, 42, and 42A attached to the horizontally positioned cask 11 was described. The heat removal structure of the buffer attached to the horizontally positioned cask 11 and the heat removal 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 ends in the longitudinal direction (vertical direction) opening above the buffer 42, and their lower ends in the longitudinal direction (vertical direction) opening below the buffer 42.

[0054] [Third Embodiment] Figure 10 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 10, the buffers 41B and 42B of the third embodiment have a heat removal function. The buffers 41B and 42B have almost the same configuration, and the buffer 42B will be described in detail.

[0056] The buffer body 41B has a tubular member 121 arranged inside. The tubular member 121 is arranged inside the shock absorber 53 along the vertical direction (radial direction of the buffer body 41B). When the buffer body 41B is attached to the cask 11 which is placed horizontally, the tubular member 121 of the buffer body 41B is arranged along the vertical direction. That is, the tubular member 121 along the radial direction of the buffer body 41B is arranged inside the shock absorber 53 on the side of the disc portion 71 of the outer shell member 52. Multiple tubular members 121 may be arranged at intervals in the horizontal or axial direction. The end (upper end) of the tubular member 121 in the longitudinal direction (vertical direction) opens above the buffer body 41B, and the end (lower end) in the longitudinal direction (vertical direction) opens below the buffer body 41B.

[0057] The buffer body 41B is provided with a medium supply device 122 that supplies a cooling medium to the pipe member 121. The pipe member 121 has an inlet 121a at its lower end and an outlet 121b at its upper end. The medium supply path 123 has its base end connected to the outlet 121b of the pipe member 121 and its tip connected to the inlet 121a. Here, the cooling medium is, for example, air or nitrogen, but it may also be a liquid such as water. Furthermore, it is preferable that the cooling medium is a fluid at a temperature lower than room temperature. The medium supply path 123 is provided 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 circulates the cooling medium discharged from the outlet 121b of the pipe member 121 to the inlet 121a of the pipe member 121 via the medium supply path 123. The flow control valve 126 functions as an adjustment member that adjusts the flow rate of the cooling medium flowing inside the pipe member 121, and adjusts the flow rate of the cooling medium supplied from the medium supply path 123 to the pipe member 121 by adjusting the degree of opening.

[0058] Furthermore, a cooling device 128 is provided in the medium supply path 123. The cooling device 128 is, for example, a heat exchanger. The cooling device 128 is located downstream of the pump 125 in the medium supply path 123, but it may also be located upstream of the pump 125. The cooling device 128 cools the cooling medium supplied from the medium supply path 123 to the pipe member 121, and supplies the pipe member 121 with a cooling medium that is, for example, cooler than the outside air.

[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 41B. The medium supply device 122 is powered by the electricity generated by the power supply unit 127A having a thermoelectric element, and the pump 125 of the medium supply device 122 is operated by the electricity generated by the power supply unit 127A having a thermoelectric element. By providing a power supply unit 127A having a thermoelectric element, the heat from the cask 11 can be used to secure power for the medium supply device 122, eliminating the need for a separate power supply unit and simplifying the device.

[0060] <The heat-removing effect of buffers> The medium supply device 122 drives the pump 125 to supply the cooling medium from the medium supply path 123 to the inlet 121a of the pipe member 121. The cooling medium supplied to the inlet 121a of the pipe member 121 rises inside the pipe member 121 and is discharged from the outlet 121b to the medium supply path 123.

[0061] The buffers 41B and 42B are attached to the cask 11, and heat is transferred from the cask 11, causing their temperature to rise. At this time, the heat from the buffers 41B and 42B is transferred to the pipe member 121, and the cooling medium supplied to the inside of the pipe member 121 is heated. The cooling medium, which has been heated and whose temperature has risen inside the pipe member 121, rises inside the pipe member 121 and is discharged into the medium supply path 123.

[0062] In other words, when heat from the buffers 41B and 42B is transferred to the pipe member 121 and the cooling medium inside is heated, the heated cooling medium rises inside the pipe member 121 and is discharged from the upper end, and new cooling medium enters the inside from the lower end of the pipe member 121. As a result, the cushioning material of the shock absorber 53 in the buffers 41B and 42B is cooled by the air flowing inside the pipe member 101, causing its temperature to drop and suppressing deterioration of the cushioning material due to temperature rise.

[0063] In this configuration, the base end of the media supply path 123 is connected to the outlet 121b of the pipe member 121, 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 media supply path 123 may be connected to the media supply source of the cooling medium, and the tip end may be connected to the inlet 121a. In this case, by driving the pump 125, the cooling medium from the media supply source is continuously supplied to the inlet 121a of the pipe member 121 via the media supply path 123.

[0064] Furthermore, in the third embodiment, one type of pipe member 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 11 is a schematic diagram showing the buffer body of the fourth embodiment installed in a radioactive material storage container, and Figure 12 is a cross-sectional view taken along line XII-XII in Figure 11, 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 11 and 12, the buffers 41C and 42C of the fourth embodiment have a heat removal function, a temperature measurement function, and a humidity measurement 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 tubular member 131 arranged inside. The tubular member 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 tubular member 131 of the buffer body 42C is arranged vertically. Multiple tubular members 131 may be arranged at intervals in the horizontal or axial direction. The end (upper end) of the tubular member 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 temperature measuring device 132 for measuring the temperature of the shock absorber 53. Multiple temperature measuring devices 132 are arranged inside the shock absorber 53 in the buffer body 42C. The multiple temperature measuring devices 132 are arranged at intervals in the radial, circumferential, and axial directions of the shock absorber 53.

[0069] Furthermore, the buffer body 42C has a moisture meter 133 for measuring the moisture content of the shock absorber 53. Multiple moisture meters 133 are arranged inside the shock absorber 53 in the buffer body 42C. The multiple moisture meters 133 are arranged at intervals in the radial, circumferential, and axial directions of the shock absorber 53.

[0070] Multiple temperature measuring devices 132 and multiple moisture measuring devices 133 are connected to a control unit 134, and the measurement results are output to the control unit 134. The connection between the temperature measuring devices 132 and moisture measuring devices 133 and the control unit 134 may be wireless, or it may be wired by running a signal cable inside the pipe member 101. A display unit 135 is connected to the control unit 134. The control unit 134 can determine deterioration based on the temperature of the cushioning material measured by the temperature measuring devices 132 and the moisture content of the cushioning material measured by the moisture measuring devices 133. The control unit 134 can display the temperature of the cushioning material, the moisture content of the cushioning material, and the deterioration determination result on the display unit 135.

[0071] The moisture meter 133 is a voltage sensor that measures the voltage of the cushioning material in the shock absorber 53. The control unit 134 calculates the electrical resistivity based on the voltage of the cushioning material measured by the voltage sensor (moisture meter 133), 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.

[0072] Furthermore, the moisture meter 133 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 134 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 meter 133. 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.

[0073] Furthermore, the moisture meter 133 may be a gas sensor or the like, and measures the moisture content in the gas (water vapor) generated from the cushioning material in the shock absorber 53. The control unit 134 calculates the moisture content by analyzing the moisture content of the cushioning material measured by the gas sensor acting as the moisture meter 133. 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.

[0074] The temperature measuring instrument 132, moisture measuring instrument 133, control unit 134, and display unit 135 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 buffer 42C.

[0075] [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, in which tubular members 101, 102, 103, 121, 131 are arranged inside, and one end and the other end in the longitudinal direction are open to the outside.

[0076] According to the first embodiment of the buffer, the heat transferred from the cask 11 to the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C is removed by the air flowing inside the tubular members 101, 102, 103, 121, and 131. As a result, the temperature rise of the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C is suppressed, and deterioration is suppressed, thereby preventing a decrease in the buffering function.

[0077] The buffer according to the second embodiment is the buffer according to the first embodiment, and furthermore, the pipe members 101, 102, 103, 112, 121, and 131 are formed of a metal material. As a result, the heat transferred from the cask 11 to the buffer members 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C efficiently raises the temperature of the pipe members 101, 102, 103, 121, and 131, and the heat transferred to the pipe members 101, 102, 103, 121, and 131 can be appropriately removed by the air flowing inside.

[0078] The buffer according to the third embodiment is a buffer according to the first or second embodiment, further comprising pipe members 101, 102, 103, 121, and 131 arranged vertically. This allows the air inside the pipe members 101, 102, 103, 121, and 131, whose temperature has risen due to the heat of the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C, to be appropriately discharged to the outside by the chimney effect.

[0079] The buffer body according to the fourth embodiment is a buffer body according to any one of the first to third embodiments, and furthermore, one end of the tube members 101, 102, 103, 121, and 131 in the longitudinal direction opens vertically upward, and the other end in the longitudinal direction opens vertically downward. As a result, the air heated by the chimney effect of the tube members 101, 102, 103, 121, and 131 can be discharged to the outside from the top and outside air can be taken in from the bottom, thereby appropriately cooling the buffer bodies 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C.

[0080] 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 tubular members 101, 102, 103, 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 tubular members 101, 102, 103, 121, and 131 to be properly positioned.

[0081] The buffer according to the sixth embodiment is a buffer according to any one of the first to fifth embodiments, further comprising a plurality of working holes 55 for inserting bolts 81 to be fixed to the cask 11, spaced apart in the circumferential direction, and the pipe members 101, 102, 103, 121, and 131 are arranged between the plurality of working holes 55. This allows the pipe members 101, 102, 103, 121, and 131 to be properly positioned without interfering with the working holes 55.

[0082] The buffer according to the seventh embodiment is a buffer according to any one of the first to sixth embodiments, and furthermore, at least a portion of the tubular members 101, 102, 103, 121, and 131 is exposed at the mounting portion 54 that is attached to the cask 11. As a result, the tubular members 101, 102, 103, 121, and 131 come into direct contact with the cask 11, and the temperature rise of the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C can be appropriately suppressed.

[0083] The buffer according to the eighth embodiment is a buffer according to any one of the first to seventh embodiments, and is further provided with a medium supply device 122 that supplies a cooling medium to the pipe members 101, 102, 103, 121, and 131. As a result, by supplying a cooling medium to the pipe members 101, 102, 103, 121, and 131 by the medium supply device 122, the heat transferred from the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C to the pipe members 101, 102, 103, 121, and 131 can be appropriately removed by the cooling medium.

[0084] The buffer according to the ninth embodiment is a buffer according to any one of the first to eighth embodiments, and further comprises a hollow outer shell member 52, a shock absorber 53 disposed inside the outer shell member 52, and a temperature measuring device 132 for measuring the temperature of the shock absorber 53. As a result, the deterioration of the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C can be determined by measuring the temperature of the shock absorber 53 with the temperature measuring device 132.

[0085] The buffer according to the tenth embodiment is a buffer according to any one of the first to ninth embodiments, and further includes a moisture meter 133 for measuring the moisture content of the shock absorber 53. By measuring the moisture content of the shock absorber 53 with the moisture meter 133, the deterioration of the buffers 41, 41A, 41B, 41C, 42, 42A, 42B, and 42C can be determined. [Explanation of Symbols]

[0086] 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 55 Working holes 101,102,103,121,131 Pipe members 106,107 Lid members 122 Media supply device 123 Media supply route 125 pump 126 Flow control valve 127,127A power supply section 128 Cooling device 132 Temperature measuring device 133 Moisture Meter 134 Control Unit 135 Display section

Claims

1. A buffer to be attached to a container for radioactive materials, A tubular member is arranged inside, with one end and the other end in the longitudinal direction open to the outside. buffer body.

2. The aforementioned pipe member is formed from a metal material. The buffer according to claim 1.

3. The aforementioned pipe member is arranged along the vertical direction. The buffer according to claim 1.

4. The aforementioned pipe member 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 tubular member 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. Multiple work holes for inserting bolts to fix the radioactive material storage container are provided at circumferential intervals, and the pipe member is positioned between the multiple work holes. The buffer according to claim 1.

7. At least a portion of the tubular member is exposed in the attachment portion to be attached to the radioactive material storage container. The buffer according to claim 1.

8. A medium supply device is provided to supply a cooling medium to the aforementioned pipe member. The buffer according to claim 1.

9. It comprises a hollow outer shell member, a shock absorber disposed inside the outer shell member, and a temperature measuring device for measuring the temperature of the shock absorber. The buffer according to claim 1.

10. The shock absorber has a moisture meter for measuring the humidity of the shock absorber, The buffer according to claim 9.

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