JP7770286B2 - Buffer body and radioactive material storage container - Google Patents

Description

This disclosure relates to a buffer that protects a radioactive material storage container and the radioactive material storage container.

At nuclear facilities, radioactive waste such as spent fuel generated in reactors is stored in radioactive material storage containers and transported to storage facilities or reprocessing facilities for storage or reprocessing. A radioactive material storage container consists of a cylindrical body with a bottom and an open top, and a lid that is fixed to the top of the body and closes the opening. A buffer body is also provided at the axial end of the radioactive material storage container. The buffer body deforms to absorb impact when the radioactive material storage container is dropped, tipped over, or hit.

A buffer is constructed by placing a buffer material inside a support member. Because buffer materials can deteriorate over long periods of use depending on the material used and the environment in which they are used, it is preferable to monitor the deterioration of the buffer material. One example of technology for monitoring the deterioration of buffer materials is described in Patent Document 1 below.

Japanese Patent Application Laid-Open No. 2022-11603

In the aforementioned Patent Document 1, a deterioration monitoring member made of a material with similar deterioration properties over time to the buffer material is placed around the radioactive material storage container. However, the buffer body is constructed by sealing the buffer material inside a support member and fixing it to the radioactive material storage container. Therefore, the environment in which the buffer material of the shock absorber and the deterioration monitoring member described in Patent Document 1 are placed are different, which may affect the deterioration determination of the buffer material.

The present disclosure aims to solve the above-mentioned problems and provide a buffer and a radioactive material storage container that improves the accuracy of determining the deterioration of the buffer material.

To achieve the above objective, the buffer of the present disclosure comprises a hollow support member provided on the outside of a radioactive material storage container, a buffer material disposed inside the support member that absorbs impact by deforming, and a displacement measuring device that estimates the amount of displacement of the buffer material.

The radioactive material storage container disclosed herein also includes a body portion, a lid portion that seals the body portion, and the buffer body.

The buffer body and radioactive material storage container disclosed herein can improve the accuracy of determining the deterioration of the buffer material.

FIG. 1 is a perspective view of a radioactive material storage container with a part cut away. FIG. 2 is a plan view showing a radioactive material storage container equipped with a buffer body. FIG. 3 is a front view showing the radioactive material storage container with the buffer body attached in a vertically placed state. FIG. 4 is a front view showing a state in which the radioactive material storage container with the buffer body attached is placed horizontally. FIG. 5 is a cross-sectional view showing the internal structure of the buffer body. FIG. 6 is a front view showing the buffer body of the first embodiment. FIG. 7 is a cross-sectional view showing a main part of a buffer body that represents the displacement amount measuring device. FIG. 8 is a deterioration determination map showing the amount of displacement of the test material over time. FIG. 9 is a cross-sectional view showing a main part of the buffer body of the second embodiment. FIG. 10 is a deterioration determination map showing the amount of displacement of the cushioning material over time. FIG. 11 is a cross-sectional view showing a main part of the buffer body of the third embodiment. FIG. 12 is a cross-sectional view showing a main part of the buffer body of the fourth embodiment. FIG. 13 is a cross-sectional view showing a main part of the buffer body of the fifth embodiment.

Preferred embodiments of the present disclosure are described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, they also include configurations that combine the various embodiments. Furthermore, the components in the embodiments include those that would be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[First embodiment]
<Radioactive material storage container>
FIG. 1 is a perspective view of a radioactive material storage container according to a first embodiment, with a part cut away.

As shown in FIG. 1, the cask 11 serving as a radioactive material storage container comprises a trunk 12 and a lid 13. The trunk 12 has a container body 21. The container body 21 is cylindrical (in this embodiment, cylindrical) with an opening 22 formed at the upper end and a closed lower end. The container body 21 has an internal cavity 23, in which a basket 24 is provided. The basket 24 is provided with multiple cells 25 capable of independently storing radioactive material (e.g., spent fuel assemblies). The container body 21 is a forged product made of carbon steel with gamma ray shielding properties, although stainless steel can also be used instead of carbon steel. The container body 21 can also be a cast product made of spheroidal graphite cast iron, carbon steel cast steel, or the like.

The barrel 12 has an outer cylinder 26 disposed on the outer peripheral surface of the container body 21 with a predetermined gap between them. The container body 21 has multiple copper heat transfer fins 27 arranged circumferentially to conduct heat between its outer peripheral surface and the inner peripheral surface of the outer cylinder 26. In the space enclosed by the outer cylinder 26 and the heat transfer fins 27, the container body 21 is fitted with a resin (neutron shielding body) 28, a polymeric material containing a large amount of hydrogen and containing boron or a boron compound with neutron shielding properties.

The body 12 has a bottom 29 that protrudes below the closed lower end of the container body 21. The bottom 29 is formed with dimensions smaller than the outer diameter of the container body 21. The bottom 29 has a space surrounded by the closed lower end of the container body 21, and resin (neutron shielding) is provided in the space.

The barrel 12 is provided with a trunnion 30 for lifting the cask 11 on the vessel body 21. The trunnion 30 extends from the vessel body 21 through the outer cylinder 26 and protrudes furthest outward from the cask 11.

The lid portion 13 is provided at the opening 22 of the vessel body 21 and closes the opening 22 to hermetically seal the vessel body 21 (body portion 12). The lid portion 13 is composed of a primary lid 31 and a secondary lid 32. The primary lid 31 is formed in a disk shape from carbon steel or stainless steel that shields against gamma rays. The secondary lid 32 covers the primary lid 31 and appears on the outside of the cask 11. Like the primary lid 31, the secondary lid 32 is also formed in a disk shape from carbon steel or stainless steel that shields against gamma rays. A resin (neutron shield) 28 may be provided between the primary lid 31 and secondary lid 32. A tertiary lid may also be provided on the lid portion.

The primary lid 31 is attached to the container body 21 by being fixed to the first step 22a formed at the opening 22 of the container body 21 with bolts (not shown) made of carbon steel or stainless steel. The secondary lid 32 is attached to the container body 21 by being fixed to the second step 22b formed at the opening 22 of the container body 21 with bolts (not shown) made of carbon steel or stainless steel. Although not shown, metal gaskets are provided between the primary lid 31 and the first step 22a and between the secondary lid 32 and the second step 22b. The metal gaskets ensure airtightness between the primary lid 31 and the first step 22a and between the secondary lid 32 and the second step 22b.

The barrel 12 surrounds the secondary lid 32 at the opening 22 of the vessel body 21, forming a cylindrical upper edge 22c that is visible on the outside of the cask 11. The upper surface of the upper edge 22c is located higher than the surface of the secondary lid 32, and surrounds the secondary lid 32. The upper surface of the upper edge 22c has multiple bolt holes 33 spaced circumferentially for attaching the buffer body A, described below.

<Buffer>
FIG. 2 is a plan view showing a radioactive material storage container equipped with a protective device according to the first embodiment, and FIG. 3 is a front view showing a state in which the radioactive material storage container equipped with the protective device is placed upright.

As shown in Figures 2 and 3, the cask 11 is provided with a buffer body 41. The buffer body 41 is attached to the cask 11 after it is transported to a storage facility, which is, for example, a storage location.

In a nuclear power plant, the cask 11 contains, for example, spent fuel assemblies stored in the cells 25 of the basket 24 of the vessel body 21 and is 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 transportation. When the cask 11 is transported to the storage facility (the storage location), the transport buffer is removed and the cask 11 is stored upright on the floor F with the lid 13 facing upward, and a buffer 41 is attached to the lid 13 side. During storage, the bottom 29 of the cask 11 is fitted into a frame 37 installed on the floor F, or the trunnion is fastened to the frame, and the cask 11 is stored in an upright position with its central axis O aligned vertically.

The buffer 41 has a support member 42 and a buffer material 43.

The support member 42 has a disk portion 51 and a cylindrical portion 52. The cylindrical portion 52 is integrally formed on the radially outer side of the disk portion 51. The support member 42 is hollow and made of a metal plate such as a steel plate, and is deformable under a predetermined load. The predetermined load is the load of an anticipated falling object or the load that would be applied to the cask 11 when it hits the floor F if the cask 11 were to tip over while standing on the floor F. The disk portion 51 is positioned above the lid portion 13 of the cask 11, along the surface of the secondary lid 32 that is visible on the outside of the lid portion 13. The disk portion 51 is positioned so as to cover the surface of the secondary lid 32 and the surface of the upper edge 22c of the vessel body 21. The disk portion 51 is fixed to the vessel body 21 by bolts (not shown) attached to bolt holes 33 provided in the upper edge 22c. If a tertiary lid is provided as the lid portion, the disk portion 51 is positioned along the surface of the tertiary lid that appears on the outside of the lid portion 13, and is positioned so as to cover the surface of the tertiary lid and the surface of the upper edge 22c of the container body 21.

The cylindrical portion 52 is positioned to surround the outside of the upper edge 22c of the body portion 12. In other words, the cylindrical portion 52 is positioned radially outward from the lid portion 13 and protrudes radially outward from the body portion 12.

The buffer material 43 is placed inside and supported by the support member 42. The buffer material 43 deforms when subjected to a predetermined load. The buffer material 43 is made of wood, foam, or a polymer compound.

Figure 4 is a front view showing a radioactive material storage container equipped with a protective device placed horizontally.

Also, as shown in Figure 4, the cask 11 may be stored horizontally with its central axis O aligned horizontally. The cask 11 is stored vertically with its body 12 fitted into a stand 38 installed on the floor F, with its central axis O aligned vertically. In this case, a buffer 41 is attached to one side of the cask 11 along the central axis O (the lid 13 side), and a buffer 46 is attached to the other side of the cask 11 along the central axis O (the bottom 29 side). The buffer 46 has a configuration similar to that of the buffer 41.

<Internal structure of the buffer body>
FIG. 5 is a cross-sectional view showing the internal structure of the protection device.

As shown in Figure 5, the buffer 41 has a support member 42 and buffer material 43, with the buffer material 43 disposed inside the hollow support member 42. The buffer material 43 is composed of a first buffer material 43a, a second buffer material 43b, and a third buffer material 43c. The first buffer material 43a, the second buffer material 43b, and the third buffer material 43c are formed by combining multiple blocks of wood.

The first buffer material 43a is provided along the circumferential direction on the outside of the peripheral surface side member 53 and the outside of the end surface side member 54 of the support member 42. The first buffer material 43a is composed of multiple blocks divided into multiple parts along the circumferential direction of the buffer body 41.

The second buffer material 43b is provided adjacent to the first buffer material 43a, along the circumferential direction on the outer side of the peripheral surface side member 53 and the upper side of the end surface side member 54 of the support member 42. The second buffer material 43b is composed of multiple blocks divided into multiple parts in the circumferential direction of the buffer body 41.

The third buffer material 43c is provided adjacent to the second buffer material 43b along the inner periphery of the second buffer material 43b. The third buffer material 43c is composed of multiple blocks divided in the circumferential direction of the buffer body 41.

The first material making up the first buffer material 43a has the highest compressive strength of all the materials making up the buffer material 43, and is, for example, oak. The second material making up the second buffer material 43b has a lower compressive strength than the first material, and is, for example, red cedar. The third material making up the third buffer material 43c has a lower compressive strength than the second material, and is, for example, balsa. Here, compressive strength refers to the Young's modulus or compressive strength when the buffer material 43 is compressed.

Note that the cushioning material 43 is not limited to wooden blocks. Instead of wood, the cushioning material 43 may be, for example, a foam material or a polymer compound.

<Detailed structure of the buffer body>
FIG. 6 is a front view showing the buffer body of the first embodiment.

As shown in Figure 6, the buffer 41 includes a support member 42, a buffer material 43, and a displacement measuring device 61.

The displacement measuring device 61 is provided inside the support member 42. The displacement measuring device 61 estimates the displacement of the buffer material 43. Specifically, the displacement measuring device 61 is placed in the same temperature environment as the buffer material 43 and measures the displacement of a test material made of a material with similar aging deterioration properties to the buffer material 43.

The cushioning material 43 is composed of a combination of a first cushioning material 43a, a second cushioning material 43b, and a third cushioning material 43c. Therefore, multiple displacement measuring devices 61a, 61b, and 61c are provided for the cushioning materials 43a, 43b, and 43c, each with a different compressive strength. That is, a first displacement measuring device 61a is provided for the first cushioning material 43a. A second displacement measuring device 61b is provided for the second cushioning material 43b. A third displacement measuring device 61c is provided for the third cushioning material 43c. Furthermore, multiple displacement measuring devices 61a, 61b, and 61c are provided for each of the cushioning materials 43a, 43b, and 43c.

Here, we will explain the structure of displacement measuring devices 61a, 61b, and 61c. However, since the structures of displacement measuring devices 61a, 61b, and 61c are almost identical, we will only explain the structure of displacement measuring device 61a and will omit explanations of the structures of displacement measuring devices 61b and 61c.

<Displacement measuring device>
FIG. 7 is a cross-sectional view showing the main part of the buffer body representing the displacement amount measuring device, and FIG. 8 is a deterioration determination map showing the displacement amount of the test material over time.

As shown in FIG. 7, the displacement measuring device 61 has a load applying device 62 and a displacement meter 63. The displacement measuring device 61 is placed in the same temperature environment as the buffer material 43 and measures the displacement of a test material 44 made of a material with similar aging deterioration properties to the buffer material 43. That is, the test material 44 used in the displacement measuring device 61 is made of a material with similar aging deterioration properties to the first buffer material 43a. In other words, when the first buffer material 43a is wood (oak), the test material 44 is also wood (oak). Furthermore, when the first buffer material 43a is a foam material or a polymer compound, the test material 44 is also made of the same type of foam material or polymer compound.

The support member 42 has a protrusion 64 that protrudes outward from its surface. The support member 42 has a first space 65 and a second space 66. The first space 65 and the second space 66 are connected to each other. The first space 65 houses the first buffer material 43a, and the second space 66 is formed by the protrusion 64 and houses the displacement measuring device 61. The first buffer material 43a is housed in the first space 65 and is positioned on the inner surface of the support member 42 without any gaps, although there may be a small gap between the outer surface of the first buffer material 43a and the inner surface of the support member 42.

The test material 44 is placed on one inner surface 66a of the second space 66 in the support member 42. The load-applying device 62 is placed on the other inner surface 66b of the second space 66 in the support member 42, opposite the inner surface 66a. The load-applying device 62 is, for example, a weight or a compression spring. The load-applying device 62 applies a compressive load to the test material 44 by pressing the test material 44 toward the inner surface 66a, using the inner surface 66a as a fulcrum. The displacement meter 63 is supported by the load-applying device 62 or the support member 42. When the load-applying device 62 applies a compressive load to the test material 44, the displacement meter 63 measures the displacement of the test material 44. The support member 42 has a transparent observation window 67 at the position of the protrusion 64 facing the displacement meter 63, and the measurement results of the displacement meter 63 can be read from outside through the observation window 67. Alternatively, instead of providing an observation window 67, wiring may be routed from the outside of the support member 42 to the displacement meter 63, and the measurement results of the displacement meter 63 may be output externally via wiring.

In the buffer 41, the buffer material 43 is supported inside the support member 42. That is, the buffer material 43 is covered by the hollow support member 42. The support member 42 is preferably made of a steel material such as stainless steel, and hermetically covers the buffer material 43. If the buffer material 43 were made of wood, foam, or a polymer compound, it would be exposed to the outside air and deteriorate over time. In the buffer 41 of this embodiment, the buffer material 43 is covered by the support member 42, so deterioration over time is suppressed. However, if the buffer material 43 of the buffer 41 were hermetically covered by the support member 42, the buffer material 43 would not be exposed to the outside air and would deteriorate over time primarily due to temperature. By hermetically covering the buffer material 43 with the support member 42, the primary cause of deterioration over time can be limited to temperature.

Because the buffer material 43 is supported in a sealed state by the support member 42, temperature is the primary factor that causes it to deteriorate over time. As the buffer material 43 deteriorates over time, its compressive strength decreases, and the amount of displacement when a compressive load is applied increases. Therefore, when the buffer material 43 has been used over a long period of time, the degree of deterioration of the buffer material 43 can be determined by measuring the amount of displacement, which is proportional to the compressive strength of the buffer material 43. The degree of deterioration of the buffer material 43 can be determined, for example, by drop analysis or the like, to determine whether it has the shock absorption performance to maintain the integrity of the cask 11, even when taking into account the results (degree of deterioration) of the compression test obtained in the deterioration determination test.

In this case, as shown in Figure 8, a deterioration determination map is prepared that shows the amount of displacement according to the usage time (usage period) of the buffer material 43. In the deterioration determination map of Figure 8, upper and lower limit values are set for the determination value. In the deterioration determination map, the region between the upper and lower limit values is the healthy region. In this case, the buffer material 43 is first heated at a predetermined temperature for a predetermined time, and the amount of displacement when a compressive load is applied to the buffer material 43 after the heat treatment is measured. The determination value is set based on this measured value. Then, during use of the buffer 41, the amount of displacement when a compressive load is applied to the test material 44 is measured using the displacement amount measuring device 61. The usage time and measured values are then applied to the deterioration determination map to determine the health of the test material 44, i.e., the buffer material 43.

The buffer 41 of the first embodiment houses a test material 44, which is made of the same material as the buffer material 43, inside the support member 42, and is equipped with a displacement measuring device 61 that measures the amount of displacement when a compressive load is applied to the test material 44. This eliminates the need to cut the support member 42 and remove part of the buffer material 43, improving workability.

Second Embodiment
Fig. 9 is a cross-sectional view showing the main part of the shock absorber of the second embodiment, and Fig. 10 is a deterioration determination map showing the displacement of the shock absorber over time. Note that components having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof will be omitted.

As shown in FIG. 9, the buffer 41A includes a support member 42, a buffer material 43, and a displacement measuring device 61A. The displacement measuring device 61A has a load applying device 62A and a displacement meter 63. The displacement measuring device 61A measures the displacement of the buffer material 43. The support member 42 has a first space 65 in which the first buffer material 43a is housed, and a second space 66 in which the displacement measuring device 61A is disposed.

The load-applying device 62A has a pressing member 71 and a compression spring 72. The pressing member 71 is provided with a pressing pin 71a. The pressing member 71 is movably supported on the protrusion 64 and can move toward and away from the first buffer material 43a. The tip of the pressing pin 71a of the pressing member 71 contacts the surface 43a1 of the first buffer material 43a. The compression spring 72 is disposed between the pressing member 71 and the protrusion 64 and biases the pressing member 71 in a direction toward the first buffer material 43a against the protrusion 64. A stopper 73 is provided between the support member 42 and the protrusion 64. The stopper 73, against which the pressing member 71 abuts, limits the amount of pressure applied by the pressing member 71 to the first buffer material 43a.

The load-applying device 62A applies a compressive load to the first cushioning material 43a by pressing the first cushioning material 43a using the protrusion 64 as a fulcrum. That is, the pressing member 71 applies a compressive load by pressing the pressing pin 71a against the first cushioning material 43a due to the biasing force of the compression spring 72. The displacement meter 63 is supported by the protrusion 64 of the support member 42. When the load-applying device 62A applies a compressive load to the first cushioning material 43a, the displacement meter 63 measures the amount of displacement, which is the amount of contraction of the first cushioning material 43a. The displacement meter 63 is mounted on the protrusion 64, and wiring is drawn to the outside, and the measurement results of the displacement meter 63 are output to the outside via the wiring.

Because the cushioning material 43 is supported in a sealed state by the support member 42, it deteriorates over time, primarily due to temperature. As the cushioning material 43 deteriorates over time, its compressive strength decreases and the amount of displacement when a compressive load is applied increases. Therefore, when the cushioning material 43 has been used over an extended period of time, the degree of deterioration of the cushioning material 43 can be determined by measuring the amount of displacement, which is proportional to the compressive strength of the cushioning material 43.

In this case, as shown in Figure 10, a deterioration determination map is prepared that shows the amount of displacement according to the usage time (usage period) of the buffer material 43. In the deterioration determination map of Figure 10, upper and lower limit values are set for the determination value. In the deterioration determination map, the area between the upper and lower limit values is the healthy area. In this case, the buffer material 43 is heated in advance at a predetermined temperature for a predetermined time, and the amount of displacement when a compressive load is applied to the buffer material 43 after the heat treatment is measured. The determination value is set based on this measured value. Then, while the buffer 41 is in use, the amount of displacement when a compressive load is applied to the buffer material 43 is measured using the displacement amount measuring device 61A. The usage time and the measured value are then applied to the deterioration determination map to determine the health of the buffer material 43.

The buffer 41A of the second embodiment is provided with a displacement measuring device 61A inside the support member 42 that measures the amount of displacement when a compressive load is applied to the buffer material 43. This eliminates the need to cut the support member 42 and remove part of the buffer material 43, improving workability. It also eliminates the need to provide a test material 44 equivalent to the buffer material 43.

[Third embodiment]
11 is a cross-sectional view showing the main part of the buffer body of the third embodiment. Note that the same reference numerals are used to designate members having the same functions as those of the second embodiment described above, and detailed description thereof will be omitted.

As shown in FIG. 11, the buffer 41B includes a support member 42, a buffer material 43, and a displacement measuring device 61B. The displacement measuring device 61B includes a load applying device 62B and a displacement meter 63B. The displacement measuring device 61B is placed in the same temperature environment as the buffer material 43 and measures the displacement of a test material 44 made of a material with similar aging deterioration properties to the buffer material 43. In other words, the test material 44 used in the displacement measuring device 61B is made of a material with similar aging deterioration properties to the first buffer material 43a. The support member 42 has the first buffer material 43a housed in the first space 65, and the displacement measuring device 61B placed in the second space 66.

The load-applying device 62B has a pressure screw 81 and a nut 82. The nut 82 is fixed to the protrusion 64. The pressure screw 81 threads onto the nut 82. The pressure screw 81 moves axially by rotating circumferentially relative to the nut 82. The displacement meter 63B includes a load cell. When a load is applied, the load cell converts the load into an electrical signal and outputs it. The displacement meter 63B converts the electrical signal output from the load cell into a displacement and outputs it. The displacement meter 63B converts the displacement into an electrical signal, which is then converted into a displacement and output. The displacement meter 63B may also include a load cell. In this case, the load cell converts minute displacements caused by the load into an electrical signal, which is then converted into a load and output. The displacement meter 63B is clamped between a pair of support plates 83, 84. The test material 44 is positioned between the outer surface of the support member 42 and the support plate 83. The pressure screw 81 has its tip located in the second space 66 and its rear end located outside the protrusion 64 (support member 42). The tip of the pressure screw 81 contacts the support plate 84. The load-applying device 62B can adjust the compressive load applied to the first buffer material 43a. That is, by rotating the pressure screw 81 and moving it axially, a compressive load is applied to the test material 44 via the displacement meter 63B and support plates 83, 84. At this time, the compressive load applied to the first buffer material 43a can be adjusted depending on the amount of rotation of the pressure screw 81.

The bellows 85 has a cylindrical bellows shape and is supported between the support plate 84 and the protrusion 64. The displacement meter 63B has a cable 86 that is pulled out to the outside through a penetration 87 fixed to the protrusion 64.

The load-applying device 62B applies a compressive load to the test material 44 by pressing the test material 44 using the protrusion 64 as a fulcrum. That is, by rotating the pressure screw 81 from outside the support member 42 and moving it axially, the test material 44 is pressed via the displacement meter 63B and support plates 83, 84, thereby applying a compressive load. When the load-applying device 62B applies a compressive load to the test material 44, the displacement meter 63B measures the amount of displacement, which is the compressive load. The displacement meter 63B converts the measured compressive load into an electrical signal and outputs it externally via cable 86.

Because the cushioning material 43 is supported in a sealed state by the support member 42, temperature is the primary factor that causes it to deteriorate over time. As the cushioning material 43 deteriorates over time, its compressive strength decreases, and the amount of displacement when a compressive load is applied increases. Therefore, when the cushioning material 43 is used over a long period of time, the degree of deterioration of the cushioning material 43 can be determined by measuring the amount of displacement, which is proportional to the compressive strength of the cushioning material 43. In this case, as described above, a deterioration determination map is prepared that shows the amount of displacement according to the usage time (usage period) of the cushioning material 43. Then, during use of the cushioning body 41, the amount of displacement when a compressive load is applied to the test material 44 is measured using the displacement amount measuring device 61B. The usage time and the measured value are then applied to the deterioration determination map to determine the soundness of the test material 44, i.e., the cushioning material 43.

The buffer 41B of the third embodiment is provided with a displacement measuring device 61B inside the support member 42 that measures the amount of displacement when a compressive load is applied to the buffer material 43. This eliminates the need to cut the support member 42 and remove part of the buffer material 43, improving workability. It also eliminates the need to provide a test material 44 equivalent to the buffer material 43. It also allows the compressive load applied to the buffer material 43 to be specified or adjusted, enabling highly accurate measurement of the amount of displacement.

[Fourth embodiment]
12 is a cross-sectional view showing the main part of the shock absorber of the fourth embodiment. Note that the same reference numerals are used to designate members having the same functions as those of the third embodiment described above, and detailed description thereof will be omitted.

As shown in FIG. 12, the buffer 41C includes a support member 42, a buffer material 43, and a displacement measurement device 61C. The displacement measurement device 61C includes a load application device 62B and a displacement meter 63B. The load application device 62B and the displacement meter 63B are configured in the same manner as in the third embodiment, and therefore will not be described here.

The displacement measuring device 61C also has a first storage 91, a loading device 92, and a second storage 93. The first storage 91 stores a plurality of unused test materials 44. The loading device 92 sequentially supplies the test materials 44 in the first storage 91 to the load-applying device 62B. The second storage 93 stores used test materials 44a. The support member 42 has the first storage 91 and the loading device 92 arranged on one side of the protruding portion 64, and the second storage 93 arranged on the other side of the protruding portion 64. The loading device 92 is, for example, an air cylinder, and sequentially supplies unused test materials 44 stored in the first storage 91 to the load-applying device 62B. Test materials 44 used in the load-applying device 62B are transported to and stored in the second storage 93 as used test materials 44a. It is preferable to provide a transport device between the sequential load applying device 62B and the second storage cabinet 93.

The loading device 92 supplies unused test material 44 stored in the first storage facility 91 to the load-applying device 62B. The load-applying device 62B applies a compressive load to the test material 44 by pressing the test material 44 using the protrusion 64 as a fulcrum. That is, by rotating the pressure screw 81 from outside the support member 42 and moving it axially, the test material 44 is pressed via the displacement meter 63B and support plates 83, 84 to apply a compressive load. When the load-applying device 62B applies a compressive load to the test material 44, the displacement meter 63B measures the displacement, which is the compressive load. The displacement meter 63B converts the measured compressive load into an electrical signal and outputs it to the outside via cable 86. The used test materials 44a used in the load-applying device 62B are transported to the second storage 93, and the loading device 92 supplies unused test materials 44 stored in the first storage 91 to the load-applying device 62B.

Because the cushioning material 43 is supported in a sealed state by the support member 42, temperature is the primary factor that causes it to deteriorate over time. As the cushioning material 43 deteriorates over time, its compressive strength decreases, and the amount of displacement when a compressive load is applied increases. Therefore, when the cushioning material 43 is used over a long period of time, the degree of deterioration of the cushioning material 43 can be determined by measuring the amount of displacement, which is proportional to the compressive strength of the cushioning material 43. In this case, as described above, a deterioration determination map is prepared that shows the amount of displacement according to the usage time (usage period) of the cushioning material 43. Then, during use of the cushioning body 41, the amount of displacement when a compressive load is applied to the test material 44 is measured using the displacement amount measuring device 61C. The usage time and the measured value are then applied to the deterioration determination map to determine the soundness of the test material 44, i.e., the cushioning material 43.

The buffer 41C of the fourth embodiment is provided with a displacement measuring device 61C inside the support member 42 that measures the amount of displacement when a compressive load is applied to the buffer material 43. This eliminates the need to cut the support member 42 and remove part of the buffer material 43, improving workability. Furthermore, by storing multiple test materials 44 inside the support member 42, it is possible to measure the amount of displacement multiple times depending on the usage time.

Fifth Embodiment
13 is a cross-sectional view showing the main part of the buffer body of the fifth embodiment. Note that the same reference numerals are used to designate members having the same functions as those of the first embodiment described above, and detailed description thereof will be omitted.

As shown in FIG. 13, the buffer 41D includes a support member 42, a buffer material 43, and a displacement measuring device 61D. The displacement measuring device 61D has a load applying device 62D and a displacement meter 63D. The displacement measuring device 61D measures the displacement of the buffer material 43. The support member 42 has a first space 65 in which the first buffer material 43a is housed, and a second space 66 in which the displacement measuring device 61D is disposed.

The load-applying device 62D has a pressing member 101 and a pressing device 102. Multiple pressing members 101 (three in this embodiment) are provided at different positions on the protruding portion 64. Each pressing member 101 is positioned opposite a different position on the first buffer material 43a. Each pressing member 101 has a similar configuration. A pressing pin 101a is provided on the pressing member 101. The pressing member 101 is movably supported on the protruding portion 64 and can move toward and away from the first buffer material 43a. The tip of the pressing pin 101a of the pressing member 101 contacts the surface 43a1 of the first buffer material 43a. A bellows 103 is provided for each pressing member 101. The bellows 103 has a cylindrical bellows shape and is supported between the pressing member 101 and the protruding portion 64. A stopper 104 is provided between the support member 42 and the protrusion 64. The stopper 104 restricts the amount of pressure applied by the pressing member 101 to the first buffer material 43a when the pressing member 101 abuts against it.

The pressing device 102 can apply a load to one of the multiple pressing members 101. The pressing device 102 is detachably attached to a position axially opposing the multiple pressing members 101. The protrusion 64 has mounting holes 164a formed in positions axially opposing each pressing member 101. The pressing device 102 has a pressing rod 105. The pressing device 102 can move the pressing rod 105 in the axial direction. The displacement meter 63D includes a load cell. When a load is applied, the load cell converts the load into an electrical signal and outputs it. The displacement meter 63D converts the electrical signal output from the load cell into a displacement amount and outputs it. The displacement meter 63D is attached to the tip of the pressing rod 105 of the pressing device 102 and can be connected to the pressing member 101 via a pusher rod 106. Here, the pressing device 102, displacement meter 63D, and pressing rod 106 can be attached and detached as a single unit to the mounting hole 164a of the protrusion 64.

The unit consisting of the pressing device 102, displacement meter 63D, and push rod 106 is attached to one of the mounting holes 164a of the protrusion 64. Here, the load-applying device 62D activates the pressing device 102, causing the pressing member 101 to press the first buffer material 43a and apply a compressive load to the first buffer material 43a. That is, when the pressing device 102 extends the pressing rod 105, the pressing force is transmitted to the pressing member 101 via the displacement meter 63D and push rod 106, and the pressing member 101 presses the first buffer material 43a, applying a compressive load. When the load-applying device 62D applies a compressive load to the first buffer material 43a, the displacement meter 63D measures the amount of displacement, which is the compressive load. The displacement meter 63D converts the measured compressive load into an electrical signal and outputs it externally via a cable (not shown).

Once the displacement measuring device 61D measures the displacement at a predetermined position on the first cushioning material 43a, a unit consisting of the pressing device 102, displacement meter 63D, and pushing rod 106 is attached to another mounting hole 64a on the protrusion 64, and the displacement at a predetermined position on the first cushioning material 43a is measured in the same manner.

Because the cushioning material 43 is supported in a sealed state by the support member 42, temperature is the primary factor that causes it to deteriorate over time. As the cushioning material 43 deteriorates over time, its compressive strength decreases, and the amount of displacement when a compressive load is applied increases. Therefore, when the cushioning material 43 has been used for an extended period of time, the degree of deterioration of the cushioning material 43 can be determined by measuring the amount of displacement, which is proportional to the compressive strength of the cushioning material 43. In this case, as described above, a deterioration determination map is prepared that shows the amount of displacement according to the usage time (usage period) of the cushioning material 43. Then, while the cushioning body 41 is in use, the displacement amount measurement device 61DB measures the amount of displacement when a compressive load is applied to the cushioning material 43. The usage time and the measured value are then applied to the deterioration determination map to determine the soundness of the cushioning material 43.

The buffer 41D of the fifth embodiment is provided with a displacement measuring device 61D inside the support member 42 that measures the amount of displacement when a compressive load is applied to the buffer material 43. This eliminates the need to cut the support member 42 and remove part of the buffer material 43, improving workability. Furthermore, by placing multiple pressing members 101 inside the support member 42, it is possible to measure the amount of displacement multiple times depending on the length of use. It is also possible to measure the amount of displacement of buffer materials 43 placed in different positions.

[Effects of this embodiment]
The buffer body of the first aspect comprises a support member 42 having a hollow shape and provided on the outside of a cask (container for storing radioactive material) 11, a buffer material 43 that is arranged inside the support member 42 and absorbs impact by deforming, and displacement amount measuring devices 61, 61A, 61B, 61C, 61D that estimate the amount of displacement of the buffer material 43.

With the buffer body of the first aspect, the degree of deterioration of the buffer material 43 can be determined by periodically (e.g., every few years) estimating the displacement of the buffer material 43 using the displacement measuring devices 61, 61A, 61B, 61C, and 61D during storage in the cask 11. As a result, the soundness of the buffer material 43 during storage can be confirmed, and the soundness of the buffer material 43 can be maintained. Furthermore, when determining the degree of deterioration of the buffer material 43, there is no need to cut the support member 42 and remove part of the buffer material 43, which improves workability and improves the accuracy of determining the deterioration of the buffer material 43.

The buffer according to the second aspect is the buffer according to the first aspect, except that the support member 42 has a first space 55 that houses the buffer material 43 and a second space 56 that communicates with the first space 55, and the displacement measuring devices 61, 61A, 61B, 61C, and 61D are disposed in the second space 56. By disposing the displacement measuring devices 61, 61A, 61B, 61C, and 61D in the space that houses the buffer material 43, the accuracy of determining deterioration of the buffer material 43 can be improved.

The buffer according to the third aspect is the buffer according to the second aspect, and furthermore, the second space 56 is formed by a protrusion 64 that protrudes outward from the support member 42. This allows for efficient placement of the displacement measuring devices 61, 61A, 61B, 61C, and 61D.

The buffer according to the fourth aspect is a buffer according to any one of the first to third aspects, and furthermore, the displacement measuring devices 61, 61A, 61B, 61C, and 61D measure the displacement of the buffer material 43 or the displacement of a test material 44 that is placed in the same temperature environment as the buffer material 43 and is made of a material with similar aging deterioration properties to the buffer material 43. This allows the degree of deterioration of the buffer material 43 to be determined with high accuracy.

The buffer according to the fifth aspect is the buffer according to any one of the first to fourth aspects, and further includes a displacement measuring device 61, 61A, 61B, 61C, 61D that includes a load applying device 62, 62A, 62B, 62D that applies a compressive load to the buffer material 43 or test material 44, and a displacement meter 63, 63B, 63D that measures the displacement of the buffer material 43 or test material 44. As a result, when the load applying device 62, 62A, 62B, 62D applies a compressive load to the buffer material 43 or test material 44, the displacement meter 63, 63B, 63D measures the displacement of the buffer material 43 or test material 44, making it possible to easily measure the displacement of the buffer material 43 or test material 44.

The buffer according to the sixth aspect is a buffer according to any one of the first to fifth aspects, and furthermore, the load-applying device 62B is capable of adjusting the compressive load applied to the buffer material 43 or the test material 44. This makes it possible to precisely specify the compressive load applied to the buffer material 43 and to adjust the compressive load applied to the buffer material 43 according to the test conditions, thereby enabling highly accurate measurement of the displacement of the buffer material 43.

The buffer according to the seventh aspect is a buffer according to any one of the sixth to sixth aspects, and further includes a displacement measuring device 61C having a first storage 91 that stores multiple test materials 44 and a loading device 92 that sequentially supplies the test materials 44 from the first storage 91 to the load applying device 71B. By sequentially supplying multiple test materials 44 to the displacement measuring device 61C, the displacement of the buffer material 43 can be measured multiple times depending on the usage time of the buffers 41, 41A, 41B, 41C, and 41D.

The buffer according to the eighth aspect is a buffer according to any one of the first to seventh aspects, and further includes a load-applying device 62D that has a plurality of pressing members 101 capable of pressing different positions on the buffer material 43, and a pressing device 102 that applies a load to one of the pressing members 101. This makes it possible to measure the displacement of the buffer material 43 multiple times depending on the usage time of the buffers 41, 41A, 41B, 41C, and 41D, and to measure the displacement of buffer materials 43 placed in different positions.

The radioactive material storage container according to the ninth aspect comprises a body 12, a lid 13 that seals the body 12, and buffers 41, 41A, 41B, 41C, and 41D. This allows the buffers 41, 41A, 41B, 41C, and 41D to be used to check the integrity of the buffer material 43 during storage, and the integrity of the buffer material 43 can be maintained.

In the above-described embodiment, the second space 56 is formed by the protruding portion 64 protruding outward from the support member 42, and the displacement measuring devices 61, 61A, 61B, 61C, and 61D are disposed therein. However, the second space 56 may be formed by a flat portion protruding outward from the support member 42, and the displacement measuring devices 61, 61A, 61B, 61C, and 61D may be disposed therein.

11 Cask (container for storing radioactive materials)
12 Body 13 Lid 31 Primary lid 32 Secondary lid 41, 41A, 41B, 41C, 41D, 46 Cushioning body 42 Support member 43, 43A, 43B, 43C, 43D Cushioning material 43a First cushioning material 43b Second cushioning material 43c Third cushioning material 44 Test material 51 Disk portion 52 Cylindrical portion 61, 61A, 61B, 61C, 61D Displacement measuring device 62, 62A, 62B, 62D Load applying device 63, 63B, 63D Displacement meter 64 Protrusion 65 First space 66 Second space 67 Observation window 71 Pressing member 72 Compression spring 81 Pressing screw 82 Nut 91 First storage cabinet 92 Loading device 93 Second storage 101 Pressing member 102 Pressing device

Claims (9)

a support member having a hollow shape and provided on the outside of the radioactive material storage container;
a buffer material that is disposed inside the support member and deforms to absorb impact;
a displacement measuring device for estimating the displacement of the buffer material;
A buffer body comprising: the support member has a first space portion that houses the buffer material and a second space portion that communicates with the first space portion, and the displacement amount measuring device is disposed in the second space portion.
The shock absorber according to claim 1 . The second space is formed by a protrusion that protrudes outward from the support member.
The shock absorber according to claim 2 . the displacement measuring device measures the displacement of the buffer material or the displacement of a test material that is placed in the same temperature environment as the buffer material and is made of a material that has similar aging deterioration properties to the buffer material;
The buffer body according to any one of claims 1 to 3. The displacement measuring device includes a load applying device that applies a compressive load to the buffer material or the test material, and a displacement meter that measures the displacement of the buffer material or the test material.
The shock absorber according to claim 4. The load-applying device is capable of adjusting the compressive load applied to the buffer material or the test material.
The shock absorber according to claim 5 . The displacement measuring device includes a storage container for storing a plurality of the test materials, and a loading device for sequentially supplying the test materials from the storage container to the load applying device.
The shock absorber according to claim 5 . the load applying device includes a plurality of pressing members each capable of pressing a different position of the buffer material, and a pressing device that applies a load to one of the pressing members.
The shock absorber according to claim 5 . A torso and
a lid portion that seals the body portion;
The buffer body according to claim 1;
A radioactive material storage container comprising: