Buffer body and radioactive material storage container

Abstract

To provide a buffer and radioactive material storage container, which improve buffer material deterioration determination accuracy.SOLUTION: A buffer is provided, comprising a hollow-shaped support member provided outside a radioactive material storage container, a buffer material provided inside the support member to absorb shock through deformation, and a displacement measurement device for estimating displacement of the buffer material.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a buffer for protecting a radioactive material storage container and the radioactive material storage container. [Background technology]

[0002] At nuclear facilities, radioactive waste such as spent fuel generated in reactors and other facilities is stored in radioactive material storage containers and transported to storage facilities, reprocessing facilities, etc., for storage or reprocessing. A radioactive material storage container consists of a cylindrical body with an open top and a bottom, and a lid that is fixed to the top of the body and closes the opening. A buffer body is 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.

[0003] The buffer body is configured by disposing a buffer material inside a support member. The buffer material may deteriorate over long periods of use depending on the material used and the environment in which it is used, so it is preferable to monitor the deterioration state of the buffer material. For example, Patent Document 1 below describes a technology for monitoring the deterioration state of the buffer material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-11603 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned Patent Document 1, a deterioration monitoring member made of a material with similar deterioration characteristics to the buffer material is arranged around the radioactive material storage container. However, the buffer body is configured by sealing the buffer material inside a support member and fixed 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 is different, which may affect the deterioration judgment of the buffer material.

[0006] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a buffer body and a radioactive material storage container that improve the accuracy of determining deterioration of the buffer material. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the buffer of the present disclosure comprises a support member having a hollow shape and provided on the outside of a radioactive material storage container, a buffer material that is placed inside the support member and absorbs impact by deforming, and a displacement amount measuring device that estimates the amount of displacement of the buffer material.

[0008] The radioactive material storage container of the present disclosure also includes a body portion, a lid portion that seals the body portion, and the buffer body. [Effects of the Invention]

[0009] According to the buffer body and radioactive material storage container of the present disclosure, it is possible to improve the accuracy of determining deterioration of the buffer material. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a radioactive material storage container with a part cut away. [Figure 2] FIG. 2 is a plan view showing a radioactive substance storage container equipped with a buffer body. [Figure 3] FIG. 3 is a front view showing the radioactive substance storage container with the buffer body attached in an upright position. [Figure 4] FIG. 4 is a front view showing a state in which the radioactive substance storage container with the buffer body attached is placed horizontally. [Figure 5] FIG. 5 is a cross-sectional view showing the internal structure of the buffer body. [Figure 6] FIG. 6 is a front view showing the buffer body of the first embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing a main part of a buffer body that represents the displacement amount measuring device. [Figure 8] FIG. 8 is a deterioration determination map showing the amount of displacement of the test material over time. [Figure 9] FIG. 9 is a cross-sectional view showing a main part of the buffer body of the second embodiment. [Figure 10] FIG. 10 is a deterioration determination map showing the displacement of the cushioning material over time. [Figure 11] FIG. 11 is a cross-sectional view showing a main part of the buffer body of the third embodiment. [Figure 12] FIG. 12 is a cross-sectional view showing a main part of the buffer body of the fourth embodiment. [Figure 13] FIG. 13 is a cross-sectional view showing a main part of the buffer body of the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present disclosure will be 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, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can 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.

[0012] [First embodiment] <Radioactive material storage container> FIG. 1 is a perspective view of a radioactive substance storage container of the first embodiment, with a part cut away.

[0013] As shown in FIG. 1, a cask 11 serving as a radioactive material storage container includes a trunk portion 12 and a lid portion 13. The trunk portion 12 has a container body 21. The container body 21 is cylindrical (in this embodiment, cylindrical), has an opening 22 formed at the upper end, and is closed at the lower end. The container body 21 has a cavity 23 therein, and a basket 24 is provided in the cavity 23. The basket 24 is provided with a plurality of cells 25 that can independently store radioactive material (e.g., spent fuel assemblies). The container body 21 is a forged product made of carbon steel that has a gamma ray shielding function, but 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.

[0014] In the trunk 12, an outer cylinder 26 is disposed on the outer peripheral surface of the container body 21 with a predetermined gap therebetween. The container body 21 is provided with a plurality of copper heat transfer fins 27 in the circumferential direction, which perform heat conduction between the outer peripheral surface and the inner peripheral surface of the outer cylinder 26. In the space surrounded by the outer cylinder 26 and the heat transfer fins 27, the container body 21 is provided with a resin (neutron shielding body) 28, which is a polymer material containing a large amount of hydrogen and contains boron or a boron compound that has a neutron shielding function.

[0015] The body 12 is provided with a bottom 29 that protrudes below the closed lower end of the container body 21. The bottom 29 is formed to have 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 a resin (neutron shielding body) is provided in the space.

[0016] The barrel 12 is provided with a trunnion 30 for lifting the cask 11 on the vessel body 21. The trunnion 30 is provided penetrating the outer cylinder 26 from the vessel body 21, and protrudes most outward from the cask 11.

[0017] 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 (torso 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 a material such as 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, and like the primary lid 31, is also formed in a disk shape from a material such as carbon steel or stainless steel that shields against gamma rays. A resin (neutron shield) 28 may be provided between the primary lid 31 and the secondary lid 32. In addition, a tertiary lid may be provided on the lid portion.

[0018] The primary lid 31 is fixed to a first step 22a formed at the opening 22 of the container body 21 with bolts (not shown) made of carbon steel or stainless steel, and is attached to the container body 21. The secondary lid 32 is fixed to a second step 22b formed at the opening 22 of the container body 21 with bolts (not shown) made of carbon steel or stainless steel, and is attached to the container body 21. 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 sealing between the primary lid 31 and the first step 22a and between the secondary lid 32 and the second step 22b.

[0019] The barrel 12 surrounds the secondary lid 32 at the opening 22 of the vessel body 21, and has a cylindrical upper edge 22c that appears 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 a plurality of bolt holes 33 spaced apart in the circumferential direction for attaching a buffer body A, which will be described later.

[0020] <Buffer> FIG. 2 is a plan view showing a radioactive material storage container equipped with a protective device of the first embodiment, and FIG. 3 is a front view showing a state in which the radioactive material storage container equipped with a protective device is placed upright.

[0021] 2 and 3, the cask 11 includes a buffer body 41. The buffer body 41 is attached to the cask 11 that has been transported to a storage facility, which is, for example, a storage location.

[0022] In a nuclear power plant, the cask 11 contains, for example, spent fuel assemblies stored in cells 25 of a basket 24 of a vessel body 21, and is sealed by a lid 13. The cask 11 is transported, for example, from a 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, which is 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 the central axis O aligned vertically.

[0023] The buffer body 41 includes a support member 42 and a buffer material 43 .

[0024] 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 standing on the floor F were to tip over. The disk portion 51 is disposed above the lid portion 13 of the cask 11, along the surface of the secondary lid 32 that is exposed on the outside of the lid portion 13. The disk portion 51 is disposed 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. In addition, when a tertiary lid is provided as the lid portion, the disc portion 51 is arranged along the surface of the tertiary lid that appears on the outside of the lid portion 13, and is arranged so as to cover the surface of the tertiary lid and the surface of the upper edge 22c of the container body 21.

[0025] The cylindrical portion 52 is disposed so as to surround the outside of the upper edge 22c of the body portion 12. That is, the cylindrical portion 52 is disposed radially outward from the lid portion 13 and protrudes radially outward from the body portion 12.

[0026] The buffer material 43 is disposed inside and supported by the support member 42. The buffer material 43 deforms under a predetermined load. The buffer material 43 is made of wood, a foam material, or a polymer compound.

[0027] FIG. 4 is a front view showing a state in which the radioactive material storage container equipped with the protective device is placed horizontally.

[0028] 4, the cask 11 may also 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.

[0029] <Internal structure of the buffer body> FIG. 5 is a cross-sectional view showing the internal structure of the protection device.

[0030] 5, the buffer 41 has a support member 42 and a buffer material 43, and the buffer material 43 is disposed inside the hollow support member 42. The buffer material 43 is configured by combining 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.

[0031] The first buffer material 43a is provided along the circumferential direction on the outer side of the peripheral surface side member 53 and the outer side of the end surface side member 54 of the support member 42. The first buffer material 43a is made up of a plurality of blocks divided in the circumferential direction of the buffer body 41.

[0032] 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 on the upper side of the end surface side member 54 of the support member 42. The second buffer material 43b is composed of a plurality of blocks divided into blocks in the circumferential direction of the buffer body 41.

[0033] 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 a plurality of blocks divided in the circumferential direction of the buffer body 41.

[0034] The first material constituting the first buffer material 43a has the highest compressive strength of all the materials constituting the buffer material 43, and is, for example, oak. The second material constituting the second buffer material 43b has a lower compressive strength than the first material, and is, for example, red cedar. The third material constituting 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.

[0035] The buffer material 43 is not limited to a wooden block, but may be, for example, a foam material or a polymer compound other than wood.

[0036] <Detailed structure of the buffer body> FIG. 6 is a front view showing the buffer body of the first embodiment.

[0037] As shown in FIG. 6, the buffer 41 includes a support member 42, a buffer material 43, and a displacement measuring device 61.

[0038] The displacement amount measuring device 61 is provided inside the support member 42. The displacement amount measuring device 61 estimates the displacement amount of the buffer material 43. Specifically, the displacement amount measuring device 61 measures the displacement amount of a test material that is placed in the same temperature environment as the buffer material 43 and is made of a material that has the same aging deterioration properties as the buffer material 43.

[0039] The buffer material 43 is configured by combining a first buffer material 43a, a second buffer material 43b, and a third buffer material 43c. Therefore, the displacement measuring device 61 is provided with a plurality of displacement measuring devices 61a, 61b, and 61c corresponding to the buffer materials 43a, 43b, and 43c, which have different compressive strengths. That is, the first displacement measuring device 61a is provided corresponding to the first buffer material 43a. The second displacement measuring device 61b is provided corresponding to the second buffer material 43b. The third displacement measuring device 61c is provided corresponding to the third buffer material 43c. Furthermore, a plurality of displacement measuring devices 61a, 61b, and 61c are provided for each of the buffer materials 43a, 43b, and 43c.

[0040] Here, the structures of the displacement measuring devices 61a, 61b, and 61c will be explained. However, since the structures of the displacement measuring devices 61a, 61b, and 61c are almost the same, only the structure of the displacement measuring device 61a will be explained, and explanations of the structures of the displacement measuring devices 61b and 61c will be omitted.

[0041] <Displacement measurement 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.

[0042] As shown in FIG. 7, the displacement measuring device 61 includes 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.

[0043] The support member 42 is provided with a protrusion 64 that protrudes outward from the 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 in communication with 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 arranged on the inner surface of the support member 42 without any gaps, but 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.

[0044] 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 a position on 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. It is also possible to wire from the outside of the support member 42 to the displacement meter 63 without providing the observation window 67, and output the measurement results of the displacement meter 63 to the outside via the wire.

[0045] 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 is made of wood, a foam material, a polymer compound, or the like, it will 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 is hermetically covered by the support member 42 in the buffer 41, the buffer material 43 will not be exposed to the outside air and will deteriorate over time mainly due to temperature. By hermetically covering the buffer material 43 with the support member 42, the main cause of deterioration over time can be limited to temperature.

[0046] The buffer material 43 deteriorates over time, primarily due to temperature, because it is supported in a sealed state by the support member 42. As the buffer material 43 deteriorates over time, its compressive strength decreases, and the amount of displacement increases when a compressive load is applied. Therefore, when the buffer material 43 is 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 the buffer material 43 has enough 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.

[0047] In this case, as shown in FIG. 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 FIG. 8, an upper limit value and a lower limit value are set for the determination value. In the deterioration determination map, the region between the upper limit value and the lower limit value is the sound region. In this case, the buffer material 43 is heat-treated in advance at a predetermined temperature for a predetermined time, and the amount of displacement when a compressive load is applied to the heat-treated buffer material 43 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 the measured values ​​are then applied to the deterioration determination map to determine the soundness of the test material 44, i.e., the buffer material 43.

[0048] The buffer 41 of the first embodiment accommodates a test material 44, which is made of the same material as the buffer material 43, inside the support member 42, and is provided with a displacement measuring device 61 that measures the amount of displacement when a compressive load is applied to the test material 44. Therefore, there is no need to cut the support member 42 and remove part of the buffer material 43, improving workability.

[0049] [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 members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed explanations will be omitted.

[0050] 9, the buffer 41A includes a support member 42, a buffer material 43, and a displacement amount measuring device 61A. The displacement amount measuring device 61A has a load applying device 62A and a displacement meter 63. The displacement amount measuring device 61A measures the displacement of the buffer material 43. The support member 42 has a first space 65 in which a first buffer material 43a is housed, and a second space 66 in which the displacement amount measuring device 61A is disposed.

[0051] 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 by the protruding portion 64 and can move toward and away from the first cushioning material 43a. The tip of the pressing pin 71a of the pressing member 71 contacts the surface 43a1 of the first cushioning material 43a. The compression spring 72 is disposed between the pressing member 71 and the protruding portion 64 and biases the pressing member 71 in a direction toward the first cushioning material 43a with respect to the protruding portion 64. A stopper 73 is provided between the support member 42 and the protruding portion 64. The stopper 73, against which the pressing member 71 abuts, regulates the amount of pressure applied by the pressing member 71 to the first cushioning material 43a.

[0052] 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 causing the pressing pin 71a to press the first cushioning material 43a with 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 provided on the protrusion 64, and wiring is drawn to the outside, and the measurement result of the displacement meter 63 is output to the outside through the wiring.

[0053] The buffer material 43 deteriorates over time, primarily due to temperature, because it is supported in a sealed state by the support member 42. 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 for 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.

[0054] In this case, as shown in FIG. 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 FIG. 10, an upper limit value and a lower limit value are set for the determination value. In the deterioration determination map, the region between the upper limit value and the lower limit value is the sound region. In this case, the buffer material 43 is previously 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 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 soundness of the buffer material 43.

[0055] The buffer 41A of the second embodiment is provided with a displacement measuring device 61A inside the support member 42, which 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. In addition, there is no need to provide a test material 44 equivalent to the buffer material 43.

[0056] [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.

[0057] 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.

[0058] 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 is threadedly engaged with 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, converts the signal into a displacement, and outputs it. Note that the displacement meter 63B may include a load cell. In this case, the load cell converts minute displacements due to the load into an electrical signal, and converts the signal into a load and outputs it. The displacement meter 63B is clamped between a pair of support plates 83, 84. The test material 44 is placed between the outer surface of the support member 42 and the support plate 83. The pressure screw 81 has a tip located in the second space 66 and a 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 is capable of adjusting 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 the support plates 83, 84. At this time, the compressive load applied to the first buffer material 43a can be adjusted according to the amount of rotation of the pressure screw 81.

[0059] The bellows 85 has a cylindrical bellows shape and is supported between a support plate 84 and the protruding portion 64. The displacement meter 63B has a cable 86 that is led out through a penetration 87 fixed to the protruding portion 64 to the outside.

[0060] The load-applying device 62B applies a compressive load to the test material 44 by pressing the test material 44 with 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 amount of 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 a cable 86.

[0061] Because the buffer material 43 is supported in a sealed state by the support member 42, it deteriorates over time, primarily due to temperature. 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 is used for 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. 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 buffer material 43. Then, during use of the buffer 41, the displacement amount 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 buffer material 43.

[0062] 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 a portion 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.

[0063] [Fourth embodiment] 12 is a cross-sectional view showing the main part of the buffer body 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.

[0064] 12, the buffer 41C includes a support member 42, a buffer material 43, and a displacement amount measuring device 61C. The displacement amount measuring device 61C has a load applying device 62B and a displacement meter 63B. The load applying device 62B and the displacement meter 63B have the same configurations as those in the third embodiment, and therefore a description thereof will be omitted.

[0065] 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 the unused test materials 44 stored in the first storage 91 to the load-applying device 62B. The 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 93.

[0066] The loading device 92 supplies unused test materials 44 stored in the first storage 91 to the load-applying device 62B. The load-applying device 62B applies a compressive load to the test materials 44 by pressing the test materials 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 materials 44 are pressed via the displacement meter 63B and support plates 83 and 84, thereby applying a compressive load. When the load-applying device 62B applies a compressive load to the test materials 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 to the outside via a cable 86. The used test materials 44a used by the load-applying device 62B are sequentially 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.

[0067] Because the buffer material 43 is supported in a sealed state by the support member 42, it deteriorates over time, primarily due to temperature. 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 is used for 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. 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 buffer material 43. 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 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 buffer material 43.

[0068] 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. In addition, by storing multiple test materials 44 inside the support member 42, the amount of displacement can be measured multiple times depending on the usage time.

[0069] [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.

[0070] 13, the buffer 41D includes a support member 42, a buffer material 43, and a displacement amount measuring device 61D. The displacement amount measuring device 61D has a load applying device 62D and a displacement meter 63D. The displacement amount measuring device 61D measures the displacement of the buffer material 43. The support member 42 has a first space 65 in which a first buffer material 43a is housed, and a second space 66 in which the displacement amount measuring device 61D is disposed.

[0071] The load-applying device 62D has a pressing member 101 and a pressing device 102. A plurality of pressing members 101 (three in this embodiment) are provided at different positions on the protruding portion 64. Each pressing member 101 is disposed facing a different position on the first buffer material 43a. Each pressing member 101 has the same 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 is brought into contact with the pressing member 101, thereby restricting the amount of pressing of the pressing member 101 against the first buffer material 43a.

[0072] 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, the displacement meter 63D, and the pressing rod 106 are detachably attached to the attachment hole 164a of the protruding portion 64 as a single unit.

[0073] A unit consisting of the pressing device 102, displacement meter 63D, and pusher 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 the pusher rod 106, and the pressing member 101 presses the first buffer material 43a and applies 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 displacement, which is the compressive load. The displacement meter 63D converts the measured compressive load into an electrical signal and outputs it to the outside via a cable (not shown).

[0074] 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, the displacement meter 63D, and the pushing rod 106 is attached to another mounting hole 64a of the protrusion 64, and the displacement at a predetermined position on the first cushioning material 43a is measured in a similar manner.

[0075] Because the buffer material 43 is supported in a sealed state by the support member 42, it deteriorates over time, primarily due to temperature. 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 is used for 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. 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 buffer material 43. 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 61DB. The usage time and the measured value are then applied to the deterioration determination map to determine the soundness of the buffer material 43.

[0076] 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 a portion of the buffer material 43, improving workability. Furthermore, by arranging multiple pressing members 101 inside the support member 42, it is possible to measure the amount of displacement multiple times depending on the duration of use. Furthermore, it is possible to measure the amount of displacement of buffer materials 43 arranged in different positions.

[0077] [Effects of this embodiment] The buffer body of the first embodiment 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 arranged inside the support member 42 and absorbing impact by deforming, and displacement measuring devices 61, 61A, 61B, 61C, 61D for estimating the displacement of the buffer material 43.

[0078] According to the buffer body of the first aspect, during storage of the cask 11, the displacement of the buffer material 43 can be estimated periodically (for example, every few years) using the displacement amount measuring devices 61, 61A, 61B, 61C, and 61D, thereby determining the degree of deterioration of the buffer material 43. 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, it is not necessary to cut the support member 42 and remove a portion of the buffer material 43, which improves workability and improves the accuracy of determining the deterioration of the buffer material 43.

[0079] The buffer according to the second aspect is the buffer according to the first aspect, further comprising: support member 42 having first space 55 for accommodating buffer material 43; and second space 56 communicating with first space 55; displacement measuring devices 61, 61A, 61B, 61C, and 61D disposed in second space 56. By disposing displacement measuring devices 61, 61A, 61B, 61C, and 61D in the space for accommodating buffer material 43, the accuracy of determining deterioration of buffer material 43 can be improved.

[0080] The buffer according to the third aspect is the buffer according to the second aspect, and further, the second space 56 is formed by a protrusion 64 that protrudes outward from the support member 42. This allows the displacement measuring devices 61, 61A, 61B, 61C, and 61D to be arranged efficiently.

[0081] The buffer according to the fourth aspect is the buffer according to any one of the first to third aspects, and furthermore, displacement measuring devices 61, 61A, 61B, 61C, and 61D measure the displacement of buffer material 43 or the displacement of test material 44 that is placed in the same temperature environment as buffer material 43 and is made of a material with similar aging deterioration properties to buffer material 43. This makes it possible to determine the degree of deterioration of buffer material 43 with high accuracy.

[0082] A buffer according to a 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 having load applying devices 62, 62A, 62B, 62D that apply a compressive load to buffer material 43 or test material 44, and a displacement meter 63, 63B, 63D that measures the displacement of buffer material 43 or test material 44. As a result, when load applying devices 62, 62A, 62B, 62D apply a compressive load to buffer material 43 or test material 44, displacement meter 63, 63B, 63D measures the displacement of buffer material 43 or test material 44, and the displacement of buffer material 43 or test material 44 can be easily measured.

[0083] The buffer according to the sixth aspect is the 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 specify the compressive load applied to the buffer material 43 with high precision, and to adjust the compressive load applied to the buffer material 43 according to the test conditions, thereby enabling the displacement of the buffer material 43 to be measured with high precision.

[0084] The buffer according to the seventh aspect is the buffer according to any one of the sixth form to sixth aspect, and further includes a displacement measuring device 61C having a first storage 91 that stores a plurality of 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 the plurality of 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.

[0085] The buffer according to the eighth aspect is the 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 that can press 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 amount of displacement of the buffer material 43 multiple times depending on the usage time of the buffers 41, 41A, 41B, 41C, 41D, and to measure the amount of displacement of the buffer material 43 arranged at different positions.

[0086] The radioactive material storage container according to the ninth aspect includes a body 12, a lid 13 that seals the body 12, and buffers 41, 41A, 41B, 41C, and 41D. This makes it possible to check the soundness of the buffer material 43 during storage using the buffers 41, 41A, 41B, 41C, and 41D, and maintain the soundness of the buffer material 43.

[0087] 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 arranged therein. However, the second space 56 may also 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 also be arranged therein. [Explanation of symbols]

[0088] 11 Cask (container for storing radioactive materials) 12 Torso 13 Lid 31 Primary lid 32 Secondary lid 41,41A,41B,41C,41D,46 Buffer 42 Support member 43,43A,43B,43C,43D Cushioning material 43a 1st buffer material 43b Second buffer material 43c 3rd buffer material 44 Test material 51 Disc 52 Cylindrical part 61, 61A, 61B, 61C, 61D Displacement measuring device 62, 62A, 62B, 62D Load application device 63, 63B, 63D Displacement Meter 64 Protrusion 65 1st space part 66 Second space 67 Observation window 71 Pressing member 72 Compression spring 81 Press screw 82 Nut 91 1st Storage 92 Loading device 93 2nd Storage 101 Pressing member 102 Pressing device

Claims

1. 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:

2. 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 .

3. The second space is formed by a protrusion that protrudes outward from the support member. The shock absorber according to claim 2 .

4. 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.

5. 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.

6. 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 .

7. 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 in the storage container to the load applying device. The shock absorber according to claim 5 .

8. 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 .

9. A torso and a lid portion that seals the body portion; The buffer body according to claim 1; A radioactive material storage container comprising:

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