Protective device for radioactive material storage container and radioactive material storage container

Abstract

To provide a radioactive material storage container protection device and radioactive material storage container, which improve buffer material deterioration determination accuracy.SOLUTION: A protection device for protecting a radioactive material storage container is provided, comprising a hollow-shaped support member provided outside the radioactive material storage container, a buffer material provided inside the support member to absorb shock through deformation, and a deterioration monitoring member made of a material having an aging property similar to that of the buffer material and placed in the same temperature environment as the buffer material.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a protection device for a radioactive material storage container that contains and stores radioactive material, 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 protection device for a radioactive material storage container and a radioactive material storage container that improves the accuracy of determining deterioration of a buffer material. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the protective device for a radioactive material storage container of the present disclosure is a protective device for protecting a radioactive material storage container, and includes a support member having a hollow shape and provided on the outside of the radioactive material storage container, a buffer material that is placed inside the support member and absorbs impact by deforming, and a deterioration monitoring member that is placed in the same temperature environment as the buffer material and is made of a material with similar deterioration properties over time to the buffer material.

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

[0009] According to the protection device for a radioactive material storage container and the 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 protection device for a radioactive material storage container of the first embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing the main part of the protection device. [Figure 8] FIG. 8 is a schematic diagram showing a protection device for a radioactive material storage container according to the second 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 material storage container 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 with a buffer body attached, and FIG. 3 is a front view showing a state in which the radioactive material storage container with a buffer body attached 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 buffer body.

[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] <Protective device> FIG. 6 is a front view showing the protection device for a radioactive material storage container of the first embodiment, and FIG. 7 is a cross-sectional view showing the main part of the protection device.

[0037] 6, a protection device 61 of the first embodiment is for protecting a cask (container for storing radioactive material) 11. The protection device 61 includes a deterioration monitoring member 62 in addition to a buffer body 41.

[0038] The deterioration monitor member 62 is placed in the same temperature environment as the buffer material 43 and is made of the same material as the buffer material 43 or a material with similar aging deterioration properties.

[0039] 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 deteriorate over time due to exposure to the outside air. 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 is hermetically covered by the support member 42, 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.

[0040] Therefore, in the first embodiment, the deterioration monitoring member 62 is made of the same material as the buffer material 43 or a material with similar deterioration properties over time, and is placed inside the support member 42, which is in the same temperature environment as the buffer material 43. Therefore, the protection device 61 can accurately check the soundness of the buffer material 43 using the deterioration monitoring member 62.

[0041] The buffer 41 is configured by disposing a buffer material 43 inside a 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 material that constitutes the first buffer material 43a has the highest compressive strength, and is, for example, oak. The second material that constitutes the second buffer material 43b has a lower compressive strength than the first material, and is, for example, red cedar. The third material that constitutes the third buffer material 43c has a lower compressive strength than the second material, and is, for example, balsa.

[0042] Therefore, multiple deterioration monitoring members 62a, 62b, 62c are provided corresponding to the cushioning materials 43a, 43b, 43c with different compressive strengths. That is, a first deterioration monitoring member 62a is provided corresponding to the first cushioning material 43a. A second deterioration monitoring member 62b is provided corresponding to the second cushioning material 43b. A third deterioration monitoring member 62c is provided corresponding to the third cushioning material 43c. Furthermore, multiple deterioration monitoring members 62a, 62b, 62c are provided for each of the cushioning materials 43a, 43b, 43c.

[0043] Here, we will explain the arrangement structure of the deterioration monitoring members 62a, 62b, and 62c. However, since the arrangement structures of the deterioration monitoring members 62a, 62b, and 62c are almost the same, we will only explain the arrangement structure of the deterioration monitoring member 62a, and will omit explanation of the arrangement structures of the deterioration monitoring members 62b and 62c.

[0044] 7, the first cushioning material 43a is provided with a recess 66 that opens to the surface. The recess 66 has a cylindrical shape and has an inner peripheral surface 66a and a bottom surface 66b.

[0045] The first deterioration monitoring member 62a is cylindrical and has an outer peripheral surface 62a1, a bottom surface 62a2, and a surface 62a3. The first deterioration monitoring member 62a is made of the same material as the first buffer material 43a or a material with similar deterioration properties over time. That is, if the first buffer material 43a is made of wood (oak), the first deterioration monitoring member 62a is also made of wood (oak). If the buffer material 43a is made of a foam material or a polymer compound, the first deterioration monitoring member 62a is also made of the same type of foam material or polymer compound.

[0046] The first deterioration monitoring member 62a is placed in a recess 66 formed in the first buffer material 43a. The axial length of the first deterioration monitoring member 62a is the same as the axial length of the recess 66. The radial length (diameter) of the first deterioration monitoring member 62a is slightly shorter than the radial length (diameter) of the recess 66. That is, when the first deterioration monitoring member 62a is placed in the recess 66 of the first buffer material 43a, the bottom surface 62a2 of the first deterioration monitoring member 62a is in close contact with the bottom surface 66b of the recess 66. At this time, the surface 62a3 of the first deterioration monitoring member 62a and the surface 43a3 of the first buffer material 43a are at the same height, with no step. Furthermore, a small gap is formed between the outer peripheral surface 43a1 of the first deterioration monitoring member 62a and the outer peripheral surface of the inner peripheral surface 66a of the recess 66.

[0047] The outer peripheral surface 62a1 of the first deterioration monitoring member 62a is bonded to the inner peripheral surface 66a of the recess 66 with adhesive 67. That is, the minute gap between the outer peripheral surface 62a1 of the first deterioration monitoring member 62a and the outer peripheral surface of the inner peripheral surface 66a of the recess 66 is filled. However, the bottom surface 62a2 of the first deterioration monitoring member 62a and the bottom surface 66b of the recess 66 are not bonded with adhesive 67. Only the outer peripheral surface 62a1 of the first deterioration monitoring member 62a and the inner peripheral surface 66a of the recess 66 are bonded with adhesive 67. Note that the first deterioration monitoring member 62a may be simply inserted into the recess 66 without being bonded to the inner peripheral surface 66a.

[0048] A gap is formed between the inner surface of the support member 42 and the outer surface of the first buffer material 43a. The support member 42 has an opening 42a formed at a position facing the recess 66. The opening 42a is circular, with an inner diameter larger than the inner diameter of the recess 66 of the first buffer material 43a. The support member 42 is provided with a lid 68 that can open and close the opening 42a from the outside. The lid 68 is circular, with an outer diameter larger than the inner diameter of the opening 42a. That is, the lid 68 is fixed to the surface of the support member 42 so as to close the opening 42a from the outside of the buffer body 41. The lid 68 is fixed to the support member 42 by a connecting portion 69 formed on the outer periphery of the lid 68, for example, by spot welding. In this case, a metal seal is preferably disposed between the lid 68 and the support member 42 to prevent leakage of water vapor from inside the support member 42. However, the material is not limited to a metal seal, and silicone rubber or the like may also be used.

[0049] The first deterioration monitoring member 62a is placed in a recess 66 of the first buffer material 43a, and its outer peripheral surface 43a1 is bonded to an inner peripheral surface 66a of the recess 66 with an adhesive 67. The support member 42 has a lid portion 68 fixed to the opening 42a. In this state, the buffer 41 is attached to the cask 11.

[0050] In the above description, one first deterioration monitor member 62a is placed in the recess 66 of the first cushioning material 43a, but this configuration is not limited to this. For example, as shown by the two-dot chain line in Figure 7, the recess 66 of the first cushioning material 43a may be elongated in the axial direction, and multiple first deterioration monitor members 62a may be placed vertically in the recess 66.

[0051] When a predetermined number of years have passed and the soundness of the buffer material 43 in the buffer 41, i.e., the degree of temperature-related deterioration of the buffer material 43, is to be determined, the deterioration monitoring member 62 (first deterioration monitoring member 62a) provided inside the buffer 41 is removed. First, the connecting portion 69 is removed using a cutting tool or the like, and the lid portion 68 is removed from the support member 42 to open the opening 42a. Next, the adhesive 67 between the outer peripheral surface 62a1 of the first deterioration monitoring member 62a and the inner peripheral surface 66a of the recess 66 is removed using, for example, a cylindrical cutting tool. Next, the first deterioration monitoring member 62a arranged in the recess 66 is removed using a predetermined removal tool and removed from the buffer 41. A deterioration determination test is then performed on the first deterioration monitoring member 62a.

[0052] The deterioration assessment test for the first deterioration monitoring member 62a involves evaluating the degree of deterioration through a uniaxial compression test of the first deterioration monitoring member 62a. During the manufacturing process of the first buffer material 43a, a compression test is conducted using a first deterioration monitoring member 62a of the same type as the first buffer material 43a, and the measured value is set as a reference value. For example, the uniaxial compression test involves placing the first deterioration monitoring member 62a inside a restraining ring and compressing only the first deterioration monitoring member 62a. In this case, the restraining ring is made of wood that has not deteriorated over time, as it serves as a boundary condition for the first deterioration monitoring member 62a. Furthermore, the uniaxial compression test is conducted at room temperature to ensure stable conditions. Alternatively, the test may be conducted at a high temperature equivalent to the temperature environment of the buffer material 41.

[0053] In the protection device 61 of the first embodiment, the deterioration monitoring member 62 is placed in the same temperature environment as the buffer material 43. In other words, the temperature environment in which the deterioration monitoring member 62 is placed is the same as the temperature environment of the buffer material 43 inside the buffer body 41 attached to the cask 11, so the deterioration monitoring member 62 will have the same degree of deterioration as the buffer material 43. Therefore, the deterioration monitoring member 62 can be used to determine the degree of deterioration of the buffer material 43 with high accuracy. The degree of deterioration of the buffer material 43 is 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 a compression test obtained in a deterioration determination test.

[0054] After removing the first deterioration monitoring member 62a from the recess 66 of the first cushioning material 43a, a new first deterioration monitoring member 62a is placed in the recess 66 and fixed with adhesive 67, and a lid portion 68 is fixed to the opening 42a of the support member 42 to close it.

[0055] [Second embodiment] 8 is a schematic diagram showing a protection device for a radioactive material storage container according to the second embodiment. Note that members 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.

[0056] As shown in Figure 8, the cask 11 is supported on a stand 38 in a horizontal position with its central axis O aligned horizontally. A buffer body 41 is attached to one side of the cask 11 along the central axis O, and a buffer body 46 is attached to the other side of the cask 11 along the central axis O. The buffer bodies 41 and 46 have substantially the same configuration.

[0057] The protection device 61A of the second embodiment protects the cask 11. In addition to the buffer body 41, the protection device 61A includes a deterioration monitoring member 62. The deterioration monitoring member 62 is placed in the same temperature environment as the buffer material 43 and is made of the same material as the buffer material 43 or a material with similar aging deterioration properties.

[0058] Moreover, the protection device 61A includes a storage 71, temperature sensors 72 and 73, and a control device 74 in addition to the buffer body 41 and the deterioration monitor member 62.

[0059] The storage cabinet 71 is a so-called constant temperature room that has a temperature regulator 75 that can adjust the temperature inside. The storage cabinet 71 is provided with a plurality of shelves inside, and a plurality of deterioration monitor members 62 (62a, 62b, 62c) are arranged on the shelves.

[0060] The first temperature sensor 72 measures the temperature of the buffer materials 43 (43a, 43b, 43c) in the buffer body 41. In this case, it is preferable that the first temperature sensor 72 measures the temperature of the buffer materials 43a, 43b, 43c in the hottest area. It is also preferable that the first temperature sensor 72 measures the temperature of the buffer materials 43a, 43b, 43c that will deform the most when the cask 11 is dropped, overturned, or collided. The second temperature sensor 73 measures the temperature of the air inside the storage facility 71. The first temperature sensor 72 and the second temperature sensor 73 are connected to a control device 74. The control device 74 receives the measurement results of the first temperature sensor 72 and the second temperature sensor 73. The control device 74 controls the temperature regulator 75 based on the temperature of the buffer materials 43 and the temperature inside the storage facility 71.

[0061] That is, the control device 74 controls the temperature regulator 75 so that the temperature inside the storage facility 71 approaches the temperature of the buffer material 43. As a result, the temperature inside the storage facility 71 becomes the same temperature as the temperature of the buffer material 43 inside the buffer body 41. In other words, the deterioration monitoring members 62 (62a, 62b, 62c) arranged inside the storage facility 71 are in the same temperature environment as the buffer materials 43 (43a, 43b, 43c) arranged inside the buffer body 41.

[0062] Furthermore, since the buffer materials 43a, 43b, and 43c are in slightly different temperature environments, the interior of the storage facility 71 may be divided into multiple compartments, with buffer materials 43a, 43b, and 43c placed in each compartment, and temperature control may be performed for each compartment.Furthermore, a first humidity sensor may be provided to measure the humidity of the buffer material 43 in the buffer body 41, and a second humidity sensor may be provided to measure the humidity inside the storage facility 71, and the control device 74 may control the humidity regulator so that the humidity inside the storage facility 71 approaches the humidity of the buffer material 43.

[0063] The control device 74 is a controller, and is realized by, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) executing various programs stored in a storage unit using a RAM as a working area.

[0064] Every time a predetermined number of years have passed, when the soundness of the buffer material 43 in the buffer body 41, that is, the degree of deterioration of the buffer material 43 due to temperature, is to be determined, the deterioration monitoring member 62 provided inside the storage facility 71 is removed. Then, a deterioration determination test is performed on the deterioration monitoring member 62. The deterioration determination test on the deterioration monitoring member 62 is the same as in the first embodiment.

[0065] [Effects of this embodiment] The protection device for a radioactive material storage container according to the first aspect comprises a support member 42 having a hollow shape and provided on the outside of a cask (radioactive material storage container) 11, a buffer material 43 that is placed inside the support member 42 and absorbs impact by deforming, and a deterioration monitoring member 62 that is placed in the same temperature environment as the buffer material 43 and is made of a material with similar deterioration properties over time to the buffer material 43.

[0066] According to the protection device for a radioactive material storage container of the first aspect, during storage in the cask 11, the deterioration monitoring member 62 is removed periodically (e.g., every few years). If the compressive strength of the deterioration monitoring member 62 falls below a specified value, it can be determined that the buffering function of the buffer material 43 has deteriorated, and the buffer body 41 or the buffer material 43 is replaced. As a result, the integrity of the buffer material 43 during storage can be confirmed, and the integrity of the buffer material 43 can be maintained. Furthermore, the deterioration monitoring member 62 is placed in the same temperature environment as the buffer material 43 and is made of a material that has the same deterioration characteristics as the buffer material 43. Therefore, the deterioration monitoring member 62 will have the same degree of deterioration as the buffer material 43, and the deterioration degree of the buffer material 43 can be determined with high accuracy using the deterioration monitoring member 62, thereby improving the accuracy of determining the deterioration of the buffer material 43.

[0067] The protection device for a radioactive material storage container according to the second aspect is the protection device for a radioactive material storage container according to the first aspect, further comprising: a recess 66 that opens onto the surface of the buffer material 43; and a deterioration monitoring member 62 that is disposed in the recess 66. By disposing the deterioration monitoring member 62 in the recess 66 of the buffer material 43, the deterioration monitoring member 62 and the buffer material 43 are disposed in the same environment, and the deterioration monitoring member 62 can be used to determine the degree of deterioration of the buffer material 43 with high accuracy.

[0068] The protection device for a radioactive material storage container according to the third aspect is the protection device for a radioactive material storage container according to the second aspect, and further, the deterioration monitoring member 62 has a cylindrical shape, which allows the shape of the deterioration monitoring member 62 to be simplified.

[0069] The protection device for a radioactive material storage container according to the fourth aspect is the protection device for a radioactive material storage container according to the third aspect, and furthermore, the outer peripheral surface of the deterioration monitoring member 62 is adhered to the inner peripheral surface of the recess 66 with an adhesive 67. This makes it possible to suppress damage to the deterioration monitoring member 62. It also makes it possible to reduce the temperature difference with the surrounding buffer material 43.

[0070] The protection device for a radioactive material storage container according to the fifth aspect is the protection device for a radioactive material storage container according to any one of the second to fourth aspects, and further, the support member 42 has an opening 42a facing the recess 66 and a lid 68 that can open and close the opening 42a from the outside. This makes it possible to maintain the inside of the buffer body 41 in a sealed state, and by opening the lid 68, the deterioration monitoring member 62 can be easily removed.

[0071] The protection device for a radioactive material storage container according to the sixth aspect is the protection device for a radioactive material storage container according to the first aspect, further comprising a storage cabinet 71 having a temperature regulator 75 capable of regulating the internal temperature, and a deterioration monitoring member 62 disposed inside the storage cabinet 71. By disposing the deterioration monitoring member 62 in the storage cabinet 71, the deterioration monitoring member 62 and the buffer material 43 are disposed in the same environment, and the deterioration monitoring member 62 can be used to determine the degree of deterioration of the buffer material 43 with high accuracy. Furthermore, there is no need to modify the buffer body 41, which prevents the buffer body 41 from becoming more complicated and expensive.

[0072] The protection device for a radioactive material storage container according to the seventh aspect is the protection device for a radioactive material storage container according to the sixth aspect, further comprising a first temperature sensor 72 that measures the temperature of the buffer material 43, a second temperature sensor 73 that measures the temperature inside the storage vault 71, and a control device 74 that controls a temperature regulator 75 based on the measurement results of the first temperature sensor 72 and the second temperature sensor 73 so that the temperature inside the storage vault 71 approaches the temperature of the buffer material 43. This makes the temperature environments of the deterioration monitoring member 62 in the storage vault 71 and the buffer material 43 in the buffer body 41 the same, and the deterioration degree of the buffer material 43 can be determined with high accuracy using the deterioration monitoring member 62. Furthermore, if the buffer material 43 is not in an atmospheric environment, for example, if the installation space of the buffer material 43 is purged with nitrogen, helium, or the like and then sealed, the deterioration monitoring member 62 is placed in a nitrogen- or helium-purged sealed container before being placed in the storage vault 71.

[0073] The protection device for a radioactive material storage container according to an eighth aspect is the protection device for a radioactive material storage container according to any one of the first to seventh aspects, further comprising: the buffer material 43 being a combination of multiple buffer materials 43a, 43b, 43c with different compressive strengths; and the deterioration monitoring member 62 being provided with multiple deterioration monitoring members 62a, 62b, 62c corresponding to the buffer materials 43a, 43b, 43c with different compressive strengths. Thus, by providing the deterioration monitoring members 62a, 62b, 62c corresponding to the buffer materials 43a, 43b, 43c with different deterioration states, the deterioration degrees of the buffer materials 43a, 43b, 43c can be determined in detail using the deterioration monitoring members 62a, 62b, 62c.

[0074] The radioactive material storage container according to the ninth aspect includes a body 12, a lid 13 that seals the body 12, and a protection device 61, 61A for a radioactive material storage container according to any one of the first to eighth aspects. As a result, in the protection devices 61, 61A, the deterioration monitoring member 62 has the same degree of deterioration as the buffer material 43, and the deterioration monitoring member 62 can be used to determine the degree of deterioration of the buffer material 43 with high accuracy, thereby improving the accuracy of determining the deterioration of the buffer material 43.

[0075] In the first embodiment described above, the shape of the deterioration monitoring member 62 and the recess 66 is cylindrical, but this shape is not limited to this, and the deterioration monitoring member may be a polygonal shape such as a cube or rectangular prism, or any other shape.

[0076] In addition, in the second embodiment described above, the control device 74 is configured to control the temperature regulator 75 so that the temperature inside the storage facility 71 approaches the temperature of the buffer material 43, but the temperature regulator 75 may also be operated by an operator. [Explanation of symbols]

[0077] 11 Cask (container for storing radioactive materials) 12 Torso 13 Lid 31 Primary lid 32 Secondary lid 41,46 Buffer 42 Support member 43 Cushioning material 43a 1st buffer material 43b Second buffer material 43c 3rd buffer material 51 Disc 52 Cylindrical part 61,61A Protective device 62 Deterioration monitoring components 62a First deterioration monitoring member 62b Second deterioration monitoring member 62c Third deterioration monitoring member 66 Recess 67 Adhesive 68 Lid 69 Connection 71 Storage 72 First temperature sensor 73 Second temperature sensor 74 Control Device 75 Temperature controller

Claims

1. A protection device for protecting a radioactive material storage container, 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 deterioration monitor member that is placed in the same temperature environment as the buffer material and is made of a material that has the same deterioration characteristics as the buffer material; A protection device for a radioactive material storage container.

2. The buffer material has a recessed portion that opens to a surface thereof, and the deterioration monitor member is disposed in the recessed portion. The protection device for a radioactive material storage container according to claim 1.

3. The deterioration monitoring member has a cylindrical shape. The protection device for a radioactive material storage container according to claim 2.

4. The deterioration monitoring member has an outer circumferential surface bonded to the inner circumferential surface of the recess with an adhesive. The protection device for a radioactive material storage container according to claim 3.

5. The support member has an opening facing the recessed portion and a lid that can open and close the opening from the outside. The protection device for a radioactive material storage container according to any one of claims 2 to 4.

6. a storage cabinet having a temperature regulator capable of adjusting the temperature inside the storage cabinet is provided, and the deterioration monitoring member is disposed inside the storage cabinet; The protection device for a radioactive material storage container according to claim 1.

7. a first temperature sensor that measures the temperature of the buffer material, a second temperature sensor that measures the temperature inside the storage facility, and a control unit that controls the temperature regulator based on the measurement results of the first temperature sensor and the measurement results of the second temperature sensor so that the temperature inside the storage facility approaches the temperature of the buffer material, The protection device for a radioactive material storage container according to claim 6.

8. The buffer material is configured by combining a plurality of buffer materials having different compressive strengths, and a plurality of the deterioration monitor members are provided corresponding to the buffer materials having different compressive strengths. The protection device for a radioactive material storage container according to claim 1.

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

Images