Buffers and radioactive material storage containers

Abstract

To provide a buffer and radioactive material storage container that ensures long-term buffering and heat dissipation performance and is easy to manufacture. [Solution] The buffer body of the present invention is a buffer body 10 installed in a radioactive material storage container C, comprising an outer shell 10k constituting the case of the buffer body 10, partition members 2 that partition the inside of the outer shell 10k, and a buffer member 1 housed inside the outer shell 10k between the partition members 2, wherein the outer shell 10k and the partition members 2 are formed of metal material, and the buffer member 1 is formed of metal material and has a box-like or tubular shape, and is provided inside the outer shell 10k between the partition members 2 without being fixed.

Description

Technical Field

[0001] The present invention relates to a buffer and a radioactive substance storage container.

Background Art

[0002] Generally, spent fuel used in a nuclear power plant is first stored in a cooling pool provided in the nuclear power plant until the radiation dose decreases to a certain level or below. Thereafter, the spent fuel is stored in a cask (radioactive substance storage container) having four safety functions (criticality prevention, shielding, heat removal, and confinement functions), and transported to a fuel processing facility or the like. Alternatively, it is transported to an intermediate storage facility and stored in a cask.

[0003] Since a cask is a heavy object containing radioactive substances, it is necessary to prepare for any accidents during transportation, handling, and storage. That is, for example, it must have predetermined safety functions even if it falls from a high place, topples over, or is hit by a falling object. For this reason, a buffer is attached to the upper end or both the upper and lower ends of the cask to mitigate the impact acting on the cask during falling, toppling over, and collision with a falling object. As a buffer material for absorbing impact, materials having a small specific gravity and a large impact absorption capacity, such as wood and foamed materials, are often adopted, but there are also cases where it is made of a metal material.

[0004] For example, Patent Document 1 describes a protection device (buffer) having a metal member made of a metal material such as an aluminum alloy, stainless steel, or carbon steel and formed in a block shape.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Casks containing spent fuel are stored in storage facilities for several decades after transport. The buffers installed during storage need to maintain their buffering and heat dissipation performance over long storage periods, making the use of metal materials advantageous. However, compared to materials like wood, which have a low specific gravity and are easy to process and shape, metal materials have a high specific gravity, requiring volume limitations. Therefore, a design that balances buffering performance, weight, and manufacturability is necessary.

[0007] This invention was devised to solve the above problems, and aims to provide a buffer and a radioactive material storage container that can ensure long-term buffering and heat dissipation performance and has excellent manufacturability. [Means for solving the problem]

[0008] To solve the aforementioned problems, the buffer body of the present invention is a buffer body installed in a radioactive material storage container, comprising an outer shell constituting the case of the buffer body, partition members dividing the inside of the outer shell, and a buffer member housed inside the outer shell between the partition members, wherein the outer shell and the partition members are formed of metal, and the buffer member is formed of metal and has a box-like or tubular shape, and is provided inside the outer shell between the partition members without being fixed. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a buffer and a radioactive material storage container that can ensure long-term buffering and heat dissipation performance and have excellent manufacturability. [Brief explanation of the drawing]

[0010] [Figure 1A] This is a perspective view including a schematic longitudinal section showing the buffer body of the first embodiment of the present invention installed in a cask. [Figure 1B] This is an enlarged view of section I in Figure 1A. [Figure 2A] This is a cross-sectional view taken along line II-II in Figure 1A. [Figure 2B] It is a cross-sectional view taken along the line III-III of FIG. 2A. [Figure 2C] It is a view seen in the direction of arrow IV of FIG. 2A. [Figure 3A] It is a perspective view showing a buffer member housed in a buffer body. [Figure 3B] It is a development view of the buffer member. [Figure 4] It is a view corresponding to FIG. 2B of the second embodiment. [Figure 5A] It is a perspective view showing a first buffer member storage material used for the buffer body of the second embodiment. [Figure 5B] It is a development view of the first buffer member storage material of the second embodiment. [Figure 6A] It is a perspective view showing a second buffer member storage material used for the buffer body of the second embodiment. [Figure 6B] It is a development view of the second buffer member storage material of the second embodiment. [Figure 7A] It is a cross-sectional view taken along the line V-V of FIG. 4. [Figure 7B] It is a cross-sectional view taken along the line VI-VI of FIG. 4. [Figure 8A] It is a view corresponding to FIG. 2B showing the buffer body of the third embodiment. [Figure 8B] It is a cross-sectional view taken along the line VII-VII of FIG. 8A. [Figure 8C] It is a cross-sectional view taken along the line VIII-VIII of FIG. 8B. [Figure 9] It is a view seen in the direction of arrow IX of FIG. 8B. [Figure 10] It is a view corresponding to the view seen in the direction of arrow IX of FIG. 8B of a modification of the third embodiment. [Figure 11A] It is a view corresponding to FIG. 2B showing the buffer body of the fourth embodiment. [Figure 11B] It is a view seen in the direction of arrow X of FIG. 11A. [Figure 12A] It is a schematic cross-sectional view of an annular buffer body and a cylindrical-annular mounting bracket of the fifth embodiment. [Figure 12B] It is a cross-sectional view taken along the line XI-XI of FIG. 12A. [Figure 13A] It is a cross-sectional view showing the process of restraining the buffer members of four square tubes with a metal tie. [Figure 13B] This is a cross-sectional view showing the process of restraining the cushioning members of the four square tubes with metal ties. [Figure 13C] This is a cross-sectional view showing the process of restraining the cushioning members of the four square tubes with metal ties. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[0012] <<First Embodiment>> Figure 1A is a perspective view including a schematic longitudinal section showing the buffer body 10 of the first embodiment of the present invention installed in a radioactive material storage container (cask C). Figure 1B is an enlarged view of part I of Figure 1A.

[0013] <Overview of buffer 10> Cask C is a container for storing, transporting, and containing spent fuel n discharged from nuclear power plants. Cask C has a roughly cylindrical shape and consists of a bottomed cylindrical body C1 and a lid C2 attached to the upper opening of the body C1. The lid C2 contains a resin layer, which is a resin that absorbs neutrons. A buffer 10 is installed near the lid c2 of cask C (a container for radioactive materials). The buffer 10 is a shock absorber used when the cask C is stored. For example, the buffer 10 absorbs the impact when the cask C is dropped or tipped over, or when an object (such as a piece of concrete) falls on it.

[0014] When the cask C is stored vertically (with the axis o1 of the cask C in a nearly vertical direction), the cask buffer 10 is installed near the lid c2 of the cask C, as shown in Figure 1A. When the cask C is stored horizontally (with the axis o1 of the cask C in a nearly horizontal direction), the buffer 10 is installed near the lid c2 on one side of the cask C and at the other end of the cask C, as shown in Figure 1A.

[0015] The buffer 10 in the first embodiment is an example of a buffer made of stainless steel plate (SUS304) and consisting of identical rectangular prisms. The buffers 10 to 50 of the first to fifth embodiments described below are not limited to specific spent fuel casks, but are also applicable to buffers used in other radioactive material storage containers.

[0016] As shown in Figure 1A, the buffer 10 is an annular structure with a diameter larger than that of the cask C. In the first embodiment, the buffer 10 is fixed to the cask C by bolts so as to cover the vicinity of the lid c2 on one side of the cask C and the bottom (not shown) on the other side of the cask C.

[0017] Figure 1A shows the state in which the buffer 10 is attached near the lid c2 on one side of the cask C. Figure 2A is a cross-sectional view taken along line II-II of Figure 1A. Figure 2B is a cross-sectional view taken along line III-III of Figure 2A, and Figure 2C is a view taken in the direction of arrow IV of Figure 2A.

[0018] Figures 2A to 2C show the interior of the annular buffer 10.

[0019] The buffer 10 shown in Figure 2B has an inner cylinder 10a, a front disc 10b, a back disc 10c, and an outer cylinder 10d, forming an annular outer shell 10k. The outer shell 10k is constructed as an annular metal case. The inner cylinder 10a, front disc 10b, back disc 10c, and outer cylinder 10d that form the outer shell 10k are welded all around by linear welding, for example, using TIG welding. Furthermore, the buffer body 10 has a mounting bracket b on the cask C side, and the mounting bracket b is an annular member having a cylindrical plate shape and an annular plate shape. The mounting bracket b is formed by welding an inner annular plate b2 and an outer annular plate b3 all around a cylindrical member b1. Mounting bracket b is formed using, for example, a stainless steel plate (e.g., SUS304) with a thickness of approximately 20 mm. Mounting bracket b may be made of other steel plates as long as they are treated to prevent rusting. Mounting bracket b is welded all around to the edges of the inner cylinder 10a and the back surface disc 10c that form the outer shell 10k, and constitutes the shell of the buffer body 10.

[0020] Figure 3A is a perspective view showing the cushioning member 1 housed within the cushioning body 10. Figure 3B is an unfolded view of the cushioning member 1. The buffer member 1 is composed of an elongated rectangular prism-shaped box with isosceles trapezoids as its base 1a and top 1b. The buffer member 1 is made from a stainless steel plate (for example, SUS304, etc.) with the shape 1m shown in Figure 3B. The shape 1m shown in Figure 3B represents the buffer member 1 before bending. The shape of the buffer member 1 is formed by bending the shape 1m shown in Figure 3B along the dashed line. Then, the outer circumference 1m1 of the shape 1m is welded all around using linear welding, for example, TIG welding, a type of arc welding, to form the buffer member 1, which is a long, slender rectangular prism-shaped box (see Figure 3A).

[0021] The bottom surface 1a (see Figure 3A) of the buffer member 1 is in contact with the outer cylinder 10d of the outer shell 10k case. The thickness t1 (see Figure 3A) of the buffer member 1 is aligned with the axis o1 (see Figure 2B) of the cask C of the radioactive material storage container. As shown by the thick solid line in Figure 2A, the cushioning member 1 is also used as radial ribs 2 that define the inside of the cushioning body 10 into eight chambers. As shown in Figures 2A and 2C, in the first embodiment, a total of 32 cushioning members 1 are joined together in rows of four to form eight rows of radial ribs 2. By welding the radial ribs 2 to the mounting bracket b, the inner cylinder 10a, the back surface disc 10c, etc., the radial ribs 2 that form the rib structure of the cushioning body 10 can also absorb the impact load applied to the cask C.

[0022] The buffer member 1 shown in Figure 3A is housed in the space between the radial ribs 2 within the buffer body 10, in contact with or in close proximity to it, without being joined and fixed, as shown in Figures 2A to 2C. A gap may be provided between the buffer member 1 and the outer shell 10k. The presence of this gap allows the buffer member 1 to be smoothly inserted into the outer shell 10k.

[0023] Thus, a total of 256 buffer members 1 are housed inside the buffer body 10 without being fixed: 8 in the circumferential direction as shown in Figure 2A, and 4 in the thickness direction (axis o1 direction) as shown in Figures 2B and 2C. When these are combined with the buffer members 1 that make up the 8 radial ribs 2, a total of 288 buffer members 1 are housed within the structure 10t of the buffer body 10.

[0024] <Effects and Effects> According to the buffer body 10 of the first embodiment, the impact load acting on the cask C can be mitigated by housing 256 buffer members 1 between the radial ribs 2 without joining them, contacting them, or fixing them in close proximity. Specifically, the buffer 10 can absorb thrust impact loads and radial impact loads. Furthermore, since the buffer 10 is made of metal, it can ensure long-term buffering and heat dissipation performance. In addition, the buffer 10 has a limited number of welding points, making it easy to manufacture. In the first embodiment, a case was shown in which radial ribs 2 were constructed using a three-dimensional buffer member 1. However, plate-shaped radial ribs 2 may also be made using a perforated plate of a corrosion-resistant metal material (metal plate) such as stainless steel.

[0025] <<Second Embodiment>> Figure 4 is a diagram corresponding to Figure 2B of the second embodiment. In Figure 4, pipes k21 and k22 are schematically shown, and pipe k22 is shown as an example where the pipe diameters are the same. The buffer body 20 of the second embodiment has a configuration consisting of an annular first buffer region 20A and an annular second buffer region 20B arranged in two rows in the axial direction o1 of the cask C. The first buffer region 20A of the first row is fabricated so that a roughly rectangular box in the cylindrical radial direction is contained inside a fan-shaped box (see Figure 7A). A radial pipe k21 may be housed inside this roughly rectangular box. The pipe k21 can be a circular pipe, a square pipe, a hexagonal pipe, or any other type of pipe.

[0026] The second buffer region 20B in the second row shown in Figure 4 contains a tube (which can be circular, square, or hexagonal) k22 (see Figure 7B) in the direction of the axis o1 of the cask C within a fan-shaped box. Tubes k21 and k22 may be fixed radially with metal ties. Figure 5A is a perspective view showing the first cushioning member housing material 11A used in the cushioning body 20 of the second embodiment. Figure 5B is an exploded view of the first cushioning member housing material 11A of the second embodiment. Figure 7A is a cross-sectional view of the VV section of Figure 4. The first buffer region 20A has eight first buffer member housings 11A (see Figure 5A) inside (see Figure 7A). Figure 6A is a perspective view showing the second cushioning member housing material 11B used in the cushioning body 20 of the second embodiment. Figure 6B is an exploded view of the second cushioning member housing material 11B of the second embodiment. Figure 7B is a cross-sectional view taken along the line VI-VI in Figure 4. The second buffer region 20B has eight second buffer member housings 11B (see Figure 6A) inside (see Figure 7B).

[0027] The first buffer member housing material 11A and the second buffer member housing material 11B have their outer arc sides in contact with the divided outer cylinder 20d1 of the case. The annular outer shell 20k of the buffer body 20 is made of austenitic stainless steel plate with a thickness of 6 to 18 mm. By using austenitic stainless steel, the outer shell 20k has excellent corrosion resistance, ductility and toughness, as well as good cold workability and weldability. As shown in Figure 4, the annular outer shell 20k has an annular flat plate outer shell 20k1 of the first buffer region 20A, an annular flat plate outer shell 20k2 of the second buffer region 20B, eight divided outer cylinders 20d1, and a cylindrical inner cylinder 20d2. The 20k outer shell is perforated as needed. In some cases, the 20k outer shell is formed using a perforated plate. By using a perforated plate for the 20k outer shell, weight reduction can be achieved, and impact absorption performance can also be expected due to the deformation of the 20k outer shell itself.

[0028] The buffer body 20 of the second embodiment is modified by changing the buffer member 1 of the first embodiment to a box-shaped first buffer member housing material 11A (see Figure 5A) having a fan-shaped bottom surface 11a, and a box-shaped second buffer member housing material 11B (see Figure 6A) having a fan-shaped bottom surface 11b1.

[0029] The first buffer member housing 11A shown in Figure 5A is made by preparing a rust-resistant metal plate in the shape shown in Figure 5B. Then, the rust-resistant metal plate in the shape shown in Figure 5B is bent along the dashed line and the contact points 11s (see Figure 5A) are welded (continuously welded). This forms the first buffer member housing 11A having two triangular prisms 11b shown in Figure 5A. The contact points 11s are grooved as necessary so that welding can be performed across the thickness of the plate. Furthermore, the second buffer member housing material 11B shown in Figure 6A is made from a rust-resistant metal material (metal plate) in the shape shown in Figure 6B. The rust-resistant metal plate in the shape shown in Figure 6B is then bent along the thick solid line to form the second buffer member housing material 11B shown in Figure 6A. The rust-resistant metal plates used for the first buffer member housing material 11A and the second buffer member housing material 11B are, for example, stainless steel plates such as SUS304, rust-resistant galvanized steel plates, rust-resistant painted steel plates, etc.

[0030] The first cushioning member housing material 11A (see Figure 5A) and the second cushioning member housing material 11B (see Figure 6A) are perforated as necessary to satisfy the required cushioning performance of the cushioning body 20 or to meet the weight limit of the cushioning body 20. For example, the first cushioning member housing material 11A (see Figure 5A) and the second cushioning member housing material 11B (see Figure 6A) are formed using perforated steel plates.

[0031] The first buffer region 20A (see Figure 4) of the second embodiment has an annular outer shell 20k (see Figure 4) similar to the buffer body 10 of the first embodiment, and eight first buffer member housings 11A (see Figure 7A).

[0032] As shown in Figure 7A, the first buffer region 20A (see Figure 4) is fixed to the annular outer shell 20k1 by line welding (continuous welding) eight first buffer member housing members 11A (Figure 5A) at approximately 45-degree intervals. As shown in Figure 7A, the first buffer region 20A (see Figure 4) contains pipes k21, such as circular pipes and square pipes, in the radial direction around its entire circumference without being fixed.

[0033] After the pipes k21, such as the circular and rectangular pipes shown in Figure 7A, are accommodated, the front disc 20b1 (see Figure 4) is line-welded to the front to form the first buffer region 20A (see Figure 4). Furthermore, if the shock can be absorbed solely by the first cushioning member housing material 11A (see Figure 5A) in the first cushioning region 20A, then the pipe k21, such as a circular pipe or a square pipe, does not need to be housed within it.

[0034] As shown in Figure 7B, the second buffer region 20B (see Figure 4) of the second embodiment has eight second buffer member housings 11B.

[0035] As shown in Figure 7B, the second buffer region 20B (see Figure 4) is fixed to the front disc 20b1 (see Figure 4) by line welding (continuous welding) eight second buffer member housings 11B (Figure 6A) at approximately 45-degree intervals. In addition, a cylindrical inner cylinder 20d2 is fixed to the mounting bracket b by line welding (continuous welding). Subsequently, as shown in Figure 7B, the circular pipe k22 is housed around the entire circumference of the cask C in the direction of axis o1 (see Figure 4) between the second buffer member housing materials 11B without being fixed. Subsequently, eight divided outer cylinders 20d1 (see Figure 4) are line-welded to the side circumferences of the first buffer region 20A and the second buffer region 20B. In addition, an annular flat plate outer shell 20k2 is line-welded (continuously welded) to the inner cylinder 20d2 and the eight divided outer cylinders 20d1 to form the buffer body 20. Of the eight divided outer cylinders 20d1 (see Figure 4), the half closest to Cask C (the side closer to Cask C) is included in the first buffer region 20A, while the half furthest from Cask C (the side further from Cask C) is included in the second buffer region 20B.

[0036] The buffer 20 shown in Figure 4 is bolted to the cask C via the mounting bracket b. The assembly method for the buffer 20 can be selected as appropriate.

[0037] <Effects and Effects> According to the buffer 20 of the second embodiment, impact loads in the axial direction o1 of the cask C and impact loads in the radial direction of the cask C can be absorbed. Furthermore, since the buffer 20 is made of corrosion-resistant metal material, long-term buffering and heat dissipation performance can be ensured. In addition, the buffer 20 has a limited number of welding points, making it easy to manufacture.

[0038] <<Third Embodiment>> Figure 8A is a diagram corresponding to Figure 2B of the third embodiment, showing the buffer body 30 of the third embodiment. Note that Figure 8A shows a cross-section of the buffer body 30 of the third embodiment near the radial ribs 32.

[0039] Figure 8B is a cross-sectional view taken along line VII-VII of Figure 8A. Figure 8C is a cross-sectional view taken along line VIII-VIII of Figure 8B. In the third embodiment, the buffer body 30 is configured such that the radial ribs 32, which are partitions in the buffer member 1 of the can body in the first embodiment, are changed from a fabricated can structure to welded square tubes 32a (see Figure 8A). The square tubes 32a are tubes with a square cross-section. Furthermore, the buffer member 21 of the third embodiment (see Figure 8B) differs from the buffer member 1 of the first embodiment in that it is a rectangular tube bent into an arc shape. The buffer members 21 (see Figure 8B) are not fixed to any one other but are in contact with or close to each other and are housed within the outer shell 30k of the buffer body 30. The buffer members 21 are positioned so that the cut ends of the rectangular tubes are in contact with the radial ribs 32 of the can body.

[0040] The buffer 30 shown in Figure 8A is fixed to the cask C by bolts via the mounting bracket b. As shown in Figure 8A, the outer shell 30k of the buffer 30 has an inner cylinder 30a and a back surface disc 30c. The rear disc 30c and the inner cylinder 30a are welded all around to the mounting bracket b.

[0041] The three square tubes 32a forming the radial ribs 32 shown in Figure 8A are welded to each other. The three square tubes 32a of the radial ribs 32 are then line-welded to the back surface disc 30c and the inner cylinder 30a. In this way, as shown in Figure 8B, the eight radial ribs 32 are fixed to the buffer body 30.

[0042] Figure 9 is a view from the direction of arrow IX in Figure 8B. As shown in Figures 8B and 9, nine cushioning members 21 made of arc-shaped bent rectangular tubes are housed between one radial rib 32 and another radial rib 32, in contact with or in close proximity to each other without being fixed to either. In other words, a total of nine cushioning members 21 are housed between the three rectangular tubes 32a (see Figure 8B) that constitute the welded radial rib 32: three in the radial direction and three in the thickness direction (see Figure 9). As shown in Figure 8C, the nine rectangular tube buffer members 21 are secured to the mounting bracket b using stainless steel metal ties 19.

[0043] <Effects and Effects> According to the third embodiment of the buffer 30, it is possible to absorb the impact load of the cask C in the thrust direction (axis o1 direction) and the impact load of the cask C in the radial direction. Furthermore, since the buffer 30 is made of metal, it can ensure long-term buffering and heat dissipation performance. In addition, the buffer 30 has a limited number of welding points, making it easy to manufacture. Furthermore, the first row (the row closest to the mounting bracket b in the thrust direction (axis o1 direction)) and the second row of the cushioning member 21 may be configured according to the first or second embodiment, and the third row according to the third embodiment, for example, by combining the first, second, and third embodiments.

[0044] <<Modification of the third embodiment>> Figure 10 is a modified example of the third embodiment, viewed from the direction of arrow IX in Figure 8B. In the modified buffer 30A, the rectangular tubes 32a1 forming the radial ribs 32r are rotated approximately 45 degrees and welded together so that the end faces where they are joined form a V-shape. Between one radial rib 32r and the other radial rib 32r, a cushioning member 21a (see Figure 8B) made of a rectangular tube bent into an arc shape is housed without being fixed in place, with a recess at its end 21a1 that fits into the corner 32a2 of the rectangular tube 32a1. In other words, by cutting out the end 21a1 of the cushioning member 21a in a V-shape, it fits into the corner 32a2 of the rectangular tube 32a1, preventing the cushioning member 21a from shifting during impact absorption.

[0045] <Effects and Effects> According to a modified version of the third embodiment, when the buffer 30A fixed to the cask C is deformed by impact, the curved rectangular tube buffer member 21a is fitted with the recess at its end 21a1 without being fixed to the corner 32a2 of the rectangular tube 32a1 of the radial rib 32r, thus preventing displacement or movement in the radial or thrust direction. Regarding the radial ribs 32r of the can body, the square tubes may be fixed after being rotated by approximately 45°, and the square tubes 32a1 that serve as buffer members may be 4x4 square tubes, combinations of rectangular cross-section tubes, or combinations of large and small tubes.

[0046] <<Fourth Embodiment>> Figure 11A is a diagram corresponding to Figure 2B showing the buffer body 40 of the fourth embodiment. Figure 11B is a view in the direction of the arrow in the X direction of Figure 11A. The buffer body 40 of the fourth embodiment is constructed by welding 18 short rectangular tubes 40a1, 40a2, and 40a3, which make up the buffer member 31, alternately to the partition plate 42 (see Figure 11B), and welding three regular 18-sided rectangular tubes 40a1, 40a2, and 40a3 to each other along their entire length. In other words, the buffer body 40 is constructed by the buffer member 31 to form an outer shell 40k with three annular shapes.

[0047] The outer shell 40k, consisting of 18 square tubes 40a1, 40a2, and 40a3 around its circumference, and the partition plate 42 are welded and fixed to the mounting bracket 4b, which is a connecting plate. The mounting bracket 4b has a cylindrical plate 4b1, an outer ring plate 4b2, and an inner ring plate 4b3. The mounting bracket 4b is made of a thick stainless steel plate, and the buffer body 40 is bolted to the outer circumference of the end of the cask C of the radioactive material storage container via the mounting bracket 4b. The buffer body 40 is made of a corrosion-resistant metal plate such as a stainless steel plate (for example, SUS304, etc.) or a corrosion-resistant hot-dip galvanized steel plate.

[0048] Furthermore, tubular or box-shaped members made of thin-walled stainless steel plates may be housed inside each of the square tubes 40a1, 40a2, and 40a3. Figure 11A shows an example in which a tubular member is housed inside the square tube 40a2.

[0049] For example, as shown in Figure 11B, the second square tube 40a3 in the second row is constructed using a perforated plate, and nothing is housed inside the square tube 40a3. Multiple tubes, such as circular and rectangular tubes, are housed radially within the regular 18-sided rectangular tube 40a2 in the second layer of the first row (see Figure 11A). The regular 18-sided rectangular tube 40a1 in the first layer of the first row contains nothing.

[0050] The regular 18-sided rectangular tube 40a3 in the second layer of the second row absorbs the thrust direction impact load (in the direction of the axis o1 of the cask C) on the cask C. The regular 18-sided rectangular tube 40a2 in the second layer of the first row absorbs the radial impact load on the cask C. The 18-sided rectangular tube 40a1 in the first layer of the first row has a larger diameter than the rectangular tube 40a2 in the second layer of the first row, and the rectangular tube 40a3 in the second layer of the second row, thereby reducing the impact load value per unit area.

[0051] <Effects and Effects> According to the fourth embodiment of the buffer 40, it is possible to absorb thrust impact loads (in the direction of the axis o1 of the cask C) and radial impact loads on the cask C. Furthermore, since the buffer 40 is made of metal material, long-term buffering and heat dissipation performance can be ensured.

[0052] <<Fifth Embodiment>> Figure 12A is a schematic cross-sectional view of the annular buffer 50 of the fifth embodiment. Figure 12B is a cross-sectional view taken along line XI-XI in Figure 12A. The fifth embodiment describes a method for restraining the cushioning members 41 in an annular cushioning body 50 that includes four rectangular tube cushioning members 41.

[0053] The annular buffer body 50 of the fifth embodiment has a cylindrical annular mounting bracket B, the mounting bracket B having a cylindrical plate e1 and an annular plate e2. The cylindrical plate e1 of the mounting bracket B has a counterbore e1a formed in it, which is an elongated recess through which the metal tie 52 described later passes. The buffer body 50 has an inner cylinder 50a, a front disc 50b, a back disc 50c, and an outer cylinder 50d, forming an annular outer shell 50k. The outer shell 50k is configured as an annular metal case.

[0054] The inner cylinder 50a is welded and fixed to the end of the cylindrical plate e1 of the mounting bracket B. The rear disc 50c is welded and fixed to the end of the annular plate e2 of the mounting bracket B.

[0055] As shown in Figure 12A, four rectangular tubular buffer members 41 are housed within the outer shell 50k of the buffer body 50. Each buffer member 41 is not fixed to any other, but is housed in contact with or in close proximity to the others. There is a small gap s1 between the outer shell 50k and the cushioning members 41 of the four rectangular tubes inside the outer shell 50k.

[0056] The four rectangular tube buffer members 41 shown in Figure 12A are secured by metal ties 52 that pass through the gap s1 and the counterbore e1a of the cylindrical plate e1 of the mounting bracket B, and are fixed at the buckles 51a (see Figure 13A) at the ends 51t1. A long retaining plate 53 (see Figure 12B) is fixed to the cylindrical plate e1 of the mounting bracket B by multiple bolts b0 on the outside of the metal tie 52 that passes through the counterbore e1a of the cylindrical plate e1 of the mounting bracket B. The retaining plate 53 has internal threads into which the bolts b0 are screwed. The cylindrical plate e1 of the mounting bracket B (see Figure 12A) has through holes (not shown) through which the bolts b0 are inserted.

[0057] In the buffer body 50, metal ties 52 are applied in 3 to 4 places in a point-symmetrical manner with respect to the axis (o1) of the cask C. As a result, the four rectangular tube buffer members 41 are restrained by the metal ties 52, and even if vibrations occur during handling of the buffer body 50, their movement within the outer shell 50k is suppressed.

[0058] <Securing the four cushioning members 41 with metal ties 52> Figures 13A to 13C are cross-sectional views showing the process of restraining the cushioning members 41 of the four square tubes with metal ties 52.

[0059] As shown in Figure 13A, the inner cylinder 50a is welded and fixed to the cylindrical plate e1 of the mounting bracket B. The rear disc 50c is welded and fixed to the annular plate e2 of the mounting bracket B. The outer cylinder 50d is welded and fixed to the rear disc 50c. In this state, the metal tie 52 is aligned with the inner surface of the outer cylinder 50d, the inner surface of the back disc 50c, the counterbore e1a of the cylindrical plate e1 of the mounting bracket B, and the inner surface of the inner cylinder 50a. Then, as shown by arrow α11 in Figure 13A, the retaining plate 53 is used to hold down the metal tie 52 inside the counterbore e1a.

[0060] Next, as shown in Figure 13B, the four cushioning members 41 are placed on the metal tie 52 without being fixed in place. One end 52t1 of the metal tie 52 and the other end 52t2 are bent and brought together, and then secured with the buckle 52a. Then, as indicated by arrow α12 in Figure 13B, the bolt b0 is passed through the insertion hole in the cylindrical plate e1 of the mounting bracket B and screwed into the female thread of the retaining plate 53. By attaching the retaining plate 53, the cushioning members 41 are fixed to the mounting bracket B by the metal tie 52.

[0061] Next, as shown in Figure 13C, the front disc 50b is welded and fixed to the ends of the outer cylinder 50d and the inner cylinder 50a. As a result, the metal tie 52, which has secured the four cushioning members 41, is fixed to the retaining plate 53 and the mounting bracket B.

[0062] <Effects and Effects> According to the fifth embodiment, since the four unfixed cushioning members 41 are secured with metal ties 52, movement of the four cushioning members 41 within the cushioning body 50 is suppressed when vibrations occur during handling of the cushioning body 50 or the cask C in which the cushioning body 50 is installed.

[0063] <<Other Embodiments>> 1. The buffers 10 to 50 in the first to fifth embodiments described above may be replaced with rust-resistant steel perforated plates as appropriate.

[0064] 2. The configurations of the first to fifth embodiments and modified examples described above may be combined as appropriate.

[0065] 3. The present invention is not limited to the embodiments and modified configurations described above, and various modified and specific forms are possible within the buffer or radioactive material storage container of the appended claims. [Explanation of symbols]

[0066] 1. Cushioning member (hollow member) 11b Triangular prism (hollow member) 19 Stainless steel metal ties (metal ties) 21, 31, 41, 51 Cushioning material 2. Radial ribs (partition members) 10, 20, 30, 30A, 40, 50 buffer 10k, 20k, 30k, 40k, 50k outer shell 32a Square tube (hollow component) 32a1 Square tube (hollow component) 52 Metal Tie 53. Retaining plate (lid) b, B Mounting bracket C Cask (container for radioactive materials) e1a Counterbore section (groove)

Claims

1. It is a buffer installed in a container for radioactive materials. The outer shell that constitutes the case of the buffer, A partition member that divides the inside of the outer shell, The interior of the outer shell includes a buffer member housed between the partition members, The outer shell and the partition member are formed of a metal material. The cushioning member is It has a box-like or tubular shape formed of a metal material, and is provided inside the outer shell without being fixed between the partition members. A buffer characterized by the following features.

2. In the buffer according to claim 1, The partition member is composed of a hollow member made of a metal plate. A buffer characterized by the following features.

3. In the buffer according to claim 1, There is a gap between the outer surfaces of the cushioning member and the inner surface of the outer shell. A buffer characterized by the following features.

4. In the buffer according to claim 1, The partition member or the cushioning member is formed from a perforated plate. A buffer characterized by the following features.

5. In the buffer described in claim 4, The aforementioned perforated plate is made of austenitic stainless steel. A buffer characterized by the following features.

6. In the buffer according to claim 3 or claim 4, The cushioning member is restrained using a metal tie. A buffer characterized by the following features.

7. In the buffer according to claim 6, The buffer body is provided with a mounting bracket for attaching it to the radioactive material storage container, The metal tie is passed through the groove formed in the mounting bracket, the cushioning member is restrained by the metal tie, and the groove is covered. A buffer characterized by the following features.

8. In the buffer according to claim 1, The aforementioned buffer member has a tube provided inside. A buffer characterized by the following features.

9. It is a buffer installed in a container for radioactive materials. The outer shell that constitutes the case of the buffer, It comprises a partition member that divides the inside of the outer shell, The outer shell has multiple chambers, and its interior is either hollow or has multiple tubes inside. A buffer characterized by the following features.

10. In the buffer according to claim 9, A radioactive material storage container equipped with a buffer as described in any one of claims 1 to 9. 。

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