JP4486685B2 - Shock absorbing structure, radioactive material storage container and shock absorbing method - Google Patents

Description

In the present invention, the first container for storing the radioactive material is shielded with the second container having a shielding function, as in the case where the canister in which the radioactive material such as spent nuclear fuel assembly or radioactive waste is sealed is stored in the concrete cask. The present invention relates to a shock absorbing structure , a radioactive substance storage container, and a shock absorbing method in a radioactive substance storage container that can absorb an impact load generated when the container is dropped.

  Nuclear fuel assemblies that have finished predetermined combustion in a nuclear reactor, so-called spent nuclear fuel assemblies (hereinafter referred to as “used fuel”) are cooled and cooled in a cooling pit of a nuclear power plant for a predetermined period, and then transported and stored. In order to carry out the process, it is stored in a canister together with helium gas and sealed. The canister thus sealed with the spent fuel is transported to a destination such as an intermediate storage facility or a reprocessing facility while being accommodated in a metal cask that is a container for transportation.

Conventionally, there are the following three methods for storing spent fuel in intermediate storage facilities and the like.
(1) A bold canister is stored in a semi-underground building, where radiation is shielded in the semi-underground building and cooled by natural ventilation in the storage area.
(2) A metal cask method A canister is stored in a building in a state where it is housed in a metal cask. The metal cask is used to shield radioactivity and to be cooled by natural ventilation in the storage area.
(3) Concrete cask method A canister is housed in a concrete cask installed in a building. The concrete cask and the building are shielded against radioactivity and cooled by natural ventilation in the concrete cask and the building. .

  In any of the storage systems described above, a canister is used that houses a large number of slender shaped spent fuel and seals it with helium gas. The canister is a metal container in which spent fuel is stored in a container body whose cylindrical bottom is closed with a bottom plate, and then the upper opening is covered and sealed. The canister is stored and held in the internal space in a state where a large number of spent fuels are inserted into the basket, and is sealed together with the injected helium gas. The helium gas injected here is for the purpose of promoting the cooling of the spent fuel. This helium gas improves the thermal conductivity and increases the cooling efficiency by convection.

  In the case of the concrete cask method described above, the canister is stored and stored in the concrete cask. This concrete cask is composed of a cylindrical cask body having a cylindrical storage space for storing a canister and closed at the bottom, and a lid for closing an upper opening for taking in and out the canister. The cask body is composed of a metal plate and a concrete layer, and is made of concrete in which a metal plate is affixed to the inner peripheral surface forming the storage space. The lid portion is also made of concrete having a metal plate and a concrete layer.

  Further, a support member is formed on the bottom surface of the storage space formed in the cask body so as to support a canister load at a predetermined storage position and to form a cooling air flow passage for convection cooling with the canister. Is provided. This support member also has a function as a shock absorber that absorbs the fall energy by deformation when an abnormality occurs such as when the canister falls during handling.

Hereinafter, a conventional support member structure will be described with reference to the drawings. 21 is a plan view showing a conventional support member structure, FIG. 22 is a cross-sectional view of a main part of FIG. 21, and FIG. 23 is a cross-sectional view of FIG. The support member 25 is composed of eight plate members 25a each having a rectangular shape. Each plate member 25a is positioned on the radiation evenly distributed at a 45-degree pitch from the center of the storage space 21 having a circular cross section, and is arranged so that both ends draw a concentric circle covering a part of the bottom surface 21a. . In addition, each plate member 25a is fixed to the metal plate 22a on the bottom surface of the storage space by a welded portion W in a state of standing vertically from the bottom surface 21a, and the height H from the bottom surface is all constant. (See FIGS. 1 and 2 of Patent Document 1)

JP 2001-318185 A

As described above, in the conventional concrete cask, the support member 25 provided on the bottom surface 21a of the storage space 21 performs the following three functions.
(1) Canister load support (normal)
(2) Formation of cooling air passage (normal)
(3) Shock absorption when the canister is dropped (when abnormal)
Further, the above-described support member 25 is required to withstand storage for a long period of at least 60 years for the purpose of use of the concrete cask, and therefore needs to be made of metal.

  By the way, the support member 25 having the conventional structure described above has no particular problem with respect to normal functions such as load support and cooling passage formation. However, as for the shock absorbing function when the canister falls during handling, when the impact load F reaches the peak value Fp, as is clear from the relationship between the impact load F and the deformation amount δ shown in FIG. δ decreases rapidly. For this reason, the energy absorption amount E given by the area of the shaded portion is relatively small, and in order to obtain a sufficient shock absorbing capability, it is necessary to increase the height H of the plate member 25a to increase the deformation amount δ. . Note that the concrete cask support member 25 is required to have an impact absorption capacity that suppresses the acceleration to 50 G or less when, for example, a 30-ton canister 10 drops from a position of 6 m in height.

  On the other hand, if the height H of the plate member 25a is increased at the bottom surface 21a of the narrow storage space 21 to secure the deformation amount δ, there is a limit because the adjacent plate members 25a may interfere with each other during deformation. Further, increasing the height H of the plate member 25a is not preferable because it increases the overall height of the concrete cask 20. Accordingly, there is a demand for a concrete cask support member structure capable of exhibiting sufficient shock absorbing capability without increasing the height H.

The present invention has been made in view of the above circumstances, and provides a shock absorbing structure , a radioactive substance storage container, and a shock absorbing method in a radioactive substance storage container capable of improving the shock absorbing capacity while suppressing the height H. It is aimed.

The present invention employs the following means in order to solve the above problems. The shock absorbing structure for a radioactive substance storage container according to the present invention comprises a first container for containing a radioactive substance, a first container placed in a storage space from the upper opening to support the bottom, and the upper opening is covered. And a second container with a shielding function that is stored in the first container is provided with a shock-absorbing material having a cross-girder structure that absorbs impact energy when the first container is dropped.

In the shock absorbing structure in the radioactive substance storage container of the present invention, the shock absorbing material is characterized in that the height on the outer peripheral side is higher than the center.

The shock absorbing structure of the present invention is fixed to a support structure that can be attached to and detached from the first container.

Further, the radioactive substance storage container of the present invention includes the first container for storing a radioactive substance, the first container being put into the storage space from the upper opening to support the bottom surface, and the upper opening being covered. and said second container with shielding function for storing Te, and the shock absorbing structure for absorbing impact energy at the time of fall of the first container is provided between the first container and the second container It is provided with.

The shock absorbing method for a radioactive substance storage container according to the present invention is the shock absorbing method for the radioactive substance storage container described above , wherein the shock absorbing structure is input in stages with a time difference from the first container to the shock absorbing structure. It is characterized by absorbing.

  According to the present invention, since the shock absorbing material such as the cross beam structure is provided, the height can be suppressed and the shock absorbing ability can be increased.

According to the present invention, in addition to the above effects, by the height set high an outer peripheral side of the bottom center, you will receive the input first from the outer circumferential side of the first container, the first container This is advantageous in preventing breakage of the steel.

According to the present invention, in addition to the above effects, it is possible to attach the shock absorbing structure only when necessary in the first container, in a state where removed easily handled shorter total length of the first container become.

According to the present invention, it is possible to obtain the radioactive substance storage container to achieve the above effects.

According to the present invention, the input acts stepwise with a time difference, and the peak load is generated stepwise with the time difference, so that even a relatively low height shock absorbing structure can absorb a large impact energy. .

  Hereinafter, an embodiment of a shock absorbing structure for a radioactive substance storage container according to the present invention will be described with reference to the drawings. As shown in FIG. 19, a canister 10 as a first container is made of a metal (steel made up of a container main body 11 in which a cylindrical bottom is closed with a bottom plate and a lid 12 that closes an upper opening. Or a stainless steel container). The lid portion 12 includes an inner primary lid 12a and an outer secondary lid 12b, and a shielding block 13 is further provided on the inner side of the primary lid 12a.

  The canister 10 is stored and held in the internal space in a state where a large number of spent fuels 14 are inserted into the basket 15, helium gas is injected, and the lid portion 12 is welded to be sealed. The helium gas injected here is for the purpose of promoting the cooling of the spent fuel 14, and this helium gas improves the thermal conductivity and increases the cooling efficiency by convection. In addition, the code | symbol 16 in a figure is a lid | cover material which closes the opening part which is provided in the primary lid 12a and is used for draining. The basket 15 is a holding container for the spent fuel 14 having a grid-like cross section, and has a function of storing and holding one spent fuel 14 for each grid 15a.

  In the case of the concrete cask method described above, as shown in FIG. 20, the canister 10 is stored and stored in a concrete cask 20 as a second container. The concrete cask 20 includes a cylindrical cask main body 22 having a cylindrical storage space 21 for storing the canister 10 and closed at the bottom, and a lid portion 24 for closing the upper opening 23 for taking in and out the canister 10. It is constituted by. The cask main body 22 includes a metal plate 22a and a concrete layer 22b, and is made of concrete in which the metal plate 22a is attached to the inner peripheral surface forming the storage space 21. The lid portion 24 is constituted by a metal plate 24a, a concrete layer 24b, and a lid mounting bolt 24c. It has become.

  On the bottom surface 21 a of the storage space 21 formed in the cask body 22, there is provided a flow path (space) of cooling air CA that supports the load of the canister 10 at a predetermined storage position and performs convection cooling with the canister 10. A support member 25 is provided to form. The support member 25 is composed of, for example, a plurality of plate members 25a that are radially arranged on the bottom surface and are erected vertically. When the canister 10 falls during handling, the shock absorber absorbs the fall energy by deformation. It also has a function as.

  Further, in order to convectively cool the storage space 21 by natural ventilation, air introduction ports 26 for introducing the cooling air CA are provided at a plurality of locations on the lower side surface of the cask main body 22. The cooling air CA introduced from the air introduction port 26 enters the storage space 21 through the bent flow path, rises along the side surface of the canister 10, and then bends between the cask main body 22 and the lid portion 24. Then, it flows out to the outside through a plurality of air outlets 27 that open to the upper side surface. As a result, the storage space 21 of the concrete cask 20 is ventilated and cooled by natural ventilation of the outside air introduced as the cooling air CA.

<Examination example 1>
FIG. 1 shows a partial cross-sectional structure of the bottom surface 21 a of the storage space 21 of the concrete cask 20. In addition, the code | symbol 22a in a figure is a metal plate of the cask main body 22, 22b is a concrete layer, 30 is a board | plate material which comprises a supporting member.

  In this examination example, a plurality of plate members 30 erected on the bottom surface 21a of the storage space 21 constitute a support member that receives the impact load when the canister 10 falls during handling and supporting the load of the canister 10 during normal operation. ing. Eight sheets of the plate 30 are provided on radiation extending at an equal pitch of, for example, 45 degrees from the center of the circular bottom surface 21a (see FIG. 21). Each plate member 30 is bent into a substantially square shape at an angle θ from an appropriate position of a rectangular plate. One end of the plate 30 is inserted into a groove 22c provided in the metal plate 22a, and is fixed at the weld W by welding between the metal plate 22a.

  Thus, when the plate member 30 is inclined at an angle θ, not only can the height be reduced compared to the conventional example provided vertically (θ = 0), but also the amount of impact energy absorbed can be secured. The peak load can be stabilized. One impact energy absorption amount is considered to be due to the two-stage deformation as shown in FIG. That is, in addition to the bending deformation that occurs in the bent portion of the plate member 30, large impact energy can be absorbed by two bending deformations that are reversed in the middle from the upper end side.

  Also, regarding the stabilization of the peak load, it is difficult to stand the plate 30 vertically with an inclination angle θ = 0 accurately, which involves a great increase in work man-hours and costs. This is also because the angle varies. That is, although the peak load of the plate member 30 that is accurately installed vertically is increased, the peak load is decreased even if it is slightly inclined, so that the peak load value varies and the design becomes difficult. However, as described above, by providing the plate member 30 with the inclination angle θ, the fluctuation range of the peak load can be reduced and stabilized even if there is some variation in the inclination angle. It becomes easy to design a shock absorbing structure using

  There is an optimum value for the inclination angle θ of the plate member 30 described above. This will be described with reference to FIG. FIG. 3 shows four types of inclination angles θ () regarding the relationship between the ratio (δ / L) of the deformation amount δ with respect to the height L of the plate member 30 and the ratio (F / F0) of the impact load F to the sectional yield load F0. 0 degrees, 7 degrees, 30 degrees, 45 degrees).

According to this figure, although there is a problem that the variation is large at θ = 0 °, the absorption amount of the peak load and impact energy is large. However, if the angle is greatly tilted to θ = 45 degrees, the peak load is greatly reduced and hardly exists, and the amount of absorption of impact energy is small.
When θ = 30 degrees, the peak load is small but clearly present, and the amount of shock energy absorbed can be secured.

  In particular, when θ = 7 degrees, the peak load is considerably large, and the impact energy absorption amount is larger than that when θ = 0 degrees. Accordingly, the inclination angle θ of the plate member 30 is preferably set as appropriate within a range of 0 <θ ≦ 30 in consideration of the plate thickness, material, and the like of the plate member 30, and in particular, θ = 7 ± 3 degrees is the most. This is a preferred value.

  Further, it is preferable that the radially arranged plate members 30 are inclined so that the direction of the inclination angle θ is the same direction, that is, in either the clockwise direction or the counterclockwise direction in the circumferential direction. Thereby, when the board | plate material 30 which received the impact load deform | transforms, it can prevent that adjacent board | plate materials mutually interfere. Accordingly, each plate 30 can be deformed as designed to ensure a desired amount of impact energy absorption.

  Further, when the plate member 30 is welded and fixed to the metal plate 22a, the base portion 30a on the lower end side is inserted and embedded in the groove portion 22c provided in the metal plate 22a forming the bottom surface 21a. Weld. By adopting a welding structure that welds the welded portion W in this way, it is possible to stabilize the fixation of the plate member 30 by welding.

<Examination example 2>
In this examination example, a support member 40 made of an impact absorbing material having an excellent impact absorbing capability is provided on the bottom surface 21a of the storage space 21. In the embodiment shown in FIG. 4, a hollow material (pipe) 41 having a circular cross section is used as the shock absorbing material. Eight hollow members 41 are arranged on radiation extending at an equal pitch of, for example, 45 degrees from the center of the circular bottom surface 21a. In this case, the outer diameters and lengths of the hollow members 41 are the same, and therefore the height H from the bottom surface 21a is all constant, and the eight hollow members 41 have concentric circles at both ends. Are arranged. In addition, about the arrangement | positioning state and the number of arrangement | positioning of the hollow material 41, it is not limited to what was shown in FIG. 4, Moreover, about the cross-sectional shape of the hollow material 41, it is not limited to a circular pipe, For example, A square pipe may be used.

  When such a hollow material 41 is used, a standardized material can be cut and used. Therefore, the hollow material 41 is fixed to the bottom surface 21a so that the height H becomes uniform, or the impact energy absorption capacity is designed to a desired value. It's easy. The use of the hollow member 41 is also excellent in terms of forming a passage for the cooling air CA.

  Now, for the impact absorbing material using the hollow material 41 described above, for example, the configuration of the first modification shown in FIG. 5 is possible. In the configuration of the first modification, a plurality of hollow materials 41 are stacked and appropriately combined. In the illustrated configuration example, a total of 10 hollow members 41 are stacked in four stages, so that the entire height is set to H. In the illustrated configuration example, all the hollow members 41 having the same outer diameter are stacked, but hollow members having different outer diameters may be appropriately combined.

  With such a configuration, various heights H can be set using the standard hollow material 41, and the impact load is input to each of the stacked hollow materials 41 stepwise with a time difference. As a result, the amount of impact energy absorbed can be increased. In addition, the operation and effect when the impact load is input stepwise with a time difference will be described in detail in Study Example 3 described later.

  Next, a second modification using the hollow material 41 described above will be described with reference to FIG. In this modification, the outer side of the hollow member 41 stacked in a plurality of stages is surrounded by a plate member 42 bent in a U-shaped cross section. Even in such a configuration, the impact load is input to the plate member 42 and the hollow member 41 in stages, so that the amount of shock energy absorbed can be increased.

  The third modified example shown in FIG. 7 shows a configuration example in which a honeycomb structure material 43 that absorbs a large amount of impact energy is used as the impact absorbing material. In the example shown in the figure, a columnar honeycomb structure material 43 provided with a honeycomb structure portion is adopted in a hollow material having a rectangular cross section, and is arranged radially at a pitch of 45 degrees on the bottom surface 21a. In the illustrated configuration example, the height H of all the honeycomb structure materials 43 is constant, but the height may be different so that the impact load is input stepwise with a time difference.

<First embodiment of the present invention>
The first embodiment of the present invention shown in FIG. 8 shows a cross beam structure as an impact absorbing material. In order to give a time difference to the input of the impact load described later, the cross beam structure 44 has a higher height on the outer peripheral side than the central portion (H1>H2> H3). Good. Moreover, the integral cross-girder structure 44 may be installed uniformly over the entire bottom surface 21a, or a plurality of divided structures may be appropriately dispersed and arranged. In the example shown in the figure, a cross-girder structure having one stage in the vertical direction is adopted, but a plurality of stages may be used.

<Examination example 3>
The concrete cask / canister shock absorbing structure shown in FIG. 9 is provided with a support member 50 for receiving an impact load with a time difference on the bottom surface 21a of the storage space 21, and a plurality of plate members 51a, 51b, 51c having different heights. (Hereinafter, the three pieces are referred to as a plate member 51 as one set), and the sets are arranged radially from the center of the circular bottom surface 21a. In addition, about 1 set of board | plate materials 51, it is not limited to 3 sheets 1 set mentioned above, It is good also considering 2 sheets or 4 sheets or more as 1 set.

  In the illustrated configuration example, eight sets of plate members 51 are erected on radiation extending at an equal pitch of 45 degrees, for example. Each plate 51 may be erected vertically (inclination angle θ = 0) from the bottom surface 21a, but it is preferable to provide an appropriate inclination angle θ as shown in Study Example 1. Further, as shown in FIG. 1, each plate member 51 is preferably welded in a state where a base portion is inserted into a groove portion provided in the metal plate 22a.

  A set of plate members 51 arranged on the radiation is H1> H2> if the height of the outer plate member 51a is H1, the height of the intermediate plate member 51b is H2, and the height of the inner plate member 51c is H3. The relationship is H3, and is set lower as it goes from the outside to the inside. The eight plate members 51a erected on the outer peripheral side, the eight plate members 51b erected in the middle, and the plate member 51c erected on the inner side have the same length, and each end portion Are arranged on the same circumference.

  With the support member 50 having such a configuration, when the canister 10 is dropped and an impact load is applied, the first input is applied to the plate member 51a on the outer peripheral side whose height is H1 and which is the highest. As a result, the plate material 51a is first deformed to absorb the impact load, and the first peak load F1 is generated as shown in FIG. Thereafter, the peak load F2 is generated by the impact load acting on the plate material 51b having the height H2, and finally the peak load F3 is generated by the impact load acting on the plate material 51c having the height H3. Thus, since the plate materials 51a, 51b, 51c are sequentially deformed with a time difference to generate the peak weights F1, F2, F3, large impact energy can be absorbed as a whole. That is, since the hatched area E of FIG. 2 has three peaks, the height H of the plate 51 can be suppressed and the amount of impact energy absorbed can be increased.

  Further, since the height H of the plate material 51 is increased toward the outer side so as to receive the impact load first, on the canister 10 side which is a hollow container, the vertical wall (cylindrical) portion forming the container body 11 at the time of dropping This is convenient for preventing the canister 10 from being damaged.

  FIG. 11 shows a first modification according to Study Example 3. In this configuration example, the point that the plate members 51 are radially arranged at the same pitch and the point that the outer plate member 51 is made higher are the same, but the arrangement of the set of three pieces is different. That is, it is the arrangement | positioning which combined the board | plate material 51 from which height differs in the circumferential direction. As a specific example, the plate material 51a having a height H1 and the plate material 51c having a height H3 are arranged on a radiation having a pitch of 45 degrees, and the plate material 51b having a height H2 is located at an intermediate position between the plate materials 51a and 51c in the radial direction. And also in the circumferential direction, it is arrange | positioned in the intermediate position (position rotated only by 22.5 degrees which divided 45 degrees into 2) adjacent to the radiation.

  With such a configuration, not only the effects similar to those of FIG. 9 described above can be obtained, but also the length in the radial direction can be increased for each plate 51, so that the amount of absorption of impact energy can be increased. it can. In addition, arrangement | positioning of the board | plate material 51 is not limited to FIG. 11, A various modification is possible with the number of the board | plate materials 51. FIG.

  FIG. 12 shows a second modification example according to the examination example 3. In this configuration example, the direction of the plate material 51 erected on the bottom surface 21a is different from that in FIGS. 9 and 11 described above. That is, in FIG. 9 and FIG. 11 described above, eight sets of plate members 51 that are erected on the radiation are arranged so as to draw a polygon on a concentric circle. Also in this case, the height H1 of the plate 51a arranged on the outside is set to the highest, and the height H3 of the plate 51c arranged on the inside is set to the lowest. In addition, about the radial direction of each board | plate material 51, as shown in the figure, the center of the three board | plate materials 51a, 51b, 51c may correspond on the same radiation, and the arrangement | positioning shifted suitably is also possible. Even with such a configuration, it is possible to suppress the height H of the plate 51 and increase the amount of impact energy absorbed.

  FIG. 13 shows a third modification example according to the examination example 3. In this case, the height of the plate material 51 is inclined so as to change from H1 to H2. That is, unlike the above-described divided structure, the height is changed by one plate material 51. Even in this configuration example, it is preferable that the plate material 51 erected on the radiation has an outer height H1 larger than an inner height H2. Moreover, you may provide an appropriate flat part on the outer side instead of making it incline over the full length as needed.

  In the above modification, the support member 50 is configured by the plate material 51. However, in the modification described below, a configuration example using the shock absorbing material described in the examination example 2 will be described. In the fourth modified example according to Study Example 3 shown in FIG. 14, two types of hollow materials 41A and 41B having different outer diameters are alternately arranged in a radial manner, and the support member 50 having different heights is configured in two stages. Yes. Specifically, since the outer diameter of the hollow member 41A is d and the outer diameter of the hollow member 41B is D, the support member 50 has two stages of height D and d (D> d).

Therefore, the dropped canister 10 first deforms the hollow material 41B having the outer diameter D, thereby generating the first stage peak load and absorbing the impact energy.
Furthermore, since the hollow material 41A having the outer diameter d is deformed after a time difference, the second stage peak load is generated and the impact energy can be further absorbed. In the illustrated example, two types of hollow materials 41A and 41B having different outer diameters are used, but it goes without saying that three or more combinations are possible.

  In the fifth modification example according to Study Example 3 shown in FIG. 15, for example, three types of hollow materials 41A, 41B, and 41C having different heights H depending on the outer diameter are arranged on the radiation. Specifically, the hollow material 41A having the height H1, the hollow material 41B having the height H2, and the hollow material 41C having the height H3 are set as one set, and are arranged so that the outside is raised and the inside is lowered. is there. That is, the fifth modification has a configuration in which the plate member 51 shown in FIG. 9 is replaced with the hollow member 41, and therefore the operation and effect thereof are substantially the same. Further, the arrangement of the hollow members 41A, 41B, and 41C, each consisting of three types, is not limited to the illustrated example, and may be the same as the plate members 51a, 51b, and 51c shown in FIGS. Good. In the illustrated example, one set combines three types of hollow materials, but two types or four or more types may be used.

  In the sixth modified example according to the examination example 3 shown in FIG. 16, the plate material 51 and the hollow material 41 described above are combined, and the height H is provided with a difference and is alternately arranged. In the illustrated configuration example, the height of the plate material 51 is H1, and the three hollow materials 41 are stacked to a height H2. In this case, the plate material 51 and the hollow material 41 are arranged in a radial pattern, and the plate material 51 is first deformed by receiving an impact load, and a first peak load is generated to absorb the impact energy. Then, after the plate member 51 is deformed to some extent, an impact load is input to the hollow member 41, and a second peak load is generated by the deformation of the hollow member 41 to further absorb the impact energy.

  In addition, by considering the conditions of the impact load that acts, the strength and thickness of the material constituting the support member, etc., by appropriately selecting from the plate material 51, the hollow material 41, the honeycomb structure material 43, the cross beam structure 44, etc. Optimal shock absorbing structures with various combinations of different heights are possible.

<Examination example 4>
In the embodiment and the examination example described above, the support member is provided on the bottom surface 21a of the concrete cask 20, but, for example, a similar configuration can be provided in the canister 10 as shown in FIG. In this case, since the support member is fixedly provided on the bottom surface 11a of the container body 11, the metal plate 22a that has formed the bottom surface 21a in the above-described embodiment and examination example is formed by forming the bottom surface 11a of the container body 11. What is necessary is just to read as the bottom member which is present. In addition, in FIG. 17, the perspective view at the time of employ | adopting the structure of the 1st modification (refer FIG. 11) which concerns on the examination example 3 is shown, and the same code | symbol is attached | subjected about the supporting member 50. FIG.

<Second Embodiment>
In the second embodiment shown in FIG. 18, the support member 50 attached to the bottom surface 11 a of the canister 10 has a detachable structure. In this embodiment, a support structure 60 separate from the canister 10 is prepared, and the support member 50 is fixedly attached to the bottom surface 61 thereof. Therefore, instead of the bottom surface 11 a of FIG. 17, the support member 50 is fixedly provided on the bottom surface 61 of the support structure 60. The support structure 60 has a cylindrical fitting portion 62 that substantially matches the outer diameter of the canister 10 and has an inner diameter that can accommodate the bottom of the canister 10. The support structure 60 and the canister 10 are attached and detached by, for example, bolts 63.

  With such a detachable configuration, the support structure 60 can be attached and used only when necessary, so that the overall length is shorter than that of the structure fixed to the canister 10, and handling is accordingly performed. Becomes easier. In addition, the support structure 60 mentioned above can also be used as components fixed by welding etc. as needed.

  As described above, according to the impact absorbing structure between the concrete cask / canister of the present invention, since the support member that receives the impact load with a time difference is provided, the peak load is generated in a plurality of stages even if the height H is suppressed. Therefore, the impact energy absorption capability can be increased. Therefore, it is possible to realize an impact absorbing method having a high impact energy absorbing capability in which impact energy is absorbed by giving input from the canister to the support member stepwise with a time difference. When a plate material is used as the support member, the peak load can be stabilized and a large impact energy absorption amount can be ensured by inclining it at an inclination angle θ.

  The shock absorbing structure having such a structure includes (1) a support member installed on the bottom surface of the concrete cask 20, (2) a support member installed on the bottom surface of the canister 10, and (3) a support structure detachable from the canister. Any structure may be adopted among the installation of the support member on the bottom surface.

  In addition, the structure of this invention is not limited to embodiment mentioned above, For example, the shape of a board | plate material etc. can be suitably changed in the range which does not deviate from the summary of this invention.

It is a fragmentary sectional view which shows the examination example 1 of the shock absorber in the radioactive substance storage container which concerns on this invention. It is sectional drawing which shows the state which the board | plate material of FIG. 1 received the impact load and deform | transformed. It is a graph which shows the relationship between the ratio (delta / L) of deformation amount (delta) with respect to the height L of a board | plate material, and the ratio (F / F0) of the impact load F with respect to a cross-section yield load F0. It is a figure which shows the examination example 2 of the shock absorber in the radioactive substance storage container which concerns on this invention, (a) is a top view, (b) is AA sectional drawing of (a). It is a figure which shows the 1st modification of the examination example 2 shown in FIG. It is a figure which shows the 2nd modification of the examination example 2 shown in FIG. It is a figure which shows the 3rd modification of the examination example 2 shown in FIG. 4, (a) is a top view, (b) is BB sectional drawing of (a). It is a perspective view which shows 1st Embodiment of the shock absorber in the radioactive substance storage container which concerns on this invention. It is a figure which shows the examination example 3 of the shock absorber in the radioactive substance storage container which concerns on this invention, (a) is a top view, (b) is sectional drawing of (a). It is a graph which shows the relationship between deformation amount ((delta)) and an impact load (F) about the examination example 3 shown in FIG. It is a figure which shows the 1st modification of the examination example 3 shown in FIG. 9, (a) is a top view, (b) is sectional drawing of (a). It is a figure which shows the 2nd modification of the examination example 3 shown in FIG. 9, (a) is a top view, (b) is sectional drawing of (a). It is a figure which shows the 3rd modification of the examination example 3 shown in FIG. 9, (a) is sectional drawing, (b) is a top view. It is a top view which shows the 4th modification of the examination example 3 shown in FIG. It is sectional drawing which shows the 5th modification of the examination example 3 shown in FIG. It is sectional drawing which shows the 6th modification of the examination example 3 shown in FIG. It is a perspective view which shows the bottom part of a canister as the examination example 4 of the shock absorber in the radioactive substance storage container which concerns on this invention. It is a perspective view which shows the bottom part of a canister as 2nd Embodiment of the shock absorber in the radioactive substance storage container which concerns on this invention. It is a fragmentary sectional perspective view which shows the structural example of a canister. It is a principal part cross-sectional perspective view which shows the state which accommodated the canister in the concrete cask. It is a top view which shows the prior art example of the shock absorption structure between concrete cask / canister. It is sectional drawing of the prior art example shown in FIG. It is CC sectional drawing of FIG. It is a graph which shows the relationship between deformation amount (delta) and impact load (F) about the prior art example shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Canister 11 ... Container main body 11a ... Bottom 12 ... Lid 20 ... Concrete cask 21 ... Storage space 21a ... Bottom 22 ... Cask main body 22a ... Metal plate 22b ... Concrete layer 24 ... Lid 30 ... Plate material 40 ... Supporting member 41 ... Hollow material 44 ... Well beam structure 50 ... Support member 60 ... Support structure

Claims (6)

Between the first container for storing the radioactive substance and the second container with a shielding function for storing the first container in the storage space from the upper opening, supporting the bottom surface, and covering the upper opening for storage. Further, the shock absorbing structure between the first container and the second container that absorbs impact energy when the first container is dropped ,
A support member that receives an impact load with a time difference on the bottom surface of the storage space or the bottom surface of the first container,
The impact-absorbing structure, wherein the support member has a plurality of plates that are erected from the bottom surface of the storage space or the bottom surface of the first container and are arranged radially from the center of the bottom surface.   Each of the plurality of plate members has a different height,
  The shock absorbing structure according to claim 1, wherein a height of the plate material provided on the outer peripheral side of the bottom surface is higher than a height of the plate material provided on the center side of the bottom surface.   The shock absorbing structure according to claim 1 or 2, wherein the height of the plate material is inclined so as to decrease from the outer peripheral side of the bottom surface toward the center side of the bottom surface.   The shock absorbing structure according to any one of claims 1 to 3, wherein the support member is fixed to a support structure that can be attached to and detached from the first container. The first container for storing a radioactive substance, and the second container with a shielding function for storing the first container in the storage space through the upper opening, supporting the bottom surface, and covering the upper opening with a lid. a container, shock absorption according to any one of claims 1 to 4 for absorbing the impact energy at the time of fall of the first container is provided between the first container and the second container radioactive substance storage container, characterized in that a structure. 6. The method for absorbing shock in a radioactive substance storage container according to claim 5 , wherein the shock absorbing structure is provided by stepwise input from the first container to the shock absorbing structure with a time difference to absorb the shock. Shock absorption method.

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