JP2021139746A - Buffer for cask - Google Patents

Abstract

To provide a buffer for a cask that can increase an impact adsorption amount without increasing the outer size of a buffer.SOLUTION: A buffer for cask 10 of the present invention includes: a buffer outer shell 11 set in a cask 1 when the cask 1 is containing a radioactive material and is carried, and forming the outer shell of a buffer; a radial rib 13 in the outer shell 11; a first impact absorber group 15 for absorbing an impact in a direction parallel to end surfaces 1s, 1u of the cask 1; a second impact absorber group 16 for absorbing an impact in a direction intersecting with or inclined to the end surfaces 1s, 1u of the cask 1; a third impact absorber group 17 for absorbing an impact in a direction intersecting with the end surfaces 1s, 1u of the cask 1; and a plate structure member 20 across the first impact absorber group 15 and the second impact absorber group 16.SELECTED DRAWING: Figure 3B

Description

The present invention relates to a cask buffer.

Generally, the spent fuel discharged from a nuclear power plant is first stored in a cooling pool provided in the nuclear power plant until the radiation dose drops below a certain level. After that, the spent fuel is stored in a cask having a shielding function and a sealing function, and is transported to a fuel processing facility or the like. Since the cask is a heavy object containing radioactive materials, it is obligatory to have a predetermined shielding function and sealing function (hereinafter, simply referred to as "safety function") even in the event of a drop during transportation and handling. Has been done. For this reason, when transporting and handling the cask, measures are taken to mitigate the impact when the cask is dropped by attaching a cask buffer to the upper and lower ends of the cask.

Examples of accidental drops of the cask include vertical drops, horizontal drops, tilted drops, and corner drops.
A vertical fall is a fall event in which the central axis of the cask is in a vertical position. A horizontal fall is a fall event in which the central axis of the cask is in a horizontal position.

An inclined fall is a fall event in which the central axis of the cask falls at a shallow angle with the horizontal axis. A corner fall is a fall event in which the drop point of the cask falls at an angle on a vertical line passing through the center of gravity of the cask.
Therefore, it is necessary for the buffer for cask to maintain the safety function of the cask even if the cask falls in any posture.

The cask shock absorber is required to efficiently absorb the impact at the time of dropping within a limited amount of deformation regardless of the posture in which the cask falls. Therefore, as a material that absorbs impact (impact absorber group), a material having a small specific density and a large impact absorbing capacity, such as wood or a foam material, is often adopted. In addition, a structure that can absorb impact more effectively by adjusting the arrangement and direction of the impact absorber group is adopted.

For example, in Patent Document 1, "a plurality of plate bodies made of steel materials are formed at intervals between plate surfaces facing each other, and the plate surface of the plate body is arranged along the end surface of the cask on the end face side. A member and a peripheral surface member which forms a tubular body made of a steel material and one end thereof is joined to the peripheral edge of the end face side member and is arranged along the outer peripheral surface of the end portion of the cask. A cask shock absorber characterized in that the shock absorber that absorbs the above-mentioned material is provided on the outer side of the end face side member and the peripheral surface side member "is described.

According to the buffer for cask of Patent Document 1, the shock absorption performance can be improved against various possible drop events, and the end face side member made of steel material is not significantly deformed, so that a local load on the end face of the cask can be obtained. Can be reduced.

Japanese Unexamined Patent Publication No. 2012-013625

As described above, the cask buffer needs to efficiently absorb the impact when the cask falls within a limited amount of deformation. If the amount of deformation of the shock absorber increases and the strain of the shock absorber group inside the shock absorber increases, the impact load acting on the cask increases, and the load on the sealed boundary that maintains the safety function of the cask may also increase. There is. In addition, the buffer area that can be installed on the outer periphery of the cask is limited, especially when the vehicle is dropped horizontally or tilted. Therefore, if the amount of deformation of the shock absorber increases, the distance between the trunnion or the like used for lifting and fixing the cask protrusion and the falling surface may become short, and it is necessary to absorb the impact more efficiently.

One solution to this problem is to increase the shock-absorbing area by making the buffer thicker. However, due to restrictions on the equipment used for transportation, the maximum external dimensions of the cask after mounting the shock absorber are set.
Therefore, if the area of the buffer is increased, the cask size is reduced by that amount and the fuel storage area is reduced, or the number of fuel storage bodies needs to be reduced, and the fuel storage efficiency is lowered.

In Patent Document 1, the plurality of impact absorber groups absorb the impact force at the time of dropping or collision, and the end face side member and the peripheral surface side member are not significantly deformed to suppress the deformation of the cask lid portion. Can be done. However, in the configuration described in Patent Document 1, each shock absorber group mainly absorbs only the impact force in a specific drop direction or collision direction, and the impact absorbing region may be limited. be.

The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a cask buffer capable of increasing the amount of shock absorption without increasing the external dimensions of the shock absorber.

In order to solve the above problems, the buffer for cask of the present invention is installed in the cask during transportation of the cask containing the radioactive substance, and is installed in the outer shell of the hollow buffer forming the outer shell and inside the outer shell. The radial ribs provided, the first shock absorber group that absorbs the shock in the direction parallel to the end face of the cask, and the second shock absorption that absorbs the shock in the direction orthogonal to or diagonally to the end face of the cask. A body group, a third shock absorber group that absorbs a shock in a direction orthogonal to the end face of the cask, and a plate structural member that straddles the first shock absorber group and the second shock absorber group. It has.

According to the present invention, since the area capable of absorbing impact can be increased by the plate structural member straddling the group of impact absorbers, the amount of impact absorption with respect to the amount of deformation of the shock absorber for cask can be increased without increasing the external dimensions of the buffer. It is possible to provide a buffer for cask that can be used.

The schematic diagram which looked at the state which installed the cushion for cask of the embodiment which concerns on this invention on a cask from the side of a lid. FIG. 1A is a cross-sectional view taken along the line I-I. The schematic cross-sectional view which shows the falling posture of a horizontal fall of a cask and a group of shock absorbers which absorb a shock. Schematic cross-sectional view showing the falling posture of the corner drop of the cask and the group of shock absorbers that absorb the shock. The schematic cross-sectional view which shows the falling posture of a vertical drop of a cask and a group of shock absorbers which absorb a shock. The schematic cross-sectional view which shows the falling posture of the inclined fall of a cask and the group of shock absorbers which absorb a shock. The upper surface schematic diagram of the buffer for cask in Embodiment 1. FIG. II-II cross-sectional view of FIG. 3A of the cask buffer according to the first embodiment. FIG. 3B is a cross-sectional view taken along the line III-III. The upper surface schematic diagram of the buffer for cask in Embodiment 2. FIG. 3B is a schematic view corresponding to a cross section of III-III of FIG. 3B showing a configuration around a cask lid portion of a cask buffer according to the second embodiment. The upper surface schematic diagram of the buffer for cask in Embodiment 3. FIG. 6A is a schematic cross-sectional view of the IV-IV cross section of FIG. 6A. FIG. 6B is a schematic cross-sectional view taken along the line VV. FIG. 3B is a schematic view corresponding to a cross section of FIG. 3B of FIG. Schematic diagram corresponding to the III-III cross section of FIG. 3B of the cushioning body for cask that employs the arc-shaped plate structural member of the modified example 2.

The present invention relates to a cask buffer attached during transport of a cask containing radioactive material. In particular, it relates to the shape and arrangement of the plate structural members arranged in the outer shell of the cask buffer.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

FIG. 1A is a schematic view of a state in which the cask buffer 10 of the embodiment according to the present invention is installed on the cask 1 as viewed from the side of the lid 3. FIG. 1B is a cross-sectional view taken along the line I-I of FIG. 1A.
The embodiment in which the cask buffer 10 of the embodiment is installed in the cask 1 will be described. The cask buffer 10 of the embodiment is not limited to the specific spent fuel cask, and can be applied to a buffer used for other spent fuel transport containers.

The cask 1 shown in FIG. 1B is a container for internally storing, transporting, and storing the spent fuel 8 discharged from the nuclear power plant. The cask 1 has a substantially cylindrical shape, and has a bottomed cylindrical body portion 2 and a lid portion 3 attached to the upper opening of the body portion 2.
A neutron absorbing material 5 is provided on the outside of the body portion 2, and an outer cylinder 6 is provided surrounding the neutron absorbing material 5.
The cask 1 is provided with a trunnion 7 used for lifting and fixing on the outside of the body 2.

The cask buffer 10 of the embodiment is equipment for preparing for a fall accident during transportation and handling of the cask 1.
The cask buffer 10 is fixed by using bolts or the like so as to cover the lid 3 of the cask 1 and the bottom 4 of the body 2. The cask buffer 10 attached to the lid 3 and the bottom 4 respectively has a structure composed of similar components.
The cask buffer 10 absorbs an impact by deforming within a certain range when the cask 1 is dropped at various angles such as a vertical drop, a horizontal drop, an inclined drop, and a corner drop. The impact load on the lid 3 and the bottom 4 is relaxed.

2A to 2D are schematic cross-sectional views showing the falling posture of the cask 1 and the shock absorber groups 15 to 17 that absorb the shock.
FIG. 2A shows a horizontal fall, and FIG. 2B shows a corner fall. FIG. 2C shows a vertical fall, and FIG. 2D shows a tilted fall.
As described above, the horizontal fall shown in FIG. 2A is a fall event in which the central axis O of the cask 1 falls in a horizontal position. The corner drop shown in FIG. 2B is a drop event in which the drop point 1f of the cask 1 falls at an angle on the vertical line passing through the center of gravity of the cask 1. The vertical fall shown in FIG. 2C is a fall event in which the central axis O of the cask 1 falls in a vertical position. The inclined fall shown in FIG. 2D is a falling event in which the central axis O of the cask 1 falls in a posture at a shallow angle with the horizontal plane.

The outer shell of the cask buffer 10 is formed by a hollow buffer outer shell 11, and one side of the buffer outer shell 11 has a buffer outer shell recess 12 in which the end of the cask is housed. .. A first shock absorber group 15, a second shock absorber group 16, and a third shock absorber group 17 are arranged in the space surrounded by the buffer outer shell 11.
The first shock absorber group 15 has an annular shape and is arranged on the side of the cask 1.
The second shock absorber group 16 has an annular shape and is arranged at a corner portion of the cask 1.

The third shock absorber group 17 has a disk-like shape and is arranged at the upper end (1u) or the lower end (1s) of the cask 1.
A case where the cask 1 falls in the direction of the arrow shown in FIGS. 2A to 2D and collides with the falling surface 100 such as the floor surface will be described in detail.

In a horizontal drop in which the cask 1 shown in FIG. 2A collides with the falling surface 100 in a posture close to horizontal, the cask 1 is mainly arranged on the side portion that absorbs the impact in the direction parallel to the end surface (cover surface) 1u and 1s of the cask 1. The first shock absorber group 15 absorbs the shock at the time of dropping.

In a corner drop in which the cask 1 shown in FIG. 2B collides with the falling surface 100 at an angle, the corner portion mainly absorbs the impact in the direction orthogonal to the upper and lower end surfaces 1u and 1s of the cask 1 or in the oblique direction. The second shock absorber group 16 arranged to absorb the shock at the time of dropping.

In a vertical drop in which the cask 1 shown in FIG. 2C collides perpendicularly with the falling surface 100, a third arranged at the upper end or the lower end mainly absorbing the impact in the direction orthogonal to the upper and lower end surfaces 1u and 1s of the cask 1. The shock absorber group 17 of the above absorbs the shock at the time of dropping.

In an inclined drop in which the central axis O of the cask 1 shown in FIG. 2D collides with the horizontal plane (falling surface 100) at a shallow angle, the impact is mainly in the direction parallel to the end surface (cover surface) 1u and 1s of the cask 1. The first shock absorber group 15 arranged on the side portion that absorbs the impact, and the second impact absorber group 15 arranged mainly on the corner portion that absorbs the impact in the direction orthogonal to the upper and lower end surfaces 1u and 1s of the cask 1 or in the oblique direction. The shock absorber group 16 of the above absorbs the shock at the time of dropping.

<< Embodiment 1 >>
The configuration of the cask buffer 10A of the first embodiment will be described with reference to FIGS. 3 and 4.
FIG. 3A is a schematic top view of the cask buffer 10A according to the first embodiment. FIG. 3B is a cross-sectional view taken along the line II-II of FIG. 3A of the cask buffer 10A according to the first embodiment.

FIG. 4 is a schematic cross-sectional view of the III-III cross section of FIG. 3B showing the configuration around the lid portion 3 (see FIG. 1) of the cask 1 of the cask buffer 10A according to the first embodiment.

As shown in FIGS. 3B and 4, in the cask buffer 10A of the first embodiment, an outer shell is formed by a hollow buffer outer shell 11 around the lid portion 3 of the cask 1, and the buffer outer shell 11 is formed. On one side of the body, there is a buffer outer shell recess 12 in which the end of the cask is housed.
The cask buffer 10A includes a radial rib 13 (see FIG. 4) and a cylindrical rib 14 (see FIG. 3B) inside the buffer outer shell 11. The radial ribs 13 are not limited to the number and arrangement shown in FIG.
The cask buffer 10A has a side first shock absorber group 15a and 15b arranged in a space sandwiched between the buffer outer shells 11 and a second shock absorber group 16 arranged at a corner. It also has a third shock absorber group 17 arranged on the upper and lower ends (1u, 1s) side. In addition, in the cask buffer 10A, a fan-shaped plate structural member 20 (see FIGS. 3B and 4) straddling the first impact absorber groups 15a and 15b and the second impact absorber group 16 is arranged. .. The plate structural member 20 has a role of transmitting an impact to the first impact absorber groups 15a and 15b and the second impact absorber group 16.

The first shock absorber groups 15a and 15b are each divided into two regions, an inner peripheral side and an outer peripheral side, by a fan-shaped plate structural member 20. That is, it is divided into a first shock absorber group 15a arranged on the inner peripheral side of the fan-shaped plate structure member 20 and a first shock absorber group 15b arranged on the outer peripheral side of the plate structure member 20. ..

The first shock absorber groups 15a and 15b are arranged around the lid portion 3 (see FIG. 1B), and are mainly parallel to the upper and lower end surfaces 1u and 1s of the cask 1 in the shock absorber (10). Absorbs directional impact.

The second impact absorber group 16 is arranged in a region between the first impact absorber groups 15a and 15b on the side and the third impact absorber group 17. The second shock absorber group 16 mainly absorbs shocks in the buffer (10A) in a direction orthogonal to the upper and lower end surfaces 1u and 1s of the cask 1.
The third shock absorber group 17 is arranged on the upper surface (upper end surface 1u) of the lid portion 3 (see FIG. 1B), and is mainly orthogonal to the upper end surface 1u of the cask 1 in the shock absorber (10). Absorbs the impact in the direction of

Based on the above characteristics, in the first embodiment, the fan-shaped plate structural member 20 is arranged so as to straddle the first shock absorber groups 15a and 15b on the side portion and the second shock absorber group 16 on the corner portion. doing. That is, the fan-shaped plate structure member 20 is configured to have a portion that is in contact with or penetrates the first impact absorber groups 15a and 15b at the side portion and the second impact absorber group 16 at the corner portion. ..

As shown in FIG. 4, the plate structural member 20 is arranged between the radial ribs 13. The fan-shaped plate structural member 20 has a structure in which neither the buffer outer shell 11 shown in FIG. 3B nor the radial rib 13 shown in FIG. 4 is joined. A part of the plate structural member 20 may be joined to either the buffer outer shell 11 or the radial rib 13 by welding or the like.
If the fan-shaped plate structural member 20 is joined to the buffer outer shell 11 and the radial rib 13, a skeleton structure can be obtained, and the strength of the buffer (10) can be increased. In addition, it is possible to prevent the shock absorbers (15a, 15b, 16) from shifting when the buffer (10) is crushed.

On the other hand, if the plate structural member 20 is separated from the buffer outer shell 11 and the radial rib 13, welding or the like is not required, so that the plate structural member 20 can be easily installed. Further, since the fan-shaped plate structural member 20 is movable when the buffer body (10) is crushed, the load generated by crushing the outer shell (11) and the rib (13) can be suppressed to a low level.

The material of the plate structural member 20 is the same metal as that of the buffer outer shell 11, but a fiber reinforced material (for example, FRP) or the like having sufficient strength can be used as a substitute. In the first embodiment, the fan-shaped plate structural member 20 in the buffer (10) is shown at a position exactly intermediate between the buffer outer shell 11 and the buffer outer shell recess 12, but the present invention is not limited to this.
According to the configuration of the first embodiment, when the cask 1 having the outer cask buffer 10A collides with the falling surface 100 such as the floor surface when the cask 1 falls horizontally (see FIG. 2A) or tilts (see FIG. 2D). The amount of shock absorption with respect to the amount of deformation of the cask buffer 10A can be increased.

When the cask buffer 10A collides with the falling surface 100, the first shock absorber groups 15a and 15b arranged around the lid 3 of the cask 1 begin to be deformed (compressed), and the lid 3 is subjected to deformation (compression). The impact load is transmitted. Further, as the deformation of the first shock absorber groups 15a and 15b progresses, a difference in the amount of deformation occurs between the first shock absorber groups 15a and 15b and the second shock absorber group 16. The fan-shaped plate structure member 20 transmits the load of the first shock absorber groups 15a and 15b to the second shock absorber group 16.

Therefore, the impact absorber group (15a, 15b, 16) in a wide range is deformed as compared with the case where the plate structure member 20 is not arranged, and more impact can be absorbed. As a result, the amount of shock absorption per amount of deformation of the cask buffer 10 can be increased. Further, by absorbing the impact force in a wider range, the load acting on the lid portion 3 can be dispersed in the axial (O) direction of the cask 1. Further, since the plate structural member 20 is integrally arranged over the entire circumference in the shock absorbers (15a, 15b, 16), the above-mentioned effect is obtained regardless of whether the cask 1 receives a load from any of 360 degrees. Can be demonstrated.

Further, since the first embodiment can be achieved with the same external dimensions of the shock absorber and the same amount of shock absorbers as before, it can be applied to the existing cask 1 and the manufacturing cost of the shock absorber (10) is maintained. Or it can be suppressed.
In the first embodiment, it is assumed that the cask buffer 10 has a bottomed tubular structure, and the shock absorbers arranged inside have a fan-shaped structure with a central angle of 45 °. For example, for cask. It is applicable even if the shock absorber 10 is polygonal and the internal shock absorber group has another shape according to the outer shell shape.

The shock absorber groups (15a, 15b, 16, 17) shown in FIGS. 3B and 4 are shown in one region, respectively, but the shock absorber groups (15a, 15b, 16, 17) are shown in each region. ) May be further divided. The impact absorber group (15a, 15b, 16, 17) is made of anisotropic wood or isotropic foam material, but other members having similar impact absorption characteristics can also be applied. be.

According to the above configuration, the region capable of absorbing impact can be increased by the plate structural member 20 straddling the impact absorber groups (15a, 15b, 16). Therefore, the amount of shock absorption with respect to the amount of deformation of the cask buffer 10 can be increased without increasing the external dimensions of the buffer (10).

<< Embodiment 2 >>
FIG. 5A is a schematic top view of the cask buffer 10B according to the second embodiment. FIG. 5B is a schematic view corresponding to a cross section of FIG. 3B, which shows the configuration around the cask lid portion of the cask buffer 10B according to the second embodiment.

Next, the configuration of the cask buffer 10B of the second embodiment will be described.
The description of the same configuration as that of the first embodiment described above will be omitted.
As shown in FIG. 3B, the schematic cross-sectional view of the cask buffer 10B of the second embodiment is the same as that of the first embodiment.

As shown in FIGS. 5A and 5B, the cask buffer 10B of the second embodiment has a different configuration around the lid 3 from the first embodiment.
The outer shell of the cask buffer 10B of the second embodiment is formed by the hollow buffer outer shell 11.
The cask buffer 10B includes a radial rib 13 and a cylindrical rib 14 (see FIGS. 3B and 5A) inside the buffer outer shell 11.

The cask buffer 10B includes first shock absorber groups 15a and 15b arranged in a space sandwiched between the shock absorber outer shells 11, second shock absorber groups 16 (see FIG. 3B), and a second shock absorber group 16 (see FIG. 3B). It is provided with 3 shock absorber groups 17 (see FIG. 3B). Further, the cask shock absorber 10B straddles the first shock absorber groups 15a and 15b and the second shock absorber group 16 and is integrated with the shock absorber (10A) in the circumferential direction. And have.
In the tubular plate structural member 21 of the second embodiment, a part of the radial rib 13 is divided and arranged. The tubular plate structure member 21 has a structure in which neither the buffer outer shell 11 nor the radial rib 13 is joined.

A part of the tubular plate structure member 21 may be joined to either the buffer outer shell 11 or the radial rib 13 by welding or the like.
According to the second embodiment, due to the configuration of the cylindrical plate structural member 21, the cask buffer when the cask 1 falls horizontally (see FIG. 2A) or tilts (see FIG. 2D) as compared with the first embodiment. The amount of shock absorption with respect to the amount of deformation of 10B can be further increased.

When the cask buffer 10B of the second embodiment collides with the falling surface 100, the first shock absorber groups 15a and 15b arranged around the cask lid portion 3 are first deformed (compressed) as in the first embodiment. ) Is started, the impact load is transmitted to the lid portion 3.

Further, as the deformation of the first shock absorber groups 15a and 15b progresses, a difference in the amount of deformation occurs between the first shock absorber group 15 and the second shock absorber group 16. Therefore, the tubular plate structure member 21 transmits the load of the first impact absorber groups 15a and 15b to the second impact absorber group 16. Further, when the shock absorber (10B) and the first shock absorber groups 15a and 15b are deformed, the tubular plate structural member 21 is positioned adjacent to the shock absorber groups 15a and 15b shown in FIG. 5 in the circumferential direction. The shock absorbers 15a and 15b of the above are deformed while being rolled up.

Therefore, the impact absorber group (15a, 15b, 16) in a wider range is deformed as compared with the first embodiment, and more impact can be absorbed.
As a result, the amount of shock absorption per amount of deformation of the cask buffer 10B can be increased. Further, the load acting on the lid portion 3 can be dispersed in the circumferential direction of the lid portion 3 (see FIG. 1B) of the cask 1.
Further, since the cylindrical plate structure member 21 is arranged over the entire circumference in the buffer body (10B), even if the cask 1 receives a load from 360 degrees around the central axis O, the above-mentioned effect is obtained. Can be demonstrated.

<< Embodiment 3 >>
FIG. 6A is a schematic top view of the cask buffer 10C according to the third embodiment, and FIG. 6B is a schematic cross-sectional view of the IV-IV cross section of FIG. 6A.

FIG. 7 is a schematic cross-sectional view showing the configuration around the lid 3 of the cask 1 of the cask buffer 10C according to the third embodiment, and is a schematic cross-sectional view of the position shown in the VV cross section of FIG. 6B.
Next, the configuration of the cask buffer 10C of the third embodiment will be described with reference to FIGS. 6A, 6B, and 7.
The description of the same configuration as that of the above-described first and second embodiments will be omitted.

As shown in FIGS. 6A and 6B, the cask buffer 10B of the third embodiment has an outer shell formed by a hollow buffer outer shell 11 around the lid portion 3.
The cask buffer 10C includes a first shock absorber group 15 at the side, a second shock absorber group 16 at the corner, and a third shock absorber group at the upper end (1u) or the lower end (1s). 17 and an L-shaped plate structural member 22 are provided.
The first shock absorber group 15 is arranged on a side portion in the space sandwiched by the buffer outer shell 11.

The L-shaped plate structural member 22 includes a first shock absorber group 15 at the side portion, a second shock absorber group 16 at the corner portion, and a third shock absorber at the upper end (1u) or the lower end (1s). It is arranged across groups 17. The L-shaped plate structural member 22 has a bent portion 22 m (see FIG. 6B).

As shown in FIG. 7, the L-shaped plate structural member 22 is arranged between the radial ribs 13. The L-shaped plate structural member 22 in the third embodiment has a structure in which neither the buffer outer shell 11 nor the radial rib 13 is joined.
The L-shaped plate structure member 22 may be partially joined to either the buffer outer shell 11 or the radial rib 13 by welding or the like.
According to the configuration of the third embodiment, as described below, the configuration of the L-shaped plate structural member 22 causes not only the case where the cask 1 falls horizontally (see FIG. 2A) or tilts (see FIG. 2D). Even when the cask 1 falls in a corner (see FIG. 2B) or vertically (see FIG. 2C), the shock absorption amount with respect to the deformation amount of the cask buffer 10C can be further increased.

The effect of the cask buffer 10C of the third embodiment when the cask 1 falls horizontally (see FIG. 2A) is the same as that of the above-described first and second embodiments.
In the cask buffer 10C, when the cask 1 falls into a corner (see FIG. 2B), first, the second impact absorber group 16 at the corner shown in FIG. 6B starts to be deformed (compressed). Further, as the deformation of the second shock absorber group 16 progresses, the L-shaped plate structural member 22 together with the second shock absorber group 16 becomes the first shock absorber group 15 on the side and the upper end. The third shock absorber group 17 is deformed while being rolled up. Therefore, the impact absorber group (16, 15, 17) in a wider range is deformed as compared with the case where the L-shaped plate structure member 22 is not arranged, and more impact can be absorbed.

Similarly, in the cask buffer 10C of the third embodiment, when the cask 1 falls vertically (see FIG. 2C), the third shock absorber group 17 at the end is first deformed (compressed). Further, as the deformation of the third shock absorber group 17 progresses, the L-shaped plate structural member 22 shown in FIG. 6B, together with the third shock absorber group 17, the second shock absorber group 16 at the corner portion. Then, the first shock absorber group 15 on the side is deformed while being rolled up.

Therefore, the impact absorber group (17, 16, 15) in a wider range is deformed as compared with the case where the L-shaped plate structure member 22 is not arranged, and more impact can be absorbed. As a result, the amount of shock absorption per amount of deformation of the cask buffer 10C can be increased.
Further, the L-shaped plate structure member 22 can be easily extended toward the first impact absorber group 15 on the side portion and can be extended toward the third impact absorber group 17.

<Modification example>
FIG. 8A is a schematic view corresponding to a cross section of FIG. 3B of FIG. 3B of a cask buffer 10D that employs the V-shaped plate structural member 22A of the first modification.

FIG. 8B is a schematic view corresponding to a cross section of FIG. 3B of FIG. 3B of the cask buffer 10E that employs the arc-shaped plate structural member 22B of the modified example 2.
The dogleg-shaped plate structural member 22A of the cask buffer 10D of the modified example 1 shown in FIG. 8A is an annular member having a dogleg-shaped cross section bent at the bent portion 22 Am.

The arcuate plate structure member 22B of the cask buffer 10E of the modified example 2 shown in FIG. 8B is an annular member having a cross section having an arcuate curvature.
If the plate structure member is a dogleg-shaped plate structure member 22A, the strength can be made higher than that of the L-shaped plate structure member 22. Further, if the shape has bent portions 22m and 22Am such as the L-shaped plate structure member 22 or the dogleg-shaped plate structure member 22A, the strength of the plate structure member is high.
Further, if the plate structure member is an arc-shaped plate structure member 22B, the strength is even higher than that of the dogleg-shaped plate structure member 22A.

The L-shaped plate structure member 22 may be a dogleg-shaped plate structure member 22A, an arc-shaped plate structure member 22B, or a plate structure member having any other shape.
Examples of the plate structural member having other shapes include an annular member having a curved cross section. The arc-shaped plate structure member 22B is an annular member having a cross section having a curvature at the edge.
The V-shaped plate structure member 22A, the arc-shaped plate structure member 22B, and the plate structure members having other shapes are formed of the first shock absorber group 15 on the side and the corner portion, as in the third embodiment. The above effect can be obtained if the configuration is arranged so as to straddle the second shock absorber group 16 and the third shock absorber group 17 on the upper end surface 1s or the lower end surface 1u.

The present invention is not limited to the above-described first to third embodiments, and includes various modifications. The above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

1 Cask 1s Lower end face (end face)
1u Upper end face (end face)
8 Spent fuel (radioactive material)
10, 10A, 10B, 10C, 10D Cask buffer 11 Buffer outer shell (outer shell)
12 Cushion outer shell recess (outer shell)
13 Radial rib 14 Cylindrical rib 15 First impact absorber group 16 Second impact absorber group 17 Third impact absorber group 20 Plate structural member (plate structural member)
21 Cylindrical plate structure member (plate structure member)
22 L-shaped plate structure member (plate structure member)
22A V-shaped plate structure member (plate structure member)
22B Arc-shaped plate structure member (plate structure member)
22m, 22Am bend

Claims (8)

Installed in the cask when transporting the cask that stores radioactive materials,
The buffer outer shell that forms the outer shell,
Radial ribs provided inside the outer shell and
A first group of shock absorbers that absorb shocks in a direction parallel to the end face of the cask,
A second group of impact absorbers that absorb impacts in the orthogonal or oblique direction to the end face of the cask, and
A third group of shock absorbers that absorb shocks in the direction orthogonal to the end face of the cask,
A cask buffer body including a plate structural member straddling the first impact absorber group and the second impact absorber group. In the cask buffer according to claim 1,
A cask buffer characterized in that the plate structural member is not coupled to the outer shell or the radial ribs. In the cask buffer according to claim 1,
A cask buffer characterized in that the plate structural member is coupled to the outer shell or the radial ribs. In the cask buffer according to claim 1,
A cask buffer body characterized in that the plate structural member is integrated over the entire circumference of the cask buffer body. In the cask buffer according to claim 1,
The plate structural member is integrated over the entire circumference of the cask buffer.
A cask buffer body characterized in that the plate structural member has a tubular shape. In the cask buffer according to claim 1,
The plate structural member is a shock absorber for cask, which is provided across the first shock absorber group, the second shock absorber group, and the third shock absorber group. In the cask buffer according to claim 1,
The plate structural member is
It is provided across the first shock absorber group, the second shock absorber group, and the third shock absorber group, and is provided.
A cask buffer characterized by having a curved cross section. In the cask buffer according to claim 1,
The plate structural member is
It is provided across the first shock absorber group, the second shock absorber group, and the third shock absorber group, and is provided.
A cask buffer characterized by having an L-shaped or dog-legged or arcuate or curved cross section.

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