JP2021004831A - Buffer structure - Google Patents

Abstract

To reduce burden acting on a cask in collision while downsizing a buffer structure.SOLUTION: A buffer structure 1 absorbs an impact between a cask and a floor surface 81 when a columnar cask housing a fuel assembly falls. The buffer structure 1 comprises a first site 21 and a second site 22. The first site 21 is formed of a porous material. The second site 22 is formed of a porous material having a density different from that of the first part 21, and overlaps the first part 21 in a vertical direction. Consequently, it is possible to reduce burden acting on the cask in collision while downsizing the buffer structure 1.SELECTED DRAWING: Figure 2

Description

The present invention relates to a buffer structure that absorbs an impact between a cask and a floor surface when a columnar cask containing a fuel assembly falls.

Conventionally, spent fuel used in nuclear reactors and the like is stored in a cooling pool provided in a nuclear power plant until the radiation dose falls below a predetermined level, and then a cask having a shielding function and a sealing function. Will be housed in the facility and transported to an interim storage facility or fuel reprocessing facility. The cask is required to maintain a predetermined shielding function, sealing function, etc. in the event of a fall accident such as during transportation.

Therefore, when the cask is transported, cushioning bodies are attached to the upper and lower ends of the cask, and measures are taken to reduce the impact applied to the cask in the unlikely event of a fall. For example, Patent Document 1 proposes a buffer structure in which an annular member in which hard wood and soft wood are combined is coated with a metal coating plate. Further, Patent Document 2 proposes a shock absorber in which two or more types of wood having different axial hardness are filled inside a metal outer shell.

On the other hand, in the cushioning body of Patent Document 3, a cushioning material formed by arranging a plurality of metal polyhedral frames in a three-dimensional net pattern is housed inside the casing. Further, in the shock absorber of Patent Document 4, a large number of hollow tubular shock absorbing members formed by laminating FRP sheets are arranged inside the casing. The shock absorber may be placed on the floor surface of the moving path of the cask by the crane. Patent Document 5 proposes a porous metal shock absorber arranged on the floor surface of a fuel pool. Metal plates such as iron or stainless steel are attached to the upper surface and the lower surface of the shock absorber.

Japanese Unexamined Patent Publication No. 2004-294191 Japanese Unexamined Patent Publication No. 2006-90705 JP-A-2017-150943 JP-A-2017-114564 Japanese Unexamined Patent Publication No. 2014-48190

By the way, in such a buffer structure, not only the impact reduction when the cask is dropped but also the miniaturization is required so as not to hinder the transport of the cask.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the load acting on the cask at the time of collision while reducing the size of the buffer structure.

The invention according to claim 1 is a buffer structure that absorbs an impact between the cask and the floor surface when a columnar cask containing a fuel assembly falls, and is formed of a porous material. The first portion is formed of a porous material having a density different from that of the first portion, and includes a second portion that overlaps the first portion in the vertical direction.

The invention according to claim 2 is the buffer structure according to claim 1, wherein the first portion and the second portion are each formed of a foamed resin or a foamed metal.

The invention according to claim 3 is the buffer structure according to claim 1 or 2, wherein the design density of the lower density portion of the first portion and the second portion is 0.1 g / g. The design density of the part having a higher density of cm ³ or more and 0.65 g / cm ³ or less is 0.2 g / cm ³ or more and 0.8 g / cm ³ or less, and the actual first part is actually The density is 90% or more and 110% or less of the design density of the first part, and the actual density of the second part is 90% or more and 110% or less of the design density of the second part.

The invention according to claim 4 is the buffer structure according to any one of claims 1 to 3, which includes the first portion and the second portion and is placed on a floor surface. A mounting block that receives a cask falling from above is further provided, and the first portion is located at the uppermost stage of the above-mentioned mounting block, has an upper surface that is larger than the end face of the cask and extends horizontally, and the second portion. The portion abuts on the lower surface of the first portion.

The invention according to claim 5 is the buffer structure according to claim 4, wherein the density of the first portion is lower than the density of the second portion.

The invention according to claim 6 is the buffer structure according to claim 4, wherein the density of the first portion is higher than the density of the second portion.

The invention according to claim 7 is the buffer structure according to any one of claims 4 to 6, wherein each of the first portions has a flat plate shape extending in the horizontal direction and is laminated in the vertical direction. The second buffer layer is provided with a plurality of first buffer layers to be formed, or the second portion includes a plurality of second buffer layers each having a flat plate shape extending in the horizontal direction and laminated in the vertical direction.

The invention according to claim 8 is the cushioning structure according to claim 7, wherein each of the plurality of first buffer layers includes a plurality of first plate members continuously arranged in the horizontal direction. The boundary line between the two first plate members horizontally adjacent to each other in one first buffer layer is the main surface of the first plate member in the other first buffer layer vertically adjacent to the first buffer layer. Each of the plurality of second buffer layers is provided with a plurality of second plate members arranged continuously in the horizontal direction, and two second plates vertically adjacent to each other in one second buffer layer. The boundary line of the member overlaps with the main surface of the second plate member in the other second buffer layer adjacent to the first second buffer layer in the vertical direction.

The invention according to claim 9 is the cushioning structure according to claim 8, wherein each first plate member is another first plate adjacent to each other in the vertical direction at a plurality of bonding points located at the outer edge portion. The member and the second plate member are point-bonded by an adhesive, or each second plate member is point-bonded to another second plate member adjacent in the vertical direction by an adhesive at a plurality of bonding points located at the outer edge portion.

The invention according to claim 10 is the cushioning structure according to any one of claims 4 to 9, further comprising a casing that covers the side surface of the above-described block.

In the present invention, it is possible to reduce the load acting on the cask at the time of collision while reducing the size of the buffer structure.

It is a side view of the buffer structure which concerns on 1st Embodiment. It is a vertical sectional view of the buffer structure. It is a perspective view of the mounting block. It is a vertical cross-sectional view which shows the cushioning structure in the state which received the dropped cask. It is a vertical cross-sectional view which shows the cushioning structure in the state which received the dropped cask. It is a vertical sectional view of the buffer structure which concerns on 2nd Embodiment. It is a vertical cross-sectional view which shows the cushioning structure in the state which received the dropped cask. It is a vertical cross-sectional view which shows the other buffer structure.

FIG. 1 is a side view showing the buffer structure 1 according to the first embodiment of the present invention. FIG. 2 is a vertical cross-sectional view showing the buffer structure 1. The buffer structure 1 is a member that absorbs an impact between the cask and the floor surface 81 when the cask falls. In the example shown in FIG. 1, the cushioning structure 1 is a substantially rectangular parallelepiped laying type cushioning structure mounted on the floor surface 81, and receives, for example, a cask that freely falls from above.

A cask is a substantially columnar container in which a spent fuel assembly (hereinafter, simply referred to as "fuel assembly") is housed. The cask has a shielding function that shields radiation, a sealing function that seals radioactive substances, a subcritical maintenance function that maintains the fuel assembly in a subcritical state, and a heat removal function that dissipates heat from the fuel assembly. .. When the cask is conveyed, for example, the cask is lifted by a crane or the like so that the direction in which the central axis of the cask faces (hereinafter, also referred to as "longitudinal direction") is substantially parallel in the vertical direction. Alternatively, the cask may be lifted so that the central axis faces the horizontal direction.

The buffer structure 1 includes a mounting block 2, a casing 3, and a cover 4. The casing 3 is a substantially rectangular parallelepiped member having a bottom surface portion 31 and a side wall portion 32 formed by a plate member. In other words, the casing 3 is an open bottomed box-shaped member. The casing 3 is made of a metal such as stainless steel. The length, width and height of the casing 3 are, for example, 2 m to 4 m, 4 m to 6 m, and 2 m to 5 m. The material and size of the casing 3 may be changed in various ways. The mounting block 2 is a substantially rectangular parallelepiped cushioning material formed of a porous material. The mounting block 2 is housed in a substantially rectangular parallelepiped internal space of the casing 3 and mounted on the floor surface 81 to receive a cask falling from above. The bottom surface and the side surface of the mounting block 2 are surrounded and covered with the casing 3. In the example shown in FIG. 2, the upper surface of the mounting block 2 and the upper end of the casing 3 are located at substantially the same positions in the vertical direction.

A plurality of through holes 33 are provided in the side wall portion 32 of the casing 3. In the example shown in FIG. 1, each of the plurality of through holes 33 has a substantially oval shape or a substantially rectangular shape extending substantially parallel to the horizontal direction. The plurality of through holes 33 are arranged in a staggered manner over substantially the entire surface of the four side wall portions 32, for example. Further, the side wall portion 32 of the casing 3 is provided with a thick plate-shaped or substantially semi-cylindrical reinforcing member 34 extending substantially parallel to the horizontal direction. The reinforcing member 34 is provided over substantially the entire circumference of the casing 3. In the example shown in FIG. 1, a plurality of reinforcing members 34 are arranged in the vertical direction. The plurality of reinforcing members 34 are arranged at a central portion in the vertical direction of the casing 3 and below the central portion. The shape, number and arrangement of the through holes 33 and the shape, number and arrangement of the reinforcing member 34 may be changed in various ways.

The cover 4 is a sheet-like member that covers the upper surface of the mounting block 2 over substantially the entire surface. The cover 4 is formed of, for example, a non-flammable and impermeable non-woven fabric or the like. The cover 4 is fixed to the casing 3 by, for example, a nonflammable rope (not shown).

The mounting block 2 includes a first portion 21 and a second portion 22. In FIG. 2, different parallel diagonal lines are attached to the first part 21 and the second part 22. The first part 21 and the second part 22 are substantially rectangular parallelepiped parts, respectively. The first portion 21 and the second portion 22 overlap each other in the vertical direction in the casing 3. The first portion 21 is located at the uppermost stage of the mounting block 2. In other words, the upper surface of the first portion 21 is the upper surface of the mounting block 2. The upper surface of the first portion 21 is a substantially flat surface that is larger than the longitudinal end surface of the cask and extends in a substantially horizontal direction. The second part 22 is located directly below the first part 21, and the upper surface of the second part 22 is in contact with the lower surface of the first part 21. In a plan view, the first portion 21 and the second portion 22 have substantially the same shape and overlap over substantially the entire surface.

The first part 21 and the second part 22 are each made of a porous material. The first site 21 and the second site 22, respectively, may be formed of various porous materials, for example, a plastically deformable porous resin or a porous metal. Preferably, the first site 21 and the second site 22 are each made of foamed resin or foamed metal. The material of the porous material forming the first portion 21 (that is, the type of material constituting the porous material) and the material of the porous material forming the second portion 22 may be the same or different. May be. In the present embodiment, the first portion 21 and the second portion 22 are formed of rigid polyurethane foam.

The density of the porous material forming the first portion 21 and the density of the porous material forming the second portion 22 are different. In the example shown in FIG. 2, the density of the first site 21 is lower than the density of the second site 22. Further, the porosity of the first site 21 is higher than the porosity of the second site 22. The design density of the first portion 21 (that is, the portion having the lower density) is, for example, 0.1 g / cm ³ or more and 0.65 g / cm ³ or less, preferably 0.1 g / cm ³ or more and It is 0.3 g / cm ³ or less. The actual density of the first site 21 is 90% or more and 110% or less, preferably 95% or more and 105% or less of the design density of the first part 21. The design density of the second portion 22 (that is, the portion having the higher density) is, for example, 0.2 g / cm ³ or more and 0.8 g / cm ³ or less, preferably 0.3 g / cm ³ or more and It is 0.65 g / cm ³ or less. The actual density of the second site 22 is 90% or more and 110% or less, preferably 95% or more and 105% or less of the design density of the second part 22. The above-mentioned design density is a density set by a manufacturing apparatus or the like when manufacturing the first part 21 and the second part 22.

FIG. 3 is a perspective view showing the mounting block 2. In FIG. 3, in order to make it easier to understand the structure of the mounting block 2, the first part 21 and the second part 22 are drawn vertically separated from each other, and the center of the first part 21 and the second part 22 in the vertical direction. The illustration of the part is omitted. Actually, as described above, the upper surface of the second portion 22 is in contact with the lower surface of the first portion 21.

The first portion 21 includes a plurality of first buffer layers 211 having substantially the same shape and which are laminated in the vertical direction. Each first buffer layer 211 is a substantially flat portion extending in the horizontal direction. Each first buffer layer 211 is substantially rectangular in plan view. The thickness of each first buffer layer 211 is, for example, 10 mm to 300 mm, preferably 50 mm to 200 mm, and more preferably 70 mm to 100 mm. The number of the first buffer layers 211 is, for example, 10 to 20 layers. The shape, thickness and number of the first buffer layer 211 may be varied.

Each first buffer layer 211 includes a plurality of first plate members 212 that are continuously arranged in the horizontal direction. Each first plate member 212 is a substantially flat plate-shaped member that extends in the horizontal direction. Each first plate member 212 is substantially rectangular in a plan view. As described above, the plurality of first plate members 212 are arranged so as to be substantially rectangular in a plan view. In each first buffer layer 211, the side surfaces of two horizontally adjacent first plate members 212 are in contact with each other.

In the first portion 21, a plurality of first plate members 212 of the plurality of first buffer layers 211 are laminated in the vertical direction by so-called netting. In other words, the arrangement state of the plurality of first plate members 212 in the one first buffer layer 211 is the plurality of first in the other first buffer layer 211 vertically adjacent to the first buffer layer 211. It is different from the arrangement state of the plate member 212. Therefore, the boundary line between the two first plate members 212 that are horizontally adjacent to each other in the first buffer layer 211 is the first in the other first buffer layer 211 that is vertically adjacent to the first buffer layer 211. 1 It overlaps with the main surface of the plate member 212 (that is, the upper surface or the lower surface in FIG. 3).

An adhesive is applied in a dot shape (for example, a substantially circular shape having a diameter of about 30 mm) in the vicinity of the four corners of each first plate member 212. The first plate member 212 is point-bonded to another vertically adjacent first plate member 212 via the adhesive (not shown). The plurality of regions (that is, the plurality of adhesive locations) to which the adhesive is applied on the first plate member 212 are not necessarily limited to the vicinity of the corners, and may be located at the outer edge portion of the first plate member 212. Just do it.

The second portion 22 includes a plurality of second buffer layers 221 having substantially the same shape that are laminated in the vertical direction. Each second buffer layer 221 is a substantially flat portion extending in the horizontal direction, similarly to the first buffer layer 211. Each second buffer layer 221 has a substantially rectangular shape having substantially the same shape as the first buffer layer 211 in a plan view. The thickness of each second buffer layer 221 is, for example, 10 mm to 300 mm, preferably 50 mm to 200 mm, and more preferably 70 mm to 100 mm, similarly to the first buffer layer 211. The number of the second buffer layers 221 is, for example, 10 to 20 layers. The shape, thickness and number of the second buffer layer 221 may be varied.

Each second buffer layer 221 includes a plurality of second plate members 222 arranged continuously in the horizontal direction. Each second plate member 222 is a substantially flat plate-shaped member that extends in the horizontal direction. Each second plate member 222 is substantially rectangular in a plan view. As described above, the plurality of second plate members 222 are arranged so as to be substantially rectangular in a plan view. In each second buffer layer 221 the side surfaces of two horizontally adjacent second plate members 222 are in contact with each other.

At the second portion 22, a plurality of second plate members 222 of the plurality of second buffer layers 221 are laminated in the vertical direction by so-called netting. In other words, the arrangement state of the plurality of second plate members 222 in the first second buffer layer 221 is the plurality of second in the other second buffer layer 221 vertically adjacent to the first second buffer layer 221. It is different from the arrangement state of the plate member 222. Therefore, the boundary line between the two second plate members 222 that are horizontally adjacent to each other in the first second buffer layer 221 is the first in the other second buffer layer 221 that is vertically adjacent to the first second buffer layer 221. It overlaps the main surface of the two-plate member 222 (that is, the upper surface or the lower surface in FIG. 3).

Similar to the first plate member 212, the adhesive is applied in a dot shape (for example, a substantially circular shape having a diameter of about 30 mm) in the vicinity of the four corners of each second plate member 222. The second plate member 222 is point-bonded to another second plate member 222 adjacent in the vertical direction via the adhesive (not shown). Further, the second plate member 222 located at the uppermost stage of the second portion 22 is point-bonded to the first plate member 212 located at the lowermost stage of the first portion 21 by the adhesive applied in the vicinity of the four corners. Will be done. The plurality of regions (that is, the plurality of adhesive points) to which the adhesive is applied on the second plate member 222 are not necessarily limited to the vicinity of the corners as in the case of the first plate member 212, and the second plate member It may be located at the outer edge of 222.

4 and 5 are cross-sectional views showing an example of a state in which the cask 9 dropped from above is received by the buffer structure 1. The example shown in FIG. 4 shows a case where the cask 9 has fallen from an assumed maximum drop height (for example, about 40 m above). In the example shown in FIG. 4, the lower end of the cask 9 collides with the upper surface of the mounting block 2 of the buffer structure 1, and the cask 9 deforms the low-density first portion 21 and moves inside the first portion 21. Move down. At this time, the energy due to the fall of the cask 9 is absorbed by the deformation of the first portion 21. Then, when the lower end of the cask 9 reaches the lower surface of the first portion 21, the cask 9 moves downward inside the second portion 22 while deforming the high-density second portion 22. At this time, the energy due to the fall of the cask 9 is absorbed by the deformation of the second portion 22. The cask 9 finally stops in a state of being stuck in the mounting block 2.

The example shown in FIG. 5 shows a case where the cask 9 is dropped from a position lower than the above-mentioned maximum drop height. In the example shown in FIG. 5, the dropped cask 9 moves downward inside the first part 21 while deforming the low-density first part 21, and does not reach the second part 22 but reaches the first part. It stops in the state of being stuck in 21. In this case, the energy due to the fall of the cask 9 is absorbed almost exclusively by the first portion 21. The cask 9 finally stops in a state of being stuck in the mounting block 2.

Here, a mounting block having substantially the same size as the mounting block 2 described above, having a substantially uniform density as a whole, and capable of absorbing substantially the same falling energy (hereinafter, “mounting of the first comparative example”. It is called a "block".) The density of the mounting block of the first comparative example is higher than the density of the first site 21 in the mounting block 2 of the buffer structure 1 described above, and lower than the density of the second site 22. In the mounting block 2 of the buffer structure 1, as described above, the low-density first portion 21 is preferentially deformed by the collision with the cask 9. At this time, the amount of deformation of the first portion 21 is larger than that in the case where the cask 9 collides with the mounting block of the first comparative example. Therefore, in the buffer structure 1, the load acting on the cask 9 at the time of collision can be reduced as compared with the buffer structure having the mounting block of the first comparative example. In particular, as shown in FIG. 5, when most of the energy due to the fall of the cask 9 is absorbed by the first portion 21, the load acting on the cask 9 at the time of collision is compared with the mounting block of the first comparative example. , Can be further reduced.

In the buffer structure 1, the amount of deformation of the second portion 22 is smaller than that in the case where the cask 9 collides with the mounting block of the first comparative example. However, even when the second portion 22 is deformed as shown in FIG. 4, the deformation is not immediately after the collision with the cask 9 having a large energy due to the fall, but after the energy is considerably absorbed. Occurs just before the descent stop of. Therefore, the load acting on the cask 9 due to the deformation of the second portion 22 is not so large, and the influence on the cask 9 is small.

On the other hand, a mounting block having the same density as the low-density first portion 21 and capable of absorbing falling energy substantially similar to that of the mounting block 2 described above (hereinafter, "the second comparative example is described". Assuming (referred to as "placement block"), the height of the placement block of the second comparative example is made much higher than that of the placement block 2 (for example, 6 to 8 times higher). )There is a need. On the other hand, in the above-mentioned buffer structure 1, the mounting block 2 is provided with a low-density first portion 21 and a high-density second portion 22, so that the buffer structure 1 is miniaturized in the vertical direction. Can be done.

Next, the buffer structure 1a according to the second embodiment of the present invention will be described. FIG. 6 is a vertical cross-sectional view showing the buffer structure 1a. The buffer structure 1a includes a mounting block 2a having a structure different from that of the mounting block 2 in place of the mounting block 2 shown in FIG. In the mounting block 2a, the density of the first portion 21a is higher than the density of the second portion 22a. Except for this point, the buffer structure 1a has substantially the same configuration as the buffer structure 1. In the following description, the same reference numerals are given to the configurations of the buffer structure 1 and the configurations of the buffer structure 1a shown in FIGS. 1 to 3.

FIG. 7 is a cross-sectional view showing an example of a state in which the cask 9 dropped from above is received by the buffer structure 1a. The example shown in FIG. 7 shows a case where the cask 9 is dropped from the above-mentioned maximum drop height. In the example shown in FIG. 7, the lower end of the cask 9 collides with the upper surface of the mounting block 2a of the buffer structure 1a, and the cask 9 deforms so much while preferentially deforming the low-density second portion 22a. It moves downward with the high-density first site 21a that is not. At this time, the energy due to the fall of the cask 9 is mainly absorbed by the deformation of the second portion 22a. Then, when the deformation of the second part 22a progresses to some extent, the cask 9 moves downward inside the first part 21a while deforming the first part 21a. At this time, the energy due to the fall of the cask 9 is absorbed by the deformation of the first portion 21a and the second portion 22a. The cask 9 finally stops in a state of being stuck in the mounting block 2a.

In the mounting block 2a of the buffer structure 1a, as described above, the low-density second portion 22a is preferentially deformed by the collision with the cask 9. At this time, the amount of deformation of the second portion 22a is larger than that in the case where the cask 9 collides with the mounting block of the first comparative example. Therefore, in the buffer structure 1a as well, as in the buffer structure 1, the load acting on the cask 9 at the time of collision can be reduced as compared with the buffer structure having the mounting block of the first comparative example. ..

As described above, the buffer structures 1, 1a absorb an impact between the cask 9 and the floor surface 81 when the columnar cask 9 containing the fuel assembly falls. The buffer structure 1,1a includes a first portion 21,21a and a second portion 22, 22a. The first portions 21 and 21a are formed of a porous material. The second parts 22, 22a are formed of a porous material having a density different from that of the first parts 21,21a, and overlap the first parts 21,21a in the vertical direction. As a result, as described above, the load acting on the cask 9 at the time of collision can be reduced while reducing the size of the buffer structures 1, 1a as compared with the buffer structure provided with the mounting blocks having a uniform density.

As described above, it is preferable that the first portions 21 and 21a and the second portions 22, 22a are each formed of a foamed resin or a foamed metal. Thereby, the first portions 21 and 21a and the second portions 22, 22a having desired densities can be easily produced.

As described above, the design density of the lower density part of the first part 21,21a and the second part 22,22a is 0.1 g / cm ³ or more and 0.65 g / cm ³ or less. The design density of the portion having the higher density is preferably 0.2 g / cm ³ or more and 0.8 g / cm ³ or less. The actual density of the first sites 21 and 21a is 90% or more and 110% or less of the design density of the first sites 21 and 21a, and the actual density of the second sites 22 and 22a is the second site 22. , 22a is preferably 90% or more and 110% or less of the design density. As a result, deviation of the densities of the first sites 21 and 21a and the second sites 22 and 22a from the design values is suppressed, and the first sites 21 and 21a and the second sites 22 and 22a having desired densities can be easily obtained. Can be obtained.

As described above, the buffer structure 1, 1a includes the first portion 21,21a and the second portion 22, 22a, and the mounting block 2 is mounted on the floor surface 81 and receives the cask 9 that falls from above. , 2a are further provided. The first portions 21 and 21a are located at the uppermost stage of the mounting blocks 2 and 2a, and have an upper surface that is larger than the end surface of the cask 9 and extends in the horizontal direction. The second portions 22, 22a abut on the lower surface of the first portions 21, 21 a. As a result, the buffer structures 1, 1a can be miniaturized in the vertical direction, and the load acting on the cask 9 when colliding with the cask 9 falling from above toward the floor surface 81 can be reduced. ..

As described above, in the buffer structure 1 shown in FIG. 2, the density of the first site 21 is lower than the density of the second site 22. In this way, by first receiving the dropped cask 9 by the low-density first portion 21, the first portion 21 is greatly deformed at the contact portion with the cask 9. As a result, the load acting on the cask 9 immediately after the contact with the mounting block 2 can be reduced. Further, when the dropped cask 9 is stopped on the buffer structure 1, the buried length of the cask 9 in the mounting block 2 (that is, the length of the portion of the cask 9 stuck in the mounting block 2). Therefore, it is possible to preferably prevent the cask 9 from bouncing off the mounting block 2 or falling toward the surroundings.

On the other hand, in the buffer structure 1a shown in FIG. 6, the density of the first portion 21a is higher than the density of the second portion 22a. In this way, by first receiving the dropped cask 9 by the high-density first portion 21a, the stress at the time of dropping the cask 9 propagates through the first portion 21a and reaches the low-density second portion 22a. By, it spreads widely in the horizontal direction. Therefore, the second portion 22a is greatly deformed over a wide range. As a result, the load acting on the cask 9 immediately after the contact with the mounting block 2a can be reduced.

As described above, it is preferable that the first portions 21 and 21a are provided with a plurality of first buffer layers 211 each having a flat plate shape extending in the horizontal direction and laminated in the vertical direction. As a result, when the stress at the time of dropping the cask 9 propagates downward through the first portions 21 and 21a, the spread of the stress in the horizontal direction is caused by slipping of each of the two first buffer layers 211 adjacent in the vertical direction. Is suppressed by. As a result, it is possible to prevent the first portions 21 and 21a from splitting and greatly reducing the amount of fall energy absorbed, and it is possible to prevent the cask 9 from penetrating the first portions 21 and 21a.

Further, it is preferable that the second portions 22, 22a are provided with a plurality of second buffer layers 221 each having a flat plate shape extending in the horizontal direction and being laminated in the vertical direction. As a result, when the stress at the time of dropping the cask 9 propagates downward through the second portions 22, 22a, the spread of the stress in the horizontal direction is caused by slipping of each of the two second buffer layers 221 adjacent in the vertical direction. Is suppressed by. As a result, it is possible to prevent the second portions 22 and 22a from splitting and greatly reducing the amount of fall energy absorbed, and it is possible to prevent the cask 9 from penetrating the second portions 22 and 22a.

As described above, it is preferable that each of the plurality of first buffer layers 211 includes a plurality of first plate members 212 that are continuously arranged in the horizontal direction. Further, the boundary line between the two first plate members 212 that are horizontally adjacent to each other in the first buffer layer 211 is the first in the other first buffer layer 211 that is vertically adjacent to the first buffer layer 211. It is preferable that it overlaps with the main surface of one plate member 212. In this way, in the first portions 21 and 21a, the plurality of first plate members 212 are laminated by netting, so that the cask 9 is formed along the boundary line between the first plate members 212. It is possible to suppress the penetration of 21a.

Further, it is preferable that each of the plurality of second buffer layers 221 includes a plurality of second plate members 222 continuously arranged in the horizontal direction. Further, the boundary line between the two second plate members 222 horizontally adjacent to each other in the first second buffer layer 221 is the first in the other second buffer layer 221 vertically adjacent to the first second buffer layer 221. It is preferable that it overlaps with the main surface of the two-plate member 222. In this way, in the second portion 22, 22a, the plurality of second plate members 222 are laminated by netting, so that the cask 9 is formed along the boundary line between the second plate members 222. It is possible to suppress the penetration of 22a.

As described above, it is preferable that each of the first plate members 212 is point-bonded to other first plate members 212 adjacent in the vertical direction by an adhesive at a plurality of bonding points located at the outer edge portion. By adhering the first plate members 212 adjacent to each other in the vertical direction in this way, it is possible to prevent the first plate member 212 from scattering upward due to the collision with the cask 9. In addition, it is possible to facilitate the transportation of the first parts 21 and 21a and the positioning of the first plate member 212 at the time of manufacturing. Further, by adhering the first plate members 212 adjacent to each other in the vertical direction to each other as a point bond, it is possible to suppress the inhibition of slippage between the first buffer layers 211 adjacent to each other in the vertical direction, and the first portion 21, When the stress propagates downward in 21a, the spread of the stress in the horizontal direction can be suitably suppressed. As a result, the splitting of the first sites 21 and 21a can be suppressed.

Further, it is preferable that each second plate member 222 is point-bonded with another second plate member 222 adjacent in the vertical direction at a plurality of bonding points located at the outer edge portion by an adhesive. By adhering the second plate members 222 that are adjacent to each other in the vertical direction in this way, it is possible to prevent the second plate member 222 from scattering upward due to the collision with the cask 9. Further, it is possible to facilitate the transportation of the second parts 22 and 22a and the positioning of the second plate member 222 at the time of manufacturing. Further, by adhering the second plate members 222 adjacent to each other in the vertical direction to each other as a point bond, it is possible to suppress the inhibition of slippage between the second buffer layers 221 adjacent to each other in the vertical direction, and the second portion 22, When the stress propagates downward in 22a, the horizontal spread of the stress can be suitably suppressed. As a result, the splitting of the second sites 22, 22a can be suppressed.

The side surfaces of each first plate member 212 may be joined to other horizontally adjacent first plate members 212 by an adhesive. As a result, it is possible to prevent the first plate member 212 from scattering upward due to the collision with the cask 9. In addition, it is possible to facilitate the transportation of the first parts 21 and 21a and the positioning of the first plate member 212 at the time of manufacturing.

Further, the side surfaces of each second plate member 222 may be joined to each other by an adhesive with another second plate member 222 adjacent in the horizontal direction. As a result, it is possible to prevent the second plate member 222 from scattering upward due to the collision with the cask 9. Further, it is possible to facilitate the transportation of the second parts 22 and 22a and the positioning of the second plate member 222 at the time of manufacturing.

As described above, it is preferable that the buffer structures 1, 1a further include a casing 3 that covers the side surfaces of the mounting blocks 2, 2a. As a result, it is possible to prevent the mounting blocks 2 and 2a from expanding laterally due to the collision of the dropped cask 9. As a result, it is possible to prevent the mounting blocks 2 and 2a from splitting, and it is possible to suitably reduce the load acting on the cask 9 at the time of collision.

As described above, it is preferable that the side wall portions 32 of the casing 3 are provided with a plurality of through holes 33, each of which extends in the horizontal direction. As a result, the casing 3 is easily deformed in the vertical direction. Therefore, even if the cask falling from above collides with the upper end portion of the casing 3, the casing 3 is easily deformed downward to absorb the impact, so that the load acting on the cask 9 at the time of collision can be reduced. Can be done. Further, even when the cask 9 is received by the mounting blocks 2 and 2a, the air in the casing 3 is released from the through hole 33, so that the deformation of the mounting blocks 2 and 2a can be promoted.

As described above, the side wall portion 32 of the casing 3 is provided with a reinforcing member 34 extending in the horizontal direction. Therefore, it is possible to prevent the side wall portion 32 from being deformed (that is, bulging outward) due to the force transmitted from the mounting blocks 2 and 2a to the side wall portion 32 of the casing 3 when colliding with the cask 9. ..

Further, in the buffer structure 1 shown in FIG. 2, the force transmitted from the high-density second portion 22 to the side wall portion 32 at the time of collision with the cask 9 is the force transmitted from the low-density first portion 21 to the side wall portion 32. Greater than Therefore, in the casing 3, the plurality of reinforcing members 34 are preferably arranged in a region below the central portion in the vertical direction of the side wall portion 32 (that is, a region facing the second portion 22). As a result, deformation of the side wall portion 32 at the time of collision with the cask 9 can be further suppressed.

As described above, the buffer structures 1, 1a preferably further include a cover 4 that covers the upper surfaces of the mounting blocks 2, 2a. As a result, it is possible to prevent the mounting blocks 2 and 2a from scattering upward when colliding with the cask 9. Further, it is possible to prevent the quality deterioration of the mounting blocks 2 and 2a due to contact with a liquid such as water and the quality deterioration of the mounting blocks 2 and 2a due to ultraviolet rays.

Various changes can be made in the buffer structures 1, 1a described above.

For example, the design densities of the first sites 21 and 21a and the second sites 22, 22a are not necessarily limited to the above range and may be changed in various ways. Further, the difference between the design density of the first portions 21 and 21a and the second portions 22, 22a and the actual density is not necessarily limited to the above range.

In the mounting blocks 2 and 2a, the joining mode such as the shape, position, and number of the bonding points between the first plate members 212 adjacent to each other in the vertical direction is not limited to the above example, and may be changed in various ways. Further, the first plate members 212 may not be joined to each other. The same applies to the joining of the second plate members 222 and the joining of the first plate member 212 and the second plate member 222.

In the first portions 21 and 21a, the plurality of first plate members 212 do not necessarily have to be laminated by netting, and may be laminated by another laminating method. Further, the first plate member 212 does not necessarily have to have a flat plate shape, and may be, for example, a curved plate shape. Alternatively, the plurality of first plate members 212 may be provided with irregularities having a stackable shape on the main surface. Each first buffer layer 211 does not necessarily have to be formed by a plurality of first plate members 212, and may be a single porous plate member spreading in the horizontal direction. Further, the first portions 21 and 21a do not necessarily have to be a laminated body of a plurality of first buffer layers 211, and may be one porous member.

At the second portions 22, 22a, the plurality of second plate members 222 do not necessarily have to be laminated by netting, and may be laminated by another laminating method. Further, the second plate member 222 does not necessarily have to have a flat plate shape, and may be, for example, a curved plate shape. Alternatively, the plurality of second plate members 222 may be provided with irregularities having a stackable shape on the main surface. Each second buffer layer 221 does not necessarily have to be formed by a plurality of second plate members 222, and may be a single porous plate member that extends in the horizontal direction. Further, the second portions 22, 22a do not necessarily have to be a laminated body of a plurality of second buffer layers 221 and may be one porous member.

The mounting block 2 may include a part other than the first part 21 and the second part 22. For example, the mounting block 2 may have a three-stage structure including a third portion that abuts on the lower surface of the second portion 22. The density of the third site may be, for example, equal to or higher than the density of the second site 22, may be a density between the first site 21 and the second site 22, and may be equal to or lower than the density of the first site 21. It may be. The mounting block 2 may have a structure of four or more stages.

Similarly, the mounting block 2a may include a portion other than the first portion 21a and the second portion 22a. For example, the mounting block 2a may have a three-stage structure including a third portion that abuts on the lower surface of the second portion 22a. The density of the third portion may be, for example, less than or equal to the density of the second portion 22a, may be the density between the first portion 21a and the second portion 22a, and may be greater than or equal to the density of the first portion 21a. It may be. The mounting block 2a may have a structure of four or more stages.

The shapes of the mounting blocks 2 and 2a and the casing 3 may be variously changed, and may be, for example, cylindrical. Further, in the casing 3, the through hole 33 and the reinforcing member 34 may be omitted, respectively. In the buffer structures 1, 1a, the casing 3 and the cover 4 may be omitted, respectively.

In the above example, the laying type cushioning structures 1, 1a have been described, but the above structure is applied to the mounting type cushioning structure 1b attached to the longitudinal end of the cask 9 as shown in FIG. May be done. Although only one end of the cask 9 is shown in FIG. 8, the buffer structure 1b is attached to both ends of the cask 9 in the longitudinal direction.

As shown in FIG. 8, the buffer structure 1b includes a first portion 21b formed of a porous material and a second portion 22b that overlaps the first portion 21b in the vertical direction. The second portion 22b is formed of a porous material having a density different from that of the first portion 21b. As a result, it is possible to reduce the load acting on the cask 9 at the time of collision while reducing the size of the buffer structure 1b, substantially similar to the above-mentioned buffer structures 1 and 1a.

In the example shown in FIG. 8, the buffer structure 1b has a substantially cylindrical shape and abuts on the side surface of the longitudinal end surface of the cask 9 and the outer peripheral portion of the longitudinal end surface. The first portion 21b is arranged at a portion (that is, an inner peripheral portion) of the buffer structure 1b that abuts on the cask 9. The second portion 22b is provided on the radial outer side of the first portion 21b and on the side opposite to the cask 9 in the longitudinal direction. The density of the first site 21b is lower than the density of the second site 22b. As a result, even when the cask 9 falls in various postures, the energy at the time of the fall is absorbed by the large deformation of the low-density first portion 21b, so that the load acting on the cask 9 is reduced. To. The density of the first portion 21b may be higher than the density of the second portion 22b.

The fall of the cask 9 means a free fall from the lifted state and a downward movement of the upper end of the cask 9 due to a fall of the cask 9 in a vertical posture (that is, a posture in which the longitudinal direction is parallel to the vertical direction). It is a concept that includes (that is, the fall of the upper end). The drops in various postures of the cask 9 include a vertical fall in which the central axis of the cask 9 falls in a vertical direction, a horizontal fall in which the central axis falls in a horizontal direction, and a central axis. Is a concept that includes a corner fall in which the player falls in a posture of tilting in the vertical direction and the horizontal direction.

The above-described embodiments and configurations in the respective modifications may be appropriately combined as long as they do not conflict with each other.

1,1a, 1b Buffer structure 2,2a Mounting block 3 Casing 9 Casing 21,21a 1st part 22, 22a 2nd part 81 Floor surface 211 1st buffer layer 212 1st plate member 221 2nd buffer layer 222 2-plate member

Claims (10)

A buffer structure that absorbs impact between the cask and the floor surface when a columnar cask containing a fuel assembly falls.
The first part formed of a porous material and
A second site that is formed of a porous material having a density different from that of the first site and that overlaps the first site in the vertical direction.
A buffer structure characterized by comprising. The buffer structure according to claim 1.
A buffer structure characterized in that the first portion and the second portion are each formed of a foamed resin or a foamed metal. The buffer structure according to claim 1 or 2.
The design density of the lower density part of the first part and the second part is 0.1 g / cm ³ or more and 0.65 g / cm ³ or less, and the design density of the higher density part is , 0.2 g / cm ³ or more and 0.8 g / cm ³ or less,
The actual density of the first part is 90% or more and 110% or less of the design density of the first part.
A buffer structure characterized in that the actual density of the second portion is 90% or more and 110% or less of the design density of the second portion. The buffer structure according to any one of claims 1 to 3.
In addition to including the first portion and the second portion, a mounting block that is mounted on the floor surface and receives a cask that falls from above is further provided.
The first portion is located at the uppermost stage of the above-mentioned placed block, and has an upper surface that is larger than the end face of the cask and extends in the horizontal direction.
The second portion is a buffer structure characterized in that it abuts on the lower surface of the first portion. The buffer structure according to claim 4.
A buffer structure characterized in that the density of the first site is lower than the density of the second site. The buffer structure according to claim 4.
A buffer structure characterized in that the density of the first site is higher than the density of the second site. The buffer structure according to any one of claims 4 to 6.
The first portion includes a plurality of first buffer layers, each of which has a flat plate shape extending in the horizontal direction and is laminated in the vertical direction.
Alternatively, the second portion is a buffer structure comprising a plurality of second buffer layers each having a flat plate shape extending in the horizontal direction and laminated in the vertical direction. The buffer structure according to claim 7.
Each of the plurality of first buffer layers includes a plurality of first plate members arranged continuously in the horizontal direction, and the boundary line between the two horizontally adjacent first plate members in one first buffer layer is , Overlapping with the main surface of the first plate member in the other first buffer layer adjacent to the first buffer layer in the vertical direction.
Alternatively, each of the plurality of second buffer layers includes a plurality of second plate members arranged continuously in the horizontal direction, and a boundary between two horizontally adjacent second plate members in one second buffer layer. The line is a buffer structure characterized in that it overlaps with the main surface of the second plate member in another second buffer layer adjacent to the first second buffer layer in the vertical direction. The buffer structure according to claim 8.
Each first plate member is point-bonded to other first plate members adjacent in the vertical direction by an adhesive at a plurality of bonding points located at the outer edge portion.
Alternatively, the buffer structure is characterized in that each second plate member is point-bonded to another second plate member adjacent in the vertical direction by an adhesive at a plurality of bonding points located at the outer edge portion. The buffer structure according to any one of claims 4 to 9.
A cushioning structure further comprising a casing that covers the sides of the above-described block.

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