JP4410072B2 - Cask - Google Patents

Description

  The present invention relates to a cask that contains and stores spent nuclear fuel assemblies that have finished burning, and more particularly to a cask that includes a cask buffer that relieves impact force applied to the cask from the outside.

  In the field of handling nuclear fuel, a nuclear fuel assembly that has finished burning at the end of the nuclear fuel cycle is called spent fuel.

  Since this spent fuel contains a highly radioactive substance, heat is generated by the fission reaction. For this reason, for example, at a nuclear power plant, spent fuel is cooled in a cooling pit, for example, for 6 months, then stored in a cask (shielded container), transported by truck, ship, etc. Stored in a treatment facility.

  The cask transferred to the reprocessing facility by truck is over 100 tons including spent fuel to be accommodated, and falls during the transfer due to some impact force from the outside in an unstable state. Or if it falls and cracks or breakage occurs, it may cause a serious accident.

  For this reason, in recent caskes, a cask buffer body is provided on both ends of the cask body (body), and the impact force from the outside is absorbed by the cask buffer body. The action is mitigated.

Recently, for example, a cask cushion is filled with wood as a shock-relieving material in a thin metal shell, and has a technology that selects wood with high absorption capacity against external impact force. For example, it is disclosed in Japanese Patent Application Laid-Open No. 2001-83291 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2002-31186 (Patent Document 2).
JP 2001-83291 A JP 2002-31186 A

  The technique disclosed in Japanese Patent Application Laid-Open No. 2001-83291 and Japanese Patent Application Laid-Open No. 2002-31186, when using wood for a cask buffer, it is arranged using the grain of the wood, and balsa material as the arranged wood Although it is effective in selecting redwood laminated timber and suppressing variation in impact absorption characteristics of the wood, the following problems are still raised.

The above-mentioned technique assumes a fall accident or a fall accident during transportation or loading / unloading, for example, and as shown in FIG. respectively thin regions _a 1, _{a 2} of the body 2, and partition ... in the regions _a 1, _{a 2} was partitioned, ... for each and combined into one timber covered with the jacket, the block _{B 1} , B ₂ ,..., C ₁ , C ₂ ,.

However, each of the wood materials as the blocks B ₁ , B ₂ ,..., C ₁ , C ₂ ,... Housed in the areas A ₁ , A ₂ ,. Further, the grain directions AR ₁ , AR ₂ ,... Are aligned in the same direction within one region.

Therefore, when a compressive force is applied to the entire blocks B ₁ , B ₂ ,..., C ₁ , C ₂ ,..., Cracks occur in one of the woods constituting the block B ₁ , for example. Since the surrounding wood is the same material and the grain is aligned in the same direction, the surrounding wood bears a compressive force and cannot bear and resist, as shown in FIG. As described above, plastic deformation is induced from the compressive stress σc, and finally, it is broken or broken, so that the compressive stress σc is directly received by the cask main body 1 itself, which leads to a dangerous state.

Further, each of the blocks B ₁ , B ₂ ,..., C ₁ , C ₂ ,... Housed in each of the divided areas A ₁ , A ₂ ,. In addition, even when the grain directions AR ₁ , AR ₂ ,... Are aligned in the same direction within one region, the impact force is not necessarily applied from the same direction.

  For example, when the cask main body 1 falls, an impact force may be applied from the axial direction of the cask main body 1 or an impact force may be applied from a direction intersecting the axial direction of the cask main body 1. Further, the impact force may be applied from the oblique direction of the cask main body 1, that is, from the corner portion of the cask impact bodies 2 and 3.

  Here, the wood covered with the jacket and serving as one component of the cask buffers 2 and 3 has a property that the compressive force varies depending on the direction of the grain.

  Therefore, when the cask buffers 2 and 3 are made of the same kind of wood, it is difficult to reduce the impact force from various directions when used regardless of the grain direction of the wood.

  Moreover, in order to absorb and relieve the impact force that gives the cask main body 1 a falling posture, the cask cushions 2 and 3 have a technique and arrangement in which the impact force is applied in a direction parallel to the wood grain direction. is there.

  However, even with this method and arrangement, depending on the form of damage to the wood, it may appear in a direction that intersects the grain direction. When an impact force is applied in the direction intersecting the grain direction of the wood, the wood will buckle, and the deformation force generated during the buckling is urged one after another to the adjacent wood, and finally the jacket covering the wood. May lead to damage.

  Further, there is a possibility that stress concentration may occur in the corner portion of the jacket covering the wood. When the cask main body 1 is dropped, an impact force is applied to the stress concentration and the jacket is damaged. There is a possibility that it may jump out and cause a fire, and may not be able to maintain its original role as a cask buffer.

  The present invention has been made based on such circumstances, and even when an impact force is applied in a direction intersecting the grain direction of the wood constituting the cask buffer, the wood is buckled based on the impact force. An object of the present invention is to provide a cask that suppresses the deforming force so that the deforming force generated on the wood is not urged one after another on the adjacent wood and damages the jacket, thereby maintaining the cask buffer safely.

Cask according to the present invention, in order to achieve the above object, the both ends of the cask body for accommodating the spent fuel assemblies, is accommodated as a block in the space chamber surrounded by jacket collectively cushioning element In the cask provided with the cask buffer, the impact force absorber is provided in the outer casing, and the buffer elements are collectively accommodated as blocks in the space chamber, while the buffer elements gathered as blocks are stored in one region. When storing, the same type of material and the grain direction are aligned in the same direction, and between the buffer elements to be accommodated in the adjacent area, the direction of the adjacent buffer elements crossing each other is made different. A balsa, a sheet metal honeycomb, and a urethane foam covering the entire area of the buffer element between the outer cover and the buffer element and configured as a belt-like continuous body It is characterized in that the interposing et selected shock absorber made of soft material.

  The cask according to the present invention is a block in which buffer elements that are arranged differently by crossing the grain direction for each region are arranged in a region in a cask buffer body formed by overlapping an outer jacket, an impact force absorber, and the like. As a block, the shock absorbing element and the shock absorbing body that are combined into a single block absorb the impact force from the outside. It is possible to protect the corner portion of the jacket covering the cask buffer body and the cask main body from damage, and the cask main body and the like can be maintained safely.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of a cask according to the invention will be described with reference to the drawings and reference numerals attached to the drawings.

  1 to 3 are conceptual diagrams showing a first embodiment of a cask (shielding container) according to the present invention.

  1 is a partially broken perspective view showing the entire cask, FIG. 2 is a longitudinal sectional view of FIG. 1, and FIG. 3 is a side sectional view of a portion A in FIG. It is.

  As shown in FIGS. 1 to 2, the cask has a cask main body 5 formed in a horizontally long cylindrical shape, and the end portions 6 and 7 of the cask main body 5 are bulged in the radial direction so as to cover the cask. Buffer bodies (cask can bodies) 8a and 8b.

  Moreover, the cask main body 5 includes a cylindrical space chamber 12 constituted by, for example, a sheet metal outer shell 9, a neutron shielding resin 10, and a body 11 in order from the outer diameter side to the inner diameter side.

  In the space chamber 12, for example, a basket 13 which is incorporated in a lattice shape and extends in the axial direction is accommodated, and a spent nuclear fuel assembly 14 is accommodated in the basket 13.

  Further, the cask main body 5 is provided with a double-structured lid of a primary lid 15 and a secondary lid 16 on one end portion 6 side, so that the space chamber 12 that accommodates the basket 13 is securely sealed. . The casing 9 is provided with a suspension fitting 17 such as a trunnion for lifting and moving the cask body 5.

  On the other hand, each of the end portions 6 and 7 of the cask main body 5 is provided with a cask buffer body (cask can body) 8a and 8b.

As shown in FIGS. 1 to 3, the cask buffer bodies (cask can bodies) 8 a and 8 b are covered with a jacket 21 made of, for example, a stainless steel thin plate, and the corner portion of the jacket 21 is welded and connected. , area _a 1 that partitions thinner therein, _{a 2,} ... cushioning element 18a each, 18b filling, accommodating, filling, accommodating the damping elements 18a, 18b, ... the block 19a, 19b, ... one on the It is summarized.

  In addition, the cask buffer bodies 8a, 8b are disposed between the outer cover 21 and the buffer elements 18a, 18b,... Combined as a block 19a, 19b,. An impact force absorber 20 is provided so as to cover it.

  The buffer elements 18a, 18b,... Are made of a relatively hard material, for example, Douglas fir ply or oak, and are made of the same type of material in one region, and the grain direction AR is aligned in the same direction from the outside. Addressing the impact force applied.

  However, it is only in one area that the grain directions AR of the buffer elements 18a, 18b,... Are aligned in the same direction, and the grain directions AR are arranged in a direction crossing each other in relation to adjacent areas. .

  In addition, the impact force absorber 20 interposed between the jacket 21 and the buffer elements 18a, 18b,... Is divided into some parts along the way, but is configured as a belt-like continuous body, for example, balsa, thin plate A soft material such as a metal honeycomb or urethane foam is used.

  Incidentally, as shown in FIG. 14, the conventional cask cushions 8a and 8b generate a compressive stress σc in the buffer elements 18a, 18b,... When an external impact force is applied. Even if σc can be absorbed, it will eventually become impossible to resist the compressive stress σc, the fibers of the buffer elements 18a, 18b,... will crack (buckling), and only the displacement in the transverse direction will increase. The corners and the like were broken.

However, in this embodiment, the urethane foam is formed between the outer casing 21 and the blocks 19a, 19b,..., Which are relatively hard materials, for example, buffer elements 18a, 18b,. Since the impact force absorber 20 made of a soft material such as is interposed and the grain direction AR of the buffer elements 18a, 18b,... Is different for each of the areas A ₁ , A ₂ ,. When the impact force applied from the outside is not strong, the impact force absorber 20 is used to prevent the cask main body 5 from being affected.

In addition, when the impact force applied from the outside is strong, in the present embodiment, in addition to the impact force absorber 20 formed of a soft material, the buffer elements 18a, 18b,. Are provided as blocks 19a, 19b,..., And the grain directions AR of the buffer elements 18a, 18b,... Are made different for each of the areas A ₁ , A ₂ ,. Therefore, as shown in FIG. 15, the strength of the compressive stress σc can be further increased as compared with the compressive stress σc shown in FIG. 14, and the corner portion of the outer cover 21 is damaged under high strength. The cask main body 5 can be maintained in a safe state.

In this way, the present embodiment combines the impact force absorber 20 made of a soft material and the buffer elements 18a, 18b,... Made of a hard material, and the regions A ₁ , of the buffer elements 18a, 18b,. Arrange the grain direction AR differently for each of A ₂ ,... And double and triple protection against impact force applied from the outside, so even if there is a strong impact force applied from the outside, the cask body 5 Can prevent and protect from breakage.

  FIG. 4 is a conceptual diagram showing a second embodiment of a cask according to the present invention. 4 is a partial cross-sectional view extracted from part A of FIG.

Cask buffer body 8a to apply to the cask according to the present invention (8b), the area _A 1, _{A 2,} envelope to Kutsugae設damping elements 18a, 18b, ... and made different by intersecting the grain direction AR to ... each For example, a shock absorber 20 made of a soft material such as balsa or urethane foam is provided between the _two and the boundary between the regions A ₁ , A ₂ ,... A restraint plate 22 made of resin or the like is provided. The grain direction of the impact force absorber 20 and the grain direction of the restraining plate 22 are aligned in the same direction.

As described above, in the present embodiment, the restraint plate 22 is provided in several peripheral areas of the boundary that partitions the regions A ₁ , A ₂ ,. Since the impact force absorber 20 is provided between the outer cover 21 and the outer cover 21, the impact force applied from the outside is equally shared by the triple and quadruple protective means, so there is a strong impact force applied from the outside. However, it is possible to protect and prevent the corner portion of the outer casing 21 from being damaged, and to maintain the cask body 5 in a safe state.

In the present embodiment, the restraint plate 22 is provided at some of the boundaries that define the regions A ₁ , A ₂ ,... The impact force absorber 20 is provided between the two, and the load applied from the outside is equally shared by the triple and quadruple protection means. However, the present invention is not limited to this example. The deformation preventing piece 23 that supports the restraining plate 22 and prevents deformation may be arranged in a direction intersecting the wood grain direction AR of the buffer elements 18a, 18b,... areas a _1, a 2, may be provided constraining plate 22 over _... the entire circumference of the boundary.

  FIG. 7 is a conceptual diagram showing a cask according to a fifth embodiment of the present invention. FIG. 7 is a partial cross-sectional view extracted from part A of FIG.

Cask buffer body 8a to apply to the cask according to the present invention (8b), the area _A 1, _{A 2,} envelope to Kutsugae設damping elements 18a, 18b, ... and made different by intersecting the grain direction AR to ... each For example, a shock absorber 20 made of a soft material such as balsa or urethane foam is provided between the _two and the boundary between the regions A ₁ , A ₂ ,... While the restraint plate 22 made of resin or the like is provided, the corner portion between the shock absorbing elements 18a, 18b,... And the impact force absorber 20 is made of a soft material such as a triangular shape such as urethane foam. A corner buffer 24 is provided, the impact force applied from the outside is absorbed by the corner buffer 24, and the prevention of breakage of the corner portion of the outer cover 21 welded and connected is enhanced.

  As described above, in the present embodiment, the corner buffer body 24 is provided at the corner portion between the buffer elements 18a, 18b,... And the impact force absorber 20, and the impact force applied from the outside is absorbed by the corner buffer body 24. In addition, since the corner portion of the outer cover 21 is protected and strengthened, the corner portion of the outer cover 21 can be prevented from being damaged.

  FIG. 8 is a conceptual diagram showing a sixth embodiment of a cask according to the present invention. FIG. 8 is a partial cross-sectional view extracted from part A in FIG.

Cask buffer body 8a to apply to the cask according to the present invention (8b), the area _A 1, _{A 2,} envelope to Kutsugae設damping elements 18a, 18b, ... and made different by intersecting the grain direction AR to ... each For example, an impact force absorber 20 made of a soft material such as balsa or urethane foam is provided between the slider 21 and the sliding plate 25 made of a thin metal plate between the impact force absorber 20 and the jacket 21. When an impact force is applied from the outside, the sliding plate 25 is slid to relieve the impact force, thereby preventing the corner portion of the outer cover 21 from being damaged.

  As described above, according to the present embodiment, a sliding plate 25 that is slidable is provided between the impact force absorber 20 and the outer cover 21, and the sliding plate 25 is slid to apply an impact applied from the outside. Since the force is relaxed and the corner portion of the outer cover 21 is prevented from being damaged, the corner portion of the outer cover 21 can be maintained in a stable state even when an impact force is applied from the outside.

  In the present embodiment, the cask buffer 8a (8b) is triple and quadruple protected and strengthened, so that it is possible to sufficiently cope with a fire accident.

  In the present embodiment, the slidable sliding plate 25 is provided between the impact force absorber 20 and the outer jacket 21, but the present invention is not limited to this example. For example, as shown in FIG. A heat-resistant paint layer 26 may be formed between the force absorber 20 and the outer cover 21 to cope with a fire accident.

  FIG. 10 is a conceptual diagram showing an eighth embodiment of a cask according to the present invention. FIG. 10 is a partial cross-sectional view extracted from part A in FIG.

The cask buffer body 8a (8b) applied to the cask according to the present invention includes the area A ₁ , A ₂ ,... Of the area A ₁ , A ₂ ,. ₁ , a first buffer portion 27 made of a hard material, for example, oak, Douglas fir ply, or the like is disposed in the center portion, and the characteristics of the materials are sequentially directed toward the outer diameter side with respect to the first buffer portion 27. And a second buffer portion 28 for gradually transferring the hard material to the soft material, for example, a final end portion 29 made of a soft material such as urethane foam or foamed resin, and the first buffer at the center portion. The fourth buffer part 30 and the fifth buffer part 31, for example, urethane foam, foamed resin, etc., which change the characteristics of the materials in order toward the inner diameter side with respect to the part 27 and gradually transfer the hard material to the soft material. Place the final end 32 made of soft material Filling the first buffer block body 33 solidified by compressing the respective buffer portions in blocks, in which were housed.

In the region A _2, a hard material in the central portion, for example, oak, placing a buffer portion 35 prepared in Douglas Fir ply or the like, and both sides of the cushioning portion 35, such as urethane foam, soft like foamed resin The final end portions 36a and 36b made of a material are arranged, and the second buffer block body 34, in which these buffer portions are compressed and solidified in a block shape, is filled and accommodated. In the remaining areas A ₃ , A ₄ ,..., The first buffer block body 33 and the second buffer block body 34 are alternately filled and accommodated. The grain directions AR of the block bodies 33, 34,... Are aligned in the same direction in one area, and are arranged so as to be different from each other by intersecting in relation to adjacent areas.

As described above, in the present embodiment, the first buffer block body 33, the second buffer block body 34,..., Which are made by compressing and solidifying wood having different characteristics to form blocks, the outer cover 21, the heat resistant paint layer 26, and the impact force absorption. When the region A ₁ , A ₂ ,... Formed by overlapping the body 20 is filled and accommodated and an impact force is applied from the outside, the first buffer block body 33 and the second buffer block body 34. Since it is configured to bulge, even if an impact force is applied from the outside, the first buffer block body 33, the second buffer block body 34... Bulge outward, and the impact force is absorbed by the bulge output. It is possible to prevent breakage of the corner portion of the jacket 21.

In the present embodiment, the first buffer block body 33, the second buffer block body 34,..., Which are made by compressing and solidifying the buffer portions having different characteristics to form blocks, the outer cover 21, the heat-resistant paint layer 26, and the impact force absorber. The regions A ₁ , A ₂ ,... Formed by overlapping 20 are filled and accommodated. However, the present invention is not limited to this example. For example, as shown in FIG. 11, a first buffer block body 33 and a second buffer block body 34 are used. Each block body of ... may be surrounded by a restraint plate 37 to strengthen the restraint force.

  FIG. 12 is a conceptual diagram showing a tenth embodiment of a cask according to the present invention. FIG. 12 is a partial cross-sectional view extracted from part A in FIG.

The cask buffer 8a (8b) applied to the cask according to the present invention has different characteristics in the regions A ₁ , A ₂ ,... Formed by overlapping the outer cover 21, the heat-resistant paint layer 26, and the impact force absorber 20. For example, an isotropic aggregate 38 in which pieces of wood such as oak, Douglas fir ply, cedar, and pine are compressed and solidified into a block shape is filled and contained as a buffer material.

As described above, in the present embodiment, the isotropic accumulation body 38 is filled and accommodated in the regions A ₁ , A ₂ ,... Formed by overlapping the outer jacket 21, the heat resistant paint layer 26, and the impact force absorber 20. Therefore, it is possible to absorb the load evenly in the entire area of the isotropic stack 38 against the impact force applied from the outside, and to prevent the corner portion of the outer cover 21 from being damaged.

The partially broken perspective view which shows the whole cask which concerns on this invention. The longitudinal cross-sectional view of FIG. The sectional side view which shows 1st Embodiment of the cask which concerns on this invention extracted from the A section of FIG. The conceptual diagram which shows 2nd Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 3rd Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 4th Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 5th Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 6th Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 7th Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 8th Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 9th Embodiment of the cask which concerns on this invention. The conceptual diagram which shows 10th Embodiment of the cask which concerns on this invention. The conceptual diagram which shows the conventional cask schematically. The diagram which shows the compressive stress and deformation amount of the conventional buffer for cask. The diagram which shows the compressive stress and deformation amount of the cask which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,5 Cask body 2 Cask buffer body 3 Cask buffer body 6 End portion 7 End portions 8a and 8b Cask buffer body 9 Cover 10 Resin 11 Body 12 Space chamber 13 Basket 14 Used nuclear fuel assembly 15 Primary lid 16 Secondary lid 17 Suspension bracket 18a, 18b,... Buffer element 19a, 19b,... Block 20 Impact force absorber 21 Outer jacket 22 Restraint plate 23 Deformation prevention piece 24 Corner buffer body 25 Sliding plate 26 Heat resistant paint layer 27 First buffer Part 28 second buffer part 29a, 29b final end part 30 fourth buffer part 31 fifth buffer part 32 final end part 33 first buffer block body 34 second buffer block body 35 buffer part 36a, 36b final end part 37 restraint plate 38 Isotropic Aggregates

Claims (13)

Both ends of the cask body for accommodating the spent fuel assemblies in a cask having a cask buffer body to accommodated as a block in the space chamber surrounded by jacket together cushioning element, the impact on the outer within the object While including a force absorber and accommodating the buffer elements together as a block in the space chamber, when accommodating the buffer elements combined as a block in one region, the same kind of material and the grain direction in the same direction Between the cushioning elements to be accommodated in the adjacent region, the direction of the graining of the neighboring cushioning elements intersects each other and is different from each other, and the cushioning element is arranged between the jacket and the cushioning element. balsa configured as strip-shaped continuous body covering the entire area, thin metal honeycomb, the interposing shock absorber made of soft selected from urethane foam material Cask and features. The area for accommodating the buffer elements collected in a block includes a restraint plate selected from thin wood, metal, and resin, and the shock absorber is provided between the restraint plate and the outer cover. The cask according to claim 1. The cask according to claim 2, wherein the restraining plate is provided over an entire circumferential region that accommodates the buffer elements collected in a block. Region that accommodates the cushioning element, summarized in the block is provided with a thin plate of wood, metal, a constraining plate selected from a resin, Rutotomoni provided the shock absorber between the jacket and the constraining plate, the The cask according to claim 1, further comprising a deformation preventing piece that supports the restraining plate and prevents deformation of the buffer element . The cask according to claim 4, wherein the deformation preventing pieces are arranged in a direction intersecting a grain direction of the buffer elements collected in a block. The area for accommodating the cushioning elements collected in a block is provided with a corner cushion for protecting and strengthening the corner at a corner between the cushioning element and the shock absorber. The described cask. Cask according to claim 1, further comprising a sliding plate to slide when the external impact force is applied between the envelope and the impact force absorbing member. Cask according to claim 1, further comprising a heat-resistant paint layer between the envelope and the impact force absorbing member. The cushioning element collected as the block is a cushioning block obtained by compressing and solidifying a cushioning piece having different characteristics from the central part toward the outer diameter side and the inner diameter side, or from the central part toward both outer sides for each region in the space chamber. The cask according to claim 8, wherein the cask is a body. Claims, characterized in that the provided buffer block body region Laminated wood for accommodating a metal, a constraining plate selected from a resin, provided with the shock absorbing member between the casing and the restraining plate 9. The cask according to 9 . The buffer block body has a configuration in which a hard material is disposed at a central portion, and a soft material that is softer than the hard material is disposed at an end facing the outer diameter side, the inner diameter side, or both outer sides from here. The cask according to claim 9 or 10, characterized in that The cask according to claim 11, wherein the hard material is selected from oak and Douglas fir ply. The cask according to claim 11, wherein the soft material is one selected from urethane foam and foamed resin.

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