JP2008064767A - Radioactive material container and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To absorb the axial thermal elongation of a neutron shield. <P>SOLUTION: A radioactive material container is equipped with a neutron shield consisting of a main trunk for shielding from radiation, an outer cylinder placed around the main trunk via heat-transfer fins, a precast resin placed in a space demarcated by the main trunk, the heat-transfer fins and the outer cylinder and a resin poured and solidified around the precast resin, and baskets which are placed in a cavity of the main trunk, are made of materials including neutron moderators and constitute cells for accommodating recycle fuel assemblies. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radioactive substance storage container for storing an assembly of fuel rods used for nuclear power generation for recycling and a method for manufacturing the same.

  A radioactive substance storage container called a cask for transporting a recycle fuel assembly from a nuclear power plant to a storage facility and storing it for a certain period is known. Normally, a cask is stored in each cell of a basket in which a PWR or BWR recycled fuel assembly is provided, and a γ-ray shielding barrel body is placed around the basket and a neutron consisting of a resin layer around it. This is a structure provided with a shield. The trunk body is provided with a plurality of heat transfer fins, and these penetrate through the neutron shield and are connected to the inner surface of the outer container.

  As an example of a conventional cask, a basket is housed in a thin inner container, and the inner container is housed in a thick outer container (see, for example, Patent Document 1). The inner container and the outer container constitute a trunk body that substantially shields the γ rays. Since the sealing performance is maintained by the inner container, the outer container only needs to have a γ-ray shielding function. Therefore, the outer container is assembled into a container shape by fixing a plurality of constituent materials with bolts, and the inner container has a structure in which a bottom plate is welded to a stainless steel cylinder, and the flange portion of the outer container Fixed to the end face. The basket has a structure in which, for example, plate materials including a neutron moderator are alternately combined into a confectionery shape, and a stainless steel square pipe is inserted into a lattice formed thereby. A neutron shield is filled between the outer container, the outer cylinder, and the heat transfer fin.

JP 2000-131491 (pages 3-5, FIG. 1)

  By the way, in the above-mentioned conventional cask, the neutron shield is filled in the space defined by the heat transfer fins and the outer cylinder and the outer container, and the inside of the cavity containing the recycled fuel assembly is about 200 ° C. As the temperature rises, the neutron shield softens, fluidizes inside, and falls downward due to the influence of gravity, so that a portion where no neutron shield exists can be generated.

  In addition, the neutron shield undergoes thermal elongation due to temperature rise. In particular, the total length of the recycled fuel assembly is close to 5 m, the length of the neutron shield itself reaches 5 m or more, and the thermal elongation in the cask axis direction is considerable. However, the configuration of the cask has a problem in that measures for the axial extension of the neutron shield are insufficient and the thermal elongation cannot be sufficiently absorbed.

  An object of the present invention is to provide a radioactive substance storage container that can prevent the neutron shield from being lost, or that can effectively absorb the thermal elongation in the axial direction of the neutron shield, and a method for manufacturing the same.

  In order to achieve the above-mentioned object, a radioactive substance storage container according to the present invention includes a bottomed integral trunk body that shields radiation, and an outer cylinder that is provided around the trunk body via a plurality of heat transfer fins. A space defined by the trunk body, the heat transfer fins, and the outer cylinder is divided in the axial direction by a dividing plate, and the resin is a precast neutron shield enclosed in the divided space, and in the cavity of the trunk body And a basket made of a material containing a neutron moderator and constituting a plurality of cells for storing the recycled fuel assemblies. Preferably, the dividing plate is provided obliquely or stepwise.

  A radioactive substance storage container according to the next invention includes a trunk main body having a bottomed shape that shields radiation, an outer cylinder provided around the trunk body via a plurality of heat transfer fins, the trunk main body, and the heat transfer fins. And a resin that is a neutron shield filled in a space defined by the outer cylinder, a resin injection port provided at an upper portion in a storage posture of a member that forms the space, and a cavity that is provided in the cavity of the trunk body, It is made of a material including a neutron moderator, and includes a basket that constitutes a plurality of cells that store the recycled fuel assemblies.

  A radioactive substance storage container according to the next invention includes a trunk main body having a bottomed shape that shields radiation, an outer cylinder provided around the trunk body via a plurality of heat transfer fins, the trunk main body, and the heat transfer fins. And a resin that is arranged in a space defined by the outer cylinder and is a neutron shielding body that is precast and has a plate on one surface and has an elastic body positioned between the plate and the trunk body or the outer cylinder And a basket which is provided in the cavity of the trunk body and is made of a material containing a neutron moderator and which constitutes a plurality of cells for storing the recycled fuel assemblies.

  A radioactive substance storage container according to the next invention includes a trunk main body having a bottomed shape that shields radiation, an outer cylinder provided around the trunk body via a plurality of heat transfer fins, the trunk main body, and the heat transfer fins. And a neutron shield composed of a precast resin disposed in a space defined by the outer cylinder and injected and solidified around the precast resin; and a neutron moderator provided in the cavity of the trunk body And a basket that constitutes a plurality of cells that contain a recycled fuel assembly.

  A radioactive substance storage container according to the next invention includes a trunk main body having a bottomed shape that shields radiation, an outer cylinder provided around the trunk body via a plurality of heat transfer fins, the trunk main body, and the heat transfer fins. And a plurality of square pipes made of a material including a neutron moderator and a release material provided on the inner surface of the space defined by the outer cylinder, a neutron shield placed in the space, and a cavity of the trunk body And a basket constituting a plurality of cells for storing the recycled fuel assemblies.

  In the present invention, if the basket is formed using the square pipes, the surfaces of the square pipes come into contact with each other, and the decay heat of the recycled fuel assembly can be efficiently transmitted to the trunk body. For this reason, it is necessary to absorb the thermal elongation of the neutron shield, and in response to such a request, even if the neutron shield undergoes thermal elongation in the axial direction due to the release material provided on the inner surface of the space, the release material shields the neutron. The body itself slides to absorb the thermal elongation. Further, in the present invention, when an impact is applied to the inside due to dropping or the like during transportation, the square pipes are gathered in a face-to-face manner, so that it becomes easy to withstand the load.

  The radioactive substance storage container according to the next invention comprises an inner container in the shape of a bottomed integral container, and an outer container that constitutes a trunk body that shields radiation together with the inner container and is thicker than the inner container provided outside the inner container. The outer cylinder provided around the outer container via a plurality of heat transfer fins, the release material provided on the inner surface of the space defined by the outer container, the heat transfer fins and the outer cylinder, and put in the space A neutron shield on the side, provided in a cavity of the inner container, and provided in a basket constituting a plurality of cells for storing a recycled fuel assembly, and a lid attached to the bottom of the outer container and the opening of the inner container And a neutron shield on both ends.

  In this invention, the structure that absorbs the thermal expansion in the axial direction of the neutron shield provided on the side ensures the soundness of the side neutron shield and is attached to the bottom of the outer container and the opening of the inner container. By providing a neutron shield on the lid, it is possible to reliably trap neutrons.

   In the radioactive substance storage container according to the next invention, in the above-described configuration, the neutron shield is set to a length so as not to emit at least a certain amount of neutrons from the recycled fuel assembly to the outside in a state before thermal expansion. The axial thermal expansion margin formed by the outer cylinder and the short plate has a dimension suitable for the thermal elongation amount of the neutron shield.

  When the neutron shield is actively slid by the release material, neutron trapping must be performed reliably before and after stretching. For this reason, the length is set so as not to emit a certain amount of neutrons to the outside even in a state before thermal expansion.

  The radioactive substance storage container according to the next invention is characterized in that, in the above-mentioned configuration, the neutron shield is formed by molding a holding body having a large number of small spaces with a resin.

  The radioactive substance storage container according to the next invention has the above-described configuration, wherein the heat transfer fin has a cup-shaped cross section and a release material is provided in the cup, and a neutron having a predetermined gap from the top of the cup in contact with the outer cylinder. The exposed surface of the shield is present.

  A radioactive substance storage container according to the next invention includes a trunk main body having a bottomed shape that shields radiation, an outer cylinder provided around the trunk body via a plurality of heat transfer fins, the trunk main body, and the heat transfer fins. And a neutron shield having a structure in which a holder having a large number of small spaces is molded with a resin, and a recycle fuel assembly is provided in the cavity of the trunk body. And a basket constituting a plurality of cells to be stored.

  A radioactive substance storage container according to the next invention includes a trunk main body having a bottomed shape that shields radiation, an outer cylinder provided around the trunk body via a plurality of heat transfer fins, the trunk main body, and the heat transfer fins. And a neutron shield placed in a space defined by an outer cylinder, and a basket that is provided in a cavity of the trunk body and that constitutes a plurality of cells that store a recycled fuel assembly, the heat transfer fin The cross-section is cup-shaped, and the exposed surface of the neutron shield exists with a predetermined gap from the top of the cup in contact with the outer cylinder.

  The manufacturing method of the radioactive substance storage container according to the next invention includes a trunk body that shields γ rays constituting the radioactive substance storage container, a heat transfer fin that is thermally connected to the periphery of the trunk body, and a thermal transfer to the heat transfer fin. A holding body having a large number of small spaces is inserted into a mold having a shape corresponding to a space defined by an outer cylinder connected to the inner cylinder, and the resin is inserted into the holding body to allow the resin to enter the small spaces. Then, a neutron shield is formed, and the neutron shield is inserted into the space.

  In a method for manufacturing a radioactive substance storage container according to the next invention, a plurality of cup-shaped heat transfer fins are arranged in a space between a trunk body and an outer cylinder provided around the trunk body, and the heat transfer fins are connected to the trunk body and the outer casing. Before making contact with both of the tubes, the heat transfer fin is placed on the floor, and in that state, the resin is injected and solidified to form a neutron shield, and the exposed surface of the neutron shield is the top of the heat transfer fin. With the heat transfer fin inserted into the space, the top of the heat transfer fin is in contact with the outer cylinder, and the exposed surface of the outer cylinder and the neutron shield A thermal expansion margin is formed between the two.

  As described above, according to the radioactive substance storage container of the present invention, the release material is provided in the space defined by the trunk main body, the heat transfer fin, and the outer cylinder, so that the neutron shield itself can slide in the axial direction. The thermal elongation of the shield can be absorbed by its own slip.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same.

(Embodiment 1)
1 is an axial sectional view and a partial radial sectional view showing a cask according to Embodiment 1 of the present invention. The cask is disposed in a trunk body 1 that shields γ rays, a neutron shield 2 disposed around the trunk body 1, an outer cylinder 3 that houses the neutron shield 2, and a cavity 4 in the trunk body 1. And a basket 5. The basket 5 has a configuration in which a plurality of square pipes 6 are accommodated in the cavity 4, and constitutes a plurality of cells 7 in which recycled fuel assemblies used as fuel for nuclear power generation are accommodated. The square pipe 6 is made of, for example, a material obtained by adding boron or a boron compound to an aluminum material or an aluminum alloy. Boron may be added together with an aluminum base material, or boron powder may be mixed with aluminum powder and mixed by a mixer or mechanically alloyed by mechanical alloying. This square pipe 6 is formed by extruding a billet of boron aluminum alloy by a port hole die or the like.

  The trunk body 1 includes an inner container 8 mainly having a sealing function and an outer container 9 mainly having a γ-ray shielding function. The inner container 8 is thinner than the outer container 9 and is molded as a bottomed integral container. A flange 11 for attaching the lid 10 is formed on the opening side end face. The inner container 8 is made of a material having excellent corrosion resistance such as stainless steel. The inner container 8 needs to have a sealing property, but since it is thin, it can be integrally formed as a bottomed container, so there is no seam and sufficient sealing performance is maintained as long as the soundness of the structural material is maintained. The problem of leakage of radioactive materials does not occur. Furthermore, by not welding the bottom part to the cylinder part, problems such as generation of weld hardened portions of HAZ and leakage of radioactive substances such as weld cracks often found in stainless steel are not caused. In addition, when forming a bottomed cylinder shape by welding, it can apply to a cask if the soundness of welding is fully confirmed by implementation of various tests after welding construction.

  The outer container 9 is made of inexpensive carbon steel and has a bottomed container shape that is thicker than the inner container 8, and the inner container 8 is shrink-fitted inside the outer container 9. Moreover, the outer container 9 should just have a gamma ray shielding function, and the sealing function like the inner container 8 is not requested | required. For this reason, it is not necessary to integrally mold the outer container 9, and it is not necessary to completely weld and join the constituent members.

  Thus, the trunk body 1 is composed of the inner container 8 and the outer container 9, and the inner container 8 has corrosion resistance such as stainless steel and has a sealing function, while the outer container 9 has a sealing function. The cask 100 can be easily and inexpensively manufactured by using carbon steel that provides a shielding function and is inexpensive. Further, in order to enhance the strength and hermeticity of the outer container 9, it is better to butt weld the bottom plate 13 to the cylindrical body 12. For butt welding, high frequency induction welding, high frequency resistance welding, flash welding, or the like is used. Since welding is performed on substantially the entire contact surface between the cylindrical body 12 and the bottom plate 13, the sealing performance of the outer container 9 is improved and the mechanical strength is improved.

  The neutron shield 2 is composed of a resin 102 containing a predetermined amount of hydrogen, and is filled in a space (resin filling space 105) partitioned by the trunk body 1, the outer cylinder 3 and the heat transfer fins 17. This space 1056 is divided into a plurality of portions in the axial direction. The dividing plate 101 is welded obliquely, and the material thereof is the same as that of the heat transfer fin. The reason why the dividing plate 101 is welded obliquely is as follows. FIG. 2 is an explanatory diagram showing the softening flow of the neutron shield. In the divided space 105 partitioned by the dividing plate 101, as shown in FIG. 5A, a resin 102 precast at another place is enclosed. In this state, since the dividing plate 101 is inclined, the precast resin 102 is in contact with the outer surface of the outer container 9. A void layer 106 is formed between the outer cylinder 3 and the outer cylinder 3.

  Next, heat is applied to the resin 102 to soften the resin 102 and enter a fluid state. For this reason, the resin 102 moves to the void layer 106 and moves downward under the influence of gravity. For this reason, some space 107 is generated in the upper part, but since the dividing plate 101 is inclined, the resin 102 is also present above the dividing plate 101 of the space 107. Neutrons do not leak. As a shape having the same effect, the dividing plate 104 may be stepped as shown in FIG. Also in this case, even if the resin 102 is fluidized and a space is generated upward, the neutron does not leak because the resin 102 exists on the upper side across the dividing plate 104.

  Further, by dividing the divided space 105 between the outer cylinder 3 and the outer container 9 into a plurality of parts, it is possible to prevent a defective space of the resin 102 gathered upward. That is, the upper defective space that can be generated without the divided plate 101 is shared by the divided space 105, and streaming due to the resin defective space that can occur even in a small size may form the divided plate 101 diagonally or in a staircase shape. It can be solved by forming it. Further, the use of the precast resin 102 can simplify the manufacture of the cask. Injecting and solidifying the liquid resin over the entire resin filling space requires a longer casting time and requires a larger casting apparatus. However, each precast resin 102 is small, so it is easy to mold and casting time is short. A small casting machine is sufficient. The precast resin 102 only needs to be inserted into the resin filling space 105 when assembling an actual cask.

  The decay heat of the recycle combustion assembly is first transmitted through the basket 5 constituted by the square pipe 6, and is transmitted to the trunk body 1 through the spacer 16. The heat transmitted to the trunk body 1 is mainly transmitted to the outer cylinder 3 via the heat transfer fins 17 and is radiated to the outside. When the basket 5 is configured by using the square pipes 6, heat transfer is efficiently performed because they are in surface contact with each other. Further, the spacer 16 substantially contacts the body 1 and heat transfer to the body 1 is sufficiently performed. When a basket is made by alternately assembling plate materials made of neutron moderators and inserting stainless steel square pipes into the lattice, there are many contact interfaces, so the aluminum square pipe 6 is in surface contact. Compared with the basket 5 assembled in a state, heat transferability is inferior.

  Further, if the basket 5 having a structure in which the square pipes 6 formed by extruding the boron aluminum material are assembled, the number of cells can be increased even if the cavity shape of the inner container 8 is cylindrical. For example, in the case of a recycled fuel assembly of BWR fuel, one side is known to be about 150 mm. For this reason, the plate thickness of the material which comprises the basket 5 can be made small compared with what combines the board | plate material comprised with the neutron moderator in a grid | lattice form, and inserts a stainless steel square pipe in the grid | lattice, In the case of the cavity 4, the number of cells can be increased accordingly. In addition, the outer diameter can be reduced if the number of storage bodies is the same. That is, since the diameter of the trunk body 1 can be reduced if the outer shape is reduced, there is an advantage that the cask 100 can be drastically reduced in weight. The same applies to the recycled fuel assembly for PWR. In addition, when subjected to an impact load, if the square pipes 6 are gathered and are in close contact with each other, the portion where stress concentration occurs is reduced compared to a basket in which plate materials are assembled in a lattice shape, and there is a risk of breakage. Can be minimized.

  Moreover, it is preferable that the surface of the outer container 9 made of carbon steel is subjected to a rust prevention treatment with an overlay of stainless steel. Further, when the bottom plate 13 is bolted to the cylindrical body 12 of the outer container 9, a soft metal such as copper is interposed in the joining portion and a seal made of silicon or the like is provided on the outside in order to prevent moisture from entering inside. It is preferable to apply (not shown). Thereby, it is possible to prevent moisture from entering between the inner container 8 and the outer container 9 to cause electrolytic corrosion. Furthermore, when the bottom plate 13 of the outer container 9 is welded to the cylindrical body 12, a certain welding depth may be secured by electron beam welding, and a certain degree of sealing may be provided. The welding of the flange 11 and the outer container 9 end is the same. The sealing performance of the cask 100 can be further increased and the welding load can be reduced.

(Embodiment 2)
FIG. 4 is a partial axial sectional view showing a cask according to Embodiment 2 of the present invention. In the cask 200, as described in the first embodiment, the resin deficient space 201 can be formed above the resin filling space due to the flow of the resin as the neutron shielding material. Therefore, after the cask 200 is stored, when a deficient space 201 occurs in the resin filling space after a certain period of time, a liquid resin is injected from the resin injection port 202 provided in the end plate 3a, and the deficient space 201 is injected. Try to refill the resin. The resin inlet 202 of the end plate 3 a can be plugged with a bolt 203. In this way, since the resin deficient space 201 can be eliminated, neutron shielding can be performed reliably.

(Embodiment 3)
FIG. 5 is a perspective view and a partial sectional view showing a neutron shield of a cask according to Embodiment 3 of the present invention. In this cask, the resin 301 that is the neutron shield of the cask 100 of the first embodiment is precast in another place in advance, and as shown in FIG. 5A, the plate 302 is placed on one surface (surface on the outer cylinder side). The elastic body 303 is provided on the plate 302. The elastic body 303 is, for example, a rod-shaped body 303 a having a C-shaped cross section as shown in the figure, and the opening side is attached in a direction substantially parallel to the plate 302.

  The neutron shield 301 is inserted into a resin filling space 304 formed by the outer container 9, the outer cylinder 3 and the heat transfer fins 17 as shown in FIG. Press against the outer container 9. In addition, the elastic body 303 can be made of a material having good thermal conductivity, thereby contributing to improvement in heat dissipation. Even if the resin 301 softens due to the temperature rise in the cask and becomes in a fluid state, the elastic body 303 presses the resin 301 through the plate 302 by its elastic force, so even if the resin 301 fluidizes, The state can be maintained. That is, the resin 301 is prevented from flowing into the void layer due to the fluidization of the resin 301 by the plate 302, and as a result, a deficit space is generated by the volume fraction flowing into the void layer. It is preventing.

  For this reason, since a large defect space does not occur above the resin filling space 304, it is possible to reliably shield neutrons. The shape of the elastic body 303 is not limited to the rod-shaped body 303a having a C-shaped cross section. For example, as shown in FIG. 6A, a corrugated plate material 303b may be used. By inserting this neutron shield 301 into the resin filling space 304, the elastic body 303 acts to press the resin 301 against the outer container 9 through the plate 302 as shown in FIG. For this reason, even if the resin 301 is fluidized, a large defect space is not generated in the upper part. In addition, according to the corrugated plate material 303b, the contact area between the plate 302 and the outer cylinder 3 is increased, so that the heat conduction efficiency between them is improved. In the above embodiment, the elastic body 303 is disposed and inserted between the resin 301 and the outer cylinder 2, but the elastic body 303 may be disposed between the outer container 9 and the resin 301.

(Embodiment 4)
FIG. 7 is a partial axial cross-sectional view showing a cask according to Embodiment 4 of the present invention. FIG. 8 is a partial radial cross-sectional view of the cask shown in FIG. The cask 400 has substantially the same configuration as the cask of the first embodiment, but the pre-cast resin 401 is inserted into the resin filling space 404, and the liquid resin 402 is placed in the space between the filling space 404 and the resin 401. The difference is that it is filled by injection. The precast resin 401 is divided into several pieces in the axial direction, and is manufactured in another place and inserted into the resin filling space 404. A protrusion 403 is provided on the top of the precast resin 401. By providing a predetermined gap between the protrusion 403 and the upper resin 401, the liquid resin 402 can easily flow between the precast resin 401 and the precast resin 401 as shown in FIG. 9.

  Thus, by inserting the precast resin 401 into the resin filling space 404 and injecting and solidifying the liquid crystal resin 402 into the gap between the filling space 404 and the precast resin 401, there is no gap in the resin filling space 404. Resins 401 and 402 can be filled. The liquid resin 402 is injected from the resin injection port 405 of the end plate 3a. Further, if the precast material is inserted into the resin filling space 404 and then the gap is filled, the casting time of the resin 402 can be greatly shortened. That is, when a liquid resin is poured and solidified into the entire resin filling space 404, it is necessary to perform work with a large casting apparatus in consideration of the pot life, but according to the present invention, a separate small precast resin is required. Since 401 is molded and the gap is cast with a small amount of liquid resin 402, the casting apparatus can be downsized, and the casting time is greatly reduced.

  FIG. 10 is an axial sectional view showing another modified example of the cask. The cask 450 is characterized in that a release material 406 is applied to the inner surface of the resin filling space 404. The release material 406 is made of, for example, a silicon-based material or a material using polyvinyl alcohol (PVA) as a raw material. In addition to the release material 406, a material that satisfies the conditions that the resins 401 and 402 as the neutron shield 2 can be slid in the axial direction as a whole and can withstand high temperatures up to about 200 ° C. can be used. By providing the release material 406, the thermal elongation of the neutron shield 2 can be absorbed by the neutron shield 2 itself sliding in the axial direction. For this reason, the stress of the structure resulting from the thermal elongation in the axial direction of the neutron shield 2 can be relaxed.

  Examples of the mold release material 406 include “MOLD RELEASE QZ13” (trade name: Nagase ChemteX Corporation).

(Embodiment 5)
FIG. 11 is an axial sectional view showing the cask according to Embodiment 1 of the present invention. 12 is a radial cross-sectional view of the cask shown in FIG. The cask 500 is disposed in a trunk body 501 that shields γ rays, a neutron shield 502 disposed around the trunk body 501, an outer cylinder 503 that houses the neutron shield 502, and a cavity 504 in the trunk body 501. Basket 505. The basket 505 has a configuration in which a plurality of square pipes 506 are accommodated in a cavity 504, and constitutes a plurality of cells 507 that accommodate a recycled fuel assembly used as fuel for nuclear power generation. The square pipe 506 is made of, for example, a material obtained by adding boron or a boron compound to an aluminum material or an aluminum alloy. Boron may be added together with an aluminum base material, or boron powder may be mixed with aluminum powder and mixed by a mixer or mechanically alloyed by mechanical alloying. This square pipe 506 is formed by extruding a billet of boron aluminum alloy by a port hole die or the like.

  The trunk body 501 includes an inner container 508 mainly having a sealing function and an outer container 509 mainly having a γ-ray shielding function. The inner container 508 is thinner than the outer container 509 and is molded as a bottomed integral container. A flange 511 for attaching the lid 510 is formed on the opening side end face. The inner container 508 is made of a material having excellent corrosion resistance such as stainless steel. The inner container 508 needs to have a sealing property, but since it is thin, it can be integrally formed as a bottomed container, so there is no seam and sufficient sealing performance is maintained as long as the soundness of the structural material is maintained. The problem of leakage of radioactive materials does not occur. Furthermore, by not welding the bottom part to the cylinder part, problems such as generation of weld hardened portions of HAZ and leakage of radioactive substances such as weld cracks often found in stainless steel are not caused. In addition, when forming a bottomed cylinder shape by welding, it can apply to a cask if the soundness of welding is fully confirmed by implementation of various tests after welding construction.

  The outer container 509 is made of inexpensive carbon steel and has a bottomed container shape that is thicker than the inner container 508, and the inner container 508 is shrink-fitted inside the outer container 509. Further, the outer container 509 only needs to have a γ-ray shielding function, and a sealing function like the inner container 508 is not required. For this reason, it is not necessary to integrally mold the outer container 509, and it is not necessary to completely weld and join the constituent members. For example, as shown to (a) of FIG. 14, the baseplate 513 can be fixed with respect to the cylinder 512 by fillet welding (welding part 514). Although not shown, the bottom plate 513 may be bolted to the cylinder 512.

  Further, as shown by a dotted line in FIG. 12, the outer container 509 is divided in the axial direction, and the divided bodies 509a can be fixed to each other by bolts or welding. In this case, since the divided body 509a of the outer container 509 can be fixed from the outside of the inner container 508, a shrink fitting operation of the inner container 508 with respect to the outer container 509 is not necessary. As described above, the trunk body 501 includes the inner container 508 and the outer container 509, and the inner container 508 has a corrosion resistance and a sealing function such as stainless steel, while the outer container 509 has a sealing function. The cask 500 can be easily and inexpensively manufactured by using carbon steel that provides a shielding function and is inexpensive. Further, in order to enhance the strength and hermeticity of the outer container 509, the bottom plate 513 is preferably butt-welded to the cylindrical body 512. For butt welding, high frequency induction welding, high frequency resistance welding, flash welding, or the like is used. By this welding, welding is performed on substantially the entire contact surface between the cylindrical body 512 and the bottom plate 513, so that the sealing performance of the outer container 509 is improved and the mechanical strength is improved.

  As shown in FIG. 14B, the flange 511 of the inner container 508 is in contact with the end surface 509b of the outer container 509 and is fixed by fillet welding (welded portion 515). Further, a seal groove may be provided on the flange side, and a metal gasket may be disposed in the seal groove (not shown). Further, a step portion 511a is provided inside the flange 511 in order to insert the spigot portion (510a) of the lid 510. The flange 511 is welded to the opening side end after integrally molding the bottomed container. In addition, it can also be integrally formed by holding with a die when deep drawing is performed hot. In this case, since the welded portion can be removed from the entire inner container 508, the performance such as sealing performance of the inner container 508 is further improved.

  A spacer 516 is interposed between the square pipe 506 constituting the basket 505 and the cavity 504 of the trunk body 501. The spacer 516 can efficiently transfer the decay heat of the recycled fuel assembly from the square pipe 506 to the trunk body 501. The square pipes 506 may be bound together in advance with a band or the like and inserted into the cavity 504, or the square pipe 506 may be restrained inside the cavity 504 using the spacer 516. Further, the spacer 516 may be spot welded in advance inside the inner container 508.

  The neutron shield 502 is made of a resin containing a predetermined amount of hydrogen, and is filled and molded into a plurality of heat transfer pipes 517 provided between the trunk body 501 and the outer cylinder 503 as shown in FIG. The The heat transfer pipe 517 is made of a material having high thermal conductivity, such as copper or aluminum. A release material 541 is provided on the inner surface of the heat transfer pipe 517. The release material 541 is made of, for example, a silicon-based material or a material using polyvinyl alcohol (PVA) as a raw material. In addition to the release material 541, a material that satisfies the conditions that the neutron shield 502 can be slid entirely in the axial direction and can withstand high temperatures up to about 200 ° C. can be used. Examples of the mold release material 406 include “MOLD RELEASE QZ13” (trade name: Nagase ChemteX Corporation).

  Further, the release material 541 may be provided only on a part of the inner surface of the heat transfer pipe 541. By providing the release material 541, the thermal elongation of the neutron shield 502 can be absorbed by the neutron shield 502 itself sliding in the axial direction. For this reason, the stress of the structure resulting from the thermal elongation in the axial direction of the neutron shield 502 can be relaxed. Further, as shown in FIG. 11, the outer cylinder 503 and its end plate 503a are partitioned on one side (upward side in the standing state) of the outer cylinder 503 by the thermal elongation of the neutron shield 502. A space 542 is provided. Further, the neutron shield 502 reliably shields neutrons even when they are not thermally stretched, so that a certain amount or more of neutrons do not go outside at the end of the cask.

  Here, the decay heat of the recycle combustion assembly is first transmitted through the basket 505 constituted by the square pipe 506, and is transmitted to the trunk body 501 through the spacer 516. The heat transmitted to the body 501 is mainly transmitted to the outer cylinder 503 via the heat transfer pipe 517 and is radiated to the outside. When the basket 505 is configured using the square pipe 506, heat transfer is efficiently performed because the surfaces are in surface contact with each other. In addition, the spacer 516 substantially contacts the body 501 and heat transfer to the body 501 is sufficiently performed. When a basket is manufactured by alternately assembling plate materials made of neutron moderators and inserting stainless steel square pipes into the lattice, there are many contact interfaces, so the aluminum square pipe 506 is in surface contact. The heat transferability is inferior to the basket 505 assembled in a state.

  FIG. 13 is a cross-sectional view showing a state where a lid is attached to the trunk body. As shown in FIG. 14C, the lid 510 has a structure in which two circular plate members 510a and 510b are bonded together, and the diameter of the plate member 510a constituting the spigot portion is small. The two circular plates 510a and 510b are welded from the outside (welded portion 519). Further, a seal groove 520 for interposing a metal gasket is formed on the surface 510c that contacts the flange 511 of the inner container 508. The lid 510 has an inlay portion inserted into the step portion 511 a of the flange 511, and is fixed to the flange 511 with a plurality of bolts 521 at the periphery thereof. The bolt 521 is screwed only into the flange 511 and does not reach the end of the outer container 509.

  Further, as shown in FIG. 15, the lid 510 may have a structure in which one of circular plate members 510 a and 510 b is filled and filled with a neutron shielding material 522. In that case, an auxiliary shield (not shown) may be attached only around the flange 511. Moreover, as shown in FIG. 16, you may comprise a lid | cover double. Specifically, the two-step contact surfaces 511b and 511c are processed and formed on the flange 511 of the inner container 508, and the seal surface 523a of the primary lid 523 is in close contact with the first contact surface 511b. The primary cover 523 is fixed with a plurality of bolts 526 at the periphery thereof with a metal gasket 525 interposed in the seal groove 524.

  Similarly, the secondary lid 527 has a metal gasket 529 interposed in the seal groove 528 and is fixed with a plurality of bolts 530 at the periphery thereof. Further, a neutron shielding material 531 is enclosed in the secondary lid 527. A slight space 532 is formed between the primary lid 523 and the secondary lid 527, and helium gas is sealed in the space 532 with a pressure higher than the air pressure. The pressure in the space 532 is monitored by a pressure sensor (not shown). As described above, by introducing the inspection gas such as helium gas into the space with the lid having a double structure, it is possible to reliably prevent leakage of the radioactive substance inside the cask. Further, since the inside of the cavity 504 has a negative pressure and the space 532 has a positive pressure, leakage from the inside of the cavity 504 is prevented and the leakage can be detected by the pressure in the space. Further, by providing a double lid on the flange 511 of the inner container 508, the sealing performance by the inner container 508 is ensured.

  In addition, as shown in FIG. 17, when the secondary lid 527 (or primary lid; not shown) is provided with a protrusion 533 and a load is applied to the secondary lid 527 due to the fall of the cask 500, the secondary lid 527 and the primary lid 527 It is good also as a structure which can receive a load in both the secondary lid | cover 527 and the primary lid | cover 523 by making it the lid | cover 523 contact mutually. In addition, since the space 532 can be secured between the lids by providing the projection 533, the inside can be filled with the inspection gas. Although not shown, a member to be the protrusion 533 may be separately manufactured and attached to the secondary lid 527 or the primary lid 523. For example, with the contact surface 527a of the secondary lid 527 as a reference, the top portion 533a of the protrusion 533 is processed with a minus tolerance, so that the lids 523 and 527 come into contact when the load is applied. Specifically, in the case of a cask that accommodates around 560 recycled fuel assemblies, it is preferable that the gap between the top 533a of the protrusion 533 and the facing surface 523b be 0.5 mm or less. The protrusions 533 may be provided radially in the radial direction or may be provided in a spiral shape. A plurality of protrusions 533 may be provided in a scattered manner or regularly.

  Further, if the basket 505 having a structure in which the square pipes 6 formed by extruding the boron aluminum material are assembled, the number of cells can be increased even if the cavity shape of the inner container 508 is cylindrical. For example, in the case of a recycled fuel assembly of BWR fuel, one side is known to be about 150 mm. For this reason, the plate thickness of the material constituting the basket 505 can be reduced compared with the case where a plate made of neutron moderator is combined in a lattice shape and a stainless steel square pipe is inserted into the lattice, and the same inner diameter is achieved. In the case of the cavity 504, the number of cells can be increased accordingly. Further, the outer diameter can be reduced if the same number of storage bodies is provided. That is, since the diameter of the trunk body 501 can be reduced if the outer shape is reduced, there is an advantage that the cask 500 can be drastically reduced in weight. The same applies to the recycled fuel assembly for PWR. In addition, when subjected to an impact load, if the square pipes 506 are gathered and are in close contact with each other, the portion where stress concentration occurs is reduced compared to a basket in which plate materials are assembled in a lattice shape, and there is a risk of breakage. Can be minimized.

  Moreover, it is preferable that the surface of the outer container 509 made of carbon steel is subjected to a rust prevention treatment with an overlay of stainless steel. Further, when the bottom plate 513 is bolted to the cylindrical body 512 of the outer container 509, a soft metal such as copper is interposed in the joint portion and the outside is sealed with silicon or the like in order to prevent moisture from entering inside. It is preferable to apply (not shown). Thereby, it is possible to prevent moisture from entering between the inner container 508 and the outer container 509 and causing electrolytic corrosion. Further, such processing is preferably performed in the same manner when the outer container 509 is constituted by a plurality of divided bodies 509a and bolted to each other. Furthermore, when the bottom plate 513 of the outer container 509 is welded to the cylindrical body 512, a certain welding depth may be secured by electron beam welding, and a certain degree of sealing may be provided. The same applies to the welding of the flange 511 and the outer container 509 end. The sealing performance of the cask 500 can be further improved and the welding load can be reduced.

  FIG. 19 is a cross-sectional view showing a modified example of the cask. As shown in FIG. 6A, the heat transfer pipe 543 has a stepped cross section as a countermeasure against streaming. The step portion 543a of the heat transfer pipe 543 is fitted to the step portion 543b of the adjacent heat transfer pipe 543. Further, a release material 544 is provided on the inner surface of the heat transfer pipe 543 along the shape of the heat transfer pipe 543. The neutron shield 545 is filled in the heat transfer pipe 543. In this way, the thermal elongation in the axial direction of the neutron shield 545 can be absorbed, and neutron shielding can be performed reliably. Further, as shown in FIG. 5B, the heat transfer pipe 546 is arranged so that the cross section is substantially trapezoidal and in surface contact with the adjacent heat transfer pipe 546 installed in the opposite direction. A release material 547 is provided on the inner side surface of the heat transfer pipe 546. Further, a neutron shield 548 is filled in the heat transfer pipe 546 provided with the release material 547. In this case as well, the thermal elongation in the axial direction of the neutron shield 545 can be absorbed and the neutron can be shielded reliably.

(Embodiment 6)
FIG. 20 is a perspective view showing a cask according to Embodiment 6 of the present invention. In the cask 600, an inner container 508 and an outer container 509 constitute a trunk main body 501. A plurality of heat transfer fins 550 are joined to the outer periphery of the outer container 509, and the heat transfer fins 550 further include an outer cylinder. It is joined to the inner surface of 503. Further, a neutron shield 552 molded at another location is inserted into a space 551 defined by the outer container 509, the outer cylinder 503, and the heat transfer fins 550. A release material 555 is provided on the inner surface of the space 551. The neutron shield 552 has a structure in which an internal space of an aluminum or copper honeycomb material is filled with a resin. FIG. 21 is an explanatory view showing a method of manufacturing the neutron shield 552. As shown in FIG. 6A, a honeycomb material 554 having the same shape is placed in a cylindrical split mold 553 for forming the shape of the neutron shield 552.

  Next, as shown in FIG. 6B, the split mold 553 is filled with a predetermined liquid material for mixing two liquids, and enters the internal space of the internal honeycomb material 554. The dimensions of the honeycomb are such that the liquid constituting the resin can enter the inside. Then, after waiting for a predetermined reaction time, as shown in FIG. 5C, the split dies 553 are divided and the neutron shield 552 formed inside is taken out. The neutron shield 552 formed in this way has a structure in which the honeycomb material 554 is filled with resin.

  FIG. 22 is a cross-sectional view showing a state where the neutron shield 552 is inserted into the space 551. Thus, by inserting the neutron shield 552 into the space 551 provided with the release material 555, the thermal expansion in the axial direction of the neutron shield 552 is absorbed by the neutron shield 552 itself sliding. Further, since the honeycomb material 554 has a structure in which the resin is filled in the honeycomb, the thermal conductivity of the neutron shield 552 itself is extremely high, and the decay heat inside the cask can be efficiently transmitted to the outer cylinder 503. become able to. In the above example, the structure in which the release material 555 is provided in the space 551 is shown. However, since the neutron shield 552 is inserted after molding, a release material may be applied around the neutron shield 552 in advance. good. Further, a configuration in which the release material 555 is omitted may be employed. That is, when the honeycomb material 554 is filled with a resin, the material of the honeycomb material 554 is exposed on the outer peripheral surface of the neutron shield 552 and can slide to some extent with respect to the inner surface of the space 551, This is because when the resin is filled in the honeycomb, the expansion is first inhibited by the honeycomb material 554, and it is difficult to expand compared to the case of the resin alone.

  In the above, the neutron shielding body 552 is molded using the honeycomb material 554, but in addition to the honeycomb material, a resin holding body having a large number of small spaces into which the resin can enter, or a skeleton-like structure having an internal space. If you can, you can use it. For example, a rectangular plate-like body may be combined in a lattice shape, or a long corrugated plate may be combined side by side.

(Embodiment 7)
FIG. 23 is a partial cross-sectional view in the radial direction showing the cask according to the seventh embodiment of the present invention. The cask 700 has a configuration in which a neutron shield is filled and solidified in a long cup-shaped heat transfer fin 701 and then inserted between an outer container 509 and an outer cylinder 503. FIG. 24 is an explanatory view showing a method for forming a neutron shield. In this neutron shield 702, as shown in FIG. 2A, a long cup-shaped heat transfer fin 701 is placed horizontally, and a predetermined liquid solvent is put therein to be mixed and solidified. The heat transfer fin 701 is made of a material having good thermal conductivity such as aluminum or copper.

  Here, the filling amount of the resin is set to be slightly lower than the top 701a of the heat transfer fin 701 (gap G) as shown in FIG. This is because the top 701a of the heat transfer fin 701 is brought into contact with the inner surface of the outer cylinder 503 while the heat transfer fin 701 is inserted between the outer container 509 and the outer cylinder 503, while neutron shielding is performed. This is because the exposed surface of the body 702 (the portion not in contact with the heat transfer fin 701) does not contact the inner surface of the outer cylinder 703, and the thermal expansion margin 704 is formed. In this way, the thermal expansion margin 704 can be easily made. The heat transfer fins 701 are in contact with adjacent heat transfer fins 701 and are fixed in the space between the outer container 509 and the outer cylinder 503. Note that the long cup-shaped heat transfer fins 701 shown in FIG. That is, it may be used as a wall when fluidly filling the resin and removed after the resin has solidified.

  Further, as shown in FIG. 5C, the resin may be filled after a release material 703 is applied to the inner surface of the heat transfer fin 701. In this way, in addition to the above effect, there is an effect that the thermal expansion in the axial direction of the neutron shield 702 can be absorbed by the neutron shield 702 itself sliding.

It is the axial direction sectional view and radial direction partial sectional view which show the cask which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the softening flow of a neutron shield. It is explanatory drawing which shows the modification of the cask of FIG. It is a partial axial sectional view showing a cask according to Embodiment 2 of the present invention. It is the perspective view and partial sectional view which show the neutron shielding body of the cask which concerns on Embodiment 3 of this invention. It is explanatory drawing which shows the modification of the cask shown in FIG. It is a partial axial sectional view showing a cask according to Embodiment 4 of the present invention. FIG. 8 is a partial radial cross-sectional view of the cask shown in FIG. 7. It is explanatory drawing which shows the flow of the resin of the cask of FIG. It is an axial direction sectional view showing another modification of a cask. It is axial direction sectional drawing which shows the cask which concerns on Embodiment 5 of this invention. It is radial direction sectional drawing of the cask shown in FIG. It is sectional drawing which shows the state which attached the lid | cover to the trunk | drum main body. It is an enlarged view of each part of a cask. It is explanatory drawing which shows the modification of the cask shown in FIG. It is explanatory drawing which shows the modification of the cask shown in FIG. It is explanatory drawing which shows the modification of the cask shown in FIG. It is explanatory drawing which shows the heat-transfer pipe etc. which insert a neutron shield. It is sectional drawing which shows the modification of the cask shown in FIG. It is a perspective view which shows the cask which concerns on Embodiment 6 of this invention. It is explanatory drawing which shows the manufacturing method of this neutron shield. It is sectional drawing which shows the state which inserted the neutron shield in space. It is a partial cross section figure of the radial direction which shows the cask which concerns on Embodiment 7 of this invention. It is explanatory drawing which shows the shaping | molding method of a neutron shield.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Cask 1 Body 2 Neutron shield 3 Outer cylinder 4 Cavity 5 Basket 6 Square pipe 7 Cell 8 Inner container 9 Outer container 10 Lid 11 Flange 12 Tubular body 13 Bottom plate 17 Heat transfer pipe 41 Release material 42 Escape space

Claims (10)

A trunk body that shields radiation;
An outer cylinder provided around the trunk body via a plurality of heat transfer fins;
A neutron shield composed of a precast resin disposed in a space defined by the trunk body, heat transfer fins, and an outer cylinder, and a resin injected and solidified around the precast resin,
A basket that is provided in the cavity of the trunk body and is made of a material containing a neutron moderator, and constitutes a plurality of cells that store the recycled fuel assemblies,
A radioactive substance storage container comprising: A trunk body that shields radiation;
An outer cylinder provided around the trunk body via a plurality of heat transfer fins;
A release material provided on the inner surface of the space defined by the trunk body, the heat transfer fins and the outer cylinder,
A neutron shield placed in the space;
A basket that is provided in the cavity of the trunk body and constitutes a plurality of cells that accommodate a plurality of square pipes made of a material containing a neutron moderator and accommodates a recycled fuel assembly,
A radioactive substance storage container comprising: An inner container,
An outer container that constitutes a trunk body that shields radiation together with the inner container and is thicker than the inner container provided outside the inner container;
An outer cylinder provided around the outer container via a plurality of heat transfer fins;
A release material provided on the inner surface of the space defined by the outer container, the heat transfer fin and the outer cylinder,
A lateral neutron shield placed in the space;
A basket which is provided in the cavity of the inner container and constitutes a plurality of cells for storing the recycled fuel assemblies;
Provided on the lid attached to the bottom of the outer container and the opening of the inner container, neutron shields on both sides,
A radioactive substance storage container comprising:   The neutron shield is set to a length so as not to emit at least a certain amount of neutrons from the recycled fuel assembly to the outside in a state before thermal expansion, and is formed in an axial direction formed by an outer cylinder and a short plate The radioactive substance storage container according to claim 2 or 3, wherein the thermal expansion margin has a dimension suitable for the thermal expansion amount of the neutron shield.   The radioactive substance storage container according to any one of claims 2 to 4, wherein the neutron shield is obtained by molding a holding body having a large number of small spaces with a resin.   The heat transfer fin is cup-shaped in cross section, and a release material is provided in the cup, and the exposed surface of the neutron shield exists with a predetermined gap from the top of the cup in contact with the outer cylinder. Item 6. The radioactive substance storage container according to any one of Items 2 to 5. A trunk body that shields radiation;
An outer cylinder provided around the trunk body via a plurality of heat transfer fins;
A neutron shield having a structure in which a holding body that is put in a space defined by the trunk body, the heat transfer fins, and the outer cylinder and has a plurality of small spaces is molded with a resin;
A basket which is provided in the cavity of the trunk body and which constitutes a plurality of cells for storing the recycled fuel assemblies;
A radioactive substance storage container comprising: A trunk body that shields radiation;
An outer cylinder provided around the trunk body via a plurality of heat transfer fins;
A neutron shield placed in a space defined by the trunk body, the heat transfer fins, and the outer cylinder;
A basket which is provided in the cavity of the trunk body and which constitutes a plurality of cells for storing the recycled fuel assemblies;
With
The heat transfer fin has a cup-shaped cross section, and the exposed surface of the neutron shield exists with a predetermined gap from the top of the cup in contact with the outer cylinder. Corresponds to a trunk body that shields the γ rays constituting the radioactive substance storage container, a heat transfer fin that is thermally connected to the periphery of the trunk body, and a space defined by an outer cylinder that is thermally connected to the heat transfer fin. Insert a holding body having a large number of small spaces into a mold having a shape to
By filling the resin in this, let the resin enter the small space, mold the neutron shield,
A method of manufacturing a radioactive substance storage container, wherein the neutron shield is inserted into the space. Before placing a plurality of cup-shaped heat transfer fins in the space between the trunk body and the outer cylinder provided around it, so that the heat transfer fins are in contact with both the trunk body and the outer cylinder,
The heat transfer fin is placed on the floor, and in that state, the resin is injected and solidified to mold the neutron shield, and the exposed surface of the neutron shield has a predetermined gap with the top of the heat transfer fin.
With the heat transfer fin inserted into the space, the top of the heat transfer fin is in contact with the outer cylinder, and a thermal expansion margin is formed between the outer cylinder and the exposed surface of the neutron shield. A method for manufacturing a radioactive substance storage container.

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