JP2008107359A - Radioactive material container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of the low mechanical strength of a container because of the fillet welding done for a bottom plate of an outer container, and also to improve the sealing performance of a cask. <P>SOLUTION: The outer container 9 is placed outside an inner container 8 molded integrally by deep drawing. The outer container 9 is made of carbon steel and has the gamma-ray shielding function, but the sealing performance is not required of the outer container 9. Since the inner container 8 is shaped like a bottomed container by integral molding, it can prevent radioactive materials inside it from leaking. Especially, the container is characterized in that it has a neutron shield 2 placed outside the outer container 9 and baskets 5 located in a cavity 4 of the inner container 8 and constituting cells for accommodating recycle fuel assemblies through the plane alignment of square pipes composed of aluminum materials or materials made by adding boron or boron compounds to aluminum alloy and in that the outer container 9 consists of segments, which are located on the outer periphery of the inner container 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radioactive substance storage container for storing a fuel rod assembly used for nuclear power generation for recycling.

  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.

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

  However, the conventional cask has the following problems. Since the inner container is manufactured by welding, defects are likely to occur. Since the bottom plate of the outer container is fillet welded, the mechanical strength is low.

  This invention is based on earnest research by the inventors of the present patent applicant, and was created so that the cask having the above-described configuration has a performance capable of satisfying the laws and regulations of Japan. Moreover, it solves any of the above problems.

  In order to achieve the above-mentioned object, a radioactive substance storage container according to the present invention comprises an inner container having a sealing function in the shape of a bottomed integral container, a trunk body that shields radiation together with the inner container, and is disposed outside the inner container. An outer container that is not required to have a thicker sealing function than the inner container provided, a neutron shield provided outside the outer container, and provided in the cavity of the inner container, and boron or boron in an aluminum material or an aluminum alloy A plurality of square pipes made of a material to which a compound is added to face each other and a basket that constitutes a plurality of cells for storing the recycled fuel assemblies, and the outer container is composed of a plurality of divided bodies. Is arranged on the outer periphery of the inner container. The outer container may be composed of a plurality of divided bodies divided in the axial direction, and these divided bodies are arranged on the outer periphery of the inner container.

  Sealing is secured by the inner container in the shape of a bottomed integral container, and radiation such as γ rays is shielded by the thick outer container. Although this outer container is thick, welding or the like having a sealing function is unnecessary, and it may not be integrated as a whole (a divided structure may be bolted or the like), as long as it has a radiation shielding function. good. For this reason, the inner container requiring sealing properties is thin and easy to process, and even if an expensive material having corrosion resistance and rust prevention is used, the cost does not increase. Furthermore, the present invention is characterized in that a basket is formed by combining a plurality of square pipes. If a basket is constructed using 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. Further, when an impact is applied to the inside due to a drop or the like during transportation, the square pipes are gathered to meet each other, so that it becomes easy to withstand the load. In particular, since the outer container is composed of a plurality of divided bodies, and these divided bodies are arranged on the outer periphery of the inner container, the outer container is focused on shielding the radiation. It may be configured to be disposed on the outer periphery of the inner container, and it is easier to assemble if divided on the contrary and disposed on the outer periphery of the inner container. Moreover, it is easier to manufacture if the outer container is divided.

  In addition, a bottomed container-shaped inner container formed integrally with the bottom using a mold, a barrel main body that shields radiation together with the inner container, and an outer container thicker than the inner container provided outside the inner container, A neutron shield provided on the outer side of the outer container and a basket having a plurality of cells provided in the cavity of the inner container and storing the recycled fuel assembly may be provided.

  Since the inner container is integrally formed using a mold (for example, a deep drawing die and punch), a bottomed container with high sealing performance can be formed. Thereby, it can prevent reliably that a radioactive substance leaks from the inside. In addition, what is shape | molded using a type | mold does not include the case where a bottom is welded. This is because when welding is performed, a great deal of labor is devoted to the soundness of the welded portion. In the same way as described above, the thick outer container is processed and assembled so that sealing performance is not required with emphasis on the radiation shielding function, and the inner container is made thin and easy to process with emphasis on sealing. The cost is not increased even if it is used.

  In addition, a bottomed container-shaped inner container formed integrally with the bottom using a mold, a barrel main body that shields radiation together with the inner container, and an outer container thicker than the inner container provided outside the inner container, Recycled fuel by combining a neutron shield provided on the outside of the outer container and a plurality of square pipes made of a material obtained by adding boron or a boron compound to an aluminum material or an aluminum alloy while being provided in the cavity of the inner container It is good to provide the basket which comprises a plurality of cells which store an aggregate.

  In addition, the inner container in the shape of a bottomed integral container, the trunk body that shields radiation together with the inner container, and is thicker than the inner container provided on the outer side of the inner container, and is composed of a cylindrical body and a bottom plate, An outer container having a structure in which the bottom plate is brought into contact with the cylindrical body and welded on substantially the entire contact surface, a neutron shield provided on the outer side of the outer container, provided in the cavity of the inner container, and recycled fuel It is good to provide the basket which has a plurality of cells which store an aggregate.

  The outer container is composed of a cylindrical body and a bottom plate, and the contact surface between the bottom plate and the cylindrical body is welded over the entire surface in order to improve the airtightness of the outer container itself. Thereby, confidentiality can be given also to outer container itself, and the confidentiality of the whole radioactive substance storage container can be improved. Moreover, the mechanical strength of the outer container can be improved. In addition, as a method of welding on the whole contact surface of a cylinder and a baseplate, butt welding, such as high frequency resistance welding, can be mentioned, for example.

  Moreover, in the said structure, it is good to have a flange in the opening side of the said inner container, and to attach a lid | cover to this flange doubly. By providing a double lid with respect to the flange, the inner container and the double lid can enhance the airtightness inside the cavity and prevent leakage of radioactive material inside.

  Moreover, in the said structure, it is good to have a flange in the opening side of the said inner container, to pile up a board | plate material on this flange, and to attach the lid | cover which enclosed the neutron shield between these board | plate materials.

  The lid may have a configuration in which plate materials are overlapped and joined, and by attaching a neutron shield inside the plate material, the attachment of the auxiliary shield at the axial end can be omitted in whole or in part.

  The radioactive substance storage container according to the next invention is characterized in that, in the above configuration, of the plurality of divided bodies constituting the outer container, the divided body located near the center in the axial direction is thickened.

  Since the radiation dose is relatively large near the center, the divided body near the center in the axial direction is thickened. In this case, since the outer container has a divided structure, it is easier to manufacture because the thickness of each divided body can be adjusted as compared with the case where the thickness of the single outer container is changed only near the center. That is, a relatively thick divided body is arranged in a portion where the radiation dose is large so that the thickness of the trunk body is appropriate throughout.

  The radioactive substance storage container according to the next invention is characterized in that, in the above-described configuration, a portion located near the center in the axial direction of the neutron shield is further thickened. Similarly, since a portion of the neutron located near the center in the axial direction increases, the neutron shield of the portion is made thick.

  Also, an inner container in the shape of a bottomed integral container, a trunk body that shields radiation together with the inner container, and an outer container that is thinner than the inner container provided on the outer side of the inner container, and a neutron provided on the outer side of the outer container A shield and a basket provided in the cavity of the inner container and having a plurality of cells for storing the recycled fuel assemblies may be provided. The outer container is made thin and the sealing function is emphasized, and the inner container is focused on radiation shielding.

  Moreover, the said structure WHEREIN: The cavity of the said inner container is good in the shape match | combined with the external shape of the said basket containing square cross-sectional shape.

  Since the inner container is thick, the shape can be processed according to the outer shape of the basket. When the cavity shape of the inner container matches the shape of the basket, the thickness of the trunk body becomes relatively uniform along the shape of the basket, reducing the weight of the radioactive substance storage container and reducing the size. In addition, by matching the inner container to the outer shape of the basket, the contact area between the basket and the inner container can be dramatically increased, and heat transfer can be improved.

  Moreover, the said structure WHEREIN: The said inner container is comprised from a some division body, and it is good to be restrained in the said outer container by inserting a basket. The inner container is fixed in the outer container by putting the inner container into the outer container in a divided state and stuffing the basket. Thereby, the inner container can be easily fixed.

  Moreover, the said structure WHEREIN: The said division body is good to mutually self-restraint within the said outer container. In addition, the radioactive substance storage container according to the next invention is characterized in that, in the above configuration, a neutron shielding material is sealed in a portion corresponding to the bottom of the container between the inner container and the outer container.

  The radioactive substance storage container according to the next invention has the above-described configuration, wherein the inner container has a flange on the opening side, and a joint surface between the flange side surface and the end side surface of the outer container into which the inner container is fitted. It is characterized in that it is welded substantially planarly with the end face of the outer container.

  In addition, a container for storing the radioactive substance, and a double lid including a primary lid and a secondary lid provided on the opening side of the container, the double lid is positioned higher than a sealing surface between the secondary lid and the container end. It is preferable to have a mating surface.

  In addition, the apparatus includes a container for storing a radioactive substance, and a double lid including a primary lid and a secondary lid provided on the opening side of the container, and the double lid is located at a position lower than a sealing surface between the secondary lid and the container end. It is preferable to have a mating surface.

  Moreover, the said structure WHEREIN: Furthermore, the drain hole which connects the said sealing surface and the outer side of a container is good.

  In addition, the apparatus includes a container for storing a radioactive substance, and a double cover including a primary cover and a secondary cover provided on the opening side of the container. The double cover has a tapered peripheral surface and a ring around the periphery. A member is disposed, and the ring member is fixed to the container end portion, and a tapered surface provided inside thereof is preferably in contact with the tapered surface of the primary lid.

  As described above, according to the radioactive substance storage container of the present invention, the square pipe is faced to form the basket, so that the thermal conductivity is improved and the decay heat of the recycled fuel assembly can be efficiently released to the outside. Further, the mechanical strength of the basket is improved. In particular, since the outer container is composed of a plurality of divided bodies, and these divided bodies are arranged on the outer periphery of the inner container, the outer container is focused on shielding the radiation. It is also possible to have a configuration in which it is arranged on the outside, and it is easier to assemble if it is divided on the contrary and arranged on the outer periphery of the inner container. Moreover, it becomes easier to assemble the outer container by dividing it in the axial direction. Moreover, it is easier to manufacture if the outer container is divided.

  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 showing a cask according to Embodiment 1 of the present invention. FIG. 2 is a radial sectional view of the cask shown in FIG. The cask 100 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. Further, the outer container 9 only needs to have a gamma ray shielding function, and the sealing function like the inner container 8 is not 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. For example, as shown to (a) of FIG. 4, the baseplate 13 can be fixed with respect to the cylinder 12 by fillet welding (welding part 14). Although not shown, the bottom plate 13 may be bolted to the cylinder 12. Further, as shown by a dotted line in FIG. 2, the outer container 9 is divided in the axial direction, and the respective divided bodies 9a can be fixed by bolts or welding. In this case, since the divided body 9a of the outer container 9 can be attached and fixed from the outside of the inner container 8, there is no need for a shrink fitting operation for the outer container 9 of the inner container 8. 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.

  As shown in FIG. 4B, the flange 11 of the inner container 8 is in contact with the end surface 9b of the outer container 9, and is fixed by fillet welding (welded portion 15). Further, a seal groove may be provided on the flange side, and a metal gasket may be disposed in the seal groove (not shown). In addition, a step portion 11 a is provided inside the flange 11 in order to insert the spigot portion (10 a) of the lid 10. The flange 11 is welded to the opening side end after integrally forming 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 8, the performance of the inner container 8 such as sealing performance is further improved.

  A spacer 16 is interposed between the square pipe 6 constituting the basket 5 and the cavity 4 of the trunk body 1. The spacer 16 can efficiently transfer the decay heat of the recycled fuel assembly from the square pipe 6 to the trunk body 1. The bundling of the square pipes 6 may be previously bundled outside with a band or the like and inserted into the cavity 4, or the square pipe 6 may be restrained inside the cavity 4 using the spacer 16. Further, the spacer 16 may be spot-welded in advance inside the inner container 8.

  The neutron shield 2 is made of a resin containing a predetermined amount of hydrogen, and is filled into a space defined by a plurality of heat transfer fins 17 provided between the trunk body 1 and the outer cylinder 3. The heat transfer fins 17 are made of a material having high thermal conductivity, for example, copper or aluminum. In addition, a thermal expansion margin 18 that absorbs thermal expansion is provided between the neutron shield 2 and the outer cylinder 3. The thermal expansion margin 18 can be formed by, for example, putting a mold release or disappearance mold in advance and filling the resin. Further, a honeycomb material may be interposed in the thermal expansion margin 18 in order to enhance heat transfer in addition to absorption of thermal expansion. Here, 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.

  FIG. 3 is a cross-sectional view showing a state where a lid is attached to the trunk body. As shown in FIG. 4C, the lid 10 has a structure in which two circular plate members 10a and 10b are bonded together, and the diameter of the plate member 10a constituting the spigot portion is reduced. The two circular plates 10a and 10b are welded from outside (welded portion 19). In addition, a seal groove 20 for interposing a metal gasket is formed on the surface 10c that contacts the flange 11 of the inner container 8. The lid 10 has an inlay portion inserted into the step portion 11 a of the flange 11, and is fixed to the flange 11 with a plurality of bolts 21 at the periphery thereof. The bolt 21 is screwed only to the flange 11 and does not reach the end of the outer container 9.

  Further, as shown in FIG. 5, the lid 10 may have a structure in which one of the circular plate members 10 a and 10 b is filled with a neutron shielding material 22. In that case, an auxiliary shield (not shown) may be attached only around the flange 11. Moreover, as shown in FIG. 6, you may comprise a lid | cover double. Specifically, the two-step contact surfaces 11b and 11c are processed and formed on the flange 11 of the inner container 8, and the seal surface 23a of the primary lid 23 is in close contact with the first contact surface 11b. The primary lid 23 is fixed with a plurality of bolts 26 at the periphery thereof with a metal gasket 25 interposed in the seal groove 24. Similarly, the secondary lid 27 is also provided with a metal gasket 29 in the seal groove 28 and fixed with a plurality of bolts 30 at the periphery thereof. Furthermore, a neutron shielding material 31 is enclosed in the secondary lid 27. A slight space 32 is formed between the primary lid 23 and the secondary lid 27, and helium gas is sealed in the space 32 with a pressure higher than the air pressure. The pressure in the space 32 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 4 has a negative pressure and the space 32 becomes a positive pressure, the leakage from the inside of the cavity 4 is prevented and the leakage can be detected by the pressure in the space. Furthermore, by providing a double lid on the flange 11 of the inner container 8, the sealing performance by the inner container 8 is ensured.

  Further, as shown in FIG. 7, when the secondary lid 27 (or primary lid; not shown) is provided with a projection 33 and a load is applied to the secondary lid 27 due to the fall of the cask 100 or the like, the secondary lid 27 and the primary lid It is good also as a structure which can receive a load by both the secondary lid | cover 27 and the primary lid | cover 23 by making it the lid | cover 23 contact mutually. Moreover, since the space 32 can be secured between the lids by providing the projection 33, the inside can be filled with the inspection gas. Although not shown, a member to be the protrusion 33 may be separately manufactured and attached to the secondary lid 27 or the primary lid 23. For example, with the contact surface 27a of the secondary lid 27 as a reference, the top 33a of the projection 33 is processed with a minus tolerance, so that the lids 23 and 27 come into contact when the load is applied. Specifically, in the case of a cask that houses around 60 recycled fuel assemblies, it is preferable that the gap between the top 33a of the protrusion 33 and the facing surface 23b be 0.5 mm or less. The protrusions 33 may be provided radially in the radial direction or may be provided in a spiral shape. A plurality of protrusions 33 may be provided in a scattered or regular manner.

  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. 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 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. Further, such processing is preferably performed in the same manner when the outer container 9 is composed of a plurality of divided bodies 9a and bolted to each other. 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.

  FIG. 8 is a radial sectional view showing a modified example of the cask. In the cask 110, as shown in FIG. 5A, a basket 5 constituted by a square pipe 6 has a flat portion 5a and a square cross-sectional portion 5b. The flat portion 40a of the flat portion 5a and the inner container 40 This is a configuration in which the shape is deformed so as to be in surface contact. A portion 40b corresponding to the angular cross-sectional shape 5b of the inner container 40 has an arc shape. The inner container 40 can be easily formed by using a die having a shape that can be formed into the shape during deep drawing. Further, the outer container 41 may be manufactured by dividing the flat portion 41a and the arc portion 41b and assembled on the outer periphery of the inner container 40, and the divided bodies 41a and 41b may be fixed to each other by bolts or welding.

  According to the configuration shown in the figure, the cask 110 can be configured more compactly. Moreover, since the volume of the trunk | drum main body 1 becomes small, it can contribute to the weight reduction of the cask 110. FIG. Furthermore, the inner container 43 may have an octagonal cross section as shown in FIG. In that case, the four surfaces 43a are in surface contact with the flat portion 5a of the basket 5 of the square pipe 6, and the other four surfaces 43b are located along a line connecting the vertices of the angular cross-section portions 5b of the basket 5, A slight gap 6S is formed between the two. In the gap 6S, a spacer is preferably interposed in the same manner as described above (not shown). Further, the outer container 44 has an octagonal cross section along the shape of the inner container 43, and a plate-like divided body 44a is attached to each surface. The divided bodies 44a are fixed to each other by welding or bolts. Even with such a configuration, the cask 120 can be made compact and lightweight.

(Embodiment 2)
FIG. 9 is an axial sectional view showing a cask according to Embodiment 2 of the present invention. FIG. 10 is an explanatory diagram showing an assembly procedure of the cask shown in FIG. The cask 200 has a structure in which an inner container 201 made of stainless steel is manufactured as a bottomed container shape by integral molding by deep drawing, and an outer container 202 divided into the outside of the inner container 201 is inserted. In the example shown in FIG. 9, the outer container 202 is divided into five parts, and the cask sides and the center of the divided body 202 are slightly thick. This is because the dose of γ-rays at the part is large and sufficient shielding performance is required as compared with other parts. The outer container 202 is made of carbon steel and can be manufactured at low cost.

  Moreover, although the division body 202a of the outer container 202 is shrink-fitted and fixed to the inner container 201, the division bodies 202a may be fixed to each other by welding. Further, as shown in FIG. 10, a plurality of heat transfer fins 203 are provided on the peripheral surface of each divided body 202 a of the outer container 202. The heat transfer fins 203 are actually welded to the outer periphery of the divided body 202a after shrink-fitting each divided body 202a of the outer container 202. The heat transfer fins 203 are joined to the outer cylinder 204 in a state where the cask 200 is assembled. Next, in the example shown in the left half of FIG. 9, the neutron shield 205 has a structure in which a neutron shield 205 and an outer cylinder 204 are formed for each divided body 202 a of the outer container 202 and fitted into the inner container 201 together with these. is there. In this case, since the neutron shield 205 also needs to have a neutron shielding capability on both sides and the center of the cask 200, the thickness of the neutron shield 205 provided on the split body 202 on both sides and the center increases. In the example shown in the right half of FIG. 9, the outer cylinder 204 is provided in common with the divided body 202 a of the outer container 202, and the resin is filled in the space defined by the outer container 202, the outer cylinder 204, and the heat transfer fins 203. Thus, the neutron shield 206 is formed. With this configuration, the configuration of the cask 200 can be simplified.

  The outer surface of the outer container 202 can be a free-form surface according to the dose distribution. For example, the vicinity of the center may be thickened so as to have a barrel shape as a whole. At this time, the outer container 202 may be a combination of the divided bodies 202a or a non-divided structure.

(Embodiment 3)
FIG. 11 is an axial sectional view showing a cask according to Embodiment 3 of the present invention. 12 is a radial cross-sectional view of the cask shown in FIG. The cask 300 is characterized in that the outer container 302 constituting the trunk body 301 is thin and the inner container 303 is thick. The outer container 302 has a bottomed container shape made of a rust-proof material such as stainless steel, and is integrally formed by hot deep drawing. A flange 304 is welded to the opening side of the outer container 302. The flange 304 is formed with a step portion 304a to which the lid 305 is attached. The outer container 302 has a sealing property so that the radioactive material inside does not leak. Furthermore, the use of a highly rust-proof material such as stainless steel eliminates the need for rust prevention treatment on the outer surface.

  Inside the outer container 302, an inner container 303 made of carbon steel divided radially is fitted. The inner container 303 is used to shield γ rays, and is composed of, for example, eight divided bodies 303a, and is inserted inside while avoiding interference with the flange 304. In addition, the cavity 306 of the inner container 303 is processed into a shape that combines a square cross-sectional shape and a planar shape so as to match the outer shape of the basket 307. The basket 307 has a configuration in which a plurality of square pipes 308 are assembled, and each square pipe 308 is the same as that described in the first embodiment. For this reason, the flat surface portion 303 a of the inner container 303 comes into surface contact with the flat surface portion 307 a of the basket 307. Similarly, the square cross-sectional portion 303b of the inner container 303 is in surface contact with the square cross-sectional portion 307b of the basket 307. Thereby, the decay heat of the recycled fuel assembly is efficiently transferred to the inner container 303 in surface contact via the basket 307.

  On the other hand, a plurality of heat transfer fins 308 are joined to the outer container 302, and the heat transfer fins 312 are joined to an outer cylinder 309 formed in a cylindrical shape. A space defined by the heat transfer fins 312, the trunk body 301, and the outer cylinder 309 is filled and solidified with the neutron shield 310. A bottom plate 311 is fixed to the bottom of the inner container 303 by welding. Note that the bottom plate 311 may be disposed on the bottom of the inner container 303. As described above, since the joint portion exposed to the outside is almost eliminated by putting the inner container 303 inside, there is no need to seal the contact portion between the divided bodies. Further, by inserting the basket 307, the inner container 303 is in a restrained state in the outer container 302, and there is no particular need for joining the divided bodies 303a.

  According to the above configuration, since the divided body 303a and the square pipe 308 of the inner container 303 are inserted into the outer container 302 and assembled inside, there is no need for a process such as fitting using thermal expansion. The cask 300 can be easily assembled. In addition, since there are almost no joining portions on the outside, water from the outside does not enter the joining surface, and electrolytic corrosion or the like can be prevented. Further, since the inner container 303 is thick, the cavity shape of the inner container 302 of the trunk body 301 can be processed to match the outer shape of the basket 307. For this reason, heat conductivity can be improved and an impact can be directly transmitted from the basket 307 to the trunk body. Furthermore, since the volume of the trunk body 301 can be reduced, the cask 300 can be reduced in weight.

  Further, if the flange 304 as shown in the figure is not projected inward but is projected outward, the inner container 303 can be inserted into the outer container 302 without being divided. Or the freedom degree of the division | segmentation form of the inner container 303 increases. That is, since there is no obstacle to the insertion of the inner container 303, the divided body 303a of the inner container 303 can be manufactured in a shape that is easy to manufacture.

  FIG. 13 is a radial cross-sectional view showing a modified example of the cask of the third embodiment. Like the cask 310, a part of the inner container 303 may be matched to the outer shape of the basket 307. Even if a part of the inner container 303 is matched to the outer shape of the basket 307 and a part of the basket 307 is in contact with the groove 313 of the inner container 303, the heat transfer can be improved and the load can be easily transmitted to the trunk body 301. A spacer may be inserted into the gap 306S between the basket 307 and the cavity 306 (not shown).

  Although not shown, a plurality of axial grooves may be provided in a part of the inner container of the cask according to the first embodiment, and the corners of the basket may be engaged with the grooves. That is, heat conductivity and load transmission can be improved by matching a part of the thin inner container to the outer shape of the basket. Next, in Embodiments 1 to 3, the square pipes are assembled without gaps to configure the basket, but the square pipes may be arranged in a staggered manner to configure the basket. In that case, cells are formed inside the square pipe and between the square pipes. With this configuration, the number of square pipes can be reduced although the wall is thick.

  FIG. 14 is a partial cross-sectional view showing another modified example of the cask. This cask has substantially the same structure as the cask 100 shown in FIG. 1, but is composed of a bottom plate 8a and a cylinder 8b of the inner container 8, and has a cross section between the end of the cylinder 8b and the bottom plate 8a. A U-shaped metal seal 8c may be welded to increase the confidentiality of the inner container 8. The seal 8c can maintain the confidentiality of the inside and can easily bring the flange 11 of the inner container 8 into contact with the end surface of the outer container 9 by some elastic deformation. Further, since the inner container 8 is not formed by drawing and a normal sheet metal operation is sufficient, the manufacturing is easy.

(Embodiment 4)
FIG. 15 is an axial sectional view showing a cask according to Embodiment 4 of the present invention. This cask has a configuration in which a neutron shielding material is sealed between the bottom plate of the outer container and the bottom plate of the inner container of the cask 200 shown in FIG. The other configuration is the same as that of the cask shown in FIG. The cask 200 ′ forms a recess 202 c that encloses the neutron shielding material 208 in the bottom plate 202 b of the outer container 202, fills the recess 202 c with the neutron shielding material 208, and fits the inner container 201 into the outer container 202. By inserting it, the neutron shielding material 208 is sealed. Note that the neutron shielding material 208 is preferably solidified in a state of being placed in the recess 202c. Although not shown, a neutron shielding material may be enclosed in the boundary portion between the outer container 13 and the inner container 9 corresponding to the bottom of the cask 100 shown in FIG.

(Embodiment 5)
FIG. 16 is a radial cross-sectional view showing a cask according to Embodiment 5 of the present invention. The cask 300 ′ is obtained by dividing the inner container 303 of the cask 300 shown in FIG. 12, and the divided bodies 303a and 303c are fitted and restrained to each other. There are features. The other configuration is the same as that of the cask 300 shown in FIG.

  The inner container 303 is divided into eight divided bodies 303a and 303c. The four divided bodies 303a are positioned so as to come into contact with the flat portion of the basket 307, and the remaining four divided bodies 303c are arranged on the basket 307. It is located so as to contact the angular cross section and between the divided bodies. The adjacent divided bodies 303a and 303c have step portions 303d and 303e. Specifically, first, the four divided bodies 303a are inserted and arranged in the outer container 302, and the remaining divided bodies 303c are already arranged. In this case, the step portions 303d and 303e of the adjacent divided bodies 303a and 303c are fitted to each other. Accordingly, the divided bodies 303a and 303c are restrained each other, and the inner container 303 is fixed in the outer container. The shape of the portion where each of the divided bodies 303a and 303c is fitted to each other is not limited to the staircase shape as shown in FIG. For example, the division bodies 303a and 303c may be fitted to each other by a dovetail groove, or may be performed by a bowl shape (both not shown). That is, any shape may be used as long as the divided bodies 303a and 303c are self-constrained.

(Embodiment 6)
FIG. 17 is a radial cross-sectional view showing a cask according to Embodiment 6 of the present invention. The cask 300 ″ shown in FIG. 17 is a staggered arrangement (or checkered arrangement) of baskets 307 of the cask 300 ′ (with the inner container 303 having a divided structure) shown in FIG. 16. The basket 307 is a square pipe. By arranging 308 in a staggered manner, a plurality of cells are formed. Specifically, one cell is formed by the inside of the square pipe 308, and the other cell is formed by a space defined by the outer surfaces of the square pipe 308. The square pipes 308 are combined with the square pipes 308 adjacent to each other at the corners, but the constraining shape may be a simple inclined surface as shown in FIG. In this way, the number of the square pipes 308 can be reduced, and the thickness of the square pipes 308 has a desired neutron absorption performance. Based on this, it is necessary to make it larger than the square pipe shown in FIG.

(Embodiment 7)
FIG. 18 is a partial cross-sectional view showing a cask according to Embodiment 7 of the present invention. This cask relates to the lid structure of the cask shown in FIG. The other configuration is the same as that of the cask, and the description thereof is omitted. First, the cask lid structure is configured such that the seal surface 11e of the secondary lid 27 is positioned higher than the mating surface 11d of the secondary lid 27 and the flange 11 of the inner container 8, as shown in FIG. . The mating surface 11d refers to a surface of the stepped surface where the secondary lid 27 and the flange 11 are in contact, excluding the sealing surface 11e with the metal gasket 29 interposed therebetween (hereinafter the same). Specifically, the back surface of the secondary lid 27 is machined so that the outer peripheral portion protrudes downward, and the protruding portion 27a comes into contact with the concave portion 11k provided on the outer peripheral edge of the flange 11 to form the mating surface 11d. . The seal groove 28 is formed inside a protrusion 27a provided on the peripheral edge of the secondary lid 27, and the mating surface 11d is below the seal surface 11e in a state where the secondary lid 27 is attached to the flange 11.

  In this way, when the cask is erected and stored for a long period of time, it is difficult for condensed water to enter the seal surface 11e, so that it is possible to effectively prevent moisture from entering into the interior in combination with the sealing effect. Further, by accurately machining the protrusion 27a that forms the mating surface 11d and the recess 11k of the flange 11, the secondary lid 27 and the flange 11 are fitted to each other, contributing to prevention of the displacement of the secondary lid 27. it can.

  FIG. 19 is a partial cross-sectional view showing a cask according to another embodiment of the present invention. This cask relates to the lid structure of the cask shown in FIG. The other configuration is the same as that of the cask, and the description thereof is omitted. First, as shown in FIG. 19, the cask lid structure is configured such that the mating surface 11f of the secondary lid 27 and the flange 11 of the inner container 8 is higher than the sealing surface 11e of the secondary lid 27. . Specifically, the back surface of the secondary lid 27 is machined to form a concave portion 27b on the outer peripheral edge, and the concave portion 27b comes into contact with the protruding portion 11m provided on the outer peripheral edge of the flange 11 to form the mating surface 11f. The seal groove 28 is formed inside a recess 27b provided on the peripheral edge of the secondary lid 27, and the mating surface 11e is located above the seal surface 11f in a state where the secondary lid 27 is attached to the flange 11.

  In this way, when it is necessary to reinforce the sealing performance due to the deterioration of the sealing performance due to the metal gasket 29, the sealing material is filled from the mating surface 11f above the sealing surface 11e to improve the sealing performance. be able to. That is, by injecting the fluidized seal material from the mating surface 11f, the seal material enters from the upper mating surface 11f and reaches the seal surface 11e through which the metal gasket 29 is interposed via the vertical portion. When the sealing material is solidified in this state, a new sealing surface is formed. This is particularly effective when it is necessary to temporarily and urgently improve the sealing performance. In addition, as shown in FIG. 20, the dew condensation water etc. which entered the seal surface 11e are preferably discharged to the outside by providing a drain hole 70. Specifically, the drain hole 70 is formed by machining a drainage channel 71 communicating from the side surface of the flange 11 to the seal surface 11 e, and the opening exposed to the outside is normally plugged by a plug 72. The drainage channel 71 is preferably formed in a seal portion by the metal gasket 29 and a seal portion outside the seal portion. When filling the sealing material, first, the internal moisture is discharged to the outside from the drain hole 70. Note that the structure shown in FIG. 18 and the structure shown in FIG. 19 are inventions of different viewpoints, and therefore, either one may be selected according to the purpose.

  FIG. 21 is a partial sectional view showing a cask according to another embodiment of the present invention. This cask is characterized in that the upper surface 23a of the primary lid 23 is above the seal surface 11e between the secondary lid 27 and the flange 11 (the seal surface 11e is higher than the mating surface 11d). The other configuration is the same as that of the cask shown in FIG. Since the upper surface 23a of the primary lid 23 is set to be higher than the sealing surface 11d, the cask has a pool on the upper surface 23a of the primary lid 23 when the primary lid 23 is temporarily placed in the pool and the cask is taken out from the pool. There is no water left. That is, when the primary lid 23 is attached, the upper surface 23a of the primary lid 23 is at the highest position of the cask, so that the pool water spills around and does not remain on the upper surface 23a of the primary lid 23. For this reason, decontamination when it takes out from a pool can be performed easily. The reason why the mating surface 11d is lower than the sealing surface 11e is that if the mating surface 11d is higher than the sealing surface 11e, pool water accumulates inside the mating surface 11d as a bank.

(Embodiment 8)
FIG. 22 is a partial sectional view showing a cask according to the eighth embodiment of the present invention. The cask has a configuration in which a ring member 81 is held around the primary lid 23 in order to prevent the primary lid 23 from being laterally displaced. A tapered surface 81a is formed inside the ring member 81, and a tapered surface 23b is also formed on the side surface of the primary lid 23 so as to correspond to this. By fixing the ring member 81 to the flange 11 with the bolt 26, the tapered surface 81 a of the ring member 81 comes into contact with the tapered surface 23 b of the primary lid 23, and the primary lid 23 is aligned along the radial direction of the primary lid 23. Absorb the gap. Here, when tightened, the positions of the bolt holes are set so that the tapered surfaces 81a and 23b of the primary lid 23 and the ring member 81 are maintained in a pressure contact state. Further, the angles of the tapered surfaces 81a and 23b need to be such that the primary lid 23 can be fixed. If the primary lid 23 is fixed by the ring member 81, the rigidity of the ring member 81 is relatively low, so that the ring member 81 comes into contact with the tapered surfaces 81 a and 23 b of the primary lid 23 while being slightly bent by tightening the bolt 26. Thereby, the lateral displacement of the primary lid 23 is prevented.

  In order to make use of the adjustment function of the ring member 81, a predetermined gap is formed between the lower surface 81b of the ring member 81 and the seal surface 11b. In addition, it is preferable that a predetermined gap is formed between the upper surface 81 c of the ring member 81 and the lower surface 27 b of the secondary lid 27. Further, the cask shown in the figure is similar to the one shown in the seventh embodiment, and the mating surface 11d of the secondary lid 27 and the flange 11 is located below the seal surface 11e. Intrusion into the seal surface 11e is prevented, and the secondary lid 27 is engaged with the flange 11 to prevent lateral displacement of the secondary lid 27. That is, the ring member 81 prevents the primary lid 23 from shifting laterally, and the meshing prevents the secondary lid 27 from shifting laterally, thereby preventing the cask lid structure from shifting as a whole.

(Embodiment 9)
FIG. 23 is a partial cross-sectional view of a cask according to Embodiment 9 of the present invention. This cask is formed by welding the flange 11 of the inner container 8 of the cask shown in FIG. 1 and the end of the outer container 9 (welded portion 91). The inner container 8 and the outer container 9 are fixed with almost no gap by cold fitting, shrink fitting, or a combination of these, but in order to strengthen the bolt fixing, it melts between the flange 11 and the end of the outer container 9. Make a deep weld. For example, for such welding, electron beam welding which can be joined in a short time with minimum heat input is suitable. Note that a predetermined groove may be formed between the flange 11 and the outer container 9 end, and welding may be performed by TIG welding or the like.

  Further, as shown in FIG. 24, the joint surface between the end of the outer container 9 and the flange 11 may be formed into a stepped shape 93, and only the outer joint surface may be welded (welded portion 92). In this way, the welding depth can be small. In short, this embodiment is characterized in that welding can be performed in a short time by minimizing heat input by performing the welding portion in a planar manner.

It is an axial sectional view showing a cask according to Embodiment 1 of the present 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 radial direction sectional drawing which shows the modification of the cask shown in FIG. It is axial direction sectional drawing which shows the cask which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the assembly procedure of the cask shown in FIG. It is axial direction sectional drawing which shows the cask which concerns on Embodiment 3 of this invention. It is radial direction sectional drawing of the cask shown in FIG. It is radial direction sectional drawing which shows the modification of the cask of the said Embodiment 3. It is a partial cross section figure which shows the modification of the cask of the said Embodiment 1. FIG. It is radial direction sectional drawing which shows the cask which concerns on Embodiment 5 of this invention. It is radial direction sectional drawing which shows the cask which concerns on Embodiment 5 of this invention. It is radial direction sectional drawing which shows the cask which concerns on Embodiment 6 of this invention. It is a partial cross section figure which shows the cask which concerns on Embodiment 7 of this invention. It is a partial cross section figure which shows the cask which concerns on another embodiment of this invention. FIG. 20 is a partial cross-sectional view showing a modified example of the cask shown in FIG. 19. It is a partial cross section figure which shows the cask which concerns on another embodiment of this invention. It is a partial cross section figure which shows the cask which concerns on Embodiment 8 of this invention. It is a partial cross section figure of the cask which concerns on Embodiment 9 of this invention. It is a partial cross section figure of the cask which concerns on Embodiment 9 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Cask 1 Body 2 Neutron shielding body 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 fin

Claims (5)

An inner container with a sealing function in the shape of a bottomed integral container;
An outer container that constitutes a trunk body that shields radiation together with the inner container and does not require a thicker sealing function than the inner container provided outside the inner container;
A neutron shield provided outside the outer vessel,
A basket which is provided in the cavity of the inner container and constitutes a plurality of cells which accommodate a plurality of square pipes made of a material obtained by adding boron or a boron compound to an aluminum material or an aluminum alloy to store a recycled fuel assembly. When,
The radioactive container is characterized in that the outer container is composed of a plurality of divided bodies, and these divided bodies are arranged on the outer periphery of the inner container.   2. The radioactive substance storage container according to claim 1, wherein among the plurality of divided bodies constituting the outer container, a divided body positioned near the center in the axial direction is thickened in accordance with a dose of γ rays.   The radioactive substance storage container according to claim 2, wherein a portion located near the center in the axial direction of the neutron shield is thickened.   The radioactive substance storage container according to any one of claims 1 to 3, wherein a neutron shielding material is sealed in a portion corresponding to the bottom of the container between the inner container and the outer container.   The inner container has a flange on the opening side, and the joining surface between the flange side surface and the end side surface of the outer container into which the inner container is fitted is welded to the end surface of the outer container in a substantially planar manner. The radioactive substance storage container according to any one of claims 1 to 4.

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