JP6574352B2 - Dissimilar metal structures and radioactive material storage containers - Google Patents

Description

  The present invention relates to a dissimilar metal structure composed of dissimilar metal materials, and a radioactive substance storage container to which the dissimilar metal structure is applied to store, transport and store radioactive waste.

  Radioactive waste generated in a nuclear power plant nuclear reactor or the like is stored in a radioactive material storage container, transported to a storage facility or a reprocessing facility, and stored or reprocessed. As disclosed in Patent Document 1, such a radioactive substance storage container has a cylindrical body with a bottom with an open top and a plurality of cells that can individually store a plurality of radioactive substances. It is comprised from the basket and the cover part fixed to the upper part of a trunk | drum. Non-Patent Document 1 discloses a structure that suppresses corrosion by a stainless steel boss or aluminum spraying at the lid.

JP 2013-104793 A

Nuclear Fuel Cycle Safety Subcommittee Interim Storage Working Group Study Committee on Welding of Spent Fuel Storage Facility (Second) Handout Document 2-2

  For example, if at least a part of the lid portion is corroded (rusted) by contact with water, the performance of the radioactive substance storage container may be deteriorated. As one of the prior arts to suppress the occurrence of corrosion, part of the lid part that is highly likely to corrode or that requires high rust prevention is made of stainless steel, and the other part is made of carbon steel. There is a technology of dissimilar metal structures. Costs can be reduced by making a part of the lid part stainless steel. However, if rust prevention is required for the carbon steel material, a surface treatment film such as plating is applied to the surface of the carbon steel material.

  However, when the surface treatment film is not necessary for the stainless steel material, the end portion of the surface treatment film exists at the boundary portion between the stainless steel material and the carbon steel material. In this case, the surface treatment film is easily peeled off from the end.

  The present invention solves the above-described problems, and an object thereof is to provide a dissimilar metal structure and a radioactive substance storage container that can prevent the surface treatment film from peeling off at the boundary between dissimilar metals.

  In order to achieve the above object, the dissimilar metal structure of the present invention is a dissimilar metal structure in which a surface treatment film is provided on at least the surface of the carbon steel material obtained by overlay welding or welding joining a stainless steel material to a carbon steel material. A groove or a step is formed along a boundary portion between the surfaces of the carbon steel material and the stainless steel material.

  According to this dissimilar metal structure, the end of the surface treatment film is separated from the surface of the carbon steel material and the stainless steel material by forming the groove or step along the boundary portion of the surface of the carbon steel material and the stainless steel material. Arranged. As a result, it becomes difficult to apply an external force to the end portion of the surface treatment film, so that the surface treatment film can be prevented from being peeled off at the boundary between different kinds of metals.

  In the dissimilar metal structure of the present invention, an auxiliary groove communicating with the groove or the step is formed on at least one surface of the carbon steel material or the stainless steel material.

  According to this dissimilar metal structure, by providing the auxiliary groove, foreign matter such as water entering the groove or the step portion can be discharged from the auxiliary groove, and the surface treatment film accompanying the corrosion of the groove or the step portion is accompanied. Can be prevented.

  In the dissimilar metal structure according to the present invention, the stainless steel material is characterized in that a contact surface with which a seal member contacts is formed on the surface, and a plurality of fine grooves are formed on the contact surface.

  According to this dissimilar metal structure, the seal member is disposed so as to contact a large number of fine grooves, and the seal member is fitted into the irregularities formed by the large number of fine grooves, so that a high sealing function can be obtained. . As a result, the reliability of the sealing function of the sealing member can be improved.

  Further, in the dissimilar metal structure of the present invention, a recess is formed on the surface of the stainless steel material, and the position of the surface in the range from the periphery of the recess to at least the boundary between the carbon steel material and the stainless steel material is the surface treatment film. It is located in the bottom face side of the said recessed part rather than the surface position of the said carbon steel material provided with.

  A sheet for masking the stainless steel material on the inner surface of the recess by forming a recess on the surface of the stainless steel material and closing the recess at the periphery of the recess from the viewpoint of manufacturing for providing a portion not subjected to surface treatment on the stainless steel material A sticking surface is formed. For this reason, the position of the surface in the range from the peripheral edge of the recess to at least the boundary between the carbon steel material and the stainless steel material is located on the bottom surface side of the recess with respect to the surface position of the carbon steel material provided with the surface treatment film. Is formed in a portion recessed from the surface of the carbon steel material. Therefore, according to this dissimilar metal structure, in consideration of the case where additional processing of the pasting surface is required in the masking sheet peeling work after the surface treatment, the pasting surface is provided at a position where flatness is not required. This can contribute to improvement in workability and cost reduction.

  In the dissimilar metal structure according to the present invention, the pasting surface is subjected to a surface finish corresponding to the pasting of the sheet.

  According to this dissimilar metal structure, the surface of the bonding surface formed in the recessed portion from the surface of the carbon steel material is subjected to surface finishing such as roughing or polishing, which makes it difficult for the sheet to peel off and the reliability of masking It becomes easy to control the position of the edge part of a surface treatment film | membrane, and it can contribute to workability | operativity improvement and cost reduction.

  In order to achieve the above object, a radioactive substance storage container according to the present invention is a radioactive substance storage container comprising a trunk part that stores a radioactive substance, and a lid part that closes an opening part of the trunk part. The dissimilar metal structure described above is applied to at least one of the body portion and the seal portion of the lid portion.

  According to this radioactive substance storage container, the end of the surface treatment film is separated from the surface of the carbon steel material and the stainless steel material by forming a groove or a step along the boundary portion of the surface of the carbon steel material and the stainless steel material. Arranged. As a result, it becomes difficult to apply an external force to the end portion of the surface treatment film, so that the surface treatment film can be prevented from being peeled off at the boundary between different kinds of metals. By applying this structure to at least one of the seal part of the body part or the lid part, it is possible to prevent a situation where foreign matter generated due to corrosion due to peeling of the peeled surface treatment film or the surface treatment film is caught in the seal part. And the sealing performance can be improved.

  According to the present invention, it is possible to prevent the surface treatment film from being peeled off at the boundary between different kinds of metals.

FIG. 1 is a side sectional view showing an example of a cask as a radioactive substance storage container to which a dissimilar metal structure according to an embodiment of the present invention is applied. FIG. 2 is a plan sectional view of the cask shown in FIG. FIG. 3 is a partially enlarged cross-sectional view of the cask shown in FIG. FIG. 4 is a cross-sectional view of a general dissimilar metal structure. FIG. 5 is a cross-sectional view of a general dissimilar metal structure. FIG. 6 is a cross-sectional view of a general dissimilar metal structure. FIG. 7 is a cross-sectional view of a state in which a surface treatment film is provided in a form in which a stainless steel material is welded and welded to a carbon steel material. FIG. 8 is a cross-sectional view of a state in which a surface treatment film is provided in a form in which a stainless steel material is welded and joined to a carbon steel material. FIG. 9 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 10 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 11 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 12 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 13 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 14 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 15 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 16 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 17 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 18 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 19 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. 20 is a bottom view of the dissimilar metal structure shown in FIG. FIG. 21 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. 22 is a bottom view of the dissimilar metal structure shown in FIG. FIG. 23 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 24 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 25 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 26 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 27 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 28 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 29 is a partially enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 30 is a partial enlarged cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 31 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 32 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention. FIG. 33 is a cross-sectional view of a dissimilar metal structure according to an embodiment of the present invention.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a side sectional view showing an example of a cask as a radioactive substance storage container to which a dissimilar metal structure according to this embodiment is applied. FIG. 2 is a plan sectional view of the cask shown in FIG.

  A cask 11 as a radioactive substance storage container includes a body portion 12, a lid portion 13, and a basket 14. The trunk portion 12 has a cylindrical shape in which an opening 22 is formed in one upper portion of the trunk body 21 and a bottom portion (blocking portion) 23 is formed in the lower portion that is the other. The trunk body 21 is provided with a cavity 24 inside, and the cavity 24 has a shape that matches the outer peripheral shape of the basket 14. The basket 14 has, for example, a plurality of cells that individually store radioactive materials (not shown) that are spent fuel assemblies. The basket 14 has a basket body 14A as shown in FIG. In the basket body 14A, radioactive substance storage portions 14B as cells arranged parallel to each other at a predetermined interval are formed continuously in the vertical direction. Here, the vertical direction is a direction along the longitudinal direction X that is the extending direction of the cylindrical central axis of the trunk body 21 in the cask 11, and corresponds to the vertical direction of the trunk body 21. And the bottom part 23 of the trunk | drum main body 21 is weld-joined or integrally molded by the lower part, and this trunk | drum main body 21 and the bottom part 23 are forged products made from carbon steel which has a gamma ray shielding function. Stainless steel can also be used for the trunk | drum main body 21 and the bottom part 23 instead of carbon steel. Further, the trunk main body 21 and the bottom 23 can be made of cast products such as spheroidal graphite cast iron or carbon steel cast steel.

  The body portion 12 is provided with an outer cylinder 25 with a predetermined gap on the outer peripheral side of the body main body 21, and conducts heat between the outer peripheral surface of the body main body 21 and the inner peripheral surface of the outer cylinder 25. A plurality of heat transfer fins 25A made of copper or steel are welded at equal intervals in the circumferential direction. The body 12 is a resin (neutron shielding body) 26 containing boron or a boron compound which is a polymer material containing a large amount of hydrogen and has a neutron shielding function in the space between the body body 21 and the outer cylinder 25. Is injected and solidified through a pipe (not shown) in a fluidized state.

  The body 12 may have a bottom plate 28 connected to the lower side of the bottom 23 with a plurality of connecting plates 27 with a predetermined gap, and a resin (neutron) in a space between the connecting plate 27 and the bottom plate 28. A shield) 29 is provided. The connecting plate 27 may not be provided. Further, the trunnion 30 is fixed to the side surface 35 of the trunk portion 12.

  As shown in FIG. 1, the lid portion 13 includes a primary lid 31, a secondary lid 32, and a tertiary lid 33. The primary lid 31 is detachably attached to the opening 22 of the trunk main body 21 in the trunk 12. The secondary lid 32 is detachably attached to the opening 22 outside the primary lid 31. The tertiary lid 33 is detachably attached to the opening 22 outside the secondary lid 32. The primary lid 31 maintains a negative pressure on the cavity 24 side to prevent leakage of the gas filled in the cavity 24 and shields radiation (γ rays) emitted from the radioactive material stored in the cavity 24. Further, the primary lid 31 is provided with a resin (neutron shield) 34 on the secondary lid 32 side. The secondary lid 32 has a pressure monitoring boundary pressurized against the atmosphere with the primary lid 31, and prevents leakage of gas from the primary lid 31 and maintains a negative pressure on the cavity 24 side. . The tertiary lid 33 protects the secondary lid 32 from external impacts and maintains a negative pressure on the cavity 24 side. Although not clearly shown in the figure, a buffer portion that absorbs the impact of the secondary lid 32 may be provided between the primary lid 31 and the secondary lid 32.

  Here, attachment of the primary lid 31, the secondary lid 32, and the tertiary lid 33 to the opening 22 will be described. FIG. 3 is a partially enlarged cross-sectional view of the cask shown in FIG.

  As shown in FIG. 3, the trunk portion 12 is formed with a stepped portion on the inner peripheral portion of the opening 22 of the trunk body 21. The stepped portion includes a first step portion 41, a second step portion 42, and a third step portion 43 from the inside of the opening 22.

  The first step portion 41 has a first inner peripheral portion 41A and a first seat surface portion 41B. The first inner peripheral portion 41 </ b> A forms the inner periphery of the trunk body 21, and extends outside the opening 22 in the longitudinal direction X. The first seat surface portion 41 </ b> B extends from the extending end of the first inner peripheral portion 41 </ b> A to the outer side in the radial direction of the trunk body 21 and forms a surface facing the outer side of the opening 22. The first seat surface portion 41 </ b> B is provided with a plurality of screw holes 41 </ b> C along the periphery of the trunk body 21. In the first step portion 41, the primary lid 31 is fixed to the trunk body 21.

  The second step portion 42 is located outside the opening 22 with respect to the first step portion 41 in the longitudinal direction X. The second step portion 42 has a second inner peripheral portion 42A and a second seat surface portion 42B. The second inner peripheral portion 42 </ b> A forms the inner periphery of the trunk body 21 and extends from the outer peripheral end of the first seat surface portion 41 </ b> B of the first step portion 41 to the outside of the opening portion 22 in the longitudinal direction X. The second seat surface portion 42 </ b> B extends from the extending end of the second inner peripheral portion 42 </ b> A to the radially outer side of the trunk body 21 and forms a surface facing the outer side of the opening portion 22. The second seat surface portion 42 </ b> B is provided with a plurality of screw holes 42 </ b> C along the periphery of the trunk body 21. In the second step portion 42, the secondary lid 32 is fixed to the trunk body 21.

  The third step portion 43 is located outside the opening portion 22 in the longitudinal direction X with respect to the second step portion 42. The third step portion 43 has a third inner peripheral portion 43A and a third seat surface portion 43B. The third inner peripheral portion 43 </ b> A forms the inner periphery of the trunk body 21, and extends from the outer peripheral end of the second seat surface portion 42 </ b> B of the second step portion 42 to the outside of the opening portion 22 in the longitudinal direction X. The third seat surface portion 43 </ b> B extends from the opening edge of the opening 22, which is the extended end of the third inner peripheral portion 43 </ b> A, to the outer side in the radial direction of the trunk body 21, and forms a surface facing the outside of the opening 22. The third seat surface portion 43 </ b> B forms an end surface on the outer side of the opening 22 in the trunk body 21. The third seat surface portion 43 </ b> B is provided with a plurality of screw holes 43 </ b> C along the periphery of the trunk body 21. In the third step portion 43, the tertiary lid 33 is fixed to the trunk body 21.

  The primary lid 31 has a disc part 31A and a protruding part 31B. The disc portion 31A is formed in a disc shape having a size that can be inserted inside the second inner peripheral portion 42A of the second step portion 42. The protruding portion 31B is provided so as to protrude from the one side surface 31Aa at the central portion of the disc portion 31A, and is formed in a columnar shape with a size that can be inserted inside the first inner peripheral portion 41A of the first step portion 41. . One side surface 31Aa of the disc portion 31A is disposed on the outer peripheral portion of the disc portion 31A. The primary lid 31 has a seal groove 31C formed on one side surface 31Aa of the disc portion 31A. A seal member (for example, a metal gasket) 31D is inserted into the seal groove 31C. Further, the primary lid 31 is provided with a plurality of through holes 31E along the circumferential direction at a position on the outer peripheral portion of the disc portion 31A and avoiding the seal groove 31C. The through hole 31 </ b> E is provided corresponding to the screw hole 41 </ b> C provided in the first seat surface portion 41 </ b> B of the first step portion 41. The primary lid 31 is configured to screw the bolt 51 inserted into the through hole 31E into the screw hole 41C in a state where the one side surface 31Aa of the disc portion 31A faces the first seat surface portion 41B of the first step portion 41. Thus, the side surface 31Aa is tightened so as to be pressed against the first seat surface portion 41B, and the seal member 31D is sandwiched between the one side surface 31Aa side and the first seat surface portion 41B side, so that the opening of the trunk body 21 22, the position of the first step 41 is sealed.

  The secondary lid 32 has a disc part 32A and a protrusion part 32B. The disc portion 32 </ b> A is formed in a disc shape having a size that can be inserted inside the third inner peripheral portion 43 </ b> A of the third step portion 43. The protrusion 32B is provided so as to protrude from the one side surface 32Aa at the center of the disk portion 32A, and is formed in a columnar shape with a size that can be inserted inside the second inner peripheral portion 42A of the second step portion 42. . One side surface 32Aa of the disc portion 32A is disposed on the outer peripheral portion of the disc portion 32A. Further, the secondary lid 32 has a seal groove 32C formed on one side surface 32Aa of the disc portion 32A. A seal member (for example, a metal gasket) 32D is inserted into the seal groove 32C. In addition, the secondary lid 32 is provided with a plurality of through holes 32E along the circumferential direction at a position that is the outer peripheral portion of the disc portion 32A and avoids the seal groove 32C. The through hole 32 </ b> E is provided corresponding to the screw hole 42 </ b> C provided in the second seat surface portion 42 </ b> B of the second step portion 42. In the secondary lid 32, the bolt 52 inserted through the through hole 32 </ b> E is screwed into the screw hole 42 </ b> C in a state where the one side surface 32 </ b> Aa of the disk portion 32 </ b> A faces the second seat surface portion 42 </ b> B of the second step portion 42. Thus, the one side surface 32Aa is tightened so as to be pressed against the second seat surface portion 42B, and the seal member 32D is sandwiched between the one side surface 32Aa side and the second seat surface portion 42B side, thereby opening the body main body 21. The position of the second step portion 42 in the portion 22 is sealed.

  The tertiary lid 33 has a disc part 33A and a projection part 33B. The disc portion 33A is formed in a disc shape with a size that covers the third seat surface portion 43B. The protrusion 33B is provided so as to protrude from the one side surface 33Aa at the central portion of the disc portion 33A, and is formed in a columnar shape with a size that can be inserted inside the third inner peripheral portion 43A of the third step portion 43. . One side surface 33Aa of the disc portion 33A is disposed on the outer peripheral portion of the disc portion 33A. The tertiary lid 33 has a seal groove 33C formed on one side surface 33Aa of the disc portion 33A. A seal member (for example, a rubber O-ring) 33D is inserted into the seal groove 33C. Further, the tertiary lid 33 is provided with a plurality of through holes 33E along the circumferential direction at a position on the outer peripheral portion of the disc portion 33A and avoiding the seal groove 33C. The through hole 33 </ b> E is provided corresponding to the screw hole 43 </ b> C provided in the third seat surface portion 43 </ b> B of the third step portion 43. The tertiary lid 33 is configured to screw the bolt 53 inserted into the through hole 33E into the screw hole 43C in a state where the one side surface 33Aa of the disk portion 33A faces the third seat surface portion 43B of the third step portion 43. Then, the side surface 33Aa is tightened so as to be pressed against the third seat surface portion 43B, and the seal member 33D is sandwiched between the one side surface 33Aa side and the third seat surface portion 43B side, so that the opening of the trunk body 21 22, the position of the third step 43 is sealed.

  The radioactive substance is inserted into the basket 14 of the cavity 24 in the trunk body 21 in water and sealed with the primary lid 31. Thereafter, drainage and suction are performed from a drain port (not shown) provided in the primary lid 31, and gas (for example, inert gas) is injected from a sealing port (not shown) provided in the primary lid 31. As a result, the inside sealed by the primary lid 31 is set to a negative pressure and filled with gas. Thereafter, the secondary lid 32 and the tertiary lid 33 are attached. Thus, the radioactive substance is stored in the cask 11 by attaching the primary lid 31, the secondary lid 32, and the tertiary lid 33 to the trunk body 21. Although not clearly shown in the figure, the cask 11 has a configuration having only the primary lid 31, a configuration having only the primary lid 31 and the secondary lid 32, and a configuration having only the primary lid 31 and the tertiary lid 33.

  Hereinafter, the dissimilar metal structure of this embodiment will be described. 4 to 6 are cross-sectional views of a general dissimilar metal structure. 9 to 18 are cross-sectional views of the dissimilar metal structure according to the present embodiment.

  The dissimilar metal structure of the present embodiment is applied to the cask 11 described above, but its application is not limited to the cask 11.

  First, a general dissimilar metal structure applied to the above-described cask 11 will be described with reference to FIGS.

  The dissimilar metal structure shown in FIG. 4 is applied to the primary lid 31 and the secondary lid 32 of the lid 13, and the primary lid 31 and the secondary lid 32 themselves are carbon steel material CS, and the seal grooves 31 </ b> C and 32 </ b> C are used. Is a stainless steel material SS. Specifically, the stainless steel material SS is overlay welded or welded to the carbon steel material CS of the primary lid 31 or the secondary lid 32, and the stainless steel material SS itself is formed so as to form recesses constituting the seal grooves 31C and 32C. Has been. And the inner surface of the recessed part which is the seal grooves 31C and 32C becomes contact surfaces 31Ca and 32Ca which contact the seal members 31D and 32D (not shown). In the dissimilar metal structure shown in FIG. 4, a surface treatment film 61 for rust prevention is applied to the surface of the carbon steel material CS of the primary lid 31 and the secondary lid 32. The surface treatment film 61 is formed by, for example, electroless nickel plating, and the surface treatment film 61 is applied by immersing the primary lid 31 or the secondary lid 32 in a plating solution and the surface comes into contact with the plating solution. In the electroless nickel plating process, the surface treatment film 61 is formed on the surface of the carbon steel material CS, but is hardly formed on the surface of the stainless steel material SS. Accordingly, the surface treatment film 61 is applied only to the surface of the carbon steel material CS of the primary lid 31 and the secondary lid 32. However, there is a possibility that the surface treatment film 61 may be formed on the stainless steel material SS, although it is extremely small. The contact surfaces 31Ca and 32Ca of the seal grooves 31C and 32C made of the stainless steel material SS are portions that come into contact with the seal members 31D and 32D, and are important in the sealing function of the primary lid 31 and the secondary lid 32. It is preferable to cover with a sheet for masking so that 61 is not applied. In the dissimilar metal structure shown in FIG. 4, since the inner surfaces of the recesses that are the seal grooves 31C and 32C become the contact surfaces 31Ca and 32Ca, a sheet is stuck on the opening edge of the recess or the inner surface of the recess so as to close the recess. Attached. For this reason, the surface treatment film 61 is the surface of the carbon steel material CS, and the end is located at the boundary portion with the stainless steel material SS. The end portion of the surface treatment film 61 is slightly hung on the stainless steel material SS side so as to be surely applied to the surface of the carbon steel material CS.

  The dissimilar metal structure shown in FIG. 5 is applied to the primary lid 31 and the secondary lid 32 of the lid portion 13, and the primary lid 31 and the secondary lid 32 themselves are carbon steel material CS, and the seal grooves 31C and 32C. Is a stainless steel material SS. Specifically, the carbon steel material CS of the primary lid 31 and the secondary lid 32 is formed with recesses constituting the seal grooves 31C and 32C, and a part of the recesses (opposing the first seat surface portion 41B and the second seat surface portion 42B). The stainless steel material SS is welded to the portion to be welded. And the surface of stainless steel material SS becomes contact surface 31Ca and 32Ca which contact seal member 31D and 32D (not shown). Further, in the dissimilar metal structure shown in FIG. 5, a surface treatment film 61 for rust prevention is applied to the surface of the carbon steel material CS of the primary lid 31 and the secondary lid 32. The surface treatment film 61 is formed by, for example, electroless nickel plating. Also here, it is preferable to cover the contact surfaces 31Ca and 32Ca made of the stainless steel material SS with a sheet for masking so that the surface treatment film 61 is not applied. In the dissimilar metal structure shown in FIG. 5, a sheet is affixed to the contact surfaces 31Ca and 32Ca on the surface of the stainless steel material SS. For this reason, the surface treatment film 61 is the surface of the carbon steel material CS, and the end is located at the boundary portion with the stainless steel material SS. The end portion of the surface treatment film 61 is slightly hung on the stainless steel material SS side so as to be surely applied to the surface of the carbon steel material CS.

  The dissimilar metal structure shown in FIG. 6 is applied to the tertiary lid 33 of the lid portion 13. The tertiary lid 33 itself is a carbon steel material CS, and the seal groove 33 </ b> C is a stainless steel material SS. Specifically, the stainless steel material SS is build-up welded or welded to the carbon steel material CS of the tertiary lid 33, and the stainless steel material SS itself is formed so as to form a recess that constitutes two seal grooves 33C. Then, the inner surface of the recess that is the seal groove 33C serves as a contact surface 33Ca that comes into contact with the seal member 33D (not shown). In the dissimilar metal structure shown in FIG. 6, a surface treatment film 61 for rust prevention is applied to the surface of the carbon steel material CS of the tertiary lid 33. The surface treatment film 61 is formed by, for example, electroless nickel plating. Also here, it is preferable to cover with a sheet for masking so that the surface treatment film 61 is not applied to the contact surface 33Ca of the seal groove 33C made of the stainless steel material SS. In the dissimilar metal structure shown in FIG. 6, since the inner surface of the recess that is the seal groove 33C serves as the contact surface 33Ca, a sheet is attached to the opening edge of the recess or the inner surface of the recess so as to close the recess. For this reason, the surface treatment film 61 is the surface of the carbon steel material CS, and the end is located at the boundary portion with the stainless steel material SS. The end portion of the surface treatment film 61 is slightly hung on the stainless steel material SS side so as to be surely applied to the surface of the carbon steel material CS.

  The dissimilar metal structures shown in FIGS. 4 to 6 described above may cause the following problems. In the dissimilar metal structure shown in FIGS. 4 and 6, the end portion of the surface treatment film 61 comes into contact with the first seat surface portion 41B, the second seat surface portion 42B, or the third seat surface portion 43B, and an external force is applied. Since the end portion of the surface treatment film 61 is exposed, an external force is likely to be applied from the side surface direction of the surface treatment film, and there is a possibility of peeling. Then, the peeled piece of the surface treatment film 61 enters the seal grooves 31C and 32C and the seal groove 33C and is sandwiched between the contact surfaces 31Ca and 32Ca and the seal members 31D and 32D or between the contact surface 33Ca and the seal member 33D. And there exists a possibility that sealing performance may be impaired. Further, the dissimilar metal structure shown in FIG. 5 may be peeled off due to an external force applied to the end of the surface treatment film 61 when the contact surfaces 31Ca and 32Ca are wiped and washed. And if the peeling piece of the surface treatment film 61 enters the seal grooves 31C and 32C and is sandwiched between the contact surfaces 31Ca and 32Ca and the seal members 31D and 32D, the sealing performance may be impaired.

  Here, FIG. 7 is a cross-sectional view of a state in which a surface treatment film is provided in a form in which a stainless steel material is welded and bonded to a carbon steel material. In this case, the end of the surface treatment film 61 is a carbon steel material. It is applied along the surface of the welding material N (for example, nickel) of overlay welding for joining CS and the stainless steel material SS. FIG. 8 is a cross-sectional view of a state in which a surface treatment film is provided in a form in which a stainless steel material is welded and joined to a carbon steel material. In this case, the end of the surface treatment film 61 is joined. It is applied along the surfaces of the carbon steel material CS and the stainless steel material SS.

  The dissimilar metal structure of this embodiment is configured to prevent the surface treatment film 61 from being peeled off at the boundary between dissimilar metals. This will be specifically described with reference to FIGS.

  The dissimilar metal structure shown in FIG. 9 corresponds to the dissimilar metal structure shown in FIG. 4, and the groove 1 is formed along the boundary portion between the surfaces of the carbon steel material CS and the stainless steel material SS. Further, the dissimilar metal structure shown in FIG. 10 corresponds to the dissimilar metal structure shown in FIG. 5, and the groove 1 is formed along the boundary portion between the surfaces of the carbon steel material CS and the stainless steel material SS. Further, the dissimilar metal structure shown in FIG. 11 corresponds to the dissimilar metal structure shown in FIG. 6, and the groove 1 is formed along the boundary portion between the surfaces of the carbon steel material CS and the stainless steel material SS.

The groove 1 is characterized in that the following dimensional conditions are satisfied so that the seal members 31D and 32D do not enter the groove 1 and come into contact with the end portion of the surface treatment film 61 when the seal members 31D and 32D are attached. And
W <0.5R
And in the case of FIGS. 9 and 11, D> R−√ {R ² − (W / 2) ² }
In the case of FIG. 10, D> 2d
At this time, W: width of the groove 1, D: depth of the groove 1, R: cross-sectional radius of the seal members 31D and 32D, and d: thickness of the surface treatment film 61.

  9 and 11, the groove 1 is formed in an arch shape as shown in FIG. 12 or a rectangular shape as shown in FIG. The cross-sectional shape of the groove 1 is not limited to an arch shape or a rectangular shape, and is not clearly shown in the drawing, but may be, for example, a triangular shape or a trapezoidal shape. Further, as shown in FIGS. 16 and 17, the step portion 2 ′ may be formed after the groove 1 is formed. The step portion 2 ′ is characterized in that it is positioned between the surface of the carbon steel material CS and the surface of the sheet in the depth direction of the groove 1.

9 and 11, instead of the groove 1, as shown in FIG. 18, a step 2 is formed along the boundary portion of the surface of the carbon steel material CS and the stainless steel material SS. In the primary lid 31, the secondary lid 32, and the tertiary lid 33, the step portion 2 is separated from the side surfaces 31Aa, 32Aa, and 33Aa that are in contact with the first seat surface portion 41B, the second seat surface portion 42B, and the third seat surface portion 43B. The part formed in steps. The step portion 2 is located between the surface of the carbon steel material CS and the surface of the sheet in the depth direction of the groove 1, and the seal members 31D and 32D are at the end of the surface treatment film 61 when the seal members 31D and 32D are handled. It is characterized by satisfying the following dimensional conditions so as not to contact.
A> 2d
And (A)> 2d
And (A) + A <2R
And B <R
At this time, A: the distance in the depth direction of the surface of the carbon steel material CS and the stepped portion 2 (the distance in the depth direction between the sheet surface and the stepped portion 2), B: the width of the stepped portion 2, R: the sealing member 31D, A cross-sectional radius of 32D, d: the thickness of the surface treatment film 61.

  Thus, according to the dissimilar metal structure of the present embodiment, as shown in FIGS. 9 and 11 to 18, the groove 1 or the step 2 along the boundary portion of the surface of the carbon steel material CS and the stainless steel material SS. Is formed, the end portion of the surface treatment film 61 is spaced apart from the surface (one side surface 31Aa, 32Aa, 33Aa) of the carbon steel material CS and the stainless steel material SS. As a result, it is difficult to apply an external force to the end portion of the surface treatment film 61, so that the surface treatment film 61 can be prevented from being peeled off at the boundary between different kinds of metals.

  Moreover, according to the dissimilar metal structure of this embodiment, as shown in FIGS. 10, 14, and 15, the grooves 1 are formed along the boundary portions of the surfaces of the carbon steel material CS and the stainless steel material SS. The end portion of the surface treatment film 61 is spaced from the surface (contact surfaces 31Ca, 32Ca) of the stainless steel material SS. As a result, it is difficult to apply an external force to the end portion of the surface treatment film 61, so that the surface treatment film 61 can be prevented from being peeled off at the boundary between different kinds of metals.

  19 and 21 are cross-sectional views of the dissimilar metal structure according to this embodiment, FIG. 20 is a bottom view of the dissimilar metal structure shown in FIG. 19, and FIG. 22 is a dissimilar metal structure shown in FIG. FIG. In FIG. 19, FIG. 21, FIG. 20, and FIG. 22, the surface treatment film 61 is omitted.

  In the dissimilar metal structure shown in FIGS. 18 to 22, an auxiliary groove 3 communicating with the groove 1 or the step portion 2 is formed on at least one surface of the carbon steel material CS and the stainless steel material SS. 19 and 20, the auxiliary groove 3 communicating with the groove 1 is formed in the carbon steel material CS and the stainless steel material SS. In FIGS. 18 and 21, the auxiliary groove 3 communicating with the groove 1 or the step portion 2 is formed only in the carbon steel material CS. 18 to 20, the auxiliary groove 3 is characterized in that the depth thereof is shallower than the depth of the groove 1 or the stepped portion 2. 21 and 22, the auxiliary groove 3 is characterized in that the depth thereof is shallower than the depth of the sheet grooves (31C, 32C).

  According to this dissimilar metal structure, by providing the auxiliary groove 3, foreign matter that enters the groove 1 or the stepped portion 2 and the sheet groove (31 </ b> C, 32 </ b> C) can be discharged from the auxiliary groove 3. In the case of the cask 11, the primary lid 31 is drained after being attached, but water (foreign matter) that has entered the groove 1 or the stepped portion 2 and the sheet groove (31C, 32C) is removed from the auxiliary groove 3 to the outside of the primary lid 31. Alternatively, by discharging to the inside, it is possible to prevent water from collecting in the groove 1 or step 2 and the sheet groove (31C, 32C), and the surface treatment film 61 is peeled off due to corrosion of the groove 1 or step 2 by water. Further, corrosion and deterioration of the sealing member 31D can be prevented. That is, for example, the auxiliary groove 3 communicates with the outer end of one side surface 31Aa of the disk portion 31A on the outer side of the seal groove 31C in the primary lid 31, and on the inner side of the one side surface 31Aa on the inner side of the seal groove 31C. It is connected to the end and the protruding portion 31B. In the case of the cask 11, it is preferable to provide a plurality of auxiliary grooves 3 in the circumferential direction of the primary lid 31 (for example, four places in a cross shape) in order to appropriately discharge foreign matter. 19 and 21 show an example in which the auxiliary groove 3 is provided for the primary lid 31 and the secondary lid 32, the auxiliary groove 3 may be provided in the tertiary lid 33.

  23, 24, and 25 are cross-sectional views of the dissimilar metal structure according to the present embodiment. 23, 24, and 25, the surface treatment film 61 is omitted. 26 and 27 are examples of the groove 1 of FIG. 23, FIGS. 28 and 29 are examples of the groove 1 of FIGS. 24 and 25, and FIG. 30 is a groove of FIGS. 24 and 25. This is an example in which a step 2 is applied instead of 1.

  In the dissimilar metal structure shown in FIGS. 23, 24, and 25, the stainless steel material SS has a recess 4 formed on the surface thereof, and closes the recess 4 at the periphery of the recess 4 to mask the surface treatment film 61. The affixing surface 5 of the sheet 100 is formed in a portion recessed from the surface (one side surface 31Aa, 32Aa, 33Aa) of the carbon steel material CS.

  In FIG. 23, it is the structure which provided the recessed part 4 newly in the form shown in FIG. 10, and the inner surface of the said recessed part 4 becomes contact surface 31Ca and 32Ca. 24, the groove 1 and the step 2 'shown in FIG. 16 or 17 are provided in the form shown in FIG. 9, the step 2' is configured as the affixing surface 5, and the seal grooves 31C and 32C are configured as the recess 4. Although not shown in the figure, in the case of the configuration shown in FIG. 11 as well, the groove 1 and step 2 ′ of FIG. 16 or 17 are provided, the step 2 ′ serves as the affixing surface 5, and the seal groove 33C serves as the recess 4. Configured as

  According to this dissimilar metal structure, even if an event such as a scratch on the pasting surface 5 when the sheet 100 is peeled off or the sheet 100 not easily peeled off, the pasting surface 5 has a flatness and dimensions. Since it is a surface where accuracy is not required, it can contribute to workability improvement and cost reduction in additional machining.

  In FIGS. 23, 24, and 25, the stainless steel material SS on which the bonding surface 5 is formed is disposed at a position recessed from the surface of the carbon steel material CS, and the bonding surface 5 is a surface corresponding to the bonding of the sheet 100. Processing is performed. Specifically, the surface processing is processing corresponding to a material for attaching the sheet 100, and includes rough processing, polishing processing, and the like.

  According to this dissimilar metal structure, the sheet 100 is hardly peeled off, and the masking reliability can be improved. In the case of the cask 11, by improving the reliability of masking, it is possible to prevent the material (plating solution) of the surface treatment film 61 from adhering to the contact surfaces 31Ca, 32Ca, 33Ca.

  31 to 33 are cross-sectional views of the dissimilar metal structure according to the present embodiment. 31 to 33 show other application examples in the dissimilar metal structure of the above-described embodiment. In other words, the dissimilar metal structure is applied to each seating surface portion 41B, 42B, 43B of each step portion 41, 42, 43 in the trunk body 21 of the cask 11. Specifically, the trunk main body 21 (each seat surface portion 41B, 42B, 43B) is formed of a carbon steel material CS, is a part of each seat surface portion 41B, 42B, 43B, and seals the lids 31, 32, 33. The stainless steel material SS is welded and joined to the portion where the openings of the grooves 31C, 32C, and 33C face each other (that is, the contact surface that the seal members 31D, 32D, and 33D contact).

  And the dissimilar-metal structure shown in FIG. 31 has the groove | channel 1 formed along the boundary part of the surface of carbon steel material CS and stainless steel material SS. In the dissimilar metal structure shown in FIG. 32, the auxiliary groove 3 is formed. In the dissimilar metal structure shown in FIG. 33, the concave portion 4 is formed, and the pasting surface 5 is formed in a portion recessed from the surface of the carbon steel material CS. Further, the pasting surface 5 is subjected to a surface treatment corresponding to the pasting of the sheet 100.

  That is, in the case of the cask 11, the dissimilar metal structure can be applied not only to the lid 13 side but also to the trunk body 21 side.

  By the way, in the dissimilar metal structure of the present embodiment, contact surfaces 31Ca, 32Ca, and 33Ca that contact the seal members 31D, 32D, and 33D are formed on the surface of the stainless steel material SS, and a large number of the contact surfaces 31Ca, 32Ca, and 33Ca are formed. A narrow groove is preferably formed. Further, it is preferable that the contact surfaces (41B, 42B, 43B) to the seal members 31D, 32D are similarly formed with a large number of narrow grooves.

  The narrow groove is formed by serration processing. That is, the seal members 31D, 32D, and 33D are arranged so as to contact a large number of narrow grooves. When the sealing members 31D, 32D, and 33D come into contact with a large number of narrow grooves, the sealing members 31D, 32D, and 33D are fitted into the irregularities formed by the large number of narrow grooves, and a high sealing function can be obtained. As a result, the reliability of the sealing function of the sealing members 31D, 32D, and 33D can be improved.

DESCRIPTION OF SYMBOLS 1 Groove 2 Step part 3 Auxiliary groove 4 Recessed part 5 Sticking surface 61 Surface treatment film | membrane 100 Sheet CS Carbon steel material SS Stainless steel material 11 Cask (radioactive substance storage container)
12 trunk 13 lid 31 primary lid 31C seal groove 31Ca contact surface 31D seal member 32 secondary lid 32C seal groove 32Ca contact surface 32D seal member 33 tertiary lid 33C seal groove 33Ca contact surface 33D seal member

Claims (5)

A dissimilar metal structure in which a surface treatment film is provided on the surface of at least the carbon steel material obtained by overlay welding or welding joining a stainless steel material to a carbon steel material,
A dissimilar metal structure , wherein a groove or a step is formed along a boundary portion between the surfaces of the carbon steel material and the stainless steel material, and an end of the surface treatment film is disposed in the groove or the step portion. body.   The dissimilar metal structure according to claim 1, wherein an auxiliary groove communicating with the groove or the step portion is formed on at least one surface of the carbon steel material or the stainless steel material.   3. The dissimilar metal structure according to claim 1, wherein the stainless steel material has a contact surface on the surface thereof that contacts the seal member, and a plurality of fine grooves formed on the contact surface.   A recess is formed on the surface of the stainless steel material, and the position of the surface in the range from the periphery of the recess to at least the boundary between the carbon steel material and the stainless steel material is more than the surface position of the carbon steel material on which the surface treatment film is provided. The dissimilar metal structure according to claim 1, wherein the dissimilar metal structure is located on a bottom surface side of the recess. A radioactive substance storage container comprising: a trunk part that stores a radioactive substance; and a lid part that closes an opening of the trunk part,
The radioactive substance storage container according to any one of claims 1 to 4, wherein the dissimilar metal structure according to any one of claims 1 to 4 is applied to at least one of the seal portion of the trunk portion and the lid portion.

Images