JP2020024232A - Cask - Google Patents

Abstract

To suppress deformation of an outer peripheral part of a lid upon dropping a cask.SOLUTION: A cask 1 has a second area G2a. The second area G2a is an area included in a second gap G2 that is a gap in an axis direction between a secondary lid 70 and a tertiary lid 80. The second region G2a is a region where the gap in the axial direction X is smaller than other regions of the second gap G2, and a region arranged at a position sandwiched between the outer peripheral part of the secondary lid 70 and the outer peripheral part of the tertiary lid 80. The cask is configured such that at least one of a primary lid 60 and the secondary lid 70 comprises a neutron shielding material 75, and the tertiary lid 80 does not comprise the neutron shielding material 75. The second region G2a is located only outside the neutron shielding material 75 in a radial direction Y.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cask.

  2. Description of the Related Art Conventionally, there are casks for storing radioactive substances (see, for example, FIG. 3 of Patent Document 1 and FIG. 3 of Patent Document 2). Some casks have three lids (a primary lid, a secondary lid, and a tertiary lid) that close the opening of the cask body. The cask described in Patent Literature 2 has a cushion that covers the outer peripheral portion of the tertiary lid.

Japanese Patent No. 5371681 JP 2014-145677 A

  There is an axial gap (axial gap) between the lids. For example, in the technique described in FIG. 3 of Patent Document 1, there is an axial gap having a uniform size between the secondary lid and the tertiary lid. Further, for example, in the technique described in FIG. 3 of Patent Document 2, there is an axial gap having a uniform size between the outer peripheral portion of the primary lid and the outer peripheral portion of the secondary lid.

  Here, when the cask is dropped vertically (details are described below), the impact force is transmitted from the internal storage of the cask body to the primary lid, and the impact force is transmitted from the buffer to the outer peripheral portion of the tertiary lid. At this time, the outer peripheral portion of the lid (at least the secondary lid) may be easily deformed due to the axial gap between the lids. Due to this deformation, the stress on the outer peripheral portion of the lid may be higher than the allowable stress. Usually, a member for sealing the lid and the cask main body is provided at the outer peripheral portion of the lid, so that if the stress of the outer peripheral portion of the lid increases, the sealing performance of the lid may not be ensured.

  Then, an object of this invention is to provide the cask which can suppress the deformation of the outer peripheral part of a lid at the time of a fall.

  The cask of the present invention includes a cask main body, a primary lid, a secondary lid, a tertiary lid, and a buffer. The cask main body has a bottomed cylindrical shape having a bottom, an axially long body, and an opening, and stores a radioactive substance. The primary lid closes the opening. The secondary lid is disposed axially outside the primary lid, and closes the opening. The tertiary lid is disposed axially outside the secondary lid, and closes the opening. The buffer covers an outer peripheral portion of the tertiary lid. The cask has a second area. The second area is an area included in a second gap that is an axial gap between the secondary lid and the tertiary lid, and an area in which an axial gap is smaller than other areas of the second gap. And an area disposed between the outer peripheral portion of the secondary lid and the outer peripheral portion of the tertiary lid.

  By the above means, deformation of the outer peripheral portion of the lid when the cask falls can be suppressed. As a result, it is possible to suppress a decrease in the sealing performance of the lid, which may occur when the cask is dropped.

It is sectional drawing which shows the cask 1. FIG. FIG. 2 is an enlarged view of a portion II shown in FIG. 1. FIG. 2 is a sectional view showing a primary lid 60 and a secondary lid 70 shown in FIG. 1. FIG. 2 is a view of the secondary lid 70 shown in FIG. 1 as viewed from a head side X1 toward a bottom 11. It is a figure which shows the state which the body flange part 30 (refer FIG. 1) etc. deform | transformed by the impact when the conventional cask was dropped vertically. FIG. 3 is a diagram corresponding to FIG. 2, showing a part of a cask 201 of a second embodiment. FIG. 10 is a diagram corresponding to FIG. FIG. 8 is a diagram corresponding to FIG. 4 showing the secondary lid 70 shown in FIG. 7. FIG. 9 is a diagram corresponding to FIG. 8, illustrating a modified example of the secondary lid seat running part 372 shown in FIG. 8. It is a figure equivalent to FIG. 2 which shows a part of cask 401 of 4th Embodiment. It is a figure equivalent to FIG. 2 which shows a part of cask 501 of 5th Embodiment.

(1st Embodiment)
The cask 1 of the first embodiment will be described with reference to FIGS.

  The cask 1 is a container for transporting and storing radioactive materials (radioactive material transport storage container). As shown in FIG. 1, the cask 1 includes a cask main body 10, a basket 40, a lid 50, and a buffer 90.

  The cask main body 10 is a portion for storing a radioactive substance, and has a bottomed cylindrical shape (a shape obtained by adding a bottom to a cylinder). The cask body 10 has a bottom 11, an opening 13, and a trunk 20. A direction parallel to the central axis of the cask main body 10 is defined as an axial direction X. In the axial direction X, the side (or direction) from the bottom 11 toward the opening 13 is the head side X1, and the opposite side is the bottom side X2. Hereinafter, the “radial direction Y” and the “circumferential direction” are based on the central axis of the cask main body 10.

  The trunk 20 includes a cylindrical trunk main body 21 that is long in the axial direction X, a trunk neutron shielding material 23, and a trunk flange 30. The material of the trunk main body 21 is a metal material (for example, forged carbon steel or stainless steel) (the same applies to the material of the trunk flange 30). The trunk neutron shielding member 23 is a member that shields neutrons emitted from the radioactive substance in the cask main body 10, and is disposed outside the trunk main body 21 in the radial direction Y.

  The body flange 30 extends (extends) outward from the head side X1 and radially outward from the head side X1 end of the body main body 21. The body flange portion 30 is configured so that the cover 50 can be attached, and suppresses the movement of the cover 50. As shown in FIG. 2, the body flange portion 30 includes a primary lid mounting portion 31, a secondary lid mounting portion 32, and a tertiary lid mounting portion 33.

  The primary lid attachment part 31 is a part to which the primary lid 60 (described below) is attached and to which the primary lid 60 is fixed. The primary lid attachment portion 31 includes a wall portion 31b, a fixing portion 31c, and a wall portion 31d in order from the bottom side X2 to the head side X1. The “fixing portion” such as the fixing portion 31c is a portion that suppresses the movement of the lid 50 to the bottom side X2, and is, for example, a surface whose normal direction is in the axial direction X (a surface orthogonal to the axial direction X). The “wall portion” such as the wall portion 31b is a portion that suppresses the movement of the lid 50 in the radial direction Y, and is, for example, a surface in the normal direction in the radial direction Y. Note that the shape of the primary lid attachment portion 31 may be changed according to the shape of the lid 50 (the same applies to the secondary lid attachment portion 32 and the tertiary lid attachment portion 33).

  The secondary lid attachment part 32 is a part to which a secondary lid 70 (described below) is attached and to which the secondary lid 70 is fixed. The secondary lid attachment portion 32 includes a fixing portion 32e and a wall portion 32f in order from the bottom side X2 to the head side X1. The vicinity of the corner formed by the fixing portion 32e and the wall portion 31d is defined as a trunk inner surface corner 32A. The trunk inner surface corner 32A is a portion 32B (see FIG. 5) in contact with the secondary lid sealing portion 74 (described below) and a portion in the vicinity thereof.

  The tertiary lid attachment part 33 is a part to which the tertiary lid 80 (described below) is attached and to which the tertiary lid 80 is fixed. The tertiary lid attachment portion 33 includes a fixing portion 33g.

  As shown in FIG. 1, the basket 40 is a member that is housed in the cask main body 10 and houses a fuel assembly (radioactive substance), and has a plurality of cells (lattice-like spaces). In FIG. 2, the basket 40 is omitted.

  The lid 50 is a member that closes the opening 13 as shown in FIG. The lid 50 includes a primary lid 60, a secondary lid 70, and a tertiary lid 80. Each of the primary lid 60, the secondary lid 70, and the tertiary lid 80 has a disk shape (including a substantially disk shape, the same applies hereinafter). The material of each of the primary lid 60, the secondary lid 70, and the tertiary lid 80 is mainly metal, and a portion other than metal (for example, a secondary lid neutron shielding material 75 (a neutron shielding material described below) (see FIG. 2)) There may be.

  The primary lid 60 is attached to the primary lid attaching section 31, as shown in FIG. The primary lid 60 includes a disk-shaped primary lid main body 61, a primary lid flange portion 62, a primary lid bolt 63, and a primary lid sealing seal portion 64.

  The primary lid flange portion 62 is provided at a fastening portion of the primary lid bolt 63 to the cask main body 10. The primary lid flange portion 62 has a flange structure that is recessed from the head side X1 end surface of the primary lid main body 61 to the bottom side X2. The primary lid flange portion 62 is disposed at a radially outer end of the primary lid 60 in the radial direction Y. The primary lid flange portion 62 is a surface portion, and includes a surface having a normal direction in the radial direction Y and a surface having the normal direction in the axial direction X.

  The primary lid bolt 63 is a bolt for fixing the primary lid main body 61 and the cask main body 10. The primary cover bolt 63 is passed through a through hole formed in the primary cover flange portion 62 (and the primary cover main body 61 of the bottom side X2 thereof), and is fixed to a screw hole formed in the fixing portion 31c.

  The primary lid sealing portion 64 hermetically seals a gap (axial gap X) between the primary lid 60 and the cask body 10 in the axial direction X. The primary lid sealing portion 64 is disposed (provided) on the surface on the bottom side X2 of the primary lid 60. The surface (sealing surface) on the bottom side X2 of the primary lid sealing portion 64 is in contact with the fixing portion 31c. The primary lid sealing portion 64 is a gasket, and its material is metal.

  The secondary lid 70 is arranged on the head side X1 (outside in the axial direction X) from the primary lid 60. The secondary lid 70 includes a disk-shaped secondary lid main body 71, a secondary lid flange 72, a secondary lid bolt 73, a secondary lid sealing seal 74, a secondary lid neutron shielding material 75, A first outer peripheral convex portion 76, a second outer peripheral convex portion 77 (secondary lid convex portion), and a central convex portion 78 (see FIG. 3) are provided. The secondary lid 70 is configured substantially similarly to the primary lid 60.

  The secondary lid flange 72 is provided at a portion where the secondary lid bolt 73 is fastened to the cask main body 10, and has substantially the same configuration as the primary lid flange 62. The secondary lid flange portion 72 has a flange structure that is recessed toward the bottom side X2 from the head side X1 end surface (the end surface on the tertiary lid 80 side) of the second outer peripheral projection 77. The secondary lid flange 72 is arranged adjacent to the radially outer end of the second outer peripheral projection 77. More specifically, the position in the radial direction Y (radial Y position) of the radially Y inner end of the secondary lid flange 72 and the radial Y position of the radially Y outer end of the second outer peripheral projection 77. And match.

  The secondary lid bolt 73 is a bolt for fixing the secondary lid main body 71 and the cask main body 10, and has the same configuration as the primary lid bolt 63.

  The secondary lid sealing portion 74 is a portion that hermetically seals the gap between the secondary lid 70 and the cask main body 10 in the axial direction X, and is configured similarly to the primary lid sealing portion 64.

  The secondary lid neutron shielding material 75 is a member (a neutron shielding material) that shields neutrons emitted from the radioactive substance in the cask body 10. As shown in FIG. 3, the secondary lid neutron shielding material 75 is installed inside the secondary lid main body 71. As shown in FIG. 2, for example, the radial Y position of the radially Y outer end portion of the secondary lid neutron shielding material 75 is substantially the same as the radial Y position of the inner surface of the trunk main body 21. It is as follows. (A) It is desirable that the position of the first region G1a, particularly the position of the radially inner end of the first region G1a, be closer to the radially Y position of the inner surface of the body 21. The reason for this is to make it easier to transmit the outer peripheral reaction force F2 (see FIG. 5) to the trunk main body 21 through the position of the first region G1a. (B) Further, the radial direction Y position of the first region G1a is desirably at or near a portion where the secondary lid neutron shielding material 75 is not provided. More specifically, the position of the first region G1a is preferably a position where the region without the secondary lid neutron shielding material 75 and the first region G1a overlap when viewed in the axial direction X. The reason for this is to transmit the outer peripheral reaction force F2 to the trunk main body 21 through the region of the secondary lid main body 71 where the secondary lid neutron shielding material 75 is not provided. Considering the above (a) and (b), inevitably, the radial Y position of the radially outer end of the secondary lid neutron shielding material 75 is substantially equal to the radial Y position of the inner surface of the trunk body 21. Be in the same position. The secondary lid neutron shielding material 75 is more easily deformed than the secondary lid main body 71 (metal), for example, easily plastically deformed, for example, easily elastically deformed. The material of the secondary lid neutron shielding material 75 is rubber (eg, ethylene propylene rubber, silicon rubber), or resin (eg, epoxy resin or polyester resin).

  The first outer peripheral portion 76 transmits an impact force between the outer peripheral portion of the secondary lid 70 (hereinafter, “outer peripheral portion”) and the outer peripheral portion of the primary lid 60 when the head is vertically dropped (described below). Part. The first outer peripheral convex portion 76 forms a first region G1a (described below) together with the primary lid 60. The first outer peripheral projection 76 protrudes from the secondary lid main body 71 to the bottom side X2 (the primary lid 60 side). The first outer peripheral convex portion 76 has a ring shape, is circular when viewed from the axial direction X, and is provided over the entire circumference in the circumferential direction (the same applies to the second outer peripheral convex portion 77 as shown in FIG. 4). . The first outer peripheral projection 76 shown in FIG. 2 is preferably provided over the entire circumference in the circumferential direction, but need not be provided over the entire circumference in the circumferential direction.

  The second outer peripheral convex portion 77 (secondary lid convex portion) is a portion where an impact force is transmitted between the outer peripheral portion of the secondary lid 70 and the outer peripheral portion of the tertiary lid 80 when the head falls vertically. The second outer peripheral projection 77 forms a second region G2a (described below) together with the tertiary lid 80. The second outer peripheral projection 77 projects from the secondary lid main body 71 to the head side X1 (tertiary lid 80 side).

  The central convex portion 78 (see FIG. 3) is a portion where an impact force is transmitted between the radially Y central portion of the secondary lid 70 and the radially Y central portion of the primary lid 60 when the head is vertically dropped. . As shown in FIG. 3, the central convex portion 78 protrudes from the center in the radial direction Y of the secondary lid body 71 to the bottom side X2 (the primary lid 60 side shown in FIG. 2).

  The tertiary lid 80 is disposed closer to the head side X1 (outer side in the axial direction X) than the secondary lid 70 is. The tertiary lid 80 includes a disk-shaped tertiary lid main body 81, a tertiary lid flange 82, a tertiary lid bolt 83, and a tertiary lid sealing seal 84. The tertiary lid 80 is configured substantially similarly to the primary lid 60.

  The tertiary lid flange portion 82 is provided at a portion where the tertiary lid bolt 83 is fastened to the cask body 10, and has the same configuration as the primary lid flange portion 62.

  The tertiary lid bolt 83 is a bolt for fixing the tertiary lid main body 81 and the cask main body 10, and has the same configuration as the primary lid bolt 63.

  The tertiary lid sealing portion 84 is a portion for hermetically sealing a gap between the tertiary lid 80 and the cask body 10 in the axial direction X, and has substantially the same configuration as the primary lid sealing portion 64. The tertiary lid sealing portion 84 may be a rubber O-ring or a metal gasket.

  As shown in FIG. 1, the shock absorber 90 is a member that reduces the impact acceleration when the cask 1 falls. The buffer 90 includes a bottom buffer 91 and a head buffer 93. The bottom buffer 91 covers the outer periphery of the bottom 11. The head buffer 93 includes a main head buffer 93a and a head auxiliary buffer 93b. The main head buffer 93a covers the outer peripheral portion of the tertiary lid 80. The head main buffer 93a is arranged at a position outside the tertiary lid 80 in the radial direction Y and at a position on the head side X1 with respect to the tertiary lid 80. The head auxiliary buffer 93b is disposed radially inward of the main head buffer 93a in the radial direction Y, is disposed near the radial center of the tertiary lid 80, and is closer to the head than the tertiary lid 80. X1.

(Gap in the axial direction X)
As shown in FIG. 2, the lid 50 has a first gap G1 and a second gap G2.
The first gap G1 is a gap between the primary lid 60 and the secondary lid 70 in the axial direction X (hereinafter, also referred to as an axial X gap). The first gap G1 is filled with an inert gas such as helium gas. By monitoring the gas pressure, it is confirmed whether or not there is a leak in the sealing portion (the secondary lid sealing portion 74 and the like). By maintaining the gas pressure in the first gap G1 at a positive pressure during the long-term storage period, the first gap G1 has a function for pressure monitoring that there is no leakage of the primary lid 60 and the secondary lid 70. . The first gap G1 has a first area G1a and a third area G1c.

  The first area G1a is an area in which the axial X gap is smaller than other areas of the first gap G1. The “region” means the range of the radial Y position (the same applies to the “region” in the description of the first gap G1 and the second gap G2 below). The “other region of the first gap G1” is at least a part of the first gap G1, excluding the first region G1a. The size of the gap X in the axial direction of the first region G1a (“the size of the gap X in the axial direction” is also simply referred to as “gap”) is set at least as in the following [Setting a]. It may be set to at least one of [setting e]. [Setting a] In the first gap G1, there is a portion having a larger gap than the first area G1a. [Setting b] In the first gap G1 between the outer peripheral portion of the primary lid 60 and the outer peripheral portion of the secondary lid 70, there is a portion having a larger gap than the first region G1a. [Setting c] In the first gap G1, only a portion having a larger gap than the first area G1a is present in a region between the outer peripheral portion of the primary lid 60 and the outer peripheral portion of the secondary lid 70. [Setting d] In a region between the radial center Y of the primary lid 60 and the radial center Y of the secondary lid 70, there may be a portion where the size of the gap is substantially the same as that of the first region G1a. . Specifically, the gap between the central projection 78 (see FIG. 3) and the primary lid 60 and the gap in the first region G1a may be substantially the same. [Setting e] In a region other than the first region G1a of the first gap G1, there may be only a portion having a larger gap than the first region G1a (not shown).

  The first region G1a is arranged between the outer peripheral portion of the primary lid 60 and the outer peripheral portion of the secondary lid 70. The “outer peripheral portion” is a portion on the outer side in the radial direction Y. The width in the radial direction Y of the “outer peripheral portion” of a certain lid (for example, the primary lid 60) is で of the radius of this lid (in this case, the primary lid 60). The width in the radial direction Y of the “outer peripheral portion” of a certain lid may be defined as １ ／, １ ／, or ５ of the radius of the lid. . Note that the width of the “outer peripheral portion” in the radial direction Y with respect to the radius of the lid may be different for each lid. For example, when the width of the outer peripheral portion of the primary lid 60 in the radial direction Y is の of the radius of the primary cover 60, the width of the outer peripheral portion of the secondary lid 70 in the radial direction Y is smaller than the radius of the secondary lid 70. It does not have to be 1/4.

  The first region G1a is located in a region where the first outer peripheral protrusion 76 is arranged, and is located between the first outer peripheral protrusion 76 and the primary lid 60 (between the axial directions X).

  At least a part of the first region G1a is in a region where the trunk 20 is extended in the axial direction X (on the extension in the axial direction X), and is in a region where the trunk main body 21 is extended in the axial direction X. When viewed from the axial direction X, the first region G <b> 1 a overlaps the trunk 20 and overlaps the trunk main body 21. The first region G1a is disposed radially inward of the primary lid bolt 63 and radially inward of the primary lid flange 62, and is adjacent to the primary lid flange 62 in the radial direction Y (substantially adjacent). May be used).

  As shown in FIG. 3, the third region G1c is a region where the X-direction gap is smaller than other regions of the first gap G1. The third region G1c is a region in the first gap G1 where the X-direction gap is smaller than the region excluding the first region G1a and the third region G1c. The third region G1c is within a region (on the extension in the axial direction X) in which the head assist buffer 93b (see FIG. 1) is extended in the axial direction X. When viewed from the axial direction X, the third region G1c overlaps the head assist buffer 93b (see FIG. 1). The third region G <b> 1 c is arranged between the radial center Y of the primary lid 60 and the radial center Y of the secondary lid 70. The third region G1c is in a region where the central convex portion 78 is arranged, and is between the central convex portion 78 and the primary lid 60 (between the axial direction X).

  The second gap G2 is a gap between the secondary lid 70 and the tertiary lid 80 in the axial direction X, as shown in FIG. The second gap G2 has a second region G2a. The second region G2a is a region in which the axial X gap is smaller than other regions of the second gap G2. The second region G2a in the second gap G2 is configured substantially the same as the first region G1a in the first gap G1 (mainly differences will be described below). The second region G2a is arranged between the outer peripheral portion of the secondary lid 70 and the outer peripheral portion of the tertiary lid 80. The second region G2a is located in a region where the second outer peripheral protrusion 77 is arranged, and is located between the second outer peripheral protrusion 77 and the tertiary lid 80 (between the axial direction X). The second region G2a (for example, the whole or at least a part thereof) is in a region where the trunk 20 is extended in the axial direction X, and is in a region where the trunk main body 21 is extended in the axial direction X. At least a part of the second region G2a is in a region where the body flange portion 30 radially outside the primary lid attachment portion 31 (wall portion 31d) is extended in the axial direction X. The second region G2a is located outside the secondary lid neutron shielding material 75 in the radial direction Y, and is preferably located only outside the secondary lid neutron shielding material 75 in the radial direction Y. The second region G2a is located radially inward of the secondary lid bolt 73, radially inner of the secondary lid flange 72, and adjacent to the secondary lid flange 72 in the radial direction Y.

(Size of the gap in the axial direction X)
The size of the axial X gap between the first area G1a and the second area G2a is set as follows. At the time of a vertical head drop (specifically, a 9-meter vertical head drop, details are described below), the primary lid 60 and the secondary lid 70 are brought into contact in the first area G1a (so that an impact force is transmitted). The size of the gap X in the axial direction of the first region G1a is set. The position where the primary lid 60 and the secondary lid 70 hit when the head is vertically dropped is the position (the position where there is a gap) that was the first area G1a before the head was dropped vertically. Further, the size of the axial X gap in the second area G2a is set so that the secondary lid 70 and the tertiary lid 80 come into contact with each other in the second area G2a when the head is vertically dropped.

(Deformation of lid 50, etc. when head falls vertically)
In the cask 1 shown in FIG. 1, a vertical head drop is assumed. In the vertical head drop, the cask 1 falls vertically (vertically) with respect to the floor surface or the ground (hereinafter, floor surface) with the head side X1 being the lower side and the bottom side X2 being the upper side. It is to be. The cask 1 that has fallen vertically in the head collides with the floor surface and receives an impact. In the vertical drop of the head, the cask 1 falls from a predetermined height. The “predetermined height” is, for example, 9 m (the vertical drop at the head at this time is “9 m vertical drop at the head”).

  The conventional cask without the first area G1a (see FIG. 2) and the second area G2a has the following problem when the head falls vertically. In the following, description will be made by attaching the reference numerals of the components of the cask 1 of the present embodiment to the components of the conventional cask. In the following, a problem mainly due to the absence of the first region G1a will be described. FIG. 5 is a diagram showing a state in which the secondary lid 70, the tertiary lid 80, and the body flange 30 are deformed by an impact when the head is vertically dropped. In the same figure, the state before deformation is shown by a two-dot chain line, the primary lid 60 is omitted, and only the outline of the cross section is shown (the hatching indicating the cross section is not attached). Note that the direction of the axial direction X in FIG. 5 is opposite to the direction of the axial direction X in FIGS. 1 and 2. The portion 32B shown in FIG. 5 is a portion of the fixing portion 32e where the sealing surface of the secondary lid sealing portion 74 contacts. When the head is vertically dropped, a stress exceeding the yield stress of the secondary lid sealing portion 74 is generated in the portion 32B. At this time, the surface stress of the sealing surface of the secondary lid sealing portion 74 exceeds the yield stress of the secondary lid sealing portion 74 over the entire sealing surface. The cause of such a large stress in the portion 32B is as follows.

  The large stress generated in the portion 32B is caused by the outer peripheral portion of the secondary lid 70 deforming convexly toward the bottom side X2 (the primary lid 60 side), and the outer peripheral portion of the secondary lid 70 hitting the inner surface corner 32A. I do. The details are as follows. The impact force transmitted to the lid 50 and the like when the head falls vertically includes an inertial force F1 and an outer peripheral reaction force F2. The inertia force F1 is the inertia force (delayed impact load) of the internal storage (radioactive material and basket 40) of the cask main body 10 shown in FIG. The outer peripheral reaction force F2 (see FIG. 5) is a force transmitted from the main head cushion 93a to the outer peripheral portion of the tertiary lid 80. When the inertial force F1 shown in FIG. 5 acts on the primary lid 60, the primary lid 60 is deformed convexly toward the secondary lid 70 (head side X1) (not shown). When the deformation of the primary lid 60 reaches the central convex portion 78 of the secondary lid 70, the central part in the radial direction Y of the secondary lid 70 is deformed to be convex toward the head side X1. Here, if the outer peripheral reaction force F2 does not act on the tertiary lid 80, the outer peripheral portion of the secondary lid 70 is deformed in a direction away from the inner surface corner 32A (head side X1). Does not hit the inner surface corner 32A. However, since the outer peripheral reaction force F2 acts on the tertiary lid 80, a one-sided contact occurs as described below.

  The outer peripheral reaction force F2 is transmitted to the tertiary lid 80, the secondary lid 70, the primary lid 60, and the trunk flange 30 in the regions A1 to A4. The details are as follows. The area A1 is an area outside the radial outer Y end of the secondary lid 70 in the radial outside Y. The area A2 is an area where the secondary lid flange 72 is arranged. The region A3 is a region between the secondary lid flange 72 and the secondary lid neutron shielding material 75 (between the radial directions Y). The area A4 is an area where the outer peripheral portion of the secondary lid neutron shielding material 75 is arranged. The outer peripheral reaction force F2 in the area A1 is transmitted to the body flange 30 through the tertiary lid 80. On the other hand, in the area A2, there is a space (gap) in the axial direction X between the tertiary lid 80 and the secondary lid 70. In the area A4, there is a secondary lid neutron shielding material 75 that is more easily deformed than the secondary lid main body 71 (the secondary lid neutron shielding material 75 in a deformed state is not shown). Therefore, the outer peripheral reaction force F2 of the area A2, the area A3, and the area A4 is transmitted through the tertiary lid 80 to the area A3 of the secondary lid 70 (a part thicker in the axial direction X than other parts). If this reaction force can be transmitted from the secondary lid 70 to the primary lid 60, the deformation of the secondary lid 70 in the area A3 can be suppressed. However, in the conventional cask, the area A3 between the secondary lid 70 and the primary lid 60 has an axial X gap larger than that of the present embodiment. Therefore, it is difficult for the reaction force of the secondary lid 70 in the region A3 to be properly transmitted to the primary lid 60. For this reason, the outer peripheral portion of the secondary lid 70 is deformed convexly toward the primary lid 60 (bottom side X2) (convex deformation of the outer peripheral portion of the secondary lid 70). Therefore, it is considered that the outer peripheral portion of the secondary lid 70 hits the inner surface corner 32 </ b> A of the body at one side. As a result, a stress greater than the yield stress of the secondary lid sealing portion 74 is generated in the secondary lid sealing portion 74.

(Stress control of the outer peripheral part of the secondary lid 70)
As shown in FIG. 2, the cask 1 of the present embodiment includes a first region G1a (including a first outer peripheral convex portion 76). Therefore, when the head falls vertically, the reaction force of the secondary lid 70 in the area A3 (see FIG. 5) is transmitted to the primary lid 60 through the first outer peripheral convex portion 76 at the position of the first area G1a. Therefore, the convex deformation of the outer peripheral portion of the secondary lid 70 is suppressed. Therefore, the side contact of the outer peripheral portion of the secondary lid 70 with the inner surface corner 32 </ b> A is suppressed. As a result, the stress on the outer peripheral portion of the secondary lid 70 is suppressed. As a result, the stress on the sealing surface of the secondary lid sealing portion 74 is suppressed.

(Stress control of secondary lid bolt 73)
In the conventional cask, the convex deformation of the outer peripheral portion of the secondary lid 70 (see FIG. 5) generates tensile stress on the secondary lid bolt 73, which may cause a problem. On the other hand, in the cask 1 of the present embodiment, since the convex deformation of the outer peripheral portion of the secondary lid 70 is suppressed by the first region G1a, the tensile stress of the secondary lid bolt 73 is suppressed.

(Stress control of primary lid bolt 63)
In a conventional cask, the tensile stress of the primary lid bolt 63 may be a problem. The details of this problem are as follows. The primary lid 60 directly receives the inertial force F1 shown in FIG. Therefore, the central part in the radial direction Y of the primary lid 60 is deformed to be convex toward the head side X1. As a result, tensile stress is generated in the primary lid bolt 63 shown in FIG. 2, which may cause a problem. On the other hand, in the cask 1 of the present embodiment, the outer peripheral reaction force F2 (see FIG. 5) transmitted from the tertiary lid 80 to the secondary lid 70 is transmitted from the secondary lid 70 to the primary lid 60 through the first region G1a. Therefore, displacement and deformation of the outer periphery of the primary lid 60 toward the head side X1 are suppressed. Therefore, the tensile stress of the primary lid bolt 63 is suppressed (relaxed).

(Operation by the second region G2a)
The force is easily transmitted between the secondary lid 70 and the tertiary lid 80 by the second region G2a (by the second outer peripheral projection 77). Therefore, the deformation of the outer peripheral portion of the tertiary lid 80 is suppressed by the second region G2a in the same manner as the outer peripheral portion of the secondary cover 70 is suppressed by the first region G1a. As a result, deformation and stress of the outer peripheral portion of the secondary lid 70 are suppressed. Further, similarly to the case where the tensile stress of the primary lid bolt 63 and the secondary lid bolt 73 is suppressed by the first region G1a, the tensile stress of the secondary lid bolt 73 and the tertiary lid bolt 83 is suppressed by the second region G2a. You.

(Supported by the primary lid 60, the secondary lid 70, and the tertiary lid 80)
Some conventional casks are designed to allow the primary lid 60 to be plastically deformed by the inertial force F1 shown in FIG. 5 when the head is vertically dropped (for example, see Patent Document 1). In such a conventional cask, even when the sealing performance is ensured by the secondary lid 70 and the tertiary lid 80 when the head is vertically dropped, the sealing performance of the primary lid 60 may be broken. Therefore, in order to ensure more reliable sealing performance, it is desirable that the sealing performance of the primary lid 60 be maintained. On the other hand, in the cask 1 of the present embodiment shown in FIG. 2, when the head falls vertically, the primary lid 60 to which the inertial force F1 (see FIG. 5) is applied passes through the first region G1a and the second region G2a. It is supported by the secondary lid 70 and the tertiary lid 80. Therefore, plastic deformation of the primary lid 60 is suppressed, and the sealing performance of the lid 50 is easily secured (maintained).

(Effect of the first invention)
The effects of the cask 1 shown in FIG. 1 are as follows. The cask 1 includes a cask main body 10, a primary lid 60, a secondary lid 70, a tertiary lid 80, and a buffer 90. The cask body 10 has a bottomed cylindrical shape having a bottom portion 11, a body portion 20 long in the axial direction X, and an opening portion 13, and stores a radioactive substance. The primary lid 60 closes the opening 13. The secondary lid 70 is disposed outside the primary lid 60 in the axial direction X (head side X1), and closes the opening 13. The tertiary lid 80 is disposed outside the secondary lid 70 in the axial direction X (head side X1), and closes the opening 13. The head main buffer 93 a (the buffer 90) covers the outer peripheral portion of the tertiary lid 80. As shown in FIG. 2, the cask 1 has a first area G1a.
[Configuration 1] The first area G1a is an area included in the first gap G1, which is an axial gap between the primary lid 60 and the secondary lid 70. The first area G1a is an area in which the axial X gap is smaller than other areas of the first gap G1. The first region G1a is disposed between the outer peripheral portion of the primary lid 60 and the outer peripheral portion of the secondary lid 70.

  The cask 1 includes the above [Configuration 1]. Therefore, when the head is vertically dropped, an impact force is easily transmitted at the position of the first region G1a between the outer peripheral portion of the primary lid 60 and the outer peripheral portion of the secondary lid 70. Therefore, at least the deformation of the outer peripheral portion of the secondary lid 70 at the time of the vertical drop of the head can be suppressed. As a result, it is possible to suppress a decrease in the sealing performance of the lid 50, which may occur when the cask 1 is dropped vertically.

  As a result of suppressing deformation of the outer peripheral portion of the secondary lid 70, the following effects may be obtained. Usually, on the outer peripheral portion of the secondary lid 70, there is a member for sealing the secondary lid 70 and the cask main body 10 (a sealing member for the secondary lid 70). The sealing member of the secondary lid 70 is, for example, a secondary lid sealing portion 74 and a secondary lid bolt 73. As a result, deformation of the outer peripheral portion of the secondary lid 70 can be suppressed, so that stress generated in the sealing member of the secondary lid 70 can be suppressed. Therefore, it is easy to secure the sealing performance between the secondary lid 70 and the cask body 10. In addition, as a result of suppressing deformation of the outer peripheral portion of the secondary cover 70, deformation of the primary cover 60 and the tertiary cover 80 is suppressed.

(Effect of the Second Invention)
[Configuration 2] The cask 1 has a second area G2a. The second area G2a is an area included in the second gap G2, which is an axial X gap between the secondary lid 70 and the tertiary lid 80. The second region G2a is a region in which the axial X gap is smaller than other regions of the second gap G2. The second region G2a is arranged between the outer peripheral portion of the secondary lid 70 and the outer peripheral portion of the tertiary lid 80.

  The cask 1 includes the above [Configuration 2]. Therefore, when the head falls vertically, an impact force is easily transmitted at the position of the second region G2a between the outer peripheral portion of the secondary lid 70 and the outer peripheral portion of the tertiary lid 80. Therefore, at least the deformation of the outer peripheral portion of the secondary lid 70 at the time of the vertical drop of the head can be suppressed. As a result, it is possible to suppress a decrease in the sealing performance of the lid 50, which may occur when the cask 1 is dropped vertically.

(Effect of the third invention)
Since the cask 1 includes the above [Configuration 1] and [Configuration 2], a decrease in the sealing performance of the lid 50 can be further suppressed as compared to the case where only one of [Configuration 1] and [Configuration 2] is provided. .

(Effect of the fourth invention)
[Configuration 4] The first region G1a is in a region where the trunk portion 20 extends in the axial direction X.

  According to the above [Configuration 4], of the force (see the outer peripheral reaction force F2 in FIG. 5) applied from the buffer body 90 to the tertiary lid 80 when the head is vertically dropped, the force passing through the position of the first region G1a is: It can be reliably transmitted to the trunk 20. Therefore, the secondary lid 70 is reliably supported by the trunk 20. Therefore, the deformation of the secondary lid 70 can be further suppressed.

(Effect of the fifth invention)
[Configuration 5] The second region G2a is in a region where the trunk portion 20 extends in the axial direction X.

  According to the above [Configuration 5], of the force (see the outer peripheral reaction force F2 in FIG. 5) applied from the buffer body 90 to the tertiary lid 80 when the head is vertically dropped, the force passing through the position of the second area G2a is It can be reliably transmitted to the trunk 20. Therefore, the secondary lid 70 is reliably supported by the trunk 20. Therefore, the deformation of the secondary lid 70 can be further suppressed.

(Effect of Sixth Invention) Since the cask 1 includes the above [Configuration 4] and [Configuration 5], the secondary lid is compared with the case where only one of the above [Configuration 4] and [Configuration 5] is provided. 70 can be further suppressed.

(Effect of the eighth invention)
The secondary lid 70 includes a secondary lid main body 71, a secondary lid bolt 73, and a secondary lid neutron shielding material 75. The secondary lid bolt 73 fixes the secondary lid main body 71 and the cask main body 10. The secondary lid neutron shielding material 75 is installed inside the secondary lid main body 71.
[Configuration 8] The second region G2a is located outside the secondary cover neutron shielding material 75 in the radial direction Y and inside the secondary cover bolt 73 in the radial direction Y.

  Usually, the secondary lid neutron shielding material 75 is more easily deformed than the secondary lid main body 71. Further, in some cases, for example, a secondary lid flange portion 72 is provided at a position where the secondary lid bolt 73 is disposed, so that the force cannot be properly transmitted. Therefore, the second region G2a is arranged as in the above [Configuration 8]. Therefore, the force transmitted between the secondary lid 70 and the tertiary lid 80 can be reliably transmitted. As a result, the deformation of the secondary lid 70 can be further suppressed.

(Effect of the tenth invention)
The secondary lid 70 includes a secondary lid main body 71, a secondary lid bolt 73, a second outer peripheral convex portion 77 (secondary lid convex portion), and a secondary lid flange portion 72. The secondary lid bolt 73 fixes the secondary lid main body 71 and the cask main body 10.
[Configuration 10] The second outer peripheral projection 77 protrudes from the secondary lid main body 71 toward the tertiary lid 80, and forms a second region G2a together with the tertiary lid 80. The secondary lid flange portion 72 is provided at a fastening portion of the secondary lid bolt 73 to the cask main body 10, and has a flange structure in which the second outer peripheral projection 77 is recessed on the bottom side X <b> 2 from the end surface on the tertiary lid 80 side. , Are arranged adjacent to the radially outer end of the second outer circumferential projection 77.

  In the above [Configuration 10], the radially outer end of the second outer circumferential projection 77 in the radial direction Y and the radially inner end of the secondary lid flange 72 are also used. Therefore, the secondary lid 70 can be configured simply, and the secondary lid 70 can be easily manufactured, as compared with the case where these are not shared.

(Effect of the thirteenth invention)
As shown in FIG. 1, the buffer 90 includes a main head buffer 93 a that covers the outer peripheral portion of the tertiary lid 80, and a head auxiliary buffer 93 b that covers the radial Y center of the tertiary lid 80. As shown in FIG. 3, the cask 1 has a third area G1c.
[Configuration 13] The third region G1c is a region included in the first gap G1, which is an X-direction gap between the primary lid 60 and the secondary lid 70. The third region G1c is a region where the gap in the axial direction X is smaller than other regions of the first gap G1. The third region G1c is a region arranged in a region extending in the axial direction X from the head auxiliary buffer 93b shown in FIG.

  According to the above [Configuration 13], when the head is vertically dropped, the impact force transmitted from the head auxiliary buffer 93b to the secondary lid 70 through the tertiary lid 80 passes through the position of the third area G1c (see FIG. 3). And easily transmitted to the primary lid 60. Therefore, the deformation of at least the secondary lid 70 at the time of the vertical drop of the head can be further suppressed.

(2nd Embodiment)
With reference to FIG. 6, differences between the cask 201 of the second embodiment and the first embodiment will be described. Note that, of the casks 201, the points common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted. The differences are the following (a) to (c). (A) The primary lid 60 includes a primary lid neutron shielding material 265 (neutron shielding material). (B) As shown in FIG. 2, in the first embodiment, a first outer peripheral projection 76 forming a first region G <b> 1 a is provided on the secondary lid 70. On the other hand, as shown in FIG. 6, in the second embodiment, a first outer peripheral convex portion 266 (primary lid convex portion) forming the first region G1a is provided on the primary lid 60. (C) As shown in FIG. 2, in the first embodiment, a second outer peripheral projection 77 that forms the second region G <b> 2 a is provided on the secondary lid 70. On the other hand, as shown in FIG. 6, in the second embodiment, a second outer peripheral convex portion 287 (tertiary lid bottom side convex portion) forming the second region G2a is provided on the tertiary lid 80.

  The differences between the primary lid neutron shielding material 265 and the secondary lid neutron shielding material 75 (see FIG. 2) are as follows. The primary lid neutron shielding material 265 is installed inside the primary lid main body 61 and is more easily deformed than the primary lid main body 61.

  The differences from the first outer peripheral convex portion 76 (see FIG. 2), such as the first outer peripheral convex portion 266 (primary lid convex portion), are as follows. The first outer peripheral projection 266 protrudes from the primary lid main body 61 toward the secondary lid 70 (head side X1), and forms a first region G1a together with the secondary lid 70. The first outer peripheral convex portion 266 (the first region G1a) is radially outside the primary lid neutron shielding member 265 in the radial direction Y and radially inside the primary lid bolt 63 in the radial direction Y. The primary lid flange portion 62 has a flange structure that is recessed toward the bottom side X2 from the end surface of the first outer peripheral projection 266 on the secondary lid 70 side (head side X1). The primary lid flange portion 62 is disposed adjacent to a radially outer end of the first outer peripheral convex portion 266 in the radial direction Y.

  The difference between the second outer peripheral convex portion 287 (tertiary lid convex portion) and the second outer peripheral convex portion 77 (see FIG. 2) is as follows. The second outer peripheral projection 287 protrudes from the tertiary lid main body 81 toward the secondary lid 70 (bottom side X2), and forms a second region G2a together with the secondary lid 70.

(Effect of the seventh invention)
The effects of the cask 201 shown in FIG. 6 are as follows. The primary lid 60 includes a primary lid main body 61, a primary lid bolt 63 for fixing the primary lid main body 61 and the cask main body 10, and a primary lid neutron shielding member 265 installed inside the primary lid main body 61.
[Configuration 7] The first region G1a is located outside the primary lid neutron shielding material 265 in the radial direction Y and inside the primary lid bolt 63 in the radial direction Y.

  Usually, the primary lid neutron shielding material 265 is more easily deformed than the primary lid main body 61. In addition, in some cases, for example, a primary lid flange portion 62 is provided at a position where the primary lid bolt 63 is disposed, so that the force cannot be properly transmitted. Therefore, the first region G1a is arranged as in the above [Configuration 7]. Therefore, the force transmitted between the primary lid 60 and the secondary lid 70 can be transmitted reliably. Therefore, the deformation of the primary lid 60 can be suppressed, and as a result, the deformation of the secondary lid 70 can be suppressed.

(Effect of the ninth invention)
The primary lid 60 includes a primary lid main body 61, a primary lid bolt 63, a first outer peripheral convex portion 266 (primary lid convex portion), and a primary lid flange portion 62. The primary lid bolt 63 fixes the primary lid main body 61 and the cask main body 10.
[Configuration 9] The first outer peripheral projection 266 projects from the primary lid main body 61 toward the secondary lid 70, and forms a first region G1a together with the secondary lid 70. The primary lid flange portion 62 is provided at a fastening portion of the primary lid bolt 63 to the cask body 10 and has a flange structure that is recessed on the bottom side X2 from the end surface of the first outer peripheral projection 266 on the secondary lid 70 side, The first outer peripheral projection 266 is disposed adjacent to the radially outer end of the first outer peripheral projection 266.

  In the above [Configuration 9], the radially Y outer end of the first outer peripheral projection 266 and the radially Y inner end of the primary lid flange 62 are also used. Therefore, the primary lid 60 can be configured simply, and the primary lid 60 can be easily manufactured, as compared with the case where these are not shared.

(Third embodiment)
With reference to FIGS. 7 to 9, differences between the cask 301 of the third embodiment and the first embodiment will be described. The differences are as follows. As shown in FIG. 7, the primary lid 60 includes a primary lid seating portion 362 instead of the primary lid flange 62 (see FIG. 2). The secondary lid 70 includes a secondary lid seating portion 372 instead of the secondary lid flange 72 (see FIG. 2). Note that in FIG. 8, only a part of the secondary lid seating portion 372 is denoted by a reference numeral.

  As shown in FIG. 7, the primary lid seating portion 362 is provided around a fastening portion of the primary lid bolt 63 to the cask body 10. The primary lid seating portion 362 has a counterbore structure that is recessed on the bottom side X2 from the end face of the head side X1 of the primary lid 60. In the first embodiment, the first region G1a is arranged only radially inward of the radially inner end of the primary lid flange 62 as shown in FIG. 2 in the first embodiment. As shown in the figure, the primary lid seating portion 362 is also disposed radially outside the radially inner end of the primary lid seating portion 362. Therefore, the first region G1a can be made wider than in the first embodiment. Therefore, compared to the first embodiment, the impact force is easily transmitted at the position of the first region G1a. In addition, the first region G1a in the region on the axial extension X of the trunk body 21 can be widened. Therefore, compared to the first embodiment, the impact force passing through the position of the first area G1a is more easily transmitted to the trunk body 21. As a result, the deformation of the secondary lid 70 can be suppressed.

  The secondary lid seating portion 372 has the same configuration as the primary lid seating portion 362 in the primary lid 60. Therefore, the second region G2a can be widened in the same manner as the first region G1a can be widened by the primary lid seating portion 362, so that the deformation of the secondary lid 70 can be suppressed. In addition, if the area of the secondary lid neutron shielding material 75 is simply enlarged, the secondary lid 70 is easily deformed. However, the provision of the secondary lid seating portion 372 can suppress the deformation of the secondary lid 70. Therefore, the area of the secondary lid neutron shielding material 75 can be enlarged. As shown in FIG. 8, when viewed from the axial direction X, a portion of the secondary lid seat extending portion 372 extending in the axial direction X is defined as a surface 372a.

  The surface 372a is substantially U-shaped surrounding the secondary cover bolt 73 when viewed from the axial direction X. As shown in FIG. 9, the surface 372a may be arranged so as to surround the secondary lid bolt 73 with a closed shape such as a circle when viewed from the axial direction X. In this case, the second region G2a can be made wider than when the surface 372a does not surround the secondary cover bolt 73 in a closed shape as shown in FIG. Note that a configuration similar to the configuration in which the surface 372a surrounds the secondary lid bolt 73 in a closed shape as shown in FIG. 9 may be provided in the primary lid seating portion 362 shown in FIG. 7 (see FIG. 10). See primary lid seating section 462).

(Effect of the eleventh invention)
The effects of the cask 301 shown in FIG. 7 are as follows. The primary lid 60 includes a primary lid main body 61 and a primary lid bolt 63 for fixing the primary lid main body 61 and the cask main body 10.
[Configuration 11] The primary lid 60 includes a primary lid seating portion 362. As shown in FIG. 8, the primary lid seating portion 362 is provided around a fastening portion of the primary lid bolt 63 to the cask body 10. As shown in FIG. 7, the primary lid seating portion 362 has a counterbore structure in which the primary lid 60 is recessed on the bottom side X2 from the end surface of the head side X1.

  According to the above [Configuration 11], the first region G1a can be made wider than in the case where the primary lid flange portion 62 (see FIG. 2) is provided at the fastening portion of the primary lid bolt 63 to the cask main body 10. Therefore, the impact force is more easily transmitted between the outer peripheral portion of the primary lid 60 and the outer peripheral portion of the secondary lid 70 at the position of the first region G1a. Therefore, deformation of at least the outer peripheral portion of the secondary lid 70 can be further suppressed.

(Effect of the twelfth invention)
The secondary lid 70 includes a secondary lid main body 71, and a secondary lid bolt 73 for fixing the secondary lid main body 71 and the cask main body 10.
[Configuration 12] The secondary lid 70 includes a secondary lid seating portion 372. The secondary lid seating portion 372 is provided around a fastening portion of the secondary lid bolt 73 to the cask main body 10, and has a counterbore structure in which the secondary lid 70 is recessed on the bottom side X2 from the end surface of the head side X1 of the secondary lid 70. Have.

  With the above [Configuration 12], the second region G2a can be made wider than when the secondary lid flange portion 72 (see FIG. 2) is provided at the fastening portion of the secondary lid bolt 73 to the cask main body 10. Therefore, between the outer peripheral portion of the secondary lid 70 and the outer peripheral portion of the tertiary lid 80, the impact force is more easily transmitted at the position of the second region G2a. Therefore, deformation of at least the outer peripheral portion of the secondary lid 70 can be further suppressed.

(Fourth embodiment)
With reference to FIG. 10, the difference between the cask 401 of the fourth embodiment and the third embodiment (see FIG. 7) will be described. The main difference is that the wall portion 31d of the primary lid attachment portion 31 has a step 431a, and that the wall portion 32f of the secondary lid attachment portion 32 has a step 432a.

  The wall portion 31d of the primary lid attachment portion 31 includes a step 431a, a large-diameter portion 431b closer to the head X1 than the step 431a, and a small-diameter portion 431c closer to the bottom X2 than the step 431a. The radial Y dimension of the small diameter section 431c is smaller than the radial Y dimension of the large diameter section 431b. With this configuration, the following effects can be obtained. When the primary lid 60 is installed on the body flange 30, the primary lid 60 is dropped into the opening 13 inside the primary lid mounting part 31. At the beginning of the drop, the primary lid 60 is put into the large diameter portion 431b. Therefore, it is easier to install the primary lid 60 on the primary lid mounting part 31 than when the primary lid 60 is placed in a portion having a smaller diameter than the large diameter portion 431b at the beginning of dropping.

  The wall part 32f of the secondary lid attachment part 32 is configured similarly to the wall part 31d of the primary lid attachment part 31. The wall portion 32f includes a step 432a, a large-diameter portion 432b closer to the head X1 than the step 432a, and a small-diameter portion 432c closer to the bottom X2 than the step 432a. With this configuration, similarly to the primary lid 60, the secondary lid 70 can be easily installed on the secondary lid mounting portion 32.

(Size of the gap in the radial direction Y of the primary lid 60 [Case 1-a])
A gap in the radial direction Y (hereinafter, also referred to as a radial Y gap) is provided between the outer peripheral surface (the outer end face in the radial direction Y, etc.) of the primary lid 60 and the cask main body 10 (the body flange portion 30). There is a lid peripheral gap G4. There is a fourth region G4a in the primary lid outer peripheral gap G4. The fourth area G4a is an area where the radial Y gap is smaller than other areas of the primary lid outer circumferential gap G4. Specifically, the fourth area G4a is a radial Y gap between the small diameter portion 431c and the primary lid 60. The size of the radial Y gap of the fourth region G4a is smaller than the radial Y gap of the region on the head side X1 of the primary lid outer circumferential gap G4 than the fourth region G4a. The “region on the head side X1 than the fourth region G4a” is a radial Y gap between the step 431a and the primary lid 60, and a radial Y gap between the large diameter portion 431b and the primary lid 60.

(Size of radial gap Y of secondary lid 70 [Case 1-b])
Between the outer peripheral surface of the secondary lid 70 and the cask main body 10, there is a secondary lid outer peripheral gap G5 which is a radial Y gap. There is a fifth region G5a in the secondary lid outer peripheral gap G5. The fifth region G5a is a region in which the radial Y gap is smaller than other areas of the secondary lid outer peripheral gap G5. Specifically, the fifth region G5a is a radial Y gap between the small diameter portion 432c and the secondary lid 70. The size of the radial Y gap of the fifth region G5a is smaller than the radial Y gap of the region on the head side X1 of the secondary lid outer circumferential gap G5 than the fifth region G5a. The “region on the head side X1 than the fifth region G5a” is a radial Y gap between the step 432a and the secondary lid 70 and a radial Y gap between the large diameter portion 432b and the secondary lid 70. .

  The primary lid outer peripheral gap G4 and the secondary lid outer peripheral gap G5 do not include a radial Y gap at a position where it is not expected to transmit an impact force during a horizontal drop described below. Specifically, for example, the radial Y gap between the wall 31b and the primary lid 60 is a large gap in which fitting is not controlled, and is not included in the primary lid outer peripheral gap G4. The radial Y gap between the secondary lid flange 72 and the wall 32f is not included in the secondary lid outer peripheral gap G5. In the present embodiment, the above [Case 1-a] and [Case 1-b] are satisfied, but only one of the [Case 1-a] and [Case 1-b] is satisfied. Is also good.

(Horizontal drop, action by the fourth area G4a and the fifth area G5a)
In the cask 401, a horizontal drop is assumed. Horizontal drop means that the cask 401 falls in the vertical direction with the axial direction X being the horizontal direction. At the time of horizontal drop, the lid 50 acts as a support member for the body flange 30 and suppresses deformation of the body flange 30. Here, as described above, the fourth region G4a is provided in the primary lid outer peripheral gap G4. Therefore, at the position of the fourth region G4a, the function as a support member of the primary lid 60 works, and as a result, the stress of each hermetically sealed portion (the primary lid hermetically sealed portion 64, the secondary lid hermetically sealed portion 74, etc.) is suppressed. it can. Similarly to the operation by the fourth region G4a, the fifth region G5a is provided in the secondary lid outer peripheral gap G5, so that the operation as a support member of the secondary lid 70 works, and as a result, the stress of each sealing portion is suppressed. it can.

(Effect of the Fourteenth Invention)
The effects of the cask 401 shown in FIG. 10 are as follows.
[Configuration 14] The cask 401 has a fourth area G4a. The fourth area G4a is an area included in the primary lid outer peripheral gap G4, which is a radial Y gap between the primary lid 60 and the cask main body 10. The fourth area G4a is an area where the radial Y gap is smaller than other areas of the primary lid outer circumferential gap G4.

  The cask 401 has the above [Configuration 14]. Therefore, at the time of horizontal drop, an impact force is likely to be transmitted at the position of the fourth region G4a between the trunk flange portion 30 of the cask main body 10 and the primary lid 60. Therefore, the function of the primary lid 60 as a support member of the body flange 30 can be secured. For example, even in a case where the radial Y gap in a partial area of the primary lid outer circumferential gap G4 is wider than the radial Y gap in the fourth area G4a in order to easily install the primary lid 60 in the cask main body 10. The primary lid 60 can act as a support member for the body flange 30. Therefore, when the cask 401 falls horizontally, deformation of the outer peripheral portion of the primary lid 60 due to the impact force transmitted from the trunk flange 30 to the primary lid 60 can be suppressed. As a result, it is possible to suppress a decrease in the sealing performance of the lid 50, which may occur when the cask 401 falls horizontally.

(Effect of the fifteenth invention)
[Configuration 15] The cask 401 has a fifth area G5a. The fifth region G5a is a region included in the secondary lid outer peripheral gap G5 that is a radial Y gap between the secondary lid 70 and the cask main body 10. The fifth region G5a is a region in which the radial Y gap is smaller than other areas of the secondary lid outer peripheral gap G5.

  The cask 401 has the above [Configuration 15]. Therefore, at the time of horizontal drop, an impact force is easily transmitted at the position of the fifth region G5a between the trunk flange portion 30 of the cask main body 10 and the secondary lid 70. Therefore, when the cask 401 falls horizontally, deformation of the outer peripheral portion of the secondary lid 70 can be suppressed. As a result, it is possible to suppress a decrease in the sealing performance of the lid 50, which may occur when the cask 401 falls horizontally.

(Effect of the Sixteenth Invention)
[Configuration 16] The cask 401 includes the above [Configuration 15] and [Configuration 16]. Therefore, compared to the case where only one of [Configuration 15] and [Configuration 16] is provided, a decrease in the sealing performance of the lid 50, which can occur when the cask 401 falls horizontally, can be further suppressed.

(Fifth embodiment)
With reference to FIG. 11, the difference between the cask 501 of the fifth embodiment and the fourth embodiment (see FIG. 10) will be described. The main difference is that the primary lid 60 has a step 561a, and that the secondary lid 70 has a step 571a. The wall 31d does not include the step 431a (see FIG. 10), and the wall 32f does not include the step 432a (see FIG. 10).

  The outer peripheral portion of the primary lid main body 61 includes a step 561a, a large-diameter portion 561b closer to the head X1 than the step 561a, and a small-diameter portion 561c closer to the bottom X2 than the step 561a. The radial Y dimension of the small diameter section 561c is smaller than the radial Y dimension of the large diameter section 561b. With this configuration, when the primary lid 60 is installed on the body flange 30, the primary lid 60 is inserted into the primary lid mounting part 31 from the small diameter part 561 c at the beginning of dropping the primary lid 60 into the primary lid mounting part 31. . Therefore, it is easier to install the primary lid 60 on the primary lid mounting part 31 than when a part having a larger diameter than the small diameter part 561c is put into the primary lid mounting part 31 at the beginning of dropping.

  The outer peripheral portion of the secondary lid main body 71 is configured similarly to the outer peripheral portion of the primary lid main body 61. The outer peripheral portion of the secondary lid body 71 includes a step 571a, a large-diameter portion 571b closer to the head X1 than the step 571a, and a small-diameter portion 571c closer to the bottom X2 than the step 571a. With this configuration, similarly to the primary lid 60, the secondary lid 70 can be easily installed on the secondary lid mounting portion 32.

(Size of radial Y gap for primary lid 60 [Case 2-a])
The fourth region G4a is a radial Y gap between the large diameter portion 561b and the wall 31d. The size of the radial Y gap of the fourth region G4a is smaller than the radial Y gap of the region on the bottom X2 side of the fourth region G4a in the primary lid outer circumferential gap G4. The “region on the bottom side X2 with respect to the fourth region G4a” is a radial Y gap between the small diameter portion 561c and the primary lid 60, and a radial Y gap between the step 561a and the primary lid 60. The size of the radial Y gap of the primary lid outer circumferential gap G4 in the radial Y gap between the wall 31d and the primary lid 60 is set (gradually) smaller in order from the bottom side X2 to the head side X1. This setting is referred to as “setting of the primary lid outer peripheral gap G4”.

(Size of the gap in the radial direction Y with respect to the secondary lid 70 [Case 2-b])
The fifth region G5a is a radial Y gap between the large diameter portion 571b and the secondary lid 70. The size of the radial Y gap in the fifth region G5a is smaller than the radial Y gap in the region on the bottom X2 side of the fifth region G5a in the secondary lid outer circumferential gap G5. The “region on the bottom side X2 with respect to the fifth region G5a” is a radial Y gap between the step 571a and the secondary lid 70 and a radial Y gap between the small diameter portion 571c and the secondary lid 70. The size of the radial direction Y gap of the secondary lid outer circumferential gap G5 is set (gradually) smaller in order from the bottom side X2 to the head side X1. This setting is referred to as “setting of the secondary lid outer peripheral gap G5”.

  In this embodiment, the above [Case 2-a] and [Case 2-b] are satisfied, but only one of the [Case 2-a] and [Case 2-b] is satisfied. Is also good. Further, the above [Case 1-a] and [Case 2-b] may be satisfied. The above [Case 1-b] and [Case 2-a] may be satisfied.

(Operation by setting the primary lid peripheral gap G4 and the secondary lid peripheral gap G5)
In the fourth embodiment, when the cask 401 (see FIG. 10) is horizontally dropped, the function as a support member of the primary lid 60 works at the position of the fourth area G4a. Further, in the fifth embodiment shown in FIG. 11, the above-mentioned "setting of the primary lid outer peripheral gap G4" is performed. Therefore, the function of the primary lid 60 as a supporting member acts more toward the head side X1, and more specifically, acts more toward the side on which the deformation of the trunk 20 is likely to occur if the primary lid 60 is not provided. Therefore, the effect of the primary lid 60 as a support member works effectively by the “setting of the primary lid outer peripheral gap G4”. As a result, for example, as compared with a case where the radial Y gap of the primary lid outer circumferential gap G4 is equal between the bottom side X2 and the head side X1, each of the hermetic seal portions (the primary lid hermetic seal portion 64, the secondary lid hermetic seal portion 74). ) Can be suppressed. Similar to the setting of the primary lid outer peripheral gap G4, the above-mentioned “setting of the secondary lid outer peripheral gap G5” effectively acts as a support member of the secondary lid 70, and as a result, the stress of each hermetically sealed portion is reduced. Can be suppressed.

  When the sealing performance of the primary lid 60 is evaluated by the primary lid sealing portion 64, the following effects are obtained. When the “setting of the primary lid outer peripheral gap G4” is performed, the impact load applied to the primary lid 60 at the time of horizontal drop acts on the head side X1 (the side farther from the sealing performance evaluation position). High stress is generated near the region where the impact load is applied. On the other hand, the stress generated in the primary lid sealing portion 64 distant from the impact load application region is smaller than the stress generated in the impact load application region. Therefore, the influence of the impact load at the time of horizontal drop on the evaluation of the sealing performance of the primary lid 60 can be reduced. As in the case of the primary lid 60, when the “setting of the secondary lid outer peripheral gap G5” is performed, the stress generated in the secondary lid sealing portion 74 is generated in the region where the impact load acting on the secondary lid 70 is applied. It becomes smaller than the stress. Therefore, the influence of the impact load at the time of horizontal drop on the evaluation of the sealing performance of the secondary lid 70 can be reduced.

(Effect of the seventeenth invention)
The effects of the cask 501 shown in FIG. 11 are as follows.
[Configuration 17] The size of the radial Y gap in the fourth area G4a is smaller than the radial Y gap in the area on the bottom side X2 of the primary lid outer circumferential gap G4 than the fourth area G4a.

  The cask 501 has the above [Configuration 17]. Therefore, when the cask 501 falls horizontally, the primary lid as a support member for the body flange 30 is compared with the case where the impact force is transmitted at a position X2 on the bottom side of the fourth area G4a in the primary lid outer circumferential gap G4. 60 can increase the action. Therefore, when the cask 501 falls horizontally, deformation of the outer peripheral portion of the primary lid 60 due to the impact force transmitted from the trunk flange portion 30 to the primary lid 60 can be suppressed. As a result, it is possible to suppress a decrease in the sealing performance of the lid 50, which may occur when the cask 501 falls horizontally.

(Effect of the eighteenth invention)
[Configuration 18] The size of the radial Y gap in the fifth region G5a is smaller than the radial Y gap in the region on the bottom X2 side of the fifth region G5a in the secondary lid outer circumferential gap G5.

  The cask 501 has the above [Configuration 18]. Therefore, when the cask 501 is horizontally dropped, the impact force is transmitted at a position X2 on the bottom side of the fifth region G5a in the outer peripheral gap G5 of the secondary lid. The action of the next lid 70 can be increased. Therefore, when the cask 501 falls horizontally, deformation of the outer peripheral portion of the secondary lid 70 due to the impact force transmitted from the body flange portion 30 to the secondary lid 70 can be suppressed. As a result, it is possible to suppress a decrease in the sealing performance of the lid 50, which may occur when the cask 501 falls horizontally.

(Modification)
Each of the above embodiments may be variously modified.
Components of different embodiments may be combined with each other. For example, in the first embodiment, the second outer peripheral projection 77 of the tertiary lid 80 shown in FIG. 6 may be provided without the second outer peripheral projection 77 of the secondary lid 70 shown in FIG.
Some of the components may not be provided. For example, the central projection 78 shown in FIG. 3 may not be provided. For example, the head assist buffer 93b shown in FIG. 1 may not be provided.
The number of components may be changed. Fixing or mounting may be direct or indirect.

DESCRIPTION OF SYMBOLS 1, 201, 301, 401 Cask 10 Cask main body 11 Bottom 13 Opening 20 Trunk 60 Primary lid 61 Primary lid main body 62 Primary lid flange 63 Primary lid bolt 70 Secondary lid 71 Secondary lid main body 72 Secondary lid flange 73 Secondary lid bolt 75 Secondary lid neutron shielding material (neutron shielding material)
76 1st outer periphery convex part 76 (secondary lid bottom side convex part)
77 2nd outer periphery convex part (secondary lid convex part)
80 Tertiary lid 90 Buffer 93a Head main buffer (main buffer)
93b Head auxiliary buffer (auxiliary buffer)
265 Primary lid neutron shielding material (neutron shielding material)
266 First Peripheral Convex (Primary Lid Convex)
287 Second outer peripheral convex part (tertiary lid bottom side convex part)
362 Primary lid seating part 372 Secondary lid seating part G1 First gap G1a First area G1c Third area G2 Second gap G2a Second area G4 Primary lid outer peripheral gap G4a Fourth area G5 Secondary lid outer peripheral gap G5a First 5 areas X axis direction Y radial direction

Claims (7)

A bottom, a cylindrical body with a bottom that has an axially long body, and an opening, and stores a radioactive substance;
A primary lid that closes the opening,
A secondary lid disposed axially outside the primary lid and closing the opening,
A tertiary lid disposed axially outside the secondary lid and closing the opening,
A buffer covering the outer periphery of the tertiary lid,
With
An area included in a second gap that is an axial gap between the secondary lid and the tertiary lid, and an area having an axial gap smaller than other areas of the second gap; There is a second region that is a region located at a position sandwiched between the outer peripheral portion of the next lid and the outer peripheral portion of the tertiary lid,
The outer peripheral portion of the secondary lid is a portion from a radially outer end of the secondary lid to a position radially inward by half the radius of the secondary lid,
The outer peripheral portion of the tertiary lid is a portion from a radially outer end of the tertiary lid to a position radially inward by half the radius of the tertiary lid,
The primary lid, and at least one of the secondary lid includes a neutron shielding material,
The tertiary lid is configured not to include the neutron shielding material,
The second region, when viewed from the axial direction, overlaps with the region without the neutron shielding material,
Cask. The cask according to claim 1, wherein
The second region is in a region where the trunk portion is extended in the axial direction,
Cask. The cask according to claim 1 or 2,
The secondary lid is
A secondary lid body,
A secondary lid bolt fixing the secondary lid body and the cask body,
A secondary lid neutron shielding material, which is the neutron shielding material installed inside the secondary lid body,
With
The second region is radially outside of the secondary lid neutron shielding material and radially inside of the secondary lid bolt,
Cask. The cask according to any one of claims 1 to 3,
The secondary lid is
A secondary lid body,
A secondary lid bolt fixing the secondary lid body and the cask body,
A secondary lid protrusion protruding from the secondary lid body toward the tertiary lid side and forming the second region together with the tertiary lid,
A flange structure is provided at a fastening portion of the secondary lid bolt to the cask main body, and has a flange structure recessed toward the bottom side from an end surface of the secondary lid projection on the tertiary lid side. A secondary lid flange portion arranged adjacent to the radially outer end portion,
A cask. The cask according to any one of claims 1 to 3,
The secondary lid is
A secondary lid body,
A secondary lid bolt fixing the secondary lid body and the cask body,
A secondary lid seating portion provided around a fastening portion of the secondary lid bolt to the cask body and having a counterbore structure recessed toward the bottom side from an end surface of the secondary lid on the tertiary lid side,
A cask. The cask according to any one of claims 1 to 3,
The secondary lid is
A secondary lid body,
A secondary lid bolt fixing the secondary lid body and the cask body,
A flange structure is provided at a fastening portion of the secondary lid bolt to the cask main body, and has a flange structure recessed to the bottom side from an end surface of the secondary lid main body on the tertiary lid side, and radially outside the secondary lid. A secondary lid flange portion arranged at the end,
With
The tertiary lid,
A tertiary lid body,
A tertiary lid bottom-side projection that projects from the tertiary lid body toward the secondary lid and forms the second region with the secondary lid;
A cask. The cask according to any one of claims 1 to 6,
The buffer is
A main buffer covering an outer peripheral portion of the tertiary lid,
An auxiliary buffer covering a radially central portion of the tertiary lid,
With
An area included in a first gap which is an axial gap between the primary lid and the secondary lid, and an area having an axial gap smaller than other areas of the first gap, and There is a third region which is a region arranged in a region where the buffer extends in the axial direction.
Cask.

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