JP2008175693A - Cask fixing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cask fixing method that improves the earthquake-proof strength, and suppresses adverse influence to a floor or frame while securing the cooling function to a cask. <P>SOLUTION: In this cask fixing method, the cask is fixed to the floor or frame in an erected state via a cask fixture. The cask fixture comprises a first fixing means for bolt-fixing the cask and cask fixture via a first bolt hole group to a first tap hole group disposed in the bottom surface of the cask, and a second fixing means for bolt-fixing the floor or frame and the cask fixture via a second bolt hole group to a second tap hole group disposed in the floor or frame. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cask fixing method. More specifically, the present invention relates to a cask fixing method for fixing a cask in an upright state on a floor surface of a cask storage building or a frame in a facility for storing spent fuel in a cask.

  The spent fuel assembly generated in the nuclear power plant is stored in a dedicated container called a cask 1 as shown in FIG. The cask 1 in which the fuel assemblies are stored is stored in the cask storage building (hereinafter simply referred to as “building”) with the fuel assemblies stored therein until the fuel assemblies are subjected to reprocessing. Stored.

The cask 1 is equipped with a protrusion hanging device called a trunnion 2, and the trunnion 2 is fastened to a gantry using a trunnion fixing bracket (upper) 3, a trunnion fixing bracket (lower) 4 and a trunnion fixing bolt 5. A method of fixing the cask 1 to the gantry 6 is employed (Patent Document 1).
Japanese Patent Laid-Open No. 2003-287592

  In addition, when the cask is fixed to the building, the temperature of the cask surface becomes high due to the heat generated from the spent fuel loaded in the cask, and thus the cask needs to be cooled. Generally, concrete is usually used for the floor surface of a building (hereinafter simply referred to as “floor surface”), and the heat resistance temperature is defined by the material of the concrete. The cask surface is cooled by the air flow in the building so that the floor surface temperature does not exceed the specified temperature due to heat transfer and radiation from the cask. However, in consideration of the local influence on the concrete, it is desirable to cause an air flow in the bottom portion of the cask. Therefore, conventionally, a space is provided under the bottom of the cask by separately providing a block-shaped cask seat on the gantry or floor.

  However, this trunnion is originally used to lift, lay down or stand up a cask using a wire rope through a cask suspension ring. Basically, this trunnion uses the weight of the loaded fuel assembly. Designed to receive only the weight of the cask included.

  Depending on the location conditions of the cask storage facility, the acceleration due to the earthquake is large, and it is problematic in terms of seismic strength to make the cask independent by fixing only two trunnions. That is, depending on the seismic acceleration, the load applied to the two trunnions may greatly exceed the weight of the cask, including the weight of the loaded fuel assembly. In the worst case, the trunnion breaks down and the cask May fall.

  In addition, the block-shaped cask seating part is not simply fixed to the cask or the pedestal, but has no function to prevent the cask from overturning when the trunnion breaks. .

  The present invention solves the above-mentioned problems of the conventional cask fixing method using a trunnion, improves seismic strength, and suppresses the thermal effect on the floor surface or gantry while ensuring a cooling function for the cask. It is an object of the present invention to provide a cask fixing method that can be used.

In view of the above problems, the present inventor, as a result of earnest research, does not directly fix the cask and the floor surface or the gantry as in the prior art, but a cask fixture having first and second fixing means. It was found that the above-mentioned problems can be solved by fixing the cable, and the present invention has been completed.
Hereinafter, the invention of each claim will be described.

The invention described in claim 1
A cask fixing characterized in that it has a first fixing means for the cask and is fixed to the floor or the gantry in an upright state via a cask fixture having a second fixing means for the floor or the gantry. Is the method.

  The invention of this claim is not a direct bolt fixing of the cask and the floor surface or the gantry as in the conventional case, but a method of fixing the cask and the floor surface or the gantry via the cask fixture. Therefore, the seismic strength is improved, the safety is improved, and the direct thermal influence from the cask to the floor or the gantry can be suppressed.

Invention of Claim 2 is the said cask fixing method, Comprising:
A first tap hole group is provided on the bottom surface of the cask, and a second tap hole group is provided on the floor surface or the mount.
The cask fixture has a first bolt hole group corresponding to the first tap hole group, and a second bolt hole group corresponding to the second tap hole group,
The first fixing means is for fixing the cask and the cask fixture to the first tap hole group via the first bolt hole group,
The cask characterized in that the second fixing means is for fixing the floor surface or the gantry and the cask fixing tool to the second tap hole group via the second bolt hole group. It is a fixing method.

  According to the present invention, the first bolt hole group and the second bolt hole having a plurality of bolt holes are used instead of fixing the cask and the floor surface or the gantry with only two trunnions as in the prior art. Since the cask and the cask fixing tool are fixed by the first fixing means through the group, and the floor surface or the gantry and the cask fixing tool are fixed by the second fixing means, the conventional fixing is performed. Compared with the method, safety is improved.

  The size and number of holes in each tapped hole group and each bolted hole group are appropriately designed in consideration of the location conditions of the cask storage facility. If it arrange | positions so that it may be located in equal intervals, positioning of a tap hole and a bolt hole becomes easy, and it is preferable. Further, when the second bolt hole group is positioned outside the first bolt hole group, a large contact area between the cask fixture and the floor surface or the gantry can be secured, and safety is improved.

  Further, if counterbore holes are provided in the bolt holes constituting the first and second bolt hole groups, it is not necessary to use long bolts when fixing the bolts, which is preferable in terms of earthquake resistance. If the bolt is too long, the spring constant of the bolt itself becomes small, which is not preferable for seismic evaluation. In addition, when the cask fixture and the cask are bolted, the lower plane of the cask fixture (the surface in contact with the floor surface) can be flush with the cask fixture to ensure a large contact area between the cask fixture and the floor surface or mount. Can be fixed stably.

  In addition, conventionally, a tapped hole for mounting a shock absorber is provided on the bottom surface of the cask to attach a shock absorber for protecting the cask from an impact during transportation. The first tap is provided on the bottom surface of the cask. Providing the hole group is not technically problematic. Moreover, you may divert the buffer body attachment tap hole as a tap hole which comprises a 1st tap hole group.

Invention of Claim 3 is said cask fixing method, Comprising:
The cask fixing tool is a cask fixing method, wherein the cask fixing tool is plate-shaped, and the plate thickness in the vicinity of each bolt hole constituting the first bolt hole group is thicker than the plate thickness of other portions.

  In the invention of this claim, in the cask fixture, since the plate thickness in the vicinity of each bolt hole constituting the first bolt hole group is made thicker than the plate thickness of other portions, a space can be secured under the bottom of the cask, Convective heat dissipation is promoted, and cooling of the bottom surface of the cask can be promoted. Further, since the contact area between the cask and the cask fixture is reduced, the heat transfer area is suppressed, and the thermal effect on the floor surface is reduced.

  Also, instead of providing a counterbore in each bolt hole constituting the second bolt hole group described above, the plate thickness is reduced, and there is no need to use a long bolt when fixing the bolt. From the viewpoint of earthquake resistance.

  Furthermore, since the weight of the entire cask fixture can be reduced, cost reduction and ease of handling can be obtained.

Invention of Claim 4 is the said cask fixing method, Comprising:
In the cask fixing tool, a portion other than the vicinity of each bolt hole constituting the first bolt hole group is cut out.

  In the invention of this claim, in the cask fixture, the portions other than the vicinity of each bolt hole constituting the first bolt hole group are cut out so that air flows under the bottom of the cask, so that convective heat radiation is further promoted. Therefore, it is preferable for cooling the bottom surface of the cask. In addition, since the contact area between the cask and the cask fixture is made smaller, the heat transfer area can be further suppressed, and the thermal effect on the floor surface can be reduced. Moreover, the weight of the entire cask fixture can be further reduced.

  Furthermore, if the center part of the cask fixture is also cut out to form a ring-shaped cask fixture, a larger space can be secured below the bottom of the cask, so that convective heat dissipation is further promoted and cooling of the bottom of the cask is achieved. Is more preferable. Moreover, the weight of the entire cask fixture can be further reduced.

  According to the present invention, compared with a conventional cask fixing method using a trunnion, the seismic strength is improved, the safety is improved, and a cooling function for the cask is secured, while the cask is directly applied to the floor or the gantry. Thermal effects can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

  FIG. 1 is a diagram illustrating a cask fixing method according to the present invention. As shown in FIG. 1, a plurality of tap holes (first tap hole group) 9 are provided on the peripheral edge of the bottom surface of the cask 1. On the other hand, the cask fixture 10 is provided with a plurality of bolt holes (first bolt hole group) 11 corresponding to the tap holes 9, and on the outside of the first bolt hole group 11, A plurality of bolt holes (second bolt hole group) 12 are provided corresponding to the tap holes (second tap hole group: not shown).

  The cask 1 and the cask fixing tool 10 are fixed to the first tap hole 9 by screwing with the first bolt 13 through the first bolt hole 11. Next, the cask fixing tool 10 to which the cask 1 is fixed by screwing to the second tap hole (not shown) using the second bolt 14 through the second bolt hole group 12 is fixed to the floor surface or Secure to the gantry.

An example of the cask fixture 10 is shown in a perspective view in FIG. Moreover, an example of the shape of the 1st bolt hole 11 and the 2nd bolt hole 12 is shown to Fig.3 (a)-(c).
When the first bolt hole 11 is screwed into the first tap hole 9 using the first bolt 13 and the counterbore hole 11c is provided so that the head of the first bolt 13 does not pop out, the cask fixture 10 It can be fixed to the building floor or pedestal on the entire surface.

  In addition, with respect to the second bolt hole 12, if the second bolt 14 is too long, the spring constant of the bolt itself is reduced, which is not preferable in terms of seismic evaluation. Therefore, a counterbore hole 12a is provided as shown in FIG. As shown in FIG. 3 (c), the plate thickness in the vicinity of the second bolt hole 12 is made thinner than the plate thickness in the first bolt hole 11 to make the substantial bolt length appropriate.

  FIG. 2 shows a cask fixture corresponding to FIG. The cask fixture 10 is designed to have a thin plate thickness except in the vicinity of the first bolt hole group 11, and the cask fixture 10 can be reduced in weight. Moreover, since a space is provided under the cask bottom, heat transfer from the cask to the floor or the gantry can be suppressed.

Another example of the cask fixture 10 is shown in perspective views in FIGS.
FIG. 4 shows the cask fixture shown in FIG. 2 in which an intermediate portion other than each bolt hole vicinity 11 a is cut out in the vicinity of the first bolt hole group 11. Since the notch 11b serves as a passage for air circulation, the effect of promoting cooling of the cask bottom can be obtained.

  FIG. 5 shows the cask fixture shown in FIG. 4 in which a center hole opening 10a is provided inside the cask fixture 10 by cutting out the inner side of the first bolt hole group 11 to form a ring shape. Thereby, the space under the cask bottom can be made larger.

  In the present embodiment, the outer shape of the cask fixture 10 has been described as a disk shape. However, based on the gist of the present invention, the outer shape may be a rectangular or polygonal disk shape.

It is a figure explaining the cask fixing method of this invention. It is a perspective view which shows an example of the cask fixing tool of this invention. It is a figure which shows an example of the shape of the bolt hole in the cask fixing tool of this invention. It is a perspective view which shows another example of the cask fixing tool of this invention. It is a perspective view which shows another example of the cask fixing tool of this invention. It is a figure explaining the cask fixing method of a prior art.

Explanation of symbols

1 cask 2 trunnion 3 trunnion fixing bracket (top)
4 Trunnion fixing bracket (bottom)
5 trunnion fixing bolt 6 mount 9 first tap hole group (single tap holes use the same reference)
DESCRIPTION OF SYMBOLS 10 Cask fixing tool 10a Center hole opening part 11 1st bolt hole group of a cask fixing tool (The same code | symbol is used also for a single bolt hole)
11a 1st bolt hole vicinity 11b Side notch part 11c Counterbore hole 12 of 1st bolt hole 2nd bolt hole group (A single bolt hole uses the same code | symbol)
12a Counterbore hole 13 of the second bolt hole 13 First bolt 14 Second bolt

Claims (4)

  A cask fixing characterized in that it has a first fixing means for the cask and is fixed to the floor or the gantry in an upright state via a cask fixture having a second fixing means for the floor or the gantry. Method. A first tap hole group is provided on the bottom surface of the cask, and a second tap hole group is provided on the floor surface or the mount.
The cask fixture has a first bolt hole group corresponding to the first tap hole group, and a second bolt hole group corresponding to the second tap hole group,
The first fixing means is for fixing the cask and the cask fixture to the first tap hole group via the first bolt hole group,
The second fixing means is configured to bolt the floor surface or the gantry and the cask fixing tool to the second tap hole group via the second bolt hole group. Item 2. The cask fixing method according to Item 1.   The said cask fixing tool is plate shape, The plate | board thickness of each bolt hole vicinity which comprises the said 1st bolt hole group is thicker than the plate | board thickness of another location, The Claim 1 or Claim characterized by the above-mentioned. 2. The cask fixing method according to 2.   4. The cask fixing method according to claim 1, wherein a portion other than the vicinity of each bolt hole constituting the first bolt hole group is cut out in the cask fixing tool. 5. .

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