JP2007248186A - Fixing structure of cask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing structure of a cask capable of fixing the cask on a storage pedestal without the intermediary of a trunnion, and having simple processability and superior workability. <P>SOLUTION: A fixing ring 9, having through holes 12 formed at equal intervals in the circumferential direction, is provided on the storage pedestal 8, and screw holes 13 are bored similarly at equal intervals in the circumferential direction on the outer circumferential surface of a cask lower part 5. The cask lower part 5 is fitted with the fixing ring 9, and each bolt is screwed with the screw hole 13 through the through hole 12, to thereby fix the cask 1 on the storage pedestal 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing structure for storing a metal cask of spent fuel.

  Nuclear fuel (spent fuel) used in a nuclear power reactor for a certain period is taken out of the core and then temporarily stored in a spent fuel water pool for cooling of decay heat. After this predetermined cooling period, spent fuel is reprocessed in a reprocessing plant, and the recovered uranium and plutonium are processed again as fuel and reused in nuclear power reactors. .

  However, the amount of spent fuel generated from nuclear power plants is expected to reach several thousand tons U per year, but the annual processing capacity of the reprocessing plant is only about 800 tons U. During this period, spent fuel must be stored and stored in an intermediate storage facility.

  There are two types of spent fuel storage methods: metal cask storage and pool storage. However, intermediate storage facilities do not need to handle spent fuel directly at the time of loading / unloading. The use of a metal cask storage system is planned.

  In this metal cask storage system, as shown in the side view of FIG. 7, a metal cask 31 that contains spent fuel (not shown) is placed vertically and is provided at the lower portion 35. Storage storage is performed in a state of being fixed on the storage stand 38 via the individual lower trunnions 37.

A conventional cask fixing structure is shown in FIG. FIG. 8 is an enlarged view of a portion X in FIG.
The lower trunnion 37 is a cylindrical metal fitting that protrudes radially from the outer peripheral surface of the cask lower portion 35 at equal intervals, and a step portion 37a is formed at a portion near the tip. The fixing on the storage stand 38 is performed by receiving the stepped portion 37a by the lower plate 41 fixed to the storage stand 38, sandwiching it from above with the upper plate 42, and tightening with the two bolts 43.

  However, since at least four lower trunnions 37 are necessary to perform stable fixing by the above-described fixing method, there is a problem that the structure of the cask 1 is complicated and the weight of the cask 1 is increased. .

  In order to solve such a problem, Patent Document 1 describes a structure in which a fixing tool that contacts a stepped groove formed on the bottom of a cask from above is fixed on a storage stand.

However, in the structure described in Patent Document 1 described above, the work of attaching the fixture must be performed in a narrow space between the groove and the storage frame, so that workability is poor and the amount of exposure of workers increases. there were.
Japanese Patent No. 3207834

  The present invention has been made in view of such problems, and the cask can be fixed on the storage frame without using a trunnion. The structure of the cask is simple, easy to process, and excellent in workability. The object is to provide a fixing structure.

  To achieve the above object, the present invention provides a cask fixing structure for fixing a cask vertically on a gantry, wherein the fixing structure is formed at a predetermined interval in a circumferential direction of an outer peripheral surface of the cask lower part. A plurality of screw holes, a fixing tool having a plurality of through-holes standing on the base in a ring shape or a lug shape and formed at the same interval as the predetermined interval, and a fixing bolt, The cask fixing structure is characterized in that the cask is fixed on the gantry by fitting a lower part of the cask into the fixing tool, inserting the fixing bolt into the through hole, and screwing the fixing bolt into the screw hole. .

  According to a second aspect of the present invention, there is provided a cask structure according to the first aspect, further comprising alignment means for aligning the circumferential positions of the plurality of screw holes and the plurality of through holes.

  The present invention described in claim 3 is characterized in that the positioning means comprises a guide hole formed in the bottom surface of the cask and a guide pin installed on the mount. This is a cask fixing structure.

  According to a fourth aspect of the present invention, the positioning means includes a concave key groove formed on the inner surface of the fixture and a convex key groove formed on the outer peripheral surface of the cask lower part. The cask fixing structure according to claim 2, wherein:

  According to the first aspect of the present invention, a fixing ring having a plurality of through holes in the radial direction is installed on the storage frame, and a lower part of the cask having a plurality of screw holes formed on the outer peripheral surface is fitted into the fixing ring. By fixing the cask by screwing the bolt into the screw hole through the through hole, the cask can be fixed on the storage stand without going through the trunnion, so the number of triions is reduced. The cask structure can be simplified. Further, since the cask can be fixed from a wide radial space, the workability is excellent and the exposure amount of the operator can be reduced.

  According to the second aspect of the present invention, the workability in the cask fixing operation can be further improved by adding the positioning means for the through hole and the screw hole.

  A cask fixing structure according to an embodiment of the present invention will be described below with reference to the drawings.

  A cask fixing structure according to a first embodiment of the present invention is shown in FIG. FIG. 1 is a side view of the cask during storage.

  The cask 1 has a bottomed cylindrical shape made of steel, and a spent fuel and a neutron shielding body surrounding it are accommodated in an inside sealed by the upper lid 2. The main body of the cask 1 is roughly divided into a cask upper part 3, an intermediate cylinder 4 and a cask lower part 5, and the cask upper part 3 and the lower part 5 are smaller in diameter than the intermediate cylinder 4. An upper trunnion 6 is installed on the outer peripheral surface of the upper cask 3, and a lower trunnion 7 is installed on the outer peripheral surface of the lower cask. These trunnions 6 and 7 are cylindrical metal fittings having stepped portions, and are used for cask transportation and lifting work.

  The lower end portion of the cask lower part 5 is fitted to a fixing ring 9 installed on the storage stand 8, and the cask 1 is placed on the storage stand 8 via the fixing ring 9 by a fixing bolt 10 inserted from the outside. It is fixed to.

  Details of the fixing structure are shown in FIGS. 2 is a perspective view in a state where the cask is not fixed, and FIG. 3 is a cross-sectional view taken along the line AA in FIG.

  The fixing ring 9 is fixed on the storage stand 8 by welding, and a taper 11 is applied to the upper portion so that the diameter gradually decreases inward, and a plurality of fixing rings 9 are provided at predetermined intervals in the circumferential direction of the side surface. Through-holes 12 are formed. Also, bolt holes 13 are drilled on the outer peripheral surface of the cask lower part 5 at the same interval as in the case of the through holes 12.

  A guide pin 14 is installed on the storage frame 8 inside the fixing ring 9, and a guide hole 16 is formed in the bottom surface 15 of the cask lower part 5.

  A cask fixing procedure using the cask fixing structure having such a structure will be described below with reference to FIG.

  First, the cask 1 is lifted and moved until the cask lower part 5 is positioned above the fixing ring 9 (see FIG. 4A). Next, the cask 1 is lowered toward the fixing ring 9, and after the cask lower part 5 reaches the upper end of the fixing ring 9, the cask 1 is lowered along the taper 11 to fit the cask lower part 5 to the fixing ring 9. The through hole 12 and the screw hole 13 are aligned in the circumferential direction so that the guide pin 14 is inserted into the guide hole 16 (see FIG. 4B). After the bottom surface 15 of the cask lower part 5 is grounded on the storage stand 8, the fixing bolt 17 is screwed into the screw hole 13 through the through hole 12 (see FIG. 4C). Then, the cask 1 is fixed onto the storage rack 8 via the fixing ring 9 by tightening the fixing bolt 17 (see FIG. 4D).

  Thus, since the cask 1 can be fixed on the storage stand 8 without using the lower trunnion 7, the number of lower trunnions 7 can be reduced to two necessary for transportation, and the structure of the cask 1 is simplified. can do. Moreover, since the fixing operation | work of the cask 1 can be performed from the space extended in a horizontal direction, workability | operativity can be improved and the exposure amount of a worker can be reduced. Furthermore, since it is easy to use a remote tool (for example, a bolt wrench with a long handle), the amount of exposure can be greatly reduced.

  In order to perform stable fixing, the interval between the through hole 12 and the screw hole 13 is preferably equal in the circumferential direction, and the number thereof is preferably 8 to 16 in consideration of workability. .

  As for the arrangement and the number of the guide pins 14 and the guide holes 16, it is desirable that a plurality of guide pins 14 and guide holes 16 be provided at positions that are symmetrical with respect to the central axis in the longitudinal direction of the cask 1 so as to facilitate alignment.

  FIG. 5 shows a cask fixing structure according to the second embodiment of the present invention. FIG. 5 is a perspective view in a state where the cask is not fixed, and the same parts as those in FIG.

  In the present embodiment, a plurality of fixing lugs 20 are used as a fixing tool. The fixed lugs 20 are arranged at equal intervals so as to form a ring shape as a whole, and one through hole 21 is formed in each. By setting it as such a structure, the installation and fixing operation | work of a fixing tool on the storage stand 8 become easy.

  A cask fixing structure according to a third embodiment of the present invention is shown in FIG. FIG. 6 is a perspective view in a state where the cask is not fixed. The same parts as those in FIG.

  In the present embodiment, a keyway is used as a means for aligning the through hole 12 and the screw hole 13.

  Specifically, the positioning means is constituted by a concave key groove 22 formed on the inner surface of the fixing ring 9 and a convex key groove 23 formed on the outer peripheral surface of the cask lower part 5. By using such key grooves 22 and 23, the operator can confirm the alignment state from the outside, so that the alignment operation can be easily performed.

It is a side view which shows the fixed state of the cask which concerns on 1st Embodiment of this invention. 1 is a cask fixing structure according to a first embodiment of the present invention. It is sectional drawing of the AA arrow shown in FIG. It is a figure explaining the fixing procedure of the cask by this invention. It is a cask fixing structure which concerns on 2nd Embodiment of this invention. It is a cask fixing structure which concerns on 3rd Embodiment of this invention. It is a side view which shows the fixed state of the cask by the conventional cask fixing structure. It is an enlarged view of X part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cask 2 Upper cover 3 Cask upper part 4 Intermediate trunk 5 Cask lower part 6 Upper trunnion 7 Lower trunnion 8 Storage stand 9 Fixing ring 10 Fixing bolt 11 Taper 12 Through-hole 13 Screw hole 14 Guide pin 15 Cask bottom face 16 Guide hole 20 Fixing lug 21 Through hole 22 Concave keyway 23 Convex keyway
31 Cask 32 Upper lid 33 Cask upper part 34 Intermediate trunk 35 Cask lower part 36 Upper trion 37 Lower trion 38 Storage stand 41 Lower plate 42 Upper plate 43 Bolt

Claims (4)

A cask fixing structure for fixing a cask vertically on a gantry,
The fixing structure is
A plurality of screw holes formed at predetermined intervals in the circumferential direction of the outer peripheral surface of the cask lower part,
A fixture having a plurality of through-holes standing on the base in a ring shape or a rug shape and formed at the same interval as the predetermined interval;
With fixing bolts,
A cask fixing structure in which the cask is fixed onto the gantry by fitting the lower part of the cask into the fixing tool, inserting the fixing bolt into the through hole, and screwing into the screw hole. The cask structure according to claim 1, further comprising an alignment unit that aligns positions of the plurality of screw holes and the plurality of through holes in a circumferential direction. The alignment means includes
A guide hole formed in the bottom surface of the cask;
The cask fixing structure according to claim 2, comprising a guide pin installed on the mount. The alignment means includes
A concave keyway formed on the inner surface of the fixture;
The cask fixing structure according to claim 2, comprising a convex key groove formed on an outer peripheral surface of the lower part of the cask.

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