JP2995536B2 - Fuel assembly support grid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a support grid for a PWR fuel assembly, and more particularly to a support grid for minimizing interference between mixing vanes and dimples during assembly.

[0002]

2. Description of the Related Art Nuclear fuel for nuclear power generation is formed by bundling a large number of fuel rods containing nuclear fuel material with a support grid.

[0003] As shown in FIG. 3, a group of straps 2 having slits 1 on the upper side and a group of straps 3 having slits 1 on the lower side are combined in a direction perpendicular to each other. Are welded at the intersections of. As shown in FIG. 5, the strap is formed by pressing a large number of dimples 4, mixing vanes 8, springs 5, slits 1 and the like, and has a three-dimensionally complex shape.

[0004] At present, the assembling work of combining these straps to form a support grid is performed manually, but requires skill because of the complicated shape of the straps. In the assembling work, as shown in FIG. 5, the interference between the mixing vane 8 'and the dimple 4' tends to be an obstacle. However, as the assembling work progresses and the number of straps increases, the number of possible points of the interference increases. The difficulty increases further.

[0005]

SUMMARY OF THE INVENTION The present invention addresses the above situation, minimizes the interference between the mixing vanes and dimples of the straps constituting the support grid, and facilitates the assembly of the support grid. The purpose is to tighten.

[0006]

That is, a feature of the support grid of the present invention that meets the above object is that a strap having a plurality of slits cut at regular intervals on the upper side and the above-mentioned slits on the lower side are provided. A support lattice formed by forming a large number of straps and each slit into a lattice shape by fitting the slits together, and forming a large number of mixing vanes bent from the upper ends of the straps to the cell side of the lattice; The portion is formed in an arc shape on the adjacent slit side. In the support lattice of the present invention, it is also preferable that the tip of the mixing vane is bent in a direction opposite to the bending direction.

[0007]

In the support lattice according to the present invention, even when the mixing vane and the dimple interfere with each other when assembling the straps, the arc shape and the bend formed at the tip of the mixing vane slide the dimple. Therefore, it is possible to avoid the catching of both, and to facilitate the work of assembling the support grid.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a perspective view of an essential part showing an assembled state of a support lattice according to an embodiment of the present invention, FIG. 2 is an enlarged view of a portion A in FIG. 1, and FIG. Schematic diagram, Figure 4
FIG. 3 is a plan view showing the entire support grid of the example.

As shown in FIG. 3, the support grid of this embodiment is composed of a group of straps 2 having a plurality of slits 1 cut at regular intervals on the upper side and a plurality of straps 2 also cut at regular intervals. A group of straps 3 having the slits 1 on the lower side is formed in a lattice shape as shown in FIG.

[0011] As shown in FIG.
Has a large number of dimples 4, springs 5, and mixing vanes 6. The mixing vanes 6 are arranged so as to bend from the upper ends of the straps 2 and 3 to the cell 7 side of the lattice.

In the embodiment of the present invention, each tip portion 6a of the mixing vane 6 is formed in an arc shape so that an R portion is formed at least on the adjacent slit 1a side, in contrast to the conventional shape shown in FIG. And each of these tip portions 6a
Are bent in a direction opposite to the bending direction of the mixing vane 6 main body as shown in FIG.

Thus, in the present invention, in the assembling work of the support grid, the interference between the mixing vanes 6 and the dimples 4 of the straps 2 and 3 constituting the support grid is minimized, and the strap is provided for facilitating the assembly. It provides a shape.

That is, when assembling the straps 2 and 3, for example, the dimples 4 'and the mixing vanes 6' shown in FIG. 1 are likely to interfere with each other, and are hidden by the straps 3. Although the mixing vane at a position symmetrical to 6 'is warped to the near side in the drawing and easily interferes with the dimple 4 "on the upper right of the strap 3, in the above-mentioned support lattice of the embodiment of the present invention, the mixing vanes are not connected to each other. Mixing vane 6 during assembly
Even if the dimples 4 interfere with each other, the arc shape and the bend formed on the tip 6a of the mixing vane 6 can slide the dimples 4, thereby avoiding the two to be caught and supporting the dimples 4. The work of assembling the lattice can be facilitated.

Further, the automation of the assembling work, which has conventionally been difficult due to the interference between the mixing vane 6 and the dimple 4, can be made more feasible.

[0016]

As described above, in the support lattice of the present invention, the tip of the mixing vane is formed in an arc shape on the adjacent slit side, or the tip is bent in the direction opposite to the bending direction of the main body. Even if the mixing vane and the dimple interfere with each other when the straps are assembled, the arc shape and the bending applied to the tip of the mixing vane allow the dimple to slide, thereby preventing the two from being caught. As a result, there is a remarkable effect that the assembling work of the support lattice is facilitated and the above-mentioned assembling work, which has been conventionally difficult due to the interference, can be automated.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part showing an assembled state of a support grid according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a schematic view showing an entire assembled state of the supporting grid of the embodiment.

FIG. 4 is a plan view showing the entire support grid of the embodiment.

FIG. 5 is a perspective view of a main part showing an assembled state of a conventional support grid.

FIG. 6 is an enlarged view of a portion A in FIG. 5;

[Explanation of symbols]

 1, 1a slit 2 strap 3 strap 4, 4, 4 ', 4 "dimple 5 spring 6, 6' mixing vane 6a tip 7 cell

Claims (2)

(57) [Claims] 1. A strap having a large number of slits cut at regular intervals on the upper side and a plurality of straps having the slits on the lower side are formed in a lattice shape by fitting the slits together. In a support lattice of a fuel assembly in which a number of mixing vanes bent from the upper end of the strap to the cell side of the lattice are formed, the tip of the mixing vane is formed in an arc shape on an adjacent slit side. Fuel assembly support grid. 2. A support grid for a fuel assembly according to claim 1, wherein a tip end of said mixing vane is bent in a direction opposite to said bending direction.