JPH0220717Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a support grid for a nuclear reactor fuel assembly.
In particular, the invention relates to something that can increase the strength of the support grid without increasing the thickness of the straps that make up the support grid.

[Prior Art] A fuel assembly loaded in a nuclear reactor is constructed as shown in FIG.

That is, as shown in FIG. 2, this fuel assembly includes an upper nozzle 1 and a lower nozzle 2 arranged parallel to each other and spaced apart from each other vertically in the figure, and a plurality of supports arranged at predetermined intervals between them. The upper and lower ends of the upper and lower nozzles 1 and 2 are inserted through the grid 3 and predetermined grid spaces 5 in a large number of grid spaces 4 formed in these support grids 3, as shown in FIG. A control rod guide tube 6 which is connected to form the framework of a fuel assembly is inserted into a predetermined lattice space 7 of the support lattice 3 and supported by a spring 8 and a dimple 9 as shown in FIG. The fuel rod 12 has a large number of fuel pellets 10 and a pressure spring 11 sealed therein.

The support grid 3 of such a fuel assembly is formed by incorporating a large number of straps 13 shown in FIG. 5 vertically and horizontally.

That is, this strap 13 is made by cutting a rectangular thin heat-resistant alloy plate in a direction perpendicular to its longitudinal direction to form a large number of slits 14, and between each of these slits there is a section of the alloy plate on one side of the alloy plate. While forming a spring 8 by protruding a part,
Slots 15 are formed by punching out both sides of the spring 8, and dimples 9 are formed by partially protruding upper and lower portions of the spring 8 to one side of the alloy plate in FIG. This is what happens.

FIG. 6 is a partially cutaway perspective view of the support grid 3 formed by enclosing the straps 13.

[Problems to be solved by the invention] In such a conventional support grid, the strength near the spring 8 and the slot 15 tends to be weak compared to other parts. This has caused the inconvenience of having to make other parts unnecessarily strong.

That is, the size of the slot 15 must be larger than a certain value from the viewpoint of ensuring circulation of cooling water and sufficient cooling of the fuel rods 12, etc., and the spring 8 must be designed so that the spring 8 has no tension when formed. This is because the area near the slot 15 and the spring 8 can hardly be expected to contribute to the strength because it is extended and thinner than other parts.

In order to compensate for this strength, the thickness of the strap 13 itself may be increased, but this would change the spring constant and lattice spacing of the spring 8, which would undesirably necessitate a change in the design of the fuel assembly.

Furthermore, the thicker the plate, the more difficult it is to process the strap.

The object of the present invention is to obtain a support grid for a nuclear reactor fuel assembly that eliminates the above-mentioned drawbacks.

[Means for Solving the Problems] The present invention involves forming a large number of slits in a rectangular thin plate at regular intervals in a direction perpendicular to its longitudinal direction, and inserting the thin plate between each of these slits. A part of the straps are made to protrude to one side to form a spring, and both sides of the spring are punched out to form slots.The straps are assembled vertically and horizontally by fitting the slits of these straps into each other. In the support lattice of a nuclear reactor fuel assembly formed in a lattice shape, reinforcing plates are provided at both ends of the spring of the strap, respectively, along the longitudinal direction of the strap, and at the center of the spring and both the slots. The reinforcing plates are attached horizontally and twisted at the center of each of the reinforcing plates.

[Function] In the support grid of the reactor fuel assembly of the present invention, the strength of the straps at both ends of the spring and the straps at the sides of both slots is reinforced by the reinforcing plate, thereby increasing the strength of the entire strap. A support grid with sufficient strength can be obtained without increasing the thickness.

[Embodiment] FIG. 1 is a partially cutaway perspective view of an embodiment of the present invention.

In FIG. 1, the reference numeral 13a indicates straps that are assembled vertically and horizontally to form a support grid, and each of these straps 13a has, as shown in FIG.
A spring 8a is formed by projecting a part of the strap toward one side, that is, the rear side of the paper in the figure, and a slot 15a is formed by punching out both sides of the spring 8a.
Dimples 9a formed by projecting a portion of the strap 13a toward the front in the drawing are provided above and below the spring 8a and the slot 15a.

Further, reinforcing plates 16 are provided at both ends of the spring 8a of the strap 13a, respectively.
A reinforcing plate 16 is attached to the strap 13a along the longitudinal direction of the spring 8a.
It is attached across the central part (protrusion) of the slot 15a and both the slots 15a. The center portions of the three reinforcing plates 16 are twisted.

The above embodiment has the following advantages.

That is, since the vicinity of the spring 8a and the slot 15a, which have weak strength, are reinforced by the reinforcing plate 16, the strength of the entire support grid can be made sufficient without increasing the thickness of the entire strap 13a.

Further, since the reinforcing plate 16 is used as a reinforcing plate, there is no problem in terms of strength even if the slot 15a is made sufficiently large.

Furthermore, the twisted portion added to the reinforcing plate 16 further enhances the reinforcing effect, and also makes it possible to effectively make the cooling water a turbulent flow, thereby significantly improving the cooling effect.

[Effects of the invention] As detailed above, the present invention involves forming a large number of slits in a rectangular thin plate at regular intervals in a direction perpendicular to its longitudinal direction, and forming the slits between each of these slits. A spring is formed by making a part of a thin plate protrude on one side, and a number of straps are formed by punching out both sides of the spring to form slots, and the slits of these straps are fitted into each other to form a spring. In the support lattice of a reactor fuel assembly formed in a lattice shape, reinforcing plates are attached to both ends of the spring of the strap along the longitudinal direction of the strap, and reinforcing plates are attached to the strap at the center part of the spring and Since the reinforcing plates are attached across both slots and twisted at the center, the reinforcing plates reinforce the strength of the straps at both ends of the spring and the straps at the sides of both slots. By doing so, it is possible to obtain a support grid with sufficient strength without increasing the thickness of the entire strap, and by adding twist to the center of the reinforcing plate, the reinforcing effect can be further enhanced, and the fuel assembly In the loaded state, the cooling water can be effectively made into a turbulent flow, and the cooling effect can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view showing an embodiment of the present invention, Fig. 2 is a view showing a nuclear reactor fuel assembly, Fig. 3 is a sectional view taken along the line - - of Fig. FIG. 5 is a partially enlarged view of the figure, FIG. 5 is a view showing a strap, and FIG. 6 is a partially cutaway perspective view showing a support grid of a conventional nuclear reactor fuel assembly. 8a...Spring, 13a...Strap,
15a...Slot, 16...Reinforcement plate.

Claims (1)

[Claims for Utility Model Registration] A number of cuts are made in a rectangular thin plate at regular intervals in a direction perpendicular to its longitudinal direction to form slits, and a part of the thin plate is placed between each of the slits on one side. A nuclear reactor in which a large number of straps are formed by protruding to the side to form a spring and punching out both sides of the spring to form slots, and the slits of these straps are fitted into each other and assembled vertically and horizontally to form a lattice shape. In the support grid of the fuel assembly, reinforcing plates are attached to both ends of the spring of the strap, respectively, along the longitudinal direction of the strap, and across the center of the spring and both slots, and each reinforcing plate is attached to each end of the spring of the strap. A support grid for a nuclear reactor fuel assembly characterized by a twist in the center of the plate.