JP6244172B2 - Reactor fuel assembly grid - Google Patents

Description

  The present invention relates to a fuel assembly grid for a nuclear reactor used to support fuel rods in a fuel assembly loaded in a reactor core.

  A fuel assembly used in a nuclear reactor supports and bundles fuel rods by a plurality of fuel assembly grids (fuel assembly support grids) (for example, Patent Document 1).

  This fuel assembly grid is generally formed in a lattice shape by crossing a plurality of support plates 30 made of thin metal plates, as shown in FIG. 6, in accordance with a fuel assembly having a square cross-sectional shape. ing.

  Then, each of the plurality of cylindrical fuel rods 34 is vertically inserted and supported in each of the square spaces (cells) 32 formed by the support plate 30 so that the plurality of fuel rods 34 are square. The fuel assembly is configured by being arranged in a lattice pattern. If necessary, a control rod guide tube may be used in place of some fuel rods.

  As shown in FIG. 7, the support plate 30 includes a plurality of flat plate-shaped first support plates 30a formed with slits 31a on the lower side and a plurality of plate-shaped plates formed with slits 31b on the upper side. The second support plate 30b. The slits 31a and the slits 31b are engaged with each other and the first support plate 30a and the second support plate 30b are combined so as to be orthogonal to each other, thereby forming a fuel assembly grid. Note that the joint portion between the first support plate 30a and the second support plate 30b is fixed by welding or the like.

  Then, the plurality of fuel assemblies configured as described above are loaded into the reactor core.

JP 2003-75574 A

  However, a plurality of fuel assemblies loaded in the reactor core in this manner sways in the lateral direction when an earthquake occurs. May end up.

  When such a collision occurs and the grid is impacted by the collision, the support plate 30 is buckled as shown in FIG. 8, and the shape of the cell 32 is deformed from a square to a rhombus, and the fuel assembly is deformed. In addition, there is a risk of damaging the supporting fuel rod, and the control rod guide tube may be displaced or deformed, making it difficult to insert the control rod.

  For this reason, even when a plurality of fuel assemblies collide with each other due to an earthquake or the like, there is a strong demand for a fuel assembly having a fuel assembly grid that does not buckle the support plate and cause cell deformation. It was done.

  Such demands were equally strong for existing fuel assemblies, but the fuel assembly shape and the arrangement of fuel rods and control rod guide tubes in the reactor cannot be changed. It was necessary to prevent changes in the shape and arrangement of the assembly.

  Therefore, the present invention maintains compatibility by maintaining the same number and position of the fuel rods and control rod guide tubes that are supported by the conventional square lattice fuel assembly grid, and by means of an earthquake or the like, It is an object of the present invention to provide a fuel assembly grid that has excellent seismic performance that does not cause buckling of the support plate and does not cause cell deformation even when the grid collides.

The invention described in claim 1
A grid for a nuclear fuel assembly comprising a support plate for supporting each of a plurality of fuel rods arranged in a square shape,
With the support plate, cells in an isosceles triangle shape are formed so as to be alternately continuous vertically and horizontally with the upside down,
The isosceles triangle shape is formed into an isosceles triangle shape having a base that is twice as long as the arrangement pitch of the fuel rods and a height that is equal to the arrangement pitch of the fuel rods. This is a grid for a fuel assembly of a nuclear reactor.

The invention described in claim 2
The support plate is composed of a plurality of flat plate-shaped first support plates and a plurality of second support plates having a shape in which mountain folding and valley folding are repeated, and the first support plate and the second support plate 2. The nuclear reactor fuel according to claim 1, wherein the cells are formed in an isosceles triangle shape so as to be alternately arranged in the vertical and horizontal directions upside down. This is an aggregate grid.

  In order to improve the seismic performance of the support plate and prevent the deformation of the cell in solving the above problems, the present inventor changed the cell, which has been conventionally formed in a square shape, to a triangular shape or a trapezoidal shape. I thought I should do it. In other words, the square shape is easily deformed into a rhombus when a load is applied, but by forming the cell in a triangular shape or a trapezoidal shape, it is not easily deformed even with respect to the load, and is sufficient for the lateral load. Since it can withstand, the seismic performance of the grid is improved, and buckling of the support plate and deformation of the cells are suppressed.

  And, when the above triangle shape is an isosceles triangle shape or the trapezoidal shape is an isosceles trapezoidal shape, it can be placed alternately in the vertical and horizontal directions upside down, and the force applied to each cell And the impact can be supported by two overlapping sides of two adjacent cells, so that the seismic performance is further improved.

  In this way, the seismic performance of the grid is improved, and buckling of the support plate and cell deformation are suppressed, so that even when multiple fuel assemblies collide with each other due to an earthquake, etc. Since the occurrence of buckling of the plate and deformation of the cell is suppressed, the seismic performance of the fuel assembly is greatly improved as compared with the conventional case.

  Furthermore, the present inventor further has an isosceles triangular shape or an isosceles trapezoidal shape of such a cell in an existing fuel assembly in which a plurality of fuel rods are arranged in a square shape without changing the arrangement of the fuel rods. If it could be provided, it was considered that it could be used with good compatibility with conventional fuel assemblies.

  As a result, in the case of a cell having an isosceles triangle shape, it may be an isosceles triangle shape having a bottom having a length twice the fuel rod arrangement pitch and a height equal to the fuel rod arrangement pitch. In the case of an isosceles trapezoidal cell, the sum of the lengths of the upper and lower bases is twice as long as the arrangement pitch of the fuel rods, and the height is equal to the arrangement pitch of the fuel rods. It has been found that an isosceles trapezoidal shape is sufficient, and the present invention has been completed.

  According to the present invention, a conventional square lattice fuel assembly grid and the number and position of fuel rods and control rod guide tubes to be supported are the same to maintain compatibility. Even when the grid collides, it is possible to provide a grid for a fuel assembly that is excellent in seismic performance without buckling of the support plate and without causing deformation of the cell.

It is a figure explaining the grid for fuel assemblies of the nuclear reactor which concerns on the 1st Embodiment of this invention. FIG. 2 is an assembly diagram of the fuel assembly grid shown in FIG. 1. It is a figure explaining the grid for fuel assemblies of the nuclear reactor which concerns on the 2nd Embodiment of this invention. FIG. 4 is an assembly diagram of the fuel assembly grid shown in FIG. 3. It is a figure explaining the grid for fuel assemblies of the nuclear reactor which concerns on the 3rd Embodiment of this invention. It is a figure explaining the grid for the conventional fuel assembly. It is an assembly drawing of the grid for the conventional fuel assembly. It is a figure explaining generation | occurrence | production of buckling by the impact in the conventional grid for fuel assemblies.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

1. First Embodiment FIG. 1 is a diagram for explaining a fuel assembly grid of a nuclear reactor according to a first embodiment, and is provided in a frame of a fuel assembly. In FIG. 1, reference numeral 2 denotes a cell formed on the fuel assembly grid 1, and reference numeral 4 denotes a fuel rod supported by the support plate 8 in the cell 2. FIG. 2 is an assembly view of the fuel assembly grid 1 shown in FIG.

  As shown in FIG. 1, the fuel assembly grid 1 includes a support plate 8 including a plurality of first support plates 8a and a plurality of second support plates 8b.

  The plurality of first support plates 8a are made of a thin plate-like metal plate, and are arranged in the lateral direction of the fuel assembly grid 1.

  The plurality of second support plates 8b are formed of thin metal plates having a shape in which mountain folds and valley folds are repeated at right angles so as to form an angle of ± 45 degrees with each first support plate 8a. It is arranged in the horizontal direction.

  As shown in FIG. 2, the first support plate 8a and the second support plate 8b are combined so that the second support plate 8b faces each other with the first support plate 8a interposed therebetween, and the joint portion is fixed by welding or the like. Has been. As a result, as shown in FIG. 1, a fuel assembly grid 1 is formed in which isosceles triangular cells 2 are alternately arranged in the vertical and horizontal directions upside down.

  The isosceles triangle shape of the cell 2 is an isosceles side having a base that is twice as long as the arrangement pitch of the fuel rods 4 arranged in a square lattice and a height that is equal to the arrangement pitch of the fuel rods 4. It is formed in a triangular shape.

  As described above, the cells 2 formed in an isosceles triangle shape are alternately arranged in the vertical and horizontal directions upside down, so that the cells 2 formed in the vicinity of the frame of the fuel assembly are excluded. The force applied to most of the cells 2 becomes uniform, and the impact can be supported by the overlapping sides of the two adjacent cells 2.

  As a result, even when grids collide with each other in a plurality of fuel assemblies due to an earthquake or the like, the buckling of the support plate 8 and the deformation of the cell 2 are suppressed, and the buckling of the support plate 8 caused by the collision is suppressed. Since resistance to deformation of the cell 2 is improved, the seismic performance of the fuel assembly is greatly improved as compared with the conventional case.

  And by making the isosceles triangle shape in the cell 2 into the shape as described above, as shown in FIG. 1, the fuel is arranged without changing the arrangement of the plurality of fuel rods 4 arranged in the conventional square lattice shape. The aggregate grid 1 can be formed.

  That is, it is arranged in a conventional fuel assembly grid cell 32 (see FIG. 6) formed by a support plate 30 indicated by a dotted line in FIG. 1 and a lateral support plate (overlapping with the first support plate 8a). The fuel assembly grid 1 can be formed without changing the arrangement of the formed fuel rods 4.

  Therefore, the fuel assembly grid 1 according to the first embodiment can be used with good compatibility with the conventional fuel assembly, and the conventional fuel assembly grid 1 is replaced with the conventional fuel assembly grid. The seismic performance can be greatly improved while maintaining the same fuel assembly and fuel rod arrangement.

2. Second Embodiment FIG. 3 is a diagram for explaining a fuel assembly grid of a nuclear reactor according to a second embodiment, which is provided in a frame of the fuel assembly. In FIG. 3, reference numeral 12 denotes a cell formed on the fuel assembly grid 10, and reference numeral 4 denotes a fuel rod supported by the support plate 18 in the cell 12. FIG. 4 is an assembly diagram of the fuel assembly grid 10 shown in FIG. 3.

  As shown in FIG. 3, the fuel assembly grid 10 includes a support plate 18 including a plurality of first support plates 18 a and a plurality of second support plates 18 b.

  The plurality of first support plates 18 a are made of a thin plate-like metal plate, and are arranged in the lateral direction of the fuel assembly grid 10.

  The plurality of second support plates 18b are formed of a thin metal plate that is repeatedly folded in a mountain shape and a valley in an isosceles trapezoidal shape, and is disposed in the lateral direction of the fuel assembly grid 10.

  As shown in FIG. 4, the first support plate 18a and the second support plate 18b are combined so that the second support plate 18b faces each other with the first support plate 18a interposed therebetween, and the joint portion is fixed by welding or the like. Has been. As a result, as shown in FIG. 3, a fuel assembly grid 10 is formed in which isosceles trapezoidal cells 12 are alternately arranged in the vertical and horizontal directions upside down.

  The isosceles trapezoidal shape of the cell 12 is twice as long as the arrangement pitch of the fuel rods 4 in which the sum of the lengths of the upper base and the lower base is arranged in a square lattice pattern, and the height is the arrangement of the fuel rods 4. It is formed in an isosceles trapezoidal shape equal to the pitch.

  In this way, the cells 12 formed in an isosceles trapezoidal shape are alternately arranged in the vertical and horizontal directions upside down, so that the cells 12 formed in the vicinity of the frame of the fuel assembly are excluded. The force applied to most of the cells 12 can be made uniform, and the impact can be supported by the overlapping sides of the two adjacent cells 12.

  As a result, even when grids collide with each other in a plurality of fuel assemblies due to an earthquake or the like, the buckling of the support plate 18 and the deformation of the cell 12 are suppressed, and the buckling of the support plate 18 caused by the collision is suppressed. Since the resistance to deformation of the cell 12 is improved, the seismic performance of the fuel assembly is greatly improved as compared with the conventional case.

  Then, by making the isosceles trapezoidal shape in the cell 12 as described above, as shown in FIG. 3, without changing the arrangement of the plurality of fuel rods 4 arranged in a conventional square lattice, the fuel The aggregate grid 10 can be formed.

  That is, it is arranged in a conventional fuel assembly grid cell 32 (see FIG. 6) formed by a support plate 30 indicated by a dotted line in FIG. 3 and a lateral support plate (overlapping with the first support plate 18a). The fuel assembly grid 10 can be formed without changing the arrangement of the formed fuel rods 4.

  For this reason, the fuel assembly grid 10 according to the second embodiment can be used with good compatibility with the conventional fuel assembly. By replacing the fuel assembly grid 10 in the conventional fuel assembly, the conventional fuel assembly grid 10 can be used. The seismic performance can be greatly improved while maintaining the same fuel assembly and fuel rod arrangement.

3. Third Embodiment FIG. 5 is a diagram for explaining a fuel assembly grid of a nuclear reactor according to a third embodiment, which is provided in the frame of the fuel assembly. In FIG. 5, 22 is a cell formed on the fuel assembly grid 20, and 4 is a fuel rod supported by the support plate in the cell 22.

  As shown in FIG. 5, the fuel assembly grid 20 includes thin metal plate support plates 28a to 28f arranged in the lateral direction, and support plates 24a to 24e and 26a arranged at an angle of ± 45 degrees, respectively. To 26e are combined to form an isosceles triangular cell 22, and the cells 22 are alternately arranged vertically and horizontally in the upside down direction.

  The isosceles triangle shape of the cell 22 has a base that is twice as long as the arrangement pitch of the fuel rods 4 arranged in a square lattice and a height that is equal to the arrangement pitch of the fuel rods 4. It is formed in an isosceles triangle shape.

  Thus, since the cells 22 formed in an isosceles triangle shape are alternately arranged vertically and horizontally with the top and bottom reversed, except for the cells formed near the frame of the fuel assembly, The force applied to most cells is equalized, and the impact can be supported by two overlapping sides of two adjacent cells.

  As a result, even when grids collide with each other in multiple fuel assemblies due to an earthquake or the like, buckling of the support plate and cell deformation are suppressed, and buckling of the support plate and cell deformation caused by the collision are suppressed. As a result, the seismic performance of the fuel assembly is greatly improved compared to the conventional case.

  Then, by forming the isosceles triangle shape in the cell 22 as described above, as shown in FIG. 5, the fuel assembly is not changed without changing the arrangement of the plurality of fuel rods arranged in the conventional square lattice shape. A body grid can be formed.

  That is, for a conventional fuel assembly formed by a longitudinal support plate and a lateral support plate (overlapping the support plates 28a to 28f) in the conventional fuel assembly grid indicated by a dotted line in FIG. The fuel assembly grid can be formed without changing the arrangement of the fuel rods arranged in the cells of the grid.

  For this reason, the grid according to the third embodiment can be used with compatibility with the conventional fuel assembly, and the conventional fuel assembly is replaced with the grid for the fuel assembly in the conventional fuel assembly. The seismic performance can be greatly improved while keeping the fuel rod arrangement the same.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above-described embodiments within the same and equivalent scope as the present invention.

1, 10, 20 Fuel assembly grids 2, 12, 22, 32 Cells 4, 34 Fuel rods 8, 18 Support plates 8a, 18a First support plates 8b, 18b Second support plates 24a-24e, 26a-26e ( Support plates 28a-28f (in a diagonal direction) Support plates 30 (in a lateral direction) Support plates 30a (in a conventional fuel assembly grid) First support plate 30b (in a conventional fuel assembly grid) (Conventional fuel assembly) Second support plate (in body grid)

Claims (2)

A grid for a nuclear fuel assembly comprising a support plate for supporting each of a plurality of fuel rods arranged in a square shape,
With the support plate, cells in an isosceles triangle shape are formed so as to be alternately continuous vertically and horizontally with the upside down,
The isosceles triangle shape is formed into an isosceles triangle shape having a base that is twice as long as the arrangement pitch of the fuel rods and a height that is equal to the arrangement pitch of the fuel rods. Reactor fuel assembly grid.   The support plate is composed of a plurality of flat plate-shaped first support plates and a plurality of second support plates having a shape in which mountain folding and valley folding are repeated, and the first support plate and the second support plate 2. The nuclear reactor fuel according to claim 1, wherein the cells are formed in an isosceles triangle shape so as to be alternately arranged in the vertical and horizontal directions upside down. Aggregate grid.

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