Spacer Grid Of Nuclear Fuel Assembly Having Simple Shape Structure

Abstract

A spacer grid of a nuclear fuel assembly having a simple shape structure is proposed. The spacer grid includes square grid cells having respective inner walls and constituting a square lattice structure. Each of the grid cells includes a plurality of springs for elastically supporting a fuel rod. Each of the plurality of the springs has a fixed end along a vertical direction on each of the inner walls and a free end curvedly provided in a horizontal direction from the fixed end. The grid cells also include a plurality of flow channels each provided in the vertical direction to each of the grid cells and a plurality of mixing vanes each protrudingly provided in a downstream direction of cooling water flow at end parts of each of the grid cells.

Claims

1. A spacer grid of a nuclear fuel assembly for supporting fuel rods of the nuclear fuel assembly, the spacer grid comprising: square grid cells having respective inner walls and constituting a square lattice structure, wherein each of the grid cells includes a plurality of springs for elastically supporting a fuel rod, each of the plurality of the springs having a fixed end along a vertical direction on each of the inner walls and a free end by being curvedly provided in a horizontal direction from the fixed end; a plurality of flow channels each provided in the vertical direction to each of the grid cells; and a plurality of mixing vanes each protrudingly provided in a downstream direction of cooling water flow at end parts of each of the grid cells.

2. The spacer grid of claim 1, wherein each of the flow channels is provided at an intersection of the grid cells.

3. The spacer grid of claim 2, wherein each of the plurality of the springs and each of the flow channels each have the same height as height of each of the grid cells.

4. The spacer grid of claim 1, wherein the plurality of the springs is provided on two inner walls disposed at a right angle to each other among four inner walls constituting each of the grid cells, and each of dimples is provided, facing each of the plurality of the springs, on each of remaining two inner walls; and each of the dimples is curvedly provided in the horizontal direction along the vertical direction on each corresponding inner wall and has fixed opposite ends fixed to the corresponding inner wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features, and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0021] FIG. 1 is a perspective configuration diagram of a spacer grid of a nuclear fuel assembly according to an embodiment of the present invention;

[0022] FIG. 2 is a perspective configuration diagram of the spacer grid of the nuclear fuel assembly cut along the line A-A of FIG. 1;

[0023] FIG. 3 is a plan configuration diagram of the spacer grid of the nuclear fuel assembly according to the embodiment of the present invention; and

[0024] FIG. 4 is a plan configuration diagram of a spacer grid of a nuclear fuel assembly according to another embodiment of the present.

DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinbelow, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Throughout the drawings, the same reference numerals will refer to the same or like parts.

[0026] Specific structural or functional descriptions presented in the embodiments of the present invention are illustrated only for the purpose of describing the embodiments according to the inventive concept, and the embodiments according to the inventive concept may be implemented in various forms. In addition, the present invention should not be construed as limited to the embodiments described herein but should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

[0027] Meanwhile, the term used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention.

[0028] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0029] The term “comprise” and “have” herein is intended to designate that there is a feature, a number, a step, an action, a component, a part, or a combination thereof that is implemented, and it should be understood that they do not exclude in advance the possibility of the presence or addition of at least one another feature, number, step, action, component, part or combinations thereof.

[0030] The present invention is to provide a spacer grid that may be manufactured using metal 3D printing with the exclusion of sheet metal working and welding processing in a manufacturing process of the spacer grid, thereby eliminating restrictions on geometrical design of the spacer grid manufactured by conventional sheet metal working and welding processing and shortening manufacturing processes.

[0031] In general, various metal 3D printing apparatuses have been released. For example, a 3D printing apparatus of CONPCEPTLASER of Germany has a maximum fabricable size of 250×250×280 mm.sup.3, whereby a full-size spacer grid may be manufactured. Here, the 3D printing apparatus uses a powder bed fusion (PBF) method, in which a product is manufactured in a manner that a powder layer of several tens pm is laid on a powder bed having a predetermined area in a powder supply device and is melted and laminated one by one after having been selectively irradiated by laser or electron beams according to a design drawing. Meanwhile, the spacer grid of the present invention may adopt a general metal lamination manufacturing method applied in general metal 3D printing and is not limited to a specific method.

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0033] FIG. 1 is a perspective configuration diagram of a spacer grid of a nuclear fuel assembly according to an embodiment of the present invention, FIG. 2 is a perspective configuration diagram of the spacer grid of the nuclear fuel assembly cut along the line A-A of FIG. 1, and FIG. 3 is a plan configuration diagram of the spacer grid of the nuclear fuel assembly according to the embodiment of the present invention. In the following description, a vertical direction corresponds to a z-axis direction on the drawing, and a horizontal direction refers to an x-y plane.

[0034] With reference to FIGS. 1 to 3, in the spacer grid 100 of the present embodiment, square grid cells 110 having respective inner walls 111 and constituting a square lattice (n×n) structure are fixed by being touched one another externally, and each of the grid cells 110 is integrally provided with a plurality of springs 120, a plurality of flow channels 130, and a plurality of mixing vanes 140 in the vertical direction (the z-axis direction).

[0035] Height of each of the plurality of the springs 120 and each of the flow channels 130 may be the same as height H of each of the grid cells 110.

[0036] Each grid cell 110 is a solid plate without having slots or holes provided therein and is provided with the plurality of springs 120 that is curvedly and protrudingly provided. Each of the springs 120 may have a fixed end 121 along the vertical direction on each inner wall 111 and have a free end 122 by being curvedly provided in the horizontal direction (x-y plane) from the fixed end 121. Here, each of the springs 120 may have a substantially semi-cylindrical cross section and have an arc angle θ of at least 180°.

[0037] In particular, with reference to FIG. 3, each grid cell 110 is provided with four springs 120 each curvedly provided in a horizontal direction (x-y plane) along a vertical direction on four inner walls 111 each having a square, and a point at maximum height of each of the springs 120 from each corresponding inner wall 111 is located at a distance that is the same as a radius r from a center of the grid cell 110. When the radius is defined by a diameter “D2”, the diameter D2, which is a distance between the springs 120 facing each other, is smaller than the outer diameter “D1” of the fuel rod 10 (D2<D1). Therefore, the fuel rod 10 is elastically supported by the springs 120.

[0038] Because four springs are provided at an equal angle) (90°) in each square grid cell of the spacer grid of the present invention, the spacer grid configured as above isotropically and elastically supports the fuel rods 10 and at the same time is capable of performing cooling water mixing functions. On the other hand, arrangement of the plurality of the springs disposed at the equal angle on inner sides of each grid cell could not be implemented by conventional sheet metal or welding alone but may be easily manufactured using 3D printing with high degree of design freedom.

[0039] The flow channel 130 is integrally provided along the grid cell 110 in the vertical direction, may have a hollow cylindrical shape, and is provided at an intersection of the grid cells 110.

[0040] Such a flow channel 130 is integrally provided in the vertical direction to the grid cell 110 to increase the heat exchange efficiency by increasing the contact area with the cooling water and, in particular, is disposed at the intersection of the grid cells 110, thereby dispersing the stress concentration in the spacer grid having the overall square structure and improving the impact characteristics to a diagonal direction of a flank surface of the spacer grid.

[0041] The mixing vane 140 is protrudingly provided in a downstream direction of the cooling water flow at an end part of the grid cell 110, and the mixing vane 140 is shown being provided at the top end of the grid cell 110 in the present embodiment. Such a mixing vane 140 having a predetermined angle is disposed at the top end of the grid cell 110 to induce cross flow mixing and rotational flow mixing, and a plurality of mixing vanes having different shapes and angles may be provided according to positions.

[0042] FIG. 4 is a plan configuration diagram of a spacer grid of a nuclear fuel assembly according to another embodiment of the present, and it will be described on the basis of differences omitting description duplicated on the same configuration as the above embodiment.

[0043] With reference to FIG. 4, in a spacer grid 200 of the present embodiment, a plurality of springs 221 is provided on two inner walls disposed at a right angle to each other among four inner walls constituting each of the grid cells, and each of dimples is provided, facing each of the plurality of the springs, on each of remaining two inner walls.

[0044] Each of the springs 221 has a fixed end along the vertical direction in the inner wall in the same manner as in the previous embodiment and has a free end by being curvedly provided in the horizontal direction from the fixed end. Meanwhile, each of the dimples 222 is curvedly provided in a horizontal direction along a vertical direction on the corresponding inner wall and has fixed opposite ends fixed to the corresponding inner wall.

[0045] In the present embodiment, an edge R of the corner of the spacer grid has a chamfer of a curved surface, and this configuration may minimize the interference at the corner edges between the spacer grids disposed adjacent to each other in the fuel assembly. In addition, in the manufacturing of the spacer grid by sheet metal working in the conventional art, it was difficult to implement the spacer grid having such a structure, but it may be easily implemented by 3D printing.

[0046] Meanwhile, reference numerals 230 and 240 denote a flow channel and a mixing vane, respectively.

[0047] The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it will be evident to those who have ordinary knowledge in the art that various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention.