KR20140019925A - Protective grid of a nuclear fuel assembly to have resisted structure for flow-induced vibration - Google Patents

Abstract

The present invention relates to a protective grid of a nuclear fuel assembly and more specifically, to a protective grid satisfying both the filtration of foreign substances and reduction of fluid induced vibrations by improving the top end structure for filtering the foreign substances. The protective grid (100) includes a dimple (110) for supporting a fuel rod and a foreign substance filter part (120), wherein the protective grid is composed of multiple planar straps (101) forming a unit lattice cell, and a strap-shaped reinforcing member (130) is additionally bonded to a surface of the top end of each planar strap (101), whereby a trade-off between the filtration of foreign substance and the reduction of fluid induced vibrations can be achieved, thereby remarkably reducing fatigue damage to the grid through the increase of the degree of freedom in designing the foreign substance filter part while reducing the fluid induced vibrations concurrently.

Description

Protective grid of a nuclear fuel assembly to have resisted structure for flow-induced vibration}

The present invention relates to a protective support lattice of a nuclear fuel assembly having a fluid-induced vibration resistance shape, and in particular, by improving an upper structure of the protective support lattice for filtration of foreign substances, it is possible to satisfy both the fluid-induced vibration reduction and the improvement of the foreign matter filtration function. A protective lattice of a nuclear fuel assembly.

A nuclear reactor is a device for artificially controlling the fission reaction of a fissile material and using thermal energy generated from fission as a power source.

The nuclear fuel used in a nuclear reactor is formed by compacting the enriched uranium into cylindrical pellets of a predetermined size and then manufacturing a plurality of pellets in the fuel rod. These multiple fuel rods constitute a fuel assembly and are loaded into the core of the reactor The combustion takes place through the nuclear reaction.

Referring to FIG. 1, a nuclear fuel assembly generally includes a plurality of fuel rods 10 arranged in the axial direction, a plurality of support grids 20 provided in the lateral direction of the fuel rods 10 to support the fuel rods, A plurality of guide tubes 30 fixed to the grid 20 to constitute the skeleton of the aggregate and an upper fixture 40 and a lower fixture 50 to support upper and lower ends of the guide tube 30 respectively.

The fuel rods 10 constituting the nuclear fuel assembly are composed of approximately 200 or more, and each fuel rod 1 is charged with a concentrated uranium pellet into a predetermined size.

The upper fixing body 40 and the lower fixing body 50 are for supporting the upper and lower ends of the guide tube 30, respectively, the upper fixing body 40 is the hydraulic pressure of the cooling water flowing through the upper portion through the lower portion of the nuclear fuel assembly. A plurality of elastic bodies are provided to prevent the lifting of the nuclear fuel assembly by means of pressing and fixing the upper end of the nuclear fuel assembly. The lower fixture 50 fixes and supports the lower end portion of the guide pipe and has a plurality of flow holes to which cooling water is supplied.

A plurality of support grids 20 are disposed in the axial direction of the fuel rod 10 and are provided with intermediate support grids in accordance with their arrangement positions and functions and a mixed support grating for improving cooling water mixing performance, Can be distinguished.

Referring to FIG. 2, such support grids are commonly assembled such that a plurality of plate-shaped straps have a lattice shape, and one fuel rod or guide rod is disposed in each of the divided lattice cells .

Specifically, the support grid 20 includes a plurality of outer grid plates 21 constituting the outer frame of the structure, a horizontal grid plate 22 disposed and fixed in a grid form inside the outer grid plate 21, ).

In the grid cell 20a formed in the support grid 20 constructed as described above, the fuel rod is inserted and the guide grid cell 20b into which the guide tube is inserted is provided.

The assembly of the support grid and the fuel rod is provided with dimples and springs in the grid forming the unit grid cell to elastically support the fuel rod, and the assembly of the support grid and the guide tube may be fixed by welding or mechanically fixed through the sleeve. Can be.

On the other hand, in the process of supplying the cooling water through the flow hole of the lower fixture 50, the metal particles, chip, or shavings generated during the production, installation, or repair of the cooling facility or piping facility, The same foreign matter can be mixed with the cooling water through the flow hole of the lower fixture 50.

These foreign substances may damage the cladding tube when they are mixed with the cooling water, and therefore it is necessary to prevent the foreign substances from flowing into the fuel assembly together with the cooling water.

Among the support grids, the protective grating 60 disposed closest to the lower fixed body 50 functions not only to support the fuel rods but also to filter debris that can flow into the reactor together with the cooling water in the circulation process of the cooling water And the protective support grid is also referred to as a support grid for foreign matter filtration.

For example, the present applicant's registered patent No. 10-0898114 (registered date: 2009.05.11), registered patent No. 10-0918486 (registered date: 2009.09.15), registered patent No. 10-0907634 (registered date: 2009.07.07), registered patent No. 10-0907625 (registered date: 2009.07.07), registered patent No. 10-0982302 (registered date: 2010.09.08), registered patent No. 10-0927133 (registered date: 2009.11. 10). ≪ / RTI >

Such a conventional protective support grid is provided with a foreign matter filtration unit protruding from the lattice planes so as to be able to filter foreign substances on the support grid and capable of filtering foreign matter, The present invention aims at minimizing the pressure drop that may occur due to reduction of the flow path area while improving the filtration performance of the foreign matter.

FIG. 3 is a perspective view showing a protective grating according to the prior art. FIG. 3 shows only one grating cell formed of a plurality of grating plates.

Referring to FIG. 3, the conventional protective support grid 60 is formed on the grating plate 61 to support the fuel rods, and the foreign matter filtering unit protruding when the arch has a curved shape to filter foreign matters. 63 is provided, and although not shown, a spring may be provided to elastically support the fuel rod.

Meanwhile, in the protection grating, the foreign material filtering unit 63 may have a complicated shape or a large cross-sectional area to prevent the foreign matter from entering, thereby reducing the size of the foreign matter filtering unit 63 through which foreign matter can pass. However, since the pressure drop of the cooling water is proportional to the cross-sectional area of the support grid viewed in the axial direction, the shape of the foreign matter filtering portion can not simply be set to be complicated in order to enhance the foreign matter filtering performance.

Therefore, the shape structure of the foreign matter filtering portion or the dimple in the protection grating greatly affects the pressure drop of the cooling water, and fluid induced vibrations may be generated by the cooling water flowing at a high speed.

At this time, when the natural frequency of the protective support lattice and the frequency of the fluid-induced vibration due to the vortex release formed at the end of the lattice plate of the protective support lattice are in the same range, the protective support lattice is exposed to large vibration due to resonance, When exposed, they can be damaged or broken into fatigue, acting as a damaging mechanism for the fuel assembly.

Thus, a support grid, particularly a protective grid that is disposed immediately adjacent the bottom fixture, is required to have a design capable of reducing fluid induced vibrations.

The present invention is to solve the problems of the prior art, in the protective support grid of the nuclear fuel assembly for foreign material filtration, to provide a protective support grid of the nuclear fuel assembly that can satisfy both the foreign matter filtration function and the fluid induced vibration reduction. I would like to.

In the protective support lattice of the nuclear fuel assembly according to the present invention for achieving the above object, provided in the lower portion of the nuclear fuel assembly, the protective support lattice comprising a dimple for supporting the fuel rod and a foreign matter filtering unit for filtering foreign matter, The protective support grid is composed of a plurality of flat plate gratings constituting each unit grating cell, the grating plate is achieved by the additional surface joining of the plate-shaped reinforcement member on the top.

Preferably in the present invention, the reinforcing member is fixed to the grating plate by welding, more preferably, the reinforcing member is a reinforcing plate having a same width along the inner surface of the grating plate, the surface bonded do.

The protective support lattice of the nuclear fuel assembly according to the present invention is composed of a plurality of flat lattice plates constituting each unit lattice cell, and the lattice plate has a flat reinforcing member bonded to the upper surface thereof, thereby filtering foreign matters of the protective support lattice. By improving the trade-off between improving and reducing the fluid induced vibration, the design freedom of the foreign matter filtering unit is extended while reducing the fluid induced vibration, thereby reducing the fluid induced vibration and greatly reducing the fatigue damage of the support grid.

1 is a view showing a general nuclear fuel assembly,
2 is a plan view of a general support grid,
Figure 3 is a perspective view of a prior art protective grating,
4 is a perspective view showing a protective support grid according to the present invention,
5 is a plan view of a protective support grid according to the present invention.

The specific structure or functional description presented in the embodiment of the present invention is merely illustrative for the purpose of illustrating an embodiment according to the concept of the present invention, and embodiments according to the concept of the present invention can be implemented in various forms. And should not be construed as limited to the embodiments described herein, but should be understood to include all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Meanwhile, in the present invention, the terms first and / or second etc. may be used to describe various components, but the components are not limited to the terms. The terms may be referred to as a second element only for the purpose of distinguishing one element from another, for example, to the extent that it does not depart from the scope of the invention in accordance with the concept of the present invention, Similarly, the second component may also be referred to as the first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but it should be understood that there may be other elements in between something to do. On the other hand, when it is mentioned that an element is "directly connected" or "directly contacted" to another element, it should be understood that there are no other elements in between. Other expressions for describing the relationship between components, such as "between" and "between" or "adjacent to" and "directly adjacent to" should also be interpreted.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. It will be further understood that the terms " comprises ", or "having ", and the like in the specification are intended to specify the presence of stated features, integers, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.

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

Referring to FIG. 4, the protective support lattice 100 of the nuclear fuel assembly of the present invention includes a dimple 110 for supporting the fuel rod and a protective support lattice 100 including a foreign matter filtering unit 120 for filtering foreign matters. In this case, the protective support grid 100 is composed of a plurality of flat plate grating plate 101 constituting each unit grid cell, the grid plate 101 is a planar reinforcing member 130 is further interviewed at the top It is characterized by.

In the present invention, the dimple 110 and the foreign matter filtering unit 120 are the same as in the related art, and although not shown, a spring may be provided to elastically support the fuel rod.

In particular, in the present invention, the support grid is a technical feature that the reinforcing member 130, which is a flat surface is further provided on the top of the single flat grid plate 101 is provided.

Such a reinforcing member may be provided by a reinforcing plate of a flat plate, and the reinforcing plate may have the same width along the inner side surface of each lattice plate constituting the unit lattice cell and may be face bonded. Bonding of the grating plate 101 and the reinforcement plate may be fixed by brazing.

By adding a reinforcing member to the upper portion of the lattice plate 101 constituting the protective support grid configured as described above, it is possible to reduce the fluid-induced vibration that may occur due to the complicated structural shape of the foreign matter filtering unit provided to improve the foreign matter filtration function.

In particular, the reinforcing member is added to the upper portion of the grid plate 101, thereby increasing the design freedom of the foreign matter filter unit to improve the foreign matter filtration function while suppressing the fluid induced vibration, and the fluid induced by the vortex discharge formed at the upper end of the grid plate 101 By reducing vibration, fatigue damage can be greatly reduced.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

10: nuclear fuel rod 20: support grid
30: guide tube 40: upper fixing body
50: bottom fixture 60, 100: protective support grid
101: grid 110: dimple
120: foreign matter filtration unit 130: reinforcement plate

Claims (3)

In the protective support grid provided in the lower portion of the nuclear fuel assembly, including a dimple for supporting the fuel rod and a foreign matter filtering unit for filtering foreign matter,
The protective support grid is composed of a plurality of flat grid grating constituting each unit cell,
The lattice plate is a protective support grid of the nuclear fuel assembly having a fluid-induced vibration resistance shape, characterized in that the surface is further bonded to the plate-shaped reinforcement member on the top The protective support grid of claim 1, wherein the reinforcing member is fixed to the grating plate by brazing welding. The protective support lattice of claim 1 or 2, wherein the reinforcing member is a reinforcing plate having a same width along the inner surface of the grating plate and bonded to the surface.

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