KR101851181B1 - Bottom nozzle including filtering device for nuclear fuel assembly - Google Patents

Abstract

The present invention relates to a bottom fixture for a nuclear fuel assembly and, more specifically, to a bottom fixture for a nuclear fuel assembly with a foreign material filtering device formed therein, which includes a foreign material filtering device between flow path holes in order to improve foreign material filtering performance and enhance cooling water distribution effects thereof. In addition, the bottom fixture for a nuclear fuel assembly with a foreign material filtering device formed therein comprises: a plate (110) which is formed on the top surface thereof; a plurality of flow path holes (120) which are formed on the plate (110), and of which at least a portion is formed by being divided by a plurality of horizontal elements (112) and vertical elements (114) at right angles to the horizontal elements (112); a connection hole (130) which is formed at an area where the horizontal element (112) and the vertical element (114) meet; and a plurality of wings (140) which are formed in the plurality of flow path holes (120) by being extended from the connection hole (130) in a radius direction and extended in a curved manner in the thickness direction of the plate (110) at the same time.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a nuclear fuel assembly,

The present invention relates to a lower end fixed body for fuel assemblies, and more particularly, to a bottom end fixed body for fuel assemblies, which comprises a foreign matter filtering device between the flow holes to improve the foreign matter filtering performance of the lower end fixed body for nuclear fuel assemblies, To a lower fixture for a nuclear fuel assembly in which an apparatus is formed.

A reactor is a device that can be used for various purposes such as generating heat by artificially controlling the chain fission reaction of a fissile material or producing radioactive isotopes and plutonium or forming a radiation field.

Generally, in light water reactors, enriched uranium is used, which increases the ratio of uranium-235 to 2-5%. In order to process the nuclear fuel used in the nuclear reactor, the uranium is formed into a cylindrical pellet with a weight of about 5 g. These pellets are bundled into a bundle of hundreds of pellets in a vacuum state in a Zircaloy cladding, in which a spring and helium gas are placed, and a top end stop is welded to produce a fuel rod. The fuel rod thus produced finally constitutes a nuclear fuel assembly and is burned through the nuclear reaction in the reactor.

Nuclear fuel assemblies emit heat by fission in the reactor and heat from the nuclear fuel assemblies is absorbed by the cooling water. The cooling water circulates the reactor and reactor piping by the reactor cooling pump and promotes the heat transfer from the fuel assembly to the cooling water.

Such a nuclear fuel assembly 1 is shown in Fig. The nuclear fuel assembly 1 includes a skeletal body composed of the upper fixture 2, the lower fixture 4, the support grid 6, the guide tube 8 and the measurement tube 12 and the support grid 6, And a fuel rod (10) charged and supported in the fuel tank (6). The support grid 6 is arranged at about 10 to 13 upper and lower sides in the nuclear fuel assembly 1 and is welded to a guide pipe 8 having a length of 4 m. Assembly of the nuclear fuel assembly 1 is completed by fixing the upper end fixing body 2 and the lower end fixing body 4 after fixing the fuel rod 10 to the skeleton. In short, the fuel assembly 1 is constructed such that the fuel rod 10 is held between the upper fixing body 2 and the lower fixing body 4 by the support grating 6 and the guide pipe 8, as shown in Fig. 1 It is installed to maintain a constant interval.

 2A and 2B show a general bottom fixing body 4. In Fig. The lower fixed body 4 includes a guide hole 24 and a measurement hole 26 to which the guide pipe 8 and the measurement pipe 12 are respectively connected and a flow hole 28 which is a cooling water passage hole. Cooling water flows into the region of the fuel rod 10 through the flow hole 28 and passes through the fuel rods 10 to remove heat generated in the fuel rod 10. [

On the other hand, when the cooling water flows into the region of the fuel rod 10 through the flow hole 28, the foreign substances remaining in the cooling water also come into the region of the fuel rod 10 in the same path as the cooling water. That is, as shown in FIGS. 2A and 2B, a plurality of flow holes 28 are formed in the lower solidification body 4 of the existing nuclear fuel assemblies, and various types of foreign substances flowing along with the cooling water during the operation of the reactor Passes through the flow hole 28 and flows into the region where the fuel rod 10 of the nuclear fuel assembly is located and can be sandwiched between the fuel rod and the fuel rod or between the fuel assembly lowermost support grid and the fuel rod.

In other words, among the foreign substances introduced into the fuel assembly 1 by the cooling water flowing at a high speed, if the foreign substance having a comparatively large size flows like the cooling water, Vibrate and vibrate in contact with the adjacent fuel rod closure tube, thereby mechanically abrading the fuel rod closure tube, eventually damaging the closure of the fuel rod 10.

When the fuel rod 10 is damaged and a hole is formed, the nuclear reaction products generated due to the nuclear reaction of the nuclear material in the fuel rod 10 are leaked out of the fuel rod cladding to contaminate the cooling water with the radioactive materials, Circulating the primary cooling system of the primary cooling water.

In fact, in the case of overseas nuclear power plants, damage to nuclear fuel has been reported due to foreign matter. As described above, if the primary cooling system is broken, if a coolant loss accident occurs, the cooling water contaminated with radioactive radiation leaks, . In order to prevent such problems, the flow hole is designed in various shapes such as a mesh shape to filter foreign matters generated in the reactor.

Designing a very dense flow hole shape for foreign matter filtration has a great influence on the neutron economics of the nuclear fuel because it becomes difficult to pass through the cooling water. Therefore, in order to prevent the foreign matter from damaging the nuclear fuel assembly, there is a need to improve the foreign matter filtering function in the lower fixture, which is the section where the cooling water enters the nuclear fuel assembly, and at the same time to design the relatively large flow hole to smooth the cooling water flow.

Open Patent Publication No. 2000-0061665 (published on October 25, 2000)

The present invention has been made to solve the above-mentioned problems,

It is an object of the present invention to provide a bottom fixture for a nuclear fuel assembly having improved foreign matter filtering performance.

It is also an object of the present invention to provide a bottom fixture for nuclear fuel assemblies which has improved cooling water distribution performance and can improve thermal tolerance.

It is to be understood that the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be understood by those skilled in the art to which the present invention belongs .

The features of the present invention for achieving the objects of the present invention as described above and performing the characteristic functions of the present invention described below are as follows.

A bottom fixture for a nuclear fuel assembly in which a foreign matter filtering apparatus according to the present invention is formed comprises: a plate formed on an upper surface; And a plurality of flow-through holes formed in the plate, wherein at least a part of the plurality of flow-through holes is divided by a plurality of transverse elements and vertical elements perpendicular to the transverse elements, And a plurality of wings extending in a radial direction from the connection hole and extending in a curved shape in the thickness direction of the plate are formed in the plurality of channel holes.

Preferably, at least a part of the plurality of passage holes is defined by a transverse element, a longitudinal element, and a curved element connecting the transverse element and the longitudinal element by a curved line.

Preferably, the plurality of wings are each formed to be inclined at different angles from a vertical direction above the plate, so that the lower side is not visible through the flow hole when viewed from above the plate.

Preferably, the outer circumference of the connection hole defines a curved protrusion protruding in an arc shape toward the flow passage hole.

According to the lower end fixture for a nuclear fuel assembly in which the foreign matter filtering apparatus of the present invention is formed, a lower end fixture for fuel assembly having enhanced foreign matter filtering performance is provided by including a foreign matter filtering device between the flow holes of the lower fixture.

Further, according to the lower end fixture for a nuclear fuel assembly in which the foreign matter filtering apparatus of the present invention is formed, the foreign matter passing through the flow passage hole rotates together with the cooling water, thereby enhancing the possibility that the foreign matter is filtered through the support grid assembled on the lower end fixture .

Further, according to the bottom end fixture for a nuclear fuel assembly in which the foreign matter filtering apparatus of the present invention is formed, it is possible to improve the thermal margin by having improved cooling water distribution performance.

The effects of the present invention are not limited to those described above, and other effects not mentioned may be clearly recognized by those skilled in the art from the following description.

Figure 1 shows a typical nuclear fuel assembly,
2A shows a perspective view of a bottom fixture of a general nuclear fuel assembly,
FIG. 2B is a top view of a bottom stationary fixture of a typical nuclear fuel assembly,
3A shows an upper side view of a lower fixture for a nuclear fuel assembly according to the present invention,
Figure 3b shows a partial enlarged view of part B of Figure 3a,
3C shows a side view of the lower fixture for a nuclear fuel assembly according to the present invention,
Figure 3d shows a cross-sectional view of AA 'shown in Figure 3a.

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.

Like reference numerals designate like elements throughout the specification. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprises " and / or " comprising ", as used herein, unless the recited element, step, operation, and / Or additions.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is provided to let you know.

FIG. 3B is a partially enlarged view of a portion B of FIG. 3A. FIG. 3C is a cross-sectional view of the lower fixture for a nuclear fuel assembly according to the present invention. FIG. And FIG. 3D shows a cross-sectional view of AA 'shown in FIG. 3A.

A bottom fixture for a nuclear fuel assembly in which a foreign matter filtering apparatus according to the present invention is formed comprises: a plate formed on an upper surface; And a plurality of flow-through holes formed in the plate, wherein at least a part of the plurality of flow-through holes is divided by a plurality of transverse elements and vertical elements perpendicular to the transverse elements, And a plurality of wings extending in a radial direction from the connection hole and extending in a curved shape in a thickness direction of the plate.

As shown in FIG. 3A, the bottom fixture 100 for a fuel assembly in which the foreign matter filtering apparatus according to the present invention is formed includes a plate 110 formed on an upper surface thereof. The plate 110 may be formed integrally with the lower fixture 100 or may be separately formed and attached to the lower fixture 100 It is possible.

The plate 110 includes a plurality of flow holes 120 through which cooling water can flow. The plurality of channel holes 120 are defined by the transverse elements 112 formed in the plate 110 and the vertical elements 114 formed substantially perpendicular to the transverse elements 112.

The plate 110 may further include a curved element 116 that connects the transverse element 112 and the longitudinal element 114 in a curved shape in addition to the transverse element 112 and the longitudinal element 114, 120 may in this case be defined by the transverse element 112, the longitudinal element 114 and the curved element 116. As shown in the left and right upper and lower left and right upper and lower ends of FIG. 3A, when the channel element 120 is divided by the horizontal element 112, the vertical element 114 and the curved element 116, a channel hole 120 having a different size and shape is formed .

A hole for connecting the measuring tube is formed at the center of the plate 110. A connecting hole 130 for inserting a guide tube is formed at a portion where the transverse element 112 and the longitudinal element 114 meet or a portion where the transverse element 112, the longitudinal element 114 and the curved element 116 meet .

3B, the plate 110 is provided with a plurality of through holes 130, which are arranged around the respective through holes 120 of the plurality of through holes 120, from one of the connection holes 130 A plurality of radially extending wings 140 are disposed. That is, the wing 140 extends in the radial direction at a corner of one connection hole 130, and a plurality of wings form a propeller shape. The wings 140 are configured to extend in a radial direction, and furthermore, to extend at a same angle at an equal angle and to extend in a curved shape in the thickness direction of the plate 110. [ Further, the angle at which the wing 140 extends in a curved shape in the thickness direction may be different for each wing. The plurality of wings 140 formed in one channel hole 120 start to extend in the radial direction substantially parallel to the connection hole 130 side and extend in the thickness direction with different predetermined angles.

According to the present invention, when the channel hole 120 is viewed from the upper side of the lower fixed body 100, the lower side is not seen. 3C to 3D, each of the plurality of wings 140 is formed by being inclined at different angles from a vertical direction above the plate 110 so that the flow path hole 120 (see FIG. So that the lower side is not visible. With this configuration, since the lower portion of the flow hole does not pass through when viewed from below the lower fixed body, the foreign matter becomes difficult to pass straight through. Since the cooling water is rotated due to the structure of the flow passage hole 120 in which the plurality of wings 140 are formed, the foreign matter passing through the flow passage hole 120 also rotates together, The support grid can be more easily filtered.

3B, according to the present invention, a curved protrusion 132 protruding in the shape of an arc toward the channel hole 120 may be formed on the outer circumference of the connection hole 130. As shown in FIG. Thereby providing a surface on which the wings 140 are formed. In the figure, the curved protrusion 132 is shown only in the hole for inserting the measuring tube, but it can also be applied to the connection hole 130.

As described above, the lower end fixture for a nuclear fuel assembly in which the foreign matter filtering apparatus according to the present invention is formed has a very large flow hole, and a plurality of propeller- By forming the foreign matter filtering device composed of the wings, the foreign matter is efficiently filtered and the cooling water is distributed.

The propeller-type flow path hole in which the plurality of wings are formed according to the present invention is preferably realized by 3D printing technology rather than by conventional machining. For example, the propeller-type flow hole may be re-machined on the lower fixture previously prepared by machining, or the lower fixture including the propeller-type flow hole may be processed by using the 3D printing technique.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be apparent to those of ordinary skill in the art.

1: Nuclear fuel assembly 2: Top fixture
4: bottom fixture 6: support grid
8: guide tube 12: measuring tube
22, 100: lower fixture 24: guide hole
26: measurement hole 28, 120: flow hole
110: plate 112: transverse element
114: vertical element 116: curved element
130: connection hole 132: curved protrusion
140: Wing

Claims (4)

As a lower fixture for a nuclear fuel assembly,
A plate formed on the upper portion of the lower fixed body
The plate being defined by a plurality of transverse elements and a plurality of vertical elements perpendicular to the transverse elements, and the remaining part of the transverse elements and the longitudinal elements and the transverse elements and the longitudinal elements being curved A flow hole partitioned by a curved element
A connection hole formed at a portion where the horizontal element and the vertical element meet,
A plurality of wings in the form of a propeller formed on the inner surface of the plurality of flow holes and extending in a radial direction from the connection hole and forming a curve in a thickness direction of the plate,
The plurality of wings are each formed by being inclined at different angles from a vertical direction above the plate,
Wherein the angle is different from the angle formed by the channel hole when viewed from above the plate,
And preventing the cooling water flowing through the flow hole from flowing straight in the vertical direction of the plate Wherein the bottom filter assembly is formed with a foreign matter filtering device.
delete delete The bottom fixing device for a nuclear fuel assembly according to claim 1, wherein an outer periphery of the connection hole forms a curved protrusion protruding in an arc shape toward the flow hole.

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