KR100967119B1 - Space grid having pipe-shaped springs which are inserted into interior grid intersection regions - Google Patents

Abstract

PURPOSE: A spacer grid is provided to properly control a spring constant of a tubular spring by connecting both ends of a slot of the tubular spring to a unit grid. CONSTITUTION: A spacer grid includes a plurality of unit grids(100,100'). The unit grid has a slit(110) for inserting a tubular spring(200). The tubular spring is inserted into a cross region of the plurality of unit grids and includes four slots(210). The length of the slot of the tubular spring is 85 to 95 % of the height of the tubular spring. The length of the slit for inserting the tubular spring is 5 to 15% of the height of the tubular spring. Both sides of the slot of the tubular spring are connected to the unit grid.

Description

Space grid having pipe-shaped springs which are inserted into interior grid intersection regions}

The present invention includes a plurality of rectangular plate-shaped unit grids having a plurality of slits vertically cut at half the height and spaced at equal intervals along one end surface in the longitudinal direction, wherein each of the unit grids is formed in the slits. It relates to the support grid of the nuclear fuel rods coupled to be orthogonal to each other through the fitting between each other forming a plurality of fuel rod cells, in particular having four slots cut along the longitudinal direction spaced at an equal angle of 90 ° And a tubular spring body inserted into the cross section, wherein the length of the slot of the tubular spring body is 85 to 95% of the height of the tubular spring body, and the tubular spring body is formed in the unit grid at the point where the slot is inserted. The length of the dragon slit is 5 to 15% of the height of the tubular spring body, and only the ends of the slots have the unit grid. Connected to the support relates to the price itself.

1 is a perspective view schematically showing a fuel assembly according to the prior art, Figure 2 is a cross-sectional plan view schematically showing a cross section of the fuel assembly according to the prior art, Figure 3 is a support grid applied to the fuel assembly according to the prior art Figure 4 is a plan view schematically showing a part of, Figure 4 is a perspective view schematically showing a part of the support grid applied to the nuclear fuel assembly according to the prior art, Figure 5 is a unit of the support grid supporting the fuel rod according to the prior art It is a perspective view which shows a grid board schematically.

As shown in the figure, the nuclear fuel assembly 100 is composed of a nuclear fuel rod 110, a guide tube 140, the support grid 150, the upper fixture 120 and the lower fixture 130.

Here, the nuclear fuel rod 110 includes a cylindrical uranium sintered body in the zirconium alloy cladding tube, the high temperature heat is generated by the nuclear fission reaction of the uranium sintered body.

On the other hand, the guide tube 140 is used as a passage of the control rod to move up and down in order to control the output of the reactor core and to stop the fission reaction, the support grid 150 is supported by one of the components of the fuel assembly Springs 118 and dimples 119 in their respective grids have a function of supporting the nuclear fuel rods 110 to be arranged at a predetermined position.

The upper fixture 120 and the lower fixture 130 serve to fix and support the nuclear fuel assembly 100 in the upper and lower structures of the core, and the lower fixture 130 filters foreign substances floating in the core. Filtration device (foreign filter, not shown) for.

In addition, the support grid 150 is usually made of a zirconium alloy, and there are guide rod cells into which the nuclear fuel rod cell and the guide tube 140 are inserted to support the nuclear fuel rods 110, and each of the nuclear fuel rod cells is one from each other. A total of two grid springs 118 and the upper and lower sides of the springs, respectively, two drips 119 on each of the two remaining surfaces to support the nuclear fuel rod 110 at six support points. In addition, the nuclear fuel rod 110 is charged with a cylindrical uranium dioxide sintered body, and the coolant is surrounded by four nuclear fuel rods 110, or is surrounded by three nuclear fuel rods 110 and one guide tube 140. It flows rapidly from the bottom of the core to the top in the axial direction through the sub channel 115. Here, the sub-channel 115 refers to a space enclosed by the nuclear fuel rods 110 and has a side that is open and refers to a passage through which fluid can freely move to a neighboring flow path.

Meanwhile, instead of the cylindrical nuclear fuel rod 110 as described above, as illustrated in FIGS. 6 and 7, a technique related to the dual-cooled nuclear fuel rod 10 having an annular structure has been developed in recent years, and the US Patent Publication 3,928,132 and 6,909,765 disclose related information.

Here, the advantages of the dual-cooled nuclear fuel rod 10 having an annular structure is composed of an sintered body 11 formed in an annular shape, an inner cladding tube 12 provided on the inner circumference and an outer cladding tube 13 provided on the outer circumference. Therefore, the coolant flows not only to the outside of the dual cooling nuclear fuel rod 10 but also to the internal heat transfer, thereby maintaining the surface temperature of the dual cooling nuclear fuel rod 10 low and damaging the fuel by increasing the central temperature of the nuclear fuel. By increasing the safety margin of the dual-cooled nuclear fuel rods 10 by lowering the possibility of high combustion and high power is possible.

However, even in the case of applying the dual-cooled fuel rod 10, in order to be structurally compatible with the existing pressurized water reactor core, the fuel assembly 100 may be Since the outer diameter of the nuclear fuel rods has been increased while having to accommodate structural limitations that the position of the core structural components, for example, the guide tube 140, cannot be changed, the gap between the dual-cooled fuel rods 10 and the grid is considerably larger than before. There is no choice but to narrow it. For example, as shown in FIG. 7, if the fuel assembly is constructed according to the 12 × 12 dual-cooled fuel assembly design, the gap between the fuel rod and the unit grid is reduced to about 0.39 mm from the existing 1.45 mm. Therefore, due to the narrow spacing between the fuel rod and the unit grid, a problem that the fuel rod support structure has been formed on the surface of the unit grid in order to support the nuclear fuel rod is difficult to apply in the case of the dual-cooled fuel rod. .

In order to solve the above problems, the present applicant has applied for a patent application No. 2007-0073545 to the invention "support grid of the dual-cooled nuclear fuel rod using the cross-point support". Various prior embodiments have been described in the above patent application, the basic concept of which can be understood through one embodiment shown in FIGS. 8 to 10. In the above embodiment, the support rod 40 of the nuclear fuel rod was made by using a cylindrical tube having a circular cross section, and the slit portions 41 arranged at intervals of 90 degrees were pressed by a press device or the like. Then, by inserting the support 40 near the intersection of the first lattice plate 20 and the second lattice plate 30 and joining by welding or the like, the double-cooled nuclear fuel rod 10 is placed in a square space surrounded by each lattice plate. Received. By such a configuration, the outer diameter portion of the double-cooled nuclear fuel rod 10 is in direct contact with the outer circumferential surface of the support 40 having a circular cross section inserted at each intersection point, and the double-cooled nuclear fuel rod 10 is opened by the rigidity of the support 40 itself. I was able to support it stably.

Applicant's prior patent application as described above overcomes the structural limitation that the gap between the dual-cooled nuclear fuel rod and the unit lattice is narrow, and can support the dual-cooled nuclear fuel rod by using the rigidity of the support itself made of a cylindrical tube. It is worth evaluating at. The prior patent application discloses various embodiments of a support having a square or circular cross section provided with a spring in addition to a cylindrical tube, in particular, a support made of a cylindrical tube is very simple in structure and easy to manufacture. Has the advantage.

However, there is a technical problem to be solved when actually applying the configuration of the upper cylindrical tube support to the intersection of the inner lattice in the fuel assembly. When the support, which is a cylindrical tube, is firmly fixed to each other by welding after being inserted into the grating, a cylindrical tube defined by a joint surface with two orthogonal gratings, unless a separate spring structure is made on the surface of the support. The quadrant of itself comes from the structure that it must act as a spring. In particular, since the radius of the support of the cylindrical tube is actually in the range of several mm, the quadrant of the support firmly fixed to the grating has a fairly high spring constant, and thus the fuel loaded into the fuel rod cell of the support grid. The rod is subjected to a strong spring force.

If the spring force of the support is too small, the fuel rod may not be supported in the fixed position, which may lead to loss of support integrity of the fuel rod. On the contrary, if the spring force is too large, excessive friction may occur when inserting the fuel rod into the support grid itself. Resistance can cause scratches, such as scratches on the surface of the nuclear fuel rods, and the nuclear fuel rods will bend due to inability to adequately accommodate the longitudinal growth of the nuclear fuel rods by neutron irradiation during reactor operation, resulting in bowing of the fuel rods. Can be. When the fuel rods are bent, they come into close contact with or in contact with adjacent fuel rods, narrowing or blocking the coolant flow paths, or sub-channels, between the fuel rods. Departure from Nuclear Boiling, which causes phenomena and is a major cause of reduced fuel output. DNB) is more likely to occur.

It is also commonly known that the flow of reactor coolant flowing around a fuel rod creates a large turbulent flow, or high Reynolds number flow, in the coolant flow around the fuel rod to enhance thermal performance. The turbulence of the coolant flow around the fuel rods is the main cause of flow induced vibrations in the fuel rods. These flow-induced vibrations cause the relative movement of the fuel rods in the contact surface with the spring structure of the lattice, causing local wear on the contact surfaces of the fuel rods, causing the fuel rods to be progressively damaged. Damage ".

In particular, since such fretting wear occurs more severely when the stiffness or spring constant of the spring is large, the support of the cylindrical tube applied in the prior patent application has a problem that it is vulnerable to fretting wear.

Therefore, the present invention by devising a new coupling structure between the tubular spring body and the unit grid to be inserted into the intersection of the two orthogonal unit grid, the spring constant of the quadrant of the tubular spring body defined by the interface between the two unit grid The aim is to ensure that is in the proper range.

The support grid having a tubular spring body inserted into an intersecting area of the internal lattice according to the present invention has a plurality of slits vertically cut to a half length of height spaced at equal intervals along one end surface in the longitudinal direction. In the support grid of a nuclear fuel rod comprising a plurality of rectangular plate grids, each unit grid plate is orthogonally coupled to each other through the fitting between the slits, forming a plurality of nuclear fuel rod cells, in particular 90 ° It includes a tubular spring body spaced apart in the road and inserted into the cross section of the unit grid plates having four slots cut along the longitudinal direction, the length of the slot of the tubular spring body is 85 to 95% of the height of the tubular spring body The length of the tubular spring body insertion slit formed in the unit grid at the point where the slot is inserted is the tube And 5 to 15% of the height of the spring body, characterized in that only the ends of the slot is connected to the unit grid.

At this time, the height of the tubular spring body is the same as the height of the unit grid.

In addition, the width of the slot of the tubular spring body may be formed to be larger than the thickness of the unit grid.

In addition, any two surfaces connected to each other among the four surfaces of the unit grid forming the fuel rod cell may be formed with dimples protruding into the fuel rod cell, respectively, wherein two dimples are formed up and down. desirable.

In addition, at least the upper and lower edges of the tubular spring body or the upper and lower edges of the dimple have rounded edges facing the inside of the nuclear fuel rod cell, or the upper and lower edges of the tubular spring body or the upper and lower edges of the dimple are formed of the fuel rod cell. It may be bent in a direction toward the outside.

The tubular spring body provided in the support grid according to the present invention may be formed so that the shape of the cross section perpendicular to the longitudinal direction is circular.

In this case, a concave curved surface having a curvature corresponding to the curvature of the nuclear fuel rod may be formed along the length direction between the four slots of the tubular spring body having a circular cross section.

In addition, the tubular spring body provided in the support grid according to the present invention may be formed so that the shape of the cross section perpendicular to the longitudinal direction forms a square.

In this case, a concave curved surface having a curvature corresponding to the curvature of the nuclear fuel rod is formed along the longitudinal direction in the plane between the four slots of the tubular spring body having a square cross section, or the four slots of the tubular spring body. Convex curved surfaces are respectively formed along the longitudinal direction in the plane between them.

Meanwhile, the tubular spring body having a square cross section may have an arch shape in which four slots are curved inwardly toward the center of a plane adjacent thereto, and a fuel rod support part protruding outward may be formed in the middle part of the plane. have.

At this time, it is preferable that the surface of the nuclear fuel rod support is formed of a concave curved surface having a curvature corresponding to the curvature of the nuclear fuel rod, and each plane between the four slots of the tubular spring body is previously formed from the four corners. More preferably, the fuel rod support has a shape that is cut along a virtual contour spaced at a predetermined interval, and is formed in a leg shape that connects the middle portions of the remaining slots.

According to the present invention, since the tubular spring body inserted into the cross section of two orthogonal unit grids has a structure in which only both ends of the slot are connected to the unit grid, both sides of the tubular spring body quadrant defined by the interface with the two unit grids There is an advantage that there is an elongated slot having no joining structure with the unit grid, so that the spring constant of the tubular spring body is in an appropriate range which is not excessively high.

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

However, in describing an embodiment of the support grid body 10 according to the present invention, the support grid body 10 is spaced apart at equal intervals along one end surface in the longitudinal direction and a plurality of vertically cut in half length of the height A plurality of unit grid plates (100, 100 ') having a rectangular plate shape having a slit, and each of the unit grid plates (100, 100') are coupled to be orthogonal to each other through the fitting between the slit, a plurality of nuclear fuel rod cell (20) Since the configuration constituting a) is not significantly different from the above-described prior art, a detailed description of the contents already disclosed in the prior art will be omitted in view of more clearly describing the characteristic configuration of the present invention.

11 is a lattice formed by the unit grids 100 and 100 ′ disposed inside the lattice that surrounds the outermost of the inner lattice, that is, the lattice surrounding the support lattice 10 (see FIG. 13). ) Is a perspective view showing in detail the structure of the tubular spring body 200 inserted into the intersection region of the (). As shown in FIG. 11, the support grid 10 according to the present invention includes a tubular spring body 200 having four slots 210 cut along the length direction at an isometric angle of 90 °. It has a structure inserted in the intersection area of the grid plates (100, 100 '). Preferably, the center of the cross sections which vertically cut the longitudinal direction of the tubular spring body 200 and the intersection point 130 of the unit grid are on the same line. At this time, the length (L) of the slot of the tubular spring body is 85 to 95% of the height (h) of the tubular spring body, formed on the unit grid plate (100, 100 ') at the point where the slot 210 is inserted. The length H 'of the tubular spring body insertion slit 110 is 5 to 15% of the height of the tubular spring body h, and only the two ends of the slot 210, that is, only the upper and lower ends of the unit grid plate. It is connected to (100, 100 ') by welding or the like.

According to this configuration, since the length of the tubular spring body insertion slit 110 is very short while the length of the slot 210 of the tubular spring body 200 is approximately 10 times longer, the two unit grids 100 and 100 'and On both sides of the quadrant of the tubular spring body 200, which is limited to the boundary surface of the tubular spring body 200, there is an elongated slot 210 having no joining structure with the unit grids 100 and 100 ', and thus the slot 210 part is formed as a unit grid plate 100 and 100'. Compared with the prior art, which had a high spring constant welded with), the tubular spring body 200 could have a lower level of spring constant than this. It is preferable here that the height h of a tubular spring body and the height H of a unit grid are the same.

In addition, the width of the slot 210 of the tubular spring body 200 may be formed to be the same as the thickness of the unit grid (100, 100 '), but in order to further lower the spring constant, the tubular spring body 200 It is also possible to form the width of the slot 210 larger than the thickness of the unit grid (100, 100 '). If the width of the slot 210 is larger than the thickness of the unit grid (100, 100 '), the contact area between the tubular spring body 200 and the unit grid (100, 100') is reduced and the empty space is created therebetween, As a result, the spring constant of the tubular spring body 200 is further reduced.

In addition, the dimples 120 protruding into the fuel rod cell 20 may be formed on any two surfaces connected to each other among four surfaces of the unit grids 100 and 100 ′ forming the nuclear fuel rod cell 20. The role of the dimple 120 is to prevent the nuclear fuel rod 30 from excessively approaching the adjacent nuclear fuel rod cell 20. At this time, the dimples 120, in consideration of the balance of the spring force acting on the nuclear fuel rod 30, it is preferable to form two up and down of the unit grid (100, 100 '). FIG. 13 shows an example in which the coupling structure of the unit grids 100 and 100 'and the tubular spring body 200 shown in FIG. 11 is applied to a nuclear fuel rod cell 20 having an arrangement of 5 × 5. The plan view shows that the nuclear fuel rod 30 loaded in the nuclear fuel rod cell 20 is elastically supported by four tubular spring bodies 200 and four dimples 120.

In addition, as shown in FIG. 15, at least one of upper and lower edges of the tubular spring body 200 and upper and lower edges of the dimple 120 is rounded toward the inside of the nuclear fuel rod cell 20, or Upper and lower edges of the tubular spring body 200 or upper and lower edges of the dimple 120 may be bent in a direction toward the outside of the nuclear fuel rod cell 20. Of course, it is also possible to round both the upper and lower edges of the tubular spring body 200 or both sides of the upper and lower edges of the dimple 120. This can reduce the possibility of fretting wear due to scratches on the surface of the nuclear fuel rods or flow-induced vibrations caused by the flow of coolant when charging the nuclear fuel rods 30 into the nuclear fuel rod cells 20. It is also advantageous that the pressure resistance of the cooling water passing through 10) can be reduced.

And in the embodiment of the present invention, the overall shape of the cross section perpendicular to the longitudinal direction of the tubular spring body 200 is largely divided into circular and square. Of course, in addition to round and square, it is also possible to have an octagon, but considering the ease and efficiency of processing, the above two shapes are the most realistic. Various shapes of the tubular spring bodies 200 and 200 'will be described in detail with reference to FIGS. 16 to 19. The structure in which the tubular spring bodies 200 and 200' are coupled to an intersection area of the unit grids 100 and 100 'is described above. Since it is the same as the description, duplicate description will be omitted.

The overall shape of the cross section perpendicular to the longitudinal direction of the tubular spring body 200 is shown in Figures 11 to 14 well, as a variant thereof Figure 16 is a tubular spring body 200 having a circular cross section The concave surface 220 having a curvature corresponding to the curvature of the nuclear fuel rod 30 between the four slots 210 of the is shown in the longitudinal direction, respectively. In this modified example, the concave curved surface 220 is in contact with the nuclear fuel rod 30 to be elastically supported.

17 to 18 show modifications in which the overall shape of the cross section perpendicular to the longitudinal direction of the tubular spring body 200 'is square. The slots 210 'provided in the tubular spring body 200' of the square cross section are formed at an isometric angle of 90 °, that is, along four corners of the longitudinal length of the square pillar, and thus, the portion to support the nuclear fuel rod 30 is square. Four sides in the longitudinal direction of the column.

The concave curved surface 220 'having the curvature corresponding to the curvature of the nuclear fuel rod 30 is formed on the four surfaces of the square pillar in the longitudinal direction, that is, the plane between the four slots 210' of the tubular spring body 200 '. It is formed along the longitudinal direction, respectively. This is similar to the configuration shown in FIG.

In addition, the tubular spring body 200 ′ of the square cross section may have a convex curved surface 230 formed in a plane between the four slots 210 ′, respectively, along its length direction. This may be expressed as a shape in which a tubular spring body 200 ′ having a square cross section and a tubular spring body 200 having a circular cross section are mixed.

As described above, when the curved surfaces 220 'and 230 are formed along four corners of the square pillar in the longitudinal direction, the tubular spring bodies 200 having a circular cross section are assuming that the thicknesses of the tubular spring bodies 200 and 200' are the same. Has a spring constant that is less than This is because deformation is easier because the external force is concentrated on the interface between the protruding surfaces 220 'and 230 and the plane when the surfaces 220' and 230 protruding on the plane form the contact surface than when the contact surface is formed only by the circumferential surface. Because it happens.

Meanwhile, the tubular spring body 200 ′ having a square cross section has an arch shape in which four slots 210 ′ are curved inward toward the center of a plane adjacent thereto, as shown in FIG. 18, and a middle portion of the plane. The fuel rod support 240 protruding outward may be formed, wherein the surface of the fuel rod support 240 is formed of a concave curved surface 242 having a curvature corresponding to the curvature of the nuclear fuel rod 30. It is desirable to be. In addition, each plane between the four slots 210 'of the tubular spring body 200' has a shape cut along the imaginary contour spaced at predetermined intervals from the four corners, but the nuclear fuel rod The supporter 240 is more preferably formed in the shape of a leg connecting the middle portions of the left and left slots 210 '. Such a shape may be regarded as similar in the structure of the nuclear fuel rod support part 240 and the prior art of FIG. 5 in which the spring 118 is formed on the surface of the unit grid. Since the structure of FIG. 19 has the structure of a conventional spring 118 in which the nuclear fuel rod support 240 is supported by four branches, its spring characteristics are also similar to those of the conventional art, and thus many research data have been accumulated. The advantage is that it can be applied to the actual support grid in a short time.

While the invention has been illustrated and described in connection with specific embodiments, it will be understood that various modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims. Anyone who owns it can easily find out.

1 is a front view schematically showing a nuclear fuel assembly according to the prior art.

Figure 2 is a plan sectional view schematically showing a cross section of the nuclear fuel assembly according to the prior art.

Figure 3 is a plan view schematically showing a support grid applied to the nuclear fuel assembly according to the prior art.

Figure 4 is a perspective view schematically showing a support grid applied to the nuclear fuel assembly according to the prior art.

Figure 5 is a perspective view schematically showing a unit grid of the support grid supporting the nuclear fuel rods according to the prior art.

6 is a plan sectional view schematically showing a cross section of a dual-cooled nuclear fuel rod.

7 is a plan sectional view schematically showing a cross section of a dual-cooled fuel assembly.

8 is a perspective view of a cylindrical tube support applied to a dual cooled fuel assembly.

9 is a plan view of the support grid applied to the cylindrical tube support of FIG.

10 is a perspective view of a support grid to which the cylindrical tube support of FIG. 8 is applied.

Figure 11 is an exploded perspective view schematically showing an embodiment of the coupling process of the unit grid and the tubular spring body forming the support grid according to the present invention.

12 is a perspective view schematically showing a coupling state of the support grid of FIG.

FIG. 13 is a perspective view illustrating a 5 × 5 support grid formed of a coupling structure of the unit grid body and the tubular spring body of FIG. 11. FIG.

14 is a plan view showing a support structure of one nuclear fuel rod cell of the support grid of FIG.

15 is a cross-sectional view schematically showing a machining state of the upper and lower edges of the tubular spring body and the dimple provided in the support grid according to the present invention.

Figure 16 is a perspective view showing a modification of the tubular spring body of the circular cross section applied to the embodiment of the present invention.

Figure 17 is a perspective view showing one embodiment of a tubular spring body of a square cross section applied to the support grid of the present invention.

18 is a perspective view showing another embodiment of the tubular spring body of the square cross section applied to the support grid of the present invention.

19 is a perspective view showing another embodiment of the tubular spring body of the square cross section applied to the support grid of the present invention.

DESCRIPTION OF REFERENCE NUMERALS

10: support grid 20: nuclear fuel rod cell

30: nuclear fuel rods

100,100 ': Unit grid 110: Slit for inserting tubular spring

120: dimple 130: intersection of unit grids

200,200 ': Tubular spring 210,210': Slot

220,220 ': concave surface 230: convex surface

240: nuclear fuel rod support 242: concave curved surface of the nuclear fuel rod support

H: height of unit grid

H ': Length of the slit for inserting tubular spring

h: height of tubular spring body

L: length of the slot formed in the tubular spring body

Claims (14)

And a plurality of rectangular plate-shaped unit grids each having a plurality of slits vertically cut at half the height, spaced at equal intervals along one end surface in the longitudinal direction, wherein the unit grids are sandwiched between the slits. In the support grid of the nuclear fuel rods that are coupled to be orthogonal to each other through fitting to form a plurality of nuclear fuel rod cells, And a tubular spring body having four slots cut along the longitudinal direction and spaced at an isometric angle of 90 ° and inserted into an intersection area of the unit grids, wherein the length of the slot of the tubular spring body is equal to the height of the tubular spring body. 85 to 95%, and the length of the tubular spring body insertion slit formed on the unit grid at the point where the slot is inserted is 5 to 15% of the height of the tubular spring body, and only both ends of the slot are connected to the unit grid. A support grid of a nuclear fuel rod, characterized in that connected. The method according to claim 1, The height of the tubular spring body support grid body of the nuclear fuel rod, characterized in that the same as the height of the unit grid. The method according to claim 1, The width of the slot of the tubular spring body is the support grid of the nuclear fuel rod, characterized in that larger than the thickness of the unit grid. The method according to claim 1, The support grid of the nuclear fuel rod, characterized in that dimples protruding into the fuel rod cell are formed on any two surfaces connected to each other among the four surfaces of the unit grid forming the fuel rod cell. The method according to claim 4, The dimple is a support grid of the nuclear fuel rod, characterized in that formed two up and down. The method according to claim 4, At least one of the upper and lower edges of the tubular spring body and the upper and lower edges of the dimple is rounded toward the inside of the nuclear fuel rod cell, or the upper and lower edges of the tubular spring body or the upper and lower edges of the dimple are connected to the outside of the nuclear fuel rod cell. A support grid of a nuclear fuel rod, which is bent in a direction to face. The method according to any one of claims 1 to 6, The support grid of the nuclear fuel rod, characterized in that the cross section perpendicular to the longitudinal direction of the tubular spring body is circular. The method of claim 7, And a concave curved surface having a curvature corresponding to the curvature of the nuclear fuel rod between the four slots of the tubular spring body, respectively, along the longitudinal direction thereof. The method according to any one of claims 1 to 6, The support grid of the nuclear fuel rod, characterized in that the cross section perpendicular to the longitudinal direction of the tubular spring body is square. The method according to claim 9, And a concave curved surface having a curvature corresponding to the curvature of the nuclear fuel rod in a plane between the four slots of the tubular spring body, each along the longitudinal direction thereof. The method according to claim 9, The support grid of the nuclear fuel rod, characterized in that the convex curved surface is formed in the plane between the four slots of the tubular spring body respectively along the longitudinal direction. The method according to claim 9, The four slots of the tubular spring body has an arch shape curved inward toward the center of the plane adjacent thereto, and the fuel rod support grid of the fuel rod, characterized in that the middle portion of the plane has a fuel rod support projecting outwardly. The method according to claim 12, The nuclear fuel rod support grid, characterized in that the surface of the fuel rod support is formed of a concave curved surface having a curvature corresponding to the curvature of the nuclear fuel rod. 14. The method of claim 13, Each plane between the four slots of the tubular spring body has a shape cut along an imaginary contour spaced at predetermined intervals from the four corners, wherein the fuel rod support is cut out of the remaining two slots. The support grid of the nuclear fuel rod, characterized in that formed in the shape of the bridge connecting the middle portion.

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