JP4401513B2 - Inner strap of support grid - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a support grid constituting a nuclear fuel assembly used in a nuclear reactor, and more particularly to an inner strap of the support grid.
[0002]
[Prior art]
Conventionally, for example, a nuclear fuel assembly used in a nuclear reactor of a light water reactor has a plurality of support grids arranged at predetermined intervals between an upper nozzle and a lower nozzle, and an instrument tube and a plurality of control rod guide tubes are provided for each support grid. And a plurality of fuel rods are inserted and held in the lattice space of each support lattice.
The support grid crosses the thin strip-shaped inner straps in a lattice pattern, and the thin strip-shaped outer straps are arranged on the four sides forming the outer surface, and are separated by the inner straps and the inner straps and the outer straps. Fuel rods are inserted and held in a large number of lattice spaces.
In each lattice space 2 of the support lattice 1 shown in FIG. 3, dimples 4 and 4 protrude from two adjacent wall surfaces 3a and 3a, respectively, and springs 5 and 5 protrude from two wall surfaces 3b and 3b facing each dimple 4. Each protrudes. The fuel rods are elastically pressed and supported by two opposing dimples 4 and springs 5.
[0003]
The thin strip-shaped inner strap 6 and the outer strap 7 constituting such a support grid 1 are made of, for example, a Zircaloy alloy, and the outer strap 7 is short along the longitudinal direction of the thin strip as shown in FIG. A plurality of springs 5 extending in a row are arranged, and each spring 5 is arranged to protrude into each lattice space 2. For this purpose, the inner strap 6 is arranged in the longitudinal direction with two dimples 4 and 4 projecting from the surface facing the outer strap 7 in the short direction (P direction in the figure), and on the opposite surface is a spring. 5 ... protrudes and is arranged in the longitudinal direction.
The inner strap 6 has a spring 5 projecting from one side in the center in the lateral direction and dimples 4 and 4 provided on both sides in the lateral direction of the spring 5 to project from the opposite side. The spring 5 and the dimple 4 are formed on opposite surfaces by punching.
[0004]
In this way, when the inner straps 6 are sequentially arranged in a lattice shape from the outer strap 7 side to the inner side, the inner two straps constituting the lattice space rows A and B intersecting the cross in the center of the support lattice 1 are arranged. Since all the straps are configured so that the springs 5 and 5 protrude in the respective lattice spaces 2, the fuel rods cannot be stably held. Therefore, each of the two inner straps 6A constituting the opposing wall surfaces 3a, 3b of the lattice space rows A and B intersecting the central cross is different from the other inner straps 6 and shown in FIGS. Thus, the dimples 4 are all arranged in the longitudinal direction on one surface facing the outer strap 7 side, and the springs 5 are arranged only on the half surface in the longitudinal direction on the other surface shown in FIG. A pair of dimples 4, 4.
As a result, the springs 5 and the dimples 4 are arranged opposite to each other in the two pairs of wall surfaces 3a, 3b, 3a, 3b facing each other in each lattice space 2 constituting the central lattice space row A and B, thereby firmly holding the fuel rod. It will be possible.
[0005]
In order to attach the fuel rod to the support grid 1 having such a configuration, a bending jig 7 as shown in FIGS. 5 and 6 is inserted into the grid space 2. This bending jig 7 has a taper pin 9 having a taper portion attached to a tool 8 divided into four in the circumferential direction so as to be movable in the axial direction, and the bending jig 7 is positioned in the lattice space 2. By pulling the taper pin 9 in this state, the diameter of the tool 8 can be increased and the spring 5 can be bent as shown in FIG. Next, as shown in FIG. 7, the long and rod-like key member 10 is rotated after being inserted through the key window 11 intersecting the cross shape of the lattice space 2, and the hook 13 of the key member 10 is turned on the wall surfaces 3a and 3b. The springs 5 are held in a bent state by engaging with the ribs 12 respectively.
In this state, the bending jig 7 is removed, and then the fuel rod is inserted into the lattice space 2 and the key member 10 is pulled out. Then, the spring 5 is released and the fuel rod is elastically pressed against the opposing dimple 4. Can be fixedly held.
[0006]
[Problems to be solved by the invention]
However, in the fuel rod mounting method as described above, when the key member 10 is inserted from the key window 11 of each lattice space 2 in the lattice space rows A and B having a cross shape at the center, the springs 5 are arranged. In the region, the key member 10 advances while abutting against the side wall of the central protrusion 5a of the spring 5 or the protruding surface 5b on the front and back thereof, but these serve as a guide. However, in the region where the dimples 4 are arranged, the dimple 4 Although the central portion of each of the projections 3a or 3b projecting at both ends in the short direction is flat, the traveling direction of the key member 10 is not fixed and it is difficult to accurately insert the key member 10 along the key window 11. As a result, there may be a problem that the one row of springs 5... Cannot be restrained by the key member 10.
[0007]
An object of the present invention is to provide an inner strap of a support lattice that can accurately insert a key member into the lattice space in view of the above situation.
[0008]
[Means for Solving the Problems]
Inner strap support grid according to the present invention, the to straps and thin strip by intersecting in a grid to form a plurality of lattice spaces, short of one of the opposed wall surfaces of four walls forming each lattice space In the inner strap of the support grid that sandwiches the fuel rod with the spring provided in the center in the hand direction and the dimples provided on both sides in the short direction of the other wall surface,
In the inner strap, wall surfaces extending in the short direction are continuously arranged along the longitudinal direction, and a spring is provided on each wall surface along the longitudinal direction of these wall surfaces, and other portions along the longitudinal direction. Each of the wall surfaces is provided with dimples without springs, and key member guide protrusions are arranged in the middle of the dimples on both sides in the lateral direction on the wall surface provided with the dimples .
When the key member is inserted into the lattice space of the support lattice in order to constrain the spring in a compressed state, the key member moves along the protrusion while being guided by the protrusion on the wall surface provided with dimples without the spring. It can be inserted accurately and smoothly, each spring can be reliably restrained in a compressed state, and a fuel rod can be inserted. The protrusions may be positioned between dimples provided at both ends in the short direction.
The protrusion may be provided on the longitudinal extension of the central contact portion of the spring.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIG. 1 and FIG. 2, and the same parts as those of the above-described prior art will be described using the same reference numerals. 1A and 1B relate to an inner strap according to an embodiment of the invention. FIG. 1A is a front view, FIG. 1B is a cross-sectional view taken along the line XX of FIG. It is a partially broken perspective view which shows the state which inserts a key member in the lattice space row | line | column of a lattice center part.
The inner strap 20 of the support grid 1 shown in FIG. 1 is made of, for example, a Zircaloy alloy, and its main body 21 is formed in a thin strip shape. This inner strap 20 is provided in place of the above-mentioned inner strap 6A, and relates to two pairs of inner straps 20 ... constituting the cross-shaped lattice space arrangements A and B in the center of the support lattice 1. For example, the inner strap has the same configuration as the inner strap 6 described above.
The inner strap 20 is provided with a slit 22 extending from one edge in the longitudinal direction to the central portion in the short direction (P direction), and the other end of the slit 22 communicates with a key window 25 arranged in the central portion of the main body 21. ing. The slits 22 and the key windows 25 are arranged along the longitudinal direction (direction perpendicular to the P direction) with the width of one wall 3a (or 3b) of one lattice space 2 as one pitch.
This inner strap 20 is provided with a spring 23 at the center in the short direction for each wall 3a partitioned by the slit 22 in a region (half surface 21aA) on the right side in the longitudinal direction as viewed in FIG. A plurality (for example, six in FIG. 1) of the springs 23 are arranged along the longitudinal direction.
[0010]
The spring 23 is formed by punching the main body 21 so as to protrude from one surface 21a into a substantially trapezoidal cross section, and from the upright portions 23a, 23a on both the upper and lower sides, the flat portion 23b connecting the upright portions 23a, 23a, and the flat portion 23b. Furthermore, it is comprised by the center contact part 23c which protrudes and presses a fuel rod. The first dimples 24A and 24A are respectively formed by punching in the same manner and adjacent to the upper and lower sides of the spring 23 in the short direction, and the protruding direction of the first dimple 24A is opposite to the spring 23 on the main body 21. The other surface 21b. Moreover, on the other surface 21b of the main body 21, two first dimples 24A and 24A are arranged vertically in the lateral direction for each wall surface 3a over the entire length direction.
In addition, a wall surface 3a 'without springs 23 is formed between the three springs 23 ... and 23 ... arranged in this manner. This means that when a lattice space is formed, a control rod guide tube or an instrument tube is used. The first dimples 24A and 24A are provided at both ends in the lateral direction also on the wall surface 3a '.
[0011]
The other half surface 21aB not provided with the spring 23, which is the remaining region of the one half surface 21aA of the main body 21, is a pair of first dimples provided on both upper and lower sides excluding the central portion in the lateral direction for each wall surface 3a. Another pair of second dimples 24B and 24B are provided inside 24A and 24A, respectively. Since the second dimple 24B is formed to protrude from the same surface 21a as the spring 23, it protrudes in the opposite direction to the first dimple 24A.
Further, on the half surface 21aB, protrusions 27 are formed by punching on the central portion of each wall surface 3a, that is, on the extension of the central contact portion 23c of the spring 23 in the arrangement direction (longitudinal direction). The shape of the protrusion 27 may be set as appropriate. For example, the protrusion 27 is formed in a substantially trapezoidal shape in a sectional view by standing parts 27a and 27a rising from the wall surface 3a and a top part 27b connecting the both rising parts 27a and 27a. Therefore, on the half surface 21aB, the protrusion 27 and the pair of second dimples 24B and 24B and the first dimples 24A and 24A are arranged in a line in the short direction for each wall surface 3a, and are arranged in the longitudinal direction.
[0012]
The inner strap 20 according to the present embodiment is configured as described above, and when the support lattice 1 is formed by fitting the inner straps 6 and the outer straps 7 in the orthogonal state by the respective slits, particularly the central cross shape. The lattice space rows A and B are formed by fitting each pair of inner straps 20 in a substantially orthogonal state at each slit 22.
The procedure for inserting the fuel rods into the cross-shaped lattice space rows A and B in the center of the support lattice 1 will be described. After the bending jigs 7 are inserted into the lattice spaces 2 in a reduced diameter state and positioned. Then, the diameter of the tool 8 is expanded by pulling the taper pin 9, and the springs 23, 23 in each lattice space 2 are bent. Next, the long and rod-like key member 10 is inserted along the inner strap 20 having one of the two key windows 25 (11) and 25 intersecting with the cross shape of the lattice space 2. At this time, the key member 10 is in contact with the side wall of the compressed flat surface portion 23b or the central contact portion 23c of each spring 23 on the half surface 21aA provided with the spring 23, and serves as a guide to the key window 25 of each lattice space 2. (11) When passing through the inner surface 21aB without the spring 23, the pair of second dimples 24B and 24B extend on the wall surface 3a located on both sides in the short direction, and this time, the center is located at the center of each wall surface 3a. It is possible to insert the protrusion 27 further straight as a guide while abutting against the side wall of the protrusion 27.
[0013]
Therefore, the key member 10 can be accurately inserted along the key window 25 (11) even when traveling on the wall surface 3a in which the second dimples 24B and 24B are partially arranged, and penetrates the lattice space 2 of one row. If the key member 10 is rotated after being moved, the spring 23 can be restrained in a compressed state between the ribs 12 of the wall surface 3a (3b) by entering into the other key window 25 where the hook portion 13 intersects. .
If the fuel rod is inserted into the lattice space 2 in this state and then recovered by removing the key member 10, the fuel rod can be firmly held by the two pairs of springs 23 and the second dimple 24B.
[0014]
As described above, according to this embodiment, the springs 23 are arranged on the half surface 21aA and the pair of second dimples 24B and 24B are arranged on the remaining half surface 21aB. When the key member 10 is inserted into the lattice space rows A and B at the center, the protrusion 27 between the pair of second dimples 24B and 24B can be inserted accurately and smoothly.
In addition, what is necessary is just to set the shape of the spring 23, the dimple 24A, 24B, and the protrusion 27 suitably. The number of springs 23 and second dimples 24B of the inner strap 20 is arbitrary.
[0015]
【The invention's effect】
As described above, the inner strap of the support grid according to the present invention supports the key member in order to restrain the spring in a compressed state because the projection for guiding the key member is arranged on the wall surface provided with the dimple. When inserting into the lattice space of the lattice, the key member moves while using the protrusion as a guide on the wall surface without the spring, so that the key member can be inserted accurately and smoothly, and each spring can be reliably restrained in a compressed state.
[Brief description of the drawings]
FIGS. 1A and 1B show an inner strap of a support grid according to an embodiment of the present invention, where FIG. 1A is a front view and FIG. 1B is a horizontal sectional view taken along line XX in FIG.
2 is a partially cutaway perspective view showing a state in which a key member is inserted into a lattice space using the inner strap shown in FIG. 1. FIG.
FIG. 3 is a plan view showing a lattice space of a conventional support lattice.
4 is a plan view showing an inner strap of the support grid shown in FIG. 3. FIG.
FIG. 5 is a side view of a bending jig.
FIG. 6 is a plan view showing a state in which a bending jig is inserted into the lattice space.
FIG. 7 is a partially broken perspective view showing a state in which the key member is inserted into the lattice space of the support lattice.
[Explanation of symbols]
1 Support Grid 20 Inner Strap 23 Spring 24A First Dimple 24B Second Dimple 25 Key Window 27 Projection

Claims (1)

The to straps and thin strip by intersecting in a grid to form a plurality of lattice spaces, springs and other wall surface which is provided in the lateral direction center of one of opposed wall surfaces of four walls forming each lattice space In the inner strap of the support grid that holds the fuel rods with the dimples provided on both sides in the short direction of
In the inner strap, the wall surfaces extending in the short direction are continuously arranged along the longitudinal direction, and the springs are provided on a part of the wall surfaces along the longitudinal direction of the inner straps along the longitudinal direction. Each wall surface of the other part has no spring and the dimples are provided, and key member guide protrusions are arranged in the middle of the dimples on both sides in the lateral direction on the wall surface provided with the dimples. Features an internal strap.

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