JPH06249993A - Inserting/removing method of fuel rod into/from supporting grid - Google Patents

Abstract

PURPOSE:To provide a method for pressing a resilient protrusion on a supporting grid cell using a key member and inserting a fuel rod into a space thus provided in which durability of the key member is enhanced automation of the operation is facilitated. CONSTITUTION:A plurality of lever keys 1 each having a recess 2 matching the slit 8 in a supporting grid cell 7 are combined with a plurality of set keys 3 to be fit in the recess 2 while crossing each other. The lever keys 1 are subsequently shifted to press against a resilient protrusion 10 on the cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to PWR fuel assemblies, and more particularly to fuel for inserting or withdrawing fuel rods from a support grid which holds a number of fuel rods in parallel at regular intervals. It relates to a method of inserting and removing a stick.

[0002]

2. Description of the Related Art In a nuclear fuel assembly, fuel rods are provided with a predetermined interval so that they are securely held between upper and lower nozzles so that they can sufficiently perform their performance during operation of a nuclear reactor. , A plurality of support grids are arranged at predetermined intervals in the longitudinal direction of the fuel rod. In order to remove heat from the surface of the fuel rods that generate heat, the support lattices are usually arranged in parallel in a large number of cells divided by the lattices, with a large number of fuel rods and control rod guide thimble tubes in some predetermined positions. In addition, it maintains the necessary gap between the fuel rods and ensures the flow of coolant. This support grid is generally formed by pressing a thin plate of iron-chromium-nickel-based superalloy Inconel into a predetermined shape, as shown in FIG.
As shown in (B), elastic projections 10 and fixing projections 12 that elastically hold fuel rods (not shown) in the cells 7 are provided, and lattice plates with slits are assembled in a vertical and horizontal lattice shape and intersect with each other. It is manufactured by connecting and integrating the upper and lower parts with various metallurgical joining means such as welding and brazing.

On the other hand, the large number of fuel rods are elastically held by the elastic projections and the fixed projections in each cell of the support grid as described above. The elastic projections must be pressed and retracted so that they do not damage the fuel rods. Therefore, conventionally, when the fuel rod is inserted into or removed from the support grid, as shown in FIG.
As shown in (A) and (B), the key member 14 provided with a plurality of protrusions 13 ... 13 according to the intervals of the slit grooves 8 ... After being inserted vertically, the key member is rotated by 90 degrees, and the protrusions 13 ... 13 are pressed against the groove edges 11 ... 11 as shown in the drawing, so that the key member 14 causes the elastic projections 10 ...
Was pressed to form a space in the cell 7 into which the fuel rod enters in a non-contact state.

[0004]

However, according to the above-mentioned conventional method, in order to press the elastic projection, first, as described above, the key member is arranged so that its protrusion is vertical to the slit groove. An operation of inserting the key member and then rotating the key member by 90 degrees is required, and if the key member is used many times in this method, the force in the twisting direction repeatedly applied causes fatigue failure of the key member eventually. . In addition, the above-mentioned rotation work is currently performed directly by hand, and this work of rotating an extremely large number of jigs per fuel assembly requires a great deal of labor and time, and reduces radiation exposure. Some improvement is desired from the viewpoint of machine automation.

The present invention has been made in view of the above situation, and by finding a new structure for the insertion / removal key member, the elastic protrusion of the cell is pressed without rotating the key member. At the very least, it is possible to use a machine to insert / pull out the key member into / from the support grid, so that the fuel rod can be inserted / pulled out in a short time and the radiation exposure of the worker can be greatly reduced. The purpose is.

[0006]

That is, the feature of the method for inserting and removing the fuel rods into and from the supporting grid of the present invention which meets the above-mentioned object is that the fuel cells are inserted into the slit grooves provided at the corners of each cell of the supporting grid. A lever key is formed by notching a plurality of fitting recesses having a required width on one side of the rod-shaped body in accordance with the intervals of the slit grooves, and on the other hand, the lever key is inserted so as to be orthogonal to the lever key, and the lever key Forming a rod-shaped set key to be inserted into the fitting recess of the above-mentioned, and so as to be orthogonal to the cell side wall provided with the elastic projections for pressing the plurality of lever keys, a plurality of slit grooves of the side wall are individually formed. Then, the fitting recesses of these lever keys are aligned with the slit grooves of the side wall orthogonal to the side wall of the elastic protrusion, and then the plurality of set keys are inserted.
Pass the front of the elastic projection from each slit groove of the orthogonal side walls, and individually inserted into the fitting recesses of the lever key,
Further, the lever key is moved to the rear side of the elastic protrusions, the elastic protrusions are pressed by the set keys, and the fuel rods are inserted into or pulled out from the cells pressed by these elastic protrusions.

In the method of the present invention, it is also preferable to provide a lock mechanism or the like so that when the lever key is moved to the rear side of the elastic protrusion, the lever key can be fixed at the moved position. .

[0008]

By performing the fuel rod insertion / removal method of the present invention, a complicated procedure for rotating each key member can be omitted, and a large number of elastic projections can be simultaneously pressed by one movement of the lever key. These also make it possible to implement mechanical automation of key operations more easily.
Further, since neither the lever key nor the set key is subjected to the above-mentioned rotation operation, there is no fear of fatigue fracture due to twisting as in the conventional case, and the durability of the key member can be improved.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a partially cutaway perspective view showing a lever key according to an embodiment of the present invention, FIG. 2 is a partially cutaway perspective view showing a state where the set key according to the embodiment is assembled with a lever key, and FIG. FIG. 4 is a plan view showing a state in which keys and are inserted, and FIG. 4 is a vertical sectional view of FIG.

As shown in FIGS. 3 and 4, the lever key 1 is a rod-shaped body which is inserted into slit grooves 8 ... 8 provided at the corners of the cells 7 ... 7 of the support grid S. As shown in FIG. 2, one side portion of the rod-shaped body is formed with fitting recesses 2 ... 2 having the same width as the slit grooves 8 ... ing. The lever key 1 is preferably a plate-shaped one as shown in FIGS. 1 and 2, and the length thereof is appropriate so as to penetrate the support grid. In addition, the depth of the fitting recess 2 is set by the set key 3 as shown in FIGS.
It is desirable that it fits perfectly.

At the end of the lever key 1, it is preferable to provide a lock mechanism for keeping the position as it is while the elastic projection 10 is pressed through the set key 3. Further, assuming that a machine is used, it is possible to provide an engaging portion that can engage with a predetermined portion of this machine and provide a lock mechanism on the machine side.

On the other hand, as shown in FIG. 2, the set key 3 is formed of a straight rod-shaped member having a thickness that loosely fits in the fitting recesses 2 ... 2 of the lever key 1, and the support grid S also has slit grooves 8 ... 8 has a length penetrating in the row or column direction. Although it is preferable that the cross section of the set key 3 is substantially uniform, the cross section may have any shape such as a square, a rectangle, a circle, or an ellipse. Further, the width of the set key 3 may be arbitrarily determined within a range in which there is a margin with respect to the diameter 5 of the fuel rod 4 when the elastic protrusion 10 is expanded as shown in FIGS.

Therefore, the method of inserting and removing the fuel rods to and from the support grid according to the embodiment of the present invention is as shown in FIGS. 3 and 4 for the cell 7 of the support grid S in the state shown in FIGS. 5A and 5B. As shown in FIG. 1, first, at least two (1 in the figure) the lever keys 1 are arranged parallel to each other so as to be orthogonal to the cell side walls 6 ... 6 provided with the elastic projections 10 ... 10 to be pressed. …
6 are individually inserted into the slit grooves 8 ... 8, and then the fitting recesses 2 ... 2 of these lever keys 1 are slit grooves 8 ... Of side walls 9 ... 9 orthogonal to the side wall 6 on the side of the elastic projection 10. Align to 8.

Then, from the slit grooves 8 ... 8 of the side walls 9 ... 9 orthogonal to the set key 3 described above, only the number of these slit grooves is changed to the elastic protrusions 10 ... 10 as shown in FIGS. 2 are individually inserted into the fitting recesses 2 ... 2 of the lever key 1 through the front thereof.

As shown in FIGS. 3 and 4, a plurality of lever keys 1 are simultaneously moved to the rear side (anti-projection side) of the elastic projections 10 ... 10 and the plurality of set keys 3 ... 3 are used. The elastic projections 10 ... 10 are pressed, and finally the fuel rods 4 ... 4 are inserted into or pulled out from the cells 7 ... 7 on which the elastic projections 10 ... 10 are pressed.

Further, in order to press the elastic projections in one direction of the support grid S by the above method while pressing the elastic projections in the other direction, as shown by the alternate long and short dash line in FIG. Change 90 degrees and operate the lever key and the set key in the same procedure.

To remove the lever key 1 and the set key 3 after inserting / pulling out the fuel rod 4, after returning the lever key 1 to the position before the movement, all the set keys 3 are removed, and then the lever key 1 is removed. Good.

Although the embodiment of the present invention has been described above, the shape of the fitting recess 2 of the lever key 1 can be appropriately changed.
For example, it is also possible to form an L shape or to close the upper part to form a through hole.

[0019]

As described above, according to the method of inserting and removing the fuel rods to and from the support grid of the present invention, a lever key provided with a fitting recess corresponding to the spacing of the slit grooves of each cell, and the fitting of this lever key. By using a set key that fits into the recess, a plurality of these key members are combined so that they cross, and then the lever key is moved to press the elastic protrusions of the cell. By dividing the key member, it is not necessary to rotate the key member as in the conventional case, and stress in the twisting direction is not applied to the key member, and the durability and reliability thereof can be improved.

Furthermore, in the case of the conventional key member,
In order to secure the space through which the fuel rods pass inside the cell, it is necessary to excavate the key member largely except for the parts located at the corners of the cell, and it cannot be said that the key member has sufficient strength and rigidity. However, in the method of the present invention described above, such a need is not necessary, and even a lever key provided with a fitting recess can be formed in a considerably wide range within the range permitted by the length of the slit groove. Sufficient rigidity is secured.

Further, according to the method of the present invention, the complicated procedure of rotating each key member as in the prior art is omitted,
By the parallel movement of the lever key, a large number of elastic protrusions can be pressed at the same time, which has the remarkable effect that the machine for operating the key member can be simplified and the operation of the key member by this machine can be extremely facilitated. It is a thing.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a lever key according to an embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view showing a state where the set key of the embodiment is assembled with a lever key.

FIG. 3 is a plan view showing a state in which the lever key and the set key are respectively inserted into a support grid.

FIG. 4 is a vertical sectional view of FIG.

FIG. 5 (A) is a plan view of a supporting grid cell before inserting a key member. (B) It is a longitudinal cross-sectional view of FIG.

FIG. 6 (A) is a plan view showing a usage state of a conventional fuel rod inserting / removing jig. (B) It is the same longitudinal cross-sectional view.

[Explanation of symbols]

 1 Lever Key 2 Fitting Recess 3 Set Key 4 Fuel Rod 5 Fuel Rod Diameter 6 Cell Side Wall 7 Cell 8 Slit Groove 9 Cell Side Wall (Orthogonal Side) 10 Elastic Protrusion 11 Slit Groove Edge 12 Fixing Protrusion 13 Protrusion 14 Conventional Key Element

Claims (1)

[Claims] 1. A plurality of fitting recesses having a required width are cut out at one side of a rod-shaped body inserted into a slit groove provided at a corner portion of each cell of the support grid so as to match the interval of the slit groove. The lever key is formed, and on the other hand, a rod-shaped set key that is inserted into the slit groove so as to be orthogonal to the lever key and is inserted into the fitting recess of the lever key is formed. The protrusions are individually inserted into a plurality of slit grooves of the side wall so as to be orthogonal to the side wall of the cell, and then the fitting recesses of these lever keys are inserted into the plurality of slits of the side wall orthogonal to the side wall of the elastic protrusion. Align with the groove, then insert a plurality of the set keys through the slit grooves of the orthogonal side walls through the front of the elastic protrusion and insert them individually into the fitting recesses of the lever keys. Further, by moving the lever key to the rear side of the elastic protrusions and pressing the elastic protrusions with the set key, the fuel rod is inserted into or pulled out from the cells pressed by these elastic protrusions. How to insert and remove the rod from the support grid.