JPS6349757Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a jig for assembling a nuclear fuel assembly having spacers that hold a plurality of fuel rods in a lattice shape.
In particular, the present invention relates to an assembly jig that prevents damage to the surface of fuel rods during assembly.

[Technical background of the invention and its problems]

Generally, in a fuel assembly for a nuclear reactor, fuel rod spacers are provided at a plurality of locations in the longitudinal direction of the fuel assembly to maintain the spacing between the plurality of fuel rods.

That is, FIG. 4 is a longitudinal cross-sectional view of the fuel assembly for the above-mentioned nuclear reactor, and in the fuel channel 1,
A plurality of fuel rods 4 and water rods 5 are installed in an array, with their upper and lower ends supported by an upper tie plate 2 and a lower tie plate 3, respectively. A plurality of spacers 6 are provided in the axial direction of the fuel rods 4 for restraining vibration and ensuring a coolant flow path.

The spacer 6 has a square outer frame 7, as shown in FIGS. 5 and 6, and is comprised of bars 8, 9 and dividers 10, 11 arranged in a grid pattern within the outer frame 7. A plurality of cells 12 are formed. Furthermore, a lantern spring 13 having a leaf spring 13a projecting outward on each side is attached to each intersection of the bars 8 and 9, and the fuel rod 4 inserted into each cell 12 is connected to the lantern spring 13. ,
The dividers 10 and 11 from the corner of the cell 12
It is adapted to be elastically pressed against the S-bends 10a, 11a or the dimples 14 formed in the.

Therefore, when assembling the above-mentioned nuclear fuel assembly, the lower tie plate 3 and spacer 6 are fixed at predetermined positions, and the fuel rods 4 and water rods 5 are
into the cells 12 of the spacer 6,
The lower end is attached to the lower tie plate 3, and the upper tie plate 2 is attached and fixed to the upper end.

However, in assembling the fuel assembly as described above, when each fuel rod 4 is inserted into the cell 12, the fuel rod is inserted into the leaf spring portion 13a of the lantern spring 13 of the spacer 6 and the s-bend 10.
a, 11a or the dimple 14, the surface of the fuel rod may be scratched.

Therefore, conventionally, in order to prevent the surface of the fuel rod from being damaged, the leaf spring portion 13a of the lantern spring 13 of the spacer 6 and the s-bend 10
a and 11a with a string to hold down the protruding part of the spring to enlarge the space into which the fuel rod is inserted, or to store the fuel rod at sub-zero temperatures to form a film of ice or frost on its surface. Alternatively, methods such as cooling a mixture of water, alcohol, or other substances and using the mixture as a lubricant have been taken.

However, the method of tying the spring part with a string is very complicated and time-consuming, and in order to form a coating such as ice on the surface of the fuel rod, the fuel rod must be kept below freezing point beforehand. Furthermore, when a lubricant is used, there is a risk that impurities will adhere to the fuel rod, reducing its performance, so a cleaning process must be provided.

It has also been proposed to assemble nuclear fuel rods using a jig in which multiple cylindrical films are arranged in a straight line (Japanese Patent Application No. 1983-69521).
In this case, if the cylindrical film is inserted into the waterrod cell of the spacer, there is a risk that the cylindrical film will be damaged because the waterrod is provided with a protrusion or the like for preventing vertical movement of the spacer. Therefore, in order to prevent the above damage, when inserting fuel rods into the row where the water rod is located, for example, a cylindrical film of a jig is inserted into each cell above the water rod cell, and each Insert the fuel rod into the cell,
Thereafter, it is necessary to remove the jig, insert the cylindrical film of the jig into each cell below the waterrod cell, and insert the fuel rod into each cell. Therefore, it is necessary to operate the jig twice for simply inserting a fuel rod into one row of cells, or it is necessary to prepare two jigs, and the drive control of the jig is required accordingly. There are problems such as complexity.

[Purpose of invention]

In view of these points, the present invention aims to provide a jig for assembling nuclear fuel assemblies that can reliably prevent damage to the surface of fuel rods using a relatively simple method. do.

[Summary of the idea]

The present invention is an assembly jig for a nuclear fuel assembly having spacers that hold a plurality of fuel rods in a lattice pattern, in which the spacers are inserted into each cell on the same row and cover the portions in contact with the surface of the fuel rods. A plurality of cylindrical films formed of a material having axial cuts and having self-lubricating properties at least on the surface side of the fuel rods are placed in correspondence with each cell on the same row of the spacer. The cylindrical films are arranged in a row parallel to each other on one side of the support rod, and the cylindrical films at positions corresponding to the horizontal rows of cells including the water rod cells are laterally offset from the row of cylindrical films, It is characterized in that it is provided so as to correspond to cells in adjacent columns.

[Example of idea]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

Figure 1 shows a jig 20 for assembling a fuel assembly according to the present invention.
In this perspective view, on one side of the support rod 21 which is longer than the width of the spacer 6, a cylindrical film 22 formed so as to be inserted into each cell 12 on the same row of the spacer 6 is attached to each other. They are hung in a parallel line.

By the way, FIG. 2 shows the nuclear fuel rods F and water rods W inserted into each cell 12 of the spacer 6.
FIG. 2 is a plan view showing the arrangement of the spacer 6, in which a water rod W is inserted into a cell 12a at an approximately central portion of a spacer 6, and a nuclear fuel rod F is inserted into the other cells.

A notch 21a is formed in a portion of the support rod 21 of the jig 20 corresponding to the water rod cell 12a, and a cylindrical film 22a is provided in the notch 21a. That is, a cylindrical film 22 is provided on one side of the support rod 21 and is formed so as to be inserted into each cell 12 on the same row of spacers as described above. The cylindrical film 22a at the position relative to the cell in the horizontal row containing the cells 12a is laterally offset from the row of the cylindrical film 22, and the cylindrical film 22a is located in the row adjacent to the row of cells into which the cylindrical film 22 is inserted. It is arranged at a position where it can be inserted into a cell.

The cylindrical films 22, 22a are made of a self-lubricating film such as a polyester film, and have axial cuts 23, 2.
3a is formed, and the length is such that when inserted into each cell, it can cover the S vents 10a, 11a or dimples 14 in each cell.

Moreover, spacers 6 are provided on both end surfaces of the support rod 20.
On the other hand, a handle 25 is provided on the side opposite to the side on which the tubular films 22, 22a are provided.

Therefore, when assembling the fuel assembly, the jig 20 is brought to one side of the spacer 6, and the row of cylindrical films 22 are inserted into the water rod cells 12a.
This jig 20 is advanced in the direction of the spacer 6, and each cylindrical film 22, 22a is inserted into the corresponding cell.
The surfaces of the vent 11a and the dimple 14 are covered (FIG. 3), and then a plurality of fuel rods are inserted into the cylindrical films 22, 22a, respectively.

After the fuel rods have been inserted into the cylindrical films 22, 22a in this way, the jig 20 is inserted into the spacer 6.
The cylindrical films 22, 22a are pulled out from the cells 12, 12a of the spacer 6 by moving the jig 20 in a direction perpendicular to the axis of the fuel rod. ，
22a is removed through the slits 23, 23a, and the row of cylindrical film 22 is aligned with the next row of cells. Thereafter, fuel rods are inserted into each cell in the same manner as described above.

In the above embodiment, the jig 20 is moved manually, but the jig 20 can be moved in the direction of approaching and separating from the spacer and in the direction parallel to the plane of the spacer. The movement may be automatically performed by a driving device that causes the movement. Furthermore, the fuel rods are inserted into the two rows of cells in the center of the spacer using two jigs, and then the two jigs are successively separated and the fuel rods are inserted into the cells of each row. Good too.

[Effect of idea]

Since the present invention is configured as described above, when assembling a nuclear fuel assembly, the part of the spacer that contacts the fuel rod in the cell can be covered with a cylindrical film, and then the fuel rod can be inserted into the cell. It is possible to reliably prevent damage to the outer surface of the rod, and the assembly process does not become particularly complicated, nor does it require complicated equipment. Furthermore, since the cylindrical film is not inserted into the cell for the water rod, the cylindrical film is not damaged by the water rod, and each cell in the row including the cell for the water rod is There is an advantage that there is no need to insert the fuel rod into the fuel rod twice, upper and lower.

[Brief explanation of drawings]

Figure 1 is a perspective view of the assembly jig of the present invention, Figure 2 is a diagram showing how the fuel rods and water rods are inserted into each cell of the spacer, Figure 3 is an explanatory diagram of the assembled state, and Figure 4 is Vertical cross-sectional view of nuclear fuel assembly, No. 5
The figure is an enlarged plan view of the spacer, and FIG. 6 is a cross-sectional side view taken along the line - in FIG. 5. 4...Fuel rod, 6...Spacer, 11a...s
Bend, 12...Cell, 12a...Cell for waterrod, 13...Lantern spring, 20...
...Jig, 21... Support rod, 22, 22a... Cylindrical film, 23, 23a... Cutting.

Claims (1)

[Scope of utility model registration request] In a jig for assembling a nuclear fuel assembly having a spacer that holds a plurality of fuel rods in a lattice pattern, the spacer is inserted into the cell and is formed to cover the portion that contacts the surface of the fuel rod, and is cut in the axial direction. A plurality of cylindrical films made of a material having a self-lubricating property at least on the surface side of the fuel rods are placed parallel to each other on one side of the support rod, corresponding to each cell on the same row of the spacer. The cylindrical films are arranged in a row in the form of
A jig for assembling a nuclear fuel assembly, characterized in that the jig is laterally offset from the row of cylindrical films and is provided so as to correspond to cells in an adjacent row.