JPS64678B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for assembling a nuclear fuel assembly, and in particular to a method for assembling a nuclear fuel assembly that reliably prevents damage to the surface of fuel rods during assembly. Regarding the assembly method.

[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. 1 is a longitudinal sectional side view of the fuel assembly for a nuclear reactor, and in the fuel channel 1 there are a plurality of fuel rods whose upper and lower ends are supported by an upper tie plate 2 and a lower tie plate 3, respectively. Fuel rods 4 and water rods 5 are arranged and mounted, and the fuel rods 4 are aligned and supported.
A plurality of spacers 6 are provided in the axial direction of the fuel rods 4 to restrain lateral vibrations of the fuel rods 4 and to secure a coolant flow path.

The spacer 6 has a square outer frame 7, as shown in FIGS. 2 and 3, 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. Further, at each intersection of the bars 8 and 9, a leaf spring portion 13a protruding outward on each side is provided.
A lantern spring 13 having
The dividers 10 and 11 from the corner of the cell 12
S-bends 10a, 11a or outer frame 7 formed in
It is adapted to come into elastic pressure contact with a protrusion 7a etc. provided on the inner surface of the holder.

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 comes into sliding contact with the leaf spring portion 13a of the lantern spring 13 of the spacer 6, etc.
There are problems such as scratches on the surface of the fuel rods.

[Purpose of the invention]

In view of these points, the present invention provides a nuclear fuel assembly that reliably prevents damage to the surface of fuel rods and prevents deterioration of the quality of the nuclear fuel assembly using a relatively simple method. The purpose is to learn how to assemble the body.

[Summary of the invention]

The present invention involves inserting fuel rods from one side into a cell formed of bars etc. arranged in a lattice shape and having at least one elastic member for pressing the fuel rods, and maintaining the spacing between the fuel rods. In the method for assembling a nuclear fuel assembly, when the fuel rod is inserted into the cell, a spacer is provided so that the elastic member provided in the cell is positioned downward, and the fuel rod is supported in a horizontal state. The inserted nuclear fuel rod is pressed downward by a presser roller near the cell entrance, and a tape is placed between the inserted fuel rod and the spacer, and the tape is placed in the same direction as the insertion direction of the fuel rod. This is characterized by the fact that the fuel rods are transported in different directions, thereby preventing scratches from occurring on the surface of the fuel rods.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 4 is an explanatory view of an assembled state showing an embodiment of the method for assembling a nuclear fuel assembly according to the present invention. In assembling, first, the spacer 6 is rotated around its axis, and at least one or more cells 1 are assembled.
The plate spring portion 13a of the lantern spring 13 disposed in the cell 12 is positioned at the bottom of the cell 12. Therefore, a tape 14 made of, for example, stainless steel, synthetic material, or fiber is inserted into the cell 12 so as to cover the leaf spring portion 13a, and the fuel rod 4 inserted into the cell 12 is held by the presser roller 15. Insert the fuel rod 4 into the cell 12 by pressing it downward so that the fuel rod 4 contacts only the tape 14 and not other parts of the cell. At the same time, the tape 14
is transferred in the same direction as the insertion direction of the fuel rod 4 at substantially the same speed as the fuel rod insertion speed, and when the fuel rod 4 reaches a predetermined position, the tape 14 is completely removed from the spacer cell 12.

In other words, fuel rods generally have almost no bending due to their material and design, and when a fuel rod is supported horizontally and inserted into a spacer cell, the tip only tilts slightly downward due to its own weight. . Therefore, when the fuel rod is pressed downward near the entrance to the cell by the presser roller, the lantern spring 13 located at the lower part of the cell is pressed through the fuel rod, and the fuel rod is pushed into the cell. shall not come into contact with other protrusions. However, in such a state, the lantern spring 1
A tape 14 is placed between the leaf spring portion 13a of No. 3 and the fuel rod.
By interposing the fuel rod, direct contact between the fuel rod and the inner surface of the cell is prevented, sliding contact between the fuel rod and the inner surface of the cell is eliminated, and scratches and the like on the surface of the fuel rod are prevented.

In the above embodiment, the tape 14 is inserted into the cell prior to insertion of the fuel rod 4 to cover the leaf spring portion 13a, but the tape 14 and the fuel rod 4 are inserted into the cell 12 at the same time. It may be inserted inside.

Further, the tape 14 can be transferred by an appropriate means. For example, as shown in FIG. 5, the tape 14 is attached to the tip of the fuel rod 4, and
Alternatively, as shown in FIG. 6, a freely or manually actuated tape winding device 16 may be provided on the lower tie plate side of at least one spacer 6. Alternatively, the tape 14 may be transferred by the tape winding device 16.

〔Effect of the invention〕

As explained above, in the present invention, when a fuel rod is inserted into a cell of a spacer, most of the load is applied to the elastic member for pressing the fuel rod, such as a lantern spring of the spacer, and the inserted fuel A tape was placed between the rod and the spacer, and the tape was transferred in the same direction as the insertion direction of the fuel rod, so the inserted fuel rod did not touch any part of the cell. ,
In addition, the tape that comes into direct contact with the fuel rods is transported at approximately the same speed as the fuel rods while covering an elastic member such as a lantern spring, so that there is no sliding contact with the outer surface of the fuel rods, and the tape cells of the fuel rods are transported at approximately the same speed as the fuel rods. When inserted into the interior, scratches on the outer surface due to the lantern spring etc. are reliably prevented. Therefore, the fuel rods are assembled into the spacer intact, and deterioration in the quality of the fuel assembly can be prevented.

[Brief explanation of the drawing]

Figure 1 is a longitudinal side view of the nuclear fuel assembly, Figure 2 is an enlarged plan view of the spacer, and Figure 3 is the same as in Figure 2.
The cross-sectional side view taken along the line and FIGS. 4 to 6 are explanatory views showing the method of assembling the nuclear fuel assembly of the present invention, respectively. 4... Fuel rod, 6... Spacer, 12... Cell, 13... Lantern spring, 13a... Leaf spring portion, 14... Tape, 15... Presser roller.

Claims (1)

[Claims] 1. Fuel rods are inserted from one side into a cell formed of bars etc. arranged in a lattice pattern and each having at least one elastic member for pressing the fuel rods, so as to maintain the spacing between the fuel rods. In the method for assembling a nuclear fuel assembly according to the present invention, when the fuel rod is inserted into the cell, a spacer is arranged so that the elastic member provided in the cell is located downward;
A nuclear fuel rod supported in a horizontal state is pressed downward by a presser roller near the cell entrance, and a tape is placed between the inserted fuel rod and the spacer, and the tape is placed around the fuel rod. characterized by being transferred in the same direction as the insertion direction,
How to assemble a nuclear fuel assembly.