JPH06317689A - Fuel rod spacer - Google Patents

Abstract

PURPOSE:To simplify cell assembly and form a spring in a simple way. CONSTITUTION:The center part of a rectangular plate having a single end part 6 at the lower end is punched into C-shape to form a spring 4 with a tongue-shape part 7. This spring 4 is inserted into the outer peripheral part of each cell 1 from above, and the single end part 6 is hooked to the cutout part 5 of the cell 1. Since the plate is machined to form the spring 4, the spring 4 can be formed in a simple way. Also, since the springs 4 are fitted one by one to the respective cells 1, the cells 1 can be assembled easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a fuel rod spacer,
In particular, the present invention relates to a fuel rod spacer having an improved spring for maintaining the distance between fuel rods in a fuel assembly for a boiling water reactor.

[0002]

2. Description of the Related Art In general, a fuel assembly is basically constructed as shown in FIG.
As shown in, inside the square-shaped tubular fuel channel 11,
A large number of fuel rods 12 containing nuclear fuel and water rods 13 not containing nuclear fuel are arranged in a square lattice shape, and their upper and lower ends are fixed by an upper tie plate 14 and a lower tie plate 15, respectively. The intermediate portion is arranged and supported by a plurality of fuel rod spacers 16 arranged at appropriate intervals in the axial direction.
The fuel rod spacer 16 supports the fuel rods 12 and the water rods 13 in an aligned manner, and restrains horizontal vibration of the fuel rods 12.

When designing such a fuel rod spacer 16, consideration should be given to the spacing between the fuel rods 12, the thermal expansion margin of the fuel rods 12, the ease of assembly at the time of assembling the fuel assembly, and the contact surface with the fuel rods. To maximize the thermal limit by minimizing the change in coolant flow and the resulting neutron absorption, and also to maintain sufficient mechanical strength to withstand the operating reactor conditions. .

In order to satisfy such design requirements, various fuel rod spacers have been proposed and used in the past, and a typical example thereof is, for example, JP-A-59-6.
There is one disclosed in Japanese Patent No. 5287.

As shown in FIGS. 7 and 8, the fuel rod spacer includes a substantially rectangular outer frame 17 and an outer frame 1.
It is composed of a large number of cylindrical cells 18 arrayed in 7 and an annular spring 19 supported between adjacent cells 18.

The spring 19 is shown in FIGS. 9 and 10.
As shown in FIG. 5, the cells are mounted by being sandwiched between the C-shaped notches 20 provided on the side surfaces of the two adjacent cells 18 respectively. Depending on the design, the cutout 20 may be formed in an E shape.

As shown in FIGS. 10 and 11, an arcuate protrusion 21 is formed at both upper and lower ends of the spring 19, and the center of the spring 19 has an arcuate shape for supporting the fuel rod 12. The protrusion 22 is formed. The bow-shaped protrusion 22 is provided in the fuel rod insertion path 23.
When 2 is inserted and assembled in the cell 18, it becomes a contact point with the fuel rod 12, as shown in FIG. Then, the spring 19 is displaced as shown by the solid line in FIG. 11, and by this displacement, a pressing load is applied to the fuel rod 12 via the contact point of the spring 19. Note that FIG.
In FIG. 2, the chain double-dashed line indicates the original shape of the spring 19, and this pressing load elastically restrains the vibration of the fuel rod 12 in the horizontal direction and holds the fuel rod 12 at a predetermined interval.

[0008]

The conventional fuel rod spacer 16 is mounted by being sandwiched between two adjacent cells 18, so that the assembling process is complicated and
Since one cell is installed between two cells, an even number of cells 18
Or it is necessary to add some structure in the case of an odd number of cells 18 and it is desired to partially remove the cells 18 in order to reduce the pressure loss, the degree of freedom of the position of the cells 18 to be removed There is a problem that there are few. Also, spring 1
No. 9 is required to have high accuracy in terms of function, but it is very difficult to mold it when processing a ring.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a fuel rod spacer which is easy to assemble cells, has a high degree of freedom in cell arrangement, and is excellent in spring formability. To aim.

[0010]

As a means for achieving the above-mentioned object, the present invention has a plurality of fuel rods arranged in a lattice, and a plurality of fuel rods are arranged in the axial direction to form a substantially rectangular shape. In a fuel rod spacer having an outer frame, a plurality of cylindrical cells arranged in the outer frame, and a spring that holds a space between fuel rods inserted in each cell, the spring is a plate member. It consists of a processed plate spring,
This plate-shaped spring is arranged in each of the cells. Further, in the present invention, it is preferable that the plate spring is mounted and fixed to the notch provided in each cell.

[0011]

In the fuel rod spacer according to the present invention, the spring is composed of a plate-shaped spring formed by processing a plate material. For this reason, it is possible to easily form the spring and easily obtain a highly accurate spring. Further, since the plate-shaped spring is arranged in each cell, it is easy to assemble, and cells at any position can be partially removed, and the degree of freedom in cell arrangement is great. Further, in the present invention, by mounting and fixing the plate-shaped spring in the notch provided in each cell, the mounting of the plate-shaped spring in the cell becomes easier.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. It should be noted that the present invention is characterized only in the cells and springs of the fuel rod spacer, and the other portions have the same configuration as the conventional fuel rod spacer 16,
Only this characteristic part will be described below.

1 to 3, reference numeral 1 is a cylindrical cell, and a fuel rod insertion passage 3 for inserting a fuel rod 2 is formed in the cell 1 and a spring 4 is provided. A notch 5 for mounting and fixing is provided.

The spring 4 is shown in FIGS. 4 (a) and 4 (b).
As shown in, using a rectangular plate-like material such as nickel alloy having appropriate strength, corrosion resistance and elasticity,
One end portion 6 is formed at one end thereof, the inside is punched out into a C shape, and the tongue portion 7 is bent and formed inside thereof, and this spring 4 is formed.
As shown in FIG. 3, the tongue-shaped portion 7 is positioned inside the fuel rod insertion passage 3, and the outer frame portion 8 is positioned outside the cell 1 so that the tongue-shaped portion 7 is inserted and mounted in the cell 1. At this time, the one end 6 is fitted and locked in the notch 5 of the cell 1, so that the spring 4 is mounted and fixed to the cell 1.

The portion of the cell 1 corresponding to the outer frame portion 8 is bent toward the inner diameter side as shown in FIG.
A portion of the cell 1 corresponding to the tongue portion 7 is bent and formed on the outer diameter side to stabilize the mounting position of the spring 4 on the cell 1 and to prevent the spring 4 from adjoining the cell 1. Prevents contact. Then, since the spring 4 is attached and fixed to the notch 5 of each cell 1,
Assembling becomes easier than fixing by welding.

[0016]

As described above, according to the present invention, since the spring is a plate-shaped spring formed by processing a plate material, the spring can be easily manufactured and a highly accurate spring can be easily obtained. Further, since the plate spring is arranged in each cell, it is easy to assemble, and cells at any position can be partially removed, and a large degree of freedom in cell arrangement can be obtained.

In the present invention, the plate spring is attached and fixed to the notch provided in each cell,
It becomes easier to attach the plate spring to the cell as compared with fixing by welding or the like.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing a fuel rod spacer according to an embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a configuration diagram of a mounted state of a spring viewed from the outside of a cell.

FIG. 4A is a front view of a spring, and FIG. 4B is a central longitudinal sectional view thereof.

5 is an enlarged view of a main part of FIG.

FIG. 6 is a partially cutaway perspective view showing the structure of a fuel assembly.

FIG. 7 is a plan view showing the structure of a conventional fuel rod spacer.

8 is a front view showing a cutaway portion of the fuel rod spacer of FIG. 7. FIG.

FIG. 9 is a perspective view showing the structure of a cell.

FIG. 10 is a cross-sectional view showing a mounted state of a spring.

11 is an enlarged view of a main part of FIG.

[Explanation of symbols]

 1 Cell 2 Fuel Rod 3 Fuel Rod Insertion Path 4 Spring 5 Notch 6 One End 7 Tongue 8 Outer Frame

Claims (2)

[Claims] 1. An outer frame having a substantially rectangular shape and a plurality of fuel rods arranged in a lattice shape in the axial direction of a fuel assembly, and a cylindrical outer frame arranged in the outer frame. In a fuel rod spacer having a plurality of cells and a spring that holds a distance between fuel rods inserted in each cell, the spring is constituted by a plate-shaped spring obtained by processing a plate material, and the plate-shaped spring is A fuel rod spacer characterized by being arranged in each cell. 2. The fuel rod spacer according to claim 1, wherein the plate spring is attached and fixed to a notch provided in each cell.