JPH0854485A - Fuel assembly - Google Patents

Abstract

PURPOSE:To keep the lower part of a channel fastener from getting caught in an obstacle, and prevent the damage to the channel fastener before it happens by forming a notch at the corner of a channel guard for the channel fastener. CONSTITUTION:A channel fastener 2 is installed in the upper corner of a channel box 1 so that inner or flat surfaces of the channel fastener 2 can touch each other. Therefore, the outer curvature radius of the box 1 is set longer than the inner curvature radius of the fastener 2. The fastener 2 consists of a pair of bent plate springs 3 and a channel guard 4 protecting it, and a circular corner notch 6a and a plane incline part 6b are provided on a guide slope 6 at the lower end of the guard 4. When an upper tie plate 5 of the box 1 is hung in a reactor by being grasped by a fuel exchanging machine, the lower end of the fastener 2 may touch structures in the reactor. Nevertheless, since there is no gap in the guide slope 6, the box 1 may be inserted smoothly into the reactor and damage to the fastener 2 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a boiling water reactor (BW).
R) and the like, and more particularly to a fuel assembly having an improved channel fastener.

[0002]

2. Description of the Related Art A fuel assembly for a boiling water reactor has a large number of fuel rods containing fuel pellets housed in a channel box, which is a case. It is configured to be possible.

By the way, in this type of fuel assembly, a set of four bodies constitutes one cell so as to sandwich a control rod having a cross-shaped cross section and is loaded into the core. It is supported while maintaining a space. As a member for maintaining the distance, as shown in FIGS. 5 and 6, a member in which a channel fastener 2 is attached to an upper corner portion of a channel box 1 is known. The channel fastener 2 is generally provided with a pair of leaf springs 3 that are bent in a V shape and a channel guard 4 that protects the lower ends of the leaf springs 3.
The distance between the channel boxes 1 is regulated by the elastic force of. An upper tie plate 5 is attached to the upper portion of the channel box 1 for moving in and out of the core using a fuel exchanger (not shown).

In the conventional fuel assembly thus constructed, the upper tie plate 5 is gripped to move it into and out of the core, but a part of the internal structure is partially suspended in the channel fastener 2 while being suspended from the core or the like. May come into contact with the bottom edge of. At this time, the lower end of the channel guard 4 comes into contact with an obstacle, and a guide slope 6 for smoothly sliding and guiding the fuel assembly is formed at the lowermost end of the guard 4, so that normally the obstacle is obstructed. The fuel assembly can be inserted into the core without being caught by an object.

[0005]

By the way, as shown in FIG. 7, in order to bring the channel box 1 and the channel guard 4 into close contact with each other at the contact surface (flat surface) S, the guide slope 6 of the channel guard 4 is fixed. The size of the corner portion R1 must be set smaller than the size of the corner portion R2 of the channel box 1. Therefore, there is a slight gap at the corner between the channel box 1 and the guide slope 6.

Therefore, in some cases, the corner portion of the guide slope 6 of the channel guard 4 may hit an obstacle and be caught. In this case, the total load of the fuel assembly is added to the channel fastener 2 and the channel fastener 2 It is assumed that there will be damage to the product.

The present invention has been made in consideration of the above circumstances, and even if the lower portion of the channel fastener comes into contact with an obstacle, it can be smoothly suspended without being caught,
An object of the present invention is to provide a fuel assembly capable of preventing damage to a channel fastener in advance.

[0008]

In order to solve the above-mentioned problems, the first aspect of the present invention is to provide a channel fastener at the upper end of a rectangular tubular channel box for accommodating a nuclear fuel rod, and to provide an outer surface of the channel box. A fuel assembly in which the radius of curvature is made larger than the radius of curvature of the inner surface of the channel fastener, and the outer surface of the channel box and the inner surface of the channel fastener contact each other at their flat portions. Is
A bent leaf spring and a channel guard for protecting the leaf spring are provided, and a notch is formed at a corner portion of the channel guard.

A second aspect of the present invention is characterized in that the notch according to the first aspect is formed in an arc shape.

According to a third aspect of the present invention, the channel guard according to the first aspect has a guide slope for guiding the assembly main body, and the notch is formed by notching the corner of the guide slope. Characterize.

[0011]

According to the first aspect of the present invention, the cutout is formed in the corner portion of the channel guard of the channel fastener so that even if the lower portion of the channel fastener comes into contact with an obstacle, the channel fastener is not caught. It is possible to prevent the fastener from being damaged.

According to the second aspect of the present invention, the notch portion according to the first aspect is formed in an arc shape, which facilitates manufacturing.

According to a third aspect of the present invention, the channel guard according to the first aspect has a guide slope for guiding the assembly main body, and the notch is formed by notching the corner of the guide slope. As a result, there is no gap at the corner between the channel box and the guide slope.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIGS. 4 and 5.

1 and 2 show a first embodiment of a fuel assembly according to the present invention. As shown in FIG. 1, fuel rods containing fuel pellets are housed in a square arrangement of 8 rows and 8 columns in a channel box 1 formed in a rectangular tube shape. Further, in the upper corner portion of the channel box 1, the inner surface of the channel fastener 2 is arranged so as to abut on the outer surface of the channel box 1 at their flat portions. Therefore, the outer surface radius of curvature of the channel box 1 is set larger than the inner surface radius of curvature of the channel fastener 2.

This channel fastener 2 has a pair of leaf springs 3 bent in a V shape, a channel guard 4 for protecting the lower ends of these leaf springs 3, and a leaf spring 3 on the upper end of the channel box 1. It is provided with a cap screw 7 for fixing. And channel box 1
An upper tie plate 5 for loading and unloading the core is attached to the upper part of the core using a fuel exchanger (not shown).

As shown in FIG. 2, a thick guide slanting surface 6 is provided at the lower end of the channel guard 4, and the guide slanting surface 6 has a corner notch 6a formed by cutting a corner in an arc shape. And a plane taper portion 6b formed in a tapered shape. In addition, as shown in FIG. 1, a channel fastener 2 is provided on the channel box 1.
At the same time, a channel spacer 8 that regulates the interval between the channel boxes 1 is provided.

Next, the operation of this embodiment will be described.

In the fuel assembly constructed as described above, the upper tie plate 5 is gripped by a fuel handling device such as a fuel exchanger, and is suspended in the reactor and loaded into the reactor core. As described above, the lower end of the channel fastener 2 may come into contact with an obstacle such as a reactor internal structure when the fuel assembly is handled, particularly when it is hung down.

However, a corner cutout 6a is formed on the guide slope 6.
By forming the above, there is no gap in the corner portion between the channel box 1 and the guide slope 6 as shown in FIG. 3, and the flat taper portion 6b is inserted first,
It is guided upward along the guide slope 6.

Therefore, according to this embodiment, the corner portion of the guide slope 6 is prevented from being caught by the obstacle, and the channel fastener 2 does not receive the full load of the fuel assembly. As a result, damage to the channel fastener 2 can be prevented and the fuel assembly can be smoothly inserted into the core. Further, since the corner cutout portion 6a is formed by cutting out in an arc shape, it is easy to manufacture. After the core is inserted, the four fuel assemblies forming one cell are held at a predetermined interval by the elastic force of the leaf spring 3 and the channel spacer 8.

FIG. 4 is an enlarged sectional view of the essential parts showing a second embodiment of the fuel assembly according to the present invention. The same parts as those in the first embodiment will be described with the same reference numerals.

In this embodiment, the corner portion of the guide slope 6 is notched in a rectangular shape to form a corner notch portion 6c.
Therefore, according to the present embodiment, the channel box 1
There is no gap at the corner between the guide slope 6 and the guide slope. The rest of the configuration and operation are the same as in the first embodiment, so a description thereof will be omitted.

[0024]

As described above, according to the first aspect of the present invention, since the notch is formed in the corner portion of the channel guard of the channel fastener, the lower portion of the channel fastener contacts the obstacle. However, it is possible to prevent the channel fastener from being damaged without being caught. As a result, the reliability of the fuel assembly can be improved.

According to the second aspect, since the notch portion according to the first aspect is formed in the arc shape, the manufacturing becomes easy.

According to a third aspect of the present invention, the channel guard according to the first aspect has a guide slope for guiding the assembly main body, and a corner portion of the guide slope is cut out to form a cutout. As a result, there is no gap at the corner between the channel box and the guide slope, and it is possible to reliably prevent damage to the channel fastener.

[Brief description of drawings]

FIG. 1 is a perspective view showing an upper portion of a first embodiment of a fuel assembly according to the present invention.

FIG. 2 is an enlarged perspective view of a main part of FIG.

FIG. 3 is an enlarged cross-sectional view of a main part of FIG.

FIG. 4 is an enlarged perspective view of essential parts showing a second embodiment of the fuel assembly according to the present invention.

FIG. 5 is a perspective view showing an upper portion of a conventional fuel assembly.

6 is an enlarged perspective view of a main part of FIG.

7 is an enlarged cross-sectional view of a main part of FIG.

[Explanation of symbols]

 1 channel box 2 channel fastener 3 leaf spring 4 channel guard 5 upper tie plate 6 guide slope 6a corner notch 6b flat taper 6c corner notch 7 cap screw 8 channel spacer

Claims (3)

[Claims] 1. A channel fastener is provided at an upper end of a rectangular tube-shaped channel box for accommodating nuclear fuel rods, and an outer surface radius of curvature of the channel box is made larger than an inner surface radius of curvature of the channel fastener. The fuel assembly is arranged so that the inner surfaces of the channel fasteners come into contact with each other at their flat portions, and the channel fasteners include bent leaf springs and a channel guard that protects the leaf springs. A fuel assembly comprising: a cutout portion formed at a corner portion of the channel guard. 2. The fuel assembly according to claim 1, wherein the cutout portion is formed in an arc shape. 3. The channel guard has a guide slope for guiding the insertion of the assembly main body, and a corner portion of the guide slope is cut out to form a cutout. The described fuel assembly.