JPH05150070A - Upper nozzle of fuel assembly - Google Patents

Abstract

(57) [Abstract] [Purpose] In the upper nozzle of the fuel assembly, the leaf leg retaining pin used for mounting the preload leaf spring, its pin hole, and the welding work of the pin are eliminated, and the upper nozzle is processed. , And leaf spring mounting,
Also, improve the appearance of the upper nozzle. [Structure] The opposite side of the convex portion (6) of the leaf leg (3) fitted into the slit groove (4) of the upper nozzle (1) can be inserted into the slit groove (4) together with the convex portion (6). To form the narrow width portion (7) and to allow the movement of the convex portion (6) below the slit groove (4), and the leaf leg (3) at the time of mounting. ), The upper counterbore part (9) provided outside the sliding range of the above and capable of accommodating the convex part (6).
And the slit grooves (4) are formed with the required depths left.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an upper nozzle of a fuel assembly used in a pressurized water reactor, and more particularly to a mounting structure of the upper nozzle and a leaf spring provided above the upper nozzle.

[0002]

2. Description of the Related Art A fuel assembly used in a pressurized water reactor has a large number of fuel rods (12) arranged in parallel as shown in FIG.
In addition, it is composed of a fuel support part mixed with a control rod guide tube (13) and the like and supported by a plurality of support grids (14), an upper nozzle (15) and a lower nozzle (16) for fixing the fuel support part. The upper nozzle (15) is provided with a leaf spring that abuts the upper core plate and applies a downward reaction force to the fuel assembly in order to prevent the fuel assembly from being lifted up by the flow force of the cooling water during the reactor operation. (17) are attached to the four sides of the nozzle.

As shown in FIG. 5, the base of the leaf spring (17) is fixed to the corner of the upper nozzle (15) by a bolt (5) with its tip projecting obliquely upward, and the tip is also fixed. A leaf leg (18) is hung from the above to fit into a slit groove (19) provided on the upper surface of the upper nozzle. The leaf leg (18) slides up and down in the slit groove (19) according to the bending of the leaf spring (17) to guide the spring (17), and as shown in FIG. The protrusions (6) protruding from the lower ends of the legs prevent the leaf springs from coming off from the slit grooves (19) and prevent the leaf spring from coming off from the upper nozzle when it breaks near the base.

The structure for mounting the leaf spring and the upper nozzle having such a structure is as shown in FIG. 5, and the end of the slit groove (19) has a round hole (20) wider than the groove (19). Insert the convex part (6) of the leaf leg,
After lowering the convex portion (6) to a position where it does not interfere, the leaf leg (18) is moved into the slit groove (19), and the base portion of the spring (17) is fixed with the bolt (5). And
In order to prevent the leaf leg (18) from coming out of the round hole (20) again, the pin (21) is attached to the round hole (2) as shown in the drawing.
Inserted from the side of 0) and welded. That is, in the leaf leg (18), the projection (6) at the lower end of the leaf leg (18) has a slit groove (1).
By hitting 9), the upward disengagement is prevented.

The groove width of the slit groove (19) is
If the width of the leaf leg (18) excluding the convex portion (6) is 8 mm, it is about the same as the leg width plus a small gap of 0.1 mm. Therefore, as described above, the leaf spring (1
Even if breakage occurs in 7), the slit groove (19) does not allow the leaf leg (18) to rotate, and holds the bent leaf spring (17) without rotating it.

[0006]

However, in the above-described conventional leaf spring mounting structure, welding work is required in addition to the processing of the pin and the processing of the pin hole, which is troublesome in the manufacturing process and the mounting work. There was a problem that it took time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation and has an object of facilitating the processing and assembly of components by finding a new structure in the slit groove of the upper nozzle and a part of the leaf leg. Is.

[0008]

That is, the feature of the upper nozzle of the fuel assembly of the present invention which meets the above-mentioned object is that the leaf leg of the leaf spring provided on the upper part is slidably and non-rotatably fitted. A fuel assembly upper nozzle in which a slit groove having a width is provided along the spring, and at the lower end portion of the leaf leg is provided a convex portion that protrudes to one side in the width direction of the slit groove and engages with the groove to prevent slipping out. At
First, the non-convex portion side of the leaf leg is deleted from the lower end to a required height so as to be inserted into the slit groove to form a narrow width portion, and the groove portion is formed in the lower portion of the slit groove. Is left deeper than the height of the leaf leg narrow portion excluding the convex portion by a required amount to form a lower counterbore portion that allows movement of the convex portion, and the groove is removed from the groove except the convex portion. This is because the upper counterbore part that can accommodate the convex part is formed outside the sliding range of the leaf leg when the leaf spring is attached, while leaving the shallow part by a required amount less than the height of the narrow part.

[0009]

The method of attaching the upper nozzle and the leaf spring of the present invention having the above-described structure will be described. First, the narrow width portion of the leaf leg is inserted into the slit groove together with the convex portion above the upper counterbore portion. When the leaf leg is moved to the upper counterbore portion side at the time when the narrow width portion is completely inserted, the convex portion is accommodated in the upper counterbore portion, whereby the leaf leg is positioned at the regular position in the slit groove width direction. Move to. Further, in this state, the leaf leg is lowered, and then the convex portion is horizontally moved in parallel with the slit groove to be sent from the upper counterbore portion to the lower counterbore portion, and the leaf spring is fixed by a conventional method. ..

That is, according to the leaf spring fixing structure of the present invention, even when the leaf spring is broken near the base in the reactor, the upper core plate of the reactor restricts the upward movement of the spring. Therefore, there is no fear that the leaf leg will come off due to the reverse process to the above, and the rotation of the leaf leg can be prevented by the same fitting of the leaf leg and the slit groove as in the conventional case.

[0011]

Embodiments of the fuel assembly upper nozzle of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a perspective view showing an upper nozzle of the embodiment of the present invention, and FIG. 3 is a perspective view showing a leaf spring of the embodiment.
Is a top nozzle, (2) is a leaf spring, (3) is a leaf leg, and (4) is a slit groove. The leaf spring (2) has a bolt (5) at its base and a corner of the upper nozzle (1). The tip is fixed to the portion by projecting it obliquely upward. The leaf spring (2) has a leaf leg (3) hanging from the tip thereof, and the leaf leg (3) is provided on the upper surface of the upper nozzle (1) in parallel with the leaf spring so as to have a constant width. It is fitted in the groove (4).

The leaf leg (3) is, as shown in FIG.
Both ends (3a) thereof are formed parallel to the longitudinal direction of the slit groove (4), and the width (L) thereof is the slit groove (4).
It is set to leave a minute gap of about 0.1 mm with respect to the groove width. That is, with this structure, the leaf leg (3) is slidably and non-rotatably fitted in the slit groove (4).

Further, at the lower end of the leaf leg (3),
As shown in FIG. 4, a protrusion (6) for preventing slipping out is provided which protrudes to one side in the width direction of the slit groove (4), and the opposite side of the protrusion (6) has a required height from the lower end. (A +
The slit groove (4) is provided with a narrow width portion (7) having a width that can be inserted together with the above-mentioned convex portion (6) by cutting out over b). The cut width (n) for forming the narrow width portion (7) is equal to or larger than the width (m) of the convex portion (6).

On the other hand, in the lower part of the slit groove (4) of the upper nozzle (1), as shown in FIGS. 1 (A) and 1 (B),
The groove (4) is left approximately 5 mm deeper than the height (b) of the leaf leg narrow portion (7) excluding the convex portion height (a) over the groove length of the slit groove (4), and the leaf is removed. Leg protrusion (6)
A lower counterbore (8) is formed to allow vertical and horizontal movement along the slit groove (4). This lower counterbore (8) is a leaf leg (3) including the protrusion (6) shown in FIG.
Is wider than the width (m + L) by about 1 mm and has a constant width.

In the slit groove (4), as shown in FIG.
As shown in (B), the groove (4) is left about 1 mm shallower than the height (b) of the leaf leg narrow portion (7) excluding the protrusion height (a), and the leaf leg protrusion (6) is left. An upper counterbore part (9) capable of accommodating the spring is formed at the base side of the leaf spring (2) at the time of mounting, that is, outside the sliding range of the leaf leg (3) at the time of mounting the spring (2). There is. The upper counterbore (9) is formed in a semicircular shape as shown in this embodiment, but is not limited to this.

Next, a method of attaching the leaf spring to the upper nozzle of the embodiment of the present invention having the above-mentioned structure will be described. First, as shown in FIG. 1 (A), the leaf leg narrow portion (7) of the leaf spring (2) together with the convex portion (6) are
Inserted in the slit groove (4) above the upper counterbore (9). When the leaf leg (3) is moved toward the upper counterbore (9) side as shown by an arrow at the time when the narrow portion (7) is completely inserted, the convex portion (9) is moved to the upper counterbore (9). By accommodating 6), the leaf leg (3) moves to a regular position in the slit groove width direction.

Then, in this state, the leaf leg (3) is further lowered, and then the upper convex portion (6) is moved horizontally in parallel with the slit groove (4) to lower the upper counterbore portion (9). Feed to the spot facing (8), leaf spring (2)
Is attached to the upper nozzle (1) by fixing its base with bolts (5) as shown in FIG.

That is, in the leaf spring fixing structure of the present invention, the leaf spring (2) is installed in the reactor.
Even if is broken near the base part, the upper core plate (not shown) provided in the reactor restricts the upward movement of the spring (2), so that the leaf leg (3) is processed by the reverse process to the above. There is no danger of slipping out, and the leaf legs (3)
1B, the leaf leg (3) and the slit groove (4) are fitted together (10), or the protrusion (6) and the lower counterbore (8) are fitted together. Can be prevented by.

[0019]

As described above, in the fuel assembly upper nozzle of the present invention, the leaf leg of the leaf spring provided on the upper portion is slidably and non-rotatably fitted in the slit groove of a constant width provided in the nozzle. In the upper nozzle which is fitted and is prevented from coming off of the leaf leg by the convex portion provided at the lower end portion thereof, the non-convex portion side of the leaf leg is deleted so that it can be inserted into the slit groove together with the convex portion. To form a narrow part,
Also, a lower counterbore part that allows the movement of the leaf leg protrusion is provided in the lower part of the slit groove, and an upper counterbore part that is provided outside the sliding range of the leaf leg at the time of mounting and can accommodate the leaf leg protrusion. The slit grooves are formed with the required depths left, respectively.Compared to the conventional upper nozzle, the processing of the pin hole for inserting the pin for retaining the leaf leg and the processing of the pin, and the welding of the pin are further performed. By eliminating the processing, the processing of the upper nozzle and the installation work of the leaf spring are simplified, the appearance of the upper nozzle is improved, and even if the spring is damaged, its rotation is prevented as in the past. It plays.

[Brief description of drawings]

FIG. 1A is a plan view showing a slit groove of an upper nozzle of an embodiment of the present invention. (B) It is the XX sectional view taken on the line of FIG. 1 (A).

FIG. 2 is a perspective view showing an upper nozzle of an embodiment of the present invention.

FIG. 3 is a perspective view showing a leaf spring of the same embodiment.

FIG. 4 is an enlarged perspective view showing a leaf leg of the embodiment.

FIG. 5 is a perspective view showing a conventional upper nozzle.

FIG. 6 is a perspective view showing a conventional leaf spring.

FIG. 7 is a schematic diagram showing a PWR fuel assembly.

[Explanation of symbols]

 (1) Upper nozzle (2) Leaf spring (3) Leaf leg (4) Slit groove (5) Bolt (6) Convex part (7) Narrow part (8) Lower counterbore part (9) Upper counterbore part ( 10) Mating part

Claims (1)

[Claims] 1. A leaf spring is provided on an upper portion of the leaf spring, and a slit groove having a constant width is slidably and non-rotatably fitted into a leaf leg of the leaf spring. In the lower end portion of the leaf leg, in the fuel assembly upper nozzle provided with a convex portion that protrudes to one side in the width direction of the slit groove and engages with the groove to prevent coming off, the non-convex portion side of the leaf leg, From the lower end to the required height, a narrow portion is formed by deleting it so that it can be inserted into the slit groove, while on the other hand, at the bottom of the slit groove, the groove of the leaf leg narrow portion excluding the convex portion is formed. A lower counterbore that allows the protrusion to move is formed by leaving the groove deeper than the height by a required amount, and the groove is left in the slit groove by a required amount less than the height of the narrow portion excluding the convex portion. Upper counterbore part that can accommodate the part, An upper nozzle of a fuel assembly characterized in that it is formed outside the sliding range of the leaf leg when the leaf spring is attached.