JPH053998Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a support grid for a fuel assembly for a nuclear reactor.

[Prior Art] A fuel assembly loaded into a nuclear reactor is formed by arranging a large number of long fuel rods, in which a large number of short cylindrical pellets are sealed, parallel to each other at regular intervals. ing. In this case, a support grid is used as a means for holding the fuel rods in this positional relationship.

As shown in FIG. 8, this support grid consists of an inner strap assembly 1 and outer straps 2 attached to the four circumferences of the inner strap assembly 1.

The inner strap assembly 1 is shown in FIGS. 8 to 10.
It consists of an inner strap indicated by numeral 3 in the figure. The inner strap 3 is made by punching out a rectangular thin plate made of heat-resistant alloy, and has a number of slits (fitting grooves) 4 at regular intervals in the direction perpendicular to its longitudinal direction, as shown in Fig. 9. As shown in FIG. 10, side tabs 5 are formed to protrude from both ends in the longitudinal direction. The slit 4 of the inner strap 3 forming the vertical member and the inner strap 3 forming the horizontal member
The inner strap assembly 1 is constructed by aligning the inner straps 3 with the slits 4 and holding the inner straps 3 in a positional relationship perpendicular to each other, and integrating the inner straps 4 vertically and horizontally by fitting the inner straps 4 into each other.

On the other hand, the outer strap 2, like the inner strap 3, is made by punching out a thin plate made of heat-resistant alloy into a rectangular shape. A large number of slots (fitting grooves) 6 as shown in FIG. 10 are formed at opposing positions. The outer strap 2 is attached to the four circumferences of the inner strap assembly 1 by fitting the slots 6 into the side tabs 5 of the inner strap 3. In this case, the side tabs 5 protrude outward from the slots 6 to provide brazing allowance. Each side tab 5 of the inner strap 3 is then bent as shown in FIG. 11 to pre-assemble the support grid.

Next, apply brazing material to each intersection point of the inner strap 3 and the part where the slot 6 of the outer strap 2 is fitted into the side tab 5 of the inner strap 3, so that these parts are as shown in FIGS. 9 and 10. to be brazed. 7 is a welded and solidified brazing filler metal. Thereafter, the side tabs 5 are ground away, this portion is finished, and further subjected to aging treatment to form the final support grid.

By inserting fuel rods between each lattice of the support lattice constructed in this way and installing this support lattice at several locations in the longitudinal direction of the fuel rods, it is possible to support a large number of fuel rods in parallel at regular intervals. A fuel assembly can be constructed.

[Problems to be solved by the invention] However, in such a conventional support grid, the slits 4 of the inner strap 3 and the slots 6 of the outer strap 2 are simply formed by punching, so that the brazing material of each strap is As shown in FIGS. 9 and 10, the adhesion area of No. 7 is limited to the cross-sectional area of each strap and a portion around which the brazing material is eluted. The thickness of each strap is 0.3
Since it is extremely thin, measuring about mm, the brazing strength alone tends to be insufficient.

In addition, since a large number of side tabs 5 are formed, there are many places that require grinding work, which takes time. There was a problem that the attachment strength decreased.

[Means for Solving the Problems] The present invention has been made to solve the above problems, and uses a rectangular plate body in which a large number of fitting grooves are formed at intervals in the width direction. It is formed by using a large number of plates, fitting the other plate into the fitting groove of one plate, incorporating each plate vertically and horizontally so as to be orthogonal to each other, forming a lattice shape, and brazing each fitting part. The supporting grid for a nuclear reactor fuel assembly is characterized in that the edge of the fitting groove of the plate is bent at a substantially right angle to the surface of the plate.

[Embodiment] Hereinafter, one embodiment of the present invention will be described with reference to Figs. 1 to 7.

In FIG. 1, what is indicated by the reference numeral 10 is
This strap assembly 10 is a strap assembly used in the fuel assembly support grid manufacturing process.
An inner strap assembly 12 consisting of inner straps 11 assembled vertically and horizontally, and this inner strap assembly 1
It consists of an outer strap 13 attached to the four circumferences of the strap.

FIG. 2 shows the inner strap 11. The inner strap 11 is punched into a rectangular shape from a thin plate made of a heat-resistant alloy, and slits 14, which are fitting grooves into which the inner strap 3 fits, are provided at regular intervals in the width direction. This slit 14 is
As shown in FIGS. 4 and 5, a thin cut is made and the longitudinal edge of the cut is bent at a substantially right angle in one direction, thereby forming a bent portion 15. The width of this slit 14 is made to be slightly larger than the thickness of the inner strap 11. Further, as shown in FIG. 2, two protruding side tabs 16 each having a length equal to the thickness of the outer strap 13 are formed at both ends of the inner strap 11 in the longitudinal direction.

With such an inner strap 11, the slit 14 of the inner strap 11 constituting the vertical member and the slit 14 of the inner strap 11 constituting the horizontal member
The inner strap assembly 12 is formed in a lattice shape by abutting the inner straps 11 against each other and holding the inner straps 11 in a positional relationship perpendicular to each other, and by fitting the slits 14 into each other and assembling them vertically and horizontally.
At this time, the bent portions 15 formed on the inner strap 11 are formed on each of the vertical and horizontal members.
They are built to face in the same direction.

FIG. 3 shows the outer strap 13. Like the inner strap 11, the outer strap 13 is punched into a predetermined shape from a thin plate made of heat-resistant alloy, and when placed facing the four circumferences of the inner strap assembly 12, it faces the side tabs 5 of the inner strap 11. A large number of slots 17 are provided as fitting grooves into which the side tabs 5 fit. This slot 17, as shown in FIG.
A thin cut is made and the longitudinal edge of the cut is bent at right angles in one direction, thereby forming the bent portion 18. The width of this slot 17 is the same as that of the inner strap 11.
It is formed slightly larger than the width of the

Then, the outer strap 13 having such a configuration
are attached to the four circumferences of the inner strap assembly 12 by being fitted into the slots 17 and the side tabs 16 of the inner strap 11. In this state, the side tabs 16 of the inner strap 11 are
It is designed not to protrude outward from the outer surface of the outer strap 13.

After the support grid is temporarily assembled as described above, brazing material is applied to the intersections of each inner strap 11 and the intersections of the inner straps 11 and outer straps 13, and the areas where the brazing material is applied are vacuumed. Brazed and the support grid is manufactured.

Here, the brazed state of the intersection of each inner strap 11 and the brazed state of the inner strap 11 and outer strap 13 are as shown in FIGS. 5 and 7. In these figures, 19
is the welded and solidified brazing material.

That is, in FIG. 5, if 11 is an inner strap configuring the horizontal member and 11a is an inner strap configuring the vertical member, the brazing material 19 is attached to the inner edge A of the bent portion 15 and the bent portion 1.
From the outer starting point of 5, the inner strap 11 of the longitudinal member
It spreads to a and solidifies. Therefore, the area to which the brazing material is attached to both inner straps 11 and 11a is considerably larger than the cross-sectional area of the inner strap 11. Additionally, along with this, the amount of brazing material deposited between the inner straps 11 and 11a has increased. With these, both inner straps 11, 11
The brazing strength between a and a is high.

On the other hand, the brazed state of the intersection between the inner strap 11 and the outer strap 13 is as shown in FIG. That is, the brazing material 19 extends from the inner edge C of the bent portion 18 toward the inner strap 11 on the inner side, and covers the end face of the side tab 16 of the inner strap 11 in a planar shape on the outer surface side. They are integrated with the inner strap 11 in between and welded and solidified.

In this case as well, as in the case where the inner straps 11 are brazed together, the brazing area and the amount of brazing material are large, so the brazing strength is high.

As described above, according to the support grid of this embodiment, the slits 14 of the inner strap 3 and the outer strap 2
Since the edges of the slots 17 are bent and each slit is brazed at this portion, the brazing strength is high, and the strength of the support grid itself is also greatly improved.

In addition, since the brazing strength increases in this way, as in the conventional method, the side tab of the inner strap protrudes outward from the slot of the outer strap to create a brazing margin, and after brazing, this protruding portion is ground. This means that the work can be omitted.

In this embodiment, when forming the slit 14 of the inner strap 11, the bent portions 15 on both edges of the slit 14 are oriented in the same direction, but one is bent to the opposite side, and the vertical and horizontal members are bent. The strength of the support grid can be further improved by incorporating both inner straps 11 and arranging the bent portions 15 in a cross shape when the fulcrums are viewed from above.

[Effects of the invention] As explained above, according to the support grid of the invention, the edges of the fitting grooves of each plate are bent approximately at right angles to the plate surface of the plate. Therefore, the adhesion area of the brazing material on each plate to be brazed to each other is:
It is considerably larger than before. Additionally, along with this, the amount of brazing filler metal deposited between each plate is increasing. As a result, the brazing strength between the plates is increased, and the strength of the support grid itself is also significantly improved. In addition, since the brazing strength is increased in this way, it is possible to omit the conventional work of protruding the plate from the fitting groove to create a brazing margin and grinding this protruding portion after brazing. There is also.

[Brief explanation of drawings]

Figures 1 to 7 show one embodiment of the present invention, in which Figure 1 is a partially omitted plan view, Figure 2 is a front view of the inner strap, and Figure 3 is a front view of the outer strap. Fig. 4 is an enlarged front view of the main part of the inner strap, Fig. 5 is a sectional view taken along the - line in Fig. 4, Fig. 6 is a front view of the main part of the outer strap, and Fig. 7 is a front view of the main part of the outer strap. It is an enlarged sectional view along the - line. 8 is a perspective view of a conventional support grid, FIGS. 9 and 10 are enlarged sectional views of the main parts thereof, and FIG. 11 is a plan view of the inner strap. 11...Inner strap (plate body), 13...Outer strap (plate body), 14...Slit (fitting groove),
17...Slot (fitting groove).

Claims (1)

[Scope of utility model registration request] A large number of rectangular plates each having a large number of fitting grooves formed at intervals in the width direction are used, and one plate is fitted into the fitting groove of the other plate so that the plates are perpendicular to each other. In a support lattice for a nuclear reactor fuel assembly formed by incorporating vertically and horizontally into a lattice-like structure and brazing each fitting part, the edges of the fitting grooves of each plate are connected to the plates of the same plate. A support grid for a fuel assembly for a nuclear reactor, characterized in that it is bent substantially at right angles to a plane.