JPH0511873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention relates to a support grid for a nuclear reactor fuel assembly that supports a plurality of fuel rods.

``Prior Art'' Hitherto, the support grids shown in FIGS. 6 to 8 have been known as support grids for this type of nuclear reactor assembly.

In FIG. 6, reference numeral 1 indicates a fuel assembly.
The fuel assembly 1 includes an upper nozzle 2 and a lower nozzle 3 that are horizontally separated from each other, a support grid 4 disposed between these, and a sleeve (to be described later) of the support grid 4 to connect the upper nozzle 2 and the lower nozzle 3. The control rod guide tube 5 connects the fuel rods 6 to the support lattice 4, and the fuel rods 6 are disposed through the lattice spaces of the support lattice 4, which will be described later.

The support grid 4 is constructed by using a strap 8 in which slits 7 are formed at regular intervals in a direction perpendicular to the longitudinal direction of a rectangular thin plate as shown in FIG. As shown in FIG. 8, a large number of lattice spaces 9 are formed. A cylindrical sleeve 10 is installed in the grid space 9 with a certain interval and its axis coincides with the grid space 9.

The support grid 4 having the above structure has a sleeve 10
Insert the control rod guide tube 5 into the control rod guide tube 5.
is fixed to the sleeve 10 to constitute the framework of the fuel assembly 1. Further, the fuel rods 6 are inserted into the lattice space 9, and the fuel rods 6 are supported so as to be parallel to each other at regular intervals.

"Problems to be Solved by the Invention" By the way, the conventional support grid 4 had a drawback in that, when forming a fuel assembly, the outside strength of the part where the sleeve 10 was attached was weaker than the inside strength.

That is, on the inside of the part where the sleeve 10 is attached, the control rod guide tube 5 is arranged through the sleeve 10, and the control rod guide tube becomes a reinforcing member, so the strength is increased, and on the outside, the control rod guide tube is installed. Since there is no inner layer, the strength is relatively weak compared to the inner side.

In order to compensate for the strength of the outside of the part where the sleeve 10 is attached, it is possible to increase the thickness of the strap 8, but this increases the amount of neutron absorbing material, which is undesirable from the economic point of view of reactor operation. .

The present invention provides a sleeve 10 in the support grid 4.
The problem is how to improve the weak strength of the outer part of the strap 8 by suppressing an increase in the thickness of the entire strap 8.

``Means for Solving the Problems'' This invention provides that, in a support grid of a nuclear reactor fuel assembly, the thickness of the straps on the outside is greater than the thickness of the straps located on the outermost side of the sleeve to be installed as a reference. It is made thicker.

Embodiment FIGS. 1 to 5 are diagrams showing an embodiment of the present invention. In FIG. 1, the same elements as those in FIG. 8 are given the same reference numerals, and their explanations will be omitted.

The support grid 11 shown in FIG. 1 differs from the support grid 4 shown in FIG. 8 in that the thickness of the straps is different on the inside and outside of the support grid. That is, the support grid 11 includes an inner part 12 based on the outermost strap of the sleeve 10 attached to the support grid 11, and an outer part 13 having a thicker strap than the inner part 12. This is what happens.

The inner part 12 is formed by using vertical straps 14 and horizontal straps 15, and as shown in FIG. It is. Vertical strap 14 and horizontal strap 15
A plate-shaped joint portion 16 extending in the longitudinal direction is formed at both ends in the longitudinal direction.

As shown in FIG. 3, the outer part 13 is formed by using vertical straps 17 and horizontal straps 18, and forming a lattice shape by assembling the vertical straps 17 and horizontal straps 18 vertically and horizontally, respectively, in the same manner as in the conventional example. It is something. Furthermore, an opening 19 is formed inside the outer portion 13 . A short strap 20 having a short length of the vertical strap 17 and the horizontal strap 18 is formed with a plate-shaped joint portion 21 extending in the longitudinal direction.

The inner part 12 and the outer part 13 are connected to the strap of the inner part 12 and the outer part 1, as shown in FIGS.
The joint portion 16 and the joint portion 21 are combined with each other so that their centers in the thickness direction coincide with those of the strap No. 3, and the joint portion 16 and the joint portion 21 are connected by brazing or the like.

The first part that combines the joint part 16 and the joint part 21
As shown in FIG. 4, the joint part 16 is inserted between the side surface of the joint part 21 and the slit 7 of the strap of the outer part 13, and the joint part 16 is inserted along the outer surface of the strap of the outer part 13. Bending, joint part 2
1 along the inner surface of the strap of the outer part 13. The second method is to insert the joint part 16 between the side surface of the joint part 21 and the slit 7 of the strap of the outer part 13, as shown in FIG.

According to the support grid 11 having the above structure, since the thickness of the straps of the outer part 13 is made thicker than that of the inner part 12, when the support grid 11 is assembled into the fuel assembly 1, The weakened outer portion 13 can be reinforced, and the overall strength of the support grid 11 can be made sufficient without increasing the thickness of the entire strap. Therefore, it is possible to minimize the increase in the thickness of the strap for reinforcing the outer part 13.
An increase in the price of the support grid 11 can be minimized.

"Effects of the Invention" According to the present invention, in the support grid of a nuclear reactor fuel assembly, the thickness of the outer strap is thicker than that of the inner strap, based on the strap located at the outermost part of the sleeve to be attached. When the support grid is assembled into a fuel assembly, it is possible to reinforce the outer straps, which have relatively weaker strength than the inner side of the support grid, without increasing the overall thickness of the support grid. can have sufficient overall strength. Therefore, it is possible to minimize the increase in the thickness of the strap for reinforcing the outer strap.
The increase in the price of the support grid can be minimized.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a support grid shown as an embodiment of the present invention, FIG. 2 is a perspective view showing the inside part of the support grid, FIG. 3 is a perspective view showing the outside part of the support grid, and FIG. Figures 4 and 5 are explanatory diagrams showing how to combine the joints of the support grid, Figure 6 is a front view showing the fuel assembly, Figure 7 is a front view showing the straps forming the support grid, and Figure 8 The figure is a plan view showing a conventional support grid. 1... Fuel assembly, 4, 11... Support grid, 7
...slit, 8...strap, 9...lattice space, 10...sleeve.

Claims (1)

[Claims] 1 Using a large number of straps formed by forming slits by making a large number of cuts at regular intervals in a direction perpendicular to the longitudinal direction of a rectangular thin plate,
The above-mentioned slits of these straps are fitted into each other and assembled vertically and horizontally to form a large number of lattice spaces,
In the support grid of a reactor fuel assembly in which a cylindrical sleeve is mounted with its axis aligned with one of these grid spaces, the strap located at the outermost part of the sleeve to be mounted is used as a reference, and A support grid for a nuclear reactor fuel assembly characterized by having thicker straps.