JPH057597Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a support structure that supports a plurality of fuel elements (fuel rods) in a nuclear reactor fuel assembly.

[Prior Art] Conventionally, as this type of support structure, those shown in FIGS. 3 and 4 have been provided. this is,
A plurality of straps 1... are connected to a large number of grid spaces 2...
A support grid 3 assembled to define a support grid 3;
It is composed of a plurality of control rod guide tubes (hereinafter referred to as guide tubes) 4 that are inserted through mutually corresponding grid spaces 2 of a plurality of support gratings 3, and the guide tubes 4 are arranged in an array. Lattice space 2 other than
A fuel element (not shown) consisting of a fuel cladding tube and nuclear fuel pellets enclosed in the fuel cladding tube is inserted into and supported. Each guide tube 4 is
A control rod (not shown) for controlling the nuclear reaction is inserted inside, and is made of Zircaloy, which has a low ability to absorb neutrons. Each guide tube 4 has its upper and lower ends fixed by an upper nozzle (not shown) and a lower nozzle 5 for flowing cooling water into the space of the support structure. Since the guide tube 4 and the support grid 3 are connected to each other by joining different metals and cannot be joined by ordinary brazing, a structure as shown in FIGS. 5 and 6 is adopted. That is, inside the grid space 2, there is a guide tube 4 whose inner diameter is
The sleeve 6 is slightly larger than the outer diameter of the strap 1.
This sleeve 6
After inserting the guide tube 4 into the tube, the two tubes are expanded together at an appropriate location where they overlap to form convex portions 7 and concave portions 8 that engage with each other.

[Problems to be solved by the invention] However, in the conventional technique as described above, a large device and labor are required for the tube expansion work, and the guide tube 4 may be bent and deformed due to the tube expansion. , a process is required to correct the deformation. Furthermore, if tube expansion fails at even one of the many fixing points in one support structure, not only that guide tube 4 but also the support grid 3 already fixed to that guide tube 4 and the support grid 3 will be damaged.
There was a problem in that all the other guide tubes 4 fixed to the tube had to be replaced, and a new one had to be assembled in the end.

[Means for Solving the Problems] In order to solve the above-mentioned problems, this invention has a support grid formed by assembling a plurality of straps so as to define a large number of grid spaces, and a plurality of the above-mentioned support grids. A support structure comprising a guide tube inserted through mutually corresponding grid spaces of a support grid, in which the guide tube is covered with a suspension member that comes into contact with mutually adjacent support grids to maintain the spacing between these support grids. It is.

[Operation] Such a support structure can be assembled by passing the support grid and the spacing member through the guide tube alternately, without directly fixing the guide tube and the support grid.

[Example] Hereinafter, an example of this invention will be described with reference to FIGS. 1 and 2. Note that the same reference numerals are used for the same parts as in the conventional example described above.

A support tube 11 as shown in FIG. 2 is attached to a lattice space 2 of a support lattice 3 formed by vertically and horizontally combining straps 1 made of thin strips of nickel alloy (Conconel). This support tube 11 is formed into a tube shape from stainless steel, and rectangular window portions 12 are provided in the center of the support tube 11 at four locations in the circumferential direction and whose lengths are set equal to the width of the strap 1 at the top and bottom.
is formed, and four straps 1 are fixed to the grid space 2 by being sandwiched between the upper and lower end surfaces of the window 12. This window part 1
2 is formed so that the strap 1 does not protrude from the inner surface of the support cylinder 11 when the strap 1 is attached. A guide tube 4 is inserted through the support tube 11 , and a collar (suspension member) 13 having approximately the same diameter as the support tube 11 is attached to the guide tube 4 between the support tubes 11 of the support grids 3 that are vertically adjacent to each other. The support grids 3 are inserted and installed, thereby keeping the spacing between the support grids 3 constant. This collar 13 is manufactured from the same Zircaloy as the guide tube 4. It is not necessary to install it on all the guide tubes 4 arranged in plurality as shown in FIG. 3 or 4.
It is only necessary to perform this on appropriate ones, for example, the guide tubes 4 at the four corners.

To construct such a support structure, the lower end of the guide tube 4 is fixed to the lower nozzle 5, and the support lattice 3 and the collar 1, in which the support tube 11 is installed in the lattice space 2 in advance, are assembled.
3 and 3 are inserted into the guide tube 4 alternately. After the fuel element is inserted into the other grid space 2, the upper nozzle is attached, and the upper nozzle and the upper end of the guide tube 4 are fixed.

In such a support structure, the support grid 3
The load is not applied to the guide tube 4 as in the conventional case, but is applied mainly to the collar 13 and the support tube 11, so the mechanical strength of the guide tube 4 itself may be small, and therefore the guide tube The walls of 4 can be made thinner, reducing the absorption of neutrons and increasing the control effect of the control rods. In addition, as can be easily understood from the explanation of the construction method above, the guide tube 4
Since no processing is performed to plastically deform the material, there is no need for any equipment for that purpose, which saves time and effort, and there is no generation of defective products due to processing.

Note that the implementation of this invention is not limited to the above example, and the joint surfaces of the support tube 11 and the collar 13 may be provided with grooves or projections and depressions that fit into each other to prevent misalignment. .

Furthermore, the collar 13 may be provided with a window similar to the support tube shown in FIG. 2 to further reduce the amount of neutron absorption.Also, instead of the cylindrical collar 13, a spacing member of an appropriate shape may be provided. May be adopted.
Alternatively, a backlash absorbing mechanism may be provided between the support tube 11 and the guide tube 4 to eliminate a gap for fitting.

[Effects of the invention] As detailed above, this invention has a support lattice formed by assembling a plurality of straps to define a number of lattice spaces, and a support lattice that is inserted through the corresponding lattice spaces of the plurality of support lattices. In the support structure equipped with a guide tube, the guide tube is covered with a cylindrical member that comes into contact with mutually adjacent support grids and maintains the spacing between these support grids. When doing so, the conventional tube expansion process is no longer necessary, and the equipment and labor involved can be saved, and the excellent effects of preventing the production of defective products due to tube expansion are achieved.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway view of the main part of an embodiment of this invention, Fig. 2 is a perspective view of the main part of the same embodiment, Fig. 3 is a perspective view of a conventional example, and Fig. 4. 5 is a sectional view of the same, FIG. 5 is a sectional view of the conventional example, and FIG. 6 is a view taken along the - arrow in FIG. DESCRIPTION OF SYMBOLS 1... Strap, 2... Grid space, 3... Support grid, 4... Guide tube, 13... Collar (suspension member).

Claims (1)

[Claims for Utility Model Registration] (1) A support grid formed by assembling a plurality of straps to define a large number of grid spaces, and a guide tube inserted through the mutually corresponding grid spaces of the plurality of support grids. 1. A support structure comprising: a support structure, wherein the guide tube is sheathed with a spacing member that abuts on mutually adjacent support grids to maintain a spacing between the support grids. (2) The support structure according to claim 1, wherein the suspension member is cylindrical.