JPS63148195A - Nuclear fuel aggregate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application) The present invention relates to a nuclear fuel assembly disposed within the core of a fast breeder reactor.

(Prior Art) Generally, a large number of nuclear fuel assemblies filled with fissile material are arranged in the core of a nuclear reactor, and the fissile material in the nuclear fuel assemblies contains 3! ! Energy is extracted by causing a chain nuclear fission reaction.

Figure 3 shows the main parts of a conventional nuclear fuel assembly placed in the core of a fast breeder reactor.Inside the trumpet tube 1, which is formed into a hexagonal cylindrical shape by Sudenres et al., there are many fuel cladding tubes. A large number of fuel rods 2 filled with fuel pellets, etc., are regularly arranged, and a spiral wire 3 is wound around the fuel rods 2 at a pitch of, for example, about 20 Cl to 30 Cl.

(Problems to be Solved by the Invention) However, in the conventional nuclear fuel assembly described above, due to the fluid pressure, temperature, neutron irradiation, etc. of the high-temperature coolant circulated within the core, for example, As shown in Figure 4, a bulging deformation occurs in which the trumpet tube swells outward, causing stress to be applied to adjacent nuclear fuel assemblies and making it difficult to pull out the nuclear fuel assembly, resulting in replacement of the nuclear fuel assembly. There is a problem that the virility of the fast breeder reactor is impaired, such as making it impossible.

The present invention has been made in response to such conventional circumstances, and provides a nuclear fuel assembly that can significantly reduce the amount of bulging deformation compared to the conventional one and maintain the integrity of a fast breeder reactor. This is what I am trying to do.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention provides a nuclear fuel assembly in which a large number of fuel rods each having a spiral wire wound therein are regularly arranged in a cylindrical wrapper tube. The present invention is characterized in that a plurality of reinforcing members connecting the inner walls of the wrapper tubes are arranged at positions in the wrapper tube near the center plane of the reactor core that do not contact the spiral wires.

(Function) In the nuclear fuel fI assembly of the present invention, a plurality of reinforcing members that connect the inner walls of the trumpet tube are arranged at positions that do not come into contact with the spiral wire inside the trumpet tube.

This reinforcing member can suppress bulging deformation of the trumpet tube, and can significantly reduce the amount of bulging deformation compared to the conventional method.

(Example) Examples of the nuclear fuel assembly of the present invention will be described below with reference to the drawings.

FIG. 1 shows the main parts of a nuclear fuel assembly according to an embodiment of the present invention. In the nuclear fuel fI assembly of this embodiment, a trumpet tube 11 formed in a hexagonal cylindrical shape of stainless steel or the like includes:
A large number of fuel rods 12 each having a fuel cladding tube filled with a large number of fuel pellets etc. are regularly arranged at intervals of, for example, about 1.4nra, and around the fuel rods 12,
For example, the spiral wire 13 is wound at a pitch of about 20 Cl to 30 Cl.

In addition, when the nuclear fuel assembly is placed in the reactor core, inside the trumpet tube 11 located near the axial center of the reactor core,
Along the arrangement of the fuel rods 12, a plurality of reinforcing members 14 that connect the inner wall of the wrapper tube are arranged in a distributed manner in the axial direction at positions that do not come into contact with the spiral wire 13.

The reinforcing member 14 is formed into a plate shape from the same material as the wrapper tube 11 or the fuel cladding tube, such as stainless steel, and its thickness is equal to or less than the distance between the fuel rods 12.
For example, it is about 111r8, and the vertical length is 176 or less of the winding pitch of the spiral wire 13, for example, about several centimeters.

As shown in FIGS. 2(a), 2(b), and 2(c), the reinforcing member 14 is placed in a position where it does not come into contact with the spiral wire 13, and extends parallel to the row formed by the cross section of the spiral wire 13. Distributed at two or more locations in the axial direction of the tube 11, at least one or more pieces are arranged on the side wall of each trumpet tube 11, that is, three or more pieces per nuclear fuel assembly, and approximately near the center of each side of the trumpet tube 11. It is fixed by welding etc.

That is, in the nuclear fuel assembly of this embodiment having the above configuration,
A reinforcing member 14 that connects the side walls is arranged inside the side walls forming each side of the hexagonal cylindrical trumpet tube 11. In addition, in general, the amount of deformation due to bulging deformation is
It is approximately proportional to the fourth power of the length of a piece of the side wall of the trumpet tube 11.

Therefore, the reinforcing member 1 is placed approximately in the center of the trumpet tube 11.
In the nuclear fuel assembly of this embodiment in which the reinforcing member 14 is fixed, the amount of bulging deformation in the fixed portion of the reinforcing member 14 is as follows:
Similar to the case where the length of a piece of the side wall of the trumpet tube 11 is reduced by approximately 1/2, the length can be reduced to about 1/16 compared to a conventional nuclear fuel assembly in which the reinforcing member 14 is not arranged6. In the above-described embodiment, the reinforcing member 14 is formed into a plate shape, but the present invention is not limited to such an embodiment. It may be composed of Further, the number and arrangement thereof may be arbitrary as long as at least one or more of them are arranged on each side wall, that is, three or more of them are arranged per nuclear fuel assembly.

[Effects of the Invention] As described above, in the nuclear fuel assembly of the present invention, the amount of bulging deformation can be significantly reduced compared to the conventional one, and the integrity of the fast breeder reactor can be maintained.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing essential parts of a nuclear fuel assembly according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the nuclear fuel assembly shown in FIG. 1, and FIG. 3 is a conventional nuclear fuel assembly. FIG. 4 is a partially cutaway perspective view showing the main parts of the body, and FIG. 4 is a cross-sectional view showing an example of bulging deformation of the nuclear fuel assembly shown in FIG. 3. 11...Trumpet tube 12...Fuel rod 13...Spiral wire 14...
...Reinforcement member applicant Japan Atomic Vehicle Industry Co., Ltd. Applicant Toshiba Corporation Agent Patent attorney Sa Suyama - Figure 1 (1) + (C) Figure 2 Figure 3

Claims (2)

[Claims] (1) In a nuclear fuel assembly in which a large number of fuel rods each having a spiral wire wound around a cylindrical trumpet tube are regularly arranged, a position in the trumpet tube near the center of the core that does not come into contact with the spiral wire. A nuclear fuel assembly characterized in that a plurality of reinforcing members are arranged to connect the inner walls of the wrapper tubes. (2) The nuclear fuel assembly according to claim 1, wherein the reinforcing member is composed of a plate-like member whose length in the vertical direction is 1/6 or less of the winding pitch of the spiral wire.