JPH01112191A - Fuel assembly - Google Patents

Abstract

PURPOSE:To enable the insertion of control rods without interference with fuel bundles by housing the four fuel bundles into one channel box and providing passages for insertion of the control rods between the fuel bundles. CONSTITUTION:This fuel assembly is constituted by installing 4 pieces of the fuel bundles into the 4 sub-channels 5 of the channel box 1. The passages 4 for insertion of the control rods are formed of 4 sheets of chevron partition plates 3 between the fuel bundles of this fuel assembly and, therefore, the control rods are inserted into the passages without interfering with the fuel bundles at all when the control rods are inserted therein from above. Water discarding holes 8 which are coarsened toward the lower part in the axial direction are provided on the side faces of a square cylindrical box 2 corresponding to the control rod passages 4 of the channel box 1; therefore, the control rods falling at the time of scram are controlled by a water pressure so that said rods can be stopped in home positions.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel assembly used in a nuclear reactor, and in particular, to a fuel assembly used in a boiling water light water reactor in which control rods are inserted from the top. Regarding fuel assembly #massage☆.

(Prior Art) The fuel assembly of a conventional boiling water light water reactor (hereinafter referred to as BWR) is as shown in Fig. The fuel rods 15 housed in the cladding tube are arranged regularly, the lower ends of these fuel rods are supported by the upper tie plate 16 and the lower tie plate 18, and the fuel rods are arranged at appropriate intervals between the two lower cylinder tie plates. The fuel rods are supported by a plurality of provided fuel rod spacers 17 to maintain a constant spacing between the fuel rods. (Hereinafter, the above structure inside the channel box will be referred to as a fuel bundle.) In addition, in the second part of the fuel assembly, the four fuel assemblies that make up the core lattice are properly spaced, and the control rods are A channel fastener 19 and a channel spacer 20 are installed to form an insertion passage.

By the way, in conventional BWRs, control rods are inserted from the bottom of the core by a control rod drive mechanism located at the bottom of the core, but recently,
In order to further improve reliability during scram, a method of inserting control rods from the top of the core is being considered.

(Problem to be solved by the invention) However, the conventional BWR is
Considering the case where the fuel assembly (Fig. 4) is loaded, since the channel fastener 19 and the channel spacer 20 are located in the control rod insertion passage as shown in Fig. 5, the control rod 21 (broken line If the control rod 21 is inserted from the top (shown by ), a problem arises in that the control rod 21 interferes with the fuel assembly.

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide a fuel assembly in which the control rods do not interfere with the fuel when the control rods are inserted from the top, that is, are suitable for the top insertion type BWR.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a fuel assembly in which the fuel bundles are accommodated in a channel box.
This fuel assembly is housed in two channel boxes, and is characterized by having a cross-shaped control rod guide between the fuel bundles.

(Function) In a fuel assembly configured in this way, when a control rod is inserted from the top, the control rod is guided by a cross-shaped control rod guide, and can be inserted reliably without interfering with the fuel. Become.

(Example) The present invention will be described in detail below with reference to the drawings.

Fig. 1 is a diagram showing an example of a channel box that is a component of a fuel assembly, Figure 2 is a diagram showing an example of a fuel bundle that is a component of a fuel assembly, and Figure 3 is a diagram showing an example of a fuel bundle that is a component of a fuel assembly. FIG. 3 is a view of one embodiment of the body;

In the channel box 1, four dogleg-shaped partition plates 3 are installed in the center of a rectangular cylindrical box 2 to form a cross-shaped control rod insertion passage 4, and four fuel bundles (described later) are installed in the channel box 1. Four square prism spaces 5 (hereinafter referred to as subchannels) are formed in which the channels are installed. At the bottom of the rectangular cylindrical box 2, there is a pedestal 6 on which four fuel bundles (described later) can be installed, and a lower nozzle 7 having a downwardly convex shape for installing fuel assemblies in the reactor core. Formed by being integrally connected. Note that the shape of the lower nozzle 7 is determined by the core lower structure, so it is not limited to the downwardly convex shape shown in FIG. 1.

Further, a plurality of water waste removal holes 8 are formed on the side surface of the rectangular cylindrical box 2 corresponding to the control rod insertion passage 4 at intervals that become coarser toward the bottom in the axial direction. Furthermore, a window 9 (opening) for handling the channel box 1 is formed on the upper side surface of the rectangular cylindrical box 2.

As shown in FIG. 2, the fuel bundle consists of regularly arranged fuel rods 10 containing uranium oxide in a sealed cladding tube made of zirconium alloy material, and the upper and lower ends of these fuel rods 10 are connected to an upper tie plate 11 and a lower tie plate lattice. 12
The fuel rod spacers 13 are supported by the upper tie plate 11 and the lower tie plate lattice portion 12 and are configured to contact the tapered portions 6a of a plurality of fuel rod spacers 13 arranged at appropriate intervals.

The fuel assembly of this embodiment has four subchannels 5 of the channel box 1 shown in FIG.
It is constructed by installing four fuel bundles shown in the figure.

FIG. 3 shows an upward arrow view of the fuel assembly of this example.
As shown in FIG. 3, in the fuel assembly of this embodiment, a control rod insertion passage 4 is formed between the fuel bundles by four dogleg-shaped partition plates 3, so the control rods are inserted from the top. When inserted, the control rods are inserted without any interference with the fuel bundle.

In addition, on the side surface of the rectangular cylindrical box 2 corresponding to the control rod passage 4 of the channel box 1, water waste removal holes 8 are provided at intervals that become coarser toward the bottom in the axial direction. The rod can be braked by water pressure and stopped in a fixed position.

In addition, since a channel box handling window 9 is provided on the upper side of the rectangular cylindrical box 2 of the channel box 1, it is possible to handle only the channel box, or to store fuel bundles in the subchannel 5 of the channel box. It becomes possible to handle fuel assemblies installed in the body.

Being able to handle multiple fuel bundles at the same time leads to improved efficiency during fuel exchange during periodic inspections and during shirt ringing.

〔Effect of the invention〕

As explained above, in the fuel assembly of the present invention, four fuel bundles are housed in one channel box, and control rod insertion passages are provided between the fuel bundles, so the control rods are inserted from the top. At this time, the control rods can be inserted without interfering with the fuel bundle.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a channel box that is a component of the fuel assembly of the present invention, FIG. 2 is a side view of a fuel bundle that is a component of the fuel assembly of the present invention, and FIG. 4 is a perspective view showing a conventional fuel assembly with 7 parts cut away, and FIG. 5 is a conventional fuel assembly 4.
FIG. 1.14... Channel box 2... Square tubular box 3... Partition plate 4... Control rod insertion passage 5... Sub channel 6... Pedestal 7... Lower nozzle 8...・Water waste removal hole
9... Handling windows 10, 15... Fuel rods 11, 16... Upper tie plate 12... Lower tie plate ff1 13, 17... Fuel rod spacer 18... Lower tie plate 19. ...Channel fastener 20...Channel spacer 21...Control rod agent Patent attorney Noriyuki Chika Kendai Daishimaru 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A plurality of fuel rods, upper and lower tie plates that support the upper and lower ends of the fuel rods, a spacer that supports the intermediate portion of the fuel rods, and a fuel bundle formed by bundling these parts together;
In a fuel assembly consisting of a channel box containing four of these fuel bundles, the channel box has a cross-shaped control rod insertion passage formed by four dogleg-shaped partition plates, and the four Four fuel bundles are installed in the space inside the channel box divided by a dogleg-shaped partition plate, and water and waste are removed so that the intervals become coarser toward the bottom in the axial direction of the solid axis on the side of the channel box. A fuel assembly characterized by having holes.