JPH02276993A - Fuel assembly - Google Patents

Abstract

PURPOSE:To improve the efficiency of disassembly and assembly by forming a cut, which reaches a hole part where a fitting screw is inserted, in the upper end part of an elastic body part and giving the fitting screw a tensile force by parts which adjoin to the cut. CONSTITUTION:A cap screw 10 is inserted into the center of the upper end part 11A of the leaf spring 11 of a channel fastener 9 and the cut 11B which reaches the hole part 11C is formed. Parts 11A1 and 11A2 of the upper end part 11A adjoining to the cut 1B are different in height. The screw part 10F of the cap screw 10 is engaged with a screw hole 13A formed in a guard 13 through the hole part 11C of the leaf spring 11 and the cap screw 10 is rotated to make the screw part 10F reaches the bottom of the screw hole 13A completely. In this state, the cap screw 10 is held so that it never falls from the guard 13. This guard 13 is arranged at the corner part of a channel box 8 and when the cap screw 10 is rotated, the guard 13 contacts a holding plate 14 while the screw part 10F engages the screw hole formed in a post 3 to operates as a spring washer.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a fuel assembly, and in particular to a fuel assembly for a boiling water reactor that is applied to a light water reactor and whose channel box can be easily attached and detached. be.

[Conventional technology]

Conventionally, fuel channel boxes are attached to corner posts on the upper tie plate by cap screws rotatably mounted on the channel fasteners. The cap screw is provided with a thread at the bottom, and this thread engages with the corner post. Because the spring washer is attached to the cap screw and is located between the channel fastener and the channel box, there is a possibility that the spring washer will dissipate when assembled and then disassembled again.

As a device to improve this, the Utility Model Publication No. 63-36314
As described in the publication, a sleeve material is inserted between the cap screw and the guard from the lower end of the guard, and after the cap screw is fastened, the sleeve material expands upward and bites into the guard.

[Problem to be solved by the invention]

In the above-mentioned prior art, it is necessary to insert the sleeve material from the lower end of the guard, tighten it, and then expand the upper end of the sleeve material. For this reason, there is no problem with workability in the air, but for underwater remote control work, the necessary jigs become complicated and require considerable skill to operate, so consideration has been given to this point. Therefore, there was a problem in that it was difficult to shorten the time required for disassembling and reassembling fuel assemblies in the spent fuel pool.

An object of the present invention is to provide a fuel assembly that can improve the efficiency of disassembly and reassembly.

[Means to solve the problem]

The above purpose is to provide a notch in the upper end of the elastic body, which is an element constituting the channel fastener, that reaches the hole into which the mounting screw is inserted; This can be achieved by applying tension to the mounting screws by section.

[Effect]

A notch is provided at the upper end of the elastic body of the channel fastener,
Since the height of a part of the upper end adjacent to the notch is changed, the upper end of the elastic body has the same function as a spring washer. That is, since an upward tensile force is applied to the mounting screw by the upper end of the elastic body portion, it is possible to prevent the mounting screw from loosening. Therefore, a spring washer is not required, and the channel fastener can be attached to and removed from the post of the upper tie plate in a short time.

This reduces the time required to disassemble and reassemble the light water reactor fuel assembly in the spent fuel pool, which in turn makes it possible to shorten the periodic inspection time of the nuclear power plant.

〔Example〕

A fuel assembly according to an embodiment of the present invention suitable for use in a boiling water reactor will be described with reference to FIGS. 1 to 3.

The fuel assembly 1 of this embodiment includes an upper tie plate 2, a lower tie plate 4. Fuel body5. It is equipped with a water rod 6 and a fuel spacer 7. Both ends of the fuel body 5 and water rod 6 are held by the upper tie plate 2 and the lower tie plate 4. The upper and lower tie plates are joined by a joining fuel body, not shown. Each fuel body 5 is supported horizontally by a fuel spacer 7. Therefore, a coolant passage having a predetermined width is formed between each fuel body 5.

The channel box 8 is a cylindrical body with a square cross section, and is attached to the corner post 3 of the upper tie plate 2 by a cap screw 10 provided on the channel fastener 9.
mounted on. Such a channel box 8 is
It surrounds the fuel bundle bundled by the fuel spacer 7.

The channel fasteners 9 press each fuel assembly 1 loaded in the core against a core upper support plate (not shown) that supports the upper end of the fuel assembly 1 on a leaf spring 11, which will be described later.

The structure of the installation of the channel box 8 will be explained in detail with reference to FIG.

First, the structure of the channel fastener will be explained with reference to FIG. The channel fastener 9 has a cap screw 10.
Leaf spring 11. and a guard 13. When the channel fastener 9 is attached to one corner post 3, the guard 13 is located at one corner of the channel box 8.

The leaf spring 11 is arranged on the guard 13. Leaf spring 11
The majority of the guard 13 faces two side surfaces formed on the outside of the guard 13. The camp screw 10 has the function of a set screw for attaching the channel fastener 9 and the channel box 8 to the upper tie plate 2.

The cap screw 1o has a tool engaging portion 10A.

It has a flange portion 10B, a narrow diameter portion 10E, and a threaded portion 10F. Tool engaging portion 10A, flange portion 10B.

The large diameter portion 10D and the threaded portion 10F are located in this order from above in the axial direction, and have an integral structure. Tool engaging portion 10A located above the flange portion 10B
As shown in FIG. 1, a plurality of vertical grooves are provided which engage with a tool for rotating the channel fastener 9. Narrow diameter part 1
0F is provided between the flange portion 10B and the threaded portion 10F.

The threaded portion 10F is located at the lower part of the cap screw 10, and is connected to the flange portion 10B via the narrow diameter portion 10E.

The diameter of the narrow diameter portion 10E is equal to the diameter at the valley portion of the threaded portion 10F.

A notch IIB is provided in the center of the upper end portion 11A of the leaf spring 11 of the channel fastener 9, which reaches the hole portion 11C into which the cap screw 10 is inserted. Portions 11A1 and 11A2 of the upper end portion 11A adjacent to this notch IIB are as follows:
The heights are different.

The threaded portion 10F of the camp screw 10 passes through the hole 11C of the leaf spring 11 to form a threaded hole 13 provided in the girt 13.
By engaging with A and rotating the cap screw 1o, the threaded portion 10F completely reaches below the threaded hole 13A. In this state, the cap screw 1o is held so that it will not come off the guard 13 unless it is rotated.

A guard 13 to which a camp screw 10 and a leaf spring 11 are attached is arranged at a corner of the channel box 8. After that, the cap screw 10 is rotated. Thereby, the threaded portion 10F of the cap screw 10 meshes with the threaded hole provided in the post 3. A retaining plate 1 in which the threaded portion 10F and the threaded hole of the post 3 are completely engaged, and the guard 13 is provided at the corner of the channel box 8.
Contact 4. Further, the lower surface of the holding plate 14 contacts the upper end of the post 3. In this way, the channel box 8 and the channel fastener 9 are connected to the cap screw 1o.
It is attached to the post 3 by. Part 11 of leaf spring 11
When the cap screw 10 is attached to the post 3, A1 and the portion 11A2 are compressed in the axial direction from the state shown in FIG. 2 by the flange portion 10B and the upper surface of the guard 13, and are located at the same level. In this state, the portion 11AI of the leaf spring 11
The portion 11A2 applies a load in the direction of pulling up the cap screw 1°. This effect is obvious,
Like a spring washer, it generates a tensile load on the cap screw 10 and functions to prevent the cap screw 10 from loosening. In addition, since the spring washer is no longer required, disassembly and reassembly of the fuel assembly (removal of the channel box 8 from the fuel bundle,
installation into the fuel bundle). The channel box is removed from the fuel bundle when inspecting the fuel rods or servicing the fuel assembly. This embodiment makes it possible to shorten the time required for inspecting such fuel assemblies.

The fuel bundle is obtained by removing the channel box 8 from the fuel assembly 1 shown in FIG.

〔Effect of the invention〕

According to the present invention, since no washer is required, the efficiency of the disassembly and reassembly work of the fuel assembly is improved and the work can be carried out in a short time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the mounting state of the channel fastener and channel box of the fuel assembly according to the embodiment of the present invention shown in FIG. 3, and FIG. 2 is a perspective view of the leaf spring shown in FIG. 1. 3 are longitudinal sectional views of a fuel assembly according to an embodiment of the present invention, and FIG. 4 is a longitudinal sectional view of the channel fastener shown in FIGS. 1 and 3. 1... Fuel assembly, 2... Upper tie plate, 3...
...Post, 4...Lower tie plate, 5...Fuel rod, 8...Channel box, 9...Channel fastener, 10...Cap screw, 11 - Leaf spring, IIB map

Claims (1)

[Claims] 1. an upper tie plate having a post at a corner portion; a lower tie plate; a plurality of fuel rods having upper ends held by the upper tie plate and lower ends held by the lower tie plate; A fuel assembly having a channel fastener arranged therein, wherein the channel fastener has an elastic body portion that maintains a distance between the fuel assemblies in the reactor core, and a mounting screw that attaches the elastic body portion to the post. , the elastic body part has a notch at its upper end that reaches the hole into which the mounting screw is inserted, and a part of the upper end of the elastic body part adjacent to the notch has a notch at its upper end. A fuel assembly characterized in that a tensile force is applied to the mounting screw.