JPS60230088A - 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 [Technical Field of the Invention] The present invention relates to a fuel assembly used in a boiling water nuclear reactor.

[Technical Background of the Invention] As shown in FIG. 1 with a portion cut away, a fuel assembly consists of a large number of fuel rods 1 bundled together in a square column shape, with the upper end connected to an upper tie plate 2,
The main parts thereof include a fuel bundle whose lower end is supported by a lower tie plate 3 and whose middle part is supported by a spacer 4, and a square columnar channel box 5 that accommodates the fuel handle.

The lower end of the channel box 5 is pressed and supported by a flat spring 6 inserted into the lower tie plate 3. Posts 2A, 2B, and 2G are provided at the four corners of the upper surface of the upper tie plate 2. The bosses 2A, 28, 20 serve as guides when the channel box 5 is inserted into the bundle of fuel rods 1 from above, and the boss 2B is in contact with the triangular stop member 5A at the upper end of the channel box 5. . A concave thread 2D is cut in the boss 2C, and as shown in FIG. There is. Further, the upper tie plate 2 is provided with a handle 2E#i5t for moving the fuel assembly.

A channel fastener 6 is installed at one corner of the top of the fuel assembly.
Fitted with fuel handle and channel box 5
The spring 6B of the channel fastener 6 pushes the fuel assemblies against each other in the core (not shown) of a boiling water reactor, thereby keeping the fuel assemblies vertical and controlling them. It has important functions such as maintaining a gap for insertion of a rod (not shown).

Further, the channel fastener 6 is installed and removed underwater in a fuel pool (not shown) using an automatic operating device (not shown) for inspection of the fuel assembly. Therefore, the structure is such that its constituent parts cannot be separated inadvertently. That is, as shown in FIG. 2, the channel fastener 6 passes through a guard 6A that contacts the top corner of the channel box 5, a spring 6B provided on the outside of the guard 6Δ, and a hole in the spring 6B and a hole in the guard 6A. A lock washer 6D is inserted between the provided cap screw 6C and the head of the cap screw 6C and the spring 6B.
and a retaining ring 6F (shown in the detailed drawings of the channel fastener in FIGS. 3 and 4), which is attached to the cap screw ○C after assembly. Note that the hole of the spring 6B and the hole of the guard 6A have a larger diameter than the diameter of the threaded portion 60C of the cap screw 6C. As shown in FIG. 4, the retaining ring 6F is inserted into a groove formed above the threaded portion 6CG of the cap screw 6G to prevent the cap screw 6C from being pulled out after the channel fastener 6 is assembled.

[Problem in the background art 1] The fuel assembly configured as described above is taken out from the core and the channel box 5 is removed under water in a fuel pool or the like.
When performing installation work, the following problems may occur. The retaining ring 6E of the channel fastener 6 is a small snap ring with an outer diameter of about gmm, a thickness of about Q, and 5 mm, and if it is expanded a little too much when assembling the channel fastener 6, there is a risk that permanent deformation will remain. If the cap screw 6C with the permanently deformed resonating ring 6E is loosened by remote control from above the fuel pool and the channel fastener 6 is moved away from the channel box 5, the resonating ring 6E will be 1! ! If the channel fastener 6 comes off, the component parts of the channel fastener 6 may also separate and fall into the fuel pool water. Furthermore, in the worst case, there is a possibility that these components may become stuck between the fuel rods 1 and cannot be removed.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a fuel assembly in which there is no risk of the component parts being lost when the fuel assembly is handled.

[Summary of the Invention J In order to achieve the above-mentioned objects, the fuel assembly and combination according to the present invention has a channel fastener without a resonating ring, and is characterized by a structure that does not easily disassemble after the channel fastener is assembled. ing.

[Embodiments of the Invention] Hereinafter, embodiments of the fuel assembly according to the present invention will be described with reference to the drawings.

FIG. 5 is a partially cutaway side view of the channel fastener, in which a concave thread 7AA is cut in the guard 7A to match the convex thread of the cap screw 7C.

Further, the outlet side portion 7AB of this concave screw 7AA is chamfered. This shape is shown in FIG. 6, which is an enlarged view of section B in FIG. 5. As shown in FIG. 7, the cap screw 7C consists of a head 7CA, a cylindrical rod portion 7CB, and a convex threaded portion 7CG. The length of the cylindrical rod portion 7CB is approximately 5 mm longer than the sum of the plate thicknesses of the spring 7B and the guard 7A.

The diameter of the convex screw portion 7CG is larger than the diameter of the cylindrical rod portion 70B. A procedure for assembling a member having such a structure as the channel fastener 7 will be described. Place spring 7B on guard 7A and lock washer 7.
Screw in the cap screw 7C through D from the spring side. After the threaded portion 7CC of the cap screw 7C passes through the concave threaded portion 7AA of the guard 7A, 1? As shown in FIG. 8, the screw thread of the threaded portion 7CG of the screw thread 70 on the concave screw side of the guard 7A is formed into an umbrella shape 7CD using a predetermined jig. The length of the screw thread to be crushed is about 1/2 pitch to 3/2 pitch. After crushing the threads, the chamfered outlet side portion 7AB of the guard 7A is pressed and rubbed together. By rubbing together, the surfaces are aligned so that they rotate smoothly in the left and right directions.

When a fuel assembly incorporating a channel fastener 7 having such a structure is handled underwater such as in a fuel pool, even if the cap screw 7C is pulled with a force of several kg and turned with an automatic handling device, it will not rotate in either direction. It rotates smoothly and has good workability. Furthermore, since the concave screw side portion of the guard 7A of the threaded portion 7CG of the cap screw 7C is crushed into an umbrella shape 7GD, it rotates idly. Therefore, after the cap screw 7C is removed from the post 2C, it will not fall out from the guard 7A. Therefore, since the channel fastener 7 will not separate, there is no risk of it falling into water such as a fuel pool. It also has fewer components than conventional models, making it more reliable. Also, no welding is required.

In the above-described embodiment, the threaded hole of the guard 7A is crushed after the threaded portion 7CG of the cap screw 7C is inserted therethrough, but it may be formed after the channel fastener 7 is assembled.

Further, the concave screw exit portion 7AB of the guard 7A may not be chamfered, but the concave screw exit portion 7AB may be crushed.

FIG. 9 shows an example of the thread crushing process of the concave screw exit portion 7AB of the guard 7A. Other examples of crushed shapes are shown in FIGS. 10 and 11.

Furthermore, other embodiments of the cap screw 7C having an umbrella-like crushed shape are shown in FIGS. 12 and 13.

Of course, these thread crushing processes are also possible with cap screw 7.
The fuel assembly of the present invention is machined so that it comes into smooth contact with the flattened part of the convex thread of C. - [Effects of the Invention] As explained above, the fuel assembly of the present invention is free from the risk of component parts being lost during handling. can provide more reliable fuel assemblies without

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional fuel assembly with a portion cut away, Figure 2 is a perspective view of the upper end of a conventional fuel assembly, and Figure 3 is a perspective view of a conventional channel fastener with a portion cut away. 4 is a cross-sectional view taken along the line AA in FIG. 3, FIG. 5 is a side view showing the channel fastener of the present invention with a portion cut away, and FIG. 6 is an enlarged view of part B in FIG. 5. FIG. 7 is a side view of the cap screw according to the present invention, FIG. 8 is a partially enlarged view of the threaded portion of the cap screw according to the present invention, FIG.
FIGS. 10 and 11 are enlarged sectional views of the threaded portion of the guard according to the present invention, and FIG. FIG. 13 is an enlarged view of the processed portion of the cap screw according to the present invention. 1...Fuel rod, 2...Upper tie plate, 3...
Lower tie plate, 4... Spacer, 5... Channel box, 6... Channel fastener, 7...
Channel fastener, 7A...guard, 7B...spring, 7C...cap screw, 7D...
Lockwash Applicant Hisashi Hatano Figure 2 Figure 3 Figure 12 Figure 10 Figure 13 Figure 11

Claims (1)

[Claims] Fuel rods bundled into a 1° square column, an upper tie plate that supports the upper ends of the fuel rods and has posts at the upper corners, and a lower type that supports the lower ends of the fuel rods. A rectangular cylindrical channel box that almost encloses the fuel handle, which includes the spacer, the fuel rod, the upper tie plate, and the lower tie plate as the main components; A spring located at the upper corner of the channel box and maintaining a gap between the adjacent channel boxes, a guard sandwiched between this spring and the channel box, a hole provided in this guard, and a hole provided in the above spring. A fuel assembly comprising a channel fastener comprising a hole and a cap screw that passes through the hole of the channel box and is screwed to the post of the upper tie plate, the channel fastener having a concave screw that matches the convex screw of the cap screw. A guard with a concave screw exit hole cut with a chamfer, a spring with a hole larger than the diameter of the convex screw of the cap screw, and a convex screw of the cap screw that passes through the hole of the spring and engages with the concave screw of the guard. After passing through the convex screw, crush the thread on the guard side of this convex screw into an umbrella shape, press and rub the concave screw hole of the guard and the crushed part of the convex screw of the cap screw together so that they rotate smoothly. A fuel assembly characterized in that it has a channel fastener comprising a mated cap screw. 2. The concave screw exit hole of the guard is not chamfered before assembling the channel fastener, but is chamfered after the convex screw portion of the cap screw passes through. The fuel assembly according to item 1. 3. After the convex threaded part of the cap screw passes through the concave threaded part of the guard, smooth the threads on the guard side of this convex screw to make the concave threaded hole of the guard and the convex thread of the cap screw smooth. 3. The fuel assembly according to claim 1, wherein the crushed portion is pressed and rubbed together. 4. The umbrella-shaped inclined surface of the thread crushing portion of the cap screw is formed as a concave arc surface that is concave toward the axis, and the curvature corresponding to this concave arc surface allows the screw hole of the guard to The fuel assembly according to claim 1, which is formed of a convex arc surface that bulges toward the center. 5. The pin-shaped inclined surface of the thread crushing part of the cap screw is formed by a convex arc surface that bulges outward, and the curvature corresponding to this convex arc surface makes the screw hole crushing part of the guard Claim 1 formed by a concave arc surface concave toward the axis
Fuel assemblies described in Section.