JPH06123790A - Fuel assembly for nuclear reactor - Google Patents

Abstract

(57) [Summary] [Purpose] Reactor that facilitates mounting and demounting work of fuel rod fixing nuts for couplings and washers with claws, and also shortens working time by preventing interference when mounting channel boxes. A fuel assembly for use is provided. [Structure] A groove is provided in the fixing nut 10 of the connecting fuel rod 9 so that the claw 19 of the washer 11 with a claw can be fitted, and the number of claws of the washer with a claw is at least 1 in correspondence with the fixing nut. Let's make one. In addition, the fixing nut has a cap nut structure or a structure in which the upper part of the nut is inclined.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fuel assembly for a nuclear reactor.

[0002]

2. Description of the Related Art A fuel assembly for a boiling water reactor is a rectangular channel box in which a large number of fuel rods filled with a nuclear fuel material are regularly arranged inside a metal cladding tube. FIG. 11 shows an example of a fuel assembly currently used in a nuclear reactor. That is, in the fuel assembly 1, a plurality of fuel rods 2 and a single or a plurality of water rods 3 are fixed by an upper tie plate 4, a spacer 5, and a lower tie plate 6, and the outside thereof is a channel box 7.
It is configured to be surrounded by. 12 and 13 show the detailed relationship between the upper tie plate 4 and the channel box 7. The upper tie plate 4 includes a cylindrical boss 13 arranged according to the arrangement of the fuel rod 2 and the water rod 3, and a rib 1 that connects adjacent bosses 13 to each other.
4, a handle 12 for handling a fuel body, three posts 16 standing at four corners, and one fixing post 1
5 and eight channel pads 18 in total, two on each side. These boss 13 and rib 14
Is basically the minimum necessary size in terms of strength in order to maximize the flow passage area of the coolant during fuel use and reduce the pressure loss. The upper and lower ends of the fuel rod 2 are an upper tie plate 4 and a lower tie plate 6.
It is inserted into and supported by the boss hole of the boss 13 provided on the. Some of the fuel rods 2 are joining fuel rods 9 that are threaded at the upper and lower ends, the lower ends of which are screwed into the lower tie plate 6. The upper end of the connecting fuel rod 9 penetrates through the boss hole of the boss 13 and the hole of the washer 11 with a claw, and is fixed by screwing the fixing nut 10 on the upper surface of the upper tie plate 4. The fixing nut 10 is also
By bending the claw 19 of the washer 11 with a claw upward, it is prevented from rotating and loosening during use. The fixing nut 10 is a hexagonal nut as shown in FIG. 14, and the claw 19 of the washer 11 with a claw is bent upward so as not to rotate and loosen during use.
As shown in FIG. 15, the pawl washer 11 has a structure in which four rings are connected together. The two outer rings are washers for the fixing nuts 10, and each is one on the extension of the center line of the ring and radially fixes every other hexagonal side of the fixing nuts 10 in the direction rotated by 120 °. Is provided with a claw 19 for connecting two fuel rods 9 for joining.
The fixing nut 10 can be fixed at the same time, and the fixing nut 10 itself does not rotate. The channel box 7 is vertically covered from above the fuel assembly 1 in the reactor building. Clips 17 are provided at two opposite corners of the upper end of the channel box 7 and are mounted on the upper ends of the posts 16 of the upper tie plate 4. One of the posts 16 in contact with the clip 17 is a fixing post 15, which has a threaded hole. The channel box 7 is screwed through the clip 17 by screwing the screw of the channel fastener 8 through the clip 17. Fixed to 1. The three posts 16 excluding the fixing posts 15 are upright cylinders having the same diameter and the same diameter as the boss 13 directly below in order to reduce the pressure loss. On the other hand, in order to make the screw holes for the channel fasteners, the fixing posts 15 and the bosses 11 therebelow have a larger diameter than the other posts 16 and are upright cylinders whose center lines deviate from the fuel rods 2 immediately below. In order to facilitate the work of mounting the channel box 7 on the fuel assembly 1,
The upper tie plate 4 has a lead-in structure as shown in Japanese Patent Publication No. 58-6919. In FIGS. 12 and 13, a lead-in structure is provided by forming an inclined bridge 20 between the handle 12 and the adjacent post 16 and chamfering the channel pad 18.

[0003]

In the prior art, the rings at both ends of the washer 11 with the claws are provided at intervals of 120 °.
By arranging the claws 19 on the hexagonal side of the fixing nut 10 so that they are aligned with each other and bending the claws upward, the fixing nut 10 that is tightening the connecting fuel rod 9 rotates during use. So that it doesn't come loose. But,
In the prior art, the upper tie plate 4 is removed for temporary disassembly and reassembly during or after the use of the fuel assembly 1 for the purpose of testing or the like. It was necessary to release or bend the sheets one by one, or to release or bend them at once using a dedicated jig.

In the prior art, the channel box 7
The post 16 has a lead-in structure in order to facilitate the attachment work to the fuel assembly 2. For the attachment work up to the head of the post 16 of the upper tie plate 4, the lower end of the channel box 7 is Although it did not interfere with the upper tie plate 4, after the channel box 7 passed the head of the post 16, the channel box 7
No consideration was given to the interference between the claw and the claw of the washer 11 with a claw bent to prevent the fixing nut 10 from rotating. Therefore, there is a possibility that interference may occur when the channel box 7 is attached to the fuel assembly 1 in the reactor building.

An object of the present invention is to enable mounting of a washer with a claw for locking a fixing nut in a nuclear reactor building, improvement of desorption workability and shortening of work time, and shortening of channel box mounting work time. To provide a nuclear reactor fuel assembly.

[0006]

In order to solve the above-mentioned problems, a groove is provided in the fixing nut 10 of the connecting fuel rod 9 so that the claw 19 of the washer 11 with a claw can be fitted, and the fixing nut is fixed. Correspondingly, the number of claws on the washer with claws should be at least one. In addition, the fixing nut has a cap nut structure or a structure in which the upper part of the nut is inclined.

[0007]

When the fuel assemble 1 is disassembled and reassembled during or after the use of the fuel assembly 1 for the purpose of assembling and testing the fuel editing body 1, the upper tie plate 4 is removed and fixed. 10 nails of washer 11 with nails
At least one claw needs to be provided on the washer with claws by providing the groove so that the claw 9 can be fitted, and therefore the work of bending or releasing the claw can be performed easily and in a short time.

Further, the fixing nut 10 has a cap nut structure or a structure in which the nut is inclined so that the lead-in function of the fixing nut itself when the channel box 7 is attached to the fuel assembly 1. It is possible to prevent interference when the channel box 7 is attached to the fuel assembly 1.

[0009]

Embodiments of the present invention will be described with reference to FIGS. In this embodiment, one of the hexagonal sides of the fixing nut 10 of the connecting fuel rod 9 has a groove that can be fitted when the claw 19 of the washer 11 with a claw is bent. The washer 11 has a structure having only one claw 19. The height of the fixing nut 10 is set so that the hooks 19 of the washer 11 with hooks can be easily fitted when the hooks 19 are bent, but they should not interfere with the clips 17 or the like when the channel box 7 is mounted. There is a need. The state of the fixing nut 10 and the pawl washer 11 during assembly is shown in FIGS. 3 and 4. Due to this combination, when the fuel assembly 1 is temporarily disassembled during use or after use for the purpose of assembling and testing the fuel assembly 1, and the upper tie plate 4 is detached and reassembled, the conventional claws are used. While it was necessary to release or bend the three claws 19 of the attached washer 11 one by one, or to release or bend them at once using a dedicated jig, it is possible to easily attach and detach in a short time. Become. Further, since the number of the claws 19 of the washer 11 with the claws is reduced, the possibility that the bent claws are projected to the outside of the outer peripheral surface of the upper tie plate is reduced, and the channel when mounting the channel box 7 on the fuel assembly 1 is reduced. The possibility of interference with the box 7 can be reduced. Further, the claws 19 of the washer 11 with claws are arranged near the center line extensions of the four rings of the washer 11 with claws as shown in FIG. 2 (b), or as shown in FIG. 2 (a). With washer 11
The claws 19 of each of the four rings are arranged on either side with respect to the center lines of the four rings, and when the claws 19 are assembled so that the claws 19 face the inside of the assembly, the claws 19 interfere with the channel box 7. Can be further reduced.

FIG. 5 shows a second embodiment of the present invention. In this embodiment, a washer 1 with a claw provided on the fixing nut 10 is provided.
It has a plurality of grooves which can be fitted when the first claw 19 is bent. When the fixing nut 10 of the present embodiment is used in combination with the washer 11 with a claw shown in FIG.
As compared with the case of the embodiment described above, the chance of circumferential alignment of the groove of the fixing nut 10 and the claw 19 of the washer 11 with a claw when the fixing nut 10 is fastened to the joining fuel rod is increased, Workability can be improved. FIG. 6 shows a third embodiment of the present invention. In this embodiment, there are two claws 19 of the washer 11 with a claw, and by using it in combination with the fixing nut 10 shown in FIG. 1, one of the claws 19 becomes a groove of the fixing nut 10. It is used for fitting and the other is used without bending.
However, the claws that are used without bending should be placed so that they will not interfere with other fuel rods. Figure 6
FIG. 6A shows an example in which another claw is placed at a position where it interferes with another fuel rod, and FIG. 6B shows another claw at a position where it does not interfere with another fuel rod. The present embodiment arranged is shown. The other claw used without bending was broken when the upper tie plate was removed and installed for the purpose of testing and the like, and the claw 19 of the washer with claw 11 was released or bent again. In this case, it is provided as a spare claw, and is characterized in that it can be used without replacing the washer 11 with a claw with a new one.

FIG. 7 shows a fourth embodiment of the present invention. Figure 1
By making the shape of the groove provided in the fixing nut 10 shown in FIG. 6 have an inclination, it is possible to easily bend the inside of the claw 19 while guiding it when fitting the claw 19 of the washer 11 with a claw. is there. FIG. 8 shows a fifth embodiment of the present invention. FIG. 8A shows a groove formed in the fixing nut 10 shown in FIG. 1 through the groove in the axial direction.
(B) is a groove formed in the fixing nut 10 shown in FIG. In the case of this embodiment, the groove can be processed more easily than the fixing nut shown in FIGS. 1 and 5, and when the hook 19 of the washer 11 with a hook is bent, the groove of the fixing nut is surely moved from the root of the hook. The feature is that they can be fitted.

FIG. 9 shows a sixth embodiment of the present invention. The present embodiment is characterized in that the fixing nut 10 shown in FIG. 1 is provided with an inclination on the upper part, and the fixing nut itself has a lead-in function when the channel box is mounted. That is, when the channel box 7 is mounted on the fuel assembly 1, the channel box 7 is guided along the inclination of the fixing nut 10, so that interference when mounting the channel box 7 on the fuel assembly 1 is prevented. be able to.

FIG. 10 shows a seventh embodiment of the present invention. In this embodiment, the fixing nut 10 shown in FIG. 9 has a cap nut structure. When the nut shown in FIG. 9 is used, the upper end of the connecting fuel rod 9 is slightly protruded above the nut so that the channel While there is a possibility that the lead-in function at the time of mounting the box is not sufficient, in the present embodiment, the interference between the channel box 7 and the upper ends of the fuel rods 9 for coupling is eliminated, so that when mounting the channel box on the fixing nut itself. It is an enhancement of the lead-in function of.

[0014]

According to the present invention, the upper tie plate is attached or detached at the time of temporarily disassembling and reassembling during or after the use of the fuel assembly for the purpose of assembling and testing the fuel assembly. In this case, by providing a groove so that the claw of the washer with a claw can be fitted to the fixing nut of the connecting fuel rod, the work of bending or releasing the claw can be performed easily and in a short time.

In addition, when the channel nut is attached to the fuel assembly by using a structure in which the upper portion of the fixing nut is inclined, or a cap nut or a structural nut, the channel box is mounted by the lead-in function of the fixing nut itself. It is possible to prevent interference when mounting the fuel assembly.

[Brief description of drawings]

FIG. 1 is a front view (b), a plan view (a), and a side view (c) of a fixing nut according to a first embodiment of the present invention.

FIG. 2 is a plan view of a washer with a claw according to the first embodiment of the present invention.

FIG. 3 is a plan view of an assembled state of the fixing nut and the washer with the claw according to the first embodiment of the present invention.

FIG. 4 is a side view showing the assembled state of the fixing nut and the washer with the claw according to the first embodiment of the present invention.

FIG. 5 is a front view (b) and a plan view (a) of a fixing nut according to a second embodiment of the present invention.

FIG. 6 is a plan view of a washer with a claw according to a third embodiment of the present invention.

FIG. 7 is a front view (b), a plan view (a) and a side view (c) of a fixing nut according to a fourth embodiment of the present invention.

FIG. 8 is a front view (c), (d), a plan view (a), and (b) of a fixing nut according to a fifth embodiment of the present invention.

FIG. 9 is a front view (b) and a plan view (a) of a fixing nut according to a sixth embodiment of the present invention.

FIG. 10 is a front view (b) and a plan view (a) of a fixing nut according to a seventh embodiment of the present invention.

FIG. 11 is a front view of a conventional fuel assembly structure for a nuclear reactor.

FIG. 12 is a front view of a conventional nuclear reactor fuel assembly superstructure.

FIG. 13 is a plan view of a conventional nuclear reactor fuel assembly superstructure.

FIG. 14 is a front view (b) and a plan view (a) of a conventional fixing nut.

FIG. 15 is a plan view of a conventional washer with a claw.

[Explanation of symbols]

4 ... Upper tie plate, 9 ... Fuel rod for joining, 10 ... Nut for fixing fuel rod for joining, 11 ... Washer with claw, 19 ...
Washer claws.

Claims (5)

[Claims] 1. A plurality of fuel rods filled with a nuclear fuel material are arranged in a lattice inside a metal cladding tube, and the upper ends of the fuel rods are fitted or penetrated to an upper tie plate and held.
In a fuel assembly in which the upper part of the penetrated fuel rod is fixed by a fixing nut and a washer with a claw for stopping nut rotation, a groove is formed so that the claw of the washer with a claw can be fitted to the fixing nut. A fuel assembly for a nuclear reactor characterized by being provided. 2. The fuel assembly for a nuclear reactor according to claim 1, wherein the fixing nut is provided with grooves equal to or more than the number of claws of the washer with a claw. 3. The fuel assembly for a nuclear reactor according to claim 1, wherein an inclination is provided on an upper portion of the fixing nut. 4. The fuel assembly for a nuclear reactor according to claim 1, wherein the fixing nut has a cap nut structure. 5. The fuel assembly for a reactor according to claim 1, wherein the washer with claws has at least one claw.