JPH056558Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to an upper nozzle equipped with a nozzle spring for pressing a nuclear fuel assembly downward.

"Conventional technology" In general, nuclear fuel assemblies loaded into nuclear reactors are
As shown in FIG. 6, an upper nozzle 1 and a lower nozzle 2 are arranged at both the upper and lower ends, and
A large number of fuel rods 5 are bundled and supported by a structure consisting of a control rod guide tube 3 provided between them and a support grid 4 fixed to the control rod guide tube 3.

Incidentally, the reactor vessel is filled with cooling water for transferring energy released by nuclear fission.

Since this cooling water flows from below to above the nuclear fuel assembly at a considerable flow velocity, the nuclear fuel assembly is subjected to a force that lifts it from below.

Therefore, in order to stably hold the nuclear fuel assembly, it is necessary to press the nuclear fuel assembly downward.

Therefore, the upper nozzle 1 of the nuclear fuel assembly is
A nozzle spring 6 is provided on the upper surface of the main body, and by pressing the upper core plate of the nuclear reactor (not shown), the nuclear fuel assembly is pressed and supported against the lower core plate. There is.

FIG. 7 is a perspective view showing the structure of the upper nozzle 1. In the figure, the upper nozzle main body 10 is shaped like a regular square prism and has a substantially square shape when viewed from above. A recessed portion 12 is provided, and a side portion 11a of this peripheral portion 11 is provided with a downwardly curved hook-shaped first spring 6a and a pair of flat plate-shaped second and third springs 6b and 6c. There is.

That is, these first, second, and third springs 6a, 6b, and 6c are stacked one on top of the other, and their bases are fixed to the corners of the side portion 11a by screws 14 via clamp members 13. This is what is being done.

However, in the conventional upper nozzle 1, each spring 6a, 6 of the nozzle spring 6
b, 6c to the upper nozzle body 10,
Since the upper nozzle main body 10 is fixed by a screw 14 via a clamp member 13 which is a separate member, if the screw 14 is broken due to vibration or some other cause, the nozzle spring 6 will be damaged. There was an undeniable fear that the clamp member 13 would be immediately released or the clamp member 13 etc. would come off.

Therefore, in order to solve the above conventional problems, for example, as shown in FIGS. 8 to 10, a protrusion 20 that protrudes upward is integrally formed on the upper surface peripheral portion 11 of the upper nozzle body 10. , and the protrusion 20 is provided with a mounting recess 21 into which one end (base) of the nozzle spring 6 is mounted, and the nozzle spring 6 is mounted in the mounting recess 21.
While the one end of the nozzle spring 6 is attached, the leg 22a of the screw 22 is fitted to the one end of the nozzle spring 6, and the head 22b of the screw 22 is placed above the attachment recess 21 of the protrusion 20. A device in which the two are screwed together has been devised.

"Problems to be solved by the invention" However, in the mounting structure of the nozzle spring 6 shown in FIG.
The shapes of the second and third springs 6b and 6c are very similar, and the leg portion 22a of the screw 22 is formed in a straight cylindrical shape, and one end of the nozzle spring 6 facing the leg portion 22a is formed in a straight cylindrical shape. Since the hole 6d is formed in a straight shape,
It is easy to install the second and third springs 6b and 6c upside down, and if you accidentally install them upside down, it is difficult to detect. Therefore, when installing the nozzle spring 6, please be careful. It is necessary to pay attention to

This invention was made in view of the above circumstances,
The purpose is to provide an upper nozzle for a nuclear fuel assembly that can prevent installation errors when installing a nozzle spring, and that can also be easily installed and greatly improve workability. There is a particular thing.

"Means for Solving the Problems" In order to achieve the above object, the present invention provides a screw on the head of a spring screw that fixes a nozzle spring made up of a plurality of stacked elastic members to an upper nozzle body. A stepped portion is formed on the leg of the spring screw, and a mounting recess for mounting one end of the nozzle spring is provided in the protruding portion of the upper surface of the upper nozzle main body, and the protruding portion A screw hole is formed above the mounting recess to fit into the threaded portion of the spring screw, and a stepped hole is formed at one end of the nozzle spring to fit into the stepped portion of the spring screw. It forms a through hole.

"Function" In the upper nozzle of the nuclear fuel assembly of this invention, when the nozzle spring is attached to the mounting recess of the protruding portion of the upper nozzle body, the multiple elastic members of the nozzle spring can be easily and accurately assembled by fitting the stepped portion of the spring screw into the stepped through hole of the nozzle spring.

"Embodiment" Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 to 5.

In the figure, the square upper surface of the upper nozzle main body 30, which is a regular square prism and has a substantially square shape in plan view, has a recess 3 in the center, leaving a peripheral portion 31.
2 is provided, and a nozzle spring 33 is fixed to a side portion 31a of this peripheral portion 31.

A protrusion 34 that protrudes upward is integrally formed at two opposing corners of the side 31 a of the peripheral portion 31 . This protrusion 34 is
It has two extension parts 34a extending by a certain distance along the two sides 31a, and the extension part 3
4a are provided with two mounting recesses 34b whose bottom surfaces coincide with the surface of the side portion 31a.

Further, wall portions 34c and 34d are left on both sides of each of the mounting recesses 34b, and the extension portion 34a is provided with walls extending from the surface of the mounting recess 34b.
A screw hole 34e penetrating through the inside b is bored.
In the mounting recess 34b, a base (one end) of a nozzle spring 33, which is made up of a hook-shaped first spring 33a and a pair of upper and lower flat plate-shaped second and third springs 33b and 33c, is provided. is inserted.

A spring screw 35 is engaged with the base of the nozzle spring 33. This spring screw 35, as shown in FIG.
A head 35c having a pin mounting groove 35a and a threaded portion 35b, and continuing below the head 35c,
The leg portion 35f has a stepped portion 35d whose diameter is gradually reduced from the diameter of the threaded portion 35b, and a tip portion 35e in the shape of an inverted truncated cone. The threaded portion 35b of the head 35c is screwed into the threaded hole 34e of the protrusion 34. Further, the base of the nozzle spring 33 is formed with an inverted convex stepped through hole 33d into which the leg 35f of the spring screw 35 is fitted. That is, the bases of the first and second springs 33a and 33b of the nozzle spring 33 have through holes 33e and 33f into which the upper large diameter portion 35g of the stepped portion 35d of the spring screw 35 is loosely fitted.
However, the base of the third spring 33c is provided with a through hole 33g into which the lower small diameter portion 35h of the stepped portion 35d is loosely fitted. Furthermore, a mortar-shaped recess 34f into which the tip 35e of the spring screw 35 is loosely fitted is formed on the bottom surface of the mounting recess 34b directly below the screw hole 34e of the protrusion 34.

In the upper nozzle configured as above,
When attaching the nozzle spring 33 to the upper nozzle body 30, first insert the attachment recess 3 of the protrusion 34.
After inserting one end of the nozzle spring 33 into the nozzle spring 4b, the spring screw 35 may be screwed in with the screw hole 34e of the protrusion 34 and the stepped through hole 33d of the nozzle spring 33 aligned. In this case, each through hole 33f of the second and third springs 33b and 33c of the nozzle spring 33,
33g are easily distinguishable because they have different diameters, and will not be assembled upside down. Also, in case the second and third springs 33
b, 33c are stacked upside down, the lower surface of the upper large diameter portion 35g of the spring screw 35 is locked to the upper surface of the third spring 33c, so the spring screw 35
The head 35c remains protruding from the upper surface of the protrusion 34 and does not sink to a sufficient depth. Therefore, an assembly error can be immediately discovered, and the second and third springs 33b, 33c This can prevent the parts from being assembled upside down. Furthermore, the diameters of the through holes 33e and 33f of the first and second springs 33a and 33b of the nozzle spring 33 are different from those of the lower small diameter portion 35 of the spring screw 35.
Since the spring screw 35 is sufficiently larger than the diameter of h, it is extremely easy to insert the spring screw 35 from the screw hole 34e of the protrusion 34 into the stepped through hole 33d of the nozzle spring 33, thereby improving workability. .

In this way, the upper surface of the nozzle spring 33 is pressed by the lower surface of the head of the spring screw 35 and is firmly fixed to the upper nozzle body 30.

"Effects of the Invention" As explained above, the present invention forms a threaded part in the head of the spring screw that fixes the nozzle spring made up of a plurality of stacked elastic members to the upper nozzle body, and A stepped portion is formed on the leg of the spring screw, and a mounting recess for mounting one end of the nozzle spring is provided in a protrusion on the periphery of the upper surface of the upper nozzle main body, and A screw hole is formed at the upper position to be screwed into the threaded part of the spring screw, and a stepped through hole is formed at one end of the nozzle spring to fit the stepped part of the spring screw. Therefore, when installing the nozzle spring in the mounting recess of the protruding part of the upper nozzle body, by fitting the stepped part of the spring screw into the stepped through hole of the nozzle spring, the multiple elasticity of the nozzle spring can be adjusted. This has the excellent effect of allowing members to be assembled easily and accurately, preventing assembly errors, and greatly improving work efficiency.

[Brief explanation of the drawing]

Figures 1 to 5 show an embodiment of the present invention, in which Figure 1 is a sectional view illustrating the nozzle spring mounting structure, Figure 2 is a partially cutaway perspective view of the upper nozzle, and Figure 3 is a partially cutaway perspective view of the upper nozzle. is an enlarged view of the upper nozzle body, Fig. 4 is a side view of the spring screw, Fig. 5 is a side view of the nozzle spring, Fig. 6 is a schematic configuration diagram showing the entire nuclear fuel assembly, and Fig. 7 is a conventional A partially cutaway perspective view of an upper nozzle using a clamp member,
Figures 8 to 10 show a conventional clamp-integrated upper nozzle, Figure 8 is a sectional view explaining the nozzle spring mounting structure, Figure 9 is a side view of the spring screw, and Figure 10. is a side view of the nozzle spring. 30... Upper nozzle body, 31... Upper surface peripheral portion, 33... Nozzle spring, 34... Projection, 35... Spring screw, 33a...
First spring, 33b...Second spring, 3
3c...Third spring, 33d...Stepped through hole, 34b...Mounting recess, 34e...Screw hole, 3
5b...screw part, 35c...head part, 35d...stepped part, 35f...leg part.

Claims (1)

[Scope of utility model registration request] A protrusion projecting upward is formed on the upper surface of the upper nozzle main body, and a mounting recess for mounting a nozzle spring made of a plurality of stacked elastic members is provided in the protrusion. in an upper nozzle of a nuclear fuel assembly, in which one end of the nozzle spring is engaged with the upper nozzle body, and a spring screw is fitted to the one end of the nozzle spring to press and fix the nozzle spring to the upper nozzle body; A threaded portion is formed on the head of the spring screw, and a stepped portion is formed on the leg of the spring screw, and a stepped portion is formed in the protrusion at a position above the mounting recess.
A screw hole is formed to be screwed into the threaded part of the spring screw, and a stepped through hole is formed at one end of the nozzle spring to fit the stepped part of the spring screw. The upper nozzle of a nuclear fuel assembly.