JPH0376876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an upper nozzle equipped with an elastic member for pressing a fuel assembly downward.

"Prior Art" Generally, in a nuclear reactor 1, as shown in FIG. 7, an upper core plate 12 and a lower core plate 13 are provided in a reactor vessel 11.
A large number of fuel assemblies 14 . . . are provided in parallel between the three fuel assemblies 14 . As shown in FIG. 8, this fuel assembly 14 has upper nozzles 1 disposed at both upper and lower ends.
5, a lower nozzle 16, a control rod guide tube 17 provided between these two nozzles, and this control rod guide tube 17.
A large number of fuel rods 19 are bundled and fixed to a structure consisting of a support grid 18 fixed to a fuel rod.

Incidentally, the reactor vessel 11 is filled with cooling water for transferring energy released by nuclear fission. Since this cooling water flows from below to above the fuel assembly 14 at a considerable flow velocity, the fuel assembly is subjected to a force that lifts it from the lower core plate 13. Therefore, in order to stably hold the fuel assembly 14, it is necessary to press the fuel assembly 14 downward.

Therefore, the upper nozzle 15 of the fuel assembly 14
has a nozzle spring on the upper surface of its main body, and by pressing the upper core plate 12, the fuel assembly 14 is pressed and fixed to the lower core plate 13.

Conventionally, this upper nozzle 15 has a configuration as shown in FIGS. 9 and 10. The upper nozzle 15 has an upper nozzle body 20 in the shape of a regular quadrangular prism that is approximately square in plan view. The square-shaped upper surface of the upper nozzle main body 20 is provided with a recessed portion 22 at its center, leaving a peripheral portion 21.

In such an upper nozzle main body, the main nozzle spring 2 is attached to the side portion 21a of the peripheral portion 21.
3 is provided. This main nozzle spring 2
3 is made of a leaf spring, and the side portion 2
Attach the screw 2 to one end of 1a via the clamp member 24.
5 and the base 23a fixed by the base 2
A spring portion 23 formed to protrude upward from 3a toward the other end of the side portion 21a.
b, and a guide portion 23c that is then bent and extended downward. This guide part 23
c is fitted into a hole 26 provided on the other end side of the side portion 21a, and the main nozzle spring 23
guides the peripheral portion 21 so that it does not shift inward or outward. The main nozzle spring 23 is configured to generate an upward pressing force by bending the spring portion 23b downward.

On the other hand, a sub nozzle spring 27 is provided below the main nozzle spring 23.
This sub-nozzle spring 27 has the side portion 21a
The base 2 of the main nozzle spring 23 is attached to one end of the main nozzle spring 23.
Clamp member 24 and screw 25 are stacked on the underside of 3a.
a base 27a fixed by a base 27a;
A spring portion 27 is provided to protrude upward from 7a toward the other end of the side portion 21a.
It has b. And this spring part 2
A guide hole 27c is provided at the tip of the main nozzle spring 23.
c, and guides the sub nozzle spring 27 so that it does not shift. When the spring portion 23b of the main nozzle spring 23 is bent downward, the sub nozzle spring 27 comes into contact with the spring portion 27b of the sub nozzle spring 27, thereby increasing the upward pressing force.

The main nozzle spring 23 and the sub nozzle spring 27 are provided on each side 21a of the peripheral portion 21, respectively. The main nozzle spring 23 and the sub nozzle spring 27 have their respective bases 23a and 27a.
It is arranged so as to be located at two inner diagonal corners of the four corners of the peripheral portion 21 .

Of the four corners of the peripheral portion 21, positioning holes 28, 28 are provided downward in the corners other than the corners where the base portions 23a, 27a are located. The upper nozzle 15 is positioned by fitting into a guide pin provided on the upper core plate 12.

Further, a large number of through holes 29 are provided at the bottom of the recess 22 to allow cooling water to pass therethrough.

"Problems to be Solved by the Invention" However, in the case of the upper nozzle 15 as described above, since the nozzle spring is an elastic body with one end fixed and the other end free, the pressing force of the spring is weak. There was a problem. Further, for this reason, it is necessary to provide a sub-nozzle spring to increase the pressing force, resulting in a problem of high cost. Furthermore, since the clamp member is fixed to the upper nozzle body with a screw, there is a risk that the clamp may come loose if the screw is damaged.

"Objective of the Invention" An object of the present invention is to provide an upper nozzle having an elastic member with improved pressing force.

"Structure of the Invention" The present invention provides an elastic member formed in a substantially V-shape, with a central portion thereof protruding upward relative to both end portions, and at least one of the two end portions extending above the two end portions. The structure is such that it is attached to the upper nozzle body so that it can be slid in the tying direction.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 6. In addition, in these figures, the same reference numerals are given to the parts having the same configuration as those of the conventional example, and the explanation thereof will be omitted.

1 and 3 are diagrams showing an upper nozzle 3 according to the present invention. The upper nozzle 3 has an upper nozzle main body 31 in the shape of a regular quadrangular prism, which is substantially square in plan view, as in the conventional example. A recess 33 is provided in the center of the square-shaped upper surface of the upper nozzle main body 31, leaving a peripheral portion 32.

At both ends of each side 32a of the peripheral portion 32,
End grooves 34, 34 are provided. This end groove 34 is for engaging both ends of a substantially V-shaped elastic member, and has a U-shaped cross section as shown in FIG. It is set in. Further, this end groove 34 is formed deeper toward both ends of the side portion 32a, and a lid body is engaged with a portion of the opening edge formed in the longitudinal direction of the side portion 32a. A step portion 34a is provided for the purpose.

An elastic member 35 is provided in such an end groove 34. The elastic member 35 is formed by forming a spring material having a circular cross section into a substantially V shape.
A V-shaped elastic member main body 35b consisting of two legs 35a, and engaging parts (both ends) 35c protruding outward from both ends of the elastic member main body 35b within a plane including the elastic member main body 35b. It is composed of.

Such an elastic member 35 is disposed such that engaging portions 35c, 35c at both ends thereof are engaged with the end grooves 34, 34. At this time, this elastic member 35
, when no external force is applied, the engaging portions 35c at both ends engage the side portion 3 within the end groove 34.
It is formed so as to be located at the center side of 2a.
Then, in a state in which the engaging portion 35c of the elastic member 35 is engaged with the end groove 34, a lid 3
6 is engaged with and welded to the step portion 34a.

Such an upper nozzle 3 is incorporated into the fuel assembly 14 and installed between the upper and lower core plates 12 and 13. At this time, the upper nozzle 3
5 is pressed downward by the upper core plate 12, and the two V-shaped legs 35a, 35a are elastically deformed to spread outward. This creates an upward pressing force.

In this way, for this upper nozzle 3, V
The leg portion 35a that is elastically deformed is attached to the letter-shaped elastic member 35.
Since there are two of them, the upward pressing force can be strengthened. Further, since no clamp member, screw, etc. are required to fix the elastic member 35 to the upper nozzle main body 31, the number of parts can be reduced. In addition, in this upper nozzle 3, the upper end protrusion of the elastic member 35 is connected to the upper core plate 1 at four points.
Because it comes into contact with the fuel assembly 1
4 can be held stably.

Next, FIGS. 4 to 6 show an upper nozzle 4 which is another embodiment of the present invention.
This upper nozzle 4 also has an upper nozzle main body 41 similarly to the upper nozzle 3 described above. This upper nozzle body 41 is the same except that a central groove 42 is provided in the center of the side portion 32a of the upper nozzle body 31. This central groove 42 is for engaging the center part of the elastic member having a substantially W shape, and has a U-shaped cross section as shown in FIG.
It is provided in the longitudinal direction of the side portion 32a. This central groove 42 is formed so that it is deepest at the center in the longitudinal direction and becomes shallower toward both ends, and, like the end groove 34, the central groove 42 is formed in the longitudinal direction of the side part 32a of the opening edge. The formed portion is provided with a stepped portion 42a for engaging the lid.

Elastic members 43 are provided in the end grooves 34 and the central groove 42 of the upper nozzle main body 4. This elastic member 43 is formed by forming a spring material having a circular cross section into a substantially W-shape, and has four leg portions 43.
A W-shaped elastic member main body 43b consisting of a W-shaped elastic member main body 43b, and engaging parts (both end parts) 43c protruding outward from both ends of the elastic member main body 43b within a plane containing this elastic member main body 43b. ing.

Such an elastic member 43 has engaging portions 43c at both ends engaged with the end grooves 34, 34, and bent portions (both end portions) 43d at the center thereof engaged with the central groove 42. It is arranged. On this occasion,
Similar to the elastic member 35, this elastic member 43 is formed such that the engaging portions 43c at both ends thereof are located on the central groove 42 side within the end groove 34 when no external force is applied. There is. The engaging portion 43c of the elastic member 43 is engaged with the end groove 34 by the lid body 36, similarly to the engaging portion 35c of the elastic member 35. In addition, the bent portion 4
3d is engaged with the central groove 42, and a lid body 44 is engaged with and welded to the step part 42a, with the bent part 43d being locked, at the center of the central groove 42. Ru.

In such an upper nozzle 4, when the upper end protrusion of the elastic member 43 is pressed downward, the four W-shaped legs 43a, 43a, 43a, 43a are elastically deformed so as to spread outward. This creates an upward pressing force.

In this way, in this upper nozzle 4, W
A leg portion 43a that is elastically deformed is attached to the letter-shaped elastic member 43.
Since there are four of them, the upward pressing force can be greatly increased. Further, since no clamp member, screw, etc. are required to fix the elastic member 43 to the upper nozzle main body 41, the number of parts can be reduced. Also, regarding this upper nozzle 4,
Since the upper end protrusion of the elastic member 43 comes into contact with the upper core plate 12 at eight points, the fuel assembly 14 can be stably held.

Although four elastic members 43 are provided in the upper nozzle 4, the present invention is not limited to this, and two elastic members 43 may be provided on two opposing sides 32a. . Even in this case, it is possible to contact the upper core plate 12 at four locations, and the fuel assembly can be stably held.

In the above embodiment, the elastic member is formed of a spring material having a circular cross section, but it is not limited to this, and may be formed of a spring material having a rectangular cross section.

"Effects of the Invention" As explained above, according to the present invention, the elastic member is formed into a substantially V-shape, and the center part of the elastic member projects upwardly with respect to both ends, and Since at least one of the springs is attached to the upper nozzle body so as to be movable in the direction connecting the two ends, the pressing force of the elastic member can be improved. Since screws are not used, there is an advantage that damage to the screws and separation of the clamp member will not occur.

[Brief explanation of drawings]

1 to 3 are views showing one embodiment of the present invention, in which FIG. 1 is a partially cutaway front view thereof, FIG. 2 is a plan view thereof, and FIG. 3 is a line taken along the line in FIG. 4 to 6 are views showing other embodiments of the present invention, in which FIG. 4 is a partially cutaway front view, FIG. 5 is a plan view, and FIG. Figure 5 is a cross-sectional view showing the nuclear reactor;
Figure 8 is a partially cutaway front view showing the fuel assembly;
1 and 10 are views showing a conventional upper nozzle, with FIG. 9 being a partially cutaway perspective view thereof, and FIG. 10 being a partially cutaway front view thereof. 3... Upper nozzle, 4... Upper nozzle, 14...
...Fuel assembly, 31... Upper nozzle body, 32...
...Peripheral part, 35...Elastic member, 35c...Engaging part (both ends), 41...Upper nozzle main body, 43...Elastic member, 43c...Engaging part (both ends), 43d...
...Bent part (both ends).

Claims (1)

[Claims] 1. In an upper nozzle of a fuel assembly in which an elastic member for pressing the fuel assembly downward is provided on the periphery of the upper surface of the upper nozzle main body, the elastic member is formed into a substantially V-shape, and the elastic member is , an upper nozzle that is attached to the upper nozzle main body so that its central portion projects upwardly relative to both ends, and at least one of the ends is movable in a direction connecting the both ends. .