JPH0222714Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to an upper nozzle for a nuclear reactor fuel assembly that is provided with an elastic member for pressing the fuel assembly downward.

``Prior Art'' Generally, as shown in FIG. 7, a fuel assembly 10 loaded into a nuclear reactor has an upper nozzle 11 and a lower nozzle 12 disposed at both upper and lower ends, and a fuel assembly 10 provided between the two nozzles. A large number of fuel rods 15 are bundled and supported by a structure consisting of a control rod guide tube 13 and a support grid 14 fixed to the control rod guide tube 13.

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 fuel assembly 10 at a considerable flow velocity, the fuel assembly 10 is subjected to a force that lifts it from below.

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

Therefore, the upper nozzle 11 of the fuel assembly 10
has a nozzle spring on the upper surface of its main body, and by pressing the upper core plate of the reactor (not shown), the fuel assembly 10 is pressed against and supported by the lower core plate. .

8 to 10 are views showing the structure of this upper nozzle 11, FIG. 8 is a partially cutaway perspective view thereof, and FIGS. 9 and 10 are lines AA and B in FIG. 8, respectively. -B sectional view.

In the figure, an upper nozzle body 20 in the shape of a regular quadrangular prism having a substantially square shape in plan view has a recessed portion 22 in the center of the upper nozzle, leaving a peripheral portion 21 on its upper surface.
A main nozzle spring 23 and a sub-nozzle spring 23a are provided on the side portion 21a of the peripheral portion 21.

That is, these nozzle springs 23 and 23a
are stacked one on top of the other, and have their bases fixed to the corners of the side portions 21a with screws 25 via clamp members 24.

``Problem that the invention attempts to solve'' However, the conventional upper nozzle 11 as described above
In this case, the nozzle springs 23 and 23a are fixed to the upper nozzle body 20 by screws 25 via a clamp member 24 which is a separate member from the upper nozzle body. If the tensile force due to the reaction force of the nozzle springs 23 and 23a acts on the screw 25 and causes stress corrosion cracking or breaks due to some other cause, the nozzle springs 23 and 23a
There was also an undeniable fear that the fixation of the clamp member 24 would be immediately released or that the clamp member 24 and the like would come off.

The purpose of this invention is to provide an upper nozzle that eliminates these drawbacks.

"Means for Solving the Problems" This invention provides an upper nozzle for a nuclear reactor fuel assembly in which a plate-shaped elastic member is provided around the upper surface of the upper nozzle body to press the fuel assembly downward. A protruding portion that partially protrudes upward is formed in the upper nozzle body upper surface periphery, and this protruding portion has an extension portion that extends vertically with a gap from the upper nozzle body upper surface periphery. an engagement groove for engaging one end of the elastic member is formed by the bottom surface of the extension part and the upper surface of the upper surface peripheral part of the upper nozzle main body, and a through hole is formed in the one end of the elastic member. is formed in the extension part, a screw hole penetrating into the engagement groove from the upper surface of the extension part, a screw member for fixing the elastic member is provided in the screw hole, and the screw member is A threaded portion that is screwed into the screw hole and a tapered portion that is fitted into the through hole of the elastic member are integrally formed on the same axis, and the tapered portion has a smaller diameter than the screw hole. , the diameter of the end on the threaded portion side is formed to be larger than the through hole of the elastic member, and with this structure, the reaction force of the elastic member acts on the threaded member as a compressive force. , the possibility of stress corrosion cracking occurring is eliminated, and as a result, the elastic member can be easily and reliably fixed to the upper nozzle body.

Embodiment FIG. 1 is a partially cutaway perspective view showing an upper nozzle of a nuclear reactor fuel assembly according to an embodiment of the present invention.

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 peripheral portion (upper surface peripheral portion of the upper nozzle main body) 31.
A recess 32 is provided in the central part of the peripheral part 31, and a main nozzle spring 33 and a sub-nozzle spring 3 are provided in the side part 31a of this peripheral part 31, as will be described in detail below.
3a is fixed.

That is, two opposing corners of the side portion 31a of the peripheral portion 31 are protruded upward to form a protrusion 34.

2 to 5 are views showing the vicinity of this protrusion 34, in which FIG. 2 is an enlarged perspective view, FIG. 3 is a plan view, and FIG. 4 is a cross-sectional view taken along the - line in FIG.
FIG. 5 is a sectional view taken along the - line in FIG. 4.

In the figure, the protrusion 34 is formed with two extensions 34a that extend a certain distance along the two sides 31a and are vertically spaced apart from the top surface of the sides 31a. There is. and,
An engagement groove 34b is formed by the bottom surface of the extension portion 34a and the top surface of the side portion 31a.

In addition, wall portions 34c and 34d are left on both sides of each of the engagement grooves 34b, and
The engagement groove 3 is inserted into the extension portion 34a from the upper surface thereof.
A screw hole 34c is formed to pass through the inside of 4b.

The base portions (one end portions) of the main nozzle spring 33 and the sub nozzle spring 33a, which are stacked vertically, are inserted into the engagement groove 34b.

Through holes 33b and 33c are formed in the bases of the main and sub nozzle springs 33 and 33a, respectively, and these through holes 33b and 33c have a tapered shape that matches the tapered portion of the tapered screw (screw member) 36. is formed.

The tapered screw 36 is coaxially formed integrally with a threaded portion shaped to be screwed into the screw hole 34e and a tapered portion fitted into the through holes 33b and 33c. The diameter of the tapered portion is smaller than that of the screw hole 34e, and the diameter of the end on the screw portion side is smaller than that of the through holes 33b, 3.
3c (the maximum diameter of the through holes 33b and 33c).

This tapered screw 36 is inserted into the screw hole 34e of the extension portion 34a from its tapered portion side, and by screwing the threaded portion into the screw hole 34e, the tapered portion is inserted into the through holes 33b, 33c. . Then, the through hole 33 due to the tapered portion
b, 33c are pushed downward, and as a result, the bases of the main and sub nozzle springs 33, 33a are pushed into the engagement groove 34.
It comes to be fixed by being pressed against the upper surface of the side portion 31a in b.

Further, on the upper surface of the side portion 31a in the engagement groove 34b, a recess 3 is provided at a position corresponding to the tip of the tapered screw 36 into which the tip of the tapered portion can be inserted.
4f is provided. Therefore, the taper screw 36 is inserted into the main and sub nozzle springs 33, 33 with its tip slightly fitted into the recess 34f.
It will firmly fix the base of a.

Further, after the taper screw 36 is screwed, a locking pin 36a is attached to the head of the taper screw 36 by means such as welding.

The above embodiment has the following advantages.

That is, a corner of the upper surface peripheral portion 31 of the upper nozzle main body 30 is made to protrude upward to form a protrusion 34, and this protrusion 34 has an engagement groove in which the main nozzle spring 33 and the sub nozzle spring 33a are engaged. 34b is provided, and a part of each nozzle spring is engaged with this engagement groove 34b to be supported on the upper nozzle body, thereby making it possible to provide extremely reliable support, unlike the conventional method. There is no inconvenience that would occur if the upper nozzle body is supported by a clamp member that is a separate member.

Moreover, each of the nozzle springs 33 and 33a
Since the base of the nozzle is strongly pressed against the engagement groove 34b by the tapered portion of the tapered screw 36, the reaction force of each nozzle spring acts on the tapered screw as a compressive force, thereby preventing stress corrosion cracking or the like from occurring. Not only that, but the fixation is also strong.

Furthermore, since the nozzle springs can be attached simply by inserting the nozzle springs into the engagement grooves 34b and then screwing the tapered screws 36, the attachment work is extremely easy.

In addition, in the above embodiment, the taper screw 3
Although an example has been described in which the taper portion 6 is a straight taper type that is uniformly inclined, the present invention is not limited to this. For example, as shown in FIG. Only the portion that extends through the nozzle spring 33a may be formed into a tapered shape, and the portion that penetrates the sub nozzle spring 33a may be formed into a simple cylindrical shape.

Further, in the above embodiment, an example was given in which two leaf springs, the main nozzle spring 33 and the sub-nozzle spring 33a, were used as the elastic members, but the present invention is not limited to this, and one or three leaf springs are used. Of course, this also includes cases where the above leaf springs are used.

"Effects of the invention" As detailed above, this invention provides an upper nozzle for a nuclear reactor fuel assembly in which a plate-shaped elastic member is provided around the upper surface of the upper nozzle body to press the fuel assembly downward. In the above, a protruding portion with a part thereof protruding upward is formed on the periphery of the upper surface of the upper nozzle body, and the protruding portion extends with a gap in the vertical direction with respect to the periphery of the upper surface of the upper nozzle body. an extension part is formed, an engagement groove for engaging one end part of the elastic member is formed by a bottom surface of the extension part and an upper surface of the upper surface peripheral part of the upper nozzle main body, and an engagement groove for engaging one end part of the elastic member is formed in the one end part of the elastic member. A through hole is formed in the extension portion, and a screw hole is formed in the extension portion to penetrate into the engagement groove from the upper surface thereof, and a screw member for fixing the elastic member is provided in the screw hole, and the screw member wherein a threaded portion that is screwed into the screw hole and a tapered portion that is fitted into the through hole of the elastic member are integrally formed on the same axis, and the tapered portion is formed from the screw hole. The elastic member has a small diameter, and the diameter of the end on the threaded portion side is larger than the through hole of the elastic member, and with this structure, the reaction force of the elastic member is applied to the threaded member as a compressive force. As a result, the front elastic member can be easily and reliably fixed to the upper nozzle body without causing stress corrosion cracking or the like.

[Brief explanation of the drawing]

Figures 1 to 6 are views showing one embodiment of this invention, in which Figure 1 is a partially cutaway perspective view, Figure 2 is a partially enlarged view of Figure 1, and Figure 3 is a partially cutaway perspective view of the invention. 2
4 is a sectional view taken along the - line in FIG. 3; FIG. 5 is a sectional view taken along the - line in FIG. 4; FIG. 6 is a diagram showing another embodiment of the invention; FIG. 7 is a partially cutaway front view showing a fuel assembly, FIGS. 8 to 10 are views showing a conventional upper nozzle, and FIG. 8 is a partially cutaway perspective view thereof.
Figure 9 is a sectional view taken along the line A-A in Figure 8, and
The figure is a sectional view taken along the line BB in FIG. 8. 30... Upper nozzle main body, 31... Peripheral part (upper surface peripheral part of upper nozzle main body), 33, 33a... Main nozzle spring and sub nozzle spring constituting the elastic member, 33b, 33c... Through hole, 34
...Protrusion part, 34a... Extension part, 34b... Engagement groove, 34e... Screw hole, 36... Taper screw (screw member).

Claims (1)

[Scope of Claim for Utility Model Registration] In an upper nozzle of a nuclear reactor fuel assembly in which a plate-shaped elastic member is provided around the upper surface of the upper nozzle body to press the fuel assembly downward, the upper nozzle around the upper surface of the upper nozzle body A protruding part with a part thereof protruding upward is formed in the part, and an extension part is formed in the protruding part to extend vertically with a gap from the periphery of the upper surface of the upper nozzle body, and the extension part An engagement groove for engaging one end of the elastic member is formed by the bottom surface of the upper nozzle body and the upper surface of the upper surface peripheral portion of the upper nozzle main body, a through hole is formed in the one end of the elastic member, and the extension A screw hole penetrating into the engagement groove from the top surface is formed in the part, and a screw member for fixing the elastic member is provided in the screw hole, and the screw member is screwed into the screw hole. A threaded portion that fits into the through hole of the elastic member and a tapered portion that fits into the through hole of the elastic member are integrally formed on the same axis, and the tapered portion has a smaller diameter than the screw hole and is located on the side of the threaded portion. An upper nozzle for a nuclear reactor fuel assembly, wherein the diameter of the end portion is larger than that of the through hole of the elastic member.