JPS5842993A - Press torsion spring - 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 The present invention provides I! Pressing spring device K for fixing the atomic core (core) K fuel assembly to #
WIJ.

Normally, a nuclear reactor for power generation has an upward f! It has a core of material to be split to heat the cooling water flowing through it. The fissile material is stored in a large number of elongated fuel rods arranged and assembled into a square cross-section, generally called a fuel assembly.
l! It is wrapped in 1 bag. The fuel rods are held parallel and spaced apart by several spanner rods spaced along the length of the assembly. Furthermore,
The fuel assembly has upper end fittings provided at its top and bottom.

and held in alignment by a core grid plate mated to the lower end inset.

Typically, a presser spring device is provided between the upper end insert and the upper core grid plate to provide sufficient holding force to counteract the hydraulic press-up force within the core.

This spring allows for axial elongation of the fuel assembly due to differential thermal expansion or irradiation induced material expansion. Therefore, the design problem is whether it is possible to maintain sufficient holding down force to counteract the pushing up force, yet still provide sufficient room for elongation. Moreover, the stiffness/volume efficiency of the spring, which requires sufficient material strength and stiffness within a certain limited volume, is extremely important when used as a holding device in the nuclear reactor sector.

Currently, there are two types of springs used as holding devices for fuel assemblies: the helical tm and the leaf spring type. The amount of m is also common. Rice!
No. 141 No. 4072.562 discloses a single torsion type tortoise force i, but a reactor Kltj of the configuration 11 has never been used.

The helical spring has a stiffness of 71! if the spring is placed at the center of the upper ditch member of the assembly where the maximum available space volume exists. One of the drawbacks of the 10-engine clearing method, which was intended to solve the problem of load efficiency, is that a spring must be placed in the load to allow the control rod to be moved in and out.

Since the spring is completely exposed to the flow of cooling water, it may be subject to dynamic stresses such as sand-induced vibrations caused by the flow.

There is one nuclear car manufacturing company that uses a leaf spring type holding device, but this type is limited in pressure transfer and cannot sufficiently absorb the axial elongation of the fuel rod. Since the fuel assembly cannot be elongated by horizontal firing, it is difficult to elongate the fuel assembly.
In addition, the leaf springs must be stacked one on top of the other in order to obtain sufficient holding force.

A screwdriver type spring is an extremely efficient device. For springs of the same weight, a screwdriver can store four times as much energy as a screwdriver under the stress of Oka et al. The disadvantages of using L-shaped and screw-shaped pars are:
The problem is that sufficient dimensions are not available within the fuel assembly to allow sufficient e*feng of the par. Normally, the shear area of a fuel assembly is only 2.5 billion angles, so the dimension of the screw arm is set to be 11 times less than elm (2al damage).

If the length of the threaded par is limited to 8 inches (2 (Lsaz) or less), and if the diameter of the par is made large to provide sufficient holding force, such a thick par will cause the axis of the fuel rod to t-112ff sufficient to absorb the elongation in the direction
Can't twist.

The present invention overcomes the conventional double-pack torsion-type compression spring by providing a double-pack torsion-type compression spring consisting of a screw par with an actuating lever arm and a screw sand tube mounted over the torsion par and connected to the torsion par at one end. This device overcomes the above-mentioned drawbacks of the device. The spring device of the present invention is assembled by inserting a solid rod (screw bar) into a torsion tube, and the screw bar and the screw sand tube are connected by a connecting member interposed between them. . The connecting member may be an integral part of the threaded sand pipe or may be a part of the printing section. It is twisted around the constructed restraint (fixation) member.

According to the invention, at least two major problems are solved. One is the problem with the conventional single-par twisted par structure K11l. In the case of a single par-type threaded spring, its thread #) flexibility (capable amount of thread sand) is determined by the length of the spring that meets the thread that fits into the end fitting structure of the fuel rod assembly. According to the present invention,
The shortcoming of the torsion spring is overcome by inserting a torsion tube centrally on the outside of the screw bar, thereby doubling the effective length of the torsion spring within the same length dimension. . This increases the torsion angle of the entire torsion spring, and therefore lengthens the stroke of the lever arm (the travel distance in the direction in which the fuel rods are attached). Therefore, not only does the pressing force of the screw spring against the fuel assembly become large, but also the screw spring is tightened between the upper and lower grid plates.
:The degree of elasticity that allows axial extension due to stroke etc. is greater than that of a conventional single par spring by the increase in the above-mentioned stroke, and this increase in stroke also
A second problem solved by the present invention, which also overcomes some of the drawbacks of conventional leaf spring type pressers, is the problem of flow-induced vibrations associated with conventional helical springs.

A helical spring is like a cylindrical body that crosses the flow of cooling water, and vibrates when affected by eddies and turbulence. This vibration causes fatigue of the material of the spring, causing wear at the contact area between the coils of the spring.

Because the double pack torsion parr type spring of the present invention is largely enclosed from the flow of cooling water, substantially no flow induced vibration problems occur.

One of the advantages of the present invention is that it avoids the need to use a wrap spring when a longer stroke than a leaf spring is required. Screw springs do not have the disadvantages of helical springs mentioned above.

Another advantage of the torsion spring of the present invention is that it can be manufactured in a conventionally equipped machining shop using special spring winding equipment.

Additionally, the use of threaded springs allows for modifications to be made to the upper end insert that are not possible in the case of helical springs, allowing for a reduction in pressure drop to be achieved. , it is possible to change the end fittings in the field.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a presser spring for a nuclear reactor fuel assembly, in particular a threaded press spring tube with a long effective length.

The scope and other objects, features and advantages of the present invention will become more clearly understood from the following description made with reference to the accompanying drawings. Niro.

Referring to FIG. 1, a nuclear fuel assembly is shown consisting of a number of fuel rods 11 having a longitudinal axis 1512.

These fuel rods 11 are arranged in the core of the reactor between the lower core grid # (not shown) and the upper core grid 1 [15] and are in the form of a generally square framework with the base grid 14. 4 pieces 10 fitted at the upper end (see 4 in Figure 2)
e' held parallel to each other and spaced apart by K
[1! The lever arm 21 of each spring device, which has a hole for receiving the input body fot-I,! ! , 23.24 (
(see also FIG. 2) has four projections 16 each aligned with the lever arm so as to depress the lever arm (see also FIG. 2). FIG. 2 is a top view of the end fitting body 1o.

The relative positional relationship of arms 21% 22.25.24 is seen.

Referring again to FIG.
It is shown.

The spring 1s includes a torsion tube 26 and a threaded parser 2s disposed inside the tube and having one end attached to the tube 26' via a connecting member 2a. A bushing 3° having a spline 29 is fixed to the other end of the tube 26. The pusher 36 has a receiving hole 31t for receiving the par 25. A spline slot s1 is formed at the open end of the hole 17 to receive a spline 29 of the push unit. The lever arm 22 is elongated at right angles to the par 2591 ('c), and when the lever arm is pushed down by the protrusion 14IC, the par 25# and the tube 24 are twisted. In order to receive the axial force of the reactor and transmit the axial force to the fuel assembly,
! i7 is provided.

Referring to FIG. 3, an enlarged view of spring 15 is shown. The threaded hole 25 inside the threaded pipe 24 is.

The pipes 26VC are connected by a connecting member 27.

FIG. 4 is a cross-sectional view showing the connecting member 27 having a hole 33 located at the protruding end 28Kf of the hole 25. As shown in FIG.

The hole 3s and the end portion 2B have a detent shape that prevents relative rotation therebetween. In the preferred embodiment shown in FIG. 5, the holes 35 and 38 are square and glossy, while in the preferred example shown in FIG. 7, end 2 of par 25
Grooved hole s6 for receiving spline 32 provided in 11
is formed. FIG. 4 shows a welded portion 40 for fixing the connecting member 27 to the threaded pipe 24.

When using, lever arm 21.22,! Tomb.

When 24 is pressed down, the pressing movement is fixedly connected by the connecting member 27! 1" is resisted by the thread forming spring force generated by the twisted par 25 and the twisted pipe z'4t6'=twisted (twisted 11) K. The twisted pipe!6 is
As previously mentioned, the bushing is held against twisting by the spline 29 received in the slot 51 of the end fitting body 10. The axial force applied to the fuel rod 11 by depression of the lever arm is transmitted to the fuel assembly via the block 57.

Torsion part in which four mutually opposed springs 1s oppose each other) tII! on the material aggregate, their thread-second knots cancel each other out to zero.

FIG. 7 shows yet another embodiment, in which an arm is projected through a slot s4 from a presser droplet (not shown) disposed in the upper part of the end fitting body 10. Use I5. Upward: Press down Agelid 1s, *rise 16
is the arm is<ass, and the arm 3s is the slope 1 of the lever arm 2.
? il (pressure contact)

When arm 5s pushes arms 2 and 6 down to position K shown by provisional **, it will impulse along % II True 199711, so
When the arm 211 is straight, the movement distance of the arm ss can be made longer than when the arm 211 is straight. That's k seconds, twist par 2s
and screw sand pipe! As the material for 6, it is possible to use horsetail wood, which has a high degree of rigidity.

Although the present invention has been described above with reference to examples, the present invention is not limited to the structure and shape of the embodiments illustrated herein, but rather departs from the spirit and scope of the invention. It will be apparent to those skilled in the art that many different embodiments are possible and that various changes and modifications can be made without any modifications.

[Brief explanation of the drawing]

Figure 1 is a partially cutaway elevational view of the upper end fitting member of a fuel assembly using the compression spring device of the present invention, and Figure 2 is a partially cut away elevational view of the upper WWJ and base of the end fitting member in Figure 1. The figure is a perspective view of the double pack screw fryer of the present invention, and FIG. 4 is a line 4-- in FIG.
4KiB is attached, Figure 5 is a schematic diagram of the twisting machine in Figure 3, No. 41!1 is a schematic diagram of a screw machine of another embodiment,
FIG. 7 is an elevational view of another embodiment of the screw sash. 10: Upper end fitting body 1s: Torsion spring 14: Subesag νtsudo 15: Upper grid plate 16: Collection and delivery 17: Hole 1! : Inclined surface 21 Nile lever arm 25: Screw cutting bar 26: Screw sand pipe 27: Connecting member 30: Push FIG, 1 -523 1

Claims (1)

[Scope of Claims] 1) An upper grid plate, a lower grid plate, an upright protruding from the center of the upper grid plate, and an end fitting body; an apparatus for receiving axial forces in a nuclear reactor having a fuel assembly disposed between a threaded sand pipe fixedly connected to the end fitting; a lever arm inserted coaxially into the tube and connected to the screw tube at one end; a lever arm extending approximately perpendicular to the screw tube and connected to the other end of the screw tube; at least 1 with
A device comprising two torsion springs arranged so that the torsion nozzle 1 and the lever arm are biased against the projection. 2) The threaded spring is provided with 411, each threaded spring being arranged to align its torsion tube and threaded spring parka parallel to the corresponding side edge of the end fitting. An apparatus according to claim 1. S) The connection between one end of the threaded parr and the threaded pipe is made through a connecting member that is in contact with one end of the twisted pipe KfII, and the connecting member has a hole for receiving one end of the twisted parr. The patent claims that the hole has a shape that prevents relative rotation between the torsion par and the connecting member! The apparatus described in Section 2 of the ll-kan. 4) The device according to claim 3, wherein the front threaded tube is disposed in a receiving hole formed in the end fitting. 5) A pusher is fixed on the other end of the screw 1 tube.
5. The apparatus of claim 4, wherein said pusher has at least one centrally extending spline and said receiving hole has a slot for receiving said spline. 6) The end fitting has a plurality of slots in the axial direction, and the arms of the presser ring extend through each of the slots so that the presser ring can be inserted into the presser ring. 6. The device according to claim 5, wherein the arm is arranged so as to be in contact with an inclined WK provided on the lever arm.