JP2002350586A - Tube expander and assembling method for fuel assembly thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fuel assembly with small distortion after assembling and good dimensional accuracy. SOLUTION: A tube expander body 20 is put on a floating table 32 put on a moving table 31. After positioning the moving table 31 by stopping, a floating lock 33 is released and the floating table 32 is made movable in the axial direction of the control rod guide tube 8 so that the tube expander 20 is supported movably in the axial direction of the control rod guide tube 8 and simultaneously operated to expand a tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for assembling a fuel assembly, and more particularly to a method for connecting a sleeve previously fixed to a support grid and an upper nozzle to a control rod guide tube by an expanding operation. And a method for assembling a fuel assembly using the same.

[0002]

2. Description of the Related Art As a fuel assembly of this type, there is one generally described in, for example, Japanese Patent Application Laid-Open No. 6-308267. In this fuel assembly 10, as shown in FIG. 3, the upper nozzle 1 and the lower nozzle 2 are arranged at predetermined intervals.
A plurality of support grids 3 are disposed at predetermined intervals between the nozzles 1 and 2, a sleeve 4 is provided on the upper nozzle 1, a sleeve 5 is provided on the support grid 3, and a lowermost support grid 3 is provided.
The insert 6 is fixed to each of them in advance. A large number of fuel rods 7 are inserted and supported in the lattice space of each support lattice 3. The control rod guide tube 8 is connected to the upper nozzle 1
And the lower nozzle 2, is inserted into the grid space of the support grid 3, and is connected to the support grid 3. For example, the control rod guide tube 8 is fitted to the sleeve 4 of the upper nozzle 1 and the sleeve 5 of the support grid 3 and is fixed by a tube expansion (bulge) operation, and tube expansion portions A and B are provided.

[0003] By the way, in the pipe expanding operation for forming such pipe expanding sections A and B, for example, a pipe expanding apparatus as shown in an enlarged sectional view of a main part of FIG. 4 is used. The tube expansion device main body 20 includes a plurality of crimp dies 21 each having a substantially cylindrical shape and having a substantially cylindrical tapered pin 23 inserted into an inner periphery thereof so as to project in parallel in the same direction. . The crimp die 21 has a base end connected to and fixed to the tube expansion device main body 20 and a distal end portion formed in a spring plate shape divided into a plurality of pieces along the axial direction. A convex portion protruding radially outward is formed to form a tube expanding die 22. Also,
The base end of the taper pin 23 is connected to and fixed to the main body 20 of the expansion device, but can be moved in the axial direction (relative movement with the crimp die 21) by a double-acting cylinder or the like. A tapered portion 24 is formed which gradually increases in diameter as it goes to the side. Such a pipe expansion device main body 20 is placed on a moving table, and positioning of a position where the pipe expansion section is formed is performed by moving the moving table.

In order to perform the pipe expanding operation, first, the moving table is moved so that the crimp dies 21 and the taper pins 23 of the pipe expanding apparatus main body 20 are moved to the respective control rod guide pipes 8.
And the tube expanding die 22 of the crimp die 21 is positioned at a position where the tube expanding portion B (A) is to be formed. Then, by retracting the taper pin 23 by a double-acting cylinder or the like, the taper portion 24 of the taper pin 23 pushes the pipe expanding die 22 radially outward, and thereby the sleeve 5 of the support grid 3 (the sleeve 4 of the upper nozzle 1). ) And the control rod guide tube 8 are locally pushed outward in the radial direction to form the expanded portion B (A).

[0005]

Here, in the conventional pipe expanding apparatus, during the pipe expanding operation after the positioning of the pipe expanding apparatus main body 20 by the moving table is completed, the pipe expanding apparatus main body mounted on the moving table is required. 20 is fixed at a fixed position, that is, there is no deviation from the position where the position of the tube expanding die 22 is positioned. In addition, both ends of the control rod guide tube 8, the support grid 3, and the upper nozzle 1 are also fixed to a base or the like. Therefore, when the pipe expansion operation is performed in this fixed state, the expansion section B (A) at the fitting portion between the sleeve 5 of the support lattice 3 (the sleeve 4 of the upper nozzle 1) and the control rod guide pipe 8 is formed. As shown in the schematic diagram of FIG. 5, an excessive stress R is applied along the axis O of the control rod guide tube 8. Thus, in the fuel assembly 10 assembled while the excessive stress R is applied, the support grid 3 and the upper nozzle 1
Misalignment occurs, mounting accuracy deteriorates, and the fuel assembly 10
However, there has been a problem in that distortion occurs and dimensional accuracy varies. On the other hand, an excessive tensile stress is also applied to the pipe expansion device main body 20, and as a result, the crimp die 21 may be deformed or, in severe cases, the crimp die 21 may be broken.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a pipe expanding apparatus capable of assembling a fuel assembly with less distortion after assembly and good dimensional accuracy, and a method of assembling a fuel assembly using the same. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems,
In order to achieve such an object, the tube expansion device of the present invention includes a sleeve previously fixed to a support grid or an upper nozzle and a control rod guide tube fitted to the sleeve when assembling the fuel assembly. In a tube expanding device to be connected by a tube expanding operation, the tube expanding device main body is supported so as to be movable in the axial direction of the control rod guide tube during the tube expanding operation. Further, according to the method for assembling a fuel assembly of the present invention, the control rod guide tube is fitted to a sleeve previously fixed to the support grid or the upper nozzle, and the expansion device main body is moved in the axial direction of the control rod guide tube. It is characterized in that the tube expanding operation is performed while supporting the tube as much as possible. According to the present invention, during the pipe expansion operation, the pipe expansion device main body is supported so as to be movable in the axial direction of the control rod guide pipe, so that the stress applied to the pipe expansion section can be released, and the pipe expansion operation can be performed. Distortion in the completed fuel assembly after assembly can be reduced, and good dimensional accuracy can be maintained. Further, unlike the conventional case, an excessive tensile stress is not applied to the pipe expanding device main body.

[0008] The method of assembling a fuel assembly according to the present invention comprises:
In the step of fitting the control rod guide tube to a sleeve previously fixed to the support lattice and connecting the control rod guide tube by a tube expanding operation, the tube expanding operation is performed without fixing one end of the control rod guide tube. . According to the present invention, one end of the control rod guide tube is released, and the control rod guide tube is formed as the expanded portion is formed at the fitting portion between the sleeve of the support grid and the control rod guide tube. Since the guide tube can be contracted, the wall thickness at the expanded portion does not become thin.

[0009] The method for assembling a fuel assembly according to the present invention comprises:
In a step of fitting the control rod guide tube to a sleeve previously fixed to the upper nozzle and joining the control rod guide tube by a pipe expanding operation,
The pipe expanding operation is performed while supporting the upper nozzle so as to be movable in the axial direction of the control rod guide pipe. According to the present invention as described above, in particular, when forming the expanded portion at the fitting portion between the sleeve of the upper nozzle and the control rod guide tube, the stress applied to the expanded portion is moved by the upper nozzle and the expanding device body. In this way, the fuel assembly can be reliably released, and a fuel assembly with less distortion and higher dimensional accuracy can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. FIG. 1 is an explanatory view showing a case where a sleeve of a support grid is connected to a control rod guide tube using the tube expansion device according to the present embodiment. FIG. It is explanatory drawing at the time of joining.

As shown in FIG. 1, in the pipe expanding apparatus according to the present embodiment, a pipe expanding apparatus main body 20 having the same configuration as that of the above-mentioned prior art is placed on a floating table 32. And the floating table 32 is placed on the moving table 31. The moving table 31 is used for positioning when performing a tube expanding operation as in the related art.
Control is performed so that movement in the same direction as the direction in which each crimp die 21 and the taper pin 23 are protruded is possible, that is, the direction of the axis O of the control rod guide tube 8 when the tube expansion device is arranged at the initial position. (Left and right directions in FIG. 1). The floating table 32 is installed on the moving table 31 so as to be movable in the direction of the axis O. As a result, the pipe expansion device main body 20 placed on the floating table 32 is The control rod guide tube 8 is supported on the moving table 31 so as to be movable in the axis O direction. Except during the pipe expansion operation, the floating lock 33
Is fixed to the moving table 31.

A description will be given of a case where a sleeve previously fixed to the support lattice 3 and the control rod guide tube 8 are connected by a tube expanding operation using the tube expanding device having such a configuration. First, as shown in FIG. 1, one end (one end X) of each control rod guide tube 8 inserted and fitted into each sleeve 5 of a plurality of support grids 3 arranged at a predetermined interval. On the other hand, the tube expanding device is arranged such that the crimp dies 21 and the taper pins 23 of the tube expanding device main body 20 face each other in the direction of the axis O of the control rod guide tube 8. At this time, the moving direction of the pipe expansion device main body 20 by the moving table coincides with the axis O direction of the control rod guide tube 8. Here, each control rod guide tube 8
Is such that one end (one end X) is not fixed and is a free end, and the other end (one end Y) is fixed so as not to move. Each support grid 3 is fixed to the base.

Next, the moving table 31 is moved, and the crimp dies 21 and the taper pins 23 of the pipe expanding device main body 20 are moved.
Are inserted into the control rod guide tubes 8 fitted to the respective sleeves 5 of the support lattice 3 and the expanding die 22 is positioned at the position where the expanding portion B is to be formed. Is stopped, and the pipe expansion device main body 20 is fixed. By releasing the floating lock 33, the floating table 32 can be moved in the direction of the axis O, and the pipe expansion device main body 20 is supported so as to be movable in the direction of the axis O.

In this state, the pipe expanding operation is performed by retracting the taper pin 23, and the sleeve 5 of the support grid 3 is moved.
An expanded portion B is formed at the fitting portion between the control rod guide tube 8 and the control rod guide tube 8. At this time, since one end (one end X) of the control rod guide tube 8 is not fixed and is released, the length of the control rod guide tube 8 becomes longer as the expanded portion B is formed. Shrink. Thereafter, the taper pin 23 is advanced to release the push-out of the expanding die 22 by the tapered portion 24, and the expanding operation is completed.
3 fixes the floating table 32 so that it cannot move on the moving table 31. By repeating such operations, the sleeve 5 of the support grid 3 and the control rod guide tube 8
By connecting the fitting portions to the fixed control rod guide tube 8 sequentially from one end Y side of the fixed control rod guide tube 8 by a pipe expanding operation,
In a state where one end X of the control rod guide tube 8 is not fixed, the sleeve 5 of the support lattice 3 and the control rod guide tube 8 can be connected.

Next, a case where the sleeve 4 previously fixed to the upper nozzle 1 and the control rod guide tube 8 are connected by a pipe expanding operation will be described. First, with respect to the fuel assembly 10 mounted on the base with each sleeve 4 of the upper nozzle 1 fitted to the tip of each control rod guide tube 8, FIG.
As shown in (a), the tube expanding device is arranged such that the crimp die 21 and the taper pin 23 of the tube expanding device main body 20 face each other in the direction of the axis O of the control rod guide tube 8 (the left-right direction in FIG. 2). At this time, the moving direction of the pipe expansion device main body 20 by the moving table coincides with the axis O direction of the control rod guide tube 8.

Here, the upper nozzle 1 is connected to the pipe expansion device main body 2.
0, the upper nozzle 1 is supported so that the control rod guide tube 8 can freely move in the direction of the axis O. The floating table 41 on which the upper nozzle 1 is mounted is also fixed by the floating lock 42 except during the pipe expansion operation.

Next, as shown in FIG. 2B, the moving table 31 is moved so that the pipe expansion device main body 20 is moved.
The crimping die 21 and the taper pin 23 are inserted into the control rod guide tube 8 fitted to the sleeve 4 of the upper nozzle 1, and the expansion die 22 is positioned at the position where the expansion portion A is to be formed. After that, the moving table 31 is stopped, and the pipe expansion device main body 20 is fixed. By releasing the floating locks 33 and 42, the floating table 32 can be moved on the moving table 31 and the floating table 41 can be moved.
Are movably supported in the direction of the axis O.

In this state, as shown in FIG. 2 (c), the pipe expanding operation is performed by retracting the tapered pin 23, and the pipe expanding section is formed at the fitting portion between the sleeve 4 of the upper nozzle 1 and the control rod guide pipe 8. A is formed. Thereafter, as shown in FIG. 2D, the taper pin 23 is advanced to
4. The pushing of the tube expanding die 22 by the tube 4 is released to end the tube expanding operation, and the floating table 32 on which the tube expanding device main body 20 is mounted by the floating lock 33 again.
Are fixed so that they cannot move on the moving table 31, and the floating lock 42 fixes the floating table 41 on which the upper nozzle 1 is mounted so as not to move. Thus, the support grid 3 and the upper nozzle 1
The fuel assembly 10 in which the sleeves 5, 4 previously fixed to the control rod guide tube 8 and the control rod guide tube 8 are connected by a pipe expanding operation is completed.

When the expanded portion A is formed in the fitting portion between the sleeve 4 of the upper nozzle 1 and the control rod guide tube 8 by the expanding operation, the support lattice 3 located closest to the upper nozzle 1 side. The distance between the nozzle and the upper nozzle 1 is reduced, but this can be dealt with by measuring the distance of the contraction in advance and separating the distance by that amount.

As described above, according to this embodiment, when the pipe expanding operation is performed on the fitting portion between the control rod guide tube 8 and the sleeve 5 of the support grid 3 and the sleeve 4 of the upper nozzle 1, the control is performed. Since the rod guide tube 8 is supported so as to be movable in the direction of the axis O, unreasonable stress is not applied to the formed expanded portions B and A, and the stress applied to these expanded portions B and A can be released. As a result, distortion in the assembled fuel assembly 10 after the pipe expansion operation is completed can be reduced, and good dimensional accuracy can be maintained. Also, no excessive tensile stress is applied to the pipe expansion device main body, and the pipe expansion device main body 2
It is possible to eliminate the risk of deformation or breakage of the zero crimp die 21.

Further, in the step of fitting the control rod guide tube 8 to the sleeve 5 fixed to the support lattice 3 and connecting the control rod guide tube 8 by an expanding operation, one end of the control rod guide tube 8 is released, so that the expanded tube is expanded. As the portion B is formed, the control rod guide tube can contract, so that the wall thickness of the expanded portion B does not become thin. Further, since the control rod guide tube 8 does not contract after the expansion operation is completed, the dimensional accuracy between the support lattices 3 is reduced due to the contraction of the control rod guide tube 8 after the expansion operation as in the related art. There is no going away.

Also, in the step of fitting the control rod guide tube 8 to the sleeve 4 fixed to the upper nozzle 1 and connecting the control rod guide tube 8 by a pipe expanding operation, the upper nozzle 1 is also controlled by the control rod guide pipe 8 like the pipe expander body 20. In particular, the stress applied to the expanded portion A can be reliably released, and a fuel assembly with less distortion and higher dimensional accuracy can be obtained.

[0023]

According to the present invention, during the pipe expansion operation, the pipe expansion device body is supported so as to be movable in the axial direction of the control rod guide pipe, so that the stress applied to the pipe expansion section can be released. Thus, distortion in the assembled fuel assembly after the pipe expansion operation is completed can be reduced, and good dimensional accuracy can be maintained. Further, unlike the conventional case, an excessive tensile stress is not applied to the pipe expanding device main body.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram when a sleeve of a support grid and a control rod guide tube are connected using the tube expanding device according to the present embodiment.

FIG. 2 is an explanatory diagram when the sleeve of the upper nozzle and the control rod guide tube are connected using the tube expansion device according to the present embodiment.

FIG. 3 is a side view showing a main part configuration of a general fuel assembly.

FIG. 4 is an enlarged sectional view showing a main part of a conventional pipe expanding device main body.

FIG. 5 is a schematic diagram showing stress applied during a pipe expanding operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper nozzle 3 Support grid 4 Sleeve 5 Sleeve 8 Control rod guide tube 10 Fuel assembly 20 Expander main body 21 Crimp die 23 Taper pin 31 Moving table 32 Floating table 33 Floating lock 41 Floating table 42 Floating lock O Axis line of control rod guide pipe

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shuji Yamazaki 622-1, Funaishikawa, Tokai-mura, Naka-gun, Ibaraki Pref.

Claims (4)

[Claims] 1. A pipe expanding apparatus for connecting a sleeve fixed to a support grid or an upper nozzle and a control rod guide tube fitted to the sleeve by a pipe expanding operation when assembling the fuel assembly. Is supported so as to be movable in the axial direction of the control rod guide tube during a tube expansion operation. 2. A control rod guide tube is fitted to a sleeve previously fixed to a support grid or an upper nozzle, and a pipe expansion operation is performed while supporting a pipe expansion device body movably in an axial direction of the control rod guide tube. A method for assembling a fuel assembly. 3. The method for assembling a fuel assembly according to claim 2, wherein the control rod guide tube is fitted to a sleeve previously fixed to the support grid and connected by a pipe expanding operation. A method for assembling a fuel assembly, wherein a pipe expanding operation is performed without fixing one end of a rod guide tube. 4. The method for assembling a fuel assembly according to claim 2, wherein the control rod guide tube is fitted to a sleeve fixed to the upper nozzle in advance and joined by a pipe expanding operation. A method for assembling a fuel assembly, comprising performing a pipe expanding operation while supporting the upper nozzle so as to be movable in an axial direction of the control rod guide pipe.