JPH09257979A - Control rod cluster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce generation of risk of work at the time of producing control rod cluster and prevent generation of interboundary corrosion and clutter by forming a recess at a part of an upper end plug inserted in a sleeve, and caulking the sleeve in this recess. SOLUTION: A recess 8 having two parallel flat surfaces is formed on the circumferential surface of cylindrical upper end plug 5 inserted into a sleeve 4 of a finger 3. Fitting the sleeve 4 in the recess 8 and caulked it from the outside by an exclusive jig, thereby carrying out the turning-stop of thread connection of spider 1 and each control rod 2. In each control rod cluster, the trunhing stop of thread of the rod 2 is carried out by caulking 9 of the sleeve 4 to the recess 8 of the upper end plug 5, thereby dispensing with boring work after the connection of the control rod 2, pin work and welding work, leading to restraining of work risk at the final stage to the minimum and prevention of generation of ineterparticle corrosion or craking in stainless steel caused by the welding.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a control rod cluster used in a pressurized water nuclear power plant.

[0002]

BACKGROUND OF THE INVENTION Pressurized water nuclear power plants use control rod clusters (RCCs) to control and shut down nuclear reactors. The control rod cluster is inserted into and withdrawn from the fuel assembly along a thimble tube provided in the fuel assembly.

The control rod cluster has, for example, a spider 1 as an upper structure and a large number of elongated rod-shaped control rods 2 as shown in FIG. The upper end plug 5'of the control rod 2 is attached to the sleeve 4.
And insert the upper end plug 5'upper end male thread 6
Is assembled by being screwed into the female thread portion 7 at the back of the sleeve 4.

During operation of the nuclear reactor, the reactor internals are repeatedly vibrated by the effect of cooling water flowing,
In order to prevent the control rod 2 from falling out of the spider 1 due to vibration of running water, a pin 10 for preventing the screw from rotating is welded to the control rod cluster as shown in FIG.

[0005]

The pin 10 for preventing rotation is attached after the finger 3 of the spider 1 and the upper end plug 5'of the control rod 2 are screwed together. As shown in FIG. 3, a hole 11 common to the sleeve 4 of the finger 3 and the upper end plug 5'is made by machining, and the hole 11 is fitted into the hole 11 and then welded to the sleeve 4 (1
2 indicates a welded portion).

In this case, since drilling machining or welding work is required after the spider and the control rod are coupled, the processing risk is inevitably increased, and the welding also causes a thermal effect on the stainless steel of the spider. There is a possibility of intergranular corrosion of the welded portion and a possibility of cracking in the welded portion. Since the above-mentioned screw detent is performed at the final stage of manufacturing the control rod cluster, it is particularly necessary to minimize the processing risk.

The present invention has been made to cope with such an actual situation, and by finding a new structure for the above-mentioned screw rotation stopper, the processing risk at the time of manufacturing the control rod cluster is reduced, and the intergranular corrosion and cracks are generated. The purpose is to prevent the above.

[0008]

That is, the feature of the present invention which meets the above-mentioned object is to have a spider and a control rod as described above, and to insert the upper end plug of the control rod into the sleeve below the finger of the spider. Then, in the control rod cluster in which the screw part at the upper end of the upper end plug is connected to the screw part at the back of the sleeve, a recess is formed in a part of the upper end plug inserted into the sleeve, and the sleeve is caulked into the recess. It is in.

[0009]

In the control rod cluster of the present invention described above, since the screw of the control rod connecting portion is prevented from rotating by caulking the sleeve into the recess of the upper end plug, the conventional control rod connecting portion is drilled and the pin is formed. Processing and welding are not required, and intergranular corrosion and cracking can be prevented.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

FIG. 1 (A) is a partial sectional view showing a connecting portion between a control rod and a spider of a control rod cluster according to an embodiment of the present invention,
FIG. 2B is a sectional view taken along line XX of FIG. 2A, and FIG. 2 is a front view showing the upper part of the control rod cluster.

As shown in FIG. 2, the control rod cluster of the above embodiment has an upper structure spider 1 and a large number of elongated rod-shaped control rods 2. As shown in FIG. The upper end plug 5 of the control rod 2 is inserted into the sleeve 4 below the finger 3 and the male screw portion 6 at the upper end of the upper end plug 5 is screwed into the female screw portion 7 at the back of the sleeve 4. are doing.

In the embodiment of the present invention, as shown in FIGS. 1A and 1B, the sleeve 4 of the finger 3 is used.
On the peripheral surface of the cylindrical upper end plug 5 inserted in the above, two flat recesses 8 which are parallel to each other are formed, and the sleeve 4 is caulked from the outside with a dedicated jig. Thus, the screw connection between each control rod 2 and the spider 1 is prevented. In the figure, reference numeral 9 denotes a caulking portion of the sleeve 4, but in this case, the maximum diameter of the sleeve 4 of the finger 3 is kept within a range not deviating from the machining tolerance even by the caulking.

In the control rod cluster according to the embodiment of the present invention, however, since the screw of the control rod 2 is prevented from rotating by the caulking 9 of the sleeve 4 with respect to the recess 8 of the upper end plug 5, the conventional control is performed. Drilling after rod connection,
Pin processing and welding are not required, and it is possible to minimize the processing risk in the final stage and prevent the intergranular corrosion and crack generation of stainless steel due to welding.

The embodiment of the present invention has been described above.
The shape of the recessed portion 8 of the control rod upper end plug 5 can be appropriately changed to, for example, a bowl-shaped depression or a vertical groove shape.

[0016]

As described above, according to the control rod cluster of the present invention, in the control rod cluster in which the spider and the control rod are screwed together, a recess is formed in a part of the upper end plug inserted into the sleeve of the finger of the spider. Since the sleeve is swaged in this recess as well as formed, the rotation of the threaded connection of the control rod is prevented by swaging the sleeve with respect to the recess of the upper end plug. Since machining, pin machining and welding are not required, the risk of machining at the final stage of control rod cluster manufacturing is minimized, and the intergranular corrosion and crack generation of stainless steel due to the above welding are also prevented, which is a remarkable effect. It is a thing.

[Brief description of drawings]

FIG. 1A is a partial cross-sectional view showing a connecting portion between a control rod and a spider of a control rod cluster according to an embodiment of the present invention. (B) It is the XX sectional view taken on the line of FIG.

FIG. 2 is a front view showing an upper portion of a control rod cluster.

FIG. 3 is a partial cross-sectional view showing a connecting portion between a control rod and a spider of a conventional control rod cluster.

[Explanation of symbols]

 1 Spider 2 Control Rod 3 Finger 4 Sleeve 5 Upper End Plug 6 Male Thread 7 Female Thread 8 Recess 9 Caulking

Claims (1)

[Claims] 1. A control rod having a spider and a control rod, wherein an upper end plug of the control rod is inserted into a sleeve below a finger of the spider, and a threaded portion at an upper end of the upper end plug is coupled with a threaded portion at the back of the sleeve. In the cluster, a control rod cluster is characterized in that a recess is formed in a part of an upper end plug inserted into the sleeve, and the sleeve is caulked in the recess.