JPS6312555B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for attaching and detaching a stretch tube nut of an internal pump of a boiling water nuclear reactor.

Generally, in boiling water reactors, coolant is recirculated using a recirculation pump outside the reactor pressure vessel and a jet pump inside the reactor pressure vessel, but such a recirculation system has a complex structure and the jet pump causes cavitation. Furthermore, since the piping between the reactor pressure vessel and the recirculation pump forms a boundary for the coolant, there is a problem in that a rupture of this piping may cause loss of coolant. Therefore, attempts have been made to use an internal pump that has a pump built into the reactor pressure vessel and directly circulates the coolant. As shown in FIG. 1, this internal pump has a pump main body 1 housed in a reactor pressure vessel 2, and this pump main body 1 has an interface formed in the lower mirror part of the reactor pressure vessel 2 so as to protrude inward. It is attached to the inner end of the null pump nozzle 3. This pump body 1 has a rotor shaft 4 inserted into the internal pump nozzle 3.
It is driven by a wet-type motor 5 provided outside the reactor pressure vessel 2 via the reactor pressure vessel 2. The pump body 1 consists of an impeller 1A and a diffuser 1B, each of which is removed from above the reactor pressure vessel 2. The upper end of a stretch tube 6 is engaged with the inner surface of the lower end of the diff user 1B, and the stretch tube 6 is used to fix the diff user 1B. And this stretch
A stretch tube nut 7 is screwed onto the outer periphery of the lower end of the tube 6, and by tightening this, the stretch tube 6 is pulled and the pump body 1 is fixed to the motor casing 5A.
At this time, the stretch tube nut 7 is tightened with a large torque to prevent it from loosening.
A large tension is applied to the stretch tube 6. When performing periodic inspections, etc., first stop the reactor operation, fill the reactor pressure vessel with water, fill the reactor well with water, shield the reactor pressure vessel lid, and remove the steam from the reactor pressure vessel. Remove the generator etc. Then, the internal pump is removed and its components are transported to a maintenance facility for inspection and maintenance. This internal pump removal work is performed from above and below the reactor pressure vessel 2, and the work is performed in the following order. First, remove the impeller 1A and rotor shaft 4 from above. Next, after blocking the opening of the differential user 1B to prevent reactor water from flowing out, the motor casing 5A
Drain the reactor water inside. Next, the motor 5 and the like are removed from below the motor casing 5A, and the reactor water inside the motor casing 5A is discharged. Then, stretch
Remove the tube nut 7 from below the motor casing 5A. After closing the motor casing 5A again, the operator grasped the diffuser 1B from above the reactor pressure vessel 2 and removed the diffuser 1B and the stretch tube 6. However, the stretch tube nut 7 is tightened with a large torque as described above, making it difficult to attach and detach it. In particular, when the stretch tube nut 7 is stuck, it is difficult to remove it.

Since the work of removing the stretch tube nut 7 is carried out inside the narrow motor casing 5A, it is expected that the work will be difficult under poor working conditions. As a result, inspection and maintenance take a long time, resulting in a prolonged shutdown period of the reactor and a reduction in operating efficiency. Furthermore, since the work is carried out inside the reactor containment vessel where radiation levels are high, it is not desirable for workers to enter the reactor containment vessel and perform the above-mentioned difficult work from the standpoint of radiation exposure.

The present invention has been made in consideration of the above circumstances, and its purpose is to provide a stretch tube nut for an internal pump that can automatically and easily attach and detach the stretch tube nut.
The object of the present invention is to obtain a tube nut attachment/detachment device.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. Figure 2 shows the stretch tube of the internal pump of the present invention by removing the motor, rotor shaft, impeller, etc. of the internal pump and emptying the inside of the motor casing 5A.
This shows the state in which the nut attaching/detaching device is installed. In the figure, 2 indicates the reactor pressure vessel 5A is the motor casing, 3 indicates the internal pump nozzle, and 1
B is a diffuse user, 6 is a stretch tube,
7 indicates a stretch tube nut. 8 in the figure is the mounting board and the motor casing 5
Attached to the lower flange surface of A. A stretch tube tensioning mechanism 21 is attached to this mounting board 8, and this mechanism will be explained below. A pneumatic cylinder 9, which is driven by high pressure air from the outside, is fixed to the mounting board 8, for example. A cylindrical rod extension 10 is fixed to the tip of the rod 9A of the pneumatic cylinder 9. At the top of this rod extension body 10 is a cap 1.
0A is attached to the cap 10A, and a tension body 11 is inserted through the cap 10A so as to be movable forward and backward. The upper part of the tension body 11 is provided with an engaging part 11A that screws into a spiral groove pre-cut on the lower surface of the stretch tube 6, and the lower part of the tension body 11 is provided with a gear 11B. . Further, a motor 12 driven by an external power source is housed within the rod extension body 10, and a small gear 12A is attached to the rotating shaft of the motor 12. The small gear 12A is configured to mesh with the gear 11B of the tension body 11 to transmit the rotation of the motor 5. Further, a stretch tube nut rotation mechanism 21 is attached to the upper outer periphery of the rod extension body 10A, and the structure thereof will be explained below. The upper part of the outer peripheral surface of the rod extension body 10 has a threaded portion 1.
0A is provided, and the shaft support 1 is provided below this threaded part.
0B is provided. And this screw part 10
A nut removal work body 13 is screwed into A.
This nut removal work body 13 is provided with a plurality of pins 14 as engaging portions so as to be protrusive and retractable from the top surface.
It is biased in the projecting direction by a spring 15 housed inside the nut handling work body 13. Further, a plurality of holding parts 16 made of spring steel are provided on the upper surface of the nut removal work body 13, and are configured to elastically abut on the inner surface of the stretch tube nut 7 and hold it. has been done. Furthermore, a plurality of sliding holes 13A are formed in the lower surface of the nut handling work body 13. Next, a rotating body 17 is pivotally supported on the shaft support 10B of the rod extension body 10. A sliding pin 17 is provided on the upper surface of this rotating body 17.
B... are formed and inserted into the sliding hole 13A of the nut handling work body 13. This sliding pin 17B
... is configured to be slidable so that the rotation of the rotating body 17 is transmitted to the nut removal work body 13, and the nut removal work body 13, which is screwed into the threaded portion 10A, can rise and fall according to the rotation. There is. Further, a gear portion 17A is provided on the lower inner surface of the rotating body 17. A motor 18 driven by an external power source is fixed to the outer circumferential surface of the rod extension 10 at the bottom of the rotating body 17. This motor 1
A gear 18A is attached to the rotating shaft 8 and meshes with the gear portion 17A.

The stretch tube nut attaching/detaching device for the internal pump constructed as described above operates as follows. First of all, the pneumatic cylinder 9 is extended to stretch the engagement part of the tension body into the stretch tube 6.
touch the bottom edge of the Then, the motor 12 is rotated to screw the engaging portion 11A into the spiral groove on the inner surface of the lower part of the stretch tube 6. Next, the pneumatic cylinder 9 is shortened and the tension body 11 is pulled down together with the rod extension body 10 to open the stretch tube 6.
Eliminates the pre-applied tensile force. Second, the motor 18 is rotated to raise the nut removing work body 13. At this time, since pins 14 are provided on the upper surface of the nut removal work body 13 and urged to protrude by springs 15, the pins 14 are inserted into the locking grooves 7A on the lower surface of the stretch tube nut 7. is locked.

Next, when the motor 18 is reversed, the stretch
The tube nut 7 is rotated together with the nut removal working body 13 and removed from the stretch tube 6. At this time, since the stretch tube nut 7 is held by the nut removal work body 13 by the holding parts 16, the removed stretch tube nut 7 will not fall. Incidentally, when installing the stretch tube nut 7, the motor 18 may be rotated in the reverse direction.

This kind of internal pump stretching/
The tube nut attaching/detaching device removes the tensile force previously applied to the stretch tube 6 to attach/detach the stretch tube nut 7, making it easy to carry out the work even when the nut is stuck. can. Therefore, the working time can be shortened and the operating rate of the nuclear reactor can be improved. In addition, this device is equipped with a motor casing 5
If installed in A, the device can be remotely controlled to perform the above-mentioned operations, thereby significantly reducing the amount of radiation exposure of workers. Further, the stretch tube tensioning mechanism is threaded into a helical groove on the inner surface of the stretch tube. Therefore, the engaging portion 11A can be screwed together using the motor 12 with a small output, and since the spiral groove and the engaging portion 11A have a large contact area, there is no risk of damaging the spiral groove.

The stretch tube nut attaching/detaching device for an internal pump according to the present invention is not limited to the above embodiment. For example, motors 12, 18 may be pneumatically or hydraulically driven to generate high torque at low speeds. Further, the locking and moving means housed in the nut handling work body 13 is not limited to the springs 15, but a cylinder driven by air pressure or water pressure can also be used.

As explained above, the stretch tube nut attaching/detaching device for an internal pump according to the present invention has two parts: A pump body, a stretch tube that is inserted into the motor casing and whose upper end engages with the pump body, and a tightener that is threaded onto the lower end of the stretch tube to pull the stretch tube and tighten the pump part. Stretch wire to be fixed to the motor casing above.
In an internal pump equipped with a tube nut for attaching and detaching the stretch tube nut, the stretch tube screws into a spiral groove previously provided on the inner surface of the stretch tube to apply tension to the stretch tube. The apparatus is equipped with a tube tensioning mechanism and a stretch tube nut rotation mechanism for rotating the stretch tube nut. Therefore, the work of removing the stretch tube nut, which is carried out inside the narrow internal pump motor casing, can be done easily and in a short time, thereby improving the operating rate of the reactor and significantly reducing the radiation exposure of workers. The effects are great, such as being able to do the following.

[Brief explanation of the drawing]

Figure 1 is a vertical sectional view of the internal pump, Figure 2
The figure is a longitudinal sectional view of a stretch tube nut attaching/detaching device for an internal pump according to an embodiment of the present invention, and FIG. 3 is an enlarged view of a portion of FIG. 2. 5A...Motor casing, 8...Mounting board, 9...
Pneumatic cylinder, 10...Rod extension body, 11...Tension body, 12, 18...Motor, 13...Nut removal work body, 14...Pin, 15...Spring, 16...Holding part, 17...Rotating body, 20 ...Stretching body Tube tension mechanism, 21 ...Stretch tube nut rotation mechanism.

Claims (1)

[Claims] 1. A motor casing provided through the lower mirror portion of the reactor pressure vessel, a pump body attached to the inner end of the motor casing, and a pump body inserted into the motor casing. A stretch tube whose upper end engages with the pump body, and a stretch tube which is screwed into the lower end of the stretch tube and tightened to pull the stretch tube and fix the pump section to the motor casing. In the device for attaching and detaching the stretch tube nut of an internal pump having a nut, the stretch tube tensioner is screwed into a spiral groove previously provided on the inner surface of the stretch tube to apply tension to the stretch tube. 1. A stretch tube nut attaching/detaching device for an internal pump, comprising: a stretch tube nut rotation mechanism; and the stretch tube nut rotation mechanism described above. 2. The stretch tube nut of the internal pump according to claim 1, wherein the stretch tube nut rotation mechanism is provided on the tensile force generation side of the stretch tube tension mechanism. Attachment and detachment device. 3. The internal device according to claim 2, wherein the stretch tube tensioning mechanism and the stretch tube nut rotation mechanism are set at predetermined positions by being attached to the motor casing. Pump stretch tube nut attachment/detachment device.