JPS6312556B2 - - 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. This is a problem that can occur easily and forms a boundary for the coolant in the piping between the reactor pressure vessel and the recirculation pump, resulting in the possibility of loss of coolant due to rupture of this piping. 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 body 1 housed in a reactor pressure vessel 2, and this pump body 1 is formed on the lower mirror portion of the reactor pressure vessel 2 so as to protrude inward. It is attached to the inner end of the internal 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 the stretch tube 6 is engaged with the inner surface of the lower end of the differential user 1B.
Diff user 1B with this stretch tube 6
This is to fix the A stretch tube nut 7 is screwed onto the outer periphery of the lower end of the stretch 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 loosening, and 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 diffuser 1B to prevent the outflow of reactor water, the reactor water in the motor casing 5A is drained. 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, the stretch tube nut 7 is removed from below the motor casing 5A. Then, after closing the motor casing 5A again, the differential user 1B is grasped from above the reactor pressure vessel 2 and the differential user 1B is closed.
B and stretch tube 6 had been removed. 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 is the reactor pressure vessel, 5A is the motor casing, 3 is the internal pump nozzle,
1B is a diffuse user, 6 is a stretch tube, and 7 is a stretch tube nut.
Reference numeral 8 in the figure denotes a mounting board, which is mounted on the lower flange surface of the motor casing 5A. A stretch tube tensioning mechanism 20 is attached to the mounting board 8, and this mechanism will be described below. A pneumatic cylinder 9, which is driven by high pressure air from the outside, is fixed to the mounting board 8, for example. Rod 9A of this pneumatic cylinder 9
A cylindrical rod extension 10 is fixed to the tip of the rod. Engaging bodies 11 are fixed to the upper end of this rod extension 10. As shown in FIG. The engaging bodies 11 are made of spring steel and are biased inward. A pneumatic cylinder 12 is mounted inside the rod extension 10 and is driven by high pressure air from the outside. The rod of the pneumatic cylinder 12 is provided with a pressing body 12A having an inverted truncated round shape, and the outer peripheral surface of the pressing body 12A is in contact with the inner surface of the engaging bodies 11. Therefore, by shortening and expanding the pneumatic cylinder 12, the locking body 1
1... can be engaged with and disengaged from the spiral groove on the inner surface of the stretch tube 6. Further, a stretch tube nut rotation mechanism 21 is attached to the upper outer periphery of the rod extension body 10, and the structure thereof will be explained below. A threaded portion 10A is provided at the upper part of the outer circumferential surface of the rod extension body 10, and a shaft support 10B is provided below this threaded portion. A nut removing work body 13 is screwed into this threaded portion 10A. The nut removing work body 13 is provided with a plurality of pins 14 serving as engaging portions so as to be protruding and retractable from the top surface, and are urged in the projecting direction by springs 15 housed inside the nut handling work body 13. There is. Further, a plurality of holding parts 16 made of spring steel are provided on the upper surface of the nut removal work body 13,
It is configured to elastically abut and hold the inner surface of the stretch tube nut. Further, 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 attached to the shaft support 10B of the rod extension body 10.
is pivoted. Sliding pins 17B are formed on the upper surface of this rotating body 17 and inserted into the sliding holes 13A of the nut handling work body 13. This sliding pin 17B...transmits the rotation of the rotary body 17 to the nut removal work body 13, and slides so that the nut removal work body 13, which is screwed into the threaded portion 10A, can rise and fall in accordance with the rotation. configured to be possible. Further, a gear portion 17A is provided on the lower inner surface of the rotating body 17. And this rotating body 1
A motor 18 driven by an external power source is fixed to the outer peripheral surface of the rod extension 10 at the lower part of the rod extension 10. A gear 18A is attached to the rotating shaft of the motor 18, 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, the pneumatic cylinder 9 is extended and the engaging members 11 of the tension member are inserted into the spiral groove portion of the inner surface of the stretch tube 6. At this time, the engaging bodies 11 are inserted in a state of being retracted inward as shown by the two-dot chain line in FIG. When the pneumatic cylinder 12 is extended, the engaging bodies 11 are pushed by the pressing body 12A and expand outward to engage with the spiral groove on the inner surface of the stretch tube 6. Then, the pneumatic cylinder 12 is shortened to pull down the engaging bodies 11 together with the rod extension body 10, thereby eliminating the tensile force previously applied to the stretch tube 6. And secondly, motor 1
8 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 are urged in the protruding direction 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 attachment/detachment device removes the tension applied to the stretch tube 6 in advance to attach/detach the stretch tube nut 7.
Work can be easily carried out even when nuts are stuck. Therefore, the working time can be shortened and the operating rate of the 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 expands the engaging bodies 11 from the inside to the outside to engage the spiral grooves on the inner surface of the stretch tube. Therefore, it can be used with stretch tubes of different diameters, and has the advantage of being versatile. 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 internal pump stretch tube nut attaching/detaching device according to the present invention is attached to the motor casing provided through the lower head of the reactor pressure vessel, and to the inner end of the motor casing. a stretch tube that is inserted into the motor casing and whose upper end engages with the pump body; and a stretch tube that is screwed into the lower end of the stretch tube and tightened to pull the stretch tube. A stretch tube nut for attaching and detaching the stretch tube nut of the internal pump, which is equipped with a stretch tube nut for fixing the stretch tube nut to the motor casing, the stretch tube nut being engaged with the inner surface of the stretch tube. - Equipped with a stretch tube tensioning mechanism that applies tension to the tube and a stretch tube nut rotation mechanism that rotates the stretch tube nut. Therefore, the stretch tube nut removal work performed inside the narrow internal pump motor casing can be done easily and in a short time, improving the operating rate of the reactor and significantly reducing the radiation exposure of workers. The effect is great.

[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,
12...Pneumatic cylinder, 10...Rod extension body, 1
DESCRIPTION OF SYMBOLS 1... Engaging body, 18... Motor, 13... Nut removal work body, 14... Pin, 15... Spring, 16... Holding part, 17... Rotating body, 20 ... Stretch tube tensioning 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 equipped with a nut, the stretch tube expands from the inside and engages with 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 interlunar pump, characterized in that it is equipped with a stretch tube tensioning mechanism to provide a stretch tube, and a stretch tube nut rotation mechanism as described above. 2. The stretch tube of the internal pump according to claim 1, wherein the stretch tube nut rotation mechanism is provided on the stretch tube tension generation side.
Tube nut attachment/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.