JPH0531960B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a method for blocking the lower end opening of a pump casing during periodic inspection of an internal pump used in an improved boiling water reactor (ABWR). The present invention relates to a main flange mounting nut attachment/detaching device for an internal pump for attaching/detaching a main flange attachment nut.

[Technical Background of the Invention] Conventional boiling water reactors (BWRs) generally distribute coolant between a recirculation pump installed outside the reactor pressure vessel and a jet pump installed inside the reactor pressure vessel. Coolant is sent to the reactor core through forced circulation, but such an external recirculation system not only has a complicated structure, but also requires a recirculation system that connects the reactor pressure vessel and the recirculation pump. The piping acts as a boundary for the coolant, so if the recirculation piping breaks due to some kind of accident, there is a possibility of loss of coolant. Therefore, in order to prevent such loss of coolant accidents, an improved boiling water reactor (ABWR) is developed in which coolant is forced to circulate within the reactor pressure vessel.
is being developed.

Figure 4 is a cross-sectional view of ABWR showing one example.
In the figure, 1 is the reactor pressure vessel. A reactor core 2 consisting of a large number of fuel assemblies (not shown) is provided within the reactor pressure vessel 1 and housed within a cylindrical shroud 3. A water supply spargeer 5 connected to a water supply pipe 4 is provided above the core 2, and a steam separator 6 and a steam dryer 7 are further provided above the water supply spargeer 5. Further, a plurality of internal pumps 8 are provided in the lower mirror portion of the reactor pressure vessel 1 . As shown in FIG. 5, these internal pumps 8 are composed of a pump section 11 and a motor section 12. By driving the pump section 11 with the motor section 12, the coolant inside the reactor pressure vessel 1 is forcedly circulated. I'm starting to let them do it. The pump section 11 is composed of an impeller 13, a differential user 14, a stretch tube 15, a secondary seal 16, etc., and the impeller 13 is connected to the motor section 12 via a drive shaft 17. The diff user 14 also includes a nozzle 18 provided on the lower mirror portion of the reactor pressure vessel 1.
It is fixed by a stretch tube 15. The stretch tube 15 is provided in the upper part of the pump casing 20 and is fixed by a stretch tube nut 19. Further, the secondary seal 16 is provided below the stretch tube nut 19 to prevent the coolant from flowing out when the internal pump 8 is installed or removed. On the other hand, the motor section 12 is composed of a rotor 21, a stator 22, etc., and a pump casing 2
It is contained within 0. This pump casing 2
0 has a main flange 23 that closes the lower end opening of the pump casing 20, and a plurality of main flange mounting stud bolts (hereinafter referred to as main flange studs) 24 protruding from the lower end of the pump casing 20 and these main flanges. It is firmly fixed by a main flange mounting nut 25 (hereinafter referred to as the mounting nut) which is screwed onto the stud 24. In addition, the pump casing 2
Cooling water circulation pipes 26 are connected to the upper and lower parts of the pump casing 20, and the cooling water circulates within the pump casing 20 to prevent the motor section 12 from burning out.

Since such an internal pump 8 is housed in a pump casing 20 with excellent watertightness, it does not require a sliding shaft sealing device, and has a simple structure with less possibility of reactor water leakage, making it reliable. Excellent in sex. Furthermore, because ABWR does not require an external recirculation system like conventional BWRs, it can significantly reduce piping space within the reactor containment vessel and reduce the capacity of the emergency core cooling system, improving safety and reliability. It has the advantage of being excellent.

By the way, with the adoption of such an ABWR with excellent safety and reliability, it is necessary to periodically perform maintenance and inspection work on the internal pump 8. Maintenance and inspection work for the internal pump 8 is performed by first stopping the operation of the reactor, filling the reactor pressure vessel 1 with water to shield radiation, and then removing the reactor cover 1a of the reactor pressure vessel 1. After filling the furnace well with water and removing the steam dryer 7, steam/water separator 6, shroud head 3a, etc., the internal pump 8 is removed. The removal work of the internal pump 8 is performed from above and below the reactor pressure vessel 1, and the work procedure is as follows.

First, the secondary seal 16 seals between the pump casing 20 and the drive shaft 17 to shut off the reactor water in the reactor pressure vessel 1, and then the water in the pump casing 20 is discharged. Then, tighten the mounting nut 25
from the main flange stud 24, and remove the motor section 12 together with the main flange 23 from below the pump casing 20. Next, a closing flange is attached to the lower end of the pump casing 20 using the main flange stud 24, and after filling the inside of the pump casing 20 with makeup water, the secondary seal 16 is released. In this state, the impeller 13 and the drive shaft 17 are removed from above the reactor pressure vessel 1. Next, the opening of the diffuser 14 is closed from above the reactor pressure vessel 1 with an upper closing plate, and the water in the pump casing 20 is discharged. In this state, remove the closing flange from below the pump casing 20, and then remove the secondary seal 1 from inside the pump casing 20.
6 and stretch tube nut 19. Next, after attaching the closing flange to the lower end of the pump casing 20 again, the pump casing 20 is filled with make-up water. In this state, the upper closing plate, diffuser 14, and stretch tube 15 are removed from above the reactor pressure vessel 1. After removal, each part is inspected and maintained at a maintenance facility, and then reassembled by reversing the removal procedure.

[Problems with the Background Art] However, the installation and removal work of the internal pump 8 is expected to be difficult because the work is performed in a narrow space. In particular, when pulling out the motor section 12 of the internal pump 8 from below the pump casing 20 after removing the main flange 23, the control rod drive mechanism housings 9 are arranged in a dense row in the lower part of the reactor pressure vessel 1. Furthermore, since there are pipes on both the right and left sides, the work must be done in a very narrow space. Moreover, main flange 23
Since the mounting nut 25 fixing the is tightened with a large torque, it is expected that it will take a long time to remove it. For this reason, inspection and maintenance of the internal pump 8 takes a long time, prolonging the period when the nuclear reactor is out of operation, and as a result, there is a risk that the operating rate of the reactor will decrease.

[Object of the Invention] The present invention has been made based on the above-mentioned circumstances, and its purpose is to facilitate the attachment and detachment of the mounting nut for fixing the main flange by remote control during maintenance and inspection of the internal pump. To provide a device for attaching and detaching a main flange attaching nut of an internal pump, which can be attached and detached in a short time.

[Summary of the Invention] In order to achieve the above object, the present invention includes a support plate that supports from below a main flange that closes a lower end opening of a pump casing of an internal pump, and a stud provided at the lower end of the pump casing. a nut attaching/detaching unit for attaching and detaching the main flange attaching nut screwed onto the stud bolt while applying downward tension to the bolt; a rotation mechanism for rotating the nut attaching/detaching unit in the circumferential direction of the pump casing; and a support plate for these; The nut attachment/detachment unit includes a ball spline that supports the nut attachment/detachment unit and the rotation mechanism in a vertically movable manner, and a base that supports the ball spline so as to be movable up and down below the pump casing. The top surface of the unit cover is located on the same plane and is characterized by having no protrusions on the top surface.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

1 to 3 are views showing one embodiment of the present invention, and FIG. 1 is an overall side view of the main flange mounting nut attaching/detaching device according to the present invention. As shown in the figure, brackets 101, 101 are provided at the bottom of the pump casing 20 of the internal pump 8, projecting horizontally from both sides.
The upper ends of guide screws 102, 102 are rotatably held in these brackets 101, 101.
It is designed to be rotationally driven by a drive device (not shown) provided below 02. Further, nut portions 104, 104 of a base 103, which moves up and down below the pump casing 20, are screwed into the guide screws 102, 102. These nut parts 104, 104 are attached to both ends of the base 103, and when the guide screw 102 rotates, they move in the vertical direction to raise and lower the base 103.

A ball spline 105 is provided in the center of the base 103 to support the main flange 23 of the internal pump 8 from below. A hydraulic cylinder (not shown) is incorporated inside the ball spline 105, and the load of the motor of the internal pump 8 is supported by the support plate 106 at the tip of the hydraulic cylinder. Also,
A nut attachment/detachment tool main body 107 for attaching and detaching the mounting nut 25 of the main flange 23 is provided above the ball spline 105. The nut attaching/detaching tool body 107 is moved up and down above the ball spline 105 by the hydraulic cylinder, and further rotated by a servo motor 109 provided near the nut attaching/detaching tool body 107. The servo motor 109 includes a rotating gear 110 and a driving gear 11 fixed to the outer periphery of the nut attaching/detaching tool body 107.
1, and by rotationally driving this drive gear 111, the nut attachment/detachment tool main body 107
is rotated via a rotation gear 110.

Further, a plurality of nut attaching/detaching units 112 are integrally provided around the nut attaching/detaching tool main body 107. These nut attachment/detachment units 1
12 is a nut attaching/detaching tool main body 10 as shown in FIG.
There are 4 pieces arranged at approximately 90° intervals around the outer circumference of 7.
As shown in FIG. 3, each nut attaching/detaching unit 112 has a bolt tensioning mechanism 113 that applies a tensile load to the main flange stud 24 and a nut rotation mechanism 114 that rotates the mounting nut 25, respectively. The bolt tensioning mechanism 113 has a threaded portion 115 that is screwed into the tensioning threaded portion 24a provided at the lower end of the main flange stud 24, and the threaded portion 115 is screwed into the tensioning threaded portion 24a and pulled downward. The main flange stud 24 is configured to apply a tensile load to the main flange stud 24.
A hydraulic cylinder 116 is located below the threaded portion 115.
is provided, and the threaded portion 115 is pulled downward by this hydraulic cylinder 116 via a connecting rod 117. In addition, the screw portion 1
15 is provided inside a rotating body 119 having a rotating gear 118 formed on its outer peripheral surface, and this rotating body 11
9 is a lower clutch mechanism 120 and a connecting rod 11 in the first half.
7 so that rotational motion is transmitted to the threaded portion 115 via the connecting rod 117. The engagement of this clutch mechanism 120 is caused by the rotation of the rotating body 11.
This is possible by moving 9 up and down. A driving gear 123 connected to an air motor 121 and a torque limiter 122 meshes with the rotating gear 118 of the rotating body 119.
is rotatably driven by an air motor 121 via a drive gear 123. Further, the nut rotation mechanism 114 has a nut socket 124 that engages with the mounting nut 25 of the main flange 23, and this nut socket 124 is connected to the rotating body 119.
It is fixed to the upper end of the rotating body 119 and rotates together with the rotating body 119. The air motor 121, hydraulic cylinder 116, etc. are connected to the air supply and hydraulic control device 12 provided at the bottom of the base 103.
5. Further, a pulse encoder (not shown) is attached to the nut attaching/detaching tool main body 107, and the position of each nut attaching/detaching unit 112 can be indexed by this pulse encoder and the servo motor 109. There is.

Next, the operation of this embodiment configured as described above will be explained. First, the guide screws 102, 102 are set on the brackets 101, 101 provided at the lower part of the pump casing 20, respectively. Then, the base 1 is attached to the guide screws 102, 102.
After installing the nut parts 104, 104 of 03, the guide screws 102, 10 are moved by a drive device (not shown).
2 and attach the base 103 to the pump casing 2.
When the base 103 approaches the lower end of the pump casing 20, the rotation of the guide screw 102 is stopped. Next, the support plate 10 is moved by the hydraulic cylinder of the ball spline 105.
6 upward so that it comes into contact with the lower surface of the main flange 23, and the nut attachment/detachment tool main body 107
is moved upward, and just before the cover 125 of the nut attachment/detachment nut 112 comes into contact with the lower surface of the main flange 23, the extension operation of the hydraulic cylinder incorporated in the ball spline 105 is stopped, and the attachment/detachment of the attachment nut 25 is performed. When removing the mounting nut 25, first the threaded portion 115 is inserted into the tensioning threaded portion 24a of the main flange stud 24 and screwed onto the tip of the tensioning threaded portion 24a. Next, when the tip of the tensioning screw part 24A is screwed into the threaded part 115, the air motor 121 is driven to rotate the threaded part 115 in a predetermined direction.
As a result, the tension threaded portion 24a is screwed into the threaded portion 115, and the threaded portion 115 moves to the upper part of the tension threaded portion 24a together with the rotating body 119. and,
When the threaded portion 115 reaches the top of the tension threaded portion 24a, the clutch mechanism 120 is actuated to remove the threaded portion 11.
Stop the rotation of 5. Next, in this state, a specified pressure is applied to the hydraulic cylinder 116 to apply a tensile load to the main flange stud 24. Also, at this time, the nut socket 124 engages with the mounting nut 25 and applies a predetermined rotational torque to the nut 24. As a result, the mounting nut 25 is applied with rotational torque while the main flange stud 24 is under tension, so that it is loosened with a relatively small torque and removed from the main flange stud 24. Then, by rotating the nut attaching/detaching tool body 107 and performing this operation on all the mounting nuts 25 (usually 16 nuts),
The motor section 12 of the internal pump 8 can be pulled out from below the pump casing 20.

In this way, in this embodiment, the mounting nut 25
Since the installation work is performed while applying tension to the main flange stud 24, it can be removed easily and in a short time with a relatively small torque. Additionally, all of these tasks are remotely controlled, so they can be easily performed even in tight spaces. In addition,
According to this embodiment, the attachment of the attachment nut 25 to the main flange stud 24 can be easily and quickly carried out by operations similar to those described above, and the torque limiter 122 can prevent excessive tightening of the attachment nut 25.

[Effects of the Invention] As explained above, according to the present invention, the main flange mounting nut of the internal pump can be easily attached and detached with a relatively small torque, and the main flange mounting nut and the nut attachment/detachment unit can be easily attached and detached. can be easily aligned.

[Brief explanation of drawings]

1 to 3 are views showing one embodiment of the present invention, in which FIG. 1 is a side view of the main flange mounting nut attachment/detaching device, FIG. 2 is a plan view thereof, and FIG. 3 is the interior of the nut attachment/detachment unit. FIG. 4 is a sectional view of the ABWR, and FIG. 5 is a sectional view of the internal pump. 8...Internal pump, 24...Main flange stud, 25...Mounting nut, 101...
...Bracket, 102...Guide screw, 1
03...Base, 105...Ball spline, 1
07... Nut attaching/detaching tool main body, 112... Nut attaching/detaching unit, 113... Bolt tension mechanism, 114
...Nut rotation mechanism.

Claims (1)

[Claims] 1 A support plate that supports from below a main flange that closes the lower end opening of the pump casing of the internal pump, and a main that is screwed into the stud bolt provided at the lower end of the pump casing while applying downward tension to the stud bolt. A nut attachment/detachment unit for attaching/detaching a flange attachment nut, a rotation mechanism for rotating the nut attachment/detachment unit in the circumferential direction of the pump casing, and a ball supporting these support plates, the nut attachment/detachment unit, and the rotation mechanism in a vertically movable manner. The ball spline is provided with a base that supports the ball spline so as to be movable up and down below the pump casing, and the upper surface of the support plate and the upper surface of the cover of the nut attachment/detachment unit are located on the same plane, and A main flange mounting nut attachment/detaching device for internal pumps that is characterized by the absence of protrusions.