JPH02156194A - Secondary sealing of internal pump - Google Patents

Abstract

PURPOSE:To obtain a sealing of which attaching and detaching work can be performed easily and quickly by making an upper and an lower structures of the sealing freely movable upward and downward when the lower structure is fixed to an lower part of the upper structure. CONSTITUTION:A motor part is housed in a motor casing 22 fixed to a bottom part of a nuclear reactor pressure vessel, and the motor part is connected to a pump shaft 15. An upper structure part 27 has a sealant 26 which is positioned in the motor casing 22 and swells inwardly by a hydraulic pressure completely to make contact with a surrounding part of the pump shaft 15. On an inner surrounding surface of the motor casing 22, an annular groove 39 is provided and a locking ball 41 engaging with the annular groove 39 supports the upper structure 27. A lower structure 28 provided at a bottom part of the upper structure 27 is equipped with an inner surrounding sleeve 44 which is connected to the upper structure 27 through a spring part 43. With this procedure, a handling tool of a secondary sealing can be simplified and the replacement of the second sealing device can be conducted in a condition where it is fixed to the pump shaft 15.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is designed to prevent leakage of reactor water within a nuclear reactor during disassembly and reassembly of an internal pump incorporated in a boiling water reactor. This invention relates to a secondary seal device for an internal pump used to prevent

(Prior art) Figure 8 shows a conventional boiling water reactor (hereinafter referred to as BWR)
This is a sectional view showing the schematic configuration of the BWR.
Explain. That is, a recirculation system 2 is connected to the reactor pressure vessel 1 . This recirculation system 2 includes a recirculation pump 3 installed outside the reactor pressure vessel 1 and a recirculation pump 3 installed outside the reactor pressure vessel 1.
A jet pump 4 installed in the recirculation pipe 5 that connects the recirculation pump 3 and the jet pump 4.
It is composed of. The recirculation system 2 is configured to forcefully circulate the coolant 7 within the reactor core 6.

In a BWR with such a configuration, a recirculation pump 3 and a recirculation pipe 5 are installed outside the reactor pressure vessel 1,
The recirculation pipe 5 thus forms a boundary for the coolant 7. Therefore, if the recirculation pipe 5 were to break, a loss of coolant accident would occur, which could lead to secondary disasters. In anticipation of such an accident, emergency core cooling systems have been installed, but the number of piping and attached equipment has increased, making the configuration complex and the equipment larger. Instead of such an external circulation type BWR, an improved internal pump type BWR is known in which a pump is built into the reactor pressure vessel 1 and the coolant 7 is directly circulated therein.

The configuration of this improved BWR will be explained below.

FIG. 9 is a vertical sectional view showing a schematic configuration of the improved BWR. Note that the same parts as in the configuration of the external circulation type BWR described above are denoted by the same reference numerals, and the explanation thereof is omitted. A plurality of internal pumps 9 are installed below the downcomer part 8, passing through the lower mirror IA of the reactor pressure vessel 1, at equal intervals in the circumferential direction. This internal pump 9 has a configuration as shown in FIG. 1O. That is, the internal pump 9 is composed of a pump section 10 and a motor section 11. The pump section 9 includes an impeller 12 and a differential user 13
and a differential user wear ring 14. The impeller 12 is connected to the motor section 11 via a pump shaft 15. The diffuser 13 is fixed to the upper part of a nozzle 16 protruding from the bottom of the reactor pressure vessel 1 via a stretch tube 17, and the stretch tube 17 is fixed by a stretch tube nut 18. A secondary seal 19 is attached below the stretch tube nut 18.

The motor unit 11 is composed of a rotor 20, a stator 21, etc., and its tip is inserted into the nozzle 16, and is housed in a motor casing 22 welded to the lower mirror IA of the reactor pressure vessel 1. Note that reference numeral 23 in the figure indicates a cooling water circulation pipe, and cooling water is circulated within the motor section 11 via this cooling water circulation pipe 23 to prevent the motor section 11 from burning out.

An improved BWR with such a configuration is the external recirculation BWR described above.
Unlike R, a recirculation pump is not installed outside the reactor pressure vessel 1, so there is no need for recirculation piping, and therefore -
Next, the space within the recirculation equipment within the containment vessel can be significantly reduced. Furthermore, since the assumed fracture area is reduced by the amount of the recirculation pump and recirculation piping, the capacity of the emergency core cooling equipment can be reduced. Furthermore, since the motor section 11 is housed in a motor casing 22 with excellent watertightness, it is a sliding type shaft sealing device! (Gland part) is not required, and therefore the risk of core leakage is small.

In the above configuration, maintenance and inspection work for the internal pump is performed by the following means. First, the secondary seal 19 seals between the motor casing 22 and the pump shaft 15 to shut off water in the reactor pressure vessel 1, and then drains the water in the motor casing 22. After that, remove the auxiliary cover 24 on the lower surface of the motor section 11, remove the coupling stud nut 25, and then remove the pump shaft 15.
and the motor section 11 are disconnected. Next, auxiliary cover 2
4, fills the motor casing 22 with make-up water and releases the secondary seal 19. In this state, loosen the main stud nut 25 and remove the motor part 11 and pump shaft 1.
5 is lowered by about 10 nw due to its own weight. As a result, the protrusion 15A provided inside the furnace of the pump shaft 15 comes into contact with the upper surface of the nozzle portion 16, and sealing of the reactor water (hereinafter referred to as "secondary seal") is achieved. In this state, the above-mentioned secondary sealing operation is performed to drain the water inside the motor casing 22, and the main stud nut 25 is removed and the motor section 11 is removed.

Next, after attaching the auxiliary cover 24 to the lower end of the motor casing 22, makeup water is filled inside the motor casing 22, and then the secondary seal 19 is released.

In this state, the impeller 12 and the pump shaft 15 are removed from above the reactor pressure vessel 1. Next, the opening of the diffuser 13 is closed from above the reactor pressure vessel 1 with an upper closing plate, and the water in the motor casing 22 is discharged. In this state, the closing flange is removed from below the motor casing 22, and the secondary seal 19 and stretch tube nut 18 are removed from inside the motor casing 22. After the closing flange is attached to the lower end of the motor casing 22 again, makeup water is filled. In this state, the upper closing plate, the differential user 13, the differential user wear ring 14, and the stretch tube 17 are removed from above the reactor pressure vessel 1. After inspection and maintenance, the installation is performed in the reverse order.

In addition, among the steps shown above, the steps up to the removal of the motor are simplified, and first the motor part 11 and pump shaft 15 are removed.
It is also possible to follow the steps of achieving the primary seal by lowering the seal by mm, activating the secondary seal, draining water, releasing the coupling stud, and removing the motor.

FIG. 11 shows the details of a device including a secondary seal 19 that prevents reactor water from leaking into the motor casing 22 during the maintenance and inspection work described above. It is held by a body 27 and a lower structure 28. The outer periphery of the seal member 26 is connected to the upper structure 2
7 and a through hole 29a provided in the motor casing 22
, 29b to an external water pressure source (not shown). When the secondary seal is activated, the seal member 26 is pressurized from the outer circumferential side by pressurized water supplied from an external water pressure source, and the pump shaft (reference numeral 15 in FIG. 10) It contracts to the side and comes into close contact with the pump shaft 15. On the other hand, an O-ring 30 is attached to the outer peripheral surface of the upper structure 27 and is in close contact with the inner surface of the motor casing 22. This stops the flow of reactor water above the secondary seal.

(Problem M to be solved by the invention) Motor casing 2 of the secondary seal device 19 described above
2, as shown in FIG.
This was done by fitting it into the annular groove 32 of. However, when removing the secondary seal 19, the washer 31
mechanically bend it as shown by the two-dot chain line and lower it from the inside of the secondary seal using a special jig, or remove the washer mounting bolt 33 and lower the lower structure 28, and then slide the washer 31 laterally. Then, the upper structure is disengaged from the annular groove 32 and lowered, and the upper structure is further lowered. This is a complicated operation, and there is a problem in that in either case, the pump shaft cannot be carried out unless the pump shaft is pulled out above the reactor pressure vessel 1.

In this case, the upward removal and attachment work of the pump shaft 15, the differential user 13°, the differential user wear ring 14, and the stretch tube 17 is a remote underwater operation using a special jig. Furthermore, as shown in FIG. 12, there is a problem of interference with the reactor pressure vessel l, the upper grate plate 35 of the core shroud 34, and the water supply sparger 36. Especially for the upper grid plate 35 and the water supply sparger 36, yX
This is a state in which passage is possible only in limited directions of the child reactor pressure vessel 1. Therefore, it is necessary to remove the pump shaft 15 and the like and rotate the attached parts about the central axis of the reactor pressure vessel 1, which is an extremely difficult task.

As described above, the work of attaching and detaching the secondary seal device according to the prior art is complicated because the work of attaching and detaching the main body of the secondary seal 19 is complicated, and also requires the attachment and detachment of multiple other parts.
The problem was that it required long hours of work and the radiation exposure of the workers was large.

The present invention has been made to solve the above problems, and its purpose is to provide a secondary seal device for an internal pump that can be easily and quickly attached and detached.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a motor casing attached to the bottom of a nuclear reactor pressure vessel, a motor part housed in this motor casing, a pump shaft connecting this motor part, and a motor casing that connects the motor part. an upper structure having a sealing member that expands inwardly due to water pressure located inside and comes into close contact with the periphery of the pump shaft; an annular groove provided on the inner peripheral surface of the motor casing; and an upper structure that engages with the annular groove; A locking member for holding a structure, a lower structure provided at a lower part of the upper structure, and an inner circumferential sleeve located in the lower structure and connected to the lower structure via a spring member. It is characterized by what it did.

(Function) When the locking member is attached to the lower part of the upper structure, the upper and lower structures become vertically movable. The lower structure is easy to fit with the secondary seal handling tool, simplifying the secondary seal handling tool. This allows the secondary seal device to be easily replaced with the pump shaft attached. Therefore, the work of attaching and detaching the secondary seal device is greatly simplified, and there is no need to remove the pump shaft.

(Example) An example of the present invention will be described with reference to FIGS. 1 and 5. In addition, the same parts in FIG. 1 as in FIG. 11 are indicated by the same reference numerals, that is, as shown in FIG. 1, a secondary sealing device 19 is provided at the lower end of the stretch tube 18. has an upper structure 27 that fits into the motor casing 22 via an O ring 30, and a lower structure 28 that is attached to this upper structure 27 via an O ring 37 with bolts 38, and has a surface structure. A seal member 26 is provided between bodies 27 and 28. The upper structure 27 has a tapered hole 40, and a ball 41 as a locking member fits into this tapered hole 4.
It is held by a tapered surface of 0 and an inner sleeve 44. A spring member 43 is provided on the outer periphery of the inner sleeve 44,
The upper end of the spring member 43 is held by an inner sleeve 44, and the lower end is held by an end plate 42. inner sleeve 4
4 is pushed up by the spring member 43, the locking ball 41 is pushed outward by the outer peripheral surface of the inner sleeve 44, and is in a state of protruding from the outer peripheral surface of the upper structure 27. It fits within the annular groove 39 of the motor casing 22 facing this, thereby restricting vertical movement of the secondary seal device 19. Further, when the inner sleeve 44 is pulled down against the elastic force of the spring member, the ball 41 serving as a locking member fits into the notch 44b provided at the upper end of the inner sleeve 44, and thereby the secondary seal 19 is closed. The vertical constraint is released. Furthermore, a key 45 is attached to the outer circumferential surface of the lower structure 28 and is fitted into the key groove of the motor casing 22 to restrict rotation of the secondary seal device 19.

Here, the sealing member 26 is made of an elastic material such as synthetic rubber, and communicates with an external water pressure source through through holes 29a and 29b provided in the upper structure 27 and the motor casing 22. When disassembling the internal pump, pressurized water is supplied from an external water pressure source to contract the sealing member 26 to seal the gap with the pump shaft 15.

In addition, when operating the internal pump, pressurization from the external water pressure source is stopped and the contraction of the seal member 26 is released so that the pump shaft 15 and the seal member 2
A gap is provided between the motor and the motor so as to have no effect on the operation.

A handling device for removing and installing the secondary seal device 19 will be described with reference to FIG. 2. Figure 2 shows the rotor 20 and stator 21 inside the motor casing 22 removed.
The pump body (not shown) and the pump shaft 15 remain, and a primary seal is achieved in which the lower surface of the outer peripheral protrusion of the pump shaft 15 contacts the upper surface of the reactor pressure vessel nozzle inside the reactor above the pump shaft 15. in a state of
The reactor water is now sealed. A bracket 46 is attached to the lower side surface of the motor casing 22, and a pair of screw mechanisms 47 are attached to this bracket 46. Below this screw mechanism 47 is a screw mechanism 47.
A drive motor (not shown) is installed to rotate the .

A base 48 is detachably attached to the nut portion 47a of the screw machine [47]. A cylindrical secondary seal handling tool 49 passes through this base 48 . The lower surface of a flange 50 provided at the bottom of this secondary seal handling tool 49 is installed on the base 48 via a ball bearing 51, and the flange 50 is installed on the base 48 via a ball bearing 51.
The upper surface of is held by a cover 52 fixed to the base 48, and has a rotatable structure. Further, the cylindrical secondary seal handling tool 49 has a gap that encloses the pump shaft 15, and the upper end is provided with a plurality of claw members 49a and an adjustment nut, as shown in detail in an enlarged view in FIG. A plurality of stop bolts 5 held by 54 and movable in the vertical direction
5 and a stop ring 56 for positioning the secondary seal handling tool. Note that the reference numeral 53 in FIG. 1 indicates a guide roller attached to the upper outer periphery of the secondary seal handling tool 49.

Next, a method for removing the secondary seal device using the handling device having the above configuration will be explained. Namely.

The drive motor raises the base 48 until the stop ring 56 contacts the motor casing 22. Next, rotate the secondary seal handling tool 49 to remove the claw member 49a at the tip of the handling tool.
is engaged with the protrusion 45 of the inner circumferential sleeve shown in FIG. In this state, the secondary seal handling tool 49 is
descend. As a result, as shown in FIG. 4, the inner sleeve 44 moves downward, the locking ball 41 moves inward, the engagement with the motor casing 22 is released, and the secondary seal handling tool 49 is continuously lowered. This allows the removal of the secondary sealing device [19]. In addition, in the above-mentioned removal work, the stopper 55 attached to the secondary seal handling tool 49 is sufficiently lowered.When installing the secondary seal 19 next, the claw member 49a of the secondary seal handling tool 49 and the inner periphery are Engage the protrusion 45 of the sleeve 44, and push up the stopper 55 with the 1g adjustment nut 54.
Set the spring member 43 in a contracted state. At this time, the key 45 of the secondary seal 19 and the keyway 3 of the motor casing 22
9b, and then operate the drive motor to move the secondary sealing device 1 until the upper surface of the stop ring 56 and the lower surface of the motor casing 22 come into contact with each other, as shown in FIG.
Raise 9. In this state, when the secondary seal handling tool 49 is rotated to release the engagement between the secondary seal handling tool 49 and the inner sleeve 44, the inner sleeve 44 rises and the locking ball 41 and the motor casing 22 are engaged. This completes the installation of the secondary seal device 19. Thereafter, the secondary seal handling tool 49 is removed.

Another embodiment of the present invention will be described with reference to FIGS. 6 and 7. In each figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and the explanation of the overlapping parts will be omitted, and only the main points will be explained.

FIG. 6 shows an example in which a cylindrical sleeve 57 is provided as a locking member, and this cylindrical sleeve 57 has a strip-shaped slit on its circumference and is folded so that a taper is also formed in the portion where the slit is provided. It is bent. This cylindrical sleeve 57 is attached to the lower structure 28 of the secondary seal 26, and the secondary seal device is held by the engagement of the tapered portion with the circumferential groove 39 of the motor casing 22. In the embodiment shown in FIG. 7, a threaded portion 58 is formed at the lower end of the lower structure 28 of the secondary seal device, and the connection with the secondary seal handling tool 49 is made by a screw connection method. Since the operation and effect are almost the same as those of the embodiment shown in FIG. 1, the explanation thereof will be omitted.

〔Effect of the invention〕

According to the present invention, it becomes easy to attach and detach the secondary seal device that seals between the pump shaft and the motor casing when disassembling and assembling the internal pump. In addition, by simplifying the secondary seal handling device, it is no longer necessary to remove the pump shaft when replacing the secondary seal device, significantly shortening the work time and improving the operating rate of the reactor.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the secondary sealing device according to the present invention, FIG. 2 is a vertical cross-sectional view showing the installation and removal handling device of the secondary sealing device in FIG. 1, and FIG. 5 is a side view partially showing the main parts of the handling device in FIG. 2. FIG. A longitudinal sectional view showing the installation of the secondary sealing device by the handling device, and FIGS. 6 and 7 are longitudinal sectional views showing other embodiments of the present invention, respectively.
8 and 9 are vertical sectional views schematically showing the BWR, FIG. 10 is a vertical sectional view showing an internal pump incorporated in the BWR shown in FIG. 9, and FIG. 11 is a conventional secondary pump. FIG. 12 is a vertical sectional view schematically showing the inside of the reactor pressure vessel when the internal pump is disassembled. 1...Reactor pressure vessel IA...Lower mirror 2...Recirculation system 3...Recirculation pump 4...Jet pump 5...Recirculation piping 6...Reactor core 7... Coolant 8・Downcomer section 9...Internal pump 10...Pump section 11...Motor section 12...Impeller 13...Diff user 14...Diff user wear ring 15...Pump shaft 15A ... Protrusion 16 ... Nozzle 17 ... Stretch tube 18 ... Stretch tube nut 19 ... Secondary sealing device 20 ... Rotor 21 ... Stator 22 ... Motor casing 23 ... Cooling water circulation pipe 24...Auxiliary cover 25...Main stud nut 26...Seal member 27...Upper structure 28...Lower structure 29a...Through hole 29b...Through hole 30... ... O-ring 31 ... Washer 32 ... Annular groove 33 ... Washer mounting bolt 34 ... Core shroud 35 ... Upper grid plate 36 ... Water supply sparger 37 ... O-ring 38 ... Bolt 39...Annular groove 39b...Keyway 40...Tapered hole 41...Lock ball 42...End plate 43...Spring member 44...Inner circumferential sleeve 44a...Protrusion 44b... Notch 45... Key 46... Bracket 47... Screw mechanism 48... Base 49... Secondary seal handling tool 49a... Claw member 50... Flange 51... ... Ball bearing 52 ... Cover 53 ... Adjustment nut 54 ... Adjustment nut 55 ... Stop bolt 56 ... Stop ring 57 ... Cylindrical sleeve 58 ... Threaded part

Claims (1)

[Claims] a motor casing attached to the bottom of the reactor pressure vessel; a motor section housed within the motor casing;
a pump shaft that connects the motor section; an upper structure having a sealing member located within the motor casing that expands inwardly due to water pressure and comes into close contact with the periphery of the pump shaft; an annular groove, a locking member that engages with the annular groove and holds the upper structure, a lower structure provided at a lower part of the upper structure, and a spring member located in the lower structure. A secondary sealing device for an internal pump, comprising an inner peripheral sleeve connected to the lower structure.