JPH0553957B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a recirculation pump built into a nuclear reactor that controls the flow rate of coolant flowing in a nuclear reactor core, and particularly to a recirculation pump built into a nuclear reactor that controls the flow rate of coolant flowing in a nuclear reactor core. , relates to a thrust bearing device that supports the weight of this shaft.

[Background of the invention]

A reactor-integrated recirculation pump controls the flow rate of coolant to the reactor core by driving a pump that is suspended directly from the bottom of the reactor pressure vessel.

This recirculation pump will be explained with reference to FIG. 1. A through hole 2 is formed at the bottom of a reactor pressure vessel 1, and a cylindrical nozzle 3 is welded and attached to this through hole 2. An upper case 4a of a motor case 4 is inserted into the cylindrical nozzle 3 and welded to the cylindrical nozzle 3. A pump shaft 5 is provided inside the motor case 4, and this shaft 5 is connected to a thrust bearing 8 via journal bearings 6a, 6b and a thrust collar 7 at the lower end of the shaft 5.
a, 8b. The lower end surface of the motor case 4 is closed with a motor cover 9.
On the other hand, the upper part of the pump shaft 5 passes through the nozzle 3 and is located inside the reactor pressure vessel 1, and an impeller 10 is attached to the upper end of the shaft 5.

A diffuser 11 is arranged around the outer periphery of the impeller 10 with a slight gap therebetween. 12 is a motor rotor, and a motor stator 13 is arranged inside the motor case 4 on the outer periphery of the motor rotor.

The thrust collar 7 has radial holes 7a formed therein and constitutes an auxiliary impeller 14. The auxiliary impeller 14 rotates as the shaft 5 is driven, circulates the coolant filled in the motor case 4 as shown by arrow A in the figure, and cools the motor rotor 12 and motor stator 13.

15 is a heat exchanger disposed in this coolant circulation flow path. When the circulation pump is started, the total weight of the rotating bodies, such as the impeller 14 and the pump shaft 5 including the thrust collar 7, rests on the lower thrust bearing 8b and is in fixed contact.
When started in this state of solid contact, there is a drawback that a lubricating film is not formed between the two, resulting in significant wear and the sliding surface being easily burnt out. As the rotation speed of the shaft 5 increases, the impeller 10 guides the coolant from above to below the pressure vessel 1, whereby the pressure on the outlet side of the impeller 10 becomes higher than that on the inlet side. Shaft 5 via impeller 10
A thrust force is generated to pull up the shaft 5, and the thrust collar 7 fixed to the shaft 5 floats above the thrust bearing 8b, and the solid contact is released. Therefore, it is necessary to take measures to minimize solid contact when starting and stopping the pump.

[Purpose of the invention]

The purpose of the present invention is to minimize the wear and burnout of the thrust bearing sliding surface when starting the circulation pump,
The objective is to provide a highly reliable thrust bearing device.

[Summary of the invention]

In order to achieve the above object, the present invention provides a thrust bearing device for a circulation pump built into a nuclear reactor, in which an auxiliary bearing support is disposed at the lower end of the shaft center via a sliding member, and when the shaft is started or stopped, It is characterized by being designed to support weight.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 2 to 5.

FIG. 2 is an enlarged view of a portion corresponding to the X section in FIG.

The same parts as in FIG. 1 will be described with the same reference numerals.

In the figure, 5 is a pump shaft, and a thrust collar 7 is formed at the lower end of the pump shaft. This thrust collar 7 is provided with radial holes 7a to constitute an auxiliary impeller 14 for transporting the coolant as indicated by the arrow in the figure. Thrust bearings 8a and 8b are arranged at the upper and lower ends of this auxiliary impeller 14.

The lower thrust bearing 8b has a spring arranged at the lower end,
It is supported by an elastic material 15 such as rubber. Further, an auxiliary bearing support 17 is disposed at the lower end of the shaft center of the shaft 5 with a sliding member 16 interposed therebetween.
It is constructed to support the weight of the vehicle when it is started or stopped.

Since the present invention is configured as described above, when the pump is started or stopped, the thrust collar 7 contacts the lower thrust bearing 8b due to its weight including the impeller 10 and the pump shaft 5, but supports the lower thrust bearing 8b. Depending on the amount of deflection of the elastic material 15, the auxiliary bearing support 17 is
I support b. Therefore, the load on the lower thrust bearing 8b can be reduced compared to the conventional structure. Therefore, it is easy to form a lubricating water film on the lower thrust bearing 2b from the stage when the pump is started, and the lower thrust bearing 8b is protected by the formation of the lubricating water film. Therefore, wear of the lower thrust bearing 8b is suppressed, and the life of the lower thrust bearing can be improved.

Further, the sliding member 16 of the auxiliary bearing body is used only for a very short time during startup, and the amount of heat generated is small because the bearing diameter is small and the peripheral rotational speed is slow. This sliding member 16 is made of ceramic, cemented carbide,
By selecting the material of the carphone, etc., a long life can be obtained.

3 to 5 show other embodiments of the auxiliary bearing support, and in the case of FIG. 3, the auxiliary bearing support 17 and the sliding body 16 are point supported, By doing so, there is an advantage that no excessive force is applied to the pump shaft 5 because it is not restricted by the inclination of the thrust collar 7.

In the case of FIG. 4, the sliding body 16 has a hemispherical shape, thereby achieving the same effect as above.

In the case of FIG. 5, a single or cross-shaped groove is bored on the surface of the thrust collar 7 of the sliding body 16, which activates the state of the lubricating water film, prevents abnormal wear of the sliding body 16, and prevents uneven contact. It has the advantage of alleviating the negative effects.

[Effects of the Invention] As explained above, in the present invention, since the auxiliary bearing support is arranged at the lower end of the shaft center, it is possible to prevent abnormal wear of the thrust bearing, especially the lower thrust bearing. By improving the lubricity between the thrust collar and the lower thrust bearing, the starting torque is reduced, and by reducing the starting current of the motor, the life of the motor can be extended.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a conventional circulation pump built into a nuclear reactor, and FIGS. 2 to 5 are enlarged sectional views of essential parts showing an embodiment of the thrust bearing device of a recirculation pump built into a nuclear reactor according to the present invention. , FIG. 2 is an enlarged sectional view of the X portion in FIG. 1, and FIGS. 3 to 5 are enlarged sectional views of the auxiliary bearing support portion. 5... Pump shaft, 7... Thrust collar, 8a, 8b... Thrust bearing, 15... Elastic material, 16... Sliding member, 17... Auxiliary bearing support.

Claims (1)

[Scope of Claims] 1. A motor case suspended and supported at the bottom of a reactor pressure vessel, a shaft to which an impeller is connected, which is housed in the motor case and has an upper portion protruding into the pressure vessel, and the shaft. In the reactor built-in recirculation pump, the recirculation pump is equipped with a journal bearing and a thrust bearing that are supported in the motor case, and an auxiliary bearing support body is disposed at the lower end of the axial center of the shaft via a sliding member, and the shaft A thrust bearing device for a recirculation pump built into a nuclear reactor, characterized in that it supports the weight of the recirculation pump when it starts and stops. 2. A thrust bearing device for a recirculation pump built into a nuclear reactor according to claim 1, wherein the sliding member is point-supported on an auxiliary bearing support and is tiltable. 3. An atom according to claim 1, characterized in that the thrust bearing side of the sliding member is formed into a hemispherical shape, and the shaft facing the hemispherical sliding member is bored into a hemispherical shape. Thrust bearing device for recirculation pump with built-in furnace. 4. A thrust bearing device for a recirculation pump built into a nuclear reactor according to claim 1, characterized in that the sliding member facing the shaft is provided with a groove through which lubricating fluid flows.