Reactor coolant pump set

Abstract

Non-Volume displacement pumps used at nuclear power plants (NPP) in reactor coolant pump sets for the primary coolant circuit of the nuclear power system. The reactor coolant pump set comprising a vertical vane-type single-stage pump with bottom arrangement of the impeller, the pump shaft is connected to the electric motor shaft by a rigid coupling, the radial-axial bearing, installed in the electric motor upper chamber, is made of two main elements: a radial bearing made in the form of a rotor metallic bushing installed on the cylindrical part of the collar and an axial bearing consisting of two stator lever-type balance arm systems with cover plates of antifriction material and rotor cover plates of antifriction material. The radial-axial bearing is cooled by water from the NPP system, pressure head whereof is increased by the screw-type pump located on the upper butt of the radial-axial bearing collar.

Claims

1. A reactor coolant pump set, comprising a vertical vane-type single-stage pump with a bottom arrangement of an impeller, a lower radial journal bearing arranged on a pump shaft above the impeller and lubricated by a transferred medium, a pump shaft seal assembly made in the form of a multistage block of face seals, arranged above the lower radial bearing, a flywheel installed under a radial bearing of the electric motor, characterized in that: (i) a pump shaft is connected to an electric motor shaft of the electric motor by a rigid coupling; (ii) a radial-axial bearing installed in an electric motor upper chamber of the electric motor is made of two main elements: a radial bearing made in the form of a rotor metallic bushing installed on a cylindrical part of a collar, installed on the motor shaft by way of cone fitting and fastened by means of bolts and a pressure flange on an upper butt of the electric motor shaft, and an axial bearing consisting of two stator lever-type balance arm systems with cover plates of antifriction material and rotor cover plates of antifriction material, installed on a flat part of the collar; (iii) the radial-axial bearing is cooled by water from a nuclear power plant system, pressure head whereof is increased by a screw-type pump located on an upper butt of the radial-axial bearing collar, and composed of a stator and a rotor bushing with a screw thread; (iv) water flows from the electric motor upper chamber via a pipeline, installed on an electric motor wall of the electric motor, to an electric motor lower chamber of the electric motor, the electric motor lower chamber being made in the form of a stainless steel cylinder, and the water that flows from the electric motor upper chamber lubricates the electric motor radial bearing made in the form of a rotor metallic bushing and a stator bushing of antifriction material; and (v) water from the electric motor lower chamber is withdrawn via a bleeding pipeline to the nuclear power plant system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The proposed device (in a particular version) is explained by drawings:

(2) FIG. 1—RCPS overall view

(3) FIG. 2—Upper chamber of electric motor

(4) FIG. 3—Lower chamber of electric motor

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The vertical vane-type single-stage cantilever pump, (FIG. 1) with bottom arrangement of impeller 1, wherein pump body shaft 2 with lower radial bearing 3 cooled by the working medium is connected to electric motor shaft 4 by means of coupling 5, transmitting the torque and resultant axial force between the shafts. Radial-axial bearing 6, receiving all axial loads acting on the unit rotor, is installed in the electric motor upper chamber. Electric motor radial bearing 7 is installed in the electric motor lower chamber. Flywheel 8 is installed under the lower radial bearing of the electric motor.

(6) Lubricating water in the reactor coolant pump set is supplied from the remote cooler of the NPP system via pipeline 9 to electric motor upper chamber 10. Pipeline 9 is connected with the upper chamber by flange connector 11. Upper chamber 10 is a leakproof structure made of stainless steel in cylinder shape. Chamber 10 consists of housing 12 (FIG. 2), whereon by means of bolted joints the stator elements of the radial-axial bearing and tank 13 in the form of a cylinder, closed in the top and with a flange connector in the bottom, are installed. The tank is removable and fastened on housing 12 by means of bolts 14.

(7) Collar 15 of the radial-axial bearing is installed on the motor shaft by way of cone fitting. Collar 15 is fastened by means of bolts 16 and pressure flange 17 to the shaft's upper butt. Antifriction backup cover plates 18 are installed on the flat part of bearing collar 15. Metallic bushing 19 of the upper radial bearing is installed on the cylindrical part of collar 15. Metallic bushing 20 with screw thread is installed on the collar top. Together with mating screw bushing 21, fixed on the stator part of the radial-axial bearing, it forms a screw-type pump for cooling liquid circulation during pump unit operation. Radial bearing housing 22 is installed on housing 12 by means of a bolted joint. Upper stator thrust ring 23, consisting of lever-type balance arm system and cover plates made of antifriction material is installed between radial bearing housing 22 and collar 15. The lower thrust ring of similar design is installed between collar 15 and the bottom of housing 12.

(8) Face seal 24 is installed in the bottom of the upper chamber to prevent water ingress in the motor stator cavity. Seal leak comes to bleeding pipeline 25, connected via flanged joint 26 with leak collector 27 (FIG. 1).

(9) In the lower part of housing 12 bleeding pipe 28 is welded, which by means of flanged joint 29 is connected to adapter pipeline 30, being a pipe fixed on the external motor wall.

(10) Pressure head of the water for bearing lubrication, flowing to the upper chamber, is increased by the screw-type pump formed by the bushings with screw thread, and the water is pumped through the radial-axial bearing and then comes via the bleeding pipe to the adapter pipeline. The adapter pipeline by means of flanged joint 31 is connected with intake pipe 32 (FIG. 3) welded into the housing of lower chamber 33. The housing of the lower chamber is a leakproof cylindrical structure made of stainless steel, wherein motor radial bearing 7 is installed. Above the housing is upper face seal 34 to prevent leakage into the stator cavity. Face seal 35 is installed on the housing lower butt to prevent leakage into the cavity under the motor. The motor lower radial bearing is steel bushing 36 fastened on the motor shaft and stator bushing made of antifriction material 37, fastened on bearing housing 38, which in its turn is fastened by means of a bolted joint on the housing of lower chamber 33. Under the screw-type pump pressure head the water, flowing to the intake pipe of the lower chamber, lubricates the lower radial bearing and is withdrawn from the lower chamber via welded-in bleeding pipe 39 (FIG. 1) to bleeding pipeline 40, connected to the bleeding pipe by means of flanged joint 41. Water flows via the bleeding pipeline to the NPP remote cooler.

(11) To inspect and repair the radial-axial bearing, it is sufficient to unscrew bolts 14 and remove tank 13, unscrew and remove radial bearing housing 22; unscrew bolts 16, remove mounting flange 17, remove collar 15 and stator thrust rings of radial-axial bearing 23.

(12) Thus, reliability in this invention is increased due to installation of the radial-axial bearing lubricated with water not in the pump body, but in the electric motor upper chamber, and due to the rigid coupling transmitting the axial force and torque. This allows using the weight of the motor rotor with the flywheel to compensate the expulsive force and reduce the resultant force, and, consequently, the bearing loads.