Добавил:
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
01 POWER ISLAND / Overview of Light Water.docx
Скачиваний:
0
Добавлен:
01.04.2025
Размер:
8.88 Mб
Скачать

  1. Reactor coolant pumps

The RCPs circulate the reactor coolant through the RV and the SG, to transfer heat generated in the reactor core to the secondary coolant in the shell side of the SG.

  1. Design requirements

The followings are the main items of the RCP design requirements:

(D The pump capacity represented by the flow rate and the head should satisfy the flow rate required for cooling of the reactor core.

(D The available net positive suction head should have a sufficient margin for the required NPSH of the pump.

(3) A flywheel should be installed on the pump motor shaft to give additional rotating inertia, so that in the event of an electric power supply loss, a rapid flow coast-down, and a resultant sharp decrease in the core cooling capability of the coolant can be avoided.

@ The mechanical integrity of the pump should be maintained even at an overspeed condition up to 125% of the normal operating speed.

  1. The pump casing should satisfy the applicable temperature-pressure criteria and seismic design criteria, as an integral part of the reactor coolant pressure boundary.

(§) The shaft seal system has three shaft seal assemblies of which the primary one employs a non-contact controlled leakage design, while the second and the third employ contact type mechanical seal designs.

© The pump should be designed to make maintenance tasks and in-service inspections easy and reliable.

(8) The design and manufacturing of the RCPs

must be made in accordance with the applicable technical codes pertaining to the structures of NPPs.

  1. Structures and functions

Three models of RCPs, 93A-1, 93A and 100D are used in the standard PWR plant designs. The 93A-1 model pump is an improved version of the 93A pump, and the model 100D pump is for plants in the area with the electric power of 50 Hz frequency (the other two models are for the 60 Hz frequency area). All three models have basically the same design, and the model 93A-1 pump design is described as follows.

  1. Main specifications

The main specifications of a Model 93A reactor coolant pump are given in Table 3.4.7.

  1. Structure of pumps

A cross-sectional view of a RCP is shown in Figure 3.4.9. The pump is connected to the motor by a rigid coupling, and the axial thrust of the pump is supported by the thrust bearing of the motor. The pump casing, thermal barrier flanges, bolting rings and casing bolts are pressure­resistant parts of the reactor pump. A thermal barrier above the impeller limits the heat transfer from hot reactor coolant to the bearings and the shaft seals. Cold seal water is injected into the section between the bearing and the shaft seal to protect them against being exposed to hot reactor coolant. Even if the injection of the seal water stops, reactor coolant which enters into the bearing -shaft seal area is cooled with the thermal barrier cooling coil. A spool piece is installed between the pump coupling and the motor shaft to allow disassembling and re-assembling of the shaft seals without removing the motor.

  1. Shaft seal system

The pump has 3 shaft seal assemblies. The No.2 and No.3 seals used in the design of the improved type pumps, are easily maintainable cartridge type seals. The cross sectional drawings of the shaft seal assemblies, and the seal water flow diagram are shown in Figures 3.4.10 and 3.4.11, respectively. a.No. 1 seal

The No. 1 seal bears a differential pressure almost equal to the RCS pressure, serving as the primary shaft seal. It employs a non-

NSRA, Japan

3-44

Chapter 3 Systems of PWR Nuclear Power Plants

Table 3.4.7 Reactor coolant pump (Type 93 A-1) main data

Item

Data

Item

Data

Pump Type

Vertical shaft, single stage,

Seal Injection Flow rate

~1.8m’/h

diagonal flow pump

Thermal Barrier Coolant-Flow rate

,'-9. Im’/h

Pump Catalogue No.

93A-1

Motor Type

3-phase, induction closed

Max. Design Pressure

17.16 MPa [gage]

squirrel cage type motor

Mix. Design Temperature

343°C

Motor Output

4, 480kW

Re led Operating Pressure

15.4 MPa [gage]

Power Supply

60Hz, 6,600V

(suction)

Inertia of Rotating Parts

GDZ=13,840kg • m=

Reled Operating Temperature

2sa rc

Total Height

''-'7, 853tirn (pump and motor)

Reled Flow Rale Reted Total Head Synchronous speed Coolant Density

20. lOOm’/h

84.4m

l,200rpm

Cold-1.0 Hot-fl. 748

Total Weight

■~”86. 3ton (pump and motor)