JPH0350404A - Control of feed water/condensate pump - Google Patents

Abstract

PURPOSE:To suppress variations in the water level in a reactor by connecting the suction side of a turbine-driven reactor feed water pump and a motor-driven reactor feed water pump to a minimum flow rate system for the turbine-driven reactor feed water pump through a condensate minimum flow rate line having a flow control valve and a flow limiting orifice. CONSTITUTION:Minimum flow rate systems 17, 17 each having a minimum flow rate control valve 9 for securing a minimum flow rate through a turbine-driven reactor feed water pump 6 are independently provided for each pump, and are connected to a condenser 2. A condensate minimum flow rate line 12 is provided to extend from the suction side of the feed water pump 6, 10 to one of the minimum flow rate systems 17 for the turbine-driven reactor feed water pumps 6, and the line 12 is provided with a condensate minimum flow rate control valve 13 and a condensate minimum flow rate control orifice 14, whereas the one minimum flow rate system 17 is provided with a check valve 15 on the upstream of the point of connection with the line 12. Even where all the feed water pumps are stopped, a required minimum flow rate corresponding to the capacity of two high-pressure condensate pumps 4 can be secured by the functions of minimum flow rate control valves 11, the valve 13 and the orifice 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a control method for a water supply and condensate pump in a nuclear power plant, which improves the minimum flow rate control system of the water supply and condensate pump.

(Prior art) In the minimum flow rate control system of feed and condensate pumps in nuclear power plants, turbine-driven reactor feed water pumps (T/DRF
Only one motor-driven reactor feed pump (M/DRFP) is installed as a standby unit for the condensate pump and the motor-driven reactor feed pump (referred to as P), and the minimum flow rate is shared between the condensate pump and the motor-driven reactor feed pump. has been done.

FIG. 2 shows a main system diagram of a nuclear power plant having only one motor-driven reactor feed water pump. In FIG. 2, the steam that has done work in the turbine 1 is cooled by seawater and becomes condensed water, which accumulates in the condenser 2. This condensate is pressurized by a low pressure condensate pump 3 and sent to a high condensate pump 4. Here, the condensate is further pressurized and sent to the turbine-driven reactor feedwater pump 6 via the low-pressure feedwater heater 5 . The condensate is raised to a pressure that can be sent to the reactor 8 by a turbine-driven reactor feedwater pump 6, and is sent to the reactor 8 via a high-pressure feedwater heater 7. Here, electric motor driven reactor feed water pump 1G
is used as a backup water pump in case of failure of the turbine-driven reactor feed water pump 6.

Now, in general, the minimum flow rate required for pumps to avoid heating due to shut-off operation and to perform stable operation is determined, and if the demand for water supply from the reactor 8 is less than this, the pump is restored via the minimum flow rate system. By circulating the condensate to the water container 2, a minimum flow rate is ensured.

In FIG. 2, the minimum flow rate system 16 is shared between the high-pressure condensate pump 4 and the motor-driven reactor feed water pump 10, and has a system for circulating to the condenser 2 via the minimum flow control valve 11. On the other hand, the turbine-driven nuclear reactor feedwater pump 6 also has a minimum flow system 17 that circulates to the condenser via the minimum flow control valve 9 independently for each pump. To give an example of the capacity of the minimum flow rate system 16 including the minimum flow rate control valve II, the discharge pressure during operation of the motor-driven reactor feed water pump 10 is approximately 150 kg/am2, which is equivalent to the capacity of two high-pressure condensate pumps 4. The design is such that the required minimum flow rate is 7Q OT/H.

This is the required minimum flow f of the motor-driven reactor feed water pump 10.
fi larger than 600T/H and high pressure condensate pump 4
This is because the required minimum flow rate of 350 T/H for two high-pressure condensate pumps 4 can be flowed at a discharge pressure of about 50 Kg/cm' during operation. On the other hand, the minimum flow control valve 9 of the turbine-driven nuclear reactor feed water pump 6 is designed to have a capacity for each line to flow about 1000 T/H at a discharge pressure of about 15 [1 kg 7 cm 2 ] when the feed water pump 6 is in operation.

(Problems to be Solved by the Invention) However, such a design is only possible in a plant having two motor-driven reactor feed water pumps 10.

This is because when an abnormal situation occurs, such as when all reactor water pumps are stopped, a situation where two high-pressure condensate pumps 4 are operated while the motor-driven reactor feed water pump 10 is stopped can occur, and in this case, the electric If there are two driven nuclear reactor feed water pumps 10, it is possible to flow the required minimum flow rate 7rJOT/)I for two high pressure condensate pumps 4 at the discharge pressure of the high pressure condensate pump 4, but if there are two driven nuclear reactor feed water pumps 10, Furnace water pump 10
This is not possible in a plant with only one unit.

As a countermeasure to this problem, it is possible to increase the capacity of the minimum flow rate system 16 of the motor-driven reactor feed water pump 10, but conventionally, fluctuations in the reactor water level due to fluctuations in the feed water flow rate when the minimum flow control valve 11 opens and closes are However, increasing the capacity of the minimum flow system is impossible because it would further increase fluctuations in the reactor water level.

As mentioned above, if the capacity of the minimum flow system is such that the fluctuation in the reactor water level when the minimum flow control valve 11 opens and closes during normal operation including plant start-up and shutdown is set to a minimum, the motor-driven reactor feed water pump 10 When stopped, the required minimum flow rate for two high-pressure condensate pumps 4 is 700T/
If H cannot be secured and the minimum flow system is designed to have a capacity that can flow the minimum flow rate of 700T/H for two high-pressure condensate pumps when the motor-driven reactor feed water pump 10 is stopped, the minimum flow rate adjustment valve There was a problem in that fluctuations in the reactor water level when No. 11 was opened and closed increased to an unacceptable level.

The purpose of the present invention is to suppress fluctuations in the reactor water level within an allowable range when the minimum flow control valve opens and closes when all feedwater pumps stop when two high-pressure condensate pumps are in operation, and to An object of the present invention is to provide a control method for a water supply and condensate pump that can ensure a minimum flow rate.

[Structure of the Invention] (Means for Solving the Problems) A method for controlling a feed and condensate pump of the present invention is such that only one motor-driven reactor feed water pump is installed as a standby unit for a turbine-driven reactor feed water pump, In a water supply and condensation system of a nuclear power plant in which a minimum flow system shared by the motor-driven reactor feed water pump and the high-pressure condensate pump is provided between the discharge side of the motor-driven reactor feed water pump and the condenser, The suction side of the driven nuclear reactor feed pump and the motor-driven reactor feed water pump and the minimum flow system of the turbine driven reactor feed water pump are connected by a condensate minimum flow line having a flow rate regulating valve and a flow rate limiting orifice, and the condensate pump When all the feed water pumps including the motor-driven reactor feed water pump stop while multiple units are in operation, a portion of the minimum flow rate of the condensate pump is passed through the minimum flow system of the motor-driven reactor feed water pump. At the same time, the remainder of the minimum flow rate of the condensate pump is passed through the minimum condensate line.

(Function) In the present invention, when all the water supply pumps stop,
With two high-pressure condensate pumps operating, with the motor-driven reactor feed water pump operating, and with the minimum flow rate system of one motor-driven reactor feed water pump, the discharge pressure when the two high-pressure condensate pumps are operating. The water is circulated to the condenser via the minimum flow control valve. The flow rate at this time is insufficient to the minimum flow rate of approximately 70OT/H when two high-pressure condensate pumps are operated. However, at the same time, the insufficient flow rate is circulated through the condensate minimum flow line using the discharge pressure of the high-pressure condensate pump, and the high-pressure condensate pump
Ensure minimum flow rate for each vehicle.

(Example) The present invention will be described below with reference to an example shown in FIG. FIG. 1 is a control system diagram of a water supply and condensate pump to which the water supply and condensate pump control method of the present invention is applied, and the same parts as in FIG. 2 are given the same reference numerals and their explanations are omitted.

In FIG. 1 illustrating a control system to which the feed condensate pump control method of the present invention is applied, condensate pressurized by a high pressure condensate pump 4 passes through a low pressure feed water heater 5 and a turbine driven reactor feed water pump 6. 6 and a motor-driven reactor feedwater pump 1o, where the pressure is further increased and the water is sent to the reactor 8 via a high-pressure feedwater heater 7.

In addition, the water supply request from the reactor 8 is controlled from the discharge side of the motor-driven reactor feed water pump 10 to the minimum flow control valve 1j in order to ensure the minimum flow rate of the motor-driven reactor feed water pump lO and the high-pressure condensate pump 4 when the water supply is low. Water supply through condenser 2
A minimum flow rate system 16 is installed to return the flow rate to the minimum flow rate. The capacity of the minimum flow rate system 16 is such that fluctuations in the reactor water level can be suppressed within an allowable range even when the minimum flow rate control valve 11 is opened and closed.

On the other hand, the minimum flow system 17 has a minimum flow control valve 9 for ensuring the minimum flow rate of the turbine-driven reactor feed water pump 6.
17 is provided independently for each pump, and each condenser 2
is connected to. In addition, a condensate minimum flow rate line 12 is connected from the suction side of the feed water pumps 6 and 10 to one of the minimum flow rate systems 17 of the turbine-driven reactor feed water pump 6, and this line 1
2 is provided with a condensate minimum flow rate control valve 13 and a condensate minimum flow rate control orifice 14, and a check valve I5 is provided in the minimum flow rate system 17 of the turbine-driven reactor feed water pump 6 on the upstream side of the connection point.
has been established.

Next, a control method when all the water supply pumps are stopped in the water supply and condensate pump control system configured as described above will be explained. In this case, first, the two condensate pumps 4 are kept in continuous operation at high pressure.

(1) The water is circulated to the condenser 2 via the minimum flow rate system 16 of the condensate motor-driven reactor feed water pump 10.

At this time, the flow rate flowing through the minimum flow rate system 16 of the motor-driven reactor feed water pump 10 is originally designed to ensure the minimum flow rate of the feed water pump 10 at the operating discharge pressure of the motor-driven reactor feed water pump 10. Therefore, the discharge pressure of the high-pressure condensate pump 4 is several minutes lower than the discharge pressure of the motor-driven reactor feed water pump lO, so the operating pressure of the high-pressure condensate pump 4 is lower (approximately Ql/ h) is insufficient for the minimum flow rate for two high-pressure condensate pumps 4 (approximately 7H-Q l/h is insufficient).

(2) At this time, the remaining flow rate flows through the condensate minimum flow line 12 that connects the suction side of the feed water pump 6, IO and the minimum flow rate system 17 of one unit of the turbine-driven reactor feed water pump 6, and the remaining flow is caused to flow under high pressure. This will ensure the shortfall in the minimum flow rate of the condensate pump 4.

As a result, the minimum flow rate control valve 11 of the motor-driven reactor feed water pump 10 can be maintained at its conventional capacity (and compared to a dedicated minimum flow system for circulating the high-pressure condensate pump 4 to the condenser 2 independently). All that is required is the addition of a minimum condensate flow rate system with a sufficiently small capacity.

Even if all the water supply pumps are stopped in this way, the required minimum flow rate for the two high-pressure condensate pumps 4 is the minimum flow rate control valve 11, the minimum condensate flow rate control valve 13, and the minimum condensate flow rate orifice. 14.

[Effects of the Invention] As described above, according to the present invention, in a plant in which a single electric motor-driven reactor feed water pump is adopted, fluctuations in the reactor water level are within the permissible range even when the minimum flow control valve is opened and closed. Even if the capacity of the minimum flow system is suppressed to , it is possible to secure the required minimum flow rate of the high-pressure condensate pump when all the water supply pumps are stopped.

[Brief explanation of drawings]

FIG. 1 is a water supply and condenser system diagram of a nuclear power plant implementing the water supply and condensate pump control method of the present invention, and FIG. 2 is a conventional water supply and condensate system diagram. 1... Turbine 2... Condenser 3... Low pressure condensate pump 4... High pressure condensate pump 5... Low pressure feed water heater 6... Turbine driven reactor feed water pump 7... High-pressure feed water heater 8...Reactor 9...Minimum flow rate control valve 0...Motor driven reactor feed water l...Minimum flow rate control valve 2...Condensate minimum flow rate line 3...Condensate Minimum flow rate control valve 4...Condensate minimum flow rate control orifice 5...Check valve 6...Motor-driven reactor feed water pump minimum flow system 7.
...Turbine-driven reactor feed water pump minimum flow system (87
33) Agent: Yoshiaki Inomata, patent attorney (and 1 other person)

Claims (1)

[Claims] Only one motor-driven reactor feed water pump is installed as a standby unit for the turbine-driven reactor feed water pump, and the minimum flow system shared by the motor-driven reactor feed water pump and high-pressure condensate pump is In a water supply and condensation system of a nuclear power plant provided between a discharge side and a condenser, a minimum flow system of the turbine-driven reactor feed water pump and the suction side of the motor-driven reactor feed water pump and the turbine-driven reactor feed water pump. are connected by a condensate minimum flow rate line having a flow rate regulating valve and a flow rate limiting orifice, and when all the feed water pumps including the motor-driven reactor feed water pump stop while a plurality of the condensate pumps are in operation, A portion of the minimum flow rate of the condensate pump is passed through the minimum flow rate system of the motor-driven reactor feed water pump, and the remainder of the minimum flow rate of the condensate pump is passed through the minimum condensate line. How to control a water supply and condensate pump.