JPS6217121B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reactor feed water control system, and more particularly to a reactor water supply system suitable for rescuing a nuclear reactor from a scram caused by a drop in water level in a boiling water nuclear power plant.

Feedwater and condensate systems (hereinafter referred to as feedwater and condensate systems) in conventional boiling water (BWR) nuclear power plants
The main turbine condenser is used as a water source, and the pressure is increased step by step using a low pressure condensate pump (hereinafter referred to as LPCP) and a high pressure condensate pump (hereinafter referred to as HPCP), and finally the feed water pump (hereinafter referred to as RFP) is used. Through the reactor, water is supplied to the reactor with the flow rate controlled by a water supply flow rate control device. The reactor water level, feed water flow rate, and main steam flow rate are input as process detection signals to the feed water flow rate control device, which calculates them and provides a feed water flow rate request signal to the RFP, which controls the flow rate of the RFP. The range is designed to be within the design maximum flow rate of the condensate pump.

However, if the RFP receives a water supply request that exceeds the design capacity of the condensate pump due to transient changes in the plant,
Alternatively, if a bypass line of the water supply and condensate system (a line that returns from the middle of the water supply and condensate system to the condenser and is closed during normal operation) is formed due to malfunction or operation, the LPCP discharge flow rate, that is, the Since the water flow rate exceeds the design capacity of LPCP and the system pressure of the water supply and condensate system decreases rapidly, HPCP, RFP
The pump protection function works and all HPCP and RFP units trip.

In addition, if one of the LPCP, HPCP, etc. trips due to an operational problem, the standby unit will automatically start up, but during this time, the water supply demand will become excessive due to transient changes in the reactor water level, and the system pressure of the water supply and condensate system will increase. The trip point of protection will be approached. If the system pressure of the water supply and condensate system falls below the trip point,
All HPCP and RFP units trip, resulting in what is called a loss of water supply, resulting in a drastic drop in the reactor water level, and the emergency core cooling system (hereinafter referred to as ECCS) is activated, reducing unnecessary heat to the reactor pressure vessel. This will add stress. Preventing this is also important in improving the safety of nuclear reactors.

The present invention was developed in view of the current situation, and its purpose is to avoid reactor scrams caused by water supply and condensate pump tripping, and to avoid ECCS caused by a large drop in reactor water level due to loss of all water supply water. Unnecessary operation of the system can be prevented. To provide reactor water supply control equipment.

The present invention includes a maximum water supply flow rate limiting means that limits the maximum value of a water supply request signal that controls the water supply flow rate to within an allowable value according to the conditions of the water supply system and the condensate system;
A reactor output tracking means is provided to reduce the reactor output in accordance with the limit value when this limit value falls below the reactor output, thereby preventing the suction pressure of the feed and condensate pump from falling below the trip point. At the same time, the reactor water level control was carried out smoothly.

The present invention will be described below based on an illustrated embodiment.

In Fig. 1, 1 is a nuclear reactor, and steam from this reactor 1 is supplied to a main turbine 3 via a main steam pipe 2, and after doing work there, it is cooled in a condenser 4 and condensed. It is becoming like water.

Condensate from condenser 4 is LPCP5 and HPCP
6, and is supplied to the nuclear reactor 1 through the RFP 8, which is controlled by the water supply control device 7 according to the present invention. Between the LPCP 5 and HPCP 6, as shown in FIG. 1, an auxiliary condenser 9 and a demineralizer 10 are installed.
In addition, a water heater 11 is installed between HPCP6 and RFP8.
are provided for each. The water supply control device 7
1, the main steam flow rate signal 1 from the main steam flow rate detector 12 provided in the main steam pipe 2 is detected.
3. Reactor water level signal 15 from the reactor water level detector 14 provided in the reactor 1, feed water flow rate signal 17 from the feed water flow rate detector 16 provided in the water supply system, HPCP suction pressure as system pressure of the water supply and condensate system Detection signal 18 and reactor power detector 1 provided in the reactor 1
Reactor output signals 20 from 9 are respectively inputted, and from the water supply control device 7, a water supply request signal 21 that controls the RFP 8 and a reactor recirculation flow rate control device (hereinafter referred to as PLR) are input. PLR runback signals 22 are output respectively.

As shown in FIG. 2, the feed water control device 7 includes a reactor water level control circuit (hereinafter referred to as FWC) 23, a maximum feed water flow rate limiting circuit (hereinafter referred to as MFWL) 24, and a low value priority device (hereinafter referred to as LVG) 25. and a reactor power follow-up circuit (hereinafter referred to as LFC) 26, and the FWC 23 includes a main steam flow rate signal 1.
3. The reactor water level signal 15 and the feed water flow rate signal 17 are respectively input as process detection signals, and
The HPCP suction pressure detection signal 18 is input to the MFWL24, and the reactor output signal 2 is input to the LFC26.
0 is now entered. and,
The output signal 27 from the FWC 23 and the output signal 28 from the MFWL 24 are input to the LVG 25, where both signals 27 and 28 are compared, and the low value signal 27 or 28 is selected as the water supply request signal 21.
It is set to be output from LVG25.
The output signal 28 of the MFWL 24 is also coupled to the LFC 26 along with the reactor power signal 20 as shown in FIG.
When the output signal 28 is less than the value of the reactor output signal 20, the PLR runback signal 22 is output from the LFC 26, and the output of the reactor 1 is reduced. It's becoming like that.

The MFWL 24 has a built-in function generator (hereinafter referred to as F/G) 29 as shown in FIG.
The deviation signal 31 after comparing the set pressure signal 30 is inputted, and the MFWL24 is input from the F/G29.
An output signal 28 is output.

Next, the operation of the present invention will be explained.

F/G29 of MFWL24 outputs a constant signal equivalent to the design flow rate of LPCP5 and HPCP6 when the system pressure exceeds the set pressure, that is, for a positive input deviation signal, and when the system pressure is below the set pressure. In other words, for a negative input deviation signal, the maximum flow rate of the water supply and condensate system is limited to a value that compensates for the characteristics shown in FIG. 4 in accordance with the deviation signal. As a result, if the system flow rate is within the design flow rate of LPCP5 and HPCP6, the output of MFWL24 is constant.
Since the output of FWC23 is smaller, the water supply request signal 21 from LVG25 is the output signal 2 of FWC23.
7, and the water supply flow rate is controlled in the same manner as before.

In the transient state of the plant, the water supply request is LPCP5,
If the flow rate exceeds the design flow rate of HPCP6, or if the bypass line of the water supply and condensate system malfunctions or a flow path is formed due to incorrect operation, the condensate flow rate
5. The design flow rate of HPCP6 may be exceeded. In this case, the HPCP suction pressure detection signal 18 of the MFWL24 falls below the set pressure signal 30, and depending on the deviation, the MFWL2
The output of 4 is throttled.

When the output signal 28 of the MFWL 24 falls below the value of the output signal 27 from the FWC 23, the water supply request signal 21 from the LVG 25 is regulated and throttled by the output signal 28, and acts on the RFP 8 to reduce the condensate flow rate.

On the other hand, when the water supply flow rate falls below the reactor output in response to the water supply request signal 21, the water level in the reactor 1 decreases and reactor water level control becomes impossible. To solve this problem, when the output signal 28 of the MFWL 24 falls below the value of the reactor output signal 20, the LFC 26 detects this and outputs a PLR runback signal 22 to the PLR to increase the reactor output. reduce

When the water supply flow rate is throttled, the HPCP suction pressure is restored and the output of the MFWL 24 increases. and,
When the PLR runs back, the reactor water level rises.
Since the output of FWC23 decreases, FWC23
The output of the reactor will control the reactor feed water flow rate.

However, for some reason, the condensate flow rate may become LPCP.
5. Even if the design flow rate of HPCP6 is exceeded, the MFWL24 detects this and throttles the water supply flow rate to keep the condensate flow rate below the design flow rate of LPCP5 and HPCP6, and the suction pressure of HPCP6 and RFP8 reaches the trip point. Prevent this from happening. Furthermore, the MFWL 24 functions to reduce the output of the reactor 1 by throttling the water supply flow rate and at the same time runback the PLR, so that subsequent reactor water level control is performed smoothly.

As explained above, according to this embodiment, the condensate flow rate is automatically controlled to prevent the suction pressure of the feed and condensate pump from dropping below the trip point due to transient conditions of the plant or malfunction of the feed and condensate system. It is possible to prevent all water supply and condensate pumps from tripping. This will not only improve the plant's operating efficiency, but also allow the reactor water level to drop significantly.
The ECCS system is activated to prevent unnecessary thermal stress from being applied to the original reactor pressure vessel.

The present invention has been described above based on the preferred embodiments. According to the present invention, it is possible to avoid a reactor scram caused by a feed water pump trip, and a large drop in reactor water level due to loss of all feed water. by
Unnecessary activation of ECCS can be prevented.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing one embodiment of the present invention, Figure 2 is a system diagram showing an embodiment of the present invention.
The figure is a block diagram showing the configuration of the water supply control device according to the present invention, FIG. 3 is a block diagram showing the configuration of the MFWL, and FIG. 4 is a system pressure characteristic diagram of the water supply and condensate system. 1... Nuclear reactor, 4... Condenser, 7... Water supply control device,
8... RFP, 13... Main steam flow rate signal, 15... Reactor water level signal, 17... Feed water flow rate signal, 18... HPCP suction pressure detection signal, 20... Reactor output signal, 21... Water supply request signal, 22... PLR runback signal, 23...
FWC, 24...MFWL, 25...LVG, 26...
LFC, 29...F/G, 30...Setting pressure signal, 3
1... Deviation signal.

Claims (1)

[Claims] 1. In the reactor feed water control system that controls the water supplied from the condenser to the reactor via the feed water pump, the maximum value of the water supply request signal that controls the feed water flow rate is adjusted according to the conditions of the water supply system and the condensate system. It is characterized by comprising a maximum water supply flow rate limiting means for limiting the flow rate to within a permissible value, and a reactor output follower means for reducing the reactor output in accordance with the limit value when this limit value falls below the reactor output. Reactor water supply control system.