JPH03233398A - Feed water heating system for nuclear reactor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention relates to a feed water heater system for a nuclear power plant,
In particular, the present invention relates to a feed water heater drain pump up system that increases the pressure of drain condensed in a feed water heater using a drain pump and sends the pressure to a condensate pipe.

(Prior Art) Generally, in a nuclear power plant, condensate or feed water is heated by turbine bleed air in a feed water heater and then sent to a steam generator.

The turbine bleed air condensed in the feedwater heater becomes a drain and is sequentially sent to each feedwater heater on the low pressure side, and finally recovered to the condenser.

However, as a means to further improve the thermal efficiency of nuclear power plants, instead of cascading the drain from the feedwater heater and recovering it to the condenser, it is supplied to the condensate pipe that supplies condensate via a drain pump. systems, ie, feed water heater drain pump-up systems, are being adopted.

In this feedwater heater drain pump-up system, the saturated drain condensed in the feedwater heater is directly mixed with condensate, which greatly contributes to raising the condensate temperature and feedwater temperature, improving the efficiency of the power plant by approximately 0.5%. You can. For this reason, the latest nuclear power plants tend to adopt the above-mentioned feed water heater drain pump-up system.

On the other hand, the feedwater heater drain pump-up system can be broadly divided into (1) high-pressure drain pump-up system that pumps up the drain of the high-pressure feedwater heater and supplies it to the condensate pipe, and ■ pumps up the drain of the low-pressure feedwater heater. There are two types of low-pressure feedwater heater drain pump-up systems that supply water to condensate pipes, and these are used singly or in combination.

An example of a high-pressure feedwater heater drain pump-up system that has already been proposed is shown in Fig. 3. The prior art will be explained below with reference to the drawings.

The exhaust gas of the turbine 1 is condensed in a condenser 2, becomes condensate and temporarily stagnates, is then boosted in pressure by a condensate pump 3, passes through a condensate purifier 4, and is then heated in low pressure feed water heaters 5a and 5b. The water is sent to the water supply pump 7 through the condensate pipe 6. The condensate whose pressure is further increased by the feed water pump 7 becomes feed water and is supplied to the high pressure feed water heater 8a.

After being further heated at 8b, it is fed through a water supply pipe 9 to a steam generator (not shown). On the other hand, the low pressure feed water heater 5a
, 5b and the high pressure feed water heaters 8a, 8b are connected to the turbine l.
The bleed air is sent to a bleed pipe (not shown), and is condensed through heat exchange in each feed water heater 5a, 5b, 8a, 8b to produce drain. High pressure water heater 8a, 8b
The drain is collected into the drain tank 11 through the drain pipe 10a and lob, and the drain temporarily stored in the drain tank 11 is led to the drain pump 13 installed in the drain pipe 12, and the drain pump 13 increases the pressure. After that, it is supplied to the condensate pipe 6 and mixed with condensate.

On the other hand, a water level transmitter 14 is installed in the drain tank 11. The signal from the water level transmitter 14 is processed by the water level controller 15 and sent to the water level control valve 16 installed at the outlet of the drain pump 13, so that the water level in the drain tank 11 becomes the specified value. The opening degree of 16 is adjusted.

In addition, when the drain pump 13 is stopped, etc., the drain tank 1
An emergency drain pipe 17 is installed in case the water level of the tank 1 rises abnormally.

An emergency water level control valve 18 is attached to the emergency drain pipe 17, and when the water level in the drain tank 11 rises abnormally, a "water level high" signal from the water level transmitter 14 is sent to the emergency water level controller 15. The signal is transmitted to the emergency water level control valve 18, and the emergency water level control valve 18 is opened. As described above, when the water level in the drain tank 11 rises abnormally, the excess drain in the drain tank 11 is passed through the emergency water level control valve 18 to the condenser 2.
It is configured to be discharged.

In this way, the feedwater heater drain pump-up system described above can directly mix the drains of the high-pressure feedwater heaters 8a and 8b with condensate to increase the condensate temperature and the feedwater temperature, thereby improving the thermal efficiency of the power plant. It is possible to improve the

(Problem to be Solved by the Invention) However, the above-mentioned feedwater heater drain pump-up system has a serious effect on the water supply to the steam generator if the emergency water level control valve 18 is shut down due to a failure during plant operation. It had the disadvantage of giving

In other words, if the emergency water level control valve 18 makes a false alarm for some reason, the drain in the drain tank 11 will leak to the condenser 2 even though the water level in the drain tank 11 is normal.
This will result in leakage. In particular, since the emergency water level control valve 18 is used as a backup for the water level control valve 16, if the operating air for the emergency water level control valve 18 is lost, the emergency water level control valve 18 will fail. It is often open. Therefore, due to loss of working air or other failure, the emergency water level control valve 18 becomes fully open, causing a situation in which a large amount of condensate flows out into the condenser 2.

In such a state, the water level in the drain tank 11 will drop rapidly, and the drain pump 13 will become idle, so the drain pump 13 has to be stopped and the drain from the high-pressure feed water heaters 8a and 8b is stopped. It becomes impossible to send condensate water to the water supply. This results in a sudden decrease in the amount of water supplied to the steam generator, which has a major impact on the operation of the nuclear power plant.In the worst case scenario, significant fluctuations in the flow rate of the steam generator feed water may cause a scram (emergency shutdown) of the reactor. There is also a risk of causing problems, and there is also a risk of interfering with the healthy operation of the power generation plant.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to maintain the water level of the drain tank even when the emergency water level control valve of the drain tank fails, and to improve reliability during operation. shall be.

[Structure of the invention]

(Means for Solving the Problems) The present invention achieves the above object, and includes a feed water heater that heats feed water by exchanging heat with bleed air from a turbine, and a water heater that condenses the bleed air. A drain tank that collects the drain obtained from the process, a drain pipe that leads the drain in the drain tank to the water supply on the upstream side of the feed water heater by increasing the pressure of the drain pump, and a drain pipe installed in the middle of the drain pipe and inside the drain tank. A water level control valve that adjusts the water level, an emergency drain pipe that guides the drain in the drain tank to the condenser of the turbine, and an emergency drain pipe installed in the middle of this emergency drain pipe that adjusts the water level in the drain tank in case of an emergency. In a reactor feed water heater device having a water level*i valve, a shutoff valve is disposed in the middle of an emergency drain pipe in series with the emergency water level control valve.

(Function) In the present invention, by providing a shutoff valve in the emergency drain pipe and fully opening the shutoff valve, even if the emergency water level control valve misreads for some reason, the drain will flow out and the water level of the drain tank will drop. prevent. Furthermore, the above-mentioned shutoff valve is fully opened only when the level switch installed in the drain tank sends a high water level signal, and when the drain tank water level is below the specified value, the shutoff valve is fully opened, so even if the emergency water level control valve is Even if the valve is fully opened due to a failure, condensate will not flow out to the condenser through the emergency water level control valve.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. In the present invention, the same constituent members as those in the above-mentioned specific example will be described with the same reference numerals.

In FIG. 1, an electrically or pneumatically operated shutoff valve 19 is installed in the emergency drain pipe 17. Further, the drain tank 11 is provided with a level switch 20, and a signal from the level switch 20 is sent to the cutoff valve 19. The level switch 20 generates a control signal to fully open the shutoff valve 19 when the water level in the drain tank 11 reaches a "water level high" which is slightly higher than the specified value, and when the water level is lower than the "water level high", the shutoff valve 19 is configured so that a full open signal is sent to the

In the embodiment described above, the drain from the drain tank 11 is not fed to the condensate pipe 6 when the drain pump 13 is stopped. Therefore, the water level rises to the above-mentioned "water level high" due to the drain accumulated in the drain tank, and the level switch 20
The shut-off valve 19 is fully opened by the signal from. For this reason,
Drain from the drain tank 11 is fed to the condenser 2 through an emergency drain pipe 17. Further, the water level of the drain tank 11 is controlled by a signal from the water level transmitter 14 sent to the emergency water level 5J control valve 18 via the water level controller 15, and the emergency water level control valve 18 is activated to maintain the "water level high" level. The opening degree is adjusted and the water level of the drain tank 11 is controlled.

On the other hand, when the drain pump 13 is in operation, so-called steady operation, drain from the drain tank 11 is being fed to the condensate pipe 6 by the drain pump 13 . The water level in the drain tank 11 is sent to a water level controller 15 by a water level transmitter 14, and the water level controller 15 is connected to a water level control valve 16.
In order to send a control signal so that the water level of the drain tank 11 becomes the specified value, the water level of the drain tank 11 is controlled at the specified value. Here, since the water level of the drain tank 11 is lower than the specified value, that is, the "water level high", the shutoff valve 19 is fully opened by the signal from the level switch 20.

In this way, according to this embodiment, the shutoff valve 19 is fully open during steady plant operation, so even if the emergency drain water level control valve 18 misreads due to some kind of malfunction, the emergency drain pipe 17 will not be closed. Drainage does not flow out into the condensate pipe 2, and the water level in the drain tank 11 is not affected at all. Furthermore, since there is no problem with the operation of the drain pump 13, the water supply to the steam generator does not change at all.

The present invention is not limited to the level switch 20 as a means for fully opening the shutoff valve I9 during steady plant operation. For example, as shown in FIG. 2, the shutoff valve 19 may be fully opened or controlled to be fully opened by a signal from a flow rate switch 21 provided at the outlet of the drain pump 13. That is, when the drain pump 13 is stopped, the shutoff valve 19 is fully opened by a low flow rate signal, and when the drain pump 13 is in operation and the drain flow rate exceeds a certain value, it is determined that the plant is in a steady operating state, and the shutoff valve 19 is fully opened. It is controlled to be closed.

〔Effect of the invention〕

As described above, according to the present invention, a shutoff valve is provided in the emergency drain pipe that discharges drain from the drain tank to the condenser in an emergency. It can prevent the condenser hedren from flowing out through the drain pipe, and the reliability of the feedwater heater drain pump-up system can be improved.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of a feedwater heater device for a nuclear reactor according to the present invention, Fig. 2 is a system diagram showing another embodiment according to the invention, and Fig. 3 is a system diagram showing an already proposed feedwater heater device. It is a system diagram showing an apparatus. l...Turbine 2...Condenser 3...
Condensate pump 4... Condensate purifier 5a, 5b
...Low pressure feed water heater 6...Condensate pipe 7...Water supply pump 8a, 8b...High pressure feed water heater 9...Water supply pipe 1
0a, lOb...Drain pipe 11...Drain tank 12...Drain pipe 13...Drain pump 14...Water level transmitter 16...Water level control valve 18...Emergency water level control valve 20 ... Level switch 15 ... Water level controller 17 ... Emergency drain pipe 19 ... Shutoff valve 21 ... Flow rate switch

Claims (3)

[Claims] (1) A feed water heater that heats the feed water by exchanging heat with the bleed air from the turbine; a drain tank that stores the drain obtained by condensing the bleed air in the feed water heater; A drain pipe that leads to the water supply upstream of the feed water heater by increasing the pressure by the drain pump, a water level control valve disposed in the middle of this drain pipe to adjust the water level in the drain tank, and a water level control valve that controls the water level in the drain tank by a turbine. A feed water heater device for a nuclear reactor, comprising an emergency drain pipe leading to a condenser, and an emergency water level control valve disposed in the middle of the emergency drain pipe to adjust the water level in the drain tank in an emergency. A feedwater heater device for a nuclear reactor, characterized in that a cutoff valve is disposed in series with the emergency water level control valve in the middle of the emergency drain pipe. (2) The reactor feedwater heater device according to claim 1, wherein the shutoff valve opens when the water level in the drain tank is higher than a predetermined level, and closes when the water level is lower than the predetermined level. . (3) The feedwater heater device for a nuclear reactor according to claim 1, wherein the shutoff valve is opened when the flow rate in the drain pipe is less than a predetermined value, and closed when the flow rate is greater than the predetermined value.