JP2927860B2 - Feed water heater for reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a feed water heater system of a nuclear power plant, and more particularly, to a drain pump condensed by a feed water heater, which is pressurized by a drain pump and restored. The present invention relates to a feed water heater drain pump-up system for feeding a water pipe.

(Related Art) Generally, in a nuclear power plant, condensed water or feedwater is supplied to a steam generator after being heated by turbine bleed in a feedwater heater. The turbine bleed air condensed in the feed water heater is drained, sequentially cascaded to the respective feed water heaters on the low pressure side, and finally collected in the condenser.

However, as a means to further improve the thermal efficiency of the nuclear power plant, instead of cascading the drain of the feed water heater and collecting it in the condenser, it is supplied to the condenser pipe for sending the condensate via a drain pump. In other words, a feed water heater drain pump-up system has been adopted. In this feed water heater drain pump-up system, the saturated drain condensed in the feed water heater is mixed directly with the condensate to greatly contribute to the rise in condensate temperature and feed water temperature, thereby improving the efficiency of the power plant by about 0.5%. I can do it. For this reason, the latest nuclear power plants tend to employ the feedwater heater drain pump-up system.

On the other hand, the feedwater heater drain pump-up system is roughly classified into (1) a high-pressure drain pump-up system that pumps up the drain of the high-pressure feedwater heater and supplies the drain to the condenser pipe;
(2) There are two types of low-pressure feedwater heater drain pump-up systems that pump up the drain of the low-pressure feedwater heater and supply it to the condensate pipe, and these are used alone or in combination.

FIG. 3 shows an example of a previously proposed high pressure feed water heater drain pump-up system. The related art will be described below with reference to the drawings.

The exhaust gas of the turbine 1 is condensed in the condenser 2, becomes condensed water, temporarily stays, and then is pressurized by the condensate pump 3.
After passing through the condensate purification device 4, it is heated in the low-pressure feedwater heaters 5 a and 5 b and sent to the feedwater pump 7 through the condensate pipe 6. The condensed water further pressurized by the feedwater pump 7 becomes feedwater, is further heated by the high-pressure feedwater heaters 8a, 8b, and is sent through a feedwater pipe 9 to a steam generator (not shown). On the other hand, the bleed air from the turbine 1 is sent to the low pressure feed water heaters 5a, 5b and the high pressure feed water heaters 8a, 8b to an extraction pipe (not shown), and the heat is fed to Exchange and condense to produce drain. The drains of the high-pressure feed water heaters 8a and 8b are collected in a drain tank 11 through drain pipes 10a and 10b, and the drain temporarily stored in the drain tank 11 is guided to a drain pump 13 installed in a drain pipe 12. , This drain pump
After the pressure is raised at 13, the water is supplied to the condenser 6 and mixed with the condenser.

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 a water level control valve 16 installed at the outlet of the drain pump 13.
The opening of the water level control valve 16 is adjusted so that the water level of the drain tank 11 becomes a specified value. Further, an emergency drain pipe 17 is provided in case the water level of the drain tank 11 rises abnormally, for example, when the drain pump 13 stops. An emergency water level control valve 18 is attached to the emergency drain pipe 17, and when the water level of the drain tank 11 rises abnormally,
The "high water level" signal from the water level transmitter 14 is transmitted to the emergency water level control valve 18 via the water level control device 15, 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 discharged to the condenser 2 through the emergency water level control valve 18.

As described above, the above-described feed water heater drain pump-up system can directly mix the drain of the high-pressure feed water heaters 8a and 8b with the condensate water and raise the condensate water temperature and the feed water temperature. Can be improved.

(Problems to be Solved by the Invention) However, the above-described feed water heater drain pump-up system has a serious problem in supplying water to the steam generator when the emergency water level control valve 18 is opened due to a failure during plant operation. There was a drawback of affecting.

That is, when the emergency water level control valve 18 is erroneously opened for some reason, the drain in the drain tank 11 flows out to the condenser 2 even though the water level in the drain tank 11 is normal. . In particular, since the emergency water level control valve 18 is used as a backup for the water level control valve 16, when the operating air for the emergency water level control valve 18 is lost, the emergency water level control valve 18 is fully opened, that is, when the emergency water level control valve 18 is failed. Often open. Accordingly, the emergency water level control valve 18 is fully opened due to the loss of the working air or another failure, and a large amount of drain may flow out to the condenser 2.

In such a state, the water level in the drain tank 11 drops rapidly, and eventually the drain pump 13 runs idle, so the drain pump 13 must be stopped, and the drains of the high-pressure water heaters 8a and 8b are turned off. It will not be possible to send water to condensate and water supply. This causes a sudden decrease in the water supply to the steam generator, which has a major impact on the operation of the nuclear power plant, and in the worst case, causes a significant fluctuation in the steam generator water supply flow, resulting in a reactor scram (emergency stop). And may hinder the sound operation of the power plant.

The present invention has been made in view of the above circumstances,
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 the reliability during operation.

[Configuration of the invention]

(Means for Solving the Problems) The present invention achieves the above object, and a feedwater heater that heats feedwater by exchanging heat with bleed air from a turbine;
A drain tank for storing a drain obtained by condensing the bleed air in the feedwater heater, a drain pipe for guiding the drain in the drain tank to feedwater on the upstream side of the feedwater heater by pressure increase by a drain pump, and a drain pipe. A water level control valve arranged in the middle of the pipe to adjust the water level in the drain tank;
An atom having an emergency drain pipe that guides the drain in the drain tank to the condenser of the turbine, and an emergency water level control valve that is provided in the middle of the emergency drain pipe and that adjusts the water level in the drain tank in an emergency. The feed water heater device for a furnace has a shut-off valve which is arranged in series with the emergency water level control valve in the middle of the emergency drain pipe, and is fully closed when the water level in the drain tank is below a specified value.

(Operation) In the present invention, by providing a shut-off valve in the emergency drain pipe and fully closing the shut-off valve, even if the emergency water level control valve is erroneously opened for some reason, drainage of drain and water level of the drain tank are prevented. Prevent drop. Furthermore, the shut-off valve is fully opened only when the level switch installed in the drain tank sends a signal of high water level, and when the drain tank water level is less than the specified value,
Since the shutoff valve is fully closed, even if the emergency water level control valve is fully opened due to a failure, the drain does not flow out to the condenser through the emergency water level control valve.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the present invention, the same components as those in the above-described specific example will be described with the same reference numerals.

In FIG. 1, an electric or pneumatic shut-off valve 19 is installed in the emergency drain pipe 17. Also, drain tank
11 is provided with a level switch 20, and a signal from the level switch 20 is sent to a shutoff valve 19. The level switch 20 generates a control signal to fully open the shut-off valve 19 when the water level of the drain tank 11 reaches a slightly higher level than the specified value. Is configured to send a fully closed signal.

In the above-described embodiment, the drain of the drain tank 11 is not supplied to the condenser 6 when the drain pump 13 is stopped. Therefore, the water level rises to the above “high water level” due to the drain staying in the drain tank, and the shutoff valve 19 is fully opened by the signal from the level switch 20. For this reason, the drain of the drain tank 11 passes through the emergency drain pipe 17 and the condenser 2
Sent to In addition, the signal from the water level transmitter 14 is sent to the emergency water level control valve 18 via the water level controller 15 to open the emergency water level control valve 18 so that the “water level high” level is maintained. The degree is adjusted, and the water level of the drain tank 11 is controlled.

On the other hand, during a so-called steady operation in which the drain pump 13 is operating, the drain of the drain tank 11 is supplied to the condenser 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
Since the control signal is sent so that the water level of 11 becomes a 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 a specified value, that is, “high water level”, the shutoff valve 19 is fully closed by a signal from the level switch 20.

Thus, according to the present embodiment, since the shut-off valve 19 is fully closed during the steady operation of the plant, even if the emergency drain water level control valve 18 is erroneously opened due to some failure, the emergency drain pipe 17 Drain does not flow out to the condenser pipe 2 through the drain pipe 11 and does not affect the water level of the drain tank 11 at all. Also, since there is no problem in the operation of the drain pump 13,
The water supply to the steam generator does not fluctuate at all.

The present invention is not limited to the level switch 20 as means for fully closing the shutoff valve 19 during the steady operation of the plant. For example, as shown in FIG. 2, control may be performed such that the shut-off valve 19 is fully opened or fully closed by a signal from a flow rate switch 21 provided at the outlet of the drain pump 13. That is, while the drain pump 13 is stopped, the shut-off valve 19 is fully opened by the flow rate low signal. It is controlled to be closed.

〔The invention's effect〕

As described above, according to the present invention, since the emergency drain pipe that discharges the drain of the drain tank to the condenser in an emergency is provided with the shut-off valve, even if the emergency water level adjusting valve is erroneously opened due to a failure, the emergency The drain can be prevented from flowing out to the condenser through the drain pipe, and the reliability of the feed water heater drain pump-up system can be improved.

[Brief description of the drawings]

1 is a system diagram showing an embodiment of a feed water heater for a nuclear reactor according to the present invention, FIG. 2 is a system diagram showing another embodiment of the present invention, and FIG. 3 is a feed water heater already proposed. It is a system diagram showing an apparatus. 1 ... Turbine 2 ... Condenser 3 ... Condenser pump 4 ... Condensate purifier 5a, 5b ... Low pressure feed water heater, 6 ... Condenser pipe 7 ... Feed water pump 8a, 8b ... High pressure feed water heater, 9… Water supply pipes 10a, 10b… Drain pipe, 11… Drain tank 12… Drain pipe, 13… Drain pump 14… Water level transmitter, 15… Water level controller 16… Water level control valve, 17 Emergency drain pipe 18 Emergency water level control valve 19 Shutoff valve 20 Level switch 21 Flow switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁶ , DB name) G21D 1/00 G21D 1/02 G21D 3/00 G21D 3/04 G21D 3/08

Claims (3)

(57) [Claims] A feedwater heater for exchanging heat with bleed air from a turbine to heat feedwater; a drain tank for storing drain obtained by condensing the bleed air with the feedwater heater; A drain pipe that guides the drain into the water supply on the upstream side of the feed water heater by pressurization by a drain pump, a water level control valve disposed in the middle of the drain pipe to adjust a water level in the drain tank, and a drain in the drain tank. Drain water pipe for supplying water to a turbine condenser, and an emergency water level control valve disposed in the middle of the emergency drain pipe to adjust a water level in the drain tank in an emergency. The emergency drain device has a shut-off valve that is arranged in series with the emergency water level control valve in the middle of the emergency drain pipe and that is fully closed when the water level in the drain tank is equal to or less than a specified value. Reactor for the feed water heater and wherein. 2. The reactor feedwater heating system according to claim 1, wherein said shut-off valve is opened when a water level in said drain tank is higher than a predetermined level, and is closed when said water level is lower than a predetermined level. Equipment. 3. The reactor feedwater heater according to claim 1, wherein the shut-off valve is opened when a flow rate in the drain pipe is smaller than a predetermined value, and closed when the flow rate is larger than a predetermined value. apparatus.