JPH09178107A - Steam generator for station service of nuclear power station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance deaeration effect of a deaerator at all supply water flow rates within a wide range of supply water flow rates, suppress disturbance occurring at the time of switching a boiler and a flash tank and reduce pressure in the flash tank at the time of stopping a station service steam generator. SOLUTION: A water supply valve for controlling water supply rate to a deaerator 5 is provided on at least one of a plurality of the deaerators 5 for the purpose of effecting spray water supply to the deaerators 5 and the water supply valve 21 is opened and closed by an interlock circuit 26 according to quantity of steam generated by a flash tank 8 and discharge pressure of a water supply pump. An exhaust line 27 is provided for discharging station service steam within the flash tank 8 into atmospheric air or to a device capable of recovering heat at the time of changing a boiler 20 and the flash tank 8, and the interlock circuit 28 opens and closes an exhaust valve 24 according to manual operation or operation status signals of the boiler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a domestic steam generator for a nuclear power plant for generating domestic steam by using radioactive steam generated in a nuclear reactor as a heating source.

[0002]

2. Description of the Related Art In general, an internal steam generator for a nuclear power plant generates non-radio internal steam by using radioactive steam generated in a nuclear reactor of the nuclear power plant as a heating source. FIG. 5 shows a conventional example of such an in-house steam generator of a nuclear power plant. The on-site steam generator performs indirect heat exchange by the heat exchanger 10 using the radioactive turbine bleed air as heating steam at a certain plant output or more, which is the purpose of effective use of nuclear reactor heat, and thereby the demand within the nuclear power plant. In-house steam is supplied according to. This on-site steam generator is roughly divided into the following three systems.

The first system is a radioactive turbine extraction 12
Is a heating steam for the heat exchanger 10, and heat is exchanged as the heating steam for the heat exchanger 10, and the drain condensed there is recovered in the feed water heater 13.

The second system is a pressurized circulation system or the like for generating non-radioactive hot water heated by the heat exchanger 10 to the flash tank 8 through the adjusting valve 11 and flushing it to generate the in-house steam. . The non-radioactive steam generated in the flash tank 8 of the pressurized circulation system is flowmeter 14 and adjusting valve 1.
5, it is sent to the steam consumption system 17 in the nuclear power plant via the check valve 16. Further, the hot water stored in the flash tank 8 is boosted by the circulation pump 9 and is again heated by the heat exchanger 10.
Sent to Furthermore, the pressure adjustment of the flash tank 8 is performed by the adjustment valve 11.

The third system is a water supply system for supplying water to the flash tank 8. In this water supply system, in order to maintain the water level in the flash tank 8, the water is boosted from the water supply drain tank 1 by the water supply pump 2, the flow rate is adjusted by the adjusting valve 3, and the water is flushed through the water supply line 4 and the deaerator 5. Fill tank 8 with water. Here, the adjusting valve 3 adjusts the flow rate according to the water level of the flash tank 8 by the signal from the water level transmitter 7 of the flash tank 8. Further, the deaerator 5 is installed for the purpose of reducing the dissolved oxygen concentration in the feed water, and the feed water from the water supply line 4 is sprayed into the deaerator by the spray nozzle at the inlet of the deaerator 5. The heating steam for the deaerator 5 is supplied from the flash tank 8 and heats the feed water to a temperature close to the saturation temperature of the deaerator internal pressure. As a result, the non-condensable gas (mainly oxygen) dissolved in the feed water is degassed.
The non-condensed gas that is degassed and emerges is cooled by the cooler 6 and discharged to the outside of the system. Then, the deaerated water supply flows into the flash tank 8.

Since the on-site steam generator supplies the on-site steam above a predetermined plant output,
Below the plant output, the steam is sent to each steam consuming system 17 having a device that uses this steam in the plant via a regulating valve 19 and a check valve 18 by a boiler 20 installed in another system in the plant.

[0007]

However, such an on-site steam generator is to supply steam at a flow rate as necessary to equipment using steam in a nuclear power plant. If the usage amount fluctuates over a wide range, proper operation may not be possible.

That is, as the amount of steam used in the plant fluctuates over a wide range, the flow rate of steam generated in the flash tank 8 and the flow rate of water supplied from the feed water drain tank 1 to the flash tank 8 also fluctuate over a wide range. Therefore, the deaerator 5 in the water supply system cannot cover this large flow rate range with only a certain number of nozzles, and a sufficient deaeration effect cannot be obtained in the entire range of this flow rate range.

Further, when the output of the plant is increased or decreased, the flash tank 8 and the boiler 20 are switched, but since the switching method has not been established, the fluctuation of the internal pressure of the flash tank 8 is caused. May cause disturbances such as

An object of the present invention is to sufficiently enhance the deaerating effect of the deaerator in a wide range of feed water flow rate, to suppress the disturbance generated at the time of switching between the flash tank and the boiler, and to improve the internal steam generator. It is an object of the present invention to provide a steam generator for a nuclear power plant capable of depressurizing a flash tank when stopped.

[0011]

According to the invention of claim 1, a heat exchanger for exchanging heat with radioactive steam generated from a nuclear reactor as a heating source, and hot water heated by the heat exchanger are flushed, and nuclear power generation is performed. When the output of the reactor is low, a flash tank that generates non-radioactive in-house steam used in the plant, a water supply system that boosts the water from the water supply tank with a water supply pump and feeds it to the flash tank through a deaerator, A nuclear power plant that is equipped with a boiler that generates internal steam, and uses a flash tank to generate internal steam when the reactor output is high, and uses a boiler to generate internal steam when the reactor output is low. An on-site steam generator, which adjusts the flow rate of the water supplied to the deaerator, which is provided in at least one of the plurality of water supply line systems for spraying water to the deaerator and the water supply line system. A water supply valve because, is provided with a interlock circuit for opening and closing the water supply valve based on the outlet pressure of the generated steam flow and the water supply pump in the flash tank.

According to the first aspect of the invention, when the output of the nuclear reactor fluctuates and it is necessary to increase or decrease the feed water flow rate to the flash tank, the interlock circuit adjusts the generated steam flow rate of the flash tank and the outlet pressure of the feed water pump. Open and close the water supply valve based on this.

According to a second aspect of the present invention, in the first aspect of the present invention, an exhaust line is provided for discharging internal steam in the flash tank to the atmosphere or equipment capable of recovering heat when switching between the boiler and the flash tank. Is.

According to the second aspect of the present invention, when switching between the boiler and the flash tank, the vapor in the flash tank is discharged through the exhaust line to depressurize the flash tank and suppress disturbance.

[0015] The invention of claim 3 is claim 1 or claim 2.
In the invention described above, an exhaust valve installed in the exhaust line and an interlock circuit that opens and closes the exhaust valve manually or when a boiler is switched to a flash tank based on an operating state signal of the boiler are provided.

In the invention of claim 3, when switching between the boiler and the flash tank, the exhaust valve of the exhaust line is opened and closed by the interlock circuit to depressurize the flash tank and suppress disturbance.

[0017]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram showing an embodiment of the present invention.
This embodiment is different from the conventional example shown in FIG. 5 in that a plurality of water supply line systems 4a and 4b for spraying water to the deaerator 5 are provided.
And a water supply valve 21 provided in at least one of the water supply line systems 4a and 4b for adjusting the supply water flow rate to be supplied to the deaerator 5, and the generated steam flow rate of the flash tank 8 obtained from the flow rate transmitter 22. The interlock circuit 26 that opens and closes the water supply valve 21 based on the outlet pressure of the water supply pump 2 obtained from the pressure transmitter 23, and when the boiler 20 and the flash tank 8 are switched, the internal steam in the flash tank 8 is released into the atmosphere or heat. Based on an exhaust line 27 that discharges to a recoverable device (outdoor 25), an exhaust valve 24 that is installed in the exhaust line 27, and a operating state signal of the boiler 20 when switching between the boiler 20 and the flash tank 8 An interlock circuit 28 for opening and closing the exhaust valve 24 is provided.

In FIG. 1, the water supply line 4 from the water supply drain tank 1 to the flash tank 8 is branched from the water supply line 4 between the regulating valve 3 and the deaerator 5 to provide a water supply line system 4a, 4b. The water supply valve 21 which is an ON-OFF valve is provided in one of the water supply line systems 4b. The water supply valve 21 is connected to the interlock circuit 2
It is opened and closed at 6.

The interlock circuit 26 receives the generated steam flow rate signal of the flash tank 8 from the flow rate transmitter 22 and outputs the outlet pressure signal of the water feed pump 2 to the pressure transmitter 2.
3 is received and the water supply valve 21 is operated. This interlock circuit 26 is shown in FIG.

It is necessary for the spray nozzle at the inlet of the deaerator 5 to secure a flow rate above a certain level, and at a high flow rate, one spray nozzle cannot obtain a sufficient degassing effect. Need to be two.

Therefore, as shown in FIG. 2, when the generated steam flow rate of the flash tank 8 which is proportional to the water supply flow rate is low (when the water supply flow rate is low), the water supply valve 21 is fully closed. The flow rate of the deaerator inlet spray nozzle connected to the water supply line system 4a is secured.

On the other hand, when the flow rate of generated steam in the flash tank 8 is not low (when the feed water flow rate is high), the water feed valve 21 is fully opened to provide two deaerator inlet sprayers connected to the water feed lines 4a and 4b. Deaerator 5 for water supply from the nozzle
Spray into the container. The deaerator 5 exhibits a sufficient deaerating effect. In addition, as a backup, the water supply pump outlet pressure high signal from the pressure transmitter 23 causes the water supply valve 21 to operate even when the water supply pump outlet pressure is high (when the water supply flow rate is low).
Will be fully closed, otherwise it will be fully opened.

That is, the flash tank generated steam flow rate low signal 29 and the feed water pump outlet pressure high signal 30 are input to the logical sum circuit 31, and when either of these signals 29 and 30 is established, the feed water control valve 21. Is closed. Also,
When the output of the OR circuit 31 has the logical value "0", the water supply valve 21 is opened through the NOT circuit 32.

Next, referring to FIG. 1, the flash tank 8
Through the regulating valve 15 and the check valve 16 to the steam consuming system 17 for using steam in the nuclear power plant, an exhaust line 27 is provided branching from the steam generating mother pipe at the outlet of the flash tank 8. There is. An exhaust valve 24 is provided in the exhaust line 27, and the exhaust valve 24 discharges steam to the outside 25. As a result, after the on-site steam generator stops, the exhaust valve 24 is fully opened to reduce the pressure of the flash tank 8. That is, the energy held in the flash tank 8 is released to the outside of the system. In this case, the exhaust valve 24 is opened and closed by the interlock circuit 28.

FIG. 3 shows a logic circuit of the interlock circuit 28. As shown in FIG. 3, the exhaust valve 24 is opened / closed by a manual opening command signal 33 and a closing command signal 34 of the exhaust valve 24, a circuit breaker ON signal 35 and a disconnection signal 36 (boiler 20 status signal) of the boiler 20. Operated.

In FIG. 3, an exhaust valve manual opening command signal 33
Is input to the OR circuit 37. Also, the OR circuit 37
Is a wiper (WO) circuit 38, which is an input signal 35 of the breaker of the boiler 20 (hereinafter referred to as a boiler input signal 35).
Be entered via. The WO circuit 38 is a logic circuit configured by a combination of a NOT circuit and a logical product circuit, and the output of the timer circuit 39 is input to the logical product circuit together with the boiler input signal 35 through the negative circuit, and the result of the logical operation is It will be output as an output signal of the WO circuit 38. Therefore, when the boiler incoming signal 35 is input, W
The O circuit 38 instantaneously outputs an output signal of logical value "1",
It returns after the time limit of the timer circuit 39 elapses, and the logical value is "0".
To output the output signal. From this, it is necessary to set the time limit of the timer circuit 38 to a time period longer than the time required to complete the opening operation of the exhaust valve 24.

Similarly, the exhaust valve manual closing command signal 43 is input to the OR circuit 40, and the OR circuit 40 receives the cutoff signal 36 of the circuit breaker of the boiler 20 (hereinafter referred to as the boiler cutoff signal 36). It is input via the wipeout (WO) circuit 41. The WO circuit 41 is a logic circuit composed of a combination of a NOT circuit and an AND circuit, and the output of the timer circuit 41 is passed through the NOT circuit to the boiler cutoff signal 36.
Is input to the AND circuit together with the result of the logical operation
It is output as an output signal of the O circuit 41. Therefore, when the boiler cutoff signal 36 is input, the WO circuit 38 instantaneously outputs an output signal of logical value "1", and the WO circuit 38 recovers after the time limit of the timer circuit 42 and outputs an output signal of logical value "0". Output. From this, the timer circuit 42
As the time limit, it is necessary to set a time period longer than the time required to complete the closing operation of the exhaust valve 24.
That is, the timer circuits 39 and 42 are time delay timers that are longer than the opening / closing time of the exhaust valve 24.

Next, the operation of the in-house steam generator according to the embodiment of the present invention when the output of the plant (reactor) is increased and decreased is described.

First, the procedure for switching from the boiler 20 to the flash tank 8 when the output of the plant (reactor) is increased will be described. (1) Fully open the exhaust valve 24 manually. That is, the manual exhaust valve opening command signal 33 is input to the interlock circuit 28. As a result, the exhaust valve 24 is fully opened. (2) The circulation pump 9 is started to bring the turbine extraction air 12 into service to the heat exchanger 10. (3) It is confirmed that the internal pressure of the flash tank 8 is automatically controlled by the adjusting valve 11 so as to reach the set pressure. (4) Fully open the adjusting valve 15 at the outlet of the flash tank 8. (5) Stop the boiler 20. This then
The front-rear pressure of the check valve 18 drops, the check valve 16 at the outlet of the flash tank is fully opened, and the check valve 18 at the outlet of the boiler 20 is completely closed. And the supply of steam in the plant is the boiler 20.
Switch to flash tank 8 from the side. At the same time, the exhaust valve 24 is gradually fully closed by the interlock circuit 28. (6) The exhaust valve 24 is fully closed.

Next, when switching from the flash tank 8 to the boiler 20 while the output of the plant (reactor) is decreasing, the exhaust valve 24 is fully opened by the interlock circuit 28 of FIG. Flash tank 8
Switch to the supply of on-site steam. As shown in this procedure, according to the interlock circuit 28 of FIG. 3, by opening and closing the exhaust valve 24 by the manual and boiler cutoff signal 36, the fluctuation of the internal pressure of the flash tank 8 changes as shown in FIG. Become.

In FIG. 4, Pr is the flash tank 8
And P1 is a change in the internal pressure of the flash tank 8 when the exhaust valve 24 is fully opened when the boiler 20 is switched to the flash tank 8. That is, it is a characteristic curve of the pressure P1 in the flash tank 8 when the exhaust valve 24 according to the present invention is fully opened when the boiler 20 and the flash tank 8 are switched, and ΔP1 is the maximum swing width of the pressure P1 from the set pressure Pr. Is shown.

On the other hand, P2 shows the change in the internal pressure of the flash tank 8 when the exhaust valve 24 is fully closed, and the pressure P2 of the flash tank 8 in the conventional example when the exhaust valve 24 of the present invention is not provided. It is a characteristic curve, ΔP of pressure P2
2 is the maximum swing width from the set pressure Pr.

Further, a time point t1 is a time point when the pressures P1 and P2 reach the set pressure Pr of the flash tank 8, and a time point t2.
Is the time when the supply source of steam into the plant was transferred from the flash tank 8 to the boiler 20.

That is, from time t0 to time t1 in FIG. 4, the pressures P1 and P2 are increased by the change characteristic of the internal pressure of the flash tank after the flash tank 8 is started in the procedure (2). Yes, at time t1, the set pressure Pr in step (3) is reached. After that, in step (5), the check valve 16 is fully opened. As a result, steam flows out to the steam consuming system 17 in the plant. This time point is t2 in FIG.

In this state, the exhaust valve 2
Since 4 is manually fully opened, steam is flowing from the flash tank 8 to the outside (outdoor) 25 through the exhaust line 27 from the beginning. Therefore, the amount of steam generated in the flash tank 8 does not change so much, and the internal pressure P1 of the flash tank 8 does not change so much. That is, the fluctuation amount of the pressure P1 is a fluctuation of only the maximum ΔP1 with respect to the set pressure Pr.

On the other hand, when the procedure (1) is not performed, the fluctuation amount of the pressure P2 is ΔP2 at the maximum, and the procedure (1)
The maximum variation amount ΔP1 in the case of the present invention in which is performed is smaller than that in the case where the procedure (1) is not performed. Therefore, the disturbance when switching between the boiler 20 and the flash tank 8 is reduced. Further, at that time, the exhaust valve 24 of the exhaust line 27 is gradually closed, so that the pressure P1 is not affected.

When switching from the flash tank 8 to the boiler 20 when the output of the plant (reactor) drops,
When the breaker of the boiler 20 is turned on, the exhaust valve 24 is opened by the interlock circuit 28, so the pressure of the boiler 20 rises and the exhaust valve is opened before the steam supply is switched from the flash tank 8 to the boiler 20 side. 24 opens. Therefore, the disturbance to the flash tank 8 is prevented as in the case of switching from the boiler 20 to the flash tank 8.

As described above, in the present invention, in order to increase the number of deaerator inlet spray nozzles of the water supply line 4 from the water supply tank 1 to the flash tank 8 through the water supply pump 2, the adjusting valve 3 and the deaerator 5, the water supply nozzle is supplied. The line system is made into a multi-series system, and the water supply line systems 4a and 4b are sequentially fully opened for each series installed.
As a control of the remotely controllable water supply valve 21 that is fully closed, an interlock circuit 26 that fully opens and fully closes is provided according to the signals of the generated steam flow rate of the flash tank 8 and the outlet pressure signal of the water supply pump 2, which are indicators of the water supply flow rate. There is.

Further, an exhaust line 27 is provided which branches from the generated steam mother pipe at the outlet of the flash tank 8 and discharges the steam to the atmosphere side or equipment capable of heat recovery via an exhaust valve 24 which can be operated remotely. Exhaust valve 2 of this exhaust line 27
An interlock circuit 28 is provided for opening and closing 4 according to an on / off signal of the circuit breaker of the flash tank 8 and the boiler 20.

Therefore, when the feed water flow rate fluctuates, the remotely controllable water feed valve 21 installed in each line of the water feed line system is used to change the amount of steam generated in the flash tank 8 which serves as a guide for the change in the water feed flow rate, and to supply water. By the interlock circuit 26 that opens and closes according to the change in the outlet pressure of the pump 2,
The number of spray nozzles at the inlet of the deaerator 5 is controlled by the feed water flow rate, and the deaerator 5 can sufficiently enhance the deaerating effect in all flow rate ranges.

Further, the exhaust valve 24 of the exhaust line 27, which branches from the generated steam mother pipe at the outlet of the flash tank 8 and discharges the steam through the remotely controllable exhaust valve 24, is fully opened when the flash tank 8 is stopped. Thus, when the flash tank 8 is stopped, the flash tank 8 can be depressurized. That is, the energy held in the flash tank 8 can be flown out of the system.

When the output of the plant (reactor) is increased or decreased, the exhaust valve 24 is opened by the interlock circuit 28 which is opened / closed by the ON / OFF signal of the breaker of the boiler 20 when switching between the steam generator for the plant and the boiler. It is opened and closed to adjust the internal pressure of the flash tank 8. As a result, disturbance on the flash tank 8 can be prevented.

[0043]

As described above, according to the present invention,
In order to increase the number of input spray nozzles of the deaerator, the remotely controllable water supply valve installed for each system from the adjusting valve of the multi-system flash tank to the deaerator is used as a guide for the water supply flow rate. Since an interlock circuit that can be opened and closed by changing the generated steam flow rate and the feed pump outlet pressure is provided, the deaerator can exert a sufficient deaeration effect over a wide range of remotely controllable feed water flow rate. .

Further, an exhaust line for branching the generated steam mother pipe at the outlet of the flash tank to exhaust the steam to the atmosphere or a device capable of recovering heat is provided, and the exhaust valve on the exhaust line is fully opened after the flash tank is stopped. Therefore, decompression of the flash tank is possible. Further, when switching between the flash tank and the boiler, an interlock circuit that opens and closes the exhaust valve manually and by the ON / OFF signal of the circuit breaker of the boiler is assembled and operated, so that disturbance to the flash tank can be prevented.

As described above, according to the present invention, in the water supply system from the water supply tank to the flash tank of the on-site steam generator, the deaerating effect of the deaerator can be sufficiently enhanced over a wide range of water supply flow rate, and the plant It is possible to reduce disturbance to the flash tank when switching between the flash tank and the boiler when the output is increased or decreased, and to reduce the pressure of the flash tank when the flash tank is stopped.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a logic circuit diagram of an interlock circuit 26 of the present invention.

FIG. 3 is a logic circuit diagram of an interlock circuit according to the present invention.

FIG. 4 is a characteristic diagram of the internal pressure of the flash tank of the present invention.

FIG. 5 is a configuration diagram of a conventional example.

[Explanation of symbols]

 1 Water tank 2 Water pump 3 Adjustment valve 4 Water supply line 4a Water supply line system 4b Water supply line system 5 Deaerator 6 Cooler 7 Water level transmitter 8 Flash tank 9 Circulation pump 10 Heat exchanger 11 Regulator valve 12 Extraction air 13 Water heater 14 Flowmeter 15 Adjusting valve 16 Check valve 17 Steam consumption system 18 Check valve 19 Adjusting valve 20 Boiler 21 Water supply valve 22 Flow rate transmitter 23 Pressure transmitter 24 Exhaust valve 25 Outdoor 26 Interlock circuit 27 Exhaust line 28 Interlock circuit 29 Flash tank generated steam flow low signal 30 Water supply pump outlet pressure high signal 31 Logical sum circuit 32 Negative circuit 33 Exhaust valve manual open command signal 34 Exhaust valve manual close command signal 35 Boiler entry signal 36 Boiler cut signal 37 Logical sum circuit 38 Wipe Out circuit 39 Timer circuit 40 Logical sum circuit 4 Wipe-out circuit 42 timer circuit

Claims (3)

[Claims] 1. A heat exchanger for exchanging heat with radioactive steam generated from a nuclear reactor as a heating source, and non-radioactive internal steam for flushing hot water heated by the heat exchanger for use in a nuclear power plant. And a flash tank,
A water supply system for boosting the water from the water supply tank with a water supply pump to supply water to the flash tank via a deaerator, and a boiler for generating the in-house steam when the output of the reactor is low, In the on-site steam generator of a nuclear power plant, which generates the on-site steam in the flash tank when the power of the reactor is high, and generates the on-site steam by the boiler when the reactor output is low. , A plurality of water supply line systems for spraying water supply to the deaerator, a water supply valve provided in at least one of the water supply line systems for adjusting a water supply flow rate to be supplied to the deaerator, and generation of the flash tank An on-site steam generator for a nuclear power plant, comprising an interlock circuit that opens and closes the water supply valve based on a steam flow rate and an outlet pressure of the water supply pump. . 2. An exhaust line is provided for discharging the in-house steam in the flash tank to the atmosphere or a device capable of recovering heat when switching between the boiler and the flash tank. On-site steam generator for the described nuclear power plant. 3. An exhaust valve installed in the exhaust line,
The nuclear power supply system according to claim 1 or 2, further comprising: an interlock circuit that opens or closes the exhaust valve manually or based on an operating state signal of the boiler when switching between the boiler and the flash tank. On-site steam generator for power plants.