JP2023086015A - nuclear power plant - Google Patents

Abstract

To provide a nuclear power plant capable of increasing the output control width of steam extraction throttle operation responding to the load following command from the demand side.SOLUTION: The nuclear power plant includes: an atomic reactor; a turbine; a power generator; a steam condenser; a feed water heater; an air-bleeding line that supplies part of the steam produced in the atomic reactor to the feed water heater as extraction steam; a bleeding valve that adjusts the flow rate of the air-bleeding line; and a control unit that controls the valve opening of the bleeding valve. Any one of the operation modes is selected out of a first operating mode in which the output of the power generator is constant, a second operating mode in which the output of the power generator is adjusted to follow the load and a third operating mode in which the output of the power generator is constant. In the third operating mode, at least some of the bleeding valves have a large valve opening compared with the first operating mode.SELECTED DRAWING: Figure 1

Description

In response to a load following command (increase in output) from the demand side, the present invention instantaneously reduces the extraction steam for heating the feed water heater to increase the turbine work (generator output). It relates to a nuclear power plant in operation (CT).

In order to prevent global warming, the proportion of renewable energy (solar power generation, wind power generation, etc.) that does not generate _CO2 in power generation is increasing.
Conventionally, nuclear power plants have played the role of stably supplying a substantially constant amount of electricity by operating at a constant rated thermal output.
However, in the future, with the increase in the amount of renewable energy, where the amount of power generation is unstable because it is greatly affected by the weather, power demand from the grid (system demand) due to fluctuations in power demand and renewable energy Accordingly, it is expected that there will be an increasing need for load-following operation that flexibly changes the electrical output.

From the viewpoint of fuel damage prevention, nuclear power plants cannot take measures to increase the thermal power of the core against system demands exceeding the rated thermal power (100%).
In response to such a system requirement, a method for improving the amount of power generation by instantaneously increasing the amount of steam flowing into the turbine for power generation is required. Specifically, the amount of extracted steam to the feedwater heater installed on the feedwater line is temporarily throttled to heat the low-temperature feedwater after it has been condensed in the condenser, and the amount of steam flowing into the turbine is reduced. to increase Such an operating method is called bleed throttling operation (CT).

A typical nuclear power plant is equipped with a plurality of feedwater heaters and a plurality of extraction lines, and a method of controlling them to perform CT is well known (see Patent Document 1, for example).

JP 2017-194312 A

Patent Document 1 mentioned above discloses, as a prior art, a method of controlling the output of a nuclear power plant by controlling the valve opening degrees of a plurality of extraction valves provided on a plurality of extraction lines with an extraction valve control device. (see FIG. 11 of Patent Document 1).
However, the CT controllable output increase range is limited to the amount of steam extracted to the feed water heater, and there is no output increase means for a load change request beyond this.

The present invention has been made in view of such a background, and the present invention instantaneously reduces the extracted steam for heating the feed water heater in response to a load following command (increase in output) from the demand side. An object of the present invention is to provide a nuclear power plant capable of expanding the output control range of extraction throttling operation (CT) that increases turbine work (generator output) by

In addition, the above and other objects of the present invention and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

The nuclear power plant of the present invention comprises a nuclear reactor, a turbine driven by steam generated in the nuclear reactor, a generator driven by the turbine to generate electric power, a condenser for condensing exhaust steam from the turbine, A feedwater heater, which heats the condensed water condensed in the condenser with steam extraction, is installed between the reactor and the condenser. A nuclear power plant includes a bleed line to supply the bleed air, a bleed valve for adjusting the flow rate of the bleed line, and a control unit for controlling the valve opening of the bleed valve.
The nuclear power plant of the present invention has a first operation mode in which the output of the generator is constant, a second operation mode in which the output of the generator is adjusted to follow the load, and a It has three operation modes, ie, a third operation mode in which the output is constant and is operated, and operation is performed by selecting any one operation mode from the three operation modes.
Further, in the nuclear power plant of the present invention, in the second operation mode, the valve opening degree of the extraction valve is adjusted by the control of the control unit so that the output of the generator follows the load, and in the third operation mode, Under the control of the control unit, the valve opening degree of at least some of the bleed valves is set to be larger than that in the first operation mode.

According to the above-described nuclear power plant of the present invention, any one of the three operation modes including the third operation mode in which the degree of opening of at least some of the bleed valves is larger than that in the first operation mode One operation mode is selected and operation is performed.
In the third operation mode, at least some of the bleed valves are in a state where the degree of valve opening is large. Therefore, the control range of the valve opening of the bleed valve can be increased.
As a result, in response to a load following command (increase in output) from the demand side, extraction throttling operation ( CT) output control width can be expanded.

Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is a system diagram of a first embodiment of a nuclear power plant of the present invention; FIG. FIG. 2 is a schematic configuration diagram of an operation mode recording device for the nuclear power plant in FIG. 1; FIG. 2 is a schematic configuration diagram of a normal operating state recording device for the nuclear power plant in FIG. 1; FIG. 2 is a schematic configuration diagram of a heat balance changing device of the nuclear power plant of FIG. 1; FIG. 2 is a schematic configuration diagram of a bleed valve control device for the nuclear power plant in FIG. 1 ; It is a system diagram of a second embodiment of the nuclear power plant of the present invention. FIG. 7 is a schematic configuration diagram of a normal operating state recording device for the nuclear power plant of FIG. 6; FIG. 7 is a schematic configuration diagram of a heat balance changing device of the nuclear power plant of FIG. 6; FIG. 7 is a schematic configuration diagram of a bleed valve control device for the nuclear power plant in FIG. 6 ;

An embodiment of a nuclear power plant according to the present invention will be described below with reference to the drawings. In each embodiment, the same parts are denoted by the same reference numerals, and overlapping descriptions are omitted. It should be noted that each drawing is only schematically shown to the extent that the present invention can be fully understood, and is not limited to the following contents or the contents of the illustrations, and can be arbitrarily modified within a range that does not significantly impair the effects of the present invention. Or they can be implemented in combination.

The nuclear power plant of the present invention comprises a nuclear reactor, a turbine driven by steam generated in the nuclear reactor, a generator driven by the turbine to generate electric power, a condenser for condensing exhaust steam from the turbine, A feedwater heater, which heats the condensed water condensed in the condenser with steam extraction, is installed between the reactor and the condenser. A nuclear power plant includes a bleed line to supply the bleed air, a bleed valve for adjusting the flow rate of the bleed line, and a control unit for controlling the valve opening of the bleed valve.
In other words, the nuclear power plant of the present invention is configured to be able to execute extraction throttling operation (CT) by controlling the valve opening of the extraction valve that adjusts the flow rate of the extraction line.

Further, the nuclear power plant of the present invention has a first operation mode in which the output of the generator is constant, a second operation mode in which the output of the generator is adjusted to follow the load, and a It has three operation modes, ie, a third operation mode in which the output is constant and is operated, and operation is performed by selecting any one operation mode from the three operation modes.
Further, in the nuclear power plant of the present invention, in the second operation mode, the valve opening degree of the extraction valve is adjusted by the control of the control unit so that the output of the generator follows the load, and in the third operation mode, Under the control of the control unit, the valve opening degree of at least some of the bleed valves is set to be larger than that in the first operation mode.
That is, the nuclear power plant of the present invention, in addition to first and second modes of operation similar to those implemented in a nuclear power plant performing conventional extraction throttling (CT), has at least a portion of the bleed air. A third operation mode is added in which the valve opening degree is large.

According to the configuration of the nuclear power plant of the present invention, any one of three operation modes including a third operation mode in which the degree of opening of at least some of the extraction valves is larger than that in the first operation mode. One operation mode is selected and operation is performed.
In the third operation mode, at least some of the bleed valves are in a state where the degree of valve opening is large. Therefore, the control range of the valve opening of the bleed valve can be increased.
As a result, in response to a load following command (increase in output) from the demand side, extraction throttling operation ( CT) output control width can be expanded.

In the configuration of the nuclear power plant described above, the control unit includes an operation mode recording device for retaining the state of the operation mode, and when the generator is operated in either the first operation mode or the third operation mode, A normal operating state recording device that records the output and the valve opening of the bleed valve, and a valve opening of the bleed valve when a command to change the adjustment range of the output of the generator is input in the first operation mode and a function to change the opening degree of the bleed valve to the third operation mode while in the third operation mode. A heat balance changing device having the function of returning to the state in which it was in the operating mode and changing to the first operating mode, and a command to adjust the output of the generator when operating in the second operating mode. In this case, it is also possible to have a bleed valve control device for adjusting the opening degrees of the plurality of bleed valves.
That is, in the case of this configuration, when a command to change the adjustment range of the output of the generator is input by the heat balance changing device, the valve opening degree of the bleed valve is increased or decreased, and the first operation mode and the second operation mode are controlled. 3 change from one of the operating modes to the other. Thus, when a command to change the adjustment range of the output of the generator is input, the valve opening degree of the bleed valve is specifically changed to switch the operation mode between the first operation mode and the third operation mode. be able to.

In the nuclear power plant having this configuration, when the bleed valve control device adjusts the opening degrees of the plurality of bleed valves in response to a command for adjusting the output of the generator, the valve opening degrees of the plurality of bleed valves are It can be configured to perform control to multiply by a constant.
As a result, the valve opening degrees of the plurality of bleed valves are controlled by multiplying them by a constant to adjust the valve opening degrees of the plurality of bleed valves. Output can be adjusted.

In the configuration of the nuclear power plant described above, the bleed valve is composed of two types of the first bleed valve and the second bleed valve, and the first bleed valve has the same valve opening degree in the first operation mode and the third operation mode. , the second bleed valve can be configured to be in a state in which the valve opening degree is larger in the third operation mode than in the first operation mode.
As a result, the valve opening degree of the first bleed valve in the first operation mode and the third operation mode is combined with the change in the valve opening degree of the second bleed valve between the first operation mode and the third operation mode. The output control range of the extraction throttling operation (CT) can be expanded up to the required amount. Therefore, it is possible to expand the output control range beyond the output control range that can be achieved with only the first bleed valve or only with the second bleed valve.

In the nuclear power plant having this configuration, the first bleed valve is fully open during the first and third operation modes, and the second bleed valve is fully closed during the first operation mode. The control unit has a function of fully opening the second bleed valve and changing to the third operation mode when a command to change the adjustment range of the output of the generator is input in the first operation mode. and a function of fully closing the second bleed valve and changing to the first operation mode when a command to change the adjustment range of the output of the generator is input in the third operation mode. A heat balance changing device and a bleed valve control device for adjusting the valve opening of a plurality of bleed valves when a command to adjust the output of the generator is input while operating in the second operation mode. and can be configured to have.
That is, in the case of this configuration, when a command to change the adjustment range of the output of the generator is input by the heat balance changing device, the valve opening degree of the second bleed valve is increased or decreased, and the first operation mode is selected. and the third operation mode from one to the other. As a result, when a command to change the adjustment range of the output of the generator is input, the valve opening degree of the second bleed valve is specifically changed to switch between the first operation mode and the third operation mode. You can switch between driving modes.
Further, in the case of this configuration, the first bleed valve is fully open in both the first and third operation modes, and the second bleed valve is in the fully open state in the first and third operation modes. , the valve opening degree changes from one of the fully closed state and the fully open state to the other.
This makes it possible to simplify the control of the opening degrees of the first and second bleed valves when changing between the first and third operation modes.
Further, since the degree of opening of the second bleed valve changes from one of the fully closed state and the fully open state to the other, it is necessary to increase the change in the valve opening degree between the first operation mode and the third operation mode. Therefore, it is not necessary to increase the design heat exchange capacity of the heat exchanger of the feed water heater. As a result, the cost of the feed water heater can be reduced compared to the case where the second bleed valve is not provided.
In addition, since the control of the opening degrees of the first and second bleed valves can be simplified and the cost of the feed water heater can be reduced, the equipment configuration of the nuclear power plant can be rationalized.

In the nuclear power plant with this configuration, two extraction lines for supplying extraction steam to one feedwater heater are connected, and the extraction line having the higher temperature of the steam to be supplied out of the two extraction lines is the second extraction line. It is possible to adopt a configuration in which two bleed valves are provided and the first bleed valve is provided in the bleed line to which the temperature of the steam to be supplied is lower.
As a result, the amount of change in the energy of the extracted steam due to the opening and closing of the second extraction valve can be increased, so that the design heat exchange capacity of the heat exchanger of the feed water heater can be further reduced.

In the configuration of the nuclear power plant described above, in the third operation mode, the opening degree of at least some of the extraction valves is larger than in the first operation mode. That is, all the bleed valves are set to a large opening degree, or some of the plurality of bleed valves are set to a large opening degree.
In the third operation mode, at least some of the bleed valves have a larger degree of opening than in the first operation mode. The adjustment range of the valve opening of the bleed valve can be expanded more than when shifting from the operation mode.

In actual operation, when the output is not changed for a while, it is desirable to adopt the first operation mode so that the time during which the engine is operated in the first operation mode is the longest.
When expanding the adjustment range of the valve opening of the bleed valve before shifting to the second operation mode, the operation mode is changed from the first operation mode to the third operation mode. However, when there is no plan to shift to the second operation mode for a while due to a change in schedule or the like, it is desirable to return from the third operation mode to the first operation mode. In the third operation mode, the valve opening degree of the extraction valve is made larger than in the first operation mode, so the amount of extracted steam increases, and the amount of steam going to the turbine decreases accordingly, resulting in the output of the nuclear reactor. This is because it is not suitable for long-term operation because the efficiency of the power generation amount for the battery decreases.

Next, specific embodiments of the nuclear power plant of the present invention will be described.

(First embodiment)
FIG. 1 is a system diagram of a first embodiment of a nuclear power plant according to the present invention.

As shown in FIG. 1, the nuclear power plant of this embodiment includes a reactor pressure vessel (RPV) 1, a high pressure turbine 4, a moisture separator 5, a low pressure turbine 6, a condenser 7, a generator 8, a plurality of Equipped with feed water heaters 11, 12, 13, 14.

A reactor pressure vessel (RPV) 1 contains a core 2 .
The reactor pressure vessel 1 is also connected to a high pressure turbine 4 , a moisture separator 5 and a low pressure turbine 6 via a main steam line 3 .
A condenser 7 is installed downstream of the low-pressure turbine 6 . The condenser 7 is connected to the reactor pressure vessel 1 by a water supply line 15 . On the feed water line 15, a condensate pump 9, a plurality of feed water heaters (first stage feed water heater 11, second stage feed water heater 12, third stage feed water heater 13, fourth stage feed water heater 14 ), and a water supply pump 10 is installed.
A high pressure turbine 4 and a low pressure turbine 6 are connected to a generator 8 . 1, illustration of the connection between the high-pressure turbine 4 and the generator 8 is omitted.

Moisture separator 5 is connected to the shell side of the heat exchanger of third stage feedwater heater 13 via condensed water discharge line 17 .
The main steam line 3 branches between the high pressure turbine 4 and the moisture separator 5, the branched lines forming a bleed line 24 to the stage 4 feedwater heater and a bleed valve 25 to the stage 4 feedwater heater. It is connected to the shell side of the heat exchanger of the fourth-stage feedwater heater 14 via.
Also, three lines branch off from the low-pressure turbine 6 . The first line from the left is connected to the shell side of the third-stage feed water heater 13 via the bleed line 22 to the third-stage feed water heater and the bleed valve 23 to the third-stage feed water heater. . The second line from the left is connected to the shell side of the second stage feed water heater 12 via the bleed line 20 to the second stage feed water heater and the bleed valve 21 to the second stage feed water heater. . The third line from the left is connected to the shell side of the heat exchanger of the first stage feed water heater 11 via the bleed line 18 to the first stage feed water heater and the bleed valve 19 to the first stage feed water heater. Connected to the torso. The shell sides of the heat exchangers of these feed water heaters 13 , 12 , 11 are connected to the condenser 7 via drain lines 16 .

Bleed valve 19 to stage 1 feedwater heater, bleed valve 21 to stage 2 feedwater heater, bleed valve 23 to stage 3 feedwater heater, and bleed valve 25 to stage 4 feedwater heater A bleed valve control device 34, a heat balance changing device 35, a normal operation state recording device 36, and an operation mode recording device 38 are installed as control devices for controlling the degree of opening. An input/output connection mechanism 43 connects the inputs and outputs of the four devices 34 , 35 , 36 and 38 .
The extraction valve control device 34, the heat balance changing device 35, the normal operating state recording device 36, and the operation mode recording device 38 provided in the input/output connection mechanism 43 are the valves of the extraction valve in the nuclear power plant of the present invention. It constitutes the above-described control unit for controlling the degree of opening.

In addition, the input/output connection mechanism 43 is connected to the bleed valve 19 to the first-stage feed water heater 11, the bleed valve 21 to the second-stage feed water heater 12, and the third-stage feed water heater 13 as input signals from the outside. Information on the valve opening degree of the extraction valve 23 to and the fourth stage feed water heater 14, the generator output adjustment command 39, the generator output adjustment width change command 40, and the generator output 42 are connected. ing.

Hereinafter, in the nuclear power plant according to the present embodiment, the extraction throttle operation (CT) in which the extraction steam is momentarily reduced to increase the turbine work (generator output) in order to heat the feedwater heater will be described. A typical method for expanding the output control width will be described.

Steam generated in the core 2 is sent to the high-pressure turbine 4 and the low-pressure turbine 6 via the main steam line 3, and the work that rotates the turbine blades is converted into electric power via the generator 8 and transmitted to the system side. . The steam that has finished work in the low-pressure turbine 6 is cooled by seawater or the like in the condenser 7 to become low-temperature condensed water. The low-temperature condensed water is sent to the water supply line 15, heated and raised in temperature when passing through a plurality of water supply heaters 11, 12, 13, 14, and pressurized by the condensate pump 9 and the water supply pump 10. After that, it is returned to the reactor pressure vessel 1 .
A part of the feedwater returned to the reactor pressure vessel 1 becomes steam in the reactor core 2 and is sent to the turbines 4 and 6 again, so that the system diagram shown in FIG. are doing.

Hot steam laden with moisture is supplied to the shell side of the heat exchanger to heat the feed water passing through the tube side of the heat exchanger of the feed water heater.
In the present embodiment, the steam after passing through the high-pressure turbine 4 is supplied to the fourth-stage feed water heater 14 via the extraction line 24 to the fourth-stage feed water heater and the extraction valve 25 to the fourth-stage feed water heater. is supplied to the shell side of the heat exchanger.
Similarly, three bleed steams from the low pressure turbine 6 are sent to the third stage feed water heater 13 via the bleed line 22 to the third stage feed water heater and the bleed valve 23 to the third stage feed water heater, Bleed line 20 to the second stage feedwater heater and bleed valve 21 to the second stage feedwater heater into the second stage feedwater heater 12 via the bleed line 18 to the first stage feedwater heater and the first stage It is supplied to the shell side of the heat exchanger of the first-stage feedwater heater 11 via the bleed valve 19 to the feedwater heater.
Steam (condensed water) condensed by exchanging heat with low-temperature feed water in the heat exchanger is sent to the condenser 7 via the drain line 16 and becomes part of the feed water.

During normal operation of the nuclear power plant, the amount of steam flowing into the turbines 4 and 6, the amount of extracted steam to the feed water heaters 11, 12, 13, and 14, and the heating of the feed water by the feed water heaters 11, 12, 13, and 14 It is operated in a steady state so that the amount, etc., is constant.

A conventional nuclear power plant that performs extraction throttling operation (CT) has two operation modes: an operation mode in which the output is constant during normal operation, and an operation mode in which the output of the generator is adjusted to follow the load. I am switching and driving.
On the other hand, in the nuclear power plant of the present embodiment, the following three operation modes are adopted, and operation is performed by switching between these operation modes.
Operation mode 1 is a normal operation mode in which the output of the generator is constant.
Operation mode 2 is an operation mode in which the output of the generator is adjusted to follow the load.
Operation mode 3 is a normal operation mode in which the output of the generator is constant, but compared to operation mode 1, the opening degree of the extraction valves 19, 21, 23, and 25 is large. is.

Here, FIG. 2 shows a schematic configuration diagram of the operation mode recording device 38 of the nuclear power plant of FIG. In FIG. 2, steps S11 to S13 of the processing performed by the driving mode recording device 38 and the driving mode recorder 38A in the driving mode recording device 38 are shown in a block diagram.

An operation mode 41 is input to the operation mode recording device 38 shown in FIG. When the current operation mode is set, a signal indicating the set operation mode is input as the operation mode 41 . If the operation mode is not set, the operation mode 41 is not entered.
In step S11, it is determined whether or not there is an input for the operation mode 41. If there is an input (No), the process proceeds to step S12, and if there is no input (Yes), the process proceeds to step S13.
In step S13, the operation mode 1, which is the initial value when the operation mode 41 does not exist, is set, and the process proceeds to step S12.
In step S12, it is determined whether the operation mode is not the operation mode 2, and if the operation mode is not the operation mode 2 (Yes), the operation mode recorder 38A is performed. In addition, when it is operation mode 2 (No), nothing is performed.
The operation mode recorder 38A records the state of the operation mode (operation mode 1 or operation mode 3) as a recorded value 41s, and outputs the recorded value 41s of the state from the operation mode recorder 38 to the outside.
Although details will be described later, the operation mode 41 is overwritten by the heat balance changing device 35 shown in FIG. 4 or the extraction valve control device 34 shown in FIG. Then, every time the operation mode 41 is overwritten, the operation mode recording device 38 shown in FIG. 2 changes the recorded value 41s of the operation state.

Next, FIG. 3 shows a schematic configuration diagram of the normal operating state recording device 36 of the nuclear power plant of FIG. In FIG. 3, step S21 of the processing performed by the normal operating state recording device 36 and the normal operating state recorder 36A in the normal operating state recording device 36 are shown in a block diagram.

The generator output 42 and the valve opening degrees of the four bleed valves 19, 21, 23 and 25 shown in FIG. 1 are input to the normal operating state recording device 36 shown in FIG.
In step S21, it is determined whether or not the operation mode is not the operation mode 2. If the operation mode is not the operation mode 2 (Yes), the process proceeds to the normal operation state recorder 36A. In addition, when it is operation mode 2 (No), nothing is performed.
In the normal operation state recorder 36A, the opening degrees of the four bleed valves 19, 21, 23, 25 and the generator output 42 are recorded as recorded values 19s, 21s, 23s, 25s, 42s. is output from the normal operating state recording device 36 to the outside.

Next, FIG. 4 shows a schematic configuration diagram of the heat balance changing device 35 of the nuclear power plant of FIG. In FIG. 4, steps S31 to S35 of the processing performed by the heat balance changing device 35 are shown in a block diagram.

A generator output adjustment range change command 40 and a recorded value 41s of the operation mode are input to the heat balance change device 35 shown in FIG.
In step S31, the operation mode is determined, and in the case of operation mode 1, the process proceeds to steps S32 and S33, and in the case of operation mode 3, the process proceeds to steps S34 and S35.
In step S<b>32 , the valve opening degrees of the bleed valves 19 , 21 , 23 , 25 are changed to fully open, and the changed valve opening degrees are output to the outside of the heat balance changing device 35 .
In step S<b>33 , the operation mode is changed to operation mode 3 and the changed operation mode 41 is output to the outside of the heat balance changing device 35 .
In step S34, the valve opening degrees of the bleed valves 19, 21, 23, and 25 are changed to the valve opening degrees of operation mode 1 (during normal operation), and the changed valve opening degrees are sent to the outside of the heat balance changing device 35. Output.
In step S<b>35 , the operation mode is changed to operation mode 1 and the changed operation mode 41 is output to the outside of the heat balance changing device 35 .

Next, FIG. 5 shows a schematic configuration diagram of the extraction valve control device 34 of the nuclear power plant of FIG. FIG. 5 is a block diagram showing steps S41 to S45 of the processing performed by the bleed valve control device 34, and a calculator for subtraction and a calculator for multiplication.

A generator output adjustment command 39, a record value 42s of the generator output, and a record value 41s of the operation mode are input to the bleed valve control device 34 shown in FIG. Then, the difference (39-42s) between the generator output adjustment command 39 and the recorded generator output value 42s is calculated.
In step S41, the operation mode is discriminated from the inputted operation mode record value 41s. If the operation mode is 1, the process proceeds to step S42.
In step S42, the previously calculated difference is used as the horizontal axis of the graph, and the extraction valve opening magnification ratio corresponding to the difference in the graph is obtained. The obtained bleed valve opening magnification is multiplied by the recorded values 19s, 21s, 23s, and 25s of the valve opening during normal operation of each bleed valve in an individual computing unit for each bleed valve to obtain the valve after the change. Aperture is calculated. The calculated valve opening degrees are output to the outside of the bleed valve control device 34, respectively.
In step S43, with the previously calculated difference as the horizontal axis of the graph, the extraction valve opening ratio corresponding to the difference in the graph is obtained. The obtained bleed valve opening magnification is multiplied by the recorded values 19s, 21s, 23s, and 25s of the valve opening during normal operation of each bleed valve in an individual computing unit for each bleed valve to obtain the valve after the change. Aperture is calculated. The calculated valve opening degrees are output to the outside of the bleed valve control device 34, respectively. Although step S43 is the same operation as step S42, the graph of the relationship between the difference and the bleed valve opening magnification is different.
In step S44, it is determined whether or not there is an input of the generator output adjustment command 39. If there is an input (Yes), the process proceeds to step S45. If there is no input (No), nothing is executed.
In step S<b>45 , the operation mode is changed to operation mode 2 and the changed operation mode 41 is output to the outside of the bleed valve control device 34 .

Next, operations of the nuclear power plant according to the present embodiment will be described with reference to FIGS. 1 to 5. FIG.
First, the operation during normal bleed throttling operation (CT) will be described, and then the operation principle of CT with an expanded output control range according to the present embodiment will be described.

When the system request, that is, the generator output adjustment command 39 is input to the bleed valve control device 34 shown in FIG. Along with this, the difference from the generator output 42s during steady operation (generator output increase width) is calculated.
In normal CT, the operation mode 41s=1 (operation mode 1) during normal operation, and the differential signal propagates to step S42 in FIG. In step S42, the difference signal is input, and an opening magnification by which the valve opening of the bleed valve is multiplied is calculated based on the graph. In the graph of step S42, a represents the maximum generator output increase range that can be controlled by normal CT.
When the difference is a, the opening magnification becomes zero. When the difference is negative or 0, the opening magnification is 1.0. When 0<difference<a, the opening scale factor corresponds to the straight line of the graph.
The maximum generator output increase range is the maximum power generation obtained by fully closing the four extraction valves 19, 21, 23, and 25 from the valve openings of 19s, 21s, 23s, and 25s during normal operation. It can be evaluated as an increase in machine output. By multiplying the valve opening degrees 19s, 21s, 23s, and 25s of the bleed valve during normal operation recorded in the normal operation state recording device 36 by the bleed valve opening magnification calculated from the difference, the valve opening of the bleed valve is calculated. The degree is narrowed down, and the power generation amount increase corresponding to the generator output adjustment command 39 is realized. As a result, the generator output can be increased to "rated output +a".

Next, the operating principle of the CT with an expanded output control range in this embodiment will be described.
In order to increase the CT output increase width, the nuclear power plant of the present embodiment is provided with the heat balance changing device 35 shown in FIGS. 1 and 4 .
When the operation mode record value 41s=1 (operation mode 1), when the generator output adjustment width change command 40 is input to the heat balance change device 35, the command signal propagates from step S31 to step S32 and step S33 in FIG. do. As a result, in step S32, the opening degrees of the four extraction valves 19, 21, 23, and 25 whose valve opening degrees were controlled so as to obtain the necessary amount of extracted steam in operation mode 1 are fully opened. At the same time, the operation mode 1 is switched to the operation mode 3 in step S33.
By fully opening the four extraction valves 19, 21, 23, and 25, the steady state of the system (the amount of steam flowing into the turbine, the feed water The amount of steam extracted to the heater, the amount of feed water heated by the feed water heater, etc.) changes, but due to the function of the control system of the nuclear power plant, the nuclear power plant is set to a new steady state (steady state 2). be.

Note that when the generator output adjustment range change command 40 is input to the heat balance changing device 35 in the state of the operation mode 3, the operation mode 3 is returned to the operation mode 1 in step S35, and the air is extracted in step S34. The valve opening degree of the valve is also returned to the operation mode 1 state.
That is, the heat balance changing device 35 has a function of switching between the operation mode 1 and the operation mode 3 using the generator output adjustment width change command 40 as a trigger.

The state of operation mode 3 is recorded as a recorded value 41s by the operation mode recording device 38 of FIG. Further, the valve openings 19, 21, 23, 25 of the four bleed valves in the fully opened state and the generator output 42 in the steady state 2 are stored in the operating state recorder 36A in the normal operating state recorder 36 in FIG. Recorded values are recorded as 19s, 21s, 23s, 25s and 42s.

In this state, when the generator output adjustment command 39 is input to the bleed valve control device 34 shown in FIG. A signal (generator output increase width signal) propagates.
In the state of operation mode 3, the valve opening degrees of the four bleed valves 19, 21, 23, 25 are larger than in the normal state, so the maximum increase in generator output obtained by fully closing the bleed valves is obtained. The width increases from a to a+b.
That is, as shown in the system diagram of FIG. 1, by using four devices (bleeding valve control device 34, heat balance change device 35, normal operation state recording device 36, and operation mode recording device 38), CT time can be increased from a to a+b.

According to the nuclear power plant of the present embodiment, in operation mode 3, the opening degrees of the extraction valves 19, 21, 23, and 25 are larger than in operation mode 1. Therefore, when the operation mode 3 is shifted to the operation mode 2 (the operation mode in which the output of the generator is adjusted to follow the load), the bleed valves 19 and 21 are compared with the case where the operation mode 1 is shifted. , 23 and 25 can be widened.
As a result, the output control range of the extraction throttling operation (CT) can be expanded in response to the load follow-up command (output increase) from the demand side.

(Second embodiment)
FIG. 6 is a system diagram of a second embodiment of the nuclear power plant of the present invention.
7 shows a schematic configuration diagram of the normal operating state recording device 36 for the nuclear power plant of FIG. 6, and FIG. 9 shows a schematic configuration diagram of the extraction valve control device 34 for the nuclear power plant of FIG.

The nuclear power plant according to the second embodiment differs from the nuclear power plant according to the first embodiment in that the extraction lines for supplying extraction steam to the four feedwater heaters 11, 12, 13, and 14 are In addition to the four (18, 20, 22, 24) of the embodiment, four (26, 28, 30, 32) are added, and the four bleeds of the first embodiment In addition to valves (herein referred to as first bleed valves) 19, 21, 23 and 25, second bleed valves 27, 29, 31 and 33 are added on the four additional bleed lines. It is in.
Hereinafter, in the second embodiment, the same bleed lines 18, 20, 22, and 24 as in the first embodiment are defined as the first bleed lines, and the added bleed lines 26, 28, 30, and 32 are used as the second bleed lines. 2 bleed lines.

The locations of the four added second bleed lines 26, 28, 30, 32 from the turbines 4, 6 or the main steam line 3 are the first bleed lines 18, 20, 22 common to those in FIG. , 24 on the upstream side (high temperature side).

Also, the four second bleed valves 27, 29, 31, 33 are kept fully closed in the first operation mode.

Here, FIG. 7 shows a schematic configuration diagram of the normal operating state recording device 36 of the nuclear power plant of FIG. FIG. 7 shows a block diagram of step S51 of the processing performed by the normal operating state recording device 36 and the normal operating state recorder 36A in the normal operating state recording device 36. As shown in FIG.

The generator output 42 and the valve opening degrees of the eight extraction valves 19, 21, 23, 25, 27, 29, 31, and 33 shown in FIG. be done.
In step S51, it is determined whether or not the operation mode is not the operation mode 2. If the operation mode is not the operation mode 2 (Yes), the process proceeds to the normal operation state recorder 36A. In addition, when it is operation mode 2 (No), nothing is performed.
In the normal operation state recorder 36A, the opening degrees of the eight extraction valves 19, 21, 23, 25, 27, 29, 31, 33 and the generator output 42 are recorded as the recorded values 19s, 21s, 23s, 25s, 27s, 29 s, 31 s, 33 s, and 42 s are recorded, and the recorded values are output from the normal operating state recording device 36 to the outside.

Next, FIG. 8 shows a schematic configuration diagram of the heat balance changing device 35 of the nuclear power plant of FIG. In FIG. 8, steps S61 to S65 of the processing performed by the heat balance changing device 35 are shown in a block diagram.

In the heat balance changing device 35 shown in FIG. 8, similarly to the heat balance changing device 35 of the first embodiment shown in FIG. is entered.
In step S61, the operation mode is determined, and in the case of operation mode 1, the process proceeds to steps S62 and S63, and in the case of operation mode 3, the process proceeds to steps S64 and S65.
In step S<b>62 , the valve opening degrees of the second bleed valves 27 , 29 , 31 , 33 are changed to fully open, and the changed valve opening degrees are output to the outside of the heat balance changing device 35 .
In step S<b>63 , the operation mode is changed to operation mode 3 and the changed operation mode 41 is output to the outside of the heat balance changing device 35 .
In step S<b>64 , the valve opening degrees of the second extraction valves 27 , 29 , 31 , 33 are changed to fully closed, and the changed valve opening degrees are output to the outside of the heat balance changing device 35 .
In step S<b>65 , the operation mode is changed to operation mode 1 and the changed operation mode 41 is output to the outside of the heat balance changing device 35 .

Next, FIG. 9 shows a schematic configuration diagram of the extraction valve control device 34 of the nuclear power plant of FIG. FIG. 9 shows a block diagram of steps S71 to S74 of the processing performed by the bleed valve control device 34, and a calculator that performs subtraction and a calculator that performs multiplication.

A generator output adjustment command 39 and a recorded generator output value 42s are input to the bleed valve control device 34 shown in FIG. Then, the difference (39-42s) between the generator output adjustment command 39 and the recorded generator output value 42s is calculated.
In step S71, with the previously calculated difference as the horizontal axis of the graph, the extraction valve opening ratio corresponding to the difference in the graph is obtained. The obtained bleed valve opening magnification is multiplied by the recorded values 19s, 21s, 23s, and 25s of the valve opening of each of the first bleed valves in an individual computing unit for each bleed valve to obtain the changed valve opening. is calculated. The calculated valve opening degrees are output to the outside of the bleed valve control device 34, respectively.
In step S72, the previously calculated difference is used as the horizontal axis of the graph, and the extraction valve opening magnification ratio corresponding to the difference in the graph is obtained. The obtained bleed valve opening magnification is multiplied by the recorded values 27s, 29s, 31s, and 33s of the valve opening during normal operation of each of the second bleed valves in individual calculators for each bleed valve, and is calculated. The calculated valve opening degrees are output to the outside of the bleed valve control device 34, respectively. In step S72, the graph of the relationship between the difference and the bleed valve opening magnification is different from that in step S71.
In step S73, it is determined whether or not there is an input of the generator output adjustment command 39, and if there is an input (Yes), the process proceeds to step S74. If there is no input (No), nothing is executed.
In step S<b>74 , the operation mode is changed to operation mode 2 and the changed operation mode 41 is output to the outside of the bleed valve control device 34 .

With such a configuration, the nuclear power plant of the present embodiment is improved in the following points compared with the nuclear power plant of the first embodiment.

In the first embodiment, in order to increase the width of increase in output during CT, the valve opening degrees of the four first bleed valves 19, 21, 23, and 25 in the generator output constant operation mode (during normal operation) are is not fully opened (intermediate opening state), and when the operation mode is switched to operation mode 3, by changing the valve opening of the four first bleed valves to the fully open state, load following operation A method of expanding the CT generator output increase range at the time (generator output adjustment operation mode (load following)) has been adopted.
However, when adopting this method of expanding the range of increase in output, the completely condensed steam (condensed water) returns through the drain line 16 even when the four first bleed valves 19, 21, 23, 25 are fully open. Since it is necessary to send water to the water device 7, the design heat exchange capacity of the four feed water heaters 11, 12, 13, and 14 is designed to be large, assuming the possibility that the four first bleed valves will be fully open. need to keep Therefore, in the generator output constant operation mode (during normal operation), that is, when the opening degrees of the four first bleed valves 19, 21, 23, and 25 are in the intermediate opening state, the four feed water heaters 11 and 12 , 13 and 14 are less than the design specification (design heat exchange capacity), and the feed water heater during constant thermal output operation (steady operation) becomes overspecified.

In contrast, in the present embodiment, four second extraction lines 26, 28, 30, 32 and four second extraction valves 27, 29, 31, 33 for guiding high-temperature steam to the feed water heater By adding , it is possible to eliminate the drawback that the feed water heater is overspecified and to simplify the control of the bleed valve.

In order to demonstrate the advantages described above, the operating principle of the CT with an expanded output control range according to the present embodiment will be described below.
Note that the operation mode recording device 38 can be realized by the operation mode recording device 38 having the configuration shown in FIG. 2, as in the first embodiment, so the description of the operation will be omitted.

When the operation mode record value 41s=1 (operation mode 1), when the generator output adjustment width change command 40 is input to the heat balance change device 35, the command signal is sent from step S61 to step S62 and step S63 in FIG. propagate. As a result, in step S62, the opening degrees of the four second bleed valves 27, 29, 31, and 33, which were fully closed in operation mode 1, are fully opened, and in step S63, operation mode 1 to operation mode 3.
By fully opening the four second extraction valves 27, 29, 31, and 33, the steady state of the system (the amount of steam flowing into the turbine , the amount of steam extracted to the feed water heater, the amount of feed water heated by the feed water heater, etc.) change, but as in the first embodiment, the control system of the nuclear power plant controls the It shifts to a new steady state (steady state 2').
In the present embodiment, when shifting to the steady state 2', instead of adjusting the opening degrees (steam flow rates) of the first bleed valves 19, 21, 23, 25, the second bleed valves 27, 29, 31, Hot steam is added by changing 33 from fully closed to fully open. This embodiment differs from the first embodiment in this respect.

In this embodiment, the average temperature of the steam supplied to each feed water heater 11, 12, 13, 14 is increased as compared with the nuclear power plant of the first embodiment.
In general, the amount of heat exchanged by a heat exchanger is proportional to the difference between the temperature of the fluid on the shell side (steam temperature) and the temperature of the fluid on the pipe side (feed water temperature). The heat exchange amount in the feed water heater can be increased without using a feed water heater with a large heat exchange capacity as shown in the embodiment.
Due to the above effects, in the present embodiment, it is possible to suppress the equipment cost of the feed water heater.

Note that when the generator output adjustment range change command 40 is input to the heat balance changing device 35 in the state of the operation mode 3, the operation mode 3 is returned to the operation mode 1 in step S65. The valve opening degree of the second bleed valve is also returned to the state (fully closed state) in operation mode 1.
That is, the heat balance changing device 35 has a function of switching between the operation mode 1 and the operation mode 3 using the generator output adjustment width change command 40 as a trigger.
Comparing FIG. 4 and FIG. 8, in FIG. 4, it is necessary to control the four bleed valves to an intermediate opening state in the branch of operation mode 3 (step S34), whereas in FIG. It is only necessary to control the two second bleed valves to the fully closed state. Therefore, in the present embodiment, there is an advantage that the valve control at the time of switching the operation mode can be simplified.

The state of operation mode 3 is recorded as a recorded value 41s by the operation mode recording device 38 of FIG. Further, the valve opening degrees of the eight bleed valves 19, 21, 23, 25, 27, 29, 31, and 33 in the fully open state and the generator output 42 in the steady state 2' are recorded in the normal operation state recording apparatus of FIG. Recorded values 19 s, 21 s, 23 s, 25 s, 27 s, 29 s, 31 s, 33 s, and 42 s are recorded in an operating state recorder 36 A in 36 .

In this state, when the generator output adjustment command 39 is input to the bleed valve control device 34 shown in FIG. 9, the operation mode is switched to operation mode 2 in step S74 as in the normal CT and the first embodiment.
In the present embodiment, unlike the first embodiment, the bleed valve control device 34 does not have a branch related to the operation mode, and instead controls the first bleed valve (the upper four valves in FIG. 9). and control of the second bleed valve (control of the four valves on the lower side of FIG. 9) are performed simultaneously.

In this embodiment, valve opening/closing control is performed from the first bleed valves 19 , 21 , 23 , and 25 . In FIG. 9, a is the generator output increase width obtained by changing the opening degree of the first bleed valve from fully open to fully closed.
Then, only when the value of the difference signal between the generator output adjustment command 39 and the generator output 42s is larger than a, in addition to the first bleed valve, when increasing the output increase width during CT, the fully closed state to the fully open state. In FIG. 9, c denotes the generator output increase width obtained by changing the valve opening degree of the second bleed valve from fully open to fully closed.
For both the first bleed valve and the second bleed valve, the bleed valve opening ratio is calculated according to the generator output increase width (difference), and the valve opening of the bleed valve in the steady state recorded in the normal operating state recording device 36 By multiplying the degrees 19s, 21s, 23s, 25s, 27s, 29s, 31s, and 33s, the bleed valve opening during load following operation is calculated, and the valve opening of the eight bleed valves is adjusted. This makes it possible to increase the generator output to "rated output +a+c".

As described above, compared with the first embodiment, the nuclear power plant of the present embodiment has four second extraction lines 26, 28, 30, 31 for supplying high-temperature steam to the feed water heater. and second bleed valves 27, 29, 31, 33, but it is not necessary to increase the design heat exchange capacity of the feed water heater, and the cost of the feed water heater can be reduced, and the first bleed valve and It becomes possible to simplify the control method of the second bleed valve, and to rationalize the equipment configuration.

According to the nuclear power plant of the present embodiment, the opening degrees of the second extraction valves 27, 29, 31, and 33 are fully open in operation mode 3, fully closed in operation mode 1, and fully closed in operation mode 3. The opening degree of the second bleed valves 27, 29, 31, 33 is large. Therefore, when the operation mode 3 is shifted to the operation mode 2 (the operation mode in which the output of the generator is adjusted to follow the load), compared with the case where the operation mode 1 is shifted, the entire bleed valve (the second 1 bleed valve and 2nd bleed valve) can be widened.
As a result, the output control range of the extraction throttling operation (CT) can be expanded in response to the load follow-up command (output increase) from the demand side.

Furthermore, according to the nuclear power plant of the present embodiment, as described above, the cost of the feed water heater can be reduced, and the method of controlling the first and second extraction valves can be simplified. Configuration can be streamlined.

(Modification)
In each of the above-described embodiments, the feed water heaters are provided in four stages, and each of the feed water heaters 11, 12, 13, and 14 is connected to one bleed line in the first embodiment. In the configuration of , two bleed lines were connected.
In the nuclear power plant of the present invention, the number of stages of feedwater heaters and the number of extraction lines connected to each feedwater heater are not limited to the numbers in each embodiment, and may be other numbers.
If one or more feed water heaters and one or more bleed lines are provided, the present invention can be applied to operate in three operation modes, first to third operation modes. be.

In each of the above-described embodiments, in FIGS. 5 and 9, the same opening degree multiplication factor is used to obtain the valve opening degrees of the four bleed valves.
On the other hand, it is also possible to give a coefficient to each of a plurality of bleed valves, weight them, and multiply them in consideration of the difference in the temperature of the bleed steam in each bleed line.
Also, when changing the valve opening degree of a plurality of bleed valves, the timing of opening and closing the bleed valves should be such that even if all the bleed valves are opened and closed all at once, the bleed valves are opened and closed sequentially from the high temperature side or the low temperature side. Either way is possible.

In the above-described second embodiment, the first bleed valve is fully opened in both the first operation mode and the third operation mode, the second bleed valve is fully closed in the first operation mode, and the third operation is performed. In the mode, it was in a fully open state.
The states of the opening degrees of the first and third bleed valves in the first and third operation modes, respectively, may have other configurations.
For example, as described above, the first bleed valve is set to the same degree of opening in the first and third operation modes, and the second bleed valve is set to the same degree in the third operation mode as compared to the first operation mode. , the valve opening may be large. In this case, the valve opening degree of the first bleed valve in the first and third operation modes and the change in the valve opening degree of the second bleed valve between the first and third operation modes are combined. The output control range of the extraction throttling operation (CT) can be expanded up to the required amount. Therefore, it is possible to expand the output control range beyond the output control range that can be achieved with only the first bleed valve or only with the second bleed valve.
Further, for example, the first bleed valve is fully opened in both the first and third operation modes, as in the second embodiment, and the second bleed valve is a valve different from that in the second embodiment. A case where it is set as an opening degree is conceivable. In this case, a large amount of extracted steam can be ensured by the fully opened first extraction valve in the first operation mode, so the design heat exchange capacity of the feed water heater does not need to be increased, and the cost of the feed water heater can be reduced.
Further, for example, the first bleed valve is set to the same valve opening degree in the first and third operation modes, and the second bleed valve is set to the same valve opening degree as in the second embodiment. It is conceivable that In this case, the opening degree of the first bleed valve is the same, and the second bleed valve changes between the fully closed state and the fully opened state. Therefore, the method of controlling the first and second bleed valves is simplified. becomes possible.

It should be noted that the present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments and examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

1: Reactor Pressure Vessel (RPV), 2: Core, 3: Main Steam Line, 4: High Pressure Turbine, 5: Moisture Separator, 6: Low Pressure Turbine, 7: Condenser, 8: Generator, 9: Condensate pump, 10: feed water pump, 11: first stage feed water heater, 12: second stage feed water heater, 13: third stage feed water heater, 14: fourth stage feed water heater, 15: feed water line, 16: drain line, 17: condensate discharge line, 18: (first) bleed line to first stage feedwater heater, 19: (first) bleed valve to first stage feedwater heater, 20: second (first) bleed line to stage feedwater heater, 21: (first) bleed valve to second stage feedwater heater, 22: (first) bleedline to third stage feedwater heater, 23: third (first) bleed valve to stage 3 feedwater heater, 24: (first) bleed line to stage 4 feedwater heater, 25: (first) bleed valve to stage 4 feedwater heater, 26: Second bleed line to first stage feedwater heater 27: Second bleed valve to first stage feedwater heater 28: Second bleed line to second stage feedwater heater 29: Second stage feedwater heating 30: Second bleed line to stage 3 feedwater heater; 31: Second bleed valve to stage 3 feedwater heater; 32: Second bleed valve to stage 4 feedwater heater; Bleed line 33: Second bleed valve to fourth stage feed water heater 34: Bleed valve control device 35: Heat balance change device 36: Normal operating state recorder 38: Operation mode recorder 39: Power generation Generator output adjustment command 40: Generator output adjustment range change command 41: Operation mode 42: Generator output 43: Input/output connection mechanism

Claims (6)

a nuclear reactor;
a turbine driven by steam generated in the reactor;
a generator driven by the turbine to generate electrical power;
a condenser for condensing exhaust steam from the turbine;
a feed water heater that heats the condensed water condensed in the condenser with extracted steam;
a steam extraction line installed between the nuclear reactor and the condenser for supplying part of the steam generated in the nuclear reactor to the feed water heater as the steam extracted;
a bleed valve for adjusting the flow rate of the bleed line;
a control unit that controls the valve opening of the bleed valve;
A nuclear power plant comprising
The nuclear power plant has a first operation mode in which the output of the generator is constant, a second operation mode in which the output of the generator is adjusted to follow the load, and an output of the generator. has three operation modes, a third operation mode in which the is operated with constant, and one operation mode is selected from the three operation modes, and the operation is performed,
In the second operation mode, the valve opening degree of the bleed valve is adjusted by the control of the control unit so that the output of the generator follows the load,
A nuclear power plant according to claim 1, wherein in the third operation mode, under the control of the control unit, at least some of the bleed valves are brought into a state in which the degree of valve opening is larger than that in the first operation mode. The control unit includes an operation mode recording device for holding the state of the operation mode, and an output of the generator and the a normal operating condition recording device for recording the valve opening of the extraction valve; and a function to change the operating mode to the third operating mode, and a valve opening of the bleed valve when a command to change the adjustment range of the output of the generator is input in the third operating mode. a heat balance changing device having the function of returning the temperature to the state at the time of the first operation mode and changing to the first operation mode, and changing the output of the generator when operating in the second operation mode. 2. The nuclear power plant according to claim 1, further comprising a bleed valve controller for adjusting opening degrees of the plurality of bleed valves when an adjustment command is input. The bleed valve control device performs control to multiply the opening degrees of the plurality of bleed valves by a constant when adjusting the valve opening degrees of the plurality of bleed valves in response to a command for adjusting the output of the generator. 3. A nuclear power plant according to claim 2. The bleed valve is composed of two types of a first bleed valve and a second bleed valve,
The first bleed valve has the same valve opening degree in the first operation mode and the third operation mode,
2. The nuclear power plant according to claim 1, wherein said second bleed valve is in a state of being larger in valve opening in said third operation mode than in said first operation mode. The first bleed valve is fully opened during the first operation mode and the third operation mode,
The second bleed valve is fully closed during the first operation mode,
The control unit fully opens the second bleed valve and switches to the third operation mode when a command to change the adjustment range of the output of the generator is input in the first operation mode. and when a command to change the adjustment range of the output of the generator is input in the third operation mode, the second bleed valve is fully closed and the first operation mode is performed. and a heat balance changing device having a function of changing the bleed valve to open the plurality of bleed valves when a command to adjust the output of the generator is input while operating in the second operation mode. 5. The nuclear power plant of claim 4, further comprising a bleed valve controller for adjusting the degree. Two bleed lines for supplying the bleed steam are connected to one feed water heater, and the second bleed valve is provided in the bleed line to which the temperature of the steam to be supplied is higher among the two bleed lines. 5. The nuclear power plant according to claim 4, wherein said first bleed valve is provided in said bleed line having a lower temperature of steam to be supplied.

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