Nuclear Power Plant

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

[Technical field]

[0001] The present invention relates to a nuclear power plant that performs extraction throttle operation (CT) in which extraction steam for heating a feed water heater is instantaneously reduced to increase turbine work (generator output) in response to a load following command (output increase) from the demand side. [Background technology]

[0002] In order to prevent global warming, the proportion of total electricity generation that is accounted for by renewable energies (such as solar power and wind power), which do not emit CO2 during power generation, is increasing. Conventionally, nuclear power plants have played a role in steadily supplying a nearly constant amount of electricity by operating at a constant rated thermal output. However, as the amount of renewable energy, which is highly dependent on weather and therefore has unstable power generation capacity, increases in the future, it is expected that there will be an increasing need for load-following operation, which flexibly changes electrical output in response to power requests from the grid (grid demand) resulting from fluctuations in power demand and renewable energy.

[0003] From the perspective of preventing fuel damage, nuclear power plants cannot take measures to increase the thermal power output of the reactor core in response to system demands that exceed the rated thermal power output (100%). To meet such system demands, a method is required to increase the amount of power generation by momentarily increasing the amount of steam flowing into the power generation turbine. Specifically, the amount of extracted steam to the feedwater heater installed on the feedwater line to heat the low-temperature feedwater after condensation in the condenser is temporarily reduced, and the amount of steam flowing into the turbine is increased. This type of operation is called throttling operation (CT).

[0004] A typical nuclear power plant is equipped with multiple feedwater heaters and multiple extraction steam lines, and a method for controlling them to perform CT is publicly known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-194312 A Summary of the Invention [Problem to be solved by the invention]

[0006] The above-mentioned Patent Document 1 describes, as a conventional technique, a method for controlling the output of a nuclear power plant by controlling the valve openings of a plurality of bleed valves provided on a plurality of bleed lines using a bleed valve control device (see FIG. 11 of Patent Document 1). However, the range of power increase that could be controlled by the CT was limited to the amount of extracted steam to the feedwater heater, and there was no means of increasing power beyond this in response to load change requests.

[0007] The present invention has been made in view of the above background, and has an object to provide a nuclear power plant that is capable of expanding the output control range of extraction throttling operation (CT), which instantaneously reduces the extraction steam for heating the feed water heater in response to a load following command (output increase) from the demand side to increase the turbine work volume (generator output).

[0008] The above and other objects of the present invention and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0009] The nuclear power plant of the present invention is a nuclear power plant including a nuclear reactor, a turbine driven by steam generated in the reactor, a generator driven by the turbine to generate electric power, a condenser for condensing exhaust steam from the turbine, a feedwater heater for heating the condensed water condensed in the condenser with extraction steam, an extraction line installed between the reactor and the condenser for supplying a portion of the steam generated in the reactor as extraction steam to the feedwater heater, a bleeding valve for adjusting the flow rate of the bleeding line, and a control unit for controlling the opening degree of the bleeding valve. The nuclear power plant of the present invention has three operation modes: a first operation mode in which the generator output is operated at a constant level; a second operation mode in which the generator output is adjusted to follow the load; and a third operation mode in which the generator output is operated at a constant level. One of the three operation modes is selected for operation. In addition, in the second operation mode of the nuclear power plant of the present invention, The valve opening of the bleed valve is smaller than the valve opening of the bleed valve in the first operation mode, The control unit controls the valve opening of the bleed valves so that the output of the generator follows the load, and in the third operation mode, the control unit controls the valve opening of at least some of the bleed valves to be larger than in the first operation mode. Effect of the Invention

[0010] According to the nuclear power plant of the present invention described above, one of three operation modes including a third operation mode in which the valve opening degree of at least some of the air extraction valves is set to a larger degree than that of the first operation mode is selected, and operation is performed. In the third operating mode, the valve opening of at least some of the bleed valves is set to a large value. Therefore, when transitioning from the third operating mode to the second operating mode, the control range of the valve opening of the bleed valves can be made larger than when transitioning from the first operating mode. This makes it possible to expand the output control range of the extraction throttling operation (CT), which instantaneously reduces the extraction steam used to heat the feedwater heater in response to a load following command (output increase) from the demand side, thereby increasing the turbine work volume (generator output).

[0011] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0012] [Figure 1] 1 is a system diagram of a nuclear power plant according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of an operation mode recording device for the nuclear power plant of FIG. 1. [Diagram 3]FIG. 2 is a schematic diagram of a normal operation state recording device of the nuclear power plant of FIG. 1. [Figure 4] FIG. 2 is a schematic configuration diagram of a heat balance changing device of the nuclear power plant of FIG. [Diagram 5] FIG. 2 is a schematic configuration diagram of a bleeding valve control device of the nuclear power plant of FIG. [Figure 6] FIG. 4 is a system diagram of a nuclear power plant according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a schematic diagram of a normal operation state recording device of the nuclear power plant of FIG. 6. [Figure 8] FIG. 7 is a schematic configuration diagram of a heat balance changing device of the nuclear power plant of FIG. 6. [Figure 9] FIG. 7 is a schematic configuration diagram of a bleeding valve control device of the nuclear power plant of FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the nuclear power plant according to the present invention will be described with reference to the drawings. In each embodiment, the same parts are given the same reference numerals, and duplicated explanations will be omitted. Note that each figure is merely a schematic illustration to the extent that the present invention can be fully understood, and the present invention is not limited to the following contents and the contents shown in the drawings, and can be modified or combined as desired within the scope that does not significantly impair the effects of the present invention.

[0014] The nuclear power plant of the present invention is a nuclear power plant including a nuclear reactor, a turbine driven by steam generated in the reactor, a generator driven by the turbine to generate electric power, a condenser for condensing exhaust steam from the turbine, a feedwater heater for heating the condensed water condensed in the condenser with extraction steam, an extraction line installed between the reactor and the condenser for supplying a portion of the steam generated in the reactor as extraction steam to the feedwater heater, a bleeding valve for adjusting the flow rate of the bleeding line, and a control unit for controlling the opening degree of the bleeding valve. That is, the nuclear power plant of the present invention is configured to be able to perform throttling operation (CT) by controlling the valve opening of the extraction valve that adjusts the flow rate in the extraction line.

[0015] Furthermore, the nuclear power plant of the present invention has three operation modes: a first operation mode in which the generator output is operated at a constant level; a second operation mode in which the generator output is adjusted to follow the load; and a third operation mode in which the generator output is operated at a constant level. One of the three operation modes is selected for operation. In addition, in the nuclear power plant of the present invention, in the second operation mode, the control unit controls the valve opening of the air bleed valves so that the output of the generator follows the load, and in the third operation mode, the control unit controls the valve opening of at least some of the air bleed valves to be larger than in the first operation mode. That is, in the nuclear power plant of the present invention, in addition to the first and second operation modes which are similar to the operation modes executed in a nuclear power plant which executes a conventional throttling operation (CT), a third operation mode is added in which the valve opening degree of at least some of the bleed valves is set to a large value.

[0016] According to the configuration of the nuclear power plant of the present invention, one of three operation modes is selected and operation is performed, including a third operation mode in which the valve opening degree of at least some of the air extraction valves is set to a larger degree than that of the first operation mode. In the third operating mode, the valve opening of at least some of the bleed valves is set to a large value. Therefore, when transitioning from the third operating mode to the second operating mode, the control range of the valve opening of the bleed valves can be made larger than when transitioning from the first operating mode. This makes it possible to expand the output control range of the extraction throttling operation (CT), which instantaneously reduces the extraction steam used to heat the feedwater heater in response to a load following command (output increase) from the demand side, thereby increasing the turbine work volume (generator output).

[0017] In the above-mentioned configuration of the nuclear power plant, the control unit may be configured to include an operation mode recording device for retaining the state of the operation mode, a normal operation state recording device for recording the output of the generator and the valve opening of the bleed valve when operating in either the first operation mode or the third operation mode, a heat balance change device having a function of increasing the valve opening of the bleed valve and changing the operation mode to the third operation mode when a command to change the adjustment range of the generator output is input when operating in the first operation mode, and a function of returning the valve opening of the bleed valve to the state in the first operation mode and changing the operation mode to the first operation mode when a command to change the adjustment range of the generator output is input when operating in the third operation mode, and a bleed valve control device for adjusting the valve openings of the multiple bleed valves when a command to adjust the output of the generator is input when operating in the second operation mode. That is, in the case of this configuration, when a command to change the adjustment range of the output of the generator is inputted by the heat balance change device, the valve opening of the bleed valve is increased or decreased, and the operation mode is changed from one of the first operation mode and the third operation mode to the other. As a result, when a command to change the adjustment range of the output of the generator is inputted, the valve opening of the bleed valve is specifically changed, and the operation mode can be switched between the first operation mode and the third operation mode.

[0018] In a nuclear power plant having this configuration, the bleed valve control device can be further configured to control the valve openings of the multiple bleed valves to be multiplied by a constant when adjusting the valve openings of the multiple bleed valves in response to a command to adjust the output of the generator. As a result, the valve openings of the multiple air bleed valves are adjusted by controlling the valve openings of the multiple air bleed valves to be multiplied by a constant, so that the bleed air amount can be adjusted and the generator output can be adjusted with a relatively simple configuration and method.

[0019] In the configuration of the nuclear power plant described above, the air bleed valve may be configured to include two types of air bleed valves, a first air bleed valve and a second air bleed valve, the first air bleed valve has the same valve opening in the first operation mode and the third operation mode, and the second air bleed valve has a larger valve opening in the third operation mode compared to the first operation mode. This makes it possible to expand the output control range of the bleed throttle operation (CT) to the sum of the valve opening of the first bleed valve in the first and third operation modes and the change in the valve opening of the second bleed valve between the first and third operation modes. Therefore, it becomes possible to expand the output control range more than the output control range possible with only the first bleed valve or only the second bleed valve.

[0020] In the nuclear power plant having this configuration, the first bleed valve is fully open in the first operation mode and the third operation mode, and the second bleed valve is fully closed in the first operation mode, and the control unit can have a heat balance change device having a function of bringing the second bleed valve into the fully open state and changing the operation mode 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 bringing the second bleed valve into the fully closed state and changing the operation mode 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, and a bleed valve control device for adjusting the valve openings of the multiple bleed valves when a command to adjust the output of the generator is input while operating in the second operation mode. That is, in the case of this configuration, when a command to change the adjustment range of the output of the generator is input, the heat balance change device increases or decreases the valve opening of the second bleed valve and switches from one of the first operation mode and the third operation mode 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 of the second bleed valve is specifically changed, and the operation mode can be switched between the first operation mode and the third operation mode. In the case of this configuration, the first bleed valve is in a fully open state in both the first operating mode and the third operating mode, and the second bleed valve changes its valve opening from one of a fully closed state and a fully open state to the other when switching between the first operating mode and the third operating mode. This makes it possible to simplify the control of the valve opening degrees of the first and second bleed valves when switching between the first and third operating modes. In addition, since the second bleed valve changes its valve opening from one of a fully closed state and a fully open state to the other, the change in valve opening between the first operation mode and the third operation mode can be made large, so there is no need to increase the designed heat exchange capacity of the heat exchanger of the feed water heater. This makes it possible to reduce the cost of the feed water heater compared to a case in which the second bleed valve is not provided. Furthermore, since the control of the valve opening degree of the first and second bleed valves can be simplified and the cost of the feedwater heater can be reduced, the equipment configuration of the nuclear power plant can be rationalized.

[0021] In a nuclear power plant having this configuration, it is further possible to configure the following: two extraction lines for supplying extraction steam to one feedwater heater are connected; a second extraction valve is provided in the extraction line supplying steam of a higher temperature, and a first extraction valve is provided in the extraction line supplying steam of a lower temperature. This makes it possible to increase the amount of change in the energy of the bleed steam caused by opening and closing the second bleed valve, making it possible to further reduce the designed heat exchange capacity of the heat exchanger of the feed water heater.

[0022] In the above-mentioned configuration of the nuclear power plant, in the third operation mode, the valve opening degree of at least some of the bleed valves is set to a larger state compared to the first operation mode. That is, the valve opening degree of all the bleed valves is set to a larger state, or the valve opening degree of some of the plurality of bleed valves is set to a larger state. In the third operating mode, the valve opening of at least some of the bleed valves is larger than in the first operating mode. Therefore, when transitioning from the third operating mode to the second operating mode, the adjustment range of the valve opening of the bleed valves can be made larger than when transitioning from the first operating mode.

[0023] 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 spent operating in the first operation mode is the longest. When the adjustment range of the opening degree of the extraction valve is expanded before switching to the second operation mode, the operation mode is changed from the first operation mode to the third operation mode. However, if there is no plan to switch to the second operation mode for a while due to a change in schedule, it is desirable to switch back from the third operation mode to the first operation mode. In the third operation mode, the opening degree of the extraction valve is made larger than in the first operation mode, so the amount of extraction steam increases and the amount of steam going to the turbine decreases accordingly, which reduces the efficiency of the power generation relative to the output of the reactor, and therefore it is not suitable for long-term operation.

[0024] Next, a specific embodiment of the nuclear power plant of the present invention will be described.

[0025] (First embodiment) FIG. 1 is a system diagram of a nuclear power plant according to a first embodiment of the present invention.

[0026] 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, and a plurality of feed water heaters 11, 12, 13, and 14.

[0027] A reactor pressure vessel (RPV) 1 contains a reactor core 2. In addition, the reactor pressure vessel 1 is 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 feedwater line 15. On the feedwater line 15, a condensate pump 9, a plurality of feedwater heaters (first stage feedwater heater 11, second stage feedwater heater 12, third stage feedwater heater 13, fourth stage feedwater heater 14), and a feedwater pump 10 are installed. The high-pressure turbine 4 and the low-pressure turbine 6 are connected to a generator 8. Note that in Fig. 1, the connection between the high-pressure turbine 4 and the generator 8 is omitted.

[0028] The moisture separator 5 is connected to the shell side of the heat exchanger of the third stage feed water heater 13 via a condensate discharge line 17 . The main steam line 3 branches between the high-pressure turbine 4 and the moisture separator 5, and the branched line is connected to the shell side of the heat exchanger of the fourth stage feedwater heater 14 via an extraction line 24 to the fourth stage feedwater heater and an extraction valve 25 to the fourth stage feedwater heater. 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 feedwater heater 13 via an extraction line 22 to the third stage feedwater heater and an extraction valve 23 to the third stage feedwater heater. The second line from the left is connected to the shell side of the second stage feedwater heater 12 via an extraction line 20 to the second stage feedwater heater and an extraction valve 21 to the second stage feedwater heater. The third line from the left is connected to the shell side of the heat exchanger of the first stage feedwater heater 11 via an extraction line 18 to the first stage feedwater heater and an extraction valve 19 to the first stage feedwater heater. The shell sides of the heat exchangers of these feedwater heaters 13, 12, and 11 are connected to the condenser 7 via a drain line 16.

[0029] As control devices for controlling the valve openings of the extraction valve 19 to the first stage feedwater heater, the extraction valve 21 to the second stage feedwater heater, the extraction valve 23 to the third stage feedwater heater, and the extraction valve 25 to the fourth stage feedwater heater, there are provided an extraction valve control device 34, a heat balance changing device 35, a normal operation state recording device 36, and an operation mode recording device 38. An input / output connection mechanism 43 connects the inputs and outputs of the four devices 34, 35, 36, and 38. The bleeding valve control device 34, the heat balance changing device 35, the normal operation state recording device 36, and the operation mode recording device 38 provided in the input / output connection mechanism 43 constitute the above-mentioned control section for controlling the valve opening degree of the bleeding valve in the nuclear power plant of the present invention.

[0030] In addition, the input / output connection mechanism 43 is connected to external input signals, such as information on the valve opening degrees of the extraction valve 19 to the first stage feedwater heater 11, the extraction valve 21 to the second stage feedwater heater 12, the extraction valve 23 to the third stage feedwater heater 13, and the extraction valve 25 to the fourth stage feedwater heater 14, a generator output adjustment command 39, a generator output adjustment range change command 40, and generator output 42.

[0031] Hereinafter, a specific method for expanding the output control range during extraction throttle operation (CT) in a nuclear power plant according to this embodiment will be described, in which the extraction steam is instantaneously reduced to heat the feed water heater and the turbine work (generator output) is increased.

[0032] Steam generated in the reactor core 2 is sent to a high-pressure turbine 4 and a low-pressure turbine 6 via a main steam line 3, and the work of rotating the turbine blades is converted into electricity via a generator 8 and sent to the grid. After completing its work in the low-pressure turbine 6, the steam is cooled by seawater or the like in a condenser 7 to become low-temperature condensed water. The low-temperature condensed water is sent to a feedwater line 15, heated and raised in temperature as it passes through a number of feedwater heaters 11, 12, 13, and 14, pressurized by a condensate pump 9 and a feedwater pump 10, and then returned to the reactor pressure vessel 1. A portion of the feed water returned to the reactor pressure vessel 1 becomes steam in the core 2 and is sent again to the turbines 4, 6, so that the system diagram shown in FIG. 1 forms a closed loop for steam and feed water.

[0033] Hot, humid steam is supplied to the shell side of the heat exchanger of the feedwater heater to heat the feedwater passing through the tube side of the heat exchanger. In this embodiment, the steam after passing through the high-pressure turbine 4 is supplied to the shell side of the heat exchanger of the fourth stage feedwater heater 14 via an extraction line 24 to the fourth stage feedwater heater and an extraction valve 25 to the fourth stage feedwater heater. Similarly, three extraction steam lines from the low-pressure turbine 6 are supplied to the third stage feedwater heater 13 via an extraction line 22 to the third stage feedwater heater and an extraction valve 23 to the third stage feedwater heater, to the second stage feedwater heater 12 via an extraction line 20 to the second stage feedwater heater and an extraction valve 21 to the second stage feedwater heater, and to the shell side of the heat exchanger of the first stage feedwater heater 11 via an extraction line 18 to the first stage feedwater heater and an extraction valve 19 to the first stage feedwater heater. The steam (condensed water) condensed by heat exchange with low-temperature feed water in the heat exchanger is sent to the condenser 7 via a drain line 16 and becomes part of the feed water.

[0034] During normal operation of a nuclear power plant, the amount of steam flowing into the turbines 4, 6, the amount of extracted steam to the feedwater heaters 11, 12, 13, 14, the amount of heating of the feedwater in the feedwater heaters 11, 12, 13, 14, etc. are kept constant, i.e., the plant is operated in a steady state.

[0035] Conventional nuclear power plants that use throttling operation (CT) switch between two operating modes: one in which output is constant during normal operation, and another in which the generator output is adjusted to follow the load. In contrast, the nuclear power plant of this embodiment employs the following three operation modes, and is operated by switching between these operation modes. Operation mode 1 is an operation mode during normal operation 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. The operation mode 3 is an operation mode during normal operation in which the output of the generator is constant. However, compared to the operation mode 1, the valve opening degree of the air extraction valves 19, 21, 23, and 25 is larger.

[0036] Here, a schematic configuration diagram of the operation mode recording device 38 of the nuclear power plant in Fig. 1 is shown in Fig. 2. In Fig. 2, steps S11 to S13 of the process performed in the operation mode recording device 38 and an operation mode recorder 38A in the operation mode recording device 38 are shown in a block diagram.

[0037] An operation mode 41 is input to the operation mode recording device 38 shown in Fig. 2. When a currently operating operation mode is set, a signal indicating the set operation mode is input as the operation mode 41. When no operation mode is set, the operation mode 41 is not input. In step S11, it is determined whether or not the operation mode 41 has been input. If the operation mode 41 has been input (No), the process proceeds to step S12, and if the operation mode 41 has not been input (Yes), the process proceeds to step S13. In step S13, the operation mode 41 is set to the operation mode 1, which is the initial value when the operation mode does not exist, and the process proceeds to step S12. In step S12, it is determined whether or not the operation mode is 2, and if the operation mode is not 2 (Yes), the process proceeds to the operation mode recorder 38A. However, if the operation mode is 2 (No), no process 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 that state from the operation mode recorder 38 to the outside. The operation mode 41, the details of which will be described later, is overwritten by the heat balance change device 35 shown in Fig. 4 or the bleed valve control device 34 shown in Fig. 5. Every time the operation mode 41 is overwritten, the recorded value 41s of the operation state is changed by the operation mode recording device 38 shown in Fig. 2.

[0038] Next, a schematic configuration diagram of the normal operation state recording device 36 of the nuclear power plant in Fig. 1 is shown in Fig. 3. In Fig. 3, step S21 of the process performed in the normal operation state recording device 36 and a normal operation state recorder 36A in the normal operation state recording device 36 are shown in a block diagram.

[0039] 1. The normal operating state recording device 36 shown in FIG. 3 receives the generator output 42 and the valve openings of the four air bleed valves 19, 21, 23, and 25 shown in FIG. In step S21, it is determined whether or not the operation mode is 2, and if the operation mode is not 2 (Yes), the process proceeds to the normal operation state recorder 36A. However, if the operation mode is 2 (No), no processing is performed. The normal operation state recorder 36A records the valve openings of the four bleed valves 19, 21, 23, 25 and the generator output 42 as recorded values ​​19s, 21s, 23s, 25s, 42s, and outputs the recorded values ​​from the normal operation state recorder 36 to the outside.

[0040] Next, a schematic configuration diagram of the heat balance changing device 35 of the nuclear power plant of Fig. 1 is shown in Fig. 4. In Fig. 4, steps S31 to S35 of the process performed by the heat balance changing device 35 are shown in a block diagram.

[0041] 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. If the operation mode is 1, the process proceeds to steps S32 and S33, and if the operation mode is 3, the process proceeds to steps S34 and S35. In step S32, the valve openings of the air bleed valves 19, 21, 23, and 25 are changed to full open, and the changed valve openings are output to the outside of the heat balance change device . In step S33, the operation mode is changed to operation mode 3, and the changed operation mode 41 is output to the outside of the heat balance change device . In step S34, the valve openings of the air extraction valves 19, 21, 23, and 25 are changed to the valve openings of the operation mode 1 (normal operation), and the changed valve openings are output to the outside of the heat balance change device 35. In step S35, the operation mode is changed to operation mode 1, and the changed operation mode 41 is output to the outside of the heat balance change device 35.

[0042] Next, a schematic configuration diagram of the bleeding valve control device 34 of the nuclear power plant in Fig. 1 is shown in Fig. 5. In Fig. 5, steps S41 to S45 of the process performed in the bleeding valve control device 34, and a computing unit that performs subtraction and a computing unit that performs multiplication are shown in a block diagram.

[0043] A generator output adjustment command 39, a recorded value 42s of the generator output, and a recorded value 41s of the operation mode are input to the bleed valve control device 34 shown in Fig. 5. Then, the difference (39-42s) between the generator output adjustment command 39 and the recorded value 42s of the generator output is calculated. In step S41, the operation mode is determined from the input operation mode record value 41s. If the operation mode is 1, the process proceeds to step S42, and if the operation mode is 3, the process proceeds to step S43. In step S42, the previously calculated difference is plotted on the horizontal axis of a graph, and a bleed valve opening magnification that corresponds to the difference on the graph is calculated. The calculated bleed valve opening magnification is multiplied by the recorded valve opening values ​​19s, 21s, 23s, and 25s of each bleed valve during normal operation in an individual calculator for each bleed valve, to calculate the changed valve opening. The calculated valve openings are output to the outside of the bleed valve control device 34. In step S43, the previously calculated difference is plotted on the horizontal axis of a graph, and the bleed valve opening magnification corresponding to the difference in the graph is calculated. The calculated 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 calculator for each bleed valve, to calculate the changed valve opening. The calculated valve openings are output to the outside of the bleed valve control device 34. Note that step S43 is the same operation as step S42, but the graph showing the relationship between the difference and the bleed valve opening magnification is different. In step S44, it is determined whether the generator output adjustment command 39 has been input, and if it has been input (Yes), the process proceeds to step S45. If it has not been input (No), nothing is executed. In step S45, the operation mode is changed to the operation mode 2, and the changed operation mode 41 is output to the outside of the air bleed valve control device .

[0044] Next, the operation of the nuclear power plant of this embodiment will be described with reference to FIGS. First, the operation during normal bleed throttle operation (CT) will be described, and then the operating principle of the CT with an expanded output control range according to this embodiment will be described.

[0045] When the system requirements, that is, the generator output adjustment command 39 is input to the extraction valve control device 34 shown in FIG. 5, it is determined that there is an input in step S44, and in step S45, the operation mode is changed to operation mode 2, and the difference from the generator output 42s during steady operation (generator output increase width) is calculated. In a normal CT, the operation mode 41s = 1 (operation mode 1) during normal operation, and the difference signal propagates to step S42 in FIG. 5. In step S42, using the difference signal as an input, based on the graph, the opening magnification to be multiplied by the opening degree of the extraction valve is calculated. In the graph of step S42, a represents the maximum generator output increase width controllable by a normal CT. When the difference is a, the opening magnification becomes 0. When the difference is negative and 0, the opening magnification becomes 1.0. When 0 < difference < a, the opening magnification corresponds to the straight line of the graph. The maximum generator output increase width can be evaluated as the maximum generator output increase width obtained by closing the four extraction valves 19, 21, 23, 25 from the valve opening degrees 19s, 21s, 23s, 25s during normal operation. By multiplying the extraction valve opening magnification calculated from the difference by the valve opening degrees 19s, 21s, 23s, 25s of the extraction valves during normal operation recorded in the normal operation state recording device 36, the valve opening degree of the extraction valve is throttled, and an increase in the power generation amount corresponding to the generator output adjustment command 39 is realized. Thereby, the generator output can be increased to "rated output + a".

[0046] Next, the operating principle of the CT with an expanded output control range in this embodiment will be described. In order to expand the output increase width of the CT, the nuclear power plant of this embodiment is provided with the thermal balance change device 35 shown in FIGS. 1 and 4. When the operation mode recorded value 41s=1 (operation mode 1), if a generator output adjustment range change command 40 is input to the heat balance change device 35, a command signal is propagated from step S31 to steps S32 and S33 in Fig. 4. As a result, in step S32, the valve openings of the four extraction valves 19, 21, 23, 25, the valve openings of which were controlled so as to obtain the amount of extracted steam required in operation mode 1, are fully opened, and in step S33, the operation mode is switched from operation mode 1 to operation mode 3. When the four extraction valves 19, 21, 23, 25 are fully opened, the steady state of the system (the amount of steam flowing into the turbine, the amount of extracted steam to the feedwater heater, the amount of heating of the feedwater in the feedwater heater, etc.) changes in the operation mode (normal operation) in which the generator output is operated at a constant level, but the nuclear power plant's control system works to settle the nuclear power plant into a new steady state (steady state 2).

[0047] When the generator output adjustment range change command 40 is input to the heat balance change device 35 in the operation mode 3, the operation mode is returned from the operation mode 3 to the operation mode 1 in step S35, and the valve opening of the extraction valve is also returned to the state of the operation mode 1 in step S34. That is, the heat balance change device 35 has a function of switching between the operation mode 1 and the operation mode 3 using the generator output adjustment range change command 40 as a trigger.

[0048] The state of operation mode 3 is recorded as a recorded value 41s by operation mode recording device 38 in Fig. 2. In addition, valve openings 19, 21, 23, 25 of the four bleed valves that are in the fully open state and generator output 42 in steady state 2 are recorded as recorded values ​​19s, 21s, 23s, 25s, 42s in operation state recorder 36A in normal operation state recording device 36 in Fig. 3.

[0049] In this state, when a generator output adjustment command 39 is input to the bleed valve control device 34 shown in FIG. 5, the operation mode is switched to operation mode 2 in step S45, as in the case of a normal CT, and a difference signal (generator output increase amount signal) is propagated to step S43. In the operation mode 3, the valve openings 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 increases from a to a+b. That is, as shown in the system diagram of FIG. 1, by using four devices (a bleed valve control device 34, a heat balance change device 35, a normal operation state recording device 36, and an operation mode recording device 38), it is possible to increase the generator output increase during CT from a to a+b.

[0050] According to the nuclear power plant of this embodiment, in the operation mode 3, the valve openings of the extraction valves 19, 21, 23, and 25 are set to a larger state compared to the operation mode 1. Therefore, when the operation mode is shifted from the operation mode 3 to the operation mode 2 (an operation mode in which the output of the generator is adjusted to follow the load), the control width of the valve openings of the extraction valves 19, 21, 23, and 25 can be made larger compared to the case of shifting from the operation mode 1. This makes it possible to expand the output control range of the extraction throttle operation (CT) in response to a load following command (output increase) from the demand side.

[0051] (Second embodiment) FIG. 6 is a system diagram of a nuclear power plant according to a second embodiment of the present invention. 7 shows a schematic configuration diagram of the normal operation state recording device 36 of the nuclear power plant of FIG. 6, and FIG. 9 shows a schematic configuration diagram of the air bleeding valve control device 34 of the nuclear power plant of FIG.

[0052] The nuclear power plant of the second embodiment differs from the nuclear power plant of the first embodiment in that four more extraction lines (26, 28, 30, 32) for supplying extraction steam to the four feedwater heaters 11, 12, 13, 14 are added in addition to the four lines (18, 20, 22, 24) in the first embodiment, and in that second extraction valves 27, 29, 31, 33 are added on the four added extraction lines in addition to the four extraction valves (referred to as first extraction valves here) 19, 21, 23, 25 in the first embodiment. Hereinafter, in this second embodiment, the bleed lines 18, 20, 22, 24 similar to those in the first embodiment will be referred to as first bleed lines, and the added bleed lines 26, 28, 30, 32 will be referred to as second bleed lines.

[0053] The locations at which the four added second extraction lines 26, 28, 30, 32 extract steam from the turbines 4, 6 or the main steam line 3 are located upstream (higher temperature side) than the first extraction lines 18, 20, 22, 24 common to FIG.

[0054] Furthermore, the four second bleed valves 27, 29, 31, 33 are maintained in a fully closed state during operation mode 1.

[0055] Here, a schematic configuration diagram of the normal operation state recording device 36 of the nuclear power plant in Fig. 6 is shown in Fig. 7. In Fig. 7, step S51 of the process performed in the normal operation state recording device 36 and a normal operation state recorder 36A in the normal operation state recording device 36 are shown in a block diagram.

[0056] 6. The normal operation state recording device 36 shown in FIG. 7 receives the generator output 42 and the valve openings of the eight air bleed valves 19, 21, 23, 25, 27, 29, 31, and 33 shown in FIG. In step S51, it is determined whether or not the operation mode is 2, and if the operation mode is not 2 (Yes), the process proceeds to the normal operation state recorder 36A. However, if the operation mode is 2 (No), no processing is performed. The normal operation state recorder 36A records the valve openings of the eight bleed valves 19, 21, 23, 25, 27, 29, 31, 33 and the generator output 42 as recorded values ​​19s, 21s, 23s, 25s, 27s, 29s, 31s, 33s, 42s, and outputs the recorded values ​​from the normal operation state recorder 36 to the outside.

[0057] Next, a schematic configuration diagram of the heat balance changing device 35 of the nuclear power plant of Fig. 6 is shown in Fig. 8. In Fig. 8, steps S61 to S65 of the process performed by the heat balance changing device 35 are shown in a block diagram.

[0058] Similar to the heat balance change device 35 of the first embodiment shown in FIG. 4, the heat balance change device 35 shown in FIG. 8 receives a generator output adjustment range change command 40 and a recorded value 41s of the operation mode. In step S61, the operation mode is determined. If the operation mode is 1, the process proceeds to steps S62 and S63, and if the operation mode is 3, the process proceeds to steps S64 and S65. In step S62, the valve openings of the second bleed valves 27, 29, 31, and 33 are changed to full open, and the changed valve openings are output to the outside of the heat balance change device . In step S63, the operation mode is changed to operation mode 3, and the changed operation mode 41 is output to the outside of the heat balance change device . In step S64, the valve openings of the second bleed valves 27, 29, 31, and 33 are changed to fully closed, and the changed valve openings are output to the outside of the heat balance change device . In step S65, the operation mode is changed to operation mode 1, and the changed operation mode 41 is output to the outside of the heat balance change device .

[0059] Next, a schematic configuration diagram of the air bleed valve control device 34 of the nuclear power plant in Fig. 6 is shown in Fig. 9. In Fig. 9, steps S71 to S74 of the process performed by the air bleed valve control device 34, and a computing unit that performs subtraction and a computing unit that performs multiplication are shown in a block diagram.

[0060] A generator output adjustment command 39 and a recorded value 42s of the generator output are input to the bleed valve control device 34 shown in Fig. 9. Then, the difference (39-42s) between the generator output adjustment command 39 and the recorded value 42s of the generator output is calculated. In step S71, the previously calculated difference is plotted on the horizontal axis of a graph, and a bleed valve opening magnification that corresponds to the difference on the graph is calculated. The calculated bleed valve opening magnification is multiplied by the recorded valve opening values ​​19s, 21s, 23s, and 25s of each first bleed valve in an individual calculator for each bleed valve, to calculate the changed valve opening. The calculated valve openings are output to the outside of the bleed valve control device 34. In step S72, the previously calculated difference is plotted on the horizontal axis of a graph, and the bleed valve opening magnification corresponding to the difference in the graph is calculated. The calculated bleed valve opening magnification is multiplied by the recorded values ​​27s, 29s, 31s, and 33s of the valve opening during normal operation of each second bleed valve in an individual calculator for each bleed valve, to calculate the changed valve opening. The calculated valve openings are output to the outside of the bleed valve control device 34. Note that step S72 differs from step S71 in the graph showing the relationship between the difference and the bleed valve opening magnification. In step S73, it is determined whether the generator output adjustment command 39 has been input, and if it has been input (Yes), the process proceeds to step S74. If it has not been input (No), nothing is executed. In step S74, the operation mode is changed to the operation mode 2, and the changed operation mode 41 is output to the outside of the air bleed valve control device .

[0061] By adopting such a configuration, the nuclear power plant of this embodiment has the following improvements over the nuclear power plant of the first embodiment.

[0062] In the first embodiment, in order to increase the output increase range during CT, the valve openings of the four first bleed valves 19, 21, 23, 25 during the generator output constant operation mode (normal operation) are maintained in a state other than fully open (intermediate opening state), and when the operation mode is switched to operation mode 3, the valve openings of the four first bleed valves are changed to the fully open state, thereby expanding the generator output increase range during CT during load following operation (generator output adjustment operation mode (load following)). However, when this method of expanding the output increase is adopted, even when the four first bleed valves 19, 21, 23, 25 are fully open, the fully condensed steam (condensed water) needs to be sent to the condenser 7 via the drain line 16, so the designed heat exchange capacity of the four feedwater heaters 11, 12, 13, 14 needs to be designed to be larger, assuming the possibility that the four first bleed valves will be fully open. Therefore, in the constant generator output operation mode (normal operation), that is, when the valve openings of the four first bleed valves 19, 21, 23, 25 are in an intermediate opening state, the heat exchange capacity of the four feedwater heaters 11, 12, 13, 14 is less than the design specification (design heat exchange capacity), resulting in the disadvantage that the feedwater heaters during constant thermal output operation (steady operation) have excessive specifications.

[0063] In contrast to this, in the present embodiment, by adding four second extraction lines 26, 28, 30, 32 and four second extraction valves 27, 29, 31, 33 for directing high-temperature steam to the feedwater heater, the drawback of the feedwater heater being over-specified can be eliminated and the control of the extraction valves can be simplified.

[0064] In order to demonstrate the above advantages, the operating principle of the CT with an expanded output control width in this embodiment will be described below. Incidentally, 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, and therefore a description of the operation will be omitted.

[0065] When the operation mode recorded value 41s=1 (operation mode 1), if the generator output adjustment range change command 40 is input to the heat balance change device 35, a command signal is propagated from step S61 to step S62 and step S63 in Fig. 8. As a result, in step S62, the valve openings of the four second bleed valves 27, 29, 31, 33 that were in a fully closed state in operation mode 1 are changed to a fully open state, and in step S63, the operation mode is switched from 1 to 3. By fully opening the four second extraction valves 27, 29, 31, 33, the steady state of the system (the amount of steam flowing into the turbine, the amount of extracted steam to the feedwater heater, the amount of heating of the feedwater in the feedwater heater, etc.) changes in the operation mode in which the generator output is operated at a constant (normal operation). However, as in the first embodiment, the nuclear power plant transitions to a new steady state (steady state 2') due to the action of the control system of the nuclear power plant. In this embodiment, when transitioning to the steady state 2', high-temperature steam is added by changing the second bleed valves 27, 29, 31, 33 from fully closed to fully open, instead of adjusting the valve opening (steam flow rate) of the first bleed valves 19, 21, 23, 25. This is what makes this embodiment different from the first embodiment.

[0066] In this embodiment, the average temperature of the steam supplied to each of the feedwater heaters 11, 12, 13, and 14 is increased, as compared with the nuclear power plant of the first embodiment. Generally, the heat exchange amount of 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 tube side (feedwater temperature). Therefore, in this embodiment, the heat exchange amount in the feedwater heater can be increased without using a feedwater heater with a large heat exchange capacity as shown in the first embodiment. Due to the above-mentioned effects, in this embodiment, it is possible to reduce the installation costs of the feed water heater.

[0067] When the generator output adjustment range change command 40 is input to the heat balance change device 35 in the operation mode 3, the operation mode is returned from the operation mode 3 to the operation mode 1 in step S65, and the valve opening of the second bleed valve is also returned to the state in the operation mode 1 (fully closed state) in step S64. That is, the heat balance change device 35 has a function of switching between the operation mode 1 and the operation mode 3 using the generator output adjustment range change command 40 as a trigger. Comparing Figure 4 with Figure 8, in Figure 4, it is necessary to control the four bleed valves to an intermediate opening state at the branching of operation mode 3 (step S34), whereas in Figure 8, it is only necessary to control the four second bleed valves to a fully closed state. Therefore, this embodiment has the advantage that the valve control at the time of switching the operation mode can be simplified.

[0068] The state of operation mode 3 is recorded as a recorded value 41s by operation mode recording device 38 of Fig. 2. In addition, the valve opening degrees of the eight bleed valves 19, 21, 23, 25, 27, 29, 31, 33 that are in the fully open state and the generator output 42 in steady state 2' are recorded as recorded values ​​19s, 21s, 23s, 25s, 27s, 29s, 31s, 33s, 42s in operation state recorder 36A in normal operation state recording device 36 of Fig. 7.

[0069] In this state, when a generator output adjustment command 39 is input to the bleed valve control device 34 shown in FIG. 9, the operation mode is switched to the operation mode 2 in step S74, similarly to the normal CT and the first embodiment. In this embodiment, unlike the first embodiment, there is no branching related to the operating mode in the bleed valve control device 34, and instead, control of the first bleed valves (control of the four valves on the upper side of Figure 9) and control of the second bleed valves (control of the four valves on the lower side of Figure 9) are performed simultaneously.

[0070] In this embodiment, valve opening and closing control is performed using the first bleed valves 19, 21, 23, and 25. In Fig. 9, the generator output increase obtained by changing the valve opening of the first bleed valve from the fully open state to the fully closed state is denoted as a. 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, the valve openings of the second bleed valves 27, 29, 31, 33, which change the fully closed state to the fully open state when increasing the output increase range during CT, are also controlled. In Fig. 9, the generator output increase range obtained by changing the valve opening of the second bleed valve from the fully open state to the fully closed state is denoted as c. For both the first and second bleed valves, the bleed valve opening magnification corresponding to the generator output increase width (difference) is calculated, and by multiplying this by the bleed valve openings 19s, 21s, 23s, 25s, 27s, 29s, 31s, and 33s in the steady state recorded in the normal operation state recorder 36, the bleed valve opening during load following operation is calculated, and the valve openings of the eight bleed valves are adjusted. This makes it possible to increase the generator output to "rated output + a + c".

[0071] As described above, in the nuclear power plant of this embodiment, compared to the first embodiment, four second extraction lines 26, 28, 30, 31 and second extraction valves 27, 29, 31, 33 must be added to supply high-temperature steam to the feedwater heater; however, there is no need to increase the design heat exchange capacity of the feedwater heater, which reduces the cost of the feedwater heater and simplifies the control method for the first extraction valve and the second extraction valve, thereby streamlining the equipment configuration.

[0072] According to the nuclear power plant of this embodiment, the valve openings of the second bleed valves 27, 29, 31, 33 are fully open in operation mode 3 and fully closed in operation mode 1, and the valve openings of the second bleed valves 27, 29, 31, 33 are large in operation mode 3. Therefore, when transitioning from operation mode 3 to operation mode 2 (an operation mode in which the output of the generator is adjusted to follow the load), the control range of the valve openings of all the bleed valves (the first bleed valve and the second bleed valve) can be made larger than when transitioning from operation mode 1. This makes it possible to expand the output control range of the extraction throttle operation (CT) in response to a load following command (output increase) from the demand side.

[0073] Furthermore, according to the nuclear power plant of this embodiment, as described above, the cost of the feedwater heater can be reduced, and the control method of the first bleeding valve and the second bleeding valve can be simplified, thereby streamlining the equipment configuration.

[0074] (Modification) In each of the above-mentioned embodiments, the feed water heater is arranged in four stages, and in the first embodiment, one extraction line is connected to each of the feed water heaters 11, 12, 13, and 14, while in the second embodiment, two extraction lines are connected to each of the feed water heaters 11, 12, 13, and 14. 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. As long as one or more feed water heaters and one or more extraction lines are provided, the present invention can be applied to operate the plant in three operation modes, the first operation mode, the second operation mode, and the third operation mode.

[0075] In each of the above-described embodiments, in Figs. 5 and 9, the opening degree multiplication factors used to obtain the valve opening degrees of the four air bleed valves are the same. On the other hand, taking into consideration differences in the temperature of the bleed steam in each bleed line, it is also possible to weight and multiply each of a plurality of bleed valves by giving a coefficient to each bleed valve. In addition, when changing the valve openings of a plurality of air bleed valves, the timing for opening and closing the air bleed valves may be either such that all the air bleed valves are opened and closed simultaneously, or such that the air bleed valves are opened and closed sequentially starting from the air bleed valve on the high temperature side or the air bleed valve on the low temperature side.

[0076] In the second embodiment described above, the first bleed valve is fully open in both the first operation mode and the third operation mode, and the second bleed valve is fully closed in the first operation mode and fully open in the third operation mode. The valve opening states of the first bleed valve and the third bleed valve in each of the first and third operation modes may be configured in other ways. For example, as described above, it is possible to set the first bleed valve to the same valve opening in the first and third operation modes, and the second bleed valve to a larger valve opening in the third operation mode compared to the first operation mode. In this case, the output control width of the bleed throttle operation (CT) can be expanded to the sum of the valve opening of the first bleed valve in the first and third operation modes and the change in the valve opening of the second bleed valve between the first and third operation modes. Therefore, it becomes possible to expand the output control width beyond the output control width possible with only the first bleed valve or only the second bleed valve. Also, for example, it is possible to consider a case where 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 has a valve opening degree different from that in the second embodiment. In this case, a large amount of bleed steam can be secured by the first bleed valve being fully opened in the first operation mode, so that it is not necessary to increase the designed heat exchange capacity of the feedwater heater, and the cost of the feedwater heater can be reduced. Also, for example, it is possible to consider a case where the first bleed valve has the same valve opening in the first and third operation modes, and the second bleed valve has the same valve opening as in the second embodiment. In this case, the first bleed valve has the same valve opening, and the second bleed valve changes between a fully closed state and a fully open state, so that it is possible to simplify the method of controlling the first bleed valve and the second bleed valve.

[0077] The present invention is not limited to the above-described embodiments, but includes various modified examples. For example, the above-described embodiments and examples have been described in detail to easily explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. [Explanation of symbols]

[0078] 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: Feedwater pump, 11: 1st stage feedwater heater, 12: 2nd stage feedwater heater, 13: 3rd stage feedwater heater, 14: 4th stage feedwater heater, 15: Feedwater line, 16: Drain line, 17: condensate drain line, 18: (first) bleed line to first stage feedwater heater, 19: (first) bleed valve to first stage feedwater heater, 20: (first) bleed line to second stage feedwater heater, 21: (first) bleed valve to second stage feedwater heater, 22: (first) bleed line to third stage feedwater heater, 23: (first) bleed valve to third stage feedwater heater, 24: fourth stage feedwater heater (1st) bleed line to heater, 25: (1st) bleed valve to 4th stage feedwater heater, 26: 2nd bleed line to 1st stage feedwater heater, 27: 2nd bleed valve to 1st stage feedwater heater, 28: 2nd bleed line to 2nd stage feedwater heater, 29: 2nd bleed valve to 2nd stage feedwater heater, 30: 2nd bleed line to 3rd stage feedwater heater, 31: 2nd bleed valve to 3rd stage feedwater heater, 32: 2nd bleed line to 4th stage feedwater heater, 33: 2nd bleed valve to 4th stage feedwater heater, 34: bleed valve control device, 35: heat balance change device, 36: normal operating state recorder, 38: operating mode recorder, 39: generator output adjustment command, 40: generator output adjustment range change command, 41: operating mode, 42: generator output, 43: input / output connection mechanism

Claims

1. 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 feed water heater that heats the condensed water condensed by the condenser with extracted steam; an extraction line that is installed between the reactor and the condenser and that supplies a portion of the steam generated in the reactor to the feed water heater as the extraction steam; A bleed valve for adjusting the flow rate of the bleed line; A control unit for controlling a valve opening degree of the air bleed valve; A nuclear power plant comprising: the nuclear power plant has three operation modes, namely, a first operation mode in which the output of the generator is kept constant, a second operation mode in which the output of the generator is adjusted to follow a load, and a third operation mode in which the output of the generator is kept constant, and one of the three operation modes is selected to perform operation; In the second operation mode, a valve opening degree of the bleed valve is smaller than a valve opening degree of the bleed valve in the first operation mode, and the valve opening degree of the bleed valve is adjusted by control of the control unit so that an output of the generator follows a load. In the third operation mode, the control unit controls the valve opening degree of at least a part of the air bleed valves to be larger than that in the first operation mode.

1. A nuclear power plant comprising:

2. 2. The nuclear power plant according to claim 1, wherein the control unit comprises: an operation mode recording device for retaining a state of the operation mode; a normal operation state recording device for recording an output of the generator and a valve opening of the bleed valve when the nuclear power plant is operated in either the first operation mode or the third operation mode; a heat balance change device having a function of increasing the valve opening of the bleed valve and changing the operation mode to the third operation mode when a command to change an adjustment range of the output of the generator is input when the nuclear power plant is operated in the first operation mode, and a function of returning the valve opening of the bleed valve to a state in the first operation mode and changing the operation mode to the first operation mode when a command to change the adjustment range of the output of the generator is input when the nuclear power plant is operated in the second operation mode; and a bleed valve control device for adjusting the valve openings of the plurality of bleed valves when a command to adjust the output of the generator is input when the nuclear power plant is operated in the second operation mode.

3. 3. The nuclear power plant according to claim 2, wherein the bleed valve control device performs control to multiply the valve openings of the plurality of bleed valves by a constant when adjusting the valve openings of the plurality of bleed valves in response to a command to adjust an output of the generator.

4. The bleed valve is composed of two types of valves, 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 the second bleed valve is set to a state in which the valve opening degree is larger in the third operation mode than in the first operation mode.

5. In the first operation mode and the third operation mode, the first bleed valve is in a fully open state, In the first operating mode, the second bleed valve is fully closed, 5. The nuclear power plant according to claim 4, wherein the control unit comprises: a heat balance change device having a function of fully opening the second bleed valve and changing to the third operation mode when a command to change an adjustment range of an 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 an adjustment range of the output of the generator is input in the third operation mode; and a bleed valve control device for adjusting valve openings of the plurality of bleed valves when a command to adjust the output of the generator is input while operating in the second operation mode.

6. 5. The nuclear power plant according to claim 4, wherein two of the extraction lines for supplying the extraction steam are connected to one of the feedwater heaters, and the second extraction valve is provided in the extraction line which supplies steam at a higher temperature of the two extraction lines, and the first extraction valve is provided in the extraction line which supplies steam at a lower temperature.

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