JP4526494B2 - Natural circulation boiling water reactor water supply controller and nuclear power plant - Google Patents

Description

  The present invention relates to a boiling water reactor, and more particularly to a feed water control device for a natural circulation boiling water reactor that circulates a coolant by natural circulation, and a nuclear power plant controlled by the feed water control device.

  In general, boiling water reactors can be roughly classified into forced circulation type and natural circulation type depending on the circulation method of the coolant (cooling water). A forced circulation boiling water reactor (hereinafter referred to as a forced circulation nuclear reactor) is equipped with a jet pump or an internal pump, and the pump is used to forcibly feed cooling water into the core. It has become.

  On the other hand, a natural circulation boiling water reactor (hereinafter referred to as a natural circulation nuclear reactor) does not have a pump for forcibly circulating cooling water like the above forced circulation nuclear reactor, Cooling water is circulated by the natural circulation force based on the density difference (water head difference) between the cooling water outside the surrounding reactor shroud and the gas-liquid mixed flow in which water and steam inside the reactor shroud are mixed. .

  In this way, in a natural circulation reactor, cooling water is circulated by natural circulation force, so that a cooling water flow rate in the core equivalent to a forced circulation reactor in which cooling water is forcibly circulated by a pump is obtained. As a result, the core power density tends to be smaller than that of the forced circulation reactor.

  For this reason, in order to increase the core power density by increasing the coolant flow rate in the core, the shroud is extended upward, and a space called chimney filled with boiling water is provided above the core, thereby creating a density difference between the inside and outside of the shroud. It is known to increase the flow rate of cooling water in the core (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2003-130982

  In the case of a natural circulation type nuclear reactor, there is no recirculation pump that forcibly circulates the core, so the core flow rate in the reactor depends on the reactor water level (hydrostatic head) in the downcomer section. When the core flow rate in the reactor increases, the reactivity is introduced into the reactor and the reactor power increases. Therefore, control of the reactor water level is important in natural circulation reactors.

  However, the conventional water supply control system in a forced circulation reactor is based on a control method that keeps the reactor water level constant, and it has been conventionally performed to control the reactor power control and the reactor water level correspondingly. I have not been told.

  The present invention has been made in view of this point, and an object of the present invention is to positively utilize control of the reactor water level so as to satisfactorily control the natural circulation reactor.

The present invention, when performing feed water control of a natural circulation boiling water reactor, the main steam flow output from the reactor, the feed water flow to the reactor, the water level measurement signal in the reactor, the reactor The deviation from the set water level is detected, and the water flow rate control to the reactor from this detected deviation and the load demand deviation signal which is the difference signal between the total steam flow demand signal and the output of the reactor power setter A signal is calculated, a signal corresponding to the reactor output control signal is added to the calculated feed water flow control signal , and the rotation speed command of the feed pump to the reactor is created by the added output It is.

  According to the present invention, the feed water flow rate of the feed water pump that feeds water to the natural circulation boiling water reactor is controlled based on the deviation between each measured value and the water level setting value of the reactor and the load request deviation signal. By doing so, it becomes possible to suppress fluctuations in the power fluctuation unique to the natural circulation boiling water reactor by controlling the feed water flow rate, and as a result, it contributes to stabilizing the control of the reactor power.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic diagram showing the overall configuration of a nuclear power plant equipped with a natural circulation boiling water light water reactor (hereinafter abbreviated as BWR) and its control system of this example.

  As shown in FIG. 1, the nuclear power plant according to the present embodiment includes a natural circulation type BWR 1 and a turbine system 2 connected thereto. The natural circulation type BWR 1 has a core 6 in which a fuel rod assembly 4 in which a plurality of fuel rods are aligned and a control rod 5 that is inserted into or extracted from a gap between the fuel rod assemblies 4 to control the reactivity of the core. The reactor pressure vessel 7 is included. Although not shown, a control rod drive mechanism that drives the control rod 5 in the reactor core 6 so that it can be inserted and removed in the vertical direction is provided below the reactor pressure vessel 7. The control rod adjusts the reactor power, that is, the core power, and is controlled by the control rod controller 36.

  A cylindrical shroud 8 is disposed in the reactor pressure vessel 7 so as to surround the core 6. An ascending flow path for the coolant to rise is formed inside the shroud 8, and a downcomer 13, which is a descending flow path for the coolant to descend, is formed in the gap between the shroud 8 and the reactor pressure vessel 7. Is formed. A chimney 9, which is a device for increasing the natural circulation flow rate, is installed in the upper part of the core, and a steam separator 11 and a steam dryer 12 are provided above the chimney 9.

  The turbine system 2 has a main steam pipe 14 connected to the reactor pressure vessel 7 and a water supply pipe 15 for supplying a coolant. The steam generated in the reactor, that is, the reactor pressure vessel 7 is supplied to the main steam pipe 14. The main steam pipe 14 is connected to a high-pressure turbine 17 via a steam control valve 16 connected to the main steam pipe 14, and further connected to a low-pressure turbine 19 via a moisture separator or a moisture separation heater 18. A generator 20 is connected to each turbine 17, 19. The steam control valve 16 is an adjustment valve that adjusts the amount of steam flowing from the main steam pipe 14 into the high-pressure turbine 17. The flow rate of the steam in the main steam pipe 14 is detected by the main steam flow detector 33, and a reactor steam flow signal S4, which is a detection signal thereof, is supplied to the water supply control device 40 described later.

  A condenser 21 that condenses steam discharged from the low-pressure turbine 19 is installed at the outlet of the low-pressure turbine 19, and a low-pressure feed water heater 22, a feed water pump 23, and a high-pressure feed water heater are disposed downstream of the condenser 21. 24 is installed. A feed water pipe 15 is connected to the outlet of the high pressure feed water heater 24 and supplied to the reactor pressure vessel 7. The flow rate of the cooling water (coolant) in the feed water pipe 15 is detected by the feed water flow rate detector 34, and a reactor feed water flow rate signal S3, which is a detection signal thereof, is supplied to the feed water control device 40 described later.

  On the downstream side of the condenser 21, that is, in the middle of the feed pipe 15 from the condenser 21 to the reactor pressure vessel 7, a low-pressure feed water heater 22 that sequentially heats the feed water supplied from the condenser 21, A feed water pump 23 that pressurizes the feed water and supplies it to the reactor pressure vessel 7 and a high-pressure feed water heater 24 that heats the feed water are disposed. In the feed water pump 23, the rotation speed of the feed water pump corresponding to the feed water amount is controlled by a pump drive device 38 to be described later. The pump drive device 38 is supplied with a pump rotation speed command S7 from the water supply control device 40 to control the rotation speed.

  In the natural circulation type BWR 1, the gas-liquid two-phase coolant heated in the core 6 and partially boiled to become steam flows through the chimney 9 in an upward flow, and the steam-water separator 11 and the steam dryer 12 Separated. Of the separated vapor, the vapor in the vapor phase is sent to the main vapor pipe 14 and the high temperature water in the liquid phase is recirculated water. The recirculated water and the coolant in the upward flow flowing through the core 6 and the chimney 9 are separated by the shroud 8 and do not mix with each other. The recirculated water flows as a downward flow, mixed with water supplied from the water supply nozzle 25 of the water supply pipe 15 on the way, and supplied from the lower part of the core 6 after passing through the lower plenum 28.

  In the reactor pressure vessel 7, the volume density of the gas-liquid two-phase rising fluid flowing in the chimney 9 is smaller than the liquid single phase, and the volume density of the descending fluid (coolant) outside the chimney 9 is high. Due to the difference, the coolant is naturally circulated.

  On the other hand, the steam sent from the reactor pressure vessel 7 to the main steam pipe 14 is guided to the high-pressure turbine 17 through the steam control valve 16 and further to the low-pressure turbine 19 via the moisture separator or the moisture separation heater 18. The generator 20 connected to the turbines 17 and 19 is rotated to generate power.

  The steam that has rotated the low-pressure turbine 19 is introduced into the condenser 21 and condensed. The cooling water (condensate) condensed in the condenser 21 is returned to the reactor pressure vessel 7 from the feed water pipe 15 by the feed water pump 23. The cooling water (condensate) from the condenser 21 is heated to an appropriate temperature by the low-pressure feed water heater 22 and the high-pressure feed water heater 23 in the middle of the feed water pipe 15.

  Two reactor water level detectors 31 and 32 are attached in the reactor pressure vessel 7 to detect the water level in the reactor. Each of the water level detectors 31 and 32 is set to a range in which the detection range for detecting the water level is different. For the water supply control of this example, either one of the detections is performed according to the target water level control range. Output is used. The water level detector 31 outputs the first reactor water level detection signal S2 and supplies it to the water supply control device 40. The water level detector 32 outputs the second reactor water level detection signal S8 and supplies it to the water supply control device 40.

  In addition, a pressure sensor 35 that detects the pressure in the reactor pressure vessel 7 is provided, and a reactor pressure signal S 1 output from the pressure sensor 35 is supplied to the output control device 37. The output control device 37 outputs an output request signal S5 and a load request deviation signal S9 in response to the supplied reactor pressure signal S1, supplies the output request signal S5 to the control rod control device 36, and outputs it to the water supply control device 40. A request signal S5 and a load request deviation signal S9 are supplied.

  The control rod controller 36 supplies a control rod drive command S6 to the drive system of the control rod 5 in response to the output request signal S5. In the water supply control device 40, based on the water level detection signal S2 or S8, the reactor water supply flow signal S3, the reactor steam flow signal S4, the output request signal S5, and the load request deviation signal S9, the pump rotation speed command S7 is generated and supplied to the pump drive unit 38.

  FIG. 2 is a diagram illustrating a configuration example of the water supply control device 40 illustrated in FIG. 1. The water supply control device 40 includes a reactor water level setting device 41, and the reactor water level setting device 41 outputs a water level setting signal in the reactor and supplies it to the adder 42. Further, the output request signal S5 from the output control device 37 is supplied to the signal converter 43 to be an output request signal having the required characteristics, and the converted output request signal is supplied to the adder 42 so that the water level is Add with the setting signal. The addition output of the adder 43 is supplied to the subtracter 44.

  The first reactor water level detection signal S2 and the second reactor water level detection signal S8 supplied to the water supply control device 40 are supplied to the changeover switch 45 to selectively subtract one of the water level detection signals a1. To the container 44. Switching of the selector switch 45 is controlled by a water level signal switching signal a4. The reactor feedwater flow rate signal S3 and the reactor steam flow rate signal S4 are supplied to the subtractor 46 to detect the difference between the steam flow rate and the feedwater flow rate, and the difference detection signal is supplied to the coefficient multiplier 47 to obtain the coefficient. A detection signal of a difference obtained by multiplying the coefficient by the multiplied value is supplied to the subtractor 44.

  In the subtractor 44, the water level detection signal a1 output from the changeover switch 45 and the output of the coefficient multiplier 47 are subtracted from the output of the adder 42 to obtain a subtracted output. The subtraction output of the subtracter 44 is supplied to the subtracter 50. Further, the load request deviation signal S9 is supplied to the signal converter 48, the characteristic of the load request deviation signal S9 is converted, the converted load request deviation signal is supplied to the integrator 49 and integrated, and the integral signal is subtracted. Supply to the vessel 50.

  The subtracter 50 subtracts the output of the subtractor 44 from the integral signal of the load request deviation signal output from the integrator 49 and supplies the reactor water level deviation signal a2 as the subtraction signal to the main water level controller 51. The main water level controller 51 outputs a main water level controller output signal a3 based on the supplied reactor water level deviation signal a2, and the main water level controller output signal a3 is an output signal of the water supply control device 40. The pump rotation speed command S7 is supplied to the pump drive device 38 (FIG. 1).

  FIG. 3 is a diagram showing a configuration example of the output control device 37 shown in FIG. The output control device 37 includes a reactor pressure setting device 61, and a subtracter 62 obtains a difference between the reactor pressure signal S 1 from the pressure sensor 35 and the set output signal of the reactor pressure setting device 61. The obtained difference signal is supplied to the coefficient multiplier 63 to obtain a difference signal having a predetermined characteristic to obtain a total steam flow rate request signal b1.

  The obtained total steam flow rate request signal b1 is supplied to the subtractor 64, takes a difference from the output of the reactor power setting unit 65, and the obtained difference signal is set as a load request deviation signal S9. Further, the output of the reactor power setting unit 65 is output as it is as the output request signal S5.

  Note that the reactor water supply flow rate control by the water supply control device 40 shown in FIG. 2 is basically performed in a state where the output of the reactor is stable in the rated state in the case of this example.

Next, a state where water supply control to the nuclear reactor is performed by the water supply control device 40 in the configuration of this example will be described.
First, FIG. 4 shows an example in which the water level is set and controlled by changing the output request signal S5. In this example, there is an example when there is an instruction to change the output of the reactor, and in particular, FIG. 4 is an example when there is an instruction to increase the output. Since there is an instruction to increase the output, the output request signal S5 supplied to the signal converter 43 in FIG. 2 becomes high, and as shown in FIG. 4A, the water supply control is performed at the timing T0 when the instruction is given. The reactor water level setting value (output of the adder 42) in the device 40 is increased by a value Δl corresponding to the output increase amount. If it becomes high like this, as shown in FIG.4 (b), a reactor water level will rise comparatively rapidly. As shown in FIG. 4C, the feed water flow rate also gradually increases as the reactor power gradually increases. The main steam flow rate, which is the reactor power, also increases as shown in FIG. 4 (d), and it can be seen that the output gradually increases.

  FIG. 5 is a flowchart showing the control state shown in FIG. Referring to the flowchart of FIG. 5, first, it is determined whether or not the reactor power is in a rated operation state in which the reactor power is more than a certain level and the power within a certain range is maintained (step S101). Here, the rated operation state is determined, and the control of this example becomes possible. In this example, it is determined whether or not there is an output increase instruction (step S102). When there is an output increase instruction, the water supply control device 40 performs a process for changing the reactor set water level (step S103), the amount of water supply increases accordingly (step S104), and finally, as shown in FIG. The reactor power gradually increases. The examples in FIGS. 4 and 5 are examples in which the output is increased, but the control to decrease the output may be performed by the reverse process.

  Next, an example in the case where the process for suppressing the fluctuation is performed by controlling the amount of supplied water when there is a fluctuation in the reactor output will be described with reference to FIG. In this example, as shown in FIG. 6 (d), it is assumed that the reactor output temporarily decreases due to some factor in the rated operation state. In such a case, as shown in FIG. 6 (a), the reactor water level set value gradually increases as the reactor power decreases, and as shown in FIG. 6 (b), the reactor water level also increases. To rise. The feed water flow rate temporarily decreases as shown in FIG. As shown in FIG. 6E, the load request deviation signal S9 output from the output control device 37 increases as the reactor output decreases.

  When such control is performed and the water level shown in FIG. 6 (a) rises, a decrease in the reactor power is suppressed, and the original power is gradually restored. When the output is restored, the feed water flow rate returns to the original value, and the load request deviation signal S9 gradually returns to the original value.

  FIG. 7 is a flowchart showing the control state shown in FIG. Referring to the flowchart of FIG. 7, first, it is determined whether or not the reactor power is in a rated operation state in which the reactor power is higher than a certain level and the power within a certain range is maintained (step S201). Here, after determining the rated operation state, it is determined whether or not the reactor power has decreased (step S202). If it is determined that the reactor power has decreased, the set water level of the reactor is set to a value corresponding to the decrease. Change (increase) (step S203). Then, the feed water flow rate shown in FIG. 6C corresponding to the decrease in output is adjusted (step S204), and as a result, the reactor output is adjusted to return to the original state (step S205). 6 and 7 are control examples when the output temporarily decreases, but the control when the output temporarily increases may be performed by the reverse process.

  Next, an example of switching processing of the two reactor water level detectors 31 and 32 attached to the reactor will be described with reference to FIG. Of the two reactor water level detectors 31 and 32, the reactor water level detector 31 is used in a normal state, and the reactor water level detector 32 is used in an ATWS (Anticipated Trangent Without Scram). . As shown in FIG. 8A, the set water level range H is set in the normal state, and the set water level range L is set during ATWS. When the set water level range H, the water level detector 31 with a high detection range is used, and when the set water level range L, the water level detector 32 with a low detection range is used. Switching between the water level detectors 31 and 32 is performed by a changeover switch 45 (FIG. 2).

  As shown in FIG. 8 (a), when the ATWS state is reached at timing T1 and the set water level range L is reached, the reactor water level is relatively lowered as shown in FIG. 8 (b), and the amount of water supply is also shown. As shown in FIG. 8 (c), the main steam flow rate (FIG. 8 (d)), which is the reactor power, is finally reduced, and the reactor can be maintained in a safe state.

  FIG. 9 is a flowchart showing the control state shown in FIG. The flowchart of FIG. 9 will be described. First, it is determined whether or not the state is the ATWS state (step S301). If it is determined that the ATWS state has been reached, the set water level is lowered (step S302), and the water level detector is switched from the normal water level detector 31 to the water level detector 32 (step S303). As a result of the control for lowering the set water level relatively in this manner, all of the water level in the reactor, the amount of feed water, and the main steam flow rate are reduced as shown in FIG. Decreases (step S305).

  As described above, according to the configuration of this example, the reactor output can be controlled based on the water supply control, and the control of the increase and decrease of the output in the stable operation state, the stable operation state It is possible to control the fluctuation of output in Further, output reduction control during ATWS can be performed.

  2, the output request signal S5 is added to the output of the reactor water level setter 41, but the output request signal S5 is added to the output of the main water level controller 51. You may make it add. That is, for example, as shown in FIG. 10, the output of the reactor water level setting device 41 as the water supply control device 40 ′ is supplied as it is to the subtractor 44 to take a difference from other signals. The output request signal S5 input to the water supply control device 40 ′ is converted into signal characteristics by the signal converter 52 and then supplied to the adder 53. The output request signal S3 of the main water level controller 51 and the signal converter 52 are supplied. And the added signal is used as a pump rotation speed command S7. The other portions are configured in the same manner as the water supply control device 40 shown in FIG.

  FIG. 11 shows a control example in the case of the control configuration shown in FIG. In this example, as shown in FIG. 11A, the reactor water level set value is increased at timing T2. By increasing the reactor water level set value at the timing T2 in this way, the reactor water level rises as shown in FIG. 11 (b), and the feed water flow rate also increases as shown in FIG. 11 (c). Thus, as shown in FIG. 11 (d), the main steam flow, which is the reactor power, increases. By reducing the reactor water level setting value, it is possible to control the reactor output to decrease. In the cases of FIGS. 10 and 11 as well, the same control as in the above-described embodiment is possible.

  2, 3, and 10, which have been described so far, have been configured with a hardware configuration for adding input signals, for example, a similar signal is input to a data processing arithmetic device such as a computer device. Then, similar control data may be output by software processing such as arithmetic processing or table reference in the apparatus.

It is a block diagram which shows the example of the nuclear power plant and its control system by one embodiment of this invention. It is a block diagram which shows the example of the water supply control apparatus by one embodiment of this invention. It is a block diagram which shows the example of the output control apparatus by one embodiment of this invention. It is a timing diagram which shows the example of water level control by one embodiment of this invention. It is a flowchart which shows the control processing state of the example of FIG. It is a timing diagram which shows the example of water level control by one embodiment of this invention. It is a flowchart which shows the control processing state of the example of FIG. It is a timing diagram which shows the example of water level control by one embodiment of this invention It is a flowchart which shows the control processing state of the example of FIG. It is a block diagram which shows the example of the water supply control apparatus by other embodiment of this invention. It is a timing diagram which shows the example of water level control by other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Natural circulation type BWR, 2 ... Turbine system, 4 ... Fuel rod assembly, 5 ... Control rod, 6 ... Reactor core, 7 ... Reactor pressure vessel, 8 ... Shroud, 9 ... Chimney, 11 ... Steam-water separator, DESCRIPTION OF SYMBOLS 12 ... Steam dryer, 13 ... Downcomb, 14 ... Main steam pipe, 15 ... Feed water pipe, 16 ... Steam control valve, 17 ... High pressure turbine, 18 ... Moisture separation heater, 19 ... Low pressure turbine, 20 ... Generator, 21 ... Condenser, 22 ... Low pressure feed water heater, 23 ... Feed water pump, 24 ... High pressure feed water heater, 31, 32 ... Reactor water level detector, 33 ... Main steam flow rate detector, 34 ... Feed water flow rate detector, 35 ... Pressure sensor, 36 ... Control rod control device, 37 ... Output control device, 38 ... Pump drive device, 40, 40 '... Feed water control device, 41 ... Reactor water level setting device, 42 ... Adder, 43 ... Signal conversion 44 ... subtractor 45 ... changeover switch 46 ... subtraction , 47 ... coefficient multiplier, 48 ... signal converter, 49 ... integrator, 50 ... subtractor, 51 ... main water level controller, 61 ... reactor pressure setter, 62 ... subtractor, 63 ... coefficient multiplier, 64 ... subtractor, 65 ... reactor power setter, S1 ... reactor pressure signal, S2 ... first water level detection signal, S3 ... reactor feedwater flow signal, S4 ... reactor steam flow signal, S5 ... output request signal, S6: Control rod drive command, S7: Pump rotation speed command, S8: Second water level detection signal, S9: Load request deviation signal

Claims (8)

Cylindrical chimney is placed inside the reactor pressure vessel,
Forming a coolant ascending channel inside the chimney and a coolant descending channel outside the chimney;
In the water supply control device for a natural circulation boiling water reactor that circulates the coolant by the density difference between the coolant in the ascending channel and the coolant in the descending channel,
Detect the deviation between the main steam flow output from the reactor, the feed water flow to the reactor, the water level measurement signal in the reactor, and the water level setting value of the reactor, and the detected deviation and the total steam flow A water level control means for calculating a feed water flow rate control signal to the reactor from a load request deviation signal which is a difference signal between the request signal and the output of the reactor power setting device ;
Adding means for adding a signal corresponding to the output control signal of the reactor to the feed water flow rate control signal output by the water level control means;
A feed water control device for a natural circulation boiling water reactor, wherein a rotation speed command of a feed water pump to the reactor is created by an output of the adding means . The water supply control device for a natural circulation boiling water reactor according to claim 1,
An addition signal obtained by adding a signal corresponding to the reactor power control signal to the reactor water level setting value,
The water level control means detects a deviation between the addition signal, the main steam flow output from the reactor, the feed water flow rate to the reactor, the water level measurement signal in the reactor, and the water level setting value of the reactor. Then, a feed water control apparatus for a natural circulation boiling water reactor, wherein a feed water flow rate control signal to the reactor is calculated from the detected deviation and the load request deviation signal. The water supply control device for a natural circulation boiling water reactor according to claim 1,
The water level measurement signal in the nuclear reactor is a water level measurement signal input from a plurality of water level measurement means of different detection ranges, and the water level measurement of any one of the plurality of water level measurement means according to a target water level control range A feed water control device for a natural circulation boiling water reactor characterized by using a signal. The water supply control device for a natural circulation boiling water reactor according to claim 1,
A water supply control device for a natural circulation boiling water reactor, characterized in that the water supply control using the water supply flow rate control signal by the water level control means is performed at the time of operation in which the reactor power is almost rated and stable. A cylindrical chimney is disposed inside the reactor pressure vessel, a coolant ascending channel is formed inside the chimney, and a coolant descending channel is formed outside the chimney, and cooling in the ascending channel is performed. A natural circulation boiling water reactor that circulates the coolant according to the density difference between the coolant and the coolant in the downflow path;
A turbine driven by main steam output from the reactor;
Condensing means for condensing the main steam;
A feed water pump for sending the coolant condensed by the condensing means to the reactor;
Main steam flow rate measuring means for measuring the main steam flow rate;
Feed water flow rate measuring means for measuring the feed water flow rate to the reactor;
Water level measuring means in the reactor;
A main steam flow rate measured by the main steam flow rate measurement unit, a feed water flow rate to the reactor measured by the feed water flow rate measurement unit, a water level measurement signal in the reactor detected by the water level measurement unit, and an atom The deviation from the set value of the reactor water level is detected, and the feed water flow rate to the reactor from this detected deviation and the load requirement deviation signal, which is the difference between the total steam flow demand signal and the output of the reactor power setter Water level control means for calculating a control signal ;
Adding means for adding a signal corresponding to the output control signal of the reactor to the feed water flow rate control signal output by the water level control means;
A nuclear power plant characterized in that a rotation speed command of the feed water pump is created by an output of the adding means . In the nuclear power plant according to claim 5 ,
Comprising the reactor power control means,
The water level control means obtains an addition signal obtained by adding a signal corresponding to the reactor power control signal output from the power control means to the water level set value of the reactor, and is measured by the main steam flow rate measuring means. Detects deviations between the main steam flow rate, the feed water flow rate to the reactor measured by the feed water flow rate measuring means, the water level measurement signal in the reactor detected by the water level measuring means, and the water level setting value of the reactor And calculating a feed water flow rate control signal to the reactor from the detected deviation and the load request deviation signal. In the nuclear power plant according to claim 5 ,
As the water level measurement means in the nuclear reactor, the first water level measurement means and the second water level measurement means of different detection ranges, respectively,
The nuclear power plant, wherein the water level control means uses a water level measurement signal of any one of the plurality of water level measurement means according to a target water level control range. In the nuclear power plant according to claim 5 ,
A nuclear power plant characterized in that the water supply control using the water supply flow rate control signal by the water level control means is performed during an operation in which the reactor power is almost stable at a rated state.

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