Nuclear power plant and its operation method

Abstract

To provide a nuclear power plant and a method for operating the same that can efficiently use heat output and prevent a change in heat output from a nuclear reactor, while adjusting output to a power system according to a load requirement.SOLUTION: When there is no excess in heat output from a nuclear reactor over a load requirement, a nuclear power plant performs first operation of introducing a total amount of heat output from the nuclear reactor to a steam turbine to generate power and stopping a hydrogen production system, when there is the excess in heat output from the nuclear reactor and the excess in heat output is equal to or less than an upper limit of the hydrogen production system, performs second operation of maintaining the heat output from the nuclear reactor, and introducing part of the heat output to the steam turbine to generate power and supplying the rest of the heat output to the hydrogen production system to produce hydrogen, and when the excess in heat output from the nuclear reactor exceeds the upper limit of the hydrogen production system, performs third operation of reducing the heat output from the nuclear reactor so that the excess in heat output becomes equal to or less than the upper limit of the hydrogen production system, and introducing part of the heat output to the steam turbine to generate power and supplying the rest of the heat output to the hydrogen production system to produce hydrogen.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a nuclear power plant and an operating method thereof, and more particularly to a nuclear power plant capable of simultaneously producing electric power and hydrogen using steam generated in a nuclear reactor, and an operating method thereof. [Background technology]

[0002] The application of solid oxide electrolysis cells (SOEC) is being considered as a method of producing hydrogen in nuclear power plants. SOECs are stacked cells, each of which has an electrolyte that allows ions to pass through it, sandwiched between a hydrogen electrode and an oxygen electrode. By supplying water vapor to the hydrogen electrode of each cell and applying a voltage to both electrodes, hydrogen is extracted from the hydrogen electrode and oxygen is extracted from the oxygen electrode. The electrolysis of water vapor using SOECs has the advantage of being able to keep energy consumption low. Therefore, it is expected that the production of hydrogen by operating SOECs using thermal energy from nuclear power derived from non-fossil fuels in nuclear power plants will both reduce greenhouse gas emissions, which are considered to be the main cause of global warming, and provide fuel for a hydrogen society.

[0003] A method for producing hydrogen in a nuclear power plant is described in, for example, Patent Document 1. In a nuclear power plant that performs the hydrogen production method described in Patent Document 1, a part of steam (coolant) from a nuclear reactor (heat source) that rotates a turbine is introduced into a steam generator to generate steam using the thermal energy of the steam (coolant), the steam is heated in a heat exchanger (first heating means) and then further heated by electric energy in an electric heater (second heating means), and the heated steam is introduced into a steam electrolysis device to generate hydrogen. That is, the nuclear power plant is equipped with a hydrogen production system including a steam generator that generates steam using the thermal energy of the steam from the nuclear reactor, a heat exchanger and an electric heater that heat the steam generated in the steam generator, and a steam electrolysis device that electrolyzes the steam heated by the heat exchanger and the electric heater to generate hydrogen. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-307290 A Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to the nuclear power plants mentioned above, various power plants such as thermal power plants, hydroelectric power plants, solar power plants, and wind power plants are connected to the domestic power grid (power system). The power system is operated so that the power supply from the above-mentioned power plants always matches the daily power demand. Since the amount of power generated by renewable energy power plants such as solar power plants and wind power plants varies from moment to moment depending on the time of day and the weather and climate, thermal power plants mainly balance the demand and supply in the power system. However, since thermal power plants are the main source of greenhouse gas emissions, it is necessary to assume that the operation of thermal power plants will be stopped. In this case, nuclear power plants are candidates for a means of balancing the demand and supply in the power system. In other words, nuclear power plants are required to operate in such a way that they adjust the power output to the power system according to the load demand given from outside (for example, the central load dispatching center).

[0006] In the operation of a nuclear power plant, there is a noticeable delay in the actual power output relative to the change in the target power output. This is due to the delay between the start of operation of the means for adjusting the nuclear reactivity in the reactor (e.g., control rods) and the actual increase or decrease in the nuclear reaction, and the delay between the transfer of heat generated in the nuclear fuel by the increased or decreased nuclear reaction to the cooling water. For this reason, it is difficult for a nuclear power plant to rapidly change the thermal output of the reactor in response to load demands.

[0007] Also, assume that a nuclear power plant performing the hydrogen production method described in Patent Document 1 is operated as a means for balancing supply and demand in a power system. In this case, when the load demand on the nuclear power plant decreases, a part of the thermal output of the nuclear reactor may become surplus. The rated thermal output of a nuclear reactor is generally much higher than the upper limit that the hydrogen production system can accept. Therefore, in the nuclear power plant described in Patent Document 1, the hydrogen production system may not be able to utilize the surplus thermal output of the nuclear reactor. In this case, the thermal output of the nuclear reactor cannot be effectively utilized, leading to a decrease in the efficiency of the nuclear power plant.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a nuclear power plant and an operating method thereof that are capable of effectively utilizing the thermal output of a nuclear reactor and suppressing changes in the thermal output of the nuclear reactor while adjusting the power generation output to the power grid in response to load requirements. [Means for solving the problem]

[0009] The present application includes a plurality of means for solving the above-mentioned problems. For example, the present application includes a nuclear power generation system connected to an electric power system and generating electricity by driving a steam turbine with steam generated in a nuclear reactor, a hydrogen production system configured to be able to supply the steam generated in the nuclear reactor and generating steam from raw water using thermal energy of the steam generated in the nuclear reactor and producing hydrogen by electrolyzing the generated steam, and a plant control device that receives a load request from the outside indicating a power output required for the nuclear power generation system to the electric power system and controls the nuclear power generation system and the hydrogen production system based on the load request, and when there is no surplus in the thermal output of the nuclear reactor relative to the load request, the plant control device performs a first operation in which the entire amount of the thermal output of the nuclear reactor is introduced into the steam turbine to generate electricity while the hydrogen production system is stopped, and the hydrogen production system is stopped in response to the load request. When there is a surplus in output and the surplus thermal output of the reactor is equal to or less than the upper limit that can be accepted by the hydrogen production system, a second operation is performed in which the thermal output of the reactor is maintained, and part of the thermal output of the reactor is introduced into the steam turbine to send electric power according to the load request to the electric power system, and the remainder of the thermal output of the reactor is supplied to the hydrogen production system to produce hydrogen; when there is a surplus in the thermal output of the reactor with respect to the load request and the surplus thermal output of the reactor exceeds the upper limit of the hydrogen production system, a third operation is performed in which the thermal output of the reactor is reduced so that the surplus thermal output of the reactor is equal to or less than the upper limit of the hydrogen production system, and part of the thermal output of the reactor is introduced into the steam turbine to send electric power according to the load request to the electric power system, and the remainder of the thermal output of the reactor is supplied to the hydrogen production system to produce hydrogen. the hydrogen production system includes a hydrogen production device that generates steam from raw water by utilizing thermal energy of steam generated in the nuclear reactor and electrolyzes the generated steam to produce hydrogen, and a heat storage facility that can store the thermal energy of the steam supplied from the nuclear reactor and supply the stored thermal energy to the hydrogen production device, the upper limit of the hydrogen production system being the sum of the upper limit that can be accepted by the hydrogen production device and the upper limit that can be accepted by the heat storage facility, and when performing the second operation, if the surplus of the thermal output of the nuclear reactor is equal to or less than the upper limit of the hydrogen production device, the plant control device controls the hydrogen production device to utilize the entire amount of the thermal energy of the steam supplied from the nuclear reactor to the hydrogen production system, and if the surplus of the thermal output of the nuclear reactor exceeds the upper limit of the hydrogen production device, controls the hydrogen production device to utilize a portion of the thermal energy of the steam supplied from the nuclear reactor to the hydrogen production system and store the remaining thermal energy of the steam in the heat storage facility. It is characterized by: Effect of the Invention

[0010] According to the present invention, the thermal output of the reactor is maintained or changed and the allocation of the reactor's thermal output to the steam turbine and the hydrogen production system is changed depending on three conditions: when there is no surplus thermal output of the reactor in relation to the load demand; when there is surplus thermal output of the reactor and the surplus thermal output of the reactor is equal to or less than the upper limit of the hydrogen production system; and when there is surplus thermal output of the reactor and the surplus thermal output of the reactor exceeds the upper limit of the hydrogen production system.This makes it possible to effectively utilize the thermal output of the reactor and suppress changes in the thermal output of the reactor while adjusting the power generation output of the nuclear power generation system for the power grid in accordance with the load demand. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a schematic configuration of a nuclear power plant according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a system diagram showing a detailed configuration of the nuclear power plant according to the first embodiment shown in FIG. [Diagram 3] 2 is a block diagram showing a configuration of a hydrogen production device in the nuclear power plant according to the first embodiment shown in FIG. 1. FIG. [Figure 4] 3 is a block diagram showing a functional configuration of a plant control device in the nuclear plant according to the first embodiment shown in FIG. 2. [Diagram 5] 5 is a flowchart showing an example of a calculation procedure of a plant overall load calculation unit in the plant control device for the nuclear plant according to the first embodiment shown in FIG. 4. [Figure 6] FIG. 2 is an explanatory diagram showing distribution of thermal output (thermal load) of a nuclear reactor in the nuclear power plant operation method according to the first embodiment. [Figure 7] FIG. 2 is a block diagram showing a schematic configuration of a nuclear power plant according to a modified example of the first embodiment of the present invention. [Figure 8] FIG. 5 is a block diagram showing a schematic configuration of a nuclear power plant according to a second embodiment of the present invention. [Figure 9]FIG. 9 is a system diagram showing a detailed configuration of a nuclear power plant according to a second embodiment shown in FIG. 8. [Figure 10] FIG. 9 is a block diagram showing a configuration of a hydrogen production device in a nuclear power plant according to a second embodiment shown in FIG. 8. [Figure 11] 10 is a block diagram showing a functional configuration of a plant control device in a nuclear plant according to a second embodiment shown in FIG. 9. [Figure 12] 12 is a flowchart showing an example of a calculation procedure of a plant overall load calculation unit in the plant control device for the nuclear plant according to the second embodiment shown in FIG. [Figure 13] FIG. 11 is an explanatory diagram showing distribution of thermal output (thermal load) of a nuclear reactor in a method for operating a nuclear power plant according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of a nuclear power plant and an operating method thereof according to the present invention will be described with reference to the drawings. The embodiment described below is an example of application to a nuclear power plant equipped with a boiling water reactor (BWR). Each drawing is a schematic illustration to an extent that the present invention can be fully understood, and the present invention is not limited to the illustrated examples.

[0013] [First embodiment] First, a schematic configuration of a nuclear power plant according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a block diagram showing a schematic configuration of the nuclear power plant according to the first embodiment.

[0014] 1, a nuclear power plant 1 according to this embodiment is a power and hydrogen co-production plant that generates power and produces hydrogen by using nuclear power. The nuclear power plant 1 includes a nuclear power generation system 2 that generates power using steam generated by thermal energy of nuclear power, and a hydrogen production system 3 that produces hydrogen from raw water using the power supplied from the nuclear power generation system 2 and the thermal energy of the steam.

[0015] The nuclear power generation system 2 mainly comprises a nuclear reactor 11 that generates steam using thermal energy produced by energy of nuclear fission of nuclear fuel, a steam turbine 12 that is rotated by the introduction of steam generated in the nuclear reactor 11, and a generator 13 that generates electricity and is mechanically linked to the steam turbine 12. The generator 13 is electrically connected to a power system 100 and sends the generated electricity to the power system 100. The nuclear power generation system 2 is configured to be capable of supplying a portion of the steam generated in the nuclear reactor 11 (the surplus steam excluding the steam that flows into the steam turbine 12) to the hydrogen production system 3, and to be capable of supplying the electricity generated by the generator 13 to the hydrogen production system 3.

[0016] The hydrogen production system 3 mainly comprises a hydrogen production device 31 that generates steam by heating raw water supplied from the outside and produces hydrogen by electrolyzing the generated steam, and a hydrogen storage device 32 that stores the hydrogen produced by the hydrogen production device 31. Furthermore, the hydrogen production system 3 comprises a heat storage facility 33 that stores the thermal energy of the steam supplied from the nuclear power generation system 2 (reactor 11) and supplies the stored thermal energy to the hydrogen production device 31. That is, the hydrogen production system 3 of this embodiment is configured to supply the thermal energy of the steam supplied from the reactor 11 to the hydrogen production device 31 via the heat storage facility 33.

[0017] The hydrogen production device 31 electrolyzes water vapor (superheated steam) having a higher temperature (for example, 800 to 1000°C) than the temperature of the steam generated in the nuclear reactor 11. The hydrogen production device 31 according to this embodiment is configured to generate low-temperature water vapor (saturated steam) by heating raw water using thermal energy supplied from the heat storage equipment 33, and to generate high-temperature water vapor (superheated steam) by heating the generated low-temperature water vapor using electric power supplied from the nuclear power generation system 2. The specific configuration of the hydrogen production device 31 will be described later.

[0018] The heat storage equipment 33 receives thermal energy of the steam supplied from the reactor 11 and has a heat medium that transfers the received thermal energy to the hydrogen production device 31. The heat storage equipment 33 has, for example, a heat storage material inside that can store the thermal energy of the steam from the reactor 11, and is configured to transfer the thermal energy to the heat medium via the heat storage material. In other words, the heat storage equipment 33 transfers the thermal energy of the steam supplied from the reactor 11 to the hydrogen production device 31 via the heat medium.

[0019] Next, a detailed configuration of the nuclear power plant according to the first embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 2 is a system diagram showing a detailed configuration of the nuclear power plant according to the first embodiment shown in Fig. 1. Fig. 3 is a block diagram showing a configuration of a hydrogen production device in the nuclear power plant according to the first embodiment shown in Fig. 1.

[0020] The reactor 11 in the nuclear power generation system 2 is a pressure vessel in which fuel assemblies (fuel rods) are loaded and which is filled with cooling water up to a certain level. The reactor 11 is equipped with a control rod 11a for controlling the nuclear fission reaction of the fuel assemblies and a recirculation system 11b for controlling the amount of heat exchange between the fuel assemblies and the cooling water, as means for controlling the output of the reactor 11. The control rod 11a is moved in and out of the core by a drive mechanism. The drive of the control rod 11a (the drive mechanism of the control rod 11a) is controlled by a control rod position command Cr, described later, of the plant control device 5. The recirculation system 11b extracts a portion of the cooling water from the bottom of the reactor 11 and returns it to the center of the reactor 11. In the recirculation system 11b, the flow rate of the circulating cooling water is adjusted by a recirculation pump 11c. The drive (flow rate) of the recirculation pump 11c is controlled by a recirculation flow rate command Cp, described later, of the plant control device 5.

[0021] The steam turbine 12 in the nuclear power generation system 2 is composed of, for example, a high-pressure turbine 12a to which steam generated in the nuclear reactor 11 is introduced, and a low-pressure turbine 12b located downstream of the high-pressure turbine 12a. The high-pressure turbine 12a and the low-pressure turbine 12b are mechanically connected by a turbine shaft 12c, and the generator 13 is rotated and driven via the turbine shaft 12c. A heater 14 is disposed in a flow path connecting the high-pressure turbine 12a and the low-pressure turbine 12b. The heater 14 reheats the steam discharged from the high-pressure turbine 12a by using steam supplied from the nuclear reactor 11, and supplies the reheated steam to the low-pressure turbine 12b.

[0022] In addition to the above-mentioned reactor 11, steam turbine 12, and generator 13, the nuclear power generation system 2 is provided with a condensate water supply system that condenses steam discharged from the steam turbine 12 (low-pressure turbine 12b) and supplies the water generated by condensing the steam to the reactor 11 again. The condensate water supply system includes a condenser 15 that condenses the steam discharged from the steam turbine 12 and stores the condensate, a low-pressure feedwater heater 16 that heats the condensate supplied from the condenser 15, and a high-pressure feedwater heater 17 that heats the condensate supplied from the low-pressure feedwater heater 16. The condensate water supply system also includes a condensate pump 18 that sends the condensate stored in the condenser 15 to the low-pressure feedwater heater 16, and a feedwater pump 19 that pressurizes the condensate from the low-pressure feedwater heater 16, supplies it to the high-pressure feedwater heater 17, and sends it to the reactor 11 as feedwater. The low pressure feed water heater 16 and the high pressure feed water heater 17 are supplied with steam extracted from the low pressure turbine 12b and the high pressure turbine 12a, respectively, as a heat source.

[0023] As shown in Figs. 1 and 2, the nuclear power generation system 2 is configured so that steam generated in the nuclear reactor 11 is supplied to a high-pressure turbine 12a (steam turbine 12) via a main steam pipe 21. A bypass line 22 branches off from the main steam pipe 21 and is connected to a heat storage facility 33 of the hydrogen production system 3. That is, the nuclear power generation system 2 is configured so that a part of the steam generated in the nuclear reactor 11 (surplus steam) is supplied to the heat storage facility 33 via the bypass line 22. The nuclear power generation system 2 is also configured so that the steam supplied to the heat storage facility 33 is recovered in the system 2 by guiding it to the condenser 15 via a return line 23. That is, the nuclear power generation system 2 is configured so that the steam containing a radioactive source generated in the nuclear reactor 11 is supplied to the hydrogen production system 3, but circulated within a closed system of the system 2.

[0024] A steam control valve 25 is provided in the main steam pipe 21, and a bypass valve 26 is provided in the bypass line 22. The steam control valve 25 adjusts the steam flow rate supplied from the reactor 11 to the high-pressure turbine 12a (steam turbine 12), and its opening is controlled by a later-described opening command Cv1 of the plant control device 5. The bypass valve 26 adjusts the steam flow rate supplied from the reactor 11 to the hydrogen production system 3 (thermal storage equipment 33), and its opening is controlled by a later-described opening command Cv2 of the plant control device 5.

[0025] The nuclear power generation system 2 is provided with a pressure sensor 28 for detecting the pressure inside the reactor 11, and a power meter 29 for detecting the power output of the generator 13. The pressure sensor 28 and the power meter 29 output to the plant control device 5 a detection signal Ps corresponding to the detected pressure value and a detection signal Es corresponding to the detected power value, respectively.

[0026] The hydrogen production device 31 of the hydrogen production system 3 adjusts the amount of hydrogen production by controlling the power supplied from the generator 13 of the nuclear power generation system 2 in response to a power request command Ce (described later) of the plant control device 5. The hydrogen production device 31 produces high-temperature (e.g., 800 to 1000°C) steam (superheated steam) from raw water using thermal energy (heat medium) supplied from the heat storage facility 33 and the power supplied from the nuclear power generation system 2, and produces hydrogen by electrolyzing the produced high-temperature steam using the power supplied from the nuclear power generation system 2. As shown in FIG. 3, for example, the hydrogen production device 31 includes, in order from the upstream side, a steam generator 41, a heat exchanger 42, a steam heater 43, a steam electrolysis device 44, and a hydrogen separation device 45.

[0027] The steam generator 41 generates steam (saturated steam) from raw water using thermal energy supplied from the thermal storage equipment 33, and introduces the generated steam (saturated steam) into the heat exchanger 42. Since the thermal energy stored in the thermal storage equipment 33 is originally the thermal energy of steam supplied from the reactor 11 of the nuclear power generation system 2, the steam generator 41 can also be said to generate steam (saturated steam) from raw water using the thermal energy of the steam supplied from the reactor 11. The supply of thermal energy to the steam generator 41 (flow rate of the heat medium) is regulated by the regulating valve 35 (see FIGS. 1 and 2).

[0028] The heat exchanger 42 heats the saturated steam generated in the steam generator 41 to raise its temperature and generate superheated steam, and introduces the heated steam into the steam heater 43. A mixed gas, which will be described later, discharged from the steam electrolysis device 44 is introduced into the heat exchanger 42 as a heat source. That is, the heat exchanger 42 reuses the thermal energy of the mixed gas discharged from the steam electrolysis device 44 to heat the saturated steam from the steam generator 41.

[0029] The steam heater 43 further heats the steam heated by the heat exchanger 42 using electric power supplied from the nuclear power generation system 2 to raise the temperature to the operating temperature of the steam electrolysis device 44, and introduces the heated high-temperature steam into the steam electrolysis device 44. The steam heater 43 is formed, for example, of an electric heater that converts electric power into thermal energy.

[0030] The steam electrolysis device 44 generates hydrogen by electrolyzing high-temperature steam heated by the steam heater 43 using power supplied from the power system 100. The steam electrolysis device 44 includes, for example, a solid oxide electrolysis cell (SOEC) and operates at 800 to 1000°C. The SOEC is a stack of cells having a structure in which an electrolyte that passes ions is sandwiched between a hydrogen electrode (cathode) that extracts hydrogen from steam and an oxygen electrode (anode) that extracts oxygen. In the SOEC, when a voltage is applied to both electrodes, oxygen is generated at the oxygen electrode and hydrogen is generated at the hydrogen electrode. The mixed gas containing hydrogen and oxygen generated in the steam electrolysis device 44 and unused steam that has not been electrolyzed remains in a high-temperature state. Therefore, the mixed gas (steam containing hydrogen and steam containing oxygen) discharged from the steam electrolysis device 44 is introduced into the heat exchanger 42 and used as a heating source for the heat exchanger 42.

[0031] The hydrogen separation device 45 separates hydrogen from the mixed gas discharged from the water vapor electrolysis device 44. The hydrogen separation device 45 is configured to send the separated hydrogen to the hydrogen storage device 32 (see FIG. 1 ), while merging the water vapor from which hydrogen has been separated with the saturated steam generated in the steam generator 41.

[0032] In the hydrogen production device 31 configured as described above, a circulation cycle is established in which the steam from which hydrogen has been removed by the hydrogen separator 45 is introduced again into the steam electrolysis device 44 via the heat exchanger 42 and the steam heater 43 for electrolysis. In addition, the hydrogen production device 31 is configured so that, when there is no surplus heat output of the reactor 11 relative to the load demand, the steam electrolysis device 44 is stopped and each component of the hydrogen production device 31 is kept warm during the stoppage. For example, the steam electrolysis device 44 uses a heat insulating material (not shown) in order to suppress a sudden cooling of the cells during the stoppage and drainage of the steam in the device. In addition, the steam generator 41 and the heat exchanger 42, which are peripheral devices other than the steam electrolysis device 44, are configured to suppress a drop in temperature by using thermal energy (thermal energy of the stored steam of the reactor 11) supplied from the heat storage facility 33. In this way, by keeping the various components 41, 42, 43, 44 of the hydrogen production device 31 warm while it is stopped, and by keeping the water vapor circulating through the hydrogen production device 31 warm, the water vapor electrolysis device 44, which is stopped, can be returned to its operating temperature in a short period of time, and hydrogen production by the hydrogen production device 31 can be resumed quickly.

[0033] Returning to FIG. 2, the heat storage equipment 33 is configured so that a part of the steam (surplus steam) generated in the reactor 11 is supplied via the bypass line 22 and the bypass valve 26. The thermal energy stored in the heat storage equipment 33 is adjusted by the bypass valve 26. The heat storage equipment 33 is configured so that the steam supplied from the reactor 11 (nuclear power generation system 2) is returned to the condenser 15 (nuclear power generation system 2) via the return line 23. The heat storage equipment 33 is also configured so that the stored thermal energy (thermal energy of the steam from the reactor 11) is supplied to the hydrogen production device 31 via the control valve 35. The control valve 35 adjusts the amount of thermal energy supplied from the heat storage equipment 33 to the hydrogen production device 31, that is, the flow rate of the heat medium, and the opening degree of the control valve 35 is controlled by a heat amount command Ch of the plant control device 5, which will be described later. The heat storage equipment 33 is provided with a heat sensor 36 that detects the amount of heat stored in the heat storage equipment 33. The heat sensor 36 outputs a detection signal Ts corresponding to the detected amount of heat storage to the plant control device 5. The detection value of the heat quantity sensor 36 serves as an index for determining whether the heat storage facility 33 is in a full storage state or not.

[0034] The heat storage equipment 33 has the following two functions. The first function is to recover the thermal energy of the steam generated in the reactor 11 and supply the recovered thermal energy as thermal energy for generating steam as a hydrogen source in the hydrogen production device 31. The steam generated in the reactor 11 contains a radioactive source derived from nuclear fuel, and it is unsafe to generate hydrogen by directly subjecting the steam from the reactor 11 to thermal electrolysis. Therefore, it is necessary to produce hydrogen by electrolyzing steam different from the steam from the reactor 11, and thermal energy is required to generate steam from raw water. The second function is to temporarily store the thermal energy of the steam generated in the reactor 11 and use the stored thermal energy to keep the hydrogen production device 31 warm during shutdown. In the hydrogen production device 31, if the temperatures of the components 41, 42, 43, and 44 drop during shutdown, it will take time to restore the temperature of the steam electrolysis device 44 to the operating temperature when the hydrogen production device 31 is restarted, and the resumption of hydrogen production by the steam electrolysis device 44 will be delayed. By using the thermal energy stored in the heat storage equipment 33 to keep the components 41, 42, 43, and 44 warm while the hydrogen production device 31 is stopped, hydrogen production by the water vapor electrolysis device 44 can be quickly restarted.

[0035] The plant control device 5 receives a load request from the outside (for example, a central load dispatching center, not shown) instructing the power generation output to the power grid 100 required of the nuclear power generation system 2. Also, a detection signal Ps corresponding to the pressure of the reactor 11 detected by a pressure sensor 28 and a detection signal Es corresponding to the power generation output of the generator 13 detected by a power meter 29 are input. Also, a detection signal Ts corresponding to the amount of heat stored in the heat storage facility 33 detected by a heat quantity sensor 36 of the heat storage facility 33 is input.

[0036] The plant control device 5 controls the nuclear power generation system 2 and the hydrogen production system 3 based on the input load request, the detection value of the pressure sensor 28 (pressure of the reactor 11), the detection value of the power meter 29 (power generation output of the generator 13), and the detection value of the heat sensor 36 (heat storage amount of the heat storage facility 33). The control of the nuclear power generation system 2 by the plant control device 5 includes controlling the thermal output (amount of generated steam) of the reactor 11 based on a control rod position command Cr for the drive mechanism of the control rod 11a and a recirculation flow rate command Cp for the recirculation pump 11c, and controlling the output of the steam turbine 12 (generator 13) based on an opening command Cv1 for the steam control valve 25. The control of the hydrogen production system 3 by the plant control device 5 controls the amount of thermal energy of steam supplied from the reactor 11 to the hydrogen production device 31 and the heat storage equipment 33 (thermal output of the reactor 11) based on an opening command Cv2 for the bypass valve 26 and a heat amount command Ch for the control valve 35, and also controls the power supplied to the hydrogen production device 31 based on a power request command Ce for the hydrogen production device 31, thereby controlling the output (hydrogen production) of the hydrogen production device 31 and the heat storage and release of the heat storage equipment 33. A specific method of operating the nuclear plant 1 by the plant control device 5 will be described in detail later.

[0037] Next, the hardware configuration and the functional configuration of the plant control device in the nuclear plant according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a block diagram showing the configuration of the plant control device in the nuclear plant according to the first embodiment shown in Fig. 2.

[0038] 4, the plant control device 5 includes, as its hardware configuration, a storage device 51 including a ROM, a RAM, etc., and a processing device 52 including a CPU, an MPU, etc. The storage device 51 stores in advance programs and various information required for controlling the nuclear power generation system 2 and the hydrogen production system 3. The processing device 52 appropriately reads various programs and information from the storage device 51, and executes processing according to the programs, thereby implementing various functions.

[0039] The plant control device 5 of this embodiment performs constant thermal output operation in which the thermal output of the reactor 11 (thermal energy of steam generated in the reactor 11) is basically kept constant. Furthermore, the plant control device 5 performs operation in which the thermal output of the reactor 11 is appropriately allocated to the steam turbine 12 and the hydrogen production system 3 (hydrogen production device 31 and heat storage facility 33) with the highest priority being given to satisfying the load requirements. In the allocation of the thermal output of the reactor 11 in the hydrogen production system 3, hydrogen production by the hydrogen production device 31 takes precedence over heat storage by the heat storage facility 33. In other words, the plant control device 5 performs operation in which the highest priority is given to the nuclear power generation system 2 outputting power that satisfies the load requirements to the power grid 100, and, depending on the load requirement situation, performs operation in which surplus thermal output of the reactor 11 is used in the hydrogen production system 3 to produce hydrogen and, in some cases, stores the thermal energy of the steam from the reactor 11. Furthermore, when the surplus thermal output of the reactor 11 relative to the load request exceeds the upper limit that can be accepted by the hydrogen production system 3, the plant control device 5 changes the constant thermal output operation of the reactor 11 to reduce the thermal output of the reactor 11, thereby performing operation to make the surplus thermal output of the reactor 11 equal to or less than the upper limit that can be accepted by the hydrogen production system 3. Furthermore, when there is no surplus thermal output of the reactor 11 relative to the load request, the plant control device 5 stops hydrogen production by the hydrogen production device 31 of the hydrogen production system 3 and performs a heat retention operation to keep the hydrogen production device 31 warm using the thermal energy stored in the heat storage equipment 33.

[0040] The plant control device 5 has the following functional units in order to execute the above-mentioned operations. The plant control device 5 generally has functional units of a nuclear power generation system control unit 60 that controls the nuclear power generation system 2, and a hydrogen production system control unit 70 that controls the hydrogen production system 3. The nuclear power generation system control unit 60 is made up of functional units of a plant overall load calculation unit 61, a reactor power control unit 62, and a turbine governor control unit 63. The hydrogen production system control unit 70 is made up of functional units of a hydrogen production control unit 71 and a heat storage control unit 72.

[0041] A load request is input from the outside to a plant overall load calculation unit 61 of the nuclear power generation system control unit 60, and the power output of the generator 13, which is the detection value Es of the power meter 29, and the heat storage amount of the heat storage facility 33, which is the detection value Ts of the heat sensor 36, are also input. Based on the input load request, the detection value Es of the power meter 29, and the detection value Ts of the heat sensor 36, the plant overall load calculation unit 61 calculates the thermal loads of the respective components of the nuclear plant 1, i.e., the thermal load Q1 (target thermal output) of the reactor 11, the thermal load Q2 (target output) of the steam turbine 12, the thermal load Q3 required for hydrogen production by the hydrogen production device 31, and the thermal load Q4 as the thermal energy stored in the heat storage facility 33 or the thermal energy released from the heat storage facility 33 (per unit time). The plant overall load calculation unit 61 outputs the calculation result of the thermal load Q1 of the reactor 11 (hereinafter sometimes referred to as reactor load Q1) to the reactor power control unit 62, the calculation result of the thermal load Q2 of the steam turbine 12 (hereinafter sometimes referred to as turbine load Q2) to the turbine governor control unit 63, the calculation result of the thermal load Q3 of the hydrogen production device 31 (hereinafter sometimes referred to as hydrogen production load Q3) to the hydrogen production control unit 71 of the hydrogen production system control unit 70, and the calculation result of the thermal load Q4 of the heat storage facility 33 (hereinafter sometimes referred to as heat storage load Q4) to the heat storage control unit 72. Details of the calculation contents of the plant overall load calculation unit 61 will be described later.

[0042] The reactor power control unit 62 receives the pressure of the reactor 11, which is the detection value Ps of the pressure sensor 28, and also receives the reactor load Q1, which is the calculation result of the plant overall load calculation unit 61. The reactor power control unit 62 controls the reactor 11 so that the detection value Ps of the pressure sensor 28 coincides with a preset pressure value and the actual thermal output of the reactor 11 coincides with the reactor load Q1. Specifically, the reactor power control unit 62 outputs a control rod position command Cr to the drive device of the control rod 11a to control the position of the control rod 11a, and outputs a recirculation flow rate command Cp to the recirculation pump 11c to control the recirculation flow rate of the recirculation system 11b, thereby achieving the above-mentioned control of the reactor 11. The set pressure value is stored in advance in the storage device 51, for example.

[0043] A turbine load Q2, which is the result of calculation by the plant overall load calculation unit 61, is input to the turbine governor control unit 63. The turbine governor control unit 63 controls the driving of the steam turbine 12 so that the output of the steam turbine 12 coincides with the turbine load Q2. Specifically, the above-mentioned output control of the steam turbine 12 is realized by outputting an opening command Cv1 to the steam control valve 25 to control the opening of the steam control valve 25.

[0044] The hydrogen production load Q3, which is the calculation result of the plant overall load calculation unit 61, is input to the hydrogen production control unit 71 of the hydrogen production system control unit 70. The hydrogen production control unit 71 calculates the steam generation heat load Q3S and the power demand command Ce based on the hydrogen production load Q3. The steam generation heat load Q3S is the thermal energy (per unit time) required to heat raw water in the steam generator 41 of the hydrogen production device 31 to generate low-temperature steam, and corresponds to the thermal energy (steam flow rate) of the steam to be supplied from the nuclear reactor 11 to the hydrogen production device 31 via the heat storage facility 33. The power demand command Ce requests the electric power required for the electric heater as the steam heater 43 of the hydrogen production device 31 to heat the low-temperature steam to the operating temperature of the steam electrolysis device 44 and the electric power required for the steam electrolysis device 44 to electrolyze the steam. The hydrogen production control unit 71 outputs the steam generation heat load Q3S, which is the calculation result, to the heat storage control unit 72, and outputs the electric power demand command Ce, which is the calculation result, to the hydrogen production device 31. The hydrogen production control unit 71 controls hydrogen production by causing the hydrogen production device 31 to supply electric power according to the electric power demand command Ce.

[0045] The heat storage control unit 72 receives the steam generation heat load Q3S, which is the calculation result of the hydrogen production control unit 71, and the heat storage load Q4, which is the calculation result of the plant overall load calculation unit 61. When the steam generation heat load Q3S is not 0, the heat storage control unit 72 controls the thermal energy of the steam (steam flow rate) supplied from the reactor 11 to the heat storage facility 33 to match the sum of the steam generation heat load Q3S and the heat storage load Q4. Specifically, the opening command Cv2 according to the steam generation heat load Q3S and the heat storage load Q4 is output to the bypass valve 26 to control the opening of the steam control valve 25, thereby realizing the heat supply control to the heat storage facility 33. Furthermore, the heat storage control unit 72 controls the thermal energy (heat medium flow rate) supplied from the heat storage facility 33 to the hydrogen production device 31 to match the steam generation heat load Q3S. Specifically, the heat supply control from the nuclear reactor 11 to the hydrogen production device 31 via the heat storage equipment 33 is realized by outputting a heat amount command Ch according to the steam generation heat load Q3S to the control valve 35 to control the opening of the control valve 35. The difference between the amount of heat energy supplied by the heat supply control to the heat storage equipment 33 and the amount of heat energy supplied by the heat supply control to the hydrogen production device 31 becomes the heat storage of the heat storage equipment 33. That is, the heat storage control unit 72 realizes the heat storage control of the heat storage equipment 33 by controlling the heat supply to the heat storage equipment 33 and the heat supply to the hydrogen production device 31. Furthermore, when the steam generation heat load Q3S is 0, the heat storage control unit 72 does not execute the heat supply control to the heat storage equipment 33, but executes only the heat supply control to the hydrogen production device 31 according to the heat storage load Q4, thereby realizing the heat retention control of the hydrogen production device 31 by the heat release of the heat storage equipment 33.

[0046] Next, the calculation of the overall plant load calculation unit of the plant control device in the nuclear plant according to the first embodiment will be described with reference to Fig. 5. Fig. 5 is a flow chart showing an example of the calculation procedure of the overall plant load calculation unit in the plant control device in the nuclear plant according to the first embodiment shown in Fig. 4.

[0047] 5, the plant overall load calculation unit 61 (see FIG. 4) of the plant control device 5 first calculates the thermal load Qt1D of the reactor 11 corresponding to the load demand QeD (unit of power) (step S10). This calculation corresponds to calculating the thermal energy of steam generated by the reactor 11 per unit time, which is required for the generator 13 of the nuclear power generation system 2 to output the power of the load demand QeD.

[0048] Next, it is determined whether or not the rated value Qt1R of the thermal output of the reactor 11 is greater than the thermal load Qt1D of the reactor 11, which is the calculation result of step S10 (step S20). The rated value Qt1R of the reactor 11 is stored in advance in, for example, the storage device 51. In this embodiment, the thermal output of the reactor 11 is basically maintained constant at the rated value and operated. In other words, the above determination is to determine whether or not the thermal output of the reactor 11 is in excess of the load request. If the rated value Qt1R of the thermal output of the reactor 11 is equal to or less than the thermal load Qt1D of the calculation result (if NO), the process proceeds to step S30, whereas if the rated value Qt1R of the thermal output of the reactor 11 is greater than the thermal load Qt1 of the calculation result (if YES), the process proceeds to step S40.

[0049] If the result in step S20 is NO (Qt1R≦Qt1D), that is, if there is no surplus in the thermal output of the reactor 11 relative to the load request, the plant overall load calculation unit 61 sets the thermal load Q1 (target thermal output) of the reactor 11 to the rated value Qt1R. Also, the thermal load Q2 (target output) of the steam turbine 12 is set so that the entire amount of the thermal output (generated steam) of the reactor 11 (i.e., equivalent to the rated value Qt1R, which is the thermal load Q1 of the reactor 11) is introduced into the steam turbine 12. Also, the thermal load Q3 of the hydrogen production device 31 is set so as to correspond to a stopped state of hydrogen production by the hydrogen production device 31. That is, the thermal load Q3 of the hydrogen production device 31 is set to 0. Also, the thermal load Q4 of the heat storage equipment 33 is set so as to set the hydrogen production device 31 to a heat-retaining state. That is, in step S30, when there is no surplus thermal output of the reactor 11 relative to the load requirement, the entire amount of the thermal output of the reactor 11 is introduced into the steam turbine 12 to generate electricity, while a first operation is performed to stop hydrogen production by the hydrogen production system 3, and at the same time, a heat retention operation is performed to keep the hydrogen production device 31 warm by dissipating heat from the heat storage equipment 33.

[0050] In the case of YES in step S20 (Qt1R>Qt1D), that is, in the case where there is a surplus in the thermal output of the reactor 11 relative to the load request, it is determined whether or not the rated value Qt1R of the thermal output of the reactor 11 is greater than the sum of the thermal load Qt1D, which is the calculation result of step S10, and the thermal load Qt3R at the rated operation of the hydrogen production device 31 (Qt1R>Qt1D+Qt3R) (step S40). The above determination is to determine whether or not the surplus of the thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production device 31 of the hydrogen production system 3 when there is a surplus in the thermal output of the reactor 11 relative to the load request. If Qt1R≦Qt1D+Qt3R (NO), the process proceeds to step S50, whereas if Qt1R>Qt1D+Qt3R (YES), the process proceeds to step S60.

[0051] If the result in step S40 is NO (Qt1R≦Qt1D+Qt3R), that is, if there is a surplus in the thermal output of the reactor 11 relative to the load request and the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production device 31 of the hydrogen production system 3, the plant overall load calculation unit 61 sets the thermal load Q1 of the reactor 11 to the rated value Qt1R. That is, even if there is a surplus in the thermal output of the reactor 11, the rated thermal output constant operation is maintained to keep the thermal output of the plant reactor 11 constant at the rated value. In addition, the thermal load Q3 of the hydrogen production device 31 is set to (Qt1R−Qt1D). The thermal load Q4 of the heat storage equipment 33 is set to 0, which is a state in which there is neither heat storage nor heat release. In addition, the thermal load Q2 of the steam turbine 12 is set to the thermal load Qt1D corresponding to the load request QeD, taking into account the power required for hydrogen production by the hydrogen production device 31.

[0052] That is, step S50 sets, when there is a surplus in the thermal output of the reactor 11 relative to the load request and the surplus thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3, to maintain the thermal output of the reactor 11 and to perform a second operation in which part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to generate electricity and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system to produce hydrogen. More specifically, when the surplus thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production device 31, it sets to perform control in which the entire amount of thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized by the hydrogen production device 31.

[0053] If the answer is YES (Qt1R>Qt1D+Qt3R) in step S40, that is, if there is a surplus in the thermal output of the reactor 11 relative to the load request and the surplus of the thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production device 31 of the hydrogen production system 3, it is determined whether or not the rated value Qt1R of the thermal output of the reactor 11 is greater than the sum of the thermal load Qt1D, which is the calculation result of step S10, the thermal load Qt3R at the rated operation of the hydrogen production device 31, and the thermal load Qt4R at the rated thermal storage of the thermal storage device 33 (Qt1R>Qt1D+Qt3R+Qt4R) (step S60). The above determination is to determine whether or not the surplus of the thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production system 3 (the hydrogen production device 31 and the thermal storage device 33) when there is a surplus in the thermal output of the reactor 11 relative to the load request. If Qt1R≦Qt1D+Qt3R+Qt4R (if NO), proceed to step S70, whereas if Qt1R>Qt1D+Qt3R+Qt4R (if YES), proceed to step S80.

[0054] If the result in step S60 is NO (Qt1R≦Qt1D+Qt3R+Qt4R), that is, if there is a surplus in the thermal output of the reactor 11 with respect to the load request, and if the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3 but exceeds the upper limit that can be accepted by the hydrogen production device 31, the plant overall load calculation unit 61 sets the thermal load Q1 of the reactor 11 to the rated value Qt1R. That is, even if there is a surplus in the thermal output of the reactor 11, the rated thermal output constant operation is maintained, which keeps the thermal output of the plant reactor 11 constant at the rated value. In addition, the thermal load Q3 of the hydrogen production device 31 is set to the rated value Qt3R. In addition, the thermal load Q4 of the thermal storage facility 33 is set to (Qt1R-Qt1D-Qt3R). Further, the heat load Q2 of the steam turbine 12 is set by adding the electric power required for hydrogen production by the hydrogen production device 31 to the heat load Qt1D corresponding to the load request QeD.

[0055] That is, step S70 sets, when there is a surplus of the thermal output of the reactor 11 with respect to the load request and the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3, to maintain the thermal output of the reactor 11, introduce part of the thermal output of the reactor 11 into the steam turbine 12 to generate electricity, and supply the remainder of the thermal output of the reactor 11 to the hydrogen production system to produce hydrogen, to perform a second operation. More specifically, when the surplus of the thermal output of the reactor 11 exceeds the upper limit of the hydrogen production device 31, it sets the control to use part of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 in the hydrogen production device 31 and store the remaining thermal energy of the steam in the thermal storage facility 33. After processing step S70, the plant overall load calculation unit 61 proceeds to step S90.

[0056] In the case of YES (Qt1R>Qt1D+Qt3R+Qt4R) in step S60, that is, when there is a surplus in the thermal output of the reactor 11 with respect to the load request and the surplus of the thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production system 3, the plant overall load calculation unit 61 sets the thermal load Q1 of the reactor 11 to be reduced by (Q1tR-Qt1D-Qt3R-Qt4R=ΔQ1v) from the rated value Qt1R. In other words, when the surplus of the thermal output of the reactor 11 cannot be fully utilized by the hydrogen production system 3, the constant thermal output operation of the reactor 11 is changed to an operation to reduce the thermal output of the reactor 11. In addition, the thermal load Q3 of the hydrogen production device 31 is set to the rated Qt3R. In addition, the thermal load Q4 of the heat storage facility 33 is set to the rated Qt4R. Further, the heat load Q2 of the steam turbine 12 is set by adding the electric power required for hydrogen production by the hydrogen production device 31 to the heat load Qt1D corresponding to the load request QeD.

[0057] That is, in step S80, when there is a surplus in the thermal output of the reactor 11 relative to the load request and the surplus thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production system 3, the thermal output of the reactor 11 is reduced so that the surplus thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3, and a third operation is set in which part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to generate electricity and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3 (hydrogen production device 31 and heat storage equipment 33) to produce hydrogen. After processing step S80, the plant overall load calculation unit 61 proceeds to step S90.

[0058] Next, the plant overall load calculation unit 61 judges whether or not the heat storage equipment 33 has reached a full storage state and is in a state in which heat storage is not possible (a state in which heat energy cannot be stored) (step S90). When the plant control device 5 performs heat storage control of the heat storage equipment 33 for a long time, the heat storage equipment 33 may reach a full storage state and become in a state in which heat storage is not possible. The above judgment takes this situation into consideration. If the heat storage equipment 33 is in a state in which heat storage is not possible (if YES), the process proceeds to step S100 and then returns to step S10, whereas if the heat storage equipment is in a state in which heat storage is possible (if heat energy can be stored) (if NO), the process returns to step S10.

[0059] If the answer is YES in step S90, the plant overall load calculation unit 61 sets the thermal load Q1 of the reactor 11 to be reduced by (Q1tR-Qt1D-Qt3R=ΔQ1f) from the rated value Qt1R. That is, since the thermal output of the reactor 11 becomes surplus by the thermal load Q4 of the thermal storage equipment 33 that was supplied for storing heat in the thermal storage equipment 33, the operation is performed to reduce the thermal output of the reactor 11. In addition, the thermal load Q3 of the hydrogen production device 31 is set to the rated value Qt3R. In addition, the thermal load Q4 of the thermal storage equipment 33 is set to 0, which is a state in which there is neither heat storage nor heat release. In addition, the thermal load Q2 of the steam turbine 12 is set to the thermal load Qt1D corresponding to the load request QeD, taking into account the power required for hydrogen production by the hydrogen production device 31.

[0060] In other words, in step S100, when there is surplus thermal output of the reactor 11 relative to the load requirement and the surplus thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production system 3, and the heat storage equipment 33 has reached the upper limit of the thermal energy that can be stored and is no longer able to store heat, the thermal output of the reactor 11 is reduced so that the surplus thermal output of the reactor 11 is below the upper limit of the hydrogen production system 3, and control is performed so that the entire amount of thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized by the hydrogen production device 31.

[0061] Next, a method for operating a nuclear power plant according to a first embodiment of the present invention will be described with reference to Fig. 5 and Fig. 6. Fig. 6 is an explanatory diagram showing distribution of thermal output (thermal load) of a nuclear reactor in the method for operating a nuclear power plant according to the first embodiment.

[0062] The plant control device 5 operates the nuclear plant 1 based on the thermal load Q1 (target thermal output) of the reactor 11, the thermal load Q2 (target output) of the steam turbine 12, the thermal load Q3 of the hydrogen production device 31, and the thermal load Q4 of the thermal storage facility 33, which are set by the plant overall load calculation unit 61 performing the calculation process of the flowchart shown in Fig. 5. The operation of the nuclear plant 1 by the plant control device 5 distributes the thermal output of the reactor 11 as follows, thereby controlling the power generation of the nuclear power generation system 2 and the hydrogen production and thermal storage of the hydrogen production system 3. Note that the explanation here assumes that the thermal output of the reactor 11 is basically at the rated value.

[0063] First, when there is no surplus thermal output of the reactor 11 relative to the load request, as shown in the characteristics diagram at the top of Fig. 6, the entire amount of thermal output of the reactor 11, i.e., the rated value Qt1R of the thermal output of the reactor 11, is introduced into the steam turbine 12 to generate power, while the hydrogen production by the hydrogen production system 3 is stopped, in a first operation. The first operation is based on the setting of step S30 shown in Fig. 5 of the plant overall load calculation unit 61, and is an operation mode in which the nuclear power generation system 2 outputs power to the power grid 100 in response to the load request while maintaining the thermal output of the reactor 11 constant (rated value Qt1R). In other words, the first operation corresponds to the operation mode of a normal nuclear power plant.

[0064] Secondly, when there is a surplus of the thermal output of the reactor 11 relative to the load demand and the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3, as shown in the second or third characteristic diagram from the top in Fig. 6, the thermal output of the reactor 11 is maintained at the rated value Qt1R, a part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to send electric power according to the load demand to the electric power system 100, and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3 to produce hydrogen. The second operation is an operation form for co-producing electric power and hydrogen in which the thermal output of the reactor 11 is maintained constant (rated value Qt1R), the power output of the nuclear power generation system 2 relative to the electric power system 100 is adjusted according to the load demand, and the surplus of the thermal output of the reactor 11 is used for hydrogen production. The second operation is further divided into two operation forms.

[0065] Specifically, when the surplus thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production device 31, control is performed so that the entire amount of thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized by the hydrogen production device 31, as shown in the second characteristic diagram in Fig. 6. This operation is based on the setting of step S50 shown in Fig. 5 of the plant overall load calculation unit 61, and is an operation form for concurrent power and hydrogen production in which the power generation output of the nuclear power generation system 2 to the power grid 100 is adjusted according to the load request, and the surplus thermal output of the reactor 11 is utilized only for hydrogen production.

[0066] Furthermore, when the surplus thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production device 31, as shown in the third characteristic diagram of Fig. 6, control is performed such that part of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is used in the hydrogen production device 31 to produce hydrogen, and the remaining thermal energy of the steam is stored in the thermal storage facility 33. This operation is based on the setting of step S70 shown in Fig. 5 of the plant overall load calculation unit 61. That is, this operation is an operation mode in which the power generation output of the nuclear power generation system 2 for the power grid 100 is adjusted according to the load request, and in addition to the operation of electric power and hydrogen co-production in which part of the surplus thermal output of the reactor 11 is used for hydrogen production, a thermal storage operation in which the remaining surplus thermal output of the reactor 11 is stored in the thermal storage facility 33 is simultaneously performed.

[0067] Thirdly, when there is a surplus of the thermal output of the reactor 11 with respect to the load demand and the surplus of the thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production system 3, as shown in the fourth or fifth characteristic diagram from the top in Fig. 6, the thermal output of the reactor 11 is reduced so that the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3, and a part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to send electric power according to the load demand to the power grid 100, and the remaining thermal output of the reactor 11 is supplied to the hydrogen production system 3 to produce hydrogen. The third operation is an operation form for co-producing electric power and hydrogen in which the power output of the nuclear power generation system 2 for the power grid 100 is adjusted according to the load demand and the surplus of the thermal output of the reactor 11 is used for hydrogen production. However, if the thermal output of the reactor 11 is maintained constant, a part of the surplus of the thermal output of the reactor 11 cannot be used by the hydrogen production system 3. Therefore, the third operation is an operation mode in which the thermal output of the reactor 11 is suppressed and adjusted so that the entire amount of the surplus thermal output of the reactor 11 can be used by the hydrogen production system 3. The third operation is further divided into two operation modes.

[0068] Specifically, when the heat storage facility 33 is in a state capable of storing thermal energy, as shown in the fourth characteristic diagram of Fig. 6, hydrogen production control is performed in which part of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is used in the hydrogen production device 31 to produce hydrogen, and heat storage control is performed in which the remainder is stored in the heat storage facility 33. This operation is based on the setting of step S80 shown in Fig. 5 of the plant overall load calculation unit 61. That is, this operation is an operation form in which the power generation output of the nuclear power generation system 2 for the power grid 100 is adjusted according to the load request, and in addition to the operation of electric power and hydrogen co-production in which part of the surplus thermal output of the reactor 11 is used for hydrogen production, a heat storage operation is simultaneously performed in which the remainder of the surplus thermal output of the reactor 11 is stored in the heat storage facility 33. This operation can reduce the reduction in the thermal output of the reactor 11 by the amount of heat storage in the heat storage facility 33.

[0069] When the heat storage facility 33 is full and cannot store heat energy, hydrogen production control is performed to produce hydrogen by using the entire amount of heat energy of the steam supplied from the reactor 11 to the hydrogen production system 3 in the hydrogen production device 31, as shown in the fifth characteristic diagram in Fig. 6. This operation is based on the setting of step S100 shown in Fig. 5 of the plant overall load calculation unit 61. That is, this operation is an operation form for power and hydrogen co-production in which the power generation output of the nuclear power generation system 2 to the power grid 100 is adjusted according to the load request, and the surplus heat output of the reactor 11 is used for hydrogen production. This operation requires a larger reduction in the heat output of the reactor 11 by the amount that cannot be stored in the heat storage facility 33.

[0070] As described above, the nuclear power plant 1 according to the first embodiment includes the nuclear power generation system 2 connected to the power system 100 and generating power by driving the steam turbine 12 with steam generated in the nuclear reactor 11, the hydrogen production system 3 configured to be able to supply the steam generated in the nuclear reactor 11 and generating steam from raw water using thermal energy of the steam generated in the nuclear reactor 11 and electrolyzing the generated steam to produce hydrogen, and the plant control device 5 which receives a load request from the outside instructing the power output to the power system 100 required by the nuclear power generation system 2 and controls the nuclear power generation system 2 and the hydrogen production system 3 based on the load request. When there is no surplus of thermal output of the nuclear reactor 11 relative to the load request, the plant control device 5 performs a first operation in which the entire amount of thermal output of the nuclear reactor 11 is introduced into the steam turbine 12 to generate power, while hydrogen production by the hydrogen production system 3 is stopped. Furthermore, when there is a surplus in the thermal output of the reactor 11 relative to the load request and the surplus thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3, a second operation is performed in which the thermal output of the reactor 11 is maintained, a part of the thermal output of the reactor 11 is introduced into the steam turbine 12, electric power according to the load request is sent to the power grid 100, and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3 to produce hydrogen. When there is a surplus in the thermal output of the reactor 11 relative to the load request and the surplus thermal output of the reactor 11 exceeds the upper limit of the hydrogen production system 3, a third operation is performed in which the thermal output of the reactor 11 is reduced so that the surplus thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3, a part of the thermal output of the reactor 11 is introduced into the steam turbine 12, electric power according to the load request is sent to the power grid 100, and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3 to produce hydrogen.

[0071] According to this configuration, the thermal output of the reactor 11 is maintained or changed and the allocation of the thermal output of the reactor 11 to the steam turbine 12 and the hydrogen production system 3 is changed depending on three conditions: when there is no surplus thermal output of the reactor 11 in relation to the load requirement; when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3; and when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 exceeds the upper limit of the hydrogen production system 3. Therefore, it is possible to effectively utilize the thermal output of the reactor 11 and suppress changes in the thermal output of the reactor 11 while adjusting the power generation output of the nuclear power generation system 2 for the power system 100 in accordance with the load requirement.

[0072] In addition, the hydrogen production system 3 of this embodiment includes a hydrogen production device 31 that uses the thermal energy of steam generated in the reactor 11 to generate steam from raw water and electrolyzes the generated steam to produce hydrogen, and a heat storage facility 33 that is capable of storing the thermal energy of the steam supplied from the reactor 11 and supplying the stored thermal energy to the hydrogen production device.

[0073] According to this configuration, since the hydrogen production system 3 is equipped with the heat storage equipment 33, it is possible to keep the hydrogen production device 31 warm while hydrogen production is stopped by using the thermal energy stored in the heat storage equipment 33. In addition, since the surplus thermal output of the reactor 11 can be stored in the heat storage equipment 33, the thermal output of the reactor 11 can be utilized more effectively.

[0074] In addition, in this embodiment, the plant control device 5 is configured, when performing the first operation, to simultaneously perform a heat retention operation in which the thermal energy stored in the heat storage equipment 33 is supplied to the hydrogen production device 31 to keep the hydrogen production device 31 warm.

[0075] According to this configuration, the hydrogen production device 31 is kept warm when it is stopped, so that the hydrogen production device 31 can be returned to its operating temperature in a short period of time, enabling the hydrogen production device 31 to quickly resume hydrogen production.

[0076] In the nuclear power plant 1 according to this embodiment, the upper limit of the hydrogen production system 3 is the sum of the upper limit that can be accepted by the hydrogen production device 31 and the upper limit that can be accepted by the heat storage facility 33. When the second operation is performed, if the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production device 31, the plant control device 5 performs control so that the hydrogen production device 31 utilizes all of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3. On the other hand, if the surplus of the thermal output of the reactor 11 exceeds the upper limit of the hydrogen production device 31, the plant control device 5 performs control so that the hydrogen production device 31 utilizes part of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 and stores the remaining thermal energy of the steam in the heat storage facility 33.

[0077] According to this configuration, the allocation of thermal energy of the steam supplied to the hydrogen production device 31 and the heat storage equipment 33 is changed depending on the magnitude relationship of the surplus thermal output of the reactor 11 relative to the upper limit of the hydrogen production device 31, so that the surplus thermal output of the reactor 11 can be effectively utilized without changing the thermal output of the reactor 11.

[0078] Furthermore, in the nuclear power plant 1 according to this embodiment, when the plant control device 5 performs the third operation, if the heat storage equipment 33 is in a state in which it can store thermal energy, control is performed so that a part of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized in the hydrogen production device 31 and the remainder is stored in the heat storage equipment 33. On the other hand, if the heat storage equipment 33 is fully charged and cannot store thermal energy, control is performed so that the entire amount of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized in the hydrogen production device 31.

[0079] According to this configuration, the distribution of thermal energy of the steam supplied to the hydrogen production device 31 and the heat storage equipment 33 is changed depending on the storage state of thermal energy in the heat storage equipment 33, so that it is possible to effectively utilize the surplus thermal output of the reactor 11 while suppressing the amount of reduction in the thermal output of the reactor 11.

[0080] Moreover, the nuclear power plant 1 according to this embodiment is configured so that the thermal energy of the steam generated in the nuclear reactor 11 is always transferred to the hydrogen production device 31 via the heat storage facility 33 .

[0081] According to this configuration, since a line for directly supplying steam from the nuclear reactor 11 to the hydrogen production device 31 is not required, the configuration for supplying thermal energy to the hydrogen production device 31 can be simplified.

[0082] The method of operating the nuclear power plant 1 according to the first embodiment described above is to operate the nuclear power plant 1, which includes the nuclear power generation system 2 that generates electricity by driving the steam turbine 12 with the steam generated in the nuclear reactor 11, and the hydrogen production system 3 that produces hydrogen by electrolyzing steam generated from raw water using the thermal energy of the steam generated in the nuclear reactor 11, based on a load request of the power system given from the outside. In this operation method, when there is no surplus thermal output of the nuclear reactor 11 relative to the load request, the entire thermal output of the nuclear reactor 11 is introduced into the steam turbine 12 to generate electricity, while a first operation is performed in which hydrogen production by the hydrogen production system 3 is stopped. Moreover, when there is a surplus of the thermal output of the reactor 11 relative to the load request and the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3, a second operation is performed in which the thermal output of the reactor 11 is maintained, a part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to send electric power according to the load request to the electric power system 100, and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3 to produce hydrogen. Moreover, when there is a surplus of the thermal output of the reactor 11 relative to the load request and the surplus of the thermal output of the reactor 11 exceeds the upper limit of the hydrogen production system 3, a third operation is performed in which the thermal output of the reactor 11 is reduced so that the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3, a part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to send electric power according to the load request to the electric power system 100, and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3 to produce hydrogen.

[0083] According to this method, the thermal output of the reactor 11 is maintained or changed and the allocation of the thermal output of the reactor 11 to the steam turbine 12 and the hydrogen production system 3 is changed depending on three conditions: when there is no surplus thermal output of the reactor 11 in relation to the load requirement; when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3; and when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 exceeds the upper limit of the hydrogen production system 3. This makes it possible to effectively utilize the thermal output of the reactor 11 and suppress changes in the thermal output of the reactor 11 while adjusting the power generation output of the nuclear power generation system 2 for the power system 100 in accordance with the load requirement.

[0084] In addition, in the operating method of the nuclear plant 1 according to this embodiment, when the first operation is performed, a heat retention operation is simultaneously performed in which the thermal energy stored in the heat storage equipment 33 is supplied to the hydrogen production device 31 to keep the hydrogen production device 31 warm.

[0085] According to this method, by keeping the stopped hydrogen production device 31 warm, the stopped hydrogen production device 31 can be returned to its operating temperature in a short period of time, making it possible to quickly resume hydrogen production by the hydrogen production device 31.

[0086] In the operation method of the nuclear power plant 1 according to this embodiment, the upper limit of the hydrogen production system 3 is the sum of the upper limit that can be accepted by the hydrogen production device 31 and the upper limit that can be accepted by the heat storage facility 33. In addition, in the case of performing the second operation, this operation method performs control so that the hydrogen production device 31 utilizes all of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 when the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production device 31. On the other hand, when the surplus of the thermal output of the reactor 11 exceeds the upper limit of the hydrogen production device 31, control is performed so that part of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized by the hydrogen production device 31 and the remaining thermal energy of the steam is stored in the heat storage facility 33.

[0087] According to this method, the distribution of thermal energy of the steam supplied to the hydrogen production device 31 and the heat storage equipment 33 is changed depending on the magnitude relationship of the surplus thermal output of the reactor 11 relative to the upper limit of the hydrogen production device 31, so that the surplus thermal output of the reactor 11 can be effectively utilized without changing the thermal output of the reactor 11.

[0088] Furthermore, in the operating method of the nuclear power plant 1 according to this embodiment, when the third operation is performed, if the heat storage equipment 33 is in a state in which it is capable of storing thermal energy, control is performed so that a part of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized in the hydrogen production device 31 and the remainder is stored in the heat storage equipment 33. On the other hand, if the heat storage equipment 33 is fully charged and cannot store thermal energy, control is performed so that the entire amount of the thermal energy of the steam supplied from the reactor 11 to the hydrogen production system 3 is utilized in the hydrogen production device 31.

[0089] According to this method, the distribution of thermal energy of the steam supplied to the hydrogen production device 31 and the heat storage equipment 33 is changed depending on the storage state of thermal energy in the heat storage equipment 33, so that it is possible to effectively utilize the surplus thermal output of the reactor 11 while suppressing the amount of reduction in the thermal output of the reactor 11.

[0090] [Modification of the first embodiment] Next, a nuclear power plant according to a modified example of the first embodiment of the present invention will be described with reference to Fig. 7. Fig. 7 is a block diagram showing a schematic configuration of a nuclear power plant according to a modified example of the first embodiment of the present invention. In Fig. 7, the same reference numerals as those in Figs. 1 to 6 denote similar parts, and therefore detailed description thereof will be omitted.

[0091] A nuclear power plant 1A according to a modification of the first embodiment shown in FIG. 7 differs from the first embodiment in that the electric power required for hydrogen production in the hydrogen production system 3A is received from the electric power grid 100, rather than from the nuclear power generation system 2. In detail, electric power is supplied from the electric power grid 100 to a steam heater 43 (see FIG. 3) serving as an electric heater in the hydrogen production device 31A. Similarly, electric power is supplied from the electric power grid 100 to a steam electrolysis device 44 (see FIG. 3). The rest of the configuration is the same as that of the first embodiment.

[0092] The operation method of the nuclear plant 1A is also different in that the power supplier for hydrogen production by the hydrogen production device 31A is changed from the power generation system 2 to the power grid 100. In this case, however, the power output of the nuclear power generation system 2 can be lower than that of the first embodiment because the output to the hydrogen production device 31 in the first embodiment is not required. For example, the heat load Q2 of the steam turbine in steps S50, S70, S80, and S100 of the flowchart shown in Fig. 5 does not need to take into account the power for hydrogen production by the hydrogen production device 31A.

[0093] In this modification, the hydrogen production device 31A is configured to receive electricity purchased preferentially from a renewable energy power plant 110 connected to the power grid 100. Since electricity, including grid wheeling charges, is charged, it is desirable to use inexpensive electricity from a separate grid. In this modification, it is possible to co-produce electricity and hydrogen using existing renewable energy power generation.

[0094] According to the nuclear power plant 1A and its operating method related to the modified example of the first embodiment described above, as in the case of the first embodiment, the thermal output of the reactor 11 is maintained or changed and the allocation of the thermal output of the reactor 11 to the steam turbine 12 and the hydrogen production system 3A is changed depending on three conditions: when there is no surplus thermal output of the reactor 11 relative to the load request; when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3A; and when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 exceeds the upper limit of the hydrogen production system 3A. Therefore, it is possible to effectively utilize the thermal output of the reactor 11 and suppress changes in the thermal output of the reactor 11 while adjusting the power generation output of the nuclear power generation system 2 for the power system 100 in response to the load request.

[0095] Further, in the nuclear power plant 1A according to this modification, control is performed so that electric power is supplied from the electric power system 100 to the hydrogen production in the hydrogen production system 3.

[0096] Moreover, the method of operating the nuclear power plant 1A according to this modification uses electric power from the power grid 100 for hydrogen production in the hydrogen production system 3.

[0097] This configuration and method make it possible to use inexpensive electricity for hydrogen production in the hydrogen production system 3. In addition, by using electricity from existing renewable energy power generation, it becomes possible to co-produce electricity and hydrogen using renewable energy.

[0098] [Second embodiment] Next, a nuclear power plant and an operating method thereof according to a second embodiment of the present invention will be described. First, the configuration of the nuclear power plant according to the second embodiment will be described with reference to Figs. 8 to 10. Fig. 8 is a block diagram showing a schematic configuration of the nuclear power plant according to the second embodiment of the present invention. Fig. 9 is a system diagram showing a detailed configuration of the nuclear power plant according to the second embodiment shown in Fig. 8. Fig. 10 is a block diagram showing a configuration of a hydrogen production device in the nuclear power plant according to the second embodiment shown in Fig. 8. In Figs. 8 to 10, the same reference numerals as those shown in Figs. 1 to 7 indicate similar parts, and detailed description thereof will be omitted.

[0099] The nuclear power plant 1B according to the second embodiment and its operating method are different from those of the first embodiment in that the hydrogen production system 3B shown in Figs. 8 and 9 does not include a heat storage facility (see Figs. 1 and 2) and that the absence of the heat storage facility means that the heat storage operation is not performed. In detail, as shown in Figs. 8 and 9, the hydrogen production system 3B is configured to directly supply thermal energy of steam supplied from the nuclear reactor 11 to the hydrogen production device 31B. A bypass line 22B and a return line 23B are connected to the hydrogen production device 31B of the hydrogen production system 3B. More specifically, as shown in Fig. 10, the bypass line 22B and the return line 23B are connected to a steam generator 41B of the hydrogen production device 31B. In the nuclear power plant 1B, a part of the steam (surplus steam) generated in the nuclear reactor 11 is supplied to the hydrogen production device 31B via the bypass line 22, and the steam supplied to the hydrogen production device 31B is recovered in the condenser 15. Returning to FIGS. 8 and 9, the amount of steam supplied to the hydrogen production device 31B is adjusted by the bypass valve .

[0100] The plant control device 5B shown in FIG. 9 performs constant thermal output operation in which the thermal output of the reactor 11 (thermal energy of steam generated in the reactor 11) is basically kept constant. Furthermore, the plant control device 5B performs operation in which the nuclear power generation system 2 gives top priority to outputting electric power that satisfies the load request to the power grid 100, and performs operation in which hydrogen is produced by utilizing the surplus thermal output of the reactor 11 in the hydrogen production device 31B of the hydrogen production system 3B depending on the load request situation. Since there is no heat storage facility here, there is no heat storage control operation. Furthermore, when the surplus thermal output of the reactor 11 relative to the load request exceeds the upper limit that can be accepted by the hydrogen production device 31B of the hydrogen production system 3B, the plant control device 5B performs operation in which the constant thermal output operation of the reactor 11 is changed to lower the thermal output of the reactor 11, thereby making the surplus thermal output of the reactor 11 equal to or less than the upper limit that can be accepted by the hydrogen production device 31B. Furthermore, when the thermal output of the reactor 11 is not sufficient for the load request, the plant control device 5B performs an operation to stop hydrogen production by the hydrogen production device 31B.

[0101] Next, the functional configuration of the plant control device in the nuclear plant according to the second embodiment will be described with reference to Fig. 11. Fig. 11 is a block diagram showing the functional configuration of the plant control device in the nuclear plant according to the second embodiment shown in Fig. 9.

[0102] 11 differs from the functional units of the plant control device 5 of the first embodiment mainly in that it does not have the functional unit of a heat storage control unit 72. Furthermore, the absence of the heat storage control unit 72 results in different calculation processing by the plant overall load calculation unit 61B, among the functional units of the plant control device 5B, and also results in a different control target by the hydrogen production control unit 71B.

[0103] Unlike the first embodiment, the plant overall load calculation unit 61B calculates the thermal load Q1 (target thermal output) of the reactor 11, the thermal load Q2 (target output) of the steam turbine 12, and the thermal load Q3 of the hydrogen production device 31 based on the load request and the detection value Es of the power meter 29.

[0104] The hydrogen production control unit 71B calculates an opening command Cv2 and a power demand command Ce based on the hydrogen production load Q3, which is the calculation result of the plant overall load calculation unit 61B. The opening command Cv2 commands the opening of the bypass valve 26 according to the thermal energy (per unit time) required to heat the raw water in the steam generator 41B of the hydrogen production equipment 31B and generate low-temperature steam. The hydrogen production control unit 71B controls the opening of the bypass valve 26 using the opening command Cv2 to supply the required thermal energy to the hydrogen production equipment 31B from the reactor 11 and to supply power according to the power demand command Ce to the hydrogen production equipment 31B, thereby controlling hydrogen production.

[0105] Next, the calculation of the overall plant load calculation unit of the plant control device in the nuclear plant according to the second embodiment will be described with reference to Fig. 12. Fig. 12 is a flow chart showing an example of the calculation procedure of the overall plant load calculation unit in the plant control device in the nuclear plant according to the second embodiment shown in Fig. 11.

[0106] The flowchart of the calculation procedure of the plant overall load calculation unit 61B of the plant control device 5B according to the second embodiment shown in Fig. 12 differs from the calculation procedure of the plant overall load calculation unit 61 of the plant control device 5 according to the first embodiment in that the hydrogen production system 3B does not include a heat storage facility, and therefore steps S60, S70, S90, and S100 of the calculation process of the plant overall load calculation unit 61 of the first embodiment shown in Fig. 5 are deleted. Also, the settings of steps S30B, S50B, and S80B in the flowchart shown in Fig. 12 are different.

[0107] Specifically, in step S30B, that is, when there is no surplus thermal output of the reactor 11 relative to the load demand, the entire thermal output of the reactor 11 is introduced into the steam turbine 12 to generate electricity, while a first operation is performed to stop hydrogen production by the hydrogen production system 3B. At this time, since the hydrogen production system 3B does not have a heat storage facility, it is impossible to perform a heat retention operation to keep the hydrogen production device 31B warm.

[0108] Furthermore, in step S50B, that is, when there is a surplus in the thermal output of the reactor 11 relative to the load request and the surplus thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3B (hydrogen production device 31B), a second operation is set to be performed in which the thermal output of the reactor 11 is maintained, part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to generate electricity, and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3B (hydrogen production device 31B) to produce hydrogen. However, since the hydrogen production system 3B does not include a heat storage facility, there is no need to set the thermal load of the heat storage facility.

[0109] In step S80B, that is, when there is a surplus in the thermal output of the reactor 11 with respect to the load request and the surplus of the thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production system 3B (hydrogen production device 31B), the thermal output of the reactor 11 is reduced so that the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3B (hydrogen production device 31B), and a third operation is performed in which a part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to generate electricity and the remaining thermal output of the reactor 11 is supplied to the hydrogen production system 3B (hydrogen production device 31B) to produce hydrogen. Specifically, the thermal load Q1 of the reactor 11 is set to be reduced by (Q1tR-Qt1D-Qt3R=ΔQ1v) from the rated value Qt1R.

[0110] Next, a method for operating a nuclear power plant according to a second embodiment will be described with reference to Fig. 12 and Fig. 13. Fig. 13 is an explanatory diagram showing distribution of thermal output (thermal load) of a nuclear reactor in the method for operating a nuclear power plant according to the second embodiment.

[0111] The operation of the nuclear plant 1B by the plant control device 5B of the second embodiment controls the power generation of the nuclear power generation system 2 and the hydrogen production of the hydrogen production system 3 by distributing the thermal output of the reactor 11 as follows:

[0112] First, when there is no surplus thermal output of the reactor 11 relative to the load request, a first operation is performed in which the entire amount of thermal output of the reactor 11, i.e., the rated value Qt1R of the thermal output of the reactor 11, is introduced into the steam turbine 12 to generate power, while hydrogen production by the hydrogen production system 3 is stopped, as shown in the characteristics diagram in the upper part of Fig. 13. The first operation is based on the setting of step S30B shown in Fig. 12 of the plant overall load calculation unit 61B, and is an operating mode in which the nuclear power generation system 2 outputs power to the power grid 100 in response to the load request while maintaining the thermal output of the reactor 11 constant (rated value Qt1R).

[0113] Secondly, when there is a surplus in the thermal output of the reactor 11 relative to the load demand and the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit that can be accepted by the hydrogen production system 3B (hydrogen production device 31B), the thermal output of the reactor 11 is maintained at the rated value Qt1R, part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to send electric power according to the load demand to the power grid 100, and the remainder of the thermal output of the reactor 11 is supplied to the hydrogen production system 3B (hydrogen production device 31B) to produce hydrogen, as shown in the characteristic diagram in the middle part of Fig. 13. The second operation is an operation form for co-producing electric power and hydrogen in which the thermal output of the reactor 11 is kept constant (rated value Qt1R), the power output of the nuclear power generation system 2 relative to the power grid 100 is adjusted according to the load demand, and the surplus of the thermal output of the reactor 11 is used to produce hydrogen.

[0114] Thirdly, when there is a surplus in the thermal output of the reactor 11 relative to the load demand and the surplus of the thermal output of the reactor 11 exceeds the upper limit that can be accepted by the hydrogen production system 3B (hydrogen production device 31B), as shown in the characteristic diagram in the lower part of Fig. 13, the thermal output of the reactor 11 is reduced so that the surplus of the thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3B (hydrogen production device 31B), and a part of the thermal output of the reactor 11 is introduced into the steam turbine 12 to send electric power according to the load demand to the electric power system 100, and the remaining thermal output of the reactor 11 is supplied to the hydrogen production system 3B (hydrogen production device 31B) to produce hydrogen, in a third operation. The third operation is an operation form for co-producing electric power and hydrogen in which the power output of the nuclear power generation system 2 relative to the electric power system 100 is adjusted according to the load demand and the surplus of the thermal output of the reactor 11 is used to produce hydrogen. The third operation is an operation mode in which the thermal output of the reactor 11 is suppressed and adjusted so that the entire amount of surplus thermal output of the reactor 11 is available for use in the hydrogen production system 3B (hydrogen production device 31B).

[0115] According to the nuclear power plant 1B and its operating method of the second embodiment described above, as in the case of the first embodiment, the thermal output of the reactor 11 is maintained or changed and the allocation of the thermal output of the reactor 11 to the steam turbine 12 and the hydrogen production system 3B (hydrogen production device 31B) is changed depending on three conditions: when there is no surplus thermal output of the reactor 11 relative to the load request; when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 is equal to or less than the upper limit of the hydrogen production system 3B (hydrogen production device 31B); and when there is surplus thermal output of the reactor 11 and the surplus thermal output of the reactor 11 exceeds the upper limit of the hydrogen production system 3B (hydrogen production device 31B). Therefore, it is possible to effectively utilize the thermal output of the reactor 11 and suppress changes in the thermal output of the reactor 11 while adjusting the power generation output of the nuclear power generation system 2 for the power grid 100 in response to the load request.

[0116] [others] The present invention is not limited to the above-mentioned first and second embodiments and their modifications, but includes various modifications. The above-mentioned embodiments have been described in detail to easily explain the present invention, and are not necessarily limited to those having all the configurations described. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0117] For example, in the above-described embodiment, the reactor 11 is a boiling water reactor, but the reactor may be a pressurized water reactor.

[0118] In the above-described first embodiment, an example of the nuclear power plant 1 is shown, which is configured so that the thermal energy of the steam supplied from the nuclear reactor 11 of the nuclear power generation system 2 to the hydrogen production system 3 is temporarily stored in the heat storage equipment 33 of the hydrogen production system 3 and then supplied to the hydrogen production device 31 via a heat medium. However, the nuclear power plant 1 can also be configured so that the steam supplied from the nuclear reactor 11 to the hydrogen production system 3 is directly supplied to the hydrogen production device 31, bypassing the heat storage equipment 33. [Explanation of symbols]

[0119] 1, 1A, 1B... nuclear power plant, 2... nuclear power generation system, 3, 3A, 3B... hydrogen production system, 5, 5B... plant control device, 11... nuclear reactor, 12... steam turbine, 31, 31A, 31B... hydrogen production device, 33... heat storage facility, 100... power system

Claims

1. a nuclear power generation system that is connected to a power grid and generates electricity by driving a steam turbine with steam generated in a nuclear reactor; a hydrogen production system configured to be able to receive steam generated in the nuclear reactor, and which generates steam from raw water by utilizing thermal energy of the steam generated in the nuclear reactor, and which produces hydrogen by electrolyzing the generated steam; a plant control device that receives a load request from an external source, the load request indicating a power output to be supplied to the power grid by the nuclear power generation system, and controls the nuclear power generation system and the hydrogen production system based on the load request; The plant control device includes: When there is no surplus thermal output of the reactor relative to the load request, a first operation is performed in which the entire amount of thermal output of the reactor is introduced into the steam turbine to generate power, while hydrogen production by the hydrogen production system is stopped; when there is a surplus of thermal power of the reactor relative to the load request and the surplus of thermal power of the reactor is equal to or less than an upper limit that can be accepted by the hydrogen production system, a second operation is performed in which the thermal power of the reactor is maintained, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the electric power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; when there is a surplus of thermal power of the reactor relative to the load request and the surplus thermal power of the reactor exceeds the upper limit of the hydrogen production system, a third operation is performed in which the thermal power of the reactor is reduced so that the surplus thermal power of the reactor is equal to or less than the upper limit of the hydrogen production system, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; The hydrogen production system includes: a hydrogen production device that generates steam from raw water by utilizing thermal energy of the steam generated in the nuclear reactor and produces hydrogen by electrolyzing the generated steam; a heat storage facility capable of storing thermal energy of steam supplied from the nuclear reactor and supplying the stored thermal energy to the hydrogen production device, the upper limit of the hydrogen production system is a sum of an acceptable upper limit of the hydrogen production device and an acceptable upper limit of the heat storage facility, When the second operation is performed, the plant control device When the surplus thermal output of the reactor is equal to or less than the upper limit of the hydrogen production device, control is performed so that the entire amount of thermal energy of the steam supplied from the reactor to the hydrogen production system is utilized by the hydrogen production device; When the surplus thermal output of the reactor exceeds the upper limit of the hydrogen production device, a part of the thermal energy of the steam supplied from the reactor to the hydrogen production system is utilized in the hydrogen production device, and the remaining thermal energy of the steam is stored in the heat storage facility.

1. A nuclear power plant comprising:

2. a nuclear power generation system that is connected to a power grid and generates electricity by driving a steam turbine with steam generated in a nuclear reactor; a hydrogen production system configured to be able to receive steam generated in the nuclear reactor, and which generates steam from raw water by utilizing thermal energy of the steam generated in the nuclear reactor, and which produces hydrogen by electrolyzing the generated steam; a plant control device that receives a load request from an external source, the load request indicating a power output to be supplied to the power grid by the nuclear power generation system, and controls the nuclear power generation system and the hydrogen production system based on the load request; The plant control device includes: When there is no surplus thermal output of the reactor relative to the load request, a first operation is performed in which the entire amount of thermal output of the reactor is introduced into the steam turbine to generate power, while hydrogen production by the hydrogen production system is stopped; when there is a surplus of thermal power of the reactor relative to the load request and the surplus of thermal power of the reactor is equal to or less than an upper limit that can be accepted by the hydrogen production system, a second operation is performed in which the thermal power of the reactor is maintained, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the electric power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; when there is a surplus of thermal power of the reactor relative to the load request and the surplus thermal power of the reactor exceeds the upper limit of the hydrogen production system, a third operation is performed in which the thermal power of the reactor is reduced so that the surplus thermal power of the reactor is equal to or less than the upper limit of the hydrogen production system, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; The hydrogen production system includes: a hydrogen production device that generates steam from raw water by utilizing thermal energy of the steam generated in the nuclear reactor and produces hydrogen by electrolyzing the generated steam; a heat storage facility capable of storing thermal energy of steam supplied from the nuclear reactor and supplying the stored thermal energy to the hydrogen production device, When the third operation is performed, the plant control device When the heat storage facility is in a state capable of storing thermal energy, a part of the thermal energy of the steam supplied from the nuclear reactor to the hydrogen production system is utilized in the hydrogen production device, and the remaining thermal energy of the steam is stored in the heat storage facility. When the heat storage facility reaches a full storage state and is unable to store thermal energy, control is performed so that the entire amount of thermal energy of the steam supplied from the nuclear reactor to the hydrogen production system is utilized by the hydrogen production device.

1. A nuclear power plant comprising:

3. The nuclear power plant according to claim 1 or 2, When the plant control device performs the first operation, the plant control device simultaneously performs a heat retention operation for supplying the thermal energy stored in the heat storage facility to the hydrogen production device to keep the hydrogen production device warm.

1. A nuclear power plant comprising:

4. The nuclear power plant according to claim 1 or 2, The hydrogen production system is configured so that thermal energy of steam generated in the nuclear reactor is always transferred to the hydrogen production device via the heat storage facility.

1. A nuclear power plant comprising:

5. The nuclear power plant according to claim 1 or 2, The plant control device controls the supply of electric power from the power grid to the hydrogen production system.

1. A nuclear power plant comprising:

6. A method for operating a nuclear power plant, comprising: a nuclear power generation system which generates electricity by driving a steam turbine with steam generated in a nuclear reactor; and a hydrogen production system which produces hydrogen by electrolyzing steam produced from raw water using thermal energy of the steam generated in the nuclear reactor, the method comprising the steps of: operating the nuclear power plant based on an externally applied load request of a power system, the method comprising the steps of: When there is no surplus thermal output of the reactor relative to the load request, a first operation is performed in which the entire amount of thermal output of the reactor is introduced into the steam turbine to generate power, while hydrogen production by the hydrogen production system is stopped; when there is a surplus of thermal power of the reactor relative to the load request and the surplus of thermal power of the reactor is equal to or less than an upper limit that can be accepted by the hydrogen production system, a second operation is performed in which the thermal power of the reactor is maintained, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the electric power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; when there is a surplus of thermal power of the reactor relative to the load request and the surplus thermal power of the reactor exceeds the upper limit of the hydrogen production system, a third operation is performed in which the thermal power of the reactor is reduced so that the surplus thermal power of the reactor is equal to or less than the upper limit of the hydrogen production system, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; The hydrogen production system includes: a hydrogen production device that generates steam from raw water by utilizing thermal energy of the steam generated in the nuclear reactor and produces hydrogen by electrolyzing the generated steam; a heat storage facility capable of storing thermal energy of steam supplied from the nuclear reactor and supplying the stored thermal energy to the hydrogen production device, the upper limit of the hydrogen production system is a sum of an acceptable upper limit of the hydrogen production device and an acceptable upper limit of the heat storage facility, In the case of performing the second operation, When the surplus thermal output of the reactor is equal to or less than the upper limit of the hydrogen production device, the entire amount of thermal energy of the steam supplied from the reactor to the hydrogen production system is utilized by the hydrogen production device; When the surplus thermal output of the reactor exceeds the upper limit of the hydrogen production device, a part of the thermal energy of the steam supplied from the reactor to the hydrogen production system is utilized in the hydrogen production device, and the remaining thermal energy of the steam is stored in the heat storage facility.

2. A method for operating a nuclear power plant comprising the steps of:

7. A method for operating a nuclear power plant, comprising: a nuclear power generation system which generates electricity by driving a steam turbine with steam generated in a nuclear reactor; and a hydrogen production system which produces hydrogen by electrolyzing steam produced from raw water using thermal energy of the steam generated in the nuclear reactor, the method comprising the steps of: operating the nuclear power plant based on an externally applied load request of a power system, the method comprising the steps of: When there is no surplus thermal output of the reactor relative to the load request, a first operation is performed in which the entire amount of thermal output of the reactor is introduced into the steam turbine to generate power, while hydrogen production by the hydrogen production system is stopped; when there is a surplus of thermal power of the reactor relative to the load request and the surplus of thermal power of the reactor is equal to or less than an upper limit that can be accepted by the hydrogen production system, a second operation is performed in which the thermal power of the reactor is maintained, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the electric power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; when there is a surplus of thermal power of the reactor relative to the load request and the surplus thermal power of the reactor exceeds the upper limit of the hydrogen production system, a third operation is performed in which the thermal power of the reactor is reduced so that the surplus thermal power of the reactor is equal to or less than the upper limit of the hydrogen production system, a part of the thermal power of the reactor is introduced into the steam turbine to send electric power according to the load request to the power grid, and the remainder of the thermal power of the reactor is supplied to the hydrogen production system to produce hydrogen; The hydrogen production system includes: a hydrogen production device that generates steam from raw water by utilizing thermal energy of the steam generated in the nuclear reactor and produces hydrogen by electrolyzing the generated steam; a heat storage facility capable of storing thermal energy of steam supplied from the nuclear reactor and supplying the stored thermal energy to the hydrogen production device, In the case of performing the third operation, When the heat storage facility is in a state capable of storing thermal energy, a portion of the thermal energy of the steam supplied from the nuclear reactor to the hydrogen production system is utilized in the hydrogen production device, and the remaining thermal energy of the steam is stored in the heat storage facility; When the heat storage facility is fully charged and cannot store thermal energy, the entire amount of thermal energy of the steam supplied from the nuclear reactor to the hydrogen production system is utilized by the hydrogen production device.

2. A method for operating a nuclear power plant comprising the steps of:

8. The method for operating a nuclear power plant according to claim 6 or 7, When the first operation is performed, a heat-retention operation is also performed at the same time to supply the thermal energy stored in the heat storage facility to the hydrogen production device to keep the hydrogen production device warm.

2. A method for operating a nuclear power plant comprising the steps of:

9. The method for operating a nuclear power plant according to claim 6 or 7, The hydrogen production system uses electric power from the power grid to produce hydrogen.

2. A method for operating a nuclear power plant comprising the steps of:

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