Water level control method and water level control device

Abstract

To prevent water level of a steam generator from sharply lowering during steam dump.SOLUTION: A water level control device includes: a turbine governor valve 42 provided for a steam pipe 11 connecting a steam generator 4 and a steam turbine 12; a turbine bypass pipe valve 41 provided for a turbine bypass pipe 40 connected to a condenser 13 from the steam pipe 11; and a feed water valve 45 provided for a water supply pipe 14 supplying a steam relief valve 43 and a steam generator 4 provided in the steam pipe 11 with secondary coolant. In a nuclear power facility 1 generating steam from the secondary coolant by heat exchange between the secondary coolant inside the steam generator 4 and a primary coolant of a reactor coolant system 100 and generating power with the steam turbine 12, at least either opening operation of the steam relief valve 43 or opening increase operation of the feed water valve 45 is performed when water level in the steam generator 4 is lowered after closing operation of the turbine governor valve 42 is performed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water level control method and a water level control device. [Background technology]

[0002] For example, Patent Document 1 discloses a water supply device that aims to control water supply so as to suppress fluctuations in the water supply flow rate and to suitably maintain the water level in a steam generator at a target water level. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5733929 Summary of the Invention [Problem to be solved by the invention]

[0004] In nuclear power plants, steam generators release steam into steam turbines to generate electricity. If, for some reason, the power generation output suddenly drops and the load suddenly drops, excessive power generation is prevented by reducing the amount of steam flowing from the steam generator to the steam turbine and by operating the turbine bypass valve to send the excess steam that would otherwise flow from the steam generator to the steam turbine to the condenser, a steam dump is required. If, for example, the turbine bypass valve operates later than expected or fails to operate, the pressure inside the steam generator increases due to the trapping effect of the excess steam, making boiling difficult and causing a sudden drop in the water level in the steam generator. This situation could lead to the nuclear power plant determining that the water level in the steam generator is low, triggering a reactor trip and potentially preventing continued operation.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a water level control method and a water level control device that can prevent the water level in a steam generator from suddenly dropping during steam dump. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a water level control method according to one aspect of the present disclosure includes a turbine governor valve provided in a steam pipe connecting a steam generator and a steam turbine, a turbine bypass valve provided in a turbine bypass pipe connecting the steam pipe to a condenser, a steam relief valve provided in the steam pipe, and a feedwater valve provided in a feedwater pipe that supplies secondary coolant to the steam generator, and in a nuclear power generation facility that generates power using the steam turbine by generating steam from the secondary coolant through heat exchange between the secondary coolant inside the steam generator and the primary coolant of a reactor cooling system, when the water level inside the steam generator drops after the turbine governor valve is closed, at least one of opening the steam relief valve and increasing the opening of the feedwater valve is performed.

[0007] In order to achieve the above-mentioned object, a water level control device according to one aspect of the present disclosure includes a turbine governor valve provided in a steam pipe connecting a steam generator and a steam turbine, a turbine bypass valve provided in a turbine bypass pipe connecting the steam pipe to a condenser, a steam relief valve provided in the steam pipe, and a feedwater valve provided in a feedwater pipe that supplies secondary coolant to the steam generator, and in a nuclear power generation facility that generates power using the steam turbine by generating steam from the secondary coolant through heat exchange between the secondary coolant inside the steam generator and the primary coolant of a reactor cooling system, the water level control device outputs at least one of an opening operation signal to the steam relief valve and an opening degree increase operation signal to the feedwater valve upon detection of a drop in the water level inside the steam generator based on a closing operation signal of the turbine governor valve. [Effects of the Invention]

[0008] The present disclosure can prevent a sudden drop in the water level in the steam generator during a steam dump. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a nuclear power plant. [Figure 2]FIG. 2 is a control block diagram of the water level control device according to the embodiment. [Figure 3] FIG. 3 is a flowchart of the water level control method according to the embodiment. [Figure 4] FIG. 4 is an explanatory diagram of the operation of the water level control device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0011] As shown in Fig. 1, a nuclear power plant 1 has a nuclear reactor 2. For example, a pressurized water reactor (PWR) is used as the nuclear reactor 2. The nuclear power plant 1 using this pressurized water reactor 2 is made up of a reactor cooling system (primary cooling system) 100 including the nuclear reactor 2, and a turbine system (secondary cooling system) 200 that exchanges heat with the reactor cooling system 100. Primary coolant flows through the reactor cooling system 100, and secondary coolant flows through the turbine system 200.

[0012] The reactor coolant system 100 has a steam generator 4 connected to the reactor 2 via a cold leg 3a and a hot leg 3b. The hot leg 3b is provided with a pressurizer 5, and the cold leg 3a is provided with a primary coolant pump 6. The reactor 2, the cold leg 3a, the hot leg 3b, the steam generator 4, the pressurizer 5, and the primary coolant pump 6 are housed in a reactor containment vessel 7.

[0013] As described above, the reactor 2 is a pressurized water reactor, and its interior is filled with a primary coolant. The primary coolant is light water with boron dissolved therein, which is used as a neutron moderator. The reactor 2 also contains a number of fuel assemblies 8, each of which is fitted with a number of removable control rods 9 that control the nuclear fission of the fuel assembly 8.

[0014] A series of operations in the reactor coolant system 100 of the nuclear power plant 1 will be described. When nuclear fission is caused in the fuel assemblies 8 while the nuclear fission reaction is controlled by the control rods 9 in the reactor 2, thermal energy is generated by the nuclear fission. This thermal energy heats the primary coolant in the reactor 2, and the heated primary coolant is sent to the steam generator 4 via the hot leg 3b by the primary coolant pump 6. The high-temperature primary coolant passing through the hot leg 3b is pressurized by the pressurizer 5 to suppress boiling, and flows into the steam generator 4 in a high-temperature, high-pressure state. The high-temperature, high-pressure primary coolant that flows into the steam generator 4 is cooled by heat exchange with the secondary coolant, and the cooled primary coolant is sent to the reactor 2 via the cold leg 3a by the primary coolant pump 6. The cooled primary coolant then flows into the reactor 2, cooling the reactor 2. In this manner, the primary coolant circulates between the reactor 2 and the steam generator 4.

[0015] The turbine system 200 is disposed outside the reactor containment vessel 7 and includes a steam turbine 12 connected to the steam generator 4 of the reactor cooling system 100 via a steam pipe 11, a condenser 13 connected to the steam turbine 12, and a feedwater pump 15 installed in a feedwater pipe 14 connecting the condenser 13 and the steam generator 4. A generator 16 is connected to the steam turbine 12.

[0016] The steam pipe 11 is connected to the cooling pipe 17 of the condenser 13 via a turbine bypass pipe 40. A turbine bypass valve 41 is provided on the turbine bypass pipe 40. A turbine governor valve 42 is provided on the steam pipe 11 downstream of where the turbine bypass pipe 40 is connected and immediately before where the steam pipe 11 is connected to the steam turbine 12. A steam relief pipe 44 having a steam relief valve 43 and capable of being opened to the atmosphere is provided on the steam pipe 11 upstream of where the turbine bypass pipe 40 is connected. A feedwater valve 45 is provided on the feedwater pipe 14 downstream of the feedwater pump 15.

[0017] A series of operations in the turbine system 200 of the nuclear power plant 1 will be described. When steam flows from the steam generator 4 into the steam turbine 12 via the steam pipe 11, the steam turbine 12 rotates. As the steam turbine 12 rotates, the generator 16 connected to the steam turbine 12 generates electricity. After this, the steam flowing out from the steam turbine 12 flows into the condenser 13. The condenser 13 has a cooling pipe 17 disposed therein. One end of the cooling pipe 17 is connected to an intake pipe 18 for supplying cooling water (e.g., seawater), and the other end of the cooling pipe 17 is connected to a discharge pipe 19 for discharging the cooling water. The condenser 13 cools the steam flowing in from the steam turbine 12 using the cooling pipe 17, thereby returning the steam to a liquid. The liquid secondary coolant is sent to the steam generator 4 via the feedwater pipe 14 by the feedwater pump 15. The secondary coolant sent to the steam generator 4 exchanges heat with the primary coolant in the steam generator 4, thereby becoming steam again. The secondary coolant is supplied to the steam generator 4 via the feedwater pipe 14 and the feedwater pump 15 while the flow rate is controlled by the feedwater valve 45 .

[0018] The turbine governor valve 42 is open when normal power generation is being performed and is closed when power generation is not being performed. The turbine bypass valve 41 is closed when normal power generation is being performed, and is open when power generation is not being performed, for example, to prevent steam from being sent from the steam generator 4 to the steam turbine 12. When the turbine bypass valve 41 is open, steam from the steam generator 4 is sent through the turbine bypass pipe 40 to the cooling pipe 17 of the condenser 13 without passing through the steam turbine 12.

[0019] The nuclear power plant 1 also has a water level gauge 46 provided in the steam generator 4, a turbine inlet pressure gauge 47 provided at the inlet of the steam turbine 12, and a bypass flow meter 48 provided in the turbine bypass pipe 40. The water level gauge 46 is provided inside the steam generator 4 and measures the water level of the secondary coolant inside the steam generator 4. The water level gauge 46 measures the water level of the secondary coolant inside the steam generator 4, for example, by means of the pressure difference between the top and bottom inside the secondary system of the steam generator 4. The turbine inlet pressure gauge 47 is the inlet pressure of the steam turbine 12, and measures the steam pressure around the first stage stator blades, which are around the inlet of the steam turbine 12 (turbine first stage pressure). The bypass flow meter 48 measures the flow rate of the secondary coolant in the turbine bypass pipe 40.

[0020] As shown in Fig. 1, the water level control device 51 of the embodiment is provided in the above-described nuclear power plant 1. The water level control device 51 is a computer, and includes a storage unit 52 and a water level adjustment unit 53 as shown in Fig. 2.

[0021] The memory unit 52 is a memory that stores various information such as the calculation contents and programs of the water level adjustment unit 53, and includes at least one of, for example, a main memory device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), and an external memory device such as an HDD (Hard Disk Drive).

[0022] The water level adjustment unit 53 is a calculation device and includes a calculation circuit such as a CPU (Central Processing Unit). The water level adjustment unit 53 performs the processing shown in FIG. 3 by reading and executing a program (software) from the storage unit 52. The water level adjustment unit 53 may perform the processing using one CPU, or may be provided with multiple CPUs and perform the processing using those multiple CPUs. The water level adjustment unit 53 may also realize the processing using a hardware circuit. The program for the water level adjustment unit 53 saved in the storage unit 52 may be stored in a recording medium readable by the water level control device 51.

[0023] The water level adjustment unit 53 acquires the water level of the secondary coolant inside the steam generator 4, measured by the water level gauge 46. The water level adjustment unit 53 acquires the inlet pressure of the steam turbine 12, measured by the turbine inlet pressure gauge 47. The water level adjustment unit 53 acquires the flow rate of the secondary coolant in the turbine bypass pipe 40, measured by the bypass flow meter 48. The water level adjustment unit 53 receives a governor valve operation signal for opening and closing the turbine governor valve 42 from the nuclear power plant 1. The water level adjustment unit 53 receives a bypass valve operation signal for opening and closing the turbine bypass valve 41 from the nuclear power plant 1. The water level adjustment unit 53 receives a bypass valve open / close state signal from the limit switch of the turbine bypass valve 41. The water level adjustment unit 53 outputs a steam relief valve operation signal for opening and closing the steam relief valve 43. The water level adjustment unit 53 outputs a feedwater valve operation signal for opening and closing the feedwater valve 45. The water level adjustment unit 53 includes a timer that measures time based on the input and output of each signal.

[0024] A water level control method, which is the operation of the water level control device 51, will be described below with reference to FIGS.

[0025] In step S1, the water level control device 51 inputs a governor valve operation signal (governor valve opening operation signal) for closing the turbine governor valve 42 in the nuclear power generation facility 1. In step S1, the water level control device 51 receives information that the turbine governor valve 42 is to be closed in order to stop the supply of steam from the steam generator 4 to the steam turbine 12 in the nuclear power generation facility 1 and reduce the power generation output.

[0026] Next, in step S2, the water level control device 51 inputs a bypass valve operation signal for opening the turbine bypass valve 41 in the nuclear power plant 1. In step S2, the water level control device 51 obtains information that, due to the closing operation of the turbine governor valve 42 in the nuclear power plant 1, the turbine bypass valve 41 is to be opened to perform a steam dump in which excess steam that would otherwise flow from the steam generator 4 into the steam turbine 12 is sent to the condenser.

[0027] Next, in step S3, the water level control device 51 acquires the water level of the secondary coolant inside the steam generator 4 measured by the water level gauge 46, and determines whether the water level has dropped after step S2.

[0028] At the same time, in step S4, the water level control device 51 acquires the inlet pressure of the steam turbine 12 measured by the turbine inlet pressure gauge 47 and determines whether a sudden load decrease has occurred, causing a sudden decrease in the steam flow rate on the secondary system side from the steam generator 4 to the steam turbine 12. In step S4, if a sudden load decrease has occurred (step S4: Yes), the water level control device 51 can determine that the turbine governor valve 42 is in a closed state based on the governor valve operation signal input in step S1.

[0029] At the same time, in step S5, the water level control device 51 determines whether there is a malfunction in the opening operation of the turbine bypass valve 41. In step S5, the water level control device 51 can determine whether there is a malfunction in the opening operation of the turbine bypass valve 41 when the bypass valve open / close state signal from the limit switch is not in the open state (the open / close states do not match despite the input of the open operation signal) even after a certain time has elapsed since the input of a bypass valve operation signal (bypass valve open operation signal) that opens the turbine bypass valve 41 in step S2. Also, in step S5, the water level control device 51 can determine whether there is a malfunction in the opening operation of the turbine bypass valve 41 even when steam is not flowing through the turbine bypass pipe 40 by acquiring the flow rate of the secondary coolant in the turbine bypass pipe 40 measured by the bypass flow meter 48.

[0030] Next, if the water level control device 51 determines in step S3 that the water level has dropped (step S3: Yes), determines in step S4 that the load has suddenly decreased (step S4: Yes), and determines in step S5 that the opening operation of the turbine bypass valve 41 is faulty (step S5: Yes), then in step S6 it outputs an opening operation signal to the steam relief valve 43 and an opening increase operation signal to the feedwater valve 45.

[0031] In step S6, the water level control device 51 determines that the drop in the water level of the steam generator 4 in step S3 is due to a sudden load decrease caused by the closing operation of the turbine governor valve 42 in step S4 and a malfunction of the turbine bypass valve 41 in step S5, and then opens the steam relief valve 43 to release excess steam in the steam pipe 11 to the atmosphere, and increases the opening of the water supply valve 45 to increase the amount of water supplied to the steam generator 4 compared to normal operation.

[0032] In Fig. 4, solid line A shows the water level response of the steam generator 4 during a sudden load drop when water level control is performed by the water level control device 51 of the embodiment, and dashed line B shows the water level response when the water level control of the embodiment is not performed. As shown in Fig. 4, when the water level control of the embodiment is not performed, if the turbine bypass valve 41 malfunctions after the turbine governor valve 42 closes, the steam pressure increases, reducing voids inside the steam generator 4, causing the water level in the steam generator 4 to drop and potentially reach water level L, at which a reactor trip should be determined. In contrast, when the water level control of the embodiment is performed, if the turbine bypass valve 41 malfunctions after the turbine governor valve 42 closes, the steam relief valve 43 is opened to release excess steam in the steam pipe 11 to the atmosphere, and the opening of the feedwater valve 45 is increased to increase the amount of water fed to the steam generator 4. This suppresses the drop in the water level in the steam generator 4 and prevents it from reaching water level L, at which a reactor trip should be determined.

[0033] Next, in step S7, the water level control device 51 determines whether a predetermined time has elapsed after step S6.

[0034] Then, in step S8, after a predetermined time in step S6 (step S6: Yes), a closing operation signal is output to the steam relief valve 43, and a return operation signal is output to the water supply valve 45 to return it to the opening degree when the opening degree was increased, thereby terminating this control.

[0035] In step S8, the water level control device 51 determines that a predetermined time has elapsed in step S6, and returns the steam relief valve 43 to a closed state to stop the release of excess steam to the atmosphere, and returns the opening of the water supply valve 45 to its original position to restore the amount of water supplied to the steam generator 4 to that during steady-state operation.

[0036] If the water level has not dropped in step S3 (step S3: No), and if the turbine bypass valve 41 is not malfunctioning in opening in step S5 (step S5: No), the operation of the turbine bypass valve 41 is normal and there is no cause for a drop in the water level in the steam generator 4, so this control is terminated. Also, if there is no sudden drop in load in step S4 (step S4: No), the turbine governor valve 42 is not in the closed state, and there is no cause for a drop in the water level in the steam generator 4, so this control is terminated.

[0037] Here, in the water level control device 51 of the embodiment, it is preferable to make all judgments from step S3 to step S5, but step S6 may be performed based on at least the judgment of step S3 alone. Alternatively, in the water level control device 51 of the embodiment, step S6 may be performed based on the judgments of step S3, step S3, and step S6 from step S3 to step S5.

[0038] Furthermore, in the water level control device 51 of the embodiment, it is preferable to perform both the opening operation of the steam relief valve 43 and the operation of increasing the opening degree of the water supply valve 45 in step S6, but it is also possible to perform at least one of them.

[0039] Furthermore, in normal operation of the nuclear power plant 1, the steam relief valve 43 outputs an opening operation signal when the pressure in the steam pipe 11 exceeds a predetermined pressure for some reason. In this regard, in the water level control device 51 of the embodiment, if a drop in the water level of the steam generator 4 is determined in step S3, if a sudden load decrease is determined in step S4, or if a malfunction in the opening operation of the turbine bypass valve 41 is determined in step S5, an opening operation signal is output to the steam relief valve 43, and the valve is operated before the pressure in the steam pipe 11 reaches the above-mentioned predetermined pressure.

[0040] As described above, the water level control method of the embodiment is characterized by including a turbine governor valve 42 provided in the steam pipe 11 connecting the steam generator 4 and the steam turbine 12, a turbine bypass valve 41 provided in the turbine bypass pipe 40 connecting the steam pipe 11 to the condenser 13, a steam relief valve 43 provided in the steam pipe 11, and a feedwater valve 45 provided in the feedwater pipe 14 that supplies secondary coolant to the steam generator 4, and in a nuclear power generation facility 1 that generates power using the steam turbine 12 by generating steam from the secondary coolant through heat exchange between the secondary coolant inside the steam generator 4 and the primary coolant of the reactor cooling system 100, if the water level inside the steam generator 4 drops after the turbine governor valve 42 is closed, at least one of an opening operation of the steam relief valve 43 and an increasing opening operation of the feedwater valve 45 is performed.

[0041] According to this water level control method, if the water level inside the steam generator 4 drops when the turbine governor valve 42 is closed, at least one of opening the steam relief valve 43 and increasing the opening of the feedwater valve 45 is performed to suppress the drop in the water level in the steam generator 4. Therefore, according to this water level control method, it is possible to prevent a sudden drop in the water level in the steam generator 4 even if the turbine bypass valve 41 fails to open during a steam dump. As a result, according to this water level control method, unnecessary reactor trips can be avoided and the continuous operation capability (availability) of the nuclear power plant can be improved.

[0042] In addition, in the water level control method of the embodiment, when the water level inside the steam generator 4 drops and a sudden decrease in the load on the steam turbine 12 occurs, at least one of opening the steam relief valve 43 and increasing the opening degree of the water supply valve 45 is performed.

[0043] According to this water level control method, it is possible to determine that the turbine governor valve 42 has been closed due to a sudden decrease in the load on the steam turbine 12, and it is possible to determine that a drop in the water level inside the steam generator 4 has caused the turbine bypass valve 41 to malfunction in opening, so it is possible to determine whether to open the steam relief valve 43 and increase the opening of the feedwater valve 45.

[0044] In addition, in the water level control method of the embodiment, if the water level inside the steam generator 4 drops, the load on the steam turbine 12 suddenly decreases, and a malfunction occurs in the opening operation of the turbine bypass valve 41, at least one of the following is performed: opening the steam relief valve 43 or increasing the opening degree of the water supply valve 45.

[0045] According to this water level control method, it is possible to determine that the turbine governor valve 42 has been closed due to a sudden decrease in the load on the steam turbine 12, and it is possible to determine the possibility that the turbine bypass valve 41 has malfunctioned in opening due to a drop in the water level inside the steam generator 4. Furthermore, since it is possible to directly determine that the turbine bypass valve 41 has malfunctioned in opening, it is possible to more accurately determine whether the steam relief valve 43 should be opened and whether the feedwater valve 45 should be opened to increase its opening.

[0046] In addition, in the water level control method of the embodiment, if a discrepancy occurs in the open / closed state for a certain period of time after the opening operation of the turbine bypass valve 41, it is determined that the opening operation of the turbine bypass valve 41 is defective.

[0047] According to this water level control method, it is possible to reliably determine whether the turbine bypass valve 41 is malfunctioning.

[0048] Furthermore, in the water level control method of the embodiment, when the steam relief valve 43 is opened, the steam relief valve 43 is closed after a predetermined time has elapsed.

[0049] According to this water level control method, it is possible to prevent the water level in the steam generator 4 from suddenly dropping, while suppressing the amount of steam discharged by the steam relief valve 43.

[0050] Furthermore, in the water level control method according to the embodiment, when the opening degree of the water supply valve 45 is increased, the opening degree of the water supply valve 45 is returned to the increased opening degree after a predetermined time.

[0051] According to this water level control method, it is possible to prevent the water level in the steam generator 4 from dropping suddenly, while suppressing excessive water supply.

[0052] In addition, the water level control device 51 of the embodiment outputs at least one of an opening operation signal to the steam relief valve 43 and an opening increase operation signal to the feedwater valve 45 based on a closing operation signal of the turbine governor valve 42 and upon detection of a drop in the water level inside the steam generator 4.

[0053] In addition, when the water level control device 51 of the embodiment detects a drop in the water level inside the steam generator 4 and a sudden decrease in the load on the steam turbine 12, it outputs at least one of an opening operation signal to the steam relief valve 43 and an opening increase operation signal to the water supply valve 45.

[0054] In addition, the water level control device 51 of the embodiment detects a drop in the water level inside the steam generator 4, detects a sudden decrease in the load on the steam turbine 12, and if it detects a discrepancy in the opening / closing status for a certain period of time from the input of the opening operation signal of the turbine bypass valve 41, outputs at least one of an opening operation signal to the steam relief valve 43 and an opening increase operation signal to the feedwater valve 45.

[0055] Furthermore, when the water level control device 51 of the embodiment outputs an opening operation signal to the steam relief valve 43, it outputs a closing operation signal to the steam relief valve 43 after a predetermined time has elapsed.

[0056] Furthermore, when the water level control device 51 of the embodiment outputs an opening increase operation signal to the water supply valve 45, it outputs a return operation signal to return the water supply valve 45 to the opening degree at the time of the increased opening degree after a predetermined time.

[0057] These water level control devices 51 can realize the water level control method described above.

[0058] The present disclosure includes the following inventions. [Invention 1] a turbine governor valve provided in a steam pipe connecting the steam generator and the steam turbine; a turbine bypass valve provided in a turbine bypass pipe connecting the steam pipe to a condenser; a steam relief valve provided in the steam pipe; a feedwater valve provided in a feedwater pipe for supplying secondary coolant to the steam generator; Including, In a nuclear power plant that generates steam from the secondary coolant by heat exchange between the secondary coolant inside the steam generator and the primary coolant of a reactor cooling system, and generates power in the steam turbine, When the water level inside the steam generator drops after the turbine governor valve is closed, performing at least one of an opening operation of the steam relief valve and an increasing operation of the opening degree of the feedwater valve; Water level control method. [Invention 2] When the water level inside the steam generator drops and a sudden decrease in the load of the steam turbine occurs, performing at least one of an opening operation of the steam relief valve and an increasing operation of the opening degree of the feedwater valve; The water level control method according to Invention 1. [Invention 3] When the water level inside the steam generator drops, a sudden decrease in the load on the steam turbine occurs, and a malfunction occurs in the opening operation of the turbine bypass valve, performing at least one of an opening operation of the steam relief valve and an increasing operation of the opening degree of the feedwater valve; The water level control method according to Invention 1. [Invention 4] a case in which a discrepancy in the open / closed state occurs for a certain period of time after the opening operation of the turbine bypass valve is determined to be a malfunction in the opening operation of the turbine bypass valve; The water level control method according to Invention 3. [Invention 5] When the steam relief valve is opened, the steam relief valve is closed after a predetermined time. A water level control method according to any one of Inventions 1 to 4. [Invention 6] When the opening degree of the water supply valve is increased, the opening degree of the water supply valve is returned to the increased opening degree after a predetermined time. A water level control method according to any one of Inventions 1 to 4. [Invention 7] a turbine governor valve provided in a steam pipe connecting the steam generator and the steam turbine; a turbine bypass valve provided in a turbine bypass pipe connecting the steam pipe to a condenser; a steam relief valve provided in the steam pipe; a feedwater valve provided in a feedwater pipe for supplying secondary coolant to the steam generator; Including, In a nuclear power plant that generates steam from the secondary coolant by heat exchange between the secondary coolant inside the steam generator and the primary coolant of a reactor cooling system, and generates power in the steam turbine, and outputting at least one of an opening signal to the steam relief valve and an opening increase signal to the feedwater valve in response to detection of a drop in the water level inside the steam generator based on the closing signal to the turbine governor valve. Water level control device. [Invention 8] When a drop in the water level inside the steam generator and a sudden decrease in the load of the steam turbine are detected, outputting at least one of an opening operation signal to the steam relief valve and an opening degree increasing operation signal to the feedwater valve; The water level control device according to invention 7. [Invention 9] When a drop in the water level inside the steam generator is detected, a sudden decrease in the load of the steam turbine is detected, and a discrepancy in the open / close state for a certain period of time is detected from the input of the turbine bypass valve opening operation signal, outputting at least one of an opening operation signal to the steam relief valve and an opening degree increasing operation signal to the feedwater valve; The water level control device according to invention 7. [Invention 10] When the steam relief valve is opened, a closing operation signal is output to the steam relief valve after a predetermined time. A water level control device according to any one of inventions 7 to 9. [Invention 11] When the water supply valve is operated to increase its opening degree, a return operation signal is output after a predetermined time to return the water supply valve to the opening degree at the time of the increased opening degree. A water level control device according to any one of inventions 7 to 9. [Explanation of symbols]

[0059] 1. Nuclear power plants 4. Steam generator 11 Steam Pipe 12 Steam turbine 13 Condenser 14 Water supply pipe 40 Turbine bypass pipe 41 Turbine bypass valve 42 Turbine governor valve 43 Steam relief valve 45 Water supply valve 100 Reactor cooling system

Claims

1. a turbine governor valve provided in a steam pipe connecting the steam generator and the steam turbine; a turbine bypass valve provided in a turbine bypass pipe connecting the steam pipe to a condenser; a steam relief valve provided in the steam pipe; a feedwater valve provided in a feedwater pipe for supplying secondary coolant to the steam generator; Including, In a nuclear power plant that generates steam from the secondary coolant by heat exchange between the secondary coolant inside the steam generator and the primary coolant of a reactor cooling system, and generates power in the steam turbine, When the water level inside the steam generator drops after the turbine governor valve is closed, performing at least one of an opening operation of the steam relief valve and an increasing operation of the opening degree of the feedwater valve; Water level control method.

2. When the water level inside the steam generator drops and a sudden decrease in the load of the steam turbine occurs, performing at least one of an opening operation of the steam relief valve and an increasing operation of the opening degree of the feedwater valve; The water level control method according to claim 1 .

3. When the water level inside the steam generator drops, a sudden decrease in the load on the steam turbine occurs, and a malfunction occurs in the opening operation of the turbine bypass valve, performing at least one of an opening operation of the steam relief valve and an increasing operation of the opening degree of the feedwater valve; The water level control method according to claim 1 .

4. a case in which a discrepancy in the open / closed state occurs for a certain period of time after the opening operation of the turbine bypass valve is determined to be a malfunction in the opening operation of the turbine bypass valve; The water level control method according to claim 3.

5. When the steam relief valve is opened, the steam relief valve is closed after a predetermined time. The water level control method according to claim 1 .

6. When the opening degree of the water supply valve is increased, the opening degree of the water supply valve is returned to the increased opening degree after a predetermined time. The water level control method according to claim 1 .

7. a turbine governor valve provided in a steam pipe connecting the steam generator and the steam turbine; a turbine bypass valve provided in a turbine bypass pipe connecting the steam pipe to a condenser; a steam relief valve provided in the steam pipe; a feedwater valve provided in a feedwater pipe for supplying secondary coolant to the steam generator; Including, In a nuclear power plant that generates steam from the secondary coolant by heat exchange between the secondary coolant inside the steam generator and the primary coolant of a reactor cooling system, and generates power in the steam turbine, and outputting at least one of an opening signal to the steam relief valve and an opening increase signal to the feedwater valve in response to detection of a drop in the water level inside the steam generator based on the closing signal to the turbine governor valve. Water level control device.

8. When a drop in the water level inside the steam generator and a sudden decrease in the load of the steam turbine are detected, outputting at least one of an opening operation signal to the steam relief valve and an opening degree increasing operation signal to the feedwater valve; The water level control device according to claim 7.

9. When a drop in the water level inside the steam generator is detected, a sudden decrease in the load of the steam turbine is detected, and a discrepancy in the open / close state for a certain period of time is detected from the input of the turbine bypass valve opening operation signal, outputting at least one of an opening operation signal to the steam relief valve and an opening degree increasing operation signal to the feedwater valve; The water level control device according to claim 7.

10. When the steam relief valve is opened, a closing operation signal is output to the steam relief valve after a predetermined time. The water level control device according to claim 7.

11. When the water supply valve is operated to increase its opening degree, a return operation signal is output after a predetermined time to return the water supply valve to the opening degree at the time of the increased opening degree. The water level control device according to claim 7.

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