Steam generator water level control method and system after shutdown of a pressurized water reactor

Abstract

The present application relates to a method and system for controlling the steam generator water level after a pressurized water reactor (PWR) reactor shutdown. The system generates a steam generator water level set value and a steam generator feedwater flow rate signal during shutdown based on the thermal power load signal of the reactor core during shutdown; generates a shutdown steam generator water level control signal; executes the steam generator water level control logic; and switches the steam generator water level control logic to automatic control after a predetermined period of time. The system solves the problem of excessive steam generator water level deviation caused by thermal-hydraulic parameter disturbances after reactor shutdown under different initial states. By triggering the shutdown signal under different initial states and adopting a load-dependent control signal, the steam generator water level can be stably controlled for a period of time after shutdown, preventing the steam generator water level from being too high or too low and potentially damaging the reactor equipment. This prevents abnormal steam generator regulation after shutdown, improves the stability of the steam generator, and thereby improves the reliability of the equipment and the safety of the reactor.

Description

Technical Field

[0001] The present application relates to the field of nuclear power technology, and in particular to a method and system for controlling the water level of a steam generator after a pressurized water reactor is shut down. Background Art

[0002] The main feedwater flow control system is a critical system in pressurized water reactor (PWR) nuclear power plant design. It provides sufficient feedwater for the steam generator (SG) to extract heat from the primary coolant circuit, generating saturated steam for the secondary power plant. Furthermore, the saturated steam generator (SG) used in PWR nuclear power plant designs uses the main feedwater flow control system to control the SG water level near the set point, determined by load. This prevents transient water levels from flooding the dryer, increasing outlet steam humidity and damaging turbine blades. It also prevents the water level from falling too low, causing the primary coolant temperature to rise, resulting in insufficient core cooling and damage to the SG heat transfer tubes.

[0003] To accurately control feedwater flow under varying power operating conditions in pressurized water reactor (PWR) nuclear power plants, steam generator (SGR) water level mismatch and steam-water mismatch are typically used to calculate feedwater demand and adjust feedwater valves. However, traditional automatic water level control functions are designed for normal operation and lack specific SGR water level control methods and systems for reactor shutdown. These methods and systems focus more on valve operation and the overall control process.

[0004] That is, after the nuclear power plant triggers a shutdown, the reduction in nuclear power leads to a decrease in the heat exchange of the steam generator, and the water level of the steam generator shrinks rapidly, causing disturbances in the feedwater valve controlled by the steam generator. Abnormal adjustment of the feedwater flow may eventually cause damage to the reactor equipment and threaten the safety of the reactor. Summary of the Invention

[0005] Based on this, it is necessary to provide a method and system for controlling the water level of a steam generator after a pressurized water reactor is shut down.

[0006] In one embodiment, a method for controlling the water level of a steam generator after a pressurized water reactor shutdown comprises the steps of:

[0007] S400, generating a steam generator water level setting value and a steam generator feedwater flow rate signal during shutdown according to a thermal power load signal of the reactor core during shutdown;

[0008] S500, generating a shutdown steam generator water level control signal by using the shutdown steam generator water level set value and the steam generator feedwater flow signal;

[0009] S600, executing steam generator water level control logic using the shutdown steam generator water level control signal;

[0010] S700: After a predetermined time, the steam generator water level control logic is switched to automatic control.

[0011] The above-mentioned method for controlling the water level of a steam generator after shutdown of a pressurized water reactor is applicable to the control of a reactor using a saturated steam generator. It solves the problem of excessive deviation of the steam generator water level caused by disturbance of thermal-hydraulic parameters after shutdown of the reactor under different initial states. The method is applicable to shutdowns of reactors under various initial states. By triggering a shutdown signal under different initial states and adopting a control signal that varies with the load, the steam generator water level can be stably controlled for a period of time after shutdown, avoiding damage to reactor equipment caused by excessively high or low steam generator water levels. The method then switches back to automatic control, thereby avoiding abnormal adjustment of the steam generator after shutdown, improving the stability of the steam generator, and thereby improving the reliability of the equipment and the safety of the reactor.

[0012] In one embodiment, before step S400, the method for controlling the water level of a steam generator after a pressurized water reactor shutdown further includes: S300, when a reactor shutdown signal is generated, recording a thermal power load signal of the core when the reactor shutdown signal is generated.

[0013] In one embodiment, in step S300, a thermal power load signal of the core is recorded, and a reactor shutdown signal is used as a trigger logic signal;

[0014] When the trigger logic signal is true, recording the thermal power load signal of the core when the reactor shutdown signal is generated and continuously outputting the recorded thermal power load signal;

[0015] When the trigger logic signal is false, the output is abandoned, the input signal is used as the output signal, or the thermal power load signal of the core is continuously recorded in an iterative recording manner.

[0016] In one embodiment, in step S400, when the trigger logic signal is true, the continuously output thermal power load signal is transmitted to two independent function generators, and the two function generators query in a preset function table according to the thermal power load signal, and respectively obtain and output the steam generator water level setting value and the steam generator feed water flow signal corresponding to the thermal power load signal during shutdown.

[0017] In one embodiment, before step S300, the steam generator water level control method after the pressurized water reactor reactor is shut down includes: step S100, automatically controlling the steam generator water level; and in step S700, after switching the steam generator water level control logic to automatic control, returning to step S100.

[0018] In one embodiment, step S100 includes:

[0019] S110, when no reactor shutdown signal is generated, selecting a steam generator water level set value under normal operation and calculating the difference between the set value and the steam generator water level measurement signal to obtain a steam generator water level deviation;

[0020] S120, using the steam generator water level deviation, obtaining a water level deviation adjustment signal through a water level controller, and summing the signal with the steam flow in the pipeline to obtain a feed water flow demand signal for control calculation;

[0021] S130, selecting the water flow demand signal obtained by the control calculation and the water flow in the pipeline to obtain a water flow deviation signal by performing difference calculation;

[0022] S140, using the water flow deviation signal to obtain a water flow regulation signal through a flow controller;

[0023] S150: Control the water supply valve using the water supply flow rate adjustment signal.

[0024] In one embodiment, step S500 includes:

[0025] S510, when a reactor shutdown signal is generated, selecting the steam generator water level set value under shutdown, and calculating the difference between the set value and the steam generator water level measurement signal to obtain a steam generator water level deviation;

[0026] S520, using the steam generator water level deviation, obtaining a water level deviation adjustment signal through a water level controller, and summing the signal with the steam flow in the pipeline to obtain a feedwater flow demand signal for control calculation for automatic control;

[0027] S530, selecting the steam generator feedwater flow signal and the feedwater flow in the pipeline and performing a difference calculation to obtain a feedwater flow deviation signal;

[0028] S540, using the feedwater flow deviation signal to obtain a shutdown steam generator water level control signal through a flow controller;

[0029] Furthermore, in step S600, the shutdown steam generator water level control signal is used to execute the steam generator water level control logic to control the feedwater valve.

[0030] In one embodiment, in step S500, a signal of a downstream feedwater flow rate is further used to generate a shutdown steam generator water level control signal.

[0031] In one embodiment, in step S700, a trigger that lasts for a predetermined time is used to switch the steam generator water level control logic to automatic control.

[0032] In one embodiment, a steam generator water level control system for a pressurized water reactor after shutdown includes:

[0033] a thermal power load signal recording module, which records the thermal power load signal of the core when the reactor shutdown signal is generated;

[0034] A signal generation module generates a steam generator water level setting value and a steam generator feedwater flow signal during shutdown according to the thermal power load signal of the reactor core during shutdown;

[0035] a signal processing module, which generates a shutdown steam generator water level control signal by using the shutdown steam generator water level set value and the steam generator feed water flow signal;

[0036] a control logic module, which executes steam generator water level control logic using the shutdown steam generator water level control signal;

[0037] The switching control module switches the steam generator water level control logic to automatic control after a predetermined time.

[0038] In one embodiment, the switching control module is a timing trigger. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 1 is a flow chart of an embodiment of a method for controlling the water level of a steam generator after a pressurized water reactor shutdown as described in the present application.

[0041] Figure 2 This is a flow chart of another embodiment of the method for controlling the water level of a steam generator after a pressurized water reactor shutdown described in the present application.

[0042] Figure 3 This is a flow chart of another embodiment of the method for controlling the water level of a steam generator after a pressurized water reactor shutdown described in the present application.

[0043] Figure 4 This is a schematic diagram of the principle of generating the steam generator water level set value and feed water flow rate after the shutdown of another embodiment of the steam generator water level control method after the shutdown of the pressurized water reactor reactor described in this application.

[0044] Figure 5This is a flow chart of another embodiment of the method for controlling the water level of a steam generator after a pressurized water reactor shutdown described in the present application.

[0045] Figure 6 This is a schematic diagram showing the principle of a steam generator water level control scheme triggered by a shutdown signal according to another embodiment of the method for controlling the steam generator water level after shutdown of a pressurized water reactor described in this application.

[0046] Figure 7 for Figure 6 Schematic diagram of main physical quantities of the illustrated embodiment.

[0047] Figure 8 This is a schematic diagram of thermal power changes at different powers after shutdown of another embodiment of the method for controlling the water level of a steam generator after shutdown of a pressurized water reactor described in this application. DETAILED DESCRIPTION

[0048] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0049] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it may be directly on the other component or there may be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of this application are for illustrative purposes only and do not represent the only implementation method.

[0050] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0051] In this application, unless otherwise expressly specified or limited, a first feature being “above” or “below” a second feature may mean that the first feature is directly in contact with the second feature, or that the first feature and the second feature are indirectly in contact through an intermediate medium. Furthermore, a first feature being “above,” “above,” or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below,” “below,” or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0052] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more of the relevant listed items.

[0053] The present application discloses a method and system for controlling the water level of a steam generator after a pressurized water reactor (PWR) reactor shutdown, which includes some or all of the technical features of the following embodiments; for example, the method for controlling the water level of a steam generator after a PWR reactor shutdown includes some or all of the following steps. In one embodiment of the present application, a method for controlling the water level of a steam generator after a PWR reactor shutdown includes the following steps: generating a shutdown steam generator water level set value and a steam generator feedwater flow signal based on a thermal power load signal of the core during shutdown; generating a shutdown steam generator water level control signal using the shutdown steam generator water level set value and the steam generator feedwater flow signal; executing a steam generator water level control logic using the shutdown steam generator water level control signal; and switching the steam generator water level control logic to automatic control after a predetermined time. The above-mentioned method for controlling the water level of a steam generator after shutdown of a pressurized water reactor is applicable to the control of a reactor using a saturated steam generator. It solves the problem of excessive deviation of the steam generator water level caused by disturbances in thermal-hydraulic parameters after shutdown of the reactor under different initial states. The method is applicable to shutdowns of reactors under various initial states. By triggering a shutdown signal under different initial states and adopting a control signal that varies with the load, the steam generator water level can be stably controlled for a period of time after shutdown, avoiding damage to reactor equipment caused by excessively high or low steam generator water levels. The method then switches back to automatic control, thereby avoiding abnormal adjustment of the steam generator after shutdown, improving the stability of the steam generator, and thus improving the reliability of the equipment and the safety of the reactor.

[0054] The design concept of each embodiment of the present application is to make a record before the shutdown, and use the steam generator water level setting value and the steam generator feed water flow signal to control the shutdown, and then automatically control it in the original way after returning to normal. In one embodiment, a method for controlling the steam generator water level after the shutdown of a pressurized water reactor is as follows: Figure 1 As shown, it includes the following steps: S400, generating a steam generator water level setting value and a steam generator feed water flow signal under shutdown according to the thermal power load signal of the core during shutdown; S500, generating a shutdown steam generator water level control signal using the shutdown steam generator water level setting value and the steam generator feed water flow signal; S600, executing the steam generator water level control logic using the shutdown steam generator water level control signal; S700, switching the steam generator water level control logic to automatic control after a predetermined time. Such a design can be used as an automatic steam generator water level control solution to cope with abnormal operating conditions, and is suitable for steam generator water level control after shutdown of a pressurized water reactor. Figure 2 When the reactor shutdown signal is generated, the thermal power signal at the time of the shutdown signal is recorded through the memory module. The unit of the thermal power signal is load % FP, ranging from 0% FP to 100% FP, representing the load at the time of shutdown. The signal is input into two function generators to obtain the steam generator feedwater flow and steam generator water level set values under shutdown, respectively. These are used as inputs in the steam generator water level control logic. After a period of time, the steam generator water level control logic switches back to automatic control according to the set time. This effectively addresses the phenomenon of excessive steam generator water level deviation caused by thermal-hydraulic parameter disturbances after reactor shutdown under different initial states, avoids the damage to reactor equipment caused by excessively high or low steam generator water levels, and improves the stability of the steam generator.

[0055] In one embodiment, before step S400, the steam generator water level control method after the pressurized water reactor reactor is shut down further includes: S300, when the reactor shutdown signal is generated, recording the thermal power load signal of the core when the reactor shutdown signal is generated. In one embodiment, a steam generator water level control method after the pressurized water reactor reactor is shut down is as follows: Figure 3As shown, the method includes the following steps: S300, when a reactor shutdown signal is generated, recording the thermal power load signal of the reactor core at the time of the shutdown signal; S400, generating a shutdown steam generator water level set value and a steam generator feedwater flow rate signal based on the shutdown thermal power load signal; S500, generating a shutdown steam generator water level control signal using the shutdown steam generator water level set value and the steam generator feedwater flow rate signal; S600, executing the steam generator water level control logic using the shutdown steam generator water level control signal; and S700, switching the steam generator water level control logic to automatic control after a predetermined time. The remaining embodiments are similar and are not described in detail here.

[0056] Based on the consideration of convenient control, in one embodiment, in step S300, the thermal power load signal of the core is recorded, and the reactor shutdown signal is used as the trigger logic signal; when the trigger logic signal is true, the thermal power load signal of the core when the reactor shutdown signal is generated is recorded and the recorded thermal power load signal is continuously output; when the trigger logic signal is false, the output is abandoned, the input signal is used as the output signal, or the thermal power load signal of the core is continuously recorded in an iterative recording manner. In one embodiment, in step S400, when the trigger logic signal is true, the continuously output thermal power load signal is transmitted to two independent function generators, and the two function generators query in a preset function table according to the thermal power load signal, and respectively obtain and output the shutdown steam generator water level setting value and the steam generator feed water flow signal corresponding to the thermal power load signal. Further, as Figure 4 As shown in the figure, after obtaining the steam generator water level setpoint and steam generator feedwater flow rate after shutdown at different initial loads, for the trigger logic signal on the right, the memory module records the current input signal when the trigger logic signal is true and continuously outputs the recorded signal. When the trigger logic signal is false, the memory function is canceled and the output signal is the input signal. When the reactor protection system's shutdown signal is triggered, the memory module records the reactor's thermal power signal at the time of shutdown to determine the initial state of the reactor unit at that time and transmits this signal to two independent function generators. Based on the input signal, the function generators query a pre-set function table to obtain a signal and output the steam generator water level setpoint and feedwater flow rate used for control at that time.

[0057] In one embodiment, before step S300, the steam generator water level control method after the pressurized water reactor reactor is shut down includes: step S100, automatically controlling the steam generator water level; and in step S700, after the steam generator water level control logic is switched to automatic control, returning to step S100. In one embodiment, a steam generator water level control method after the pressurized water reactor reactor is shut down is as follows: Figure 5As shown, it includes the following steps: step S100, automatically controlling the steam generator water level; S300, when a reactor shutdown signal is generated, recording the thermal power load signal of the core when the reactor shutdown signal is generated; S400, generating a shutdown steam generator water level set value and a steam generator feed water flow signal according to the thermal power load signal of the core when the reactor is shutdown; S500, generating a shutdown steam generator water level control signal using the shutdown steam generator water level set value and the steam generator feed water flow signal; S600, executing the steam generator water level control logic using the shutdown steam generator water level control signal; S700, switching the steam generator water level control logic to automatic control after a predetermined time, and returning to step S100 for execution.

[0058] In one embodiment, step S100 includes: S110, when no reactor shutdown signal is generated, selecting the steam generator water level set value under normal operation, and calculating the difference between the steam generator water level measurement signal and the steam generator water level deviation; S120, using the steam generator water level deviation, obtaining a water level deviation adjustment signal through a water level controller, and obtaining a feed water flow demand signal as a control calculation by summing the signal with the steam flow in the pipeline; S130, selecting the feed water flow demand signal of the control calculation and the feed water flow in the pipeline by calculating the difference to obtain a feed water flow deviation signal; S140, using the feed water flow deviation signal to obtain a feed water flow adjustment signal through a flow controller; S150, using the feed water flow adjustment signal to control the feed water valve.

[0059] Furthermore, in one embodiment, the shutdown steam generator water level control signal is generated as follows: Figure 6As shown, the shutdown steam generator water level control signal is generated by a trigger. This signal is false when no shutdown signal is present. The trigger inputs a reactor shutdown signal from the protection system and a module with a delay signal. When a shutdown signal is generated, the signal in the delay module becomes false. At this point, the shutdown steam generator water level control signal becomes true, switching to the shutdown steam generator water level control mode. After the time set by the delay module, the delay module signal changes from false to true, the shutdown steam generator water level control signal becomes false, and the shutdown steam generator water level control mode switches to automatic control mode. When no shutdown signal is present, the shutdown steam generator water level control signal becomes false. Selector 1 selects the steam generator water level set value under normal operation. This is then combined with the steam generator water level measurement signal through a difference calculation module to obtain the steam generator water level deviation. A water level deviation adjustment signal is generated by a water level controller and summed with the steam flow rate in the pipeline to form the feedwater flow demand signal for control calculation. The water level controller can be comprised of a proportional-integral-differential-PID module. In the absence of a shutdown signal, selector 2 selects the feedwater flow demand signal of the control calculation and the feedwater flow in the pipeline to generate a feedwater flow deviation signal. This signal is used to obtain a feedwater flow adjustment signal through a flow controller and is used for valve control. The flow controller is composed of a proportional-integral-differential-PID module. When the shutdown signal is generated, the shutdown steam generator water level control signal is true, and selector 1 switches to the steam generator water level setting value under shutdown, and selector 2 switches to the feedwater flow under shutdown, which is used for the calculation of the control logic. Flow measurement is as follows: Figure 7 As shown, the steam flow is measured at the steam outlet of the steam generator, and the feed water flow is measured before the water inlet of the steam generator. This makes it easy to control the feed water flow of the steam generator through the feed water regulating valve, and to perform work on the steam turbine by controlling the steam flow.

[0060] Specifically, in one embodiment, step S500 includes: S510, when a reactor shutdown signal is generated, selecting the steam generator water level set value under shutdown, and calculating the difference between the steam generator water level measurement signal and the steam generator water level deviation; S520, using the steam generator water level deviation, obtaining a water level deviation adjustment signal through a water level controller, and calculating the sum with the steam flow in the pipeline to obtain a feedwater flow demand signal as a control calculation for automatic control; S530, selecting the steam generator feedwater flow signal and the feedwater flow in the pipeline to obtain a feedwater flow deviation signal through a difference calculation; S540, using the feedwater flow deviation signal to obtain a shutdown steam generator water level control signal through a flow controller; and, in step S600, using the shutdown steam generator water level control signal to execute the steam generator water level control logic to perform feedwater valve control. Furthermore, in step S510, after calculating the steam generator water level deviation, the steam generator water level will rapidly contract due to changes in steam generator pressure after the reactor is shut down. The selected steam generator water level setpoint matches the contracted steam generator water level, preventing excessive feedwater flow rate adjustment caused by an excessively large steam generator water level deviation signal. Furthermore, in step S520 or before step S520, before the pressurized water reactor is shut down, the steam generator feedwater flow rate is calculated using automatic control. Alternatively, in one embodiment, in step S500, a signal downstream of the feedwater flow rate is also used to generate a shutdown steam generator water level control signal. This design is suitable for controlling reactors using saturated steam generators and for reactor shutdowns under different initial conditions. By using a load-dependent control signal to trigger the shutdown signal under different initial conditions, the steam generator water level can be stably controlled for a period of time after the reactor is shut down, avoiding abnormal steam generator adjustment after shutdown and improving equipment reliability and reactor safety.

[0061] In one embodiment, in step S700, a trigger that lasts for a predetermined time switches the steam generator water level control logic to automatic control. Furthermore, in step S300, upon determining that a reactor shutdown signal has been generated, a trigger is activated to initiate a timer or countdown. Furthermore, the predetermined time is adjusted based on testing and operation. This design facilitates adaptation to different initial states of the reactor core. The primary and secondary circuits have significant differences in key thermal-hydraulic parameters. When the shutdown signal is generated, the reactor undergoes a series of actions. During this process, there may be a mismatch in thermal loads between the primary and secondary circuits, resulting in significant disturbances in thermal-hydraulic parameters. As a critical device for heat transfer between the primary and secondary circuits, the steam generator can experience excessively high or low water levels during system dynamics at the time of shutdown. Determining the water level setpoint signal and feedwater flow rate signal for steam generator water level control based on different initial states allows for meeting the heat removal requirements of the reactor after shutdown at different loads, ensuring the safety of the reactor and steam generator equipment.

[0062] Furthermore, the following is a test description of the steam generator water level control method after the PWR reactor shutdown: first, theoretical analysis and estimation are performed, then system program calculation and analysis are performed, then the correction function is calibrated through experiments, and finally, the method is put into test operation.

[0063] The theoretical valuation is explained as follows: For different nuclear reactors, there are differences in core power and main pump heat. The heat within 100 seconds after shutdown under different initial states will also be different. Theoretical analysis methods can be used to analyze thermal parameters such as reactor thermal power and main pump heat under different initial states, and obtain the initial thermal power that changes with reactor power, and provide sufficient feed water flow after shutdown.

[0064] The system program analysis is explained as follows: In the design process of a nuclear reactor, a thermal-hydraulic system program is usually used for simulation analysis, and the decay heat after shutdown is analyzed through shutdown transient analysis; among them, the thermal-hydraulic system program is a program used to calculate the steady-state and transient changes of reactor parameters such as heat, fluid, and nuclear power.

[0065] The test calibration is described as follows: the post-shutdown feedwater flow demand curve is analyzed using a system program, and a shutdown test is conducted to verify the curve, adjusting the feedwater flow for different loads based on the actual project conditions.

[0066] The system program is used to analyze the thermal power change process after shutdown at different powers, and the test curve is obtained as follows: Figure 8 As shown, the time-averaged method is used to determine the feedwater flow rate required after the shutdown of the pressurized water reactor at different initial powers, and it can be determined that the steam generator water level control method after the pressurized water reactor shutdown truly reflects the steam generator water level after the pressurized water reactor shutdown; Figure 8The curves from bottom to top show the time-dependent changes in post-shutdown thermal power for 15%, 30%, 50%, 70%, and 100% thermal power, respectively. This design, by setting the steam generator water level and feedwater flow rate in response to the thermal power load during shutdown, selects different steam generator water level setpoints and feedwater flow rates for control based on different initial states. Furthermore, a trigger that lasts for a certain period of time switches between the shutdown steam generator water level control mode and automatic control. This ensures stable steam generator water level control for a period of time after shutdown, preventing abnormal steam generator regulation after shutdown and improving equipment reliability and reactor safety.

[0067] In one embodiment, a steam generator water level control system after a pressurized water reactor reactor is shut down is implemented using the steam generator water level control method after a pressurized water reactor reactor is shut down as described in any embodiment; that is, the steam generator water level control system after a pressurized water reactor reactor is shut down has corresponding functional modules for executing the steam generator water level control method after a pressurized water reactor reactor is shut down as described in any embodiment. In one embodiment, a steam generator water level control system for a pressurized water reactor after shutdown includes: a thermal power load signal recording module, which records the thermal power load signal of the core at the time of the reactor shutdown signal generation; a signal generation module, which generates a shutdown steam generator water level set value and a steam generator feedwater flow signal based on the shutdown core thermal power load signal; a signal processing module, which uses the shutdown steam generator water level set value and the steam generator feedwater flow signal to generate a shutdown steam generator water level control signal; a control logic module, which uses the shutdown steam generator water level control signal to execute the steam generator water level control logic; and a switching control module, which switches the steam generator water level control logic to automatic control after a predetermined time. The remaining embodiments are similar and are not described in detail here. In one embodiment, the switching control module is a timer trigger. The steam generator water level control system after shutdown of a pressurized water reactor is suitable for controlling reactors using saturated steam generators. It solves the problem of excessive deviation of the steam generator water level caused by disturbances in thermal-hydraulic parameters after shutdown of the reactor under different initial states. The system is applicable to reactor shutdowns under various initial states. By triggering a shutdown signal under different initial states and adopting a control signal that varies with the load, the steam generator water level can be stably controlled for a period of time after shutdown, avoiding damage to reactor equipment caused by excessively high or low steam generator water levels. The system then switches back to automatic control, thereby avoiding abnormal adjustment of the steam generator after shutdown, improving the stability of the steam generator, and thereby improving the reliability of the equipment and the safety of the reactor.

[0068] It should be noted that other embodiments of the present application also include a method and system for controlling the water level of a steam generator after a pressurized water reactor shutdown, which is formed by combining the technical features in the above embodiments.

[0069] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0070] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of patent protection for the present application shall be determined by the appended claims.

Claims

1. A method for controlling the water level of a steam generator after a pressurized water reactor shutdown, characterized in that: Including steps: S100, automatically controls the steam generator water level; S300, when a reactor shutdown signal is generated, recording a thermal power load signal of the core when the reactor shutdown signal is generated; S400, generating a steam generator water level setting value and a steam generator feedwater flow rate signal during shutdown according to a thermal power load signal of the reactor core during shutdown; S500, generating a shutdown steam generator water level control signal by using the shutdown steam generator water level set value and the steam generator feedwater flow signal; S600, executing steam generator water level control logic using the shutdown steam generator water level control signal; S700, after a predetermined time, the steam generator water level control logic is switched to automatic control, and the process returns to step S100; Wherein, step S100 includes: S110, when no reactor shutdown signal is generated, selecting a steam generator water level set value under normal operation and calculating the difference between the set value and the steam generator water level measurement signal to obtain a steam generator water level deviation; S120, using the steam generator water level deviation, obtaining a water level deviation adjustment signal through a water level controller, and summing the signal with the steam flow in the pipeline to obtain a feed water flow demand signal for control calculation; S130, selecting the water flow demand signal obtained by the control calculation and the water flow in the pipeline to obtain a water flow deviation signal by performing difference calculation; S140, using the water flow deviation signal to obtain a water flow regulation signal through a flow controller; S150: Control the water supply valve using the water supply flow rate adjustment signal.

2. The method for controlling the water level of a steam generator after a pressurized water reactor shutdown according to claim 1, wherein: In step S300, the thermal power load signal of the core is recorded, and the reactor shutdown signal is used as a trigger logic signal; When the trigger logic signal is true, recording the thermal power load signal of the core when the reactor shutdown signal is generated and continuously outputting the recorded thermal power load signal; When the trigger logic signal is false, the output is abandoned, the input signal is used as the output signal, or the thermal power load signal of the core is continuously recorded in an iterative recording manner.

3. The method for controlling the water level of a steam generator after a pressurized water reactor shutdown according to claim 2, wherein: In step S400, when the trigger logic signal is true, the continuously output thermal power load signal is transmitted to two independent function generators. The two function generators query in a preset function table according to the thermal power load signal, and respectively obtain and output the steam generator water level setting value and the steam generator feed water flow signal corresponding to the thermal power load signal during shutdown.

4. The method for controlling the water level of a steam generator after a pressurized water reactor shutdown according to claim 1, wherein: Step S500 includes: S510, when a reactor shutdown signal is generated, selecting the steam generator water level set value under shutdown, and calculating the difference between the set value and the steam generator water level measurement signal to obtain a steam generator water level deviation; S520, using the steam generator water level deviation, obtaining a water level deviation adjustment signal through a water level controller, and summing the signal with the steam flow in the pipeline to obtain a feedwater flow demand signal for control calculation for automatic control; S530, selecting the steam generator feedwater flow signal and the feedwater flow in the pipeline and performing a difference calculation to obtain a feedwater flow deviation signal; S540, using the feedwater flow deviation signal to obtain a shutdown steam generator water level control signal through a flow controller; Furthermore, in step S600, the shutdown steam generator water level control signal is used to execute the steam generator water level control logic to control the feedwater valve.

5. The method for controlling the water level of a steam generator after a shutdown of a pressurized water reactor according to any one of claims 1 to 4, characterized in that: In step S500, a signal downstream of the feedwater flow is further used to generate a shutdown steam generator water level control signal; and / or, in step S700, a trigger lasting a predetermined time is used to switch the steam generator water level control logic to automatic control.

6. A steam generator water level control system for a pressurized water reactor after shutdown, characterized in that: The method for controlling the water level of a steam generator after a pressurized water reactor shutdown according to any one of claims 1 to 5 is adopted, wherein the steam generator water level control system after a pressurized water reactor shutdown comprises: a thermal power load signal recording module, which records the thermal power load signal of the core when the reactor shutdown signal is generated; A signal generation module generates a steam generator water level setting value and a steam generator feedwater flow signal during shutdown according to the thermal power load signal of the reactor core during shutdown; a signal processing module, which generates a shutdown steam generator water level control signal by using the shutdown steam generator water level set value and the steam generator feed water flow signal; a control logic module, which executes steam generator water level control logic using the shutdown steam generator water level control signal; The switching control module switches the steam generator water level control logic to automatic control after a predetermined time.

7. The steam generator water level control system after shutdown of a pressurized water reactor according to claim 6, characterized in that: The switching control module is a timing trigger.

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