A method and device for determining the capacity requirement of a passive residual heat removal system

Abstract

This application belongs to the field of pressurized water reactor nuclear power plant design technology, specifically relating to a method and apparatus for determining the capacity requirements of a passive residual heat removal system. The method includes: compiling a list of design basis accidents that the passive residual heat removal system must handle based on the design characteristics of the nuclear power plant; clarifying the effects of the passive residual heat removal system after each accident based on the design basis accident list; determining the limiting operating conditions of the passive residual heat removal system based on the clarified effects after each accident; analyzing the determined limiting operating conditions, conservatively considering initial operating conditions, reactor protection and control, and core-related assumptions, to determine the capacity requirements of the passive residual heat removal system under each limiting operating condition; and comprehensively considering the analysis results of the limiting operating conditions to determine a suitable capacity range for the passive residual heat removal system, providing support for the capacity design of passive residual heat removal systems in new nuclear power plants.

Description

Technical Field

[0001] This application belongs to the field of pressurized water reactor nuclear power plant design technology, specifically relating to a method and apparatus for determining the capacity requirements of a passive residual heat removal system. Background Technology

[0002] Traditional nuclear power plants use an auxiliary feedwater system as a dedicated safety facility to supply water to the secondary side of the steam generator during accident conditions to remove residual heat from the reactor core until the normal residual heat removal system (RHR) is allowed to operate. The auxiliary feedwater system supplies auxiliary feedwater to the steam generator using steam-driven and electric pumps. As active equipment, these pumps are affected by steam quality and power supply, which may lead to system failure. To improve the inherent safety of nuclear power plants and reduce the need for active equipment, new pressurized water reactor nuclear power plants are designed with a passive residual heat removal system to handle design basis accidents, with one passive residual heat removal series installed on the secondary side of the steam generator in each loop. Under design baseline accident conditions, the steam generated by the steam generator enters the steam pipe of the passive residual heat removal system on the secondary side, and then enters the tube side of the residual heat cooler to exchange heat with the cooling water in the accident cooling water tank. The steam transfers heat to the cooling water and is condensed into water. The condensate returns to the secondary side of the steam generator under the action of gravity, thereby removing the core residual heat and reducing the temperature and pressure of the primary loop to the level that allows the normal residual heat removal system (RHR) to be put into operation.

[0003] New nuclear power plants use passive residual heat removal systems as dedicated safety facilities. To address design basis accidents, corresponding requirements must be set for the capacity of these systems. If the passive residual heat removal system capacity is too small, core heat may not be able to dissipate, leading to temperature and pressure increases in the primary coolant loop, endangering core safety. If the passive residual heat removal system capacity is too large, primary coolant and pressure reduction may be implemented. Due to the negative reactivity of the moderator in pressurized water reactors, this could introduce positive reactivity into the reactor, causing core recriticality and potentially deviating from nucleation boiling, thus jeopardizing core safety. Summary of the Invention

[0004] The purpose of this application is to provide a method and apparatus for determining the capacity requirements of a passive waste heat removal system, thereby solving the problems caused by the passive waste heat removal system having too small or too large a capacity.

[0005] The technical solution to achieve the purpose of this application is as follows:

[0006] This application provides a method for determining the capacity requirement of a passive waste heat removal system, the method comprising:

[0007] Based on the design characteristics of nuclear power plants, a list of design baseline accidents that passive waste heat removal systems must address is compiled.

[0008] Based on the design baseline accident list, clarify the effect achieved by the passive waste heat removal system after each accident occurs;

[0009] Based on the clearly defined effects achieved by the passive waste heat removal system after each accident, determine the limiting operating conditions of the passive waste heat removal system.

[0010] The determined limiting conditions are analyzed, and conservative considerations are taken into account from the initial conditions, reactor protection and control, and core-related assumptions to determine the capacity requirements of the passive residual heat removal system under each limiting condition.

[0011] Based on the analysis of the limiting operating conditions, a suitable capacity range for the passive waste heat removal system is determined by comprehensive consideration.

[0012] Optionally, based on the design characteristics of the nuclear power plant, a list of design baseline accidents that the passive waste heat removal system must address is compiled, specifically including:

[0013] For nuclear power plants with a passive residual heat removal system on the secondary side of the steam generator, the corresponding design basis accidents in the event of a reduced secondary loop heat removal include: loss of non-emergency AC power to auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines.

[0014] When a secondary loop heat exhaust accident occurs, the corresponding design basis accidents include: accidental start-up of the passive waste heat exhaust system and main steam pipeline rupture.

[0015] In the event of a steam generator heat transfer tube rupture accident, the passive residual heat removal system should have sufficient capacity to remove core decay heat, establish pressure balance between the reactor primary loop and the secondary side of the steam generator, and prevent further leakage through the steam generator heat transfer tube.

[0016] The long-term heat removal requirements include: being able to smoothly bring the nuclear power plant to a state where the normal residual heat removal system is put into operation within a specific time; and during the cooling process, the rate of cooling and depressurization of the primary loop should not be too fast to avoid the reactor returning to criticality.

[0017] Optionally, the step of clarifying the effect achieved by the passive waste heat removal system after each accident, based on the design baseline accident list, specifically includes:

[0018] For accidents involving reduced heat removal from the secondary coolant loop, the passive residual heat removal system should be automatically activated to remove residual heat from the core, reducing the temperature and pressure of the primary coolant loop and preventing it from rising too high and affecting core safety. For Category II accidents, after the passive residual heat removal system is automatically activated, the integrity of the fuel cladding should be ensured, the pressure on the primary and secondary sides should not exceed the limits, and the release of radioactive materials should not exceed the prescribed limits. For Category IV accidents, the core geometry should be unaffected, core cooling should be guaranteed, and the release of radioactive materials should not exceed the prescribed limits.

[0019] For accidents involving increased heat release from the secondary coolant loop, the initial cause event leads to a decrease in temperature and pressure in the primary coolant loop, triggering a safety injection signal. This signal then triggers the automatic activation of the passive residual heat removal system. Due to the negative feedback effect of the moderator, the decrease in temperature and pressure in the primary coolant loop introduces positive reactivity into the reactor, posing a risk of repeated criticality. For Category II accidents, the integrity of the fuel cladding must be ensured, and the release of radioactive materials must not exceed the limits specified in GB 6249-2011. For Category IV accidents, the core geometry must be unaffected, and core cooling must be guaranteed. The release of radioactive materials must not exceed the specified limits, and the containment pressure must also be considered to ensure that it does not exceed the design limits.

[0020] In the event of a steam generator heat transfer tube rupture accident, leakage occurs from the primary loop to the secondary loop. Low pressurizer pressure triggers a safety injection signal, which in turn triggers the isolation of the main feedwater system and activates the passive residual heat removal system to remove residual heat from the reactor core. Once the pressures on the primary and secondary sides of the damaged steam generator are balanced, there will be no more leakage from the primary side to the secondary side. A steam generator heat transfer tube rupture accident is classified as a Category III condition, which allows for a small amount of fuel assembly damage, but the geometry of the reactor core must not be damaged to ensure core cooling, and the release of radioactive materials should not exceed the prescribed limits.

[0021] Long-term heat removal requires that the nuclear power plant be brought to a state where the normal residual heat removal system is put into operation within a specified time.

[0022] Optionally, the limiting conditions include: maximum capacity requirements, minimum capacity requirements, and requirements for other accidents;

[0023] The reactor safety will not be compromised when the passive waste heat removal system is at its maximum or minimum capacity.

[0024] This application embodiment also provides a device for determining the capacity requirement of a passive waste heat removal system, the device comprising:

[0025] The inventory compilation module is used to compile a list of design baseline accidents that the passive residual heat removal system must address, based on the design characteristics of the nuclear power plant.

[0026] The effect determination module is used to determine the effect achieved by the passive waste heat removal system after each accident, based on the design baseline accident list.

[0027] The operating condition determination module is used to determine the limiting operating conditions of the passive waste heat removal system based on the clearly defined effects achieved by the passive waste heat removal system after each accident.

[0028] The module is required to analyze the defined limiting conditions, taking conservative considerations from the initial operating conditions, reactor protection and control, and core-related assumptions, to determine the capacity requirements of the passive residual heat removal system under each limiting condition.

[0029] The range determination module is used to determine the appropriate capacity range of the passive waste heat removal system based on the analysis results of the limiting operating conditions.

[0030] Optionally, the list organization module is specifically used for:

[0031] For nuclear power plants with a passive residual heat removal system on the secondary side of the steam generator, the corresponding design basis accidents in the event of a reduced secondary loop heat removal include: loss of non-emergency AC power to auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines.

[0032] When a secondary loop heat exhaust accident occurs, the corresponding design basis accidents include: accidental start-up of the passive waste heat exhaust system and main steam pipeline rupture.

[0033] In the event of a steam generator heat transfer tube rupture accident, the passive residual heat removal system should have sufficient capacity to remove core decay heat, establish pressure balance between the reactor primary loop and the secondary side of the steam generator, and prevent further leakage through the steam generator heat transfer tube.

[0034] The long-term heat removal requirements include: being able to smoothly bring the nuclear power plant to a state where the normal residual heat removal system is put into operation within a specific time; and during the cooling process, the rate of cooling and depressurization of the primary loop should not be too fast to avoid the reactor returning to criticality.

[0035] Optionally, the effect determination module is specifically used for:

[0036] For accidents involving reduced heat removal from the secondary coolant loop, the passive residual heat removal system should be automatically activated to remove residual heat from the core, reducing the temperature and pressure of the primary coolant loop and preventing it from rising too high and affecting core safety. For Category II accidents, after the passive residual heat removal system is automatically activated, the integrity of the fuel cladding should be ensured, the pressure on the primary and secondary sides should not exceed the limits, and the release of radioactive materials should not exceed the prescribed limits. For Category IV accidents, the core geometry should be unaffected, core cooling should be guaranteed, and the release of radioactive materials should not exceed the prescribed limits.

[0037] For accidents involving increased heat release from the secondary coolant loop, the initial cause event leads to a decrease in temperature and pressure in the primary coolant loop, triggering a safety injection signal. This signal then triggers the automatic activation of the passive residual heat removal system. Due to the negative feedback effect of the moderator, the decrease in temperature and pressure in the primary coolant loop introduces positive reactivity into the reactor, posing a risk of repeated criticality. For Category II accidents, the integrity of the fuel cladding must be ensured, and the release of radioactive materials must not exceed the limits specified in GB 6249-2011. For Category IV accidents, the core geometry must be unaffected, and core cooling must be guaranteed. The release of radioactive materials must not exceed the specified limits, and the containment pressure must also be considered to ensure that it does not exceed the design limits.

[0038] In the event of a steam generator heat transfer tube rupture accident, leakage occurs from the primary loop to the secondary loop. Low pressurizer pressure triggers a safety injection signal, which in turn triggers the isolation of the main feedwater system and activates the passive residual heat removal system to remove residual heat from the reactor core. Once the pressures on the primary and secondary sides of the damaged steam generator are balanced, there will be no more leakage from the primary side to the secondary side. A steam generator heat transfer tube rupture accident is classified as a Category III condition, which allows for a small amount of fuel assembly damage, but the geometry of the reactor core must not be damaged to ensure core cooling, and the release of radioactive materials should not exceed the prescribed limits.

[0039] Long-term heat removal requires that the nuclear power plant be brought to a state where the normal residual heat removal system is put into operation within a specified time.

[0040] Optionally, the limiting conditions include: maximum capacity requirements, minimum capacity requirements, and requirements for other accidents;

[0041] The reactor safety will not be compromised when the passive waste heat removal system is at its maximum or minimum capacity.

[0042] The beneficial technical effects of this application are as follows:

[0043] This application provides a method and apparatus for determining the capacity requirements of a passive waste heat removal system. By reviewing the list of design basis accidents that the passive waste heat removal system must cope with, the effects achieved by the passive waste heat removal system after each accident are clarified, the corresponding limiting conditions are determined, the corresponding limiting condition analysis is carried out, and the capacity range of the passive waste heat removal system is determined, providing support for the capacity design of passive waste heat removal systems in new nuclear power plants. Attached Figure Description

[0044] Figure 1 This is a flowchart illustrating a method for determining the capacity requirement of a passive waste heat removal system, as provided in an embodiment of this application. Detailed Implementation

[0045] To enable those skilled in the art to better understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of this application, and not all of them. Based on the embodiments described in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] See Figure 1 The figure is a flowchart illustrating a method for determining the capacity requirement of a passive waste heat removal system according to an embodiment of this application.

[0047] This application provides a method for determining the capacity requirement of a passive waste heat removal system, including:

[0048] S101: Based on the design characteristics of nuclear power plants, compile a list of design baseline accidents that the passive residual heat removal system must address;

[0049] S102: Based on the design baseline accident list, clarify the effect achieved by the passive waste heat removal system after each accident occurs;

[0050] S103: Based on the clearly defined effects achieved by the passive waste heat removal system after each accident, determine the limiting operating conditions of the passive waste heat removal system;

[0051] S104: Analyze the determined limiting conditions, and conservatively consider the initial conditions, reactor protection and control, core-related assumptions, etc., to determine the capacity requirements of the passive residual heat removal system under each limiting condition.

[0052] S105: Based on the analysis results of the restricted operating conditions, a suitable capacity range for the passive waste heat removal system shall be determined by comprehensive consideration.

[0053] In some possible implementations of the embodiments of this application, step S101 specifically includes:

[0054] For nuclear power plants with a passive residual heat removal system on the secondary side of the steam generator, the corresponding design basis accidents in the event of a reduced secondary loop heat removal include: loss of non-emergency AC power to auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines.

[0055] When a secondary loop heat exhaust accident occurs, the corresponding design basis accidents include: accidental start-up of the passive waste heat exhaust system and main steam pipeline rupture.

[0056] In the event of a steam generator heat transfer tube rupture accident, the passive residual heat removal system should have sufficient capacity to remove core decay heat, establish pressure balance between the reactor primary loop and the secondary side of the steam generator, and prevent further leakage through the steam generator heat transfer tube.

[0057] The long-term heat removal requirements include: being able to smoothly bring the nuclear power plant to a state where the normal residual heat removal system is put into operation within a specific time; and during the cooling process, the rate of cooling and depressurization of the primary loop should not be too fast to avoid the reactor returning to criticality.

[0058] For nuclear power plants that have a passive waste heat removal system installed on the secondary side of the steam generator, the functional requirements for the design of the passive waste heat removal system are as follows:

[0059] (1) In the event of a secondary loop heat loss accident, the passive residual heat removal system can be automatically activated. Steam generated by the steam generator enters the tube side of the residual heat cooler for cooling, and the condensed water returns to the secondary side of the steam generator by gravity, fully cooling the reactor coolant and removing core heat. Corresponding design basis accidents include: loss of non-emergency AC power to power plant auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines.

[0060] (2) In the event of a secondary loop heat exhaust accident, the passive residual heat removal system should not exhaust excessive heat, and the reactor core should not be damaged. Corresponding design basis accidents include: accidental activation of the passive residual heat removal system and main steam pipe rupture.

[0061] (3) In the event of a steam generator heat transfer tube rupture accident, the passive residual heat removal system should have sufficient capacity to remove the core decay heat, so as to establish pressure balance between the reactor primary loop and the secondary side of the steam generator and prevent further leakage through the steam generator heat transfer tube.

[0062] (4) Long-term heat dissipation requirements

[0063] The long-term heat removal requirements include: being able to smoothly bring the nuclear power plant to a state where the normal residual heat removal system is put into operation within a specific time; and during the cooling process, the rate of cooling and depressurization of the primary loop should not be too fast to avoid the reactor returning to criticality.

[0064] In some possible implementations of the embodiments of this application, step S102 specifically includes:

[0065] For accidents involving reduced heat removal from the secondary coolant loop, the passive residual heat removal system should be automatically activated to remove residual heat from the core, reducing the temperature and pressure of the primary coolant loop and preventing it from rising too high and affecting core safety. For Category II accidents, after the passive residual heat removal system is automatically activated, the integrity of the fuel cladding should be ensured, the pressure on the primary and secondary sides should not exceed the limits, and the release of radioactive materials should not exceed the prescribed limits. For Category IV accidents, the core geometry should be unaffected, core cooling should be guaranteed, and the release of radioactive materials should not exceed the prescribed limits.

[0066] For accidents involving increased heat release from the secondary coolant loop, the initial cause event leads to a decrease in temperature and pressure in the primary coolant loop, triggering a safety injection signal. This signal then triggers the automatic activation of the passive residual heat removal system. Due to the negative feedback effect of the moderator, the decrease in temperature and pressure in the primary coolant loop introduces positive reactivity into the reactor, posing a risk of repeated criticality. For Category II accidents, the integrity of the fuel cladding must be ensured, and the release of radioactive materials must not exceed the limits specified in GB 6249-2011. For Category IV accidents, the core geometry must be unaffected, and core cooling must be guaranteed. The release of radioactive materials must not exceed the specified limits, and the containment pressure must also be considered to ensure that it does not exceed the design limits.

[0067] In the event of a steam generator heat transfer tube rupture accident, leakage occurs from the primary loop to the secondary loop. Low pressurizer pressure triggers a safety injection signal, which in turn triggers the isolation of the main feedwater system and activates the passive residual heat removal system to remove residual heat from the reactor core. Once the pressures on the primary and secondary sides of the damaged steam generator are balanced, there will be no more leakage from the primary side to the secondary side. A steam generator heat transfer tube rupture accident is classified as a Category III condition, which allows for a small amount of fuel assembly damage, but the geometry of the reactor core must not be damaged to ensure core cooling, and the release of radioactive materials should not exceed the prescribed limits.

[0068] Long-term heat removal requires that the nuclear power plant be brought to a state where the normal residual heat removal system is put into operation within a specified time.

[0069] (1) For accidents involving reduced heat removal from the secondary loop, the passive residual heat removal system should be automatically activated to remove residual heat from the reactor core, thereby reducing the temperature and pressure of the primary loop and preventing excessive rise in the primary loop temperature and pressure, which could affect the safety of the reactor core. For Class II accidents, such as loss of non-emergency AC power to auxiliary equipment or loss of normal feedwater flow, after the passive residual heat removal system is automatically activated, the integrity of the fuel cladding should be ensured, the pressure on the primary and secondary sides should not exceed the limits, and the release of radioactive materials should not exceed the limits specified in GB6249-2011. For Class IV accidents, such as feedwater system pipeline rupture accidents, the reactor core geometry should be ensured to remain unaffected, and core cooling should be guaranteed. The release of radioactive materials should not exceed the limits specified in GB6249-2011.

[0070] (2) For accidents involving increased heat release from the secondary coolant loop, the initial cause event leads to a decrease in temperature and pressure in the primary coolant loop, triggering a safety injection signal. This signal then triggers the automatic activation of the passive residual heat removal system. Due to the negative feedback effect of the moderator, the decrease in temperature and pressure in the primary coolant loop introduces positive reactivity into the reactor, posing a risk of repeated criticality. For Category II accidents, such as the accidental activation of the passive residual heat removal system, the integrity of the fuel cladding must be ensured, and the release of radioactive materials should not exceed the limits specified in GB 6249-2011. For Category IV accidents, such as the accident involving a ruptured main steam pipe, the core geometry must be unaffected, and core cooling must be guaranteed. The release of radioactive materials should not exceed the limits specified in GB 6249-2011, and the containment pressure must also be considered to ensure it does not exceed the design limits.

[0071] (3) In the event of a steam generator heat transfer tube rupture accident, leakage occurs from the primary loop to the secondary loop. Low pressurizer pressure triggers a safety injection signal, which in turn triggers the isolation of the main feedwater system and activates the passive residual heat removal system to remove residual heat from the reactor core. When the pressures on the primary and secondary sides of the damaged steam generator are balanced, there will be no more leakage from the primary side to the secondary side. The steam generator heat transfer tube rupture accident is classified as a Category III operating condition, which allows for a small amount of fuel assembly damage. However, the geometry of the reactor core must not be damaged to ensure core cooling, and the release of radioactive materials should not exceed the limits specified in GB6249-2011.

[0072] (4) Long-term heat removal requires that the nuclear power plant be brought to the state of normal waste heat removal system operation within a specified time.

[0073] In one example, the limiting conditions include: maximum capacity requirements, minimum capacity requirements, and requirements for other accidents;

[0074] The reactor safety will not be compromised when the passive waste heat removal system is at its maximum or minimum capacity.

[0075] In some possible implementations of the embodiments of this application, step S103 specifically includes:

[0076] (1) Maximum capacity requirement

[0077] When the passive residual heat removal system is at its maximum capacity, reactor safety is not compromised. However, in the event of a secondary coolant exhaust accident, the passive residual heat removal system can adversely affect reactor safety. Therefore, it is necessary to consider whether the passive residual heat removal system at its maximum capacity will not compromise reactor safety under a secondary coolant exhaust accident. Corresponding accidents include: main steam system accidental depressurization, accidental activation of the passive residual heat removal system, and main steam pipeline rupture.

[0078] (2) Minimum capacity requirements

[0079] When the passive residual heat removal system is at its minimum capacity, reactor safety will not be compromised. However, in the event of a secondary coolant reduction accident, the passive residual heat removal system, due to the removal of reactor residual heat, must be considered at its minimum capacity to ensure reactor safety. Corresponding accidents include loss of non-emergency AC power to plant auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines.

[0080] (3) Other accident requirements

[0081] The capacity of the passive waste heat removal system should be sufficient to remove reactor waste heat in the event of a steam generator heat transfer tube rupture accident. The initial power of the reactor and the operation of the main pump will affect the capacity of the passive waste heat removal system, so an analysis of the steam generator heat transfer tube rupture accident is required.

[0082] The capacity of the passive residual heat removal system must meet the long-term heat removal requirements of the reactor, be able to smoothly bring the nuclear power plant to the state of normal residual heat removal system operation within a specific time, and not cause the reactor to return to criticality due to excessively rapid cooling and depressurization rate of the primary loop, thus endangering reactor safety.

[0083] In some possible implementations of the embodiments of this application, step S104 takes a new type of nuclear power plant as an example, and the capacity range of the passive waste heat removal system under various restricted operating conditions is shown in Table 1 below.

[0084] Table 1 Capacity range of passive waste heat removal system under various limiting operating conditions

[0085]

[0086] The capacity requirement is the percentage of power discharged by the passive waste heat removal system relative to the reactor's rated power.

[0087] In some possible implementations of the embodiments of this application, step S105 takes a new type of nuclear power plant as an example. According to the capacity range of the passive waste heat removal system under each restricted operating condition in Table 1, the capacity of the passive waste heat removal system is less than 6%FP and greater than 2%FP. At the same time, considering other accident requirements, the capacity of the passive waste heat removal system is determined to be 2% to 4%FP.

[0088] Based on the method for determining the capacity requirement of a passive waste heat removal system provided in the above embodiments, this application also provides a device for determining the capacity requirement of a passive waste heat removal system.

[0089] This application provides an embodiment of a device for determining the capacity requirement of a passive waste heat removal system, comprising:

[0090] The inventory compilation module is used to compile a list of design baseline accidents that the passive residual heat removal system must address, based on the design characteristics of the nuclear power plant.

[0091] The effect determination module is used to determine the effect achieved by the passive waste heat removal system after each accident, based on the design baseline accident list.

[0092] The operating condition determination module is used to determine the limiting operating conditions of the passive waste heat removal system based on the clearly defined effects achieved by the passive waste heat removal system after each accident.

[0093] The module is required to analyze the defined limiting conditions, taking conservative considerations from the initial operating conditions, reactor protection and control, and core-related assumptions, to determine the capacity requirements of the passive residual heat removal system under each limiting condition.

[0094] The range determination module is used to determine the appropriate capacity range of the passive waste heat removal system based on the analysis results of the limiting operating conditions.

[0095] In one example, the list organization module is specifically used for:

[0096] For nuclear power plants with a passive residual heat removal system on the secondary side of the steam generator, the corresponding design basis accidents in the event of a reduced secondary loop heat removal include: loss of non-emergency AC power to auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines.

[0097] When a secondary loop heat exhaust accident occurs, the corresponding design basis accidents include: accidental start-up of the passive waste heat exhaust system and main steam pipeline rupture.

[0098] In the event of a steam generator heat transfer tube rupture accident, the passive residual heat removal system should have sufficient capacity to remove core decay heat, establish pressure balance between the reactor primary loop and the secondary side of the steam generator, and prevent further leakage through the steam generator heat transfer tube.

[0099] The long-term heat removal requirements include: being able to smoothly bring the nuclear power plant to a state where the normal residual heat removal system is put into operation within a specific time; and during the cooling process, the rate of cooling and depressurization of the primary loop should not be too fast to avoid the reactor returning to criticality.

[0100] In another example, the effect determination module is specifically used for:

[0101] For accidents involving reduced heat removal from the secondary coolant loop, the passive residual heat removal system should be automatically activated to remove residual heat from the core, reducing the temperature and pressure of the primary coolant loop and preventing it from rising too high and affecting core safety. For Category II accidents, after the passive residual heat removal system is automatically activated, the integrity of the fuel cladding should be ensured, the pressure on the primary and secondary sides should not exceed the limits, and the release of radioactive materials should not exceed the prescribed limits. For Category IV accidents, the core geometry should be unaffected, core cooling should be guaranteed, and the release of radioactive materials should not exceed the prescribed limits.

[0102] For accidents involving increased heat release from the secondary coolant loop, the initial cause event leads to a decrease in temperature and pressure in the primary coolant loop, triggering a safety injection signal. This signal then triggers the automatic activation of the passive residual heat removal system. Due to the negative feedback effect of the moderator, the decrease in temperature and pressure in the primary coolant loop introduces positive reactivity into the reactor, posing a risk of repeated criticality. For Category II accidents, the integrity of the fuel cladding must be ensured, and the release of radioactive materials must not exceed the limits specified in GB 6249-2011. For Category IV accidents, the core geometry must be unaffected, and core cooling must be guaranteed. The release of radioactive materials must not exceed the specified limits, and the containment pressure must also be considered to ensure that it does not exceed the design limits.

[0103] In the event of a steam generator heat transfer tube rupture accident, leakage occurs from the primary loop to the secondary loop. Low pressurizer pressure triggers a safety injection signal, which in turn triggers the isolation of the main feedwater system and activates the passive residual heat removal system to remove residual heat from the reactor core. Once the pressures on the primary and secondary sides of the damaged steam generator are balanced, there will be no more leakage from the primary side to the secondary side. A steam generator heat transfer tube rupture accident is classified as a Category III condition, which allows for a small amount of fuel assembly damage, but the geometry of the reactor core must not be damaged to ensure core cooling, and the release of radioactive materials should not exceed the prescribed limits.

[0104] Long-term heat removal requires that the nuclear power plant be brought to a state where the normal residual heat removal system is put into operation within a specified time.

[0105] As an example, limiting conditions include: maximum capacity requirements, minimum capacity requirements, and requirements for other accidents;

[0106] The reactor safety will not be compromised when the passive waste heat removal system is at its maximum or minimum capacity.

[0107] This application embodiment clarifies the effects of the passive waste heat removal system after each accident by compiling a list of design basis accidents that the passive waste heat removal system must address, determines the limiting operating conditions corresponding to the design basis accidents, conducts corresponding design basis accident analysis, and determines the capacity range of the passive waste heat removal system, thus providing support for the capacity design of passive waste heat removal systems in new nuclear power plants.

[0108] The present application has been described in detail above with reference to the accompanying drawings and embodiments. However, the present application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present application. All content not described in detail in this application can be derived from existing technology.

Claims

1. A passive residual heat removal system capacity requirement determination method, characterized by, The method includes: Based on the design characteristics of nuclear power plants, a list of design baseline accidents that passive waste heat removal systems must address is compiled. Based on the design baseline accident list, clarify the effect achieved by the passive waste heat removal system after each accident occurs; Based on the clearly defined effects achieved by the passive waste heat removal system after each accident, determine the limiting operating conditions of the passive waste heat removal system. The determined limiting conditions are analyzed, and conservative considerations are made from the aspects of initial conditions, reactor protection and control, and core-related assumptions to determine the capacity requirements of the passive residual heat removal system under each limiting condition. Based on the analysis results of the restricted operating conditions, the capacity range of the passive waste heat removal system is determined by comprehensive consideration. Based on the clearly defined effects achieved by the passive waste heat removal system after each accident, the limiting operating conditions of the passive waste heat removal system are determined, specifically including: Secondary loop heat discharge accidents include: main steam system accidental depressurization, accidental activation of the passive residual heat discharge system, and main steam pipeline rupture; the passive residual heat discharge system at its maximum capacity will not endanger reactor safety. Secondary loop heat discharge reduces accidents, including: loss of non-emergency AC power to power plant auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines; when the passive residual heat discharge system is at its minimum capacity, it will not endanger reactor safety. The capacity of the passive waste heat removal system is sufficient to remove reactor waste heat under the condition of steam generator heat transfer tube rupture accident and to meet the requirements of long-term reactor heat removal. The analysis of the defined limiting operating conditions, taking conservative considerations from the aspects of initial operating conditions, reactor protection and control, and core-related assumptions, determines the capacity requirements of the passive residual heat removal system under each limiting operating condition, specifically including: When the passive waste heat removal system is accidentally started, the maximum capacity requirement for the passive waste heat removal system is 6% FP; In the event of a main steam pipe rupture, the maximum capacity requirement for the passive waste heat removal system is 6% FP. When the non-emergency AC power supply to power plant auxiliary equipment is lost, the minimum capacity requirement for the passive waste heat removal system is 2% FP; When normal water supply flow is lost, the minimum capacity requirement for the passive waste heat removal system is 2% FP; When the main water supply system pipeline ruptures, the minimum capacity requirement for the passive waste heat removal system is 2% FP; When the heat transfer tube of the steam generator ruptures, the capacity requirement for the passive waste heat removal system is 1% FP to 4% FP. For long-term heat removal, the capacity requirement for the passive residual heat removal system is 1% FP to 5% FP; where the capacity requirement is the percentage of power discharged by the passive residual heat removal system relative to the reactor's rated power.

2. The passive residual heat removal system capacity demand determination method according to Claim 1, characterized by, Based on the design characteristics of nuclear power plants, a list of design baseline accidents that passive residual heat removal systems must address is compiled, specifically including: For nuclear power plants with a passive residual heat removal system on the secondary side of the steam generator, the corresponding design basis accidents in the event of a reduced secondary loop heat removal include: loss of non-emergency AC power to auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines. When a secondary loop heat exhaust accident occurs, the corresponding design basis accidents include: accidental start-up of the passive waste heat exhaust system and main steam pipeline rupture. In the event of a steam generator heat transfer tube rupture accident, the passive residual heat removal system has the ability to remove the core decay heat, establish pressure balance between the reactor primary loop and the secondary side of the steam generator, and prevent further leakage through the steam generator heat transfer tube. The long-term heat removal requirements include: being able to smoothly bring the nuclear power plant to a state where the normal residual heat removal system is put into operation within a specified time; and during the cooling process, the rate of cooling and depressurization of the primary loop should not be too fast to avoid the reactor returning to criticality.

3. The passive residual heat removal system capacity demand determination method according to claim 2, characterized by, The description of the passive waste heat removal system's performance after each accident, based on the design baseline accident list, specifically includes: For accidents involving reduced heat removal from the secondary coolant loop, the passive residual heat removal system is automatically activated to remove residual heat from the core, reducing the temperature and pressure of the primary coolant loop and preventing it from rising too high and affecting core safety. For Category II accidents, after the passive residual heat removal system is automatically activated, the integrity of the fuel cladding is ensured, the pressure on the primary and secondary sides must not exceed the limits, and the release of radioactive materials must not exceed the prescribed limits. For Category IV accidents, the core geometry is ensured to remain unaffected, core cooling is guaranteed, and the release of radioactive materials must not exceed the prescribed limits. For accidents involving increased heat release from the secondary coolant loop, the initial cause event leads to a decrease in temperature and pressure in the primary coolant loop, triggering a safety injection signal. This signal then triggers the automatic activation of the passive residual heat removal system. Due to the negative feedback effect of the moderator, the decrease in temperature and pressure in the primary coolant loop introduces positive reactivity into the reactor, posing a risk of repeated criticality. For Category II accidents, the integrity of the fuel cladding must be ensured, and the release of radioactive materials must not exceed the limits specified in GB 6249-2011. For Category IV accidents, the core geometry must be unaffected, core cooling must be guaranteed, and the release of radioactive materials must not exceed the specified limits, while also ensuring that the containment pressure does not exceed the design limits. In the event of a steam generator heat transfer tube rupture accident, leakage occurs from the primary loop to the secondary loop. Low pressurizer pressure triggers a safety injection signal, which in turn triggers the isolation of the main feedwater system and activates the passive residual heat removal system to remove residual heat from the reactor core. Once the pressures on the primary and secondary sides of the damaged steam generator are balanced, there will be no more leakage from the primary side to the secondary side. A steam generator heat transfer tube rupture accident is classified as a Category III condition, which allows for a small amount of fuel assembly damage, but the geometry of the reactor core must not be damaged to ensure core cooling, and the release of radioactive materials must not exceed the prescribed limits. Long-term heat removal requires that the nuclear power plant be brought to a state where the normal residual heat removal system is put into operation within a specified time.

4. A passive residual heat removal system capacity demand determination apparatus, characterized by, The device includes: The inventory compilation module is used to compile a list of design baseline accidents that the passive residual heat removal system must address, based on the design characteristics of the nuclear power plant. The effect determination module is used to determine the effect achieved by the passive waste heat removal system after each accident, based on the design baseline accident list. The operating condition determination module is used to determine the limiting operating conditions of the passive waste heat removal system based on the clearly defined effects achieved by the passive waste heat removal system after each accident. The module is required to analyze the defined limiting conditions, taking conservative considerations from the aspects of initial conditions, reactor protection and control, and core-related assumptions, to determine the capacity requirements of the passive residual heat removal system under each limiting condition. The range determination module is used to determine the capacity range of the passive waste heat removal system based on the analysis results of the limiting operating conditions and by taking into account all factors. Based on the clearly defined effects achieved by the passive waste heat removal system after each accident, the limiting operating conditions of the passive waste heat removal system are determined, specifically including: Secondary loop heat discharge accidents include: main steam system accidental depressurization, accidental activation of the passive residual heat discharge system, and main steam pipeline rupture; the passive residual heat discharge system at its maximum capacity will not endanger reactor safety. Secondary loop heat discharge reduces accidents, including: loss of non-emergency AC power to power plant auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines; when the passive residual heat discharge system is at its minimum capacity, it will not endanger reactor safety. The capacity of the passive waste heat removal system is sufficient to remove reactor waste heat under the condition of steam generator heat transfer tube rupture accident and to meet the requirements of long-term reactor heat removal. The analysis of the defined limiting operating conditions, taking conservative considerations from the aspects of initial operating conditions, reactor protection and control, and core-related assumptions, determines the capacity requirements of the passive residual heat removal system under each limiting operating condition, specifically including: When the passive waste heat removal system is accidentally started, the maximum capacity requirement for the passive waste heat removal system is 6% FP; In the event of a main steam pipe rupture, the maximum capacity requirement for the passive waste heat removal system is 6% FP. When the non-emergency AC power supply to power plant auxiliary equipment is lost, the minimum capacity requirement for the passive waste heat removal system is 2% FP; When normal water supply flow is lost, the minimum capacity requirement for the passive waste heat removal system is 2% FP; When the main water supply system pipeline ruptures, the minimum capacity requirement for the passive waste heat removal system is 2% FP; When the heat transfer tube of the steam generator ruptures, the capacity requirement for the passive waste heat removal system is 1% FP to 4% FP. For long-term heat removal, the capacity requirement for the passive residual heat removal system is 1% FP to 5% FP; where the capacity requirement is the percentage of power discharged by the passive residual heat removal system relative to the reactor's rated power.

5. The passive residual heat removal system capacity demand determining apparatus according to claim 4, characterized by, The list compilation module is specifically used for: For nuclear power plants with a passive residual heat removal system on the secondary side of the steam generator, the corresponding design basis accidents in the event of a reduced secondary loop heat removal include: loss of non-emergency AC power to auxiliary equipment, loss of normal feedwater flow, and rupture of main feedwater system pipelines. When a secondary loop heat exhaust accident occurs, the corresponding design basis accidents include: accidental start-up of the passive waste heat exhaust system and main steam pipeline rupture. In the event of a steam generator heat transfer tube rupture accident, the passive residual heat removal system has the ability to remove the core decay heat, establish pressure balance between the reactor primary loop and the secondary side of the steam generator, and prevent further leakage through the steam generator heat transfer tube. The long-term heat removal requirements include: being able to smoothly bring the nuclear power plant to a state where the normal residual heat removal system is put into operation within a specified time; and during the cooling process, the rate of cooling and depressurization of the primary loop should not be too fast to avoid the reactor returning to criticality.

6. The passive residual heat removal system capacity demand determination method according to claim 5, characterized by, The effect determination module is specifically used for: For accidents involving reduced heat removal from the secondary coolant loop, the passive residual heat removal system is automatically activated to remove residual heat from the core, reducing the temperature and pressure of the primary coolant loop and preventing it from rising too high and affecting core safety. For Category II accidents, after the passive residual heat removal system is automatically activated, the integrity of the fuel cladding is ensured, the pressure on the primary and secondary sides must not exceed the limits, and the release of radioactive materials must not exceed the prescribed limits. For Category IV accidents, the core geometry is ensured to remain unaffected, core cooling is guaranteed, and the release of radioactive materials must not exceed the prescribed limits. For accidents involving increased heat release from the secondary coolant loop, the initial cause event leads to a decrease in temperature and pressure in the primary coolant loop, triggering a safety injection signal. This signal then triggers the automatic activation of the passive residual heat removal system. Due to the negative feedback effect of the moderator, the decrease in temperature and pressure in the primary coolant loop introduces positive reactivity into the reactor, posing a risk of repeated criticality. For Category II accidents, the integrity of the fuel cladding must be ensured, and the release of radioactive materials must not exceed the limits specified in GB 6249-2011. For Category IV accidents, the core geometry must be unaffected, core cooling must be guaranteed, and the release of radioactive materials must not exceed the specified limits, while also ensuring that the containment pressure does not exceed the design limits. In the event of a steam generator heat transfer tube rupture accident, leakage occurs from the primary loop to the secondary loop. Low pressurizer pressure triggers a safety injection signal, which in turn triggers the isolation of the main feedwater system and activates the passive residual heat removal system to remove residual heat from the reactor core. Once the pressures on the primary and secondary sides of the damaged steam generator are balanced, there will be no more leakage from the primary side to the secondary side. A steam generator heat transfer tube rupture accident is classified as a Category III condition, which allows for a small amount of fuel assembly damage, but the geometry of the reactor core must not be damaged to ensure core cooling, and the release of radioactive materials must not exceed the prescribed limits. Long-term heat removal requires that the nuclear power plant be brought to a state where the normal residual heat removal system is put into operation within a specified time.

7. The passive residual heat removal system capacity demand determining apparatus according to any one of claims 4 to 6, characterized by, The limiting conditions include: maximum capacity requirements, minimum capacity requirements, and requirements for steam generator heat transfer tube rupture and long-term heat dissipation; The reactor safety will not be compromised when the passive waste heat removal system is at its maximum or minimum capacity.

Images