A passive core makeup tank rapid design method for nuclear reactors

Abstract

The application relates to the field of reactor thermal hydraulic design and safety technology, and particularly discloses a kind of quick design methods for passive core makeup tank of nuclear reactor. By analyzing the operation mode and the hydrodynamic flow characteristics of the passive core makeup tank, a quick calculation method for the injection flow of the passive core makeup tank in water-water circulation and steam-water circulation is constructed, then a large number of sampling calculations are carried out on the structural design parameters, and the calculated flow curve is compared with the design flow value, so as to determine the design parameter range of the core makeup tank under the premise of meeting the safety requirements, guide the structural design of the core makeup tank, and solve the problem of low design efficiency of the passive core makeup tank, which has important economic significance and use value.

Description

Technical Field

[0001] This invention belongs to the field of reactor thermal-hydraulic design and safety technology, specifically relating to a rapid design method for a passive core makeup water tank in a nuclear reactor. Background Technology

[0002] The passive core makeup water tank is a crucial dedicated system in passive nuclear reactors and is part of the emergency core cooling system. In the event of a reactor accident, especially a coolant loss-of-coolant accident, the core makeup water tank primarily performs the functions of replenishing the core with water and boronizing the coolant. The tank's inlet is connected to the main pump outlet via a balance pipe, and its outlet is connected to the direct injection line via an outlet pipeline.

[0003] The passive core makeup water tank operates in two modes: water-to-water circulation and steam-to-water circulation. In the water-to-water circulation phase, the density of the cooled water in the tank is greater than that of the cooling system in the primary loop, and it is injected into the core due to this density difference. In the steam-to-water circulation phase, the balance pipe contains vapor, and the core makeup water tank injects water into the pressure vessel under gravity. Before the core makeup water tank starts up, if the main pump is still running, the pressure at the main pump outlet is slightly higher than the pressure at the direct injection line nozzle in the downcomer chamber; that is, the inlet pressure of the core makeup water tank is slightly higher than the outlet pressure. This is one of the driving forces for the core makeup water tank to start operating.

[0004] The primary design objective of passive reactor core makeup water tanks is to meet the safety injection flow requirements under accident conditions. Therefore, their design process necessitates achieving specific injection flow rates, with different flow requirements in water-water and steam-water cycles. Current methods for designing passive reactor core makeup water tanks are relatively passive. First, the structural geometry of each component is given. Then, a detailed reactor model is built using a thermal-hydraulic system program to demonstrate the safety and conservatism of the design. If the design fails to meet reactor safety requirements, repeated modifications and modeling analyses are necessary. This iterative process is time-consuming, labor-intensive, and makes economic optimization difficult. Summary of the Invention

[0005] The technical problem this invention aims to solve is the low efficiency of the existing passive reactor core makeup tank design process, which involves repeatedly modifying the design scheme during the modeling and derivation process after determining the structure first. This invention analyzes the operating mode and hydraulic flow characteristics of the passive reactor core makeup tank and constructs a rapid calculation method for the injection flow rate in water-water and steam-water cycles. Subsequently, by performing extensive sampling calculations on the structural design parameters and comparing the calculated flow rate curves with the design flow rate values, the design parameter range of the core makeup tank under the premise of meeting safety requirements is determined. This guides the structural design of the core makeup tank and solves the problem of low design efficiency in passive reactor core makeup tanks.

[0006] To address the above problems, the technical solution of this invention is as follows: A rapid design method for a passive core makeup water tank in a nuclear reactor, comprising the following steps:

[0007] S1: Perform rapid calculation of the water circulation injection flow rate in the reactor core makeup water tank;

[0008] S2: Perform rapid calculation of the steam-water circulation injection flow rate in the core makeup water tank;

[0009] S3: Conduct rapid design of the reactor core makeup water tank.

[0010] Step S1 includes the following operational steps:

[0011] S11: Determine the initial cold water section height as the height difference between the top of the core makeup water tank and the direct injection pipeline;

[0012] S12: Calculate the total flow head of the water circulation;

[0013] S13: Calculate the water circulation injection flow rate;

[0014] S14: Determine whether the cold water in the reactor core makeup water tank has been drained. If it has not been drained, proceed to steps S12 to S13. If it has been drained, record the draining time and the water circulation injection flow rate.

[0015] Step S2 includes the following operations:

[0016] S21: Determine the initial coolant height as the height difference between the top of the core makeup water tank and the direct injection pipeline;

[0017] S22: Calculate the total flow head of the steam-water circulation;

[0018] S23: Calculate the steam-water circulation injection flow rate;

[0019] S24: Determine whether the coolant in the core makeup water tank has been emptied. If not, proceed to steps S22 to S23. If it has been emptied, record the emptying time and the steam-water circulation injection flow rate.

[0020] Step S3 includes the following operations:

[0021] S31: Determine the flow requirements and generate the flow requirement curves for water circulation injection into the core makeup water tank and steam-water circulation injection into the core makeup water tank.

[0022] S32: Set the design parameter range for the core makeup water tank;

[0023] S33: Set the total number of design iterations;

[0024] S34: Randomly select a set of core makeup water tank design parameters within the range of each design parameter described in step S32;

[0025] S35: Through steps S1 and S2, determine the water-water circulation injection flow rate curve and the steam-water circulation injection flow rate curve of the core makeup water tank under the design parameters of the core makeup water tank described in step S34.

[0026] S36: Compare the water-to-water circulation injection flow rate curve and steam-to-water circulation injection flow rate curve of the core makeup water tank in step S35 with the water-to-water circulation injection flow rate demand curve and steam-to-water circulation injection flow rate demand curve of the core makeup water tank in step S31. If the water-to-water circulation injection flow rate curve and steam-to-water circulation injection flow rate curve of the core makeup water tank in step S35 are higher than the water-to-water circulation injection flow rate demand curve and steam-to-water circulation injection flow rate demand curve of the core makeup water tank in step S31, then save the design scheme; otherwise, discard the design scheme.

[0027] S37: Record the number of times steps S34 to S36 are executed. If the number of executions is less than the total number of scheme designs in step S33, then repeat steps S34 to S36. If the number of executions is equal to the total number of scheme designs in step S33, then execute step S38.

[0028] S38: Organize all design schemes, determine the range of feasible core makeup water tank design parameters, and guide engineering design.

[0029] In step S12, assuming no hot or cold mixing in the core makeup tank, the total flow driving head ΔP of the water circulation is calculated using equation (1), where: ρ CT This represents the density of the supercooled water in the core makeup tank, calculated using the pressure in the cold pipe section and the highest design temperature of the core makeup tank; ρ CL This represents the density of the coolant in the cold pipe section, calculated using the pressure and temperature of the cold pipe section; g is the gravitational constant; h cold The height of the coolant in the core makeup water tank is the height of the direct injection pipeline inlet. This height decreases continuously as coolant is injected into the core makeup water tank.

[0030] ΔP=(ρ CT -ρ CL )·g·h cold (1)

[0031] In step S13, Darcy's formula is used to obtain the injection flow rate q of the reactor core makeup water tank in water-to-water circulation mode through the total water-to-water circulation driving head ΔP obtained in step S12. The relationship between the total water-to-water circulation driving head ΔP and the injection flow rate q of the reactor core makeup water tank in water-to-water circulation mode is shown in equation (2):

[0032] ΔP=R·q 2 (2)

[0033] The total flow driving head of the steam-water circulation in step S22 is calculated using equation (3), where ρ l,sub This represents the density of the supercooled water in the core makeup water tank, calculated using the pressure during venting of the cold pipe section and the highest design temperature of the core makeup water tank; ρ g,sat The density of saturated vapor corresponds to the pressure at which the cold pipe section is vented; g is the gravitational constant; h l The height of the coolant level in the core makeup water tank from the injection port of the direct injection pipeline is the height of the coolant level. This height decreases continuously as coolant is injected into the core makeup water tank.

[0034] ΔP=(ρ l,sub -ρ g,sat )·g·h l (3)

[0035] Step S23 utilizes Darcy's formula to obtain the total flow driving head ΔP of the steam-water circulation and the injection flow rate q of the core makeup water tank in the water-water circulation mode through step S22. The relationship between the total flow driving head ΔP of the water-water circulation and the injection flow rate q of the core makeup water tank in the water-water circulation mode is shown in equation (4):

[0036]

[0037] The significant advantages of this invention are as follows: The rapid design method for a passive core makeup water tank in a nuclear reactor, as described in this invention, analyzes the operating mode and hydraulic flow characteristics of the passive core makeup water tank. Starting from the perspective of accident safety requirements, it conducts a forward stochastic design of the scheme to determine the design parameter range of the core makeup water tank that meets the requirements, and can further optimize the scheme design. Compared with the multi-disciplinary iterative design and demonstration used in traditional design methods, this method shortens the equipment design cycle and facilitates equipment design optimization, reduces equipment footprint, and lowers construction costs, thus possessing significant economic and practical value. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the rapid design method for a passive core makeup water tank of a nuclear reactor according to the present invention. Detailed Implementation

[0039] The technical solutions of the invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort are within the scope of the invention.

[0040] In the description of this invention, it should be noted that the use of terms such as "above" to indicate orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings and is only for the purpose of facilitating and simplifying the description. It does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0041] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] like Figure 1 As shown, a rapid design method for a passive core makeup water tank in a nuclear reactor is provided, which includes the following steps:

[0044] S1: Rapid calculation of water circulation injection flow rate in the reactor core makeup water tank.

[0045] The core makeup water circulation refers to the process where, when the core makeup water tank is put into use, the primary loop is filled with coolant. The subcooled coolant in the core makeup water tank is injected into the core through the direct injection line. At the same time, the higher-temperature coolant in the cold pipe section of the reactor primary loop flows into the top of the core makeup water tank from the balance line, thus forming a natural circulation process.

[0046] S11: Determine the initial cold water section height as the height difference between the top of the core makeup water tank and the direct injection pipeline.

[0047] S12: Calculate the total flow head of the water circulation;

[0048] In the water-to-water circulation mode, the driving head of the flow in the loop is the gravity head due to the difference in water density from the cold water surface in the core makeup tank to the height of the injection port of the direct injection pipeline. Assuming there is no hot or cold mixing in the core makeup tank, the total driving head ΔP can be calculated by equation (1):

[0049] ΔP=(ρ CT -ρ CL )·g·h cold (1)

[0050] In the formula: ρ CTThis represents the density of the supercooled water in the core makeup tank, calculated using the pressure in the cold pipe section and the highest design temperature of the core makeup tank; ρ CL This represents the density of the coolant in the cold pipe section, calculated using the pressure and temperature of the cold pipe section; g is the gravitational constant; h cold The height of the coolant in the core makeup water tank is the height of the direct injection pipeline inlet. This height decreases continuously as coolant is injected into the core makeup water tank.

[0051] S13: Calculate the water circulation injection flow rate.

[0052] After calculating the total driving head ΔP, the Darcy formula can be used to calculate the injection flow rate q of the core makeup water tank under the water-water circulation mode. The Darcy formula can be expressed as shown in equation (2):

[0053] ΔP=R·q 2 (2)

[0054] In the formula, R represents the total flow resistance coefficient of the core makeup water tank pipeline under the water-water circulation mode.

[0055] S14: Determine whether the cold water in the reactor core makeup water tank has been drained. If it has not been drained, proceed to steps S12 to S13. If it has been drained, record the draining time and the water circulation injection flow rate.

[0056] S2: Rapid calculation of steam-water circulation injection flow rate in the core makeup water tank.

[0057] The definition of steam-water circulation in the core makeup tank, relative to water-water circulation, refers to the injection mode in which the balance line and the connected cold pipe section are filled with steam when the core makeup tank is put into use. At this time, the subcooled coolant in the core makeup tank is injected into the core through the direct injection line. At the same time, the saturated steam in the cold pipe section of the reactor primary loop flows into the top of the core makeup tank from the balance line and partially condenses in the upper space of the core makeup tank, thus forming a natural circulation process.

[0058] S21: Determine the initial coolant height as the height difference between the top of the core makeup water tank and the direct injection pipeline;

[0059] S22: Calculate the total flow head of the steam-water circulation;

[0060] In the steam-water circulation mode, the driving head of the flow in the loop is the gravity head of the density difference between the subcooled water and saturated steam from the coolant liquid level in the core makeup water tank to the height of the injection port of the direct injection pipeline. The total driving head can be calculated by equation (3):

[0061] ΔP=(ρ l,sub -ρ g,sat )·g·h l (3)

[0062] In the formula: ρl,sub This represents the density of the supercooled water in the core makeup water tank, calculated using the pressure during venting of the cold pipe section and the highest design temperature of the core makeup water tank; ρ g,sat The density of saturated vapor corresponds to the pressure at which the cold pipe section is vented; g is the gravitational constant; h l The height of the coolant level in the core makeup water tank from the injection port of the direct injection pipeline is the height of the coolant level. This height decreases continuously as coolant is injected into the core makeup water tank.

[0063] S23: Calculate the flow rate of the steam-water circulation injection.

[0064] After calculating the total driving head ΔP, the injected coolant flow rate q of the core makeup water tank in the steam-water circulation mode can be calculated using Darcy's formula, as shown in equation (5-4). Compared with water-water circulation, the pressure drop calculation for steam-water circulation is somewhat different and needs to be calculated separately according to the coolant state.

[0065]

[0066] In the formula, R1 represents the total resistance coefficient of the coolant flow channel injected into the core makeup water tank under the steam-water circulation mode, and R2 represents the total resistance coefficient of the saturated steam flow channel of the cold pipe section under the steam-water circulation mode.

[0067] S24: Determine whether the coolant in the core makeup water tank has been emptied. If not, proceed to steps S22 to S23. If it has been emptied, record the emptying time and the steam-water circulation injection flow rate.

[0068] S3: Rapid design of the reactor core makeup water tank

[0069] S31: Determine traffic demand and generate a traffic demand curve;

[0070] The core makeup water tank is mainly used to maintain the stability of the reactor coolant charge. Its limit flow requirement is the coolant loss accident. Therefore, the flow requirement of the core makeup water tank can be determined based on the break flow rate of the coolant loss accident.

[0071] S32: Set the design parameter range for the core makeup water tank;

[0072] The design parameters of the reactor core makeup water tank include the tank height, inner diameter, arrangement height, and injection pipeline diameter.

[0073] S33: Set the total number of design iterations;

[0074] S34: Randomly select a set of core makeup water tank design parameters within the range of each design parameter described in step S32;

[0075] S35: Through steps S1 and S2, determine the water-to-water circulation and steam-to-water circulation injection flow rate curves of the core makeup water tank under the design parameters of the core makeup water tank described in step S34;

[0076] S36: Compare the injection flow rate curves of the water-water circulation and steam-water circulation of the core makeup water tank in step S35 with the flow rate demand curve determined in step S31. If the injection flow rate curve provided by the core makeup water tank is higher than the flow rate demand curve, then save the design scheme; otherwise, discard the design scheme.

[0077] S37: Record the number of times steps S34 to S36 are executed. If the number of executions is less than the total number of scheme designs described in step S33, then repeat steps S34 to S36. If the number of executions is equal to the total number of scheme designs described in step S33, then execute step S38.

[0078] S38: Organize all design schemes, determine the range of feasible core makeup water tank design parameters, and guide engineering design.

[0079] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A rapid design method for a passive core makeup water tank in a nuclear reactor, characterized in that: The following steps are included: S1: Perform rapid calculation of the water circulation injection flow rate in the reactor core makeup water tank; S2: Perform rapid calculation of the steam-water circulation injection flow rate in the core makeup water tank; S3: Conduct rapid design of the reactor core makeup water tank.

2. The rapid design method for a passive core makeup water tank of a nuclear reactor according to claim 1, characterized in that: Step S1 includes the following operational steps: S11: Determine the initial cold water section height as the height difference between the top of the core makeup water tank and the direct injection pipeline; S12: Calculate the total flow head of the water circulation; S13: Calculate the water circulation injection flow rate; S14: Determine whether the cold water in the reactor core makeup water tank has been drained. If it has not been drained, proceed to steps S12 to S13. If it has been drained, record the draining time and the water circulation injection flow rate.

3. The rapid design method for a passive core makeup water tank of a nuclear reactor according to claim 1, characterized in that: Step S2 includes the following operations: S21: Determine the initial coolant height as the height difference between the top of the core makeup water tank and the direct injection pipeline; S22: Calculate the total flow head of the steam-water circulation; S23: Calculate the steam-water circulation injection flow rate; S24: Determine whether the coolant in the core makeup water tank has been emptied. If not, proceed to steps S22 to S23. If it has been emptied, record the emptying time and the steam-water circulation injection flow rate.

4. The rapid design method for a passive core makeup water tank of a nuclear reactor according to claim 1, characterized in that: Step S3 includes the following operations: S31: Determine the flow requirements and generate the flow requirement curves for water circulation injection into the core makeup water tank and steam-water circulation injection into the core makeup water tank. S32: Set the design parameter range for the core makeup water tank; S33: Set the total number of design iterations; S34: Randomly select a set of core makeup water tank design parameters within the range of each design parameter described in step S32; S35: Through steps S1 and S2, determine the water-water circulation injection flow rate curve and the steam-water circulation injection flow rate curve of the core makeup water tank under the design parameters of the core makeup water tank described in step S34. S36: Compare the water-to-water circulation injection flow rate curve and steam-to-water circulation injection flow rate curve of the core makeup water tank in step S35 with the water-to-water circulation injection flow rate demand curve and steam-to-water circulation injection flow rate demand curve of the core makeup water tank in step S31. If the water-to-water circulation injection flow rate curve and steam-to-water circulation injection flow rate curve of the core makeup water tank in step S35 are higher than the water-to-water circulation injection flow rate demand curve and steam-to-water circulation injection flow rate demand curve of the core makeup water tank in step S31, then save the design scheme; otherwise, discard the design scheme. S37: Record the number of times steps S34 to S36 are executed. If the number of executions is less than the total number of scheme designs in step S33, then repeat steps S34 to S36. If the number of executions is equal to the total number of scheme designs in step S33, then execute step S38. S38: Organize all design schemes, determine the range of feasible core makeup water tank design parameters, and guide engineering design.

5. The rapid design method for a passive core makeup water tank of a nuclear reactor according to claim 2, characterized in that: In step S12, assuming no hot or cold mixing in the core makeup tank, the total flow driving head ΔP of the water circulation is calculated using equation (1), where: ρ CT This represents the density of the supercooled water in the core makeup tank, calculated using the pressure in the cold pipe section and the highest design temperature of the core makeup tank; ρ CL This represents the density of the coolant in the cold pipe section, calculated using the pressure and temperature of the cold pipe section; g is the gravitational constant; h cold The height of the coolant in the core makeup water tank is the height of the direct injection pipeline inlet. This height decreases continuously as coolant is injected into the core makeup water tank. ΔP=(ρ CT -r CL )·g·h cold (1) 6. The rapid design method for a passive core makeup water tank of a nuclear reactor according to claim 5, characterized in that: In step S13, Darcy's formula is used to obtain the injection flow rate q of the reactor core makeup water tank in water-to-water circulation mode through the total water-to-water circulation driving head ΔP obtained in step S12. The relationship between the total water-to-water circulation driving head ΔP and the injection flow rate q of the reactor core makeup water tank in water-to-water circulation mode is shown in equation (2): ΔP=R·q 2 (2) 7. The rapid design method for a passive core makeup water tank of a nuclear reactor according to claim 3, characterized in that: The total flow driving head of the steam-water circulation in step S22 is calculated using equation (3), where ρ l,sub This represents the density of the supercooled water in the core makeup water tank, calculated using the pressure during venting of the cold pipe section and the highest design temperature of the core makeup water tank; ρ g,sat The density of saturated vapor corresponds to the pressure at which the cold pipe section is vented; g is the gravitational constant; h l The height of the coolant level in the core makeup water tank from the injection port of the direct injection pipeline decreases continuously as coolant is injected into the core makeup water tank. ΔP=(ρ l,sub -r g,sat )·g·h l (3) 8. The rapid design method for a passive core makeup water tank of a nuclear reactor according to claim 7, characterized in that: Step S23 utilizes Darcy's formula to obtain the total flow driving head ΔP of the steam-water circulation and the injection flow rate q of the core makeup water tank in the water-water circulation mode through step S22. The relationship between the total flow driving head ΔP of the water-water circulation and the injection flow rate q of the core makeup water tank in the water-water circulation mode is shown in equation (4):

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