A fast design method for passive containment injection tank of nuclear reactor

Abstract

The application relates to the technical field of reactor thermal hydraulic design and safety analysis, and particularly discloses a quick design method of a passive pressure accumulation injection tank of a nuclear reactor. Through analysis on a coolant loss accident process and phenomenon, injection flow rate requirements of the passive pressure accumulation injection tank are determined, operation modes and hydraulics flow characteristics of the injection tank are analyzed, a quick calculation method of the injection flow rate of the injection tank is constructed, a large number of sampling calculations are carried out on design parameters such as geometric structures and state parameters, and the calculated flow rate curves are compared with the flow rate requirements, so that a feasible design parameter range of the injection tank under the premise of meeting safety requirements is determined, the structure design of the injection tank is guided, and the application has important economic significance and use value.

Description

Technical Field

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

[0002] The safe operation of passive nuclear reactors has always been a major concern in the development and application of nuclear energy. Among the many hypothetical initiation events in nuclear reactors, a loss-of-coolant accident refers to an accident in which a breach or rupture occurs at the pressure boundary of the reactor's main coolant loop, resulting in the leakage of some or most of the coolant. To ensure the safety of the nuclear reactor during a loss-of-coolant accident, coolant must be replenished into the reactor's main coolant system promptly after the accident to remove residual heat and prevent core exposure and meltdown. Coolant replenishment during a loss-of-coolant accident is primarily performed by the emergency core cooling system.

[0003] The passive accumulator safety injection tank is a crucial dedicated system in passive nuclear reactors and is part of the emergency core cooling system. In the event of a coolant loss accident, especially one with a large breach, the safety injection tank's primary function is to rapidly replenish the reactor coolant system. The tank is filled with concentrated borosilicate water, and the upper part of the tank is pressurized with compressed nitrogen to enable rapid injection. The tank's outlet pipe connects to the direct injection line on the reactor pressure vessel.

[0004] The primary design objective of passive accumulator safety injection tanks is to meet the safety injection flow requirements under coolant loss-of-coolant accident conditions, especially in cases of large-break coolant loss-of-coolant accidents where the reactor core is exposed. In such cases, the safety injection tank must provide a large flow of coolant to reflood the core and prevent it from overheating and melting. Currently, the methods used for designing passive accumulator safety injection tanks for nuclear reactors are relatively passive. First, design parameters such as the tank's geometry, gas space pressure, and steam-to-water ratio are given. Then, a detailed reactor model is built using a thermal-hydraulic system program to demonstrate the safety and conservatism of the equipment design in a coolant loss-of-coolant accident. If the design fails to meet the reactor's safety requirements, the design must be repeatedly modified and modeled and analyzed. This iterative process is time-consuming and labor-intensive, and economic optimization is difficult to achieve. Summary of the Invention

[0005] The technical problem this invention aims to solve is that in the existing technology, the design process of passive accumulator safety injection tanks involves first performing geometric design and then modeling and demonstrating the design, leading to repeated modifications and low iteration efficiency. This invention provides a rapid design method for passive accumulator safety injection tanks in nuclear reactors. By analyzing the process and phenomena of coolant loss accidents, the injection flow rate requirements of the passive accumulator safety injection tank are determined. Furthermore, the operating mode and hydraulic flow characteristics of the safety injection tank are analyzed to construct a rapid calculation method for the injection flow rate. Subsequently, through extensive sampling calculations of design parameters such as geometric structure and state parameters, and by comparing the calculated flow rate curve with the flow rate requirements, the feasible design parameter range of the safety injection tank under the premise of meeting safety requirements is determined, guiding the structural design of the safety injection tank.

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

[0007] S1: Determine the minimum required injection flow rate for the ampoule;

[0008] S2: Determine the design parameter range for the injection chamber;

[0009] S3: The number of design iterations for the overall design of the injection tank;

[0010] S4: Randomly select a set of design parameters for the injection tank from the range of design parameters for the injection tank determined in step S2;

[0011] S5: Determine the initial liquid level in the ampoule tank;

[0012] S6: Calculate the injection flow rate curve of the injection tank using the design parameters of the injection tank extracted in step S4;

[0013] S7: Record the injection flow rate curve of the injection tank at each injection tank liquid level height calculated in step S6;

[0014] S8: Record the number of times steps S4 to S7 are executed, and determine the relationship between the number of executions and the number of design attempts described in step S3. If the number of executions is less than the number of design attempts described in step S3, then execute steps S4 to S7. If the number of executions is equal to the number of design attempts described in step S3, then execute step S9.

[0015] S9: After all the design calculations are completed, compare the injection flow curve of the safety injection tank obtained from each design calculation with the minimum injection flow requirement of the safety injection tank determined in step S1. Delete the schemes that do not meet the flow requirement, perform statistical evaluation on the remaining schemes, and obtain the feasible design parameter range of the safety injection tank.

[0016] Step S6 includes the following steps:

[0017] S61: Calculate the total driving head based on the gas space pressure and liquid level in the injection tank;

[0018] S62: Calculate the injected flow at the current moment;

[0019] S63: Calculate the volume of coolant injected at the current moment;

[0020] S64: Calculate the remaining coolant volume at the current moment;

[0021] S65: Calculate the pressure in the top gas space at the current moment;

[0022] S66: Move to the next time step;

[0023] S67: Calculate the liquid level in the ampoule tank at the next moment;

[0024] S68: Determine whether the liquid in the safety injection tank has been drained. If the safety injection tank has not been drained, proceed to steps S61 to S67. If the liquid in the safety injection tank has been drained, obtain the flow curve of the material replacement water tank and the pressure relief protection system.

[0025] The total driving head mentioned in step S61 can be calculated using equation (1):

[0026]

[0027] In the formula: ρ ACC The density of the supercooled water in the injection tank is represented by g; g is the gravitational constant; h ACC Indicates the water level inside the injection tank; h ACC-DVI Indicates the height of the bottom of the ampoule tank from the DVI injection line; P N2 This indicates the pressure of N2 inside the injection tank; P RCS This represents the pressure change curve of the primary loop system after the accident.

[0028] The injection flow rate is obtained by obtaining the total driving head ΔP in step S61, and then calculated using Darcy's formula, which is shown in equation (2):

[0029] ΔP=R·q 2 (2)

[0030] In the formula, R represents the flow resistance coefficient of the injection pipeline of the injection tank, and q is the injection flow rate.

[0031] The ρ ACC Calculations were made based on the current pressure of the injection chamber and the maximum design temperature of the injection chamber.

[0032] The design parameters of the injection tank include shape, height, inner diameter, air space pressure, and air-to-water ratio.

[0033] Step S63 is calculated using the following formula:

[0034] The volume of coolant injected at the current time step = injection flow rate * time step / injection water density.

[0035] Step S64 is calculated using the following formula:

[0036] Remaining volume = Remaining volume at the previous time step - Injected volume at the current time step.

[0037] The significant advantages of this invention are as follows: The rapid design method for passive accumulator safety injection tanks in nuclear reactors, as described in this invention, is based on the analysis of the operating modes and hydraulic flow characteristics of the passive accumulator safety injection tanks. Starting from the perspective of accident safety requirements, it proactively conducts statistical-based scheme design to determine the range of design parameters for the safety injection 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 technology shortens the equipment design cycle and facilitates equipment design optimization, reduces equipment footprint, and lowers construction costs, thus possessing significant economic significance and practical value. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the rapid design method for a passive accumulator safety injection tank in 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 The rapid design method for a passive accumulator safety injection tank in a nuclear reactor, as shown, mainly includes the following steps:

[0044] S1: Determine the minimum required injection flow rate for the ampoule;

[0045] The safety injection tank is designed to drain the core decay heat during a coolant loss accident and to reflood the reactor core during a large-break coolant loss accident. Therefore, the minimum flow rate requirement for the safety injection tank can be determined based on the reactor decay heat level and the core geometry.

[0046] S2: Determine the design parameter range for the injection chamber;

[0047] The design parameters of the safety injection tank include shape, height, inner diameter, air space pressure, and air-to-water ratio. The initial range of the safety injection tank design parameters is determined based on engineering experience and the limitations of the actual plant.

[0048] S3: The number of design iterations for the overall design of the injection tank;

[0049] S4: Randomly select a set of design parameters for the injection tank from the range of design parameters for the injection tank determined in step S2;

[0050] S5: Determine the initial liquid level in the ampoule tank;

[0051] S6: Calculate the injection flow rate curve of the injection tank using the design parameters of the injection tank extracted in step S4;

[0052] The driving head during the operation of the injection tank consists of two parts: the gravity head between the liquid level in the injection tank and the height of the direct injection line (DVI), and the pressure difference between the nitrogen pressure above the injection tank and the outlet coolant pressure. The total driving head can be calculated using equation (1):

[0053]

[0054] In the formula: ρ ACC This represents the density of the supercooled water in the injection tank, calculated using the current pressure and maximum design temperature of the injection tank; g is the gravitational constant; h ACCThis indicates the water level inside the injection tank, which decreases continuously as coolant is continuously injected into the tank; h ACC-DVI This indicates the height of the bottom of the ampoule tank from the DVI injection line; this height is a fixed value. (P) N2 This indicates the pressure of N2 inside the injection tank; P RCS This represents the pressure change curve of the primary loop system after the accident.

[0055] After calculating the total driving head ΔP, the injection flow rate q of the injection tank is calculated using Darcy's formula, which can be expressed as shown in equation (2):

[0056] ΔP=R·q 2 (2)

[0057] In the formula, R represents the flow resistance coefficient of the injection pipeline of the injection tank.

[0058] Since the injection flow rate of the ampoule is a quantity that varies with time, it is necessary to rely on a discrete algorithm to calculate its flow rate curve. For each time step, the instantaneous flow rate is calculated sequentially according to the following process:

[0059] S61: Using formula (1), calculate the total driving head based on the gas space pressure and liquid level in the injection box;

[0060] S62: Use equation (2) to calculate the injection flow at the current moment;

[0061] S63: Calculate the volume of coolant injected at the current moment;

[0062] Current time step injected coolant volume = Injection flow rate * Time step / Injected water density

[0063] The current time step injection volume is in units of (m³). 3 The injection flow rate is in kg / s, the time step is in seconds, and the injection water density is in kg / m³. 3 .

[0064] S64: Calculate the remaining coolant volume at the current moment;

[0065] Remaining volume = Remaining volume at the previous time step - Injected volume at the current time step

[0066] S65: Calculate the pressure in the top gas space at the current moment;

[0067] P N2This indicates the pressure of N2 inside the injection chamber, which is a parameter that changes dynamically over time. Since the injection chamber is a passive device, its injection drive primarily provides a pressure differential for the nitrogen stored inside. During the injection process, the volume of the nitrogen gas space increases, causing the nitrogen pressure to continuously decrease. This pressure can be represented by a PV (Potential Voltage) sensor. K The values ​​are calculated while keeping them constant, where P is the real-time pressure in the injection tank, V is the real-time gas volume in the injection tank, and K is the gas phase expansion coefficient.

[0068] S66: Move to the next time step;

[0069] S67: Calculate the liquid level in the ampoule tank at the next moment;

[0070] S68: Determine whether the liquid in the safety injection tank has been drained. If the safety injection tank has not been drained, proceed to steps S61 to S67. If the liquid in the safety injection tank has been drained, obtain the flow curve of the material replacement water tank and the pressure relief protection system.

[0071] S7: Record the injection flow rate curve of the injection tank at each injection tank liquid level height calculated in step S6;

[0072] S8: Record the number of times steps S4 to S7 are executed, and determine the relationship between the number of executions and the number of design attempts described in step S3. If the number of executions is less than the number of design attempts described in step S3, then execute steps S4 to S7. If the number of executions is equal to the number of design attempts described in step S3, then execute step S9.

[0073] S9: After all the design calculations are completed, compare the injection flow curve of the safety injection tank obtained from each design calculation with the minimum injection flow requirement of the safety injection tank determined in step S1. Delete the schemes that do not meet the flow requirement, perform statistical evaluation on the remaining schemes, and obtain the feasible design parameter range of the safety injection tank.

[0074] 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 accumulator safety injection tank in a nuclear reactor, characterized in that: The main operating steps are as follows: S1: Determine the minimum required injection flow rate for the ampoule; S2: Determine the design parameter range for the injection chamber; S3: The number of design iterations for the overall design of the injection tank; S4: Randomly select a set of design parameters for the injection tank from the range of design parameters for the injection tank determined in step S2; S5: Determine the initial liquid level in the ampoule tank; S6: Calculate the injection flow rate curve of the injection tank using the design parameters of the injection tank extracted in step S4; S7: Record the injection flow rate curve of the injection tank at each injection tank liquid level height calculated in step S6; S8: Record the number of times steps S4 to S7 are executed, and determine the relationship between the number of executions and the number of design attempts described in step S3. If the number of executions is less than the number of design attempts described in step S3, then execute steps S4 to S7. If the number of executions is equal to the number of design attempts described in step S3, then execute step S9. S9: After all the design calculations are completed, compare the injection flow curve of the safety injection tank obtained from each design calculation with the minimum injection flow requirement of the safety injection tank determined in step S1. Delete the schemes that do not meet the flow requirement, perform statistical evaluation on the remaining schemes, and obtain the feasible design parameter range of the safety injection tank.

2. The rapid design method for a passive accumulator safety injection tank in a nuclear reactor according to claim 1, characterized in that: Step S6 includes the following steps: S61: Calculate the total driving head based on the gas space pressure and liquid level in the injection tank; S62: Calculate the injected flow at the current moment; S63: Calculate the volume of coolant injected at the current moment; S64: Calculate the remaining coolant volume at the current moment; S65: Calculate the pressure in the top gas space at the current moment; S66: Move to the next time step; S67: Calculate the liquid level in the ampoule tank at the next moment; S68: Determine whether the liquid in the safety injection tank has been drained. If the safety injection tank has not been drained, proceed to steps S61 to S67. If the liquid in the safety injection tank has been drained, obtain the flow curve of the material replacement water tank and the pressure relief protection system.

3. The rapid design method for a passive accumulator safety injection tank in a nuclear reactor according to claim 2, characterized in that: The total driving head mentioned in step S61 can be calculated using equation (1): In the formula: ρ ACC The density of the supercooled water in the injection tank is represented by g; g is the gravitational constant; h ACC Indicates the water level inside the injection tank; h ACC-DVI Indicates the height of the bottom of the ampoule tank from the DVI injection line; P N2 This indicates the pressure of N2 inside the injection tank; P RCS This represents the pressure change curve of the primary loop system after the accident.

4. The rapid design method for a passive accumulator safety injection tank in a nuclear reactor according to claim 3, characterized in that: The injection flow rate is obtained by obtaining the total driving head ΔP in step S61, and then calculated using Darcy's formula, which is shown in equation (2): ΔP=R·q 2 (2) In the formula, R represents the flow resistance coefficient of the injection pipeline of the injection tank, and q is the injection flow rate.

5. The rapid design method for a passive accumulator safety injection tank in a nuclear reactor according to claim 3, characterized in that: The ρ ACC Calculations were made based on the current pressure of the injection chamber and the maximum design temperature of the injection chamber.

6. The rapid design method for a passive accumulator safety injection tank in a nuclear reactor according to claim 1, characterized in that: The design parameters of the injection tank include shape, height, inner diameter, air space pressure, and air-to-water ratio.

7. The rapid design method for a passive accumulator safety injection tank in a nuclear reactor according to claim 2, characterized in that: Step S63 is calculated using the following formula: The volume of coolant injected at the current time step = injection flow rate * time step / injection water density.

8. The rapid design method for a passive accumulator safety injection tank in a nuclear reactor according to claim 2, characterized in that: Step S64 is calculated using the following formula: Remaining volume = Remaining volume at the previous time step - Injected volume at the current time step.

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