Response prediction method and device after pressure suppression type containment is broken, computer program and storage medium

Abstract

The invention discloses a method for predicting the response of a suppression type containment after breaking, belongs to the technical field of nuclear energy engineering, and particularly relates to the technical field of suppression type containment response analysis in nuclear safety and nuclear reactor engineering. The method comprises the following steps: S1, predicting a loop response state according to reactor parameters and crevasse conditions of a to-be-predicted suppression type containment; s2, predicting the response state of the containment on the basis of the obtained response state of the primary loop; s3, on the basis of the response state of the containment, predicting the response state of the water space of the pressure suppression box; and S4, based on the response state of the containment, predicting the response state of the pressure suppression box air space. According to the method, the problems of insufficient precision, lack of systematicness and incapability of comprehensively considering multi-factor interaction in the traditional method are solved, so that the safety and the emergency response capability of the nuclear power plant in major accidents are improved. The method is applicable to the field of nuclear energy, in particular to safety design of a nuclear power station and safety evaluation of a nuclear reactor.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear energy engineering, and specifically relates to the technical field of suppression containment response analysis in nuclear safety and nuclear reactor engineering. Background Art

[0002] The suppression containment (Containment Vessel) is a key safety barrier in nuclear power plants and nuclear power installations, mainly used to prevent radioactive substances from entering the environment in the event of a severe accident. Compared with traditional dry containments, the suppression containment design has higher safety. Especially when high-temperature and high-pressure coolant is sprayed into the containment, it can effectively suppress the pressure rise inside the containment and reduce the breakage risk in the initial stage of the accident. Its principle is mainly to control the pressure through a suppression system installed inside the containment to reduce the damage to the containment during an accident.

[0003] In the design of the suppression containment, compressed gas, heat absorption devices, and efficient heat exchange systems are usually used to absorb and dissipate heat, so as to ensure that the containment can remain intact under high-temperature and high-pressure conditions and effectively avoid radioactive substance leakage. Compared with the dry containment, the advantage of the suppression containment is that its design pressure is lower, which can reduce the volume and weight of the structure itself.

[0004] The core advantage of the suppression containment also lies in its filtering and retention ability for radioactive substances. In the event of a large-break loss-of-coolant accident (LOCA), the containment can quickly filter radioactive gases and control the release of radioactive substances through a retention system. Multiple studies have shown that the efficient filtering ability of the suppression containment plays an important role in reducing environmental pollution during a severe accident. By reasonably designing and optimizing the structure of the suppression containment, the safety of nuclear power plants can be greatly improved and potential risks can be reduced.

[0005] Currently, the prediction methods for the response of suppression containments usually have problems of insufficient accuracy and lack of systematicness. Traditional methods often do not fully consider the details of the coolant during different spraying stages, especially during subcooled spraying and saturated spraying, and fail to accurately simulate the dynamic behavior of the coolant. This makes it impossible to accurately predict the effect of coolant spraying and the pressure change inside the containment during a nuclear accident, thus affecting the emergency response and safety assessment of the accident.

[0006] In addition, traditional prediction methods usually focus on the analysis of single factors and fail to comprehensively consider the interactions among coolant, steam, and gas. In actual accidents, these factors interact with each other. Therefore, traditional methods lack systematicness and are difficult to accurately reflect the comprehensive response of the entire reactor system. Especially for the prediction of gas mixtures, such as the interaction between air and steam in the containment, mass conservation, and temperature changes, traditional methods also fail to fully consider, resulting in large errors in pressure prediction and affecting safety assessment.

[0007] In addition, when traditional methods predict the response of the suppression pool, they often treat the water space and gas space separately, ignoring their interactions, especially the influence of the water and steam condensation process on pressure and temperature changes. This makes the cooling and pressure control functions of the suppression pool in nuclear accidents not fully evaluated, thus reducing the overall safety of nuclear power plants. Summary of the Invention

[0008] A method for predicting the response after a break in a suppression-type containment of the present invention ensures the close cooperation of each link by comprehensively considering multiple factors such as the coolant ejection process, gas mixing and change, and the dynamic response of the suppression pool, and provides more accurate pressure prediction and accident response capabilities, as follows:

[0009] A method for predicting the response after a break in a suppression-type containment, the suppression-type containment including a suppression tank, the method being implemented based on reactor parameters and break conditions, the method comprising:

[0010] S1. A step of predicting the response state of the primary loop according to the reactor parameters and break conditions of the suppression-type containment to be predicted;

[0011] S2. A step of predicting the response state of the containment based on the obtained response state of the primary loop;

[0012] S3. A step of predicting the response state of the water space of the suppression tank based on the response state of the containment;

[0013] S4. A step of predicting the response state of the gas space of the suppression tank based on the response state of the containment.

[0014] Further, the reactor parameters in S1 include: the pressure and temperature of the primary loop, the water inventory of the suppression tank, the volume of the pressurizer, and the volume of the containment; the break condition is the break diameter.

[0015] Further, the response state of the primary loop in S1 includes the coolant subcooled ejection stage;

[0016] In the coolant subcooled ejection stage, the single-phase water is ejected from the break;

[0017] During the blowdown process, the mass conservation of the coolant is as follows:

[0018]

[0019] Among them, M 1 is the total mass of the primary coolant, M 12 is the mass of the coolant that blows through the break into the containment per unit time in the primary loop, and t is time;

[0020] Using the orifice flow method, the blowdown flow rate of single-phase water is obtained as follows:

[0021]

[0022] Among them, D is the break diameter; c d is the flow coefficient; ρ 1 is the density of the primary coolant; p 1 and p 2 are the primary loop pressure and the containment pressure respectively.

[0023] Furthermore, the predicted containment response state described in S2 includes:

[0024] S21. Predicting the water column clearing time:

[0025]

[0026] Among them, l is the true length of the water column; D 23 represents the diameter of the discharge pipe; g represents the gravitational acceleration constant; ρ 3,w represents the water density in the water space of the suppression pool; p 3 represents the pressure in the water space of the suppression pool;

[0027] S22. Predicting the containment pressure response:

[0028] S221. Predicting the air mass conservation in the containment:

[0029]

[0030] M 2,a represents the air mass in the containment; W a represents the mass fraction of air in the containment; M 23 represents the mass of the mixed gas discharged from the containment into the suppression pool per unit time;

[0031] S222. Predicting the steam mass conservation according to the primary loop response state:

[0032]

[0033] M 2,s represents the mass of steam in the containment;

[0034] S223. Obtain the relative molecular mass of the air and steam mixture inside the containment according to the air quality conservation in the containment:

[0035]

[0036] Among them, M m represents the relative molecular mass of the mixed gas, 29 is the relative molecular mass of air, and 18 is the relative molecular mass of water molecules;

[0037] S224. Combine steps S221 - S223 to obtain the temperature of the air and steam mixture inside the containment:

[0038]

[0039] Among them, c p,s and c p,a respectively represent the specific heat at constant pressure of steam and air, T sat represents the saturation temperature at the corresponding steam partial pressure inside the containment, and T 2 represents the temperature inside the containment;

[0040] S225. Obtain the pressure response inside the containment according to the temperature of the air and steam mixture inside the containment:

[0041]

[0042] Among them, M 2 represents the mass of the mixed gas, V 2 represents the volume inside the containment, and 8.314 is the ideal gas constant.

[0043] Furthermore, the predicted response state of the water space in the suppression pool described in S3 includes:

[0044] S31. Predict the mass conservation of the water space in the suppression pool based on the response state of the containment:

[0045]

[0046] S32. Obtain the heating rate of the water space in the suppression pool according to the mass conservation of the water space in the suppression pool:

[0047]

[0048] Among them, T 3 represents the temperature of the water space in the suppression pool, M 3 represents the mass of the water space in the suppression pool, h fg represents the latent heat of vapor condensation, and c p,w represents the specific heat at constant pressure of water.

[0049] Further, the predicted response state of the suppression pool gas space in S4 includes:

[0050] S41. Predict the mass conservation of the suppression pool gas space based on the response state of the containment:

[0051]

[0052] S42. Obtain the volume change of the suppression pool gas space according to the mass conservation of the suppression pool gas space:

[0053]

[0054] S43. Obtain the pressure of the suppression pool gas space according to the volume change of the suppression pool gas space:

[0055] p 4 = p 4,a + p sat (T 4 )

[0056] wherein, M 4 represents the mass of the suppression pool gas space, V 4 represents the volume of the suppression pool gas space, T 4 represents the temperature of the suppression pool gas space, and p sat () represents the vapor saturation pressure at the corresponding temperature.

[0057] Based on the same inventive concept, the present invention also provides a method for predicting the response after a break in a suppression type containment, the device including:

[0058] A module for predicting the response state of the primary loop according to the reactor parameters and break conditions of the suppression type containment to be predicted;

[0059] A module for predicting the response state of the containment based on the obtained response state of the primary loop;

[0060] A module for predicting the response state of the suppression pool water space based on the response state of the containment;

[0061] A module for predicting the response state of the suppression pool gas space based on the response state of the containment.

[0062] Based on the same inventive concept, the present invention also provides a computer storage medium for storing a computer program, when the computer program is read by a computer, the computer executes the method of the present invention.

[0063] Based on the same inventive concept, the present invention also provides a computer, including a processor and a storage medium, when the processor reads the computer program stored in the storage medium, the computer executes the method of the present invention.

[0064] Based on the same inventive concept, the present invention also provides a computer program product. As a computer program, when the computer program is read, the method described in the present invention is implemented.

[0065] Beneficial effects

[0066] (1) The present invention can improve the prediction accuracy of the coolant injection process. During the subcooled injection and saturated injection stages of the coolant, through refined modeling, the present invention first considers multiple factors such as the coolant flow coefficient, coolant density, and steam density for comprehensive and detailed prediction. Especially during the subcooled injection stage, traditional methods ignore the non-ideal state changes during the injection process, while the present invention makes the prediction more accurate by comprehensively considering the dynamic changes of various physical parameters. However, during the initial model construction process, the R & D team encountered the non-linear relationship between the coolant injection flow rate and the initial coolant state. Attempting to simplify the prediction through linear approximation, it was found that the accuracy could not meet the requirements. After multiple experiments and optimizations, the R & D team finally found the best solution to balance prediction accuracy and complexity, ensuring that the injection behavior can be accurately simulated and reducing the prediction errors existing in traditional methods.

[0067] (2) The present invention comprehensively considers the interactions of multiple physical factors. During the development of the present invention, it was realized that the interactions between the coolant, steam, and gas have an impact on the prediction results. Through comprehensive multi-physical field analysis using methods such as the mass conservation equation and energy conservation equation, the present invention can more comprehensively reflect the behavior of the coolant injection and various substances in the containment. However, during the initial combination of these equations, complex problems caused by the interactions between variables in multi-physical field coupled prediction were encountered. For this reason, the team made a large number of attempts and failures, and gradually proposed to effectively separate different physical factors through algorithms combined with optimization methods. Finally, through step-by-step prediction, the coupling errors in physical interactions were avoided, ensuring the accurate prediction of the gas pressure and temperature in the containment.

[0068] (3) The present invention can improve the accuracy of the prediction of the containment pressure response. When simulating the containment pressure response, the R & D team organically combines the mass conservation of the gas mixture with the temperature change, and optimizes the prediction of the pressure evolution by accurately simulating the interactions and mixing states of the gases. However, during the R & D process, the initial gas mixing model could not accurately predict the behavior of the gas under high-temperature conditions, resulting in deviations in the prediction results. After multiple rounds of adjustment and model optimization, the R & D team successfully overcame this challenge and made innovations in the complexity of gas behavior. Especially in terms of the accuracy of the containment pressure response, the R & D team significantly improved the prediction reliability by introducing a new steam-air mixture state equation, avoiding the errors in traditional methods.

[0069] (4) The present invention can optimize the response prediction of the water space and gas space in the suppression pool. During the development process, the R & D team realized that the interaction between the water space and gas space is extremely important for the overall safety system. Through detailed prediction of mass conservation and temperature change, the present invention can accurately predict the dynamic response of the suppression pool. Initially, there were certain deviations in the estimation of the water space heating rate and gas space pressure change in the prediction, resulting in insufficient expected effects. To overcome this problem, the R & D team continuously adjusted the prediction model. Through repeated experiments and algorithm optimization, it was finally able to accurately simulate the water space heating and gas space pressure change, ensuring the cooling and pressure control functions of the suppression pool in major accidents.

[0070] (5) The present invention can improve the overall safety and emergency response ability. By accurately predicting multiple links such as coolant injection, reactor pressure, and the water-gas response in the suppression pool, the present invention can provide more reliable safety assessments for designers. However, during the R & D process, the R & D team faced many failures. Especially when simulating complex accident scenarios, the traditional methods could not fully consider the coupling effects between various links, resulting in inaccurate prediction results. The R & D team gradually broke through these technical bottlenecks by continuously modifying the algorithm, ensuring that the present invention can accurately simulate the coolant injection, reactor pressure change, and the response of the suppression pool after an accident, improving the emergency response ability of nuclear power plants in major accidents.

[0071] (6) The present invention can improve the design quality of designers in the product design stage. Through the prediction method of the present invention, more accurate data support can be provided for designers during R & D. Through these data, the space of the suppression containment can be optimized. During the R & D process, the R & D team was once in trouble due to the computational complexity of multiple variables. Especially in the response prediction under different break conditions, the traditional methods could not consider all possible accident situations, resulting in design limitations. After many attempts and repeated verifications, the R & D team proposed a new prediction method. Through accurate modeling and multi-variable prediction, more accurate parameter basis is provided for the field of suppression containment design, improving the reliability of the overall design.

[0072] The present invention is applicable to the nuclear energy field, especially the safety design of nuclear power plants and the safety assessment of nuclear reactors. It provides an accurate prediction method for the suppression containment design, and can accurately simulate the coolant injection, pressure change, and the response of the suppression pool in the event of a severe accident, such as a large-break loss-of-coolant accident (LOCA). This is crucial for the design and operation safety of nuclear power plants and can improve the accident response ability of nuclear power plants in emergencies.

[0073] In addition, the present invention can also be applied to the design of nuclear power plants (such as nuclear submarines, aircraft carriers, etc.). Especially in surface or underwater nuclear power plants, the design requirements for the containment are extremely strict, and the present invention can help optimize its compressive capacity and safety. During the research and development process of nuclear safety technology, the present invention can also provide a reliable prediction basis for a new generation of nuclear energy equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 is a flowchart of the prediction method for the response after the break of the suppression type containment described in Embodiment 1;

[0075] Figure 2 is the primary loop pressure response curve under different break size conditions described in Embodiment 6

[0076] Figure 3 is the post-accident containment pressure response curve described in Embodiment 6

[0077] Figure 4 is the influence of the immersion depth of the discharge pipe on the maximum pressure of the containment described in Embodiment 6

[0078] Figure 5 is the influence of the flow area of the discharge pipe on the maximum pressure of the containment described in Embodiment 6

[0079] Figure 6 is the influence of the water space volume of the suppression pool on the maximum pressure of the containment described in Embodiment 6 EMBODIMENT

[0081] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0082] Embodiment 1

[0083] Combined with the attached Figure 1 To illustrate this embodiment, this embodiment provides a prediction method for the response after the break of a suppression type containment. The suppression type containment includes a suppression tank. The method is implemented based on reactor parameters and break conditions, and the method includes:

[0084] S1. A step of predicting the response state of the primary loop according to the reactor parameters and break conditions of the suppression type containment to be predicted;

[0085] S2. A step of predicting the response state of the containment based on the obtained response state of the primary loop;

[0086] Step S3: Predicting the response status of the suppression pool water space based on the response status of the containment;

[0087] Step S4: Predicting the response status of the suppression pool gas space based on the response status of the containment.

[0088] This embodiment provides a systematic prediction method for the response of a suppression-type containment rupture. Based on the reactor parameters and rupture conditions, a complete process covering the prediction of the response status of the primary loop, containment, suppression pool water space, and gas space is constructed. This enables a comprehensive and coherent analysis of the complex physical processes after a rupture in a suppression-type containment.

[0089] Furthermore, the reactor parameters in S1 include: the pressure and temperature of the primary loop, the water inventory of the suppression pool, the volume of the pressurizer, and the volume of the containment; the rupture condition is the rupture diameter.

[0090] Constructed for the specific object of a suppression-type containment based on the actually obtainable reactor parameters and rupture conditions, the method has strong pertinence and practicality and can be directly applied to relevant nuclear facility safety analysis scenarios.

[0091] Embodiment Two

[0092] This embodiment is a further explanatory description of Embodiment One. Furthermore, the response status of the primary loop in S1 includes the coolant subcooled spray phase;

[0093] In the coolant subcooled spray phase, the single-phase water is sprayed from the rupture;

[0094] During the spray process, the mass conservation of the coolant is:

[0095]

[0096] where M 1 is the total mass of the primary loop coolant, M 12 is the mass of the coolant sprayed from the rupture of the primary loop into the containment per unit time, and t is the time;

[0097] Using the orifice flow method, the spray flow rate of the single-phase water is obtained as:

[0098]

[0099] where D is the rupture diameter; c d is the flow coefficient; ρ 1 is the density of the primary loop coolant; p 1 and p 2 are the primary loop pressure and the containment pressure respectively.

[0100] This embodiment defines the coolant subcooled spray stage in the primary loop response state, and accurately depicts the single-phase water spray and the spray process in this stage. By giving the coolant mass conservation equation and the single-phase water spray flow formula based on the orifice flow method, the spray situation of the primary loop coolant after the break can be accurately predicted, providing accurate initial conditions and data basis for subsequent analysis of the containment and other parts, and helping to improve the accuracy of the entire prediction method for the response analysis of the primary loop system.

[0101] Embodiment 3

[0102] This embodiment is a further explanatory description of Embodiment 1. Further, the predicted containment response state in S2 includes:

[0103] S21. Predict the water column cleaning time:

[0104]

[0105] where l is the true length of the water column; D 23 represents the discharge pipe diameter; g represents the gravitational acceleration constant; ρ 3,w represents the water density in the suppression pool water space; p 3 represents the pressure in the suppression pool water space;

[0106] S22. Predict the containment pressure response:

[0107] S221. Predict the air mass conservation in the containment:

[0108]

[0109] M 2,a represents the air mass in the containment; W a represents the mass fraction of air in the containment; M 23 represents the mass of the mixed gas discharged from the containment into the suppression pool per unit time;

[0110] S222. Predict the steam mass conservation according to the primary loop response state:

[0111]

[0112] M 2,s represents the steam mass in the containment;

[0113] S223. Obtain the relative molecular mass of the air and steam mixture in the containment according to the air mass conservation in the containment:

[0114]

[0115] where M mrepresents the relative molecular mass of the mixture gas, 29 is the relative molecular mass of air, and 18 is the relative molecular mass of water molecules;

[0116] S224. Combine steps S221 - S223 to obtain the temperature of the air and steam mixture inside the containment:

[0117]

[0118] where c p,s and c p,a represent the specific heat at constant pressure of steam and air respectively, T sat represents the saturation temperature at the corresponding steam partial pressure inside the containment, and T 2 represents the temperature inside the containment;

[0119] S225. Obtain the pressure response inside the containment based on the temperature of the air and steam mixture inside the containment:

[0120]

[0121] where M 2 represents the mass of the mixed gas, V 2 represents the volume inside the containment, and 8.314 is the ideal gas constant.

[0122] This embodiment predicts and analyzes the response state of the containment from multiple aspects such as the water column cleaning time, air mass conservation, steam mass conservation, relative molecular mass of the mixture, temperature, and pressure response. These calculations are interrelated and comprehensively reflect the mass changes of air and steam inside the containment after a break, as well as the resulting temperature and pressure responses, providing rich and detailed data support for accurately evaluating the overall physical state and safety of the containment after a break. For example, by predicting air mass conservation and steam mass conservation, the dynamic changes of different component substances inside the containment can be clearly understood; by obtaining the temperature and pressure responses of the mixture, the stability of the internal environment of the containment can be intuitively judged.

[0123] Embodiment Four

[0124] This embodiment is a further explanatory description of Embodiment One. Further, the prediction of the response state of the water space in the suppression pool in S3 includes:

[0125] S31. Predict the mass conservation of the water space in the suppression pool based on the response state of the containment:

[0126]

[0127] S32. Obtain the heating rate of the water space in the suppression pool according to the mass conservation of the water space in the suppression pool:

[0128]

[0129] Among them, T 3 represents the temperature of the water space in the suppression pool, M 3 represents the mass of the water space in the suppression pool, h fg represents the latent heat of vapor condensation, c p,w represents the specific heat capacity of water at constant pressure.

[0130] This embodiment focuses on the response state of the water space in the suppression pool. Through the prediction of mass conservation and the heating rate, it deeply reveals the thermo-dynamic response of this space after a break. The mass conservation equation clearly defines the internal relationship of the mass change in the water space of the suppression pool, and the prediction of the heating rate quantifies the temperature change caused by energy conversion. This provides core data for evaluating the stability and safety of the water space in the suppression pool within the entire containment system, and helps to understand the physical property changes of the water space under complex working conditions.

[0131] Embodiment 5

[0132] This embodiment is a further explanatory description of Embodiment 1. Further, the prediction of the response state of the gas space in the suppression pool in S4 includes:

[0133] S41. Predict the mass conservation of the gas space in the suppression pool based on the response state of the containment:

[0134]

[0135] S42. Obtain the volume change of the gas space in the suppression pool according to the mass conservation of the gas space in the suppression pool:

[0136]

[0137] S43. Obtain the pressure of the gas space in the suppression pool according to the volume change of the gas space in the suppression pool:

[0138] p 4 = p 4,a + p sat (T 4 ),

[0139] Among them, M 4 represents the mass of the gas space in the suppression pool, V 4 represents the volume of the gas space in the suppression pool, T 4 represents the temperature of the gas space in the suppression pool, p sat () represents the saturated vapor pressure at the corresponding temperature.

[0140] In this embodiment, a complete analysis system is formed by successively predicting the mass conservation, volume change, and pressure of the suppression pool gas space, comprehensively and deeply revealing the response characteristics of the suppression pool gas space after a break. This is of great significance for deeply understanding the function and action mechanism of the suppression pool gas space in the entire containment system. For example, by analyzing the response of the gas space at different stages, the design and operation strategies of the containment system can be optimized, the ability of the system to cope with break accidents can be improved, and the safe and stable operation of nuclear facilities can be ensured.

[0141] Embodiment Six

[0142] This embodiment aims to provide a specific example to give a detailed explanation of Embodiments One to Five in combination with the actual situation, as follows:

[0143] This embodiment combines the typical initial parameters of a pressurized water reactor and uses the method for predicting the response of a suppression-type containment after a break of the present invention for detailed analysis and application. By simulating the response processes of the reactor primary loop, suppression pool, and containment under different break diameters, the effectiveness of this method is verified, and its application advantages are further clarified.

[0144] Step 1: Define the key parameters of the reactor and the break conditions;

[0145] The acquisition method is the factory design of the reactor as a product. The key parameters of the reactor include: primary loop pressure, temperature, water inventory, pressurizer volume, and containment volume. The break conditions include: break diameter.

[0146] The "primary loop" refers to an important part of the cooling system in a nuclear power plant, usually used to describe the working principle and process of the primary coolant system. It is a term in the nuclear power plant heat exchange system and is used to represent the path of the nuclear reactor coolant circulation.

[0147] The "pressurizer" is one of the conventional components of the cooling system in a nuclear power plant, and its function is to keep the pressure and temperature in the reactor cooling system within a safe range to avoid equipment damage or cooling system failure caused by too high or too low pressure.

[0148] This embodiment selects some typical initial parameters of the reactor and performs calculations based on them:

[0149] Primary loop pressure: 15.5 MPa

[0150] Primary loop temperature: 280 °C

[0151] Primary loop water inventory: 100 m 3

[0152] Pressurizer volume: 10 m 3

[0153] Total volume of the containment and suppression pool: 1000 m 3

[0154] Break diameter: 0.1 m, 0.2 m, 0.3 m and 0.4 m respectively

[0155] These parameters represent a typical initial state of a pressurized water reactor. By analyzing these initial parameters, the response process of an actual nuclear power plant during a LOCA (Loss of Coolant Accident) can be better simulated.

[0156] Step 2: Calculate the primary loop response;

[0157] 1. Subcooled coolant ejection phase

[0158] Since the initial state of the primary loop coolant is subcooled, at the initial stage of the ejection after the accident, the single-phase water is discharged from the break. Because the ejection process time is very short, the change in the enthalpy value of the coolant during the ejection process can be ignored. Thus, the subcooled ejection phase ends when the primary loop pressure drops to the saturation pressure corresponding to the initial specific enthalpy of the coolant. Assume that during the subcooled ejection, an isentropic expansion process occurs in the vapor space of the pressurizer, and the rate of the primary loop pressure reduction can be alleviated during the expansion process.

[0159] During the ejection process, the mass conservation of the primary loop coolant can be expressed as:

[0160]

[0161] where M 1 is the total mass of the primary loop coolant, M 12 is the mass of the coolant ejected from the break into the containment per unit time in the primary loop; d is the derivative, and t is the time;

[0162] Assume that the break position is close to the reactor pressure vessel during the ejection process, and the orifice flow formula can be used to calculate the ejection flow rate of the single-phase water as:

[0163]

[0164] where D is the break diameter; c d is the flow coefficient; ρ 1 is the density of the primary loop coolant; ρ 1 and ρ 2 are the primary loop pressure and the containment pressure respectively;

[0165] In this embodiment, it is adopted that: break diameter D = 0.1; flow coefficient c d = 0.8; density of the primary loop coolant ρ 1 = 1000 kg / m 3 ; primary loop pressure p1 = 15.5 MPa = 15.5×10 6 Pa; The containment pressure p 2 = 2 MPa = 2×10 6 Pa;

[0166] Substituting into formula (2), M can be obtained 12 ≈ 41.12 kg / s.

[0167] As the subcooled spray discharge process progresses, the pressure in the primary loop of the reactor drops, and the saturated water in the pressurizer flashes, resulting in an increase in the volume of the vapor space. According to the volume conservation, neglecting the change in the specific volume of single-phase water, the increased steam volume in the pressurizer is equal to the volume of the single-phase water discharged, that is:

[0168]

[0169] where V 0 is the volume of the vapor space in the pressurizer, m 3 .

[0170] Substituting the result of formula (2) into formula (3), we can obtain

[0171] Assuming that the process occurring in the vapor space of the pressurizer is an isentropic expansion process, its process equation can be expressed as:

[0172]

[0173] The superscript 0 represents the state before the accident. For steam, the adiabatic index κ = 1.3 is taken.

[0174] By calculating the coolant discharge amount under different break sizes, we can obtain the pressure response of the primary loop.

[0175] After the primary loop coolant is discharged into the containment, the coolant will gradually turn into a two-phase flow of steam and water and enter the saturated spray discharge stage. The calculation of the discharge amount in this stage uses the formula for critical flow and combines the energy conservation equation to calculate the mass change of steam and water in the primary loop, ensuring that the conversion and condensation of the coolant discharge amount and energy change in the containment can be effectively managed.

[0176] 2. Saturated spray discharge stage

[0177] As the LOCA accident develops, when the pressure in the primary loop drops to the saturated pressure corresponding to the initial specific enthalpy of the coolant, the coolant reaches the saturated state and the saturated spray discharge process begins. Assuming that the saturated steam is discharged from the break during the saturated spray discharge process, using the orifice flow formula, the steam flow rate can be calculated as follows:

[0178]

[0179] Among them, ρ s represents the steam density, kg / m 3 ; p cr represents the critical pressure, Pa.

[0180] Considering that there may be a critical flow state of steam at this stage,

[0181] Therefore, when p 1 > 2p 2 , p cr = 0.5p 1 ;

[0182] When p 1 < 2p 2 , p cr = p 2 .

[0183] In this embodiment, the following are adopted: the break diameter D = 0.1; the flow coefficient c d = 0.8; the steam density ρ s = 1.7 kg / m 3 ; the critical pressure p cr = 0.5 × p 1 (when p 1 > 2p 2 , the critical pressure is p cr = 0.5p 1 );

[0184] Substituting into formula (5), M 12 ≈ 40.63 kg / s can be obtained.

[0185] In the saturated ejection stage, the primary coolant is in a two-phase saturated state. If the heating effect of the decay heat of the reactor core on the coolant is ignored, the energy equation satisfied by the mixture composed of steam and saturated water can be expressed as:

[0186]

[0187] After arrangement, it is obtained that:

[0188]

[0189] Among them, M 1w represents the mass of the primary saturated water, kg; 1w and 1s respectively represent the specific enthalpies of the primary saturated water and steam, J / kg. M 10 represents the initial mass of the primary coolant.

[0190] The ejection flow rate M of the coolant during the subcooled ejection stage 12≈41.12 kg / s, the volume change rate of the pressurizer steam space is 0.04112 m 3 / s; the steam discharge flow rate M during the saturated blowdown stage 12 ≈40.63 kg / s.

[0191] Step 3: Calculate the containment response;

[0192] Before the occurrence of the LOCA accident, there will be a water column in the discharge pipeline. When the accident occurs, the mixture from the containment will first remove the water column originally retained in the discharge channel immersed in the pool, and then the mixture in the containment will start to be substantially discharged into the suppression pool.

[0193] 1 Water column cleaning in the discharge pipe

[0194] Considering the inertia of the water body in the water space, it is assumed that there is an additional water column with a height equal to the pipeline diameter below the lower part of the real water column in the discharge pipe. According to Newton's third law, the motion equation of the liquid column can be expressed as:

[0195]

[0196] where, l represents the real length of the water column, m; D 23 represents the discharge pipeline diameter, m; g represents the gravitational acceleration constant; ρ 3,w represents the water density in the suppression pool water space, kg / m 3 ; p 3 represents the pressure in the suppression pool water space, pa.

[0197] According to Equation (8) and the initial conditions:

[0198]

[0199] where, l sm represents the immersion depth of the discharge pipeline;

[0200] In this embodiment, the following are adopted: the real length of the water column l = 2 m; the discharge pipeline diameter D 23 = 0.1 m; the gravitational acceleration g = 9.81 m / s 2 ; the water density ρ in the suppression pool water space 3,w = 1000 kg / m 3 ; the containment pressure p 2 = 2×10 6 Pa; the pressure p in the suppression pool water space 3 = 2×10 5 Pa;

[0201] Substituting into formula (8), the acceleration of the water column in the discharge pipe can be obtained:

[0202]

[0203] Combined with the initial conditions, the cleaning time of the water column in the discharge pipe is obtained:

[0204] t≈0.208s

[0205] 2. Containment pressure response

[0206] After the LOCA accident occurs, the coolant sprayed into the containment in the primary circuit flashes, and at the same time, the steam-air mixture in the containment is continuously discharged into the suppression pool. Assuming that the steam and air in the containment are completely mixed, the mass conservation equation of the air therein can be described as:

[0207]

[0208] Among them, M 2,a represents the air mass in the containment, kg; W a represents the mass fraction of air in the containment; M 23 represents the mass of the mixed gas discharged from the containment into the suppression pool per unit time, kg / s.

[0209] The mass conservation equation satisfied by the steam in the mixed gas can be expressed as:

[0210]

[0211] M 2，s represents the mass of steam in the containment.

[0212] The gas discharge rate between the containment and the suppression pool is also calculated using the orifice flow formula, and its expression is:

[0213]

[0214] Among them, c d represents the flow coefficient; ρ2 represents the density of the gas in the suppression pool;

[0215] Considering the possible critical flow phenomenon in the saturated spray stage,

[0216] it can be considered that when p 2 > 2p 3 , p cr = 0.5p 2 ;

[0217] when p 2 < 2p 3 , p cr = p 3 .

[0218] This embodiment adopts: the mass fraction W of air in the containment a= 0.8; Flow coefficient c d = 0.6; Density ρ of the gas in the suppression pool 2 = 0.6 kg / m 3 ; Critical pressure p cr = 0.5 × p 2 ;

[0219] Substitute into formula (11) to obtain the mass of the mixed gas discharged from the containment into the suppression pool per unit time

[0220] M 23 = 3.65 kg / s.

[0221] Assume that the steam * air mixture gas satisfies the ideal gas state equation, and the relative molecular mass of the mixed gas can be expressed as:

[0222]

[0223] M m Represents the relative molecular mass of the mixed gas; 29 is the relative molecular mass of air; 18 is the relative molecular mass of water molecules.

[0224] This embodiment adopts: Mass fraction W of air in the containment a = 0.8;

[0225] Substitute into formula (12) to obtain the relative molecular mass M of the mixed gas m ≈ 27.15.

[0226] According to the heat balance relationship, the temperature of the mixture in the containment can be calculated according to the following relationship:

[0227]

[0228] Among them, c p，s and c p，a Respectively represent the specific heat at constant pressure of steam and air, J / kgK; T sat Saturation temperature corresponding to the partial pressure of steam in the containment, °C, T 2 Represents the temperature in the containment;

[0229] This embodiment adopts:

[0230] Specific heat at constant pressure c of steam p，s = 2000 J / kg·K;

[0231] Specific heat at constant pressure c of air p，a = 1005 J / kg·K;

[0232] Substitute into formula (13) to obtain the temperature T in the containment 2 = 50.01 °C.

[0233] According to the state equation of the mixed gas, the pressure response in the containment during the blowdown phase can be calculated, and its expression can be written as:

[0234]

[0235] M 2 represents the mass of the mixed gas, V 2 represents the volume inside the containment, and 8.314 is the ideal gas constant.

[0236] This embodiment adopts: the volume V inside the containment 2 = 500 m 3 ;

[0237] Substituting into formula (14), the pressure response p in the containment during the blowdown phase is obtained 2 V 2 ≈ 149595.4 Pa

[0238] Step Four: Calculate the water space response of the suppression pool;

[0239] Assuming that the water vapor in the steam-air mixture entering the suppression pool is completely condensed, the mass conservation equation in the water space of the suppression pool can be expressed as:

[0240]

[0241] According to the energy balance, the heating rate of the water space in the suppression pool can be expressed as:

[0242]

[0243] Among them, M 3 represents the mass of the water space in the suppression pool, kg; fg represents the latent heat of vapor condensation, J / kg; c p,w represents the specific heat capacity at constant pressure of water, J / kgK.

[0244] Step Five: Calculate the gas space response of the suppression pool;

[0245] If the steam in the mixed gas discharged into the suppression pool is completely condensed, the air enters the gas space of the suppression pool, and the mass conservation equation satisfied by the air can be expressed as:

[0246]

[0247] Since the suppression pool is a rigid structure, considering the increase in the volume of the water space in the suppression pool, the volume change of the gas space in the suppression pool can be expressed as:

[0248]

[0249] Assuming that the temperature of the water space in the suppression pool is the same as that of the gas space, the state equation of the gas space in the suppression pool can be expressed as:

[0250]

[0251] According to Dalton's law of partial pressures, the pressure in the gas space of the suppression pool is equal to the sum of the steam partial pressure and the air partial pressure:

[0252] p 4 =p 4,a +p sat (T 4 ) (20)

[0253] where M 4 represents the mass of the gas space in the suppression pool, kg; V 4 represents the volume of the gas space in the suppression pool, m 3 ; p 4,a represents the partial pressure of air in the gas space of the suppression pool, Pa; T 4 represents the temperature of the gas space in the suppression pool, °C; p sat () represents the saturated steam pressure at the corresponding temperature, Pa.

[0254] Results display and analysis:

[0255] Figure 2 Shows the variation curves of the primary loop pressure under different break diameters (0.1 m, 0.2 m, 0.3 m, and 0.4 m). As the break diameter increases, the increase in the coolant discharge rate causes the pressure drop rate in the primary loop to accelerate. For example, when the break diameter is 0.4 m, the time for the primary loop pressure to drop to 2 MPa is 200 seconds, while when the break diameter is 0.1 m, it is 10 seconds.

[0256] Figure 3 Shows the containment pressure response curve. Under larger break conditions, the pressure inside the containment rises rapidly, increasing the burden on the containment. By optimizing the design of the discharge pipeline, the pressure of the containment can be reduced.

[0257] Figure 4 Shows the variation of the maximum containment pressure at different immersion depths of the discharge pipe. As the immersion depth of the discharge pipe increases, the water column cleaning time prolongs, delaying the time for the containment to discharge the medium to the suppression pool, resulting in an increase in the containment pressure.

[0258] Figure 5 Shows the variation of the maximum containment pressure at different flow areas of the discharge pipe. When the flow area is greater than 0.28 m 2 , the peak pressure of the containment tends to be stable, indicating that the influence of the discharge pipe flow area on the containment pressure gradually saturates.

[0259] Figure 6 It shows the variation of the maximum containment pressure under different suppression pool water volumes. By optimizing the ratio of the water volume to the gas volume, the containment pressure can be effectively controlled to prevent the system from failing due to excessive pressure.

[0260] Conclusion:

[0261] Through the calculation and analysis of this embodiment, it is verified that the prediction method of the present invention can effectively predict and control the containment response after a reactor break accident. The optimization of different break sizes, discharge pipe designs, and suppression pool volumes can significantly improve the response efficiency of the system, reduce the containment pressure during the accident, and ensure the safety of the nuclear power plant during a LOCA accident.

[0262] The technical solutions provided by the present invention are further described in detail through the above several specific embodiments to highlight the advantages and beneficial effects of the technical solutions provided by the present invention. However, the above several specific embodiments are not used as limitations on the present invention. Any reasonable modifications and improvements to the present invention, combinations of embodiments, and equivalent replacements within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0263] Those skilled in the art can understand that the above are only the preferred embodiments of the present invention. The features described in each embodiment and / or claim of the present disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. It is not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0264] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention. Obviously, those skilled in the art can make various changes and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for predicting the response of a pressure-suppressed containment vessel after a breach, wherein the pressure-suppressed containment vessel comprises a pressure suppression box and a pressurizer, wherein: The method is implemented based on the heap parameters and breach conditions, and the method includes: S1. A step of predicting a primary loop response state according to the reactor parameters and breach conditions of the suppression containment to be predicted; S2, a step of predicting a containment response state based on the obtained primary loop response state; S3, a step of predicting the response state of the water space of the suppression tank based on the response state of the containment shell; S4. A step of predicting the response state of the gas space in the suppression box based on the response state of the containment shell.

2. The response prediction method according to claim 1, characterized in that: The stack parameters in S1 include: the pressure and temperature of the primary circuit, the water content of the suppression tank, the volume of the pressurizer, and the volume of the containment vessel; the breach condition is the breach diameter.

3. The response prediction method according to claim 1, characterized in that: The primary loop response state in S1 includes the coolant supercooling spraying stage; In the coolant supercooling spraying stage, single-phase water is sprayed from the breach; During the spraying process, the mass of the coolant is conserved: Among them, M1 is the total mass of the primary coolant, M 12 is the mass of coolant sprayed into the containment through the breach in one circuit per unit time, and t is the time; Using the orifice flow method, the spray flow rate of single-phase water is obtained as follows: Where D is the diameter of the breach; c d is the flow coefficient; ρ1 is the primary coolant density; p1 and p2 are the primary pressure and containment pressure, respectively.

4. The response prediction method according to claim 1, characterized in that: S2 The predicted containment response state includes: S21. Predicted water column cleanup time: Where l is the true length of the water column; D 23 represents the diameter of the discharge pipe; g represents the gravitational acceleration constant; ρ 3,w represents the water density of the water space in the suppression tank; p3 represents the water space pressure in the suppression tank; S22. Prediction of containment pressure response: S221. Prediction of containment air mass conservation: M 2,a Represents the air quality in the containment; W a Represents the mass fraction of air in the containment; M 23 Represents the mass of mixed gas discharged from the containment into the suppression tank per unit time; S222. Predict steam quality conservation based on the primary circuit response state: M 2,s Represents the mass of steam in the containment; S223. According to the conservation of containment air mass, the relative molecular mass of the mixture of air and steam in the containment is obtained: Among them, M m Represents the relative molecular mass of the mixed gas, 29 is the relative molecular mass of air, and 18 is the relative molecular mass of water molecules; S224. Combine steps S221-S223 to obtain the temperature of the air and steam mixture in the containment: Among them, c p,s and c p,a Represent the specific heat of steam and air at constant pressure, T sat represents the saturation temperature at the corresponding steam partial pressure in the containment, and T2 represents the temperature in the containment; S225. According to the temperature of the air and steam mixture in the containment, the pressure response in the containment is obtained: Among them, M2 represents the mass of the mixed gas, V2 represents the volume inside the containment, and 8.314 is the ideal gas constant.

5. The response prediction method according to claim 1, characterized in that: S3 predicts the response state of the water space of the suppression tank, including: S31. Based on the response state of the containment, predict the mass conservation of the water space in the suppression tank: S32. According to the mass conservation of the water space in the suppression box, the temperature rise rate of the water space in the suppression box is obtained: Among them, T3 represents the temperature of the water space in the suppression tank, M3 represents the mass of the water space in the suppression tank, and h fg represents the latent heat of condensation of steam, c p,w It stands for water-to-constant-pressure hot melt.

6. The response prediction method according to claim 1, characterized in that: S4 said predicting the response state of the suppression box air space includes: S41. Based on the response state of the containment, predict the mass conservation of the suppression box gas space: S42. According to the mass conservation of the suppression box air space, the volume change of the suppression box air space is obtained: S43. Obtain the pressure of the suppression box air space according to the volume change of the suppression box air space: p4=p 4,a +p sat (T4), Among them, M4 represents the mass of the suppression box air space, V4 represents the volume of the suppression box air space, T4 represents the temperature of the suppression box air space, and p sat () represents the steam saturation pressure at the corresponding temperature.

7. A response prediction device after a pressure suppression containment breach, characterized in that: The device comprises: A module for predicting the response state of a primary circuit according to the reactor parameters and breach conditions of the suppression containment to be predicted; A module for predicting the response state of the containment based on the obtained primary loop response state; A module for predicting the response state of the water space in the suppression tank based on the response state of the containment shell; A module that predicts the response state of the suppression box gas space based on the response state of the containment.

8. A computer storage medium for storing a computer program, characterized in that: When the computer program is read by a computer, the computer executes the method according to any one of claims 1 to 6.

9. A computer, comprising a processor and a storage medium, characterized in that: When the processor reads the computer program stored in the storage medium, the computer executes the method according to any one of claims 1 to 6.

10. A computer program product, being a computer program, characterized in that When the computer program is read, the method according to any one of claims 1 to 6 is implemented.

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