Thermal fatigue damage assessment method, system and equipment for waste heat discharge pipeline and medium

Abstract

The invention provides a thermal fatigue damage assessment method, system, equipment and medium for a waste heat removal pipeline, and the method comprises the steps: obtaining parameter information of the waste heat removal pipeline, building a finite element model according to the parameter information, and carrying out the parametric coupling simulation of a leakage opening degree combination of a valve in the finite element model, generating and fitting a thermal stress simulation result with the leakage opening combination, and generating a function relationship between the thermal stress and the leakage opening combination; generating a leakage opening degree combination when the thermal stress is the maximum value according to the function relationship, and recording the leakage opening degree combination as a typical leakage opening degree; according to the typical leakage opening degree and the parameter information, constructing a typical finite element model for fluid-structure interaction simulation, and generating leakage thermal stress; performing steady-state stress simulation analysis on the typical finite element model to generate steady-state stress; and calculating a fatigue damage value according to the leakage thermal stress and the steady-state stress. According to the method, real-time evaluation and monitoring of the thermal fatigue damage of the waste heat removal pipeline are realized, potential risks can be predicted, and the abnormal response speed and safety are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal fatigue damage assessment of nuclear power pipelines, and particularly to a method, system, device and medium for assessing thermal fatigue damage of residual heat removal pipelines. Background Art

[0002] During the operation of a nuclear power plant, it is crucial to ensure the safety of double-valve pipelines in the residual heat removal system, as this directly affects the reactor cooling process and the overall safety of the power plant. The pipelines in the residual heat removal system usually include multiple valve configurations for fluid control and maintaining system pressure when needed. However, due to reasons such as adaptation problems, material aging or mechanical failures, these valves may experience internal leakage, resulting in the flow of low-temperature fluid behind the valve towards the branch pipe, generating a horizontal thermal stratification phenomenon, which in turn causes significant thermal stress and exacerbates the thermal fatigue damage of the pipeline.

[0003] Currently, research on pipeline thermal stress and thermal fatigue mainly relies on empirical analysis and actual monitoring techniques. Although these methods can, to a certain extent, evaluate the structural safety of pipelines, they require a large number of monitoring devices and real-time data processing, increasing the operation and maintenance costs. In addition, these methods are insufficient in predicting the minute changes at the initial stage of leakage and the location of the maximum thermal stress caused by leakage, restricting the early identification and prevention of potential damage to pipelines. Therefore, there is room for improvement. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method, system, device and medium for assessing thermal fatigue damage of residual heat removal pipelines, aiming to solve the technical problem in the prior art of lacking an effective method to accurately predict thermal fatigue damage in the case of leakage of double-valve residual heat removal pipelines.

[0005] To achieve the above object and other related objects, the present invention provides a method for assessing thermal fatigue damage of residual heat removal pipelines. One end of the residual heat removal pipeline is connected to the primary pipeline of the nuclear power unit, and a valve is provided on the branch pipeline at the other end. The thermal fatigue damage assessment method includes:

[0006] Obtain parameter information of the residual heat removal pipeline;

[0007] Construct a finite element model based on the parameter information, perform parametric coupling simulation on the leakage opening combinations of the valves in the finite element model, generate thermal stress simulation results, and perform fitting processing on the thermal stress simulation results and the corresponding leakage opening combinations to generate a functional relationship between the thermal stress of the target area on the residual heat removal pipeline and the leakage opening combinations;

[0008] According to the functional relationship, generate the combination of leakage opening degrees corresponding to the maximum thermal stress in the target area, and denote it as the typical leakage opening degree;

[0009] According to the typical leakage opening degree and the parameter information, construct a corresponding typical finite element model, perform fluid-structure interaction simulation on the typical finite element model, generate the thermal stress in the target area, and denote it as the leakage thermal stress;

[0010] Perform steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress in the target area;

[0011] Calculate the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress.

[0012] In an embodiment of the present invention, the step of constructing a finite element model according to the parameter information, performing parametric coupling simulation on the combination of leakage opening degrees of valves in the finite element model, generating a thermal stress simulation result, and performing fitting processing on the thermal stress simulation result and the corresponding combination of leakage opening degrees to generate the functional relationship between the thermal stress in the target area of the residual heat discharge pipeline and the combination of leakage opening degrees includes:

[0013] According to the parameter information and multiple combinations of leakage opening degrees of all valves, construct multiple corresponding finite element models, and under preset conditions, perform temperature distribution simulation analysis on the multiple finite element models to generate pipeline temperature distribution data corresponding to each finite element thermal analysis model;

[0014] According to the pipeline temperature distribution data, perform thermal stress response simulation analysis on the corresponding finite element model to generate the thermal stress generated in the target area of the residual heat discharge pipeline under each combination of leakage opening degrees;

[0015] Perform fitting processing on all the combinations of leakage opening degrees and the corresponding thermal stresses to generate the functional relationship between the thermal stress in the target area and the combination of leakage opening degrees.

[0016] In an embodiment of the present invention, when the number of valves is two, the functional relationship satisfies the following formula:

[0017]

[0018] Wherein, σ represents the thermal stress in the target area, (x A , x B ) represents the combination of leakage opening degrees, x A represents the leakage opening degree of one of the valves, x B represents the leakage opening degree of the other valve, k1, k2, k3, k4, and k5 represent coefficients, and k0 represents a constant.

[0019] In one embodiment of the present invention, the step of generating the leakage opening combination corresponding to the maximum thermal stress of the target area according to the function relationship and denoting it as the typical leakage opening includes:

[0020] Using a genetic optimization algorithm or a Newton gradient algorithm, calculate the leakage opening combination corresponding to the maximum thermal stress of the target area according to the function relationship, and denote it as the typical leakage opening.

[0021] In one embodiment of the present invention, the step of constructing a corresponding typical finite element model according to the typical leakage opening and the parameter information, performing a fluid-structure interaction simulation on the typical finite element model, generating the thermal stress of the target area, and denoting it as the leakage thermal stress includes:

[0022] Construct a corresponding typical finite element model according to the typical leakage opening and the parameter information, and calculate the leakage flow rates corresponding to all the valves;

[0023] Take the leakage flow rate as a boundary condition, perform a fluid-structure interaction simulation on the typical finite element model to generate temperature distribution data, and generate corresponding thermal stress distribution data according to the temperature distribution data;

[0024] Calculate and generate the thermal stress of the target area according to the thermal stress distribution data, and denote it as the leakage thermal stress.

[0025] In one embodiment of the present invention, the step of performing a steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress of the target area includes:

[0026] Apply a preset first load inside the pipeline of the typical finite element model, perform a finite element analysis on the typical finite element model to obtain the corresponding internal pressure load stress;

[0027] Apply a preset second load at the pipeline ends and the two valves of the typical finite element model, perform a finite element analysis on the typical finite element model to obtain the corresponding pipe-end load stress;

[0028] Calculate the steady-state stress according to the internal pressure load stress, the pipe-end load stress, and the preset load stress.

[0029] In one embodiment of the present invention, the step of calculating the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress includes:

[0030] Calculate the total stress of the target area according to the leakage thermal stress and the steady-state stress, and calculate the stress amplitude of the target area according to the total stress;

[0031] Calculate the fatigue damage value of the target area according to the stress amplitude.

[0032] The present invention also provides a method for evaluating the thermal fatigue damage of a waste heat discharge pipeline, including:

[0033] A parameter acquisition module for acquiring parameter information of the waste heat discharge pipeline;

[0034] A simulation fitting module for parametrically coupling and simulating the leakage opening combinations of the valve according to the parameter information, generating a thermal stress simulation result, and performing a fitting process on the thermal stress simulation result and the corresponding leakage opening combination to generate a functional relationship between the thermal stress of the target area on the waste heat discharge pipeline and the leakage opening combination;

[0035] A function calculation module for generating the leakage opening combination corresponding to the maximum thermal stress of the target area according to the functional relationship, and recording it as a typical leakage opening;

[0036] A fluid-structure interaction simulation module for constructing a corresponding typical finite element model according to the typical leakage opening and the parameter information, performing a fluid-structure interaction simulation on the typical finite element model, generating the thermal stress of the target area, and recording it as the leakage thermal stress;

[0037] Perform a steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress of the target area;

[0038] A steady-state simulation module for calculating the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress.

[0039] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the method for evaluating the thermal fatigue damage of the waste heat discharge pipeline as described in any one of the above are implemented.

[0040] The present invention also provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the steps of the method for evaluating the thermal fatigue damage of the waste heat discharge pipeline as described in any one of the above are implemented.

[0041] As described above, a method, system, device and medium for evaluating thermal fatigue damage of a residual heat removal pipeline according to the present invention have the following beneficial effects: By the method for deriving the leakage flow rate of the maximum thermal stress, the present invention realizes the real-time evaluation and monitoring of the thermal fatigue damage of the residual heat removal pipeline with double valves in a nuclear power plant, can predict potential risks without actual detection, improves the abnormal response speed and safety, and reduces the operation cost at the same time, providing a scientific decision-making basis for the management of the nuclear power plant. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It shows a schematic structural diagram of a residual heat removal pipeline in an embodiment of the present invention;

[0043] Figure 2 It is a schematic flow chart of a method for evaluating thermal fatigue damage of a residual heat removal pipeline provided by an embodiment of the present invention;

[0044] Figure 3 It shows a schematic diagram of multiple groups of leakage opening combinations of two valves in an embodiment of the present invention;

[0045] Figure 4 It shows a schematic diagram of the shape of the valve leakage part in an embodiment of the present invention;

[0046] Figure 5 It shows a typical finite element model diagram of a residual heat removal pipeline in an embodiment of the present invention;

[0047] Figure 6 It shows a stress nephogram of fluid-structure interaction simulation of a typical finite element model in an embodiment of the present invention;

[0048] Figure 7 It shows a structural block diagram of a thermal fatigue damage evaluation system of a residual heat removal pipeline provided by an embodiment of the present invention;

[0049] Figure 8 It shows a schematic structural diagram of an electronic device in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] The following specific examples illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0051] It should be noted that the illustrations provided in the following embodiments only schematically illustrate the basic concept of the present invention. Therefore, only the components related to the present invention are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0052] In the following description, a large number of details are explored to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0053] The present invention provides a method, system, device, and medium for evaluating the thermal fatigue damage of a residual heat removal pipeline, which relates to the technical field of thermal fatigue damage evaluation of nuclear power pipelines. It can be specifically used to accurately infer and predict the thermal fatigue damage of a double-valve residual heat removal pipeline in a leakage state, providing more reliable technical support for the safety assessment and maintenance of nuclear power plants. The present invention solves the problems existing in the prior art through advanced numerical simulation technology combined with a typical leakage flow rate calculation method, improving the safety monitoring and maintenance efficiency of nuclear power pipelines. The following is a detailed description through specific embodiments.

[0054] Please refer to Figure 1 , one end of the residual heat removal pipeline 110 is connected to the primary pipeline 120 of the nuclear power unit. The other end of the residual heat removal pipeline 110 includes two branch pipelines, namely the first branch pipeline 111 and the second branch pipeline 112. A valve is provided on each of the first branch pipeline 111 and the second branch pipeline 112. The method, system, device, and medium for evaluating the thermal fatigue damage of the residual heat removal pipeline provided by the present invention can be used to predict the thermal fatigue damage of the target area on the above-mentioned residual heat removal pipeline, that is, the thermal fatigue damage of the weld 113. Thermal fatigue damage refers to the phenomenon that materials such as metals and ceramics under the action of repeated temperature changes (temperature gradient cycles), due to the cyclic action of thermal stress or thermal strain, cause fatigue cracks to generate inside the material and eventually fail.

[0055] Please refer to Figure 2 , the present invention provides a method for evaluating the thermal fatigue damage of a residual heat removal pipeline, which may include the following steps:

[0056] Step S100, obtain the parameter information of the residual heat removal pipeline;

[0057] Step S200: Construct a finite element model based on the parameter information, perform parametric coupling simulation on the leakage opening combinations of the valves in the finite element model, generate the thermal stress simulation results, and perform fitting processing on the thermal stress simulation results and the corresponding leakage opening combinations to generate the functional relationship between the thermal stress and the leakage opening combinations in the target area of the residual heat discharge pipeline;

[0058] Step S300: Generate the leakage opening combination corresponding to the maximum thermal stress in the target area according to the functional relationship, and record it as the typical leakage opening;

[0059] Step S400: Construct a corresponding typical finite element model according to the typical leakage opening and the parameter information, perform fluid-structure coupling simulation on the typical finite element model, generate the thermal stress in the target area, and record it as the leakage thermal stress;

[0060] Step S500: Perform steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress in the target area;

[0061] Step S600: Calculate the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress.

[0062] In an embodiment of the present invention, when step S100 is executed, the parameter information of the residual heat discharge pipeline is obtained. Specifically, the parameter information of the residual heat discharge pipeline to be evaluated is obtained from the pipeline design report. In this embodiment, the parameter information may include the geometric parameters of the pipeline, material properties, and operating conditions parameters, etc. Among them, the geometric parameters include, for example, the total length and shape of the main pipeline, the length and shape of the branch pipelines, the pipe diameter, the wall thickness, and the valve installation positions, spacings, etc. The material properties include, for example, the thermal conductivity, specific heat capacity, density, elastic modulus, Poisson's ratio, and thermal expansion coefficient of the pipeline material. In addition, the material properties may also include the properties of the valves and sealing materials. The operating conditions parameters may include, for example, the preset liquid flow rate, inlet temperature, ambient temperature, etc. Further, it is also necessary to determine the fluid type (such as water, oil, etc.) and its physical properties parameters (viscosity, density, etc.).

[0063] In one embodiment of the present invention, when step S200 is executed, that is, a finite element model is constructed according to parameter information, parametric coupling simulation is performed on the leakage opening combinations of the valves in the finite element model to generate a thermal stress simulation result, and the thermal stress simulation result is fitted with the corresponding leakage opening combination to generate a functional relationship between the thermal stress and the leakage opening combination in the target area of the waste heat discharge pipeline. It should be noted that parametric coupling simulation is a technique used in multi-physics field or multi-system interaction simulation. It allows engineers and researchers to study the impact of these changes on system performance by changing design variables (such as geometry, material properties, etc.). This simulation method is particularly suitable for complex systems that need to consider the interaction of multiple physical processes, such as fluid-structure interaction, thermal-electric coupling effect, or electromagnetic-mechanical system analysis. In this embodiment, the opening degrees of two valves are defined as variable parameters for simulation analysis, so as to generate a functional relationship between the thermal stress response in the target area of the waste heat discharge pipeline and the leakage opening degrees of the two valves. Specifically, step S200 may include the following steps:

[0064] Step S210: Construct a plurality of corresponding finite element models according to the parameter information and the multiple leakage opening combinations of all valves, and perform temperature distribution simulation analysis on the plurality of finite element models under preset conditions to generate pipeline temperature distribution data corresponding to each finite element thermal analysis model;

[0065] Step S220: Perform thermal stress response simulation analysis on the corresponding finite element model according to the pipeline temperature distribution data to generate the thermal stress generated in the target area of the waste heat discharge pipeline under each leakage opening combination;

[0066] Step S230: Perform fitting processing on all leakage opening combinations and the corresponding thermal stresses to generate a functional relationship between the thermal stress in the target area and the leakage opening combination.

[0067] In one embodiment of the present invention, when step S210 is executed, that is, a plurality of corresponding finite element models are constructed according to the parameter information and the multiple leakage opening combinations of all valves, and under preset conditions, temperature distribution simulation analysis is performed on the plurality of finite element models to generate pipeline temperature distribution data corresponding to each finite element thermal analysis model. Specifically, first, multiple groups of leakage opening combinations of two valves are preset. As Figure 3 shown, each identification point in the figure represents a group of leakage opening combinations. The abscissa of the identification point represents the leakage opening combination of the first pipeline 111, that is, the first leakage opening x A , and the ordinate of the identification point represents the leakage opening combination of the second pipeline 112, that is, the second leakage opening x B . For example, the first leakage opening x A = 0.5%, and the second leakage opening x B= 1%; or, the first leakage opening degree x A = 2%, the second leakage opening degree x B = 4%; or, the first leakage opening degree x A = 6%, the second leakage opening degree x B = 0 and so on. The combinations of the leakage opening degrees of the two branch pipes need to cover the complete range from the fully closed state to the fully open state of the valve.

[0068] Please refer to Figure 4 , the cross-section of the valve is circular, and the radius of this cross-section is the inner diameter D of the pipe i . The crescent-shaped shaded part at the bottom of the cross-section represents the fluid part where the valve leaks, and the part above the crescent represents the non-leaking part. Therefore, the opening degree x when the valve leaks can be expressed as:

[0069]

[0070] where D i represents the inner diameter of the pipe, and h represents the leakage height of the valve, that is, the height of the crescent-shaped shaded part. According to the above formula, the leakage height of the valve corresponding to each set of leakage opening degree combinations can be calculated.

[0071] Please refer to Figure 5 , use CAD software (such as SolidWorks, ANSYS) to create a three-dimensional model of the residual heat removal pipeline, including the main pipeline, branch pipelines, valve structure and connections. Define the pipeline dimensions (such as inner diameter, outer diameter) and valve structure (such as seat, valve plate, seal ring position) according to the parameter information. Mesh the three-dimensional model, focusing on key parts such as the valve leakage area and the pipeline weld position, and use a finer mesh to improve the accuracy. Then, set the material properties of the three-dimensional model. Specifically, input the thermodynamic parameters of the material, such as thermal conductivity, specific heat capacity, density, thermal expansion coefficient, etc. Among them, the heat conduction characteristics of the sealing material (such as rubber, alloy steel) of the valve need to be defined separately. Finally, according to multiple sets of leakage opening degree combinations of the two preset branch pipelines, calculate the leakage height of the valve corresponding to each set, and adjust the valve height parameter in the three-dimensional model according to the valve leakage height to generate multiple finite element thermal analysis models. Among them, the range of the valve leakage height of the first branch pipeline 111 is 0 to D i ; the range of the valve leakage height of the second branch pipeline 112 is 0 to D i .

[0072] Next, define the boundary conditions of all the constructed finite element thermal analysis models, which can include fluid conditions and thermal boundary conditions. Among them, the fluid conditions can include liquid flow rate and temperature, for example, the inlet temperature is 95°C and the flow rate is 2 m / s. The thermal boundary conditions can include the ambient temperature, for example, the ambient convective heat transfer coefficient is 50 W / (m 2·K), as well as the heat loss or heat input at the valve leakage, such as the heat exchange between the leaking fluid and the pipe wall. After defining the boundary conditions, a steady-state thermal analysis simulation calculation is performed on each finite element thermal analysis model, so as to output the pipe temperature distribution data corresponding to each model. Specifically, a CFD module (such as Fluent) is used to simulate fluid flow and heat transfer, and calculate the flow field and temperature field. In this embodiment, the pipe temperature distribution data characterizes the law or state of the temperature change of each point inside or on the surface of the pipe with position within a certain spatial range. It describes the temperature change characteristics in space (along the axial and radial directions of the pipe) of the waste heat discharge pipe during operation due to factors such as medium flow, environmental heat exchange, and material properties.

[0073] The simulation calculation of the steady-state thermal analysis includes two steps: fluid heat transfer calculation and solid domain heat transfer calculation. Among them, for the fluid heat transfer calculation, first, a CFD module (such as Fluent) is used to simulate fluid flow and heat transfer, calculate the flow field and temperature field, and at the same time, consider the turbulence model (such as the k-ε model) and transient / steady-state analysis (selected according to the leakage duration). For the solid domain heat transfer calculation, the temperature field of the fluid domain is mapped to the pipe wall surface, and the temperature distribution of the solid domain is solved. Save the pipe wall surface temperature distribution data under each leakage opening degree, such as a temperature-coordinate table in CSV format, or a visual temperature field.

[0074] In an embodiment of the present invention, when step S220 is executed, that is, based on the pipe temperature distribution data, a thermal stress response simulation analysis is performed on the corresponding finite element model to generate the thermal stress generated in the target area of the waste heat discharge pipe under each leakage opening degree combination. Specifically, based on the pipe temperature distribution data, the stress response of the waste heat discharge pipe under the corresponding thermal load is calculated, so as to identify the risks in the target area. Specifically, first, the pipe temperature distribution data obtained in the previous step is imported into a structural analysis module (such as ANSYS Mechanical). Then, set the boundary conditions and constraints of the finite element model of the waste heat discharge pipe. For example, fix the displacement at the pipe end or flange connection to simulate the actual installation constraints; at the same time, ignore the mechanical load and only consider the thermal stress, that is, assume that there is no external force acting. Then, use the thermal-structural coupling analysis module to solve the stress and strain caused by thermal expansion, so as to output the maximum equivalent stress (VonMises Stress), thermal strain distribution, and displacement field in the target area of the waste heat discharge pipe. In this embodiment, the target area on the waste heat discharge pipe refers to the weld 113.

[0075] In an embodiment of the present invention, when step S230 is executed, that is, fitting processing is performed on all leakage opening degree combinations and the corresponding thermal stresses to generate a functional relationship between the thermal stress in the target area and the leakage opening degree combination. Specifically, the multiple groups of leakage opening degree combinations (the first leakage opening degree xA and the second leakage opening x B ) is fitted with the thermal stress response σ of the corresponding target area to establish the functional relationship of σ = f(x A , x B ). First, parameter preparation and preprocessing are carried out. For example, each group of leakage opening combinations (x A , x B ) and their corresponding thermal stress responses σ are sorted out, and the leakage opening combinations (x A , x B ) are mapped to the interval [0, 1], corresponding to 0% - 100% opening, to avoid the influence of dimensional differences on the fitting accuracy; and abnormal stress values caused by calculation errors or grid distortions are removed. Then, a fitting model is selected. In this embodiment, a polynomial response surface model is used to characterize the functional relationship of σ = f(x A , x B ), and this functional relationship can satisfy the following formula:

[0076] [[ID=2३]]

[0077] where σ represents the thermal stress response of the target area, (x A , x B ) represents the leakage opening combination, x A represents the first leakage opening, x B represents the second leakage opening, k0 represents a constant, and k1, k2, k3, k4, and k5 represent coefficients.

[0078] Next, the coefficients k0, k1, k2, k3, k4, and k5 are solved by the least squares method, and finally the fitting formula is output. In this embodiment, when the inner diameter of the residual heat discharge pipe is 736.60 mm, the outer diameter is 746.60 mm, and the distance between the two valves is 812 mm, the fitting formula corresponding to the target area on this pipe is:

[0079]

[0080] In an embodiment of the present invention, when step S300 is executed, that is, according to the functional relationship, the leakage openings of the two valves corresponding to the maximum thermal stress response of the target area are calculated and recorded as typical leakage openings. Specifically, it may include the following steps:

[0081] Step S310: Obtain the corresponding gradient vector and Hessian matrix according to the functional relationship;

[0082] Step S320: Select the iterative initial point of the leakage opening combination, perform iterative calculations on the gradient vector and the Hessian matrix until the maximum number of iterations is reached, generate the leakage opening combination corresponding to the maximum thermal stress in the target area, and denote it as the typical leakage opening.

[0083] In an embodiment of the present invention, when steps S310 to S320 are executed, specifically, based on the fitting formula of the functional relationship, solve for the leakage opening combination (z A ,z B ) when the thermal stress response in the target area is the maximum. It can be understood that the functional relationship of σ = f(x A ,x B ) is a binary quadratic equation. Therefore, the genetic optimization algorithm or the Newton gradient descent algorithm can be used for solution to obtain the global maximum value of the equation and the corresponding values of (x A ,x B ). For example, when using the Newton gradient descent algorithm, first, obtain the corresponding gradient vector and Hessian matrix according to the functional relationship. Then, judge the type of extreme value according to the Hessian matrix. If the Hessian matrix is negative definite, that is, all sequential principal minors are negative, then there is a maximum value; if the Hessian matrix is indefinite or positive definite, then there is no maximum value, and the genetic algorithm needs to be used or the constraint boundary needs to be checked. Next, select the iterative initial point of the leakage opening combination, perform iterative calculations on the gradient vector and the Hessian matrix until the maximum number of iterations is reached, generate the leakage opening combination corresponding to the maximum thermal stress in the target area, and denote it as the typical leakage opening. It can be understood that for a binary quadratic equation, the extreme value point can be solved by one-step iteration of the Newton method.

[0084] In this embodiment, when the inner diameter of the residual heat discharge pipe is 736.60 mm, according to the above steps, the leakage opening combinations of the two branch pipes corresponding to the maximum thermal stress condition in the target area of this embodiment can be determined as and Record this set of leakage openings as the typical leakage openings. It can be seen from this that through the above steps, the correlation law between the leakage opening combination and the thermal stress can be quantitatively established, and the most dangerous working condition can be located, providing a core basis for the leakage prevention and control and life assessment of the pipeline system.

[0085] In an embodiment of the present invention, when step S400 is executed, that is, according to the typical leakage opening and the parameter information, construct the corresponding typical finite element model, and perform fluid-structure interaction simulation on the typical finite element model to generate the thermal stress in the target area, and denote it as the leakage thermal stress. Specifically, it includes the following steps:

[0086] Step S410: Construct a corresponding typical finite element model based on the typical leakage opening and parameter information, and calculate the leakage flow rates corresponding to all valves.

[0087] Step S420: Use the leakage flow rate as a boundary condition to perform a fluid-structure interaction simulation on the typical finite element model, generate temperature distribution data, and generate corresponding thermal stress distribution data based on the temperature distribution data.

[0088] Step S430: Calculate and generate the thermal stress of the target area based on the thermal stress distribution data, and record it as the leakage thermal stress.

[0089] In an embodiment of the present invention, when step S410 is executed, that is, a corresponding typical finite element model is constructed based on the typical leakage opening and parameter information, and the leakage flow rates corresponding to all valves are calculated. Specifically, first, according to the typical leakage opening determined in step S300, calculate the corresponding valve leakage height, adjust the three-dimensional model of the waste heat discharge pipeline according to the valve leakage height, and generate a corresponding finite element model. This finite element model corresponds to the state when the thermal stress response of the target area on the waste heat discharge pipeline is the largest. Then, calculate the leakage flow rate according to the leakage velocity and leakage area.

[0090] In this embodiment, based on the function relationship between the leakage velocity and the opening of the valve obtained from previous research and relevant experience summaries. In this embodiment, this function relationship can satisfy the following formula:

[0091]

[0092] Among them, v represents the leakage velocity, and x represents the leakage opening of the valve. Based on the typical leakage openings of the double valves obtained in step S300 and Combining the above formula, the leakage velocity v of each valve at the corresponding leakage opening can be obtained A and v B .

[0093] Please refer to Figure 4 , the crescent-shaped shaded part at the bottom of the cross-section represents the fluid part where the valve leaks, and the part above the crescent represents the part where no leakage occurs. Therefore, the leakage area S corresponding to the crescent part can satisfy the following formula:

[0094]

[0095] Among them, D i represents the inner diameter of the pipeline, θ represents the central angle corresponding to the leakage area, and x represents the leakage opening of the valve.

[0096] It can be seen from this that the leakage flow rate Q can satisfy the following formula:

[0097] Q = v × S

[0098] Please refer to Figure 6 , in an embodiment of the present invention, when step S420 is executed, the leakage flow rate is used as the boundary condition to perform fluid-structure interaction simulation on the residual heat removal pipeline, generate temperature distribution data, and generate corresponding thermal stress distribution data according to the temperature distribution data. Specifically, first, according to the magnitude of the influence of the fluid on the structural deformation, select whether to perform one-way coupling (One-way FSI) or two-way coupling (Two-way FSI). One-way coupling first calculates the fluid temperature field and then maps the temperature load to the solid domain for thermal stress analysis. It is applicable to scenarios where the influence of the fluid on the structural deformation is small. Two-way coupling alternately solves the fluid and the solid, and exchanges temperature and displacement data in real time. It is applicable to working conditions where the thermal deformation significantly changes the flow channel shape (such as large deformation valves). Then, set the boundary conditions for the simulation analysis, which can be divided into the fluid domain and the solid domain. Among them, the fluid domain conditions use the leakage flow rate as the inlet and the ambient pressure as the outlet, and the wall heat transfer coefficient is determined according to the flow regime (laminar / turbulent). The solid domain conditions use fixed support constraints (such as pipeline end flanges) and ambient temperature radiation / convection heat dissipation conditions. In this embodiment, with the leakage flow rate as the boundary condition, perform fluid-structure interaction simulation to obtain temperature distribution data and thermal stress field data. The temperature distribution data and the thermal stress field data are displayed in the form of temperature contour maps and stress contour maps to visually locate the dangerous areas.

[0099] In an embodiment of the present invention, when step S430 is executed, that is, according to the thermal stress distribution data, calculate and generate the thermal stress of the target area, and record it as the leakage thermal stress. Specifically, post-process the thermal stress distribution data generated in step S420, extract the thermal stress response of the target area, and record it as the leakage thermal stress, providing input for subsequent fatigue analysis. For the residual heat removal pipeline given in the above embodiment, after post-processing calculation, its leakage thermal stress S t is 80 MPa.

[0100] In an embodiment of the present invention, when step S500 is executed, that is, perform steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress of the target area. Specifically, in addition to the thermal stress response obtained from the finite element simulation, other steady-state stresses of the residual heat removal pipeline need to be considered, including: internal pressure load stress S p , pipe end load stress S h , seismic load stress S o , assembly stress S assemmle , welding residual stress S welding , and mechanical grinding stress S polish。Through steady-state stress simulation analysis, the stress distributions under different load conditions are synthesized, and the steady-state response of the target area is calculated to provide a basis for structural safety assessment. In this embodiment, step S500 may include the following steps:

[0101] Step S510: Apply a preset first load inside the pipeline of the typical finite element model, perform finite element analysis on the typical finite element model, and obtain the corresponding internal pressure load stress;

[0102] Step S520: Apply a preset second load at the pipeline ends and two valves of the typical finite element model, perform finite element analysis on the typical finite element model, and obtain the corresponding pipe-end load stress;

[0103] Step S530: Calculate the steady-state stress based on the internal pressure load stress, pipe-end load stress, and preset load stress.

[0104] In an embodiment of the present invention, when step S510 is executed, that is, a preset first load is applied inside the pipeline of the typical finite element model, and finite element analysis is performed on the typical finite element model to obtain the corresponding internal pressure load stress. Specifically, through finite element analysis, the stress distribution caused by the internal pressure load of the pipeline is calculated. Based on the finite element model constructed in step S400, the boundary conditions of the internal load are set. For example, using the static module of ANSYS Workbench or SolidWorks Simulation, a preset internal load is applied to the inner wall surface of the pipeline of the typical finite element model. Then, through finite element calculation, the internal pressure load stress at the weld position of the residual heat removal pipeline can be obtained. In this embodiment, the first load is selected as 15 Mpa, and the corresponding internal pressure load stress S p = 63 MPa.

[0105] In an embodiment of the present invention, when step S520 is executed, that is, a preset second load is applied at the pipeline ends and two valves of the typical finite element model, and finite element analysis is performed on the typical finite element model to obtain the corresponding pipe-end load stress. Specifically, first, based on the finite element model constructed in step S400, the boundary conditions of the pipe-end load are set. For example, according to the design report data, a second load is applied at the main pipeline ends and two branch valves of the residual heat removal pipeline. Then, through the finite element calculation results, the pipe-end load stress at the weld position of the residual heat removal pipeline can be obtained. For example, the pipe-end load stress S h = 69 MPa.

[0106] In an embodiment of the present invention, when step S530 is executed, that is, the steady-state stress is calculated based on the internal pressure load stress, pipe-end load stress, and preset load stress. Specifically, without considering the occurrence of an earthquake, so the earthquake load stress S i= 0. The assembly stress S assemmle , the welding residual stress S welding , and the mechanical grinding stress S polish are respectively taken as 0. Based on the above stress data for summation calculation, the steady-state stress S total can satisfy the following formula:

[0107] S total = S p + S + S o + S assemmle + S welding + S polis

[0108] For the residual heat removal pipeline given in the above embodiment, its steady-state stress S total calculated according to the above steps is 132 MPa.

[0109] In an embodiment of the present invention, when step S600 is executed, that is, according to the leakage thermal stress and the steady-state stress, calculate the fatigue damage value of the target area. Specifically, the following steps may be included:

[0110] Step S610: According to the leakage thermal stress and the steady-state stress, calculate the total stress of the target area, and according to the total stress, calculate the stress amplitude of the target area;

[0111] Step S620: According to the stress amplitude, calculate the fatigue damage value of the target area.

[0112] In an embodiment of the present invention, when step S610 is executed, that is, according to the leakage thermal stress and the steady-state stress, calculate the total stress of the target area, and according to the total stress, calculate the stress amplitude of the target area. Specifically, first, according to the leakage thermal stress S t of the target area determined in step S400 total and the steady-state stress S determined in step S500, calculate the total stress response of the target area, that is, the maximum total stress response of the residual heat removal pipeline during leakage is 212 MPa. Then, according to the rainflow counting method given in the ASME code, starting from the zero-stress state of the pipeline (i.e., the total stress is 0) and ending at the maximum total stress state during leakage, the stress amplitude corresponding to this working condition can be calculated as 212 MPa.

[0113] In an embodiment of the present invention, when step S620 is executed, that is, according to the stress amplitude, calculate the fatigue damage value of the target area. Specifically, according to the stress amplitude determined in step S610 and the material S-N curve given in the ASME code and the stress amplitude determined in step S610, the corresponding fatigue damage can be obtained. For example, when the stress amplitude is 212 MPa, the corresponding fatigue damage is 1.3495E-05.

[0114] It is understandable that only one load cycle is involved in this embodiment, so the situation of damage accumulation is not involved. For the case including not less than one load cycle, the linear damage accumulation law can be used to linearly sum up the damage conditions under each cycle to obtain the final total fatigue damage, so as to realize the fatigue damage assessment of the residual heat removal pipeline.

[0115] Please refer to Figure 7 , the present invention also provides a thermal fatigue damage assessment system for a residual heat removal pipeline, and the thermal fatigue damage assessment system corresponds one by one to the assessment method in the above embodiment. The thermal fatigue damage assessment system may include a parameter acquisition module 201, a simulation fitting module 202, a function calculation module 203, a fluid-structure interaction simulation module 204, a steady-state simulation module 205, and a fatigue damage calculation module 206. The detailed description of each functional module is as follows:

[0116] The parameter acquisition module 201 can be used to acquire the parameter information of the residual heat removal pipeline. Further, the parameter acquisition module 201 can specifically be used to acquire the parameter information of the residual heat removal pipeline to be evaluated from the pipeline design report. In this embodiment, the parameter information may include the geometric parameters, material properties, and working condition parameters of the pipeline. Among them, the geometric parameters include, for example, the total length and shape of the main pipeline, the length and shape of the branch pipeline, the pipe diameter, the wall thickness, and the valve installation position and spacing. The material properties include, for example, the thermal conductivity, specific heat capacity, density, elastic modulus, Poisson's ratio, and thermal expansion coefficient of the pipeline material. In addition, the material properties may also include the properties of the valve and sealing materials. The working condition parameters may include, for example, the preset liquid flow rate, inlet temperature, ambient temperature, etc. Further, it is also necessary to determine the fluid type (such as water, oil, etc.) and its physical property parameters (viscosity, density, etc.).

[0117] The simulation fitting module 202 can be used to construct a finite element model according to the parameter information, perform parametric coupling simulation on the leakage opening combinations of the valves in the finite element model, generate the thermal stress simulation results, and perform fitting processing on the thermal stress simulation results and the corresponding leakage opening combinations to generate the functional relationship between the thermal stress and the leakage opening combination of the target area on the residual heat removal pipeline. Further, the simulation fitting module 202 can specifically be used to construct multiple corresponding finite element models according to the parameter information and the multiple leakage opening combinations of all valves, and perform temperature distribution simulation analysis on the multiple finite element models under preset conditions to generate the pipeline temperature distribution data corresponding to each finite element thermal analysis model; according to the pipeline temperature distribution data, perform thermal stress response simulation analysis on the corresponding finite element model to generate the thermal stress generated in the target area of the residual heat removal pipeline under each leakage opening combination; perform fitting processing on all leakage opening combinations and the corresponding thermal stress to generate the functional relationship between the thermal stress and the leakage opening combination of the target area.

[0118] The function calculation module 203 can be used to generate a leakage opening combination corresponding to the maximum thermal stress in the target area according to the function relationship, and record it as the typical leakage opening. Further, through the genetic optimization algorithm or the Newton gradient algorithm, calculate the leakage opening combination corresponding to the maximum thermal stress in the target area according to the function relationship, and record it as the typical leakage opening.

[0119] The fluid-structure interaction simulation module 204 can be used to construct a corresponding typical finite element model according to the typical leakage opening and parameter information, and perform fluid-structure interaction simulation on the typical finite element model to generate the thermal stress in the target area, and record it as the leakage thermal stress. Further, the fluid-structure interaction simulation module 204 can specifically be used to construct a corresponding typical finite element model according to the typical leakage opening and parameter information, and calculate the leakage flow rate corresponding to all valves; use the leakage flow rate as the boundary condition to perform fluid-structure interaction simulation on the typical finite element model to generate temperature distribution data, and generate corresponding thermal stress distribution data according to the temperature distribution data; calculate and generate the thermal stress in the target area according to the thermal stress distribution data, and record it as the leakage thermal stress.

[0120] The steady-state simulation module 205 can be used to perform steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress in the target area. Further, the steady-state simulation module 205 can specifically be used to apply a preset first load inside the pipeline of the typical finite element model, perform finite element analysis on the typical finite element model to obtain the corresponding internal pressure load stress; apply a preset second load at the pipeline end and two valves of the typical finite element model, perform finite element analysis on the typical finite element model to obtain the corresponding pipe end load stress; calculate the steady-state stress according to the internal pressure load stress, pipe end load stress and preset load stress.

[0121] The fatigue damage calculation module 206 can be used to calculate the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress. Further, the fatigue damage calculation module 206 can specifically be used to calculate the total stress of the target area according to the leakage thermal stress and the steady-state stress, and calculate the stress amplitude of the target area according to the total stress; calculate the fatigue damage value of the target area according to the stress amplitude.

[0122] For the specific limitations of the thermal fatigue damage assessment system for the residual heat removal pipeline, reference can be made to the limitations of the thermal fatigue damage assessment method in the above text, which will not be elaborated here. Each module in the above thermal fatigue damage assessment system can be implemented in whole or in part by software, hardware and their combination. The above modules can be embedded in the processor of the computer device in hardware form or independent of it, or stored in the memory of the computer device in software form, so as to facilitate the processor to call and execute the operations corresponding to the above modules.

[0123] An embodiment of the present invention further provides an electronic device, including: one or more processors; a storage device for storing one or more programs, which, when executed by the one or more processors, cause the electronic device to implement the thermal fatigue damage assessment method for the waste heat discharge pipeline provided in each of the above embodiments.

[0124] Please refer to Figure 8 , the electronic device 300 may include a memory 310, a processor 320, and a bus, and may further include a computer program stored in the memory 310 and executable on the processor 320, such as a thermal fatigue damage assessment program.

[0125] Among them, the memory 310 includes at least one type of readable storage medium, and the readable storage medium includes flash memory, mobile hard disk, multimedia card, card-type memory (such as: SD or DX memory, etc.), magnetic memory, magnetic disk, optical disc, etc. The memory 310 may be an internal storage unit of the electronic device 300 in some embodiments, such as the mobile hard disk of the electronic device 300. The memory 310 may also be an external storage device of the electronic device 300 in other embodiments, such as a plug-in mobile hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the electronic device 300. Further, the memory 310 may include both an internal storage unit and an external storage device of the electronic device 300. The memory 310 can be used not only to store application software and various types of data installed in the electronic device 300, such as the code for thermal fatigue damage assessment, etc., but also to temporarily store data that has been output or will be output.

[0126] The processor 320 may be composed of integrated circuits in some embodiments. For example, it may be composed of a single packaged integrated circuit, or may be composed of multiple integrated circuits with the same or different functions, including a combination of one or more Central Processing Units (CPUs), microprocessors, digital processing chips, graphics processors, and various control chips, etc. The processor 320 is the control core (Control Unit) of the electronic device 300, connecting various components of the entire electronic device 300 through various interfaces and lines, and by running or executing programs or modules stored in the memory 310 (such as the thermal fatigue damage assessment program, etc.), and calling data stored in the memory 310, to execute various functions of the electronic device 300 and process data.

[0127] The processor 320 executes the operating system of the electronic device 300 and various installed application programs. The processor 320 executes the application programs to implement the steps in the above-mentioned method for evaluating the thermal fatigue damage of the residual heat discharge pipeline.

[0128] Exemplarily, the computer program can be divided into one or more modules. One or more modules are stored in the memory 310 and executed by the processor 320 to complete the present application. One or more modules can be a series of computer program instruction segments capable of completing specific functions, and these instruction segments are used to describe the execution process of the computer program in the electronic device 300. For example, the computer program can be divided into a parameter acquisition module 201, a simulation fitting module 202, a function calculation module 203, a fluid-structure interaction simulation module 204, a steady-state simulation module 205, and a fatigue damage calculation module 206.

[0129] The above-mentioned integrated units implemented in the form of software function modules can be stored in a computer-readable storage medium. The computer-readable storage medium can be non-volatile or volatile. The above-mentioned software function modules are stored in a storage medium and include several instructions to enable a computer device (which can be a personal computer, a computer device, or a network device, etc.) or a processor to execute part of the functions of the method for evaluating the thermal fatigue damage of the residual heat discharge pipeline in various embodiments of the present application.

[0130] In summary, a method, a system, a device, and a medium for evaluating the thermal fatigue damage of a residual heat discharge pipeline disclosed by the present invention can be applied to the evaluation of the thermal fatigue damage when a leakage occurs in a residual heat discharge pipeline such as the double-valve residual heat discharge in the primary loop of a nuclear power plant. The present invention allows the operation and maintenance personnel of a nuclear power plant to evaluate and monitor the thermal fatigue damage of the double-valve residual heat discharge pipeline of the nuclear power plant in real time, timely discover potential risk points, and effectively prevent and control the occurrence of leakage accidents. For the double-valve residual heat discharge and other residual heat discharge pipelines in a nuclear power plant, the present invention adopts a method for inferring the leakage flow rate with the maximum thermal stress, which is a prediction method that can be carried out without actual leakage detection and can be carried out without affecting the normal operation of the nuclear power plant, thereby reducing the operating costs generated by frequent maintenance and inspections. The present invention helps to improve the overall safety management level of the nuclear power plant. By accurately monitoring and predicting the pipeline system, the response speed and effectiveness to abnormal situations are increased, and the overall safety of the nuclear power plant is greatly improved. The detailed data and analysis results provided can be used as a scientific basis for decision-making support in the nuclear power plant to help the management formulate more reasonable and effective operation strategies and maintenance plans. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0131] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for evaluating thermal fatigue damage of a waste heat discharge pipeline, characterized in that, One end of the residual heat removal pipeline is communicated with the primary pipeline of the nuclear power unit, and a valve is provided on the branch pipeline at the other end. The thermal fatigue damage assessment method includes: Obtain the parameter information of the residual heat removal pipeline; Construct a finite element model according to the parameter information, perform parametric coupling simulation on the leakage opening combinations of the valves in the finite element model, generate a thermal stress simulation result, and perform fitting processing on the thermal stress simulation result and the corresponding leakage opening combination to generate a functional relationship between the thermal stress of the target area on the residual heat removal pipeline and the leakage opening combination; According to the functional relationship, generate the leakage opening combination corresponding to the maximum thermal stress of the target area, and record it as the typical leakage opening; Construct a corresponding typical finite element model according to the typical leakage opening and the parameter information, perform fluid-structure coupling simulation on the typical finite element model, generate the thermal stress of the target area, and record it as the leakage thermal stress; Perform steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress of the target area; Calculate the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress.

2. The thermal fatigue damage assessment method for the waste heat discharge pipeline according to claim 1, wherein The step of constructing a finite element model according to the parameter information, performing parametric coupling simulation on the leakage opening combinations of the valves in the finite element model, generating a thermal stress simulation result, and performing fitting processing on the thermal stress simulation result and the corresponding leakage opening combination to generate a functional relationship between the thermal stress of the target area on the residual heat removal pipeline and the leakage opening combination includes: Construct a plurality of corresponding finite element models according to the parameter information and the multiple leakage opening combinations of all valves, and perform temperature distribution simulation analysis on the plurality of finite element models under preset conditions to generate the pipeline temperature distribution data corresponding to each finite element thermal analysis model; According to the pipeline temperature distribution data, perform thermal stress response simulation analysis on the corresponding finite element model to generate the thermal stress generated in the target area of the residual heat removal pipeline under each leakage opening combination; Perform fitting processing on all the leakage opening combinations and the corresponding thermal stresses to generate a functional relationship between the thermal stress of the target area and the leakage opening combination.

3. The method for evaluating thermal fatigue damage of the waste heat discharge pipeline according to claim 1, wherein When the number of valves is two, the functional relationship satisfies the following formula: Among them, σ represents the thermal stress of the target area, (x A , x B ) represents the leakage opening combination, x A represents the leakage opening of one of the valves, x B represents the leakage opening of the other valve, k1, k2, k3, k4, and k5 represent coefficients, and k0 represents a constant.

4. The method for evaluating thermal fatigue damage of the waste heat discharge pipeline according to claim 3, characterized in that, The step of generating the leakage opening combination corresponding to the maximum thermal stress of the target area according to the functional relationship and recording it as the typical leakage opening includes: Calculate the leakage opening combination corresponding to the maximum thermal stress of the target area according to the functional relationship by using a genetic optimization algorithm or a Newton gradient algorithm, and record it as the typical leakage opening.

5. The method for evaluating thermal fatigue damage of the waste heat discharge pipeline according to claim 1, characterized in that, The step of constructing a corresponding typical finite element model according to the typical leakage opening and the parameter information, performing fluid-structure coupling simulation on the typical finite element model, generating the thermal stress of the target area, and recording it as the leakage thermal stress includes: Construct a corresponding typical finite element model according to the typical leakage opening and the parameter information, and calculate the leakage flow rates corresponding to all the valves; Taking the leakage flow rate as a boundary condition, performing a fluid-structure interaction simulation on the typical finite element model to generate temperature distribution data, and generating corresponding thermal stress distribution data according to the temperature distribution data; Calculating and generating the thermal stress of the target area according to the thermal stress distribution data, and denoting it as leakage thermal stress.

6. The method for evaluating thermal fatigue damage of the waste heat discharge pipeline according to claim 1, characterized in that, The step of performing a steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress of the target area includes: Applying a preset first load inside the pipeline of the typical finite element model, performing a finite element analysis on the typical finite element model to obtain the corresponding internal pressure load stress; Applying a preset second load at the pipeline ends and the two valves of the typical finite element model, performing a finite element analysis on the typical finite element model to obtain the corresponding pipe-end load stress; Calculating the steady-state stress according to the internal pressure load stress, the pipe-end load stress and the preset load stress.

7. The method for evaluating thermal fatigue damage of the waste heat discharge pipeline according to claim 1, wherein The step of calculating the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress includes: Calculating the total stress of the target area according to the leakage thermal stress and the steady-state stress, and calculating the stress amplitude of the target area according to the total stress; Calculating the fatigue damage value of the target area according to the stress amplitude.

8. A method for evaluating thermal fatigue damage of a waste heat discharge pipeline, characterized in that, Including: A parameter acquisition module for acquiring parameter information of the residual heat removal pipeline; A simulation fitting module for constructing a finite element model according to the parameter information, performing a parametric coupling simulation on the leakage opening combinations of the valves in the finite element model, generating a thermal stress simulation result, and performing a fitting process on the thermal stress simulation result and the corresponding leakage opening combination to generate a functional relationship between the thermal stress of the target area on the residual heat removal pipeline and the leakage opening combination; A function calculation module for generating the leakage opening combination corresponding to the maximum thermal stress of the target area according to the functional relationship, and denoting it as the typical leakage opening; A fluid-structure interaction simulation module for constructing a corresponding typical finite element model according to the typical leakage opening and the parameter information, performing a fluid-structure interaction simulation on the typical finite element model to generate the thermal stress of the target area, and denoting it as leakage thermal stress; Performing a steady-state stress simulation analysis on the typical finite element model to generate the steady-state stress of the target area; A steady-state simulation module for calculating the fatigue damage value of the target area according to the leakage thermal stress and the steady-state stress.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, it implements the steps of the thermal fatigue damage assessment method for the residual heat removal pipeline according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the thermal fatigue damage assessment method for the residual heat removal pipeline according to any one of claims 1 to 7.

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