Method for evaluating fuel assembly plate spring stress corrosion cracking

Abstract

This application belongs to the field of nuclear reactor technology, specifically relating to a method for evaluating stress corrosion cracking in fuel assembly leaf springs. The method includes: constructing a high-temperature-irradiation coupled material constitutive model of the leaf spring; establishing a parameterized geometric model of the leaf spring structure; applying coupled boundary conditions of icebreaking load and compression variation over its service life; performing stress corrosion cracking sensitivity analysis based on the finite element method to obtain stress analysis results; and establishing a multi-parameter mapping spring stress corrosion cracking prediction model based on the stress analysis results to predict the stress corrosion cracking risk of the leaf spring structure under specific operating conditions. This application can comprehensively reflect the impact of high temperature, irradiation, icebreaking impact load, and compression variation on the service condition of leaf springs, improving the accuracy of risk assessment and the efficiency of design optimization.

Description

Technical Field

[0001] This application belongs to the field of nuclear reactor technology, specifically relating to a method for evaluating stress corrosion cracking of fuel assembly plate springs. Background Technology

[0002] Nuclear-powered icebreakers are primarily used for icebreaking operations in polar regions such as the Arctic and Antarctic. Their operating environment is characterized by low temperatures, high salinity, high corrosiveness, and intense impact loads. During operation in polar waters, icebreakers not only need to withstand extremely low temperatures and corrosive seawater, but also experience impacts from ice fracturing, inertial forces from hull swaying, and dynamic loads caused by complex navigation attitudes. Therefore, the nuclear power plant and its key components on nuclear-powered icebreakers must operate stably and reliably over long periods with high reliability and safety requirements.

[0003] Fuel assemblies are critical components of the nuclear reactor core. The upper tube holder of the fuel assembly is mainly used to position the fuel assembly within the core, as well as to position other structures such as guide tubes and instrument tubes within the fuel assembly. It also serves to transfer the load on the fuel assembly and guide the coolant out of the fuel assembly. The leaf spring, installed in the upper tube holder, is a crucial elastic structural component for ensuring the fuel assembly's clamping performance. During the service life of the fuel assembly, the fuel assembly and core structure will grow to varying degrees in the height direction due to factors such as irradiation. The leaf spring needs to compensate for these height differences through its own deformation to maintain the stable positioning and reliable clamping of the fuel assembly within the core. Therefore, the structural integrity and mechanical properties of the leaf spring directly affect the service safety of the fuel assembly and the operational safety of the reactor.

[0004] However, nuclear-powered icebreaker fuel assemblies are subjected to extreme environments for extended periods, including high temperatures, high pressures, corrosive water, radiation, and complex dynamic loads. Leaf springs are typically under high stress during service, making them susceptible to stress corrosion cracking (SCCC) due to material degradation, corrosive media, and the coupling of external loads. SCCC can lead to the initiation and propagation of localized cracks in the spring structure, potentially causing plastic failure or reduced clamping capacity, thus affecting the stability of the fuel assembly within the reactor core and even jeopardizing the safe operation of the nuclear-powered icebreaker. Therefore, accurately assessing the SCCC tendency of leaf springs under extreme service conditions is crucial for the optimized design of fuel assembly structures and the safe operation of the reactor.

[0005] Existing methods for evaluating stress corrosion cracking (SCR) in materials typically employ experimental or simulation approaches. These methods simulate the service environment by controlling conditions such as temperature, humidity, corrosive media, and stress levels to assess the material's susceptibility to SCR. However, for the upper tube seat leaf springs of fuel assemblies in nuclear-powered icebreakers, their actual service condition is influenced not only by material properties and the hydrochemical environment but also by the coupled effects of multiple factors, including icebreaking impact loads, hull motion, irradiation-induced material performance degradation, and changes in spring compression over their service life. Traditional evaluation methods struggle to simultaneously reflect these complex operating conditions, particularly in accurately simulating the combined impact of dynamic impact loads and irradiation-induced growth compensation on spring stress distribution during polar icebreaking operations. This can lead to discrepancies between the evaluation results and the actual service condition.

[0006] Furthermore, some existing technologies focus on stress corrosion cracking simulation analysis of fuel cladding materials, while others characterize the stress corrosion cracking sensitivity of materials through magnetic parameters or crack initiation time inversion. The research objects, evaluation indicators, or technical routes of these methods do not fully match the service characteristics of the leaf springs on the fuel assemblies of nuclear-powered icebreakers. For leaf spring structures, relying solely on a single maximum stress index or conventional static simulation results for risk assessment is insufficient to meet the needs of refined and rapid risk assessment in complex polar operating environments.

[0007] Therefore, there is an urgent need to provide a stress corrosion cracking evaluation method for leaf spring structures of fuel assemblies in nuclear-powered icebreakers. This method should comprehensively consider factors such as high temperature, radiation, corrosive environment, icebreaking impact load, and compression variation during the service life. Through parametric modeling, finite element simulation analysis, and multi-parameter prediction models, it can achieve rapid and accurate evaluation of the stress corrosion cracking tendency of leaf springs, providing technical support for spring structure optimization design, material selection, and safe operation of fuel assemblies. Summary of the Invention

[0008] The purpose of this application is to provide a method for evaluating stress corrosion cracking of fuel assembly leaf springs, which is used to assess the stress corrosion cracking sensitivity of leaf springs and provide a scientific basis for the selection of new spring materials and structural design.

[0009] To achieve the above objectives, the method for evaluating stress corrosion cracking of fuel assembly leaf springs provided in this application includes the following steps: S1, Construct a constitutive model of the high-temperature-irradiation coupled material of the leaf spring; S2, Establish a parametric geometric model of the leaf spring structure; S3, apply the coupled boundary condition of icebreaking load and compression variation during service life; S4. Based on the finite element analysis method, stress corrosion cracking sensitivity analysis is performed on the leaf spring to obtain stress analysis results; S5. Based on the stress analysis results, establish a multi-parameter mapping spring stress corrosion cracking prediction model, and use the spring stress corrosion cracking prediction model to predict the stress corrosion cracking risk of leaf springs under specific working conditions.

[0010] Optionally, step S1 includes: inputting the physical property parameters of GH4169 alloy in the range of -40℃ to 350℃ as a function of temperature, such as elastic modulus, Poisson's ratio, and yield strength, to establish a material constitutive relationship that includes temperature sensitivity.

[0011] Optionally, step S1 further includes: introducing an irradiation-accelerated creep model and defining a decay function for the mechanical property parameters of GH4169 material as a function of neutron flux rate or service time, in order to characterize the performance degradation of GH4169 material under long-term high-temperature irradiation.

[0012] Optionally, the irradiation-accelerated creep model is a creep model based on a combined time-hardening model, wherein the creep model uses at least neutron flux, irradiation ambient temperature, and service time as input parameters.

[0013] Optionally, step S2 includes: based on the actual physical structure of the leaf spring, selecting at least one of the spring length, spring width, spring height, and spring chord length as parameterized variables, and establishing geometric constraint relationships between the parameterized variables, so that when any parameterized variable is modified, the parameterized geometric model of the leaf spring structure can be automatically updated.

[0014] Optionally, step S2 further includes: discretizing the parameterized geometric model of the leaf spring structure to establish a numerical simulation model of the spring; wherein the discretization process uses at least one of shell elements, beam elements, and solid elements.

[0015] Optionally, step S3 includes: constructing an icebreaking impact load spectrum with time-varying characteristics, wherein the icebreaking impact load spectrum is formed by superimposing the swaying inertial force of the nuclear-powered icebreaker and the ice fracture impact force, and is used to simulate the dynamic load of the nuclear-powered icebreaker in polar operations.

[0016] Optionally, the icebreaking impact load spectrum is used to characterize the force state of a nuclear-powered icebreaker in vertical, tilted, swaying, or turning operating postures.

[0017] Optionally, step S3 further includes: dynamically adjusting the compression of the leaf spring based on the difference in height-direction irradiation growth between the fuel assembly and the reactor core during their service life as the neutron flux and service time increase, in order to simulate the change in compression during the service life.

[0018] Optionally, the input parameters in step S3 include at least one of the following: total fuel assembly height, total core height, operating temperature, system pressure, coolant flow rate, coolant density, vibration frequency, mechanical stress, neutron flux, and burnup.

[0019] Optionally, step S4 includes: performing finite element simulation calculations based on the parameterized geometric model of the leaf spring structure and the coupled boundary conditions to extract the stress distribution cloud map, stress peak data, and the size of the stress-sensitive region of the leaf spring.

[0020] Optionally, the stress-sensitive region is the region on the leaf spring where the stress is higher than a preset proportion of the material's yield strength, wherein the preset proportion is 80% or 90%.

[0021] Optionally, step S4 further includes: obtaining the stress peak value and stress-sensitive area size of the leaf spring under different working conditions through finite element simulation calculations with multiple sets of different input parameters, so as to quantitatively evaluate the stress corrosion cracking risk of the leaf spring under different working conditions.

[0022] Optionally, step S5 includes: using at least one of the working load, material state, and geometric parameters as input parameters, and at least one of the stress peak value and stress-sensitive region size as output response, fitting the mapping relationship between the input parameters and the stress corrosion cracking sensitivity of the leaf spring to obtain the spring stress corrosion cracking prediction model.

[0023] Optionally, the mapping relationship is established using a random forest regression algorithm.

[0024] Optionally, the spring stress corrosion cracking prediction model is configured to: after inputting operating parameters and design parameters, output the stress peak value and stress-sensitive area size of the leaf spring under the corresponding working conditions, and determine the risk of stress corrosion cracking of the leaf spring based on the stress peak value and stress-sensitive area size.

[0025] Optionally, the risk of stress corrosion cracking of the leaf spring includes: comparing the predicted stress peak value and the size of the stress-sensitive area with the results of the benchmark model to determine the stress corrosion cracking risk level of the leaf spring under the current working conditions.

[0026] Compared with the prior art, this application has at least the following beneficial effects: The method for evaluating stress corrosion cracking in fuel assembly leaf springs of this application involves constructing a high-temperature-irradiation coupled material constitutive model of the leaf spring, establishing a parameterized geometric model of the leaf spring structure, applying coupled boundary conditions of icebreaking load and compression variation over its service life, performing stress corrosion cracking sensitivity analysis on the leaf spring based on the finite element method, obtaining stress analysis results, and then establishing a multi-parameter mapped spring stress corrosion cracking prediction model based on the stress analysis results. This spring stress corrosion cracking prediction model is then used to predict the stress corrosion cracking risk of the leaf spring under specific operating conditions. Therefore, this application can... This system comprehensively considers factors such as high temperature, radiation, dynamic impact loads, and changes in compression during the service life of nuclear-powered icebreakers in polar icebreaking operations. It more realistically reflects the stress state and material performance degradation of leaf springs under complex service environments, improving the accuracy and reliability of stress corrosion cracking risk assessment. At the same time, it enables rapid evaluation under different working conditions and structural parameters through parametric modeling and prediction models, reducing reliance on physical test specimens and long-term corrosion tests, improving design iteration efficiency, and providing a basis for leaf spring structural optimization, material selection, and safe operation of fuel assemblies for nuclear-powered icebreakers. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions in the embodiments of this application are clearly and completely described below. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this application. Other implementation methods obtained by those skilled in the art based on the embodiments described in this application without creative effort should all fall within the scope of protection of this application.

[0028] This embodiment provides a method for evaluating stress corrosion cracking of a fuel assembly leaf spring, wherein the leaf spring is a compression leaf spring for the upper tube seat of a fuel assembly used in a nuclear-powered icebreaker. This method is used to evaluate the stress corrosion cracking risk of the leaf spring under the combined effects of polar icebreaking conditions, high-temperature and high-pressure water environments, irradiation environments, and changes in compression during its service life. The method includes the following steps: S1, Construct a constitutive model of the high-temperature-irradiation coupled material of the leaf spring.

[0029] Specifically, considering the material service characteristics of the leaf springs on the fuel assembly of a nuclear-powered icebreaker, a material constitutive relation incorporating temperature sensitivity is established. The leaf spring is made of GH4169 alloy. First, the material property parameter variation curves of GH4169 alloy in the range of -40℃ to 350℃ are input. These material property parameters include at least one of elastic modulus, Poisson's ratio, and yield strength. For example, the elastic modulus of GH4169 alloy at -40℃ can be set to 210 GPa, Poisson's ratio to 0.30, and yield strength to 1080 MPa; at 20℃, the elastic modulus to 200 GPa, Poisson's ratio to 0.29, and yield strength to 1030 MPa; and at 350℃, the elastic modulus to 184 GPa, Poisson's ratio to 0.27, and yield strength to 780 MPa. A temperature-dependent material parameter table is then established based on the material property parameters at different temperatures for subsequent finite element simulation calculations.

[0030] Furthermore, considering the impact of neutron irradiation on leaf springs during long-term service in the reactor core environment, an irradiation-accelerated creep model is introduced. A decay function is defined for the mechanical property parameters of GH4169 material as a function of neutron flux rate or service time, to characterize the performance degradation of GH4169 material under long-term high-temperature irradiation. This irradiation-accelerated creep model can be a creep model based on a combined time-hardening model, which requires at least neutron flux, irradiation ambient temperature, and service time as input parameters. Through this high-temperature-irradiation coupled material constitutive model, the changes in material properties of the leaf spring caused by variations in the service environment can be reflected in subsequent simulations.

[0031] S2, Establish a parametric geometric model of the leaf spring structure.

[0032] Specifically, based on the actual physical structure of the leaf spring on the fuel assembly of a nuclear-powered icebreaker, key structural dimensions of the spring are extracted as parametric variables. These parametric variables include at least one of the following: spring length, spring width, spring height, and spring chord length. During modeling, geometric constraint relationships between the parametric variables are established according to the geometric compatibility conditions of the leaf spring. This ensures that when any parametric variable is modified, the parametric geometric model of the leaf spring structure can be automatically updated according to the preset geometric constraint relationships.

[0033] For example, when performing optimization analysis on a spring structure, the spring length, spring width, spring height, and spring chord length can be set as adjustable parameters. When the spring thickness, spring chord length, or spring height changes, the parametric geometric model can automatically update the corresponding bending region, connection region, and stress region, thereby obtaining a new leaf spring structure model. This parametric modeling method avoids re-creating a 3D model for each structural scheme, improving the modeling efficiency of different spring structure schemes and providing a foundation for subsequent batch simulations and structural optimization.

[0034] Furthermore, the parametric geometric model of the leaf spring structure is discretized to establish a numerical simulation model of the spring. Depending on the requirements for computational accuracy and efficiency, discretization can employ at least one of shell elements, beam elements, or solid elements. In this embodiment, to balance computational efficiency and the representation of key stress characteristics, shell elements are selected to discretize the leaf spring geometric model, and the mesh is refined for the bending region, compression contact region, and stress concentration region to improve the accuracy of the stress analysis results.

[0035] S3 applies a coupled boundary condition of icebreaking load and compression variation over the service life.

[0036] Specifically, considering the actual stress characteristics of nuclear-powered icebreakers during polar icebreaking operations, a time-varying icebreaking impact load spectrum is constructed. This spectrum is formed by the superposition of the swaying inertial force of the nuclear-powered icebreaker and the impact force of ice fracturing, and is used to simulate the dynamic loads on nuclear-powered icebreakers during polar operations. The icebreaking impact load spectrum can be used to characterize the stress state of nuclear-powered icebreakers in vertical, tilted, swaying, or rotating operating postures.

[0037] In this embodiment, the icebreaking operation in a vertical running posture can be selected as an example. A constant axial preload is used as the base load, while dynamic loads caused by coolant flow, hull vibration, and ice fracture impact are superimposed to simulate the stress state of a leaf spring during normal icebreaking operations on a nuclear-powered icebreaker. During the calculation, at least one of the following operating parameters is input: total fuel assembly height, total core height, operating temperature, system pressure, coolant flow rate, coolant density, vibration frequency, mechanical stress, neutron flux, and burnup.

[0038] Furthermore, based on the difference in height-direction irradiation growth between the fuel assembly and the reactor core due to increases in neutron flux and service time throughout the reactor's lifespan, the compression of the leaf spring is dynamically adjusted to simulate the compression variation over the lifespan. Specifically, in the early stages of service, the compression of the leaf spring can be set to the design compression. As service time increases, the fuel assembly and reactor core structure experience varying degrees of irradiation growth in the height direction. The spring compression is updated based on the difference between the fuel assembly growth and the increase in the distance between the upper and lower plates of the reactor core, enabling the simulation model to reflect the actual stress state of the leaf spring as it compensates for height-direction growth differences throughout its lifespan.

[0039] S4. Based on the finite element analysis method, stress corrosion cracking sensitivity analysis of leaf springs was performed to obtain stress analysis results.

[0040] Specifically, based on the parametric geometric model of the leaf spring structure established in step S2, and the coupled boundary conditions of the ice-breaking load and the compression variation during its service life applied in step S3, finite element simulation calculations are performed. These finite element simulation calculations can be completed using ANSYS, ABAQUS, or other finite element analysis software.

[0041] During the finite element method (FEM) calculation, the high-temperature-irradiation coupled material constitutive model constructed in step S1 is applied to the numerical simulation model of the leaf spring, and corresponding loads, constraints, and contact conditions are set according to different operating conditions. After the simulation is completed, the stress analysis results of the leaf spring are extracted. The stress analysis results include at least one of the following: stress distribution, peak stress data, and the size of the stress-sensitive region.

[0042] The stress-sensitive region is defined as the area on the leaf spring where the stress exceeds a preset percentage of the material's yield strength, which can be 80% or 90%. When shell or beam elements are used in the finite element simulation, the size of the stress-sensitive region can be characterized by its area; when solid elements are used, the size can be characterized by its volume. In this embodiment, if shell elements are used to discretize the leaf spring, the region on the spring structure where the stress exceeds 90% of the material's yield strength can be defined as the stress-sensitive region, and the area of ​​this region can be extracted as a feature parameter for evaluating the susceptibility to stress corrosion cracking.

[0043] Furthermore, through finite element simulations with multiple sets of different input parameters, the peak stress and stress-sensitive region size of the leaf spring under different operating conditions are obtained to quantitatively evaluate the stress corrosion cracking risk of the leaf spring under different operating conditions. The different input parameters may include different ice-breaking impact loads, different operating temperatures, different neutron fluxes, different service times, different spring compressions, and different spring structural dimensions. This allows for the acquisition of a simulation dataset covering various operating conditions and structural schemes.

[0044] S5. Based on the stress analysis results, a multi-parameter mapping spring stress corrosion cracking prediction model is established, and the spring stress corrosion cracking prediction model is used to predict the stress corrosion cracking risk of leaf springs under specific working conditions.

[0045] Specifically, based on the multiple sets of finite element simulation data obtained in step S4, a dataset is constructed between the input parameters and the output response. The input parameters include at least one of the following: operating load, material state, and geometric parameters. The operating load may include at least one of icebreaking impact load, axial preload, and dynamic vibration load; the material state may include at least one of operating temperature, neutron flux, service time, and material performance degradation parameters; and the geometric parameters may include at least one of spring length, spring width, spring height, and spring chord length. The output response includes at least one of the following: peak stress and size of the stress-sensitive region.

[0046] After obtaining the aforementioned dataset, a data processing method is used to fit the mapping relationship between the input parameters and the stress corrosion cracking sensitivity of the leaf spring, thereby obtaining a spring stress corrosion cracking prediction model. The data processing method can be a statistical method or an intelligent algorithm. In this embodiment, a random forest regression algorithm can be used to establish a nonlinear mapping relationship between the input parameters and the output response. Specifically, by modifying the parameterized dimensions and changing the load input parameters, multiple sets of simulation experiments are conducted to obtain a dataset containing the input parameters and output response. Subsequently, the dataset is divided into a training set and a test set. The random forest regression algorithm is used to train the training set, and the test set is used to verify the model's prediction accuracy, thus obtaining the trained leaf spring stress corrosion cracking prediction model.

[0047] The spring stress corrosion cracking prediction model is configured to: after inputting operating parameters and design parameters, output the peak stress and stress-sensitive region size of the leaf spring under the corresponding operating condition, and determine the risk of stress corrosion cracking of the leaf spring based on the peak stress and stress-sensitive region size. Specifically, the predicted peak stress and stress-sensitive region size can be compared with the results of a benchmark model to determine the stress corrosion cracking risk level of the leaf spring under the current operating condition. When the predicted peak stress is high, or the stress-sensitive region size is significantly larger than the benchmark model result, it can be determined that the risk of stress corrosion cracking of the leaf spring under this operating condition is high; when the predicted peak stress and stress-sensitive region size are both within the allowable range, it can be determined that the risk of stress corrosion cracking of the leaf spring under this operating condition is low.

[0048] Furthermore, when a leaf spring is determined to have a high risk of stress corrosion cracking under a certain operating condition, its structural or material parameters can be adjusted. Simulation calculations can then be performed again based on the adjusted parameters, or the aforementioned stress corrosion cracking prediction model can be used for rapid prediction until a spring structure that meets the stress corrosion cracking risk requirements is obtained. Therefore, this application enables the assessment of stress corrosion cracking risk of leaf springs for fuel assemblies in nuclear-powered icebreakers under various extreme operating conditions while reducing reliance on physical specimen manufacturing and long-term corrosion testing. This provides a basis for optimizing the leaf spring structure, selecting materials, and ensuring the safe operation of the fuel assembly.

[0049] The specific embodiments of this application have been described above, but this application is not limited to the above embodiments. For those skilled in the art, various changes, substitutions or improvements can be made without departing from the concept of this application, and such changes, substitutions or improvements should all fall within the protection scope of this application.

Claims

1. A method for evaluating fuel assembly plate spring stress corrosion cracking, characterized by, Includes the following steps: S1, Construct a constitutive model of the high-temperature-irradiation coupled material of the leaf spring; S2, Establish a parametric geometric model of the leaf spring structure; S3, apply the coupled boundary condition of icebreaking load and compression variation during service life; S4. Based on the finite element analysis method, stress corrosion cracking sensitivity analysis is performed on the leaf spring to obtain stress analysis results; S5. Based on the stress analysis results, establish a multi-parameter mapping spring stress corrosion cracking prediction model, and use the spring stress corrosion cracking prediction model to predict the stress corrosion cracking risk of leaf springs under specific working conditions.

2. The fuel assembly plate spring stress corrosion cracking evaluation method according to claim 1, characterized by, The leaf spring is a pressure leaf spring for the upper tube seat of the fuel assembly of a nuclear-powered icebreaker, and the material of the leaf spring is GH4169 alloy.

3. The fuel assembly plate spring stress corrosion cracking evaluation method according to claim 2, characterized by, Step S1 includes: inputting the physical property parameters of GH4169 alloy in the range of -40℃ to 350℃ as a function of temperature, such as elastic modulus, Poisson's ratio and yield strength, to establish a material constitutive relationship that includes temperature sensitivity.

4. The method for evaluating stress corrosion cracking of fuel assembly plate springs according to claim 2, characterized in that, Step S1 further includes: introducing an irradiation-accelerated creep model and defining a decay function for the mechanical property parameters of GH4169 material as a function of neutron flux rate or service time, in order to characterize the performance degradation of GH4169 material under long-term high-temperature irradiation.

5. The method for evaluating stress corrosion cracking of fuel assembly plate springs according to claim 4, characterized in that, The irradiation-accelerated creep model is a creep model based on a combined time-hardening model, and the creep model uses at least neutron flux, irradiation ambient temperature, and service time as input parameters.

6. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 1, characterized in that, Step S2 includes: based on the actual physical structure of the leaf spring, selecting at least one of the spring length, spring width, spring height and spring chord length as parameterized variables, and establishing geometric constraint relationships between the parameterized variables so that the parameterized geometric model of the leaf spring structure can be automatically updated when any parameterized variable is modified.

7. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 6, characterized in that, Step S2 further includes: discretizing the parameterized geometric model of the leaf spring structure to establish a numerical simulation model of the spring; wherein the discretization process uses at least one of shell elements, beam elements, and solid elements.

8. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 1, characterized in that, Step S3 includes: constructing an icebreaking impact load spectrum with time-varying characteristics. The icebreaking impact load spectrum is formed by superimposing the swaying inertial force of the nuclear-powered icebreaker and the ice fracture impact force, and is used to simulate the dynamic load of the nuclear-powered icebreaker in polar operations.

9. The method for evaluating stress corrosion cracking of fuel assembly plate springs according to claim 8, characterized in that, The icebreaking impact load spectrum is used to characterize the force state of a nuclear-powered icebreaker in vertical, tilted, swaying, or turning operating postures.

10. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 1, characterized in that, Step S3 further includes: dynamically adjusting the compression of the leaf springs based on the height-direction irradiation growth difference between the fuel assembly and the reactor core during their service life as the neutron flux and service time increase, in order to simulate the compression variation during the service life.

11. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 10, characterized in that, The input parameters in step S3 include at least one of the following: total fuel assembly height, total core height, operating temperature, system pressure, coolant flow rate, coolant density, vibration frequency, mechanical stress, neutron flux, and burnup.

12. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 1, characterized in that, Step S4 includes: performing finite element simulation calculations based on the parameterized geometric model of the leaf spring structure and the coupled boundary conditions, and extracting the stress distribution cloud map, stress peak data, and the size of the stress-sensitive region of the leaf spring.

13. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 12, characterized in that, The stress-sensitive region is the area on the leaf spring where the stress is higher than a preset proportion of the material's yield strength, where the preset proportion is 80% or 90%.

14. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 1, characterized in that, Step S4 further includes: obtaining the stress peak value and stress-sensitive area size of the leaf spring under different working conditions through finite element simulation calculations with multiple sets of different input parameters, so as to quantitatively evaluate the stress corrosion cracking risk of the leaf spring under different working conditions.

15. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 1, characterized in that, Step S5 includes: using at least one of the working load, material state, and geometric parameters as input parameters, and at least one of the stress peak value and stress sensitive region size as output response, fitting the mapping relationship between the input parameters and the stress corrosion cracking sensitivity of the leaf spring to obtain the spring stress corrosion cracking prediction model.

16. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 15, characterized in that, The mapping relationship is established using the random forest regression algorithm.

17. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 15, characterized in that, The spring stress corrosion cracking prediction model is configured to: after inputting operating parameters and design parameters, output the stress peak value and stress-sensitive area size of the leaf spring under the corresponding working conditions, and determine the risk of stress corrosion cracking of the leaf spring based on the stress peak value and stress-sensitive area size.

18. The method for evaluating stress corrosion cracking of fuel assembly leaf springs according to claim 17, characterized in that, The method for determining the risk of stress corrosion cracking in leaf springs includes: comparing the predicted stress peak value and the size of the stress-sensitive area with the results of the benchmark model to determine the stress corrosion cracking risk level of the leaf spring under the current operating conditions.