A method for evaluating the service life of a venturi in a nuclear power plant

Abstract

The application provides a nuclear power plant Venturi tube life evaluation method, comprising the following steps: constructing a fluid dynamics parameter library of the whole working condition of a Venturi tube to be evaluated; obtaining real-time operation parameters of the Venturi tube to be evaluated under a current working condition; matching the real-time operation parameters from the fluid dynamics parameter library, and obtaining simulation calculation data under the current working condition; selecting a high sensitive area of the Venturi tube to be evaluated according to the simulation calculation data, and calculating a real-time corrosion rate of the high sensitive area; and calculating the residual life of the Venturi tube to be evaluated according to the real-time corrosion rate. The nuclear power plant Venturi tube life evaluation method can realize real-time dynamic evaluation and has high evaluation precision.

Description

Technical Field

[0001] This invention relates to the field of venturi tube life assessment technology in nuclear power plants, and more particularly to a method for assessing the life of venturi tubes in nuclear power plants. Background Technology

[0002] Venturi tubes, as key throttling and measurement components in the steam-water loop of nuclear power plants, are widely used in core processes such as coolant flow monitoring and pressure regulation. Their unique contraction-throat-diffuser structure causes strong turbulent pulsations in the fluid inside the tube, generating significant shear stress on the tube wall. This easily leads to flow-accelerated corrosion, causing continuous thinning of the Venturi tube wall. If not monitored and assessed in a timely manner, this can lead to serious safety accidents such as pipeline leaks and ruptures, directly threatening the operational safety and economic efficiency of the nuclear power plant. Existing methods for assessing the lifespan of venturi tubes in nuclear power plants mostly rely on post-hoc analysis of ultrasonic thickness measurement data from periodic overhauls. These methods cannot achieve real-time dynamic assessment, struggle to capture sudden corrosion changes under fluctuating operating conditions, and have low assessment accuracy. Summary of the Invention

[0003] This invention provides a method for assessing the lifespan of venturi tubes in nuclear power plants, which enables real-time dynamic assessment with high accuracy.

[0004] This invention provides a method for assessing the lifespan of venturi tubes in nuclear power plants, comprising:

[0005] Construct a fluid dynamics parameter library for all operating conditions of the Venturi tube to be evaluated; Obtain the real-time operating parameters of the Venturi tube to be evaluated under its current operating conditions; Match real-time operating parameters from the fluid dynamics parameter library and obtain simulation calculation data under the current operating conditions; The highly sensitive area of ​​the venturi tube to be evaluated was selected based on the simulation calculation data, and the real-time corrosion rate of the highly sensitive area was calculated. The remaining life of the venturi tube to be evaluated is calculated based on the real-time corrosion rate.

[0006] In one embodiment of the present invention, a fluid dynamics parameter library for the venturi tube under all operating conditions to be evaluated is constructed, specifically including: Obtain the basic parameters of the venturi tube to be evaluated, including the material and geometric parameters of the venturi tube to be evaluated; Establish a basic parameter database based on the basic parameters; Based on the basic parameter database, the full-condition data of the Venturi tube to be evaluated is calculated in batches. The full-condition data includes the three-dimensional coordinates of the inner wall of the Venturi tube to be evaluated, the wall shear stress, the turbulent kinetic energy dissipation rate and the near-wall velocity. A fluid dynamics parameter library was built based on full-condition data.

[0007] In one embodiment of the present invention, the full-condition data of the venturi tube to be evaluated is calculated in batches according to the basic parameter database, specifically including: The database of basic parameters is used as input; Determine the full-condition envelope range of the Venturi tube to be evaluated, and generate discrete operating points within the full-condition envelope range with a preset step size; A working condition matrix is ​​constructed based on discrete operating points, and point working condition data is calculated. Full-condition data for the Venturi tube to be evaluated is constructed based on point condition data.

[0008] In one embodiment of the present invention, the real-time operating parameters include the upstream and downstream operating parameters of the venturi tube to be evaluated and real-time water chemistry data.

[0009] In one embodiment of the present invention, matching real-time operating parameters from a fluid dynamics parameter library and obtaining simulation calculation data under the current operating conditions specifically includes: Centered on the real-time operating parameters under the current working conditions, the simulation calculation data under the current working conditions is calculated by using a multi-dimensional interpolation retrieval method in the full-condition fluid dynamics parameter library.

[0010] In one embodiment of the present invention, the highly sensitive area of ​​the venturi tube to be evaluated is selected based on simulation calculation data, and the real-time corrosion rate of the highly sensitive area is calculated, specifically including: Obtain the turbulent kinetic energy dissipation rate data of the Venturi tube to be evaluated from the simulation calculation data; The turbulent kinetic energy dissipation rate data are sorted by numerical value, and the regions corresponding to the data that meet the preset conditions are selected as high-sensitivity areas. Collect thickness measurement records from all major overhauls of the venturi tube to be evaluated, establish a unified coordinate system by associating it with high-sensitivity areas, and filter the wall thickness data corresponding to the high-sensitivity areas. Calculate the wall thickness reduction rate in the highly sensitive area based on the wall thickness data; The real-time corrosion rate is calculated based on the wall thickness reduction rate.

[0011] In one embodiment of the present invention, calculating the wall thickness reduction rate of the highly sensitive region based on wall thickness data specifically includes: Remove outliers from thickness measurement data; Perform linear drift correction; Apply physical constraints; Construct a spatiotemporal trend curve for wall thickness; The wall thickness reduction rate in the highly sensitive region is calculated based on the spatiotemporal trend curve of wall thickness.

[0012] In one embodiment of the present invention, the calculation of the real-time corrosion rate based on the wall thickness reduction rate specifically includes: A fluid dynamics sub-model, an electrochemical corrosion sub-model, and an oxide film evolution sub-model were constructed respectively. A corrosion rate calculation model was constructed, which coupled the wall shear stress output by the fluid dynamics sub-model, the corrosion potential output by the electrochemical corrosion sub-model, and the film state parameters output by the oxide film evolution sub-model, and substituted them into the corrosion rate calculation model to calculate the real-time corrosion rate.

[0013] In one embodiment of the present invention, the remaining life of the venturi tube to be evaluated is calculated based on the real-time corrosion rate, prior to which the following steps are included: A training set was constructed using wall thickness reduction rate as the label data and a fluid dynamics parameter library as the feature variables. The corrosion rate calculation model is inverted and calibrated to ensure that the deviation between the predicted and measured values ​​is controlled within a preset range.

[0014] In one embodiment of the present invention, calculating the remaining life of the venturi tube to be evaluated based on the real-time corrosion rate specifically includes: Obtain the power plant's medium- and long-term operation plan and generate the probability distribution of operating conditions; The corrosion rate calculation model is coupled with the operating condition probability distribution to generate a wall thickness evolution prediction curve for the highly sensitive area. Determine the minimum permissible wall thickness of the venturi tube to be evaluated; The remaining lifetime is calculated as the operating time required for the wall thickness to be reduced to the minimum allowable wall thickness. Output lifespan warning information.

[0015] The beneficial effects of this invention are: The present invention provides a method for assessing the lifespan of venturi tubes in nuclear power plants. By constructing a fluid dynamics parameter library for the venturi tube under all operating conditions and matching it with real-time operating parameters under the current conditions, the traditional post-overhaul monitoring is transformed into continuous real-time monitoring. This enables dynamic tracking of the venturi tube's service status. The method then matches the current operating conditions from the fluid dynamics parameter library in real time and obtains corresponding simulation calculation data. This allows for timely reflection of the impact of fluctuations in current operating conditions on the flow field distribution, effectively capturing changes in corrosion behavior caused by these fluctuations. Based on the simulation calculation data, highly sensitive areas are accurately identified and their real-time corrosion rates are calculated. Finally, the remaining lifespan is calculated based on the real-time corrosion rates. This method enables real-time dynamic assessment, allowing the lifespan prediction results to be dynamically corrected according to the actual operating conditions of the venturi tube. The high accuracy of the assessment significantly improves the precision and reliability of venturi tube lifespan assessment in nuclear power plants, providing a more scientific technical basis for preventative maintenance. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0017] In the attached diagram: Figure 1 This is a schematic diagram of the process structure of a method for assessing the lifespan of a venturi tube in a nuclear power plant, provided in an embodiment of the present invention. Detailed Implementation

[0018] The following specific examples illustrate the implementation 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 embodiments. 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. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0019] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0020] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0021] Please see Figure 1 This invention provides a method for assessing the lifespan of a venturi tube in a nuclear power plant, comprising the following steps: Step S1: Construct a fluid dynamics parameter library for the venturi tube under all operating conditions to be evaluated; In one embodiment of the present invention, step S1 may specifically include: Step S11: Obtain the basic parameters of the venturi tube to be evaluated. The basic parameters include the material and geometric parameters of the venturi tube to be evaluated. This step can be based on nuclear power plant piping drawings to extract the geometric parameters of the Venturi tube to be evaluated from the design drawings, including the diameter, angle and length parameters of each section, such as the inlet diameter of the contraction section, the diffusion angle, the throat diameter, and the outlet diameter of the diffusion section. Specifically, the elemental composition of the Venturi tube to be evaluated can be determined based on the material certificate, and the content of elements that affect corrosion performance, such as chromium and carbon, should be recorded.

[0022] Step S12: Establish a basic parameter database based on the basic parameters; This step involves establishing a basic parameter database based on the basic parameters. This can be done using conventional techniques in the field, including but not limited to entering the basic parameters of the venturi tube into the database software according to a preset format, establishing the basic parameter database for storage and management, etc. The preset format includes, but is not limited to, device ID, parameter type, value and unit fields, etc., and setting indexes to support fast query and retrieval.

[0023] Step S13: Calculate the full-condition data of the Venturi tube to be evaluated in batches according to the basic parameter database. The full-condition data includes the three-dimensional coordinates of the inner wall of the Venturi tube to be evaluated, the wall shear stress, the turbulent kinetic energy dissipation rate and the near-wall velocity. In one embodiment of the present invention, step S13 may specifically include: Step S131: Use the basic parameter database as input; Step S132: Determine the full-condition envelope range of the venturi tube to be evaluated, and generate discrete running points within the full-condition envelope range with a preset step size; The envelope range and preset step size in this step can be flexibly set according to actual usage needs. However, to obtain more comprehensive full-condition data for the venturi tube to be evaluated, in one embodiment of the present invention, the full-condition envelope range of the venturi tube to be evaluated may include a flow rate dimension and a temperature dimension. The flow rate dimension covers 0%FP to 120%FP, with a step size of 3%FP to 10%FP. The temperature dimension covers the design temperature ±20℃, with a step size of 1℃ to 5℃. In other embodiments, the flow rate dimension covers 0%FP to 120%FP, and the step size can also be set to 3%FP, 5%FP, 6%FP, 7%FP, 10%FP, etc. The temperature dimension covers the design temperature ±20℃, with a step size of 1℃, 2℃, 3℃, 5℃, etc.

[0024] Step S133: Construct a working condition matrix based on discrete operating points and calculate point working condition data; The calculation of point load data in this step can be performed using conventional techniques in the field, including but not limited to offline CFD batch calculation. Specifically, a high-performance workstation can be used with ANSYS Fluent or Star-CCM+ software to perform scripted batch calculations on the above load matrix to obtain point load data.

[0025] Step S134: Construct full-condition data for the Venturi tube to be evaluated based on the point condition data.

[0026] The step of constructing full-condition data for the Venturi tube to be evaluated based on point condition data can employ conventional techniques in the field, including but not limited to using Realizable k-ε or SST k-ω models to capture the near-wall shear flow of the Venturi tube to be evaluated. After the calculation converges, the three-dimensional coordinates, wall shear stress, turbulent kinetic energy dissipation rate, and near-wall velocity of all points on the inner wall of the Venturi tube to be evaluated are extracted to construct full-condition data.

[0027] Step S14: Construct a fluid dynamics parameter library based on full-condition data.

[0028] This step of building a fluid dynamics parameter library based on full-condition data can employ conventional techniques in the field, including but not limited to storing full-condition data in HDF5 or SQL format, establishing a multi-dimensional index of operating parameters, spatial coordinates, and flow field characteristics, and supporting rapid retrieval by temperature, pressure, and flow rate dimensions.

[0029] Step S2: Obtain the real-time operating parameters of the venturi tube to be evaluated under the current operating conditions; This step can obtain upstream and downstream operating parameters of the Venturi tube to be evaluated through the DCS system, including medium temperature, pressure and flow rate; and can obtain real-time water chemistry data through the online chemical system, including pH value, dissolved oxygen concentration and conductivity, to ensure continuous and uninterrupted data acquisition, and mark and temporarily store any occasional abnormal data.

[0030] Step S3: Match real-time operating parameters from the fluid dynamics parameter library and obtain simulation calculation data under the current operating conditions; In one embodiment of the present invention, step S3 may specifically include: Step S31: Taking the real-time operating parameters under the current working condition as the center, calculate the simulation calculation data under the current working condition using a multi-dimensional interpolation retrieval method in the full-condition fluid dynamics parameter library; The multidimensional interpolation retrieval methods in this step include, but are not limited to, trilinear interpolation, quadlinear interpolation, or higher-dimensional linear interpolation methods. Specifically, using the real-time operating parameters under the current working conditions as the target point, the two adjacent points are located in the parameter library. n Each working condition node (where n is the dimension) is linearly weighted based on its distance from the target point to obtain the simulation data for the current working condition. As an example of this step, using the real-time operating parameters under the current working condition as the center, a trilinear interpolation search is performed in the full-condition fluid dynamics parameter library to find the eight nearest neighbor working conditions for the current working condition, quickly obtaining the simulation data for the current working condition.

[0031] Step S4: Select the highly sensitive area of ​​the venturi tube to be evaluated based on the simulation calculation data, and calculate the real-time corrosion rate of the highly sensitive area; The highly sensitive area in this step refers to the local area on the inner wall of the Venturi tube that is strongly affected by fluid turbulence. Due to the high turbulent kinetic energy dissipation rate in this area, the shear stress and mass transfer rate between the fluid and the wall are significantly increased, which can easily lead to the destruction of corrosion product film or accelerated corrosion. As a result, the corrosion rate is significantly higher than in other areas, making it a key part that restricts the overall service life of the Venturi tube.

[0032] In one embodiment of the present invention, step S4 may specifically include: Step S41: Obtain the turbulent kinetic energy dissipation rate data of the Venturi tube to be evaluated from the simulation calculation data; Step S42: Sort the turbulent kinetic energy dissipation rate data by numerical value and select the regions corresponding to the data that meet the preset conditions as high-sensitivity regions; The preset conditions for this step can be flexibly set as needed. In one embodiment of the present invention, the preset conditions can be that the top 10% of the turbulent kinetic energy dissipation rate data are taken and the continuous area is greater than 25 cm². 2 By using the top 10% of the turbulent kinetic energy dissipation rate data as the screening threshold, the local location on the inner wall of the Venturi tube to be evaluated that is most severely impacted by turbulence can be accurately identified. These areas are often the key locations where flow-accelerated corrosion or erosion corrosion is most likely to occur due to the concentrated dissipation of fluid kinetic energy and significant shear stress on the wall. At the same time, by setting a constraint condition with a continuous area greater than 25 cm², outliers in the numerical calculation can be effectively eliminated, ensuring that the selected high-sensitivity areas have spatial continuity on an actual engineering scale, which significantly improves the reliability of the evaluation results.

[0033] Step S43: Collect the wall thickness records of the venturi tube to be evaluated for each major overhaul, establish a unified coordinate system by associating it with the high-sensitivity area, and filter the wall thickness data corresponding to the high-sensitivity area. This step involves collecting thickness measurement records from previous overhauls and establishing a unified coordinate system corresponding to the highly sensitive areas. This allows for precise spatial matching of historical inspection data with these areas. By filtering the thickness measurement data corresponding to the highly sensitive areas, subsequent calculations of the wall thickness reduction rate can be based on the actual wall thickness changes in these critical regions, effectively improving the accuracy of real-time corrosion rate calculations. To standardize the wall thickness data, after collecting wall thickness records from previous overhauls of the Venturi tube to be evaluated, a unified coordinate system is established using the inlet flange end face of the Venturi tube as a reference. All wall thickness points are then renumbered and their coordinates calibrated to eliminate reference deviations from different inspection cycles. Finally, wall thickness data corresponding to the highly sensitive areas is selected.

[0034] Step S44: Calculate the wall thickness reduction rate of the highly sensitive area based on the wall thickness data; The calculation of the wall thickness reduction rate of the highly sensitive region based on the wall thickness data in this step can be performed using conventional techniques in the art. However, to ensure the accuracy of the thinning rate calculation, in one embodiment of the present invention, step S44 specifically includes: Step S441: Remove outliers from the thickness measurement data; This step can use statistical outlier testing methods to remove outliers from the thickness measurement data. Statistical outlier testing methods include, but are not limited to, the Grubbs criterion.

[0035] Step S442: Perform linear drift correction; The linear correction in this step may specifically include: establishing a linear relationship between measurement time and indication drift based on the historical calibration data of the ultrasonic thickness gauge on a standard test block, calculating the drift correction amount according to the measurement time corresponding to the thickness measurement data, and compensating each thickness measurement data proportionally.

[0036] Step S443: Apply physical constraints; The physical constraints of this step include, but are not limited to, the following: non-negative wall thickness constraint, i.e., the remaining wall thickness must be greater than zero and less than or equal to the initial wall thickness; monotonically decreasing constraint, i.e., the wall thickness at the same measuring point should monotonically decrease or remain unchanged over time during each major overhaul; upper and lower limit constraints of the rate, i.e., the wall thickness reduction rate must be between zero and the theoretical maximum corrosion rate of the material under the corresponding working conditions; and spatiotemporal continuity constraint, i.e., the wall thickness change rate at adjacent measuring points and adjacent time steps should smoothly transition within a reasonable range.

[0037] Step S444: Construct the spatiotemporal trend curve of wall thickness; Based on the wall thickness data of the highly sensitive area processed in the previous steps, a discrete sequence of the wall thickness evolution of each measuring point over time is plotted with the time of each major overhaul as the horizontal axis and the corresponding wall thickness measurement value as the vertical axis. Furthermore, by using the least squares method or spline interpolation method, the wall thickness data of the same measuring point or all measuring points in the highly sensitive area are fitted into a continuous and smooth spatiotemporal trend curve, thereby intuitively presenting the overall thinning trend and local fluctuation characteristics of the wall thickness of the key area with the service years.

[0038] Step S445: Calculate the wall thickness reduction rate in the high-sensitivity region based on the spatiotemporal trend curve of wall thickness; Linear regression analysis is performed on the spatiotemporal trend curve of wall thickness constructed in step S444. The absolute value of the slope of the fitted line is used as the average wall thickness reduction rate of the high-sensitivity area during the evaluation period. If the trend curve is obviously nonlinear, multiple service stages are divided and piecewise linear fitting is performed. The weighted average of the slopes of each stage is used as the overall thinning rate, or the instantaneous derivative of the curve is used to characterize the real-time thinning rate at a specific moment. Finally, the measured value of the wall thickness reduction rate of the high-sensitivity area is output for the verification and calibration of the corrosion rate calculation model.

[0039] The above steps, by sequentially performing outlier removal, linear drift correction, and applying physical constraints, effectively filter out thickness measurement data, ensuring the reliability of the wall thickness reduction rate calculation. Based on this, a spatiotemporal trend curve of wall thickness is constructed, transforming the thickness measurement data into a continuous evolution trend. This allows the calculated wall thickness reduction rate to truly reflect the stable corrosion law of the material during long-term service, significantly improving the accuracy and reliability of subsequent corrosion rate calculations.

[0040] Step S45: Calculate the real-time corrosion rate based on the wall thickness reduction rate.

[0041] In one embodiment of the present invention, step S45 may specifically include: Step S451: Construct the fluid dynamics sub-model, electrochemical corrosion sub-model, and oxide film evolution sub-model respectively; The fluid dynamics sub-model in this step can be constructed based on the Reynolds-averaged Navier-Stokes (RANS) equations, with inputs being real-time operating parameters and a geometric model, and outputs being wall shear stress τ_w and turbulent kinetic energy dissipation rate ε; the electrochemical corrosion sub-model can be constructed based on the mixed potential theory, with inputs being water chemical parameters (pH value, dissolved oxygen concentration, conductivity) and temperature, and outputs being corrosion potential E_corr and corrosion reaction activation energy E_a; the oxide film evolution sub-model can be constructed based on oxide film growth kinetics and flow-induced stripping mechanisms, with inputs being material chromium content, temperature, and wall shear stress, and outputs being oxide film thickness δ and film bonding strength σ_b.

[0042] Step S452: Construct a corrosion rate calculation model by coupling the wall shear stress τ_w output by the fluid dynamics sub-model, the activation energy E_a of the corrosion reaction output by the electrochemical corrosion sub-model, and the film bonding strength σ_b output by the oxide film evolution sub-model, and then substituting them into the corrosion rate calculation model to calculate the real-time corrosion rate.

[0043] The corrosion rate calculation model for this step can be: v=k×(τ_w / σ_b)×exp(-E_a / (RT))×(C_O2)^m×(pH)^n The parameters are defined as follows: v is the real-time corrosion rate of flow-accelerated corrosion (FAC); k is the rate constant related to material properties; τ_w is the wall shear stress output by the fluid dynamics sub-model, characterizing the mechanical scouring effect of the fluid on the wall; σ_b is the film bonding strength output by the oxide film evolution sub-model, reflecting the film's resistance to peeling; E_a is the activation energy of the corrosion reaction output by the electrochemical corrosion sub-model; R is the ideal gas constant; T is the absolute temperature; C_O2 is the dissolved oxygen concentration; m is the dissolved oxygen concentration influence index; pH is the medium acidity / alkalinity; and n is the pH value influence index.

[0044] The above steps, by constructing separate sub-models for fluid dynamics, electrochemical corrosion, and oxide film evolution, enable modular modeling of different physicochemical mechanisms affecting the corrosion behavior of Venturi tubes. Each sub-model can be independently constructed and validated based on the theoretical foundations of its corresponding discipline, ensuring the clarity of the model structure and the integrity of the physical mechanisms. Furthermore, by establishing parameter transfer relationships between the sub-models, the coupling relationship between fluid dynamic factors (wall shear stress) and mass transfer processes, electrochemical factors (corrosion potential) and reaction driving forces, and oxide film factors (film state parameters) and corrosion kinetics is realized. Then, through the corrosion rate calculation model, multi-physics information is organically integrated, enabling real-time corrosion rate calculations to comprehensively reflect the synergistic effects of flow field characteristics, material electrochemical properties, and surface film dynamic evolution. This overcomes the limitations of single empirical models in taking into account the coupled effects of multiple factors, significantly improving the mechanistic and accurate prediction of corrosion rates, and providing more reliable technical support for the life assessment of Venturi tubes under complex operating conditions in nuclear power plants.

[0045] Step S5: Calculate the remaining life of the venturi tube to be evaluated based on the real-time corrosion rate; In one embodiment of the present invention, the following may be included before step S5: Step S51: Construct a training set using the wall thickness reduction rate as the label data and the fluid dynamics parameter library as the feature variables; Step S52: Perform inversion calibration on the corrosion rate calculation model to control the deviation between the predicted value and the measured value of the corrosion rate calculation model within a preset range.

[0046] This step can use the wall thickness reduction rate calculated in step S44 as the label data, and use the wall shear stress, turbulent kinetic energy dissipation rate, water chemical parameters, material chromium content, temperature, pressure, and flow rate from the fluid dynamics parameter library as feature variables to construct a machine learning training set; and can use gradient boosting decision tree (GBDT) or random forest algorithms to perform online inversion optimization of the key coefficients (k, m, n) in the corrosion rate calculation model, iteratively adjusting the model parameters until the relative deviation between the model prediction value and the measured thinning rate is controlled within ±15%.

[0047] The above steps, by constructing a training set using wall thickness reduction rate as label data and fluid dynamics parameter library as feature variables, can fully utilize the measured data resources accumulated during the historical service of Venturi tubes, organically link the actual corrosion evolution law with the theoretical model, and control the deviation between the model prediction value and the measured value within a preset range by inverting and calibrating the corrosion rate calculation model. This can effectively correct the deviation, thereby achieving adaptive matching between the theoretical model and engineering reality, and significantly improving the applicability and prediction accuracy of the corrosion rate calculation model under specific operating conditions of nuclear power plants.

[0048] In one embodiment of the present invention, step S5 may specifically include: Step S53: Obtain the power plant's medium- and long-term operation plan and generate the probability distribution of operating conditions; The power plant's medium- and long-term operation plan in this step includes, but is not limited to, load change curves, refueling cycles, and chemical condition adjustment schemes for the next 3-5 years. The generation of the operating condition probability distribution may specifically include: using the Monte Carlo random sampling method, generating multiple sets of future operating condition samples based on the historical fluctuation range and probability density function of each operating parameter, statistically analyzing the probability of occurrence of each operating condition interval, and forming an operating condition probability distribution to cover the parameter fluctuation range and duration.

[0049] Step S54: Couple the corrosion rate calculation model with the operating condition probability distribution to generate the wall thickness evolution prediction curve for the highly sensitive area; Specifically, this step involves using a corrosion rate calculation model to calculate the real-time corrosion rate under the corresponding working condition for each set of future working condition samples generated by Monte Carlo. Based on the current wall thickness integral, the wall thickness reduction amount to the next time step is calculated. The wall thickness time series data of each monitoring point within the prediction period is obtained through iterative recursion. Probabilistic statistical analysis is performed on the wall thickness time series data of all samples to generate a wall thickness evolution prediction curve containing confidence intervals.

[0050] Step S55: Determine the minimum allowable wall thickness of the venturi tube to be evaluated; The minimum allowable wall thickness for this step can be determined according to nuclear power plant design specifications or ASME standards. Specifically, it is the structural strength requirement wall thickness after subtracting the corrosion allowance from the design wall thickness, or it can be determined comprehensively based on the pressure-bearing capacity of the venturi tube, the flow measurement accuracy requirements, and the structural integrity evaluation results.

[0051] Step S56: Calculate the operating time required for the wall thickness to decrease to the minimum allowable wall thickness as the remaining life; Step S57: Output lifespan warning information.

[0052] The above steps, by acquiring the power plant's medium- and long-term operation plan and generating the probability distribution of operating conditions, combine the corrosion rate calculation model with actual operation scheduling. This allows the wall thickness evolution prediction curve to no longer be based on a single constant operating condition assumption, but to fully reflect multiple possible combinations of operating conditions and their probabilities of occurrence. This significantly improves the adaptability of the life prediction results to the real operating environment. Furthermore, by coupling the corrosion rate calculation model with the operating condition probability distribution, a dynamic correlation between corrosion kinetics and operating strategies is achieved. This enables the remaining life calculation to proactively consider the impact of actual factors on the cumulative corrosion effect. Finally, by determining the minimum allowable wall thickness and calculating the operating time required for the wall thickness to drop to that value, a quantitative closed loop from real-time corrosion monitoring to life warning is established. This provides operators with clear decision-making basis and sufficient response time, thereby effectively avoiding the risk of sudden failure and significantly improving the initiative and safety of venturi tube life management in nuclear power plants.

[0053] In summary, the venturi tube life assessment method for nuclear power plants of this invention integrates real-time operational data and in-service inspection data to construct a multi-physics dynamic corrosion prediction model. This model accurately identifies highly corrosion-sensitive areas and predicts wall thickness evolution and remaining life in real time. It achieves precise quantification of the thinning rate of key corrosion points in venturi tubes and dynamic assessment of remaining life, while also considering timeliness, accuracy, and reliability. This provides a scientific basis for preventive maintenance and life management of venturi tubes in nuclear power plants, ensuring the safe and stable operation of the equipment. It solves the problems of discontinuous data assessment after traditional inspections, the bottleneck of computing power for real-time flow field modeling, and insufficient model prediction accuracy. It significantly improves the accuracy and timeliness of FAC life assessment, can cover the service life of venturi tubes, and provides a scientific basis for preventive maintenance decisions in nuclear power plants.

[0054] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for assessing the lifespan of a venturi tube in a nuclear power plant, characterized in that, include: Construct a fluid dynamics parameter library for all operating conditions of the Venturi tube to be evaluated; Obtain the real-time operating parameters of the venturi tube to be evaluated under the current operating conditions; Match the real-time operating parameters from the fluid dynamics parameter library and obtain the simulation calculation data under the current operating condition; The highly sensitive area of ​​the venturi tube to be evaluated is selected based on the simulation calculation data, and the real-time corrosion rate of the highly sensitive area is calculated. The remaining life of the venturi tube to be evaluated is calculated based on the real-time corrosion rate.

2. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 1, characterized in that, A fluid dynamics parameter library for the Venturi tube under all operating conditions to be evaluated is constructed, specifically including: Obtain the basic parameters of the venturi tube to be evaluated, including the material and geometric parameters of the venturi tube to be evaluated; A basic parameter database is established based on the aforementioned basic parameters; The full-condition data of the Venturi tube to be evaluated is calculated in batches based on the basic parameter database. The full-condition data includes the three-dimensional coordinates of the inner wall of the Venturi tube to be evaluated, the wall shear stress, the turbulent kinetic energy dissipation rate, and the near-wall velocity. The fluid dynamics parameter library is constructed based on the full-condition data.

3. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 2, characterized in that, Based on the aforementioned basic parameter database, batch calculations are performed on the full-condition data of the Venturi tube to be evaluated, specifically including: Using the aforementioned basic parameter database as input; Determine the full-condition envelope range of the Venturi tube to be evaluated, and generate discrete operating points within the full-condition envelope range with a preset step size; A working condition matrix is ​​formed based on the discrete operating points, and the point working condition data is calculated; The full-condition data of the venturi tube to be evaluated is constructed based on the point condition data.

4. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 3, characterized in that, The real-time operating parameters include the upstream and downstream operating parameters and real-time hydrochemical data of the Venturi tube to be evaluated.

5. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 4, characterized in that, Matching the real-time operating parameters from the fluid dynamics parameter library and obtaining the simulation calculation data under the current operating condition specifically includes: Using the real-time operating parameters under the current operating condition as the center, the simulation calculation data under the current operating condition is calculated by using a multi-dimensional interpolation retrieval method in the full-condition fluid dynamics parameter library.

6. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 5, characterized in that, Based on the simulation calculation data, the highly sensitive area of ​​the venturi tube to be evaluated is selected, and the real-time corrosion rate of the highly sensitive area is calculated, specifically including: The turbulent kinetic energy dissipation rate data of the Venturi tube to be evaluated are obtained from the simulation calculation data; The turbulent kinetic energy dissipation rate data are sorted by numerical value, and the regions corresponding to the data that meet preset conditions are selected as the high-sensitivity regions. Collect the wall thickness records of each major overhaul of the Venturi tube to be evaluated, establish a unified coordinate system by associating it with the high-sensitivity area, and filter the wall thickness data corresponding to the high-sensitivity area. Calculate the wall thickness reduction rate of the highly sensitive region based on the wall thickness data; The real-time corrosion rate is calculated based on the wall thickness reduction rate.

7. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 6, characterized in that, The wall thickness reduction rate of the highly sensitive region is calculated based on the wall thickness data, specifically including: Remove outliers from the thickness measurement data; Perform linear drift correction; Apply physical constraints; Construct a spatiotemporal trend curve for wall thickness; The wall thickness reduction rate of the highly sensitive region is calculated based on the spatiotemporal trend curve of the wall thickness.

8. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 7, characterized in that, The real-time corrosion rate is calculated based on the wall thickness reduction rate, specifically including: A fluid dynamics sub-model, an electrochemical corrosion sub-model, and an oxide film evolution sub-model were constructed respectively. A corrosion rate calculation model is constructed by coupling the wall shear stress output by the fluid dynamics sub-model, the corrosion potential output by the electrochemical corrosion sub-model, and the film state parameters output by the oxide film evolution sub-model, and then substituting them into the corrosion rate calculation model to calculate the real-time corrosion rate.

9. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 8, characterized in that, The remaining life of the venturi tube to be evaluated is calculated based on the real-time corrosion rate, prior to which the following steps are included: A training set is constructed using the wall thickness reduction rate as the label data and the fluid dynamics parameter library as the feature variables. The corrosion rate calculation model is inverted and calibrated to control the deviation between the predicted value and the measured value within a preset range.

10. The method for assessing the lifespan of a venturi tube in a nuclear power plant according to claim 8, characterized in that, The remaining life of the venturi tube to be evaluated is calculated based on the real-time corrosion rate, specifically including: Obtain the power plant's medium- and long-term operation plan and generate the probability distribution of operating conditions; The corrosion rate calculation model is coupled with the operating condition probability distribution to generate the wall thickness evolution prediction curve of the highly sensitive area. Determine the minimum permissible wall thickness of the venturi tube to be evaluated; The remaining lifetime is calculated as the operating time required for the wall thickness to decrease to the minimum permissible wall thickness. Output lifespan warning information.

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