One-two-dimensional coupling calculation method and system for river network nuclide migration and diffusion

Abstract

The invention provides a one-dimensional and two-dimensional coupling calculation method and system for river network nuclide migration and diffusion, and the method comprises the steps: predicting the spatial and temporal distribution of radionuclides in a whole river network through a one-dimensional model, and extracting a nuclide flux time sequence at the intersection section of the river network and a two-dimensional calculation domain; sorting the nuclide flux time sequence and generating an interface file in a standard format; based on data in the interface file, performing intelligent local encryption on a two-dimensional calculation grid in an entrance area where the one-dimensional river network and the two-dimensional water area intersect; and based on the encrypted grid and the interface file, setting a dynamic source item boundary of the two-dimensional numerical model, synchronously promoting coupling calculation of the one-dimensional numerical model and the two-dimensional numerical model, and simulating continuous migration of nuclides from the river network to the estuary. According to the one-dimensional and two-dimensional coupling calculation method for river network nuclide migration and diffusion, rapid calculation of efficient and precise coupling of the one-dimensional model and the two-dimensional model is achieved, and the simulation precision of a key area is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of radionuclide migration and diffusion simulation technology, and in particular to a one- or two-dimensional coupled calculation method and system for radionuclide migration and diffusion in river networks. Background Technology

[0002] The migration and diffusion of radionuclides in river network-estuary areas is a complex environmental problem involving multiple physicochemical processes, including hydrodynamics, sediment adsorption-desorption, radionuclide decay, and biological uptake. With the development of nuclear energy and the widespread application of nuclear technology, environmental safety assessments and accident emergency responses for nuclear facilities place higher demands on the timeliness and accuracy of simulation predictions.

[0003] Currently, simulations of river networks and estuaries often employ separate calculations using one-dimensional analytical models and two-dimensional numerical models. One-dimensional analytical models are suitable for simulating longitudinal nuclide transport along river channels, offering high computational efficiency but failing to reflect lateral diffusion and two-dimensional distribution characteristics in estuaries. Two-dimensional numerical models, while capable of accurately depicting the planar distribution of estuaries, are computationally intensive and time-consuming, making them particularly unsuitable for rapid simulation and emergency response, especially in large basins with multiple tributaries and complex terrain. Furthermore, the independent operation of one-dimensional and two-dimensional numerical models leads to discontinuous information transmission at the junction of the river network and the estuary, affecting the overall accuracy and consistency of the simulation.

[0004] Therefore, a computational method that can couple one-dimensional and two-dimensional models is needed to simulate the migration and diffusion process of radionuclides in river network estuaries more quickly and accurately. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a one- or two-dimensional coupled calculation method and system for the migration and diffusion of radionuclides in river networks, which significantly improves computational efficiency while ensuring the simulation accuracy of key areas.

[0006] To achieve the above objectives, the present invention provides a one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks, comprising the following steps: The spatiotemporal distribution of radionuclides in the entire river network is predicted using a one-dimensional model, and the time series of radionuclide fluxes at the intersection of the river network and the two-dimensional computational domain are extracted; the time series of radionuclide fluxes includes flow rates and concentrations arranged in time. The time series of the nuclide fluxes are organized and generated into a standard format interface file; Based on the data in the interface file, the two-dimensional computational grid is intelligently locally densified in the entrance region where the one-dimensional river network intersects with the two-dimensional water area; based on the densified grid and the interface file, the dynamic source term boundary of the two-dimensional numerical model is set, and the coupled computation of the one-dimensional and two-dimensional numerical models is promoted simultaneously to simulate the continuous migration of nuclides from the river network to the river mouth.

[0007] Furthermore, the step of predicting the spatiotemporal distribution of radionuclides throughout the river network using a one-dimensional model and extracting the time series of nuclide fluxes at the intersection of the river network and the two-dimensional computational domain further includes: A one-dimensional river network analytical model was established and run to predict the spatiotemporal distribution of radionuclides throughout the river network; the governing equations of the one-dimensional river network analytical model are: ; Where C(x,t) is the pollutant concentration at a distance of x meters from the emission outlet at time t seconds, x is the distance from the emission outlet, t is the diffusion duration after the emission occurs, M is the instantaneous total mass of pollutants emitted, A is the cross-sectional area, and E... x denoted as the longitudinal diffusion coefficient of pollutants, k as the comprehensive attenuation coefficient of pollutants, and u as the flow velocity at the river cross section.

[0008] Furthermore, the step of organizing the nuclide flux time series and generating a standard format interface file further includes: the standard format interface file contains flux and concentration data pairs arranged in time series.

[0009] Furthermore, the step of intelligently localizing the two-dimensional computational grid in the inlet area where the one-dimensional river network intersects with the two-dimensional water area based on the data in the interface file further includes: extending a set distance along the direction of water flow to set a core encryption zone, and using a grid of a first size in the encryption zone; using a grid of a second size in the background area outside the encryption zone, wherein the first size is smaller than the second size.

[0010] Furthermore, in the step of intelligently localizing the two-dimensional computational grid in the entrance region where the one-dimensional river network intersects with the two-dimensional water area based on the data in the interface file, the intelligent localization is based on the flux gradient information in the nuclide flux time series to dynamically determine the range and grid density of the densification area.

[0011] Furthermore, the step of setting the dynamic source term boundary of the two-dimensional numerical model based on the encrypted mesh and the interface file, and simultaneously advancing the coupled calculation of the one-dimensional and two-dimensional numerical models to simulate the continuous migration of nuclides from the river network to the estuary, also includes: A synchronized advancement mechanism is employed using an explicit loosely coupled iterative feedback mechanism, specifically including: Within each coupling time step: The one-dimensional model calculates and outputs the predicted nuclide flux at the intersection at the end of the current step. The interface file transmits the predicted nuclide flux to the two-dimensional numerical model. The two-dimensional numerical model uses the received predicted nuclide flux as the source term input for the inlet boundary within the current time step to complete the calculation for the current time step.

[0012] Furthermore, after the two-dimensional numerical model takes the received predicted nuclide flux as the source term input of the inlet boundary within the current time step and completes the calculation of the current time step, it also includes an iterative correction step: taking the hydraulic information fed back by the two-dimensional numerical model at the intersection as a reference for correcting the downstream boundary conditions of the one-dimensional model, and performing iterative calculations until the preset convergence conditions are met.

[0013] Furthermore, the step of setting the dynamic source term boundary of the two-dimensional numerical model based on the encrypted mesh and the interface file, and simultaneously advancing the coupled calculation of the one-dimensional and two-dimensional numerical models to simulate the continuous migration of nuclides from the river network to the estuary, also includes: the one-dimensional model and the two-dimensional numerical model advancing the calculation with a unified time step.

[0014] Furthermore, the two-dimensional numerical model is a numerical model based on finite volume, finite element, or particle tracking that supports dynamic boundary conditions and local mesh refinement.

[0015] On the other hand, the present invention also provides a one- or two-dimensional coupled computational system for the migration and diffusion of radionuclides in river networks, employing the one- or two-dimensional coupled computational method for the migration and diffusion of radionuclides in river networks as described above, the system comprising: The data preprocessing unit is used to import river topography data, hydrological and meteorological data, and nuclide accident source term data, and format the data into normalized input data; the core computing engine is connected to the data preprocessing unit and is used to perform one-dimensional and two-dimensional coupled calculations based on the normalized input data; the visualization and result analysis unit is connected to the core computing engine and is used to display and analyze the simulation results of nuclide concentration distribution.

[0016] The one-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks provided by this invention achieves rapid calculation with efficient and accurate coupling between one-dimensional and two-dimensional models by introducing a standardized data interface and intelligent local mesh densification based on one-dimensional results. This solves the problems of low calculation efficiency and poor connection accuracy caused by traditional separate modeling.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a one- or two-dimensional coupled computational system for the migration and diffusion of radionuclides in river networks, according to an embodiment of the present invention. Detailed Implementation

[0019] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0021] The term "comprising" and its variations as used in this invention are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0022] It should be noted that the concepts of "first" and "second" may be mentioned in this invention only to distinguish different devices, components or parts, and are not used to limit the order of the functions performed by these devices, components or parts or their interdependence.

[0023] It should be noted that the terms "one" and "multiple" used in this invention are illustrative rather than restrictive. Those skilled in the art should understand that, unless explicitly stated otherwise in the context, they should be understood as "one or more". "Multiple" should be understood as two or more.

[0024] Example 1 This embodiment uses a river network-estuary system near a coastal nuclear facility as an example to illustrate the specific implementation steps of the method of the present invention. Before describing each step in detail, the overall architecture and workflow of this method are first explained. The present invention constructs a collaborative computing system consisting of a one-dimensional river network analysis module, a standardized data interface and processing module, and a two-dimensional estuary intelligent coupling simulation module. Its core is as follows: the one-dimensional module first calculates to obtain the spatiotemporal sequence of nuclide flux at the river network outlet section; through the standardized interface, this sequence is transformed into dynamic input source terms that the two-dimensional module can recognize; at the same time, the interface data drives the two-dimensional module to perform adaptive mesh densification in key areas and set boundary conditions accordingly; finally, the two modules iterate alternately under the unified time step control to complete the continuous and efficient simulation from linear river network to area estuary. This architecture ensures a seamless transition from macroscopic to local, and from rapid analysis to fine simulation.

[0025] Figure 1 The following is a flowchart of a one- or two-dimensional coupled calculation method for the migration and diffusion of nuclides in river networks according to an embodiment of the present invention. Figure 1 The embodiments of the present invention will be described in further detail.

[0026] Step 101: Establish and run a one-dimensional river network analytical model to predict the spatiotemporal distribution of radionuclides throughout the river network.

[0027] Hydrological and geographical data (channel cross-section, slope, roughness, etc.) and radionuclide release source term information (release location, intensity, time series) of the main stream and tributaries of the target river network are collected. A one-dimensional river network analytical model is used to quickly simulate and predict the migration and diffusion of radionuclides in the river network.

[0028] Specifically, the governing equations of the one-dimensional river network analytical model used are: ; In the formula: To be at the distance from the outlet At (m), (s) represents the pollutant concentration at time s, in mg / L. Distance from the emission outlet, in meters (m); The duration of diffusion after emission occurs, in seconds; M represents the total instantaneous mass of pollutants emitted, in grams. A is the cross-sectional area, in meters (m²). 2 ; The longitudinal diffusion coefficient of pollutants, in meters. 2 / s; k is the overall pollutant decay coefficient (a comprehensive coefficient considering decay, adsorption, desorption, etc.), in units of s. -1 ; u represents the cross-sectional velocity of the river, in m / s.

[0029] This step obtains the nuclide concentration distribution at different times for each section in the entire river network through iterative calculation, and extracts the time series of nuclide flux (including flow rate (Q) and concentration (C)) at the intersection of the river network and the two-dimensional computational domain as the core output.

[0030] In step 102: The nuclide flux time series output by the one-dimensional river network analytical model is organized and generated into a standard format interface file to provide dynamic input for two-dimensional simulation.

[0031] This step will output the flow rate at the confluence section from the one-dimensional river network analytical model. With concentration Over time The change sequence is standardized and formatted to form a unified data interface file, providing dynamic boundary conditions for the two-dimensional numerical model.

[0032] It should be understood that the two-dimensional numerical model refers to the mathematical model and its computer solution program used to simulate and calculate the migration and diffusion process of radionuclides in two-dimensional planar water areas such as estuaries, lakes or nearshore sea areas. It does not refer to a specific software or a single model, but rather to a general term for a class of models with common functions (simulating two-dimensional planar migration and diffusion) and technical characteristics (the ability to set dynamic boundaries and support mesh refinement).

[0033] In this embodiment, the interface file format is shown as follows: ***Explanation of Calculation Results from the One-Dimensional River Network Analytical Model******The results represent the boundary flow concentration conditions at the intersection of the one-dimensional river network and the two-dimensional computational domain***T0, Q0, C0 T1, Q1, C1 T2, Q2, C2 … Tn, Qn, Cn in, For the output time, The traffic volume at that moment. This represents the nuclide concentration at that moment.

[0034] In step 103: Based on the interface data, the computational grid is intelligently locally densified at the intersection of the one-dimensional and two-dimensional regions and then transitioned to the background region, thereby improving computational efficiency while ensuring accuracy.

[0035] The intelligent local encryption includes: extending a set distance along the direction of water flow to set a core encryption zone, and using a grid of a first size in the encryption zone; using a grid of a second size in the background area outside the core encryption zone, wherein the first size is smaller than the second size.

[0036] In this embodiment of the invention, a two-dimensional numerical model computational domain is constructed based on the estuary topography and hydrodynamic characteristics. According to the intersection location and flow information output by the one-dimensional river network analytical model, intelligent mesh generation is guided: at the entrance region where the one-dimensional river network intersects with the two-dimensional water area, a core dense area is set up extending a certain distance (e.g., 1 km) along the flow direction, with a finer mesh size (e.g., 5 m × 5 m); gradually transitioning outwards to a coarser background mesh (e.g., 50 m × 50 m). This meshing strategy can significantly reduce the total number of meshes and improve computational efficiency, such as... Figure 2 This is a bolded schematic diagram of the discrete intersection and encryption of one-dimensional and two-dimensional computational domain grids (the black box represents encryption).

[0037] This intelligent local encryption strategy is not uniform or arbitrary encryption; its key technology lies in dynamically determining the encryption range and density based on flux gradient information provided by the one-dimensional river network analytical model. Specifically, at the intersection of the one-dimensional and two-dimensional domains, periods of drastic flux changes are identified based on the rate of change of nuclide flux (Δ(QC) / Δt) in adjacent time steps output by the one-dimensional river network analytical model. For the corresponding flow front regions, the encryption zone is appropriately extended along the flow direction in the two-dimensional domain to ensure that the nuclide concentration front can be captured at high resolution in the two-dimensional simulation, avoiding accuracy loss due to numerical diffusion. During periods of stable flux, the depth of the encryption zone can be appropriately reduced. This adaptive grid optimization based on the dynamic characteristics of the source term is one of the core mechanisms by which this method significantly improves computational efficiency while ensuring accuracy.

[0038] In step 104: Based on the encrypted mesh and interface file, the dynamic source term boundary of the two-dimensional numerical model is set, and the one-dimensional and two-dimensional coupled calculations are carried out simultaneously to realize the simulation of the continuous migration of nuclides from the river network to the estuary.

[0039] In an embodiment of the present invention, this step includes: Set the inlet boundary of the two-dimensional numerical model (i.e., the boundary of the encrypted area) as the "mass inflow boundary", and directly assign the nuclide flux time series provided by the interface file in step 102 to this boundary to realize the dynamic and seamless input of the output of the one-dimensional river network analytical model to the two-dimensional numerical model; The one-dimensional river network analytical model and the two-dimensional numerical model use synchronized time steps (e.g., Δt = 10 s) to advance the calculation; Within each computation time step, the one-dimensional river network analytical model provides the nuclide flux at the confluence section at the current step size; the two-dimensional numerical model receives this flux and distributes it evenly to each fine grid at the inlet boundary as the source term input for that time step, thereby calculating the two-dimensional diffusion, transport, deposition and decay processes of nuclides in the estuary region. Repeat the above iterative process until the simulation ends, to achieve a closed-loop coupling of the entire process from river network to estuary simulation.

[0040] The propulsion calculation employs an explicit loosely coupled iterative feedback mechanism, within each coupled time step (e.g., T). i To T i+1 ): One-dimensional advancement: One-dimensional river network analytical model based on T i The state at time T is calculated independently. i+1 At time T, the output intersection section is located at... i+1 Predicted nuclide flux at time (Q) i+1 C i+1 ); Data transfer: The standardized interface will immediately transmit (Q) i+1 C i+1 ) is passed to the two-dimensional numerical model; Two-dimensional propagation: The two-dimensional numerical model uses the received flux value as its value in T. i To T i+1 Inputting constant source terms at the inlet boundary within the time period, we complete the two-dimensional hydrodynamic and nuclide diffusion calculations for this time period and update it to T. i+1 The state at any given moment.

[0041] Iterative Correction (Optional): To improve the accuracy of mass conservation at the boundary, an iterative loop can be introduced: the water level or velocity information fed back from the two-dimensional numerical model at the boundary is used as a correction reference for the downstream boundary conditions of the one-dimensional river network analytical model, and at most 1 to 2 rapid iterations are performed until the flow error at the boundary is less than a set threshold (e.g., 1%), before proceeding to the next time step. This mechanism effectively enhances the physical consistency at the one-dimensional and two-dimensional connection while ensuring computational speed.

[0042] Step 105: Output and verify the nuclide concentration distribution of the entire region, and evaluate the simulation accuracy and computational efficiency of key locations.

[0043] This step outputs the spatiotemporal distribution map and time series of radionuclides throughout the entire river network-estuary system, focusing on concentration changes in sensitive areas such as downstream of nuclear facilities and water intakes. Case studies have demonstrated that this method has the following beneficial effects: High computational efficiency: By using one-dimensional analytical fast calculation and local mesh refinement strategy, compared with traditional global two-dimensional fine simulation, the total number of meshes can be reduced by more than 80%, and the calculation time is shortened by 70%-85%.

[0044] High simulation accuracy: Mesh refinement and flux matching are performed in the one- and two-dimensional connection area, ensuring the continuity of the physical process. The concentration prediction error at key sensitive points (such as water intake) can be reduced by 30%-60%.

[0045] Wide applicability: Applicable to large river basins (such as the Pearl River and Yangtze River basins), complex terrain, numerous tributaries, or river network-estuary systems with reservoirs, providing efficient and reliable technical support for marine environmental impact assessments and accident emergency simulations of coastal nuclear facilities.

[0046] In the above embodiments, the encrypted mesh of the two-dimensional numerical model is a regular rectangle. In other embodiments, the mesh of the encrypted area can also be an unstructured triangular mesh, and a transition layer mesh can be set between the encrypted area and the background coarse mesh area to achieve more flexible fitting of complex shoreline boundaries. In this case, intelligent local encryption is manifested as local refinement control of the size and density of the triangular mesh, and the determination logic of the refinement area (based on one-dimensional flux information) is the same as in Embodiment 1.

[0047] In some implementations, the two-dimensional numerical model may employ numerical methods based on finite volume, finite element, or particle tracking, supporting dynamic boundary conditions and local mesh refinement.

[0048] In some implementations, the format of the standardized data interface can be adjusted according to the specific simulation platform, and it can include a time-flow-concentration sequence. The range and density of the grid refinement can also be flexibly set according to the actual terrain, flow velocity distribution, and accuracy requirements.

[0049] In summary, the one-to-two-dimensional coupled computational method for nuclide migration and diffusion in river networks provided by this invention successfully resolves the contradiction between low computational efficiency and poor connection accuracy caused by traditional separate modeling by creatively introducing two core technical means: a standardized data interface and intelligent local mesh refinement based on one-dimensional results. Its main technical effects are reflected in: (1) Efficiency breakthrough: By replacing the two-dimensional calculation of most river network areas with a one-dimensional model and combining local encryption, a paradigm shift from full-domain fine and slow to overall fast and local fine has been achieved, reducing the calculation time by an order of magnitude and meeting the timeliness requirements of emergency response.

[0050] (2) Accuracy assurance: The interface ensures the accurate transfer of mass flux between one and two dimensions, and the densification of the grid on the critical migration path effectively suppresses numerical diffusion, thus significantly improving the prediction accuracy at key locations.

[0051] (3) Strong versatility: The interface and coupling framework are independent of the specific one-dimensional and two-dimensional numerical model code, have good modularity and scalability, are easy to integrate with different commercial or open source hydrodynamic and water quality models, and have a wide range of applications.

[0052] Example 2 This embodiment, based on the calculation method described in Embodiment 1, provides a system integration and application example for emergency prediction of radionuclides in river networks and estuaries, namely, a one- or two-dimensional coupled calculation system for the migration and diffusion of radionuclides in river networks. The system adopts a modular design and mainly includes a data preprocessing unit 201, a core calculation engine 202, and a visualization and intelligent result analysis unit 203. These components work together to implement the one- or two-dimensional coupled calculation method steps for the migration and diffusion of radionuclides in river networks as described in the above embodiment.

[0053] Figure 2 This is a schematic diagram of a one- or two-dimensional coupled computational system for the migration and diffusion of nuclides in river networks according to an embodiment of the present invention. The following will be combined with... Figure 2 The system implementation of the present invention will be described in detail.

[0054] The data preprocessing unit 201 is responsible for preparing normalized input data for the entire computation process. Its specific functions include: Multi-source data import and fusion, and data standardization and formatting. First, raw data from different databases or files is automatically imported and integrated, including: river geographic information data (such as digital river network topology, cross-sectional geometry, riverbed elevation, etc.), dynamic hydrological and meteorological data (such as upstream and downstream boundary flow / water level time series, wind speed and direction, rainfall and evaporation data, etc.), accident source term data (including the precise location of nuclide releases (corresponding to river network nodes)), release intensity time series, and a library of physicochemical parameters for nuclide types (such as decay constants, sediment-water partition coefficients, etc.). This multi-source, heterogeneous raw data is then transformed and encapsulated according to the specific data structure and format required by the core computing engine 202. For example, the river topology is constructed as an adjacency list, and the time series data is unified into arrays with fixed sampling intervals, ultimately generating a complete set of configuration files and input data files that can directly drive the model.

[0055] The core computing engine 202 is the "brain" of the system, encapsulating and automating the one-to-two-dimensional coupled fast computation method for river network nuclide migration and diffusion described in Example 1. Specifically, it includes: The one-dimensional calculation module calls the data formatted by the preprocessing unit and automatically runs the one-dimensional river network analytical model to complete the rapid prediction of nuclide migration at the river network scale.

[0056] The intelligent coupling controller is responsible for: The system manages a standardized data interface. In this implementation, this interface is not a traditional file, but rather preferably implemented using a shared memory region or inter-process communication (IPC) pipes. The one-dimensional module writes the calculated cross-sectional nuclide flux sequence into this shared region in real time. Based on dynamic analysis of the flux data, it sends grid encryption commands to the two-dimensional calculation module to determine the location, range, and density of the encryption region; it controls the synchronization timing of the one-dimensional and two-dimensional modules, directing the two modules to alternately advance the calculation according to a preset coupling time step (e.g., Δt).

[0057] The two-dimensional computation module receives grid instructions and source term data from the coupled controller, solves the two-dimensional hydrodynamic and mass transport equations on a locally refined grid, and completes a detailed simulation of the estuary region.

[0058] The visualization and intelligent results analysis unit 203 is used to transform calculation results into intuitive, decision-making information, such as: Dynamic visualization: Real-time or post-processing display of two-dimensional / three-dimensional spatiotemporal distribution cloud maps and animations of nuclide concentrations in river networks and estuaries, as well as concentration history curves at designated sensitive points (such as water intakes and ecological protection areas).

[0059] Automatic analysis and early warning: Based on preset safe concentration thresholds, it automatically identifies the range of pollution clouds, the time of arrival at sensitive points, and the duration of exceeding the standard, and generates alarms and brief assessment reports.

[0060] Results Validation Module: (Optional) Provides tools to compare simulation results with historical monitoring data or other benchmark model results to quantitatively evaluate the accuracy of the system simulation, such as calculating the root mean square error (RMSE) or Nash efficiency coefficient (NSE).

[0061] The system's workflow is as follows: When a simulated or actual nuclear accident occurs, the operator imports or sets the accident source item through the system interface and starts the calculation. The system automatically executes the entire process from data preprocessing and coupled calculation to result output.

[0062] By implementing the method of Embodiment 1 in this system, the following beneficial effects are achieved in an engineering manner: Full-process automation and high efficiency: The originally tedious data preparation, model setup, and coupling debugging processes are integrated and automated, reducing the startup time of emergency simulations from hours to minutes. Combined with memory-level data exchange and local mesh encryption, the overall computational efficiency is improved by 1-2 orders of magnitude compared to traditional manual coupling methods.

[0063] Intuitive Decision Support: Integrated visualization and analysis capabilities can quickly transform complex simulation data into clear information needed for command and decision-making (such as "when and where the pollution front will arrive"), greatly improving the timeliness and scientific rigor of emergency response.

[0064] Systematicity and Reliability: The validated coupling algorithm is solidified into a stable software system, avoiding errors that may be introduced by manual operation and ensuring the consistency and reliability of each simulation calculation.

[0065] It will be understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks, characterized in that, Includes the following steps: The spatiotemporal distribution of radionuclides in the entire river network is predicted using a one-dimensional model, and the time series of radionuclide fluxes at the intersection of the river network and the two-dimensional computational domain are extracted; the time series of radionuclide fluxes includes flow rates and concentrations arranged in time. The time series of the nuclide fluxes are organized and generated into a standard format interface file; Based on the data in the interface file, the two-dimensional computational grid is intelligently locally densified in the entrance region where the one-dimensional river network intersects with the two-dimensional water area; based on the densified grid and the interface file, the dynamic source term boundary of the two-dimensional numerical model is set, and the coupled computation of the one-dimensional and two-dimensional numerical models is promoted simultaneously to simulate the continuous migration of nuclides from the river network to the river mouth.

2. The one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to claim 1, characterized in that, The step of predicting the spatiotemporal distribution of radionuclides in the entire river network using a one-dimensional model and extracting the time series of radionuclide fluxes at the intersection of the river network and the two-dimensional computational domain further includes: A one-dimensional river network analytical model was established and run to predict the spatiotemporal distribution of radionuclides throughout the river network; the governing equations of the one-dimensional river network analytical model are: ； Where C(x,t) is the pollutant concentration at a distance x meters from the emission outlet at time t seconds, x is the distance from the emission outlet, t is the diffusion time after the emission occurs, M is the instantaneous total mass of pollutants emitted, A is the cross-sectional area, and E... x denoted as the longitudinal diffusion coefficient of pollutants, k as the comprehensive attenuation coefficient of pollutants, and u as the flow velocity at the river cross section.

3. The one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to claim 1, characterized in that, The step of organizing the nuclide flux time series and generating a standard format interface file further includes: the standard format interface file contains flux and concentration data pairs arranged in time series.

4. The one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to claim 1, characterized in that, The step of intelligently and locally encrypting the two-dimensional computational grid in the entrance area where the one-dimensional river network and the two-dimensional water area intersect, based on the data in the interface file, further includes: extending a set distance along the direction of water flow to set a core encryption zone, and using a grid of a first size in the encryption zone; using a grid of a second size in the background area outside the encryption zone, wherein the first size is smaller than the second size.

5. The one- or two-dimensional coupled calculation method for radionuclide migration and diffusion in river networks according to claim 1, characterized in that, In the step of intelligently localizing the two-dimensional computational grid in the entrance region where the one-dimensional river network intersects with the two-dimensional water area based on the data in the interface file, the intelligent localization is based on the flux gradient information in the nuclide flux time series to dynamically determine the range and grid density of the densification area.

6. The one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to claim 1, characterized in that, The steps of setting dynamic source term boundaries for the two-dimensional numerical model based on the encrypted mesh and the interface file, and simultaneously advancing the coupled calculation of the one-dimensional and two-dimensional numerical models to simulate the continuous migration of nuclides from the river network to the estuary, also include: A synchronized advancement mechanism is employed using an explicit loosely coupled iterative feedback mechanism, specifically including: Within each coupling time step: The one-dimensional model calculates and outputs the predicted nuclide flux at the intersection at the end of the current step. The interface file transmits the predicted nuclide flux to the two-dimensional numerical model. The two-dimensional numerical model uses the received predicted nuclide flux as the source term input for the inlet boundary within the current time step to complete the calculation for the current time step.

7. The one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to claim 6, characterized in that, After the two-dimensional numerical model takes the received predicted nuclide flux as the source term input of the inlet boundary within the current time step and completes the calculation of the current time step, it also includes an iterative correction step: taking the hydraulic information fed back by the two-dimensional numerical model at the intersection as a reference for correcting the downstream boundary conditions of the one-dimensional model, and performing iterative calculations until the preset convergence conditions are met.

8. The one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to claim 1, characterized in that, The steps of setting dynamic source term boundaries for the two-dimensional numerical model based on the encrypted mesh and the interface file, and simultaneously advancing the coupled calculation of the one-dimensional and two-dimensional numerical models to simulate the continuous migration of nuclides from the river network to the estuary, also include: the one-dimensional model and the two-dimensional numerical model advancing the calculation using a unified time step.

9. The one- or two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks according to claim 1, characterized in that, The two-dimensional numerical model is a numerical model based on finite volume, finite element, or particle tracking that supports dynamic boundary conditions and local mesh refinement.

10. A one- or two-dimensional coupled computational system for the migration and diffusion of nuclides in river networks, characterized in that, The system employs the one-to-two-dimensional coupled calculation method for the migration and diffusion of radionuclides in river networks as described in any one of claims 1 to 9, the system comprising: The data preprocessing unit is used to import river topography data, hydrological and meteorological data, and nuclide accident source term data, and format the data into normalized input data; the core computing engine is connected to the data preprocessing unit and is used to perform one-dimensional and two-dimensional coupled calculations based on the normalized input data; the visualization and result analysis unit is connected to the core computing engine and is used to display and analyze the simulation results of nuclide concentration distribution.

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