A method and system for simulating the physical and chemical coupling of atmospheric diffusion in a nuclear complex accident scenario

Abstract

The application provides a method and system for simulating the physical and chemical coupling of atmospheric diffusion under a nuclear and chemical integrated accident scene. The method first constructs a parameterized model of a nuclear and chemical integrated source term, determines the distribution ratio of nuclides on particles of different chemical properties according to the physical characteristics of nuclides and the release rate of chemical components; then runs the aerosol dynamics coupling evolution operator to monitor the concentration of hazardous chemicals and the relative humidity in the simulation space in real time, calculates the particle size change and density change of the nuclide carrier aerosol in the diffusion process; based on the evolved physical parameters, the settling term in the atmospheric diffusion equation is corrected in real time, and the dynamic diffusion distribution of radioactive nuclides in three-dimensional space is deduced by using the iterative step method; finally, the ground pollution correction map and the synergistic damage evaluation results under the nuclear and chemical integrated accident are output in combination with the chemical and radiation synergistic factors. The application solves the problem of diffusion prediction distortion caused by the neglect of the physical and chemical interaction in the traditional model, and improves the accuracy of complex disaster consequence evaluation.

Description

Technical Field

[0001] This invention relates to the field of computer data processing technology, and in particular to a method and system for simulating atmospheric diffusion physicochemical coupling under nuclear-chemical complex accident scenarios. Background Technology

[0002] In modern industrial layouts, it is not uncommon for nuclear facilities to be located adjacent to chemical industrial parks. In the event of extreme accidents such as explosions or fires, there is a risk of the simultaneous release of radioactive nuclides and toxic and hazardous chemicals, forming a complex pollution cloud. Currently, most emergency simulation assessment systems for such accidents use a decoupled computational model, that is, running nuclear accident consequence assessment models and chemical gas diffusion models separately, assuming that the two types of pollutants do not interfere with each other during atmospheric transport, and ultimately only performing a simple spatial superposition of their concentration distributions at the geographic information level. While this approach has high computational efficiency and some applicability in single disaster scenarios, it often neglects the complex microscopic physicochemical interactions between substances when dealing with nuclear-chemical complex accidents, leading to fundamental differences between simulation results and real-world scenarios.

[0003] In actual nuclear-chemical mixed plumes, radionuclides are typically adsorbed onto combustion dust or aerosol carriers. When exposed to a chemical atmosphere containing strong acid mist, ammonia, or high concentrations of hygroscopic salts, the physical properties of the microscopic particles undergo significant changes. The chemical components and moisture in the environment induce hygroscopic growth in aerosol particles, leading to particle volume expansion, or cause collisions and aggregation under turbulence and Brownian motion, thus altering the effective particle density. These evolutions in particle size and density exhibit high spatiotemporal dynamics and directly determine the particle settling velocity in a gravitational field. Existing simulation techniques fail to incorporate this cross-medium physicochemical coupling mechanism into the real-time solution of the atmospheric diffusion equation, typically employing only static dry deposition rate parameters. This prevents the model from reflecting the inducing effect of the chemical environment on radioactive deposition trajectories, resulting in significant deviations in predictions of near-field high-concentration areas and ground hotspot distribution.

[0004] Furthermore, in terms of biological effect assessment, traditional methods simply accumulate physical doses without considering the damaging effects of chemical toxic substances on the body's physiological barriers. Inhalation of highly corrosive or irritating chemical gases can damage respiratory mucosal epithelial cells, altering the body's efficiency in blocking and absorbing radionuclides, thus affecting the actual level of internal radiation dose. Current technologies lack a quantitative description of this synergistic chemical and radiation damage mechanism, making it difficult for the final injury assessment results to accurately reflect the health risks under combined exposure, and failing to meet the practical needs of refined, tiered medical treatment and targeted decontamination decisions. Summary of the Invention

[0005] One of the objectives of this invention is to provide a method and system for simulating atmospheric diffusion physicochemical coupling under nuclear-chemical complex accident scenarios, so as to solve the problems pointed out in the background art.

[0006] In a first aspect, the present invention provides a method for simulating atmospheric diffusion physicochemical coupling under a nuclear-chemical complex accident scenario, comprising the following steps: Step S1: Construct a nuclear-chemical integrated source term parameterization model. Based on the input physical characteristics of radionuclides, the release rate of chemical components, and the initial aerosol particle size distribution, determine the distribution ratio of nuclides on particles with different chemical properties. Step S2: Run the aerosol dynamics coupling evolution operator, monitor the concentration of hazardous chemicals and relative humidity in the simulation space in real time, and calculate the particle size and density changes of the radionuclide carrier aerosol during the diffusion process; Step S3: Based on the particle size and density changes obtained in step S2, the sedimentation term in the atmospheric diffusion equation is corrected in real time, and the dynamic diffusion distribution of radionuclides in three-dimensional space is deduced using an iterative step method. Step S4: After the diffusion simulation is completed, combine the chemical-radiation synergy factor to output the ground contamination correction map and synergistic damage assessment results under the nuclear-chemical complex accident.

[0007] Optionally, in step S1, determining the distribution ratio of the nuclide on particles with different chemical properties specifically includes: Establish an adsorption characteristic matrix and define the partition coefficients of radionuclides on particles with different chemical properties such as acidity, alkalinity, and hygroscopicity. and the allocation coefficient As the initial weights for subsequent coupling evolution, the physical characteristic quantities include at least the initial activity of the radionuclide.

[0008] Optionally, in step S2, the calculation of the particle size change of the radionuclide carrier aerosol during the diffusion process specifically employs an environmentally sensitive growth model, using Köhler's theory to correct the hygroscopic growth factor of the aerosol. The calculation formula is as follows: ; in, for Aerosol particle size after real-time correction; The initial aerosol particle size; It is a hygroscopic growth factor, which relates to the concentration of hazardous chemicals. relative humidity Transitive parameters The function; This represents the concentration of hazardous chemicals in the current grid within the simulation space. Relative humidity; Physical property parameters considering the solubility of chemical components.

[0009] Optionally, in step S2, calculating the density change of the radionuclide carrier aerosol specifically includes: When the concentration of hazardous chemicals in the simulation space exceeds a preset threshold, the nucleochemical collision and aggregation subroutine is triggered. Calculate the collision cross-section between hazardous chemical droplets and radionuclide-containing aerosol particles, and dynamically update the effective density of the aerosol based on the collision results. .

[0010] Optionally, in step S3, the real-time correction of the sedimentation term in the atmospheric diffusion equation specifically involves calculating the dynamic gravity sedimentation velocity. The calculation formula is as follows: ; in, This refers to the dynamic gravity-induced settling velocity. It is the acceleration due to gravity; The dynamically updated effective density of the aerosol; The corrected aerosol particle size obtained from the calculation; This is the Cunningham slip correction factor; It is the aerodynamic viscosity.

[0011] Optionally, step S3, which employs an iterative step-by-step deduction method, specifically includes: Within each simulation step, read the concentration of chemical components in the current grid; The sedimentation probability of radionuclides in the grid region at the next time step is updated based on the concentration of the chemical components. The updated sedimentation probability is fed back into the diffusion equation to calculate the nuclide spatial location for the next simulation step.

[0012] Optionally, in step S4, the calculation of the synergistic damage assessment result specifically includes: Introducing the chemical-radiative synergistic factor ; Based on the aforementioned synergistic factors The study calculates the changes in radionuclide absorption rate caused by damage to respiratory epithelial cells from chemical pollutants, and then calculates the effective inhalation dose.

[0013] Optionally, in step S4, outputting the ground pollution correction map specifically includes: Data on the distribution of radionuclides in the near-field region after being affected by the physical and chemical effects of hazardous chemicals is generated. This distribution data is used to guide the selection of decontamination agents for sediments with different acid and alkali properties.

[0014] Optionally, the initial aerosol particle size The activity median aerodynamic diameter (AMAD) was used for characterization; the chemical components included sulfur dioxide, ammonia, or strong acid mist.

[0015] Secondly, an embodiment of the present invention provides an atmospheric diffusion physicochemical coupling simulation system under a nuclear-chemical complex accident scenario, comprising: The source term modeling module is used to construct a nuclear-chemical integrated source term parameterized model. Based on the input physical characteristics of radionuclides, the release rate of chemical components, and the initial aerosol particle size distribution, it determines the distribution ratio of nuclides on particles with different chemical properties. The Coupled Evolution module is used to run the aerosol dynamics coupled evolution operator, monitor the concentration of hazardous chemicals and relative humidity in the simulation space in real time, and calculate the particle size and density changes of radionuclide carrier aerosols during the diffusion process. The diffusion simulation module is used to correct the sedimentation term in the atmospheric diffusion equation in real time based on changes in particle size and density, and to simulate the dynamic diffusion distribution of radionuclides in three-dimensional space using an iterative step method. The assessment output module is used to output a ground contamination correction map and synergistic damage assessment results under a nuclear-chemical complex accident, after the diffusion simulation is completed, by combining the chemical-radiation synergistic factor.

[0016] The present invention has achieved the following beneficial effects: This invention establishes a dynamic correlation between macroscopic atmospheric transport and microscopic particle physicochemical behavior by constructing a parameterized model of the integrated nuclear and chemical source term and coupling evolution operators with aerosol dynamics. During simulation, it can calculate the hygroscopic growth factor and aggregation effect of radionuclide carrier aerosols in real time based on the concentration of chemical components and ambient humidity within local grids, and dynamically correct the gravity settling velocity term in the atmospheric diffusion equation accordingly. This objectively reflects the nonlinear influence of complex physicochemical environments on the three-dimensional spatial distribution of pollutants, improving the physical realism of near-field settling predictions. Simultaneously, this invention introduces a chemical and radiation synergistic factor, correcting the dose calculation logic of simple physical superposition in traditional models, quantifying the additive effect of chemical damage on the hazards of radionuclide inhalation. Combined with the output ground pollution correction map including acid-base properties and chemical types, this provides data support consistent with objective laws for post-accident graded medical treatment, targeted decontamination agent selection, and protection plan formulation, enhancing the scientific rigor of emergency auxiliary decision-making for nuclear and chemical complex accidents.

[0017] The features and advantages of the present invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the method flow for a simulation method of atmospheric diffusion physicochemical coupling under a nuclear-chemical complex accident scenario in an embodiment of the present invention; Figure 2 This is a schematic diagram of the composition and structure of an atmospheric diffusion physicochemical coupling simulation system under a nuclear-chemical complex accident scenario in an embodiment of the present invention. Detailed Implementation

[0020] 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.

[0021] The present invention provides a method and system for atmospheric diffusion physicochemical coupling simulation under nuclear and chemical complex accident scenarios. Its core is to solve the decoupling distortion problem of traditional single disaster models when dealing with complex nuclear and chemical associated scenarios.

[0022] The simulation system in this embodiment preferably runs on a high-performance computing (HPC) cluster or a dedicated emergency command server. Specific hardware configurations include: Computing nodes employ a heterogeneous computing architecture, configured with dual Intel Xeon Scalable processors at a minimum clock speed of 3.2GHz for fundamental calculations of atmospheric flow fields (such as WRF or CFD modules). Each node is also equipped with 2-4 NVIDIA Tesla A100 or equivalent GPGPU (General Purpose Graphics Processing Unit) accelerator cards. The aerosol dynamics coupling evolution operator of this invention is encapsulated as a CUDA kernel function for large-scale parallel execution on the GPU.

[0023] Storage Subsystem: Given the need to read and write massive amounts of meteorological field data (gridized wind speed, temperature and humidity fields) and particle trajectory data in real time during the simulation, the system adopts a distributed all-flash array based on the NVMe protocol to build a Lustre parallel file system, providing an aggregate read and write bandwidth of no less than 50GB / s to ensure that I / O does not become a bottleneck during iterative steps.

[0024] Visualization terminal: The front end is equipped with a high-performance graphics workstation that supports OpenGL 4.6 and above, which is used to perform volume rendering of the calculated three-dimensional concentration field and ground subsidence map, and intuitively display the dynamic evolution process of nuclear and chemical composite pollution.

[0025] Based on the aforementioned hardware, the system software architecture of this embodiment strictly adheres to the design principles of high cohesion and low coupling, and is divided into a data layer, a core computation layer, and an application layer from bottom to top. The core computation layer integrates the four functional modules of this invention, such as... Figure 2 As shown, it includes: Source term modeling module: responsible for executing step S1, which is used to parse the input accident source term, construct a parameterized model that includes the physical characteristics of nuclides and the release characteristics of chemical components, and generate the initial nucleochemical correlation particle swarm.

[0026] Coupled Evolution Module: Responsible for executing step S2, embedding an aerosol dynamics coupled evolution operator. This module monitors the mesh environment parameters in real time, calls the hygroscopic growth model and the collision aggregation model, and dynamically updates the particle size. and density .

[0027] Diffusion simulation module: responsible for executing step S3, based on dynamically corrected settlement velocity. Using three-component wind field data, the spatiotemporal migration of pollutants is extrapolated using an Eulerian-Lagrange hybrid algorithm.

[0028] Evaluation output module: responsible for executing step S4, combining the chemical-radiative synergistic factor. It calculates and outputs ground pollution correction maps and human injury assessment reports.

[0029] Please refer to the appendix to this invention specification. Figure 1 The method flow shown includes the following steps: The first step is to construct a parameterized model of the nuclear-chemical integrated source term.

[0030] In traditional nuclear accident consequence assessment systems (such as MACCS and COSYMA), source term inputs typically only include nuclide species and activity; while in chemical accident models (such as ALOHA and PHAST), only chemical concentrations are included. This embodiment constructs a nuclear-chemical integrated source term parameterized model, in The physical connection between the two was established at that moment.

[0031] The system first receives real-time monitoring data from the accident site through a human-machine interface or SCADA (Supervisory Control and Data Acquisition) interface.

[0032] In addition to the usual nuclide names (such as...) , , , ) and total release activity ( In addition to the unit (Bq), this embodiment specifically requires defining the initial aerosol particle size distribution of the nuclide. This is because in accidents accompanied by explosions or fires, radioactive materials are not monatomic gases, but rather aerosols attached to combustion smoke or debris. The system uses the Activity Median Aerodynamic Diameter (AMAD) to characterize this distribution.

[0033] Users can input a set AMAD value (e.g.) ) and geometric standard deviation ( (e.g., 2.5). Based on this, the system uses a log-normal distribution function to sample and generate an initial particle swarm, with each particle assigned an initial particle size. This treatment conforms to the ICRP (International Commission on Radiation Protection) recommended model standards for inhaled dose.

[0034] The system supports inputting source strength information for various associated chemicals.

[0035] Input parameters include chemical type (identifier), release rate ( (Unit: kg / s), release temperature, and phase. This embodiment focuses particularly on three key chemical components: strongly acidic gases (such as...) ), alkaline gases (such as ) and highly hygroscopic salts.

[0036] In complex accidents, the adsorption capacity of carrier particles with different chemical properties (such as acidic droplets) for nuclides varies greatly. To quantify this phenomenon, this embodiment introduces an adsorption characteristic matrix. This matrix is ​​a... A two-dimensional data table, where rows represent types of radionuclides. The column represents the chemical property category of the carrier particles. Carrier category It includes at least: acidic highly hygroscopic particles (such as sulfuric acid droplets), basic neutralizing particles (such as ammonium salts), hydrophobic inert particles (such as dust or carbon black), and lipophilic organic particles. Partition coefficient Matrix elements Defined the first Nuclide in the Assignment weights on the carrier class. Assume the accident scenario is an explosion of a nitric acid waste storage tank at a nuclear fuel reprocessing plant. The environment simultaneously contains large amounts of nitric acid mist (acidic / hygroscopic) and concrete dust (alkaline / inert). For readily soluble cesium (… ), on acidic droplets The value is set to 0.8, and 0.2 for inert dust; while for sparingly soluble plutonium (… ), its properties on inert dust The value is set to 0.9.

[0037] The system is based on The value will release the total activity. Assigned to different types of Lagrange particles: ; This means that at the start of the simulation, some particles are labeled as having high hygroscopic potential, while others are labeled as inert.

[0038] The second step is to run the aerosol dynamics coupling evolution operator.

[0039] In the traditional Gaussian plume model, the diffusion parameter The changes are monotonically dependent on distance, completely ignoring the physical evolution of the particles themselves. This embodiment achieves real-time updates to the state of microscopic particles by invoking the aerosol dynamics coupling evolution operator at each simulation time step (e.g., 10 seconds). This operator contains two core sub-models: an environment-sensitive growth model and a physicochemical aggregation model.

[0040] When radionuclide-loaded aerosol particles enter a high-concentration chemical plume (such as an ammonia leak area), if the ambient humidity is high, the particles will undergo hygroscopic growth due to the solute effect. This embodiment uses a modified Köhler theory to describe this process. The system reads the concentration of hazardous chemicals in the grid where the particle is located in real time. (unit: ) and relative humidity (Unit: %). The calculation formula is as follows: ; In this formula: Indicates the current simulation time. The aerodynamic diameter of an aerosol after correction for interactions with its physical and chemical environment. Unit: micrometer (µm) This parameter is the direct input for subsequent settlement calculations, and even a small change in its value will have a quadratic effect on the settlement rate.

[0041] Indicates the initial particle size or the particle size at the previous time step. Unit: micrometer (µm) ).

[0042] This indicates the mass concentration of hazardous chemicals at the current spatial location. This value is provided by a parallel chemical gas diffusion solver. It should be noted that the system will use the chemical thermodynamic equilibrium module to determine the concentration of gaseous precursors (such as...) The concentration is converted into the corresponding aerosol solute (e.g.) Equivalent concentration, because the latter is the main driver of hygroscopic growth.

[0043] This represents the relative humidity of the current local environment. In accidents involving fire or steam ejection, this value includes not only the background meteorological humidity but also the increase in water vapor released from the source term.

[0044] This represents the physical properties taking into account the solubility of the chemical components. It is a dimensionless thermodynamic parameter that comprehensively reflects the molecular weight, density, van der Hoff factor (degree of dissociation), and ability to reduce water activity of the chemical components. In this embodiment, The value is dynamic. For example, when particles adsorb ammonium sulfate (… )hour, The value is approximately 0.61; if it is sodium chloride ( ), The value is approximately 1.28; while for organic carbon, The value may be as low as 0.01.

[0045] This refers to the hygroscopic growth factor. It is related to... The nonlinear function. In the specific code implementation of this system, the following is adopted. -Köhler approximation formula: ; When a cloud of acidic aerosol carrying radionuclides ( When it drifts into an area with a relative humidity of 95%, the calculated value is... This means particle size It will expand from 1 micrometer to 2.3 micrometers, increasing its volume to more than 12 times its original size, with most of the volume consisting of liquid water.

[0046] In the near-field region near the source of a hazardous chemical leak, the number concentration of chemical aerosols is extremely high (possibly exceeding [a certain value]). indivual / At this point, particle collisions are no longer negligible low-probability events. This embodiment simulates this process using a nucleation-collision aggregation subroutine, thereby correcting the effective density of the aerosol. .

[0047] The system sets a hazardous chemical concentration threshold (e.g.) When the grid concentration exceeds this value, clustering calculation is initiated.

[0048] The subroutine comprehensively considers Brownian collisions, turbulent shear collisions, and gravity-induced sedimentation collisions. The system calculates the collision kernel function between the scavenger (such as large acid droplets) and the target (such as small nuclide particles). .

[0049] Once aggregation is determined, the system assumes that the two particles have fused into a sphere and updates the effective density according to the law of conservation of mass: ; in, and Representing mass and volume respectively, subscripts Represents nuclide particles, Represents chemical droplets.

[0050] Radioactive metal oxides typically have a higher density. ), while the density of chemical droplets is relatively small ( Moisture absorption and agglomeration typically reduce effective density. Decrease. However, due to particle size The increase in density (cubic relation) is far greater than the effect of density decrease, and overall it still leads to a sharp increase in settlement velocity. However, without real-time calculation... However, using only the density of water or the initial density of the nuclide would lead to orders of magnitude deviations in the calculation results. This step ensures that the physical parameters within each time step are consistent and accurate.

[0051] The third step is atmospheric diffusion simulation based on dynamic settlement correction.

[0052] In existing technical systems (such as the Gaussian plume model or the standard CALPUFF model), settlement velocity is usually simplified to a static parameter related to surface type (dry settlement velocity). This leads to an inability to reflect the dramatic increase in sedimentation caused by chemical reactions in complex accidents. This invention addresses this by introducing a fluid dynamics correction algorithm to reconstruct the particle trajectory in real time within each simulation step.

[0053] At each simulation time step Within a timeframe (e.g., 10 seconds), the system iterates through every active Lagrange particle in the computational domain. Based on the output of step S2, the particle's position at the current time... Corrected particle size and effective density The system no longer uses the lookup table method, but instead strictly calculates its terminal settlement velocity according to the modified Stokes' law. The specific calculation formula is as follows: ; In this formula: (Dynamic gravity settling velocity) represents the terminal vertical downward drift velocity of a particle when gravity, buoyancy, and air viscous drag reach a dynamic equilibrium, measured in meters per second (m / s). In nucleochemical complex scenarios, this value exhibits significant time-varying characteristics. For example, for an initial particle size of... The nuclide particles have an initial settling velocity of approximately m / s (approximately suspended); when it absorbs moisture and grows in the acidic plume to At that time, its settling velocity will jump to The speed is above m / s, with an increase of more than 20 times.

[0054] (Gravity acceleration) is measured in meters per second squared. In the computational kernel of this embodiment, a standard constant is used. For simulations involving high-altitude areas (such as plateau nuclear facilities), the system supports adjusting the simulation based on altitude. right The value is finely adjusted and corrected using the following formula: ,in The radius is the Earth's radius.

[0055] (Aerosol effective density) is expressed in kilograms per cubic meter. This parameter is the average density of the composite particles output by the aforementioned nucleochemical collision aggregation subroutine. It reflects the average density of the mixed particles consisting of a radioactive nuclide core (such as a high-density metal oxide) and chemical droplets (such as a low-density acid or water) encapsulating its surface. In the code implementation, the system maintains the mass composition of each particle in real time (nuclide mass + water mass + chemical component mass) and updates it accordingly. .

[0056] (The corrected aerosol particle size at time t) is in meters (m). This parameter directly calls the real-time output value of the aforementioned environmentally sensitive growth model. It should be noted that in the formula... and Proportional to the square ( This means that linear growth in particle size will lead to a geometric progression in sedimentation velocity, reflecting the nonlinear characteristics of the physicochemical coupling effect.

[0057] (Aerodynamic viscosity) is measured in Pascal-seconds (Pa·s). Considering the potential high-temperature fields generated by fires and explosions at the accident site, air viscosity cannot be considered constant. This system incorporates Sutherland's Law, which is applied based on the real-time air temperature of the grid containing the particles. (Kelvin) Dynamic Calculation : ; Among them, reference viscosity Reference temperature Sutherland constant This design ensures the model's applicability in high-temperature fire environments (where gas viscosity increases, resistance increases, and settling slows down).

[0058] The Cunningham slip correction factor is a dimensionless parameter. When the aerosol particle size is extremely small (close to the mean free path of air molecules), it is considered a dimensionless parameter. When air exhibits discontinuity, the drag on particles is less than the Stokes drag under the assumption of a continuous medium. The calculation formula is: ; The introduction of this coefficient ensures that the model can accurately cover the ultrafine nuclei condensates from the initial stage of the accident ( From the large droplets after absorbing moisture () The full spectrum of settlement behavior.

[0059] To accurately simulate the bidirectional coupling process of chemical field-induced nuclide precipitation and the subsequent alteration of spatial concentration distribution by this precipitation, this embodiment employs an iterative stepping method based on time splitting. The specific implementation process is as follows: The three-dimensional computational domain is discretized into an Eulerian mesh system. In the... At the start of each time step, the system first maps the mass of all chemical component particles to the grid nodes and updates the three-dimensional chemical concentration field. and relative humidity field .

[0060] Traversing each radioactive nuclide particle: Retrieve the current coordinates of the particle Belonging to the grid index .

[0061] Read the grid and .

[0062] Execute the coupling operator in step S2 to update the particle's... and .

[0063] Calculate the current dynamic settlement velocity .

[0064] Calculate the particle's next time step using a random walk model The spatial location. The location update equation explicitly includes a dynamic settlement term: ; ; ; in, The grid-averaged wind speed component. This represents the turbulent velocity components. The key is the vertical direction. Item, due to It changes in real time, which makes the particle trajectory exhibit a distinct downward characteristic in areas with high chemical concentrations.

[0065] For particles near the ground (e.g.) The system calculates the dry settlement probability within the current step size. : ; If sedimentation is determined to have occurred, the radioactivity of the particle is added to the sedimentation flux of the ground grid, and the particle is removed from the air. This process updates the sedimentation probability of nuclide particles in the area at the next time step based on the current chemical composition concentration within the grid.

[0066] Step 4: Composite exposure dose assessment subsystem.

[0067] After the simulation, the system output a refined three-dimensional nuclide concentration field and ground subsidence field. However, for emergency decision-makers, purely physical quantities (such as...) This approach is insufficient to directly guide medical treatment. This embodiment further introduces a biodynamic-level collaborative damage assessment module.

[0068] Furthermore, this invention quantifies the amplification effect of chemical toxicity on radiation dose. In nuclear-chemical complex accidents, highly corrosive gases (such as ammonia, sulfur dioxide, and chlorine) or acidic aerosols can severely damage the human respiratory mucosa, disrupt the integrity of the epithelial cell barrier, and lead to a significant increase in the rate at which radionuclides enter the bloodstream.

[0069] This system defines the chemical-radiation synergistic factor. And perform the calculation according to the following logic: For each assessment point (such as a residential area), the system integral calculates the chemical exposure load at that point. .

[0070] Perform synergistic factor modeling: ; in: It is a dimensionless cooperating factor. .

[0071] This is the synergistic sensitivity coefficient. It is applicable to strongly acidic gases (such as...). ), the value is set to For asphyxiating gases, the value is relatively small. This parameter is pre-set in the system's toxicology database.

[0072] This represents the average inhalation concentration of the chemical pollutant during the exposure period.

[0073] The threshold concentration for which the chemical poses an immediate threat to life and health.

[0074] Perform inhalation effective dose correction: Final effective inhalation dose (Unit: Sieverts Sv) The calculation formula is revised as follows: ; in, Respiratory rate; For the first The air integral concentration of a nuclide; This refers to the standard dose conversion factor as specified by the International Commission on Radiation Protection (ICRP). One of the final outputs of the system is a ground contamination correction map. This map is not merely a radiometric thermogram, but a comprehensive guide map including physicochemical properties.

[0075] Specifically, each pixel in the computational domain contains triplet information: .in Radioactive surface activity ( ), The pH of the sediment. It is the main chemical component type.

[0076] Furthermore, we recommend intelligent disinfection methods: Scenario A (Acidic Sedimentation): If the spectrum shows a certain area The system outputs the following instructions: "We recommend using weakly alkaline (sodium bicarbonate-based) chelated foam for decontamination. Acidic detergents are strictly prohibited to prevent further corrosion; direct high-pressure water rinsing is strictly prohibited to prevent acidic radionuclide waste liquid from seeping into underground pipe networks." Scenario B (Organic Sedimentation): If the spectrum shows that the sediment is lipophilic organic matter, the system outputs the instruction: "It is recommended to use an organic solvent containing surfactant for emulsification and cleaning". Scenario C (Hygroscopic Salts): If the graph shows a high concentration of hygroscopic salts, the system will prompt: "Beware of deliquescence. It is recommended to perform dry cleaning or vacuuming during periods of low relative humidity to avoid deep penetration of contaminants due to wet operations." This invention also provides a simulation system based on a computer hardware architecture, which is typically deployed on an emergency command vehicle or a high-performance computing cluster in a data center.

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for simulating atmospheric diffusion physicochemical coupling under a nuclear-chemical complex accident scenario, characterized in that, Includes the following steps: Step S1: Construct a nuclear-chemical integrated source term parameterization model. Based on the input physical characteristics of radionuclides, the release rate of chemical components, and the initial aerosol particle size distribution, determine the distribution ratio of nuclides on particles with different chemical properties. Step S2: Run the aerosol dynamics coupling evolution operator, monitor the concentration of hazardous chemicals and relative humidity in the simulation space in real time, and calculate the particle size and density changes of the radionuclide carrier aerosol during the diffusion process; Step S3: Based on the particle size and density changes obtained in step S2, the sedimentation term in the atmospheric diffusion equation is corrected in real time, and the dynamic diffusion distribution of radionuclides in three-dimensional space is deduced using an iterative step method. Step S4: After the diffusion simulation is completed, combine the chemical-radiation synergy factor to output the ground contamination correction map and synergistic damage assessment results under the nuclear-chemical complex accident.

2. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 1, characterized in that, In step S1, determining the distribution ratio of the nuclide on particles with different chemical properties specifically includes: Establish an adsorption characteristic matrix and define the partition coefficients of radionuclides on particles with different chemical properties such as acidity, alkalinity, and hygroscopicity. and the allocation coefficient As the initial weights for subsequent coupling evolution, the physical characteristic quantities include at least the initial activity of the radionuclide.

3. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 1, characterized in that, In step S2, the calculation of the particle size change of the radionuclide carrier aerosol during the diffusion process is specifically carried out using an environmentally sensitive growth model. The Köhler theory is used to correct the hygroscopic growth factor of the aerosol, and the calculation formula is as follows: ； in, for Aerosol particle size after real-time correction; The initial aerosol particle size; It is a hygroscopic growth factor, which relates to the concentration of hazardous chemicals. relative humidity Transitive parameters The function; This represents the concentration of hazardous chemicals in the current grid within the simulation space. Relative humidity; Physical property parameters considering the solubility of chemical components.

4. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 3, characterized in that, In step S2, calculating the density change of the radionuclide carrier aerosol specifically includes: When the concentration of hazardous chemicals in the simulation space exceeds a preset threshold, the nucleochemical collision and aggregation subroutine is triggered. Calculate the collision cross-section between hazardous chemical droplets and radionuclide-containing aerosol particles, and dynamically update the effective density of the aerosol based on the collision results. .

5. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 4, characterized in that, In step S3, the real-time correction of the sedimentation term in the atmospheric diffusion equation specifically involves calculating the dynamic gravity sedimentation velocity. The calculation formula is as follows: ； in, This refers to the dynamic gravity-induced settling velocity. It is the acceleration due to gravity; The dynamically updated effective density of the aerosol; The corrected aerosol particle size obtained from the calculation; This is the Cunningham slip correction factor; It is the aerodynamic viscosity.

6. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 1, characterized in that, In step S3, the iterative step-by-step deduction specifically includes: Within each simulation step, read the concentration of chemical components in the current grid; The sedimentation probability of radionuclides in the grid region at the next time step is updated based on the concentration of the chemical components. The updated sedimentation probability is fed back into the diffusion equation to calculate the nuclide spatial location for the next simulation step.

7. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 1, characterized in that, In step S4, the calculation of the synergistic damage assessment result specifically includes: Introducing the chemical-radiative synergistic factor ; Based on the aforementioned synergistic factors The study calculates the changes in radionuclide absorption rate caused by damage to respiratory epithelial cells from chemical pollutants, and then calculates the effective inhalation dose.

8. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 1, characterized in that, In step S4, outputting the ground pollution correction map specifically includes: Data on the distribution of radionuclides in the near-field region after being affected by the physical and chemical effects of hazardous chemicals is generated. This distribution data is used to guide the selection of decontamination agents for sediments with different acid and alkali properties.

9. The atmospheric diffusion physicochemical coupling simulation method under a nuclear-chemical complex accident scenario according to claim 3, characterized in that, The initial aerosol particle size The activity median aerodynamic diameter (AMAD) was used for characterization; the chemical components included sulfur dioxide, ammonia, or strong acid mist.

10. A coupled physicochemical simulation system for atmospheric diffusion under a nuclear-chemical complex accident scenario, characterized in that, include: The source term modeling module is used to construct a nuclear-chemical integrated source term parameterized model. Based on the input physical characteristics of radionuclides, the release rate of chemical components, and the initial aerosol particle size distribution, it determines the distribution ratio of nuclides on particles with different chemical properties. The Coupled Evolution module is used to run the aerosol dynamics coupled evolution operator, monitor the concentration of hazardous chemicals and relative humidity in the simulation space in real time, and calculate the particle size and density changes of radionuclide carrier aerosols during the diffusion process. The diffusion simulation module is used to correct the sedimentation term in the atmospheric diffusion equation in real time based on changes in particle size and density, and to simulate the dynamic diffusion distribution of radionuclides in three-dimensional space using an iterative step method. The assessment output module is used to output a ground contamination correction map and synergistic damage assessment results under a nuclear-chemical complex accident, after the diffusion simulation is completed, by combining the chemical-radiation synergistic factor.

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