Radioactive substance diffusion prediction method based on random consumption and particle size parallel algorithm

Abstract

The invention relates to a radioactive substance diffusion prediction method, in particular to a radioactive substance diffusion prediction method based on a random depletion and particle size parallel algorithm, and mainly solves the problems that in the prior art, space-time specific processing of a source item is rough, depletion is not considered in dry-wet settlement correction, the particle size is single, statistics is insufficient, and calculation is time-consuming. The method comprises the following steps: 1, setting source item parameters, meteorological parameters and parallel computing parameters; 2, preprocessing the parameters respectively; 3, performing diffusion calculation on the particles of each particle size in the radioactive substance at each moment by adopting a parallel algorithm to obtain position information of all the particles, and storing the position information; 4, performing statistics to obtain space grid time integral activity concentration values and ground grid settlement activity values of the radioactive substances corresponding to each moment, and storing the space grid time integral activity concentration values and the ground grid settlement activity values into a hard disk according to a moment sequence; and 5, calculating to obtain the total time integral activity concentration and the total sedimentation activity of the radioactive substance, thereby realizing diffusion prediction of the radioactive substance.

Description

Technical Field

[0001] The invention relates to a radioactive material diffusion prediction method, and in particular to a radioactive material diffusion prediction method based on random depletion and particle size parallel algorithm. Background Art

[0002] Nuclear energy and nuclear technology are widely used in the world, bringing huge benefits but also huge risks. The release and emission of radioactive materials from nuclear reactors, explosion and leakage of radioactive materials, dirty bomb attacks, leakage of gas radioactive sources and many other scenarios all have the possibility of releasing radioactive materials into the environment, which then diffuses and settles in the atmosphere, causing great harm to the natural environment, human health and public safety. Studying the diffusion and sedimentation of radioactive materials in the atmosphere and evaluating the hazards to people and the environment caused by the diffusion of radioactive materials are of great significance to environmental impact assessment, real-time consequence assessment of accidents and emergency decision-making.

[0003] The diffusion of radioactive substances in the atmosphere mainly depends on the average wind speed and turbulent motion of the atmospheric environment. However, in the small scale range, the release characteristics and physical forms of radioactive substances themselves, such as the size of the source term, geometric characteristics, release time length characteristics, and diffusion particle size (gas or aerosols of different particle sizes), have a great influence on the diffusion and deposition distribution. For the prediction of the diffusion law of radioactive substances in a small scale range, various calculation modes can be used, such as Gaussian mode, Euler mode, CFD mode, Lagrangian mode, Lagrangian-Euler nested mode, etc. Among them, the Gaussian mode is the main theoretical mode for simulating the atmospheric diffusion of radioactive substances. The mode has clear physical concepts, high computational efficiency and spatial resolution, and is suitable for calculations in small scale ranges in steady-state flow fields. The Euler mode is based on solving the spatial position concentration of the atmospheric transport equation, which can well simulate the large-scale long-distance migration and diffusion of radionuclides, and can also simulate their spatial distribution in the vertical direction, but it is difficult to simulate the near-source simulation and the closure problem of the original equation. The CFD model is a computational fluid dynamics model. By solving the Navier-Stokes equations, complex microscale wind fields and turbulence fields are obtained. It is suitable for areas within 2 km of a nuclear power plant. It can simulate the blind spots of the mainstream model and has a good effect on small-scale diffusion simulation.

[0004] The Lagrangian model uses the first-order or second-order random modes of many particle motions to describe the diffusion and migration of radioactive materials in the atmosphere. It is also called the random walk model. It is currently the most widely used and mature model for simulating the diffusion of radionuclides. For example, the open literature "Boughton, BA; DeLaurentis, JM. Description and validation of ERAD: An atmospheric dispersion model for high explosive detonations [R]. Sandia Report SAND 92-2069, 1992." and "Chi Bing, Fang Dong, Li Hong. Development and application of random walk atmospheric diffusion model in nuclear accident emergency [J]. Nuclear Science and Engineering, 2006, 26 (1): 39-45." both introduce the basic idea of ​​the random walk method, model description and parameter determination, and give the basic simulation calculation process of random walk atmospheric diffusion. At the same time, the public documents "Xu Zhiyan. Application of random walk particle-puff atmospheric model in nuclear accidents [D]. Harbin Engineering University: Harbin Engineering University, 2014.", "Zhuo Jun, Huang Liuxing, Niu Shengli, et al. Simulation and calculation of radioactive dose distribution after dirty bomb attack based on random walk method [J]. Atomic Energy Science and Technology, 2018, (6).", "Lipták, L'., Fojcíková, E., Krpelanová, M.at el. The ESTE Decision Support System for Nuclear and Radiological Emergencies: Atmospheric Dispersion Models [J]. Atmosphere 2021, 12, 204.", etc. have respectively used basic random walk atmospheric diffusion to carry out application expansion and given application examples of combined diffusion or dose calculation with other models. In addition, the Chinese patent with publication number CN 107145699A also published a technology for simulating the long-distance atmospheric diffusion and migration of airborne radionuclides using a particle random walk method, the main feature of which is that the turbulence parameters and mesoscale wind pulsation parameters in the large-scale atmospheric migration trajectory are determined with specificity. The Chinese patent with publication number CN 111650672 A also proposed a method for realizing the rapid prediction of atmospheric diffusion of air pollutants using a time stack, thereby solving the problems of excessive memory usage, long calculation time, and low calculation efficiency.

[0005] However, the above methods mainly consider continuous point sources and cylindrical sources released by instantaneous explosions when dealing with source terms, and no expression methods for other time-space specific source terms are given. Moreover, the treatment of dry and wet deposition in the diffusion of radioactive materials mainly adopts a macro correction method, which cannot truly reflect the microscopic physical process of particle depletion after deposition; a single numerical calculation is used for the particle size of source term particles, which has a large deviation from the gaseous state, a certain particle size distribution aerosol state, and even a mixed form of radioactive materials. As a result, the final physical quantity statistics may be insufficient due to the scarcity of particles in ground deposition and far-field diffusion. In addition, for radioactive materials in the form of mixed gas and aerosol, separate calculations still have the problem of long calculation time and low calculation efficiency. This shows that there is a lot of room for improvement in the use of particle random walk method to predict the diffusion of radioactive materials. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of the existing prediction methods for the diffusion of radioactive substances in the atmosphere, such as rough processing of source terms in time and space, no consideration of depletion in dry and wet deposition correction, single particle size and insufficient statistics, and time-consuming calculation, and to provide a method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm.

[0007] To achieve the above objectives, the technical solutions provided by the present invention are:

[0008] A method for predicting the diffusion of radioactive materials based on stochastic depletion and particle size parallel algorithm, which is special in that it includes the following steps:

[0009] Step [1]: Set source term parameters, meteorological parameters and parallel calculation parameters according to the release characteristics of radioactive materials, and set spatial grid division parameters according to the size of the calculation domain;

[0010] Step [2], pre-processing the source parameters, meteorological parameters and parallel computing parameters respectively;

[0011] Step [3]: Based on step [2], combined with the sampling simulation sedimentation process, a parallel algorithm is used to perform diffusion calculations on particles of each particle size in the radioactive material at each moment, thereby obtaining position information of all particles and storing the position information;

[0012] Step [4], extracting the location information described in step [3], statistically obtaining the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value of the radioactive material corresponding to each moment, and storing them in the hard disk in time sequence;

[0013] Step [5]: Based on the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value obtained in step [4], combined with the nuclide type characteristics of the radioactive material, the total time-integrated activity concentration and total sedimentation activity of the radioactive material are calculated to achieve the diffusion prediction of the radioactive material.

[0014] Furthermore, in step [1], the source term parameters include the number of released source terms, spatial geometric parameters, release time and radioactive material decay characteristic parameters; the meteorological parameters are meteorological parameters including rainfall, geostrophic wind and uniform or non-uniform wind field; the parallel calculation parameters include time step, particle number release rate, parallel calculation core number, minimum number of particles displayed, each particle size value of aerosol particle size distribution and the corresponding normalized share.

[0015] Furthermore, in step [2], preprocessing the source item parameters means constructing the spatial geometry of the release source at the initial moment based on the source item parameters by random sampling, mathematical analysis and splicing combination, and constructing uniform or non-uniform moment information by random sampling and time step setting;

[0016] Preprocessing meteorological parameters means obtaining wind speed and direction, diffusion parameters, Lagrangian autocorrelation coefficients, and dry and wet deposition depletion constants at each moment based on meteorological parameters and combined with Lagrangian autocorrelation function theory and turbulence statistics theory;

[0017] Preprocessing the parallel computing parameters refers to segmenting aerosol particles of different particle sizes into multiple particle sizes, and setting separate tracking particles and parallel computing core numbers for particles of each particle size.

[0018] Furthermore, step [3] is specifically as follows:

[0019] 3.1. Based on step [2], read the source parameters and meteorological parameters at the initial moment, combine the sampling simulation sedimentation process, use a parallel algorithm to calculate the position information of each particle corresponding to any particle size in the radioactive material at the next moment, and store the position information;

[0020] 3.2. According to the method in step 3.1, calculate the position information of each particle corresponding to all other particle sizes in the radioactive material at the next moment, and store the position information;

[0021] 3.3. According to the methods of steps 3.1 to 3.2, calculate the position information of all particles corresponding to each particle size in the radioactive material at other times, and store the position information.

[0022] Furthermore, step [4] specifically includes extracting the position information described in steps 3.1, 3.2 and 3.3, firstly counting the position information of all particles corresponding to each particle size in the radioactive material at each moment, then counting the position information corresponding to all particle sizes at that moment, and finally obtaining the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value of the radioactive material corresponding to each moment, and storing them in the hard disk in time sequence.

[0023] Furthermore, in step [4], the spatial grid time-integrated activity concentration value C i,j,k The calculation formula is:

[0024]

[0025] Where Q is the normalized source strength; T i,j,k,m is the time that the mth particle stays in the grid (i, j, k); N is the total number of released particles; ΔxΔyΔz is the volume of the spatial grid;

[0026] The ground grid sedimentation activity value D i,j,k The calculation formula is:

[0027]

[0028] Where n represents the total number of particles settled in the grid (i, j, k), and ΔxΔy represents the area of ​​the ground grid.

[0029] Furthermore, step [4] also includes, according to display requirements, using random sampling to intercept the position information corresponding to the corresponding particle size at the corresponding time for separate storage and display.

[0030] Furthermore, in step [5], the calculation formula for the total time-integrated activity concentration is:

[0031]

[0032] In the formula, C i ' ,j,k It represents the total time-integrated activity concentration of radioactive material in the grid (i, j, k) at any time t, Q l Indicates the source intensity of the first radionuclide in the radioactive material, λ l It represents the decay constant of the lth radionuclide in the radioactive material, t represents any time, t>0;

[0033] The calculation formula of the total sedimentation activity is:

[0034]

[0035] Where D i ',j,k Represents the total sedimentation activity of radioactive material in the grid (i, j, k) at any moment.

[0036] Furthermore, step [5] also includes, according to display requirements, selecting the total time-integrated activity concentration and the total sedimentation activity at the corresponding moment for display.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The present invention pre-sets source parameters, meteorological parameters and parallel calculation parameters, pre-processes them respectively, and then uses a parallel algorithm to calculate the diffusion process, and finally performs statistics and storage respectively. This method has sufficient statistics and high calculation efficiency, so that refined prediction results can be obtained.

[0039] 2. The present invention pre-processes the source term parameters, meteorological parameters and parallel calculation parameters respectively, which not only makes the initial form of the release source authentic and diverse, but also makes the precision and accuracy of the subsequent diffusion calculation higher.

[0040] 3. The present invention adopts a sampling simulation sedimentation process in the parallel calculation process, which can calculate the dry sedimentation and wet sedimentation processes in sequence. The particles are continuously consumed in the diffusion calculation process, which conforms to the real diffusion and sedimentation physical process, making the prediction result more realistic.

[0041] 4. The present invention stores the calculation results in time during the calculation process, and calls the computer CPU core resources released due to particle depletion and no longer needing calculation according to the dry and wet deposition depletion, thereby optimizing the computer's calculation efficiency.

[0042] 5. The present invention can also select corresponding information for real-time display according to actual display needs, so that the diffusion process of radioactive substances can be observed more intuitively. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flowchart diagram and a specific prediction process diagram of an embodiment of the present invention.

[0044] Figure 2 1 is a geometric structure diagram of the explosion source term obtained after preprocessing the source term parameters in an embodiment of the present invention; wherein (a) is a three-dimensional structure diagram, and (b) is a two-dimensional structure diagram.

[0045] Figure 3 This is a result diagram of total ground settlement activity at a certain moment in an embodiment of the present invention.

[0046] Figure 4 This is a graph showing the total time-integrated activity concentration of ground air at a certain moment in an embodiment of the present invention.

[0047] Figure 5 This is a graph showing the time-integrated total activity concentration of ground air within a certain diffusion time in an embodiment of the present invention.

[0048] Figure 6 Schematic diagram of particle distribution at a certain moment in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0050] like Figure 1 As shown, this embodiment provides a method for predicting the diffusion of radioactive materials based on random depletion and particle size parallel algorithm, comprising the following steps:

[0051] Step [1]: Set the source term parameters, meteorological parameters and parallel calculation parameters according to the release characteristics of the radioactive material, and set the spatial grid division parameters according to the size of the calculation domain.

[0052] In this embodiment, the source term parameters include the number of released source terms, spatial geometric parameters, release time, and radioactive material decay characteristics. Meteorological parameters include meteorological parameters such as rainfall, geostrophic wind, and uniform or non-uniform wind field. Parallel calculation parameters include time step, particle number release rate, parallel calculation core number, minimum number of particles displayed, each particle size value of aerosol particle size distribution and corresponding normalized share, etc.

[0053] Specifically, the number of parallel computing cores nm for each particle size is determined by the number of cores of the computing resource platform hardware, and is generally set to nm=4.

[0054] Step [2]: Preprocess the source parameters, meteorological parameters and parallel computing parameters respectively.

[0055] Among them, preprocessing of source term parameters refers to constructing the spatial geometry of the release source at the initial moment based on the source term parameters by random sampling, mathematical analysis and splicing combination, and constructing uniform or non-uniform moment information by random sampling and time step setting, so that the description of release time length and intensity changes is more accurate, and the prediction of radioactive material diffusion is more precise; at the same time, the decay constants required for the calculation of total activity concentration and total sedimentation activity are obtained. Through this processing, the initial form of the release source has authenticity and diversity.

[0056] In this embodiment, the refined spatial geometric description of the release source is constructed by random sampling, mathematical analysis and splicing combination, such as Figure 2As shown in the figure, the geometric structure of the explosion source term is shown, where (a) is a three-dimensional structure diagram and (b) is a two-dimensional structure diagram. It can be seen from the figure that it is constructed using a hemisphere and three cylinders of different radii and heights, and a specified number of particles are uniformly generated by spatial sampling, which is an instantaneous release of radiation source. The refined uniform or non-uniform time variation description of the release source is constructed by random sampling and time step setting, that is, if there are T time steps, there are T release data, and when the T release data are different, it is a non-uniform release.

[0057] Preprocessing of meteorological parameters refers to obtaining wind speed and direction at each time, diffusion parameters, Lagrangian autocorrelation coefficients, and dry and wet deposition depletion constants based on the set meteorological parameters in combination with Lagrangian autocorrelation function theory and turbulence statistics theory.

[0058] In this embodiment, the Lagrangian autocorrelation functions of the three speeds, wind volume and wind directions u, v and w are defined as R u , R v , R w According to the statistical theory of turbulence, it is generally in exponential form, that is:

[0059]

[0060] Among them, T u 、T v 、T w They represent the Lagrangian time scale of wind speeds u, v, and w respectively, and Δt is the time step.

[0061] Preprocessing the parallel computing parameters refers to segmenting aerosol particles of different particle sizes into multiple particle sizes, and setting separate tracking particles and parallel computing core numbers for particles of each particle size.

[0062] According to the particle size distribution, multiple particle sizes are segmented, and each particle size is set with a separate tracking particle. The gas is set to a single particle size of 0. This method makes the statistics of particles at long distances downwind of radioactive material diffusion more sufficient. Assuming the total particle size is sd, the number of particle size segments that need to be calculated in parallel is determined according to the particle size. When the particle size is greater than 150μm, the gravity sedimentation is relatively large, and the particles fall to the ground quickly, so parallel calculation is not required. Assuming the number of particle sizes that need to be calculated in parallel is np, the number of computer CPU cores required for parallel calculation is: nd = sd + np × nm.

[0063] Step [3]: Based on step [2], combined with the sampling simulation sedimentation process, a parallel algorithm is used to perform diffusion calculations on each particle size in the radioactive material at each moment, obtain the position information of all particles, and store the position information. Specifically:

[0064] 3.1. According to the pre-processed source parameters, meteorological parameters and parallel calculation parameters, read the source parameters and meteorological parameters at the initial moment, combine the sampling simulation sedimentation process, use the parallel algorithm to calculate the position information of each particle corresponding to any particle size in the radioactive material at the next moment, and store the position information.

[0065] The particle position information is calculated using the following formula:

[0066] X(t+Δt)=X(t)+V(t)Δt+V'(t)Δt

[0067] Among them, X is the three-dimensional coordinate component of the particle (x, y, z); V is the average wind speed component (u, v, w); V′ is the turbulent pulsating velocity component (u′, v′, w′); t is the time series; Δt is the time step.

[0068] The turbulent fluctuation velocity (u′, v′, w′) at different times is calculated using the following formula:

[0069]

[0070] In the formula, ξ is a random number that conforms to the normal distribution (mean value is 0 and standard deviation is σ); and is the standard deviation of the pulsation quantity V′ in three directions; R u , R v , R w These are the Lagrangian autocorrelation functions of the three speeds, wind volume and wind direction, u, v and w.

[0071] In this process, according to the number of particle sizes of the multi-particle size segmentation set by the source item and the computing hardware resource conditions, particles of each particle size use the same number of computer CPU cores to carry out parallel computing.

[0072] 3.2. According to the method in step 3.1, the position information of each particle corresponding to all other particle sizes in the radioactive material at the next moment is calculated and stored. Timely storage solves the problem of excessive memory usage of random walk calculation.

[0073] 3.3. According to the method of steps 3.1 to 3.2, calculate the position information of all particles corresponding to each particle size in the radioactive material at other times, and store the position information. The position information at multiple times can reflect the particle motion trajectory at one or more time steps.

[0074] In the above calculation process, the uniform distribution random sampling method is used to calculate the dry deposition and wet deposition processes in turn. The probability of particles being removed is exp(-ΛΔt), where Δt is the time step.

[0075] When calculating the dry deposition process, Λ=v d / h,v d is the sedimentation velocity component, v d Determined by the particle size, that is:

[0076]

[0077] Where: g is the acceleration due to gravity, 9.8m / s 2 ρ P is the particle density, g / cm 3 ; C0 is the Cunningham correction factor; D P is the particle diameter, cm; μ is the air viscosity, g / cm.s; h is the reference height.

[0078] When calculating the wet deposition process, Λ is the removal coefficient, which is determined by the rainfall intensity in the meteorological parameters. The particles are continuously consumed during the diffusion calculation process, which is consistent with the actual diffusion and deposition physical process.

[0079] Step [4]: ​​extract the location information described in step [3], obtain the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value of the radioactive material corresponding to each moment, and store them in the hard disk in time sequence, specifically:

[0080] Extract the position information described in steps 3.1, 3.2 and 3.3, first count the position information of all particles corresponding to each particle size in the radioactive material at each moment, then count the position information corresponding to all particle sizes at that moment, and finally obtain the spatial grid time-integrated activity concentration value and ground grid sedimentation activity value of the radioactive material corresponding to each moment, and store them in the hard disk in time sequence, so as to obtain the spatial grid time-integrated activity concentration value and ground grid sedimentation activity value of the radioactive material at one or more moments.

[0081] At this time, the spatial grid time-integrated activity concentration value C i,j,k The statistical formula is:

[0082]

[0083] In the formula, C i,j,k represents the time-integrated activity concentration value of all particles in the radioactive material in the grid (i, j, k) at any time; Q is the normalized source strength, Bq; N is the total number of released particles; T i,j,k,m is the time that the mth particle stays in the grid (i, j, k), s; ΔxΔyΔz is the grid volume, m 3 .

[0084] Ground grid sedimentation activity value D i,j,k The statistical formula is:

[0085]

[0086] D i,j,k represents the activity concentration value of radioactive substances in the grid (i, j, k) at any time; n represents the total number of particles of radioactive substances settled in the grid (i, j, k); ΔxΔy represents the area of ​​the ground grid. The parallel calculation results are then stored in the hard disk, and according to the dry and wet deposition depletion, the computer CPU core resources released due to particle depletion and no longer needing to be calculated are called to optimize the computer calculation efficiency.

[0087] According to display requirements, the position information corresponding to the corresponding particle size at the corresponding time can be intercepted by random sampling for separate storage and display.

[0088] Step [5], based on the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value obtained in step [4], combined with the nuclide type characteristics of the radioactive material, the total activity concentration and total sedimentation activity of the radioactive material are calculated, thereby realizing the diffusion prediction of the radioactive material. This method solves the problem of particle diffusion simulation calculation of mixed release of multiple radionuclides.

[0089] The calculation formula for the total time-integrated activity concentration is:

[0090]

[0091] In the formula, C i ' ,j,k represents the total time-integrated activity concentration of radioactive material in the grid (i, j, k) at any time; Q l Indicates the source intensity of the first radionuclide in the radioactive material, λ l It represents the decay constant of the lth radionuclide in the radioactive material, L represents the number of types of radioactive material, t represents any moment, t>0.

[0092] Total sedimentation activity D i ' ,j,k The calculation formula is:

[0093]

[0094] Where D i ' ,j,k Represents the total sedimentation activity of radioactive material in the grid (i, j, k) at any moment.

[0095] like Figure 3As shown in the figure, the total ground settlement activity result diagram of a certain example at 5400s is displayed. The figure gives the ground settlement activity density data of each specific location in the downwind calculation domain at 5400s after the release of radioactive materials in a certain example. The superposition of results at multiple times can obtain the changing trend and size of the settlement amount at each downwind location over time.

[0096] like Figure 4 As shown in the figure, the result diagram of the time-integrated activity concentration of the air in the near-ground layer at 5400s in a certain example is displayed. The figure gives the radioactive time-integrated activity concentration data in the near-ground layer in the downwind calculation domain at 5400s after the release of radioactive material in a certain example. The superposition of results at multiple times can obtain the trajectory and change trend of the radioactive time-integrated activity concentration in the near-ground layer in the downwind direction over time.

[0097] Calculation of total time-integrated activity concentration value of ground grid within total diffusion time:

[0098]

[0099] Figure 5 This is a result diagram of the total time-integrated activity concentration of the ground air within the diffusion time of 5400s for a certain example. The figure gives the time-integrated activity concentration data of the radioactivity in the near-ground layer air in the downwind calculation domain within the diffusion time of 5400s after the release of radioactive materials in a certain example, providing input data for estimating and predicting the radioactive sampling or absorbed dose at a fixed downwind position at a specific time.

[0100] In addition, according to the display requirements, the total time-integrated activity concentration and total sedimentation activity corresponding to the corresponding moment or time step can be selected for display. At the same time, the particle movement trajectory and distribution of the release source diffusion and sedimentation process at each moment can also be displayed, such as Figure 6 When displaying the particle trajectory and distribution, random sampling is used to determine the appropriate fixed number of particles that meet the display needs, which not only meets the display needs but also takes into account the capacity of the graphics card memory.

[0101] In summary, the present invention adopts random sampling to construct the refined spatial geometry of the release source, performs multi-particle size segmentation according to the particle size distribution, adopts random sampling to simulate the dry and wet sedimentation process, adopts a multi-particle size and multi-computer CPU core parallel algorithm, and timely stores the position information of each step, thereby achieving the refined prediction of the diffusion of radioactive materials.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for predicting the diffusion of radioactive materials based on random depletion and particle size parallel algorithm, characterized in that: The following steps are involved: Step [1]: Set source term parameters, meteorological parameters and parallel calculation parameters according to the release characteristics of radioactive materials, and set spatial grid division parameters according to the size of the calculation domain; Step [2], pre-processing the source parameters, meteorological parameters and parallel computing parameters respectively; Step [3]: Based on step [2], combined with the sampling simulation sedimentation process, a parallel algorithm is used to perform diffusion calculations on particles of each particle size in the radioactive material at each moment, thereby obtaining position information of all particles and storing the position information; Step [4], extracting the location information described in step [3], statistically obtaining the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value of the radioactive material corresponding to each moment, and storing them in the hard disk in time sequence; Step [5]: Based on the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value obtained in step [4], combined with the nuclide type characteristics of the radioactive material, the total time-integrated activity concentration and total sedimentation activity of the radioactive material are calculated to achieve the diffusion prediction of the radioactive material.

2. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to claim 1 is characterized in that: In step [1], the source term parameters include the number of released source terms, spatial geometric parameters, release time and radioactive material decay characteristic parameters; the meteorological parameters are meteorological parameters including rainfall, geostrophic wind and uniform or non-uniform wind field; the parallel calculation parameters include time step, particle number release rate, parallel calculation core number, minimum number of particles displayed, each particle size value of aerosol particle size distribution and the corresponding normalized share.

3. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to claim 2 is characterized in that: In step [2], preprocessing the source item parameters means constructing the spatial geometry of the release source at the initial moment based on the source item parameters by random sampling, mathematical analysis and splicing combination, and constructing uniform or non-uniform moment information by random sampling and time step setting; Preprocessing the meteorological parameters means obtaining the wind speed and direction, diffusion parameters, Lagrangian autocorrelation coefficient and dry and wet deposition depletion constant at each moment based on the set meteorological parameters and combined with Lagrangian autocorrelation function theory and turbulence statistics theory; Preprocessing the parallel computing parameters refers to segmenting aerosol particles of different particle sizes into multiple particle sizes, and setting separate tracking particles and parallel computing core numbers for particles of each particle size.

4. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to claim 3 is characterized in that: Step [3] is as follows: 3.

1. Based on step [2], read the source parameters and meteorological parameters at the initial moment, combine the sampling simulation sedimentation process, use a parallel algorithm to calculate the position information of each particle corresponding to any particle size in the radioactive material at the next moment, and store the position information; 3.

2. According to the method in step 3.1, calculate the position information of each particle corresponding to all other particle sizes in the radioactive material at the next moment, and store the position information; 3.

3. According to the methods of steps 3.1 to 3.2, calculate the position information of all particles corresponding to each particle size in the radioactive material at other times, and store the position information.

5. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to claim 4 is characterized in that: Step [4] specifically extracts the position information described in steps 3.1, 3.2 and 3.3, firstly counts the position information of all particles corresponding to each particle size in the radioactive material at each moment, then counts the position information corresponding to all particle sizes at that moment, and finally counts the spatial grid time-integrated activity concentration value and the ground grid sedimentation activity value of the radioactive material corresponding to each moment, and stores them in the hard disk in time sequence.

6. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to claim 5, characterized in that: In step [4], the spatial grid time-integrated activity concentration value C i,j,k The calculation formula is: Where Q is the normalized source strength; T i,j,k,m is the time that the mth particle stays in the grid (i, j, k); N is the total number of released particles; ΔxΔyΔz is the volume of the spatial grid; The ground grid sedimentation activity value D i,j,k The calculation formula is: Where n represents the total number of particles settled in the grid (i, j, k), and ΔxΔy represents the area of ​​the ground grid.

7. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to any one of claims 1 to 6, characterized in that: Step [4] also includes, according to display requirements, using random sampling to intercept the position information corresponding to the corresponding particle size at the corresponding time for separate storage and display.

8. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to claim 6, characterized in that: In step [5], the total time-integrated activity concentration is calculated as: In the formula, C i ' ,j,k It represents the total time-integrated activity concentration of radioactive material in the grid (i, j, k) at any time t, Q l Indicates the source intensity of the first radionuclide in the radioactive material, λ l represents the decay constant of the lth radionuclide in the radioactive material, L represents the number of types of radioactive material, t represents any moment, and t>0; The calculation formula of the total sedimentation activity is: Where D i ' ,j,k Represents the total sedimentation activity of radioactive material in the grid (i, j, k) at any moment.

9. The method for predicting the diffusion of radioactive substances based on random depletion and particle size parallel algorithm according to claim 1, characterized in that: Step [5] also includes selecting the total time-integrated activity concentration and the total sedimentation activity at the corresponding moment for display according to display requirements.

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