A method for ranking radionuclide hazards

Abstract

A method for ranking the hazard of radionuclides, which ranks the hazard of radionuclides by calculating the total effective dose produced by different radionuclides within a certain geographical range in the spread of radioactive contamination, and then screens and controls the types and quantities of radionuclides; wherein the calculation of the effective dose comprehensively considers the influence of radioactive decay, radionuclide deposition, air immersion external exposure, ground deposition external exposure, inhalation internal exposure and other factors. The method can realize the rapid ranking of radionuclides, and achieves a good balance between calculation efficiency and accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nuclear accident consequence assessment and radioactive atmospheric pollution prediction, in particular to a method for ranking the hazard of radionuclides. BACKGROUND

[0002] When an event involving large-scale atmospheric diffusion of radioactive substances such as a nuclear accident, nuclear explosion, or dirty bomb attack occurs, it is necessary to predict and evaluate the scope and level of pollution caused by the accident. In this process, it is necessary to first determine the types and quantities of radionuclides.

[0003] Currently, there is no published research on methods for ranking the hazard of radionuclides. Most research and technology focuses on simulating the diffusion of radioactivity, obtaining aerosol concentrations, such as document 1 (Invention Patent CN 114547890 A "Method for simulating radioactive aerosol contamination in nuclear accidents"), which mainly studies how to improve atmospheric diffusion models; or calculating radiation doses, such as document 2 (Hu Erbang "Model and parameters of emergency local real-time dose evaluation system for nuclear power plant accidents"), which introduces how to perform three-dimensional atmospheric diffusion simulation and dose calculation; or analyzing public damage, rather than comparing multiple radionuclides, such as Invention Patent CN 114547890 A "Method for evaluating public toxicity impact after nuclear facility accidents".

[0004] The more types of radionuclides selected, the higher the accuracy, but the calculation time increases, and it often takes several hours to perform three-dimensional diffusion simulation of radioactive substances, which may greatly delay decision-making efficiency. The fewer radionuclides selected, the faster the calculation speed, but the accuracy is not high, which reduces the reliability of decision-making. How to balance the calculation speed and the accuracy of the prediction results, and select the appropriate types and quantities of radionuclides, is a problem that needs to be solved in the field of radioactive substance diffusion simulation.

[0005] In actual operation, there are two commonly used methods: one is to calculate all radionuclide types, but a nuclear accident can release hundreds of radionuclides, which will take a lot of time; the other is to select only based on the total amount of released radionuclide activity, which reduces the reliability of the calculation results. Since each radionuclide has different half-life, physical and chemical properties, and toxicity, the effective dose it causes to the human body is also different, and radionuclides cannot be selected based on a single indicator.

[0006] Therefore, for large-scale multi-radionuclide pollution diffusion problems, the release amount and physical and chemical properties of each radionuclide need to be considered to quickly select the appropriate types of radionuclides, achieving the purpose of balancing the calculation timeliness and accuracy. SUMMARY

[0007] The disclosure provides a radionuclide hazard ranking method capable of balancing the calculation timeliness and accuracy in emergency decision-making.

[0008] The radionuclide hazard ranking method provided by the disclosure comprises the following steps:

[0009] An original nuclide information matrix and a spatial geographic grid information matrix are constructed. Preferably, the nuclide information matrix specifically contains the name, total activity of environmental release, half-life, deposition rate, air immersion dose conversion factor, ground deposition dose conversion factor, and inhalation internal radiation dose conversion factor of each nuclide; and the spatial geographic grid information matrix specifically includes the coordinates, horizontal diffusion parameter, and vertical diffusion parameter of each geographic grid.

[0010] A radionuclide two-dimensional atmospheric diffusion model under the influence of multiple factors is established to calculate the whole body effective dose of each nuclide in each geographic grid. Preferably, the Gaussian plume model is discretized, and the source is corrected by using a decay factor and a deposition factor, considering that radioactive decay and deposition will affect the change of the source: Q i '=Q i f r,i,k f d,i,k

[0011] The corrected discretized Gaussian plume model is used to calculate the air concentration of each nuclide at each grid:

[0012]

[0013] The total effective dose of each nuclide in a specific range is calculated.

[0014] According to the total effective dose of each nuclide, or further calculating the proportion of the hazard impact of each nuclide, the ranking of the hazard of each nuclide is determined.

[0015] Further, the method further comprises the step of: according to the hazard ranking, quickly screening the appropriate nuclide type and quantity.

[0016] The radionuclide hazard ranking method provided by the disclosure ranks the hazard of radionuclides by calculating the total effective dose of different radionuclides in a certain geographic range during the diffusion of radioactive pollution, and then screens and controls the nuclide type and quantity; wherein the calculation of the effective dose comprehensively considers the influence of radioactive decay, nuclide deposition, air immersion external radiation, ground deposition external radiation, and inhalation internal radiation.

[0017] Compared with the prior art, the disclosure has the following beneficial effects:

[0018] (1) Since the effective dose can be used to characterize the damage of the personnel, the disclosure proposes to use the sum of the effective dose of all the grid points in a certain range for each nuclide to characterize the harm of the nuclide in this range; the calculation of the effective dose also fully considers the properties of the nuclide itself (release activity, half-life, air immersion dose conversion factor, ground dose deposition conversion factor, inhalation dose conversion factor), and the influence of deposition rate and aerodynamic transport, which is more accurate than considering only the influence of a single factor; thus, a good balance between calculation efficiency and accuracy is achieved.

[0019] (2) The disclosure considers the influence of radioactive decay and deposition on the basis of the two-dimensional mode; since the two-dimensional mode input is simple, it is not necessary to prepare complex source terms and three-dimensional wind fields (which are difficult to quickly obtain under emergency conditions) as in the three-dimensional mode, the calculation principle is simpler, and the calculation speed is faster.

[0020] (3) The selected nuclides are input into other three-dimensional modes, so that the radiation field can be quickly obtained under the premise of maintaining accuracy.

[0021] (4) It has good universality. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which like reference characters refer to the like parts throughout the different views of the drawings.

[0023] Figure 1 A flowchart according to an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0024] Preferred embodiments of the present disclosure will be described in more detail by making reference to the accompanying drawings. Although preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0025] Currently, there is no published research on how to screen nuclides in large-scale multi-nuclide atmospheric diffusion. The present disclosure provides a method for ranking the harm of radioactive nuclides, which can quickly determine the ranking of the harm of each nuclide. Based on the ranking, the appropriate type and number of nuclides can be quickly screened.

[0026] The calculation process according to an exemplary embodiment of the present disclosure is shown in FIG. 1, which includes the following steps: Figure 1

[0027] ​S100: Create the nuclide information matrix and the space information matrix.

[0028] Obtain the initial source term information of the radioactive accident, mainly including the name and total activity of each nuclide released into the environment.

[0029] Count the total number of initial nuclides, denoted as N. According to the nuclide name, call the corresponding half-life, deposition rate, air immersion dose conversion factor, ground deposition dose conversion factor, and inhalation internal radiation dose conversion factor values in the nuclide library.

[0030] Create a nuclide information matrix, which specifically contains the name, total activity released into the environment, half-life, deposition rate, air immersion dose conversion factor, ground deposition dose conversion factor, and inhalation internal radiation dose conversion factor of each nuclide.

[0031]

[0032] Where ST is the name of the nuclide information matrix, NUC is the name of the nuclide, Q is the activity of the nuclide, T 1 / 2 is the half-life of the radioactive nuclide, V d is the deposition rate of the nuclide, DCF a is the air immersion concentration dose conversion factor of the nuclide, DCF g is the ground deposition dose conversion factor, and DCF in is the inhalation dose conversion factor, and subscripts 1, 2, N, etc. represent the nth nuclide, and N is the total number of initial nuclides.

[0033] Set the spatial range X×Y (unit: square kilometers) and the geographical horizontal resolution Δx (unit: meters) to be predicted with the release source as the center, divide it into regular geographical grids, and label each grid point with a unique identifier. The total number of grids is denoted as K.

[0034] According to the geographical grid, call the diffusion parameter calculation function to calculate the horizontal diffusion parameter and the vertical diffusion parameter. The specific calculation method of the diffusion parameter can refer to GB3840-91 "Technical Methods for Formulating Local Atmospheric Pollutant Emission Standards" or other public technologies.

[0035] Create a space information matrix, which specifically includes the horizontal coordinate, vertical coordinate, horizontal diffusion parameter, and vertical diffusion parameter corresponding to the geographical grid.

[0036]

[0037] Where x is the horizontal coordinate of the grid point in the evaluation area, y is the vertical coordinate, σ xy is the horizontal diffusion parameter, and σ z is the vertical diffusion parameter, and subscripts 1, 2, K represent the geographical grid arrangement identifier, and K is the total number of grids.

[0038] S200: Establish a radionuclide two-dimensional atmospheric diffusion model under the influence of multiple factors;

[0039] Set the prediction time range, such as 0 hours of the accident to 2 days after the accident.

[0040] Call the radionuclide information matrix and the spatial information matrix, and calculate the decay factor of each nuclide at each grid using the decay factor calculation model, wherein the decay factor calculation model is:

[0041]

[0042] Wherein, f r,i,k (x) is the decay factor of the i-th nuclide at the k-th geographical grid, and the value is between 0 and 1. T 1 / 2,i is the half-life of the i-th nuclide, is the average wind speed, x k is the x-axis coordinate value of the k-th geographical grid;

[0043] Call the radionuclide information matrix and the spatial information matrix, and calculate the deposition factor of each nuclide at each grid using the deposition factor calculation model, wherein the calculation model of the deposition factor is:

[0044]

[0045] Wherein, f d,i,k is the deposition factor of the i-th nuclide at the k-th geographical grid, and the value is between 0 and 1. V d,i is the deposition rate of the nuclide i, and the deposition rate is related to the properties of the nuclide and the geographical environment; Δx is the resolution size of the geographical grid.

[0046] The average wind speed is directly given by the field measurement wind speed, and the influence of the wind direction does not have to be considered.

[0047] The average wind speed, grid size, and evaluation geographical range will not affect the ranking of the hazard of the nuclide.

[0048] On the basis of the Gaussian plume model, considering the influence of radioactive decay and deposition, a two-dimensional atmospheric diffusion model of radionuclides under the influence of multiple factors is established, which can calculate the aerosol concentration of each nuclide at different positions in space. The radionuclide information matrix and the spatial information matrix are input into the improved two-dimensional Gaussian plume model, so as to solve the air concentration of each nuclide at each grid, and the model is:

[0049]

[0050] Wherein, C a,i,k is the concentration of the i-th nuclide at the k-th geographical grid, y k， z kQkis the kth spatial grid coordinate i Aikis the environmental release activity of the ith nuclide, f r,i,k Aikis the decay factor of the ith nuclide in the kth geographical grid, f d,i,k Aikis the deposition factor of the ith nuclide in the kth geographical grid, σ y,k Aikis the horizontal dispersion parameter of the kth geographical grid, σ z,k Aikis the vertical dispersion parameter of the kth geographical grid, Aikis the average wind speed of all geographical grids, Δh is the radioactive plume lifting height, H is the height of the release source.

[0051] Δh and H are directly and quickly given according to field measurement, saving time.

[0052] Δh and H do not affect the ranking of nuclide hazard.

[0053] The air immersion ineffective dose is calculated:

[0054] D a,i,k = C a,i,k · DCF a,i

[0055] where D a,i,k ikis the air immersion ineffective dose caused by the ith nuclide in the kth grid, DCF a,i ikis the air immersion dose conversion factor of the ith nuclide.

[0056] The ground deposition concentration of each nuclide in each geographical grid is calculated using the ground deposition module:

[0057] D g,i,k = C a,i,k (1-f d,i,k )· DCF g,i

[0058] where D g,i,k ikis the ground deposition effective dose caused by the ith nuclide in the kth grid, DCF g,i ikis the ground deposition dose conversion factor of the ith nuclide.

[0059] The effective dose of each nuclide in each geographical grid is calculated using the dose conversion module;

[0060] D in,i,k = C a,i,k · DCF in,i · B in

[0061] where D in,i,k ikis the inhaled internal irradiation effective dose caused by the ith nuclide in the kth grid, DCF in,iThe inhaled internal radiation dose conversion factor of the i-th nuclide, B in The human respiratory rate, constant.

[0062] Solve the effective dose, which is the sum of the air immersion effective dose, the ground deposition effective dose and the inhalation effective dose:

[0063] D i,k = D a,i,k + D g,i,k + D in,i,k

[0064] Where D i,k is the whole body effective dose of nuclide i caused by the k-th grid.

[0065] S300: According to the two-dimensional atmospheric diffusion model of the radioactive nuclide, the total effective dose of each nuclide in a certain range is calculated;

[0066] Extract the effective dose D i,k of each nuclide in each geographical grid;

[0067] The effective dose of all geographical grids of this nuclide is accumulated as the total effective dose of the nuclide, and the calculation model is:

[0068]

[0069] Where D i is the total effective dose of the i-th nuclide, D i,k is the effective dose of the i-th nuclide in the k-th grid, and K is the total number of all grids.

[0070] S400: According to the total effective dose of each nuclide, determine the ranking of the harm of each nuclide, and calculate the harm influence proportion of each nuclide, including:

[0071] Extract the total effective dose of each nuclide, which must be greater than 0;

[0072] According to the total effective dose D i of each nuclide, sort according to the size relationship, the larger D i , the higher the ranking of nuclide i, the greater the harm to people and the environment.

[0073] The total effective dose of all nuclides is accumulated to get the total effective dose of the radiation field as the total harm of radioactivity;

[0074] Divide the total effective dose of each nuclide by the total effective dose of the radiation field as the harm influence proportion of each nuclide, the model is:

[0075]

[0076] η i is the proportion of the total hazard of the radiation field, N is the total number of the nuclides;

[0077] The nuclides can also be ranked according to the proportion of the hazard impact, and the result is the same as the ranking of the total effective dose of the nuclides.

[0078] S500: According to the hazard ranking and the proportion of the hazard impact, the suitable nuclide type and quantity are quickly screened.

[0079] The required nuclide quantity S' is determined, or the radiation field accuracy R is determined;

[0080] Method 1: The nuclides ranked in the top S' are directly selected;

[0081] Method 2: The sum of the hazard impact proportions is determined, and then the hazard ranking and the impact proportion of each nuclide are reversely positioned to select the required nuclide type and quantity. If the sum of the hazard impact proportions of the top S nuclides is greater than the pre-set radiation field accuracy, the S nuclides are determined. The model is

[0082]

[0083] Wherein, R is the radiation field accuracy, j is the ranking, and S is the number of screened nuclides. If the sum of the impact proportions of the top S nuclides is greater than R, the required nuclide type and quantity are screened.

[0084] The three-dimensional model in the prior art calculates more than 50 nuclides, and the simulation time of a single server is about 4 hours. After screening according to the present disclosure, only 10 nuclides need to be calculated (the accuracy is more than 90% of the original), and the calculation can be completed in less than 1 hour.

[0085] The technical solutions described above are only exemplary embodiments of the present application. For those skilled in the art, on the basis of the application disclosed herein, various types of improvements or modifications can be easily made without being limited to the methods described in the above embodiments. Therefore, the above-described methods are only preferred and not limited.

Claims

1. A method for ranking the hazard of radionuclides, comprising the following steps: S1: Construct a nuclide information matrix and a spatial geographic grid information matrix for radioactive accidents; S2: Establish a two-dimensional atmospheric diffusion model of radionuclides under the influence of multiple factors, and calculate the effective dose of each nuclide to the whole human body in each geographic grid. S3: Calculate the total effective radioactive dose of each nuclide within a specific range; S4: Rank the hazard of each nuclide based on the total effective dose of each nuclide; Step S1 includes: Obtain initial source term information for a radioactive accident; Construct a nuclide information matrix, including the name of each nuclide, total environmental release activity, half-life, deposition rate, air immersion dose conversion factor, ground deposition dose conversion factor, and inhaled internal radiation dose conversion factor: in, ST The nuclide information matrix name is NUC, where NUC is the nuclide name. Q The activity of the nuclide. T 1 / 2 The half-life of a radioactive nuclide. V d The deposition rate of the nuclide, DCF a The air immersion concentration dose conversion factor for the radionuclide. DCF g For ground deposition dose conversion factor, DCF in Inhalation dose conversion factor; subscripts 1, 2, ... N The numbers represent the nuclide numbers, respectively. N This represents the total number of nuclides initially acquired; Centered on the release source, the spatial range to be predicted is divided into a regular two-dimensional geographic grid; Based on the geographic grid, call the diffusion parameter calculation function to calculate the horizontal and vertical diffusion parameters; Construct a spatial geographic grid information matrix, including the x-coordinate, y-coordinate, horizontal diffusion parameter, and vertical diffusion parameter corresponding to each geographic grid: in, x Let x be the x-coordinate of the grid points within the region to be evaluated. y The vertical axis is , For horizontal diffusion parameters, These are vertical diffusion parameters, subscripts 1, 2, ... K These represent the geographic grid arrangement identifiers. K Total number of grid cells; Step S2 includes: Set the forecast time range; The decay factor of each nuclide at each grid was calculated using a decay factor calculation model. The deposition factor of each nuclide at each grid was calculated using a deposition factor calculation model. Based on the radioactive plume model, the air concentration of each nuclide at each grid point is calculated, wherein the radioactive plume model includes: in, For the first i Nuclide in the k Concentration at each geographic grid y k、 z k The first k The vertical and vertical coordinates of each geographic grid. For the first i Environmental release activity of the nuclide For the first i Nuclide in the k Decay factor of a geographic grid For the first i Nuclide in the k Sedimentation factors of a geographic grid For the first k Horizontal diffusion parameters of a geographic grid For the first k Vertical diffusion parameters of a geographic grid The average wind speed across all geographic grids. The height at which the radioactive plume rises. H To release the height of the source; Calculate the ineffective dose of air immersion: in For the first i Nuclide in the k The air immersion caused by a geographic grid has no effective dose. For the first i Air immersion dose conversion factor for a particular nuclide; Calculate the surface sediment concentration: in, For the first i Nuclide in the k The effective dose of ground deposition caused by a geographic grid For the first i Ground deposition dose conversion factor for a particular nuclide; Calculate the inhaled internal radiation dose; in For the first i Nuclide in the k The effective dose of inhaled internal radiation caused by each geographic grid For the first i Inhalation internal radiation dose conversion factor of a certain nuclide Human respiratory rate; Calculate the effective whole-body dose for each nuclide in each geographic grid: in, For the first i Nuclide in the k The effective dose to the whole human body caused by a geographic grid; Step S4 includes: Based on the total effective dose of each nuclide Sort according to size. The larger the size, the more nuclide it contains. i The higher the ranking of the harmfulness of a substance, the greater its harm to people and the environment. Alternatively, the total effective dose of radioactivity of all nuclides can be summed to obtain the total effective dose of the radiation field. The total effective dose of radioactivity of each nuclide can be divided by the total effective dose of the radiation field to obtain the proportion of hazard impact of each nuclide. Nuclides are then ranked according to the size of their proportion of hazard impact. The calculation model for the proportion of hazard impact includes: nuclide i The proportion of radiation hazards in the total radiation field hazards. N The total number of nuclides; It also includes the following steps: S5: Based on the hazard ranking, quickly screen the appropriate types and quantities of nuclides; Step S5 includes: Select the required nuclides directly based on their hazard level. Alternatively, based on a pre-set radiation field accuracy, select nuclides whose sum of the proportions of the first few types of hazards meets the radiation field accuracy requirements.

2. The sorting method according to claim 1, characterized in that, Step S3 specifically includes: Effective doses of each nuclide in each geographic grid By summing the results, the total effective radioactive dose of the nuclide is obtained: in, For the first i The total effective dose of the radionuclides, For the first i Nuclide in the k The effective dose of each grid, K is the total number of all grids.

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