Nuclear accident external irradiation dose field calculation method based on limited smoke cloud model and computer readable storage medium

Abstract

The invention discloses a nuclear accident external irradiation dose field calculation method based on a limited smoke cloud model and a computer readable storage medium, and solves the technical problems of poor matching performance, relatively long calculation time, relatively low efficiency and the like in the prior art. The method comprises the following steps: firstly, acquiring a radionuclide source item file released by a nuclear accident and corresponding original data; calculating to obtain a source item nuclide information data matrix; according to the gamma ray energy of each nuclide, calculating to obtain a gamma ray linear attenuation coefficient and an air energy mass absorption coefficient of each nuclide; calculating to obtain the grid number and the grid number of each grid penetrated by gamma rays of other grids in the smoke cloud activity concentration field and the ground deposition activity field; finally, the deposition external irradiation dose and the smoke cloud external irradiation dose of each grid are obtained through calculation, and therefore nuclear accident external irradiation dose field calculation is completed. According to the method, automatic and refined calculation of the external irradiation dose during the nuclear accident can be realized, and the calculation efficiency is relatively high.

Description

Technical Field

[0001] The invention relates to a nuclear accident consequence assessment method, and in particular to a nuclear accident external radiation dose field calculation method based on a finite smoke cloud model and a computer-readable storage medium. Background Art

[0002] Although the safety of nuclear energy utilization is very high, the risk of nuclear accidents still exists. When a nuclear accident occurs, airborne radioactive materials will move with the atmosphere and diffuse into the environment, and eventually act on people and the environment through the ionizing radiation effect of high-energy rays. In order to deal with possible nuclear accidents, many countries have developed nuclear accident consequence assessment and emergency decision-making support systems. Their external exposure dose models generally use semi-infinite smoke cloud models or use the list method for rapid calculation. However, the semi-infinite smoke cloud model does not take into account the uneven distribution characteristics of body sources and the influence of topography. Under weather conditions that are not conducive to diffusion and within a few kilometers from the release point, its calculation results differ several times from the values ​​derived by more rigorous calculation methods. In addition, for some radioactive fallout prediction models, the activity values ​​of radionuclides attached to particles are converted into dose fields through spatial integration, and then the K factor is directly introduced to calculate the dose field distribution. The K factor is the dose rate value formed by a radioactive source with a certain geometric distribution at a specific location, which can be considered as the superposition of the dose rate values ​​of multiple point sources at that location.

[0003] On this basis, more accurate finite cloud models have been developed, such as the photon "range" method, discrete point approximation method, and graphical method. For example, Wang Xingyu, Shi Zhongqi, et al. published "A method for calculating external radiation dose in finite cloud - photon "range" method [J]. Radiation Protection, 2001. (02)", which disclosed the principle of a finite cloud model and divided the cloud around the irradiated person within a range of 5 times the mean free path of photons in the air into some volume elements to calculate the external radiation dose, but did not disclose the specific calculation method, and it is also unknown how to obtain the core parameters required for the calculation.

[0004] Chen Xiaoqiu et al. published a paper titled "Comparison of graphical method and discrete point approximation method for estimating external exposure doses caused by limited clouds of gamma-radioactive nuclides in atmospheric emissions [J]. Radiation Protection, 1993. (05)", which disclosed a simpler manual fast calculation method, but this method is poorly compatible with current computer models.

[0005] Li Xinpeng et al. published "Research on Radiation Risk Prediction of Airborne Radionuclides under Nuclear Accidents [M]. Beijing: Tsinghua University Press, first edition in February 2023", which proposed a fast calculation method for non-equidistant three-dimensional dose field based on NFFT, but this method only optimized the integral calculation process and listed the calculation results of one of the nuclides. However, nuclear accidents take various forms and release a wide variety of radionuclides. After the concentration field and precipitation field are calculated by the atmospheric diffusion program, it is also necessary to connect and calculate the external radiation dose field of all grids. It can be seen from this that if this calculation method is used to obtain the calculation results of all nuclides, the calculation time is long and the calculation efficiency is low. Summary of the invention

[0006] The purpose of the present invention is to solve the technical problems that the existing calculation methods are poorly compatible with computer models, or the calculation time is long and the efficiency is low, and to provide a method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model and a computer-readable storage medium.

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

[0008] A method for calculating external radiation dose field of nuclear accident based on finite smoke cloud model is characterized in that it comprises the following steps:

[0009] 【1】 Obtain the radionuclide source item files, smoke cloud activity concentration field and ground deposition activity field files released by the nuclear accident and their corresponding grid numbers and spatial distance size data of each grid;

[0010] [2] Extract the nuclide type and activity data of each nuclide from the radioactive nuclide source term file, and then read the source term nuclide information data matrix of the corresponding nuclide type from the pre-made nuclide database; the source term nuclide information data matrix includes the nuclide name, the gamma ray energy of each nuclide and the corresponding yield and activity;

[0011] 【3】, according to the gamma ray energy of each nuclide, calculate the gamma ray linear attenuation coefficient and air energy mass absorption coefficient of each nuclide, and add them to the source nuclide information data matrix obtained in step 【2】;

[0012] 【4】 Based on the smoke cloud activity concentration field and ground deposition activity field files and their corresponding grid numbers and spatial distance dimension data of each grid, calculate the number of grids and grid points in the smoke cloud activity concentration field and ground deposition activity field that are penetrated by the gamma rays of other grids;

[0013] 【5】Based on the source nuclide information data matrix obtained in step 【3】, combined with the number of grids and grid points obtained in step 【4】, all grids in the smoke cloud activity concentration field are traversed, and the deposited external radiation dose and smoke cloud external radiation dose caused by each grid itself and other grids are calculated respectively, thereby completing the calculation of the nuclear accident external radiation dose field based on the finite smoke cloud model.

[0014] Furthermore, in step [3], the gamma-ray linear attenuation coefficient and air energy mass absorption coefficient of each nuclide are obtained by fitting the gamma-ray energy of the corresponding nuclide through a spline function.

[0015] Furthermore, step [4] is specifically as follows:

[0016] 4.1. Based on the smoke cloud activity concentration field and ground deposition activity field files, and the corresponding number of grids and the spatial distance size data of each grid, the number of grids in the smoke cloud activity concentration field and the ground deposition activity field that are penetrated by the gamma rays of other grids is calculated respectively; wherein, in any grid, the number of grids penetrated by the gamma rays in the x-axis direction is n x Calculated by the following formula:

[0017] n x =fix(1000 / Δx)+1

[0018] In the formula, fix is ​​the rounding operation, Δx is the distance size of any grid in the x-axis direction;

[0019] The number of grids penetrated by gamma rays in the y-axis direction n y Calculated by the following formula:

[0020] n y =fix(1000 / Δy)+1

[0021] Where Δy is the distance dimension of any grid in the y-axis direction;

[0022] The number of gamma rays penetrating the grid in the z-axis direction is related to the uniformity of the grid height. When the grid height in the z-axis direction is uniform and unchanged, the number of gamma rays penetrating the grid in the positive direction of the z-axis direction is n. z1 :

[0023] n z1 =fix(1000 / Δz)+1

[0024] Where Δz is the distance dimension of any grid in the z-axis direction;

[0025] The number of grids penetrated by gamma rays in the negative z-axis direction n' z1 :

[0026]

[0027] In the formula, z n is the layer number of any grid in the z-axis direction, where the layer close to the ground is the first layer;

[0028] When the grid height in the z-axis direction changes with the atmospheric pressure, the number of grids penetrated by the positive gamma ray in the z-axis direction is n. z2 The expression of the layer number z of any grid in the z-axis direction n related:

[0029] n z2 =mz n

[0030] In the formula, m satisfies Indicates that the number of layers in the z-axis direction is z n The height of the grid layer; and the number of grids penetrated by the negative γ-ray in the z-axis direction is n′ z2 The expression is:

[0031]

[0032] 4.2. Based on step 4.1, the number of grid points of any grid is obtained;

[0033] The number of grid points m on the x-axis in any grid x For: m x =2n x +1;

[0034] The number of grid points on the y-axis is m y For: m y =2n y +1;

[0035] When the grid height along the z-axis is uniform and constant, the number of grid points along the z-axis is m. z1 It is expressed as:

[0036] m z1 =n′ z1 +n z1 ;

[0037] When the grid height in the z-axis direction changes with the atmospheric pressure, the number of grid points in the z-axis m z2 It is expressed as:

[0038] m z2 =n′ z2 +n z2 .

[0039] Furthermore, in step [5], after calculating the number of grids and grid points of any grid that are penetrated by gamma rays from other grids, it also includes calculating the external radiation dose contribution of all gamma rays in each nuclide separately by parallel calculation, and discarding the gamma rays in each nuclide whose total external radiation dose contribution is less than 1% by automatically cutting off the error.

[0040] Furthermore, in step [5], the calculation formula for the deposited external radiation dose is:

[0041]

[0042] Where D1 is the dose rate at the center height z0 of any grid; f is the energy unit conversion coefficient; μ a is the air energy mass absorption coefficient of the kth γ-ray produced by the nuclide decay; q is the radioactivity; E k and FE k are the energy and corresponding yield of the kth γ-ray produced by the decay of the nuclide; μ is the linear attenuation coefficient of the kth γ-ray produced by the decay of the nuclide; B(μr)=1+kμr, where k=(μ-μ a ) / μ a , S is the surface space of the ground deposition source; r is the distance between each point on the surface of the ground deposition source and the height z0 of the center of any grid. At this time,

[0043] Furthermore, in step [5], the calculation formula for the smoke cloud external radiation dose is:

[0044]

[0045] Where D2 is the dose rate at the center height z0 of any grid; V is the source volume space; r2 is the distance between each point on the source volume space and the center height z0 of any grid. At this time,

[0046] In addition, the present invention also provides a computer-readable storage medium on which a computer program or instruction is stored. The special feature of the present invention is that when the computer program or instruction is executed by a processor, the steps of the method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model are implemented.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. The present invention first obtains the source item nuclide information data matrix based on the radioactive nuclide source item file and the pre-made nuclide database; then calculates the γ-ray linear attenuation coefficient and the air energy mass absorption coefficient of each nuclide, and adds them to the source item nuclide information data matrix; then calculates the number of grids and grid points of all grids in the smoke cloud activity concentration field and the ground deposition activity field that are penetrated by the γ-rays of other grids; finally, calculates the deposition external radiation dose and smoke cloud external radiation dose caused by each grid itself and other grids, thereby completing the calculation of the external radiation dose field of nuclear accidents based on the finite smoke cloud model. This method can realize the automatic and refined calculation of the external radiation dose in nuclear accidents, and the calculation time is short and the calculation efficiency is high.

[0049] 2. The present invention can be applied to computer-readable storage media, has a high degree of compatibility with current computer models, and further improves computing efficiency.

[0050] 3. Based on the deposition external radiation dose and the smoke cloud external radiation dose calculated by the present invention, the total external radiation dose can be obtained by adding the two together, and the two can also be compared with the corresponding activity data respectively. Therefore, the application of the data is more flexible and extensive.

[0051] 4. The present invention can be used to solve the problem of the refined calculation process of the dose field formed by multiple nuclides in grids with different distances. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a flow chart of an embodiment of the present invention.

[0053] Figure 2 It is a diagram of the smoke cloud activity concentration data structure in an embodiment of the present invention.

[0054] Figure 3 It is a diagram of the structure of ground deposition activity data in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] 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.

[0056] Semi-infinite smoke cloud computing dose field calculation is commonly used in traditional nuclear accident consequence assessment systems. Even if a finite smoke cloud model is used, there is no specific calculation process. In addition, nuclear accidents take various forms, and many types of radionuclides are released. After the concentration field and even the precipitation field are calculated through the atmospheric diffusion program, it is necessary to connect and calculate the external radiation dose field of all grids. Based on this, the present invention designs an automatic calculation process for the dose field formed by a large number of grids with different distances and multiple nuclides, so that the external radiation dose in the event of a nuclear accident can be automatically and finely calculated. The calculation method can reduce the calculation time and improve the calculation efficiency.

[0057] like Figure 1 As shown, this embodiment provides a method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model, comprising the following steps:

[0058] [1] Obtain the radionuclide source item file released by the nuclear accident, the smoke cloud activity concentration field data file and the ground deposition activity field data file, as well as the corresponding grid number and the spatial distance size data of each grid. Figure 2 is the three-dimensional space activity concentration data structure, Figure 3 Two-dimensional spatial surface sediment activity data structure.

[0059] [2] Extract the nuclide type and activity data of each nuclide from the radioactive nuclide source term file, and then read the source term nuclide information data matrix of the corresponding nuclide type from the pre-made nuclide database. The source term nuclide information data matrix includes the nuclide name, the gamma ray energy (MeV) of each nuclide and the corresponding yield and activity.

[0060] The nuclide database is a pre-made nuclide information database, which mainly contains common nuclide names, all gamma ray energies (MeV) produced by decay, and corresponding yields, half-lives and other information.

[0061] 【3】 According to the gamma-ray energy of each nuclide, the gamma-ray linear attenuation coefficient and air energy mass absorption coefficient of each nuclide are calculated and added to the source nuclide information data matrix obtained in step 【2】.

[0062] In this embodiment, the linear attenuation coefficient of gamma rays and the air energy mass absorption coefficient of each nuclide are obtained by fitting the gamma rays of the corresponding nuclide through a spline function.

[0063] 【4】 Calculate the number of grids and grid points in the smoke cloud activity concentration field and ground deposition activity field that are penetrated by gamma rays from other grids.

[0064] In this embodiment, when calculating the dose of a certain grid, the contribution of the rays that can reach the grid in other surrounding grids is taken into account. In particular, when calculating the external irradiation dose of the aerial grid, the contribution of the radionuclides deposited on the ground is taken into account. Specifically,

[0065] 4.1. Based on the smoke cloud activity concentration field and ground deposition activity field files, and their corresponding grid numbers and spatial distance size data of each grid, calculate the number of grids in the smoke cloud activity concentration field and ground deposition activity field that are penetrated by the gamma rays of other grids; among which, the number of grids in any grid that are penetrated by the gamma rays in the x-axis direction is n x Calculated by the following formula:

[0066] n x =fix(1000 / Δx)+1

[0067] Where fix is ​​the rounding operation, and Δx is the distance size of any grid in the x-axis direction.

[0068] The number of grids that gamma rays penetrate in the y-axis direction n y Calculated by the following formula:

[0069] n y =fix(1000 / Δy)+1

[0070] Where Δy is the distance dimension of any grid in the y-axis direction.

[0071] The number of gamma rays penetrating the grid in the z-axis direction is related to the uniformity of the grid height, and is divided into the number of gamma rays penetrating the grid in the positive z-axis direction and the number of gamma rays penetrating the grid in the negative z-axis direction. When the grid height in the z-axis direction is uniform and unchanged, the number of gamma rays penetrating the grid in the positive z-axis direction (upward) is n. z1 :

[0072] n z1 =fix(1000 / Δz)+1

[0073] Where Δz is the distance between grid points in the z-axis direction.

[0074] The number of grids penetrated by gamma rays in the negative (downward) z-axis direction n' z1 :

[0075]

[0076] In the formula, z n It is the layer number of the grid point in the z-axis direction (the first layer is close to the ground).

[0077] When the grid height in the z-axis direction changes with the atmospheric pressure, the number of grids penetrated by the positive (upward) gamma rays in the z-axis direction is n. z2 The expression of the grid point in the z-axis direction is related to the layer number z n related:

[0078] n z2 =mz n

[0079] In the formula, m satisfies The layer number in the z-axis direction is z n The height of the grid layer.

[0080] At the same time, the number of gamma rays penetrating the grid in the negative (downward) z-axis direction is n' z2 The expression is:

[0081]

[0082] 4.2. Based on step 4.1, the number of grid points of any grid is obtained, that is, the number of grid points m on the x-axis of any grid x For: m x =2n x +1

[0083] The number of grid points on the y-axis is m y For: m y =2n y +1;

[0084] When the grid height of the z-axis is uniform and constant, the number of grid points on the z-axis is m. z1 :

[0085] m z1 =n' z1 +n z1 ;

[0086] When the grid height of the z-axis changes with the atmospheric pressure, the number of grid points m on the z-axis z2 :

[0087] m z2 =n′ z2 +n z2 .

[0088] 【5】Based on the source nuclide information data matrix obtained in step 【3】, combined with the number of grids and grid points calculated in step 【4】, all grids in the smoke cloud activity concentration field are traversed to calculate the deposited external radiation dose and smoke cloud external radiation dose caused by each grid itself and other grid points, thereby completing the calculation of the nuclear accident external radiation dose field based on the finite smoke cloud model.

[0089] The traversal method of this embodiment is:

[0090] ① First traverse the z-axis direction. When the height of the grid in the z-axis direction is uniform and unchanged, start from the first layer on the ground. When the number of grid layers in the z-axis direction is less than or equal to the number of grids penetrated by the positive (upward) gamma ray in the z-axis direction, nz1 When the grid layer number in the z-axis direction is greater than the grid number n, the calculation of the exposure dose of this layer of grids takes into account the contribution of external exposure caused by ground deposition activity and the contribution of external exposure caused by smoke cloud activity at each height layer around. z1 When , only the contribution of external irradiation caused by smoke activity in the surrounding altitude layers is considered; in both cases, the total number of grid points affected by the γ-rays in the z-axis direction is m z1 When the grid height in the z-axis direction changes with the atmospheric pressure, starting from the first layer on the ground, when the grid layer number in the z-axis direction is less than or equal to the number of gamma rays penetrating the grid in the positive (upward) direction of the z-axis, n z2 When the grid layer number in the z-axis direction is greater than the grid number n, the calculation of the exposure dose of this layer of grids takes into account the contribution of external exposure caused by ground deposition activity and the contribution of external exposure caused by smoke cloud activity at each height layer around. z2 When , only the contribution of external irradiation caused by smoke activity in the surrounding altitude layers is considered; in both cases, the total number of grid points affected by the γ-rays in the z-axis direction is m z2 .

[0091] ② In each z-axis height layer, starting from the leftmost layer in the x-axis direction, the number of grids affected by the gamma rays in the x-axis direction is n x , the number of grids affected by the gamma rays in the y-axis direction is n y For each horizontal grid (x, y) of the radiation dose, consider the horizontal symmetry of the x-axis n x grids, that is, the number of grid points traversed in the horizontal direction of the x-axis is m x , considering the symmetry of the y-axis horizontal direction y grids, that is, the number of grid points traversed in the horizontal direction of the y-axis is m y , calculate the external irradiation contribution of the gamma rays of these grid points to the smoke cloud and ground deposition formed by each horizontal grid (x, y) one by one. When the grid (x, y) is at the edge of the space and there is no symmetric grid, the non-existent symmetric grid is directly set to zero.

[0092] Since there are many types of nuclides released in nuclear accidents, each nuclide has different quantities and energies of gamma rays. Therefore, the number of all rays remaining after discarding the rays with a total contribution of less than 1% is taken as the total amount for calculation. Specifically, after calculating the number of grids and grid points of all grids penetrated by gamma rays from other grids, the grid is regarded as a body source. For the external radiation dose contribution of all gamma rays in each nuclide in the grid body source, parallel calculation is used, and the gamma rays with a total external radiation dose contribution of less than 1% in each nuclide are discarded by automatically cutting off the error.

[0093] This example uses the dosage calculation formula:

[0094]

[0095] D is the dose rate, Gy / s; f is the energy unit conversion factor 1.6×10 -13 , J / MeV, μ a is the air energy mass absorption coefficient of the kth γ-ray produced by the nuclide decay, m 2 / kg; q is the radioactivity, Bq; E k and FE k are the energy (MeV) and the corresponding yield of the kth γ-ray produced by the decay of the nuclide; μ is the linear attenuation coefficient of the kth γ-ray produced by the decay of the nuclide, 1 / m; B(μr)=1+kμr, and k=(μ-μ a ) / μ a , r is the distance between each point in space and the center height z0 of the calculation grid point, m; when calculating the external radiation dose of smoke clouds, V is the source volume space, and when calculating the external radiation dose of ground deposition, V is the source surface space, and the triple integral is reduced to a double integral.

[0096] The above-mentioned automatic truncation error method is specifically to convert the coefficient μ of each γ ray in each nuclide into a ·q·E k ·FE k A combination is made, that is, the product of the mass absorption coefficient, activity, energy and their corresponding yield, and this combination of all nuclides is used as the basis for size arrangement. The contribution of error cutoff to the calculation efficiency is analyzed, and rays with a total contribution of less than 1% are discarded.

[0097] As described above, in this embodiment, the calculation formula for the deposition external radiation dose of each nuclide received by any grid is:

[0098]

[0099] Where D1 is the dose rate at the height z0 of the center of any grid (related to the position of the grid and its z-axis spatial distance); S is the surface space of the ground deposition source, r is the distance between each point on the ground deposition source surface and the height z0 of the center of any grid. At this time,

[0100] The calculation formula for the external radiation dose of smoke cloud for each nuclide in any grid is:

[0101]

[0102] Where D2 is the dose rate at the center height z0 of any grid; V is the source volume space; r is the distance between each point on the source volume space and the center height z0 of any grid. At this time,

[0103] After the calculation of the external radiation dose field of nuclear accidents based on the finite smoke cloud model is completed, the smoke cloud external radiation dose field data and the ground deposition external radiation dose field data are output. The file format of the data is the same as the smoke cloud activity concentration field data structure and file format. Figure 2 or Figure 3 The data structure shown is output to facilitate the subsequent process to display the external radiation dose generated by the smoke cloud and the external radiation dose deposited on the ground. The total external radiation dose can be obtained by adding the two external radiation doses, or it can be compared with the corresponding activity data.

[0104] The present invention reads the type of nuclide and its activity from the source term file, produces the source term nuclide information data for dose calculation, and uses fitting calculation to obtain the mass absorption coefficient and line absorption coefficient of gamma rays used for dose calculation, which is suitable for calculation of dose consequences of nuclear contamination diffusion in different scenarios. In addition, based on the present invention, a large number of automatic calculation processes for dose fields formed by multiple nuclides in grids with different distances can be designed, so that the external irradiation dose in nuclear accidents can be automatically and finely calculated, the calculation time is greatly shortened, and the calculation efficiency is significantly improved.

[0105] This embodiment also provides a computer-readable storage medium on which a computer program or instruction is stored. When the computer program or instruction is executed by a processor, the steps of the method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model described in this embodiment are implemented.

[0106] 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 calculating external radiation dose field of nuclear accidents based on a finite smoke cloud model, characterized in that: The following steps are involved: 【1】 Obtain the radionuclide source item files, smoke cloud activity concentration field and ground deposition activity field files released by the nuclear accident and their corresponding grid numbers and spatial distance size data of each grid; [2] Extract the nuclide type and activity data of each nuclide from the radioactive nuclide source term file, and then read the source term nuclide information data matrix of the corresponding nuclide type from the pre-made nuclide database; the source term nuclide information data matrix includes the nuclide name, the gamma ray energy of each nuclide and the corresponding yield and activity; 【3】, according to the gamma ray energy of each nuclide, calculate the gamma ray linear attenuation coefficient and air energy mass absorption coefficient of each nuclide, and add them to the source nuclide information data matrix obtained in step 【2】; 【4】 Based on the smoke cloud activity concentration field and ground deposition activity field files and their corresponding grid numbers and spatial distance dimension data of each grid, calculate the number of grids and grid points in the smoke cloud activity concentration field and ground deposition activity field that are penetrated by the gamma rays of other grids; 【5】Based on the source nuclide information data matrix obtained in step 【3】, combined with the number of grids and grid points obtained in step 【4】, all grids in the smoke cloud activity concentration field are traversed, and the deposited external radiation dose and smoke cloud external radiation dose caused by each grid itself and other grids are calculated respectively, thereby completing the calculation of the nuclear accident external radiation dose field based on the finite smoke cloud model.

2. The method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model according to claim 1 is characterized in that: In step [3], the gamma-ray linear attenuation coefficient and air energy mass absorption coefficient of each nuclide are obtained by fitting the gamma-ray energy of the corresponding nuclide through a spline function.

3. The method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model according to claim 1 is characterized in that: Step [4] is as follows: 4.

1. Based on the smoke cloud activity concentration field and ground deposition activity field files, and the corresponding number of grids and the spatial distance size data of each grid, the number of grids in the smoke cloud activity concentration field and the ground deposition activity field that are penetrated by the gamma rays of other grids is calculated respectively; wherein, in any grid, the number of grids penetrated by the gamma rays in the x-axis direction is n x Calculated by the following formula: n x =fix(1000 / Δx)+1 In the formula, fix is ​​the rounding operation, Δx is the distance size of any grid in the x-axis direction; The number of grids penetrated by gamma rays in the y-axis direction n y Calculated by the following formula: n y =fix(1000 / Δy)+1 Where Δy is the distance dimension of any grid in the y-axis direction; The number of gamma rays penetrating the grid in the z-axis direction is related to the uniformity of the grid height. When the grid height in the z-axis direction is uniform and unchanged, the number of gamma rays penetrating the grid in the positive direction of the z-axis direction is n. z1 : n z1 =fix(1000 / Δz)+1 Where Δz is the distance dimension of any grid in the z-axis direction; The number of grids penetrated by gamma rays in the negative z-axis direction n' z1 : In the formula, z n is the layer number of any grid in the z-axis direction, where the layer close to the ground is the first layer; When the grid height in the z-axis direction changes with the atmospheric pressure, the number of grids penetrated by the positive gamma ray in the z-axis direction is n. z2 The expression of the layer number z of any grid in the z-axis direction n Relevant, namely: n z2 =m-z n In the formula, m satisfies Δz zn Indicates that the number of layers in the z-axis direction is z n The height of the grid layer; and the number of grids penetrated by the negative γ-ray in the z-axis direction is n' z2 The expression is: 4.

2. Based on step 4.1, the number of grid points of any grid is obtained; The number of grid points m on the x-axis in any grid x For: m x =2n x +1; The number of grid points on the y-axis is m y For: m y =2n y +1; When the grid height along the z-axis is uniform and constant, the number of grid points along the z-axis is m. z1 It is expressed as: m z1 =n z1 +n z1 ; When the grid height in the z-axis direction changes with the atmospheric pressure, the number of grid points in the z-axis m z2 It is expressed as: m z2 =n' z2 +n z2 。 4. The method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model according to claim 1 is characterized in that: In step [4], after calculating the number of grids and grid points of any grid that are penetrated by gamma rays from other grids, it also includes the step of calculating the external radiation dose contribution of all gamma rays in each nuclide separately by parallel calculation, and discarding the gamma rays in each nuclide whose total external radiation dose contribution is less than 1% by automatically cutting off the error.

5. The method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model according to claim 4 is characterized in that: In step [5], the calculation formula for the deposited external radiation dose is: Where D1 is the dose rate at the center height z0 of any grid; f is the energy unit conversion coefficient; μ a is the air energy mass absorption coefficient of the kth γ-ray produced by the nuclide decay; q is the radioactivity; E k and FE k are the energy and corresponding yield of the kth γ-ray produced by the decay of the nuclide; μ is the linear attenuation coefficient of the kth γ-ray produced by the decay of the nuclide; B(μr)=1+kμr, where k=(μ-μ a ) / μ a , S is the surface space of the ground deposition source; r is the distance between each point on the surface of the ground deposition source and the height z0 of the center of any grid. At this time, 6. The method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model according to claim 5 is characterized in that: In step [5], the calculation formula for the smoke cloud external radiation dose is: Where D2 is the dose rate at the center height z0 of any grid; V is the source volume space; r is the distance between each point on the source volume space and the center height z0 of any grid. At this time, 7. A computer-readable storage medium having a computer program or instruction stored thereon, characterized in that: When the computer program or instruction is executed by a processor, the steps of the method for calculating the external radiation dose field of a nuclear accident based on a finite smoke cloud model as described in any one of claims 1 to 6 are implemented.

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