A method for quickly obtaining the source height corresponding to the maximum value of the near-ground point source radiation environment parameters

Abstract

The present invention provides a method for quickly obtaining the source height corresponding to the maximum value of near-ground point-source radiation environment parameters, which is used to solve the technical problem that there is no relevant research on the source height corresponding to the maximum value of radiation environment parameters at present. The method of the present invention is as follows: establish an atmospheric-ground interface point-source radiation transport model; determine the radiation source term parameters, the types of radiation environment parameters, and the ground medium parameters; select the measurement point height h and the projection distance R range; use the Monte Carlo calculation method for numerical simulation to generate a two-dimensional numerical table of radiation environment parameters under different source heights H and projection distances R; then obtain a series of R-Hmax data pairs, plot them to generate a two-dimensional curve graph; then perform data fitting on the two-dimensional curve graph to obtain the fitting relationship between Hmax and R when the fitting variance is the smallest; and then obtain the source height Hmax corresponding to the maximum value of radiation environment parameters within the set parameter range.

Description

Technical Field

[0001] The present invention belongs to the field of nuclear radiation, and particularly relates to a method for quickly obtaining the source height corresponding to the maximum value of near-surface point-source radiation environment parameters. Background Art

[0002] The prompt part source term in early nuclear radiation belongs to a strong radiation source, including a large number of neutrons and γ rays released in a very short time. These strong radiation sources are usually set as point sources. The radiation environment parameters generated during the transport of rays mainly include neutron fluence, neutron tissue dose, neutron silicon dose, neutron secondary γ fluence, neutron secondary γ tissue dose, neutron secondary γ silicon dose, γ fluence, γ tissue dose, γ silicon dose, etc. During the transport of rays, various reactions will occur with the medium, and the rays will continuously attenuate. The speed of ray attenuation is greatly related to the type of medium. If the medium is the atmosphere, due to the very small density of the atmosphere, the rays will transport a long distance in the atmosphere. If the medium is the ground (such as concrete, soil), due to the much higher density than the atmosphere, the rays will attenuate very quickly. The calculation of near-surface point-source radiation environment is a typical atmosphere-ground interface problem. The rays will transport in the atmosphere and ground media. In this problem, there is a source height corresponding to the maximum value of the radiation environment parameter. The calculation of this source height has important guiding significance for the nuclear radiation shielding of personnel and equipment. Traditional early nuclear radiation environment calculations did not conduct detailed research on this source height. Summary of the Invention

[0003] The purpose of the present invention is to solve the current technical problem that there is no relevant determination method for the source height corresponding to the maximum value of near-surface point-source radiation environment parameters, and to provide a method for quickly obtaining the source height corresponding to the maximum value of near-surface point-source radiation environment parameters.

[0004] To achieve the above purpose, the technical solution of the present invention is as follows:

[0005] A method for quickly obtaining the source height corresponding to the maximum value of near-surface point-source radiation environment parameters, characterized by including the following steps:

[0006] 1. Establish a point-source radiation transport model for the atmosphere-ground interface problem;

[0007] 2. Determine the radiation source term parameters; the radiation source term parameters include source type, energy spectrum, and emission direction;

[0008] 3. Determine the type of radiation environment parameters according to the source type;

[0009] 4. Determine the ground medium parameters;

[0010] 5. Select the measurement point height h and the range of the projection distance R; the projection distance R is the projection distance on the ground from the source to the measurement point;

[0011] The selectable range of the height h of the measurement point is: 0 ≤ h ≤ 10 m, and the selectable range of the projection distance R is 0 ≤ R ≤ 4 km;

[0012] 6] According to the atmospheric-ground boundary problem point source radiation transport model established in step 1] and the parameter ranges set in steps 2]-5], use the Monte Carlo calculation method for numerical simulation to generate a two-dimensional numerical table of radiation environment parameters under different source heights H and projection distances R;

[0013] 7] Conduct data search based on the two-dimensional numerical table generated in step 6] to find the source height H corresponding to the maximum environmental parameter for each projection distance R max , and obtain a series of R-H max data pairs;

[0014] 8] Plot a two-dimensional curve graph according to the R-H max data pairs obtained in step 7]; then perform data fitting on the two-dimensional curve graph to obtain the fitting relationship between H max and R when the fitting variance is the smallest;

[0015] 9] According to the fitting relationship between H max and R when the fitting variance is the smallest obtained in step 8], obtain the source height H corresponding to the maximum value of the radiation environment parameters within the parameter ranges set in steps 2]-5] max .

[0016] Further, in step 8], the data fitting of the two-dimensional curve graph is specifically:

[0017] Perform data fitting on the two-dimensional curve graph by means of linear fitting.

[0018] Further, in step 3], the determination of the types of radiation environment parameters according to the source type is specifically:

[0019] If the source type is a neutron source, the selectable radiation environment parameters include neutron fluence, neutron tissue dose, neutron silicon dose, neutron secondary γ fluence, neutron secondary γ tissue dose, and neutron secondary γ silicon dose; if the source type is a gamma source, the selectable radiation environment parameters include γ fluence, γ tissue dose, and γ silicon dose.

[0020] Advantages of the present invention:

[0021] 1. The method for quickly obtaining the source height corresponding to the maximum value of the near-surface point source radiation environment parameters provided by the present invention calculates the source height H of the maximum environmental parameter for the first time and provides a fast calculation method for nuclear radiation shielding of personnel and equipment, filling the gap in this aspect in the field of radiation shielding for the atmospheric-ground boundary problem. max It fills the gap in this area of the radiation shielding field for the atmospheric-ground boundary problem.

[0022] 2. A fast acquisition method for the source height corresponding to the maximum value of the near-ground point source radiation environment parameters provided by the present invention calculates a two-dimensional data table based on the Monte Carlo calculation method for data search and fitting. Since the numerical simulation by the Monte Carlo method can achieve high accuracy, the source height H corresponding to the maximum value of the radiation environment parameters obtained by the present invention max can also reach a relatively high accuracy in the results.

[0023] 3. A fast acquisition method for the source height corresponding to the maximum value of the near-ground point source radiation environment parameters provided by the present invention can effectively reduce the calculation time while having high calculation accuracy, so as to quickly give the source height H corresponding to the maximum value of the radiation environment parameters for any projection distance R under the set scenario conditions max . BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flowchart of a fast acquisition method for the source height corresponding to the maximum value of the near-ground point source radiation environment parameters of the present invention;

[0025] Figure 2 is the point source radiation transport model of the atmospheric-ground boundary problem established in step 1] of the present invention;

[0026] Figure 3 is the two-dimensional numerical table of the radiation environment parameters under different source heights H and projection distances R in the embodiment of the present invention; among them, Figure 3-1 is the two-dimensional numerical table of the radiation environment parameters under the conditions that the 31 groups of source heights H and projection distances R are 1, 3, 5, 10, 20, 40, 60, 80, 100, 150, 200 respectively, Figure 3-2 is the two-dimensional numerical table of the radiation environment parameters under the conditions that the 31 groups of source heights H and projection distances R are 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000 respectively;

[0027] Figure 4 is the R-H max two-dimensional curve graph and the schematic diagram of the fitting relationship in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To make the objectives, advantages and features of the present invention clearer, the following further details a fast acquisition method for the source height corresponding to the maximum value of the near-ground point source radiation environment parameters proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention, and the purpose is not to limit the protection scope of the present invention.

[0029] In this embodiment, taking the tissue dose field of a monoenergetic isotropic neutron source as an example, based on the simulation results of the Monte Carlo method, a data search and fitting method is used to give the maximum environmental parameter source height H corresponding to any projection distance R max .

[0030] As Figure 1 shown, a fast acquisition method for the source height corresponding to the maximum value of the near-surface point source radiation environment parameters proposed by the present invention specifically includes the following steps:

[0031] 1] Establish a point source radiation transport model for the atmosphere-ground interface problem as Figure 2 shown, where Figure 2 Source in it represents the source, Atmosphere represents the atmosphere, Groud represents the ground medium, and Detector represents the detector.

[0032] The atmospheric density is 1.225×10 -3 g / cm 3 . In the present invention, the atmosphere-ground interface problem refers to the transport of particles emitted by the radiation source in the near-surface atmosphere (source height within 2 km). After the particles enter the ground medium from the atmosphere, they will be scattered and absorbed by the ground medium. Some particles will be reflected by the ground medium and re-enter the atmosphere, and some particles cannot enter the atmosphere again due to being absorbed by the ground medium, thus affecting the particle count and energy spectrum distribution in the near-surface atmosphere.

[0033] 2] Determine the radiation source term parameters

[0034] The radiation source term parameters include the source type, energy spectrum, and emission direction, including the source type; among them, the source type is neutron or gamma, the energy spectrum is monoenergetic or distributed source, and the emission direction is isotropic. In this embodiment, the radiation source term is a monoenergetic isotropic neutron source, the neutron energy is 1 MeV, and the total number of simulated neutrons is 10 20 pieces.

[0035] 3] Determine the types of radiation environment parameters according to the source type

[0036] If the source type is a neutron source, the selectable radiation environment parameters mainly include neutron fluence, neutron tissue dose, neutron silicon dose, neutron secondary γ fluence, neutron secondary γ tissue dose, and neutron secondary γ silicon dose; if the source type is a gamma source, the selectable radiation environment parameters mainly include γ fluence, γ tissue dose, and γ silicon dose. Since the source type in this embodiment is neutron, the type of radiation environment parameter is the total neutron tissue dose; specifically, the total neutron tissue dose is the sum of the neutron tissue dose of the neutron itself and the neutron secondary γ tissue dose generated.

[0037] 4] Determine the ground medium parameters

[0038] The parameters of the ground medium include type, nuclide composition, density, thickness, mass fraction, etc.; among them, the types of ground medium include concrete, soil, water, etc. In this embodiment, the type of ground medium is selected as concrete, and the density is 2.3 g / cm 3 , the thickness is 2 m, and the nuclide composition and mass fraction of the concrete are shown in Table 1.

[0039] Table 1 Nuclide composition and mass fraction of concrete

[0040]

[0041]

[0042] 5】Select the measurement point height h and the range of the projection distance R

[0043] In the present invention, the projection distance R represents the projection distance on the ground from the source to the measurement point. The measurement point height h is selected within the following range: 0 ≤ h ≤ 10 m, and in this embodiment, h = 1 m; the projection distance R is selected within the following range: 0 ≤ R ≤ 4 km, and in this embodiment, R ≤ 1000 m.

[0044] 6】According to the atmospheric-ground boundary problem point source radiation transport model established in step 1】 and the parameter ranges set in steps 2】-5】, use the Monte Carlo (MC) method to perform numerical simulations for different source heights H and projection distances R, and generate a two-dimensional numerical table of radiation environment parameters under different source heights H and projection distances R.

[0045] In this embodiment, 22 groups of data are selected for the projection distance R, which are 1, 3, 5, 10, 20, 40, 60, 80, 100, 150, 200, 250, 300, 350, 400, 450, 500, 600, 700, 800, 900, 1000; 31 groups of data are selected for the source height H, which are 1, 2, 4, 6, 8, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400. As Figure 3 shown, it is a two-dimensional numerical table of radiation environment parameters under different source heights H and projection distances R.

[0046] 7】Perform data search according to the two-dimensional numerical table generated in step 6】 to find the source height H corresponding to the maximum environmental parameter under each projection distance R max , and obtain a series of R-H max data pairs, as shown in Table 2 specifically;

[0047] Table 2 R-H max data pairs

[0048] R 1 3 5 10 20 40 60 80 100 150 200 250 300 350 400 450 500 600 700 800 900 1000 <![CDATA[H max > 1 1 1 2 4 10 15 20 30 50 60 80 90 100 120 120 140 160 180 200 220 240

[0049] 8】Plot the R-H max data pairs to generate a two-dimensional curve graph; then perform data fitting on the generated two-dimensional curve graph to minimize the fitting variance and obtain H max and the fitting relationship between R; since the measuring point height h is 1 m, the vertical axis intercept is 1 m, and the obtained H max and the fitting relationship between R have very good linearity. H max and the fitting relationship between R is represented by the following formula:

[0050] H max = 1 + 0.25575R

[0051] As Figure 4 shown, in this embodiment, the schematic diagram of the R-H max two-dimensional curve graph and the fitting relationship, where Intercept in the fitting relationship represents the vertical axis intercept, Slope represents the slope, and R-Square is the goodness of fit; in this embodiment, Intercept is 1, Slope is 0.25575, and R-Square is 0.99454. Since the closer R-Square is to 1, the better the linearity of the R-H max two-dimensional curve graph. Therefore, it shows that the linearity of this embodiment is very good. In the present invention, existing fitting methods can be used to perform data fitting on the generated two-dimensional curve graph line. However, since the linearity of the two-dimensional curve graph line obtained in this embodiment is very good, preferably, linear fitting is used to perform data fitting on the generated two-dimensional curve graph.

[0052] 9】According to the fitting relationship between H max and R obtained in step 8】, the maximum source height H of the radiation environment parameter corresponding to the set parameter range in steps 2】-5】 can be obtained max .

[0053] As a comparison, the Monte Carlo (MC) calculation method was used to calculate the maximum neutron total tissue dose source height H corresponding to R being 50 m, 225 m, 550 m, 750 m, and 950 m respectively in the set parameter range of steps 2】-5】 max . The results and relative deviations are shown in Table 3. It can be seen from Table 3 that when R is 50 m and 225 m, the relative deviations are relatively large. This is because R is relatively close and the absolute value of H max is relatively small, resulting in relatively large relative deviations. Considering that the Monte Carlo (MC) calculation method has inherent statistical errors, and the shielding scale of the near-surface atmosphere for particle radiation is in the order of hundreds of meters to kilometers, the distance difference of about 10 m has little impact on radiation shielding. It can be considered that the calculation results of the two are consistent.

[0054] Table 3 Maximum total neutron tissue dose source height H max and relative deviation

[0055] R 50 225 550 750 950 MC method / m 12.0 70.0 150.0 190.0 230.0 Fitting formula / m 13.8 58.5 141.7 192.8 244.0 Relative deviation / % 15.0 16.4 5.5 1.5 6.1

[0056] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and 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 rapid acquisition method for the source height corresponding to the maximum value of near-ground point source radiation environment parameters, characterized in that It includes the following steps:

1. Establish an atmospheric-ground interface problem point source radiation transport model; 2. Determine the radiation source term parameters; the radiation source term parameters include source type, energy spectrum, and emission direction; 3. Determine the types of radiation environment parameters according to the source type; 4. Determine the ground medium parameters; 5. Select the measurement point height h and the range of the projection distance R; the projection distance R is the projection distance on the ground from the source to the measurement point; The selectable range of the measurement point height h is: 0 ≤ h ≤ 10 m, and the selectable range of the projection distance R is 0 ≤ R ≤ 4 km; 6. According to the atmospheric-ground interface problem point source radiation transport model established in step 1 and the parameter ranges set in steps 2 to 5, use the Monte Carlo calculation method for numerical simulation to generate a two-dimensional numerical table of radiation environment parameters under different source heights H and projection distances R; 7】Search for data according to the two-dimensional numerical table generated in step 6】 to find the maximum environmental parameter source height H corresponding to each projection distance R max to obtain a series of R-H max data pairs; 8】Plot the R-H max data pairs obtained in step 7】 to generate a two-dimensional curve graph; then perform data fitting on the two-dimensional curve graph to obtain the fitting relationship between H max and R when the fitting variance is minimized; 9】Obtain the source height H corresponding to the maximum value of the radiation environment parameter within the parameter range set in steps 2】-5】 according to the fitting relationship between H max and R when the fitting variance obtained in step 8】 is the smallest max .

2. The method for quickly obtaining the source height corresponding to the maximum value of the near-ground point source radiation environment parameters according to claim 1, wherein: In step 8, the data fitting of the two-dimensional curve graph is specifically: Perform data fitting on the two-dimensional curve graph by linear fitting.

3. The method for quickly obtaining the source height corresponding to the maximum value of the near-ground point source radiation environment parameters according to claim 1 or 2, wherein: In step 3, the determination of the types of radiation environment parameters according to the source type is specifically: If the source type is a neutron source, the selectable radiation environment parameters include neutron fluence, neutron tissue dose, neutron silicon dose, neutron secondary γ fluence, neutron secondary γ tissue dose, neutron secondary γ silicon dose; If the source type is a gamma source, the selectable radiation environment parameters include γ fluence, γ tissue dose, and γ silicon dose.

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