A method and system for risk assessment of external radiation pathways to radionuclide contaminated sites

Abstract

This invention relates to a method for assessing the risk of external exposure pathways to radionuclide-contaminated sites, comprising the steps of: establishing a dose evaluation model; statistically analyzing relevant parameters of the environmental transfer coefficient of the external exposure pathway; establishing a probability distribution function for the relevant parameters of the environmental transfer coefficient of the external exposure pathway; and forming a dose risk assessment model for the external exposure pathway. This invention also provides a system for assessing the risk of external exposure pathways to radionuclide-contaminated sites. By employing the method and system for assessing the risk of external exposure pathways to radionuclide-contaminated sites, the probability distribution of the environmental transfer coefficient of the external exposure pathway can be obtained by studying the probability distribution of the model input parameters, ultimately establishing a probability-based risk assessment model for radionuclide-contaminated sites.

Description

Technical Field

[0001] This invention belongs to the field of radiation protection risk assessment, specifically relating to a method and system for assessing the risk of external irradiation pathways to sites contaminated by radioactive nuclides. Background Technology

[0002] Currently, the assessment models for radionuclide-contaminated sites in China are standardized, general models. These models are based on the premise that the site medium is homogeneous and the relevant risk assessment parameters are fixed values. However, they lack sufficient consideration of the uncertainties in these parameter values, neglecting their impact on risk assessment. This leads to conservative assessment results that fail to accurately reflect the current state of contamination impact. Research into probabilistic risk assessment methods, supplementing and improving deterministic methods, can more accurately reflect the impact of parameter changes on risk assessment results, enabling uncertainty analysis of input parameters, and ultimately obtaining and confirming the confidence level of the risk assessment results. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for risk assessment of external irradiation pathways to radionuclide-contaminated sites, thereby establishing a probability-based risk assessment method for radionuclide-contaminated sites.

[0004] To achieve the above objectives, the technical solution adopted by this invention is: a method for risk assessment of external radiation pathways in radionuclide-contaminated sites, comprising the steps of: establishing a dose evaluation model; statistically analyzing the relevant parameters of the environmental transfer coefficient of the external radiation pathway; establishing a probability distribution function of the relevant parameters of the environmental transfer coefficient of the external radiation pathway; and forming a dose risk assessment model for the external radiation pathway.

[0005] Furthermore, the dose evaluation model selects a deterministic risk assessment model.

[0006] Furthermore, the relevant parameters of the environmental transfer coefficient of external radiation pathways include area correction factor, residence factor, depth correction factor, and coverage correction factor.

[0007] Furthermore, a triangular fuzzy function is used to represent the membership degree of the environmental transfer coefficient of the external irradiation pathway.

[0008] Furthermore, the membership function is expressed as:

[0009]

[0010] Where a, b, and c are the minimum value, the most likely value, and the maximum value, respectively.

[0011] Furthermore, the probability distribution function of the parameters related to the environmental transfer coefficient of the external irradiation pathway is:

[0012]

[0013] Wherein, a, b, and c correspond to the maximum, expected, and minimum values ​​of the relevant parameters of the statistical external irradiation pathway environmental transfer coefficient, respectively.

[0014] Furthermore, in forming the external radiation dose risk assessment model, the Monte Carlo method is used to simulate and generate random numbers for each parameter, thereby obtaining the probability density distribution function of the environmental transfer coefficient:

[0015] ETF i (t)=ρ b，土 ×FO×FA×FD i [ρ b，土 , T(t)]×FC i [ρ b，盖 [Cd(t)]

[0016] Where, ρ b，土 The overall density of the contaminated soil; FO is the residence factor; FA is the area correction factor; FD i [ρ b，土 [T(t)] is the depth correction coefficient of nuclide i with respect to time t; FC i [ρ b，盖 [Cd(t)] is the coverage correction coefficient of nuclide i at time t; T(t) is the thickness of the contamination layer at time t; ρ b，盖 Cd(t) represents the overall density of the covering material; Cd(t) represents the thickness of the covering layer at time t.

[0017] Furthermore, when using the Monte Carlo method to simulate and generate random numbers for each parameter separately, calculations are considered at 10,000, 100,000, and 1,000,000 times.

[0018] Furthermore, the dose risk assessment model for the external irradiation route is as follows:

[0019] DSR i =DCF i ×ETF i ×SF i

[0020] Among them, DCF i ETF (Quantitative Conversion Factor) i SF is the environmental transfer coefficient via external radiation pathway. i This is the source characteristic correction coefficient.

[0021] This invention also provides a risk assessment system for external radiation pathways in radionuclide-contaminated sites, comprising: a dose evaluation model generation unit for establishing a dose evaluation model; a statistical unit for statistically analyzing relevant parameters of the environmental transfer coefficient of the external radiation pathway; a probability distribution function generation unit for establishing a probability distribution function of the relevant parameters of the environmental transfer coefficient of the external radiation pathway; and an evaluation unit for forming a dose risk assessment model for the external radiation pathway.

[0022] The advantages of this invention are as follows: by researching foreign methods and models for risk assessment of radioactive contaminated sites, comparing and analyzing them, a deterministic model with a wide range of applications and high maturity is selected, and a relatively common external exposure pathway is chosen. The probability distribution functions of parameters such as area correction coefficient, residence coefficient, depth correction coefficient, and coverage correction coefficient are studied, thereby obtaining the probability distribution function of the environmental transfer coefficient of the external exposure pathway. Finally, the dose value of the external exposure pathway based on the probability distribution is obtained, laying the foundation for the assessment of the dose received by the public. Attached Figure Description

[0023] Figure 1 This is a flowchart of the steps in a method for risk assessment of external irradiation pathways to radioactive nuclide-contaminated sites according to the present invention. Detailed Implementation

[0024] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, this invention proposes a method for risk assessment of external irradiation pathways at sites contaminated with radioactive nuclides, comprising the following steps:

[0026] S1, Establish a dose evaluation model;

[0027] Specifically, we investigated the risk assessment methods and models for radioactive contaminated sites in countries such as the United States, France, and Japan, as well as the IAEA. Through comparative analysis, we selected widely used and mature models and methods. Combining the characteristics of radioactive contaminated sites in my country, we chose a deterministic risk assessment model.

[0028] It is understood that, in some embodiments, the specific dose evaluation model may vary depending on the actual situation.

[0029] S2, relevant parameters for the environmental transfer coefficient of external radiation pathways;

[0030] Specifically, the relevant parameters for the environmental transfer coefficient of external radiation pathways include the area correction factor (FA), the residence factor (FO), and the depth correction factor (FD). i [ρ b，土 [T(t)] and coverage correction factor (FC) i [ρ b，盖 [,Cd(t)]).

[0031] A survey of domestic and international research on parameters related to environmental transfer factors of external radiation pathways, including area correction factor (FA), residence factor (FO), and depth correction factor (FD), was conducted. i [ρ b，土 [T(t)] and coverage correction factor (FC) i [ρ b，盖 Based on empirical values, literature data, and historical data of Cd(t), combined with actual measurement data of radioactive contaminated sites in China, the results are presented in the following format after collation, summarization, and statistical analysis, as shown in Table 1.

[0032]

[0033]

[0034] Table 1. Values ​​of relevant parameters for environmental transfer coefficient in risk assessment of external radiation routes.

[0035] S3, Establish the probability distribution function of the parameters related to the environmental transfer coefficient of the external irradiation pathway;

[0036] Specifically, fuzzy distributions mainly take various forms, including triangular distribution, trapezoidal distribution, rectangular distribution, normal distribution, and Cauchy distribution. Since triangular distributions are easier to algebraically perform and facilitate reference function processing, this embodiment uses triangular fuzzy numbers to represent the membership degrees of environmental transfer coefficients for external irradiation pathways in terrestrial plants, meat, and milk. The definition of a triangular fuzzy number is as follows: Let A be a fuzzy number in the real number field R, and define a membership function μ(x), x∈R, expressed as:

[0037]

[0038] A is called a canonical triangular fuzzy number, denoted as A = (a, b, c), where a, b, and c are the minimum, most likely, and maximum values, respectively. A is a definite real number when a = b = c.

[0039] According to equation (1), by dividing the fuzzy distribution by the area (ca) / 2 enclosed by the x-axis, we finally obtain the probability density function of A:

[0040]

[0041] The maximum, expected, and minimum values ​​of the environmental transfer coefficient parameters related to the external irradiation pathway are statistically analyzed and assigned to a, b, and c, respectively. The probability density distribution functions of each parameter are then established.

[0042] S4, to develop a dose risk assessment model for external irradiation routes;

[0043] Specifically, based on the probability density distribution function of the parameters related to the environmental transfer coefficient, the Monte Carlo method is used to simulate and generate random numbers for each parameter, thus obtaining the probability density distribution function of the environmental transfer coefficient:

[0044] ETF i (t)=ρ b，土 ×FO×FA×FD i [ρ b，土 , T(t)]×FC i [ρ b，盖 ,Cd(t)] (3)

[0045] Where, ρ b，土 The overall density (bulk weight) of the contaminated soil, in g / m³ 3 FO is the residency factor; FA is the area correction factor; FD i [ρ b，土 [T(t)] is the depth correction coefficient of nuclide i with respect to time t; FC i [ρ b，盖 [Cd(t)] is the coverage correction factor for nuclide i at time t, m 3 / a; T(t) is the thickness of the contamination layer at time t, in meters; ρ b，盖 To cover the overall density of the material, g / m 3 Cd(t) is the thickness of the overlay at time t, in meters.

[0046] It is understandable that when using the Monte Carlo method to simulate and generate random numbers for each parameter separately, calculations of 10,000, 100,000, and 1,000,000 times are considered to reduce errors through comparative analysis.

[0047] Based on the probability density distribution function of the environmental transfer coefficient through external radiation pathway, the dose (DSR) produced by a unit concentration of radionuclide I in the soil is calculated. i Establish a risk assessment model for external radiation pathways to radioactive contaminated sites:

[0048] DSR i =DCF i ×ETF i ×SF i (4)

[0049] Among them, DCF i ETF (Quantitative Conversion Factor) ij SF is the environmental transfer coefficient through external radiation pathway. i This is the source characteristic correction factor. Based on the external radiation pathway risk assessment model, the dose produced by a unit concentration of the corresponding nuclide in the soil can be calculated.

[0050] This invention also provides a risk assessment system for external radiation pathways to radionuclide-contaminated sites, comprising:

[0051] The dose evaluation model generation unit is used to establish a dose evaluation model;

[0052] Statistical unit, used to statistically analyze relevant parameters of the environmental transfer coefficient of external radiation pathways;

[0053] The probability distribution function generation unit is used to establish the probability distribution function of the parameters related to the environmental transfer coefficient of the external irradiation path;

[0054] Evaluation unit, used to develop a dose risk assessment model for external radiation routes.

[0055] As can be seen from the above embodiments, the beneficial effects of the present invention are as follows: by investigating the methods and models for risk assessment of radioactive contaminated sites abroad, comparing and analyzing them, selecting the deterministic model that has a wide range of applications and high maturity, choosing a relatively common external exposure pathway, studying the probability distribution functions of parameters such as area correction coefficient, residence coefficient, depth correction coefficient, and coverage correction coefficient, thereby obtaining the probability distribution function of the environmental transfer coefficient of the external exposure pathway, and finally obtaining the dose value of the external exposure pathway based on the probability distribution, laying the foundation for the dose assessment received by the public.

[0056] The methods and systems described in this invention are not limited to the embodiments described in the specific implementation. Other implementation methods derived by those skilled in the art based on the technical solutions of this invention also fall within the scope of technical innovation of this invention.

Claims

1. A method for assessing the risk of external exposure pathways to radionuclide-contaminated sites, characterized in that, include: Establish a dose evaluation model; The relevant parameters for the environmental transfer coefficient of external radiation pathways include area correction factor, residence factor, depth correction factor, and coverage correction factor; Establish the probability distribution function of the parameters related to the environmental transfer coefficient of the external irradiation pathway; Develop a dose risk assessment model for external irradiation routes; The probability distribution function of the parameters related to the environmental transfer coefficient of the external irradiation pathway is: Where a, b, and c correspond to the maximum, expected, and minimum values ​​of the relevant parameters of the statistical external radiation pathway environmental transfer coefficient, respectively. The dose risk assessment model for the external irradiation route is as follows: DSR i =DCF i ×EFT i ×SF i Among them, DCF i ETF (Quantitative Conversion Factor) i SF is the environmental transfer coefficient via external radiation pathway. i This is the source characteristic correction coefficient.

2. The method for assessing the risk of external radiation pathways to a radionuclide-contaminated site as described in claim 1, characterized in that: The dose evaluation model adopts a deterministic risk assessment model.

3. The method for assessing the risk of external radiation pathways to a radionuclide-contaminated site as described in claim 1, characterized in that: A triangular fuzzy function is used to represent the membership degree of the environmental transfer coefficient of the external irradiation pathway.

4. The method for risk assessment of external radiation pathways to a radionuclide-contaminated site as described in claim 3, characterized in that: The membership function is expressed as: Where a, b, and c are the minimum value, the most likely value, and the maximum value, respectively.

5. The method for risk assessment of external radiation pathways to a radionuclide-contaminated site as described in claim 1, characterized in that: When forming the external radiation dose risk assessment model, the Monte Carlo method is used to simulate and generate random numbers for each parameter, thereby obtaining the probability density distribution function of the environmental transfer coefficient: ETF i (t)=ρ b，土 ×FO×FA×FD i [ρ b,土 ,T(t)]×FC i [ρ b,盖 ,Cd(t)] Where, ρ b，土 The overall density of the contaminated soil; FO is the residence factor; FA is the area correction factor; FD i [ρ b,土 [T(t)] is the depth correction coefficient of nuclide i with respect to time t; FC i [ρ b,盖 [Cd(t)] is the coverage correction coefficient of nuclide i at time t; T(t) is the thickness of the contamination layer at time t; ρ b,盖 Cd(t) represents the overall density of the covering material; Cd(t) represents the thickness of the covering layer at time t.

6. The method for risk assessment of external radiation pathways to a radionuclide-contaminated site as described in claim 5, characterized in that: When using the Monte Carlo method to simulate and generate random numbers for each parameter separately, consider calculations of 10,000, 100,000, and 1,000,000 times.

7. A risk assessment system for external radiation pathways to radionuclide-contaminated sites, characterized in that, include: The dose evaluation model generation unit is used to establish a dose evaluation model; The statistical unit is used to calculate the relevant parameters of the environmental transfer coefficient of external radiation pathways, including area correction coefficient, residence coefficient, depth correction coefficient and coverage correction coefficient. The probability distribution function generation unit is used to establish the probability distribution function of the parameters related to the environmental transfer coefficient of the external irradiation path; Evaluation unit, used to develop a dose risk assessment model for external radiation routes; The probability distribution function of the parameters related to the environmental transfer coefficient of the external irradiation pathway is: Where a, b, and c correspond to the maximum, expected, and minimum values ​​of the relevant parameters of the statistical external radiation pathway environmental transfer coefficient, respectively. The dose risk assessment model for the external irradiation route is as follows: DSR i =DCF i ×ETF i ×SF i Among them, DCF i ETF (Quantitative Conversion Factor) i SF is the environmental transfer coefficient via external radiation pathway. i This is the source characteristic correction coefficient.

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