Method and apparatus for acquiring radioactive aerosol data in a confined space

Abstract

The application belongs to the technical field of radiation protection, and particularly relates to a method and device for obtaining radioactive aerosol data in a closed space. The method comprises the following steps: obtaining a pre-established aerosol diffusion model and an aerosol deposition model; the aerosol diffusion model and the aerosol deposition model are obtained according to the properties of radioactive aerosol and the environmental parameters and ventilation system parameters of the closed space, and the radioactive decay, physical deposition and chemical deposition factors of the radioactive aerosol are considered; and the space radioactive aerosol concentration and the ground radioactive aerosol concentration in the closed space are obtained according to the aerosol diffusion model, the aerosol deposition model, the parameters of the closed space and the properties of the radioactive aerosol. The method solves the problem of dependence of radioactive aerosol on sampling measurement, and provides data for on-site radiation protection.

Description

Technical Field

[0001] This application belongs to the field of radiation protection technology, specifically relating to a method and apparatus for acquiring radioactive aerosol data in a confined space. Background Technology

[0002] During the operation of nuclear facilities, radioactive materials may exist in the form of aerosols in various process rooms due to leakage of the return water, refueling maintenance, cutting and other operations. Radioactive aerosols can cause internal radiation and external radiation through immersion to the staff. Therefore, in order to protect the staff and the environment, it is necessary to calculate data such as the diffusion of radioactive aerosols and the deposition activity concentration in closed process rooms.

[0003] Currently, the activity concentration of space radioactive aerosols is generally obtained by taking samples on-site and sending them to the laboratory for energy spectrum analysis. This method cannot quickly obtain the aerosol activity concentration and has a large error margin for radionuclides with short half-lives. Radioactive aerosols inside process rooms not only pose challenges to the protection of staff and the environment but also cause surface contamination of facilities and equipment. Summary of the Invention

[0004] The purpose of this application is to provide a method and apparatus for acquiring radioactive aerosol data in confined spaces, thereby solving the problem that in the prior art, aerosols inside confined process rooms of nuclear facilities have long relied on measurement and sampling, resulting in data lag and the inability to quickly and accurately provide on-site personnel with radioactive aerosol activity concentration data.

[0005] The technical solution to achieve the purpose of this application is as follows:

[0006] The first aspect of this application provides a method for acquiring radioactive aerosol data in a confined space, the method comprising:

[0007] A pre-established aerosol diffusion model and aerosol deposition model are obtained; the aerosol diffusion model and the aerosol deposition model are obtained based on the properties of radioactive aerosols and the environmental parameters and ventilation system parameters of the confined space, taking into account the radioactive decay, physical deposition and chemical deposition factors of the radioactive aerosols;

[0008] Based on the aerosol diffusion model, the aerosol deposition model, the parameters of the confined space, and the properties of the radioactive aerosols, the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration within the confined space are obtained.

[0009] Optionally, the aerosol diffusion model is specifically as follows (1):

[0010]

[0011]

[0012] In the formula, c i c is the aerosol activity concentration of the enclosed space. i,∞ V is the concentration of isotope i in the sealed space, v2 is the flow rate of the radionuclide leaking into the process room, A2 is the leakage area of ​​the radionuclide, V is the free volume of the sealed space after removing obstacles, and L is the number of air changes in the sealed space. st V is the aerosol gravity settling velocity. st Let A be the aerosol gravitational settling velocity. flr Let t be the ground area of ​​the enclosed space, t be the diffusion time, ΔP be the pressure of the enclosed space, and P0 be the air pressure.

[0013] Optionally, the aerosol deposition model is specifically as follows (3):

[0014]

[0015]

[0016]

[0017]

[0018] In the formula, c i,st V represents the concentration of aerosols on the floor of the confined space. st v is the aerosol gravitational settling velocity. out A represents the velocity of the exhaust vent in the enclosed space. out v1 is the exhaust vent area of ​​the enclosed space, v2 is the flow velocity of the radioactive nuclide leaking into the enclosed space, and ρ is the exhaust vent area of ​​the enclosed space. p ρ is the aerosol density, g is the gravitational acceleration, μ is the air viscosity, and r is the aerosol radius.

[0019] Optionally, after obtaining the concentration of radioactive aerosols in the confined space and the concentration of radioactive aerosols on the ground, the method further includes:

[0020] Based on the concentration of radioactive aerosols in the confined space and the concentration of radioactive aerosols on the ground, and according to a pre-obtained radiation dose model, the radiation dose when an operator enters the confined space is obtained.

[0021] Optionally, the radiation dose model is specifically as follows (7):

[0022]

[0023] In the formula, D TEDE The systemic effective dose for the operator, ω i(t) represents the total activity of radionuclide i in the confined space at time t, and λ i Let V be the decay constant of radioactive nuclide i, and V be the free volume of the enclosed space after removing the obstacles. SF is the effective radiation dose conversion factor for external irradiation of space radionuclide i. cls The radiation dose shielding factor for external space exposure. Let be the total activity of radionuclide i on the ground in the enclosed space at time t, and A be the ground area of ​​the enclosed space. SF is the effective radiation dose conversion factor for external irradiation of ground-based radionuclide i. grs The ground external radiation dose shielding factor. BR is the internal radiation dose conversion factor, SF is the operator's respiratory rate, and BR is the internal radiation dose conversion factor. inh This is the internal radiation dose shielding factor.

[0024] Optionally, obtaining the radiation dose when an operator enters the confined space further includes:

[0025] An airflow organization simulation and verification program was established based on COMSOL software to realize the calculation of airflow field inside the enclosed space, calculation of radioactive aerosol diffusion concentration field, calculation of radioactive aerosol deposition, rapid assessment of worker radiation dose, optimization design and visualization of ventilation system.

[0026] A second aspect of this application provides an apparatus for acquiring radioactive aerosol data in a confined space, the apparatus comprising:

[0027] The model building module is used to obtain a pre-established aerosol diffusion model and aerosol deposition model. The aerosol diffusion model and the aerosol deposition model are obtained based on the properties of radioactive aerosols and the environmental parameters and ventilation system parameters of the confined space, taking into account the radioactive decay, physical deposition and chemical deposition factors of the radioactive aerosols.

[0028] The concentration acquisition module is used to obtain the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration in the confined space based on the aerosol diffusion model, the aerosol deposition model, the parameters of the confined space, and the properties of the radioactive aerosol.

[0029] Optional, also includes:

[0030] The dose acquisition module is used to obtain the radiation dose when an operator enters the confined space based on the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration, according to a pre-obtained radiation dose model.

[0031] The beneficial technical effects of this application are as follows:

[0032] This application provides a method and apparatus for acquiring radioactive aerosol data in a confined space. It offers a method for calculating the ground deposition concentration and spatial concentration of radioactive aerosols in a confined process room, solving the problem of relying on sampling measurements for radioactive aerosols. By establishing a model of aerosol diffusion, migration, and deposition, it ultimately enables the calculation of the radioactive aerosol diffusion concentration field, the radioactive aerosol deposition concentration field, and the rapid assessment of worker exposure dose within a confined process room of a nuclear facility, providing data for on-site radiation protection. Attached Figure Description

[0033] Figure 1 A flowchart illustrating a method for acquiring radioactive aerosol data in a confined space, provided as an embodiment of this application;

[0034] Figure 2 This is a schematic diagram of a device for acquiring radioactive aerosol data in a confined space, provided as an embodiment of this application. Detailed Implementation

[0035] To enable those skilled in the art to better understand this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of this application, and not all of them. Based on the embodiments described in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] To address existing problems, this application provides a CFD-based system for analyzing the influence mechanism of aerosol diffusion and deposition patterns in process rooms. Based on the COMSOL manual's Navier-Stokes equations, which describe the momentum conservation law of laminar flow and can also be considered Newton's second law of fluid motion, an aerosol diffusion model that conforms to actual conditions is established. This model calculates the radioactive aerosol diffusion concentration field, the radioactive aerosol deposition concentration field, and provides rapid assessment of worker radiation dose within a closed process room. This solves the long-standing problem of relying on measurement and sampling for aerosol data acquisition in closed process rooms of nuclear facilities, resulting in delayed data acquisition and an inability to quickly and accurately provide on-site workers with radioactive aerosol activity concentration data. Therefore, it provides fundamental radiation protection data for protecting workers and the environment.

[0037] Based on the above, in order to clearly and in detail illustrate the advantages of this application, the specific embodiments of this application will be described below in conjunction with the accompanying drawings.

[0038] See Figure 1The figure is a flowchart illustrating a method for acquiring radioactive aerosol data in a confined space, as provided in an embodiment of this application.

[0039] This application provides a method for acquiring radioactive aerosol data in a confined space, comprising:

[0040] Step S101: Obtain the pre-established aerosol diffusion model and aerosol deposition model; the aerosol diffusion model and aerosol deposition model are obtained based on the properties of radioactive aerosols and the environmental parameters and ventilation system parameters of the confined space, taking into account the radioactive decay, physical deposition and chemical deposition factors of radioactive aerosols.

[0041] Step S102: Based on the aerosol diffusion model, aerosol deposition model, parameters of the confined space, and properties of radioactive aerosols, obtain the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration within the confined space.

[0042] It should be noted that radioactive materials forming aerosols within the process room (i.e., a confined space) can cause radiation damage to personnel operating within it. Currently, the aerosol activity concentration inside process rooms in my country's nuclear facilities relies on sampling measurements, which are time-consuming and prone to errors due to the presence of short-lived nuclides. The release of radioactive aerosols inside process rooms not only poses challenges to personnel protection and environmental conservation but also causes surface contamination of facilities and equipment. Therefore, the calculation technology for radioactive aerosol deposition and diffusion inside process rooms is a crucial factor influencing on-site emergency strategies and refueling / maintenance process decisions, and is also a primary basis for radiation protection activities. This necessitates that personnel calculate and simulate the aerosol activity concentration in the process room in advance.

[0043] In the embodiments of this application, based on the source term, particle size and density of radioactive aerosols, ambient temperature, pressure and relative humidity, ventilation system parameters, and considering factors such as radioactive decay of aerosols, physical deposition and chemical deposition, an aerosol diffusion model and an aerosol deposition model are established, ultimately realizing the calculation of the radioactive aerosol diffusion concentration field and the radioactive aerosol deposition concentration field inside the closed process room of the nuclear facility.

[0044] In one example, based on the source term, particle size and density of radioactive aerosols, ambient temperature and pressure, ventilation rate, ventilation duct size and air intake and exhaust locations, and considering factors such as radioactive decay, physical deposition and chemical deposition of aerosols, an aerosol diffusion model is established, and the concentration field of radioactive aerosol diffusion is finally calculated.

[0045] In another example, an aerosol deposition model is established based on the radioactive aerosol source term, particle size and density, ambient temperature and pressure, ventilation rate, ventilation duct size and air intake and exhaust locations, taking into account factors such as aerosol radioactive decay, physical deposition and chemical deposition, and finally realizing the calculation of radioactive aerosol deposition.

[0046] Specifically, in some possible implementations of the embodiments of this application, the aerosol diffusion model is as follows: (1)

[0047]

[0048]

[0049] In the formula, c i c represents the aerosol activity concentration in a confined space. i,∞ Vi is the concentration of isotope i in the sealed space, v2 is the flow rate of the radionuclide leaking into the process room, A2 is the leakage area of ​​the radionuclide, V is the free volume of the sealed space after removing obstacles, and L is the number of air changes in the sealed space. st V is the aerosol gravity settling velocity. st Let A be the aerosol gravitational settling velocity. flr Let t be the ground area of ​​the enclosed space, t be the diffusion time, ΔP be the pressure of the enclosed space, and P0 be the air pressure.

[0050] In another example, the aerosol deposition model is as follows (3):

[0051]

[0052]

[0053]

[0054]

[0055] In the formula, c i,st V represents the concentration of aerosols on the ground of a confined space. st v is the aerosol gravitational settling velocity. out A is the speed of the exhaust vent in a confined space. out v1 is the exhaust vent area of ​​the confined space, v2 is the velocity of the radioactive nuclide leaking into the confined space, and ρ is the exhaust vent area of ​​the confined space. p ρ is the aerosol density, g is the gravitational acceleration, μ is the air viscosity, and r is the aerosol radius.

[0056] In some possible implementations of the embodiments of this application, after obtaining the concentration of radioactive aerosols in the confined space and the concentration of radioactive aerosols on the ground, the following may be further included:

[0057] Based on the concentration of radioactive aerosols in the confined space and the concentration of radioactive aerosols on the ground, and according to a pre-obtained radiation dose model, the radiation dose when an operator enters the confined space is obtained.

[0058] As an example, the radiation dose model is as follows (7):

[0059]

[0060] In the formula, D TEDE For the operator's systemic effective dose, ω i (t) represents the total activity of radionuclide i in the confined space at time t, λ i Let be the decay constant of radioactive nuclide i, and V be the free volume of the confined space after removing the obstruction. SF is the effective radiation dose conversion factor for external irradiation of space radionuclide i. cls The radiation dose shielding factor for external space exposure. Let be the total activity of radioactive nuclide i on the ground in the confined space at time t, and let A be the ground area of ​​the confined space. SF is the effective radiation dose conversion factor for external irradiation of ground-based radionuclide i. grs The ground external radiation dose shielding factor. BR is the internal radiation dose conversion factor, SF is the operator's respiratory rate, and BR is the internal radiation dose conversion factor. inh This is the internal radiation dose shielding factor.

[0061] In one example, obtaining the radiation dose when an operator enters a confined space, followed by:

[0062] A simulation and verification program for airflow organization was established based on COMSOL software, which can realize the calculation of airflow field in confined space, calculation of radioactive aerosol diffusion concentration field, calculation of radioactive aerosol deposition, rapid assessment of worker radiation dose, optimization design and visualization of ventilation system.

[0063] The following is a detailed explanation of a method for acquiring radioactive aerosol data in a confined space, provided by an embodiment of this application, using a specific example.

[0064] This application provides a method for acquiring radioactive aerosol data in a confined space, specifically including:

[0065] (1) Establish source term database, process room database, obstacle information database, and ventilation system database. The source term database includes the half-life of radionuclides, internal and external radiation dose conversion factor, total activity, radionuclide velocity, and aerosol particle size; the process room database includes the required process room dimensions; the obstacle information database includes the dimensions and locations of internal obstacles; and the ventilation system parameters include the number, size, and location of air supply outlets, the number, size, and location of exhaust outlets, air change rate, and negative pressure.

[0066] (2) Establish the boundary conditions for the airflow organization model of the ventilation system.

[0067] To provide a comfortable working environment for staff and to dilute the concentration of radioactive materials within the process room, a powerful ventilation system is installed. This system not only ensures a high air exchange rate to reduce the concentration of radioactive materials but also maintains a certain negative pressure to prevent the leakage of radioactive materials from the process room into the outside environment. The gases exhausted from the process room through the ventilation system, along with any aerosols contained within them, undergo rigorous filtration. Therefore, the final mass of radioactive material leaking from the process room into the environment is negligible.

[0068] By retrieving ventilation system parameters, the inlet area, outlet area, and inlet air velocity are calculated, and the differential pressure parameters input into the process room are determined.

[0069] The total area of ​​the air inlets is as follows (8).

[0070] A in =n in π(d in / 2) 2 (8)

[0071] In the formula, A in n is the air inlet area. in d represents the number of air inlets. in This refers to the diameter of the air inlet.

[0072] The total area of ​​the air outlets is as follows (9):

[0073] A out =n out π(d out / 2) 2 (9)

[0074] In the formula, A out n is the area of ​​the air outlet. out d represents the number of air outlets. out This refers to the diameter of the air outlet.

[0075] The air inlet velocity is as follows (10):

[0076]

[0077] In the formula, v in V represents the inlet air velocity, L represents the number of air changes, and V represents the free volume of the process room after removing obstacles.

[0078] The air outlet velocity is as follows (11):

[0079]

[0080]

[0081] In the formula, v out L is the velocity of the exhaust vent, V is the number of air changes, and A is the free volume of the process room after removing obstacles. out Where is the exhaust vent area, ΔP is the negative pressure, and P0 is the air pressure.

[0082] (3) Calculate the spatial radioactive aerosol concentration in the process room at any time using the process room aerosol diffusion model.

[0083] (4) Calculate the ground radioactive aerosol concentration in the process room at any time using the process room aerosol deposition model.

[0084] (5) Using the calculation results of processes (3) and (4) as input, calculate the immersion external radiation, ground deposition external radiation and internal radiation received by the staff when performing radioactive operations in the process room according to the radiation dose model.

[0085] (6) Mesh sensitivity analysis: By using the functions of airflow organization simulation and verification program mesh division sensitivity, the optimal mesh division recommendation value based on different spatial models can be realized.

[0086] (7) By controlling the location and time of staff operation, the design of the ventilation system’s air inlet and outlet positions, negative pressure and ventilation design can be optimized.

[0087] In a specific example, a rectangular process room is selected as the calculation case space. The calculations include: airflow field calculation, radioactive aerosol diffusion concentration field calculation, radioactive aerosol deposition calculation, rapid assessment of worker exposure dose, ventilation system optimization design, and visualization display.

[0088] This application provides a method for acquiring radioactive aerosol data in a confined space, and offers a method for calculating the ground deposition concentration and spatial concentration of radioactive aerosols in a confined process room. This method solves the problem of relying on sampling measurements for radioactive aerosols. By establishing a model of aerosol diffusion, migration, and deposition, it ultimately enables the calculation of the radioactive aerosol diffusion concentration field, the radioactive aerosol deposition concentration field, and the rapid assessment of worker exposure dose within a confined process room of a nuclear facility, providing data for on-site radiation protection.

[0089] Based on the method for acquiring radioactive aerosol data in a confined space provided in the above embodiments, this application also provides an apparatus for acquiring radioactive aerosol data in a confined space.

[0090] See Figure 2 The figure is a schematic diagram of a device for acquiring radioactive aerosol data in a confined space, provided in an embodiment of this application.

[0091] This application provides an apparatus for acquiring radioactive aerosol data in a confined space, comprising:

[0092] The model building module 100 is used to obtain the pre-established aerosol diffusion model and aerosol deposition model. The aerosol diffusion model and aerosol deposition model are obtained based on the properties of radioactive aerosols and the environmental parameters and ventilation system parameters of the confined space, taking into account the radioactive decay, physical deposition and chemical deposition factors of radioactive aerosols.

[0093] The concentration acquisition module 200 is used to obtain the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration in a confined space based on the aerosol diffusion model, the aerosol deposition model, the parameters of the confined space, and the properties of the radioactive aerosol.

[0094] In one example, the device also includes:

[0095] The dose acquisition module is used to obtain the radiation dose when an operator enters the confined space based on the concentration of radioactive aerosols in the confined space and the concentration of radioactive aerosols on the ground, according to a pre-obtained radiation dose model.

[0096] The present application has been described in detail above with reference to the accompanying drawings and embodiments. However, the present application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present application. All content not described in detail in this application can be derived from existing technology.

Claims

1. A method for acquiring radioactive aerosol data in a confined space, characterized in that, The method includes: A pre-established aerosol diffusion model and aerosol deposition model are obtained; the aerosol diffusion model and the aerosol deposition model are obtained based on the properties of radioactive aerosols and the environmental parameters and ventilation system parameters of the confined space, taking into account the radioactive decay, physical deposition and chemical deposition factors of the radioactive aerosols; Based on the aerosol diffusion model, the aerosol deposition model, the parameters of the confined space, and the properties of radioactive aerosols, the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration within the confined space are obtained. The aerosol diffusion model is specifically as follows (1): （1） （2） In the formula, The aerosol activity concentration of the enclosed space. isotopes The concentration in the enclosed space, The velocity at which a radioactive nuclide leaks into the confined space. This represents the area where a radioactive nuclide leaked. The free volume of the enclosed space after removing the obstacles. The number of air exchanges in the enclosed space. This refers to the aerosol gravity settling velocity. The area of ​​the enclosed space is denoted as . For diffusion time, The pressure in the enclosed space. Air pressure; The aerosol deposition model is specifically defined as follows (3): （3） （4） （5） （6） In the formula, This represents the concentration of aerosols on the floor of the enclosed space. For aerosol gravitational settling velocity, 𝑣 𝑜𝑢𝑡 The velocity of the exhaust vent in the enclosed space. The area of ​​the exhaust vent of the enclosed space. The velocity at which a radioactive nuclide leaks into the confined space. The density of the aerosol. It is the acceleration due to gravity. air viscosity, Let be the aerosol radius.

2. The method for acquiring radioactive aerosol data in a confined space according to claim 1, characterized in that, After obtaining the concentration of radioactive aerosols in the confined space and the concentration of radioactive aerosols on the ground, the method further includes: Based on the concentration of radioactive aerosols in the confined space and the concentration of radioactive aerosols on the ground, and according to a pre-obtained radiation dose model, the radiation dose when an operator enters the confined space is obtained.

3. The method for acquiring radioactive aerosol data in a confined space according to claim 2, characterized in that, The radiation dose model is specifically shown in equation (7): （7） In the formula, This is the systemic effective dose for the operator. for Radioactive nuclides in the confined space at the specified time Total activity, Radioactive nuclides decay constant, The free volume of the enclosed space after removing the obstacles. Space radionuclides External irradiation effective radiation dose conversion factor The radiation dose shielding factor for external space exposure. for Ground-based radionuclides in the confined space at the specified time Total activity, The area of ​​the enclosed space is denoted as . Ground-based radionuclides External irradiation effective radiation dose conversion factor The ground external radiation dose shielding factor. Internal radiation dose conversion factor, The operator's respiratory rate, This is the internal radiation dose shielding factor.

4. The method for acquiring radioactive aerosol data in a confined space according to claim 2, characterized in that, The process of obtaining the radiation dose when an operator enters the confined space further includes: An airflow organization simulation and verification program was established based on COMSOL software to realize the calculation of airflow field inside the enclosed space, calculation of radioactive aerosol diffusion concentration field, calculation of radioactive aerosol deposition, rapid assessment of worker radiation dose, optimization design and visualization of ventilation system.

5. An apparatus for acquiring radioactive aerosol data in a confined space, characterized in that, The device includes: The model building module is used to obtain a pre-established aerosol diffusion model and aerosol deposition model. The aerosol diffusion model and the aerosol deposition model are obtained based on the properties of radioactive aerosols and the environmental parameters and ventilation system parameters of the confined space, taking into account the radioactive decay, physical deposition and chemical deposition factors of the radioactive aerosols. The concentration acquisition module is used to obtain the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration in the closed space based on the aerosol diffusion model, the aerosol deposition model, the parameters of the closed space, and the properties of the radioactive aerosol. The aerosol diffusion model is specifically as follows (1): （1） （2） In the formula, The aerosol activity concentration of the enclosed space. isotopes Concentration in a sealed space, The velocity at which a radioactive nuclide leaks into the process room. This represents the area where a radioactive nuclide leaked. The free volume of the enclosed space after removing the obstacles. The number of air exchanges in the enclosed space. This refers to the aerosol gravity settling velocity. This refers to the aerosol gravity settling velocity. The area of ​​the enclosed space is denoted as . For diffusion time, The pressure in the enclosed space. Air pressure; The aerosol deposition model is specifically defined as follows (3): （3） （4） （5） （6） In the formula, This represents the concentration of aerosols on the floor of the enclosed space. For aerosol gravitational settling velocity, 𝑣 𝑜𝑢𝑡 The velocity of the exhaust vent in the enclosed space. The area of ​​the exhaust vent of the enclosed space. The velocity at which a radioactive nuclide leaks into the confined space. The density of the aerosol. It is the acceleration due to gravity. air viscosity, Let be the aerosol radius.

6. The apparatus for acquiring radioactive aerosol data in a confined space according to claim 5, characterized in that, Also includes: The dose acquisition module is used to obtain the radiation dose when an operator enters the confined space based on the spatial radioactive aerosol concentration and the ground radioactive aerosol concentration, according to a pre-obtained radiation dose model.

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