Method for assessing the dose of a person in the event of a spill of a solution containing uranium
By using CFD software to simulate gas-solid two-phase flow and Bernoulli's formula for calculation, the problem of inaccurate aerosol diffusion in uranium-containing solution spill accidents was solved, enabling accurate assessment of the inhalation dose for workers and guidance for safe evacuation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 中核第七研究设计院有限公司
- Filing Date
- 2026-03-18
- Publication Date
- 2026-06-19
AI Technical Summary
Existing technology has failed to accurately calculate the diffusion and deposition of radioactive aerosols within the plant during uranium-containing solution spills, leading to inaccurate assessments of inhalation doses for workers.
Transient gas-solid two-phase flow simulation was performed using CFD software. Aerosol diffusion was simulated using the DPM discrete phase model. The leakage rate was calculated using Bernoulli's formula. The aerosol distribution characteristics were obtained through gas-solid two-phase flow calculations. The inhalation dose was assessed based on the personnel's residence time.
It enables accurate assessment of the inhalation dose for workers in the event of a uranium-containing solution spill, provides guidance on safe evacuation times, reduces assessment costs, and improves safety.
Smart Images
Figure CN122242355A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nuclear radiation safety and accident simulation technology, specifically to a method for assessing personnel dose in the event of a uranium-containing solution spill. Background Technology
[0002] In uranium purification and conversion processes, when a uranium-containing solution spills or sputters, varying proportions of inhalable aerosol particles will be released depending on the accident scenario and solution properties. Inhalation of these particles by workers can lead to internal radiation exposure and pose significant biological toxicity. Experience with nuclear fuel cycle facilities indicates that after a spill, the average concentration method or spherical diffusion method is often used to calculate the aerosol concentration within the facility. However, the diffusion and deposition of radioactive aerosols within the facility are influenced by the particle's own characteristics, the carrier airflow state, and external physical fields. The average concentration method or spherical diffusion method does not consider these factors, resulting in inaccurate aerosol distribution calculations.
[0003] To more accurately assess the inhalation dose to workers in the event of a spill, it is necessary to explore the aerosol propagation patterns within the factory and improve existing radiation dose assessment methods. Summary of the Invention
[0004] The present invention provides a method for assessing personnel dosage in the event of a spill of uranium-containing solution, which can at least solve one of the technical problems in the background art.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for assessing personnel dose in the event of a uranium-containing solution spill includes the following steps: S1. Based on the equipment and ventilation layout in the plant, a physical model is determined. Spaceclaim software is used for modeling and ICEM is used for mesh generation. CFD software is used for transient gas-solid two-phase flow simulation. The DPM discrete phase model is used to simulate the diffusion of aerosols in the plant. The boundary conditions of the inlet and outlet are determined according to the ventilation situation of the plant. The velocity field distribution of the plant before the accident is obtained by numerical simulation without releasing DPM particles. S2. Calculate the proportion of inhalable radioactive aerosols generated by solution sputtering based on interpolation of uranium-containing solution concentration, pressure and temperature. Calculate the leakage amount using Bernoulli's formula based on the size and height of the breach. The accident source term is calculated as the proportion of inhalable radioactive aerosols × the leakage amount. S3. Perform gas-solid two-phase flow calculations to obtain the aerosol distribution characteristics within the plant; divide the plant into zones to obtain the aerosol concentration over time in the 1-2m breathing zone for workers after the accident; based on the time integral of the aerosol concentration in the 1-2m zone with respect to the time of the workers' stay after the accident, obtain the radioactive aerosol inhalation amount, and calculate the radioactive dose received by the workers due to this accident using a formula.
[0006] As a preferred embodiment of the personnel dose assessment method under uranium-containing solution spillage accident described in this invention, the physical model includes the plant where the leak occurred, the ventilation distribution of the plant, the location of the leak and splash, and equipment that has a significant impact on aerosol diffusion.
[0007] As a preferred embodiment of the personnel dose assessment method under uranium-containing solution spillage accident described in this invention, wherein: in step S2: When the concentration of uranium-containing solution At a concentration of 100 g / L, the weight of inhalable radioactive aerosols formed by sputtering a 100 g / L solution is 1, and the weight of inhalable radioactive aerosols formed by sputtering a 200 g / L solution is 0. When the concentration of uranium-containing solution At a concentration of 200 g / L, the weight of inhalable radioactive aerosols formed by sputtering a 100 g / L solution is 0, and the weight of inhalable radioactive aerosols formed by sputtering a 200 g / L solution is 1. When 100 g / L < uranium-containing solution concentration < 200 g / L, the proportion of inhalable radioactive aerosols formed by sputtering a 100 g / L solution is: The proportion of inhalable radioactive aerosols formed by sputtering a 200 g / L solution is [percentage missing]. ; The weightings for the formation of inhalable radioactive aerosols from sputtering a 100 g / L solution and the weightings for the formation of inhalable radioactive aerosols from sputtering a 200 g / L solution were respectively used... and express; When the solution temperature At 40℃, select 1MPa, the inhalable radioactive aerosol content corresponding to 40℃; When the solution temperature At 90℃, 1MPa was selected, and the proportion of inhalable radioactive aerosols corresponding to 90℃ was determined. When 40℃ < solution temperature < 90℃, the proportion of inhalable radioactive aerosols was calculated using interpolation at 1MPa. and ; When solution pressure At 0.1 MPa, the proportion of inhalable radioactive aerosols corresponding to 60℃ at 0.1 MPa was selected; When solution pressure At 2MPa, the proportion of inhalable radioactive aerosols corresponding to 2MPa and 60℃ is selected. When 0.1 MPa < solution pressure < 2 MPa, the proportion of inhalable radioactive aerosols was calculated using interpolation at 60℃. and The proportion of radioactive aerosols is: .
[0008] As a preferred embodiment of the personnel dose assessment method under uranium-containing solution spillage accident described in this invention, in step S1, ICEM is used to perform structured grid division, and the number of grids is gradually increased by double to verify grid sensitivity until the change in velocity and aerosol concentration in the plant is less than 5%.
[0009] As a preferred embodiment of the personnel dose assessment method under uranium-containing solution spillage accidents described in this invention, wherein: the DPM method in step S1 is a method based on a Lagrangian system, using domain to track the physical properties of individual particles; for discrete phases, the Lagrangian method is adopted, and the force balance formula for particles is equation:
[0010] In the formula Represents particle mass; Represents particle velocity; Represents particle density; Represents resistance; This represents the relaxation time.
[0011] As a preferred embodiment of the personnel dose assessment method under uranium-containing solution spillage accident described in this invention, wherein: the Bernoulli formula in step S2 is:
[0012] in, For liquids, the constant value is 0.6. The area of the breach; The initial absolute pressure of the container; Atmospheric pressure; The density of the solution; This represents the liquid level difference between the solution surface height and the orifice height.
[0013] As a preferred embodiment of the personnel dose assessment method under uranium-containing solution spillage accident described in this invention, wherein the gas-solid two-phase flow calculation formula in step S3 includes: Gas phase continuity equation:
[0014] Gas phase momentum equation:
[0015] In the formula For speed in Component of direction; and The fluid position is and The coordinate components of the direction; For fluid density; For pressure; The fluid's kinematic viscosity; The external force acting on a unit mass of fluid.
[0016] As a preferred embodiment of the personnel dose assessment method under uranium-containing solution spillage accident described in this invention, the formula conversion in step S3 is specifically as follows:
[0017] in, It refers to the dose received by personnel; It is the person's breathing rate; The change in aerosol concentration in the factory over time; It is the solution density; It refers to the uranium content of the uranium-containing solution; It is the dose conversion factor of natural uranium.
[0018] The beneficial effects of this invention are: By combining theoretical and experimental data, the conversion ratio of aerosols generated by solution sputtering was obtained and used as the accident source term. The diffusion phenomenon of aerosol particles in the plant was numerically simulated, thereby obtaining the diffusion distribution of aerosol particles in the plant over time and statistically analyzing the changes in aerosol particle concentration over time in different regions. The results were used to analyze the safe evacuation time after solution leakage and the amount of uranium aerosol inhaled by those who did not evacuate in time. Attached Figure Description
[0019] Figure 1 This is a flowchart illustrating the steps of the method for assessing personnel dosage in the event of a uranium-containing solution spillage accident according to the present invention.
[0020] Figure 2 A physical model of diffusion within a solution sputtering aerosol plant is shown.
[0021] Figure 3 This demonstrates structured mesh generation using ICEM.
[0022] Figure 4 The velocity field distribution inside the factory building before the accident is shown.
[0023] Figure 5 This shows the change of the velocity field inside the factory building over time after the accident.
[0024] Figure 6 This shows the diffusion of aerosol particles within the factory after the accident.
[0025] Figure 7The curve showing the change in aerosol concentration over time in the 1-2m area after the accident is displayed. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.
[0027] like Figure 1 As shown, a method for assessing personnel dosage in the event of a uranium-containing solution spill includes the following steps: S1. Based on the equipment and ventilation layout in the plant, a physical model is determined. Spaceclaim software is used for modeling and ICEM is used for mesh generation. CFD software is used for transient gas-solid two-phase flow simulation. The DPM discrete phase model is used to simulate the diffusion of aerosols in the plant. The boundary conditions of the inlet and outlet are determined according to the ventilation situation of the plant. The velocity field distribution of the plant before the accident is obtained by numerical simulation without releasing DPM particles. S2. Calculate the proportion of inhalable radioactive aerosols generated by solution sputtering based on interpolation of uranium-containing solution concentration, pressure and temperature. Calculate the leakage amount using Bernoulli's formula based on the size and height of the breach. The accident source term is calculated as the proportion of inhalable radioactive aerosols × the leakage amount. S3. Perform gas-solid two-phase flow calculations to obtain the aerosol distribution characteristics within the plant; divide the plant into zones to obtain the aerosol concentration over time in the 1-2m breathing zone for workers after the accident; based on the time integral of the aerosol concentration in the 1-2m zone with respect to the time of the workers' stay after the accident, obtain the radioactive aerosol inhalation amount, and calculate the radioactive dose received by the workers due to this accident using a formula.
[0028] The following are specific embodiments for assessing the diffusion of aerosols generated by solution splashing in uranium purification facilities and the dosage for workers. The main technical parameters are as follows: (1) The air velocity at the factory inlet is 0.1 m / s; (2) The pressure at the air outlet of the factory building is 0.1 MPa; (3) The solution contains 100 g / L of uranium; (4) Solution temperature 60℃; (5) Solution pressure: 0.1 MPa; (6) The height difference between the rupture and the liquid surface is 3m; (7) The dose conversion factor of natural uranium is 15.3 mSv / gU; (8) Breakage area 0.02 ; 1. Identify radioactive aerosol source terms 1.1 Obtain the proportion of inhalable aerosols based on experimental data. Based on the uranium-containing solution concentration, temperature, and pressure parameters in Tables 1 and 2, the proportion of inhalable aerosols generated by sputtering of the uranium-containing solution is 1.011E-05, as shown in Table 1 below: Table 1: ARF×RF fraction of inhalable aerosols formed by sputtering of 100 g / L uranium-containing solution
[0029] Table 2: ARF×RF fraction of inhalable aerosols formed by sputtering of 200 g / L uranium-containing solution
[0030] 1.2 Theoretical Analysis Based on the rupture area, the pressure difference between the solution and the plant, and the height difference between the rupture and the liquid surface, the solution leakage rate can be calculated to be 101 kg / s using Bernoulli's formula.
[0031] 1.3 Combining Theory and Experiment The radioactive aerosol generation rate was calculated to be approximately 1 g / s by multiplying the experimentally measured fraction of inhalable radioactive aerosols generated by solution spillage by the theoretically determined leakage rate, and this was used as the accident source term.
[0032] 2. Numerical simulation of diffusion of uranium-containing solution-splashed aerosols within a plant. 2.1 Physical Model Building This embodiment excludes equipment and sets the study area as a 4m×4m×3m cuboid structure. Because the model is symmetrically distributed, the three-dimensional diffusion of the uranium aerosol plant can be simplified to a 4m×3m two-dimensional diffusion, thus accelerating the calculation. The plant has top-down ventilation. The physical model is as follows: Figure 2 As shown.
[0033] 2.2 Mesh Generation Using ICEM Software ICEM was used to perform structured mesh generation on the physical model, thereby improving computational speed and accuracy. The total mesh size was 29250, with a minimum mass greater than 0.995, a maximum aspect ratio of 1.43, and a minimum orthogonal mass of 1. The mesh model was generated as follows: Figure 3 As shown.
[0034] 2.3 Numerical simulation of gas-solid two-phase flow using CFD software The inlet and outlet boundary conditions are determined as follows: the aerosol particle density is 1100 kg / m³; the flow velocity at the upper right inlet is 0.1 m / s, and the lower left outlet is the exhaust outlet, with atmospheric pressure. A leak occurs in the pipeline containing uranium solution, and the uranium solution impacts the ground to form aerosol particles. The ground area is taken as the initial location for aerosol particle generation, with a generation rate of 1 g / s. The leak source can generally be cut off within 5 minutes after the uranium solution leaks, at which point aerosol release stops. Therefore, it is assumed that the generation time of uranyl nitrate particles is 300 s. The wall is set as the adsorption wall, and the particle trajectory calculation terminates when the particles hit the pipe wall.
[0035] A pressure-velocity coupled calculation method is employed to simultaneously solve the momentum equation and the continuity equation, where the pressure gradient term is discretized as follows:
[0036] The momentum equation is discretized as follows:
[0037] The continuity equation is discretized as follows:
[0038] The discretized control equations can be expressed as:
[0039] In the formula The diagonal submatrix represents the effect of velocity itself through convection and diffusion, while the off-diagonal submatrix represents the coupling between pressure and velocity. For the pressure and velocity correction values of each unit, , For the correction of stress, , , These are corrections for the velocity components; The residual of the current iteration step. , For the residual of pressure, , , These are the residuals of the velocity components; Indicates that the mesh cell is in Projected area in the direction; For grid center pressure; The pressure-velocity coupling coefficient represents the mesh size. Pressure on the mesh The effect of speed; The coupling coefficient between velocities represents the mesh. Speed of the grid The impact; For grid cells On velocity components; and Based on Rhie-Chow interpolation, the mass flow rate at the interface will be expressed as a function of the grid pressure; This includes volume forces, unsteady time terms, and source terms arising from boundary conditions; The main issue is the imbalance in mass flow rate; Pressure, momentum, turbulent kinetic energy, and turbulent dissipation rate were all calculated using a second-order scheme. To make the research results more consistent with engineering practice, bidirectional coupling between the discrete phase and the continuous phase was enabled.
[0040] Before the accident, the ventilation system in the factory was operating normally. At this time, the velocity field distribution in the factory was as follows: Figure 4 As shown.
[0041] 2.4 Results Analysis Figure 5 The graph shows the velocity field variation over time within the plant for different incident mass flow rates during 300 s of solution sputtering aerosol generation. As can be seen from the graph, the flow velocity in the lower right side of the plant space is relatively small (< ). Therefore, after injecting denser aerosol particles (m / s), the flow field cannot provide enough kinetic energy to drive the aerosol particles to flow along the streamlines of the initial flow field. The aerosol particles bring some disturbance to the continuous phase flow on the lower right side, disrupting the originally stable flow field. However, due to the higher velocity on the diagonal sides of the continuous phase inlet and outlet, and the smaller number of aerosol particles diffusing into this region, the flow field in this region is not significantly affected as the mass flow rate of aerosol particles increases.
[0042] Figure 6 The graph shows the diffusion profile of aerosol particles over time. It reveals that the aerosol particle distribution is largely consistent with the velocity field distribution within the plant. After generation, aerosol particles are concentrated in the lower right region of the plant due to the influence of the air vortex. They diffuse slowly with the streamlines. Near the continuous phase inlet and diagonally opposite the outlet, where the flow velocity is higher and fewer aerosol particles diffuse to, the particles entering these areas flow out with the streamlines and cannot remain in the area for long. Furthermore, aerosol particles have essentially diffused throughout the lower right region by 100 seconds. When aerosol particle generation is stopped at 300 seconds, the number of aerosol particles in the plant decreases sharply between 300 and 400 seconds, and by 600 seconds, almost no diffused aerosol particles remain. This demonstrates the significant role of good plant ventilation in preventing aerosol inhalation.
[0043] Figure 7The graph shows the aerosol concentration change over time within a 1-2m area of the plant after a solution splash for 300 seconds. As can be seen, no aerosol particles diffused into this area within approximately 0-80 seconds after the solution leak. However, the aerosol particle concentration increased significantly after 80 seconds. Even after the leak source was cut off, the aerosol particle concentration in the 1-2m area did not show a rapid decrease. Since the 1-2m area is a regular breathing and ventilation area for workers, inhalation of aerosol particles from this area would lead to a serious internal radiation accident. Therefore, the optimal evacuation time after a solution leak should be within 80 seconds, at which point there are no aerosol particles in the 1-2m area, and the inhalation dose for workers is zero.
[0044] 3. Assess the amount of radioactive aerosol inhaled and the dose received by staff. Assuming that after a solution spill, two workers remain within a 4m x 4m area centered on the leak source for 300s and 600s respectively to handle the incident, then by... Figure 7 Integrating the data, we can obtain the masses of radioactive aerosols inhaled by the two individuals as 1.34E-06 kg and 4.33E-06 kg, respectively. Conversion, we can determine the radiation doses received by the two individuals as 1.86E-04 mSv and 6.02E-04 mSv, respectively.
[0045] This invention enables numerical simulation of aerosol distribution within a plant after a uranium-containing solution spill and sputtering accident, offering lower costs and higher safety compared to experimental methods. Based on the simulation results, a regional method is used to rapidly assess the dose received by personnel after the accident, providing more accurate results than the average concentration method and the spherical diffusion method.
[0046] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0047] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.
[0048] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for assessing personnel dosage in the event of a uranium-containing solution spill, characterized in that, Includes the following steps: S1. Based on the equipment and ventilation layout in the plant, a physical model is determined. Spaceclaim software is used for modeling and ICEM is used for mesh generation. CFD software is used for transient gas-solid two-phase flow simulation. The DPM discrete phase model is used to simulate the diffusion of aerosols in the plant. The boundary conditions of the inlet and outlet are determined according to the ventilation situation of the plant. The velocity field distribution of the plant before the accident is obtained by numerical simulation without releasing DPM particles. S2. Calculate the proportion of inhalable radioactive aerosols generated by solution sputtering based on interpolation of uranium-containing solution concentration, pressure and temperature. Calculate the leakage amount using Bernoulli's formula based on the size and height of the breach. The accident source term is calculated as the proportion of inhalable radioactive aerosols × the leakage amount. S3. Perform gas-solid two-phase flow calculations to obtain the aerosol distribution characteristics within the plant; divide the plant into zones to obtain the aerosol concentration over time in the 1-2m breathing zone for workers after the accident; based on the time integral of the aerosol concentration in the 1-2m zone with respect to the time of the workers' stay after the accident, obtain the radioactive aerosol inhalation amount, and calculate the radioactive dose received by the workers due to this accident using a formula.
2. The method for assessing personnel dosage in the event of a uranium-containing solution spill as described in claim 1, characterized in that: The physical model includes the plant where the leak occurred, the ventilation distribution of the plant, the location of the leak and splash, and the equipment that has a significant impact on aerosol diffusion.
3. The method for assessing personnel dosage in the event of a uranium-containing solution spill as described in claim 1, characterized in that: In step S2: When the concentration of uranium-containing solution At a concentration of 100 g / L, the weight of inhalable radioactive aerosols formed by sputtering a 100 g / L solution is 1, and the weight of inhalable radioactive aerosols formed by sputtering a 200 g / L solution is 0. When the concentration of uranium-containing solution At a concentration of 200 g / L, the weight of inhalable radioactive aerosols formed by sputtering a 100 g / L solution is 0, and the weight of inhalable radioactive aerosols formed by sputtering a 200 g / L solution is 1. When 100 g / L < uranium-containing solution concentration < 200 g / L, the proportion of inhalable radioactive aerosols formed by sputtering a 100 g / L solution is: The proportion of inhalable radioactive aerosols formed by sputtering a 200 g / L solution is [percentage missing]. ; The weightings for the formation of inhalable radioactive aerosols from sputtering a 100 g / L solution and the weightings for the formation of inhalable radioactive aerosols from sputtering a 200 g / L solution were respectively used... and express; When the solution temperature At 40℃, select 1MPa, the inhalable radioactive aerosol content corresponding to 40℃; When the solution temperature At 90℃, 1MPa was selected, and the proportion of inhalable radioactive aerosols corresponding to 90℃ was determined. When 40℃ < solution temperature < 90℃, the proportion of inhalable radioactive aerosols was calculated using interpolation at 1MPa. and ; When solution pressure At 0.1 MPa, the proportion of inhalable radioactive aerosols corresponding to 60℃ at 0.1 MPa was selected; When solution pressure At 2MPa, the proportion of inhalable radioactive aerosols corresponding to 2MPa and 60℃ is selected. When 0.1 MPa < solution pressure < 2 MPa, the proportion of inhalable radioactive aerosols was calculated using interpolation at 60℃. and The proportion of radioactive aerosols is: 。 4. The method for assessing personnel dosage in the event of a uranium-containing solution spill as described in claim 3, characterized in that: In step S1, ICEM is used to perform structured mesh generation, and the number of meshes is gradually increased by double to verify mesh sensitivity until the changes in velocity and aerosol concentration in the plant are less than 5%.
5. The method for assessing personnel dosage in the event of a uranium-containing solution spill as described in claim 1, characterized in that: The DPM method in step S1 is a method based on the Lagrangian system, which uses domain to track the physical properties of individual particles; for discrete phases, the Lagrangian method is adopted, and the force balance formula for particles is: In the formula Represents particle mass; Represents particle velocity; Represents particle density; Represents resistance; This represents the relaxation time.
6. The method for assessing personnel dosage in the event of a uranium-containing solution spill as described in claim 1, characterized in that: Bernoulli's formula in step S2 is: in, For liquids, the constant value is 0.
6. The area of the breach; The initial absolute pressure of the container; Atmospheric pressure; The density of the solution; This represents the liquid level difference between the solution surface height and the orifice height.
7. The method for assessing personnel dosage in the event of a uranium-containing solution spill as described in claim 1, characterized in that: The calculation formula for gas-solid two-phase flow in step S3 includes: Gas phase continuity equation: Gas phase momentum equation: In the formula For speed in Component of direction; and The fluid position is and The coordinate components of the direction; For fluid density; For pressure; The fluid's kinematic viscosity; The external force acting on a unit mass of fluid.
8. The method for assessing personnel dosage in the event of a uranium-containing solution spill as described in claim 1, characterized in that: The formula conversion in step S3 is specifically as follows: in, It refers to the dose received by personnel; It is the person's breathing rate; The change in aerosol concentration in the factory over time; It is the solution density; It refers to the uranium content of the uranium-containing solution; It is the dose conversion factor of natural uranium.