CN114444407A - Key parameter value design method suitable for emission characteristics of post-treatment plant - Google Patents
Key parameter value design method suitable for emission characteristics of post-treatment plant Download PDFInfo
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Abstract
The invention relates to a key parameter value design method suitable for emission characteristics of a post-processing plant, which estimates vertical and horizontal diffusion parameters for the post-processing plant by utilizing an atmospheric diffusion tracer experiment of the plant, calculates the horizontal and vertical diffusion parameters in a near region and under a stable layer junction of the post-processing plant by adopting a Lagrange particle model and a CFD (computational fluid dynamics) calculation method, makes diffusion evaluation on the plant in the near region and under a stable condition more reasonable, and gives values of dry and wet deposition of typical nuclides in the post-processing plant. The invention provides technical support for promoting the radiation protection work of a nuclear fuel post-processing plant, improving the radiation protection level of the nuclear fuel post-processing plant, protecting the health and environmental safety of surrounding public and further providing safe operation of engineering.
Description
Technical Field
The invention belongs to a nuclide diffusion simulation technology of radioactive gaseous effluents, and particularly relates to a key parameter value design method suitable for emission characteristics of a post-treatment plant.
Background
The key parameters required by the analysis of the atmospheric dispersion characteristics and the engineering design of the site of the post-treatment plant site comprise diffusion parameters, dry and wet deposition values of typical nuclides and the like. The reasonable value design of the key parameters can provide basis for judging whether the influence of the radioactive gaseous effluent discharged by a plant area on the environment meets the requirements of relevant laws and regulations in China or not, and provide technical support for promoting the radiation protection work of a nuclear fuel post-processing plant, improving the radiation protection level of the nuclear fuel post-processing plant, protecting the health of peripheral public and environmental safety and further providing technical support for the safe operation of engineering.
At present, no special post-treatment plant atmospheric diffusion evaluation model and parameter research is developed in China. Therefore, it is urgent and necessary to conduct relevant engineering studies on the migration and diffusion of gaseous effluents in the environment. The method provides key parameters such as diffusion parameters of main nuclides in radioactive gaseous effluents, dry and wet deposition factors and the like for a post-treatment plant site through a test, numerical simulation and mode verification method. At present, diffusion parameter value taking methods for reference nuclear power plants mainly comprise: an empirical diffusion curve method based on stability classification; a method of combining the standard deviation of wind speed with a diffusion function; a method for carrying out theoretical calculation through conventional meteorological data. The first method can adopt modes of fuming photography, smoke measurement by laser radar and atmosphere tracing experiments, obtains corresponding diffusion parameters after determining the stability class during observation or experiment, and has the defect that the diffusion parameters under different conditions cannot be obtained frequently. The second method measures the standard deviation of wind speed by using a bidirectional vane or a three-dimensional ultrasonic anemometer, and calculates diffusion parameters by combining diffusion functions, but the measured diffusion parameters only represent the result of a certain height. The third method is easy to implement, but cannot acquire the characteristic parameter characteristics of the factory address. According to the invention, the diffusion parameters are obtained by combining a field tracing experiment with a numerical simulation method, so that the actual diffusion characteristics of a plant site can be obtained, and the condition of field loss can be supplemented.
Disclosure of Invention
The invention aims to provide a value design method for main nuclide diffusion simulation key parameters of radioactive gaseous effluents for a post-treatment plant, and the reasonable value of the key parameters of the post-treatment plant is recommended through necessary tests and numerical simulation.
The technical scheme of the invention is as follows: a key parameter value design method suitable for emission characteristics of an after-treatment plant comprises the following steps:
(1) carrying out atmospheric diffusion tracing experiments under different weather stability conditions, fitting the concentration distribution of arc pollutants by adopting a least square method to estimate a standard deviation, and estimating horizontal and vertical diffusion parameters under different weather types;
(2) analyzing a factory floor atmospheric diffusion result and estimating a factory floor diffusion parameter by adopting a Computational Fluid Dynamics (CFD) calculation method and considering the influence of factory floor buildings; utilizing a Lagrange particle model, considering the actual three-dimensional wind field characteristics and turbulence characteristics of a plant site area, supplementing and simulating atmospheric diffusion characteristics in the plant site area, and estimating diffusion parameters under different stable layer junctions by combining computational fluid dynamics simulation results;
(3) and (4) verifying the numerical simulation result by using the atmospheric diffusion tracing experiment result, and recommending the final diffusion parameters of the typical nuclide in the plant site and the values of the corresponding dry and wet deposition factors.
Further, the method for designing the value of the key parameter suitable for the emission characteristic of the post-treatment plant as described above, wherein the content of the atmospheric diffusion tracing experiment in the step (1) includes: selecting typical weather conditions, arranging sampling points and collecting and analyzing samples.
Further, the method for designing the value of the key parameter suitable for the emission characteristics of the post-treatment plant is as follows, wherein the method for estimating the horizontal and vertical diffusion parameters in the step (1):
assuming that the diffusion conditions of the tracing experiment obey the gaussian diffusion mode, the ground concentration formula of the overhead continuous point source is as follows:
wherein C (x, y, O; He) represents the concentration that would result from a source having a source intensity Q and an effective source height He at any point (x, y) down-wind to the ground (0 represents ground height); u is the average wind speed at high source; sigmay，σzHorizontal and vertical diffusion parameters, respectively;
suppose σy，σzThe following power function relationship exists with the downwind distance x:
in the formula, py，qy，pz，qzConsidered as a constant, the surface concentration formula can be expressed as:
determination of the constant p by means of the least-squares methody，qy，pz，qzCalculating to obtain sigmay，σz；
The constant p is determined by using the least square methody，qy，pz，qzIs a calculated value C of the ground density of the sampling point iiAnd measured value CmiS is represented by the following formula:
in the formula, N is the total number of the points of the sample collected in all sampling points of one tracing experiment.
Furthermore, the sample collection method of the experiment belongs to unequal precision measurement, and the weight g of the measurement precision of the mark is introduced as an index of relative importance degree of different data when the data is processed, so that S can be expressed as:
in the formula, giWeight, g, for each sample pointiThe values are as follows:
gi＝Cmi/Cm,max
Cm，maxthe maximum concentration measurements in all sample points taken in this experiment.
Further, the method for designing the value of the key parameter suitable for the emission characteristic of the post-processing plant is described above, wherein a Computational Fluid Dynamics (CFD) calculation method is adopted in the step (2), and the method for estimating the plant diffusion parameter is as follows:
the wind profiles are distributed as follows:
wherein, UzAnd U10Representing the z-height and the wind speed 10 meters high, respectively, the power index n of the wind profile is 0.083,
according to the formula of the atmospheric layer wind speed
The friction speed u can be obtained by solving a linear equation of two elements by adopting wind speeds at different heights*And a roughness height z0Taking the Von-Karman constant as 0.4,
the calculation formula of the height of the atmospheric boundary layer is as follows:
wherein f is a ground parameter; omega is the rotational angular velocity of the earth 7.2722 multiplied by 10-5rad; lambda is the latitude of the plant address; u. of*In order to determine the speed of the friction,
designing chimney parameters and calculating working conditions, processing simulation results of different working conditions, and estimating diffusion parameters of a plant area as follows:
wherein sigma is a diffusion parameter, y is the distance between the smoke cloud and the central axis of the smoke cloud, and q is the concentration at the distance.
Further, the method for designing the value of the key parameter suitable for the emission characteristic of the post-processing plant is as follows, wherein the method for estimating the diffusion parameter under different stable layer junctions by using the lagrangian particle model in the step (2) comprises the following steps:
assuming no interaction between the particles, the change in position of any particle at one point P (x, y, z) in space can be written as:
dx/dt＝U+u′
dy/dt＝V+v′
dz/dt＝W+w′
wherein x, y and z are position coordinates of the particles; u, V, W mean wind speed; u ', v ', w ' are pulse velocities, U, V, W and u ', v ', w ' can be determined from meteorological patterns or parameterisation methods, and for any time t and its subsequent time t + Δ t, u ', v ', w ' can be written as:
wherein R isu、Rv、RwFor the turbulence velocity-related coefficient, σu、σv、σwFor turbulent velocity variance, Γ1、Γ2、Γ3For the standard normal distribution random numbers independent of each other, the turbulence velocity correlation coefficients in three directions can take the form:
Ru(Δt)＝exp(-Δt/TLu)
Rv(Δt)＝exp(-Δt/TLv)
Rw(Δt)＝exp(-Δt/TLw)
wherein, TLu、TLv、TLwTo correspond to the lagrange turbulence integral scale of the three directions,
the track of the particle in space motion can be calculated according to the above formulas, and the position of each moment can be determined;
for the concentration calculation of any time t and spatial position r, the kernel function or the smoke cluster concept comprises:
wherein c is the concentration, rjAnd mjFor the spatial position and mass of the jth particle, K is the kernel function, l is the characteristic scale of the kernel function, which is in principle determined by the spatial distribution density of the particles, a (r) is the concentration correction factor at the near boundary, for the case of no boundary a (r) is identical to 1, taking the kernel function in the form of a gaussian function, the above formula is very similar to the gaussian plumes formula, i.e.:
processing diffusion results with different stability degrees, and supplementing and estimating diffusion parameters under the stable condition of a factory area, wherein the adopted method comprises the following steps:
wherein sigma is a diffusion parameter, y is the distance between the smoke cloud and the central axis of the smoke cloud, and q is the concentration at the distance.
Further, the method for designing the value of the key parameter suitable for the emission characteristic of the post-processing plant is described as follows, wherein the method for recommending the final diffusion parameter of the typical nuclide in the plant site in the step (3):
a) selecting corresponding weather conditions for simulation by numerical simulation for weather conditions which are not captured by the atmospheric diffusion tracing experiment, and calculating corresponding diffusion parameters as supplements;
b) calculating approximate diffusion parameters for the numerical simulation result and the atmospheric diffusion tracing experiment, and taking an average value as a final diffusion parameter;
c) and for the diffusion parameter with larger difference between the numerical simulation result and the atmospheric diffusion tracing experiment, taking the determined other stability diffusion parameter as reference, and taking the diffusion parameter which is closer to the extrapolation or interpolation result as the diffusion parameter under the weather type.
Further, the method for designing the value of the key parameter suitable for the emission characteristic of the post-treatment plant is as follows, wherein the method for calculating the dry and wet deposition factors in the step (3):
cw＝ca(1-exp(-Λt))
wherein, CaDenotes the concentration in air without deposition, CdRepresents the air concentration of the contaminants after dry deposition, CwRepresents the air concentration, V, of the wet-precipitated contaminantsdDenotes the dry deposition rate, KzRepresents the turbulent exchange coefficient in the vertical direction, t represents the time that the contaminant has elapsed from the calculated position to the release point, and Λ represents the washout coefficient.
The invention has the following beneficial effects: the invention provides parameter data required by atmospheric dispersion characteristic analysis and engineering design of the location of the post-processing plant site through necessary tests and numerical simulation, wherein the parameter data comprises diffusion parameters, dry and wet deposition values of typical nuclides and the like, so that the diffusion evaluation of the plant site in the near area and under stable conditions is more reasonable, a basis is provided for judging whether the influence of radioactive gaseous effluents discharged by the plant site on the environment meets the requirements of relevant laws and regulations in China, and a technical support is provided for promoting the radiation protection work of the nuclear fuel post-processing plant, improving the radiation protection level of the nuclear fuel post-processing plant, protecting the health and environmental safety of surrounding public and further providing technical support for the safe operation of engineering.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention recommends the values of key nuclide diffusion parameters and dry and wet deposition factors of a post-treatment plant by combining an atmospheric diffusion tracing experiment with a numerical simulation result, and the specific method comprises the following steps:
1) and fitting the concentration distribution of the arc pollutants by a least square method to estimate a standard deviation by developing a field atmospheric diffusion tracing experiment to obtain horizontal and vertical diffusion parameters. The realization method comprises the following steps: a) the atmosphere diffusion tracing experiment under different stability types is carried out, and the atmosphere diffusion tracing experiment mainly comprises the following contents: selecting typical weather conditions, arranging sampling points and collecting and analyzing samples. b) Processing the tracing experiment data, calculating diffusion parameters, and adopting a least square method as follows:
assuming that the diffusion conditions of the tracing experiment obey the gaussian diffusion mode, the ground concentration formula of the overhead continuous point source is as follows:
wherein C (x, y, O; He) represents the concentration (mg/m) (m) that a source having a source intensity of Q (mg/s) and an effective source height of He (m) results at any point (x, y) (m) downwind to the ground (0 represents the ground height)3)；
Average wind speed at source altitude (mg/s); sigmay，σzThe diffusion parameters (m) are transverse and vertical, respectively.
Suppose σy，σzThe following power function relationship exists with the downwind distance x (m):
in the formula, py，qy，pz，qzCan be considered as a constant. The surface concentration formula can be expressed as:
thus, only the constant p is determinedy，qy，pz，qzThen, sigma is givenyAnd σz。
py，qy，pz，qzThe determination of (c) may utilize a least squares method. Even calculated value C of ground concentrationi[Ci＝C(xi，yi，0；He)]And measured value CmiS is represented by the following formula:
in the formula, N is the total number of the points of the sample collected in all sampling points of one tracing experiment.
The sample collection method in the experiment belongs to unequal precision measurement, and in order to balance different precisions of various data, the weight g for marking the measurement precision is introduced as an index of relative importance degree of different data when the data is processed. Then S can be expressed as:
in the formula, giAs a weight for each sample point. The determination of the weights is manifold and, for convenience, giTaking the following steps:
gi＝Cmi/Cm，max
in the formula, Cm，maxThe maximum concentration measurements in all sample points taken in this experiment.
2) And simulating diffusion characteristics under different stabilities in the post-treatment plant area by adopting a CFD (computational fluid dynamics) method, simulating the diffusion characteristics of the plant area under different stabilities by adopting a Lagrange particle model, and finally supplementing diffusion parameters under the plant area near area and the stable layer junction according to the diffusion characteristics.
For the CFD simulation method, the following conditions are adopted for calculation after modeling the plant area:
adopting software: STAR-CCM +
A grid generator: surface Remesher, Automatic Surface Repair, Trimmed Cell Mesher, Prism Layer Mesher.
Wind profile distribution:
wherein, UzAnd U10Representing z-height and 10 meters high wind speed, respectively, with a wind profile power exponent n of 0.083.
In ABL (Atmospheric Boundary layer) analysis, the Standard k-epsilon correction parameters as shown in Table 1 were typically selected for calculation.
TABLE 1Standard k- ε correction parameters
The Von-Karman constant was taken to be 0.4.
According to the formula of the atmospheric layer wind speed
The friction speed u can be obtained by solving a linear equation of two elements by adopting wind speeds at different heights*And a roughness height z0The value of (a).
Atmospheric boundary layer height:
the ABL boundary layer height calculation formula is as follows:
wherein f is a ground parameter; omega is the rotational angular velocity of the earth 7.2722 multiplied by 10-5rad; lambda is the latitude of the plant address; u. u*Is the friction speed.
Chimney parameters:
the release rate is as follows: 1 Bq/s;
exit velocity: 16.99 m/s;
simulation of nuclide: kr-85, I-131 and Cs-137;
the chimney discharge temperature: the ground temperature was 9.9 ℃ corresponding to a 100m high atmospheric temperature.
Specific operating conditions are shown in table 2.
TABLE 2 calculation conditions
Processing simulation results of different working conditions, and estimating diffusion parameters of a factory area, wherein the adopted method comprises the following steps:
wherein sigma is a diffusion parameter, y is the distance between the smoke cloud and the central axis of the smoke cloud, and q is the concentration at the distance.
3) Calculating a stable layer junction diffusion parameter using a Lagrange particle model
The random walk particle-kernel function pattern is composed of two parts in principle, one is a normal random walk particle pattern, and the other is concentration field calculation using a kernel function or a smoke cluster concept. The particles here actually represent the centroid of the contaminant micelles. For the randomly-wandering particle diffusion section, assuming no interaction between particles, the change in position of any particle at one point P (x, y, z) in space can be written as:
dx/dt＝U+u′
dy/dt＝V+v′
dz/dt＝W+w′
wherein x, y and z are position coordinates of the particles; u, V, W mean wind speed; u ', v ', w ' are the pulse velocities. U, V, W and u ', v ', w ' can be determined by meteorological patterns or parameterisation methods. For any time t and its subsequent time t + Δ t, u ', v ', w ' can be written as:
wherein R isu、Rv、RwIs a turbulent velocity correlation coefficient; sigmau、σv、σwIs the turbulence velocity variance. Gamma-shaped1、Γ2、Γ3The random numbers are independent standard normal distribution random numbers. The turbulent velocity correlation coefficients for the three directions may take the form:
Ru(Δt)＝exp(-Δt/TLu)
Rv(Δt)＝exp(-Δt/TLv)
Rw(Δt)＝exp(-Δt/TLw)
wherein, TLu、TLv、TLwLagrange turbulence integral scales for the three directions.
The trajectory of the particle in space motion can be calculated by the above formulas to determine the position of each time.
The second part of the particle diffusion calculation is to sample the distribution of the random traveling particles using an appropriate kernel function. For the concentration calculation of any time t and spatial position r, the kernel function or the smoke cluster concept comprises:
wherein c is the concentration; r isjAnd mjIs the spatial position and mass of the jth particle; k is a kernel function; 1 is the characteristic scale of the kernel function, which is determined in principle by the spatial distribution density of the particles. A (r) is a concentration correction factor at the near-boundary, and in the case of no boundary, A (r) is equal to 1. Taking the kernel function in the form of a gaussian function, the above equation is very similar to the gaussian blob equation, i.e.:
processing diffusion results with different stability degrees, and supplementing and estimating diffusion parameters under the stable condition of a factory area, wherein the adopted method comprises the following steps:
wherein sigma is a diffusion parameter, y is the distance between the smoke cloud and the central axis of the smoke cloud, and q is the concentration at the distance.
After the diffusion parameters are obtained through calculation of numerical method results, the value taking method is as follows:
a) selecting corresponding weather conditions for simulation by numerical simulation for the weather conditions which are not captured by the tracing experiment, and calculating corresponding diffusion parameters as supplements;
b) calculating approximate diffusion parameters for the numerical simulation result and the atmospheric diffusion tracing experiment, and taking an average value as a final diffusion parameter;
c) and for the diffusion parameter with larger difference between the numerical simulation result and the atmospheric diffusion tracing experiment, taking the determined other stability diffusion parameter as reference, and taking the diffusion parameter which is closer to the extrapolation or interpolation result as the diffusion parameter under the weather type.
4) Method for calculating dry and wet deposition amounts of typical nuclides on plant site
Wherein the dry and wet deposition amounts are calculated as follows:
cw＝ca(1-exp(-Λt))
wherein C isaDenotes the concentration in air without deposition, CdRepresents the air concentration of the contaminants after dry deposition, CwRepresenting the air concentration of the wet-settled contaminants. VdIndicating the dry deposition rate, iodine was taken as 0.01m/s and other nuclides were taken as 0.0015 m/s. KzRepresenting the turbulent exchange coefficient in the vertical direction, t time elapsed for the contaminant from the calculated position to the release point. The expression Λ is the washing coefficient, the washing coefficient Λ(s) of iodine and other particle state elements-1) The values are as follows:
| precipitation intensity, mm/h | Iodine | Other elements in particle form |
| ＜1 | 3.7×10-5 | 2.9×10-5 |
| 1-3 | 1.1×10-4 | 1.22×10-4 |
| ＞3 | 2.37×10-4 | 3.4×10-4 |
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (8)
1. A key parameter value design method suitable for emission characteristics of an after-treatment plant is characterized by comprising the following steps:
(1) carrying out atmospheric diffusion tracing experiments under different weather stability conditions, fitting the concentration distribution of arc pollutants by adopting a least square method to estimate a standard deviation, and estimating horizontal and vertical diffusion parameters under different weather types;
(2) analyzing the atmospheric diffusion result of the plant area by adopting a computational fluid dynamics calculation method and considering the influence of the buildings of the plant area, and estimating the diffusion parameters of the plant area; utilizing a Lagrange particle model, considering the actual three-dimensional wind field characteristics and turbulence characteristics of a plant site area, supplementing and simulating atmospheric diffusion characteristics in the plant site area, and estimating diffusion parameters under different stable layer junctions by combining computational fluid dynamics simulation results;
(3) and (4) verifying the numerical simulation result by using the atmospheric diffusion tracing experiment result, and recommending the final diffusion parameters of the typical nuclide in the plant site and the values of the corresponding dry and wet deposition factors.
2. The method for designing the value of the key parameter suitable for the emission characteristic of the post-treatment plant according to claim 1, wherein the content of the atmospheric diffusion tracer experiment in the step (1) comprises: selecting typical weather conditions, arranging sampling points and collecting and analyzing samples.
3. The method for designing the value of the key parameter applicable to the emission characteristics of the post-treatment plant according to claim 1 or 2, wherein the method for estimating the horizontal and vertical diffusion parameters in the step (1) is as follows:
assuming that the diffusion conditions of the tracing experiment obey the gaussian diffusion mode, the ground concentration formula of the overhead continuous point source is as follows:
wherein C (x, y, O; He) represents the concentration of a source with a source intensity of Q and an effective source height of He at any point (x, y) on the downwind ground;
the average wind speed at high source; sigmay，σzHorizontal and vertical diffusion parameters, respectively;
suppose σy，σzThe following power function relationship exists with the downwind distance x:
in the formula, py，qy，pz，qzConsidered as a constant, the surface concentration formula can be expressed as:
determining the constant p by means of least squaresy，qy，pz，qzCalculating to obtain sigmay，σz；
The constant p is determined by using the least square methody，qy，pz，qzIs a calculated value C of the ground density of the sampling point iiAnd measured value CmiS is represented by the following formula:
in the formula, N is the total number of the points of the sample collected in all sampling points of one tracing experiment.
4. The method for designing the value of the key parameter applicable to the emission characteristic of the post-processing plant as claimed in claim 3, wherein the sample collection method of the experiment belongs to the unequal accuracy measurement, and the weight g for marking the measurement accuracy is introduced as the index of the relative importance degree of different data when processing the data, then S can be expressed as:
in the formula, giWeight, g, for each sample pointiThe values are as follows:
gi＝Cmi/Cm,max
Cm,maxthe maximum concentration measurements in all sample points taken in this experiment.
5. The method for designing the value of the key parameter suitable for the emission characteristic of the post-processing plant according to claim 1, wherein the computational fluid dynamics calculation method is adopted in the step (2), and the method for estimating the diffusion parameter of the plant area comprises the following steps:
the wind profiles are distributed as follows:
wherein, UzAnd U10Representing the z-height and the wind speed 10 meters high, respectively, the power index n of the wind profile is 0.083,
according to the formula of the atmospheric layer wind speed
The friction speed u can be obtained by solving a linear equation of two elements by adopting wind speeds at different heights*And a roughness height z0Taking the Von-Karman constant as 0.4,
the calculation formula of the height of the atmospheric boundary layer is as follows:
wherein f is a ground parameter; omega is the rotational angular velocity of the earth 7.2722 multiplied by 10-5rad; lambda is the latitude of the plant address; u. of*In order to determine the speed of the friction,
designing chimney parameters and calculating working conditions, processing simulation results of different working conditions, and estimating diffusion parameters of a plant area as follows:
wherein sigma is a diffusion parameter, y is a distance from the smoke cloud to a central axis of the smoke cloud, and q is a concentration at the distance.
6. The method for designing the values of the key parameters suitable for the emission characteristics of the post-processing plant according to claim 1 or 5, wherein the method for estimating the diffusion parameters under different stable layer junctions by using the Lagrangian particle model in the step (2) is as follows:
assuming no interaction between the particles, the change in position of any particle at one point P (x, y, z) in space can be written as:
dx/dt＝U+u′
dy/dt＝V+v′
dz/dt＝W+w′
wherein x, y and z are position coordinates of the particles; u, V, W mean wind speed; u ', v ', w ' are pulse velocities, U, V, W and u ', v ', w ' can be determined from meteorological patterns or parameterisation methods, and for any time t and its subsequent time t + Δ t, u ', v ', w ' can be written as:
wherein R isu、Rv、RwFor the turbulence velocity-related coefficient, σu、σv、σwIs the turbulence velocity variance, Γ1、Γ2、Γ3For the standard normal distribution random numbers independent of each other, the turbulence velocity correlation coefficients in three directions can take the form:
Ru(Δt)＝exp(-Δt/TLu)
Rv(Δt)＝exp(-Δt/TLv)
Rw(Δt)＝exp(-Δt/TLw)
wherein, TLu、TLv、TLwTo correspond to the lagrange turbulence integral scale of the three directions,
the track of the particle in space motion can be calculated according to the above formulas, and the position of each moment can be determined;
for the concentration calculation of any time t and spatial position r, the kernel function or the smoke cluster concept comprises:
wherein c is the concentration, rjAnd mjFor the spatial position and mass of the jth particle, K is the kernel function, l is the characteristic scale of the kernel function, which is in principle determined by the spatial distribution density of the particles, a (r) is the concentration correction factor at the near boundary, for the case of no boundary a (r) is identical to 1, taking the kernel function in the form of a gaussian function, the above formula is very similar to the gaussian plumes formula, i.e.:
processing diffusion results with different stability degrees, and supplementing and estimating diffusion parameters under the stable condition of a factory area, wherein the adopted method comprises the following steps:
wherein sigma is a diffusion parameter, y is the distance between the smoke cloud and the central axis of the smoke cloud, and q is the concentration at the distance.
7. The method for designing the value of the key parameter suitable for the emission characteristic of the post-processing plant as claimed in claim 1, wherein the method for recommending the final diffusion parameter of the typical nuclide at the plant site in the step (3) is as follows:
a) selecting corresponding weather conditions for simulation by numerical simulation for weather conditions which are not captured by the atmospheric diffusion tracing experiment, and calculating corresponding diffusion parameters as supplements;
b) calculating approximate diffusion parameters for the numerical simulation result and the atmospheric diffusion tracing experiment, and taking an average value as a final diffusion parameter;
c) and for the diffusion parameter with larger difference between the numerical simulation result and the atmospheric diffusion tracing experiment, taking the determined other stability diffusion parameter as reference, and taking the diffusion parameter which is closer to the extrapolation or interpolation result as the diffusion parameter under the weather type.
8. The method for designing the value of the key parameter suitable for the emission characteristic of the post-treatment plant according to claim 1, wherein the dry and wet deposition factors are calculated in the step (3) as follows:
cw＝ca(1-exp(-Λt))
wherein, CaDenotes the concentration in air without deposition, CdRepresents the air concentration of the contaminants after dry deposition, CwRepresents the air concentration, V, of the wet-precipitated contaminantsdDenotes the dry deposition rate, KzRepresents the turbulent exchange coefficient in the vertical direction, t represents the time that the contaminant has elapsed from the calculated position to the release point, and Λ represents the washout coefficient.
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| CN107145699A (en) * | 2016-03-01 | 2017-09-08 | 中国辐射防护研究院 | Airborne radionuclide long-distance migration Lagrangian Particle Dispersion computational methods |
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