CN-121787131-B - Radionuclide emission inversion method and system integrating four-dimensional variation and Euler mode

CN121787131BCN 121787131 BCN121787131 BCN 121787131BCN-121787131-B

Abstract

The application relates to a radionuclide emission inversion method and system integrating four-dimensional variation and Euler mode, belonging to the technical field of nuclear pollution prediction. The method comprises the steps of collecting multi-type radionuclide observation data, high space-time resolution weather forecast data and nuclear accident/nuclear leakage reports, dividing the multi-type radionuclides into different particle size sections, constructing an assimilation system based on a four-dimensional variation theory and a nuclear pollution forecast Euler mode, carrying out differential adaptation design on turbulence diffusion and dry settlement rules of the different particle size sections by the assimilation system, inputting priori information of the nuclear accident/nuclear leakage reports into the nuclear pollution forecast Euler mode to forecast, outputting forecast results with high space-time resolution weather forecast data constraint, driving the assimilation system, carrying out assimilation inversion by combining the constraint of the observation data, and obtaining emission positions, intensities and emission amounts of the radionuclides every hour in a research period. By adopting the method, the accuracy of nuclear pollution prediction can be improved.

Inventors

HU YIWEN
ZANG ZENGLIANG
LI YI
LONG QUN
YOU WEI
LIU LANG
LIU NING
YANG XUEMEI
DAI WEI

Assignees

中国人民解放军国防科技大学

Dates

Publication Date: 20260512
Application Date: 20260304

Claims (9)

1. A radionuclide emission inversion method integrating four-dimensional variation and euler modes, characterized in that the method comprises: Collecting multi-type radionuclide observation data, high space-time resolution weather forecast data and nuclear accident/nuclear leakage reports after nuclear accidents occur, and dividing the multi-type radionuclides into fine-particle-diameter-section nuclides and coarse-particle-diameter-section nuclides; Constructing a four-dimensional variation target functional of a radionuclide emission source item, adopting a nuclear pollution forecast Euler mode, constructing a forward mode operator used for describing the evolution process of the radionuclide in the atmosphere in the four-dimensional variation target functional, and constructing an assimilation system of radionuclide emission intensity and emission position according to the four-dimensional variation target functional comprising the forward mode operator, wherein in the forward mode operator, turbulence diffusion items corresponding to the nuclides of two types of particle size sections adopt differential adaptive turbulence diffusion coefficients, and corresponding dry sedimentation items adopt differential adaptive dry sedimentation speeds; the radionuclide emission position, time and emission quantity recorded and estimated by the nuclear accident/nuclear leakage report are used as priori information, the priori information is input into a nuclear pollution forecast Euler mode to carry out simulation forecast, and under the constraint of high-space-time resolution weather forecast data, a continuous gas image field and a radionuclide pollution concentration field in a research period are simulated and output and used as driving data; inputting the driving data into an assimilation system, and performing assimilation inversion under the constraint of multi-type radionuclide observation data to obtain radionuclide emission positions, emission intensities and emission amounts hour by hour in a research period; the forward mode operator constructed by adopting the Euler mode for nuclear pollution prediction is expressed as: ; Wherein, the Is the first The radionuclide pollution concentration at the moment, subscripts s and l respectively represent the nuclides of the fine particle size section and the coarse particle size section, and the total concentration of the nuclides of the two particle size sections is used as the radionuclide pollution concentration; is a advection diffusion term of the nuclide with a fine particle size, Is a advection diffusion term of the nuclide of the coarse grain diameter section, Representing the wind speed in the horizontal direction, Wind speed representing the vertical direction; is a turbulent diffusion term of the nuclide with a fine particle size, The turbulence diffusion items of the nuclides in the coarse grain diameter section are smaller than the corresponding advection diffusion items; Representing turbulence diffusion coefficients of two kinds of particle size nuclides in horizontal direction and vertical direction, aiming at the motion characteristic difference of the two kinds of particle size nuclides, adopting differential adaptation of the turbulence diffusion coefficients, wherein the fine particle size nuclides adopt dynamic turbulence diffusion coefficients in horizontal direction based on real-time correction of turbulence pulsation intensity And Dynamic adjustment along with the change of atmospheric turbulence for improving the simulation precision of fine particle diffusion, and static turbulence diffusion coefficient of the coarse particle diameter section nuclide in the horizontal direction by adopting the coupling gravity sedimentation effect And Adapting to the motion characteristics of coarse particle gravity sedimentation dominant, and meeting That is, the turbulent diffusion term ratio of the fine-grain-diameter section nuclide is higher than that of the coarse-grain-diameter section nuclide; respectively represents dry sedimentation items of the nuclides of the fine particle size section and the nuclides of the coarse particle size section, The dry sedimentation rates of the nuclides in the fine particle size section and the nuclides in the coarse particle size section are respectively represented and satisfy The method comprises the steps of establishing a dry sedimentation velocity model of fine particle diameter section nuclides based on air particle exchange coefficients and surface adsorption efficiency, adapting the characteristic that the fine particle diameter section nuclides are easy to be adsorbed by atmospheric particulates and frequent in air particle exchange, establishing the dry sedimentation velocity model of coarse particle diameter section nuclides based on gravity sedimentation velocity and ground roughness, and representing the characteristic that the fine particle diameter section nuclides are dominant by gravity sedimentation and are obviously influenced by ground retardation; in order for the decay term to be a function of, Is the decay rate of the radionuclide; For the emission term, the increase in the concentration of the radionuclide in the atmosphere caused by the emission of the radionuclide is represented, Is the actual air density of the air, For the mode layer height corresponding to the height of the emission source, And The method comprises the steps of dynamically distributing the total emission in the fine-grain-diameter section nuclides and the coarse-grain-diameter section nuclides according to the ratio of the two kinds of grain-diameter section nuclides based on the actual measurement grain-diameter spectrum distribution characteristics of emission sources of historical statistics, updating distribution coefficients according to real-time actual measurement data, and adapting to the grain-diameter distribution differences of different emission sources; And Is in the horizontal direction and is in the vertical direction, Is in the vertical direction.
2. The radionuclide emission inversion method combining a four-dimensional variation and an euler mode according to claim 1, wherein a four-dimensional variation target functional of a radionuclide emission source term is constructed, expressed as: ; Wherein, the Is the objective function value; Is a state variable representing the hourly radionuclide emissions at the site of nuclear accident or at the site of nuclear leakage likely to occur, For a priori radionuclide emissions from nuclear accident reports when the location of the nuclear accident is specified, And Are one-dimensional vectors, whereas in the case of nuclear leakage, And Are three-dimensional vectors, and comprise grid areas representing possible nuclear leakage and nuclear leakage time; Representing the time; The length of time released in the atmosphere for radionuclide emissions; Background error covariance of radionuclide emissions, its dimension and Consistent, vector dimensions differ in different cases; is an observation vector; Taking the multi-type radionuclide observation data as constraint conditions to participate in assimilation inversion in the assimilation time window; The covariance of the observed errors of the radionuclide observed data of different types is distinguished by the covariance of the observed errors in the form of a diagonal matrix; a forward mode operator constructed for the Euler mode of nuclear pollution forecast; for observing operators, for The described radionuclide pollution concentration is converted into an observation operator with the same type as radionuclide observation data, and the space matching between the observation site and the mode format is simultaneously carried out Representing the vector transpose.
3. The radionuclide emission inversion method combining a four-dimensional variation and euler mode according to claim 2, wherein when constructing a four-dimensional variation target functional of a radionuclide emission source term, the method further comprises: Based on the prior radionuclide emission amount, the position and the height of the state variable are dynamically adjusted based on the uncertainty characteristic of the state variable, so that the background error covariance of the prior radionuclide emission amount adapting to the four-dimensional variation assimilation requirement is calculated, the observation error covariance of various radionuclide observation data is calculated according to the heterogeneity of the multi-type radionuclide observation data, and a special observation operator adapting to the four-dimensional variation assimilation mode of various radionuclide observation data is designed in a targeted manner, wherein the position of the state variable is considered to be fixed under the condition of determining the position of a nuclear accident emission source, only inversion assimilation is carried out on the emission intensity, and the position area where the emission is likely to occur is dynamically adjusted under the condition of uncertainty of the nuclear leakage radionuclide position, and the radionuclides in the grid where the area is used as the state variable.
4. A radionuclide emission inversion method combining a four-dimensional variation and an euler mode according to claim 3, wherein the special observation operator for adapting the four-dimensional variation assimilation mode of various radionuclide observation data is designed in a targeted manner, and the method comprises the following steps: The multi-type radionuclide observation data comprises specific activity observation data, sedimentation rate observation data and dose rate observation data of the radionuclides, wherein specific activity observation operators corresponding to the specific activity observation data are formed by unit conversion of the specific activity observation data and interpolation of grid points, the specific activity observation operators belong to the linear calculation problem, and for sedimentation rate observation operators corresponding to the sedimentation rate observation data and dose rate observation operators corresponding to the dose rate observation data, correlation among sedimentation rate, dose rate and radionuclide emission intensity is statistically analyzed according to a forecast result output by a nuclear pollution forecast Euler mode, a lookup table is constructed, and then the corresponding observation operators and accompanying programs thereof are provided through the lookup table for direct calling.
5. The radionuclide emission inversion method combining a four-dimensional variation and euler mode according to claim 1, wherein when inputting priori information into a nuclear pollution forecast euler mode for performing simulation forecast, the method further comprises: In the simulation forecasting process of the Euler mode of nuclear pollution forecasting, adopting a windward differential format to calculate advection diffusion terms in a forward mode operator, updating turbulence diffusion coefficients and dry sedimentation speeds which are differentially adapted to two types of particle size section nuclides in the forward mode operator, and adopting an implicit differential format to carry out space-time discrete solution on a concentration gradient diffusion equation in the integration process of the Euler mode of nuclear pollution forecasting.
6. The radionuclide emission inversion method combining a four-dimensional variation and an euler mode according to claim 5, wherein updating turbulence diffusion coefficients and dry settling speeds of two kinds of particle size segment nuclide differential adaptations in a forward mode operator comprises: The updating mode of the turbulence diffusion coefficient of the nuclide with the fine particle size section is as follows: ; ; Wherein, the Respectively the turbulence diffusion coefficients of the nuclides of the fine particle size segments in the horizontal direction and the vertical direction, Is a constant of the turbulence and is, Is the turbulent kinetic energy of the atmosphere; Is a turbulent energy dissipation rate, and is used for reflecting turbulent attenuation characteristics; is a correction function of turbulence diffusion coefficient and is matched with the adsorption efficiency of the surface of the nuclide of the fine particle size section Related to the nuclide exchange coefficient of the fine particle size segment In relation to the use of a liquid crystal display device, The method is used for reacting the mass exchange efficiency between the nuclide of the fine particle size section and the atmosphere; The updating mode of the turbulence diffusion coefficient of the nuclide in the coarse particle size section is as follows: ; ; Wherein, the Respectively the turbulence diffusion coefficients of the nuclides of the coarse grain diameter section in the horizontal direction and the vertical direction, Is the gravity sedimentation velocity of the nuclide in the coarse grain diameter section A related correction function; characterizing the characteristic length of turbulent motion for the mixing length, correlated to the atmospheric knots and underlying surface roughness; the updating mode of the dry sedimentation velocity of the nuclides in two particle size sections is as follows: ; Wherein, the For dry sedimentation rate, subscript Representing a fine particle size fraction species and a coarse particle size fraction species, Is the speed of gravity sedimentation, and the gravity sedimentation speed, Is aerodynamic resistance, and is positively correlated with the roughness of the underlying surface; is the laminar sub-layer resistance, the resistance of the reaction particles passing through the atmospheric laminar sub-layer; Is the surface resistance, is set as a look-up table according to the underlying surface type, and is used to correct the dry settling velocity.
7. The radionuclide emission inversion method integrating four-dimensional variation and euler modes according to claim 1, wherein the forward mode operator and the driving data are both constructed and calculated by a nuclear pollution forecast euler mode under an euler coordinate system, are completely coupled to realize matching based on the same coordinate system, and drive assimilation inversion of radionuclides through a complete coupling structure.
8. The method of radionuclide emission inversion fusing four-dimensional variation and euler patterns according to claim 1, further comprising, after collecting multi-type radionuclide observations after nuclear accident occurrence: preprocessing is carried out on the multi-type radionuclide observed data, wherein the preprocessing mode comprises background data analysis, threshold value check analysis, space-time consistency analysis and cross-validation analysis.
9. A radionuclide emission inversion system that fuses a four-dimensional variation and an euler mode, the system comprising: the data acquisition module is used for acquiring multi-type radionuclide observation data, high space-time resolution weather forecast data and nuclear accident/nuclear leakage reports after nuclear accidents occur and dividing the multi-type radionuclides into fine-particle-diameter section nuclides and coarse-particle-diameter section nuclides; The assimilation system construction module is used for constructing a four-dimensional variation target functional of a radionuclide emission source item, adopting a nuclear pollution forecast Euler mode, constructing a forward mode operator used for describing the evolution process of the radionuclide in the atmosphere in the four-dimensional variation target functional, and constructing an assimilation system of radionuclide emission intensity and emission position according to the four-dimensional variation target functional comprising the forward mode operator, wherein in the forward mode operator, turbulence diffusion items corresponding to the two types of nuclides with particle size sections adopt differentially adaptive turbulence diffusion coefficients, and corresponding dry sedimentation items adopt differentially adaptive dry sedimentation speeds; the prior forecasting module is used for taking the radionuclide emission position, time and emission amount recorded and estimated by the nuclear accident/nuclear leakage report as prior information, inputting the prior information into a nuclear pollution forecasting Euler mode to carry out simulation forecasting, and under the constraint of high-space-time resolution weather forecasting data, simulating and outputting a continuous gas image field and a radionuclide pollution concentration field in a research period as driving data; The emission inversion module is used for inputting the driving data into an assimilation system, and performing assimilation inversion under the constraint of the multi-type radionuclide observation data to obtain radionuclide emission positions, emission intensities and emission amounts every hour in a research period; the forward mode operator constructed by adopting the Euler mode for nuclear pollution prediction is expressed as: ; Wherein, the Is the first The radionuclide pollution concentration at the moment, subscripts s and l respectively represent the nuclides of the fine particle size section and the coarse particle size section, and the total concentration of the nuclides of the two particle size sections is used as the radionuclide pollution concentration; is a advection diffusion term of the nuclide with a fine particle size, Is a advection diffusion term of the nuclide of the coarse grain diameter section, Representing the wind speed in the horizontal direction, Wind speed representing the vertical direction; is a turbulent diffusion term of the nuclide with a fine particle size, The turbulence diffusion items of the nuclides in the coarse grain diameter section are smaller than the corresponding advection diffusion items; Representing turbulence diffusion coefficients of two kinds of particle size nuclides in horizontal direction and vertical direction, aiming at the motion characteristic difference of the two kinds of particle size nuclides, adopting differential adaptation of the turbulence diffusion coefficients, wherein the fine particle size nuclides adopt dynamic turbulence diffusion coefficients in horizontal direction based on real-time correction of turbulence pulsation intensity And Dynamic adjustment along with the change of atmospheric turbulence for improving the simulation precision of fine particle diffusion, and static turbulence diffusion coefficient of the coarse particle diameter section nuclide in the horizontal direction by adopting the coupling gravity sedimentation effect And Adapting to the motion characteristics of coarse particle gravity sedimentation dominant, and meeting That is, the turbulent diffusion term ratio of the fine-grain-diameter section nuclide is higher than that of the coarse-grain-diameter section nuclide; respectively represents dry sedimentation items of the nuclides of the fine particle size section and the nuclides of the coarse particle size section, The dry sedimentation rates of the nuclides in the fine particle size section and the nuclides in the coarse particle size section are respectively represented and satisfy The method comprises the steps of establishing a dry sedimentation velocity model of fine particle diameter section nuclides based on air particle exchange coefficients and surface adsorption efficiency, adapting the characteristic that the fine particle diameter section nuclides are easy to be adsorbed by atmospheric particulates and frequent in air particle exchange, establishing the dry sedimentation velocity model of coarse particle diameter section nuclides based on gravity sedimentation velocity and ground roughness, and representing the characteristic that the fine particle diameter section nuclides are dominant by gravity sedimentation and are obviously influenced by ground retardation; in order for the decay term to be a function of, Is the decay rate of the radionuclide; For the emission term, the increase in the concentration of the radionuclide in the atmosphere caused by the emission of the radionuclide is represented, Is the actual air density of the air, For the mode layer height corresponding to the height of the emission source, And The method comprises the steps of dynamically distributing the total emission in the fine-grain-diameter section nuclides and the coarse-grain-diameter section nuclides according to the ratio of the two kinds of grain-diameter section nuclides based on the actual measurement grain-diameter spectrum distribution characteristics of emission sources of historical statistics, updating distribution coefficients according to real-time actual measurement data, and adapting to the grain-diameter distribution differences of different emission sources; And Is in the horizontal direction and is in the vertical direction, Is in the vertical direction.

Description

Radionuclide emission inversion method and system integrating four-dimensional variation and Euler mode Technical Field The application relates to the technical field of nuclear pollution prediction, in particular to a radionuclide emission inversion method and system integrating four-dimensional variation and Euler mode. Background Accurate acquisition of radionuclide emission is a precondition for developing nuclear pollution accurate forecasting and early warning, however, in an actual scene, the nuclide emission intensity of most nuclear accidents is difficult to directly acquire, and in a nuclear leakage scene, the nuclide emission position is in an unknown state. The problems not only severely restrict the accuracy of nuclear pollution prediction, but also bring great challenges to the efficient development of nuclear safety emergency guarantee work. At present, aiming at the estimation of the radionuclide emission in nuclear accidents, the main stream technical scheme is realized based on the combination of a traditional pollution diffusion model conforming to Gaussian distribution and observation data, namely, the inverse problem of emission source intensity and concentration distribution is solved by acquiring the data such as wind speed, wind direction, radionuclide concentration and the like around the nuclear accidents, and then the nuclide emission is estimated in an inversion mode. However, the Gaussian model has poor adaptability to the problem of nuclide diffusion under complex meteorological conditions, so that the nuclide emission obtained by inversion has higher uncertainty. In addition, a small amount of research is performed on the inversion of the nuclide emission based on the combination of particle diffusion distribution and radionuclide observation data in a Lagrange mode, but in a region far away from a pollution source, the inversion precision is obviously reduced due to the reduction of the number of tracked particles, meanwhile, the inversion performance is limited due to the fact that the inversion is coupled with a Euler model adopted by the current mainstream weather forecast, and key data such as a weather wind field cannot be fully utilized. Disclosure of Invention Based on the above, it is necessary to provide a radionuclide emission inversion method and system integrating four-dimensional variation and euler mode, which can rapidly and efficiently dynamically estimate the radionuclide emission position, emission intensity and emission amount from hour to hour, can be used for researching a nuclear pollution forecasting and early-warning mode, accurately improves the accuracy of nuclear pollution forecasting, and overcomes the defects of the existing traditional method. A radionuclide emission inversion method that fuses a four-dimensional variation and an euler mode, the method comprising: Collecting multi-type radionuclide observation data, high space-time resolution weather forecast data and nuclear accident/nuclear leakage reports after nuclear accidents occur, and dividing the multi-type radionuclides into fine-particle-diameter-section nuclides and coarse-particle-diameter-section nuclides; Constructing a four-dimensional variation target functional of a radionuclide emission source item, adopting a nuclear pollution forecast Euler mode, constructing a forward mode operator used for describing the evolution process of the radionuclide in the atmosphere in the four-dimensional variation target functional, and constructing an assimilation system of radionuclide emission intensity and emission position according to the four-dimensional variation target functional comprising the forward mode operator, wherein in the forward mode operator, turbulence diffusion items corresponding to the nuclides of two types of particle size sections adopt differential adaptive turbulence diffusion coefficients, and corresponding dry sedimentation items adopt differential adaptive dry sedimentation speeds; the radionuclide emission position, time and emission quantity recorded and estimated by the nuclear accident/nuclear leakage report are used as priori information, the priori information is input into a nuclear pollution forecast Euler mode to carry out simulation forecast, and under the constraint of high-space-time resolution weather forecast data, a continuous gas image field and a radionuclide pollution concentration field in a research period are simulated and output and used as driving data; and inputting the driving data into an assimilation system, and performing assimilation inversion under the constraint of the multi-type radionuclide observation data to obtain the radionuclide emission position, emission intensity and emission amount in the research period hour by hour. In one embodiment, a four-dimensional variational objective functional of the radionuclide emission source term is constructed, expressed as: ; Wherein, the Is the objective function value; Is a state variab