Multi-scale coupling method and system for radionuclide generation and release

Abstract

The invention discloses a radionuclide generation and release multi-scale coupling method and system, and the method comprises the steps: building a single crystal cell structure model of a crystal based on the first principle of a material unit cell system according to the determined chemical components and structure of a material, and automatically expanding the single crystal cell structure model into a multi-unit cell structure model; adsorption atoms are introduced into the multi-unit-cell structure model, a convergence test is carried out, and a stable system structure is determined through energy minimization; establishing a diffusion coefficient library of radionuclides in a main material in the reactor based on a stable system structure; calling a multi-physics field coupling program to establish a one-dimensional node model, and searching a diffusion coefficient library according to the one-dimensional node model to complete material parameter setting; and calculating the nuclide concentration distribution of the one-dimensional node model, and obtaining the nuclide release rate within the calculation time according to the concentration difference value before and after calculation. Important input parameters are provided for accurately estimating the release condition of the accumulation amount of the reactor core, isolated and conservative hypotheses are reduced, and the calculation precision is improved.

Description

Technical Field

[0001] The present invention relates to the field of nuclear reactor computing technology, and in particular to a multi-scale coupling method and system for radioactive nuclide generation and release. Background Art

[0002] During normal operation, fission products generated in the fuel elements of the reactor core will migrate from the fuel core to the external materials under the effects of temperature and concentration differences and material irradiation. Generally, due to design considerations, the release of fission products from the core needs to pass through several safety barriers, mainly the fuel cladding, the primary pressure boundary and the containment. The barriers of different types of reactors may be different, but they all meet the requirements of defense in depth.

[0003] The most fundamental measure of the performance of reactor fuel elements is the ability to retain fission products. The fission products released from the core mainly come from the contamination and failure of fissile materials during the manufacturing process of fuel elements. In addition, volatile metals (such as Cs and Sr) can also be released from the barrier by diffusion at a sufficiently long time and high temperature. There are three main forms of nuclides: atomic, molecular and aerosol. Due to the huge number of nuclides, they are generally grouped according to their physical and chemical properties, and each group is represented by a major nuclide. The grouping method of nuclides can refer to the 8 levels of 54 nuclides divided by the IAEA. Studying the release of radionuclides in reactor fuel elements is of particular importance for the normal operation of the reactor and the maintenance dose rate. However, the release of radionuclides involves the study of the adsorption microscopic mechanism of nuclide atoms and material structures. The existing nuclide data are measured based on the irradiation tests and post-irradiation inspection results of early scientists, which have great uncertainty and technical limitations.

[0004] Therefore, based on the first principles method, a multi-scale coupling method connecting the microscopic, mesoscopic and macroscopic levels is established, which not only avoids the technical and safety requirements of irradiation testing and post-irradiation inspection, reduces the cost of radionuclide diffusion research, but also improves the efficiency and adaptability of microscopic mechanistic research on nuclides in different materials. Summary of the invention

[0005] In view of the above existing problems, the present invention is proposed.

[0006] Therefore, the present invention provides a multi-scale coupling method and system for the production and release of radionuclides to solve the problems of data uncertainty, mechanism complexity, difficulty in controlling experimental conditions, and insufficient model prediction accuracy in prior art research.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a multi-scale coupling method for the production and release of radioactive nuclides, comprising: constructing a single cell structure model of the crystal based on the first principles of the material unit cell system according to the determined chemical composition and structure of the material, and automatically expanding it to a multi-cell structure model; introducing adsorbed atoms into the multi-cell structure model and performing a convergence test, and determining the stable system structure of the system composed of the multi-cell structure model and the adsorbed atoms through energy minimization; establishing a diffusion coefficient library of radioactive nuclides in the main materials in the pile based on the stable system structure; calling a multi-physics field coupling program to establish a one-dimensional node model, searching the diffusion coefficient library according to the one-dimensional node model, and completing the material parameter setting; calculating the nuclide concentration distribution of the one-dimensional node model, and obtaining the nuclide release rate within the calculation time according to the concentration difference before and after the calculation.

[0009] As a preferred solution of the multi-scale coupling method for radionuclide generation and release described in the present invention, the acquisition of the multi-cell structure model includes:

[0010] Determine the type of reactor under study, the form of fuel elements, the moderator material and its pore volume fraction, the cooling material, the type X of main materials in the reactor and the amount of materials, determine the chemical composition of the main material type X in the reactor, including the standard value, factory value, and atomic number of each element, and determine the structure of each material, including the atomic number and crystal form;

[0011] The control flow program calls the nuclear design software to calculate the total amount of radioactivity in the core and writes the result into an output file, and the control flow program determines the type Y of radioactive nuclide in the core according to the output file;

[0012] The control flow program selects the i-th material, where i=1...X, and automatically establishes a single cell structure model of the crystal based on the first principles of the material unit cell system according to the determined chemical composition and structure of the material. The control flow program calls the first principles software to expand the single cell structure model into a polycell structure model, and the polycell structure model includes a body-centered cubic structure and a face-centered cubic structure.

[0013] As a preferred solution of the multi-scale coupling method for radionuclide generation and release described in the present invention, the determination of the stable architecture includes:

[0014] Introducing an adsorbed atom j into the polycell structure model, wherein j=1...Y, and the adsorbed atom is the radionuclide under study, i.e., one of the types of the core radionuclide;

[0015] The control flow program calls the first principle software to perform a convergence test, that is, the first principle software determines the plane wave cutoff energy and K point network setting of the polycell model through a convergence test, determines the N-layer structure of the adsorption system, fixes the m layers on one side of the adsorption system, performs relaxation calculations on the other Nm layers, and ensures that sufficient energy exchange is performed between atoms, and the adsorbed atoms reach an optimal adsorption height;

[0016] The adsorption energy, charge difference density, and state density of the adsorption system when it is stable are calculated in sequence, and the adsorption energy, charge difference density, and state density are used as control flow software to preliminarily evaluate the adsorption relationship between the adsorbed atom j and the material i;

[0017] The stable system structure of the system consisting of a polycell structure model and one adsorbed atom is determined by energy minimization calculation. At this time, the interstitial position is the most stable interstitial position that meets the lowest energy point.

[0018] As a preferred embodiment of the multi-scale coupling method for radionuclide generation and release described in the present invention, it also includes:

[0019] The first principle software searches for the optimal positional diffusion transition state of the adsorbed atom in the adjacent interstitial atomic layer in the adsorption structure according to the most stable system structure corresponding to the determined most stable interstitial position, and obtains the diffusion activation energy curve. The difference between the highest energy point and the lowest energy point in the diffusion activation energy curve is E α is the diffusion barrier or diffusion activation energy, and the highest energy point in the diffusion activation energy curve is the transition state of diffusion;

[0020] According to transition state theory, there is a functional relationship between the diffusion coefficient and the transition frequency of the atom, and the transition frequency satisfies the Arrhenius formula;

[0021] The first principle software outputs adsorption energy, charge differential density, state density, transition distance, transition frequency, diffusion barrier or diffusion activation energy, and diffusion coefficient formula, and writes them into the output file.

[0022] As a preferred solution of the multi-scale coupling method for radionuclide generation and release described in the present invention, the establishment of the diffusion coefficient library includes:

[0023] The control flow program reads the adsorption energy in the output file, and for all combinations of the type X of radionuclides and the type Y of main materials, if the adsorption energy is positive, it is exothermic, and spontaneous adsorption can be carried out; if the adsorption energy is negative, it is endothermic, indicating that the adsorbed atoms are heated or otherwise in the adsorption structure and are unstable after adsorption;

[0024] The control flow program reads the charge differential density in the output file, and for all combinations of the type X of radioactive nuclides and the type Y of main materials, if the charge density of the electron cloud portion of the adsorbed atom j increases, electrons are obtained from the material i, and if the charge density of the electron cloud portion of the adsorbed atom j decreases, electrons are lost from the material i; according to the elemental properties of the adsorbed atom j and the material i, it is judged whether the number of electrons gained and lost can enable the adsorbed atom j or the material i to form a stable chemical bond, and if it cannot be formed, it means that the electronic element of the material i and the adsorbed atom j has not changed, that is, the adsorbed atom and the material cannot be adsorbed to each other;

[0025] The control flow program reads the state density in the output file, discards the combination in which the adsorbed atom and the material cannot be adsorbed to each other, and judges the adsorption properties of the remaining combinations from the state density. If a strong resonance peak appears in the state density of the adsorbed atom j, it means that the adsorbed atom j interacts with the material i. If the Fermi level of the adsorption system is not offset, the adsorbed atom j is physically adsorbed to the material i, otherwise it is chemically adsorbed. If the state density of the adsorbed atom j does not show a strong resonance peak or has a small fluctuation, the adsorbed atom j is physically adsorbed to the material i.

[0026] The control flow program reads the diffusion coefficient formula in the output file, obtains the diffusion coefficient of the radioactive nuclide in the solid material by using the diffusion coefficient formula, marks the radioactive nuclide and the matrix material according to certain numbers, writes the diffusion coefficient formula of the radioactive nuclide in the matrix material into the diffusion coefficient library file of the nuclide and saves the file;

[0027] The above steps are repeated until all combinations of the type X of radionuclides and the type Y of main materials are calculated. At this time, the control flow program has established and updated the diffusion coefficient library of the radionuclides in the main materials in the reactor.

[0028] As a preferred solution of the multi-scale coupling method for radionuclide generation and release described in the present invention, the material parameter setting includes:

[0029] According to the determined reactor type, fuel element form and geometric structure, moderator material, and cooling material, the control flow program calls the multi-physics field coupling program to respectively establish one-dimensional geometric nodes of the fuel element, one-dimensional geometric nodes of the moderator material grains, and one-dimensional geometric nodes of the pores in the moderator material, wherein the physical field corresponding to the one-dimensional node model is the Fick diffusion field;

[0030] The total amount and type of radioactive nuclides and the calculation time are passed to the one-dimensional node model of the fuel element in the multi-physics field coupling program, the total amount and type of radioactive nuclides are set as the initial conditions for the release calculation in the fissile material region, the calculation time of the one-dimensional node model of the fuel element is set, the corresponding material in the diffusion coefficient library is searched according to the material of the one-dimensional geometric node model of the fuel element, and the diffusion coefficient formula in the diffusion coefficient library is assigned to the material physical field parameter setting of the model, and in the same way, the multi-physics field setting of the one-dimensional geometric node model of the moderator material grains and the one-dimensional geometric node model of the pores in the moderator material is completed.

[0031] As a preferred solution of the multi-scale coupling method for radionuclide generation and release described in the present invention, the calculation of the nuclide release rate includes:

[0032] The multi-physics coupling program calculates the nuclide concentration distribution in each material layer of the one-dimensional geometric node model of the fuel element, the one-dimensional geometric node model of the grains of the moderator material, and the one-dimensional geometric node model of the pores in the moderator material in a parallel manner within the calculation time of the radioactive nuclide j;

[0033] According to the one-dimensional geometric node model of the moderator material grains, the volume of the grains is calculated, and according to the volume occupied by the macroscopic moderator material in the direction of the geometric node model surrounding the fuel element, the concentration of radionuclides retained by the moderator material on a macroscopic scale is obtained;

[0034] The control flow software reads the output file of the multi-physics field coupling program, and obtains the nuclide release rate within the calculation time according to the difference between the nuclide concentrations before and after the calculation time.

[0035] In a second aspect, the present invention provides a multi-scale coupled system for the generation and release of radionuclides, comprising:

[0036] A model building unit is used to build a single-cell structure model of a crystal based on the first principles of the material unit cell system according to the determined chemical composition and structure of the material, and automatically expand it to a multi-cell structure model;

[0037] A structure determination unit, used for introducing adatoms into the polycell structure model and performing a convergence test, and determining a stable system structure of a system consisting of the polycell structure model and the adatoms by energy minimization;

[0038] A coefficient library establishment unit, used to establish a diffusion coefficient library of radioactive nuclides in main materials in the pile based on the stable system structure;

[0039] A parameter setting unit, used for calling a multi-physics field coupling program to establish a one-dimensional node model, searching the diffusion coefficient library according to the one-dimensional node model, and completing material parameter setting;

[0040] The parameter calculation unit is used to calculate the nuclide concentration distribution of the one-dimensional node model and obtain the nuclide release rate within the calculation time according to the concentration difference before and after the calculation.

[0041] In a third aspect, the present invention provides a computing device, comprising:

[0042] Memory and processor;

[0043] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the method are implemented.

[0044] In a fourth aspect, the present invention provides a computer-readable storage medium storing computer-executable instructions, which implement the steps of the method when executed by a processor.

[0045] Compared with the prior art, the beneficial effects of the present invention are: ① The present invention links the microscopic mechanism of nuclide diffusion in materials with the macroscopic diffusion phenomenon, and can provide a multi-dimensional evaluation of the adsorption properties of each nuclide; ② The multi-scale coupling method proposed in the present invention avoids the technical and safety requirements of irradiation testing and post-irradiation inspection, and reduces the cost of radionuclide diffusion research; ③ The calculation method proposed in the present invention establishes a diffusion database of all radioactive nuclides and in-pile materials, which improves the applicability of the method to different reactors. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0047] Figure 1 This is an overall flow chart of a multi-scale coupling method for radionuclide generation and release according to an embodiment of the present invention;

[0048] Figure 2 A schematic diagram of the steps of a multi-scale coupling method for radionuclide generation and release according to an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of a fuel element and a moderator material (including grains and pores in the moderator material) of a multi-scale coupling method for radionuclide production and release according to an embodiment of the present invention;

[0050] Figure 4A schematic diagram of a unit cell structure model of a certain material (Fe-Mo-Cr) of different system crystals in the multi-scale coupling method for radionuclide generation and release according to an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of the calculation results of the diffusion barrier of different systems of a certain material (Fe-Mo-Cr) according to the multi-scale coupling method for the production and release of radionuclides described in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0053] Example 1

[0054] Reference Figure 1 to Figure 3 This is an embodiment of the present invention. In order to meet the requirements of establishing a true and reliable radionuclide adsorption parameter library and adapting to the calculation of new reactor source terms, the present invention provides a multi-scale coupling calculation method for studying the diffusion and release of radionuclides generated in materials to realize nuclear reactor source term analysis. Specifically, the following steps are included:

[0055] S100: According to the determined chemical composition and structure of the material, a single cell structure model of the crystal is constructed based on the first principles of the material unit cell system, and it is automatically expanded to a multi-cell structure model;

[0056] In the embodiments of the present application, Figure 2 As shown, the acquisition of the polycell structure model includes:

[0057] Determine the type of reactor being studied, the form of fuel elements, the moderator material and its pore volume fraction, the cooling material, the main material type X in the reactor and the amount of material, such as Figure 3 As shown, determine the chemical composition of the main material type X in the pile, including the standard value (%), factory value (%), and atomic number (expressed in the simplest integer ratio) of each element, and determine the structure of each material, including atomic number and crystal form;

[0058] The control flow program calls the nuclear design software to calculate the total amount of radioactivity in the core and writes the result into the output file. The control flow program determines the type of radionuclide Y in the core based on the output file.

[0059] The control flow program selects the i-th material, where i=1...X, and automatically establishes a single cell structure model of the crystal based on the first principles of the material unit cell system according to the determined chemical composition and structure of the material. The control flow program calls the first principles software to expand the single cell structure model into a polycell structure model, and the polycell structure model includes a body-centered cubic structure and a face-centered cubic structure.

[0060] S200: Introducing adatoms into the polycell structure model and conducting convergence tests, and determining the stable architecture of the system consisting of the polycell structure model and adatoms through energy minimization;

[0061] In the embodiments of the present application, Figure 2 As shown, the determination of a stable architecture includes:

[0062] Introduce one adatom j into the polycell structure model, where j = 1...Y, and the adatom is the radionuclide under study, i.e. one of the types of radionuclide in the core;

[0063] The control flow program calls the first principle software to perform a convergence test, that is, the plane wave cutoff energy and K-point network settings set by the first principle software for the polycell model are determined through convergence tests;

[0064] Determine the N-layer structure of the adsorption system, fix the m-layer on one side of the adsorption system, perform relaxation calculations on the other Nm-layers, and ensure that sufficient energy exchange occurs between atoms and that the adsorbed atoms reach the optimal adsorption height;

[0065] The adsorption energy, charge difference density, and state density are calculated in sequence when the adsorption system is stable. The adsorption energy, charge difference density, and state density are used as the control flow software to preliminarily evaluate the adsorption relationship between the adsorbed atom j and the material i.

[0066] The stable system structure of the system consisting of a multi-cell structure model and one adsorbed atom is determined by energy minimization calculation. At this time, the interstitial position is the most stable interstitial position that meets the lowest energy point. S300: Based on the stable system structure, a diffusion coefficient library of the main materials of the radioactive nuclides in the pile is established;

[0067] In the embodiments of the present application, Figure 2 As shown in the figure, the first principle software searches for the optimal positional diffusion transition state of the adsorbed atom in the adjacent interstitial atomic layer in the adsorption structure according to the most stable system structure corresponding to the determined most stable interstitial position, and obtains the diffusion activation energy curve. The difference between the highest energy point and the lowest energy point in the diffusion activation energy curve is E α is the diffusion barrier or diffusion activation energy. The highest energy point in the diffusion activation energy curve is the transition state of diffusion.

[0068] According to the transition state theory, there is a functional relationship between the diffusion coefficient and the transition frequency of the atom, and the transition frequency satisfies the Arrhenius formula, which is expressed as:

[0069]

[0070] Where D is the diffusion coefficient, L is the transition distance, v0 is the transition frequency, N A is Avogadro's constant, about 6.0221×10 23 mol -1 , R is the ideal gas constant, about 8.3141 J·mol -1 ;

[0071] The first-principles software outputs adsorption energy, charge differential density, state density, transition distance, transition frequency, diffusion barrier or diffusion activation energy, and diffusion coefficient formula, and writes them into the output file;

[0072] Furthermore, the control flow program reads the adsorption energy in the output file. For all combinations of the type X of the radionuclide and the type Y of the main material, if the adsorption energy is positive, it is exothermic, and the adsorption can proceed spontaneously. If the adsorption energy is negative, it is endothermic, indicating that the adsorbed atom is heated or otherwise in the adsorption structure and is unstable after adsorption.

[0073] Furthermore, the control flow program reads the charge differential density in the output file, and for all combinations of the type X of radioactive nuclides and the type Y of main materials, if the charge density of the electron cloud portion of the adsorbed atom j increases, electrons are obtained from the material i, and if the charge density of the electron cloud portion of the adsorbed atom j decreases, electrons are lost from the material i; according to the elemental properties of the adsorbed atom j and the material i, it is determined whether the number of electrons gained and lost can enable the adsorbed atom j or the material i to form a stable chemical bond, and if not, it means that the electronic element of the material i and the adsorbed atom j has not changed, that is, the adsorbed atom and the material cannot be adsorbed to each other;

[0074] Furthermore, the control flow program reads the state density in the output file, discards the combination in which the adsorbed atom and the material cannot be adsorbed to each other, and judges the adsorption properties of the remaining combinations from the state density. If a strong resonance peak appears in the state density of the adsorbed atom j, it means that the adsorbed atom j interacts with the material i. If the Fermi level of the adsorption system is not offset, the adsorbed atom j is physically adsorbed to the material i, otherwise it is chemically adsorbed. If the state density of the adsorbed atom j does not show a strong resonance peak or has a small fluctuation, the adsorbed atom j is physically adsorbed to the material i.

[0075] Further, the control flow program reads the diffusion coefficient formula in the output file, obtains the diffusion coefficient of the radioactive nuclide in the solid material through the diffusion coefficient formula, marks the radioactive nuclide and the matrix material according to certain numbers, writes the diffusion coefficient formula of the radioactive nuclide in the matrix material into the diffusion coefficient library file of the nuclide and saves the file;

[0076] Furthermore, the above steps are repeated until all combinations of the type X of radionuclides and the type Y of main materials are calculated, at which point the control flow program has established and updated the diffusion coefficient library of the reactor's radionuclides in the main materials in the reactor.

[0077] S400: calling a multi-physics field coupling program to establish a one-dimensional node model, searching a diffusion coefficient library according to the one-dimensional node model, and completing material parameter setting;

[0078] In the embodiments of the present application, Figure 2 As shown in the figure, according to the determined reactor type, fuel element form and geometric structure, moderator material, and cooling material, the control flow program calls the multi-physics field coupling program to respectively establish the one-dimensional geometric nodes of the fuel element, the one-dimensional geometric nodes of the moderator material grains, and the one-dimensional geometric nodes of the pores in the moderator material. Among them, the physical field corresponding to the one-dimensional node model is the Fick diffusion field, which is defined by the Fick diffusion theorem:

[0079]

[0080] Among them, J x is the diffusion flux, atom·m -2 ·s; D is the diffusion coefficient, m -2 ·s; c is the concentration, atom·m -3 ; x is position or length, m;

[0081] The total amount and type of radionuclides and the calculation time are passed to the one-dimensional node model of the fuel element in the multi-physics coupling program, the total amount and type of radionuclides are set as the initial conditions for the release calculation in the fissile material region, the calculation time of the one-dimensional node model of the fuel element is set, the corresponding material in the diffusion coefficient library is searched according to the material of the one-dimensional geometric node model of the fuel element, and the diffusion coefficient formula in the diffusion coefficient library is assigned to the material physical field parameter setting of the model;

[0082] In the same way, complete the multi-physics field settings of the one-dimensional geometric node model of the grains of the slowing material and the one-dimensional geometric node model of the pores in the slowing material.

[0083] S500: Calculate the nuclide concentration distribution of the one-dimensional node model, and obtain the nuclide release rate within the calculation time according to the concentration difference before and after the calculation;

[0084] In the embodiments of the present application, Figure 2 As shown, the multi-physics coupling program calculates the nuclide concentration distribution in each material layer of the one-dimensional geometric node model of the fuel element, the one-dimensional geometric node model of the moderator material grains, and the one-dimensional geometric node model of the pores in the moderator material in parallel within the calculation time. The diffusion calculation satisfies the mass conservation theorem:

[0085]

[0086] Where V is the volume, m 3 ; S is the surface area, m 2 ; p is the production rate per unit volume, m -3 ·s -1 ; c is the concentration per unit volume, m -3 ; λ is the decay constant, s -1 ; J is the transport flux through all external surfaces, m -2 ·s -1 ; where λ and p describe the disappearance and production of nuclides in a general way and may involve some additional processes;

[0087] According to the one-dimensional geometric node model of the moderator material grains, the volume of the grains is calculated. According to the volume occupied by the macro-scale moderator material in the direction of the geometric node model and surrounding the fuel element, the concentration of radionuclides retained by the moderator material on a macro scale is obtained (the concentration has taken into account the influence of the pores in the moderator material, and the pore fraction is the value determined in step 1. The one-dimensional geometric node model of the pores is processed in the same way as the one-dimensional geometric node model of the grains);

[0088] The control flow software reads the output file of the multi-physics coupling program and obtains the nuclide release rate within the calculation time according to the difference in nuclide concentration before and after the calculation time.

[0089] Therefore, it can be seen from the above that in order to establish a radioactive nuclide adsorption parameter library for new nuclear power plant materials, the present invention provides a multi-scale coupling calculation method for source term calculation work in the field of radiation protection design of new reactor nuclear power plants. Starting from the first principles of the material unit cell system, the method realizes the calculation of the diffusion coefficient of radioactive nuclides in the material through the transition state theory, and provides important input parameters for accurately estimating the release of the reactor core stockpile. In addition, the method establishes the whole process of the generation and release of radioactive nuclides, reduces isolated conservative assumptions, and improves the accuracy of calculation.

[0090] The above is a schematic scheme of a multi-scale coupling method for radionuclide production and release in this embodiment. It should be noted that the technical scheme of the multi-scale coupling system for radionuclide production and release and the technical scheme of the multi-scale coupling method for radionuclide production and release described above belong to the same concept. For details not described in detail in the technical scheme of the multi-scale coupling system for radionuclide production and release in this embodiment, please refer to the description of the technical scheme of the multi-scale coupling method for radionuclide production and release described above.

[0091] This embodiment also provides a multi-scale coupling system for the generation and release of radionuclides, including:

[0092] A model building unit is used to build a single-cell structure model of a crystal based on the first principles of the material unit cell system according to the determined chemical composition and structure of the material, and automatically expand it to a multi-cell structure model;

[0093] The structure determination unit is used to introduce adatoms into the polycell structure model and perform convergence tests, and to determine the stable architecture of the system consisting of the polycell structure model and adatoms through energy minimization;

[0094] A coefficient library establishment unit is used to establish a diffusion coefficient library of radionuclides in the main materials in the reactor based on a stable system structure;

[0095] A parameter setting unit is used to call a multi-physics field coupling program to establish a one-dimensional node model, search a diffusion coefficient library according to the one-dimensional node model, and complete material parameter setting;

[0096] The parameter calculation unit is used to calculate the nuclide concentration distribution of the one-dimensional node model and obtain the nuclide release rate within the calculation time according to the concentration difference before and after the calculation.

[0097] This embodiment also provides a computing device, including:

[0098] Memory and processor;

[0099] The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the method proposed in the above embodiment.

[0100] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method proposed in the above embodiment is implemented.

[0101] The storage medium proposed in this embodiment and the method proposed in the above embodiment belong to the same inventive concept. The technical details not fully described in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0102] Through the above description of the implementation methods, the technicians in the relevant field can clearly understand that the present invention can be implemented by means of software and necessary general hardware, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (RandomAccess Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform the methods of various embodiments of the present invention.

[0103] Example 2

[0104] Reference Figure 4 and Figure 5 Based on the previous embodiment, this embodiment provides an application example of a multi-scale coupling method and system for the production and release of radionuclides, in order to verify and illustrate the technical effects adopted in this method.

[0105] In this embodiment, the reactor type, fuel element form, moderator material and its pore volume fraction, cooling material, main material type X and material quantity in the reactor are determined, the chemical composition of the main material type X in the reactor is determined, including the standard value (%), factory value (%), and atomic number (expressed in the simplest integer ratio) of each element, and the structure of each material is determined, including the atomic number and crystal form, as shown in the following table;

[0106]

[0107] Then, the control flow program calls the nuclear design software to calculate the total amount of radioactivity in the core and writes the result into the output file. The control flow program determines the type of radioactive nuclide Y in the core according to the output file. The control flow program selects a material and automatically establishes a single cell structure model of the crystal based on the first principle of the material unit cell system according to the determined chemical composition and structure of the material, such as Figure 4 As shown, the control flow program calls the first principle software to expand the single cell structure model into a polycell structure model, and the polycell structure model includes a body-centered cubic structure and a face-centered cubic structure.

[0108] An adsorbed atom is introduced into the polycell structure model, and the adsorbed atom is the radionuclide under study, that is, one of the types of core radionuclides; the control flow program calls the first-principles software to perform a convergence test, that is, the plane wave cutoff energy and K-point network settings set by the first-principles software for the polycell model are determined through a convergence test; the N-layer structure of the adsorption system is determined, the m layers on one side of the adsorption system are fixed, and relaxation calculations are performed on the other Nm layers, and it is ensured that sufficient energy exchange occurs between atoms and that the adsorbed atoms reach the optimal adsorption height; the adsorption energy, charge difference density, and state density are calculated in turn when the adsorption system is stable, and the adsorption energy, charge difference density, and state density are used as the control flow software to preliminarily evaluate the adsorption relationship between the adsorbed atom j and the material i; the stable system structure of the system composed of the polycell structure model and one adsorbed atom is determined through energy minimization calculation, and the interstitial position at this time is the most stable interstitial position that meets the lowest energy point.

[0109] Then, the first-principles software searches for the optimal positional diffusion transition state of the adsorbed atoms in the adjacent interstitial atomic layer in the adsorption structure according to the most stable system structure corresponding to the determined most stable interstitial position, and obtains the diffusion activation energy curve, such as Figure 5 As shown in the figure, the difference between the highest and lowest energy points in the diffusion activation energy curve is E α is the diffusion barrier or diffusion activation energy. The highest energy point in the diffusion activation energy curve is the transition state of diffusion. According to the transition state theory, there is a functional relationship between the diffusion coefficient and the transition frequency of the atom, and the transition frequency satisfies the Arrhenius formula. The first-principles software outputs adsorption energy, charge differential density, state density, transition distance, transition frequency, diffusion barrier or diffusion activation energy, and diffusion coefficient formula, and writes them into the output file.

[0110] Furthermore, the control flow program reads the adsorption energy in the output file. For all combinations of the type X of the radionuclide and the type Y of the main material, if the adsorption energy is positive, it is exothermic, and the adsorption can proceed spontaneously. If the adsorption energy is negative, it is endothermic, indicating that the adsorbed atom is heated or otherwise in the adsorption structure and is unstable after adsorption.

[0111] Furthermore, the control flow program reads the charge differential density in the output file, and for all combinations of the type X of radioactive nuclides and the type Y of main materials, if the charge density of the electron cloud portion of the adsorbed atom j increases, electrons are obtained from the material i, and if the charge density of the electron cloud portion of the adsorbed atom j decreases, electrons are lost from the material i; according to the elemental properties of the adsorbed atom j and the material i, it is determined whether the number of electrons gained and lost can enable the adsorbed atom j or the material i to form a stable chemical bond, and if not, it means that the electronic element of the material i and the adsorbed atom j has not changed, that is, the adsorbed atom and the material cannot be adsorbed to each other;

[0112] Furthermore, the control flow program reads the state density in the output file, discards the combination in which the adsorbed atom and the material cannot be adsorbed to each other, and judges the adsorption properties of the remaining combinations from the state density. If a strong resonance peak appears in the state density of the adsorbed atom j, it means that the adsorbed atom j interacts with the material i. If the Fermi level of the adsorption system is not offset, the adsorbed atom j is physically adsorbed to the material i, otherwise it is chemically adsorbed. If the state density of the adsorbed atom j does not show a strong resonance peak or has a small fluctuation, the adsorbed atom j is physically adsorbed to the material i.

[0113] Further, the control flow program reads the diffusion coefficient formula in the output file, obtains the diffusion coefficient of the radioactive nuclide in the solid material through the diffusion coefficient formula, marks the radioactive nuclide and the matrix material according to certain numbers, writes the diffusion coefficient formula of the radioactive nuclide in the matrix material into the diffusion coefficient library file of the nuclide and saves the file;

[0114] Furthermore, the above steps are repeated until all combinations of the type X of radionuclides and the type Y of main materials are calculated, at which point the control flow program has established and updated the diffusion coefficient library of the reactor's radionuclides in the main materials in the reactor.

[0115] Then, according to the determined reactor type, fuel element form and geometric structure, moderator material, and cooling material, the control flow program calls the multi-physics coupling program to respectively establish one-dimensional geometric nodes of fuel elements, one-dimensional geometric nodes of moderator material grains, and one-dimensional geometric nodes of pores in the moderator material, wherein the physical field corresponding to the one-dimensional node model is the Fick diffusion field; the total amount and type of radioactive nuclides and the calculation time are passed to the one-dimensional node model of the fuel element in the multi-physics coupling program, the total amount and type of radioactive nuclides are set as the initial conditions for the release calculation in the fissile material region, the calculation time of the one-dimensional node model of the fuel element is set, and the corresponding material in the diffusion coefficient library is searched according to the material of the one-dimensional geometric node model of the fuel element, and the diffusion coefficient formula in the diffusion coefficient library is assigned to the material physical field parameter setting of the model; in the same way, the multi-physics setting of the one-dimensional geometric node model of the moderator material grains and the one-dimensional geometric node model of the pores in the moderator material is completed.

[0116] Finally, the multi-physics coupling program calculates the nuclide concentration distribution in each material layer of the one-dimensional geometric node model of the fuel element, the one-dimensional geometric node model of the moderator material grains, and the one-dimensional geometric node model of the pores in the moderator material in parallel within the calculation time; the volume of the grains is calculated based on the one-dimensional geometric node model of the moderator material grains, and the concentration of radioactive nuclides retained in the moderator material on a macro scale is obtained based on the volume occupied by the macro-scale moderator material in the direction of the geometric node model surrounding the fuel element (the concentration has taken into account the influence of the pores in the moderator material, the pore fraction is the value determined in step 1, and the one-dimensional geometric node model of the pores is processed in the same way as the one-dimensional geometric node model of the grains); the control flow software reads the output file of the multi-physics coupling program, and obtains the nuclide release rate within the calculation time based on the difference in the nuclide concentrations before and after the calculation time.

[0117] Therefore, it can be seen from the above that in order to establish a radioactive nuclide adsorption parameter library for new nuclear power plant materials, the present invention provides a multi-scale coupling calculation method for source term calculation work in the field of radiation protection design of new reactor nuclear power plants. Starting from the first principles of the material unit cell system, the method realizes the calculation of the diffusion coefficient of radioactive nuclides in the material through the transition state theory, and provides important input parameters for accurately estimating the release of the reactor core stockpile. In addition, the method establishes the whole process of the generation and release of radioactive nuclides, reduces isolated conservative assumptions, and improves the accuracy of calculation.

[0118] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A multi-scale coupling method for radionuclide production and release, characterized in that: include: According to the determined chemical composition and structure of the material, a single cell structure model of the crystal is constructed based on the first principles of the material unit cell system, and automatically expanded to a multi-cell structure model; Introducing adatoms into the polycell structure model and performing a convergence test, and determining a stable architecture of a system consisting of the polycell structure model and the adatoms by energy minimization; Establishing a diffusion coefficient library of radioactive nuclides in the main materials of the pile based on the stable system structure; Calling a multi-physics field coupling program to establish a one-dimensional node model, searching the diffusion coefficient library according to the one-dimensional node model, and completing material parameter setting; The nuclide concentration distribution of the one-dimensional node model is calculated, and the nuclide release rate within the calculation time is obtained according to the concentration difference before and after the calculation.

2. The multi-scale coupling method for radionuclide production and release according to claim 1, characterized in that: The acquisition of the polycell structure model includes: Determine the type of reactor under study, the form of fuel elements, the moderator material and its pore volume fraction, the cooling material, the type X of main materials in the reactor and the amount of materials, determine the chemical composition of the main material type X in the reactor, including the standard value, factory value, and atomic number of each element, and determine the structure of each material, including the atomic number and crystal form; The control flow program calls the nuclear design software to calculate the total amount of radioactivity in the core and writes the result into an output file, and the control flow program determines the type Y of radioactive nuclide in the core according to the output file; The control flow program selects the i-th material, where i=1...X, and automatically establishes a single cell structure model of the crystal based on the first principles of the material unit cell system according to the determined chemical composition and structure of the material. The control flow program calls the first principles software to expand the single cell structure model into a polycell structure model, and the polycell structure model includes a body-centered cubic structure and a face-centered cubic structure.

3. The multi-scale coupling method for radionuclide production and release according to claim 2, characterized in that: The determination of the stable architecture includes: Introducing an adsorbed atom j into the polycell structure model, wherein j=1...Y, and the adsorbed atom is the radionuclide under study, i.e., one of the types of the core radionuclide; The control flow program calls the first principle software to perform a convergence test, that is, the first principle software determines the plane wave cutoff energy and K point network setting of the polycell model through a convergence test, determines the N-layer structure of the adsorption system, fixes the m layers on one side of the adsorption system, performs relaxation calculations on the other Nm layers, and ensures that sufficient energy exchange is performed between atoms, and the adsorbed atoms reach an optimal adsorption height; The adsorption energy, charge difference density, and state density of the adsorption system when it is stable are calculated in sequence, and the adsorption energy, charge difference density, and state density are used as control flow software to preliminarily evaluate the adsorption relationship between the adsorbed atom j and the material i; The stable system structure of the system consisting of a polycell structure model and one adsorbed atom is determined by energy minimization calculation. At this time, the interstitial position is the most stable interstitial position that meets the lowest energy point.

4. The multi-scale coupling method for radionuclide production and release according to claim 3, characterized in that: Also includes: The first principle software searches for the optimal positional diffusion transition state of the adsorbed atom in the adjacent interstitial atomic layer in the adsorption structure according to the most stable system structure corresponding to the determined most stable interstitial position, and obtains the diffusion activation energy curve. The difference between the highest energy point and the lowest energy point in the diffusion activation energy curve is E α is the diffusion barrier or diffusion activation energy, and the highest energy point in the diffusion activation energy curve is the transition state of diffusion; According to transition state theory, there is a functional relationship between the diffusion coefficient and the transition frequency of the atom, and the transition frequency satisfies the Arrhenius formula; The first principle software outputs adsorption energy, charge differential density, state density, transition distance, transition frequency, diffusion barrier or diffusion activation energy, and diffusion coefficient formula, and writes them into the output file.

5. The multi-scale coupling method for radionuclide production and release according to claim 4, characterized in that: The establishment of the diffusion coefficient library includes: The control flow program reads the adsorption energy in the output file, and for all combinations of the type X of radionuclides and the type Y of main materials, if the adsorption energy is positive, it is exothermic, and spontaneous adsorption can be carried out; if the adsorption energy is negative, it is endothermic, indicating that the adsorbed atoms are heated or otherwise in the adsorption structure and are unstable after adsorption; The control flow program reads the charge differential density in the output file, and for all combinations of the type X of radioactive nuclides and the type Y of main materials, if the charge density of the electron cloud portion of the adsorbed atom j increases, electrons are obtained from the material i, and if the charge density of the electron cloud portion of the adsorbed atom j decreases, electrons are lost from the material i; according to the elemental properties of the adsorbed atom j and the material i, it is judged whether the number of electrons gained and lost can enable the adsorbed atom j or the material i to form a stable chemical bond, and if it cannot be formed, it means that the electronic element of the material i and the adsorbed atom j has not changed, that is, the adsorbed atom and the material cannot be adsorbed to each other; The control flow program reads the state density in the output file, discards the combination in which the adsorbed atom and the material cannot be adsorbed to each other, and judges the adsorption properties of the remaining combinations from the state density. If a strong resonance peak appears in the state density of the adsorbed atom j, it means that the adsorbed atom j interacts with the material i. If the Fermi level of the adsorption system is not offset, the adsorbed atom j is physically adsorbed to the material i, otherwise it is chemically adsorbed. If the state density of the adsorbed atom j does not show a strong resonance peak or has a small fluctuation, the adsorbed atom j is physically adsorbed to the material i. The control flow program reads the diffusion coefficient formula in the output file, obtains the diffusion coefficient of the radioactive nuclide in the solid material by using the diffusion coefficient formula, marks the radioactive nuclide and the matrix material according to certain numbers, writes the diffusion coefficient formula of the radioactive nuclide in the matrix material into the diffusion coefficient library file of the nuclide and saves the file; The above steps are repeated until all combinations of the type X of radionuclides and the type Y of main materials are calculated. At this time, the control flow program has established and updated the diffusion coefficient library of the radionuclides in the main materials in the reactor.

6. The multi-scale coupling method for radionuclide production and release according to claim 5, characterized in that: The material parameter settings include: According to the determined reactor type, fuel element form and geometric structure, moderator material, and cooling material, the control flow program calls the multi-physics field coupling program to respectively establish one-dimensional geometric nodes of the fuel element, one-dimensional geometric nodes of the moderator material grains, and one-dimensional geometric nodes of the pores in the moderator material, wherein the physical field corresponding to the one-dimensional node model is the Fick diffusion field; The total amount and type of radioactive nuclides and the calculation time are passed to the one-dimensional node model of the fuel element in the multi-physics field coupling program, the total amount and type of radioactive nuclides are set as the initial conditions for the release calculation in the fissile material region, the calculation time of the one-dimensional node model of the fuel element is set, the corresponding material in the diffusion coefficient library is searched according to the material of the one-dimensional geometric node model of the fuel element, and the diffusion coefficient formula in the diffusion coefficient library is assigned to the material physical field parameter setting of the model, and in the same way, the multi-physics field setting of the one-dimensional geometric node model of the moderator material grains and the one-dimensional geometric node model of the pores in the moderator material is completed.

7. The multi-scale coupling method for radionuclide production and release according to claim 6, characterized in that: The calculation of the nuclide release rate includes: The multi-physics coupling program calculates the nuclide concentration distribution in each material layer of the one-dimensional geometric node model of the fuel element, the one-dimensional geometric node model of the grains of the moderator material, and the one-dimensional geometric node model of the pores in the moderator material in a parallel manner within the calculation time of the radioactive nuclide j; According to the one-dimensional geometric node model of the moderator material grains, the volume of the grains is calculated, and according to the volume occupied by the macroscopic moderator material in the direction of the geometric node model surrounding the fuel element, the concentration of radionuclides retained by the moderator material on a macroscopic scale is obtained; The control flow software reads the output file of the multi-physics field coupling program, and obtains the nuclide release rate within the calculation time according to the difference between the nuclide concentrations before and after the calculation time.

8. A system using the multi-scale coupling method for radionuclide generation and release as claimed in claim 1, characterized in that: include: A model building unit is used to build a single-cell structure model of a crystal based on the first principles of the material unit cell system according to the determined chemical composition and structure of the material, and automatically expand it to a multi-cell structure model; A structure determination unit, used for introducing adatoms into the polycell structure model and performing a convergence test, and determining a stable system structure of a system consisting of the polycell structure model and the adatoms by energy minimization; A coefficient library establishment unit, used to establish a diffusion coefficient library of radioactive nuclides in main materials in the pile based on the stable system structure; A parameter setting unit, used for calling a multi-physics field coupling program to establish a one-dimensional node model, searching the diffusion coefficient library according to the one-dimensional node model, and completing material parameter setting; The parameter calculation unit is used to calculate the nuclide concentration distribution of the one-dimensional node model and obtain the nuclide release rate within the calculation time according to the concentration difference before and after the calculation.

9. An electronic device, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, the steps of the method described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having computer program instructions stored thereon, wherein the computer-executable instructions, when executed by a processor, implement the steps of the method according to any one of claims 1 to 7.

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