Simulation method and system for migration behavior of nuclide in fractured rock mass and medium

Abstract

The invention provides a method and system for simulating the migration behavior of nuclide in fractured rock mass and a medium, and relates to the technical field of nuclide migration simulation, and the method comprises the steps: obtaining the fracture opening degree representing spatial change characteristics, and dividing the fracture opening degree into a plurality of fracture segments; determining adsorption coefficients of different fracture segments according to the identification result of the main mineral types; independently assigning the fracture opening degree and the adsorption coefficient of each fracture segment, and constructing a control equation of nuclide in different fracture segments after assignment based on a dual-pore medium model; according to boundary condition derivation, nuclide concentration transfer functions at different fracture segment fractures and matrixes are obtained, convolution integration is carried out, nuclide output of the concentration of each fracture segment becomes input of the nuclide concentration of the next fracture segment, and a simulation result of the nuclide migration process in the heterogeneous fracture is obtained. According to the method, the physical heterogeneity and the chemical heterogeneity of the fractured rock mass are represented by obtaining the fracture opening degree and the mineral adsorption coefficient, and the simulation precision of the migration behavior is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of nuclide migration simulation, and in particular to a simulation method, system and medium for nuclide migration behavior in a fractured rock mass. Background Art

[0002] As the global demand for clean energy continues to grow, the development and application of nuclear energy as an efficient and low-carbon energy form is increasingly becoming the focus of international attention. However, the safe disposal of radioactive nuclides (referred to as nuclides) associated with the use of nuclear energy has become a major technical challenge that needs to be solved urgently. At present, the recognized treatment solution for high-level radioactive waste is deep geological disposal, which aims to protect the ecological environment and human health by building a stable geological barrier to ensure that nuclides will not leak into the external environment during the natural evolution process over a long time scale. To achieve this goal, an in-depth evaluation of the safety performance of geological barriers is particularly critical, and its core lies in accurately simulating the migration behavior of nuclides in fractured media.

[0003] The simulation methods of nuclide migration in fractures are mainly divided into two categories: numerical method and analytical method. Although the numerical method can accurately characterize the heterogeneous characteristics of fractured rock mass, its modeling is complex and the calculation is time-consuming. The analytical method solves the control equations that characterize the migration of nuclides in fractured rock mass, which has the advantages of simplicity and efficiency and is often used to analyze experimental data. Although the analytical solution has the above advantages, it is usually derived under the assumptions of uniform rock medium, simple boundary conditions, etc. Therefore, in the simulation process, an idealized parallel plate model is used to simplify the fracture structure and the rock mass is equivalent to a homogeneous body with a single mineral property, and the equivalent parameters after "average" are used for calculation. However, real natural fractured rock mass is usually heterogeneous, and the distribution characteristics such as fracture opening and rock mass minerals often change with space. The prediction ability of using traditional analytical solutions cannot meet the strict requirements of high precision for geological disposal safety assessment. Summary of the invention

[0004] To solve the above problems, the present invention provides a method for simulating the migration behavior of nuclides in fractured rock masses. The method obtains two parameters, namely, fracture opening degree and mineral adsorption coefficient, as two characteristic variables characterizing the physical heterogeneity and chemical heterogeneity of fractured rock masses, so as to simulate the migration process of nuclides in heterogeneous fractured rock masses and effectively improve the simulation accuracy.

[0005] To achieve the above object, the present invention provides the following technical solutions.

[0006] A method for simulating the migration behavior of nuclides in a fractured rock mass comprises the following steps:

[0007] Construct a three-dimensional model of the fractured rock mass surface, set a reference plane parallel to the fractured rock mass surface, obtain the fracture opening that characterizes the spatial variation characteristics according to the height difference between the upper and lower surfaces of the fractured rock mass relative to the reference plane, and divide the fractured rock mass into several fracture segments with representative fracture openings;

[0008] According to the identification results of the main mineral types in different fracture segments, the adsorption coefficients of different fracture segments are determined;

[0009] The fracture opening and adsorption coefficient of each fracture segment are assigned independently, and the control equations for the migration of nuclides in the fractures and matrix of different fracture segments after the assignment are constructed based on the principle of dual-porosity medium model.

[0010] The control equations are derived according to the boundary conditions to obtain the nuclide concentration transfer functions of different fracture segments and matrices and perform convolution integration so that the nuclide output of each fracture segment becomes the input of the nuclide concentration of the next fracture segment, and the simulation results of the nuclide migration process in the fracture are obtained.

[0011] Preferably, the constructing of the three-dimensional model of the surface of the fractured rock mass comprises the following steps:

[0012] Use a three-dimensional laser profile scanner to scan the upper and lower surfaces of the fractured rock mass to obtain reflection signals from the surface of the fractured rock mass;

[0013] A three-dimensional model of the rough surface of the crack is constructed based on the intensity and time difference information of the reflected signal.

[0014] Preferably, the acquisition of the adsorption coefficients of different fracture segments comprises the following steps:

[0015] Determine the mineral types of the rock mass obtained through X-ray diffraction testing, and determine the grayscale threshold of each mineral type;

[0016] The surface of the fractured rock mass is photographed and imaged by a high-resolution camera to obtain a high-resolution image of the surface of the fractured rock mass;

[0017] The high-resolution image of the fractured rock surface is interpreted into grayscale values, which are compared with the grayscale thresholds of each component mineral type to identify the main mineral types in different fracture segments. The adsorption coefficients of the main mineral types in different fracture segments are determined based on the main mineral types in different fracture segments.

[0018] Preferably, the control equations for the migration of nuclides in the fissures and matrices of different fissure segments after assignment based on the principle of the dual-porosity medium model include the following steps:

[0019] It is determined that in the dual-porosity medium model, when water flow occurs in the fracture, the water in the matrix pores is saturated and static, and the solute in the fracture enters the water in the matrix pores under the action of matrix diffusion; among them, convection occurs in the direction parallel to the fracture, and matrix diffusion occurs in the direction perpendicular to the fracture;

[0020] Determine the basic parameters of the remaining fracture segments, including fluid velocity, diffusion coefficient, matrix thickness, matrix tortuosity, matrix and fracture porosity, matrix density, fracture adsorption coefficient, fracture size parameter, and molecular diffusion coefficient;

[0021] Based on the precondition that the nuclides follow equilibrium adsorption and the water flow velocity in the fracture segment does not change, the control equation for the migration of nuclides in the fracture and matrix of one fracture segment is determined according to the basic parameters of the fracture segment, which is expressed as:

[0022] Control equation of fracture dissolution phase:

[0023]

[0024] Control equation of crack adsorption phase:

[0025]

[0026] Matrix dissolved phase governing equation:

[0027]

[0028] Matrix adsorption phase governing equation:

[0029]

[0030] In the formula, C f is the concentration of nuclides in the crack; C m is the concentration of radionuclides in the matrix; S f is the concentration of radionuclides on the crack surface; S m is the concentration of radionuclides on the matrix surface; v f is the fluid velocity in the fracture; D f is the diffusion coefficient in the crack; D m is the molecular diffusion coefficient in the matrix; ρ f is the bulk density of the material in the crack; ρ B is the matrix bulk density; η is the fracture porosity; φ is the matrix porosity; b is the fracture radius; L is the distance between the parallel fracture center lines in the medium; k ff is the adsorption rate constant on the crack surface; k fr is the desorption rate constant of the crack surface; k mf is the substrate surface adsorption rate constant; k mr is the substrate surface desorption rate constant; α i ,βi are the adsorption isotherm parameters, i=f is the crack; i=m is the matrix; δ(t) is the Dirac function.

[0031] Preferably, the control equation is derived according to the boundary conditions to obtain the nuclide concentration transfer function at different fracture segments and the matrix, comprising the following steps:

[0032] Assuming that the initial nuclide concentration at any position of the fracture and matrix is ​​0, and the concentration at the position where the fracture and matrix contact is the same, the governing equations satisfy the following initial and boundary conditions:

[0033] C f (x,0)=0

[0034] C f (0,t)=δ(t)

[0035] C f (∞,t)=0

[0036] S f (x,0)=0

[0037] C m (y,x,0)=0

[0038] C m (b,x,t)=C f (x,t)

[0039]

[0040] S m (y,x,0)=0

[0041] By removing the time derivative from the equation through Laplace transform, it is converted into a solvable ordinary differential equation form:

[0042] Fracture dissolution phase ordinary differential equation:

[0043]

[0044] Ordinary differential equation of crack adsorption phase:

[0045]

[0046] Matrix solution phase ordinary differential equation:

[0047]

[0048] Ordinary differential equation of matrix adsorption phase:

[0049]

[0050] Where s is the Laplace transform of the independent variable and - is the Laplace transform of the dependent variable.

[0051] The ordinary differential equations of the fracture adsorption phase and the matrix adsorption phase are solved and the results are substituted into the ordinary differential equations of the fracture dissolution phase and the matrix dissolution phase to obtain the transfer function characterizing the nuclide concentration at different positions:

[0052]

[0053] Where:

[0054]

[0055] The transfer functions of different fracture segments are multiplied in the Laplace domain, so that the output of each fracture concentration becomes the input of the next fracture concentration, thereby simulating the nuclide migration process in the entire heterogeneous fracture.

[0056] Preferably, determining the nuclide concentration at the crack outlet according to the simulation results of the nuclide migration process in the crack comprises the following steps:

[0057] The fast Fourier transform algorithm is used to inversely transform the product of the transfer function in the Laplace domain to obtain the solution of the equation in the time domain and the change of the nuclide concentration at different times at the crack outlet.

[0058] A simulation system for the migration behavior of nuclides in a fractured rock mass, the system comprising:

[0059] processor;

[0060] a memory having stored thereon a computer program executable on the processor;

[0061] Wherein, when the computer program is executed by the processor, the steps of the method for simulating the migration behavior of nuclides in fractured rock mass are implemented.

[0062] A computer-readable storage medium stores a data processing program, which, when executed by a processor, implements the steps of a method for simulating the migration behavior of nuclides in a fractured rock mass.

[0063] Beneficial effects of the present invention:

[0064] The present invention proposes a simulation method, system and medium for the migration behavior of nuclides in fractured rock mass. The method uses high-precision geological exploration and imaging technology and image interpretation technology to finely characterize the spatial distribution characteristics of the opening degree and constituent minerals of the fractured rock mass. On this basis, the fractured rock mass is segmented according to the identification accuracy, and then the analytical solution of the migration of nuclides in the heterogeneous fractured rock mass is derived. In the calculation process, the two parameters of fracture opening degree and mineral adsorption coefficient are respectively used as two characteristic variables to characterize the physical heterogeneity and chemical heterogeneity of the fractured rock mass, so that the model is more in line with the actual heterogeneous fractured rock mass. By assigning different opening degrees and adsorption coefficients to different fracture segments according to the heterogeneous characteristics of the fractured rock mass during the simulation process, the migration process of nuclides in the heterogeneous fractured rock mass is simulated, which effectively improves the simulation accuracy and meets the strict requirements of geological disposal safety assessment for high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a flow chart of a method for simulating the migration behavior of nuclides in a fractured rock mass according to an embodiment of the present invention;

[0066] Figure 2 It is a schematic diagram of heterogeneous fractured rock mass;

[0067] Figure 3 It is a conceptual model of dual-porosity media;

[0068] Figure 4 It is a comparison diagram of the simulation results and experimental results of the change of nuclide concentration at different times at the crack outlet of the embodiment of the present invention. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0070] Example 1

[0071] Real natural fractured rock masses are usually heterogeneous, such as Figure 2 As shown in Figure 1, the distribution characteristics of fracture opening and rock minerals often change with space, and the prediction ability of traditional analytical solutions cannot meet the strict requirements of high accuracy for geological disposal safety assessment. To this end, a simulation method for the migration behavior of nuclides in fractured rock mass of the present invention is as follows: Figure 1 As shown, the following steps are included:

[0072] S1: Construct a three-dimensional model of the fractured rock mass surface, set a reference plane parallel to the fractured rock mass surface, obtain the fracture opening that characterizes the spatial variation characteristics according to the height difference between the upper and lower surfaces of the fractured rock mass relative to the reference plane, and divide the fractured rock mass into several fracture segments with representative fracture openings.

[0073] S2: Based on the identification results of the main mineral types in different fracture segments, determine the adsorption coefficients of different fracture segments.

[0074] S3: The fracture opening and adsorption coefficient of each fracture segment are independently assigned, and the control equations for the migration of nuclides in the fractures and matrix of different fracture segments after the assignment are constructed based on the principle of the dual-porosity medium model.

[0075] S4: The control equation is derived according to the boundary conditions to obtain the nuclide concentration transfer function at the fracture and matrix of different fracture segments and perform convolution integration so that the nuclide output of each fracture segment becomes the input of the nuclide concentration of the next fracture segment, and the simulation results of the nuclide migration process in the fracture are obtained.

[0076] Specifically, constructing a three-dimensional model of the fractured rock mass surface includes the following steps:

[0077] The upper and lower surfaces of the fracture are scanned using a 3D laser profile scanner. The fracture surface is scanned by a laser beam and its reflection signal is recorded. Then, a 3D model of the rough surface of the fracture is constructed based on information such as the intensity and time difference of the reflection signal. During the scanning process, the separated fracture surface is compacted as much as possible, and a reference plane parallel to the fracture surface is set. The height difference between the upper and lower surfaces of the fracture relative to the reference plane is calculated to obtain the spatial variation characteristics of the fracture opening. Based on the recognition accuracy and results, the fractured rock mass is divided into several fractured rock mass segments with representative openings.

[0078] Furthermore, the acquisition of the adsorption coefficients of different fracture segments includes the following steps:

[0079] The surface of the fractured rock mass is photographed with a high-resolution camera, and the constituent mineral types of the rock mass are obtained through X-ray diffraction testing. The rock image is then interpreted into grayscale values, and the main mineral types on different fracture segments are identified based on the grayscale threshold of the mineral. The adsorption coefficient values ​​corresponding to different mineral types can be obtained from the existing experimental database.

[0080] In this embodiment, the control equations for nuclide transport in heterogeneous fractured rock mass are established based on the dual-porosity medium conceptual model. The dual-porosity medium model is a commonly used conceptual model for simulating water flow and solute transport in fractured rock mass. The model follows the law of conservation of mass, that is, the difference in mass of the solute flowing into and out of the fracture is equal to its change. The model assumes that water flow mainly occurs in the fractures, the water in the matrix pores is considered to be saturated and static, and the solutes in the fractures can enter the water in the matrix pores under the action of matrix diffusion. It is assumed that convection only occurs in the direction parallel to the fracture (x direction), and matrix diffusion occurs in the direction perpendicular to the fracture (y direction). The schematic diagram of the model is shown in the figure. Figure 3 shown.

[0081] Assuming that the nuclides follow equilibrium adsorption and the water flow velocity in the fracture segment does not change, the governing equation for the migration of nuclides in one of the fractures and the matrix can be expressed as:

[0082] Control equation of fracture dissolution phase:

[0083]

[0084] Control equation of crack adsorption phase:

[0085]

[0086] Matrix dissolved phase governing equation:

[0087]

[0088] Matrix adsorption phase governing equation:

[0089]

[0090] In the formula, C f is the concentration of nuclides in the crack, M / L 3 ; C m is the concentration of radionuclides in the matrix, M / L 3 ; S f is the concentration of radionuclides on the crack surface, M / M solid; S m is the concentration of radionuclides on the matrix surface, M / M solid; v f is the fluid velocity in the fracture, L / T; D f is the diffusion coefficient in the crack, L 2 / T;D m is the molecular diffusion coefficient in the matrix, L 2 / T;ρ f is the bulk density of the material in the crack, M / L 3 ρ B is the matrix bulk density, M / L 3; η is the fracture porosity; φ is the matrix porosity; b is the fracture radius, L; L is the distance between parallel fracture centerlines in the medium, L; k ff is the adsorption rate constant of the crack surface, 1 / T (linear condition); k fr is the crack surface desorption rate constant, M / L 3 ;k mf is the substrate surface adsorption rate constant, 1 / T (linear condition); k mr is the substrate surface desorption rate constant, M / L 3 ; α i ,β i are the adsorption isotherm parameters, i=f is the crack; i=m is the matrix; δ(t) is the Dirac function.

[0091] Assuming that the initial nuclide concentration at any position of the crack and the matrix is ​​0, and the concentration at the position where the crack and the matrix contact is the same, the above equation satisfies the following initial and boundary conditions:

[0092] C f (x,0)=0

[0093] C f (0,t)=δ(t)

[0094] C f (∞,t)=0

[0095] S f (x,0)=0

[0096] C m (y,x,0)=0

[0097] C m (b,x,t)=C f (x,t)

[0098]

[0099] S m (y,x,0)=0

[0100] By removing the time derivative from the equation through Laplace transform, it is converted into a solvable ordinary differential equation form:

[0101] Fracture dissolution phase ordinary differential equation:

[0102]

[0103] Ordinary differential equation of crack adsorption phase:

[0104]

[0105] Matrix solution phase ordinary differential equation:

[0106]

[0107] Ordinary differential equation of matrix adsorption phase:

[0108]

[0109] Where s is the Laplace transform of the independent variable and - is the Laplace transform of the dependent variable.

[0110] The ordinary differential equations of the fracture adsorption phase and the matrix adsorption phase are solved and the results are substituted into the ordinary differential equations of the fracture dissolution phase and the matrix dissolution phase to obtain the transfer function characterizing the nuclide concentration at different positions:

[0111]

[0112] Where:

[0113]

[0114] The transfer functions of different fracture segments are convolved and integrated, that is, the transfer functions of different fracture segments are multiplied in the Laplace domain, so that the output of each fracture concentration becomes the input of the next fracture concentration, thereby simulating the nuclide migration process in the entire heterogeneous fracture.

[0115] The fast Fourier transform algorithm is used to inversely transform the Laplace domain product of the transfer function to obtain the solution of the equation in the time domain and the change of the nuclide concentration at different times at the outlet of the variable opening crack.

[0116] This example uses the above method to conduct a strontium tracing experiment on a granite fissure with a length of 9 cm and a diameter of 6.2 cm.

[0117] The upper and lower surfaces of the granite cracks were scanned with a 3D laser scanner at a scanning accuracy of 0.2 mm, and the spatial distribution of the crack opening was calculated by coordinate transformation. The granite cracks were used to conduct a strontium nuclide tracer experiment and the experimental results were fitted using the analytical simulation method established in the method of the present invention. In the simulation, the cracks were divided into 450 segments based on the opening recognition results and were assigned separately. The remaining parameter settings are shown in Table 1:

[0118] Table 1 Basic parameters

[0119]

[0120] The simulation results are as follows Figure 4As shown, it is a comparison diagram of the simulation results and experimental results of the change of nuclide concentration at different times at the crack outlet. From the fitting results, it can be seen that the analytical method established in the present invention can accurately simulate the nuclide migration process in one-dimensional variable opening cracks.

[0121] The above is a simulation method for the migration behavior of nuclides in fractured rock mass provided by one embodiment of this embodiment. Based on the same idea, this embodiment also provides a corresponding simulation system for the migration behavior of nuclides in fractured rock mass. The specific definition of the simulation system for the migration behavior of nuclides in fractured rock mass can be found in the above definition of the simulation method for the migration behavior of nuclides in fractured rock mass, which will not be repeated here. Each module in the above simulation system for the migration behavior of nuclides in fractured rock mass can be fully or partially implemented by software, hardware and a combination thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0122] This embodiment also provides a computer-readable storage medium, which stores a computer program, which can be used to execute the above Figure 1 A simulation method for the migration behavior of nuclides in fractured rock masses is provided.

[0123] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0124] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for simulating the migration behavior of nuclides in fractured rock mass, characterized in that: The following steps are involved: Construct a three-dimensional model of the fractured rock mass surface, set a reference plane parallel to the fractured rock mass surface, obtain the fracture opening that characterizes the spatial variation characteristics according to the height difference between the upper and lower surfaces of the fractured rock mass relative to the reference plane, and divide the fractured rock mass into several fracture segments with representative fracture openings; According to the identification results of the main mineral types in different fracture segments, the adsorption coefficients of different fracture segments are determined; The fracture opening and adsorption coefficient of each fracture segment are assigned independently, and the control equations for the migration of nuclides in the fractures and matrix of different fracture segments after the assignment are constructed based on the principle of dual-porosity medium model. The control equations are derived according to the boundary conditions to obtain the nuclide concentration transfer functions of different fracture segments and matrices and perform convolution integration so that the nuclide output of each fracture segment becomes the input of the nuclide concentration of the next fracture segment, and the simulation results of the nuclide migration process in the fracture are obtained.

2. The method for simulating the migration behavior of nuclides in fractured rock mass according to claim 1, characterized in that: The construction of the three-dimensional model of the fractured rock mass surface comprises the following steps: Use a three-dimensional laser profile scanner to scan the upper and lower surfaces of the fractured rock mass to obtain reflection signals from the surface of the fractured rock mass; A three-dimensional model of the rough surface of the crack is constructed based on the intensity and time difference information of the reflected signal.

3. The method for simulating the migration behavior of nuclides in fractured rock mass according to claim 1, characterized in that: The acquisition of the adsorption coefficients of the different fracture segments comprises the following steps: Determine the mineral types of the rock mass obtained through X-ray diffraction testing, and determine the grayscale threshold of each mineral type; The surface of the fractured rock mass is photographed and imaged by a high-resolution camera to obtain a high-resolution image of the surface of the fractured rock mass; The high-resolution image of the fractured rock surface is interpreted into grayscale values, which are compared with the grayscale thresholds of each component mineral type to identify the main mineral types in different fracture segments. The adsorption coefficients of the main mineral types in different fracture segments are determined based on the main mineral types in different fracture segments.

4. The method for simulating the migration behavior of nuclides in fractured rock mass according to claim 1, characterized in that: The control equations for the migration of nuclides in the cracks and matrices of different crack segments after assignment based on the dual-porosity medium model principle include the following steps: It is determined that in the dual-porosity medium model, when water flow occurs in the fracture, the water in the matrix pores is saturated and static, and the solute in the fracture enters the water in the matrix pores under the action of matrix diffusion; among them, convection occurs in the direction parallel to the fracture, and matrix diffusion occurs in the direction perpendicular to the fracture; Determine the basic parameters of the remaining fracture segments, including fluid velocity, diffusion coefficient, matrix thickness, matrix tortuosity, matrix and fracture porosity, matrix density, fracture adsorption coefficient, fracture size parameter, and molecular diffusion coefficient; Based on the precondition that the nuclides follow equilibrium adsorption and the water flow velocity in the fracture segment does not change, the control equation for the migration of nuclides in the fracture and matrix of one fracture segment is determined according to the basic parameters of the fracture segment, which is expressed as: Control equation of fracture dissolution phase: Control equation of crack adsorption phase: Matrix dissolved phase governing equation: Matrix adsorption phase governing equation: In the formula, C f is the concentration of nuclides in the crack; C m is the concentration of radionuclides in the matrix; S f is the concentration of radionuclides on the crack surface; S m is the concentration of radionuclides on the matrix surface; v f is the fluid velocity in the fracture; D f is the diffusion coefficient in the crack; D m is the molecular diffusion coefficient in the matrix; ρ f is the bulk density of the material in the crack; ρ B is the matrix bulk density; η is the fracture porosity; φ is the matrix porosity; b is the fracture radius; L is the distance between the parallel fracture center lines in the medium; k ff is the adsorption rate constant on the crack surface; k fr is the desorption rate constant of the crack surface; k mf is the substrate surface adsorption rate constant; k mr is the substrate surface desorption rate constant; α i ,β i are the adsorption isotherm parameters, i=f is the crack; i=m is the matrix; δ(t) is the Dirac function.

5. The method for simulating the migration behavior of nuclides in fractured rock mass according to claim 4, characterized in that: The control equation is derived according to the boundary conditions to obtain the nuclide concentration transfer function at different fracture segments and matrices, including the following steps: Assuming that the initial nuclide concentration at any position of the fracture and matrix is ​​0, and the concentration at the position where the fracture and matrix contact is the same, the governing equations satisfy the following initial and boundary conditions: C f (x,0)=0 C f (0,t)=δ(t) C f (∞,t)=0 S f (x,0)=0 C m (y,x,0)=0 C m (b,x,t)=C f (x,t) S m (y,x,0)=0 By removing the time derivative in the equation through Laplace transform, it is converted into a solvable ordinary differential equation form: Fracture dissolution phase ordinary differential equation: Ordinary differential equation of crack adsorption phase: Matrix solution phase ordinary differential equation: Ordinary differential equation of matrix adsorption phase: Where s is the Laplace transform of the independent variable and - is the Laplace transform of the dependent variable. The ordinary differential equations of the fracture adsorption phase and the matrix adsorption phase are solved and the results are substituted into the ordinary differential equations of the fracture dissolution phase and the matrix dissolution phase to obtain the transfer function characterizing the nuclide concentration at different positions: Where: The transfer functions of different fracture segments are multiplied in the Laplace domain, so that the output of each fracture concentration becomes the input of the next fracture concentration, thereby simulating the nuclide migration process in the entire heterogeneous fracture.

6. The method for simulating the migration behavior of nuclides in fractured rock mass according to claim 5, characterized in that: The method also includes determining the nuclide concentration at the crack outlet according to the simulation results of the nuclide migration process in the crack, including the following steps: The fast Fourier transform algorithm is used to inversely transform the product of the transfer function in the Laplace domain to obtain the solution of the equation in the time domain and the change of the nuclide concentration at different times at the crack outlet.

7. A simulation system for the migration behavior of nuclides in fractured rock mass, characterized in that: The system comprises: processor; a memory having stored thereon a computer program executable on the processor; Wherein, when the computer program is executed by the processor, the steps of the method for simulating the migration behavior of nuclides in a fractured rock mass as described in any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a data processing program, which, when executed by a processor, implements the steps of the method for simulating the migration behavior of nuclides in a fractured rock mass according to any one of claims 1 to 6.

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