High radioactive waste disposal simulation method and system based on multi-field coupling

Abstract

The invention relates to a high-radioactive waste disposal simulation method and system based on multi-field coupling. The method comprises the following steps: constructing a three-dimensional finite element model of a high-radioactive waste repository and a surrounding geological medium based on physical field simulation; simulating temperature change around the high-radioactive waste repository, underground water flow velocity change and radionuclide concentration change; based on a geochemical calculation model, performing chemical reaction calculation on the distribution of the radioactive concentration of the high-radioactive waste in underground water and rock-soil media, including dissolution, precipitation, adsorption and ion exchange of the high-radioactive waste; and carrying out iterative coupling on the physical field simulation and the geochemical calculation model, and outputting a high-radioactive waste disposal simulation result which comprises a radionuclide concentration three-dimensional distribution diagram, a migration flux vector diagram and temperature field distribution. Through iterative coupling of a physical field and a chemical field, high-precision simulation prediction of nuclide migration behaviors in a high-radioactive waste long-term disposal environment is realized, and a simulation result is close to an actual migration process.

Description

Technical Field

[0001] This invention relates to the field of high-level radioactive waste disposal technology, and in particular to a simulation method and system for high-level radioactive waste disposal based on multi-field coupling. Background Technology

[0002] In the design of waste disposal repositories, coupled simulation can be used to optimize the repository layout, buffer material selection, and barrier structure. The simulation results can be used as a reference for actual high-level radioactive waste disposal methods. In long-term safety assessments, it can predict nuclide migration flux and concentration distribution, providing a basis for safety permits and environmental impact assessments.

[0003] In related technologies, simulations of high-level radioactive waste disposal typically employ independent geochemical software (such as PHREEQC) to calculate the chemical reactions between groundwater and soil media, including processes such as dissolution, precipitation, adsorption, and ion exchange. These methods usually only provide single-step or static chemical equilibrium results, lacking consideration of factors such as groundwater flow, thermal field changes, or radionuclide migration during actual treatment. Consequently, they fail to fully reflect the actual treatment effects, leading to significant discrepancies between the simulation results and reality in the final disposal evaluation.

[0004] The above problems urgently need to be addressed. Summary of the Invention

[0005] This invention discloses a simulation method and system for the disposal of highly radioactive waste based on multi-field coupling, aiming to solve the technical problems existing in the prior art.

[0006] The present invention adopts the following technical solution: On one hand, this invention provides a simulation method for the disposal of highly radioactive waste based on multi-field coupling, which includes: constructing a three-dimensional finite element model of a highly radioactive waste disposal site and its surrounding geological media based on physical field simulation; using the three-dimensional finite element model to simulate temperature changes, groundwater flow rate changes, and radionuclide concentration changes around the highly radioactive waste disposal site; performing chemical reaction calculations on the distribution of radioactive concentration of highly radioactive waste in groundwater and soil media based on a geochemical calculation model, wherein the chemical reaction calculations include the dissolution, precipitation, adsorption, and ion exchange of highly radioactive waste; iteratively coupling the physical field simulation with the geochemical calculation model, feeding back the physical field data and chemical field data to output highly radioactive waste disposal simulation results, wherein the disposal simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution.

[0007] Optionally, the construction of a three-dimensional finite element model of the high-level radioactive waste repositories and surrounding geological media based on physical field simulation includes: constructing groundwater flow equations for incompressible water and soil media with minimal changes in pore size, based on Darcy's law and the principle of continuity; constructing heat conduction-convection equations by simulating the distribution of groundwater pressure, velocity, and temperature fields; constructing solute transport equations considering the convection, diffusion, and dispersion effects of groundwater; and simulating and constructing the three-dimensional finite element model based on the groundwater flow equations, the heat conduction-convection equations, and the solute transport equations.

[0008] Optionally, based on Darcy's law and the principle of continuity, for incompressible water and soil media with minimal changes in pore size, a groundwater flow equation is constructed, which includes: in, Porosity is the porosity of the porous medium. The density of groundwater, For time, For divergence operators, This is the groundwater seepage velocity vector. For the source and sink terms of nuclides.

[0009] Optionally, the distribution of groundwater pressure, velocity, and temperature fields is simulated to construct a heat conduction-convection equation, wherein the heat conduction-convection equation includes: in, The density of the porous medium, The combined specific heat capacity of the porous medium and the porous fluid. For temperature, For time, The density of groundwater, The specific heat capacity of groundwater. This represents the seepage velocity vector of groundwater. The temperature gradient vector. For divergence operators, The equivalent thermal conductivity coefficient, It refers to the source and sink of heat.

[0010] Optionally, considering the convection, diffusion, and dispersion effects of groundwater, a solute transport equation is constructed, wherein the solute transport equation includes: in, As a blocking factor, Porosity is the porosity of the porous medium. This represents the concentration of the solute in the groundwater. For time, For divergence operators, This represents the seepage velocity vector of groundwater. For the equivalent dispersion coefficient tensor, Let be the gradient vector of solute concentration. Let be the decay constant of the solute. These are the source and sink terms for solutes.

[0011] Optionally, based on a geochemical calculation model, chemical reaction calculations are performed to assess the distribution of radioactive concentrations of highly radioactive waste in groundwater and soil media. These calculations include: calculating electrostatic adsorption, surface complexation, and ion exchange between radionuclides and the surface of soil media to determine the migration hysteresis value of the radionuclides in the soil media; calculating the concentration of water-soluble complexes formed by metal ions and ligands in the groundwater solution; simulating the transformation of metal ion redox pairs in the groundwater environment to calculate the influence of redox on the valence state of radionuclides; and simulating the decay of radionuclides in highly radioactive waste over time to calculate the change in radioactive concentration over time.

[0012] Optionally, the physical field simulation and the geochemical calculation model are iteratively coupled, and the physical field data and chemical field data are fed back to each other. This includes: determining temperature changes, flow rate changes, and radionuclide concentration changes based on the physical field simulation, wherein the radionuclide concentration changes include the initial radionuclide concentration; mapping the temperature changes, flow rate changes, and radionuclide concentration changes to the geochemical calculation model, and calculating the first radionuclide concentration and porosity after the chemical reaction; using the first radionuclide concentration and the initial radionuclide concentration, calculating the rate of change of radionuclide concentration; re-inputting the rate of change of radionuclide concentration into the physical field simulation to obtain a new radionuclide concentration change; iterating the new radionuclide concentration change into the geochemical calculation model until a preset convergence condition is reached, and then stopping the iteration process.

[0013] Optionally, the new radionuclide concentration change is iterated in the geochemical calculation model until a preset convergence condition is met, at which point the iteration process stops. The preset convergence condition includes: comparing the difference between the latest radionuclide concentration output by the geochemical calculation model and the radionuclide concentration before the iteration; continuing iteration if the difference is greater than a preset difference value; and confirming the latest radionuclide concentration as the target radionuclide concentration and stopping the iteration if the difference is not greater than the preset difference value.

[0014] Optionally, the simulation results of high-level radioactive waste disposal are output, wherein the disposal simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution, including: constructing the three-dimensional distribution map of radionuclide concentration based on the target radionuclide concentration; constructing the migration flux vector map based on all radionuclide concentrations generated during the iteration process; and determining the temperature field distribution based on the temperature changes in the physical field simulation.

[0015] According to another aspect of the present invention, a simulation system for the disposal of high-level radioactive waste based on multi-field coupling is also provided, comprising: a physical simulation module for constructing a three-dimensional finite element model of a high-level radioactive waste disposal site and its surrounding geological media based on physical field simulation; a dynamic output module for simulating temperature changes, groundwater flow rate changes, and radionuclide concentration changes around the high-level radioactive waste disposal site using the three-dimensional finite element model; a chemical calculation module for performing chemical reaction calculations on the distribution of radioactive concentration of high-level radioactive waste in groundwater and soil media based on a geochemical calculation model, wherein the chemical reaction calculations include the dissolution, precipitation, adsorption, and ion exchange of high-level radioactive waste; and an iterative coupling module for iteratively coupling the physical field simulation with the geochemical calculation model, providing feedback between the physical field data and the chemical field data, and outputting high-level radioactive waste disposal simulation results, wherein the disposal simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution.

[0016] The technical solution adopted in this invention can achieve at least one of the following beneficial effects: In this embodiment of the invention, high-precision prediction of radionuclide migration behavior in the long-term disposal environment of high-level radioactive waste is achieved through iterative coupling of physical fields (groundwater flow, thermal field) and chemical fields (geochemical reactions, nuclide migration). Specifically, by simultaneously considering the comprehensive influence of flow rate, pressure, temperature, and chemical reactions on nuclide migration, the method can handle multi-component solutions, complex mineral assemblages, and the dissolution, precipitation, adsorption, and ion exchange processes of nuclide decay products, thus improving the reliability of long-term migration prediction. The iterative calculation mechanism can dynamically reflect changes in environmental conditions, making the simulation method applicable to different waste types, disposal schemes, and geological conditions, thereby enhancing its universality. The multi-field coupling and iterative calculation overcome the shortcomings of insufficient coupling, limited chemical reaction simulation capabilities, and low accuracy of long-term migration prediction in existing technologies, improving the realism of the simulation results. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1This is a flowchart of a simulation method for the disposal of highly radioactive waste based on multi-field coupling in Embodiment 1 of the present invention; Figure 2 This is a coupled calculation framework diagram of a simulation method for high-level radioactive waste disposal based on multi-field coupling in Embodiment 1 of the present invention; Figure 3 This is a flowchart of an optional simulation method for the disposal of highly radioactive waste based on multi-field coupling in Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of a high-radioactive waste disposal simulation system based on multi-field coupling in Embodiment 3 of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0020] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] To address the problems existing in related technologies, this application provides a simulation method and system for the disposal of highly radioactive waste based on multi-field coupling.

[0022] Example 1 This embodiment provides a simulation method for the disposal of highly radioactive waste based on multi-field coupling, such as... Figure 1 As shown, Figure 1This is a flowchart of a simulation method for the disposal of highly radioactive waste based on multi-field coupling, according to Embodiment 1 of the present invention. The method includes: Step S102: Construct a three-dimensional finite element model of the high-level radioactive waste disposal site and the surrounding geological medium based on physical field simulation; Optionally, constructing a three-dimensional finite element model of the high-level radioactive waste repository and its surrounding geological media can clarify the multi-physics coupling relationship, divide a reasonable finite element mesh, and set precise boundaries and initial conditions, ultimately achieving numerical simulation of the long-term safety of the repository.

[0023] Optionally, high-level radioactive waste (such as spent fuel and high-level vitrified solids) repositories can be built in deep geological strata (such as granite, claystone, and salt rock, buried at depths of 300 to 1000 meters). Their three-dimensional finite element models need to simulate the core physical fields and coupling relationships. Specifically, the core physical fields can be thermal fields, seepage fields, stress-strain fields, and nuclide migration fields. The thermal field represents the temperature rise of the repository and surrounding rock caused by the heat released during waste decay, affecting the rock's mechanical properties and seepage characteristics. The seepage field represents the flow of groundwater in the surrounding rock's cracks or pores, concerning the channels and rates of nuclide migration. The stress-strain field represents the coupling effect of initial geostress, temperature stress, and seepage stress in the surrounding rock, determining whether the rock mass cracks or deforms. The nuclide migration field represents the diffusion, adsorption, and convection of radionuclides in the water-rock system, a core indicator for evaluating the repository's safety. Coupling these multiple physical fields forms a coupled field based on heat-seepage-force (THM), and superimposing nuclide migration data results in THMC coupling, forming a three-dimensional finite element model.

[0024] In some preferred embodiments, the method includes: constructing a three-dimensional finite element model of the high-level radioactive waste repositories and surrounding geological media based on physical field simulation, including: constructing groundwater flow equations for incompressible water and soil media with minimal changes in pore size, based on Darcy's law and the principle of continuity; constructing heat conduction-convection equations by simulating the distribution of groundwater pressure, velocity, and temperature fields; constructing solute transport equations considering the convection, diffusion, and dispersion effects of groundwater; and simulating and constructing a three-dimensional finite element model based on the groundwater flow equations, heat conduction-convection equations, and solute transport equations.

[0025] Optionally, a three-dimensional finite element model of the high-level radioactive waste disposal site and surrounding geological media can be established using COMSOL Multiphysics simulation software, including the waste bins / repository body, buffer layer, soil and rock media, and groundwater system; groundwater flow equations (Darcy's law), continuity equations, and heat conduction equations can be set to simulate the distribution of groundwater pressure field, velocity field, and temperature field; solute transport equations can be set to consider convection, diffusion, and dispersion effects, providing a physical field basis for the calculation of radionuclide migration.

[0026] In some preferred embodiments, based on Darcy's law and the principle of continuity, a groundwater flow equation is constructed for incompressible water and soil media with minimal changes in pore size. This groundwater flow equation includes: in, Porosity is the porosity of the porous medium. The density of groundwater, For time, For divergence operators, This is the groundwater seepage velocity vector. For the source and sink terms of nuclides.

[0027] Optionally, porosity is the proportion of pore volume to total volume in a porous medium, and is dimensionless. Since the changes in the medium are minor, it can be considered a constant here. Although the density of groundwater is assumed to be "incompressible water," the equation retains the density term; in reality, when water is incompressible... It is a constant, and the unit is kg / m³. 3 Time is the time variable of the seepage process; the divergence operator represents the degree of spatial divergence of a physical quantity (here, mass flux), describing the mass change flowing into or out of the control volume; the groundwater velocity vector is the groundwater velocity vector passing through a unit area per unit time, and the direction of the vector represents the direction of seepage. The groundwater velocity vector satisfies Darcy's law. =-K h, kg / (m 2 .s). Here, the negative sign indicates that the seepage direction is opposite to the direction of the hydraulic gradient; groundwater always flows from high-head areas to low-head areas. K is the permeability coefficient (also called "hydraulic conductivity coefficient"), a parameter describing the water permeability of porous media. The larger the value, the easier the medium is to permeate (for example, the K of sand is much larger than that of clay). h is the hydraulic gradient vector. It is the gradient operator (representing the rate of change in space), and h is the hydraulic head (the total mechanical energy per unit weight of water, including position head and pressure head). h describes the spatial trend of water head change ("in which direction the water head drops the fastest"). The source-sink term of a nuclide is the mass replenishment (positive) or consumption (negative) per unit volume of medium per unit time (such as the injection or extraction of groundwater, mass changes due to nuclide decay, etc.) kg / (m³). 3 .s).

[0028] In some preferred embodiments, the distribution of groundwater pressure, velocity, and temperature fields is simulated to construct heat conduction-convection equations, which include: in, The density of the porous medium, The combined specific heat capacity of the porous medium and the porous fluid. For temperature, For time, The density of groundwater, The specific heat capacity of groundwater. This represents the seepage velocity vector of groundwater. The temperature gradient vector. For divergence operators, The equivalent thermal conductivity coefficient, It refers to the source and sink of heat.

[0029] Optionally, the density of the porous medium includes the overall density of the solid skeleton and the pore fluid (or refers only to the density of the solid medium, depending on the scenario); the equivalent specific heat capacity is the combined specific heat capacity (weighted average equivalent parameter) considering both the porous medium (solid) and the pore fluid (water); the temperature is the thermodynamic temperature of the system (temperature distribution in the seepage zone); time is the time variable of the heat transfer process; the density of groundwater is the density of the fluid (water) in the pores; the specific heat capacity of groundwater is the specific heat capacity of water (the heat required to raise the temperature of a unit mass of water by 1 K); the seepage velocity vector of groundwater is the flow velocity of water in the porous medium (satisfying Darcy's law). =-K h); the temperature gradient vector is the spatial trend of temperature variation (gradient operator). It acts on temperature T; the divergence operator describes the degree of spatial divergence of heat flux (the change in heat flowing into or out of the control volume); the equivalent thermal conductivity coefficient is the combined thermal conductivity of porous media (solids) and porous fluids (water) (a weighted average equivalent parameter); the heat source and sink terms are the heat replenishment (positive, such as the heat release from nuclear waste decay) or consumption (negative, such as heat loss) per unit volume of medium per unit time.

[0030] In some preferred embodiments, the convection, diffusion, and dispersion effects of groundwater are considered to construct a solute transport equation, which includes: in, As a blocking factor, Porosity is the porosity of the porous medium. This represents the concentration of the solute in the groundwater. For time, For divergence operators, This represents the seepage velocity vector of groundwater. For the equivalent dispersion coefficient tensor, Let be the gradient vector of solute concentration. Let be the decay constant of the solute. These are the source and sink terms for solutes.

[0031] Optionally, the retardation factor describes the degree to which the solute is adsorbed by the porous medium (R≥1, R=1 indicates no adsorption), determined by adsorption isotherms (e.g., Langmuir, Freundlich); porosity is the proportion of pore volume to total volume in the porous medium (considered a constant due to the small changes in the medium); the solute concentration in groundwater is the mass (or amount of substance) of the solute per unit volume of groundwater; time is the time variable of the solute migration process; and the divergence operator describes the degree of spatial divergence of physical quantities (convergent flux, diffuse flux); groundwater... The water seepage velocity vector represents the flow velocity of water in porous media, satisfying Darcy's law; the equivalent dispersion coefficient tensor is a coefficient that combines molecular diffusion and mechanical dispersion, describing the diffusion or dispersion ability of solutes in groundwater; the solute concentration gradient vector describes the spatial trend of concentration variation; the solute decay constant describes the decay rate of radioactive solutes, and for non-radioactive solutes, λ=0, λ=ln2 / T1 / 2 (T1 / 2 is the half-life); the solute source and sink terms represent the solute replenishment (positive) or consumption (negative) per unit volume of medium per unit time.

[0032] Step S104: A three-dimensional finite element model is used to simulate the temperature changes, groundwater flow rate changes, and radionuclide concentration changes around the high-level radioactive waste disposal repository. Step S106: Based on the geochemical calculation model, chemical reaction calculations are performed on the distribution of radioactive concentration of high-level radioactive waste in groundwater and soil media. The chemical reaction calculations include the dissolution, precipitation, adsorption, and ion exchange of high-level radioactive waste. Optionally, the PHREEQC simulation software can be used to calculate the chemical reactions between groundwater and soil media, including dissolution, precipitation, adsorption, ion exchange, and radionuclide decay. Reaction equations and kinetic parameters can be set based on literature, field measurements, or experimental data, generating reaction rates and concentration changes at each time step. It can handle multi-component solutions and complex mineral assemblages, ensuring long-term simulation accuracy. It should be noted that for many geochemical reactions, the net reaction rate R typically consists of an intrinsic rate term, a thermodynamic driving term, and an inhibition / promotion term. These terms take different forms for different reaction rates and concentrations, making it difficult to summarize all reactions with a single equation.

[0033] In some preferred embodiments, based on geochemical calculation models, chemical reaction calculations are performed to assess the distribution of radioactive concentrations of highly radioactive waste in groundwater and soil media. These calculations include: calculating electrostatic adsorption, surface complexation, and ion exchange between radionuclides and the surface of soil media to determine the migration lag value of radionuclides in the soil media; calculating the concentration of water-soluble complexes formed by metal ions and ligands in groundwater solutions; simulating the transformation of metal ion redox pairs in the groundwater environment to calculate the influence of redox on the valence state of radionuclides; and simulating the decay of radionuclides in highly radioactive waste over time to calculate the degree of change in radioactive concentration over time.

[0034] Optional calculations of chemical reactions between groundwater and soil media include: calculating the dissolution or precipitation rates of minerals (such as calcite and montmorillonite) in aqueous solutions, as well as the formation and disappearance of amorphous substances. This can simulate the interaction between groundwater and rock, and assess changes in porosity and permeability over time, which is the basis for THC coupling. Calculating the electrostatic adsorption, surface complexation, and ion exchange interactions between radionuclides (such as Cs, Sr, and U) and the surface of soil media can determine the migration hysteresis of nuclides in the medium, which is core to assessing barrier safety. Calculating the interactions between metal ions and ligands (such as Cl-) in aqueous solutions... - ,OH - CO32 - The concentration of water-soluble complexes formed by Fe in simulated groundwater environments can significantly alter the solubility and migration ability of nuclides. 2+ / Fe 3+ , S 2- SO4 2- The transformation of redox pairs affects the valence state of nuclides, and the valence state of a nuclide (such as U(IV) or U(VI)) determines its solubility and adsorption. Simulating the decay of radionuclides in high-level waste over time is the only irreversible process, effectively determining the decrease in radioactivity in the environment over time.

[0035] Optionally, relevant parameters for thermodynamic and kinetic calculations can be obtained in advance and incorporated into chemical reaction calculations to complete the calculation process within the geochemical calculation model. These relevant parameters include: solubility constant (the logarithmic constant for mineral dissolution or precipitation under equilibrium conditions); complexation constant (the equilibrium constant for the formation of specific complexes in solution); ion exchange capacity (the ability of a medium to exchange cations); activity coefficient model (used to calculate ion activity and correct for differences between real and ideal solutions); reaction rate constant (the intrinsic rate constant for mineral dissolution or precipitation); reaction order (the degree to which reactant concentration affects the reaction rate); activation energy (describing the sensitivity of the rate constant to temperature, determined by the Arrhenius equation); specific surface area (the effective contact area of ​​the minerals participating in the reaction); and decay half-life (the characteristic decay time of a radionuclide).

[0036] Step S108 involves iteratively coupling the physical field simulation with the geochemical calculation model, feeding back the physical field data and chemical field data to output the simulation results of high-level radioactive waste disposal. The simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution.

[0037] Optionally, a bidirectional coupling mechanism enables iterative bidirectional data exchange and synchronous solution between the COMSOL (finite element / heat transfer / hydraulic) and PHREEQC (geochemical) models, rather than unidirectional data transfer. Simultaneously, precise mesh or node mapping relationships can be established between different solvers (COMSOL mesh nodes and PHREEQC elements) through the discretization and mapping of the physical field space, ensuring spatial consistency of hydrological, heat transfer, solute transport, and geochemical reactions. Time step synchronization and control are employed to achieve time step synchronization or adaptive control during the coupled solution process, ensuring that geochemical reactions and transport processes reach equilibrium or convergence within each time step. A solute source term treatment method is used to accurately integrate the solute concentration change rate or mass change caused by geochemical reactions calculated by PHREEQC into the COMSOL solute transport equations as source / sink terms. In addition, a parameter feedback mechanism is set up to feed back the changes in parameters such as porosity and permeability caused by mineral precipitation / dissolution calculated by PHREEQC to the COMSOL hydraulic conduction and solute transport modules in real time, so as to realize the real coupling of the water-chemical-mechanical (THC) process.

[0038] Optionally, data interaction between COMSOL and PHREEQC is achieved based on multi-field coupling, including: COMSOL outputting flow rate, pressure, temperature, and physical field boundary conditions; PHREEQC outputting chemical reaction rate, solute concentration, and mineral equilibrium state; using an iterative calculation mechanism to feed back the physical and chemical field results to achieve multi-field coupling simulation; providing an interface that supports multi-threaded or batch calculations to improve the computational efficiency of large-scale 3D models.

[0039] In some preferred embodiments, the physical field simulation and the geochemical calculation model are iteratively coupled, with feedback between the physical field data and the chemical field data. This includes: determining temperature changes, flow rate changes, and radionuclide concentration changes based on the physical field simulation, wherein the radionuclide concentration change includes the initial radionuclide concentration; mapping the temperature changes, flow rate changes, and radionuclide concentration changes to the geochemical calculation model, calculating the first radionuclide concentration and porosity after the chemical reaction; calculating the rate of change of radionuclide concentration using the first radionuclide concentration and the initial radionuclide concentration; re-inputting the rate of change of radionuclide concentration into the physical field simulation to obtain a new radionuclide concentration change; iterating the new radionuclide concentration change into the geochemical calculation model until a preset convergence condition is reached, at which point the iteration process stops. Figure 2 As shown, Figure 2 This is a coupled calculation framework diagram of a simulation method for the disposal of highly radioactive waste based on multi-field coupling in Embodiment 1 of the present invention.

[0040] Optionally, the solution can be obtained using COMSOL. Specifically, based on the old parameters, the time, seepage velocity, and initial radionuclide concentration C (the concentration of the solute in the groundwater) are calculated. Then, the data obtained from the above physical field is mapped to the PHREEQC solution, specifically, the time and initial radionuclide concentration are mapped. Mapping to PHREEQC, the concentration C of the first radionuclide after the chemical reaction is calculated. final and porosity changes .

[0041] Optionally, after each output of nuclide concentration in the geochemical calculation model, source-sink term feedback and COMSOL correction are required. Specifically, this will... Substituting the source and sink terms of the solute into the COMSOL solute transport equation and resolving (correcting) yields the new concentration. Simultaneously, the porosity gradient vector is fed back to update the COMSOL permeability (seepage rate).

[0042] In some preferred embodiments, the new radionuclide concentration changes are iterated into the geochemical calculation model until a preset convergence condition is met, at which point the iteration process stops. The preset convergence condition includes: comparing the difference between the latest radionuclide concentration output by the geochemical calculation model and the radionuclide concentration before the iteration; if the difference is greater than a preset difference value, the iteration continues; if the difference is not greater than the preset difference value, the latest radionuclide concentration is confirmed as the target radionuclide concentration, and the iteration stops.

[0043] Optionally, the convergence determination method is comparison. and Specifically, when the difference exceeds a preset difference value, use... As a new Simultaneously, return to PHREEQC to continue calculations for the next sub-iteration. When the difference is less than the preset difference value (at which point convergence is achieved), confirm. To achieve the final result, proceed to the next time step. .

[0044] In some preferred embodiments, simulation results of high-level radioactive waste disposal are output. These simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution. Specifically, the simulation results include: constructing a three-dimensional distribution map of radionuclide concentration based on the target radionuclide concentration; constructing a migration flux vector map based on all radionuclide concentrations generated during the iteration process; and determining the temperature field distribution based on temperature changes in the physical field simulation.

[0045] Optionally, the coupled calculation results can be visualized by presenting the discrete or continuous digital data (nuclide concentration, temperature, etc.) output by the terminal on the screen using graphics rendering technology. Specifically, this can be achieved by: constructing three-dimensional field distribution maps, such as isosurface maps of nuclide concentration and temperature field slice maps; constructing vector field maps, such as migration flux vector maps (showing the direction and intensity of nuclide migration); and constructing two-dimensional curve maps, such as nuclide leakage rate (flux) curves changing over time and concentration penetration curves at key locations.

[0046] Through the above steps S102 to S108, the system provides functions for calculating long-term safety evaluation indicators, such as cumulative migration flux, identification of areas exceeding concentration limits, and prediction of barrier failure in the treatment facility; it also supports data export and report generation, providing decision-making basis for treatment facility design optimization and regulatory approval.

[0047] Example 2 Based on the above embodiments and optional embodiments, the present invention also proposes an optional implementation method. Figure 3 This is a flowchart of an optional simulation method for the disposal of highly radioactive waste based on multi-field coupling, as described in Embodiment 2 of the present invention. Figure 3 As shown, the method includes: Step S1, Model Building: In COMSOL, a three-dimensional finite element mesh model of the high-level radioactive waste disposal site and the surrounding soil and rock media is established. Boundary conditions (such as groundwater inlet flow rate, outlet pressure, and geothermal boundary) and initial conditions (such as initial hydrochemical conditions, temperature field, and solute concentration) are set. Physical parameters, including permeability coefficient, specific heat capacity, thermal conductivity, porosity, and dispersion coefficient, are also set.

[0048] Since grid partitioning should balance computational accuracy and efficiency, locally refined grids can be used to process key areas surrounding waste.

[0049] Step S2, Solving for the physical fields: COMSOL was used to solve the groundwater flow equation, heat conduction-convection equation, and solute transport equation to obtain the flow velocity, pressure, temperature, and solute concentration at each time step. The physical field results were then passed to the geochemical calculation module as boundary conditions for chemical reaction calculations.

[0050] The time step should be set according to the nuclide migration rate and chemical reaction kinetics to ensure numerical stability.

[0051] Step S3, Geochemical Calculations: Input the initial hydrochemical conditions, mineral composition, reaction equations, and kinetic parameters into PHREEQC; calculate the solute concentration changes, reaction rates, and mineral equilibrium states at each time step; output the results to COMSOL to update the reaction terms in the solute transport equations.

[0052] Among them, chemical reaction parameters (equilibrium constant, adsorption coefficient, precipitation rate, etc.) can be set based on experimental data or literature values.

[0053] Step S4, Coupled Iterative Calculation: At each time step, the physical and chemical fields are iterated: COMSOL updates the flow rate, pressure, and temperature, while PHREEQC updates the solute concentration and reaction rate. At the same time, the convergence conditions are checked, such as when the change in solute concentration is less than a set threshold or the number of iterations reaches the upper limit. The iteration is repeated until the predetermined total simulation time or the convergence condition is reached.

[0054] Among them, when the system supports parallel computing and batch simulation, it can quickly evaluate different treatment options; other physical field simulations, such as mechanical stress fields or gas migration fields, can be added according to actual needs.

[0055] Step S5, Result Output and Analysis: Outputs three-dimensional distribution maps of radionuclide concentrations, migration flux vector maps, and temperature field distributions; generates long-term safety assessment reports, including barrier effectiveness, nuclide migration paths, and potential leakage risks; supports rapid comparative analysis of different waste types, different disposal schemes, and different geological conditions.

[0056] Through the above steps S1 to S5, multi-field iterative coupling of physical fields (groundwater flow, thermal field) and chemical fields (geochemical reactions, nuclide migration) is realized, which improves the accuracy of long-term migration prediction; supports high-precision simulation of complex mineral assemblages, multi-component solutions and nuclide decay processes; and provides unified and safety evaluation indicators and visualization analysis tools to facilitate the optimization of disposal plans and regulatory approval.

[0057] Example 3 This embodiment also provides a simulation system for the disposal of high-level radioactive waste based on multi-field coupling. This system is used to implement the above embodiments and preferred embodiments, and details already described will not be repeated. As used below, the terms "module" and "system" can refer to a combination of software and / or hardware that performs a predetermined function. Although the system described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0058] According to embodiments of the present invention, a system embodiment for implementing the above-described simulation method for the disposal of highly radioactive waste based on multi-field coupling is also provided. Figure 4 This is a schematic diagram of a high-level radioactive waste disposal simulation system based on multi-field coupling in Embodiment 3 of the present invention, as shown below. Figure 4 As shown, the above system includes: a physical simulation module 301, a dynamic output module 302, a chemical calculation module 303, and an iterative coupling module 304, wherein: The physical simulation module 301 constructs a three-dimensional finite element model of the high-level radioactive waste disposal site and its surrounding geological media based on physical field simulation. The dynamic output module 302 uses a three-dimensional finite element model to simulate temperature changes, groundwater flow rate changes, and radionuclide concentration changes around the high-level radioactive waste disposal site. The chemical calculation module 303, based on the geochemical calculation model, performs chemical reaction calculations on the distribution of radioactive concentrations of high-level radioactive waste in groundwater and soil media. The chemical reaction calculations include the dissolution, precipitation, adsorption, and ion exchange of high-level radioactive waste. The iterative coupling module 304 iteratively couples the physical field simulation with the geochemical calculation model, feeds back the physical field data and chemical field data to each other, and outputs the simulation results of high radioactive waste disposal. The disposal simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution.

[0059] It should be noted that the above modules can be implemented by software or hardware. For example, for the latter, it can be implemented in the following ways: the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0060] It should be noted that the aforementioned physical simulation module 301, dynamic output module 302, chemical calculation module 303, and iterative coupling module 304 correspond to steps S102 to S108 in the embodiments. The instances and application scenarios implemented by these modules and their corresponding steps are the same, but they are not limited to the content disclosed in the above embodiments. It should be noted that the above modules, as part of the system, can run on a computer terminal.

[0061] It should be noted that the optional or preferred implementation methods of this embodiment can be found in the relevant descriptions in the embodiments, and will not be repeated here.

[0062] The aforementioned simulation system for the disposal of high-level radioactive waste based on multi-field coupling may also include a processor and a memory. The aforementioned physical simulation module 301, dynamic output module 302, chemical calculation module 303, and iterative coupling module 304 are all stored in the memory as program modules, and the processor executes the aforementioned program modules stored in the memory to realize the corresponding functions.

[0063] The processor contains a core that retrieves the corresponding program modules from memory. One or more cores may be configured. Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, like read-only memory (ROM) or flash RAM. Memory includes at least one memory chip.

[0064] According to an embodiment of this application, an embodiment of a non-volatile storage medium is also provided. Optionally, in this embodiment, the non-volatile storage medium includes a stored program, wherein, when the program runs, it controls the device containing the non-volatile storage medium to execute any of the above-mentioned simulation methods for high-level radioactive waste disposal based on multi-field coupling.

[0065] Optionally, in this embodiment, the non-volatile storage medium may be located in any computer terminal in a group of computer terminals in a computer network, or in any mobile terminal in a group of mobile terminals, and the non-volatile storage medium includes stored programs.

[0066] Optionally, during program execution, the device containing the non-volatile storage medium may perform the following functions: construct a three-dimensional finite element model of the high-level radioactive waste disposal site and its surrounding geological media based on physical field simulation; simulate temperature changes, groundwater flow rate changes, and radionuclide concentration changes around the high-level radioactive waste disposal site using the three-dimensional finite element model; perform chemical reaction calculations on the distribution of radioactive concentration of high-level radioactive waste in groundwater and soil media based on a geochemical calculation model, including the dissolution, precipitation, adsorption, and ion exchange of high-level radioactive waste; iteratively couple the physical field simulation with the geochemical calculation model, provide feedback between the physical field data and the chemical field data, and output the high-level radioactive waste disposal simulation results, including a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution.

[0067] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0068] If the aforementioned integrated modules are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable non-volatile storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a non-volatile storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned non-volatile storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0069] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A simulation method for the disposal of highly radioactive waste based on multi-field coupling, characterized in that, include: A three-dimensional finite element model of the high-level radioactive waste repository and its surrounding geological media was constructed based on physical field simulation. The three-dimensional finite element model was used to simulate the temperature changes, groundwater flow rate changes, and radionuclide concentration changes around the high-level radioactive waste disposal site. Based on a geochemical calculation model, chemical reaction calculations are performed to assess the distribution of radioactive concentrations of high-level radioactive waste in groundwater and soil media. These chemical reaction calculations include the dissolution, precipitation, adsorption, and ion exchange of high-level radioactive waste. The physical field simulation and the geochemical calculation model are iteratively coupled, and the physical field data and chemical field data are fed back to each other to output the simulation results of high radioactive waste disposal. The disposal simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution.

2. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 1, characterized in that, The three-dimensional finite element model of the high-level radioactive waste repository and its surrounding geological media, constructed based on physical field simulation, includes: Based on Darcy's law and the principle of continuity, a groundwater flow equation is constructed for incompressible water and soil media with minimal changes in pore size. Simulate the distribution of groundwater pressure, velocity, and temperature fields, and construct heat conduction-convection equations; Considering the convection, diffusion, and dispersion effects of groundwater, a solute transport equation is constructed. Based on the groundwater flow equation, the heat conduction-convection equation, and the solute transport equation, the three-dimensional finite element model is constructed through simulation.

3. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 2, characterized in that, Based on Darcy's law and the principle of continuity, groundwater flow equations are constructed for incompressible water and soil media with minimal changes in porosity. These equations include: in, Porosity is the porosity of the porous medium. The density of groundwater, For time, For divergence operators, This is the groundwater seepage velocity vector. For the source and sink terms of nuclides.

4. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 2, characterized in that, The distribution of groundwater pressure, velocity, and temperature fields is simulated to construct a heat conduction-convection equation, which includes: in, The density of the porous medium, The combined specific heat capacity of the porous medium and the porous fluid. For temperature, For time, The density of groundwater, The specific heat capacity of groundwater. This represents the seepage velocity vector of groundwater. The temperature gradient vector. For divergence operators, The equivalent thermal conductivity coefficient, It refers to the source and sink of heat.

5. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 2, characterized in that, Considering the convection, diffusion, and dispersion effects of groundwater, a solute transport equation is constructed, wherein the solute transport equation includes: in, As a blocking factor, Porosity is the porosity of the porous medium. This represents the concentration of the solute in the groundwater. For time, For divergence operators, This represents the seepage velocity vector of groundwater. For the equivalent dispersion coefficient tensor, Let be the gradient vector of solute concentration. Let be the decay constant of the solute. These are the source and sink terms for solutes.

6. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 1, characterized in that, Based on a geochemical calculation model, chemical reaction calculations are performed to assess the distribution of radioactive concentrations of high-level radioactive waste in groundwater and soil media. These chemical reaction calculations include: Calculate the electrostatic adsorption, surface complexation, and ion exchange interactions between radionuclides and the surface of rock and soil media to determine the migration hysteresis value of the radionuclides in the rock and soil media; Calculate the concentration of water-soluble complexes formed by metal ions and ligands in the groundwater solution; The transformation of metal ion redox pairs in the groundwater environment was simulated, and the influence of redox on the valence state of radionuclides was calculated. The decay of radionuclides in highly radioactive waste over time is simulated to calculate the degree of change in the radioactive concentration over time.

7. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 1, characterized in that, The physical field simulation and the geochemical calculation model are iteratively coupled, and the physical field data and chemical field data are fed back to each other, including: Based on the physical field simulation, the temperature change, flow rate change, and radionuclide concentration change are determined, wherein the radionuclide concentration change includes the initial radionuclide concentration; The temperature change, the flow rate change, and the radionuclide concentration change are mapped to the geochemical calculation model to calculate the first radionuclide concentration and porosity after the chemical reaction. The rate of change of radionuclide concentration is calculated using the first radionuclide concentration and the initial radionuclide concentration. The rate of change of radionuclide concentration is re-input into the physical field simulation to obtain a new change in radionuclide concentration. This new change in radionuclide concentration is then iterated into the geochemical calculation model until a preset convergence condition is met, at which point the iteration process stops.

8. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 7, characterized in that, The new radionuclide concentration change is iterated into the geochemical calculation model until a preset convergence condition is reached, at which point the iteration process stops. The preset convergence condition includes: Compare the differences between the latest radionuclide concentration output by the geochemical calculation model and the radionuclide concentration before the iteration; If the difference is greater than a preset difference value, continue iterating; If the difference is not greater than the preset difference value, the latest radionuclide concentration is confirmed as the target radionuclide concentration, and the iteration stops.

9. The simulation method for high-level radioactive waste disposal based on multi-field coupling according to claim 8, characterized in that, Output simulation results for the disposal of high-level radioactive waste, including a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution, comprising: Based on the target radionuclide concentration, a three-dimensional distribution map of the radionuclide concentration is constructed. The migration flux vector diagram is constructed based on the concentrations of all radionuclides generated during the iteration process. The temperature field distribution is determined based on the temperature changes in the physical field simulation.

10. A simulation system for the disposal of highly radioactive waste based on multi-field coupling, characterized in that, include: The physical simulation module constructs a three-dimensional finite element model of the high-level radioactive waste disposal site and its surrounding geological media based on physical field simulation. The dynamic output module uses the three-dimensional finite element model to simulate temperature changes, groundwater flow rate changes, and radionuclide concentration changes around the high-level radioactive waste disposal site. The chemical calculation module, based on a geochemical calculation model, performs chemical reaction calculations on the distribution of radioactive concentrations of highly radioactive waste in groundwater and soil media. The chemical reaction calculations include the dissolution, precipitation, adsorption, and ion exchange of highly radioactive waste. The iterative coupling module iteratively couples the physical field simulation with the geochemical calculation model, provides feedback between the physical field data and the chemical field data, and outputs simulation results for the disposal of high-level radioactive waste. The disposal simulation results include a three-dimensional distribution map of radionuclide concentration, a migration flux vector map, and a temperature field distribution.

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