Nuclear reactor modular sub-channel analysis method

Abstract

The invention discloses a modular sub-channel analysis method for a nuclear reactor, relates to the field of sub-channel analysis of nuclear reactors, and solves the problem that the conventional sub-channel analysis program is difficult to adapt to design requirements of various nuclear reactor cores, and the conventional sub-channel analysis program is difficult to adapt to design requirements of novel fuel rod models, different coolants, reactor core structures and the like. The method comprises the following steps: constructing a sub-channel thermal hydraulic analysis and calculation overall framework, and performing decomposition and recombination by utilizing modular program design; discretizing the sub-channel conservation equation set, embedding the sub-channel conservation equation set into a corresponding module, and determining model parameters of each module according to parameters input by a user; modeling based on the divided modules and the determined parameters; and finally, linking and coupling each module, and constructing an overall modular analysis model for sub-channel analysis and verification. The method is also suitable for the application field of the modular programming method in the aspect of subchannel thermal hydraulic calculation.

Description

Technical Field

[0001] The present invention relates to the technical field of sub-channel analysis of nuclear reactors, and particularly to a modular sub-channel analysis method for nuclear reactors. Background Art

[0002] In the field of core design in nuclear reactors, sub-channel calculation programs are widely used in simulation work to achieve the purpose of cost savings. With the continuous development of nuclear energy research, nuclear reactors using liquid metal as a coolant have gradually become the focus of research. Traditional sub-channel calculation programs using water as a coolant are no longer sufficient to meet the needs of modern liquid metal nuclear reactor design and verification. To achieve high-precision calculations of nuclear reactors under different coolant conditions, it is necessary to adopt a sub-channel analysis method based on modular programming.

[0003] In the framework of traditional sub-channel calculation programs, although custom coolant physical properties can be added, in the traditional calculation process, the calculation of newly defined coolant physical properties usually relies on linear interpolation of physical property tables, which has a certain deviation from the actual physical properties of the coolant in the sub-channel and cannot accurately calculate the flow and heat transfer characteristics of the coolant in the sub-channel. In traditional sub-channel programs that support liquid metal calculations, most can only perform sub-channel analysis of a single liquid metal and cannot conduct thermal-hydraulic analysis of nuclear reactors with different coolant media. If the coolant parameters in the sub-channel analysis program need to be changed, not only the parameters need to be adapted to the overall program, but also the heat transfer relational expressions related to the coolant and other key global parameters need to be changed, which will greatly increase the workload of program modification and improvement, and this process is prone to errors. Summary of the Invention

[0004] The present invention solves the adaptation problem of traditional sub-channel analysis programs in the face of various nuclear reactor core design requirements. Limited by the overall framework and design method of traditional programs, it is difficult to quickly, accurately, and comprehensively improve program functions in the face of design requirements such as new fuel rod models, different coolants, and core structures. When adjustments are needed to meet new requirements, not only the main conservation equations in the entire program need to be corrected, but also the overall program needs to be debugged, and this process is extremely prone to problems such as errors.

[0005] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0006] Solution 1: The present invention proposes a modular sub-channel analysis method for nuclear reactors, and the method includes the following steps:

[0007] S1. Use a top-down design method to establish a sub-channel thermal-hydraulic analysis calculation model;

[0008] S2. According to the sub-channel thermohydraulic calculation model described in S1, decompose and reorganize the sub-channel thermohydraulic calculation model using the modular programming method, and confirm the connections and calculation sequences among the various modules;

[0009] S3. Solve the sub-channel mass, energy, and momentum conservation equations and the heat conduction equation using the sub-channel analysis method and perform discretization processing, and input them into the corresponding equation model modules;

[0010] S4. Determine the model parameters of the various different modules according to the geometric parameters of the object to be analyzed and the sub-channel thermohydraulic analysis calculation model, where the model parameters include equation model parameters, fluid model parameters, heat conduction model parameters, physical property model parameters, special-shaped structure model parameters, and output model parameters;

[0011] S5. Link and couple the various model parameters according to the various different modules divided by the model parameters determined in S4, and construct an overall modular analysis model;

[0012] S6. Obtain the overall modular analysis model in S5, and perform iterative solution of the temperature field of the overall modular analysis model according to the heat conduction model set in S4. Determine whether the coolant temperature and the fuel rod temperature reach the convergence standard. If the convergence standard is reached, proceed to the next calculation. If not, repeat the iteration in S6 until convergence is determined or the maximum number of iterations is reached;

[0013] S7. Obtain the temperature field of the overall modular analysis model in S6, solve the energy conservation equation, and obtain the enthalpy distribution of the overall modular analysis model;

[0014] S8. Obtain the enthalpy distribution in S7, solve the physical properties of the overall modular analysis model according to the physical property model parameters selected in S4, and use the obtained physical property model parameters and the enthalpy distribution to solve the momentum conservation equation to obtain the overall pressure distribution;

[0015] S9. Obtain the enthalpy distribution of the overall modular analysis model in S7 and the overall pressure distribution in S8, and determine whether the coolant enthalpy, the coolant pressure distribution, and the coolant flow rate distribution all reach the convergence standard. If the standard is reached, complete the sub-channel analysis model calculation. If not, return to S6 and repeat the iteration until convergence is determined or the maximum number of iterations is reached.

[0016] Furthermore, a preferred embodiment is provided, before using the top-down design method in S1, the sub-channel thermal-hydraulic analysis calculation model also includes an input unit, a calculation unit, and an output unit, wherein the input unit includes reading operating condition settings, preliminary processing of input cards, output parameter settings, and allocating time-step data memory; the calculation unit includes a calculation equation model, a fluid model, a heat conduction model, a turbulent flow model, a heat transfer coefficient model, a physical property model, and a special-shaped structure model; the output unit includes the steps of calculating the mean and the overall output.

[0017] Further, a preferred implementation is provided, in S3, the method for solving the sub-channel mass, energy and momentum conservation equations by using the sub-channel analysis method is:

[0018] The mass conservation equation is obtained by solving the heat conduction equation and the energy conservation equation separately, and then the mass conservation equation is substituted into the axial momentum conservation equation and then solved simultaneously with the transverse momentum conservation equation.

[0019] Furthermore, a preferred embodiment is provided, wherein the sub-channel thermal-hydraulic analysis and calculation model includes a heat transfer model, an equation model, a physical property model, and a special-shaped structure model.

[0020] Furthermore, a preferred embodiment is provided, wherein the physical property model includes a water model, a liquid sodium or liquid sodium-potassium alloy model, a liquid lead-bismuth alloy model, a liquid lithium model, and a supercritical carbon dioxide model.

[0021] Furthermore, a preferred embodiment is provided, wherein the heterogeneous structure model includes a petal-shaped fuel rod model, a rib-wound fuel rod model, a wire-wound fuel rod model, and a core-subchannel coupling model.

[0022] Furthermore, a preferred implementation is provided, in which the modular programming method described in S2 is implemented using Fortran language.

[0023] Further, a preferred implementation is provided, in which the method for solving the energy conservation equation in S7 is:

[0024]

[0025] Where: i and j represent the subchannel number and radial node number respectively; A i is the axial flow area of ​​sub-channel (i, j), in m 2 ; Δt is the time step, in seconds; ρ is the coolant density; h is the coolant enthalpy, in J / kg; h nis the coolant enthalpy value at the previous time step, in J / kg; ΔX is the axial height of the sub-channel (i,j), in m; m is the axial mass flow rate of the coolant, in kg / s; e is 1 or -1 in the cross-flow direction; w is the cross-flow velocity of the coolant, in kg / m 2 / s; h * is the enthalpy value of the previous sub-channel or the next sub-channel according to the direction of the coolant mass flow, in J / kg; P is the heated perimeter, in m; φ is the correction factor; q is the heat flux density of the fuel rod entering the coolant, in W / m 2 ; C is the transverse thermal conductivity, in W / m 2 / K; s is the gap length, in m; T is the temperature, in K; r Q is the power generated by the fuel rod directly entering the coolant, in W / m; q ’ is the fuel rod power, in W / m.

[0026] Solution 2: A computer device, including a memory and a processor. A computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the method described in any one of Solution 1.

[0027] Solution 3: A computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the steps of the method described in any one of Solution 1 are implemented.

[0028] The advantages of the present invention are as follows:

[0029] In the modular sub-channel analysis method of a nuclear reactor described in the present invention, relying on the advantages of modular programming, each functional module can independently carry out development, testing and maintenance work. When facing new design requirements, only specific modules need to be adjusted, greatly improving the flexibility and response speed of the program. When dealing with new models and new structures, the program functions can also be quickly extended and optimized by flexibly calling and adjusting the corresponding modules, effectively breaking through the predicament of traditional sub-channel analysis programs and meeting the continuously developing technical requirements in the field of nuclear reactors.

[0030] In the modular sub-channel analysis method of a nuclear reactor described in the present invention, more detailed modular distinctions are added to various coolants, nuclear reactor structures and calculation models, so that the overall simulation of the sub-channels in the nuclear reactor can better fit the actual working conditions.

[0031] In the modular sub-channel analysis method of a nuclear reactor according to the present invention, relying on the advantages of modular programming, each functional module of the present invention can independently carry out development, testing, and maintenance work. The program architecture is modularly decomposed, and even in the case where the design of other modules is not clear, local debugging and testing can be carried out. Moreover, when adjustments are made later, it is possible to effectively avoid synchronously changing other modules, thereby improving the flexibility and response speed of the program, enhancing the generality and debuggability of the model, quickly expanding and optimizing the program functions, improving the sub-channel analysis efficiency, breaking through the traditional dilemma, and meeting the needs of technological development;

[0032] In the modular sub-channel analysis method of a nuclear reactor according to the present invention, modular programming makes the development, testing, and maintenance work of each module relatively independent, reducing the cooperation difficulty of the development team, shortening the development cycle and maintenance cost, and improving the economic benefits of the project;

[0033] The modular sub-channel analysis method of a nuclear reactor according to the present invention can be well compatible with the existing data and algorithms related to nuclear reactors, and can conveniently integrate new models and technologies, providing convenience for subsequent function upgrades and expansions.

[0034] The present invention is also applicable to the application field of modular programming methods in sub-channel thermal-hydraulic calculations. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is the overall architecture diagram of the modular sub-channel analysis method of a nuclear reactor described in Embodiment 1.

[0036] Figure 2 It is the hierarchical and modular design diagram of the nuclear reactor sub-channel analysis program described in Embodiment 1.

[0037] Figure 3 It is the flow chart of the nuclear reactor sub-channel analysis program described in Embodiment 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application.

[0039] Embodiment 1. This embodiment proposes a modular sub-channel analysis method for a nuclear reactor, and the method includes the following steps:

[0040] S1. Use the top-down design method to establish a sub-channel thermal-hydraulic analysis and calculation model;

[0041] S2. According to the sub-channel thermohydraulic calculation model described in S1, use the modular programming method to decompose and reorganize the sub-channel thermohydraulic calculation model, and confirm the connections and calculation sequences between each module;

[0042] S3. Use the sub-channel analysis method to solve the sub-channel mass, energy, and momentum conservation equations and the heat conduction equation, and perform discretization processing, and input them into the corresponding equation model modules;

[0043] S4. According to the geometric parameters of the object to be analyzed and the sub-channel thermohydraulic analysis calculation model, determine the model parameters of each different module, where the model parameters include equation model parameters, fluid model parameters, heat conduction model parameters, physical property model parameters, special-shaped structure model parameters, and output model parameters;

[0044] S5. According to each different module divided by the model parameters determined in S4, link each model parameter and perform coupling to construct an overall modular analysis model;

[0045] S6. Obtain the overall modular analysis model in S5, and according to the heat conduction model set in S4, perform iterative solution on the temperature field of the overall modular analysis model, and determine whether the coolant temperature and the fuel rod temperature reach the convergence standard. If the convergence standard is reached, proceed to the next calculation. If it does not converge, repeat the iteration in S6 until convergence is determined or the maximum number of iterations is reached;

[0046] S7. Obtain the temperature field of the overall modular analysis model in S6, solve the energy conservation equation, and obtain the enthalpy distribution of the overall modular analysis model;

[0047] S8. Obtain the enthalpy distribution in S7, and according to the physical property model parameters selected in S4, solve the physical properties of the overall modular analysis model, and use the obtained physical property model parameters and the enthalpy distribution to solve the momentum conservation equation to obtain the overall pressure distribution;

[0048] S9. Obtain the enthalpy distribution of the overall modular analysis model in S7 and the overall pressure distribution in S8, and determine whether the coolant enthalpy, the coolant pressure distribution, and the coolant flow rate distribution all reach the convergence standard. If the standard is reached, complete the sub-channel analysis model calculation. If it does not converge, return to S6 and repeat the iteration until convergence is determined or the maximum number of iterations is reached.

[0049] Implementation method 2. This implementation method is a further limitation of the modular sub-channel analysis method of the nuclear reactor described in implementation method 1. Before using the top-down design method in S1, the sub-channel thermal-hydraulic analysis calculation model also includes an input unit, a calculation unit, and an output unit. The input unit includes reading the operating condition setting, preliminary processing of the input card, output parameter setting, and allocating time-step data memory; the calculation unit includes a calculation equation model, a fluid model, a heat conduction model, a turbulent flow model, a heat transfer coefficient model, a physical property model, and a special-shaped structure model; the output unit includes the steps of calculating the mean and the overall output.

[0050] Embodiment 3: This embodiment further limits the modular sub-channel analysis method of the nuclear reactor described in Embodiment 1. The method for solving the sub-channel mass, energy and momentum conservation equations by using the sub-channel analysis method in S3 is:

[0051] The mass conservation equation is obtained by solving the heat conduction equation and the energy conservation equation separately, and then the mass conservation equation is substituted into the axial momentum conservation equation and then solved simultaneously with the transverse momentum conservation equation.

[0052] Embodiment 4: This embodiment further limits the modular sub-channel analysis method of the nuclear reactor described in embodiment 1. The sub-channel thermal-hydraulic analysis calculation model includes a heat transfer model, an equation model, a physical property model, and a special-shaped structure model.

[0053] Embodiment 5. This embodiment is a further limitation of the modular sub-channel analysis method of a nuclear reactor described in Embodiment 4, wherein the physical property model includes a water model, a liquid sodium or liquid sodium-potassium alloy model, a liquid lead-bismuth alloy model, a liquid lithium model, and a supercritical carbon dioxide model.

[0054] Embodiment 6. This embodiment further limits the modular sub-channel analysis method of the nuclear reactor described in Embodiment 4, and the heterogeneous structure model includes a petal-type fuel rod model, a rib-wound fuel rod model, a wire-wound fuel rod model, and a core-sub-channel coupling model.

[0055] Embodiment 7: This embodiment further limits the modular sub-channel analysis method of a nuclear reactor described in Embodiment 4. The modular programming method described in S2 is implemented using Fortran language.

[0056] Embodiment 8: This embodiment further limits the modular sub-channel analysis method of the nuclear reactor described in Embodiment 4. The method for solving the energy conservation equation in S7 is:

[0057]

[0058] where: i and j respectively represent the sub-channel number and the radial node number; A i is the axial flow area of the sub-channel (i,j), with the unit of m 2 ; Δt is the time step, with the unit of s; ρ is the coolant density; h is the coolant enthalpy, with the unit of J / kg; h n is the coolant enthalpy at the previous time step, with the unit of J / kg; ΔX is the axial height of the sub-channel (i,j), with the unit of m; m is the axial mass flow rate of the coolant, with the unit of kg / s; e takes 1 or -1 in the cross-flow direction; w is the cross-flow velocity of the coolant, with the unit of kg / m 2 / s; h * is the enthalpy of the previous sub-channel or the next sub-channel according to the direction of the coolant mass flow, with the unit of J / kg; P is the heating perimeter, with the unit of m; φ is the correction factor; q is the heat flux density of the fuel rod entering the coolant, with the unit of W / m 2 ; C is the transverse thermal conductivity, with the unit of W / m 2 / K; s is the gap length, with the unit of m; T is the temperature, with the unit of K; r Q is the power generated by the fuel rod directly entering the coolant, with the unit of W / m; q ’ is the fuel rod power, with the unit of W / m.

[0059] Embodiment 9. This embodiment proposes a computer device, including a memory and a processor. A computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the method described in any one of Embodiments 1 to 8.

[0060] Embodiment 10. This embodiment proposes a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, the steps of the method described in any one of Embodiments 1 to 8 are implemented.

[0061] Embodiment 11. This embodiment proposes an example, and the example is used to explain the above Embodiments 1 to 10. The specific example is as follows:

[0062] Referring to Figures 1 to 3 to illustrate this embodiment. Based on the advantages of modular programming, each functional module of the present invention can independently carry out development, testing, and maintenance work. The program architecture is modularly decomposed. Even when the design of other modules is not clear, local debugging and testing can be carried out. Moreover, when adjustments are made later, it can effectively avoid synchronously changing other modules, thereby improving the flexibility and response speed of the program, enhancing the generality and adjustability of the model, quickly expanding and optimizing the program function, improving the sub-channel analysis efficiency, breaking through the traditional dilemma, and meeting the needs of technological development.

[0063] Step 1: As shown in Figure 1 Figure 1 , the invention implemented in this application adopts a top-down design method. First, the thermal-hydraulic analysis and calculation of the sub-channel are divided into three parts: input, calculation, and output.

[0064] Furthermore, the input part includes four parts: reading the operating condition settings, preliminary processing of the input card, output parameter settings, and allocating the memory for time-step data; the calculation part includes seven parts: calculation equation model, fluid model, heat conduction model, turbulent flow model, heat transfer coefficient model, physical property model, and special-shaped structure model; the output part includes two parts: calculation mean value and overall output.

[0065] Step 2: Given that the sub-channel analysis has extremely high requirements for the rigor of scientific computing, in terms of program writing, the Fortran language can be considered to build the entire program. The Fortran language has the characteristic of supporting modular program design, which highly coincides with the modular sub-channel analysis method of the nuclear reactor proposed in this invention.

[0066] Furthermore, the currently more common compilers for compiling the Fortran language are CVF (Compaq Visual Fortran), IVF (Intel Visual Fortran), GNU Fortran (Gfortran), PGI Fortran, and NAG Fortran. To adapt to the version issues of the Fortran language, the modular sub-channel analysis method of the nuclear reactor using the IVF compiler is introduced next. The advantages and disadvantages of each compiler are as follows in the table:

[0067] Table 1 Advantages and Disadvantages of Compilers and Their Configuration Environments

[0068]

[0069] Step 3: According to the compilation language and compiler determined in Step 2, the program structure described in Step 1 can be created. Among them, the main program starts with the program keyword, and each sub-module starts with the module keyword.

[0070] Specifically, in Fortran, a module is a structure that organizes related data, variables, functions, and subroutines together. It allows the program to be divided into logically independent parts, improving the readability, maintainability, and reusability of the code. The following is a simple Fortran code example:

[0071] Example of Module and Main Program:

[0072] module my_module

[0073] implicit none

[0074] ! Define subroutines within the module

[0075] subroutine my_subroutine()

[0076] my_variable = my_variable + 1

[0077] write(*,*) my_variable

[0078] end subroutine my_subroutine

[0079] end module my_module

[0080] program main

[0081] use my_module

[0082] implicit none

[0083] ! Call the subroutine within the module

[0084] call my_subroutine()

[0085] end program main

[0086] In the program: module my_module defines a module named my_module; implicit none forces explicit declaration of variables to avoid errors caused by implicit type conversion; integer::my_variable declares an integer variable my_variable within the module; contains indicates that the following part will contain subroutines or functions within the module; subroutine my_subroutine() defines a subroutine named my_subroutine, whose function is to increment the value of my_variable by 1 and output it; program main defines the main program; use my_module uses the my_module module; call my_subroutine() calls the my_subroutine subroutine within the my_module module.

[0087] Step 4: After completing the implementation of the overall architecture of the nuclear reactor sub-channel analysis program in Step 3, the next step is to consider the coupling method between each module. In the Fortran language, there is a method of common coupling, which can be achieved by using the common keyword.

[0088] Specifically, the common keyword is used to declare common variables, and multiple program units (such as the main program, subroutines, functions, etc.) can share these common variables. To optimize memory, we can adopt a clever technique: first declare a common array variable large enough, and then store each subsequent declared variable in this common array. The advantage of doing this is that the size of the common array can be flexibly changed according to the number of variables required by the sub-channel model, thereby achieving the optimization of the running memory. The following is a simple Fortran code example:

[0089] Code example of the keyword common:

[0090] program common_example

[0091] implicit none

[0092] integer::i,j

[0093] real::a,b

[0094] real,dimension(100)::common_array

[0095] common / my_common_block / common_array

[0096] i = 1

[0097] a = 3.14

[0098] common_array(i) = a

[0099] i = 2

[0100] b = 2.718

[0101] common_array(i) = b

[0102] write(*,*)common_array(1),common_array(2)

[0103] end program common_example

[0104] In the program: real::a,b declares two real variables a and b; real,dimension(100)::common_array declares a real array common_array with 100 elements, which will be used as a common array; common / my_common_block / common_array uses the common keyword to declare common_array as a common variable and places it in the common block named my_common_block; i = 1; a = 3.14; common_array(i) = a stores the value of variable a in the first position of the common array common_array; i = 2; b = 2.718; common_array(i) = b stores the value of variable b in the second position of the common array common_array; write(*,*)common_array(1),common_array(2) outputs the values of a and b stored in the common array.

[0105] Furthermore, in the actual programming process, it is inevitable to encounter matrix solutions. In this case, it is necessary to propose a storage method for pointers. By using pointers for data transfer, data can be passed between different modules, avoiding data replication and improving performance. Pointers can be used to access and modify data stored in common variables, managing memory in a more flexible way. For complex data structures such as dynamic data or linked lists, pointers can be used to construct and operate on them, improving the scalability of the program. The following is an example of using pointers in a module:

[0106] Example of pointers in a module:

[0107] module pointer_module

[0108] implicit none

[0109] integer,pointer::my_module_pointer

[0110] subroutine init_pointer()

[0111] integer,target::local_variable = 5

[0112] my_module_pointer => local_variable

[0113] end subroutine init_pointer

[0114] subroutine use_pointer()

[0115] ! Check if the pointer is associated

[0116] if(associated(my_module_pointer))then

[0117] write(*,*)my_module_pointer

[0118] else

[0119] write(*,*)"Pointer is not associated"

[0120] end if

[0121] end subroutine use_pointer

[0122] end module pointer_module

[0123] program main

[0124] use pointer_module

[0125] implicit none

[0126] call init_pointer()

[0127] call use_pointer()

[0128] end program main

[0129] In the program: integer, pointer::my_module_pointer declares a pointer in the module; subroutine init_pointer() is a subroutine for initializing the pointer; integer, target::local_variable = 5 declares a local variable; my_module_pointer => local_variable associates the module pointer with the local variable; subroutine use_pointer() is a subroutine for using the pointer; if(associated(my_module_pointer))then checks if the pointer is associated, and if it is, outputs its value, otherwise outputs a prompt message.

[0130] Step 5: It should be noted that in the overall framework diagram of the nuclear reactor modular sub-channel analysis method, it is mainly divided into three parts: the main module, the core module, and the underlying module according to the importance of the modules. As Figure 2 shown, according to the modular and hierarchical design concept, and based on the functions to be realized and the coupling degree between modules, it is divided into 4 levels from top to bottom (Level 1: Program; Level 2: Functional Module; Level 3: Core Module; Level 4: Component). The sub-channel analysis program is divided into three Level 2 modules: the input module, the calculation module, and the output module. The equation coupling logic calculation function that was originally scattered in each functional module is decomposed and a unified equation coupling module is formed, which is specifically responsible for the coupling operation of the four conservation equations of the entire sub-channel analysis program. It is worth mentioning that the lower the level of the module, the higher its replaceability. For example, the physical property module and the equation solving module are located in the Level 4 module, and the coupling relationship with other modules is mainly composed of non-direct coupling, and can be replaced arbitrarily according to the actual situation of the sub-channel analysis model. However, for the relatively important Level 2 and Level 3 modules, it is not easy to achieve arbitrary replacement of the modules. The reason is that the coupling methods between the modules at this level are mainly composed of data coupling, marker coupling, control coupling, external coupling, and common coupling, resulting in too high coupling degree between the modules and unable to achieve the ideal effect of complete replacement.

[0131] Furthermore, due to the low coupling degree of the Level 4 modules, even in the case where the design of other modules is not clear, local debugging and testing work can still be carried out. Moreover, when making adjustments in the later stage, this module can effectively avoid the need to change other modules simultaneously, thereby improving the generality and debuggability of the constructed model, and at the same time improving the efficiency of nuclear reactor sub-channel analysis.

[0132] Specifically, in software development, the coupling degree refers to the degree of mutual dependence between modules. The low coupling degree of the Level 4 modules means that they are independent of each other and have less dependence on other modules. Therefore, when the design and implementation of other modules have not been completed, since the Level 4 modules have a low dependence on the data, control signals, or markers of other modules, they can be tested and debugged in a relatively independent environment without being overly affected by the progress of other modules. From the perspective of development and maintenance, this not only facilitates the development of the underlying modules, but also improves the maintainability and scalability of the entire program. When it is necessary to update and optimize the entire nuclear reactor sub-channel analysis system, the underlying modules can be adjusted independently according to different requirements without the need to make a large number of modifications to the code of other modules, reducing the development cost and risk.

[0133] Step 6: Before completing the writing of the entire subchannel analysis program, corresponding data interfaces need to be added at the positions where each module interacts with each other. At the same time, the writing process of the underlying modules should be standardized with documents to ensure that they follow certain standards and specifications, and finally form a complete modular program.

[0134] Specifically, in software development, information exchange and collaboration are required between modules, and the data interface is the bridge for communication between modules. For the modular subchannel analysis program of a nuclear reactor, the design of the data interface is crucial because different modules are responsible for different functions, and the data interaction between them needs to achieve accurate and reliable links through the interface to ensure the integrity and consistency of the data. The following is an example of a Fortran data interface:

[0135] Data interface example:

[0136] module pointer_module

[0137] module subchannel_module

[0138] implicit none

[0139] ! Define an interface that can be used for different function implementations

[0140] interface c_physical_property

[0141] module procedure c_density,c_viscosity

[0142] end interface

[0143] contains

[0144] end module subchannel_module

[0145] In the program: The interface c_physical_property defines an interface named c_physical_property. This interface can contain multiple specific function implementations, including the functions c_density and c_viscosity here; the module procedure c_density, c_viscosity associates the c_density and c_viscosity functions with the c_physical_property interface, so that different functions can be called by invoking the c_physical_property interface according to different situations. When new physical property calculations need to be added, only new functions need to be added to the module and associated with the interface, without modifying other parts that call these functions. For the documentation specification, the following is an example of the documentation content:

[0146] Example of documentation specification:

[0147] Module name: subchannel_module

[0148] Function description: Provide calculations for density and viscosity.

[0149] Function c_physical_property interface:

[0150] Description: This interface can be used to calculate different physical properties depending on the specific function used during the call.

[0151] Input: temperature (real number): Represents the temperature parameter during the calculation of physical properties, with the unit of K.

[0152] Return value: Density (c_density) or viscosity (c_viscosity), with the units of kg / m 3 and Pa·s respectively.

[0153] Function c_density:

[0154] Description: Calculate the density of the coolant based on the input temperature.

[0155] Input: temperature (real number): The temperature during the density calculation, with the unit of K.

[0156] Return value: density (real number): The calculated density, with the unit of kg / m 3 .

[0157] An embodiment of the present invention provides an analysis method for simulating the thermal-hydraulic behavior of subchannels in a nuclear reactor. The following is combined with Figure 3The implementation steps of the analysis method for simulating the thermal-hydraulic behavior of sub-channels in a nuclear reactor proposed by the present invention are described in detail.

[0158] First step: Establish a mathematical model based on the core structure parameters and fuel rod bundle structure parameters of the nuclear reactor to obtain the geometric conditions such as the cross-sectional area of the sub-channel, the gap width, and the distance between sub-channels, as well as the boundary conditions such as the coolant mass flow rate, temperature, and pressure of each sub-channel. These conditions will serve as the basic data for the subsequent analysis. The geometric parameters and operating conditions are read by the input module in the main module, and the core module in the input module is responsible for allocating data memory for the analysis program and performing preliminary processing of the model parameters.

[0159] Second step: After the preprocessing of the geometric parameters and model parameters in the first step is completed, start to allocate space for each module. According to the selection of the model parameters in the input data, allocate a module combination that meets the current operating conditions to the heat conduction module, fluid module, heat transfer coefficient module, physical property module, and special-shaped structure module in the calculation module, and further optimize the operating memory of the program on this basis.

[0160] Third step: Based on the analysis and preprocessing of the first two steps, give the predicted sub-channel temperature field, and solve the sub-channel temperature field through data coupling and control coupling of the selected heat conduction module and heat transfer coefficient module. During this process, the temperature field is iteratively solved according to the input internal iteration relaxation factor.

[0161] Fourth step: Judge whether the solution of the temperature field is completed, and judge through the temperature residual and enthalpy residual. If the convergence judgment criterion is reached, end the temperature field calculation and proceed to the next step; if the convergence judgment criterion is not reached, return to the third step to repeat the iteration until convergence is determined or the maximum number of iterations is reached.

[0162] Fifth step: According to the converged temperature field obtained by solving in the third step, use the energy conservation equation to solve the enthalpy distribution. The expression of the energy conservation equation is:

[0163]

[0164] In the formula: i and j respectively represent the sub-channel number and the radial node number; A i is the axial flow area of the sub-channel (i, j), with the unit of m 2 ; Δt is the time step, with the unit of s; ρ is the coolant density; h is the coolant enthalpy, with the unit of J / kg; h n is the coolant enthalpy of the previous time step, with the unit of J / kg; ΔX is the axial height of the sub-channel (i, j), with the unit of m; m is the axial mass flow rate of the coolant, with the unit of kg / s; e takes 1 or -1 in the cross-flow direction; w is the cross-flow velocity of the coolant, with the unit of kg / m 2 / s;h * = is the enthalpy value of the previous subchannel or the next subchannel according to the direction of the coolant mass flow rate, in J / kg; P is the heating circumference, in m; φ is the correction factor; q is the heat flux density of the fuel rod entering the coolant, in W / m 2 ; C is the transverse thermal conductivity, unit is W / m 2 / K; s is the gap length, in m; T is the temperature, in K; r Q is the power generated by the fuel rods directly entering the coolant, in W / m; q ’ is the fuel rod power, in W / m.

[0165] In formula (1), the first term represents the energy stored in the sub-channel, the second term represents the enthalpy of axial coolant inflow and outflow, the third term represents the enthalpy of lateral inflow and outflow, the fourth term represents the heating of channel i by the fuel rod, and the fifth, sixth and seventh terms represent the fission power appearing in channel i.

[0166] Step 6: According to the temperature field in step 3 and the enthalpy distribution obtained in step 5, the mass conservation equation is substituted into the axial momentum conservation equation, and the pressure distribution is solved by using the new conservation equation and the lateral momentum conservation equation. In this process, the pressure field is iteratively solved according to the input external iterative relaxation factor. The expression after the mass conservation equation is substituted into the axial momentum conservation equation is:

[0167]

[0168] Where: i and j represent the subchannel number and radial node number respectively; P is the pressure (Pa); ΔX is the axial height of the subchannel (i, j), in meters; m is the axial mass flow rate of the coolant, in kg / s; ρ is the coolant density; θ is the inclination angle of the channel relative to the vertical direction (°); m n A is the coolant axial mass flow rate in the previous time step, in kg / s; i is the axial flow area of ​​sub-channel (i, j), unit: m 2 ; Δt is the time step, unit: s; e is the cross-flow direction, which is 1 or -1; w is the cross-flow velocity of the cooling agent, unit: kg / m2 / s; U is the momentum, unit: kg·m / s; f T is the lateral momentum factor. ij The expression is:

[0169]

[0170] Where: f is the friction factor; D his the hydraulic diameter, with the unit of m; K is the positioning grid spacer correction factor. In the first term of Equation (2), it is the acting force on the sub-channel; the second term is the pressure drop caused by wall friction and form drag; the third term is the vertical component of the fluid gravity; the fourth term is the momentum storage in the sub-channel; the fifth term is the sum of the lateral momentum inflow and outflow and the lateral momentum exchange caused by turbulent mixing between the connected channels; the sixth term is the sum of the axial momentum inflow and outflow and the pressure drop caused by wall friction.

[0171] Step 7: Determine whether the pressure solution converges, which is judged by the pressure residual, axial flow residual, temperature residual, thermal power residual, and enthalpy residual. If the convergence judgment criterion is met, end the calculation of the current time step of the sub-channel and proceed to the next step; if the convergence judgment criterion is not met, return to Step 3 to repeat the iteration until convergence is determined or the maximum number of iterations is reached.

[0172] Furthermore, the property model can be arbitrarily replaced in the form of a module according to the requirements of the analysis model. The property model mainly includes the water model, liquid sodium / liquid sodium-potassium alloy model, liquid lead-bismuth alloy model, liquid lithium model, and supercritical carbon dioxide model; the special-shaped structure model can also be arbitrarily replaced in the form of a module according to the specific details of the analysis model. The special-shaped structure model mainly includes the petal-shaped fuel rod model, rib-wound fuel rod model, wire-wound fuel rod model, and core-subchannel coupling model, etc.

[0173] With the significant advantages of modular programming, the present invention can achieve high-precision simulation of the thermal-hydraulic behavior of nuclear reactor sub-channels at a low cost. Each functional module can independently carry out development, testing, and maintenance work. It effectively overcomes the defects of traditional programs limited by the overall framework and design methods. When facing the design requirements such as new fuel rod models, different coolants, and core structures, traditional programs are difficult to quickly, accurately, and comprehensively improve program functions. When the present invention faces new design requirements, only specific modules need to be adjusted, greatly improving the flexibility and response speed of the program. When dealing with new models and new structures, it can also quickly realize the expansion and optimization of program functions by flexibly calling and adjusting the corresponding modules, successfully breaking through the dilemma of traditional sub-channel analysis programs and meeting the continuously developing technical requirements in the field of nuclear reactors.

[0174] Those skilled in the art can understand that the above description is only the preferred embodiment of the present invention. The features described in each embodiment and / or claim of the present disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. It is not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0175] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention. Obviously, those skilled in the art can make various changes and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A modular sub-channel analysis method for a nuclear reactor, characterized in that: The method comprises the following steps: S1. Use the top-down design method to establish the sub-channel thermal hydraulic analysis and calculation model; S2. According to the sub-channel thermal-hydraulic calculation model described in S1, the sub-channel thermal-hydraulic calculation model is decomposed and reorganized using a modular programming method to confirm the connection between the modules and the calculation sequence; S3, using the sub-channel analysis method to solve the sub-channel mass, energy, momentum conservation equations and heat conduction equations and discretize them, and input them into the corresponding equation model module; S4, determining the model parameters of different modules according to the geometric parameters of the object to be analyzed and the sub-channel thermal hydraulic analysis calculation model, wherein the model parameters include equation model parameters, fluid model parameters, heat conduction model parameters, physical property model parameters, special-shaped structure model parameters and output model parameters; S5, according to the different modules divided by the model parameters determined in S4, linking and coupling the various model parameters to construct an overall modular analysis model; S6, obtaining the overall modular analysis model in S5, iteratively solving the temperature field of the overall modular analysis model according to the heat conduction model set in S4, determining whether the coolant temperature and the fuel rod temperature meet the convergence standard, and if so, proceeding to the next step of calculation, and if not, repeating S6 iteration until convergence is determined or the maximum number of iterations is reached; S7, obtaining the temperature field of the overall modular analysis model in S6, solving the energy conservation equation, and obtaining the enthalpy value distribution of the overall modular analysis model; S8, obtaining the enthalpy distribution in S7, solving the physical properties of the overall modular analysis model according to the physical property model parameters selected in S4, and solving the momentum conservation equation using the obtained physical property model parameters and the enthalpy distribution to obtain the overall pressure distribution; S9, obtaining the enthalpy distribution of the overall modular analysis model in S7 and the overall pressure distribution in S8, and determining whether the coolant enthalpy, coolant pressure distribution, and coolant flow distribution all meet the convergence criteria. If so, the sub-channel analysis model calculation is completed. If not, return to S6 and repeat the iteration until convergence is determined or the maximum number of iterations is reached.

2. The modular sub-channel analysis method for a nuclear reactor according to claim 1, characterized in that: Before using the top-down design method in S1, the sub-channel thermal-hydraulic analysis calculation model also includes an input unit, a calculation unit, and an output unit. The input unit includes reading the operating condition settings, preliminary processing of the input card, output parameter settings, and allocating time-step data memory; the calculation unit includes a calculation equation model, a fluid model, a heat conduction model, a turbulent flow model, a heat transfer coefficient model, a physical property model, and a special-shaped structure model; the output unit includes the steps of calculating the mean and the overall output.

3. The modular sub-channel analysis method for a nuclear reactor according to claim 1, characterized in that: The method of using subchannel analysis method in S3 to solve the subchannel mass, energy and momentum conservation equations is: The mass conservation equation is obtained by solving the heat conduction equation and the energy conservation equation separately, and then the mass conservation equation is substituted into the axial momentum conservation equation and then solved simultaneously with the transverse momentum conservation equation.

4. The method for analyzing modular sub-channels of a nuclear reactor according to claim 1, characterized in that: The sub-channel thermal hydraulic analysis and calculation model includes a heat transfer model, an equation model, a physical property model, and a special-shaped structure model.

5. The modular sub-channel analysis method for a nuclear reactor according to claim 4, characterized in that: The physical property models include a water model, a liquid sodium or liquid sodium-potassium alloy model, a liquid lead-bismuth alloy model, a liquid lithium model, and a supercritical carbon dioxide model.

6. The method for analyzing modular sub-channels of a nuclear reactor according to claim 4, characterized in that: The heterogeneous structure models include a petal-shaped fuel rod model, a rib-wound fuel rod model, a wire-wound fuel rod model and a core-subchannel coupling model.

7. The modular sub-channel analysis method for a nuclear reactor according to claim 4, characterized in that: The modular programming method described in S2 is implemented in Fortran.

8. The method for analyzing modular sub-channels of a nuclear reactor according to claim 4, characterized in that: The method for solving the energy conservation equation in S7 is: Where: i and j represent the subchannel number and radial node number respectively; A i is the axial flow area of ​​sub-channel (i, j), in m 2 ; Δt is the time step, in seconds; ρ is the coolant density; h is the coolant enthalpy, in J / kg; h n is the coolant enthalpy value of the previous time step, in J / kg; ΔX is the axial height of the subchannel (i, j), in m; m is the coolant axial mass flow rate, in kg / s; e is 1 or -1 in the cross-flow direction; w is the coolant cross-flow velocity, in kg / m 2 / s;h * The enthalpy value of the previous subchannel or the next subchannel is taken according to the direction of the coolant mass flow rate, in J / kg; P is the heating circumference, in m; φ is the correction factor; q is the heat flux density of the fuel rod entering the coolant, in W / m 2 ; C is the transverse thermal conductivity, unit is W / m 2 / K; s is the gap length, in m; T is the temperature, in K; r Q is the power generated by the fuel rods directly entering the coolant, in W / m; q ’ is the fuel rod power, in W / m.

9. A computer device comprising a memory and a processor, characterized in that: A computer program is stored in the memory. When the processor runs the computer program stored in the memory, the processor executes the method according to any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

Images