Simulation method for dynamic reactor core power distribution measurement and related product

Abstract

The invention relates to the field of theoretical calculation simulation of a nuclear reactor core state, in particular to a simulation method for dynamic reactor core power distribution measurement and a related product, and the method comprises the following steps: obtaining accurate burnup data; establishing a steady-state reactor core theoretical model based on accurate burnup; solving a three-dimensional neutron kinetic equation by taking the steady-state reactor core theoretical model as an initial state and taking a relation curve of reactor core operation power and operation time as input to obtain a dynamic reactor core theoretical model taking time as a function; inputting the power and time relation corresponding to the power and time relation corresponding to the power plant test plan into the dynamic reactor core theoretical model to obtain a database; according to the method, the steady-state theoretical model is constructed by utilizing accurate burnup data, dynamic reactor core simulation is carried out through a transient reactor core neutronics calculation model and the like, a dynamic reactor core model completely consistent with an actual test state can be generated, and actually measured data of dynamic reactor core power distribution can be directly processed and accepted.

Description

Technical Field

[0001] The invention relates to the field of theoretical calculation simulation of nuclear reactor core states, and in particular to a simulation method for dynamic core power distribution measurement and related products. Background Art

[0002] In the design and operation of nuclear power plants, physical startup tests are key steps to comply with nuclear safety regulations, guidelines and industry standards, especially during commissioning and refueling startup. Among these tests, the power-up test is particularly important, which verifies whether the theoretical design and safety performance of the reactor meet the acceptance criteria by testing at different power levels. One of the core components is the power distribution measurement test, which is carried out on different power platforms (from 0% to full power). The power distribution of the core is measured by the in-core detector, and the measured results are compared with the theoretical design values ​​to ensure that the core power distribution meets the design criteria.

[0003] However, the power distribution measurement of the reactor faces challenges caused by the dynamic changes of xenon and other fission products. Xenon is a nuclide with a large thermal neutron absorption cross section, and its concentration changes have a significant impact on the neutron flux and power distribution of the reactor. After the power change, the production and disappearance of xenon depends not only on the fission process, but also on its physical decay characteristics, which usually takes several hours to reach equilibrium. This dynamic change requires a long wait before the core reaches a stable state, which directly affects the economic benefits and load factors of the nuclear power plant. Current measurement methods usually require that it be carried out after a steady state is reached, but this limits the flexibility and efficiency of nuclear power plants in actual operation.

[0004] Therefore, developing a method that can accurately simulate and predict the dynamic core power distribution in real time is of great significance for optimizing the startup test process of nuclear power plants and improving their operating economy. Summary of the invention

[0005] The present invention provides a simulation method and related products for dynamic core power distribution measurement for power platform test in physical startup test of nuclear power plants in my country, which can obtain a theoretical database consistent with the dynamic core state, directly perform data expansion processing on the real results obtained from the dynamic core measurement test, and accept the test results. The test conducted by the present invention can enable the nuclear power plant to complete the power distribution test without waiting for the core to reach the stable state of xenon equilibrium, and without any correction of the measured data, and obtain the same test effect as the current steady-state power distribution measurement test.

[0006] The present invention is achieved through the following technical solutions:

[0007] A simulation method for dynamic core power distribution measurement, comprising:

[0008] Carry out fuel consumption estimation calculation at the test state point according to the power plant operation plan to obtain accurate fuel consumption data;

[0009] Using accurate burnup data as input, the steady-state neutron transport equation is solved and a steady-state core theoretical model based on accurate burnup is established;

[0010] Taking the steady-state core theoretical model as the initial state and the relationship curve between the core operating power and the operating time as the input, the three-dimensional neutron kinetic equation is solved to obtain the dynamic core theoretical model with time as a function;

[0011] The power and time relationship corresponding to the power plant test plan is input into the dynamic core theory model to obtain the dynamic core theory value and dynamic core theory database consistent with the test state.

[0012] Specifically, the calculation formula for accurate fuel consumption data is: u =∫0 T P(t)dt / Wu, where Bu is the accurate burnup data that can be used to establish the core theoretical model, P(t) is the core power at time t, Wu is the mass of fissile nuclear material, and T is the total time of the current power-up phase.

[0013] Specifically, the core neutronics parameters that vary with time include: iodine yield and xenon yield, which are calculated using a transient core neutronics calculation model. The core neutron calculation model is:

[0014]

[0015] Where I(t) is the iodine concentration at time t, and X(t) is the xenon concentration at time t;

[0016] γ I is the fission yield of iodine, γ X is the fission yield of xenon;

[0017] ∑ f is the core macroscopic fission cross section;

[0018] λ I is the decay constant of iodine, λ X is the decay constant of xenon;

[0019] σ X is the microscopic absorption cross section of xenon;

[0020] Φ(t) is the core neutron flux at instant t;

[0021] Φ nom is the rated average core neutron injection rate;

[0022] Pr(t) is the core power level at instant t.

[0023] Optionally, the initial core theoretical model is obtained by solving the steady-state neutron transport equation using the actual core material, geometry, fuel consumption, power, etc. as input. The steady-state neutron transport equation and its solution method are general techniques. The typical simplified expression of the neutron transport equation at point r in space is: where D is the spatially dependent diffusion coefficient, is the Laplace operator related to the coordinate system, φ(r) is the neutron flux at point r in space, and S(r) is the neutron source intensity at point r in space.

[0024] Specifically, the steady-state core model is used as the initial state, the relationship curve between the core operating power and the operating time is used as input, and the three-dimensional neutron kinetic equation is solved to obtain the dynamic core theoretical model;

[0025] Optionally, the method for performing core dynamic simulation includes:

[0026] According to the power increase strategy of the power plant, the curve corresponding to the power and operation time in the power increase stage before the test is obtained;

[0027] Taking the actual power and the corresponding operating time as input, a dynamic core theoretical model is used to obtain a database of core flux values ​​and their distribution in the core geometry varying with time.

[0028] Furthermore, a database reading program is used to read the database corresponding to the test power and test time, and the parameters required for the test are output according to the format required for on-site data processing.

[0029] A simulation terminal for dynamic core power distribution measurement includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method described above is implemented.

[0030] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method described above is implemented.

[0031] A computer program product comprises a computer program / instruction, which implements the method described above when executed by a processor.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] The present invention uses accurate burnup data to construct a steady-state theoretical model, and performs dynamic core simulation through transient core neutronics calculation models, etc., to generate a dynamic core model that is completely consistent with the actual test state, and directly processes and accepts the measured data of dynamic core power distribution, and can directly perform data expansion processing on the real results obtained from the dynamic core measurement test, and accept the test results. The test conducted by the present invention allows the nuclear power plant to complete the power distribution test without waiting for the core to reach a stable state of xenon equilibrium, and without any correction of the measured data, and obtain the same test effect as the current steady-state power distribution measurement test. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, are used to explain the principles of the present invention. These drawings are included to provide a further understanding of the present invention, and the accompanying drawings are included in and constitute a part of this specification and do not constitute a limitation of the embodiments of the present invention.

[0035] Figure 1 It is a flow chart of a simulation method for dynamic core power distribution measurement according to the present invention. DETAILED DESCRIPTION

[0036] To make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and implementation methods. It is understood that the specific implementation methods described herein are only used to explain the relevant content, rather than to limit the present invention.

[0037] It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the drawings.

[0038] In the absence of conflict, the embodiments and features of the embodiments of the present invention may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] The power distribution measurement test is carried out by using the in-core detector when the reactor is at 0% FP, 10% FP, 30% FP, 50% FP, 75% FP and 100% FP (full power) platforms, and the actual measurement results are compared with the theoretical design values ​​to prove that the core power distribution meets the design criteria and verify that the core hot spot factor FQ, nuclear enthalpy rise factor F△H and component power are within safety limits.

[0040] After the core power changes, due to changes in the core neutron flux, temperature, etc., some fission products with large thermal neutron absorption cross sections, such as xenon (135Xe), will continue to change for a period of time thereafter, causing the core state parameters to be in dynamic change. Xenon can be produced directly by fission and by the decay of the parent nucleus (mainly 135I), where the half-life of the parent nucleus 135I is about 6.7 hours. Xenon disappears through two pathways: neutron capture and decay. Its neutron capture cross section is large, and its decay half-life is about 9.2 hours.

[0041] After the core power level changes, the neutron flux changes accordingly. The xenon produced by fission and lost by capture changes instantaneously with the flux change, but the xenon produced by decay will take several hours to reach equilibrium. At the same time, the xenon lost by decay will take some time after the production reaches a stable level before the production and disappearance of xenon in the core can reach the final equilibrium state. Therefore, after the core reaches the target power platform from the previous power platform, the core power distribution will undergo certain dynamic changes with the dynamic changes of xenon. According to the physical properties of xenon nuclides, the xenon production in the core generally reaches equilibrium after 48 hours. As the concentration and distribution of xenon in the core reach equilibrium, the core state parameters also reach a stable state.

[0042] The core power distribution measurement test compares the power distribution under the test state with the theoretical calculated value to determine whether the core state meets the operation requirements. Due to the lack of accurate calculation methods for dynamic core power distribution, the current core power distribution measurement test generally requires the core to be tested in a steady state (i.e., after reaching the test state and waiting for 48 hours) or near a steady state (generally after reaching the test state and waiting for 24 hours).

[0043] Since the economic benefits of a nuclear power plant are closely related to the full-power operation time, the time the reactor stays at low power directly affects the load factor of the nuclear power plant. Therefore, in order to solve the above-mentioned problem, the method of the present invention is adopted, which can significantly shorten the overall time of the power increase test. In theory, the power distribution test can be carried out at any time from 0h to 24h after reaching the power increase platform.

[0044] Taking Qinshan Second Nuclear Power Plant as an example, according to relevant design requirements, the power platform for power distribution measurement test during the power increase test in the core physical startup test of refueling includes two low-power platforms, 50% FP and 75% FP. The method of the present invention is used on these two power platforms, which can effectively shorten the low-power operation time of the power plant by up to 48 hours. The method proposed by the present invention is theoretically complete, does not require the power plant to carry out hardware modification or add additional operations, and has obvious optimization effect on the overall startup physical test process, which can significantly improve the reactor core load factor and increase the economic efficiency of power plant operation.

[0045] Embodiment 1

[0046] like Figure 1 As shown, a simulation method for dynamic core power distribution measurement is provided, comprising:

[0047] According to the power plant operation plan, the fuel consumption of the test state point is estimated and calculated to obtain accurate fuel consumption data; this calculation requires the actual startup and power increase plan of the power plant to be determined in advance. The fuel consumption is calculated according to the following formula: Bu = ∫0 T P(t)dt / Wu, where Bu is the accurate burnup data that can be used to establish the core theoretical model, P(t) is the core power at time t, Wu is the mass of fissile nuclear material, and T is the total time of the current power-up phase. Due to the different cycle operation characteristics of each nuclear power plant and the differences in other debugging processes during the power-up process, the accurate burnup is slightly different. The calculation needs to be adjusted according to the actual situation.

[0048] The precise fuel consumption data is input into the initial core theoretical model to establish a steady-state theoretical model; the calculation procedure and calculation method for establishing the steady-state core theoretical model are consistent with the current common methods, and can be understood and implemented by those skilled in the art. The initial core theoretical model is obtained by solving the steady-state neutron transport equation using the actual initial conditions of the core, such as material, geometry, fuel consumption, power, etc. as input. The steady-state neutron transport equation and its solution method are general technologies. The typical simplified expression of the neutron transport equation at point r in space is: where D is the spatially dependent diffusion coefficient, is the Laplace operator related to the coordinate system, φ(r) is the neutron flux at point r in space, and S(r) is the neutron source intensity at point r in space.

[0049] A dynamic core calculation model is constructed, and according to the power increase strategy of the power plant, the core neutronic parameters that change with time are obtained; the main reason for the dynamic change of the reactor neutronic parameters is the change of xenon concentration and distribution in the core after the reactor power changes. Xenon concentration and xenon distribution are related to power changes and operating time of the power plant. Therefore, it is necessary to construct a transient core neutronic calculation model according to the actual operating conditions. The transient core neutronic calculation program used in the present invention is the Trans_xenon program in the SCIENCE program package. The calculation program obtains the yields of xenon and iodine nuclides related to time and core power level based on the following calculation formula:

[0050]

[0051] Where I(t) is the iodine concentration at time t, and X(t) is the xenon concentration at time t;

[0052] γ I is the fission yield of iodine, γ X is the fission yield of xenon;

[0053] ∑ f is the core macroscopic fission cross section;

[0054] λ I is the decay constant of iodine, λ X is the decay constant of xenon;

[0055] σ X is the microscopic absorption cross section of xenon;

[0056] Φ(t) is the core neutron flux at instant t;

[0057] Φ nom is the rated average core neutron injection rate;

[0058] Pr(t) is the core power level at instant t.

[0059] The dynamic core neutronics calculation program solves the core based on general theories and methods. Since the time-varying xenon and iodine yields are used in the solution process, the solution results that vary with time can be output.

[0060] Based on the steady-state theoretical model and the transient core neutronics calculation model, the initial theoretical model of the experimental power platform is obtained according to the power plant operation calculation; on the basis of the steady-state theoretical model based on accurate burnup calculation, the transient core neutronics parameter calculation program is used to input the power and operation time relationship information determined by the power plant operation plan, so as to obtain the initial theoretical model of the experimental power platform.

[0061] The core neutronics parameters are input into the initial theoretical model, and a dynamic core simulation is performed to obtain a dynamic core theoretical model. By using the transient core neutronics parameter calculation program and inputting information such as the control rod position and test implementation time given by the power plant's test plan, a dynamic core theoretical model consistent with the test state can be obtained.

[0062] Method for obtaining the dynamic core theoretical model: Taking the initial core theoretical model as the initial boundary condition for calculation, solving the three-dimensional core neutron kinetic equation, and obtaining the corresponding relationship between the core neutron flux value and the reactor power and operating time.

[0063] The method for performing core dynamic simulation includes: obtaining a curve corresponding to power and operating time in a power increase stage before a test according to a power increase strategy of a power plant, taking the curve corresponding to actual power and operating time as input, and using a dynamic core theoretical model to obtain a core flux value and its distribution in core geometry and the corresponding relationship with time; that is, the method for performing core dynamic simulation includes: obtaining a curve corresponding to power and operating time according to an actual power increase strategy of a power plant, taking the curve corresponding to actual power and operating time as input, and using a dynamic core theoretical model to obtain a database of core flux values ​​and their distribution in core geometry that change with time.

[0064] The time and power corresponding to the power plant test plan are input into the dynamic core theoretical model to obtain the dynamic core design theoretical value and the dynamic core theoretical database.

[0065] The database reading program is used to read the database corresponding to the test power and test time, and the test parameters required are output according to the format required for on-site data processing. Specific parameters include: three-dimensional power distribution of the core, power peak factor, etc.

[0066] Embodiment 2

[0067] A specific embodiment is provided.

[0068] According to relevant design requirements, the medium and low power platforms in the power increase test process during the physical startup test of the refueling core include two power platforms: 50% FP and 75% FP.

[0069] Taking the 50% FP power platform as an example, the production and distribution of dynamic core xenon are affected by multiple factors such as core burnup history, power increase history and power platform stabilization time. Among them, the burnup history and power increase history mainly affect the production of xenon, while the power platform stabilization time mainly affects the distribution of xenon. Therefore, the numerical simulation of the dynamic core needs to take various factors into consideration comprehensively, and through reasonable assumptions and simplifications of the complex operation history, the simulation and calculation of key parameters that meet the core power distribution measurement accuracy requirements can be achieved under the conditions of existing calculation tools. The specific implementation method is as follows:

[0070] 1) According to the test and operation plan of the power plant, based on the actual operation time, operation power and fuel loading of the power plant, the core burnup during the test is estimated. The estimated burnup is used as input to establish a steady-state theoretical model based on accurate burnup calculation using a general steady-state core calculation program;

[0071] 2) Use the transient core neutronics calculation program to simulate the actual power increase process of the power plant and obtain the xenon, iodine and other nuclides that vary with time and power. Based on the steady-state core theoretical model established in step 1), the influence of the xenon and iodine yields that vary with time and power obtained by the above calculation on the core flux distribution and power distribution is superimposed to achieve dynamic core simulation;

[0072] 3) According to the test plan of the power plant and based on the dynamic core theoretical model in step 2), the theoretical database and key test parameters required for the test are obtained under the core state corresponding to the test.

[0073] Embodiment 3

[0074] A simulation terminal for dynamic core power distribution measurement includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the method described above is implemented.

[0075] The memory can be used to store software programs and modules. The processor executes various functional applications and data processing of the terminal by running the software programs and modules stored in the memory. The memory can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, an execution program required for at least one function, etc.

[0076] The data storage area can store data created according to the use of the terminal, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0077] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method described above is implemented.

[0078] Without loss of generality, computer readable media may include computer storage media and communication media. Computer storage media include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer readable instruction data structures, program modules or other data. Computer storage media include RAM, ROM, EPROM, EEPROM, flash memory or other solid-state storage technology, CD-ROM, DVD or other optical storage, cassettes, magnetic tapes, disk storage or other magnetic storage devices. Of course, those skilled in the art will appreciate that computer storage media are not limited to the above. The above-mentioned system memory and mass storage devices can be collectively referred to as memory.

[0079] A computer program product comprises a computer program / instruction, which implements the method described above when executed by a processor.

[0080] A computer program product includes a computer program or set of instructions for performing specific tasks or implementing specific functions. These programs or instructions are designed to be executed by a processor to implement a series of predefined steps or operations. The program product may be stored in various forms of computer storage media, such as memory, hard disk, solid-state drive, optical disk or other forms of digital storage devices. It may exist in the form of compiled binary code or in the form of scripts or bytecodes that can be executed by an interpreter. The program product uses carefully designed algorithms and logical instructions to enable the processor to process data in a specific order and manner to complete various functions such as data analysis, user interaction, device control, etc.

[0081] In the description of this specification, the description with reference to the terms "one embodiment / method", "some embodiments / methods", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments / methods or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0082] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0083] It should be understood by those skilled in the art that the above embodiments are only for the purpose of clearly illustrating the present invention, and are not intended to limit the scope of the present invention. For those skilled in the art, other changes or modifications may be made based on the above invention, and these changes or modifications are still within the scope of the present invention.

Claims

1. A simulation method for dynamic core power distribution measurement, characterized in that: include: Carry out fuel consumption estimation calculation at the test state point according to the power plant operation plan to obtain accurate fuel consumption data; The accurate burnup data is used as input to solve the steady-state neutron transport equation, establish a steady-state core theoretical model based on accurate burnup, and obtain the neutron flux distribution and core nuclide distribution of the three-dimensional steady-state core; Taking the neutron flux distribution and core nuclide distribution given by the steady-state core theoretical model as the initial state and the relationship curve between the core operating power and the operating time as the input, the dynamic core equation is solved to obtain the dynamic core theoretical model with time as a function; The power and time relationship corresponding to the power plant test plan is input into the dynamic core theoretical model to obtain the dynamic core design theoretical values ​​and dynamic core theoretical database consistent with the test status.

2. The simulation method for dynamic core power distribution measurement according to claim 1, characterized in that: The calculation formula for the precise burnup data is: Bu = ∫0TP(t)dt / Wu, where Bu is the precise burnup data that can be used to establish the core theoretical model, P(t) is the actual power of the core at time t, Wu is the mass of the fissile nuclear material, and T is the total actual operating time of the current power-up phase.

3. The simulation method for dynamic core power distribution measurement according to claim 1, characterized in that: The steady-state core theoretical model takes the actual initial conditions of the core as input and solves the steady-state neutron transport equation. The typical simplified expression of the steady-state neutron transport equation at point r in space is: where D is the spatially dependent diffusion coefficient, is the Laplace operator related to the coordinate system, φ(r) is the neutron flux at point r in space, and S(r) is the neutron source intensity at the point in space.

4. The simulation method for dynamic core power distribution measurement according to claim 1, characterized in that: The dynamic core equation is: Where I(t) is the iodine concentration at time t, and X(t) is the xenon concentration at time t; γ I is the fission yield of iodine, γ X is the fission yield of xenon; ∑ f is the core macroscopic fission cross section; λ I is the decay constant of iodine, λ X is the decay constant of xenon; σ X is the microscopic absorption cross section of xenon; Φ(t) is the core neutron flux at instant t; φ nom is the rated average core neutron injection rate; Pr(t) is the core power level at instant t.

5. The simulation method for dynamic core power distribution measurement according to claim 5, characterized in that: The method for performing core dynamic simulation includes: obtaining a curve corresponding to power and operating time according to the actual power increase strategy of the power plant, taking the curve corresponding to actual power and operating time as input, and using a dynamic core theoretical model to obtain a database of core flux values ​​and their distribution in core geometry changing with time.

6. The simulation method for dynamic core power distribution measurement according to claim 1, characterized in that: The database reading program is used to read the database corresponding to the test power and test time, and the parameters required for the test are output according to the format required for on-site data processing.

7. A simulation terminal for dynamic core power distribution measurement, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 4 is implemented.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 4 is implemented.

9. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the method described in any one of claims 1 to 4 is implemented.

Images