Method and medium for modeling a coolant system of a small land-based nuclear power plant

Abstract

The application discloses a modeling method and medium for a coolant system of a nuclear power plant onshore small reactor, and comprises the following steps: establishing a reactor core heat source model; establishing a coolant system model, wherein the coolant system model comprises multiple nodes, each node has a design parameter value and a performance parameter value; coupling the reactor core heat source model and the coolant system model on a preset simulation platform; simulating the operation of the coolant entering the coolant system under the design parameter value and the performance parameter value, calculating thermal parameters; judging whether the thermal parameters meet the stable operation requirement, if yes, completing the modeling of the coolant system; if not, modifying the design parameter value and the performance parameter value of each node until the stable operation requirement is met. The application simulates the operation of the coolant in the coolant system through the parameter values of the nodes, realizes full-power natural circulation through the non-active mode operation of the non-main circulating pump, and adjusts the parameter values of the nodes through the monitoring of the thermal parameters, thereby solving the problem of unstable natural circulation flow.

Description

Technical Field

[0001] This invention relates to the field of nuclear power simulation technology, and in particular to a modeling method and medium for a land-based small modular reactor coolant system in a nuclear power plant. Background Technology

[0002] Existing nuclear power modeling is mostly for large-scale nuclear power plants, research reactors, or large-scale floating reactors at sea, and is mainly used for safety analysis and control design.

[0003] The core of modeling small modular reactors (SMRs) on land lies in their high degree of integration and variations in physical effects. High integration is reflected in the fact that key equipment such as the steam generator and main pumps are integrated within the reactor pressure vessel, making the flow and heat transfer of the coolant system extremely complex. For example, the mixing and bypassing of areas such as the descending channel, lower chamber, core, and ascending section are difficult to simulate accurately. Variations in physical effects are reflected in the fact that most SMRs rely primarily on natural circulation without a main circulation pump. Their low driving force and small flow rate make them highly sensitive to drag characteristics and localized heat losses, making modeling them far more difficult than forced circulation.

[0004] Therefore, traditional modeling methods for large-scale reactors are not entirely applicable to small-scale land-based reactors. Compared to large-scale reactors, the channels in small-scale land-based reactors are smaller, and the influence of wall friction and local resistance on flow is much greater. Traditional empirical formulas for drag coefficients based on large-scale experiments are no longer accurate. Furthermore, small-scale land-based reactors may experience natural circulation flow instability, posing a challenge to the stability of the coolant system, requiring extremely high-precision dynamic modeling. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a modeling method and medium for the coolant system of a land-based small modular reactor in a nuclear power plant, addressing at least one deficiency of the related technologies mentioned in the background section.

[0006] The technical solution adopted by this invention to solve its technical problem is: a modeling method for a land-based small modular reactor (SMR) coolant system in a nuclear power plant, the method comprising the following steps: S1: Establish a heat source model for the core of a small onshore reactor; S2: Establish a coolant system model, which includes multiple nodes, and each node corresponds to design parameter values ​​and performance parameter values; S3: Couple the core heat source model and the coolant system model on a pre-set simulation platform; S4: Under the current design parameter values ​​and performance parameter values, simulate the operation of the coolant system after it enters the coolant system on the preset simulation platform, and calculate the thermal parameters; S5: Determine whether the thermal parameters of each monitoring point meet the preset stable operation requirements. If yes, complete the modeling of the coolant system; otherwise, proceed to step S6. S6: Modify the design parameter values ​​and performance parameter values ​​corresponding to each node, and execute step S4 until the thermal parameters meet the preset stable operation requirements.

[0007] In some embodiments, in step S1, the core heat source model corresponds to the core of different partitions; In step S2, the coolant system model includes a core coolant channel model; The coolant channel model includes bypass channels and sub-channels corresponding to different core sections.

[0008] In some embodiments, the coolant system model further includes a pressure vessel model; The multiple nodes of the coolant system model are the sub-channels and bypass channels in the coolant channel model, and the pressure vessel in the pressure vessel model are divided according to structural characteristics.

[0009] In some embodiments, in step S2, the design parameter value corresponding to each node includes the elevation difference of each node; In step S3, under the current design parameter values, the operation of the coolant after entering the coolant system is simulated, including: under the current design elevation difference of each node, the static pressure head generated by the elevation difference is used to simulate the natural circulation loop operation of the coolant after entering the coolant channel model.

[0010] In some embodiments, the pressure vessel model includes a pressure vessel top gas space; In step S4, the thermal parameters include the coolant level in the gas space at the top of the pressure vessel. The method further includes: adjusting the coolant level in the gas space at the top of the pressure vessel to regulate the pressure in the gas space, thereby achieving pressure stabilization of the coolant system model.

[0011] In some embodiments, the method further includes: establishing an intermediate loop flow network model, wherein the intermediate loop flow network model and the coolant system model interact with each other on a preset simulation platform through a preset interface program; The coolant system model also includes a main heat exchanger model, used to obtain the thermal parameters of the coolant operating in the coolant channel model.

[0012] In some embodiments, the calculation of thermal parameters in step S4 includes: S41: The calculation parameters of the coolant system model are obtained and transmitted to the intermediate loop flow network model through a preset interface program; the calculation parameters include at least heat parameters; S42: Calculate the thermal parameters by using the intermediate loop flow network model to calculate the parameters transferred from the coolant system model.

[0013] In some embodiments, in step S1, the core of the simulated core heat source model is a boron-free core, and the onshore small reactor includes a rod assembly model acting on the boron-free core to regulate the core reaction of the boron-free core.

[0014] In some embodiments, in step S1, the rod group model includes a compensation rod group and a regulating rod group, and the core heat source model achieves reactivity regulation of the boron-free core through hydraulic drive of the compensation rod group in conjunction with the regulating rod group.

[0015] The present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the modeling method for the coolant system of a land-based small modular reactor in a nuclear power plant as described in any of the above embodiments.

[0016] By implementing this invention, the following beneficial effects are achieved: This invention first establishes a core heat source model and a coolant system model for a small land-based reactor. The coolant system model includes multiple nodes, each with corresponding design and performance parameter values. Then, the core heat source model and the coolant system model are coupled on a pre-defined simulation platform. Next, under the current design and performance parameter values, the operation of the coolant after entering the coolant system is simulated on the pre-defined simulation platform, and thermal parameters are calculated. Finally, it is determined whether the thermal parameters at each monitoring point meet the pre-defined stable operation requirements. If so, the modeling of the coolant system is completed; otherwise, the design and performance parameter values ​​corresponding to each node are modified, and the thermal parameters are recalculated until the thermal parameters meet the pre-defined stable operation requirements. This invention simulates the operation of the coolant in the coolant system through the parameter values ​​of each node, achieves full-power natural circulation through a passive operation without a main circulation pump, and solves the problem of unstable natural circulation flow by adjusting the parameter values ​​of each node through monitoring thermal parameters. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 A flowchart of one embodiment of a modeling method for a land-based small modular reactor (SMR) coolant system in a nuclear power plant is shown. Figure 2 A schematic diagram of the core partitioning in the core heat source model of a land-based small modular reactor (SMR) in an embodiment of a modeling method for the coolant system of a nuclear power plant is shown. Figure 3 A flowchart of step S4 in an embodiment of a modeling method for a land-based small modular reactor coolant system in a nuclear power plant is shown; Figure 4 A flowchart of step S42 of an embodiment of the modeling method for the coolant system of a land-based small modular reactor in a nuclear power plant is shown; Figure 5A schematic diagram of the natural circulation of coolant in a coolant system model is shown in one embodiment of a modeling method for a land-based small modular reactor (SMR) coolant system in a nuclear power plant. Detailed Implementation

[0018] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] It should be noted that the flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0020] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0021] like Figure 1 As shown, this invention discloses a modeling method for a coolant system of a land-based small modular reactor (SMR) in a nuclear power plant. The method includes the following steps: S1: Establish a heat source model for the core of a small onshore reactor; S2: Establish a coolant system model. The coolant system model includes multiple nodes, and each node corresponds to design parameter values ​​and performance parameter values. S3: Couple the core heat source model and the coolant system model on a pre-set simulation platform; S4: Under the current design parameter values ​​and performance parameter values, simulate the operation of the coolant system after it enters the coolant system on the preset simulation platform, and calculate the thermal parameters; S5: Determine whether the thermal parameters of each monitoring point meet the preset stable operation requirements. If yes, complete the modeling of the coolant system; otherwise, proceed to step S6. S6: Modify the design parameter values ​​and performance parameter values ​​corresponding to each node, and execute step S4 until the thermal parameters meet the preset stable operation requirements.

[0022] The coolant system model is used for thermal-hydraulic simulation analysis of light water reactor nuclear power plants. Developed in training simulators and engineering simulators, it calculates the dynamic response of nuclear power plant parameters and is used in operator training, emergency drills, accident analysis, and design verification. It is applicable to small reactor types such as onshore small modular reactors (SMRs), and the calculations cover the entire range of operating conditions from maintenance cold shutdown to full-power operation, fault / accident operation, and the entire range of operating procedures (including plant conditions during refueling shutdowns). The coolant system model meets the technical specifications of the training simulator and relevant regulations and standards, and the software features scalability, fast response time, high reliability, high compatibility, and high stability.

[0023] The coolant system model simulation program is embedded into the simulation platform. The simulation platform is used to couple the core heat source model and the coolant system model with data, or with data from other models, to realize the interaction, calculation, control and feedback of data (such as power, temperature and other parameters) between models.

[0024] In this embodiment, the various components of the land-based small modular reactor (SMR) coolant system are integrated and simulated. By using node design parameters and performance parameters, the main circulation pump is eliminated from simulation, and the system operates in a passive mode that conforms to the operating mode of the SMR, achieving full-power natural circulation. In addition, by monitoring thermal parameters and adjusting the design parameters and performance parameters of each node, the problem of inconsistent flow rate of the natural circulation system of the SMR, which varies with the power of the SMR, is solved.

[0025] In some embodiments, such as Figure 2 As shown, in step S1, the core heat source model corresponds to the core of different partitions; In step S2, the coolant system model includes a core coolant channel model; The coolant channel model includes bypass channels and sub-channels corresponding to different core sections.

[0026] For example, if the core heat source model divides the core into three zones, then the coolant channel model includes three sub-channels and one bypass channel. The sub-channels correspond one-to-one with the core zones to improve the cooling efficiency of the simulated core.

[0027] In some embodiments, the coolant system model also includes a pressure vessel model; The multiple nodes of the coolant system model are the sub-channels and bypass channels in the coolant channel model, and the pressure vessel in the pressure vessel model are divided according to structural characteristics.

[0028] The sub-channel is configured to pass through the core heat source to cool it down. On the simulation platform, this is represented by the simulation of the sub-channel passing through the core heat source model and interacting with the core heat source model; while the bypass channel does not pass through the core heat source model.

[0029] In this embodiment, the pressure vessel model simulates a pressure vessel including an upper chamber and a lower chamber. For example, the sub-channels and bypass channels are each divided into 4 nodes, for a total of 12 nodes; the pressure vessel itself has the upper chamber near the core divided into 4 nodes, and the lower chamber into 2 nodes. This node division balances accuracy and real-time performance. Too many nodes, while resulting in more detailed calculations, could slow down the computation and affect real-time performance. Therefore, the node division aims to be as detailed as possible while maintaining real-time performance.

[0030] In some embodiments, in step S2, the design parameter value corresponding to each node includes the elevation difference of each node; In step S3, under the current design parameter values, the operation of the coolant after entering the coolant system is simulated, including: under the current design elevation difference of each node, the static pressure head generated by the elevation difference is used to simulate the natural circulation loop operation of the coolant after entering the coolant channel model.

[0031] The challenge in modeling onshore small modular reactors (SMRs) lies in the fact that traditional pressurized water reactors (PWRs) rely on a main circulation pump for forced coolant circulation. However, the natural circulation of SMRs is a characteristic of integrated SMR design. On the simulation platform, this manifests as the need for absolutely precise input of elevation differences; the elevation difference for each node must be entered exactly as shown in the design drawings. More specifically, the elevation difference refers to the height difference of each node, as the static pressure head generated by this height difference is the core driver of natural circulation. Furthermore, the natural circulation pressure head is typically only tens of kilopascals, and even a small error can lead to incorrect flow direction.

[0032] In some embodiments, the design parameter values ​​for each node also include the set parameters of each node, while the performance parameters include parameters such as drag coefficient, pump characteristics, and initial operating conditions (pressure, temperature, liquid level). In the initial stage of establishing the coolant system model, the design parameter values ​​and performance parameter values ​​of each node are used as inputs to build the model. Due to the unstable flow rate of the natural circulation in the onshore small reactor, it is necessary to modify the design parameter values ​​and performance parameter values ​​corresponding to each node in step S6 to ensure the stable operation of the coolant system model. Generally, modifications are made primarily to the performance parameter values, and more specifically, to the drag coefficient.

[0033] In some embodiments, the pressure vessel model includes a pressure vessel top gas space; In step S4, the thermal parameters include the coolant level in the gas space at the top of the pressure vessel; The method also includes: adjusting the coolant level in the gas space at the top of the pressure vessel to regulate the pressure in the gas space, thereby achieving pressure stabilization of the coolant system model.

[0034] Traditional reactor cores have pressurizers, which are electrically heated pressurizers. When the system pressure drops, the electric heating elements submerged in the water in the gas space are energized to heat the water and generate steam, increasing the pressure in the gas space. When the pressure is too high, the spray valve at the top opens and sprays cold water (usually from the cold tube section) into the gas space, causing the steam to condense and the pressure to drop rapidly.

[0035] The unique design of the natural circulation integrated small modular reactor (SMR) on land is that there is no pressure regulator. Therefore, pressure stabilization needs to be achieved within the pressure vessel. The coolant level in the top chamber of the pressure vessel is obtained through a simulation platform. The coolant level can be calculated to form a compressible gas chamber at the top of the pressure vessel, i.e., the gas space at the top of the pressure vessel. The water level is adjusted by simulating water replenishment or drainage through the simulation platform, thereby adjusting the volume of the gas space at the top of the pressure vessel and thus fine-tuning the internal pressure of the pressure vessel.

[0036] In some embodiments, the method further includes: establishing an intermediate loop flow network model, wherein the intermediate loop flow network model and the coolant system model interact with each other on a preset simulation platform through a preset interface program; The coolant system model also includes a main heat exchanger model, which is used to obtain the thermal parameters of the coolant operating in the coolant channel model.

[0037] In this embodiment, the intermediate loop flow network model is established based on the intermediate loop system. A break in the intermediate loop system will lead to a loss of water volume in the intermediate loop, a decrease in pressure, an instantaneous increase in the flow rate of the broken intermediate loop system followed by a rapid decrease, and at the same time, a low pressure difference between the intermediate loop volume compensator and the primary loop, and a low liquid level in the intermediate loop volume compensator. If the specified set value is reached to trigger a reactor trip, it can be covered by the power operation mode. If the specified set value cannot be reached to trigger a reactor trip, in order to control reactivity, it is necessary to manually shut down the reactor, manually isolate all intermediate loop systems, and manually put into operation the intact reactor core residual heat removal system (RHR). The reactor core residual heat is removed through the reactor core residual heat removal system.

[0038] This invention establishes an intermediate loop flow network model and interacts with the coolant system model through the main heat exchanger model. The purpose is to test typical accident conditions. Specifically, after the thermal parameters meet the requirements for stable operation, that is, after the coolant system model enters steady-state operation, different complex operating conditions can be simulated by interacting with the intermediate loop flow network model, thereby increasing the diversity of simulation data.

[0039] like Figure 3 As shown, in some embodiments, step S4, calculating the thermal parameters includes: S41: The calculation parameters of the coolant system model are obtained and transmitted to the intermediate loop flow network model through a preset interface program; the calculation parameters include at least the heat parameters; S42: Calculate the thermal parameters by using the intermediate loop flow network model to calculate the parameters transferred from the coolant system model.

[0040] like Figure 4 As shown, in some embodiments, the intermediate loop flow network model uses a fixed boundary parameter method to obtain thermal parameters. The fixed boundary parameter method includes: S421: Determine the fixed boundary parameters based on the calculation parameters of each node in the coolant system model, and perform initialization calculations on the fixed boundary parameters; S422: Substitute the fixed boundary parameters into the intermediate loop flow network model to obtain the thermal parameters; S423: Determine whether the thermal parameters meet the preset steady-state convergence conditions. If yes, output the thermal parameters; otherwise, proceed to step S424. S424: Correct the fixed boundary parameters and re-execute step S422 until the obtained thermal parameters meet the preset steady-state convergence conditions.

[0041] In some embodiments, in step S1, the core of the simulated core heat source model is a boron-free core; the onshore small reactor includes a rod assembly model acting on the boron-free core to regulate the core reaction of the boron-free core.

[0042] In this invention, the onshore small reactor core differs from other traditional large reactor types. In the boron cores of other traditional large reactor types, that is, the coolant in the coolant system of other traditional large reactor types contains boron. In simulation modeling, this is usually reflected as: the coolant in the coolant system model of other traditional large reactors contains boron, and the boron parameter is transferred to the core heat source model for the core heat source model to carry out the core reaction.

[0043] The onshore small modular reactor (SMR) core is a boron-free core. A boron-free core means that the coolant in the onshore SMR coolant system does not contain soluble boron. During modeling, the boron-free core simulation is achieved by reading the boron branch from the shielded component reaction section library. Specifically, the boron-free branch is selected for reading, thus treating the entire core calculation as if the boron concentration were zero, achieving zero-boron input. Based on the simulation settings of the boron-free core, the reactivity control of the core relies entirely on the interaction of the rod assembly model, combustible poisons, and other factors.

[0044] In some embodiments, in step S1, the rod group model includes a compensation rod group and a regulating rod group, and the core heat source model achieves reactivity regulation of the boron-free core through hydraulic drive of the compensation rod group in conjunction with the regulating rod group.

[0045] In this embodiment, the slow-changing reactivity is compensated by changes in boric acid concentration through hydraulically driven compensation rod groups. The compensation rod groups act as solid-state boron regulators, matching burnup and poisoning changes through slow rod lifting. The regulating rod groups, on the other hand, perform the same regulating functions as traditional large reactor control rod groups, including rapid regulation, emergency shutdown, and partial burnup compensation. In the simulation model, this is reflected in the interaction between the compensation rod groups and regulating rod groups in the small-scale onshore reactor model to generate reaction parameters. These parameters are then transmitted to the boron-free core in the core heat source model, achieving reactivity regulation of the boron-free core. This regulates the core reaction, eliminating the risk of boron dilution accidents and avoiding the complex impact of boron poisoning on reactivity feedback. The built-in hydraulically driven compensation rod groups in the boron-free core replace the boric acid regulation of traditional large-scale boron reactor cores, avoiding problems such as boron dilution, boron crystallization, and boron corrosion, and simplifying the chemical volume control system.

[0046] The coolant system model includes a coolant piping model, a pressure vessel model, and a main heat exchanger model. The simulation model depicts the natural circulation loop of the coolant within the coolant system model as follows: The coolant system model operates around the heat source model of the onshore small reactor core. Specifically, the coolant piping model, located inside the pressure vessel and surrounding the core heat source model, simulates the direct cooling of fuel and the carrying of heat by the coolant. The pressure vessel model serves as the pressure boundary of the coolant system model, providing a closed installation space and pressurized environment for the coolant channel models. The main heat exchanger model is connected to the pressure vessel model via flow channels, and includes the primary and secondary sides of the main heat exchanger. The simulation platform simulates the coolant absorbing heat from the coolant channel model, flowing through the pressure vessel model and the primary side of the main heat exchanger model, and the secondary side of the main heat exchanger extracting heat parameters from the primary side. These three models together constitute a complete coolant cycle, simulating the continuous heat removal and heat exchange from the reactor core.

[0047] More specifically, the cyclic simulation of coolant in the coolant system model is as follows: Figure 5 As shown, the simulation platform simulates the coolant entering the lower chamber 519 of the pressure vessel model, then entering the core inlet 520, and being diverted to the sub-channels 501 to 503 of the coolant channel model, as well as the bypass channel 510. Then, it is mixed in the first upper chamber 533 through the rising channel 531, and diverted to the two main heat exchanger loops in the second upper chamber 534. That is, the coolant is diverted to the primary side 105 of the first main heat exchanger and the primary side 205 of the second main heat exchanger, and the heat is transferred to the rising section 150 of the secondary side of the first main heat exchanger and the rising section 250 of the secondary side of the second main heat exchanger. Finally, the coolant returns to the lower chamber 519 through the first descending chamber 538 and the second descending chamber 528 in the first and second main heat exchangers respectively to complete the simulation of a natural circulation loop.

[0048] In addition, the main heat exchanger model also includes a third upper chamber 535 connected to the second upper chamber 534. The third upper chamber 535 simulates the storage of non-flowing coolant, which forms a pressure vessel top gas space with the upper head 536. This gas space is used to adjust the pressure of the pressure vessel top gas space by simulating the filling or draining of water into the third upper chamber 535 through the simulation platform, thereby simulating the pressure stabilization of the entire pressure vessel model.

[0049] The first primary heat exchanger secondary side rising section 150 and the second primary heat exchanger secondary side rising section 250 of the primary heat exchanger model transmit the acquired data to the intermediate loop flow network model through the first intermediate loop output boundary 125 and the second intermediate loop output boundary 225, respectively. The intermediate loop flow network model inputs data to the first primary heat exchanger secondary side falling section 165 and the second primary heat exchanger secondary side falling section 265 through the first intermediate loop input boundary 120 and the second intermediate loop input boundary 220, thus completing the data interaction between the coolant system model and the intermediate loop flow network model.

[0050] The present invention also discloses a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the modeling method for the coolant system of a land-based small modular reactor in a nuclear power plant as described in any of the above embodiments.

[0051] It is understood that the above embodiments only illustrate some implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above embodiments or technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. That is, the embodiments described "in some embodiments" can be freely combined with any of the preceding and following embodiments. Therefore, all equivalent transformations and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.

Claims

1. A modeling method for a land-based small modular reactor (SMR) coolant system in a nuclear power plant, characterized in that, The method includes the following steps: S1: Establish a heat source model for the core of a small onshore reactor; S2: Establish a coolant system model, which includes multiple nodes, and each node corresponds to design parameter values ​​and performance parameter values; S3: Couple the core heat source model and the coolant system model on a pre-set simulation platform; S4: Under the current design parameter values ​​and performance parameter values, simulate the operation of the coolant system after it enters the coolant system on the preset simulation platform, and calculate the thermal parameters; S5: Determine whether the thermal parameters of each monitoring point meet the preset stable operation requirements. If yes, complete the modeling of the coolant system; otherwise, proceed to step S6. S6: Modify the design parameter values ​​and performance parameter values ​​corresponding to each node, and execute step S4 until the thermal parameters meet the preset stable operation requirements.

2. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 1, characterized in that, In step S1, the core heat source model corresponds to the core of different partitions; In step S2, the coolant system model includes a core coolant channel model; The coolant channel model includes bypass channels and sub-channels corresponding to different core sections.

3. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 2, characterized in that, The coolant system model also includes a pressure vessel model; The multiple nodes of the coolant system model are the sub-channels and bypass channels in the coolant channel model, and the pressure vessel in the pressure vessel model are divided according to structural characteristics.

4. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 3, characterized in that, In step S2, the design parameter value corresponding to each node includes the elevation difference of each node; In step S3, under the current design parameter values, the operation of the coolant after entering the coolant system is simulated, including: under the current design elevation difference of each node, the static pressure head generated by the elevation difference is used to simulate the natural circulation loop operation of the coolant after entering the coolant channel model.

5. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 3, characterized in that, The pressure vessel model includes a gas space at the top of the pressure vessel; In step S4, the thermal parameters include the coolant level in the gas space at the top of the pressure vessel. The method further includes: adjusting the coolant level in the gas space at the top of the pressure vessel to regulate the pressure in the gas space, thereby achieving pressure stabilization of the coolant system model.

6. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 3, characterized in that, The method further includes: establishing an intermediate loop flow network model, and the intermediate loop flow network model and the coolant system model interacting with each other on a preset simulation platform through a preset interface program; The coolant system model also includes a main heat exchanger model, used to obtain the thermal parameters of the coolant operating in the coolant channel model.

7. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 6, characterized in that, In step S4, the calculation of thermal parameters includes: S41: The calculation parameters of the coolant system model are obtained and transmitted to the intermediate loop flow network model through a preset interface program; the calculation parameters include at least heat parameters; S42: Calculate the thermal parameters by using the intermediate loop flow network model to calculate the parameters transferred from the coolant system model.

8. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 1, characterized in that, In step S1, the core of the simulated core heat source model is a boron-free core, and the onshore small reactor includes a rod assembly model acting on the boron-free core to regulate the core reaction of the boron-free core.

9. The modeling method for the coolant system of a small land-based nuclear power plant according to claim 8, characterized in that, In step S1, the rod group model includes a compensation rod group and a regulating rod group. The core heat source model achieves reactivity regulation of the boron-free core through hydraulic drive of the compensation rod group in conjunction with the regulating rod group.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the modeling method for the coolant system of a land-based small modular reactor in a nuclear power plant as described in any one of claims 1-9.

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