Reactor top high-temperature ventilation test method

Abstract

The invention discloses a reactor top high-temperature ventilation test method. The method comprises the following steps: acquiring conservative working conditions of each group of CRDM, determining operating parameters of each group of CRDM, and establishing a prototype reactor top CFD model based on the parameters; analyzing the prototype reactor top flow field and the temperature field through CFD to obtain a first analysis result; then, constructing an initial test reactor top CFD model, and adjusting the heating power and the number of heating bodies to ensure that the heating power and the number of heating bodies are consistent with the first analysis result; performing an entity test to obtain data of a flow field and a temperature field, comparing the data with an analysis result, and adjusting model parameters until the difference of each result meets the requirement; and finally, determining parameters of the target test reactor top model, and verifying the prototype reactor top model. By implementing the method disclosed by the invention, comprehensive simulation of the reactor top flow field and the temperature field can be efficiently realized at low cost, the test effectiveness is ensured, the design parameters are optimized, and the flow field and the temperature field of the test can be ensured to be close to the prototype reactor top area.

Description

Technical Field

[0001] The present invention relates to the reactor top structure of a nuclear power plant, and more specifically to a high-temperature ventilation test method for a reactor top. Background Art

[0002] In a nuclear power plant, the reactor top assembly is an important component, installed above the top cover of the RPV (Reactor Pressure Vessel). During normal operation, this assembly is fixed to the top cover of the RPV, and is lifted and replaced together with the top cover of the RPV and the CRDM (Control Rod Drive Mechanism) during reactor shutdown and refueling. The main functions of this assembly include: during reactor maintenance, being lifted together with the reactor top cover to simplify the disassembly and assembly process; providing seismic support for the control rod drive mechanism, restricting its excessive deformation under seismic conditions to maintain its normal function; providing a cooling ventilation channel to ensure effective cooling of the yoke coil of the control rod drive mechanism and ensure its normal operation; guiding the cables and other system components in the reactor top area to the specified civil engineering interfaces. In terms of the cooling of the yoke coil of the control rod drive mechanism, the traditional method relies on the ventilation hood assembly at the reactor top for forced ventilation. As shown in Figure 1 and Figure 2 , the lower coil components from top to bottom are the fixed coil, the moving coil, and the lifting coil. However, with the research and development of high-temperature resistant coils and cables, the reactor top cooling method has gradually changed to natural convection or assisted ventilation. To adapt to this change, it is very necessary to conduct a high-temperature ventilation test on the reactor top. The main purposes include evaluating the ventilation and heat dissipation effect, verifying the rationality of the structural design, providing a basis for design parameters, and optimizing the reactor top structure. Specifically, analyze the temperature, flow rate, and heat dissipation distribution of the reactor top components in the natural or assisted ventilation state after canceling forced ventilation; check whether the yoke coil and cables of the control rod drive mechanism can remain within their tolerance temperature range under the new cooling method to ensure that the equipment will not be damaged due to high temperature or high flow rate; determine the appropriate ventilation volume, ventilation temperature, ventilation port size, etc. to provide support for the design of other systems; through sensitivity tests, find a more ideal reactor top structure plan.

[0003] Since the actual reactor top typically contains multiple control rod drive mechanisms (60 - 90 groups), and their motion states and step - by - step speeds vary according to the requirements of the reaction inside the reactor, it is very challenging to fully simulate the situation of these mechanisms during actual operation in experiments. In addition, other structural components on the reactor top (such as the top cover, seismic plate, cable tray, etc.) will also affect the flow field and temperature field. There are two existing experimental methods. One is to conduct experiments with a single - group control rod drive mechanism under different motion states and different step - by - step speeds, and wrap heat - insulating materials around it to simulate extreme environments, mainly focusing on the temperature tolerance of the yoke coils of the control rod drive mechanism. However, this method only uses a single - group CRDM and cannot simulate the mutual influence between multiple CRDMs; the use of heat - insulating materials lacks a quantitative reference, which may lead to poor heat dissipation and affect the experimental results; it can only measure the parameters of a single - group CRDM and cannot obtain the flow field and temperature field data of the overall reactor top; it ignores the influence of other structural components on the reactor top on the flow field and temperature field. The second method is to conduct experiments with 5 groups of CRDMs and measure the temperatures of each component through different motion modes and step - by - step speeds. Although this scheme improves the number of CRDMs to a certain extent, the cost of using 5 groups of CRDM components is high; 5 groups of CRDMs cannot simulate the environmental conditions of 60 - 80 groups of CRDMs in the actual reactor top, and the results may be quite different from the actual reactor top situation, especially the temperature distribution in the top - cable area; it can only measure the parameters of the 5 groups of CRDMs themselves and is difficult to comprehensively understand the flow field and temperature field of the reactor top; it ignores the influence of other components on the reactor top on the flow field and temperature field.

[0004] In summary, the existing experimental methods use a small number of CRDMs for simulation and cannot obtain a flow field and temperature field close to that of the prototype reactor top area.

[0005] Therefore, it is necessary to design a new method to achieve a comprehensive simulation of the flow field and temperature field of the reactor top efficiently and at low cost, ensure the effectiveness of the experiment and optimize the design parameters, and ensure that the flow field and temperature field of the experiment are close to those of the prototype reactor top area. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a high - temperature ventilation test method for the reactor top.

[0007] To achieve the above - mentioned purpose, the present invention adopts the following technical solutions: A high - temperature ventilation test method for the reactor top, including:

[0008] According to the functional requirements of control rod control and position indication during the operation of the reactor, determine the operating parameters of each group of CRDMs under the most conservative working conditions;

[0009] Based on the operating parameters of each group of CRDMs under the most conservative operating conditions, a CFD model of the reactor top of the prototype reactor is established, and the internal flow field of the reactor is analyzed, and key parameters are extracted to obtain the first analysis result. Among them, the first analysis result includes the key parameters in the flow field and temperature field of the reactor top of the prototype reactor;

[0010] An initial CFD model of the test reactor top is established, where the initial CFD model of the test reactor top includes the real prototype of CRDM and the CRDM simulation body;

[0011] Adjust the heating power and the number of heating elements of the CRDM simulation body in the initial CFD model of the test reactor top until the difference between the second analysis result obtained by analyzing the internal flow field of the reactor with the adjusted initial CFD model of the test reactor top and the first analysis result meets the first condition set in advance to obtain the target three-dimensional flow field model of the test reactor top;

[0012] Conduct physical tests on the target three-dimensional flow field model of the test reactor top to obtain test results, where the test results include the flow field and temperature field of the reactor top under various operating conditions;

[0013] Determine whether it is necessary to adjust the parameters involved in the target three-dimensional flow field model of the test reactor top according to the test results and the second analysis result;

[0014] When it is necessary to adjust the parameters involved in the target three-dimensional flow field model of the test reactor top, adjust the parameters involved in the target three-dimensional flow field model of the test reactor top to update the target three-dimensional flow field model of the test reactor top, and verify it using the CFD model of the reactor top of the prototype reactor until the differences among the updated first analysis result, the updated second analysis result, and the test results meet the requirements;

[0015] Determine the final CFD model of the reactor top of the prototype reactor according to the parameters of the updated target three-dimensional flow field model of the test reactor top.

[0016] Its further technical solution is: the operating parameters related to each group of CRDMs include the coil heating power and boundary parameters of each group of CRDMs under the most conservative operating conditions;

[0017] Determine the operating parameters of each group of CRDMs under the most conservative operating conditions according to the functional requirements of control rod control and position indication during the operation of the reactor, including:

[0018] Obtain the motion sets of each group of CRDMs under different operating conditions based on the functional requirements of the rod control and rod position system;

[0019] Determine the most conservative operating condition according to the motion sets;

[0020] Calculate the coil heating power of each group of CRDMs according to the CRDM resistance value, voltage value corresponding to the most conservative working condition, and the current change during a period of time during the movement at different step speeds.

[0021] Determine the boundary parameters according to the actual environmental conditions at the reactor top and the power plant operation requirements. Among them, the boundary parameters include the pressure and inlet temperature of the coolant inside the CRDM, the air temperature of the environment where the reactor top is located, the heat flux density of the thermal insulation layer of the reactor pressure vessel head, the wind speed and wind temperature of the auxiliary ventilation.

[0022] Its further technical solution is: The determination of the most conservative working condition according to the movement set includes:

[0023] Comprehensively determine the most conservative working condition according to the number of control rod movements, movement speed, and distance from the center corresponding to each element in the movement set.

[0024] Its further technical solution is: Based on the operation-related parameters of each group of CRDMs, establish a prototype reactor top CFD model and conduct an internal flow field analysis of the reactor to obtain a first analysis result, including:

[0025] Construct a prototype reactor top CFD model consistent with the actual reactor top structure based on the operation-related parameters of each group of CRDMs;

[0026] Perform mesh division on the prototype reactor top CFD model to obtain a mesh model of the prototype reactor top;

[0027] Determine the calculation parameters;

[0028] According to the calculation parameters, conduct an internal flow field analysis of the reactor on the mesh model of the prototype reactor top to obtain the flow field and temperature field of the prototype reactor top;

[0029] Extract the key parameters of the flow field and temperature field of the prototype reactor top to obtain a first analysis result.

[0030] Its further technical solution is: The key parameters include the highest temperature of the CRDM yoke coil, the highest temperature of the rod position detector coil, and the highest air temperature above the CRDM top cable lead-out problem.

[0031] Its further technical solution is as follows: The calculation parameters include working fluid properties, calculation models, boundary conditions, and solution settings. The working fluid properties include material, density, viscosity, thermal conductivity, and specific heat capacity. The boundary conditions include ambient temperature, ambient pressure, coil heating power, CRDM simulator heating power, top cover insulation heating power, auxiliary vent inlet temperature and inlet flow rate, coolant inlet temperature and pressure. The calculation models include turbulence model, buoyancy model, and thermal radiation model. The solution settings include difference format, number of iteration steps, time scale, and convergence criterion.

[0032] Its further technical solution is as follows: A real CRDM prototype is arranged at the central position of the initial test reactor top CFD model, and CRDM simulators are used at other positions. And the number of the real CRDM prototypes is no more than 9 groups.

[0033] Its further technical solution is as follows: Adjust the heating power and the number of heating elements of the CRDM simulators in the initial test reactor top CFD model until the difference between the second analysis result obtained from the internal flow field analysis of the adjusted initial test reactor top CFD model and the first analysis result meets a preset first condition, so as to obtain a target test reactor top three-dimensional flow field model, including:

[0034] Adjust the heating power and the number of heating elements of the CRDM simulators in the initial test reactor top CFD model to obtain an adjusted initial test reactor top CFD model;

[0035] Conduct an internal flow field analysis of the adjusted initial test reactor top CFD model to obtain a second analysis result;

[0036] Judge whether the difference between the second analysis result and the first analysis result meets the preset first condition;

[0037] If the difference between the second analysis result and the first analysis result meets the preset first condition, determine the adjusted initial test reactor top CFD model as the target test reactor top three-dimensional flow field model;

[0038] If the difference between the second analysis result and the first analysis result does not meet the preset first condition, execute the adjustment of the heating power and the number of heating elements of the CRDM simulators in the initial test reactor top CFD model to obtain an adjusted initial test reactor top CFD model.

[0039] The preset first condition includes that the maximum temperature difference of the CRDM yoke coil does not exceed 10°C, the maximum air temperature above the cable outlet position at the top of the CRDM does not exceed 10°C, and the position range above the high-temperature area at the reactor top does not exceed 15%.

[0040] Its further technical solution is: performing an internal reactor flow field analysis on the adjusted initial test reactor top CFD model to obtain a second analysis result, including:

[0041] Performing grid division on the adjusted initial test reactor top CFD model to obtain a grid model of the adjusted initial test reactor top;

[0042] Performing an internal reactor flow field analysis on the grid model of the adjusted initial test reactor top according to the calculation parameters to obtain the flow field and temperature field of the test reactor top;

[0043] Extracting key parameters of the flow field and temperature field of the test reactor top to obtain a second analysis result;

[0044] Wherein, when the gap between the second analysis result obtained by performing an internal reactor flow field analysis on the adjusted initial test reactor top CFD model and the first analysis result meets a preset first condition, the grid model of the adjusted initial test reactor top is the grid model of the target test reactor top.

[0045] Its further technical solution is: performing a physical test on the three-dimensional flow field model of the target test reactor top to obtain a test result, including:

[0046] Building a physical reactor top according to the three-dimensional flow field of the target test reactor top;

[0047] Arranging temperature measurement points and velocity measurement points at key parts in the physical reactor top;

[0048] Arranging heat flux sensors on the surfaces at different heights of the real CRDM prototype in the physical reactor top;

[0049] Conducting a test according to the heating power of the three-dimensional flow field model of the target test reactor top and performing a sensitivity analysis on different parameters to obtain a test result.

[0050] Its further technical solution is: the key parts in the physical reactor top include inside each coil of the real CRDM prototype, surfaces at different heights of the real CRDM prototype, the internal coolant area of the real CRDM prototype, cable positions at different heights above the top seismic plate, positions at different heights on the surface of the CRDM simulation body, gap positions at different heights between the real CRDM prototype and the CRDM simulation body, and auxiliary ventilation air outlets.

[0051] Its further technical solution is: determining whether it is necessary to adjust the parameters involved in the three-dimensional flow field model of the target test reactor top according to the test result and the second analysis result, including:

[0052] When the gap between the test result and the second analysis result does not meet the requirements, it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model.

[0053] Its further technical solution is: when it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model, adjust the parameters involved in the target test reactor top three-dimensional flow field model to update the target test reactor top three-dimensional flow field model, and use the prototype reactor top CFD model for verification until the gaps among the first analysis result, the second analysis result, and the test result meet the requirements, including:

[0054] When it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model, adjust the parameters involved in the target test reactor top three-dimensional flow field model to update the target test reactor top three-dimensional flow field model;

[0055] Conduct an internal reactor flow field analysis on the updated target test reactor top three-dimensional flow field model to update the second analysis result;

[0056] Judge whether the gap between the updated second analysis result and the test result meets the requirements;

[0057] If the gap between the updated second analysis result and the test result meets the requirements, input the parameters involved in the adjusted target test reactor top three-dimensional flow field model into the prototype reactor top CFD model to update the prototype reactor top CFD model, and conduct an internal reactor flow field analysis on the updated prototype reactor top CFD model again to update the first analysis result;

[0058] Judge whether the gap between the updated first analysis result and the updated second analysis result meets a preset first condition;

[0059] If the gap between the updated first analysis result and the updated second analysis result meets the preset first condition, execute the determination of the final prototype reactor top CFD model according to the parameters of the updated target test reactor top three-dimensional flow field model;

[0060] If the gap between the updated second analysis result and the test result does not meet the requirements, execute the adjustment of the parameters involved in the target test reactor top three-dimensional flow field model to update the target test reactor top three-dimensional flow field model;

[0061] If the difference between the updated first analysis result and the updated second analysis result does not meet the preset first condition, iteratively adjust the heating power and the number of heating elements of the CRDM simulator of the target test reactor top three-dimensional flow field model, conduct an internal reactor flow field analysis to update the second analysis result until the difference between the updated second analysis result and the first analysis result meets the set first condition; conduct a physical test again to update the test result, and iteratively adjust the heating power and the number of heating elements of the CRDM simulator of the target test reactor top three-dimensional flow field model until the differences among the updated test result, the updated second analysis result, and the first analysis result meet the requirements.

[0062] Its further technical solution is: the parameters involved in the target test reactor top three-dimensional flow field model include the grid model of the target test reactor top, the calculation model, and the solution settings.

[0063] The beneficial effects of the present invention compared with the prior art are as follows: the present invention determines the operating related parameters by obtaining the conservative conditions of each CRDM, and then establishes a three-dimensional flow field model of the prototype reactor top; analyzes the flow field and temperature field of the prototype reactor top through CFD, extracts key parameters, and obtains the first analysis result; establishes an initial test reactor top CFD model, which includes the real prototype of the CRDM and the simulator; adjusts the heating power and the number of heating elements in the initial test reactor top model to make the second analysis result meet the preset conditions with the first analysis result, and obtains the target test reactor top model; conducts a physical test to obtain the test results of the flow field and temperature field, and adjusts the parameters in the target model according to the comparative analysis; through continuous adjustment and verification, finally determines the target test reactor top model consistent with the prototype reactor top CFD model, ensures the effectiveness of the test and design optimization, realizes the comprehensive simulation of the reactor top flow field and temperature field efficiently and at low cost, ensures the test effectiveness and optimizes the design parameters, and can ensure that the flow field and temperature field of the test are close to the prototype reactor top area.

[0064] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0066] Figure 1 It is a schematic structural diagram of the reactor top of the prior art;

[0067] Figure 2Schematic diagram of the internal heat source of the CRDM in the prior art;

[0068] Figure 3 Schematic flow chart of a reactor top high-temperature ventilation test method provided by an embodiment of the present invention;

[0069] Figure 4 Sub-flow schematic of a reactor top high-temperature ventilation test method provided by an embodiment of the present invention Figure 1 ;

[0070] Figure 5 Sub-flow schematic of a reactor top high-temperature ventilation test method provided by an embodiment of the present invention Figure 2 ;

[0071] Figure 6 Sub-flow schematic of a reactor top high-temperature ventilation test method provided by an embodiment of the present invention Figure 3 ;

[0072] Figure 7 Sub-flow schematic of a reactor top high-temperature ventilation test method provided by an embodiment of the present invention Figure 4 ;

[0073] Figure 8 Sub-flow schematic of a reactor top high-temperature ventilation test method provided by an embodiment of the present invention Figure 5 ;

[0074] Figure 9 Schematic diagram for determining the conservative working condition provided by an embodiment of the present invention;

[0075] Figure 10 Schematic diagram of the natural ventilation calculation model of the prototype reactor top and the test reactor top provided by an embodiment of the present invention (the reactor cavity pool wall is not shown);

[0076] Figure 11 Schematic diagram of the auxiliary ventilation calculation model of the prototype reactor top and the test reactor top provided by an embodiment of the present invention (including the reactor cavity pool wall and the auxiliary ventilation air inlets);

[0077] Figure 12 Schematic diagram of the layout of 69 groups of CRDMs in a typical nuclear power plant reactor provided by an embodiment of the present invention. Detailed implementation manners

[0078] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0079] It should be understood that when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.

[0080] It should also be understood that the terms used in this specification of the present invention are merely for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in this specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0081] It should be further understood that the term "and / or" used in this specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0082] The reactor top assembly is an important component in a nuclear power plant, and its main functions include providing seismic support, cooling ventilation, and cable guidance. The traditional forced ventilation method is gradually changing to natural convection or assisted ventilation, so a high-temperature ventilation test of the reactor top is required. There are deficiencies in existing test methods. For example, using a single set or a small number of control rod drive mechanisms cannot comprehensively simulate the actual reactor top situation and cannot effectively analyze the mutual influence between multiple CRDMs. Existing tests can only obtain limited flow field and temperature field data and cannot comprehensively understand the overall environment of the reactor top.

[0083] Therefore, the embodiments of the present invention provide a method for high-temperature ventilation test of a reactor top, which can efficiently and low-costly achieve a comprehensive simulation of the flow field and temperature field of the reactor top, ensure the effectiveness of the test and optimize the design parameters, and can ensure that the flow field and temperature field of the test are close to the prototype reactor top area.

[0084] Specifically, by using a small number of real CRDM prototypes, several groups of CRDM simulation bodies, and other local reactor top structures, the flow field and temperature field simulation of the entire prototype reactor top can be achieved. The entire prototype reactor top includes dozens of real CRDM prototypes and other reactor top structures, which greatly saves economic costs and time, and a single pressure vessel improves the safety and reliability of the test. By comparing the results obtained from the CFD analysis of the prototype reactor top with the results obtained from the CFD analysis of the test reactor top, the test scale and power parameters can be estimated before the formal test, so as to ensure the effectiveness of the test and save the time and cost required for test commissioning; after the test, by verifying and correcting the CFD analysis process, the accuracy and usability of the reactor top flow field calculation model can be further improved, and for the parameters that cannot be directly measured in the test, the CFD analysis can provide corresponding prediction results.

[0085] Please refer to Figure 3 , Figure 3 which is a schematic flowchart of the high-temperature ventilation test method for the reactor top provided by the embodiment of the present invention. The method includes the following steps S110 to S180.

[0086] S110. Determine the operating parameters of each set of CRDMs under the most conservative conditions according to the functional requirements of control rod control and position indication during the operation of the reactor.

[0087] In this embodiment, the conservative conditions refer to those situations that can represent the operating states of the control rod assemblies under the most extreme conditions, which consider the principles of the largest number of control rods moving simultaneously, the maximum moving speed of the control rods, and the positions of the control rods closest to the center. The conservative conditions are used to ensure the maximum safety margin for system design and operation.

[0088] Specifically, the definition of the conservative conditions is based on the following three points:

[0089] Largest number of control rods: Select as many control rods as possible to move at the same time.

[0090] Highest control rod speed: Adopt the maximum allowable moving speed of each type of control rod.

[0091] Control rod positions closest to the center: Give priority to the movement conditions of those control rods closer to the center position of the reactor, because the heat dissipation is usually more difficult and the temperature is higher at these positions.

[0092] The operating parameters related to each set of CRDMs include the coil heating power and boundary parameters of each set of CRDMs under the most conservative conditions.

[0093] Specifically, the operating parameters related to each set of CRDMs include but are not limited to the following:

[0094] Coil heating power: Calculated according to the resistance value, voltage value of the CRDM under the most conservative conditions and the current change during a period of time during the movement at different step speeds.

[0095] Boundary parameters: Refer to the external conditions affecting the operation of the CRDM, such as the pressure and inlet temperature of the internal coolant, the air temperature of the environment where the reactor top is located, the heat flux density of the thermal insulation layer of the reactor pressure vessel top cover, etc.

[0096] In one embodiment, please refer to Figure 2 , and the above step S110 may include steps S111 to S114.

[0097] S111. Obtain the movement sets of each set of CRDMs under different conditions based on the functional requirements of the rod control and rod position system.

[0098] In this embodiment, the movement set refers to the set of all possible CRDM movement states, which covers the sequential movement of each group of CRDMs under different working conditions. For example, during the power increase process, the power regulating rods can be gradually inserted into or withdrawn from the core in sequences such as A, A + B, B, B + C, C, C + D, etc.; similarly, the temperature regulating rods can also have similar sequences. These sequences constitute a comprehensive movement set, reflecting the CRDM operation modes under different working conditions.

[0099] According to the functional requirements of the rod control and rod position system, combined with different operation conditions of the reactor (such as power increase), collect and sort out all the movement states that each group of CRDMs may experience under various circumstances, forming a complete movement set.

[0100] S112. Determine the most conservative working condition according to the movement set.

[0101] In this embodiment, the most conservative working condition is comprehensively determined according to the number of control rod movements, movement speed, and distance from the center corresponding to each element in the movement set.

[0102] Screen out the states that meet the definition of the conservative working condition from the movement set obtained in step S111, that is, those with the largest number of control rods, the highest movement speed, and the control rod positions closest to the center.

[0103] S113. Calculate the coil heating power of each group of CRDMs according to the CRDM resistance value, voltage value, and the current change situation during a period of time during different step speeds of movement corresponding to the most conservative working condition.

[0104] In this embodiment, use electrical parameters such as resistance value and voltage value, and dynamic movement data such as current change to calculate the heating power of the CRDM coil under the conservative working condition, providing basic data for subsequent thermal-hydraulic analysis.

[0105] Specifically, each CRDM coil operates at a fixed voltage during its operation, and its current can be set to 1 to 3 different step values. Since the coil resistance will change slightly with the change of current, the actual power consumption will also fluctuate. Generally, the power consumption P of the coil can be calculated by the formula P = U×I, where U represents the operating voltage of the coil, and I is the current intensity flowing through the coil.

[0106] When the CRDM performs movement, the current intensity in the coil not only depends on the set step value, but also dynamically adjusts according to the movement speed of the control rod, and this current intensity changes with time. When calculating the specific heating power, consider the cumulative effect of the voltage and current experienced by the coil over a period of time to determine the total power output.

[0107] This power output is directly related to the movement speed of the control rod and serves as an important input parameter for subsequent flow field analysis and experimental verification. This means that for the movement of the control rod at different speeds, the average voltage and current during the corresponding time period are accurately measured or estimated to ensure that the total power consumption during this period can be correctly calculated, thereby providing reliable data support for thermal analysis.

[0108] In short, the heating power of the CRDM coil is calculated based on the voltage and current conditions of the coil within a certain period of time. This not only reflects the electrical performance of the coil itself but also is directly related to the movement characteristics of the control rod and provides key data for subsequent engineering analysis.

[0109] S114. Determine the boundary parameters according to the actual environmental conditions at the reactor top and the operation requirements of the power station. Among them, the boundary parameters include the pressure and inlet temperature of the coolant inside the CRDM, the air temperature of the environment where the reactor top is located, the heat flux density of the thermal insulation layer of the reactor pressure vessel top cover, the wind speed and wind temperature of the auxiliary ventilation.

[0110] In this embodiment, the boundary parameters refer to those factors that directly affect the working conditions of the CRDM, and they are key variables that must be considered during design and analysis.

[0111] Considering the specific conditions around the CRDM in the actual operation environment (such as coolant temperature and pressure, reactor top air temperature, etc.), determine the boundary parameters to ensure the authenticity and reliability of the analysis results.

[0112] The design and operation of nuclear power plants rely on a series of precisely defined parameters, which ensure the safety and efficiency of the facilities. For example, the environmental temperature at the reactor top is usually controlled between 30 and 40 degrees Celsius. For conservative reasons, the highest value of 40 degrees Celsius is used as a reference during design.

[0113] For the CRDM, the working pressure of its internal coolant is approximately 15.5 MPa, which is a typical pressure level of the primary loop system of a general pressurized water reactor nuclear power plant. The temperature of the coolant matches the temperature at the outlet of the reactor pressure vessel, and the inlet and outlet temperatures of the RPV coolant are usually fixed. The inlet temperature range is approximately between 285 and 295 degrees Celsius, and the outlet temperature is about 320 to 335 degrees Celsius. When calculating, specific parameters are usually determined based on the values corresponding to the optimal estimated flow rate during the normal operation of the power station.

[0114] Regarding the heat flux density of the thermal insulation layer of the reactor pressure vessel top cover, it refers to the heat flux density after the heat dissipated from the RPV top cover reaches the surface of the thermal insulation layer. This value is obtained through detailed analysis or experimental evaluation of the top cover thermal insulation layer during the design stage of the nuclear power plant, aiming to ensure effective thermal management and maintain appropriate operating conditions;

[0115] The wind speed refers to the air flow speed provided by the auxiliary ventilation system to the inside of the reactor containment. Appropriate wind speed is crucial for maintaining the cooling of the reactor and its surrounding equipment, and also affects the heat exchange efficiency between the air and the surface.

[0116] The wind temperature refers to the air temperature provided by the auxiliary ventilation system. Controlling the temperature of the input air can effectively manage the thermal environment inside the reactor containment, avoid adverse effects on equipment performance caused by overheating, and ensure the safety and comfort of the staff.

[0117] These two parameters are part of the boundary conditions, which are used to simulate and analyze the thermal behavior of the reactor under different operating conditions, including normal operating states and assumed accident conditions. For example, in the event of an accident, the correct wind speed and wind temperature can help with effective heat dissipation and prevent material failure or other safety issues caused by excessive temperature. In addition, these parameters also affect the working environment of key components such as CRDM (Control Rod Drive Mechanism), so they must be strictly monitored and maintained within the design range.

[0118] The purpose of the auxiliary ventilation system is to ensure that the temperature of the thermal insulation layer on the top cover of the reactor pressure vessel does not exceed the allowable range due to changes in the external environment or the heat release of the reactor itself, thereby protecting the integrity and function of the thermal insulation layer and ensuring the safe and stable operation of the entire reactor system.

[0119] In short, the above boundary parameters reflect the strict control of key factors such as temperature, pressure, and heat flux density in the design and operation of nuclear power plants to ensure the stable and reliable operation of the system and provide basic data for engineering analysis.

[0120] Through the above steps, the operating parameters of each group of CRDM under the most conservative operating conditions can be accurately determined, thus ensuring the safe and stable operation of the nuclear reactor.

[0121] In this embodiment, in the reactor design, the control rods are divided into different groups according to their functions, such as power regulating rods (A, B, C,...), temperature regulating rods (a, b, c,...), and shutdown rods (X, Y, Z). These control rods are operated according to a specific sequence and logic to meet the requirements of different operating conditions of the reactor. For example, during the power increase process, the power regulating rods may be gradually inserted into or withdrawn from the core in the order of A--A+B--B--B+C--C--C+D..., and the temperature regulating rods can be adjusted in a similar pattern. Therefore, the most conservative operating conditions are those in which the largest number of control rods move simultaneously, such as combinations like A+B+a+b or C+D+c+d.

[0122] Each type of control rod has a set maximum movement speed, which is usually to ensure safety and mechanical integrity. For example, the maximum speed of power control rods is about 72 steps per minute, while that of temperature regulating rods is about 60 steps per minute. After selecting the combination with the largest number of control rods, the maximum speeds of these control rod types should be considered as the most conservative conditions in terms of speed.

[0123] Considering the heat dissipation efficiency, the positions closer to the reactor center are more difficult to dissipate heat, which may lead to higher temperatures. Therefore, in the case of the same number and speed, the combination of control rods closer to the center will be regarded as a more conservative operating condition. For example, as Figure 9 shown, if the numbers and speeds of A+B+a+b and C+D+c+d are the same, but A+B+a+b is closer to the center, it is considered a more conservative operating condition.

[0124] For cases that are difficult to directly judge by the above criteria, such as a group that is closer to the center but has fewer control rods than another group, computational fluid dynamics analysis can be used for evaluation. Specifically, the flow fields under different operating conditions can be simulated, and key parameters such as CRDM coil temperature and reactor top temperature can be compared to determine which operating condition is the most conservative. If there are multiple similar and indistinguishable operating conditions, the CFD method can also be used for further screening.

[0125] Step S110 of this embodiment to determine the most conservative CRDM motion state needs to comprehensively consider the number, speed and relative position of the control rods. First, identify the combination with the largest number of control rods moving simultaneously, then apply the maximum allowable speeds of these control rods, and finally select the most conservative state according to their positions relative to the reactor center. For any uncertain or controversial cases, auxiliary decision-making is carried out with the help of tools such as CFD to ensure that the selected operating condition can represent the most severe operating conditions, thus ensuring the safe operation of the reactor.

[0126] S120. Based on each set of CRDM operation-related parameters, establish a prototype reactor top CFD model, conduct an internal flow field analysis of the reactor, and extract key parameters to obtain a first analysis result, where the first analysis result includes key parameters in the flow field and temperature field of the prototype reactor top.

[0127] In this embodiment, a detailed three-dimensional flow field model that conforms to the actual reactor top structure is constructed according to each set of operation-related parameters of the control rod drive mechanism (CRDM) determined previously. This model will be used for computational fluid dynamics (CFD) analysis to evaluate and optimize the flow field and temperature field characteristics inside the reactor. The ultimate goal is to obtain a series of key parameters as the first analysis result to provide a reference for subsequent tests.

[0128] In one embodiment, referring to Figure 5 , step S120 described above may include steps S121 to S125.

[0129] S121. Build a prototype reactor top CFD model consistent with the actual reactor top structure based on the relevant parameters of each set of CRDM operations.

[0130] In this embodiment, a professional modeling software (such as SolidWorks) is used to create a three-dimensional geometric model including CRDM components, top cover components, reactor top structure components (such as lifting tool components, seismic support devices, cable trays, and cable bridge components, etc.), and boundary wall surfaces (such as reactor pit wall surfaces, top cover insulation layers, etc.). Specifically, for the CRDM components, the model needs to include its internal coolant (the temperature, pressure, and flow state can be set as needed), pressure-resistant shell components, hook claw components, coil components (the heating power is set according to the coil heating power in the relevant parameters of each set of CRDM operations), and rod position detector components (including internal coils that may generate heat). To simplify the calculation and maintain the accuracy, the structural details with less influence on the flow field and temperature field can be appropriately simplified.

[0131] Specifically, when it comes to the complex structure of the actual reactor top, there are numerous small parts (such as bolts and nuts) and discontinuities (such as sharp corners, depressions, protrusions, and stepped surfaces). If these details are directly simulated without treatment, it will require extremely fine mesh division, which not only greatly increases the demand for computing resources and calculation time but may also lead to numerical instability and calculation divergence problems due to excessive changes in the mesh size. Therefore, at the initial stage of establishing the three-dimensional model, simplification measures are taken for these elements with less influence on the flow field and temperature field (such as small bolts and nuts, sharp corners, depressions, protrusions, and stepped surfaces) and structural components far from the area of concern. Specifically, small fasteners can be removed, sharp edges can be smoothed, depressions can be filled, protrusions and stepped surfaces can be flattened to make the overall structure smoother.

[0132] Through such simplification processing, not only can the complexity of mesh division and the required number of meshes be reduced, but also the efficiency of subsequent computational fluid dynamics analysis can be significantly improved, and the calculation time can be reduced. CFD analysis is usually performed using professional software such as ANSYS CFX, ANSYS FLUENT, or STAR CCM+. When setting the CFD analysis parameters, the heating positions and coil powers of each group of CRDMs follow the boundary parameters specified in the relevant parameters of each set of CRDM operations, while other conditions such as the pressure and temperature of the coolant, the ambient air temperature, and the insulation layer power follow the settings of the relevant parameters of each set of CRDM operations.

[0133] In summary, by reasonably simplifying the structural details in the model that have little impact on the results, we can improve the computational efficiency and ensure numerical stability without affecting the analysis accuracy.

[0134] S122, meshing the prototype stack top CFD model to obtain a mesh model of the prototype stack top.

[0135] In this embodiment, the mesh model of the prototype reactor top refers to a discretized representation created for numerical simulation of a physical object in computer-aided engineering (CAE) analysis. The prototype reactor top refers to the actual or designed model of the reactor top structure, and the mesh model refers to the result of mathematical abstraction and discretization of the prototype reactor top by computational fluid dynamics (CFD) software such as ICEM CFD or HyperMesh.

[0136] For example, discretization is performed in ICEM CFD or HyperMesh. This step involves decomposing the continuous geometric shape into a large number of discrete small units - meshes. For areas with complex structures or high requirements for result accuracy, finer mesh division will be used to ensure the accuracy of subsequent simulations.

[0137] In this process, continuous geometric shapes are broken down into many small, simple geometric units (also called elements or cells), which can be tetrahedrons, hexahedrons, prisms or other types of polyhedral shapes. Each unit is defined by nodes, which are the intersections between units and where the solver calculates physical quantities (such as pressure, velocity, temperature, etc.).

[0138] For complex structures like the reactor top, especially those with irregular shapes or strict requirements on thermodynamic performance, finer meshes are usually used in these areas. This practice can better capture the details in fluid flow and heat transfer behavior and improve the accuracy of simulation results. At the same time, coarser meshes are used in less important areas to reduce the demand for computing resources and shorten calculation time.

[0139] S123. Determine calculation parameters.

[0140] In this embodiment, the calculation parameters include working fluid properties, calculation models, boundary conditions and solution settings, the working fluid properties include material, density, viscosity, thermal conductivity and specific heat capacity; the boundary conditions include ambient temperature, ambient pressure, coil heating power, CRDM simulation body heating power, top cover insulation layer heating power, auxiliary vent inlet temperature and inlet flow rate, coolant inlet temperature and pressure; the calculation model includes turbulence model, buoyancy model, thermal radiation model; the solution settings include difference format, iteration steps, time scale, convergence criterion.

[0141] Specifically, when preparing for CFD analysis, a series of calculation parameters must be defined first. These parameters determine the authenticity and accuracy of the simulation. Specifically:

[0142] The properties of the working fluid refer to the physical properties of the medium (such as coolant, air, and metal components) participating in the flow or heat exchange, such as material, density, viscosity, thermal conductivity, and specific heat capacity.

[0143] The calculation model refers to the mathematical model used to describe the flow characteristics, such as the turbulence model (used to handle complex turbulence phenomena), the buoyancy model (considering the influence of density changes), the thermal radiation model (a mathematical or physical model used to describe and calculate the process of heat transfer between objects through electromagnetic waves (especially infrared rays)), etc. When selecting a calculation model, it is usually determined based on past experience and specific application scenarios. For example, when dealing with fully developed turbulent flow with a relatively high flow rate, the k-epsilon turbulence model is preferably used; for natural convection phenomena, the SST (Shear Stress Transport) turbulence model is more preferred for simulation. When density changes are involved, the buoyancy model is a necessary choice.

[0144] Boundary conditions are the physical conditions applied to the model boundaries, such as ambient temperature, ambient pressure, coil heating power, CRDM simulator heating power, top cover insulation heating power, auxiliary vent inlet temperature and inlet flow rate, coolant inlet temperature and pressure, etc.

[0145] The solution settings include the difference scheme (determining the method of converting continuous differential equations into algebraic equations that can be numerically solved on a computer), the number of iteration steps (i.e., the number of loops in the solution process), the time scale (i.e., the total time and single-step calculation time used to control the calculation in unsteady-state calculations), and the convergence criterion (the criterion for determining when to stop the iteration, such as the residuals of the continuity equation, momentum equation, and energy equation being less than a preset threshold).

[0146] Regarding the selection of the number of iteration steps, the initial setting is usually based on empirical judgment, such as initially setting it to 5000 steps. Subsequently, by monitoring the changes in the key parameters of the three basic equations, namely the continuity equation, momentum equation, and energy equation, during the calculation process, as well as the data trends of the preset monitoring points, the convergence is evaluated. If it is found that the change amplitude of these parameters is extremely small, or the preset convergence criterion has been met (for example, the difference between two adjacent iterations does not exceed 10 -4 ), it can be considered that the current number of iteration steps is sufficient to achieve convergence. Conversely, if the desired convergence effect is not achieved, the number of iteration steps needs to be adjusted, the mesh division optimized, or the choice of the calculation model reconsidered to promote faster and more stable convergence results.

[0147] In summary, the selection of the computational model and the control of the iterative process are a dynamically adjusted process, which requires flexible response according to the actual calculation results to ensure the final accurate and reliable numerical solution.

[0148] S124. Perform an internal reactor flow field analysis on the grid model of the prototype reactor head according to the calculation parameters to obtain the flow field and temperature field of the prototype reactor head.

[0149] Using the selected CFD analysis software (such as ANSYS CFX, ANSYS FLUENT, STAR CCM+, etc.), import the meshed file, and set the aforementioned working fluid properties, boundary conditions, computational model, and solution settings. Subsequently, by solving the continuity equation, momentum equation, and energy equation, numerically simulate the flow field and temperature field in each grid cell. This process aims to accurately reproduce the fluid flow and heat transfer inside the reactor, thereby obtaining the flow field and temperature field distributions of the prototype reactor head.

[0150] S125. Extract the key parameters of the flow field and temperature field of the prototype reactor head to obtain the first analysis result.

[0151] In this embodiment, the key parameters include the highest temperature of the CRDM yoke coil, the highest temperature of the rod position detector coil, and the highest air temperature above the CRDM top cable outlet problem.

[0152] Specifically, a series of key parameters are extracted from the flow field and temperature field of the prototype reactor head as the first analysis result, especially focusing on those indicators directly related to the safety and performance of the equipment. For example, in this embodiment, the highest temperature of the CRDM yoke coil, the highest temperature of the rod position detector coil, and the highest air temperature above the CRDM top cable outlet position are extracted. These data not only help to verify the effectiveness of the design but also provide a scientific basis for further engineering decisions.

[0153] Generally speaking, the entire CFD analysis process is as follows:

[0154] Use 3D modeling software such as SolidWorks to construct the geometric model of the computational object. This includes the fluid region and the solid structure part that interacts with it. The geometric model of the object refers to the CFD model of the prototype reactor head.

[0155] Next, import the above-established 3D model into a dedicated grid generation tool, such as ICEM CFD or HyperMesh, for discretization processing. This step involves decomposing the continuous geometric shape into a large number of discrete small cells - grids. For regions with complex structures or high requirements for result accuracy, finer grid divisions will be adopted to ensure the accuracy of subsequent simulations.

[0156] Then, load the previously prepared mesh file into a professional CFD solver such as ANSYS CFX, ANSYS Fluent, or STAR-CCM+ and set a series of necessary physical conditions. These conditions cover working fluid properties (such as the materials, density, viscosity, thermal conductivity, and specific heat capacity of coolants, air, and metal materials), boundary conditions (such as inlet temperature, flow rate, outlet pressure, ambient temperature, and heating power), and the selection of appropriate physical models (such as the choice of turbulence model, whether to consider the influence of gravity, whether there are heat exchange or radiation effects, and steady-state or transient analysis). After setting the iteration parameters, the solver iteratively solves the basic control equations (continuity equation, momentum equation, and energy equation) for each grid, and finally obtains the distribution of physical quantities (such as temperature, pressure, and velocity fields) at each grid point.

[0157] Finally, use the data analysis function provided by the solver or a third-party visualization tool to analyze and display the calculation results. This includes extracting the temperature or velocity distribution diagrams of specific cross-sections, identifying the maximum temperature or highest pressure points of key components, etc., to facilitate engineers to intuitively understand and interpret the simulation data.

[0158] It should be noted that the CFD model of the prototype reactor top uses all real CRDM prototypes, that is, the structures in the model are constructed 1:1 according to the real CRDM prototypes.

[0159] S130. Establish an initial test reactor top CFD model based on each set of CRDM operation-related parameters, where the initial test reactor top CFD model includes a real CRDM prototype and a CRDM simulation body.

[0160] In this embodiment, a real CRDM prototype is arranged at the central position of the initial test reactor top CFD model, and a CRDM simulation body is used at other positions; and the number of real CRDM prototypes is no more than 9 groups.

[0161] Specifically, one or more groups (which can be scaled up to 5 or 9 groups based on the budget and research requirements) of real CRDM prototypes are placed at the central position of the CFD model of the initial test reactor top. For non-central positions, simulated CRDM bodies are used. These bodies have the same outer shape as the real CRDM prototypes, but surface heat flux density or thin-layer heating is used to represent internal heat generation, and different heating powers can be set for different regions. All structural components at the top of the prototype reactor are replicated as much as possible, especially those key components that may affect the flow field and temperature distribution around the CRDM, such as seismic plates, cable trays and their support structures, lifting devices, shroud or truss (if any), insulation layer, and pool wall, etc. Components that have a significant impact on ventilation and heat dissipation are retained, such as the simulated seismic plates and insulation layers, while components that have a relatively small impact on ventilation and heat dissipation, such as lifting devices and cable brackets, can be selectively ignored to simplify the modeling process and reduce the number of grids.

[0162] When there is a shroud, it dominates the ventilation path, so the influence of the pool wall becomes secondary and can be ignored. However, in the absence of a shroud or special seismic structure, the role of the pool wall in ventilation and heat dissipation cannot be ignored and should be retained. The principle for deciding whether to retain a certain structure is to evaluate whether its influence on the temperature of key parts exceeds 5°C. If it is difficult to judge, it can be determined through sensitivity analysis, that is, by comparing the results with and without a specific structure.

[0163] To ensure the simulation accuracy, each boundary condition needs to be set according to the method described in the previous steps. This includes but is not limited to:

[0164] The real CRDM prototypes at the central position set the power at different step speeds according to the specified method, specifically set according to the coil heating power of each group of CRDMs.

[0165] Parameters such as the coolant pressure and temperature inside the CRDM prototypes, the ambient air temperature, and the insulation layer power are also configured according to the aforementioned boundary parameters.

[0166] Select a suitable calculation model, such as a steady-state or transient analysis mode, and a suitable turbulence model. This content can be set according to the corresponding content involved in the CFD analysis in step S120.

[0167] Define the physical properties, such as density, thermal conductivity, and viscosity (for fluids), according to the specific conditions of the working medium (such as temperature and pressure) for all materials involved, including air, coolant, coils, and other CRDM components.

[0168] In summary, by carefully designing and finely adjusting these settings, a CFD model that accurately reflects the actual operating conditions can be constructed, thus supporting an in-depth understanding of the flow field characteristics at the test reactor top.

[0169] S140. Adjust the heating power and the number of heating elements of the CRDM simulator in the initial test reactor top CFD model until the difference between the second analysis result obtained from the internal reactor flow field analysis of the adjusted initial test reactor top CFD model and the first analysis result meets a preset first condition, so as to obtain a target test reactor top three-dimensional flow field model.

[0170] In this embodiment, the target test reactor top three-dimensional flow field model refers to a CFD model that can accurately simulate the flow field and temperature field characteristics of the actual reactor top after a series of adjustments. This model not only needs to reproduce the geometric structure of the prototype reactor top, but also needs to correctly set the physical properties, boundary conditions, and heating characteristics of each component, especially the heating power distribution of the CRDM simulator, in order to obtain thermohydraulic characteristics consistent with the operating state of the prototype reactor.

[0171] In this process, the goal is to continuously adjust the heating power and the number of heating elements of the CRDM (control rod drive mechanism) simulator in the initially established test reactor top three-dimensional flow field model, so that the result obtained from the internal reactor flow field analysis of this model - that is, the second analysis result, is as close as possible to the first analysis result of the actual prototype reactor top under the same conditions. This process aims to optimize the model to ensure that it can accurately reflect the thermohydraulic behavior of the real reactor top.

[0172] In one embodiment, please refer to Figure 6 , the above step S140 may include steps S141 to S144.

[0173] S141. Adjust the heating power and the number of heating elements of the CRDM simulator in the initial test reactor top CFD model to obtain an adjusted initial test reactor top CFD model.

[0174] In this embodiment, at the beginning, based on previous research or experience, the heating power and the number of heating elements of the CRDM simulator are initially set. For example, 8 groups of full-heating simulators are arranged around a real CRDM prototype, and it is particularly emphasized that the heating plates at the yoke position are applied with higher power, and all the heating elements in the top rod position detector area are heated. Gradually adjust the heating power at different positions as needed, such as being set in segments to 1 KW (rod position detector position), 2 KW (yoke position), 1 KW (position below the yoke), and try different heating ranges (only the coil position is heated, or both the coil position and the rod position detector position are heated, or the entire CRDM model body is heated).

[0175] S142. Conduct an internal reactor flow field analysis on the adjusted initial test reactor top CFD model to obtain a second analysis result.

[0176] In this embodiment, the second analysis result refers to a data set obtained after performing a flow field calculation analysis on the adjusted initial test reactor top CFD model. These data include, but are not limited to, key parameters such as flow field velocity distribution, pressure distribution, and temperature distribution. Specifically, it refers to the flow field and temperature field of the test reactor top simulated by CFD software, especially the highest temperature of the CRDM yoke coil, the highest air temperature above the top cable outlet position, and the position range of the high-temperature area at the reactor top.

[0177] In one embodiment, step S142 described above may include steps S1421 to S1423.

[0178] S1421. Perform mesh generation on the adjusted initial test reactor top CFD model to obtain a mesh model of the adjusted initial test reactor top;

[0179] S1422. Perform an internal reactor flow field analysis on the mesh model of the adjusted initial test reactor top according to the calculation parameters to obtain the flow field and temperature field of the test reactor top.

[0180] S1423. Extract the key parameters of the flow field and temperature field of the test reactor top to obtain the second analysis result;

[0181] Wherein, when the gap between the second analysis result obtained by performing an internal reactor flow field analysis on the adjusted initial test reactor top CFD model and the first analysis result meets a preset first condition, the mesh model of the adjusted initial test reactor top is the mesh model of the target test reactor top.

[0182] In this embodiment, an internal reactor flow field analysis is performed on the adjusted model using a CFD tool. In this step, according to the defined calculation parameters, such as the selection of turbulence model and the accuracy of mesh generation, a detailed numerical simulation is performed on the mesh model of the adjusted initial test reactor top to obtain the flow field and temperature field information of the test reactor top. Then, key parameters are extracted from the simulation results to form the second analysis result. Steps S1421 to S1422 are the same as steps S123 to S124 and will not be elaborated here.

[0183] S143. Determine whether the gap between the second analysis result and the first analysis result meets a preset first condition.

[0184] In this embodiment, the preset first condition includes that the difference in the highest temperature of the CRDM yoke coil does not exceed 10°C, the highest air temperature above the CRDM top cable outlet position does not exceed 10°C, and the difference in the position range above the high-temperature area at the reactor top does not exceed 15%.

[0185] Specifically, compare the second analysis result with the previously obtained first analysis result to determine whether the difference between the two meets a preset first condition. The conditions here include but are not limited to that the maximum temperature difference of the CRDM yoke coil does not exceed 10°C, the maximum air temperature above the cable outlet position at the top of the CRDM does not exceed 10°C, and the position range above the high-temperature area at the top of the reactor does not exceed 15%. If the gap meets these conditions, it indicates that the model is already close enough to the actual situation; otherwise, it is necessary to return to step S141 to continue the adjustment.

[0186] S144. If the gap between the second analysis result and the first analysis result meets the preset first condition, determine the adjusted initial test reactor top CFD model as the target test reactor top three-dimensional flow field model;

[0187] If the gap between the second analysis result and the first analysis result does not meet the preset first condition, execute step S141.

[0188] Once it is confirmed that the gap between the second analysis result and the first analysis result meets the preset first condition, it can be considered that the optimal solution has been found, and the model at this time is the target test reactor top three-dimensional flow field model. Conversely, if the conditions are not met, it is necessary to re-evaluate and adjust the model settings until the expected consistency is achieved.

[0189] To sum up, this series of operations is to ensure that the three-dimensional flow field model created through numerical simulation can accurately reflect the complex thermal-hydraulic phenomena at the top of the actual reactor.

[0190] In this embodiment, what is the same between the prototype reactor top CFD model and the test reactor top CFD model is the outer contour of the CRDM prototype or simulation body. Specifically, the internal structures of the prototype and the simulation body are different, and the heating methods are also different; the boundary conditions, specifically, the environmental temperature, the pressure and inlet temperature of the internal coolant at the coolant inlet, the air temperature of the environment where the reactor top is located, the heat flux density of the thermal insulation layer on the reactor pressure vessel head; the turbulence model, the buoyancy model, the thermal radiation model (the thermal radiation can be not set), and the solution settings.

[0191] What is different between the prototype reactor top CFD model and the test reactor top CFD model is: the mesh model, because the internal structures are different, the meshes are also different; the heating method, the prototype is that the internal coil generates heat and conducts it to the outside, and the simulation body is heated by surface heating wires or heating plates; the number of CRDM heating simulation bodies, which is not available in the prototype reactor top CFD model; the power of the CRDM heating simulation body, which is not available in the prototype reactor top CFD model.

[0192] S150. Conduct a physical test on the target test reactor top three-dimensional flow field model to obtain test results, where the test results include the flow field and temperature field at the top of the reactor under various working conditions.

[0193] In this embodiment, the purpose of this step is to convert the target test reactor top three-dimensional flow field model previously optimized by numerical simulation into an actual physical experimental device, and conduct a series of tests on it to verify the accuracy and reliability of the model. Specifically, this includes building a physical test device, arranging measurement points, implementing heating and motion control, and conducting sensitivity parameter tests. Ultimately, through these physical tests, actual data on the flow field and temperature field of the reactor top under different working conditions can be obtained, providing an important reference for reactor design.

[0194] In one embodiment, see Figure 7 , the above-mentioned step S150 may include steps S151 to S154.

[0195] S151, constructing a physical pile top according to the target test pile top three-dimensional flow field.

[0196] In this embodiment, a real test structure is built according to the design of the target test reactor top three-dimensional flow field model. This test structure should include a group of CRDM real prototypes located in the middle, CRDM simulation bodies surrounding the middle prototype (the number is the total number of CRDMs minus 1), and structural components that may affect the flow field and temperature in the CRDM component area, such as top seismic plate assemblies, cable brackets and cable bracket assemblies, hanger assemblies, reactor top shrouds or trusses (if any), top cover insulation layer simulation parts, reactor cavity pool wall simulation parts, etc. Figures 10 to 12 As shown, ensure that all components are arranged in the same spacing and arrangement as the actual stack top, and the size and position maintain a 1:1 ratio. In particular, the CRDM simulation body should have the same appearance and structural dimensions as the real CRDM prototype, and be able to arrange heating plates or heating wires in different areas to apply different heating powers. Figure 10 The mark 1 is the insulation layer of the reactor pressure vessel (RPV) top cover; 2 is the control rod drive mechanism (CRDM); 3 is the lower suspension rod; 4 is the seismic ring; 5 is the cable bracket; 6 is the cable bridge (because it is far away from the CRDM heating position and does not generate heat itself, it is not considered in general tests); Figure 11 The mark 1 inside is the reactor pressure vessel (RPV) top cover insulation layer simulation part; 2 is the control rod drive mechanism (CRDM) simulation part; 3 is the lower suspension rod simulation part; 4 is the seismic ring simulation part; 5 is the cable bracket simulation part; 6 is the cable bridge simulation part (because it is far away from the CRDM heating position and does not generate heat itself, it is generally not considered in the test); 7 is the reactor cavity pool wall simulation part; 8 is the auxiliary ventilation vents.

[0197] S152, arranging temperature measuring points and speed measuring points at key locations in the physical pile top.

[0198] In this embodiment, the key parts in the entity reactor top include the inside of each coil of the CRDM real prototype, the surfaces at different heights of the CRDM real prototype, the internal coolant area of the CRDM real prototype, the cable positions at different heights above the top seismic plate, the surfaces at different heights of the CRDM mock-up, the gap positions at different heights between the CRDM real prototype and the CRDM mock-up, and the auxiliary ventilation air inlets.

[0199] Specifically, in order to accurately measure the temperature and velocity changes of each key part during the test, temperature measurement points and velocity measurement points are reasonably arranged on each test piece. The positions that are mainly considered include the internal coils of the CRDM real prototype, the surfaces at different heights, the internal coolant area, the cable positions at different heights above the top seismic plate, the surfaces at different heights of the CRDM mock-up, the gap positions at different heights between the CRDM real prototype and the CRDM mock-up, the auxiliary ventilation air inlets, etc. For the positions that are particularly concerned, for example, several temperature measurement points of the coils can be set at different angles to determine whether the maximum tolerable temperature of the coils is exceeded; more temperature measurement points can be added around the cables at the cable positions on the reactor top to determine whether the maximum tolerable temperature of the cables is exceeded; several heat flux densities at different heights from top to bottom of the CRDM can be placed to calculate the heat dissipation of the entire CRDM; several coolant temperature measurement points are also set at the top and bottom inside the CRDM to determine whether the coolant temperature exceeds the saturation temperature.

[0200] S153. Arrange heat flux sensors on the surfaces at different heights of the CRDM real prototype in the entity reactor top.

[0201] In this embodiment, in order to measure the heat flux density on the surfaces at different heights of the CRDM real prototype, heat flux sensors are arranged at these positions. This is to more accurately understand the heat distribution of the CRDM at different heights, which helps to analyze the heat dissipation performance of the CRDM subsequently, and further determine the appropriate power configuration of the reactor cavity temperature control air conditioner.

[0202] S154. Conduct tests according to the heating power of the target test reactor top three-dimensional flow field model, and perform sensitivity analysis on different parameters to obtain test results.

[0203] Based on the heating power setting defined in the target test reactor top three-dimensional flow field model, heat the entity test device. At the same time, let the CRDM real prototype in the middle position move at different preset step speeds (for example: stay in the state, 48 steps / minute, 60 steps / minute, 72 steps / minute). On this basis, repeat the above process, and conduct sensitivity parameter tests for different parameters (such as different coolant temperatures, different movement strokes, different auxiliary ventilation heights, different auxiliary ventilation wind speeds, different auxiliary ventilation temperatures, etc.). After each test, collect and record the data of each measurement point to form test results.

[0204] The test results refer to a set of data on the flow field and temperature field at the reactor top obtained through the above-mentioned physical tests. These data not only reflect the fluid flow characteristics and temperature distribution under specific working conditions, but also reveal the influence laws of different parameters on the reactor top environment. By analyzing these data, the accuracy of the three-dimensional flow field model of the target test reactor top can be evaluated, and it can be confirmed whether it can effectively predict the complex thermal-hydraulic phenomena at the actual reactor top. In addition, the results of the sensitivity analysis can also help engineers understand which factors most significantly affect the flow field and temperature field, thereby guiding further design optimization and technical improvement work. In short, these test results play a crucial role in ensuring the safe operation of nuclear reactors and improving their efficiency.

[0205] S160. Determine whether it is necessary to adjust the parameters involved in the three-dimensional flow field model of the target test reactor top according to the test results and the second analysis result.

[0206] In this embodiment, when the gap between the test results and the second analysis result does not meet the requirements, it is necessary to adjust the parameters involved in the three-dimensional flow field model of the target test reactor top.

[0207] It should be noted that this requirement can be the same as the first condition, or it can be required that the test results are the same as the analysis results.

[0208] S170. When it is necessary to adjust the parameters involved in the three-dimensional flow field model of the target test reactor top, adjust the parameters involved in the three-dimensional flow field model of the target test reactor top to update the three-dimensional flow field model of the target test reactor top, and verify it using the CFD model of the prototype reactor top until the gaps among the updated first analysis result, the updated second analysis result, and the test results meet the requirements.

[0209] This step aims to ensure the consistency between the data obtained through numerical simulation and physical experiments. By continuously iteratively optimizing the parameter settings of CFD (Computational Fluid Dynamics), the simulation results can be made as close as possible to the actual test results. The ultimate goal is to establish a reliable CFD model of the prototype reactor top, which can not only be used for analysis under the current working conditions, but also quickly respond when facing new working conditions or structural changes without repeating time-consuming and costly physical tests.

[0210] In one embodiment, please refer to Figure 8 , the above step S170 may include steps S171 to S176.

[0211] S171. When it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model, adjust the parameters involved in the target test reactor top three-dimensional flow field model to update the target test reactor top three-dimensional flow field model.

[0212] In this embodiment, the parameters involved in the target test reactor top three-dimensional flow field model include the calculation parameters and the heating power.

[0213] When it is found that there is a deviation between the second analysis result and the physical test result, first adjust some key parameters in the target test reactor top three-dimensional flow field model. These parameters include calculation parameters such as the selection of the turbulence model, the setting of the buoyancy model, the number of iteration steps, and the working fluid physical properties. The purpose of the adjustment is to improve the accuracy of the model so that it can more accurately reflect the physical phenomena inside the actual reactor. For example, if it is found that the error between the velocity field predicted by the model and the actual measured value is large, the turbulence model can be changed or the number of iterations can be increased to improve the matching degree.

[0214] In this embodiment, the calculation parameters are adjusted first, and then the heating power is adjusted. It should be noted that if the heating power is adjusted, the physical test in step S150 needs to be re-executed to update the test results, and the updated test results are used to determine again whether it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model. Continuously iterate the judgment and adjustment until the gap among the updated first analysis result, the updated second analysis result, and the test result meets the requirements.

[0215] S172. Perform an internal flow field analysis of the reactor on the updated target test reactor top three-dimensional flow field model to update the second analysis result.

[0216] In this embodiment, the CFD analysis is re-run with the updated parameter settings to obtain the new flow field and temperature field distribution, that is, the updated second analysis result. This step is a key link to verify the effect of parameter adjustment, and it will directly determine whether further adjustment of the model parameters is required in the future.

[0217] S173. Determine whether the gap between the updated second analysis result and the test result meets the requirements.

[0218] In this embodiment, the updated second analysis result is compared with the real data measured in the physical test. The requirement here is usually to control the error between the two within an acceptable range, such as the error being less than 5%. If this condition is met, it means that the current parameter settings are accurate enough; if not, it is necessary to return to S171 to continue adjusting the parameters until the optimal solution is found.

[0219] S174. If the gap between the updated second analysis result and the test result meets the requirements, the parameters involved in the adjusted three-dimensional flow field model of the target test reactor top are input into the prototype reactor top CFD model to update the prototype reactor top CFD model, and the internal flow field analysis of the reactor is carried out again on the updated prototype reactor top CFD model to update the first analysis result.

[0220] In this embodiment, once it is confirmed that the updated parameters can make the simulation result match the test result, these parameters can be applied to the prototype reactor top CFD model. The prototype model represents the complete and non-simplified reactor top environment, so analyzing it can obtain a more comprehensive dataset, including those positions that are difficult to measure in the test. The first analysis result generated in this step not only includes the data around the CRDM prototype, but also includes the flow field and temperature field information within the entire reactor top area.

[0221] In addition, the parameters in the optimized three-dimensional flow field model of the target test reactor top are applied to the prototype reactor top CFD model, and the internal flow field analysis of the reactor is carried out again. This step has two purposes:

[0222] Verify the effectiveness of the parameters: Confirm that these parameters can not only improve the simulation accuracy in the target test model under simplified or specific conditions, but also produce consistent and accurate results in a more complex and complete prototype model. This step helps to ensure the robustness and generality of the model parameters, that is, these parameters can provide reliable prediction performance whether in the laboratory environment or the actual application environment.

[0223] Ensure consistency: By analyzing the prototype model, the position data that cannot be directly measured in the experiment can be extracted, so as to further verify the consistency of the entire system behavior. Since the prototype model represents a more realistic engineering scenario, its analysis result can be used as the final judgment basis to measure the ability of the CFD model to reproduce the real world. If the analysis result of the prototype model is in good agreement with the test result and the updated second analysis result, it indicates that the model has a high credibility and can be used to guide the subsequent design and decision-making process.

[0224] S175. Judge whether the gap between the updated first analysis result and the updated second analysis result meets the preset first condition;

[0225] If the gap between the updated first analysis result and the updated second analysis result meets the preset first condition, execute the step S180;

[0226] If the gap between the updated second analysis result and the test result does not meet the requirements, execute the step S171;

[0227] S176. If the difference between the updated first analysis result and the updated second analysis result does not meet the preset first condition, iteratively adjust the heating power and the number of heating elements of the CRDM simulator of the target test reactor top three-dimensional flow field model, perform an internal reactor flow field analysis to update the second analysis result until the difference between the updated second analysis result and the first analysis result meets the set first condition; conduct the physical test again to update the test result, and iteratively adjust the heating power and the number of heating elements of the CRDM simulator of the target test reactor top three-dimensional flow field model until the differences among the updated test result, the updated second analysis result, and the first analysis result meet the requirements.

[0228] In this embodiment, the parameters involved in the target test reactor top three-dimensional flow field model include the grid model of the target test reactor top, the calculation model, and the solution settings.

[0229] Compare the first analysis result of the prototype model with the second analysis result of the target test model to check whether the difference between the two is within the preset threshold. If it meets the requirements, it is considered that the entire model calibration process is completed and the loop can be ended; otherwise, it is necessary to return to S171 to readjust the parameters. In addition, if it is found in S173 that the difference between the updated second analysis result and the test result does not meet the requirements, it should also immediately return to S171 for a new round of parameter adjustment. Similarly, if the difference between the updated first analysis result and the second analysis result does not meet the preset first condition, the number of heating elements and the heating power are also iteratively adjusted.

[0230] Specifically, after the test is completed, if it is found that there is a difference between the test result and the second analysis result, that is, the computational fluid dynamics result of the CFD model for the test reactor top, then it is necessary to adjust the parameters that only exist in the numerical simulation but not in the physical test. These adjustable factors include the settings of the grid model, the turbulence model, the buoyancy model, and the thermal radiation model (the thermal radiation model can be selected not to be enabled), as well as the iterative solution conditions. Since these factors do not exist in the actual physical test and are artificially set in the simulation process, they can be adjusted to improve the consistency.

[0231] For the parameters that exist in both the test and the CFD simulation, such as the boundary conditions, the working fluid properties, and the heating power, they should be kept consistent and not changed to ensure the authenticity and reliability of the simulation.

[0232] Once the consistency between the test results and the second analysis results is achieved, the next step should be to apply all the parameters adjusted in the CFD model analysis of the test reactor top to the CFD model of the prototype reactor top and check whether the adjusted first analysis results still match the second analysis results. If they are inconsistent, the number and power settings of the heating elements in the CFD model of the test reactor top need to be adjusted until the first analysis results tend to be consistent with the second analysis results.

[0233] If the above adjustments need to be made to the CFD model of the test reactor top, the same adjustments should also be implemented in the physical test, that is, adjusting the number and power of the heating elements and verifying the consistency between the physical test results and the second analysis results again. Usually, the difference between the two is already very small at this stage. If there are still any significant differences, the process should return to step three for iterative adjustment until it is ensured that the first analysis results, the second analysis results, and the physical test results are consistent.

[0234] In other words, the whole process is a process of repeated calibration. By continuously comparing and adjusting the parameters between the simulation and the test, it is ensured that the final simulation results can accurately reflect the real-world test situation.

[0235] The above process is not only to ensure the accuracy of the CFD model, but also to build a flexible and efficient tool, enabling engineers to quickly evaluate the impact of new working conditions or structural changes without relying on expensive and complex physical tests. For example, when changing from a conservative working condition (such as A+B+a+b) to other possible combinations (such as C+D+c+d, A+b, E+f, etc.), only the working condition input parameters in the CFD analysis need to be simply modified to quickly obtain new calculation results. This method greatly improves work efficiency, reduces R & D costs, and at the same time ensures the safety and reliability of the design. In this way, engineers can identify potential problems at an early stage and make timely adjustments, thus accelerating the pace of innovation and technological progress.

[0236] S180. Determine the final CFD model of the prototype reactor top according to the parameters of the updated three-dimensional flow field model of the target test reactor top.

[0237] The CFD model of the prototype reactor top established after completing the above steps is not only applicable to the specific working conditions of the current research, but can also easily adapt to various new working conditions or structural changes that may occur in the future. For example, when facing new operating conditions (C+D+c+d), different combination methods (A+b, E+f), or any other factors that may affect the flow field, there is no need to conduct time-consuming and expensive physical experiments again. Instead, only the input conditions need to be simply modified and the CFD analysis is re-run to obtain the corresponding calculation results, which greatly improves work efficiency and reduces costs.

[0238] For the case where the parameters of the three-dimensional flow field model of the target test reactor top do not need to be adjusted, the prototype reactor top CFD model determined in step S120 is used as the final prototype reactor top CFD model.

[0239] In summary, the method of this embodiment uses a small number (ideally 1 set) of real prototypes of control rod drive mechanisms (CRDMs) and several simulation bodies to replace the complete prototype reactor top structure, achieving accurate simulation of the flow field and temperature field in the reactor top region. This method not only significantly reduces the economic input and time cost required for the test, but also significantly improves the safety and reliability of the test by using only a single pressure vessel (i.e., the CRDM pressure shell).

[0240] Before the formal test, by comparing the computational fluid dynamics (CFD) results of the prototype reactor top and the test reactor top, the test scale and the required power parameters can be predicted in advance to ensure the effectiveness of the test design, while reducing the commissioning time and cost. In addition, validating and correcting the models involved in the CFD analysis after the test helps to improve the accuracy of the models, enabling data that is difficult to directly measure in the test to be obtained from the simulation results.

[0241] In this embodiment, the recommended number of real CRDM prototypes is 1 set. Of course, it can also be flexibly adjusted to different numbers such as 5 sets or 9 sets according to the specific project budget.

[0242] The method of this embodiment first selects a conservative operating condition, then analyzes the flow field at the top of the prototype reactor, followed by the analysis of the flow field at the top of the test reactor. Subsequently, formal test activities are carried out, then the study of sensitivity parameters is conducted, and finally the results of the flow field analysis are corrected. This set of methods ensures a complete closed-loop from theory to practice and then to verification. By constructing and running a computational fluid dynamics (CFD) simulation model of the prototype reactor top, the present invention can provide an important preliminary prediction for the results of actual tests, enabling researchers to have a clear expected framework before the tests begin. Before the formal tests, by performing CFD sensitivity analysis on the test reactor top and comparing these analysis results with the CFD analysis data of the prototype reactor top, the scale required for the tests and the power parameters that may be involved can be evaluated in advance, thereby optimizing the test design and improving efficiency. To reduce test costs and enhance safety, a small number (ideally 1 set) of real CRDM prototypes are used, combined with other mock-ups that have the external characteristics of CRDMs and can externally install heating elements to simulate the heat generation behavior, to replace the method of deploying dozens of real CRDM prototypes conventionally required. This method not only saves resources but also ensures the effectiveness and accuracy of the tests. In the test setup, special attention is paid to retaining key structural components that may significantly affect the flow field and temperature distribution in the reactor top area, such as seismic plate components, cable trays and their related components, lifting tool components, cylinders or trusses (if applicable), insulation layer mock-ups, and pool wall mock-ups, etc. This practice ensures that the test environment is as close to the actual situation as possible, enhancing the authenticity of the simulation. Using the actual measurement data collected after the tests to re-verify and make necessary adjustments to the CFD flow field analysis of the target test reactor top three-dimensional flow field model, and then improving the CFD analysis of the prototype reactor top CFD model. Through such an iterative process, the obtained model has wider applicability and higher accuracy. Even in the face of new operating conditions or structural changes, local adjustments can be made to the existing model without restarting large-scale tests, greatly improving the flexibility and economy of research and development work. It improves the accuracy and efficiency of simulating the flow field and temperature field in the reactor top area of nuclear reactors, and also lays a solid foundation for future related research and technological development.

[0243] The above-mentioned high-temperature ventilation test method for the reactor top determines the operating-related parameters by obtaining the conservative operating conditions of each CRDM, and then establishes a three-dimensional flow field model of the prototype reactor top; analyzes the flow field and temperature field of the prototype reactor top through CFD, extracts key parameters, and obtains the first analysis result; establishes an initial CFD model of the test reactor top, including the real prototype of the CRDM and the simulation body; adjusts the heating power and the number of heating elements in the initial test reactor top model to make the second analysis result meet the preset conditions, and obtains the target test reactor top model; conducts physical tests, obtains the test results of the flow field and temperature field, and adjusts the parameters in the target model according to the comparative analysis; through continuous adjustment and verification, finally determines the target test reactor top model that is consistent with the CFD model of the prototype reactor top, ensures the effectiveness of the test and design optimization, realizes the comprehensive simulation of the flow field and temperature field of the reactor top efficiently and at low cost, ensures the test effectiveness and optimizes the design parameters, and can ensure that the flow field and temperature field of the test are close to the prototype reactor top area.

[0244] Those of ordinary skill in the art can realize that the algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0245] In several embodiments provided by the present invention, it should be understood that the disclosed method can be implemented in other ways. For example, the device embodiments described above are merely illustrative.

[0246] The steps in the method embodiments of the present invention can be adjusted, combined, and deleted according to actual needs. The units in the device embodiments of the present invention can be combined, divided, and deleted according to actual needs. In addition, the functional units in each embodiment of the present invention can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit.

[0247] As mentioned above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A reactor top high temperature ventilation test method, characterized in that: include: According to the requirements of control rod control and position indication functions during reactor operation, the operating parameters of each group of CRDM under the most conservative operating conditions are determined; Establishing a prototype reactor top CFD model based on the operating parameters of each group of CRDM under the most conservative operating conditions, conducting an internal flow field analysis of the reactor, and extracting key parameters to obtain a first analysis result, wherein the first analysis result includes key parameters in the flow field and temperature field of the prototype reactor top; Establishing an initial test reactor top CFD model, wherein the initial test reactor top CFD model includes a CRDM real prototype and a CRDM simulation body; Adjusting the heating power and the number of heating elements of the CRDM simulation body in the initial test reactor top CFD model until the difference between the second analysis result obtained by the adjusted initial test reactor top CFD model for analyzing the reactor internal flow field and the first analysis result meets the first condition set in advance, so as to obtain a target test reactor top three-dimensional flow field model; Conducting a physical test on the three-dimensional flow field model of the target test reactor top to obtain test results, wherein the test results include the flow field and temperature field of the reactor top under various working conditions; Determining whether it is necessary to adjust parameters involved in the target test reactor top three-dimensional flow field model according to the test result and the second analysis result; When it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model, adjust the parameters involved in the target test reactor top three-dimensional flow field model to update the target test reactor top three-dimensional flow field model, and use the prototype reactor top CFD model for verification until the gap between the updated first analysis result, the updated second analysis result and the test result meets the requirements; The final prototype reactor top CFD model is determined according to the updated parameters of the target test reactor top three-dimensional flow field model.

2. A reactor top high temperature ventilation test method according to claim 1, characterized in that: Each group of CRDM operation related parameters includes the coil heating power and boundary parameters of each group of CRDM under the most conservative working condition; According to the requirements of the control rod control and position indication functions during the operation of the reactor, the operating parameters of each group of CRDM under the most conservative operating conditions are determined, including: Based on the functional requirements of the rod control and rod position system, the motion set of each group of CRDM under different working conditions is obtained; Determining the most conservative operating condition based on the set of motions; Calculate the coil heating power of each group of CRDM according to the CRDM resistance value, voltage value and current change during a period of time during the different step speed movements corresponding to the most conservative working condition; The boundary parameters are determined according to the actual environmental conditions of the reactor top and the power plant operation requirements, wherein the boundary parameters include the pressure and inlet temperature of the coolant inside the CRDM, the air temperature of the environment where the reactor top is located, the heat flux density of the insulation layer of the reactor pressure vessel top cover, and the wind speed and temperature of the auxiliary ventilation.

3. A reactor top high temperature ventilation test method according to claim 2, characterized in that: Determining the most conservative working condition according to the motion set includes: The most conservative operating condition is determined comprehensively according to the control rod movement quantity, movement speed and distance from the center corresponding to each element in the movement set.

4. A reactor top high temperature ventilation test method according to claim 1, characterized in that: The method of establishing a prototype reactor top CFD model based on the operating parameters of each group of CRDM under the most conservative operating conditions and conducting an analysis of the internal flow field of the reactor to obtain a first analysis result includes: Based on the operating parameters of each group of CRDM under the most conservative operating conditions, a prototype reactor top CFD model consistent with the actual reactor top structure is constructed; Meshing the prototype stack top CFD model to obtain a mesh model of the prototype stack top; Determine calculation parameters; Performing reactor internal flow field analysis on the grid model of the prototype reactor top according to the calculation parameters to obtain the flow field and temperature field of the prototype reactor top; The key parameters of the flow field and the temperature field of the prototype pile top are extracted to obtain a first analysis result.

5. A reactor top high temperature ventilation test method according to claim 4, characterized in that: The key parameters include the maximum temperature of the CRDM yoke coil, the maximum temperature of the rod position detector coil, and the maximum air temperature above the CRDM top cable lead-out problem.

6. A reactor top high temperature ventilation test method according to claim 4, characterized in that: The calculation parameters include working fluid properties, calculation models, boundary conditions and solution settings. The working fluid properties include material, density, viscosity, thermal conductivity and specific heat capacity; the boundary conditions include ambient temperature, ambient pressure, coil heating power, CRDM simulation body heating power, top cover insulation layer heating power, auxiliary vent inlet temperature and inlet flow rate, coolant inlet temperature and pressure; the calculation model includes turbulence model, buoyancy model, thermal radiation model; the solution settings include difference format, iteration steps, time scale, and convergence standard.

7. A reactor top high temperature ventilation test method according to claim 1, characterized in that: A CRDM real prototype is arranged at the central position of the initial test reactor top CFD model, and CRDM simulation bodies are used at other positions; and the number of the CRDM real prototypes is not more than 9 groups.

8. A reactor top high temperature ventilation test method according to claim 6, characterized in that: The step of adjusting the heating power and the number of heating elements of the CRDM simulation body in the initial test reactor top CFD model until the difference between the second analysis result obtained by the adjusted initial test reactor top CFD model for analyzing the internal flow field of the reactor and the first analysis result meets a preset first condition, so as to obtain a target test reactor top three-dimensional flow field model, includes: Adjusting the heating power and the number of heating elements of the CRDM simulation body in the initial test reactor top CFD model to obtain an adjusted initial test reactor top CFD model; Performing reactor internal flow field analysis on the adjusted initial test reactor top CFD model to obtain a second analysis result; Determining whether the difference between the second analysis result and the first analysis result meets a preset first condition; If the difference between the second analysis result and the first analysis result meets a preset first condition, the adjusted initial test reactor top CFD model is determined as the target test reactor top three-dimensional flow field model; If the difference between the second analysis result and the first analysis result does not meet the preset first condition, the heating power and the number of heating elements of the CRDM simulation body in the initial test reactor top CFD model are adjusted to obtain the adjusted initial test reactor top CFD model.

9. A reactor top high temperature ventilation test method according to claim 8, characterized in that: The preset first conditions include that the maximum temperature difference of the CRDM yoke coil does not exceed 10°C, the maximum air temperature above the CRDM top cable lead-out position does not exceed 10°C, and the position range above the high temperature area on the top of the stack does not differ by more than 15%.

10. A reactor top high temperature ventilation test method according to claim 4, characterized in that: The step of performing reactor internal flow field analysis on the adjusted initial test reactor top three-dimensional flow field model to obtain a second analysis result includes: Meshing the adjusted initial test pile top CFD model to obtain an adjusted mesh model of the initial test pile top; Performing reactor internal flow field analysis on the adjusted initial test reactor top grid model according to the calculation parameters to obtain the flow field and temperature field of the test reactor top; Extracting key parameters of the flow field and temperature field at the top of the test pile to obtain a second analysis result; Among them, when the difference between the second analysis result obtained by conducting reactor internal flow field analysis using the adjusted initial test reactor top CFD model and the first analysis result meets the preset first condition, the adjusted grid model of the initial test reactor top is the grid model of the target test reactor top.

11. A reactor top high temperature ventilation test method according to claim 1, characterized in that: The physical test of the target test reactor top three-dimensional flow field model is carried out to obtain the test results, including: Building a physical pile top according to the three-dimensional flow field of the target test pile top; Arrange temperature measuring points and speed measuring points at key positions in the physical pile top; Arranging heat flux sensors on the surface of the CRDM real prototype at different heights in the physical pile top; The test is conducted according to the heating power of the target test reactor top three-dimensional flow field model, and sensitivity analysis is performed on different parameters to obtain test results.

12. A reactor top high temperature ventilation test method according to claim 11, characterized in that: The key parts in the physical stack top include the inside of each coil of the CRDM real prototype, the surface at different heights of the CRDM real prototype, the internal coolant area of ​​the CRDM real prototype, the cable positions at different heights above the top seismic plate, the different heights on the surface of the CRDM simulation body, the gap positions at different heights between the CRDM real prototype and the CRDM simulation body, and the auxiliary ventilation vents.

13. A reactor top high temperature ventilation test method according to claim 1, characterized in that: The determining whether it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model according to the test result and the second analysis result includes: When the difference between the test result and the second analysis result does not meet the requirements, it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model.

14. A reactor top high temperature ventilation test method according to claim 1, characterized in that: When it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model, the parameters involved in the target test reactor top three-dimensional flow field model are adjusted to update the target test reactor top three-dimensional flow field model, and the prototype reactor top CFD model is used for verification until the gap between the first analysis result, the second analysis result and the test result meets the requirements, including: When it is necessary to adjust the parameters involved in the target test reactor top three-dimensional flow field model, adjust the parameters involved in the target test reactor top three-dimensional flow field model to update the target test reactor top three-dimensional flow field model; Performing reactor internal flow field analysis on the updated target test reactor top three-dimensional flow field model to update the second analysis result; Determine whether the gap between the updated second analysis result and the test result meets the requirements; If the difference between the updated second analysis result and the test result meets the requirements, the parameters involved in the adjusted target test reactor top three-dimensional flow field model are input into the prototype reactor top CFD model to update the prototype reactor top CFD model, and the reactor internal flow field analysis is performed again on the updated prototype reactor top CFD model to update the first analysis result; Determining whether the difference between the updated first analysis result and the updated second analysis result meets a preset first condition; If the difference between the updated first analysis result and the updated second analysis result meets the preset first condition, then determining the final prototype reactor top CFD model according to the updated parameters of the target test reactor top three-dimensional flow field model is performed; If the gap between the updated second analysis result and the test result does not meet the requirement, the parameters involved in adjusting the target test reactor top three-dimensional flow field model are executed to update the target test reactor top three-dimensional flow field model; If the gap between the updated first analysis result and the updated second analysis result does not meet the preset first condition, the heating power and the number of heating elements of the CRDM simulation body of the target test reactor top three-dimensional flow field model are iteratively adjusted, and the internal flow field analysis of the reactor is performed to update the second analysis result until the gap between the updated second analysis result and the first analysis result meets the set first condition; a physical test is performed again to update the test result, and the heating power and the number of heating elements of the CRDM simulation body of the target test reactor top three-dimensional flow field model are iteratively adjusted until the gap among the updated test result, the updated second analysis result and the first analysis result meets the requirement.

15. A reactor top high temperature ventilation test method according to claim 8, characterized in that: The parameters involved in the target test pile top three-dimensional flow field model include the target test pile top grid model, the calculation model and solution settings.

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