A reactor head high temperature venting test method

Abstract

The application discloses a reactor top high-temperature ventilation test method. The method comprises the following steps: obtaining the conservative working condition of each CRDM, determining the operation parameters, and establishing a prototype top CFD model based on the parameters; analyzing the prototype top flow field and temperature field through CFD to obtain a first analysis result; subsequently, constructing an initial test top CFD model, adjusting the heating power and the number of heat generators, and ensuring consistency with the first analysis result; performing entity tests, obtaining flow field and temperature field data, comparing with the analysis result, adjusting the model parameters, and until the gap between the results meets the requirements; finally, determining the parameters of the target test top model, and verifying the prototype top model. Through the method of the application, the comprehensive simulation of the top flow field and temperature field can be realized efficiently and at low cost, the test effectiveness is ensured, the design parameters are optimized, and the flow field and temperature field of the test can be ensured to be close to the prototype top area.

Description

TECHNICAL FIELD

[0001] The present application relates to the reactor head structure of nuclear power plant, more particularly to a reactor head high temperature ventilation test method. BACKGROUND

[0002] In nuclear power plant, reactor head assembly is an important component, which is installed above the top cover of RPV (Reactor Pressure Vessel). During normal operation, the assembly is fixed to the RPV top cover, and during shutdown and refueling, it is hoisted and put back together with the RPV top cover and CRDM (Control Rod Drive Mechanism). The main functions of the assembly include: during reactor maintenance, hoist with the reactor head cover to simplify the disassembly and assembly process; provide seismic support for the control rod drive mechanism to limit its excessive deformation under seismic conditions to maintain its normal function; provide cooling ventilation channels to ensure effective cooling of the control rod drive mechanism yoke coil to ensure its normal operation; guide the cables and other system components in the head region to the specified civil interface. In terms of cooling of the control rod drive mechanism yoke coil, the traditional method relies on the forced ventilation of the head ventilation cover assembly, as shown in Figure 1 and Figure 2 The lower coil components are fixed coil, moving coil and lifting coil from top to bottom. However, with the development of high-temperature resistant coils and cables, the cooling method of the reactor head has gradually changed to natural convection or assisted ventilation. In order to adapt to this change, it is necessary to conduct a reactor head high temperature ventilation test, the main purposes of which include evaluating the ventilation cooling effect, verifying the rationality of the structure design, providing a basis for design parameters and optimizing the reactor head structure, specifically, analyzing the temperature, flow rate and heat dissipation distribution of the reactor head components under natural or assisted ventilation after the forced ventilation is cancelled; checking whether the control rod drive mechanism yoke coil and cable can remain within its temperature tolerance range under the new cooling method to ensure that the equipment will not be damaged due to high temperature or high flow rate; determining the appropriate ventilation volume, ventilation temperature, ventilation port size, etc. to provide support for other system design; through sensitivity test, find a more ideal reactor head structure scheme.

[0003] Since the actual reactor head usually contains multiple control rod drive mechanisms (60-90 groups), and their motion state and step speed will vary according to the needs of the reactor, it is very challenging to fully simulate these mechanisms in actual work in the test. In addition, other structural components of the reactor head (such as the head cover, seismic plate, cable bracket, etc.) will also affect the flow field and temperature field. The existing test methods include two kinds, one is to use a single control rod drive mechanism to test under different motion states and different step speeds, and to use external thermal insulation materials to simulate extreme environments, mainly focusing on the temperature resistance of the control rod drive mechanism yoke coil; however, this method only uses a single CRDM, and cannot simulate the mutual influence between multiple CRDMs; the use of thermal insulation materials lacks quantitative reference, which may cause poor heat dissipation and affect the experimental results; only the parameters of a single CRDM can be measured, and the flow field and temperature field data of the overall reactor head cannot be obtained; the effects of other structural components of the reactor head on the flow field and temperature field are ignored. The second is to use 5 CRDMs for testing, and measure the temperature of each component by different motion methods and step speeds. Although this scheme improves the number of CRDMs to some extent, the use of 5 CRDM assemblies is costly; 5 CRDMs cannot simulate the environmental conditions of 60-80 CRDMs in the actual reactor head, and the results may differ greatly from the actual reactor head conditions, especially the temperature distribution in the top cable area; only the parameters of the 5 CRDMs themselves can be measured, and it is difficult to fully understand the flow field and temperature field of the reactor head; the effects of other components of the reactor head on the flow field and temperature field are ignored.

[0004] In summary, the existing test method uses a small number of CRDMs for simulation, and cannot obtain a flow field and temperature field close to the prototype reactor head region.

[0005] Therefore, it is necessary to design a new method to efficiently and cost-effectively simulate the overall flow field and temperature field of the reactor head, ensure the effectiveness of the test and optimize the design parameters, and ensure that the flow field and temperature field of the test are close to the prototype reactor head region. SUMMARY

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

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a reactor head high-temperature ventilation test method, comprising:

[0008] According to the control rod control and position indication function requirements during the operation of the reactor, the operating parameters of each group of CRDMs under the most conservative working condition are determined;

[0009] establish a prototype reactor top CFD model based on the operation parameters of each group of CRDMs under the most conservative working condition, and carry out reactor internal flow field analysis, and extract key parameters to obtain first analysis results, wherein the first analysis results include key parameters in the flow field and temperature field of the prototype reactor top;

[0010] establish an initial test reactor top CFD model, wherein the initial test reactor top CFD model includes a CRDM real machine and a CRDM simulation body;

[0011] adjust the heating power and the number of heat generating bodies of the CRDM simulation body in the initial test reactor top CFD model until the second analysis results obtained by adjusting the initial test reactor top CFD model to carry out reactor internal flow field analysis and the first analysis results meet the first condition set in advance, to obtain a target test reactor top three-dimensional flow field model;

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

[0013] determine whether the parameters involved in the target test reactor top three-dimensional flow field model need to be adjusted according to the test results and the second analysis results;

[0014] when the parameters involved in the target test reactor top three-dimensional flow field model need to be adjusted, 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 verify it by using the prototype reactor top CFD model until the differences among the updated first analysis results, the updated second analysis results and the test results meet the requirements;

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

[0016] Further technical solutions are as follows: the operation-related parameters of each group of CRDMs include the coil heating power and boundary parameters of each group of CRDMs under the most conservative working condition;

[0017] determining the operation parameters of each group of CRDMs under the most conservative working condition according to the control rod control and position indication function requirements during the operation of the reactor, includes:

[0018] obtain the motion set of each group of CRDMs under different working conditions based on the function requirements of the rod control and position system;

[0019] determine the most conservative working condition according to the motion set;

[0020] The coil heat generation power of each group of CRDM is calculated according to the CRDM resistance value, voltage value corresponding to the most conservative working condition and the current change in a period of time during the motion at different step speeds;

[0021] The boundary parameters are determined according to the actual environment condition of the reactor top and the operation requirement of the power station, wherein the boundary parameters include the pressure and inlet temperature of the coolant in the CRDM, the air temperature of the environment where the reactor top is located, the heat flow density of the heat insulation layer of the reactor pressure vessel top cover, the wind speed of the auxiliary ventilation and the wind temperature.

[0022] A further technical scheme is that the most conservative working condition is determined according to the motion set, and the method comprises the following steps.

[0023] The most conservative working condition is determined according to the motion quantity, motion speed and distance from the center corresponding to each element in the motion set.

[0024] A further technical scheme is that the prototype reactor top CFD model is established based on the operation related parameters of each group of CRDM, and the internal flow field of the reactor is analyzed to obtain the first analysis result, and the method comprises the following steps.

[0025] The prototype reactor top CFD model consistent with the real reactor top structure is constructed based on the operation related parameters of each group of CRDM.

[0026] The grid model of the prototype reactor top is obtained by performing grid division on the prototype reactor top CFD model.

[0027] The calculation parameters are determined.

[0028] The internal flow field of the reactor is analyzed according to the calculation parameters to obtain the flow field and temperature field of the prototype reactor top.

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

[0030] A further technical scheme is that 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.

[0031] Further technical solutions are as follows: the calculation parameters include working medium properties, calculation models, boundary conditions and solution settings, the working medium 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 ventilation inlet temperature and inlet flow rate, coolant inlet temperature and pressure; the calculation models include turbulence model, buoyancy model and thermal radiation model; and the solution settings include difference format, iteration step number, time scale and convergence standard.

[0032] Further technical solutions are as follows: the CRDM real machines are arranged at the center positions of the initial test reactor top CFD model, and the CRDM simulation bodies are arranged at other positions; and the number of the CRDM real machines is not more than 9 groups.

[0033] Further technical solutions are as follows: the heating power and the number of heating bodies of the CRDM simulation bodies in the initial test reactor top CFD model are adjusted until the difference between the second analysis result obtained by carrying out reactor internal flow field analysis on the adjusted initial test reactor top CFD model and the first analysis result meets a pre-set first condition, so as to obtain a target test reactor top three-dimensional flow field model, including:

[0034] Adjusting the heating power and the number of heating bodies of the CRDM simulation bodies in the initial test reactor top CFD model to obtain an adjusted initial test reactor top CFD model;

[0035] Carrying out reactor internal flow field analysis on the adjusted initial test reactor top CFD model to obtain a second analysis result;

[0036] Judging whether the difference between the second analysis result and the first analysis result meets a pre-set first condition;

[0037] If the difference between the second analysis result and the first analysis result meets the pre-set first condition, the adjusted initial test reactor top CFD model is determined 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 pre-set first condition, the adjusting of the heating power and the number of heating bodies of the CRDM simulation bodies in the initial test reactor top CFD model is executed to obtain an adjusted initial test reactor top CFD model.

[0039] Further technical solutions are as follows: the pre-set first condition includes that the highest temperature of the CRDM magnet yoke coil differs by not more than 10℃, the highest air temperature above the CRDM top cable outlet position is not more than 10℃, and the position range above the reactor top high-temperature area differs by not more than 15%.

[0040] Further technical solutions are as follows: the adjusted initial test reactor top CFD model is subjected to reactor internal flow field analysis to obtain a second analysis result, including:

[0041] The adjusted initial test reactor top CFD model is subjected to grid division to obtain an adjusted initial test reactor top grid model;

[0042] The adjusted initial test reactor top grid model is subjected to reactor internal flow field analysis according to the calculation parameters to obtain a test reactor top flow field and temperature field;

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

[0044] When the second analysis result obtained by adjusting the initial test reactor top CFD model to carry out reactor internal flow field analysis and the first analysis result meet a pre-set first condition, the adjusted initial test reactor top grid model is a target test reactor top grid model.

[0045] Further technical solutions are as follows: the target test reactor top three-dimensional flow field model is subjected to entity test to obtain a test result, including:

[0046] An entity reactor top is built according to the target test reactor top three-dimensional flow field;

[0047] Temperature measuring points and velocity measuring points are arranged at key positions in the entity reactor top;

[0048] Heat flow sensors are arranged on different height surfaces of a CRDM real machine in the entity reactor top;

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

[0050] Further technical solutions are as follows: the key positions in the entity reactor top include the inside of each coil of the CRDM real machine, different height surfaces of the CRDM real machine, the inside of the coolant of the CRDM real machine, different height cable positions above the top anti-vibration plate, different height positions on the surface of the CRDM simulation body, gap positions between the CRDM real machine and the CRDM simulation body at different heights, and auxiliary ventilation air outlets.

[0051] Further technical solutions are as follows: whether the parameters involved in the target test reactor top three-dimensional flow field model need to be adjusted is determined according to the test result and the second analysis result, including:

[0052] When the difference between the test result and the second analysis result does not meet the requirement, the parameters related to the target test reactor core top three-dimensional flow field model need to be adjusted.

[0053] Further technical solutions are as follows: when the parameters related to the target test reactor core top three-dimensional flow field model need to be adjusted, the parameters related to the target test reactor core top three-dimensional flow field model are adjusted to update the target test reactor core top three-dimensional flow field model, and the prototype reactor core top CFD model is verified until the difference between the first analysis result, the second analysis result and the test result meets the requirement, including:

[0054] When the parameters related to the target test reactor core top three-dimensional flow field model need to be adjusted, the parameters related to the target test reactor core top three-dimensional flow field model are adjusted to update the target test reactor core top three-dimensional flow field model.

[0055] The updated target test reactor core top three-dimensional flow field model is subjected to reactor internal flow field analysis to update the second analysis result.

[0056] It is judged whether the difference between the updated second analysis result and the test result meets the requirement.

[0057] If the difference between the updated second analysis result and the test result meets the requirement, the adjusted parameters related to the target test reactor core top three-dimensional flow field model are input into the prototype reactor core top CFD model to update the prototype reactor core top CFD model, and the updated prototype reactor core top CFD model is subjected to reactor internal flow field analysis again to update the first analysis result.

[0058] It is judged whether the difference between the updated first analysis result and the updated second analysis result meets a first condition set in advance.

[0059] If the difference between the updated first analysis result and the updated second analysis result meets the first condition set in advance, the final prototype reactor core top CFD model is determined according to the updated parameters of the target test reactor core top three-dimensional flow field model.

[0060] If the difference between the updated second analysis result and the test result does not meet the requirement, the parameters related to the target test reactor core top three-dimensional flow field model are adjusted to update the target test reactor core top three-dimensional flow field model.

[0061] 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 heat generating bodies of the CRDM simulation body of the target test reactor top three-dimensional flow field model are iteratively adjusted, the reactor internal flow field analysis 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; the entity test is performed again to update the test result, and the heating power and the number of heat generating bodies of the CRDM simulation body of the target test reactor top three-dimensional flow field model are iteratively adjusted until the gap between the updated test result, the updated second analysis result and the first analysis result meets the requirement.

[0062] Further technical solutions are that the parameters related to the target test reactor top three-dimensional flow field model include a grid model of the target test reactor top, the calculation model and solving settings.

[0063] Compared with the prior art, the beneficial effects of the present application are that: the present application determines the operation related parameters by obtaining the conservative working condition of each group of CRDM, and then establishes a three-dimensional flow field model of the prototype reactor top; the first analysis result is obtained by extracting key parameters through CFD analysis of the flow field and temperature field of the prototype reactor top; the initial test reactor top CFD model is established, and the real prototype and simulation body of the CRDM are included; the heating power and the number of heat generating bodies in the initial test reactor top model are adjusted to make the second analysis result meet the preset condition, and the target test reactor top model is obtained; the entity test is performed to obtain the test result of the flow field and the temperature field, and the parameters in the target model are adjusted according to the comparative analysis; the target test reactor top model consistent with the prototype reactor top CFD model is finally determined through continuous adjustment and verification, the effectiveness of the test is ensured, and the design optimization is realized, the comprehensive simulation of the reactor top flow field and temperature field is realized efficiently and at low cost, the test effectiveness is ensured and the design parameters are optimized, and the flow field and temperature field of the test can be ensured to be close to the prototype reactor top area.

[0064] The present application will be further described below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below, and obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

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

[0067] Figure 2A schematic diagram of an internal heat source of a CRDM in the prior art;

[0068] Figure 3 A flowchart of a reactor top high-temperature ventilation test method provided by an embodiment of the present application;

[0069] Figure 4 A sub-flowchart of a reactor top high-temperature ventilation test method provided by an embodiment of the present application Figure 1 ;

[0070] Figure 5 A sub-flowchart of a reactor top high-temperature ventilation test method provided by an embodiment of the present application Figure 2 ;

[0071] Figure 6 A sub-flowchart of a reactor top high-temperature ventilation test method provided by an embodiment of the present application Figure 3 ;

[0072] Figure 7 A sub-flowchart of a reactor top high-temperature ventilation test method provided by an embodiment of the present application Figure 4 ;

[0073] Figure 8 A sub-flowchart of a reactor top high-temperature ventilation test method provided by an embodiment of the present application Figure 5 ;

[0074] Figure 9 A schematic diagram of a conservative working condition determination provided by an embodiment of the present application;

[0075] Figure 10 A schematic diagram of a prototype top and test top natural ventilation calculation model provided by an embodiment of the present application (without showing the pool wall of the reactor cavity);

[0076] Figure 11 A schematic diagram of a prototype top and test top auxiliary ventilation calculation model provided by an embodiment of the present application (including the pool wall of the reactor cavity and the auxiliary ventilation port);

[0077] Figure 12 A schematic diagram of a typical nuclear power plant reactor 69-group CRDM arrangement provided by an embodiment of the present application. DETAILED DESCRIPTION

[0078] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

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

[0080] It should also be understood that the terms used in the specification and the appended claims are intended to describe particular embodiments and do not intend to limit the present application. As used in the specification and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

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

[0082] The reactor head 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 gradually changes to natural convection or auxiliary ventilation, so that the head high-temperature ventilation test needs to be carried out. The existing test method has defects, such as using a single or small number of control rod drive mechanisms, which cannot comprehensively simulate the actual head top condition, and cannot effectively analyze the mutual influence between multiple CRDMs. The existing test can only obtain limited flow field and temperature field data, and cannot comprehensively understand the overall environment of the head top.

[0083] Therefore, the embodiment of the present application provides a reactor head high-temperature ventilation test method, which can efficiently and at low cost realize comprehensive simulation of the flow field and temperature field of the head 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 head top region.

[0084] Specifically, by using a small number of CRDM real machines, a plurality of groups of CRDM simulation bodies and other local head top structures, the flow field and temperature field simulation of the entire prototype head top can be realized, the entire prototype head top includes dozens of groups of CRDM real machines and other head top structures, which greatly saves the economic cost and time, and a single pressure vessel improves the safety and reliability of the test. By comparing the results obtained by CFD analysis of the prototype head top with the results obtained by CFD analysis of the test head 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 debugging; after the test is completed, the accuracy and availability of the head top flow field calculation model can be further improved by verifying and correcting the CFD analysis process, 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 The schematic flow chart of the reactor top high temperature ventilation test method provided by the embodiment of the present application. The method comprises the following steps S110 to S180.

[0086] S110, according to the control rod control and position indication function requirements during the operation of the reactor, determine the operating parameters of each group of CRDMs under the most conservative working condition.

[0087] In this embodiment, the conservative working condition refers to those situations that can represent the operating state of the control rod assembly under the most extreme conditions, which considers the principle of the maximum number of simultaneously moving control rods, the maximum movement speed of the control rods and the control rod position closest to the center. The conservative working condition is used to ensure the maximum safety margin of system design and operation.

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

[0089] Maximum number of control rods: as many control rods as possible are selected to move at the same time.

[0090] Maximum control rod speed: the maximum allowable movement speed of each type of control rod is used.

[0091] Control rod position closest to the center: priority is given to the movement of control rods closer to the center position of the reactor, because these positions are usually more difficult to dissipate heat and have higher temperatures.

[0092] Each group of CRDM operating related parameters includes the coil heating power of each group of CRDMs under the most conservative working condition and boundary parameters.

[0093] Specifically, each group of CRDM operating related parameters includes but is not limited to the following:

[0094] Coil heating power: calculated according to the resistance value, voltage value of the CRDM under the most conservative working condition and the current change during the different step speed movement for a period of time.

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

[0096] In an embodiment, please refer to Figure 2 The above step S110 can comprise steps S111-S114.

[0097] S111, based on the functional requirements of the rod control and rod position system, obtain the movement set of each group of CRDMs under different working conditions.

[0098] In the embodiment, the motion set refers to a set of all possible CRDM motion states, which covers the sequential motion of each group of CRDMs under different operating conditions. For example, in the power-up process, the power regulating rods can be gradually added or removed from the core in the sequence of 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 motion set, reflecting the CRDM operation mode under different operating conditions.

[0099] According to the functional requirements of the rod control and rod position system, combined with different operating conditions of the reactor (such as power-up), all motion states that each group of CRDMs can experience under various conditions are collected and sorted to form a complete motion set.

[0100] S112, determining the most conservative operating condition according to the motion set.

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

[0102] From the motion set obtained in step S111, the states that meet the definition of the conservative operating condition are filtered out, i.e. those with the most number of control rods, the highest movement speed, and the control rod position closest to the center.

[0103] S113, calculating the coil heating power of each group of CRDMs according to the CRDM resistance value, voltage value corresponding to the most conservative operating condition, and current change during the different step speed motion for a period of time.

[0104] In the embodiment, the heating power of the CRDM coil under the conservative operating condition is calculated using electrical parameters such as resistance value, voltage value, and dynamic motion data such as current change, 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 motion, the current intensity in the coil not only depends on the set step value, but also dynamically adjusts according to the speed of the control rod movement, and this current intensity changes over time. When calculating the specific heating power, the cumulative effect of the voltage and current experienced by the coil over a period of time is considered 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 control rod movement at different speeds, the average voltage and current during the corresponding period are accurately measured or estimated to ensure that the total power consumption during that 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 of the coil within a certain time, which 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, determining boundary parameters according to the actual environmental conditions at the top of the stack and the operation requirements of the power plant, wherein the boundary parameters include the pressure and inlet temperature of the CRDM internal coolant, the air temperature of the environment at the top of the stack, the heat flux density of the insulation layer of the reactor pressure vessel top cover, the wind speed of the auxiliary ventilation, and the wind temperature.

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

[0111] Considering the specific conditions around the CRDM in the actual operating environment, such as coolant temperature and pressure, and stack top air temperature, boundary parameters are determined 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 that ensure the safety and efficiency of the facility. For example, the environmental temperature at the top of the reactor is usually controlled between 30 and 40 degrees Celsius, and for conservative considerations, the highest value of 40 degrees Celsius is used as a reference in design.

[0113] For the CRDM, the working pressure of its internal coolant is about 15.5 MPa, which is the typical pressure level of the primary 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, with the inlet temperature ranging from about 285 to 295 degrees Celsius and the outlet temperature being about 320 to 335 degrees Celsius. When calculating, the specific parameters are usually determined according to the values corresponding to the optimal estimated flow during normal operation of the power plant.

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

[0115] Wind speed refers to the air flow rate provided by the auxiliary ventilation system to the interior of the reactor containment. Proper wind speed is crucial for maintaining the cooling of the reactor and its surrounding equipment, while also affecting the efficiency of heat exchange between air and surfaces.

[0116] Wind temperature refers to the temperature of the air provided by the auxiliary ventilation system. Controlling the temperature of the incoming air can effectively manage the thermal environment within the reactor containment, avoiding adverse effects on equipment performance due to overheating, and ensuring the safety and comfort of personnel.

[0117] These two parameters are part of the boundary conditions used to simulate and analyze the thermal behavior of the reactor under different operating conditions, including normal operation and hypothetical accident conditions. For example, in the event of an accident, correct wind speed and temperature can help effectively dissipate heat and prevent excessive temperatures that could lead to material failure or other safety issues. In addition, these parameters also affect the working environment of critical components such as CRDM (Control Rod Drive Mechanism), so they must be strictly monitored and kept within the design range.

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

[0119] In summary, 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 stable and reliable system operation 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, thereby ensuring the safe and stable operation of the nuclear reactor.

[0121] In this embodiment, in the reactor design, 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 operate according to specific sequences and logic to meet the requirements of different operating conditions of the reactor. For example, during the power-up process, power regulating rods may gradually enter or exit the core in the order A--A+B--B--B+C--C--C+D..., while temperature regulating rods can be adjusted according to a similar pattern. Therefore, the most conservative operating conditions are those with the largest number of control rods moving simultaneously, such as A+B+a+b or C+D+c+d combinations.

[0122] Each type of control rod has a set maximum motion speed, which is usually set for safety and mechanical integrity. For example, the maximum speed of power control rods is about 72 steps per minute, while the maximum speed of temperature regulating rods is about 60 steps per minute. After the combination with the most number of control rods has been selected, the maximum speed of these control rod types should be considered as the most conservative condition in terms of speed.

[0123] Considering the heat dissipation efficiency, the position closer to the center of the reactor tends to be more difficult to dissipate heat, which may result in higher temperature. Therefore, under the same number and speed, the combination of control rods closer to the center position will be considered as a more conservative working condition. For example, as shown in FIG. 1, if the number and speed 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 as a more conservative working condition. Figure 9

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

[0125] The step S110 of the embodiment determines the most conservative CRDM motion state by considering the number, speed and relative position of the control rods. First, the combination with the maximum number of control rods moving simultaneously is identified, then the maximum allowed speed of these control rods is applied, and finally the most conservative state is selected according to their position relative to the center of the reactor. For any uncertain or controversial cases, tools such as CFD are used to assist decision-making, ensuring that the selected working condition can represent the most severe operating conditions, thereby ensuring the safe operation of the reactor.

[0126] S120, based on the running related parameters of each group of CRDM, a prototype reactor top CFD model is established, and the flow field analysis inside the reactor is carried out, and the key parameters are extracted to obtain the first analysis result, wherein the first analysis result includes the 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 consistent with the actual reactor top structure is constructed according to the running related parameters of each group of control rod drive mechanisms (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, which provides a reference for subsequent experiments. ​

[0128] In an embodiment, referring to Figure 5 The step S120 described above can include steps S121-S125.

[0129] S121, based on the operating-related parameters of each group of CRDM, a prototype reactor head CFD model consistent with the actual reactor head structure is constructed.

[0130] In the present embodiment, a three-dimensional geometric model is created using professional modeling software (such as SolidWorks) that includes CRDM components, top cover components, reactor head structure components (such as hoist assembly, seismic support device, cable bracket and cable bridge assembly, etc.), and boundary walls (such as reactor pit walls, top cover insulation layer, etc.). In particular, for the CRDM components, the model needs to include its internal coolant (which can be set according to the required temperature, pressure and flow state), pressure shell components, hook components, coil components (set to the coil heating power according to the coil heating power in the operating-related parameters of each group of CRDM), and rod position detector components (including internal coils that may generate heat). In order to simplify the calculation and maintain accuracy, structural details that have little effect on the flow field and temperature field can be appropriately simplified.

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

[0132] Through such simplification processing, not only can the complexity of mesh division and the number of required meshes be reduced, but also the efficiency of subsequent computational fluid dynamics analysis can be significantly improved, and the computing 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 location and coil power of each group of CRDM are in accordance with the boundary parameters of each group of CRDM operating-related parameters, while the coolant pressure and temperature, ambient air temperature, insulation layer power and other conditions follow the settings of each group of CRDM operating-related parameters.

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

[0134] S122, grid the prototype top CFD model to obtain a grid model of the prototype top.

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

[0136] Such as ICEM CFD or HyperMesh for discretization. This step involves breaking down continuous geometry into a large number of discrete small elements - grids. For areas with complex structures or high accuracy requirements, finer grid division will be used to ensure the accuracy of subsequent simulation.

[0137] In this process, continuous geometry is broken down into many small, simple geometric elements (also known as elements or cells), which can be tetrahedrons, hexahedrons, prisms or other types of polyhedral shapes. Each element is defined by nodes, which are the intersection points between elements and are used by solvers to calculate physical quantities such as pressure, velocity, temperature, etc.

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

[0139] S123, determine the calculation parameters.

[0140] In this embodiment, the calculation parameters include working fluid properties, calculation model, 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 ventilation 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 criteria.

[0141] Specifically, a series of calculation parameters must be defined before the CFD analysis can be performed, which determines the authenticity and accuracy of the simulation. Specifically:

[0142] Working substance properties refer to the physical properties of the medium involved in the flow or heat exchange, such as the coolant, air, and metal components, 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 variation), 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 based on past experience and specific application scenarios. For example, when dealing with fully developed turbulence with high flow velocity, the k-epsilon turbulence model is preferred; for natural convection phenomena, the SST (Shear Stress Transport) turbulence model is preferred for simulation. When dealing with density variation, the buoyancy model is necessary.

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

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

[0146] Regarding the selection of iteration steps, the initial setting is usually based on experience, such as initially setting 5000 steps. Subsequently, by monitoring the changes in key parameters of the three basic equations, such as continuity equation, momentum equation, and energy equation, and the data trend of the pre-set monitoring points, the convergence is evaluated. If the variation amplitude of these parameters is found to be very small, or the pre-set convergence criteria (such as the difference between adjacent two iterations being less than 10 -4 ), it can be considered that the current iteration steps are sufficient to achieve convergence. Conversely, if the desired convergence effect cannot be achieved, the iteration steps need to be adjusted, the grid division needs to be optimized, or the selection of the calculation model needs to be reconsidered to promote faster and stable convergence results.

[0147] In summary, the selection of computational models and the control of iterative processes are a dynamic adjustment process that needs to be flexible in response to actual calculation results to ensure that accurate and reliable numerical solutions are ultimately obtained.

[0148] S124, performing a reactor internal flow field analysis on the prototype top grid model according to the calculation parameters to obtain a flow field and a temperature field of the prototype top.

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

[0150] S125, extracting key parameters of the flow field and temperature field of the prototype top to obtain a first analysis result.

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

[0152] Specifically, a series of key parameters are extracted from the flow field and temperature field of the prototype top as the first analysis result, especially those indicators that are directly related to the safety and performance of the equipment. For example, in this embodiment, the highest temperature of the CRDM magnetic yoke coil, the highest temperature of the rod position detector coil, and the highest air temperature above the CRDM top cable exit 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] In general, the entire CFD analysis process is as follows:

[0154] Use three-dimensional modeling software such as SolidWorks to build the geometric model of the calculation object. This includes the fluid region and the solid structure interacting with it, and the geometric model of the object refers to the prototype top CFD model.

[0155] Next, the three-dimensional model established above is imported into a specialized mesh generation tool, such as ICEM CFD or HyperMesh, for discretization processing. This step involves breaking down continuous geometric shapes into a large number of discrete small units - meshes. For complex structures or areas with high accuracy requirements, finer mesh division will be used to ensure the accuracy of subsequent simulations.

[0156] Then, the prepared mesh file is loaded into a professional CFD solver such as ANSYS CFX, ANSYS Fluent, or STAR-CCM+, and a series of necessary physical conditions are set. These conditions cover working fluid properties (e.g., material properties, density, viscosity, thermal conductivity, and specific heat capacity of coolants, air, and metals), boundary conditions (e.g., inlet temperature, flow velocity, outlet pressure, ambient temperature, and heating power), and the selection of an appropriate physical model (e.g., choice of turbulence model, whether to consider gravity effects, whether heat exchange or radiation effects exist, steady-state or transient analysis). After setting the iteration parameters, the solver iteratively solves the basic governing equations (continuity equation, momentum equation, and energy equation) within each mesh, ultimately obtaining the distribution of physical quantities (e.g., temperature, pressure, and velocity fields) at each mesh point.

[0157] Finally, the calculation results are analyzed and displayed using the solver's built-in data analysis functions or third-party visualization tools. This includes extracting temperature or velocity distribution maps of specific cross-sections and identifying the maximum temperature or highest pressure points of key components, so that engineers can intuitively understand and interpret the simulation data.

[0158] It is important to note that the prototype top-of-the-line CFD model uses only CRDM real prototypes, meaning that the structures within the model are built 1:1 according to the CRDM real prototype.

[0159] S130. Based on the CRDM operation-related parameters of each group, establish an initial test reactor top CFD model, wherein the initial test reactor top CFD model includes a real CRDM prototype and a CRDM simulator.

[0160] In this embodiment, a real CRDM prototype is placed at the center of the initial test reactor top CFD model, while CRDM simulators are used in other locations; and the number of real CRDM prototypes is no more than 9 sets.

[0161] Specifically, one or more groups (scalable to 5 or 9 groups based on budget and research needs) of real CRDM prototypes are placed at the center position of the initial test reactor top CFD model. For non-central positions, simulated CRDM bodies are used, which have the same shape as the real CRDM prototypes but use surface heat flux or thin layer heating to represent internal heat generation, and different regions can be set to different heating powers. All structural components of the prototype reactor top are replicated as much as possible, especially the key components that can affect the flow field and temperature distribution around the CRDM, such as the seismic plate, cable bridge and its support structure, lifting device, containment cylinder or truss (if present), insulation layer, and pool wall, etc. Components that have a significant impact on ventilation and heat dissipation, such as seismic plate and insulation layer simulations, are retained, while components such as lifting devices and cable supports that have less impact on ventilation and heat dissipation can be selectively ignored to simplify the modeling process and reduce the number of grids.

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

[0163] To ensure the accuracy of the simulation, the boundary conditions need to be set according to the methods described in the previous steps. This includes but is not limited to:

[0164] The real CRDM prototypes at the center position are set to different step-jump speeds according to the specified method, specifically according to the coil heat power of each group of CRDMs.

[0165] The coolant pressure and temperature in the CRDM prototype, the ambient air temperature, the insulation layer power, and other parameters are also configured according to the aforementioned boundary parameters.

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

[0167] Define 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 adjusting these settings, a CFD model that accurately reflects the actual operating conditions can be constructed, thereby supporting a deep understanding of the flow field characteristics of the test reactor top.

[0169] S140, adjusting the heating power and the number of heating bodies of the CRDM simulation body in the initial test reactor top CFD model until the second analysis result obtained by the adjusted initial test reactor top CFD model in the reactor internal flow field analysis meets the first condition of the first analysis result, 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 the CFD model finally determined after a series of adjustments, which can accurately simulate the characteristics of the actual reactor top flow field and temperature field. This model not only needs to reproduce the geometry 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 simulation body, so as to obtain the thermal hydraulic characteristics consistent with the operation state of the prototype reactor.

[0171] In this process, the goal is to continuously adjust the heating power and the number of heating bodies of the CRDM (control rod drive mechanism) simulation body in the initially established test reactor top three-dimensional flow field model, so that the result obtained by the model in the reactor internal flow field analysis, 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 thermal hydraulic behavior of the real reactor top.

[0172] In an embodiment, referring to Figure 6 The above step S140 can include steps S141-S144.

[0173] S141, adjusting the heating power and the number of heating bodies of the CRDM simulation body in the initial test reactor top CFD model to obtain an adjusted initial test reactor top CFD model.

[0174] In this embodiment, initially, the heating power and the number of heating bodies of the CRDM simulation body are preliminarily set based on previous research or experience. For example, 8 groups of full heating simulation bodies are arranged around a CRDM real machine, and the heating plates at the magnetic yoke position are particularly emphasized to apply higher power, and all heating bodies at the top rod position detector area are heated. The heating power at different positions is adjusted step by step as needed, such as segmented setting of 1KW (rod position detector position), 2KW (magnetic yoke position), 1KW (position below the magnetic yoke), and different heating ranges are tried (only coil position heating, or coil position and rod position detector position heating, or entire CRDM model body heating).

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

[0176] In the embodiment, the second analysis result refers to a data set obtained after the adjusted initial test reactor top CFD model is subjected to flow field calculation analysis. The data includes but is not limited to key parameters such as flow field velocity distribution, pressure distribution, temperature distribution, etc. Specifically, it refers to the flow field and temperature field of the test reactor top simulated by the CFD software, especially the points of interest such as the highest temperature of the CRDM magnetic yoke coil, the highest air temperature above the top cable exit position, and the position range of the high-temperature area of the reactor top.

[0177] In an embodiment, the step S142 described above can include steps S1421-S1423.

[0178] S1421, performing mesh division on the adjusted initial test reactor top CFD model to obtain a mesh model of the adjusted initial test reactor top;

[0179] S1422, performing reactor internal 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, extracting key parameters of the flow field and temperature field of the test reactor top to obtain the second analysis result;

[0181] Wherein, when the difference between the second analysis result obtained by the adjusted initial test reactor top CFD model in the reactor internal flow field analysis and the first analysis result meets the pre-set first condition, the mesh model of the adjusted initial test reactor top is the mesh model of the target test reactor top.

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

[0183] S143, judging whether the difference between the second analysis result and the first analysis result meets the pre-set first condition.

[0184] In the embodiment, the pre-set first condition includes that the difference in the highest temperature of the CRDM magnetic yoke coil is not more than 10℃, the highest air temperature above the top cable exit position of the CRDM is not more than 10℃, and the difference in the position range above the high-temperature area of the reactor top is not more than 15%.

[0185] Specifically, the second analysis result is compared with the previously obtained first analysis result to determine whether the difference between the two meets a pre-set first condition. The conditions here include but are not limited to that the maximum temperature difference of the CRDM yoke coil is not more than 10℃, the maximum air temperature above the CRDM top cable exit position is not more than 10℃, and the position range above the high-temperature area of the reactor top is not more than 15%. If the gap meets these conditions, it means that the model has been close enough to the actual situation; otherwise, it is necessary to return to step S141 to continue adjustment.

[0186] S144, if the gap between the second analysis result and the first analysis result meets the pre-set first condition, the adjusted initial test reactor top CFD model is determined 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 pre-set first condition, the step S141 is performed.

[0188] Once it is confirmed that the gap between the second analysis result and the first analysis result meets the pre-set first condition, it is considered that the optimal solution is found, and the model at this time is the target test reactor top three-dimensional flow field model. Conversely, if the condition is not met, the model setting needs to be re-evaluated and adjusted until the expected consistency is reached.

[0189] In summary, the series of operations are to ensure that the three-dimensional flow field model created by numerical simulation can accurately reflect the actual complex thermal-hydraulic phenomena at the top of the reactor.

[0190] In the present embodiment, the same parts of the prototype reactor top CFD model and the test reactor top CFD model are 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 ambient temperature, the pressure and the inlet temperature of the internal coolant at the coolant inlet, the air temperature of the environment at the reactor top, the heat flux density of the thermal insulation layer of the reactor pressure vessel head cover; the turbulence model, the buoyancy model, the thermal radiation model (which can not be set); the solution setting.

[0191] The different parts of the prototype reactor top CFD model and the test reactor top CFD model are: the grid model, because the internal structures are different, the grids are also different; the heating method, the prototype is internal coil heating conduction to the outside, and the simulation body is surface heating wire or heating plate heating; the number of CRDM heating simulation bodies, the prototype reactor top CFD model has none; the power of the CRDM heating simulation body, the prototype reactor top CFD model has none.

[0192] S150, performing physical tests on the target test reactor top three-dimensional flow field model to obtain test results, wherein the test results include the flow field and temperature field of the reactor top under each working condition.

[0193] In the embodiment, the purpose of this step is to convert the target test reactor top three-dimensional flow field model optimized by numerical simulation before into an actual physical test device, and a series of tests are carried out to verify the accuracy and reliability of the model. Specifically, this includes building a physical test device, arranging measuring points, implementing heating and motion control, and carrying out sensitivity parameter tests, etc. Finally, through these physical tests, the actual data of the flow field and temperature field of the reactor top under different working conditions can be obtained, which provides an important reference basis for reactor design.

[0194] In an embodiment, referring to Figure 7 The above step S150 can include steps S151-S154.

[0195] S151, according to the target test reactor top three-dimensional flow field, a physical reactor top is built.

[0196] In the embodiment, according to the design of the target test reactor top three-dimensional flow field model, a real test mechanism is built. This test mechanism should include a group of CRDM real machines located in the middle position, CRDM simulation bodies (the number is the total number of CRDM minus 1) around the middle simulation body, and structural components that may affect the flow field and temperature of the CRDM component area, such as top anti-seismic plate assembly, cable bracket and cable bracket assembly, lifting assembly, reactor top surrounding cylinder or truss (if any), top cover insulation layer simulation piece, reactor cavity pool wall simulation piece, etc. As shown in Figures 10 to 12 , ensure that all components are arranged in the same spacing and arrangement as the actual reactor top, and the size and position are kept in a 1:1 ratio, especially the CRDM simulation body has the same external structure size as the CRDM real machine, and can be arranged in different heating power by partitioning the heating plate or heating wire. Among them, Figure 10 The label 1 in the figure is the reactor pressure vessel (RPV) top cover insulation layer; 2 is the control rod drive mechanism (CRDM); 3 is the lower lifting rod; 4 is the anti-seismic ring; 5 is the cable bracket; 6 is the cable bridge (since it is far away from the CRDM heat position and itself does not generate heat, it is generally not considered in the test); Figure 11 The label 1 in the figure is the reactor pressure vessel (RPV) top cover insulation layer simulation piece; 2 is the control rod drive mechanism (CRDM) simulation piece; 3 is the lower lifting rod simulation piece; 4 is the anti-seismic ring simulation piece; 5 is the cable bracket simulation piece; 6 is the cable bridge simulation piece (since it is far away from the CRDM heat position and itself does not generate heat, it is generally not considered in the test); 7 is the reactor cavity pool wall simulation piece; 8 is the auxiliary ventilation port.

[0197] S152, temperature measuring points and velocity measuring points are arranged at key positions in the physical reactor top.

[0198] In the embodiment, the key positions in the entity stack top include the inside of each coil of the CRDM real machine, the surfaces at different heights of the CRDM real machine, the inside coolant area of the CRDM real machine, the cable positions at different heights above the top anti-vibration plate, the surfaces at different heights of the CRDM simulation body, the gap positions at different heights between the CRDM real machine and the CRDM simulation body, and the auxiliary ventilation air outlet.

[0199] Specifically, in order to accurately measure the temperature and speed changes of the key positions in the test process, the temperature measuring points and the speed measuring points are reasonably arranged on each test piece. The positions that are mainly considered include the inside coil of the CRDM real machine, the surfaces at different heights, the inside coolant area, the cable positions at different heights above the top anti-vibration plate, the surfaces at different heights of the CRDM simulation body, the gap positions at different heights between the CRDM real machine and the CRDM simulation body, and the auxiliary ventilation air outlet. For the positions that are particularly concerned, such as the temperature measuring points of several coils, more temperature measuring points can be arranged at different angles to determine whether the highest temperature tolerance of the coil is exceeded; more temperature measuring points can be arranged around the cable at the stack top cable position to determine whether the highest temperature tolerance of the cable is exceeded; more heat flux density measuring points can be arranged at different height positions of the CRDM from top to bottom to calculate the heat dissipation of the entire CRDM; and more coolant temperature measuring points can be arranged at the top and bottom of the CRDM inside to determine whether the coolant temperature exceeds the saturation temperature.

[0200] S153, arranging heat flux sensors on the surfaces at different heights of the CRDM real machine in the entity stack top.

[0201] In the embodiment, in order to measure the heat flux density on the surfaces at different heights of the CRDM real machine, 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 and further determine the appropriate power configuration of the stack cavity temperature control air conditioner.

[0202] S154, performing a test according to the heating power of the target test stack top three-dimensional flow field model, and performing a sensitivity analysis on different parameters to obtain a test result.

[0203] Based on the heating power setting defined in the target test stack top three-dimensional flow field model, the entity test device is heated. At the same time, the CRDM real machine at the intermediate position is moved according to the preset different step jump speeds (for example: a holding state, 48 steps per minute, 60 steps per minute, and 72 steps per minute). On this basis, the above process is repeated, and a sensitivity parameter test is performed on different parameters (such as different coolant temperatures, different movement strokes, different auxiliary ventilation heights, different auxiliary ventilation air speeds, different auxiliary ventilation temperatures, etc.). After each test, the data of each measuring point is collected and recorded to form a test result.

[0204] The test results refer to a series of data sets about the flow field and temperature field at the top of the reactor obtained through the aforementioned physical test. These data not only reflect the fluid flow characteristics and temperature distribution under specific working conditions, but also reveal the influence law of different parameters on the top environment of the reactor. Through the analysis of these data, the accuracy of the target test reactor top three-dimensional flow field model can be evaluated, and it can be confirmed whether it can effectively predict the complex thermal-hydraulic phenomena at the top of the actual reactor. In addition, the results of 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 summary, these test results play a crucial role in ensuring the safe operation of nuclear reactors and improving their efficiency.

[0205] S160, determining whether the parameters involved in the target test reactor top three-dimensional flow field model need to be adjusted according to the test results and the second analysis results.

[0206] In this embodiment, when the gap between the test results and the second analysis results does not meet the requirements, the parameters involved in the target test reactor top three-dimensional flow field model need to be adjusted.

[0207] It should be noted that this requirement can be consistent with the first condition, or it can require the test results to be the same as the analysis results.

[0208] S170, when the parameters involved in the target test reactor top three-dimensional flow field model need to be adjusted, adjusting 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 using the prototype reactor top CFD model for verification until the gap between the updated first analysis results, the updated second analysis results and the test results meets the requirements.

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

[0210] In an embodiment, referring to Figure 8 The above step S170 can include steps S171-S176.

[0211] S171, when it is needed to adjust the parameters involved in the target test reactor core three-dimensional flow field model, the parameters involved in the target test reactor core three-dimensional flow field model are adjusted to update the target test reactor core three-dimensional flow field model.

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

[0213] When the second analysis result is found to deviate from the entity test result, some key parameters in the target test reactor core three-dimensional flow field model are first adjusted. These parameters include the selection of the turbulence model, the setting of the buoyancy model, the iteration step number, the working medium physical property, and the like calculation parameters. The purpose of 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 predicted velocity field of the model and the actual measured value is large, the turbulence model can be changed or the iteration number can be increased to improve the matching degree.

[0214] In the embodiment, the calculation parameters are preferentially adjusted, and then the heating power is adjusted. It needs to be noted that if the heating power is adjusted, the entity test of step S150 needs to be re-executed to update the test result, and the updated test result is used to determine again whether the parameters involved in the target test reactor core three-dimensional flow field model need to be adjusted. The iterative judgment and adjustment are continuously performed until the difference between the updated first analysis result, the updated second analysis result, and the test result meets the requirement.

[0215] S172, the reactor internal flow field analysis is performed on the updated target test reactor core three-dimensional flow field model to update the second analysis result.

[0216] In the embodiment, the CFD analysis is re-run by using the updated parameter setting to obtain the new flow field and temperature field distribution, i.e., the updated second analysis result. This step is a key link for verifying the parameter adjustment effect, which will directly determine whether the model parameters need to be further adjusted.

[0217] S173, it is judged whether the difference between the updated second analysis result and the test result meets the requirement.

[0218] In the embodiment, the updated second analysis result is compared with the real data measured in the entity test. The requirement here is usually to control the error between the two within an acceptable range, such as less than 5%. If this condition is met, it means that the current parameter setting is accurate enough; if not, the parameters need to be continuously adjusted until the optimal solution is found.

[0219] S174, if the difference between the updated second analysis result and the test result meets the requirement, input the parameters related to the adjusted target test reactor top three-dimensional flow field model to the prototype reactor top CFD model to update the prototype reactor top CFD model, and perform reactor internal flow field analysis on the updated prototype reactor top CFD model again 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 unsimplified reactor top environment, so the analysis on it can obtain a more comprehensive data set, including the positions that are difficult to measure in the test. The first analysis result generated in this step contains not only the data around the CRDM prototype, but also the flow field and temperature field information in the entire reactor top region.

[0221] In addition, the parameters in the optimized target test reactor top three-dimensional flow field model are applied to the prototype reactor top CFD model, and the reactor internal flow field analysis is performed again. The purpose of this step is twofold:

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

[0223] Ensure consistency: through the analysis on 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 reproduction ability of the CFD model to the real world. If the analysis result of the prototype model maintains good consistency with the test result and the updated second analysis result, it means that the model has high credibility and can be used to guide the subsequent design and decision-making process.

[0224] S175, judge whether the difference between the updated first analysis result and the updated second analysis result meets the pre-set first condition;

[0225] If the difference between the updated first analysis result and the updated second analysis result meets the pre-set first condition, execute the step S180;

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

[0227] S176, if the gap between the updated first analysis result and the updated second analysis result does not meet the pre-set first condition, iteratively adjust the heating power and the number of heat generating bodies of the CRDM simulation body of the target test reactor core three-dimensional flow field model, perform the reactor internal flow field analysis to update the second analysis result until the gap between the updated second analysis result and the first analysis result meets the pre-set first condition; perform the physical test again to update the test result, and iteratively adjust the heating power and the number of heat generating bodies of the CRDM simulation body of the target test reactor core three-dimensional flow field model until the gap between the updated test result, the updated second analysis result and the first analysis result meets the requirement.

[0228] In the embodiment, the parameters related to the target test reactor core three-dimensional flow field model include the grid model of the target test reactor core, the calculation model and the solution setting.

[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 pre-set threshold. If the requirement is met, it is considered that the whole model calibration process is completed, and the cycle can be ended; otherwise, it is necessary to return to S171 to adjust the parameters again. In addition, if it is found in S173 that the gap between the updated second analysis result and the test result does not meet the requirement, it is also necessary to return to S171 to perform a new round of parameter adjustment. Similarly, if the gap between the updated first analysis result and the second analysis result does not meet the pre-set first condition, the number of heat generating bodies and the heating power are 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, i.e., the result of the computational fluid dynamics for the test reactor core CFD model, it is necessary to adjust the parameters that exist only in the numerical simulation but not in the physical test. These adjustable factors include the grid model, the turbulence model, the buoyancy model and the thermal radiation model setting (the thermal radiation model can be selected not to be enabled), and the iterative solution condition. Because these factors do not exist in the actual physical test, they are artificially set in the simulation process, so they can be adjusted to improve the consistency.

[0231] For the parameters such as boundary conditions, working medium properties and heating power, which exist in both the test and the CFD simulation, they should be kept consistent and should not be 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 analysis of the test CFD model to the prototype CFD model, and check whether the adjusted first analysis results still match the second analysis results. If not, the number and power settings of the heat-generating bodies in the test CFD model need to be adjusted until the first analysis results tend to be consistent with the second analysis results.

[0233] If the above adjustments to the test CFD model are necessary, the same adjustments should also be implemented in the physical test, i.e., adjusting the number and power of the heat-generating bodies, and verifying the consistency between the physical test results and the second analysis results again. Generally, at this stage, the difference between the two is already very small. If there is still any significant difference, it is necessary to go back to step three and continue the iterative adjustment process until the consistency between the first analysis results, the second analysis results, and the physical test results is ensured.

[0234] In other words, the whole process is a process of repeated correction, which ensures that the final simulation results can accurately reflect the real-world test situation by constantly comparing and adjusting the parameters between simulation and test.

[0235] The above process not only ensures the accuracy of the CFD model, but also builds a flexible and efficient tool that allows engineers to quickly evaluate the impact of new operating conditions or structural changes without relying on expensive and complex physical tests. For example, when transitioning from a conservative operating condition (such as A+B+a+b) to other possible combinations (such as C+D+c+d, A+b, E+f, etc.), it is only necessary to simply modify the operating condition input parameters in the CFD analysis to quickly obtain new calculation results. This method greatly improves work efficiency and reduces research and development costs, while ensuring the safety and reliability of the design. In this way, engineers can identify potential problems at an early stage and make timely adjustments, thereby accelerating the pace of innovation and technological progress.

[0236] S180, determining a final prototype CFD model according to the updated parameters of the target test CFD model.

[0237] The prototype CFD model established after completing the above steps not only applies to the specific operating conditions of the current research, but also easily adapts to various new operating conditions or structural changes that may occur in the future. For example, when facing new operating conditions (C+D+c+d), different combinations (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, simply modifying the input conditions and re-running the CFD analysis can obtain the corresponding calculation results, greatly improving work efficiency and reducing costs.

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

[0239] In summary, the method of the embodiment achieves accurate simulation of the flow field and temperature field of the reactor top region by using a small number (most ideally one set) of real prototypes of control rod drive mechanisms (CRDM) and a number of simulation bodies to replace the complete prototype reactor top structure. This method not only greatly reduces the economic investment 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 and reduce the debugging time and cost overhead. In addition, after the test is completed, the models involved in the CFD analysis are verified and corrected, which helps to improve the accuracy of the models and enables data that is difficult to directly measure in the test to be obtained from the simulation results.

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

[0242] The method of this embodiment first selects conservative conditions, then analyzes the prototype top-of-pile flow field, followed by analysis of the test top-of-pile flow field, then conducts formal test activities, followed by sensitivity parameter research, and finally revises the flow field analysis results. This method ensures a complete closed loop from theory to practice to verification. By constructing and running a computational fluid dynamics (CFD) simulation model of the prototype top-of-pile, the invention can provide an important early prediction of the results of actual tests, allowing researchers to have a clear framework of expectations before the tests begin. By performing CFD sensitivity analysis of the test top-of-pile and comparing the results with the CFD analysis data of the prototype top-of-pile before the formal test, the scale of the test and the power parameters that may be involved can be assessed in advance, thereby optimizing the test design and improving efficiency. In order to reduce test costs and improve safety, a small number (ideally 1 set) of CRDM real machines are used in combination with other simulation bodies with CRDM external features and external heating elements to simulate the heating behavior to replace the traditional method of deploying dozens of CRDM real machines. This method not only saves resources, but also ensures the effectiveness and accuracy of the test. In the test setup, special attention is paid to retaining key structural components that can significantly affect the flow field and temperature distribution in the top-of-pile area, such as seismic plate assemblies, cable brackets and related components, lifting assembly, containment or truss (if applicable), insulation layer simulation, and pool wall simulation. This approach ensures that the test environment is as close to reality as possible, enhancing the authenticity of the simulation. Using the actual measurement data collected after the test, the CFD flow field analysis of the target test top-of-pile three-dimensional flow field model is re-verified and adjusted as necessary, and the CFD analysis of the prototype top-of-pile CFD model is improved. Through this iterative process, the model obtained has wider applicability and higher accuracy, and even in the face of new conditions or structural changes, it can be adjusted locally without the need to restart large-scale tests, greatly improving the flexibility and economy of research and development work. Improving the accuracy and efficiency of the simulation of the flow field and temperature field in the top-of-pile area of the nuclear reactor, while also laying a solid foundation for future related research and technological development.

[0243] The reactor top high-temperature ventilation test method has the advantages that the conservative working condition of each group of CRDM is obtained, the operation related parameters are determined, and then the three-dimensional flow field model of the prototype top is established; the flow field and the temperature field of the prototype top are analyzed through CFD, key parameters are extracted, and the first analysis result is obtained; the initial test top CFD model is established, and the real prototype of the CRDM and the simulation body are included; the heating power and the number of heating bodies in the initial test top model are adjusted, so that the second analysis result meets the preset condition, and the target test top model is obtained; the entity test is performed, the test result of the flow field and the temperature field is obtained, and the parameters in the target model are adjusted according to the comparative analysis; the target test top model consistent with the prototype top CFD model is finally determined through continuous adjustment and verification, the effectiveness and design optimization of the test are ensured, the overall simulation of the flow field and the temperature field of the top is realized efficiently and 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 top area.

[0244] Those skilled in the art can appreciate that the algorithm steps of each example described in combination with the embodiments disclosed herein can be realized in electronic hardware, computer software or a combination of both, and in order to clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been described in the above description. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

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

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

[0247] The above description is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for conducting high-temperature ventilation tests at the top of a reactor, characterized in that, include: Based on the control rod control and position indication function requirements during reactor operation, the operating parameters of each CRDM group under the most conservative operating conditions are determined. Based on the operating parameters of each CRDM under the most conservative operating condition, a prototype reactor top CFD model is established, and the internal flow field of the reactor is analyzed. Key parameters are extracted to obtain the first analysis result, which includes key parameters in the flow field and temperature field of the prototype reactor top. An initial test reactor top CFD model is established, wherein the initial test reactor top CFD model includes a real CRDM prototype and a CRDM simulator; The heating power and number of CRDM simulators in the initial test reactor top CFD model are adjusted until the difference between the second analysis result obtained from the reactor internal flow field analysis of the adjusted initial test reactor top CFD model and the first analysis result meets the first pre-set condition, so as to obtain the target test reactor top three-dimensional flow field model. A physical test was conducted on the three-dimensional flow field model at the top of the target test reactor to obtain test results, wherein the test results include the flow field and temperature field at the top of the reactor under various operating conditions; Based on the experimental results and the second analysis results, determine whether it is necessary to adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor. When it is necessary to adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor, adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor to update the three-dimensional flow field model at the top of the target test reactor, and verify it using the prototype reactor top CFD model until the difference between the updated first analysis result, the updated second analysis result, and the test result meets the requirements. The final prototype top CFD model is determined based on the parameters of the updated target test reactor top three-dimensional flow field model.

2. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 1, characterized in that, The relevant operating parameters for each group of CRDMs include the coil heating power and boundary parameters of each group of CRDMs under the most conservative operating conditions. The process of determining the operating parameters of each CRDM under the most conservative operating conditions, based on the control rod control and position indication function requirements during reactor operation, includes: Based on the functional requirements of the rod control and rod position system, obtain the motion set of each CRDM under different working conditions; The most conservative operating condition is determined based on the set of motions. The coil heating power of each CRDM is calculated based on the CRDM resistance value, voltage value, and current change over a period of time during different step speed movements, corresponding to the most conservative operating condition. The boundary parameters are determined based on the actual environmental conditions at the reactor top and the power plant's operational requirements. These boundary parameters include the pressure and inlet temperature of the coolant inside the CRDM, the air temperature of the environment at the reactor top, the heat flux density of the reactor pressure vessel top cover insulation layer, and the wind speed and temperature of the auxiliary ventilation.

3. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 2, characterized in that, The step of determining the most conservative working condition based on the set of motions includes: The most conservative operating condition is determined by comprehensively considering the number of control rod movements, movement speed, and distance from the center for each element in the motion set.

4. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 1, characterized in that, The prototype reactor top CFD model is established based on the operating parameters of each CRDM under the most conservative operating condition, and the internal flow field analysis of the reactor is carried out to obtain the first analysis results, including: Based on the operating parameters of each CRDM under the most conservative operating conditions, a prototype reactor top CFD model consistent with the actual reactor top structure is constructed. The prototype top CFD model is meshed to obtain the mesh model of the prototype top. Determine the calculation parameters; The internal flow field of the prototype reactor top is analyzed based on the calculated parameters to obtain the flow field and temperature field at the prototype reactor top. Key parameters of the flow field and temperature field at the top of the prototype reactor were extracted to obtain the first analysis results.

5. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 4, characterized in that, 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 point.

6. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 4, characterized in that, The calculation parameters include working fluid properties, calculation model, boundary conditions, and solution settings. The working fluid properties include material properties, 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 layer heating power, auxiliary vent inlet temperature and inlet velocity, and coolant inlet temperature and pressure. The calculation model includes a turbulence model, a buoyancy model, and a thermal radiation model. The solution settings include a difference scheme, number of iterations, time scale, and convergence criteria.

7. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 1, characterized in that, The CRDM real prototype is arranged at the center of the initial test reactor top CFD model, and CRDM simulations are used in other positions; and the number of CRDM real prototypes is no more than 9 sets.

8. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 6, characterized in that, The process of adjusting the heating power and number of heating elements of the CRDM simulator within the initial test reactor top CFD model until the difference between the second analysis result obtained from the reactor internal flow field analysis of the adjusted initial test reactor top CFD model and the first analysis result meets a pre-set first condition, in order to obtain the target test reactor top three-dimensional flow field model, includes: The heating power and number of heating elements of the CRDM simulator in the initial test reactor top CFD model are adjusted to obtain the adjusted initial test reactor top CFD model; The reactor internal flow field was analyzed using the adjusted initial test reactor top CFD model to obtain the second analysis results; Determine whether the difference between the second analysis result and the first analysis result meets a pre-set first condition; If the difference between the second analysis result and the first analysis result meets the first pre-set condition, then the adjusted initial test reactor top CFD model will be 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, then the heating power and number of heating elements of the CRDM simulator in the initial test reactor top CFD model are adjusted to obtain the adjusted initial test reactor top CFD model.

9. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 8, characterized in that, The pre-set first conditions include a maximum temperature difference of no more than 10°C between the highest temperatures of the CRDM yoke coils, a maximum air temperature of no more than 10°C above the top cable lead-out position of the CRDM, and a position range difference of no more than 15% above the high-temperature area on the top of the stack.

10. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 4, characterized in that, The process 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: The adjusted initial test reactor top CFD model is meshed to obtain the adjusted initial test reactor top mesh model; Based on the calculation parameters, the internal flow field of the reactor is analyzed using the adjusted initial test reactor top mesh model to obtain the flow field and temperature field at the test reactor top. Key parameters of the flow field and temperature field at the top of the test reactor were extracted to obtain the second analysis results; Wherein, when the difference between the second analysis result obtained from the reactor internal flow field analysis of the adjusted initial test reactor top CFD model and the first analysis result meets the preset first condition, the adjusted initial test reactor top mesh model is the target test reactor top mesh model.

11. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 1, characterized in that, The physical test of the three-dimensional flow field model at the top of the target test reactor to obtain test results includes: Construct a physical reactor top according to the three-dimensional flow field of the target test reactor top; Temperature and velocity measuring points are installed at key locations within the top of the solid stack. Heat flow sensors were arranged on the surfaces of the CRDM prototype at different heights in the top of the physical stack. The experiment was conducted based on the heating power of the three-dimensional flow field model at the top of the target test reactor, and sensitivity analysis was performed on different parameters to obtain the experimental results.

12. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 11, characterized in that, Key components of the physical stack include the interior of each coil of the CRDM prototype, the surfaces of the CRDM prototype at different heights, the internal coolant area of ​​the CRDM prototype, the cable positions at different heights above the top anti-vibration plate, the different heights on the surface of the CRDM simulator, the gap positions between the CRDM prototype and the CRDM simulator at different heights, and the auxiliary ventilation vents.

13. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 1, characterized in that, The step of determining whether to adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor based on the test results and the second analysis results includes: When the difference between the experimental results and the second analysis results does not meet the requirements, it is necessary to adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor.

14. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 1, characterized in that, When it is necessary to adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor, the parameters involved in the three-dimensional flow field model at the top of the target test reactor are adjusted to update the three-dimensional flow field model at the top of the target test reactor, and the prototype reactor top CFD model is used for verification until the difference between the first analysis result, the second analysis result, and the experimental result meets the requirements, including: When it is necessary to adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor, adjust the parameters involved in the three-dimensional flow field model at the top of the target test reactor to update the three-dimensional flow field model at the top of the target test reactor. The reactor internal flow field is analyzed using the updated three-dimensional flow field model at the top of the target test reactor to update the second analysis results; Determine whether the difference between the updated second analysis result and the experimental 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 to 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. Determine 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 the step of determining the final prototype top CFD model based on the parameters of the updated target test reactor top three-dimensional flow field model is executed. If the difference between the updated second analysis result and the test result does not meet the requirements, then the parameters involved in adjusting the three-dimensional flow field model at the top of the target test reactor are executed to update the three-dimensional flow field model at the top of the target test reactor. If the difference between the updated first analysis result and the updated second analysis result does not meet the preset first condition, the heating power and number of heating elements of the CRDM simulator of the three-dimensional flow field model at the top of the target test reactor are iteratively adjusted, and the internal flow field analysis of the reactor is performed to update the second analysis result until the difference between the updated second analysis result and the first analysis result meets the preset first condition; the physical test is performed again to update the test result, and the heating power and number of heating elements of the CRDM simulator of the three-dimensional flow field model at the top of the target test reactor are iteratively adjusted until the difference between the updated test result, the updated second analysis result, and the first analysis result meets the requirements.

15. The method for conducting a high-temperature ventilation test at the top of a reactor according to claim 8, characterized in that, The parameters involved in the three-dimensional flow field model of the target test reactor top include the mesh model of the target test reactor top, the calculation model, and the solution settings.

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