Device and method for detecting heat carrying capacity of residual heat removal system of miniature gas cooled reactor

Abstract

The invention discloses a device and a method for detecting heat-carrying capacity of a residual heat removal system of a miniature gas-cooled reactor. Comprising a Brayton cycle system used for simulating the normal operation condition of the miniature gas cooled reactor, a data acquisition and control system connected with the Brayton cycle system, and a residual heat removal system used for simulating the operation state of an active and passive residual heat removal system under the shutdown or accident condition of the miniature gas cooled reactor, according to the invention, different gas working media, different reactor core simulation sections and heat exchangers can be flexibly adjusted to simulate active and passive residual heat removal characteristics under different gas working media and different reactor core and heat exchanger configurations, and a Brayton cycle state, an active residual heat removal state and a passive residual heat removal state of a miniature gas cooled reactor; and switching of different operation states can be realized.

Description

Technical Field

[0001] The present invention relates to a technology in the field of reactor control, in particular to a device and method for detecting the heat carrying capacity of a residual heat removal system of a micro gas-cooled reactor. Background Art

[0002] The micro gas-cooled reactor based on the Brayton cycle has the characteristics of small size, light weight, long endurance and high power, and can be used as a reliable power source in remote areas. The residual heat removal system is a safety facility to ensure the safety of nuclear power plants during shutdown and accident conditions. Its importance has been widely practiced in the third-generation pressurized water reactors. However, the operating working fluid, thermal cycle system composition and usage scenarios of the micro gas-cooled reactor are very different from those of the pressurized water reactor. At present, domestic and foreign research on the heat transfer and flow performance of the residual heat removal system of the micro gas-cooled reactor in the steady-state, transient and operating state switching process is only in the theoretical stage and lacks experimental verification. Summary of the invention

[0003] In view of the shortcomings of the prior art that, due to the limitation of working fluids, the sceneries of active-passive state switching such as shutdown and startup in a micro gas-cooled reactor cannot be simulated, and the design requirements of the micro gas-cooled reactor in terms of operating working fluids and temperature range cannot be met, a device and method for detecting the heat carrying capacity of a residual heat removal system of a micro gas-cooled reactor is proposed. The device and method can flexibly adjust different gas working fluids, different core simulation sections and heat exchangers to simulate the active and passive residual heat removal characteristics under different gas working fluids and different core and heat exchanger configurations, as well as the Brayton cycle state, active residual heat removal state and passive residual heat removal state of the micro gas-cooled reactor, and can realize switching between different operating states.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a device for detecting the heat carrying capacity of a residual heat removal system of a micro gas-cooled reactor, comprising: a Brayton cycle system for simulating the normal operating conditions of a micro gas-cooled reactor, and a data acquisition and control system respectively connected thereto, and a residual heat removal system for simulating the operating states of active and passive residual heat removal systems under shutdown or accident conditions of the micro gas-cooled reactor. When the residual heat removal system is in an active residual heat removal condition, gas flows out from an outlet of a compressor, passes through a preheater and a core simulation section in sequence, flows to a first heat exchanger, and flows into the compressor again after passing through a second heat exchanger to complete a cycle; when the residual heat removal system is in a passive condition, high-temperature gas flows out from an outlet of the core simulation section, and under the driving force formed by a density difference, after flowing through the first heat exchanger and transferring heat to the heat exchanger, the gas temperature drops and the density rises, and after flowing through a natural circulation driving section, it flows into the core simulation section again to complete a cycle. Technical Effects

[0006] The present invention uses a Brayton cycle system to simulate the normal operating conditions of a micro gas-cooled reactor, and uses a residual heat removal system to simulate the core residual heat removal conditions of a gas-cooled reactor under shutdown and accident conditions. The compressor in the Brayton cycle system is used to drive the working medium in the loop, and the start and stop and speed of the compressor can be controlled by a data acquisition and control system. A buffer tank is provided before and after the compressor to stabilize the loop pressure and reduce the flow fluctuation of the loop. High-temperature resistant alloys are used as materials for pipelines, experimental sections and heat exchangers in the loop, and welding connections are used between each device and the pipeline to achieve high temperature resistance and low gas leakage rate; the valves in the loop are controlled by the data material and control system, and can be quickly opened and closed and the opening can be adjusted. During the experiment, the switching between different operating states of the loop can be achieved by controlling the opening and closing of the valves. This design enables the present invention to meet the temperature and leakage rate requirements of the micro gas-cooled reactor, and the types of experimental conditions that can be achieved are greatly increased compared with similar devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic diagram of the structure of the present invention;

[0008] In the figure: 1 compressor, 2 first pressure-suppressing tank, 3 regenerator, 4 preheater, 5 core simulation section, 6 first heat exchanger, 7 natural circulation driving section, 8 pressure reducing plate, 9 second heat exchanger, 10 second pressure-suppressing tank, 11 gas collection and analysis device, 12 data acquisition cabinet, 13 control module, V1 to V12 first valve to twelfth valve, M1 to M3 first flow meter to third flow meter, T1 to T12 first temperature measuring mechanism to twelfth temperature measuring mechanism, P1 to P5 first pressure transmitter to fifth pressure transmitter, DP1 to DP3 first differential pressure transmitter to third differential pressure transmitter;

[0009] Figure 2 This is a schematic diagram of the present invention. DETAILED DESCRIPTION

[0010] like Figure 1 As shown, this embodiment relates to a natural circulation heat carrying capacity detection system for gas in a passive residual heat removal state, including: a Brayton cycle system and a residual heat removal system, a data acquisition system and a control module respectively connected thereto.

[0011] The Brayton cycle system comprises: a regenerator 3 for transferring heat from the hot side fluid to the cold side, a second heat exchanger 9 connected in sequence, a second surge tank 10 for reducing fluid and pressure vibrations in the loop, a compressor 1 for providing driving force for the fluid, a first surge tank 2 for reducing fluid and pressure vibrations in the loop, and a preheater 4 connected in sequence, a core simulation section 5 for simulating the heat generation power, structure and physical-thermal coupling properties of a real reactor core and heating the gas, and a pressure reducing plate 8 for simulating a turbine device, wherein: the output of the first surge tank 2 A first valve V1 and a second valve V2 are arranged between the end and the cold side inlet of the reheater 3 in sequence, the cold side outlet of the reheater 3 is connected to the input end of the preheater 4, the hot side inlet of the reheater 3 is connected to the pressure reducing plate 8, a sixth valve V6 is arranged between the hot side outlet of the reheater 3 and the second heat exchanger 9, an eighth valve V8 is arranged between the second heat exchanger 9 and the second pressure stabilizing tank 10, a third valve V3 is arranged between the input end of the preheater 4 and the second valve V2, a fourth valve V4 is arranged between the output end of the preheater 4 and the core simulation section 5, and a fifth valve V5 is arranged between the core simulation section 5 and the pressure reducing plate 8.

[0012] The input end of the second pressure stabilizing tank 10 is provided with a ninth valve V9.

[0013] The residual heat removal system includes: a fourth pressure differential transmitter DP4, a fifth pressure transmitter DP5, a first heat exchanger 6 for extracting heat under residual heat removal conditions, and a natural circulation driving section 7 for providing driving force for the fluid under non-passive residual heat removal conditions, wherein: the first heat exchanger 6 is connected to the core simulation section 5 through the eleventh valve V11; the fourth pressure differential transmitter DP4 is connected in parallel with the first heat exchanger 6; the first heat exchanger 6 is connected to the natural circulation driving section 7; the fifth pressure transmitter DP5 is connected in parallel with the natural circulation driving section 7, and the output end of the natural circulation driving section 7 is connected to the second heat exchanger 9 through the twelfth valve V12.

[0014] A tenth valve V10 is provided between the input end of the core simulation section 5 and the output end of the natural circulation driving section 7 .

[0015] The data acquisition and control system includes: a control module 13, a data acquisition cabinet 12, and a gas acquisition and analysis device 11, a first to a twelfth temperature measuring mechanism T1-T12, a first to a fifth pressure transmitter P1-P5 and a first to a third flow meter M1-M3 respectively connected to the data acquisition cabinet 12, wherein: the gas acquisition and analysis device 11 is arranged at the output end of the second heat exchanger 9; the first to the twelfth temperature measuring mechanism T1-T12 are respectively arranged at the output end of the compressor 1, the cold side inlet of the regenerator 3, and the cold side outlet of the regenerator 3 , the input end of the preheater 4, the input end and output end of the core simulation section 5, the hot side inlet and outlet of the regenerator 3, the input end and output end of the second heat exchanger 9 and the input end and output end of the first heat exchanger 6; the first to fifth pressure transmitters P1-P5 are respectively arranged at the output end of the compressor 1, the cold side inlet of the regenerator 3, the input end of the core simulation section 5, the hot side outlet of the regenerator 3 and the input end of the compressor 1; the first to third flow meters M1-M3 are respectively arranged at the input end and output end of the second valve V2 and the natural circulation drive section 7.

[0016] The pipeline materials used for connecting the equipment of the Brayton cycle system and the waste heat removal system are all high-temperature resistant alloys, and the connection method between the pipeline and the equipment is welding to meet the high temperature operating environment and low gas leakage rate requirements of the micro gas-cooled reactor.

[0017] There is a height difference between the first heat exchanger 6 and the core simulation section 5, and the first heat exchanger 6 is located at a higher position to form a natural circulation through the height difference and the gas temperature difference. In order to reduce heat leakage, the pipelines in the loop are wrapped with insulation cotton and aluminum foil materials. The device is suitable for chemically inert gases such as helium and argon and their mixed gases.

[0018] like Figure 2 As shown, this embodiment relates to a method for detecting the heat carrying capacity of gas in the residual heat discharge state based on the above system, comprising:

[0019] Step 1) After installing the core simulation section 5 and the first heat exchanger 6 of the micro gas-cooled reactor to be tested, start the data acquisition system to carry out leakage rate detection and stamping test to ensure that the loop meets the required leakage rate and pressure performance.

[0020] Step 2) According to the working conditions to be simulated, through the data acquisition and control system, the instruments in the control loop reach the state required to carry out the corresponding experiment, and carry out experimental testing.

[0021] The experimental tests include: passive residual heat removal experiment, Brayton cycle steady-state and transient experiment, active residual heat removal steady-state and transient experiment, Brayton cycle-active residual heat removal shutdown experiment, Brayton cycle-passive residual heat removal shutdown experiment, active residual heat removal-passive residual heat removal switching experiment, active residual heat removal-Brayton cycle startup experiment, passive residual heat removal-Brayton cycle startup experiment, and passive-active residual heat removal switching experiment.

[0022] The passive residual heat removal experiment includes:

[0023] i) Ensure that the seventh valve V7 is in the closed state and the other valves are in the open state. After the air in the circuit is extracted through the ninth valve V9, the gas to be tested is injected into the circuit. After the pressure in the circuit reaches the predetermined pressure, the ninth valve V9 is closed and the first heat exchanger 6 and the second heat exchanger 9 are opened.

[0024] ii) Close the fourth valve V4, the fifth valve V5 and the twelfth valve V12, start the core simulation section 5, gradually increase its electric heating power to a predetermined value, ensure that the tenth valve V10 and the eleventh valve V11 are fully opened, and then carry out the passive residual heat removal experiment.

[0025] The Brayton cycle steady-state and transient experimental method is as follows: after step i), the third valve V3, the tenth valve V10, the eleventh valve V11 and the twelfth valve V12 are closed, and a series of devices in the Brayton cycle system are started, and the system reaches the Brayton cycle state.

[0026] The active residual heat removal steady-state and transient experimental method is as follows: after step i), the fifth valve V5, the sixth valve V6 and the tenth valve V10 are closed, and the compressor 1 and the core simulation section 5 are opened. At this time, the system reaches the active residual heat removal state.

[0027] The Brayton cycle-active residual heat removal shutdown test method is to first close the third valve V3, the tenth valve V10, the eleventh valve V11 and the twelfth valve V12 after the operation of step i), start the series of equipment in the Brayton cycle system, and achieve the Brayton cycle steady-state and transient test state. Then, by opening the eleventh valve v11 and the twelfth valve V12 and closing the fifth valve v5 and the sixth valve v6 at the same time, the device operation state is switched from the Brayton cycle to the active residual heat removal state.

[0028] The Brayton cycle-passive residual heat removal shutdown test method is as follows: after step i), the third valve V3, the tenth valve V10, the eleventh valve V11 and the twelfth valve V12 are first closed, and a series of equipment in the Brayton cycle system are started to achieve the Brayton cycle steady-state and transient test state. Subsequently, the tenth valve v10 is opened, the compressor 1 is closed, the eleventh valve v11 is opened, and the fifth valve v5 is closed in sequence, and the device operation state is switched from the Brayton cycle to the passive residual heat removal state.

[0029] The active residual heat removal-passive residual heat removal switching experimental method is to close the fifth valve V5, the sixth valve V6 and the tenth valve V10 after the operation of step i), open the compressor 1 and the core simulation section 5, and reach the active residual heat removal state. Then, the compressor 1 is closed in sequence, the tenth valve v10 is opened, and the twelfth valve v12 is closed, and the device operation state is switched from the active residual heat removal state to the passive residual heat removal state.

[0030] The active residual heat removal-Brayton cycle start-up experimental method is to close the fifth valve V5, the sixth valve V6 and the tenth valve V10 after the operation of step i), open the compressor 1 and the core simulation section 5, and reach the active residual heat removal state. Then, the fifth valve v5 and the sixth valve v6 are opened in sequence, and the eleventh valve v11 and the twelfth valve v12 are closed, and the device operation state is switched from the active residual heat removal state to the Brayton cycle.

[0031] The passive residual heat removal-Brayton cycle start-up experimental method is to close the fourth valve V4, the fifth valve V5 and the twelfth valve V12 after the operation of step i), start the core simulation section 5, and reach the passive residual heat removal state. Then, the fifth valve v5 is opened in sequence, the compressor 1 is started, the tenth valve v10 and the eleventh valve v11 are closed, and the device operation state is switched from the passive residual heat removal state to the Brayton cycle.

[0032] The passive-active residual heat removal switching experimental method is to close the fourth valve V4, the fifth valve V5 and the twelfth valve V12 after the operation of step i), start the core simulation section 5, and reach the passive residual heat removal state. Then, the fourth valve v4 and the twelfth valve v12 are opened in sequence, the compressor 1 is started, and the tenth valve v10 is closed to change the device operation state from the passive residual heat removal state to the active residual heat removal state.

[0033] Step 3) When the flow rate of the loop is monitored by the data acquisition and control system and the change is less than 5% within 2000 seconds, and the change in the outlet temperature of the experimental section is less than 5% of the total temperature rise, it is considered that the flow and heat exchange at this time have reached a stable state. The data at this time is recorded using the data acquisition and control system to obtain the loop operation parameters under this condition.

[0034] Step 4) After data recording is completed, the core simulation section 5 is closed, and after the temperatures measured by all temperature measuring mechanisms drop below 100° C., the first heat exchanger 6 and the second heat exchanger 9 are closed, and the test is completed.

[0035] After computational fluid dynamics simulation, based on the above passive waste heat removal experiment, the above device was operated with the parameters in Table 1 under the setting of helium as the working fluid, and the data that can be obtained are shown in Table 2.

[0036] Table 1. Experimental parameter settings parameter value unit Gas purity 99.9％ -- Tenth valve opening 100％ -- 11th valve opening 100％ -- Circuit average pressure 1.2 MPa Core simulation section power 2100.0 W First heat exchanger cooling water temperature 15.00 ℃ Height difference between core simulation section and first heat exchanger 5 m

[0037] Table 2. Experimental device operating parameters parameter value unit flow <![CDATA[5.9×10 -4 ]]> kg / s Circuit average pressure 2.5 MPa Core simulation section inlet temperature 15.1 ℃ Core simulation section outlet temperature 698.1 ℃ Maximum temperature of core simulation section structural material 732.3 ℃ Core simulation section pressure drop 23.3 Pa Pressure drop on the helium side of the first heat exchanger 107.0 Pa Natural circulation driving section pressure drop 212.0 Pa

[0038] It can be seen from the results in Table 2 that at this time, driven only by the density difference, helium can bring out the heat in the core simulation section, and the maximum temperature of the gas is 698.1°C, and the maximum temperature of the structural material is 732.3°C, both of which are within the applicable temperature range of the high-temperature resistant alloy Inconel 625. Therefore, the waste heat removal system built on this alloy has a good heat carrying capacity and can achieve long-term stable heat output.

[0039] Compared with the prior art, the present invention uses a Brayton cycle system to simulate the normal operating conditions of a micro gas-cooled reactor, and uses a residual heat removal system to simulate the core residual heat removal conditions of a gas-cooled reactor under shutdown and accident conditions. The compressor in the Brayton cycle system is used to drive the working fluid in the loop, and the start and stop and speed of the compressor can be controlled by a data acquisition and control system. A buffer tank is provided before and after the compressor to stabilize the loop pressure and reduce the flow fluctuation of the loop. High-temperature resistant alloys are used as materials for pipelines, experimental sections and heat exchangers in the loop, and welding is used between each device and the pipeline to achieve high temperature resistance and low gas leakage rate; the valves in the loop are controlled by the data material and control system, and can be quickly opened and closed and the opening can be adjusted. During the experiment, the switching between different operating states of the loop can be achieved by controlling the opening and closing of the valves. This design enables the present invention to meet the temperature and leakage rate requirements of the micro gas-cooled reactor, and the types of experimental conditions that can be achieved are greatly increased compared with similar devices.

[0040] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A device for detecting heat carrying capacity of a residual heat removal system of a micro gas-cooled reactor, characterized in that: include: A Brayton cycle system for simulating the normal operating conditions of a micro gas-cooled reactor and a data acquisition and control system respectively connected thereto and a residual heat removal system for simulating the operating conditions of an active and passive residual heat removal system under shutdown or accident conditions of the micro gas-cooled reactor; The residual heat removal system comprises: a fourth differential pressure transmitter, a fifth pressure transmitter, a first heat exchanger for removing heat under residual heat removal conditions, and a natural circulation driving section for providing a driving force for a fluid under passive residual heat removal conditions, wherein: the first heat exchanger is connected to the core simulation section through an eleventh valve; the fourth differential pressure transmitter is connected in parallel with the first heat exchanger; the first heat exchanger is connected to the natural circulation driving section; the fifth pressure transmitter is connected in parallel with the natural circulation driving section, and the output end of the natural circulation driving section is connected to the second heat exchanger through a twelfth valve; When the waste heat removal system is in the active waste heat removal condition, the gas flows out from the compressor outlet, passes through the preheater and the core simulation section in turn, flows to the first heat exchanger, and flows into the compressor again after passing through the second heat exchanger to complete a cycle; when the waste heat removal system is in the passive condition, the high-temperature gas flows out from the core simulation section outlet, and under the driving force formed by the density difference, after flowing through the first heat exchanger and transferring heat to the heat exchanger, the gas temperature drops and the density rises, and after flowing through the natural circulation driving section, it flows into the core simulation section again to complete the cycle.

2. The heat carrying capacity detection device for the residual heat removal system of a micro gas-cooled reactor according to claim 1 is characterized in that: The Brayton cycle system includes: a regenerator for transferring heat from its hot side fluid to the cold side, a second heat exchanger connected in sequence, a second pressure-stabilizing tank for reducing fluid and pressure vibrations in the loop, a compressor for providing driving force for the fluid, a first pressure-stabilizing tank for reducing fluid and pressure vibrations in the loop and a preheater connected in sequence, a core simulation section for simulating the heating power, structure and physical-thermal coupling properties of a real reactor core and heating the gas, and a pressure reducing plate for simulating a turbine device, wherein: a first valve and a second valve are arranged in sequence between the output end of the first pressure-stabilizing tank and the cold side inlet of the regenerator, the cold side outlet of the regenerator is connected to the input end of the preheater, the hot side inlet of the regenerator is connected to the pressure reducing plate, a sixth valve is arranged between the hot side outlet of the regenerator and the second heat exchanger, an eighth valve is arranged between the second heat exchanger and the second pressure-stabilizing tank, a third valve is arranged between the input end of the preheater and the second valve, a fourth valve is arranged between the output end of the preheater and the core simulation section, and a fifth valve is arranged between the core simulation section and the pressure reducing plate.

3. The heat carrying capacity detection device for the residual heat removal system of a micro gas-cooled reactor according to claim 2 is characterized in that: The input end of the second pressure-stabilizing tank is provided with a ninth valve.

4. The heat carrying capacity detection device for the residual heat removal system of a micro gas-cooled reactor according to claim 1 is characterized in that: A tenth valve is provided between the input end of the core simulation section and the output end of the natural circulation driving section.

5. The heat carrying capacity detection device for the residual heat removal system of a micro gas-cooled reactor according to claim 1 is characterized in that: The data acquisition and control system includes: a control module, a data acquisition cabinet, and a gas acquisition and analysis device respectively connected to the data acquisition cabinet, the first to the twelfth temperature measuring mechanism, the first to the fifth pressure transmitter and the first to the third flow meter, wherein: the gas acquisition and analysis device is arranged at the output end of the second heat exchanger; the first to the twelfth temperature measuring mechanism are respectively arranged at the output end of the compressor, the cold side inlet of the regenerator, the cold side outlet of the regenerator, the input end of the preheater, the input end and the output end of the core simulation section, the hot side inlet and outlet of the regenerator, the input end and the output end of the second heat exchanger and the input end and the output end of the first heat exchanger; the first to the fifth pressure transmitters are respectively arranged at the output end of the compressor, the cold side inlet of the regenerator, the input end of the core simulation section, the hot side outlet of the regenerator and the input end of the compressor; the first to the third flow meter are respectively arranged at the input end and the output end of the second valve and the natural circulation drive section.

6. The heat carrying capacity detection device for the residual heat removal system of a micro gas-cooled reactor according to claim 1 is characterized in that: The pipeline materials used for connecting the equipment of the Brayton cycle system and the waste heat removal system are all high-temperature resistant alloys, and the connection method between the pipeline and the equipment is welding to meet the high temperature operating environment and low gas leakage rate requirements of the micro gas-cooled reactor.

7. The heat carrying capacity detection device for the residual heat removal system of a micro gas-cooled reactor according to claim 1 is characterized in that: There is a height difference between the first heat exchanger and the core simulation section, and the first heat exchanger is located at a higher position to form a natural circulation through the height difference and the gas temperature difference. In order to reduce heat leakage, the pipelines in the loop are wrapped with thermal insulation cotton and aluminum foil materials.

8. A method for detecting the heat carrying capacity of gas in the residual heat discharge state of the system according to any one of claims 1 to 7, characterized in that: include: Step 1) After installing the core simulation section and the first heat exchanger of the micro gas-cooled reactor to be tested, start the data acquisition system to carry out leakage rate detection and stamping test to ensure that the loop meets the required leakage rate and pressure performance; Step 2) According to the working conditions to be simulated, the instruments in the control loop are controlled through the data acquisition and control system to reach the state required for carrying out the corresponding experiment, and the experimental test is carried out; Step 3) When the flow rate of the loop is monitored to change by less than 5% within 2000 seconds through the data acquisition and control system, and the change of the outlet temperature of the experimental section is less than 5% of the total temperature rise, it is considered that the flow and heat exchange at this time have reached a stable state, and the data at this time are recorded by the data acquisition and control system to obtain the loop operation parameters under this working condition; Step 4) After data recording is completed, the core simulation section is closed, and after the temperatures measured by all temperature measuring mechanisms drop below 100° C., the first heat exchanger and the second heat exchanger are closed, and the detection is completed.

9. The heat carrying capacity detection method according to claim 8, characterized in that: The experimental tests include: passive residual heat removal experiment, Brayton cycle steady-state and transient experiment, active residual heat removal steady-state and transient experiment, Brayton cycle-active residual heat removal shutdown experiment, Brayton cycle-passive residual heat removal shutdown experiment, active residual heat removal-passive residual heat removal switching experiment, active residual heat removal-Brayton cycle startup experiment, passive residual heat removal-Brayton cycle startup experiment, and passive-active residual heat removal switching experiment.

10. The heat carrying capacity detection method according to claim 9, characterized in that: The passive residual heat removal experiment includes: i) Ensure that the seventh valve is in the closed state and the other valves are in the open state. After the air in the circuit is extracted through the ninth valve, gas is injected into the circuit. After the pressure in the circuit reaches the predetermined pressure, the ninth valve is closed and the first heat exchanger and the second heat exchanger are opened; ii) Close the fourth valve, the fifth valve and the twelfth valve, start the core simulation section, gradually increase its electric heating power to a predetermined value, and ensure that the tenth valve and the eleventh valve are fully opened, and then carry out the passive residual heat removal experiment; The Brayton cycle steady-state and transient experimental method is as follows: after step i), the third valve, the tenth valve, the eleventh valve and the twelfth valve are closed, and a series of devices in the Brayton cycle system are started, and the system reaches the Brayton cycle state; The active residual heat removal steady-state and transient experimental method is as follows: after step i), the fifth valve, the sixth valve and the tenth valve are closed, and the compressor and the core simulation section are opened, and the system reaches the active residual heat removal state; The Brayton cycle-active residual heat removal shutdown test method is as follows: after step i), the third valve, the tenth valve, the eleventh valve and the twelfth valve are first closed, and a series of equipment in the Brayton cycle system is started to achieve the Brayton cycle steady-state and transient test state; then, the device operation state is switched from the Brayton cycle to the active residual heat removal state by opening the eleventh valve and the twelfth valve and closing the fifth valve and the sixth valve at the same time; The Brayton cycle-passive residual heat removal shutdown test method is as follows: after step i), the third valve, the tenth valve, the eleventh valve and the twelfth valve are first closed, and a series of equipment in the Brayton cycle system is started to achieve the Brayton cycle steady-state and transient test state; then, the tenth valve is opened, the compressor is closed, the eleventh valve is opened, and the fifth valve is closed in sequence, and the device operation state is switched from the Brayton cycle to the passive residual heat removal state; The active residual heat removal-passive residual heat removal switching experimental method is as follows: after step i), the fifth valve, the sixth valve and the tenth valve are closed, and the compressor and the core simulation section are opened to achieve the active residual heat removal state; then, the compressor is closed in sequence, the tenth valve is opened, and the twelfth valve is closed to switch the device operation state from the active residual heat removal state to the passive residual heat removal state; The active residual heat removal-Brayton cycle start-up experimental method is as follows: after step i), the fifth valve, the sixth valve and the tenth valve are closed, and the compressor and the core simulation section are opened to achieve the active residual heat removal state; then, the fifth valve and the sixth valve are opened in sequence, and the eleventh valve and the twelfth valve are closed to switch the device operation state from the active residual heat removal state to the Brayton cycle; The passive residual heat removal-Brayton cycle start-up experimental method is as follows: after step i), the fourth valve, the fifth valve and the twelfth valve are closed, the core simulation section is started, and the passive residual heat removal state is reached; then, the fifth valve is opened in sequence, the compressor is started, the tenth valve and the eleventh valve are closed, and the device operation state is switched from the passive residual heat removal state to the Brayton cycle; The passive-active residual heat removal switching experimental method is as follows: after step i), the fourth valve, the fifth valve and the twelfth valve are closed, and the core simulation section is started to reach the passive residual heat removal state; then the fourth valve and the twelfth valve are opened in sequence, the compressor is started, and the tenth valve is closed to change the operating state of the device from the passive residual heat removal state to the active residual heat removal state.

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