Experimental system and method for lead-bismuth reactor damaged core melt migration

Abstract

The invention relates to a lead-bismuth reactor damaged core melt migration experiment system and method, and the system comprises an experiment section, a simulation fuel rod, a shielding gas module, a direct current power supply heating module, a shooting recording module and an instrument module, a direct-current power supply is used for heating an electric heating wire simulation core block to serve as an internal heat source to generate heat to melt a fuel rod, air in a system is exhausted by filling argon, and inert environment protection is provided; the melting of lead and bismuth is realized by the heating of the heating wire; and the specific behaviors of gathering and migration of the melt above the lead-bismuth liquid level can be observed through the visible window on the top cover. The simulated fuel pellet is made of metal molybdenum, the simulated fuel rod cladding is made of stainless steel, and liquid lead bismuth serves as a cooling agent. Meanwhile, a multi-layer structure is designed for the experimental section, and stainless steel serving as a shell is prevented from being melted along with melting of the stainless steel cladding of the fuel rod. According to the invention, simulation experiments of melting of a single fuel rod and a fuel rod bundle, pellet fragmentation and melt migration can be carried out, and a reference is provided for safety design of a lead-bismuth reactor.

Description

Technical Field

[0001] The invention belongs to the technical field of reactor damage research under severe accident conditions of nuclear reactors, and specifically relates to an experimental system and method for the migration of molten material in a damaged core of a lead-bismuth reactor. Background Art

[0002] Lead-bismuth fast reactor is the main reactor type candidate of the International Forum on the Fourth Generation of Nuclear Energy Systems (GIF), which uses liquid lead-bismuth as coolant. In the early stage of the accident, as the core temperature increased, the stainless steel cladding melted. The stainless steel melt may condense and cause the coolant channel to be blocked during the migration process in the reactor, causing further temperature rise, resulting in the rupture of the fuel pellets and interaction with the coolant, and a series of complex migration movements with the coolant as the carrier. The pellets may be transported to the upper chamber of the lead-bismuth and stagnate, causing the core to return to criticality, or they may form aggregates at the bottom of the core under the action of natural circulation after the accident. Due to the opacity of lead-bismuth, the study of the melting of the lead-bismuth reactor core and the migration of the melt has become an urgent problem to be solved. In terms of experimental research, a large number of experimental studies at home and abroad are carried out on sodium-cooled fast reactors or experiments using alternative materials. The phenomena and processes of severe accidents in lead-bismuth reactors are very different from those in pressurized water reactors and sodium-cooled fast reactors. Therefore, experimental research on severe accidents in lead-bismuth reactors is not sufficient. In terms of theoretical research and program development, only a small number of studies have used the SIMMER program to analyze severe accidents in lead-bismuth reactors. The SIMMER program has been verified by a large number of severe accident experiments in sodium-cooled fast reactors, and its application in the analysis of lead-bismuth reactors needs further verification.

[0003] REF01: The invention patent "Visualization Experimental Device and Method for Simulating Lead-Bismuth Stack Cladding Melting and Fragment Migration" (CN202210720578.9) discloses a visualization experimental device and method for simulating lead-bismuth stack cladding melting and fragment migration, the experiment includes a visualization experimental chamber, a heating device, a simulated fuel rod, a temperature measuring device, a shooting device, a liquid storage tank and a heat exchanger; the invention can be used to carry out visualization simulation experiments on cladding melting and fragment migration of single rod or multiple rods, but because the cladding substitute material used is paraffin, the melting process of paraffin during the melting process is very different from the melting process of the real stainless steel cladding, and the melts formed by the two are also very different. The melt formed by paraffin is floc-like, while the melt formed by stainless steel is drop-like or block-like. Therefore, it is impossible to analyze a series of complex behaviors of the cladding melting, condensation, channel blockage and melt migration under real conditions.

[0004] REF02: The invention patent "A method and system for analyzing the migration of core melt in a nuclear power plant" (CN202211632241.9) discloses a method and system for analyzing the migration of core melt in a nuclear power plant, including: obtaining the first penetration position, and obtaining the mass, time series of the core melt when the core melt pool first migrates into the lower head and the information of water evaporation in the lower head according to the first penetration position; obtaining the material distribution, mass and volume of the blocking layer formed on the lower support plate of the core and in the core annular gap according to the melting points and oxidation conditions of the materials in the core above the first penetration position; analyzing the secondary migration of the core melt according to the order and time of the remaining materials in the core and the materials in the formed blocking layer heating up to the melting point and the remaining water volume in the lower head after the first migration. This invention can conduct more detailed analysis and evaluation on core melting and migration, thus providing more effective support for the evaluation of the effectiveness of melt retention in nuclear power safety analysis. However, since the technology involved in this invention is a numerical simulation program, and the experimental research on severe accidents of lead-bismuth fast reactors is insufficient, and the numerical simulation programs used for lead-bismuth reactors are mostly verified based on sodium-cooled fast reactors, this invention cannot obtain the specific behavior of melt migration under severe accident conditions of lead-bismuth reactors. Summary of the Invention

[0005] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an experimental system and method for the migration of molten core melt in a lead-bismuth reactor, which provides the possibility for studying core damage, cladding melting, melt condensation causing coolant channel blockage and further temperature rise, pellet fragmentation and interaction with coolant, and a series of complex migration movements carried by the coolant under more realistic accident conditions, and also provides comparative experimental data for the development and verification of numerical simulation programs, so as to clarify the relevant mechanisms of molten core melt migration in lead-bismuth reactors.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] An experimental system for the migration of molten core melt in a lead-bismuth reactor includes an experimental section 21, simulated fuel rods 13, a protective gas module, a DC power heating module, a shooting and recording module, and an instrument and meter module; it is used to simulate the thermohydraulic phenomena of core damage, cladding melting, pellet fragmentation and melt migration in coolant during the melting process of fuel rods when a severe accident occurs in a lead-bismuth reactor; among them, the experimental section 21 is a pressure vessel that simulates the working environment of the lead-bismuth reactor core.

[0008] The top of the experimental section 21 is sealed. The experimental section 21 adopts a multi-layer coating layer, a heating device is arranged in the coating layer, lead-bismuth alloy is filled in the coating layer as the coolant, and the simulated fuel rods 13 are inserted into the lead-bismuth alloy.

[0009] The simulated fuel rod 13 consists of five parts, namely, a high-temperature heating wire 23 in the innermost radial layer, a substitute metal molybdenum 24 for the simulated fuel rod pellets in the middle radial layer, a stainless steel 25 for the simulated fuel rod cladding in the outermost radial layer, an insulating gasket 22 in the inner layer at the axial ends, and an electrode 16 in the outer layer at the axial ends;

[0010] The protective gas module includes an argon gas cylinder 1, a pressure reducing valve 2, and an intake valve 3;

[0011] The DC power supply heating module includes a DC power supply 4. The DC power supply 4 is connected to both ends of the simulated fuel rod through an electrode 16 in the outer layer at the axial ends of the simulated fuel rod 13 and outputs a rated current to conduct to the high-temperature heating wire part in the simulated fuel rod. Electrical energy is converted into heat energy in the high-temperature heating wire to simulate the heat generation of the fuel rod pellets;

[0012] The photographing and recording module includes a high-speed camera 5 and a light source 6. There is also a visualization window opened on the top flange cover of the experimental section 21, namely, a fuel rod fixing window 18 for fixing the simulated fuel rod, a light source installation window 19 for installing the light source, and a high-speed camera installation window 20 for the high-speed camera to take pictures, which are used to photograph and record the aggregation and migration process of the melt at the liquid lead-bismuth interface;

[0013] The instrument and meter module includes a high-temperature thermocouple 14 and a pressure measuring device 15. The melting process and the energy release degree of the simulated fuel rod 13 during the damage process of the lead-bismuth reactor are obtained through the high-temperature thermocouple 14 and the pressure measuring device 15.

[0014] The cladding of the entire experimental section 21 consists of four layers. The innermost layer is an alumina ceramic 8, which is used to withstand the high temperature of the liquid lead-bismuth in the experimental section and conduct the heat out; the second layer is an electric heating wire 9, which is used to conduct the heat to the solid lead-bismuth in the experimental section 21 and melt it into liquid lead-bismuth 12; the third layer is a heat insulation layer 10, which is used to isolate the heat transfer and prevent the heat from melting the fourth layer of stainless steel shell and causing an accident endangering the safety of the experimental personnel; the fourth layer is a stainless steel shell 11, which is used to withstand the pressure of the lead-bismuth gravity on the experimental section 21 and prevent the bottom layer of the experimental section 21 from cracking.

[0015] The top of the experimental section 21 is sealed with a flange cover. The flange cover is provided with five windows, namely, a fuel rod fixing window 18 for fixing the simulated fuel rod in the center, light source installation windows 19 on both sides for installing the light source, and high-speed camera installation windows 20 on both sides for the high-speed camera to take pictures.

[0016] An exhaust valve 7 is provided on the experimental section 21.

[0017] The experimental method of the experimental system for the migration of the melt in the damaged core of the lead-bismuth reactor is as follows:

[0018] On the premise of ensuring the sealing of the experimental section and the placement of materials, equipment, and instruments, the experimental section 21 is purged with argon. After closing all valves, the pressure reducing valve 2 and the inlet valve 3 are opened, and argon is filled into the experimental section 21. A lit candle is placed at the outlet of the exhaust valve 7. When the candle flame is extinguished by the discharged gas, it proves that the experimental section is filled with argon. The pressure reducing valve 2 and the inlet valve 3 are adjusted to maintain the internal pressure of the experimental section 21 near one atmosphere.

[0019] Under the argon protection atmosphere, the pressure regulator is turned on to heat the electric heating wire to melt the solid lead-bismuth alloy in the experimental section 21, and the experimental system is insulated through the heat preservation layer 10. The openings of the pressure reducing valve 2 and the inlet valve 3 are adjusted to control the internal pressure of the experimental section 21 to be maintained near one atmosphere.

[0020] The DC power supply 4 is started to melt the simulated fuel rod 13 in the lead-bismuth alloy. At the same time, the light source 6 and the high-speed camera 5 are turned on to observe the fluctuation of the lead-bismuth liquid level and the aggregation and migration of the melt on the lead-bismuth liquid surface. At the same time, the temperature of the simulated fuel rod 13 in the experimental section 21 and the pressure change data of argon are monitored and saved with the help of the high-temperature thermocouple 14 and the pressure measuring device 15 connected to the acquisition system.

[0021] According to the variation of temperature and pressure data with time during the experiment, judge the melting process of the fuel rod and the severity of energy release during the damage process of the lead-bismuth reactor.

[0022] After the migration of the melt is completed and the temperature of the entire experimental section 21 drops to room temperature, all valves are closed, the pipeline between the experimental section 21 and the argon cylinder 1 is disassembled, and the electrode of the DC power supply 4 and the simulated fuel rod 13 is disconnected. After the entire experimental section 21 is removed, the experimental section 21 is cut open using metal cutting technology, and the measurement data of the size and mass of the melt fragments are statistically analyzed to evaluate the fragmentation degree of the pellet material after being subjected to thermal stress and the fragmentation degree after the interaction between the molten cladding and the coolant. At the same time, combined with the images taken at the flange cover window and the position data of the melt distribution after the experimental section is cut open, infer the migration behavior mechanism of the melt in the liquid lead-bismuth coolant.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] An experimental system and method for the migration of molten core melt in a lead-based reactor according to the present invention are for studying a series of complex migration movements caused by the blockage of coolant channels due to core damage, cladding melting, and melt condensation under severe accidents in a lead-based reactor, as well as further temperature rise, pellet fragmentation, and interaction with the coolant, and the coolant as a carrier. The experimental system of the present invention uses a high-purity lead-bismuth alloy with the same ratio as that in a lead-bismuth reactor and a fuel cladding identical to that of a real lead-bismuth reactor fuel rod. The experimental conditions can meet the requirements of the real working conditions of a lead-bismuth reactor, ensuring the practical significance of the experimental results and having reference significance for engineering practice.

[0025] The experimental process in the experimental section of the present invention is visualized. There are five windows opened at the top cover of the experimental section, namely, a window for fixing the fuel rod, a window for installing a light source, and a window for a high-speed camera to take pictures. The rationality of the window opening can ensure that the camera can observe and record the aggregation and migration of the melt on the lead-bismuth liquid surface comprehensively and throughout the process under dark conditions.

[0026] The experimental section designed by the present invention is a multi-layer structure to prevent the experimental section from melting after the stainless steel cladding of the fuel rod melts. The innermost layer is alumina ceramic, the second layer is a heating wire, the third layer is a heat-insulating layer, and the fourth layer is a stainless steel shell.

[0027] The density ratio of real material oxide pellets, stainless steel cladding, and liquid lead-bismuth is 1:0.75:0.96. The substitute material metal molybdenum of the pellets is similar to the real oxide pellets in terms of physical properties such as density, hardness, melting point, and thermal conductivity. The density ratio of the three selected substitutes is 1:0.72:0.97, which is very close to the real situation. At the same time, the cladding selects the real material stainless steel, and the pellets also select metal molybdenum with properties similar to those of oxide pellets, which can more accurately simulate phenomena such as core damage, pellet fragmentation, and melt migration. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of an experimental system for studying the interaction between molten core melt and coolant in a lead-based reactor according to the present invention.

[0029] Figure 1 In the figure: 1 is an argon gas cylinder, 2 is a pressure reducing valve, 3 is an intake valve, 4 is a DC power supply, 5 is a high-speed camera, 6 is a light source, 7 is an exhaust valve, 8 is alumina ceramic; 9 is a heating wire, 10 is heat-insulating cotton, 11 is a stainless steel shell, 12 is liquid lead-bismuth, 13 is a simulated fuel rod, 14 is a high-temperature thermocouple; 15 is a pressure measuring device, 16 is an electrode, 17 is a flange cover.

[0030] Figure 2 In the figure: 18 is a fuel rod fixing window, 19 is a light source installation window, 20 is a high-speed camera installation window.

[0031] Figure 3 Among them: 21 is the experimental section.

[0032] Figure 4 Among them: 16 is the electrode, 22 is the insulating gasket, 23 is the heating wire, 24 is molybdenum metal, and 25 is stainless steel. Specific implementation manner

[0033] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation manners:

[0034] As Figure 1 shown, an experimental system for molten material migration of a damaged core of a lead-bismuth reactor according to the present invention includes an experimental section 21, a simulated fuel rod 13, a protective gas module, a DC power supply heating module, a shooting and recording module, and an instrument and meter module; wherein the experimental section 21 is a pressure vessel simulating the working environment of the core of a lead-bismuth reactor;

[0035] The top of the experimental section 21 is sealed with a flange cover. The experimental section 21 is provided with four layers of cladding layers. The cladding layers are filled with lead-bismuth alloy as a coolant, and the simulated fuel rod 13 is inserted into the lead-bismuth alloy. The four layers of cladding layers specifically include: the innermost layer is alumina ceramic 8, which is used to withstand the high temperature of the liquid lead-bismuth in the experimental section and conduct heat out; the second layer is an electric heating wire 9, which is used to conduct heat to the solid lead-bismuth in the experimental section 21 and melt it into liquid lead-bismuth 12; the third layer is a heat insulation layer 10, which is used to isolate heat transfer and prevent heat from melting the fourth layer of stainless steel shell and causing an accident endangering the safety of experimental personnel; the fourth layer is a stainless steel shell 11, which is used to withstand the pressure of the lead-bismuth gravity on the experimental section 21 and prevent the bottom layer of the experimental section 21 from cracking;

[0036] The simulated fuel rod 13 is composed of five parts, namely a high-temperature heating wire 23 in the innermost layer in the radial direction, a substitute molybdenum metal 24 for the simulated fuel rod core block in the middle layer in the radial direction, a stainless steel 25 for the simulated fuel rod cladding in the outermost layer in the radial direction, an insulating gasket 22 in the inner layer at the axial end, and an electrode 16 in the outer layer at the axial end;

[0037] The protective gas module includes an argon gas cylinder 1, a pressure reducing valve 2, and an inlet valve 3. Since the experimental section 21 involves a high-purity lead-bismuth alloy with the same ratio as that of an actual lead-bismuth reactor, in order to prevent lead-bismuth from being oxidized, a protective gas environment needs to be established. Before heating and melting the lead-bismuth alloy, the internal space of the experimental section needs to be replaced with argon gas through the argon gas cylinder 1 to remove air. A pressure reducing valve 2 and an inlet valve 3 are sequentially arranged on the pipeline connecting the argon gas cylinder 1 and the experimental section 21;

[0038] The DC power heating module includes a DC power supply 4. The DC power supply 4 is connected to both ends of the simulated fuel rod through the electrodes 16 on the outer layer of the axial end of the simulated fuel rod 13 and outputs a rated current to conduct to the high-temperature heating wire part in the simulated fuel rod. Electrical energy is converted into heat energy in the high-temperature heating wire to simulate the heat generation of the fuel rod pellets.

[0039] The shooting and recording module includes a high-speed camera 5 and a light source 6. There is also a visualization window opened on the top flange cover of the experimental section 21, including a fuel rod fixing window 18 for fixing the simulated fuel rod, a light source installation window 19 for installing the light source, and a high-speed camera mounting window 20 for the high-speed camera to take pictures, which is used to shoot and record the aggregation and migration process of the melt at the liquid lead-bismuth surface. In this embodiment, there are a total of five visualization windows. The fuel rod fixing window 18 is one and located in the center. The light source installation windows 19 are two and located on both sides of the fuel rod fixing window 18. The high-speed camera mounting windows 20 are two and located on the other two sides of the fuel rod fixing window 18.

[0040] The instrument and meter module includes a high-temperature thermocouple 14 and a pressure measuring device 15, and obtains the melting process and energy release degree of the simulated fuel rod 13 during the damage of the lead-bismuth reactor through the high-temperature thermocouple 14 and the pressure measuring device 15.

[0041] Before using the above experimental system provided by the present invention to carry out experiments, on the premise of ensuring the sealing of the experimental section and the placement of materials, equipment and instruments, the experimental section 21 is replaced with argon. After closing all valves, open the pressure reducing valve 2 and the intake valve 3 to fill the experimental section 21 with argon. Place a lit candle at the outlet of the exhaust valve 7. When the candle flame is extinguished by the discharged gas, it proves that the experimental section is full of argon. Adjust the pressure reducing valve 2 and the intake valve 3 to keep the internal pressure of the experimental section 21 near one atmosphere.

[0042] Under the argon protection atmosphere, turn on the voltage regulator to heat the heating wire to melt the solid lead-bismuth alloy in the experimental section 21, and insulate the experimental system through the heat insulation layer 10. Adjust the opening degrees of the pressure reducing valve 2 and the intake valve 3 to control the internal pressure of the experimental section 21 to be maintained near one atmosphere.

[0043] Start the DC power supply 4 to melt the simulated fuel rod 13 in the lead-bismuth alloy. At the same time, turn on the light source 6 and the high-speed camera 5 to observe the fluctuations of the lead-bismuth liquid surface and the aggregation and migration of the melt on the lead-bismuth liquid surface. At the same time, monitor and save the temperature change data of the simulated fuel rod 13 and the pressure change data of argon in the experimental section 21 with the help of the high-temperature thermocouple 14 and the pressure measuring device 15 connected to the NI acquisition system.

[0044] According to the change of temperature and pressure data with time during the experiment, judge the melting process of the fuel rod and the severity of energy release during the damage of the lead-bismuth reactor.

[0045] After the migration of the melt ends and when the temperature of the entire experimental section 21 drops to room temperature level, i.e., 25 °C, close all valves, disassemble the pipeline between the experimental section 21 and the argon gas cylinder 1, and disconnect the DC power supply 4 from the electrodes of the simulated fuel rod 13; after removing the entire experimental section 21, use metal cutting technology to cut the experimental section 21 open, and conduct statistical analysis on the measurement data of the size and mass of the melt fragments to evaluate the fragmentation degree of the pellet material after being subjected to thermal stress and the fragmentation degree after the interaction between the molten cladding and the coolant. At the same time, combining the images taken at the flange cover window and the position data of the melt distribution after the experimental section is cut open, infer the migration behavior mechanism of the melt in the liquid lead-bismuth coolant, providing theoretical guidance for the safety design and evaluation of lead-bismuth fast reactors.

[0046] The present invention eliminates the design of a lead-bismuth storage tank, directly heats and melts lead-bismuth in the experimental section, saving experimental materials and simplifying the experimental steps; in order to simulate as much as possible the heat transfer of the rod bundle, the melting of the cladding, the fragmentation of the pellets, and the migration process of the melt in the coolant during the damage process of a lead-bismuth reactor under real conditions, and at the same time considering the density ratio principle of real substances, the material of the simulated fuel pellets is molybdenum metal, the material of the simulated fuel rod cladding is stainless steel, and liquid lead-bismuth is used as the coolant. At the same time, a multi-layer structure is designed for the experimental section to prevent the stainless steel serving as the shell from melting as the stainless steel cladding of the fuel rod melts. The present invention can conduct simulation experiments on the melting, pellet fragmentation, and melt migration of a single fuel rod and a fuel rod bundle, providing a reference for the safety design of lead-bismuth reactors.

[0047] The above content is a further detailed description of the present invention in combination with a specific experimental scheme, but it is not a limitation on the implementation mode of the present invention. For those skilled in the art to which the present invention pertains, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A molten core debris migration experimental system for a lead-bismuth reactor, characterized in that: It includes an experimental section (21), a simulated fuel rod (13), a protective gas module, a DC power heating module, a shooting and recording module, and an instrument module; it is used to simulate the thermohydraulic phenomena of core damage, cladding melting, pellet fragmentation, and the migration of melt in the coolant during a severe accident in a lead-bismuth reactor; among them, the experimental section (21) is a pressure vessel that simulates the working environment of the lead-bismuth reactor core. The top of the experimental section (21) is sealed. The experimental section (21) adopts a multi-layer coating layer, a heating device is arranged in the coating layer, lead-bismuth alloy is filled in the coating layer as the coolant, and the simulated fuel rod (13) is inserted into the lead-bismuth alloy. The simulated fuel rod (13) is composed of five parts, namely, a high-temperature heating wire (23) in the innermost radial layer, a substitute metal molybdenum (24) for the simulated fuel rod pellets in the middle radial layer, a stainless steel (25) for the simulated fuel rod cladding in the outermost radial layer, an insulating gasket (22) in the inner layer at the axial end, and an electrode (16) in the outer layer at the axial end. The protective gas module includes an argon gas cylinder (1), a pressure reducing valve (2), and an intake valve (3). The DC power heating module includes a DC power supply (4). The DC power supply (4) is connected to both ends of the simulated fuel rod through the electrode (16) in the outer layer at the axial end of the simulated fuel rod (13) and outputs a rated current to conduct to the high-temperature heating wire part in the simulated fuel rod. Electrical energy is converted into heat energy in the high-temperature heating wire to simulate the heat generation of the fuel rod pellets. The shooting and recording module includes a high-speed camera (5) and a light source (6). There is also a visualization window opened on the top flange cover of the experimental section (21), namely a fuel rod fixing window (18) for fixing the simulated fuel rod, a light source mounting window (19) for mounting the light source, and a high-speed camera mounting window (20) for the high-speed camera to shoot, which is used to shoot and record the aggregation and migration process of the melt at the liquid lead-bismuth surface. The instrument module includes a high-temperature thermocouple (14) and a pressure measuring device (15). The melting process and energy release degree of the simulated fuel rod (13) during the damage of the lead-bismuth reactor are obtained through the high-temperature thermocouple (14) and the pressure measuring device (15).

2. The experimental system for molten core debris migration in a lead-bismuth reactor core meltdown according to claim 1, wherein: The coating layer of the entire experimental section (21) is composed of four layers. The innermost layer is alumina ceramic (8), which is used to withstand the high temperature of the liquid lead-bismuth in the experimental section and conduct the heat out; the second layer is an electric heating wire (9), which is used to conduct the heat to the solid lead-bismuth in the experimental section (21) and melt it into liquid lead-bismuth (12); the third layer is a heat insulation layer (10), which is used to isolate heat transfer and prevent heat from melting the fourth layer of stainless steel shell and causing an accident that endangers the safety of experimental personnel; the fourth layer is a stainless steel shell (11), which is used to withstand the pressure of the lead-bismuth gravity on the experimental section (21) and prevent the bottom layer of the experimental section (21) from cracking.

3. The experimental system for the migration of molten core melt in a lead-bismuth reactor core damage according to claim 1, characterized in that: The top of the experimental section (21) is sealed with a flange cover. The flange cover is provided with five windows, namely a fuel rod fixing window (18) for fixing the simulated fuel rod in the center, light source mounting windows (19) on both sides for mounting the light source, and high-speed camera mounting windows (20) on both sides for the high-speed camera to shoot.

4. An experimental system for the migration of molten core melt in a lead-bismuth reactor core damage, according to claim 1, characterized in that: An exhaust valve (7) is provided on the experimental section (21).

5. The experimental method of the lead-bismuth reactor damaged core melt migration experimental system according to any one of claims 1 to 4, characterized in that: The method includes: On the premise of ensuring the sealing of the experimental section and the placement of materials, equipment, and instruments, perform argon replacement on the experimental section (21); after closing all valves, open the pressure reducing valve (2) and the intake valve (3) to fill the experimental section (21) with argon; place a lit candle at the outlet of the exhaust valve (7), and when the candle flame is extinguished by the discharged gas, it proves that the experimental section is filled with argon; adjust the pressure reducing valve (2) and the intake valve (3) to maintain the internal pressure of the experimental section (21) near one atmosphere; Under the argon protection atmosphere, turn on the voltage regulator to heat the electric heating wire to melt the solid lead-bismuth alloy in the experimental section (21), and insulate the experimental system through the heat insulation layer (10), and adjust the opening degrees of the pressure reducing valve (2) and the intake valve (3) to control the internal pressure of the experimental section (21) to be maintained near one atmosphere; Start the DC power supply (4) to melt the simulated fuel rod (13) in the lead-bismuth alloy. At the same time, turn on the light source (6) and the high-speed camera (5) to observe the fluctuations of the lead-bismuth liquid level and the aggregation and migration of the melt on the lead-bismuth liquid surface; at the same time, monitor and save the temperature change data of the simulated fuel rod (13) and the pressure change data of argon in the experimental section (21) with the help of the high-temperature thermocouple (14) connected to the acquisition system and the pressure measuring device (15); According to the change of temperature and pressure data with time during the experiment, judge the melting process of the fuel rod and the severity of energy release during the damage of the lead-bismuth reactor; After the migration of the melt is completed, when the temperature of the entire experimental section (21) drops to room temperature, close all valves, disassemble the pipeline between the experimental section (21) and the argon cylinder (1), and disconnect the electrodes of the DC power supply (4) and the simulated fuel rod (13); after removing the entire experimental section (21), use metal cutting technology to cut open the experimental section (21), and statistically analyze the measurement data of the size and mass of the melt fragments to evaluate the fragmentation degree of the pellet material after being subjected to thermal stress and the fragmentation degree after the interaction between the molten cladding and the coolant; at the same time, combine the images taken at the flange cover window and the position data of the melt distribution after the experimental section is cut open to infer the migration behavior mechanism of the melt in the liquid lead-bismuth coolant.

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