CN111650235A

CN111650235A - Experimental device and experimental method for researching boiling bubble behavior in pit under serious accident

Info

Publication number: CN111650235A
Application number: CN202010272075.0A
Authority: CN
Inventors: 谷海峰; 尹威凯; 周艳民; 孙中宁; 孙庆洋; 虞想; 阎昌琪; 孟兆明
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2020-04-09
Filing date: 2020-04-09
Publication date: 2020-09-11
Anticipated expiration: 2040-04-09
Also published as: CN111650235B

Abstract

The invention aims to provide an experimental device and an experimental method for researching the behavior of boiling bubbles in a pit under a serious accident. The method can intuitively simulate the decay heat of the aerosol in the pit, and is convenient for deeply researching the behavior of the boiling bubbles in the pit. The heating boiling behavior of the aerosol in the pit can be studied independently, and the boiling behavior in the pit with the melt can also be studied simultaneously.

Description

Experimental device and experimental method for researching boiling bubble behavior in pit under serious accident

Technical Field

The invention relates to a simulation experiment device and an experiment method, in particular to a simulation experiment device and an experiment method for boiling bubbles in a pit after a nuclear accident.

Background

After a serious accident of the reactor occurs, the fuel element cladding of the reactor core can fail in a large area, and radioactive nuclides are released from a primary circuit to the containment. Aerosols are one of the main states of radionuclides and migrate and settle in the containment. Meanwhile, as a special safety facility is put into use (for example, a spraying system sprays cooling water into the containment), most of aerosol can be settled and gathered into a pit of the containment. These aerosol particles suspended in the pit release decay heat. Under the action of decay heat, water in the pit is continuously heated to boiling and generates boiling bubbles, the bubbles rise to the surface of the liquid pool to be broken, and the aerosol in the pit is re-entrained and released to the gas space of the containment vessel in the process. Although the entrainment is limited in a short time, the entrained radioactive aerosol will be very considerable as time goes on, so the calculation of the entrainment of the aerosol caused by the bubble breaking is very important for the evaluation of the source item in the containment. Meanwhile, due to the fact that the reactor core is melted down in a serious accident, if the melting degree of the reactor core is serious, melt can fall to a lower end socket of the pressure vessel, once the melt cannot be effectively cooled, the integrity of the pressure vessel can be damaged, and the melt falls into a pit. The melt entering the pit inevitably heats the surrounding water to boil to generate bubbles, and the aerosol in the water also influences the boiling bubble behavior on the surface of the melt, so that the entrainment behavior caused by bubble breakage is also influenced. In summary, the re-entrainment process of the aerosol in the pit is related to the bubble breaking process on the surface of the liquid pool, and the bubble breaking process is influenced by the behavior of the boiling bubbles (such as bubble size and bubble rising speed), so that the research on the behavior of the boiling bubbles in the pit is of great significance.

Due to the presence of a large amount of radioactive aerosol in the pit, the decay heat released by the aerosol will heat the surrounding liquid, raising the temperature of the liquid to boiling producing bubbles. If the research is directly carried out by using radioactive aerosol particles, the research is not realistic from the perspective of safety and experiments, so that other ways for simulating the process need to be considered. At present, the commonly used boiling bubble behavior research device uses a heating element to heat liquid, the mode is only to locally heat the liquid on the surface of the heating element, the liquid is heated unevenly, and boiling bubbles are only generated on the heating element. The boiling of the liquid in the pit is caused by the heating of an internal heat source of radioactive aerosol particles, the boiling occurs on the surfaces of the radioactive particles, the radioactive particles are uniformly dispersed in the liquid pool, bubbles can freely rise under the action of buoyancy after the boiling occurs, the bubbles do not grow on the heating surface and then break away, and the specific boiling characteristics determine that the behavior of the boiling bubbles in the pit can not be simulated by the boiling bubbles on the surface of a conventional heating element, so the conventional schemes have great defects. In order to realize the research on the boiling behavior in the pit, an experimental device capable of realizing the heating of an internal heat source is needed.

The research shows that the experimental devices related to the heating of the internal heat source mainly have the following three types: 1. heating by heating element is adopted, such as Chinese patent application text "heating system for simulating heat source in molten pool" (published 2018, 1, 16, publication No. CN107591214A, 2016, 7, 6). The heating element is embedded in the test piece in such a way that it is more efficient and the power control is relatively easy. Boiling bubbles are still generated only at the surface of the heating element and the decay heat of the aerosol cannot be simulated. 2. Microwave heating is adopted, such as the documents "Microwave heating device for internal heating control experiments, applied to Earth's mobile dynamics". The main principle is that polar molecules (mainly water) are continuously rotated by using a rapidly-changing high-frequency electromagnetic field so as to generate heat by friction. This type of heating can heat the liquid uniformly and is well-established (e.g. microwave oven), but this process is not self-heating of the particles and is different from the actual situation, so it cannot be used for aerosol decay thermal simulation. 3. An electromagnetic heating mode is adopted, for example, in the Chinese patent application text 'experiment device for forced convection heat transfer of molten salt in channels of large-size pellet beds with strong internal heat sources' (published as 2014, 8.13.8.7; published as CN 103983661A; published as 2014, 5.8.8.5.7.3). The main principle is that the metal ball generates eddy current and generates heat by using the law of electromagnetic induction and an external alternating electric field. The heating mode of the type is that the heat generated by the solid per se is dissipated outwards, and the experimental device can be used for simulating the heating of the ball bed, but the experimental device for researching the flowing heat exchange has certain requirements on the volume of the metal ball, and the experimental device can also be used for simulating the decay heat of the aerosol because bubbles are generated on the surface of the metal ball after the experiment device is boiled.

Disclosure of Invention

The invention aims to provide an experimental device and an experimental method for researching the behavior of boiling bubbles in a pit under serious accidents, which can realize the simulation of the boiling state in the pit under different conditions and provide basic data for the calculation of the entrainment amount of surface bubbles.

The purpose of the invention is realized as follows:

the invention relates to an experimental device for researching the behavior of boiling bubbles in a pit under a serious accident, which is characterized in that: including the glass container, the condensate tank, prepare the water tank, the top cap is installed to the upper end of glass container, the base is installed to the lower extreme of glass container, the top cap passes through the top of first tube coupling condensate tank, the bottom of glass container lower part through second tube coupling condensate tank, the lower part of water tank is prepared in the upper portion of condensate tank through the third tube coupling, the outside spiral coil of winding electromagnetic inductor of glass container leaves the clearance that is used for shooing between the spiral coil, set up heater and agitator in the configuration water tank.

The experimental device for researching the behavior of boiling bubbles in the pit under the serious accident can also comprise:

1. the glass container lower part sets up first trap, condensate water tank lower part sets up the second trap, set gradually first solenoid valve on the first pipeline between top cap and the condensate water tank, pressure sensor, the second solenoid valve, the vacuum pump pipe is stretched out at the condensate water tank top, the vacuum pump union coupling vacuum pump, install the third solenoid valve on the vacuum pump pipe, set up the fourth solenoid valve on the second pipeline, set gradually the fifth solenoid valve on the third pipeline between condensate water tank and the preparation water tank, a water pump, the sixth solenoid valve, preparation water tank top sets up the water injection valve, preparation water tank bottom sets up the third trap.

2. The base is a non-metal structure base.

3. The base is the metal structure base, the metal structure base includes Teflon base, O type sealing washer, metal disc, double-screw bolt, and metal disc and double-screw bolt are fixed together, and Teflon base inside sets up the internal thread, and the double-screw bolt is in the same place through the internal thread connection of its external screw thread with Teflon base, and Teflon base's top sets up the spill step, and the metal disc is located Teflon base's spill step, and O type sealing washer is placed to the circular slot of spill step department processing.

The invention relates to an experimental method for researching the behavior of boiling bubbles in a pit under a serious accident, which is characterized by comprising the following steps: adopting an experimental device for researching the boiling bubble behavior in a pit under a serious accident as claimed in claim 1;

injecting quantitative deionized water into a preparation water tank, opening a heater to heat the deionized water to boiling for half an hour, removing non-condensable gas in the deionized water, pouring magnetic nanoparticle suspension into the water tank, opening a stirrer to dilute the magnetic nanoparticle suspension, uniformly mixing, firstly opening a fifth valve and a sixth valve, then opening a second electromagnetic valve, a fourth electromagnetic valve and a first electromagnetic valve, opening a water pump after the valves are opened to inject the suspension into the condensed water tank until the liquid level of the condensed water tank is raised to a preset position, closing the water pump, the fifth electromagnetic valve, the sixth electromagnetic valve and the first electromagnetic valve, opening a power supply of an electromagnetic inductor, generating heat by the magnetic nanoparticles to boil the suspension in a quartz glass container, opening a third electromagnetic valve and a vacuum pump to extract partial gas along with the rise of the pressure of a steam generation system, and closing the vacuum pump and the third electromagnetic valve when steam is discharged from an outlet of the vacuum pump, regulating the flow of a condensing coil in a condensing water tank to condense steam in the condensing water tank, generating negative pressure by condensation to suck the steam into the condensing water tank, and refluxing to a glass container to finally maintain the system pressure and the suspension concentration to be stable; after the system is stable, shooting and recording the bubble behavior of the glass container by using a camera, and starting data recording by using a temperature and pressure acquisition system; when the experiment is finished, firstly, closing a medium-high frequency power supply of the electromagnetic inductor, and closing the acquisition system when the temperature is reduced to a safety limit value; and opening the first drain valve and the second drain valve to discharge the turbid liquid, and cleaning each experimental device by using deionized water.

The invention has the advantages that:

1. the decay heat of the aerosol in the pit can be intuitively simulated. By utilizing the magnetocaloric effect of the magnetic nanoparticles, the magnetic nanoparticles directly generate heat to heat the surrounding water environment, and the released heat can heat the experimental section to boil to generate bubbles, so that the behavior of the boiling bubbles in the pit is deeply researched.

2. The heating boiling behavior of the aerosol in the pit can be studied independently, and the boiling behavior in the pit with the melt can also be studied simultaneously. The experimental bases were designed as follows: (1) the base with the non-metal structure is used for researching the bubble behavior of liquid boiling when only aerosol exists in the pit. (2) The base of the metal structure is used for researching the boiling bubble behavior in the pit when the aerosol and the melt exist at the same time, and can also analyze the heat exchange behavior of the structure in the suspension.

3. The concentration of aerosol particles can be kept constant during the experiment. The experiment section is direct to link to each other with the condenser, and the pipeline that links to each other at the top is favorable to steam flow, and the negative pressure that condenser condensation produced inhales the steam of experiment section, and the pipeline that links to each other at the bottom is favorable to the lime set backward flow in the condenser to get into the experiment section to it is unchangeable to guarantee the turbid liquid concentration in the experiment section.

4. The experiments can be carried out under defined pressure. Because the actual pressure in the containment vessel is not atmospheric pressure, the device can be adjusted to a certain pressure during the experiment. During the experiment, the flow of the condensing pipe and the medium-high frequency power supply can be adjusted to ensure that the evaporation capacity is the same as the condensation capacity so as to maintain the pressure stability of the system.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2a is a schematic view of a non-metal structure base, and FIG. 2b is a schematic view of a metal structure base;

FIG. 3 is a schematic view of a stud and a metal plate.

Detailed Description

The invention will now be described in more detail by way of example with reference to the accompanying drawings in which:

the invention provides an experimental device for simulating the behavior of boiling bubbles in a pit after an accident, which is combined with the drawings of fig. 1-3, and consists of main body boiling

experimental sections

2, 3, 5, 6, 7,

condensation sections

12, 13, 14, 15, 16, 17,

solution preparation sections

19, 20, 21, 22, 23, 24, 25 and connecting pipelines, wherein relevant parts of the pipelines are provided with electromagnetic valves 9, 11, 26 and pressure sensors 10, temperature measuring points 1, 8, 18 are arranged at different positions and are connected with a collecting system, and high-speed photography 4 is arranged outside the device and is used for shooting the behavior of bubbles. The basic principle of the experimental device is as follows: dissolve magnetic nanoparticle in the boiling experiment section, the particulate matter receives the influence that changes the magnetic field can produce the heat and heat to water on every side, and the boiling bubble that produces of water heating utilizes high-speed photography to shoot the record to experimental phenomena. Meanwhile, in order to research the boiling behavior of the liquid pool when the melt falls into the pit, a metal plate with a surface processed into a porous structure is adopted to simulate the melt falling into the pit from the lower end enclosure, the particles and the melt generate heat simultaneously under the action of a changing magnetic field to heat the liquid to boil, and then the boiling bubble phenomenon is photographed and recorded.

The boiling experiment section consists of a base 2, a quartz glass container 6, an electromagnetic inductor 5 and a top cover 7. Wherein the base comprises a non-metal structure base 2a and a metal structure base 2b which can be replaced with each other. The non-metal structure base 2a is directly processed by Teflon. The metal structure base 2b is composed of a Teflon base 2b.1, an O-shaped rubber ring 2b.2, a metal plate 2b.3 and a stud 2b.4, the metal plate 2b.3 can be embedded into the Teflon base 2b.1 through a bottom thread 2b.4, and the thread is used for sealing. The base 2, the quartz glass container 6 and the top cover 7 are sequentially connected through flanges, and the bolts and the gaskets are made of non-metal materials to avoid the influence of electromagnetic induction. The helical coil of the electromagnetic inductor 5 is wound on a quartz glass vessel 6 and powered by a medium-high frequency power supply, leaving a certain gap when deployed for high-speed photography 4 to photograph boiling bubbles. The boiling experiment section is the core part of whole experimental apparatus, mainly makes the interior magnetic field that produces the change of experimental apparatus through well high frequency heating power, and the magnetic nanoparticle that dissolves in the solution constantly releases the heat under the magnetic field effect, and this part heat can continuously be with the water heating boiling production bubble, adopts the action of interior heat source heating's mode research boiling bubble in the pit like this. If the boiling bubble condition in the pit when the melt exists is researched, the nonmetal structure base of the boiling experimental section needs to be replaced by the metal structure base, the surface of the metal plate embedded into the container base is of a porous structure and can be used for simulating the melt falling into the pit from the lower end socket of the pressure container, the changing magnetic field can enable the metal plate and the particles to release heat simultaneously to heat the surrounding water to boil, and the observation of the behavior of the boiling bubbles in the pit is realized through a series of measures.

The condensing section consists of a vacuum pump 13, a condensing water tank 14, a condensing coil 15,

valves

12, 16 and 17 and connected pipelines. The suction valve 12 is connected to a vacuum pump 13, and a part of the gas is sucked out at the beginning of the experiment, so that the steam flows into the condensation section. The condenser coil 15 dress is in condensate tank 14, lets in the cooling water in the condenser coil 15 during the experiment, to steam condensation and produce certain negative pressure, with the steam of experiment section constantly the suction condensate tank 14 in, the condensate tank 14 bottom links to each other so the condensate can constantly flow back to the experiment section with quartz glass container 6 to guarantee that the concentration of turbid liquid keeps unchangeable in the experiment section.

The solution preparation water tank mainly comprises a stirrer 20, a water tank 21, a heater 22, a water pump 25 and

valves

19, 23 and 24. The heater 22 is installed at a lower portion of the water tank 21 and heats the deionized water to boil at an initial time to remove non-condensable gas therefrom. The stirrer 20 is fixed on the top cover of the water tank 21, and can stir the suspension uniformly during suspension preparation, and pump the suspension into the condensed water tank 14 through the water pump 25 after the suspension preparation is completed.

The measuring system consists of a high-speed photography 4 and a data acquisition system. The high-speed photography 4 is used for photographing the bubble form and the rising speed and transmitting the photographing data to the computer in real time; the data acquisition system includes

temperature signal acquisition

1, 8, 18 and pressure signal acquisition 10. The temperature is mainly set with the following three measuring points: 1. on the base metal sheet, the measuring point is reserved at the bottom of the metal sheet 2b.3 and is used for monitoring the superheat degree of the metal sheet in the experiment, and the superheat degree can be directly measured by adopting the K-type thermocouple 1 due to the skin effect and is led out through a reserved channel at the bottom of the metal sheet. 2. In the boiling experiment section, the temperature of the boiling experiment section is measured by using the optical fiber temperature probe 8, and the optical fiber temperature probe can completely eliminate the influence of the electromagnetic environment on the temperature measurement because the experiment section is in a strong electromagnetic environment. 3. In the preparation water tank, the preparation water tank 21 needs to monitor the temperature in the boiling exhaust process. The pressure sensor 10 is arranged at the high position of the pipeline of the experimental device, and monitors the pressure of the experimental device during the experiment to ensure that the experiment is carried out at the required pressure.

The core part is the experimental section of device, including base 2, quartz glass container 6 and top cap 7, the triplex uses the flange to connect gradually, uses non-metallic bolt and gasket when connecting for eliminating electromagnetic induction's influence flange. The spiral coil of the electromagnetic inductor 5 is wound on the quartz glass container 6, and a gap is reserved to ensure the shooting of the high-speed photography 4. The upper and lower pipes of the condensation section 14 are respectively connected with the top cover 7 and the quartz glass container 6, and the pipes are provided with electromagnetic valves 9, 11 and 26 to ensure the safety of the opening and closing of the valves during the experiment. The suspension preparation section is connected with a condensed water tank 14 through a pipeline, two electromagnetic valves 17 and 24 are reserved on the pipeline, and a water pump (25) is installed on an outlet pipeline of the preparation water tank to provide an injection pressure head. The acquisition system accesses the signals to be acquired into the computer. Thus, the experimental parts are connected into a whole.

The experimental method for simulating the behavior of boiling bubbles in a pit is as follows. 1. An experiment preparation stage: a certain amount of deionized water is injected into the solution preparation water tank 21, and the heater 22 is turned on to heat the deionized water to boiling for half an hour to remove non-condensable gases in the deionized water. Pouring prepared high-concentration magnetic nanoparticle suspension, opening the stirrer 20 to dilute the high-concentration suspension to low concentration, opening valves 17 and 24 on pipelines of the suspension preparation water tank 21 and the condensed water tank 14 when the suspension is uniformly mixed, opening valves 11 and 26 and an exhaust valve 9 on pipelines connecting the condensed water tank 14 and the

experimental sections

2, 3, 5, 6 and 7, and opening a water pump 25 to inject the suspension into the condensed water tank 14 after the valves are opened. Until the liquid level of the condensed water tank 14 rises to a predetermined position, the water pump 25, the valves 17 and 24 and the exhaust valve 9 are closed. 2. And (3) an experimental stage: the power supply of the electromagnetic inductor 5 is turned on, and the magnetic nanoparticles generate heat under the action of the alternating electric field, so that turbid liquid in the quartz glass container 6 is boiled. And (3) opening the air extraction valve 12 and the vacuum pump 13 on the condensed water tank to extract certain gas at the moment along with the pressure rise of the steam generation system, and closing the pump and the valve when steam is discharged from the outlet of the vacuum pump 13. The steam in the condensate water tank 14 is condensed by adjusting the flow of the condensing coil 15, and the steam is continuously pumped into the condensate water tank 14 due to the negative pressure generated by condensation and flows back to the quartz glass container 6 through a pipeline connected with the bottom, so that the system pressure and the suspension concentration are finally maintained to be stable. After the system is stable, shooting and recording the bubble behavior of the experimental section by using the high-speed photography 4, and starting data recording by using the temperature and pressure acquisition system. 3. And (4) finishing the experiment: when the experiment is finished, the medium-high frequency power supply of the electromagnetic inductor 5 is firstly closed, and the acquisition system is closed when the temperature is reduced to a safety limit value. The

drain valves

3 and 16 are opened to discharge the suspension, and the experimental apparatus is washed with deionized water.

As shown in FIG. 1, the boiling experiment section consists of a base 2, a trap 3, an electromagnetic inductor 5, a quartz glass container 6 and a top cover 7. The base 2, the quartz glass container 6 and the top cover 7 are sequentially connected by flanges, and nonmetal bolts and gaskets are used for eliminating the influence of electromagnetic induction on flange connection. As shown in fig. 2, the chassis includes a non-metallic structural chassis 2a and a metallic structural chassis 2b which are replaceable with each other. The metal structure base 2b comprises a Teflon base 2b.1, an O-shaped sealing ring 2b.2, a metal disc 2b.3 and a stud 2 b.4. The metal disc 2b.3 and the stud 2b.4 are welded together, the external thread of the stud 2b.4 can be matched with the internal thread of the Teflon base 2b.1, a wire of the K-type thermocouple is led out from the inner part of the stud 2b.4 through a drilling hole, and the lower end of the stud is polished and formed so as to be screwed by a wrench during installation. A circular groove is processed at the concave step of the Teflon base 2b.1 to place the O-shaped sealing ring 2b.2, and the sealing ring 2b.2 is tightly pressed by continuously screwing threads during installation to ensure the sealing of the experimental device. The quartz glass container 6 is integrally a cuboid, two ends of the cuboid are provided with flange structures which are respectively connected with the top cover 7 and the base 2, and the bottom end of the container is provided with a drain valve 3 for draining water after the experiment is finished. The lower end flange structure of the top cover 7 is connected with the quartz glass container 6, and the upper end connecting pipeline is connected to the condensed water tank 14. The spiral coil of the electromagnetic inductor 5 is wound on the quartz glass container 6, a certain gap is reserved for experiment shooting, and the coil is connected with a medium-high frequency power supply.

As shown in fig. 1, the condensing section is composed of a condensing water tank 14, a condensing coil 15,

valves

12, 16, 17, a vacuum pump 13 and connecting pipes. The upper end and the lower end of the condensed water tank 14 are respectively connected with the upper end and the lower end of the boiling experiment section through pipelines. The condenser coil 15 was attached to the condensate tank 14 and was used for steam condensation during the experiments. The air suction valve 12 is arranged at the upper part of the condensed water tank 14 and is connected to the vacuum pump 13 through a pipeline, and steam can be sucked into the condensed water tank 14 at the beginning of an experiment. A water injection valve 17 on the side surface of the condensed water tank 14 is connected with the suspension preparation section through a pipeline, and a drain valve 16 at the bottom plays a role in draining water.

As shown in fig. 1, the suspension preparing section is composed of a stirrer 20, a preparing water tank 21, a heater 22, a water pump 25, and

valves

19, 23, and 24. The heater 22 is installed at the bottom of the preparation water tank 21, and deionized water can be heated to boil to discharge non-condensable gas in the deionized water during experiments. The top opening of the preparation tank is provided with a filling valve 19 for initial filling and the bottom opening is provided with a drain valve 23 for draining. The stirrer 20 is fixed on the top of the preparation water tank 21, and can stir the suspension uniformly when the suspension is prepared, and pump the suspension into the condenser through the water pump 25 after the suspension is prepared.

The measuring system consists of a high-speed camera 4 and an acquisition system. The high-speed photography 4 is arranged in front of the boiling experiment section and used for shooting bubble behaviors and recording the bubble behaviors in a computer for subsequent processing, and meanwhile, a fixed light source is arranged on the other side and used for supplementing light in the shooting process. The acquisition system is used for acquiring

temperature

1, 8, 18 and pressure 10 signals, and the computer records the temperature and the pressure in real time.

Claims

1. An experimental device for researching the behavior of boiling bubbles in a pit under a serious accident is characterized in that: including the glass container, the condensate tank, prepare the water tank, the top cap is installed to the upper end of glass container, the base is installed to the lower extreme of glass container, the top cap passes through the top of first tube coupling condensate tank, the bottom of glass container lower part through second tube coupling condensate tank, the lower part of water tank is prepared in the upper portion of condensate tank through the third tube coupling, the outside spiral coil of winding electromagnetic inductor of glass container leaves the clearance that is used for shooing between the spiral coil, set up heater and agitator in the configuration water tank.

2. An experimental apparatus for studying the behavior of boiling bubbles in a pit under severe accident as claimed in claim 1, wherein: the glass container lower part sets up first trap, condensate water tank lower part sets up the second trap, set gradually first solenoid valve on the first pipeline between top cap and the condensate water tank, pressure sensor, the second solenoid valve, the vacuum pump pipe is stretched out at the condensate water tank top, the vacuum pump union coupling vacuum pump, install the third solenoid valve on the vacuum pump pipe, set up the fourth solenoid valve on the second pipeline, set gradually the fifth solenoid valve on the third pipeline between condensate water tank and the preparation water tank, a water pump, the sixth solenoid valve, preparation water tank top sets up the water injection valve, preparation water tank bottom sets up the third trap.

3. An experimental apparatus for studying the behavior of boiling bubbles in a pit under severe accident as claimed in claim 1 or 2, wherein: the base is a non-metal structure base.

4. An experimental apparatus for studying the behavior of boiling bubbles in a pit under severe accident as claimed in claim 1 or 2, wherein: the base is the metal structure base, the metal structure base includes Teflon base, O type sealing washer, metal disc, double-screw bolt, and metal disc and double-screw bolt are fixed together, and Teflon base inside sets up the internal thread, and the double-screw bolt is in the same place through the internal thread connection of its external screw thread with Teflon base, and Teflon base's top sets up the spill step, and the metal disc is located Teflon base's spill step, and O type sealing washer is placed to the circular slot of spill step department processing.

5. An experimental method for researching the behavior of boiling bubbles in a pit under a serious accident is characterized in that: adopting an experimental device for researching the boiling bubble behavior in a pit under a serious accident as claimed in claim 1;