Radioactive source item heat and mass transfer visualization experimental device

Abstract

The application discloses a radioactive source term heat and mass transfer visualization experiment device, one end of an experiment main body system is divided into three paths, one path is connected with a gaseous iodine sampling and measuring system, a second path is connected with an aerosol sampling and measuring system, and a third path is connected with a gaseous iodine generation and distribution system, an aerosol generation and distribution system, a steam distribution system and an air distribution system through a gas mixing system; the other end of the experiment main body system is provided with a high-speed photography system and is connected with a water replenishing system, a liquid phase sampling system and a spray droplet system. The device can simulate the aerosol, gaseous iodine and methyl iodine environment under different steam proportions, temperatures and pressures, and further realize the research on the removal and retention characteristics of the source term under different flow rates and different heat and mass transfer forms, thereby providing data support for the dose evaluation of the radioactive source term after an accident and the modification of a source term prediction model.

Description

Technical Field

[0001] This invention belongs to the field of visualization experimental technology, specifically relating to a visualization experimental device for heat and mass transfer of radioactive source terms. Background Technology

[0002] In nuclear power plant accidents, the migration of radioactive source terms is a frequent occurrence. Typically, these terms travel with the gas flow to different spaces, but during this flow, they are retained by the liquid phase through various mechanisms. Therefore, to determine the amount of source term migration after an accident, it is necessary to study the retention mechanisms of the source terms in water. The retention mechanisms between the source term gas and the liquid phase during an accident are mainly based on heat and mass transfer between them, primarily occurring in three forms: droplets, bubbles, and pools. Therefore, this paper uses the gas immersion jet phenomenon, which includes these three forms, as an example to illustrate the forms of source term retention.

[0003] If a heat transfer tube ruptures after an SGTR accident, the high-temperature, high-pressure water from the primary loop, along with its radioactive source phases, flashes and enters the secondary loop liquid phase of the steam generator as a steam jet. Besides SGTR accidents, submerged jet phenomena also exist in containment depressurization filtration systems. When a severe accident occurs at a nuclear power plant, the temperature and pressure inside the containment become excessively high. To maintain the integrity of the containment, the filtration and venting system needs to be activated to filter radioactive gases from the containment and release them into the atmosphere, thus cooling and depressurizing the containment. Wet scrubbing filtration, as the first-stage filtration equipment in the system, allows for submerged jet filtration. This process is similar to the SGTR steam jet; a certain proportion of radioactive source phases from the containment atmosphere enters the liquid phase and is either captured by the liquid phase or reacts with it and remains in the liquid phase. The remaining portion may penetrate the liquid phase with the steam and enter the gas phase. Submerged jet phenomena also exist in the containment depressurization pool after a severe accident. After a loss-of-coolant accident, large advanced pressurized water reactors employ passive cooling measures to reduce the temperature and pressure of the containment. For small modular reactors, due to the small free volume of the containment, the high-temperature and high-pressure coolant leaking from the breach enters the containment and undergoes a phase change, causing the containment temperature and pressure to rise rapidly and even reach the design limits. By adding a pressure-suppressing pool device, the high-temperature steam in the containment can be discharged into the pressure-suppressing pool under the action of pressure difference, thereby limiting the peak pressure of the containment and removing heat. At the same time, under the conditions of immersion jet, a certain proportion of radioactive source terms in the steam will enter the liquid phase and be captured by the liquid phase or react with the liquid phase and retained in the liquid phase, reducing the radioactivity concentration in the gas phase.

[0004] In the three accident scenarios mentioned above, radioactive sources mainly appear in the form of aerosols, gaseous iodine, and methyl iodine. The particle size of aerosols is generally in the range of 10⁻⁵ to 10⁻⁶ m. At higher temperatures, gaseous iodine and aerosols exist in the gaseous phase. Therefore, during an accident, aerosols, gaseous iodine, and methyl iodine will mix with air and vapor, entering the containment atmosphere or other space atmospheres. If the containment integrity is compromised, radioactive sources will be further released into the external environment, posing serious radioactive hazards to surrounding personnel and the environment. To assess the potential radioactive threat and design corresponding accident mitigation measures, it is necessary to quantify the doses of aerosols, gaseous iodine, and methyl iodine to determine the dose of radioactive sources at different locations. However, the post-accident environment is complex and variable, making many measurement methods impossible. Therefore, it is necessary to develop corresponding prediction models to estimate the dose of radioactive sources. Currently, there is a lack of source term prediction models both domestically and internationally, especially for models concerning the removal and retention mechanisms of radioactive sources by gas-immersed jets and spray droplets, which are very incomplete. Therefore, specialized and refined experiments are needed for correction and verification.

[0005] Currently, there are many experimental devices for the removal mechanism of radioactive source terms. For example, the experimental system for studying the retention characteristics of radioactive materials in steam generators has studied the factors affecting the release of source terms after SGTR accidents. However, this device lacks observation of the gas and liquid phases, so it cannot explore the influencing mechanism. There is also an experimental device for studying the deposition characteristics of radioactive source terms in pipelines. This experimental device can study the deposition characteristics of radioactive aerosols on metal walls, but it cannot study the retention characteristics of source terms such as gaseous iodine and methyl iodine in the liquid phase. Moreover, the experimental device is completely closed, so it is impossible to observe the real-time experimental progress.

[0006] In summary, this study proposes a refined experimental setup for the removal mechanism of radioactive source terms (aerosols, gaseous iodine, methyl iodine, etc.) after a nuclear power plant accident. This setup is highly visual, precise, and involves three forms: droplets, bubbles, and pools. It is designed for studying radioactive source terms under high temperature and pressure and has significant engineering implications for improving source term prediction models and optimizing safety settings within nuclear power plants. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a visualization experimental device for heat and mass transfer of radioactive source terms in gas and liquid phases, which is used to explore the heat and mass transfer mechanism of radioactive source terms in gas and liquid phases under complex and variable thermal conditions. This solves the technical problems of low measurement accuracy, inability to conduct visualization research, and difficulty in tracking the coupling form of gas and liquid phases in traditional experimental devices.

[0008] The present invention adopts the following technical solution:

[0009] A visualization experimental device for heat and mass transfer from a radioactive source term includes:

[0010] The main experimental system is used to provide a closed environment with different temperatures, pressures, vapor fractions, and air fractions.

[0011] A gaseous iodine generation and delivery system is used to convert solid iodine particles or liquid methyl iodine into a gaseous state, which is then delivered into the main experimental system via a gas mixing system.

[0012] An aerosol delivery and generation system is used to deliver powdered aerosols into the main experimental system via a gas mixing system;

[0013] A steam delivery system is used to supply steam to the main experimental system via a gas mixing system;

[0014] An air delivery system is used to supply air to the main experimental system via a gas mixing system;

[0015] The water supply system is used to provide water to the main experimental system and to replenish water during the experiment.

[0016] A gaseous iodine sampling system is used to measure the concentration of gaseous iodine in the gas phase space during experiments.

[0017] Aerosol sampling system is used to measure the concentration of aerosols in the gas phase space during experiments;

[0018] A liquid phase sampling system is used to sample high-temperature and high-pressure liquid phases during experiments.

[0019] A gas mixing system is used to mix steam, air, and different source components and then jet them into the main experimental system.

[0020] A spray droplet system is used to generate spray droplets and spray them into the main experimental system;

[0021] A high-speed photography system is used to capture information about the gas-liquid two-phase flow within the main experimental system during the experiment.

[0022] Preferably, the experimental main system includes a main body, which is set on a base plate, which is set on a frame. An integrated replaceable first nozzle is set at the bottom of the main body. The first nozzle is symmetrically arranged at the center of the bottom surface of the main body and connected to a drain valve. High borosilicate glass is set on one side of the main body and is connected to the main body by a metal strip. A first thermocouple is set on the axis of the other side wall of the main body according to the height. An opening is set on the axis of the wall and a flange is set at the opening. A first nozzle for simulating transverse jet is set on the flange blind plate. An electric heating rod is set on one side of the bottom of the main body. A first pressure transmitter, a first safety valve and an exhaust valve are respectively set on the main body.

[0023] Preferably, the gaseous iodine generation and delivery system includes a constant temperature water tank, an iodine generator is installed in the constant temperature water tank, and the iodine generator is connected to a first pressure reducing valve in sequence through a first outlet needle valve, a first inlet needle valve and a first gas mass flow meter via pipelines.

[0024] Preferably, the aerosol delivery generation system includes an aerosol generator, the inlet end of which is connected in sequence to a second inlet needle valve, a second gas mass flow meter, and a second pressure reducing valve via a pipeline, and the outlet end is provided with a second outlet needle valve.

[0025] Preferably, the steam delivery system includes a steam generator, on which a second safety valve is installed; the steam generator is connected in sequence to an outlet gate valve, a second pressure transmitter, a third gas mass flow meter, and a pipeline drain valve via pipelines;

[0026] The air delivery system includes an air tank, which is equipped with a third safety valve and a first pressure gauge. One end of the air tank is connected to an air compressor, and the other end is connected to multiple branches through an air source processing triplet. Each branch is equipped with a first inlet valve, a third pressure transmitter, a fourth gas mass flow meter, and a first outlet valve in sequence.

[0027] Preferably, the water replenishment system includes a water tank, which is equipped with a water inlet valve, a drain valve, and a stirring impeller. The drain valve is connected in sequence to a multi-stage centrifugal pump, a second inlet valve, a check valve, and a second outlet valve via pipelines. The stirring impeller is connected to a motor.

[0028] Preferably, the gaseous iodine sampling system includes a proportional unloading valve, which is connected in sequence to an adjusting needle valve, a gas washing rod, a dehumidifier and a fifth gas mass flow meter via a pipeline. The gas washing rod includes multiple gas washing rods connected in series, and each gas washing rod is connected to a corresponding gas washing bottle.

[0029] The aerosol sampling system includes a high-pressure gas chamber, which is connected in sequence to a sixth gas mass flow meter, a gas equalization device, a cooling device, and a scanning electromigration particle size analyzer via pipelines.

[0030] Preferably, the liquid phase sampling system includes a loop ball valve, with both ends of the loop ball valve connected to the main body via pipes to form a loop. A condensing device is connected in parallel on the loop, with both ends of the condensing device connected to the loop ball valve via corresponding third inlet needle valves. Both ends of the condensing device are also connected to corresponding third outlet needle valves via heating sleeves.

[0031] Preferably, the gas mixing system includes a housing, an internal gas distribution plate, a pressure transmitter and a second thermocouple connected to the housing, a heating device on the outside of the housing, and a condensate needle valve on one side of the bottom of the housing.

[0032] Preferably, the spray droplet system includes a deionized water tank, which is connected in sequence to a second nozzle, a seventh gas mass flow meter, and a third pressure reducing valve via pipes.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] A visualization experimental device for heat and mass transfer of radioactive source terms is disclosed. This device can generate uniformly distributed mixed gases under different vapor fractions, source term components, temperatures, and pressures. It can also photograph the droplets and bubbles formed after the gas enters the experimental device, obtaining gas-liquid two-phase data. Furthermore, it can accurately measure and record temperature, pressure, concentrations of various iodine species in the liquid phase, and aerosol concentration during the experiment, enabling the study of source term heat and mass transfer mechanisms under different conditions. This experimental device can study the heat and mass transfer mechanisms of single droplets, bubbles, single-component droplets, bubbles, and multi-component droplets / bubbles in gas-liquid systems. The design of the experimental device takes into account the retention of source terms on the metal and other material walls of the experimental device, reducing measurement errors. It has many advantages, including high measurement accuracy, strong stability, high reliability, wide applicability, and ease of operation.

[0035] Furthermore, the main experimental setup is used to simulate the environment involved in the mass transfer of gaseous iodine in the liquid phase and the iodine chemistry process, and to measure the degree of coupling between mass transfer and chemical processes.

[0036] Furthermore, the gaseous iodine generation and delivery system is used to simulate gaseous iodine generated after an accident, and can provide iodine vapor of different concentrations for experiments.

[0037] Furthermore, the aerosol delivery and generation system is used to simulate aerosols generated after an accident, and can provide aerosols of different concentrations, particle sizes, and dispersions for experiments.

[0038] Furthermore, the steam delivery system and the air delivery system, as carrier gases, provide different temperatures and steam-air ratios to transport gaseous iodine or aerosols of different concentrations to the main experimental apparatus.

[0039] Furthermore, the water replenishment system is used to replenish the experimental water in the main experimental apparatus during the initial stage and process of the experiment.

[0040] Furthermore, the gaseous iodine sampling system and the aerosol sampling system are used to measure parameters such as the concentration of gaseous iodine and aerosol entering and exiting the experimental apparatus during the experiment, and the experimental results are determined through relevant data processing.

[0041] Furthermore, the liquid phase sampling system is used to sample the liquid phase in the experimental setup during the experiment, and to analyze and measure the retention of source terms in the liquid phase using offline gaseous iodine and aerosol measurement methods, thereby increasing the confidence level of the experimental results.

[0042] Furthermore, the gas mixing system is used to mix air, steam, gaseous iodine, aerosols, etc. at different temperatures and proportions to prevent uneven mixing from affecting the experimental results.

[0043] Furthermore, the spray droplet system is used to generate spray droplets during the experiment, simulating the spray system in the containment, and can be coupled with other removal mechanisms during the experiment.

[0044] In summary, this invention has a simple structure, highly replaceable components, and stable and reliable operation. It enables the study of source term removal and retention characteristics under different flow rates and heat and mass transfer modes, providing data support for dose assessment of radioactive source terms after accidents and modification of source term prediction models.

[0045] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0046] Figure 1 Here is a structural diagram of the experimental setup;

[0047] Figure 2 This is a cross-sectional view of the main system of the experimental setup;

[0048] Figure 3 This is a schematic diagram of a gaseous iodine generation and delivery system;

[0049] Figure 4 This is a schematic diagram of an aerosol delivery and generation system;

[0050] Figure 5 This is a schematic diagram of a steam delivery system;

[0051] Figure 6 This is a schematic diagram of an air delivery system;

[0052] Figure 7 This is a schematic diagram of the water replenishment system;

[0053] Figure 8 This is a schematic diagram of a gaseous iodine sampling system;

[0054] Figure 9 This is a schematic diagram of an aerosol sampling system;

[0055] Figure 10 This is a schematic diagram of a liquid phase sampling system;

[0056] Figure 11 This is a schematic diagram of a gas mixing system;

[0057] Figure 12 This is a schematic diagram of a spray droplet system;

[0058] Figure 13 This is a schematic diagram of a high-speed photography system.

[0059] The system comprises: 1. Main experimental system; 101. Main body; 102. Frame; 103. Base plate; 104. High borosilicate glass; 105. Metal pressure strip; 106. Electric heating rod; 107. First nozzle; 108. First thermocouple; 109. First pressure transmitter; 1010. First safety valve; 1011. Drain valve; 1012. Exhaust valve; 2. Gaseous iodine generation and delivery system; 201. Constant temperature water tank; 202. First pressure reducing valve; 203. First gas mass flow meter; 204. First inlet needle valve; 205. First outlet needle valve; 206. Iodine generator; 3. Aerosol delivery and generation system; 301. Aerosol generator; 302. Second... 303. Pressure reducing valve; 304. Second gas mass flow meter; 305. Second inlet needle valve; 306. Second outlet needle valve; 4. Steam delivery system; 401. Steam generator; 402. Outlet gate valve; 403. Third gas mass flow meter; 404. Second pressure transmitter; 405. Second safety valve; 406. Pipeline drain valve; 5. Air delivery system; 501. Air compressor; 502. Air tank; 503. Third safety valve; 504. First pressure gauge; 505. Gas source treatment triplet; 506. First inlet valve; 507. Third pressure transmitter; 508. Fourth gas mass flow meter; 509. First outlet valve; 6. Water supply system; 601. Water tank; 602. Water inlet valve; 603. Drain valve; 604. Motor; 605. Stirring impeller; 606. Multistage centrifugal pump; 607. Second inlet valve; 608. Second outlet valve; 609. Check valve; 6010. Second pressure gauge; 7. Gaseous iodine sampling system; 701. Proportional unloading valve; 702. Adjusting needle valve; 703. Washing rod; 704. Washing bottle; 705. Dehumidifier; 706. Fifth gas mass flow meter; 8. Aerosol sampling system; 801. High-pressure gas chamber; 802. Sixth gas mass flow meter; 803. Gas equalization device; 804. Cooling device; 805. Scanning electromigration particle size analyzer; 9. Liquid phase sampling. System; 901. Condensation device; 902. Loop ball valve; 903. Third inlet needle valve; 904. Third outlet needle valve; 905. Heating sleeve; 10. Gas mixing system; 1001. Housing; 1002. Fourth pressure transmitter; 1003. Second thermocouple; 1004. Gas distribution plate; 1005. Drainage needle valve; 1006. Heating device; 11. Spray droplet system; 1101. Second nozzle; 1102. Deionized water tank; 1103. Third pressure reducing valve; 1104. Seventh gas mass flow meter; 12. High-speed photography system; 1201. Camera; 1202. Tripod; 1203. Lighting plate; 1204. Computer. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0062] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0063] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0064] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0065] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0066] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0067] This invention provides a visualization experimental device for the heat and mass transfer of radioactive source terms, which can simulate the aerosol, gaseous iodine, and methyl iodine environments under different steam fractions, temperatures, and pressures. This enables the study of the removal and retention characteristics of source terms under different flow rates and heat and mass transfer modes, providing data support for dose assessment of radioactive source terms after an accident and modification of source term prediction models.

[0068] Please see Figure 1 The present invention provides a visualization experimental device for heat and mass transfer of a radioactive source, comprising an experimental main system 1, a gaseous iodine generation and delivery system 2, an aerosol delivery and generation system 3, a steam delivery system 4, an air delivery system 5, a water replenishment system 6, a gaseous iodine sampling system 7, an aerosol sampling system 8, a liquid phase sampling system 9, a gas mixing system 10, a spray droplet system 11, and a high-speed photography system 12.

[0069] One end of the main experimental system 1 is divided into three paths: one path connects to the gaseous iodine sampling system 7, the second path connects to the aerosol sampling system 8, and the third path connects to the gaseous iodine generation and delivery system 2, the aerosol delivery and generation system 3, the steam delivery system 4, and the air delivery system 5 via the gas mixing system 10. The other end of the main experimental system 1 is equipped with a high-speed photography system 12, which is connected to the water replenishment system 6, the liquid phase sampling system 9, and the spray droplet system 11.

[0070] The main experimental system 1 is used to provide a closed environment with different temperatures, pressures, vapor fractions, and liquid fractions.

[0071] The gaseous iodine generation and delivery system 2 is used to convert solid iodine particles or liquid methyl iodine into gaseous form and allow it to enter the main gas pipeline;

[0072] The aerosol delivery and generation system 3 is used to carry powdered aerosols into the main gas pipeline;

[0073] Steam delivery system 4 is used to generate steam;

[0074] Air delivery system 5 is used to generate air;

[0075] Water supply system 6 is used to initially supply water to the main experimental system 1 and to replenish water during the experiment;

[0076] The gaseous iodine sampling system 7 is used to measure the concentration of gaseous iodine in the gas phase space during the experiment;

[0077] The aerosol sampling system 8 is used to measure the concentration of aerosols in the gas phase space during the experiment.

[0078] The liquid phase sampling system 9 is used to sample the high-temperature and high-pressure liquid phase during the experiment;

[0079] Gas mixing system 10 is used to mix steam, air and different source components and then inject them into the jet for jetting;

[0080] The spray droplet system 11 is used to generate spray droplets and spray them into the main experimental system 1;

[0081] The high-speed photography system 12 is used to capture information on gas-liquid two-phase flow such as droplets, bubbles, and surface ripples during the experiment.

[0082] Please see Figure 2 The main experimental system 1 includes a stainless steel square structure 101, an aluminum alloy frame 102, a stainless steel base plate 103 for load-bearing, high borosilicate glass 104, metal pressure strips 105, an electric heating rod 106, an integrated replaceable first nozzle 107, a first thermocouple 108, a first pressure transmitter 109, a first safety valve 1010, a drain valve 1011, and an exhaust valve 1012.

[0083] High borosilicate glass 104 is installed on the three observation windows provided in the main body 101. A metal strip 105 is then pressed onto the high borosilicate glass 104, and bolts are used to secure the three together. Silicone gaskets are added between the high borosilicate glass 104, the stainless steel square main body 101, and the metal strip 105 to prevent damage to the integrity of the glass by the metal. The main function of the metal strip is to ensure a tighter connection between the high borosilicate glass 104 and the stainless steel square main body 101 to meet airtightness requirements. Four electric heating rods 10 are installed on the bottom surface of the main body 101 near the main body wall. 6. The PID controller and the first thermocouple 108 are used to control the temperature of water or air during the experiment. Five one-piece replaceable first nozzles 107 are symmetrically arranged at the center of the bottom surface of the main body 101. Each first nozzle 107 consists of a ferrule, a section of stainless steel tube, and a standard nozzle. The stainless steel tube is welded to the nozzle to ensure airtightness. Five stainless steel tubes are welded to the first nozzles 107 on the bottom surface of the main body 101. Before the experiment, the welded first nozzles 107 can be connected to the stainless steel tubes welded to the bottom surface using the ferrule. The left side of the main body 101 is a metal wall. Four first thermocouples 108 are installed along the axis of the wall at different heights to monitor the temperature of the liquid phase and the gas phase at different heights in the main body 101 during the experiment. At the same time, an opening is provided along the axis of the wall. This opening is sealed with a flange, and a first nozzle 107 is welded to the flange blind plate and connected to it to simulate transverse jet. The nozzle angle can also be adjusted to achieve the purpose of conducting jet experiments at different angles. A pressure transmitter 109 is connected to a data acquisition system to monitor the pressure of the experimental main body system 1. A first safety valve 1010 is used to release pressure when the experimental main body system 1 is over-pressurized to ensure the integrity of the experimental device. A drain valve 1011 is used to discharge the liquid phase in the experimental main body system 1 after the experiment is completed. An exhaust valve 1012 is used to discharge the gas during the experiment.

[0084] Please see Figure 3 The gaseous iodine generation and delivery system 2 includes a constant temperature water tank 201, a first pressure reducing valve 202, a first gas mass flow meter 203, a first inlet needle valve 204, a first outlet needle valve 205, and an iodine generator 206.

[0085] The first pressure reducing valve 202 reduces the air pressure so that it enters the iodine generator 206. The first gas mass flow meter 203 is connected to the data acquisition system to monitor the air flow rate entering the iodine generator 206. The first inlet needle valve 204 is located after the first gas mass flow meter 203 and before the iodine generator 206 to regulate the air flow rate entering the iodine generator 206. The first outlet needle valve 205 controls the flow rate of the gaseous iodine and air mixture exiting the iodine generator 206. The iodine generator 206 is placed in a constant temperature water tank 201. By adjusting the temperature of the water in the constant temperature water tank, the amount of solid elemental iodine or liquid methyl iodine in the iodine generator 206 converted into gaseous phase is controlled, thereby controlling the concentration of gaseous iodine entering the main experimental system 1.

[0086] Please see Figure 4 The aerosol delivery and generation system 3 includes an aerosol generator 301, a second pressure reducing valve 302, a second gas mass flow meter 303, a second inlet needle valve 304, and a second outlet needle valve 305.

[0087] The second pressure reducing valve 302 reduces the air pressure, allowing it to enter the aerosol generator 301. The second gas mass flow meter 303 is connected to the data acquisition system to monitor the air flow rate entering the aerosol generator 301. The second inlet needle valve 304 is located after the second gas mass flow meter 303 and before the aerosol generator 301 to regulate the air flow rate entering the aerosol generator 301. The second outlet needle valve 305 controls the flow rate of the aerosol-air mixture exiting the aerosol generator 301, thereby controlling the concentration of aerosol entering the main experimental system 1.

[0088] Please see Figure 5 The steam delivery system 4 includes a steam generator 401, an outlet gate valve 402, a third gas mass flow meter 403, a second pressure transmitter 404, a second safety valve 405, and a pipeline drain valve 406.

[0089] Steam generator 401 is used to generate saturated steam or near-saturated steam at different pressures. Outlet gate valve 402 is used to regulate the steam fraction entering the main experimental system 1. Third gas mass flow meter 403 is connected to the data acquisition system to monitor the steam flow rate entering the main experimental system 1. Second pressure transmitter 404 is connected to the data acquisition system to monitor the pipeline pressure in the steam distribution system 4. Second safety valve 405 is used to release pressure when the small steam generator 401 overpressures. Since some steam condenses in the pipeline, a pipeline drain valve 406 is installed on the steam pipeline to drain water from the steam pipeline to prevent water hammer.

[0090] Please see Figure 6The air delivery system 5 includes an air compressor 501, an air tank 502, a third safety valve 503, a first pressure gauge 504, an air source treatment triplet 505, and three sets of parallel air ducts.

[0091] Each set of pipelines is equipped with a first inlet valve 506, a third pressure transmitter 507, a fourth gas mass flow meter 508, and a first outlet valve 509. An air compressor 501 compresses the air to a specific pressure. An air tank 502 stores the compressed air and also mixes the incoming air. A third safety valve 503 and a first pressure gauge 504 are installed on the air tank 502; the former provides overpressure protection, and the latter monitors pressure. An air source treatment unit 505 is located at the outlet of the air tank 502 and is used for pre-filtration and pre-pressure reduction of the compressed air. The first inlet valve 506 and the first outlet valve 509 are combined to more precisely control the air flow. The third pressure transmitter 507 is connected to a data acquisition system to monitor the air pipeline pressure; the fourth gas mass flow meter 508 is connected to the data acquisition system to monitor the air flow in the pipeline.

[0092] Please see Figure 7 The water replenishment system 6 includes a water tank 601, a water inlet valve 602, a drain valve 603, a motor 604, a stirring vane 605, a multi-stage centrifugal pump 606, a second inlet valve 607, a second outlet valve 608, a check valve 609, and a second pressure gauge 6010.

[0093] Water tank 601 stores experimental water and serves as a stirring vessel when necessary. Water inlet valve 602 and drain valve 603 control water inlet and outlet of the tank, respectively. Motor 604 and stirring vane 605 work together to accelerate the dissolution of difficult-to-dissolve chemicals in water tank 601. Multistage centrifugal pump 606 is used to fill the main experimental system 1 with experimental water. Second inlet valve 607, second outlet valve 608, and check valve 609 work together to prevent backflow of liquid phase in the main experimental system during the experiment and to facilitate check valve replacement. Second pressure gauge 6010 is safely located downstream of multistage centrifugal pump 606 to monitor pipeline pressure and prevent excessive pressure in multistage centrifugal pump 606 due to blockage, which could lead to motor burnout.

[0094] Please see Figure 8 The gaseous iodine sampling system 7 includes a proportional unloading valve 701, an adjusting needle valve 702, a gas washing rod 703, a gas washing bottle 704, a dehumidifier 705, and a fifth gas mass flow meter 706.

[0095] After exiting from the top of the main experimental system 1, the gas to be tested is depressurized by a proportional unloading valve 701, and the flow rate of the gas to be tested is adjusted by a regulating needle valve 702. A gas washing device is formed by a washing rod 703 and a washing bottle 704. Three gas washing devices are connected in series to form a group. The washing bottle 704 contains a pre-prepared iodine ion solution. After passing through the gas washing device, the gaseous iodine and water vapor in the gas to be tested are retained. The remaining non-condensable gas passes through a dehumidifier 705, where silica gel absorbs the small droplets. The flow rate of the non-condensable gas is measured by a fifth gas mass flow meter 706. Based on the vapor fraction, gaseous iodine content, and total amount of non-condensable gas in the gas to be tested during the measurement period, the concentration of gaseous iodine in the gas to be tested can be deduced.

[0096] Please see Figure 9 The aerosol sampling system 8 includes a high-pressure gas chamber 801, a sixth gas mass flow meter 802, a gas equalization device 803, a cooling device 804, and a scanning electromigration particle size analyzer 805.

[0097] The test gas containing aerosol exits from the top of the main experimental system 1 and is diluted by high-pressure hot air in the high-pressure gas chamber 801. A sixth gas mass flow meter 802 is installed after the high-pressure gas chamber 801 to control the flow rate of the dilution air. The test gas and the high-pressure hot air are mixed evenly in the gas equalization device 803 to reduce the vapor partial pressure. The mixed gas is then cooled by the cooling device 804 to meet the measurement temperature of the scanning electromigration particle size spectrometer 805.

[0098] Please see Figure 10 The liquid phase sampling system 9 includes a condenser 901, a loop ball valve 902, a third inlet needle valve 903, a third outlet needle valve 904, and a heating sleeve 905.

[0099] Two small holes are made on the left side of the metal wall of the main body 101, and two stainless steel pipes are welded to them. The two stainless steel pipes are connected to form a loop, and a loop ball valve 902 is set in the middle to ensure that the liquid phase in the loop can flow and be renewed after sampling. During sampling, the third inlet needle valve 903 is opened to allow the liquid phase sample to enter the condenser 901. After the sample is condensed to a certain temperature, the third outlet needle valve 904 is opened to remove the sample. Then, fresh liquid phase is injected and heated using a heating sleeve. Afterward, the third inlet needle valve 903 and the loop ball valve 902 are opened to allow the fresh liquid phase to enter the loop circulation.

[0100] Please see Figure 11 The gas mixing system 10 includes a housing 1001, a fourth pressure transmitter 1002, a second thermocouple 1003, a gas equalization plate 1004, a hydrophobic needle valve 1005, and a heating device 1006.

[0101] The gas mixing plate 1004 has several small holes and is installed at different heights on the stainless steel housing 1001. After entering the stainless steel housing 1001, the gas is thoroughly mixed by passing through two gas mixing plates 1004. The fourth pressure transmitter 1002 and the second thermocouple 1003 are used to monitor the pressure and temperature of the gas mixing system 10, respectively. The second thermocouple 1003 heats the stainless steel housing 1001 through the PID control heating device 1006 to prevent steam condensation inside. However, due to temperature fluctuations, some steam will always condense, so a condensate needle valve 1005 is used to drain the condensate from the gas mixing system 10.

[0102] Please see Figure 12 The spray droplet system 11 includes a second nozzle 1101, a deionized water tank 1102, a third pressure reducing valve 1103, and a seventh gas mass flow meter 1104.

[0103] Air is drawn from the air delivery system 5, depressurized by the third pressure reducing valve 1103, and then enters the seventh gas mass flow meter 1104 for flow monitoring. After that, it is connected to the air inlet of the second nozzle 1101. A pipe is drawn from the deionized water tank 1102 into the water inlet of the second nozzle 1101. The high-pressure air creates a vacuum space in the second nozzle 1101, causing water from the deionized water tank 1102 to be drawn into the nozzle. By adjusting the air pressure and flow rate, the size of the spray droplets and the spray area in the radial direction can be adjusted.

[0104] Please see Figure 13 The high-speed photography system 12 includes a camera 1201, a tripod 1202, a lighting board 1203, and a computer 1204.

[0105] Camera 1201 is mounted on a tripod and aimed at the glass surface to be photographed in the main experimental system 1. A light plate 1203 is installed behind the main experimental system 1, directly facing the lens of camera 1201, to provide a light source for the high-speed camera. Computer 1204 sets the shooting parameters and controls the shooting by connecting to camera 1201 via a data cable.

[0106] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0107] The working process of the radioactive source term heat and mass transfer visualization experimental device of the present invention is as follows:

[0108] Before the experiment, open the exhaust valve 1012 to connect the internal space of the main experimental system 1 with the atmosphere. Then open the water inlet valve 602, the second inlet valve 607, and the second outlet valve 608. At this time, turn on the multi-stage centrifugal pump 606 to pump the experimental water in the water tank 601 into the main experimental system 1. When the experimental water level reaches the predetermined position, close all the valves that have been opened.

[0109] After the main system is filled with water, the electric heating rod 106 is turned on to heat the water, the constant temperature water tank 201 is turned on to preheat the iodine generator 206, the steam generator 401 is turned on to generate steam at the required pressure, and the screw air compressor 501 is turned on to generate air, which is then processed by the air source treatment unit 505 and stored in the air storage tank 502 for later use. When the steam pressure reaches the predetermined value, the outlet gate valve 402 is opened to allow the steam to enter the experimental pipeline for preheating. During this period, the pipeline drain valve 406 is opened multiple times to drain the condensate in the pipeline until the pipeline temperature is close to the steam temperature.

[0110] Once the temperature in the main experimental system 1 reaches the specified temperature, the electric heating rod 106 is switched to frequency conversion mode to maintain a constant water temperature. Simultaneously, the exhaust valve 1012 is opened to adjust the internal pressure of the main experimental system 1 to the required operating pressure. Then, the first inlet valve 506 and the first outlet valve 509 are opened, and the first outlet needle valve 205 is opened to allow air, steam, and gaseous iodine to mix in the gas mixing system 10. During this process, the condensate needle valve 1005 is opened multiple times to allow for condensation. At this point, the pre-experiment preparations are complete, and the experiment can begin at any time.

[0111] The first nozzle 107 is opened to allow the mixed gas to enter the main experimental system 1. At the same time, the camera 1201 is used to record the gas-liquid two-phase flow in the main experimental system 1. Simultaneously, the downstream and upstream regulating needle valves 702 are opened to periodically measure the concentration of gaseous iodine entering and escaping the main experimental system 1. At the same time, the liquid phase sampling system 9 is used to periodically sample the experimental liquid phase until the water absorbs gaseous iodine to a near-saturation state.

[0112] After the experiment is stopped, based on the fluid dynamics characteristics, first close all downstream valves of the gas, then close the upstream valves, and then close each subsystem in sequence. Open the exhaust valve 1012 to reduce the pressure of the main experimental system 1. When the pressure is 0, open the drain valve 1011 to drain the water, and the experiment ends.

[0113] When conducting aerosol experiments, the specific operations of the gaseous iodine generation and delivery system 2 and the gaseous iodine sampling system 7 in the above embodiments are performed at the same level as the aerosol delivery and generation system 3 and the aerosol sampling system 8.

[0114] When conducting the spray droplet experiment, gaseous iodine or aerosol is pre-introduced into the main experimental system 1, but water is not introduced. Then, the spray droplet system 11 is turned on, and the remaining measurement operations are the same. After the experiment, each subsystem is turned off at once, and the exhaust valves 10 and 12 are opened to exhaust the air, thus ending the experiment.

[0115] In summary, the radioactive source term heat and mass transfer visualization experimental device of the present invention has the following characteristics:

[0116] This invention enables the simulation of accident environments under different temperatures, pressures, steam fractions, and air fractions, allowing for the study of the removal and retention of different source components under accident environments, thus addressing the current lack of relevant experiments.

[0117] This invention can study the heat and mass transfer mechanisms of different source term components (such as gaseous elemental iodine, methyl iodine, and aerosol) in bubbles, droplets, and pools, and can determine the basic data of heat and mass transfer of several different source term components, providing data support for source term prediction models.

[0118] This invention can simultaneously study the two-phase flow behavior of droplets, bubbles, pool ripples and spray droplets generated by immersion jets, and can also study the effect of a single phenomenon on heat and mass transfer, providing a solution for the coupling and decoupling of experimental influence parameters.

[0119] This invention uses a bolted metal pressure strip structure, which allows for the visualization and imaging of droplets, bubbles, etc. generated during the experiment, while simultaneously ensuring the airtightness of the experimental device under high temperature and high pressure.

[0120] This invention can measure gaseous iodine and aerosol concentration under high temperature and high pressure, and takes into account the influence of the experimental device on the measurement results during the measurement process, thus improving the accuracy of source term concentration measurement.

[0121] This invention designs a liquid phase sampling system under high temperature and high pressure, which can perform online sampling of liquid phase samples during the experiment and improves sampling safety;

[0122] The metal surface of the main body of the invention is coated with a Teflon coating. This coating is resistant to high temperature and high pressure and can prevent substances in the liquid phase from reacting with the metal wall, thereby improving the reliability of experimental measurement results.

[0123] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A visualization experimental device for heat and mass transfer from a radioactive source term, characterized in that, include: The main experimental system (1) is used to provide a closed environment with different temperatures, pressures, steam fractions, and air fractions; A gaseous iodine generation and delivery system (2) is used to convert solid iodine particles or liquid methyl iodine into gaseous form and then send it into the main experimental system (1) via a gas mixing system (10). The aerosol delivery and generation system (3) is used to deliver powdered aerosols into the main experimental system (1) via the gas mixing system (10). A steam delivery system (4) is used to supply steam to the experimental main system (1) via a gas mixing system (10); An air delivery system (5) is used to supply air to the experimental host system (1) via a gas mixing system (10); Water supply system (6) is used to supply water to the main experimental system (1) and to replenish water during the experiment; A gaseous iodine sampling system (7) is used to measure the concentration of gaseous iodine in the gas phase space during the experiment. Aerosol sampling system (8) is used to measure the concentration of aerosols in the gas phase space during the experiment; The liquid phase sampling system (9) is used to sample the high-temperature and high-pressure liquid phase during the experiment. A gas mixing system (10) is used to mix steam, air and different source components and then jet them into the main experimental system (1); A spray droplet system (11) is used to generate spray droplets and spray them into the main experimental system (1); High-speed photography system (12) is used to capture gas-liquid two-phase flow information in the main experimental system (1) during the experiment.

2. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The experimental main system (1) includes a main body (101), which is set on a base plate (103). The base plate (103) is set on a frame (102). An integrated replaceable first nozzle (107) is set at the bottom of the main body (101). The first nozzle (107) is symmetrically arranged at the center of the bottom surface of the main body (101) and connected to a drain valve (1011). High borosilicate glass (104) is set on one side of the main body (101). The high borosilicate glass (104) is connected to a metal strip (1011). 05) Connected to the main body (101), a first thermocouple (108) is set on the axis of the other side wall of the main body (101) according to the height, an opening is set on the axis of the wall, a flange is set at the opening, a first nozzle (107) for simulating transverse jet is set on the flange blind plate, an electric heating rod (106) is set on one side of the bottom of the main body (101), and a first pressure transmitter (109), a first safety valve (1010) and an exhaust valve (1012) are respectively set on the main body (101).

3. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The gaseous iodine generation and delivery system (2) includes a constant temperature water tank (201), an iodine generator (206) is installed in the constant temperature water tank (201), and the iodine generator (206) is connected to the first pressure reducing valve (202) through a pipeline via the first outlet needle valve (205), the first inlet needle valve (204) and the first gas mass flow meter (203).

4. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The aerosol delivery generation system (3) includes an aerosol generator (301). The inlet end of the aerosol generator (301) is connected in sequence to a second inlet needle valve (304), a second gas mass flow meter (303), and a second pressure reducing valve (302) via a pipeline. The outlet end is provided with a second outlet needle valve (305).

5. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The steam delivery system (4) includes a steam generator (401), on which a second safety valve (405) is installed; the steam generator (401) is connected in sequence to an outlet gate valve (402), a second pressure transmitter (404), a third gas mass flow meter (403) and a pipeline drain valve (406) via pipelines. The air delivery system (5) includes an air tank (502), on which a third safety valve (503) and a first pressure gauge (504) are installed; one end of the air tank (502) is connected to an air compressor (501), and the other end is connected to multiple branches through an air source processing triplet (505). Each branch is sequentially equipped with a first inlet valve (506), a third pressure transmitter (507), a fourth gas mass flow meter (508), and a first outlet valve (509).

6. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The water replenishment system (6) includes a water tank (601), which is equipped with a water inlet valve (602), a drain valve (603) and a stirring vane (605). The drain valve (603) is connected to a multi-stage centrifugal pump (606), a second inlet valve (607), a check valve (609) and a second outlet valve (608) in sequence through a pipeline. The stirring vane (605) is connected to a motor (604).

7. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The gaseous iodine sampling system (7) includes a proportional unloading valve (701), which is connected in sequence to an adjusting needle valve (702), a gas washing rod (703), a dehumidifier (705), and a fifth gas mass flow meter (706) via a pipeline. The gas washing rod (703) includes multiple rods, which are connected in series. Each gas washing rod (703) is connected to a corresponding gas washing bottle (704). The aerosol sampling system (8) includes a high-pressure gas chamber (801), which is connected in sequence to a sixth gas mass flow meter (802), a gas equalization device (803), a cooling device (804), and a scanning electromigration particle size spectrometer (805) via pipelines.

8. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The liquid phase sampling system (9) includes a loop ball valve (902). The two ends of the loop ball valve (902) are connected to the main body (101) through pipes to form a loop. A condenser (901) is installed in parallel on the loop. The two ends of the condenser (901) are connected to the loop ball valve (902) through the corresponding third inlet needle valve (903). The two ends of the condenser (901) are also connected to the corresponding third outlet needle valve (904) through the heating sleeve (905).

9. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The gas mixing system (10) includes a housing (1001), an internal gas distribution plate (1004) is provided inside the housing (1001), a fourth pressure transmitter (1002) and a second thermocouple (1003) are respectively connected to the housing (1001), a heating device (1006) is provided on the outside of the housing (1001), and a hydrophobic needle valve (1005) is provided on one side of the bottom of the housing (1001).

10. The radioactive source term heat and mass transfer visualization experimental device according to claim 1, characterized in that, The spray droplet system (11) includes a deionized water tank (1102), which is connected in sequence to a second nozzle (1101), a seventh gas mass flow meter (1104) and a third pressure reducing valve (1103) via pipes.

Images