System and method for testing thermophoresis behavior of aerosol in containment

Abstract

A system for testing the thermophoresis behavior of aerosol in a containment vessel comprises a simulated containment vessel for providing a containment environment; the aerosol injection system is used for injecting aerosol into the simulated containment; the hot air injection system provides a heat source; the containment cooling water spraying system and the hot air injection system jointly form a temperature gradient in the simulated containment; a data acquisition system; and a control system. The test system can accurately simulate the thermophoresis behavior of the aerosol in the containment vessel under the actual accident condition, improves the simulation precision of the aerosol behavior, and provides data support for the safety design and safety management of a nuclear power plant. The invention also provides a method for testing the thermophoresis behavior of the aerosol in the containment.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power, and in particular relates to a system and method for testing the thermophoresis behavior of aerosols in a containment vessel. Background Art

[0002] After a core meltdown accident in a nuclear power plant, the gasified core material may diffuse in the form of aerosols after a continuous cooling transient. As the last barrier of nuclear safety, it is necessary to study the behavior of aerosols in the atmospheric environment under accident conditions. Under accident conditions, the main forms of aerosol movement include gravity sedimentation under the action of gravity, diffusion phoresis caused by the condensation of steam on the wall surface, and thermophoresis caused by the air temperature gradient. Due to the complex mutual influence between the aerosol movement mechanisms, it is necessary to conduct experimental studies on different movement mechanisms separately. However, existing test facilities usually use the form of heating or cooling the outer wall of the containment simulation body to establish non-isothermal accident simulation conditions. There is a lack of simulation of hot air conditions in the containment, and it is difficult to accurately obtain test data for aerosol thermophoresis. Therefore, providing a test system for thermophoresis behavior of aerosols in the containment is of great value for improving the safety management level of nuclear power plants. Summary of the invention

[0003] The purpose of the present invention is to provide a test system for thermophoresis of aerosols in a containment to accurately simulate the thermophoresis of aerosols under accident conditions. The present invention also provides a test method for thermophoresis of aerosols in a containment.

[0004] According to an embodiment of one aspect of the present invention, there is provided a system for testing the thermophoresis behavior of aerosols in a containment, the system comprising: a simulated containment, the simulated containment providing a containment environment simulating an actual containment structure; an aerosol injection system, the aerosol injection system being used to inject aerosols into the simulated containment; a hot air injection system, the hot air injection system being used to inject hot air into the simulated containment to provide a heat source; a containment cooling water spray system, the containment cooling water spray system being used to cool the simulated containment sprayed cooling water, the containment cooling water spray system and the hot air injection system jointly forming a temperature gradient in the simulated containment; a data acquisition system, comprising a plurality of temperature sensors, a plurality of pressure sensors and a plurality of aerosol detectors arranged at different positions in the simulated containment; and a control system, the control system being connected to the aerosol injection system, the hot air injection system, the containment cooling water spray system and the data acquisition system signals and providing control instructions.

[0005] The system can accurately simulate the thermal environment under accident conditions and establish an aerosol thermophoresis test environment, thereby accurately and independently simulating the thermophoresis behavior of aerosols in the containment under accident conditions, eliminating interference from other aerosol movement mechanisms and improving the accuracy of simulation tests.

[0006] Furthermore, in some embodiments, the aerosol injection system includes an air source, an aerosol generator and an aerosol pre-loader, wherein the air source provides a pressurized airflow, the aerosol generator provides aerosol particles, and the aerosol pre-loader contains the aerosol.

[0007] Furthermore, in some embodiments, the aerosol injection system includes one or more aerosol discharge ports disposed in the simulated containment vessel to allow aerosol to be input into the simulated containment vessel through the discharge ports.

[0008] Furthermore, in some embodiments, the hot air injection system includes a gas source, a gas pipeline, an air preheater and a controller, wherein the gas source provides pressurized gas; the controller controls the air preheater to heat the gas output by the gas source to a preset temperature; the gas pipeline connects the gas source, the air preheater and the simulated containment, and the gas pipeline is provided with a heating tape.

[0009] Furthermore, in some embodiments, the hot air input system includes a plurality of air delivery ports disposed at different positions in the simulated containment vessel, so as to allow the hot air generated by the hot air input system to enter the simulated containment vessel through the air delivery ports.

[0010] Furthermore, in some embodiments, the containment cooling water spray system includes a water storage device and a water distribution device, wherein the water storage device stores cooling water and transports the cooling water to the water distribution device, and the water distribution device is used to transport the cooling water to one or more locations on the simulated containment surface.

[0011] Furthermore, in some embodiments, the water storage device is configured as a passive water tank, and the water distribution device is configured as a spray ring with adjustable flow rate and spray area.

[0012] Furthermore, in some embodiments, the control system is configured as a PLC control system.

[0013] According to an embodiment of another aspect of the present invention, a method for testing the thermophoretic behavior of aerosols in a containment is provided, which adopts the thermophoretic behavior of aerosols in a containment provided in any of the aforementioned embodiments, and includes the following steps: according to the simulated reactor accident conditions, using the control system to control the hot air injection system to input a hot air flow with a given temperature and pressure into the simulated containment, and spraying cooling water into the simulated containment through the containment cooling water spray system to simulate the process of transient response of the containment; inputting aerosols into the simulated containment through the aerosol injection system, and measuring the temperature and pressure data in the simulated containment and the thermophoretic migration data of the aerosols in the simulated containment through the data acquisition system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the structure of a hot air injection system in one embodiment;

[0015] Figure 2 Schematic diagram of the structure of a water distribution device in one embodiment.

[0016] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. For the sake of simplicity, the above drawings only schematically illustrate the structures related to the technical features of the present invention, and do not strictly follow the actual proportions to draw the complete structure and all details. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0018] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0019] In the description of this article, unless otherwise clearly specified and limited, the technical terms "installed", "connected", "connected" and the like should be understood in a broad sense, for example, it can be a movable connection, a fixed connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0020] In the description of this document, terms indicating orientation or positional relationships, such as "up", "down", "left", "right", "horizontal", "vertical", "height", "length", and "width", are intended to accurately describe the embodiments and simplify the description, but are not intended to limit the parts or structures involved to have a specific orientation, be installed or operate in a specific orientation, and should not be construed as a limitation on the embodiments in this document.

[0021] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0022] After a core meltdown accident occurs in a nuclear power plant, the gasified core material migrates to the containment through a primary loop. During this process, the core material undergoes a continuous cooling transient and may condense on existing aerosol particles under the action of a heterogeneous nucleation mechanism, or spontaneously condense to form new aerosol particles under the action of a homogeneous nucleation mechanism and diffuse. The containment is the last barrier to nuclear safety, so it is necessary to study the diffusion behavior of aerosols in the atmospheric environment under accident conditions to guide the safety design and management of nuclear power plants and reduce the potential risk of radioactive substances leaking out of the containment after an accident. Related research requires the establishment of a simulation test system to simulate the environmental conditions after an accident, and to carry out the measurement and analysis of aerosol concentration and particle size distribution to provide technical support for accident source analysis and radioactive consequence assessment, and to provide data support for the verification of accident analysis procedures and mitigation measures.

[0023] During the accident, fission product aerosols were released from the damaged core into the containment along with a large amount of steam and non-condensable gases. The movement of aerosols mainly includes: gravity settling under the action of gravity, diffusion phoresis due to condensation of steam in the air on the wall surface, and thermophoresis caused by the existence of temperature gradient in the air.

[0024] Among them, gravity sedimentation is affected by the combined effects of gravity, buoyancy and air resistance; diffusion phoresis is affected by the liquefaction and condensation of vapor and has nothing to do with the size of the aerosol; and thermophoresis is caused by the temperature difference of the gas.

[0025] Specifically, for the thermophoresis mechanism, the kinetic energy of gas molecules increases with the increase of gas temperature. When the aerosol is in an area with temperature difference, part of the surface is affected by gas molecules with higher kinetic energy, and part of the surface is affected by gas molecules with lower kinetic energy. The difference in kinetic energy of gas molecules on both sides will cause the aerosol to flow from the high-temperature area to the low-temperature area along the gas temperature gradient; at the same time, since the temperature in the center of the internal space of the containment (close to the damaged core area) is higher than the temperature of the containment wall, the aerosol shows a tendency to move toward the wall on a macroscopic scale, and when the aerosol contacts the wall, it will be adsorbed on the wall of the containment.

[0026] Aerosol thermophoresis deposition rate V th It has a certain relationship with the size of the aerosol, V th Proportional to the temperature gradient, or equivalently proportional to the rate of heat transfer to the wall. Aerosol thermophoretic deposition rate V th It can be calculated by the following formula:

[0027]

[0028] Among them, C s is the slip correction factor, C n is the Cunninggham slip modification factor, μ g is the viscosity of the gas, ρ g is the density of the gas, α is the ratio of the thermal conductivity of the gas to the aerosol, C T is the heat adjustment coefficient, Kn is the Knudsen number, C M is the momentum adjustment coefficient, T is the wall temperature, and y is the wall geometry. th (cm / s) is related to both the gas temperature difference and the wall temperature gradient.

[0029] Since the movement mechanisms of the above three aerosols will affect each other, in order to carry out accurate experimental research, it is necessary to carry out simulation tests on different movement mechanisms step by step in a certain order. First, gravity sedimentation test is carried out, then gravity sedimentation and thermophoresis test is carried out, and finally gravity sedimentation, thermophoresis and diffusophore mixed test is carried out. Since gravity sedimentation is ubiquitous, conventional test conditions will naturally include the influence of gravity sedimentation mechanism on aerosol movement. However, the current test device for aerosol movement behavior establishes non-isothermal accident simulation conditions by heating and cooling the outer wall of the containment. This type of device is very different from the actual environment where non-passive containment accidents occur, and it is impossible to simulate the hot air test conditions inside the containment; moreover, for large-scale containment simulation bodies, it is difficult to achieve large-scale heating and cooling through the wall. Some other schemes are difficult to avoid the occurrence of diffusophore phenomenon in the containment, resulting in the inability to distinguish the characteristics of thermophoresis and diffusophore.

[0030] In order to solve the above problems, an embodiment of one aspect of the present invention provides a system for testing the thermophoresis behavior of aerosols in a containment. The system includes a simulated containment, an aerosol injection system, a hot air injection system, a containment cooling water spray system, a data acquisition system and a control system. Among them, the simulated containment is used to simulate the containment of a nuclear power plant reactor, providing a closed environment for structural simulation and aerosol containment in the test; the aerosol injection system is used to inject aerosols into the simulated containment; the hot air injection system is used to inject hot air into the simulated containment, and the hot air is used as a heat source for the simulation test; the containment cooling water spray system is used to cool the simulated containment by spraying cooling water, and the containment cooling water spray system and the hot air injection system jointly form the temperature, pressure, temperature gradient and other thermal environments required for the simulation test in the simulated containment; the data acquisition system includes a plurality of temperature sensors, pressure sensors and aerosol detectors arranged at different positions in the simulated containment, which are used to detect the thermal state in the simulated containment and the diffusion state of the aerosol in real time; the control system is used to collect signals of the test system and control the operation of the test system.

[0031] Specifically, in a preferred embodiment, the aerosol injection system includes an air source (air compressor), an aerosol generator and an aerosol pre-loader. The air compressor provides a pressurized airflow, which passes through a purifier and enters a pressure storage tank, and then passes through a dryer and enters an aerosol generator to mix with aerosol particles to form an aerosol. The aerosol passes through a pipe covered by a heat transfer belt and enters the aerosol pre-loader for storage. After receiving instructions from the control system, it is injected into the simulated containment from an aerosol discharge port. An anemometer is provided on the aerosol pipeline to control the flow rate of the pressurized airflow. In a further preferred embodiment, a plurality of aerosol discharge ports are provided in the simulated containment according to the simulated accident conditions. In different embodiments, the aerosol injection system can adopt an existing technical solution capable of generating aerosols, and select different types of aerosol particles according to different test schemes.

[0032] In a preferred embodiment, the structure of the hot air injection system is as follows Figure 1As shown, it includes a gas source (high-pressure gas tank 2), a gas pipeline 3, an air preheater 4 and a controller 5. Among them, the high-pressure gas tank 2 provides pressurized gas, and the controller 5 controls the air preheater 4 to heat the air output from the high-pressure gas tank 2 to a preset temperature according to the control signal of the control system received. The gas pipeline 3 connects the high-pressure gas tank 2, the air preheater 4 and the simulated containment shell 1. A plurality of gas delivery ports 6 with different axial heights are arranged in the simulated containment shell 1, which are used to input hot air into different areas in the simulated containment shell 1. In a further preferred embodiment, the gas pipeline 3 is also provided with a heating belt for further temperature control. A plurality of thermocouples 7 are arranged at different positions in the simulated containment shell 1 for detecting the temperature distribution in the simulated containment shell 1. Pressure sensors and aerosol detectors are also arranged at different positions in the simulated containment shell 1 for detecting the pressure distribution and the movement state of the aerosol.

[0033] In a preferred embodiment, the containment cooling water spray system includes a water storage device and a water distribution device. The water storage device is used to store cooling water and transport the cooling water to the water distribution device, and the water distribution device transports the cooling water to the location where the simulated containment surface needs to be cooled. In different embodiments, the spraying location may include one or more. In a further preferred embodiment, the water storage device is configured as a passive water storage tank, such as a gravity water storage tank or a pressure water storage tank; the water distribution device adopts a Figure 2 The spray ring shown has an adjustable flow rate and spray area.

[0034] In a preferred embodiment, the control system adopts a PLC control system, which can accurately control the thermal environment in the simulated containment according to preset parameters and data in the simulated containment collected by the data acquisition system, accurately simulate reactor accident conditions, and thus improve the simulation test accuracy of aerosol thermophoresis behavior.

[0035] According to another embodiment of the present invention, a method for testing the thermophoresis behavior of aerosols in a containment is provided. The method uses the thermophoresis behavior testing system for aerosols in a containment provided in any of the above embodiments, and comprises the following steps:

[0036] Given the reactor accident conditions to be simulated, determine the thermal environment data in the simulated containment, and input the relevant data into the PLC control system. The PLC control system controls the hot air injection system to input a hot air flow with corresponding temperature and pressure into the simulated containment to form a high-temperature heat source; controls the containment spray system to spray cooling water into the simulated containment to reduce the temperature of the simulated containment wall, and form a temperature gradient in the simulated containment, thereby establishing the simulated thermal environment. The aerosol injection system is instructed by the PLC control system to release aerosols into the simulated containment to simulate the migration of aerosols under accident conditions. During the test, the PLC control system controls the input of hot air and the spraying of cooling water in real time according to the data collected by the sensors of the data acquisition system, simulates the transient response process of the containment under the reactor accident, and realizes precise control of the thermal environment in the simulated containment. By detecting the thermal data at different positions in the simulated containment during the test, effective test data of aerosol thermophoresis behavior are obtained.

[0037] The aerosol thermophoresis behavior test system in the containment provided in the above-mentioned embodiment can fully simulate the thermal environment under accident conditions and establish an aerosol thermophoresis test environment. Through the hot air injection system, the injection position, hot air temperature, etc. can be accurately controlled; by controlling the flow rate and coverage of water distribution, the containment wall temperature can be accurately simulated. Simulate the transient process of the aerosol thermophoresis test under accident conditions to obtain effective test data. Since the entire process is benchmarked against the accident process, it can fully simulate the establishment of accident conditions and the transient response process of the containment; therefore, the obtained test data effectively supports the development and verification of autonomous software, and provides technical support for the large-scale elimination of radioactive materials in nuclear power plants. It also lays a technical foundation for the subsequent optimization design of reactors and the improvement of safety and economy.

[0038] The test system and test method provided in the above-mentioned embodiments can overcome the deficiency of the existing aerosol test system in the containment that lacks the test conditions for simulating hot air in the containment, can effectively improve the degree of matching between the simulated environment and the actual accident conditions, and provide the experimental research capability for aerosol migration behavior under single accident conditions, especially in the thermal phoresis test environment.

[0039] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the structures or method steps involved, and the combination of implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. An aerosol thermophoresis behavior test system in a containment vessel, characterized in that: include A simulated containment shell, wherein the simulated containment shell provides a containment environment that simulates an actual containment shell structure; an aerosol injection system, the aerosol injection system being used to inject aerosol into the simulated containment vessel; A hot air injection system, the hot air injection system is used to inject hot air into the simulated containment to provide a heat source; A containment cooling water spray system, wherein the containment cooling water spray system is used to cool the simulated containment spray cooling water, and the containment cooling water spray system and the hot air injection system together form a temperature gradient in the simulated containment; A data acquisition system, comprising a plurality of temperature sensors, a plurality of pressure sensors and a plurality of aerosol detectors arranged at different positions in the simulated containment vessel; A control system, wherein the control system is connected to the aerosol injection system, the hot air injection system, the containment cooling water spray system and the data acquisition system signals and provides control instructions.

2. The aerosol thermophoresis behavior test system in the containment according to claim 1, characterized in that: The aerosol injection system comprises an air source, an aerosol generator and an aerosol pre-packer, wherein the air source provides a pressurized airflow, the aerosol generator provides aerosol particles, and the aerosol pre-packer contains aerosol.

3. The aerosol thermophoresis behavior test system in the containment according to claim 1 or 2, characterized in that: The aerosol injection system includes one or more aerosol discharge ports disposed in the simulated containment vessel to allow aerosol to be input into the simulated containment vessel through the discharge ports.

4. The aerosol thermophoresis behavior test system in the containment according to claim 1, characterized in that: The hot air injection system includes an air source, an air pipeline, an air preheater and a controller, wherein the air source provides pressurized gas; the controller controls the air preheater to heat the gas output by the air source to a preset temperature; the air pipeline connects the air source, the air preheater and the simulated containment, and the air pipeline is provided with a heating tape.

5. The aerosol thermophoresis behavior test system in the containment according to claim 1 or 4, characterized in that: The hot air input system includes a plurality of air delivery ports arranged at different positions in the simulated containment shell to allow the hot air generated by the hot air input system to enter the simulated containment shell through the air delivery ports.

6. The aerosol thermophoresis behavior test system in the containment according to claim 1, characterized in that: The containment cooling water spray system includes a water storage device and a water distribution device. The water storage device stores cooling water and delivers the cooling water to the water distribution device. The water distribution device is used to deliver the cooling water to one or more locations on the simulated containment surface.

7. The aerosol thermophoresis behavior test system in the containment according to claim 6, characterized in that: The water storage device is configured as a passive water storage tank, and the water distribution device is configured as a spray ring with adjustable flow rate and spray area.

8. The aerosol thermophoresis behavior test system in the containment according to claim 1, characterized in that: The control system is configured as a PLC control system.

9. A method for testing the thermophoresis behavior of aerosols in a containment vessel, characterized in that: The aerosol thermophoresis behavior test system in a containment vessel as claimed in any one of claims 1 to 8 is used, and comprises the following steps: According to the simulated reactor accident conditions, the control system is used to control the hot air injection system to input a hot air flow with a given temperature and pressure into the simulated containment, and the containment cooling water spray system is used to spray cooling water into the simulated containment to simulate the transient response process of the containment; aerosol is input into the simulated containment through the aerosol injection system, and the temperature and pressure data in the simulated containment and the thermophoretic migration data of the aerosol in the simulated containment are measured through the data acquisition system.

Images