Liquid lead-bismuth environment fission product migration behavior test system and method

Abstract

The present application belongs to the technical field of severe accident mechanism research of nuclear power plant, and particularly relates to a kind of liquid lead bismuth environment fission product migration behavior test system and method.The present application includes mechanism test main unit, transient evolution sampling unit, decoupling power control unit;Mechanism test main unit includes sealed reaction kettle, and the outer wall of reaction kettle is integrated with sectional type heating temperature control component, and the diffusion migration of fission product simulant in liquid phase and gas phase is induced by adjusting temperature gradient;Transient evolution sampling unit includes sampling probe distributed along the axial and radial array of reaction kettle, and the "dynamic trajectory" of fission product simulant migration with time is restored in spatial dimension by multi-point space sampling, and transient evolution image is obtained;Decoupling power control unit includes carrier gas supply component, and migration behavior is divided into "pure diffusion" and "diffusion-convection coupling" two modes, and diffusion coefficient and mass transfer coefficient are quantitatively extracted.

Description

Technical Field

[0001] This invention belongs to the technical field of nuclear power plant severe accident mechanism research, specifically relating to a test system and method for the migration behavior of fission products in a liquid lead-bismuth environment. Background Technology

[0002] Current research on fission products in lead-based reactors largely relies on "black box" simulations, observing only the final release fraction. These devices typically mix factors like temperature and flow rate, making it impossible to distinguish whether the migration of fission products is dominated by microscopic diffusion within the liquid phase or macroscopic convection at the gas-liquid interface. When faced with varying operating conditions such as pump failure or localized overheating, existing experimental setups cannot provide predictive mechanistic models. Furthermore, current devices lack methods for measuring the migration process, specifically the "evolution of distribution over time." Summary of the Invention

[0003] The purpose of this invention is to provide a test system and method for the migration behavior of fission products in liquid lead-bismuth environment.

[0004] A test system for the migration behavior of fission products in a liquid lead-bismuth environment includes a mechanism test main unit, a transient evolution sampling unit, and a decoupled dynamic control unit;

[0005] The main unit for the mechanism test includes a sealed reaction vessel, which contains an experimental chamber for containing liquid lead bismuth and fission product simulants. The outer wall of the reaction vessel is integrated with a segmented heating and temperature control assembly, which is used to induce the diffusion and migration of fission product simulants in the liquid and gas phases by adjusting the temperature gradient.

[0006] The transient evolution sampling unit includes sampling probes arrayed along the axial and radial directions of the reactor, used to simultaneously measure the concentration of fission product simulants at different spatial coordinate points at different times;

[0007] The decoupled power control unit includes a carrier gas supply component and a temperature control component.

[0008] Furthermore, the main unit for the mechanism experiment is also connected to a water washing characteristic evolution module, which includes a transparent water washing observation container and a high-speed microscopic imaging component, used to observe the dynamic removal process of aerosol simulated substances that migrate and precipitate through the reaction vessel in the aqueous phase.

[0009] Furthermore, the sampling probes of the transient evolution sampling unit are arranged in a spiral staggered pattern in the liquid phase region and in an equally spaced layered pattern in the gas phase region, which is used to construct a full-path concentration gradient model of the fission product simulant migrating from the interior of liquid lead-bismuth to the gas space.

[0010] Furthermore, the carrier gas supply assembly is connected to the reactor via a Venturi jet or a porous gas distribution plate.

[0011] Furthermore, the decoupled power control unit also includes a gas phase circulation pump and a pressure compensation valve located at the top of the reactor, used to maintain the convection circulation condition inside the gas space in a closed state without introducing external carrier gas.

[0012] A method for testing the migration behavior of fission products in liquid lead-bismuth environments, including static diffusion studies:

[0013] Liquid lead-bismuth was loaded into a reactor and a specific proportion of fission product simulants were added. The carrier gas supply component was turned off, and a temperature gradient from bottom to top was formed inside the lead-bismuth molten pool in the reactor through a temperature control component. The measurement values ​​of each sampling probe were periodically obtained through a transient evolution sampling unit to study the static diffusion evolution of the fission product simulants in the liquid lead-bismuth and gas space over time.

[0014] Furthermore, the static diffusion evolution of the fission product simulant over time within the liquid lead-bismuth and gas space will form a concentration cloud map that changes over time, revealing how the fission product simulant passes through the lead-bismuth layer through molecular thermal motion.

[0015] Furthermore, after completing the static diffusion study experiment, a dynamic convection study experiment was conducted:

[0016] By maintaining a constant temperature, turning on the carrier gas supply component, and conducting multiple experiments by adjusting the flow rate of the carrier gas supply, the measurement values ​​of each sampling probe were periodically obtained through the transient evolution sampling unit in each experiment. Through multiple experiments, the influence of different gas phase flow rates on the migration trajectory and spatial distribution evolution of fission product simulants was studied.

[0017] Furthermore, based on the results of static diffusion and dynamic convection studies, the diffusion coefficient and convection mass transfer coefficient were extracted to construct a mathematical analytical model of the migration behavior of fission product simulants.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention decomposes the migration behavior into two modes, "pure diffusion" and "diffusion-convection coupling," through a carrier gas supply component, and quantitatively extracts the diffusion coefficient and mass transfer coefficient. Through multi-point spatial sampling, the "dynamic trajectory" of the fission product simulation material migrating over time is reconstructed in the spatial dimension, and transient evolution images are obtained. The spiral arrangement of the sampling needles effectively avoids wall effect interference, ensuring the accuracy of mechanism research. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall system for testing the migration behavior of fission products in a liquid lead-bismuth environment according to the present invention.

[0021] Figure 2This is a schematic diagram of the probe layout of the transient sampling unit in this invention.

[0022] Figure 3 This is a schematic diagram of the decoupled control panel in an embodiment of the present invention. Detailed Implementation

[0023] The present invention will now be further described with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the present invention provides a test system for the migration behavior of fission products in a liquid lead-bismuth environment, including a mechanism test main unit 1, a transient evolution sampling unit, and a decoupled dynamic control unit; Figure 1 It also includes liquid lead-bismuth 13 and a gas space 14; such as Figure 2 As shown, it includes the inner wall of the reactor 111, the liquid level line 2, the liquid phase spiral sampling point 21, the gas phase layered sampling point 22, and the concentration evolution diffusion path 3.

[0025] The main unit 1 for mechanism testing includes a sealed reactor 11. Inside the reactor 11 is an experimental chamber for containing liquid lead bismuth and fission product simulants. The outer wall of the reactor 11 is integrated with a segmented heating and temperature control component 12, which is used to induce the diffusion and migration of fission product simulants in the liquid and gas phases by adjusting the temperature gradient. The main unit 1 for mechanism testing is also connected to a water washing characteristic evolution module, which includes a transparent water washing observation container 41 and a high-speed microscopic imaging component, used to observe the dynamic removal process of aerosol simulants that migrate and precipitate through the reactor 11 in the aqueous phase.

[0026] The transient evolution sampling unit 2 includes sampling probes arrayed along the axial and radial directions of the reactor 11, used to simultaneously measure the concentration of fission product simulants at different spatial coordinate points at different times; such as Figure 2 As shown, the sampling probes of the transient evolution sampling unit 2 are arranged in a spiral staggered pattern in the liquid phase region and in an equally spaced layered pattern in the gas phase region, which is used to construct a full-path concentration gradient model of the fission product simulant migrating from the interior of liquid lead bismuth to the gas space.

[0027] The decoupled power control unit 3 includes a carrier gas supply component and a temperature control component. The carrier gas supply component is connected to the reactor 11 via a Venturi jet or a porous gas distribution plate. It also includes a gas phase circulation pump 33 and a pressure compensation valve located at the top of the reactor 11, which are used to maintain the convection circulation condition inside the gas space in a closed state without introducing external carrier gas.

[0028] A method for testing the migration behavior of fission products in liquid lead-bismuth environments, including static diffusion studies:

[0029] Liquid lead-bismuth 13 was loaded into reactor 11 and a specific proportion of fission product simulants was added. The carrier gas supply component was turned off, and a temperature field gradient from bottom to top was formed inside the lead-bismuth molten pool in reactor 11 by the temperature control component. The measurement values ​​of each sampling probe were periodically obtained by the transient evolution sampling unit 2 to study the static diffusion evolution of fission product simulants in the liquid lead-bismuth and gas space over time.

[0030] The static diffusion evolution of fission product simulants over time in the liquid lead-bismuth and gas space forms a concentration cloud map that changes over time, revealing how fission product simulants pass through the lead-bismuth layer through molecular thermal motion.

[0031] After completing the static diffusion study experiment, a dynamic convection study experiment will be conducted:

[0032] Maintain a constant temperature, turn on the carrier gas supply component, and conduct multiple experiments by adjusting the flow rate of the carrier gas supply. In each experiment, the measurement values ​​of each sampling probe are periodically obtained through the transient evolution sampling unit 2. Through multiple experiments, the influence of different gas phase flow rates on the migration trajectory and spatial distribution evolution of fission product simulants is studied.

[0033] Based on the results of static diffusion and dynamic convection studies, the diffusion coefficient and convection mass transfer coefficient were extracted, and a mathematical analytical model of the migration behavior of fission product simulants was constructed.

[0034] Example 1:

[0035] This embodiment discloses a test system and method for the migration behavior of fission product simulants in a liquid lead-bismuth environment, belonging to the field of nuclear safety mechanism research. The system addresses the transient distribution evolution of fission products under complex environments by decoupling the diffusion and convection driving forces through a segmented heating assembly and a precision flow rate control knob. The system utilizes an array of sampling probes to acquire the simulant concentration at different spatial locations within the reactor in real time, thereby accurately characterizing the dynamic evolution process of fission product simulants precipitating from the liquid lead-bismuth assembly and migrating into the gas space. This invention solves the problem of traditional simulation experiments struggling to distinguish mass transfer influencing factors. Through targeted decoupling design, it can deeply reveal the underlying physical mechanisms of fission product migration under accident conditions, providing high-precision experimental data support for nuclear power safety assessment.

[0036] like Figure 3 The diagram shown is a schematic of the decoupled control panel in this embodiment, including a flow meter 31, a temperature gauge 32, a temperature knob 33, a panel 34, a flow rate knob 35, a sampling switch 4, and an emergency stop button 5.

[0037] Step 1: System Initialization and Physical Quantity Preset

[0038] Liquid lead-bismuth 13 is loaded into reactor 11, and a specific proportion of fission product simulants (such as CsI powder) is added. The power of each section of the heater in the reactor is set by the temperature adjustment knob on the panel, so that a temperature gradient from bottom to top is formed inside the lead-bismuth molten pool.

[0039] Step 2: Static diffusion transient evolution determination;

[0040] At this point, keep the gas pump off (flow rate knob set to 0). Trigger the sampling switch, and the transient evolution sampling unit will extract sample gas / liquid from probes at different heights at a set frequency (e.g., once every 10 minutes). The analysis results will form a concentration cloud map that changes over time, revealing how the simulant passes through the lead-bismuth layer via molecular thermal motion.

[0041] Step 3: Study on the superposition effect of convection migration;

[0042] While maintaining a constant temperature gradient, rotate the flow rate adjustment knob 3 to turn on the carrier gas. Observe the changes in the concentration cloud map: the addition of gas flow significantly accelerates mass exchange at the gas-liquid interface. By comparing the data from steps two and three, researchers can use Fick's law and the convective mass transfer formula to deduce the contribution rate of flow rate to migration behavior.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test system for the migration behavior of fission products in a liquid lead-bismuth environment, characterized in that: It includes the main unit for mechanism testing (1), the transient evolution sampling unit, and the decoupled dynamic control unit; The main unit (1) of the mechanism test includes a sealed reaction vessel (11). The reaction vessel (11) is provided with an experimental chamber for containing liquid lead bismuth and fission product simulants. The outer wall of the reaction vessel (11) is integrated with a segmented heating and temperature control component (12) for inducing the diffusion and migration of fission product simulants in the liquid and gas phases by adjusting the temperature gradient. The transient evolution sampling unit (2) includes sampling probes arrayed along the axial and radial directions of the reactor (11) for synchronously measuring the concentration of fission product simulants at different spatial coordinate points at different times; The decoupled power control unit (3) includes a carrier gas supply component and a temperature control component.

2. The experimental system for testing the migration behavior of fission products in a liquid lead-bismuth environment according to claim 1, characterized in that: The main unit (1) of the mechanism test is also connected to a water washing characteristic evolution module, which includes a transparent water washing observation container (41) and a high-speed microscopic imaging component, used to observe the dynamic removal process of aerosol simulated substances that migrate and precipitate through the reaction vessel (11) in the aqueous phase.

3. The experimental system for testing the migration behavior of fission products in a liquid lead-bismuth environment according to claim 1, characterized in that: The sampling probes of the transient evolution sampling unit (2) are arranged in a spiral staggered pattern in the liquid phase region and in an equally spaced layered pattern in the gas phase region, which are used to construct a full-path concentration gradient model of fission product simulants migrating from the interior of liquid lead bismuth to the gas space.

4. The experimental system for testing the migration behavior of fission products in a liquid lead-bismuth environment according to claim 1, characterized in that: The carrier gas supply assembly is connected to the reactor (11) via a Venturi jet or a porous gas distribution plate.

5. The experimental system for testing the migration behavior of fission products in a liquid lead-bismuth environment according to claim 1, characterized in that: The decoupled power control unit (3) also includes a gas phase circulation pump (33) and a pressure compensation valve installed on the top of the reactor (11) to maintain the convection circulation condition inside the gas space in a closed state without introducing external carrier gas.

6. A test method using the liquid lead-bismuth environmental fission product migration behavior test system as described in claim 1, characterized in that: Including static diffusion research experiments: Liquid lead-bismuth (13) is loaded into the reactor (11) and a specific proportion of fission product simulant is added. The carrier gas supply component is turned off, and the temperature control component is used to form a temperature field gradient from bottom to top inside the lead-bismuth molten pool in the reactor (11). The measurement values ​​of each sampling probe are periodically obtained through the transient evolution sampling unit (2) to study the static diffusion evolution of the fission product simulant in the liquid lead-bismuth and gas space over time.

7. The method for testing the migration behavior of fission products in a liquid lead-bismuth environment according to claim 6, characterized in that: The static diffusion evolution of the fission product simulants over time within the liquid lead-bismuth and gas space will form a concentration cloud map that changes over time, revealing how the fission product simulants pass through the lead-bismuth layer through molecular thermal motion.

8. The method for testing the migration behavior of fission products in a liquid lead-bismuth environment according to claim 6, characterized in that: After completing the static diffusion study experiment, a dynamic convection study experiment will be conducted: Keep the temperature constant, turn on the carrier gas supply component, and conduct multiple tests by adjusting the flow rate of the carrier gas supply. In each test, the measurement values ​​of each sampling probe are periodically obtained through the transient evolution sampling unit (2). Through multiple tests, the influence of different gas phase flow rates on the migration trajectory and spatial distribution evolution of fission product simulators is studied.

9. The method for testing the migration behavior of fission products in a liquid lead-bismuth environment according to claim 8, characterized in that: Based on the results of static diffusion and dynamic convection studies, the diffusion coefficient and convection mass transfer coefficient were extracted, and a mathematical analytical model of the migration behavior of fission product simulants was constructed.

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