Activity monitoring and coating testing method and device in Po-210 aerosol migration loop

Abstract

The invention belongs to the technical field of fourth-generation advanced fast neutron reactors, and particularly relates to an activity monitoring and coating testing method and device in a Po-210 aerosol migration loop. The device comprises an aerosol migration loop and a Po-210 in-situ monitoring device, and the aerosol migration loop is used for carrying out in-situ monitoring on mCi-magnitude Po-210 released at high temperature in a lead-bismuth alloy sample; the gaseous Po-210 moving in the sealed environment is in contact with the surfaces of four functional coating materials of antifouling, protection, sealing and decontamination and generates electrostatic adsorption, chemical adsorption or particle elastic collision effects, and the Po-210 in-situ monitoring device is used for monitoring the activity concentration level of Po-210 aerosol circularly moving in an aerosol migration loop in the whole test process. According to the invention, the adsorption performance test of the Po-210 aerosol on the surfaces of special coatings with four functions of antifouling, decontamination, sealing and protection and the like and transported can be safely and efficiently completed, and the activity level of the Po-210 aerosol transported in the gas space of a sealing system can be accurately monitored.

Description

Technical Field

[0001] This invention belongs to the field of fourth-generation advanced fast neutron reactor technology, specifically relating to a method and apparatus for activity monitoring and coating testing in a Po-210 aerosol migration loop. Background Technology

[0002] During operation, the fourth-generation advanced fast neutron reactor, which uses heavy metals as a coolant, produces the highly toxic nuclide Po-210 under neutron irradiation conditions, along with other volatile activating or fissile nuclides. The types of radiation produced include alpha, beta, and gamma rays. Po-210 has a half-life of 138.4 days and a specific activity of 1.66 × 10⁻⁶ days. 14 Po-210 decays by emitting 5.30 MeV alpha particles and 0.001% 0.803 MeV gamma rays. According to Appendix D of GB18871-2002, "Basic Standards for Ionizing Radiation Protection and Radiation Source Safety," which categorizes radionuclides by toxicity, Po-210 ranks second in the extremely toxic group when all chemical toxins are present in equal amounts. Volatile nuclides such as Po-210 may be released into the environment along with the reactor top cover gas. Upon contact with air, they form radioactive aerosols, which, carried by aerosol particles in the plant's ventilation system, diffuse and migrate unpredictably. These aerosols may adhere to and settle on the walls, floors, and surfaces of critical metal equipment within the reactor system, causing radioactive contamination. This could restrict personnel access and increase reactor maintenance costs and collective dose. To prevent Po-210 aerosol from re-entering the system space environment due to airflow on the surfaces of structures and equipment within nuclear facilities, thus posing a potential risk of internal radiation exposure to personnel, it is necessary to employ surface antifouling, protection, sealing, and decontamination technologies for the prevention and post-event elimination of Po-210. There is an urgent need to develop a test method for evaluating the interaction between Po-210 and the surface of coating materials. This method, conducted within a specific sealed test apparatus, can monitor the activity concentration of gaseous Po-210 interacting with the surface of the coating material in situ.

[0003] Regarding the service performance testing of coatings, currently, in addition to conventional mechanical and structural performance tests and thermal aging performance tests, there is a lack of radiation stability tests for coating materials, as well as evaluation methods for the adsorption of real nuclides on the surface of coating materials. Given the radiotoxicity and chemical toxicity of the highly toxic alpha nuclide Po-210, relevant tests need to be conducted in sealed enclosures with high sealing levels and in locations with ventilation capabilities. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method and apparatus for monitoring the activity and testing coatings in the migration loop of Po-210 aerosols. This method can safely and efficiently perform adsorption performance tests on the surfaces of four types of functional special coatings (anti-fouling, decontamination, sealing, and protection) and on the transported Po-210 aerosols. It can also accurately monitor the activity level of the transported Po-210 aerosols in the gas space of the sealed system, providing a test evaluation method for the stability of the service performance of special coatings in typical radiation scenarios in fourth-generation advanced fast neutron reactor systems.

[0005] The technical solution adopted in this invention is as follows:

[0006] An activity monitoring and coating testing device for Po-210 aerosol migration loop includes an aerosol migration loop and a Po-210 in-situ monitoring device. The aerosol migration loop is used to simulate the surface contamination environment formed by the diffusion and migration of aerosols and their deposition during the actual service of a protective coating, using Po-210 at the mCi level released at high temperatures from a lead-bismuth alloy sample. In this sealed environment, the gaseous Po-210 migrates and comes into contact with the surfaces of four functional coating materials: antifouling, protection, sealing, and decontamination, resulting in electrostatic adsorption, chemical adsorption, or elastic collision of particles. The Po-210 in-situ monitoring device monitors the activity concentration level of Po-210 aerosols circulating within the aerosol migration loop throughout the entire testing process.

[0007] The aerosol migration circuit includes a sealed shielded enclosure, a high-temperature evaporation device, an aerosol circulation device, and a functional coating testing device. The high-temperature evaporation device, aerosol circulation device, and functional coating testing device are located inside the sealed shielded enclosure. The high-temperature evaporation device is used for programmed control and gradient heating of lead-bismuth alloy samples containing Po-210. The aerosol circulation device is used for programmed control of the test circulation gas path and the exhaust gas purification gas path, so that the typical Po-210 gas or aerosol required for the test circulates and moves within the gas path and the exhaust gas is purified. The functional coating testing device is a testing device for four functional special coating materials.

[0008] The sealed shielded enclosure has through holes for connecting to the Po-210 in-situ monitoring device and the gas delivery device.

[0009] The sealed shielded enclosure includes a three-stage exhaust filter and a one-stage intake filter. The one-stage intake filter removes particulate impurities from the air entering the enclosure, ensuring a clean environment inside the enclosure. The intake of the three-stage exhaust filter receives the purified test gas, which undergoes further three-stage purification before being discharged into the ventilation system of the test site through an exhaust pipe welded to the exhaust port.

[0010] The high-temperature evaporation device includes a programmable temperature-controlled heating device, a programmable temperature-controlled cabinet, a quartz sample chamber, and a gas buffer mixing device. The programmable temperature-controlled heating device is located at the bottom of the sealed shielded box. The quartz sample chamber is located inside the programmable temperature-controlled heating device. A lead-bismuth alloy sample containing Po210 is placed in the quartz sample chamber. A gas buffer mixing device is provided above the quartz sample chamber. The high-temperature evaporation device is equipped with a pressure gauge and a thermometer.

[0011] The high-temperature evaporation device is equipped with a gas delivery interface, which is connected to a gas delivery device located outside the sealed shielded box.

[0012] The gas delivery device is connected to a centralized on-site gas supply facility or an air compressor. The Ar carrier gas provided by the centralized on-site gas supply facility and the air or other test gases provided by the air compressor are mixed to form a typical Po-210 gas or aerosol required for the test.

[0013] The high-temperature evaporation device is equipped with an interface for connecting to the Po-210 aerosol circulation device.

[0014] The aerosol circulation device includes a gas mass flow controller, a first gas sampling pump, and an exhaust gas purification device. The components are connected by antistatic carbon black tubes to form a gas passage. The entire aerosol circulation device is supported by a bracket to form a three-dimensional spatial structure. The typical Po-210 gas or aerosol generated by the high-temperature evaporation device is connected to the gas mass flow controller through the carbon black tube. The other end of the gas mass flow controller is connected to the first gas sampling pump. The outlet of the first gas sampling pump is connected to the exhaust gas purification device, which is connected to a three-stage exhaust filter.

[0015] The first gas sampling pump is equipped with an interface for connecting to a functional coating test device. The functional coating test device is equipped with 20L cylindrical containers A and B, both used to hold coating samples. The first gas sampling pump is connected to containers A and B respectively. The other end of containers A and B is connected to an interface for connecting a high-temperature evaporation device. Gaseous Po-210 is delivered to containers A and B through an aerosol circulation device, providing a spatial environment for the coating sample surface to contact with gaseous Po-210. The sample contacts and interacts with the surfaces of four functional coating materials: antifouling, protection, sealing, and decontamination, to study the contamination behavior of Po-210 on the coating sample surface. After the test, the alpha radioactivity level of the coating sample surface is monitored by a portable low-background alpha-beta meter, and the color change of the coating sample surface after the test is measured in real time inside the chamber by a colorimeter.

[0016] In the aerosol circulation device and functional coating testing device, an electric ball valve is provided between any components, and the start and stop of the electric ball valve is controlled by a program control cabinet; the gas mass flow controller is connected in parallel with an electric ball valve.

[0017] The ventilation system includes a nuclear-grade filter and a special exhaust duct. The three-stage exhaust filter is connected to the nuclear-grade filter by welding a stainless steel exhaust duct. After being filtered and purified by the nuclear-grade filter, the air enters the special exhaust duct.

[0018] The in-situ monitoring device includes a Po-210 online monitoring unit, inlet and outlet connections, a monitoring sealed box, and a monitoring control cabinet. The monitoring sealed box 1 is divided into upper and lower chambers. The Po-210 online monitoring unit is located inside the upper chamber of the monitoring sealed box. The Po-210 online monitoring unit is used for nuclide identification and vacuum energy spectrum quantitative measurement. After coupling with an aerosol migration circuit, it can monitor the activity concentration of the Po-210 gas source in the gas migration circuit in situ. The Po-210 online monitoring unit includes a multi-stage sampler and a filter. The membrane adsorption device and electrostatic adsorption device are controlled by analysis software in the monitoring and control cabinet, which controls the related sampling and measurement processes. The membrane adsorption device uses low-energy laser to ablate and remove radioactive materials adhering to the inner wall of the chamber, and induces the depolymerization and homogenization of alpha nuclide aerosols. Simultaneously, it can automatically identify filter membrane information and nuclide measurement parameters, monitor the paper feeding force of the filter membrane in real time, and dynamically adhere flexible sealing materials to the filter membrane edges to ensure the vacuum level of the chamber. Under vacuum conditions, the energy resolution for alpha nuclide detection is ≤ that of nuclide detection, improving low-activity detection. The accuracy of Po-210 concentration measurement is ensured. The multi-stage sampler is a device for impact-type graded sampling based on the particle size distribution characteristics of Po-210 aerosol. The activity concentration of Po-210 aerosol samples with different particle size ranges is analyzed by alpha energy dispersive spectroscopy. The electrostatic adsorption device uses a gold-silicon surface detector to convert the signal of alpha particles released by electrostatically adsorbed Po-210 aerosol into electrical pulse counting, thereby detecting the radioactivity of alpha particles. The lower chamber of the monitoring sealed box is equipped with a second gas sampling pump, a first vacuum pump, a second vacuum pump, a third vacuum pump, and a fourth vacuum pump. The second gas sampling pump provides power for the intake sampling of the filter membrane adsorption device. The first vacuum pump delivers source gas to the electrostatic adsorption device, and the second vacuum pump delivers source gas to the multi-stage sampler. The third and fourth vacuum pumps maintain a negative pressure environment in the upper chamber of the monitoring sealed box. The monitoring control cabinet is equipped with a Po-210 online monitoring and analysis program, which controls the sampling and monitoring tasks of the Po-210 online monitoring unit.

[0019] A method for monitoring the activity and testing the coating in a Po-210 aerosol migration loop includes the following steps:

[0020] S1. Preparation of test conditions and debugging of test equipment;

[0021] S2, Adsorption test of Po-210 on the surface of coating material in the circuit;

[0022] Po-210 in-situ monitoring in S3 loop;

[0023] Testing of the coating sample after the S4 test.

[0024] The adsorption test of Po-210 on the surface of the coating material in the circuit specifically includes:

[0025] S201, Po-210 and anti-fouling functional coating tests:

[0026] After weighing the neutron-irradiated lead-bismuth target sample containing Po-210 stored in the chamber, it was transferred to the quartz sample chamber of the high-temperature evaporation device. The anti-fouling functional coating sample was transferred to container A of the functional coating test device in the chamber and suspended. Air at 5000 Pa was introduced into the gas buffer mixing device of the aerosol migration circuit using an air compressor. The heating temperature was controlled at 600°C in the program interface, and the circuit button of the coating test device on the control interface was lit to form a circuit and start the program heating. The gas flow rate of the circuit was set to 4 L / min. Under the heating temperature of 600°C, Po-210 evaporated from the lead-bismuth alloy, mixed with air to form an aerosol, and circulated in the circuit for 30 minutes to fully contact the anti-fouling functional coating sample.

[0027] Tests of S202, Po-210 and detergency-removing functional coatings:

[0028] Simultaneously with step 201, the stain-removing functional coating sample is transferred into container B of the functional coating test apparatus inside the chamber and suspended for later use. After the previous test is completed, the program interface controls the closing of the previous loop button and then opens the second loop button to form a pathway. Air at 3600Pa is introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor. Po-210, which is continuously evaporated from the lead-bismuth alloy at a heating temperature of 600°C, mixes with the newly introduced air to form an aerosol, which circulates in the loop for 30 minutes to fully contact the stain-removing functional coating sample. The anti-fouling functional coating and the stain-removing functional coating are then removed.

[0029] S203, Po-210 and Protective Functional Coating Test: Following the same procedure as step 201, the protective functional coating sample was transferred into container A of the functional coating test apparatus inside the chamber and suspended. Air at 3499 Pa was introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor. The heating temperature was controlled at 600°C via the program interface, and the loop button of the coating test apparatus on the control interface was activated to form a circuit, starting the programmed heating. The gas flow rate of the loop was set to 4 L / min. Under a heating temperature of 600°C, Po-210 evaporated from the lead-bismuth alloy, mixed with air to form an aerosol, and circulated in the loop for 30 minutes, ensuring full contact with the protective functional coating sample.

[0030] S204, Po-210 and Sealing Functional Coating Test: Consistent with the test method in step 202, the sealing functional coating sample is simultaneously transferred into container B of the functional coating test device inside the chamber and suspended for later use; after the previous test is completed, the program interface controls to close the previous loop button and then open the next loop button to form a path; air at 3600Pa is introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor; Po-210 continuously evaporated from the lead-bismuth alloy at a heating temperature of 6004°C mixes with the newly introduced air to form an aerosol, which circulates in the loop for 30 minutes to fully contact the sealing functional coating sample.

[0031] In-situ monitoring of Po-210 in the circuit specifically includes:

[0032] S301, Branch sealing protection: After 30 minutes of aerosol circulation test, the activity level of Po-210 in the aerosol circulation loop was monitored in situ using the Po-210 online monitoring device on the branch of the aerosol migration loop device; the entire cycle of in-situ monitoring was carried out safely in the protection of the sealed box, and the gas leakage rate was <0.025 vol% / h.

[0033] S302. Gas / Aerosol Sampling: On the analysis interface of this in-situ monitoring device, open the solenoid valves of the inlet and outlet connecting pipes to form a gas / aerosol sampling and measurement path; set the sampling flow rate to 13L / min, circulate sampling for 10min, and start sampling by turning on the gas sampling pump.

[0034] S303, Nuclide Vacuum Measurement: Turn on the vacuum pump and filter membrane feeding device, automatically identify filter membrane information and nuclide measurement parameters, monitor the paper feeding force of the filter membrane in real time, measure for 10 minutes under low vacuum, and obtain the activity concentration level of Po-210 in the circulation loop.

[0035] S304, Nuclide Removal: The low-energy laser ablation function in the analysis software is automatically activated to remove radioactive materials adhering to the inner wall of the chamber and induce the depolymerization and homogenization of α-nuclide aerosols.

[0036] S305. Exhaust Gas Purification: After the in-situ monitoring is completed, the centralized gas supply facilities on site are used to purge the gas paths of containers A and B with nitrogen / argon gas. This ensures that the Po-210 aerosol in the gas path is purified by the exhaust gas purification device, and then enters the special exhaust after being highly purified by the three-stage exhaust filter in the enclosure. The special exhaust vent also has a primary purification stage and a nuclear-grade high-efficiency purifier to ensure the safety of emissions into the environment.

[0037] The testing of the coating samples after the experiment specifically includes:

[0038] S401, Surface radioactivity monitoring: After the entire test apparatus is restored to room temperature, four types of coating samples are taken out from container A and container B. The total α count of the sample surface is performed using a portable background αβ meter in a sealed shielded box to determine the degree of adsorption or adhesion of Po-210 on the surface of the coating sample.

[0039] S402. Radiation aging assessment: After surface radioactivity monitoring, four types of coating samples were marked, sealed in sealed bags, and placed in a covered stainless steel box for static treatment. The samples were taken out after 1 day, 4 days, 7 days, 15 days, 30 days, 60 days, 90 days, and 120 days. The total α count of the sample surface was measured using a portable background αβ meter in a sealed shielded box, and the change in surface color was measured using a colorimeter.

[0040] S403. Radiation Simulation Calculation: Based on the Lindhard computational model and the improved Kinchin-Pease model derived from Robinson's modified Lindhard energy partition theory, the physical process of transporting 5.3 MeV alpha particles emitted by Po-210 in four functional coating materials was simulated using the Geant 4 Monto Carlo application software package. The range of the 5.3 MeV alpha particles in the material target is on the order of tens of micrometers. In the simulation calculation, the thickness of the coating material target was set to 100 material to ensure that the energy of all alpha particles was deposited in the material. The number of alpha particles simulated was 1 × 10⁻⁶. 8 The QGSP_BIC_AIIHP physical process is used to extract the required physical parameters such as particle energy, spatial coordinates, and angles from the function. When alpha particles are incident on the material, the PKA (photonic scattering) is mainly an elastic scattering process. The data extracted by Geant 4 is processed using Python programming to calculate the radiation damage of the coating material.

[0041] The beneficial effects of this invention are:

[0042] (1) The present invention provides a method and apparatus for monitoring the activity and testing coatings in a Po-210 aerosol migration loop. It employs four functional coating materials specific to Po-210: antifouling, protection, sealing, and defouling. These materials are primarily designed to address the uncontrollable aerosols formed by the characteristic highly toxic nuclide Po-210 produced by fourth-generation advanced fast neutron reactors and the flexible treatment of surface contamination. For areas where Po-210 may be present, such as walls and floors, a long-life, light-coated water-based epoxy-based antifouling coating is used for effective antifouling, provided the surface is uncontaminated or has already been treated. For irregularly shaped metal equipment surfaces that have been contaminated, depending on the specific needs, a peelable water-based polyurethane protective coating can be used for effective protection, decontamination, and sealing. This type of coating is used in a typical radioactive environment, where, in addition to the alpha rays emitted by Po-210, the reactor produces other volatile nuclides such as I-129, Kr-85, Xe-133, Cs-137, and tritium, which emit beta and gamma rays. This type of coating has undergone performance testing under both alpha and gamma irradiation, demonstrating excellent radiation resistance and mechanical properties.

[0043] (2) The present invention provides a method and device for activity monitoring and coating test in a Po-210 aerosol migration loop. The aerosol migration loop coupled with in-situ monitoring function can carry out Po-210 tests at the mCi level in a sealed shielded box that has been tested for seismic resistance. It can safely and efficiently complete the adsorption performance tests of four functional special coatings, namely anti-fouling, decontamination, solidification and protection, and the transported Po-210 aerosol. It can also accurately monitor the activity level of the Po-210 aerosol transported in the gas space of the sealed system.

[0044] (3) The present invention provides a method and apparatus for monitoring activity and testing coatings in the Po-210 aerosol migration loop. Based on the characteristics of the coating material itself and the working environment, it forms a unique material testing method for judging the service stability of coatings in the complex service environment of fourth-generation advanced fast neutron reactor systems facing α, β and γ rays represented by Po-210. It also combines radiation simulation calculations to assist in the test evaluation of the radiation damage of coating materials, which has great engineering practical significance and scientific research value.

[0045] (4) The present invention provides a method and apparatus for monitoring the activity of Po-210 aerosol migration loop and testing coatings, which can heat and release Po-210 generated by neutron irradiation of a lead-bismuth alloy sample that is consistent with the coolant composition and content of the fourth-generation advanced fast neutron reactor system; simulate the surface pollution environment formed by the diffusion and migration of aerosols and their deposition in actual service of protective coatings; monitor the activity concentration level of Po-210 aerosols circulating in the sealed system of the test device throughout the entire test process; and test the contact between gaseous Po-210 transported in the sealed environment and the surfaces of four functional coating materials for antifouling, protection, solidification and decontamination, and the generation of electrostatic adsorption, chemical adsorption or elastic collision of particles. Attached Figure Description

[0046] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in describing the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments recorded in the present invention. Those skilled in the art can derive other drawings from the following drawings without any creative effort.

[0047] Figure 1 This is a schematic diagram of the activity monitoring and coating testing device in the Po-210 aerosol migration loop provided by the present invention;

[0048] Figure 2 This is a connection diagram of the Po-210 in-situ monitoring device;

[0049] Figure 3 This describes the overall pressure holding status of the Po-210 aerosol circulation loop from 10:40 to 15:03.

[0050] Figure 4 This is a test diagram of the energy resolution of the Po-210 online monitoring device;

[0051] Figure 5 This is a color difference curve of the coating material under MGy dose α irradiation;

[0052] Figure 6 This is a three-dimensional track distribution map of α particles incident on an epoxy-based coating material: a) only α particles; b) including secondary particles;

[0053] Figure 7 This is a three-dimensional track distribution map of α particles incident on a polyurethane-based coating material: a) only α particles; b) including secondary particles;

[0054] In the diagram: 1-Aerosol migration loop, 2-Sealed shielded enclosure, 3-Three-stage exhaust filter, 4-First-stage intake filter, 5-Special ventilation system, 6-Nuclear-grade filter, 7-Special exhaust duct, 8-High-temperature evaporator, 9-Gas delivery device, 10-Programmed temperature-controlled heating device, 11-Programmed temperature-controlled cabinet, 12-Quartz sample chamber, 13-Gas buffer mixing device, 14-Lead-bismuth alloy sample containing Po-210, 15-Pressure gauge, 16-Thermometer, 17-Aerosol circulation device, 18-Gas mass flow controller, 19-First gas sampling pump, 20-V1-V8. Va, Vb, Vc electric ball valves, 21-exhaust gas purification device, 22-functional coating testing device, 23-portable background low αβ measuring instrument, 24-colorimeter, 25-Po-210 in-situ monitoring device, 26-Po-210 online monitoring unit, 27-inlet and outlet connection, 28-multi-stage sampler, 29-filter membrane adsorption device, 30-electrostatic adsorption device, 31-monitoring sealed box, 32-monitoring control cabinet, 33-second gas sampling pump, 34-first vacuum pump, 35-second vacuum pump, 36-third vacuum pump, 37-fourth vacuum pump. Detailed Implementation

[0055] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0056] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., refer to the orientation or positional relationship shown in the accompanying drawings, and are used 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," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0057] 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 a connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0058] This invention addresses the issue of evaluating the service stability of epoxy-based and peelable polyurethane-based coatings used for surface contamination treatment in fourth-generation advanced fast neutron reactor systems under real Po-210 radiation conditions. It provides a device for monitoring activity in the Po-210 aerosol migration loop and testing coatings, such as… Figure 1 As shown, the device includes an aerosol migration loop 1 and a Po-210 in-situ monitoring device 25. The aerosol migration loop 1 is used to simulate the surface contamination environment formed by the diffusion and migration of aerosols and their deposition during the actual service of the protective coating by using the mCi-level Po-210 released at high temperature in the lead-bismuth alloy sample 14. In this sealed environment, the gaseous Po-210 migrates and comes into contact with the surface of the four functional coating materials of antifouling, protection, sealing and decontamination, and generates electrostatic adsorption, chemical adsorption or elastic collision of particles. The Po-210 in-situ monitoring device 25 is used to monitor the activity concentration level of Po-210 aerosols circulating in the aerosol migration loop 1 throughout the entire test process.

[0059] The aerosol migration loop 1 includes a sealed shielded enclosure 2, a high-temperature evaporation device 8, an aerosol circulation device 17, and a functional coating testing device 22; the high-temperature evaporation device 8, the aerosol circulation device 17, and the functional coating testing device 22 are located inside the sealed shielded enclosure 2.

[0060] The sealed shielded enclosure 2 is the airtightness protection test device for the Po-210 aerosol migration loop 1, carrying the main test of Po-210 aerosol migration and serving as a safe operating platform for coating testing. Simultaneously, it provides the source gas circulation branch for the Po-210 in-situ monitoring device 25 through the inlet and outlet connections 27, and can also be connected to an external on-site gas supply device, such as a centralized on-site gas supply facility, aerosol generator, or air compressor, through the gas delivery device 9. The sealed shielded enclosure 2 includes a three-stage exhaust filter 3 and a one-stage inlet filter 4. The one-stage inlet filter 4 removes particulate impurities from the air entering the enclosure, ensuring a clean environment inside. The inlet of the three-stage exhaust filter 3 receives the purified test gas, which undergoes further three-stage purification before being discharged into the ventilation system 5 of the test site through an exhaust pipe welded to the outlet.

[0061] The main body of the sealed shielded enclosure 2 is made of 304 stainless steel. Specifically, a 10mm lead plate is sandwiched between the 304 stainless steel cladding inside and outside the enclosure. The inner wall of the enclosure is smooth with a surface roughness better than Ra 0.8. The inner wall has a smooth transition without dead corners, and the radius of curvature R is 10mm to 20mm. It is equipped with a nitrogen purging gun to prevent surface contamination. Surface contamination can be easily removed by blowing or wiping. Its viewing window is a composite structure with two layers of 8mm tempered glass and a 20mm lead glass shielding layer in between to prevent breakage. Its supporting structure is a 304 stainless steel support frame, and the four support feet contact the ground through rubber pads. All contact surfaces are... The chamber is secured with anchor bolts to prevent movement, loosening, or deformation due to vibration. The atmosphere inside the chamber can be automatically circulated and purified according to the test requirements. It features an overall seismic design and structural configuration, negative pressure protection, and a Class I sealing function that exceeds the requirements of EJ / T1096, ensuring the safe conduct of radioactive tests.

[0062] The high-temperature evaporation device 8 is used for programmed and gradient heating of lead-bismuth alloy samples containing Po-210. The designed temperature is 1000℃, and the test temperature range is room temperature to 800℃, causing the Po-210 in the test sample to evaporate and release. It includes a gas delivery device 9, a programmed temperature-controlled heating device 10, a programmed temperature-controlled cabinet 11, a quartz sample chamber 12, and a gas buffer mixing device 13. The programmed temperature-controlled heating device 10 is located at the bottom of the sealed shielded enclosure 2. The quartz sample chamber 12 is located inside the programmed temperature-controlled heating device 10. The lead-bismuth alloy sample 14 containing Po-210 is placed in the quartz sample chamber 12. A gas buffer mixing device 13 is provided above the cavity 12. A pressure gauge 15 and a thermometer 16 are provided on the high-temperature evaporation device 8. A gas delivery interface is provided on the high-temperature evaporation device 8. The gas delivery interface is connected to a gas delivery device 9 located outside the sealed shielded box 2. The gas delivery device 9 is connected to a centralized gas supply facility or an air compressor. The Ar carrier gas provided by the centralized gas supply facility and the air or other test gas provided by the air compressor are mixed to form the typical Po-210 gas or aerosol required for the test. An interface 17 is provided on the high-temperature evaporation device 8 for connection to the Po-210 aerosol circulation device.

[0063] The aerosol circulation device 17 is used for program-controlled test circulation gas path and exhaust gas purification gas path, so that the typical Po-210 gas or aerosol required for the test circulates and moves within the gas path and the exhaust gas is purified. The gas flow rate is ~0.4L / min, which can simulate the diffusion and migration behavior of Po-210 released from the fourth-generation advanced fast neutron reactor system. It includes a gas mass flow controller 18, a first gas sampling pump 19, an electric ball valve 20, an exhaust gas purification device 21, etc. The above components are connected by anti-static carbon black tubes to form a gas passage. The entire aerosol circulation device 17 is supported by a bracket to form a three-dimensional spatial structure. The typical Po-210 gas or aerosol generated by the high-temperature evaporation device 8 is connected to the gas mass flow controller 18 through a carbon black tube. The other end of the gas mass flow controller 18 is connected to the first gas sampling pump 19. The first gas sampling pump 19 is provided with an interface for connection to the functional coating test device 22. The first gas sampling pump 19 outputs... The outlet is connected to the exhaust gas purification device 21, which is connected to the three-stage exhaust filter 3. The functional coating test device 22 is a test device for four functional special coating materials. It is equipped with 20L cylindrical containers A and B, both used to hold coating samples. The first gas sampling pump 19 is connected to containers A and B respectively. The other end of containers A and B is connected to the interface of the high-temperature evaporation device 8. Gaseous Po-210 is delivered to containers A and B through the aerosol circulation device 17 to provide a spatial environment for the coating sample surface to contact with gaseous Po-210. It contacts and interacts with the surfaces of the four functional coating materials: antifouling, protection, sealing and defouling, to study the pollution behavior of Po-210 on the coating sample surface. After the test, the α radioactivity level of the coating sample surface is monitored by a portable low-background αβ measuring instrument 23, and the color difference meter 24 is used to measure the color change of the coating sample surface in real time inside the chamber.

[0064] In the aerosol circulation device 17 and the functional coating test device 22, all components are connected via anti-static carbon black tubes. Electric ball valves 20 are installed between components, and the opening and closing of these electric ball valves are controlled by the program control cabinet 11, thus setting the gas path connection method. The power for gas circulation within the tubes is provided by the first gas sampling pump 19. The gas mass flow controller 16 is connected in parallel with electric ball valve V5, and its inlet and outlet ends are connected to electric ball valves V4 and V3 respectively, used to set the gas paths for testing and post-test gas cleaning. The electric ball valves 20 (V1-V8, Va, Vb, Vc) serve as gas transport interfaces for the aerosol circulation device's gas path. To prevent aerosol leakage, they are welded and sealed within a stainless steel enclosure for protection. After the test, the gas containing Po-210 is purified by adsorption of silver-loaded activated carbon particles in the exhaust gas purification device 21, then enters the three-stage exhaust filter 3 in the sealed shielded box 2 for further purification, before being introduced into the special ventilation system 5 at the test site.

[0065] The ventilation system 5 includes a nuclear-grade filter 6 and a special exhaust ventilation duct 7. The three-stage exhaust filter 3 is connected to the nuclear-grade filter 6 by welding a stainless steel exhaust duct. After being filtered and purified by the nuclear-grade filter 6, the air enters the special exhaust ventilation duct 7.

[0066] The in-situ monitoring device 25 includes a Po-210 online monitoring unit 26, an inlet and outlet connection 27, a monitoring sealed box 31, and a monitoring control cabinet 32. The monitoring sealed box 31 functions similarly to the sealed shielding box 2, containing any Po-210 aerosol that may leak from the atmosphere inside the box. The monitoring sealed box 31 is divided into upper and lower boxes. The upper box contains an interface for centralized on-site gas supply and serves as a container and protection device for the Po-210 online monitoring unit 26. It allows for manual replacement of the filter paper in its measuring chamber or cutting filter paper samples for offline Po-210 analysis. Figure 2 As shown, the Po-210 online monitoring unit 26 is located inside the upper chamber of the monitoring sealed box 31. The Po-210 online monitoring unit 26 is used for nuclide identification and vacuum energy spectrum quantitative measurement. After coupling with the aerosol migration circuit, it can monitor the activity concentration of the Po-210 gas source in the gas migration circuit 1 in situ. The Po-210 online monitoring unit 26 includes a multi-stage sampler 28, a filter membrane adsorption device 29, and an electrostatic adsorption device 30, etc. The related sampling and measurement processes are controlled by the analysis software of the monitoring control cabinet 32. The filter membrane adsorption device 29 is equipped with a novel measurement chamber vacuum system. This system utilizes low-energy laser ablation to remove radioactive materials adhering to the inner wall of the chamber and induces the depolymerization and homogenization of alpha nuclide aerosols. Simultaneously, it automatically identifies filter membrane information and nuclide measurement parameters, monitors the paper feed force of the filter membrane in real time, and uses flexible sealing materials to dynamically adhere to the filter membrane edges, ensuring the vacuum level of the chamber. Under vacuum conditions, the device's energy resolution for alpha nuclide detection is ≤ that of nuclide detection, improving the accuracy of Po-210 measurements at low activity concentrations (<1 Bq / m³). The multi-stage sampler 28 is a device for impact-based graded sampling based on the particle size distribution characteristics of Po-210 aerosols. The activity concentration of Po-210 aerosol samples with different particle size ranges is analyzed using alpha energy dispersive spectroscopy. The electrostatic adsorption device 30 uses a gold-silicon surface detector to convert the signal of alpha particles released from electrostatically adsorbed Po-210 aerosols into electrical pulse counting, thereby detecting the radioactivity of alpha particles.

[0067] The lower chamber of the monitoring sealed box 31 is equipped with a second gas sampling pump 33, a first vacuum pump 34, a second vacuum pump 35, a third vacuum pump 36, and a fourth vacuum pump 37. The second gas sampling pump 33 provides power for the intake gas sampling of the filter membrane adsorption device 29, with continuously adjustable flow rate, and provides a high vacuum environment (<15kPa) for its vacuum energy spectrum quantitative measurement. The first vacuum pump 34 supplies source gas to the electrostatic adsorption device 30, and the second vacuum pump 35 supplies source gas to the multi-stage sampler 28. The third vacuum pump 36 and the fourth vacuum pump 37 maintain the negative pressure environment of the upper chamber of the monitoring sealed box 31. The monitoring control cabinet 32 ​​is equipped with the Po-210 online monitoring and analysis program, which controls the sampling and monitoring tasks of the Po-210 online monitoring unit 26.

[0068] The inlet and outlet connections 27 are both connected to the gas buffer mixing device 13 of the aerosol migration loop 1 and the Po-210 online monitoring unit 26 of the Po-210 in-situ monitoring device 25 through the shielded sealed enclosure 2 and the monitoring sealed enclosure 31. The gas buffer mixing device 13 is the transport center for the Po-210 test gas or aerosol throughout the entire cycle, providing source gas to the Po-210 online monitoring unit 26 and the aerosol circulation device 17. The gas after the test is transported to the exhaust gas purification device 21 of the aerosol circulation device 17 for purification before being discharged into the ventilation exhaust system 5.

[0069] A method for monitoring activity and testing coatings in a Po-210 aerosol migration loop is disclosed. The coatings include four types of functional coatings: a surface-coated epoxy-based special coating for antifouling on reactor building structures, and a peelable polyurethane-based special coating for surface protection, sealing, and decontamination of key metal equipment in reactor supporting systems. The surface-coated epoxy-based special coating is used as a self-leveling protective layer for structures such as floors and walls, while the peelable polyurethane-based coating is used as a functional protective film for decontamination, sealing, and protection of key metal equipment such as irregularly shaped three-dimensional equipment, pipes, and valves.

[0070] Furthermore, the aforementioned stain-resistant epoxy self-leveling protective layer for structures such as floors and walls consists of roller-coated epoxy primer (A:B = 5:2, mixed evenly), intermediate epoxy mortar (A:B = 5:1, mixed evenly and then 40% of 80-100 mesh quartz sand is added, and mixed evenly again), and trowel-coated epoxy topcoat (A:B = 5:1, mixed evenly). The roller-coated epoxy primer is evenly roller-coated onto the concrete substrate surface as a support surface. After it dries overnight, the intermediate epoxy mortar is scraped onto the primer surface with a flat trowel to level it. After 24 hours of drying, it is smoothed with a louvered grinding disc. The epoxy topcoat is then evenly spread on the smoothed surface with a 2mm trowel. After 24 hours of drying, a self-leveling layer is formed. Its features include a smooth, mirror-like surface with high hardness, wear resistance, pressure resistance, corrosion resistance, and washability. It can effectively prevent moisture or Po-210 aerosol particles in the air from adhering to its surface, and can further effectively block the Po-210 nuclides carried by the surface deposits from penetrating into the membrane. It can also effectively wipe away contaminants adhering to its surface, ensuring surface cleanliness. Its service life can reach more than 15 years.

[0071] Furthermore, the aforementioned decontamination-type polyurethane-based protective film for critical metal equipment such as irregularly shaped three-dimensional equipment, pipes, valves, etc., is coated with a polyurethane coating containing 0.3% graphene oxide, 0.5% modified SCT bentonite, and 0.5% sodium diethyldithiocarbamate, a complexing agent, and other functional fillers. Its characteristic is that the primer of the uniform and dense dithiocarbamate coating film with a thickness of approximately 250 mm coats encapsulates and decontaminates the Po-210 radioactive contamination on the surface of the metal equipment. Simultaneously, the topcoat of the outer layer adsorbs and fixes Po-210 aerosol particles in contact with the air, preventing the diffusion and migration of Po-210 contamination. After a period of time, the film is peeled off, and the Po-210 contaminants on the equipment surface are removed along with the film and disposed of as solid waste. The method of use is relatively flexible, and the formed film has good adhesion, excellent mechanical properties, good thermal stability, and good peeling effect.

[0072] Furthermore, the polyurethane-based protective film used as a sealant for metal equipment such as irregularly shaped three-dimensional equipment and components dismantled during reactor operation and maintenance and contaminated with Po-210, is coated with a polyurethane coating containing 3% sericite, a layered filler that blocks heavy metal ions such as Po-210; 5% potassium octatitanate whiskers, a filler that provides some radiation resistance to alpha rays emitted by Po-210 and enhances the flexibility of the film; and 0.5% sodium diethyldithiocarbamate, a complexing agent, and other functional fillers, forming a uniform layer. A uniform and dense coating film with a thickness of approximately 200 μm is used to encapsulate and seal the Po-210 radioactive contamination on the surface of metal equipment. After the Po-210 has fully decayed to a level suitable for maintenance, the film is removed. The Po-210 contaminants on the equipment surface are removed along with the film and disposed of as solid waste. The equipment can be maintained and put back into operation, reducing manual operation costs and risks. The resulting film has good adhesion, excellent mechanical properties, and good peeling effect. Its service life can reach 2-3 years, achieving the purpose of decontamination and protection of equipment, personnel safety, and dose reduction.

[0073] Furthermore, the protective polyurethane-based protective film, used as a protective layer for key metal equipment such as irregularly shaped three-dimensional equipment and components before being put into service in the reactor system, contains 3% sericite, a layered filler that blocks heavy metal ions such as Po-210; 5% barium sulfate, a filler that has a certain radiation resistance to 5.3 MeV alpha rays emitted by Po-210 and can enhance the flexibility of the film; and 5% potassium octatate whiskers, a filler that can enhance the flexibility of the film. The resulting uniform, dense, and flexible coating film, approximately 200 μm thick, protects the metal equipment from Po-210 radioactive contamination on its surface during reactor system service, while also preventing moisture or Po-210 aerosol particles in the air from adhering to its surface or migrating into the film. After a certain period of protection, the contaminated membrane on the equipment surface can be peeled off, and the Po-210 contaminants attached to the membrane surface can be removed and disposed of as solid waste. The equipment surface can be coated with a protective film again for continuous protection, reducing the risk of equipment contamination. The resulting membrane has good adhesion, excellent mechanical properties, and good peeling effect, and its service life can reach 2 to 3 years.

[0074] A method for activity monitoring and coating testing in a Po-210 aerosol migration loop is disclosed. This method simulates the diffusion and migration behavior of Po-210 released from a fourth-generation advanced fast neutron reactor system, ensuring that the Po-210 gas flow moves unidirectionally within a sealed environment, without releasing into the test site or environment, thus preserving the radiation safety of test personnel. The specific steps are as follows:

[0075] S1. Preparation of test conditions and debugging of test equipment

[0076] S101, Sealed and shielded enclosure: The test results meet the following requirements: leakage rate < 0.005 vol% / h, vacuum is maintained during enclosure operation, and pressure change ΔP < 1%, which means the enclosure's sealing function is considered normal.

[0077] S102, Po-210 aerosol circulation loop: If the circuit device commissioning results meet the requirement that the gas pressure during operation is ≤ aerosol circulation loop and the gas pressure can be maintained for 2h to 3h (pressure change ΔP < 10%), then the circuit device with complex interfaces is considered to have basically normal sealing function and can be tested in a sealed shielded box.

[0078] S103, Po-210 Online Monitoring Device: If the commissioning results of the online monitoring device meet the following conditions during operation: the vacuum degree of the measurement chamber is <15kPa, and the energy resolution of the device for α nuclide detection under vacuum is ≤1 / 3 of the α nuclide detection, then the device is considered to have normal measurement function.

[0079] S2, Adsorption test of Po-210 on the surface of coating material in the circuit

[0080] S201, Po-210 and antifouling functional coating test: ① Weigh the neutron-irradiated lead-bismuth target sample (~1g) containing Po-210 stored in the chamber and transfer it to the quartz sample chamber of the high-temperature evaporation device; ② Transfer the antifouling functional coating sample to container A of the functional coating test device in the chamber and suspend it; ③ Use an air compressor to introduce 5000Pa air into the gas buffer mixing device of the aerosol migration circuit; ④ Control the heating temperature to 600°C using the program interface and light up the circuit button of coating test device 1 on the control interface to form a circuit and start the program heating; ⑤ Set the gas flow rate of the circuit to 4L / min; ⑥ Under the heating temperature of 600°C, Po-210 evaporates from the lead-bismuth alloy, mixes with air to form an aerosol, circulates in the circuit for 30 minutes, and fully contacts the antifouling functional coating sample.

[0081] S202, Po-210 and Decontamination Functional Coating Test: ① Simultaneously with step 201, transfer the decontamination functional coating sample into container B of the functional coating test device inside the chamber, suspend it for later use; ② After the first test is completed, the program interface controls to close the loop button of 1) and then open the loop button of 2) to form a circuit; ③ Use an air compressor to introduce 3600Pa air into the gas buffer mixing device of the aerosol migration circuit; ④ Po-210 continuously evaporated from the lead-bismuth alloy under a heating temperature of 600°C mixes with the newly introduced air to form an aerosol, which circulates in the circuit for 30 minutes to fully contact the decontamination functional coating sample; ⑤ Take out the anti-fouling functional coating of 1) and the decontamination functional coating of 2);

[0082] S203, Po-210 and Protective Functional Coating Test: ① Same as the test method of loop 1), transfer the protective functional coating sample into container A of the functional coating test device inside the chamber and suspend it; ② Use an air compressor to introduce air at 3499Pa into the gas buffer mixing device of the aerosol migration loop; ③ Control the heating temperature to 600°C on the program interface and light up the loop button of coating test device 1 on the control interface to form a circuit and start the program heating; ④ Set the gas flow rate of the loop to 4L / min; ⑤ Under the heating temperature of 600°C, Po-210 evaporates from the lead-bismuth alloy, mixes with air to form an aerosol, circulates in the loop for 30 minutes, and fully contacts the protective functional coating sample;

[0083] S204) Po-210 and Solid-Type Functional Coating Test: ① The test method is the same as in 2). Simultaneously with 3), the solid-type functional coating sample is transferred into container B of the functional coating test device inside the chamber and suspended for later use; ② After the 3) test is completed, the program interface controls to close the loop button of 3) and then open the loop button of 4) to form a circuit; ③ Air at 3600Pa is introduced into the gas buffer mixing device of the aerosol migration circuit using an air compressor; ④ Po-210 continuously evaporated from the lead-bismuth alloy at a heating temperature of 6004°C mixes with the newly introduced air to form an aerosol, which circulates in the circuit for 30 minutes to fully contact the solid-type functional coating sample.

[0084] Po-210 in-situ monitoring in S3 circuit

[0085] S301, Branch Circuit Sealing Protection: After 30 minutes of aerosol circulation testing in steps 2) 1) to 4), the activity level of Po-210 in the aerosol circulation loop was monitored in situ using an online Po-210 monitoring device on each branch of the aerosol migration loop device. The entire in-situ monitoring cycle was conducted safely within the protection of the sealed enclosure, with a gas leakage rate <0.025 vol% / h.

[0086] S302. Gas / Aerosol Sampling: On the analysis interface of this in-situ monitoring device, open the solenoid valves of the inlet and outlet connecting pipes to form a gas / aerosol sampling and measurement pathway. Set the sampling flow rate to 13 L / min, circulate the sampling for 10 min, and then start the gas sampling pump.

[0087] S303, Nuclide Vacuum Measurement: Based on 2) above, turn on the vacuum pump and filter paper feeding device, automatically identify filter information and nuclide measurement parameters, monitor the paper feeding force of the filter membrane in real time, measure for 10 minutes under low vacuum, and obtain the activity concentration level of Po-210 in the circulation loop.

[0088] S304, Nuclide Removal: The low-energy laser ablation function in the analysis software is automatically activated to remove radioactive materials adhering to the inner wall of the chamber and induce the depolymerization and homogenization of α-nuclide aerosols.

[0089] S305. Exhaust Gas Purification: After the in-situ monitoring is completed, the centralized gas supply facilities on site are used to purge the gas paths of containers A and B with nitrogen / argon gas. This ensures that the Po-210 aerosol in the gas path is purified by the exhaust gas purification device, and then enters the special exhaust after being highly purified by the three-stage exhaust filter in the enclosure. The special exhaust vent also has a primary purification stage and a nuclear-grade high-efficiency purifier to ensure the safety of emissions into the environment.

[0090] Testing of coating samples after S4 test

[0091] S401, Surface radioactivity monitoring: After the tests in steps (2) and (3) are completed, the entire test device is restored to room temperature. Four types of coating samples are taken out from containers A and B. The total α count of the sample surface is performed using a portable background αβ meter in a sealed shielded box to determine the degree of adsorption or attachment of Po-210 on the surface of the coating sample.

[0092] S402. Radiation aging assessment: After surface radioactivity monitoring, four types of coating samples were marked, sealed in sealed bags, and placed in a covered stainless steel box for static treatment. The samples were taken out after 1 day, 4 days, 7 days, 15 days, 30 days, 60 days, 90 days, and 120 days. The total α count of the sample surface was measured using a portable background αβ meter in a sealed shielded box, and the change in surface color was measured using a colorimeter.

[0093] S403. Radiation Simulation Calculation: Based on the Lindhard computational model and the improved Kinchin-Pease model derived from Robinson's modified Lindhard energy partition theory, the physical process of transporting 5.3 MeV alpha particles emitted by Po-210 within four functional coating materials was simulated using the Geant 4 Monto Carlo application software package. The range of the 5.3 MeV alpha particles in the material target is on the order of tens of micrometers. In the simulation, the thickness of the coating material target was set to 100 material to ensure that the energy of all alpha particles was deposited in the material. The number of alpha particles simulated was 1 × 10⁻⁶. 8 The QGSP_BIC_AIIHP physical process was used to extract the necessary physical parameters such as particle energy, spatial coordinates, and angles from the function. When alpha particles are incident on the material, the PKA (photonic scattering) process is mainly elastic scattering. Python programming was used to process the data extracted by Geant 4 to calculate the radiation damage to the coating material. Specific calculation steps are attached. Figure 3 As shown, this is for auxiliary experimental evaluation.

[0094] Example 1: Preparation of test conditions and debugging of test equipment

[0095] 1) Sealed shielded enclosure: Before conducting the Po-210 and coating material tests, the leakage rate of the enclosure was tested according to EJ / T1096-1999 "Classification and Test Methods for Sealing Performance of Sealed Enclosures" 5.1 Oxygen Method (see Table 1), and the negative pressure change of the enclosure was tested according to 5.2 Pressure Change Method. The result was 0.4% (see Table 2), indicating that the enclosure has good sealing performance.

[0096] 2) Po-210 aerosol circulation loop: Before conducting the Po-210 and coating material tests, refer to EJ / T1096-1999 "Classification and Test Methods for Sealing Performance of Sealed Chambers" 5.2 Pressure Variation Method to test the pressure maintenance in the Po-210 aerosol circulation loop over approximately 4 hours. See [link to relevant documentation]. Figure 3 ;

[0097] 3) Po-210 Online Monitoring Device: Before conducting tests on Po-210 and coating materials, the vacuum level of the online monitoring device's measuring chamber was tested to be 11.2 kPa, and the energy resolution of the device for α-nuclides detection under vacuum was tested to be 1.2%. (See attached document). Figure 4 .

[0098] Table 1 Leakage rate test data based on oxygen-containing method

[0099]

[0100] Table 2 Test data based on the pressure change method

[0101]

[0102] In summary, the sealing performance of the shielded enclosure, the pressure maintenance of the Po-210 aerosol circulation loop, and the operation of the Po-210 online monitoring device are all good, and it is feasible to conduct adsorption tests of Po-210 on the surface of the coating material in the aerosol circulation loop.

[0103] Example 2: Adsorption test of Po-210 on the surface of the coating material in the circuit

[0104] After weighing approximately 1 g of neutron-irradiated lead-bismuth target material containing Po-210 stored in the chamber, it was transferred to the quartz sample chamber of the high-temperature evaporation device. The anti-fouling functional coating sample was transferred to container A of the functional coating test apparatus within the chamber and symmetrically suspended in the center of the container. Air at 5000 Pa was introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor, with a gas flow rate of 4 L / min. The loop button of the coating test apparatus 1, which illuminates the interface, was activated by program control, forming a circuit. The programmed temperature rise to 600℃ was initiated, causing Po-210 to evaporate from the lead-bismuth alloy, mix with air to form an aerosol, and circulate in the loop for 30 minutes, ensuring full contact with the anti-fouling functional coating sample.

[0105] Simultaneously with step 1), the stain-removing functional coating sample is transferred into container B of the functional coating test apparatus inside the chamber and suspended for later use. After the first test, the program interface controls to close the loop button of step 1) and then open the loop button of step 2), forming a circuit. Air at 3600 Pa is introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor. Po-210, continuously evaporated from the lead-bismuth alloy at a heating temperature of 600℃, mixes with the newly introduced air to form an aerosol, which circulates in the loop for 30 minutes, ensuring full contact with the stain-removing functional coating sample.

[0106] Example 3: In-situ monitoring of Po-210 in the loop

[0107] After 30 minutes of aerosol circulation tests in Examples 1 and 2, the activity level of Po-210 in the aerosol circulation loop was monitored in situ using an online Po-210 monitoring device on a branch of the aerosol migration loop device: 1) the α count rate of Po-210 in the coated gas path was 0.193 cps, and 2) the α count rate of Po-210 in the coated gas path was 0.200 cps. After in-situ monitoring, the gas paths of containers A and B were purged with nitrogen / argon using the centralized gas supply facilities on site. This ensured that the Po-210-containing aerosols in the gas paths were purified by the exhaust gas purification device, then highly purified by the three-stage exhaust filter in the enclosure before entering the special exhaust system. The special exhaust vent also underwent primary purification and nuclear-grade high-efficiency purification treatment to ensure safe emissions into the environment.

[0108] Example 4: Testing of the coating samples after the experiment

[0109] After all experiments in Examples 1-3 were completed, the entire experimental setup was restored to room temperature. Coating samples were removed from containers A and B, and the total α count on the sample surface was performed using a portable background αβ meter within a sealed shielded chamber (see Table 3). The data in Table 3 indicate the degree of Po-210 adsorption or adhesion on the coating sample surface. The antifouling coating showed effective antifouling against Po-210 in the gas space, while the decontamination coating showed significant adsorption against Po-210 in the gas space.

[0110] After surface radioactivity monitoring, the coating samples were marked, sealed in airtight bags, and placed in a covered stainless steel box for standing. They were then removed after 1, 4, 7, 15, 30, 60, 90, and 120 days. A colorimeter was used to measure the coating surface; no color change was observed. Figure 5 As shown, this indicates that the coating is less affected by radiation environments with low-activity Po-210 alpha particle emission. For comparison, see accelerator vacuum alpha irradiation data. Figure 6 It was found that under α irradiation with doses of 0-6 MGy, the color changes of each coating were still not obvious, but there was still a tendency for discoloration.

[0111] The physical process of 5.3 MeV alpha particles emitted by Po-210 being transported in four functional coating materials was simulated using the Geant 4 Monto Carlo application software package. In the simulation, the thickness of the coating material target was set to 100 μm to ensure that the energy of all alpha particles was deposited within the material. The number of alpha particles simulated was 1 × 10⁻⁶. 8 Using the QGSP_BIC_AIIHP physics procedure, the required physical parameters such as particle energy, spatial coordinates, and angles were extracted from the function. Python programming was then used to process the data extracted by Geant4 to calculate the radiation damage of the coating material. The simulation results are shown below. Figure 6-7 .

[0112] Table 3 Total α count data on the surface of coated samples

[0113]

[0114] While those skilled in the art will recognize that the present invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention, the embodiments should be considered illustrative and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and therefore all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0115] Furthermore, it should be understood that although the present invention is described according to embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A device for monitoring activity and testing coatings in a Po-210 aerosol migration loop, characterized in that, The system includes an aerosol migration loop (1) and a Po-210 in-situ monitoring device (25). The aerosol migration loop (1) is used to simulate the surface contamination environment formed by the diffusion and migration of aerosols and their deposition in the actual service of the protective coating by using the mCi-level Po-210 released at high temperature in the lead-bismuth alloy sample (14). In this sealed environment, the gaseous Po-210 migrates and comes into contact with the surface of the four functional coating materials of antifouling, protection, sealing and decontamination, and generates electrostatic adsorption, chemical adsorption or elastic collision of particles. The Po-210 in-situ monitoring device (25) is used to monitor the activity concentration level of Po-210 aerosols that circulate and migrate within the aerosol migration loop (1) throughout the entire test process.

2. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 1, characterized in that, The aerosol migration circuit (1) includes a sealed shielded box (2), a high-temperature evaporation device (8), an aerosol circulation device (17), and a functional coating test device (22); the high-temperature evaporation device (8), the aerosol circulation device (17), and the functional coating test device (22) are located inside the sealed shielded box (2); the high-temperature evaporation device (8) is used for programmed control and gradient heating of lead-bismuth alloy samples containing Po-210; the aerosol circulation device (17) is used for programmed control of the test circulation gas path and the exhaust gas purification gas path, so that the typical Po-210 gas or aerosol required for the test circulates and moves within the gas path and the exhaust gas is purified; the functional coating test device (22) is a test device for four functional special coating materials.

3. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 2, characterized in that, The sealed shielded box (2) has through holes for connecting to the Po-210 in-situ monitoring device (25) and the gas delivery device (9).

4. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 3, characterized in that, The sealed shielded enclosure (2) includes a three-stage exhaust filter (3) and a first-stage inlet filter (4). The first-stage inlet filter (4) removes particulate impurities from the air entering the enclosure to ensure a clean environment inside the enclosure. The air inlet of the three-stage exhaust filter (3) receives the purified test gas, which is then further purified in three stages before being discharged into the ventilation system (5) of the test site through an exhaust pipe welded to the outlet.

5. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 4, characterized in that, The high-temperature evaporation device (8) includes a programmable temperature-controlled heating device (10), a programmable temperature-controlled cabinet (11), a quartz sample chamber (12), and a gas buffer mixing device (13). The programmable temperature-controlled heating device (10) is located at the bottom of the sealed shielded box (2). The quartz sample chamber (12) is located inside the programmable temperature-controlled heating device (10). A lead-bismuth alloy sample (14) containing Po210 is placed in the quartz sample chamber (12). The gas buffer mixing device (13) is provided above the quartz sample chamber (12). The high-temperature evaporation device (8) is equipped with a pressure gauge (15) and a thermometer (16).

6. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 5, characterized in that, The high-temperature evaporation device (8) is provided with a gas delivery interface, which is connected to a gas delivery device (9) located outside the sealed shielded box (2).

7. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 6, characterized in that, The gas delivery device (9) is connected to a centralized gas supply facility or an air compressor on site. The Ar carrier gas provided by the centralized gas supply facility on site, the air provided by the air compressor, or other test gases are mixed to form a typical Po-210 gas or aerosol required for the test.

8. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 7, characterized in that, The high-temperature evaporation device (8) is provided with an interface for connecting to the Po-210 aerosol circulation device (17).

9. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 8, characterized in that, The aerosol circulation device (17) includes a gas mass flow controller (18), a first gas sampling pump (19), and an exhaust gas purification device (21). The components are connected by antistatic carbon black tubes to form a gas passage. The entire aerosol circulation device (17) is supported by a bracket to form a three-dimensional spatial structure. The typical Po-210 gas or aerosol generated by the high-temperature evaporation device (8) is connected to the gas mass flow controller (18) through a carbon black tube. The other end of the gas mass flow controller (18) is connected to the first gas sampling pump (19). The outlet of the first gas sampling pump (19) is connected to the exhaust gas purification device (21). The exhaust gas purification device (21) is connected to the three-stage exhaust filter (3).

10. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 9, characterized in that, The first gas sampling pump (19) is provided with an interface for connecting to the functional coating test device (22). The functional coating test device (22) is equipped with 20L cylindrical containers A and B, both of which are used to hold coating samples. The first gas sampling pump (19) is connected to containers A and B respectively. The other end of containers A and B is connected to the interface for connecting the high-temperature evaporation device (8). Gaseous Po-210 is delivered to containers A and B through the aerosol circulation device (17) to provide a spatial environment for the coating sample surface to contact with gaseous Po-210. It contacts and interacts with the surfaces of four functional coating materials: antifouling, protection, sealing and defouling, and studies the contamination behavior of Po-210 on the surface of the coating sample. The α-radioactivity level of the coated sample surface after the test was monitored by a portable low-background αβ measuring instrument (23), and the color change of the coated sample surface after the test was measured in real time in the chamber by a colorimeter (24).

11. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 10, characterized in that, In the aerosol circulation device (17) and the functional coating test device (22), an electric ball valve (20) is provided between any components, and the start and stop of the electric ball valve (20) is controlled by the program control cabinet (11); the gas mass flow controller (16) is connected in parallel with an electric ball valve.

12. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 11, characterized in that, The ventilation system (5) includes a nuclear-grade filter (6) and a special exhaust ventilation pipe (7). The three-stage exhaust filter (3) is connected to the nuclear-grade filter (6) by welding a stainless steel exhaust pipe. After being filtered and purified by the nuclear-grade filter (6), the air enters the special exhaust ventilation pipe (7).

13. The activity monitoring and coating testing device in the Po-210 aerosol migration loop according to claim 12, characterized in that, The in-situ monitoring device (25) includes a Po-210 online monitoring unit (26), an inlet and outlet connection (27), a monitoring sealed box (31), and a monitoring control cabinet (32). The monitoring sealed box (31) is divided into upper and lower boxes. The Po-210 online monitoring unit (26) is located inside the upper box of the monitoring sealed box (31). The Po-210 online monitoring unit (26) is used for nuclide identification and vacuum energy spectrum quantitative measurement. After coupling with the aerosol migration circuit, it can monitor the activity concentration of the Po-210 gas source in the gas migration circuit (1) in situ. The Po-210 online monitoring unit (26) includes The device includes a multi-stage sampler (28), a filter membrane adsorption device (29), and an electrostatic adsorption device (30). The sampling and measurement processes are controlled by the analysis software in the monitoring and control cabinet (32). The filter membrane adsorption device (29) uses low-energy laser to ablate and remove radioactive materials attached to the inner wall of the chamber, and induces the depolymerization and homogenization of α-nucleoside aerosols. At the same time, it can automatically identify filter membrane information and nuclide measurement parameters, monitor the paper feeding force of the filter membrane in real time, and use flexible sealing materials to dynamically adhere to the edge of the filter membrane to ensure the vacuum degree of the chamber. Under vacuum conditions, the energy resolution of the device for α-nucleoside detection is ≤ that of the nuclide detection, improving the detection efficiency of low-activity concentration Po-2.

10. Measurement accuracy; The multi-stage sampler (28) is a device for impact-type graded sampling according to the particle size distribution characteristics of Po-210 aerosol. The activity concentration of Po-210 aerosol samples with different particle size ranges is analyzed by α-energy spectroscopy; The electrostatic adsorption device (30) uses a gold-silicon surface detector to convert the signal of α particles released by electrostatically adsorbed Po-210 aerosol into electrical pulse counting, thereby detecting the radioactivity of α particles; The lower chamber of the monitoring sealed box (31) is equipped with a second gas sampling pump (33), a first vacuum pump (34), a second vacuum pump (35), and a third vacuum pump (36). 6) The fourth vacuum pump (37) and the second gas sampling pump (33) provide power for the intake sampling of the filter membrane adsorption device (29); the first vacuum pump (34) delivers source gas to the electrostatic adsorption device (30), and the second vacuum pump (35) delivers source gas to the multi-stage sampler (28); the third vacuum pump (36) and the fourth vacuum pump (37) maintain the negative pressure environment of the upper box of the monitoring sealed box (31); the monitoring control cabinet (32) is equipped with the Po-210 online monitoring and analysis program, which controls the sampling and monitoring tasks of the Po-210 online monitoring unit (26).

14. A method for monitoring activity and testing coatings in a Po-210 aerosol migration loop, characterized in that, Includes the following steps: S1. Preparation of test conditions and debugging of test equipment; S2, Adsorption test of Po-210 on the surface of coating material in the circuit; Po-210 in-situ monitoring in S3 loop; Testing of the coating sample after the S4 test.

15. The method for activity monitoring and coating testing in the Po-210 aerosol migration loop according to claim 14, characterized in that, The adsorption test of Po-210 on the surface of the coating material in the circuit specifically includes: S201, Po-210 and anti-fouling functional coating tests: After weighing the neutron-irradiated lead-bismuth target sample containing Po-210 stored in the chamber, it was transferred to the quartz sample chamber of the high-temperature evaporation device. The anti-fouling functional coating sample was transferred to container A of the functional coating test device in the chamber and suspended. Air at 5000 Pa was introduced into the gas buffer mixing device of the aerosol migration circuit using an air compressor. The heating temperature was controlled at 600°C in the program interface, and the circuit button of the coating test device on the control interface was lit to form a circuit and start the program heating. The gas flow rate of the circuit was set to 4 L / min. Under the heating temperature of 600°C, Po-210 evaporated from the lead-bismuth alloy, mixed with air to form an aerosol, and circulated in the circuit for 30 minutes to fully contact the anti-fouling functional coating sample. Tests of S202, Po-210 and detergency-removing functional coatings: Simultaneously with step 201, the stain-removing functional coating sample is transferred into container B of the functional coating test apparatus inside the chamber and suspended for later use. After the previous test is completed, the program interface controls the closing of the previous loop button and then opens the second loop button to form a pathway. Air at 3600Pa is introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor. Po-210, which is continuously evaporated from the lead-bismuth alloy at a heating temperature of 600°C, mixes with the newly introduced air to form an aerosol, which circulates in the loop for 30 minutes to fully contact the stain-removing functional coating sample. The anti-fouling functional coating and the stain-removing functional coating are then removed. S203, Po-210 and Protective Functional Coating Test: Following the same procedure as step 201, the protective functional coating sample was transferred into container A of the functional coating test apparatus inside the chamber and suspended. Air at 3499 Pa was introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor. The heating temperature was controlled at 600°C via the program interface, and the loop button of the coating test apparatus on the control interface was activated to form a circuit, starting the programmed heating. The gas flow rate of the loop was set to 4 L / min. Under a heating temperature of 600°C, Po-210 evaporated from the lead-bismuth alloy, mixed with air to form an aerosol, and circulated in the loop for 30 minutes, ensuring full contact with the protective functional coating sample. S204, Po-210 and Sealing Functional Coating Test: Consistent with the test method in step 202, the sealing functional coating sample is simultaneously transferred into container B of the functional coating test device inside the chamber and suspended for later use; after the previous test is completed, the program interface controls to close the previous loop button and then open the next loop button to form a path; air at 3600Pa is introduced into the gas buffer mixing device of the aerosol migration loop using an air compressor; Po-210 continuously evaporated from the lead-bismuth alloy at a heating temperature of 6004°C mixes with the newly introduced air to form an aerosol, which circulates in the loop for 30 minutes to fully contact the sealing functional coating sample.

16. The method for activity monitoring and coating testing in the Po-210 aerosol migration loop according to claim 15, characterized in that, In-situ monitoring of Po-210 in the circuit specifically includes: S301, Branch sealing protection: After 30 minutes of aerosol circulation test, the activity level of Po-210 in the aerosol circulation loop was monitored in situ using the Po-210 online monitoring device on the branch of the aerosol migration loop device; the entire cycle of in-situ monitoring was carried out safely in the protection of the sealed box, and the gas leakage rate was <0.025 vol% / h. S302. Gas / Aerosol Sampling: On the analysis interface of this in-situ monitoring device, open the solenoid valves of the inlet and outlet connecting pipes to form a gas / aerosol sampling and measurement path; set the sampling flow rate to 13L / min, circulate sampling for 10min, and start sampling by turning on the gas sampling pump. S303, Nuclide Vacuum Measurement: Turn on the vacuum pump and filter membrane feeding device, automatically identify filter membrane information and nuclide measurement parameters, monitor the paper feeding force of the filter membrane in real time, measure for 10 minutes under low vacuum, and obtain the activity concentration level of Po-210 in the circulation loop. S304, Nuclide Removal: The low-energy laser ablation function in the analysis software is automatically activated to remove radioactive materials adhering to the inner wall of the chamber and induce the depolymerization and homogenization of α-nuclide aerosols. S305. Exhaust Gas Purification: After the in-situ monitoring is completed, the centralized gas supply facilities on site are used to purge the gas paths of containers A and B with nitrogen / argon gas. This ensures that the Po-210 aerosol in the gas path is purified by the exhaust gas purification device, and then enters the special exhaust after being highly purified by the three-stage exhaust filter in the enclosure. The special exhaust vent also has a primary purification stage and a nuclear-grade high-efficiency purifier to ensure the safety of emissions into the environment.

17. The method for activity monitoring and coating testing in the Po-210 aerosol migration loop according to claim 16, characterized in that, The testing of the coating samples after the experiment specifically includes: S401, Surface radioactivity monitoring: After the entire test apparatus is restored to room temperature, four types of coating samples are taken out from container A and container B. The total α count of the sample surface is performed using a portable background αβ meter in a sealed shielded box to determine the degree of adsorption or adhesion of Po-210 on the surface of the coating sample. S402. Radiation aging assessment: After surface radioactivity monitoring, four types of coating samples were marked, sealed in sealed bags, and placed in a covered stainless steel box for static treatment. The samples were taken out after 1 day, 4 days, 7 days, 15 days, 30 days, 60 days, 90 days, and 120 days. The total α count of the sample surface was measured using a portable background αβ meter in a sealed shielded box, and the change in surface color was measured using a colorimeter. S403. Radiation Simulation Calculation: Based on the Lindhard computational model and the improved Kinchin-Pease model derived from Robinson's modified Lindhard energy partition theory, the physical process of transporting 5.3 MeV alpha particles emitted by Po-210 in four functional coating materials was simulated using the Geant 4 Monto Carlo application software package. The range of the 5.3 MeV alpha particles in the material target is on the order of tens of micrometers. In the simulation calculation, the thickness of the coating material target was set to 100 material to ensure that the energy of all alpha particles was deposited in the material. The number of alpha particles simulated was 1 × 10⁻⁶. 8 The QGSP_BIC_AIIHP physical process is used to extract the required physical parameters such as particle energy, spatial coordinates, and angles from the function. When alpha particles are incident on the material, the PKA (photonic scattering) is mainly an elastic scattering process. The data extracted by Geant 4 is processed using Python programming to calculate the radiation damage of the coating material.

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