A multi-stage impactor aerosol sampler and continuous monitoring system

Abstract

This invention proposes a multi-stage impactor aerosol sampler and continuous monitoring system, belonging to the field of radioactive environment monitoring. It addresses the problem of extremely high exposure risks during filter replacement when traditional impactor samplers are applied to high-intensity radioactive environments. It includes a cylindrical sealed tower body containing multiple longitudinally connected aerodynamic separation units. Each separation unit has a radial opening on the tower wall, with the radial openings arranged spirally and staggered along the circumference of the tower body. A drawer-type sampling box includes a shielded drawer box, which can be radially inserted and removed into the radial openings. A bypass channel and sliding valve linkage mechanism, located inside the tower body, includes a bypass branch connected in parallel with the main gas channel, and a sliding valve located at the intersection of the main gas channel and the bypass branch. It is primarily used in the uranium mining field.

Description

Technical Field

[0001] This invention belongs to the field of radioactive environmental monitoring, aerosol sampling and nuclide analysis technology, and in particular relates to a multi-stage impactor aerosol sampler. Background Technology

[0002] In nuclear-related locations such as uranium mining, nuclear facility operation, and radiopharmaceutical production, aerosol particles carrying radioactive nuclides such as uranium, plutonium, iodine-131, and cesium-137 may be suspended in the air. Once inhaled, these radioactive aerosols will cause continuous internal radiation exposure, seriously threatening the health of workers and the public. Therefore, continuous monitoring and sampling analysis of radioactive aerosols in and around the workplace is crucial for assessing internal radiation dose, tracing the source of contamination, and ensuring radiation safety. Impaction samplers are commonly used devices based on the principle of aerodynamic inertial separation. They accelerate airflow through a series of nozzles of specific sizes before impacting a collection plate, thereby classifying and collecting particles of different aerodynamic diameters into different levels. This classified collection capability is of great significance for analyzing the particle size distribution characteristics of radionuclides.

[0003] However, when traditional impact samplers are applied to the aforementioned high-intensity radioactive environments, their inherent structural design limitations lead to a series of insurmountable technical defects and safety risks. First, the exposure risk during filter replacement is extremely high. Traditional samplers are mostly integral or have open-top designs; replacing a particular filter requires opening the equipment casing or complete disassembly, exposing the operator's hands and body directly to the concentrated radioactive material in the filter, resulting in avoidable additional radiation doses. This severely violates the fundamental principle of ALARA (Average Radiation Amount) in radiation protection. Second, this process is highly susceptible to cross-contamination. In multi-stage cascaded samplers, the radioactivity collected by each filter stage can vary significantly. Complete disassembly and reassembly exposes all collected filters to the same operating space simultaneously, potentially causing cross-contamination of radioactive materials between different stages. This severely impacts the accurate analysis of the activity of nuclides within specific particle size ranges.

[0004] Furthermore, the reliability of the sealing structure of traditional equipment is difficult to guarantee after frequent disassembly and maintenance. Aging of sealing rings and wear of flange surfaces can lead to the leakage of radioactive aerosols from equipment gaps, causing not only workplace contamination but also directly endangering the safety of maintenance personnel. In addition, this type of structure cannot meet the rigid requirements of 24 / 7 continuous monitoring in nuclear facilities. When any stage of the filter membrane reaches its dust holding capacity and needs replacement, the entire sampling system must be shut down, resulting in gaps in monitoring data—an unacceptable safety hazard in both emergency response and routine monitoring. The underlying technical reason for this problem is that existing impact samplers generally lack an effective internal bypass flow channel design. When a filter membrane unit is removed, the gas path for that stage is physically interrupted, causing the airflow in the entire system to stagnate, and sampling operations at other stages are also forced to stop.

[0005] Finally, regarding equipment maintenance and decommissioning, the integrated or complex cavity structure of traditional samplers has a large number of cleaning dead spots, making it difficult to thoroughly decontaminate after contamination. The radioactive substances remaining on the equipment surface will become a continuous source of contamination, increasing the risk of radiation exposure for subsequent maintenance personnel and also increasing the difficulty and cost of disposing of the equipment as radioactive waste. Summary of the Invention

[0006] In view of this, the present invention aims to propose a multi-stage impactor aerosol sampler and continuous monitoring system to solve the problem of extremely high exposure risk during filter membrane replacement when traditional impactor samplers are applied to high-intensity radioactive environments.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a multi-stage impactor aerosol sampler, the sampler comprising: A cylindrical sealed tower body is provided with a multi-stage aerodynamic separation unit connected in series along the longitudinal direction. The tower wall has radial openings corresponding to each separation unit, and the radial openings of each stage are arranged in a spiral staggered manner along the circumference of the tower body. A drawer-type sampling box includes a shielded drawer box, which is radially insertable into the radial opening; The bypass flow channel and the sliding plate valve linkage mechanism are located inside the tower body. It includes a bypass branch connected in parallel with the main air channel and a sliding plate valve located at the intersection of the main air channel and the bypass branch. The sliding plate valve is kept in a normally closed state by a return spring. The front end of the drawer-type sampling box is provided with a top pressure flange. The top pressure flange is used to drive the sliding plate valve to operate when the drawer-type sampling box is pushed in, so as to connect the main air channel and close the bypass branch.

[0008] Furthermore, a preferred embodiment is proposed, wherein the front end of the shielded drawer box is provided with an elastic shielding plug, and the inner side of the radial opening of the tower body is provided with a self-closing shielding valve; when the drawer-type sampling box is completely pulled out, the self-closing shielding valve closes the radial opening.

[0009] Furthermore, a preferred embodiment is proposed in which the drawer-type sampling box further includes an aluminum sampling cup and a quick clamp. The front end of the aluminum sampling cup is fitted with a metal sealing ring and is detachably installed in the shielded drawer box via the quick clamp.

[0010] Furthermore, a preferred embodiment is proposed in which the sliding valve linkage mechanism further includes a roller, the roller being disposed on the side of the sliding valve facing the drawer-type sampling cartridge, and the top pressure flange at the front end of the drawer-type sampling cartridge contacting the roller during the pushing in or pulling out process.

[0011] Furthermore, a preferred embodiment is proposed, wherein the sampler further includes a locking-sealing-shielding linkage mechanism, which includes a double slide rail guide system disposed on both sides of the radial opening, a magnetic locking unit disposed at the rear end of the drawer in the direction of withdrawal, and a wedge-shaped self-locking clamping mechanism disposed at the front end of the drawer. The inclined surface of the wedge-shaped self-locking clamping mechanism is used to convert the horizontal pushing force into a radial clamping force when the drawer is pushed in.

[0012] Furthermore, a preferred embodiment is proposed, wherein the locking-sealing-shielding linkage mechanism further includes a dual sealing system, which includes an outer circumferential radiation sealing ring disposed between the shielding drawer box and the tower body, and a central gas path sealing ring disposed between the metal sealing ring of the aluminum sampling cup and the upper-level nozzle plate.

[0013] Furthermore, a preferred embodiment is proposed in which the sampler further includes a vacuum release interlock system, comprising a vacuum release valve, a pressure sensor, and an electromagnetic interlock. The vacuum release valve is used to inflate the mechanical cavity outside the drawer to balance the negative pressure. The pressure sensor is used to monitor the pressure difference. The electromagnetic interlock is used to release the lock on the drawer when the pressure difference is lower than a set threshold.

[0014] Furthermore, a preferred embodiment is proposed, wherein the multi-stage aerodynamic separation unit includes a multi-stage nozzle plate, each stage of which has a rectangular accelerating nozzle in the center, and the front surface of the aluminum sampling cup also serves as the impact plate for the corresponding stage.

[0015] Furthermore, a preferred embodiment is proposed in which the spiral staggered arrangement is such that adjacent two-stage radial openings are staggered by 90° to 120°.

[0016] Based on the same inventive concept, the present invention also proposes a continuous monitoring system for radioactive aerosols, including a multi-stage impactor aerosol sampler as described in any one of the above, and multiple spare drawer-type sampling cartridges; when a drawer-type sampling cartridge of a certain stage is pulled out, its corresponding slide valve switches to a state that allows the airflow to pass through a bypass branch.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention breaks away from the traditional tandem exposure mode of samplers, which places multiple stages of filter membranes within a common sealed cavity. Its core feature is that each impactor and filter membrane is independently encapsulated in a drawer-type sampling box with built-in radiation shielding. This sampling box, as a pre-packaged standard module, can be horizontally pulled out through a radial opening in the side wall of the tower. This design achieves complete isolation of each sampling unit in terms of both physical and radiation protection. During replacement, the object being handled is no longer the exposed filter membrane, but the entire module in a fully shielded state, fundamentally eliminating the possibility of operators directly contacting the radiation source.

[0018] To resolve the fundamental contradiction of requiring system shutdown during single-stage module replacement, this invention incorporates a bypass branch connected in parallel with the main sampling gas path and incorporates a sliding valve linkage mechanism. Its core control logic lies in timing differential: when the drawer module is pulled out, the linkage mechanism ensures the sliding valve prioritizes opening the bypass branch before completely cutting off the main gas path; the reverse occurs when it is pushed in. This guarantees that at least one main or bypass path remains unobstructed at any given moment during operation, achieving seamless airflow relay, maintaining a constant total system flow, and allowing continuous sampling at other stages.

[0019] To address the potential spatial interference between multi-level, interconnected tower structures and horizontal pull-out operations, this invention arranges the radial openings of each drawer in a spiral staggered pattern along the circumference of the tower. This arrangement cleverly utilizes the cylindrical circumferential space of the tower, staggering pull-out paths that might overlap vertically on the horizontal projection plane. This ensures that each drawer has an independent, interference-free insertion / extraction trajectory, resolving the layout conflict of multi-level quick-change drawers in a compact space.

[0020] To ensure smooth and safe drawer operation under high negative pressure and to absolutely prevent radioactive leakage, this invention integrates a vacuum release interlock and a locking-sealing-shielding linkage mechanism. The principle is as follows: before operation is permitted, the pressure difference inside and outside the drawer cavity is balanced through an independent air path to release the negative pressure suction force; a magnetic locking unit provides mechanical counterforce to directly counteract residual suction. For sealing, a wedge-shaped self-locking mechanism amplifies the horizontal thrust into a radial sealing force, combined with a self-closing shielding valve and a sliding seal with the drawer's elastic shielding plug, forming multiple, continuous seals and shielding barriers during dynamic extraction and static closure, achieving complete closure during operation and at rest.

[0021] Based on the multi-stage impactor aerosol sampler proposed in this invention, operators do not need to directly face or contact the contaminated filter membrane. The replacement operation involves the entire module within a fully shielded container. Combined with the increased operating distance and significantly reduced time, the radiation dose received by personnel during filter membrane replacement is reduced by several orders of magnitude, strictly adhering to the ALARA principle. Furthermore, the sampler proposed in this invention, from dynamic operation to static sealing, employs a multi-layered, interconnected sealing and shielding design to ensure that radioactive aerosols are reliably confined within the system or shielded container under any operating condition, preventing the leakage of harmful substances and protecting the working environment and personnel safety. Because each sampling unit is independently encapsulated and isolated, when replacing one stage, the other stages remain completely enclosed within the tower body, with no exposed communication between them, fundamentally eliminating cross-contamination of radioactive materials of different levels, activities, or nuclides. Thanks to the uninterrupted switching principle of the bypass gas path, when any sampling module in the continuous monitoring system is replaced, the gas path at that system level remains unobstructed, and the sampling work at other levels is not affected. The system can continuously produce monitoring data, meeting the mandatory requirement of nuclear facilities to conduct 24 / 7 uninterrupted environmental monitoring. Easily contaminated components such as sampling cups and sealing rings are integrated into quick-release drawer modules, which can be disposed of as consumables or decontamination units separately. The smooth inner wall and simple structure of the main tower, without the complex internal protrusions and dead corners of traditional equipment, make the radioactive decontamination operation of the entire equipment simple and thorough, reducing the long-term exposure risk and handling costs for maintenance personnel. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a cross-sectional view of the overall structure of the multi-stage impact aerosol sampler described in this invention; Figure 2 This is a detailed structural diagram of the drawer-type sampling box described in this invention; Figure 3 This is a schematic diagram of the gas path described in this invention; Figure 4 This is a schematic diagram of the radiation protection calculation described in this invention; Figure 5 This is a top view of the multi-stage radially open spiral arrangement described in this invention; Figure 6 This is a schematic diagram of the linkage mechanism between the slide valve and the drawer-type sampling box described in this invention; Figure 7 Detailed drawings of the wedge-shaped clamping mechanism and sealing structure described in this invention; Figure 8This is a flowchart illustrating the operation of replacing the radioactive environmental filter membrane according to the present invention.

[0023] In the picture: 1-Cylindrical sealing tower body; 1.1-Airflow inlet; 1.2-Airflow outlet; 1.3-Radial opening; 2-Drawer-type sampling box; 2.1-Shielded drawer box; 2.2-Aluminum sampling cup; 2.11-Top pressure flange; 2.21-Metal sealing ring; 2.3-Quick clamp; 2.4-Elastic shielding plug; 3-Bypass flow channel and slide valve linkage mechanism; 3.1-Bypass branch; 3.2-Slide valve; 3.3-Reset spring; 3.4-Roller; 3.5-Spring seat; 3.6-Slide rail 4-Locking-Sealing-Shielding Linkage Mechanism, 4.1-Dual Slide Rail Guiding System, 4.2-Magnetic Locking Unit, 4.3-Wedge Self-Locking Pressing Mechanism, 4.4-Dual Sealing System, 4.41-Outer Peripheral Radial Sealing Ring, 4.42-Central Air Path Sealing Ring, 4.5-Shielding Valve, 5-Vacuum Release Interlock System, 5.1-Vacuum Release Valve, 5.2-Pressure Sensor, 5.3-Electromagnetic Interlock, 6-Multi-Stage Aerodynamic Separation Unit, 6.1-Three-Stage Nozzle Plate, 6.2-Impact Plate. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0025] Implementation Method 1: This implementation method addresses the issue of extremely high exposure risks during filter membrane replacement when traditional impactor samplers are applied in high-intensity radioactive environments. It proposes a multi-stage impactor aerosol sampler, comprising: A cylindrical sealed tower body 1 has a multi-stage aerodynamic separation unit 6 connected in series along the longitudinal direction inside. The tower wall has a radial opening 1.3 corresponding to each separation unit. The radial openings 1.3 of each stage are arranged in a spiral staggered manner along the circumference of the tower body. The drawer-type sampling box 2 includes a shielded drawer box 2.1, which is radially insertable into the radial opening 1.3; The bypass flow channel and the sliding plate valve linkage mechanism 3 are located inside the tower body 1. It includes a bypass branch 3.1 connected in parallel with the main air channel, and a sliding plate valve 3.2 located at the intersection of the main air channel and the bypass branch. The sliding plate valve 3.2 is kept in a normally closed state by a return spring 3.3. The front end of the drawer-type sampling box 2 is provided with a top pressure flange 2.11. The top pressure flange is used to drive the sliding plate valve 3.2 to operate when the drawer-type sampling box 2 is pushed in, so as to connect the main air channel and close the bypass branch 3.1.

[0026] In this embodiment, the front end of the shielded drawer box 2.1 is provided with an elastic shielding plug 2.4, and the inner side of the radial opening 1.3 of the tower body 1 is provided with a self-closing shielding valve 4.5; when the drawer-type sampling box 2 is completely pulled out, the self-closing shielding valve 4.5 closes the radial opening.

[0027] In this embodiment, the drawer-type sampling box 2 further includes an aluminum sampling cup 2.2 and a quick clamp 2.3. The front end of the aluminum sampling cup is fitted with a metal sealing ring 2.21 and is detachably installed in the shielded drawer box 2.1 through the quick clamp 2.3.

[0028] In this embodiment, the sliding valve linkage mechanism 3 further includes a roller 3.4, which is disposed on the side of the sliding valve 3.2 facing the drawer-type sampling box 2. The top pressing flange 2.11 at the front end of the drawer-type sampling box 2 contacts the roller 3.4 during the pushing or pulling process.

[0029] In this embodiment, the sampler further includes a locking-sealing-shielding linkage mechanism 4, which includes a double slide rail guide system 4.1 disposed on both sides of the radial opening 1.3, a magnetic locking unit 4.2 disposed at the rear end of the drawer in the direction of drawer withdrawal, and a wedge-shaped self-locking pressing mechanism 4.3 disposed at the front end of the drawer. The inclined surface of the wedge-shaped self-locking pressing mechanism 4.3 is used to convert the horizontal pushing force into a radial pressing force when the drawer is pushed in.

[0030] In this embodiment, the locking-sealing-shielding linkage mechanism 4 further includes a double sealing system 4.4, which includes an outer peripheral radiation sealing ring 4.41 disposed between the shielding drawer box 2.1 and the tower body 1, and a central gas path sealing ring 4.42 disposed between the metal sealing ring 2.21 of the aluminum sampling cup 2.2 and the upper-level nozzle plate.

[0031] In this embodiment, the sampler further includes a vacuum release interlock system 5, which includes a vacuum release valve 5.1, a pressure sensor 5.2, and an electromagnetic interlock 5.3. The vacuum release valve 5.1 is used to inflate the mechanical cavity outside the drawer to balance the negative pressure. The pressure sensor 5.2 is used to monitor the pressure difference. The electromagnetic interlock 5.3 is used to release the lock on the drawer when the pressure difference is lower than a set threshold.

[0032] In this embodiment, the multi-stage aerodynamic separation unit 6 includes a multi-stage nozzle plate 6.1, with a rectangular acceleration nozzle in the center of each nozzle plate 6.1, and the front end plane of the aluminum sampling cup 2.2 also serves as the impact plate 6.2 of the corresponding stage.

[0033] In this embodiment, the spiral staggered arrangement is such that adjacent two-stage radial openings 1.3 are staggered by 90° to 120°.

[0034] Implementation Method 2, see below Figures 1 to 8 This embodiment describes a complete implementation of a multi-stage impact aerosol sampler proposed in Embodiment 1, comprising six main parts: a cylindrical sealed tower body 1, a drawer-type sampling box 2, a bypass flow channel and slide valve linkage mechanism 3, a locking-sealing-shielding linkage mechanism 4, a vacuum release interlocking system 5, and a multi-stage aerodynamic separation unit 6.

[0035] The cylindrical sealing tower body 1 serves as the outer shell and shielding structure of the device. It is a cylindrical shell structure made of a composite material of 316L austenitic stainless steel (3mm thick) and an inner lead lining (2mm thick). The 316L stainless steel provides structural strength and corrosion resistance, while the lead lining provides gamma-ray shielding capability. The two are combined using a low-temperature silver brazing process to prevent creep of the lead layer caused by high temperatures. The top of the tower body 1 has a circular airflow inlet 1.1, connected to the upstream gas path via a CF flange to initially guide and stabilize the incoming airflow; the bottom has an airflow outlet 1.2, connected to a negative pressure source. The side walls of the tower body 1 have radial openings 1.3 corresponding to each separation unit, as shown in the attached diagram. Figure 5 As shown, the openings at each level are arranged in a spiral staggered pattern along the circumference of the drawer body, with adjacent levels offset by 90°~120° to avoid interference when the drawers are pulled out. The edges of the openings are equipped with stainless steel double slide rails 1.4, with a Teflon PTFE coating to reduce the coefficient of friction, ensuring that the drawers can still be smoothly pulled out with one hand even under a 5kg load.

[0036] The drawer-type sampling box 2 is the core component for achieving quick filter membrane replacement and radiation shielding, including a shielded drawer box 2.1, an aluminum sampling cup 2.2, and a quick-release clamp 2.3. The shielded drawer box 2.1 is integrally machined from tungsten-nickel-iron alloy (density 17 g / cm³), with a wall thickness of 5 mm and optimized dimensions of 80 mm × 60 mm × 35 mm (length × width × height). It effectively shields β and γ rays, reducing the operator's hand dose rate by two orders of magnitude. The drawer itself constitutes a shielding container; even after being pulled out, the filter membrane remains shielded within the box, preventing radiation exposure during transport. The front end of the drawer box 2.1 is equipped with an elastic shielding plug 2.4, which, in the pulled-out state, cooperates with a self-closing shielding valve to form a secondary seal. The aluminum sampling cup 2.2 is a disposable component, made of 6061-T6 aluminum alloy with an anodized surface. A metal sealing ring 2.21 is embedded at the front end (interference fit with the cup body, fit accuracy H7 / p6). The cup rim is precision machined, with a surface roughness Ra≤0.8μm. The distance between the cup and the nozzle plate outlet is ensured to be ±0.05mm through drawer positioning accuracy. A quick-release chuck 2.3 is located at the front end of the drawer box 2.1, employing a cam clamping mechanism to achieve quick installation and removal of the sampling cup 2.2 in 3 seconds.

[0037] The bypass channel and the sliding valve linkage mechanism 3 are key to achieving continuous sampling, such as... Figure 6As shown, the system includes a bypass branch 3.1, a sliding plate valve 3.2, a return spring 3.3, a roller 3.4, a spring seat 3.5, and a slide rail 3.6. The sliding plate valve adopts a dual-stroke differential design, with a main air port sealing stroke of 8mm and a bypass port opening stroke of 8.8mm, achieving a 0.05-second timing delay using a 0.8mm stroke difference. The bypass branch 3.1 is located on the inner wall of tower body 1, connected in parallel with the main air duct, and has a cross-sectional area of ​​80% of the main air duct, ensuring smooth airflow and controllable pressure drop. The sliding plate valve 3.2 is a stainless steel 304 valve plate, installed in the slide rail 3.6, located at the intersection of the main air duct and the bypass branch 3.1. It is kept in a normally closed state by a small return spring 3.3 fixed to the spring seat 3.5 on the back of the valve body, closing the bypass and opening the main air duct. The roller 3.4, with a diameter of 10mm, is installed on the side of the slide valve 3.2 facing the drawer. When the front end of the drawer pushes in the top flange 2.11, it presses the roller 3.4, causing the slide valve 3.2 to move down 8mm, opening the main air port and closing the bypass port. When the drawer is pulled out, the return spring 3.3 rebounds within 0.1 seconds, opening the bypass port first, and closing the main air port after a delay of 0.05 seconds, thus avoiding airflow short circuit and sampling efficiency loss caused by dual-pass state.

[0038] The locking-sealing-shielding linkage mechanism 4 includes a double slide rail guide system 4.1, a magnetic locking unit 4.2, a wedge-shaped self-locking clamping mechanism 4.3, a double sealing system 4.4, and a self-closing shielding valve 4.5. The double slide rail guide system 4.1 uses precision ball bearing slide rails with a width of 15mm and a precision grade of P. The clearance between the slider and the slide rail is 0.01mm, ensuring the straightness and coaxiality of the drawer's pull-out. The magnetic locking unit 4.2 is located at the rear end of the drawer in the pull-out direction and uses a samarium cobalt permanent magnet (Sm2Co). 17 Array, radiation resistance better than 10 6 Gy provides ≥200N of reverse suction force to directly counteract negative pressure external suction; as shown in the attached image. Figure 4 As shown, under a negative pressure of -50 kPa, the axial suction force generated by the radial opening of 50 mm × 30 mm is 75 N. The magnetic lock provides a safety factor of over 2.6 times, ensuring that the drawer does not come off; it automatically engages and triggers the Hall position sensor when pushed into place. The wedge-shaped self-locking clamping mechanism 4.3 is located on the front side of the drawer, as shown... Figure 7 As shown, the wedge angle is 15°. The wedge-shaped inclined surface converts the horizontal thrust into an inward clamping force along the radius, with a mechanical benefit of approximately 3.73. This drives the central air passage sealing ring to achieve a tight radial end-face seal with the outlet of the previous stage nozzle plate, with a clamping force ≥200N. The dual sealing system 4.4 includes an outer peripheral radiation sealing ring 4.41 and a central air passage sealing ring 4.42. The outer peripheral radiation sealing ring 4.41 is made of radiation-resistant ethylene propylene rubber (EPDMO) ring with a wire diameter of 3.53mm, a compression ratio of 15-20%, and a gamma radiation dose resistance of 10. 6To prevent the leakage of radioactive aerosols, a 2mm thick, 25% compression ratio FKM fluororubber flat gasket is used for the central seal to ensure the integrity of the gas path seal. A self-closing shielding valve 4.5 is located inside the tower wall opening and uses a 5mm thick lead alloy baffle, which is reset by a torsion spring. During drawer removal, the elastic shielding plug 2.4 maintains a sliding seal with the tower wall opening. After complete removal, the self-closing shielding valve 4.5 closes the opening within 0.3 seconds, achieving seamless connection and forming a radiation protection barrier.

[0039] The vacuum release interlock system 5 includes a vacuum release valve 5.1, a pressure sensor 5.2, and an electromagnetic interlock 5.3. The vacuum release valve 5.1 is an electromagnetic shut-off valve located between the drawer cavity and the clean air source. Before unlocking, clean air is introduced into the mechanical cavity outside the drawer (isolated from the sampling cavity) through an independent air path to balance the negative pressure (completed in about 3 seconds, flow rate 5L / min) to prevent negative pressure adsorption that would prevent the drawer from being pulled out. The pressure sensor 5.2 monitors the pressure difference between the drawer cavity and the tower body. When the pressure difference is confirmed to be <5kPa, the electromagnetic interlock 5.3 is released, allowing the extraction operation to proceed, thus forming an intrinsically safe interlock.

[0040] The multi-stage aerodynamic separation unit 6 includes a three-stage nozzle plate 6.1 and an impact plate 6.2. Each nozzle plate 6.1 is a precision-machined stainless steel component with a centrally located rectangular accelerating nozzle: the first stage cuts particles with a diameter of 10 μm, the second stage 2.5 μm, and the third stage 0.4 μm. The spacing between the slits is ensured by precision shims, with an error controlled within ±0.1 mm. The impact plate 6.2 is also the front surface of an aluminum sampling cup 2.2. Its surface can be configured with different filter membranes according to the analysis requirements of different radionuclides, including quartz fiber membranes, activated carbon membranes, and nuclear pore membranes. This independent selection capability at each stage enhances the sampler's adaptability to the physicochemical properties of aerosols.

[0041] During assembly, first, install the dual slide rail guide system 4.1 on both sides of the radial opening 1.3 on the side wall of the tower body 1, ensuring parallelism ≤0.02mm; install the slide valve 3.2 and return spring 3.3 into the valve cavity inside the tower wall, and connect the bypass branch 3.1; install the self-closing shielded valve 4.5 inside the opening. Then, install the pre-encapsulated aluminum sampling cup 2.2 into the shielded drawer box 2.1 and lock it with the quick clamp 2.3. Push the drawer in along the slide rail. At this time, the top pressure flange 2.11 presses the roller 3.4 to switch the slide valve 3.2 to the working position. The wedge-shaped inclined surface cooperates with the tower body guide groove to generate radial clamping force. The magnetic locking unit 4.2 is attracted into place. After the position sensor confirms, the system establishes negative pressure.

[0042] Aerosol gas enters from the top inlet 1.1 of tower body 1, and is accelerated through the slits of each stage of nozzle plates 6.1. It then impacts the filter membrane surface inside the aluminum sampling cup 2.2 due to inertia, causing radioactive particles to be captured in stages. The filtered gas is discharged through the bottom outlet 1.2 of the tower body. When a stage of filter membrane reaches its dust holding capacity and needs to be replaced, such as... Figure 3 and Figure 8 As shown, the negative pressure is first balanced through the vacuum release valve 5.1. After confirming the pressure difference is <5 kPa, the magnetic attraction disengages, and the drawer is pulled out. At this time, the slide valve 3.2 rebounds and switches to the bypass position. The bypass air passage opens within 0.1s, and the main air passage closes after a 0.05s delay. The self-closing shielding valve 4.5 closes its opening within 0.3s. The airflow of this stage maintains a constant total system flow through the bypass branch 3.1, while other stages continue to operate normally. Data from this stage is marked as missing during the replacement period, rather than indicating a system shutdown. The replaced radioactive filter membrane is transferred along with the sampling cup 2.2 into the lead-shielded transport container. After the new filter membrane is installed, it is pushed into the drawer, and the system automatically resumes the sampling function of this stage.

[0043] As attached Figure 4 As shown, based on the dose calculation formula D=A×Γ×t / r², assuming the filter membrane has a Cs-137 activity of Bq, a 5mm tungsten layer provides approximately 50 times attenuation for 662keV γ-rays, with a linear attenuation coefficient μ≈7.7cm. -1 By extending the handle or robotic arm to maintain a distance of 0.5m (inverse square ratio of distance, dose rate reduced to 36%), and shortening the operation time from 15 minutes to 15 seconds (time factor 1 / 60), the radiation dose per operation is reduced from 2.5μSv in the traditional method to <0.1μSv, a reduction of about two orders of magnitude, which meets the principle of optimal radiation protection for nuclear facilities.

[0044] Implementation Method 3: This implementation method provides a specific application example of the multi-stage impactor aerosol sampler described in Implementation Method 1 or Implementation Method 2, including: An 8-stage impact sampler is used for monitoring the perimeter of nuclear facilities, with each stage covering a particle size range of 0.04–10 μm. The radial openings of each stage are arranged in a spiral staggered pattern along the circumference of the tower, with each stage offset by 45°, forming a complete 360° distribution. The tower has a diameter of 250 mm, a height of 400 mm, and a stage spacing of 40 mm. Each stage is independently equipped with a bypass channel and a sliding valve, allowing the other seven stages to continue operating even when any single stage is replaced. Differential pressure monitoring of the filter membrane load at each stage triggers automatic switching, enabling 24 / 7 unattended continuous sampling.

[0045] Implementation Method 4: This implementation method proposes a continuous monitoring system for radioactive aerosols, including a multi-stage impactor aerosol sampler as described in any one of Implementation Methods 1 to 3, and multiple spare drawer-type sampling cartridges 2; when a drawer-type sampling cartridge 2 of a certain stage is pulled out, its corresponding slide valve 3.2 switches to a state that allows the airflow to pass through the bypass branch 3.1.

[0046] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A multi-stage impactor aerosol sampler, characterized in that, The sampler includes: A cylindrical sealed tower body (1) is provided inside which a multi-stage aerodynamic separation unit (6) is connected in series along the longitudinal direction. The tower wall is provided with radial openings (1.3) corresponding to each separation unit. The radial openings (1.3) of each stage are arranged in a spiral staggered manner along the circumference of the tower body. The drawer-type sampling box (2) includes a shielded drawer box (2.1), which is radially insertable into the radial opening (1.3); The bypass flow channel and the sliding plate valve linkage mechanism (3) are located inside the tower body (1). It includes a bypass branch (3.1) connected in parallel with the main air channel and a sliding plate valve (3.2) located at the intersection of the main air channel and the bypass branch. The sliding plate valve (3.2) is kept in a normally closed state by a return spring (3.3). The front end of the drawer-type sampling box (2) is provided with a top pressure flange (2.11). The top pressure flange is used to drive the sliding plate valve (3.2) to operate when the drawer-type sampling box (2) is pushed in, so as to connect the main air channel and close the bypass branch (3.1).

2. The multi-stage impactor aerosol sampler according to claim 1, characterized in that, The front end of the shielded drawer box (2.1) is provided with an elastic shielding plug (2.4), and the inner side of the radial opening (1.3) of the tower body (1) is provided with a self-closing shielding valve (4.5); when the drawer-type sampling box (2) is completely pulled out, the self-closing shielding valve (4.5) closes the radial opening.

3. The multi-stage impactor aerosol sampler according to claim 1, characterized in that, The drawer-type sampling box (2) also includes an aluminum sampling cup (2.2) and a quick clamp (2.3). The front end of the aluminum sampling cup is fitted with a metal sealing ring (2.21) and is detachably installed in the shielded drawer box (2.1) via the quick clamp (2.3).

4. A multi-stage impactor aerosol sampler according to claim 1, characterized in that, The sliding valve linkage mechanism (3) also includes a roller (3.4), which is located on the side of the sliding valve (3.2) facing the drawer-type sampling box (2). The top pressure flange (2.11) at the front end of the drawer-type sampling box (2) contacts the roller (3.4) during the pushing or pulling process.

5. A multi-stage impactor aerosol sampler according to claim 1, wherein The sampler also includes a locking-sealing-shielding linkage mechanism (4), which includes a double slide rail guide system (4.1) disposed on both sides of the radial opening (1.3), a magnetic locking unit (4.2) disposed at the rear end of the drawer in the direction of withdrawal, and a wedge-shaped self-locking clamping mechanism (4.3) disposed at the front end of the drawer. The inclined surface of the wedge-shaped self-locking clamping mechanism (4.3) is used to convert the horizontal pushing force into the radial clamping force when the drawer is pushed in.

6. A multi-stage impactor aerosol sampler according to claim 5, wherein, The locking-sealing-shielding linkage mechanism (4) also includes a double sealing system (4.4), which includes an outer circumferential radiation sealing ring (4.41) disposed between the shielding drawer box (2.1) and the tower body (1), and a central gas path sealing ring (4.42) disposed between the metal sealing ring (2.21) of the aluminum sampling cup (2.2) and the upper-level nozzle plate.

7. A multi-stage impactor aerosol sampler according to claim 1, wherein The sampler also includes a vacuum release interlock system (5), which includes a vacuum release valve (5.1), a pressure sensor (5.2), and an electromagnetic interlock (5.3). The vacuum release valve (5.1) is used to pressurize the mechanical cavity outside the drawer to balance the negative pressure. The pressure sensor (5.2) is used to monitor the pressure difference. The electromagnetic interlock (5.3) is used to release the lock on the drawer when the pressure difference is lower than a set threshold.

8. A multi-stage impactor aerosol sampler according to claim 1, wherein, The multi-stage aerodynamic separation unit (6) includes a multi-stage nozzle plate (6.1), with a rectangular acceleration nozzle in the center of each nozzle plate (6.1), and the front end plane of the aluminum sampling cup (2.2) also serves as the impact plate (6.2) of the corresponding stage.

9. A multi-stage impactor aerosol sampler according to claim 1, characterized in that, The spiral staggered arrangement is such that adjacent two-stage radial openings (1.3) are staggered by 90° to 120°.

10. A continuous monitoring system for radioactive aerosols, characterized in that, Includes a multi-stage impact aerosol sampler as described in any one of claims 1-9, and a plurality of spare drawer-type sampling cartridges (2); when a drawer-type sampling cartridge (2) of a certain stage is pulled out, its corresponding slide valve (3.2) switches to a state that allows the airflow to pass through the bypass branch (3.1).

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