Sampling pipeline and method for uranium hexafluoride abundance laser spectrum on-line measurement

Abstract

The invention relates to a sampling pipeline and method for uranium hexafluoride abundance laser spectrum on-line measurement, and the sampling pipeline comprises a gas inlet pipeline, a gas inlet flange, a parabolic mirror, a cylindrical gas chamber made of a cylindrical gas chamber wall, a gas extraction flange, a gas extraction pipeline, an optical window mirror flange and an optical window mirror. The parabolic mirror is fixedly mounted on the inner wall of the first end of the cylindrical gas chamber, and the first end of the cylindrical gas chamber is fastened on the gas inlet flange; the optical window mirror is fixedly mounted at the second end of the cylindrical gas chamber through an optical window mirror flange; the gas inlet pipeline penetrates through the gas inlet flange and the parabolic mirror and is inserted into the cylindrical gas chamber; and the air exhaust pipeline is mounted on the wall of the cylindrical gas chamber close to the second end of the cylindrical gas chamber through an air exhaust flange. According to the invention, the spatial distribution of gas molecules is regulated through the flow field, the spectral line broadening can be inhibited while the intensity of the plasma spectral line is maintained, and the isotope abundance measurement requirement is met; and the contact between corrosive gas and the device wall can be reduced to ensure the safety of the sampling pipeline.

Description

Technical Field

[0001] This invention belongs to the field of nuclear radiation measurement technology, specifically relating to a sampling pipe for online laser spectral measurement of uranium hexafluoride abundance. Background Technology

[0002] Uranium hexafluoride (UF6) is the core material for uranium enrichment, and accurate measurement of its abundance is crucial for monitoring the operation of uranium enrichment plants, controlling product quality, and ensuring nuclear material balance. Currently, the most widely used methods for monitoring UF6 abundance are radiometric methods and mass spectrometry. Radiometric methods utilize the characteristic gamma rays produced by uranium isotopes for detection. However, because the intensity of uranium's characteristic gamma rays is relatively weak, a certain amount of time needs to be accumulated for measurement, resulting in poor measurement continuity. Furthermore, to eliminate interference from background radiation in the measurement cell, periodic background calibration is required, further reducing the continuity of process monitoring. While gas source mass spectrometry performs well in terms of accuracy and measurement time, the system is very complex, and the equipment cost and subsequent maintenance costs are very high. To achieve continuous monitoring of the production process and reduce equipment investment and subsequent maintenance costs, foreign countries have explored using laser-induced plasma spectroscopy (LIPS) technology to monitor UF6 abundance.

[0003] The core principle of LIPS for measuring uranium hexafluoride enrichment is to distinguish U-235 and U-238 by utilizing isotopic shifts of only a few picometers along the uranium atomic radiation spectrum, and to determine the uranium enrichment based on the calibration rule of spectral line intensity versus isotopic abundance. However, conventional laser-plasma spectroscopy, due to broadening caused by the Doppler and Stark effects, has atomic radiation spectral line widths approaching hundreds of picometers, making it difficult to meet the needs of uranium isotopic abundance measurement. Furthermore, the radioactivity and chemical corrosiveness of uranium hexafluoride make it difficult to ensure the safety of conventional laser-plasma spectroscopy analysis cells in special operating environments. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a sampling pipe for online laser spectroscopy measurement of uranium hexafluoride abundance. By controlling the spatial distribution of gas molecules through flow field regulation, the pipe can suppress spectral broadening while maintaining the intensity of plasma spectral lines. Furthermore, it can reduce the contact between radioactive and corrosive gas molecules and the pipe wall to ensure safety, thus providing a guarantee for laser plasma spectroscopy measurement of uranium hexafluoride abundance.

[0005] To achieve the above objectives, the technical solution adopted by this invention is as follows: a sampling pipe for online laser spectral measurement of uranium hexafluoride abundance, the sampling pipe mainly comprising an inlet pipe, an inlet flange, a parabolic mirror, a cylindrical gas chamber with a cylindrical gas chamber wall, an extraction flange, an extraction pipe, an optical window flange, and an optical window, wherein,

[0006] The parabolic mirror is fixedly installed on the inner wall of the first end of the cylindrical gas chamber, with the parabolic surface of the mirror facing into the cylindrical gas chamber. The first end of the cylindrical gas chamber is fastened to the inlet flange. The optical window is fixedly installed at the second end of the cylindrical gas chamber through the optical window flange.

[0007] The air intake pipe passes through the air intake flange and the parabolic mirror, and is inserted into the cylindrical gas chamber;

[0008] The extraction pipe is installed on the wall of the cylindrical gas chamber near the second end of the cylindrical gas chamber via an extraction flange, and the extraction pipe is in communication with the cylindrical gas chamber.

[0009] Furthermore, the materials of the air intake pipe, the cylindrical gas chamber wall, the air intake flange, the air extraction flange, the air extraction pipe, and the optical window flange are made of corrosion-resistant stainless steel.

[0010] The seals used with the pipes for the inlet flange, exhaust flange, and optical window flange are made of fluororubber.

[0011] Furthermore, when it is necessary to observe the gas movement and plasma position and morphology within the chamber, the cylindrical gas chamber wall is made of sapphire glass or metallic fluoride glass.

[0012] Furthermore, the metal fluoride glass is calcium fluoride glass or magnesium fluoride glass.

[0013] Furthermore, the material of the parabolic mirror is selected from one of corrosion-resistant stainless steel, corrosion-resistant aluminum alloy, or corrosion-resistant copper alloy; or one of sapphire glass or metallic fluoride glass is selected as the glass substrate, and a corrosion-resistant metal film layer is deposited on the parabolic side of the glass substrate.

[0014] Furthermore, in the sampling pipe, the parabolic mirror is a metal mirror with a surface processing accuracy PV < λ / 6 or a roughness Ra < 0.03 μm, or a metal-coated mirror on a glass substrate.

[0015] Furthermore, the plane containing the edge of the parabolic mirror is perpendicular to the axis of the sampling pipe, and the focal point of the parabolic mirror is located on the plane containing the edge of the parabolic mirror.

[0016] Furthermore, the optical window is a parallel plane window made of either sapphire glass or metallic fluoride glass.

[0017] Furthermore, uranium hexafluoride gas enters a low-pressure cylindrical gas chamber through the inlet pipe. After the gas flow passes through the vent on the end face of the inlet pipe, a gas molecule cloud that first shrinks and then expands is formed due to the gas flow dynamics effect, which is the uranium hexafluoride flow field.

[0018] The gas molecule cloud drifts and expands towards the second end of the cylindrical gas chamber, moving away from the parabolic mirror to avoid contact with the mirror and corrosion. Before reaching the optical window flange, the gas molecule cloud drifting towards the second end of the cylindrical gas chamber is pumped out of the sampling pipe through the extraction pipe, thereby preventing uranium hexafluoride from contacting the optical window and causing contamination and corrosion.

[0019] Furthermore, after the laser pulse passes through the optical window and enters the gas chamber from the second end of the cylindrical gas chamber, it is focused by the parabolic mirror at the focal point of the parabolic mirror; at the focal point of the parabolic mirror, the uranium hexafluoride gas is broken down to generate uranium hexafluoride plasma, and the laser energy is absorbed by the uranium hexafluoride plasma at the focal point.

[0020] Furthermore, by adjusting the focal length of the parabolic mirror and the intensity of the laser pulse, the energy density deposited in the gas molecules is controlled, and the temperature of the generated uranium hexafluoride plasma is adjusted, thereby suppressing the Doppler broadening of the uranium atom radiation spectral lines to ensure that the uranium spectral line width is less than the uranium spectral isotope shift.

[0021] Furthermore, by adjusting the depth of the intake pipe inserted into the cylindrical gas chamber and the expansion and drift speed of the gas molecular cloud, the gas molecule number density at the focal point of the parabolic mirror is controlled, thereby suppressing the Stark broadening related to the plasma electron number density and ensuring that the uranium spectral linewidth is less than the uranium spectral isotope shift.

[0022] This invention also provides a sampling pipeline application method for online laser spectroscopy measurement of uranium hexafluoride abundance, based on the aforementioned sampling pipeline for online laser spectroscopy measurement of uranium hexafluoride abundance, the method comprising the following steps:

[0023] S1. Monitor the flow rate of uranium hexafluoride gas using a flow meter and adjust the flow rate of uranium hexafluoride gas using an inlet valve. Uranium hexafluoride gas is injected from the inlet pipe into the cylindrical gas chamber. Set an appropriate gas flow rate to control the number density of gas molecules at the focal point of the parabolic mirror to meet the requirements for suppressing plasma Stark broadening.

[0024] S2. By adjusting the intensity of the laser pulse and the focal length of the parabolic mirror, the laser intensity at the focal point of the parabolic mirror is adjusted, thereby controlling the temperature of the laser-excited uranium hexafluoride plasma, suppressing the Doppler broadening of the plasma, narrowing the spectral lines, and obtaining resolvable emission characteristic spectral lines of U-235 and U-238 atoms; and the abundance of U-235 in uranium hexafluoride is estimated based on the intensity of the characteristic spectral lines of U-235 and U-238 atoms emitted in the uranium hexafluoride plasma.

[0025] S3, after uranium hexafluoride gas enters the gas chamber, it moves and diffuses towards the second end of the cylindrical gas chamber in the form of airflow to avoid contact with the parabolic mirror; and before the airflow diffuses to contact the optical window mirror, it is pumped out of the cylindrical gas chamber through the gas extraction pipe, thereby avoiding contact between the corrosive gas and the optical window mirror.

[0026] S4. The gas in the cylindrical gas chamber is discharged from the cylindrical gas chamber through the outlet valve and the pump connected to the extraction pipe, and then pumped into the gas cylinder for recovery.

[0027] The beneficial effects of this invention are as follows: The sampling pipeline and method for online laser spectral measurement of uranium hexafluoride abundance provided by this invention mainly include an inlet pipe, an inlet flange, a parabolic mirror, a cylindrical gas chamber with a cylindrical gas chamber wall, an extraction flange, an extraction pipe, an optical window flange, and an optical window. The parabolic mirror is fixedly installed on the inner wall of the first end of the cylindrical gas chamber, with its parabolic surface facing inwards. The first end of the cylindrical gas chamber is fastened to the inlet flange. The optical window is fixedly installed at the second end of the cylindrical gas chamber via the optical window flange. The inlet pipe passes through the inlet flange and the parabolic mirror and is inserted into the cylindrical gas chamber. The extraction pipe is installed on the cylindrical gas chamber wall near the second end of the cylindrical gas chamber via the extraction flange, and the extraction pipe communicates with the cylindrical gas chamber.

[0028] The sampling conduit and method for online laser spectroscopy measurement of uranium hexafluoride abundance provided by this invention, by forming a uranium hexafluoride flow field to control the spatial distribution of uranium hexafluoride gas molecules, as well as the temperature and electron number density of the laser plasma, can suppress Doppler broadening and Stark broadening of uranium atomic radiation lines while maintaining the intensity of plasma spectral lines. This ensures that the uranium spectral linewidth is less than the uranium spectral isotope shift, achieving the goal of measurable spectral isotope shift. Furthermore, this invention can reduce the contact between radioactive and corrosive gas molecules and the container walls to ensure its safety, providing a guarantee for laser plasma spectroscopy measurement of uranium hexafluoride abundance. Attached Figure Description

[0029] Figure 1A schematic diagram of the sampling pipe for online laser spectroscopy measurement of uranium hexafluoride abundance provided for an embodiment of the present invention;

[0030] Figure 2 A schematic diagram illustrating the application method of the sampling pipeline for online laser spectroscopy measurement of uranium hexafluoride abundance provided in this embodiment of the invention;

[0031] Wherein: 1—Inlet pipe, 2—Inlet flange, 3—Parabolic mirror, 4—Cylindrical gas chamber wall, 5—Uranium hexafluoride flow field, 6—Extraction flange, 7—Extraction pipe, 8—Optical window flange, 9—Optical window, 10—Flow meter, 11—Inlet valve, 12—Outlet valve, 13—Extraction pump, 14—Gas cylinder. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be further clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that in the description of the embodiments of the present invention, the terms "upper," "lower," "front," "rear," "front," "back," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present 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. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] To address the issues of spectral line broadening and safety in LIPS monitoring of uranium hexafluoride (UF6), this invention proposes a sampling and measurement pipe / chamber for online laser spectroscopy measurement of UF6 abundance. By optimizing the flow field and controlling the temperature and electron number density of the laser plasma, the invention aims to suppress spectral line broadening while maintaining the intensity of atomic radiation lines, thus meeting the requirements for isotope abundance measurement. Simultaneously, the diffusion process of the UF6 jet is controlled through flow field design, thereby reducing contact between radioactive and corrosive gases and the pipe / chamber surface, ensuring the safety of the sampling pipe.

[0035] like Figure 1 , Figure 2As shown in the figure, a sampling pipeline for on-line measurement of uranium hexafluoride enrichment by laser spectroscopy provided by an embodiment of the present invention mainly includes an intake pipeline 1, an intake flange 2, a parabolic mirror 3, a cylindrical gas chamber made of a cylindrical gas chamber wall 4, an extraction flange 6, an extraction pipeline 7, an optical window flange 8, and an optical window 9. Among them,

[0036] The parabolic mirror 3 is fixedly installed on the inner wall of the first end of the cylindrical gas chamber, and the parabolic surface of the parabolic mirror 3 faces the inside of the cylindrical gas chamber. The first end of the cylindrical gas chamber is fastened to the intake flange 2; the optical window 9 is fixedly installed at the second end of the cylindrical gas chamber through the optical window flange 8;

[0037] The intake pipeline 1 passes through the intake flange 2 and the parabolic mirror 3 and is inserted into the cylindrical gas chamber;

[0038] The extraction pipeline 7 is installed on the cylindrical gas chamber wall 4 near the second end of the cylindrical gas chamber through the extraction flange 6, and the extraction pipeline 7 is in communication with the cylindrical gas chamber.

[0039] Specifically, considering the corrosive, oxidative, and radiation characteristics of uranium hexafluoride, among the components constituting the sampling pipeline, the materials of the intake pipeline 1, the intake flange 2, the extraction flange 6, the extraction pipeline 7, and the optical window flange 8 are made of corrosion-resistant stainless steel. When uranium hexafluoride gas contacts this kind of corrosion-resistant stainless steel, a passivation layer will form on the metal surface, effectively inhibiting material corrosion and aging. The sealing parts配套 with the pipelines of the intake flange, the extraction flange, and the optical window flange should be made of fluororubber material.

[0040] Optionally, the corrosion-resistant stainless steel is selected from one of 304L and 316L.

[0041] Specifically, in the sampling pipeline, the material of the cylindrical gas chamber wall 4 should also be selected as corrosion-resistant stainless steel.

[0042] Optionally, if it is necessary to observe the internal conditions such as the gas movement and the position and shape of the plasma inside the cylindrical gas chamber, the cylindrical gas chamber wall 4 can be made of sapphire glass resistant to fluorine corrosion or metal fluoride glass, and quartz and silicate glass shall not be selected.

[0043] Specifically, the metal fluoride glass includes calcium fluoride glass or magnesium fluoride glass, etc.

[0044] In the sampling pipe, the parabolic mirror 3 is fastened to the air inlet flange 2; optionally, the material of the parabolic mirror 3 in the sampling pipe should be one of the durable metals such as corrosion-resistant stainless steel, corrosion-resistant aluminum alloy or corrosion-resistant copper alloy, or one of the fluorine corrosion-resistant sapphire glass, calcium fluoride glass or magnesium fluoride glass as the glass substrate, and a corrosion-resistant metal film layer (the corrosion-resistant metal film layer is aluminum or gold) is deposited on the parabolic side of the glass substrate.

[0045] Optionally, the corrosion-resistant stainless steel is selected from 304L and 316L; the corrosion-resistant aluminum alloy is selected from 5083 and 5052; and the corrosion-resistant copper alloy is selected from H62 and QBe2.

[0046] Specifically, in the sampling pipe, the parabolic mirror 3 is a metal mirror with a surface processing accuracy PV < λ / 6 or a roughness Ra < 0.03 μm, or a metal-coated mirror on a glass substrate.

[0047] Optionally, in the sampling pipe, the optical window 9 is a parallel plane window made of one of the following materials: sapphire glass, calcium fluoride glass, or magnesium fluoride glass, with a polished surface accuracy PV < λ / 4. Quartz or silicate glass must not be used.

[0048] The plane containing the edge of the parabolic mirror 3 should be perpendicular to the axis of the sampling pipe, and the focal point of the parabolic mirror 3 should be located on the plane containing the edge of the parabolic mirror 3.

[0049] Uranium hexafluoride gas enters a low-pressure cylindrical gas chamber through inlet pipe 1. After passing through the vents at the end of inlet pipe 1, the gas flow forms a cloud of gas molecules that first contracts and then expands due to airflow dynamics. Figure 1 The flow field of uranium hexafluoride shown in Figure 5. The gas molecule density at the focal point of the parabolic mirror can be adjusted by adjusting the depth of the inlet pipe 1 inserted into the cylindrical gas chamber. The gas molecule cloud moves towards the second end of the cylindrical gas chamber ( Figure 1 The gas molecules drift and expand to the right of the sampling pipe, moving away from the parabolic mirror, thus avoiding contact with the mirror and corrosion. Before reaching the optical window flange 8, the gas molecule cloud drifting towards the second end of the cylindrical gas chamber is pumped out of the sampling pipe through the extraction pipe 7, thereby preventing uranium hexafluoride from contacting the optical window 9 and causing contamination and corrosion.

[0050] Optionally, the low pressure in the cylindrical gas chamber is achieved by means of the exhaust valve 12 and the exhaust pump 13 connected to the exhaust pipe 7, wherein the low pressure range in the cylindrical gas chamber is 10-100 torr.

[0051] Specifically, the laser pulse passes through optical window 9 and enters from the second end of the cylindrical gas chamber. Figure 1 After entering the gas chamber from the right side of the sampling pipe, the laser is focused at the focal point of the parabolic mirror 3. The laser intensity I at the focal point of the parabolic mirror is much greater than the breakdown threshold of uranium hexafluoride gas, so breakdown will occur and plasma will be generated. The laser energy is absorbed by the uranium hexafluoride plasma at the focal point.

[0052] In one specific embodiment, according to the Gaussian beam correlation formula, near the laser beam waist, the volume of the region enclosed by the boundary where the laser intensity is half the intensity I0 at the center of the beam waist is proportional to the fourth power of the beam waist radius. According to the laser focusing formula, the beam waist radius is proportional to the focusing focal length. Therefore, by adjusting the focal length of the parabolic mirror 3 and the intensity of the laser pulse to control the energy density deposited in the gas molecules, the temperature of the generated uranium hexafluoride plasma can be adjusted, thereby suppressing the significant Doppler broadening of the uranium atom radiation spectral lines and ensuring that the uranium spectral line width is less than the uranium spectral isotope shift, i.e., the spectral isotope shift is measurable.

[0053] In another specific embodiment, the gas molecule number density at the focal point of the parabolic mirror is controlled by adjusting the depth of the air intake pipe 1 inserted into the cylindrical gas chamber and the expansion and drift speed of the gas molecule cloud. Since the gas molecule number density at the focal point is positively correlated with the final plasma electron number density, the Stark broadening related to the plasma electron number density can be suppressed by this method to ensure that the uranium spectral line width is less than the uranium spectral isotope shift, i.e., the spectral isotope shift is measurable.

[0054] The gas molecule cloud expansion and drift speed is adjusted by the outlet valve 12 and the pump 13 connected to the extraction pipe 7.

[0055] In another specific embodiment, the plasma flash emitted from the breakdown point propagates to the left (towards the first end of the cylindrical gas chamber) and, after being reflected by the parabolic mirror 3, travels to the right along the axial direction through the optical window 9 and enters the open space for uranium spectrum measurement. The parabolic mirror is designed so that approximately 50% of the plasma flash can be collected and projected outside the cavity to ensure that the uranium spectral line intensity meets the requirements for isotope abundance measurement, i.e., the isotope shift spectral intensity is measurable.

[0056] This embodiment provides a sampling pipe / chamber for online laser spectroscopy measurement of uranium hexafluoride abundance. By controlling the spatial distribution of gas molecules through flow field regulation, it can suppress spectral broadening while maintaining the intensity of plasma spectral lines. On the other hand, it can reduce the contact between radioactive and corrosive gas molecules and the container wall to ensure its safety, thus providing a guarantee for laser plasma spectroscopy measurement of uranium hexafluoride abundance.

[0057] like Figure 2As shown, the present invention also provides a sampling pipe application method for online laser spectroscopy measurement of uranium hexafluoride abundance, based on the aforementioned sampling pipe for online laser spectroscopy measurement of uranium hexafluoride abundance, for measuring uranium hexafluoride abundance, the method comprising the following steps:

[0058] S1. The flow rate of uranium hexafluoride gas is monitored by the flow meter 10 and the flow rate of uranium hexafluoride gas is adjusted by the inlet valve 11. Uranium hexafluoride gas is injected from the inlet pipe 3 into the cylindrical gas chamber. A suitable gas flow rate is set to control the number density of gas molecules at the focal point of the parabolic mirror 4 to meet the requirements for suppressing plasma Stark broadening.

[0059] S2. Simultaneously, by adjusting the intensity of the laser pulse and the focal length of the parabolic mirror, the laser intensity at the focal point of the parabolic mirror is adjusted, thereby controlling the temperature of the laser-excited uranium hexafluoride plasma, suppressing the Doppler broadening of the plasma, narrowing the spectral lines, and obtaining resolvable emission characteristic spectral lines of U-235 and U-238 atoms; and the abundance of U-235 in uranium hexafluoride is estimated based on the intensity of the characteristic spectral lines of U-235 and U-238 atoms emitted in the uranium hexafluoride plasma.

[0060] In actual operation, the control system in the plasma-excited laser source and spectral measurement system sends commands to control the laser to emit laser pulses at a certain frequency. The laser enters the cylindrical gas chamber through the optical window 9 and is reflected by the parabolic mirror 3 before converging. The low-pressure uranium hexafluoride diffusion gas flow is broken down at the focal point, generating a plasma spark. After being reflected by the parabolic mirror 4, the plasma flash exits the cylindrical gas chamber along the axis of the parabolic mirror in the form of parallel light from the optical window 9 and is measured by the plasma spectral measurement system.

[0061] S3. After entering the gas chamber, the uranium hexafluoride gas moves and diffuses away from the parabolic mirror (i.e. towards the second end of the cylindrical gas chamber) in the form of an airflow, so as to effectively avoid contact with the parabolic mirror 3; before the airflow diffuses to contact the optical window mirror 9, it is pumped out of the cylindrical gas chamber through the gas extraction pipe 7, thereby effectively avoiding contact between the corrosive gas and the optical window mirror 9.

[0062] Specifically, by appropriately adjusting the air intake valve 11, the air outlet valve 12, and the air extraction pump 13 during operation, the diffusion speed of the uranium hexafluoride flow field can be controlled to ensure the safety and durability of the cylindrical gas chamber.

[0063] S4. The gas in the cylindrical gas chamber is discharged from the chamber through the exhaust valve 12 and the exhaust pump 13 connected to the exhaust pipe 7 and pumped into the gas cylinder 14 for recovery.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention is also intended to include these modifications and variations.

Claims

1. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance, characterized in that, The sampling pipeline mainly includes an inlet pipe, an inlet flange, a parabolic mirror, a cylindrical gas chamber with cylindrical gas chamber walls, an extraction flange, an extraction pipe, an optical window flange, and an optical window. The parabolic mirror is fixedly installed on the inner wall of the first end of the cylindrical gas chamber, with the parabolic surface of the mirror facing into the cylindrical gas chamber. The first end of the cylindrical gas chamber is fastened to the inlet flange. The optical window is fixedly installed at the second end of the cylindrical gas chamber through the optical window flange. The air intake pipe passes through the air intake flange and the parabolic mirror, and is inserted into the cylindrical gas chamber; The extraction pipe is installed on the wall of the cylindrical gas chamber near the second end of the cylindrical gas chamber via an extraction flange, and the extraction pipe is in communication with the cylindrical gas chamber.

2. The sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 1, characterized in that, The air intake pipe, cylindrical gas chamber wall, air intake flange, air extraction flange, air extraction pipe, and optical window flange are made of corrosion-resistant stainless steel. The seals used with the pipes for the inlet flange, exhaust flange, and optical window flange are made of fluororubber.

3. The sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 1, characterized in that, When it is necessary to observe the gas movement and plasma position and morphology within the chamber, the cylindrical gas chamber wall is made of sapphire glass or metallic fluoride glass.

4. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 3, characterized in that, The metal fluoride glass is either calcium fluoride glass or magnesium fluoride glass.

5. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 1, characterized in that, The parabolic mirror is made of one of the following materials: corrosion-resistant stainless steel, corrosion-resistant aluminum alloy, or corrosion-resistant copper alloy; or it is made of one of the following materials: sapphire glass or metallic fluoride glass as the glass substrate, and a corrosion-resistant metal film is deposited on the parabolic side of the glass substrate.

6. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 1, characterized in that, In the sampling pipe, the parabolic mirror is a metal mirror with a surface processing accuracy of PV < λ / 6 or a roughness of Ra < 0.03 μm, or a metal-coated mirror on a glass substrate.

7. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 1, characterized in that, The optical window is a parallel plane window made of either sapphire glass or metallic fluoride glass.

8. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 1, characterized in that, The plane containing the edge of the parabolic mirror is perpendicular to the axis of the sampling pipe, and the focal point of the parabolic mirror is located on the plane containing the edge of the parabolic mirror.

9. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 1, characterized in that, Uranium hexafluoride gas enters a low-pressure cylindrical gas chamber through the inlet pipe. After the gas flow passes through the gas holes on the end face of the inlet pipe, a gas molecule cloud that first shrinks and then expands is formed due to the gas flow dynamics effect, which is the uranium hexafluoride flow field. The gas molecule cloud drifts and expands towards the second end of the cylindrical gas chamber, moving away from the parabolic mirror to avoid contact with the mirror and corrosion. Before reaching the optical window flange, the gas molecule cloud drifting towards the second end of the cylindrical gas chamber is pumped out of the sampling pipe through the extraction pipe, thereby preventing uranium hexafluoride from contacting the optical window and causing contamination and corrosion.

10. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 9, characterized in that, After the laser pulse passes through the optical window and enters the gas chamber from the second end of the cylindrical gas chamber, it is focused by the parabolic mirror at the focal point of the parabolic mirror. At the focal point of the parabolic mirror, the uranium hexafluoride gas is broken down to generate uranium hexafluoride plasma, and the laser energy is absorbed by the uranium hexafluoride plasma at the focal point.

11. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 10, characterized in that, By adjusting the focal length of the parabolic mirror and the intensity of the laser pulse, the energy density deposited in the gas molecules is controlled, and the temperature of the generated uranium hexafluoride plasma is adjusted, thereby suppressing Doppler broadening of the uranium atom radiation spectral lines and ensuring that the uranium spectral line width is less than the uranium spectral isotope shift.

12. A sampling conduit for online laser spectral measurement of uranium hexafluoride abundance according to claim 10, characterized in that, By adjusting the depth of the intake pipe inserted into the cylindrical gas chamber and the expansion and drift speed of the gas molecular cloud, the gas molecule number density at the focal point of the parabolic mirror is controlled, thereby suppressing Stark broadening related to the plasma electron number density and ensuring that the uranium spectral linewidth is less than the uranium spectral isotope shift.

13. A sampling pipe application method for online laser spectral measurement of uranium hexafluoride abundance, based on the sampling pipe for online laser spectral measurement of uranium hexafluoride abundance according to any one of claims 1-12, characterized in that, The method includes the following steps: S1. Monitor the flow rate of uranium hexafluoride gas using a flow meter and adjust the flow rate of uranium hexafluoride gas using an inlet valve. Uranium hexafluoride gas is injected from the inlet pipe into the cylindrical gas chamber. Set an appropriate gas flow rate to control the number density of gas molecules at the focal point of the parabolic mirror to meet the requirements for suppressing plasma Stark broadening. S2. By adjusting the intensity of the laser pulse and the focal length of the parabolic mirror, the laser intensity at the focal point of the parabolic mirror is adjusted, thereby controlling the temperature of the laser-excited uranium hexafluoride plasma, suppressing the Doppler broadening of the plasma, narrowing the spectral lines, and obtaining resolvable emission characteristic spectral lines of U-235 and U-238 atoms. The abundance of U-235 in uranium hexafluoride was estimated based on the intensity of the characteristic spectral lines emitted by U-235 and U-238 atoms in uranium hexafluoride plasma. S3, after uranium hexafluoride gas enters the gas chamber, it moves and diffuses towards the second end of the cylindrical gas chamber in the form of airflow to avoid contact with the parabolic mirror; and before the airflow diffuses to contact the optical window mirror, it is pumped out of the cylindrical gas chamber through the gas extraction pipe, thereby avoiding contact between the corrosive gas and the optical window mirror. S4. The gas in the cylindrical gas chamber is discharged from the cylindrical gas chamber through the outlet valve and the pump connected to the extraction pipe, and then pumped into the gas cylinder for recovery.

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