CN-122016412-A - Sampling pipeline and method for online measurement of uranium hexafluoride abundance laser spectrum

CN122016412ACN 122016412 ACN122016412 ACN 122016412ACN-122016412-A

Abstract

The invention relates to a sampling pipeline and a sampling method for online measurement of uranium hexafluoride abundance laser spectrum, wherein the sampling pipeline comprises an air inlet pipeline, an air inlet flange, a parabolic mirror, a cylindrical gas chamber formed by a cylindrical gas chamber wall, an air exhaust flange, an air exhaust pipeline, an optical window mirror flange and an optical window mirror, wherein the parabolic mirror is fixedly arranged on the inner wall of a first end of the cylindrical gas chamber, the first end of the cylindrical gas chamber is fastened on the air inlet flange, the optical window mirror is fixedly arranged at a second end of the cylindrical gas chamber through the optical window mirror flange, the air inlet pipeline penetrates through the air inlet flange and the parabolic mirror and is inserted into the cylindrical gas chamber, and the air exhaust pipeline is arranged on the cylindrical gas chamber wall close to the second end of the cylindrical gas chamber through the air exhaust flange. The invention regulates and controls the gas molecular space distribution through the flow field, can inhibit the spectrum line broadening while maintaining the spectrum line intensity of the plasma, meets the requirement of isotope abundance measurement, and can reduce the contact of corrosive gas and the wall so as to ensure the safety of a sampling pipeline.

Inventors

CHENG HONGZHI
GAO ZHIXING
GUAN CHENGMING
WANG YUANHANG
WANG ZHAO
ZHANG ZHUANG
JIAO XUESHENG
LV BOWEN
TIAN YUWEI

Assignees

中国原子能科学研究院

Dates

Publication Date: 20260512
Application Date: 20260104

Claims (13)

1. A sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum is characterized by mainly comprising an air inlet pipeline, an air inlet flange, a parabolic mirror, a cylindrical gas chamber formed by a cylindrical gas chamber wall, an air exhaust flange, an air exhaust pipeline, an optical window mirror flange and an optical window mirror, wherein, The parabolic mirror is fixedly arranged on the inner wall of the first end of the cylindrical gas chamber, the parabolic surface of the parabolic mirror faces into the cylindrical gas chamber, and the first end of the cylindrical gas chamber is fastened on the air inlet flange; The air inlet pipeline passes through the air inlet flange and the parabolic mirror and is inserted into the cylindrical gas chamber; The air exhaust pipeline is arranged on the wall of the cylindrical gas chamber close to the second end of the cylindrical gas chamber through an air exhaust flange, and the air exhaust pipeline is communicated with the cylindrical gas chamber.
2. The sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum according to claim 1, wherein the air inlet pipeline, the cylindrical gas chamber wall, the air inlet flange, the air exhaust pipeline and the optical window mirror flange are made of corrosion-resistant stainless steel; and sealing elements matched with the pipelines of the air inlet flange, the air exhaust flange and the optical window mirror flange are made of fluororubber.
3. The sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum according to claim 1, wherein when gas movement and plasma position and morphology in the chamber are to be observed, the cylindrical gas chamber wall is made of sapphire glass or metal fluoride glass.
4. A sampling tube for the on-line measurement of uranium hexafluoride abundance laser spectra as claimed in claim 3, in which the metal fluoride glass is calcium fluoride glass or magnesium fluoride glass.
5. The sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum according to claim 1, wherein the parabolic mirror is made of one of corrosion-resistant stainless steel, corrosion-resistant aluminum alloy and corrosion-resistant copper alloy, or one of sapphire glass and metal fluoride glass is used as a glass substrate, and a corrosion-resistant metal film layer is plated on one parabolic side of the glass substrate.
6. The sampling tube for on-line measurement of uranium hexafluoride abundance laser spectra according to claim 1, wherein in the sampling tube, the parabolic mirror is a metal mirror with a surface finish plane type precision PV < λ/6 or a roughness Ra <0.03 μm or a metal coated mirror of a glass substrate.
7. The sampling tube for on-line measurement of uranium hexafluoride abundance laser spectra of claim 1, wherein the optical window mirror is a parallel planar window made of one of sapphire glass or metal fluoride glass materials.
8. The sampling tube for on-line measurement of uranium hexafluoride abundance laser spectra of claim 1, wherein the plane in which the edge of the parabolic mirror is located is perpendicular to the axis of the sampling tube, and the focal point of the parabolic mirror is located on the plane in which the edge of the parabolic mirror is located.
9. The sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum according to claim 1, wherein uranium hexafluoride gas enters a low-pressure cylindrical gas chamber through the gas inlet pipeline, and after gas flow passes through a gas hole on the end face of the gas inlet pipeline, a gas molecular cloud which is contracted before expanded, namely a uranium hexafluoride flow field is formed due to aerodynamic effect; the gas molecular cloud drifting towards the second end of the cylindrical gas chamber is inflated away from the parabolic mirror to avoid corrosion caused by contact with the parabolic mirror, and is pumped out of the sampling pipeline through the air exhaust pipeline before the gas molecular cloud drifting towards the second end of the cylindrical gas chamber reaches the optical window mirror flange, so that uranium hexafluoride is prevented from being polluted and corroded caused by contact with the optical window mirror.
10. The sampling tube for on-line measurement of uranium hexafluoride abundance laser spectra of claim 9, wherein laser pulses are focused by a parabolic mirror at a parabolic mirror focal point after entering the gas chamber from a second end of the cylindrical gas chamber through an optical window mirror, uranium hexafluoride gas at the parabolic mirror focal point is broken down to produce uranium hexafluoride plasma, and laser energy is absorbed by the uranium hexafluoride plasma at the focal point.
11. The sampling tube for on-line measurement of uranium hexafluoride abundance laser spectra according to claim 10, wherein the focal length of the parabolic mirror and the intensity of the laser pulses are adjusted to control the energy density deposited in the gas molecules, and the temperature of the generated uranium hexafluoride plasma is adjusted to suppress doppler broadening of the uranium atomic emission lines to ensure that the uranium linewidth is less than the uranium spectral isotope displacement.
12. A sampling tube for the on-line measurement of the uranium hexafluoride abundance laser spectrum according to claim 10, wherein the number density of gas molecules at the parabolic mirror focal point is controlled by adjusting the depth of insertion of the gas inlet tube into the cylindrical gas chamber and the gas molecule cloud expansion drift velocity to suppress stark broadening associated with the number density of plasma electrons to ensure that the uranium linewidth is less than the uranium spectral isotope displacement.
13. A sampling pipe application method for online measurement of uranium hexafluoride abundance laser spectra, based on the sampling pipe for online measurement of uranium hexafluoride abundance laser spectra of any one of claims 1-12, the method comprising the steps of: The method comprises the steps of S1, monitoring the flow rate of uranium hexafluoride gas through a flow detector, and adjusting the flow rate of the uranium hexafluoride gas through an air inlet valve, wherein the uranium hexafluoride gas is sprayed into a cylindrical gas chamber from an air inlet pipeline, and the proper flow rate of the gas is set so as to control the molecular number density of the gas of the uranium hexafluoride gas at the focal point of a parabolic mirror to meet the requirement of inhibiting plasma Stark broadening; S2, adjusting the laser intensity at the focus of the parabolic mirror by adjusting the intensity of the laser pulse and the focal length of the parabolic mirror, so as to control the temperature of uranium hexafluoride plasma excited by the laser, inhibit Doppler broadening of the plasma, narrow spectral lines, obtain distinguishable U-235 and U-238 atomic emission characteristic spectral lines, and calculate the abundance of U-235 in uranium hexafluoride according to the intensity of the U-235 and U238 atomic emission characteristic spectral lines in the uranium hexafluoride plasma; S3, uranium hexafluoride gas moves and diffuses in an airflow form to the second end of the cylindrical gas chamber after entering the gas chamber so as to avoid contact with the parabolic mirror, and before the airflow diffuses to contact with the optical window mirror, the uranium hexafluoride gas is pumped out of the cylindrical gas chamber through the air suction pipeline so as to avoid contact between corrosive gas and the optical window mirror; S4, the gas in the cylindrical gas chamber is discharged out of the cylindrical gas chamber through a gas outlet valve and a gas pump which are connected with a gas exhaust pipeline, and the gas is pumped into a gas cylinder for recovery.

Description

Sampling pipeline and method for online measurement of uranium hexafluoride abundance laser spectrum Technical Field The invention belongs to the technical field of nuclear radiation measurement, and particularly relates to a sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum. Background Uranium hexafluoride (UF 6) is a core material for uranium enrichment, and accurate measurement of the abundance thereof is a guarantee for monitoring the running condition of a uranium enrichment plant, controlling the quality of products and balancing the nuclear material. Methods currently widely used for monitoring uranium hexafluoride abundance are radiometry and mass spectrometry. Radiometry uses characteristic gamma rays generated by uranium isotopes for detection. Because the characteristic gamma-ray intensity of uranium is weaker, a certain time is needed to be measured in an accumulated way, the measurement continuity is poorer, and background calibration is needed to be carried out regularly in order to eliminate the interference of background radiation of a measuring pool, so that the continuity of process monitoring is further reduced. Although gas source mass spectrometry is excellent in accuracy and measurement time, the system is very complex, and equipment cost and later maintenance cost are very expensive. In order to realize continuous monitoring of the production process and reduce equipment investment and later maintenance and use cost, foreign attempts are made to monitor the abundance of uranium hexafluoride by using a laser-induced plasma spectroscopy (Laser induced plasma spectroscopy, LIPS) technology. The core principle of LIPS for measuring the enrichment degree of uranium hexafluoride is that the discrimination of U-235 and U-238 is realized by utilizing the isotope displacement of only several picometers on the uranium atom radiation spectrum, and the enrichment degree of uranium is determined according to the calibration rule of spectral line intensity-isotope abundance. The conventional laser plasma spectrum line is widened due to Doppler effect and Stark effect, the atomic radiation spectrum line width is close to hundred picometers, and the requirement of uranium isotope abundance measurement is difficult to meet. Meanwhile, the radioactivity and chemical corrosiveness of uranium hexafluoride also lead to the difficulty in ensuring the safety of special operation environments in a conventional laser plasma spectrum analysis pool. Disclosure of Invention Aiming at the defects in the prior art, the invention aims to provide a sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum, and the spatial distribution of gas molecules is regulated and controlled through a flow field, so that on one hand, the aim of inhibiting the broadening of spectral lines can be fulfilled while the spectral line intensity of plasma spectrum is maintained, and on the other hand, the contact of radioactive and corrosive gas molecules with the wall can be reduced to ensure the safety of the radioactive and corrosive gas molecules, thereby providing guarantee for the laser plasma spectrum measurement of uranium hexafluoride abundance. In order to achieve the aim, the invention adopts the following technical scheme that the sampling pipeline for online measurement of uranium hexafluoride abundance laser spectrum mainly comprises an air inlet pipeline, an air inlet flange, a parabolic mirror, a cylindrical gas chamber formed by a cylindrical gas chamber wall, an air exhaust flange, an air exhaust pipeline, an optical window mirror flange and an optical window mirror, wherein, The parabolic mirror is fixedly arranged on the inner wall of the first end of the cylindrical gas chamber, the parabolic surface of the parabolic mirror faces into the cylindrical gas chamber, and the first end of the cylindrical gas chamber is fastened on the air inlet flange; The air inlet pipeline passes through the air inlet flange and the parabolic mirror and is inserted into the cylindrical gas chamber; The air exhaust pipeline is arranged on the wall of the cylindrical gas chamber close to the second end of the cylindrical gas chamber through an air exhaust flange, and the air exhaust pipeline is communicated with the cylindrical gas chamber. Furthermore, the air inlet pipeline, the cylindrical gas chamber wall, the air inlet flange, the air exhaust pipeline and the optical window mirror flange are made of corrosion-resistant stainless steel; and sealing elements matched with the pipelines of the air inlet flange, the air exhaust flange and the optical window mirror flange are made of fluororubber. Furthermore, when the gas movement, the plasma position and the shape in the cavity are required to be observed, the cylindrical gas cavity wall is made of sapphire glass or metal fluoride glass. Further, the metal fluoride glass is calcium fluoride glass or magnesium fluori