A method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters

Abstract

The present invention relates to the technical field of laser-induced breakdown spectroscopy detection, and specifically discloses a uranium content detection method for correcting the uranium signal intensity based on plasma parameters, comprising the following steps: Step 1: Use a laser-induced breakdown spectroscopy system to collect spectra of a uranium concentrate standard sample to obtain the laser-induced plasma characteristic spectra of the uranium concentrate standard sample; Step 2: Obtain the characteristic spectral peak intensity of uranium elements from the characteristic spectra; Step 3: Correct the uranium characteristic spectral peak intensity based on the plasma characteristic spectra; Step 4: Establish a calibration model for the uranium element content and the uranium characteristic peak signal intensity in the uranium concentrate standard sample; Step 5: Repeat the operations of Steps 1 to 3 for a sample to be measured with an unknown concentration, and then use the calibration model in Step 4 to inversely calculate the uranium element content in the sample to be measured. The method of the present invention can accurately eliminate the background noise in the uranium spectral signal, extract the accurate uranium characteristic spectral intensity, and greatly improve the detection accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser-induced breakdown spectroscopy detection in the field of atomic emission spectrometry measurement, and particularly relates to a method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters. Background Technique

[0002] Uranium concentrates (mainly ammonium diuranate, uranium trioxide octoxide, etc.) are the most important uranium hydrometallurgical products in China and important raw materials in the nuclear industry. Rapid and accurate determination of their uranium content is of great significance in product trading and production process control. At present, the determination of uranium in uranium concentrates mainly uses the ferrous sulfate reduction / potassium dichromate oxidation titration method. This method titrates with sodium diphenylamine sulfonate as an indicator. The operation process is complex, the degree of automation is low, the analysis time is long, and the judgment of the titration end point is greatly affected by human subjectivity, resulting in insufficient accuracy of the results.

[0003] Currently, the technologies used in on-line uranium detection are X-ray fluorescence technology and neutron-induced prompt gamma-ray analysis technology. Among them, the X-ray fluorescence technology has low measurement accuracy and sensitivity, and there may also be radiation risks; the neutron-induced prompt gamma-ray analysis technology has the disadvantages of large investment, radiation hazards, and short half-life of radioactive sources. Due to the shortcomings of these technologies themselves, they have not been widely applied. Therefore, a technology for detecting uranium content in uranium concentrates with high accuracy and capable of rapid detection is needed.

[0004] In recent years, laser-induced breakdown spectroscopy (abbreviated as LIBS) has become a new laser analysis technology due to its advantages such as high sensitivity, simple sample pretreatment, fast detection speed, and multi-element measurement, and has great application potential in the rapid and accurate detection of uranium content in uranium concentrates. However, since this technology is significantly affected by the matrix effect, the current calibration model has insufficient accuracy. Accurate quantitative measurement is the premise and basis for the LIBS system to play a role in the rapid detection of uranium concentrates, and accurate extraction of the uranium peak signal intensity is the basis for the quantification of uranium elements. In the LIBS emission spectrum, since uranium elements belong to heavy nuclear elements, the electron energy level distribution is dense, and the number of transition characteristic spectral lines exceeds 300,000, with rich emission spectra. In uranium concentrates with a high uranium content, spectral peak overlap is very likely to occur. The overlapping uranium spectral peaks are mixed with the background noise signal, which brings great difficulties to the accurate extraction of the uranium spectral signal. Therefore, a method is needed to accurately remove the background noise in the uranium spectral signal to obtain the accurate uranium signal intensity, thereby laying a foundation for improving the accuracy of detecting uranium content in uranium concentrates by the LIBS technology. Summary of the Invention

[0005] In view of the disadvantage that when LIBS is currently used to detect the uranium content in uranium concentrates, the overlapping uranium peaks and background noise in the spectrum are fused together and cannot be separated, the present invention provides a method for detecting the uranium content by correcting the uranium signal intensity based on plasma parameters, which can be applied to a laser-induced plasma spectroscopy system and solves the problem of rapid detection of the uranium content in uranium concentrates. Based on the physical laws of plasma spectral signals, the present invention extracts the signal intensity by solving the plasma parameters through the internal relationship between the plasma characteristic parameters and the spectral signal intensity. The method of the present invention comprehensively utilizes the information of laser-induced plasma spectroscopy and is convenient to be quickly implemented on a computer, which can not only perform rapid analysis but also improve the measurement accuracy.

[0006] The technical solution of the present invention is as follows:

[0007] A method for detecting the uranium content by correcting the uranium signal intensity based on plasma parameters, comprising the following steps:

[0008] Step 1: Using a laser-induced breakdown spectroscopy system to collect the spectrum of a uranium concentrate standard sample to obtain the laser-induced plasma characteristic spectrum of the uranium concentrate standard sample;

[0009] Step 2: Obtaining the characteristic spectral peak intensity of uranium element from the characteristic spectrum;

[0010] Step 3: Correcting the uranium characteristic spectral peak intensity based on the plasma characteristic spectrum;

[0011] Step 4: Establishing a calibration model for the uranium element content and the uranium characteristic peak signal intensity in the uranium concentrate standard sample;

[0012] Step 5: Repeating the operations of Step 1 to Step 3 for the unknown-concentration sample to be measured, and then using the calibration model in Step 4 to calculate the uranium element content in the sample to be measured by inversion.

[0013] In Step 2, first, the signal intensity I 1 of the uranium characteristic spectral peak is collected by a spectrometer, and then the signal intensity I B of the background is collected.

[0014] In Step 2, the signal intensity I 1 of the uranium characteristic spectral peak is the signal intensity after the collected original spectrum subtracts the dark current background, and the signal intensity I B of the background is the intensity of the continuous spectrum within the wavelength range corresponding to the selected uranium characteristic spectral peak.

[0015] In Step 2, the uranium characteristic spectral peak signal and the background signal select the same signal length.

[0016] In Step 3, the corrected uranium characteristic peak signal intensity I is obtained by I = I 1 - kI B .

[0017] In step 3, the method for determining the k value is as follows:

[0018] Screen multiple characteristic spectral lines of uranium. In the Boltzmann plane method formula, the corrected signal intensity I of the uranium characteristic peak and the corresponding energy level E k have a linear relationship. Since I 1 and I B are known, by continuously optimizing the k value until the correlation between I and the corresponding energy level E k is optimal, that is, the fitting linearity R 2 is the largest; after determining the k value, the corrected signal intensity I of the uranium characteristic peak is obtained;

[0019] The energy level E k can be looked up in the "Atomic Database".

[0020] The maximum value of the said k is 1, and the minimum value is 0.

[0021] In step 3, nine first-order ion lines of uranium are selected to determine the k value by the Boltzmann plane method, and their wavelengths are 409.013 nm, 414.122 nm, 415.541 nm, 417.159 nm, 424.166 nm, 424.437 nm, 434.169 nm, 447.233 nm, and 454.362 nm respectively.

[0022] In step 4, a standard curve calibration model is established using the corrected signal intensity I of the uranium characteristic peak and the known uranium element content in the uranium concentrate standard sample.

[0023] In step 1, a pulsed laser is used as the excitation light source. The laser emitted from the pulsed laser is focused by a focusing lens and then acts on the surface of the calibration sample to generate a plasma at the focal point. The plasma is cooled in the atmosphere of the protective gas, and the generated radiation light signal enters the optical fiber through the collection lens and is converted into an electrical signal after being processed by the spectrometer and then collected by the computer to obtain the laser-induced plasma characteristic spectrum of the uranium concentrate standard sample.

[0024] The remarkable effects of the present invention are as follows:

[0025] (1) Compared with the traditional chemical titration method for detecting uranium content, the method of the present invention can quickly detect the uranium content in the uranium concentrate sample.

[0026] (2) The method of the present invention can accurately remove the background noise in the uranium spectral signal and extract the accurate uranium characteristic spectral intensity, solving the problem that the overlapping uranium peaks and background noise in the LIBS spectrum of the current uranium concentrate sample cannot be separated, and greatly improving the detection accuracy. Description of the Drawings

[0027] Figure 1 Schematic diagram of laser-induced breakdown spectroscopy detection of uranium concentrate in the embodiment;

[0028] Figure 2 Effect of k-value optimization by Boltzmann plane method on correlation coefficient R in the embodiment; 2 of;

[0029] In the figure: 1 pulsed laser; 2 focusing lens; 3 sample; 4 collection lens; 5 optical fiber; 6 spectrometer; 7 computer. Specific implementation manner

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] A method for detecting uranium content based on plasma parameter correction of uranium signal intensity, comprising the following steps:

[0032] Step 1: Use a laser-induced breakdown spectroscopy system to collect spectra of uranium concentrate standard samples

[0033] Using a pulsed laser as the excitation source, the laser emitted from the pulsed laser is focused by a focusing lens and acts on the surface of the calibration sample, generating a plasma at the focal point. The plasma is cooled in the atmosphere of the protective gas, and the generated radiation light signal enters the optical fiber through the collection lens and is converted into an electrical signal by the spectrometer and collected by the computer to obtain the laser-induced plasma characteristic spectrum of the uranium concentrate standard sample;

[0034] Step 2: Obtain the characteristic peak intensity of uranium element from the characteristic spectrum

[0035] First collect the signal intensity I of the uranium characteristic peak from the spectrometer 1 , and then collect the signal intensity I of the background B ;

[0036] Among them, the signal intensity I of the uranium characteristic peak 1 is the signal intensity after subtracting the dark current background from the collected original spectrum, and the signal intensity I of the background B refers to the intensity of the continuous spectrum within the wavelength range corresponding to the selected uranium characteristic peak. The two signals select the same signal length;

[0037] Step 3: Correct the uranium characteristic peak intensity based on the plasma characteristic spectrum

[0038] Using I = I 1 - kI B to obtain the corrected signal intensity I of the uranium characteristic peak, where the determination method of the k value is:

[0039] Screen multiple characteristic spectral lines of uranium. In the Boltzmann plane method formula, the corrected signal intensity I of the uranium characteristic peak and the corresponding energy level Ek has a linear relationship. Since I 1 and I B are known, by continuously optimizing the value of k until the correlation between I and the corresponding energy level E k is optimal, that is, the fitting linearity R 2 is maximized; after determining the value of k, the corrected uranium characteristic peak signal intensity I is obtained, and the background noise in the uranium spectral signal is accurately removed;

[0040] The energy level E k can be looked up in the "Atomic Database";

[0041] The maximum value of the said k is 1, and the minimum value is 0;

[0042] Step 4: Establish a calibration model

[0043] Use the corrected uranium characteristic peak signal intensity I to establish a calibration curve calibration model for the known uranium element content and the uranium characteristic peak signal intensity I in the uranium concentrate standard sample;

[0044] Step 5: Detect the uranium element content in the uranium concentrate sample

[0045] Repeat the operations of Step 1 to Step 3 on the sample to be tested with unknown concentration to obtain the corrected characteristic peak signal intensity, and then use the calibration model in Step 4 to inversely calculate the uranium element content in the sample to be tested.

[0046] Example: Detecting ammonium diuranate samples

[0047] Step 1: Use the laser-induced breakdown spectroscopy system to collect the spectrum of the uranium concentrate standard sample

[0048] As Figure 1 shown, using the pulsed laser (1) as the excitation light source, the laser emitted from the laser passes through the focusing lens (2) and is focused on the surface of the calibration standard sample (3), generating a plasma at the focus point. The plasma cools in the atmosphere of the protective gas, and the generated radiation light signal enters the optical fiber (5) through the collection lens (4), and is processed by the spectrometer (6) and then converted into an electrical signal to be collected by the computer (7) to obtain the laser-induced plasma characteristic spectrum of the ammonium diuranate sample;

[0049] Step 2: Obtain the characteristic spectral line intensity of the uranium element from the characteristic spectrum

[0050] First, calculate the uranium characteristic peak signal intensity I 1 , and then calculate the signal intensity I of the background B ;

[0051] Among them, the uranium characteristic peak signal intensity I 1Refers to the signal intensity after subtracting the dark current background from the collected original spectrum, and the signal intensity of the background is I B Refers to the intensity of the continuous spectrum within the wavelength range corresponding to the selected uranium characteristic spectral peaks, and the same signal length is selected for the two signals;

[0052] Step 3: Correct the intensity of the uranium characteristic spectral peaks based on the plasma characteristic spectrum

[0053] Select nine uranium first-order ion lines to establish the Boltzmann plane method formula, and their wavelengths are 409.013 nm, 414.122 nm, 415.541 nm, 417.159 nm, 424.166 nm, 424.437 nm, 434.169 nm, 447.233 nm, 454.362 nm;

[0054] Based on the Boltzmann plane method, establish the fitting equation between the signal intensity I of the uranium characteristic peak and the energy level E at each wavelength, where I is in the form of I = I k - kI 1 for correction; continuously adjust the k value to make the fitting linearity reach the best (i.e., the correlation coefficient R B is the largest), so as to determine the k value. At this time, the signal intensity I of the uranium characteristic peak is the corrected signal intensity of the uranium characteristic peak; 2 Show the optimization result diagram of one uranium sample. When k = 0.9 in this sample, the optimal result is obtained. Then the corrected signal intensity in this sample should be I = I Figure 2 - 0.9I 1 ; B ;

[0055] Step 4: Establish a calibration model

[0056] Select the characteristic spectral line with the largest light intensity and the best correlation coefficient with the uranium content, that is, establish the calibration model between the uranium element content and the signal intensity of the uranium characteristic peak in the ammonium diuranate standard sample using the intensity of the uranium first-order ion line with a corrected wavelength of 409.013 nm;

[0057] Step 5: Detect the uranium element content in the uranium concentrate sample

[0058] When detecting a sample of ammonium diuranate with unknown content, determine the corrected signal intensity of the uranium characteristic peak through the above steps 1 - 3, and then substitute it into the calibration model in step 4 to calculate the uranium content in the sample inversely.

[0059]

[0060] The above table gives the experimental data of the uranium element content measured by the method of the present invention. It can be seen that the average relative error of the uranium element content detection by the method of the present invention is less than 2%.

[0061] The foregoing has shown and described the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and without departing from the spirit or basic features of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes that fall within the meaning and scope of the equivalent elements of the claims in the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters, characterized in that: It includes the following steps: Step 1: Use a laser-induced breakdown spectroscopy system to collect spectra of uranium concentrate standard samples, and obtain the laser-induced plasma characteristic spectra of uranium concentrate standard samples; Step 2: Obtain the characteristic peak intensity of uranium element from the characteristic spectra; First, collect the signal intensity I of the uranium characteristic spectral peak through a spectrometer 1 , and then collect the signal intensity I of the background B ; Step 3: Correct the characteristic peak intensity of uranium based on the plasma characteristic spectra; With I = I 1 -kI B The corrected uranium characteristic peak signal intensity I is obtained; Among them, the determination method of the k value is: Select multiple characteristic spectral lines of uranium. In the Boltzmann plane method formula, the corrected signal intensity I of the uranium characteristic peak and the corresponding energy level E k have a linear relationship. Since I 1 and I B are known, by continuously optimizing the k value until the correlation between I and the corresponding energy level E k is optimal, that is, the fitting linearity R 2 is the largest; after determining the k value, the corrected signal intensity I of the uranium characteristic peak is obtained; Step 4: Establish a calibration model for the uranium element content and the uranium characteristic peak signal intensity in the uranium concentrate standard sample; Use the corrected uranium characteristic peak signal intensity I and the known uranium element content in the uranium concentrate standard sample to establish a standard curve calibration model; Step 5: Repeat the operations of Step 1 to Step 3 on the unknown concentration sample to be measured, and then use the calibration model in Step 4 to inversely calculate the uranium element content in the sample to be measured.

2. A method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters as described in claim 1, characterized in that: In Step 2, the signal intensity I of the uranium characteristic spectral peak 1 is the signal intensity after subtracting the dark current background from the collected original spectrum, and the signal intensity I of the background B is the intensity of the continuous spectrum within the wavelength range corresponding to the selected uranium characteristic spectral peak.

3. A method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters as described in claim 1, characterized in that: In Step 2, the uranium characteristic peak signal and the background signal select the same signal length.

4. A method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters as described in claim 1, characterized in that: The maximum value of the said k is 1, and the minimum value is 0.

5. A method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters as described in claim 1, characterized in that: In Step 3, nine uranium first-order ion lines are selected to determine the k value by the Boltzmann plane method, and their wavelengths are 409.013 nm, 414.122 nm, 415.541 nm, 417.159 nm, 424.166 nm, 424.437 nm, 434.169 nm, 447.233 nm, 454.362 nm respectively.

6. A method for detecting uranium content by correcting the uranium signal intensity based on plasma parameters as described in claim 1, characterized in that: In Step 1, a pulsed laser is used as the excitation light source. The laser emitted from the pulsed laser is focused by a focusing lens and acts on the surface of the calibration sample. Plasma is generated at the focal point. The plasma is cooled in the atmosphere of the protective gas. The generated radiation light signal enters the optical fiber through the collection lens and is converted into an electrical signal after being processed by the spectrometer and collected by the computer to obtain the laser-induced plasma characteristic spectra of the uranium concentrate standard sample.

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