CN115791757A - A uranium content detection method based on plasma parameter correction of uranium signal intensity - Google Patents

Abstract

The invention relates to the technical field of laser-induced breakdown spectroscopy detection, and particularly discloses a uranium content detection method for correcting uranium signal intensity based on plasma parameters, which comprises the following steps: step 1: carrying out spectrum acquisition on the uranium concentrate standard sample by using a laser-induced breakdown spectroscopy system to obtain a laser-induced plasma characteristic spectrum of the uranium concentrate standard sample; and 2, step: obtaining the characteristic spectrum peak intensity of the uranium element from the characteristic spectrum; and 3, step 3: correcting the peak intensity of the uranium characteristic spectrum based on the plasma characteristic spectrum; and 4, step 4: establishing a calibration model of the uranium element content and the uranium characteristic peak signal intensity in a uranium concentrate standard sample; and 5: and (4) repeating the operation of the step (1) to the step (3) on the sample to be detected with unknown concentration, and then reversely calculating the content of the uranium element in the sample to be detected by using the calibration model in the step (4). The method can accurately eliminate the background noise in the uranium spectrum signal, extract the accurate uranium characteristic spectrum intensity and greatly improve the detection accuracy.

Description

A uranium content detection method based on plasma parameter correction of uranium signal intensity

technical field

The invention belongs to the technical field of laser-induced breakdown spectrum detection in the field of atomic emission spectrometry, and in particular relates to a method for detecting uranium content based on plasma parameter correction of uranium signal intensity.

Background technique

Uranium concentrates (mainly diuranate, U3O8, etc.) are the most important uranium hydrometallurgy products in my country and important raw materials in the nuclear industry. The rapid and accurate determination of uranium content in the product transaction and production process are very important in control. At present, the determination of uranium in uranium concentrates mainly adopts ferrous sulfate reduction/potassium dichromate oxidation titration method, which uses sodium diphenylamine sulfonate as indicator titration, the operation process is complicated, the degree of automation is low, and the analysis time is long. Moreover, the judgment of the titration end point is greatly influenced by human subjectivity, and the accuracy of the result is insufficient.

At present, the technologies used in online detection of uranium are X-ray fluorescence technology and neutron-induced prompt gamma-ray analysis technology. Among them, X-ray fluorescence technology has low measurement accuracy and sensitivity, and may also have radiation risks; 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, they have not been widely used. Therefore, there is a need for a detection technology for uranium content in uranium concentrates that has high precision and can realize rapid detection.

In recent years, laser-induced breakdown spectroscopy (LIBS for short) has become a new laser analysis technology due to its advantages of high sensitivity, simple sample pretreatment, fast detection speed and multi-element measurement. It has great application potential for rapid and accurate detection of content. However, because the technology is significantly affected by the matrix effect, the current calibration model is not accurate enough. Accurate quantitative measurement is the premise and basis for the LIBS system to play a role in the rapid detection of uranium concentrates, and the accurate extraction of uranium peak signal intensity is the basis for the quantification of uranium elements. In the LIBS emission spectrum, because uranium is a heavy nuclear element, the electronic energy levels are densely distributed, and there are more than 300,000 transition characteristic lines, which have rich emission spectra. In the case of overlapping peaks, the overlapping uranium spectral peaks are mixed with background noise signals, which brings great difficulties to the accurate extraction of uranium spectral signals. Therefore, there is a need for a method to accurately remove the background noise in the uranium spectral signal to obtain an accurate uranium signal intensity, thereby laying a foundation for improving the accuracy of LIBS technology in detecting uranium content in uranium concentrates.

Contents of the invention

The present invention aims at the defect that overlapping uranium peaks and background noise in the spectrum cannot be separated when the current LIBS detects the uranium content in the uranium concentrate, and provides a uranium content detection method based on plasma parameters to correct the uranium signal intensity, It can be applied to a laser-induced plasma spectroscopic system, and solves the problem of rapid detection of uranium content in uranium concentrates. The invention is based on the physical law of the plasma spectrum signal, and extracts the signal intensity by solving the plasma parameter through the internal relationship between the plasma characteristic parameter and the spectrum signal intensity. The method of the invention comprehensively utilizes the information of the laser-induced plasma spectrum, and is convenient for rapid realization on a computer, which can not only perform rapid analysis, but also improve measurement accuracy.

Technical scheme of the present invention is as follows:

A uranium content detection method for correcting uranium signal intensity based on plasma parameters, comprising the following steps:

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

Step 2: Obtain the characteristic spectrum peak intensity of uranium element from characteristic spectrum;

Step 3: Correcting the peak intensity of the uranium characteristic spectrum based on the plasma characteristic spectrum;

Step 4: Establish a calibration model for the content of uranium element in the standard sample of uranium concentrate and the signal intensity of the characteristic peak of uranium;

Step 5: Repeat steps 1 to 3 for the sample to be tested with unknown concentration, and then use the calibration model in step 4 to back-calculate the content of uranium in the sample to be tested.

In step 2, the signal intensity I ₁ of the characteristic spectrum peak of uranium is first collected by the spectrometer, and then the signal intensity I _B of the background is collected.

In step 2, the signal intensity _I of the uranium characteristic spectrum peak is the signal intensity after deducting the dark current background from the collected original spectrum, and the background signal intensity I _B is the intensity of the continuous spectrum within the corresponding band range of the selected uranium characteristic spectrum peak.

In step 2, the uranium characteristic spectrum peak signal and the background signal have the same signal length.

In step 3, the corrected signal intensity I of the characteristic peak of uranium is obtained by I=I ₁ -k I _B .

In step 3, the determination method of k value is:

Multiple characteristic spectral lines of uranium are screened. In the Boltzmann plane method formula, the corrected signal intensity I of the characteristic peak of uranium has a linear relationship with the corresponding energy level E _k . Since I ₁ and I _B are known, so through continuous Optimize the k value until the correlation between I and the corresponding energy level E _k is optimal, that is, the fitting linearity ^R2 is the largest; after determining the k value, the corrected signal intensity I of the characteristic peak of uranium is obtained;

The energy level E _k can be consulted from the "atomic database".

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

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, and 447.233 nm , 454.362 nanometers.

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

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

Remarkable effect of the present invention is:

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

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

Description of drawings

Fig. 1 is the schematic diagram of laser-induced breakdown spectrum detection of uranium concentrate in the embodiment;

Fig. 2 is the impact of Boltzmann plane method k value optimization on correlation coefficient ^R in the embodiment;

In the figure: 1 pulse laser; 2 focusing lens; 3 sample; 4 collecting lens; 5 optical fiber; 6 spectrometer; 7 computer.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

A uranium content detection method for correcting uranium signal intensity based on plasma parameters, comprising the following steps:

Step 1: Spectral collection of standard samples of uranium concentrate by laser-induced breakdown spectroscopy

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

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

From the spectrometer, first collect the signal intensity I ₁ of the uranium characteristic spectrum peak, and then collect the signal intensity I _B of the background;

Among them, the signal intensity _I of the uranium characteristic spectrum peak is the signal intensity after deducting the dark current background from the original spectrum collected, and the background signal intensity I _B refers to the intensity of the continuous spectrum in the corresponding band range of the selected uranium characteristic spectrum peak, two The signal selects the same signal length;

Step 3: Correct the uranium signature peak intensity based on the plasma signature spectrum

The corrected signal intensity I of the characteristic peak of uranium is obtained by I=I ₁ -k I _B , where the value of k is determined as follows:

Multiple characteristic spectral lines of uranium are screened. In the Boltzmann plane method formula, the corrected signal intensity I of the characteristic peak of uranium has a linear relationship with the corresponding energy level E _k . Since I ₁ and I _B are known, so through continuous Optimize the k value until the correlation between I and the corresponding energy level E _k is optimal, that is, the fitting linearity ^R2 is the largest; after determining the k value, the corrected uranium characteristic peak signal intensity I is obtained, and the uranium spectral signal is accurately eliminated. background noise;

The energy level E _k can be checked from the "atomic database";

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

Step 4: Build a Calibration Model

Using the corrected uranium characteristic peak signal intensity I to establish a standard curve calibration model between the known uranium element content in the uranium concentrate standard sample and the uranium characteristic peak signal intensity I;

Step 5: Detection of uranium content in uranium concentrate samples

Repeat steps 1 to 3 for the sample to be tested with an unknown concentration to obtain the corrected characteristic peak signal intensity, and then use the calibration model in step 4 to back-calculate the content of uranium in the sample to be tested.

Example: detection of ammonium diuranate sample

Step 1: Spectral collection of standard samples of uranium concentrate by laser-induced breakdown spectroscopy

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

Step 2: Obtain the characteristic line intensity of uranium element from the characteristic spectrum

First, calculate the signal intensity I ₁ of the uranium characteristic spectrum peak, and then calculate the signal intensity I _B of the background;

Among them, the signal intensity _I of the uranium characteristic spectrum peak refers to the signal intensity after deducting the dark current background from the original spectrum collected, and the background signal intensity I _B refers to the intensity of the continuous spectrum in the corresponding band range of the selected uranium characteristic spectrum peak. Select the signal length of the same length for each signal;

Step 3: Correct the uranium signature peak intensity based on the plasma signature spectrum

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, and 454.362 nm;

Based on the Boltzmann plane method, the fitting equation of the uranium characteristic peak signal intensity I and the energy level _Ek under each wavelength is established, wherein I is corrected with I=I ₁ -k I _B ; the value of k is constantly adjusted to make the fitting The linearity reaches the best (that is, the correlation coefficient R2 ^is the largest), so as to determine the k value, and the signal intensity I of the characteristic peak of uranium at this time is the signal intensity of the characteristic peak of uranium after correction; Fig. 2 shows the optimization result diagram of one of the uranium samples, The optimum result is obtained when k=0.9 in this sample, then the corrected signal intensity in this sample should be I=I ₁ -0.9I _B ;

Step 4: Build a Calibration Model

Select the characteristic spectral line with the largest light intensity and the best correlation coefficient with the uranium content, that is, use the corrected wavelength of 409.013 nanometers to establish the uranium element content and uranium characteristic peak signal in the ammonium diuranate standard sample Intensity calibration model;

Step 5: Detection of uranium content in uranium concentrate samples

When detecting diuranate samples with unknown content, the corrected uranium characteristic peak signal intensity is determined through the above steps 1 to 3, and then substituted into the calibration model in step 4 to calculate the uranium content in the sample.

The above table shows 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%.

The basic principles, main features and advantages of the present invention have been shown and described above. 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 fundamentals of the present invention. The present invention can be implemented in other specific forms without any specific features. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims (10)

1. A method for detecting uranium content based on plasma parameter correction of uranium signal intensity, characterized in that: comprising the following steps: Step 1: Using the laser-induced breakdown spectroscopy system to collect the spectrum of the uranium concentrate standard sample to obtain the laser-induced plasma characteristic spectrum of the uranium concentrate standard sample; Step 2: Obtain the characteristic spectrum peak intensity of uranium element from characteristic spectrum; Step 3: Correcting the peak intensity of the uranium characteristic spectrum based on the plasma characteristic spectrum; Step 4: Establish a calibration model for the content of uranium element in the standard sample of uranium concentrate and the signal intensity of the characteristic peak of uranium; Step 5: Repeat steps 1 to 3 for the sample to be tested with unknown concentration, and then use the calibration model in step 4 to back-calculate the content of uranium in the sample to be tested. 2. A kind of uranium content detection method based on plasma parameter correction uranium signal intensity as claimed in claim 1, it is characterized in that: in step 2, at first collect uranium characteristic spectrum peak signal intensity I ₁ by spectrometer, then collect background Signal strength I _B . 3. a kind of uranium content detection method based on plasma parameter correction uranium signal intensity as claimed in claim 2, it is characterized in that: in step 2, uranium characteristic spectrum peak signal intensity I ₁ is the original spectrum of collection deducting dark current background After the signal intensity, the background signal intensity I _B is the intensity of the continuous spectrum in the band corresponding to the selected uranium characteristic spectrum peak. 4. A method for detecting uranium content based on plasma parameter correction of uranium signal intensity as claimed in claim 2, characterized in that: in step 2, the uranium characteristic spectrum peak signal and the background signal have the same signal length. 5. A kind of uranium content detection method based on plasma parameter correction uranium signal intensity as claimed in claim 2, it is characterized in that: in step 3, obtain the uranium characteristic peak signal intensity after correction with I=I ₁ -kI _B I. 6. A method for detecting uranium content based on plasma parameter correction of uranium signal intensity as claimed in claim 5, characterized in that: in step 3, the method for determining the k value is: Multiple characteristic spectral lines of uranium are screened. In the Boltzmann plane method formula, the corrected signal intensity I of the characteristic peak of uranium has a linear relationship with the corresponding energy level E _k . Since I ₁ and I _B are known, so through continuous Optimize the k value until the correlation between I and the corresponding energy level E _k is optimal, that is, the fitting linearity ^R2 is the largest; after determining the k value, the corrected signal intensity I of the characteristic peak of uranium is obtained; The energy level E _k can be consulted from the "atomic database". 7. A method for detecting uranium content based on plasma parameter correction of uranium signal intensity as claimed in claim 6, characterized in that: the maximum value of k is 1, and the minimum value is 0. 8. A kind of uranium content detection method based on plasma parameter correction uranium signal intensity as claimed in claim 6, it is characterized in that: in step 3, select nine uranium first-order ion lines for Boltzmann plane method to determine k Values, the 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. 9. A kind of uranium content detection method based on plasma parameter correction uranium signal intensity as claimed in claim 5, it is characterized in that: in step 4, use the corrected uranium characteristic peak signal intensity I and the uranium concentrate standard sample Known uranium content to establish a standard curve calibration model. 10. A method for detecting uranium content based on plasma parameter correction of uranium signal intensity as claimed in claim 1, characterized in that: in step 1, a pulsed laser is used as the excitation light source, and the laser light emitted from the pulsed laser is focused through a focusing lens Afterwards, it acts on the surface of the calibration sample, generates plasma at the focal point, and cools the plasma in the atmosphere of protective gas. The generated radiated optical signal enters the optical fiber through the collection lens, and after being processed by the spectrometer, it is converted into an electrical signal and collected by the computer. Obtain the laser-induced plasma characteristic spectrum of the standard sample of uranium concentrate.

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