SU1702268A1 - Calibration method roentgenoradiometric analysis - Google Patents

Abstract

The invention relates to the field of research of substances when exposed to ionizing radiation. The purpose of the invention is to increase the information content of the analysis by combining the operations of determining the concentration of the element being analyzed and the density of the substance. Calibration samples with different concentrations of the element being detected and densities overlapping the entire range of changes in the composition of the substance are irradiated with gamma radiation of the source. The gamma-quantum fluxes of the characteristic and total transmitted through the sample and coherently scattered on the sample of the primary radiation are measured. According to the measurement results, two families of calibration dependences of the measured fluxes of quanta on the substance density are built at fixed values of the concentration of the element being analyzed. 4 il. Yo

Description

The invention relates to nuclear geophysics, in particular, to X-ray radiometric methods for analyzing substances of complex chemical composition, for example, various types of pulps, ash coal, etc., consisting of a single component interfering phase and a two component phase under investigation, in which it is necessary to determine the content of the analyzed an item.

A known method of calibration for X-ray spectral analysis, including the irradiation of calibration samples with X-rays, measurement of the fluxes of quanta of the characteristic X-rays of the analyzed element and scattered radiation, and the determination of communication equations. The essence of the method is to take into account the effect of the density of the medium on the intensity of scattered radiation using the equations of multiple regression.

The disadvantage of this method is the limited range of measured concentrations of the element being analyzed, moreover, this method only takes into account the influence of variations in the solids content, and special measurements are required to directly determine the values of the density of the medium.

The closest to the proposed method is a calibration method for X-ray diffraction analysis, including irradiating gamma calibration samples from: emitting a source, measuring the fluxes of quanta of the characteristic x-ray radiation of the element being analyzed and

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scattered radiation; and plotting — the radiative dependence of the ratio of the intensity of characteristic radiation to the intensity of scattered radiation on the concentration of the element being analyzed.

The disadvantage of this method lies in the limited range of measured concentrations of the element being analyzed, therefore it is used, as a rule, only for scientific research and is practically unsuitable for mass rapid control of the medium with large variations of the solids content and the concentration of the element being analyzed, and also requires additional density measurements environment.

The purpose of the invention is to increase the information content of the analysis by combining the operations of determining the concentration of the element being analyzed and the density of the substance.

This goal is achieved by the fact that in the method of calibration for X-ray radiometric analysis, including the irradiation of the calibration samples with gamma radiation from the source, measurement of the fluxes of quanta of the characteristic X-rays of the analyzed element and scattered radiation v. plotting the calibration dependence, measure the quanta fluxes of the characteristic and total primary radiation passed through the sample and coherently scattered on the sample on the series of calibration samples with different concentrations of the element being analyzed and the densities overlapping the entire range of changes in the composition of the substance, according to the results of measurements t two families of calibration dependences of the quanta fluxes of the characteristic and total radiation transmitted through the sample and coherently scattered on the sample these substances at fixed concentrations of the element being analyzed.

Figure 1 shows the graphs of the calibration dependences in the analysis of pulp for tungsten in selected limited ranges of measurable parameters; Fig. 2 is a diagram of a device for implementing the proposed method; on fig.Z - instrumental spectrum of pulp samples with different contents of the analyzed element of the first detector; figure 4 - the same, the second detector.

The essence of the method consists in the simultaneous determination of two parameters: the density of the substance and the concentration of the element being analyzed. The proposed method does not require special density measurements, its size and the effect of density variations on the concentration value of the analyzed element are automatically taken into account by the calibration dependences of mm, previously constructed from calibration samples chosen so as to cover the entire range of possible changes in the density of the medium and the concentration of the analyzed element,

0 arising in the course of a continuous process.

The calibration dependencies are presented in the form of two families of analytical graphs NX fi (c, p) and Np f2 (c, p),

5 where the Nx flux of quanta of the characteristic x-ray radiation of the analyzed element; Np is the flux of quanta of the total radiation transmitted through the sample and coherently scattered on the sample; p is the density

0 substances; c is the concentration of the element being analyzed.

Each family of plots is constructed on several series of calibration samples. The individual series differ between

5 are values of the concentration of the element being analyzed, i.e. Each curve in the family is constructed from calibration samples with the same concentration of the element being analyzed and with different density values (the ratio of the investigated and interfering phases).

Take a point with coordinates i, j on the graph NX fi (c, / o).

The coordinate i corresponds to a certain density p, and the coordinate j is a specific concentration q. The portion of the curve between points with coordinates I, j and 1 + 1, j, is approximated by a straight line. The same is done for points I.J + 1 and H-1, + 1. Between these

0 by direct approximating, a family of straight lines is constructed with concentrations located uniformly between C) and cj + i with

CJ + 1 C

interval

P

. This family pr 11

5 my approximates the dependence of the flux of characteristic radiation quanta on density for concentrations located in the interval Cj and CJ-H. Going over all I and j, we obtain a family of continuous scrap lines approximating the dependence Ых (р) in the entire range of possible concentrations. We proceed in a similar way with the graph Np h (c, p).

The method is carried out as follows.

For the test sample, the flux of quanta NX of the characteristic radiation of the element being analyzed and the flux of quanta Np of the total transmitted through the sample and

coherently scattered gamma radiation, and the measurement time is set by a constant flux of quanta of the characteristic radiation of the reference element. Using the first family of curves NX f i (c, p) for each broken line with a certain concentration, it is found at which density p 1 it takes the measured value Nx. Similarly, with the help of the second family Np f2 (c, p), according to the measured Np, we find mr2. Thus, for different concentrations, sets of p / 02, determined from two families of calibration dependencies, are obtained. From the condition of the minimum value of Lt, the desired concentration of the element to be analyzed goes, and the density of the substance will be equal to the average interdirection 2- By increasing the number of approximating broken lines, it is possible to increase the accuracy of determining the measured parameters.

The second method for determining the parameters with and rising the calibration dependences is to solve a system of equations approximating the dependences NX fi (c, p) and Np f2 (c, p). According to the parameter p, approximation is a power series with a quadratic term for Drdl of each concentration si

NX (CI) "o (ct) +" 1 (ci) Ap + "2 (ci) Ap2;

Np (C |) 0o (Cl) + 01 (Ci) Dr + fa (Cl) Ap2, (1)

here Ap - p - po, where 0 is the minimum density. The parameter Ap varies within small limits (from 0 to 0.5) and this determines the sufficiency of the approximation (1), For the resulting dependences Оо (с), "1 (с)," 2 (с), 0о (с), 01 (c) 02 (c) with a parameter with a sufficient approximation is a power series of fourth degree with c:

"O (c)" oo + "ot C +" o2 C2 + "oZ C3 +

"O4

"1 (c)" w + "and c +" 12 c2 + ai3 c3 + aw c4;

"2 (C)" 20 + "21 C +" 22 C2 + "23 C3 +" 24 C4;

00 (c) Du + Dl s + D) 2 s + 0oz c3 + 004 c4;

01 (s) 0yu + 011 s + 012 s + 013 c3 + 014 c4;

02 (С) 020 + 021 С + 022 С2 + 023 С3 + 0Z4 С4.

(2)

The determination of the coefficients a and 0ij (30 coefficients) is made on a computer from the calibration dependencies and is stored in the memory of the microcomputer of the computing unit.

From (1) we have

L-4, 2 (“o-Nx) 1/2 + $ -402 () t / 2 0, (3)

those. equation (3) does not depend on the parameter

The parameter c is determined from equation (3) with regard to (2) according to an algorithm using the method of successive approximations. Further, for any 5 of the dependences (1), taking into account the coefficients (2), using the value found, we determine the parameter p,

The gamma-quantum fluxes of the characteristic and total transmitted through pro-0 and coherently scattered radiation depend both on the composition and density of the substance, and on the activity of the radiation source. Over time, it decreases as a result of measuring concentration and density,

5 determined by the calibration dependences, taken with a different source activity, an error will be introduced. In order to eliminate the influence of the source activity on the results of the analysis, the measurement time of the quanta fluxes of the characteristic x-ray radiation of the element being analyzed and the total transmitted through the sample and coherently scattered gamma radiation of the analyzed and calibration samples is set

5 by a constant flux of quanta of the characteristic radiation of the reference element. The magnitude of the flow is chosen such as to ensure the specified statistical error of measurement. Over time

0 when the source activity decreases, the same number of quanta of the characteristic radiation of the reference element will be accumulated over a longer time and, consequently, the measurement time will increase in the selected

5 energy ranges of the test.

Example. The proposed method of X-ray radiometric analysis will be considered by the example of determining tungsten in flotation pulp with the content of basic elements L / Oz 1.5%, Mo - 0.08%, Bi - 0.02% and solid content - 25-50%.

Measurements can be carried out directly on the slurry pipeline at low currents of the pulp, and at the branches from the slurry pipeline at high flows. A flow-through measuring cell 1 of a material that weakly absorbs radiation in the energy range,

0 to exceed the K-line of the analyzed elements, and weakly subjected to wear at

passage of pulp, such as fluoroplastic.

Measurements are made with a source of Co and

two scintillation detectors.

5 Nal (TI), installed in a plane perpendicular to the pulp flow. The radiation source 2 in the collimator container is mounted on the same axis with the first tector 3, which records the total transmitted through the sample and coherently scattered radiation. The second detector 4 is located at an angle B to the radiation source close to 90 °, the exact value of which is determined experimentally when setting up the device, based on the best resolution of the peaks of the characteristic radiation of the elements being analyzed, especially in the low concentration range (about a fraction of a percent) and low density pulp. After tuning, the detectors and the radiation source are fixed rigidly and their position does not change during calibration and operation of the device. A reference element 5, for example a word, is placed between the radiation source and the second detector.

From the instrumental spectra it can be seen that the highest energy peak in the spectrum of the first detector (Fig. 3), associated with photons scattered in the medium at an angle of 1 8 0Q to the radiation source, lies in the range of the source energy (120 keV); The spectrum of the second detector (FIG. 4) is the characteristic radiation of the K-line tungsten. The intensities of both peaks depend on both the concentration of tungsten and the density of the pulp (calibration dependences in Fig. 1). The first peak in figure 4 is the characteristic radiation of a reparking element (word). The intensity of this peak does not depend on the composition and density of the pulp under study and is determined by the mass of the reference element and its geometric position.

The third high-energy peak of the detector arises due to incoherent scattering (NH) and is not used in measurements. This is due to the occurrence of uncertainty in the determination of parameters with l p at tungsten concentrations in the order of 2.5% (in this case, in the density range 1.3-1.6 g / cm3 for the third peak

1L 1-0) dp -0)

The energy spectrum contains three energy ranges — the total transmitted through the sample and coherently scattered radiation at sensor I, characteristic lines of tungsten and a reference element at sensor 2, corresponding to three channels of a multichannel spectrometer. The areas of registration of the characteristic x-ray and scattered radiation correspond to the maxima of their amplitude distribution in the spectral spectra.

When calibrating the instrument, calibration samples with various concentrations and different densities are taken. For each sample, counting the number of pulses in the first and second selected energy ranges is carried out, the measurement time is determined by a constant stream of quanta of the characteristic radiation of the reference element. As a result of the calibration, we obtain data sets of the number of pulses in 1 and 2 channels for various densities and

0 pulp concentrations. These sets in the form of two-dimensional arrays are recorded in the memory of control unit 6 computer-based,

Measurements on pulp samples are carried out by counting the number of pulses in 1 and 2

5 channels of the spectrometer until the number of pulses in channel 3 from the reference element reaches a predetermined value, for example, 0.75 10 pulses. Measured values, for example, Nx 0.89 10 pulses and Np 1.675-106 pulses are inserted into a computer, where the density ρ 1.3 g / cm and tungsten concentration C is determined by 1.7%.

The proposed method allows simultaneous analysis of several elements that have well resolvable peaks of the characteristic radiation in the spectra, Mo — W, W — Cu, etc.

0 The advantage of the proposed method in comparison with the prototype is the ability to determine the concentration of the useful component directly from the measured solid.

5 fractions of the medium with arbitrary fluctuations of its relative weight content, and the density of the medium without additional equipment in the same cuvette, which leads to an increase in the efficiency of control of continuous

technological process, such as flotation of minerals.

Claims (1)

Claims of the Invention 5 A calibration method for X-ray radiometric analysis, including irradiating calibration samples with gamma radiation from a source, recording fluxes of quanta of characteristic radiation of the analyzed element and scattered radiation, and constructing a calibration dependence, characterized in that, in order to increase the information content of the analysis by combining determination operations concentration 5 of the analyzed element and the density of the substance, measure the fluxes of quanta of the characteristic and total passed through the sample and primary emission coherently scattered on the sample on series of calibration samples with different concentrations element and density, quanta of characteristic and total overlapping the entire range of change in the sample passing through the sample and coherently varying the composition of the substance, according to the results of radiation measured by the sample from the density rhenium builds two families substances at fixed values calibration dependencies flow 5 concentration of the analyzed element. /, t3 4,3 W, 5 tf substances at fixed values & / Urp M U w / 0 №% « / m t and af 80 ten MO120 Fig.Z MO Eke B,   with- % 90 Ј Cab