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GB/T 11743-2013: Determination of radionuclides in soil by gamma spectrometry
Status: Obsolete GB/T 11743: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivered in | Standard Title (Description) | Status | PDF |
| GB/T 11743-2013 | English | 559 |
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Determination of radionuclides in soil by gamma spectrometry
| Obsolete |
GB/T 11743-2013
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| GB/T 11743-1989 | English | 399 |
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Gamma spectrometry method of analysing radionuclides in soil
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GB/T 11743-1989
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PDF similar to GB/T 11743-2013
Basic data | Standard ID | GB/T 11743-2013 (GB/T11743-2013) | | Description (Translated English) | Determination of radionuclides in soil by gamma spectrometry | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | C57 | | Classification of International Standard | 13.280 | | Word Count Estimation | 14,150 | | Older Standard (superseded by this standard) | GB/T 11743-1989 | | Regulation (derived from) | National Standards Bulletin 2013 No. 27 | | Issuing agency(ies) | General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People's Republic of China | | Summary | This standard specifies the method for routine laboratory analysis of soil with �� spectrometer radionuclide activity concentration. This standard applies to the analysis of radionuclides in soil ��. | GB/T 11743-2013: Determination of radionuclides in soil by gamma spectrometry---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Determination of radionuclides in soil by gamma spectrometry
ICS 13.280
C57
National Standards of People's Republic of China
Replace GB/T 11743-1989
Analytical method of radionuclide in soil by γ energy spectrum
Released on.2013-12-31
2014-12-01 implementation
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
Issued by the National Standardization Administration of China
Table of contents
Foreword Ⅰ
1 Scope 1
2 Apparatus 1
3 Scale of gamma spectrometer 2
4 Body standard source preparation 3
5 Sample preparation 3
6 Measurement 3
7 γ energy spectrum analysis method 4
8 Report 6
Appendix A (informative appendix) Single-energy and multi-energy nuclides for energy calibration 7
Appendix B (informative appendix) Table 8 of commonly used natural radionuclides with a probability of γ-ray emission greater than 1%
Appendix C (informative appendix) Inverse matrix method in γ energy spectrum analysis 9
Appendix D (informative appendix) Lower detection limit of gamma spectrum measurement 10
Analytical method of radionuclide in soil by γ energy spectrum
1 Scope
This standard specifies a routine method for the laboratory to analyze the activity concentration of radionuclides in soil with a gamma spectrometer.
This standard applies to the analysis of gamma radionuclides in soil.
2 Equipment
2.1 γ spectrometer
2.1.1 Detector
2.1.1.1 Sodium iodide [NaI(Tl)] detector
A cylindrical NaI(Tl) detector with a size not less than ϕ7.5cm×H7.5cm should be used to measure soil samples. Prefer low potassium NaI
(Tl) Crystal and low-noise photomultiplier tube. The entire crystal is sealed in a sealed container with a light-transmitting window, and the crystal and the photomultiplier tube form an optocoupler
Together. The resolution of the detector to the 661.6keV peak of 137Cs should be better than 9%.
2.1.1.2 Semiconductor detector
Different materials and different types of semiconductor detectors should be used according to the γ-ray energy range. Single-opening is preferred for measuring soil samples
The energy resolution (FWHM) of 60Co1332.5keV gamma rays should be better than 2.5keV, compared with
The relative efficiency of the ϕ7.5cm×H7.5cm(3″×3″) NaI(Tl) detector is not less than 20%.
2.1.2 Shield
The detector device should be placed in a metal shielded room with an equivalent lead equivalent of not less than 10cm, and the distance between the wall of the shielded room and the crystal surface
>13cm, on the inner surface of the lead chamber, there should be a multilayer inner shielding material with a decreasing atomic number, and the inner shield shall be lined with thickness from the outside to the inside.
Cadmium or tin with ≥1.6mm, copper with ≥0.4mm and plexiglass with 2mm~3mm to reduce the energy of 72keV~95keV
The influence of Pb characteristic X-ray. For example, it can be composed of 0.4mm copper, 1.6mm cadmium and 2mm~3mm thick plexiglass.
The shielded room should have doors or windows that are convenient for taking and placing samples.
2.1.3 High voltage power supply
There should be a high-voltage power supply to ensure the stable operation of the detector, and its relative ripple voltage should not be greater than ±0.01%.
0V~±5000V, continuously adjustable within the range of 1μA~100μA, without discontinuity.
2.1.4 Spectrum amplifier
There should be an amplifier with waveform adjustment that matches the preamplifier and pulse height analyzer.
2.1.5 Pulse height analyzer
The number of channels of the NaI(Tl) spectrometer should be no less than 512, and for the high purity germanium gamma spectrometer, the number of channels should be no less than 8192.
2.1.6 Computer System
It is required to match the hardware of the entire spectrometer system, and the spectrum acquisition and de-spectrum software suitable for the entire spectrometer system have been installed, as well as the supporting output terminal.
Terminal, such as a printer, etc.
2.2 Measuring vessel
According to the number of samples and the shape and size of the detector, select sample boxes of different sizes and shapes, such as. the diameter of the bottom of the container is equal to or smaller
A cylindrical sample box with the diameter of the detector or a ring-shaped sample box matching the size of the detector. The container should use natural radionuclide content
It is made of materials with low and no artificial radioactive pollution, such as ABS (acrylonitrile-styrene-butadiene copolymer) resin or polyethylene.
3 Calibration of γ spectrometer
3.1 Energy scale
3.1.1 Calibrate the gamma spectrum system with a calibration source of known nuclides
The energy scale should range from 40keV to.2000keV. Refer to Appendix A for the single-energy and multi-energy nuclides applicable to the energy scale. Energy engraved
The degree includes at least four scale points with energy evenly distributed in the required scale energy zone. Record the characteristic γ-ray energy and the corresponding all-power peak of the calibration source
Peak position and road address can be plotted on Cartesian coordinate paper or the data can be fitted with least squares straight line or parabola. The energy of high purity germanium gamma spectrometer
The absolute value of linearity should not exceed 0.5%, and the absolute value of energy nonlinearity of NaI(Tl) gamma spectrometer should not exceed 5%.
3.1.2 Changes in the relationship between energy and road sites
If the absolute value of the slope and intercept of the energy scale curve does not exceed 0.5%, the existing scale data can be used, otherwise it should be re-engraved
degree. The better the stability of the gamma spectrometer, the less likely the energy scale is to change.
3.2 Efficiency scale
3.2.1 Standard source of efficiency scale
For general soil sample measurement, the body standard source of uranium, radium, thorium, and potassium is used for efficiency calibration. Used as a standard source for efficiency scales. Its geometry
The shape should be the same as the tested sample, and the matrix density and effective atomic number should be as close as possible to the tested sample. For some involving long-life labor
For the measurement of radionuclide 137Cs, another standard source of 137Cs body should be prepared for use.
3.2.2 Efficiency scale curve
When the cascade and span effects are negligible, the detection efficiency of the γ-ray total absorption peak is a function of the γ-ray energy. Find several different energies
After the detection efficiency of the single-energy γ-ray total absorption peak, the relationship curve between the detection efficiency and the γ-ray energy (efficiency curve) can be drawn on the graph paper or used
The computer performs the weighted least squares curve fitting on the experimental points to obtain the efficiency curve. Use n logarithms in the range of 40keV~2000keV
Polynomial fitting can achieve satisfactory results, and the expression is shown in equation (1).
lnε=∑
n-1
i=0
ai(lnEγ)i (1)
Where.
ε ---Experimental γ-ray total absorption peak efficiency value;
ai ---fitting constant;
Eγ-the corresponding γ-ray energy, in kiloelectron volts (keV).
The relative standard uncertainty of the efficiency scale should be less than 5%.
4-body standard source preparation
4.1 Body standard source requirements
The volume standard source used for the efficiency calibration of the γ spectrometer is made by uniformly mixing a simulated matrix and a standard solution of a specific nuclide or a standard mineral powder.
It should meet the requirements of good uniformity, accurate nuclide activity, stability, and sealing.
4.2 Simulation matrix
The material with low radioactive background, easy to mix uniformly, and density similar to the sample to be tested is selected as the simulation matrix. For the packing density at
The volume standard source of soil samples of 0.8g/cm3~1.6g/cm3 uses a certain proportion of alumina and silica as the simulation matrix.
4.3 Body standard source activity
The activity of the body standard source should be moderate, generally 10 to 30 times that of the tested sample. The specific multiple depends on the amount and strength of the sample.
Depends.
4.4 Body standard source sealing
The prepared standard source of uranium and radium should be placed in the sample box and sealed for 3 to 4 weeks, so that the uranium and radium and its short-lived progeny have reached equilibrium.
use.
4.5 Uncertainty of body standard source
The total uncertainty of the activity of the body standard source should be within 5%.
5 Sample preparation
The soil sample from which weeds, crushed stones and other foreign matter are removed is dried at 100°C to a constant weight, crushed and sieved (40 mesh ~ 60 mesh), weighed, loaded and engraved
In the sample box with the same body standard source of the degree γ spectrometer, it shall be sealed and placed for 3 to 4 weeks and then measured.
6 measurement
6.1 Background measurement
The background spectrum of the simulated matrix and the background spectrum of the empty sample box should be measured.
The corresponding simulated matrix background count is subtracted from the number, and the almighty peak count of the soil sample should be deducted from the corresponding empty sample box background count.
6.2 Body standard source measurement
When measuring the body standard source, its position relative to the detector should be the same as when measuring the soil sample.
6.3 Measurement time and measurement count uncertainty
The measurement time depends on the strength of the standard source of the measured object or the strength of the sample. The measurement uncertainty of the body standard source should be less than 5%. Soil sample
The expanded uncertainty of the activity of the medium radionuclide (including a factor of 2) should meet. uranium is less than 20%, radium, thorium, and potassium are less than 10%, and 137Cs is small.
Less than 15%.
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