SY/T 5252-2002 Natural gamma ray spectrum analysis method for rock samples
Some standard content:
ICS 75.020
Registration number: 11426-2002
Petroleum and natural gas industry standard of the People's Republic of China SY/T5252-2002
Replaces SY/T5252-91, SY/T5253-9I Natural gamma spectrographic method of analysing for core' sample2002 -05—28 Issued
National Economic and Trade Commission
2002-08-01 Implementation
Normative reference documents
3 Terms and definitions
4 Principles of the method
4.1 Principles of the sodium iodide detector method
4.2 Principles of the high-purity germanium detector method
5 Main measuring instruments and technical indicators
5.1 Main measuring instruments and technical indicators of the sodium iodide detector method5.2 Main measuring instruments and technical indicators of the high-purity germanium detector method6 Energy calibration of sodium iodide and high-purity germanium gamma spectrometers6.1 Energy calibration of sodium iodide gamma spectrometer
6.2 Energy calibration of high-purity germanium gamma spectrometer
7 Preparation of standard samples
7.1 Preparation of standard samples for the sodium iodide detector method7.2 Preparation of high-purity germanium gamma spectrometers Preparation of standard samples for pure yttrium detector method 8 Preparation of rock samples
8.1 Preparation of rock samples for iodine clamp detector method
8.2 Preparation of rock samples for high-purity yttrium detector method
9 Measurement steps ·…
10 Measurement results and calculation of uncertainty 10.1 Measurement results and calculation of uncertainty for sodium iodide detector method 10.2 Measurement results and calculation of uncertainty for high-purity germanium detector method 11 Quality control during testing
12 Handling of special cases ·|tt||[3 Format and content of test records ·|tt||Appendix A (Normative Appendix)
Appendix 1 (Normative Appendix)
Error estimation of natural gamma radioactivity measurement Lower detection limit of gamma energy analysis ·|tt||Appendix ((Informative Appendix) Test record format SY/T 5252—2002
SY/T 5252—2002
This standard replaces SY/T5252—91 "Natural gamma spectroscopy analysis method for rock cores - sodium iodide detector method" and uses SY/T525.391 "Natural gamma spectroscopy analysis method for rock cores - high purity germanium detector method". Compared with SY/I5252--91 and SY/I5253—91, the main changes of this standard are as follows:
a) The following contents are added:
1) Normative reference documents (see Chapter 2); 2) Terms and definitions (see Chapter 3);
3) Principles of the method (see Chapter 4);
4) Requirements for the selection of standard samples (see 7.1.1); 5) Calculation of the normalized value of the energy window count of the standard sample (see 10.1.5.1); 6) Calculation of the total natural gas of the sample Gamma net count GR (10.1.6, 10.2.5); 7) Content range, uncertainty and relative uncertainty of total natural gamma net count GR (see Table 2, Table 3); 8) Quality control of test and performance [see Chapter 11); 9) Handling of special situations (see Chapter 12); 10) Content and format of test records (see Chapter 13); 11) Appendix A (normative appendix) Error estimation of natural gamma radioactivity measurement, Appendix B (normative appendix) Detection lower limit of gamma energy analysis, Appendix C (informative appendix) Test record format, b) Modified contents include:
1) Main measuring instruments and technical indicators (5.1, 5.2 of this standard; 2.1, 2.2 of SY/T525291 and SY/T525391 2.1, 2,2]:
2) Energy calibration of sodium iodide and high purity germanium ChemSpectrometer (6.1, 6.2 of this standard; 2.6 of SY/15252-91 and 2.6 of SY/T5253-91);
3) Measurement steps (Chapter 9 of this standard; 2.7, 2.8 of SY/T5252-91 and 2.7, 2.8, 2.9 of SY/T5253-91).
Appendix A and Appendix B of this standard are normative appendices, and Appendix C is an informative appendix. The standard is proposed and managed by the Petroleum Well Logging Professional Standard Promotion Committee. Drafting unit of this standard: 1 Institute of Social Technology Measurement and Research, Shixie Group Science and Technology Research Institute. The main drafters of this standard are: Yang Fang, He Biao, Hu Xiuni: The previous versions replaced by this standard are: SY/T5252-91SY/F5253--91.
1 Scope
Natural gamma spectrum analysis method of rock samples
SY/T5252-Z002
This standard specifies the conventional method of measuring the natural gamma spectrum of rock samples (hereinafter referred to as rock samples) in the laboratory using sodium iodide detectors and high-purity detectors.
This standard is applicable to the analysis of natural gamma spectra of rock samples with a minimum count rate higher than the detection limit of the spectrometer and a maximum count rate less than 104cps in the laboratory using sodium iodide detectors and commercial pure germanium detectors. 2 Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent revisions (excluding errata) or amendments are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to investigate whether the latest versions of these documents can be used. For any undated referenced document, the latest version applies to this standard. GI316354 Requirements for radiological protection using sealed radioactive sources 3 Terms and definitions
The following terms and definitions apply to this standard. 3.1
Fullwidth at half maximum The distance in energy between two points at half the height of the peak on the energy distribution curve of a monoenergetic particle. 3.2
Energy resolution
Energy resolution For a given energy, the minimum relative difference between two particle energies that a radiation spectrometer can resolve. In general applications, energy resolution is the ratio of the half-width energy of a peak in the energy distribution curve of a monoenergetic particle to the energy corresponding to the peak position. 3.3
Background count ratebackgruund countrateCount rate caused by other factors except the radioactivity of rock samples under the same environment. 3.4
Lower limit of detectionlower Himit of detectionThe lowest activity that can be detected by the spectrometer under a given confidence level. 3.5
Detector conversion efficiencydetectorefficiencyThe ratio of the number of particles detected by the detector to the total number of particles of the same kind that hit the detector in the same time interval. 3.6
Detection efficiencydetectionerficiency
Under certain detection conditions, the ratio of the number of particles detected to the total number of particles of the same kind emitted by the radiation source in the same time interval. 4 Principle of the method
4.1 Principle of the method of sodium iodide detector
This system is composed of standard nuclear instrument plug-in components: the main detector receives the signal generated by the radioactive material in the sample, and sends it to the multi-channel analyzer through the main amplifier, delay device, and linear gate through the mixer; the other path is sent to the anti-coincidence input end of the unit after amplification, screening and shaping. The signals collected by the six ring detectors are mixed, added, amplified, screened and shaped by the linear mixer, and then sent to the anti-coincidence input end of the anti-coincidence unit. If the two input signals of the anti-coincidence unit exist at the same time, it will not have an output pulse. Only when there is a signal at the coincidence input end and no signal at the anti-coincidence input end will it have an output pulse. Its output pulse is used as the gate signal of the linear gate, and its pulse amplitude is 3V and width is 3μs. The transmission signal of the linear gate is controlled by the gate signal. The gate is open only during the period of gate signal; when there is no gate signal, the gate is closed. The screen condensation chamber is used to reduce most of the background, and a small part of the background and the pulses generated by gamma rays and material Compton scattering are received by the main detector and the bad detector at the same time: the anti-coincidence technology is adopted to reduce this part of the background and the Compton effect at the same time. 4.2 Principle of high-purity zirconium detector method
High-purity zirconium detector is used in high-resolution energy spectrum measurement. High-purity zirconium detector is an IN junction detector made of extremely high-purity germanium: when measuring, a reverse voltage is applied to the detector, and the gamma rays emitted by the rock sample react with the PN junction of the detector to form electron-hole pairs that can conduct electricity. Under the action of the electric field, the electron-hole pairs drift to the two poles respectively, forming a signal in the output path. After the signal is amplified by the preamplifier, it is amplified by the spectrum amplifier, and after being analyzed by the pulse amplitude analyzer, it also displays the counts of gamma rays at different times and different energy levels (i.e., the gamma-ray energy spectrum), and finally outputs the results according to the user's requirements. 5 Main measuring instruments and techniques Technical indicators
5.1 Main measuring instruments and technical indicators of sodium iodide detector method The schematic diagram of the measuring device of sodium iodide detector method is shown in Figure 1: Anti-coincidence loop input!
Zone
Sodium iodide
Upper detector
Main detector signal
Low voltage power supply
Anti-coincidence input
Anti-coincidence
Coincidence input
Pulse amplitude
Figure 1 Schematic diagram of the measuring device of sodium iodide detector method Analyzer
Computer
Printer
SY/T 5252—2002
a) Sodium iodide main detector [Nal (ll) (referred to as detector): Use a cylindrical detector with a diameter of not less than 75mm and a length of not less than 75mm to measure rock samples. Low potassium crystal and low noise photomultiplier tube are selected, and the resolution of the detector for 137Cs661.7keV light peak is less than 10%:
b) Shielding room: The detector is placed in a metal shielding room with an equivalent lead equivalent of not less than 100rnm. The distance between the inner wall of the shielding room and the crystal surface is more than 130mm. On the inner surface of the lead room, there are multiple layers of inner shielding materials with gradually decreasing atomic numbers, such as 0.4mu copper, 1.6mm cadmium and 2mm--3mm thick organic glass. The acid shielding room has a door or hole for easy access and placement of samples:) High voltage power supply: Provide high voltage power supply for stable operation of the detector, and its ripple is between -0.01% and +0.01%. d) Low voltage power supply: Provides low voltage (+6V, 12V, 24V) for normal operation of electronic circuits. e) Spectrum amplifier: Matches with preamplifier and pulse amplitude analyzer, and has waveform adjustment function. f) Pulse amplitude analyzer (A/D): The number of channels of NaI (TI) gamma spectrum is not less than 512 channels. ) Analysis calculation and data output device: The gamma spectrum measurement system is connected to the computer, and the spectrum data is processed by the computer and output in the required format.
h) Sample box: According to the amount of samples and the shape and size of the detector, containers of different sizes and shapes can be selected. It can be a cylindrical sample box with a bottom not larger than the detector or a ring sample box matching the size of the detector. The sample box is made of plastic with low natural radioactive nuclei content. i) Anti-coincidence ring: It is composed of six identical sodium iodide detectors arranged in a ring. The crystal diameter of the ring detector is 20mm, the length is 30tm, and the photomultiplier tube model is GDB44D. ) Linear gate: The transmission signal is controlled by the gate signal. The gate is open only during the period of the gate signal; when there is no gate signal, the gate is closed.
k) Linear mixer: Linearly mix the signals from the anti-coincidence detectors into one signal output. These six signals are used as the input of the linear mixer, and the pulse amplitude should be consistent. 1) Single channel: Identify and shape the input signal output. m) Delay: Delay the input signal output. n) Mixer: Divide the input signal into two outputs: () Anti-coincidence unit: It has two input terminals, one is the coincidence input terminal, and the other is the anti-coincidence input terminal. If the two input signals of the anti-coincidence unit exist at the same time, it will not have an output pulse; only when there is a signal at the coincidence input terminal and no signal at the anti-coincidence input terminal, it will have an output pulse, and its input pulse amplitude is 3V and the width is 3us. 5.2 Main measuring instruments and technical indicators of high-purity germanium detector method The schematic diagram of the measuring device of the high-purity germanium detector method is shown in Figure 2a) High-purity germanium detector: The energy resolution of the 1332.5keV gamma ray is less than 3keV, and the relative measurement efficiency is not less than 15%.
b) Shielded room: See 5.1b).
c) High-voltage power supply: The high voltage of its input is continuously adjustable from 0kV to 5kV, without discontinuity, providing the high voltage for the detector to operate stably, and its ripple is between ~0.01% and +0.01%.
d) Low-voltage power supply: See 5.1d).
e) Spectrum amplifier: See 5.1c).
f) Pulse amplitude analyzer (A/D): The number of channels of the high-purity germanium gamma spectrum is not less than 4096.
g) Analysis calculation and data output device: See 5.tg).
h) Sample box: See 5.lh).
) Dewar flask: Dewar flask is filled with liquid nitrogen. High purity germanium detector is used at low temperature (197C), and high purity germanium detector should be cooled in liquid nitrogen for more than 6 hours before use. 3
SY/T 5252—2002
Commercial pure sales
Printer
Amplifier
Low voltage power supply
Commercial voltage source
Figure 2 Schematic diagram of the measurement device of high purity germanium detector method Energy calibration of sodium iodide and high purity germanium gamma spectrometer 6.1 Energy calibration of sodium iodide gamma spectrometer
Computer
Impulse amplitude analyzer
The energy calibration range is from 50keV to 3000keV. The monoenergetic or polyenergetic nuclides suitable for energy calibration are: 137Cs (661.7keV), 60C, (1173.2keV, 1332.5keV and the combined peak 2505.5keV eV). Record the characteristic gamma ray energy of the calibration source and the corresponding full-energy peak position, and do a least squares fit on the data. The nonlinear error is less than 0.5%. 6.2 Energy scale of high-purity germanium gamma spectrometer
The energy scale ranges from 50keV to 3000keV. The energy scale includes at least four scale points whose energies are evenly distributed in the required scale energy range. Record the characteristic gamma ray energy of the calibration source and the corresponding full-energy peak position, and do a least squares fit on the data. The nonlinear error is less than 0.5%: The single-energy or multi-energetic nuclides suitable for the energy scale are: 214Bi (609.4keV), 137cs (661.7kcV), 2Ac (911.1kcV),60 Co (1173.2keV, 1332.5keV and peak 2505.5keV),* K (1460.8keV).214Bi (1764.7keV),2TI (2614.7keV)-7 Preparation of standard samples
7.1 Preparation of standard samples for sodium iodide detector method 7.1.1 Selection requirements of standard samples (hereinafter referred to as standard samples) a) The standard samples should be national standard materials with national standard material number, validity period and standard material certificate b) A set of standard samples should have at least three types: potassium-containing standard sample with potassium as the main element, uranium-radium balance standard sample with asthenia as the main element, asthenia-containing standard sample with asthenia as the main element,
c) The content of the main element in the standard sample is generally 3 times that of the rock sample for potassium, 8 to 10 times that for wort and tantalum. d) The total uncertainty of the main element system in the standard sample should be controlled within 5%. 7.1.2 Preparation of standard samples
SY/T 5252—2002
Weigh the three selected standard substances separately for 100 hours, and the error shall not exceed 1 g. Put them into the sample box, compact them, and try to make the sample surface flat, add a box cover to seal it, and use it for 21 days to 28 days. 7.2 Preparation of standard samples for high-purity germanium detector method 7.2.1 7.1.1.
7.2.2 standard samples are weighed 300 g, and the error shall not exceed 10.1 g. Put them into the sample box, compact them, and try to make the sample surface flat, add a box cover to seal it, and use it for 21 days to 28 days. 8 Preparation of rock samples
8.1 Preparation of rock samples by sodium iodide detector method
The rock samples to be tested should be completely crushed and sorted by 0.3mm (60mm). The rock sample powder should be dried at 80℃:～100℃ for 4h, weighed 100g, and the error should not exceed +0.1g (reference value). Then put it into a sample box with the same shape and volume as the standard sample, compact it, make the sample surface as flat as possible, and seal the box for 21d-28l before measurement. When the rock sample is less than (100-0.1)g, the mass correction of the calculated three nuclides (K, L, Ih) should be carried out. 8.2 Preparation of rock samples by high-purity zirconium detector method
Prepare according to 8.1, and the rock sample should be weighed 300g, and the error should not exceed ±0.1g (reference value). 9 Measurement steps
9.1 Before measuring with a high-purity detection system, fill the Dolby bottle with liquid nitrogen to allow the detector to cool for more than 6 hours before starting up. Preheat the measurement system for 30 minutes
9.2 System energy calibration, the position of the calibration source relative to the operator is the same as when measuring the sample. The time used for calibration should ensure that the statistical error of the 137C61.7keV light peak count is within -15%! Within 15%: At the source addition peak 2505.5keV, the system energy nonlinear error meets the requirements of the sixth competition:
9.3 Measure the background of the empty sample box, standard samples, and rock samples. The measurement time of the background of the empty sample box, standard samples, and light samples shall be calculated according to the distribution of natural gamma radioactivity measurement time in Appendix 2 based on their radioactivity strength and measurement accuracy. The measurement time of the small standard sample shall ensure that the statistical error of the net count of its main element in the main energy window is within 1%·11%, and the net count of the weakest energy window shall be guaranteed to be more than 200. The measurement time is shown in Table 1. The weak rock samples in Table 1 refer to samples with a radioactivity intensity of about 3 times the lower limit of the spectrometer measurement: For the calculation of the instrument detection lower limit, see Appendix B..
Test system name
High purity equipment
Table 1 Measurement time of standard samples and various rock samples
Standard details Measurement time
Medium-strong rock sample measurement time
Meanwhile, the unit is upper
Background measurement time
9.4 During the measurement of standard samples or rock samples, the drift of 4K1460.8kcV light peak shall be checked, which shall be between -0.5% and 0.5%. 9.5 Each batch of rock samples shall be measured once, and 5% of the rock samples shall be randomly rechecked. Standard samples shall be measured at least twice, and the room sample box shall be turned on once and the background spectrum shall be measured once after the system is stable. 9.6 Each time the standard spectrum, rock sample spectrum, background spectrum and energy calibration spectrum are measured, the numbers shall be saved and the measurement results and uncertainty calculation of the test system 14.10.1 Sodium iodide detector method measurement results and uncertainty calculation 10.1.1 Adjust the energy calibration spectrum and use 37 (and Ca source 661.7keV: 1173.2k1332.5ke1SY1 The least squares fitting is performed on the four characteristic peaks of 5252-2(02
2505.5kcV and their corresponding energy values. According to the five energy window ranges (recommended values are: 150krV--5(0keV.500keV--1100keV, 1100keV-.1620keV, 1620kev--2000keV, 2000keV3000keV), the start and end channel addresses corresponding to the five energy windows are determined. 10.1. 2. Recall the measured standard sample spectrum, rock sample spectrum, and background spectrum of the empty sample box from the disk, and calculate the count of each energy window of each spectrum according to the energy window widths determined by them. 10.1.3. Calculate the average value of the five energy windows of each background spectrum of the empty sample box. 10.1.4. Calculate the average value of the energy windows of the three standard sample spectra. 10.1.5. Calculate the potassium (K), uranium (U), and thorium (Th) content of the rock sample. 10.1.5.1. Calculate the standard sample energy window count value according to formula (1): You ti-Yets
Nhi- Yun-Y ts
10.1.5.2. Calculate the rock sample energy window count normalization value according to formula (2): N
Where:
--subscript, indicating sample;
subscript, indicating standard sample:
Yw/t2\ Ye/t3
Yhit/t,-Ye;/t3
Footmark indicates the th standard sample, with values of 1, 2, 3:Footmark indicates the th standard sample, with values of 12, 3;Footmark indicates the th energy window of the standard sample, rock sample and background, with values of 1, 2, 3, 4, 5:Measurement time of standard sample, min;
Wherein:
Measurement time of rock sample, min;
Measurement time of background in empty sample box, min:The th energy window of the th standard sample Count; the 1st energy window count of the th standard sample;
the th energy window count of the th rock sample;
the th energy window count of the background of the empty sample box;
the th energy window normalized value of the th standard sample; the th energy window normalized value of the th rock sample
According to formula (3), the response coefficient matrix A is calculated as: A=NC-1
The normalized value matrix of the positive energy window counts of the three standard samples is: - the inverse matrix of the actual content of the standard
1).1.5.4, the content of the rock sample is calculated as: X- [A'WA]-IA'WN.
Wherein;
X is the content matrix of each element in the rock sample, and the units of potassium, tantalum and sodium are mg/g, g/g and ug/g respectively; AT
is the transposed matrix of A;
is the diagonal matrix composed of weight factors W (W, = 1/Nu, = 1.2,, 5); the rock sample is the column matrix of individual energy count values. 10.1.6 Calculate the total natural net count of the rock sample according to formula (5): t
is the total natural net count of the rock sample, x.
Yt:/te)
SY/T 5252—2002
10.1.7 Uncertainty of measurement results: 5% of the rock samples are randomly rechecked. The potassium (K), uranium (U) and thallium (Th) contents of each rock sample are calculated according to 10.1.1 to 10.1.6. The uncertainty of two repeated measurements and the machine uncertainty shall meet the requirements of Table 2. Table 2 Uncertainty and relative uncertainty of measurement results of sodium iodide detector method Name
Potassium (K)
Total natural gamma net count (GR)
Content mean calculated by formula (6):
Uncertainty calculated by formula (7):
Content range
25mg/g
25mg/g
<6jg/g
212/4/g
12ug/g
O H,-H,
The relative uncertainty is calculated according to formula (8):
Uncertainty
Where:
The j-th nuclide content of the rock sample, the value is 1.2,3: The i-th measurement of the rock sample, the value is 1,2; The j-th nuclide content of the rock sample; H
The average content of the i-th nuclide of the rock sample;
The uncertainty of the j-th nuclide content of the rock sample in the 1st measurement; The relative uncertainty of the j-th nuclide content of the rock sample in the ith measurement. 10.2 Calculation of measurement results and uncertainty using the high-purity germanium detector method
10.2.1 Retrieve the measured standard sample spectrum, rock sample spectrum, and background spectrum of the empty sample box from the disk respectively, and calculate the counts of each main energy peak: select 351.9keV, 609.3keV, 1120.4kcV, [764.5keV energy peaks for axis; select 583.1keV, 911k-V, 2614.5keV energy peaks for cylinder; select 1460.7keV energy peak for potassium, Www.bzxZ.net
10.2.2 Calculate the average value of the main energy peaks of the background harmonics of the empty sample box. 10.2.3 Determine the average values of the main energy peaks of the main elements in the spectrum of the standard samples, SY/T 5252-202
10.2.4 Calculate the potassium (K), uranium (U), and yttrium (yttrium) contents of the rock sample, see Wu (9), (Cw:/t--KB,/+g) /W,
Dg-(C-kn) /w)
Wherein:
Use the counting of the first energy peak of the first parent nucleus system of the sample to calculate the content of the first parent nucleus in the rock sample. The units of potassium, potassium, and yttrium elements are mg/g, ug/g, and g/g respectively: The units of potassium, potassium, and yttrium elements in the standard sample are: /g, [g/g; W. - rock sample mass, ;
standard sample mass, m;
the number of energy peaks of the th parent nuclear system in the rock sample; the number of energy peaks of the th th nuclear system in the standard sample; the number of energy peaks of the th nuclear system in the background of the empty sample box: measurement time of the standard sample, min;
rock sample measurement time, iin;
t3- measurement time of the background of the empty sample box, mino. The weighted average value of the contents of the same isotope with different energies is used to calculate the content of the isotope, that is, the content of the isotope in the rock sample is obtained according to formula (10). Total natural gamma net counts in the energy range of 150keV-3000kcV (GR (cps): GR = C/W./t\:KB/ts
W_rock sample mass, g
Total counts in the energy range of 150keV-3000keV in the rock sample spectrum -Total counts in the energy range of 150keV.-3100kV in the background spectrum of the empty sample box; KB-
Measurement time of the rock sample, min;
Measurement time of the background of the empty sample box, mine10.2.6 The uncertainty of the measurement results is shown in 10.1.7. The uncertainty and relative uncertainty of repeated measurement of rock samples are shown in Table 3. Table 3 Uncertainty and relative uncertainty of measurement results of high-purity pyrolysis detector method Name
K| ... 5252—2IM02
11.2 The test instruments and equipment shall determine the accuracy of the system measurement based on the single-item metrological verification. If the system accuracy cannot be determined, a reproducibility test shall be conducted and the discreteness of the test results shall satisfy formula (1).
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