This standard specifies the conventional method for analyzing low specific activity gamma radioactive nuclides in solid, liquid or homogeneous samples that can be converted into these two physical states using a semiconductor gamma-ray spectrometer with high energy resolution. This standard is applicable to samples whose analytical activity is greater than the detection limit LD of the spectrometer and whose gamma characteristic spectral lines of each nuclide can be distinguished. GB/T 11713-1989 Standard method for analyzing low specific activity gamma radioactive samples using semiconductor gamma spectrometer GB/T11713-1989 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Standard methods of analyzing inw specitic gamma radioaetivitysamples by semiconductor gamma spectrometers 1 Subject content and scope of application
GB 11713 89
1.1 This standard specifies the conventional method for analyzing low specific activity microradioactive nuclides in bulk, liquid or a mixture of these two substances by using a semiconductor gamma spectrometer with high energy resolution. 1.2 This standard is applicable to samples whose analytical activity is within the detection limit of the spectrometer and whose characteristic spectral lines of each nuclide can be distinguished. Therefore, generally, the sample is only subjected to simple physical treatment such as drying, powder screening, stirring, etc., without chemical separation. When the sample must be chemically separated, its parameters such as yield should be measured according to relevant procedures. 2 Method Overview
2.1 This standard stipulates that high purity ion (HPe) or lithium drift zirconium (Li) ion detectors should be used when measuring. Where possible, the former should be given priority.
2.2 The typical instrument used in this standard is shown in Figure 1. Under lower radioactivity, a spectrometer with sufficient sensitivity should be used, such as a low background spectrometer with anti-shielding, a spectrometer-anti-diffraction spectrometer, etc., and an acid source
Figure! Energy evaluation instrument block diagram
low line telephone
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2.3 The energy spectrum is the distribution of the counts of the rays according to their energy. Figure 2 is a typical energy spectrum of CS. In the energy spectrum, the location of each absorption peak (also called total energy peak or photoelectric peak) and the energy of the incident ray form the basis for the qualitative application of the energy spectrum; the net area under the total absorption peak is proportional to the number of rays of that energy acting on the detector, which is the basis for the quantitative application of the energy spectrum. In the analysis of the total absorption peak area, the Compton continuous spectrum and the counts of the technical background must be deducted. In the analysis of low-activity radioactive nuclides, the interference of the Compton continuous spectrum and the bed should be suppressed or reduced as much as possible. Approved by the Ministry of Health of the People's Republic of China on September 21, 1989 and implemented on July 1, 1990. 3 Terms, symbols and codes Aayr gy g GB 11713 89.hakevm.tt|| Sheng Bai Pa Line CS Energy Spectrum 3.1 Total nuclide detection efficiency R. (3) Total deicaion efficiency Fu nuliedeFor given measurement conditions and nuclide, the detected radiation efficiency is the ratio of the total number of decays of the nuclide in the same radiation source! 3.2 Total absorption detection efficiency (E): For a given measurement condition and the characteristic radiation emitted by the nuclide, the net count detected in the total absorption peak is the ratio of the total number of radiations emitted by the radiation source and the nuclide in the same time interval. 3.3 Total radiation detection efficiency (R): For a given measurement condition and the characteristic radiation energy emitted by the nuclide, the net count detected in the total absorption peak is the ratio of the total number of radiations emitted by the radiation source and the nuclide in the same time interval. 3.4 Total absorption detection efficiency (R): For a given measurement condition and the characteristic radiation energy emitted by the nuclide, the net count detected in the total absorption peak is the ratio of the total number of radiations emitted by the radiation source and the nuclide in the same time interval.
3.5 Background (-) Hackground
Counts caused by other factors other than the radiation source being measured, such as cosmic radiation radiation pollution, electromagnetic interference, etc. in the energy range of the spectrum,
3.6 Hir. Ne (F --- ru): bottom ftorn teckground and Comptnn sceateing In the energy range being studied, except for the spectrum counts of the event being studied, the interference spectrum caused by other factors. 3.7 Full width at half inaxinium (FWHM) The distance between the integers of the two points at the peak and half inaxinium on the distribution surface composed of only a single peak. Energy resolution FWHM (E) energytesolution3. 8
The ability of the detector to distinguish the incident electron energy. For a monoenergetic ray of a specified energy, it should be the value of the half width of the full absorption peak expressed in energy units.
3.9 Peak disturbance: peak disturbance
o# 1171389wwW.bzxz.Net
The interference caused by the total absorption peak and escape peak of the radiation from the source to the peak to be analyzed in the spectrum when the peak is too close to be completely resolved and analyzed in the spectrum
3.10 Compton scattering disturbance: The interference of the radiation source with multiple energy rays, among which the Compton scattering of higher energy rays on the lower energy rays (the interference caused by the total energy peak analysis
Background disturbance: The interference of the background on the physical quantity to be measured (such as the total absorption peak). 312 Spectrum difference disturbance: The interference of the density difference between the sample to be measured and the calibration source (more than 10%) on the physical quantity to be measured. 4 Instruments
4.1 Energy spectrometer. Figure 1 is a block diagram of a semiconductor spectrometer for low-level radioactivity measurement. 4.1.1 Semiconductor X-ray detector. The sample is usually not chemically separated. Therefore, in most cases, a high-energy-resolution semiconductor detector is used. In addition, a detector with high detection efficiency (smaller sensitive area) is required as much as possible. The energy resolution and relative detection efficiency of the semiconductor detector currently widely used for the 1332keV line of Cu are between 1.7keV and 2.4keV, respectively. 4.1.2 Shielded room The detector is placed in an external radiation shielding room made of metal with a thickness of at least 10 cm (for 1460 keV radiation of 1000 keV). The height of the shielding room from the detector is required to be at least 13 m. If the shielding room is made of lead or lead lining, and the distance from the detector is less than 25 cm, the inner surface of the shielding room should have a multi-layer inner shielding with decreasing atomic number. The inner lining is composed of 2.~3 mm thick organic glass, 0.41 mm copper and 1.6 mm cadmium. The shielding case should have a door or hole to allow access to the product. 4-1.2.1 The detector should not contain contamination other than natural radioactive nuclei in the 20 keV-3000 keV energy range: The ratio of the natural background count rate measured in the shielding room to the total absorption relative detection efficiency of 1332 keV radiation of 1000 keV should be less than 50 0i number/extension logarithmic rate)
4.1.3 High voltage power supply, select the detector high voltage according to the maximum working state of the detector used. 3000V5000V high rejection power supply is required. The power input voltage is adjustable from 0 to 100V, the voltage should not be greater than 0.01%, and the current should not be less than: 00.4.1.4 The amplifier should have a voltage adjustment and match the preamplifier and multi-channel pulse amplitude analyzer.4.1.5 Multi-channel pulse amplitude analyzer. The number of channels of the multi-channel analyzer should not be less than 4096. The channel width and number of channels of the multi-channel analyzer should be selected according to the complexity of the energy spectrum, the range of the radiation energy distribution and the energy distribution of the detector.4.1.6 It is recommended that the instrument system used should be products provided by the same manufacturer to avoid the combination of instruments from different manufacturers. The stability of the entire spectrometer system is required to be 332kV radiation of \Cc! When the total absorption peak is located near the 40°C channel, the peak position drift shall not exceed 2 channels within 21 hours.
4.1.7 Data processing system, which receives the spectrum data of the multi-channel analyzer and processes it retroactively. The data processing system is composed of computer equipment.
4.1.7.1 Data processing system software equipment should include microcomputers and matching reading and input devices. The reading equipment should include X-ray diffraction analyzers, digital printers, hard and soft disk drives, microstrip recorders, and paper tape punchers. These devices should be selected according to work needs.
4.1.7.2 Data processing system software equipment should include various routine programs for analyzing Y spectra,Other basic procedures include energy calibration, efficiency calibration, spectrum smoothing, peak selection, product calculation and peak separation. In addition, some application procedures need to be customized according to the actual measurement case. 4.2 Sample container. It should be made of low-radioactive materials or materials, such as polyethylene, organic glass, stainless steel, etc. According to the characteristics of the measured object, a suitable container shape should be adopted, such as round island shape, inverted shape, etc. If possible, a sample container with a different shape should be considered. 4.3 Sample tray. When the sample is a non-powdered solid, in order to prevent the sample from contaminating the detector, the sample must still be placed in the sample tray during the test. 4.4 Absorber: For low-concentration test pads, the sample is relatively large, and it is necessary to absorb the spray or radiation to avoid being carried away. 75
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If an absorber is needed, lead with a thickness of 6.4 mm can be used; lead with a sensitivity of 1.6 mm can be used. The design of the absorber should have a complete shadow shielding effect on the direct radiation from the sample. 4.5 Shielding Low-background spectrometer is an effective device for analyzing samples containing low-activity non-cascade radiating nuclides (such as K, Mn, Cg), and nuclides with a long metastable energy level lifetime (such as R), as well as auxiliary radiation and peak analysis. 4.6 Coincidence-anticoincidence spectrometer is an effective device for analyzing samples containing extremely low-activity cascade radiating nuclides such as Co). 5 Calibration source preparation and system calibration
5.1 Calibration source preparation. In the energy spectrum analysis, the user usually uses a calibration source prepared by adding an appropriate amount of standard radioactive material into an appropriate material to perform system calibration and detection efficiency. 5.1.1 Matrix material refers to the basic material composition that constitutes the calibration source. 5.1.1.1 The selection of the material should meet the following requirements: a. be similar to or similar to the main chemical composition of the sample; b. be the same or similar to the sample in physical form, such as solid, state, particle size, density or specific gravity; e. compared with the sample, its radioactivity can be ignored; and it is easy to be combined with the added standard radioactive material: physically and chemically stable.
5.1.2 Standard radioactive material: refers to various standard radioactive solutions, bulk (powder) and gas sources or standard sources. They must be calibrated by national metrology reference instruments or metrology reference instruments recognized by the statutory measurement department; and be provided to users after being signed and stamped by the statutory accreditation unit. The quality of standard radioactive materials imported from abroad shall be approved by the national measurement department. 5.1.2.1 The standard radioactive materials used by the user shall have the original or duplicate of the inspection certificate and other relevant information to ensure the reliability of the transfer process.
5.1.2.2 The standard radioactive materials used shall have a clear validity period and other provisions. 5.1.3 Calibration source. A radioactive source with known nuclear activity made of appropriate matrix material and appropriate amount of standard radioactive material. 5.1.3.1 The calibration source shall meet the following requirements: and: uniformity. Whether it is matrix material or standard radioactive material, its distribution in the calibration container is uniform, and no significant specific adsorption through the wall of the container will change its distribution. b Simulation. Except for the known sensitivity and activity, other properties, such as density, shape, composition, etc., are similar to or close to the sample. Stability. During the storage and use period, this product will not produce precipitation, deliquescence or condensation, and will not be susceptible to foreign matter or mildew. d High purity. Except for the added radioactive standard substances, the composition shall contain no or very little other radioactive impurities: e.
Accuracy. Under the premise of 99.7% confidence, the uncertainty of radioactive activity shall be less than ±5%; f: Sealing: It shall be sealed in a container with the same material and shape as the sample container. 5.1.4 Matrix background source. According to the requirements of the preparation of the validation source, only the bone marrow material prepared is used as a simulated source for deducting the matrix background of the calibration source. 5.7.5 Calibration source test sample and calibration test. According to the same method used to prepare the calibration source, prepare several test samples with known activities. They should include test samples of single radionuclides and multinuclear mixtures. Measure the test samples on the spectrometer 1; and analyze them with the calibration results. Compare the analysis results with the known activity of the test samples to judge the reliability of the calibration source and the feasibility of the spectrum analysis procedure. 5.2 Energy calibration. The relationship between the gamma-ray energy and the channel number is calibrated by the calibration source (or working source) of the instrument system. The gamma-ray energy emitted by the radiation source is between 50 and 3 keV, at least in the range of the radiation distribution to be investigated. Table 1 lists the main nuclides and their main gamma-ray energies suitable for energy calibration. The energy calibration covers the energy range under study with four different energies:
GB11713
Table 1 Commonly used nuclides and their main nuclear parameters suitable for energy and efficiency scales Half
270 days
30.174 years
241 days
E.2 pieces per year
+ continuous energy, key
59.54(0.259)
81.0(0.36),302.7(0.196),355.9(0.67)122.06(0.852),136.47(0.1-1)146.4(0.48)
320.03(0.102)
1G61.64.0. 851)
834-83(1, 00)
1 115. 52(0. 507 3)
1 173. 2(0. 998 6),1 392, 46 (0. 999 86)121.78(0.2b4)+$44.81(0,246),r8.87(0. 120),964. 01(0. 132),1 D85, 83(0. 097),1 112. 64(D. 124),1 408. 2(0. 19X)[ 460.83(0.11)
x98.C2(0.914)-1 836.1(0.994)510.8(0.23>,583,14(0.86),2611,6(1.c0) Note: The numbers in parentheses in the table indicate the emissivity of the corresponding energy rays. 5.2.1 If the energy range studied is 50~/2 000 keV, the system gain should be adjusted so that the 6f1.6 of 137(:x) The total absorption peak of keV rays is approximately at one-third of the full scale of the multi-channel analyzer. Record the ray energy and the total absorption peak position: keep the value unchanged, and then determine the total absorption peak positions of at least three other lines with different energy ranges, and record their peak positions and the corresponding ray energies. 5.2.2 On rectangular coordinate paper, draw a graph of each ray energy and their total absorption peak position. If the instrument operates normally, they will be linearly related, or have a nonlinear deviation of up to about 2%. If the deviation from linearity is serious, the sample should not be analyzed. According to the measurement requirements, a linear least squares fit or a nonlinear quadratic least squares fit should be made to the energy or -channel graph to obtain the corresponding energy calibration coefficient. 5.2.3 During the sample measurement, the above operation process should be repeated for at least two energies of radiation per day. The energies of the auxiliary radiation used should be close to the low energy end and the high energy end of the calibration energy range respectively. If the peak value remains basically unchanged, the calibration data remains applicable. If the change is significant, the entire calibration must be redone.
5.3 Detection efficiency calibration. To quantitatively determine the radionuclide content in the sample, the spectrometer system detection efficiency must be calibrated: calibration methods - there are nuclear total detection efficiency, radionuclide total absorption peak detection efficiency, radiation total detection efficiency and radiation total absorption peak detection efficiency calibration methods. However, the most widely used are the nuclear absorption peak detection efficiency calibration and the radiation total absorption peak detection efficiency calibration. 5.3.1 The calibration of the total absorption peak detection efficiency of the nuclear search is carried out as follows: 5.3.1.1 Under the same conditions as the sample measurement conditions, respectively obtain the calibration source (or standard source) spectrum and its background source spectrum with known nuclei and their clarity:
5.3.1.2 Use the calibration source spectrum to obtain the matrix background source spectrum after time normalization (abbreviated as benzene background normalization): 5.3.1.3 Subtract the matrix background normalization spectrum from the calibration source spectrum to obtain the net spectrum of the calibration nucleus. 5.3.1.4 Select one or more total absorption peaks of the characteristic rays from the spectrum, and obtain their net peak area (i.e., the peak area after removing the interference of the Condon scattering):
5.3.1.5 Calculate the ratio (R,) of the total absorption peak net area of ​​the selected characteristic line to the total number of decays of the element in the calibration source in the same time interval as the calibration source spectrum. 5.3.2 The calibration of the gamma-ray full-time peak detection efficiency shall be carried out as follows: 159
5.3.2.1 General procedure for calibration
GB 11713—89
5.3.2.1.1 Carry out the operation sequence of 5.3.1.1 to 5.3.1.3 in 5.3.1. in sequence. 5.3.2.1.2 Select the total absorption peak of the non-cascade characteristic ray of the nuclide from the net spectrum and obtain its net peak area. 5.3.2.1.3 Calculate the ratio of the total absorption peak net peak area of ​​the selected characteristic ray to the total number of rays of this energy emitted from the calibration source in the same time interval of obtaining the valid source spectrum, (E,). 5.3.2.2 If the selected characteristic ray is a cascade radiation, make corrections for the additive effect of paired cascade radiation when calculating the net peak pre-product. 5.3.2.3 For the case where only the energy of the ray is changed, the relationship between the total absorption peak detection efficiency of the ray and the energy base should be obtained as follows: 5.3.2.3.1 In the energy range of 50kcV=2000 (or 8000) keV, select at least seven rays with different energy levels and calibrate their total absorption peak detection efficiencies &,.
5.3.2.3.2 On the double logarithmic coordinate paper, plot the total absorption peak detection efficiency (H) and the radiation energy development, and then draw the linear efficiency calibration curve.
5.3.2.3.3 Fit the efficiency calibration curve. The general form of the fitting coefficient is: Ine'..(E') -- Ea,(n)
Where: t..(E.)
Efficiency is calculated by the linear fitting function:
Fitting constant:
The highest order of the polynomial, more than one 1;
The number of efficiency calibration points participating in the curve fitting in the corresponding energy range. -()
5-4 Under the conditions consistent with the sample measurement conditions, obtain the spectra of the calibration source and the basic background source and store them for the computer or the plotting spectrum method to analyze the mixed spectrum of color nuclides. If the energy range is calculated, It is necessary to determine the energy (or mass) range of each spectrum used for calculation. For example, if there are five radionuclides in the sample, there are five spectra to be calculated. For each spectrum, the net counting rate after deducting the matrix cloud base spectrum is obtained, and then the ratio of the net counting efficiency to the total counting rate of each spectrum is calculated. This ratio is used as a coefficient in the formula for calculating the content of each nuclide in the sample. This process must be repeated for each nuclide calibration source in order to obtain the coefficient of the sum. Therefore, if there is a nuclide in the sample, it must be determined. \ prime number. Once all coefficients are measured, they do not need to be re-measured as long as the system's energy distribution, gain and measurement conditions remain unchanged. However, if the above conditions must change, these coefficients must be re-measured! 5.5 When the calibration source and the sample loading or the degree of closure are greatly different, the efficiency calibration should be corrected. In particular, when the characteristic peaks of the nuclide content in the large sample are analyzed with radiation with energy lower than 200kev, the interference of density differences cannot be ignored. 5.6 Quality control chart. The spectrometer used should be calibrated regularly, and the material must be used when measuring the sample. The peak position and efficiency are checked with a reference source (or working source) with stable physical and chemical properties. If possible, check every day to ensure that the instrument works properly. The quality control chart drawn with the calibration source and the instrument background center will generally find serious system problems. The quality control chart can determine whether the instrument system works in accordance with statistical laws and whether it works in the way predicted by the Poisson distribution. If there is no human fluctuation, it is best to use the long-term average of the background and calibration data when calculating the actual standard.
6 Measurement steps
6.1 According to the measurement object, prepare a sample with uniform radioactivity. 6.2 Place the sample in the measuring instrument. If the calibrant to be measured is the decay product of a certain nuclide, the measuring container should be sealed and the measurement should be started only when the nuclide in the sample reaches radioactive equilibrium. Otherwise, reasonable changes must be made to the unbalanced nuclide during data processing. 6.3 Place the sample on the detector to measure the spectrum. According to the energy (or address) of the total absorption peak and the history of the sample, the nuclides present in the sample can be identified. If the evidence is not sufficient to distinguish the nuclides contained in the sample, it is necessary to conduct decay studies or chemical analysis of the components. Sometimes both studies must be done at the same time. At the beginning and end of the measurement, the background count rate of the instrument should be measured and the average value should be calculated. At the end of the measurement, the energy scale at the beginning should be calibrated. When there is basically no difference between the two, the nuclide identification can be guaranteed to be reliable. 6.4 Try to obtain a suitable source to measure the total absorption peak of the newly added nuclide and the detection efficiency of the peak. Or as described in 5.3.2.2, obtain the total absorption peak detection efficiency.
GB 11713-89
6.5: The analytical error requirement of the sample is the main factor determining the counting time. Therefore, it is generally believed that 24 h is a reasonable recording length.
7 Calculation
7.1 If the calculation is only carried out in the energy range, the activity of each nuclide (or component) in the sample must be obtained by algebraic methods. The data can be expressed as a single equation and then the simultaneous equations are solved. However, for high-energy and high-resolution flat-body spectrometers, it is recommended to use a spectrum analysis program with multiple peak analysis capabilities written based on various fitting methods. They usually combine the total absorption peak net counting efficiency and then obtain the nuclide activity. 7.2 In the analysis of very low activity samples, the total absorption peak count statistics are often not high, and the analysis of complex very weak spectra is still an ongoing research topic.
7.3 The activity of the nuclide in the sample is calculated by using the total absorption peak detection efficiency of the nuclide. Usually a smaller uncertainty is introduced. At this time, the activity of the nuclide to be measured in the sample is calculated according to (2):
A(F) = O(E,/-n(F,
Wherein, tA(E)
is the activity of the nuclide in the sample;
is the selected characteristic peak count rate of the nuclide at the measurement moment: the total absorption peak detection efficiency of the nuclide,
is the specific infrared ray energy
7.4 The activity of the nuclide in the sample is calculated by using the total absorption peak detection efficiency of the ray: Generally a larger uncertainty is introduced. At this time, the activity of the nuclide to be measured in the sample is calculated according to formula (3):
A(E,) = (E)/T - r--(E)
Where: A(F,)
The activity of the nuclide in the sample;
: The count rate of the selected characteristic peak of the nuclide measured: ·Ray peak measurement efficiency,
The probability that the nuclide emits the selected characteristic ray each time it decays: (3
7.4.1 If the selected characteristic ray is a characteristic ray in the cascade of ray of the nuclide, and there is a non-negligible coincidence addition effect in the spectrum, the coincidence addition effect should be corrected in the calculation. 8 Report
8.1 The sample analysis report shall include the nuclide confirmation data and appropriate human uncertainty. It is recommended to report twice the standard deviation for each uncertainty, i.e. 95% confidence level. However, no matter how large the uncertainty is reported, it should be marked or mentioned in the text to avoid confusion,
8. 2 Calculate the standard deviation of the sample count rate according to formula (4). :x
Where: N.
Integral count of samples in the selected energy range (passband is the full reception peak) including the base: Base integral count in the selected energy range!
Sample counting time,
8.3 In low-level radiation measurement, counting statistical error is the main source of the total uncertainty of the analysis result. However, when there are several error sources, such as counting statistical error and detection efficiency error, the error synthesis must be carried out according to the error propagation principle and reported in the report.
&4 The report should state the basic nuclear parameters used, such as the half-life of the nuclide, the emission rate, etc., and the source of the literature. This is because many basic nuclear parameters have not yet been completely and reliably determined by current technology. 8.5 When reporting the results of low-activity sample analysis, two problems are often encountered: the uncertainty term is greater than the sample value, and the sample count rate minus the background (or base) result is a negative value. For the first case, the sample value and uncertainty are usually reported as usual, such as 0.51.1.i
A1 Basic concepts and mathematical expressions
Glh 11713:89
Lower limit of illumination in low-level measurement
(Supplement)
A1.1 Judgment limit L. It is the standard for judging whether there is radioactivity exceeding the background in the sample. When the measured net count of the selected sample is W, the conclusion can be made: "Detected", that is, there is radioactivity exceeding the background in the sample. When L, a small conclusion can be made: "Not detected", that is, there is no radioactivity exceeding the background in the sample.
A1. 1. 1 The mathematical expression of the judgment limit L is: = K. VN. + N.
Where: Ne,
The total count of the background plus the sample is:
N. --·The value of the virtual count,
, corresponds to the probability of making an erroneous judgment that the radioactivity in the sample exceeds the background when the actual radioactivity in the sample does not exceed the background. Table A shows the corresponding relationship between K and ~. A1.2 Detection limit Lv. It answers the question of whether it can be detected. When 1, it can be concluded that the radioactivity in the sample can be detected. When W is less than 1, it can be concluded that the radioactivity in the sample cannot be detected. A1.2.1 The mathematical expression of the detection limit Lv is: Ln = (K.- K)N., + N.
and when there is actually radioactivity above the background in the sample, the wrong judgment is made that there is no radioactivity above the background. In the formula: R. —
The probability β is corresponding to the low. Table A1 gives the corresponding series of α, B. The commonly used values ​​corresponding to
A2 Simplified mathematical form
For low activity measurements, if the total count N can be compared with the base W, then NαN; and considering that the total count rate and β are at the same level, then. =K, one. At this time, the balanced expression of L and Lu is obtained, TK/2N.
Jn2K V2N = 2L
A3 Application Notes
-(A3
A3.1 Although the detection efficiency factor is not included in equations (A1) to (A4), the count items N and F have implicitly included the detection efficiency factor.163
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A3.2 For a spectrometer, the detection efficiency is related to the shape of the radiation source, the energy base of the radiation, and the measurement disk. Therefore, when giving the detection limit and other parameters of a spectrometer system, it must be clearly stated. The shape of the source will be a point source (point source, volume source, etc.) and the counting time.
A3.3 Considering the radioactivity of the nuclide, the detection efficiency of the instrument and the measurement time: After the same, the detection limit can be transformed into the nuclide activity detection limit An expressed by the activity of the nuclide in the sample: which is: inth
In the formula:
p() and (
For the background count rate in the total absorption peak energy region of the selected characteristic ray of the micro-estimated nuclide: Background measurement year time;
nuclide total absorption peak detection efficiency and ray total absorption barrier detection efficiency; the emission probability of the characteristic ray selected by the extreme search (A52
43.3.1 In order to facilitate the performance comparison between different spectrometer systems, this appendix recommends: using the total absorption peak 1/10 barrier full width (FWTM) as the full absorption peak calculation energy range, respectively estimate the spectrometer system for Am, 137C when the counting time is 1000 minutes and the confidence probability is 95%; and \ The detection limit of K point source. A3.4 In multi-nuclear spectrum measurement, there will always be Condensation radiation. At this time, the N, or \ in the expression of the detection limit of the spectrometer system should be understood as the basis in this energy range. Additional explanation:
This standard is proposed by the Ministry of Health: This standard is drafted by the Industrial Dust Laboratory of the Ministry of Health. The main drafters of this standard are Su Qiong and Shi Chongxing. This standard is interpreted by the Industrial Dust Laboratory of the Ministry of Health, a technical unit entrusted by the Ministry of Health. 152
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