Study on influencing factors associated with the analysis of 226Ra gamma spectra / 中华放射医学与防护杂志

Objective:To measure the influencing factors associated with the analysis of 226Ra gamma spectra in order to obtain more acurate and precise measuring result on a basis of further optimizing the gamma spectrometry method for 226Ra activity. Methods:A laboratory-based HPGe gamma spectrometer was used to carry out the studies on tracking measurement of sample sealing time, measurement of background fluctuation with lead shielding, analytical method, and selection of characteristic gamma ray energy peak of its daughter nuclides in 226Ra measurement. Results:After the sample was sealed for 12 d, the decay products of 226Ra- 222Rn basically reached equilibrium. The day and night fluctuations of 222Rn in the shielded lead room were obvious but had no obvious regularity. The way of filling nitrogen into the shielded lead room could reduce or avoid the influence of background fluctuations. For 31 soil samples measured after 23 days of sealing, the result of using the efficiency curve method showed that the 226Ra result calculated from the 351.9 keV energy peak were generally higher than the 609.3 keV energy peak, and the higher ratio ranged from 8.0% to 20.7%. The result of relative comparison method showed that the deviation ratio of the two peaks ranged from -4.1 % to 10.3 %. Conclusions:It is recommended to consider the uncertainty attributed from decay equilibrium about 4 % of measured at 12 d after the sample is sealed. When filling nitrogen through the shielded lead chamber to avoid background fluctuations, attention must be paid to the matching relationship between the volume of the lead chamber and the nitrogen filling flow. When the efficiency curve method is used to analyze the activity of 226Ra, the 214Bi ( 609.3 keV ) energy peak has the effect of cascade coincidence addition, so 214Bi(609.3 keV) energy peak should be avoided. When the relative comparison method is used to analyze the activity of 226Ra, both two energy peaks of 214Pb ( 351.9 keV ) and 214Bi ( 609.3 keV ) can be used.

Measurement of 131I activity in thyroid of workers at the place of radioiodine therapy in six hospitals / 中华放射医学与防护杂志

Objective:To investigate 131I activity in thyroid of workers at the place of radioiodine therapy and its main influencing factors. Methods:In terms of the types of hospitals, six hospitals that performed radioiodine therapy procedure were selected by quota sampling in the provinces of Shandong and Shanxi. 131I activity in thyroids of 76 workers at the place of radioiodine therapy was measured directly, and their internal doses were estimated. Results:131I activity in thyroids was found to be above the detection limit for 29 subjects (38.16%) in five hospitals. The maximum value of 131I activity was 2 468.45 Bq for a doctor who was responsible for manual distribution of radioisotopes. In general 131I activities in thyroid of workers at the place of radioiodine therapy of six hospitals were not significantly different ( P>0.05). But the measurement result in the hospitals where radioiodine was distributed manually were significantly higher than that in the hospitals where radioiodine was distributed automatically ( Z=1.75, P<0.01). Thyroid measurement result of 12 workers in two hospitals where radioiodine was distributed manually were all above the detection limit, with medians of 324.59 Bq and 331.98 Bq, respectively. The medians of 131I activities in thyroid of 12 staff in the remaining 4 hospitals were all below the detection limit. The detection frequencies of 131I above dose limit were 32.61%, 25.00%, 10.00% and 0. The measurement result for the doctors who participated in distributing 131I and the relevent cleaners were significantly higher than for the doctors who did not participate in distributing 131I at the same hospital ( Z=2.44, 2.12, P<0.05). Conclusions:There was a significant difference in the internal exposure level among workers at the different places of radioiodine therapy. Using automatic loading device could reduce the internal exposure level of the workers at the place of radioiodine therapy. It is necessary to strengthen the radiological protection for workers at the control area of the place of radioiodine therapy.

Application of sourceless efficiency calibration in activity measurement of gas source in Marinelli beaker / 中国辐射卫生

Objective To optimize the Marinelli beaker with the simulation of Laboratory Sourceless Object Calibration Software (LabSOCS), to investigate the detection efficiency of HPGe detector in measuring noble gas, and to provide a reference for the measurement and optimization of noble gas effluent from nuclear power plants. Methods LabSOCS was used to establish a Marinelli beaker model to investigate the relationship of gamma ray detection efficiency of noble gas with gas components, gas density, size and volume of the Marinelli beaker, and the shape of source container. Results The gas components had little effect on the detection efficiency of the noble gas in the Marinelli beaker. The gas density had a relatively great effect on the detection efficiency of low-energy gamma ray. The Marinelli beaker of appropriate height and radius enabled the HPGe detector to get better measurement results. For the BE5030 HPGe detector, the highest detection efficiency of the Marinelli beakers of different volumes were observed at the location where the radius/height ratio was 0.7, and the optimal values of height and radius were given for the Marinelli beakers of different volumes. Conclusion Choosing Marinelli beaker of the appropriate size can improve the detection efficiency of noble gas in the effluent from nuclear power plants.

A review of intercomparison of measurement results by gamma-ray spectrometry in three laboratories in China and Japan / 中华放射医学与防护杂志

Objective:To improve the radionuclide measurement technology by γ-spectrometry throuth a review of the intercomparisons between China and Japan results over the past 20 years.Methods:Before the beginning of each intercomparison, one of participating laboratories was agreed to be responsible for preparing the samples for the intercomparison. By intercomparison of the measurement results arnong the laboratories some potential problems during the sample pre-trement or analysis were found and solved.Results:The intercomparisons had been carried out for 11 times over the past 20 years. Totally 290 measured and analyzed results had been obtained from 20 samples of six categories. The proportion 95.5% of measurement results were in agreement with each other within the deviation range.Conclusions:The measuring and analytical capability of the laboratories involved were tested. The intercomparisons also provide long-term quality assurance measures for the radionuclide measurement and analysis in each laboratory.

Summary and analysis of national-wide γ-spectrometry assessment for radiological health institutions from 2015 to 2017 / 中华放射医学与防护杂志

Objective@#To standardize the operation and data processing in radiological health institutions in China, in order to promote the assessment of γ-spectrometry, improve the measurement and analysis capabilities of each laboratory, and accordingly improve accuracy of environment sample measuring.@*Methods@#By collecting the values of 232Th, 40K and 137Cs contents in soil samples from 2015 to 2017, the assessment results of γ-spectrometry laboratores were summarized and analyzed.@*Results@#The technical institutions from 25 provinces were involved in the assessment until 2017, including disease control and prevention centers, entry-exit inspection and quarantine agencies, research institutes, universities and companies. The number of participants was increased from 40 to 48, and the qualified rate exceeded 90%, and the excellent rate was no less than 11% each year. The percentage of relative deviation less than 10% between the measuring result of 232Th, 40K and 137Cs contents and the reference value was larger than 80% in 2017. The accuracy became better. However, the number of institutions with U and Z score less than 1 was increased from 11 to 25, suggesting that the precision of measuring result has also been greatly improved.@*Conclusions@#Radiological health institutions in China have good measurement and analysis capabilities with regard to γ-spectrometry, which can meet the needs of environmental sample measurement and in-food radionuclide risk monitoring in an emergency of nuclear and radiation. But a few institutions′ measuring results were largely different from the reference values, as a consequence, it is important to strengthen their ability of measurement and analysis.

Summary and analysis of national-wide γ-spectrometry assessment for radiological health institutions from 2015 to 2017 / 中华放射医学与防护杂志

Objective To standardize the operation and data processing in radiological health institutions in China, in order to promote the assessment of γ-spectrometry, improve the measurement and analysis capabilities of each laboratory, and accordingly improve accuracy of environment sample measuring. Methods By collecting the values of 232 Th, 40 K and 137 Cs contents in soil samples from 2015 to 2017, the assessment results of γ-spectrometry laboratores were summarized and analyzed. Results The technical institutions from 25 provinces were involved in the assessment until 2017, including disease control and prevention centers, entry-exit inspection and quarantine agencies, research institutes, universities and companies. The number of participants was increased from 40 to 48, and the qualified rate exceeded 90％, and the excellent rate was no less than 11％ each year. The percentage of relative deviation less than 10％ between the measuring result of 232 Th, 40 K and 137 Cs contents and the reference value was larger than 80％ in 2017. The accuracy became better. However, the number of institutions with U and Z score less than 1 was increased from 11 to 25, suggesting that the precision of measuring result has also been greatly improved. Conclusions Radiological health institutions in China have good measurement and analysis capabilities with regard to γ-spectrometry, which can meet the needs of environmental sample measurement and in-food radionuclide risk monitoring in an emergency of nuclear and radiation. But a few institutions′ measuring results were largely different from the reference values, as a consequence, it is important to strengthen their ability of measurement and analysis.

Analysis of background variations in low-background γ-ray spectrometer with lead shielding / 中华放射医学与防护杂志

Objective To study the variation in net count rates of natural radionuclides in background of gamma-ray spectrometer,so as to provide a scientific basis for reducing the effect of background fluctuations on sample measurement.Methods The unscheduled background spectrum obtained using two high-purity gamma-ray spectrometers during 2013-2017 were collected,and then the net count rates of 210pb,234Th,212Pb,214pb,208Tl,214Bi,228Ac and 40K were calculated and analyzed by aid of statistical method.Results There was a significant difference in the net count rates of 210Pb,234Th,212Pb,214Pb,208Tl,214Bi,228Ac and 40K in the background spectrum of gamma-ray spectrometer,and the net count rates of 214Pb,214Bi and 40K was significantly higher than those of 210Pb,234Th,212pb,208Tl and 228Ac.There were no significant differences in the net count rates of these eight natural radionuclides from 2013 to 2017,respectively (P ＞ O.05).However,the coefficients of variation in the net count rates for 214pb and 214Bi were both greater than 50％.Conclusions When the activity concentration of natural radionuclides is determined in a sample by gamma-ray spectrometer,it is critical to subtract the background spectrum obtained recently to ensure the accuracy of the measurement,especially for the low activity concentration of natural radionuclide to be measured.

Validation of the Laboratory Sourceless Calibration Software (LabSOCS) on measurement / 中华放射医学与防护杂志

Objective To validate the effect of the Laboratory Sourceless Calibration Software (LabSOCS) in the actual sample measurement,and to study the effect of sample self-absorption correction and cascade radiation coincidence correction.Methods Two standard samples from the analytics company were measured using the two gamma spectrometers at our laboratory.The result were calculated using the efficiency generated by LabSOCS.Calculated result of each nuclide were analyzed.Results were compared with the standard value provided in the certificate.Results The LabSOCS may solve the problem of sample self-absorption correction in gamma energy spectrum measurement and analysis.The maximum deviation between the values of 241Am and 109Cd analyzed by LabSOCS and the reference value was less than 4％ for the broad-energy high-purity germanium gamma-ray spectrometers.However,the coincidence additive correction caused by cascade radiation could not be solved directly.Conclusions The research shows that the LabSOCS can solve the problem of sample self-absorption correction by describing the composition and density of the samples accurately.However,when analyzing the nuclides with cascade radiation,the coincidence addition effects should be considered.The flexible simulation method of the LabSOCS can be used to increase the distance from the cascade nuclide sample to the detector and to complete the accurate measurement of the cascade nuclide.

Intercomparison and evaluation onγ-spectrometry of radionuclides in water / 中华放射医学与防护杂志

Objective To improve theγ-spectrometry analysis technology in water sample through the intercomparison conducted among the key laboratories. Methods To take part in the intercomparison of γ-spectrometry analysis in water sample organized by National Institute of Metrology ( NIM ) , the radionuclides of 238 U,226 Ra, 208 Tl, 228 Ac, 40 K, 241 Am, 137 Cs, and 60 Co in water sample were determined. The efficiency of the detector was calibrated renewedly by new standard source in 2015 and a new γ-spectrometry (BE5030) was used for sample measurement. Results Analysis and comparison of the three measurement results and the leading laboratory reference values showed that the results measured by γ-spectrometry ( BE5030 ) were better, especially for the natural radionuclides. The maximum En value between them and NIM reference value was only 0. 71. Conclusions The wide range energy γ-spectrometry (BE5030) has obvious advantages in the measurement and analysis of natural radionuclides. Due to the special structure of the wide range energy detector, its background interference is less in low energy area. This inter-comparison improved the accuracy of sample measurements and analysis, with good result achieved.

Intercomparison and evaluation onγ-spectrometry of radionuclides in water / 中华放射医学与防护杂志

Objective To improve theγ-spectrometry analysis technology in water sample through the intercomparison conducted among the key laboratories. Methods To take part in the intercomparison of γ-spectrometry analysis in water sample organized by National Institute of Metrology ( NIM ) , the radionuclides of 238 U,226 Ra, 208 Tl, 228 Ac, 40 K, 241 Am, 137 Cs, and 60 Co in water sample were determined. The efficiency of the detector was calibrated renewedly by new standard source in 2015 and a new γ-spectrometry (BE5030) was used for sample measurement. Results Analysis and comparison of the three measurement results and the leading laboratory reference values showed that the results measured by γ-spectrometry ( BE5030 ) were better, especially for the natural radionuclides. The maximum En value between them and NIM reference value was only 0. 71. Conclusions The wide range energy γ-spectrometry (BE5030) has obvious advantages in the measurement and analysis of natural radionuclides. Due to the special structure of the wide range energy detector, its background interference is less in low energy area. This inter-comparison improved the accuracy of sample measurements and analysis, with good result achieved.

Evaluation result of radionuclide γ-spectrometry in 2016 / 中华放射医学与防护杂志

Objective To evaluate the radionuclide measurability and analyzability of the γ-spectrometry laboratories in radiological technology institutions countrywide,ensure the quality of radionuclide γ-spectrometry and outlook the evaluation work in γ-spectrometry.Methods The 2016 annual evaluation of radionuclide γ-spectrometry was carried,and the accuracy and precision of 232Th,40K and 137Cs,activity concentration in soil samples were summarized and analyzed in γ-spectrometry laboratories of radiological technology institutions countrywide.Results Of received 45 revaluation receipts,43 were effective and the other two were ineffective due to the suspension of the evaluation.The relative deviation of the activity concentration values of 232Th,40K and 137Cs given by most of the institutions were within the range of ± 20％,only with two measurements beyond 20％.The evaluation results from the 43 participants were qualified with the overall qualified rate of 100％,of which five were excellent accounting for 11.6％ of all.Conclusions All of the elevation results submitted were accurate,showing better measurability.However,some submittals deviated from the references to some degree.Henceforth,it is necessary to strengthen experimental operation and data processing according to the defend procedures and improve the accuracy and precision of measurement results.