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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.
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Objective To analyze the specific activity of radionuclides based on laboratory intercomparison.Methods Intercomparison of the measurements of radioanuclides 232Th,40K and 137Cs in soil samples,organized by National Institute for Radiological Protection,China CDC,was conducted using HPGe γ-spectrometry and the method of relative comparison and efficiency curve,respectively.Results The relative deviations were all less than 5％compared to the reference values in the conditions of both relative comparison method and efficiency curve method used,respectively.The relative deviations to the reference values were less than 4％for the relative comparison method.Conclusions Both the relative comparison method and the efficiency curve method can be used to measure the activity of radionuclides in the intercomparison samples,and the latter is superior to the former.
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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.
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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.
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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.
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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.
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Objective Aselectivitystudywasconductedthroughtheexaminationofradionuclides137Cs(Cesium-137)for foodbasedondifferentdetectionconditions.Methods Atotalof48foodsampleswereselectedfromthreeareasincluding Qinshan nuclear power plant,Sanmen nuclear power plant and Hangzhou and Zhoushan respectively.1 37 Cs of these samples were determined by γspectrometry and Phosphoric acid ammonium molybdate method.The level of 48 foods were statistically analyzed,and then the time consuming,sample size requirements,influence factors were comprehensively discussed,thustheselectionreferenceproposaloftheexaminationmethodcouldbeprovided.Results Therewereno significant difference for the data of two examination method (P>0.05 ).The limit of detection of the γspectrometry was lower (P <0.05 ).Compared with Phosphoric acid ammonium molybdate method,γspectrometry had lower limit of detection,and could detect a variety of radionuclides at a time,but need more sample and time-consuming when multi-sample were detected.The limit of detection of the Phosphoric acid ammonium molybdate method was high,and the chemicalprocessingstepswerecumbersomeandwaseasytobeinterferedby134Cs.Conclusion Thelimitofdetectionof the γspectrometry is low,and the sensitivity of the Phosphoric acid ammonium molybdate method is high.Most food are recommended to be detected by γspectrometry in the practical work,and the food which were difficult collected,less ash or low content,are recommended to be detected by Phosphoric acid ammonium molybdate method.