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Objective To summarize and analyze the difficulties and key points in the measurement of gross α and gross β radioactivity in water based on the results of national measurement capability comparison assessment, and provide the basis and reference for the future work and the development of new local standards. Methods The research team participated in the comparison assessment for measurement of the gross radioactivity in water samples organized by National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention. According to the comparison assessment results and the content in the national standard GB/T 5750.13—2023 (published draft), the steps of spike recovery involved during the measurement were analyzed and discussed. Two different formulas used for spike recovery calculation were analyzed for their impact on the final measurement results. Results When the spike recovery F(derived) derived from the formulas was used for result calculation, the spike recovery ranged as follows: gross α: 63.00%−84.60%, and gross β: 95.0%−99.1%; 3/6 of the comparison results were determined as excellent and 3/6 as pass as a whole (among them, 4 were excellent and 2 were pass for both single gross α assessment items and single gross β assessment items). When the spike recovery F from the GB/T 5750.13—2023 (published draft) was used for result calculation, the spike recovery ranged as follows: gross α: 39.69%−71.57%, and gross β: 90.25%−98.21%; 5/6 of the comparison results were determined as fail and 1/6 as pass (among them, 5 were fail and 1 was pass for single gross α assessment items; 5 were excellent and 1 was pass for single gross β assessment items). When two different formulas were used for spike recovery calculation, there was a significant difference in gross α radioactivity measurement (t = 4.27, P = 0.03 < 0.05), but there was no significant difference in gross β radioactivity measurement (t = 0.667, P = 0.524 > 0.05). Conclusion In the measurement of gross α and gross β radioactivity in water, appropriate reference to the spike recovery has a great influence on the measurement results. Therefore, quality control should be strengthened to further ensure the accuracy of measurement.
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Objective To summarize and improve the related technical issues by analyzing the nationwide interlaboratory comparison of gross α and gross β radioactivity measurement over the years. Methods According to the requirements of interlaboratory comparison and the national standards, the gross α and gross β radioactivity in water were measured, and the results were analyzed to identify the influencing factors. Results From 2018 to 2022, our laboratory participated in five nationwide interlaboratory comparisons of gross α and gross β radioactivity measurement. The Z-test values for gross α and gross β measurement ranged from −0.24 to 1.8 and −1.4 to 0.35, respectively. The relative deviations ranged from −4% to 32% and −18% to 6%, respectively. All comparisons were within the acceptable ranges. Conclusion The analysis of comparisons showed that the results were within the acceptable ranges. The relative deviations between the measurement and the reference values have decreased over the years. The summary and improvement of related technologies have improved the measurement accuracy.
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Objective To explore cross-talk elimination method in the determination of gross α and gross β activities using a low-background α/β gas-flow proportional counter. Methods A CLB-104 low-background α/β gas-flow proportional counter was used in this study. First, the α threshold was increased to eliminate the cross-talk counting caused by β particles in the α channel. Then, the α-β anticoincidence threshold was reduced to eliminate the cross-talk counting induced by low-energy α particles in the β channel, and β counts were corrected to eliminate the counts induced by internal convention electrons in the β channel. Finally, gross α and gross β activities of non-saline water samples with different activity levels were determined and compared with gross α and gross β activities of the same samples determined on a BH1227 low-background α/β solid scintillation counter, in order to verify effectiveness of the cross-talk elimination method. Results By eliminating the cross-talk counts of β particles in the α channel and the cross-talk counts of α particles in the β channel, and deducting the counts of internal convention electrons in the β channel, the gross α and gross β activities of the same samples determined by CLB-104 were consistent with the values determined by BH1227. Conclusion Cross-talk counts induced by low-energy α particles or β particles can be eliminated by threshold adjustment, and the counts caused by internal convention electrons in the β channel can be eliminated by correction.
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Objective To improve the determination of gross α and gross β radioactivity in soil, establish a fast and accurate method for soil radioactivity analysis, and provide a basis for establishing standard methods for analysis of gross α and gross β radioactivity in soil. Methods Using the method of soil nuclide extraction and the sample preparation method for low background α/β counter, an extraction-enrichment method was established to monitor the radioactivity of gross α and gross β in soil. Meanwhile, the radioactivity of gross α and gross β in the same soil samples was determined using the direct paving method. An optimal method of monitoring gross α and gross β radioactivity in soil was put forward by comparing the advantages and disadvantages of the two methods. Results With the direct paving method, the radioactivity of gross α and gross β in soil was 0.47 Bq/g and 0.85 Bq/g, respectively; and the minimum detection limit was 0.04 Bq/g and 0.02 Bq/g, respectively. With the extraction-enrichment method, the radioactivity of gross α and gross β in soil was 0.32 Bq/g and 0.29 Bq/g, and the minimum detection limit was 0.02 Bq/g and 0.01 Bq/g. Conclusion Comparison of the two detection methods showed that the direct paving method is more accurate and easier to operate, while the extraction-enrichment method is complex in operation and has relatively large system error but provides a lower minimum detection limit.
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Objective:To ascertain the activity concentration of gross α and β in foods around Fuqing nuclear power plant (NPP) site.Methods:Totally 167 food samples of 25 kinds within 6 categories were collected from the surveillance areas and control areas around Fuqing NPP site. The total radioactivity was analyzed using the food samples. Paired rank sum test was used to determine the influence of the operation of Fuqing NPP on the total radioactivity in foods in surrounding areas. The multiple local rank sum test was used to assess the difference in total radioactivity in different types of foods.Results:The average gross α in poultry meat, vegetables, crops, aquatic products, milk and tea was 0.65, 1.96, 1.41, 3.80, 1.33, 7.67 Bq/kg in surveillance areas and 0.56, 3.24, 2.04, 3.70, 2.24, 9.05 Bq/kg in reference areas, respectively, around Fuqing NPP site. The average gross β (subtracting 40K) in poultry meat, vegetables, crops, aquatic products, milk and tea was 7.0, 10.5, 6.1, 23.5, 24.7, 8.6 Bq/kg in surveillance areas and 7.4, 8.3, 14.5, 22.1, 21.3, 11.0 Bq/kg in reference areas, respectively, around Fuqing NPP site. The Wilcoxon paired rank test showed that there was no significant difference in the gross α and β in foods between surveillance and reference areas around Fuqing NPP site ( P>0.05). The Kruskal-Wallis H test showed that the radioactivity of gross α and β in different foods was statistically significant ( χ2=23.325, 13.918, P<0.05). Conclusions:The increase was not found in total radioactivity in the surrounding foods since the operation of Fuqing NPP in 2015.
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Objective:To investigate the levels of gross radioactivity in drinking water in Hangzhou city before and after Qiandao Lake as the water source to the main urban area of Hangzhou.Methods:Since 2012, water samples were collected from water source, factory water and peripheral water in rainy and dry seasons, respectively, to determine their gross α and β activity concentrations for comparison and analysis.Results:The gross radioactivity levels in drinking water in Hangzhou are lower than the limits specified in the national standard "Standards for drinking water quality" (GB 5749-2006), without statistically significant difference for these water sources between the rainy and dry season ( P>0.05). The gross α(0.008±0.000)and gross β(0.034±0.013)levels in Qiandao lake were both less than those in Qiantang river ( Z=-3.235, -4.058, P<0.05), with significant difference ( Z=-2.181, -4.577, P<0.05). There was no significant difference in gross α and gross β in factory water and peripheral water before and after the operation of Qiandao Lake water supply project ( P>0.05). Conclusions:The gross radioactivity in drinking water in downtown Hangzhou are low from 2012 to 2020. The gross radioactivity levels in Qiandao Lake are lower than in the lower reaches of Qiantang river and Dongtiao steam. No impact was generated on radioactivity levels in drinking water after Qiandao lake supplied water to Hangzhou.
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Objective To study gross α and gross β radioactivity in environmental samples in Wuxi, China, and perfect the radioactivity data, and to discover possible radioactive contamination in time. Methods The BH1227 low-background α and β measuring instrument was used to determine gross α and gross β radioactivity in sedimentary dust, aerosol, drinking water, and food samples in Wuxi. Results Among environmental samples collected in Wuxi, 2014—2019, the mean gross α and gross β radioactivity levels were 0.01～5.98 Bq/kg and 9.47～547.86 Bq/kg in food samples, respectively, 1.2～22 mBq/L and 0.1～141 mBq/L in water samples, respectively, 39～44790 mBq/m3 and 743.1～101500 mBq/m3 in sedimentary dust samples, respectively, and 50～1125 μBq/m3 and 38～9510 μBq/m3 in aerosol samples, respectively. Conclusion We should strengthen radioactivity monitoring of environmental samples in Wuxi through increasing the scope and frequency of monitoring, to perfect baseline radioactivity data of Wuxi.
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Objective To understand the background level of total radioactivity in drinking water around Tianwan Nuclear Power Plant. Methods According to the original plan of the National Health and Family Planning Commission of China, the monitoring of gross α and gross β radioactivity levels in drinking water during dry and rain periods around Tianwan Nuclear Power Plant, and water samples were collected including source water, factory water, peripheral water and reservoir water. Results A gross of 200 water samples were monitored at 35 sampling sites from 2016 to 2018.The gross α and gross β radioactivity levels in the dry period were (0.038 ± 0.033) Bq/L and (0.11 ± 0.03) Bq/L. The gross α and gross β radioactivity levels in the wet period were (0.038 ± 0.024) Bq/L and (0.11 ± 0.03) Bq/L. There were statistically significant differences in gross α and gross β radioactivity levels between the source water and the other water during the dry season (P < 0.05). There were statistically significant differences in gross α and gross β radioactivity levels in different years (P < 0.05). There were statistically significant differences in gross α and gross β radioactivity levels at different distances from the nuclear power plant (P < 0.05). Conclusion The gross α level and gross β level of radioactivity in drinking water around Tianwan Nuclear Power Plant are in line with the standard of drinking water, regular, fixed and continuous monitoring should be carried out, and radionuclide monitoring and radiological investigation should be carried out on this basis.In view of the density of personnel in the vicinity of nuclear power plants in China, nuclear emergency preparedness training should also be strengthened.
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Objective To ascertain the gross α/β levels in drinking water in Inner Mongolia and to estimate the annual effective dose to the local residents from radionuclides in drinking water.Methods A total of 768 water samples were collected from 101 counties distributed over 12 cities of Inner Mongolia.Low background α/β measuring instrument was used to measure the radioactivity level;On this basis,use EPA Federal Guidance Report 11 universal method to estimate the annual effective dose to the local residents via intake of radionuclides from drinking water.Results The gross α radioactivity range was 0.016-1.003 Bq/L for tap water,O.016-0.975 Bq/L for factory water,0.017-1.544 Bq/L for river water,0.120-0.672 Bq/L for lake water,0.016-0.492 Bq/L for reservoir water,0.016-1.139 Bq/L for well water,0.032-3.156 Bq/L for spring water,respectively.The gross β radioactivity range was 0.030-0.828 Bq/L for tap water,0.031-0.571 Bq/L for factory water,0.066-0.873 Bq/L for river water,0.169-2.268 Bq/L for lake water,0.046-0.519 Bq/L for reservoir water,0.071-0.526 Bq/L for well water,0.087-1.063 Bq/L for spring water,respectively.Conclusions In Inner Mongolia,the gross α/β mean value in tap water is less than the World Health Organization-recommended value and the average annual effective dose from tap water is also less than the WHO-recommended value O.1 mSv/a.The gross α/β radioactivity from the other water samples is also within the range of the nationwide average.
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Objective To establish the baseline data about gross α and gross β radioactivity in local foods through a preliminary investigation in Urumqi City.Methods The edible parts of six types of foods, including cereals, vegetables, fruit, nuts, meat and dairy food, were pretreated and sampled.MPC 9604 low background o and gross β measuring instrument was used for determination of gross α and gross β radioactivity.Results The natural gross ot and gross β radioactivity in the cereal, vegetables, fruits, nut, meat, dairy food were 0.88-10.80 and 22.20-148.67 in cereals, 1.17-24.24 and 21.41-318.84 in vegetables, 1.44-4.89 and 43.90-112.67 in fruits, 17.49-43.72 and 287.81-747.40 in nut, 3.04 -19.77 and 41.55-164.51 in meat, and 2.07-2.94 and 44.07-59.02 Bq/kg in milk, respectively.Conclusions There are some differences in the gross natural radioactivity between Urumqi and the other provinces and cities due to possible regional differences.In order to further ascertain baseline of natural radioactivity in food in Urumqi, larger sample sizes and more diverse food types are needed for purposes of dynamic monitoring.
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Objective To measure the total β radioactive background level in the urine of normal adults,and to establish the method which can be universally used and satisfy the needs of rapid screening of samples in large batch.Methods A total of 83 urine samples from healthy adults were prepared by evaporation.And the gross β activity in urine was detected by using low background measuring instrument.Results The optimal experimental conditions were in place.The sampled volume was 200 ml,and the samples were turned to nitric acid salinization,ashed at 300℃ for 2 h,and the measured time was 1000 min.To get a more stable result,the urine residues were put aside for 24 h before measurement.The radioactivity in urine of healthy adults was between 9.40-55.92 Bq/L,and showed no correlation with age and sex.Conclusions When the radioactivity in urine is detected under the conditions mentioned above,the sample preparation process is simple and quickly,which can satisfy the needs of large batch sample screening.