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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.
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Objective To increase the cumulative measurement level of 222 Rn and 220 Rn and ensure the accuracy and reliability of the measurement result . Methods By using improved 222 Rn-220 Rn discriminative detectors ( LD-P detectors) , the radon research group of National Institute for Radiological Protection Chinese Center for Disease Control and Prevention participated with the intercomparison organized by National Institute of Radiological Science ( NIRS) , Japan. Specifically, with the 222 Rn-220 Rn discriminative detectors being sent to Japan, the comparison was completed under different conditions in the 222 Rn chamber and 220 Rn chamber in NIRS. After exposure, the detectors were sent back to our laboratory for etching and analysis, and then measurement result were informed to NIRS. Finally, NIRS returned the exposure reference values of 222 Rn and 220 Rn to our laboratory. Results Under the conditions of high and low levels of 222 Rn, the relative percentage differences ( RPD ) between the measured values and the reference value provided by the NIRS were -12. 0％ and -11. 8％, respectively, while coefficients of variation ( COV) were 3. 0％ and 6. 2％, respectively. Under the conditions of high level and low levels of 220Rn, the relative percentage differences (RPD) between the measured value and the reference value provided by the NIRS were -0. 8％ and -8. 0％, respectively; coefficients of variation ( COV ) were 6. 7％ and 4. 5％, respectively. Conclusions This intercomparison result were categorized by NIRS ( PRD<10％) , with the satisfactory result of LD-P detectors available.
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O objetivo desta pesquisa foi avaliar os níveis de concentração de radônio 222Rn em águas de poços da região metropolitana de Curitiba, Paraná. O trabalho apresenta os resultados das concentrações das medidas feitas em águas de poços da região. As concentrações de 222Rn nas amostras das águas de poços foram medidas por meio do monitor de radônio AlphaGUARD. Os cálculos das concentrações de atividade iniciais de radônio na água foram feitos a partir da curva de decaimento do 222Rn e do equilíbrio secular entre o 222Rn e o 226Ra, observados depois de 30 dias. Os resultados indicaram que cerca de 70% dos valores das concentrações de 222Rn ficaram acima do valor recomendado pela USEPA, de 11,1 Bq.L-1, representando risco radiológico causado por este radionuclídeo. O estudo de caso apresentado mostrou que medidas prévias de radônio são recomendadas para que um projeto de construção seja implementado. No caso em questão, observa-se que as concentrações de radônio diminuem cerca de 56% na primeira caixa d'água e 83% na segunda em relação ao poço. Esse fato mostra que as ações para mitigação de radônio são viáveis e não exigem grandes modificações nos sistemas usuais da construção civil.
This research objective was to assess the level of randon-222 concentration in well water of the metropolitan region of Curitiba, Paraná. Current work presents the results of indoor 222Rn activity ground water samples from artesian wells from aquifers of the region. The studies of radon activity in water were performed using the radon detector AlphaGUARD. The calculations of initial radon activity in water were done considering the 222Rn decay correction as well as equilibrium level of 222Rn and 226Ra observed after 30 days of measurements. Obtained results show that about 70% of measured activity levels of 222Rn are higher than the recommended value of 11.1 Bq.L-1, which represent the risk for the human health associated with this radionuclide. The case study showed that previous measurements of radon are recommended for a construction project is implemented. In this case, it is observed that the radon concentrations decrease about 56% in the first water tank and 83% in the second water tank over the well. This fact shows that the actions for mitigation of radon are viable and do not require major modifications to the usual systems of construction.
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Objective To guarantee the quality of measurenents with the radon-thoron discriminative detectors of our laboratory.Methods LD-P radon-thoron discriminative detector participated in the international intercomparison for integrating radon/thoron detectors organized by National Institute of Radiological Science (NIRS,Japan).Detectors were sent to NIRS for exposure.Radon intercomparison was conducted with radon chamber providing three levels of exposure:low,medium and high levels.Thoron intercomparison was carried out at thoron chamber,which also provided three levels of exposure:low,medium and high levels.Detectors were posted back to our laboratory for etching and analysis after exposure.Then the measured values were submitted to NIRS.Finally the reference values were informed of us.Results The relative percent difference (RPD) between the measured value and the reference value for radon was-13.8％,-14.4％ and-17.1％ at low,medium and high levels respectively,and that of thoron were-14.4％,8.9％ and-3.2％ at three levels respectively.Conclusions Both radon and thoron measurement of our detectors rank asCategory Ⅰ in the 4th international intercomparisons for integrating radon/thoron detectors with the NIRS radon/thoron chambers.
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Objective To study the seasonal variation of indoor 222Rn and 220Rn concentrations in Longdong district,Gansu Province.Methods A total of 44 houses from 5 different types of raw soil architectures and 5 ordinary brick houses from a typical area were selected in Longdong district,Gansu Province in China.The LD-P discriminative 222Rn and 220Rn detectors were used to measure the indoor concentrations of 222Rn and 220Rn during four seasons in one year.Results The indoor concentrations of 222Rn showed a significant seasonal variation,which varied with different types of houses.222Rn concentrations of ordinary brick houses,soil brick houses and the cave dwellings were higher in winter and autumn and lower in summer.The average concentrations of 222Rn were 55.3-90.3 Bq/m3 in winter,36.4-65.7 Bq/m3 in spring,35.6-63.9 Bq/m3 in summer,and 60.7-87.2 Bq/m3 in autumn.For cave dwellings,open-cut cave dwellings and the underground cave dwellings,222Rn concentrations were higher in summer and autumn,and lower in winter and spring.The average concentrations of 222Rn ranged from 139-184 Bq/m3 in winter,135-199 Bq/m3 in spring,179-252 Bq/m3 in summer,172-242 Bq/m3 in autumn.The seasonal variation of indoor 220Rn was basically consistent in six types of houses,and lower in winter and spring and highest in autumn.The average concentrations of 220Rn ranged from 43.4-64.3 Bq/m3 in winter,60.6-537 Bq/m3 in spring,77.7-792 Bq/m3 in summer,63.2-1077 Bq/m3 in autumn.The indoor concentrations of 222Rn and 220Rn were different among different types of houses,and they were generally higher in type of raw soft architectures than in that of ordinary brick houses.Conclusions 222Rn concentrations indoors showed a significant seasonal variation and varied with different types of houses.
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Objective To investigate the concentrations of indoor radon (222Rn) and its daughter products as well as indoor thoron (220Rn) in selected houses in Yuhang district and Sanmen county,Zhejiang province,and estimate their annual effective doses to the population.Methods Solid state nuclear track detectors were used in selected dwellings in Yuhang district and Sanmen county,and the detectors were placed in bedrooms or living rooms.Without changing the ventilation habits of residents,These detectors were continuously placed from March to September in 2009.Results Indoor 222 Rn and 220Rn concentrations in low-rise buildings were the highest among all types of houses.The indoor concentration of 222 Rn had no relation with the building age (F = 0.53,P ＞ 0.05),but that of 220 Rn was dependent on the building age (F = 3.56,P ＜ 0.05).Moreover,the investigation demonstrated indoor 220 Rn concentrations in houses with no decoration were higher than in the houses decorated (t = 2.33,P ＜0.05).The average indoor concentrations of 222Rn and 220Rn in Yuhang district were 32.5 Bq/m3 and 314.3 Bq/m3,respectively,and the annual effective doses were 0.88 mSy and 0.42 mSv respectively.The average indoor concentrations of 222Rn and 220Rn in Sanmen county were 26.8 Bq/m3 and 399.5 Bq/m3,and the annual effective doses were 0.72 mSy and 0.53 mSv respectively.Conclusion The concentrations of indoor 222 Rn in some areas of Zhejiang province are at natural background level,and the concentrations of indoor 220Rn in rural areas are relatively higher.The total annual effective dose from 220Rn and its progeny was larger than that from 222Rn and its progeny by 50 percents.