ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
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.