Detction of ~(220)Rn and Its Progency Concentrations in Some Areas in China
SHANG Bing, ZHANG Ling, CHEN Bin,et al. Laboratory Industrial Hygien , Ministry of Health Beijing, 100088, China
Objective To realize the level of 220Rn and its progeny concentrations and annual effective dose from 220Rn in different areas in China.Methods Rn and its progeny concentrations, outdoors and indoors, were obtained by using Rn - Tn solid state nuclear track detectors developed by Nagoya University, Japan, and potential energy analysis method.The annual effective dose from Rn and its progenies were calculated using the conversion coefficient from UNSCEAR 1996 report. Results Rn and its progeny concentrations in Beijing, Guangzhou, Zhuhai and Pingliang are LLD - 1326 Bq-m-3, LID - 4.7 EEC Bq-m-3 (indoors), and LLD - 2.2 EEC Bq-m-3 (outdoors) , respectively. The annual effective dose from 220Rn and its progenies calculated using preliminary measurement results is 0.18 - 0.60mSv/a, being about 13.1 % - 55.6% of the total annual effective dose from 222Rn,220 Rn and their progenies. Rn and its progeny concentrations depend on the content of Th in soil.The main factors affecting Rn indoors arc the content of 232Th in the building materials and the 220Rn emanation rates. Conclusions 220Rn concentrations indoors and outdoors in China are higher than the average of the world which correlated with Th content in soil.