Natural radiological hazard assessment of 222Rn and 220Rn in high-level radiation background areas, Northern Vietnam

Abstract The outdoor radon (222Rn) and thoron (220Rn) concentrations at 320 dwelling points at 1m above the ground in different locations surrounding rare earth elements (REE) and uranium mines in Northern, Vietnam were measured using the RAD7 equipment. Results showed that the 222Rn was always higher than 220Rn concentration with a range from 25.7 to 573 Bq/m3 and from 18.5 to 385 Bq/m3, respectively. In general, the 222Rn and 220Rn concentration showed a large variation, especially in the study location of the NX-Lai Chau. The highest 222Rn and 220Rn concentration was found in this location as well. The 222Rn and 220Rn activities surrounding the REE mines were found to be higher than those surrounding the uranium mines. The average value of annual committed effective doses originated from the inhalation of 222Rn and 220Rn outdoor dwellings is about five times higher than the worldwide average value as reported in UNSCEAR (2000).