Levels of radon and thoron in underground power house and neighbouring indoor atmosphere of Tehri dam project

Concentrations of radon and thoron were measured in underground power house of Tehri Dam and indoors of its neighbouring areas by using LR-115 Type-II plastic track detectors. In the measurements, concentrations of radon and thoron were found with a mean of 71.1 Bq.m-3 and 16.6 Bq.m-3, respectively in the indoors at New Tehri whereas in the indoors at Budhakedar, a rural area, the mean concentrations observed were 93.6 Bq.m-3 and 29 Bq.m-3 for radon and thoron, respectively. In the underground working places of Tehri Dam project, the concentrations of radon and thoron were found to vary from 49 Bq.m-3 to 389 Bq.m-3 and 3 Bq.m-3 to 238 Bq.m-3, respectively, during winter. However, during summer the concentration vary from 41 Bq.m-3 to 367 Bq.m,-3 for radon and for thoron 6 Bq.m-3 to 205 Bq.m-3. The observed levels of indoor radon were found well below the international recommendations but are above the global average. However, the concentrations of radon and thoron in underground powerhouse are some what higher compared to ICRP recommendations. (author)