Radon survey in the high natural radiation region of Niška Banja, Serbia

A radon survey has been carried out around the town of Niška Banja (Serbia) in a region partly located over travertine formations, showing an enhanced level of natural radioactivity. Outdoor and indoor radon concentrations were measured seasonally over the whole year, using CR-39 diffusion type radon detectors. Outdoor measurements were performed at 56 points distributed over both travertine and alluvium sediment formations. Indoor radon concentrations were measured in 102 living rooms and bedrooms of 65 family houses. In about 50% of all measurement sites, radon concentration was measured over each season separately, making it possible to estimate seasonal variations, which were then used to correct values measured over different periods, and to estimate annual values. The average annual indoor radon concentration was estimated at over 1500 Bq/m 3 and at about 650 Bq/m 3 in parts of Niška Banja located over travertine and alluvium sediment formations, respectively, with maximum values exceeding 6000 Bq/m 3. The average value of outdoor annual radon concentration was 57 Bq/m 3, with a maximum value of 168 Bq/m 3. The high values of indoor and outdoor radon concentrations found at Niška Banja make this region a high natural background radiation area. Statistical analysis of our data confirms that the level of indoor radon concentration depends primarily on the underlying soil and building characteristics.