Indoor radon dose assessment for Osijek

After ten years' investigation of radon's seasonal variation at three very different locations, as well as radon concentration measurements in kinderg artens, schools, air-raid shelters and cellars, systematic indoor radon mea surements were undertaken in dwellings (residential buildings) of Osijek (E ast Croatia, 130 000 citizens). Indoor radon was measured by means of the L R-115 SSNT detector at 48 town locations that gave an arithmetic mean of 71 .6 Bq/m(3), standard deviation of 44.0 Bq/m(3) and geometric mean of 60.1 : Bq/m(3), for the radon concentration range from 22.7 to 185.6 Bq/m(3). Rado n measurements, performed by the silicon Radhome detector, did not differ s ignificantly. The empirical frequency distribution of radon concentrations, with the class width of 20 Bq/m(3), was in accordance with the theoretical log-normal distribution which was shown with the chi(2)-test. The radon ma p pointed out a region of higher radon concentrations (central part of the town) that was ascribed to the geological soil structure. The average equil ibrium factor for radon and its progeny in the mentioned dwellings was 0.44 . The effective dose equivalent assessment for a few radon models was near 2 mSv/year. (C) 1999 Elsevier Science Ltd. All rights reserved.