Radon concentrations in houses around the Plomin coal-fired power plant

Investigation of radon activity concentration in houses around the Plomin coal-fired power plant (Istrian Peninsula) started in the winter of 1990 upon the assumption that certain old houses in this region were built using mortar and plaster prepared from slag and ash. This paper presents the results of a preliminary investigation carried out in the winter of 1990 and spring of 1991, when the difference between radon levels in old and newly built houses was first noted, and the subsequent data obtained by radon measurements in 40 selected houses in the period from 1992 to 1994. The average annual radon activity concentrations in the old houses ranged from 55 Bqm−3 to 426 Bqm−3 (mean value 146 ± 91 Bqm−3) and in more recently built houses from 16 Bqm−3 to 67 Bqm−3 (mean value 36 ± 13 Bqm−3). The average annual effective doses from inhalation of radon progeny for the inhabitants living in the old and newly build houses were estimated to be 2.7 mSv and 0.7 mSv, respectively.