Influence of Shallow Mine-Workings on the Radon Concentrations in Houses: A Problem of Old Mining Regions

Abstract

In some regions of the German New Federal Lands, residues from early mining characterise the radiological situation and can also influence the radon concentration in buildings. Construction on waste rock with increased radium concentration, the use of waste rock as building material and construction above shallow mine shafts and adits are important in this connection. In Saxony, for instance, one has to reckon with probably hundreds of buildings that may be influenced by radon from shallow mine workings. Very short-term changes of radon concentrations in buildings over several orders of magnitude was well as their close temporal correlation with the underground airflow clearly indicate influences from underground. In Schneeberg and Schlema, fluctuations of radon concentration in buildings of several 10,000 Bq.m-3 within one hour were observed. In Schneeberg, the old mine was ventilated artificially by installing a ventilator with an output volume of 500 m3min-1. Thus the radon concentration in buildings of the central city area has been reduced. In Schlema, the radon rich shafts of early mining are ventilated at present by the still active ventilation system of the suspended uranium ore mining. In 1992, during the first six months, 4.5 x 109 m3 of mine air with a radon activity of 6.3 x 1014Bq were extracted from the mine. If the mine ventilators are switched off, radon concentration in buildings over mine shaft increases sharply by two orders of magnitude.