Measurement of gamma-dose caused by built in coal slags with elevated Ra-226 concentration, and the modelling of shielding

Slags, derived from coal mined in the neighbourhood of the town Tatabanya i n Hungary, have been used as filling and insulating material for buildings of houses, block of flats, schools and kindergartens. The slag samples come from here have elevated concentrations of Ra-226, (range of 850-2400 Bq kg (-1)). Therefore, the external gamma dose rates at 1 m height were about fo ur times higher than the world average. It has been found, based on the mod elling, that the dose rate could be decreased with 70-80% using an appropri ate thickness of concrete or barite-concrete layers.