Radon permeability and radon exhalation of building materials

High radon concentrations indoors usually depend on the possibilities of ra don penetration from the surrounding soil into the buildings. Radon concent rations in dwellings up to 100 kBq/m(3) were found in some special regions (i.e. Schneeberg/Saxony, Umhausen/Tyrol), where the soil shows a high urani um content and additionally, a fast radon transport in the soil is possible . To reduce the radon exposure of the inhabitants in these 'radon prone are as' it is necessary to look for building and insulating materials with low radon permeability. We examined several building materials, like cements, c oncretes and bricks of different constitutions for their diffusion coeffici ents and their exhalation rates. The insulating materials, like foils and b itumen were tested also on their radon tightness. The measurements were per formed with an online radon measuring device, using electrostatic depositio n of Po-218 ions onto a surface barrier detector and subsequent alpha spect roscopy. The mean diffusion lengths for the investigated building materials range from lower than 0.7 mm (i.e. for plastic foil), up to 1.1 m for gyps um. The diffusion length R was calculated from the diffusion coefficient D with R = rootD/lambda. If the thickness of the material is more than 3 time s the diffusion length, then it is called radon-tight. The mean Rn-222 exha lation rates for the building materials varied between 0.05 and 0.4 mBq/m(2 )s. The samples were investigated as stones, plates, blocks, foils, coating s, powders etc., no statement can be made about working at the construction site of a building. Also the fabrication and processing of the materials h as to be considered, because the material characteristics may have changed. (C) 2001 Elsevier Science B.V. All rights reserved.