Evaluation of radon emanation coefficient in different types of building materials of different grain sizes

In the present study, the emanation coefficient was calculated for different types of building materials using active and passive methods. Active measurement was carried out using a scintillation detector connected to the sample containing a small chamber (volume ∼ 1582.5 c.c.) for continuous measurement of approx. 240 h. The observed growth curves for radon concentrations were used to estimate the emanation coefficients and the back diffusion rates at the equilibrium concentration inside the chamber, while the passive measurement was carried out with LR 115 type II detectors using the sealed can technique. Seven types (soil, concrete, brick, tile, slate, granite, and sand) of building materials were used for the present experiment in two size ranges: fine grains (0-300 μm) and coarse grains (300-1180 μm) in both types of measurements. The emanation coefficient was found to vary between 0.01 to 0.22 and 0.23 to 0.31 in active and passive measurement, respectively. Maximum values of the emanation coefficient were obtained for fine-grained soil samples and minimum for sand (both fine and coarse). In most cases, coarse grains have shown a higher emanation coefficient as compared to fine ones.