The study aims at measuring the gamma activity concentration (226Ra, 232Th and 40K) of sub-slabfilling gravel of Finnish houses. This study forms a part of a wider study aiming at exploring factorsaffecting high indoor radon concentrations in Finnish dwellings. The gamma activity and radonemanation were measured from gravel samples sent from 229 Finnish municipalities, the gammaactivity was reported. Gamma activity was determined by HPGe gamma spectrometry. The averageradium and thorium concentrations of the filling gravel were 23 and 27 Bq/kg, respectively.
Experimentally, it has been observed that the radon emanation coefficient, determined for geologicaland construction materials, depends principally on the porosity and water content.
Reports measurements of Radon-222 concentrations, carried out in the living rooms of 81 dwellings in Great Britain in 1976. Measurements of the activity concentration of RaA both within the room, and of the ventilation rate for the room were made. From this an estimate of the "radon output" of the room was calculated. Gives histogram of the radon outputs in picocuries of radon 222 per litre of room air per hour. Disregarding a very high measurement in a granite dwelling, the mean was 0.54 pCi/l/h.
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