Radon measurement in the environment in France

Over the last decade, the monitoring of radon gas in various environments and regions has allowed the CEA to construct a radon database. In soils, the 222Rn concentration depends on various factors, such as 226Ra content, porosity, permeability, etc. In holes drilled in soils and in underground cavities, radon concentrations between a few hundred Bq.m-3 and many thousands of Bq.m-3 were measured. Only a fraction of the radon atoms produced in the rocks escape and reach the atmosphere. Exhalation rates of between 10-3 and 50 Bq.m-2.s-1 were measured in different regions and for different types of soil. In the open air, the activity concentration of radon gas depends locally on the exhalation rate and on the conditions of atmospheric diffusion. Mean values were observed in the range of a few Bq.m-3 to several hundred Bq.m-3 outdoors. However, concentrations as high as 1000 Bq.m-3 were measured over short periods. (author)