A comprehensive review of radon emanation measurements for mineral, rock, soil, mill tailing and fly ash

To our knowledge, this paper is the most comprehensive review to cover most studies, published in the past three decades at least, of radon emanation measurements. The radon emanation fraction, a possibility of radon atoms generated in a material escaping from its grains, has been widely measured for a variety of materials. The aim of this review is to organize a huge number of such data accumulated. The representative values of the emanation fraction for minerals, rocks, soils, mill tailings and fly ashes were derived to be 0.03, 0.13, 0.20, 0.17 and 0.03, respectively. Current knowledge of the emanation processes was also summarized to discuss their affected factors. ► Recent radon emanation measurements were thoroughly reviewed. ► Averages of radon emanation fractions: 0.03 (mineral), 0.13 (rock), 0.20 (soil), 0.17 (mill tailing) and 0.03 (fly ash). ► Grain-size effect was not significantly found for size larger than 1 μm. ► Pore water generally enhances the emanation fraction by a factor of 5 or less. ► Definition of “radon emanation” should be shared among researchers.