Radon daughter equilibrium and unattached fraction in mine atmospheres

Measurements of the equilibrium between radon and its daughters in mine atmospheres are presented. The situation in mines seems to be too complex to be described by any simple theoretical model. There is however a good correlation between the equilibrium factor, F, and the individual daughter ratios. This suggests that the individual daughter concentrations may be assessed by Kusnetz-measurements of the equilibrium factor, F. Measurements by the wire screen method indicate that the dust concentration is the main influencing factor upon the unattached fraction of the radon daughters. The unattached fraction of the potential alpha-energy was lower than 0.05 in most mining situations. In areas with very clean air, the unattached fraction may however be higher than 0.3. Measurements indicated a good correlation between the unattached fraction of the potential alpha-energy and the unattached fraction of the individual daughter products. This suggests that assessments of the unattached fraction of the individual daughters may be obtained by using the Kusnetz method for measurements on the screen and back up filter.