A comparison of the attachment of the decay products of radon-220 and radon-222 to monodispersed aerosols

The adsorption of radioactive aerosols is of prime importance when assessing the hazard of inhalation of radioactive materials, especially in the uranium mining industry. In previous studies of the attachment rate, contradicting results on the dependence on particle size have been found. The attachment rate for the attachment of the decay products of Ra-222 to monodispersed polystyrene aerosols (of a diameter from 1.2 to 5.3 μm) in the concentration range 1 to 67 particles cm-3 was measured directly. This is compared with the attachment rate of radon-220 decay products which was measured in a previous experiment. As before, the attachment between the radioactive atoms and the aerosols was found to be directly proportional to the particle concentration N, as well as to the square of the particle radius R. The attachment coefficient of 4.1 x 105 R2 cm3 min-1 and the sticking probability of 0.13 for Rn-222 decay products were found to be larger than that for the decay products of Rn-220 (2.4 x 105 R2 cm3 min-1 and 0.08, respectively). The mechanism for the attachment, however, is the same. (author)