Unattached fraction and the aerosol size distribution of the radon progeny in a natural cave and mine atmospheres.

Butterweck, G; Porstendoerfer, J; Reineking, A; Kesten, J

Isotopenlab. Univ., Burckhardtweg 2, D-3400 Goettingen, Germany

Conference 5. Int. Symp. on the Natural Radiation Environment, Salzburg (Austria), 22-28 Sep 1991 Editor Janssens, A; Lowder, W; Olast, M; Sinnaeve, J; Steinhaeusler, F (eds)

THE NATURAL RADIATION ENVIRONMENT., NUCLEAR TECHNOLOGY PUBLISHING, ASHFORD, KENT (UK), 1992, pp. 167-170, Radiation Protection Dosimetry [RADIAT. PROT. DOSIMET.], vol. 45, no. 1-4 suppl. ISSN 0144-8420 NUCLEAR TECHNOLOGY PUBLISHING, ASHFORD, KENT (UK)

Measurements of the activity size distribution of aerosol-attached radon progeny and the amount of unattached radon daughters have been performed in mine atmospheres and a tourist cave. During working hours a large number (10 super(5)-10 super(6) cm super(-3)) of aerosol particles is generated in mines, mainly by diesel engines. the activity size distribution of these aerosol particles has smaller median diameters (AMAD about 200 nm) than the aged aerosol existing in the mine during non-working hours (AMAD about 350 nm). Strictly correlated to the aerosol concentrations, the unattached fraction of the radon progeny, f sub(p), in the tourist cave (3000 particles per cm super(3)) is higher (f sub(p) = 0.1) than in mines (f sub(p) = 0.01) during working hours. This yields 1.4-2.5 times higher radiation dose conversion factors in the natural cave than in mines under working conditions.