title: On improving the validity of wire screen "unattached" fraction Rn daughter measurements.
abstract: Wire screens are commonly used to estimate "unattached" Rn daughter fractions in ambient and mine atmospheres. However, it is now recognized that the "unattached" fraction is in reality an ultrafine cluster mode in the 0.5-3 nm size range and that the collection efficiency versus particle diameter characteristics of wire screens do not permit a distinct separation of the "unattached" and "attached" fractions. Wire screen penetration theory and a semi-empirically corrected diffusion coefficient equation are used to characterize "unattached" fraction measurements as a function of experimental parameters. Collection efficiency curves are estimated for previously published wire screen "unattached" fraction measurements, and improvements in wire screen methods for such measurements are discussed.
authors.affiliation: Department of Civil Engineering, University of Illinois at Urbana-Champaign 61801.
authors.forename: M
authors.initials: M
authors.lastname: Ramamurthi
authors.forename: P K
authors.initials: PK
authors.lastname: Hopke
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis; D004058:Diffusion; D005374:Filtration / Q000295:instrumentation; D011059:Polonium / Q000032:analysis*; D011829:Radiation Dosage
chemical_list: D000396:Air Pollutants, Radioactive; D011059:Polonium