Radon daughter plateout--I. Measurements.

Radon daughter plateout (surface deposition) was measured directly in 1.9 and 20-m3 chambers. To test the effect of different parameters on plateout, measurements were made over a wide range of particle concentrations and sizes. The results indicate that plateout is strongly dependent on particle concentration. The ratio of surface-deposited activity to total daughter activity in the chamber varied from 4% at particle concentrations greater than 10(5)/cm3 to 86% for particle concentrations less than 10(3)/cm3. Comparison for the experimental data with a theoretical model shows that the theory overestimates plateout and underestimates the airborne concentration by factors of about 3.5 and 3.3, respectively.