Monitoring of the unattached fraction of radon progeny by the Kodak LR-115 Type 2, nuclear track detector

The experimental Unattached Radon Progeny Fraction Monitor (URPFM) was developed for the parallel monitoring of all radon progeny and the fraction of radon progeny in air that is attached onto aerosols. The optimum monitor arrangement includes two radon progeny sampling columns with each column incorporating a $0.8\mu m$ membrane filter. The filter in the first sampling column collects all the ambient radon progeny that are measured by the Kodak LR-115 nuclear track detector. The second sampling column also includes a fine mesh that removes the unattached radon progeny from the sampled air and thus the track detector that is situated above the mesh measures the unattached radon progeny. Three, five to thirteen-day long radon progeny monitoring periods were conducted inside a sealed room of a residential house and outdoors at an open cut uranium mine. The average unattached fraction of radon progeny was measured to be between 0.09 and 0.14 for the residential house, and between 0.08 and 0.10 for the open cut uranium mine.