A workplace air monitor for uranium particulate detection

An air monitor has been developed at the Oak Ridge Y-12 Plant to sample the air in enriched uranium processing areas and to detect elevated particulate concentrations due to an upset condition. The monitor measures the alpha particle activity from material collected on 47-mm filter paper. Three energy windows are used to allow quantification of background activity from radon and thoron daughters and correction of their spillage into the uranium window. There is sufficient monitor memory to hold a history file of six days´ activity from three sampling heads at 20-min status intervals. Alarm signals are activated if the absolute level of activity on a filter exceeds a predefined level, or if an excessively fast rate of buildup is occurring, which would cause the absolute level to be exceeded. This monitor is combined with an absolute particle counter, and data are collected at a processing station where uranium dust is known to be present. The occurrence of high particle count activity in the 3.0-10.0- mu m range is followed by increased alpha activity on the filter paper.