3R-WL air sampling working level survey meter. Calibration and evaluation progress report, May 1, 1976--December 31, 1976

The design and operation of a direct-reading sampler for air-borne radon progeny are described. The instrument was designed for use by ventilation personnel in uranium mines and is small, rugged, light-weight and easily carried and operated. Direct readout of the radon progeny concentration in units of working levels, in the range of 0.01 to 10 WL, is accomplished by counting the alpha particles from 218Po and 214Po with a single detector and two energy discrimination channels. Unique features include a fixed-volume, gravity-operated pump requiring no power source and minimal calibration, automatic decay, counting and display sequencing, capacity for more than 50 samples on a single roll of membrane filter, and provisions for recording all data directly on the filter tape. For the prototype as built, calibration against the 2-count alpha spectroscopy method of measuring WL indicated an average error of less than 1 percent in the range from 0.25-25 WL. However, the standard deviation of measurements made with the 3R-WL meter increased from 7 percent above 10 WL to 71 percent at 0.25 WL. Sources of error and variability are analyzed and suggestions for improving the precision of the measurements are included