An Airborne Gamma Ray Spectrometer and Its Application in Nuclear Power Plant Site Surveys

Airborne radiometric surveys from low flying helicopters have been completed for three nuclear power plant sites in Texas. The gamma ray counting data acquired in the air are converted to ground dose rate and plotted as a series of profiles. A radial (spokes-of-a-wheel) flight line pattern provides easy position control and concentrates sampling density over the plant site. The 5- to 8-fold range of natural and man-made radiation background within 10 miles of the three plant sites is statistically well characterized by over 14,000 spectra taken directly from 3.8% of each 314 square mile survey area. The aerial dose estimates agree closely with thermoluminescence dosimeter (TLD) data taken on the ground over three month periods. The instrumentation system, survey rationales, data reduction, and analysis procedures are described.