Reconstruction of the background spectrum for processing airborne gamma survey data

The reconstruction of the background spectrum is based on a decomposition of the initial spectrum into components which are due to the radiation from naturally occurring radionuclides on the Earth’s surface, cosmic rays, and radiation from the spectrometer itself. For the spectra of the naturally occurring radionuclides, the response functions of the detector are calculated for 238 U, 232 Th, and 40 K in the soil; the instrumental and cosmic-ray background is determined by means of aircraft flights at a large altitude. The method has been tested under real conditions and has given satisfactory results for the evaluation of the soil content of naturally occurring radionuclides and 137 Cs from global fallout. The method will increase considerably the sensitivity and accuracy of the aerial gamma-ray surveys for the detection of technogenic sources of radiation, whose activity is comparable to that of naturally occurring radionuclides and which have no distinct isolated photopeaks in the observed spectrum.