MDA improvement technique for lung counter measurements of uranium workers

A practical and simple method was employed to improve the minimum detectable activity (MDA) for lung counting measurements by summing several accumulated spectra. The method was checked for natural uranium, which produces peaks due to photon energies of 63.3, 92.6 and 185.7 keV. By combining nine measurements, an overall improvement of the MDA by a factor of about 3 was achieved. Uranium contamination levels lower than the MDA of a single spectrum could be detected with acceptable accuracy when analyzing the sum spectra. Specific results are given for four workers occupationally exposed to natural uranium.