Use of activated samples to determine unknown components by gamma-ray spectrometry based on internal calibration

Calibration methods currently employed for the analysis of radioactive samples by γ-ray spectrometry apply reference sources and the accuracy of the final results is always limited by the unavoidable differences between the composition and the counting geometry of the samples and standards. Under suitable circumstances, described in this paper, the determination of elemental concentrations can be made by means of a relative detection efficiency calibration based on the spectra of multigamma-ray emitting nuclides generated by activation in the sample. The method of internal efficiency calibration may be applied to samples of different matrix composition and volume geometry to determine relative or absolute element concentrations by nuclear-induced activation reactions. Such an approach is only valid if the true coincidence effects are not significant; the criteria for selecting such γ-ray spectra are discussed. Experimental verification of the reliability of the method was carried out using certified materials analyzed by neutron activation. (orig.)