An improved formula for determination of the activity via the sum-peak method

The sum-peak method principally enables determination of the absolute activity of gamma cascade emitting sources based only on the use of spectral data, without knowledge of the detector efficiencies. However, to achieve better accuracy of the activity results, corrections due to pile-up, accidental coincidences, electronic noise and angular correlations must be introduced into the proposed method. Such corrections usually require the collection of a few gamma spectra and additional extrapolations, thereby further complicating the experimental procedures. In this paper, it is shown that by using pile-up peaks for corrections of accidental coincidences, Monte Carlo techniques for angular correlation, and LLD corrections, the source activity can be measured with accuracy and reproducibility below 1% using only one gamma spectrum, without any additional extrapolations. •Experimental procedure for the determination of the activity of the source by the sum-peak method is simplified using the Monte Carlo simulations.•Corrections due to angular correlations which take into account full and partial absorptions of gamma photons contribute to more accurate results of the measured source activities.•Residual pile-up corrections are implemented observing two pile-up peaks.•The method proposed does not include any extrapolations of experimental data.