The present work concerns the development of techniques which can be used to verify clearance of Ge-68/ Ga-68 and Co-57 sealed radioactive sources. These sources are used for the calibration of various nuclear medicine systems like Gamma camera and PET imaging. There are several types of such sources of different characteristics and geometry i.e. linear, area, volume, while after their useful life these sealed sources need to be kept in control for decay till meeting the clearance criteria. The techniques aim to determine the activity of the sources after storage for appropriate time span until the clearance criteria are met and are based on Monte Carlo simulation using the MCNPX code for evaluation of the 3x3 NaI (Tl) scintillator detector efficiency. A preliminary work was done for two types of sealed radioactive sources: i) a line source containing Ge-68/Ga-68, ii) a flood source containing Co-57. However, the determined activities were underestimated by 13.6% for Co-57 flood source and 26.9% for Ge-68 line source, compared to the source’s nominal activities. In the present study, the accuracy of the previously developed techniques has been improved by detailed detector characterization.

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