Validation of radioactive isotope activity measurement in homogeneous waste drum using Monte Carlo codes

In this work, the angular dependent efficiency recorded by collimated NaI(Tl) detector is determined a quantification of the activity of mono- and multi-energy gamma emitting isotopes positioning in a waste drum. The simulated efficiencies using both MCNP5 and Geant4 are in good agreement with experimental results. Referring to these simulated efficiencies, we recalculated the source activity with the highest deviation of 13%.