The Laboratory for Neutron Activation Analysis at CDTN/CNEN, Brazil, acquired the k0_IAEA software package during the Workshop on Nuclear Data for Activation Analysis, 2005, held at the Abdus Salam International Centre for Theoretical Physics, Italy. The IAEA distributed the software to several laboratories and has accepted suggestions from the users about the performance of the program. This paper describes the validation procedure carried out aiming at the validation of the software package. The procedure was to analyze the SMELS samples and to compare the results obtained by this software to the commercial KayWin software package, already established at CDTN/CNEN. The results were compared to the values obtained by the Jožef Stefan Institute, Slovenia. The laboratories applied the same software: k0_IAEA and KayWin. The overall results pointed out that the k0_IAEA software set up at CDTN/CNEN, Brazil, is working properly. The u-score test showed that all results, except data in SMELS Type III for Se obtained at the JSI, are within 95% confidence interval once setting up u-score as 1.96 (P = 95% or ±2σ).