Nondestructive measurements of γ-ray and X-ray emissions are often made to characterize special nuclear materials. Various
computer codes are available to determine the relative isotopic composition of uranium or plutonium (along with certain other
associated nuclides) from analysis of the spectra resulting from such measurements. MGA (Gunnink, Proceedings of the 9th ESARDA
symposium on safeguards and nuclear management 167, 1987) and MGAU (Gunnink et al., Proceedings of the IAEA symposium on international
safeguards 541, 1994) are among the major isotopic codes. The purpose of this study was to investigate MGA and MGAU performance
versus energy resolution of the counting system.