This paper details the different steps for the isotopic determination of UAmO2 discs from analytical irradiation. MARIOS and DIAMINO irradiations were performed in materials testing reactors to study the behaviour of americium bearing blanket samples in regard of heterogeneous recycling in sodium-cooled fast reactor. Six irradiated discs were dissolved in hot cells and were analyzed to determine isotope ratios of uranium, plutonium, americium and neodymium. The ratios were measured combining chemical separations and TIMS analyses. Using the double isotope dilution methodology helps measuring 238 Pu/ 238 U, 241 Am/ 238 U and 148 Nd/ 238 U ratios with uncertainty about a few per mil (k = 2).