Uranium, plutonium and neodymium isotopes were measured in twelve elements of a 19 element fuel bundle of irradiated (U, Pu)O2 fuel. Samples for U and Pu analyses were prepared by adsorption of these actinides from dissolver solution onto small anion-exchange disks, which were deposited on the centre filament of a filament assembly for thermal ionization mass spectrometry. Neodymium was separated by high performance liquid chromatography on a dynamically coated column, and a portion of the fraction was deposited directly on the side filaments. In all cases, nanogram quantities of the elements were used for analyses, and the precision of isotope ratios was between 0.1 and 0.5%. The isotope dilution technique was used for quantification, and all results were compared with the corresponding data from a computer simulation. The computer code data were within 5% of the experimental data for most isotopes.