Mixed Uranium and Plutonium Oxide Fuel Post-Irradiation Analysis Using HPLC and ICP-MS Techniques*

The United States Department of Energy (DOE) Fissile Materials Disposition Program (FMDP) is pursuing the disposal of surplus weapons-usable plutonium via reactor irradiation using the plutonium as the fissile constituent of a mixed uranium and plutonium (MOX) fuel. Lead test assemblies (LTA) have been irradiated for approximately 36 months in Duke Energy’s Catawba- 1 nuclear power plant (NPP). Per the MOX fuel qualification plan, destructive post-irradiation examinations (PIE) are to be performed on second cycle rods (irradiated to an average burn-up of approximately 45 GWd/MTHM). The Radiochemical Analysis Group at Oak Ridge National Laboratory has performed some of the detailed destructive post-irradiation examinations (PIE) on selected segments from four of the MOX fuel rods. Amongst the various analytical methodologies used for the destructive analyses of the spent fuels segments were high precision determinations of select lanthanide and actinide isotopics, and elemental assay using HPLC separation combined with isotope dilution mass spectrometry (IDMS). A detailed description of the chromatographic chemistry used for the baseline separation of the fission products and actinide elements will be presented as well as the protocols used for assays using IDMS technique. Relative comparisons of measured data to program predictions will also be discussed.