Laser Ablation ICP-MS of Actinide Oxides as Simulated Used Nuclear Fuels

摘要

The ability to examine elemental and isotopic ratios of fuels, waste forms, and other solids by direct analysis using laser ablation techniques can greatly reduce analysis costs and time. This is particularly true for actinide elements, as they contain useful information of the fuel cycle and nuclear forensics. Current methods to evaluate the composition of used fuel include a lengthy process of digestion, separations and often require multiple techniques and sample preparations to determine the elemental and isotopic composition. Furthermore all spatial information is lost during the digestion process, eliminating potentially useful data for detailed analysis. The goal of this project is to develop and optimize laser ablation inductively coupled mass spectrometry (LA-ICP-MS) for the analysis of fuel, used fuel and waste forms. This work focuses on uranium oxide simulated used nuclear fuels starting with binary systems of (U,Pu)O2, (U,Np)O2, (U,Ce)O2 and (U,Zr)O¬¬2. Methodology was successful in observing linearity of 0.995 and greater for these systems. This was achieved by minimizing the particle size distribution of the aerosol and in turn decreases the time-dependent fractionation often observed in LA-ICP-MS.The project is composed of four tasks. The first task is to prepare and characterize actinide matrices and standards. The characterization includes physical, thermodynamic, and chemical properties of the materials prepared. The second task is to develop methods for the analysis of actinide oxide materials using LA-ICP-MS evaluating the technique for: limit of detection, accuracy, and precision. The third task is to examine the ablation zone for any chemical or physical changes in the material to determine how destructive the technique is to the material. The final task is to develop a model to correlate the ablation behavior of the elements tested with physical and thermodynamic properties of the materials. The heat capacity of the materials was measured to determine trends with thermodynamic properties of the desired elements. The model will be a useful tool in determining laser power densities of the materials of interest.