Authors: Megan Frary, Darryl Butt, Matthew Luke, Thomas Hartmann, Earl Wolfrom, Batric Pesic, Michael Figueroa and William Windes
Affiliation:
Title: Microstructural Evolution during Spark Plasma Sintering
Abstract: Advanced nuclear energy concepts require fuel systems with different physical forms and compositions as compared to current commercial practice. In this project, advanced fuel forms will be processed by a novel method: spark plasma sintering (SPS). SPS has been applied to the synthesis and densification of a number of ceramic and refractory materials from powder precursors and has demonstrated the capacity to produce materials with novel compositions, homogeneous fine-grained microstructures, and reduced losses of volatile species. While these processing characteristics suggest that SPS will be advantageous in producing new fuel forms that are difficult to process by conventional methods, for example, where there is considerable concern about volatilization of actinide species, it has not yet been applied to nuclear materials. In addition, SPS process fundamentals are poorly understood. A new SPS system was installed at INL at the end of 2007 and work is currently underway to understand the role of SPS processing on microstructure. In the future, SPS will be applied to mixed uranium/actinide oxide compositions with unique ceramic matrices, refractory metal-matrix cermet fuels, and advanced coating compositions for graphite crucibles used in pyroprocessing of irradiated fuel. In situ diagnostics will be developed to determine the temperature profile of compacts during processing to help elucidate mechanisms of local heating and densification. These data will be combined with post-processing microstructural characterization and process modeling to establish the thermodynamics and kinetics of synthesis and consolidation. In addition, microstructural characteristics (e.g., crystallographic texture, grain size and size distribution, and porosity) that contribute to high temperature performance will be determined. The unique attributes of SPS, when well understood and controlled, will result in fuel forms that have improved homogeneity and performance.