Dr. Al Segall, professor in engineering science and mechanics, and Daniel Snyder, graduate student, are meeting with co-principle investigators in Sacramento, California on June 18-19 to discuss the Idaho National Laboratory (INL) project.

The project represents a collaborative effort between the Idaho National Laboratory (INL) and four educational institutions: the University of California, Davis (UCD); the University of Nevada, Las Vegas (UNLV); the Pennsylvania State University (PSU); and Boise State University (BSU). The project objectives include the development of parameters that control microstructure and properties during processing of ceramic fuels consisting of oxides, mixed oxides, and transuranic oxides. The work focuses on the use of field activation, utilizing (for the first time in nuclear fuels and materials) the spark plasma sintering (SPS) method to produce an optimum microstructure having desired composition, grain size, and porosity in the fuel pellet. The SPS method has the promise of providing enhanced control on the microstructural features needed to optimize the processing of ceramic nuclear fuels. However, this method has not been applied to processing of nuclear fuel, nor have the unique material issues encountered with ceramic fuel systems been extensively explored. Developing optimum SPS parameters will provide an understanding into the role of heating rate, pressure, and more importantly, the pulsed DC current on the microstructural development of the pellets. The advantages of developing improved microstructural characteristics has important concomitant practical benefits, including fewer processing steps, less waste production and handling, and more efficient operation.


The SPS work will be performed on materials synthesized at two institutions of this consortium and will be complemented by a modeling effort to examine the effect of heating rate, maximum temperature, dwell time, pressure, and current on the consolidation process and the concomitant microstructural changes and their spatial distribution within the pellet. In addition, a comparative study will be made using two more commonly employed fabrication routes, pressure-less sintering and hot-pressing, to provide verification for the effect of heating rate and applied current, and the predictions of the modeling effort. Calcination and solution-precipitation methods will primarily be used to produce oxide and mixed oxide powders containing U and/or surrogate elements such as Ce, Dy, Pr, Ba, and Mn. These oxides will be used individually or blended to form ceramic-ceramic (CERCER) composites for fabrication of representative fuel pellets.