b'Simulating High Burnup Structures onCeO 2and UO 2Using Field Assisted SinteringPrincipal Investigator: Rubens Ingraci NetoTeam Members/ Collaborator: Darrin Byler, Kenneth McClellan, and Erofili KardoulakiThe capability toI ncreasing the nuclear fuel burnupsLaboratory (LANL) aimed to produce beyond 62 GWdMTU-1 wouldpellets with sim HBS of CeO 2and fabricate sim-HBSreduce the fuel cycle costs andUO 2through flash sintering (FS), through FS wascould improve the performance ofusing commercial CeO 2nanopowder established at LANL andnuclear power plants. However, atand in-house synthesized CeO 2it was demonstratedhigh burnups, nuclear fuels suffer anand UO 2nanopowders. FS is a FAS by producing surrogateintense microstructure transformationtechnique that can sinter ceramics in pellets with sim HBS. that needs to be well comprehendeda few seconds at low temperatures to ensure the reliability and the safetyusing electric fields, thus it can of the operations of nuclear reactors.retain nanograined microstructures. Most of the studies on high burnupBecause the FS is faster than other structures (HBS) uses data collectedFAS methods and the FS apparatus from samples irradiated on commer- is not as complex as other FAS cial and test reactors. These studies,equipment, FS is an economic and although highly valuable, are veryfast alternative to produce pellets expensive and also complex due towith different microstructures. At the radiotoxicity of the irradiated fuelshigh burnups, UO 2fuel restructures [1, 2, 3, 4]. Besides, the time frameto form grain sizes varying from of these tests is incompatible with0.590.71 m on the surface layer the pressing needs for understanding(r/r0 ~1.00.97, ~150 m thick), high burnup performance. Simulatedgrains from 5.647.8 m at the HBS (sim-HBS), which reproduces themid-radial region (r/r0 ~0.97-0.45), small grains sizes and high porosity ofand smaller grains, 7.713.98 m, at HBS in non-irradiated materials, canthe fuel disc center (r/r0 ~ 0.45-help with these efforts 0.25) [3]. The density of UO 2also Project Description: changes drastically with burnup level. To fabricate sim-HBS of ceramicThe density of UO 2fuel pellets can fuels and their surrogates, tworeduce to 78.9% of their theoretical requisites need to be satisfied: (i)density (TD) and their porosity can obtain nanopowder of the desiredincrease to 17.5 vol.% when the ceramic material, and (ii) applyburnup reaches 90 GWdMTU-1 [12]. a sintering method that is able toTherefore, sim HBS must have similar produce pellets with nanograineddensities and porosities. Pellets with microstructure, resembling HBS.sim HBS can be used to improve the Field assisted sintering (FAS) hasmechanistic models that describe been used to fabricate sim-HBShow thermophysical and mechanical around the world [5-11]. Theproperties change as a function of the current work at Los Alamos Nationalmicrostructure of the material.22 2021|AFC ACCOMPLISHMENTS'