b'trodes, seen as porosity in Figure 2(b).obtain elevated electric power densi-Whereas at moderate current ratesties. Additionally, it was found that UN (126 mA mm-2 min-1) pellets withfully transformed to U 2 N 3during FS good integrity and densities above 92as shown in Figure 4. This is probably %TD were obtained (see Figure 2(c)).because of N 2present in the atmo-To increase understanding of thesphere when the pellet was ~1300C. sintering kinetics during FS of UO 2 Therefore, better control of the pellet the sintering activation energy oftemperature and atmosphere during FS UO 2.16was calculated using the masterare required.sintering curve (MSC) method [12]To further improve the sintering as shown in Figure 3. The activationkinetics of UO 2 -UN composites, a energy for FS, 107.5 kJ mol1, wasnew pathway has been conceived byFigure 1. Densification profile of UO 2.16found to be closer to the activationcombining axial pressure with theduring CS at different heating rates energy reported for SPS of UO 2.16byelectrical effects of FS. A pressureand FS at various current rates.Chen et al. [13], 140 kJ mol-1, than theassisted flash sintering equipment activation energy calculated during CS,has been designed and is currently 380 kJ mol-1. This finding highlightsbeing assembled. This innovative the similarities of the electrical effectssintering method has the potential to present in FS and SPS, and points todeliver high density pellets, with good a similar sintering mechanism. UNmechanical integrity and tailored pellets and other UO 2composites havemicrostructures at low furnace been successfully sintered before totemperatures and in a few minutes.high densities using SPS [14, 15]. References: Once the best parameters for controlled[1.] Zinkle, S.J., et al., Accident toler-current rate AC-FS were identified asant fuels for LWRs: A perspective. a current rate of 126 mA mm2 min-1Journal of Nuclear Materials, up to 12 A (RMS) and a dwell of 22014. 448(1-3): p. 374-379.min at this maximum current, based on experiments on UO 2.16 , a UO 2 -UN[2.] Yang, J.H., et al., UO 2 UN com-composite pellet with 10 vol% UNposites with enhanced uranium was then subjected to this same testdensity and thermal conductiv-condition under an Ar+N 2atmosphere.ity. Journal of Nuclear Materials, The pellet density obtained was 75%TD2015. 465: p. 509-515.in 14 minutes. It is expected that[3.] Johnson, K.D., et al., Fabrication further densification can be obtainedand microstructural analysis of if the current during FS exceeds 12UN-U 3 Si 2composites for accident A, the limit of the current FS setup.tolerant fuel applications. Journal By adding UN to the composite, itsof Nuclear Materials, 2016. 477: electrical resistivity decreases forcingp. 18-23.the need of higher electrical currents to 2020|AFC ACCOMPLISHMENTS 59'