b'Accomplishments: finding is that slight variation from[3.] Kashibe, S.; Une, K., Effect of In this project we provide datasetsperfectly stoichiometric to marginallyadditives (Cr 2 O 3 , Al 2 O 3 , SiO 2 , such as grain size, activation energies,hyperstoichiometric UO 2translatesMgO) on diffusional release of porosity and correlate this withto a significant increase in the133Xe from UO 2fuels. Journal of modeling efforts. Samples weredensification rate, which may accountNuclear Materials 1998, 254 (2), fabricated by Joshua White, Tashiemafor the large variation in activation234-242.Ulrich, and Arjen van Veelen at theenergies observed in experimental[4.] Bourgeois, L.; Dehaudt, P.; Los Alamos Fuels Research Laboratory.data for nominally stoichiometricLemaignan, C.; Hammou, A., The analyses of the grain size, porosityUO 2(Figure 2). The modeling alsoFactors governing microstructure was done by Tashiema Ulrich undershowed that this behavior is duedevelopment of Cr 2 O 3 -doped the supervision of Joshua White atto the increase in grain boundaryUO 2during sintering. Journal of Los Alamos National Laboratory. Thevacancy caused by the slight increaseNuclear Materials 2001, 297 (3), data suggest that larger grain sizesin O/U. Although the simulations313-326.are achieved under more oxidizingare in good qualitative agreement atmospheres, with largest grain sizeswith experimental trends, more data[5.] Cooper, M. W. D.; Stanek, C. R.; achieved under CO 2atmospheres.is needed in terms of densification/ Andersson, D. A., The role of dop-However, more data is necessarygrain growth versus stoichiometryant charge state on defect chem-to obtain grain size in low densityand phase field simulations containingistry and grain growth of doped materials in order to predict grainmore complex particle geometriesUO 2 . Acta Materialia 2018, 150, size kinetics. Activation energiesthat are better representative of403-413.were calculated by Arjen van Veelen,the microstructure of real pellets. using a custom-made script writtenThis will have to be combined with in Python. The experimental dataexperimental activation energies provided the basis for validating theobtained at lower density samples.combined atomic scale and meso-scaleReferences:modeling efforts on densification of a[1.] Arborelius, J.; Backman, K.; simple 2D 4-particle geometry. TheseHallstadius, L.; Limb.Ck, M.; Nils-models were developed by Michaelson, J.; Rebensdorff, B.; Zhou, G.; Cooper, Brandon Battas, and Prof.Kitano, K.; L.Fstr.M, R.; R.Nnberg, Michael Tonks from the University ofG., Advanced Doped UO 2Pellets Florida. The modeling is in qualitativein LWR Applications. Journal of agreement with experimental dataNuclear Science and Technology capturing the increase in densification2006, 43 (9), 967-976.rate for increased O/U. Application to high stoichiometries (e.g., O/U=2.1)[2.] Une, K., Effect of oxygen poten-is not possible within the pointtial on the initial sintering of UO 2defect assumptions of the model andand UO 2 -Gd 2 O 3compacts. Journal extension of the model would requireof Nuclear Materials 1988, 158, the inclusion of defect clustering in210-216.future work. The most significant 2021|AFC ACCOMPLISHMENTS 37'