b'more Zr (13% not 10%) to the Pd bearing pins. The U-13Zr-4Pd annular fuel microstructure is visible in Figure 2 (unfortunately the cladding detached from a closed contact with the fuel during sample preparation). In general, it seems not very dissimilar compare to the one from U-10Zr annular and the fuel radius can be divided in 4 regions as indicated in Figure 2. A more in detail description of the different regions is shown in Figure 3 from which emerge that Pd is more likely to bond with rare earths at the periphery of the fuel (region 1-2), instead in the central regions (3-4) the majority of Pd is alloyed with Zr, forming an intermetallics very close to PdZr . Figure 4 shows also an EDS 2maps of U, Zr and Pd from region 3 in which is clear the association Zr-Pd. Finally, regarding U and Zr in theFigure 4. Energy dispersive X-ray spectroscopy (EDS) maps of region 3 from matrix, there is everywhere in the fuelFigure 2 highlighting the distribution of Zr, Pd and U.the presence of a U-rich phase and a second phase U-Zr with Zr variable from 10wt% (region 1-2) to 35wt%References: (region 3-4). [1.] M. Harp, L. Capriotti, F. Cappia,ani, D.L. Porter, V. Blackwood, Z. Baseline Postirradiation Examina- Jones, D. Olson, B. Mishra, J.R. Ken-The performance of this optimizedtion of the AFC-3C, AFC-3D, andnedy, S.L. Hayes, New Fuel Alloys Pd-bearing fuel alloys seems toAFC-4A Experiments, INL/EXT- Seeking Optimal Solidus and Phase have improved and do not show18-51447. (2018). Behavior for High Burnup and TRU any obvious performance differenceBurning, in: Int. Conf. Fast React. between U Zr pins with the same[2.] G.W. Egeland, R.D. Mariani, T.Relat. Fuel Cyles Safe Technol. Sus-geometry at this burnup. The differ- Hartmann, D.L. Porter, S.L. Hayes,tain. Scenar., 2013.ence in behavior of the intermetallicJ.R. Kennedy, Reduction of FCCI formations between center andeffects in lanthanideiron diffusion[4.] J.M. Harp, H.J.M. Chichester, L. periphery and the efficiency of Pdcouples by doping with palladium,Capriotti, Postirradiation exami-as additive to mitigate FCCI needsJ. Nucl. Mater. 440 (2013) 178 nation results of several metal-more deep understanding and further192. https://doi.org/10.1016/j. lic fuel alloys and forms from verification at higher burnup. jnucmat.2013.04.060. low burnup AFC irradiations, J. [3.] R.D. Mariani, D.L. Porter, V. Black- Nucl. Mater. (2018). https://wood, Z. Jones, D. Olson, B. Mishra,doi.org/10.1016/j.jnuc-J.R. Kennedy, S.L. Hayes, R.D. Mari- mat.2018.07.003.2020|AFC ACCOMPLISHMENTS 137'