2017 | AFC ACCOMPLISHMENTS 190 high magnification backscatter electron images of the different microstructural features of this sample.The overall microstructure of the sample is shown in Figure 1.This image is a composite of about 150 images stitched together to reveal the general state of the sample. In this sample, Zr redistribution is not as pronounced as is seen with U-10Zr samples, but the central region from the center of the fuel out to about a third of the fuel radius is single phase and has more Zr than the as fabricated fuel. Beyond this region there is some large porosity then the fuel transitions to predominately a 2 phase microstructure.The contrast of these phases and local EDS analysis of these phases show that the brighter phase contains more U and less Zr than the as-fabricated composition and the darker phase contains less U and more Zr than the as fabricated composition. The size of these phases varies radially with the phase size shrinking towards the outer radius of the fuel.At the outer radius of the fuel is a very pronounced Zr rind that was formed during fabrication.This same rind was present in the as-fabricated SEM performed on this fuel.At higher magnifications it is possible to observe some very small, novel interactions between the fuel and the cladding.A backscatter image of one of these regions is shown in Figure 2 which details the near cladding microstructure observed throughout the fuel. Several features are indicated in the figure as key features. The cladding is a variant of stainless steel 316,AIM1, which contains ~0.5 wt.%Ti. It appears theTi has precipitated during irradiation. Next to the cladding is a layer of U, Pu, Zr, Si and possibly some Am.This layer of Si is an artifact from fabrication where Si from the quartz mold enters the fuel and was observed in fabrication. The Zr layer is also an artifact from fabrication where Zr from the wash used on the quartz enters the fuel and was observed in fabrication also. There are precipitates of Lanthanides (La, Ce, Nd, and others) near the Zr layer. However there does not appear to be any attack of the cladding from the major fission product lanthanides (La, Ce, Nd).The accumulation of lanthanides at the Zr rind has been observed historically.The higher Zr, lower U phase and the lower Zr, higher U phase mentioned previously are also indicated.The most significant feature observed in the figure is an infiltration of Am and Sm into the cladding. Both of these elements have high vapor pressures. It is suspected that this infiltration is assisted by these high vapor pressures, but more research into the phenomenon is needed.