2018 | AFC ACCOMPLISHMENTS 149 of the injected atom distribution (as determined by SIMS) approximately matches that of the predicted width in absence of diffusion.The measured distribution is however offset from the predicted distribution, but rather than this being due to diffusion, it is likely due to inaccuracies in the calibration data used by the algorithm that predicts the injected atom distribution. Other aspects of possible redistribution such as diffusion down grain boundaries has yet to be investigated, but this initial observation of a lack of any gross redistribution due to radiation enhanced diffusion at reactor relevant irradiation temperatures is excellent news for Fe self-ion irradiation of ferritic alloys because it appears that microstructural investigations can be performed in regions nearly free of injected atoms. Figure 1. SIMS measurement of iron distributions overlaid on predicted irradiation dose and injected atom profiles. Data are scaled and offset individually along the y axis for visualization purposes. As a result, the relative strength of the signal among different elements does not correlate with relative atomic abundance. Accomplishments: The focus for this initial study was to observe the fate of injected self-ions during ion irradiation of HT-9 that is a reference clad and duct material for sodium cooled reactors.The primary element in HT-9 is iron, so the cathode from which the ions are extracted during ion irradiation was made from Fe57. In natural iron, Fe57 has an abundance of only ~2%, so injected Fe57 atoms are readily distinguished from the iron originally present in HT-9.The ion irradiation was performed at a sodium cooled reactor relevant temperature of 400°C. Because irradiation is known to greatly enhance diffusion, there was a strong expectation that there would be substantial redistribution. However, as shown in Figure 1, the observed width