2017 | AFC ACCOMPLISHMENTS 173 Project Description: The work described here supports the AFC advanced reactor core materials campaign that seeks to design materials for clad and duct that can survive to very high burnup.This work requires assessing the effects of irradiation on the mechanical properties and dimensional stability of candidate materials to determine their value. In the last five years, the AFC has started using heavy ion irradiations to assess material performance out to very high dose (while continuing to use neutron irradiations to low doses).The effective use of ion irradiations for materials studies will greatly speed up the research cycle, thus adding substantial benefit.Thus, while ion irradiations are already actively being used, a parallel activity exists to improve its ability to provide information on neutron irradiation performance. Accomplishments: Two areas of advancement this year in the understanding of ion irradiation processes are on the effect of sputtering and the effect of carbon contamination. Heavy ion irradiations with beam energies in the 1-5 MeV range that are commonly used for structural materials studies produce irradiation damage only to a depth of ~1 ┬Ám.While sputtering is known to occur during heavy ion irradiations, it was found that its effect on the size of the irradiated region and the distribution of damage within the irradiated region has been completely overlooked. It was found that for beam energies below 1 MeV, very large amounts of sputtering occur. This causes a convolution of the damage accumulation and injected atoms as a function of depth, thereby altering the irradiation damage profile and injected atom distributions in an undesirable The AFC is not only making extensive use of ion irradiations to meet research goals but is actively working to understand and improve the method to obtain the best possible radiation effects information on candidate advanced reactor clad and duct materials.