NF616 is being considered as a candidate structural material for advanced reactors, due to their superior resistance to radiation induced void swelling, microstructural stability, and thermal properties. Based upon elevated temperature creep-rupture strength and impact toughness, HT-9 has significant weakness when compared with NF616. NF616 is being considered for nuclear applications due to its greater strength that tends to provide greater safety margins, design flexibility and lower cost of reactor components. Although elevated-temperature mechanical properties favor NF616, neutron irradiation data is very limited. Limited number of proton and neutron irradiated studies on NF616 have been recently reported. Hence, in order to get a comprehensive understanding of the mechanical behavior of NF616 under neutron irradiation, it is essential to study neutron irradiated samples at various doses and temperatures. The progressive change in the microstructure with irradiation dose and temperature includes void formation, increases in dislocation density, second phase formation, and other changes that can lead to swelling, hardening, and embrittlement. The strongest hardening and embrittlement occurs at temperatures below ~425°C in F-M steels due to strong increases in dislocation density and the formation of several different populations of second phases that all act to reduce dislocation mobility. The extreme hardening and low fracture toughness that occur for irradiation temperatures below 425°C is a serious issue for the use of NF616 because many reactor concepts call for core components to see temperatures as low as 320°C. To address the issue of low-temperature neutron irradiation hardening and embrittlement, systematic investigations on the mechanical behavior of NF616 are needed over a range of doses and temperatures. As a part of the UW-Madison Irradiation Experiment, NF616 was neutron irradiated in the ATR (387-469°C; 3-8 dpa). For irradiated F-M steels, the increase in yield strength is quite steep up to around 10 dpa. Extrapolation of the information learned from the 8 dpa irradiations is best accomplished by also examining lower dose samples because having data at two doses results in a more accurate extrapolation to higher doses. The proposed project aims to perform mechanical characterization on control (unirradiated) and neutron irradiated NF616 specimens as a function of irradiation temperatures and doses. The mechanical test data would be analyzed to understand the effects of radiation damage on NF616, and to develop appropriate temperature-dose correlations. By doing this work, our team can contribute to filling the gap in the literature on understanding irradiation effects on NF616 and F-M steels in general.