Nuclear Science User Facilities 120 As modern advanced reactors, such as those proposed within theVersatileTest Reactor and the Advanced Fuel Cycle programs, envision the use of metallic fuels, there is renewed interest in examining these fuel systems in order to comprehen- sively understand in-pile fuel behavior and maximize fuel performance while maintaining fuel integrity in a stable and predictable manner. Metallic fuels and materials require immediate and extensive testing that expands upon the historical knowledge amassed over decades [1–4] in order to provide a more fundamental and scientific understanding of metallic fuels, assess their material performance, and to validate models. Investigation into the fundamental, nano- and microscale phenomena that impact bulk fuel behavior is critical to the understanding of future fuel systems and reactor development. Historical hindrances to this effort included convoluted experi- mental parameters that are challenging to isolate during neutron irradiation, such as temperature, alloy composition, and power rate.These variable experi- mental conditions are compounded by the coexistence of various in-pile phenomena, such as constituent redis- tribution, swelling, and fuel/cladding chemical interaction. Separate effects testing has the ability to isolate these parameters and competing phenomena within single irradiation campaigns of relatively short duration. Uranium-zirconium (U-Zr) and uranium-molybdenum (U-Mo) are the two most-commonly utilized and historically studied metallic fuel systems that are also under consid- eration for advanced reactor use.To address the aforementioned gaps that exist within the metallic fuel body of knowledge, these two metallic fuels will be irradiated utilizing a separate- Disc Irradiation for Separate Effects Testing (DISECT) with Control of Temperature Walter Williams – Purdue University – Maria Okuniewski – Purdue University – The DISECT project includes the design and fabrication of a uniquely instrumented, separate effects testing vehicle; specimen fabrication and pre-characterization; irradiation; and post-irradiation examination to enable a more comprehensive understanding of in-pile phenomena.