Nuclear Science User Facilities 124 of the irradiation vehicle.This contact is ensured by the use of ball detents on the side of the specimen holder opposite the specimens. Figure 4 shows the optimization of desired irradiation temperatures for the U-Mo alloys with varying powers and spacer materials. Accomplishments A Phenomenon Identification and Ranking Table (PIRT) analysis was performed on both fuel systems to identify the phenomena to investigate and select the in-pile parameters to isolate. Following the PIRT findings, the DISECT project has completed the design review (INL) and the first stage of the committee for the evaluation of experiments for reactor insertion (SCK • CEN).The preliminary neutronics, preliminary thermal analysis, fuel fabrication, and precursory characterization of the U-Zr and U-Mo alloys were completed in FY 2018. Detailed thermal models are shown in Figure 5 for both the U-Mo disc and the U-Zr foil.These models were built with ABAQUS (v. 6.14-2) and using nominal neutronics information for the estimated insertion cycle.This model will be used to guide the specific irradiation-temperature conditions for post-irradiation characterization. Moreover, these localized models allow for discrete identification and, thus, a further understanding of phenomena such as constituent redistribution, porosity growth, fuel polygonization, and fission-gas superlattice formation as functions of temperature and/or power. The fuel was fabricated at INL based on thermal and neutronics calculations and designs. Preliminary characterization has been conducted on both the U-Zr and U-Mo alloys. Figure 4. U-Mo disc temperature as a function of power for 1.5 W/g gamma heating. The black horizontal lines represent target specimen irradiation temperatures. Various materials are considered for spacers, including aluminum, zirconia, and zircaloy, to achieve the desired irradiation temperatures.