Nuclear Science User Facilities 84 Thermal conductivity is one of the most important fuel properties driving heat transfer performance as well as temperature distribution in nuclear fuel [1].Thermal conductivity is determined by materials’ physical structure, chemical composition, and thermodynamic state.These factors are strongly affected by a variety of physical processes in nuclear fuels, such as large temperature variations, species diffusion, neutron capture, and microstructure evolution [2,3]. Fuel thermal conductivity may also change substantially after removal from the reactor due to resulting changes in the material after the dynamic condi- tions of irradiation are removed.As a result, it becomes important to gain a more complete understanding of thermal transport as a function of time-temperature-burnup [4].To do so requires accurate, spatially resolved Additive Manufacturing of Thermal Sensors for In-pile Thermal Conductivity Measurement Yanliang Zhang – University of Notre Dame – Figure 1. a, b)TEM and HRTEM d) images of the as-fabricated Pt nanoparticles. The corresponding SEAD pattern c) is also given. The printed 3-omega sensors have great potential for improving the understanding of fuel thermal transport properties through in-pile thermal conductivity measurement.