b'3.1 FUEL FABRICATION AND PROPERTIESThermal Conductivity of Irradiated Binary Metallic FuelsPrincipal Investigator: Cynthia A. Adkins Team Members/ Collaborators: Chuting Tan, Narayan Poudel, Zilong Hua, Scott Middlemas, Tiankai Yao, INL; Yong Yang, University of FloridaThese first of aM odeling and simulationfrom fission gas bubble formation tools for predicting thecan be described by an analytical effective thermal conduc- model that can be used with those kind experimentaltivity of metallic fuels, particularlyindividual properties to represent thermal conductivityU-Zr and U-Pu-Zr alloys, are limitedthe effective thermal conductivity measurements onand incomplete. The physics-basedof the bulk U-Zr alloy system irradiated high burntools that do exist in fuel performanceboth pre and post irradiation. For up U-10 wt% Zr willcodes use assumptions about the prematerials with simple physical transform the foundationand post irradiated microstructurestructures, the effective thermal for physics-based fuelof U-Zr fuel that are based on theconductivity can be modelled using performance modelingstructure being homogeneous andexisting fundamental structural of thermal conductivitythe Zr redistribution during irradia- models such as Maxwell-Eucken and used to develop newtion following a uniform gradient.Effective Medium Theory (EMT) metallic fuel forms andAs characterization techniquesmodels. These models are examples reactor designs. improve for irradiated metallic fuels,of analytical models that have a it is reported that the microstructurephysical basis in the microstructure is even more intricate and inhomo- of the materials they are used to geneous than previously reported.describe. They can be combined Therefore, it becomes even morein such a way to account for the important to associate local thermalvolume fraction of phases, pores, properties with local microstructure.and the interaction between them This study produced local thermalfor an effective thermal conductivity diffusivity and thermal conductivitycalculation. Analytical models are data that supports and improvespreferred over numerical models the calculation of effective thermalto describe the effective thermal conductivity and our understandingconductivity due to their physical of the behavior of U-Zr fuel in-pile. basis, rapid and low cost of calculation and reported reasonable accuracy Project Description:even when the microstructure is Microstructural phases in an alloyuncertain. These models require system have distinct physical andthat the thermal conductivity and chemical properties, includingvolume fraction of each defined thermal conductivity. The goalphase be known as input parameters of this study is to show that theto the calculations. This work is the different phases present, formedstarting point for further development due to Zr migration, in the U-Zrof a robust post-irradiated effective system indeed do have differentthermal conductivity model of the thermal conductivities. TheseU-Zr metal fuel system that can be phases along with the porosity 122 2022|AFC ACCOMPLISHMENTS'