2018 | AFC ACCOMPLISHMENTS 98 2.5 IRRADIATIONTESTING AND PIE TECHNIQUES Image Analysis Applied to Uranium Silicide Accident Tolerant Fuel Microstructure Principal Investigator: Jason Harp Collaborator: Fabiola Cappia Image analysis is a powerful tool capable of quantifying microstruc- tural features. It is extensively used in many fields, and in material science to relate physical properties at the micro-scale to the engineering ones at the macro-scale.When speaking about nuclear materials, the knowledge of their microstructure and how this changes under irradiation becomes a key safety factor, as the microstructure impacts the performance and safety under irradiation. Image analysis is applied as postirradiation examination (PIE) technique to investigate the microstructure of U3Si2, an Accident Tolerant Fuel (ATF) candidate, irradiated at low burnup under Light Water Reactor (LWR) conditions in the AdvancedTest Reactor (ATR) at Idaho National Laboratory (INL). Project Description: Accelerating the development of new fuels and cladding with enhanced safety and performance compared to the current fuel systems for present and future generations of LWRs is a priority of the Department of Energy, Office of Nuclear Energy (DOE-NE). A joint effort towards this goal has been undertaken by the DOE-NE, National Laboratories, Universities and industry within the ATF Campaign. Preliminary data regarding irradiation performance of the proposed new concepts are of paramount importance for qualification purposes, to down- select the most promising fuel systems and optimize the fuel development strategy. U3Si2 is one of the most attractive candidates, due to its high thermal conductivity and increased uranium loading compared to UO2. The higher thermal conductivity reduces the temperature gradients and stresses within the fuel, implying that the fuel can be operated either with a higher margin to melting or at higher power that improves economic operation without compromising safety.The higher uranium loading allows reduction of initial enrichment, and allows the deployment of alternative cladding materials with higher neutron penalty compared to Zircaloy. Irradiation of U3Si2 rodlets has been carried out to provide first performance data of U3Si2 under commercial LWR conditions. In particular, assessment of fuel microstructure integrity and fission gas behavior are the highlight of this project, being those key fuel performance parameters of merit. Integral PIE data from irradiation tests prototypical of LWR irradiation conditions are fundamental to confirm suitability of U3Si2 as ATF for advanced LWR.