The Lead-cooled Fast Reactor (LFR), a prominent category of Generation IV advanced reactors, involves design challenges for reactor plant in-service inspection (ISI) due to high operating temperatures, coolant opacities that prevent visual inspection, and the tendency for coolant corrosive attack. These challenges limit the feasibility and effectiveness of conventional ISI technologies. To overcome these challenges, acoustic methods that can operate under high temperature conditions are being actively considered in the U.S. as well as internationally. This research investigates the application of ultrasonic transducers, either piezoelectric or electro-magnetic, for LFR inspections. COMSOL Multiphysics software is used to model the effectiveness of thickness measurements, defect detections, and acoustic reflectance, for the reactor vessel and components within or in contact with the coolant. Acoustic absorption due to wave propagation through molten lead is also investigated. The models were designed in conjunction with future experimental work to provide comparison data between theory and experiment.Department of Energy, Livermore, CA 94950Outstanding ThesisLieutenant, United States NavyApproved for public release. Distribution is unlimited