[en] The Prompt Burst Energetics (PBE) program is part of the Advanced Reactor Safety Research Program conducted by Sandia Laboratories. These studies involve an in-pile experimental program and complementary analytical investigation of the energetic response of important reactor fuel-clad-coolant systems subjected to energy deposition conditions associated with super-prompt critical excursions. The objectives of the present program include identification and characterization of the phenomena which dominate the conversion of thermal energy to work, development of models which accurately predict the energetics associated with such hypothetical accidents, and provision of the necessary input data for those models. This program includes the examination of the integral effects of fuel-clad-coolant interactions, fission gas release, and fuel and fission product vapor pressure during super-prompt critical core disruptive conditions, and thus, serves to define the initial conditions for hydrodynamic expansion of the disrupted core. To date, eighteen single-pin PBE experiments have been completed. An important conclusion drawn from the PBE work to date is that FCIs do occur in both the UO₂/Na and UC/Na systems under simulated LMFBR accident conditions. This paper presents a description of the PBE experiment methods, discusses the results of four sodium-in experiments and associated interpretive analysis, and substantiates the conclusions drawn from those results. An outline of future PBE experimental work is also given