The Osiris reactor concept is one of two that emerged from the DOE-sponsored IFE reactor design study. It uses a heavy ion beam driver, a carbon cloth first wall and blanket structure that is filled with Flibe, and a steam power conversion system. The driver energy is about 5 MJ and the target yield is about 430 MJ. A 1000 MW(e) net plant requires a rep rate of about 4.6 Hz. The reactor chamber is of a leak-tolerant design where Flibe permeates a carbon cloth first wall and provides a protective coating. A Flibe spray, which supplies the pool at the bottom, condenses blowoff vapor. All components are removed as an assembly from the top of a carbon composite vacuum vessel. The study included assessments of environmental and safety aspects, economics, and technology development requirements.