Steps in the development of nuclear thermal propulsion fuels

As a result of recent increased interest in Mars exploration and other deep-space missions, the idea of a US Nuclear Thermal Propulsion (NTP) system has been rekindled, and the feasibility of such a program will be revisited. Making and qualifying an NTP fuel that meets mission performance requirements is an essential first step. Graphite fuels and ceramic metal (cermet) fuels are of particular interest since these fuels have shown significant advantages over other fuel types. This paper will address the history of NTP fuel fabrication technology as related to the Nuclear Engine for Rocket Vehicle Application, GE 710, and ANL nuclear fuel program, as well as recent efforts in recapturing heritage fuels and developing new NTP fuels. Substantial experimental databases and supporting documentation exists for the graphite composite fuel option. Some irradiation and high temperature test data is available for cermet fuels, but cermet fuels were never tested in prototypic NTP conditions. A first step in the development effort will be a fuel fabrication recapture effort to provide samples to show that the technology works and that the performance of the fuel is acceptable. Advances in fuel fabrication, materials processing, and coating technology are expected to improve and/or enhance future fuel development, maturation, and certification efforts. The current plan is to perform non-nuclear, separate-effects, and integrated tests to provide additional test data and insight into the capabilities of each fuel and to use that data to evaluate potential performance within an NTP engine stage.