Abstract
Nuclear propulsion, which utilizes a nuclear reactor to generate thrust in deep space, is an efficient method of travel for long-term surface missions to Mars and beyond. It was first investigated by NASA during the 1950s, with multiple successful tests during the Rover and NERVA programs at full power and temperature. However, in the 1970s, the program was cut due to budget cuts.To support the directive to achieve a long-term surface mission to Mars by 2030, NASA has returned to the development of a nuclear propulsion system. An important aspect of the nuclear propulsion system involves the design, fabrication, optimization, and testing of a high-uranium density fuel. Rover and NERVA utilized ceramic-metallic and carbide-based fuels, with an emphasis on fuels with highly enriched uranium. The current program requires low-enriched uranium fuels that are still high in uranium density, hence the selection of uranium nitride-based fuels. The UN fuel is dispersed in a metal matrix, such as tungsten and rhenium, or tungsten and molybdenum.
The Sirius-2A and Sirius-2B irradiation experiments featured UN-Mo-W fuels fabricated using spark plasma sintering at the Marshall Space Flight Center in Alabama. The samples were then sent to the Idaho National Laboratory Transient Reactor Test facility to be irradiated at prototypical start-up conditions. After irradiation, the fuels were characterized using non-destructive and destructive examination to determine the effects of irradiation. The objective of this study is to discuss the findings of the post-irradiation examination of the UN-Mo-W fuels irradiated for the Sirius project.