Diffusion study of uranium mononitride/zirconium carbide composite for space nuclear propulsion

Abstract

The next generation of space exploration will require extensive developments in rocket technology. Space nuclear propulsion is of interest due to its high fuel density and power; however, it also has high temperature and stability demands. This study examines a uranium mononitride (UN) and zirconium carbide (ZrC) ceramic-ceramic particle composite as a potential fuel for these missions. Based on the constituent properties, this fuel composite is expected to be thermally efficient and resistant to the hot hydrogen propellant. One of the main concerns with this composite is the unknown diffusion behavior between UN and ZrC over time. Diffusion couple experiments and isothermal furnace tests of composites were two experimental techniques used to determine how these constituents will behave when left in contact at high temperatures. UN and ZrC were found to have limited but observable diffusion at the phase boundary. The resulting phase is a UZr(CN) quaternary phase. UZr(CN) has been examined for other high temperature and gas nuclear reactors with preliminary success; however, there lacks sufficient data to fully understand this phase. Based on the limited information available, the resultant quaternary phase could be deemed acceptable and even provide better adhesion for the fuel particles (UN) to the matrix (ZrC).