Refractory Metal Coated Uranium Nitride Fuel for Nuclear Thermal Propulsion

NTP is a critical technology needed for human missions to Mars due to its high specific impulse (Isp).nbsp; To reduce cost and potential burdensome security and handling requirements, low enriched uranium (LEU) fuel is desired.nbsp; The high uranium density of uranium nitride (UN) over uranium oxide (UO2) favors the use of UN for the LEU option.nbsp; However, similar to UO2, techniques are needed to produce refractory metal coatings on the UN particles to allow fabrication of the cermet fuel element and to protect the UN from the hydrogen propellant. During this investigation, techniques for producing spherical UN particles along with methods for producing refractory metal coatings on the spherical nitride particles were developed. To facilitate development of the spheroidization process and subsequent refractory metal coating of the particles, UN surrogate materials were used.nbsp; Characterization of these materials showed the as-received nitride powders were comprised of angular particles, which is the morphology of the current UN powders. To produce spherical particles for subsequent coating, plasma processing techniques were used. Analysis of the plasma treated nitride particles demonstrated the ability to produce spherical nitride powder with significant improvements in flowability. Using these powders, the ability to refractory metal coat individual nitride particles was demonstrated, and characterization confirmed continuous, uniform coats were produced. During Phase II, the techniques will be optimized and scaled for producing kilograms of powder per run. Coated particles will be produced and used to make cermet based fuel segments for testing at NASA. At the conclusion of the Phase II effort, refractory metal coated nitride powder will be delivered to NASA for producing an NTR Element Environment Simulator (NTREES) size element.nbsp; To commercialize the materials and techniques, Plasma Processes will collaborate with BWXT and NASA during Phase II.