Feasibility of Low-Enriched Uranium Fueled Nuclear Thermal Propulsion in the Low-Thrust Region Below 16klbf

This paper establishes the feasibility of Low-Enriched Uranium fueled Nuclear Thermal Propulsion (LEU-NTP) reactors in the low-thrust region below 16klbf (71kN). A reference, 7.5klbf, HEU design is converted to 19.75% enriched LEU and shown to be capable of reaching criticality and meeting other performance requirements with minimal mass increase. At this smaller scale, historical LEU-NTP conversion techniques that focus on maximizing neutron moderation or minimizing leakage within the active core are insufficient. Thus, the 7.5klbf preliminary design requires several unique modifications, including a reduction in the number of control drums and adjustments to selected materials. To verify the design’s feasibility, several key neutronic and thermal-hydraulic performance parameters including burnup, Xenon worth, and submersion criticality are characterized with Serpent 2.0 and the Space Propulsion Optimization Code. The methods applied in this work reveal an opportunity for further LEU-NTP optimization that may directly translate to increased scalability and efficiency for future designs