NTP has multiple goals ranging from higher exhaust temperature (>1000s Isp), hot corrosion resistance (diverse propellants: H2, CH4, NH3, H2O), higher power density (thrust, >5MW/L goal), local fission product retention (materials damage, migration), manufacturability (cost, materials), safety (ground testing, flight), long core lifetime for interplanetary round trips (single fuel load, good burnup, control, 5+ years), and commonality with terrestrial applications (SMR, MNR, industrial heat, DoD/Pele) and advanced applications like reusable hypersonics, Luna/Mars surface power).
A solution, called the Coated Mixed Carbide (CMC) fuel element approach, is a hybrid between distributed solid-solution carbides from the Rover/NERVA days and localized TRISO fuel from today’s small modular reactor concepts. Very high temperature ~3500K (U,Zr)C fuel is concentrated in small kernels and protected against attack by hydrogen from outside and from fission products within by engineered multilayered coatings. An recent innovation in high-power impulse magnetron sputtering (i.e. IMPULSE® + Positive Kick™) allows conformal coatings of the small-diameter fuel kernels with ‘TRIZO-like’ protective layers to enable high-power density NTP reactors. With precision ion energy and deposition flux control, each multilayer can be engineered for specific property, such as fission gas retention, compressive stress, hydrogen permeability, ductility, etc. These 'TRIZO-like' pellets are embedded in a ZrC(W) matrix and distributed for lower peaking factor across the fuel element. Embedded propellant channels can be used for direct nuclear thermal propulsion or bimodal heat pipe power extraction for electrical power generation.
This Phase I SBIR builds on three patent-pending technologies and seeks to demonstrate feasibility of the concept, identity and rank technical risks and prioritize investment in Phase II towards retiring the necessary risks.