In this SBIR, USNC-Tech will design a next-generation NTP moderator with thermal, mechanical, and neutronic performance superior to existing insulator solutions. During Phase 1, USNC-Tech will design, optimize, and computationally demonstrate the effectiveness of next-generation NTP moderator insulator technology. During Phase 2, USNC-Tech will procure, assemble, and test promising solutions identified during Phase 1 in hot hydrogen at facilities such as the Nuclear Thermal Reactor Element Environmental Simulator (NTREES) and Compact Fuel Element Environmental Test (CFEET). Work during Phase 1 will focus on cermet NTP systems with tie tubes but will have applications to all moderated NTP systems such as systems with block moderators with other fuel types.
Currently there is no available solution for tie tube insulator in LEU cermet NTP systems. Heritage tie tube solutions are incompatible with low enriched uranium (LEU) cermet NTP systems, as the outer graphite component will compromise the integrity of the refractory metal cermet fuel by forming carbides. In addition, low-density ZrC insulators have limited availability. Refractory carbide insulator solutions without a graphite component will likely interact and diffuse into refectory metals in the cermet fuel.
Phase 1 of this work will inform the design of the insulator through analyses and trade studies. Material selection, properties, and manufacturability will be informed in part by our research partner Plasma Processes. Other insulator options that will be considered include metallic foams, high-porosity sintered materials, and fibrous materials. Refractory ceramic diffusion barriers may be used to slow diffusion. Another solution includes using different materials in the colder end of the core than those in the hotter end. USNC-Tech expects to test than one solution during Phase 2.
USNC-Tech’s work will address a crucial need in NASA’s NTP program. Tie tube insulator design drives power cycle design, and securing solutions to tie tube insulation before a flight program will save effort in development of the power cycle. Beyond NTP, next-generation insulator technology will apply to other space reactor systems. These include, most notably, power systems that require insulating hydride moderator from the fuel such as many LEU surface power and nuclear electric propulsion concepts.
Next-generation insulator technology is applicable to a number of terrestrial and non-NASA reactor applications. USNC-Tech is developing nuclear systems for civilian remote regions. In addition, several companies are working to bring advanced reactors to the market, and the novel insulator technology will have application in these markets.