SBIR-STTR Award

In this SBIR, Ultra Safe Nuclear Corporation (USNC) will investigate and develop a set of novel technologies to minimize the amount of hydrogen needed for reactor decay heat removal after the shutdown of Nuclear Thermal Propulsion (NTP) systems. Decay heat is the energy deposited during the decay of radioactive fission products after the reactor shuts down. Its management is a critical issue for NTP systems. USNC’s technology will be an effective, yet simple, solution to address decay heat removal. Central to USNC’s optimized strategy for decay heat removal is maximizing the temperature that hydrogen is ejected and maximizing radiative heat transfer from the available surfaces of the rocket and nozzle. Furthermore, USNC’s comprehensive solution generates small amounts of electrical power with the removed decay heat, increasing mission flexibility and resilience. Specifically, USNC will primarily investigate four technologies to minimize hydrogen usage: - The inclusion of coolant channels on the outside structure of the tie tube between the insulator and fuel that can heat hydrogen to hotter temperatures than the zirconium hydride moderator can maintain. - Circulating hydrogen through the tie tube and the outer structure of the core to maximize heat rejection by radiation. - Conversion of some of the heat into useful work through the addition of a power generation unit. - Using computationally-intensive optimization to find the best possible strategies and power cycle configurations to minimize the amount of hydrogen ejected from the system Potential NASA Applications NTP and its supporting technologies have great promise in spreading human presence to Mars and other locations beyond low earth orbit. USNC’s optimized decay heat removal strategies will address key needs in NTP development to make it a viable technology to fulfill NASA human exploration needs. Furthermore, USNC will also provide documented work for hydrogen mass estimates for cooldown that will help in mission planning. Potential Non-NASA Applications USNC and other companies are actively developing advanced, small, Earth-based reactors. USNC’s Earth-based reactors are compact and, like NTP systems, require effective ways to deal with decay heat. The work in this SBIR will further USNC’s Earth-based reactor work and may lead to strategies for dealing with decay heat in compact Earth-based reactors.

This SBIR will develop a decay heat solution for Nuclear Thermal Propulsion (NTP) systems that will significantly reduce the amount of hydrogen required to cool down an NTP system after operation. In addition, novel decay heat solutions will enable functionality beyond current NTP system concepts by enabling dual-mode power co-generation and high-Isp-reactor-powered Reaction Control System (RCS)/Orbital Maneuvering System (OMS). USNC’s solution to NTP decay heat removal and utilization is a high-temperature tie tube (TT) with a moderator capable of continuous operation at 1000 K. The high-temperature tie tube operates at a much higher temperature than the current baseline NTP tie tube and enables the core to remove decay heat more effectively. The high-temperature tie tube is made of high-temperature-capable structural materials and zirconium hydride (ZrH) clad with a hydrogen barrier that guarantees hydrogen integrity during cooldown conditions. This technology will be demonstrated with advanced modeling and hot hydrogen experiments. Decay heat solutions are essential for maximizing the performance of NTP systems and guaranteeing system safety. This Phase 2 SBIR will be the most in-depth look into understanding and solving NTP decay heat ever undertaken. Furthermore, the additional co-power generation and RCS/OMS capabilities enabled by high-temperature tie tubes enhances the versatility of NTP for a human Mars mission and other missions beyond low earth orbit. Potential NASA Applications (Limit 1500 characters, approximately 150 words) USNC’s novel decay heat removal and high temperature tie tubes technology utilization have many NASA applications: Increase the performance, safety and capabilities of NTP systems High fidelity estimates of hydrogen needed for cool down assisting NTP mission planning Provide a pathway to power co-generation and NTP utilization for deep space science planetary defense Surface power systems requiring high temperature moderators Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words) Decay heat removal and high temperature operation are critically important for terrestrial nuclear systems being developed by USNC. High temperature tie tubes containing a hydride moderator enable small nuclear systems. Furthermore, NTP systems have application beyond NASA in the emerging space economy for defense and transport of commercial payloads beyond LEO.