Accident Tolerant Reactor Shutdown for NTP Systems

In brief, USNC's accident submersion safe drums are control drums where a small amount of fuel is added opposite to the neutron absorber and the drums impinge on the active core to substantially increase the shutdown criticality margin of the control drums. Phase 1 results indicate that the shutdown criticality margin is more than sufficient to maintain sub-criticality in the worst-case water submersion accidents. Key accidents that the accident submersion safe drums address include submersion in freshwater and sand with a stuck drum in the full-on position and submersion in water and wet sand with reflector loss. This SBIR will develop the submersion safe reactor shutdown system for Nuclear Thermal Propulsion (NTP) identified in the Phase 1. Remaining subcritical during a during water submersion accident is a design requirement for NTP systems. As of now, all thermal spectrum NTP concepts (including LEU NTP systems) fail to remain subcritical during water submersion and thus are not water submersion safe. USNC's submersion safe control drums enable thermal spectrum NTP systems to remain subcritical during water submersion accidents. Key tasks that will be completed include: 1.Develop a detailed integrated thermal-mechanical and neutronic design of the control drums. 2.Design a power cycle and coolant paths that adequately remove heat from the submersion safe drums while minimizing complexity of the NTP system. 3.Demonstrate the Submersion safe control drum technology in a prototypical reactor experiment and raise the technology's TRL up to 4/5. 4.Deliver a set of NTP system point designs that showcase the full implementation of the drums integrated into a realistic NTP system.