Dissertation Defense: 135Xe in LEU Cermet Nuclear Thermal Propulsion Systems

Committee

• Professor Thomas Blue, Chair (NE)
• Professor Tunc Aldemir (NE)
• Professor Raymond Cao (NE)

Abstract

Nuclear Thermal Propulsion (NTP) is currently a topic of research for NASA. NASA has the goal of sending humans to Mars and Nuclear Thermal Propulsion (NTP) is an appealing technology to aid in this endeavor. In the simplest terms, an NTP system is a nuclear reactor that utilizes hydrogen that is expanded through a convergent-divergent nozzle and ejected for propulsion. NTP can shorten the travel time to Mars and reduce the mass that must be lifted into low earth orbit. Furthermore, strategies to use low enriched uranium (LEU) in NTP systems have been identified which could make NTP significantly more affordable to develop than for past NTP development efforts. This work focuses on a subset of NTP systems that use a combination of LEU and tungsten cermet fuel and addresses the issues related to 135Xe in these systems. LEU cermet NTP systems have a unique operational regime where 135Xe has a profound impact on performance and controllability. LEU cermet NTP have extremely high power densities, operate with a thermal neutron spectrum, and the reference human mission to Mars requires restarting the reactor 4 to 8 hour after full power operation. Key results of this work include: two LEU cermet NTP point designs, rigorous modeling of 135Xe with MCNP 6 and Serpent 2, identifying the possible effect of 135mXe in NTP systems, and identifying possible mitigation strategies for the effects of 135Xe on LEU cermet systems. The overarching goal of this work is to better understand NTP technology so that it may one day help with a human Mars mission and other missions beyond low earth orbit.