Shutdown Simulation of the Centrifugal Nuclear Thermal Rocket

Conventional solid-core Nuclear Thermal Propulsion (NTP) engines are limited by the melting temperature of their fuel, whereas the liquid-core Centrifugal Nuclear Thermal Rocket (CNTR) can exceed these limits to achieve higher specific impulse. A critical operational challenge for the CNTR is managing decay heat during shutdown without excessive propellant usage. This work evaluates the shutdown cooling requirements of the CNTR using a lumped-parameter Transient System Model integrated with a high-fidelity fuel element thermal model. By incorporating reactor physics data from OpenMC, this study models the effects of centrifugal fission product loss on decay heat generation. A preliminary control methodology is proposed to maintain engine thermal constraints during the transient. The results demonstrate that the loss of fission products in the CNTR significantly lowers the integral decay heat load compared to traditional solid-core engines, resulting in a lower propellant mass fraction required for safe engine shutdown.