Conceptual design and its optimization of an air-cooled nuclear reactor for aircraft propulsion considering both thermal and neutronic performance

Abstract

Air-cooled nuclear-powered engine is a good choice for low-attitude and high-speed aircraft soon. To achieve better propulsion performance, a conceptual design for air-cooled reactors with the aim of minimum size and high thrust-weight ratio is conducted in this work, where both thermal-hydraulics and neutronics targets are satisfied to make sure its safety under extreme operating conditions. The nuclear engine composed of the diffuser, the reactor, and the nozzle is modeled with simplification to mainly calculate heat transfer and pressure drop inside the flow channels of the reactor core. The relation of thrust and specific impulse is investigated to show the operation range of the engine. Geometrical dimensions of the air-cooled reactor core are minimized to offer the rated output thrust of 120 kN. For this optimal design, wall temperature of the reactor remains below the upper limit of 1644 K, and the core theoretically reaches criticality based on the critical buckling got from Monte-Carlo simulations of a fuel unit. Additionally, the neutronics analysis is then employed for the entire reactor. Attribute to Gd2O3 added in the fuel matrix, shutdown margin keeps below −1 $ under the submersion accident. This work finally proposes a design of the air-cooled reactor with a mass of 2.6 ton loaded by high-enriched uranium oxide, which could provide the high-speed cruise aircraft with the thrust of 120 kN at sea level for 15 days.