Nuclear and Emerging Technologies for Space 2015 Conference (2015) 5012.pdf

Preliminary Design Study of an Innovative High-Performance Nuclear Thermal Rocket Utilizing LEU Fuel

Seung Hyun Nam1, Paolo F. Venneri1, Jae Young Choi1, Yong Hoon Jeong1, and Soon Heung Chang1,2

1Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science & Technology, 291 Daehak-ro, Yuseong-gu, Daejeon, Korea 2Handong Global University, Pohang-si, Gyeongbuk, Korea +82-42-350-3891; [email protected]

Abstract. A Nuclear Thermal Rocket (NTR) is a viable and efficient option for manned deep-space missions such as to Mars and beyond. The NTR technology has already been developed and successfully tested for over 50 years since the 1950s by the United States (US) and Russia. The representative US NERVA type reactors traditionally load hexagonal shaped fuel elements utilizing High Enriched Uranium (HEU) due to the imperative of making a high power reactor with a minimum size. This state-of-the-art NTR technology could be applicable with contemporary space vehicles. However, even though the NTR designs utilizing HEU is the best choice in terms of rocket performance and technical maturity, they inevitably arouse nuclear proliferation obstacles on all Research and Development (R&D) activities by civilians and non-nuclear weapon states, and its eventual commercialization. To cope with the security issue to use HEU, the innovative future NTR engine concept utilizing Low Enriched Uranium (LEU) fuel is proposed in this paper. The Korea Advanced NUclear Thermal Engine Rocket utilizing LEU (KANUTER-LEU) is currently being designed at Korea Advanced Institute of Science and Technology (KAIST). The major design requirement is to make use of LEU fuel for its compact reactor, but does not sacrifice the rocket performance relative to the traditional NTRs utilizing HEU. The KANUTER-LEU mainly consists of a 250 MWth moderated Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing H2 propellant, a propulsion system housing a Propellant Feeding System (PFS), a Nozzle Assembly, etc., and an optional Electricity Generation System (EGS) as a bimodal engine. To implement LEU fuel for the EHTGR, the KANUTER adopts W-UO2 CERMET fuel to increase uranium density drastically and metal hydride moderators to thermalize neutrons in the core consequentially having a high neutron economy. The moderator and structural material selections also consider neutronic and thermo-physical characteristics to reduce non-fission neutron loss and reactor weight. The geometry design of fuel element and reactor focuses on protective cooling capability, fabricability and compactness. This paper mainly presents the preliminary design study of the KANUTER-LEU focusing on the neutronic and thermohydraulic features. The result shows comparable characteristics of high efficiency, and compact and lightweight system despite the heavier LEU fuel utilization. The reference performance is theoretically estimated at a thrust of 51.4 kN, a thrust to weight ratio of 5.5 and a specific impulse of 916 s.

Keywords: nuclear propulsion, nuclear thermal rocket, innovative space reactor, low enriched uranium