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INNOVATIVE CONCEPT FOR AN ULTRA-SMALL NUCLEAR THERMAL ROCKET UTILIZING A NEW MODERATED REACTOR
남승현,PAOLO VENNERI,김용희,이정익,장순흥,정용훈 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.6
Although the harsh space environment imposes many severe challenges to space pioneers,space exploration is a realistic and profitable goal for long-term humanity survival. One ofthe viable and promising options to overcome the harsh environment of space is nuclearpropulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for neartermhuman missions to Mars and beyond due to its relatively high thrust and efficiency. Traditional NTR designs use typically high power reactors with fast or epithermal neutronspectrums to simplify core design and to maximize thrust. In parallel there are a series ofnew NTR designs with lower thrust and higher efficiency, designed to enhance missionversatility and safety through the use of redundant engines (when used in a clusteredengine arrangement) for future commercialization. This paper proposes a new NTR designof the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket(KANUTER), for future space applications. The KANUTER consists of an Extremely HighTemperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system,and an optional electricity generation system to provide propulsion as well as electricitygeneration. The innovatively small engine has the characteristics of high efficiency,being compact and lightweight, and bimodal capability. The notable characteristics resultfrom the moderated EHTGR design, uniquely utilizing the integrated fuel element with anultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively coolingchannels and an individual pressure tube in an all-in-one package. The EHTGR can bebimodally operated in a propulsion mode of 100 MWth and an electricity generation modeof 100 kWth, equipped with a dynamic energy conversion system. To investigate the designfeatures of the new reactor and to estimate referential engine performance, a preliminarydesign study in terms of neutronics and thermohydraulics was carried out. The resultindicates that the innovative design has great potential for high propellant efficiency andthrust-to-weight of engine ratio, compared with the existing NTR designs. However, thebuild-up of fission products in fuel has a significant impact on the bimodal operation of the moderated reactor such as xenon-induced dead time. This issue can be overcome bybuilding in excess reactivity and control margin for the reactor design.