• Nuclear Engineering and Technology
• /
• 제55권7호
• /
• pp.2534-2546
• /
• 2023

Gas-cooled space reactor, which adopts He-Xe gas mixture as working fluid, is a better choice for megawatt power generation. In this paper, thermal-hydraulic characteristics of He-Xe gas mixture in 2×2 rod bundle wrapped with helical wires is numerically investigated. The velocity, pressure and temperature distribution of the coolant are obtained and analyzed. The results show that the existence of helical wires forms the vortexes and changes the velocity and temperature distribution. Hot spots are found at the contact corners between helical wires and fuel rods. The highest temperature of the hot spots reach 1600K, while the mainstream temperature is less than 400K. The helical wire structure increases the friction pressure drop by 20%-50%. The effect extent varies with the pitch and the number of helical wires. The helical wire structure leads to the reduction of Nusselt number. Comparing thermal-hydraulic performance ratios (THPR) of different structures, the THPR values are all less than 1. It means that gas-cooled space reactor adopting helical wires could not strengthen the core heat removal performance. This work provides the thermal-hydraulic design basis for He-Xe gas cooled space nuclear reactor.

• 한국수소및신에너지학회논문집
• /
• 제25권4호
• /
• pp.425-435
• /
• 2014

Simulation studies on catalytic methanation reaction in externally cooled tubular reactor filled with monolithic catalysts were carried out using a general purpose modelling tool $gPROMS^{(R)}$. We investigated the effects of operating parameters such as gas space velocity, temperature and pressure of feeding gas on temperature distribution inside the reactor, overall CO conversion, and chemical composition of product gas. In general, performance of methanation reaction is favored under low temperature and high pressure for a wide range of their values. However, methane production becomes negligible at temperatures below 573K when the reactor temperature is not high enough to ignite methanation reaction. Capacity enhancement of the reactor by increasing gas space velocity and/or gas inlet pressure resulted no significant reduction in reactor performance and heat transfer property of catalyst.

• Nuclear Engineering and Technology
• /
• 제47권6호
• /
• pp.678-699
• /
• 2015

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 of the viable and promising options to overcome the harsh environment of space is nuclear propulsion. Particularly, the Nuclear Thermal Rocket (NTR) is a leading candidate for nearterm human 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 neutron spectrums to simplify core design and to maximize thrust. In parallel there are a series of new NTR designs with lower thrust and higher efficiency, designed to enhance mission versatility and safety through the use of redundant engines (when used in a clustered engine arrangement) for future commercialization. This paper proposes a new NTR design of the second design philosophy, Korea Advanced NUclear Thermal Engine Rocket (KANUTER), for future space applications. The KANUTER consists of an Extremely High Temperature Gas cooled Reactor (EHTGR) utilizing hydrogen propellant, a propulsion system, and an optional electricity generation system to provide propulsion as well as electricity generation. The innovatively small engine has the characteristics of high efficiency, being compact and lightweight, and bimodal capability. The notable characteristics result from the moderated EHTGR design, uniquely utilizing the integrated fuel element with an ultra heat-resistant carbide fuel, an efficient metal hydride moderator, protectively cooling channels and an individual pressure tube in an all-in-one package. The EHTGR can be bimodally operated in a propulsion mode of $100MW_{th}$ and an electricity generation mode of $100MW_{th}$, equipped with a dynamic energy conversion system. To investigate the design features of the new reactor and to estimate referential engine performance, a preliminary design study in terms of neutronics and thermohydraulics was carried out. The result indicates that the innovative design has great potential for high propellant efficiency and thrust-to-weight of engine ratio, compared with the existing NTR designs. However, the build-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 by building in excess reactivity and control margin for the reactor design.

• 기술혁신학회지
• /
• 제6권4호
• /
• pp.462-479
• /
• 2003

The policy trends of use and the development of nuclear power in the United States, France, United Kingdom. Germany, Russia, China, Japan and Korea are briefly investigated. Nuclear power technology has been developed as the national policy in the nuclear-advanced countries. 50 years has passed since the declaration of "Atoms for Peace" by USA President Eisenhour in December 1953. Recently, it appears to revitalize the nuclear power program in world major countries in order to recover the shortage of electric power and to curb the excess emission of carbon dioxide as well as to secure competitiveness in electricity markets. Advanced countries are making new initiatives for the development of the fourth generation nuclear power system. Furthermore, wide-ranged use and development of nuclear power technologies are expected in district heating in commercial sectors, power in the space exploration, and propulsion power of large tankers and spaceships. High temperature gas cooled nuclear power reactor will be applied for mass production of hydrogen energy in the future.