Processing of pseudo-ternary carbide fuels for high temperature space nuclear reactors

Abstract

Single phase, solid-solution pseudo-ternary carbides such as (U, Zr, Nb)C, hold significant promise for space nuclear power and propulsion applications because of their high melting points (typically greater than 3200 K), thermochemical stability in a hot hydrogen environment, and high thermal conductivity. Their projected endurance at very high temperatures far exceeds that of fuels previously tested and signifies their potential as a fuel for increased performance characteristics (i.e. higher specific impulse and/or longer lifetime, etc.). However, insufficient test data exist under nuclear thermal propulsion (NTP) conditions of temperature and hot hydrogen environment to fully evaluate their performance. An investigation into processing techniques was conducted in order to produce a series of pseudo-ternary carbide samples for characterization and testing. Consideration was given to the real world challenges of manufacturing full-scale fuel elements. Particular consideration was given to the fabrication requirements for the innovative, square-lattice honeycomb (SLHC) fuel elements for advanced NTP cores. This paper outlines the background and technical considerations important to mixed carbide nuclear fuel development and describes the preliminary results in developing processing techniques for pseudo-ternary carbide nuclear fuels.