Space transportation systems have been advancing to meet the goals of long-distance space travel, namely faster transit speeds to maximize the time spent at the destination and to reduce the amount of radiation the crew and cargo are exposed to. The nuclear thermal propulsion rocket (NTPR) serves to reduce transit time by half that of chemical propellant rockets, but still has some fundamental technical challenges to be resolved before ideal operation can be achieved. During the experiments of the NTPR program, NERVA, the nuclear fuel elements lost significant mass throughout operation due to mechanical and chemical interactions with the high-temperature propellant, hydrogen. Different fuel compositions and coatings were tested for changes in the fuel mass loss. Niobium carbide and zirconium carbide coadngs were tested, but many others were suggested after the final tests of NERVA. Good coatings must be exceptionally resistant to the hydrogen interaction and crack propagation, have as high a thermal conductivity and melting temperature as possible, exhibit a low neutron absorption cross-section, and have the same thermal expansion coefficient as the fuel material. This paper presents a model of an NTPR reactor in the Monte Carlo N-Particle Transport Code (MCNP6). The fuel coatings and composition are varied, first to compare against the experimental NERVA results, and then novel coatings and compositions are analyzed. The goal of the modeling is to determine the best materials for reactor operation and then use the data from MCNP6 to evaluate the thermal and mechanical performance of the rocket.
展开▼
