The containment of an aggressive high-temperature reactive fluoride atmosphere, such as exists in a pulsed gaseous core nuclear system, requires the use of protective materials that will either not react in this environment or will form stable nonvolatile fluorides, thus passivating the surface against further reaction. Candidate protective materials for gaseous core reactors were identified for further investigation on the basis of their thermodynamic and mechanical properties. Materials included aluminum oxide (Al2O3), yttrium oxide (Y2O3), mixtures of Al2O3 and Y2O3, magnesium oxide (MgO), and pyrophyllite [Al2(Si2O5)2(OH)2]. Pioneering studies at the University of Florida on the use of infrared reflection spectroscopy (IRRS) for nondestructive surface analysis, along with x-ray diffraction pattern (XDP) studies, were applied to the analysis of UF6 material/surface interactions. Candidate materials were subjected to a UF6 atmosphere (973 K, 87 Torr, with 1- to 5-h exposures). The IRRS and XDP analyses of the materials after exposure showed no surface product formation in the case of the first four protective materials. For pyrophyllite, a mechanically and chemically stable protective surface fluoride film was formed.