The design of SACRe (Small Air-Cooled Reactor) fixated on evaluations of air as a potential coolant. The assessment offered in this thesis focused on reactor physic analyses, and materials review and incorporation in a system defined by a highly corrosive environment. The oxidizing nature of air at high-temperature warrants the need to examine and compare materials for their oxidation temperature, their melting and boiling temperature, and their thermal conductivity. Material choices for the fuel, the cladding, the system's casing/structural material and the reflector were evaluated in this study. Survey of materials and literature lead to the selection of six different cladding materials which are FeCrAl, APMT, Inconel 718 and stainless steel of type 304, 316 and 310. A review of their thermal properties, for a high oxidation temperature and melting temperature and the exhibition of a hard neutron spectrum lead to the selection of APMT steel material. This material was not only be selected as the fuel cladding but also as a casing for reflector and shielding materials. The design of this 600 MWth system was investigated considering reflector materials for fast spectrum. Lead-based reflectors (lead bismuth eutectic, lead oxide and pure lead), magnesium-based reflectors (magnesium oxide and magnesium aluminum oxide), and aluminum oxide reflectors were evaluated in this thesis. The design configurations were compared to determine those which provide a hard neutron spectrum, an economically appropriate cycle length, a low breeding ratio and the least amount of neutrons escaping the reactor. The assessments of these notable characteristics lead to the selection of MgO reflector. This reflector allowed the system to operate for six years, for a corresponding burnup of 85 MWd/kgU. The thermal setting of 875?C fuel temperature and 575?C of coolant and structural temperature promoted the design of a system with a fuel volume fraction smaller than that of the coolant volume fraction (40.28% - 45.01% respectively). This configuration was promoted favorable over an active core with a fuel volume fraction higher than or equal to the coolant volume fraction because of some thermal properties of air like a small thermal conductivity, specific heat and density.
