Fabrication and Characterization of Zirconium Silicide for Application to Gas-Cooled Fast Reactors

Zirconium silicide (Zr₃Si₂) is a heavy reflector material particularly effective for application to a Gas-cooled Fast Reactor (GFR) such as the General Atomics Energy Multiplier Module (EM²) and Fast Modular Reactor (FMR). In this work, the manufacturability of a high-density Zr₃Si₂ compound, in the Zr₃Si₂ phase, was investigated using hot-pressing and spark-plasma-sintering methods. The microstructure, composition, and thermal properties of the resulting hot-pressed material were measured, resulting in a 96% relative density and a 96% phase pure material. The thermal properties were consistent with those necessary for use under GFR operating conditions. The structural and dimensional stability of the material was also measured before and after neutron irradiation up to 10¹⁷ n/cm² in the research reactor, resulting in an average linear dimensional change of <0.12%. The preliminary irradiation tests also confirmed the micromechanical stability of the Zr₃Si₂ phase, with no evidence of microcracking after irradiation. The results of the irradiation tests verify the fabrication method of Zr₃Si₂ for nuclear applications, but further irradiation tests under high-temperature and high-irradiation conditions will be required to qualify the material for GFR applications.