Investigation of Aluminides as Potential Matrix Materials for Inert Matrix Nuclear Fuels

Abstract

New nuclear fuel forms are being sought in an effort to bum down plutonium inventories and for minor actinide transmutation. A study was conducted to screen two potential materials for a new fuel form. In this study, inert matrix fuels (IMFs) were considered as a nuclear fuel type, with particular emphasis on the matrix materials and their compatibility with surrogate oxides/nitrides and cladding materials. In a fuel cycle application, fuel materials need high thermal conductivity, good radiation tolerance, relatively high melting point, ease of fabrication, and suitability for separation. Due to their physical, mechanical and thermal properties, as well as relative ease of fabrication, nickel aluminide (NiAl) and ruthenium aluminide (RuAl) and their solid solutions were considered as potential matrix candidates for IMFs. Such IMFs can be of interest for fast and thermal spectrum applications. This study focused on the ease of fabrication, interaction of molten NiAl and RuAl with the oxides/nitrides, and the compatibility of NiAl and RuAl with the materials in the system, such as oxide/nitrides and typical cladding materials (Zr-4 and HT-9). Results from the experiments indicate limited interaction between the aluminides and cladding materials where inter-diffusion over the 168 hour test period occurred in the worst case a distance of about 11 μm. In light of the results, it was concluded that RuAl and NiAl are promising candidates for IMF materials, warranting further investigation.