"Phase Transitions in U-Mo alloys at Sub-Eutectoid Temperatures" 

Sukanya Majumder, MSE PhD Candidate 

Advisor: Professor Maria Okuniewski

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ABSTRACT

Since the Nuclear Regulatory Commission issued a limit on the use of highly enriched uranium as nuclear fuel, efforts have been made in developing efficient fuels at low enrichment levels. U-Mo alloys have garnered attention as an ideal nuclear fuel material because of their efficiency due to high uranium density and good resistance to the adverse effects of irradiation, like fuel swelling. The stability of U-Mo is attributed to a high temperature body centered γ-phase, which is involved in a eutectoid reaction with low temperature phases that demonstrate poor irradiation behavior. As nuclear reactors typically operate at temperatures below the eutectoid temperature, it is necessary to understand the factors that affect phase transformations in said temperature regime. This review presents the phase transformations involving this γ-phase that occurs at sub-eutectoid temperatures. The generally accepted mechanisms for the decomposition of the 𝛾-phase under thermal treatment, and for the phase reversal back into the 𝛾-phase under irradiation are discussed in detail. Furthermore, results of preliminary research already performed on U-Mo based on these principles, and what lies ahead, are discussed.