Addition of elements to pure uranium may change its properties in beneficial or deleterious ways. In metal uranium fuel the accumulation of fission poisons decreases or kills nuclear reaction efficiency. Formation of uranium alloys, however, can lead to many physical enhancements desirable for reactor operation. The study of the energetics involved in the formation of defects would be useful in the design of addition or removal of these elements. The goal of this research is the computational study of the energies of defect formation in the bulk system of the high temperature phase of metal uranium with a variety of these possible defects.<br/><br/>The crystal properties of this high temperature phase of uranium were successfully modeled in periodic boundary conditions using plane wave calculations within density functional formalism. Energy of formation of point defects in body-centered cubic γ-uranium crystal were studied with respect to a variety of possible metal substituents. Substitutional energies of molybdenum, rhodium, zinc, niobium, lanthanum, europium, and lutetium are compared. Due to the wide range of elements calculated for comparison, a general, widely applicable GGA-PBE exchange-correlation functional was used. The results of these studies show the likely energetically favorable ordering of possible defects and which may be more likely to diffuse to the uranium surface.<br/><br/>As γ-uranium is a semi-metal, thermal smearing has often been used in previous computational calculations as to improve SCF convergence. It may be possible that the change in energy on application of this method is on the order of the energy of substitution. Calculating energies across a range of thermal smearing values provides a quantitative measure of this effect and informs the degree to which the substitutional energy across different impurities are affected.

Physicochemical properties of defect laden uranium

256th National Meeting (2018)

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