Abstract
Iron-technetium alloys are of relevance to the development of waste forms for disposition of radioactive technetium-99 obtained from spent nuclear fuel. Corrosion of candidate waste forms is a function of the local cohesive energy () of surface atoms. A theoretical model for calculating is developed. Density functional theory was used to construct a modified embedded atom (MEAM) potential for iron-technetium. Materials properties determined for the iron-technetium system were in good agreement with the literature. To explore the relationship between local structure and corrosion, MEAM simulations were performed on representative iron-technetium alloys and intermetallics. Technetium-rich phases have lower , suggesting that these phases will be more noble than iron-rich ones. Quantitative estimates of based on numbers of nearest neighbors alone can lead to errors up to 0.5 eV. Consequently, atomistic corrosion simulations for alloy systems should utilize physics-based models that consider not only neighbor counts, but also local compositions and atomic arrangements.
Highlights
The development of long-term containment strategies for spent nuclear fuel requires a combination of careful experiments and theoretical studies so that the realistic lifetimes of these strategies can be confidently predicted
We have used materials properties obtained from the density functional theory computations to develop a modified embedded atom method potential for the iron-technetium system
The materials properties calculated using density functional theory were in good agreement with the available experimental literature and were, used to parameterize the modified embedded atom (MEAM) potential
Summary
The development of long-term containment strategies for spent nuclear fuel requires a combination of careful experiments and theoretical studies so that the realistic lifetimes of these strategies can be confidently predicted. A number of different containment strategies are being considered, one of which involves the storage of certain fission products within a metallic alloy waste form [1]. Chief among these fission products is technetium-99, which has a half-life of ∼105 years [2]. By developing a modified embedded atom potential for the iron-technetium binary system, we have computed cohesive energies for surface metal atoms in this system and, subsequently, identified which atoms and configurations of atoms will be more prone to release from the system due to corrosion effects. We plan to use this tool in future simulations of the active dissolution of candidate irontechnetium alloy waste forms
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