Exploring the Relationship between Uranyl Hydroxide and Uranyl Peroxide Phases: Alteration and Formation Studies

This dissertation explores the relationship between two prominent uranyl mineral phases relevant to the nuclear fuel cycle through controlled storage, irradiation, and novel synthesis studies. Nuclear materials subjected to various storage environments may undergo important chemical changes as a consequence of variables including atmospheric gases and ionizing radiation. Understanding the complexities of these alteration pathways is an essential part of responsible disposal of nuclear waste and nuclear forensics efforts, among others. The work presented herein is centered on the uranyl oxy-hydroxide hydrate phase, metaschoepite [(UO₂)₈O₂(OH)₁₂](H₂O)₁₀, and its transformation to the uranyl peroxide hydrate phase, studtite [(UO₂)(O₂)(H₂O)₂](H₂O)₂. Specifically, the origin of peroxide is investigated in systems where depleted uranium is used, and alternate methods of obtaining uranyl peroxide are described for the first time. This work is achieved through characterization techniques including powder X-ray diffraction (PXRD), Raman spectroscopy, and infrared spectroscopy to analyze changes in structure and bonding during alteration.