Abstract
The fluorite structured actinide dioxides (AnO2), especially UO2, are the most common nuclear fuel materials. A comprehensive understanding of their surface chemistry is critical because of its relevance to the safe handling, usage, and storage of nuclear fuels. Because of the ubiquitous nature of water (H2O), its interaction with AnO2 has attracted significant attention for its significance in studies of nuclear fuels corrosion and the long-term storage of nuclear wastes. The last few years have seen extensive experimental and theoretical studies on the H2O–AnO2 interaction. Herein, we present a brief review of recent advances in this area. We focus on the atomic structures of AnO2 surfaces, the surface energies, surface oxygen vacancies, their influence on the oxidation states of actinide atoms, and the adsorption and reactions of H2O on stoichiometric and reduced AnO2 surfaces. Finally, a summary and outlook of future studies on surface chemistry of AnO2 are given. We intend for this review to encourage broader interests and further studies on AnO2 surfaces.
Highlights
The fluorite structured actinide dioxides (AnO2, UO2 ) are the most common nuclear fuels currently used in nuclear reactors worldwide
The formation of H2 owing to the interaction of H2 O with AnO2 through radiolytic process or chemical reactions can lead to potential pressurization of the containers of nuclear fuels
The high reactivity of H2 O with reduced ThO2 surface is attributed to the lone electron pair at the vacancy site on ThO2 that can readily participate in the chemical reactions with H2 O
Summary
The fluorite structured actinide dioxides (AnO2 , UO2 ) are the most common nuclear fuels currently used in nuclear reactors worldwide. The understanding of the surface chemistry of AnO2 has been severely limited by the difficulties associated with the handling of radioactive actinides in experiments and the complexity of studying actinide systems using theoretical means. Theoretical calculations can supplement experimental efforts to understand the surface chemistry of the AnO2 series and some studies have tried to fill this gap. AnO from the elements Th through Cf has been observed to crystalize in a fluorite structure, Bulk In this structure, each actinide atom is eight-fold and oxygen structure, as shown in [6]. Along the (111) direction, the surface consists of alternating oxygen and actinide layers with a tri-layer structure (O-An-O). Along the (100) direction, AnO2 consists of alternating oxygen and actinide layers. Along the (100) direction, AnO2 consists of alternating oxygen and actinide with the sequence of -O2 -An-O2 -An-O2 -.
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