Title: Looking Back Over 40 Years on the Actinide Dioxides
Authors: LANDER G.h.
Citation: 43èmes Journées des Actinides Programme and Abstracts p. 22
Publisher: Dipartimento di Chimica e Chimica Industriale (DCCI) , Università di Genova, CNR Institute SPIN
Publication Year: 2013
JRC N°: JRC81485
URI: http://www.jda2013.spin.cnr.it/
http://publications.jrc.ec.europa.eu/repository/handle/JRC81485
Type: Articles in periodicals and books
Abstract: Since the actinide oxides became the choice for nuclear fuels in the 1950s, there has been great interest in understanding all physical properties and the associated electronic structure of these materials. One would think that with a clear O2– ion the actinide ion would be An4+ and the interpretation of the measurements would be simple and taught in kindergartens. Alas, this was not to be. The JdA’s started 40 years ago, and even by that time many properties of the oxides were measured, and some idea of the complexity of the task of understanding them was beginning to dawn on those involved. For example, Osborne and Westrum at ANL had measured the specific heat of UO2 and NpO2 in 1953, and a large peak at 25 K in NpO2 suggested a magnetic ground state, but neutron experiments in 1967 failed to find any microscopic evidence for such an ordered moment, which had been seen earlier in UO2. Likewise, the phonons and magnons of UO2 were measured at Chalk River by Dolling & Cowley in the late 1960s, and, at least for the magnons, the interpretation appeared extremely complex, despite the apparent simple antiferromagnetic structure. We started experiments at ANL in 1973 that led, by accident, to the discovery of the internal distortion in UO2 for T < TN. Once one starts on these materials, they have a long-term fascination bordering, perhaps, on an obsession! In this talk I shall try and look back over our understanding of the actinide oxides over this period. Many many talks were given on these systems in the JdA’s, and many people have been involved. Solutions to most, but not all, of the problems have come in the last decade. In the case of the mysterious transition in NpO2 it took a half-century to elucidate. I would especially like to thank Roberto Caciuffo and Giuseppe Amoretti for a long-term friendship and a sharing of the obsession for the electronic structure of the actinide oxides. Many others have contributed significantly, such as the authors of Ref. [1].
JRC Directorate:Nuclear Safety and Security

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