title: Molten uranium dioxide structure and dynamics.
abstract: Uranium dioxide (UO2) is the major nuclear fuel component of fission power reactors. A key concern during severe accidents is the melting and leakage of radioactive UO2 as it corrodes through its zirconium cladding and steel containment. Yet, the very high temperatures (>3140 kelvin) and chemical reactivity of molten UO2 have prevented structural studies. In this work, we combine laser heating, sample levitation, and synchrotron x-rays to obtain pair distribution function measurements of hot solid and molten UO2. The hot solid shows a substantial increase in oxygen disorder around the lambda transition (2670 K) but negligible U-O coordination change. On melting, the average U-O coordination drops from 8 to 6.7 ± 0.5. Molecular dynamics models refined to this structure predict higher U-U mobility than 8-coordinated melts.
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Mineral Physics Institute, Stony Brook University, Stony Brook, NY 11794-2100, USA. Materials Development, Inc., 3090 Daniels Court, Arlington Heights, IL 60004, USA. lawrie.skinner@gmail.com.
authors.forename: L B
authors.initials: LB
authors.lastname: Skinner
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Benmore
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Materials Development, Inc., 3090 Daniels Court, Arlington Heights, IL 60004, USA.
authors.forename: J K R
authors.initials: JK
authors.lastname: Weber
authors.affiliation: Chemical Science and Engineering, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Williamson
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: A
authors.initials: A
authors.lastname: Tamalonis
authors.affiliation: Chemical Science and Engineering, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: A
authors.initials: A
authors.lastname: Hebden
authors.affiliation: Nuclear Engineering, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: T
authors.initials: T
authors.lastname: Wiencek
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Materials Development, Inc., 3090 Daniels Court, Arlington Heights, IL 60004, USA.
authors.forename: O L G
authors.initials: OL
authors.lastname: Alderman
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.
authors.forename: M
authors.initials: M
authors.lastname: Guthrie
authors.affiliation: Chemical Science and Engineering, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: L
authors.initials: L
authors.lastname: Leibowitz
authors.affiliation: Mineral Physics Institute, Stony Brook University, Stony Brook, NY 11794-2100, USA. Photon Sciences, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Parise