Measurement of UO₂ surface oxidation using grazing-incidence x-ray diffraction: Implications for nuclear forensics

Journal Article · Wed Jan 31 00:00:00 EST 2018 · Journal of Nuclear Materials

DOI:https://doi.org/10.1016/j.jnucmat.2018.01.052· OSTI ID:1513109

Tracy, Cameron L. ^[1]; Chen, Chien-Hung ^[2]; Park, Sulgiye  ^[2]; Davisson, M. Lee ^[3]; Ewing, Rodney C. ^[2]

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1. Stanford Univ., CA (United States). Dept. of Geological Sciences and Center for International Security and Cooperation
2. Stanford Univ., CA (United States). Dept. of Geological Sciences
3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Physical and Life Sciences Directorate

Nuclear forensics involves determination of the origin and history of interdicted nuclear materials based on the detection of signatures associated with their production and trafficking. The surface oxidation undergone by UO₂ when exposed to air is a potential signature of its atmospheric exposure during handling and transport. To assess the sensitivity of this oxidation to atmospheric parameters, surface sensitive grazing-incidence x-ray diffraction (GIXRD) measurements were performed on UO₂ samples exposed to air of varying relative humidity (34%, 56%, and 95% RH) and temperature (room temperature, 50 °C, and 100 °C). Near-surface unit cell contraction was observed following exposure, indicating oxidation of the surface and accompanying reduction of the uranium cation ionic radii. The extent of unit cell contraction provides a measure of the extent of oxidation, allowing for comparison of the effects of various exposure conditions. No clear influence of relative humidity on the extent of oxidation was observed, with samples exhibiting similar degrees of unit cell contraction at all relative humidities investigated. In contrast, the thickness of the oxidized layers increased substantially with increasing temperature, such that differences on the order of 10 °C yielded readily observable crystallographic signatures of the exposure conditions.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
• Grant/Contract Number: AC52-07NA27344; SC0001089; DMR-1332208
• OSTI ID: 1513109
• Alternate ID(s): OSTI ID: 1505855
• Report Number(s): LLNL-JRNL-757741; 945687
• Journal Information: Journal of Nuclear Materials, Vol. 502, Issue C; ISSN 0022-3115
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY