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

Tracy, Cameron L.; Chen, Chien-Hung; Park, Sulgiye; Davisson, M. Lee; Ewing, Rodney C.

doi:10.1016/j.jnucmat.2018.01.052

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

Abstract

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.

Authors:

Tracy, Cameron L. ^[1]; Chen, Chien-Hung ^[2];

^[2]; Davisson, M. Lee ^[3]; Ewing, Rodney C. ^[2]

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

Publication Date:: Wed Jan 31 00:00:00 EST 2018

Research Org.:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation

OSTI Identifier:: 1513109

Alternate Identifier(s):: OSTI ID: 1505855

Report Number(s):: LLNL-JRNL-757741
Journal ID: ISSN 0022-3115; 945687

Grant/Contract Number:: AC52-07NA27344; SC0001089; DMR-1332208

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Nuclear Materials

Additional Journal Information:: Journal Volume: 502; Journal Issue: C; Journal ID: ISSN 0022-3115

Publisher:: Elsevier

Country of Publication:: United States

Language:: English

Subject:: 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY

Citation Formats


                    Tracy, Cameron L., Chen, Chien-Hung, Park, Sulgiye, Davisson, M. Lee, and Ewing, Rodney C. Measurement of UO2 surface oxidation using grazing-incidence x-ray diffraction: Implications for nuclear forensics.  United States: N. p., 2018. 
Web.  doi:10.1016/j.jnucmat.2018.01.052.

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                    Tracy, Cameron L., Chen, Chien-Hung, Park, Sulgiye, Davisson, M. Lee, & Ewing, Rodney C. Measurement of UO2 surface oxidation using grazing-incidence x-ray diffraction: Implications for nuclear forensics.  United States.  https://doi.org/10.1016/j.jnucmat.2018.01.052

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                    Tracy, Cameron L., Chen, Chien-Hung, Park, Sulgiye, Davisson, M. Lee, and Ewing, Rodney C. Wed .  
"Measurement of UO2 surface oxidation using grazing-incidence x-ray diffraction: Implications for nuclear forensics".  United States.  https://doi.org/10.1016/j.jnucmat.2018.01.052.  https://www.osti.gov/servlets/purl/1513109.

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@article{osti_1513109,

  title        = {Measurement of UO2 surface oxidation using grazing-incidence x-ray diffraction: Implications for nuclear forensics},

  author       = {Tracy, Cameron L. and Chen, Chien-Hung and Park, Sulgiye and Davisson, M. Lee and Ewing, Rodney C.},

  abstractNote = {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.},

  doi          = {10.1016/j.jnucmat.2018.01.052},

  journal      = {Journal of Nuclear Materials},

  number       = C,

  volume       = 502,

  place        = {United States},

  year         = {Wed Jan 31 00:00:00 EST 2018},

  month        = {Wed Jan 31 00:00:00 EST 2018}

}

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https://doi.org/10.1016/j.jnucmat.2018.01.052

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Cited by: 9 works

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Fig. 1: A schematic illustration of a GIXRD measurement of an oxidized UO₂ pellet. During data collection, the x-ray incident angle $ω $is fixed while the point detector rotates over the desired 2$θ$ measurement range. By varying $ω$ the penetration of x-rays into the sample surface can be controlled, suchmore »

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

Abstract

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