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Title: An XPS study on the impact of relative humidity on the aging of UO 2 powders

Abstract

High resolution x-ray photoemission spectroscopy (XPS) was used to characterize the chemical speciation of high purity uranium dioxide (UO 2) powder samples following aging for periods of up to one year under controlled conditions with relative humidity ranging from 34% to 98%. A systematic shift to higher uranium oxidation states, and thus an increase in the mean uranium valence, was found to directly correlate with the dose of water received (i.e. the product of exposure time and relative humidity). Exposure duration was found to have a greater impact on sample aging than relative humidity. Lastly, the sample aged at 98% relative humidity was found to have unique structural differences for exposure time beyond 180 days when observed by scanning electron microscopy (SEM).

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation (NA-20)
OSTI Identifier:
1347674
Alternate Identifier(s):
OSTI ID: 1411827
Report Number(s):
LLNL-JRNL-704464
Journal ID: ISSN 0022-3115; TRN: US1700867
Grant/Contract Number:
AC52-07NA27344; LL15-U_Surface_Oxidation-NDD3B
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 487; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY

Citation Formats

Donald, Scott B., Dai, Zurong R., Davisson, M. Lee, Jeffries, Jason R., and Nelson, Art J. An XPS study on the impact of relative humidity on the aging of UO2 powders. United States: N. p., 2017. Web. doi:10.1016/j.jnucmat.2017.02.016.
Donald, Scott B., Dai, Zurong R., Davisson, M. Lee, Jeffries, Jason R., & Nelson, Art J. An XPS study on the impact of relative humidity on the aging of UO2 powders. United States. doi:10.1016/j.jnucmat.2017.02.016.
Donald, Scott B., Dai, Zurong R., Davisson, M. Lee, Jeffries, Jason R., and Nelson, Art J. Fri . "An XPS study on the impact of relative humidity on the aging of UO2 powders". United States. doi:10.1016/j.jnucmat.2017.02.016. https://www.osti.gov/servlets/purl/1347674.
@article{osti_1347674,
title = {An XPS study on the impact of relative humidity on the aging of UO2 powders},
author = {Donald, Scott B. and Dai, Zurong R. and Davisson, M. Lee and Jeffries, Jason R. and Nelson, Art J.},
abstractNote = {High resolution x-ray photoemission spectroscopy (XPS) was used to characterize the chemical speciation of high purity uranium dioxide (UO2) powder samples following aging for periods of up to one year under controlled conditions with relative humidity ranging from 34% to 98%. A systematic shift to higher uranium oxidation states, and thus an increase in the mean uranium valence, was found to directly correlate with the dose of water received (i.e. the product of exposure time and relative humidity). Exposure duration was found to have a greater impact on sample aging than relative humidity. Lastly, the sample aged at 98% relative humidity was found to have unique structural differences for exposure time beyond 180 days when observed by scanning electron microscopy (SEM).},
doi = {10.1016/j.jnucmat.2017.02.016},
journal = {Journal of Nuclear Materials},
number = C,
volume = 487,
place = {United States},
year = {Fri Feb 10 00:00:00 EST 2017},
month = {Fri Feb 10 00:00:00 EST 2017}
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 1work
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  • Here, we studied the reaction of water and molecular oxygen with stoichiometric uranium dioxide (i.e. UO 2) powder at elevated temperature by high-resolution x-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, powder x-ray diffraction (XRD), and scanning electron microscopy (SEM). We observed and quatified oxidation resulting from the dissociative chemisorption of the adsorbing molecules and subsequent incorporation into the oxide lattice. Molecular oxygen was found to be a stronger oxidation agent than water at elevated temperatures but not at ambient.
  • High purity UO 2powder samples were subjected to accelerated aging under controlled conditions with relative humidity ranging from 34% to 98%. Characterization of the chemical speciation of the products was accomplished using X-ray photoelectron spectroscopy (XPS). A shift to higher uranium oxidation states was found to be directly correlated to increased relative humidity exposure. In addition, the relative abundance of O 2-, OH -, and H 2O was found to vary with exposure time. Therefore, it is expected that uranium oxide materials exposed to high relative humidity conditions during processing and storage would display a similar increase in average uraniummore » valence.« less
  • We have rf-sputter deposited MoS/sub 2/ coatings onto stainless-steel plates using two extreme combinations of deposition conditions. Raman spectroscopy indicates that there is a small but significant difference in the number of sulfur--sulfur bonds and the amount of amorphous material present in the two types of coatings. The friction and wear properties were evaluated within five days of deposition and after being stored for 150 days in 35%--45% relative humidity followed by over 75 days in (1) 2% or (2) 98% relative humidity environments. The more crystalline material had a coefficient of friction of 0.085 +- 0.017 in lab airmore » and 0.06 +- 0.005 in ultrahigh vacuum. For lab air testing the coefficient of friction increased with wet storage to 0.10 +- 0.01, and the wear life decreased by a factor of 3 for dry storage and by a factor of 10 for wet storage. The MoS/sub 2/ material with the larger amount of amorphous material has a coefficient of friction of 0.10 +- 0.013 which increased to 0.14 +- 0.04 for storage in the wet environment. The wear life of the MoS/sub 2/ coating with the greater amount of amorphous material improved significantly (by 100%) for storage in the wet environment. These results are consistent with the observations of others who noted that water vapor promotes the conversion of MoS/sub 2/ to MoO/sub 3/.« less