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Title: Oxygen point defect accumulation in single-phase U O 2 + x

Abstract

UO 2.07 was characterized using neutron total scattering in order to elucidate defect morphology in the low oxygen-to-metal regime (x < 0.125 for UO 2+x). Data were collected at temperatures (600 and 1000 °C) coinciding with the single-phase UO 2+x region of the established phase diagram, and results were compared with data of stoichiometric UO 2 collected at near-identical temperatures. Experimental data were modeled and interpreted using a holistic approach employing a combination of analyses that characterized multiple spatial length scales. Preferential modeling of long-range atomic arrangements with Rietveld refinement suggests the existence of primarily monointerstitials in UO 2.07, whereas preferential modeling of short-range atomic structures with small-box pair distribution function (PDF) refinement indicates the presence of defect clusters in UO 2.07. Simultaneous modeling of multiple length scales using complementary reverse Monte Carlo (RMC) and molecular dynamics (MD) methods confirms that excess oxygen atoms in UO 2.07 exist as small defects, such as monointerstitials and di-interstitials. RMC and MD results agree with diffraction analysis but differ significantly from small-box PDF refinements, which may be related to a lack of intermediate- and long-range structural information gained from the small-box PDF refinement procedure. Employing a combination of analysis methods with varying length-scalemore » sensitivities enabled more accurate assessment of the UO 2+x defect structure. Furthermore, our findings provide experimental support for previously predicted di-interstitial defect morphologies in UO 2+x that highly influence the accurate prediction of bulk physiochemical properties of UO 2+x, such as oxygen diffusivity.« less

Authors:
 [1];  [2];  [1];  [3];  [4];  [2];  [4];  [3];  [2];  [1];  [1]
  1. Univ. of Tennessee, Knoxville, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Rensselaer Polytechnic Inst., Troy, NY (United States)
  4. Univ. of Notre Dame, Notre Dame, IN (United States)
Publication Date:
Research Org.:
George Washington Univ., Washington, DC (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP) (NA-10); USDOE Office of Nuclear Energy (NE); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1581186
Alternate Identifier(s):
OSTI ID: 1523682; OSTI ID: 1545569
Grant/Contract Number:  
[NA0003858; SC0001089; NE0008440; NA0002006; AC05-00OR22725]
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
[ Journal Volume: 3; Journal Issue: 5]; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 36 MATERIALS SCIENCE

Citation Formats

Palomares, Raul, McDonnell, Marshall, Yang, Li, Yao, Tiankai, Szymanowski, Jennifer E. S., Neufeind, Joerg, Sigmon, Ginger E., Lian, Jie, Tucker, Matthew G., Wirth, Brian, and Lang, Maik. Oxygen point defect accumulation in single-phase UO2+x. United States: N. p., 2019. Web. doi:10.1103/PhysRevMaterials.3.053611.
Palomares, Raul, McDonnell, Marshall, Yang, Li, Yao, Tiankai, Szymanowski, Jennifer E. S., Neufeind, Joerg, Sigmon, Ginger E., Lian, Jie, Tucker, Matthew G., Wirth, Brian, & Lang, Maik. Oxygen point defect accumulation in single-phase UO2+x. United States. doi:10.1103/PhysRevMaterials.3.053611.
Palomares, Raul, McDonnell, Marshall, Yang, Li, Yao, Tiankai, Szymanowski, Jennifer E. S., Neufeind, Joerg, Sigmon, Ginger E., Lian, Jie, Tucker, Matthew G., Wirth, Brian, and Lang, Maik. Fri . "Oxygen point defect accumulation in single-phase UO2+x". United States. doi:10.1103/PhysRevMaterials.3.053611.
@article{osti_1581186,
title = {Oxygen point defect accumulation in single-phase UO2+x},
author = {Palomares, Raul and McDonnell, Marshall and Yang, Li and Yao, Tiankai and Szymanowski, Jennifer E. S. and Neufeind, Joerg and Sigmon, Ginger E. and Lian, Jie and Tucker, Matthew G. and Wirth, Brian and Lang, Maik},
abstractNote = {UO2.07 was characterized using neutron total scattering in order to elucidate defect morphology in the low oxygen-to-metal regime (x < 0.125 for UO2+x). Data were collected at temperatures (600 and 1000 °C) coinciding with the single-phase UO2+x region of the established phase diagram, and results were compared with data of stoichiometric UO2 collected at near-identical temperatures. Experimental data were modeled and interpreted using a holistic approach employing a combination of analyses that characterized multiple spatial length scales. Preferential modeling of long-range atomic arrangements with Rietveld refinement suggests the existence of primarily monointerstitials in UO2.07, whereas preferential modeling of short-range atomic structures with small-box pair distribution function (PDF) refinement indicates the presence of defect clusters in UO2.07. Simultaneous modeling of multiple length scales using complementary reverse Monte Carlo (RMC) and molecular dynamics (MD) methods confirms that excess oxygen atoms in UO2.07 exist as small defects, such as monointerstitials and di-interstitials. RMC and MD results agree with diffraction analysis but differ significantly from small-box PDF refinements, which may be related to a lack of intermediate- and long-range structural information gained from the small-box PDF refinement procedure. Employing a combination of analysis methods with varying length-scale sensitivities enabled more accurate assessment of the UO2+x defect structure. Furthermore, our findings provide experimental support for previously predicted di-interstitial defect morphologies in UO2+x that highly influence the accurate prediction of bulk physiochemical properties of UO2+x, such as oxygen diffusivity.},
doi = {10.1103/PhysRevMaterials.3.053611},
journal = {Physical Review Materials},
number = [5],
volume = [3],
place = {United States},
year = {2019},
month = {5}
}

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