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Title: Microscale Isotopic Variation in Uranium Fuel Pellets with Implications for Nuclear Forensics

Abstract

Until recently, the analysis and identification of nuclear fuel pellets in the context of a nuclear forensics investigation have been mainly focused on macroscopic characteristics, such as fuel pellet dimensions, uranium enrichment, and other reactor-specific features. Here, we report microscale isotopic heterogeneity observed in different fuel pellet fragments that were characterized in situ by nanoscale secondary ion mass spectrometry (NanoSIMS). The materials analyzed include fuel fragments obtained as part of the Collaborative Materials Exercise (CMX-4) organized by the Nuclear Forensics International Technical Working Group (ITWG), as well as a fuel pellet fragment from a commercial power reactor. Although the commercial fuel pellet showed a homogeneous 235U/ 238U ratio across the sample (within analytical error), NanoSIMS imaging of the CMX-4 fuel pellet fragments showed distinct microscale variations in the uranium isotopic composition. The average 235U enrichments were 2.2 and 2.9% for the two samples; however, the measured 235U/ 238U ratios varied between 0.0081 and 0.035 (0.79–3.3 atom % 235U) and between 0.0090 and 0.045 (0.89–4.3 atom % 235U). The measurement of 236U in one of the CMX-4 samples suggested the use of at least three uranium oxide powders of different isotopic compositions (“source terms”) in the production of the pellets. Thesemore » variations were not detected using the conventional bulk, macroscopic techniques applied to these materials. Furthermore, our study highlights the importance of characterizing samples on the microscale for heterogeneities that would otherwise be overlooked and demonstrates the potential use of NanoSIMS in guiding further nuclear forensic analysis.« less

Authors:
ORCiD logo [1]; ORCiD logo [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)
OSTI Identifier:
1572604
Report Number(s):
LLNL-JRNL-770145
Journal ID: ISSN 0003-2700; 938287
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Analytical Chemistry
Additional Journal Information:
Journal Volume: 91; Journal Issue: 18; Journal ID: ISSN 0003-2700
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY

Citation Formats

Kips, Ruth, Weber, Peter K., Kristo, Michael J., Jacobsen, Benjamin, and Ramon, Erick C. Microscale Isotopic Variation in Uranium Fuel Pellets with Implications for Nuclear Forensics. United States: N. p., 2019. Web. doi:10.1021/acs.analchem.9b01737.
Kips, Ruth, Weber, Peter K., Kristo, Michael J., Jacobsen, Benjamin, & Ramon, Erick C. Microscale Isotopic Variation in Uranium Fuel Pellets with Implications for Nuclear Forensics. United States. doi:10.1021/acs.analchem.9b01737.
Kips, Ruth, Weber, Peter K., Kristo, Michael J., Jacobsen, Benjamin, and Ramon, Erick C. Tue . "Microscale Isotopic Variation in Uranium Fuel Pellets with Implications for Nuclear Forensics". United States. doi:10.1021/acs.analchem.9b01737.
@article{osti_1572604,
title = {Microscale Isotopic Variation in Uranium Fuel Pellets with Implications for Nuclear Forensics},
author = {Kips, Ruth and Weber, Peter K. and Kristo, Michael J. and Jacobsen, Benjamin and Ramon, Erick C.},
abstractNote = {Until recently, the analysis and identification of nuclear fuel pellets in the context of a nuclear forensics investigation have been mainly focused on macroscopic characteristics, such as fuel pellet dimensions, uranium enrichment, and other reactor-specific features. Here, we report microscale isotopic heterogeneity observed in different fuel pellet fragments that were characterized in situ by nanoscale secondary ion mass spectrometry (NanoSIMS). The materials analyzed include fuel fragments obtained as part of the Collaborative Materials Exercise (CMX-4) organized by the Nuclear Forensics International Technical Working Group (ITWG), as well as a fuel pellet fragment from a commercial power reactor. Although the commercial fuel pellet showed a homogeneous 235U/238U ratio across the sample (within analytical error), NanoSIMS imaging of the CMX-4 fuel pellet fragments showed distinct microscale variations in the uranium isotopic composition. The average 235U enrichments were 2.2 and 2.9% for the two samples; however, the measured 235U/238U ratios varied between 0.0081 and 0.035 (0.79–3.3 atom % 235U) and between 0.0090 and 0.045 (0.89–4.3 atom % 235U). The measurement of 236U in one of the CMX-4 samples suggested the use of at least three uranium oxide powders of different isotopic compositions (“source terms”) in the production of the pellets. These variations were not detected using the conventional bulk, macroscopic techniques applied to these materials. Furthermore, our study highlights the importance of characterizing samples on the microscale for heterogeneities that would otherwise be overlooked and demonstrates the potential use of NanoSIMS in guiding further nuclear forensic analysis.},
doi = {10.1021/acs.analchem.9b01737},
journal = {Analytical Chemistry},
issn = {0003-2700},
number = 18,
volume = 91,
place = {United States},
year = {2019},
month = {7}
}

Journal Article:
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