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Title: A composite position independent monitor of reactor fuel irradiation using Pu, Cs, and Ba isotope ratios

Abstract

When post-irradiation materials from the nuclear fuel cycle are released to the environment, certain isotopes of actinides and fission products carry signatures of irradiation history that can potentially aid a nuclear forensic investigation into the material's provenance. In this study, combinations of Pu, Cs, and Ba isotope ratios that produce position (in the reactor core) independent monitors of irradiation history in spent light water reactor fuel are identified and explored. These position independent monitors (PIMs) are modeled for various irradiation scenarios using automated depletion codes as well as ordinary differential equation solutions to approximate nuclear physics models. Experimental validation was performed using irradiated low enriched uranium oxide fuel from a light water reactor, which was sampled at 8 axial positions from a single rod. Plutonium, barium and cesium were chemically separated and isotope ratio measurements of the separated solutions were made by quadrupole and multi-collector inductively coupled mass spectrometry (Cs and Pu, respectively) and thermal ionization mass spectrometry (Ba). The effect of axial variations in neutron fluence and energy spectrum are evident in the measured isotope ratios. Furthermore, two versions of a combined Pu and Cs based PIM are developed. A linear PIM model, which can be used to solvemore » for irradiation time is found to work well for natural U fuel with <10% 240Pu and known or short cooling times. A non-linear PIM model, which cannot be solved explicitly for irradiation time without additional information, can nonetheless still group samples by irradiation history, including high burnup LEU fuel with unknown cooling time. 137Ba/138Ba is also observed to act as a position independent monitor; it is nearly single valued across the sampled fuel rod, indicating that samples sharing an irradiation history (same irradiation time and cooling time) in a reactor despite experiencing different neutron fluxes will have a common 137Ba/138Ba ratio. Modeling of this Ba PIM shows it increases monotonically with irradiation and cooling time, and a confirmatory first order analytical solution is also presented.« less

Authors:
 [1];  [1];  [1];  [2];  [1];  [1];  [1]; ORCiD logo [3]; ORCiD logo [4];  [5]; ORCiD logo [3];  [6];  [2]; ORCiD logo [6]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Georgia Inst. of Technology, Atlanta, GA (United States)
  4. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  5. American Research Associates, Pinehurst, NC (United States)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (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:
1601553
Report Number(s):
LLNL-JRNL-724341
Journal ID: ISSN 0265-931X; 872904
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Environmental Radioactivity
Additional Journal Information:
Journal Volume: 195; Journal Issue: C; Journal ID: ISSN 0265-931X
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; Nuclear forensics; Nuclear terrorism; Environmental release; Nuclear nonproliferation; Nuclear safeguards; Reactor modeling; Plutonium isotope ratio; Cesium isotope ratio; Cesium-135; Cesium-133; Cesium-137; Barium isotope ratio; Stable isotopes; Fission products; Spent fuel analysis

Citation Formats

Robel, Martin, Isselhardt, Brett, Ramon, Erick, Hayes, Anna, Gaffney, Amy, Borg, Lars, Lindvall, Rachel, Erickson, Anna, Carney, Kevin, Battisti, Terry, Conant, Andrew, Ade, Brian, Trellue, Holly, and Weber, Charles. A composite position independent monitor of reactor fuel irradiation using Pu, Cs, and Ba isotope ratios. United States: N. p., 2018. Web. doi:10.1016/j.jenvrad.2018.08.014.
Robel, Martin, Isselhardt, Brett, Ramon, Erick, Hayes, Anna, Gaffney, Amy, Borg, Lars, Lindvall, Rachel, Erickson, Anna, Carney, Kevin, Battisti, Terry, Conant, Andrew, Ade, Brian, Trellue, Holly, & Weber, Charles. A composite position independent monitor of reactor fuel irradiation using Pu, Cs, and Ba isotope ratios. United States. doi:https://doi.org/10.1016/j.jenvrad.2018.08.014
Robel, Martin, Isselhardt, Brett, Ramon, Erick, Hayes, Anna, Gaffney, Amy, Borg, Lars, Lindvall, Rachel, Erickson, Anna, Carney, Kevin, Battisti, Terry, Conant, Andrew, Ade, Brian, Trellue, Holly, and Weber, Charles. Tue . "A composite position independent monitor of reactor fuel irradiation using Pu, Cs, and Ba isotope ratios". United States. doi:https://doi.org/10.1016/j.jenvrad.2018.08.014. https://www.osti.gov/servlets/purl/1601553.
@article{osti_1601553,
title = {A composite position independent monitor of reactor fuel irradiation using Pu, Cs, and Ba isotope ratios},
author = {Robel, Martin and Isselhardt, Brett and Ramon, Erick and Hayes, Anna and Gaffney, Amy and Borg, Lars and Lindvall, Rachel and Erickson, Anna and Carney, Kevin and Battisti, Terry and Conant, Andrew and Ade, Brian and Trellue, Holly and Weber, Charles},
abstractNote = {When post-irradiation materials from the nuclear fuel cycle are released to the environment, certain isotopes of actinides and fission products carry signatures of irradiation history that can potentially aid a nuclear forensic investigation into the material's provenance. In this study, combinations of Pu, Cs, and Ba isotope ratios that produce position (in the reactor core) independent monitors of irradiation history in spent light water reactor fuel are identified and explored. These position independent monitors (PIMs) are modeled for various irradiation scenarios using automated depletion codes as well as ordinary differential equation solutions to approximate nuclear physics models. Experimental validation was performed using irradiated low enriched uranium oxide fuel from a light water reactor, which was sampled at 8 axial positions from a single rod. Plutonium, barium and cesium were chemically separated and isotope ratio measurements of the separated solutions were made by quadrupole and multi-collector inductively coupled mass spectrometry (Cs and Pu, respectively) and thermal ionization mass spectrometry (Ba). The effect of axial variations in neutron fluence and energy spectrum are evident in the measured isotope ratios. Furthermore, two versions of a combined Pu and Cs based PIM are developed. A linear PIM model, which can be used to solve for irradiation time is found to work well for natural U fuel with <10% 240Pu and known or short cooling times. A non-linear PIM model, which cannot be solved explicitly for irradiation time without additional information, can nonetheless still group samples by irradiation history, including high burnup LEU fuel with unknown cooling time. 137Ba/138Ba is also observed to act as a position independent monitor; it is nearly single valued across the sampled fuel rod, indicating that samples sharing an irradiation history (same irradiation time and cooling time) in a reactor despite experiencing different neutron fluxes will have a common 137Ba/138Ba ratio. Modeling of this Ba PIM shows it increases monotonically with irradiation and cooling time, and a confirmatory first order analytical solution is also presented.},
doi = {10.1016/j.jenvrad.2018.08.014},
journal = {Journal of Environmental Radioactivity},
number = C,
volume = 195,
place = {United States},
year = {2018},
month = {9}
}

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