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Title: Sensitivity of the active neutron coincidence collar response during simulated and experimental fresh fuel assay

Abstract

Verification of the fissile (and fertile) content in fresh nuclear fuel assemblies is conducted by the IAEA to enforce the Nuclear Non-Proliferation Treaty using the UNCL (Uranium Neutron Collar — Light Water Reactor Fuel). The UNCL uses an uncorrelated AmLi neutron source to interrogate the fuel, producing a signal of coincident fission neutrons (Doubles rate) used to assay235U content of the fuel. The cost of producing calibration assemblies and limited availability of diverse commercial assemblies at any one time historically restricted the ability to explore the full parameter space experimentally. Monte Carlo simulations can overcome this, but introduce additional sources of uncertainty. In this work, the sensitivity of simulations and measurements to various parameters is assessed for a reference 1616 PWR assembly of uniform 3.2% enrichment. Uncertainty contributions in this evaluation include: simulated AmLi neutron source spectrum, AmLi neutron emission rate, AmLi anisotropicity, high density polyethylene (HDPE) density, the precise position of the fuel assembly within the detector, and experimentally the statistical uncertainty. The overall total systematic uncertainty estimate for the simulation of the absolute/relative Doubles rates responses are estimated to be approximately 2.0%/1.5%, and for experimental measurements systematic uncertainty reduces to 1.1%. This analysis supports further work using themore » relative Doubles rates in place of measurements for updating and extending the UNCL analysis methodology as systematic uncertainty is reasonably small.« less

Authors:
ORCiD logo [1];  [2];  [2];  [3]; ORCiD logo [4]
+ Show Author Affiliations
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Texas, Austin, TX (United States)
  2. National Nuclear Energy Commission of Brazil (CNEN), Rio de Janeiro (Brazil)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1773335
Alternate Identifier(s):
OSTI ID: 1829524
Report Number(s):
LA-UR-20-29416
Journal ID: ISSN 0168-9002; TRN: US2207041
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 1001; Journal ID: ISSN 0168-9002
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; safeguards; AmLi; fresh fuel verification; neutron collar; UNCL

Citation Formats

Broughton, David Paul, Grund, Marcos S., Renha, Jr., Geraldo, Croft, Stephen, and Favalli, Andrea. Sensitivity of the active neutron coincidence collar response during simulated and experimental fresh fuel assay. United States: N. p., 2021. Web. doi:10.1016/j.nima.2021.165243.
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Broughton, David Paul, Grund, Marcos S., Renha, Jr., Geraldo, Croft, Stephen, & Favalli, Andrea. Sensitivity of the active neutron coincidence collar response during simulated and experimental fresh fuel assay. United States. https://doi.org/10.1016/j.nima.2021.165243
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Broughton, David Paul, Grund, Marcos S., Renha, Jr., Geraldo, Croft, Stephen, and Favalli, Andrea. Tue . "Sensitivity of the active neutron coincidence collar response during simulated and experimental fresh fuel assay". United States. https://doi.org/10.1016/j.nima.2021.165243. https://www.osti.gov/servlets/purl/1773335.
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@article{osti_1773335,
title = {Sensitivity of the active neutron coincidence collar response during simulated and experimental fresh fuel assay},
author = {Broughton, David Paul and Grund, Marcos S. and Renha, Jr., Geraldo and Croft, Stephen and Favalli, Andrea},
abstractNote = {Verification of the fissile (and fertile) content in fresh nuclear fuel assemblies is conducted by the IAEA to enforce the Nuclear Non-Proliferation Treaty using the UNCL (Uranium Neutron Collar — Light Water Reactor Fuel). The UNCL uses an uncorrelated AmLi neutron source to interrogate the fuel, producing a signal of coincident fission neutrons (Doubles rate) used to assay235U content of the fuel. The cost of producing calibration assemblies and limited availability of diverse commercial assemblies at any one time historically restricted the ability to explore the full parameter space experimentally. Monte Carlo simulations can overcome this, but introduce additional sources of uncertainty. In this work, the sensitivity of simulations and measurements to various parameters is assessed for a reference 1616 PWR assembly of uniform 3.2% enrichment. Uncertainty contributions in this evaluation include: simulated AmLi neutron source spectrum, AmLi neutron emission rate, AmLi anisotropicity, high density polyethylene (HDPE) density, the precise position of the fuel assembly within the detector, and experimentally the statistical uncertainty. The overall total systematic uncertainty estimate for the simulation of the absolute/relative Doubles rates responses are estimated to be approximately 2.0%/1.5%, and for experimental measurements systematic uncertainty reduces to 1.1%. This analysis supports further work using the relative Doubles rates in place of measurements for updating and extending the UNCL analysis methodology as systematic uncertainty is reasonably small.},
doi = {10.1016/j.nima.2021.165243},
journal = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},
number = ,
volume = 1001,
place = {United States},
year = {Tue Mar 16 00:00:00 EDT 2021},
month = {Tue Mar 16 00:00:00 EDT 2021}
}
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https://doi.org/10.1016/j.nima.2021.165243
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Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate
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