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Title: Fast-Neutron Multiplicity Counter for the Detection of Diversion Scenarios

Abstract

We demonstrated the application of a fast-neutron multiplicity counter (FNMC) to detect small variations in an assembly of uranium-oxide pins. The current version of the FNMC includes eight liquid organic scintillators (EJ-309 7.62 cm diameter x 7.62 cm) and eight crystal organic scintillators (stilbene 5.08 cm diameter x 5.08 cm) in a checkerboard assembly. We measured time-correlated fast neutrons, emitted by an assembly of 32 uranium-oxide pins, using two AmLi sources to induce fissions in the sample. Each pin is a cylinder of approximately 1 cm diameter and 10 cm length, with a mass of 75.52 g and 16.37 wt% enrichment. We removed up to 16 pins from a sample consisting of 32 pins, and determined the minimum number of pins that resulted in a statistically significant decrease of neutron coincidence counts. All the measurements were performed at the Zero Power Physics Reactor facility of Idaho National Laboratory. We found that a diversion of the four innermost pins could be detected by the system in 5 minutes. The detection of time-correlated neutrons requires their discrimination from gamma-ray events. This is an especially challenging task when measuring uranium isotopes, because of the intense gamma-ray flux generated by the radioactive decay ofmore » uranium daughters. We will describe the on-board pulse shape discrimination and post processing techniques that we applied to effectively distinguish neutrons from gamma-rays. Fast-neutron measurements have several potential advantages compared to thermal and epithermal neutron counters, the most important being a shorter die-away time and therefore reduced spurious coincidences due to accidental counts. This advantage may result in a higher sensitivity in timely detecting diversion of nuclear material from peaceful uses.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1400262
Report Number(s):
INL/CON-17-41062
DOE Contract Number:  
DE-AC07-05ID14517
Resource Type:
Conference
Resource Relation:
Conference: INMM 58th Annual Meeting, Indian Wells, California USA, July 16–20, 2017
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Multiplicity; Verification

Citation Formats

Shin, T. H., Di Fulvio, A., Clarke, S. D., Chichester, D. L., and Pozzi, S. A. Fast-Neutron Multiplicity Counter for the Detection of Diversion Scenarios. United States: N. p., 2017. Web.
Shin, T. H., Di Fulvio, A., Clarke, S. D., Chichester, D. L., & Pozzi, S. A. Fast-Neutron Multiplicity Counter for the Detection of Diversion Scenarios. United States.
Shin, T. H., Di Fulvio, A., Clarke, S. D., Chichester, D. L., and Pozzi, S. A. Thu . "Fast-Neutron Multiplicity Counter for the Detection of Diversion Scenarios". United States. https://www.osti.gov/servlets/purl/1400262.
@article{osti_1400262,
title = {Fast-Neutron Multiplicity Counter for the Detection of Diversion Scenarios},
author = {Shin, T. H. and Di Fulvio, A. and Clarke, S. D. and Chichester, D. L. and Pozzi, S. A.},
abstractNote = {We demonstrated the application of a fast-neutron multiplicity counter (FNMC) to detect small variations in an assembly of uranium-oxide pins. The current version of the FNMC includes eight liquid organic scintillators (EJ-309 7.62 cm diameter x 7.62 cm) and eight crystal organic scintillators (stilbene 5.08 cm diameter x 5.08 cm) in a checkerboard assembly. We measured time-correlated fast neutrons, emitted by an assembly of 32 uranium-oxide pins, using two AmLi sources to induce fissions in the sample. Each pin is a cylinder of approximately 1 cm diameter and 10 cm length, with a mass of 75.52 g and 16.37 wt% enrichment. We removed up to 16 pins from a sample consisting of 32 pins, and determined the minimum number of pins that resulted in a statistically significant decrease of neutron coincidence counts. All the measurements were performed at the Zero Power Physics Reactor facility of Idaho National Laboratory. We found that a diversion of the four innermost pins could be detected by the system in 5 minutes. The detection of time-correlated neutrons requires their discrimination from gamma-ray events. This is an especially challenging task when measuring uranium isotopes, because of the intense gamma-ray flux generated by the radioactive decay of uranium daughters. We will describe the on-board pulse shape discrimination and post processing techniques that we applied to effectively distinguish neutrons from gamma-rays. Fast-neutron measurements have several potential advantages compared to thermal and epithermal neutron counters, the most important being a shorter die-away time and therefore reduced spurious coincidences due to accidental counts. This advantage may result in a higher sensitivity in timely detecting diversion of nuclear material from peaceful uses.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {6}
}

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