Systematic effects in neutron coincidence and multiplicity counting
Abstract
Correlated neutron counting, including neutron coincidence and multiplicity counting, is an important tool in nuclear material accountancy verification. The accuracy of such measurements is of interest to the safeguards community because as the accuracy of NDA improves, the number of samples that are required to undergo destructive analysis (DA) decreases. The accuracy of a neutron mUltiplicity measurement can be affected by a number of variables. Monte Carlo neutron transport simulations with MCNPX have been performed to understand how the properties of the sample affect the count rate. These resultant count rates have been analyzed with the 'point model' in order to determine the effect on the deduced plutonium mass. The sample properties that have been investigated are density, sample position within the detector cavity, moisture content, isotopic composition, plutonium to total actinide ratio and heavy metal fraction. These parameters affect the Singles, Doubles and Triples count rates in different ways. In addition, different analysis methods use these measured quantities in different combinations, so that the final sensitivity of the {sup 240}Pu mass to each parameter also depends on the analysis method used. For example, the passive calibration curve method only used the Doubles rate to produce the {sup 240}Pu massmore »
 Authors:

 Los Alamos National Laboratory
 Publication Date:
 Research Org.:
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 Sponsoring Org.:
 USDOE
 OSTI Identifier:
 1018698
 Report Number(s):
 LAUR1003931; LAUR103931
TRN: US1103442
 DOE Contract Number:
 AC5206NA25396
 Resource Type:
 Conference
 Resource Relation:
 Conference: INMM 51st Annual Meeting ; July 11, 2010 ; Baltimore, MD
 Country of Publication:
 United States
 Language:
 English
 Subject:
 46; ACCURACY; ACTINIDES; CALIBRATION; EFFICIENCY; HEAVY METALS; MOISTURE; MULTIPLICITY; NEUTRON TRANSPORT; NEUTRONS; PLUTONIUM; SAFEGUARDS; SENSITIVITY; VERIFICATION
Citation Formats
Evans, Louise G, Favorite, Jeffrey A, and Swinhoe, Martyn T. Systematic effects in neutron coincidence and multiplicity counting. United States: N. p., 2010.
Web.
Evans, Louise G, Favorite, Jeffrey A, & Swinhoe, Martyn T. Systematic effects in neutron coincidence and multiplicity counting. United States.
Evans, Louise G, Favorite, Jeffrey A, and Swinhoe, Martyn T. Fri .
"Systematic effects in neutron coincidence and multiplicity counting". United States. https://www.osti.gov/servlets/purl/1018698.
@article{osti_1018698,
title = {Systematic effects in neutron coincidence and multiplicity counting},
author = {Evans, Louise G and Favorite, Jeffrey A and Swinhoe, Martyn T},
abstractNote = {Correlated neutron counting, including neutron coincidence and multiplicity counting, is an important tool in nuclear material accountancy verification. The accuracy of such measurements is of interest to the safeguards community because as the accuracy of NDA improves, the number of samples that are required to undergo destructive analysis (DA) decreases. The accuracy of a neutron mUltiplicity measurement can be affected by a number of variables. Monte Carlo neutron transport simulations with MCNPX have been performed to understand how the properties of the sample affect the count rate. These resultant count rates have been analyzed with the 'point model' in order to determine the effect on the deduced plutonium mass. The sample properties that have been investigated are density, sample position within the detector cavity, moisture content, isotopic composition, plutonium to total actinide ratio and heavy metal fraction. These parameters affect the Singles, Doubles and Triples count rates in different ways. In addition, different analysis methods use these measured quantities in different combinations, so that the final sensitivity of the {sup 240}Pu mass to each parameter also depends on the analysis method used. For example, the passive calibration curve method only used the Doubles rate to produce the {sup 240}Pu mass and so is not sensitive to changes in the Singles rate (to first order). The analysis methods considered here were passive calibration curve (nonmultiplication corrected), known alpha (multiplication corrected) and multiplicity with known efficiency. The effects were studied on both a small mass MOX sample (1 g Pu) and a large MOX sample (6000 g Pu) both measured in high efficiency neutron multiplicity counters. In order to determine the final effect of each parameter it is necessary to know not only the sensitivity of the plutonium mass to that parameter, but also the range over which the parameter can realistically vary. Some estimates are given.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2010},
month = {1}
}