A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements
An extension of the point kinetics model is developed in this paper to describe the neutron multiplicity response of a bare uranium object under interrogation by an associated particle imaging deuteriumtritium (DT) measurement system. This extended model is used to estimate the total neutron multiplication of the uranium. Both MCNPXPoliMi simulations and data from active interrogation measurements of highly enriched and depleted uranium geometries are used to evaluate the potential of this method and to identify the sources of systematic error. The detection efficiency correction for measured coincidence response is identified as a large source of systematic error. If the detection process is not considered, results suggest that the method can estimate total multiplication to within 13% of the simulated value. Values for multiplicity constants in the point kinetics equations are sensitive to enrichment due to (n, xn) interactions by DT neutrons and can introduce another significant source of systematic bias. This can theoretically be corrected if isotopic composition is known a priori. Finally, the spatial dependence of multiplication is also suspected of introducing further systematic bias for high multiplication uranium objects.
 Authors:

^{[1]}
;
^{[2]};
^{[1]}
 Univ. of Tennessee, Knoxville, TN (United States)
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Publication Date:
 Grant/Contract Number:
 AC0500OR22725; NA0002493
 Type:
 Accepted Manuscript
 Journal Name:
 IEEE Transactions on Nuclear Science
 Additional Journal Information:
 Journal Volume: 64; Journal Issue: 7; Journal ID: ISSN 00189499
 Publisher:
 IEEE
 Research Org:
 Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Sponsoring Org:
 USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation (NA20)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; coincidence techniques; neutrons; nondestructive evaluation; uranium
 OSTI Identifier:
 1408632
Tweardy, Matthew C., McConchie, Seth, and Hayward, Jason P.. A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements. United States: N. p.,
Web. doi:10.1109/TNS.2017.2715238.
Tweardy, Matthew C., McConchie, Seth, & Hayward, Jason P.. A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements. United States. doi:10.1109/TNS.2017.2715238.
Tweardy, Matthew C., McConchie, Seth, and Hayward, Jason P.. 2017.
"A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements". United States.
doi:10.1109/TNS.2017.2715238. https://www.osti.gov/servlets/purl/1408632.
@article{osti_1408632,
title = {A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements},
author = {Tweardy, Matthew C. and McConchie, Seth and Hayward, Jason P.},
abstractNote = {An extension of the point kinetics model is developed in this paper to describe the neutron multiplicity response of a bare uranium object under interrogation by an associated particle imaging deuteriumtritium (DT) measurement system. This extended model is used to estimate the total neutron multiplication of the uranium. Both MCNPXPoliMi simulations and data from active interrogation measurements of highly enriched and depleted uranium geometries are used to evaluate the potential of this method and to identify the sources of systematic error. The detection efficiency correction for measured coincidence response is identified as a large source of systematic error. If the detection process is not considered, results suggest that the method can estimate total multiplication to within 13% of the simulated value. Values for multiplicity constants in the point kinetics equations are sensitive to enrichment due to (n, xn) interactions by DT neutrons and can introduce another significant source of systematic bias. This can theoretically be corrected if isotopic composition is known a priori. Finally, the spatial dependence of multiplication is also suspected of introducing further systematic bias for high multiplication uranium objects.},
doi = {10.1109/TNS.2017.2715238},
journal = {IEEE Transactions on Nuclear Science},
number = 7,
volume = 64,
place = {United States},
year = {2017},
month = {6}
}