A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements

Tweardy, Matthew C.; McConchie, Seth; Hayward, Jason P.

doi:10.1109/TNS.2017.2715238

Title: A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements

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Abstract

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 deuterium-tritium (D-T) measurement system. This extended model is used to estimate the total neutron multiplication of the uranium. Both MCNPX-PoliMi 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 D-T 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]; McConchie, Seth ^[2]; Hayward, Jason P. ^[1]

Univ. of Tennessee, Knoxville, TN (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:: 2017-06-13

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

OSTI Identifier:: 1408632

Grant/Contract Number:: AC05-00OR22725; NA0002493

Resource Type:: Accepted Manuscript

Journal Name:: IEEE Transactions on Nuclear Science

Additional Journal Information:: Journal Volume: 64; Journal Issue: 7; Journal ID: ISSN 0018-9499

Publisher:: IEEE

Country of Publication:: United States

Language:: English

Subject:: 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; coincidence techniques; neutrons; nondestructive evaluation; uranium

Citation Formats


                    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., 2017. 
Web.  doi:10.1109/TNS.2017.2715238.

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                    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.  https://doi.org/10.1109/TNS.2017.2715238

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                    Tweardy, Matthew C., McConchie, Seth, and Hayward, Jason P. Tue .  
"A Point Kinetics Model for Estimating Neutron Multiplication of Bare Uranium Metal in Tagged Neutron Measurements".  United States.  https://doi.org/10.1109/TNS.2017.2715238.  https://www.osti.gov/servlets/purl/1408632.

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@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 deuterium-tritium (D-T) measurement system. This extended model is used to estimate the total neutron multiplication of the uranium. Both MCNPX-PoliMi 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 D-T 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}

}

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