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

Journal Article · 13 June 2017 · IEEE Transactions on Nuclear Science

DOI: https://doi.org/10.1109/TNS.2017.2715238 · OSTI ID:1408632

Tweardy, Matthew C.  ^[1]; McConchie, Seth ^[2]; Hayward, Jason P. ^[1]

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

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.

• Research Organization: Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation
• Grant/Contract Number: AC05-00OR22725; NA0002493
• OSTI ID: 1408632
• Journal Information: IEEE Transactions on Nuclear Science, Vol. 64, Issue 7; ISSN 0018-9499
• Publisher: IEEECopyright Statement
• Country of Publication: United States
• Language: English