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 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 t...

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Bibliographic Details
Published in:IEEE transactions on nuclear science 2017-07, Vol.64 (7), p.1963-1969
Main Authors: Tweardy, Matthew C., McConchie, Seth, Hayward, Jason P.
Format: Article
Language:English
Subjects:
Atmospheric measurements
Bias
Coincidence techniques
Computer simulation
Constants
Depleted uranium
Error analysis
Error correction
Error detection
Interrogation
Kinetic theory
Kinetics
Mathematical model
Mathematical models
Multiplication
Multiplication & division
Neutrons
nondestructive evaluation
NUCLEAR PHYSICS AND RADIATION PHYSICS
Particle measurements
Questioning
Radioisotopes
Systematics
Tritium
Uranium
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Summary:An extension of the point kinetics model is developed 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. The spatial dependence of multiplication is also suspected of introducing further systematic bias for high multiplication uranium objects.
ISSN:0018-9499
1558-1578
DOI:10.1109/TNS.2017.2715238