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B. Goddard, W. Charlton, M. Swinhoe, Paolo Peerani, "Expanding the Capabilities of Neutron Multiplicity Measurements: Conclusions from a Four Year Project," Proceedings of the 35th ESARDA Annual Meeting, 27-30 May, 2013, Bruges, Belgium.


Neutron multiplicity measurement techniques are a powerful nondestructive assay tool for the quantification of plutonium or uranium.  One of the main limitations of this technique is the ability to quantify the content of a sample which contains more than one actinide.  The ability of inspection agencies and facility operators to measure powders containing several actinides is increasingly necessary as new reprocessing techniques and fuel forms are being developed.  These powders are difficult to measure with current techniques because neutrons emitted from induced and spontaneous fission of different nuclides are very similar.  Over the past four years at the Nuclear Security Science and Policy Institute (NSSPI), at Texas A&M University, a neutron multiplicity technique based on first principle methods was developed to measure these powders by exploiting isotope-specific nuclear properties, such as the energy-dependent fission cross sections and the neutron induced fission multiplicity.  This technique was tested by three measurement campaigns using the Active Well Coincidence Counter (AWCC) and Epithermal Neutron Multiplicity Counter (ENMC) with various (α,n) sources and measured materials.  To complement these measurements, extensive Monte Carlo N Particle eXtended (MCNPX) simulations were performed for each measured sample, as well as samples which were not available to measure.  Four potential applications of this first principal technique have been identified: measurements of U, Np, Pu, and Am materials, mixed oxide (MOX) materials, and uranium materials, as well as weapons verification in arms control agreements.  This technique still has several challenges which need to be overcome, the largest of these being the ability to produce results with acceptably small uncertainties.

Associated Project(s):

  • Quantitative NDA Measurements of Advanced Reprocessing Product Materials

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