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Title: Hybrid Enrichment Verification Array: Investigations of the High-Energy Gamma-Ray Signature Origin and Use for Partial Defect Detection

The International Atomic Energy Agency (IAEA) is exploring the use of an Unattended Cylinder Verification Station (UCVS) to provide independent verification of the declared relative 235U enrichment, 235U mass and total uranium mass of the declared UF6 cylinders moving through modern centrifuge enrichment plants. The Hybrid Enrichment Verification Array (HEVA) method is a candidate nondestructive assay method for inclusion in a UCVS. Modeling and measured data from several field campaigns have demonstrated the potential of the HEVA method to assay relative cylinder enrichment with a precision comparable to or substantially better than today’s high-resolution handheld devices. The HEVA instrument is comprised of an array of sodium iodide gamma-ray detectors that measure two primary spectral components. One of these components is the traditional, direct, weakly-penetrating 235U gamma-ray signature, which contains the 186 keV photopeak. The other spectral component is a non-traditional, high-energy (above ~3 MeV) gamma-ray signature, which is generated indirectly from neutrons emitted from within the UF6 cylinder. These neutrons are more penetrating and create high-energy gamma rays through neutron capture reactions in the steel collimators surrounding the detectors and within the detector crystals. This paper will present results from Monte Carlo simulations and analyses of the HEVA method withmore » a focus on the origins of this high-energy signature, the optimization of instrument design to enhance the signature, and the ability of this non-traditional signature to reveal partial defect scenarios wherein material is missing or substituted in the interior of the cylinder.« less
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Conference: 55th Annual Meeting of the Institute of Nuclear Materials Management (INMM 2014), July 20-24, 2014, Atlanta, Georgia, 4:2909-2916
Institute of Nuclear Materials Management (INMM), OAKBROOK TERRACE, Illinois, United States.
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
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Country of Publication:
United States
HEVA; Enrichment; IAEA; UF6; UF6 cylinder; sodium iodide