Year
2014
Abstract
High - energy delayed gamma - ray (DG) spectroscopy is a potential technique for directly assaying spent fuel assemblies and achieving the safeguards go al of quantifying nuclear material inventories for spent fuel handling, interim storage, reprocessing facilities, repository sites, and final disposal. Requirements for the gamma - ray detection system, in the energy range up to ~7 MeV, can be summarized as follows: high efficiency at high gamma - ray energies, high energy resolution, good linearity between gamma - ray energy and output signal amplitude, ability to operate at very high count - rate s , and ease of use in industrial environment s such as nuclear facili ties. High Purity Germanium Detectors (HPGe) are the state of the art and provide excellent energy resolution but are limited in their count rate capability. Note that fully - burned spent - fuel assemblies produce over 10 15 gamma - ray s/s, thus making high coun t - rate capability being an important driving criterion among the requirements. Lanthanum Bromide (LaBr 3 ) scintillation detectors offer significantly higher count - rate capability than HPGe detectors, although at lower energy resolution, and they do not need a cooling system. Thus LaBr 3 detectors may be an effective alternative for nuclear spent - fuel applications. The performance of a 2” (length) x 2” (diameter) of LaBr 3 scintillation detector system was evaluated. Spectroscopy characteristics of the detector system were measured up to count rates of ~3 Mcps. Further, experimental measurements were conducted at the Idaho Accelerator Center, Idaho State University, where ~3g of 235 U and ~3g of 239 Pu samples were irradiated with neutrons from a photon - neutron so urce and DG spectra collected. P otential capabilitie s and limitations of LaBr 3 scintillation detector s for high count rate DG spectroscopy for assay ing nuclear material were investigat ed.