In nuclear nonproliferation and safeguards, detecting and accurately characterizing special nuclear material remains one of the greatest challenges. Uranium enrichment determination is typically achieved by measuring the ratio of characteristic γ-ray emissions from 235 U and 238 U. Fission also produces β-delayed neutrons, which have been used in the past to determine uranium enrichment from the time dependence of the long-lived delayed neutron emission rate. Such measurements typically use moderated 3 He tube detectors. We demonstrate a new measurement technique that employs a fast neutron active interrogation probe and a scintillation detector to measure the enrichment of uranium using both the buildup and decay of β-delayed neutron emission. Instead of 3 He tubes, a capture-based heterogeneous composite detector consisting of scintillating Li-glass and polyvinyl toluene has been constructed and used, offering a prospect to scale delayed neutron measurements to larger detector sizes. Since the technique relies on the existing tabulated nuclear data, no calibration standards are required. It is shown that the buildup of delayed neutron emission can be used to distinguish between uranium samples and infer the uranium enrichment level, with accuracy that rivals the method that employs the time-dependent decay of delayed neutron emission.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.