Browsing by Subject "Active interrogation"
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Item A generalized method for rapid analysis of active interrogation systems for detection of special nuclear material(2013-08) Armstrong, Hirotatsu; Schneider, Erich A.Detection of special nuclear material (SNM) being smuggled into the US through ports of entry has been identified as a crucial capability for ensuring the safety and security of the US from radiological threats. Programs such as the NNSA's Second Line of Defense aim to deploy detection systems, both domestically and abroad, in an attempt to interdict the SNM before it reaches its destination. Active interrogation (AI) is a technique that relies on the detection of emitted particles which are produced when SNM is bombarded with a source of high energy photons or neutrons. This work presents a general framework that allows for fast radiation transport modeling of AI scenarios by generating families of response functions which depict neutron, gamma, or electron radiation exiting various regions within the problem, per unit source of radiation entering the region. The solution for a given scenario, typically the detector count rate, is computed by injecting a source term into the first region and applying the appropriate response functions, in sequence, for each subsequent region. For the AI systems modeled in this work, the source is an electron beam in a linear accelerator. Subsequent response functions create and transport bremsstrahlung photons into the SNM, and transport neutrons born in the problem to a detector. The computed solution is comparable to that of a full Monte Carlo simulation, but is assembled in orders of magnitude less time from pre-computed response function libraries. The ability to rapidly compute detector spectra for complicated AI scenarios opens up research and analysis possibilities not previously possible, including conducting parametric studies of scenarios spanning a large portion of the threat space and generating detector spectra used for conditioning and testing of alarm algorithms.Item Incorporation of photon analysis into an active interrogation system for shielded uranium characterization(2016-05) Canion, Bonnie Elise; Landsberger, Sheldon; McConchie, Seth; Schneider, Erich; Biegalski, Steven; Hayward, JasonIn this project I explored the ability of induced photon and neutron signatures from an associated particle imaging deuterium tritium (API-DT) neutron generator detection system to assess the enrichment of shielded uranium. Fast electronics and the associated particle technique, which provide the timing and directional information of the source 14 MeV neutron, allow for a correlated time window of tens of nanoseconds, thus enabling extraction of clear prompt fission signatures from the inspected object. This project contains three distinct investigations that involve relating API-DT neutron generator induced signatures to uranium enrichment. (1) Explore the correlated neutron and photon detection rates, separated by time-of-flight, and investigate the use of a 3-D radiation transport Monte Carlo code to predict enrichment, based on these signatures, (2) Examine the same correlated detection rates, but use a simple point kinetics technique to relate signatures to enrichment, and (3) Exploit the prompt photon energy spectrum to determine if fission neutrons activate shielding material to provide a signature that can be related to uranium enrichment. Throughout these three studies, I investigated the time, number, and energy distribution of these prompt photon signatures, which enabled me to draw conclusions about the strengths and weaknesses of these signatures for shielded uranium characterization.