The design of a mobile synthetic aperture collimated gamma detector for passive HEU sources
Chin, Michael Raymond
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This thesis covers the individual work of Michael Chin as part of the sponsored research project funded by the U.S. State Department in support of a computational design of a "Mobile Pit Verification System" (MPVS), a mobile “drive by” passive radiation detection system to be applied in special nuclear materials (SNM) storage facilities for validation and compliance purposes. The MPVS system is intended to enable a comprehensive, rapid verification and validation of stored nuclear weapon core physics packages containing SNM, or so-called “weapon pits,” in weapon materials and stockpile storage facilities. The MPVS platform is designed to move at a constant speed and accumulate a signal for each stored weapon pit container. The gamma detector was selected to be a 4 × 4 × 8 cubic inch CsI detector while the neutron detector array designed for the “Transport Simulation and Validation of a Synthetic Aperture SNM Detection System (“T-SADS”) project was used in conjunction with this work; T-SADS was a 3 year project funded by DOE-NNSA which was completed on May 2013. The computational design effort for this project was completed in April 2013, and leveraged novel computational radiation transport methods, algorithms, and SNM identification methods, including a synthetic aperture collection approach, and a new gamma ratio methodology for distinguishing between naturally occurring radiation materials and weapon class SNM materials. Both forward and adjoint transport methods were utilized to characterize the adjoint reaction rate as a function of inter-source spacing, collimation thickness, linear and angular field of view, source age, source type, source geometry, and mobile platform speed. The integrated count was then compared with background radiation and the associated probabilities of detection and false alarm were then computed. Publications resulting from this research were published in PHYSOR 2012, presented at the 53rd annual Proceedings of the INMM, and at the Mathematics & Computation 2013 Conference.