Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2005.Includes bibliographical references (leaves 195-200).A new approach to the detection of concealed nuclear weapons and fissile material aboard cargo containerships is proposed. The ship-based approach removes the constraints of current thinking by addressing the threat of containerized nuclear terror in a novel way. Critical tactical misjudgments exist in currently deployed detection systems, which expose U.S. cities to an act of nuclear terrorism. Current port-based systems position defenses within the perimeter of each coastal city and the assumption that terrorists would not remotely detonate the weapon while taxiing past urban areas en route to the port is irrational. The new approach protects this hole in national security by moving defenses outside the perimeter and onto the containership. A networked system of radiation detectors, aboard all inbound containerships, does not allow a concealed nuclear weapon to ever approach the U.S. homeland. This thesis describes the ship-based system in detail, outlines its capabilities and suggests possible deployment scenarios. The basic concept of the ship-based system is to hide detectors in empty standard 40-foot shipping containers and send them back and forth across the ocean alongside normal cargo. Containerized arrays of gamma and neutron detectors are linked to small data processing and transmitting devices.(cont.) Data is transmitted to a central U.S. location for collection, assessment, and possible dissemination to responders in the event of threat identification. Upon positive detection, an alarm condition is signaled and interception of the containership occurs while still at sea. Monte Carlo based simulations suggest that due to long count times during typical two week voyages, radiation transport is significant enough such that containerized units will detect weapons grade uranium and plutonium in implosion-type configurations with three-sigma confidence from distances averaging 22.0 and 23.5 meters of cargo respectively. The vast majority of containerships require between 3 and 15 units deployed on each ship depending on its capacity and degree of control over container placement. Given the low number of units required for each ship, deployment of a containerized detector network is practical and an initial limited deployment increases the level of deterrence by, denial against containerized nuclear terror.by Shawn P. Gallagher.S.M
