A SYSTEM FOR THE DETECTION OF SPECIAL NUCLEAR MATERIALS IN MOVING VEHICLES

The present work treats the detection of illicit nuclear materials while in transit. In this paper, we propose a geographically advantageous, sensor-based system that that utilizes both gamma-ray imaging and an accelerator-based photofission interrogation technique. The imaging component of the system is utilized not to positively identify the presence of nuclear material but rather to detect high density material suitable for shielding such as lead. High energy gamma rays are used to induce photofission in any fissile material from which delayed neutrons may be detected. A primary focus of this work is to define how well one may be able to detect the illegal transport of nuclear material at varying velocities and system parameters. We have used a combination of parameterized deterministic integral models and numerical methods to help optimize the sources used to image a vehicle and induce photofission while limiting the extent of radiation damage that may ensue. Validation and verification of the system is achieved by Monte Carlo simulations using the powerful Lawrence Livermore National Laboratory based COG radiation transport code. This work also points out areas where improvements can be anticipated in our dual system via case studies of different threat scenarios. A brief discussion is given on the sociopolitical aspects of the aforementioned system. In addition, possible applications of such a system are described, e.g. employing the system on bridges going into Manhattan in order to track possible shipments of nuclear material and to provide valuable information to Federal agencies in a short time-frame.