An Optimized International Vehicle Monitor

The security plans for many DOE facilities require the monitoring of pedestrians and vehicles to control the movement of special nuclear material (SNM). Vehicle monitors often provide the outer-most barrier against the theft of SNM. Automatic monitors determine the presence of SNM by comparing the gamma-ray and neutron intensity while occupied, to the continuously updated background radiation level which is measured while the unit is unoccupied. The most important factors in choosing automatic vehicle monitors are sensitivity, cost and in high traffic applications total monitoring time. The two types of automatic vehicle monitors presently in use are the vehicle monitoring station and the drive-through vehicle monitor. These two types have dramatically different cost and sensitivities. The vehicle monitoring station has a worst-case detection sensitivity of 40 g of highly enriched uranium, HEU, and a cost approximately $180k. This type of monitor is very difficult to install and can only be used in low traffic flow locations. The drive-through vehicle portal has a worst-case detection sensitivity of 1 kg of HEU and a cost approximately $20k. The world`s political situation has created a pressing need to prevent the diversion of SNM from FSU nuclear facilities and across international borders. Drive-through vehicle monitors would be an effective and practical nuclear material proliferation deterrent if their sensitivity can be improved to a sufficient level. The goal of this project is to evaluate different detector configurations as a means of improving the sensitivity of these instruments to achieve a vehicle monitor that is economical, practical to install, and has adequate sensitivity to be an effective barrier to illegal transportation of SNM.