Sensor fusion algorithms for the detection of nuclear material at border crossings

In this age of global terrorism the ability to detect nuclear material (i.e., radioactive sources) at border crossings is of great importance. Today radiation sensing devices range from handheld detectors to large ultra high-resolution gamma-ray spectrometers. The latter are stationary devices and often used in the form of "portals" placed at border crossings. Currently, border crossings make use of these radiation portals as isolated passive devices. A threshold is set on each detector and any time that threshold is reached an alarm is triggered. Once an alarm is triggered it is assumed that first responders with handheld detectors will disperse in order to determine the location of the radioactive source. This manner of locating a threat is highly dependent upon the reaction of the first responders, thus causing unpredictable delays. We seek to better automate the identification of radioactive sources, by using sensor fusion algorithms which combine the data from multiple sensors (radioactive, RFID, vision) to deduce the location of the source. These algorithms capitalize upon the geometry of a "typical" border crossing layout where parallel lines of vehicles or people are queued so that the location can be computed in near real-time. We find that source location is quickly computable, using using as few as one sensitive radioactive detector, augmented by a visual or RFID tracking system.