Prevention of illicit trafficking of nuclear and radioactive material at border stations by means of highly efficient detection systems

In the context of the possible threat of proliferation of nuclear material by groups of terrorist and non-state actors reliable detection techniques of such material are of great importance at points of interest such as airports, harbors, railway stations, and border crossing points. The opportunity to detect nuclear material is given at border stations in particular because vehicles and pedestrians potentially carrying such material are forced to drive or walk slowly in lines, thus providing well-defined measuring conditions. Gamma and neutron detectors with a high efficiency are required for this task. As consortium leader of the current TACIS (Technical Assistance to the Commonwealth of Independent States) project "Ukrainian Border Security" of the European Union our institute is involved in setting up modern stationary portal monitor systems at selected Ukrainian border stations in order to provide adequate detection techniques for the prevention of illicit trafficking of nuclear material at these borders. The current status of the project will be presented. Furthermore, Fraunhofer-INT operates a mobile portal monitor system manufactured by Thermo based upon our institute's requirements and specifications. It comprises two pillars containing large-volume NaI crystals which can be used separately or combined, then forming a portal of variable width. Besides providing the option to localize radioactive or nuclear material, the system also allows for the discrimination between naturally occurring radiation and artificial material by means of the implemented NBR method. The measured count rate data are transferred to a PC by radio transmission. A series of measurements was performed with this portal monitor system to test its ability to detect both radioactive and nuclear material. An overview of the measurement results are presented as an example of the capabilities and performance of current portal monitor systems.