Techniques for locating and identifying nuclear and radioactive material

Reliable measurement techniques are imperative for early detection of illicit use of nuclear and radioactive material. Nuclear safeguards are an important tool to impede the illicit use of fissionalbe material. But the scope of safeguards is only nuclear material. Other radioactive substances which are widely used in industry and medicine are not controlled to the same extend. Terrorist attacks including this type of material may have far extending consequences. Therefore it is of great importance that mobile measurement systems are available to detect and to respond to malicious acts involving radioactive or nuclear material. Fraunhofer INT has built up a mobile measurement system in a transportable container for the detection and identification of radioactive and nuclear material. The system is equipped with various types of detectors for neutron and gamma radiation, some of the detectors are similar to those used in safeguards. The measuring capabilities of the system have been extended by a gamma scanner. The scanner has two interchangeable detectors. A CsI crystal with relatively high efficiency and a CdZnTe-room-temperature semiconductor with high resolution. The area of interest is scanned sequentially and for each measuring point a standard gamma spectrum is recorded. Regions of interest can be used to select specific energy ranges. A digital optical image of the measurement area is overlaid with the color coded result of the gamma measurements. The gamma camera has been used to locate and identify radioactive sources with and without shielding material. Results of these measurements will be presented