Car-borne measurements of radioactive material

The Fraunhofer-INT performed extensive measurement campaigns for the search and identification of radioactive material. The main focus was car-borne searching. The Fraunhofer-INT has long time experience with car-borne searching and equipped a station wagon with sensitive gamma and neutron detectors. The system is called DeGeN, the abbreviation stands for DEtection of Gamma and Neutron sources. It is taken from the German word "Degen" which names a rapier and is our weapon against nuclear terrorism. The neutron component is realized by slab counters incorporating ³He tubes and the gamma detection is done using plastic scintillators with NBR functionality. The latter enables the user to distinguish between natural and artificial radiation. In the continuous process of updating and developing the whole system the gamma system has been enlarged in 2014/2015 from two 5 I probes to two 12 I probes. Results will be presented obtained during a measurement campaign before the change of the system and afterwards. In the first campaign a series of measurements with several different measurement teams was carried out. Each team went through a course searching for hidden radioactive gamma sources using the DeGeN. As a result it was proven that the system is extremely powerful and the majority of the sources was found by all participants independent on previous experience with this system. In the second campaign the larger gamma probes were used and the efficiency with the new detectors was estimated. In addition, measurements with neutron sources were carried out which could not be performed during the first campaign.