Identification measurements of nuclear material - Detective EX versus Falcon 5000

Fast and reliable identification measurements are necessary in case suspicious objects are found, especially when nuclear material is involved. Identification of radioactive and nuclear material is done by gamma analysis. The quality of the measurement results depends amongst other factors on the energy resolution of the detector. The best resolution is obtained using germanium detectors. Also relevant for the quality of the result is the analysis of the measurement data. There are some detector systems available with implemented automatic analysis routines. The manufacturers promise reliable identification results with predefined settings for all kinds of sources. In the present paper a comparison of two such detection systems will be presented. The Detective EX from ORTEC and the Falcon 5000 from Canberra were used for several measurements of various sources of special nuclear material (SNM). Both systems have germanium detectors, electrical cooling for LN2-free use, and automatic analysis routines for identification. The sources used have a big variety concerning isotopes, geometric appearance, and activity. The analyses of the measurements were all done with the predefined standard settings of the manufacturer. This is equivalent to the situation where non-expert users are using that kind of devices in case where for example suspicious objects are found. In a typical real situation the material may be disguised by surrounding material. For this reason we also investigated the effects of various shielding materials and configurations. Besides the correctness of the analysis results we focused our attention on the handling of the devices, also in terms of stress situations in the field.