IDENTIFICATION OF NUCLEAR MATERIAL WITH HAND-HELD AND PORTABLE GAMMA AND NEUTRON MEASURING DEVICES

摘要

Performing fast measurements in the field at places where suspicious objects were found isessential in the context of nuclear terrorism. Especially if nuclear material is involved, it isnecessary to identify small amounts of plutonium or uranium and to gain informationconcerning isotopic composition. Therefore, measurements at different uranium and plutoniumsamples were carried out. Samples with different isotopic compositions have been used for thepresent work. For gamma measurements hand-held and portable devices using different detectormaterials were investigated. The nuclide identification results of implemented automaticidentification routines were compared for the different devices and to the given sourceinformation. As hand-held device with germanium detector (Ge) the ORTEC Micro Detectivewith electrical cooling was used. The identiFINDER-Ultra from ICx was used as an example fora hand-held device and gamma-ray spectrometer with the most common detector materialsodium iodide (NaI). Another investigated detection system was the InSpector 1000 fromCanberra which contains a lanthanum bromide (LaBr3) crystal. A fourth type of detectormaterial is used by the INTERCEPTOR from Thermo which is equipped with cadmium-zinctelluride(CZT) crystals. Some of the measurement devices also have neutron detectors but withvery small volume and therefore low efficiency. A portable neutron detector with animplemented analysis routine for the discrimination between industrial and nuclear neutronsources is the Fission Meter from ORTEC. The paper presents results obtained with the differentmeasurement systems. The quality of the outcome of the automatic identification routines of thedifferent detection systems varied significantly. These results depended not only on the differentdetector materials but also on the type of nuclear material. In general identification of uraniumwas considerably better than the identification of plutonium.