Influence of the human factor on measurement results

The market offers an increasing number of systems for measuring nuclear and radioactive material. These systems vary in several aspects but have one thing in common: they are used by human beings. Manufacturers often promise that their devices could be used by non-experts or untrained persons without loss in terms of the quality of results. Fraunhofer INT has a long lasting experience in evaluating measuring results of different detection systems, especially in the area of nuclear material. Automated analysis routines partly lead to results which are not correct and could be recognized as such directly by experts but would be taken as correct by non-experts. Measurements with hand-held devices operated by different persons showed the influence of the human factor as well. Facts like subjective perception, individual preferences and of course the experience affect the execution of a measurement and the gained result. Studies on that topic are rare in general. Therefore we investigated the influence of the human factor by investigating measurement results obtained by a larger group of test persons using the same measurement device: our measurement car DeGeN. It is equipped with highly efficient gamma and neutron detection systems to track down and analyze nuclear or radioactive material. The test persons had different levels of experience regarding the search for nuclear or radioactive material, varying from none up to good. In teams of two people a test area was searched in which several radioactive sources were hidden. After the drive the results were documented in a result sheet. Furthermore, data were gathered concerning the experience of the test persons. Correlations between the measurement results and the experiences were drawn. The measurements were performed on the test area of the institute of the fire brigade (IdF) in Muenster, Germany. This test area allows car-borne search in a realistic environment using radioactive sources.