Performance testing of automatic vehicle radioactive sources monitors

The tests of the stationary devices for the detection of the radioactive sources in moving trucks were performed by the Czech Metrological Institute - Inspectorate for Ionising Radiation, Prague in December 1996 and September 1997. Ten different systems were installed and tested at a railway polygon. The basic part of each system - two detection units were placed symmetrically at the rail in a distance 2.3 m from the axe of the rail. The train comprising empty and scrap-filled trucks passed along the detection units at a speed of 5 to 30 km/h. The wide range of radioactive sources with 137Cs (activity ranging from 0.4 MBq to 5 GBq) were located at different positions in the truck. The purpose was to determine a detection limit under different conditions. Sources with 57Co, 60Co, 241Am were also used. The truck passed the polygon more then 1000 times. About 250 passes were free of source. All systems were also tested in a climatic chamber. The main features evaluated were the detection limit for an empty truck, detection limit for a truck filled with scrap (density 0.89 t/m3), percentage of false alarms and stability of response to different temperatures. The other features like energy dependence, position dependence, linearity and overload, detection response time, etc., were also evaluated. The tested systems showing a positive result will be sued in the field of steel recycling, metallurgy and the supervision of illegal transport. (author)