Study of the detection efficiency of a surface contamination monitor according to the distance and the surface emission rate
DOI:
https://doi.org/10.25758/set.514Keywords:
Contamination monitor, Detection efficiency, Distance, Reference radiation sources, Surface emission rateAbstract
Introduction – A radioactive contamination needs to be quantified in case it eventually occurs. Therefore it is necessary to ensure that the operating conditions of a surface contamination monitor are characterized by determining its detection efficiency. This experimental study aims to determine the detection efficiency of a contamination monitor and evaluate the distance and surface emission rate influence on the detection efficiency. Methodology – A contamination monitor Thermo Mini 900E was tested with reference radiation sources of Carbon – 14 (C-14), Cesium – 137 (Cs-137), Strontium – 90 (Sr-90), Chlorine – 36 (Cl-36), and Americium – 241 (Am-241) with its emission rate traced to the Physikalish Technischen Bundesanstalt (PTB). Sources of Sr-90 and C-14 with two different emission rates for each one and distances of 1 to 20mm were used to study their influence on the detection efficiency. Results – With the increase in distance, the detection efficiency decreases. The most energetic radiation sources have higher detection efficiency, boasting a 15% decrease over 20mm whereas the sources bearing a smaller efficiency decrease of 10%. No influence of the surface emission rate in the detection efficiency was verified. Conclusion – Thus, it is concluded that the detection efficiency of a contamination monitor is dependent on the distance between it and the contamination as well as the type and energy of the radioisotopes present in the contamination.
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