[297017] Artigo – CBMRI – Congresso Brasileiro de Metrologia das Radiações Ionizantes

Resumo: One of the goals of metrology is to provide reliability in measurement systems. Recently, portable detectors, which ones are calibrated in the ambient dose equivalent rate or exposure rate, have been applied in “in vivo” dosimetry activities. Thus, there are several methodologies for calibrating, with the usage of different anthropomorphic physical simulators, resulting in efficiency-energy calibration curves, which cannot be directly applied in intercomparison exercises. The present work suggests an easily reproducible methodology to provide the intercomparison of the efficiencies. The MCNPX mathematical simulation code was used to determine an optimized geometry. A cylindrical physical simulator filled with water, with sealed sources of the 57Co, 133Ba and 137Cs placed in the geometric centre, was submitted to a measurement of counts, where a NaI(Tl) detector was used to determine the efficiencies at 0.20 m distance. When the efficiencies of the 137Cs point source and 137Cs volumetric sources were compared, the standard deviation was 7.9%. It is expected the efficiencies reference value of the 2.7 x 10-4 CPS/Bq and an interval of ±10% of this value to intercomparison exercises and verifying the constancy of the equipment’s response in its use in internal dosimetry activities.