MEASUREMENT TECHNIQUE FOR CHARACTERIZATION AND RECORDING OF SPENT 57 Co AND 68 Ge/ 68 Ga SEALED RADIOACTIVE SOURCES

摘要

The present work concerns the development of a technique for activity determination of Ge-68/Ga-68 and Co-57 disused radioactive sources. This technique aims to determine the activity of these sources by measuring and Monte Carlo simulation using the MCNPX code. Therefore, efficiency calibrations of the 3 x 3 NaI(Tl) detector for specific source geometries were carried out. Spectrums for two types of disused radioactive sources were collected for different measurement times. The characteristic gamma rays of a flood source containing Co-57 and a line source containing Ge-68/Ga-68, were used. In case of Ge-68/Ga-68, the annihilation peak of 511 keV was also used considering the disused radioactive sources as a positron emitter. Sources of the mentioned types with certified nominal activities were used to validate MCNPX models. For the Co-57 source, 15 minutes measuring time was adequate for activity determination, and 2 hours measuring time provided adequate sensitivity, at the level of general clearance. For Ge-68/Ga-68 line source, 15 minutes measurement was adequate for activity determination by using the 511 keV from the annihilation of 1899.1 keV positrons.