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ST 1.2 –
Dosimetría externa
ONYX SAMPLES CHARACTERIZATION BY OSL TECHNIQUE FOR
HIGH-DOSE DOSIMETRY
Teixeira, Maria Ines*; Caldas, Linda
IPEN Instituo de Pesquisas Energéticas e Nucleares. Brasil.
* Responsible author, email:
miteixeira@ipen.br
The possibility of application of Brazilian onyx samples for high-dose dosimetry was studied at
IPEN, using the technique of optically stimulated luminescence. Different materials for high-
dose dosimetry have already been studied in recent years at IPEN, using the
thermoluminescence (TL), electronic paramagnetic resonance (EPR), optical absorption (OA)
and optically stimulated luminescence (OSL) techniques. Onyx is a variety of chalcedony, a
form of quartz. The colors of their tracks are white and/or black. The onyx stone is considered
nobler than marble. In this work, the OSL properties of Brazilian onyx samples exposed to
different doses of gamma radiation (60Co) were studied. Onyx samples are found in nature in
abundance in Brazil, they are of very low cost, and they have shown usefulness for high-dose
dosimetry using the TL technique. The onyx stones were extracted from a Brazilian mine, Minas
Gerais state. Pellets of onyx/Teflon were obtained for this study. The pellets were thermally
treated for reutilization at 300°/1h. The irradiations were performed using a Gamma-Cell 220
system (60Co). The irradiations were made at ambient temperature. The OSL emission curves
were obtained during 60s. The following dosimetric parameters were obtained: dose-response
curve between 50 Gy and 300 kGy, the reproducibility of OSL response and the minimum
detectable dose.