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Assunto: radiation doses ×

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    Artigo IPEN-doc 28934
    Evaluation of rare-earth sesquioxides nanoparticles as a bottom-up strategy toward the formation of functional structures
    2022 - SANTOS, SILAS C. dos; RODRIGUES JUNIOR, ORLANDO; CAMPOS, LETICIA L.
    Background: The strategy to form functional structures based on powder technology relies on the concept of nanoparticles characteristics. Rare-earth sesquioxides (RE2O3; RE as Y, Tm, Eu) exhibit remarkable properties, and their fields of application include energy, astronomy, environmental, medical, information technology, industry, and materials science. The purpose of this paper is to evaluate the characteristics of RE2O3 nanoparticles as a bottom-up strategy to form functional materials for radiation dosimetry. Methods: The RE2O3 nanoparticles were characterized by the following techniques: XRD, SEM, PCS, FTIR, ICP, EPR, and zeta potential. Results: All RE2O3 samples exhibited cubic C-type structure in accordance with the sesquioxide diagram, chemical composition over 99.9 %, monomodal mean particle size distribution, in which d50 value was inferior to 130 nm. Among all samples, only yttrium oxide exhibited an EPR signal, in which the most intense peak was recorded at 358mT and g 1.9701. Conclusion: Evaluating nanoparticle characteristics is extremely important by considering a bottom-up strategy to form functional materials. The RE2O3 nanoparticles exhibit promising characteristics for application in radiation dosimetry.
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    Artigo IPEN-doc 26138
    Stability study of the alanine epr dosimetry system at IPEN/CNEN SP
    2019 - RODRIGUES JR ., ORLANDO; SANTOS, SILAS C. dos
    The dosimetry system using alanine EPR is a standard secondary calibration system for high doses. IPEN's High Doses Dosimetry Laboratory (LDA) has an Electron Paramagnetic Resonance equipment operating in the X band which performs high dose dosimetry service for electron and X ray fields for the dose range of 10Gy to 200kGy. IPEN has established a dosimetry system based on an alanine dosimeter developed at the institute. The system is composed of pure DL alanine encapsulated in a polyethylene microtube, which allows estimated doses of 10Gy to 200kGy. The advantages of this system are the low signal fading over a long period of time (over 90 days) and dose measurements above 150kGy. The main disadvantage is the difficulty in measures below 10Gy. In order to improve quality assurance services delivered in radiotherapy, commercial alanine dosimeters are being tested and compared with the already established system for measurements with time intervals longer than 90 days. The present work is an evaluation of the commercial L alanine dosimeter signal compared to the alanine dosimeter produced in IPEN. The dosimeters were irradiated with X ray and E beam and doses of 1, 10 and 20Gy. All measurements were performed following the same laboratory protocol based in ISO/ASTM guidelines. Environmental effects such as temperature, sensitivity to light and air humidity, and other storage conditions were evaluated. The results show that the decay of commercial dosimeters over 36 months was 11% higher than that observed in the dosimeter developed in IPEN, indicating the need for a correction factor for the comparison of dosimetry systems.