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Development of a ring dosimeter using OSL technology (Optical Stimulated Luminescense)


Ionizing radiation (IR) has a wide range of applications in society bringing significant benefits. However, it has been found that IR can also bring a risk to human health. Thus, it is necessary to monitor the dose of individuals occupationally exposed (IOE). These doses should be in accordance with the personal dosimetry prescriptions elaborated by the regulatory agencies. In Brazil, the use of IR is regulated by the National Nuclear Energy Commission (CNEN) by the Ministry of Health and the Ministry of Labor. The monitoring of IOE is mandatory according to Ministry of Health Ordinance no. 453 and CNEN Standard 3.01 of CNEN (CNEN NN 3.01). Currently, the number of people monitored in Brazil is approximately 200,000 and 4 million worldwide.Sapra-Landauer is a pioneer in the individual external dosimetry service using Thermoluminescent Dosimetry (TLD) technology since 1979. In 1998, Optically Stimulated Dosimetry (OSLD) with aluminium oxide (Al2O3: C) developed by Landauer Inc., partner of Sapra-Landauer, began to be used in several countries and mainly in the United States, France, England and Japan. In Brazil, there is a strict certification system for individual external monitoring services (SMIE). The regulation of this certification is carried out by the Evaluation Committee of Testing and Calibration Services - CASEC / IRD / CNEN. From 2015 the OSLD technology became available in Brazil with the Sapra-Landauer certification. In addition, the company contributed to the development of a software that performs signal analysis on OSL reading equipment and a method of recovering Al2O3: C to the United States.Aiming at worker safety, in some cases as in Nuclear Medicine (MN), X-ray intervention, catheterization and others, the evaluation of dose in the extremities and/or crystalline becomes very important. Although OSL technology has significant advantages over TLD technology, to date, OSL dosimetry is only applied to whole body monitors and wristbands (poor ergonomics). Currently, the only commercial ring-type dosimetry system is one that uses TL technology with LiF:Mg. The main restriction for the use of Al2O3:C is due to its dependence on the luminescence response with the incident beam energy in the X-ray range (E <100keV). For whole body dosimeters and wristbands, this problem is circumvented by using more than one sensitive element and filters of different materials where the relationship between the responses of these sensitive elements allows the determination of the incident beam's average energy and thus the calculation of the dose appropriately.During the PIPE 1 it was possible to estimate two suitable geometries for the construction of the ring-type dosimeter, consisting of an Al2O3: C sensor and a thin copper disk filtering radiation and the other configuration is formed by two separate aluminium oxide sensors by a thinner copper filter with a smaller hole compared to the first geometry. In both cases the equivalent dose associated with zero-angle incident radiation was unambiguously determined.In this second phase of the research, PIPE II, the geometry that allows to satisfy the conditions required by the regulatory agencies to evaluate the Hp (0.07) quantity (dose equivalent in 0.07mm depth in the body) should be established. Irradiation tests will be performed for various exposure intensities, X-ray beam qualities at different angles of incidence and an ergonomic design for ring containment will be investigated. Other challenges include: 1) modifying the OSL MicroStarii dosimeter reader drawer to obtain a more efficient reading of the OSL sensors used in the ring, and 2) to design and manufacture an optical cleaning system of sensors (annealer) (AU)

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