This work presents the evaluation of the applicability and sensitivity of a portable detection device specially designed for in vivo measurement of high-energy photon emitters in the human body. The calibration was performed at the In-Vivo Monitoring Laboratory of the IRD. The equipment consists of a lead-collimated NaI (Tl) 3”x3” scintillation detector assembled on a tripod. The detector and its compact associated electronics are connected via USB cable to a portable PC. Spectrum acquisition and analysis is controlled by specific commercially available software. The calibration was performed using a standard liquid source of 152Eu contained in 3 L polyethylene bottles. The evaluation of the system is based on the estimation of the minimum committed effective doses associated to the minimum detectable activities, calculated using current biokinetic and dosimetric models available in the literature. The dose detection limits for selected radionuclides of interest in an emergency scenario have shown to be far below 1 mSv allowing the system to be useful in accident situations.
O ser humano está sujeito diariamente a várias fontes de radiação natural, sendo a principal delas o radônio, pertencente à cadeia de decaimento radioativo do urânio e do tório [1]. No local de estudo, estão armazenadas aproximadamente 3,3 toneladas de urânio com concentração natural. Fato este, que gerou a preocupação quanto aos níveis de dose ocupacional dos IOE's da instalação, pois sua dose efetiva terá o acréscimo devido a dose equivalente proveniente da exposição ao radônio. As medições ocorreram: no depósito de urânio; numa sala contigua e no ponto de controle. De acordo com a Norma CNEN -NN 3.01 e considerando as concentrações de radônio existentes nos três ambientes concluiu-se que: a sala de depósito de urânio é considerada uma área controlada; o ponto de controle uma área livre e a sala contígua, uma área supervisionada [2].
The directional response of identifier Micro Detective ORTEC, N-type with 15% of detection efficiency was characterized by using references sources of Cesium ( e 2,0 m) and for the angles (0°, 45°, 60° e 90°), being the measure found in angle 0º adopted as reference value; this same procedure was adopted for other distances evaluated in this work. The results showed a significant variation of the relative efficiency of the detector, for the different angles and source-detector distances. Due to the limiting conditions presented in this study, the importance and influence of background radiation in the results was evidenced. In field situations this occurrence would be treated as being false positive.
The present work showed that a wide diversity of fungi was found in the environment where the Collection Academia Brasileira de Ciências is stored, in the Henrique Morize Library, being this diversity quite common in spaces storing this kind of cellulosic material. Fungal genera such as Aspergillus, Cladosporium, Rhizopus and Trichoderma were identified through modern Molecular Biology techniques. The presence of these fungal genera is probably associated to climatization and humidity control, which prevent the occurrence of a wider diversity of microbes. However, two fungal genera, Trichoderma and Rhizopus, resisted 137Cs irradiation doses with up to 19 kGy, considered high for the elimination of fungi. On the other hand, in the National Library, particularly in some sectors, an even higher diversity of fungal species/genera was observed, a fact that seems to be compatible with the size of the library, with a much higher circulation of people. This higher microbial diversity indicated the occurrence of fungal species absolutely uncommon for in libraries and archives, such as: Diaphorte, Trametes, Arxotrichum, Grammothele, Pessiophora, Phebia and Talaromyces. Just successive samplings in the same areas will allow a confirmation if these fungal genera are permanent of occasional, due to some oscillation in the operation of circulation systems or a possible transport of these species from the outside to the library, which allows those species to remain latent in relation to growth. All microbial samples from the National Library, survived irradiation up to 16kGy.
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