The TRIGA IPR-R1 nuclear reactor at the Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN, Belo Horizonte, Brazil, has three irradiation facilities: a rotary specimen rack outside the reactor core with 40 irradiation channels which provide large scale isotope irradiation; the central tube placed at the center of the reactor core which permits sample irradiation with maximum neutron flux, as well as neutron beam extraction; a pneumatic transfer tube which makes possible the analysis of short half-life radioisotopes. The aim of this work is to evaluate the thermal and epithermal neutron fluence rates in the three irradiation facilities of the IPR-R1. Al-0.1%Au reference materials were irradiated bare and Cd-covered, at 100 kW thermal power, and gamma spectrometry was applied with an HPGe detector. For the rotary specimen rack, the values obtained for thermal and epithermal neutron fluence rates are (8.2 ± 0.2) × 10 11 n.cm −2 .s −1 and (3.5 ± 0.1) × 10 10 n.cm −2 .s −1 , respectively. For the pneumatic transfer tube and the central tube, epithermal neutron fluence rate values are respectively (3.3 ± 0.2) ×10 9 n.cm −2 .s −1 and (2.6 ± 0.1) x 10 11 n.cm −2 .s −1 . For these facilities, thermal neutron fluence rate values are (2.5 ± 0.2) × 10 11 n.cm −2 .s −1 and (2.8 ± 0.1) × 10 12 n.cm −2 .s −1 , respectively. Knowledge of these parameters will be fundamental in the planning of sample irradiation for analysis or radioisotope production in a more accurate way.

No abstract

In Brazil, there are few microPET in use and a quality control protocols standardization are needed to harmonize their use in the research field. Thus, the purpose of this study is to characterize the image quality performance of the microPET scanner (LabPET 4, GE healthcare Technologies, Waukesha, WI) using the NEMA NU 4/ 2008 standards and specific phantom. The NEMA image-quality (IQ) phantom consists of 3 different regions to analyze distinct characteristics: image noise (%SD), expressed as percentage SD in a uniform region (%SD), recovery coefficient (RC) and Spill-over (SOR) in air and water. The IQ phantom was filled with 18F-FDG calibrated at the beginning of acquisition, placed in the center of the field-of-view (FOV) and measured with the typical whole body imaging protocol. The images were reconstructed with different reconstruction methods (FBP-2D; MLEM-3D and OSEM-3D); with and without high resolution (HR) when possible. The results were compared. The LabPET 4 system produces appropriate image and with performance according to the literature. The present study is an initial step to verify the NEMA NU 4/2008 use in the Brazilian scenario for further standardization.

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As propriedades mecânicas do cimento Portland estão intrinsecamente relacionadas à composição química do clínquer, em especial à concentração de silicato tricálcico 3CaO.SiO2, ou C3S. No processo produtivo industrial, o clínquer deve ser resfriado rapidamente, para evitar a decomposição do silicato tricálcico em silicato dicálcico e cal. Esse trabalho estuda a cinética de decomposição térmica do C3S puro. A decomposição do C3S puro em resfriamento contínuo apresentou uma velocidade mais elevada do que a tradicionalmente aceita na literatura.
The mechanical properties of Portland cement are closely related to the chemical composition of the clinker, and particularly to the concentration of tricalcium silicate, 3CaO.SiO2, or C3S. In the industrial production process, the clinker must be rapidly quenched, to avoid its decomposition into dicalcium silicate and lime. This work studies the kinetics of thermal decomposition of pure C3S. The continuous cooling transformation of pure C3S showed a decomposition rate higher than the values traditionally accepted in the literature

No abstract

3'-Deoxy-3-[F]fluorothymidine, or [F]FLT, is a positron emission tomography (PET) tracer used in clinical studies for noninvasive assessment of proliferation activity in several types of cancer. Although the use of this PET tracer is expanding, to date, few studies concerning its dosimetry have been published. In this work, new [F]FLT dosimetry estimates are determined for human and mice using Monte Carlo simulations. Modern voxelized male and female phantoms and [F]FLT biokinetic data, both published by the ICRP, were used for simulations of human cases. For most human organs/tissues the absorbed doses were higher than those reported in ICRP Publication 128. An effective dose of 1.70E-02 mSv/MBq to the whole body was determined, which is 13.5% higher than the ICRP reference value. These new human dosimetry estimates obtained using more realistic human phantoms represent an advance in the knowledge of [F]FLT dosimetry. In addition, mice biokinetic data were obtained experimentally. These data and a previously developed voxelized mouse phantom were used for simulations of animal cases. Concerning animal dosimetry, absorbed doses for organs/tissues ranged from 4.47 ± 0.75 to 155.74 ± 59.36 mGy/MBq. The obtained set of organ/tissue radiation doses for healthy Swiss mice is a useful tool for application in animal experiment design.

ResumoAs propriedades do cimento Portland estão diretamente relacionadas às concentrações de suas fases constituintes, principalmente a alita, a belita, a fase ferrítica e o aluminato. A alita, de composição 3CaO.SiO 2 e abreviada por C 3 S, deve ser o constituinte majoritário do clínquer após o processamento, pois é sua reação de hidratação que confere a resistência mecânica ao cimento curado. A belita, de composição 2CaO.SiO 2 e abreviada por C 2 S, está presente como o primeiro complexo de cal e sílica formado no aquecimento e, sendo mais estável a baixas temperaturas que o C 3 S, volta a se formar no resfriamento. O aluminato está presente principalmente na forma de 3CaO.Al 2 O 3 , abreviado por C 3 A, enquanto a ferrita aparece como constituinte principalmente na forma 4CaO.Al 2 O 3 .Fe 2 O 3 , abreviada por C 4 AF. Os teores de ferrita e alumina, no entanto, alteram a estabilidade da alita, com conseqüentes alterações na reatividade do cimento. O presente trabalho estuda os efeitos de adições de Fe 2 O 3-e Al 2 O 3 sobre a estabilidade da alita e apresenta diagramas CCT para a decomposição da alita na presença desses compostos. Palavras