Higher Institute of Technologies and Applied science InSTEC

Havana, Cuba

Higher Institute of Technologies and Applied science InSTEC

Havana, Cuba
SEARCH FILTERS
Time filter
Source Type

Perez D.M.,Higher Institute of Technologies and Applied science InSTEC | Lorenzo D.E.M.,Higher Institute of Technologies and Applied science InSTEC | De Oliveira Lira C.A.B.,Federal University of Pernambuco | Hernandez C.R.G.,Higher Institute of Technologies and Applied science InSTEC | And 2 more authors.
International Journal of Nuclear Energy Science and Technology | Year: 2017

This paper is part of the ongoing efforts to contribute to the thermalhydraulic analysis of one of the most promising alternatives to produce medical isotopes and meeting current and future demand for 99Mo: The use of Aqueous Homogeneous Reactors (AHRs). In this paper, the effects of some calculation parameters like mesh refinement, time step size, turbulence models, transient schemes and numerical advection scheme on the computational modelling of key parameters of an AHR steady-state operation have been investigated. For this purpose, a 75 kWth AHR conceptual design based on the ARGUS reactor, six meshes, five time step sizes, three different models for solving flow problems, three numerical advection schemes and the available transient schemes were used in the simulations. The numerical simulations were carried out using the Computational Fluid Dynamic (CFD) code ANSYS CFX 14. The results of the CFD simulations allow developing a detailed and improved CFD model of the AHR core on which the effects of the investigated calculation parameters are quantifiable. Copyright © 2017 Inderscience Enterprises Ltd.


Milian Perez D.,Higher Institute of Technologies and Applied science InSTEC | Milian Lorenzo D.E.,Higher Institute of Technologies and Applied science InSTEC | Rodriguez Garcia L.P.,Higher Institute of Technologies and Applied science InSTEC | Cadavid Rodriguez M.,Tecnologia Nuclear Medica SpA TNM | And 3 more authors.
Journal of Thermodynamics | Year: 2015

T c 99 m is a very useful radioisotope, which is used in nearly 80% of all nuclear medicine procedures. Tc99m is produced from 99Mo decay. A potentially advantageous alternative to meeting current and future demand for 99Mo is the use of Aqueous Homogeneous Reactors (AHR). In this paper, a thermal-hydraulics study of the core of a 75 kWth AHR conceptual design based on the ARGUS reactor for 99Mo production is presented. As the ARGUS heat removal systems were designed for working at 20 kWth, the main objective of the thermal-hydraulics study was evaluating the heat removal systems in order to show that sufficient cooling capacity exists to prevent fuel solution overheating. The numerical simulations of an AHR model were carried out using the Computational Fluid Dynamic (CFD) code ANSYS CFX 14. Evaluation shows that the ARGUS heat removal systems working at 75 kWth are not able to provide sufficient cooling capacity to prevent fuel solution overheating. To solve this problem, the number of coiled cooling pipes inside the core was increased from one to five. The results of the CFD simulations with this modification in the design show that acceptable temperature distributions can be obtained. © 2015 Daniel Milian Pérez et al.


Hernandez-Tamargo C.E.,University of Habana | Montero-Alejo A.L.,University of Habana | Pujals D.C.,Higher Institute of Technologies and Applied science InSTEC | Mikosch H.,Vienna University of Technology | Hernandez M.P.,Institute Ciencias Y Tecnologias Of Materiales Imre
Journal of Chemical Physics | Year: 2014

Experimental scanning tunneling microscopy (STM) studies have shown for more than two decades rectangular formations when sulfur atoms are deposited on Au(111) surfaces. The precursors have ranged from simple molecules or ions, such as SO2 gas or sulfide anions, to more complex organosulfur compounds. We investigated, within the framework of the Density Functional Theory, the structure of these rectangular patterns assuming them entirely composed of sulfur atoms as the experimental evidence suggests. The sulfur coverage at which the simulations were carried out (0.67 ML or higher) provoked that the sulfur-sulfur association had to be taken into account for achieving a good agreement between the sets of simulated and experimental STM images. A combination of four sulfur dimers per rectangular formation properly explained the trends obtained by the experimental STM analysis which were related with the rectangles' size and shape fluctuations together with sulfur-sulfur distances within these rectangles. Finally, a projected density of states analysis showed that the dimers were capable of altering the Au(5d) electronic states at the same level as atomic sulfur adsorbed at low coverage. Besides, sulfur dimers states were perfectly distinguished, whose presence near and above the Fermi level can explain both: sulfur-sulfur bond elongation and dimers stability when they stayed adsorbed on the surface at high coverage. © 2014 AIP Publishing LLC.

Loading Higher Institute of Technologies and Applied science InSTEC collaborators
Loading Higher Institute of Technologies and Applied science InSTEC collaborators