National Nuclear Energy Commission

About: National Nuclear Energy Commission is a government organization based out in Rio de Janeiro, Brazil. It is known for research contribution in the topics: Dosimetry & Laser. The organization has 3816 authors who have published 4694 publications receiving 59951 citations.

Development and implementation of a new biomass burning emissions injection height scheme (BBEIH v1.0) for the GEOS-Chem model (v9-01-01)

Abstract: . Biomass burning is a significant source of trace gases and aerosols to the atmosphere, and the evolution of these species depends acutely on where they are injected into the atmosphere. GEOS-Chem is a chemical transport model driven by assimilated meteorological data that is used to probe a variety of scientific questions related to atmospheric composition, including the role of biomass burning. This paper presents the development and implementation of a new global biomass burning emissions injection scheme in the GEOS-Chem model. The new injection scheme is based on monthly gridded Multi-angle Imaging SpectroRadiometer (MISR) global plume-height stereoscopic observations in 2008. To provide specific examples of the impact of the model updates, we compare the output from simulations with and without the new MISR-based injection height scheme to several sets of observations from regions with active fires. Our comparisons with Arctic Research on the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) aircraft observations show that the updated injection height scheme can improve the ability of the model to simulate the vertical distribution of peroxyacetyl nitrate (PAN) and carbon monoxide (CO) over North American boreal regions in summer. We also compare a simulation for October 2010 and 2011 to vertical profiles of CO over the Amazon Basin. When coupled with larger emission factors for CO, a simulation that includes the new injection scheme also better matches selected observations in this region. Finally, the improved injection height improves the simulation of monthly mean surface CO over California during July 2008, a period with large fires.

Determination of trace elements in lichens by instrumental neutron activation analysis

Abstract: Instrumental neutron activation analysis has been applied to analyze epiphytic specimens of the lichen Canoparmelia texana. Samples collected from the barks of the trees were previously cleaned, lyophilized and ground to be irradiated under a thermal neutron flux in the IEA-RI nuclear reactor. Elements A1, As, Br, Ca, Cd, C1, Co, Cr, Cs, Fe, Hf, K, La, Ce, Nd, Sin, Eu, rib, Yb, Lu, Mg, Mn, Na, Rb, Sb, Sc, Se, Th, Ti, U, V and Zn were determined quantitatively by using short arid long irradiations. Comparisons were made between the results for washed and unwashed samples as well as those collected in two different years, from individual palm trees and also from differelat sites of Sgo Paulo State. The precision and the accuracy of the method were evaluated by analyzing NIST 1572a Citrus I_eaves, IAEA 336 Lichen and USGS W-1 Rock reference materials.

k0-Instrumental Neutron Activation Analysis Establishment at CDTN, Brazil: A successful story

Abstract: Since 1995 the k 0 instrumental neutron activation analysis has been applied at Radiochemical Laboratory, CDTN/CNEN, Brazil, by means of TRIGA MARK I IPR-R1 research reactor. At that time , f, and T n were determined and the most recent determination of these parameters confirmed the great stability of the reactor along these years. In order to verify the efficiency and accuracy of the method, several certified reference materials have been systematically analyzed. Participating in Intercomparison Exercises organized by IAEA has been an important, essential and useful procedure to quality control. CDTN is the only Brazilian Institute to apply the k 0-INAA to determine elements by means of their isotopes through short, medium and long half life using its own nuclear reactor.

Influence of the morphological structure of macroreticular amidoxime resins on their complexation capacity

Abstract: Macroreticular chelating resins containing amidoxime groups were synthesized by aqueous suspension copolymerization of acrylonitrile (AN) and divinylbenzene (DVB) and subsequent chemical modification of cyano groups by reaction with hydroxylamine. In the copolymerization, the effects of divinylbenzene proportion and dilution degree on the copolymer pore structure were investigated. Gelatin and calcium carbonate were used as suspension stabilizers and sodium sulphate was added in order to reduce acrylonitrile solubility in water, by salting out effect. The copolymers (AN/DVB) and amidoxime resins (RNH/DVB) obtained were characterized by apparent density, surface area, pore volume, optical appearance, surface morphology and by nitrogen content. The amidoxime resins were finally evaluated in relation to the complexation capacity of copper ion.