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PubMed | National University of Colombia, Brazilian Radiological Protection and Dosimetry Institute (IRD), Eletrobras, Hospital San Juan Of Dios and 14 more.
Type: Journal Article | Journal: Radiation protection dosimetry | Year: 2016

Internal dosimetry intercomparisons are essential for the verification of applied models and the consistency of results. To that aim, the First Regional Intercomparison was organised in 2005, and that results led to the Second Regional Intercomparison Exercise in 2013, which was organised in the frame of the RLA 9/066 and coordinated by Autoridad Regulatoria Nuclear of Argentina. Four simulated cases covering intakes of (131)I, (137)Cs and Tritium were proposed. Ninteen centres from thirteen different countries participated in this exercise. This paper analyses the participants results in this second exercise in order to test their skills and acquired knowledge, particularly in the application of the IDEAS Guidelines. It is important to highlight the increased number of countries that participated in this exercise compared with the first one and, furthermore, the improvement in the overall performance. The impact of the International Atomic Energy Agency (IAEA) Projects since 2003 has led to a significant enhancement of internal dosimetry capabilities that strengthen the radiation protection of workers.

PubMed | Comision Chilena de Energia Nuclear, Viña del Mar University and University of Valparaíso
Type: Journal Article | Journal: Revista medica de Chile | Year: 2016

The effectiveness against radiation of tungsten bismuth caps, used in interventional cardiology is not well known.To determine the degree of radiation protection conferred by these caps in real work conditions.We compared the gross electric charges received at brain lobe levels by three occupationally exposed professionals who participated in 22 consecutive procedures, inside and outside of the tungsten bismuth cap.The median electric charges outside and inside the cap were 3.71 (range 1.46-5.62) and 2.2 (range 1.29-3.93) nC, which correspond to a 40% radiation attenuation. However, the protection was heterogeneous.Tungsten bismuth caps provide an adequate attenuation, but its degree is heterogeneous.

Soto L.,Comision Chilena de Energia Nuclear | Soto L.,Center for Research and Applications in Plasma Physics and Pulsed Power
Journal of Physics: Conference Series | Year: 2016

The following ideas are widely accepted in Chile with respect to scientific activity: is carried out mainly in universities and science is considered a naturally university activity, that was developed in a period of more than 150 years by isolated individual efforts, c) it was transformed into an institutionalized activity at the universities after the university reform movement at the end of the 1960 decade, d) the activity is finally institutionalized in the country with the creation of the "Comisión Nacional de Investigatión Científica y Tecnológica, CONICYT (National Commission for Scientific and Technological Research) in 1967. This work presents preliminary findings showing that there are other institutional initiatives, different to the efforts from universities and directly dependent of the Chilean Government, in order to produce science and technology in Chile. This governmental initiatives start at the beginning of the Republic of Chile circa of 1810. © Published under licence by IOP Publishing Ltd.

Cardenas M.,Comision Chilena de Energia Nuclear | Cardenas M.,Center for Research and Applications in Plasma Physics and Pulsed Power
Plasma Physics and Controlled Fusion | Year: 2010

We postulate that what determines neutron yield from discharges in a deuterium-filled plasma focus apparatus is the amount of energy passed from the capacitor bank to the individual deuterons participating in the pinch. We study plasma focus discharges within the framework of the snow plow model and write down an expression for the energy passed from the capacitor bank to the particles forming the pinch. Provided the shape of the plasma focus apparatus is fixed, this expression turns out to depend on only two dimensionless parameters comprising the electric and geometric features of the system altogether. We found that the energy per particle at pinching has a unique maximum value as a function of these dimensionless parameters, so that a criterion for optimizing plasma focus performance (i.e. neutron yield) results. We use the current formalism to evaluate the performance of a collection of practical plasma focus systems of various sizes and shapes. Finally, we indicate some modifications - obtained within the framework of the snow plow model - to be introduced in a number of practical systems under examination in order to improve their performance. © 2010 IOP Publishing Ltd.

Zuniga G.E.,University of Santiago de Chile | Junqueira-Goncalves M.P.,University of Santiago de Chile | Pizarro M.,University of Santiago de Chile | Contreras R.,University of Santiago de Chile | And 2 more authors.
Radiation Physics and Chemistry | Year: 2012

Incorporating antimicrobial compounds into edible films or coatings provides a novel way to improve the safety and shelf life of ready-to-eat foods. Diverse studies with Quillaja saponaria Mol. (popularly named quillay) extracts have demonstrated their potential as antifungal agents against phytopathogenic fungi. Crosslinking induced by ionizing radiation is an effective method for the improvement of both barrier and mechanical properties of the edible films and coatings based on milk proteins. However there are few reports about the effects of γ-radiation on plant extracts. The aim of this work was to evaluate the effect of ionizing radiation (0, 5, 10, 15, 20, 25 and 35. kGy) on extracts prepared from in vitro plants of Q. saponaria to be used as antimicrobial agent in irradiated edible coating based on calcium caseinate and whey protein isolated, and also to establish the concentration of Q. saponaria extract to be added as an antifungal agent in the coating. Gamma irradiation since 15. kGy affects negatively the antimicrobial activity and metabolites composition of extract of Q. saponaria by reducing compounds of phenolic nature. Otherwise no effect on saponins profile was observed even at higher doses. It was possible to conclude that the antifungal activity of Q. saponaria extract is mainly related to phenolic compounds content. In addition, our work also shows that to obtain an efficient antifungal protection is necessary to add a minimum concentration of 6% of the extract after the coating irradiation. © 2011 Elsevier Ltd.

Avila R.E.,Comision Chilena de Energia Nuclear | Pena L.A.,Comision Chilena de Energia Nuclear | Jimenez J.C.,Comision Chilena de Energia Nuclear
Journal of Nuclear Materials | Year: 2010

The release of tritium from Li2TiO3 and Li 2ZrO3 pebbles, in batch experiments, is studied by means of temperature programmed desorption. Data reduction focuses on the analysis of the non-oxidized and oxidized tritium components in terms of release limited by diffusion from the bulk of ceramic grains, or by first or second order surface desorption. By analytical and numerical methods the in-furnace tritium release is deconvoluted from the ionization chamber transfer functions, for which a semi-empirical form is established. The release from Li2TiO 3 follows second order desorption kinetics, requiring a temperature for a residence time of 1 day (T1dRes) of 620 K, and 603 K, of the non-oxidized, and the oxidized components, respectively. The release from Li2ZrO3 appears as limited by either diffusion from the bulk of the ceramic grains, or by first order surface desorption, the first possibility being the more probable. The respective values of T1dRes for the non-oxidized component are 661 K, according to the first order surface desorption model, and 735 K within the bulk diffusion limited model. © 2010 Elsevier B.V. All rights reserved.

Inestrosa-Izurieta M.J.,Comision Chilena de Energia Nuclear | Inestrosa-Izurieta M.J.,Center for Research and Applications in Plasma Physics and Pulsed Power | Ramos-Moore E.,University of Santiago de Chile | Soto L.,Comision Chilena de Energia Nuclear | Soto L.,Center for Research and Applications in Plasma Physics and Pulsed Power
Nuclear Fusion | Year: 2015

A table top plasma focus device operating at hundreds of joules was used to simulate an equivalent damage factor than the obtained on the divertor in tokamak experiments. Using the ejected plasma produced after the pinch disruptions, the effects on tungsten targets from 50 cumulative plasma shocks with power fluxes per shot between 2.6 and 9200 kW cm-2 and with a duration time in the order of tens of nanoseconds (damage factor in the order of 100-103 (W cm-2)s1/2) were studied. Morphological analysis shows an increasing appearance of cracked surfaces with holes, fissures and defects, suggesting a potential progression of stress effects and a fast heat load that melts the surface, ending in thermal contractions that recrystallize the surface of the target. A structural analysis demonstrates a compressive stress development and suggests that part of the energy is released in the melting of the surface in case of a plasma shock with a power flux of 9.2 MW cm-2, 75 ns duration pulse, 2.5 × 103 (W cm-2)s1/2 damage factor. How to increase the damage factor by one order of magnitude up to the expected value from type I ELMs on the ITER divertor, i.e. 104 (W cm-2)s1/2 is discussed. © 2015 IAEA, Vienna.

Bora B.,Comision Chilena de Energia Nuclear | Bora B.,Center for Research and Applications in Plasma Physics and Pulsed Power
Plasma Sources Science and Technology | Year: 2015

In recent years, dual capacitively coupled radio frequency (CCRF) glow discharge plasma has been widely studied in the laboratory because of its simpler design and high efficiency for different material processing applications such as thin-film deposition, plasma etching, sputtering of insulating materials etc. The main objective of studies on dual frequency CCRF plasma has been the independent control of ion energy and ion flux using an electrical asymmetry effect (EAE). Most studies have been reported in electrode configurations that are either geometrically symmetric (both electrodes are equal) or completely asymmetric (one electrode is infinitely bigger than the other). However, it seems that most of the laboratory CCRF plasmas have finite electrode geometry. In addition, plasma series resonance (PSR) and electron bounce resonance (EBR) heating also come into play as a result of geometrical asymmetry as well as EAE. In this study, a dual frequency CCRF plasma has been studied in which the dual frequency CCRF has been coupled to the lumped circuit model of the plasma and the time-independent fluid model of the plasma sheath, in order to study the effect of finite geometrical asymmetry on the generation of dc-self bias and plasma heating. The dc self-bias is found to strongly depend on the ratio of the area between the electrodes. The dc self-bias is found to depend on the phase angle between the two applied voltage waveforms. The EAE and geometrical asymmetry are found to work differently in controlling the dc self-bias. It can be concluded that the phase angle between the two voltage waveforms in dual CCRF plasmas has an important role in determining the dc self-bias and may be used for controlling the plasma properties in the dual frequency CCRF plasma. © 2015 IOP Publishing Ltd.

Gonzalez D.,University of Chile | Diaz D.,University of Santiago de Chile | Davis S.,Comision Chilena de Energia Nuclear
European Physical Journal B | Year: 2016

Local conservation of probability, expressed as the continuity equation, is a central feature of non-equilibrium Statistical Mechanics. In the existing literature, the continuity equation is always motivated by heuristic arguments with no derivation from first principles. In this work we show that the continuity equation is a logical consequence of the laws of probability and the application of the formalism of inference over paths for dynamical systems. That is, the simple postulate that a system moves continuously through time following paths implies the continuity equation. The translation between the language of dynamical paths to the usual representation in terms of probability densities of states is performed by means of an identity derived from Bayes’ theorem. The formalism presented here is valid independently of the nature of the system studied: it is applicable to physical systems and also to more abstract dynamics such as financial indicators, population dynamics in ecology among others. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2016.

PubMed | Comision Chilena de Energia Nuclear, University of Chile and University of Santiago de Chile
Type: Journal Article | Journal: Physical review. E | Year: 2017

An estimator for the dynamical temperature in an arbitrary ensemble is derived in the framework of the conjugate variables theorem. We prove directly that its average indeed gives the inverse temperature and that it is independent of the ensemble. We test this estimator numerically by a simulation of the two-dimensional XY model in the canonical ensemble. As this model is critical in the whole region of temperatures below the Berezinski-Kosterlitz-Thouless critical temperature T_{BKT}, we use a generalization of Wolffs unicluster algorithm. The numerical results allow us to confirm the robustness of the analytical expression for the microscopic estimator of the temperature. This microscopic estimator has also the advantage that it gives a direct measure of the thermalization process and can be used to compute absolute errors associated with statistical fluctuations. In consequence, this estimator allows for a direct, absolute, and stringent test of the ergodicity of the underlying Markov process, which encodes the algorithm used in a numerical simulation.

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